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At least 595 records · Page 33Linked to original sources
PubMed1982

Effect of His-Phe, a competitive inhibitor of histidine decarboxylase, on gastric acid secretion in chronic gastric fistula rats: delay in acid secretion response to pentagastrin.

The dipeptide His-Phe, earlier shown to inhibit mammalian histidine decarboxylase, was analysed concerning its effect in vivo on pentagastrin-induced gastric acid secretion. Chronic gastric fistula rats were used and the effectors in saline were given as continuous i.v. infusions while acid was collected from the fistula. Addition of pentagastrin to the infusion solution resulted in an immediate increase in the acid output of the control runs. In the His-Phe experiments the dipeptide was introduced one hour before pentagastrin. A significant decrease in the acid output was obtained. This effect was optimal at a dose of about 6 mg/h and during the first few hours of the experiments. In spite of the continuous His-Phe infusion the acid secretion increased with time to the control values. These results are discussed in relation to preliminary observations on effects of alpha-fluoromethyl histidine on gastric acid secretion and the effect of this and His-Phe on gastric histamine content and histidine decarboxylase activity.

Animals↗
PubMed1981

Role of calcium in exocrine pancreas secretion. VII. Effect of sodium on enzyme secretion and calcium metabolism in rabbit pancreatic fragments and acinar cells.

1. The role of sodium in the pancreatic stimulus-secretion coupling has been studied. 2. Reduction of the extracellular sodium concentration or addition of ouabain to the medium inhibits the stimulation of enzyme secretion by carbachol. 3. Incubation in low sodium medium or in the presence of ouabain increases the exchangeable calcium content, but not the total calcium content of acinar cells. 4. Depending on preincubation time and the substrate replacing sodium in the low sodium medium, the carbachol-induced Ca45(2)+ efflux may be blocked, but it is not blocked by addition of ouabain to a normal Na+ medium. 5. Stimulation of enzyme secretion by the calcium ionophore A23187 in the presence of external calcium is inhibited in low sodium as well as in ouabain containing media. 6. These findings suggest that reduction of the Na+ gradient across the plasma membrane blocks the coupling between intracellular calcium release and exocytosis, while under certain conditions it also blocks the coupling between hormone-receptor interactions and intracellular calcium release.

Animals↗
PubMed1987

Regulation of antibody secretion by hybridoma cells. I. Suppression of antibody secretion by coculture of hybridoma cells with idiotype-induced suppressor cells.

In this study, we have demonstrated that antibody secretion by hybridoma cell lines can be down-regulated by idiotype-specific immune spleen cells or by nylon wool nonadherent spleen cells. This suppression of antibody secretion can be abolished by treating the idiotype-specific immune spleen cells with anti-Thy 1.2 plus complement. The hybridoma we used for most of our experiments secretes IgM specific for the cross-reacting haptens 2,4,6-trinitrophenyl (TNP) and 2,4-dinitrophenyl (DNP). Suppression was achieved by direct coculture of hybridoma cells with immune cells from animals which were injected with affinity-purified hybridoma antibody-coupled syngeneic spleen cells. The suppressed and control cultures contained similar numbers of viable hybridoma cells, suggesting that a simple cytotoxic effect is not responsible. Idiotype specificity was established in experiments showing that two idiotype immune animals immunized with antibody from two different IgM anti-TNP hybridomas could suppress the hybridoma to which they were immunized but could not affect the other hybridoma. Immune spleen cells required 3-4 days of coculture with hybridoma cells before maximum suppression was achieved. The kinetics of the response suggest that the final effector suppressor cell is generated during the coculture period and that a second signal, perhaps a product of the hybridoma cells, may be required.

Animals↗
PubMed1989

Regulation of antibody secretion by hybridoma cells. II. Mechanism of idiotype-induced suppression of antibody secretion by hybridoma cells.

We have previously reported that antibody secretion by B.22 hybridoma cells can be suppressed in an MHC-restricted manner, by idiotype-specific T cells. It was shown that T cells of both helper and suppressor phenotypes are involved, and that the suppression is mediated by soluble factors. In the present paper, we have characterized the effects of T-cell-mediated suppression at the level of B.22 antibody mRNA expression and stability. Nuclear run-on analysis comparing suppressed and control B.22 cells indicates no change in the transcription rates of heavy and light chains. Northern blot analysis demonstrates that steady-state levels of heavy and light chain mRNAs are also unchanged. Thus, the suppression of antibody secretion by B.22 cells probably occurs at the levels of translation or secretion.

