bluuebunny/crossref_metadata_2025 huggingface dataset:
Forced activity alters sleep cycle periodicity and dorsal raphe discharge rhythm
Authors: Lydic R. , McCarley R. W. , Hobson J. A.
Published: December 2017

Single-cell activity recorded from the brain stem dorsal raphe nucleus (DRN) of cats showed a regular firing pattern during wakefulness (2–3 spikes/s), decreased activity during slow-wave or synchronized sleep (1 spike/s), and cessation of regular discharge during desynchronized sleep (0.05 spikes/s). DRN discharge was negatively correlated with the onset and maintenance of the polycyclic desynchronized sleep rhythm. These findings were derived from analyses of DRN firing rate sampled during different behavioral states. The present time-course analyses of DRN discharge described for the first time the period, amplitude, and phase characteristics of DRN activity relative to the timing of behavioral states that comprise the complete sleep cycle. The time course of both DRN discharge and the occurrence of wakefulness, slow-wave (S) sleep, transition, and desynchronized (D) sleep were behaviorally manipulated. Forced locomotor activity imposed by a treadmill task shortened the period length of the sleep cycle and the duration of the DRN discharge cycle. The magnitude and direction of these shifts in period length were consistent across multiple sleep cycles, and there was a high degree of coherence between the period length of the sleep cycle and the DRN discharge profiles. The DRN discharge rate also displayed phase dependence within S and D sleep. These results support the hypothesis that the DRN has a physiological role in regulating the timing of the ultradian sleep cycle.
Angiotensin-estrogen interaction in female brain reduces drinking and pressor responses
Authors: Jonklaas J. , Buggy J.
Published: December 2017

Water intake fluctuates over the estrous cycle in rats, with daily intake lowest on the day of estrus. Since estrogen levels are highest preceding estrus and since the brain integrates thirst behavior, a possible central action of estrogen on fluid regulatory mechanisms was investigated in adult male and ovariectomized female rats. Ad libitum drinking was not changed the day of intracerebroventricular injection of estradiol benzoate (EB) but was significantly depressed the following day in females only. Drinking induced by intracerebroventricular angiotensin but not carbachol or cellular dehydration was also depressed in females the day after central EB treatment; again, no change occurred in males. To determine whether central EB depressed other centrally mediated responses to angiotensin, pressor responses to intracerebroventricular injections of angiotensin, carbachol, and hypertonic NaCl were also assessed. Only angiotensin-induced pressor responses in females were attenuated by central EB treatment, with a time course similar to that observed for the depression of drinking. We conclude that central regulatory responses to angiotensin are modulated by estrogen in female but not male brains.
Age-dependent renal effects of intrarenal dopamine infusion
Authors: Pelayo J. C. , Fildes R. D. , Jose P. A.
Published: December 2017

Three groups of anesthetized puppies 16.4 +/- 1.2 (group I), 29.6 +/- 1.6 (group II), and 49.8 +/- 2.5 (group III) days of age were used to assess the renal response to graded doses of dopamine infusion into the renal artery. Dopamine infusion at 1 microgram X kg-1 X min-1 increased renal blood flow (RBF) from 3.61 +/- 0.31 to 4.22 +/- 0.43 ml X min-1 X g kidney wet wt-1 (P less than 0.05) only in the older puppies (group III). Glomerular filtration rate (GFR) increased in groups II and III from control values of 0.69 +/- 0.14 and 0.61 +/- 0.08 to 1.08 +/- 0.19 and 0.83 +/- 0.05 ml X min-1 X g kidney wet wt-1, respectively (P less than 0.05). However, urinary flow rate and sodium excretion were variably affected. Because dopamine is known to stimulate both alpha- and beta-adrenoceptors in addition to dopamine receptors, two additional groups of puppies 11.2 +/- 1.2 (group IV) and 72.8 +/- 2.4 (group V) days of age were studied to evaluate the renal effects of dopamine during the continuous intrarenal infusion of phentolamine and nadolol (an alpha- and a beta-adrenergic blocker, respectively). Dopamine elicited increases in RBF only in the older puppies (P less than 0.05). GFR, urinary flow rate, and sodium excretion increased in both groups; however, the magnitude of the change was greater for each parameter in the older group (P less than 0.05). These experiments suggest a maturational process for specific dopamine receptors and/or effector response, which may affect the observed age-dependent increases in RBF, GFR, and renal sodium handling.
Heterogeneity of the plasma iron pool: explanation of the Fletcher-Huehns phenomenon
Authors: Huebers H. A. , Huebers E. , Csiba E. , Finch C. A.
Published: December 2017

Observations on iron uptake by reticulocytes led Fletcher and Huehns to suggest differences in the behavior of the two iron-binding sites of the transferrin molecule. To clarify the continued controversy relating to this hypothesis, the original studies employing control plasma labeled with radioiron and the same plasma preincubated with reticulocytes were reexamined. Regardless of whether human or rabbit plasma was employed, there was a considerably higher uptake from the control plasma. Isoelectric focusing procedures and electrophoresis in urea gels revealed that the conspicuous difference in the amount of iron uptake is the result of differences in the proportion of di- to monoferric transferrin in the two plasmas and the competitive advantage of the diferric moiety. These studies provide an explanation for the Fletcher-Huehns phenomenon without invoking functional differences between the two sites for iron on the transferrin molecule.
Parathyroid hormone effect on chicken renal brush-border membrane phosphate transport
Authors: Renfro J. L. , Clark N. B.
Published: December 2017

