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At least 703 records · Page 39Linked to original sources
PubMed1989

Insulin and glucagon secretion after pancreatectomies. Correlation of secretion and hormonal contents of remaining pancreas.

We studied whether insulin and glucagon secretory capacities change in relation to the corresponding hormonal contents in the pancreas remnant after pancreas resection. The following groups of dogs were used: sham operated (S-O), left pancreatectomized (L-Px), right pancreatectomized (R-Px), subtotal pancreatectomized (St-Px), and total pancreatectomized (T-Px). Endocrine functions were assessed by intravenous glucose tolerance test (IVGTT) and insulin tolerance test (ITT) in each dog under anesthesia before surgery and 1 wk after. In these five groups, the insulin secretory capacities, assessed as the integrated incremental secretion of immunoreactive insulin (sigma delta IRI) from the IVGTT, decreased to 95 +/- 11, 78 +/- 9, 48 +/- 8, 12 +/- 8, and -4 +/- 4% of the respective preoperative values, and these values were proportional to the percentage residual weight (100, 64 +/- 2, 35 +/- 2, 13 +/- 2, 0%) and IRI content (100, 59 +/- 4, 45 +/- 3, 10 +/- 2, 0%) of the pancreas remnant. After surgery, glucagon secretory capacity, the integrated incremental secretion of immunoreactive glucagon (sigma delta IRG) during the ITT, decreased significantly in the L-Px, St-Px, and T-Px groups but not in the R-Px group. The sigma delta IRG values as percentages of the preoperative values were 109 +/- 25, 46 +/- 11, 89 +/- 13, 19 +/- 11, and 3 +/- 3%, respectively, for the five groups. These values were proportional to the percentage residual IRG contents of the pancreas remnants (100, 48 +/- 6, 65 +/- 8, 12 +/- 2, 0%) rather than to the percentage residual pancreatic weights.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

Decreased expression of t-SNARE, syntaxin 1, and SNAP-25 in pancreatic beta-cells is involved in impaired insulin secretion from diabetic GK rat islets: restoration of decreased t-SNARE proteins improves impaired insulin secretion.

The physiological role of soluble N-ethylmaleimide-sensitive factor attachment protein (SNAP) receptor (SNARE) proteins in insulin exocytosis has been reported in pancreatic beta-cells. To determine whether the beta-cells of GK rats, a nonobese rodent model of type 2 diabetes, exhibit abnormalities in their SNARE proteins, we studied the expression and function of target (t)-SNAREs, syntaxin 1A, and synaptosomal-associated protein of 25 kDa (SNAP-25) in GK rat islets. Although insulin release and insulin content of islets isolated from 12-week-old GK rats were reduced, the proinsulin biosynthetic rate was about twofold higher than that in control rat islets, and no change in the preproinsulin mRNA level was observed. Pulse-chase experiments suggested the increased degradation of insulin in GK rat islets. Immunoblot analysis revealed that protein levels of syntaxin 1A and SNAP-25 in GK rat islets decreased to approximately 60% of the levels in control rat islets. We then examined whether the restoration of the decreased expression of t-SNAREs to the normal level in GK rat islets affected insulin secretion. Restoration was achieved by the overexpression of syntaxin 1A and SNAP-25 via the recombinant adenovirus-mediated gene transduction system, which recovered levels of these proteins to almost control levels. Glucose-stimulated insulin release from AdexlCA syntaxin 1A and Adex1CA SNAP-25-infected GK rat islets increased up to approximately 135 and 200%, respectively, of those from uninfected GK rat islets, although no difference in basal (2.2 mmol/l glucose) insulin release was evident between them. We conclude that decreased expression of t-SNAREs in GK rat islets is in part the defect responsible for impaired insulin secretion.

Animals↗
PubMed1986

Effects of retinoic acid on growth, insulin secretion, and hexose incorporation into macromolecules of a continuously growing, insulin-secreting cell line (RINm5F).

