Showing papers in "American Journal of Physiology in 1969"
TL;DR: A migrating electric complex that occurs in fasting dogs is described, composed of a consecutive series of slow waves, on each of which is superimposed a burst of Iargeamplitude action potentials that distinguish it from other electric activity in the small bowel of fasting dogs.
Abstract: PREVIOUS STUDIES on the motor activity of the human (6) and canine (4, 5, 7, 8, l0) small intestine have demonstrated the occurrence of migrating motor complexes. The observations, however, were confined to short segments of the bowel, and the electric events responsible for the motor complex were not studied. The purpose of this report is to describe a migrating electric complex that occurs in fasting dogs. The complex is composed of a consecutive series of slow waves, on each of which is superimposed a burst of Iargeamplitude action potentials that distinguish it from other electric activity in the small bowel of fasting dogs. The complex develops in the upper small bowel and then migrates caudad to the ileum; as it terminates there, another starts in the duodenum or upper jejunum, and the recycling continues. A correlation is made between these findings and those relating to migrating motor complexes observed by others. The term electric complex will be used when referring to the migrating bursts of action potentials. It is not meant to signify an electric event that is different from the action potential and slow wave. Rather, it is used to indicate a pattern of electric activity in which action potentials occur
809 citations
TL;DR: A sympathetic cardio-cardiac reflex is proposed, the afferent and efferent pathways of which are both in sympathetic nerves and was observed in spinal preparations.
Abstract: MALLIANI, ALBERTO, PETER J. SCHWARTZ, and ALBERTO ZANCHETTI. A sympathetic rejex elicited by experimental coronary occlusion. Am. J. Physiol. 217(3): 703-709. 1969.-The effects of transient coronary occlusion on a sympathetic outflow presumably directed to the heart have been studied on cats. Single preganglionic fibers and a few multifiber strands have been isolated from the left third thoracic ramus communicans (Ts). Coronary occlusion quickly induced an increased discharge of most of the fibers tested. A very few fibers decreased their discharge, whereas some were apparently unaffected by coronary occlusion. Increased firing neither depended on direct anoxic stimulation of preganglionic neurons nor on sinoaortic or vagal reflexes and was observed in spinal preparations. A sympathetic cardio-cardiac reflex is proposed, the afferent and efferent pathways of which are both in sympathetic nerves.
503 citations
TL;DR: Since Z-DG produced marked hyperglycemia during the period of increased feeding, these results show that the abrupt onset of decreased glucose utilization, not hypoglycemia, is a sufficient condition for feeding in mammals.
Abstract: SMITH, GERARD P., AND ALAN N. EPSTEIN. Increased feeding in response to decreased glucose utili
458 citations
TL;DR: An indicator-dilution method was developed which allowed simultaneous measurement of both portal and hepatic venous blood flow and which consisted of a constant infusion of para-aminohippuric acid into a mesenteric vein.
Abstract: KATZ, M. L., AND E. N. BERGMAN. Simultaneous measurements of hepatic and portal venous blood ji’ow in the sheep and dog. Am. J. Physiol. 216(4) : 946-952. 1969.-An indicator-dilution method was developed which allowed simultaneous measurement of both portal and hepatic venous blood flow and which consisted of a constant infusion of para-aminohippuric acid (PAH) into a mesenteric vein. The hepatic blood flow using PAH was compared with the hepatic blood flow using sulfobromophthalein (BSP). In both the sheep and dog the mean hepatic flow using BSP was 95 •t 4(x1 of that for PAH. The mean portal blood flow was 43 and 53 ml/kg per min and the mean hepatic blood flow was 55 and 65 ml/kg per min in the fed nonpregnant and pregnant sheep, respectively. The mean hepatic blood flow in sheep increased by about 45y0 3 hr after feeding and decreased after fasting to about the previous prefeeding level. The hepatic arterial flow seemed variable but averaged about 200/b of the total hepatic flow in both fed and fasted sheep. In both conscious and anesthetized dogs, the mean hepatic venous blood flow was 45 ml/kg per min and the mean hepatic arterial flows were 15-35y0 of this total hepatic flow.
