Showing papers in "American Journal of Physiology in 1971"
TL;DR: Saturability of D-glucose uptake was demonstrated and evidence presented that all of the five hexoses measurably taken up by brain shared a common carrier, two blood-brain barrier carrier systems for amino acids.
Abstract: OILIENDORF, WILLIAM EL Brain uptake of radiolaMed amino acids, nmines, and hexoses after arterial injection. Am. J. Physiol. 2 2 I(6) : 16294639. 1971 .-The loss of a 14C-labeled test substance to brain during a single capillary passage following rapid injection into the rat common carotid artery was measured relative to a simultaneously injected highly diffusible reference, 3HOHW Twenty-eight amino acids, thirteen amines, seven hexoses, and 5 relatively nondiffusible substances were studied. Amino acid uptakes ranged from unmeasurably low to 55%. Essential nutritional amino acid uptake was greater than nonessential. TWO blood-brain barrier (BBB) carrier systems for amino acids were identified. Putative transmitter substances were much less taken up by brain than precursors. Saturability of D-glucose uptake was demonstrated and evidence presented that all of the five hexoses measurably taken up by brain shared a common carrier. Nonmetabolized cycloleucine and 3-O-methylglucose showed saturable uptakes. Amino acid uptake was incompletely stereo-specific whereas glucose uptake was stereospecific. Phlorizin inhibits brain uptake of D-glucose. Relative BBB permeabilities to many of the test substances resemble red-cell permeabilities. Carrier systems for amino acids are independent of the glucose carrier.
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TL;DR: The data demonstrate that in guinea pigs the soleus, which is composed entirely of intermediate fibers, is a slow-twitch muscle and has the lowest myosin and actomyosin ATPase activities.
Abstract: BARNARD, R. JAMES, V. REGGIE EDGERTON, TETSUO FURUKAWA, AND J. B. PETER. Histochemical, biochemical, and contractile properties of red, white, and intermediate jibers. Am. J. Physiol. 220 (2) : 41 O-41 4. 197 1 .-Individual fibers from guinea pig muscles (soleus, flexor hallucis longus (FHL), flexor digitorium longus (FDL), medial gastrocnemius (MG) and the portion of the vastus lateralis (RV) which is grossly red) were classified as “red,” “white,” or “intermediate” according to their histochemical activity of NADHdiaphorase and myosin ATPase. Actomyosin and myosin ATPase activities of these muscles were determined biochemically and contraction times were measured in situ. The data demonstrate that in guinea pigs the soleus, which is composed entirely of intermediate fibers, is a slow-twitch muscle and has the lowest myosin and actomyosin ATPase activities. Conversely, muscles composed predominately of white fibers (FHL and FDL) or predominately of red fibers (MG and RV) are both fast-twitch muscles and have higher ATPase activities. Since both the soleus and RV are red in appearance the generalization that red muscles have slow contraction times is not valid. We suggest that these fibers be referred to as fast-twitch red, fast-twitch white, and slow-twitch intermediate.
420 citations
TL;DR: The findings indicate the general applicability of this methodology to the characterization of adipose tissue in mammalian species and suggest that heterogeneity in size of a fat cell population is a measurable parameter which should further as a guide to the expansion of the adipose organ.
Abstract: DI GIROLAMO, MARIO, SHELDON MENDLINGER, AND JOHN W. FERTIG. A simple method to determine fa t cell size and number in four mammalian species. Am. J. Physiol. 221 (3) : 850458. 1971 .-Adipose tissue from various fat depots in four mammalian species was characterized in terms of mean fat cell size (diameter and volume), relative dispersion in fat cell size, and fat cell number by a method based on direct microscopic determination of the diameter of isolated fat cells. The degree of precision of the various operations involved and of the final estimates of fat cell size and number were evaluated and found to be within acceptable limits. The morphology of the adipose cells was studied in ad libitum-fed rats, hamsters, guinea pigs, and dogs at different stages of development. In each species, enlargement of the fat cells in a given adipose depot led to fat cell populations that were more homoqenous in size. In the rat, at an earlier stage of development (2 mdnths of age), considerable interdepot differences were found with regard to fat cell size and number in four different locations of the adipose organ. These findings indicate the general applicability of this methodology to the characterization of adipose tissue in mammalian species. In addition, this study suggests that heterogeneity in size of a fat cell population is a measurable parameter which should further as a guide to the expansion of the adipose organ. be studied
370 citations
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TL;DR: A renin-angiotensin system, independent of that of the kidney, is present in brains of nephrectomized dogs, and levels of renin activity remain as high as in control dogs.
