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At least 631 records · Page 35Linked to original sources
PubMed1991

Changes in uterine secretion of prostaglandin F2 alpha and luteal secretion of progesterone in response to oxytocin during the porcine estrous cycle.

The purpose of this experiment was to determine whether the ability of oxytocin to stimulate uterine secretion of prostaglandin F2 alpha (PGF2 alpha) and luteal secretion of progesterone changes during the porcine estrous cycle. Nineteen multiparous sows were observed for estrus. After one estrous cycle of normal length, sows were assigned randomly to receive an injection of oxytocin (30 IU, i.v.) in the EARLY (Days 4-6; n = 6), MID (Days 9-11; n = 7), or LATE (Day 15; n = 6) stage of the estrous cycle. Concentrations of 13, 14-dihydro-15-keto-PGF2 alpha (PGFM) and progesterone were determined in jugular venous serum samples collected at -60, -45, -30, -15, 0, 2, 5, 10, 15, 30, 45, 60, 90, and 120 min after injection of oxytocin. The magnitudes of the PGFM and progesterone responses and the area under the respective response curves (AUC) were calculated for each sow. Concentrations of PGFM did not change in response to oxytocin administered during the EARLY or MID portions of the estrous cycle. Concentrations increased rapidly in 4 of 6 sows that received oxytocin LATE in the estrous cycle. Both magnitude and AUC were greater LATE in the estrous cycle than at either EARLY or MID cycle (p less than 0.05). Thus, uterine secretory responsiveness to oxytocin develops between Days 11 and 15 postestrus in the sow. For progesterone, a transient increase was observed immediately following injection of oxytocin at MID cycle (p less than 0.05), but not at the other times examined. Therefore, oxytocin appears to be capable of stimulating secretion of progesterone from the functionally mature corpus luteum.

Animals↗
PubMed1999

Secretion of ovarian inhibin and its physiologic roles in the regulation of follicle-stimulating hormone secretion during the estrous cycle of the female guinea pig.

To characterize inhibin secretion during the estrous cycle in guinea pigs, the concentrations of plasma inhibin, estradiol, progesterone, and FSH were determined. A significant positive correlation was observed between inhibin and estradiol throughout the estrous cycle. Plasma inhibin and estradiol started to increase a few days before ovulation (Day 0 = day of estimated ovulation), and decreased after ovulation. These two hormones remained low during the luteal phase. The immunoreactivity of inhibin alpha, betaA, and betaB subunits was colocalized in the granulosa cells of one or two healthy large follicles in the ovary before ovulation. There was no positive reaction of inhibin alpha and beta subunits in the corpora lutea or other follicles. Ovariectomy resulted in an abrupt decrease in plasma inhibin and a significant increase in plasma FSH. Injection of anti-inhibin serum into adult female guinea pigs induced an elevation in plasma FSH in a dose-dependent manner. This report presents the first description of sequential changes in plasma inhibin and estradiol during the estrous cycle of guinea pigs. Results suggest that inhibin is secreted mainly by granulosa cells of a few healthy large follicles in the ovary and that it plays an important role in the regulation of FSH secretion during the estrous cycle in guinea pigs.

Animals↗
PubMed2006

A putative multicopper protein secreted by an atypical type II secretion system involved in the reduction of insoluble electron acceptors in Geobacter sulfurreducens.

Extracellular electron transfer onto Fe(III) oxides in Geobacter sulfurreducens is considered to require proteins that must be exported to the outer surface of the cell. In order to investigate this, the putative gene for OxpG, the pseudopilin involved in a type II general secretion pathway of Gram-negative bacteria, was deleted. The mutant was unable to grow with insoluble Fe(III) oxide as the electron acceptor. Growth on soluble Fe(III) was not affected. An analysis of proteins that accumulated in the periplasm of the oxpG mutant, but not in the wild-type, led to the identification of a secreted protein, OmpB. OmpB is predicted to be a multicopper protein, with highest homology to the manganese oxidase, MofA, from Leptothrix discophora. OmpB contains a potential Fe(III)-binding site and a fibronectin type III domain, suggesting a possible role for this protein in accessing Fe(III) oxides. OmpB was localized to the membrane fraction of G. sulfurreducens and in the supernatant of growing cultures, consistent with the type II secretion system exporting OmpB. A mutant in which ompB was deleted had the same phenotype as the oxpG mutant, suggesting that the failure to export OmpB was responsible for the inability of the oxpG-deficient mutant to reduce Fe(III) oxide. This is the first report that proposes a role for a multicopper oxidase-like protein in an anaerobic organism. These results further emphasize the importance of outer-membrane proteins in Fe(III) oxide reduction and suggest that outer-membrane proteins other than c-type cytochromes are required for Fe(III) oxide reduction in Geobacter species.

