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  • Articles  (129)
  • calcium  (65)
  • liver  (64)
  • Springer  (129)
  • National Academy of Sciences
  • 1995-1999  (129)
  • Medicine  (129)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nutrition 36 (1997), S. 23-27 
    ISSN: 1436-6215
    Keywords: Vitamin E ; Fleisch ; Fettgewebe ; Leber ; Eigelb ; Vitamin E ; meat ; adipose tissue ; liver ; egg yolk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary The α-tocopherol content of different meat cuts was examined. Chicken thigh had the highest vitamin E content, followed by chicken breast and pork shoulder (p〈0.05). The lowest concentrations were found in longissimus dorsi muscle from pork, beef, veal and in beef shoulder. Considering the average daily lean meat consumption (105 g) in Switzerland, recommendation for daily vitamin E intake was met to 3 %. Supplementation of 200 mg α-tocopherol acetate/kg feed to pigs and laying hens significantly increased the α-tocopherol content in all examined products. The α-tocopherol accumulation differed according to the following ranking: egg yolk 〉 liver 〉 adipose tissue 〉 musculus longissimus dorsi. The α-tocopherol:energy ratios were 28.8, 7.3, 0.9 and 1.2 mg/MJ for egg yolk, liver, adipose tissue and longissimus dorsi muscle of the vitamin E supplemented groups, respectively. The results showed that meat, with the exception of chicken thigh, is not an important supplier of vitamin E, not even from animals fed a vitamin E enriched diet. Egg yolk became a good source of vitamin E for human nutrition by dietary modification.
    Notes: Zusammenfassung In der vorliegenden Studie wurde der α-Tocopherolgehalt verschiedener Fleischstücke untersucht. Hähnchenschenkel hatte den höchsten α-Tocopherolgehalt, gefolgt von Hähnchenbrust und Schweineschulter (p〈0.05). Die niedrigsten Konzentrationen wurden im Musculus longissimus dorsi vom Schwein, Rind, Kalb und in der Rindsschulter nachgewiesen. Mit dem durchschnittlichen, täglichen Verzehr an magerem Fleisch (105 g) in der Schweiz wurden die Empfehlungen für die tägliche Vitamin E-Zufuhr zu 3 % gedeckt. Die Supplementierung des Schweine- und Legehennenfutters mit 200 mg α-Tocopherolacetat/kg führte zu einem signifikanten Anstieg des α-Tocopherolgehaltes in allen untersuchten Produkten. Die α-Tocopherolakkumulierung unterschied sich gemäß folgender Rangordnung: Eigelb 〉 Leber 〉 Fettgewebe 〉Musculus longissimus dorsi. Die Nährstoffdichten betrugen 28.8, 7.3, 0.9 und 1.2 mg α-Tocopherol/MJ für Eigelb, Leber, Fettgewebe und Musculus longissimus dorsi der jeweiligen mit Vitamin E supplementierten Gruppe. Diese Ergebnisse zeigen, daß Fleisch, mit Ausnahme des Hähnchenschenkels, von Tieren mit supplementierten Diäten kein bedeutender Vitamin E-Lieferant ist. Hingegen wurde Eigelb durch fütterungsbedingte Modifikation zu einer guten Vitamin E-Quelle.
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  • 2
    ISSN: 1436-6215
    Keywords: Strontium ; oraler Strontium-Test ; Calcium ; Absorption ; gesunde Probanden ; Strontium ; oral strontium test ; calcium ; absorption ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary Intestinal strontium absorption has been discussed recently as an indirect measure for calcium uptake. Prerequisite for the clinical use of an oral strontium test is the availability of a reliable procedure including controlled strontium supply, sample pretreatment and analysis as well as the assessment of normal values. In the present study, a group of young females (n=33; 24.0 ± 2.7 y; BMI 21.5 ± 1.9) received an oral dose of 2.27 mmol strontium in a standardized breakfast that contained 0.625 mmol calcium. Before and 220 min after the bolus serum strontium concentrations were determined by means of atomic absorption spectrophotometry (coefficient of variation: within day 4.8 %, n=10; day-to-day 9.5 %, n=8). The error of the method was 2.7 %. Calculation of the fractional strontium absorption rate considered the respective distribution volume (extracellular fluid; either estimated using body weight or determined by means of bioimpedance analysis [BIA]). Average absorption rates were 13.3 ± 3.1 % and, considering BIA measurement 13.6 ± 2.6 %, respectively. Smoking, exercise and, use of oral contraceptives showed no effects. Our oral strontium test is characterized by excellent reliability, easy handling and low costs and, thus, is suitable for routine use.
    Notes: Zusammenfassung Die Erfassung der Strontiumabsorption wird heute als indirektes Verfahren zur Beurteilung der intestinalen Calciumabsorption diskutiert. Voraussetzung für die klinische Anwendung ist ein vertrauenswürdiges Testverfahren inclusive kontrollierter Strontiumgabe, Probenaufarbeitung und -analyse sowie die Erfassung von Normalwerten. Für unsere Studien wurde ein Kollektiv junger Frauen (n=33, 24,0 ± 2,7 Jahre; BMI 21,5 ± 1,9) herangezogen. Die Probandinnen erhielten eine Bolusgabe von 2,27 mmol Strontium zusammen mit einem Standardfrühstück (ca. 0,625 mmol Calcium). Vor und 220 min nach der Bolusgabe erfolgte die Bestimmung des Serum-Strontiumgehaltes mittels Atomabsorptionsspektrometrie. Der Variationskoeffizient der Methode lag innerhalb eines Tages bei 4,8 % (n=10) und von Tag zu Tag 9,5 % (n=8). Der Fehler der Methode betrug 2,7 %. Die Berechnung der fraktionellen Strontiumabsorptionsrate erfolgte unter Berücksichtigung des entsprechenden Verteilungsraumes (Extrazellulärflüssigkeit; Schätzverfahren über Körpergewicht bzw. Bioimpedanz-Analyse [BIA]). Die Strontiumabsorptionsrate lag im Mittel bei 13,3 ± 3,1 %, unter Berücksichtigung der BIA-Werte bei 13,6 ± 2,6 %. Rauchen, sportliche Aktivität bzw. Einnahme oraler Kontrazeptiva zeigten keinen Einfluß. Das hier vorgestellte Testverfahren ist aufgrund seiner hohen Vertrauenswürdigkeit und relativ einfacher Handhabung für Routine-untersuchungen geeignet.
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  • 3
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    Cellular and molecular life sciences 52 (1996), S. 554-557 
    ISSN: 1420-9071
    Keywords: Ion transport ; hepatocytes ; liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We studied the Na+/K+ pump, Na+/K+ ATPase activity, and oxygen consumption (QO2) in hepatocytes isolated from the periportal (PH) and pericentral (CH) regions of the liver lobule, to provide an insight into the functional properties of these cells. Na+/K+ pump activity was determined using86Rb+ (a functional analog of K+) and ouabain, a specific inhibitor of this transport system. Our results indicate the the Na+/K+, pump and Na+/K+ ATPase activity are significantly lower in CH than in PH, although basal ouabain-sensitive (OS) QO2 was negligible in both of these cell preparations. However, OSQO2 was significantly lower in CH than in PH when the Na+/K+ pump was activated using the ionophore nystatin in a Na+-containing medium. These results indicate that the differences in membrane ion transport exist between hepatocytes from different locations of the liver lobule.
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  • 4
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    Cellular and molecular life sciences 52 (1996), S. 795-798 
    ISSN: 1420-9071
    Keywords: Estradiol ; progesterone ; polyamine oxidase ; diamine oxidase ; polyamines ; uterus ; liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 17β-estradiol (E2) and progesterone (P) treatment of immature female rats (10 μg/100 g body weight) respectively resulted in 1.38-fold (p〈0.02) and 1.42-fold (p〈0.02) increase in the uterine polyamine oxidase activity, and 2.45-fold (p〈0.001) and 1.43-fold (p〈0.02) increase in the uterine diamine oxidase activity, as compared to the controls. E2 caused a 5-fold (p〈0.05) and a 1.36-fold (p〈0.05) increase in putrescine and spermidine concentration respectively in rat uterus. Increases of 1.7-fold (p〈0.02) and 1.6-fold (p〈0.05) in putrescine and spermine concentration were determined in the P-treated uterus, as compared to the controls. The spermidine/spermine ratio, which is regarded as an index of growth rate, was higher in the E2-treated uterus and lower in the P-treated uterus than in the control uterus. No statistically significant hormonal effects were estimated in the immature liver. The data reported suggest the possibility of an involvement of polyamine-oxidizing enzymes in the modulation of polyamine concentrations in rat uterus by the female sex hormones.
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  • 5
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    European journal of nutrition 34 (1995), S. 220-223 
    ISSN: 1436-6215
    Keywords: Ascorbic acid ; glutathioneperoxidase ; lipid peroxides ; liver ; Ascorbinsäure ; Glutathion-Peroxidase ; Lipidperoxiden ; Leber
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Verschiedene Werte an antioxidativem Potential, erzeugt mit Hilfe verschiedener Konzentrationsstufen an Ascorbinsäure (1, 10, 100 mg/Tier/Tag) führten zu Veränderungen in der GSH-Px Aktivität und der Menge den Lipidperoxiden in der Leber von Meerschweinchen. Die Gruppe mit der kleinsten Dosierung (1 mg) von Ascorbinsäure hatte die niedrigste GSH-Px Aktivität und den höchsten Anteil an Lipidperoxiden. Die zwei anderen Gruppen zeigten eine Erhöhung der GSH-Px Aktivität und Senkung von Lipidperoxiden auf. Es bestand kein Unterschied zwischen den Gruppen mit der Dosis von 10 und 100 mg Ascorbinsäure.
    Notes: Summary Differing antioxidant potentials created by graded ascorbic acid supplementation (1, 10, 100 mg per animal daily) evoked changes in the level of glutathione peroxidase activity and lipid peroxides in the liver of female guinea pigs. The group with the lowest ascorbic acid intake (1 mg) had the lowest activity of glutathione peroxidase and the highest level of lipid peroxides. The two other groups (10 and 100 mg) showed enhancement of glutathione peroxidase activity and decline in lipid peroxides. There was no difference between the groups with 10 and 100 mg ascorbic acid intake.
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  • 6
    ISSN: 1436-6215
    Keywords: Riboflavin ; Milch ; Leber ; Restkörper ; Laktation ; Ratte ; Riboflavin ; milk ; liver ; carcass ; lactation ; rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary The present study investigated the effect of various dietary riboflavin supplementations (0 to 4 000 mg/kg) during lactation on riboflavin concentrations of liver, carcass (bled body without intestine and liver), and milk in the rat. The experiment was conducted until the 14th day of lactation; milk samples were drawn on the 7th and 13th day of lactation. Riboflavin concentrations of milk raised continuously with increasing riboflavin supplementation; in the range between 0 and 10 mg/kg riboflavin supplementation, there was a linear relationship, and in the range between 12 and 4 000 mg/kg there was a logarithmic relationship between riboflavin supplementation and riboflavin concentration in the milk. Maximum riboflavin concentration of milk obtained by supplementation with 4 000 mg/kg was twelve-fold higher than without riboflavin supplementation. For riboflavin supplementation up to 12 mg/kg, riboflavin concentrations in milk on the 7th day of lactation and that on the 13th day of lactation were not different. In contrast, in rats fed diets with higher riboflavin supplementation, riboflavin concentrations were higher by 25 % in average in milk on the 13th day of lactation than in milk on the 7th day of lactation. Contrary to the milk, riboflavin concentrations in liver and carcass exhibited a saturation, which was achieved at a supplementation of 6 mg/kg (liver) and 10 mg/kg (carcass), respectively. Maximum riboflavin concentrations obtained at a supplementation of 4 000 mg/kg were 1.9- and 2.3-fold higher for liver and carcass, respectively, than concentrations obtained without riboflavin supplementation. The dose-response relationship using riboflavin concentrations of liver and carcass as response factors indicates a riboflavin requirement of 8 to 9 mg/kg for lactating rats fed a semisynthetic diet with 17.4 MJ ME/kg dry matter and 20.8 % protein in dry matter.
    Notes: Zusammenfassung In der vorliegenden Arbeit wurde der Einfluß unterschiedlicher Riboflavinzulagen zum Futter (0 bis 4 000 mg/kg) während der Laktation auf die Riboflavinkonzentrationen in Leber, Restkörper (ausgebluteter Gesamtkörper ohne Magen-Darm-Trakt und Leber) und Milch von Ratten untersucht. Der Versuch dauerte bis zum 14. Laktationstag; Milchproben wurden am 7. und am 13. Laktationstag gewonnen. Die Riboflavinkonzentration der Milch erhöhte sich mit steigender Zulage stetig, wobei im Bereich zwischen 0 und 10 mg Riboflavinzulage/kg Futter eine lineare und im Bereich zwischen 12 und 4 000 mg/kg eine logarithmische Funktion vorlag. Die maximale Riboflavinkonzentration in der Milch bei einer Zulage von 4 000 mg/kg war dabei etwa zwölfmal so hoch wie bei fehlender Zulage. Bei Riboflavinzulagen bis 12 mg/kg unterschieden sich die Riboflavinkonzentrationen der Milch am 7. und 13. Laktationstag nicht. Bei den höheren Zulagen waren die Konzentrationen der Milch am 13. Laktationstag im Mittel um 25 % höher als am 7. Laktationstag. Im Gegensatz zur Milch zeigte sich in Leber und Restkörper eine Sättigung der Riboflavinkonzentrationen, die bei einer Riboflavinzulage von 6 mg/kg (Leber) bzw. 10 mg/kg (Restkörper) erreicht war. Die maximalen Riboflavinkonzentrationen bei Zulagen von 4 000 mg/kg waren dabei 1,9 (Leber) bzw. 2,3 (Restkörper) mal so hoch wie bei fehlender Riboflavinzulage. Diese Befunde sprechen für eine ausgeprägte homöostatische Kontrolle der Riboflavinkonzentrationen im Organismus. Anhand von Dosis-Wirkungsbeziehungen mit den Riboflavinkonzentrationen in Leber und Restkörper als Wirkungskriterien leitete sich bei Verwendung des halbsynthetischen Futters (17,4 MJ ME/kg Trockenmasse (T), 20,8 % Rohprotein in T) ein Riboflavinbedarf von 8 bis 9 mg/kg Futter für die laktierende Ratte ab.
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  • 7
    ISSN: 1436-6215
    Keywords: Environmental temperature ; energy expenditure ; ouabain-sensitive respiration ; duodenal mucosa ; liver ; rats ; Umgebungstemperatur ; Energieumsatz ; Quabain-sensitive Respiration ; Duodenalmukosa ; Leber ; Ratten
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Die Wirkung der Umgebungstemperatur (18°C oder 28°C) und des Fasergehalts in der Diät (g je kg Trockensubstanz (TS) niedrig - 68, mittel - 110, hoch - 157) oder des Proteingehalts (g je kg TS niedrig - 91, mittel- 171, hoch - 262) auf den Verdauungstrakt, die Darmmasse, den Energieumsatz und auf die mit der Na+, K+-ATPase-Aktivität zusammenhängenden Respiration von Duodenalmukosa und Leber wurde bei 72 Wistar-Ratten in wiederholten Experimenten untersucht. Der Gesamte und Quabain-sensitive (ein Maß der Na+, K+-ATPase Aktivität) O2-Verbrauch der Gewebe wurde in vitro polarographisch ermittelt (YSI-biologische Sauerstoff-Erfassung nach dem Clark-Meßprinzip). Die Wärmeproduktion (WP) intakter Tiere wurde über Respirationskammern mit offenem Gasaustausch erfaßt. Die bei 18°C gehaltenen Ratten wiesen im Vergleich zu 28°C eine höhere Darmmasse auf. Die Masse an leerem Dünndarm, Caecum und Colon stieg mit ansteigendem Fasergehalt in der Diät (P〈0.05). Die WP als Korrelat der umsetzbaren Energie war nur im 1. Experiment höher (P〈0.05) bei 18°C als bei 28°C. Bei niedriger Proteinstufe war die WP signifikant höher (P 0.05) als bei den anderen Stufen. Verglichen mit 28°C erzeugte 18°C einen ansteigenden Gesamt- und Quabain-sensitiven O2-Verbrauch in der Duodenalmukosa. Die Leber reagierte nicht auf Temperaturunterschiede. Jedoch war ihr Quabain-sensitiver O2-Verbrauch bei niedrigem Proteingehalt in der Nahrung höher (P〈0.05) als bei den anderen Varianten. Bei niedrigem Fasergehalt war der gesamte und Quabain-sensitive O2-Verbrauch der Duodenalmukosa höher als bei den anderen Fasergehaltsvarianten. Die In-vitro-Ergebnisse stimmten mit der WP und dem O2-Verbrauch intakter Tiere überein.
    Notes: Summary Seventy two Wistar rats were used in two repeat studies to investigate the effect of environmental temperature (18°C or 28°C) and increasing levels of dietary fibre (low, 68 g/kg DM; medium 110 g/kg DM; high, 157 g/kg DM) or protein (low, 91 g/kg DM; medium, 171 g/kg DM; high, 262 g/kg DM) on digestive tract, visceral organ size, energy metabolism, and respiration attributable to Na+,K+-ATPase activity in duodenal mucosa and liver. Total and ouabain-sensitive (a measure of Na+,K+-ATPase activity) O2 consumptionin vitro of tissues were measured polarographically using a Clark-style YSI biological O2 monitor. Whole body heat production (in vivo) was measured using open-circuit respiration chambers. The weight of the visceral organs was higher in rats housed at 18°C than at 28°C. The empty weight of the small intestine, caecum, and colon increased as the level of dietary fibre increased (P 0.05). Heat production as a proportion of metabolizable energy was higher (P〈0.05) at 18°C than at 28°C in the first experiment but this difference was not significant in the second experiment. Rats fed the low protein diet had significantly higher (P〉0.05) heat production than those fed medium or high protein diets. Compared to 28°C, environmental temperature of 18°C caused an increased total and ouabain-sensitive O2 consumption in duodenal mucosa. There was no significant effect of environmental temperature on total and ouabain-sensitive O2 consumption in the liver. However, ouabain-sensitive O2 consumption in liver was significantly higher (P 0.05) when rats were fed a low protein diet compared to the medium or high protein diet. Total and ouabain-sensitive O2 consumption increased in duodenal mucosa of rats fed low level of dietary fibre compared to the medium or high dietary fibre diets. Thein vitro results corresponded with the whole animal energy expenditure and O2 consumptionin vivo.