Abstract: GANTEN, DETLEV, ANA MARQUIZ-JULIO, PIERRE GRANGER, KARL HAYDUK, KLAUS PETER KARSWNKY,ROGER BOUCWER, AND JACQUES GENEST. Renz'n ilz dog brain. Am. J. Physiol. 221(6): 17331737. 1971 .-Brain tissue of dogs contains high renin activity. After peritoneal dialysis in nephrectomized dogs for up to 12 days, levels of renin activity remain as high as in control dogs. Kenin substrate and angiotensin are present in brain after nephrectomy. Plasma renin and substrate do not pass the blood-cerebrospinal Auid barrier. Thus a renin-angiotensin system, independent of that of the kidney, is present in brains of nephrectomized dogs.
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289 citations
TL;DR: To determine the relationship between temperature and respiration, the consumption of isolated rat skeletal muscle mitochondria was measured at temperatures between 25 and 45 C in vitro and the results confirmed that increasing temperature had a negative effect on respiration.
Abstract: E. BEYER. Temperature, skeletal muscle mitochondrid functions, and oxygen debt. Am. J* Physiol. 220(4): 1053-1059. 1971 .-Compared to resting liver and skeletal muscle tempera- tures of 38.6 and 36.0 C, respectively, postexercise values were 43.4 and 44,l C in viva. To determine the relationship between temperature and respiration, the 02 consumption of isolated rat skeletal muscle mitochondria was measured at temperatures between 25 and 45 C in vitro. Increasing temperature had
255 citations
TL;DR: Rat liver mitochondrial functions were studied after hemorrhagic hypovolemia and Escherichia coli endotoxin shock and suggest that the mitochondrial defect caused by shock is in the adenine nucleotide translocase and/or utilization mechanism in connection with the fault in ATPase activity.
Abstract: MELA, LEENA, LEONARDO V. BACALZO, JR., AND LEONARD D. MILLER. Defective oxidatiue metabolism of rat liver mitochondria in hemorrhagic and endotoxin shock. Am. J. Physiol. 220(2) : 571477. 197 1 .-Rat liver mitochondrial functions were studied after hemorrhagic hypovolemia and Escherichia coli endotoxin shock. The respiratory activity in State 4 was increased indicating normal utilization of substrates and oxygen, but loose coupling. The electron-transfer reactions induced by substrates were unaltered. The respiratory rates in State 3, however, were inhibited in the presence of any of the substrates used, succinate, glutamate-malate, or aketoglutarate. Due to increased State 4 and decreased State 3 rates, the respiratory control ratios dropped from control values of 6-8 to about 2. The ADP utilization rate decreased parallel with the respiratory rates. Also, an addition of ADP to mitochondria prepared at final stages of shock failed to induce steady-state changes of the cytochromes. The mitochondrial uncoupler-sensitive ATPase activity was inhibited as well by 7075. All these alterations occurred both in hemorrhagic and endotoxin shock. The only significant difference was the dependence of the alterations on the length of the shock. The data suggest that the mitochondrial defect caused by shock is in the adenine nucleotide translocase and/or utilization mechanism in connection with the fault in ATPase activity.
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233 citations
TL;DR: It is concluded that the effects of baroceptor reflex on SNA to functionally different organs are quantitatively nonuniform.
