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11.
TGF-beta occurs in a latent complex of high Mr. We report the cDNA cloning and an initial structural and functional characterization of a component of the large latent TGF-beta 1 complex, denoted TGF-beta 1 binding protein (TGF-beta 1-BP). Most of the sequence of fibroblast TGF-beta 1-BP is made up of cysteine-rich repeats of two different kinds; there are 16 EGF-like repeats and three repeats with a distant resemblance to EGF, but of a distinct type hitherto not found in any other protein. beta-hydroxylated asparagine residues were identified in two of the EGF-like repeats. TGF-beta 1-BP purified from human platelets is considerably smaller than the fibroblast form (125-160 kd vs. 170-190 kd), suggesting that there is alternative splicing of the TGF-beta 1-BP gene or that TGF-beta 1-BP undergoes cell-specific proteolysis. TGF-beta 1-BP was found not to bind and inactive TGF-beta 1; its role in the latent complex is discussed.  相似文献   
12.
Y Pouny  D Rapaport  A Mor  P Nicolas  Y Shai 《Biochemistry》1992,31(49):12416-12423
Dermaseptin, a 34 amino-acid residue antimicrobial polypeptide [Mor, A., Nguyen, V. H., Delfour, A., Migliore-Samour, D., & Nicolas, P. (1991) Biochemistry 30, 8824-8830] was synthesized and selectively labeled at its N-terminal amino acid with either 7-nitrobenz-2-oxa-1,3-diazole-4-yl (NBD), rhodamine, or fluorescein. The fluorescent emission spectra of the NBD-labeled dermaseptin displayed a blue-shift upon binding to small unilamellar vesicles (SUV), reflecting the relocation of the fluorescent probe to an environment of increased apolarity. Titrations of solutions containing NBD-labeled dermaseptin with SUV composed of zwitterionic or acidic phospholipids were used to generate binding isotherms, from which were derived surface partition constants of (0.66 +/- 0.06) x 10(4) M-1 and (2.8 +/- 0.3) x 10(4) M-1, respectively. The shape of the binding isotherms, as well as fluorescence energy transfer measurements, suggests that some aggregation of membrane-bound peptide monomers occurs in acidic but not in zwitterionic vesicles. The preferential susceptibility of the peptide to proteolysis when bound to zwitterionic but not to acidic SUV suggests that these aggregates might then penetrate a relatively short distance into the hydrophobic region of the acidic membrane. Furthermore, the results provide good correlation between the peptide's strong binding and its ability to permeate membranes composed of acidic phospholipids, as revealed by a dissipation of diffusion potential and a release of entrapped calcein from SUV.  相似文献   
13.
Pasteuria penetrans spore adhesion to Meloidogyne javanica second-stage juveniles (J2) was examined following several different pretreatments of the latter. The detergents sodium dodecyl sulfate and Triton X-100, the carbohydrates fucose and α-methyl-D-mannoside, and the lectins concanavalin A and wheat germ agglutinin reduced spore attachment. Spores exposed to M. javanica surface coat (SC) extract exhibited decreased adherence to the J2 surface. Second-stage juveniles that had been treated with antibodies recognizing a 250-kDa antigen of J2 SC extract had fewer spores attached to their surfaces, as compared to nontreated J2, except in the head region. This inhibition pattern was similar to that of antibody-labelling on M. javanica J2 as observed by electron microscopy. It is suggested that several SC components, such as carbohydrate residues, carbohydrate-recognition domains, and a 250-kDa antigen, are involved in P. penetrans spore attachment to the surface of M. javanica.  相似文献   
14.
InSaccharomyces cerevisiae, most of the cellular chitin is produced by chitin synthase III, which requires the product encoded by theCSD2/CAL1/DIT101/KT12 gene. We have identified, isolated and structurally characterized aCSD2/CAL1/DIT101/KT12 homologue in the filamentous ascomyceteNeurospora crassa and have used a reverse genetics approach to determine its role in vivo. The yeast gene was used as a heterologous probe for the isolation of aN. crassa gene (designatedchs-4) encoding a polypeptide belonging to a class of chitin synthases which we have designated class IV. The predicted polypeptide encoded by this gene is highly similar to those ofS. cerevisiae andCandida albicans. N. crassa strains in whichchs-4 had been inactivated by the Repeat-Induced Point mutation (RIP) process grew and developed in a normal manner under standard growth conditions. However, when grown in the presence of sorbose (a carbon source which induces morphological changes accompanied by elevated chitin content), chitin levels in thechs-4 RIP strain were significantly lower than those observed in the wild type. We suggest that CHS4 may serve as an auxiliary enzyme inN. crassa and that, in contrast to yeasts, it is possible that filamentous fungi may have more than one class IV chitin synthase.A. Beth Din and C. A. Specht contributed equally to this work  相似文献   
15.
Taurine concentration was reduced by 40 and 65%, respectively in rat cerebellar astrocytes grown in a chemically defined medium or in culture medium containing a blocker of taurine transport (GES). Cell volume in these taurine deficient cells was 10%–16% higher than in controls. When challenged by hyposmotic conditions, astrocytes release taurine and this efflux contributes to the volume regulatory decrease observed in these cells. Taurine deficient astrocytes showed a less efficient volume recovery as compared to controls with normal taurine levels. Exposed to 50% hyposmotic medium, astrocytes with normal taurine concentration recovered 60% of their original volume whereas taurine deficient cells recovered only 30–35%. Similarly, in 30% hyposmotic medium, taurine deficient astrocytes recovered only 40% as compared to 75% in controls. No compensatory increases in the efflux of other osmolytes (free amino acids or potassium) were observed during regulatory volume decrease in taurine deficient astrocytes.  相似文献   
16.
