bluuebunny/crossref_metadata_2025 huggingface dataset:
Thyroid hormone secretion rate and milk yield in lactating rats
Authors: Grosvenor Clark E.
Published: December 2017

Thyroid secretion rate (TSR) obtained from primiparous lactating rats during the first 14 days of lactation averaged 1.93 µg/100 gm/day l-thyroxine or 130% more than obtained from nonlactating female rats of the same age and strain. TSR was significantly correlated with the amount of milk obtained from mothers on day 14 of lactation. TSR obtained from the same rats during a second 14-day period of lactation (nursing a foster litter) was significantly reduced to an average of 0.98 µg/100 gm/day l-thyroxine. A significant reduction in milk yield on day 28 accompanied the reduction in TSR. The reduction in milk secretion during the second 14 days of lactation resulted in slower growth of the foster litters. Maternal body weight was unaltered. In a second experiment the average TSR of 2.10 µg/100 gm/day obtained during the first 14 days of lactation fell to 0.75 µg/100 gm/day during a subsequent 14-day period of nonnursing. The intensity of lactation apparently is associated with the intensity of thyroid hormone output, and inadequate thyroid hormone secretion may be an important factor in the decline of milk secretion.
Oxytocin release in response to stimulation of cingulate gyrus
Authors: F. Carlos Beyer , L. Guillermo Anguiano , J. Flavio Mena
Published: December 2017

Electrical stimulation of the anterior limbic region in Nembutal-anesthetized cats evokes uterine contractions similar to those elicited by the injection of 50–100 mu of synthetic oxytocin. The contractions of the uterus caused by cortical stimulation must be related to release of an oxytocic agent carried through the blood stream, since transection of the spinal cord together with the severance of the vagi did not prevent the contractions. A moderate rise in blood pressure that appeared in the animals with spinal cord transection also suggests release of vasopressin.
Uptake and binding of thyroxine and triiodothyronine by rat diaphragm in vitro
Authors: Lein Allen , Dowben Robert M.
Published: December 2017

Hemidiaphragms from weanling Sprague-Dawley rats were incubated in Krebs-Ringer buffer containing 1.3 x 10–7 m l-thyroxine or l-triiodothyronine labeled with radioiodine. Triiodothyronine uptake was about twice as rapid as thyroxine uptake. The data were consistent with a kinetic analysis based on a two-step process: 1) simple diffusion into the tissue (rate-limiting step) and 2) binding to cellular proteins (a process that occurs very rapidly compared to diffusion). The diffusion constants were calculated to be kd(T4) = 0.153 cm3/min and kd(T3) = 0.352 cm3/min. The data suggest a single species of tissue-binding site with identical tissue-binding capacity and binding affinity for both triiodothyronine and thyroxine. Maximum binding was found to be 28 x 10–4 µm/g tissue and the affinity constant for binding was 1.4 x 104 g/µm. The difference in the rate of accumulation of thyroxine and triiodothyronine appears to be due only to the difference in the diffusion rate. A direct rate equation for the accumulation of thyroid hormone was derived. Points calculated by means of this equation fit remarkably well with the experimental data.
Tolerance of rats to a cold environment during multiple exposures to a low dose of x rays
Authors: Newsom Bernard D. , Kimeldorf Donald J.
Published: December 2017

A lethal dose of X irradiation can be made sublethal by the fractionation of a dose into a series of smaller doses separated by adequate time intervals. The results reported here demonstrate how an environmental stress, such as cold, may affect this mitigating action of dose fractionation. Rats were maintained at 6 C while receiving a total dose of 600 r in one or eight exposures with various intervals between exposures. A greater interval was required between radiation exposures at 6 C than at 23 C to reduce the lethal response following irradiation. From the results of the food consumption measurements, it appears that cold exposure emphasizes the consequence of the reduced food intake which follows daily doses of 75 r in the rat. The irradiated rat was able to increase the amount of food consumed during cold exposure; however, the increase was not sufficient for adaptation. The lowered consumption which followed eight daily 75-r exposures was sufficient to cause death in pair-fed rats maintained at 6 C, but not at 23 C.
Effect of Diamox on potential difference resistance and secretory rate of dog's stomach
Authors: Rehm W. S. , Canosa C. A. , Schlesinger H. S. , Chandler W. K. , Dennis W. H.
Published: December 2017

The effect of intravenous acetazoleamide (Diamox) was determined on secretory rate, potential difference (PD), and electrical resistance of the anesthetized dog's stomach, using the chambered gastric segment preparation. In dogs with high initial secretory rates, inhibition of H+ ion secretion exceeded 93%, whereas in dogs with low initial secretory rates, inhibition ranged from 27 to 75%. Diamox resulted in an initial decrease in PD and an initial increase in resistance in the secreting stomach. Finally, in a new steady state, the average secretory rate was about 10% of controls and PD 17 mv. less. Diamox did not produce a decrease of PD or a change in resistance of the resting stomach. Compared to controls, stimulation after Diamox injection resulted in a greater decrease in PD, a smaller decrease in resistance and a much lower H+ ion secretory rate. Application of electric current, following Diamox, from serosa to mucosa resulted in an increase in H+ ion secretory rate. It is concluded that the effects of Diamox are dependent on the presence of acid secretory activity and that Diamox inhibits both the H+ and Cl– ion mechanisms.
Gnashing induced by electrical stimulation of rabbit brain cortex
Authors: Kawamura Yojiro , Tsukamoto Shusaku , Miyoshi Kiyokatsu
Published: December 2017

