bluuebunny/crossref_metadata_2025 huggingface dataset:
Intestinal transport of monosaccharides and amino acids during postnatal development of mink
Authors: Buddington Randal K. , Malo Christiane , Sangild Per T. , Elnif Jan
Published: December 2017

Intestinal development is typically studied using omnivores. For comparative purposes, we examined an altricial carnivore, the mink ( Mustela vison). In mink, intestinal dimensions increase up to 8 wk after birth and then remain constant (length) or decrease (mass) into maturity despite continuing gains in body mass. Rates of glucose and fructose transport decline after birth for intact tissues but increase for brush-border membrane vesicles (BBMV). Rates of absorption for five amino acids that are substrates for the acidic (aspartate), basic (lysine), neutral (leucine and methionine), and imino acid (proline) carriers increase between birth and 24 h for intact tissues before declining, but increase after 2 wk for BBMV. The proportion of BBMV amino acid uptake that is Na+-dependent increases during development but for aspartate is nearly 100% at all ages. Tracer uptake by BBMV can be inhibited by 100 mmol/l of unlabeled amino acid, except for lysine. BBMV uptake of the dipeptide glycyl-sarcosine does not differ between ages, is not Na+ dependent, and is only partially inhibited by 100 mmol/l unlabeled dipeptide. Despite the ability to rapidly and efficiently digest high dietary loads of protein, rates of amino acid and peptide absorption are not markedly higher than those of other mammals.
Swim bladder gas gland cells produce surfactant: in vivo and in culture
Authors: Prem C. , Salvenmoser W. , Würtz J. , Pelster B.
Published: December 2017

Electron microscopical examination of gas gland cells of the physostome European eel ( Anguilla anguilla) and of the physoclist perch ( Perca fluviatilis) revealed the presence of significant numbers of lamellar bodies, which are known to be involved in surfactant secretion. In the perch, in which the gas gland is a compact structure and gas gland cells are connected to the swim bladder lumen via small canals, lamellar bodies were also found in flattened cells forming the swim bladder epithelium. Flat epithelial cells are absent in the eel swim bladder, in which the whole epithelium consists of cuboidal gas gland cells. In both species, Western blot analysis using specific antibodies to human surfactant protein A (SP-A) showed a cross-reaction with swim bladder tissue homogenate proteins of ∼65 kDa and in the eel occasionally of ∼120 kDa, probably representing SP-A-like proteins in a dimeric and a tetrameric state. An additional band was observed at ∼45 kDa. Western blots using antibodies to rat SP-D again resulted in a single band at ∼45 kDa in both species, suggesting that there might be a cross-reaction of the antibody to human SP-A with an SP-D-like protein of the swim bladder tissue. To localize the surfactant protein, eel gas gland cells were cultured on permeable supports. Under these conditions, the gas gland cells regain their characteristic polarity. Electron microscopy confirmed the presence of lamellar bodies in cultured cells, and occasionally, exocytotic events were observed. Immunohistochemical staining using an antibody to human SP-A demonstrated the presence of surfactant protein only in luminal membranes and in adjacent lateral membranes. Only occasionally, evidence was found for the presence of surfactant protein in lamellar bodies.
A test of biochemical symmorphosis in a heterothermic tissue: bluefin tuna white muscle
Authors: Fudge Douglas S. , Ballantyne James S. , Stevens E. Don
Published: December 2017

To test predictions of biochemical symmorphosis, we measured the activity of seven consecutive glycolytic enzymes at three positions along the heterothermic white muscle of the bluefin tuna. Biochemical symmorphosis predicts that adjustments in sequential enzyme concentrations along a thermal gradient should occur as a function of the thermal sensitivity of the enzymes to ensure that no one enzyme in the pathway is in excess at any point along the gradient. We found no evidence for adjustments in enzyme quantity or quality along the thermal gradient, as well as no evidence for the prediction that the more temperature-sensitive enzymes would exhibit more dramatic compensation. Conservation of glycolytic flux in the cold exterior and warm interior muscle may be achieved by the near insensitivity of glyceraldehyde-3-phosphate dehydrogenase to temperature in this tissue. This may have the added benefit of moderating flux during seasonal or transient changes in the thermal gradient. According to the strictest application of biochemical symmorphosis, such a mechanism represents adequate, yet suboptimal design.
Neurophysiological basis for neurogenic-mediated articular cartilage anabolism alteration
Authors: Gouze-Decaris Elvire , Philippe Lionel , Minn Alain , Haouzi Philippe , Gillet Pierre , Netter Patrick , Terlain Bernard
Published: December 2017

This study was designed to investigate the pathways involved in neurogenic-mediated articular cartilage damage triggered by a nonsystemic distant subcutaneous or intra-articular inflammation. The cartilage damage was assessed 24 h after subcutaneous or intra-articular complete Freund's adjuvant (CFA) injection measuring patellar proteoglycan (PG) synthesis (ex vivo [Na235SO4] incorporation) in 96 Wistar rats. Unilateral subcutaneous or intra-articular injection of CFA induced significant decrease (25–29%) in PG synthesis in both patellae. Chronic administration of capsaicin (50 mg · kg−1· day−1during 4 days), which blunted the normal response of C fiber stimulation, prevented the bilateral significant decrease in cartilage synthesis. Similarly, intrathecal injection of MK-801 (10 nmol/day during 5 days), which blocked the glutamatergic synaptic transmission at the dorsal horn of signal originating in primary afferent C fibers, eliminated the CFA-induced PG synthesis decrease in both patellae. Chemical sympathectomy, induced by guanethidine (12.5 mg · kg−1· day−1during 6 wk), also prevented PG synthesis alteration. Finally, compression of the spinal cord at the T3-T5 level had a similar protective effect on the reduction of [Na235SO4] incorporation. It is concluded that the signal that triggers articular cartilage synthesis damage induced by a distant local inflammation 1) is transmitted through the afferent C fibers, 2) makes glutamatergic synaptic connections with the preganglionic neurons of the sympathetic system, and 3) involves spinal and supraspinal pathways.
ACTH inhibits the capsaicin-evoked release of CGRP from rat adrenal afferent nerves
Authors: Ulrich-Lai Yvonne M. , Harding-Rose Catherine A. , Guo Athena , Bowles Walter R. , Engeland William C.
Published: December 2017