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  • 8
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    Cellular and molecular life sciences 52 (1996), S. 661-663 
    ISSN: 1420-9071
    Keywords: Non-heart-beating donor ; liver ; oxygen ; persufflation ; aerobic ischemia ; transplantation ; preservation ; resuscitation ; viability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Clinical liver transplantation has become the therapy of choice in end-stage liver disease, but the limited availability of suitable donor organs still impedes its widespread application. In order to increase the availability of donor organs for liver transplantation, it would be advantageous if ischemically damaged livers could be resuscitated from cadavers in which the heart has stopped beating. A method for doing this has been developed in a rat model. Compared to livers excised from rats in which the heart is still beating, severe deteriorations of tissue integrity and functional performance were evident in predamaged livers after cold preservation without supplementary treatment. A treatment of those livers which included an antioxidant rinse with superoxide dismutase, and venous vascular insufflation of gaseous oxygen during preservation, completely prevented tissue alterations upon reperfusion, and promoted a functional recovery of the livers, making them comparable to organs harvested from heart-beating donors.
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  • 9
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    Cellular and molecular life sciences 51 (1995), S. 589-591 
    ISSN: 1420-9071
    Keywords: Oyster mushroom (Pleurotus ostreatus) ; cholesterol ; serum ; lipoproteins ; liver ; HMG-CoA reductase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The effect of dried oyster mushroom (Pleurotus ostreatus) on cholesterol (C) content in serum, in lipoproteins and in liver, and on the activity of 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase in liver microsomes, was studied in male rats (strain Wistar, initial body weight 75 g) fed on low-cholesterol (9 mg/100 g) and high-cholesterol (0.3%) diets. Addition of 5% oyster mushroom to both diets reduced significantly the C-content in serum (by 30%), in very-low- and low-density lipoproteins (in a 1∶1 ratio to the decrease of total serum C) and in liver (by 50%), as well as the activity of HMG-CoA reductase (by more than 30%).
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  • 10
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    Cellular and molecular life sciences 52 (1996), S. 687-690 
    ISSN: 1420-9071
    Keywords: Vitamin A ; diet ; rats ; plasma ; liver ; scavengers ; antioxidant enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Twenty-seven rats were divided into three groups and fed on diets containing 0.3, 6 or 60 RE (retinol equivalent) retinyl palmitate/g food. After 7 weeks, hepatic vitamin A uptake was found to be more efficient in vitamin A-deficient rats than in rats given adequate vitamin A. We showed that during the metabolic adaptation of the animals to the level of vitamin A in the diet, extensive modifications occur in the antioxidant defences of the organism. In parallel with the increase in the level of vitamin A, the decrease in the level of α-tocopherol in the plasma can bring about a greater susceptibility of the lipoproteins to oxidative stress. Similarly, the decrease in the hepatic α-tocopherol level and in glutathione peroxidase activity leads to the weakening of the liver's antioxidant defences.
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  • 11
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    Cellular and molecular life sciences 52 (1996), S. 831-833 
    ISSN: 1420-9071
    Keywords: Paramecium caudatum ; thigmotaxis ; Ja-value ; CNR ; calcium ; ruthenium red ; LaCl3 ; caffeine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract To understand the role of calcium ions in thigmotaxis inParamecium caudatum, the effects of caffeine, ruthenium red and lanthanum (LaCl3) on thigmotaxis were examined. Thigmotaxis in the CNR mutant, which lacks voltage-dependent Ca2+-channels in the ciliary membrane, was also examined. Ruthenium red and LaCl3 suppressed thigmotaxis inP. caudatum, while caffeine enhanced it. The CNR mutant showed hardly any thigmotaxis. It can be thought that an increase in Ca2+ influx and the intraciliary concentration of Ca2+ ions induces thigmotaxis inParamecium.
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  • 12
    ISSN: 1432-1041
    Keywords: Key wordsProstaglandin E1 ; Carbonyl reductase; 13 ; 14-dihydro-15-keto-PGE1 ; 13 ; 14-dihydro-PGE1 ; human ; liver ; erythrocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: The therapeutic response to PGE1 is highly variable, and a contribution by variable formation of its active tertiary metabolite PGE0 is in question. Hence, the objective of this study was to assess the person-to-person variation of the reduction of the inactive intermediate metabolite 15-KD PGE1 by human liver and human erythrocytes in forming the active metabolite PGE0. Methods: Source of enzyme was lysed erythrocytes from 29 donors, and a bank of 37 donor livers including specimens from 15 children. Tritium-labelled 13,14-dihydro-15-keto-prostaglandin E1 (15-KD PGE1) was used at low nanomolar concentrations and found to be converted almost exclusively to the more polar compound 13,14-dihydro-prostaglandin E1 (PGE0) by an NADPH-dependent carbonyl reductase. The identity of the product PGE0 was established by comparison of its chromatographic and mass spectral characteristics with authentic PGE0. Results: Lysed erythrocytes had readily measurable enzymatic activity; differences between the preparations from 29 subjects were very small with only a twofold range of variation. In contrast to lysed erythrocytes, intact erythrocytes did not catalyse the reaction so that the erythrocyte activity should be medically immaterial. 15-KD PGE1 15-ketoreductase activity of liver cytosol averaged 61.1 fmol · min−1 · mg−1 protein in preparations from 37 human livers. Individual activities varied over an almost tenfold range, with indications of a non-normal distribution. Kinetic studies of selected specimens showed substantially different Vmax values but indistinguishable k M values, suggesting that the individual variation in 15-KD PGE1 15-ketoreduction is the result of differences in enzyme concentration rather than of structural enzyme variations. The activity in 15 livers from children was significantly lower than in those from adults. Inhibition data suggest that both the liver and the erythrocyte enzymes belong to the class of carbonyl reductases. Conclusions: The variations in hepatic enzyme activity may be expected to affect the transformation of 15-KD PGE1 to the active metabolite PGE0 in vivo. The clinical significance remains to be explored.
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  • 13
    ISSN: 1432-1041
    Keywords: Key words 6-Mercaptopurine ; Thiopurine methyltransferase ; Polymorphism; erythrocytes ; liver ; kidney ; newborns ; adults
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective. The polymorphism of erythrocyte thiopurine methyltransferase (TPMT) is genetically regulated as an autosomal codominant trait, and so should be congenital. Results. We tested this hypothesis by measuring TPMT activity in erythrocyte preparations from adults and newborns and observed polymorphic distribution of TPMT activity in the adult and newborn erythrocytes. The activity of TPMT was higher in red cells from the newborns than adults. The frequency distribution of TPMT activity was also investigated in the liver and kidney. In the kidney, TPMT activity fell into two subgroups, whereas in the liver the distribution pattern was more complex. The activity of TPMT in erythrocytes and liver from the same subject was correlated, but the values of only half the cases fell within the 95% confidence limits, suggesting that the control of hepatic and/or erythrocyte TPMT is multifactorial.
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  • 14
    ISSN: 1573-4919
    Keywords: regucalcin ; calcium-binding protein ; insulin ; calcium ; gene expression ; rat liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of refeeding on the expression of Ca2+-binding protein regucalcin mRNA in the liver of fasted rats was investigated. When rats were fasted overnight, the hepatic regucalcin mRNA level was reduced about 70% of that in feeding rats. Refeeding produced a remarkable elevation of hepatic regucalcin mRNA level (about 150–170% of fasted rats). Liver regucalcin concentration was appreciably increased by refeeding, although it was not altered by fasting. The oral administration of glucose (2 g/kg body weight) to fasted rats caused a significant increase in hepatic regucalcin mRNA level. Moreover, hepatic regucalcin mRNA level was clearly elevated by a single subcutaneous administration of insulin (10 and 100 U/kg) to fasted rats. The hormonal effect was not further enhanced by the simultaneous administration of calcium chloride (250 mg Ca/kg) to fasted rats, although calcium administration stimulated regucalcin mRNA expression in the liver. The present study suggests that the expression of hepatic regucalcin mRNA stimulated by refeeding is significantly involved in the action of insulin and/or calcium as stimulating factors.
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  • 15
    ISSN: 1573-4919
    Keywords: calcium ; calcium channels ; smooth muscle ; sarcolemma ; coronary artery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Tension generation and Ca2+ flux in smooth muscle varies depending upon the diameter of a vessel and its location. The purpose of the present investigation was to determine if the biochemical characteristics of the Na+−Ca2+ exchanger and the Ca2+ channel differ in sarcolemmal membrane preparations isolated from a large conduit vessel (thoracic aorta) or from large and small coronary arteries. We also investigated the possibility of differences between sarcolemmal membranes isolated from coronary arteries dissected from the right and left ventricles. The purification of the sarcolemmal membranes was of a similar magnitude amongst the different groups. Contamination of the sarcolemmal membranes with other membranous organelles was negligible and similar amongst the groups. The Km and Vmax of Na+-dependent Ca2+ uptake in sarcolemmal vesicles was similar amongst the groups. Calcium channel characteristics were examined by measuring [3H]PN200-110 binding to sarcolemmal vesicles. The right coronary artery membranes from both large and small caliber vessels exhibited a higher Kd and the small right coronary artery sarcolemmal preparation had a lower maximal binding density for [3H] PN200-110. The results suggest that the right coronary artery, and in particular the small diameter right coronary artery, possesses altered Ca2+ channel characteristics in isolated sarcolemmal membranes.
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  • 16
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    Molecular and cellular biochemistry 154 (1996), S. 123-132 
    ISSN: 1573-4919
    Keywords: rat pancreas ; cholecystokinin-octapeptide ; magnesium ; calcium ; secretion ; cyclic AMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This study investigates the effect of magnesium (Mg2+) on the secretory responses and the mobilization of calcium (Ca2+) and Mg2+ evoked by cholecystokinin-octapeptide (CCK-8) in the exocrine rat pancreas. In the isolated intact perfused pancreas CCK-8 (10−10 M) produced marked increases in juice flow and total protein output in zero and normal (1.1 mM) extracellular Mg2+ [Mg2+]o compared to a much reduced secretory response in elevated (5 mM and 10 mM) [Mg2+]o Similar effects of perturbation of [Mg2+]o on amylase secretion and 45Ca2+ uptake (influx) were obtained in isolated pancreatic segments. In pancreatic acinar cells loaded with the fluorescent bioprobe fura-2 acetomethylester (AM), CCK-8 evoked marked increases in cytosolic free Ca2+ concentration [Ca2+]i in zero and normal [Mg2+]o compared to a much reduced response in elevated [Mg2+]o Pretreatment of acinar cells with either dibutyryl cyclic AMP (DB2 cAMP) or forskolin had no effect on the CCK-8 induced changes in [Ca2+]i. In magfura-2-loaded acinar cells CCK-8 (10−8 M) stimulated an initial transient rise in intracellular free Mg2+ concentration [Mg2+]i followed by a more prolonged and sustained decrease. This response was abolished when sodium Na+ was replaced with N-methyl-D-glucamine (NMDG). Incubation of acinar cells with 10 mM Mg2+ resulted in an elevation in [Mg2+]i. Upon stimulation with CCK-8, [Mg2+]i. decreased only slightly compared with the response obtained in normal [Mg2+]o. CCK-8 caused a net efflux of Mg2+ in pancreatic segments; this effect was abolished when extracellular sodium [Na+]o was replaced with either NMDG or choline. The results indicate that Mg2+ can regulate CCK-8-evoked secretory responses in the exocrine pancreas possibly via Ca2+ mobilization. Moreover, the movement of Mg2+ in pancreatic acinar cells is dependent upon extracellular Na+.
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  • 17
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    Molecular and cellular biochemistry 146 (1995), S. 179-186 
    ISSN: 1573-4919
    Keywords: Ca2+-ATPase ; calcium ; nuclear DNA ; DNA fragmentation ; regucalcin ; regenerating rat liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The alteration of calcium content, Ca2+-ATPase activity, DNA content and DNA fragmentation in the nuclei of regenerating rat liver was investigated. Liver was surgically removed about 70% of that of sham-operated rats. the reduced liver weight by partial hepatectomy was completely restored at 3 days after the surgery. Regenerating liver significantly increased Ca2+-ATPase activity and DNA content in the nuclei between 1 and 5 days after hepatectomy. The nuclear calcium content was clearly increased from 2 days after hepatectomy. The increase of Ca2+-ATPase activity in regenerating liver was clearly inhibited by the presence of trifluoperazine (10 μM), staurosporine (2.5 μM) and dibucaine (10 μM), which are inhibitors of calmodulin and protein kinase, in the enzyme reaction mixture. However, the nuclear enzyme activity in normal rat liver was not significantly altered by these inhibitors. Meanwhile, the increase of nuclear DNA content in regenerating liver was completely blocked by the administration of trifluoperazine (2.5 mg/100 g body weight), suggesting an involvement of calmodulin. Now, the nuclear DNA fragmentation was significantly decreased in regenerating liver, suggesting that this decrease is partly contributed to the increase in nuclear DNA content. The present study clearly demonstrates that regenerating liver enhances nuclear Ca2+-ATPase activity and induces a corresponding elevation of nuclear calcium content. This Ca2+-signaling system may be involved in the regulation of nuclear DNA functions in regenerating rat liver.
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  • 18
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    Molecular and cellular biochemistry 148 (1995), S. 67-72 
    ISSN: 1573-4919
    Keywords: regucalcin ; calcium ; protease ; calpain ; rat liver cytosol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The increasing effect of regucalcin, isolated from rat liver cytosol, on neutral proteolytic activity in the hepatic cytosol was characterized. The proteolytic activity was markedly elevated by the addition of regucalcin (0.1–0.5 μM) in the absence of Ca2+. This increase was not significantly altered by the presence of diisopropylfluorophsophate (DPF;2.5 mM)—although DFP caused a significant decrease in the proteolytic activity. Regucalcin (0.25 μM) additively enhanced the dithiothreitol (DTT; 1.0 mM)—increased proteolytic activity, while the regucalcin or DTT effect was completely abolished by NEM (5 mM), indicating that regucalcin may act on the SH group in proteases. Also, regucalcin (0.25 μM) enhanced the effect of Ca2+ (10 μM) increasing liver proteolytic activity, suggesting that regucalcin does not influence on the active sites for Ca2+ in proteases. Moreover, the proteolytic activity of regucalcin (0.25 μM) was significantly decreased by the presence of calpastatin (24 μg/ml), an inhibitor of Ca2+-activated neutral protease (calpain). Now, regucalcin (0.25 μM) increased about 7-fold the activity ofm-calpain isolated from rabbit skeletal muscle. These observations demonstrate that regucalcin directly activates cysteinyl-proteases. Regucalcin may have a role as a potent proteolytic activator in the cytoplasm of liver cells.
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  • 19
    ISSN: 1573-4919
    Keywords: DNA adducts ; liver ; fish ; 32P-postlabelling ; polycyclic aromatic hydrocarbons ; genotoxic biomarker
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    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The levels of DNA adducts in the hepatic tissue of the white sucker fish speciesCatostomus commersoni were determined by32P-postlabelling. The fish were caught at four sites: two sites near the city of Windsor (Québec, Canada) on the St. François River, a downstream tributary of the St. Lawrence River, and two sites in the St. Lawrence River itself, near the city of Montréal (Québec, Canada). The latter sites are known to be contaminated by many pollutants including polycyclic aromatic hydrocarbons. Total adduct levels in all fish ranged from 25.1–178.0 adducts per 109 nucleotides. White sucker from the selected sites of the St. Lawrence River had a significantly higher mean level of DNA adducts than those of the St. François River (129.4 vs 56.8, respectively). These results suggest that the effluents of many heavy industries (e.g. from a Soderberg aluminium plant) flowing in the St. Lawrence River are more likely to produce genotoxic damage to fish than those released in one of its tributary, and mainly associated to the activities of a small town and a nearby pulp and paper mill.
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  • 20
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    Molecular and cellular biochemistry 149-150 (1995), S. 203-212 
    ISSN: 1573-4919
    Keywords: calcium ; mitochondria ; FAD-glycerol 3-phosphate dehydrogenase ; pyruvate dehydrogenase ; oxoglutarate dehydrogenase ; isocitrate dehydrogenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In mammalian cells, increases in calcium concentration cause increases in oxidative phosphorylation. This effect is mediated by the activation of four mitochondrial dehydrogenases by calcium ions; FAD-glycerol 3-phosphate dehydrogenase, pyruvate dehydrogenase, NAD-isocitrate dehydrogenase and oxoglutarate dehydrogenase. FAD-glycerol 3-phosphate dehydrogenase, being located on the outer surface of the inner mitochondrial membrane, is exposed to fluctuations in cytoplasmic calcium concentration. The other three enzymes are located within the mitochondrial matrix. While the kinetic properties of all of these enzymes are well characterised, the molecular basis for their regulation by calcium is not. This review uses information derived from calcium binding studies, analysis of conserved calcium binding motifs and comparison of amino acid sequences from calcium sensitive and non-sensitive enzymes to discuss how the recent cloning of several subunits from the four dehydrogenases enhances our understanding of the ways in which these enzymes bind calcium. FAD-glycerol 3-phosphate dehydrogenase binds calcium ions through a domain which is part of the polypeptide chain of the enzyme. In contrast, it is possible that the calcium sensitivity of the other dehydrogenases may involve separate calcium binding subunits.
