bluuebunny/crossref_metadata_2025 huggingface dataset:
Gastric loads potentiate inhibition of food intake produced by a cholecystokinin analogue
Authors: Schwartz G. J. , Netterville L. A. , McHugh P. R. , Moran T. H.
Published: December 2017

We have proposed that cholecystokinin's (CCK) inhibition of gastric emptying contributes to its ability to inhibit food intake. To directly test this hypothesis in rats, the effect of the presence of a 5-ml gastric saline load on the ability of a long-acting cholecystokinin analogue U-67827E (0.1-10.0 nmol/kg) to inhibit intake of a 0.5 kcal/ml glucose solution was measured. The CCK analogue alone inhibited intake at a threshold dose of 2.5 nmol/kg. Although lower doses of the CCK analogue alone had no effect on subsequent glucose intake, when combined with the gastric load such doses did significantly inhibit intake. Thus the presence of a gastric load reduced the threshold dose of the CCK analogue required to inhibit intake. Furthermore, at suprathreshold doses, the peptide-load combination suppressed intake more than the peptide alone. In addition, administration of 0.5 and 5.0 nmol/kg doses of the CCK analogue inhibited gastric emptying at 10, 20, and 30 min in a dose-dependent fashion. The CCK analogue's inhibition of food intake and gastric emptying were reversed by pretreatment with 100 micrograms/kg L364,718, indicating that the analogue was having its effects by interacting with specific type A CCK receptors. Together these data support the notion that CCK satiety derives from an integration of the visceral afferent signals generated by CCK's promotion of gastric distension and those produced directly by CCK.
Effects of pregnancy, estradiol, and progesterone on pressor responsiveness to angiotensin II
Authors: Novak K. , Kaufman S.
Published: December 2017

The pressor and heart rate responses to infused angiotensin (ANG) II were measured in conscious pregnant Long-Evans rats. Responses were recorded 7 days after chronic indwelling venous and arterial cannulas were implanted (virgin rats) and again at days 7, 14, and 21 of pregnancy. A significant reduction in the pressor response was noted as early as day 7 of pregnancy; this is comparable to the human condition. It was also noted that the reflex bradycardia associated with the pressor response was entirely absent at 21 days. To determine a possible cause of these pregnancy-induced changes, ovariectomized rats were injected subcutaneously for 10 days with estradiol, progesterone, or a combination of both. They were then tested for pressor responses to ANG II. None of the hormone-injected groups showed any significant deviation in their pressor response compared with saline-injected controls. Similar results were obtained in acutely prepared rats under chloroform anesthesia. However, the magnitude of the pressor response in the chloroformed animals was significantly reduced compared with the conscious unrestrained animals. It is concluded that 1) the rat is an appropriate model of human pregnancy in which to study changes in ANG responsiveness in pregnancy and 2) neither estradiol nor progesterone is responsible for the reduced pressor response.
Disuse atrophy in the hibernating golden-mantled ground squirrel, Spermophilus lateralis
Authors: Wickler S. J. , Hoyt D. F. , van Breukelen F.
Published: December 2017

Disuse (inactivity, bed rest, and spaceflight) may lead to a loss of muscle mass and a decrease in oxidative capacity in skeletal muscle. If such changes were to occur in hibernating animals, both locomotor and thermogenic function would be compromised. Muscle masses and oxidative capacities (as assessed by citrate synthase activity) were measured in the gastrocnemius and semitendinosus muscles, cardiac muscle (ventricle), and brown fat (axillary pad) in a group (n = 7) of prehibernating ground squirrels (Spermophilus lateralis) and after 6 mo of hibernation (n = 8). Hibernation produced significant atrophy in the gastrocnemius (14%) and semitendinosus (42%) muscles. Cardiac tissue increased (21%) in mass, as did brown adipose tissue (150%). That such changes were not due simply to fluid shifts was evidenced by similar protein concentrations between groups. In contrast to many other disuse studies, oxidative capacity was increased significantly in the gastrocnemius (65%) and semitendinosus (37%). Citrate synthase was also higher in cardiac tissue of hibernators (20%) but was not significantly different in brown fat.
Static muscle contraction reflexly increases adrenal sympathetic nerve activity in rats
Authors: Vissing J. , Wilson L. B. , Mitchell J. H. , Victor R. G.
Published: December 2017

Little is known about the mechanisms responsible for activation of sympathoadrenal function during exercise. We hypothesized that sympathoadrenal discharge is activated at the onset of exercise by a reflex arising in the contracting muscle. Adrenal sympathetic nerve activity (SNA) was recorded during 1 min stimulation of the tibial nerve at two times motor threshold, before and during neuromuscular blockade, in 12 alpha-chloralose-anesthetized rats. Static muscle contractions, induced by stimulation before neuromuscular blockade, were repeated during ganglionic blockade (n = 6) to specifically test reflex activation of preganglionic activity to the adrenal gland. During static contraction, adrenal SNA rapidly increased (P less than 0.05) to a maximum of 89 +/- 12% above basal and then declined, reaching basal levels after 30 s of muscle contraction. Tibial nerve stimulation during neuromuscular blockade had no effect on adrenal SNA. In most rats, adrenal SNA decreased with ganglionic blockade, indicating postganglionic as well as preganglionic innervation of the adrenal gland. During ganglionic blockade, static muscle contractions elicited a 140 +/- 21% increase in adrenal preganglionic SNA. In conclusion, static muscle contraction reflexly increases SNA to the adrenal gland, providing a mechanism for sympathoadrenal activation at the onset of exercise.
Freeze-thaw injury in erythrocytes of the freeze-tolerant wood frog, Rana sylvatica
Authors: Costanzo J. P. , Lee R. E.
Published: December 2017