Abstract: NINOMIYA, ISHIO, NAOKO NISIMARU, AND HIROSHI IRISAWA. Sympathetic nerve activity to the spleen, kidney, and heart in response to baroceptor input. Am. J. Physiol. 221(5): 1346-1351. 1971.-The effects of the baroceptor reflex on sympathetic nerve activity (SNA) to spleen, kidney, and heart were analyzed in anesthetized cats. The baroceptor reflex times of SNA to the spleen, kidney, and heart were 292, 199, and 164 msec, respectively. SNA to these organs changed almost inversely to changes in the absolute mean aortic pressure between 100 and 150 mm Hg. Within this pressure range the gain of baroceptor-sympathetic systems to the spleen, heart, and kidney were 5.2, 3.2, and 2.7, respectively. SNA was reduced to the noise level at the mean aortic pressure of 148, 167 and 173 mm Hg in splenic, cardiac and renal nerves, respectively. Changes of SNA were not identical among the three nerves studied in response to occlusion of the common carotid arteries, to electrical stimulation of the aortic nerve, to change in the isolated carotid sinus pressure, or to hemorrhage. The effects of baroceptor reflex on SNA to both kidneys were almost the same, but there was some difference in the reflex time. It is concluded that the effects of baroceptor reflex on SNA to functionally different organs are quantitatively nonuniform.
TL;DR: The distal potassium effects of ouabain were independent of any increase in distal sodium delivery and are thought to be due to depression of active potassium uptake across the luminal cell membrane of distal tubule cells.
Abstract: DUARTE, CRISTOBAL G., FRANCOISE CHOMETY, AND GERHARD GIEBISCH. Effects of amiloride, ouabain, and furosemide on distal tubular function in the rat. Am. J. Physiol. 221(Z) : 632-639. 1971 .-Freeflow samples of tubular fluid (TF) were collected from superficial distal rat tubules and analyzed for inulin-14C, sodium (Na), and potassium (K). The effects of the three diuretic agents, a,miloride, ouabain, and furosemide, were studied. Amiloride completely suppressed K secretion at the distal tubular level with only small modifications of distal tubular Na reabsorption. Ouabain induced distal kaliuresis and natriuresis in animals kept on a low-potassium diet. The effects of ouabain upon distal tubular electrolyte transport consisted in depression of both tubular Na and K reabsorption. The distal potassium effects of ouabain were independent of any increase in distal sodium delivery and are thought to be due to depression of active potassium uptake across the luminal cell membrane of distal tubule cells. The main kaliuretic effect of furosemide on distal potassium transport is related to the delivery to the distal tubule of a much greater than normal fraction of fluid. After furosemide administration, despite a very significant elevation of distal tubular sodium concentration, fractional Na reabsorption rate control values. along this tubular segment greatly exceeded
TL;DR: The similarity of these mechanical properties and those of skeletal muscle suggests that a similar mechanism of contraction exists in taenia coli.
Abstract: GORDON, ALLEN R., AND MARION J. SIEGMAN. Mechanical properties of smooth muscle. I. Length-tension and force-velocity relations. Am. J. Physiol. 221 (5) : 1243-1249. 1971 .-The length-tension and force-velocity relationships of rabbit taenia coli were studied at 22 C. The absence of spontaneous mechanical activity at this temperature was confirmed by test applications of epinephrine. The muscles were tetanically stimulated by means of a maximal 60 Hz, a-c transverse field. An optimum length for tension development was exhibited at which the passive tension was 30yo of the total tension. The maximum developed tension at the optimum length was 0.89 h 0.11 kg/cm2. The inverse relationship between the load or developed tension and the maximum velocity of shortening could be described by the Hill equation. The dynamic constants from the Hill equation were independent of the initial muscle length (a/P,1 = 0.331 zt 0.051; b/l = 0.010 =~t O.OOl/sec.; and V,,,/Z = 0.03 1 &. 0003/set). The similarity of these mechanical properties and those of skeletal muscle suggests that a similar mechanism of contraction exists in taenia coli.