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  • 21
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    Molecular and cellular biochemistry 179 (1998), S. 99-110 
    ISSN: 1573-4919
    Keywords: diaphragm ; oxygen-derived free radicals ; respiratory muscle fatigue ; nitric oxide ; sarcoplasmic reticulum ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract It is now recognized that respiratory muscle fatigue contributes to the development of respiratory failure in some patients with lung disease. This observation has prompted an examination into the mechanisms of development of muscle fatigue, with the understanding that an elucidation of these processes may lead to new therapeutic approaches to the treatment of these patients. A series of recent studies examining this issue have, moreover, discovered that oxygen-derived free radicals generated during strenuous contraction may modulate respiratory muscle contractile function and contribute to the development of muscle fatigue. The data supporting this concept include: (a) direct (e.g. EPR, ESR studies) and indirect (evidence of lipid peroxidation, protein carbonyl formation, glutathione oxidation) evidence that there is heightened free radical production in contracting muscle, (b) evidence that pharmacologic depletion of muscle antioxidant stores increases degree of muscle fatigue present after a period of exercise, and (c) evidence that administration of agents that act as free radical scavengers retard the development muscle fatigue. Free radicals may produce these changes in muscle force generating capacity by interacting with and altering the function of a number of intracellular-biophysical processes (i.e. sarcolemmal action potential propagation, sarcoplasmic reticulum calcium handling, mitochondrial function, contractile protein interactions).
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  • 22
    ISSN: 1573-4919
    Keywords: heart cells ; taurine ; β-alanine ; taurine-Na+ cotransport ; CBDMB ; Na+-Ca2+ exchanger ; calcium ; nucleus ; confocal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Recent studies in heart cells have shown taurine to induce a sustained increase of both intracellular Ca2+ and Na+. These results led us to believe that the increase in Na+ by taurine could be due to Na+ entry through the taurine-Na+ cotransporter which in turn favours transarcolemmal Ca2+ influx through Na+-Ca2+ exchange. Therefore, we investigated the effect of β-alanine, a blocker of the taurine-Na+ cotransporter and low concentrations of CBDMB (a pyrazine derivative, 5-(N-4chlorobenzyl)-2′,4′-dimethylbenzamil), a Na+-Ca2+ exchanger blocker on taurine-induced [Ca]i increase in embryonic chick heart cells. Using Fura-2 Ca2+ imaging and Fluo-3 Ca2+ confocal microscopy techniques, taurine (20 mM) as expected, induced a sustained increase in [Ca]i at both the cytosolic and the nuclear levels. Preexposure to 500 μM of the blocker of the taurine-Na+ cotransporter, β-alanine, prevented the amino acid-induced increase of total [Ca]i. On the other hand, application of β-alanine did not reverse the action of taurine on total [Ca]i. However, low concentrations of the Na+-Ca2+ exchanger blocker, CBDMB, reversed the taurine-induced sustained increase of cytosolic and nuclear free calcium (in presence or absence of β-alanine). Thus, the effect of taurine on [Ca]i in heart cells appears to be due to Na+ entry through the taurine-Na+ cotransporter which in turn favours transarcolemmal Ca2+ influx through the Na+-Ca2+ exchanger.
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  • 23
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    Molecular and cellular biochemistry 190 (1999), S. 185-190 
    ISSN: 1573-4919
    Keywords: calcium ; calcium wave ; calcium oscillation ; inositol 1,4,5-trisphosphate receptor ; ryanodine receptor ; excitation-concentration coupling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract After the seminal work of Ebashi and coworkers which established the essential role of the intracellular Ca2+ concentration ([Ca2+]i) in the regulation of skeletal muscle contraction, we have witnessed an explosive elongation of the list of cell functions that are controlled by the [Ca2+]i. In numerous instances, release of intracellular Ca2+ stores plays important roles in Ca2+ signalling which displays significant variation in spatio-temporal pattern. There are two families of Ca2+ release channels, ryanodine receptors and inositol 1,4,5-trisphosphate (IP3) receptors. These Ca2+ release channels are structurally and functionally similar. In particular, the activity of both types of channels is regulated by the [Ca2+]i. The [Ca2+]i dependence of the Ca2+ release channel activity provides both types of channels with properties of a Ca2+ signal amplifier. This function of the ryanodine receptor is important in striated muscle excitation-contraction coupling, whereas that of the IP3 receptor seems to be the basis of the generation of Ca2+ waves. Thus the wide variety of Ca2+ signalling patterns seem to be critically dependent on the [Ca2+]i dependence of the Ca2+ release channels.
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  • 24
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    Molecular and cellular biochemistry 190 (1999), S. 39-45 
    ISSN: 1573-4919
    Keywords: microcalorimetry ; calcium ; troponin C ; calmodulin ; parvalbumin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Results of microcalorimetric titrations of calcium-binding proteins with calcium or magnesium have been reviewed and evaluated. Results were analyzed mostly in terms of heat capacity changes, which is most closely related to the structural changes of the molecule on metal binding. Two high-affinity sites of rabbit skeletal troponin C are distinguishable in terms of their affinity to calcium and associated enthalpy changes. Heat capacity changes on calcium binding to one of the two high-affinity sites is negative and is in the range ascribed to the ligand binding. In contrast, that to the other of the high-affinity sites is large and positive, indicating that a substantial area of hydrophobic groups become exposed to the solvent. In frog skeletal troponin C, the anomalous positive heat capacity changes occur in one of the low-affinity calcium-specific sites, so that this may be involved in the regulation of contraction. Unlike skeletal troponin C, both of the two high-affinity sites of cardiac troponin C show negative heat capacity changes. In calmodulin, heat capacity changes are positive but small, indicating that calcium binding may induce clustering of the hydrophobic residues on the surface of the molecule. In parvalbumins, heat capacity changes are negative, characteristic of most ligand binding.
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  • 25
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    Keywords: Bcl-2 ; Ca2+ ; hepatoma ; liver ; mitochondrial permeability transition ; tumor cells
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    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Zajdela hepatoma mitochondria were able to accumulate two to five times more Ca2+ than rat liver mitochondria before the permeability transition was induced. Pulses of Ca2+ were given in series to determine the Ca2+ threshold by recording changes in [Ca2+] and membrane potential, the permeability transition causing the release of accumulated Ca2+ and collapse of the membrane potential. Hepatoma mitochondria had lower Ca2+ efflux rates, higher net Ca2+ uptake rates and lower phosphorylation rates than liver mitochondria. Since the differences in regard to induction of the permeability transition might be due to higher expression of the Bcl-2 protein in hepatoma cells than in hepatocytes, the transcription of Bcl-2 and the proteins reacting with a Bcl-2 polyclonal antiserum were estimated by Northern and Western blotting, respectively. Hepatoma cells had two Bcl-2 specific mRNA bands of 7 and 2.4 kb, and substantial amounts of the Bcl-2 protein, whereas in liver cells and mitochondria these were not detected. Both cell lines had a reactive band at 19-20 kDa, and hepatocytes a small band at 31-32 kDa. Bcl-2 antibodies stimulated the permeability transition potently in hepatoma mitochondria.
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  • 26
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    Molecular and cellular biochemistry 149-150 (1995), S. 263-265 
    ISSN: 1573-4919
    Keywords: NO synthase ; toxic metals ; signal transduction ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This study was designed to evaluate thein vitro effects of transition heavy metal cations on activity of constitutive isoform of nitric oxide synthase (cNOS) in rat brain. NOS activity was determined in the cytosolic fractions of rat cerebral hemispheres by conversion of3H-L-arginine to3H-L-citrulline. Different concentrations of mercury (Hg2+), nickel (Ni2+), manganese (Mn2+), zinc (Zn2+), cadmium (Cd2+), lead (Pb2+) and calcium (Ca2+) were tested on NOS activity. While all the cations caused inhibition, there were differences in the apparent inhibition constants (Ki) among the cations. With the exception of calcium ion no other cation required preincubation with the enzyme preparation. These results indicate that while calcium ion modulate cNOS activity at regulatory site(s), inhibitory influence of toxic heavy metal cations may be exerted on the catalytic site(s) either by direct binding to it or by interfering with the electron transfer during catalysis.
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  • 27
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    Molecular and cellular biochemistry 153 (1995), S. 151-155 
    ISSN: 1573-4919
    Keywords: sodium orthovanadate ; diabetes ; N-myristoyltransferase ; liver ; membrane-associated ; vanadate ; obese Zucker rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract N-Myristoyltransferase (NMT) catalyses the transfer of myristate from myristoyl-CoA to the NH2-terminal glycine residue of several proteins and are important in signal transduction. STZ-induced diabetes (an animal model for insulin-dependent diabetes mellitus, IDDM) resulted in a 2-fold increase in rat liver NMT activity as compared with control animals. In obese Zucker (fa/fa) rats (an animal model for non-insulin dependent diabetes mellitus, NIDDM) there was a∼4.7-fold lower liver particulate NMT activity as compared with the control lean rat livers. Administration of sodium orthovanadate to the diabetic rats normalised liver NMT activity. These results would indicate that the rat liver particulate N-myristoyltransferase activity appears to be inversely proportional to the level of plasma insulin, implicating insulin in the control of N-myristoylation.
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  • 28
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    Keywords: respiration ; ADP diffusion ; heart ; skeletal muscle ; liver ; brain ; in vivo regulation
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    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Very recent experimental data, obtained by using the permeabilized cell technique or tissue homogenates for investigation of the mechanisms of regulation of respiration in the cells in vivo, are shortly summarized. In these studies, surprisingly high values of apparent Km for ADP, exceeding that for isolated mitochondria in vitro by more than order of magnitude, were recorded for heart, slow twitch skeletal muscle, hepatocytes, brain tissue homogenates but not for fast twitch skeletal muscle. Mitochondrial swelling in the hypo-osmotic medium resulted in the sharp decrease of the value of Km for ADP in correlation with the degree of rupture of mitochondrial outer membrane, as determined by the cytochrome c test. Very similar effect was observed when trypsin was used for treatment of skinned fibers, permeabilized cells or homogenates. It is concluded that, in many but not all types of cells, the permeability of the mitochondrial outer membrane for ADP is controlled by some cytoplasmic protein factor(s). Since colchicine and taxol were not found to change high values of the apparent Km for ADP, the participation of microtubular system seems to be excluded in this kind of control of respiration but studies of the roles of other cytoskeletal structures seem to be of high interest. In acute ischemia we observed rapid increase of the permeability of the mitochondrial outer membrane for ADP due to mitochondrial swelling and concomitant loss of creatine control of respiration as a result of dissociation of creatine kinase from the inner mitochondrial membrane. The extent of these damages was decreased by use of proper procedures of myocardial protection showing that outer mitochondrial membrane permeability and creatine control of respiration are valuable indices of myocardial preservation. In contrast to acute ischemia, chronic hypoxia seems to improve the cardiac cell energetics as seen from better postischemic recovery of phosphocreatine, and phosphocreatine overshoot after inotropic stimulation. In general, adaptational possibilities and pathophysiological changes in the mitochondrial outer membrane system point to the central role such a system may play in regulation of cellular energetics in vivo.
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  • 29
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    Molecular and cellular biochemistry 168 (1997), S. 95-100 
    ISSN: 1573-4919
    Keywords: aluminium ; calcium ; brain ; neurodegenerative disease
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    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The present study investigates the possible effects of chronic aluminium exposure on the various aspects of calcium homeostasis in the primate central nervous system. Aluminium administration caused a marked decline in the activity of Ca2+ ATPase in the monkey brain. The total calcium content was also significantly raised following aluminium exposure. Concomittant to the increase in the calcium content, the levels of lipid peroxidation were also augmented in the aluminium treated animals, thereby further accentuating the aluminium induced neuronal damage. In addition, aluminium had an inhibitory effect on the depolarization induced 45Ca2+ uptake via the voltage operated channels. The results presented herein, indicate that the toxic effects of aluminium could be mediated through modifications in the intracellular calcium homeostasis with resultant altered neuronal function.
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  • 30
    ISSN: 1573-4919
    Keywords: nitric oxide ; endotoxin ; cardiomyocytes ; guanosine 3′, 5′-cyclic monophosphate ; calcium ; ADP-ribosylation ; phosphorylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract To evaluate the effects of the in vivo endotoxin treatment of the rat on (1) the contractile responses in the subsequently isolated papillary muscle to adrenergic and cholinergic agonists and (2) the biochemical parameters (cyclic GMP, nitric oxide synthesis, protein phosphorylation and ADP-ribosyslation) in the subsequently isolated cardiomyocytes. Following the in vivo endotoxin treatment (4 mg/kg i.p., 18 h), contractile responses to increasing amounts of isoprenaline or to increasing amounts of oxotremorine in the presence of a fixed amount of isoprenaline were determined in isolated papillary strips. Activities of nitric oxide synthase, guanylyl cyclase, as well as phosphorylation of phospholamban and troponin-inhibitory subunit, and pertussis toxin-catalyzed and endogenous ADP-ribosylations were determined in the intact cardiomyocytes and subcellular fractions. The increase in the force of contraction by isoprenaline was reduced, while its inhibition by oxotremorine was greater in the endotoxin-treated papillary strips. The activities of both nitric oxide synthase, primarily of the inducible form of the enzyme, and cytosolic guanylyl cyclase were higher while the phosphorylations of both phospholamban and troponin-inhibitory subunit were of lesser magnitude in the cardiomyocytes following the in vivo endotoxin treatment. Pertussis toxin-catalyzed ADP-ribosylation of the 41 kDa polypeptide, which is the alpha subunit of Gi, was also decreased. The results of the present study support the postulate that alterations in both the cyclic AMP and cyclic GMP signalling cascade contribute to the myocardial dysfunction caused by endotoxin and cytokines.
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    Molecular and cellular biochemistry 167 (1997), S. 73-80 
    ISSN: 1573-4919
    Keywords: cadmium ; zinc ; liver ; flavokinase ; thiol group
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    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of cadmium (Cd2+), mercury (Hg2+) and copper (Cu2+) was studied with partially purified flavokinase (ATP:riboflavin 5′-phosphotransferase EC 2.7.1.26) from rat liver. All the divalent heavy metal cations inhibited flavokinase activity in a concentration-dependent manner. The inhibitory effect of cadmium on the enzyme was completely reversed by increasing concentration, of Zinc (Zn2+) indicating a competition between Zn2+ and Cd2+ for binding with the enzyme. A competition between riboflavin and Cd2+ is also evident from the present investigation. These observations hint at the possibility that Zn2+ and Cd2+ probably compete for the same site on the enzyme where riboflavin binds. However, inhibition of flavokinase by Hg2+ could not be reversed by Zn2+. Our studies further reveal that hepatic flavokinase appears to contain an essential, accessible and functional thiol group(s) which is evident from a concentration dependent inhibition of activity by sulfhydryl reagent s like parachloromercuribenzoate (PCMB), 5,5′-dithiobis (2-nitrobenzoic acid)(DTNB), and N-ethylmaleimide (NEM). Inhibition of flavokinase by sulfhydryl reagents were protected, except in case of NEM inhibition, when the enzyme was incubated with thiol protectors like glutathione (GSH) and dithiothreitol (DTT). Furthermore, the enzyme could also be protected from the inhibitory effect of Cd2+ and Hg2+ by GSH and DTT suggesting that Cd2+ probably interacts with a reactive thiol group at or near the active site of enzyme in bringing about its inhibitory effect. (Mol Cell Biochem 167: 73-80, 1997)
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  • 32
    ISSN: 1573-4919
    Keywords: taurine ; heart cells ; calcium ; sodium ; confocal microscopy ; nucleus ; fluo-3 ; sodium green ; Ca2+ overload
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of taurine on the different types of ionic currents appears to depend on [Ca]o and [Ca]i and may also vary accordingly to tissue or cell type studied. Using microfluorometry and Ca2+ imaging techniques, short-term exposure (5–10 min) of single heart cells to taurine was found to increase total intracellular free Ca2+ in a concentration-dependent manner. However, long-term exposure of heart myocytes to taurine was found to decrease both nuclear and cytosolic Ca2+ without significantly changing either nuclear or cytosolic Na+ levels, as measured by 3-dimensional Ca2+ and Na+ confocal imaging techniques. Long- term exposure to taurine was found to prevent cytosolic and nuclear increases of Ca2+ induced by permanent depolarization of heart cells with high [K]o. This preventive effect of taurine on nuclear Ca2+ overload was associated with an increase of both cytosolic and nuclear free Na+. Thus, the effect of long-term exposure to taurine on intranuclear Ca2+ overload in heart cells seems to be mediated via stimulation of sarcolemmal and nuclear Ca2+ outflow through the Na+-Ca2+ exchanger.