Gnashing was induced in rabbits by high-frequency cortical stimulation. The frequencies ranged from 60 to 1000 cycle/sec. Strictly circumscribed anteromedial cortical areas were responsive to stimulation. These loci are similar to those which induced chewing movements with low-frequency stimulation (30 cycle/ sec). Electrical stimulation within the above-described range induced gnashing of a constant rhythm of 3–4 cycle/sec that was almost independent of the stimulation frequency. The rate of experimentally induced gnashing is slower than the rate of experimentally induced chewing movements of 5–6 cycle/sec. Gnashing motion of the lower jaw consisted of the vertical and dominant lateral movements; the lateral deflection was more predominant than that of the chewing movement. Gnashing was readily induced with low-frequency stimulation after topical application of a 0.5% solution of strychnine nitrate on the cortical jaw motor area.
Effects of repeated doses of curare on neuromuscular block in the cat
Authors: Acheson Fiona , Murphy Oliver
Published: December 2017

Comparison was made between durations of d-tubocurarine chloride (DTC)-induced blocks (0.6 mg/kg) in the anterior tibialis muscles of two legs in each of 8 cats. The animals were kept in an unheated wooden shed between experiments. Four animals (controls) received no DTC between muscle preparations; three animals received a standard dose of DTC on 12 occasions between muscle preparations; one animal received 25 standard doses of DTC before first muscle preparation. We found: a) an inverse relationship between block duration with first dose and atmospheric temperature ( r = –0.82, P < 0.02); b) block durations in second leg of experimental animals' were shorter than in first, and shortest in animal receiving 25 doses (result was significant even allowing for temperature effect: P < 0.04). It was concluded that: a) temperature effect is a consequence of long-term adaptation to environment; and b) repeated doses of DTC induce tolerance.
Flows and pressures in lymphatic and blood vessels of intestine in water absorption
Authors: Lee J. S.
Published: December 2017

Under in vitro conditions the water transported across rat intestinal wall came out mainly from the lymphatic duct (85%). When mesenteric blood and lymphatic vessels were occluded a hydrostatic pressure developed from accumulation of the fluid absorbed. Lymphatic pressure was much higher than simultaneous venous pressure. With fat absorption the milky fluid flowed out from the lymphatic duct but there was no venous flow. These observations seem to suggest that initially water is mainly absorbed into the lymphatic system. Both venous and lymphatic pressures could be affected by changing the distention pressure in the lumen, but they were not simple reflections of the latter. At zero distention pressure both lymphatic and venous pressures were significantly higher than the former. Under conditions without water absorption such as O2 lack, absence of glucose, presence of phlorhizin, or NaCN in the lavage fluid, no fluid was collected from the cannulas in the blood or lymphatic vessels and also no positive pressure could be recorded.
Effect of potassium deficiency on renal response to respiratory acidosis
Authors: Levitin Howard , Epstein Franklin H.
Published: December 2017

In potassium-deficient rats, exposure to 8% CO2 for 24 hr induces an increased excretion and net negative balance of chloride associated with a decrease in the chloride concentration of serum. The increased excretion of chloride does not correlate well with the associated increase in the excretion of ammonium or sodium and occurred when urinary excretion of potassium was minimal. It is suggested that the increased excretion of chloride results from direct interference with the tubular reabsorption of this ion by CO2.
Serum lipoprotein pattern of the hypercholesteremic gerbil
Authors: Gordon Samuel , Cekleniak Walter P.
Published: December 2017

Gerbils on a 1% cholesterol supplemented diet develop a peak hypercholesteremia within a week, which subsequently decreases after 30–60 days to an elevated plateau. No evidence of atheroma formation could be observed for periods up to 6 months. Maximum concentration of serum lipoproteins was found in the Sf 35–100 and 100–400 classes, with relatively low levels in the Sf 0–10, 10–20, and 20–35 classes. After 90 days, however, a reversal of the above pattern was observed.
Hepatic vascular response to epinephrine
Authors: Shoemaker William C. , Turk L. Newton , Moore Francis D.
Published: December 2017

Hepatic hemodynamic events were measured before and after epinephrine administration in unanesthetized dogs in which the hepatic vessels had been previously catheterized. Comparisons were made of the response after a single intravenous injection at various doses and after a constant infusion of epinephrine; comparisons were also made between portal vein and femoral vein injections. After femoral venous injection of epinephrine (1–10 µg/kg) there was a marked increase in hepatic blood flow, roughly increasing with the size of the dose. With doses of 25 µg/kg or more, an initial increase in hepatic blood flow was followed by a decreased flow; in some instances death ensued. Epinephrine injected into the femoral vein produced a rise in the arterial blood pressure, followed by a rise in the portal vein pressure, portal-hepatic venous pressure gradient, and mechanical impedance across the hepatic venous bed. When injected into the portal vein under comparable conditions, epinephrine produced little or no change in hepatic blood flow or arterial pressure, but did produce a more rapid and pronounced increase in portal vein pressure, portal-hepatic pressure gradient and hepatic venous impedance.
Metabolism of ß-hydroxybutyrate and acetoacetate by excised rat diaphragm and diaphragm homogenate
Authors: Neptune E. M. , Sudduth H. C. , Fash F. J. , Reish J. J.
Published: December 2017

