bluuebunny/crossref_metadata_2025 huggingface dataset:
A three-element model describes excised cat papillary muscle elasticity
Authors: Glantz SA
Published: December 2017

The three-element model for skeletal muscle has been widely applied to cardiac muscle. It consists of an active contractile element (CE) that represents the muscle's response to stimulation, in series with an elastic element (SE) and the CE and SE in parallel with another elastic element (PE). There have been problems in interpreting experimental data on muscle elasticity using this model. Data seem to indicate that SE force depends not only on instantaneous length, but also initial length; it is not only elastic. Recent experiments seem to indicate that the SE has time-varying properties; it is not passive. This paper formulates a three-element model in which phi(x) = alpha[e beta(x-x*)-1] governs the elastic elements, where phi = force, alpha, beta = spring constants, x = length, and x* = rest length, which avoids these problems. The SE and PE have the same properties. (Typical values: alpha approximately equals .045 g/mm2, beta approximately equals 5.9 mm-1 for cat papillary at 29 degrees C.). By accounting for the nonlinearity of the SE-PE interaction, this three-element model leads to predictions that agree with published data on excised papillary muscle's elastic properties.
Separate lateral hypothalamic pathways for extracellular and intracellular thirst
Authors: Kucharczyk J , Mogenson GJ
Published: December 2017

Small lesions of the midlateral zone of the lateral hypothalamus in rats attentuated water intake elicted by the central microinjection angiotensin or by the peripheral injection of isoproterenol or renin without attenuating drinking to peripherally administered hypertonic saline. Lesions placed further lateral in the hypothalamus, which destroyed the medial aspects of the internal capsule and globus pallidus, produced a marked decrease in water intake induced by hypertonic saline. Abaltion of the ventromedial nucleus of the hypothalamus increased drinking elicited by angiotension, isoproterenol, or renin.These results suggest that extracellular and intracellular thirst stimuli are mediated by separate neural pathways at the level of the lateral hypothalamus.
Reflex vascular responses in kidney, ileum, and forelimb to carotid body stimulation
Authors: Parker PE , Dabney JM , Scott JB , Haddy FJ
Published: December 2017

Reflex vascular responses to local carotid chemoreceptor stimulation with hypoxic-hypercapnic, hypoxic, or hypercapnic blood were investigated in pentobarbitalized dogs. Bilaterally isolated carotid chemoreceptors were perfused via an extracorporeal lung circuit. Oxygen and carbon dioxide tensions of blood perfusing the carotid bodies were altered by ventilating the isolated lung with various O2-CO2 mixtures. Ventilation of the whole animal maintained normal systemic O2 and CO2 tensions. Perfusion pressures of the isolated kidney, ileum, forelimb, gracilis and hindpaw were measured during constant-flow perfusion. Carotid chemoreceptor stimulation with hypoxic-hypercapnic blood before vagotomy increased renal vascular resistance but caused no change in intestinal or forelimb resistance. Following vagotomy, hypoxic-hypercapnic, hypoxic, or hypercapnic carotid body stimulation increased renal, intestinal, and forelimb vascular resistance. Forelimb skin and muscle vascular beds contributed about equally to the increase in forelimb resistance. Gracilis muscle and hindpaw resistance also increased during hypoxic-hypercapnic stimulation after vagotomy.
Differential in vivo pulmonary degradation of prostaglandins E1, B1, and A1
Authors: Robertson RP
Published: December 2017

Immunoreactive (IR) plasma prostaglandin (PG) levels were measured in samples collected simultaneously through catheters placed in the right ventricle and the thoracic aorta in fasting anesthetized dogs. There were significantly greater levels of IRPGB (P less than .01) and IRPGA (P less than .05), but significantly less IRPGE (P less than .01) in the aorta than in the ventricle. During femoral vein infusion of PGE1, PGB1, and PGA1, respectively, PGE1 was approximately 87% metabolized, but PGB1 and PGA1 were not degraded by the lung. There was no measurable increase in IRPGB or IRPGA levels in the thoracic aorta during intravenous PGE1 infusion. It was concluded that in the resting state PGE is actively degraded by the lung; that the lung very effectively degrades PGE1 but does not degrade PGB1 or PGA1 during infusion of these prostaglandins; and that pulmonary metabolism of PGE1 probably does not result in formation and release of PGB or PGA into the arterial circulation. Additionally, the possibility exists that in the resting state PGB and/or PGA are actively secreted by the lung, but the immunoassay methodology used does not permit resolution of this point.
Positive staircase effect in the rat heart
Authors: Henry PD
Published: December 2017

The apparent lack of a positive staircase effect in ray myocardium may reflect inadequate metabolic support. Isolated rat hearts (n equals 10) were perfused at 37 degrees C with Krebs buffer containing 5 mM glucose. In 10 preparations increases in heart rate from 240 to 480/min resulted in twofold increases in left ventricular pressure and dP/dt. Pacing at a rate of 480/min resulted in mechanical deterioration of the preparation and in 50% decreases of myocardial ATP concentration within a 10-min period. Hearts of open-chest rats driven at the same rate for the same period maintained normal ATP stores. In isolated papillary muscles contracting isometrically at a rate of 30/min, peak stress 15g/mm2 (mean plus or minus SE, n equals 8) and was not changed by increasing the concentration of glucose from 5 to 30 mM. When frequency was raised from 30 to 300/min, stress declined to 5.0 plus or minus .15 g/mm2 in the presence of 5mM glucose (P smaller than .001) but increased to 8.8 plus or minus .21 g/mm2 (P smaller than 0.001) in the presence of 30 mM glucose. Thus, rat ventricular myocardium exhibits a positive staircase effect at physiological heart rates when metabolic support is adequate.
Effect of ACTH on lipolysis in adipose tissue of normal and adrenalectomized rats in vivo
Authors: Spirovski MZ , Kovacev VP , Spasovska M , Chernick SS
Published: December 2017

