bluuebunny/crossref_metadata_2025 huggingface dataset:
Endocrine activation and altered muscle metabolism after hemorrhagic shock.
Authors: Ryan N T , George B C , Harlow C L , Hiebert J M , Egdahl R H
Published: December 2017

Studies were conducted to examine glucose and amino acid metabolism by skeletal muscle isolated from rhesus monkeys before and sequentially after an episode of resuscitated hemorrhagic shock. After shock and reinfusion, the tissue exhibited decreased effect of insulin on glucose utilization increased leucine oxidation, and a reduced rate of leucine incorporation into protein. These changes were observed 15 min after reinfusion and persisted in part for at least 3 days. All of the observed abnormalities were more pronounced 24 h after shock and reinfusion than 15 min after and returned to normal by 2-4 wk. The shock-induced metabolic abnormalities in skeletal muscle occurred in spite of prevention of shock-induced adrenal steroid and catecholamine secretion and of changes in blood insulin concentration using adrenalectomized-streptozotocin diabetic monkeys receiving replacement cortisol and insulin infusions. This study thus demonstrated that hemorrhagic shock in rhesus monkeys was followed by insulin resistance plus abnormalities of glucose and amino acid metabolism by skeletal muscle that were not dependent on the concurrent changes in plasma levels of adrenal steroids or catecholamines or on altered circulating insulin levels associated with shock.
Some characteristics of kidney Na+ -dependent glucose carrier reconstituted into sonicated liposomes.
Authors: Crane R K , Malathi P , Preiser H , Fairclough P
Published: December 2017

Studies of the Na+-gradient coupled D-glucose carrier of the brush border membrane of rabbit kidney cortex extracted with Triton X-100 and reconstituted into artificial liposomes show that the reconstituted carrier behaves in those respects so far studied in a manner very similar to the same carrier studied in natural membrane vesicles.
Protein turnover in rat skeletal muscle: effects of hypophysectomy and growth hormone.
Authors: Flaim K E , Li J B , Jefferson L S
Published: December 2017

The role of growth hormone in regulating protein turnover was examined in a perfused preparation of rat skeletal muscle. The perfused muscle maintained in vivo levels of ATP and creatine phosphate and exhibited constant rates of oxygen consumption and protein synthesis. Hypophysectomy reduced the rate of protein synthesis, the concentration of RNA, and the efficiency of protein synthesis in gastrocnemius muscle to 30, 46, and 66 percent of normal, respectively. In vivo treatment of hypophysectomized (hypox) rats with bovine growth hormone (250 microgram/day for 5 days) resulted in small increases in protein synthesis and RNA, whereas synthesis/RNA was returned to near normal. Elevation of ribosomal subunits in psoas muscle indicated an inhibition of peptide-chain initiation in hypox rats that was reversed by in vivo growth hormone treatment. Thus, hypox rats exhibited both a decreased capacity and a decreased efficiency of protein synthesis. Growth hormone replacement primarily increased efficiency of protein synthesis. The rate of protein degradation and the activity of cathepsin D in gastrocnemius muscle were decreased by hypophysectomy. Growth hormone treatment had no significant effect on degradation.
A comparison of body fat determined by underwater weighing and volume displacement.
Authors: Ward A , Pollock M L , Jackson A S , Ayres J J , Pape G
Published: December 2017

Two hydrostatic techniques, underwater weighing and water displacement, were used to determine body fat for 67 volunteer men between 25 and 61 yr of age (-/x=41 yr). All tests were administered in random order in the morning on the same day while subjects were in the postabsorptive state. Test-retest reliabilities for the underwater weighing and water displacement techniques were 0.995 and 0.96, respectively. The correlation between the two hydrostatic techniques was r=0.96. The mean percent fat determined by underwater weighing (-/x=20.1 +/- 6.4) and water displacement (-/x=19.4 +/- 6.1) were significantly different (t=28.16; df=65; P less than 0.001). These analyses showed that both techniques were reliable in measuring percent body fat, but produced slight systematic differences. Regression equations were provided to adjust for the difference.
Glucose transport in isolated rat adipocytes with measurements of L-arabinose uptake.
Authors: Foley J E , Cushman S W , Salans L B
Published: December 2017

Data is presented suggesting that rates of L-arabinose transport, calculated from L-[1-14C]arabinose uptake measurements, can be used as indicators of changes in the rates of glucose transport in isolated rat adipocytes. L-[1-14C]arabinose, at 37 degrees C, was found to be nonmetabolizable and taken up by adipocytes exponentially with time reaching 95% of equilibrium in 30 min. When L-arabinose is corrected for background, the corrected uptake values conform to the time-dependent monoexponential uptake relationshiop predicted for a facilitated transport system and are not significantly different from 0 in the presence of 70 micron cytochalasin B. Transport rates were calculated from corrected uptake values near the half-maximal uptake of L-arabinose and from a value of the total amount of L-arabinose in the cell at equilibrium. Competitive inhibition of L-arabinose transport by glucose and countertransport of L-arabinose in the presence of glucose suggest that L-arabinose and glucose share the same transport system. Data is presented demonstrating the effect of insulin and dexamethasone on the transport system that confirms the conclusions obtained by other investigators using other methods.
Erythritol and mannitol clearances with taurocholate and secretin-induced cholereses.
Authors: Barnhart J L , Combes B
Published: December 2017