The continuously growing, insulin-secreting cell line RINm5F does not respond to glucose with increased rates of insulin secretion and cell proliferation. The possibility that retinoic acid, which acts as a differentiating agent in several cell systems, could induce such responses to glucose has been investigated. Retinoic acid (10(-6)-10(-5) mol/l) failed to affect the cell viability, cell proliferation, 3H-thymidine incorporation or the DNA contents of the cultured RINm5F cells, irrespective of the glucose concentration of the culture medium. The insulin release was not affected either by glucose or by retinoic acid. Higher concentrations of the drug (10(-4) mol/l) proved toxic to the cells. The incorporation of 3H-mannose and 3H-glucosamine into TCA precipitable material of the RINm5F cells was strongly decreased by an increased glucose concentration of the medium. The incorporation of 3H-mannose, but not that of 3H-glucosamine, into macromolecules which could be precipitated with Concanavalin A or wheat germ lectin was diminished by retinoic acid (10(-5) mol/l).

Cell Division↗
PubMed1984

Diversion of bile and pancreatic secretion in the rat and its effect on cysteamine-induced duodenal and peptic ulcer development under maximal acid secretion.

In this investigation we assess whether diversion of bile and pancreatic secretion protects rats from ulceration under maximal acid secretion as it does in cysteamine-induced ulcers. The rats were divided into a cysteamine-group (Cy) comprising 16 rats and a secretagogue group (PC) with 18 white male rats. Half of the animals of each group were submitted to the diversion-operation (division of the duodenum distally from the pylorus, jejuno-duodenostomy and entero-y-anastomosis), Cy2 and PC2 respectively. The other animals were not operated (Cy1 and PC1). In the cysteamine group the rats were given twice cysteamine-HC1 injections subcutaneously and the PC group were given a 24 h infusion with pentagastrin and carbachol. All animals of the Cy1 group had duodenal ulcers, 3 perforated. However, only 2 rats had one ulcer each in the Cy2 group (p less than 0.01). The PC1 group totalled 30 duodenal ulcers in the 9 animals with 10 perforations, 13 ulcers in 6 animals with 3 perforations in PC2. Furthermore in PC1 group 34 gastric ulcers were found in 7 rats and only 4 ulcers in the PC2 group. It is therefore concluded, that the diversion operation provided protection against cysteamine-induced duodenal ulcers (p less than 0.01) and ulcer formation under maximal acid stimulation in the duodenum (p less than 0.02) as well as in the rat stomachs (p less than 0.05). In the PC group the restraint haltering of the animals promoted presumably a stress situation with bile reflux in the non-operated whereas in the operated animals (PC2) reflux did not occur.

Animals↗
PubMed1980

[Calcium and endocrine pancreas secretion. II. Effects of an infusion of calcium on insulin and glucagon secretion induced by intravenous administration of glucose].

IRI, IRG and blood glucose levels after I.V.G.T.T. in normal subjects were not significantly modified when I.V.G.T.T. was repeated during a prolonged calcium infusion (15 mg/Kg body weight per 90'). The Authors advance the hypothesis that no closed relationships exist between serum calcium levels and insulin secretion, in these experimental conditions; with regard to glucagon secretion, further experiences are of course required namely during alpha-cell stimulation.

Adult↗
PubMed1975

A general method for enumerating single cells secreting antigen: albumin-secreting hepatocytes detected as plaque-forming cells.

Sheep erythrocytes, artificially coated with purified antibody specific for mouse serum albumin (anti-MSA Ab-E) were agglutinated and lysed by mouse serum albumin. Mouse liver cells, plated with anti-MSA Ab-E formed hemolytic plaque in a modified plaque-forming cell (PFC) assay. The same cells tested with anti-MSA Ab-E did not rosette in modified immunocyto-adhesion assay. Thus, liver cells secreted molecules (albumin) which were not detectable on the cell membrane. This PFC assay with Ab-E is probably a general method for enumerating antigen-secreting cell.

Agglutination↗
PubMed1985

Monitoring human neutrophil granule secretion by flow cytometry: secretion and membrane potential changes assessed by light scatter and a fluorescent probe of membrane potential.