Erythrocytes from the freeze-tolerant wood frog (Rana sylvatica) were subjected to in vitro tests of freeze tolerance, cryoprotection, and osmotic fragility. The responses of cells from frogs acclimated to 4 or 15 degrees C were similar. Erythrocytes that were frozen in saline hemolyzed at -4 degrees C or lower. The addition of high concentrations (150 and 1,500 mM) of glucose or glycerol, cryoprotectants produced naturally by freeze-tolerant frogs, significantly reduced cell injury at -8 degrees C, but concentrations of 1.5 or 15 mM were ineffective. Hemolysis was reduced by 94% with 1,500 mM glycerol and by 84% with 1,500 mM glucose; thus glycerol was the more effective cryoprotectant. Mean fragility values for frog erythrocytes incubated in hypertonic and hypotonic saline were 1,938 and 49 mosM, respectively. Survival in freeze tolerance and cryoprotection experiments was comparable for erythrocytes from frogs and humans, suggesting that these cells may respond similarly to freezing-related stresses. However, the breadth of osmotic tolerance, standardized for differences in isotonicity, was greater for frog erythrocytes than for human erythrocytes. Our data suggest that erythrocytes from R. sylvatica are adequately protected by glucose under natural conditions of freezing and thawing.
Nonshivering thermogenesis in king penguin chicks. II. Effect of fasting
Authors: Duchamp C. , Barre H. , Rouanet J. L. , Lanni A. , Cohen-Adad F. , Berne G. , Brebion P.
Published: December 2017

The effect of fasting on the energy metabolism of skeletal muscle and liver was investigated in cold-acclimatized short-term fasting (STF) (3 wk) and naturally long-term fasting (LTF) (4-5 mo) king penguin chicks, both groups exhibiting nonshivering thermogenesis (NST). A comparison was made with nourished cold-acclimatized controls. In these chicks, no brown adipose tissue deposits could be found on electron-microscopic observations of fat deposits. Protein content and cytochrome oxidase (CO) activity of tissue homogenates were measured in liver and pectoralis and gastrocnemius muscles, as were protein content, CO activity, and respiration rates of mitochondria isolated from these organs. Fasting-induced protein loss affected the pectoralis more than the gastrocnemius muscle, thus preserving locomotor function. In STF chicks, specific mitochondrial protein content and specific tissue CO activity were preserved but total organ CO capacity was reduced by half in pectoralis and liver following the fall in organ mass. In LTF chicks, both specific and total CO activity were drastically reduced in muscles, whereas specific CO activity was preserved in liver. In these LTF chicks, muscle mitochondria showed an energized configuration associated with an increased area of inner membrane in gastrocnemius. A reduction of respiratory control ratio (RCR) was observed in subsarcolemmal muscle mitochondria of STF chicks, whereas intermyofibrillar and liver mitochondria kept high RCR values.(ABSTRACT TRUNCATED AT 250 WORDS)
Aldosterone modulates electrogenic Cl secretion in the colon of the hen (Gallus domesticus)
Authors: Clauss W. , Dantzer V. , Skadhauge E.
Published: December 2017

The regulation of Na and Cl transport in hen colon by mineralocorticoids was investigated with isolated epithelia in vitro by histological and electrophysiological techniques. The electrogenic transport of Na and Cl was measured in Ussing chambers by the short-circuit current technique and was identified by the specific inhibitors amiloride and bumetanide or by the secretagogue theophylline. Hens were maintained either on low (LS)- or on high-NaCl diets (HS), and the plasma aldosterone (PA) levels of these groups were measured with radioimmunoassay. A group of HS hens received injections of aldosterone at a 6-h schedule before experiments. A group of LS hens was resalinated, and experiments were carried out at a 24-h interval for up to 3 days after resalination. The LS diet stimulated PA levels ninefold, compared with HS hens. Na transport was modulated by the hormonal stimulus in a way that the apical Na entry switched from an electrogenic Na-amino acid-hexose cotransport system completely to an amiloride-sensitive Na channel. Electrogenic Cl secretion was induced by theophylline and was inhibited by bumetanide. NaCl deprivation, resalination or aldosterone injection modulated electrogenic Cl secretion in parallel between 7 (HS) and 14.4 mu eq.cm-2.h-1 (LS), with pronounced alteration in tissue conductance. These findings reveal a new action of aldosterone that, besides stimulating Na absorption, also directly or indirectly modulates Cl secretion.
Diminished iron acquisition by cells and tissues of Belgrade laboratory rats
Authors: Farcich E. A. , Morgan E. H.
Published: December 2017

Iron uptake from transferrin by a variety of cells and tissues of homozygous Belgrade laboratory rats was compared with heterozygotes, and normal and iron-deficient Wistar rats. In all cases the results for homozygous Belgrade rats were lower than for the other animals. The maximal rate of iron uptake by fibroblasts cultured in vitro and iron passage to homozygous fetuses in utero was less than 60% of control values. In vivo studies of 15-day-old Belgrade rats revealed a defect in the homozygotes with reduced iron transfer to heart, liver, brain, and femurs. In addition, adult Belgrade laboratory rats had impaired intestinal iron absorption compared with the genetically normal animals. It is concluded that the defect in iron metabolism in the Belgrade laboratory rat is a ubiquitous one that affects transport of iron across membranes of many types of cells, resulting in low intracellular iron levels. This suggests that the genetic defect leads to a widely expressed abnormality in the structure and/or function of a membrane carrier for iron.
Repletion of acute sodium deficit in rats drinking either low or high concentrations of sodium chloride solution
Authors: Rowland N. E. , Fregly M. J.
Published: December 2017