The biliary clearances of [14C]erythritol (Cery) and [3H]mannitol (Cmann) were measured simultaneously in dogs during cholereses induced by sodium taurocholate and by secretin. Cery increased equally with the increase in bile flow induced by taurocholate, whereas mannitol entry into bile was partially restricted; deltaCery/deltabile flow averaged 0.96; deltaCmann/deltaCery averaged 0.81. Values for erythritol clearance exceeded bile flow by a constant volume over a wide range of bile flows, a result that suggests distal reabsorption of a fixed amount of fluid, independent of canalicular bile production. During secretin-induced choleresis both Cery and Cmann accompanied 30-40% of the increase in bile flow, and the ratio of Cmann/Cery was 1.02. Thus the secretin-responsive region is permeable to both erythritol and mannitol. This affects the extent to which measured erythritol clearance accurately reflects canalicular bile formation; Cery may underestimate or overestimate canalicular bile flow. The electrolyte composition of bile remained relatively constant over a broad range of bile flows although the characteristics of taurocholate- and secretin-induced biles differed from each other. Taurocholate-stimulated bile was virtually isotonic. Secretin-induced bile had a high total concentration of electrolyte (mean concentration 367 meq/liter) rich in chloride and bicarbonate and was hypertonic.
Dietary iodine and thyroidal iodide transport in chickens: organic binding blocked.
Authors: Newcomer W S
Published: December 2017

Experimental data concerning the increase in T/S [I-] (ratio of concentration of radioiodide in thyroid to that in serum) during equilibration after a single injection of radioidide were obtained from chickens in which protein binding of radioidide was inhibted by methimazole. Equilibration data were obtained from chickens fed a low-iodine diet (2 mo) as well as the low-iodine diet to which various amounts of NaI had been added. Experimental data were compared with productions based on the open two-compartmental model of Wollman and Reed (Am. J. Physiol. 196: 113-120, 1959). Thyroidal clearance (C/m) of radioiodide (the rate at which radioiodide is transferred from blood into the thyroid and equal to the radioiodide content of C microliter serum per minute) varied inversely to iodine content of feed. Exit rate constant (KTB, the fraction of thyroidal radioiodide transferred to serum per minute) was relatively more constant. The experimental data fitted the predictions from the model within experimental error. Thirty days of feeding the low-iodine diet was required before C/m stabilized at 50 microliter/min per mg and KTB at 0.065; stabilization of C/m and KTB occurred in 12 days with the highest iodine diet.
Primary role of decreased fatty acid synthesis in insulin resistance of large rat adipocytes.
Authors: Richardson D K , Czech M P
Published: December 2017

The ability of large fat cells from spontaneously obese rats to synthesize fatty acids from D-[1-14C]glucose, D-[6-14C]glucose, or [2-14C]pyruvate was markedly diminished compared to small fat cells from lean animals. Furthermore, fatty acid synthetase and acetyl coenzyme A carboxylase activities in dialyzed homogenates of large fat cells were inhibited by 84 and 90%, respectively, compared to small cells. Pentose shunt activity, but not glycolytic flux, was also markedly inhibited in large fat cells incubated with or without insulin. However, the NADPH oxidant vitamin K5 completely restored pentose shunt activity in large cells to the elevated levels observed in small fat cells in the presence of this agent or insulin. Furthermore, inhibition of mitochondrial oxidation and fatty acid synthesis in small cells by rotenone led to a secondary inhibition of pentose shunt activity indicating a link between these two pathways. Direct measurements of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities in fat cell homogenates showed no difference between cell types. The data provide strong support for the hypothesis that the fatty acid synthetic pathway is the primary metabolic defect in large insulin-resistant rat adipocytes, a defect which secondarily leads to inhibited pentose shunt activity.
Glutamine metabolism, interorgan transport and glucogenicity in the sheep.
Authors: Heitmann R N , Bergman E N
Published: December 2017

[U-14C]glutamine and [6-3H]glucose were infused into four groups of sheep: fed, NH4Cl acidotic, fasted, and dexamethasone treated. Net and unidirectional plasma glutamine fluxes in the portal-drained viscera (PDV), liver, kidneys, and hindquarters were measured by multiplying venoarterial concentration differences and 14C extraction ratios by the rate of blood flow. In fed sheep, glutamine was released by kidneys and muscle but removed by PDV and liver. In all other sheep, renal glutamine release either decreased or switched over to net removal largely due to increased unidirectional renal utilization. This increased renal glutamine demand was compensated for, during acidosis, by a decreased net hepatic glutamine removal but, during fasting and dexamethasone treatment, by an increased muscle glutamine release. Plasma glutamine and glucose turnover rates averaged 11-12 and 19-24 mmol/h but the percentage of glutamine converted to glucose was higher during fasting and dexamethasone treatment (21%) than in normal fed sheep (17%) perhaps reflecting the increased glutamine removal by the kidneys. Since renal glutamine utilization increases with acidosis and fasting and, since glutamine turnover remains unchanged, glutamine metabolism by other body tissues must be altered to compensate for renal changes.
Endogenous prostaglandin E and contractile activity of isolated ileal smooth muscle.
Authors: Sanders K M
Published: December 2017

