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1

Digitale Medien

Effects of cytochalasin B and dihydrocytochalasin B on calcium transport by intestinal absorptive cells (1981)

Jande, Sohan S. ; Liskova-Kiar, M.

Springer

Calcified tissue international 33 (1981), S. 143-151

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ISSN: 1432-0827

Schlagwort(e): Calcium transport ; Cytochalasin B ; Dihydrocytochalasin B ; Colchicine ; Electron microscopy

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Medizin , Physik

Notizen: Summary In vivo calcium absorption was studied in normal and rachitic chicks. Cytochalasin B (CB) at a concentration of 25 µg/ml added to the medium inside the duodenal lumen inhibited calcium absorption (20 min) from 82.5±1.9% of calcium absorbed in the controls to 59.2±3% in normal and from 70.0±2.3% to 47.0±2.1% in rachitic chicks. In vitro studies by everted ileal sacs of young rabbits also showed an inhibition of active transport of calcium due to CB. Whereas in the controls the ratio of45Ca concentrations in serosal and mucosal media (60 min) was 7.2±0.32, the ratios were 5.24±0.52; 4.40±0.36; 3.40±0.42; 5.77±0.52; 1.38±0.08; and 1.06±0.02 in the presence of CB at concentrations of 5, 10 and 25 µg/ml; colchicine 10−4M, Na citrate 0.02M, and heat-devitalized conditions, respectively.45Ca concentration in the mucosal scrapings was also affected. It showed an increase from controls (15,101±404 cpm/mg) and correlated with CB concentration: 17,378±489, 19,015±1000, and 20,201±362 at 5, 10, and 25 µg/ml, respectively. Dihydrocytochalasin B also inhibited active calcium transport and caused an increase in45Ca concentration in the mucosal scrapings. Correlated electron microscopic studies showed certain changes in the brush border, especially in some actin microfilaments in the terminal web region. It seems that these morphological alterations may be related to transcytoplasmic movement of calcium.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF02409427

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2

Digitale Medien

Ultrastructure of the rat epiphyseal growth plate following chronic ethanol ingestion (1981)

Fallon, Michael D. ; Baran, Daniel T. ; Craig, R. Bruce ; [weitere]

Springer

Calcified tissue international 33 (1981), S. 381-384

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ISSN: 1432-0827

Schlagwort(e): Alcohol ; Electron microscopy ; Growth plate

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Medizin , Physik

Notizen: Summary We have previously demonstrated that ethanol has a direct toxic effect on the rat skeleton characterized by decreased trabecular bone volume. In the present study, we examined the ultrastructure of the distal radial epiphyseal growth plates in these same animals. Eight weeks of ethanol administration to 12 male rats results in serum alcohol levels of 140 mg/dl but did not alter the width or light microscopic appearance of the radial growth plate. Quantitative electron microscopy failed to demonstrate morphologic evidence of toxicity in the skeletal cells. We conclude that although ethanol appears to have a direct effect on rat bone characterized by enhanced resorption, toxicity is not attended by ultrastructural changes in the skeletal cells.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF02409460

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3

Digitale Medien

Biochemical and histological studies on various bone cell preparations (1981)

Nijweide, P. J. ; Plas, A. ; Scherft, J. P.