Renal clearance studies showed that parathyroidectomy (PTX) stimulated renal PO4 reabsorption within 90 min in 3-wk-old chicks. Subsequent parathyroid hormone (PTH) infusion caused net PO4 secretion. Kidneys were taken for brush-border membrane (BBM) preparations 3 h after PTX or sham operations and 1 h after PTH or saline injections, thus yielding four categories of PTH status: PTX/saline, sham/saline, PTX/PTH, and sham/PTH. Efficacy of PTX and PTH was confirmed by examination of serum Ca concentrations. A 100 mM NaSCN gradient, out greater than in, caused concentrative PO4 uptake by BBM from sham/saline animals. Concentrative uptake was not produced by 100 mM KSCN, out greater than in; pH 7.4in vs. pH 5.4out; or 100 mM NaC1, out = in. Removal of endogenous PTH (PTX/saline) significantly stimulated Na-dependent PO4 uptake compared with sham/saline. PTH infusion significantly depressed Na-dependent PO4 uptake in PTX/PTH and sham/PTH groups compared with sham/saline and PTX/saline. Na-dependent, concentrative glucose uptake was present and unchanged by PTH. Kinetic analysis, based on 5-s uptakes, showed that both apparent affinity and maximal velocity (Vmax) for Na-dependent PO4 transport were decreased by PTH treatment. The data suggest that PTH influences avian renal PO4 excretion at least in part through a Na-dependent PO4 transport system in proximal tubule BBM.
Effects of fasting and restricted refeeding on utilization of ingested energy in rats
Authors: Hill J. O. , Fried S. K. , DiGirolamo M.
Published: December 2017

Ingested metabolizable energy was partitioned into 3 components--storage, cost of storage, and maintenance--to study energy utilization during 20 days of refeeding following a 3-day fast in adult male Wistar rats. During the refeeding period, one experimental group was refed ad libitum, whereas two others were restricted to approximately 75 and 50%, respectively, of prefast food intake. Energy utilization in the experimental groups was compared with that in nonfasted controls. Energy conservation occurred in all experimental groups during refeeding, and the primary form of that conservation was a decrease in the energy required for maintenance. The decreased requirement for maintenance allowed a greater proportion of ingested energy to be used for restoration of carcass energy. The degree of energy conservation was, in general, proportional to the degree of food restriction during refeeding.
Specific depletion of body fat in parabiotic partners of tube-fed obese rats
Authors: Harris R. B. , Martin R. J.
Published: December 2017

One member in each of 15 parabiosed pairs of rats was fed twice its normal food intake as four tube-fed meals per day. Seven other pairs ate ad libitum. Partners of overfed rats ate approximately 90% of the intake of individual members of ad libitum pairs. After 46 days of overfeeding, blood samples were taken and the rats were killed for carcass analysis. Tube-fed parabiotic rats had gained a considerable amount of fat and some protein. Their partners had a normal lean body mass but very little fat. Serum corticosterone, reverse triiodothyronine, free fatty acids, and beta-hydroxybutyrate were the same in all parabionts. Serum triiodothyronine and insulin were increased and growth hormone was decreased in obese rats. Serum thyroxine and triiodothyronine were increased and glucose was decreased in their parabiotic partners. The results are discussed as evidence for a humoral factor that crossed the parabiotic union and acted as a "lipid-depleting" agent in the partners of overfed rats.
Modeling the action of zeitgebers on the human circadian system: comparisons of simulations and data
Authors: Gander P. H. , Kronauer R. E. , Czeisler C. A. , Moore-Ede M. C.
Published: December 2017

In our two-oscillator model for the human circadian timing system, the effect of an environmental synchronizing cycle (zeitgeber) is determined by the periods of the two oscillators and of the zeitgeber and by the zeitgeber strength. The oscillators x and y are postulated to regulate the core temperature and rest-activity rhythms, respectively. From published examples of experiments in which human subjects were exposed to artificial zeitgebers, it is possible to derive estimates of the periods of the core temperature and/or the rest-activity rhythms and the zeitgeber. Two strengths of zeitgeber input to the model that correspond to two of the common zeitgeber regimes used in human entrainment studies have now been elucidated. Thus specific model simulations can be generated for each of the available examples of entrainment of human subjects by artificial zeitgebers. Such simulations indicate that the model can reproduce, with remarkable subtlety, the types of full and partial entrainment observed experimentally. The model is thus demonstrated to accommodate the period and phase control of endogenous rhythms by environmental zeitgebers, which is a crucial functional attribute of circadian timing systems.
Regulation of fetal placental blood flow in the lamb
Authors: Anderson D. F. , Faber J. J.
Published: December 2017

Inflatable occluders were placed on the distal aorta of 11 fetal lambs. After 1 wk of control measurements, fetal placental blood flow was reduced to about two-thirds of its control value for an average period of 2 wk. No allowance was made for fetal growth. During the period of flow restriction, fetal growth was 2%/day. Femoral arterial blood pressure was reduced from a control value of 41 to 27 mmHg (P less than 0.001). There was an insignificant increase in carotid arterial blood pressure from 48 to 50 mmHg. Placental resistance to flow did not decrease more than could be accounted for by the increase in gestational age in the course of the experiment. It is concluded that fetal placental blood flow is not under feedback control, since neither of the determinants of flow (i.e., driving pressure and resistance) responded to its chronic reduction.
Participation of central alpha-receptors on hemodynamic response to E. coli endotoxin
Authors: Koyama S.
Published: December 2017