Parametrial fat-pads of fed rats were perfused in vivo. Rates of release of glycerol and free fatty acids (FFA) were determined from venous-arterial difference and plasma flow. Adrenalectomy lowered basal release of FFA and glycerol, but not reesterification of FFA within the fat-pad. ACTH (5 mug iv) in normal rats increased release of FFA and glycerol (mumol-g-1-h-1) from basal values of 0.90 and 0.48 to 3.2 and 1.3, respectively, and in adrenalectomized rats from 0.41 and 0.33 to 1.5 and 3.1, respectively. Thus in normal rats ACTH increased the molar ratio of FFA to glycerol released from 1.9 to 2.5, whereas in adrenalectomized rats the ratio fell from 1.3 to 0.5. After stimulation of lipolysis in normal rats 85% of the FFA formed were released but only 20% in adrenalectomized rats; the remainder was reesterified to triglyceride. It is concluded that adipose tissue of adrenalectomized rats is sensitive to the lipolytic activity of ACTH, but increased glucose utilization by adipocytes in the absence of glucocorticoid enhances reesterification and reduces release of FFA by the tissue.
Effects of alveolar and perfusion hypoxia and hypercapnia on pulmonary vascular resistance in the lamb
Authors: Hyman AL , Kadowitz PJ
Published: December 2017

The effects of ventilatory hypoxia and hypercapnia and perfusion hypoxia and hypercapnia on pulmonary vascular resistance were studied in the intact lamb using right heart techniques to isolate and perfuse the left lower lobe. Ventilatory hypoxia increased vascular resistance in the left lower lobe by constricting predominantly vessels upstream from small lobar veins, presumably small arteries. The response to hypoxia was not blocked by phentolamine and diphenhydramine in doses that markedly decreased pressor responses to norepinephrine and histamine in the lung. Perfusion hypoxia did not alter vascular resistance in the perfused lobe. Ventilatory hypercapnia increased vascular resistance in the lung by constricting mainly upstream vessels, whereas perfusion hypercapnia decreased resistance by dilating upstream vessels. These data indicate that histamine and catecholamines are not involved in the response to alveolar hypoxia. These results suggest that the sensor site for ventilatory hypoxia is close to the alveolus since the response is unrelated to lobar arterial Po2. It is concluded that systemic reflexes are not necessarily involved in the response of the pulmonary vascular bed to ventilatory hypoxia or hypercapnia and that the magnitude and rapidity of this response suggest that it may represent an important local mechanism for the control of ventilation-perfusion relationships in this species.
Creatinine, potassium, and calcium flux from chicken cerebrospinal fluid
Authors: Anderson DK , Heisey SR
Published: December 2017

Brains of methoxyflurane-anesthetized chickens were perfused from a lateral cerebral ventricle to cisterna magna with an artificial cerebrospinal fluid (CSF) containing trace quantities of radioiodinated human serum albumin (RIHSA) or inulin (1.0 mg/ml) to measure CSF bulk absorption. In addition, it contained either trace quantities of 22Na, 42K, 45Ca or [14C]creatinine; the concentrations of the latter three were varied to determine permeability coefficients (K-D's) as a function of concentration. A mass balance for the tracer molecules was calculated to determine their movement into brain or blood. K-D's for 45Ca, 42K, 22Na, and creatinine (Cr) were unaffected by perfusion time and the latter two were larger than previously reported (3). The lack of effect of time on K-D and the large values for K-D22Na and K-D-Cr are attributed to anesthetic effects on brain blood flow. K-D-Cr and K-D42K were larger than K-D22Na or K-D45Ca and K-D's for 45Ca, Cr, and 42K were independent of their inflow concentrations. An active transport process is suggested for potassium and creatinine, but one that is located at sites other than the ependymal wall. Bulk flow clearance accounted for RIHSA movement from CSF, whereas nonbulk clearance accounted for 50% of 22Na and 45Ca movement and 90% of 42K clearance. Fifty percent of 42K and 25% of 22Na and 45Ca were found in brain. The large recovery of 42K in brain supports the hypothesis that intracellular potassium serves as an exchangeable pool for the tracer.
Inhibition of angiotensin conversion and prevention of renal hypertension
Authors: Miller ED  , Samuels AI , Haber E , Barger AC
Published: December 2017

Renal artery constriction in the unilaterally nephrectomized, trained dog, with maintained renal arterial hypotension, produces a prompt increase in systemic renin activity and blood pressure. The hypertension normally induced by renal artery stenosis is prevented by prior treatment with the nonapeptide Pyr-Trp-Pro-Arg-Pro-Gln-Ile-Pro-Pro (SQ 20, 881), which blocks conversion of angiotensin I to angiotensin II. Constant intravenous infusion of the inhibitor over several days of renal artery constriction prevents the development of chronic renovascular hypertension. Furthermore, a single injection of the nonapeptide restores blood pressure to normal in the early phase of renovascular hypertension, but becomes progressively less effective as salt and water retention occurs in the chronic stage when plasma renin activity returns to control levels. These data provide strong evidence that the renin-angiotensin system is responsible for the initiation of renovascular hypertension in the one-kidney Goldblatt dog, but that other factors become increasingly important in chronic renovascular hypertension.
Relations of weak-electrolyte transport and acid-base metabolism in rat small intestine in vitro
Authors: Jackson MJ , Morgan BN
Published: December 2017