The effects of endogenous prostaglandin E (PGE) on the contractile activity of isolated cat ileal muscle rings were studied. Force development in circularly oriented muscle fibers were recorded. The muscles contained a mean basal PGE concentration of 1 +/- 0.6 ng PGE per g wet wt (mean +/- SE) as measured by radioimmunoassay. Acetylcholine (ACh) or elevated potassium caused contractions and enhanced PGE concentration (P less than 0.05). Removing Ca2+ from high potassium solutions blocked contraction, but PGE concentration still increased (P less than 0.02). The prostaglandin synthetase inhibitors, indomethacin and 5,8,11,14-eicosatetraenoic acid (ETA) reduced PGE concentration in muscles (less than 50 pg PGE per g muscle) and increased the magnitude of contractions induced by either ACh or elevated potassium. Spontaneous contractions were observed in many tissues after inhibition of PGE synthesis. In conclusion, endogenous PGE limits spontaneous and depolarization-induced muscular activity in cat ileal circular muscle. Synthesis of PGE was increased by depolarizing stimuli whether or not contractions were blocked by the removal of external calcium.
Extrapancreatic glucagon in control of glucose turnover in depancreatized dogs.
Authors: Ross G , Lickley L , Vranic M
Published: December 2017

Depancreatized dogs have plasma immunoreactive glucagon (IRG), which is of gastric origin and is immunologically indistinguishable from pancreatic glucagon. The effects of extrapancreatic IRG on the tracer-determined rate of glucose production were examined to establish whether this hormone contributes to the hyperglycemia observed in six conscious, depancreatized dogs after insulin withdrawal. The dogs were initially maintained normoglycemic with an intraportal insulin infusion. Insulin withdrawal resulted in a 53 and 70% decrease of serum immunoreactive insulin (IRI) at 60 and 210 min, respectively. At 60 min, plasma glucose rose and Ra increased by 50%. A somatostatin-induced decrease in IRG prevented a further increase in Ra and glucose; after somatostatin withdrawal, IRG, Ra, and plasma glucose increased. Arginine given 1 or 3 h after insulin withdrawal increased IRG by 100 pg/ml, and mean Ra rose by 8.9 mg/kg-min. Thus, in depancreatized dogs with low but detectable serum IRI, IRG suppression is associated with inhibition of Ra and further rise in plasma glucose is prevented. Stimulation of IRG release increases Ra and results in marked hyperglycemia. It is concluded that extrapancreatic glucagon has a diabetogenic effect during acute insulin defiency.
Effect of sugar and monoglyceride on fatty acid esterification.
Authors: Shiau Y F , Long W B , Weiss J B
Published: December 2017

The effect of hexose and monoolein on fatty acid esterification was studied in everted rings of rat jejunum. By use of [3H]oleic acid and [U-14C]glucose, esterification via both phosphatidic acid and monoglyceride pathways was quantified. Our results showed that 1) metabolizable sugars stimulate fatty acids esterification regardless of their mode of transport; 2) in the presence of glucose alone, in vitro fatty acid esterification is mediated entirely by the phosphatidic acid pathway; 3) glucose stimulates both esterification pathways in the presence of monoolein; 4) monoolein stimulates only the monoglyceride pathway and has no effect on the phosphatidic acid pathway; and 5) the rate-limiting factor in the presence of monoolein alone is the formation of acyl-CoA, whereas in the presence of glucose alone, the rate-limiting factor is the formation of alpha-glycerophosphate.
Inhibition of lower esophageal sphincter circular muscle by female sex hormones.
Authors: Fisher R S , Roberts G S , Grabowski C J , Cohen S
Published: December 2017

To determine the effect of estrogenic and progesteronic activity on lower esophageal sphincter (LES) circular muscle, studies were performed on 20 adult opossums. Does-response curves on circular smooth muscle strips from the LES were constructed for gastrin and acetylcholine alone, and with 17beta-estradiol and/or progesterone added. Each female hormone significantly decreased the maximal LES muscle responses to gastrin and acetylcholine. A combination of 17beta-estradiol and progesterone abolished the response to gastrin. In contrast, the male sex hormone, dihydrotestosterone, had no effect. In conclusion, administration of estrogen and progesteron, but not dihydrotestosterone, in vitro reduced LES muscle responses to gastrin and acetylcholine. These studies suggest that the female sex hormones can alter LES function and potentially may be of importance in the pathogenesis of heartburn of pregnancy.
Adrenal gland in experimental renal hypertension.
Authors: Ribeiro A B , Krakoff L R
Published: December 2017

The effect of total adrenalectomy on the mechanisms of arterial pressure control was studied in uninephrectomized rats with and without renal artery stenosis (Goldblatt one-kidney model). Four groups of rats were prepared and maintained on high-salt intake (1% NaCl): uninephrectomized-KI; KI + adrenalectomy-KIAx; uninephrectomized with renal artery stenosis-GI; and GI with adrenalectomy-GIAx. Over 3 wk blood pressure rose significantly in both GI and GIAx but the degree of increase in GI was greater. Hyponatremia, hyperkalemia, and increased plasma urea nitrogen were observed in both KIAx and GIAx. Plasma renin concentration (PRC) and plasma renine activity (PRA) were markedly increased and plasma renin substrate (PRS) was decreased in both adrenalectomized groups. Infusion of saralasin resulted in significant and similar reductions in mean arterial pressure (MAP) in KIAx and GIAx, but had no effect on MAP in KI and GI. These results allow approximations of the contribution to total MAP of identifiable components, which are: the total adrenal component, the renin-angiotensin system component, which partially compensates for loss of the adrenal secretions, and the independent effect of the renal artery clip. Thus, a multifactorial analysis of GI hypertension is provided.
Effect of chronic pentagastrin, cholecystokinin, and secretin on pancreas of rats.
Authors: Petersen H , Solomon T , Grossman M I
Published: December 2017

