bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of bilateral seminal emissions from ejaculatory ducts by a lumbar splanchnic nerve
Authors: Kihara K. , Sato K. , Ando M. , Morita T. , Oshima H.
Published: December 2017

To investigate the route of efferent signals for seminal emissions from ejaculatory ducts (SEEDs), canine lumbar splanchnic nerves (LSNs) were electrically stimulated. SEED was confirmed by visual verification of seminal flow into the exposed posterior urethra. In intact dogs, electrical stimulation of an LSN caused bilateral SEEDs in 13 of 16 dogs examined, with a greater volume at the stimulated side. After transection of a unilateral hypogastric nerve, bilateral SEEDs occurred by electrical stimulation of the contralateral LSN in 11 of 14 dogs with a greater volume at the stimulated side and by the stimulation of the ipsilateral LSN in 13 of 15 dogs with a greater volume at the contralateral side. Contraction pressure of the epididymal tail under the same conditions harmonized with the above results. We conclude that each LSN generates bilateral SEEDs by sending signals to bilateral epididymal tails and that some of the signals through each LSN cross to the other side at the caudal mesenteric plexus and/or the prostatic plexus.
Primary structures and effects on gastrointestinal motility of tachykinins from the rainbow trout
Authors: Jensen J. , Olson K. R. , Conlon J. M.
Published: December 2017

Purification and structural characterization of tachykinins from rainbow trout (Oncorhynchus mykiss) intestine has demonstrated the presence of three different peptides related to the mammalian tachykinins: substance P, neurokinin A, and neuropeptide-gamma. The substance P- and the neurokinin A-related peptides present in the intestine are identical to the tachykinins previously isolated from the trout brain. The neuropeptide-gamma-related peptide (Ser-Ser-Ala-Asn-Pro-Gln-Ile-Thr-Arg-Lys-Arg-His-Lys-Ile-Asn-Ser-Phe- Val-Gly-Leu-Met-NH2), not previously identified in brain tissue, has the sequence of the neurokinin A-related tachykinin at its COOH-terminus. Both trout substance P and neurokinin A stimulated the motility of isolated trout intestinal muscle [pD2(-log of EC50) values 8.5 +/- 0.15 and 7.35 +/- 0.08, respectively] and the vascularly perfused trout stomach (pD2 values 9.63 +/- 0.23 and 8.18 +/- 0.23, respectively). Trout substance P was 14 times more potent than trout neurokinin A in the intestine and 28 times more potent in the stomach. The data suggest that receptors interacting with tachykinins in the trout gastrointestinal tract have a similar selectivity as the mammalian NK-1 receptor.
Blood pressure effects of iontophoretically applied bioactive hormones in the anterior forebrain of the rat
Authors: Thornton S. N. , Nicolaidis S.
Published: December 2017

In the course of electrophysiological investigations using iontophoresis, we observed that in specific regions of the forebrain even these minute applications of peptide and steroid hormones can influence systemic blood pressure. In urethan-anesthetized male Wistar rats, with a catheter in the femoral artery, iontophoretic application of the peptide hormones angiotensin II (ANG II), vasopressin (AVP), and atrial natriuretic peptide (ANP) and the steroid hormone aldosterone (ALDO) was effective at locations in the midline septum, the triangularis nucleus of the septum, and the subfornical organ (SFO). Increases in blood pressure (of up to 15 mmHg) were observed after ANG II and AVP, decreases after ALDO, and either an increase or a decrease, depending on the location, after ANP. There was no clear evidence of an antagonistic effect of ANP on ANG II-induced neuronal or blood pressure responses. In addition to demonstrating the potency of these hormones even when they are restricted to tiny volumes of tissue, the present results demonstrate that the medial ventral region of the anterior forebrain may be included in the same baroreceptive circuit as the SFO (and organ vasculosum of the lamina terminalis) and hence be involved in the regulation of blood volume and perhaps in the sensing of and corrective responses to extracellular thirst.
Fetal ACTH and blood pressure responses to thromboxane mimetic U-46619
Authors: Wood C. E. , Cudd T. A. , Kane C. , Engelke K.
Published: December 2017

This study was performed to test the hypothesis that thromboxane A2 stimulates increases in fetal adrenocorticotropic hormone (ACTH), vasopressin, or renin secretion and affects fetal cardiovascular function by an action on the fetal central nervous system. We infused a stable synthetic analogue of thromboxane A2, U-46619, into one common carotid artery or inferior vena cava or infused saline into one common carotid artery in chronically catheterized fetal sheep between 127 and 140 days gestation. We found that intracarotid but not intravenous infusions of U-46619 at a rate of 750 ng/min stimulated increases in fetal plasma ACTH concentration. Infusions of U-46619 at both sites increased fetal blood pressure; the infusion into the carotid arterial blood produced a more rapid increase in blood pressure and a significant decrease in central venous pressure. None of the infusions altered plasma vasopressin concentration or plasma renin activity, blood gases, hematocrit, or plasma cortisol concentration. We conclude that thromboxane A2 stimulates fetal ACTH, but not vasopressin or renin, secretion via an action within the area perfused by carotid arterial blood. Thromboxane A2 increases blood pressure via an action at the fetal central nervous system, as well as via a direct vasoconstrictor action in the systemic circulation.
Gastric loads and cholecystokinin synergistically stimulate rat gastric vagal afferents
Authors: Schwartz G. J. , McHugh P. R. , Moran T. H.
Published: December 2017