The jejunal and ileal regions of rat small intestine in vitro exhibit different patterns of weak-electrolyte transport and acid-base metabolism. The jejunal pattern of weak-electrolyte transport is net transport of weak acids M yields S and of weak bases S yields M (M, mucosal; S, serosal), and the pattern of acid-base metabolism is luminal acidification and serosal alkalinization. In the absence of sodium or in the presence of metabolic inhibitors, weak-electrolyte transport and serosal alkalinization are inhibited, but luminal acidification is not inhibited. The ileal pattern of weak-electrolyte transport is the opposite of that of the jejunum and may be associated with the presence of a luminal alkalinization process observed in this region. In the absence of chloride the ileal patterns of weak-electrolyte transport and acid-base metabolism become similar to those of the jejunum. It is suggested that these observations support a previously proposed model for weak-electrolyte transport in the intestine consisting of a series three-compartment system in which the pH of the intermediate compartment is greater than that of the bulk phases.
Action of peptide-B from bovine fibrinogen on ATPase activity and superprecipitation of myosin B
Authors: Osbahr AJ , Custodio R
Published: December 2017

Bovine peptide-B from fibrinogen was capable of accelerating the structural and enzymatic effects associated with superprecipitation of myosin B. The rate of superprecipitation coupled with the hydrolysis of ATP are increased during the structural transformation. In the concentration range from 10-8 to 10-4 M peptide-B, the rate of superprecipitation is increased 12-fold while the hydrolysis of ATP doubles and the time to reach the final extent of superprecipitation is decreased 68%. Under these same conditions, the hydrolysis of ATP by myosin A was unaffected. The concentrations of magnesium and calcium were between 10 and 20 muM, and no additional divalent metal ions were added to the system. Superprecipitation was treated as a model for muscle contraction to explain the in vivo studies of bovine peptide-B in which the peptide behaves as a vasopressor substance producing vascular vasoconstriction. A possible mechanism for the participation of bovine peptide-B in the model for muscle contraction, based on the polarizing interaction of the highly charged density of negativity of the peptide with the actomyosin complex, is presented. Furthermore, bovine peptide-B is speculated as participating in vasoconstriction via attachment to some smooth muscle receptor.
A proposed mechanism of zinc absorption in the rat
Authors: Evans GW , Grace CI , Votava HJ
Published: December 2017

Studies were conducted at the cellular level in an attempt to describe the processes involved in zinc absorption from the intestine. A low-molecular-weight zinc-binding ligand was identified in the pancreas of rats and pancreatic secretions from a dog. The whole-body absorption of 65Zn in rats in which the common bile duct was ligated was significantly less than the absorption of 65Zn in rats in which the hepatic bile duct was ligated. The uptake of 65Zn by epithelial cells from everted intestinal segments was markedly increased in the presence of the zinc-binding ligand fraction from pancreatic secretions. Following in vivo labeling, 30% of the 65Zn in the epithelial cell was associated with the partially purified basolateral plasma membrane. When labeled basolateral plasma membranes were incubated in a medium that contained zinc-free albumin, approximately 96% of the 65Zn was transferred to the medium while less than 30% of the isotope was released to media that contained either no albumin or a 3:1 zinc: albumin complex. In rats fed a zinc-deficient diet, 65Zn absorption was inversely proportional to the serum zinc concentration, and both zinc and copper injections produced a marked decrease in 65Zn absorption. These results suggest that zinc absorption consists of interactions among a low-molecular-weight ligand, recpetor sites on the basolateral membrane, and metal-free albumin.
Modification of vagal depressor reflex by CO2 in spontaneously breathing rabbits
Authors: Ott NT , Shepherd JT
Published: December 2017

The control of hindlimb and renal vascular beds by vagal afferents was studied, in anesthetized spontaneously breathing rabbits in which the carotid sinus and aortic depressor nerves were cut, by measuring the increase in vascular resistance (constant-flow perfusion with autologous blood) during bilateral vagal cold block (VCB). The effect of hypercapnia was studied with both increased ventilation (caused by inspiration of mixtures of CO2 in O2) and decreased ventilation (caused by infusion of gallamine during O2 breathing). The increase in hindlimb resistance with VCB was correlated with respiratory minute volume but not with PCO2; the reverse was true for the increase in renal resistance. Without VCB the renal vessel constriction caused by the hypercapnia was markedly attenuated, provided that there were minimal respiratory movements; the resistance increased dramatically when these movements were abolished or with VCB. Thus, the powerful central effect of CO2 on the renal vessels can be counteracted by vagal afferents activated by lung movement; even minimal respiratory activity can cause this effect.
Effect of methylprednisolone upon arterial pressure and the renin angiotensin system in the rat
Authors: Krakoff LR , Selvadurai R , Sutter E
Published: December 2017