Pentagastrin (1.5 mg/kg), 20% pure natural cholecystokinin (CCK, 37.5 Ivy dog U/kg) or secretin (25 microgram/kg) was given in a depot carrier subcutaneously to rats 3 times daily for 15 days. The dose of CCK and secretin was submaximal for pancreatic secretion, whereas the dose of pentagastrin was supramaximal for gastric acid secretion. The pancreatic wet weight increased by 12% (P less than 0.01) in the rats treated with pentagastrin, 57% (P less than 0.001) in those treated with CCK, and 9% (P less than 0.01) in those treated with secretin. In CCK-treated rats, the maximal protein and bicarbonate outputs in response to cholecystokinin increased proportionately to the increase in pancreatic weight, but maximal bicarbonate and protein outputs in response to secretin were unaltered. The secretin-treated rats showed a lowered basal secretion of bicarbonate and a lowered sensitivity to secretin stimulation, but the maximal bicarbonate and protein outputs to secretin and CCK were unchanged. Treatment with pentagastrin produced no significant changes in pancreatic responses to secretin or CCK. We conclude that 1) the increase in pancreatic weight produced by repeated injections of cholecystokinin was accompanied by proportional increase in functional capacity as reflected by the increased maximal bicarbonate and protein outputs in response to cholecystokinin, and 2) repeated administration of secretin decreased the sensitivity of the pancreas to secretin without altering maximal bicarbonate response.
LES pressure response to pentagastrin: effect of cholinergic augmentation and inhibition.
Authors: Ryan J P , Duffy K R
Published: December 2017

Studies were performed on the anesthetized adult opossum to examine a) the pressure response of the lower esophageal sphincter (LES) to both bolus injections and continuous infusions of pentagastrin (PG), and b) how this response is affected by either cholinergic antagonism with atropine or cholinergic enhancement with edrophonium, an anticholinesterase. Both the bolus injection and the continuous infusion of PG produced dose-dependent rises in LES pressure. The peak pressure responses occurred at 1 microgram/kg and 32 microgram/kg-h, respectively. Atropine (100 microgram/kg), in a dose that significantly diminished the LES response to exogenous acetylcholine, had no significant effect on PG-induced increases in LES pressure. Similarly, edrophonium (100 microgram/kg) had no effect on the response of the LES to PG stimulation. The Sphincter's response to exogenous acetylcholine was significantly enhanced after edrophonium pretreatment. From these studied, we conclude that PG-induced increases in the LES pressure are due primarily to the direct stimulation of sphincter smooth muscle rather than to activation of excitatory cholinergic neurons.
Regulation of cardiac protein balance by hydrocortisone: interaction with insulin.
Authors: Griffin E E , Wildenthal K
Published: December 2017

In fetal mouse hearts in organ culture the rate of protein synthesis was substantially reduced and the rate of protein degradation slightly increased by hydrocortisone in the absence of insulin, but in the presence of insulin the steroid caused a small increase in protein synthesis and a significant reduction in protein degradation. Hydrocortisone promoted the net uptake (or reduced the net release) of branched-chain amino acids independent of insulin and independent of simultaneous changes in protein balance. The specific activities of the lysosomal enzymes cathepsin D and glucosaminidase were reduced by hydrocortisone in all media, whereas the specific activity of creatine kinase increased when the medium contained insulin but decreased in the absence of insulin. It is concluded that hydrocortisone regulates cardiac protein balance via alterations both in synthesis and in degradation. Some of the hormone's myocardial effects are influenced by insulin so that hydrocortisone is anabolic in its presence but catabolic in its absence.
Acid secretion and motility of isolated mammalian gastric mucosa and attached muscularis externa.
Authors: Yates J C , Schofield B , Roth S H
Published: December 2017

A procedure is described for the setting up of a preparation of mammalian gastric mucosa from kitten or ferret. The mucosa is stripped of its outer muscle coats except for a 2-mm strip of circular muscle fibers running across the diameter of the preparation. The connections of this strip to the underlying mucosa are undisturbed. The preparation is immersed on the nutrient side in Krebs-Henseleit solution, gassed with 95% O2 and 5% CO2, and the secretory side contains 5% dextrose, both at 37 degrees C. Acid secretion is determined by a pH stat method and motility is recorded by a strain gauge attached to one end of the muscle strip. Secretory and motility responses are recorded for the three main parietal cell agonists, acetylcholine (ACh), pentagastrin, and histamine. In all cases, concentrations adequate to produce secretory effects also produced modulation of motor activity. In both animals the similarity between the motility responses produced by cholinergic stimulation and pentagastrin was notable.
Cholecystokinin inhibits gastric emptying by acting on both proximal stomach and pylorus.
Authors: Yamagishi T , Debas H T
Published: December 2017

Cholecystokinin is a potent inhibitor of gastric emptying. It is known to both relax the proximal stomach and contract the pyloric sphincter, and either one or both of these actions could mediate inhibition of gastric emptying. We investigated the relative importance of these two actions by studying the effectiveness of the C-terminal octapeptide of cholecystokinin (OP-CCK) to inhibit the emptying of a liquid meal (300 ml saline) before and after operations that either remove or destroy the pyloric mechanism (antrectomy and pyloroplasty), or lead to loss of accommodation of the proximal stomach (vagotomy), and after both vagotomy and antrectomy, and vagotomy and pyloroplasty. The results show that OP-CCK causes dose-related inhibition of gastric emptying in the intact dog. After either pyloroplasty or antrectomy the effectiveness of low but not of high doses of OP-CCK is lost. After vagotomy, OP-CCK at any dose was ineffective. The findings suggest that cholecystokinin inhibits gastric emptying by acting both on the pylorus and on the proximal stomach.
Effects of intestinal bypass surgery on appetite, food intake, and body weight in obese and lean rats.
Authors: Sclafani A , Koopmans H S , Vasselli J R , Reichman M
Published: December 2017