Both gastric preloads and exogenous cholecystokinin (CCK) administration inhibit food intake, and combinations of preloads and CCK suppress feeding to a greater degree than either stimulus delivered alone. A role for the vagus nerve in mediating CCK's inhibition of food intake has been proposed, and gastric vagal afferent fibers respond to both gastric loads and local CCK infusions. To examine whether combined load and CCK stimuli may synergistically augment gastric neural afferent activity at the level of the peripheral vagus, we have examined the gastric vagal afferent responses (n = 8) to a range of gastric saline loads (1, 2, and 3 ml) and exogenous close celiac arterial CCK (10 and 100 pmol) when administered alone or in combination. Gastric loads ineffective in eliciting a significant increase in vagal afferent activity when administered alone became effective when combined with doses of CCK that were subthreshold for the production of a vagal afferent response. Gastric loads that alone were effective in producing a significant vagal afferent response yielded an even greater response when administered in combination with both subthreshold and suprathreshold doses of CCK. These data demonstrate that, in rats, signals produced by combined gastric load and exogenous CCK administration are integrated peripherally and interact synergistically. These results suggest that signals arising from the vagus may provide sufficient information for the synergistic inhibition of food intake produced by combinations of gastric loads and exogenous CCK.
Postpyloric stimuli are necessary for the normal control of meal size in real feeding and sham feeding rats
Authors: Davis J. D. , Smith G. P. , Miesner J.
Published: December 2017

When 0.8 M sucrose is sham fed, intake increases progressively on consecutive tests and then plateaus. Interspersing two real feeding tests between sham feeding tests prevents this increase in sham intake [J. D. Davis and G. P. Smith. Am. J. Physiol. 259 (Regulatory Integrative Comp. Physiol. 28): R1228-R1235, 1990]. This is consistent with an acquired control of ingestion based on an association between an oropharyngeal conditioned stimulus (CS) and a postingestional unconditioned stimulus (UCS). To determine if this postingestional UCS has a gastric or postgastric origin (or a combined one), we confined ingested 0.8 M sucrose to the stomach on real feeding and sham feeding tests by closing the pylorus with an inflatable Silastic cuff. Rats were tested on seven sham feeding tests separated by two real feeding tests and then on six consecutive sham feeding tests. In contrast to our previous results [Davis and Smith. Am. J. Physiol. 259 (Regulatory Integrative Comp. Physiol. 28): R1228-R1235, 1990], intake increased progressively on the real feeding and both types of sham feeding tests. We conclude that both gastric and postgastric stimuli act as a UCS for the acquired control of meal size.
An IL-1 receptor and an IL-1 receptor antagonist attenuate muramyl dipeptide- and IL-1-induced sleep and fever
Authors: Imeri L. , Opp M. R. , Krueger J. M.
Published: December 2017

It is hypothesized that the somnogenic and pyrogenic effects of muramyl dipeptide (MDP) are mediated via enhanced interleukin-1 (IL-1) production. To test this hypothesis the effects of intracerebroventricular (icv) administration of a recombinant human soluble type I IL-1 receptor (sIL-1r) and of the IL-1 receptor antagonist (IL-1ra) on MDP-induced sleep and fever were evaluated in rabbits. The sIL-1r recognized rabbit IL-1 beta, but it did not affect sleep or brain temperature across the dose range tested (1-50 micrograms) when injected icv into normal rabbits. Pretreatment of rabbits with 50 micrograms sIL-1r or 10 micrograms IL-1ra blocked human recombinant IL-1-enhanced nonrapid eye movement (NREM) sleep and fever. Thus both the sIL-1r and the IL-1ra were effective antagonists of IL-1 actions. When the animals were pretreated with either 50 micrograms sIL-1r or with 10 or 100 micrograms of the IL-1ra, the somnogenic effects of 150 pmol MDP were attenuated. However, the sIL-1r had little effect on MDP-induced febrile responses. These results suggest that the sIL-1r and the IL-1ra can function as antagonists of IL-1 actions in vivo and that MDP-induced sleep and fever are partially mediated by IL-1.
Characterization of suppression of food intake following acute colon inflammation in the rat
Authors: McHugh K. , Castonguay T. W. , Collins S. M. , Weingarten H. P.
Published: December 2017

Experimental colitis was induced in rats by intrarectal infusion of trinitrobenzenesulfonic acid and ethanol. Colitis was accompanied by a large suppression of food intake of 3 days duration. The reduction of food intake was effected through a reduction of meal size, with no change in meal frequency. Those same rats demonstrating approximately 70%-80% suppression of daily food intake showed no reduction of sham feeding. These data indicate that malaise alone is inadequate to explain the suppression of food intake associated with acute colitis. Rather, the data suggest that the suppression of eating results from an exaggerated postprandial satiety signal elaborated during the period of acute inflammation, an interpretation consistent with the demonstration of a slowed rate of gastric emptying in association with the colitis.
Lateral tegmental field neurons play a permissive role in governing the 10-Hz rhythm in sympathetic nerve discharge
Authors: Barman S. M. , Gebber G. L.
Published: December 2017

Recordings from sympathetic nerves in decerebrate cats show a variable mixture of 10-Hz and 2- to 6-Hz discharges. Although medullary lateral tegmental field (LTF) neurons are considered to be a source of the 2- to 6-Hz oscillation in sympathetic nerve discharge (SND), their role in the control of the 10-Hz rhythm has not been critically evaluated. This issue served as the focus of the current study. In the first series of experiments, spike-triggered averaging of inferior cardiac SND was used in an attempt to identify LTF neurons with activity correlated to the 10-Hz rhythm in SND. The discharges of only one of the 120 LTF neurons studied were correlated to this component of SND. In contrast, 17 of 79 neurons had activity correlated to the 2- to 6-Hz oscillation in experiments in which this component of SND was prominent. These data indicate that LTF neurons neither receive input from nor are components of the 10-Hz rhythm generator. In a second series of experiments, muscimol was microinjected into the LTF bilaterally. Chemical inactivation of the LTF either eliminated the 10-Hz rhythm or reduced the power and peak frequency in this band of SND. These data support the view that LTF neurons have a permissive role in governing the 10-Hz rhythm in SND, probably by acting on elements of the rhythm generator located elsewhere. As expected, muscimol microinjections reduced the power in the 2- to 6-Hz band in SND in some experiments.
Antidipsogenic actions of endothelins are exerted via the endothelin-A receptor in the brain
Authors: Samson W. K. , Murphy T. C.
Published: December 2017