346 citations
TL;DR: Adult diabetic mice (db/db) of the C57BL/Ks strain were joined in parabiosis with normal mice of the same sex and the normal partners lost weight, became hypoglycemic, and died of apparent starvation within 50 days after surgery.
Abstract: COLEMAN, D. L., AND KATHARINE P. HUMMEL. Effects of parabiosis of normal with genetically diabetic mice. Am. J. Physiol. 2 17(5) : 129% 1304. 1969.-Adult diabetic mice (db/db) of the C57BL/Ks strain were joined in parabiosis with normal mice of the same sex. Little, if any, amelioration of the disease was observed in parabiont diabetics and no symptoms of diabetes were observed in the normal parabiont. Instead, the normal partners lost weight, became hypoglycemic, and died of apparent starvation within 50 days after surgery. In contrast, the diabetic partners gained weight rapidly and remained diabetic. The similarity of this response to that observed with normal rats in parabiosis with rats having lesions in the region of the ventromedial nuclei of the hypothalamus is discussed.
331 citations
TL;DR: Segments of canine carotid artery were held at in situ length and studied in vitro after treatment with norepinephrine (NEpi) and after Treatment with potassium cyanide (KCN).
Abstract: DOBRIN, PHILIP B., AND ALLEN A, &NICK. hj%ence of mmlmsmooth muscle on contractile meclzanics and elasticity of arteries, Am, J. Physiol. 2 17(6) : 1644-1651. 1969.---Segments of canine carotid artery were held at in situ length and studied in vitro after treatment with norepinephrine (NEpi) and after treatment with potassium cyanide (KCN). Activation of the vascular muscle caused contraction and greatly increased pressure-radius hysteresis, The blood vessel muscle exhibited an active stress-strain curve u:ith a maximum stress of .88 it: .10 x lo6 dynes/cm2 for the whole wall, or 2.73 X 10” dynes/cm2 for the estimated smooth muscle component of the wall. Activation of smooth muscle increased the elastic modulus when this was plotted as a function of strain. The active muscle exhibited a maximum elastic modulus of 3.99 A .08 x lo6 dynes/cm2 for the whole wall, or 12.66 x 106 dynes/cm2 for the estimated smooth muscle component of the tvall. Activation of smooth muscle decreased the elastic modulus when this was plotted as a function of pressure. This decrease leas attributed to the reduction in radius brought about by the active muscle.
321 citations
TL;DR: Mitochondria in the skeletal muscle of trained rats were more numerous and appeared to be larger with more densely packed cristae than those in the sedentary controls, whereas swimming to exhaustion produced no change.
Abstract: GOLLNICK, PHILIP D., AND DOUGLAS W. KING. Effect of exercise and training on mitochondria of rat skeletal muscle. Am. J. Physiol. 216(6): 15021509. 1969.-Sixteen male albino rats of the Sprague-Dawley strain have been used to study the effect of exercise and training on the number and structure of skeletal muscle mitochondria. Eight of these animals were trained with a program of forced running in motor-driven work wheels. Four of the trained animals were killed 24 hr after a final exhaustive exercise bout. The remaining four trained animals were killed immediately after a similar run to exhaustion. The eight control animals were allocated into equal groups sacrificed either at rest or immediately after becoming exhausted during swimming. All animals were sacrificed by decapitation, and samples of the gastrocnemius muscle prepared for examination with an electron microscope. Mitochondria in the skeletal muscle of trained rats were more numerous (P < 0.01) and appeared to be larger with more densely packed cristae than those in the sedentary controls. Running to exhaustion prior to sacrifice produced marked swelling in both the muscle fibers and the mitochondria, whereas swimming to exhaustion produced no change.
277 citations
TL;DR: It is concluded that myelinated CSN fibers terminate in both the intermediate portion of the nucleus tractus solitarii (NTS) and on large neurons of the paramedial reticular formation of the medulla, that integration of CSN activity occurs in the intermediate portions of the NTS, and that specific reticular nuclei receive multisynaptic CSN projections.