Bacterial Outer Membrane Proteins↗
PubMed2003

The secreted protein discovery initiative (SPDI), a large-scale effort to identify novel human secreted and transmembrane proteins: a bioinformatics assessment.

A large-scale effort, termed the Secreted Protein Discovery Initiative (SPDI), was undertaken to identify novel secreted and transmembrane proteins. In the first of several approaches, a biological signal sequence trap in yeast cells was utilized to identify cDNA clones encoding putative secreted proteins. A second strategy utilized various algorithms that recognize features such as the hydrophobic properties of signal sequences to identify putative proteins encoded by expressed sequence tags (ESTs) from human cDNA libraries. A third approach surveyed ESTs for protein sequence similarity to a set of known receptors and their ligands with the BLAST algorithm. Finally, both signal-sequence prediction algorithms and BLAST were used to identify single exons of potential genes from within human genomic sequence. The isolation of full-length cDNA clones for each of these candidate genes resulted in the identification of >1000 novel proteins. A total of 256 of these cDNAs are still novel, including variants and novel genes, per the most recent GenBank release version. The success of this large-scale effort was assessed by a bioinformatics analysis of the proteins through predictions of protein domains, subcellular localizations, and possible functional roles. The SPDI collection should facilitate efforts to better understand intercellular communication, may lead to new understandings of human diseases, and provides potential opportunities for the development of therapeutics.

Cell Adhesion Molecules, Neuronal↗
PubMed1988

Platelet-associated immunoglobulins G, A and M are secreted during platelet activation: normal levels but defective secretion in grey platelet syndrome.

Platelet-associated (PA) IgG is known to be released from normal human platelets when they are stimulated by aggregating agents. We have studied whether PA-IgA and PA-IgM are also secreted during platelet activation or during blood collection and processing and whether their levels are related to those in serum. Processing of platelets from normal donors in the presence of secretion inhibitors prostaglandin E1 (PGE1) and theophylline increased levels of both surface and total PA-immunoglobulins (Ig) in intact and lysed platelets respectively, with increases being significant for surface PA-IgA and PA-IgM and total PA-IgM. About 50% of total PA-IgM, 40% PA-IgA and 20% PA-IgG was detectable on intact platelets. All three PA-Ig and PA-albumin were secreted in response to thrombin and this release was inhibited by PGE1. The platelet:serum ratio of each Ig and albumin were similar. In grey platelets deficient in alpha-granules, PA-Ig and PA-albumin levels were raised per platelet but when increased platelet size was taken into account PA-Ig were normal and PA-albumin just below normal. Although thrombin caused release of most of the small amounts of beta-thromboglobulin present, PA-Ig and PA-albumin were not released. This suggests that PA-Ig and albumin from plasma may enter a pool of secretory proteins in normal platelets, but in grey platelets they remain in some other site.

Alprostadil↗
PubMed1986

Atropine selectively blocks GHRH-induced GH secretion without altering LH, FSH, TSH, PRL and ACTH/cortisol secretion elicited by their specific hypothalamic releasing factors.