The time course of changes in mean blood pressure (MBP), heart rate (HR), and renal blood flow (RBF) in a control group of anesthetized dogs given only endotoxin (1 mg/kg iv) was compared with groups pretreated with alpha-antagonists either intravenously or intracisternally (ic). The decreases in MBP and RBF in the control group were abolished by intracisternal prazosin (0.1 mg/kg ic). MBP response to endotoxin after intravenous prazosin did not differ from that of the control group; however, the endotoxin-induced decrease in RBF after intravenous prazosin was significantly greater than that in the control group. HR responses to endotoxin were not altered by either intracisternal or intravenous prazosin. MBP and RBF responses to endotoxin after intravenous or intracisternal yohimbine (0.5 mg/kg iv or ic) did not differ from the control responses. However, significant differences occurred in the time course of changes in HR only when yohimbine was administered intracisternally. These observations suggest that the hypotensive effect and reduction of RBF due to endotoxin may be mediated by alpha 1-adrenoceptors at least in the central nervous system and that of HR response may be mediated alpha 2-adrenoceptors.
Calculation of brain elastic parameters in vivo
Authors: Walsh E. K. , Schettini A.
Published: December 2017

In an earlier study [Am. J. Physiol. 232 (Regulatory Integrative Comp. Physiol. 1): R27-R30, 1977], we defined the concept of brain elastic response in vivo as measured by a pressure-depth ratio (G0) derived from a graphic analysis of the elastic response tests. These tests have shown that brain elastic response in vivo is sensitive to changes in the intracranial system and that the response is nonlinear. In this study we identify a second parameter, G0, a second-order pressure-depth ratio that characterizes the nonlinear behavior and, along with G0, can be evaluated from a mathematical relation that models the experimental results obtained from the elastic response test. The equation is a logarithmic function relating the pressure and the subpial insertion depth. From this we obtain G0 and G0 as the slope and curvature of the response function at the subpial position. In animal experiments we correlated the changes in these parameters with those of cerebral hemodynamics during hemorrhagic and drug-induced hypotension. The calculated values of G0 and G0 are reproducible and reflect changes in cerebral blood flow and/or volume.
Relationships between aerobic and anaerobic energy production in turtle brain in situ
Authors: Lutz P. L. , McMahon P. , Rosenthal M. , Sick T. J.
Published: December 2017

To define the relationships between brain mitochondrial activity and high-energy intermediates in the turtle, brains were frozen in situ at times determined by the reduction-oxidation status of cytochrome a,a3. Increases in brain lactate indicated that transition to anaerobiosis occurred while oxidative reactions were still ongoing during hypoxia and that the signal for anaerobiosis is not the complete failure of mitochondrial electron transfer. Decreases in creatine phosphate (CrP), ATP, ADP, and AMP demonstrate that their consumption exceeded production during hypoxia. CrP decreased further during the following 120 min of anoxia, but ATP, ADP, and AMP were not significantly altered from control values.

These data suggest that ATP is not inhibitory to rate-limiting, key glycolytic enzymes such as phosphofructokinase. Calculations indicate that ATP production declined during anoxia. This study indicates that decreased CrP values, decreased ATP production, and high lactate levels do not preclude ion homeostasis and electrical activity of turtle brain and that this brain is protected against lactate or pH damage during anoxia, in contrast to mammalian brain.
Blood pressure control in pregnant rabbits: norepinephrine and prostaglandin interactions
Authors: Venuto R. , Min I. , Barone P. , Donker A. , Cunningham E.
Published: December 2017

The relationship between norepinephrine (NE) and prostaglandins in the regulation of systemic blood pressure during pregnancy was examined in conscious rabbits. The arterial prostaglandin E2 (PGE2) concentration was higher in pregnant than in nonpregnant rabbits. Resting blood pressure was slightly lower in the gravid animals. The pressor response to incremental doses of intravenous NE was blunted in the pregnant rabbits. Meclofenamate, a cyclooxygenase inhibitor, failed to alter the resting blood pressure in either group of animals, although it reduced PGE2 levels more than 60% in the pregnant rabbits. The pressor response to NE was significantly increased only in the pregnant rabbits when the NE infusion was repeated following meclofenamate. Pregnant rabbits could also be differentiated from nonpregnant by their higher peripheral blood levels of NE and their uniform hypotensive response to alpha-adrenergic blockade. These observations define an altered responsiveness to both endogenous and exogenous NE in pregnant rabbits that appears to be related to an increase in vasodilator prostaglandins.
Oxygen consumption and oxidative capacity of muscles from young obese and nonobese Zucker rats
Authors: Wardlaw G. M. , Kaplan M. L.
Published: December 2017

The contribution of muscle tissue to the increased metabolic efficiency of the obese (fa/fa) Zucker rat at 6 wk of age was examined. In vitro O2 consumption was similar in obese and nonobese soleus and extensor digitorum longus (EDL) muscles, whether the animals were fed ad libitum, fasted, or treated with triiodothyronine. No phenotypic difference in the in vitro O2 consumption was seen when the muscles were preincubated with or without exogenous insulin. Pyruvate kinase, citrate synthase, succinate dehydrogenase, and cytochrome oxidase activities were similar in the soleus and the EDL muscles of both phenotypes. Phosphofructokinase and lactate dehydrogenase activities were higher in the soleus muscles from the obese rats, whereas hexokinase activities were higher in the EDL muscles from the nonobese rats. Mitochondrial and whole muscle homogenate respiration rates were similar in both phenotypes. The soleus and EDL muscles from the obese animals weighed less than those from the nonobese, but empty carcass weights were similar. Taken together these data suggest that muscle mass, muscle O2 consumption, and muscle oxidative capacity are similar in 6-wk-old obese and nonobese rats. Therefore other tissues are probably responsible for the increased metabolic efficiency of the young obese rat.
Cardiovascular neurons of brain stem with projections to spinal cord
Authors: Brown D. L. , Guyenet P. G.
Published: December 2017

