Regulation of digestion. II. Effects of insulin and glucagon on pancreatic secretion

1984 ◽  
Vol 246 (4) ◽  
pp. G451-G456
Author(s):  
H. C. Tseng ◽  
J. H. Grendell ◽  
S. S. Rothman
Keyword(s):  
Exocrine Pancreas ◽  
Digestive Enzyme ◽  
Celiac Artery ◽  
Portal Circulation ◽  
Amylase Output ◽  
Endocrine Hormones ◽  
Dose Dependent Fashion ◽  
High Concentrations ◽  
Dose Dependent ◽  
Islet Cell Hormones

The endocrine islet-cell hormones insulin and glucagon are secreted at high concentrations into an intrapancreatic portal circulation and have been reported to affect the secretion of digestive enzyme by the exocrine pancreas. In the present experiments, insulin and glucagon were injected into the celiac artery of anesthetized rats to evaluate their effects on the secretion of amylase and trypsinogen by the pancreas. Neither hormone when given alone significantly changed the output of either enzyme. However, when given with the pancreatic secretagogue cholecystokinin, each altered the effect of injection of cholecystokinin. In a dose-dependent fashion insulin increased trypsinogen output without affecting amylase output, whereas glucagon inhibited amylase output and left trypsinogen output unchanged. Thus, both hormones produced a more trypsinogen-dominant pancreatic juice than that observed with cholecystokinin alone, although in different ways. These findings suggest that the endocrine hormones insulin and glucagon may regulate secretion of digestive enzymes by the pancreas by modulating the response to stimuli of overall protein secretion such as cholecystokinin.

Evidence for a potential role of glucagon during eye growth regulation in chicks

2002 ◽  
Vol 19 (6) ◽  
pp. 755-766 ◽  
Author(s):  
MARITA P. FELDKAEMPER ◽  
FRANK SCHAEFFEL
Keyword(s):  
Visual Processing ◽  
Growth Regulation ◽  
Amacrine Cells ◽  
Early Gene ◽  
Eye Growth ◽  
Dose Dependent Fashion ◽  
High Concentrations ◽  
Dose Dependent ◽  
Glucagon Antagonist

Eye growth and refraction are regulated by visual processing in the retina. Until now, the messengers released by the retina to induce these changes are largely unknown. Previously, it was found that glucagon amacrine cells respond to defocus in the retinal image and even to its sign. The expression of the immediate-early gene product ZENK increased in this cell population in eyes wearing plus lenses and decreased in minus lens-treated chicks. Moreover, it was shown that the amount of retinal glucagon mRNA increased during treatment with positive lenses. Therefore, it seems likely that these cells contribute to the visual regulation of ocular growth and that glucagon may act as a stop signal for eye growth. The purpose of the present study was to accumulate further evidence for a role of glucagon in the visual control of eye growth. Chicks were treated with plus and minus lenses after injection of different amounts of the glucagon antagonist des-His1-Glu9-glucagon-amide or the agonist Lys17,18,Glu21-glucagon, respectively. Refractive development and eye growth were recorded by automated infrared photorefraction and A-scan ultrasound, respectively. The glucagon antagonist inhibited hyperopia development, albeit only in a narrow concentration range, and at most by 50%, but not myopia development. In contrast, the agonist inhibited myopia development in a dose-dependent fashion. At high concentrations, it also prevented hyperopia development.

scholarly journals Hormone-induced protein phosphorylation. I. Relationship between secretagogue action and endogenous protein phosphorylation in intact cells from the exocrine pancreas and parotid.

1982 ◽  
Vol 95 (3) ◽  
pp. 903-908 ◽  
Author(s):  
S D Freedman ◽  
J D Jamieson
Keyword(s):  
Protein Phosphorylation ◽  
Exocrine Pancreas ◽  
Second Messengers ◽  
Intact Cells ◽  
Cholecystokinin Octapeptide ◽  
Phosphorylation Of Proteins ◽  
Endogenous Protein ◽  
Dose Dependent Fashion ◽  
Dose Dependent

