bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of cardiac neural inputs on rhythmic variations of heart period in the cat
Authors: Chess GF , Tam RM , Calaresu FR
Published: December 2017

Spectral analysis was used to investigate variations of heart period in 13 decerebrate cats under different conditions of neural input to the heart. Spectral density plots in intact animals showed three well-defined peaks: P1 (1.5-2.5 cycles/min), P2 (6-10 cycles/min), and P2 (respiratory frequency). In the presence of sympathetic input only the amplitudes of all peaks were decreased; when only vagal input was present the amplitudes of P1 and P2 were increased and there was no change in P3; when neither sympathetic nor vagal input was present the amplitudes of all peaks were decreased. In addition, the amplitudes of P1 and P2 were increased and there was no change in P3; when neither sympathetic nor vagal input was present the amplitudes of all peaks were decreased. In addition, the amplitudes of P1 and P2 were found to be significantly correlated with the mean heart period under the condition of vagal control only. It is concluded that P3 is related to sinus arrhythmia and that P1 and P2 may be related to spontaneous rhythms that are an intrinsic feature of the dynamic regulation of heart period by the vagus system. Sympathetic activity plays no role in the genesis of these rhythms.
Microvascular pressure distribution in skeletal muscle and the effect of vasodilation
Authors: Fronek K , Zweifach BW
Published: December 2017

In cats anesthetized with pentobarbital, 188 direct microvascular pressure and diameter measurements were made of the tenuissimus muscle. The microvascular pressure in arterioles of 70 mum in diameter or larger was proportional to the systemic arterial pressure (PA). The arterioles with diameter-s ranging from 35 to 20 mum have been shown to be the principa-l source of arteriolar resistance regulating micropressures downstream. Across the capillary bed proper, the drop in pressures was about 15% of PA. Micropressures in the smallest venules (8-15 mum) averaged 24 mmHg and reflect closely capillary blood pressure. With a background of basic microvascular data, the vasodilatory mechanism of papaverine (P) and isoproterenol (IPR) in the skeletal muscle was analyzed. Administration of IPR decreases both arteriolar and venular pressure, while P infusion decreased the pressure in arterioles wider than 20 mum in diameter; however, in smaller arterioles there was a substantial elevation in micropressure. The data establish two basically different vasodilatory effects on the terminal vasculature: one with increased capillary pressure and fluid filtration (P), a second with a decrease in capillary pressure enhancing absorption (IPR).
In vivo Na+- and Cl minus-independent transport across the skin of Rana esculenta
Authors: Garcia-Romeu F , Ehrenfeld J
Published: December 2017

The relationship between the trans-epithelial Na+ and Cl minus absorptions from dilute external solutions and the H+ and base excretions were studied in Rana esculenta in vivo. The following results relate to transport from Na2SO4 solutions: 1) The Na+ absorbed is exchanged against endogenous H+. 2) Diamox injection (1.10-4 M-kg-1) simultaneously inhibits both Na+ absorption and H+ excretion. 3) The addition of amiloride to the external medium (final concn: 5-10-5 M) inhibits Na+ absorption and H+ excretion. Measurements of chloride movements from choline chloride solutions give the following results: 1) The chloride absorbed is exchanged against a base, probably HCO3-. 2) Diamox injection (1-10-4 M-kg-1)inhibits the net fluxes of both ions. When transport is measured in NaCl solutions, it is impossible to measure the HCO3-excreted when H+ is also being excreted (HCO3- plus H+ in equilibrium CO2 plus H2O). In these solutions, therefore, only the action of Diamox on the sodium and chloride fluxes was followed and was found to have similar effects on these fluxes as those described for choline chloride and sodium sulphate solutions. The results are discussed in relation to other studies on the action of inhibitors on sodium and chloride transport in the in vitro skin.
Plasma renin activity during ovine pregnancy
Authors: Fleischman AR , Oakes GK , Epstein MF , Catt KJ , Chez RA
Published: December 2017

Chronic intravascular catheterization in maternal, fetal, and neonatal sheep was utilized to assess basal plasma renin activity (PRA) and changes in PRA in response to furosemide. Maternal PRA increased from base-line levels during the last trimester of pregnancy and remained elevated for 12 wk postpartum. Fetal basal levels of PRA were variable but usually greater than maternal levels. Intravenous administration of furosemide to pregnant ewes resulted in a prompt and significant increase in maternal PRA with inconsistent changes in fetal PRA. Fetal and neonatal animals with low basal levels showed a significant increase in PRA; maternal PRA did not change. Animals with higher basal levels did not respond to the stimulus, perhaps reflecting a maximum renin secretory rate. These data are consistent with the conclusions that fetal renin originated predominantly from the fetal kidney, that fetal PRA receives no significant contribution from the maternal circulation, and that renin does not cross the ovine placenta.
Electrophysiology of the frog gastric mucosa with sufficient CO2
Authors: Kidder GW
Published: December 2017

Changing from 5% CO2 in the serosal solution only to 10% CO2 on both sides doubles the acid secretory rate of the bullfrog stomach (as shown previously) and raises the transmural potential difference, although the short-circuit current is not changed. The secretory overshoot on reoxygenation after anaerobiosis, observed in 5% CO2, is virtually eliminated in 10% CO2, as predicted by the diffusion model which explains the secretory rate increase. It was found that the rate of rise of the secretory rate during anoxia was identical in the 2 conditions, which explains the increased secretory lag in 10% CO2 and suggests an interesting limitation on the rate with which acid secretion can be activated. During anoxia in 10% CO2, but not in 5% CO2, there occurs a sudden drop in PD to a slightly negative value associated with a fall in tissue resistance. This effect occurs under SCN-inhibition and thus seems unrelated to H+ transport per se. A working model is presented which can explain some of the events surrounding the sudden potential drop.
Characteristics of in vitro ammonia and glucose production by dog kidney cortex
Authors: Cartier P , Belanger P , Lemieux G
Published: December 2017