The effect of methylprednisolone or deoxycorticosterone upon systemic arterial blood pressure and components of the renin-angiotensin system was studied in the rat. Rats maintained on regular diets given methylprednisolone suspension 20 mg/kg body wt demonstrated a significant increase in arterial pressure of + 37 plus or minus 5 mmHg, mean plus or minus SE, over a 2-wk period, whereas those treated with DOC and untreated controls showed no significant change. On normal diets, plasma renin concentration (PRC) of methylprednisolone-treated rats was significantly higher than that of DOC-treated rats. Methylprednisolone treatment also resulted in a significant elevation of plasma renin substrate concentration (PRS). Calculated plasma renin activity (PRA) was highest in methylprednisolone-treated rats, significantly above that of the DOC and no-steroid groups. NaCl supplementation resulted in a significant fall in PRC and PRA in all three groups; however, PRS remained significantly above normal in the methylprednisolone-treated rats. The pressor effect of angiotensin II was slightly increased in methylprednisolone-treated rats. Infusion of [Sar1,Ala8]angiotensin II (P-113) in methylprednisolone-treated rats resulted in a significant fall in diastolic arterial pressure. The results imply that methylprednisolone hypertension in the rat may be in part angiotensin dependent.
Effect of vagotomy on electrical activity of the small intestine of the dog
Authors: Weisbrodt NW , Copeland EM , Moore EP , Kearley RW , Johnson LR
Published: December 2017

The effect of bilateral thoracic vagotomy on the myoelectric activity of the small intestine was determined in conscious dogs. Animals were implanted with electrodes spaced 25 cm apart along the serosal surface of the small intestine, and a cannula was placed in the most dependent portion of the stomach. Recordings were made with dogs in the fasted and fed states. Two distinct patterns of myoelectric activity were recorded: one typical of the fasted state (the interdigestive myoelectric complex) and one typical of the fed state. After completion of the control recording periods, a truncal vagotomy was performed on each animal. Completeness of vagotomy was confirmed by lack of a gastric secretory response to insulin. Gastric stasis occurred after vagotomy; therefore, the animals' stomachs were emptied via the gastric cannula to obtain a fasted condition. Vagotomy had little to no effect on the fasted pattern of myoelectric activity. The fed pattern was significantly altered in two of the three animals. This alteration could be due to the effect of vagotomy on gastrin release. We conclude that nervous pathways within the vagus may exert some influence on intestinal myoelectric activity but that other neural-humoral pathways are probably involved.
Adaptive tolerance of fish myocardium to hypercapnic acidosis
Authors: Poupa O , Johansen K
Published: December 2017

Isometric, electrically paced strips of cardiac ventricle from two species of fish (plaice, Pleuronectes platessa; cod, Gadus morrhua) with different tolerance to hypoxia were compared with respect to effects of hypercapnic acidosis. Acidosis was induced by altering the equilibrating gas mixture for the muscle strip chamber from 3% CO2 in 97% 02 to 15% CO2 in 85% O2. The pH was varied further by changing the NaHCO3 content of the Cortland-Ringer solution used in the muscle chamber. After onset of acidosis with the highest buffer value of the Cortland-Ringer solution (35.7 mM NaHCO3), the force decay was similar for the initial 10 min of exposure to high Pco2. Subsequently the cod heart continued to lose force at the same rate, whereas the plaice heart regained a cardiac contractile force that after 40 min even exceeded prehypercapnic values. When buffer values were varied by changing the bicarbonate content of the Cortland-Ringer solution in steps from 0.0 to 35.7 mM NaHCO3, the cod heart showed steep force decays at all buffer values during hypercapnic acidosis. The plaice heart showed a similar decline at low buffer values but at a bicarbonate concentration above 23.8 mM NaHCO3, the initial force decline was reversed and prehypercapnic force restored.
Cardiac output and its distribution during diving in the rat
Authors: Lin YC , Baker DG
Published: December 2017

The diving response was produced by submerging the head of the unanesthetized rat for 60 s, while it was confined in a mesh-wired cone. Heart rate and cardiac output decreased by 73% and 74% from the predive values, respectively, indicating insignificant change in stroke volume. Central systemic arterial blood pressure rose by 22% during diving and a fourfold increase in total peripheral resistance was observed. Blood flow to the coronary, cerebral, and bronchial circulations remained unchanged while a 95% reduction in the intestine and the spleen, a 97% reduction in the kidney, and greater than 99% reduction in the tail and skin were observed during diving. The blood flow reduction from predive values ranged from 50% for liver and skeletal muscle to 75% for the adrenals and 65% for the diaphragm. The redistribution of the drastically reduced cardiac output during head immersion in the rat is similar to that reported for diving mammals. It is suggested that the rat may serve as a useful cardiovascular model for further studies of the diving response in mammals.
Adrenergic responses in canine cutaneous vasculature during acute hemorrhagic hypotension
Authors: Liao JC , Zimmerman BG , Van Bergen FH
Published: December 2017

The purpose of this study was to determine the effect of acute hemorrhage on vascular responses to sympathetic nerve stimulation and norepinephrine. The experiments were carried out with sodium pentobarbital anesthesia. The preparation employed was the dog's hindpaw perfused at constant blood flow. Changes in vascular resistance in the paw were indicated by changes in perfusion pressure. Changes in perfusion pressure elicited by sympathetic nerve stimulation and intra-arterially administered norepinephrine were determined before and after hemorrhage of 15 ml/kg in normal and acutely nephrectomized animals. The response to sympathetic stimulation was increased by about 50% in normal but not in nephrectomized dogs, whereas the response to a low dose of norepinephrine (0.5-1 mug) was not significantly changed in either group of animals. In additional experiments in which the plasma renin level was measured, the potentiation of responses to sympathetic stimulation and a high dose of norepinephrine (2 mug) occurred at the time that the renin level was increased by hemorrhage. These results indicate that the level of circulating angiotensin attained after hemorrhage may facilitate vasoconstrictor responses to adrenergic stimuli.
Reflection coefficients of dog lung endothelium to small hydrophilic solutes
Authors: Perl W , Chowdhury P , Chinard FP
Published: December 2017