In urethan-anesthetized rats a portion of the rostral ventrolateral medulla, the intermediate portion of the nucleus paragigantocellularis lateralis, was explored electrophysiologically for spinally projecting cardiovascular neurons. Spinal projections were demonstrated for 48 of 300 units tested for antidromic activation following spinal cord stimulation. The cardiovascular nature of units was tested by monitoring unit activity during transient changes in arterial pressure. A total of 47 cardiovascular neurons were identified; of these, 43 showed activities inversely correlated with arterial pressure and changes in activity closely coupled in time to arterial pressure changes. At high arterial pressures these neurons also displayed activities phasically linked to the cardiac cycle. Of these 43 neurons, 13 projected to or through the thoracic cord and 5 to or through the cervical cord. Axonal conduction velocities averaged 4.7 m/s. A second type of cardiovascular neuron (4 units of 47) was found that increased activity as arterial pressure increased. Three of these neurons projected to the cord. These results provide evidence for tonically active, baroreceptor-inhibited neurons with axonal projections to the thoracic spinal cord.
Subfornical organ stimulation excites paraventricular neurons projecting to dorsal medulla
Authors: Ferguson A. V. , Day T. A. , Renaud L. P.
Published: December 2017

Electrical stimulation in the subfornical organ (SFO) of pentobarbital-anesthetized Sprague-Dawley rats was noted to influence the excitability of paraventricular nucleus (PVN) neurons antidromically identified as projecting to the dorsomedial medulla. Extracellular recordings indicated that 60% (n = 34) of these caudally projecting PVN neurons increased activity in response to single shock stimuli delivered to the SFO. Short-latency [30.0 +/- 2.7 (SE) ms] and long-latency (162.5 +/- 32.5 ms) responses were observed. The remaining neurons were either unaffected (38%) or inhibited (2%) by SFO stimulation. These data suggest functional connectivity between the SFO and the dorsomedial medulla. It is proposed that such a pathway may mediate pressor responses observed to follow electrical stimulation in the SFO.
Dietary obesity and neonatal sympathectomy. I. Effects on body composition and brown adipose
Authors: Levin B. E. , Triscari J. , Marquet E. , Sullivan A. C.
Published: December 2017

The effect of neonatal sympathectomy with guanethidine (50 mg/kg for 3 wk) on the development of diet-induced obesity (DIO) was assessed by raising guanethidine-(G) or saline-treated (S) Sprague-Dawley rats in small litters (4-5 pups/dam) and feeding a high-calorie diet from weaning (n = 29–30) or by raising similarly treated rats in normal litters (10 pups/dam) and feeding chow from weaning (n = 29–30). Sympathectomy depleted norepinephrine (NE) levels 65–98% in all organs except the adrenals and brain but had no statistically significant effect on weight gain, food intake, food efficiency, body composition, plasma glycerol, insulin, or glucose, or on basal rectal temperatures in either diet group; there was a tendency toward increased adiposity in sympathectomized rats. Despite 95–98% depletion of NE in interscapular brown adipose tissue (IBAT), sympathectomy affected only the percentage of multilocular cells that was decreased 46-69%. Rats from small litters in both treatment groups (S and G) became obese without increased food intake (increased food efficiency), had heavier IBAT pads with bigger cells and more lipid, and were also hyperlipidemic, hyperinsulinemic, and hyperglycemic compared with controls. Therefore neonatal sympathectomy was not as significant in the subsequent development of DIO as were diet and litter size.
Striatal neuronal responses to scrotal temperature changes and dopaminergic drugs
Authors: Lin M. T. , Tsay B. L.
Published: December 2017

Seventy-nine units in the striatal region were examined in 48 urethan-anesthetized rats. When these units were classified by their thermal responsiveness, proportions of the cold-responsive, warm-responsive, and thermally unresponsive units were 25.4, 35.4, and 39.2%, respectively, of the total units tested. Either microiontophoretically or systemically administered apomorphine (a dopamine agonist) and haloperidol (a dopamine antagonist) affected (inhibited and/or excited) most (86.5-100%) cold-responsive units. In contrast, only a small percentage of the warm-responsive (28.6-43.8%) or thermally unresponsive (0-19.2%) units were affected by both apomorphine and and haloperidol. Furthermore it was found that most (73-100%) cold-responsive units were inhibited by apomorphine but excited by haloperidol; the inhibitory responses of the unit activity induced by apomorphine were antagonized by haloperidol. The reciprocal relationships between apomorphine and haloperidol were not observed in most warm-responsive (76.2-85.7%) or thermally unresponsive (80.8-100%) units. The data demonstrate that many striatal neurons are influenced by thermal afferent activation in the scrotum. The results also provide a neuronal basis for the hypothesis that the dopaminergic receptors located in the cold-responsive neurons of the striatum have effects on metabolic heat production in rats.
Central pathways relaying cardiovascular afferent information to amygdala
Authors: Cechetto D. F. , Calaresu F. R.
Published: December 2017