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  • 33
    ISSN: 1573-4919
    Keywords: mitochondria ; calcium ; permeability transition ; vasopressin ; glucagon ; thapsigargin ; protein kineses and phosphatases ; rat hepatocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Ca2+ functions as an intracellular signal to transfer hormonal messages to different cellular compartments, including mitochondria, where it activates intramitochondrial Ca2+-dependent enzymes. However, excessive mitochondrial Ca2+ uptake can promote the mitochondrial permeability transition (MPT), a process known to be associated with cell injury. The factors controlling mitochondrial Ca2+ uptake and release in intact cells are poorly understood. In this paper, we investigate mitochondrial Ca2+ accumulation in intact hepatocytes in response to the elevation of cytosolic Ca2+ levels ([Ca2+]c) induced either by a hormonal stimulus (vasopressin), or by thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+ pump. After stimulation, cells were rapidly permeabilized for the determination of the mitochondrial Ca2+ content (Ca2+_m) and to analyze the susceptibility of the mitochondria to undergo the MPT. Despite very similar levels of [Ca2+]c elevation, vasopressin and thapsigargin had markedly different effects on mitochondrial Ca2+ accumulation. Vasopressin caused a rapid (〈 90 sec), but modest (〈 2 fold) increase in Ca2+m that was not further increased during prolonged incubations, despite a sustained [Ca2+]c elevation. By contrast, thapsigargin induced a net Ca2+ accumulation in mitochondria that continued for up to 30 min and reached Ca2+_m levels 10–20 fold over basal. Accumulation of mitochondrial Ca2+ was accompanied by a markedly increased susceptibility to undergo the MPT. Both mitochondrial Ca2+ accumulation and MPT activation were modulated by treatment of the cells with inhibitors of protein kineses and phosphatases. The results indicate that net mitochondrial Ca2+ uptake in response to hormonal stimulation is regulated by processes that depend on protein kinase activation. These controls are inoperative when the cytosol is flooded by Ca2+ through artificial means, enabling mitochondria to function as a Ca2+ sink under these conditions. (Mol Cell Biochem 174: 173–179, 1997)
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  • 34
    ISSN: 1573-4919
    Keywords: heart ; calcium ; magnesium ; contractility ; dietary ; L-type calcium current
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This study employs both dietary and physiological studies to investigate the relationship between calcium (Ca2+) and magnesium (Mg2+) signalling in the mammalian myocardium. Rats maintained on a low Mg2+ diet (LMD; 39 mg Kg-1 Mg2+ in food) consumed less food and grew more slowly than control rats fed on a control Mg2+ diet (CMD; 500 mg Kg-1 Mg2+ in food). The Mg2+ contents of the heart and plasma were 85 ± 3% and 34 ± 6.5%, respectively relative to the control group. In contrast, Ca2+ contents in the heart and plasma were 177 ± 5% and 95 ± 3%. The levels of potassium (K+) was raised in the plasma (129 ± 16%) and slightly decreased in the heart (88 ± 6%) compared to CMD. Similarly, sodium (Na+) contents were slightly higher in the heart and lowered in the plasma of low Mg2+ diet rats compared to control Mg2+ diet rat. Perfusion of the isolated Langendorff's rat heart with a physiological salt solution containing low concentrations (0-0.6 mM) of extracellular magnesium [Mg2+]0 resulted in a small transient increase in the amplitude of contraction compared to control [Mg2+]0 (1.2 mM). In contrast, elevated [Mg2+]0 (2-7.2 mM) caused a marked and progressive decrease in contractile force compared to control. In isolated ventricular myocytes the L-type Ca2+ current (ICa,L was significantly (p 〈 0.001) attenuated in cells dialysed with 7.1 mM Mg2+ compared to cells dialysed with 2.9 µM Mg2+. The results indicate that hypomagnesemia is associated with decrease levels of Mg2+ and elevated levels of Ca2+ in the heart and moreover, internal Mg2+ is able to modulate the Ca2+ current through the L-type Ca2+ channel which in turn may be involved with the regulation of contractile force in the heart.
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  • 35
    ISSN: 1573-4919
    Keywords: antioxidant enzymes ; sub-cellular organelles ; liver ; ischemia-reperfusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The activities of rat hepatic subcellular antioxidant enzymes were studied during hepatic ischemia/reperfusion. Ischemia was induced for 30 min (reversible ischemia) or 60 min (irreversible ischemia). Ischemia was followed by 2 or 24 h of reperfusion. Hepatocyte peroxisomal catalase enzyme activity decreased during 60 min of ischemia and declined further during reperfusion. Peroxisomes of normal density (d = 1.225 gram/ml) were observed in control tissues. However, 60 min of ischemia also produced a second peak of catalase specific activity in subcellular fractions corresponding to newly formed low density immature peroxisomes (d = 1.12 gram/ml). The second peak was also detectable after 30 min of ischemia followed by reperfusion for 2 or 24 h. Mitochondrial and microsomal fractions responded differently. MnSOD activity in mitochondria and microsomal fractions increased significantly (p 〈 0.05) after 30 min of ischemia, but decreased below control values following 60 min of ischemia and remained lower during reperfusion at 2 and 24 h in both organelle fractions. Conversely, mitochondrial and microsomal glutathione peroxidase (GPx) activity increased significantly (p 〈 0.001) after 60 min of ischemia and was sustained during 24 h of reperfusion. In the cytosolic fraction, a significant increase in CuZnSOD activity was noted following reperfusion in animals subjected to 30 min of ischemia, but 60 min of ischemia and 24 h of reperfusion resulted in decreased CuZnSOD activity. These studies suggest that the antioxidant enzymes of various subcellular compartments respond to ischemia/reperfusion in an organelle or compartment specific manner and that the regulation of antioxidant enzyme activity in peroxisomes may differ from that in mitochondria and microsomes. The compartmentalized changes in hepatic antioxidant enzyme activity may be crucial determinant of cell survival and function during ischemia/reperfusion. Finally, a progressive decline in the level of hepatic reduced glutathione (GSH) and concomitant increase in serum glutamate pyruvate transaminase (SGPT) activity also suggest that greater tissue damage and impairment of intracellular antioxidant activity occur with longer ischemia periods, and during reperfusion.
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  • 36
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    Molecular and cellular biochemistry 177 (1997), S. 209-214 
    ISSN: 1573-4919
    Keywords: regucalcin ; calmodulin ; calcium ; cyclic AMP phosphodiesterase ; rat kidney cytosol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of regucalcin, a novel Ca2+-binding protein, on Ca2+/ calmodulin-dependent cyclic adenosine monophosphate (AMP) phosphodiesterase activity in the cytosol of rat renal cortex was investigated. Regucalcin with physiologic concentration (10-7 M) in rat kidney had no effect on cyclic AMP phosphodiesterase activity in the absence of CaCl2 and calmodulin. However, the activatory effect of both CaCl2 (10 µM) and calmodulin (20 U/ml) on cyclic AMP phosphodiesterase was markedly inhibited by the addition of regucalcin (10-8 to 10-6 M) in the enzyme reaction mixture. The inhibitory effect of regucalcin on the enzyme activity was also seen in the presence of CaCl2 (5-50 µM) or calmodulin (5-50 U/ml) with increasing concentrations. The presence of trifluoperazine (10 µM), an antagonist of calmodulin, caused a partial inhibition of Ca2+ /calmodulin-dependent cyclic AMP phosphodiesterase activity. This inhibition was further enhanced by the addition of regucalcin (10-7 M). The inhibitory effect of regucalcin (10-7 M) was not seen in the presence of 20 µM trifluoperazine. Moreover, the activatory effect of calmodulin (20 U/ml) on cyclic AMP phosphodiesterase was not entirely seen, when calmodulin was added 10 min after incubation in the presence of CaCl2 (10 µM) and regucalcin (10-7 M). The present results demonstrates that regucalcin has an inhibitory effect on Ca2+ /calmodulin-dependent cyclic AMP phosphodiesterase activation in the cytosol of rat renal cortex.
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  • 37
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    Molecular and cellular biochemistry 180 (1998), S. 53-57 
    ISSN: 1573-4919
    Keywords: diabetes ; cardiomyopathy ; lipids ; lipoprotein lipase ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract It has been established that diabetes results in a cardiomyopathy, and increasing evidence suggests that an altered substrate supply and utilization by cardiac myocytes could be the primary injury in the pathogenesis of this specific heart muscle disease. For example, in diabetes, glucose utilization is insignificant, and energy production is shifted almost exclusively towards β-oxidation of free fatty acids (FFA). FFA's are supplied to cardiac cells from two sources: lipolysis of endogenous cardiac triglyceride (TG) stores, or from exogenous sources in the blood (as free acid bound to albumin or as TG in lipoproteins). The approximate contribution of FFA from exogenous or endogenous sources towards β-oxidation in the diabetic heart is unknown. In an insulin-deficient state, adipose tissue lipolysis is enhanced, resulting in an elevated circulating FFA. In addition, hydrolysis of the augmented myocardial TG stores could also lead to high tissue FFA. Whatever the source of FFA, their increased utilization may have deleterious effects on myocardial function and includes the abnormally high oxygen requirement during FFA metabolism, the intracellular accumulation of potentially toxic intermediates of FFA, a FFA-induced inhibition of glucose oxidation, and severe morphological changes. Therapies that target these metabolic aberrations in the heart during the early stages of diabetes could potentially delay or impede the progression of more permanent sequelae that could ensue from otherwise uncontrolled derangements in cardiac metabolism.
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  • 38
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    Molecular and cellular biochemistry 179 (1998), S. 135-145 
    ISSN: 1573-4919
    Keywords: calcium ; non-lysosomal proteases ; muscle damage ; neutrophils ; muscle regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract It is well established that periods of increased contractile activity result in significant changes in muscle structure and function. Such morphological changes as sarcomeric Z-line disruption and sarcoplasmic reticulum vacuolization are characteristic of exercise-induced muscle injury. While the precise mechanism(s) underlying the perturbations to muscle following exercise remains to be elucidated, it is clear that disturbances in Ca2+ homeostasis and changes in the rate of protein degradation occur. The resulting elevation in intracellular [Ca2+] activates the non-lysosomal cysteine protease, calpain. Because calpain cleaves a variety of protein substrates including cytoskeletal and myofibrillar proteins, calpain-mediated degradation is thought to contribute to the changes in muscle structure and function that occur immediately following exercise. In addition, calpain activation may trigger the adaptation response to muscle injury. The purpose of this paper is to: (i) review the chemistry of the calpain-calpastatin system; (ii) provide evidence for the involvement of the non-lysosomal, calcium-activated neutral protease (calpain) in the response of skeletal muscle protein breakdown to exercise (calpain hypothesis); and (iii) describe the possible involvement of calpain in the inflammatory and regeneration response to exercise.
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  • 39
    ISSN: 1573-4919
    Keywords: aortic cells ; steady state R-type Ca2+ channel ; ET-1 ; insulin ; calcium ; G-protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In single rabbit aortic smooth muscle cells, and at a concentration known to induce a maximum sustained increase of intracellular Ca2+ via activation of the steady-state voltage dependent R-type Ca2+ channels, endothelin-1 (10-7 M) and insulin (80 μU/ml) were found to induce a sustained increase in cytosolic free Ca2+ ([Ca]i) levels that was significantly attenuated by pre-treatment with either pertussis toxin (PTX), cholera toxin (CTX) or removal of extracellular Ca2+. However, both PTX and CTX failed to inhibit the sustained depolarization-evoked sustained Ca2+ influx and [Ca]i elevation via activation of the R-type Ca2+ channels. Moreover, ET-1 and insulin-evoked sustained increases in Ca2+ influx were not attenuated by the selective PKC inhibitor, bisindolylmaleimide (BIS), or the specific L-type Ca2+ channel blocker, nifedipine, but were completely reversed by the R-type Ca2+ channel blocker, (-) PN 200-110 (isradipine). These data suggest that both insulin and ET-1 activate the nifedipine-insensitive but isradipine-sensitive steady state voltage dependent R-type Ca2+ channels present on rabbit VSMCs and these channels are directly coupled to PTX and CTX sensitive G protein(s).
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  • 40
    ISSN: 1573-4919
    Keywords: hyperosmolality ; hyperglycemia ; calcium ; smooth muscle cells ; diabetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Hyperglycemia and/or hyperosmolality may disturb calcium homeostasis in vascular smooth muscle cells (SMCs), leading to altered vascular contractility in diabetes. To test this hypothesis, the KCl induced increases in [Ca2+]i in primarily cultured vascular SMCs exposed to different concentrations of glucose were examined. With glucose concentration in solutions kept at 5.5 mM, KCl induced a fast increase in [Ca2+]i which then slowly declined (type 1 response) in 83% of SMCs from non-diabetic rats. In 9% of non-diabetic SMCs KCl induced a slow increase in [Ca2+]i (type 2 response). Interestingly, under the same culture conditions KCl induced type 1 and type 2 responses in 47 and 35% of SMCs from diabetic rats. When SMCs from non-diabetic or diabetic rats were cultured in 36 mM glucose, KCl induced a fast increase in [Ca2+]i which, however, maintained at a high level (type 3 response). The sustained level of [Ca2+]i in the presence of KCl was significantly higher in cells cultured with 36 mM glucose than that in non-diabetic cells cultured with 5.5 mM glucose. Furthermore, the hyperglycemia-induced alterations in calcium mobilization were similarly observed in cells cultured in high concentration of mannitol (30.5 mM) or L-glucose, indicating that hyperosmolality was mainly responsible for the abnormal calcium mobilization in diabetic SMCs.
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  • 41
    ISSN: 1573-4919
    Keywords: CGRP-1 receptor ; HEK-293 cells ; calcium ; cholera toxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Calcitonin gene-related peptide (CGRP) is a neuropeptide with diverse biological properties including potent vasodilating activity. Recently, we reported the cloning of complementary DNAs (cDNAs) encoding the human and porcine CGRP receptors which share significant amino acid sequence homology with the human calcitonin receptor, a member of the recently described novel subfamily of G-protein-coupled 7TM receptors. Activation of this family of receptors has been shown to result in an increase in intracellular cAMP accumulation and calcium release. In this study, we demonstrate that HEK-293 cells expressing recombinant CGRP receptors (HEK-293HR or PR) respond to CGRP with increased intracellular calcium release (EC50 = 1.6 nM) in addition to the activation of adenylyl cyclase (EC50 = 1.4 nM). The effect of CGRP on adenylyl cyclase activation and calcium release was inhibited by CGRP (8-37), a CGRP receptor antagonist. Both effects were mediated by cholera toxin-sensitive G-proteins, but these two signal transduction pathways were independent of each other. While cholera toxin pretreatment of HEK-293PR cells resulted in permanent activation of adenylyl cyclase, the same pretreatment resulted in an inhibition of CGRP-mediated [Ca2+]i release. Pertussis toxin was without effect on CGRP-mediated responses. In addition, CGRP-mediated calcium release appears to be due to release from a thapsigargin-sensitive intracellular calcium pool. These results show that the recombinant human as well as porcine CGRP receptor can independently increase both cAMP production and intracellular calcium release when stably expressed in the HEK-293 cell line.
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  • 42
    ISSN: 1573-4919
    Keywords: glucose-6 phosphatase ; messenger RNA ; liver ; kidney ; fasting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract We have studied the role of Glc6Pase mRNA abundance in the time course of Glc6Pase activity in liver and kidney during long-term fasting in rat. Refered to the mRNA level in the fed state, Glc6Pase mRNA abundance was increased by 3.5 ± 0.5 and 3.7 ± 0.5 times (mean ± S.E.M., n = 5) in the 24 h and 48 h-fasted liver, respectively. Then, the liver Glc6Pase mRNA was decreased to the level of the fed liver after 72 and 96 h of fasting (1.0 ± 0.3 and 1.4 ± 0.3). In the kidney, Glc6Pase mRNA abundance was increased by 2.7 ± 1.0 and 5 ± 1.2 times at 24 and 48 h of fasting, respectively. Then, it plateaued at the level of the 48 h fasted kidney after 72 h and 96 h of fasting (4.5 ± 1.0 and 4.3 ± 1.0). After 24 and 48 h-refeeding, the abundance of Glc6Pase mRNA in 48 h-fasted rats was decreased to the level found in the liver and kidney of fed rats. The time course of the activity of Glc6Pase catalytic subunit during fasting and refeeding was strikingly parallel to the time course of Glc6Pase mRNA level in respective tissues. These data strongly suggest that the differential expression of Glc6Pase activity in liver and kidney in the course of fasting may be accounted for by the respective time course of mRNA abundance in both organs.
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  • 43
    ISSN: 1573-4919
    Keywords: endothelin-1 ; ventricular cardiomyocytes ; contraction ; calcium ; heart failure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Endothelin (ET-1) is found at elevated concentrations in the plasma of patients with heart failure and in animal models of cardiomyopathy. The peptide is a potent positive inotropic agent, the effects of which are mediated by increases in cytosolic Ca2+ in cardiomyocytes. The object of this study was to investigate at the cellular level, the actions of ET-1 on contractile function and on Ca2+ currents in heart-failed ventricular myocardium. Male New Zealand White rabbits (8 wks) were treated with twice weekly injections of epirubicin (4 mg/kg/wk, n=7) or with saline (n=7) for 6 wks, followed by a washout period of 2 wks. Ventricular cardiomyocytes were isolated from rabbit hearts using Langendorff perfusion with collagenase; contractile function was examined using a video microscopy method, and L-type Ca2+ currents were recorded using a whole-cell patch-clamp technique. ET-1 produced a concentration-dependent increase in contractile response (% increase from basal value) to a maximum at 1 nM ET-1 of 69 ± 11% (mean ± S.D.) in control cardiomyocytes and 33 ± 6% in heart-failed cells. However, there was no significant change in the EC50 obtained with ET-1 for healthy (0.31 ± 0.1 nM) and for failed cardiomyocytes (0.24 ± 0.1 nM). The effects of ET-1 on L-type Ca2+ channels were similar with a peak amplitude at 1 nM ET-1 of −3.26 ± 0.8 ⋬ in control cardiomyocytes and −3.32 ± 0.9 nA in heart-failed cells. The attenuation of the contractile response to ET-1 in heart-failed cells may reflect a desensitization of ET receptors as a consequence of elevated circulating levels of ET and was not reflected by alteration of transmembrane Ca2+ conductance. It is probable, therefore, that multiple signalling pathways are involved in the actions of ET on ventricular myocardium.
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  • 44
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    Molecular and cellular biochemistry 163-164 (1996), S. 125-130 
    ISSN: 1573-4919
    Keywords: cardiac myocytes ; early after depolarisations ; delayed after depolarisations ; calcium ; sarcoplasmic reticulum ; noradrenaline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract We investigated the effect of 10−8 M noradrenaline (NA) on [Ca2+], and electrical activity of single myocytes of guinea-pig ventricular myocardium loaded with Indo 1-AM. Membrane potential was recorded by means of the patch electrode and patch amplifier set to the current clamp mode. Cells were stimulated at a rate of 30/min by 3 ms pulses of the current injected through the recording electrode. Superfusion of NA resulted in slight shortening of action potentials (APs), increase in rate of rise and amplitude of the respective Ca2+ transients, and appearance of secondary Ca2+ transients of two kinds: 1. appearing before repolarisation of AP and decay of the preceding Ca2+ transient were completed and 2. appearing between the APs. We named them early after-transients (EAT) and delayed after-transients (DAT), respectively. Without any additional intervention EATS caused some prolongation of APs duration and DATs resulted in subthreshold delayed after-depolarisations (DADS). When sarcolemmal K+ conductance was decreased by tetraethylammonium (TEA) in the patch electrode or 20 μM BaCl2 in the Tyrode solution, EATs initiated early after depolarizations (EADs) and DATs initiated suprathreshold DADs triggering full-sized APs. Superfusion of 30.0 mM Na+ (replaced with LiCl) resulted in reduction of AP duration by -70% and appearance of DATs. Also, the frequent multiple oscillations of Ca 2+ concentration were often observed. Neither DATs nor the oscillations had any affect on electrical activity of the cells. Their electrogenicity could not be increased by TEA or 20.0 μM Ba2+. EATs and DATs and their respective EADs and DADs could not be initiated by NA or low Na+ superfusion in the cells pretreated with 2 × 10−7 M thapsigargin, a selective blocker of Ca2+-ATPase of sarcoplasmic reticulum (SR). We conclude that in contrast to the current hypothesis, EADs can be initiated by Ca2+ released early in the cardiac cycle from the overloaded SR, and that electrogenicity of both types of Ca2+ oscillations critically depends on the sarcolemmal K+ conductance.