The adrenal cortex is innervated by afferent fibers that have been implicated in affecting cortical steroidogenesis. Modulation of neurotransmitter release from afferents may represent a regulatory system for the control of adrenal cortical function. The present studies validate an in vitro superfusion technique for adrenal capsules employing the drug capsaicin, which activates a subset of afferent fibers and induces the release of calcitonin gene-related peptide (CGRP). Capsaicin-evoked CGRP release from adrenal afferents was blocked by capsazepine, a competitive antagonist for the capsaicin receptor, or by removal of extracellular calcium. Exogenous ACTH prevented capsaicin-evoked CGRP release, elevated basal aldosterone release, and prevented capsaicin-induced reduction in aldosterone release. Immunolabeling for the recently cloned capsaicin vanilloid receptor 1 demonstrated its presence in adrenal nerves. These results show that in vitro superfusion of adrenal capsules can be used to characterize factors that modulate neurotransmitter release from adrenal afferents. Furthermore, the results suggest that activation of adrenal afferents in vivo may attenuate aldosterone steroidogenesis and that high levels of ACTH may prevent this phenomenon.
Uteroplacental insufficiency alters hepatic fatty acid-metabolizing enzymes in juvenile and adult rats
Authors: Lane Robert H. , Kelley David E. , Gruetzmacher Elisa M. , Devaskar Sherin U.
Published: December 2017

Multiple adult morbidities are associated with intrauterine growth retardation (IUGR) including dyslipidemia. We hypothesized that uteroplacental insufficiency and subsequent IUGR in the rat would lead to altered hepatic fatty acid metabolism. To test this hypothesis, we quantified hepatic mRNA levels of acetyl-CoA carboxylase (ACC), carnitine palmitoyltransferase (CPTI), the β-oxidation-trifunctional protein (HADH), fasting serum triglycerides, and hepatic malonyl-CoA levels at different ages in control and IUGR rats. Fetal gene expression of all three enzymes was decreased. Juvenile gene expression of CPTI and HADH continued to be decreased, whereas gene expression of ACC was increased. Serum triglycerides were unchanged. A sex-specific response was noted in the adult rats. In males, serum triglycerides, hepatic malonyl-CoA levels, and ACC mRNA levels were significantly increased, and CPTI and HADH mRNA levels were significantly decreased. In contrast, the female rats demonstrated no significant changes in these variables. These results suggest that uteroplacental insufficiency leads to altered hepatic fatty acid metabolism that may contribute to the adult dyslipidemia associated with low birth weight.
Evolution of the Na-Picotransport systems
Authors: Werner Andreas , Kinne Rolf K. H.
Published: December 2017

Membrane transport systems for Pitransport are key elements in maintaining homeostasis of Piin organisms as diverse as bacteria and human. Two Na-Picotransporter families with well-described functional properties in vertebrates, namely NaPi-II and NaPi-III, show conserved structural features with prokaryotic origin. A clear vertical relationship can be established among the mammalian protein family NaPi-III, a homologous system in C. elegans, the yeast system Pho89, and the bacterial Pitransporter Pit. An alternative lineage connects the mammalian NaPi-II-related transporters with homologous proteins from Caenorhabditis elegans and Vibrio cholerae. The present review focuses on the molecular evolution of the NaPi-II protein family. Preliminary results indicate that the NaPi-II homologue cloned from V. cholerae is indeed a functional Pitransporter when expressed in Xenopus oocytes. The closely related NaPi-II isoforms NaPi-IIa and NaPi-IIb are responsible for regulated epithelial Na-dependent Pitransport in all vertebrates. Most species express two different NaPi-II proteins with the exception of the flounder and Xenopus laevis, which rely on only a single isoform. Using an RT-PCR-based approach with degenerate primers, we were able to identify NaPi-II-related mRNAs in a variety of vertebrates from different families. We hypothesize that the original NaPi-IIb-related gene was duplicated early in vertebrate development. The appearance of NaPi-IIa correlates with the development of the mammalian nephron.
Role of non-NMDA receptors in vasopressin and oxytocin release from rat hypothalamo-neurohypophysial explants
Authors: Morsette Delmore J. , Sidorowicz Hanna , Sladek Celia D.
Published: December 2017

Glutamate is recognized as a prominent excitatory transmitter in the supraoptic nucleus (SON) and is involved in transmission of osmoregulatory information from the osmoreceptors to the vasopressin (VP) and oxytocin (OT) neurons. Explants of the hypothalamo-neurohypophysial system were utilized to characterize the roles of the non- N-methyl-d-aspartate (NMDA) glutamate receptor subtypes (non-NMDA-Rs), kainic acid receptors (KA-Rs), and aminopropionic acid receptors (AMPA-Rs) and to evaluate the interdependence of NMDA-Rs and non-NMDA-Rs in eliciting hormone release. Although both KA and AMPA increased hormone release, a specific agonist of the KA-Rs, SYM-2081, was not effective. This combined with the finding that cyclothiazide, an agent that inhibits the desensitization of AMPA-Rs, increased the VP response to both KA and AMPA indicates that the increase in hormone release induced by the non-NMDA agonists is mediated via AMPA-Rs, rather than KA-Rs. Inhibition of osmotically stimulated VP and OT release by a specific AMPA-R antagonist indicated that AMPA-Rs are essential for mediating osmotically stimulated hormone release. NMDA-stimulated VP but not OT release was prevented by blockade of non-NMDA-Rs, but AMPA-stimulated VP/OT release was not prevented by NMDA-R blockade.
Diminished satiation in rats exposed to elevated levels of endogenous or exogenous cholecystokinin
Authors: Covasa Mihai , Marcuson Jeremy K. , Ritter Robert C.
Published: December 2017

