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51.
Previous work from our laboratory (Biochem. J. 219:689–697 (1984) had shown that hydrocortisone stimulated the net accumulation of the myelin-specific sulfolipid in cultures of cells dissociated from embryonic mouse cerebra. This accumulation caused by hydrocortisone was shown to be due to a decrease of sulfolipid degradation by arylsulfatase A (ASA) and not due to a stimulation of its synthesis by a sulfotransferase. Both ASA activity and the turnover of sulfolipid were decreased by hydrocortisone to 60–62% of untreated cells. In current work the same decrease in enzyme activity was obtained and enzyme linked immunosorbent assays demonstrate that hydrocortisone decreased the number of ASA protein molecules to 61% of untreated cells [(-)hydrocorcortisone 0.31±0.06 ng ASA/g protein; (+)hydrocortisone: 0.18±0.04 ng ASA/g protein]. This decrease in the number of ASA molecules correlates well with the decrease in both the enzyme activity and the sulfolipid turnover, which suggests that the major mode of inhibition of ASA activity by hydrocortisone involves a decrease in the concentration of ASA in the cells rather than some other mechanism of inhibition.The material in this paper has been included in a dissertation submitted by A.J.M. in partial fulfillment of the requirements for the degree of Doctor of Philosophy. Temple University.  相似文献   
52.
The fungicide triarimol was tested for its effect on abscisic acid (ABA) accumulation in growing culturesof Cercospora rosicola. ABA accumulation was reduced by approximately 50% with 10–8 M triarimol. Growth ofC. rosicola, as measured by dry weight accumulation, was inhibited by triarimol concentrations at or greater than 10–7 M. These results are compared with those obtained with clomazone, ancymidol, and paclobutrazol, which inhibit ABA accumulation by 50% at concentrations of 5 × 10–5, 5 × 10–6, and 5 × 10–7 M, respectively. Triarimol, therefore, is among the most potent inhibitors of ABA biosynthesis reported to date. Feeding studies with [14C]mevalonic acid confirmed the inhibition of ABA biosynthesis by 5 × 10–8 M triarimol. These results support previous suggestions that one or more of the steps in the ABA biosynthetic pathway from mevalonic acid is catalyzed by cytochrome P-450. Feeding studies with 1-deoxy-[2H]-ABA in resuspended cultures ofC. rosicola show that the conversion of this substrate is not inhibited by triarimol.  相似文献   
53.
1. Catecholamine secretion from digitonin-treated chromaffin cells is stimulated directly by micromolar Ca2+ in the medium. The permeabilized cells are leaky to proteins. 2. In this study trypsin (30-50 micrograms/ml) added to cells after digitonin treatment completely inhibited subsequent Ca2+-dependent catecholamine secretion. The same concentrations of trypsin did not inhibit secretion from permeabilized cells if trypsin was present only prior to cell permeabilization. 3. The data indicate that trypsin entered digitonin-treated chromaffin cells which were capable of undergoing secretion and that an intracellular, trypsin-sensitive protein is involved in secretion. Chymotrypsin was less potent but had effects similar to those of trypsin. 4. The enhancement of Ca2+-dependent secretion from permeabilized chromaffin cells induced by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) was inhibited by trypsin added simultaneously with Ca2+ to permeabilized cells at concentrations (3-10 micrograms/ml) which had little or no effect on Ca2+-dependent secretion from cells untreated with TPA. Ca2+-dependent secretion in TPA-treated cells was reduced by trypsin only to the level that would have occurred in cells not treated with TPA. Trypsin reduced the large TPA-induced increment of membrane-bound protein kinase C.  相似文献   
54.