The receptor subtype mediating the antidipsogenic effects of the endothelins (ETs) was determined in conscious, unrestrained, normally hydrated rats. Intracerebroventricular injection of 6, 12, and 20 ng ET-2 resulted in a significant, dose-related inhibition of water drinking in response to subsequent injection of 100 pmol angiotensin II (ANG II). Pretreatment with 50 or 100 ng ET-B receptor agonist failed to alter the subsequent drinking response to ANG II. Drinking in response to ANG II was significantly accentuated in rats pretreated with 50, 100, and 200 ng of the selective ET-A receptor antagonist BQ-123. These data indicate that the antidipsogenic effects of the ETs are mediated via the ET-A receptor subtype and further suggest that endogenous ET plays a physiologically relevant role in the central nervous system control of fluid and electrolyte homeostasis.
Transthyretin gene expression in choroid plexus first evolved in reptiles
Authors: Achen M. G. , Duan W. , Pettersson T. M. , Harms P. J. , Richardson S. J. , Lawrence M. C. , Wettenhall R. E. , Aldred A. R. , Schreiber G.
Published: December 2017

The presence of transthyretin in mammals and birds, but not amphibia, suggested that transthyretin expression first appeared in stem reptiles. Therefore, transthyretin synthesis was studied in a lizard. Transthyretin synthesis in choroid plexus pieces from Tiliqua rugosa was demonstrated by incorporation of radiactive amino acids. Oligonucleotides corresponding to conserved regions of transthyretin were used as primers in polymerase chain reaction with lizard choroid plexus cDNA. Amplified DNA was used to screen a lizard choroid plexus cDNA library. A full-length transthyretin cDNA clone was isolated and sequenced. A three-dimensional model of lizard transthyretin was obtained by homology modeling. The central channel of transthyretin, containing the thyroxine-binding site, was found to be completely conserved between reptiles and mammals. Transthyretin expression was not detected in lizard liver. These data suggest that transthyretin first evolved in the choroid plexus of the brain. Due to a change in tissue distribution of gene expression, occurring much later during evolution, transthyretin also became a plasma protein, synthesized in the liver.
Pancreatic glucagon suppresses gustatory responsiveness to glucose
Authors: Giza B. K. , Deems R. O. , Vanderweele D. A. , Scott T. R.
Published: December 2017

Peripheral administration of the gut peptide pancreatic glucagon (GGN) alters hepatic metabolism and suppresses feeding. Other physical (gastric distension) and chemical factors (hyperglycemia, hyperinsulinemia) that reduce food intake also suppress taste-evoked activity. This may attenuate the reinforcement derived from feeding and so promote termination of the meal. To determine whether this mechanism was operative with GGN administration, we studied the effect of hepatic portal infusions of 40 micrograms/kg pancreatic GGN on taste responses in the nucleus tractus solitarius of the rat. Taste activity was elicited by oral application of NaCl, glucose, HCl, and quinine HCl. Responses were monitored before and after injections of GGN or a control vehicle. Blood glucose levels were measured in separate groups of GGN- and vehicle-injected rats. Blood glucose increased significantly after GGN infusion and returned to control levels within 35 min. Taste responsiveness to glucose was significantly reduced after the GGN injection and recovered to preinjection levels by 36 min. Activity evoked by NaCl, HCl, and quinine HCl was unaffected. The suppression of responsiveness to sugars may reduce the hedonic appeal of tastants and so serve as a mechanism by which GGN could contribute to postprandial satiety.
Angiotensin II: nitric oxide interaction and the distribution of blood flow
Authors: Sigmon D. H. , Beierwaltes W. H.
Published: December 2017

Nitric oxide (NO) contributes to the regulation of regional blood flow. Inhibition of NO synthesis increases blood pressure and vascular resistance. Using radioactive microspheres and the substrate antagonist N omega-nitro-L-arginine methyl ester (L-NAME) (10 mg/kg) to block NO synthesis, we tested the hypothesis that there is a significant interaction between the vasodilator NO and the vasoconstrictor angiotensin II, which regulates regional hemodynamics. Further, we investigated the influence of anesthesia on this interaction. L-NAME increased blood pressure, decreased cardiac output, and increased total peripheral resistance in both anesthetized and conscious rats. In anesthetized rats, L-NAME decreased blood flow to visceral organs (i.e. kidney, intestine, and lung) but had little effect on blood flow to the brain, heart, or hindlimb. Treating anesthetized rats with the angiotensin II receptor antagonist losartan (10 mg/kg) attenuated the decrease in cardiac output and the increase in total peripheral resistance without affecting the pressor response to L-NAME. Losartan also attenuated the visceral hemodynamic responses to L-NAME. In conscious rats, L-NAME decreased blood flow to all organ beds. Treating these rats with losartan only marginally attenuated the increase in total peripheral resistance to L-NAME without significantly affecting the pressor response or the decrease in cardiac output. Losartan had no effect on the regional hemodynamic responses to L-NAME. These data suggest that NO-mediated vascular relaxation is an important regulator of total peripheral and organ vascular resistance. (ABSTRACT TRUNCATED AT 250 WORDS)
Effect of plasma osmolality on steady-state fluid shifts in perfused cat skeletal muscle
Authors: Hamilton M. T. , Ward D. S. , Watson P. D.
Published: December 2017