Rats maintained on a high-fat (HF) diet exhibit reduced sensitivity to the satiation-producing effect of exogenous CCK. Because more CCK is released in response to HF meals than low-fat (LF) meals, we hypothesized that increased circulating CCK associated with ingestion of HF diets contributes to the development of decreased CCK sensitivity. To test this hypothesis, we implanted osmotic minipumps filled with either NaCl or CCK octapeptide into the peritoneal cavity. Subsequently, we examined the effect of intraperitoneal NaCl or CCK (0.5 μg/kg) injection on 30-min food intake. CCK significantly reduced 30-min food intake less in rats implanted with CCK-releasing minipumps compared with those with NaCl-releasing minipumps. Because dietary protein is a potent releaser of endogenous CCK, we hypothesized that rats adapted to a high-protein (HP) diet might also exhibit reduced sensitivity to exogenous CCK. Therefore, in a second experiment, we examined CCK-induced reduction of food intake in rats maintained on LF and rats maintained on HF or HP. Ingestion of LF stimulates very little endogenous CCK secretion, whereas both HF and HP markedly increase plasma CCK concentrations. Both doses of CCK reduced food intake significantly less in HF and HP rats compared with LF rats. There were no differences in 24-h food intake, body weight, or body fat composition among LF-, HF-, and HP-fed rats. These results are consistent with the hypothesis that sustained elevation of CCK either by infusion of exogenous CCK or by dietary-induced elevation of plasma CCK contributes to the development of reduced sensitivity to exogenous CCK.
Hypoalgesia and hyperalgesia with inherited hypertension in the rat
Authors: Taylor Bradley K. , Roderick Robyn E. , St. Lezin Elizabeth , Basbaum Allan I.
Published: December 2017

Many studies indicate that blood pressure control systems can attenuate pain (hypoalgesia) of short duration; however, we recently found exaggerated nociceptive responses (hyperalgesia) of persistent duration in the spontaneously hypertensive rat (SHR). Here, we used SHR, Dahl Salt-Sensitive (SS), and normotensive control rats to evaluate the contribution of sustained elevations in arterial pressure to nociceptive responses. Compared with Sprague-Dawley and/or Wistar-Kyoto controls, SHR were 1) hypoalgesic in the hot plate test and 2) hyperalgesic in longer latency tail and paw-withdrawal tests and in two models of inflammatory nociception. These differences were not observed between SS and salt-resistant controls fed a high-salt diet. Inflammatory hyperalgesia in SHR was correlated with neither paw edema nor the number of Fos-positive spinal cord neurons. Our results indicate that “pain” phenotype of the SHR is not restricted to hypoalgesia. This phenotype is related to genetic factors or to the autonomic systems that control blood pressure and not to sustained elevations in blood pressure, differences in spinal neuron activity, or inflammatory edema.
The small intestine plays an important role in upregulating CGRP during sepsis
Authors: Zhou Mian , Arthur Angelé J. , Ba Zheng F. , Chaudry Irshad H. , Wang Ping
Published: December 2017

Although studies have indicated that calcitonin gene-related peptide (CGRP), a potent vasodilatory peptide, is upregulated after endotoxic shock, it remains controversial whether this peptide increases during sepsis and, if so, whether the gut is a significant source of CGRP under such conditions. To study this, polymicrobial sepsis was induced by cecal ligation and puncture (CLP) followed by fluid resuscitation. Plasma levels of CGRP were measured at 2, 5, and 10 h after CLP (i.e., early, hyperdynamic sepsis) and at 20 h after CLP (late, hypodynamic sepsis). The results indicate that plasma CGRP did not increase at 2–5 h but increased by 177% at 10 h after CLP ( P < 0.05). At 20 h after the onset of sepsis, however, the elevated plasma CGRP returned to the sham level. To determine the source of the increased plasma CGRP, the liver, spleen, small intestine, lungs, and heart were harvested, and tissue CGRP was assayed at 10 h after CLP in additional animals. Only the small intestine showed a significant increase in tissue levels of CGRP (by 129%, P < 0.05). Determination of portal vs. systemic levels of CGRP indicates that portal CGRP was 65.7 ± 22.7% higher than the systemic level at 10 h after CLP, whereas portal CGRP in sham-operated rats was only 4.9 ± 2.1% higher. Immunohistochemistry examination revealed that CGRP-positive stainings increased in the intestinal tissue but not in the liver at 10 h after the onset of sepsis. The distribution of CGRP stainings was associated with intestinal nerve fibers. These results, taken together, demonstrate that upregulation of CGRP occurs transiently during the progression of sepsis (at the late phase of the hyperdynamic sepsis), and the gut appears to be a major source of such an increase in circulating levels of this peptide.
Carbon monoxide is the heme oxygenase product with a pyretic action: evidence for a cGMP signaling pathway
Authors: Steiner Alexandre A. , Branco Luiz G. S.
Published: December 2017