Renal cortex slices from acidotic dogs incubated with L-glutamine 1 mM at pH 7.05 produced more ammonia and glucose than slices from nonacidotic animals but no significant difference could be demonstrated at pH 7.48. At a phosphate concentration of 20-30 mM in the medium, a 20-30% increase in ammonia and a 25-40% decrease in glucose production were observed. At L-glutamine concentrations from 0 to 8 mM, a curvilinear increase in both ammonia and glucose production was noted, the effect being greater in slices from acidotic animals. D-Glutamine had little effect on ammoniagenesis. Ammonia production (1 mM L-glutamine) in vitro was 50% lower in acidotic dogs than in vivo. Slices from the remnant left kidney (4-6 wk after right nephrectomy) did not behave differently during acidosis than those from the right kidney with regard to ammonia or glucose production. In vitro ammonia and glucose production was higher in the rat than in the dog in acidotic and nonacidotic conditions when comparable concentrations of L-glutamine substrate were used.
Baroreceptor mechanisms controlling sympathetic nervous rhythms of central origin
Authors: Taylor DG , Gebber tgl
Published: December 2017

A study was made in the anesthetized cat of the slow wave of sympathetic nervous discharge (SND) locked in a 1:1 relation to the cardiac cycle (3 cycle/s periodicity). SND was recorded from the preganglionic splanchnic and postganglionic renal nerves. The data contradict the generally accepted view that the slow wave occurs as the direct result of a waxing and waning of baroreceptor nervous discharge. Although baroreceptor denervation unlocked the phase relations between SND and the cardiac cycle, the slow wave persisted and its duration was not changed. Furthermore, the slow wave was aborted by stimuli delivered to the baroreceptor nerves or paramedian reticular nucleus during a time span which accounted for less than 1 percent of the cardiac cycle. It is concluded that the 3 cycle/s periodicity of SND is representative of a vasomotor rhythm of central origin which is entrained to the cardiac cycle by the baroreceptor reflexes. The sympathoinhibitory effect leading to the entrainment of the slow wave is mediated in the brainstem. ta spinal component of baroreceptor-induced sympathoinhibition also was demonstrated.
Absorption of trace metals in the zinc-deficient rat
Authors: Hahn CJ , Evans GW
Published: December 2017

The effects of zinc deficiency on the whole-body absorption and intestinal content of Zn, Cd, Cu, Co, Fe, Mn, and Cr were determined in the rat 1 h after oral administration of the isotopes. Both the absorption and intestinal content of Zn and Cr were increased in zinc-deficient rats, and the intestinal content of Feand Co was also increased in the zinc-deficient animals. Zinc administered orally with Cr decreased both absorption and intestinal content of the isotope in zinc-deficient rats. Chromium administered orally with Zn decreased intestinal content and absorption of Zn in zinc-deficient rats. Fractionation of mucosal supernatants by gel filtration showed that both zinc and chromium eluted in the same low molecular weight fraction. The elution patterns of zinc and cadmium from that of zinc-supplemented animals. These experiments provide some insight into the specificity of the zinc absorption pathway and present some explanations for the interaction or lack of interaction among trace elements.
Temperature responses of lambs after centrally injected prostaglandins and pyrogens
Authors: Pittman QJ , Veale WL , Cooper KE
Published: December 2017

It has been proposed that pyrogens may produce their febrile response by the release of prostaglandins in the hypothalamus. To test this theory, prostaglandin E1 (PGE1) was injected into a lateral ventricle in dosages of 2-200 ug into conscious newborn lambs, ages 4-168 h. Fiifteen of 40 injections were followed by rises in rectal temperature but the remainder were followed either by no change or by falls. Temperature responses did not appear to be related to age and a variation in responses to the same dosage of PGE was often observed. Some lambs were able to develop fevers in response to intravenous bacterial pyrogen yet did not develop fever after intraventricular PGE 1. Intraventricular bacterial pyrogen (3 ng) produced no change in body temperature, whereas three of four injections of 300 ng pyrogen caused fever. The results suggest that the newborn lamb may be able to develop a fever independently of the central involvement of PGE1. Alternatively, the intraventricular approach may not be useful for the study of the central control of body temperature in the newborn lamb.
Pituitary-thyroid function of rats in hypobaric oxygen-inert gas environments
Authors: Hendrich CE , Weiss HS
Published: December 2017

Rats (200-260 g) were exposed in sealed, recycling chambers continuously for 2-30 days to gas mixtures designed to maintain the same alveolar PO2 in the presence or absence of inert gas. Mixtures with inert gas (N2, He, or Ne) were at ground level; those without inert gas (100 percent O2) were in an altitude chamber. The O2 categories were: I-100 percent O2 at 747 torr; II-74 percent O2 + 26 percent inert and 566 torr 100 percent O2; III-47 percent O2 + 53 percent inert and 381 torr 100 percent O2; IV-21 percent O2 + 79 percent inert and 197 torr 100 percent O2. One of the two room-air controls was "restricted-fed" to the level of the lowest intake group. Measurements included body, pituitary, and thyroid weight, food and water intake, plasma volume and hematocrit, pituitary and plasma TSH, and plasma PBI. Severe depression in all variables and over 50 percent mortality was seen in I by day 4. All variables were depressed in II, but there was no mortality to 20 days. Pituitary-thyroid function appeared to be particularly sensitive to depression by hyperoxia, with plasma TSH levels reduced between 42 and 60 percent in II and III. No effect was attributable to the inert gas, whether it was N2, He, or Ne, nor was any specific effect traceable to the presence or absence of inert gas.
Pulmonary effects of paraquat in the first day after injection
Authors: Fisher HK , Clements JA , Tierney DF , Wright RR
Published: December 2017

