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  • Articles  (45)
  • Articles: DFG German National Licenses  (45)
  • Springer  (40)
  • Blackwell Publishing Ltd  (5)
  • Blackwell Science Ltd
  • 1995-1999  (24)
  • 1980-1984  (21)
  • Biology  (45)
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  • Articles  (45)
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  • 1
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Trisomy 21 human fibroblasts are more sensitive to human interferon-α (IFN-α) than are diploid controls, consistent with the location of the gene (IFRC) which codes for the IFN-α receptor on chromosome 21. When compared in the antiviral assay, the difference in sensitivity is five-to tenfold, much greater then the 50% difference in IFRC gene dosage. An understanding of the mechanism by which this amplification of gene dosage occurs is relevant to the specific pathology of Down's syndrome and as a model system for studying the pathogenic effects of chromosomal aneuploidy. The enzyme (2′–5′) oligoisoadenylate synthetase (2–5A synthetase), which is believed to be central to the interferon-induced antiviral response, is induced 50% more in trisomy 21 fibroblasts than in diploid controls. Thus the amplification in response occurs subsequent to the binding of IFN-α to its receptor and the triggering of the first set of intracellular events, the latter exemplified by the induction of 2–5A synthetase. Similar results were obtained with IFN-γ, consistent with other evidence which indicates that a gene coding for a separate IFN-γ receptor is also located on chromosome 21.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 75 (1983), S. 105-114 
    ISSN: 1432-1424
    Keywords: shark rectal gland ; ouabain binding ; (Na, K)-ATPase ; cyclic AMP ; slices ; isolated cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary In an attempt to examine the mechanisms of activation of (Na, K)-ATPase when epithelial transport is stimulated, the binding of ouabain to rectal gland tissue was measured before and after stimulation with dibutyryl cAMP and theophylline. Stimulation significantly altered the characteristics of ouabain binding to slices ofSqualus acanthias rectal gland and to isolated rectal gland cells, accelerating the rate of binding and increasing the amount of ouabain bound at equilibrium when low concentrations of ouabain (10−9 to 10−7 m) were present in the medium. Scatchard plots of ouabain binding were nonlinear, suggesting at least two classes of binding sites, one of higher and one of lower affinity. Stimulation with cAMP and theophylline appeared to increase the affinity of the high-affinity site. Ouabain binding was increased by cAMP and theophylline even in the presence of furosemide (10−4 m) or bumetanide (10−5 m), and when Li+ was substituted for Na+, or NO 3 − for Cl−-maneuvers known to inhibit rectal gland secretion. The changes in ouabain binding induced by cAMP and theophylline do not appear, therefore, to be secondary to secretory activity but may reflect a change in the configuration, environment or location of existing enzyme so as to enhance its activity. Stimulation of ouabain binding cannot be demonstrated in whole homogenates of rectal gland, indicating that intact cells are necessary for the cyclic AMP-induced increase in ouabain binding to become manifest.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 154 (1984), S. 139-144 
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary When the active sodium-potassium pump (Na−K-ATPase) of shark rectal glands is blocked by ouabain, the concentration of intracellular ions changes in the direction of equilibrium with extracellular fluid. These changes were examined when isolated perfused glands were in the basal state and also when they were stimulated to secrete with cAMP and theophylline, to see whether stimulation affected the passive movement of sodium, potassium and chloride across cell membranes. In basal glands 10−4M ouabain induced an increase of 30 meq/l in intracellular [Na+] and a decrease in intracellular [K+] of about 50 meq/l after 30 min, while intracellular [Cl−] was unchanged. In stimulated glands, these movements were exaggerated. The increase in intracellular [Na+] averaged 112 meq/l, and the decrease in intracellular [K+], 96 meq/l (P〈0.01), while mean intracellular [Cl−] rose by 80 meq/l. Furosemide, 10−4M, partially reversed the accelerated changes in intracellular electrolytes seen after ouabain was added to stimulated glands. These results are consistent with an action of cAMP upon a ouabaininsensitive cotransport of sodium, potassium and chloride in the rectal gland, analogous to that described in avian erythrocytes.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 18 (1980), S. 746-748 
    ISSN: 1741-0444