Springer

Calcified tissue international 33 (1981), S. 529-540

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ISSN: 1432-0827

Schlagwort(e): Bone cells ; Electron microscopy ; PTH ; PGE1

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Medizin , Physik

Notizen: Summary Four different cell populations—designated PF, OB, OC, and PC—were isolated from calvaria of 18-day-old chick embryos for analysis of the effects of hormones on bone tissue. The cell populations were studied with histological and biochemical methods. Apart from the well-known cell types present in calvaria, a new cell type was found in the noncalcified organic matrix between the osteoblastic layer and the calcified matrix. These cells were provisionally called osteocytic osteoblasts. They represent the “transition state” between osteoblasts and osteocytes. On the basis of histological studies with light microscopy (LM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), the PF population was considered to originate primarily from the periosteal fibroblasts, the OB population from the osteoblasts and osteocytic osteoblasts. The population of cells still present in calvaria after removal of periosteal fibroblasts and osteoblasts was called the OC population. This cell population was very much enriched with osteocytes. The fourth isolated population (PC) was a mixed population of fibroblasts, osteoblasts, and preosteoblasts. On exposure to parathyroid hormone (PTH), all four cell populations showed increased lactate production, but only the OB and OC populations displayed increased cAMP production. Prostaglandin E1 (PGE1) stimulated cAMP production in both OB and PF cells. From the results of this study it was concluded that PTH receptors are present on all of the cell types studied, but that occupancy of the receptor induces adenylate cyclase stimulation only in osteocytes and fully differentiated osteoblasts.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF02409485

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4

Digitale Medien

Crystal orientation in the shell of the domestic fowl: An electron diffraction study (1981)

Perrott, H. R. ; Scott, V. D. ; Board, R. G.

Springer

Calcified tissue international 33 (1981), S. 119-124

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ISSN: 1432-0827

Schlagwort(e): Avian eggshell ; Microstructure ; Electron microscopy ; Electron diffraction ; Calcite growth

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Medizin , Physik

Notizen: Summary The eggshell of the domestic fowl has been studied by transmission electron microscopy and diffraction. Thin sections of shell were prepared by chemical and ion-beam thinning techniques. Each calcite column of the palisade layer consisted of crystallites of diameter 20 to 30 µm with some tendency for crystallite alignment within a single column. Evidence indicates that there was no significant preferred orientation in the palisade layer as a whole. Only in the surface layer was any preferred orientation detected, and here {1014} planes tended to lie parallel to the surface. The results are compared with previously published data, and calcite nucleation and growth are discussed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF02409423

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5

Digitale Medien

Auxin uptake and action of N-1-naphthylphthalamic acid in corn coleoptiles (1981)

Sussman, Michael R. ; Goldsmith, Mary Helen M.

Springer

Planta 151 (1981), S. 15-25

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ISSN: 1432-2048

Schlagwort(e): Auxin (uptake, transport) ; Benzoic acid ; N-1-Naphthylphthalamic acid ; Zea

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract The validity of a chemiosmotic hypothesis for uptake of weak acids as an explanation for the accumulation of auxin by cells has been explored further by comparing the uptake of indole-3-acetic acid (IAA) by 1-mm segments of corn (Zea mays L.) coleoptiles with that of benzoic acid and two neutral indoles, indoleethanol and indoleacetonitrile, which do not ionize. These substances, while structurally related to IAA lack both auxin activity and polar transport. Uptake of IAA and benzoic acid increase with decreasing external pH, whereas the uptake of the two neutral indoles is independent of external pH. Although metabolism of IAA, during 90 min or less, is minimal and without significant effect on its uptake, metabolism of benzoic acid appears responsible for the apparent saturation of benzoic acid uptake at high concentrations. An inhibitor of auxin transport, N-1-naphthylphathalamic acid (NPA), stimulates uptake of IAA but has no effect on uptake of either benzoic acid or the two neutral indoles. Thus, NPA does not affect the driving forces for accumulation of weak acids but probably specifically decreases the flux of the auxin anions relative to undissociated auxin. Since the electrochemical potential of auxin anions is usually higher in than outside cells, blocking the anion flux with NPA would enhance auxin uptake. Azide, which abolishes accumulation of both IAA and benzoic acid, may simply collapse the pH gradient across the plasma membrane. In the absence of NPA, increasing concentrations of auxins or the analogoue β-naphthaleneacetic acid (β-NAA) exert two opposing effects on the uptake of IAA-depression and stimulation. Stimulation results from saturating the anion flux. With uptake fully stimulated by NPA, however, increasing concentrations of auxins or analogues only depress uptake of [3H]IAA. These results are consistent with more than one path for auxin transport each with a different dependence on concentration. In depressing NPA-stimulated IAA uptake, the effectiveness of β-NAA≧IAA≫α-NAA≫ benzoic acid, a specificity similar to that of an auxin binding site in vitro that has been implicated by others in auxin transport. The results support the general hypothesis that cellular auxin uptake and polar transport through tissues are chemiosmotically coupled to the electrochemical potential of auxin and protons.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00384232