The ability of M-protein-positive (M+) and M-protein-negative (M) strains (including an M mutant lacking the structural gene for M-protein) ofStreptococcus pyogenes to attach to human pharyngeal, buccal, and tongue epithelial cells was compared. We observed that M+ strains ofS. pyogenes attached in significantly higher numbers to human pharyngeal epithelial cells than to human buccal or tongue cells. M strains did not exhibit high-level binding to any type of epithelial cell. Also, the adhesion of an M+ and an M strain ofS. pyogenes was low to all types of rat epithelial cells tested. The apparent differences in the surface components between human pharyngeal and buccal epithelial cells were confirmed by studies utilizing radiolabeled lectins.Ulex europaeus lectin with a specificity for fucosyl residues, andTriticum vulgaris lectin with a specificity for N-acetyl glucosamine and N-acetyl neuraminic acid residues, bound in higher amounts to human pharyngeal cells than to buccal cells. Pretreatment of pharyngeal epithelial cells with microgram quantities of highly purified type 6 M-protein or miligram quantities of lipoteichoic acid (LTA) derived fromS. pyogenes decreased the subsequent attachment of the organism. However, the binding specificities of3H-LTA were different from those of intact streptococci;3H-LTA bound comparably to human pharyngeal, buccal, and tongue epithelial cells, and it bound in higher quantities to rat epithelial cells. Also, although the adsorption ofS. pyogenes cells to pharyngeal cells was inhibited by the presence of fucose and galactose, these sugars had little effect on the binding of3H-LTA to epithelial cells. In contrast, the high adhesion of M+ strains but not M mutants to pharyngeal cells suggested that M-protein may play an important role. This possibility was supported by the observation that3H-labeled purified type 6 M-protein bound in higher concentrations to human pharyngeal epithelial cells than to human buccal cells. Furthermore, human pharyngeal epithelial cells were estimated to contain larger numbers of binding sites for M-protein than buccal cells, whereas the affinity of M-protein was similar to both cell types. These adsorption parameters are similar to those previously established for intact streptococcal cells.  相似文献   
55.
Chalcone synthase (CHS) genes in Petunia hybrida comprise a multigene family containing at least 7 complete members in the strain Violet 30 (V30). Based on a high sequence homology in both coding and non-coding sequence, a number of CHS genes can be placed into two subfamilies. By restriction fragment length polymorphism (RFLP) analysis it was shown that both chromosomes II and V carry one of these subfamilies, in addition to the other CHS genes identified so far. Members of a subfamily were found to be closely linked genetically. Analysis of the Petunia species that contributed to the hybrid nature of P. hybrida (P. axillaris, P. parodii, P. inflata and P. violacea) shows that none of the CHS gene clusters is specific for either one of the parents and therefore did not arise as a consequence of the hybridization. The number of CHS genes within a subfamily varies considerably among these Petunia species. From this we infer that the CHS subfamilies arose from very recent gene duplications.  相似文献   
56.
Summary Intracellular concentrations of free amino acids (FAA) in the intertidal copepodTigriopus californicus increase in response to hyperosmotic stress and decrease in response to hypo-osmotic stress. The purpose of this study was to determine if exposure to repeated bouts of osmotic stress resulted in changes in FAA accumulation or the degree of FAA retention in subsequent episodes. Five groups ofT. californicus were exposed for 22 days to a fluctuating salinity regime which consisted of 24 h at 100% seawater followed by 24 h at either 90, 80, 70, 60 or 50% seawater (11 cycles). After the tenth exposure to 100% seawater, individuals from each treatment group were analyzed for alanine and proline concentration. Alanine and proline accumulation generally increased in proportion to the osmotic stress up to 60–100% seawater — additional osmotic stress failed to increase total accumulation. Prior exposure to fluctuating salinity increased the extent of alanine and proline retention observed upon transfer to a hypo-osmotic medium. The treatment group which had experienced the most extreme fluctuation (50–100% seawater) retained alanine and proline levels approximately 10- and 20-fold higher, respectively, than controls. A less severe salinity fluctuation was required to elicit this response for alanine (90–100% seawater) than for proline (60–100% seawater). Previous exposure to fluctuating salinity also resulted in increased alanine and proline accumulation in subsequent episodes of hyperosmotic stress. 24 h after transfer from 50 to 100% seawater, alanine and proline levels in the conditioned copepods were approximately 3- and 7-fold higher, respectively, than in copepods which had not been cycled. This facilitation in alanine and proline accumulation occurred after 10 and 11 cycles, respectively. Of the increased accumulation in alanine and proline, 7.0% and 22.5%, respectively, could be accounted for by the higher degree of FAA retention while under hypo-osmotic conditions.Abbreviation FAA free amino acids  相似文献   
57.
The TE671 human medulloblastoma cell line expresses a variety of characteristics of human neurons. Among these characteristics is the expression of membrane-bound high-affinity binding sites for alpha-bungarotoxin, which is a potent antagonist of functional nicotinic acetylcholine receptors on these cells. These toxin binding sites represent a class of nicotinic receptor isotypes present in mammalian brain. Treatment of TE671 cells during proliferative growth phase with nicotine or carbamylcholine, but not with muscarine or d-tubocurarine, induced up to a five-fold increase in the density of radiolabeled toxin binding sites in crude membrane fractions. This effect was blocked by co-incubation with the nicotinic antagonists d-tubocurarine and decamethonium, but not by mecamylamine or by muscarinic antagonists. Following a 10-13 h lag phase upon removal of agonist, recovery of the up-regulated sites to control values occurred within an additional 10-20 h. These studies indicate that the expression of functional nicotinic acetylcholine receptors on TE671 cells is subject to regulation by nicotinic agonists. Studies of the murine CNS have consistently indicated nicotine-induced up-regulation of nicotinic acetylcholine receptors, thereby supporting the identification of the toxin binding site on these cells as the functional nicotinic receptor. Although a mechanism for this effect is not apparent, nicotine-induced receptor blockade does not appear to be involved.  相似文献   
58.