The oxidation of labeled ß-hydroxybutyrate and acetoacetate to C14O2 by rat diaphragm and diaphragm homogenate was studied. Added ß-hydroxybutyrate participates extensively in the CO2 production and acetoacetate to an even greater extent. Contrary to previous studies in which added glucose depressed the oxidation of labeled butyrate, added glucose slightly augmented the oxidation of labeled ß-hydroxybutyrate. Experiments designed to elucidate the mechanism of this glucose action failed to implicate any specific metabolic sequence.
Development of chemoreceptor response sensitivity: studies in fetuses, lambs, and ewes
Authors: Reynolds S. R. M. , Mackie John D.
Published: December 2017

Fetuses fail to respond to cyanide by respiratory excitation but show typical cardiovascular effects; these are modified by vagotomy. When sensory stimulation is given (pulling on tongue), respiratory responses to cyanide occur. Similarly, when artifical respiration is instituted, cyanide causes inspiratory effort that is abolished by vagotomy. When the central end of a cut vagus nerve is stimulated, expiratory effort to injected cyanide is seen. 1–2 and 5–6-day-old lambs exhibit adult-type respiratory responses to threshold doses of cyanide without accompanying hemodynamic changes. However, the threshold is tenfold higher than in adults. At 6–7 days of age the threshold equals that of nonpregnant ewes, and is five times higher than in pregnant ewes. Vagotomy abolishes inspiratory gasps when cyanide is injected into lambs and ewes; hyperpnea persists. The threshold for hyperpnea is raised by vagotomy in lambs; in ewes it is unchanged. Oxygen increases the sensitivity of vagotomized lambs to cyanide; in ewes, oxygen abolishes the response. Full chemoreceptor response sensitivity occurs by day 6–7 in sheep, although responses occur in fetuses if there is sensory input to the central nervous system. Regulation of breathing after birth is discussed.
Motor and electric activity of the duodenum
Authors: Bass Paul , Code Charles F. , Lambert Edward H.
Published: December 2017

Recordings of pressure and electric potentials from Biebl loops of the duodenum of trained dogs were used to quantitate and to determine relationships among basic electric rhythm (BER), irregular bursts of spike potentials, and motor action of the duodenum. After control periods, morphine was used to stimulate rhythmic motor activity. The omnipresence of a stable, longitudinally propagated BER was demonstrated, each phase of which was detected simultaneously by electrodes arranged radially in the wall of the gut. Spike potentials were recorded whenever contraction of the gut wall was detected. The spikes occurred during a limited segment of the BER. Their number and amplitude were directly related to the strength of the contractions. Under control conditions, duodenal contractions associated with the spike potentials produced type I waves in the pressure record. Neither the spike potentials nor the type I contractions were conducted more than a few centimeters. With morphine only the latter portion of the BER showed minor changes. Incidence of spike potentials and contractions was increased. Occasionally morphine induced motor spasms, accompanied by a prolonged series of spike-like potentials and disruption of the BER.
Permeability of the squid axon membrane to several organic molecules
Authors: Tasaki I. , Spyropoulos C. S.
Published: December 2017

The permeability of the squid axon membrane to choline, guanidine, thiourea, urea, sucrose, starch, and cesium was investigated by use of radiotracers. In the resting state, the time constant for the loss of intracellular radioactive (free) choline, guanidine, and cesium was of the same order of magnitude as that for labeled sodium or potassium ions. Choline ion was found to bind rapidly with the constituents of the axon. In sea water containing labeled choline, there was accumulation of radioactivity by the axon. On repetitive stimulation, guanidine and cesium efflux was markedly increased; the choline efflux was slightly increased. Labeled thiourea and urea moved across the membrane far more readily than the univalent cations. Permeation of labeled sucrose and starch was very slow.
Cerebral enzyme changes and tolerance to anoxia during maturation in the rabbit
Authors: Cassin S. , Herron C. S.
Published: December 2017

Newborn rabbits tolerate 30–35 min of anoxia; adult rabbits withstand anoxia for 3–5 min. To gain more information concerning mechanisms of resistance of the newborn mammal to anoxia as compared with the adult, changes in cerebral succinic dehydrogenase and cytochrome oxidase activities were studied in rabbits varying in age from less than 24 hr to adulthood. Succinic dehydrogenase and cytochrome oxidase activities were very low at birth, but gradually increased until 15–18 days postnatally. Between 15–18 days a "critical period" in the development of these enzymes was reached; adult levels of activity were attained. It is also at this critical period in time that the tolerance of the developing rabbit to anoxia becomes as poor as that of the adult. The increase in oxidative enzyme activity is in agreement with the hypothesis that the metabolism of the mammal is transformed from predominantly anaerobic at birth to aerobic with maturation.
Acute hemodynamic responses to intravenous and intra-arterial guanethidine
Authors: Abboud Francois M. , Eckstein John W. , Pereda Santiago A.
Published: December 2017

