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991.
Dr. Francisco Gracia-Navarro David Porter Socorro García-Navarro Paul Licht 《Cell and tissue research》1989,256(3):623-630
Summary The colloidal gold immunocytochemical technique was used to determine the ultrastructural features of the glandular cells in the pituitaries of male frogs, Rana pipiens, both in vivo and after superfusion in vitro. Specific reactions to antisera against bullfrog gonadotropins, human prolactin, and synthetic 1–39 corticotropin allowed identification of the 3 corresponding types of glandular cells. No immunoreaction was obtained with antisera against human or ovine-growth hormone, human -thyrotropin hormone, and bovine S-100 protein. General morphological features of these immunocytochemically identified glandular cells were similar to those of equivalent cells previously described in other amphibian species. Non-glandular folliculo-stellate cells were distinctive. In freshly removed pituitaries, these folliculo-stellate cells contained lysosome-like structures, but did not show phagocytic vacuoles in the cytoplasm; they contained many mitochondria, and the Golgi complex and endoplasmic reticulum were relatively undeveloped. After 4 or 18 h of superfusion, some immunoreactive gonadotropic, prolactin, and corticotropic cells showed degeneration and destruction. In the same gland, folliculo-stellate cells retained a viable appearance, but showed phagocytic vacuoles containing secretory granule-like structures which were immunoreactive to gonadotropic, prolactin, and corticotropic antibodies. Some folliculo-stellate cells showed phagocytic vacuoles containing complete glandular cells. These results suggest that superfusion causes a destruction of some of the glandular cells, and that folliculo-stellate cells act as phagocytes when cellular debris or moribund cells are present in the intercellular space in the pituitary parenchyma.Supported by grant DCB 8710462 from the National Science Foundation, grant 2148-83 from the CAICYT (Spain) and the Junta de Andalucia (Spain) 相似文献
992.
Summary Innervation of the ascidian branchial basket and other structures is demonstrated by staining for cholinesterase. Cholinesterase activity is not restricted to synaptic sites but is present throughout the neurons. Primary and secondary axonal bundles form a bilaterally symmetric innervation pattern around the large dorsal visceral nerve. These bundles continue to split into progressively smaller bundles as they course throughout the basket. Axons are suspended in a fibrous matrix and run within the blood sinuses on the atrial side of the basket. Stigmatal ciliated cells of the branchial basket are innervated by highly branched distal portions of neurons, whose cell bodies are located in the ganglion. Synaptic boutons, containing electron-lucent vesicles, are found at nearly all stigmatal ciliated cells. NiCl2backfills of the visceral nerve reveal a distinct population of central neurons, some of which presumably control ciliary arrest. 相似文献
993.
A similar protein portion for two exoglucanases secreted by Saccharomyces cerevisiae 总被引:4,自引:0,他引:4
Exoglucanase (exo-1,3-β-D-glucan glycohydrolase, EC 3.2.1.56) activity secreted by Saccharomyces cerevisiae into the culture medium was separated by ion exchange chromatography into two glycoprotein isoenzymes which contributed 10%
(exoglucanase I) and 90% (exoglucanase II) towards the total activity. Analysis of the “in vitro” deglycosylated products
by polyacrylamide gel electrophoresis under native or denaturing conditions indicated that the protein portions of both exoglucanases
exhibited identical mobility, each one consisting of two polypeptides with M
r of 47000 and 48000. The same profile was shown by the exoglucanase secreted in the presence of tunicamycin. Antibodies raised
against the protein portion of exoglucanase II did react with both native exoglucanases and their deglycosylated products
with a pattern indicative of immunological identity. Digestion of the “in vitro” deglycosylated products of both exoglucanases
with Staphylococcus aureus V-8 protease or trypsin generated the same proteolytic fragments in each case. Only exoglucanase II was secreted by protoplasts.
These and previously reported results indicate that the protein portions of both isoenzymes may be the product of the same
gene (or a family of related genes), and that exoglucanase I is a product of enzyme II, modified by a process occurring beyond
the permeability barrier of the cell. 相似文献
994.
995.
996.