Step additions of small hydrophilic solutes to the perfusate of isolated dog lungs produce weight changes (Vargas-Johnson). The product: (observed reflection coefficient) times (observed filtration coefficient) for the lung endothelial barrier is obtained from the initial weight slope per unit osmolality change. The observed filtration coefficient determined from the sustained constant weight slope per increment of pulmonary outflow pressure was 0.038 plus or minus 0.011 cm/s (assumed exchange area 500 cm2/g lung). Correction to average transcapillary pressure (32% upward) and for osmotic buffering by resident solute (25% upward) gave 0.063 plus or minus 0.018 cm/s. The observed reflection coefficients were (mean plus or minus 2 SE): sodium chloride, 0.30 plus or minus 0.11; urea, 0.30 plus or minus 0.12; glucose, 0.48 plus or minus 0.26; sucrose, 0.39 plus or minus 0.17; raffinose, 0.35 plus or minus 0.16; hypotonic response: interstitial solute, 0.26 plus or minus 0.10. The observed reflection coefficient of sodium chloride, corrected for the preceding filtration coefficient effects (65% downward) and for combined flow limitation and osmotic buffering effects (50% upward) was 0.27. Transcapillary gradients of small hydrophilic solutes produce substantial osmotic effects for short times (seconds). Passive exchanges and net fluxes across the endothelium of the lung capillaries have parameters similar to those of the endothelium of skeletal muscle.
Rabbit testicular contractions: bimodal interaction of prostaglandin E1 with other agonists
Authors: Hargrove JL , Seeley RR , Ellis LC
Published: December 2017

Contractions of rabbit testicular capsules in vitro and in vivo in response to prostaglandin F2a, epinephrine, and acetylcholine were measured in the presence of prostaglandin E1 (PGE1). Contractions induced by these agents were markedly inhibited at 10-7 M concentrations of PGE1 in both preparations. Even so, lower levels of PGE1 (10-8 or 10-9 M) potentiated epinephrine- or acetylcholine-induced stimulation of increased tonus in vovo. Epinephrine, PGE1, and PGF2a caused increased tonus and contractions in vitro and in vovo; however, acetylcholine stimulated the testicular capsule much more in vivo than in vitro. The control log dose-response curve for epinephrine stimulation showed a slight decrease in the upper concentration range. Propranolol, a beta-adrenergic blocking agent, more than overcame this decrease and also prevented a theophylline inhibition of epinephrine-induced contraction. Prostaglandin E1's bimodal effect gives it the ability to modulate testicular contractions by increasing stimulation by other agonists in vovo at low concentrations of PGE1 but inhibiting it at higher concentrations. Thus PGE1 is a potential regulator of testicular capsular motility and possibly sperm transport and hemodynamics.
Effect of inhibition of peptidase activity on distribution of intrarenal blood flow
Authors: Bailie MD , Barbour JA
Published: December 2017

Experiments were performed in dogs to determine the effects of the intravenous administration of the dipeptide hydrolase inhibitor SQ 20,881 on renal hemodynamics, intrarenal blood flow distribution, and renal function. Dipeptide hydrolase converts angiotensin I to angiotensin II and inactivates bradykinin. SQ 20,881 causes an inhibition of the vasoconstrictor response after angiotensin I and potentiation of the vasodilatory activity of bradykinin. Total renal blood flow, cortical distribution of blood flow, and glomerular filtration rate were determined. In seven animals administration of SQ 20,881 (1 mg/kg) resulted in a decrease in mean systemic blood pressure of 11 mmHg, an increase in total renal blood flow of 0.71 ml/min per g, and a significant fall in glomerular filtration rate. Fractional blood flow to the superficial cortex decreased and to the juxtamedullary cortex increased. Absolute flow was unchanged in the superficial cortex and increased significantly in the deep cortex. The findings are compatible with reported effects of bradykinin on intrarenal blood flow distribution, although the experiments do not distinguish between potentiation of bradykinin or inhibition of angiotensin I conversion.
Effects of unilateral sodium replacement on sugar transport across in vitro rabbit ileum
Authors: Rinaldo JE , Jennings BL , Frizzell RA , Schultz SG
Published: December 2017

The effects of unilateral sodium replacement with either choline or mannitol on passive and active 3-O-methyl-D-glucose (3-MG) absorption by in vitro rabbit ileum were examined. The results indicate that the predominant factor influencing 3-MG absorption is the presence of sodium in the mucosal bathing solution. Replacement of sodium in the mucosal solution alone markedly inhibits passive and essentially abolishes active 3-MG absorption regardless of the presence or absence of sodium in the serosal bathing solution. The presence or absence of sodium in the serosal solution does not affect transmural 3-MG transport regardless of the sodium concentration in the mucosal solution. Further, when sodium is replaced in the mucosal solution alone, the bidirectional transmural fluxes of 3-MG do not differ markedly from those of D-mannitol, a solute whose transport is probably attributable to simple diffusion. The present findings together with those of previous studies (15, 16) are consistent with the notion that replacement of sodium in the mucosal solution alone essentially abolishes transcellular 3-MG transport and that the remaining transepithelial fluxes are largely due to diffusion through the paracellular or shunt pathway. The relation of these findings to in vivo and in vitro studies in which perfusion of a segment of small intestine with a Na-free solution disclosed little or no inhibition of sugar absorption is discussed.
Effect of infusion of pharmacologic amounts of vasopressin on renal electrolyte excretion
Authors: Kurtzman NA , Rogers PW , Boonjarern S , Arruda JA
Published: December 2017