Membrane proteins labeled in vivo from cold-acclimated and ABA-treatedalfalfa seedlings of two cultivars differing in cold-tolerancehave been compared by SDS polyacrylamide gel electrophoresisand fluorography. Results thus obtained indicate that severalqualitative changes occur in the membrane protein-profile specificallyin response to cold acclimation or ABA treatment. While somepolypeptides disappear from the non-acclimated protein patterns,others specifically appear in response to acclimation. Separationby two-dimensional gel electrophoresis and fluorography hasconfirmed the above and has enabled us to detect two proteinsof Mr 42 kDa and 120 kDa that are induced by both acclimationand ABA treatment in the freezing tolerant cultivar. (Received November 30, 1987; Accepted February 22, 1988)  相似文献   
59.
A microculture system for mouse cerebellar cells has been used to identify an immune activity, raised in rabbits against postnatal cerebellar cells, that blocks neuron-glial interactions in vitro. In the presence of blocking antibodies, stable neuron-glial contacts did not form and neuronal induction of glial process outgrowth did not occur. Subsequently, neurons were randomly arranged in the cultures rather than organized along the arms of astroglia. We have named the immune activity that blocks neuron-astroglial interactions anti-astrotactin. Partial purification of the anti-astrotactin blocking antibodies was obtained by cellular absorption with PC12 cells, a clonal cell line which expresses both the N-CAM and NILE (Ng-CAM, L1) glycoproteins. Subsequent absorption with purified cerebellar granule cells, but not with astroglial cells, removed the blocking activity, suggesting that the antigen(s) bound by blocking antibodies are neuronal. Immunoprecipitation of [35S]methionine- or [3H]fucose-radiolabeled Triton extracts of early postnatal cerebellar cells showed that the unabsorbed antiserum recognized a large number of proteins. Among these were bands with apparent molecular masses of N-CAM (180 and 140 kD) and NILE (230 kD). After absorption of the immune serum with PC12 cells, the number of bands recognized by the antiserum was reduced to a prominent band at 100 kD and a diffuse smear of material between 80 and 90 kD. The prominent band at 100 kD was removed by subsequent absorption of the immune serum with granule cells, a step which removed the blocking activity in the cerebellar microculture assay. Further evidence suggests that the astrotactin activity is missing or defective on granule cells from the neurological mutant mouse weaver, an animal that suffers a failure of glial-guided neuronal migration. When anti-astrotactin Fab fragments were pre-absorbed with weaver cerebellar neurons and then tested in the functional assay of neuron-glial interactions, the immune blocking activity was not removed. In contrast, wild-type cerebellar neurons removed the anti-astrotactin blocking activity under the same conditions. Subsequently, when [3H]fucose-radiolabeled Triton extracts of weaver and normal cells were immunoprecipitated with whole or PC12-absorbed anti-astrotactin antiserum, the intensity of the band at 100 kD was reduced by 95% in weaver cells.  相似文献   
60.
In toto staining and preservation of peripheral nervous tissue   总被引:2,自引:0,他引:2  
A simple quantitative modification of the in toto staining technique for nervous networks of Sihler is described. The results are demonstrated on the innervation pattern of the hard palate of the rat. Formalin fixed hard palates of rat were macerated and bleached in an aqueous solution of 3% potassium hydroxide with a few drops of 3% hydrogen peroxide added. Thereafter, the specimens were decalcified in Sihler's solution I (1 part glacial acetic acid, 1 part pure glycerin and 6 parts 1% chloral hydrate), the process being controlled by radiography. The specimens were next stained in Sihler's solution II (1 part Ehrlich's hematoxylin, 1 part pure glycerin and 6 parts 1% chloral hydrate). After staining, the non-nervous tissues were destained in Sihler's solution I. Destaining was checked microscopically and was stopped before the finest branches of the nerves began to fade. The specimens were then washed in a weak aqueous solution of lithium carbonate and cleared in increasing concentrations of glycerin. Good visualization of nervous structures and a deep field of observation resulted; orientation of the peripheral nerves with respect to surrounding structures was readily seen and a three-dimensional image of the nervous networks was obtained.  相似文献   
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