Fluid redistribution in isolated perfused cat calf muscle caused by rapid increases in plasma osmolality was studied using NaCl or sucrose. Extracellular tracers (51Cr-labeled EDTA or [3H]mannitol) were added to the perfusate 90 min before solutes were added, and samples were taken from plasma immediately before osmolality was increased and 17, 40, and 65 min later. Interstitial fluid volume (IFV) was calculated as extracellular volume (ECV) minus plasma volume (Evans blue dye). Total tissue water changes (delta TTW) were measured by continuous recording of tissue weight. Change in intracellular volume (delta ICV) was obtained from delta TTW--delta IFV. TTW, IFV, ICV, and plasma osmolality were in steady state after 17 min. Changes in hydrostatic and colloid osmotic pressure were insignificant in comparison with small-molecule osmotic pressure changes. The apparent volume of TTW participating in the fluid shift averaged 65 +/- 1 ml/100 g (SE) over a wide range of osmolality increases. In contrast to the large changes in TTW, IFV was not altered by osmolality. Thus decreases in TTW were similar to cell dehydration. Hence, increases in plasma volume induced by hypertonic fluids may come entirely at the expense of cell volume, not interstitial volume.
Role of intrapreoptic norepinephrine in endotoxin-induced fever in guinea pigs
Authors: Shido O. , Romanovsky A. A. , Ungar A. L. , Blatteis C. M.
Published: December 2017

The peripheral administration of pyrogens has been shown previously to affect the activity of central noradrenergic neurons, but the effects have been variable and no consensus has emerged regarding their functional significance. Because norepinephrine (NE) microdialyzed into the preoptic area (PO) of the anterior hypothalamus of conscious guinea pigs is hypothermizing, the possibility was investigated whether NE might be a febrilytic rather than a febrigenic mediator. Intravenous injections of Salmonella enteritidis lipopolysaccharide (2.0 micrograms/kg) evoked a bimodal fever, which was attenuated in a dose-dependent manner by NE microdialyzed (10 or 20 micrograms/microliters at a rate of 2 microliters/min for various durations) into the PO. The alpha 2-adrenergic receptor antagonists rauwolscine (1 or 2 micrograms/microliters) and yohimbine (1 microgram/microliter) microdialyzed intrapreoptically significantly reduced the trough of body (core) temperature (Tc) between the first and second peaks of the bimodal fever and prolonged the overall febrile course. None of these effects was associated with changes in skin temperature. The level of NE (assayed by high-performance liquid chromatography with electrochemical detection) in the preoptic extracellular fluid collected by intracerebral microdialysis was significantly elevated at the end of each rising phase of the bimodal fever, just before or about the time when Tc began to fall, compared with pyrogen-free saline controls at the same times. These results suggest that intrapreoptic NE may have a thermolytic effect on fever by reducing metabolic heat production and may thus play a physiological role in the initiation of febrilysis in guinea pigs.
De novo protein synthesis and protein phosphorylation during anoxia and recovery in the red-eared turtle
Authors: Brooks S. P. , Storey K. B.
Published: December 2017

Changes in de novo protein synthesis and protein phosphorylation were monitored during anoxia and recovery in the red-eared slider Trachemys (= Pseudemys) scripta elegans. Time courses of 35S-radiolabeled methionine incorporation into acid-precipitable material showed an increase up to 5 h postinjection and remained constant after this time. Comparison of the total and acid-precipitable 35S label incorporation into tissues from 20-h control, anoxic, and recovering animals showed differences between these groups: total radioactivity in brain was 2.9-fold lower in recovering turtles, whereas protein-associated radioactivity was 2.4-fold higher in anoxic liver, 2.3-fold lower in recovering skeletal muscle, and 3.7-fold lower in recovering brain tissue. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of radiolabeled proteins showed the existence of a newly synthesized protein band (relative molecular mass = 72 kDa) that was apparent only in 20-h recovering liver and skeletal muscle. Use of 32P labeling to monitor changes in protein phosphorylation patterns during anoxia revealed 1.6-, 1.4-, and 1.5-fold increases in 32P incorporation in anoxic brain, heart, and liver, respectively. Changes in protein phosphorylation were localized to the plasma membrane and cytosolic fractions in brain and to the cytosolic fraction in liver.
ICI 182,780 antagonizes the effects of estradiol on estrous behavior and energy balance in Syrian hamsters
Authors: Wade G. N. , Powers J. B. , Blaustein J. D. , Green D. E.
Published: December 2017

Three experiments examined the effects of ICI 182,780, a steroidal "pure" antiestrogen that is thought to be active peripherally but not in the brain when given systemically, on energy balance, estrous behavior, and in vivo cell nuclear binding of [3H]estradiol in Syrian hamsters. Pretreatment with ICI 182,780 reduced in vivo uptake of [3H]estradiol in uterus but not in pooled hypothalamus-preoptic area. Ovariectomized Syrian hamsters were treated with estradiol benzoate (EB, 5 micrograms/day), ICI 182,780 (250 micrograms/day), or both EB and ICI 182,780 for 4 wk. Estradiol treatment caused significant decreases in food intake, body weight and fat content, and linear growth. Given alone, ICI 182,780 had no effect on these measures. When they were given concurrently, ICI 182,780 attenuated the effects of estradiol on body weight, growth, and fat content but not on food intake. Treatment with ICI 182,780 significantly diminished estrous behavior induced with either EB plus progesterone or with EB alone. These findings support the hypothesis that, in addition to its actions in the brain, estradiol acts peripherally to modulate estrous behavior and energy balance.
Synchrony between breathing and shivering in three muscles of bantam hens exposed to cold eggs
Authors: Toien O.
Published: December 2017