Aqueous vasopressin was infused to bicarbonate- and glucose-loaded dogs and to nonloaded antidiuretic dogs in doses of 50 mU/kg per min or 50 mU/kg per h. Both doses caused a marked increase in sodium, chloride, and water excretion. The larger dose raised the fractional excretion (sodium clearance (C-Na)/glomerular filtration rate (GFR) times 100) of these ions from 2% or less to in excess of 20%. Blocking the pressor effects of these doses of vasopressin with sodium nitroprusside did not alter the marked natriuretic and chloriuretic effect. The maximal rate of bicarbonate and glucose reabsorption was not depressed by vasopressin infusion; fractional phosphate excretion, however, was markedly increased. Inhibiting distal hydrogen ion secretion by inducing selective aldosterone deficiency failed to uncover a vasopressin-induced inhibition of proximal bicarbonate reabsorption that might have been masked by increased distal bicarbonate reabsorption. There was no significant change in GFR, renal plasma flow, or filtration fraction. The distribution of cortical renal blood flow (measured by the radioactive microsphere technique) shifted toward the inner cortex after vasopressin administration. Vasopressin, in pharmacologic doses, is a potent diuretic that most likely exerts this effect by directly inhibiting sodium reabsorption at a point in the nephron distal to the proximal tubule.
Cardiovascular chemoreflexes from the perfused innervated ileum of the cat
Authors: Frank MH
Published: December 2017

The vascular supply of innervated segments of ileum in urethan-anesthetized cats was perfused by an electrolyte-glucose solution, containing heparinized cat blood. Addition of acetylcholine or nicotine to the perfusion inflow was followed by increases of systemic arterial pressure. Calculated mean concentrations of 32 mug/ml acetylcholine or 35 mug/ml nicotine in the perfusion fluid induced mean pressor responses of 19 and 23 mmHg. These responses began within 2-6 s, reached a maximum within 20 s, were unaffected by vagotomy, and were frequently accompanied by cardiac acceleration and increase in rate and depth of respiration. Evans blue in the perfusion fluid did not enter the general circulation. Systemic responses were abolished or markedly decreased after perfusion of 40-180 mg procaine through the innervated gut segments or by cooling the nerve fibers between the perfused ileum and the body of the animal. In itself, procaine injected into the isolated circulation or nerve cooling commonly induced decreases of arterial pressure. The vascular isolation of the perfused segments and the dependence of the systemic responses on the nervous connections indicate that the effects were reflex.
Synthesis of uric acid in isolated normothermic perfused mongrel and Dalmatian dog kidneys
Authors: Quebbemann AJ , Cumming JD , Shideman  , Toledo-Pereyra L
Published: December 2017

Renal synthesis of uric acid (urate) in the dog was demonstrated by use of two isolated kidney preparations during pulsatile perfusion at 37 degrees C with artificial perfusate or with a plasma fraction. During perfusion of mongrel and Dalmatian dog kidneys with 0.5 mg of [14C]xanthine per 100 ml, a mean of 24.3 and 25.4 mug of [14C]urate per minute, respectively, entered either urine or perfusate after its synthesis in the isolated kidney. Approximately 6.2% of the combined extracellular radiolabeled urate formed in the isolated mongrel kidney was excreted in the urine and 15.7% in the urine of isolated Dalmatian dog kidneys. Recirculating the perfusate without the kidney did not convert any radioactively labeled xanthine to urate and therefore the radioactively labeled urate appearing in the urine and recycled perfusate must have been formed in the renal parenchyma. Renal synthesis of urate was blocked by the xanthine oxidase inhibitor allopurinol. In the presence of allopurinol, [14C]xanthine was excreted unchanged into the urine.
Lipoate effect on carbohydrate and lipid metabolism and gastric H+ secretion
Authors: Harris JB , Alonso D , Park OH , Cornfield D , Chacin J
Published: December 2017

Acid secretion (QH+) and oxygen consumption (Qo2) by frog gastric mucosae in vitro were sharply stimulated by lipoate. A rapid decline followed stimulation, subsequently falling below control values. Addition of only glucose or lactate had no effect on Qo2 or QH+. Pyruvate caused slight significant stimulation of Qo2. Any one of these compounds added to lipoate-treated mucosae increased the stimulatory effect of lipoate and markedly slowed the rate of decline subsequent to maximum stimulation. Various fatty acids had a moderate-to-high stimulatory effect on Qo2 and QH+. Lipoate added prior to the addition of fatty acids decreased the stimulatory effect of buryrate (minus 56%), decanoate (minus 87%), and palmitate (minus 60%). Propionate became an inhibitor in the presence of lipoate. Lipoate increased (plus 100%) the amount of glycogen oxidized and decreased (minus 69%) the amount of triglycerides oxidized. Lipoate-treated mucosae did not respond to histamine. Addition of glucose restored responsiveness. The results indicate that beta-oxidation of fatty acids plays a major role in the acid secretory process and is centrally involved in cyclic AMP and histamine stimulation of QH+.
Valinomycin shortening of action potential of embryonic chick hearts
Authors: Shigenobu K , Sperelakis N
Published: December 2017