G Barbato R Calabria M Cartení-Farina G D'Auria M De Rosa R Sartorio S Wurzburger V Zappia 《Biochimica et biophysica acta》1989,991(2):324-329
The interaction between S-adenosyl-L-methionine (AdoMet) and sodium poly(styrene sulfonate) NaPSS) was studied by means of ultrafiltration and ultraviolet absorption spectroscopy at several pH values and sodium sulfate concentrations. The results obtained are interpreted mainly in terms of electrostatic interactions and permit the evaluation of the binding constants under different experimental conditions. Furthermore, ultraviolet absorption spectroscopy data show a specific short-range interaction between the aromatic electronic system of AdoMet and the NaPSS aromatic ring. The results indicate that the binding strength is greatly affected by the AdoMet positive charge on the adenine ring. The other positive charges on both the sulfonic pole and the amino acidic group of AdoMet contribute only weakly to the binding to the polyanionic matrix, thus assuring some stability of AdoMet even at physiological pH. 相似文献
997.
Hypothalamic contents of gonadotropin-releasing hormone (GnRH) in neonatally orchidectomized infant, juvenile, and adult monkeys were measured by a radioimmunoassay (RIA) and by an in vivo bioassay that utilized luteinizing hormone (LH) secretion in estrogen- and progesterone-treated ovariectomized rats. The results of the bioassay provided no evidence to suggest that hypothalamic GnRH content in juvenile monkeys (mean = 83 ng/hypothalamus; n = 3) was less than that in infants (mean = 54 ng/hypothalamus; n = 4) and adults (mean = 36 ng/hypothalamus; n = 3). A similar developmental pattern in hypothalamic GnRH content was also observed when the decapeptide was measured by RIA. In striking contrast to the maintenance of hypothalamic GnRH content throughout postnatal development, pituitary gonadotropin contents and serum gonadotropin concentrations were markedly reduced in juvenile monkeys. 相似文献
998.
Interactions of amiloride and small monovalent cations with the epithelial sodium channel. Inferences about the nature of the channel pore. 总被引:2,自引:0,他引:2
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The voltage dependence of amiloride-induced inhibition of current flow through apical membrane sodium channels in toad urinary bladder was studied at different ionic conditions. The "inert" salt N-methyl-D-glucamine HCl (NMDG HCl) affected neither the apparent inhibition constant (Kl) for the amiloride-induced current inhibition nor the apparent fraction of the transmembrane voltage that falls between the mucosal solution and the amiloride-binding site (delta). When NMDG+ was replaced with Na+, Kl increased, reflecting amiloride-Na+ competition, whereas delta was unchanged. Similar results were obtained with another permeant cation, Li+. When NMDG+ was replaced by K+, an impermeant but channel-blocking cation, Kl increased whereas delta decreased. Similar results were obtained using another impermeant, channel-blocking cation guanidinium. The results are interpreted on the premise that Na+ and K+ compete with amiloride by binding to cation binding sites within the channel lumen such that ion occupancy of these sites vary with voltage. Occupancy by K+, which cannot traverse the channel, will increase as the mucosal solution becomes positive, relative to the serosal solution. Occupancy by Na+, which can traverse the channel, is comparatively voltage independent. Ion movement through the channels was simulated using discrete-state kinetic models. Two types of models could describe the shape of the current-voltage relationship and the voltage dependence of the amiloride-induced channel block. One model had a single ion-binding site with a broad energy barrier at the inner (cytoplasmic) side of the site. The other model had two binding sites separated from each other and from the aqueous solutions by sharp energy barriers. 相似文献
999.
A note on a semiparametric estimator of mortality 总被引:1,自引:0,他引:1
1000.
Fluorescence lifetime studies with staphylococcal nuclease and its site-directed mutant. Test of the hypothesis that proline isomerism is the basis for nonexponential decays. 总被引:1,自引:0,他引:1
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Using frequency domain methods, the fluorescence decay of Trp-140 in staphylococcal nuclease and its site-directed mutant (Pro-117----Gly) has been examined. Based on nuclear magnetic resonance (NMR) studies (Evans, P. A., C. M. Dobson, R. A. Kautz, G. Hatfull, and R. O. Fox. 1987. Nature [Lond.]. 329:266-268), it is believed that nuclease exists in two macroscopic, native conformations and that the slow interconversion of these conformations is controlled by the cis----trans isomerization of Pro-117. The above mutant shows only one native conformation in NMR experiments. To test the hypothesis that the biexponential fluorescence decay of Trp-140 of nuclease can also be related to the existence of these conformational states of the protein, we have compared the decay patterns of the wild type and mutant. Essentially no difference was observed, which indicates that there is some other basis for the nonexponential decay of Trp-140. We have used global nonlinear least squares analysis to link the fit of data at several temperatures. 相似文献