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Biomedical subjects

J D Gardner

Publications and source records attributed to J D Gardner.

At least 271 records · Page 15Linked to original sources
PubMed1976

Action of cholecystokinin, cholinergic agents, and A-23187 on accumulation of guanosine 3':5'-monophosphate in dispersed guinea pig pancreatic acinar cells.

The COOH-terminal octapeptide of cholecystokinin (CCK-OP) and carbamylcholine each increased calcium outflux, cellular cyclic GMP and amylase secretion in dispersed guinea pig pancreatic acinar cells. Following addition of CCK-OP or carbamylcholine, cellular cyclic GMP increased as early as 15 s, became maximal after 1 to 2 min, and then decreased steadily during the subsequent incubation. For both CCK-OP and carbamylcholine there was close agreement between the dose-response curve for stimulation of calcium outflux and that for increase of cellular cyclic GMP. With CCK-OP an effect on both functions could be detected at 10(-10) M and maximal stimulation occurred at 3 X 10(-8) M. With carbamylcholine an effect on both functions could be detected at 10(-5) M and maximal stimulation occurred at 3 X 10(-3) M. Atropine inhibited stimulation of both cyclic GMP and calcium outflux by carbamylcholine but not by CCK-OP. Stimulation of calcium outflux or cellular cyclic GMP by CCK-OP or carbamylcholine did not require extracellular calcium since stimulation occurred in a calcium-free, ethylene glycol bis(beta, beta-aminoethyl ether) N,N'-tetraacetic acid (EGTA)-containing solution. The divalent cation ionophore A-23187 increased bidirectional fluxes of calcium, cellular cyclic GMP and secretion of amylase from dispersed pancreatic acinar cells. Like CCK-OP and carbamylcholine, the ionophore stimulated calcium outflux and cellular cyclic GMP in a calcium-free, EGTA-containing solution. These results suggest that in pancreatic acinar cells the initial step in the sequence of events mediating the action of ionophore as well as that of CCK-OP and carbamylcholine is stimulation of calcium outflux, and that this stimulation then increases cellular cyclic GMP.

Animals↗
PubMed1976

Interaction of porcine vasoactive intestinal peptide with dispersed pancreatic acinar cells from the guinea pig. Binding of radioiodinated peptide.

We have used 125I-labeled vasoactive intestinal peptide (VIP) to study the kinetics, stoichiometry, and chemical specificity with which the labeled peptide binds to dispersed acinar cells prepared from guinea pig pancreas. Binding of 125I-VIP to pancreatic acinar cells was moderately rapid, reversible, specific, saturable, and depended on incubation temperature. Deterioration of 125I-VIP incubated with pancreatic acinar cells at 37 degrees was reflected in a decrease in acid-precipitable radioactivity and in the amount of tracer which could bind to fresh acinar cells. On the other hand, 125I-VIP bound to pancreatic acinar cells appeared to be protected from deterioration. VIP and secretin but not glucagon or COOH-terminal octapeptide of cholecystokinin inhibited binding of 125I-VIP to pancreatic acinar cells. The dose-response curve for inhibition of 125I-VIP binding by VIP or secretin was biphasic and suggested that pancreatic acinar cells have two classes of binding sites: (a) a relatively small number of sites with a high affinity for VIP and a low affinity for secretin, and (b) a relatively large number of sites with a low affinity for VIP and a high affinity for secretin. The difference between the relative affinities of VIP and secretin for the high affinity VIP binding sites appears to be primarily attributable to the NH2-terminal portions of these molecules since synthetic COOH-terminal fragments VIP 14-28, VIP 15-28, and secretin 14-27 were equipotent in inhibiting 125I-VIP binding. On the other hand, secretin 5-27, [6-tyrosine] secretin and native secretin were equipotent in inhibiting binding of 125I-VIP to its high affinity site, and these three peptides were 5 times more potent than secretin 14-27 but 10,000 times less potent than native VIP.

Amino Acid Sequence↗
PubMed1976

Action of cholecystokinin and cholinergic agents on membrane-bound calcium in dispersed pancreatic acinar cells.