These studies investigate the relationship between expression of sodium appetite and restoration of physiological normalcy after acute sodium depletion in Sprague-Dawley rats. After depletion (treatment with diuretic and 24 h without NaCl), separate groups of rats were allowed to drink either a low (0.03 M) or a high (0.3 M) concentration of NaCl. Intake and urinary output of sodium and selected plasma measures were made at various times up to 48 h. Depleted rats with access to 0.3 M NaCl consumed more Na+ than their deficit in the first hour and were volume expanded as a result of this excessive intake, but they continued to consume NaCl for 6-12 h. Depleted rats given 0.03 M NaCl drank a comparable volume to the 0.3 M group in the first hour and thus only approximately 10% of the solute. The intake of 0.03 M NaCl slowed after 6-12 h, at which time the cumulative intake matched the deficit and the plasma parameters had returned to nondepleted levels. Under these conditions of slow intake, it appears that sodium appetite is more closely matched to need than is the case when highly concentrated sources of sodium are available. Satiation of sodium appetite seems to require the passage of time as well as repletion of body sodium.
Metabolic and cardiodynamic responses of isolated turtle hearts to ischemia and reperfusion
Authors: Wasser J. S. , Meinertz E. A. , Chang S. Y. , Lawler R. G. , Jackson D. C.
Published: December 2017

We used 31P and 1H nuclear magnetic resonance spectroscopy to measure intracellular pH, high energy phosphates, and lactate levels in hearts of turtles (Chrysemys picta bellii) subjected to 1.5 h of global ischemia followed by reperfusion. We simultaneously monitored maximum ventricular developed pressure (Pmax), maximal rate of pressure development (dP/dtmax), rate-pressure product (RPP), cardiac output, and heart rate and also measured lactate efflux from the hearts during reperfusion. Our goal was to test the hypothesis that turtle hearts would prove tolerant of prolonged global ischemia at 20 degrees C and would recover completely on reperfusion without any indication of ischemia-or reperfusion-related injury. The 1.5 h of ischemia resulted in decreases in phosphocreatine and ATP to 31.4 +/- 2.8 and 87.3 +/- 6.3% of control, respectively, while Pi rose to 236.6 +/- 26.3%. Intracellular pH decreased during this period from 7.38 +/- 0.02 to 6.87 +/- 0.04. Most of these changes occurred during the first 30 min. Tissue lactate rose during 1.5 h of ischemia from approximately 1.5 to 22.3 mumol/g wet tissue wt. However, the rate of lactate production was much higher during the first 21 min of ischemia (0.41 mumol.g-1.min-1) than during the remaining 70 min (0.10 mumol.g-1.min-1). With the onset of ischemia, Pmax, dP/dtmax, RPP, and heart rate all decreased dramatically with roughly the same time course as the changes in high-energy phosphates and intracellular pH. On reperfusion, turtle hearts rapidly restored high-energy phosphates, intracellular pH, lactate, and cardiodynamics to control levels, usually within 15-30 min, with no evidence of reperfusion injury.(ABSTRACT TRUNCATED AT 250 WORDS)
Skeletal muscle composition in dietary obesity-susceptible and dietary obesity-resistant rats
Authors: Abou Mrad J. , Yakubu F. , Lin D. , Peters J. C. , Atkinson J. B. , Hill J. O.
Published: December 2017

The intent of this study was to determine whether a relationship exists between susceptibility to high-fat diet (HFD)-induced obesity and skeletal muscle fiber type. Forty-four adult male Wistar rats were given ad libitum access to a HFD (60% of calories from fat) for 4 wk. Rats were then grouped into quartiles for total weight gain, and the top-quartile [obesity prone (OP)] rats were compared with the bottom-quartile [obesity resistant (OR)] rats. OP rats gained 1.5 times as much weight as OR rats. OR rats had a significantly higher proportion of type I muscle fibers in the medial head of the gastrocnemius muscle than OP rats both before (determined from a muscle biopsy) and after the HFD feeding period. A greater proportion of type I fibers may be associated with a greater capacity for fat oxidation, which would favor resistance to body fat accumulation. Preexisting differences in muscle fiber composition may play a role in determining susceptibility to dietary obesity.
Gravity and the circulation: "open" vs. "closed" systems
Authors: Hicks J. W. , Badeer H. S.
Published: December 2017

The elementary principles of liquid dynamics are described by the equations of Bernoulli and Poiseuille. Bernoulli's equation deals with nonviscous liquids under steady streamline flow. Pressures in such flows are related to gravity and/or acceleration. Changes in elevation affect the gravitational potential energy of the liquid and the velocity of flow determines the kinetic energy. The sum of these three factors represented in the Bernoulli equation remains constant, but the variables are interconvertible. In contrast, the Poiseuille equation describes the pressures related to viscous resistance only, and the energy of flow is dissipated as heat. A combination of the two equations describes the flow in tubes more realistically than either equation alone. In "open" systems gravity hinders uphill flow and causes downhill flow, in which the liquid acts as a falling body. In contrast, in "closed" systems, like the circulation, gravity does not hinder uphill flow nor does it cause downhill flow, because gravity acts equally on the ascending and descending limbs of the circuit. Furthermore, in closed systems, the liquid cannot "fall" by gravity from higher levels of gravitational potential to lower levels of potential. Flow, up or down, must be induced by some source of energy against the resistance of the circuit. In the case of the circulation, the pumping action of the heart supplies the needed energy gradients. Flow in collapsible tubes, like veins, obeys the same basic laws of liquid dynamics except that transmural pressures near zero or below zero reduce markedly the cross-sectional area of the tube, which increases the viscous resistance to flow.(ABSTRACT TRUNCATED AT 250 WORDS)
Neurogenic vasodilator control of rabbit ear blood flow
Authors: Taylor W. F. , DiCarlo S. E. , Bishop V. S.
Published: December 2017