We undertook studies to determine whether secretagogue action on the exocrine pancreas and parotid is accompanied by phosphorylation of proteins in intact cells. For this purpose, rat pancreatic, and parotid lobules were preincubated with 32Pi for 45 min at 37 degrees C, washed, and then incubated at 37 degrees C in the presence or absence of secretagogues that effect discharge through different second messengers. Among a variety of polypeptides exhibiting enhanced phosphorylation in pancreatic lobules upon a 30-s incubation in the presence of the secretagogues carbamylcholine, cholecystokinin octapeptide, or secretin, one species with an Mr of 29,000 was especially notable for three reasons: (a) its enhanced level of phosphorylation was dependent on the dose of secretagogue used and was still apparent after incubation for 30 min at 37 degrees C; (b) an analogous phosphorylated polypeptide was observed in isoproterenol-stimulated parotid lobules; and (c) in both tissues its selective dephosphorylation was observed upon termination of stimulation by administration of atropine to carbamylcholine-stimulated pancreatic lobules and propranolol to isoproterenol-stimulated parotid lobules. These results suggest that the phosphorylation of one protein with an Mr of 29,000 is closely correlated both temporally and in a dose-dependent fashion with secretagogue action in both the exocrine pancreas and parotid.

scholarly journals The ALK-2 and ALK-4 activin receptors transduce distinct mesoderm-inducing signals during early Xenopus development but do not co-operate to establish thresholds

Development ◽  
1997 ◽  
Vol 124 (19) ◽  
pp. 3797-3804 ◽  
Author(s):  
N.A. Armes ◽  
J.C. Smith
Keyword(s):  
Cell Types ◽  
Type I ◽  
Cell Stage ◽  
Mesodermal Cell ◽  
Threshold Phenomenon ◽  
Dose Dependent Fashion ◽  
High Concentrations ◽  
Dose Dependent ◽  
Activin Receptors ◽  
Constitutively Active

The TGFbeta family member activin induces different mesodermal cell types in a dose-dependent fashion in the Xenopus animal cap assay. High concentrations of activin induce dorsal and anterior cell types such as notochord and muscle, while low concentrations induce ventral and posterior tissues such as mesenchyme and mesothelium. In this paper we investigate whether this threshold phenomenon involves the differential effects of the two type I activin receptors ALK-2 and ALK-4. Injection of RNA encoding constitutively active forms of the receptors (here designated ALK-2* and ALK-4*) reveals that ALK-4* strongly induces the more posterior mesodermal marker Xbra and the dorsoanterior marker goosecoid in animal cap explants. Maximal levels of Xbra expression are attained using lower concentrations of RNA than are required for the strongest activation of goosecoid, and at the highest doses of ALK-4*, levels of Xbra transcription decrease, as is seen with high concentrations of activin. By contrast, the ALK-2* receptor activates Xbra but fails to induce goosecoid to significant levels. Analysis at later stages reveals that ALK-4* signalling induces the formation of a variety of mesodermal derivatives, including dorsal cell types, in a dose-dependent fashion, and that high levels also induce endoderm. By contrast, the ALK-2* receptor induces only ventral mesodermal markers. Consistent with these observations, ALK-4* is capable of inducing a secondary axis when injected into the ventral side of 32-cell stage embryos whilst ALK-2* cannot. Co-injection of RNAs encoding constitutively active forms of both receptors reveals that ventralising signals from ALK-2* antagonise the dorsal mesoderm-inducing signal derived from ALK-4*, suggesting that the two receptors use distinct and interfering signalling pathways. Together, these results show that although ALK-2* and ALK-4* transduce distinct signals, the threshold responses characteristic of activin cannot be due to interactions between these two pathways; rather, thresholds can be established by ALK-4* alone. Furthermore, the effects of ALK-2* signalling are at odds with it behaving as an activin receptor in the early Xenopus embryo.