In dispersed acinar cells prepared from guinea pig pancreas, cellular uptake of 45Ca was moderately rapid and reached a steady state by 60 min. At the steady state, 69% of total cellular 45Ca was membrane-bound. In acinar cells preloaded with 45Ca and then incubated with COOH-terminal octapeptide of cholecystokinin (CCK-OP) or carbamylcholine, total cellular 45Ca decreased by approximately 40% within 5-10 min and then steadily increased to control values by 60 min. Under identical conditions, membrane-bound 45Ca decreased by 40% within 5-10 min and remained constant for the duration of the incubation. Free cellular 45Ca did not change during the initial 30 min but then increased steadily to values three times those in control cells by 60 min. In cells preloaded with 45Ca and then incubated with EDTA, the loss of total cellular radioactivity stimulated by CCK-OP could be accounted for by loss of membrane-bound 45Ca. CCK-OP failed to alter total cellular uptake of 45Ca when both tracer and peptide were added at the beginning of the incubation. Under identical conditions, membrane-bound 45Ca was not altered by CCK-OP during the first 30 min of incubation but was significantly below control values after this time. The effect of CCK-OP on free cellular 45Ca was the same as in cells preloaded with the tracer. These results suggest that CCK-OP causes release of 45Ca from a membrane-bound compartment that equilibrates slowly with extracellular fluid and that the change in free cellular 45Ca is a secondary effect.

Animals↗
PubMed1976

Direct determination of ligand interactions with beta-adrenergic receptors on intact turkey erythrocytes: correlation of binding with biological activity.

Previous studies on the interaction of labeled beta-adrenergic blockers with beta-adrenergic receptors have employed broken cell or membrane preparations. We have now carried out direct binding analysis on intact turkey erythrocytes employing the potent, high specific activity blocker [125I]-hydroxbenzylpindolol (HYP). [125I]HYP binds to a single class of receptor sites with a K of 5.3 X 10(10)M-1 and a binding capacity of 400-500 sites/cell. These results as well as the kinetics of association and dissociation and lack of evidence for negative cooperativity all agree well with studies reported earlier on membrane preparations from the same cells. True dissociation constants (Kd) for agonists and antagonists determined by inhibition of binding of [125I]HYP are in good agreement with results in membrane preparations. These Kd's have been compared directly with activation or inhibition constants for effects on adenylate cyclase using generation of [14C]cAMP from [14C]adenine in intact cells. The close correlation between effects on binding and adenylate cyclase activity in whole cells are similar to results obtained in membrane preparations in the presence of guanine nucleotides, suggesting the presence of an analogous regulatory substance in vivo.

Adrenergic beta-Agonists↗
PubMed1976

Hyperhistaminemia and hyperchlorhydria in basophilic granulocytic leukemia.

A patient with basophilic granulocytic leukemia had hyperhistaminemia, hyperchlorhydria and gastroduodenal ulceration. Because the patient's whole blood, plasma, and urinary histamine levels were increased and the serum gastrin was normal, it was concluded that endogenous hyperhistaminemia was responsible for an ulcerogenic diathesis clinically indistinguishable from that seen in the Zollinger-Ellison syndrome.

Adult↗
PubMed1976

Cyclic AMP in pancreatic acinar cells: effects of gastrointestinal hormones.

In the presence of 5 mM theophylline, secretin and vasoactive intestinal peptide (VIP) each increased cyclic adenosine 3':5'-monophosphate (cyclic AMP) in acinar cells isolated from guinea pig pancreas. Without theophylline, neither peptide altered cellular cyclic AMP. Glucagon, which is similar to secretin and VIP both in chemical structure and spectrum of biologic activities, neither stimulated cellular cyclic AMP nor inhibited the stimulation produced by secretin or by VIP. Other agents which were tested and found not to increase cellular cyclic AMP were cholecystokinin, carboxyl-terminal octapeptide of cholecystokinin, gastrin I, gastrin II, bovine pancreatic polypeptide, carbamylcholine, and prostaglandin E1. Neither carboxyl-terminal octapeptide nor gastrin I altered the stimulation of cellular cyclic AMP produced by secretin or VIP. With natural secretin a significant increase in cellular cyclic AMP could be detected at concentrations as low as 3 x 10(-10) M and maximal stimulation occurred at 10(-8) M. VIP was approximately 1% as potent as natural secretin and maximal concentrations of secretin plus VIP increased cellular cyclic AMP to the same value as was obtained with a maximal concentration of secretin alone.