We have recently reported that the central heme oxygenase (HO) pathway has an important role in the genesis of lipopolysaccharide fever. However, the HO product involved, i.e., biliverdine, free iron, or carbon monoxide (CO), has not yet been identified with certainty. Therefore, in the present study, we tested the thermoregulatory effects of all HO products. Body core temperature (Tc) and gross activity of awake, freely moving rats was measured by biotelemetry. Intracerebroventricular administration of heme-lysinate (152 nmol), which induces the HO pathway, evoked a marked increase in Tc, a response that was attenuated by intracerebroventricular pretreatment with the HO inhibitor zinc deuteroporphyrin 2,4-bis glycol (200 nmol), indicating that an HO product has a pyretic action in the central nervous system (CNS) of rats. Besides, heme-lysinate also increased gross activity, but no correlation was found between this effect and the increase in Tc. Moreover, intracerebroventricular biliverdine or iron salts at 152 nmol, a dose at which heme-lysinate was effective in increasing Tc, produced no change in Tc. Accordingly, intracerebroventricular treatment with the iron chelator deferoxamine elicited no change in basal Tcand did not affect heme-induced pyresis. However, heme-induced pyresis was completely prevented by the soluble guanylate cyclase (sGC) inhibitor 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxaline-1-one. Because biliverdine and iron had no thermoregulatory effects and CO produces most of its actions via sGC, these data strongly imply that CO is the only HO product with a pyretic action in the CNS.
Vasopressin pressor receptor-mediated activation of HPA axis by acute ethanol stress in rats
Authors: László Ferenc A. , Varga Csaba , Pávó Imre , Gardi János , Vecsernyés Miklós , Gálfi Márta , Morschl Éva , László Ferenc , Makara Gábor B.
Published: December 2017

The plasma arginine vasopressin (AVP), ACTH, and corticosterone levels and the hypothalamic corticotropin-releasing hormone (CRH) content were measured after oral administration of 1 ml of 75% ethanol to rats, a model known to induce acute gastric erosions and stress.

Elevated plasma AVP, ACTH, and corticosterone levels were detected 1 h after ethanol administration. Treatment with the vasopressin pressor (V1) receptor antagonist [d(CH2)5Tyr(Me)-AVP] before ethanol administration significantly reduced the ACTH and corticosterone level increases. A higher hypothalamic CRH content was measured at 30 or 60 min after ethanol administration. V1receptor antagonist injection, 5 min before ethanol administration, inhibited the rise in hypothalamic CRH content. The protein synthesis blocker cycloheximide prevented the hypothalamic CRH content elevation after stress. The AVP-, CRH-, and AVP + CRH-induced in vitro ACTH release in normal anterior pituitary tissue cultures was also prevented by pretreatment with the V1receptor antagonist.

The results support the hypothesis that stress-induced AVP may not only act directly on the ACTH producing anterior pituitary cells but also indirectly at the hypothalamic level via the synthesis and release of CRH.
Caffeine stores and dopamine differentially require Ca2+channels in goldfish somatotropes
Authors: Wong Calvin J. H. , Johnson James D. , Yunker Warren K. , Chang John P.
Published: December 2017

The regulation of growth hormone (GH) secretion by intracellular Ca2+stores was studied in dissociated goldfish somatotropes. We characterized a caffeine-activated intracellular store that had been shown to mediate GH release in response to gonadotropin-releasing hormone. The peak response of caffeine stimulation was reduced by ∼28% by 100 μM ryanodine in a use-dependent manner suggesting that the first 10 min of GH release is partially mediated by a caffeine-activated ryanodine receptor. The temporal sensitivities of caffeine- and dopamine-evoked GH release to blockade of Cd2+-sensitive Ca2+channels were compared. We demonstrated that the initial phase of dopamine-evoked release was dependent on Ca2+channels, whereas the initial phase of caffeine-evoked release was sensitive only to pretreatment blockade. This would suggest that the maintenance of one class of caffeine-activated intracellular stores requires entry of Ca2+through Cd2+-sensitive Ca2+channels. This differential temporal requirement for Ca2+channels in Ca2+signaling may be a mechanism to segregate intracellular signaling pathways of multiple neuroendocrine regulators in the teleost pituitary.
Purine and pyrimidine nucleotide-sensitive phospholipase A2in ampulla from frog semicircular canal
Authors: Teixeira Marie , Bernard Christian , Ferrary Evelyne , Butlen Daniel
Published: December 2017

This study was attempted to characterize pharmacologically the P2Y receptors triggering phospholipase A2(PLA2) activation in ampulla from frog semicircular canal. A microassay was developed to screen the abilities of UTP analogs to stimulate [3H]arachidonic acid release by labeled ampullas. At 26°C UTP induced a dose-dependent and saturable increase of PLA2activity (apparent activation constant 1.3 ± 0.4 μM, Hill coefficient 0.9 ± 0.2, maximal stimulating factor 2.0 ± 0.1). The rank order of potency of agonists for PLA2activation was UTP ≥ UDP > adenosine 5′- O-(2-thiodiphosphate) = adenosine 5′- O-(3-thiotriphosphate) ≥ ATP = 2-methylthio-ATP ≥ ADP = diadenosine tetraphosphate ≥ α,β-methylene-ATP = CTP > 2′ and 3′- O-(4-benzoylbenzoyl)-ATP ≥ AMP = UMP >> uridine and adenosine. UTP- and 2-methylthio-ATP-induced PLA2activations were inhibited by U-73122, GF-109203X, and methyl arachidonyl fluorophosphate. Basal activity was stimulated by phorbol ester and epinephrine and reduced by vasotocin, isoproterenol, prostaglandin E2, cAMP, and forskolin. H-89 restored the cAMP- and forskolin-inhibited PLA2activities. Results indicate that P2Y receptor-mediated PLA2stimulation requires phopholipase C and protein kinase C activations and basal activity is inhibited by agonist-stimulated cAMP-dependent mechanisms.
Effects of postnatal dexamethasone on blood-brain barrier permeability and brain water content in newborn lambs
Authors: Sysyn Gregory D. , Petersson Katherine H. , Patlak Clifford S. , Sadowska Grazyna B. , Stonestreet Barbara S.
Published: December 2017

