bluuebunny/crossref_metadata_2025 huggingface dataset:
Bone blood flow shown with F18 and the positron camera
Authors: Dyke Donald Van , Anger Hal O. , Yano Yukio , Bozzini Carlos
Published: December 2017

Development of the positron camera has made it possible to rapidly obtain pictures of the distribution of radioactive fluorine 18 in the living animal or human being. The distribution of F18 administered intravenously as fluoride ion is uneven in the normal skeleton. Furthermore, it is markedly altered in pathological conditions and accumulates at fracture sites, tumor sites, and in the lesions of Paget's disease. The initial uptake of fluoride in bone is dependent on the rate of delivery of the isotope to each bone (blood perfusion rate) and the extraction efficiency of that bone. Evidence is presented indicating the fluoride distribution in the skeleton is determined by differences in blood perfusion rate to the various bones rather than differences in extraction efficiency. We suggest that F18 distribution is an indicator of blood flow to bone.
In vitro evaluation of relative inhibitory potency of phlorizin and its congeners
Authors: Diedrich Donald F.
Published: December 2017

The inhibitory effect of phlorizin and II phlorizin analogs on the active accumulation of glucose into pieces of hamster small intestine in vitro has been determined. Of all the compounds tested, phlorizin itself, at micromolar concentrations, was found to be the most potent inhibitor of glucose uptake. The less-active phlorizin congeners exhibited varying degrees of activity. Their order of effectiveness reported in an earlier in vivo study has been corroborated by the results of the present investigation.
Hypothalamic obesity in weanling rats
Authors: Han Paul Wei , Lin Chao-Hsiung , Chu Kang-Chu , Mu Jui-Yun , Liu An-Ch'ang
Published: December 2017

Bilateral hypothalamic lesions were placed in the ventromedial nuclei of 15 male weanling rats. Nine male littermates were used as controls. Food intake, body weight, and nose-occipital (N-O) length were followed for 90 days. Rats were killed on the 90th postoperative day and stomach weight, body fat content, and femur length were then measured. Although the daily food intake and the rate of body weight gain of the rats with lesions were comparable to those of their controls, all 15 operated rats became obese and their N-O and femur lengths were significantly shorter. It is concluded that hypothalamic obesity of weanling rats is associated with growth impairment.
Effect of alpha-methyl-dopa on heart and pulmonary arteries of hypoxic mice
Authors: Naeye Richard L.
Published: December 2017

Fifty mice were placed in an atmosphere of 10% oxygen and sacrificed at intervals. Twenty-one of the animals were simultaneously given methyl-dopate-HCI. Hypoxic control mice developed medial hyperplasia in small pulmonary arteries and right ventricular cardiac hypertrophy. These abnormalities did not develop in the drug-treated animals.
Effect of saturated fat diets on rat liver NADP-linked enzymes
Authors: Tepperman Helen M. , Tepperman Jay
Published: December 2017

The aggregate hexosemonophosphate dehydrogenase (HMPD) activity was found to be higher in livers of rats fed a diet containing saturated fat (hydrogenated coconut oil = H) for 7 days and fasted for 48 hr than it was in similarly prepared animals fed a corn oil (CO) diet. Later, a liver HMPD-increasing effect of feeding H was found in nonfasted animals. Lipogenesis (i.e., the incorporation of acetate-1-C14 into fatty acids by liver slices) was shown to be as low or lower in the H group as in the CO. Liver slices prepared from H and CO diet adapted rats were incubated with either acetate-1-C14 or palmitate-1-C14 and the extent of incorporation of C14 into individual fatty acids was measured. With both substrates more radioactivity was found in 16:1, 18:0, and 18:1 in the case of H-fed animals. It is proposed that a component of the signal for eliciting increased NADP-linked enzyme activity in the H rats was an increased rate of oxidation of NADPH attendant on monoene formation and chain lengthening.
Influence of partial immersion and exercise on lipid metabolism in the rat
Authors: Kratzing C. C.
Published: December 2017

Young rats kept on a choline-deficient diet were forced to swim 2 1/2 or 5 hr daily for 3 weeks in water at 18 or 27–30 C. Livers from rats·which swam the longer time had a total lipid and liver cholesterol content similar to that of choline-supplemented rats. The duration of swimming affected the extent to which total lipid was lowered. Factors other than exercise were involved since rats which stood in water for 2 1/2 hr had hepatic lipid and cholesterol values comparable with those which swam 2 1/2 hr.
Cardiovascular responses in prolonged hypothermia
Authors: Popovic V. P. , Kent Kenneth M.
Published: December 2017

Rats cooled to a body temperature of 15 C live for 9–10 hr. However, they do not survive the rewarming if the hypothermia has lasted more than 5 hr. Neither the cause of death in hypothermia after 10 hr, nor the cause of resuscitation failure of animals rewarmed after 5 hr in hypothermia is known. In 31 rats cooled to and maintained at a body temperature of 15 C, cardiac output decreased continually during the entire period of hypothermia, having by the end of hypothermic survival the value of only 25% of output at the beginning of the hypothermic period. The arteriovenous differences of O2 content increased, while total peripheral resistance increased continuously during this time. During the 10 hr of hypothermic survival the hematocrit ratio rose from 42 to 65–70 vol %. Because of these changes it is suggested here that the failure of circulation is the probable cause of death in hypothermia.
Capacities for regulation of heart rate in fetal, infant, and adult rats
Authors: Adolph E. F.
Published: December 2017