Purified human peripheral blood polymorphonuclear neutrophils (PMN) were incubated at 37 degrees C with the fluorescent membrane potential sensitive cyanine dye di-O-C(5)(3) and exposed to a number of stimulatory agents (N-formylmethionylleucylphenylalanine (FMLP), cytochalasin B (cyto B) + FMLP, phorbol myristate acetate (PMA). Flow cytometry was utilized to measure changes in forward light scatter (FS), orthogonal light scatter (90 degrees-SC), and fluorescence intensity of individual cells over time. A saturating (10(-6) M) dose of FMLP lead to a significant increase in the cells' FS without a change in 90 degrees-SC as well as a heterogeneous loss of di-O-C(5)(3) fluorescence. PMA (100 ng/ml) also caused an increase in FS but a uniform loss of dye fluorescence by all cells (apparent depolarization). Cyto B + FMLP produced an increase in FS, a marked loss of 90 degrees-SC, and a uniform loss of fluorescence. Secretion experiments under identical incubation conditions indicated a significantly positive relationship between loss of enzyme markers or cell granularity and orthogonal light scatter (r = 0.959, 0.998, and 0.989 for loss of 90 degrees-SC vs lysozyme, beta-glucuronidase, and granularity index, respectively). Sequential exposure of PMN to PMA and then cyto B + FMLP produced a stepwise shift in scatter parameters (increased FS then loss of 90 degrees-SC). Normalization of membrane potential dye fluorescence changes for the changes in light scatter did not abrogate the heterogeneous fluorescence response of cells to stimulus, indicating that stimulus-induced scatter changes were not responsible for such fluorescence shifts. The data demonstrate that loss of 90 degrees-SC relates closely to secretion of primary granules while changes in FS reflect alterations in cell shape and/or surface/volume ratios that accompany cell activation. Flow cytometric light scatter measurements may yield important information on the extent of prior cell degranulation or activation.

Cytochalasin B↗
PubMed1984

An enzyme-linked immunosorbent assay (ELISA) for IgG and IgA antibodies to respiratory syncytial virus in low dilutions of secretions of human serum and secretions.

An enzyme-linked immunosorbent assay (ELISA) has been developed for titration of IgG and IgA antibodies to respiratory syncytial (RS) virus in low dilutions of human serum, colostrum, and nasopharyngeal secretions. Previously the sensitivity of RS virus ELISA on such specimens has been limited by nonspecific absorption of antibody, particularly IgA, to crude antigen preparations. For IgG antibody estimation in infant sera, this unwanted binding was reduced to workable levels by increasing the serum, salt, and detergent concentration of the diluent. Residual nonspecific binding of IgA in colostra appeared mainly due to antigen lipids or to lipoproteins. This was markedly reduced by partitioning Triton X-100-treated infected cell lysate antigens in Arklone. Using the modified ELISA technique for anti-RS virus IgA, good correlations were found with unfixed cell membrane immunofluorescence (MIF) for colostra (r = 0.81, P less than 0.001) and nasal secretions from adult volunteers. In several samples nonspecific absorption of antibody precluded MIF assay, but did not affect the ELISA. Although there was an overall correlation between ELISA for anti-RS IgG antibody in sera, the complement fixation test (r = 0.75, P less than 0.001), and MIF test (r = 0.82, P less than 0.001), the sensitivity of ELISA for antibody responses in convalescent sera of infants from 3 months to 2 years was poor. Conversely, the sensitivity of ELISA for antibody in the sera of older children and for transplacentally acquired antibody in very young infants was higher than that for the other two tests. ELISA was thus less reliable than either CF or MIF for detecting antibody rises in paired infant sera, particularly where maternally acquired antibody remained in the acute serum. The reasons for this apparent disparity are discussed.

Adult↗
PubMed1995

Secretion kinetics of Alzheimer's amyloid beta-protein differs from secreted beta-amyloid precursor protein.

Amyloid beta-protein (A beta) and secreted beta-amyloid precursor protein (sAPP), derived from beta-amyloid precursor protein (APP), are normally released by cultured mammalian cells. We investigated by pulse-chase analysis the secretion kinetics of these two APP derivatives using mouse cholinergic SN49 cell lines stably transfected with mouse APP695 cDNA. After both A beta and sAPP peaked at about the second hour, sAPP decreased with a half-life of approximately 5 hours, but A beta remained almost unchanged for at least 14 hours. These results indicate that A beta is more stable than sAPP in the SN49 conditioned medium.