Jejunoileal bypass surgery or sham surgery was performed in female rats made obese with ventromedial hypothalamic (VMH) knife cuts, and in lean control rats. After bypass surgery, the VMH rats underate and lost weight until they reached the body weight of the control sham rats, and they then maintained their weight at control levels. Bypass surgery in lean rats produced much smaller reductions in food intake and body weight. Both bypass groups initially consumed less of a sucrose solution and milk diet during 1 h/day tests, but their intakes returned to near normal levels during the second postoperative month. Reconnection of the intestinal tract in the VMH-bypass rats led to renewed hyperphagia and return to obese body weights. A second experiment revealed that bypass surgery reduces food intake and body weight in genetically obese (fatty) rats, but this effect is not as pronounced as that displayed by VMH rats. These results confirm recent clinical observations that reduced appetite and caloric intake are the major causes of the weight loss produced by intestinal bypass surgery.
Effect of modified sham feeding on jejunal transport and pancreatic and biliary secretion in man.
Authors: Read N W , Cooper K , Fordtran J S
Published: December 2017

Because previous evidence suggested that intestinal secretion was under parasympathetic control, we investigated the effect of modified sham feeding on the intestinal transport of water and electrolytes by jejunal perfusion using a triple lumen tube. By measuring the concentration of amylase, protein, and bile acids entering the intestinal test segment, we were also able to obtain data on the influence of sham feeding on pancreatic and biliary secretion. Gastric contents were aspirated throughout the experiment. Although we observed a clear-cut cephalic phase of gastric acid secretion, sham feeding had no effect on jejunal transport of water and electrolytes or on the rate at which bile acids, protein, or amylase were secreted into the duodenum.
Clearance and production of dehydroepiandrosterone and its sulfate in female baboons.
Authors: Schut H A , Pepe G J , Townsley J D
Published: December 2017

Serum concentrations of dehydroepiandrosterone (D) are greater and those of D sulfate (DS) are lower in female baboons than in women, suggesting interspecies differences in relative production and catabolism of these steroids. To examine this possibility, the metabolic clearance rate (MCR), interconversion (rho), and production of D and DS were determined in five adult female baboons by constant intravenous infusion of [3H]DS and [14C]D. MCR-D (mean +/- SE) was greater (407 +/- 72.8 1/day; 23.1 +/- 3.4 1/day.kg, P less than 0.01) than MCR-DS (44 +/- 5.7 1/day; 2.5 +/- 0.3 1/day.kg). rho-D leads to DS (mean % +/- SE) was greater (45.4 +/- 3.0, P less than 0.001) than rhoDS leads to D (3.8 +/- 0.6), indicating that the equilibrium favors DS formation. Calculated D production and secretion rates were similar (4.5 and 4.4 microgram/min, respectively), whereas DS production (4.1 microgram/min) was twice its secretion rate (2.1 microgram/min). The large difference between MCR-D and MCR-DS resembles that in human beings. However, when clearance is expressed per kilogram body weight, MCR-D is similar to that in man, but MCR-DS is approximately 15-fold greater in the baboon. It is concluded that compared to values in human beings, the greater MCR-DS in baboons maintains the lower serum DS concentration, whereas the higher serum D levels probably result from the relatively greater secretion rate of D baboons.
Actions of peptides isolated from amphibian skin on pancreatic acinar cells.
Authors: May R J , Conlon T P , Erspamer V , Gardner J D
Published: December 2017

In dispersed acinar cells prepared from guinea pig pancreas, peptides isolated from amphibian skin (caerulein, bombesin, litorin, and physalaemin) as well as eledoisin, a peptide isolated from the posterior salivary gland of a Mediterranean octopod, increased outflux of 45Ca, release of bound 45Ca, accumulation of cyclic GMP, and release of amylase. In addition, bombesin, litorin, physalaemin, and eledoisin each increased the initial uptake of 45Ca by dispersed acinar cells, whereas C-terminal octapeptide of porcine cholecystokinin (CCK-OP) and carbamylcholine did not increase the initial uptake of 45Ca but, rather, abolished the increase caused by the other agents. None of the actions of these amphibian peptides was altered by concentrations of atropine sufficient to abolish the effects of muscarinic cholinergic agents. None of the amphibian peptides altered cellular cyclic AMP or the increase caused by secretin or porcine vasoactive intestinal peptide (VIP). Acinar cells preincubated with 45Ca plus bombesin showed the same rate of release of 45Ca as did control cells and this rate was not altered by adding bombesin but was increased fivefold by adding CCK-OP. In terms of their chemical structures as well as the potency and efficacy with which they alter acinar cell function, the amphibian peptides plus CCK-OP can be grouped into three pairs: caerulein with CCK-OP, bombesin with litorin, and physalaemin with eledoisin.
Effect of starvation on initiation of protein synthesis in skeletal muscle and heart.
Authors: Rannels D E , Pegg A E , Rannels S R , Jefferson L S
Published: December 2017