The role of acetylcholine in the regulation of the hypothalamo-pituitary system in man was assessed using atropine, which selectively blocks cholinergic muscarinic receptors. Paired tests were performed in 10 normal men using either GHRH (1 microgram/kg i.v.), or TRH (300 micrograms i.v.) plus LHRH (100 micrograms i.v.) plus corticotrophin releasing hormone (CRH) (1 microgram/kg i.v.) with or without atropine given 30 min previously (1 mg i.m.). The GHRH-induced GH secretory peak (17.8 +/- 3.0 ng/ml) was completely blocked by atropine administration (2.8 +/- 0.6 ng/ml) (P less than 0.05). Atropine did not, however, modify TRH-induced TSH and PRL secretion, nor FSH and LH release induced by the LHRH pulse. ACTH/cortisol secretion elicited by CRH was also unaffected by atropine. These results suggest that atropine blockade of GHRH-induced GH secretion is highly specific, and constitutes an indication of the importance of cholinergic control of GH function. Furthermore, atropine's lack of action on the other pituitary hormones rules out the possibility that it acts non-specifically, i.e. via blood flow changes or toxic effects.

Adrenocorticotropic Hormone↗
PubMed1992

The Aeromonas hydrophila exeE gene, required both for protein secretion and normal outer membrane biogenesis, is a member of a general secretion pathway.

The Aeromonas hydrophila Tn5-751 insertion mutant L1.97 is unable to secrete extracellular proteins, and is fragile because of defective assembly of its outer membrane. A KpnI 4.1 kb fragment, which complements this mutant when supplied with an exogenous promoter, was isolated and sequenced. It contains two complete genes, exeE and exeF, plus fragments of two others and may form part of an operon. The exeE and exeF open reading frames encode 501-residue M(r) 55,882 and 388-residue M(r) 43,431 proteins, respectively. These genes were expressed in vitro and their initiation codons verified by deletion analysis. Tn5-751 had inserted near the centre of the exeE gene in the L1.97 strain. Subclones of the KpnI 4.1 kb fragment which contained only the exeE gene fully complemented the mutation, indicating that its function is required both for extracellular secretion and outer membrane assembly. ExeE and ExeF are highly similar to other proteins which have been shown to be involved in extracellular secretion, suggesting that an additional export apparatus beyond that required for inner membrane translocation may be part of the physiology of many Gram-negative bacteria.

Aeromonas hydrophila↗
PubMed1997

A secreted effector protein of Salmonella dublin is translocated into eukaryotic cells and mediates inflammation and fluid secretion in infected ileal mucosa.

Enteritis induced by non-typhoid pathogenic Salmonella is characterized by fluid secretion and inflammatory responses in the infected ileum. The inflammatory response provoked by Salmonella initially consists largely of a neutrophil (PMN) migration into the intestinal mucosa and the gut lumen. The interactions between Salmonella and intestinal epithelial cells are known to play an essential role in inducing the inflammatory response. Upon interaction with epithelial cells salmonellae are able to elicit transepithelial signalling to neutrophils. This signalling is recognized as a key virulence feature underlying Salmonella-induced enteritis. However, the nature and mechanism of such signalling has not been clarified to date. Here, we characterize SopB, a novel secreted effector protein of Salmonella dublin, and present data implying that SopB is translocated into eukaryotic cells via a sip-dependent pathway to promote fluid secretion and inflammatory responses in the infected ileum.

Amino Acid Sequence↗
PubMed1993

Expression of secreted immunoglobulin heavy chain genes and immunoglobulin-secreting cells in human lymphocytes.

The numbers of immunoglobulin-secreting cells in peripheral blood mononuclear cells and the expression of mRNA for secreted type of immunoglobulin heavy chains were investigated in healthy children, compared with the percentages of surface immunoglobulin-bearing cells and the expression of mRNA for membrane-bound type of immunoglobulin heavy chains, respectively. Although a difference between expression of mu s mRNA and mu m mRNA was unclear, mu mRNA was well transcribed. The expression of gamma s mRNA or alpha s mRNA was markedly higher than that of gamma m mRNA or alpha m mRNA. However, although the detection methods could be of different sensitivities, the percentage of IgM-, IgG-, or IgA-secreting cells was markedly low, compared with the percentage of surface IgM-, IgG-, or IgA-bearing cells, respectively. Therefore, additional regulation of the pattern of the immunoglobulin gene expression may be exerted at the translational and post-translational stages.