Unrestrained, incubating bantam hens (Gallus domesticus) were exposed to cold, water-perfused eggs to induce shivering. Mean rectified electromyogram (EMG activity) was recorded from the iliotibialis, gastrocnemius, and pectoralis muscles, together with breathing and O2 consumption. EMG activity in all three muscles varied in synchrony with breathing, as confirmed by spectral analysis. The highest shivering intensity occurred during end expiration. This synchrony was also present when respiratory frequency was increased by hypercapnic/hypoxic stimuli and tended to improve with increasing respiratory frequency and tidal volume. The absolute modulation of shivering intensity remained relatively constant with increasing average intensity, indicating that breathing-modulated motor units are activated first. In the less active pectoralis muscle, all activity was modulated. Modulation is probably not restricted to one type of muscle fiber because it occurs in both predominantly red hindquarter muscles and the white pectoralis muscle. It is tentatively suggested that respiratory drive-related influence from the brain stem has a synchronizing effect on spinal cord activity. A bursting activity pattern may be more favorable for muscle circulation than a tonic discharge pattern.
Hypothermia to endotoxin involves reduced thermogenesis, macrophage-dependent mechanisms, and prostaglandins
Authors: Derijk R. H. , Van Kampen M. , Van Rooijen N. , Berkenbosch F.
Published: December 2017

At a subthermoneutral ambient temperature of 24 degrees C, intravenous administration of bacterial endotoxin (lipopolysaccharide, LPS) to rats resulted in hypothermia associated with a fall in oxygen consumption followed by fever. At the thermoneutral ambient temperature of 30 degrees C, animals only responded to LPS with fever. The hypothermia and reduction in oxygen consumption were attenuated in rats with eliminated peripheral macrophages. By contrast, macrophage elimination did not affect the febrile response to LPS. Both the hypothermia and the febrile response to LPS were prevented by peripheral administration of the cyclooxygenase inhibitor indomethacin. We conclude that hypothermia in response to LPS is caused by reduced thermogenesis, involves antipyretic products released from peripheral macrophages, and is mediated by prostaglandins. In addition, the febrile response likewise involves prostaglandins, but in contrast to the hypothermia appears to be independent of pyrogens released from peripheral macrophages. Previously, we reported the induction of the pyrogen interleukin-1 in the brain during the time course of the febrile response to LPS (34). The latter observations support the hypothesis that the second phase of biphasic fever is mediated by synthesis and action of pyrogens inside the blood-brain barrier.
Roles of skeletal muscle morphology and activity in determining Na(+)-K(+)-ATPase concentration in young pigs
Authors: Harrison A. P. , Clausen T. , Duchamp C. , Dauncey M. J.
Published: December 2017

It has been demonstrated previously that the Na(+)-K(+)-adenosinetriphosphatase (Na(+)-K(+)-ATPase) concentration (total concentration of [3H]ouabain-binding sites = maximal [3H]ouabain-binding capacity, Bmax) in longissimus dorsi muscle is higher in young pigs living in a cold than in a warm environment, with the effect being even greater in those on a low rather than a high energy intake in the cold. The importance of thyroid status, myofiber type and size, and muscular activity in determining the concentration of Na(+)-K(+)-ATPase has therefore been assessed in longissimus dorsi, semitendinosus, and soleus muscles from 8-wk-old littermate pigs, which had been living 35 or 10 degrees C on either a high or a low energy intake for 3-4 wk. Changes in neither plasma thyroid hormone concentrations nor myofiber type could account for the greater Bmax at 10 vs. 35 degrees C observed in all three muscles; instead, it was possibly related to the greater muscular activity associated with shivering in the cold. More than 50% of the increase in Bmax on the low compared with the high intake in the cold could be attributed to the smaller fiber size and hence greater membrane area in animals on the low intake, and it is concluded that membrane surface area must be assessed in studies of membrane-bound enzymes.
Increased venous PCO2 enhances dynamic responses of avian intrapulmonary chemoreceptors
Authors: Hempleman S. C. , Bebout D. E.
Published: December 2017

We quantified the neural discharge of intrapulmonary chemoreceptors (IPC) innervating the left lungs of anesthetized Pekin ducks. Right and left lungs were separately unidirectionally ventilated. Alternating steps in CO2 concentration (0-6%, 11-s period) were delivered to the left lung under control conditions [mixed venous PCO2, (PVCO2) 43 +/- 4 Torr] and under venous CO2 load conditions (PVCO2 79 +/- 6 Torr). During venous CO2 loading the right lung was ventilated with 10-20% CO2, while the left lung was ventilated with a sufficient flow of gas containing 0% CO2 to maintain normal expired PCO2 (indicated by constant IPC discharge rate). Venous loading increased the peak-to-peak amplitude of the oscillation in IPC discharge by 4.3 +/- 1.8 s-1 (n = 11, P < 0.05), left lung ventilation was increased 2.6-fold, and the IPC step response became more prompt. The mean IPC discharge rate during the CO2 stepping cycle was not significantly affected (11.8 +/- 1.4 during control vs. 10.3 +/- 1.3 s-1 during venous loading). Increased IPC discharge oscillations were due to enhancement of the dynamic overshoot in receptor discharge after the 6-0% downstep in inspired CO2 and to a depression of discharge during 6% inspired CO2. We propose that the phasic enhancement of IPC discharge oscillations during venous CO2 loading may cause feedback inhibition of ventilatory drive.
Vasopressin response to hyperosmolality and hypotension during ovine pregnancy
Authors: Keller-Wood M.
Published: December 2017