It has been suggested that cardiovascular information to the amygdala is relayed through the paraventricular nucleus of the hypothalamus (PVH) and the parabrachial nucleus (PB;7). To test this possibility spontaneously firing units in the amygdala of 12 chloralose-anesthetized cats were monitored for changes in firing frequency during electrical stimulation of PVH and PB and for their responsiveness to baroreceptor (BA) and chemoreceptor (CA) activation. In the ipsilateral amygdala 27 of 140 units responded to PVH stimulation, 9 of which also responded to CA and none to BA, whereas 46 of 150 units responded to PB stimulation, 11 of which also responded to CA and 2 to BA. To demonstrate the relative contribution of the PVH and PB in relaying cardiovascular information to the amygdala, in an additional six cats, the effect of neuronal block and lesions of these two nuclei on potentials evoked in the amygdala by stimulation of the buffer nerves was tested. Reversible neuronal block with injections of procaine in the PB significantly attenuated these evoked potentials. Electrolytic and chemical (kainic acid) lesions in the same PB sites also were effective in attenuating the responses. The potentials were unaltered by injection of procaine in the PVH. These results indicate that the PB is a site of relay of chemoreceptor and of some baroreceptor information from the medulla to the amygdala.
[14C]deoxyglucose incorporation into rat brain regions during hypothalamic or peripheral thermal stimulation
Authors: Morimoto A. , Murakami N.
Published: December 2017

The central nervous structures involved in thermoregulatory responses induced by hypothalamic or peripheral thermal stimulation were investigated in conscious rats by means of the 2-deoxy-D-[14C]glucose ([14C]-DG) autoradiographic technique. According to autoradiographs, many brain regions with significant increases or decreases in [14C]-DG incorporation were observed during thermoregulatory responses. Based on the present changes in [14C]-DG incorporation of brain regions obtained from two kinds of thermal stimulation, the following conclusions were drawn. 1) The medial preoptic area and the medial forebrain bundle are common sites for development of thermoregulatory responses being activated during cooling and warming. 2) The anterior hypothalamic area is activated during hypothalamic or peripheral warming and not during cooling. 3) The ventromedial hypothalamus, dorsomedial thalamus, caudate-putamen, globus pallidus, pars compacta of the substantia nigra, red nucleus, and the midbrain reticular formation are activated with hypothalamic or peripheral cooling. 4) The lateral preoptic area, suprachiasmatic nucleus, ventroposteromedial thalamus, pars reticulata of the substantia nigra, and the hippocampus change their activities only during peripheral cooling and warming.
Cl- -HCO3- -stimulated ATPase in intestinal mucosa of Aplysia
Authors: Gerencser G. A. , Lee S. H.
Published: December 2017

The serosa negative transepithelial potential difference across Aplysia intestine is generated by a Na+-independent, active electrogenic Cl- absorptive mechanism. In an attempt to clarify the Cl- absorptive mechanism an anion-stimulated ATPase was prepared from plasma membranes from Aplysia enterocytes utilizing differential centrifugation and sucrose density gradient techniques. ATPase activity, which could be activated by either Cl- or HCO3-, was found in the plasma membrane fraction. Maximal anion-ATPase activity was achieved with either 25 mM Cl- or 25 mM HCO3-. The apparent Km for Cl- activation of the ATPase was 10.3 mM, whereas apparent Km for HCO3- was 9.7 mM. ATP was the most effective nucleotide substrate for both HCO3- and Cl- -ATPase activities, whereas optimum pH for both activities was 7.8. These enzyme activities were inhibited more than 30% by thioacyanate (10 mM). Acetazolamide and vanadate were also found to strongly inhibit both Cl- and HCO3- -ATPase activities, whereas 10 microM 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid, 1 mM furosemide, or 1 mM ouabain had little or no effect. These results are consistent with the hypothesis that the active Cl- transport mechanism in Aplysia intestine could be a Cl- -HCO3- -stimulated ATPase found in the enterocyte plasma membrane.
Capsaicin pretreatment attenuates suppression of food intake by cholecystokinin
Authors: Ritter R. C. , Ladenheim E. E.
Published: December 2017

Capsaicin, the pungent principal in red pepper, has been shown to damage small-diameter peptide-containing sensory neurons. Suppression of feeding by cholecystokinin octapeptide (CCK OP) was attenuated after systemic pretreatment with capsaicin. Capsaicin pretreatment did not attenuate suppression of food intake by intragastric preloads. Pretreatment of rats with microgram quantities of capsaicin injected into the fourth ventricle, near the sites of vagal afferent termination, also attenuated CCK OP-induced suppression of food intake. These results suggest that the satiety-inducing effects of CCK OP are mediated, at least in part, by capsaicin-sensitive afferent neurons.
Potassium ion homeostasis and mitochondrial redox status of turtle brain during and after ischemia
Authors: Sick T. J. , Chasnoff E. P. , Rosenthal M.
Published: December 2017

To account for the remarkable capacity of turtle brain to survive without oxygen, microelectrode recordings of extracellular potassium activity (K+o) were made in intact brains of normoxic pentobarbital-anesthetized turtles during and after ischemia. Changes in redox status of brain cytochrome a,a3 were recorded simultaneously by reflection spectrophotometry. Cytochrome a,a3 became fully reduced, and K+o rose at a slow rate for approximately 60 min during complete ischemia. When K+o reached 8-12 mM, an inflection point was observed after which K+o rapidly increased to levels above 30 mM. Full recovery of baseline K+o and cytochrome a,a3 redox state occurred only if brain blood flow was restored within 60 min. These data demonstrate that maintenance of ion homeostasis in turtle brain depends on blood flow and continued delivery of systemic substrates and that viability is threatened if ischemia is prolonged beyond 60 min.
Intracellular pH transients in rainbow trout tissues measured by dimethadione distribution
Authors: Milligan C. L. , Wood C. M.
Published: December 2017