In anesthetized pregnant rats, fine-wire electrodes were inserted into fetuses 14–21 days of age; electrocardiograms were recorded. What influences can control the heart rate at stages before and after nerves are functional in the heart? Percentage changes of heart rate are reported. Uterine contraction, needle prick, hypoxia, and hypercapnia transiently decelerated the heart at the earliest preneural stages. Norepinephrine injection into fetus accelerated the heart. In older fetuses, isopropylnorepinephrine and sometimes epinephrine also accelerated the heart. The heart rate therefore became susceptible to more influences. At birth, responses to needle prick and to hypoxia began to reverse, acceleration becoming the rule. Epinephrine and norepinephrine then induced transient decelerations; hyperoxia induced deceleration and an off-effect acceleration. In infant rats, all the responses were exaggerated compared with both those in fetuses and those in adults. Adult rats still responded to all the above agents, however. Especially in the age range from fetus to infant the capacities for regulation of heart rate augmented; a multiple-factor relation may be used to express the augmentation.
Axial drift of cells and partial plasma skimming in blood flowing through glass slits
Authors: Palmer A. A.
Published: December 2017

The distribution of red cells in citrated, heparinized, human blood flowing through slitlike glass channels of minor axis 30–35 µ was investigated by measuring the hematocrits from three closely set branches. With equal flow rates from the first and third branches carrying blood from each peripheral zone, the hematocrit difference, K, between axial and peripheral samples remained constant as the flow from the second branch, carrying the axial blood, was varied from 14 to 77% of the total flow. This indicates a progressive increase in hematocrit from near the wall to the axial plane such that laminar hematocrit is a linear function of the fraction of flow between the wall and the plane considered, whence simple expressions have been derived for partial plasma skimming at a dichotomous branch, and provided the velocity profile is parabolic across the short axis, for mean hematocrit and for mean red cell velocity within the channel. K was 16%, with inflowing blood hematocrit, HM, 38.5%. As HM increased from 0.1 to 70%, K/HM fell roughly logarithmically.
Adrenal blood flow and the adrenocortical response to corticotropin
Authors: Urquhart John
Published: December 2017

The effect of variations in adrenal blood flow on the adrenocortical response to ACTH was studied. The rate of blood flow through the perfused canine adrenal gland was a significant parameter in its response to ACTH. This effect was largest when the concentration of ACTH was between 1 and 30 µU/ml blood, but was considerably reduced in magnitude or absent at higher ACTH concentrations or in the absence of ACTH. The results at a variety of blood flows and blood ACTH concentrations indicate that the rate of ACTH presentation to the adrenal gland was better correlated with the steady-state rate of cortisol secretion than was blood ACTH concentration. The time course of adrenocortical response to a twofold increase in blood flow at an ACTH concentration of 1 µU/ml corresponded to dynamic responses to an increase in ACTH concentration at constant flow. Adrenal blood flow is approximately linearly related to perfusion pressure. It is concluded that adrenocortical function is an equivocal index of ACTH release by the pituitary, unless adrenocortical blood flow is known to be constant.
Secretion of urea and thiourea in sweat
Authors: Brusilow Saul W. , Gordes Ellen H.
Published: December 2017

The high sweat-to-serum urea ratio (greater than 1) was studied by correlating this ratio with serum urea concentration and sweat-to-serum osmolal ratios. In addition, the sweat-to-serum urea and thiourea ratios were studied in cat sweat as well as in human sweat. The results showed: 1) little relationship between sweat-to-serum urea ratios and sweat-to-serum osmolal ratios; 2) variable effects of serum urea concentrations on sweat-to-serum urea ratios; 3) sweat-to-serum thiourea ratios of 0.80 in man and in cats. These observations suggest that factors apart from back diffusion of water may account for some of the urea in sweat.
Salicylate: effects on ion transport and afterpotentials in frog sciatic nerve
Authors: Hurlbut William P.
Published: December 2017

Ten-millimolar sodium salicylate inhibits almost completely the active transport of Na and K in frog nerve. Salicylate slows and reduces, but does not prevent, the postanoxic hyperpolarization of the nerve fibers, and has little effect on posttetanic hyperpolarization. Although intracellular sodium is required to produce the postanoxic hyperpolarization, these results suggest that active transport of Na or K is not the basis of this requirement.
Interaction of Ca++ binding sites of troponin: significance for Ca++ movements
Authors: Honig CR , Reddy YS
Published: December 2017

Ca++ binding data for seven preparations of troponin and 37 preparations of native tropomyosin were analyzed by the method of nonlinear least squares. The analysis was based on the assumption that two classes of independent binding sites exist. Data from one-third the preparations could not be fitted with all binding parameters at true least-squares minimum, and computed values of parameters for two-thirds the preparations were biologically uniterpretable. We conclude that troponin does not contain two classes of independent binding sites. Comparison of Scratchard plots of Ca++ binding by troponin and native tropomyosin modifies binding through a cooperative effect on troponin. Certain features of the Scratchard plots are imcompatible with the possibility that troponin possess more than two classes of independent sites. We interpret these results to mean that troponin's binding sites interact and that the interaction is increased by tropomyosin.The interaction would cause Ca++ affinity to vary with time during a muscle contraction. The effect of variable Ca++ affinity on intracellular Ca++ movements and the time course of the active state is discussed.
Sequential amino acid measurements during experimental diabetic ketoacidosis
Authors: Blackshear PJ , Alberti KGMM
Published: December 2017