Antibody-Producing Cells↗
PubMed1969

The action of caerulein on pancreatic secretion of the dog and biliary secretion of the dog and the rat.

1. Caerulein displayed a potent stimulant action on pancreatic secretion in the dog. Threshold doses were 1-5 ng/kg by rapid intravenous injection, 0.25-1 ng/kg per min by intravenous infusion and 50-100 ng/kg by subcutaneous injection. There was a conspicuous increase not only in the volume flow of pancreatic juice but also in the output of solid constituents of the juice and of amylase. However, continuous stimulation of pancreatic secretion by intravenous infusion of caerulein resulted in a progressive reduction of the amylase concentration and still more of the dry residue content of pancreatic juice. The bicarbonate concentration in pancreatic juice produced by caerulein was similar to that observed in juice secreted following pancreozymin administration or following other stimuli causing the same rate of flow of pancreatic juice.2. On a molar basis, caerulein was 25-30 times as active as human gastrin I and 3-6 times as active as cholecystokinin-pancreozymin. The presence in the molecule of caerulein of a sulphated tyrosyl residue at position 4 of the decapeptide (position 7 starting from the C-terminus) was a necessary prerequisite for the manifestation of the cholecystokinin-pancreozymin-like actions of caerulein. The C-terminal heptapeptide of caerulein retained much of the activity of the intact caerulein molecule.3. At high dose levels (50-200 ng/kg in the dog, 1 mug/kg in the rat, by rapid intravenous injection) caerulein stimulated the flow of hepatic bile in the dog and the rat. The dry residue of the bile and the cholesterol concentration were appreciably greater in rats treated with caerulein than in control rats.4. The activity spectrum of caerulein was identical with that of cholecystokinin-pancreozymin. This is readily explained on the basis of the almost identical structure of the C-terminal octapeptide of the two peptides.5. Caerulein and some caerulein-like peptides may be considered as model peptides, capable of being substituted for cholecystokinin-pancreozymin in all the possible experimental and clinical uses of the duodenal hormone, with the important advantage that they are more easily available.6. The question is raised whether cholecystokinin-pancreozymin obtained from the duodenum by acid extraction is the authentic hormone or rather a carrier polypeptide from which a smaller active peptide may be set free, when needed, into the circulation.

Amylases↗
PubMed1979

Effects of a combined oestrogen-progestin preparation on gastric acid and pepsin secretion, serum gastrin concentration and biliary secretion of bile acids, phospholipids, and cholesterol in the cat.

1 Daily ethinyloestradiol (50 mug) and norethisterone acetate (1 mg) treatment (Minovlar) was investigated on gastric acid and pepsin secretion, and fasting serum gastrin concentration in six conscious female cats prepared with chronic gastric fistulae. The effect on biliary secretion of bile acids, phospholipids, and cholesterol was investigated in three conscious female cats prepared with chronic gastric and intestinal fistulae, and cholecystectomy.2 Treatment for 49 days did not alter the gastric acid or pepsin response to either intravenous pentagastrin infusions or a food stimulus. The fasting serum gastrin concentration remained unaltered throughout the study.3 Treatment for 18 days did not alter the percentage concentration of cholesterol in the bile, but reduced the percentage concentration of phospholipid. This was mirrored by a rise in the percentage concentration of bile acids in the bile. These trends were quickly reversed on cessation of treatment.4 There was no sign of cholestasis associated with the treatment. Intestinal flow remained constant throughout the study, there was no lithocholic acid or other abnormal bile acids detectable in any samples, and there was no change in serum aspartate aminotransferase concentration.5 The results suggest that in female cats, treatment with a combined oestrogen-progestin preparation does not exert any beneficial effects on the aetiology of peptic ulceration through the reduction of acid or pepsin secretion, or the lowering of serum gastrin concentration. The preparation shows a tendency to produce more lithogenic bile, and this may partly explain the greater incidence of gall stones in women on the contraceptive pill.

Animals↗
PubMed1998

A Salmonella typhimurium strain genetically engineered to secrete effectively a bioactive human interleukin (hIL)-6 via the Escherichia coli hemolysin secretion apparatus.