To learn whether surface force changes precede the appearance of lung edema during experimental intoxication due to paraquat, we studied rats for 1 day following injection of 27 mg/kg iv. By 24 h, surface-active material recovered by lung lavage was decreased 32 percent, and changes in lung microsections and recoil pressure at half-deflation suggested decreased alveolar stability. Despite a 25 percent loss in overall body weight, lung weight increased more than 7 percent and protein concentration in lung lavage fluid increased by 158 percent. Lung edema was demonstrated morphologically as early as we could detect changes in surfactant or lung mechanical properties. Metabolic studies with lung tissue slices incubated with 4.5 times 10-4 M paraquat showed a fourfold increase in 14CO2 formed from (1-14C) glucose, but no significant change in 14CO2 form (6-14C) glucose, suggesting increased utilization of the pentose pathway for oxidation of glucose. (1-14C) Acetate oxidation was impaired slightly, but incorporation into lipid was decreased by 70 percent. we conclude that paraquat intoxication in the rat is not a suitable model for studying uncomplicated perturbation of the surfactant system.
Adrenergic mechanisms in cerebral circulation of the goat
Authors: Lluch S , Gomez B , Alborch E , Urquilla PR
Published: December 2017

The effects of electrical stimulation of the cervical sympathetic nerves and tyramine on cerebral blood flow (CBF) were investigated in 13 unanesthetized goats in which electromagnetic flow probes had been previously implanted on the internal maxillary artery. Nerve stimulation (1.5-12 cycles/s) produced frequency-dependent reductions in CBF, a decrease of 50 percent occurring with the highest frequency. Injections of tyramine (50-500 mug) into the internal maxillary artery produced dose-dependent reductions in CBF, a decrease of 36 percent occurring with the highest dose. Both reserpine and phentolamine diminished the vasoconstriction induced by nerve stimulation and tyramine. Cocaine partially abolished the effects of tyramine and did not alter those of nerve stimulation. In addition, phentolamine produced cerebral vasodilatation, which was greatly reduced by previous treatment with reserpine. These results show that sympathetic stimulation and tyramine produce cerebral vasoconstriction by the release of the transmitter from the perivascular nerve endings, and they suggest the presence of a tonic sympathetic activity in the cerebral vessels.
Geometrical distribution of capillaries in mammalian striated muscle
Authors: Plyley MJ , Groom AC
Published: December 2017

Striated muscles of hindlimb, jaw, or tongue in dogs, cats, rabbits, rats, and guinea pigs were perfused under high pressure with Microfil (a silicone elastomer of viscosity 20 cP approx.) to outline the vascular bed. When the material had set, the muscles were fixed in formalin. Exmination of histological sections, strained by a modified Gomori trichrome method, showed capillaries containing Microfil as well as some, unperfused, filled with red cells. From well-perfused bundles the numbers of capillaries surrounding each fiber were counted; in all muscles these ranged from 0 to 9 with mean values betweeen 3.2 and 4.0. This was true of both red and white muscle. The mean number of fibers sharing one capillary ranged from 2.0 to 3.2, the lower value being found when four vessels surrounded a fiber and the higher value when there was only three. The results indicate a continuum of transitional models from a square array of fibers with each capillary between two adjacent fibers to a hexagonal array with capillaries at alternate vertices.
Uptake and compartmental distribution of fatty acid by rat small intestine in vivo
Authors: Mishkin S , Yalovsky M , Kessler JI
Published: December 2017

The uptake and esterification of micellar [3-H]oleate and [14-C] palmitate were uniform along the entire length of the small intestine in vivo. Fatty acids (FA) radioactivity taken up by the small intestine could be described in terms of four functionally distinct compartments analogous to those described in vitro. The KRP-extractable compartment (KEC) and albumin-extractable compartment (AEC) contained reversibly adherent unesterified FA radioactivity, while the tissue free and esterified FA compartments contained irreversibly bound radioactivity. Wheras 27% and 63% of FA uptake were reversibly bound in the KEC and AEC by the most proximal and most distal regions of the small intestine in vitro (15), less than 10% was contained in these compartments in vivo, independent of location. Linear inverse relationships were found betweeen tissue FA esterification and proportion of FA radioactivity present in the KEC,AEC, and the tissue free FA compartment in vivo. These observations allow for the possibility that FA molecules pass through these compartments prior to esterification.
Neonatal changes in renal blood flow distribution in puppies
Authors: Aschinberg LC , Goldsmith DI , Olbing H , Spitzer A , Edelmann CM  , Blaufox MD
Published: December 2017