Intracellular pH transients in response to PCO2 changes were measured in vitro with the weak acid dimethadione (DMO) in gas-equilibrated red blood cells and a perfused trunk preparation (white muscle) of the rainbow trout. Red cell intracellular pH (pHi) was also measured directly on cell lysates. At an extracellular pH (pHe) of 7.81 +/- 0.04, PCO2 = 2 Torr, red cell pHilysate averaged 7.40 +/- 0.02, and [DMO]i/[DMO]e averaged 0.37 +/- 0.02, corresponding to a mean pHiDMO of 7.39 +/- 0.02. Decreasing pHe to 7.53 +/- 0.04 by increasing PCO2 to 8 Torr caused [DMO]i/[DMO]e to increase to 0.50 +/- 0.03 and resulted in a decline in pHi to a mean of 7.19 +/- 0.03 as measured by both techniques. With both methods red cell pHi responded rapidly (less than 5 min) to the PCO2 change, paralleling the response of pHe. In the isolated perfused trunk preparation at a perfusate pHe of 7.79 +/- 0.04 and PCO2 of 2 Torr, [DMO]i/[DMO]e averaged 0.38 +/- 0.03, yielding an average white muscle pHi of 7.35 +/- 0.04. Decreasing pHe to 7.34 +/- 0.02 by elevating PCO2 to 15 Torr caused pHi to drop to a mean of 7.11 +/- 0.03, as indicated by the significant increase in [DMO]i/[DMO]e to 0.58 +/- 0.03. The response of [DMO]i/[DMO]e was complete within 15 min. In both preparations the pHi changes were fully reversible. The DMO distribution method for measuring intracellular pH transients proved to be rapid and reliable in fish tissues.
A longitudinal study of cardiac output in unstressed pregnant guinea pigs
Authors: Myers S. A. , Tseng H. Y.
Published: December 2017

A previous study in pregnant guinea pigs failed to demonstrate any increase in cardiac output when a group of pregnant animals was compared with four nonpregnant animals. In the current study an increase in cardiac output of 35 +/- 14 (SE) ml/min, a 13% increase, was observed during an average 2-wk interval between 44 and 58 days of pregnancy (P less than 0.05, term 68 days, n = 8). A significant increase in placental blood flow of 14.8 +/- 6.2 ml/min (42% increase, P less than 0.05) was also observed during this interval without significant change in the percentage of cardiac output going to the uterus. The data on cardiac output and its distribution to the uteroplacental circulations are consistent with reports in other mammalian species; to accommodate the increased demands of the uteroplacental circulation, cardiac output increases as pregnancy advances. These data demonstrate that multiple observations in the same animal describe cardiac output and its distribution more accurately than a single observation.
Isolation and functional characterization of crustacean larval salt gland
Authors: Lowy R. J. , Conte F. P.
Published: December 2017

A batch method for isolating viable salt glands from the naupliar brine shrimp (Artemia salina) has been developed. This protocol produces a final preparation consisting of approximately 185 isolated salt glands, representing 1 X 10(4) secretory cells/g wet wt nauplii, with a final purity of 88%. Assays of cell integrity and function indicate good retention of in situ characteristics. Vital dye was excluded by 95% of the cells for at least 24 h. The O2 consumption rate was 22.7 nM O2 X min-1 X mg protein-1 and could be altered predictably by compounds known to affect oxidative phosphorylation and ion transport. The specific activity of the Na+-K+-ATPase in the salt gland, measured here for the first time, was 9.1 mM Pi X h-1 X mg protein-1. This is a substantial proportion of the body total, 17%, as expected for an active ion-transporting epithelium.
Accelerated functional recovery of isolated rat kidney with ATP-MgCl2 after warm ischemia
Authors: Sumpio B. E. , Chaudry I. H. , Clemens M. G. , Baue A. E.
Published: December 2017

Page R1047: B. E. Sumpio, I. H. Chaudry, M. G. Clemens, and A. E. Baue. “Accelerated functional recovery of isolated rat kidney with ATP-MgCl2 after warm ischemia.” Page R1048–R1049: Figs. 1–3–the inulin clearance units should read milliliters per minute.
Pineal gland influences period of circannual rhythms of ground squirrels
Authors: Zucker I.
Published: December 2017

Female golden-mantled ground squirrels were pinealectomized (Pinx) or Sham-Pinx at 70 days of age and maintained for more than 2 yr at 23 degrees C in a 10:14 light-dark photoperiod. Reproductive condition and body weight were recorded weekly and bi-weekly, respectively. Pinx and Sham-Pinx squirrels displayed circannual rhythms in body weight; the groups did not differ with respect to absolute magnitudes of annual peaks and troughs in body mass. The period of the circannual body weight cycle (measured peak to peak) was 27 and 58 days shorter in Pinx than in Sham-Pinx squirrels during the 1st and 2nd yr, respectively, after surgery. The onset of estrus during the second postoperative cycle occurred significantly earlier in Pinx than in Sham-Pinx squirrels. The pineal gland is not essential for the generation or expression of circannual or circadian cycles but may affect the period of some circannual rhythms.
Differential secretion and removal of multiple renin forms
Authors: Shier D. N. , Malvin R. L.
Published: December 2017