Human interleukin-6 (hIL-6) cDNA was genetically fused with the Escherichia coli hemolysin secretorial signal (hlyA[S]) sequence in a plasmid vector. Recombinant E. coli XL-1 Blue and attenuated Salmonella typhimurium secreted a 30 kDa hIL-6-HlyA(S) fusion protein, with an additional form of higher apparent molecular mass produced by S. typhimurium. In S. typhimurium cultures hIL-6-HlyA(S) concentrations entered a plateau at 500 to 600 ng ml(-1) culture supernatant. In contrast to E. coli XL-1 Blue, in S. typhimurium culture supernatants hIL-6-HlyA(S) was accumulated faster reaching three-fold higher maximal concentrations. The cell proliferating activity of hIL-6-HlyA(S) fusion protein(s) was equivalent to that of mature recombinant hIL-6. Furthermore. hIL-6-secreting S. typhimurium were less invasive than the attenuated control strain. Therefore, the bulky hemolysin secretorial peptide at the C-terminus of the fusion protein does not markably affect hIL-6 activity, suggesting that the hemolysin secretion apparatus provides an excellent system to study immunomodulatory effects of in situ synthesized IL-6 in Salmonella vaccine strains.

Animals↗
PubMed1992

Incompatibility of outer membrane proteins OmpA and OmpF of Escherichia coli with secretion in Bacillus subtilis: fusions with secretable peptides.

The secretion of the outer membrane proteins OmpA and OmpF of Escherichia coli has previously been found to be blocked at an early intracellular step, when these proteins were fused to a bacillar signal sequence and expressed in Bacillus subtilis. We have now fused these proteins to long secretable polypeptides, the amino-terminal portions of alpha-amylase or beta-lactamase. In spite of this, no secretion of the fusion proteins was detected in B. subtilis. With the exception of a small fraction of the beta-lactamase fusion, the proteins were cell-bound with uncleaved signal sequences. Protease accessibility indicated that the fusion proteins were not even partially exposed on the outer surface of the cytoplasmic membrane. Thus there was no change of the location compared to the OmpA or OmpF fused to the signal sequence only. We conclude that, like OmpA and OmpF, the fusion proteins fold into an export-incompatible conformation in B. subtilis before the start of translocation, which we postulate to be a late post-translational event.

Bacillus subtilis↗
PubMed1982

Effects of frequent milking on milk secretion during lactation in the goat: relation to factors which limit the rate of secretion.

Goats were milked hourly with the aid of oxytocin at different stages of lactation. Udder volume and milk yield were also measured. The marked variation between goats in the time after parturition at which peak milk yield is attained and in the rate of decline after peak is illustrated. Hourly milking had a stimulatory effect on the rate of milk secretion in early lactation (before peak) and in declining lactation (after peak), in both cases at previous milk yields of 1.1 - 1.48 g/ml udder volume . d. There was no stimulatory effect of hourly milking on milk yield at or near peak lactation (yield before the experiment greater than 1.48 g/ml volume . d) or in late lactation (less than 1.1 g/ml . d). The responses of milk yield to hourly milking are discussed in relation to the factors which limit the rate of secretion. In particular, it is concluded that a stimulatory response indicates that before the experiment the rate of secretion could not have been limited directly by the arterial supply of one or more substrates for milk synthesis. It is stressed that the results were obtained under one dietary regime only.

Animals↗
PubMed1999

Legionella pneumophila contains a type II general secretion pathway required for growth in amoebae as well as for secretion of the Msp protease.

We report the identification of a set of Legionella pneumophila genes that encode products with homology to proteins of the type II general secretion pathway of gram-negative bacteria. A strain containing a deletion-substitution mutation of two of these genes was unable to secrete the Msp protease. This strain was unable to multiply within the free-living amoeba Acanthamoeba castellanii yet was able to kill HL-60-derived macrophages. Because Msp is not required for growth in amoebae, other proteins which are important for growth in amoebae are likely secreted by this pathway.