The effects of valinomycin, an agent known to increase the K+ conductance (gK) of lipid bilayer membranes and to be an uncoupler of oxidative phosphorylation, were examined on young (3 days old) and old (15-19 days old) embryonic chick hearts. In the old hearts, valinomycin produced pronounced shortening of the action potential plateau, and often only the spike component remained. The rate of rise of the action potential was usually not affected (slightly diminished sometimes). Addition of dimethylsulfoxide (2 percent), the vehicle for the valinomycin, did not cause shortening of the plateau. The diminution of the plateau by valinomycin at 1 mug/ml was usually obtained after incubation for 1 h; larger doses produced prominent effects within 15 min. The threshold concentration was about 0.1 mug/ml. Cooling, isoproterenol, Ba++, Sr++, and tetraethylammonium partially relengthened the plateau shortened by valinomycin. Lowering of external K+ also lengthened the plateau slightly in the presence of valinomycin. Young embryonic hearts were more resistant to valinomycin, and it was necessary to incubate with 20-40 mug/ml for 1-2 h to produce a significant diminution in plateau. In both young and old hearts, the resting potential was not increased by valinomycin, even though young hearts have a low resting potential (similar to minus 40 mV) mainly because of a low gK. These results suggest that the kinetics of the changes in gK during the action potential plateau may be more greatly affected by valinomycin than the steady-state gK of the resting membrane. In addition to such a direct effect on the sarcolemma, valinomycin could also exert an indirect effect by blocking the slow inward current through ATP depletion.
Phosphorylated beta-guanidinopropionate as a substitute for phosphocreatine in rat muscle
Authors: Fitch CD , Jellinek M , Fitts RH , Baldwin KM , Holloszy JO
Published: December 2017

To evaluate phosphorylated beta-guanidinopropionate (beta-GPAP) as a substitute for phosphocreatine (PC), hypoxic tibialis anterior muscles were stimulated to contract isometrically in situ until twitch tension fell to 25 percent of the peak value. Muscles from rats fed beta-guanidinopropionic acid (beta-GPA) failed to exhibit the staircase phenomenon, and they developed 28 percent less tension than control muscles. In control muscles lactate increased from 0.75 to 20.99, ADP increased from 0.89 to 1.20, ATP decreased from 5.09 to 2.73, and PC decreased from 15.78 to 1.52 mumol/g. In muscles from rats fed beta-GPA, lactate increased from 0.85 to 14.31, ADP increased from 0.86 to 1.05, ATP decreased from 2.69 to 1.71, PC decreased from 0.73 to 0.30, and beta-GPAP decreased from 30.34 to 19.45 mumol/g. From these measurements, the use of high-energy phosphate was calculated to be reduced 32 percent in muscles from rats fed beta-GPA. The relationships between the use of high-energy phosphate was calculated to be reduced 32 percent in muscles from rats fed beta-GPA. The relationships between the use of high-energy phosphate and tension development confirm experimentally the ability of beta-GPAP to substitute for PC as a source of energy to sustain muscle contraction.
Distribution of H+ and HCO3 minus between CSF and blood during respiratory acidosis in dogs
Authors: Pavlin EG , Hornbein TF
Published: December 2017

To evaluate the regulation of (H+) and (HCO3 minus) in brain extracellular fluid during respiratory acidosis, the changes in cisternal and lumbar CSF acid-base state were assessed in six anteshetized, paralyzed, mechanically ventilated dogs rendered hypercapnic by increase in FIco2. Arterial (HCO3 minus) was held constant. The electrochemical potential difference (mu) between CSF and blood for H+ and HCO3 minus was calculated from values for (H+) and (HCO3 minus) in CSF and arterial plasma and the simultaneously measured CSF/plasma DC potential difference. Measurements were made at pHa equal to 7.40, after stable arterial values of pHa of about 7.2 were attained and 3, 4.5, and 6 h thereafter. A steady state for ion distribution was attained by 4.5 h. Values of mu for H+ and HCO3 minus at 6 h had returned to +0.7 and minus 0.7 mV of control for cisternal CSF and +1.3 and minus 0.6 mV of control for lumbar CSF. The attainment of steady-state values for mu close to control is comparable with passive distribution of these ions between CSF and blood.
Ion transport by amphibian antrum in vitro. I. General characteristics
Authors: Flemstrom G , Sachs TG
Published: December 2017

Both Necturus and bullfrog antrum show stable PD, resistance, and short-circuit current (Isc) when mounted in an Ussing chamber. Measurements of Na+ and Cl minus flux showed that both ions are actively transported across Necturus antrum, Na+ from secretory to nutrient, Cl minus from nutrient to secretory (both net fluxes being similar to 0.30 mueq cm minus 2 h minus 1). Only the Na+ transport contributed to the Isc and PD as evidenced by a) Na+ removal, b) the effects of amiloride on the secretory surface, c) the effects of ouabain on the nutrient side. Microelectrode experiments confirm the Na+ conductance of the secretory cell membrance, a HCO3 minus conductance of both cell membranes, and a KCl conductance across the nutrient cell membrane. In addition, antrum apparently secretes alkali (similar to 0.35 mueq cm minus 2 h minus 1), which secretion is sensitive to metabolic inhibitors and Diamox. Nutrientside HCO3 minus increased the rate of alkaline secretion and a transmucosal HCO3 minus gradient could contribute to ISC and PD. A model is proposed to account for the electrical properties of the tissue.
Dynamic analysis of gravimetric response of isolated dog hindlimb
Authors: Sato T , Yamashiro SM , Grodins FS
Published: December 2017