Intravenous administration of guanethidine to dogs causes an abrupt fall in systemic arterial pressure which is followed by a sustained increase. These studies were made to determine the nature of this biphasic response. Observations were made on dogs before and at frequent intervals after guanethidine was given. A fall in arterial pressure, an increase in cardiac output, and a decrease in peripheral resistance were observed within 10 sec; these changes lasted 40–50 sec. After the depressor phase, blood pressure and stroke volume increased while resistance returned to control levels. These acute changes subsided within 10–15 min. Ganglionic blockade augmented the pressor response and adrenergic blockade reduced it. Intra-arterial injection of guanethidine into perfused denervated forelegs caused brief vasodilatation followed by vasoconstriction. This response was qualitatively different from that seen with intra-arterial injection of norepinephrine. The results support indirectly the hypothesis that the systemic pressor response is caused by circulating catecholamines. The results demonstrate also that the drug has a local vasodilator action on the blood vessels of the foreleg.
Potassium secretion and reabsorption in distal nephron
Authors: Vander Arthur J.
Published: December 2017

Potassium transport in the distal nephron has been investigated, using stop flow and slow flow techniques. Results indicate that potassium is secreted in the collecting duct and far distal tubule, and that sodium must be present for this secretion to occur. The usual stop flow distal potassium dip would appear to be a true site of active potassium reabsorption. This reabsorptive area includes the collecting duct and distal tubule and is completely coextensive with the sodium reabsorptive area. Potassium reabsorption and secretion can occur simultaneously in the collecting duct and far distal tubule. This phenomenon explains the observation (confirmed in this study) that the stop flow potassium peak diminishes as duration of occlusion is increased.
Effect of vitamin D on plasma citrate and calcium response to nephrectomy
Authors: Meintzer Roger B. , Nelson Dennis R. , Freeman Smith
Published: December 2017

Young rats fed a diet deficient in vitamin D and optimal in calcium and phosphate respond to prophylactic administration of the vitamin with elevated plasma citrate and calcium levels. Feeding vitamin D to D-deficient young rats markedly increased the plasma citrate response to nephrectomy. The D-deficient animal requires between 24 and 48 hr to develop the maximal response to vitamin D as judged by the plasma citrate response to nephrectomy. The plasma citrate response to nephrectomy after administration of the vitamin is virtually linear over a narrow range of vitamin D dosage. These data are discussed in terms of the possible role of citrate in relation to parathyroid function and the maintenance of plasma concentration of calcium.
Protection of rapidly decompressed rats by pharmacologic and physical means
Authors: Lyle Carl B. , Dahl Elmer V.
Published: December 2017

In a group of rats decompressed from an ambient pressure of 520 mm Hg to 30 mm Hg in 0.075 sec, 72% died. Only 12–37% of animals treated before decompression with drugs acting on the nervous system died. No rats given a local anesthetic agent intraperitoneally prior to decompression died, and no rats whose abdomens were tensely distended with intraperitoneal saline before decompression died. In each experimental group, mortality was significantly correlated with increased lung weight. These observations lead to the speculation that, in rats, the sudden distention of gas-containing abdominal viscera has indirect, perhaps reflex, effects which are related to the development of pulmonary edema and to the survival of the animals.
Chromium excretion in the dog
Authors: Collins R. J. , Fromm P. O. , Collings W. D.
Published: December 2017

Renal clearance of chromium decreases exponentially with time after a single intravenous injection of Cr51Cl3 from 2.5 or 3 ml/min/m2 at 1 hr to less than 1 ml/min 8 hr post-injection. Equilibrium dialysis measurements showed similar results for plasma dialyzable chromium. These observations lead to the determination of a dialyzable chromium clearance (Cd-cr) in which the concentration in dialyzable chromium replaced total plasma chromium in the clearance formula. The mean and standard deviation for Cd-cr of 36.6 ± 11.6 ml/min/m2 was relatively unaffected by time after chromium administration, plasma concentration of dialyzable chromium, or rate of urine flow. Values of Cd-cr determined repeatedly in two dogs intravenously infused with Cr51Cl3 for over 7 hr also remained stable. Glomerular filtration and tubular reabsorption are involved in renal excretion of chromium. The lack of a reduction of Cd-cr at high plasma levels of dialyzable chromium favors the conclusion that tubular excretion is of minor importance. Simultaneous creatinine and PAH clearances were normal, indicating that renal function was not impaired by the doses of chromium used.
Anticonvulsant properties of amino-oxyacetic acid
Authors: Da Vanzo J. P. , Greig M. E. , Cronin M. A.
Published: December 2017

Amino-oxyacetic acid (AOAA), a compound which inhibits γ-aminobutyric-α-ketoglutaric transaminase in vitro and causes accumulations of γ-aminobutyric acid (GABA) in vivo, has anticonvulsant activity against convulsions caused by thiosemicarbazide in rats, mice, and cats and against methionine sulfoximine convulsions in cats. Pentobarbital sodium and trimethadione were slightly active in protecting against thiosemicarbazide-induced convulsions whereas chlorpromazine and methadone were inactive. Pyridoxal, ethanol (in fasted rats), and paraldehyde showed anticonvulsant activity in thiosemicarbazide convulsions. The anticonvulsant activity of AOAA did not appear to be due to increased GABA levels in the brain for the following reasons: a) maximum GABA levels occurred 6–8 hr after administration of AOAA. Optimal protection against thiosemicarbazide, however, was afforded during the first 3 hr after administration and it had fallen off markedly at 6 hr. b) Hydroxylamine, which has been reported to raise GABA levels, had no anticonvulsant activity on thiosemicarbazide.
Interactions of oxytocin, potassium, and calcium in the rat uterus
Authors: Berger Elwin , Marshall Jean M.
Published: December 2017