Amyloid beta-Peptides↗
PubMed1998

Decreased secretion of Th2 cytokines precedes Up-regulated and delayed secretion of Th1 cytokines in activated peripheral blood mononuclear cells from patients with insulin-dependent diabetes mellitus.

Recent evidence suggests that autoimmune animal diabetes is associated with an imbalance between the Th1 and Th2 arms of the cellular immune system. However, limited data is available regarding the Th1/Th2 imbalance in human Insulin dependent diabetes mellitus (IDDM) patients. Therefore, we examined the peak levels, secretory pattern and total cytokine production (calculated as the area under the curve, AUC) of the Th1 cytokines, IL-2 and IFN-gamma, and Th2 cytokines, IL-4 and IL-10, from stimulated peripheral blood mononuclear cells, from 17 IDDM patients and 24 normal controls. In contrast to controls, diabetic patients were characterized by an early, uniformly low secretion of Th2 cytokines, followed by a late increased secretion of Th1 cytokines. This resulted in significant differences in secretory patterns of IFN-gammaIL-2, IL-4 and IL-10 between the two groups; P<0.001, P<0.005, P<0.005 and P<0.001, respectively. No correlation was found in the diabetic patients between any profiles of the cytokines and their various clinical parameters, including age, gender, disease duration, insulin requirements or glycated hemoglobin levels. In conclusion, our data provides the first comprehensive evidence for an independent and persistent impairment of both Th1 and Th2 cytokine secretory patterns in IDDM patients.

Adolescent↗
PubMed1988

Ventricular and atrial myocytes of newborn rats synthesise and secrete atrial natriuretic peptide in culture: light- and electron-microscopical localisation and chromatographic examination of stored and secreted molecular forms.

We have demonstrated that atrial natriuretic peptide-like immunoreactivity is stored and secreted by ventricular and atrial myocytes in dissociated cell culture preparations from the heart of newborn rat. Culture preparations were maintained in either foetal calf serum-supplemented medium 199 or in hormone-supplemented, serum-free medium 199. The presence of atrial natriuretic peptide-like immunoreactivity in the cultured myocytes was demonstrated at both light- and electron-microscopical levels. Release of atrial natriuretic peptide-like immunoreactivity into the culture medium was measured by radioimmunoassay; molecular forms of the stored and secreted peptide were determined by gel column chromatography. The atrial natriuretic peptide-like immunoreactivity of cultured atrial and ventricular myocytes was concentrated in the perinuclear cytoplasm and was localised to electron-dense secretory granules. The number of immunoreactive ventricular myocytes and the intensity of their immunofluorescence changed with time in culture and was higher in cultures in foetal calf serum-supplemented medium than in serum-free medium. Gamma-atrial natriuretic peptide was stored and released by cultured atrial and ventricular myocytes, but was broken down to alpha-atrial natriuretic peptide in the growth medium. This process was foetal calf serum-independent, since it occurred in both the media used, indicating that cardiac myocytes in culture may release a factor that cleaves gamma-atrial natriuretic peptide to form alpha-atrial natriuretic peptide.

Animals↗
PubMed1992

Secretion of salivary immunoglobulin A in relation to age, saliva flow, mood states, secretion of albumin, cortisol, and catecholamines in saliva.

Salivary immunoglobulin A (IgA) is one characteristic humoral factor of the local immune system in the upper respiratory tract. Epidemiological studies emphasize the importance of secretory IgA in the protection from infections of the upper respiratory tract. However, due to high interindividual variability of secretion of salivary IgA, it remains difficult to define normal ranges. This series of studies focused on identification of factors influencing basal secretion of salivary IgA. The results indicate a significant relationship between age and salivary IgA concentration. Children below 7 years have lower salivary IgA concentration than children above 7 years or adults. Furthermore, a significant inverse relationship between saliva flow and salivary IgA concentration was found. Gender, mood states, salivary albumin, salivary catecholamines, and salivary cortisol were not associated with salivary IgA. It can be concluded that for defining normal ranges of salivary IgA, age and saliva flow have to be considered.

Adolescent↗
PubMed1984

Mechanism of Cl secretion in canine trachea: changes in intracellular chloride activity with secretion.