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  • 45
    ISSN: 1573-4919
    Keywords: cadmium ; glutathione S-transferase ; liver ; kidney
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Exposure of animals to cadmium (Cd) (25 mg kg-1 body wt day-1) for 10 weeks resulted in preferential accumulation of the metal in liver and kidney. Cd accumulation concomitantly increased zinc (Zn) concentration in both the organs. However, significant decrease in copper level was observed in liver, whereas kidney showed increase in copper (Cu) level. Cd exposure resulted in decreased total GST activity in liver (63%) and kidney (41%) as compared to control group monkeys on normal diet (group I). On isoelectric focusing (IFP) control liver GST segregated into thirteen isoenzymes, while in Cd-treated experimental animals (group II) liver GST resolved into nine isoenzymes. Similarly kidney GST from control animals separated into seven isoenzymes as compared to four isoenzymes from Cd-treated animals. Kinetic analysis showed that Cd exposure did not alter the affinity constant (Km) of GST for GSH and CDNB whereas maximal velocity (Vmax) for these substrates decreased as compared to controls in both the organs, indicating inhibition in GST synthesis by Cd. Cd resulted in a noncompetitive type of inhibition with respect to GSH in vitro. On isoelectric focussing GST of liver and kidney in group II resolved into nine and four isoenzymes as compared to thirteen and seven in group I, showing loss of four basic isoenzymes in case of liver and three isoenzymes in case of kidney. Monkey liver and kidney expressed all the three classes of GST isoenzymes i.e. α, µ and π, which were serologically identical to human α, µ and π GSTs. (Mol Cell Biochem 166: 55-63, 1997)
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  • 46
    ISSN: 1573-4919
    Keywords: vitamin-A ; cellular retinol-binding protein ; liver ; hepatic stellate cells ; lipocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Liver is a major site of retinoid metabolism and storage, and more than 80% of the liver retinoids are stored in hepatic stellate cells. These cells represent less than 1% of the total liver protein, reaching a very high relative intracellular retinoid concentration. The plasma level of retinol is maintained close to 2 μM, and hepatic stellate cells have to be able both to uptake or to release retinol depending upon the extracellular retinol status. In view of their paucity in the liver tissue, stellate cells have been studied in primary cultures, in which they loose rapidly the stored lipids and retinol, and convert spontaneously into the activated myofibroblast phenotype, turning a long-term study of their retinol metabolism impossible. We have analyzed the retinol metabolism in the established GRX cell line, representative of stellate cells. We showed that this cell line behaves very similarly, with respect the retinol uptake and release, to primary cultures of hepatic stellate cells. Moreover, we showed that the cellular retinol binding protein (CRBP-I) expression in these cells, relevant for both uptake and esterification of retinol, responds to the extracellular retinol status, and is correlated to the retinol binding capacity of the cytosol. Its expression is not associated with the overall induction of the lipocyte phenotype by other agents. We conclude that the GRX cell line represents an in vitro model of hepatic stellate cells, and responds very efficiently to wide variations of the extracellular retinol status by autonomous controls of its uptake, storage or release.
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  • 47
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    Molecular and cellular biochemistry 187 (1998), S. 47-55 
    ISSN: 1573-4919
    Keywords: Mimosa pudica ; apyrase ; arabinogalactan ; calcium ; circular dichroism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Mimosa pudica Linn leaves with pulvini contain unique isoforms (I and II) of apyrase enzyme (EC 3.6.1.5). The activity of isoform I depends on divalent cation Mn2+. This isoform is associated noncovalently with the polysaccharide, containing mainly of galactose and arabinose sugars. The apparent molecular mass of these 2 isoforms are 36 and 34 Kd respectively. The association of the polysaccharide with the isoform I has been found to be Ca2+ dependent which is endogenously present in this isoform. Removal of Ca2+ and polysaccharide from the enzyme (isoform I) leads to an inactivation. The enzyme activity can be restored when both Ca2+ and endogenous polysaccharide fraction were added at an optimal molar ratio of Ca2+:protein of 7:1. The endogenous polysaccharide can be replaced by the standard arabinogalactan. No other sugar or polysaccharide except the arabinogalactan can restore the apyrase activity. Calcium mediates a conformational change in the protein which helps in association of polysaccharide as evidenced from fluorometric and far UV-CD studies to restore the enzymic activity. Neither any interaction of the polysaccharide with the protein is detected in absence of Ca2+ nor the enzyme activity could be recovered under such condition.
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  • 48
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    Molecular and cellular biochemistry 187 (1998), S. 1-10 
    ISSN: 1573-4919
    Keywords: oxidant ; cardiovascular system ; signal transduction ; calcium ; mitogen activated protein kinases ; nuclear transcription factors ; tyrosine kinase ; protein kinase C ; superoxide ; hydrogen peroxide ; ischemia-reperfusion ; atherosclerosis ; phospholipases ; apoptosis ; antioxidant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Although oxidants such as superoxide (O2.-) and hydrogen peroxide (H2O2) play a role in host-mediated destruction of foreign pathogens yet excessive generation of oxidants may lead to a variety of pathological complications in the cardiovascular system. An important mechanism by which oxidants cause dysfunction of the cardiovascular system appears to be due to the increase in intracellular free Ca2+ concentration. Oxidants cause cellular Ca2+ mobilization by modulating activities of a variety of regulators such as Na+/H+ and Na+/Ca2+ exchangers, Na+/K+ ATPase and Ca2+ ATPase and Ca2+ channels that are associated with Ca2+ transport in the plasma membrane and the sarco(endo)plasmic reticular membrane of myocardial cells. Recent research have suggested that the increase in Ca2+ level by oxidants plays a pivotal role in indicing several protein kinases such as protein kinase C, tyrosine kinase and mitogen activated protein kinases. Oxindant-mediated alteration of different signal transduction systems and their interations eventually regulate a variety of pathological conditoins such as atherosclerosis, apoptosis and necrosis in the myocardium
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  • 49
    ISSN: 1573-4919
    Keywords: heart ; vascular endothelium ; vascular smooth muscle ; confocal microscopy ; pH ; calcium ; sodium ; voltage probe ; heart ; endothelin-1 ; Angiotensin II ; PAF ; nucleus ; mitochondria ; SR ; cardiomyopathy ; cells interaction ; R-type Ca2+ channel ; excitation-contraction coupling ; dystrophic mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In recent years, fluorescence microscopy imaging has become an important tool for studying cell structure and function. This non invasive technique permits characterization, localisation and qualitative quantification of free ions, messengers, pH, voltage and a pleiad of other molecules constituting living cells. In this paper, we present results using various commercially available fluorescent probes as well as some developed in our laboratory and discuss the advantages and limitations of these probes in confocal microscopy studies of the cardiovascular system.
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  • 50
    ISSN: 1573-4919
    Keywords: cyclosporin A ; mitochondrial permeability transition ; reperfusion injury ; cyclophilin ; oxidative stress ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract When loaded with high (pathological) levels of Ca2+, mitochondria become swollen and uncoupled as the result of a large non-specific increase in membrane permeability. This process, known as the mitochondrial permeability transition (MPT), is exacerbated by oxidative stress and adenine nucleotide depletion. These conditions match those that a heart experiences during reperfusion following a period of ischaemia. The MPT is caused by the opening of a non-specific pore that can be prevented by sub-micromolar concentrations of cyclosporin A (CsA). A variety of conditions that increase the sensitivity of pore opening to [Ca2+], such as thiol modification, oxidative stress, increased matrix volume and chaotropic agents, all enhance the binding of matrix cyclophilin (CyP) to the inner mitochondrial membrane in a CsA-sensitive manner. In contrast, ADP, membrane potential and low pH decrease the sensitivity of pore opening to [Ca2+] without affecting CyP binding. We present a model of pore opening involving CyP binding to a membrane target protein followed by Ca2+-dependent triggering of a conformational change to induce channel opening. Using the ischaemic/reperfused rat heart we have shown that the mitochondrial pore does not open during ischaemia, but does do so during reperfusion. Recovery of heart during reperfusion is improved in the presence of 0.2 µM CsA, suggesting that the MPT may be critical in the transition from reversible to irreversible reperfusion injury. (Mol Cell Biochem 174: 167–172, 1997)
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  • 51
    ISSN: 1573-4919
    Keywords: diabetes ; Ca2+-Mg2+-ATPase ; calcium ; liver plasma membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The alteration in calcium transport in the liver of rats with streptozocin(STZ)-diabetic state was investigated. STZ (6 mg/100 g body weight) was subcutaneously administered in rats, and 1 or 2 weeks later they were sacrificed by bleeding. STZ administration caused a remarkable elevation of serum glucose concentration. Liver calcium content was significantly increased by STZ administration. Hepatic plasma membrane (Ca2+-Mg2+)-ATPase activity was markedly elevated by STZ administration. This increase was completely abolished by the presence of staurosporine (10-7-10-5 M), an inhibitor of protein kinase C, in the enzyme reaction mixture, suggesting an involvement of protein kinase C signalling. Moreover, the STZ-induced increase in liver plasma membrane (Ca2+-Mg2+)-ATPase activity was significantly raised by the presence of okadaic acid (10-5 and 10-4 M). Meanwhile, the STZ-increased (Ca2+-Mg2+)-ATPase activity was not appreciably altered by the presence of anti-regucalcin IgG in the reaction mixture, indicating that the activatory protein regucalcin does not participate in the elevation of the enzyme activity. The present study demonstrates that STZ-induced diabetes causes the increase in hepatic plasma membrane (Ca2+-Mg2+)-ATPase activity of rats.
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  • 52
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    Keywords: chicken ; oviduct ; liver ; tissue-specific repression ; in vivo gene transfer ; gene gun
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In order to search tissue-specific elements in the 5′-upstream promoter region, gene gun was used to transfect in vivo plasmid DNAs with varying lengths of truncated ovalbumin promoter fused to the CAT reporter gene to the oviduct and liver of laying hens. The results indicated that in the oviduct, consistently high reporter gene expression was observed irrespective of the length of the truncated ovalbumin gene promoters, whereas in the liver the ovalbumin promoter extending from -3200 to +8 bp suppressed substantially the reporter gene expression compared with consistently high gene expression obtained by the ovalbumin promoters from -2800 to +8 bp or shorter length. It was concluded, therefore, that a tissue-specific silencer-like element might reside most likely in the ovalbumin gene promoter region between -3200 and -2800 bp which represses the ovalbumin gene transcription in the liver, but not in the oviduct of laying hens.
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  • 53
    ISSN: 1573-4919
    Keywords: trans polyunsaturated fatty acid ; linoleic acid ; desaturation elongation ; microsomes ; liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Several nutritional studies have shown the in vivo conversion of the 9c,12t-18:2 and 9t,12c-18:2 into long chain polyunsaturated fatty acids (PUFA) containing 20 carbons (geometrical isomers of eicosadienoic and eicosatetraenoic acids). In the present work, some in vitro studies were carried out in order to have precise information on the conversion of these two isomers. In a first set of experiments, studies were focused on the in vitro Δ6 desaturation, the first regulatory step of the biosynthesis of n-6 long chain PUFA, from 9c,12c-18:2. Rat liver microsomes were prepared and incubated under desaturation conditions with [1-14C]-9c,12c-18:2 in presence of unlabelled 9c,12t-, 9t,12c- or 9t,12t-18:2. The data show that each trans isomer induced a decrease of the Δ6 desaturation of the [1-14C]-9c,12c-18:2, but the 9c,12t-18:2 was the most potent inhibitor (up to 63%). Rat liver microsomes were also incubated with [1-14C]-9c,12c-18:2, [1-14C]-9c,12t-18:2 or [1-14C]-9t,12c-18:2 under desaturation conditions. The results indicated that 18:2 Δ9c,12t is a much better substrate for desaturase than 9t,12c-18:2. Moreover, the conversion levels of [1-14C]-9c,12t-18:2 was similar to what was observed for its all cis homologue, at low substrate concentration only. In a second set of experiments, in vitro elongation studies of each mono-trans 18:2 isomers and 9c,12c-18:2 were carried out. For that purpose, rat liver microsomes were incubated with [1-14C]-9c,12c-18:2, [1-14C]-9c,12t-18:2 or [1-14C]-9t,12c-18:2 under elongation conditions. The data show that [1-14C]-9t,12c-18:2 is better elongated than 9c,12c-18:2 while the amount of product formed from [1-14C]-9c,12t-18:2 was lower than was produced from the 9c,12c-18:2. Thus, the desaturation enzymes presented a higher affinity for the 9c,12t-18:2 whereas the elongation enzyme presented a higher affinity for the 9t,12c-18:2.
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  • 54
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    Molecular and cellular biochemistry 184 (1998), S. 393-400 
    ISSN: 1573-4919
    Keywords: ATP synthase ; phosphorylation potential ; cytosolic pH ; reperfusion damage ; calcium ; free radicals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A short period of ischemia followed by reperfusion produces a state of affairs in which the cells' potential for surviving longer ischemia is enhanced. This is called ischemic preconditioning. The effects of preconditioning are also related to the reperfusion damage which ensues upon tissue oxygenation. The role of the cellular energy state in reperfusion damage remains an enigma, although ischemic preconditioning is known to trigger mechanisms which contribute to the prevention of unnecessary ATP waste. In some species up to 80% of ATP hydrolysis in ischemia can be attributed to mitochondrial F1-F0-ATPase (ATP synthase), and a role for its inhibitor protein (IF1) in ATP preservation has been proposed. Although originally regarded as limited to large animals with a slow heart beat, inhibition by IF1 is probably a universal phenomenon. Coincidentally with ATPase inhibition, the decline in cellular ATP slows down, but even so the difference in ATP concentration between preconditioned and non-conditioned hearts is still small at the final stages of a long ischemia, when the beneficial effect of preconditioning is observable, although the energy state during reperfusion remains low in hearts which do not recover.
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  • 55
    ISSN: 1573-4919
    Keywords: calcium ; Ca2+-ATPase ; DNA fragmentation ; liver nuclei ; liver injury ; carbon tetrachloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The alteration in calcium transport in the liver nuclei of rats orally administered carbon tetrachloride (CCl4) was investigated. Rats received a single oral administration of CCl4(5, 10, and 25%, 1.0ml/100 g body weight), and 5, 24 and 48 h later the animals were sacrificed. The administration of CCl4 (25%) caused a remarkable elevetion of calcium content in the liver tissues and the nuclei of rats. Liver nuclear Ca2+-ATPase activity was markedly decreased by CCl4 (25%) administration. The presence of dibutyryl cyclic AMP(10-4 and 10-3 M) or inositol 1,4,5-trisphosphate (10-6 and 10-5 M) in the enzyme reaction mixture caused a significant decrease in Ca2+-ATPase activity in the liver nuclei obtained from normal rat, while the enzyme activity was significantly increased by calmodulin (1.0 and 2.0 μg/ml). These signaling factor's effects were completely impaired in the liver nuclei obtained from CCl4 (25%)-administered rats. DNA fragmentation in the liver nuclei obtained from CCl4 -administered rats was significantly decreased by the presence of EGTA (2 mM) in the reaction mixture, suggesting that the endogenous calcium activates nuclear DNA fragmentation. The present study demonstrates that calcium transport system in the liver nuclei is impaired by liver injury with CCl4 administration in rats.
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  • 56
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    Molecular and cellular biochemistry 194 (1999), S. 159-164 
    ISSN: 1573-4919
    Keywords: free radicals ; ischemia-reperfusion ; sarcoplasmic reticulum ; Ca2+-Mg2+-ATPase ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Reactive oxygen species (ROS, free radicals) produced during cardiac ischemia and reperfusion can damage the contractile functions of arteries. The sarcoplasmic reticulum (SR) Ca2+ pump in coronary artery smooth muscle is very sensitive to ROS. Here we show that contractions of de-endothelialized rings from porcine left coronary artery produced by the hormone Angiotensin II and by the SR Ca2+ pump inhibitors cyclopiazonic acid and thapsigargin correlate negatively with the tissue weight. In contrast, the contractions due to membrane depolarization by high KCl correlate positively. Peroxide also produces a small contraction which correlates negatively with the tissue weight. When artery rings are treated with peroxide and washed, their ability to contract with Angiotensin II, cyclopiazonic acid and thapsigargin decreases. Thus, the SR Ca2+ pump may play a more important role in the contractility of the smaller segments of the coronary artery than in the larger segments. These results are consistent with the hypothesis that ROS which damage the SR Ca2+ pump affect the contractile function of the distal segments more adversely than of the proximal segments.
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  • 57
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    Molecular and cellular biochemistry 194 (1999), S. 173-177 
    ISSN: 1573-4919
    Keywords: calcium ; ATPase ; central nervous system ; phencyclidine ; inhibition ; in vitro ; in vivo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Phencyclidine (PCP) is a potent psychotomimetic drug of abuse and has profound effect on the functioning of the central nervous system (CNS). Many of the CNS functions are known to be mediated by calcium (Ca2+). In the present study we have investigated the effects of PCP on Ca2+ ATPase activity in rat brain both in vitro and in vivo. For in vitro studies, synaptic membrane fractions prepared from normal rat brain were incubated with PCP at different concentrations (25-100 μM) before the addition of substrate. For n vivo studies, rats were treated with a single moderate dose of PCP (10 mg/kg, IP) and animals were sacrificed at 1,2, 6 and 12 h after treatment. Ca2+ ATPase activity in synaptic membrane fractions was assayed by estimation of inorganic phosphate. PCP inhibited the Ca2+ ATPase in vitro in a concentration dependent manner with significant effect at 50 and 100 μM. A significant time-dependent reduction of the Ca2+ ATPase activity was evident in vivo. As early as 2 h after the treatment of rats with PCP the ATPase activity was significantly reduced. The reduction of Ca2+ ATPase observed even at 12 h after treatment suggesting a prolonged presence of the drug in the brain tissue. Further, kinetic studies in vitro indicated PCP to be a competitive inhibitor of Ca2+ ATPase with respect to the substrate, ATP. The present findings indicate that PCP inhibits synaptic membrane Ca2+ ATPase thus altering cellular Ca2+ homeostasis in CNS which may partially explain the pharmacological effects of the drug and/or its neurotoxicity.