Hepatic clearance of renin in anesthetized dogs was measured during aortic constriction and after nephrectomy. Aortic constriction caused a transient increase in the hepatic extraction ratio for renin (ER) from 0.34 +/- 0.05 to 0.52 +/- 0.05, whereas nephrectomy caused the ER to decrease with time. Isoelectric focusing of plasma samples over an average pH gradient of 4.0-6.2 yielded several peaks of renin activity. Peaks focusing above pH 5.0 were combined and arbitrarily classified as basic renin, whereas peaks below pH 5.0 were classified as acidic renin. In each period the ER for basic renin was significantly greater than that for acidic renin. The proportion of basic renin was transiently increased at 10 min (59 +/- 4%) compared with control (41 +/- 4%). This contributed to the increased ER after constriction. The decreased ER after nephrectomy, however, was not solely due to differential removal of these forms. We conclude that hepatic clearance of renin is partly a function of the type of renin secreted by the kidney, which in turn may change with the duration of the secretory stimulus.
Spinal pathways mediating respiratory influences on sympathetic nerves
Authors: Connelly C. A. , Wurster R. D.
Published: December 2017

The location of spinal pathways mediating the respiratory modulation of sympathetic nerve activity was determined. Left inferior cardiac sympathetic, phrenic, and external intercostal (T1) nerve activities were recorded in 16 alpha-chloralose-anesthetized, vagotomized, paralyzed cats. Baroreceptor reflex activation of sympathetic activity was tested by bilateral carotid occlusion. Eight cats received C6-C7 level ventral spinal cord hemisections followed by cumulative lesions leading to total spinal cord transection. Eight other cats received C6-C7 level dorsolateral funiculus (DLF) lesions followed by dorsal spinal cord hemisection and subsequent spinal cord transection. The respiratory modulation of sympathetic activity was quantitatively assessed using respiration-triggered computer summation of sympathetic activity. Ventral hemisection had no significant effect on the respiratory modulation of sympathetic activity or bilateral carotid occlusion responses. In contrast, bilateral DLF lesions eliminated both the respiratory modulation and bilateral carotid occlusion responses. Unilateral disruption of DLF pathways ipsilateral to the recorded sympathetic nerve indicated spinal level decussations. Thus bilaterally descending DLF pathways with spinal level decussations mediate the respiratory modulation of sympathetic activity.
Annual and diurnal patterns of plasma calcium fractions in anuran Rana pipiens
Authors: Robertson D. R.
Published: December 2017

Ionized calcium [Ca2+] in the amphibian Rana pipiens was measured over 18 mo. An annual variation about the mean of 1.10 mmol/l was observed that peaked in April (1.36 mmol/l) and attained minimal levels in October (0.84 mmol/l). Plasma total calcium [Ca]t, plasma proteins, and the bound calcium fraction also exhibited annual oscillations. The annual mean binding capacity of plasma proteins for calcium was established at 0.0175 mmol/g. Of the plasma total calcium in spring animals, nonprotein-bound calcium complexes [Ca]c were less than 3% of the total whereas 80% was composed of [Ca2+] and 17% as protein-bound calcium [Ca]pb. In autumn [Ca2+] composed 40%, [Ca]pb 30%, and [Ca]c 30% of plasma total calcium. An equilibrium exists between [Ca2+] and [Ca]c, which maintains a combined annual mean of 1.48 mmol/l calcium. Diurnal variations superimposed on the annual cycles are modulated by apparent movement of plasma water and an intrinsic 12-h rhythm for [Ca2+]. No definite associations could be made with the entrainment of specific rhythms of the three calcium fractions with the light-dark cycle.
Mode of action of somatostatin to inhibit secretion by shark rectal gland
Authors: Silva P. , Stoff J. S. , Leone D. R. , Epstein F. H.
Published: December 2017

The rectal gland of the spiny dogfish Squalus acanthias is stimulated to secrete chloride by vasoactive intestinal peptide (VIP) in a way that is inhibited by somatostatin. The mechanism of inhibition by somatostatin was studied in isolated perfused rectal glands and separated rectal gland cells. Somatostatin did not alter the specific binding of VIP to rectal gland cells but inhibited their accumulation of adenosine 3',5'-cyclic monophosphate (cAMP) in response to VIP. In isolated perfused glands, somatostatin inhibited the stimulation of secretion produced by VIP, adenosine, and forskolin, as well as by dibutyryl cAMP plus a phosphodiesterase inhibitor. The results support the hypothesis of both a proximal and a distal locus, in the cascade of events leading from adenylate cyclase activation to cellular response, at which somatostatin exerts an inhibitory effect.
Neurohumoral stimulation of lipogenesis during altered states of energy balance
Authors: Melnyk R. B. , Hallonquist J. D. , Martin J. M.
Published: December 2017

Acid extracts of bovine hypothalamus stimulate lipogenic activity in adipose tissue. We employed a rat fat cell bioassay system to determine whether tissue concentrations of the active material vary as a function of spontaneous alterations in energy balance in hibernators and/or the obesity resulting from bilateral electrolytic lesions of the ventromedial area of the hypothalamus in rats. When hypothalamic extracts and partially purified plasma were fractionated using reverse-phase high-pressure liquid chromatography, both the void volume and material eluting 17 min after the start of a 25-min linear methanol gradient enhanced glucose incorporation into total lipid. Activities eluting with these two fractions were positively correlated with one another and were independent of insulin. The results indicate that a hypothalamic lipogenic factor (LHF) is detectable in plasma, that hypothalamic and circulating LHF concentrations vary in a reciprocal manner, and that elevations in plasma LHF concentration are associated with insulin resistance. The data suggest that the central regulation of lipogenesis is at least partially mediated by a hypothalamic humoral factor reaching fat depots via the circulation.
Selective efferent chemical sympathectomy of rat kidneys
Authors: LeNoble L. M. , Lappe R. W. , Brody M. J. , Struyker Boudier H. A. , Smits J. F.
Published: December 2017