Role of Ca2+ in bombesin-stimulated release of gastrin and somatostatin from isolated perfused rat stomach

1988 ◽  
Vol 255 (5) ◽  
pp. G627-G632
Author(s):  
Y. S. Guo ◽  
J. C. Thompson ◽  
P. Singh
Keyword(s):  
Inhibitory Effect ◽  
Celiac Artery ◽  
Male Rats ◽  
High Dose ◽  
Channel Blockers ◽  
Gastrin Release ◽  
Dose Dependent Fashion ◽  
Rebound Phenomenon ◽  
Dose Dependent

The role of calcium (Ca2+) in bombesin (BBS)-stimulated release of gastrin and somatostatin-like immunoreactivity (SLI) was examined in isolated perfused rat stomachs obtained from male rats fasted overnight. The stomachs were perfused via the celiac artery. BBS (1 nM) was perfused alone for 10 min or in combination with various Ca2+ antagonists, including 1) different doses of divalent cationic Ca2+ chelator (EGTA), 2) Ca2+ channel blockers (nifedipine, verapamil), and 3) calmodulin (Ca2+ binding protein) antagonist [trifluoperazine (TFP)]. The effluent was collected for measurement of gastrin and SLI. EGTA at doses of 2 or 5 mM blocked the BBS-mediated release of both gastrin and SLI. After removal of a low dose of EGTA from the perfusate, the release of both gastrin and SLI rebounded. On removal of a high dose of EGTA, however, SLI release remained depressed, but gastrin rebounded even more significantly. In the absence of BBS, the rebound of gastrin release was less dramatic, indicating that reexposure to Ca2+ partially contributed to the rebound phenomenon. Nifedipine (0.1-10 microM) markedly decreased BBS-stimulated release of gastrin and SLI in a dose-dependent fashion; the inhibitory effect of nifedipine on SLI release was significantly stronger than on gastrin release. Verapamil (10 microM) depressed BBS-induced SLI release but not gastrin release. TFP (50 or 100 microM) also resulted in inhibition of bombesin-elicited release of gastrin and SLI in a dose-related manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasminogen Interactions with Immobilized Fibrinogen

1989 ◽  
Vol 62 (04) ◽  
pp. 1078-1082 ◽  
Author(s):  
Burt Adelman ◽  
Patricia Ouynn
Keyword(s):  
Immunosorbent Assay ◽  
Aminocaproic Acid ◽  
Enzyme Linked Immunosorbent Assay ◽  
Binding Regions ◽  
Dose Dependent Fashion ◽  
Epsilon Aminocaproic Acid ◽  
Dose Dependent

SummaryThis report describes the binding of plasminogen to fibrinogen adsorbed onto polystyrene wells. Binding was determined by enzyme linked immunosorbent assay. Both glu- and lys-plasminogen bound to immobilized fibrinogen in a dose-dependent fashion. However, more lys- than glu-plasminogen bound when equal concentrations of either were added to immobilized fibrinogen. Plasminogen binding was inhibited by epsilon aminocaproic acid indicating that binding was mediated via lysine-binding regions of plasminogen. Soluble fibrinogen added in excess of immobilized fibrinogen did not compete for plasminogen binding but fibrinogen fragments produced by plasmin digestion of fibrinogen did. Treatment of immobilized fibrinogen with thrombin caused a small but significant (p <0.01) increase in plasminogen binding. These studies demonstrate that immobilized fibrinogen binds both glu- and lys-plasminogen and that binding is mediated via lysine-binding regions. These interactions may facilitate plasminogen binding to fibrinogen adsorbed on to surfaces and to cells such as platelets which bind fibrinogen.

Soluble Thrombomodulin Purified from Human Urine Exhibits a Potent Anticoagulant Effect In Vitro and In Vivo

1995 ◽  
Vol 73 (05) ◽  
pp. 805-811 ◽  
Author(s):  
Yasuo Takahashi ◽  
Yoshitaka Hosaka ◽  
Hiromi Niina ◽  
Katsuaki Nagasawa ◽  
Masaaki Naotsuka ◽  
...  
Keyword(s):  
Human Urine ◽  
Specific Activity ◽  
Anticoagulant Activity ◽  
Rabbit Lung ◽  
Soluble Thrombomodulin ◽  
Molecular Weights ◽  
Dose Dependent Fashion ◽  
Dose Dependent