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  • 58
    ISSN: 1573-4919
    Keywords: ultraviolet radiation ; oxidative stress ; calcium ; phospholipase A2 ; thrombin ; V79 fibroblast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract V79 fibroblasts were treated with ultraviolet (UV) C radiation alone as well as in conjunction with chronic oxidative stress. The effects of these treatments on calcium signaling were observed at 30 min post-irradiation. In the absence of extracellular calcium, thrombin released calcium from internal stores of UVC-irradiated V79 fibroblasts even after exposure to neomycin. In neomycin-treated control and chronic oxidative stress cells, no calcium release by thrombin was observed after chelation of external calcium. Calcium release by thrombin from internal stores of UV-irradiated and neomycin-treated cells was completely abolished by pretreatment with N-acetyl cysteine and dexamethasone. Cellular total soluble thiol content which is a good indicator of cellular reduced glutathione (GSH) level was significantly elevated 30 min after ultraviolet radiation, indicating an adaptive response after oxidative stress. Chronic oxidative stress alone resulted in a much smaller increase in GSH but chronic oxidative stress in conjunction with UVC produced a very prominent elevation in GSH levels. Our data suggest that thrombin can cause calcium release from internal stores of ultraviolet-irradiated fibroblasts which is independent of phosphatidylinositol bisphosphate hydrolysis and is directly related to the level of oxidative stress. Involvement of phopholipase A2 and a role for its products as possible mediators of calcium release from intracellular stores, is strongly indicated.
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  • 59
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    Molecular and cellular biochemistry 197 (1999), S. 25-29 
    ISSN: 1573-4919
    Keywords: regucalcin ; anti-regucalcin antibody ; protein phosphatase ; calcium ; rat liver cytosol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of anti-regucalcin monoclonal antibody on neutral phoshatase activity in rat liver cytosol was investigated. Phosphotyrosine, phosphoserine, and phosphothreonine were used as the substrate toward phosphatase asssy. Liver cytosolic phosphatase activity with three phosphoaminoacids was significantly increased in the presence of anti-regucalcin antibody (100 and 200 ng/ml) in the enzyme reaction mixture with calcium chloride (0.1 mM) or EGTA (1.0 mM). The effect of anti-regucalcin antibody was completely abolished in the presence of exogenous regucalcin (1.0 μM), indicating the involvement of endogenous regucalcin. The anti-regucalcin anti body- increased phosphatase activity was not significantly altered in the presence of trifluoperazine (20 μM), an antagonist of calmodulin, or akadaic acid (10 μM), an inhibitor of protein phosphatase, although these inihibitors caused a slight decrease in liver cytosolic phosphatase activity. The effect of endogenous regucalcin might be not related to calmodulin, and it was insensitive to okadaic acid. The present findings suggest that endogenous regucalcin is involved in the regulation of protein phasphatase in rat liver cytoplasm.
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  • 60
    ISSN: 1573-4919
    Keywords: isolated cardiac mitochondria ; cyclosporin A ; calcium ; magnesium ; oxidative phosphorylation ; high energy phosphate production ; Krebs cycle intermediates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This study was designed to determine the effect of calcium and ADP-Mg on the oxidative phosphorylation in isolated cardiac mitochondria. The influence of cyclosporin A was also evaluated. The mitochondria were extracted from rat ventricles. Their oxidative phosphorylations were determined in two respiration media with different free Ca2+ concentrations. Respiration was determined with palmitoylcarnitine and either ADP- or ADP-Mg. With elevated free Ca2+concentrations and ADP-Mg, the transition state III to state IV respiration did not occurred. The ADP:O ratio was reduced. The phenomenon was not observed in the other experimental conditions (low free Ca2+ concentration with either ADP- or ADP-Mg or elevated free Ca2+ concentration with ADP-). Uncoupling was allied with a constant AMP production, which maintained an elevated ADP level in the respiration medium and prevented the return to state IV respiration. It was also observed in a respiration medium devoid of free Ca2+ when the mitochondria were pre-loaded with Ca2+. Uncoupling was inhibited by cyclosporin A. Furthermore, the Krebs cycle intermediates released from14C-palmitoylcarnitine oxidation revealed that succinate was increased by elevated free Ca2+ and ADP-Mg. Succinate is a FAD-linked substrate with low respiration efficiency. Its accumulation could account for the decreased ADP:O ratio. The Ca2+- and ADP-Mg-induced uncoupling might be partly responsible for the mechanical abnormalities observed during low-flow ischemia. (Mol Cell Biochem 000: 000-000, 1999)
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  • 61
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    Keywords: hyperplasia ; hypertrophy ; liver ; nucleic-acid concentration ; protein-growth rate ; protein-turnover rate ; rainbow trout (Oncorhynchus mykiss) ; starvation/re-feeding cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract We report upon the effects of a cycle of long-term starvation followed by re-feeding on the liver-protein turnover rates and nature of protein growth in the rainbow trout (Oncorhynchus mykiss). We determined the protein-turnover rate and its relationship with the nucleic-acid concentrations in the livers of juvenile trout starved for 70 days and then re-fed for 9 days. During starvation the total hepatic-protein and RNA contents decreased significantly and the absolute protein-synthesis rate (AS) also fell, whilst the fractional protein-synthesis rate (KS) remained unchanged and the fractional protein-degradation rate (KD) increased significantly. Total DNA content, an indicator of hyperplasia, and the protein:DNA ratio, an indicator of hypertrophy, both fell considerably. After re-feeding for 9 days the protein-accumulation rates (KG, AG) rose sharply, as did KS, AS, KD, protein-synthesis efficiency (KRNA) and the protein-synthesis rate/DNA unit (KDNA). The total hepatic protein and RNA contents increased but still remained below the control values. The protein:DNA and RNA:DNA ratios increased significantly compared to starved fish. These changes demonstrate the high response capacity of the protein-turnover rates in trout liver upon re-feeding after long-term starvation. Upon re-feeding hypertrophic growth increased considerably whilst hyperplasia remained at starvation levels.
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  • 62
    ISSN: 1573-4919
    Keywords: Salmonella typhimurium ; diarrhoea ; porins ; calcium ; protein kinase C ; free radicals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Attachment of Salmonella typhimurium to epithelial surfaces elicit significant alterations in different cell signalling events which lead to the development of disease. The present investigation was conducted to evaluate the effect of immunization of rats with porins, on gut physiologic markers following challenge with S. typhimurium. Male albino Wistar rats were immunized with purified porins and challenged by intragastric infection with S. typhimurium. Electrolyte transport, levels of different second messengers and inflammatory mediators were studied. A net absorption of transepithelial fluxes of Na+ and Cl- in immunized-challenged group and secretion in infected group was found. Ca2+ and 3-O-methyl-D-glucose fluxes did not show any change. Significant increase in the levels of [Ca+]i, cAMP, membrane form of protein kinase C, prostaglandins, NADPH oxidase, Glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, total oxygen free radicals, reactive nitrogen intermediates, citrulline and lipid peroxidation was found in the infected group. However, in the immunized-challenged group, the values of all the parameters were found to be almost the same as that of control as well as immunized groups. Na+, K+-ATPase and calmodulin levels were unaltered in all the groups of animals. The results of this study thus suggest that immunization of rats with purified Salmonella porins followed by subsequent challenge with the organism might be helpful for the prevention of multiple physiologic derangements in isolated ideal cells.
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  • 63
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    Molecular and cellular biochemistry 151 (1995), S. 39-47 
    ISSN: 1573-4919
    Keywords: 7B2 ; calcium ; protein aggregation ; secretogranins ; protein sorting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract To study the behavior of the neuroendocrine polypeptide 7B2 in the presence of calcium, various fragments of this molecule were produced inEscherichia coli as fusion proteins to glutathione S-transferase (GST). Addition of millimolar concentrations of Ca2+ to purified preparations of hybrid molecules carrying the N-terminal segment of 7B2 induced precipitation in a manner dependent on protein and cation concentrations. This precipitation occurred at pH 7.5 but not at pH 5.2. It was augmented by 4 and 8 mM ATP, and reduced by 12 and 24 mM ATP. ADP had a similar but weaker effect. Calcium failed to cause precipitation of GST alone or of GST fused to the C-terminal peptide 7B2156–186. However, when the latter protein was mixed with a GST protein carrying a short fragment of the N-terminal region of 7B2, both proteins were precipitated by calcium. Except for the pH dependence, the behavior of 7B2 fusion proteins in the presence of calcium and adenosine nucleotides are reminiscent of those exhibited by chromogranins and secretogranins, which, like 7B2, are acidic proteins found in the secretory granules of a variety of neuroendocrine cells. As suggested for other granins, this property may underlie the segregation of 7B2 fragments into secretory granules.
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  • 64
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    Molecular and cellular biochemistry 151 (1995), S. 55-60 
    ISSN: 1573-4919
    Keywords: regucalcin ; calcium ; gene expression ; kidney damage ; rat kidney cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The alteration of Ca2+-binding protein regucalcin mRNA expression in the kidney cortex of rats administered cisplatin and cephaloridine, which can induce kidney damage, was investigated. Cisplatin (0.25, 0.5 and 1.0 mg/100 g body weight) or cephaloridine (25, 50 and 100 mg/100 g) was intraperitoneally administered in rats, and 1, 2 and 3 days later they were sacrificed. The alteration in serum findings after the administration of cisplatin (1.0 mg/100 g) or cephaloridine (50 and 100 mg/100 g) demonstrated chemically induced kidney damage; blood urea nitrogen (BUN) concentration increased markedly and serum inorganic phosphorus or calcium concentration decreased significantly. Moreover, the administration of cisplatin (1.0 mg/100 g) or cephaloridine (100 mg/100 g) caused a remarkable increase of calcium content in the kidney cortex of rats, indicating kidney damage. The expression of regucalcin mRNA in the kidney cortex was markedly reduced by the administration of cisplatin or cephaloridine in rats, when the mRNA levels were analyzed by Northern blotting using rat liver regucalcin cDNA (0.9 kb). The mRNA decreases were seen with the used lowest dose of cisplatin or cephaloridine. The present study clearly demonstrates that the mRNA expression of Ca2+-binding protein regucalcin in the kidney cortex of rats is decreased by chemically induced kidney damage.
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  • 65
    ISSN: 1573-4919
    Keywords: hyperthyroid heart ; high energy phosphates ; oxidative metabolism ; cardiac work ; calcium ; 31P-NMR spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of calcium activation on energy production was investigated in isolated perfused hearts from rats treated with triiodothyronine (T3) during 15 days (0.2 mg/kg/day) and in hearts of rats allowed to recover after T3-treatment during 15 days. Changes in phosphorylated compound concentrations were followed in the isolated hearts perfused with a glucose-pyruvate medium by 31P-NMR spectroscopy, when the external calcium concentration was increased from 0.5–1, 1.5 and 2 mM. As expected, T3-treatment resulted in the hypertrophy of the heart (50% increase in HW/BW) that was nearly reversible 15 days after discontinuation of the treatment. When compared to controls, creatine, phosphocreatine (PCr) and glycogen contents were lower (58, 24 and 17% decrease respectively) in the hypertrophied hearts and higher (10, 14 and 18% respectively) after regression of hypertrophy. Intracellular pH, ATP, inorganic phosphate concentrations and the phosphorylation potential were not altered under T3-treatment and after regression of hypertrophy, while calculated free ADP concentration was lower in hypertrophied hearts (control: 40±2 μM, T3-treatment: 21±1 μM, regression: 37±1 μM). Increasing the calcium concentration induced a similar increase in left ventricular developed pressure in the three groups of hearts, with inorganic phosphate concentration increasing with cardiac work. The PCr concentration slightly decreased while the ATP concentration did not change. In spite of different initial PCr concentrations, the evolutions of PCr and Pi concentrations for each stepwise increase in external calcium were similar in the three groups. It is concluded that, in spite of the well-known decrease in efficiency induced by the drug, the mechanisms of PCr (ATP) production ramain able to respond to an acute moderate increase in energy demand provoked by a physiological stimulus. This adaptation also persists after the treatment when the energy metabolism balance is apparently improved.
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    Molecular and cellular biochemistry 151 (1995), S. 149-155 
    ISSN: 1573-4919
    Keywords: SERCA2 ; ATPase ; calcium ; transport ; vascular
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Pig coronary artery cultured smooth muscle cells were skinned using saponin. In the presence of an ATP-regenerating system and oxalate, the skinned cells showed an ATP-dependent azide insensitive Ca2+-uptake which increased linearly with time for 〉1 h. The Ca2+-uptake occurred with Km values of 0.20±0.03 μM for Ca2+ and 400±34 μM for MgATP2−. Thapsigargin and cyclopiazonic acid inhibited this uptake with IC50 values of 0.13±0.02 and 0.56±0.04 μM, respectively. These properties of SR Ca2+-pump are similar to those reported for membrane fractions isolated from fresh smooth muscle of coronary artery and other arteries. However, optimum pH of the uptake in the skinned cells (6.2) was lower than that reported previously using isolated membranes (6.4–6.8).
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  • 67
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    Keywords: vanadate ; diabetes ; glycogen synthase ; phosphorylase ; lipogenic enzymes ; liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The insulin-mimetic action of vanadate is well established but the exact mechanism by which it exerts this effect is still not clearly understood. The role of insulin in the regulation of hepatic glycogen metabolizing and lipogenic enzymes is well known. In our study, we have, therefore, examined the effects of vanadate on these hepatic enzymes using four different models of diabetic and insulin-resistant animals. Vanadate normalized the blood glucose levels in all animal models. In streptozotocin-induced diabetic rats, the amount of liver glycogen and the activities of the active-form of glycogen synthase, both active and inactive-forms of phosphorylase, and lipogenic enzymes like glucose 6-phosphate dehydrogenase and malic enzyme were decreased and vanadate treatment normalized all of these to near normal levels. The other three animal models (db/db mouse, sucrose-fed rats and fa/fa obese Zucker rats) were characterized by hyperinsulinemia, hypertriglyceridemia, increases in activities of lipogenic enzymes, and marginal changes in glycogen metabolizing enzymes. Vanadate treatment brought all of these values towards normal levels. It should be noted that vanadate shows differential effects in the modulation of lipogenic enzymes activities in type I and type II diabetic animals. It increases the activities of lipogenic enzymes in streptozotocin-induced diabetic animals and prevents the elevation of activities of these enzymes in hyperinsulinemic animals. The insulin-stimulated phosphorylation of insulin receptor β subunit and its tyrosine kinase activity was increased in streptozotocin-induced diabetic rats after treatment with vanadate. Our results support the view that insulin receptor is one of the sites involved in the insulin-mimetic actions of vanadate.
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  • 68
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    Molecular and cellular biochemistry 154 (1996), S. 113-121 
    ISSN: 1573-4919
    Keywords: heart cells ; nucleus ; calcium ; R-type channel ; excitation-contraction coupling ; pacemaker activity ; Fura-2 ; Fluo-3 ; confocal microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In the present study, Fluo-3 Ca2+ measurement and confocal microscopy techniques were used in order to localize cytosolic [ ]c and nuclear [ ]n free Ca2+ distribution in resting and spontaneously contracting single heart cells from 10-day-old chick embryos. In resting single cells, the concentration of Ca2+ in the cytoplasm was lower than that in the nucleus. Increasing cytosolic free Ca2+ from 100–1600 nM gradually increased [Ca2+]n with a maximum capacity near 1200 nM. Results from Fura-2 microfluorometry and Fluo-3 confocal microscopy suggest a potential cross talk between the increase of cytosolic free Ca2+ and the uptake and release of Ca2+ by the nucleus during spontaneous contraction of single myocytes. Calcium waves in spontaneously contracting cells were found to spread from one cell to the next with the nucleus acting as a fluorescent beacon in which Ca2+ levels remained elevated for several milliseconds even after cytosolic Ca2+ had returned to near basal values. These results strongly suggest that the nucleus plays a negative and positive feedback role in controlling cytosolic free Ca2+ concentration during excitation-contraction coupling in heart cells.
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  • 69
    ISSN: 1573-4919
    Keywords: hydroxyl radical ; oxidant ; hydrogen peroxide ; smooth muscle tissue ; mitochondria ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract We sought to investigate the mechanism(s) by which the oxidant H2O2 stimulates Ca2+ release from mitochondria of bovine pulmonary vascular smooth muscle tissue and to test the hypothesis that hydroxyl radical is involved in this phenomenon. Treatment of the smooth muscle tissue with 1 mM H2O2 dramatically stimulated hydroxyl radical generation as measured by methane (CH4) production by GLC using dimethylsulfoxide (DMSO) as the substrate. Pretreatment of the mitochondria with the hydroxyl radical scavanger dimethylthiourea (DMTU) prevented the increase in CH4 production caused by H2O2. In the absence of EGTA, H2O2 caused stimulation of Ca2+ release from mitochondria occurred with a lag time of about 4 min. Addition of EGTA to Ca2+ loaded mitochondria resulted an immediate loss of Ca2+ and that has been found to be augmented by H2O2. The release of Ca2+ by H2O2 did not appear to occur with concommitant increase in sucrose entry into, K+ release from, and swelling of mitochondria when the Ca2+ cycling was prevented by EGTA. These observations suggested that H2O2-mediated Ca2+ release from bovine pulmonary vascular smooth muscle tissue mitochondria occurred (i) through the involvement of hydroxyl radical; (ii) via specific pathway(s); and (iii) did not appear to happen primarily via nonspecific ‘pore’ formation.