Psoas muscle of rats starved for 2 or 4 days contained increased levels of ribosomal subunits and exhibited reduced rates of protein synthesis in vitro, demonstrating a starvation-induced inhibition of peptide-chain initiation. The activity of an eIF-2-like initiation factor, assayed in postribosomal supernatants, decreased in psoas during starvation, parallel to a 25% reduction in the RNA level. Reduced eIF-2 activity did not result from nucleotide depletion or increased deacylation of initiator tRNA, nor was it abolished by extensive dialysis. Perfusion of psoas muscle in the presence of insulin reversed the starvation-induced block in peptide-chain initiation, but did not alter the activity of eIF-2 or level of RNA. Furthermore, heart muscle did not manifest a starvation-induced block in peptide-chain initiation even though the activity of eIF-2 and the level of RNA decreased as a result of food deprivation. Thus loss of eIF 2 activity in psoas and heart did not parallel changes in peptide-chain initiation but was associated with a reduction in tissue RNA. These results indicate that the level of eIF-2 is not rate-limiting for peptide-chain initiation under the conditions tested in this study.
Demethylation in erythrocytes: a reaction involving hemoglobin.
Authors: Tyce G M , Sharpless N S , Owen C A
Published: December 2017

A reaction is described in erythrocytes of rat and of man whereby O-methylated metabolites of the catecholamines are demethylated to the corresponding catechols. The reaction was studied by incubating aliquots of erythrocyte lysates with radiolabeled O-methylated compounds and isolating the catechol product by alumina adsorption chromatography. The demethylating activity was located in the cytosol of the erythrocytes. Evidence was strong that oxyhemoglobin was responsible for the reaction: the demethylase activity was inseparable from oxyhemoglobin in several chromatographic separations. In addition, although commercially available hemoglobins were inactive in the reactions, after their conversion to oxyhemoglobin and purification, they did effect demethylation. Methemoglobin did not demethylate guaiacols and in fact inhibited demethylation by oxyhemoglobin. The reaction was inhibited by the addition of reduced pyridine nucleotides and of the methyl acceptor tetrahydrofolic acid.
Chylomicron composition during duodenal triglyceride and lecithin infusion.
Authors: Clark S B
Published: December 2017

In lymph fistula rats infused intraduodenally with trioleoylglycerol emulsions, the secretion of triglyceride was enhanced and that of total and esterified cholesterol in chylomicrons was strikingly reduced when lecithin was added at 4-5 times the biliary lecithin secretion rate. During continued triglyceride secretion in the presence of lecithin, the phospholipid: unesterified cholesterol ratio of the chylomicrons increased significantly in contrast to lecithin-free emulsions. Bile-diverted lymph fistula rats secreted significantly less esterified and total cholesterol in lymph chylomicrons than controls, and the difference was magnified by lecithin administration. Cholesterol appears to become relatively unavailable for incorportion into chylomicrons when lecithin is administered at high rates.
Galactosyltransferase in fetal, neonatal, and adult colon: relationship to differentiation.
Authors: LaMont J T , Ventola A
Published: December 2017

Microsomal galactosyltransferase activity of fetal rat colon increased fourfold between 18 and 22 days of gestation and then more slowly during neonatal life reaching adult levels after 14 days. The Km for uridinediphosphate- (UDP) galactose, pH optimum, cation, and detergent requirements were identical in fetal and adult galactosyltransferase. Cytidine 5'-diphosphate-choline stimulated the adult but not fetal colonic galactosyltrasferase activity by inhibition of UDP-galactose pyrophosphatase. The increase in colonic galactosyltransferase in late fetal development is correlated with our previous observation that incorporation of [3H]galactose is markedly increased during differentiation of the fetal colon.
Renal glutamine metabolism in rats fed high-protein diets.
Authors: Brosnan J T , McPhee P , Hall B , Parry D M
Published: December 2017

The influence of protein intake on acid excretion and renal glutamine metabolism was investigated and compared to the effects of NH4Cl-induced metabolic acidosis. Rats fed a diet containing 55% casein excreted more ammonia, phosphate, sulphate, and chloride than did rats fed a 13% casein diet, but, when they were given an 0.1 M NaHCO3 solution to drink, ammonia excretion was no longer elevated. Renal phosphate-dependent glutaminase and phosphoenolpyruvate carboxykinase activities, ammoniagenesis by isolated mitochondria, and the rate of renal gluconeogenesis were all elevated in the rats fed the high-protein diet but not if these rats also drank the sodium bicarbonate solution. Increased glutaminase and phosphoenolpyruvate carboxykinase activities, mitochondrial ammoniagenesis, and gluconeogenesis were all evident in rats made acidotic with NH4Cl. It is concluded that these metabolic adaptations evident in the kidneys of rats fed the high-protein diet are due to the acidogenic effects of increased protein intake.
Jejunal phosphorylation and dephosphorylation of absorbed pyridoxine.HCl in vitro.
Authors: Middleton H M
Published: December 2017

The phosphorylation and dephosphorylation of absorbed vitamin was studied in rat jejunal everted sacs during in vitro uptake of [3H]pyridoxine.HCl. Kinetic studies during 4-min incubations demonstrated that phosphorylation was saturable (Km, 13.3 micron; Vmax, 0.906 nmol/4 min/g wet tissue) and was significantly inhibited by both structural and metabolic inhibitors. Longer incubations (30-min) demonstrated similar saturation and inhibition of net phosphorylation. Dephosphorylation of the phosphate esters formed by the phosphorylation step also occurred, as demonstrated by pulse-chase experiments. Disappearance of these phosphates was initially rapid, approximated first order kinetics, and apparently was mediated by a phosphatase. Whereas phosphorylation did not appear to affect initial uptake rates for [3H]pyridoxine.HCl by the jejunum, net phosphorylation after more prolonged incubations qualitatively paralleled accumulation of total absorbed vitamin in tissue over the same time. The primary effect of phosphorylation during jejunal uptake of pyridoxine by rat jejunum was to increase the accumulation of absorbed pyridoxine in tissue during prolonged incubations. Dephosphorylation had the net effect of limiting the magnitude of that accumulation.
Sex difference in LH response to LHRH and DBcAMP and effect of testosterone.
Authors: Tang L K
Published: December 2017