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6

Digitale Medien

Isolation and characterization of aminopterin-resistant cell lines in maize (1981)

Shimamoto, Ko ; Nelson, Oliver E.

Springer

Planta 153 (1981), S. 436-442

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ISSN: 1432-2048

Schlagwort(e): Aminopterin-resistant variants ; Cell culture ; Folate analog ; Variant selection ; Zea

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract Aminopterin-resistant cell lines of maize were isolated by two different procedures of callus selection and by plating suspension cultures on drugcontaining medium after mutagen treatment. Efficiencies of different methods of variant selection were compared. Four aminopterin-resistant cell lines were shown to be 10–40 times more resistant than the parental cell line, and they were also resistant to another folate analog, methotrexate. The results suggest that alterations in at least three different cell properties could be responsible for resistance; 1) increased dihydrofolate reductase activity, 2) altered aminopterin sensitivity of dihydrofolate reductase, and 3) reduced drug uptake. One of the resistant cell lines showed more than one alteration, but its resistance proved to be unstable. The results suggest that stable changes which may or may not be of genetic origin and also unstable physiological changes or a combination of both could lead to aminopterin resistance in maize cell cultures.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00394982

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7

Digitale Medien

Effect of zearalenone (F-2) on pea stem, maize root, and rat liver mitochondria (1981)

Vianello, A. ; Macrì, F.

Springer

Planta 153 (1981), S. 443-446

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ISSN: 1432-2048

Schlagwort(e): ATPase ; Mitochondria ; Mycotoxin ; Pisum ; Zea ; Zearalenone

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract At 5 and 10 μg ml-1 concentration, zearalenone (F-2), a mycotoxin produced by a number of species of the genus Fusarium, causes an inhibition of the oxidative phosphorylation of isolated plant mitochondria, while at 20 and 40 μg ml-1 it causes uncoupling. However, when the mitochondria are pre-incubated for 20 min with F-2, the uncoupling appears to be the prevailing effect. F-2 is also able to inhibit the mitochondrial ATPase activity (Mg2+-dependent). Conversely, F-2 (40 μg ml-1) does not alter the ATP level of maize roots and only slightly affects the ATPase activity of pea stem and maize root microsomal fractions. In addition, F-2 (10–40 μg ml-1) inhibits ATP synthesis catalyzed by rat liver mitochondria. It is suggested that the phytotoxicity of F-2, also known for its ability to collapse the transmembrane electric potential of maize roots, may be mainly linked to its ability to increase the proton permeability of the cell, similar to the common uncouplers.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00394983

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8

Digitale Medien

Light-induced inhibitors from intact and cultured caps of Zea roots (1981)

Feldman, Lewis J.

Springer

Planta 153 (1981), S. 471-475

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ISSN: 1432-2048

Schlagwort(e): Abscisic acid ; Geotropism (root) ; Growth inhibitor ; Light and root-cap inhibitor ; Root cap (inhibitor) ; Zea