Previous gravimetric studies of transcapillary fluid movement have been based on capillary filtration coefficient (CFC) estimates. In these studies only a single CFC value is estimated for the entire isolated vascular bed. We have analyzed the dynamic gravimetric responses of isolated dog hindlimb to venous pressure steps and found it possible to estimate two different CFC values. Under control conditions, one CFC value averaged .0049 ml/mmHg min per 100g tissue wt, whichagrees with results of previous investigators. The other CFC value averaged 90304, which is very close to estimates we have previously made by an independent frequency-response methods. Changes in hindlimb properties to intra-arterial infusions of acetylcholine, papaverine, isoproterenol, and norepinephrine were also studied. Drug infusion results and the presence of similar dynamic components in experiments on gracilis muscle support the existence of inhomogeneous pathwaysin tissue, which lead to fluid-exchange nonuniformity.
Kinetics of renin-antirenin reaction: micromethods for the assay of renin and antirenin
Authors: Haas E , Goldblatt H , Klick RL , Lewis L
Published: December 2017

Indirect micromethods were designed for the assay of human renin (lower limit 0.25 times 10-4 U and of antirenin to human renin (lower limit 3 times 10-4 U), with the rat used for the bioassay of the angiotensin produced by the action of renin on renin substrate. This made possible the assay of unusually small amounts (0.01 mu1) of serum for antirenin. The Michaelis-Menten concept of a dissociating complex can be applied to the antireninrenin reaction: the rate constants for the formation and for the breakdown of the complex were k1 equal to 1.65 (ml/U antirenin per min) and k3 equal to 1.97 times 10-3 (U inactivated renin/U antirenin per min), respectively; the apparent Michaelis constant was 12 times 10-4 (U renin/ml). A second method of analysis was also applied by assuming the formation of a rather tight complex, with antirenin functioning as an irreversible inactivator of renin. Both methods of analysis yielded practically the same rate constant (k1 equal to 1.65 and k1 equal to 1.71), but the treatment according to the Michaelis-Menten equation affords a slightly better fit of the experimental data (accuracy equal to plus or minus 15.5 percent) than the second method of calculation (accuracy equal to plus or minus 21.6 percent).
Polyuria and imparied ADH release following medial preoptic lesioning in the rat
Authors: van Gemert M , Miller M , Carey RJ , Moses AM
Published: December 2017

Studies were carried out in the rat to detemine if hypothalamic lesions which caused polydipsia and polyuria had their effect mediated through an alteration of the ability of the neurohypophyseal system to release ADH. Rats with medial preoptic lesions hadincreased water intake while on ad libitum access to water and slightly impaired ability to conserve water following dehydration, but with no impairment of urine-concentrating ability. These were associated with an increase in plasma osmolality both during ad libitum fluid intake and after dehydration. Urinary ADH excretion was at leastas great as in shamoperated controls during ad libitum water intake, but failed to increase during dehydration in spite of a marked increase in plasma osmolality. Pituitary ADH content did not differ from control animals either during ad libitum water intake of after dehydration. Animals with lesions in the lateral preoptic and septal areas did not differ from control animals during ad libitum fluid intake and after dehydration even though lateral preoptic lesions produced polydipsia. In all animals, lesions were remote from the supraoptic nuclei, which showed no histological evidence of damage. It is concluded thatareas of the central nervous system away from the supraoptic nuclei are involved in the regulation of both water intake and ADH release.
Micromanipulation of pressure in terminal lymphatics in the mesentery
Authors: Zweifach BW , Prather JW
Published: December 2017

The terminal lymphatics are a network of highly previous vessels that are distributed in a loose association with the blood capillary bed, in particular along with the collecting venules. The base-line pressure in these lymphatics is close to atmospheric, but after they converge to form valved collecting channels PL is increased with a pressure differential of 1-2 cmH20 built up across each valve. This increment in lymphatic pressure is clearly related to the presence of one-way valves, the contractile activity of the collecting channels, and the comparative impermeability of these channels. The pressure differential required to draw fluid from the interstitium into the lymphatics would appear to reside in the vasomotor activity of the collecting channels, although the data do not rule out changes in Pt coincident with net capillary filtration or absorption.
Possible mechanism of histamine release during active vasodilatation
Authors: Heitz DC , Brody MJ
Published: December 2017

Continuous electrical stimulation of the cut synpathetic innervation to perfused gracilis muscles restored vasoconstrictor tone and active dilatation resulted when stimulation was terminated. This dilatation was unaffected by cholinergic blockade but was blocked by the antihistamine tripelennamine. Prior vasoconstriction was not required to produce active dilatation since sympathetic stimulation applied during infusion of xylocholine (betaTM10) produced no vasoconstrictor response yet an antihistamine-sensitive vasodilatation appeared when stimulation ceased. This dilatation was also blocked by the alpha-adrenergic receptor blocker phentolamine even though adrenergic vasoconstrictor tone was absent. These results suggest that the release of histamine from its storage site is mediated by an alpha-receptor mechanism. Since betaTM10 abolished adrenergic vasoconstriction but preserved histamine-mediated vasodilatation that could be prevented by alpha-adrenergic blockade, it is proposed that histamine release may be under the control of separate adrenergic fibers without a vasoconstrictor function. This mechanism may underlie the process of active reflex vasodilatation since upon reflex withdrawal of tonic sympathetic activity an antihistamine-sensitive vasodilatation occurs.