Because luteinizing hormone-releasing hormone (LHRH) stimulates both pituitary cAMP production and LH release, cAMP has been implicated in the action of LHRH on LH release. The effects of LHRH and DBcAMP on LH release were tested in 4-h incubations with pituitary cultures prepared from male or female rats. LH contents in medium and cells were separately determined by radioimmunoassays. LH release in response to 10 nM LHRH was significantly greater in cultures prepared from female rats (female-RPC) than in cultures prepared from male rats (male-RPC), 1,070 and 418% of control, respectively. Addition of DBcAMP (3, 5, or 10 mM) significantly stimulated LH release by female-RPC (212, 206, or 286% of control, respectively) but did not affect LH release in male-RPC. Furthermore, DBcAMP significantly increased the cellular LH content in female- but not in male-RPC. Testosterone pretreatment of female-RPC significantly lowered the LHRH-induced LH release but did not affect the DBcAMP-induced LH release. These data indicate that testosterone may contribute to the sex difference in pituitary LH response to LHRH but not to DBcAMP.
Fructose-6-phosphate substrate cycling and hormonal regulation of gluconeogenesis in vivo.
Authors: Chenoweth M , Dunn A
Published: December 2017

The possible role of the hepatic fructose-6-phosphate substrate cycle (phosphofructokinase, fructose-1,6-diphosphatase) in the rapid hormonal regulation of gluconeogenesis was investigated in vivo in fasted normal and adrenalectomized rats after administration of [3-3H, U-14C]- or [3-3H, 6-14C]glucose. The plasma glucose 3H/14C ratio was used as an index of substrate cycling because the amount of 3H loss from liver hexose phosphates is determined by the extent of cycling. PFK and FDPase activities limit 3H loss during gluconeogenesis and glycolysis, respectively. Glucagon-stimulated hepatic glucose production is always accompanied by increased substrate cycling, i.e., increased FDPase and PFK activities. The high PFK activity may be a secondary event due possibly to elevated cellular fructose-6-phosphate levels. Decreased substrate cycling, i.e., lowered FDPase activity, always accompanies the depressed hepatic glucose production that occurs during hyperglycemia. Glucagon has no effect on substrate cycling in adrenalectomized rats that are insensitive to the hormone. The in vivo experiments presented provide evidence, although indirect, that glucagon administration results in changes in the fructose-6-phosphate substrate cycle in a living animal. Whether these changes are primary regulatory events or occur secondarily to hormone actions elsewhere is not known.
Influence of estrogen on renal vitamin D hydroxylases and serum 1alpha,25-(OH)2D3 in chicks.
Authors: Pike J W , Spanos E , Colston K W , MacIntyre I , Haussler M R
Published: December 2017

The influence of estrogen on the metabolism of 25-hydroxyvitamin D3 was studied in 2- to 5-wk-old chicks. Single injections of at least 500 microgram diethylstibestrol (DES) increased the conversion of 25-hydroxyvitamin D3 to 1alpha,25-dihydroxyvitamin D3 (1alpha,25-(OH)2D3) and suppressed the production of 24,25-dihydroxyvitamin D3 in chick kidney homogenates. Acute (one 5-mg) injections of testosterone or progesterone did not enhance the 25-hydroxyvitamin D3-1alpha-hydroxylase, indicating specificity. However, chronic pretreatment with DES appeared to allow the potentiation of previously unstimulatory steroids such as progesterone and testosterone. In addition, the hormonal metabolite of vitamin D3, 1alpha,25-(OH)2D3, was measured in 4- to 6-wk chick plasma after steroid treatment. Greater than 1 mg DES per day for 5 days was necessary to enhance the circulating level of 1alpha,25-(OH)2D3; testosterone alone had no effect. This elevation was rapid, occurring within 12--24 h after injection. These data suggest that estrogen (as evidenced by DES treatment) is a modulator of vitamin D metabolism along with other known regulators such as parathyroid hormone, phosphate, and 1alpha,25-(OH)2D3. The mechanism of the regulation is as yet unknown.
Effect of tolbutamide on plasma renin activity.
Authors: Sherma N K , Gossain V V , Michelakis A M , Rovner D R
Published: December 2017

The effect of tolbutamide on renin secretion in rats was studied in vivo, and in vitro. Administration of tolbutamide in doses of 12.5 and 25 mg/kg body wt ip to two groups of rats produced no significant change in plasma renin activity compared to the control group. In the in vitro experiments renal cortical slices were incubated with increasing concentrations of tolbutamide (0--4 mg/ml). No significant increase in the net renin production was observed, whereas the concentration of cyclic AMP increased significantly in the incubation medium. These findings suggest that in the intact rats tolbutamide does not increase plasma renin activity. In the renal cortical experiments although tolbutamide increased cyclic AMP production, the increase may not have been sufficient to stimulate the net renin production. These results are of biological significance because of the possible effects of tolbutamide and increased plasma renin activity on the cardiovascular system.
Interaction between gastrin, CCK, and secretin on canine antral smooth muscle in vitro.
Authors: Fara J W , Praissman M , Berkowitz J M
Published: December 2017