Ear blood flow subserves thermoregulation in the rabbit. The purpose of this study was to determine if the increase in rabbit ear blood flow, in response to increases in internal temperature (Ti) of approximately 2 degrees C (38.0-40.0 degrees C), is due to an active vasodilation or a withdrawal of adrenergic vasoconstrictor activity. New Zealand White rabbits were chronically instrumented with a pulse Doppler flow probe on the central ear artery of the left and right ear for the measurement of ear blood flow velocity (EBF, kHz). Catheters were also positioned in one occipital artery for selective administration of an alpha 1-adrenergic antagonist to one ear, while the contralateral ear served as a control. During hyperthermia (H) (increase in rectal temperature) alpha 1-adrenergic blockade had no effect on the maximum EBF (5.95 +/- 0.87 before vs. 6.11 +/- 1.04 kHz after). However, alpha 1-adrenergic blockade increased resting EBF during normothermia from 0.18 +/- 0.04 to 1.23 +/- 0.27 kHz (P less than 0.05), suggesting that a decrease in alpha 1-adrenergic tone may account for approximately 20% of the increase in EBF during heating. The second protocol was designed to determine if blockade of the auricular nerve would alter EBF response to H. During maximum EBF during H, saline or procainamide was injected in the tissue surrounding the auricular nerve. Injection of procainamide decreased EBF from 5.99 +/- 0.87 to 0.48 +/- 0.19 kHz, while injection of saline had no effect on EBF of the contralateral ear (4.33 +/- 1.16 before vs. 3.97 +/- 1.04 kHz after).(ABSTRACT TRUNCATED AT 250 WORDS)
Atrial natriuretic peptide does not alter cerebrospinal fluid formation in sheep
Authors: Chodobski A. , Szmydynger-Chodobska J. , Cooper E. , McKinley M. J.
Published: December 2017

Because the choroid plexus has been shown to have a high density of atrial natriuretic peptide (ANP) binding sites, we investigated the effect of intracerebroventricular and intravenous administrations of ANP on cerebrospinal fluid (CSF) formation. CSF formation rate was measured in conscious sheep with a dye-dilution method using blue dextran 2000 as an indicator substance. During the experiment animals were partially restrained in a sling, and their ventricular systems were perfused with artificial CSF containing the indicator substance. ANP (alpha-human ANP) administered centrally at rates of 0.015-15 ng/min, resulting in CSF ANP concentrations ranging from physiological to pharmacological CSF hormone levels, was found not to influence CSF formation. Similarly, intravenous administration of ANP at a rate of 10 ng.kg-1.min-1 did not affect CSF formation, i.e., decreases in CSF formation rate in all experiments involving ANP administration were not significantly different from those observed in time control experiments. Our results suggest that ANP does not significantly affect CSF production in sheep. It is possible that the lack of effect of ANP on CSF formation is associated with the predominance in the choroid plexus of clearance receptors over biologically active receptors.
Role of lung inflation in control of air breath duration in African lungfish (Protopterus annectens)
Authors: Pack A. I. , Galante R. J. , Fishman A. P.
Published: December 2017

Studies were conducted in the African lungfish (Protopterus annectens) to investigate the role of lung inflation on control of the duration of the lung breath. The studies were done in decerebrate spinalectomized animals. Two types of tests were performed: 1) a no-inflation test (airway occluded) in which the lungs were not inflated during an air breath, and 2) an inflation test in which the lungs were inflated at the onset of the lung breath to different levels of intrapulmonary pressure (2.5, 5.0, 7.5, and 10.0 cmH2O). Lung inflation shortened the duration of the lung breath. The relationship between intrapulmonary pressure and breath duration was curvilinear and similar to the relationship between tidal volume and inspiratory duration in mammals. Likewise, the relationship could be described by a hyperbola with a linear relationship between intrapulmonary pressure and the inverse of breath duration. This relationship was essentially not affected by changing the composition of the gas used to inflate the lungs: air, oxygen, or nitrogen. Vagotomy, however, largely abolished the effect of lung inflation on breath duration. Because there is such similarity between these results and effect of lung inflation on control of inspiratory time in mammals, it is postulated that neural circuits for control of respiratory timing were already developed and similar in the lungfish. Because the muscles used in the lungfish to ventilate the lung are totally different (buccal force pump) from those in mammals, the neural circuits for timing control and those for shaping the pattern of motor output appear to be separate.(ABSTRACT TRUNCATED AT 250 WORDS)
Vasopressin-induced antipyresis in the medial amygdaloid nucleus of conscious rats
Authors: Federico P. , Veale W. L. , Pittman Q. J.
Published: December 2017