TL;DR: The altered choice between the basal and the imbalanced or deficient diets of the rats with lesions in the critical prepyriform cortical areas suggests that these areas are involved in the regulation of food intake of rats fed amino acid-imbalanced or deficiency diets.
Abstract: LEUNG, PHILIP M.-B., AND QUINTON R. ROGERS. Importance of prepyriform cortex in food-intake response of rats to amino acids. Am. J. Physiol. 221(3): 929-935. 197 1 .-Bilateral electrolytic lesions were placed in the prepyriform cortex of male 230to 250-g rats and their food intake as affected by amino acid imbalance, deficiency, and excessive protein was examined. All rats with such lesions and groups of intact controls were fed in turn a basal, imbalanced (with either threonine or isoleucine as the limiting amino acid), or deficient diet (devoid of either threonine or isoleucine), and finally the lowor high-protein (670 or 75% casein) diet. No change in food intake was observed in rats fed the control diet after the placement of the lesions. However, animals with lesions in certain areas of the anterior prepyriform cortex showed a significant increase in food intake as compared to the intact controls fed the imbalanced or deficient diets, but the decrease in food intake was still evident in rats fed the high-protein diet. Intact animals select a protein-free diet over an imbalanced diet, whereas the rats with lesions in certain areas of the anterior prepyriform cortex chose the imbalanced diet over the protein-free diet. The altered choice between the basal and the imbalanced or deficient diets of the rats with lesions in the critical prepyriform cortical areas suggests that these areas are involved in the regulation of food intake of rats fed amino acid-imbalanced or deficient diets.
TL;DR: Analysis of the relationships betweenphrenic impulse rate and integrated electrical activity shows that with increased tidal volume there is a progressive increase in size of phrenic action potentials which correlate in turn with the size of the diaphragmatic motor unit.
Abstract: ELDRIDGE, FREDERIC L. Relationshz) between phrenic nerve activity and ventdation. Am. J. Physiol. 221(Z) : 535-543. 197 1 .-Phrenic nerve discharges were recorded in anesthetized cats simultaneously with a range of tidal volumes. Nerve impulses were processed in a variety of ways. Total impulses per breath and peak impulse frequency correlated poorly with tidal volume. Integrated electrical activity per breath showed an improved, often linear, correlation with tidal volume, but was too dependent upon inspiratory duration to be a satisfactory correlate of volume. Only integrated phrenic activity measured during the 0.1 set coincident with the peak of inspiration showed a consistently linear relationship with tidal volume under a variety of circumstances, including increasing barbiturate dosage, vagal section, and spinal cord transection below the phrenic roots. Analysis of the relationships between phrenic impulse rate and integrated electrical activity shows that with increased tidal volume there is a progressive increase in size of phrenic action potentials which correlate in turn with the size of the diaphragmatic motor unit.
TL;DR: Compared to the normal rats, those fed the special diets were tolerant to K as shown by increased survival and lower plasma K, and in high-K rats increased net K secretion was observed along the distal convolution and in lowNa rats decreased K secretion.
Abstract: AND GERHARD GIEBISCH. Potassium secretion by distal tubule after potassium adaptation. Am. J. Physiol. 22 l(2) : 437-448. 197 1 .-The renal contribution to the tolerance to acute loads of potassium conferred by a chronic high-K intake was examined in rats. Changes in sodium and potassium excretion following acute K infusion were observed in animals fed normal, high-K, low-Na, or low-K diets. Collection of tubule fluid from surface distal segments by free-flow micropuncture before and after K loading permitted us to assess changes in distal K secretion and Na reabsorption. Distal transepithelial potentials were measured in normal and high-K rats before and after K loading. Compared to the normal rats, those fed the special diets were tolerant to K as shown by increased survival and lower plasma K. In high-K rats increased net K secretion was observed along the distal convolution. In lowNa rats increased K secretion was observed along the collecting ducts as well as the distal convolution. Low-K rats showed smaller than normal increases in K secretion.