Abstract: MIURA, MITSUHIKO, AND DONALD J, REXS. Tmmktzb~ and secondary projections of carotid sinus nerve in the cat brain stem. Am. J. Physiol. 217(I): 142-153. 1969.-Field responses and unit activity evoked by electrical stimulation of the carotid sinus nerve (CSN) were recorded with microelectrodes in the medulla and pons of anesthetized, paralyzed cats. A short-latency (0.7-I .4 msec), monosynaptic, “early” response, triggered by myelinated CSN fibers, was found in the intermediate portion of the nucleus tractus solitarii (NTS) and in the paramedial reticular formation of the medulla, especially in n, paramedian reticularis; a paucisynaptic “intermediate” response (1.7 msec mean latency) was localized within the intermediate portion of the NTS; and polysynaptic “late” responses (peak > 5 msec) were found in specific subnuclei of the medullary and pontine reticular formation. We conclude that myelinated CSN fibers terminate in both the intermediate portion of the NTS and on large neurons of the paramedial reticular formation of the medulla, that integration of CSN activity occurs in the intermediate portion of the NTS, and that specific reticular nuclei receive multisynaptic CSN projections.
267 citations
TL;DR: It is proposed that the changes observed in the transmural potential due to substitution of mannitol or choline chloride for sodium chloride may also occur in vivo and thereby cause the increase in calcium absorption observed after dietary administration of lactose and similar compounds.
Abstract: MARTIN, DAVID L., AND HECTOR F. DELUCA. In$wzce of sodium on calcium transport by the rat small intestine. Am. J. Physiol. 216(6): 1351-1359. 1969.-Calcium transport by everted sacs of rat duodenum is greatly reduced when sodium is deleted from the incubation medium. Differences between these results and earlier reports of a lack of effect of sodium deletion are accounted for by differences in the incubation media used. Both longand short-term experiments indicate that calcium moves freely across the brush border of the epithelial cell even in the absence of sodium, indicating that the quantitatively important site of action of sodium must be elsewhere in the system. It is suggested that sodium acts at the basal-lateral membrane of the epithelial cell. In addition, it is proposed that the changes observed in the transmural potential due to substitution of mannitol or choline chloride for sodium chloride may also occur in vivo and thereby cause the increase in calcium absorption observed after dietary administration of lactose and similar compounds.
265 citations
TL;DR: The dilation of the coronary resistance vessels in response to short periods of myocardial ischemia can be accounted for by the adenosine released from the myocardium.
Abstract: RUBQRAFAEL, ROBERT M. BERNE, AND MAKOTO KATORI. cardial hypoxia were imposed in these studies in order to liberate quantities of adenosine which could be detected by the techniques then available. However, improvements in techniques have made possible the detection of extrelnely small amounts of adenosine in coronary venous blood. The present study was undertaken to determine whether adenosine is released from the myocardium in response to moderate degrees of myocardial hypoxia and whether the quantities released can account for the degree of coronary vasodilation observed. Release of adenosine in reactive hypercmia of the dog heart. Am. J. Physiol. 216(l): 56-62. 1969.~Brief (30-60 set) occlusions of the left coronary artery were performed in the anesthetized open-chest dog. Samples of arterial and coronary sinus blood were obtained simultaneously prior to occlusion and immediately after release of occlusion. Cellular elements were rapidly removed by centrifugation and the plasma samples were analyzed for purine derivatives. Adenosine (13 mpmoles/lOO ml of blood) was found in coronary sinus blood collected during the reactive hyperemic period but was absent in arterial and venous control samples. Studies on disappearance of adenosine in blood indicate that at least 24 mpmoles of adenosine must have been present in the capillary blood for 13 mpmoles to appear in the coronary sinus blood. If all the adenosine is in the extracellular space (a reasonable assumption based on knowledge of the activity of adenosine deaminase in the myocardial cell) a minimum concentration of 75 m~moles/lOO ml of extracellular water is reached. Adenosine infusion at concentrations of 56 m~moles/lOO ml of arterial blood elicits maximal coronary dilation. Hence, the dilation of the coronary resistance vessels in response to short periods of myocardial ischemia can be accounted for by the adenosine released from the myocardium.