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract Growth inhibitors were assayed from extracts of intact (attached) and of excised (cultured) root caps of Zea mays L., cv. Merit, the roots of which show a positive geotropic response only after exposure to light. If caps are intact at the time of illumination, at least two inhibitory substances are produced, an acid inhibitor and a neutral inhibitor, whereas if caps are detached from roots, placed in culture and then illuminated only the neutral inhibitor is formed. Cycloheximide retards inhibitor production in both intact and cultured caps. When [14C]mevalonic acid is included in the culture medium and the caps are illuminated, 15–25% of the recoverable 14C cochromatographs with the neutral inhibitor, whereas in caps cultured in the dark, this radiolabelling pattern is not observed. Cyloheximide in the light reduces the incorporation of 14C into compounds cochromatographing at the Rf of the neutral inhibitor. It is suggested that the neutral inhibitor may be important in the light-induced bending of roots.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00394989

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9

Digitale Medien

Levels of indole-3-acetic acid in intact and decapitated coleoptiles as determined by a specific and highly sensitive solid-phase enzyme immunoassay (1981)

Weiler, E. W. ; Jourdan, P. S. ; Conrad, W.

Springer

Planta 153 (1981), S. 561-571

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ISSN: 1432-2048

Schlagwort(e): Auxin (immunoassay) ; Avena ; Coleoptiles (physiological tip) ; Enzyme immunoassay ; Zea

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract A specific solid-phase enzyme immunoassay for the detection of as little as 3–4 pg of indole-3-acetic acid (IAA) is described. The assay involves minimal procedural efforts and requires only standard laboratory equipment. Up to 50 samples in triplicate, processed simultaneously, can be assayed and evaluated in 2.5 h. As little as 1 mg oat coleoptile tissue is sufficient for a quantitative IAA analysis and little or no extract purification is necessary. Using this assay, levels of IAA have been determined in coleoptiles of maize and oat. The distribution of IAA within single coleoptiles was quantitated and the production of IAA during the regeneration of the physiological tip in Avena coleoptiles was investigated. The changes in levels of IAA and other major phytohormones were quantitated during the growth of oat coleoptiles.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00385542

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10

Digitale Medien

Partial purification of endo- and exo-β-D-glucanase enzymes from Zea mays L. seedlings and their involvement in cell-wall autohydrolysis (1981)

Huber, Donald J. ; Nevins, Donald J.

Springer

Planta 151 (1981), S. 206-214

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ISSN: 1432-2048

Schlagwort(e): Cell-wall autohydrolysis ; β-D-Glucan ; Glucanase ; Hemicellulose ; Zea

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract The proteins dissociated from isolated Zea seedling cell wall using high-ionic-strength salt solutions have been found to include a number of enzymes which appear to participate in autolytic reactions of the cell wall. These enzymes caused extensive degradation of enzymatically inactive cell wall, liberating as much as 100 μg/mg dry weight over a 48-h period. Lithium chloride (3M) was shown to be most effective in yielding protein and wall-degrading activities. Molecular-sieve chromatography of the cell-wall protein resolved endo-β-D-glucanase and exo-β-1,3-glucanase (EC 3.2.1.58) activities when Avena glucan and laminarin, respectively, were employed as substrates. The exoenzyme (molecular weight around 60,000) was strongly inhibited by inorganic mercury at a concentration which suppressed the release of monosaccharide from autolytically active cell wall. The endo-β-D-glucanase (MW around 26,000), which showed a marked preference for substrates of mixed-linkage, exhibited features indicating that it initiates the autolytic solubilization of wall glucan. Cell-wall β-D-glucan, recovered as a component of an alkali-soluble cell-wall fraction, served as a substrate for the purified glucanases. Their hydrolysis pattern, assessed using gel exclusion chromatography and product analysis, confirmed that they hydrolyze β-D-glucan. The products generated by the endoglucanase were similar in molecular-size distribution to those liberated from autolytically active-wall. Exoglucanase activity was required for extensive hydrolysis of β-D-glucan in vitro. During coleoptile development the autolytic activity of the cell wall increased dramatically. This increased activity, however, did not parallel the growth potential of the tissue, but more closely reflected an increase in cell-wall β-D-glucan, the primary substrate for autolytic reactions.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00395171

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