We showed that antenatal corticosteroids reduced blood-brain barrier permeability in fetuses at 60 and 80%, but not 90% of gestation, and decreased brain water content in fetuses. Our objective was to examine the effects of postnatal corticosteroids on regional blood-brain barrier permeability and brain water content in newborn lambs. Three dexamethasone treatment groups were studied in 3- to 5-day-old lambs. A 0.01 mg/kg dose was selected to estimate the amount of dexamethasone that might have reached fetuses via antenatal treatment of ewes in our previous studies. The other doses (0.25 and 0.5 mg/kg) were chosen to approximate those used clinically to treat infants with bronchopulmonary dysplasia. Lambs were randomly assigned to receive four intramuscular injections of dexamethasone or placebo given 12 h apart on days 3 and 4 of age. Blood-brain barrier function was measured with the blood-to-brain transfer constant ( Ki) to α-aminoisobutyric acid, brain plasma volume was measured with polyethylene glycol for the calculation of Ki,and brain water was measured by wet-to-dry tissue weights. Postnatal treatment with corticosteroids did not reduce barrier permeability in newborn lambs. Brain blood volume was higher in the 0.25 and 0.5 mg/kg dose dexamethasone groups than in the placebo group. Brain water content did not differ among the groups. We conclude that postnatal treatment with corticosteroids did not reduce regional blood-brain barrier permeability or brain water content but increased the brain plasma volume in newborn lambs. These findings are consistent with our previous work indicating that barrier permeability is responsive to corticosteroids at 60 and 80% of gestation and brain water regulation at 60% of gestation, but not in near-term fetuses or newborn lambs.
Development of fetal vascular responses to endothelin-1 and acetylcholine in the sheep
Authors: Docherty Cheryl C. , Kalmar-Nagy Judit , Engelen Marc , Nathanielsz Peter W.
Published: December 2017

Responses to K+, endothelin-1 (ET-1), and acetylcholine (ACh) of isolated adrenal, femoral, middle cerebral, and renal arteries from fetal [110–145 days gestational age (dGA, term ∼148 dGA)] and 0- to 24-h newborn (NB) lambs were evaluated using the technique of wire myography. Responses at distinct developmental ages for each vascular bed were compared. In all arteries sensitivity to K+-induced vasoconstriction was similar at all fetal age points examined. In contrast, sensitivity to ET-1 increased with increasing fetal age in arteries from all vascular beds. The magnitude of the maximal vasoconstriction was positively correlated with GA for K+in adrenal, femoral, and cerebral arteries and for ET-1 in femoral, cerebral, and renal arteries. Cerebral arteries showed a greater sensitivity when compared with the other systemic arteries to K+ and ET-1 at all fetal ages and to K+ in NB. ACh evoked relaxatory responses in fetal and NB femoral and adrenal arteries. However, renal arteries relaxed comparatively less in response to ACh, and no vasodilation was noted in middle cerebral arteries at any age points examined. For femoral arteries ACh-induced vasorelaxation decreased with increasing GA but was restored in arteries from NB lambs. In summary, the responsiveness of isolated resistance arteries varies with developmental age in the fetal and perinatal sheep and these effects are both agonist and vascular bed specific. The augmented sensitivity in response to ET-1 of middle cerebral compared with other systemic arteries may reflect the importance of cerebral blood flow control during this critical developmental period.
Noradrenergic and GABAergic systems in the medial hypothalamus are activated during hypoglycemia
Authors: Beverly J. Lee , De Vries Martin G. , Bouman Stephan D. , Arseneau Linda M.
Published: December 2017

Noradrenergic and GABAergic systems in the medial hypothalamus influence plasma glucose and may be activated during glucoprivation. Microdialysis probes were placed into the ventromedial nucleus (VMH), lateral hypothalamus (LHA), and paraventricular nucleus (PVH) of male Sprague-Dawley rats to monitor extracellular concentrations of norepinephrine (NE) and GABA. During systemic hypoglycemia, induced by insulin (1.0 U/kg), NE concentrations increased in the VMH ( P < 0.05) and PVH ( P = 0.06) in a bimodal fashion during the first 10 min and 20–30 min after insulin administration. In the VMH, GABA concentrations increased ( P < 0.05) in a similar manner as NE. Extracellular NE concentrations in the LHA were slightly lower ( P = 0.13), and GABA levels remained at baseline. The increases in NE and GABA in the VMH were absent during euglycemic clamp; however, NE in the PVH still increased, reflecting a direct response to hyperinsulinemia. On the basis of these data, we propose that the activity of noradrenergic afferents to the medial hypothalamus is increased during hypoglycemia and influences the activity of local GABAergic systems to activate appropriate physiological compensatory mechanisms.
Electrogenic Na+-dependentl-alanine transport in the lizard duodenum. Involvement of systems A and ASC
Authors: Medina Virtudes , Lorenzo Antonio , Dı́az Mario
Published: December 2017

l-Alanine transport across the isolated duodenal mucosa of the lizard Gallotia galloti has been studied in Ussing chambers under short-circuit conditions. Net l-alanine fluxes, transepithelial potential difference (PD), and short-circuit current ( Isc) showed concentration-dependent relationships. Na+-dependent l-alanine transport was substantially inhibited by the analog α-methyl aminoisobutyric acid (MeAIB). Likewise, MeAIB fluxes were completely inhibited byl-alanine, indicating the presence of system A for neutral amino acid transport. System A transport activity was electrogenic and exhibited hyperbolic relationships for net MeAIB fluxes, PD, and Isc, which displayed similar apparent Kmvalues. Na+-dependentl-alanine transport, but not MeAIB transport, was partially inhibited by l-serine and l-cysteine, indicating the participation of system ASC. This transport activity represents the major pathway for l-alanine absorption and seemed to operate in an electroneutral mode with a negligible contribution to the l-alanine-induced electrogenicity. It is concluded from the present study that the active Na+-dependent l-alanine transport across the isolated duodenal mucosa of Gallotia galloti results from the independent activity of systems A and ASC for neutral amino acid transport.
Glucocorticoid modulation of cardiovascular and autonomic function in preterm lambs: role of ANG II
Authors: Segar Jeffrey L. , Bedell Kurt A. , Smith Oliva J.
Published: December 2017