Animals↗
PubMed1976

Interaction of peptides related to secretin with hormone receptors on pancreatic acinar cells.

Three analogues of the carboxyl-terminal tricosapeptide of secretin (S5-27), one with glutamine replacing glutamic acid in position 9 (9-Gln-S5-27), a second with asparagine substituted for aspartic acid in position 15 (15-Asn-S5-27), and a third with both replacements (9-Gln-15-Asn-S5-27) were tested for their ability to interact with hormone receptors on dispersed pancreatic acinar cells. Each of these analogues inhibited binding of 125I-labeled vasoactive intestinal peptide (VIP). None of the analogues increased cellular cyclic AMP but each inhibited the increase in cellular cyclic AMP produced by secretin or VIP. At the high affinity VIP receptor (the low affinity secretin receptor) each analogue had an apparent affinity which was greater than that for S5-27, whereas at he low affinity VIP receptor (the high affinity secretin receptor), each of the analogues had an apparent affinity which was the same as that for S5-27. Thus, in S5-27, substituting glutamine in position 9 or asparagine in position 15 makes the fragment more VIP-like but not less secretin-like. These results also provide additional evidence that the receptor having a low affinity for secretin and a high affinity for VIP is functionally distinct from the receptor having a high affinity for secretin and a low affinity for VIP.

Amino Acid Sequence↗
PubMed1976

Jejunal adenylate cyclase activity in human subjects during viral gastroenteritis.

The histopathological changes that occur in the jejunal mucosa of humans infected with the Norwalk or Hawaii agent of acute infectious nonbacterial gastroenteritis ("viral" gastroenteritis) have ben well characterized. The pathogenesis of diarrhea in this syndrome remains unknown; however, recent reports have suggested a possible role for the adenylate cyclase system. In this combined paper, two groups of investigators working independently and employing slightly different techniques report that: (1) there is marked interindividual variation in the apparent specific activity of adenylate cyclase in human jejunal biopsy tissue; (2) such variation can be minimized by expressing enzyme activity as a fraction of maximal that can be stimulated by 10(-2) M sodium fluoride; and (3) adenylate cyclase activity in jejunal mucosa is not increased during diarrhea or illness in human viral gastroenteritis, therefore suggesting no role for the adenylate cyclase system in the pathogenesis of diarrhea in this common clinical entity.

Adenylyl Cyclases↗
PubMed1975

Pancreatic cholera: beneficial effects of treatment with streptozotocin.

Two patients with pancreatic cholera and islet-cell carcinoma were treated with intra-arterial streptozotocin. Before therapy, they had stool volumes from 2 to 8 liters per day and required 200 to 800 mEq per day of supplemental potassium. After three to five doses of streptozotocin (1.5 per square meter), both stool volume and number and size of hepatic metastases decreased markedly. One patient has had normally formed stools for 12 months; the other had a 90 per cent reduction in stool volume for 13 months with additional therapy. Both patients' serum potassium returned to normal without need for supplementation. Jejunal adenylate cyclase activity was normal in both, and plasma vasoactive intestinal peptide was detectable in only one. After chemotherapy, these findings showed no consistent change. Pharmacologic studies suggest that arterial administration increased either tumor or hepatic extraction (or both) of streptozotocin by two times and decreased renal exposure to this nephrotoxic drug by one third.

Achlorhydria↗
PubMed1975

Effects of extracellular cations and ouabain on catecholamine-stimulated sodium and potassium fluxes in turkey erythrocytes.