This study was designed to investigate the sequential amino acid response to acute insulin deprivation. Male Wistar rats were made severly diabetic by the intravenous injection of streptozotocin, 150 mg/kg, and maintained on insulin for 7 days. Insulin was then withheld, and measurememts of whole blood and plasma amino acid concentrations were made at 24-h intervals until 120 h, by which time animal mortality was 80%. Alanine and the other gluogenic amino acids displayed a biphasic response to insulin deprivation, decreasing in plasma and whole blood until 72 h after the last insulin injection then increasing in concentration until 120 h. The branched-chain amino acids valine, leucine, and isoleucine remained constant until 72 h after insulin, after which time their concentrations increased dramatically. It was concluded that the first phase represented enhanced gluconeogenesis and in the second phase amino acid uptake for gluconeogenesis was exceeded by net peripheral amino acid release. Enzymatic measurements showed a progressive increase in erythrocyte;plasma distribution ratios for glutamate in ketoacidosis.
Creatinine exchange between mother, fetus, and amniotic fluid
Authors: Pitkin RM , Reynolds WA
Published: December 2017

Creatinine exchange between mother, fetus, and amniotic fluid was investigated in rhesus monkeys in late pregnancy in which a different radioactive-labeled form of creatinine was injected simultaneously into either of two of the three possible compartments. Creatinine specific activity was then determined for each isotope in each compartment over the ensuing 4-6 h. A rapid and extensive bidirectional exchange occurred between all three compartments. Maternal-fetal flux, while bidirectional, seemed to be predominately from mother to fetus. Approximately 35% of labeled creatinine originally injected into the fetus and 25% of labeled creatinine originally injected into the mother were present in the amniotic sac within 2 h. Creatinine pool size was calculated to be approximately 6 mg/kg in both mother and fetus. Comparison of experiments involving living had dead fetuses indicated that the route of creatinine transfer from mother to amniotic fluid was through the living fetus and directly across the chorioamnion in the dead fetus. In addition, the time required for 'mixing' of creatinine injected into the amniotic sac was longer with a dead than with a living fetus but its half-life averaged 4.5 h regardless of fetal status.
Glomerular-tubular balance for bicarbonate in the dog
Authors: Bennett CM , Springberg PD , Falkinburg NR
Published: December 2017

Previous work that apparently showed a functional relationship between GFR and maximum bicarbonate reabsorption was done at a time when the effects on the latter of several factors (PCO2, plasma potassium concentration, and extracellular fluid volume expansion) were not recognized. The present study re-examines this relationship, while controlling these factors. In 14 hydropenic dogs, bicarbonate reabsorption per unt GFR increased linearly with increases in plasma bicarbonate concentration. At any level of plasma bicarbonate concentration,the absolute rate of bicarbonate reabsorption was functionally related to the GFR. In six volume-expanded dogs, bicarbonate reabsorption remained stable at 20-22 mmol/liter GFR as plasma bicarbonate was raised to greater than 40mM. The absolute rate of bicarbonate reabsorption increased with large increases in GFR induced by methylprednisolone and high-protein diet. In a third group of dogs, bicarbonate reabsorption varied directly with increases in GFR, while plasma bicarbonate concentration was held relatively constant above the threshold. We conclude there is a close functional relationship between the absolute rate of bicarbonate reabsorption and GFR in individual dogs.
Regulation of arterial blood pressure in the common green iguana
Authors: Hohnke LA
Published: December 2017

Arterial blood pressure (ABP) responses to graded hemorrhage and passive head-up tilt were studied in restrained, anesthetized, and unanesthetized iguanas. The ABP fell slowly in response to hemorrhage up to a critical deficit of 35 plus or minus 19% of the estimated blood volume; the rate of ABP fall then increased nearly 40-fold to continued hemorrhage. Increased heart rate and decreased femoral arterial blood flow accompanied progressive hemorrhage. Propranolol (2-3 mug/kg) did not appreciably alter arterial pressure-hemorrhage curves but hemorrhage-induced increases in heart rate were diminished nearly 50%. Atropine had little effect on either the blood pressure or heart rate changes induced by hemorrhage. During passive tilts of 0-90 degrees carotid arterial pressure fell 33% before returning to control levels (2 min). Heart rate increased and femoral arterial blood flow and central venous pressure fell in response to head-up tilts. It is concluded that hemorrhage and passive head-up tilting can induce reflex cardiovascular changes that assist ABP regulation in iguanas.
Intestinal transport of tryptophan and its analogs
Authors: Bosin TR , Hathaway DR , Maickel RP
Published: December 2017

A comparative study of the intestinal transport of DL-tryptophan and its 1-methylindole (tryptophan-l-Me) and benzo[b]thiophene (tryptophan-S) analogs has been carried out in vitro, using the everted intestinal sac of the rat and hamster. Both tryptophan and tryptophan-S are actively transported across the intestine, while tryptophan-l-Me is not actively transported. The active transport of tryptophan is competitively inhibited by tryptophan-S, suggesting a similar carrier, while tryptophan-l-Me is not an inhibitor of tryptophan transport, suggesting little or no interaction with the carrier. The transport of tryptophan and tryptophan-S is depressed at concentrations (10 mM), and all three amino acids produce subtle alterations in the barrier properties of the sacs, as evidenced by increased tetraethylammonium bromide-14C diffusion.
Metabolic responses of unanesthetized rats to manipulation of skin temperature
Authors: Morhardt JE , Lattanzi D , Miller C
Published: December 2017