Experiments were undertaken to characterize a possible receptor mediating antipyretic action of arginine vasopressin (AVP) within the medial amygdaloid nucleus (meA) in the conscious rat. Additional experiments were directed at determining whether the action of endogenously released AVP can be revealed in the meA during fever in the conscious rat. These objectives were achieved using vasopressin analogues directed against vasopressor (V1a) and antidiuretic (V2) receptors. Bilateral injection of AVP (40 pmol) into the meA of conscious rats suppressed fever evoked by intracerebroventricular (icv) administration of prostaglandin E1 (PGE1, 50 ng). The V2 receptor agonist 1-desamino-8-D-AVP (40 pmol) injected into the meA evoked only moderate antipyresis compared with AVP, possibly because of interaction of this agonist with V1a receptors. The antipyretic effect of AVP was blocked when injection of the peptide was preceded by a bilateral injection of the V1a antagonist 1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid)-2-(O-methyl)tyrosine AVP [d(CH2)5Tyr(Me)AVP, 400 pmol] into the meA. Injection of d(CH2)5Tyr(Me)AVP alone into the meA was without significant effect on afebrile core temperature. Injection of d(CH2)5Tyr(Me)AVP or 1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid)-2-D-valine,4-valine AVP (a V2 antagonist) alone into the meA before icv PGE1 resulted in fevers that were not significantly different from artificial cerebrospinal fluid controls. These data are consistent with the possibility that AVP might act within the meA to evoke antipyresis via receptors that resemble V1a (vasopressor) receptors. However, the action of AVP endogenously released into the meA does not appear to be an absolute requisite in the normal modulation of PGE1 fever.
Hypertonic NaCl inhibits gastric motility and food intake in rats with lesions in the rostral AV3V region
Authors: Flanagan L. M. , Blackburn R. E. , Verbalis J. G. , Stricker E. M.
Published: December 2017

Several diverse treatments that stimulate pituitary secretion of oxytocin (OT) in rats produce a parallel inhibition of gastric motility and food intake. The present experiments demonstrate that injection of hypertonic saline (HS) is another such treatment. Systemic administration of large doses of OT had no effect on gastric motility. Lesions within the region anteroventral to the third ventricle (AV3V region) severely impaired the drinking response to HS without affecting its inhibition of either gastric motility or food intake. These and other results suggest that despite the close association of pituitary secretion of OT with inhibition of both gastric motility and food intake in intact animals after HS administration, these effects may be dissociated by lesions within the AV3V region. Consequently, osmosensitive cells located within the periventricular tissue of the rostral AV3V region, which are critical for the stimulation of thirst and pituitary OT secretion after systemic injection of HS, do not appear to be essential for the parallel inhibition of gastric motility and food intake produced by this treatment in rats.
Nucleus tractus solitarius and control of blood pressure in chronic sinoaortic denervated rats
Authors: Schreihofer A. M. , Sved A. F.
Published: December 2017

To determine the role of the nucleus tractus solitarius (NTS) in the tonic maintenance of arterial pressure (AP) following chronic baroreceptor denervation, the present study examined the effect of inhibition of the NTS on AP in chronic sinoaortic denervated (SAD) and control rats. One to two weeks after complete SAD (no residual arterial baroreceptor reflexes) mean AP was not significantly different from that of control rats. Bilateral microinjections of muscimol and lidocaine into the NTS markedly increased AP in alpha-chloralose-anesthetized control rats. However, microinjections of these neuroinhibitory drugs had no effect on AP in SAD rats. Similarly, 1 h after bilateral destruction of the NTS conscious control rats were hypertensive, while AP in SAD rats was not changed. Plasma levels of vasopressin (VP), which were also elevated in control rats 1 h after NTS lesions, were not significantly altered in SAD rats. These results demonstrate that inhibition of the NTS has no effect on AP or plasma levels of VP in chronic SAD rats. This suggests neither the NTS nor afferents to the NTS supply a tonic inhibitory influence on AP after chronic baroreceptor denervation.
Excitatory amino acids may mediate nucleus tractus solitarius input to rat parabrachial neurons
Authors: Jhamandas J. H. , Harris K. H.
Published: December 2017

The pontine parabrachial nucleus (PBN) is a recipient of predominantly excitatory input from the nucleus of the solitary tract (NTS). The presence of glutamate-like immunoreactivity at these brain stem sites suggests a role for excitatory amino acids (EAAs) in neurotransmission within the projection. We utilized electrophysiological studies in vivo to examine the ability of specific EAA antagonists, applied locally, to alter glutamate (GLU)-induced and NTS-evoked excitation of PBN neurons. Nonselective EAA antagonist kynurenic acid (KYN), the selective N-methyl-D-aspartate (NMDA) antagonist DL-2-amino-5-phosphonovalerate (APV), and non-NMDA quinoxalinedione group of blockers 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 6-nitro-7-sulfamobenzoquinoxaline-2,3-dione (NBQX) were applied by iontophoresis or micropressure ejection from multibarreled pipettes attached to the recording electrode. Extracellular recordings in urethan-anesthetized rats were obtained from 58 PBN neurons that displayed an excitatory response following electrical stimulation within the NTS. Poststimulus histogram data revealed that NTS-evoked excitation could be reversibly blocked by KYN, APV, and CNQX in 21/37 (57%), 11/21 (52%), and 10/19 cells (53%), respectively. Both NMDA and non-NMDA antagonists reversibly attenuated or blocked GLU-evoked excitation in 21 of 29 PBN neurons. These observations suggest a role for both NMDA and non-NMDA receptors in mediating the excitatory input from NTS to the PBN.
Arterial chemoreceptor input to nucleus tractus solitarius
Authors: Mifflin S. W.
Published: December 2017