Ovariectomized white rats were treated as follows: group 1, 70 µg estradiol benzoate every other day for 9 days; group 2, 3.1 mg aqueous progesterone daily for 4 days then 6.2 mg daily for 5 days; group 3, untreated controls. Spontaneous muscle contractions were recorded isometrically from isolated uterine horns. Uteri from the estrogen-treated animals were the most sensitive to the stimulatory action of oxytocin (5 mu/ml). The action of oxytocin remained essentially unchanged in the presence of a tenfold increase in external K concentration in both the estrogen-treated and progesterone-treated muscles. A reduction in the Ca concentration of the surrounding medium markedly reduced the effectiveness of oxytocin. This decline in oxytocin potency was most pronounced in the estrogen-treated uteri.
Acinar-duct transport sites for Na+ and K+ in dog submaxillary salivary gland
Authors: Henriques Basil L.
Published: December 2017

The submaxillary gland of the dog was employed to determine the relative roles of the acini and ducts in the net transport of Na+ and K+ into saliva. Three methods were used: stop flow, with periods of 2- and 8-min occlusion; retrograde injection of mercuric chloride (0.05% concentration and 0.2 cc in vol) into each submaxillary duct system, an adaptation of the method of Nicholson; time zero studies, a collection of salivary samples from a gland which had rested for at least 30 min before stimulation. The ducts were found to resorb Na+ and water at all flow rates and to secrete K+ into the saliva. K+ was found to be stored in the gland. There was evidence that Na+ and K+ were either filtered from the plasma or secreted by the acini into the lumen at concentrations similar to plasma levels.
Control of intestinal rhythmic contractions by a duodenal pacemaker
Authors: Hasselbrack Robert , Thomas J. E.
Published: December 2017

Rhythmic contractions of the small intestine were recorded in duodenal fistula dogs and in excised dog's intestine. The frequency of contraction showed a stepwise decrease from duodenum to ileum in both intact and excised intestine. Local cooling of a short segment of the upper duodenum caused a significant decrease in frequency of rhythmic contractions throughout the intestine below the cooled area but not above, without significant change in rectal temperature. The frequency of contractions in the excised intestine was 25–30% less than in corresponding areas of intact intestine. The results indicate that influences transmitted from the duodenum, perhaps associated with slow electrical waves, increase the frequency of rhythmic contractions throughout the entire small intestine probably by stimulating the muscle to contract at a frequency in excess of its inherent myogenic rhythm.
Lipid release by liver slices
Authors: Hamosh Margit , Shapiro B.
Published: December 2017

Slices were prepared from livers of rats which had received an intravenous injection of 1-C14-palmitate 20 min prior to the removal of the livers. The labeled acids were found predominantly in the neutral fat fraction (61%), smaller amounts (32%) in the phospholipids, and only 6% as unesterified fatty acids. When such slices were incubated in salt solutions, labeled lipids were released into the medium. This release could be promoted by the use of blood serum as medium or by the addition of α- or ß-lipoproteins to the salt solutions. Serum albumin was less effective. Release came rapidly to an end when an equilibrium was established between the liver and the medium and could be renewed by replacing the medium with a fresh protein solution. When unlabeled liver slices were incubated in media with labeled triglycerides, the labeled compound was assimilated by the liver. The presence of blood serum and lipoproteins increased the relative contribution of the phospholipids to the lipids released. Serum albumin and blood serum promoted the release of free fatty acids by the liver. The physiological significance of this latter process is discussed.
Persistence of a functioning bulbus cordis homologue in the turtle heart
Authors: March Harold W.
Published: December 2017

The functional and structural characteristics of a discrete myocardial segment at the base of the turtle ventricle were studied. The study indicates that this segment is a homologue of the primitive bulbus cordis. Cinematographic techniques were utilized to observe the function of this segment. It contracts later than the main ventricular chamber and acts as a sphincter at the base of the pulmonary artery in late systole. It is suggested that this mechanism serves to regulate the normal left-to-right shunt into the lungs through the incomplete ventricular septum and to maintain adequate systemic blood flow. A resemblance between the arrangement in the turtle and that seen in certain cases of human congenital heart disease is briefly discussed.
Role of inhibitory mechanisms in physiological regulation of lipogenesis
Authors: Masoro E. J. , Porter Edith , Korchak Helen
Published: December 2017

The significance of inhibitory mechanisms in the regulation of hepatic lipogenesis was investigated by utilizing the "cold-fasted" state to evaluate their quantitative importance. Lipogenic inhibitory mechanisms, located primarily in the microsomes, appear in the liver of the rat during 24-hr fast at 0–2 C. Because the fatty acid synthesizing enzymes are found to be present at not markedly reduced levels and since the reduction in levels of coenzymes and stimulators of lipogenesis, such as lipogenin, can account for only part of the depression in lipogenesis, it is evident that inhibitory mechanisms play a major role in restricting hepatic lipogenesis in that condition. The general role of inhibitory mechanisms in the homeostatic regulation of lipogenesis is discussed.
Urinary and biliary excretions of various phenol red derivatives in the anesthetized dog
Authors: Kim Jong Ho , Hong Suk Ki
Published: December 2017