The effects of cimetidine (12.5 mg i.m.) and atropine (0.125 mg i.m.) were studied on the basal (BAO) and pentagastrin (6 micrograms X kg-1 s.c.)-stimulated (MAO) gastric acid secretion; the gastric mucosal microbleeding provoked by one-day treatment with indomethacin (4 X 25 mg orally) in patients with chronic disorders of the joints. The extent of the gastric microbleeding was measured by spectrophotometric determination of haemoglobin in gastric lavage fluid. The aims of this study were to determine the doses of cimetidine and atropine in humans without any significant inhibitory effects either on the basal or on the maximal gastric acid output to evaluate the cytoprotective action of these doses of cimetidine and atropine on the indomethacin-induced gastric microbleeding in the man. It was found that cimetidine (12.5 mg i.m.) and atropine (0.125 mg i.m.) did not cause any significant inhibition either of the BAO or of the MAO; indomethacin (4 X 25 mg orally) significantly increased gastric microbleeding in the patients; cimetidine and atropine, in the above doses, were able to prevent significantly indomethacin-induced gastric microbleeding in the patients. These results provide evidence for the existence of gastric cytoprotective effects of cimetidine and atropine in humans.  相似文献   
17.
G. Bufler  Y. Mor  M. S. Reid  S. F. Yang 《Planta》1980,150(5):439-442
The rise in ethylene production accompanying the respiration climacteric and senescence of cut carnation flowers (Dianthus caryophyllus L. cv. White Sim) was associated with a 30-fold increase in the concentration of 1-aminocyclopropane-1-carboxylic acid (ACC) in the petals (initial content 0.3 nmol/g fresh weight). Pretreatment of the flowers with silver thiosulfate (STS) retarded flower senescence and prevented the increase in ACC concentration in the petals. An increase in ACC in the remaining flower parts, which appeared to precede the increase in the petals, was only partially prevented by the STS pretreatment. Addition of aminoxyacetic acid (2 mM) to the solution in which the flowers were kept completely inhibited accumulation of ACC in all flower parts.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AOA -aminoxyacetic acid - STS silver thiosulfate complex  相似文献   
18.
We have demonstrated previously that 17β-estradiol (E2) stimulates proliferation of skeletal tissues, both in vivo and in vitro, as measured by increased DNA synthesis and creatine kinase (CK) specific activity. The effect of E2 on bone is sex specific. E2 is active only in females and androgens only in males. By contrast, in cartilage of both sexes, dihydrotestosterone (DHT) as well as E2 stimulates CK specific activity and DNA synthesis. In bone, we find that sex steroids stimulate skeletal cell proliferation in gonadectomized as well as in immature rats. Ovariectomized (OVX) rats, between 1 and 4 weeks after surgery, show stimulation of CK by E2. The basal activity and response of CK changes with the varying endogenous levels of E2 in cycling rats, in which the highest basal activity is at proestrus and estrus and the highest response is in diestrus. In rats of all ages tested, both the basal and stimulated specific activity of CK is higher in diaphysis and epiphysis than in the uterus, or in the adipose tissue adjacent to the uterus, which has a response similar to that of the uterus itself. The effect of E2 in vivo, and in chrondroblasts and osteoblasts in vitro, is inhibited by high levels of the antiestrogen tamoxifen which, by itself, in similar high concentrations, shows stimulatory effects. In addition to the sex steroids, skeletal cells are also stimulated by secosteroid and peptide calciotrophic hormones. The interactions of the sex steroids and the other calciotrophic hormones. These results provide the first steps towards understanding the regulation of bone cell proliferation and growth by the concerted action of a variety of hormones and growth factors.  相似文献   
19.
Ammonium-dependent induction of a GDH isozyme in oat leaveswas proportional to light intensity and inhibited by DCMU. Thestimulation of GDH synthesis in response to ammonia was partiallyrepressed by benzimidazole. The inducible (no. 1) and noninducible(no. 2) GDH isozymes wereseparated and purified by approximately54 and 24 fold respectively. The two isozymes were highly specificfor NAD and the rate of NADH oxidation was 7 to 9 times higherthan NAD reduction. Both isozymes showed similar Km values forsubstrates of the reductive amination reaction and pH optimafor NADH oxidation. The pH optima for NAD reduction were 9 and8.2 for isozymes1 and 2 respectively. The two isozymes had asimilar molecular weight, 2.2–2.4 x 105 but differed intheir isoelectric point and temperature sensitivity. Resultssuggest that the GDH isozymes in oat leaves are two differententities but might possess a similar metabolic function. (Received January 6, 1976; )  相似文献   
20.
Equations are developed which describe variable-volume cultivations, including fed-batch systems. An analogy is drawn between the quasi-steady state in variable-volume cultivation and a dynamic steady state in variable-flow, constant-volume chemostat bioreactors. Switching procedures are developed to give a steady-state transition from batch to fed-batch and to continuous operation. In this respect, considerations in the literature have been extended. Computer solutions of the governing differential equations verify the theory and provide insight into the behavior of variable-volume stirred tank reactors. Application of variable-volume cultivation as a tool in investigating growth rates at low substrate levels is suggested. Variable-volume bioreactor systems could be also to obtain controlled dynamic conditions for research or production purposes.  相似文献   
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