SummaryWe examined the anticoagulant activity of two major molecules of soluble thrombomodulin purified from human urine. The apparent molecular weights of these urinary thrombomodulins (UTMs) were 72,000 and 79,000, respectively. Both UTMs showed more potent cofactor activity for protein C activation [specific activity >5,000 thrombomodulin units (TMU)/mg] than human placental thrombomodulin (2,180 TMU/mg) and rabbit lung thrombomodulin (1,980 TMU/mg). The UTMs prolonged thrombin-induced fibrinogen clotting time (>1 TMU/ml), APTT (>5 TMU/ml), TT (>5 TMU/ml) and PT (>40 TMU/ml) in a dose-dependent fashion. These effects appeared in the concentration range of soluble thrombomodulins present in human plasma and urine. In the rat DIC model induced by thromboplastin, administration of UTMs by infusion (300-3,000 TMU/kg) restored the hematological abnormalities derived from DIC in a dose-dependent fashion. These results demonstrate that UTMs exhibit potent anticoagulant and antithrombotic activities, and could play a physiologically important role in microcirculation.

Hepatic uptake of intact glutathione S-conjugate, inhibition by organic anions, and sinusoidal catabolism

1993 ◽  
Vol 265 (3) ◽  
pp. G547-G554
Author(s):  
C. A. Hinchman ◽  
A. T. Truong ◽  
N. Ballatori
Keyword(s):  
Guinea Pig ◽  
Rat Liver ◽  
Marked Decrease ◽  
Hepatic Uptake ◽  
Half Time ◽  
High Concentrations ◽  
Rat Livers ◽  
Dose Dependent ◽  
Uptake And Metabolism ◽  
Guinea Pig Liver

To identify potential mechanisms for hepatic removal of circulating glutathione (GSH) conjugates, uptake and metabolism of S-2,4-dinitrophenylglutathione (DNP-SG) were examined in isolated perfused livers from rat and guinea pig. Guinea pig livers perfused with 5 mumol of DNP-SG in a recirculating system (50 microM initial concn) rapidly cleared the conjugate from the perfusate (half time 3.7 min), whereas clearance was considerably slower in rat liver (half time 35 min). Disappearance of DNP-SG from the perfusate was accompanied by a simultaneous appearance of DNP-SG and its metabolites in bile. Addition of acivicin, an inhibitor of gamma-glutamyltransferase (gamma-GT), to the perfusate resulted in a marked decrease in DNP-SG clearance by guinea pig liver but had no effect in rat liver, suggesting that in the guinea pig this process is largely dependent on sinusoidal gamma-GT activity. However, even in the presence of acivicin, rat and guinea pig livers removed nearly one-half of the administered DNP-SG from the recirculating perfusate over 30 min. High concentrations of DNP-SG were found in bile (up to 3.7 mM), indicating that the liver is capable of transporting the intact conjugate from the circulation. When rat livers were perfused with higher concentrations of DNP-SG (100 and 250 microM), biliary excretion of DNP-SG increased dose dependently, with concentrations in bile reaching 10 mM at the higher dose. This was accompanied by a dose-dependent choleresis.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals IMMU-09. CONCURRENT DEXAMETHASONE LIMITS THE CLINICAL BENEFIT OF IMMUNE CHECKPOINT BLOCKADE IN GLIOBLASTOMA

2020 ◽  
Vol 22 (Supplement_2) ◽  
pp. ii106-ii106
Author(s):  
Bryan Iorgulescu ◽  
Prafulla Gokhale ◽  
Maria Speranza ◽  
Benjamin Eschle ◽  
Michael Poitras ◽  
...  
Keyword(s):  
Prognostic Factors ◽  
Immune Checkpoint ◽  
Nk Cell ◽  
Immune Checkpoint Blockade ◽  
Checkpoint Blockade ◽  
Innate Immune Responses ◽  
Dose Dependent Fashion ◽  
Dexamethasone Therapy ◽  
Clinical Correlate ◽  
Dose Dependent