The arterial chemoreceptors play an important role in the reflex regulation of blood pressure and respiration. To investigate the initial integration of chemoreceptor inputs within the central nervous system, intracellular recordings were obtained in pentobarbital-anesthetized, paralyzed, and mechanically ventilated cats, from 58 cells within the nucleus of the tractus solitarius (NTS) that were depolarized by activation of the ipsilateral carotid body chemoreceptors. Close arterial injection of less than 100 microliters CO2-saturated bicarbonate evoked depolarizations of membrane potential with amplitudes of 2.2-4.6 mV and durations of 1.8-6.7 s in 46 cells. In 12 cells, activation of the carotid body chemoreceptors evoked a depolarization-hyperpolarization sequence. Electrical stimulation of the carotid sinus nerve (500 microA, 0.2 ms) evoked EPSPs [mean latency 6.4 +/- 0.5 (SE) ms; range 2.1-18.4 ms] in 46 cells and EPSP-IPSPs (7.3 +/- 0.8 ms; range 4.2-12.4 ms) in 12 cells. The distribution of EPSP latencies exhibited two peaks, one in the 2- to 4-ms range and another in the 7- to 8-ms range. Twenty-nine chemoreceptive cells were tested for the presence of convergent inputs from the ipsilateral carotid sinus baroreceptors. No evidence was found of a convergent postsynaptic inhibitory input from the baroreceptors within the NTS; however, seven cells were found that received an excitatory input from the baroreceptors. The observation that NTS neurons do not integrate chemoreceptor afferent inputs in a homogeneous manner suggests that the multiplicity of NTS unit responses might be related to the specific reflex function of an individual cell (e.g., vagal or sympathetic outflow, respiration).(ABSTRACT TRUNCATED AT 250 WORDS)
Renal afferent input to the ventrolateral medulla of the cat
Authors: Vizzard M. A. , Standish A. , Ammons W. S.
Published: December 2017

Experiments were performed to determine if information from the kidneys projects to the rostral ventrolateral medulla. Extracellular action potentials were recorded from 148 cells within the rostral ventrolateral medulla of alpha-chloralose-anesthetized cats. Cells within the rostral ventrolateral medulla were tested for responses to electrical stimulation of both left and right renal nerves. Electrical stimulation of renal nerves excited 144 cells (97.3%) and inhibited 4. The majority of cells received either bilateral or contralateral renal nerve input. Cells with bilateral renal nerve input responded to contralateral renal nerve stimulation with a significantly greater number of impulses compared with ipsilateral renal nerve stimulation (P less than 0.05). All cells but one responding to renal nerve stimulation had convergent somatic input. Comparisons between thresholds for cell responses and activation thresholds for the A and C volleys of the compound action potential recorded in the least splanchnic nerve revealed that 44 cells required activation of A delta-fibers, and 12 cells required activation of both A delta- and C-fibers. A conditioning stimulus applied to renal nerves on one side significantly decreased the response elicited by a test stimulus applied to the renal nerves on the opposite side for at least 300 ms (P less than 0.05). The demonstration that an afferent connection exists between the kidneys and the ventrolateral medulla suggests that the rostral ventrolateral medulla may play a role in mediating supraspinal reflexes of renal origin.
Endotoxin-induced fever is modulated by endogenous glucocorticoids in rats
Authors: Coelho M. M. , Souza G. E. , Pela I. R.
Published: December 2017

This study was designed to determine if the febrile response, similar to the inflammatory response, can be modulated by endogenous glucocorticoids. A single intraperitoneal injection of lipopolysaccharide (LPS, 200 micrograms/kg) induced a significant increase in rectal temperature of unrestrained rats maintained within the thermoneutral zone. The febrile response was fully abolished following treatment with a glucocorticoid, dexamethasone (DEX), but was not affected by a mineralocorticoid, deoxycorticosterone acetate (DOCA). Adrenalectomized (ADX) rats were markedly more sensitive to the lethal effects of LPS (200 micrograms/kg), such that all the animals died during the course of the experiment. In addition, ADX rats showed an enhanced febrile response to LPS (10 micrograms/kg ip) in comparison with sham-operated or adrenal-demedullated rats. This enhanced response was reduced by chronic or acute treatment with DEX, but not DOCA. LPS (10 micrograms/kg) also induced a marked rise in plasma corticosterone levels in control rats. In contrast, ADX rats displayed very low plasma corticosterone levels, which were not changed by LPS. In conclusion, the present results reveal that endogenous glucocorticoids are important modulators of LPS-induced fever.
High-intensity light for circadian adaptation to a 12-h shift of the sleep schedule
Authors: Eastman C. I.
Published: December 2017

Male subjects had their sleep schedules shifted 12 h to accommodate eight or more consecutive simulated night shifts. They were exposed to artificial light (approximately 5,000 lux, 3- to 6-h durations) each night, slept at home in very dark bedrooms during the day, and wore dark welders goggles whenever they went outside during daylight. Body temperature was continuously measured, and daily questionnaires provided estimates of sleep time and mood. The circadian temperature rhythm phase shifted, usually approximately 2 h/day, in 21 of 24 subjects. The temperature rhythms of the other three subjects appeared to remain entrained to the 24-h zeitgebers. In the subjects whose temperature rhythms shifted, the direction of shift (advance or delay) depended on the timing of light exposure relative to the baseline temperature phase, consistent with a phase-response curve. Sleep was disturbed, and fatigue was increased during the first few days after the shift of the sleep-wake schedule.
Behavioral and tissue responses to severe phosphorus depletion in cattle
Authors: Blair-West J. R. , Denton D. A. , McKinley M. J. , Radden B. G. , Ramshaw E. H. , Wark J. D.
Published: December 2017