The mechanisms by which antenatal glucocorticoids facilitate postnatal circulatory function in preterm infants are uncertain but may be related to augmented angiotensinergic functions. To test the hypothesis that the effects of glucocorticoids on postnatal cardiovascular and sympathetic activity are mediated via the renin-angiotensin system, we studied the effects of AT1 receptor blockade on postnatal changes in heart rate (HR), mean arterial blood pressure (MABP), renal sympathetic nerve activity (RSNA), and baroreflex control of HR in prematurely delivered lambs. After maternal administration of betamethasone (12 mg im 48 and 24 h before delivery), chronically instrumented preterm lambs (118- to 123-day gestation, term 145 days) were studied before and after delivery by cesarean section; fetuses received either the AT1 receptor antagonist losartan (10 mg iv, n = 6) or saline ( n = 6) 1 h before delivery. A third group of animals ( n = 6) received losartan without prior exposure to betamethasone. Compared with fetal values, betamethasone-treated animals demonstrated significant increases ( P < 0.05) in MABP (47 ± 2 to 58 ± 2 mmHg) and RSNA (181 ± 80% of fetal value) 1 h after delivery. Betamethasone + losartan-treated lambs also displayed increases in MABP (48 ± 1 to 55 ± 3 mmHg) and RSNA (198 ± 96% of fetal value) 60 min after birth, similar to betamethasone alone lambs. Losartan alone treated animals had no postnatal increase in either MABP or RSNA, responses similar to those seen in nontreated sheep delivered at the same gestational age. The sensitivity of baroreflex-mediated changes in HR in response to increases in MABP was less in both groups of betamethasone-treated animals; no effect was seen with losartan. These results suggest the postnatal increases in MABP and RSNA seen with antenatal glucocorticoid treatment are not mediated by stimulation of peripherally accessible AT1 receptors. We speculate that augmented cardiovascular function in glucocorticoid-treated premature lambs is dependent, in part, on a generalized sympathoexcitatory response and that this effect of glucocorticoids is mediated by central mechanisms.
Muscle fiber type comparison of PDH kinase activity and isoform expression in fed and fasted rats
Authors: Peters Sandra J. , Harris Robert A. , Heigenhauser George J. F. , Spriet Lawrence L.
Published: December 2017

Fiber type specificity for expression of all three rat skeletal muscle pyruvate dehydrogenase kinase (PDK) isoforms (PDK1, 2, and 4) was determined in fed and 24-h fasted rats. PDK activity and isoform protein and mRNA contents were determined in white gastrocnemius (WG; fast-twitch glycolytic), red gastrocnemius (RG; fast-twitch oxidative), and soleus (Sol; slow-twitch oxidative) muscles. PDK activity was lower in WG compared with oxidative muscles (RG, Sol) in both fed and fasted rats. PDK activities from fed muscles were 0.12 ± 0.04, 0.30 ± 0.01, and 0.36 ± 0.08 min−1 in WG, Sol, and RG, respectively, and increased in fasted muscles (0.36 ± 0.09, 0.68 ± 0.18, and 0.80 ± 0.14 min−1). This correlated with increased PDK4 protein and to a lesser extent with PDK4 mRNA. PDK2 protein was not different between fiber types in fed or fasted rats, but PDK2 mRNA content was twofold greater in RG from fasted rats compared with fed rats. PDK1 was unaltered by fasting in all muscle types at both the protein and mRNA level, but in both fed and fasted rats had much greater protein and mRNA content in the oxidative vs. glycolytic muscles. In conclusion, PDK activity and PDK1 and 4 protein and mRNA were lower in glycolytic vs. oxidative muscles from fed and fasted rats. Fasting for 24 h induced a two- to threefold increase in PDK activity that was mainly due to increases in PDK4 protein and mRNA. PDK1 and 2 protein and mRNA were generally unaltered by fasting in all fiber types, except for increased PDK2 mRNA in the fast oxidative fibers. Because the PDK isoforms vary greatly in their kinetic properties, their relative proportions in the three fiber types at any given time during fasting could significantly alter the acute regulation of the pyruvate dehydrogenase complex.
Cerebral Na concentration, Na appetite and thirst of sheep: influence of somatostatin and losartan
Authors: Weisinger R. S. , Blair-West J. R. , Burns P. , Denton D. A. , Purcell B.
Published: December 2017