Animals↗
PubMed1982

Dopaminergic mechanisms regulating prolactin secretion in patients with prolactin-secreting pituitary adenoma. Long-term studies after selective transsphenoidal surgery.

Twenty-seven female patients with prolactin-secreting pituitary microadenoma, were studied at different intervals following selective transsphenoidal removal of the tumor. Postoperatively, all patients had normal prolactin (PRL) levels and regular menstrual cycles were restored. Sixteen of 27 patients showed positive responses to TRH and metoclopramide (MCP) within 1 mo after surgery. On the contrary, 9 patients showed evaluation of these patients demonstrated that normal neuroendocrine relationships were restored after several months since positive PRL responses to TRH and MCP could be elicited in such patients. The remaining 2 patients who showed basal PRL levels in the upper range of normal, exhibited negative responses to TRH and MCP. These patients had progressively to TRH and MCP exhibited 10-20 mo after surgery a normal decrease in PRL levels following administration of carbidopa plus L-Dopa. Negative responses to carbidopa plus L-Dopa were instead obtained in 6 postoperative patients with elevated PRL levels and negative responses to TRH and MCP. These results suggest that: 1) Hyperprolactinemia induced by "autonomous" pituitary adenomas increases hypothaLamic dopamine (DA) secretion, which in turn inhibits PRL secretion by nonadenomatous lactotropes. 2) Total selective removal of the microadenoma acutely decreases PRL concentration, but a functional inhibition of the normal lactotrope can persist for a period of few months following surgery in a certain number of patients. 3) Prolonged reduction of PRL concentration is accompanied to a normal DA tone with reestablishment of normal neuroendocrine relationships.

Adenoma↗
PubMedDate not supplied

Stimulatory effect of prolactin on human placental progesterone secretion at term in vitro: possible inhibitory effect on oestradiol secretion.

Maternal and fetal circulating prolactin (PRL) increases 10-fold compared with the non-pregnant state. We examined the effect of PRL upon placental steroidogenesis. It had a significant (P less than 0.05) time-dependent stimulatory effect upon placental explants/P4 accumulation and secretion into the medium. The maximal stimulatory effect (two-fold) in dose-dependent experiments was found to be 200 ng/ml. The effect of PRL upon oestradiol secretion was mainly inhibitory. This inhibition was most pronounced at 200 ng/ml. In conclusion, placental steroid secretion is modulated by PRL. This effect occurs mainly at concentrations seen in the placenta at term, suggestive of its physiologic role.

Dose-Response Relationship, Drug↗
PubMed1991

Purification and determination of the NH2-terminal amino acid sequence of mouse alpha-amylase secreted from Saccharomyces cerevisiae: correct processing of the secretion signal from pGKL killer 28 kDa precursor protein.

We have previously reported the construction of recombinant mouse salivary alpha-amylase secretion vector in Saccharomyces cerevisiae utilizing novel yeast secretion signal derived from killer 28 kDa precursor protein. Here, we have first purified recombinant mouse alpha-amylase to homogeneity from the culture medium of S. cerevisiae, and determined its NH2-terminal amino acid sequence. The sequencing data indicated that the 28 kDa killer secretion signal-alpha-amylase fusion protein was cleaved accurately at its native processing site, and that both the core-glycosylated and non-glycosylated alpha-amylases possessed the same NH2-terminal amino acid sequences.

Amino Acid Sequence↗
PubMed1991

High-level secretion of human apolipoprotein E produced in Escherichia coli: use of a secretion plasmid containing tandemly polymerized ompF-hybrid gene.

A gene encoding the mature form of human apolipoprotein E (h-apoE) was fused to the secretion signal coding sequence of the Escherichia coli major outer membrane protein F (ompF) which was preceded by a consensus Shine-Dalgarno sequence. Two copies of this hybrid gene were inserted tandemly into an expression vector and expressed in E. coli under the transcriptional control of two tac promoters regulated by lac repressors. By the addition of isopropyl-beta-D-thiogalactopyranoside (IPTG) to the growth media, cells synthesized h-apoE at the level of 27.2 micrograms per A600 and up to 22% of the total cellular protein. The h-apoE produced by E. coli was processed precisely, secreted into the periplasmic space and formed protein aggregates there. However, despite aggregation, they were easily dissolved in water and actively formed protein-lipid complexes with dimyristoyl phosphatidyl choline (DMPC). These results demonstrated that E. coli cells are able to synthesize and secrete a large amount of active h-apoE using a prokaryotic signal sequence.