Body temperatures of albino rats are highly variable compared to those of larger mammals. This paper demonstrates that much of that variability can be attributed to shifts of body temperature thresholds for metabolic response accompanying disturbance or arousal. It also shows that the open-loop gain (OLG) of the metabolic temperature-regulating system is as high as that in larger mammals, ruling out low gain as the source of the variability. Skin temperature (T-sk) of shaved rats was controlled by immersion to the neck in a water bath. Metabolic rate (M), measured during step changes of T-sk and during more gradual changes of colonic (T-c) and hypothalamic (T-hy) temperature, was proportional to deviations of both T-c and T-sk below their respective thresholds. The absolute values of the coupling function (alpha) relating M to T-c were proportional to T-sk; the absolute values of the coupling function (beta) relating M to T-sk were proportional to T-c. Thus, the gain of the system changed systematically with body temperatures. The thresholds of T-sk and T-c below which M increased were inversely proportional to T-c and T-sk, respectively, as well as shifting in response to some unknown variable designated arousal.
Renal function in the hibernating, and hypothermic hamster Mesocricetus auratus
Authors: Tempel GE , Musacchia XJ
Published: December 2017

Plasma and urine concentrations of Na+, K+, and urea were examined in hibernating, hypothermic, and normothermic hamsters. Plasma Na+ and K+ appear unaffected by 48 h of hypothermia (T-re 7 degrees C); however, plasma Na+ increased (P smaller than 0.05) from control values of 125.8 plus or minus 10.2 to 173 plus or minus 9.2 meg/liter in hibernators. Plasma K+ of the hibernator increased to 9.6 plus or minus 3.2 meq/liter from control values of 5.5 plus or minus 0.8 meq/liter (P smaller than 0.05). Plasma urea concentrations were increased (P smaller than 0.05) in both metabolically depressed groups from a control value of 0.5 plus or minus .05 to 0.8 plus or minus .16 and 7.2 plus or minus 2.8 mM in hypothermic and hibernating groups, respectively. Urine concentrations of solute for the hypothermic animals showed no detactable change from control values for Na+ and a decrease for both K+ and urea. Concentrations from hibernators showed a decrease from control values for both Na+ and K+ with no detectable change in urea. Renal tissue slice analysis demonstrated a marked corticomedullary solute gradient for Na+ and urea in normothermic control animals which is eliminated in hamsters hypothermic for 48 h and reduced in animals hypothermic for 15 min. Rewarming animals did not show a return of the solute gradient at T-re 18 degrees C. However, animals that had rewarmed to T-re 37 degrees C demonstrated a complete return with no difference (P greater than 0.05) from control values. Hibernators showed a slight (P smaller than 0.05) gradient for Na+ and no gradient for urea. Animals in all instances demonstrated a decrease in K+ concentration from cortex to papilla. A greater concentration of K+ was found in the renal cortex of animals hypothermic for 15 min and in hibernators (P smaller than 0.05).
Chloride transport through the n onshort-circuited isolated skin of Rana esculenta
Authors: Garcia-Romeu F , Ehrenfeld J
Published: December 2017

The effects of acetazolamide (Diamox), ouabain, and amiloride on chloride movements through the isolated, nonshort-circuited Rana esculenta skin were investigated at different external NaCl concentrations. From hyposmotic solutions of low NaCl concentration (2 mM), two principal components of the chloride uptake may be distinguished: one dependent on the osmotic water flux and the other inhibited by Diamox but not by ouabain, amiloride, or removal of sodium from the external solution. Chloride uptake from a Ringer solution is always inhibited when either the sodium transport is blocked with amiloride or ouabain or when sodium is absent from the external solution. It can be concluded that the predominant component of the chloride transport mechanism when the external solution is concentrated (Ringer) is a sodium-dependent one. When chloride is absorbed from a solution of low concentration, however, a component predominated which is independent of sodium transport. It is suggested that the latter mechanism should be capable of exchanging chloride against endogenous base as in the in vivo skin.
Conduction in descending spinal pathways initiated by somatosympathetic reflexes
Authors: Foreman RD , Wurster RD
Published: December 2017

In anesthetized, paralyzed cats, the effects of stimulation at the dorsolateral sulcus (DLS) of the spinal cord at the C8 segment were recorded from the T2 white ramus. Stimulation of the DLS at the C8 segment produced evoked responses which had average conduction latencies of 13.3, 25.8, and 43.4 ms and were designated as the early, intermediate, and late response, respectively. Intermediate and late evoked responses were also recorded when the contralateral funiculus, the third or late evoked response was abolished or greatly attenuated, but the intermediate response was still observed although it was diminished in amplitude. The early evoked response was usually observed with stimulation at the ipsilateral C8 segment following placement of the lesion. These data suggest that afferent impulses, which ascend to supraspinal segments of the central nervous system, are transmitted to preganglionic neurons of the sympathetic nervous system through descending pathways in the dorsolateral funiculus of the spinal cord. Stimulation of afferent fibers on the ipsilateral or contralateral side of the spinal cord produces volleys which ascend unilaterally and descend bilaterally to preganglionic neurons. The pathways producing the intermediate evoked response, which was still observed after an ipsilateral lesion was made in the spinal cord, may include both the ascending pathway and other connections with the preganglionic neurons.
Effect of posterior hypothalamic stimulation on ventricular fibrillation threshold
Authors: Verrier RL , Calvert A , Lown B
Published: December 2017