The intrarenal distribution of blood flow was studied in 31 newborn mongrel puppies from 18 h to 70 days using xenon washout and krypton autoradiography. Mean renal blood flow increased from 0.39 plus or minus 0.05 ml/g per min (SE) the 1st wk to 2.06 plus or minus 0.12 ml/g per min at 6 wk. During the 1st wk of life renal cortex was perfused homo-geneously at 0.88 plus or minus 0.19 ml/g per min (SE) and accounted for 35 plus or minus 4% of the renal blood flow. During the 2nd wk a narrow, rapidly perfused zone of outer cortex was identified which was perfused at 3.35 plus or minus 0.26 ml/g per min, received 19.53 plus or minus 5.05% of the total renal blood flow, and represented 15 plus or minus 4% of the mass of the total cortex. The inner cortex and outer medulla at this time received 53.40 plus or minus 4.12% of the flow at 1.07 plus or minus 0.08 ml/g per min. Outer cortical flow increased with age reaching adult values by about 6-10 wk when the rapidly perfused area represented 40 plus or minus 8% of the cortex. These changes are parallel to the results of previously reported studies with microspheres in newborn puppies and are compatible with the well established maturational changes noted in neonates of several species. They represent the first gas-washout studies in animals during the first 6 wk of life.
Phrenic and recurrent laryngeal discharge patterns and the Hering-Breuer reflex
Authors: Cohen MI
Published: December 2017

In decerebrate, spontaneously breathing cats, whole-nerve recordings of efferent phrenic (Phr) and recurrent laryngeal (Lar) discharge were analyzed with an average-response computer. The Phr inspiratory (I) burst starts abruptly and has an augmenting discharge pattern which reaches a maximum at the end of the I phase. The Lar I burst starts before onset of the Phr burst (median delay 40ms), reaches an approximately constant level till the end of the I phase. These differences are functionally appropriate for the differing respiratory roles of the innervated muscles (diaphragm and glottis dilators). The Hering-Breuer reflex, produced by occulsion at minimum lung volume (start of the I phase), lengthens the I phase and disinhibits I discarge, but differently for Lar and for Phr activity. Lar activity was increased almost from the start of the I phase. In contrast, occlusion produced no change in the Phr augmenting pattern (slope of activity increase) for most or all of the I phase, indicating that normally vagal inhibitory input shuts off Phr activity in a trigger-like manner.
Pressure-flow-diameter relationships in isolated perfused thin limb of Henle
Authors: Welling LW , Welling DJ
Published: December 2017

To measure directly the relationships between flow rate, tubule diameter, and flow resistance in thin descending limbs of Henle, isolated tubule segments from the rabbit were studied by in vitro microperfusion. Small increases in pressure and flow cause rapid enlargement of the tubule. Flow resistance is inversely related to tubule diameter and, by its effect on transmural pressure, indirectly limits the extent of tubule dilation. In a range of transmural pressures comparable to that in vivo, the tubule is capable of radial dilations as great as 35% and does not reach its structural limit of distensibility. Flow resistance may be approximately by a Poiseuille equation for cylindrical tubules. The effective luminal diameter is approximately a constant fraction of outer tubule diameter and is defined approximately by the innermost projection of semirigid epithelial nuclei.
Aggregation and release in thrombocytes of the duck
Authors: Stiller RA , Belamarich FA , Shepro D
Published: December 2017

Avian thromboyctes are aggregated by a number of substances that cause platelet aggregation, and evidence suggests that this response is related to the release of serotonin (5-hydroxytryptamine, 5-HT) from intracellular granules. In this study duck thrombocytes released 5-HT during collagen-induced aggregation, but thrombocytes incubated with 14C-labeled adenine did not release radioactive adenine nucleotides. These results indicate the existence of a metabolic pool of adenine nucleotides that is separate from released constituents of the cell. No unlabeled adenine compounds were detected in the supernatants of aggregated thrombocytes indicating either the rapid alteration of released nucleotides or the absence of a specific release pool of adenine nucleotides. Finally there is no release of the intracellular enzyme markers, lactate dehydrogenase, beta-glucuronidase, and acid phosphatase, during collagen-induced aggregation. These findings suggest that avian thrombocytes exhibit a specific release reaction and that serotonin acts as the functional counterpart of ADP in platelet aggregation.
Suppressive action of prolactin on renal response to volume expansion
Authors: Lucci MS , Bengele HH , Solomon S
Published: December 2017

The effects of prolactin on rat renal sodium and water handling during volume expansion were studied using clearance techniques. Both control and experimental adult male Wistar rats were prehydrated with an oral water load of volume equal to 2.5% body weight (BW). At least 3 h later, a continuous intravenous infusion of ovine prolactin (NIH-P-S8), 7.1 mug/h per 100 g, was started in the experimental group. After a 1-h steady-state period, the rats were given an intravenous expansion infusion of either hypotonic saline (2.5% BW), isotonic saline (2.5% and 7.5% BW), or blood (2.5% BW). In all control hypotonic and isotonic saline-expanded animals, within 1 h the rats excreted a volume of urine equal to over 50% of the volume of saline infused. The diuretic and natriuretic responses to saline expansion of prolactin-treated rats were significantly smaller than controls. In contrast to the effects of prolactin on the renal response to saline infusions, it did not alter the natriuretic or diuretic response to blood infusion. Prolactin may be counteracting the effects of physical factors on the regulation of sodium reabsorption in the proximal tubule.
Rates of lactic acid permeation and utilization in the isolated dog brain
Authors: Zimmer R , Lang R
Published: December 2017