Excretion of phenol red derivatives, e.g., phenol red (PSP), bromphenol blue (BPB), and bromcresol green (BCG), in urine and bile was studied. After a single intravenous dose of dye, urine and bile samples were obtained every 30 min for 3 hr. Normally, 75% of PSP was excreted in urine in 3 hr; only 2.7% appeared in bile. Secretion of BPB and BCG was much faster in the liver than in the kidney. When Diodrast was administered intravenously after injection of a dye, excretions of all dyes in urine and bile were significantly reduced. A similar reduction in dye excretion was observed in hypothermic dogs in absence of Diodrast. Corresponding clearances and urine-to-plasma or bile-to-plasma concentration ratios were generally lowered by both Diodrast and hypothermia, suggesting that these dyes are secreted actively by a common transport system in both the kidney and liver. Excretion of these dyes and Bromsulphalein (BSP) was studied in the liver in bilaterally nephrectomized dogs. Dye excretion was greatest in BSP and decreased in the order BCG, BPB, and PSP, indicating that BSP is probably excreted by the liver through the same transport system as phenol red derivatives.
Buffering of hypercapnic acidosis by sodium carbonate
Authors: Nahas Gabriel G. , Hassam Driss , Holmdahl Martin H:son , Manger William M.
Published: December 2017

Eight dogs were given 0.15–0.18 m solution of Na2CO3 i.v. during 1 hr of apneic oxygenation. Arterial blood pH was maintained within .1 unit of normal, whereas cerebrospinal fluid pH fell from 7.39 to 7.01. PaCOCO2 increased from 31 to 153 mm Hg, plasma HCO–3 from 18.3 to 72.7 mm/liter, Na+ from 147 to 182 mEq/liter, and osmolality from 336 to 407 mOs/liter. In the cerebrospinal fluid HCO–3 rose only from 21.5 to 30.6 mm/liter. Diuresis was maintained, but the rate of urine excreted during apnea was always lower than the rate of fluid given. Bradycardia, ECG alterations, and extreme variations in blood pressure were observed during apneic oxygenation. Cerebrospinal fluid pressure increased, as did plasma catecholamine levels and blood sugar. Two animals died shortly after the end of the experiment. Na2CO3 administration while maintaining blood pH constant did not offset the circulatory disturbances created by the acid load of apneic oxygenation.
Cerebral high-energy compounds: changes in anoxia
Authors: Lolley Richard N. , Samson Frederick E.
Published: December 2017

Acid-soluble phosphates of rat brain during anoxia were determined by ion-exchange and chemical procedures. There is a general shift during anoxia of triphosphate nucleotides to monophosphates and a very rapid breakdown of phosphoryl-creatine. However, total phosphate leaving the high-energy phosphate pool is not equal to the changes in inorganic phosphate; inorganic phosphate change is much larger than high-energy phosphate change in early anoxia and much smaller in extended anoxia. The patterns of guanosine triphosphate and uridine triphosphate changes are more complex than adenosine triphosphate changes. Nicotinamideadenine dinucleotide levels are steady until late anoxia, at which time they decrease slightly. Cytidine monophosphate is the only cytidine nucleotide detected. Inosine nucleotide concentrations in control animals were below the limit of the method, but in late anoxia inosine monophosphate appeared. The data show that the energy flow through the phosphates in brain is rapid and involves phosphate compounds other than the acid-soluble nucleotides and phosphoryl-creatine.
Suprapontine mechanisms in regulation of respiration
Authors: Fink B. R. , Katz R. , Reinhold H. , Schoolman A.
Published: December 2017

The ventilation and blood acid-base balance of 19 cats were studied after supracollicular ablation of the forebrain and again after intercollicular transection of the brain stem. The first ablation caused a marked increase in the frequency of respiration, apparently unmasking a caudad facilitory influence through the removal of forebrain inhibition. Hypocapnic apnea could not be induced in this preparation. After intercollicular section there was a sudden fall in frequency, the ventilatory response to CO2 was diminished and hypocapnic apnea was easily induced. It is concluded that a tonic facilitory effect on respiration originates in the rostral midbrain and adjacent diencephalon, possibly in the reticular activating system.
Bone, bone marrow, and brain oxygen
Authors: Misrahy G. A. , Hardwick D. F. , Brooks C. J. , Garwood V. P. , Hall W. P.
Published: December 2017

Oxygen availability (aO2) was measured polarographically in bone, bone marrow, and brains of cats. Immediately after electrodes had been implanted, the mean bone marrow oxygen was erratic. It reached a maximum around the 12th postoperative day, then decreased to a stable level within 2–3 months. "Slow waves" with a frequency slower than in brain (3–8 vs. 8–14 cycles/min) were present in bone marrow but not in compact bone. Under physiological conditions, their frequency and pattern were relatively constant, except during estrus, when they were disrupted in bone marrow, but not in brain. In general, oxygen and nitrogen affected bone marrow aO2 more than brain, but CO2 affected brain aO2 more than bone marrow. Responses of compact bone to these gases were sluggish. Vasoconstrictor drugs decreased mean bone marrow aO2 with variable effects on slow waves. Some vasodilators increased bone marrow aO2. Withdrawal of amounts of blood sufficient to induce erythropoiesis had little effect if any on bone marrow aO2. X-radiation altered the pattern of slow waves.
Adhesiveness of platelets and leukocytes during acute exsanguination
Authors: Swank Roy L.
Published: December 2017

Dogs were subjected to acute exsanguination during which their blood was tested for adhesive or aggregated blood elements by passing the blood through a microfilter with multiple precise pores 20 µ sq. During the latter half of exsanguination the leukocytes and platelets became progressively more adhesive, but significant aggregation was not observed. This was attended by a rapid fall in mean blood pressure. Treating blood containing adhesive platelets and leukocytes with Pyrex glass wool removed significant numbers of these adhesive elements from the blood.
Influence of unreabsorbed anions on renal threshold and Tm for bicarbonate
Authors: Rector Floyd C. , Seldin Donald W.
Published: December 2017