TL;DR: Using a modified Wiederhielm servo-micropipet system with pipet tips of 0.5-l p diam, dynamic arterial pressures in 42 arteries and arterioles of the pial vascular network on the surface of the parietal cortex of eight pentobarbitalanesthetized cats are measured and recorded, compatible with the “pressure equalization reservoir” concept ofThe pial arterial network.
Abstract: SHAPIRO, HARVEY M., DON D. STROMBERG, DENNIS R. LEE, AND CURT A. WIEDERHIELM. Dynamic pressures in the pial arterial microcirculation. Am. J. Physiol. 22 l(1) : 279-283. 197 1 .-Using a modified Wiederhielm servo-micropipet system with pipet tips of 0.5-l p diam, we measured and recorded dynamic arterial pressures in 42 arteries and arterioles of the pial vascular network on the surface of the parietal cortex of eight pentobarbitalanesthetized cats. Aortic pressure, mean central venous pressure, and end-tidal CO:! were also recorded. In branches of the middle cerebral artery as large as 455 p od, pressure was only 61 y0 of aortic pressure. Additional pressure-head loss from these major vessels across the pial arterial bed down to the penetrating arterioles (approx. 25 p od) was only 10 %. These results are compatible with the “pressure equalization reservoir” concept of the pial arterial network.
TL;DR: The hypothesis that a sizable portion of postexercise 02 consumption is due to increased tissue temperatures is substantiated and the classical definition of 02 debt requires revision.
Abstract: BROOKS,GEORGE A., KARL J. HITTELMAN,JOHN A. FAULKNER, AND ROBERT E. BEYER. Tissue temperatures and whole-animal oxygen consumption after exercise. Am. J. Physiol. 22 l(2) : 427-43 1. 197 l.-Forced treadmill running caused rat muscle and rectal temperatures to increase 8.1 and 5.1 C, respectively. After exercise, muscle temperature fell exponentially but did not reach control values in an hour. Rectal temperature fell rapidly for the first 20 min after exercise, after which only a slow rate of return to resting levels was apparent. An exercise-induced adjustment in the hypothalamic set point was suggested. 02 consumption was high immediately after exercise, declined rapidly for the first 20 min of recovery, and then plateaued at a level significantly above resting. The hypothesis that a sizable portion of postexercise 02 consumption is due to increased tissue temperatures is substantiated. The fact that severe exercise results in a large, prolonged elevation in tissue temperature necessitates, as a consequence of the Qlo effect, that 02 consumption be significantly elevated. Since a part of the postexercise 02 consumption is not associated with recovery from anaerobic metabolism, the classical definition of 02 debt requires revision.
TL;DR: Data indicate that angiotensin elicits a direct positive inotropic effect which is independent of intact adrenergic nerves or endogenous catecholamine stores.
Abstract: DEMPSEY, PETER J., ZENA T. MCCALLUM, KENNETH M. KENT, AND THEODORE COOPER. Direct myocardial efects of angiotensin 11. Am. J. Physiol. 220(Z) : 477-481. 1971.-There still remains speculation concerning the existence of a direct effect of angiotensin II on ventricular myocardium. Evaluation has been complicated by the sensitivity of the peripheral circulation in intact preparations, reflex mechanisms, and disagreement concerning the role of ganglia and endogenous catecholamine stores. TWO series of experiments were designed that used hearts from normal cats and from cats that had undergone extrinsic cardiac denervation to deplete catecholamines. In the first series, 19 isolated perfused hearts were studied in a Langendorff apparatus. In the second series, tension and transmembrane action potentials were recorded from 20 right ventricular papillary muscles. In normal and denervated ventricular myocardium angiotensin (lo--lo g/ml-lo-” g/ml) elicited a positive inotropic effect characterized by an increased maximum rate of tension rise and rate of relaxation, but not in a shortened time to peak tension. A change in the form of phase 2 of the action potential was noted. These data indicate that angiotensin elicits a direct positive inotropic effect which is independent of intact adrenergic nerves or endogenous catecholamine stores.