The arginine vasopressin (AVP) responses to hyperosmolality and to hypotension were compared in pregnant and nonpregnant ewes. When the responses to infusion of normal or hypertonic saline were compared, plasma AVP and Na+ concentrations were lower in pregnant ewes than nonpregnant ewes, but the relation between plasma AVP and Na+ concentrations was not altered in the pregnant state. In a second study the AVP response to hypotension, induced by the infusion of 2.5, 5.0, or 10.0 micrograms nitroprusside.kg-1.min-1, was compared in pregnant and nonpregnant ewes. Despite significantly lower mean arterial blood pressures in the pregnant ewes, the mean plasma AVP concentration after infusion of nitroprusside was not increased during pregnancy. Therefore, the relation between mean arterial pressure and AVP was significantly shifted to the left in the pregnant ewes, indicating lower AVP concentrations for a given level of arterial pressure during pregnancy. The results suggest that pregnancy alters the regulation of AVP by arterial pressure but does not affect the regulation of AVP by plasma sodium concentration in the ewe.
Nitric oxide actions in paraventricular nucleus: cardiovascular and neurochemical implications
Authors: Horn T. , Smith P. M. , McLaughlin B. E. , Bauce L. , Marks G. S. , Pittman Q. J. , Ferguson A. V.
Published: December 2017

We have examined potential functions of nitric oxide (NO) within the paraventricular nucleus (PVN) in urethan-anesthetized male Sprague-Dawley rats. Initial experiments demonstrated microinjection of 50 pmol of the NO donor, sodium nitroprusside (SNP), directly into the PVN resulted in significant decreases in mean blood pressure (BP) (-3,312 +/- 1,189 mmHg/s over 300-s response time; P < 0.05). To determine whether such effects were attributable to SNP-induced NO release, NO was administered into PVN directly by bilateral microdialysis of NO-containing artificial cerebrospinal fluid (NO-aCSF), a process that results in delivery of approximately 50 pmol NO.PVN-1 x min-1. Such microdialysis resulted in significant decreases in BP (-5,121 +/- 817 mmHg/s over 1,200-s response time; P < 0.005), while aCSF microdialysis was without effect (1,298 +/- 1,071 mmHg/s over 1,200-s response time; P > 0.1). Amino acid concentrations were measured in dialysates collected during perfusion of the same PVN sites with either aCSF or NO-aCSF by high-performance liquid chromatography (HPLC) analysis. NO-aCSF induced significant increases in aspartate (aCSF 31 +/- 7 pmol/30 min; NO-aCSF 134 +/- 33 pmol/30 min; P < 0.05), glutamate (aCSF 36 +/- 5 pmol/30 min; NO-aCSF 417 +/- 108 pmol/30 min; P < 0.02), gamma-aminobutyric acid (aCSF 4.1 +/- 0.7 pmol/30 min; NO-aCSF 104 +/- 29 pmol/30 min; P < 0.02), and taurine (aCSF 34 +/- 3 pmol/30 min; NO-aCSF 117 +/- 24 pmol/30 min; P < 0.01) concentrations, while alanine, glutamine, and serine concentrations were unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)
Chronic stress affects immunologic but not cardiovascular responsiveness to acute psychological stress in humans
Authors: Benschop R. J. , Brosschot J. F. , Godaert G. L. , De Smet M. B. , Geenen R. , Olff M. , Heijnen C. J. , Ballieux R. E.
Published: December 2017

This study deals with the effect of chronic stress on physiological responsiveness to an acute psychological stressor in male high school teachers. Chronic stress was operationalized as the self-reported number of everyday problems. Twenty-seven subjects reporting extremely low or high numbers of everyday problems were exposed to an acute psychological stressor, and changes in immunologic, endocrine, and cardiovascular parameters were monitored. The stressor included a learning process followed by a teaching session in which a confederate to the researchers was involved. Twenty subjects served as controls. The stressor had no effect on the endocrine variables measured but induced increases in heart rate and blood pressure, which were similar in both chronic stress groups. Analysis of subsets of blood lymphocytes revealed differences in natural killer (NK) and T cell responses in the low and the high stress groups. It is concluded that 1) immunologic responsiveness to an acute psychological stressor is related to problems experienced in daily life, and that 2) chronic stress differentially modifies the sensitivity of biological systems to mild acute stressors.
Effects of 2-buten-4-olide, an endogenous satiety substance, on plasma glucose, corticosterone, and catecholamines
Authors: Matsumoto I. , Oomura Y. , Nishino H. , Nemoto S. , Aou S. , Aikawa T.
Published: December 2017

Effects of 2-buten-4-olide (2-B4O), an endogenous satiety substance, on levels of plasma glucose, corticosterone, and catecholamines were examined in fed, conscious, and unrestrained rats. A vascular indwelling catheter was inserted into the right atrium of the animal from the jugular vein 1 wk before the experiment. Injection of 2-B4O and blood sampling were performed through the catheter in an unanesthetized condition. The levels of plasma glucose, corticosterone, epinephrine, and norepinephrine increased significantly for 2 h after the start of intravenous injection of 2-B4O in a dose-dependent manner. The increases in glucose and catecholamines induced by 2-B4O injection were abolished by bilateral splanchnicotomy (SPX) but not by pretreatment with anti-corticotropin-releasing factor (CRF) antibody. The increase in corticosterone was abolished not by the SPX but by pretreatment with anti-CRF antibody. These findings suggest that 2-B4O, endogenously produced during food deprivation, may facilitate sympathoadrenal and hypothalamopituitary-adrenal functions through the central nervous system.
Kinetic evaluation of muscle damage during exercise by calculation of amount of creatine kinase released
Authors: Volfinger L. , Lassourd V. , Michaux J. M. , Braun J. P. , Toutain P. L.
Published: December 2017