Amino Acid Sequence↗
PubMed1985

Secretion of mature mouse interleukin-2 by Saccharomyces cerevisiae: use of a general secretion vector containing promoter and leader sequences of the mating pheromone alpha-factor.

We have constructed a general expression vector which allows the synthesis and secretion of processed gene products in Saccharomyces cerevisiae. This vector contains yeast DNA, including the promoter of the mating pheromone (alpha-factor), its downstream leader sequence, and the TRP5 terminator. A cDNA [encoding mature mouse interleukin-2 (IL-2); Yokota et al., Proc. Natl. Acad. Sci. USA 82 (1984) 68-72] was fused immediately downstream to the alpha-factor leader sequence. The resulting recombinant plasmid directed the synthesis of mature mouse IL-2 in S. cerevisiae, with most of the T-cell growth-factor (TCGF) activity secreted into the culture fluid and extracellular space. TCGF activities in the cell extract, as well as in the culture fluid, increased in parallel with cell growth. Production of mature mouse IL-2 was inhibited by tunicamycin (TM), with precursor molecules accumulating in the cell extract. The precursor was processed accurately at the junction between the alpha-factor peptide leader sequence and the coding sequence downstream, yielding mature IL-2. The Mr of the secreted mouse IL-2 determined by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) was 17 kDal, a value expected for the mature mouse IL-2 polypeptide based on the nucleotide (nt) sequence.

Amino Acid Sequence↗
PubMed1985

Synthesis and secretion of biologically active mouse interferon-beta using a Bacillus subtilis alpha-amylase secretion vector.

Mouse interferon-beta (IFN-beta) cDNA, whose signal sequence had been removed by BAL 31 digestion, was introduced into a Bacillus subtilis secretion vector constructed by using the promoter and signal sequence of the B. subtilis alpha-amylase gene. The resultant chimeric plasmids were transferred into B. subtilis 207-25. Four kanamycin-resistant transformants were selected by both colony hybridization and a new immunoblot method for secretory proteins. They secrete the proteins which cross-react with sheep anti-mouse IFN-beta serum into the culture medium. One of them expressed a high IFN-beta activity as assayed by the L cell and vesicular stomatitis virus system, while the other three showed weak or little IFN activities. Based on our previous study [Ohmura et al., Nucl. Acids Res. 12 (1984) 5307-5319], it was suggested that the secreted IFN molecules are hybrid proteins in which the NH2-terminal region consists of part of the alpha-amylase signal peptide. Nucleotide sequence analysis revealed that plasmid pTUB502, which expressed high IFN activity, is joined to the mouse IFN-beta gene from the codon position 6 of its mature protein. The other three plasmids, pTUB506, pTUB509, and pTUB519, contain the mouse IFN-beta gene from the codon positions 3, 1, and -5, respectively. The NH2-terminal region of the mouse IFN-beta seems to be closely related to its biological activity.

Animals↗
PubMed2005

Norepinephrine in mice inhibits secretion of splenic IL-6 during the dark period but stimulates its secretion in the light period--possible role of the corticosterone tone.

In early morning hours, a rise of serum cytokines such as IL-6 was described. This study aimed to find reasons for this phenomenon focussing on NE and corticosterone. Mouse spleen slices were electrically stimulated (ES) in a microsuperfusion chamber in order to release endogenous NE. ES inhibited IL-6 secretion when animals were sacrificed at 03:00 and 06:00 (both p<0.001) but it increased its secretion from spleen slice removed at 09:00 (p=0.026). Prior administration of corticosterone or the glucocorticoid antagonist RU486 abrogated these ES effects. Endogenous NE via alpha- and beta-adrenoceptors mediated this time-dependent differential effects. This study demonstrates that cooperation of endogenous NE and corticosterone are involved in a time-dependent fall or rise of splenic IL-6 secretion.

Adrenergic alpha-Antagonists↗
PubMed2005

Effects of lichen heteroglycans on proliferation and IL-10 secretion by rat spleen cells and IL-10 and TNF-alpha secretion by rat peritoneal macrophages in vitro.