The rate of lactic acid (LA) permeation from brain tissue to venous blood and utilization in brain tissue was investigated in 13 isolated dog brains before and after an ischemic period of 3 min. LA concentration in the brain, cerebral blood flow, as well as the arteriovenous differneces of LA, glucose, and O2 were determined. LA concentration in cerebral tissue increased from a control value of 254 +/- 42 to 1,606 +/- 177 mumol/100 g brain tissue in the 2nd min after ischemia (mean values +/- SE). Before ischemia no release of LA was found, whereas in the 2nd min after ischemia LA permeation rate had increased to 25.1 +/- 8.5 mumol/100 g brain tissue per minute (P less than 0.005). Up to the 4th min after ischemia no net LA utilization was observed. Thereafter LA utilization increased rapidly and exceeded the LA permeation rate by a ratio of maximally 10:1 between the 12th and 21st min after ischemia. The O2 equivalent of the cerebral metabolic rate for lactate maximally amounted to 2.82 +/- 0.42 mumol-min-1-g-1 or 181 +/- 28%. LA output may be limited by passage of LA across the brain cell and the blood-brain barrier.
Increased cardiac contractility in acute uremia: interrelationships with hypertension
Authors: Nivatpumin T , Yipintsoi T , Penpargkul S , Scheuer J
Published: December 2017

To study the effects of acute uremia on the inotropic state of the rat heart, we subjected rats to bilateral nephrectomy and studied their hearts in the open chest 24 h later. Uremic rats had significantly higher systolic blood pressure than sham-operated animals. Left ventricular systolic pressure and maximum dP/dt, both during ejection and isovolumic contrations, were higher for any given end-diastolic pressure in hearts of uremic rats than in sham-operated animals. This difference in performance charcteristics was not abolished by doses of propranolol that blocked the heart rate response to isoproterenol. The administration of phenoxybenzamine during the 24 h of uremia abolished the blood pressure rise in uremic rats, but the increased contractile state persisted. Treatment of sham-operated animals with methoxamine to produce the same course of blood pressure as observed in uremic rats was also associated with an increased inotropic state. These results indicate that in the rat, acute uremia is associated with an increased inotropic state that is not mediated by beta-adrenergic mechanisms. The systolic hypertension of acute uremia is not the major cause of the increased contractility, although systolic hypertension without uremia can mimic the performance characteristics found in hearts of uremic rats.
Subepithelial capillary blood flow estimated from blood-to-lumen flux of barbital in ileum of rats
Authors: Csaky TZ , Varga F
Published: December 2017

The outflux of barbital from the blood into the small intestine perfused with an isosmotic buffer of pH 9.5 in anesthetized rats was measured to determine the subepithelial capillary blood flow in the gut. It was shown that barbital clearance is blood flow limited when total blood flow to the small intestine varied between 0.3 and 1.3 ml/min per g wet gut. The barbital clearance amounted to an average of 50.3% of the total blood flow. The total mucosal blood flow determined by the use of the distribution of microspheres in the layers of gut wall was 62.76% of the total blood flow. It is concluded that, because of anatomical reasons, a subepithelial blood flow available for the transport process is somewhat less than the measured total mucosal blood flow.
Reevaluation of the needle method for measuring interstitial fluid pressure
Authors: Brace RA , Guyton AC , Taylor AE
Published: December 2017

Inserting a needle into subcutaneous spaces should allow a subatmospheric pressure to be measured if interstitial fluid pressure is truly negative as measured by the capsule and wick techniques. Previous needle measurements of interstitial fluid pressure have produced a positive value, but in most instances fluid has been injected into the tissues prior to recording of pressure. Therefore, we measured subcutaneous needle pressure in anesthetized dogs without fluid injection into the tissues. Approximately 30 min are required for an equilibrium pressure after insertion of the needle. The mean 30-min pressure was 4.6 +/- 0.5 (SE) mmHg (n equals 41). With observable edema, interstitial fluid pressures as measured with the needle were always positive. However, the needle method for continuous recording of pressure lacks rapid sensitivity to changes in tissue fluid pressures. In order to develop a needle method that would follow changes in interstitial fluid pressure, 0.5-1 mul of saline was injected into or withdrawn from the tissue. With this method, pressure plateaued in 10-20 min. This plateau pressure increased with tissue hydration and decreased with dehydration.
Acid-base balance in amphibian gastric mucosa
Authors: Silen W , Machen TE , Forte JG
Published: December 2017

It has been established that H+ secretion can be maintained in frog stomach in the absence of exogenous CO2 by using a nutrient bathing fluid containing 25 mM H2PO4 (pH approximately equal to 4.5) or by lowering the pH of a nonbuffered nutrient solution to about 3.0-3.6. Exogenous CO2 in the presence of these nutrient solutions uniformly caused a marked decrease in H+ secretion, PD, adn short-circuit current (Isc) and an increase in transmucosal resistance (R). Elevation of nutrient [k+] to 83 mM reduced R significantly but transiently without change in H+ when nutrient pH less than 5.0, whereas R returned to base line and H+ increased when nutrient pH greater than 5.0. Acidification of the nutrient medium in the presence of exogenous CO2 results in inhibition of the secretory pump, probably by decreasing intracellular pH, and also interferes with conductance at the nutrient membrane. Removal of exogenous CO2 from standard bicarbonate nutrient solution reduced by 50% the H+, PD, and Isc without change in R; K+-free nutrient solutions reverse these changes in Isc and PD but not in H+. The dropping PD and rising R induced by K+-free nutrient solutions in 5% CO2 - 95% O2 are returned toward normal by 100% O2. Our findings support an important role for exogenous CO2 in maintaining normal acid-base balance in frog mucosa by acting as an acidifying agent.
Myocardial transcapillary exchange in the hypertrophied heart of the dog
Authors: Laughlin MH , Diana JN
Published: December 2017