Cl-sensitive microelectrodes were employed to investigate the mechanism of Cl secretion by canine tracheal epithelium. In control tissues with a mean calculated short-circuit current (Isc) of 18.1 microA/cm2, the intracellular Cl activity (aiCl) was 47.2 mM. This value is 30.1 mM (or 27.0 mV) above the electrochemical equilibrium for Cl across the apical membrane. Epinephrine, which stimulates Cl secretion, increased the calculated Isc to 160 microA/cm2 and decreased aiCl to 32.2 mM, a value only 11.2 mM (or 10.9 mV) above equilibrium for the apical membrane. These results indicate a secretagogue induced decrease in the impedance to Cl exist from the cell via the apical membrane. From these and prior measurements we calculate that epinephrine-induced Cl efflux from the cell can occur by simple diffusion across the apical membrane. Further implications of these calculations are also discussed.

Animals↗
PubMed1988

Experimental pitfalls in evaluating vectorial protein secretion in vitro; Sertoli cell secretion of androgen-binding protein and transferrin in two-compartment culture chambers.

We examined the influence of various Millipore filter pretreatments on the amounts of androgen-binding protein (ABP) and transferrin (Trf) found in the outer (OC) and inner (IC) compartment of two-compartment Sertoli cell (Sc) cultures. When Sc were cultured on untreated Millipore filters, less than 10% of ABP was found in OC during 3 initial culture days compared to similar cultures on pretreated filters. Most of the glycoprotein was shown to be bound by the filter. Pretreatment of Millipore filters with 5% bovine serum albumin (BSA) or 2% fetal bovine serum (FBS) maximally saturated the nonspecific protein-binding sites resulting in OC:IC ratio of ABP similar to that found in cultures on polycarbonate membranes, which exhibit very low protein-binding capacity. In contrast to ABP, about 40% of Trf was bound by the Millipore filter on Day 1, with only trace amounts bound thereafter. These differences were due to much higher secretion rate of Trf than ABP, resulting in a relatively smaller fraction of Trf bound to the filter. Again, the nonspecific binding of Trf was greatly reduced by filter pretreatment with 5% BSA or 2% FBS. It is concluded that complete saturation of protein-binding sites of cellulose ester supports is necessary for reliable evaluation of vectorial protein secretion by Sc and other polarized epithelial cells maintained in this type of culture. The implications of partial saturation of protein-binding sites of culture support in interpreting experimental results are discussed.

Androgen-Binding Protein↗
PubMed1989

Electron microscopic immunocytochemistry of prolactin secreting cells (PRL-cells) and growth hormone secreting cells (GH-cells) in the anterior pituitary gland of partially hepatectomized rats.

After 60% hepatectomy in rats, prolactin secreting cells (PRL-cells) and growth hormone secreting cells (GH-cells) of the anterior pituitary gland were distinctly identified by the protein A-gold procedure combined with electron microscopy. The animals were sacrificed by the decapitation at midnight at intervals of about 28, 76 and 124 h after the operation. The principal changes can be summarized as follows; (1) Hypertrophy of the Golgi complex, (2) Dilation of the rough endoplasmic reticulum (RER), (3) Increased numbers of secretory granules (markedly in GH-cells), and occurrence of granule extrusion or exocytosis, (4) Increased numbers of lysosomes, which were mostly seen at 124 h after the operation. These ultrastructural changes were remarkably observed in both PRL and GH-cells. Especially, the noticeable changes in PRL-cells after partial hepatectomy in the rat were new findings in this study. The above results suggest that hepatectomy induced synthesis and release of GH and PRL in cells from pars distalis.

Animals↗
PubMed1985

In vitro studies on TSH secretion and adenylate cyclase activity in a human TSH-secreting pituitary adenoma. Effects of somatostatin and dopamine.