The relation of HCO3– reabsorption to excretion was examined in dogs with normal pCO2, increased plasma pCO2, and during the administration of acetazolamide. In the presence of an intact carbonic anhydrase enzyme system HCO3– excretion began when HCO3– reabsorption exceeded 75% of the HCO3– reabsorptive capacity. Respiratory acidosis augments the HCO3– Tm without altering the pattern of HCO3– excretion which commences at near-capacity levels. Inhibition of carbonic anhydrase by acetazolamide lowers the HCO3– Tm, enormously exaggerates the HCO3– leak, and prevents the production of HCO3–-free urine at all levels of plasma HCO3–. Sodium sulfate markedly diminishes the excretion of HCO3– before the Tm is reached, both in the presence or absence of carbonic anhydrase activity, but has no effect on the HCO3– Tm, suggesting that the presence of unreabsorbed anion influences the ability of renal tubules to generate a gradient without influencing total H+ transport. It is suggested that SO4– can induce this effect because it is an unreabsorbed anion. Reasons are advanced that the anion effect occurs in the distal, not proximal, tubule and is mediated by a rise in transtubular potential.
Role of the liver in secretin inactivation
Authors: Skillman John J. , Silen William , Harper Harold A.
Published: December 2017

In order to determine the effect of the liver on the action of secretin on the pancreas, secretin was infused alternately into the femoral and portal veins of adult mongrel dogs for 15-min periods, using a constant infusion pump. The major pancreatic duct was cannulated transduodenally and pancreatic juice was continuously collected in a graduated centrifuge tube. Injection of Evans blue dye through the main pancreatic duct at the conclusion of each experiment confirmed the ligation of all ducts, other than the major one, so that collections represented total flow of pancreatic juice. In each pair of infusions (portal and systemic) the volume of pancreatic juice obtained was always greater when secretin was given by the systemic route, and this increase in volume was highly significant statistically ( P < .005). These observations indicate that the effect of secretin on the pancreas is partially inactivated by the liver.
Release and uptake of triglycerides by isolated perfused rat liver
Authors: Heimberg Murray , Weinstein Ira , Klausner Howard , Watkins M. L.
Published: December 2017

The uptake of triglycerides by the isolated perfused rat liver from synthetic neutral fat emulsions or from washed rat chylomicrons was investigated. It was observed that the uptake of triglycerides was more rapid in livers from starved rats than from normal fed animals. In the absence of added lipid to the perfusate, there was release of triglyceride from livers of fed animals, whereas there was a net uptake of endogenous perfusate triglyceride by livers from fasting rats. The data suggest that both uptake and release of triglyceride by liver occur simultaneously. In livers from fasted animals uptake may be the more rapid process, whereas in livers from fed rats both uptake and release may occur at more equal rates. In contrast to the triglycerides, no difference in rate of uptake of endogenous serum nonesterified fatty acid or of added fatty acid-albumin complex was observed with livers from either fed or fasting animals.
Flux and turnover rates of glycine in the dog liver perfused in situ
Authors: Elwyn David , Richmond Jonas E. , McMenamy Rapier H. , Shoemaker William C.
Published: December 2017

Distribution of added glycine-1-C14 in the perfused dog liver was studied. Concentrations and specific activities of glycine in liver and plasma were measured as a function of time. Calculated values for glycine fluxes between plasma and liver were for influx, 10 to 150, efflux, 10 to 90, and for net influx into liver, –10 to 80 µmole/min/kg liver. Administration of an amino acid mixture containing unlabeled glycine increased the rates of influx, efflux and net flux of glycine into the liver, as well as the concentration of glycine in plasma. The turnover rate of glycine in liver was found to be of the order of 400 µmole/min/kg liver. The specific activities of other amino acids, glucose, and glycogen were measured.
Effects of focused ultrasound on spontaneous cortical electrical potentials of the cat
Authors: Battista Arthur F. , Quint Robert
Published: December 2017

An area several millimeters square in the frontal, the parietal, or the occipital regions of the cat's brain was irradiated with focused ultrasound. The spontaneous electrical cortical potentials seen under barbiturate anesthesia were reversibly depressed over one or both cerebral hemispheres. The depression of cortical activity was of greater duration and more severe after multiple irradiations. Larger total dosages produced by longer periods of multiple irradiations, evoked only in the frontal area, generalized fast electrical epileptic cortical activity. If this activity was of high amplitude, tonic tremor seizures appeared, but no clonic component developed.
An electrophysiological study of the salt gland of the herring gull
Authors: Thesleff S. , Schmidt-Nielsen K.
Published: December 2017

When the salt gland of the herring gull excretes sodium chloride the duct of the gland becomes positive relative to the blood. Strophanthin, an inhibitor of active sodium transport, prevents the establishment of the positive potential and also blocks gland secretion. The findings suggest that an active transport of sodium from the blood to the gland lumen may be a primary secretory mechanism.
Isozymes of lactic dehydrogenase in skeletal muscle
Authors: Blanchaer M. C. , Wijhe M. Van
Published: December 2017