Myocardial transcapillary exchange was investigated in control hearts and in two types of hypertrophied hearts: exercise hypertrophy and pathological hypertrophy due to tricuspid insufficiency. Using the single-injection indicator diffusion method (6, 28), myocardial extractions (E), capillary clearances (C), and permeability surface area products (PS) of urea, sucrose, and inulin were measured in intact, pump-perfused, working hearts of anesthetized dogs. Both types of cardiac hypertrophy were associated with a decreased coronary vascular resistance. Myocardial E, C, and PS values from the exercised group were not significantly different from control. Dogs with pathological hypertrophy exhibited increased central venous pressures, RVEDP's, and heart rates which were greater than control values. The E, C, and PS values from the pathologically hypertrophied hearts were significantly greater than control. These increases in myocardial transcapillary exchange can be explained either by increasing the equivalent pore radius of myocardial capillary membranes from a control value of 70 to 100 A or by assuming that pathologically hypertrophied hearts have a myocardial capillary surface area available for exchange which is twice that of control hearts.
Histamine H1- and H2-receptors in pulmonary and systemic vasculature of the dog
Authors: Tucker A , Weir EK , Reeves JT , Grover RF
Published: December 2017

This study was conducted to identify and clarify the actions of pulmonary and systemic H1- and H2-receptors by utilizing specific histamine receptor antagonists. Histamine was infused in anesthetized dogs during control conditions, after H2-receptor blockade with metiamide, after H1-receptor blockade with chlorpheniramine, and after combined H1- and H2-receptor blockade. Histamine infusion, alone, induced marked systemic vasodilatation, pulmonary vasoconstriction, and transient increases in cardiac output and heart rate. H2-receptor blockade prevented the systemic vasocilatation and potentiated the pulmonary vasoconstriction induced by histamine. H1-receptor blockade augmented the systemic vasodilatation, prevented the pulmonary vasoconstriction, and increased the cardiac output and heart rate responses induced by histamine. Thus, H2-receptors appear to mediate the vasocilatation, tachycardia, and increased cardiac output induced by histamine, whereas H1-receptors appear to mediate the vasoconstrictor and the minimal cardiac depressent actions of histamine. Histamine stimulates only H1- and H2-receptors, since combined H1- and H2-receptor antagonism prevented almost all of the cardiovascular actions of histamine.
A quantitative histochemical approach to renal transport. I. Aspartate and glutamate
Authors: Chan AW , Burch HB , Alvey TR , Lowry OH
Published: December 2017

Renal transport was studied by direct analysis of specific segments of the nephron for the substance transported. Rats were given inulin plus loads of glutamate or aspartate. Glomeruli, six different identified segments, and patches from thin-limb and papillary areas were dissected from individual nephrons in freeze-dried sections. Large amounts of the amino acid (up to 35 mmol/kg) accumulated in segments in which transport is believed to occur. With subthreshold loads, large amino acid increments were confined to earlier proximal segments. With loads above threshold, increases occurred throughout the proximal tubule. The early convoluted tubule probably has less transport activity than the rest of the proximal tubule. Both dicarboxylic amino acids accumulate in large amount when one is given. Aspartate is probably formed within the tubule after a glutamate load. This new histochemical approach may have general applicability for more precise localization of transport cells, for assessing changes in those cells during transport, and for study of structures inaccessible to micropuncture.
Effects of testosterone and prolactin on rat prostatic weight, 5alpha-reductase, and arginase
Authors: Yamanaka H , Kirdani RY , Saroff J , Murphy GP , Sandberg AA
Published: December 2017

Prostatic weights, 5alpha-reductase, and arginase activities were utilized as indexes for the effects of prolactin in short-term experiments in intact, hypophysectomized or castrated rats. Experiments were performed in which a dose-related response in the above parameters was obtained with testosterone administration in castrated mature and immature rats in order to evaluate the effects of simultaneously administered prolactin. This approach was necessitated by the failure of prolactin alone to affect the parameters listed in intact, castrated or hypophysectomized rats. It was shown that ovine prolactin may have an enhancing effect on the prostatic weight, 5alpha-reductase, and arginase activities, but that this effect is neither consistent nor striking when compared to that of testosterone.. Nevertheless, it is still possible that the long-term effects of prolactin, even if they are only of an enhancing quality, may play an important role in normal prostatic physiology and in abnormal states.
Metabolic and respiratory responses during Helox-induced hypothermia in the white rat
Authors: Wang LC , Peter RE
Published: December 2017

Unanesthetized and unrestrained rats, chronically cannulated in the carotid artery, were exposed to normal air (NA) and Helox (21% O2, 79% He) at ambient temperatures (Ta) of 22 and -10 degrees C. In Helox at Ta = 22 degrees C, the Vo2 was 1.39 ml O2/g-h and the Vco2 0.98 ml CO2/g-h, 145 and 126%, respectively, of the values in NA at Ta = 22 degrees C. The arterial Pao2, Paco2, and pH were comparable in Helox and NA at Ta = 22 degrees C. In Helox at Ta = -10 degrees C, rats invariably became hypothermic after exposure of 0.75 to 1.5 h. During the induction of hypothermia the decrease of Vo2 and Vco2 was oscillatory, Pao2 and pH increased, and Paco2 decreased significatnly (P less than 0.05). Minimum Vo2 and Vco2 during hypothermia averaged 0.71 ml O2/g-h and 0.50 ml CO2/g-h, 23 and 22%, respectively, of the values in normothermic animals at Ta = -10 degrees C. Minimum body temperature during hypothermia was clamped at 21.7 +/- 0.3 degrees C (X +/- SE) by increasing Ta to 19 degrees C. When Helox was replaced by NA, hypothermic rats rewarmed spontaneously, returning to normothermia within 4 h. The data suggest that hypothermia induced by Helox plus cold does not seem to be due to respiratory failure, as systemic hypoxia or hypercapnia were not observed. The controlled hypothermia cycle reported here provides a model for dynamic studies of thermogenic mechanisms both at the normothermic and hypothermic states without the interference of drugs and other nonphysiological treatments.
Effect of Ca++ on renal handling of PO4 identical to: evidence for two reabsorptive mechanisms
Authors: Popovtzer MM , Robinette JB , McDonald KM , Kuruvila CK
Published: December 2017