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    Molecular and cellular biochemistry 173 (1997), S. 169-175 
    ISSN: 1573-4919
    Keywords: regucalcin ; calcium-binding protein ; calcium ; nuclear RNA synthesis ; regenerating ratliver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of regucalcin, a Ca2+-bindingf protein isolated from rat livercytosol, on ribonucleic acid (RNA) synthesis in the nuclei of normal ratliver and of regenerating rat liver was investigated. The liver weight at 1day after partial hepatectomy was increased about 50% of that ofsham-operated (control) rats. Calcium chloride (1.0-20 µM Ca2+ asfinal concentration) was added into the reaction mixture of nuclear RNAsynthesis. RNA synthesis was established by incorporation of [3H]-uridine5'-triphosphate (UTP) into the nuclear RNA. Addition of Ca2+ (5 and 10µM) caused a significant increase of RNA synthesis in the nuclei fromcontrol rat liver. Such effect of Ca2+ was potentiated in the nuclei ofregenerating liver; nuclear RNA synthesis was increased about 2 fold by the1.0 and 2.5 µM Ca2+ addition. The stimulatory effect of Ca2+ wassignificantly inhibited by the presence of a-amanitin (10-8 M), an inhibitorof RNA polymerase II. The presence of regucalcin (0.25 and 0.5 µM)significantly inhibited RNA synthesis in the nuclei from control rat liverand from regenerating rat liver. The inhibitory effect of regucalcin wasremarkable in the presence of EGTA (0.5 mM), and it was weakened by theaddition of Ca2+ (5 µM). Such regucalcin effect was not seen in thepresence of a-amanitin. The presence of anti-regucalcin IgG in the reactionmixture significantly increased RNA synthesis in the nuclei from control ratliver, indicating that the endogenous regucalcin may be involved in nuclearRNA synthesis. The present resuits demonstrate that regucalcin can inhibitnuclear RNA synthesis in rat liver. Regucalcin may have an inhibitory rolein the regulation of liver nuclear RNA synthesis.
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    Molecular and cellular biochemistry 149-150 (1995), S. 175-182 
    ISSN: 1573-4919
    Keywords: rat pancreas ; cholecystokinin ; magnesium ; calcium ; acetylcholine ; amylase secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Application of either acetylcholine (ACh, 10−5 M) or cholecystokininoctapeptide (CCK-8, 10−8 M) to the isolated rat pancreas elicited large increases in amylase secretion, radiolabelled45Ca2+ influx and cytosolic free calcium [Ca2+]i levels in zero and normal (1.1 mM) extracellular magnesium [Mg2+]o. Elevated [Mg2+]o significantly (p〈0.001) reduced the secretagogueevoked secretory responses and Ca2+ mobilisation. Stimulation of pancreatic segments with either ACh (10−5 and 10−6 M) or CCK-8 (10−8 and 10−10 M) resulted in marked elevation in Mg2+ concentration in effluent samples (net efflux). On removal of either ACh or CCK-8, Mg2+ concentration returned to resting level. In pancreatic acinar cells loaded the flourescent dye magfura, ACh and CCK-8 evoked marked reduction in cytosolic free Mg2+ concentration [Mg2+]i compared to the resting value of 0.82±0.03 mM (n=50) in normal medium in the absence of secretagogues. In elevated [Mg2+]o (10 mM) medium, [Mg2+]i rises to 0.98±0.04 mM (n=6). Addition of CCK-8 led to only a small reduction in [Mg2+ i in elevated [Mg2+]o. In Mg2+ loaded pancreatic acinar cells, Mg2+ is released in a time dependent manner and this efflux of Mg2+ was sensitive to sodium, extracellular amiloride (1 mM), dinitrophenol (10 mM) and lidocaine (1 mM). The results indicate that Mg2+ is acting as an intracellular messenger to regulate the mobilisation of Ca2+ which in turn mediates enzyme secretion.
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  • 72
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    Molecular and cellular biochemistry 176 (1997), S. 317-326 
    ISSN: 1573-4919
    Keywords: calcium ; metabolism ; glucose ; hypoxia ; rat brain
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    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In a previous communication we reported that glucose deprivation from KHRB medium resulted in a marked stimulation of Ca2+ uptake by brain tissue, suggesting a relationship between glucose and Ca2+ homeostasis in brain tissue [17]. Experiments were carried out to investigate the significance of glucose in Ca2+ transport in brain cells. The replacement of glucose with either D-methylglucoside or 2-deoxyglucose, non-metabolizable analogues of glucose, resulted in stimulation of Ca2+ uptake just as by glucose deprivation. These data show that glucose metabolism rather than glucose transfer was necessary to stimulate Ca2+ uptake in brain tissue. Inhibition of glucose metabolism with either NaF, NaCN, or iodoacetate resulted in stimulation of Ca2+ uptake similar to that produced by glucose deprivation. These results lend further support for the concept that glucose metabolism is essential for Ca2+ homeostasis in brain. Anoxia promotes glucose metabolism through glycolytic pathway to keep up with the demand for ATP by cellular processes (the Pasteur effect). Incubation of brain slices under nitrogen gas did not alter Ca2+ uptake by brain tissue, as did glucose deprivation and the inhibitors of glucose metabolism. We conclude that glucose metabolism resulting in the synthesis of ATP is essential for Ca2+ homeostasis in brain. Verapamil and nifedipine which block voltage-gated Ca2+ channels, did not alter Ca2+ uptake stimulated by glucose deprivation, indicating that glucose deprivation-enhanced Ca2+ uptake was not mediated by Ca2+ channels. Tetrodotoxin which specifically blocks Na+ channels, abolished Ca2+ uptake enhanced by glucose deprivation, but had no effect on Ca2+ uptake in presence of glucose (controls). These results suggest that stimulation of Ca2+ uptake by glucose deprivation may be related to Na+ transfer via Na-Ca exchange in brain.
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  • 73
    ISSN: 1573-4919
    Keywords: fatty acid binding protein ; liver ; intestine ; growth factor ; TGFβ1
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    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of transforming growth factor beta-1 (TGFβ1) expression on fatty acid binding proteins was examined in control and two strains of gene targeted TGFβ1-deficient mice. Homozygous TGFβ1-deficient 129 × CF-1, expressing multifocal inflammatory syndrome, had 25% less liver fatty acid binding protein (L-FABP) when compared to control mice. The decrease in L-FABP expression was not due to multifocal inflammatory syndrome since homozygous TGFβ1-deficient/immunodeficient C3H mice on a SLID background had 36% lower liver L-FABP than controls. This effect was developmentally related and specific to liver, but not the proximal intestine, where L-FABP is also expressed. Finally, the proximal intestine also expresses intestinal-FABP (1-FABP) which decreased 3-fold in the TGFβ1-deficient/immunodeficient C3H mice only. Thus, TGFβ1 appears to regulate the expression of L-FABP and I-FABP in the liver and the proximal intestine, respectively.
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  • 74
    ISSN: 1573-4919
    Keywords: carnitine palmitoyl transferase I ; mitochondrial HMG-CoA synthase ; dexamethasone ; suckling rats ; ketogenesis ; intestine ; liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The influence of the injection of dexamethasone on ketogenesis in 12 day old suckling rats was studied in intestine and liver by determining mRNA levels and enzyme activity of the two genes responsible for regulation of ketogenesis: carnitine palmitoyl transferase I (CPT 1) and mitochondrial HMG-CoA synthase. Dexamethasone produced a 2 fold increase in mRNA and activity of CPT I in intestine, but led to a decrease in mitt HMG-CoA synthase. In liver the mRNA levels and activity of both CPT I and mitt HMG-CoA synthase decreased. Comparison of these values with the ketogenic rate of both tissues following dexamethasone treatment suggests that mitt HMG-CoA synthase could be the main gene responsible for the regulation of ketogenesis in suckling rats. The changes produced in serum ketone bodies by dexamethasone, with a profile that is more similar to the ketogenic rate in the liver than that in the intestine, indicate that liver contributes more to ketone body synthesis in suckling rats. Two day treatment with dexamethasone produced no change in mRNA or activity levels for CPT I in liver or intestine. While mRNA levels for mitt HMG-CoA synthase changed little, the enzyme activity is decreased in both tissues.
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  • 75
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    Molecular and cellular biochemistry 201 (1999), S. 159-167 
    ISSN: 1573-4919
    Keywords: phospholipases A1, A2 and C ; Ureaplasma urealyticum ; calcium ; plasma membrane ; phospholipids ; pH ; detergents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The presence of endogenous phospholipase A (PL-A) activity of U. urealyticum hydrolyzing the acyl ester bond and phospholipase C (PL-C) activity hydrolyzing the phosphodiester bond is primarily localized in the membranes of ureaplasmas. Characterization of the membrane PL-A and PL-C activity in exponential growing cells of serovars 3, 4, and 8 was investigated. The pH optimum was about 8.5-9 for phospholipase A1 (PL-A1) in the three serovars. A more acidic pH optimum of 6 was observed for phospholipase A2 (PL-A2) enzymes in serovars 3 and 4. However, a very significant stimulation of PL-A2 activity in serovar 8 occurred around pH 7. The specific activity of PL-A2 was always 50-100 fold higher than PL-A1 activity in the pH range studied. Ca2+ ions only slightly stimulated PL-A1 activity in all 3 serovars. PL-A2 activity was stimulated about 6-fold from 0.5-0.8 mM Ca2+ ion concentrations for serovar 3 and 12-fold for serovar 8. Only lower concentrations (0.2-0.4 mM) of calcium stimulated PL-A2 activity in serovar 4. EDTA inhibition corresponded to Ca2+ stimulation for PL-A2 activity for serovars 3 and 8. A general stimulation of PL-A2 activity by diethyl ether was evident but the degree of stimulation varied with the serovar. Sodium deoxycholate enhanced PL-A activity of serovars 4 and 3, but partially inhibited that of serovar 8. PL-A activity in the three serovars were not significantly affected by p-hydroxymercuribenzoate, a marker of -SH groups in the enzyme. All 3 serovars were inactivated by heat. A broad pH optimum for PL-C activity was evident around 7-8. Diethyl ether enhanced PL-C activity of serovar 8. Sodium deoxycholate and heat were inhibitory to PL-C activity. The results demonstrate that the major characteristics of ureaplasma membrane bound PL-A and PL-C are basically similar to those of other mollicutes and bacteria. However, the major differences in the specific characteristics of specially PL-A1 and PL-A2 suggest that the ureaplasma phospholipases are unique enzymes different from the phospholipases of bacteria. Both the PL-A and PL-C enzymes function over the broad range at which ureaplasma can grow, pH 5-9 essential for survival. The ureaplasma PL-As are also markedly different from one serovar to another. This variation in specific activity could contribute significantly to differences in virulence among serovars in specific host milieus. There is significant variation from acidic pH of the vagina and alveolar surface of the lung to a more neutral pH of the endometrium and placenta. There are marked differences in calcium concentrations under specific circumstances in various host tissues. Thus the differences in specific activity among the phospholipases of the serovars of U. urealyticum may be of physiological importance in interactions with host tissues and pathogenesis of disease.
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  • 76
    ISSN: 1573-0646
    Keywords: somatostatin ; angiogenesis ; somatostatin receptors ; signal transduction ; xanthines ; calcium ; proteins
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    Topics: Chemistry and Pharmacology , Medicine
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  • 77
    ISSN: 1573-675X
    Keywords: Activation markers ; apoptosis ; calcium ; cytotoxicity ; mistletoe lectins ; Viscum album.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract This review focuses on the cytotoxic properties of Viscum album L. (VAL). Apart from well-established results of protein synthesis inhibition by the mistletoe lectins (MLs), namely their catalytic A chain, there is now convincing evidence that the VAL-mediated cytotoxicity is mainly due to an induction of apoptosis. Among the more than 1,000 proteins detected in VAL, the MLs and the viscotoxins (VTs) are the predominant toxic proteins. Using purified components, such as the D-galactose-specific ML I, the N-acetyl-D-galactosamine-specific ML II and ML III, crude VTs and oligosaccharides, only the MLs induced apoptosis. The in vitro studies suggest that interaction of lectin B chains with appropriate receptors on the cell surface activates distinct signalling pathways that ultimately leads to apoptosis in a large fraction of cells, while others survive, however, with a conservation of their DNA. Inhibition of protein synthesis by the A chain of the hololectin probably accelerates the B chain-induced course of events.
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  • 78
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    Cell biology and toxicology 13 (1997), S. 275-287 
    ISSN: 1573-6822
    Keywords: hydration ; liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Liver cells possess potent mechanisms to maintain their volume, i.e., their hydration state. These volume-regulatory mechanisms, however, are apparently not designed to maintain absolute cell volume constancy; they rather act as dampeners to prevent excessive cell volume deviations, which would otherwise result from cumulative substrate uptake or anisotonic stress. Furthermore, these volume-regulatory mechanisms can even be activated in the resting state by hormones and other stimuli, and by that means cell volume changes are affected secondarily. Thus, liver cell hydration can change within minutes under the influence of aniso-osmolarity, hormones, nutrients, and oxidative stress. Such short-term modulation of cell volume within a narrow range acts as an independent and potent signal which modifies hepatocellular metabolism and gene expression. Accordingly, cell volume homeostasis involves the integration of events that allow cell hydration to play a physiologic role as a regulator of cell function.
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  • 79
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    Cell biology and toxicology 11 (1995), S. 1-10 
    ISSN: 1573-6822
    Keywords: calcium ; hippocampal neurons ; neuronal differentiation ; organic lead ; triethyl lead
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Triethyl lead is the major metabolite of tetraethyl lead, which is used in industrial processes and as an antiknock additive to gasoline. We tested the hypothesis that low levels of triethyl lead (0.1 nmol/L to 5μmol/L) interfere with the normal development of cultured E18 rat hippocampal neurons, possibly through increases in intracellular free calcium ion concentration, [Ca2+]in. The study assessed survival and differentiation using morphometric analysis of individual neurons. We also looked at short-term (up to 3.75-h) changes in intracellular calcium using the calcium-sensitive dye fura-2. Survival of neurons was significantly reduced at 5 μmol/L, and overall production of neurites was reduced at ≥2 μmol/L. The length of axons and the number of axons and dendrites were reduced at ≥1 μmol/L. Neurite branching was inhibited at 10 nmol/L for dendrites and 100 nmol/L for axons. Increases in intracellular calcium were observed during a 3.75-h exposure of newly plated neurons to 5 μmol/L triethyl lead. These increases were prevented by BAPTA-AM; which clamps [Ca2+]in at about 100 nmol/L. Culturing neurons with BAPTA-AM and 5 μmol/L triethyl lead did not reverse the effects of triethyl lead, suggesting that elevation of [Ca2+]in is not responsible for decreases in survival and neurite production. Triethyl lead has been shown to disrupt cytoskeletal elements, particularly neurofilaments, at very low levels, suggesting a possible mechanism for its inhibition of neurite branching at nanomolar concentrations.
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  • 80
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    Cell biology and toxicology 12 (1996), S. 245-249 
    ISSN: 1573-6822
    Keywords: acrolein ; bronchial hyperresponsiveness ; calcium ; ozone ; excitation-contraction coupling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The aims of this work were (1) to determine the dose-response relationship between ex vivo exposure to oxidizing pollutants such as nitrogen dioxide (NO2), the aldehyde acrolein, and ozone (O3), and the reactivity to agonists in isolated human bronchial smooth muscle; and (2) to investigate the alterations in the cellular mechanisms of human airway smooth muscle contraction induced by such exposures. Experiments were performed in isolated human bronchi obtained at thoracotomy. Isometric contraction in response to a variety of agonists was compared between pollutant-exposed preparations and paired controls. Short exposures to NO2, acrolein, or O3 altered the subsequent airway smooth muscle responsiveness in a dose-dependent manner. The cellular mechanisms producing the airway hyperresponsiveness observed in vitro are shared by the three pollutants and include alterations in airway smooth muscle excitation-contraction coupling as well as indirect effects on neutral endopeptidase activity.
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  • 81
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    Cell biology and toxicology 13 (1997), S. 317-321 
    ISSN: 1573-6822
    Keywords: DNA ; hepatocytes ; liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Liver culture systems, both primary cultures of hepatocytes and replicating cell lines, can be used in a variety of ways to study the DNA-damaging effects of chemicals and radiation. The present report describes some of the available methods and their interpretation.
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  • 82
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    Cell biology and toxicology 13 (1997), S. 339-348 
    ISSN: 1573-6822
    Keywords: apoptosis ; hepatocarcinogenesis ; liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Apoptosis seems to be the predominant type of active cell death in the liver (type I), while in other tissues cells may die via biochemically and morphologically different pathways (type II, type III). Active cell death is under the control of growth factors and death signals. In the liver, endogenous factors, such as transforming growth factor β1 (TGF-β1), activin A, CD95 ligand, and tumor necrosis factor (TNF) may be involved in induction of apoptosis. Release and action of these death factors seems to be triggered by exogenous signals such as withdrawal of hepato-mitogens, food restriction, etc. During stages of hepatocarcinogenesis, not only DNA synthesis but also apoptosis gradually increase from normal to preneoplastic to adenoma and carcinoma tissue. Also, in human carcinomas, birth and death rates of cells are several times higher than in surrounding liver. (Pre)neoplastic liver cells are more susceptible than normal hepatocytes to stimulation of cell replication and of cell death. Consequently, tumor promoters may act as survival factors, i.e., inhibit apoptosis preferentially in preneoplastic and even in malignant liver cells, thereby stimulating selective growth of (pre)neoplastic lesions. On the other hand, regimens favoring apoptosis and lowering cell replication may result in selective elimination of (pre)neoplastic cell clones from the liver. Finally, we have studied the first stage of carcinogenesis, namely the appearance of putatively initiated cells after a single dose of the genotoxic carcinogen N-nitrosomorpholine (NNM). Most of these cells were found to be eliminated by apoptosis, suggesting that initiation, at the organ level, can be reversed at least partially by preferential elimination of initiated cells. These events may be regulated by autocrine or paracrine actions of survival factors.