The effect of posterior hypothalamic stimulation on cardiac susceptibility to ventricular fibrillation (VF) was studied in 34 dogs. VF threshold was determined by inducing a sequence of early extrasystoles (R/T pulsing). Hypothalamic stimulation was associated with sinus tachycardia, systemic hypertension, and a 40% reduction in VF threshold. The effects of hypothalamic stimulation on the VF threshold persisted when heart rate acceleration and the pressor response were prevented. Cervical vagotomy and bilateral adrenalectomy were likewise without effect on fibrillation threshold changes. However, the decrease in threshold was abolished by beta-adrenergic blockade. It is concluded that the reduction in VF threshold associated with hypothalamic stimulation derives from the direct action of sympathetic nerves upon the myocardium, rather than from secondary hemodynamic effects.
Hypothalamic stimulation induces acid secretion, hypoglycemia, and hyperinsulinemia
Authors: Stephens DN , Morrissey SM
Published: December 2017

Electrical stimulation of the posterior hypothalamus brought about an increase in plasma insulin accompanied by a fall in blood glucose. If glucose fell below 55 mg/100 ml, gastric secretion of HCl ensued. The same relationship between acid secretion and glucose was observed when hypoglycemia was induced by intravenous injection of insulin. Stimulation outside the posterior hypothalamus did not give either a fall in glucose or an increase in gastric acid secretion. It is concluded that posterior hypothalamic stimulation causes gastric acid secretion by inducing insulin release and a consequent hypoglycemia.
Cardiovascular responses to bladder distension in patients with spinal transection
Authors: Wurster RD , Randall WC
Published: December 2017

Arterial blood pressure, heart rate, and cutaneous volume pulses were recorded during controlled elevation of urinary bladder pressure in a group of seven patients with spinal cord transsection above vertebral level T5 and in another group of four patients below T5. Profound elevations in systolic blood pressure and pulse pressure were induced by bladder distension when the lesion was situated above T5. Lesser elevations occurred in patients with lesions below T5. Marked vasoconstriction characterized skin areas innervated by the "isolated" spinal cord, while passive dilatation occurred in areas supplied by the proximal cord. Only three of seven patients with lesions above T5 level had decreased heart rate during marked elevations in arterial blood pressure. The marked elevations in pulse pressure in patients with lesions above T5 could not be explained solelyby increased vasoconstriction and decreased heart rate, but involves also inotropic cardiac responses. These inotropic responses are mediated by cardiac sympathetic nerves which leave the spinal cord above the T5 level.
Transport of plasma FFA in cats; effect of hypothalamic stimulation
Authors: Barkai A , Allweis C
Published: December 2017

Two tracer methods, repetitive single injection of [3-H]palmitate and continuous infusion of [1 minus 14-C]palmitate, were applied simultaneously to study tracer kinetics of the free fatty acid (FFA) miscible pool in anesthetized cats before, during, and after electrical stimulation of the hypothalamus. The results indicated that the FFA pool of the cat behaved as though it consisted of two compartments which exchange FFA with each other. The data were analyzed according to a two-compartmental mammillary system model. The space of the central compartment which represents the plasma was found to be 74 ml/kg body wt. No anatomical significance could be unequivocally ascribed to the peripheral compartment. The variables of the model system were determined for each cat, and a highly significant positive linear relationship between the net FFA transport (mumol/min) and the total quantity of FFA (mumol) in both compartments was established by a regression analysis of the control data. No significant changes were observed in this relationship during or following hypothalamic stimulation which had a significant effect on the plasma FFA level. This result suggests that hypothalamic stimulation affects FFA mobilization by modifying the rate of FFA inflow into the circulation, while the mechanisms for clearing FFA from the plasma are not altered.
Uteroplacental blood flow during alkalosis in the sheep
Authors: Buss DD , Bisgard GE , Rawlings CA , Rankin JH
Published: December 2017

Uteroplacental blood flow was measured by the radioactive-microsphere technique in eight near-term pregnant ewes during a normal control period and during maternal metabolic alkalosis. All measurements were made on awake, unanesthetized animals. Alkalosis, defined for this study as an arterial pH of 7.60 or greater, was produced by the oral administration of sodium bicarbonate, 3 g/kg body wt. The rise in pH thus produced was unaccompanied by significant changes in systemic arterial blood pressure and cardiac output, while maternal arterial Pco2 rose slightly from control levels. Cotyledonary blood flow declined from a control value of 1,177 ml/min to 1,025 ml/min during alkalosis. This decline of 13 percent in cotyledonary blood flow is significant (P smaller than 0.002). Blood flow to the remaining uterine tissue, or noncotyledonary uterus, did not change with alkalosis, being maintained at approximately 195 ml/min. It is concluded that maternal alkalosis, unaccompained by major changes in Pco2 and systemic arterial pressure, causes a small increase in the resistance of the uteroplacental circulation.
Shivering and nonshivering thermogenic responses of cold-exposed rats to hypothalamic warming
Authors: Fuller CA , Horwitz BA , Horowitz JM
Published: December 2017