Na and water intakes of Na-depleted sheep are influenced by changes in cerebral Na concentration. The effect of intracerebroventricular infusion of somatostatin or losartan, the ANG II type 1 receptor antagonist, on the Na appetite and thirst of Na-depleted sheep during infusions that decrease (intracerebroventricular hypertonic mannitol) or increase (intracerebroventricular or systemic hypertonic NaCl) cerebral Na concentration was investigated. Na intake was increased but water intake was unchanged during intracerebroventricular infusion of hypertonic mannitol. The increased Na appetite caused by intracerebroventricular infusion of hypertonic mannitol was decreased by concurrent intracerebroventricular infusion of either somatostatin or losartan, with somatostatin being most effective. Water intake was increased during intracerebroventricular infusion of hypertonic mannitol and somatostatin. Na intake was decreased and water intake was increased during systemic or intracerebroventricular infusion of hypertonic NaCl. Intracerebroventricular infusion of losartan blocked both (Na and water intake), whereas somatostatin did not influence either of these changes in intake. The results further consolidate a role for somatostatin and ANG II in the central mechanisms controlling Na appetite and thirst of sheep.
Flux-balance analysis of mitochondrial energy metabolism: consequences of systemic stoichiometric constraints
Authors: Ramakrishna Ramprasad , Edwards Jeremy S. , McCulloch Andrew , Palsson Bernhard O.
Published: December 2017

Mitochondrial metabolism is a critical component in the functioning and maintenance of cellular organs. The stoichiometry of biochemical reaction networks imposes constraints on mitochondrial function. A modeling framework, flux-balance analysis (FBA), was used to characterize the optimal flux distributions for maximal ATP production in the mitochondrion. The model predicted the expected ATP yields for glucose, lactate, and palmitate. Genetic defects that affect mitochondrial functions have been implicated in several human diseases. FBA can characterize the metabolic behavior due to genetic deletions at the metabolic level, and the effect of mutations in the tricarboxylic acid (TCA) cycle on mitochondrial ATP production was simulated. The mitochondrial ATP production is severely affected by TCA-cycle mutations. In addition, the model predicts the secretion of TCA-cycle intermediates, which is observed in clinical studies of mitochondriopathies such as those associated with fumarase deficiency. The model provides a systemic perspective to characterize the effect of stoichiometric constraints and specific metabolic fluxes on mitochondrial function.
Amplification effect and mechanism of action of ET-1 in U-46619-induced vasoconstriction in pig skin
Authors: Pang Cho Y. , Xu Huai , Huang Ning , Forrest Christopher R. , Perréault Thérèse M. , Neligan Peter C.
Published: December 2017

The aim of this study was to investigate if a low concentration of endothelin-1 (ET-1; 8 × 10−10M) may amplify the skin vasoconstrictor effect of other vasoactive substances in the pathogenesis of skin vasospasm. Pig skin flaps (6 × 16 cm) were perfused with Krebs buffer equilibrated with 95% O2and 5% CO2at 37°C and pH 7.4. Skin perfusion pressure measured by a pressure transducer and skin perfusion assessed by the dermofluorometry technique were used for assessment of skin vasoconstriction. We observed that ET-1 (8 × 10−10M) significantly amplified the concentration-dependent (10−7-10−5M) skin vasoconstrictor effect of norepinephrine. More importantly, we observed for the first time that this low concentration of ET-1 also amplified the concentration-dependent (10−8-10−6M) skin vasoconstrictor effect of the thromboxane A2mimetic U-46619, and this amplification effect of ET-1 was completely blocked by the protein kinase C (PKC) inhibitor chelerythrine (5 × 10−6M). Conversely, the PKC activator phorbol 12,13-dibutyrate (10−7M) amplified the vasoconstrictor effect of U-46619. Furthermore, the sensitivity of the skin vasculature to the vasoconstrictor effect of extracellular Ca2+in U-46619-induced skin vasoconstriction was significantly enhanced in the presence of 8 × 10−10M ET-1. Finally, the cyclooxygenase inhibitor indomethacin (5 × 10−6M) did not affect the amplification effect of ET-1 on U-46619-induced skin vasoconstriction. We conclude that a low concentration of ET-1 can amplify the skin vasoconstrictor effect of U-46619 independent of endogenous cyclooxygenase products, and the mechanism may involve activation of PKC and increase in sensitivity of the contractile apparatus to Ca2+in smooth muscle cells.
Increased nitric oxide is one of the causes of changes of iron metabolism in strenuously exercised rats
Authors: Qian Zhong Ming , Xiao De Sheng , Ke Ya , Liao Qin Kue
Published: December 2017

This study was carried out to investigate the possible role of increased nitric oxide (NO) production in the development of the low iron status in strenuously exercised rats. Female Sprague-Dawley rats were randomly assigned to four groups: sedentary (S1), sedentary + nitro-l-arginine methyl ester (l-NAME; S2), exercise (E1), and exercise + l-NAME (E2). Animals in the E1 and E2 groups swam for 2 h/day for 3 mo. l-NAME in the drinking water (1 mg/ml) was administrated to rats in the S2 and E2 groups for the same period. At the end of third month, hematological indexes and nitrite and nitrate (NOx) contents in the plasma and non-heme iron and NOx levels in the liver, spleen, and bone marrow cells were measured. Three months of exercise induced a significant increase in NOx content and a decrease in iron level both in plasma and tissues. Treatment with l-NAME, an inhibitor of NO synthase (NOS), led to a significant decrease in NOx and an increase in iron level both in plasma and tissues in the exercised rats. The E2 group had a significantly lower NOx content as well as a higher iron level both in plasma and tissues than the E1 group. However, the iron contents in the plasma and tissues of the E2 group were still significantly lower than those found in S1. No difference was found in NOx levels between E2 and S1. These findings showed that exercise was associated with elevation in NOx and reduction in iron in plasma and the tissues. Treatment with l-NAME was able to completely inhibit the effect of exercise on NOx as well as partly recover the decreased iron contents in plasma and tissues resulting from exercise. This suggests that the increased production of NO might be one of the causes of the lower iron status in exercised rats.
Effect of oral contraceptives on the renin angiotensin system and renal function
Authors: Kang Amrit K. , Duncan John A. , Cattran Daniel C. , Floras John S. , Lai Vesta , Scholey James W. , Miller Judith A.
Published: December 2017