Four polysaccharides Pc-1, Pc-2, Pc-3 and Pc-4 were isolated from water and alkali extracts of the lichen Peltigera canina using ethanol fractionation, gel filtration and preparative HP-GPC. The monosaccharide composition was determined by methanolysis and GC and showed mannose and galactose as the predominating structural units. The mean M(r) was determined by HP-GPC. The heteroglycans were tested for in vitro immunomodulating activities and showed mitogenic activity in rat spleen cell proliferation assay and stimulated IL-10 secretion. In rat peritoneal macrophages, the heteroglycans stimulated TNF-alpha secretion, but not IL-10 secretion. These results indicate that the polysaccharides influence cells of the immune system both from the innate and the adaptive systems.

Animals↗
PubMed1999

Effect of opioid blockade on insulin and growth hormone (GH) secretion in patients with polycystic ovary syndrome: the heterogeneity of impaired GH secretion is related to both obesity and hyperinsulinism.

OBJECTIVE: To investigate the involvement of opioid tone, obesity, and hyperinsulinemia in GH secretion in women with polycystic ovary syndrome (PCOS). DESIGN: Controlled clinical study. SETTING: Catholic University of Sacred Heart School of Medicine in Rome, Italy. PATIENT(S): Twenty-two patients with PCOS and 14 healthy, normally ovulating volunteers, matched for age and body mass index. INTERVENTION(S): Patients underwent a GH-releasing hormone (GHRH) test and an oral glucose tolerance test before and after 4-5 weeks of treatment with 50 mg/d of naltrexone. MAIN OUTCOME MEASURE(S): Serum concentrations of GH, insulin, glucose, steroids, and gonadotropins, as well as the GH area under the curve (AUC-GH) and the insulin area under the curve (AUC-I), were measured before and after naltrexone treatment. RESULT(S): In patients with PCOS, the administration of naltrexone increased the GH response to the GHRH test without interfering with the insulin response to the oral glucose tolerance test. However, the GH response to the GHRH test was improved significantly only in lean patients with PCOS, whereas obese patients with PCOS did not show any improvement in GH secretion. In obese control subjects, the treatment reduced plasma basal insulin concentrations and increased the AUC-GH, whereas in lean control subjects, the treatment reduced the GHRH-induced response. In normoinsulinemic patients with PCOS, the GH response to the GHRH test increased significantly after treatment, whereas the AUC-I was not affected. In hyperinsulinemic patients with PCOS, treatment with naltrexone significantly reduced the AUC-I, whereas the AUC-GH increased only in lean hyperinsulinemic patients with PCOS. CONCLUSION(S): Naltrexone treatment improves GHRH-induced GH secretion in patients with PCOS. However, this GH response is heterogeneously represented in relation to both obesity and hyperinsulinism.

Adult↗
PubMed1995

Stable secretion of a soluble, oligomeric form of rabies virus glycoprotein: influence of N-glycan processing on secretion.

Rabies virus glycoprotein (RGP) is a 505 amino acid type I transmembrane glycoprotein that is important in the pathogenesis of rabies virus infection. RGP also stimulates the development of neutralizing antibodies by the host. N-linked glycosylation is required for both cell surface expression and immunogenicity of RGP. In the current study, a soluble form of RGP, constructed by insertion of a stop codon external to the transmembrane domain, was expressed in transfected Chinese hamster ovary cells. The soluble form of RGP was found to be appropriately antigenic and immunogenic. Similar to full-length RGP, the soluble form was assembled into homodimers and homotrimers. Core glycosylation was required for secretion of soluble RGP and cell surface expression of full-length RGP. In addition, initial glucose trimming of the N-glycans was necessary and sufficient for secretion of soluble RGP and cell surface expression of full-length RGP. Further N-glycan processing was not required for secretion or cell surface expression of soluble or full-length RGP, respectively.

Animals↗
PubMed2004

Avian exocrine secretions. I. Chemical characterization of the volatile fraction of the uropygial secretion of the green woodhoopoe, Phoeniculus purpureus.

Using gas chromatography-mass spectrometry in conjunction with auxiliary techniques such as solid phase microextraction and determination of double bond positions by means of dimethyl disulfide derivatization, 45 constituents of the uropygial secretion of the green woodhoopoe, Phoeniculus purpureus, have been identified. The majority of these constituents are long-chain branched and unbranched alkanes, and (Z)-alkenes such as (Z)-9-tricosene, and a number of unidentified wax esters. The more volatile fraction of the secretion contained short-chain fatty acids, aldehydes, aliphatic and heterocyclic aromatic amines, ketones, and dimethyl sulfides. This group of volatile compounds is responsible for the obnoxious odor of the secretion and also for its defensive action against predators.