The concurrent neural control of two thermoregulatory responses, shivering thermogenesis (ST) and nonshivering thermogenesis (NST), was investigated in chronically implanted cold-exposed rats. The effects of heating the preoptic/anterior hypothalamus (POAH) on shivering and on the rate of oxygen consumption (Vo2) were measured in these unanesthetized animals. With ambient temperature maintained constant (at some value between 10 and 16 degrees C), warming the hypothalamus 2-3 degrees C resulted in a significant decrease in Vo2 (Psmaller than 0.001) and an increase in shivering (Psmaller than .01), these responses being reversed on cessation of hypothalamic warming. These results are consistent with the proposal that, in the cold-exposed animal, elevated POAH temperatures directly inhibit NST even though shivering may increase (possibly as a compensation for the decrease in nonshivering heat production). They also rule out the possibility that, in the rat, signals from cutaneous and hypothalamic thermoreceptors are integrated in an indentical manner by the neural controllers for ST and NST.
Rapid effects of insulin on uridine metabolism in mammary gland explants
Authors: Rillema JA
Published: December 2017

A study was made of the early actions of insulin on uridine metabolism in mammary glang explants. A stimulation of both labeled uridine uptake and its incorporation into RNA was demonstrated as early as 15 min after addition of insulin to medium bathing the tissue; these effects persisted for several hours. The metabolic fate of [3-H] uridine to UMP, UDP, and UTP was observed, whereas insulin had no effect on the quantity of 3-H present as uridine or uracil in these tissues. Further studies were performed in which insulin was also shown to have a rapid stimulatory effect on the incorporation of [32-P] phosphate into RNA; however, the uptake of the labeled phosphate was not affected by insulin. Experiments were also carried out to determine whether the effects of insulin on labeled uridine uptake require ongoing RNA and protein synthesis and whether uridine incorporation depends on concomitant protein synthesis. Incubation of explants with antibiotics which inhibit protein synthesis resulted in the complete suppression of the effects of insulin on labeled uridine uptake and its incorporation into RNA. In contrast, the effect of insulin on labeled uridine uptake does not appear to require ongoing RNA synthesis, since this effect persisted when RNA synthesis was significantly reduced by the presence of actinomycin D.
Effect of temperature on rate of CO2 uptake by human red cell suspensions
Authors: Holland RA , Forster RE
Published: December 2017

The time course of carbon dioxide uptake by oxygenated supensions of human red cells was followed using a CO2 electrode in a Hartridge-Roughton continuous-flow rapid-reaction apparatus. Measurements were made at several temperatures from 1i to 42 degrees C, with the initial PCO2 in the reacting mixture from 40 to 60 mmHg. The initial part of the uptake curve is presumably rate limited by the intracellular hydration of CO2 with reaction-velocity constants in cell water from 280 to 960 S-1 at 42 degrees C and an activation energy of 2.4 kcal mol-1. The later stages of CO2 uptake were much slower, with half-times from greater than 1.5 s at 12 degrees C to 0.7 s at 42 degrees C, and were presumably rate limited by the chloride-bicarbonate shift and H+ interchanges. The results indicate that despite the acceleration of the hydration reaction in cell water by a factor of 5,000 at 37 degrees C and 3,800 at 42 degrees C, the later part of the exchange is too slow to permit blood to come intoC02, equilibrium with actively exercising muscles during its passage through the capillary bed.
Responses to preoptic temperature manipulation in the awake and hibernating marmot
Authors: South FE , Hartner WC , Luecke RH
Published: December 2017

Responses of normothermic and hibernating marmots to manipulations of the preoptic-hypothalamic temperature (TPO) were studied. Independent variables included alteration of TPO and, during normothermia, room temperature. Hibernation occurred at an ambient of 6 degrees C. Dependent variables include brain, subdermal, and surface temperatures, heart rate, and behavioral, electromyographic cortical, and hippocampal responses. Although normothermic autumn marmots displayed most of the usual mammalian responses to alterations of the TPO, evidence of effective dermal vasomotion was not obtained. Single episodes of water drinking accompanied prolonged raising of the TPO; sleep was not elicited. During hibernation, effective central thermoregulation was not apparent until 3 or 4 days had elapsed. After this, thermoregulation was readily demonstrable in response to both raising and lowering the TPO. The apparent open-loop gains (OLG) for rise in body temperature after lowering of the TPO showed an exponential increase in value at lower prestimulus body temperatures. It was postulated that this could be explained on the basis of the recruitment of cold-sensitive neurones, which in turn would provide an explanation for the hypothesized "alarm temperature."
Renal secretion of [35-S]furosemide and depression by albumin binding
Authors: Bowman RH
Published: December 2017