The lactic dehydrogenase (LD) isozyme patterns of red and white muscle of the guinea pig, rabbit, and mouse were examined by electrophoresis in barbiturate-buffered agar. Red muscle consistently yielded five bands of lactic dehydrogenase activity, but white muscle usually produced only two bands corresponding to isozymes IV and V. Traces of isozyme III were noted occasionally in the white muscle of the rabbit and mouse, but bands I and II were absent from the white muscle of all three species. Crystalline rabbit muscle lactic dehydrogenase produced an isozyme pattern resembling that of a mixture of red and white rabbit muscle. The lactic dehydrogenase isozyme pattern of human muscle reported by previous workers resembles that of a mixture of the red and white muscle patterns.
Effect of stretch on passive tension and contractility of isolated vascular smooth muscle
Authors: Sparks Harvey V. , Bohr David F.
Published: December 2017

Helically cut strips of the wall of small branches of dog superior mesenteric artery were stretched in a stepwise fashion. Tension developed in response to stretch or to a standard stimulus (epinephrine or electricity) was recorded isometrically. The elastic diagram of the vessel is comparable to that reported by other investigators. Contraction in response to a standard stimulus increased with stretch, as much as 100% for a 10% increase in length. The increase in response continued until the strip reached a certain optimal length (variable from strip to strip), after which the response decreased with further stretch. When the strip was released in a stepwise fashion hysteresis was observed. Possible relationships of tension and length at the level of the contractile element are discussed together with ways in which the information presented here may relate to myogenic autoregulation.
Effect of adrenergic agents on responses of smooth muscle to angiotensin
Authors: Khairallah Philip A. , Page Irvine H.
Published: December 2017

Evidence has been presented previously indicating that angiotensin acts indirectly on guinea pig intestines by stimulating the ganglion cells of Auerbach's plexus. Further studies have shown that the adrenergic nerves are not directly involved in this mechanism, although adrenergic blocking agents suppress the response to angiotensin, probably by acting directly on the cell membrane. Epinephrine, and to a lesser extent norepinephrine and isoproterenol, inhibited the contraction of ileum and uterus to angiotensin, and to electrical stimulation, possibly by reversing or blocking sodium or potassium ion flux across the cell membrane resulting from the action of the peptide. Most of the adrenergic blocking agents studied, with the exception of Dibenamine, also inhibited the response to angiotensin. Reserpine, guanethidine, and bretylium block its action, possibly by releasing catecholamines from bound tissue stores, and phentolamine and piperoxane, by their sympathetic actions imitating the catecholamines.
Carotid sinus baroceptor modifications associated with endotoxin shock
Authors: Trank John W. , Visscher Maurice B.
Published: December 2017

Carotid sinus baroceptor responses were studied in dogs before and after administration of shock-producing quantities of E. coli endotoxin. Responses were characterized as the relationship between intrasinusal stimulus pressure and baroceptor nerve discharge frequency. Both constant and pulsating pressure stimuli were used. After endotoxin administration and the onset of endotoxin shock it was found that postendotoxin discharge frequencies exceeded control discharge frequencies for most pressures. These response shifts result in a resetting of the hemoregulatory barostatic mechanism to regulate blood pressure to a new and hypotensive level. It is concluded that in the later phases of endotoxin shock, the reflex modification may play the predominant role in maintaining hypotension and that barostatic resetting partially explains the poor compensatory response to the initial profound hypotension after endotoxin administration.
Effects of DOCA, K loading, and cations on K uptake by rabbit kidney cortex
Authors: Berndt W. O. , LeSher D. A.
Published: December 2017

In previous studies the nature of the substrate requirements, as well as the effects of metabolic inhibitors on potassium uptake by rabbit renal cortex slices, have been examined. In this study a variety of factors have been examined, some of which are known to influence the renal handling of potassium in the intact animal. Pretreatment with deoxycorticosterone acetate enhanced the ability of renal slices to take up potassium from a low external source. This was true even though the fresh-tissue levels of potassium were not markedly altered. Pretreatment with potassium chloride elevated the fresh-tissue potassium level but had no effect on potassium uptake by the slices. Two organic bases which have been reported to interact with the potassium secretory process in the dog were found to have no effect on potassium uptake in vitro. Ammonium chloride was found to depress potassium uptake when present in a concentration equimolar to that of potassium.
Pancreatectomy in rats: onset of metabolic changes in liver, adipose, and diaphragm
Authors: Migliorini R. H. , Chaikoff I. L.
Published: December 2017

The time of onset of metabolic alterations in utilization of C14-labeled glucose and acetate by liver and adipose tissue, and in uptake of glucose by diaphragm was studied in "totally" depancreatized rats, a preparation in which severe manifestations of diabetes develop rapidly. The earliest changes were observed in glucose utilization by liver and adipose tissue. Two hours after pancreatectomy, conversion of glucose carbon to a) fatty acids, glycogen, and CO2 by liver slices and b) fatty acids and CO2 by adipose tissue was depressed. Defective utilization of acetate appeared earlier in adipose tissue than in liver. A decrease in the liver's capacity to convert acetate carbon to fatty acids developed some time between 4 and 14 hr after pancreatectomy. In adipose tissue this occurred between 2 and 4 hr. Defective uptake of glucose by diaphragm was observed later after pancreatectomy, some time between 4 and 14 hr. The results are discussed from the standpoint of the nature of metabolic lesions in the diabetic liver and of whether insulin has a direct or indirect action on hepatic tissue.