262 citations
TL;DR: PAH transport was studied using isolated, perfused rabbit proximal renal tubules and it was concluded that PAH is actively transported into the tubule cell at the peritubular membrane and subsequently diffuses into the luminal fluid.
Abstract: TUNE,BRUCE M., MAURICE B. BURG,AND CLIFFORD SPATLAK. Charac~eri.ctics uf p-aminohippurata transport in proximal renal tubules. Am. J. Physiol. 217(4): 1057-1063. I969,-PAH transport was studied using isolated, perfused rabbit proximal renal tubules. ,4ctive PAH secretion was found in both the convoluted and the straight portion of the proximal tubule, but the rate of secretion was approximately 3 times as great in the straight portion. During perfusion, PAH concentration was greater in tubule cells than in luminal fluid or surrounding bath. When tubules were incubated without perfusion, PAH concentration in tubule cells was higher than during perfusion and was greater in the straight than in the convoluted portion. It is concluded that PAH is actively transported into the tubule cell at the peritubular membrane and subsequently diffuses into the luminal fluid. On the basis of this model, the permeabilities of the luminal and peritubular cell membranes to PAH were calculated. Passive PAH absorption from the tubular lumen was studied, and both the rate of efflux and tissue concentration of PAH were in agreement with the predictions made from the model. Changes in perfusion rate from 3 to 10 nl min --I had no measurable effect on the PAH secretion rate.
TL;DR: In the presence of right ventricular hypertrophy, the concentration, as well as the total content of hydroxyproline, increased in both the right and the unstressed left ventricle.
Abstract: BUCCINO, R. A., E. HARRIS, J. F. SPANN, JR., AND E. H. SONNENBLICK. Response of myocardial connective tissue to development of experimental hypertrophy.. Am. J. Physiol. 2 16(2) : 425-428. 1969.-Myocardial collagen concentration was determined by measuring hydroxyproline in right and left ventricles of normal. cats and those with right ventricular hypertrophy produced by chronic constriction of the pulmonary artery. Both in normal and hypertrophied ventricles, hydroxyproline concentration was significantly higher in the epimyocardium than in endomyocardium; and in both the epimyocardium and endomyocardium, hydroxyproline was significantly higher in right ventricular than in corresponding left ventricular specimens. In the presence of right ventricular hypertrophy, the concentration, as well as the total content of hydroxyproline, increased in both the right and the unstressed left ventricle.
TL;DR: In fasting animals a regular, triphasic fluctuation in electrical potential, the pacesetter potential (PP), was detected by an orad corporal electrode and by all others caudad to it, and its velocity increased with caUDad propagation.
Abstract: KELLY, KEITH A., CHARLES F. CODE, AND LILA R. ELVEBACK. Patterns uf canine gastric electrical activity. Am. J. Physiol. 2 17C2) : 46 l-470. 1969.~Eight electrodes were implanted serially from the fundus to the pylorus on the gastric wall of 12 dogs. After recovery, electrical activity was recorded during fasting and after gastric-balloon distention and gastric instillation of water and cottonseed oil, and correlated with intraluminal pressure and cinefluoroscopic observations. In fasting animals a regular, triphasic fluctuation in electrical potential, the pacesetter potential (PP), was detected by an orad corporal electrode and by all others caudad to it. Its amplitude was greater in the antrum than in the corpus, but its frequency (5.3 cycles/min) was the same in the two sites. Its velocity increased with caudad propagation. Action potentials (AP), indicating contractions, were superimposed on 26% of the fasting antral cycles. Balloon distention decreased PP frequency, slowed the velocity of corporal and enhanced the velocity of antral propagation, and increased the incidence of antral AP. Water instillation decreased PP frequency, slowed the velocity of corporal propagation, slowed or enhanced the velocity of antral propagation, and increased the incidence of antral AP. Oil instillation caused wide variations in PP frequency, slowed the velocity of corporal and antral propagation, and decreased the incidence of antral AP,
TL;DR: Findings indicate that an inhibitory mechanism, apparently stimulated by osmotic dilution of body fluids, is involved in the regulation of water intake during hypovolemia, and may be functionally similar to the ventromedial hypothalamic 3atiety center involved inThe regulation of food intake.