It was determined by use of [35-S]furosemide and an ultrafiltration procedure that furosemide is bound extensively to bovine serum albumin. When 500 muM furosemide and albumin at a concentration of 2.5 g/100 ml were used, approximately 90% of the drug was bound. With this same amount of furosemide, but with 3 times as much albumin, binding was about 98%. Using a 25-fold lower concentration of furosemide, 20 muM, binding was nearly 98% with 2.5 g albumin/100 ml, and was over 98% with 7.5 g albumin/100 ml. These same concentrations of furosemide and albumin were used to investigate the excretory and secretory rates of [35-S]furosemide in the isolated perfused rat kidney. Tubular clearance (i.e., secretion) of [35-S]furosemide was inversely related to the concentration of albumin in the perfusate. In kidneys perfused without albumin, tubular clearance of the drug was 6-20 times that found when 2.5 or 7.5 g albumin/100 ml, respectively, was used. Probenecid, with or without albumin, reduced the clearance of furosemide to that of its filtration rate. It is concluded that at physiological albumin concentrations, a very small fraction of circulating furosemide will be available for filtration, and tubular-fluid and urinary furosemide will arise predominantly from secretion. Because of extensive binding of furosemide to albumin, the renal secretory process itself is depressed, and the rate of secretion will be dependent, in part, on the concentration of unbound drug.
A linked oscillator model of electrical activity of human small intestine
Authors: Brown BH , Duthie HL , Horn AR , Smallwood RH
Published: December 2017

The electrical slow-wave activity of the human small intestine has been simulated by a chain of 64 coupled electronic relaxation oscillators. The model simulates the frequency gradient of recorded patoentials in the human small intestine and when transected, behaves in a similar way to the transected canine small intestine. The model exhibits a spontaneous effect whereby several adjacent oscillators periodically are in the same state. This effect travels down the model in the time of 20-30 min.
Effects of elevated magnesium on discharge of myenteric neurons of cat small bowel
Authors: Wood JD
Published: December 2017

Electrical discharge of single units in myenteric ganglia of cat intestine was recorded extracellularly, and the effects on the electrical discharge of elevating the concentration of Mg++ in the Tyrode solution from 0.2 to 10.2 mM were determined. The ongoing discharge of 83% of the burst-type units was blocked by elevation of Mg++. The remainder of the burst-type units and all of the single-spike units tested continued to discharge in elevated Mg++. Frequency distribution histograms of interburst intervals of burst units that were unaffected by elevated Mg++ showed low variance of interburst interval, and multimodes on the histograms were multiples of the first mode. The variance of interburst intervals of burst-type neurons that were blocked by elevated Mg++ was greater than variance of the burst-type neurons that were unaffected by increased Mg++. If it is assumed that the action of elevated Mg++ is blockade of synaptic transmission, then the results indicated that the ongoing discharge of the neurons that were blocked by elevated Mg++ was dependent on synaptic input to the cell. The burst-type units that were unaffected by elevated Mg++ may be endogenous oscillators that do not receive synaptic input. The burst-type units that were blocked by elevated Mg++ may be driven by synaptic input from the burst-type oscillators.
Energy metabolism in kidney of heat-acclimated hamsters
Authors: Inbar I , Chayoth R , Cassuto Y
Published: December 2017

Biochemical pathways which are involved in energy metabolism were examined in the kidney of heat-acclimated hamsters. It was found that heat acclimation caused 47% reduction in glucose-6-phosphatase (G1c-6-Pase) activity and 40% lower rate of gluconeogenesis. No changes were found in the activity of hexokinase, glucose-6-phosphate dehydrogenase, pyruvate kinase, lactic dehydrogenase, or in kidney glycogen content. Isolated kidney mitochondria of heat-acclimated hamsters utilized 15% less oxygen than that of controls, but no differences were found in the P/O ratio. Determination of the content of some cytochromes showed a significant reduction in cytochromes c + c1, but no difference was found in the content of cytochromes a, a3, and b. These results suggest that the kidney plays a role in the reduction of energy metabolism during the process of heat acclimation.
Net calcium fluxes in anterior byssus retractor muscle with phasic and catch contraction
Authors: Bloomquist E , Curtis BA
Published: December 2017

Calcium in the artificial seawater bathing whole Mytilus anterior byssus retractor muscles (ABRM) was measured by a specific Ca electrode under various conditions of activation, catch, and catch relaxation. Activation in response to ACh was associated with uptake of Ca by the muscles. Phasic contractions produced a small Ca uptake; catch contractions produced a larger and sustained Ca uptake. After tension relaxation, the muscle lost an amount of Ca roughly equal to that gained. Catch relaxation by 5-hydroxytryptamine (5HT) was associated with Ca release. ACh at identical concentrations, applied to the muscle for increasingly longer times, produced increasing amounts of Ca uptake. Regardless of the previous gain of Ca by the muscle, 5HT applied for a constant interval caused release of the same amount of Ca. A model for the Ca control system in ABRM based on this and previously obtained 45Ca efflux data is proposed.
Circadian rhythm of biliary excretion and its control mechanisms in rats with chronic biliary drainage
Authors: Ho KJ , Drummond JL
Published: December 2017