In turkey erythrocytes, potassium influx can be inhibited by several cations whose order of effectiveness is Rb greater than Cs greater than Li greater than Mg = Ca = Ba. Extracellular sodium does not alter potassium influx. Sodium influx is not altered by any of these monovalent cations but magnesium, calcium, or barium reduced sodium influx by 30 to 40%. Potassium outflux is not influenced by extracellular sodium or potassium while sodium outflux is not influenced by extracellular potassium but increases progressively with increasing extracellular sodium. Isoproterenol stimulates potassium influx only when sodium or lithium is present in the medium and catecholamine stimulation increases progressively with increasing extracellular sodium. Isoproterenol-stimulated sodium influx is enhanced by extracellular potassium, rubidium or cesium, and catecholamine stimulation increases progressively with increasing extracellular potassium. Isoproterenol inhibits potassium outflux in a solution free of sodium and potassium, and this inhibition can be abolished by adding sodium but not by adding potassium. In solutions containing both sodium and potassium, isoproterenol stimulates potassium outflux, and this stimulation increases progressively with increasing extracellular sodium or potassium. Isoproterenol-stimulated sodium outflux is not influenced by extracellular sodium or potassium. Isoproterenol-stimulated cellular cyclic adenosine 3':5'-monophosphate (cyclic AMP) is reduced slightly (25%) by removing extracellular sodium and potassium from the incubation solution, but this effect is not of sufficient magnitude to account for the effects of these cations on isoproterenol-stimulated cation transport. Ouabain does not alter the effect of extracellular sodium or potassium on isoproterenol-stimulated potassium influx; however, the glycoside potentiates (by 20 to 40%) the effects of these two cations on isoproterenol-stimulated sodium influx. Ouabain does not alter potassium outflux when the incubation solution contains both sodium and potassium; however, ouabain stimulates potassium outflux in an incubation solution free of sodium or potassium.

Animals↗
PubMed1975

Refractoriness of cation transport in turkey erythrocytes to stimulation by cyclic adenosine 3':5'-monophosphate.

In turkey erythrocytes bidirectional fluxes of sodium and potassium develop a time-dependent refractoriness to stimulation by endogenous cyclic adenosine 3':5'-monophosphate (cyclic AMP). The refractoriness of potassium influx and potassium outflux (both of which require extracellular sodium and potassium for stimulation by cyclic AMP) depends on the extracellular concentrations of sodium and potassium. In contrast, the refractoriness developed by sodium outflux (which does not require extracellular sodium or potassium for stimulation by cyclic AMP) does not depend on the extracellular concentrations of sodium or potassium. The refractoriness of these fluxes to cellular cyclic AMP reflects a decrease in the amount by which they can be maximally stimulated and appears to be proportional to the extent to which the transport system is utilized during the course of the incubation. Ouabain significantly reduces the rate at which cation transport in turkey erythrocytes becomes refractory to endogenous cyclic AMP. This effect of the glycoside is independent of the extracellular concentrations of sodium or potassium and does not correlate with how it alters the initial response of the transport systems to cyclic AMP.

Animals↗
PubMed1975

Effects of beta-adrenergic catecholamines on potassium transport in turkey erythrocytes.

Isoproterenol stimulates cellular accumulation of cyclic adenosine 3':5'-monophosphate (cyclic AMP) and produces a 2- to 4-fold increase in bidirectional potassium fluxes in turkey erythrocytes. Ouabain, which does not alter catecholamine-stimulated cellular cyclic AMP, inhibits potassium influx by 50 to 70%, does not alter potassium outflux or isoproterenol-stimulated potassium influx, but increases isoproterenol-stimulated potassium outflux. Stimulation of potassium transport by isoproterenol can be reproduced by adding cyclic AMP to the medium and is inhibited by propranolol or dichloroisoproterenol but not by phentolamine. Theophylline at concentrations which inhibit cyclic nucleotide phosphodiesterase in isolated turkey erythrocyte plasma membranes by greater than 90%, does not augment isoproterenol stimulation of cellular cyclic AMP or of potassium transport but does potentiate stimulation of potassium influx produced by adding cyclic AMP to the medium. Isoproterenol-stimulated cellular cyclic AMP increases steadily for at least 2 hours. Potassium transport, however, increases rapidly, becomes maximal after 20 to 30 min of incubation, and thereafter decreases progressively so that after 2 hours of incubation potassium fluxes are only slightly greater than for the control. Ouabain prolongs the duration of catecholamine-stimulated potassium influx and potassium outflux, reflecting its ability to relieve the refractoriness developed by turkey erythroyctes to endogenous cyclic AMP.

Adrenergic beta-Antagonists↗
PubMed1975

Viral gastroenteritis induced by the Hawaii agent. Jejunal histopathology and serologic response.