Abstract: STRICKER, EDWARD hf. Osmoregdation and vokdme regulation in rats: inhibition of hypovokmk thirst by water, Am. J. Physiol. 2 17( 1) : 98-l 05, 1969.-Subcutaneous injections of hyperoncotic polyethylene glycol (PG) solutions produced hypovolemia in rats by withdrawing isosmotic plasma fluid into the local interstitium. All animals showed increased thirst, but stopped drinking water well before plasma deficits were restored. Concurrent hyperosmolality (produced by injection of hypertonic NaCl solutions) increased the water intakes of PG-treated rats in proportion to both intracellular and intravascular dehydrations, yet continued hypovolemia was again evident when drinking discontinued. Similarly, water preloads almost totally eliminated drinking in PG-treated rats but had little effect on plasma volumes. Inhibition of drinking was accompanied by significant osmotic dilution in all three experiments. In contrast, ingestion or preloads of isotonic N&l solutions, which did not affect plasma osmolality, did not eliminate thirst in PG-treated rats unless plasma deficits were repaired. These findings indicate that an inhibitory mechanism, apparently stimulated by osmotic dilution of body fluids, is involved in the regulation of water intake during hypovolemia. This mechanism, perhaps represented in the supraoptic hypothalamus, may be functionally similar to the ventromedial hypothalamic 3atiety center” involved in the regulation of food intake.
TL;DR: The conclusion that glucose transport was the step in glucose utilization affected by ventricular pressure development and fatty acids was substantiated by the demonstration that palmitate inhibited the accelerated rate of 3Gmethylglucose transport associated with increased pressure development.
Abstract: NEELY, J. R., R. H. BOWMAN, AND H. E. MORGAN. E$ects of ventricular~ressure development andpalmitate onglucose transport. Am.J. Physiol. 2 16(4) : 804-8 I 1. 1969.-The effect of ventricular pressure development and exogenous palmitate on glucose transport was studied in the isolated rat heart. when glucose was the only exogenous substrate provided, increased ventricular pressure development resulted in a threefold increase in the rate of glucose transport and net glycogenolysis. The presence of physiological concentrations of palmitate in the perfusate inhibited the accelerated rate of both glucose transport and glycogenolysis. The conclusion that glucose transport was the step in glucose utilization affected by ventricular pressure development and fatty acids was substantiated by the demonstration that palmitate inhibited the accelerated rate of 3Gmethylglucose transport associated with increased pressure development. Palmitate was also an effective inhibitor when transport was stimulated by insulin, but was ineffective when the process was accelerated by anoxia. Palmitate uptake was accelerated 5070y0 as ventricular pressure development was increased.
TL;DR: Ferrokinetic studies following ceruloplasmin infusion indicated that the increase in serum iron resulted from an increase in the rate of flow of iron into plasma, which supports the hypothesis that cerulplasmin, possibly because of its ferroxidase activity, directly affects the transfer of iron from cells to plasma.
Abstract: RAGAN, H. A., S. NACHT, G. R. LEE, C. R. BISHOP, AND G. E. CARTWRIGHT. Effect of ceruloplasmin on plasma iron in copper-deficient swine. Am. J. Physiol. 217(5) : 1320-1323. 1969.-The administration of homologous ceruloplasmin to copper-deficient swine with adequate iron stores resulted in a rapid, marked, and sustained increase in plasma iron concentration. An amount of inorganic copper equivalent to that contained in the ceruloplasmin produced only a minimal, transient increase in plasma iron. Ferrokinetic studies following ceruloplasmin infusion indicated that the increase in serum iron resulted from an increase in the rate of flow of iron into plasma. These studies support the hypothesis that ceruloplasmin, possibly because of its ferroxidase activity, directly affects the transfer of iron from cells to plasma.