Acanthamoeba↗
PubMed2005

SepZ/EspZ is secreted and translocated into HeLa cells by the enteropathogenic Escherichia coli type III secretion system.

Enteropathogenic Escherichia coli (EPEC) is a major bacterial cause of infantile diarrhea in developing countries and is the prototype for a group of gastrointestinal pathogens causing characteristic attaching and effacing (A/E) histopathology on intestinal epithelia. A/E pathogens utilize a type III secretion system (TTSS), encoded by the locus of enterocyte effacement (LEE) pathogenicity island, to deliver effector proteins into host cells. Here, we investigate sequence divergence of the LEE-encoded SepZ protein and identify it as a TTSS-secreted and -translocated molecule. SepZ is hypervariable among A/E pathogens, with sequences sharing between 60 to 81% amino acid identity with SepZ of EPEC. A SepZ-CyaA fusion was secreted and translocated into HeLa cells in a TTSS-dependent manner. Additionally, we determined that the first 20 amino acids of SepZ were sufficient to direct its translocation. In contrast to previous studies suggesting a role in invasion and the structure and/or regulation of the TTSS, we found that SepZ does not mediate uptake of EPEC into host cells or affect translocation and tyrosine phosphorylation of the translocated intimin receptor. Immunohistochemistry reveals that, after an extended HeLa cell infection, accumulated SepZ can be detected beneath the site of bacterial attachment in a subset of pedestal regions. To indicate its newly identified status as a translocated effector protein, we propose to rename SepZ as EspZ.

Adenylate Cyclase Toxin↗
PubMed2006

PopF1 and PopF2, two proteins secreted by the type III protein secretion system of Ralstonia solanacearum, are translocators belonging to the HrpF/NopX family.

Ralstonia solanacearum GMI1000 is a gram-negative plant pathogen which contains an hrp gene cluster which codes for a type III protein secretion system (TTSS). We identified two novel Hrp-secreted proteins, called PopF1 and PopF2, which display similarity to one another and to putative TTSS translocators, HrpF and NopX, from Xanthomonas spp. and rhizobia, respectively. They also show similarities with TTSS translocators of the YopB family from animal-pathogenic bacteria. Both popF1 and popF2 belong to the HrpB regulon and are required for the interaction with plants, but PopF1 seems to play a more important role in virulence and hypersensitive response (HR) elicitation than PopF2 under our experimental conditions. PopF1 and PopF2 are not necessary for the secretion of effector proteins, but they are required for the translocation of AvrA avirulence protein into tobacco cells. We conclude that PopF1 and PopF2 are type III translocators belonging to the HrpF/NopX family. The hrpF gene of Xanthomonas campestris pv. campestris partially restored HR-inducing ability to popF1 popF2 mutants of R. solanacearum, suggesting that translocators of R. solanacearum and Xanthomonas are functionally conserved. Finally, R. solanacearum strain UW551, which does not belong to the same phylotype as GMI1000, also possesses two putative translocator proteins. However, although one of these proteins is clearly related to PopF1 and PopF2, the other seems to be different and related to NopX proteins, thus showing that translocators might be variable in R. solanacearum.

Amino Acid Sequence↗
PubMed1991

Protein secretion in Pseudomonas aeruginosa: the xcpA gene encodes an integral inner membrane protein homologous to Klebsiella pneumoniae secretion function protein PulO.

xcp mutations have pleiotropic effects on the secretion of proteins in Pseudomonas aeruginosa PAO. The nucleotide sequence of a 1.2-kb DNA fragment that complements the xcp-1 mutation has been determined. Sequence analysis shows the xcpA gene product to be a 31.8-kDa polypeptide, with a highly hydrophobic character. This is consistent with a localization in the cytoplasmic membrane in P. aeruginosa, determined after specific expression of the xcpA gene under control of the T7 phi 10 promoter. A very strong homology was found between XcpA and PulO, a membrane protein required for pullulanase secretion in Klebsiella pneumoniae. This suggests the existence of a signal sequence-dependent secretion process common to these two unrelated gram-negative bacteria.

Amino Acid Sequence↗