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  • 83
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    Cell biology and toxicology 13 (1997), S. 399-403 
    ISSN: 1573-6822
    Keywords: DNA ; hepatocytes ; liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Liver culture systems, both primary cultures of hepatocytes and replicating cell lines, can be used in a variety of ways to study the DNA-damaging effects of chemicals and radiation. The present report describes some of the available methods and their interpretation.
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  • 84
    ISSN: 1573-6822
    Keywords: ATP ; energy metabolism ; calcium ; diltiazem ; rat liver perfusion ; ATP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Diltiazem causes vasoconstriction in the liver when present at high concentrations, an action that is strictly Ca2+-dependent. Diltiazem is also active on energy metabolism. This toxic action could be partly a consequence of hemodynamic effects. In the absence of Ca2+, the hemodynamic effects are no longer present and, consequently, Ca2+-free experiments are useful for distinguishing between hemodynamics-dependent and hemodynamics-independent effects. The experimental system used was the hemoglobin-free perfused rat liver from fed and fasted rats. Diltiazem was infused at various concentrations in the presence and absence of Ca2+. Several metabolic parameters were measured: lactate and pyruvate production (glycolysis), glycogenolysis, oxygen uptake, gluconeogenesis, and the cellular levels of lactate, pyruvate, glucose, AMP, ADP, and ATP. The effects of diltiazem can be divided into three groups: (1) Effects that are strictly dependent on the Ca2+-mediated hemodynamic action. This group comprises inhibition of oxygen uptake at all concentrations (50–500 μmol/L) inhibition of lactate, pyruvate, and glucose release at high concentrations; the decrease in cellular ATP; the increase in cellular AMP; and the cellular accumulation of glucose and lactate. (2) Effects that are independent of the hemodynamic action. The most relevant effect of this type is inhibition of gluconeogenesis. (3) Effects that are influenced by Ca2+ but are independent of the hemodynamic effects. This is the typical case of lactate and glucose release from endogenous glycogen, whose stimulation by low diltiazem concentrations is more pronounced in the presence of Ca2+ than in its absence.
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  • 85
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    Cell biology and toxicology 13 (1997), S. 301-315 
    ISSN: 1573-6822
    Keywords: autophagy ; carcinogenesis ; hepatocyte ; liver ; ploidy ; rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Hepatocytes have the ability to go through specialized cell cycles, which, during normal developmental liver growth, result in the formation of binuclear and polyploid cells. In the adult rat liver, the majority of the hepatocytes (about 70%) are tetraploid, 15-20% are octoploid, and only 10-15% are diploid (about 50% in humans). One-third of the hepatocytes in either rats or humans are binuclear (with two diploid or two tetraploid nuclei). Among cultured rat hepatocytes stimulated with growth factors (EGF and insulin), one-half of the mitoses are of the binucleating type (suggesting a "quantal" mechanism), causing one-third of the postmitotic cells to become binuclear. In contrast, regenerative liver growth, induced by partial hepatectomy, is predominantly nonbinucleating. During rat liver carcinogenesis, the early populations of phenotypically altered cells (foci) are predominantly diploid, as are the later neoplastic nodules and carcinomas, which can be shown to have a regeneration-like, largely nonbinucleating growth pattern. A negative correlation between growth capacity and ploidy can be demonstrated in cultured hepatocytes, regenerating livers, neoplastic nodules, and hepatocellular carcinomas, suggesting that suppression of binucleation and polyploidization may carry a growth advantage, in addition to helping to maintain a large population of diploid, potential stem cells. Since a diploid genome is less protected against mutagenic change than a polyploid genome, diploid tumor cells may, furthermore, be more prone than polyploid cells to undergo mutation-based progression toward increasing malignancy. The ability of liver tumor promoters like 2-acetylaminofluorene, cyproterone acetate, α-hexachlorocyclohexane and methylclofenapate to induce nonbinucleating hepatocyte growth may, therefore, cooperate with the selective growth stimulation of cancer cells and cancer cell precursors to promote liver carcinogenesis. Autophagy, a mechanism for the bulk degradation of cytoplasm, contributes to intracellular protein turnover and serves to restrict cellular growth. Rat liver carcinogenesis is accompanied by a progressive reduction of autophagic capacity, preneoplastic livers having 50% and hepatocellular carcinoma cells only 20% as much autophagy as normal hepatocytes. The ascites hepatoma cell line AH-130 has virtually no autophagy during logarithmic growth, but some autophagy is turned on when the cells become growth-arrested at high cell density. Ascitic fluid from AH-130 cells is able to completely inhibit autophagy in normal hepatocytes, suggesting that the cancer cells may improve their growth ability through an autocrine, autophagy-suppressive mechanism. Hepatocytes from preneoplastic livers similarly maintain a low autophagic activity under restrictive culture conditions, thereby surviving much better than normal hepatocytes, which switch on their autophagy. In the presence of an autophagy inhibitor (3-methyladenine), normal and preneoplastic hepatocytes survive equally well, testifying to the importance of autophagy as a determinant of cell survival and growth.
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  • 86
    ISSN: 1573-6822
    Keywords: bile salts ; cell culture ; immortalization ; lipoproteins ; liver ; plasma proteins ; transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Primary human hepatocytes were immortalized by stable transfection with a recombinant plasmid containing the early region of simian virus (SV) 40. The cells were cultured in serum-free, hormonally defined medium during the immortalization procedure. Foci of dividing cells were seen after 3 months. Albumin- and fibrinogen-secreting cells were selected and cloned by limiting dilution to obtain homologous cell populations. The established IHH (immortalized human hepatocyte) cell lines were evaluated for their usefulness in studying the regulation of cell growth and of certain differentiated hepatocyte functions. IHH cells retain several differentiated features of normal hepatocytes. They display albumin secretion at a level comparable to cultured primary human hepatocytes (30 µg albumin/ml per day). A portion of the IHH cells are polarized, forming bile canaliculi-like vacuoles where exogeneous organic anions accumulate. The multidrug resistance (MDR) P-glycoprotein, known to be localized at the canalicular membrane, is also present in these vacuoles. The polarized features allowed the use of IHH cells for the study of localization of the newly characterized multidrug resistance protein MRP1. The homologues of MRP were found in hepatocytes, MRP1 and MRP2 (cMOAT), both functioning in ATP-dependent excretion of anionic conjugates. In differentiated hepatocytes, MRP1 expression is extremely low. In contrast, MRP1 is highly expressed in proliferating IHH cells, where it is localized in lateral membranes. A highly differentiated feature of short-term cultured primary hepatocytes which is not detectable in IHH cells is active uptake of the bile salt taurocholate. Furthermore, IHH cells secrete triglyceride (TG)-rich lipoproteins, apolipoprotein B (0.6 µg/ml per day), and apolipoprotein A-I (1 µg/ml per day). However, they secrete apoB-containing TG-rich lipoproteins mainly in the LDL density range, while short-term cultured primary hepatocytes mainly secrete TG-rich lipoproteins in the VLDL density range. In conclusion, functions that are rapidly lost in short-term hepatocyte cultures are, in general, not displayed by IHH cells. Immortalized human hepatocytes provide a valuable tool for studying the regulation of hepatocyte proliferation-related phenomena.
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  • 87
    ISSN: 1352-8661
    Keywords: liver ; spleen contrast enhancement ; carboxydextran magnetite ; dose ; delayed imaging ; field strengths dependence ; ex vivo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics
    Notes: Abstract It has been predicted that liver and spleen enhancement after administration of superparamagnetic contrast agents may be different, depending on the strength of the main magnetic field. With the use of anex vivo model, we investigated at 0.3, 0.5, and 1.5 T the effects on liver and spleen signal intensity of 5, 15, and 45 µmol/kg body weight of dextran magnetite (SHU 555A) in 54 rats. Nine rats served as controls. At different time delays since injection, the animals were killed, and after perfusion with saline, the liver, brain, and spleen were fixed in formalin. The specimens were embedded in an agar gel matrix and imaged with inversion recovery T1-weighted, proton density spin echo, and T2*-weighted gradient recalled echo (GRE) sequences. At each magnetic field strength, peak liver and spleen signal loss increased with increasing dose of the contrast medium. Signal loss was significantly more conspicuous after a dose of 15 than 5 µmol/kg body weight, but not after a dose of 45 compared with 15 µmol/kg. No signal change was observed in the brain. GRE images showed higher enhancement than proton density-weighted spin echo and inversion recovery images but were noisier. The enhancement showed a plateau between 30 min and 24 hours. Only the signal decrease of the liver after a low dose of contrast medium on GRE images was significantly higher (p〈0.01) at 1.5 than at 0.5 and 0.3 T. Other differences in respect to the field strength were less significant (p〈0.05) or nonsignificant. Differences in the spleen enhancement were nonsignificant. SHU 555A at a dose of 15 µmol/kg is an efficient intracellular contrast agent for liver and spleen at low, mid, and high field strength. Proton density spin echo images are probably the sequence of choice to exploit SHU 555A contrast effects and a wide time window for imaging after its intravenous injection does exist.
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    Magnetic resonance materials in physics, biology and medicine 4 (1996), S. 55-59 
    ISSN: 1352-8661
    Keywords: proton NMR ; relaxation times ; liver ; cold storage ; water fractions ; tissue hydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics
    Notes: Abstract Based on recent improvements in the field, biexponential data from fresh rat liver and monoexponential data from cold storage experiments allow quantification of three distinct relaxation components in liver tissue: bound water (4.2%, R1=12.0 ± 1.7 s−1, R2=440 ± 180 s−1); structured water (59%, R1 ≈ 3.3 ± 0.07 s−1, R2 ≈ 24.9 ±1.1 s−1); and free water (≈37%, R1=R2 ≈ 0.4 s−1). However, only the relaxation rates of the structured water component change with water content: R1A (s−1)=6.53 * Ms/Mw − 0.77 (r2=0.911); R2A (s−1)=71.15 * Ms/Mw − 3.09 (r2=0.956), respectively. This suggests a slow exchange between bound and structured water in liver cells.
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  • 89
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    Bulletin of experimental biology and medicine 119 (1995), S. 408-409 
    ISSN: 1573-8221
    Keywords: lactate dehydrogenase ; alcohol dehydrogenase ; liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A possible relationship between metabolic types of regulation of liver oxidative enzymes (lactate dehydrogenase and alcohol dehydrogenase) and the blood level of cortisol and insulin in intact animals is explored. The liver enzyme activity is found to depend on the initial physiological state of the organism.
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  • 90
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    Bulletin of experimental biology and medicine 119 (1995), S. 418-419 
    ISSN: 1573-8221
    Keywords: liver ; regeneration ; ionized plasma
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    Notes: Abstract Eighty guinea pigs underwent resection of the left lateral lobe of the liver, performed with a beam of ionized plasma. Morphological analysis 32 and 45 hours after partial hepatectomy revealed minor damage to the parenchyma to a depth of 300–400 μ. Autoradiography showed proliferative activity in the organ to occur in the early post-operative period.
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  • 91
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    Bulletin of experimental biology and medicine 122 (1996), S. 772-777 
    ISSN: 1573-8221
    Keywords: hemodynamics ; respiration ; calcium ; calcium channel blockers ; ultrasound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Acute tests on cats under Nembutal anesthesia show that intravenous injection of Ca2+ causes pathological respiration of the apneustic type and slight rises in pulmonary and arterial pressures. The calcium channel blockers verapamil and nifedipine decrease the amplitude of respiratory movements, increase the respiration rate and pulmonary pulse pressure, and lower systemic pressure. The introduction of verapamil or nifedipine into the fourth ventricle of the brain does not alter respiration or hemodynamics, whereas the introduction of Ca2+ leads to irreversible respiratory standstill. Hemodynamic parameters decrease 2–3 min after the respiratory standstill.
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  • 92
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    Bulletin of experimental biology and medicine 120 (1995), S. 1070-1072 
    ISSN: 1573-8221
    Keywords: water ; time of magnetic relaxation ; liver ; small intestine ; vagotomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Bilateral subdiaphragmatic truncal vagotomy in rats results in a disturbance of water metabolism in the liver and small intestine which manifests itself in an increase of the total water content, prolongation of the spin-lattice and spin-spin relaxation, and in a distortion of the correlation between them. The dynamics of water metabolism is of a onepeak nature in the liver with a maximum after 7 days, whereas in the small intestine it is of a dual-peak type with peaks at 7 and 30 days. Near-normalization of the water balance in the digestive organs occurs 220 days later.
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  • 93
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    Bulletin of experimental biology and medicine 120 (1995), S. 1193-1195 
    ISSN: 1573-8221
    Keywords: adaptation ; hypoxia ; cytochromes ; brain ; liver ; individual resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract After a prolonged (for 30 days) adaptation of rats to intermittent hypoxia, their brains contained lowered levels of mitochondrial cytochromes, despite an increase in the number of mitochondria in the brain tissue mass, along with similar levels of high-energy compounds and more protein as compaired to the brains of unadapted controls. A mitochondrial population with novel properties presumably emerged in the brain. These effects were all more strongly marked in rats with an initially low resistance to hypoxia. In the liver of hypoxiaadapted animals, unlike in their brain, cytochrome levels in the mitochondrial and microsomal redox chains were lowered and the biogenesis of mitochondria was much less intensive.
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  • 94
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    Bulletin of experimental biology and medicine 124 (1997), S. 844-847 
    ISSN: 1573-8221
    Keywords: hippocampus ; calcium ; potassium ; CA1 ; ion-selective electrodes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The effect of various concentrations ofl-glutamate on neurotransmission in the CA1 hippocampal area was studied using hippocampal slices. Three intervals ofl-glutamate concentration were established: ≤1 mM (all studied parameters are completely reversible upon washout, transmission being preserved), from 1 to 10 mM (both responses to frequency stimulation and single population spikes remain partially suppressed after washout), and above 10 mM (more than 50% suppression of transmission persists after washout).
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  • 95
    ISSN: 1573-8221
    Keywords: liver ; experimental cirrhosis ; RNA and protein synthesis ; phospholipid preparation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Hepatoprotective effect of Phospholiv, a phospholipid preparation containing phosphatidylcholine from sunflower seeds and glycyrrhizic acid trisodium salt, is studied using a model of CCl4-induced cirrhosis of the liver. Phospholiv protects hepatic tissues from necrotic and dystrophic changes and prevents the development of cirrhosis. Phospholiv restores impaired RNA and protein synthes is under conditions of chronic intoxication.
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  • 96
    ISSN: 1573-8221
    Keywords: calcium ; befol ; amiloride ; strophanthin ; caffeine ; cardiomyocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The dynamics of the Ca-response of cardiomyocytes is studied and the efficiency of befol, verapamil, and amiodarone is compared using various experimental models of stimulation of [Ca2+]i. Befol (1–5 μM) is shown to inhibit the caffeine-and strophanthin G-induced rise of [Ca2+]i. Unlike verapamil and amiodarone, befol exhibits no Ca-blocking activity in modeled K-depolarization. It is concluded that the cardiotropic effect of befol is mediated through its primary action on Na+/Ca2+ exchange in cardiomyocytes, while the cardioplegic effect of verapamil and amiodarone is due to their ability to block the slow Ca2+ inward current.
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  • 97
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    Bulletin of experimental biology and medicine 121 (1996), S. 348-351 
    ISSN: 1573-8221
    Keywords: heart ; liver ; Na,K-ATPase ; lipid peroxidation ; stress ; adaptation to stress ; adaptation to hypoxia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Na,K-ATPase activity is shown to be lowered more than twice 2 hours after emotional pain stress in comparison with the initial level, remaining practically unchanged during the subsequent 24 hours. Adaptation to repeated stress results in a 50% activation of Na,K-ATPase. A protective effect is demonstrated in long-term stress against the background of preadaptation. Adaptation to periodic hypoxia inhibits liver Na,K-ATPase to the same extent as does acute stress. Against the background of preadaptation to periodic hypoxia, stress does not aggravate the drop of Na,K-ATPase activity. Adaptation to stress inhibits accumulation of products ofin vitro-induced lipid peroxidation in the heart 1.4-fold and does not affect it in the liver, whereas adaptation to hypoxia sharply accelerates the accumulation of oxidized products in both organs, which probably explains the activation of liver Na,K-ATPase in adaptation to stress and its inhibition in adaptation to hypoxia.
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  • 98
    ISSN: 1573-8221
    Keywords: experimental plague ; liver ; ceftriaxone ; ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Fatty dystrophy and partial cytoplasmic necrosis predominate during the preagonal period in parenchymatous organs of mice infected withYersinia pestis 231 F1+. Endothelial damage, fibrin precipitation, and microcirculatory disorders occur in sinusoidal capillaries. More pronounced changes in the liver develop during the preagonal period in mice infected withY. pestis 231 F1−. Treatment with ceftriaxone leads to 100% survival in both groups and substantial restoration of liver structure.
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  • 99
    ISSN: 1573-8221
    Keywords: catalase inhibitors ; liver ; oxidative phosphorylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Incubation of the specific catalase inhibitor 3-amino-1,2,4-triazole with liver mitochondria and administration of this drug to intact rats are shown to uncouple oxidation and phosphorylation and to inhibit adenosine nucleotide synthesis in the animal liver. These disturbances apparently results from catalase inhibition.
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  • 100
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    Bulletin of experimental biology and medicine 122 (1996), S. 701-703 
    ISSN: 1573-8221
    Keywords: calcium ; cardiomyocytes ; suphan ; Ca-ATPase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Effects of suphan, a new cardiotonic agent containing succinyl tryptophan, on the entry of Ca2+ into rat cardiomyocytes, its intracellular compartmentalization, and its exit from these cells were evaluatedin vitro. It was found that the recorded sulfan-induced rise of intracellular calcium was due to Ca2+ entering the cell via L-type calcium channels, and that a reversible reduction of its concentration in the sarcoplasm occurred through its accumulation in the sarcoplasmic reticulum and was blocked by the specific Ca2+-ATPase inhibitor thapsigargin (10 μM). Suphan did not alter the activity of Na+/Ca2+ exchange in a concentration range of 5–150 μg/ml.
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