TL;DR: Growing rats eating a lowprotein diet (8y0 casein) were markedly stunted but otherwise appeared healthy and had a greater capacity for prolonged running than the rats on the normal protein diet.
Abstract: CREWS, EUGENE L. III, K. WILLIAM FUGE, LAWRENCE B. OSCAI, JOHN 0. HOLLOSZY, AND ROBERT E. SHANK. kt’eight, food intake, and body cornposition: effects of exercise and protein dejiciency. Am. J. Physiol. 216(2): 359-363. 1969.-The effects of exercise and of protein deficiency, both separately and together, on food intake, weight gain, and body composition were studied. Exercising animals gained less weight than free-eating sedentary controls as a result of both an increase in caloric expenditure and a decrease in food intake. Exercise resulted in a significant decrease in the percentage of the carcass composed of fat, with a proportional relative increase in lean body mass. Sedentary calorie-restricted animals had a higher fat content than exercising animals of the same weight, suggesting a specific fat-mobilizing effect of exercise. Growing rats eating a lowprotein diet (8y0 casein) were markedly stunted but otherwise appeared healthy. They had a greater capacity for prolonged running than the rats on the normal protein diet. Protein deficiency resulted in a decrease in the percentage of the carcass composed of fat and an increase in the proportion made up of water. Because of the small size of the protein-deficient animals, total amounts of all four body constituents were markedly decreased.
TL;DR: It is concluded that the chief factor in the resistance of very young animals to ischemia is the low cerebral metabolic rate, not high glycolytic capacity.
Abstract: THURSTON,JEAN HOLOWACH, and DAVID B. MCDOUGAL, JR. Effect of &hernia on metabolism of the brain of the newborn mouse. Am. J. Physiol. 216(2):348-352. 1969.-Changes in six metabolites in the brains of newborn mice were followed during the ischemia induced by decapitation. Phosphocreatine fell rapidly, glucose and glucose 6-phosphate more slowly, and ATP and glycogen were the most stable of the substances measured. From the changes, the initial rate of use of highenergy phosphate (cerebral metabolic rate) was calculated to be 2.3 mmoles/kg per min, which is .09 of the adult rate following decapitation. Lactate accumulated much more slowly than in the adult. In the early stages (first 4 min) of ischemia the rate of disappearance of energy reserves was nearly linear, and much faster than the rate in the later stages of the experiment. The energy reserves of the brain arc about the same in young as in adult animals. In view of this, and the low rate of glycolysis, it is concluded that the chief factor in the resistance of very young animals to ischemia is the low cerebral metabolic rate, not high glycolytic capacity.
TL;DR: It is concluded that gastrin stimulates protein synthesis in the gastric and duodenal mucosa, and it is suggested that it may be a trophic hormone for these tissues.
Abstract: JOHNSON, LEONARD Ii., DOROTHEA AURES, AND LAWRENCE UUEN. Pentagastrin-induced sfimulafion of protein synthesis in the gasdrointestinal tract. Am. J. Physiol. 217( 1) : 25 1-254. I969.-Fasted rats were injected with either saline, 250 pg/kg pentagastrin, or I .3 mg/kg histamine base, and killed I hr later. Mucosa from the duodenum and oxyntic gland area of the stomach was isolated and homogenized. In some instances homogenates were also made from samples of liver and skeletal muscle. An aliquot of homogenate was then incubated at 37 C in a solution containing L-leucine-14C. At the end of incubation the reaction was stopped by precipitation with 5% TCA. RNA and lipids were then extracted and the incorporation of leucine into the protein pellet determined. Pentagastrin produced a 90% stimulation of amino acid incorporation into gastric mucosa and a threefold stimulation of incorporation in duodenal mucosa when compared to saline controls. The size of this effect increased with increasing doses of pentagastrin. No stimulation of protein synthesis was found in either liver or muscIe, and the incorporation in histamine-treated animals did not differ from that of the saline-injected controls, We conclude that gastrin stimulates protein synthesis in the gastric and duodenal mucosa, and suggest that it may be a trophic hormone for these tissues.