We have studied the in vitro TSH secretion and the adenylate cyclase (AC) activity of a human pituitary adenoma surgically removed from a hyperthyroid patient showing high serum TSH levels. The tumor appeared almost homogeneously constituted by cells positive for an anti-TSH-beta antiserum and showing the ultrastructural characteristics of the adenomatous thyrotrophs. Adenoma fragments released in vitro a large amount of TSH (148.4 microU/mg prot/30 min), alpha-subunit (35.5 ng/mg prot/30 min) and TSH-beta (10.1 ng/mg prot/30 min). The effects of somatostatin (GHRIH) and dopamine (DA) on the hormone release have been tested in vitro. Both agents markedly inhibited the release of intact TSH and TSH-beta whereas the release of alpha-subunit was less affected. The two agents were effective at concentrations higher than 10(-8)M. The ability of GHRIH and DA in modulating the AC activity was investigated in membrane fraction preparations. GHRIH inhibited AC at concentrations higher than 10(-7)M. The maximal inhibition was 32% at 10(-5)M. Conversely, DA slightly stimulated AC activity. This effects was not mimicked by the dopaminergic ergot CH 29-717, which was completely ineffective on the enzyme. These results suggest that: 1) in this TSH-secreting pituitary adenoma a normal secretory response to the inhibiting agents (GHRIH and DA) is present; 2) different mechanisms of transduction of the GHRIH and DA signals (cAMP dependent and cAMP independent) could be operating in this tumor.

Adenoma↗
PubMed1978

Ectopic secretion of chorionic gonadotropin by a lung carcinoma. Pituitary gonadotropin and subunit secretion and prolonged chemotherapeutic remission.

The ability of tumor markers to improve cancer therapy is not established. We studied a man with a human chorionic gonadotropin (HCG)-secreting large cell carcinoma of the lung and gynecomastia. Preoperatively, levels of HCG (109 ng/ml), its alpha and beta subunits (3.2 and 21 ng/ml, respectively) and plasma estradiol were elevated. Despite apparently complete tumor resection and total resolution of gynecomastia, HCG titers remained elevated (3.3 ng/ml), heralding tumor recurrence three weeks later. Because the pathophysiologic consequences of the ectopic secretion of HCG on pituitary function are not established, we administered 100 microgram of gonadotropin-releasing hormone (LHRH) and observed a markedly delayed increase in pituitary gonadotropins. Early chemotherapy, guided by persistence of HCG, reduced HCG to undetectable levels, restored to normal the response to LHRH and resulted in a distinctly unusual 30-month complete remission. Use of HCG as a tumor marker levels is more sensitive than the symptom of gynecomastia and may permit detection of small, potentially curable tumor foci.

Carcinoma, Small Cell↗
PubMed1986

Maturation and secretion of lipoprotein lipase in cultured adipose cells. II. Effects of tunicamycin on activation and secretion of the enzyme.

The effects of N-linked glycosylation on the activation and secretion of lipoprotein lipase were studied in Ob17 cells. The cells were first depleted of any activity and enzyme content by cycloheximide treatment and of precursors of oligosaccharide chains by tunicamycin. The repletion of lipoprotein lipase content was studied in these cells maintained in the presence of tunicamycin after cycloheximide removal. During the repletion phase, the EC50 values of inhibition by tunicamycin (approx. 0.2 microgram/ml) of the incorporation of labeled glucose, mannose or galactose into trichloroacetic acid-insoluble material were found to be identical. Under these conditions, the rate of protein synthesis was maximally decreased by 30%. The results showed clearly that the recovery in lipoprotein lipase activity was parallel to the recovery in hexose incorporation, no activity being recovered in the absence of glycosylation. An inactive form of lipoprotein lipase from tunicamycin-treated cells was detected by competition experiments with mature active lipoprotein lipase for the binding to immobilized antilipoprotein lipase antibodies, as well as by immunofluorescence staining. SDS-polyacrylamide gel electrophoresis and Western blots of cellular extracts and of extracellular media, obtained after tunicamycin-treated cells were exposed to heparin, revealed a single immunodetectable Mr 52 000 protein, whereas a single Mr 57 000 protein was detected in control cells. Therefore, the results indicate that the acquisition by lipoprotein lipase of a catalytically active conformation is linked directly or indirectly to glycosylation. Despite this lack of activation, the lipoprotein lipase molecule was able to migrate intracellularily and to undergo secretion after heparin stimulation of the tunicamycin-treated cells.

Adipose Tissue↗