We examined the effect of oral contraceptive (OC) usage on the renin angiotensin system (RAS) in two related experiments. In the first experiment, subjects were 34 healthy, normotensive, premenopausal women, 15 OC users and 19 OC nonusers, mean age 25 ± 1 yr, ingesting a controlled sodium diet. We assessed arterial pressure, glomerular filtration rate, effective renal plasma flow, renal vascular resistance (RVR), and filtration fraction (FF) using inulin and p-aminohippurate clearance techniques, both at baseline and in response to the ANG II receptor blocker losartan. In the second experiment, in similar subjects, 10 OC users and 10 nonusers, we examined circulating RAS components [angiotensinogen, ANG II, aldosterone, plasma renin activity (PRA), and active renin] in response to incremental lower body negative pressure (LBNP), to determine whether renin secretion is suppressed by OC usage. OC users exhibited elevations in systolic blood pressure, RVR, and FF compared with nonusers, which were partially corrected by losartan. In the LBNP phase of the study, baseline measures of PRA, angiotensinogen, ANG II, and aldosterone were all increased in the OC group compared with the control group. Active renin levels did not differ between groups. Incremental LBNP resulted in increased circulating levels of RAS components in both groups. We conclude that the RAS is activated in women using OCs. There was no evidence that decreases in renin secretion result in normalization of the RAS as a whole.
Adenosine signaling in outer medullary descending vasa recta
Authors: Silldorff Erik P. , Pallone Thomas L.
Published: December 2017

We tested whether dilation of outer medullary descending vasa recta (OMDVR) is mediated by cAMP, nitric oxide (NO), and cyclooxygenase (COX). Adenosine (A; 10−6 M)-induced vasodilation of ANG II (10−9 M)-preconstricted OMDVR was mimicked by the cAMP analog 8-bromoadenosine 3′,5′-cyclic monophosphate (10−10to 10−4 M) and reversed by the adenylate cyclase inhibitor SQ-22536. Adenosine (10−4 M) stimulated OMDVR cAMP production greater than threefold. NO synthase blockade with N G-nitro-l-arginine methyl ester and N G-monomethyl-l-arginine (10−4 M) did not affect adenosine vasodilation. Adenosine induced endothelial cytoplasmic calcium transients that were small. Indomethacin (10−6 M) reversed adenonsine-induced dilation of OMDVR preconstricted with ANG II, endothelin, 4-bromo-calcium ionophore A23187, or carbocyclic thromboxane A2. In contrast, selective A2-receptor activation dilated endothelin-preconstricted OMDVR even in the presence of indomethacin. We conclude that OMDVR vasodilation by adenosine involves cAMP and COX but not NO. COX blockade does not fully inhibit selective A2 receptor-mediated OMDVR dilation.
Erythroid carbonic anhydrase andhsp70expression in chick embryonic development: role of cAMP and hypoxia
Authors: Dragon Stefanie , Baumann Rosemarie
Published: December 2017

In the second half of avian embryonic development cAMP affects major aspects of red blood cell (RBC) function. At day 13/14,progressive developmental hypoxia causes the release of norepinephrine and erythroid β-adrenergic receptor stimulation initiates the coordinate induction of adaptive key events of erythroid differentiation like carbonic anhydrase (CAII) and 2,3-biphosphoglycerate synthesis. Although cAMP-dependent regulation of CAII protein synthesis has been described in detail, no data exist about the transcriptional regulation in embryonic RBC. Here we report that after day 12 of embryonic development, the caII mRNA is accumulating. Hypoxic incubation at day 10 as well as in vitro incubation of isolated RBC with cAMP-elevating agonists strongly induces erythroid caIIexpression. The induction of caII occurs fast and does not require new protein synthesis. By screening several late erythroid genes, we could identify hsp70 as another cAMP-induced gene in definitive RBC. Because caII (but not hsp70) is also induced by cAMP in primitive RBC, the signal may regulate key events of late primitive and definitive erythropoiesis.
Localization and regulation of IL-1α in rat myometrium during late pregnancy and the postpartum period
Authors: Melendez J. Andres , Vinci James M. , Jeffrey John J. , Wilcox Brian D.
Published: December 2017

Interleukin-1 (IL-1) has been implicated as a participant in preterm labor that is induced by bacterial infection. Previously, we showed that serotonin-induced production of IL-1α by myometrial smooth muscle cells in vitro is also essential for the synthesis of interstitial collagenase. It is therefore likely that IL-1α production in uterine tissues has implications for both the normal physiology of involution and for the pathophysiological mechanisms of preterm labor. The objective of this study was to characterize the serotonin-induced production of IL-1α by myometrial cultures in vitro and to assess the production of IL-1α and its relationship to collagenase production in vivo during pregnancy and the postpartum period. Immunohistochemistry demonstrated IL-1α protein in the nuclei and cytoplasm of serotonin-treated myometrial cells. IL-1α levels were decreased by treatment with progesterone or IL-1-receptor antagonist but were unaffected by lipopolysaccharide. Western analysis of myometrium from pregnant rats showed low levels of IL-1α during midpregnancy with increased concentrations at days 21 and 22 and postpartum. IL-1α mRNA levels also increased from days 15to 22. Levels of mRNA for IL-1β also increased, although to a lesser degree than IL-1α. Both mRNAs decreased postpartum. Conversely, mRNA for interstitial collagenase was barely detectable at term but increased postpartum. Together, these data show that serotonin stimulates IL-1α production in vitro and indicate that normal myometrium from pregnant rats is an identifiable source of IL-1 during late pregnancy. The findings are consistent with the possibility that myometrial IL-1α participates in normal labor as well as the postpartum production of interstitial collagenase.