Aldehydes↗
PubMed1978

Studies on secretion and endocytosis of macromolecules by cultivated skin fibroblasts. Effects of anti-microtubular agents on secretion and endocytosis of lysosomal hydrolases and of sulphated glycosaminoglycans.

Fibroblasts were incubated in the presence of the anti-microtubular drugs colchicine, vinblastine and vincristine. In concentrations between 10nm and 1 mM these drugs stimulated the secretion of beta-N-acetylglucosaminidase, alpha-N-acetylglucosaminidase and beta-glucuronidase, but not of beta-galactosidase. The endocytosis of beta-N-acetylhexosaminidase and alpha-N-acetylglucosaminidase, but not of beta-glucuronidase, was inhibited at drug concentrations higher than 0.1 micrometer. Formation, secretion and association with the cell membrane of sulphated proteoglycans were not affected by anti-microtubular drugs. Endocytosis of sulphated proteoglycans and their subsequent degradation was inhibited by drug concentrations above 0.1 micrometer. The inhibition of intracellular glycosaminoglycan degradation led to a moderate storage of these compounds. These results suggest that microtubules participate in the control of secretion and endocytosis of lysosomal enzymes, and in the endocytosis and degradation of lysosomal substrates such as sulphated proteoglycans.

Acetylglucosaminidase↗
PubMed1984

The effects of colchicine on secretion into bile of bile salts, phospholipids, cholesterol and plasma membrane enzymes: bile salts are secreted unaccompanied by phospholipids and cholesterol.

Colchicine, a drug which interferes with microtubular function, has no effect on the secretion of taurodehydrocholate into bile; it is therefore suggested that bile salts are unlikely to be packaged in vesicles during cellular transit from sinusoidal to canalicular membranes. Colchicine greatly reduces the secretion of phospholipid and cholesterol into bile; it is suggested that this is due to an interruption in the supply of vesicles bringing lipids to repair the canalicular membrane during bile salt output. In the absence of the protective effect of a continuous supply of repair vesicles, micelleforming bile salts damage the canalicular membrane; the increased concentration of plasma membrane enzymes in bile and the increased aspartate aminotransferase activity in plasma and bile are evidence of this damage. Damage to the canalicular membrane may also be an explanation for the reduction in taurocholate transport and the taurocholate-induced cholestasis which are seen with colchicine-treated livers. Such membrane damage is not observed in colchicine-treated livers during the secretion of the non-micelle forming bile salt, taurodehydrocholate.

Animals↗
PubMed2002

Impaired estrogen-induced negative feedback on gonadotropin secretion in patients with gonadotropin-secreting and nonfunctioning pituitary adenomas.

BACKGROUND: Several in vitro studies suggest that gonadotropin-secreting pituitary adenomas (Gn-omas) and non functioning pituitary adenomas (NFPA) originate from gonadotroph cells. Patients with Gn-oma and NFPA frequently show abnormal gonadotropin response to TRH. The aim of the study was to investigate whether the estrogen-induced negative feedback is operating in either patients with Gn-oma or NFPA. MATERIALS AND METHODS: Serum gonadotropin levels were evaluated at 24 h after ethinylestradiol administration (1 mg per os; EE2 test) in seven patients with a diagnosis of Gn-oma, based on the presence of high follicle-stimulating hormone (FSH) and/or lutenising hormone (LH) levels with normal or high levels of sex steroids, in 22 patients with NFPA with normal or low levels of gonadotropin and sex steroids, and 30 sex- and age-matched healthy subjects. A normal response to EE2 test was arbitrarily defined as a serum LH and FSH decrease of at least 40 and 30% below basal levels. RESULTS: Among patients with Gn-oma, only one had a normal FSH inhibition and another, a normal LH inhibition. Among the 22 patients with NFPA, the EE2 test caused a normal FSH or LH reduction in 10 and 15, respectively, while a normal reduction of both FSH and LH was observed in nine. CONCLUSIONS: The study demonstrates that estrogen-induced negative feedback of gonadotropin secretion is disrupted in almost all patients with Gn-oma and in half of those with NFPA. This defective feedback is reminiscent of the resistance to thyroid hormones and glucocorticoids observed in patients with thyroid-stimulating hormone- (TSH-) and adrenocorticotropic hormone- (ACTH-)secreting adenomas, respectively.

Adenoma↗