    Keywords: Autozeroing ; Barometric method ; Electronic circuit ; Instrumentation ; Plethysmography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract An electronic circuit is described which automatically rezeroes a physiologic signal whenever it reaches the limit of a display. This modified signal can be used for polygraph monitoring while the raw signal is processed by a wide-range high-resolution a.d. convertor. The device is currently used in conjunction with the barometric method for measuring tidal volume, but should find general use in plethysmography.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 28 (1981), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Viable merozoites of Plasmodium knowlesi were isolated and the proteins that were labeled on intact merozoites by lactoperoxidase-catalyzed radioiodination were identified. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and autoradiography of Triton soluble extracts of labeled merozoites demonstrated eight major bands ranging in apparent molecular weight from 150,000 D to 22,000 D. Exposure of intact merozoites to trypsin (10 μg/ml) for 10 min resulted in the loss of the two highest molecular weight proteins (150,000 D and 105,000 D) and the appearance of two new bands at 70,000 D and 62,000 D. Trypsin treatment under these conditions also removed the receptor(s) for merozoite attachment to erythrocytes. Therefore, these high molecular weight proteins are candidates for the merozoite component that attaches to erythrocytes. There was no evidence that the labeled membrane components were serum or erythrocyte membrane components, two potential contaminants in the preparation. Anti-rhesus erythrocyte antibody did not precipitate labeled merozoite proteins. Furthermore, the immunoprecipitation of labeled merozoite proteins by rhesus anti-merozoite serum was not inhibited by erythrocyte ghosts.
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  • 6
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The function and location of guard cells uniquely subject them to stress. First, stomatal movements require large fluctuations in the concentration of potassium salts. Second, guard cell inner walls are the first surfaces exposed to evaporation and apoplastic solutes may accumulate there as a result. We have therefore investigated whether guard cells exhibit atypical expression of dehydrin genes because dehydrins accumulate in vegetative tissues in response to water stress. We have also assayed for osmotin mRNA, which is up-regulated in leaves in response to various stresses. mRNA probes for several representative genes were used with RNA extracts from control and water-stressed Vicia faba leaflets. Correlatively, these probes were used with RNA extracts from “isolated’ guard cells that had been incubated with combinations of abscisic acid, mannitol and Ca2+. (Isolated guard cells are epidermal strips sonicated to destroy cells other than guard cells.) Hybridization with the probe prepared for a dehydrin from Pisum sativum (Psdhn 1) was detected in leaf extracts only if the leaf had been stressed. Similarly, after 1- and 6-h incubations with abscisic acid, isolated guard cells contained an mRNA that hybridized with the probe for Psdhn 1. Appearance of this abscisic acid-dependent mRNA required neither mannitol nor exogenous Ca2+. Regardless of the conditions or tissue, no hybridization was detected with the probe against osmotin, but our interpretation of this result is qualified. The simplest conclusion is that atypical expression of dehydrin is not the mechanism by which guard cells cope with their peculiar function and location.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 56 (1982), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Changes in levels of free and conjugated indole-acetic acid (IAA) resulting from ethylene treatment were examined in leaves and callus of olive (Olea europea var. Manzanillo) by electron capture gas chromotography and by isotope dilution analysis. In both olive leaves and olive tissue cultures, the level of free IAA did not change much after the exposure to ethylene, but the levels of bound IAA increased almost three times in comparison with untreated controls. This is the first report of changes in endogenous, bound auxin accompanying ethylene treatment.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 45 (1998), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Bacterial epibionts were observed on the surface of the marine sediment ciliate Geleia fossata. Rod-shaped bacteria, from 2-10 X103 per ciliate, were universally positioned in ciliated grooves, in apparent spatial association with dikinetids. SEM and TEM examination of the ciliates confirmed that a tight affiliation exists between the epibiotic bacteria and ciliate cortex infrastructures. These observations, as well as the distinct bacterial distribution pattern over ciliate surface, suggest that there is a close epibiont/host physiological integration. Epibiotic bacteria were also observed on the surfaces of other sediment ciliates from the genera Loxophyllum, Tracheloraphis, Geleia, Paraspathidium, and Cyclidium. These findings indicate that the bacterial/protozoa associations are widespread in the marine benthic environment. The potential benefits for both epibionts and their hosts are discussed.