Rats with chronic biliary drainage under a rigid lighting schedule (light on at 6 A.M. and off at 6 P.M.) exhibited a remarkable circadian rhythm of bile flow, biliary concentrations and excretory rates of bile salts, cholesterol, and phospholipid. The peak was attained at midnight and nadir at noon except for the peak concentrations of cholesterol and phospholipid occurring at 8 P.M. Cholesterol feeding abolished the circadian rhythm of biliary cholesterol and phospholipid concentrations but not their excretory rates because the daily fluctuation of the bile flow remained unchanged. Bilateral vagotomy enhanced the bile flow rate and shifted the peak of circadian rhythm of all parameters except bile salt 4 h earlier. Bilateral adrenalectomy abolished the circadian variation of the concentration of cholesterol and phospholipid and minimized that of bile salt, but the daily fluctuation of their excretory rates persisted in a lower amplitude. The studies suggested that such circadian rhythm might be controlled simultaneously by multiple factors and could not be entirely abolished by any single special treatment.
An hepatic osmoreceptor mechanism in the rat: electrophysiological and behavioral studies
Authors: Adachi A , Niijima A , Jacobs HL
Published: December 2017

Rat liver was perfused with Ringer solution through the portal vein by use of a perfusion system which was designed to switch from standard Ringer solution to hypertonic or hypotonic Ringer solution. Neural responses to the osmotic change in the perfusion solutions were analyzed. They showed that two different types of osmosensitive afferent fibers exist in the hepatic vagus; one is characterized by increasing the frequency of spike discharges responding to higher osmotic pressure, while the other shows the same response to lower osmotic pressure. Behavioral changes caused by hepatic vagotomy were also observed. Though no differences could be detected in routine behavior (e.g., daily intakes of food and water, body-weight increase) between the vagotomized and the sham-operated rats, the former lost the ability to adjust urine concentration immediately in response to osmotic changes in the internal environment. These results provide evidence for the hypothesis that hepatic osmoreceptors exist in the rat.
Cellular hypertrophy and renal function during compensatory renal growth
Authors: Northrup TE , Malvin RL
Published: December 2017

Simultaneous measurements of biochemical and physiological events of compensatory renal hypertrophy were made in groups of white Spartan rats. Thirty hours following right unilateral nephrectomy, the left kidney had an increased rate of renal plasma flow, glomerular filtration rate, and potassium excretion when compared to sham-nephrectomized rats. Kidney cells were also hypertrophied as evidenced by an increase in the ratio of ribonucleic to deoxyribonucleic acid. The effects of a single injection of cycloheximide and actinomycin D on compensatory growth were studied. Both drugs prevented the rise in glomerular filtration rate and renal plasma flow 30 h postnephrectomy while having no inhibitory effect on cell hypertrophy. The maintenance of nephrectomized rats on a low-sodium diet also interfered with the physiological components of the response while having no effect on ribonucleic or deoxyribonucleic acid. These suggest that the physiological and biochemical aspects of compensatory renal hypertrophy may be under separate control systems.
Renin response and angiotensinogen control during graded hemorrhage and shock in the dog
Authors: Beaty O , Sloop CH , Schmid HE  , Buckalew VM
Published: December 2017

Hemorrhage and hemorrhagic hypotension have been shown to be potent stimulators of renin release. However, the relationship between angiotensinogen consumption and angiotensinogen production has yet to be completely defined during this type of circulatory stress. Peripheral renin activity increased progressively as the blood pressure was decreased stepwise by hemorrhage to 50 mmHg and remained elevated throughout the shock phase of the experiment. Angiotensinogen did not change from control (809 ng/ml) throughout hemorrhabic hypotension and shock. During hemorrhagic hypotension, with the infusion of the angiotensin antagonist, [1-sarcosine, 8-alanine]angiotensin II, angiotensinogen concentration fell progressively from 693 to 208 ng/ml at 50 mmHg. Intravenous angiotensin II infused continuously after the mean blood pressure reached 50 mmHg significantly elevated plasma angiotensinogen concentration. In conclusion, during hemorrhagic hypotension and shock, the kidney and the liver appeared capable of maintaining elevated plasma renin activity and adequate plasma renin substrate, angiotensinogen, respectively. The mechanism responsible for the maintenance of plasma angiotensinogen is suggested to involve a positive-feedback effect of angiotensin II on the liver.
Saturation kinetics of sodium efflux across isolated frog skin
Authors: Biber TU , Mullen TL
Published: December 2017

Measurement of Na efflux across the frog skin epithelium from the serosal side to the outside (JNa 3 leads to 1) in a new chamber specifically designed to avoid edge damage shows that JNa 3 leads to 1 exhibits saturation kinetics with a maximal efflux (Jmax) of 31.8 nmol/cm2 per h and an apparent KNa of 4.0 mM. In contrast, JNa 3 leads to 1 measured in conventional chambers and efflux determinations in the new chamber of substances that pass the epithelium via extracellular pathways (polyethylene glycol 900, sucrose, mannitol) exhibit a linear relationship between the efflux of the substance in question and its concentration in the bath. In addition, changes in external Na concentration do not cause substantial changes in JNa 3 leads to 1. The saturation remains but both Jmax and KNa increase after application of ouabain. Amiloride, as well as dinitrophenol, eliminates the saturation and JNa 3 leads to 1 becomes a linear function of Na concentration. The separate effects of ouabain and amiloride suggest that these two inhibitors which are known to affect two distinctly different steps in the active transport pathway act also on two separate steps of JNa 3 leads to 1: the passage across the inward- (serosal) and outward-facing (apical) cell membranes of the epithelial cells, respectively. The action of dinitrophenol indicates the involvement of metabolism in JNa 3 leads to 1 probably at the latter of the two steps. The results suggest strongly that JNa 3 leads to 1 proceeds not via a paracellular but via a transcellular pathway that interacts with the active transport pathway.