To quantify the extent of muscle alteration during prolonged exercise, the release rate of creatine kinase (CK) from striated muscle was measured in six horses during a rest period (6 h) and during three exercise tests (15, 30, and 60 km) at a constant speed of 200 m/min. CK clearance was measured after intravenous bolus administration (150 U/kg) of a CK solution obtained from horse muscle. The CK steady-state volume of distribution was 0.059 +/- 0.0215 l/kg, the terminal half-life was 123 +/- 28 min, and the plasma clearance was 0.36 +/- 0.10 ml.kg-1 x min-1. After an intramuscular CK administration, the CK systemic availability was 74.1 +/- 21.2% and the half time of absorption was 9.4 +/- 5.7 h, indicating a slow process for CK transit through the lymphatic system. The CK release rate was only significantly increased during the 60-km exercise test. The increase of CK plasma activity was observed after a delay of approximately 5 h and peaked after the end of the race; the estimated CK release rate was 9.92 +/- 2.62 U.kg-1 x h-1 over a mean duration period of 65.8 +/- 15.8 h. With the CK activity of horse striated muscle taken into account, a 60-km race released a quantity of CK corresponding to an equivalent of 18.8 +/- 4.3 g striated muscle. It is concluded that the equivalent amount of damaged muscle may be considered as negligible for a 60-km test and that only very high plasma CK activity levels (at least higher than 10,000 U/l) may provide some evidence of a myolysis.
Cardiac hypertrophy and brain natriuretic peptide in experimental hypertension
Authors: Kohno M. , Fukui T. , Horio T. , Yokokawa K. , Yasunari K. , Yoshiyama M. , Kurihara N. , Takeda T.
Published: December 2017

The blood pressure was decreased after chronic treatment with enalapril, MK-954, and hydralazine in deoxycorticosterone acetate (DOCA)-salt-induced malignant hypertension of spontaneously hypertensive rats (SHR); however, ventricular weight and plasma brain natriuretic peptide (BNP) concentration were decreased after enalapril and MK-954 but not after hydralazine. The BNP secretory rates from the ventricle in enalapril- and MK-954-treated DOCA-salt SHR were decreased to approximately 50% of those in untreated DOCA-salt SHR. The BNP secretory rate from the ventricle was positively correlated with ventricular weight in untreated and treated DOCA-salt SHR. In contrast, acute administration of captopril or MK-954 did not decrease the BNP secretory rate from the heart. Results suggest that the decrease in plasma BNP after enalapril and MK-954 is attributed to a decline in the secretion from the ventricle but not from the atrium. The reduction in ventricular mass appeared to be related to this decline.
Duodenal sucrose and glucose infusions enhance suppression by cholecystokinin of sham feeding
Authors: Cox J. E.
Published: December 2017

In two experiments I examined whether intraduodenal sucrose and glucose would enhance inhibition of sham feeding by cholecystokinin-8 (CCK-8). In the first experiment, adult male Sprague-Dawley rats received infusions of 0.88 M (30%, wt/vol) sucrose or normal saline at 0.51 ml/min for the first 7.67 min of 30-min sham-feeding tests. Tests began 10 min after intraperitoneal injections of saline or 0.5, 1, or 2 micrograms/kg CCK-8. When sucrose was infused, all doses of CCK-8 reduced sham feeding of 0.88 M sucrose by 60% or more, but with saline infusions, only the highest dose was effective. In the second experiment, rats received 30-min infusions of 0.3 M (5.4%) or 0.6 M (10.8%) glucose or equimolar saline at 0.388 ml/min. Although 1 microgram/kg CCK-8 was ineffective in the absence of infusions, it significantly reduced intake in combination with both concentrations of glucose and hypertonic (0.6 M) saline. Behavioral observations indicated that reductions in intake were attributable primarily to decreased meal length and slower intake. These results suggest that an intestinal signal may contribute to the previously reported ability of preloads to potentiate CCK satiety.
Increased potency of carbachol in isolated rat left atria after chronic reserpine pretreatment
Authors: Lenz S. J. , Ramos B. L. , Stamper M. C. , Wince L. C.
Published: December 2017

Chronic reserpine pretreatment has been shown to produce postjunctional beta-adrenergic supersensitivity in cardiac tissue. The present investigation was undertaken to determine whether chronic reserpine administration also alters the heart's sensitivity to muscarinic cholinoceptor agonists. The direct and indirect (antiadrenergic) negative inotropic effects of muscarinic agonists were examined in isolated rat left atria at various times after initiation of reserpine pretreatment (1.0 mg.kg-1 x day-1 for 7 days). Supersensitivity to the positive inotropic effects of isoproterenol was demonstrated at 1, 2, and 3 wk after initiation of treatment. Concentration-response curves were then obtained for the muscarinic agonist carbachol and the adenosine A1 receptor agonist (-)-N6-(2-phenylisopropyl)-adenosine (PIA) in reducing the inotropic response to isoproterenol (3.16 microM). The potency of carbachol was increased by approximately 2.0-fold at 1, 2, and 3 wk. Also, sensitivity to the direct negative inotropic effects of carbachol was increased 1.7-fold at 1 wk but not at 2 and 3 wk. At 1 wk, reserpine pretreatment did not alter either the direct or the indirect negative inotropic effects of PIA. These results show that postjunctional beta-adrenergic supersensitivity produced by chronic reserpine pretreatment is accompanied by a reciprocal increase in sensitivity of isolated rat left atria to the negative inotropic effects of muscarinic agonists.
Gastric damage and body weight loss in LHA-lesioned rats: effects of cytoprotective geranylgeranylacetone
Authors: Namiki T. , Egawa M. , Inoue S. , Tominaga S. , Takamura Y.
Published: December 2017