The effect of hypercalcemia on renal handling of phosphorus was studied in parathyroidectomized rats during 1) extracellular volume expansion with normal saline (0.1 mg/100 g per min) and 2) parathyroid extract infusion (1 U/100 g per h). Hypercalcemia (serum calcium 12-15 mg/100 ml) blunted the phosphaturic response to volume expansion, both when serum calcium was raised acutely during volume expansion and when volume expansion was induced in rats with sustained hypercalcemia. These changes were not associated with significant variations in glomerular filtration rate and serum concentration of phosphorus. Hypercalcemia failed to alter the phosphaturic response and the increase in urinary cyclic AMP excretion following both continuous infusion and a single injection of parathyroid extract. These results are consistent with two components of tubular reabsorption of phosphorus. The first is suppressed by extracellular volume expansion and stimulated by hypercalcemia. The second is suppressed by parathyroid hormone and is not affected by hypercalcemia.
Brainstem loci for activation of electrodermal response in the cat
Authors: Davison MA , Koss MC
Published: December 2017

Brainstem loci from which electrodermal responses could be elicited were systematically explored by direct-stimulation techniques in chloralose-anesthetized and decerebrate cats. Reactive sites of the greatest amplitude were found to extend from the rostral border of the posterior hypothalamus, through the ventrolateral reticular formation of the pons and the medulla, to the cervical cord. Stimulation of these sites elicited stable, reproducible electrodermal responses of 10-30 mV in amplitude. In addition, it was found that stimulation of the ventrolateral extent of the lower brainstem evoked similar responses in the decerebrate preparation. Electrodermal responses could not be elicited from the dorsal medulla, the posterior commissure, or the midline region. The electrodermal response could be elicited from an apparently hypothalamus through the ventrolateral brainstem.
Influence of inhibitors of prostaglandin synthesis on the canine pulmonary vascular bed
Authors: Kadowitz PJ , Chapnick BM , Joiner PD , Hyman AL
Published: December 2017

The effects of two chemically dissimilar inhibitors of prostaglandin (PG) synthesis on vascular resistance and responses to pressor and depressor hormones were evaluated in the canine pulmonary vascular bed. Indomethacin or meclofenamate, 2.5-5 mg/kg iv, increased lobar arterial pressure. Since lobar blood flow was held constant and left atrial pressure did not change, the rise in pressure reflects an increase in vascular resistance. The rise in lobar pressure after indomethacin occurred in the absence of a change in lobar venous or translobar airway pressure. This agent enhanced the response to angiotensin but not to norepinephrine. Meclofenamate decreased responses to both agents. Indomethacin enhanced the dilator response to PGE1 and both indomethacin and meclofenamate increased the response to PGF2alpha. These data indicate that the rise in resistance after indomethacin or meclofenamate was the result of vasoconstriction in vessels upstream to the small veins, presumed to be small arteries. These data are consistent with the hypothesis that under resting conditions synthesis of a dilator prostaglandin may be important for the maintenance of the pulmonary vascular bed in a dilated state. However, results of the present study are not consistent with the postulate that prostaglandins modulate responses to norepinephrine but suggest that indomethacin and meclofenamate interfere with the inactivation of PGF2alpha and PGE1 in the lung.
Transalveolar transport of large polar solutes (sucrose, inulin, and dextran)
Authors: Theodore J , Robin ED , Gaudio R , Acevedo J
Published: December 2017

The in vivo transalveolar transport of three large polar solutes, sucrose, inulin, and dextran (mol wt 60,000-90,00), was compared with the transport of urea in saline-filled dog lung. Apparent permeability coefficents (p', in cm X sec-1 X 10(6)) were as follows; urea: 2.4 +/- 0.28 (SD) greater than sucrose: 0.64 +/- 0.31 (P less than 0.001) greater than inulin: 0.12 +/- .05 (P less than 0.001)--not different from dextran (mol wt 60,000-90,000): 0.08 +/- .02 (P greater then .01). Calculation of the resistance of the alveolar epithelium compared to total barrier resistance for the various solutes indicates that approximately 90% of the total resistance resides in the alveolar epithelium. Comparison of the ratio of permeability coefficients to the ratio of free-diffusion coefficients in water shows similar values for the three large polar solutes, suggesting that permeation through the alveolar epithelium occurs by means of water-filled channels. The values for permeability coefficients of alveolar epithelium fit into the spectrum of values reported for other epithelial structures (including gall bladder, frog skin, and toad bladder); it seems to have a system of channels with a small number of wide "pores" (greater than 80 A) that permit permeation of large polar solutes and is not a relatively homogeneous structure.
Mechanism of ethacrynic acid-induced choleresis in the rat
Authors: Chenderovitch J , Raizman A , Infante R
Published: December 2017