This study compared the actions and interactions of human synthetic gastrin, octapeptide-cholecystokinin (OP-CCK), cholecystokinin (CCK), and secretin on the amplitude of isometric tension developed in strips of dog antral smooth muscle in vitro. Cholecystokinin, OP-CCK, and gastrin produced maximal stimulatory effects at 7.5 x 10(-9), 4.5 x 10(-9), and 3.5 x 10(-9) M, respectively. Secretin alone was ineffective up to 2.5 x 10(-8) M. Observed maximal responses to gastrin, OP-CCK, and CCK tested alone were not significantly different. A submaximal gastrin dose added with OP-CCK, shifted the OP-CCK dose-response curve to the left and significantly reduced the D50, but the calculated maximal response (CMR) did not change. Also, submaximal OP-CCK plus gastrin shifted the gastrin dose-response curve to the left and significantly lowered the D50 with no change in CMR. Secretin decreased CMR but did not change the D50 for gastrin. Responses obtained to gastrin and OP-CCK tested alone were not affected by tetrodotoxin (1 x 10(-5) M), hexamethonium bromide (4 x 10(-5) M), or atropine (1 x 10(-7) M). Larger doses of atropine (5 x 10(-6) M) reduced peptide responses an average 30%. The results indicate that OP-CCK, CCK, and gastrin share a common noncholinergic receptor site. Secretin acts at a different receptor site.
Calcium and phosphorus deficiency in rats: effects on PTH and 1,25-dihydroxyvitamin D3.
Authors: Rader J I , Baylink D J , Hughes M R , Safilian E F , Haussler M R
Published: December 2017

Weanling male Holtzman rats were fed calcium.deficient, phosphorus-deficient, or control diets for 8 wk. Parathyroid hormone (PTH) was measured by radioimmunoassay, and 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) by a competitive binding assay. Rats fed the calcium-deficient diet (0.01% calcium, 0.6% phosphorus) became mildly hypocalcemic after 6 days. Serum calcium levels reached 5.5 +/- 0.4 mg/dl (mean +/- SD) in 5 wk (control 10.3 +/- 0.4 mg/dl). PTH increased from 285 +/- 112 to 3658 +/- 428 pg/ml within 6 wk. Maximum serum levels of 1,25(OH)2D3 (111.8 +/- 17.3 vs. control 11.4 +/- 3.8 ng/dl) were reached at 3 wk and thereafter declined to 44.6 +/- 14.0 ng/dl. In rats fed the phosphorus-deficient diet (0.6% calcium, 0.04% phosphorus), serum phosphorus fell within 24 h from 9.1 +/- 0.6 to 3.2 +/- 0.1 mg/dl, recovered to 5.6 +/- 0.4 mg/dl for 2-3 days, and then declined again. Serum calcium reached a maximum of 14.4 +/- 0.4 mg/dl at day 2 (control 10.8 +/- 0.5 mg/dl) and then slowly declined. PTH decreased within 24 h from 243 +/- 59 to 36 +/- 0 pg/ml in phosphorus-depleted rats. Serum levels of 1,25(OH)2D3 increased within 24 h and remained elevated after 6 wk of phosphorus deprivation (61.2 +/- 11.7 ng/dl vs. control 18.3 +/- 0.4 ng/dl).
Augmented vagal release of antral gastrin by 2-deoxyglucose after fundic vagotomy in dogs.
Authors: Hirschowitz B I , Gibson R G
Published: December 2017

To study the relation between gastrin released by vagal excitation and the secretion of H+ and pepsin under various conditions, central vagal excitation was induced by 2-deoxyglucose (2DG) in doses of 50, 100, and 200 mg/kg body wt given as a single intravenous injection in seven gastric fistula dogs, three with fundic vagotomy and four with intact vagi. Serum gastrin increased linearly with dose doubling in both groups but was twice as high in the vagotomized dogs. Total acid output for 3 h was related linearly to integrated gastrin output in both groups, but the slope, H+/gastrin, was 10 times steeper in the vagally intact dogs (330 vs. 34 mueq/pg gastrin-ml-30 min) and pepsin output almost 20 times greater [5,400 peptic units (PU) vs. 296 PU]. Acidification of the antrum to pH 1.2-1.4 eliminated the gastrin response to 2DG in both groups of dogs. Atropine (100 microgram/kg iv) reduced serum gastrin in the vagotomized and increased it in the intact dogs. Atropinization uncovers stimulation by 2DG by pathways that do not involve muscarinic cholinergic receptors. Stimulation by both pathways is suppressible by acid. We conclude that fundic vagotomy removes an inhibitor of vagal gastrin release.
Adrenal epinephrine in hyperuricemia induced by hypothalamic stimulation of the rat.
Authors: Sumi T , Umeda Y
Published: December 2017

Peripheral neurological mechanisms involved in hyperuricemia following ventromedial hypothalamic electrical stimulation was studied in the conscious rat. The intensity of 0.2 mA was near the maximum intensity of stimulation current producing a linear increase in plasma uric acid throughout the 15-min period of stimulation, as well as a subsequent rise and fall of plasma allantoin. Bilateral adrenal demedullation abolished the stimulation-induced hyperuricemia and markedly impaired the accompanying rise of allantoin. Prior treatment of the animal with hexamethonium significantly inhibited the uric acid increase, but did not reduce the allantoin elevation so markedly. Moreover, propranolol eliminated both responses of these plasma purine metabolites, whereas phentolamine greatly increased the response. It is concluded therefore that the hypothalamic stimulation-induced rise of plasma uric acid is the result of acceleration of epinephrine release from the adrenal medulla and that, whereas some unknown extra-adrenal mechanism may be partially involved, the primary part of the accompanying allantoin elevation is explained by the combined effects of the increased uric acid and the hepatic uricase.