We investigated the development of gastric damage and body weight (BW) loss in lateral hypothalamic area (LHA)-lesioned rats, measured 2 h and 1 and 3 days after the lesioning (experiment 1), as well as the effects of geranylgeranylacetone (GGA), a cytoprotective antiulcer agent, on these disorders (experiment 2). In experiment 1, BW of LHA-lesioned rats decreased throughout the 3-day experiment. In LHA-lesioned rats, gastric mucosal lesions appeared 1 day after lesioning in the glandular portion and persisted, whereas those in the rumenal portion appeared only after 3 days. Gastric transepithelial potential differences (PDs) of glandular portion began to decrease after 2 h and had decreased in both portions. Gastric acid output was increased transiently at 2 h but it was not high after 1 day and after 3 days was lower than that in sham-LHA-lesioned rats. In experiment 2, PDs of the rumenal decreased more in LHA-lesioned rats than in sham-LHA-lesioned rats pair fed to LHA-lesioned rats after 3 days. Three days of treatment with GGA (200 mg/kg ip) improved PDs of rumenal and glandular portions in LHA-lesioned rats and reduced lesions of the rumenal portion. Loss of BW in LHA-lesioned rats was significantly but not completely inhibited by GGA. These results indicate that disturbance to the gastric defensive mechanism plays an important role in the development of gastric lesions after LHA lesions and that the impairment of gastric functions may be a partial cause of the loss of BW in LHA-lesioned rats.
Enhanced pressor responses to ICV vasopressin after pretreatment with oxytocin
Authors: Poulin P. , Komulainen A. , Takahashi Y. , Pittman Q. J.
Published: December 2017

The role of oxytocin (OT) in the modulation of arginine vasopressin (AVP)-induced cardiovascular effects within the central nervous system was investigated in urethan-anesthetized rats. Intracerebroventricular injection of AVP (1-10 pmol) produced dose-dependent increases in mean arterial pressure (MAP) and heart rate (HR). These responses were enhanced in rats pretreated 24 h earlier with OT (10 pmol icv). The enhanced cardiovascular effects of AVP in OT-pretreated animals were dose dependent, blocked by the V1 antagonist d(CH2)5Tyr(Me)AVP, not evoked by OT alone, and occurred in the absence of changes in basal (nonstimulated) MAP and HR. In addition, central administration of AVP in OT-pretreated rats, but not in saline-pretreated controls, caused dose-dependent oscillations of the MAP and HR responses and, at higher doses, death of the animals. The enhanced cardiovascular actions of centrally injected AVP in OT-pretreated rats do not appear to be secondary to skeletal muscle contractions or the result of cerebral ischemia. Our data point to an interaction between the central oxytocinergic and vasopressinergic systems in cardiovascular control.
Relationship between body mass and biomechanical properties of limb tendons in adult mammals
Authors: Pollock C. M. , Shadwick R. E.
Published: December 2017

We investigated the allometric relationship between the mechanical properties of various limb tendons and body mass. The elastic modulus (i.e., stiffness) and hysteresis (i.e., energy dissipation) of digital flexor, ankle extensor, and digital extensor tendons from 18 species of adult quadrupedal mammals ranging in body mass from 0.5 to 545 kg were determined by cyclic tensile testing in vitro. The results show that these elastic properties do not vary significantly among tendons from animals of different body mass, nor do they differ between the digital flexor and ankle extensor tendons (those situated to act as springs during locomotion) and the digital extensor tendons (those not likely to function as springs during locomotion). Consequently, the inherent capability of different limb tendons to store elastic energy, based on their material properties, is the same for large and small animals. The relationship between tendon elastic modulus (E; in GPa) and body mass (Mb; in kg) is described by the allometric equation E = 1.22Mb0.00. The hysteresis (H), as a percentage of total strain energy, is related to body mass as H = 8.89Mb-0.03.
Effect of chronic ANG I-converting enzyme inhibition on aging processes. I. Kidney structure and function
Authors: Heudes D. , Michel O. , Chevalier J. , Scalbert E. , Ezan E. , Bariety J. , Zimmerman A. , Corman B.
Published: December 2017

The effect of angiotensin I-converting enzyme inhibition (ACEI) on the age-related changes in the kidney structure and function was investigated in rodents. Normotensive male Wistar (WAG)/Rij rats were treated with perindopril from the age of 6 mo to the day of killing at 12, 24, or 30 mo. Mean blood pressure, constant from 6 to 30 mo, was reduced by 19 mmHg in treated animals. With age, the major functional modifications were a decrease in glomerular filtration rate and in renal blood flow, a rise in intrarenal vascular resistance (IVR), a reduced tubular reabsorption of salts, and a progressive increase in proteinuria. ACEI significantly reduced IVR and proteinuria. From a structural point of view, the glomeruli showed 1) an increase in size, 2) a decrease in capillary surface, 3) a diffuse thickening of the glomerular basement membrane, 4) an expansion of the mesangial matrix, and 5) an accumulation of albumin droplets in podocytes inducing 6) a dispersed focal and segmental glomerulosclerosis which, at 30 mo, affected < 2% of glomeruli. Of these six age-related structural changes, ACEI delayed the appearance of the three latter changes.