Ethacrynic acid (EA) was injected to rats with functional nephrectomy after a control period of steady-state bile flow sustained by taurocholate infusion. Biliary clearance of [14C]mannitol was measured in order to estimate canalicular bile flow and bile salt-independent fraction (BSIF). After EA infusion, bile flow increased by 56%; bile salt excretion rate decreased by 10%; electrolyte excretion rates all increased, principally Na+ and K+. Mannitol clearance increased in parallel with bile flow. The BSIF increased. EA was excreted into bile as a metabolite identified as the cysteine adduct of EA; its excretion rate was linearly correlated with the increment in bile flow. The results are consistent with the hypothesis that the biliary excretion of an EA derivative results in an osmotic water flow increasing the canalicular BSIF. Since EA ia a Na+-K+-ATPase inhibitor, it is necessary to reconsider the relationship between secretion of canalicular BSIF and active Na+ transport mediated by the Na+-K+-ATPase system.
Interaction of anabolic steroids with glucocorticoid receptor sites in rat muscle cytosol
Authors: Mayer M , Rosen F
Published: December 2017

While glucocorticoid hormones act catabolically on skeletal muscle through their binding to glucocorticoid-specific receptors in the cytosol, androgens exert anabolic responses but no androgen-specific binding proteins could be detected in this responsive tissue. However, various nonradioactive androgens were effective in displacing labeled dexamethasone or cortisol from their respective cytoplasmic receptors in muscle, both in vitro and in vivo. The inhibition of glucocorticoid binding by androgens is competitive, and could be observed following a single or repeated administration of the androgens to adrenalectomized-castrated animals. The synthetic androgen fluoxymesterone and the hormone testosterone displayed Ki values of 7.5 X 10(-6) M and 1 X 10(-5) M, respectively, for the inhibition of [3H]dexamethasone binding in muscle cytosol. On the basis of competition experiments it is postulated that interaction of androgens with glucocorticoid receptors prevents the binding of glucocorticoids and might be responsible in part for the anabolic effects of pharmacologic doses of androgens in muscle.
Hematocrit of the fetal rabbit placenta
Authors: Newcomb SL , Power GG
Published: December 2017

51Cr-labeled erythrocytes and [125I]RISA were used simultaneously to measure the fetal rabbit whole-body and placental hematocrits (Hct) and to find the ratio of placental transit times of erythrocytes and plasma. The levels were injected into the heart of 21 fetal rabbits of 26--28 days gestation, and about 60 s mixing time, the placenta and a fetal blood sample were assayed with a gamma well-type scintillation counter. Erythrocyte and plasma activity per milliliter were determined from a standard dilution of the isotopes. Large-vessel Hct was measured as the corrected packed erythrocyte percentage in capillary tubes. Large-vessel Hct was 37.3 (+/- 3.7 SD) %, whole-body Hct was 31.3 (+/- 3.5) %, and the placental Hct was 25.3 (+/- 4.0) %. The placental/large-vessel Hct ratio was 0.676. The ratio may be estimated as 0.765 when corrected for the loss of albumin in time. The transit time of erythrocytes in the placenta was calculated to be 0.682 of that for plasma. The shorter erythrocyte transit time implies that there is less time for O2 and CO2 exchange than previously thought.
Corticosteroids and ACTH are not required for compensatory adrenal growth
Authors: Engeland WC , Shinsako J , Dallman MF
Published: December 2017

We have tested the hypothesis that unilateral adrenalectomy results in decreased glucocorticoid secretion, reflexly elevated ACTH secretion, and consequently, compensatory adrenal growth. Plasma ACTH and corticosterone and right adrenal weight were measured during the first 10 days after left adrenalectomy or sham adrenalectomy in young male rats. There is a decrease in plasma corticosterone after unilateral adrenalectomy compared to sham adrenalectomy that persists for 1 h. ACTH is elevated only at 2 h after unilateral adrenalectomy compared to shamoperated rats. Treatment with dexamethasone, shown to abolish the ACTH and corticosterone responses to laparotomy with intestinal traction, resulted in significantly increased adrenal weight after unilateral adrenalectomy by 6 h (wet or dry weight), and at 24 h. Compensatory adrenal growth also occurs after unilateral adrenalectomy in hypophysectomized rats (wet or dry weight). We conclude the compensatory adrenal growth after unilateral adrenalectomy requires neither a virtual decrease in circulating corticosterone levels nor elevated ACTH levels, and speculate that the phenomenon is neurally mediated.
Urinary acidification: CO2 transport by the rabbit proximal straight tubule
Authors: Warnock D. G. , Burg M. B.
Published: December 2017

Proximal straight tubules from rabbit kidneys were perfused in vitro in order to study transport of bicarbonate. Total CO2 content was measured in perfused and collected tubule fluid, using microcalorimetry. When the initial perfusate and bath contained 25 mM bicarbonate, the concentration of total CO2 decreased in the collected tubule fluid, indicating net reabsorption of bicarbonate. When the initial perfusate contained no bicarbonate and the bath contained 25 mM bicarbonate, total CO2 appeared in the collected tubule fluid. The rate at which total CO2 appeared in the tubule fluid was rapid, indicating a high permeability. Proximal straight tubules from superficial and juxtamedullary nephrons were compared and found to differ in permeability to CO2 and in transport rate. This functional heterogeneity may affect urinary acidification when there is redistribution of renal blood flow.