Two-year-old Aberdeen Angus heifers were depleted of phosphorus (P) by loss of phosphate in saliva from a parotid gland fistula combined with a low-P diet. The inorganic phosphate concentrations (Pi) of plasma, parotid saliva, ruminal fluid, and feces were reduced, but cerebrospinal fluid Pi was unaltered. Plasma Pi fell to less than 1.0 mM in 12 wk, and the cows displayed an avid appetite for old bones. P-deficient cows preferred old weathered bones to fresh bones until the latter had aged for approximately 1.5 yr. They did not eat blood, peritoneal fat, or meat, fresh or aged for 2-3 yr. They did not eat Na or Ca phosphate salts or bone heated to greater than 250 degrees C. P-replete cows did not take or eat bones. The behavioral effects of P deficiency were associated with failure to gain body weight and maintain condition, significant bone changes indicated by reduced bone weight and specific gravity, osteopenia indicated by radiology, evidence of reduced bone formation indicated by plasma osteocalcin levels and histology, and abnormal estrous cycles. Prolonged P deficiency was associated with increased plasma concentrations of total Ca and 1,25-dihydroxyvitamin D and reduced plasma concentrations of parathyroid hormone.
Selective activation of norepinephrine- and epinephrine-secreting chromaffin cells in rat adrenal medulla
Authors: Vollmer R. R. , Baruchin A. , Kolibal-Pegher S. S. , Corey S. P. , Stricker E. M. , Kaplan B. B.
Published: December 2017

The differential effects of insulin-induced hypoglycemia and cold exposure on adrenal medullary epinephrine (Epi) and norepinephrine (NE) cells were investigated in male Sprague-Dawley rats. In rats fasted overnight, insulin produced a marked hypoglycemia that resulted in a 70% decrease in adrenal medullary Epi content 3 h after the insulin was administered. No change in NE content was observed. Plasma Epi concentration was increased markedly after insulin, with a smaller increment in NE. In contrast, exposure to a 4 degrees C environment selectively reduced adrenal NE content, with the effect reaching statistical significance at 18 h. Cold exposure also led to a significant rise in plasma NE but not Epi. Both insulin-induced hypoglycemia and cold exposure significantly elevated adrenal dopamine, indicating that catecholamine synthesis was stimulated. Further evidence of enhanced catecholamine formation was the observation that inhibition of synthesis with alpha-methyl-p-tyrosine (AMT) greatly augmented the ability of insulin-induced hypoglycemia to selectively reduce adrenal medullary Epi content. Similarly, in cold-exposed animals, AMT pretreatment accelerated the NE depletion so that a significant decline was observed at 3 h. These results support the conclusion that the two major populations of adrenal catecholamine-secreting cells may be preferentially stimulated by different stressors. Moreover, augmented synthetic activity functions to maintain catecholamine stores in both Epi- and NE-secreting cells.
Control of adipose tissue lipolysis in ectotherm vertebrates
Authors: Migliorini R. H. , Lima-Verde J. S. , Machado C. R. , Cardona G. M. , Garofalo M. A. , Kettelhut I. C.
Published: December 2017

Lipolytic activity of fish (Hoplias malabaricus), toad (Bufo paracnemis), and snake (Philodryas patagoniensis) adipose tissue was investigated in vivo and in vitro. Catecholamines or glucagon did not affect the release of free fatty acids (FFA) by incubated fish and toad adipose tissue. Catecholamines also failed to activate snake adipose tissue lipolysis, which even decreased in the presence of epinephrine. However, glucagon stimulated both the lipolytic activity of reptilian tissue in vitro and the mobilization of FFA to plasma when administered to snakes in vivo. The release of FFA from incubated fish, amphibian, and reptilian adipose tissue increased markedly in the presence of cAMP or xanthine derivatives, inhibitors of phosphodiesterase. Forskolin or fluoride, activators of specific components of the adenylate cyclase system, strongly stimulated toad adipose tissue lipolysis. The data suggest that adipocyte triacylglycerol lipase of ectotherm vertebrates is activated by a cAMP-mediated phosphorylation and that the organization of the membrane-bound adenylate cyclase system is similar to that of mammals.
Tissue-specific effects of physiological ANP infusion on blood-tissue albumin transport
Authors: Tucker V. L. , Simanonok K. E. , Renkin E. M.
Published: December 2017

Blood-tissue transport of 131I-labeled bovine serum albumin (BSA) during intravenous infusion of synthetic atrial natriuretic peptide (ANP) was examined in anesthetized male Wistar rats. Plasma volumes were maintained at pre-ANP levels by infusion of 2% BSA in lactated Ringer solution (LR) to minimize compensatory responses to ANP-induced hypovolemia. 131I-BSA clearance was measured over 30 min, and 125I-BSA was injected terminally to correct for intravascular volume. Thirty-minute infusion of 20 ng.kg-1.min-1 ANP resulted in a tissue-selective increase in 131I-BSA clearance in jejunum and colon compared with controls given LR only. Smaller but significant increases in tracer clearance also were observed in fat, kidney, left ventricle, and skeletal muscle exposed to 400 ng.kg-1.min-1 ANP. The observed elevation in tracer albumin extravasation was not associated with any measurable increase in tissue extravascular water content. Furthermore, it was shown that coupling of 131I-BSA transport to filtration induced by hindlimb venous congestion was similar in control and ANP-treated rats. In a second series of experiments, plasma ANP levels were determined after 30-min ANP infusions from 0 to 180 ng.kg-1.min-1. Significant linear associations between physiological ANP levels (62-578 pg/ml) and 131I-BSA clearance were demonstrable for small intestine, colon, fat, kidney, and skeletal muscle but not for skin, heart, diaphragm, and lung. We conclude that raising plasma ANP by infusion of the synthetic peptide results in a filtration-independent, tissue-selective increase in albumin transport. Tissue uptake of albumin is a potential mechanism for extrarenal fluid shift during circulatory volume overload.
Morphological and physiological correlates with swimming performance in juvenile largemouth bass
Authors: Kolok A. S.
Published: December 2017