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  • 9
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Auxin conjugates play a role in the regulation of free indole-3-acetic acid (IAA) content in plants. Not much is known about the enzymes involved in either conjugate synthesis or hydrolysis. In this study we have isolated and characterized an auxin conjugate hydrolase from Chinese cabbage seedlings and investigated it during the development of both the Chinese cabbage plants and the clubroot disease. The hydrolase isolated from light- and dark-grown seedlings accepted the amide conjugates indole-3-acetic acid-alanine (IAAla), IAA-phenylalanine (IAPhe), but not IAA-aspartate (IAAsp) as substrates. We also found a substantial amount of hydrolysis of an ester conjugate (IAA-glucose, IAGlu) in our enzyme preparation. The tentative reaction product IAA was identified by HPLC and subsequent GC-MS analysis. The pH optima for the different substrates were not identical, suggesting several hydrolase isoforms. After gel filtration chromatography we found at least two peaks containing different hydrolase isoforms. The isoform, which converted IAGlu to IAA, exhibited a molecular mass of ca 63 kDa, and an isoform of ca 21 kDa converted IAAla and IAPhe. The increased free IAA content in clubroot-diseased roots of Brassicaceae can be due to either de novo synthesis or release of IAA from conjugates. To answer this question free, ester- and amide-bound IAA was measured in 24- and 30-day-old leaves and roots of healthy and Plasmodiophora brassicae-infected Chinese cabbage, and the hydrolase activity with different substrates measured in the same tissues. The amide conjugates were dramatically enhanced in infected roots, whereas free IAA was only slightly enhanced compared to the control tissue. Hydrolase activity was also enhanced in clubbed roots, but the substrate specificity differed from that found in the seedlings. Especially, IAAsp hydrolysis was induced after inoculation with P. brassicae. We conclude that different auxin conjugates can be hydrolyzed at different developmental stages or under stress.
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  • 10
    ISSN: 1432-0827
    Keywords: 1α25(OH)2D ; Hypercalcemia ; Normocalcemia ; Pulmonary tuberculosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Available evidence indicates that hypercalcemia in pulmonary tuberculosis results from increases in circulating 1α,25-dihydroxyvitamin D [1α,25(OH)2D]. To further characterize vitamin D metabolism in this disorder, the effects of vitamin D, 100,000 units a day for 4 days, were compared in 25 normal subjects and 11 patients with active pulmonary tuberculosis who were normocalcemic and had not had hypercalcemia. Serum calcium, phosphorus, 25-hydroxyvitamin D (25-OHD) and 1α,25(OH)2D were measured. Whereas vitamin D increased mean serum 25-OHD from 20±2 (±SE) to 40±5 ng/ml (P〈0.001) and did not change mean serum 1α,25(OH)2D in the normals (33±2 vs. 31±2 pg/ml), it increased mean serum 25-OHD from 21±4 to 55±13 ng/ml (P〈0.05) and mean serum 1α,25(OH)2D from 28±2 to 35±3 pg/ml (P〈0.05) in the patients. Serum calcium was normal and remained within the normal range in all subjects and patients. The findings indicate that there is a modest but significant abnormality in the regulation of circulating 1α,25(OH)2D in normocalcemic patients with pulmonary tuberculosis. The results are similar to those previously reported by us in normocalcemic patients with sarcoidosis.
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