Abstract BACKGROUND Dexamethasone, a uniquely potent corticosteroid, is frequently administered to brain tumor patients to decrease tumor-associated edema, but limited data exist describing how dexamethasone affects the immune system systemically and intratumorally in glioblastoma patients – particularly in the context of immunotherapy. METHODS We evaluated the dose-dependent effects of dexamethasone when administered with anti-PD-1 and/or radiotherapy in immunocompetent C57BL/6 mice with syngeneic GL261 or CT-2A glioblastoma tumors, including analyses of intracranial tumors, draining lymph nodes, and spleen. Clinically, the effect of dexamethasone on survival was additionally evaluated in 181 consecutive IDH-wildtype glioblastoma patients treated with anti-PD-(L)1, with adjustment for relevant prognostic factors. RESULTS Despite the inherent responsiveness of GL261 to immune checkpoint blockade, concurrent dexamethasone administration with anti-PD-1 therapy decreased survival in a dose-dependent fashion and decreased survival following anti-PD-1 plus radiotherapy in both GL261 and immunoresistant CT-2A models. Dexamethasone quantitatively decreased T lymphocytes by reducing the proliferation while increasing apoptosis. Dexamethasone also decreased lymphocyte functional capacity. Myeloid and NK cell populations were also generally reduced. Thus, dexamethasone negatively affects both the adaptive and innate immune responses. As a clinical correlate, a retrospective analysis of 181 consecutive IDH-wildtype glioblastoma patients treated with PD-(L)1 blockade revealed worse survival among those on baseline dexamethasone. Upon multivariable adjustment with relevant prognostic factors, baseline dexamethasone use – regardless of dose – was the strongest predictor of poor survival (reference no dexamethasone; &lt; 2mg HR 2.28, 95%CI=1.41–3.68, p=0.001; ≥2mg HR 1.97, 95%CI=1.27–3.07, p=0.003). CONCLUSIONS Our preclinical and clinical data indicate that concurrent dexamethasone therapy may be detrimental to immunotherapeutic approaches for glioblastoma patients. Our preclinical analyses also suggest that dexamethasone’s detrimental effects are dose-dependent, suggesting that the lowest possible dose should be used for patients when dexamethasone use is unavoidable. Careful evaluation of dexamethasone use is warranted for neuro-oncology patients undergoing immunotherapy clinical trials.

scholarly journals Anthracycline-induced cytotoxicity in the GL261 glioma model system

2021 ◽  
Author(s):  
Amber M. Tavener ◽  
Megan C. Phelps ◽  
Richard L. Daniels
Keyword(s):  
Cell Viability ◽  
Tumor Cells ◽  
Flow Cytometric Analysis ◽  
Annexin V ◽  
Chemotherapeutic Agents ◽  
Cytotoxic Effects ◽  
High Concentrations ◽  
Induced Apoptosis ◽  
Dose Dependent ◽  
Gl261 Glioma

AbstractGlioblastoma (GBM) is a lethal astrocyte-derived tumor that is currently treated with a multi-modal approach of surgical resection, radiotherapy, and temozolomide-based chemotherapy. Alternatives to current therapies are urgently needed as its prognosis remains poor. Anthracyclines are a class of compounds that show great potential as GBM chemotherapeutic agents and are widely used to treat solid tumors outside the central nervous system. Here we investigate the cytotoxic effects of doxorubicin and other anthracyclines on GL261 glioma tumor cells in anticipation of novel anthracycline-based CNS therapies. Three methods were used to quantify dose-dependent effects of anthracyclines on adherent GL261 tumor cells, a murine cell-based model of GBM. MTT assays quantified anthracycline effects on cell viability, comet assays examined doxorubicin genotoxicity, and flow cytometry with Annexin V/PI staining characterized doxorubicin-induced apoptosis and necrosis. Dose-dependent reductions in GL261 cell viability were found in cells treated with doxorubicin (EC50 = 4.9 μM), epirubicin (EC50 = 5.9 μM), and idarubicin (EC50 = 4.4 μM). Comet assays showed DNA damage following doxorubicin treatments, peaking at concentrations of 1.0 μM and declining after 25 μM. Lastly, flow cytometric analysis of doxorubicin-treated cells showed dose-dependent induction of apoptosis (EC50 = 5.2 μM). Together, these results characterized the cytotoxic effects of anthracyclines on GL261 glioma cells. We found dose-dependent apoptotic induction; however at high concentrations we find that cell death is likely necrotic. Our results support the continued exploration of anthracyclines as compounds with significant potential for improved GBM treatments.

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