Peroral jejunal biopsies were performed in seven normal volunteer subjects prior to, 48 hours after and two weeks after the administration of the Hawaii agent of viral gastroenteritis. Light and electron microscopic examination revealed an intact mucosa with blunted villi, shortened and distorted microvilli, swollen mitochondria and intercellular edema. These histologic changes were seen only in acutely ill volunteer subjects and were absent two weeks after illness in three of four who were previously ill. This reversible lesion was similar to, but not identical with, that previously described in viral gastroenteritis induced by the Norwalk agent. Serum antibody increases in response to the Hawaii agent as measured by immune electron microscopy were present in three of four ill volunteer subjects and in none of three who remained well.

Acute Disease↗
PubMed1975

Action of cholecystokinin and cholinergic agents on calcium transport in isolated pancreatic acinar cells.

COOH-terminal octapeptide of cholecystokinin (CCK-octapeptide) and the cholinergic agent carbamylcholine each produced a fourfold stimulation of calcium outflux in guinea pig isolated pancreatic acinar cells. Neither agent altered calcium influx. Stimulation of calcium outflux was rapid and specific, was abolished by reducing the incubation temperature to 4 degrees C, and was a saturable function of the secretagogue concentration. The concentrations of CCK-octapeptide and carbamylcholine that produced half-maximal stimulation of calcium outflux were 3.1 x 10(-10) M and 4.9 x 10(-5) M, respectively. The cholinergic antagonist antropine competitively inhibited carbamylcholine stimulation of calcium outflux but did not alter stimulation produced by CCK-octapeptide. Stimulation of calcium outflux by maximal concentrations of carbamycholine plus CCK-octapeptide was the same as that produced by a maximal concentration of either agent alone.Calcium outflux became refractory to stimulation by secretagogues, and incubation with either CCK-ostapeptide or carbamylcholine produced a refractoriness to both agents. The relative potencies with CCK and its related fragments stimulated calcium outflux were CCK-octapeptide greater than heptapeptide greater than CCK greater than hexapeptide = gastrin. Secretin, glucagon, and vasoactive intestinal peptide, at concentrations as high as 10(-5) M, failed to alter calcium outflux and did not affect stimulation by CCK-octapeptide or by carbamycholine.

Amylases↗
PubMed1975

Beta-adrenergic receptors, cyclic AMP, and ion transport in the avian erythrocyte.

(1) Interaction of beta-adrenergic catecholamines with specific receptors on the cell membrane causes activation of adenylate cyclase, generation of intracellular cyclic 3',5'-AMP, and enhanced sodium and potassium transport. The effects of catecholamines on each of these functions are characteristic of beta1-type receptor interactions and are specific for 1(--)isomers. The order of effectiveness of agonists is isoproterenol greater than norepinephrine approximately equal to epinephrine. (2) exogenous cyclic 3',5'-AMP enhances sodium or potassium transport in a fashion identical to that caused by catecholamines. (3) the receptor contains an ethanolamine site that recognizes the stereospecific function of the agonist. Interaction at this site can be determined by measuring specific binding of a high specific activity-radioiodinated beta-blocker analogue (125-iodohydroxybenzylpindolol). Catecholamines bind at this site with affinities that parallel their biologic effectiveness as beta-adrenergic agonist. Beta-Blockers interact at this site with affinities that parallel their potencies as specific inhibitors of biologic function. (4) the adenylate cyclase complex contains a receptor site for guanyl nucleotides that is distinct from the catalytic site for ATP. Interaction at this site can be determined by measuring binding of radioactive guanylylimidodiphosphate (GMPPNP). GMPPNP markedly enhances the adenylate cyclase response to beta-adrenergic catecholamines with a 10-fold increase in apparent affinity of isoproterenol for activation of adenylate cyclase. Concomitantly there is a shift in Km and Vmax for ATP at the catalytic site. (5) Activation of adenylate cyclase by agonist or GMPPNP alone is reversible (GMPPNP remains bound even though the system returns to basal activity). The addition of isoproterenol plus GMPPNP, however, results in a state of enzyme activity which is apparently irreversible even though, under these conditions, the beta-adrenergic catecholamine freely dissociates from its receptor site. Under these conditions also the activated enzyme is not inhibited by the specific beta-blocker propranolol. (6) There is no evidence under adenylate cyclase assay conditions for a direct interaction of guanyl nucleotides with the beta-adrenergic receptor site nor for direct interaction of the agonist with the guanyl nucleotide site.

Animals↗
PubMed1975

Pancreatic cholera.

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Adenoma, Islet Cell↗