Surgical denervation of kidneys results in interruption of both afferent and efferent renal nerves. We attempted selective efferent renal denervation in rats by slow infusions of 6-hydroxydopamine (6-OHDA) into the right renal artery. Integrity of efferent renal nerves was assessed by chemical and physiological methods and by measuring responses of mean arterial blood pressure (MAP) and heart rate (HR) to intrarenal (ir) infusion of bradykinin in conscious rats. Results were compared with those in surgically denervated and ir saline-infused rats. Surgical denervation of left kidney reduced renal norepinephrine (NE) to 58 and 14% of control levels at 1 and 7 days, respectively, after surgery. Increase in left renal resistance during posterior hypothalamus (PH) stimulation was only 70 +/- 28% (n = 5) compared with 289 +/- 69% (n = 6) in control animals. Response in opposite kidney was unchanged. Although 0.1 mg 6-OHDA ir caused considerable reduction of NE levels in both kidneys, responses to PH stimulation were unchanged. 6-OHDA (1 mg) reduced NE levels in infused and control kidney and atria. Functional evidence for denervation was only obtained in the kidney infused with 6-OHDA. Responses of MAP and HR to ir bradykinin were unchanged 7 days after 1 mg 6-OHDA. The data suggest that ir 6-OHDA results in functional efferent sympathectomy without affecting afferent renal nerves.
Use of dP/dt and rise time to estimate speed of shortening in muscle
Authors: Stevens E. D. , Renaud J. M.
Published: December 2017

We examined the relationship between the maximum speed of shortening at zero load (Vmax) and two variables occasionally used to estimate Vmax: maximal rate of change of force during an isometric tetanic contraction [(dP/dt)max] and reciprocal of one-half rise time (RHRT), the time to achieve one-half the maximal force during an isometric tetanic contraction. The relationship was examined in two experiments on isolated toad sartorius muscle: the effect of temperature and the effect of changing pHe (extracellular pH) to test the hypotheses that (dP/dt)max or RHRT can be used to estimate the magnitude of the effect of experimental variables on Vmax. In the temperature experiment both (dP/dt)max and RHRT could be used to estimate changes in Vmax. The effect of pH on Vmax was markedly overestimated by (dP/dt)max, but there was no significant difference between the magnitude of the changes in Vmax and RHRT. Our results, taken with the results of others, suggest that it is inappropriate to assume that the magnitude of the effect of a particular experimental protocol on Vmax can necessarily be predicted by measuring (dP/dt)max or RHRT.
Pressor action and dipsogenicity induced by angiotensin II and III in rats
Authors: Wright J. W. , Morseth S. L. , Abhold R. H. , Harding J. W.
Published: December 2017

The primary brain sites responsible for angiotensin-induced pressor action and dipsogenicity in the laboratory rat appear to be located in forebrain circumventricular organs (CVO). Because CVOs have a reduced blood-brain barrier, intracarotid infusion of angiotensin via a brachial arterial catheter results in direct stimulation of these sites. This investigation determined that brachial arterial infusion of angiotensin II (ANG II) into alert free-moving rats resulted in pressor and dipsogenic responses greater than those observed with equivalent doses of angiotensin III (ANG III). However, intracerebroventricular (ICV) injections of ANG II and ANG III yielded equivalent pressor and drinking responses. ICV pretreatment with the specific angiotensin receptor antagonist [Sar1, Ile8]-ANG II significantly reduced ANG II- and ANG III-induced pressor and drinking responses. This inhibition lasted approximately 20 min with recovery at 60-70 min. The results indicate that ICV-administered ANG III is a much more potent ligand than previously determined if the stickiness due to electrical charge of this compound is prevented by appropriate treatment of glassware. The receptor antagonist results encourage the possibility that ANG II and ANG III activate a common central receptor site.
Glucose dyshomeostasis and cardiovascular failure in endotoxic dogs
Authors: Kober P. M. , Thomas J. X. , Filkins J. P.
Published: December 2017

Fasted mongrel dogs were anesthetized with pentobarbital sodium and instrumented for the on-line measurement of blood glucose (BG), a lead II electrocardiogram, and pressures in the left ventricle and pulmonary and systemic artery concomitant with on-line monitoring of BG. Serum insulin was measured by radioimmunoassay, and cardiac output (CO) was determined by thermodilution. Stroke work (SW) and pulmonary and systemic resistances were calculated. After a 30-min control period dogs were treated with Escherichia coli endotoxin (E) or normal saline (S) and then observed for 10 h or until death. Preinjection control BG was maintained in S dogs, and early hyperglycemia (H) was observed in six dogs; in contrast 10 E dogs showed no hyperglycemia (NH). During the late stages all E dogs were markedly hypoglycemic. In both groups of E dogs an early hyperinsulinemia occurred. CO and SW were depressed in both groups of E dogs. These variables were significantly lower in NH than in H dogs. Pulmonary and systemic resistance progressively increased in NH dogs after endotoxin administration. The results suggest that the ability to increase blood glucose levels after endotoxin injection is important for the maintenance of cardiovascular function. Glucose dyshomeostasis leading to hypoglycemia, however, may be a factor in the development of endotoxic cardiovascular failure.