Winter- and summer-acclimatized largemouth bass (Micropterus salmoides) were collected from hatchery ponds in eastern Colorado during late winter and midsummer, then challenged with two prolonged swimming performances (step test and constant-velocity endurance). Variation in the step test performances was significantly correlated with variation in the endurance performances in the winter-acclimatized but not in the summer-acclimatized fish. Fourteen physiological and morphological traits were measured on each fish, and correlations among these traits and swimming performance were tested. None of the traits measured were correlated with performance variation in both the winter- and summer-acclimatized fish. The only significant correlate with swimming performance in the summer-acclimatized fish was white muscle lactate dehydrogenase activity (n = 19). Six of the seven factors correlating with winter swimming performance (n = 18-19) could be divided into two categories: traits associated with fasting (condition factor and liver enzymatic activity) and those associated with oxygen delivery (heart mass, heart and red muscle cytochrome oxidase activity). The results of this study suggest that morphological and physiological correlates of swimming performance in juvenile largemouth bass are profoundly influenced by seasonal variation.
Nitric oxide participates in the cerebrovasodilation elicited from cerebellar fastigial nucleus
Authors: Iadecola C.
Published: December 2017

The endothelium-derived relaxing factor, probably NO, is a potent vasodilator that mediates the vasodilating action of acetylcholine (ACh). We studied whether NO participates in the cholinergic cerebrovasodilation elicited by stimulation of the cerebellar fastigial nucleus (FN). Rats were anesthetized with halothane and ventilated. FN or pontine reticular formation (PRF) were stimulated through microelectrodes. Hypertension was prevented by spinal cord transection with arterial pressure maintained by intravenous phenylephrine. Cerebral blood flow (CBF) was continuously monitored through a cranial window over the sensory cortex by a laser-Doppler probe. The window was superfused with Ringer solution (pH 7.3-7.4; 37 degrees C). During Ringer superfusion FN stimulation (100 microA; 50 Hz) increased CBF by 90 +/- 7% (n = 27; P < 0.001, analysis of variance and Tukey's test) and PRF stimulation (100 microA; 100 Hz) by 128 +/- 18% (P < 0.001; n = 9). Superfusion with the guanylyl cyclase inhibitor methylene blue (MB) (1 mM) attenuated the CBF increase elicited by FN stimulation by 77 +/- 3% (n = 22; P < 0.001). MB did not affect the CBF increase elicited by PRF stimulation (+98 +/- 18%; n = 9; P > 0.05). Similarly, superfusion with the NO-synthase inhibitor nitro-L-arginine (L-NA) attenuated the CBF increase elicited by FN stimulation (-67 +/- 3%; n = 14; P < 0.001 from Ringer) but not PRF stimulation (P > 0.05; n = 9). The CBF increases elicited by FN stimulation were not affected by the inactive isomer of nitroarginine, D-NA (P > 0.05; n = 7).(ABSTRACT TRUNCATED AT 250 WORDS)
Exhaustive physical exercise causes oxidation of glutathione status in blood: prevention by antioxidant administration
Authors: Sastre J. , Asensi M. , Gasco E. , Pallardo F. V. , Ferrero J. A. , Furukawa T. , Vina J.
Published: December 2017

We have studied the effect of exhaustive concentric physical exercise on glutathione redox status and the possible relationship between blood glutathione oxidation and blood lactate and pyruvate levels. Levels of oxidized glutathione (GSSG) in blood increase after exhaustive concentric physical exercise in trained humans. GSSG levels were 72% higher immediately after exercise than at rest. They returned to normal values 1 h after exercise. Blood reduced glutathione (GSH) levels did not change significantly after the exercise. We have found a linear relationship between GSSG-to-GSH and lactate-to-pyruvate ratios in human blood before, during, and after exhaustive exercise. In rats, physical exercise also caused an increase in blood GSSG levels that were 200% higher after physical exercise than at rest. GSH levels did not change significantly. Thus, both in rats and humans, exhaustive physical exercise causes a change in glutathione redox status in blood. We have also found that antioxidant administration, i.e., oral vitamin C, N-acetyl-L-cysteine, or glutathione, is effective in preventing oxidation of the blood glutathione pool after physical exercise in rats.
Adipose tissue lipolysis in vitro: a predictor of diet-induced obesity in female rats
Authors: Landerholm T. E. , Stern J. S.
Published: December 2017

Wide ranges in weight and fat gain in response to high-fat diets have been reported in rats. This study measured epinephrine-stimulated lipolysis in adipose tissue of normal weight, 3-mo-old, female Sprague-Dawley rats as a metabolic predictor of "efficient gain" before feeding them a high-fat (84% kcal) diet for 11 wk. Subcutaneous (inguinal) adipose tissue (1-1.5 g) was excised, and the glycerol release was measured after incubation with 0, 10(-7), 10(-5), and 10(-3) M epinephrine. Differences in gain efficiency explained much of the variation in lipid (r = 0.78) and weight (r = 0.83) gain. Low glycerol release by 10(-5) and 10(-3) M epinephrine was significantly correlated to high final fat accumulation. Low and high quartiles based on glycerol release were not different in numbers of adipocytes or food intake but were significantly different in gain efficiency (P = 0.011), final weight (P = 0.036), carcass lipid (P = 0.033), and carcass lean mass (P = 0.017). In conclusion, female Sprague-Dawley rats are preferentially predisposed to efficiency of adipose accumulation on a high-fat diet. This tendency is negatively correlated in the preobese state to the lipolytic response to epinephrine of subcutaneous adipose tissue in vitro.