bluuebunny/crossref_metadata_2025 huggingface dataset:
Unilateral optic nerve transection alters light response of suprachiasmatic nucleus and intergeniculate leaflet
Authors: Tang I-Hsiung , Murakami Dean M. , Fuller Charles A.
Published: March 2015

The suprachiasmatic nucleus (SCN), the circadian pacemaker, receives photic input directly from the retina to synchronize the pacemaker to the environment. Additionally, the intergeniculate leaflet (IGL), which innervates the SCN, is known to modulate the retinal photic input to the SCN. To further understand the role of the IGL in mediating the photic input to the SCN, this study examined the effects of unilateral optic nerve transection (UONx) on the photic response of the SCN and IGL in adult and neonatal hamsters. UONx led to an overall reduction in light-induced c-Fos expression in the SCN and IGL. The c-Fos expression was greater in the SCN ipsilateral to the remaining eye, despite a symmetrically bilateral retinohypothalamic tract projection as revealed by intraocular injection of horseradish peroxidase. In contrast, UONx led to a greater c-Fos expression in the contralateral IGL. The contralateral IGL of UONx animals also revealed more neuropeptide Y-immunoreactive neurons, while the ipsilateral SCN of these animals exhibited a denser neuropeptide Y terminal field. The neonates with UONx showed a similar pattern with a slight compensation of the photic-induced c-Fos in the SCN. This study suggests that the IGL may have an ipsilateral inhibitory effect in mediating retinal photic input to the SCN.
Unstable heart rate and temperature regulation predict mortality in AKR/J mice
Authors: Tankersley Clarke G. , Irizarry Rafael , Flanders Susan E. , Rabold Richard , Frank Robert
Published: March 2015

Elderly populations face greater risks of mortality when exposed to changes in environmental stress. The purpose of the following study was to develop an age-dependent susceptibility model that achieved the following three goals: 1) to operationally define homeostasis by assessing the stability and periodicity in physical activity, heart rate (HR), and deep body temperature (Tdb), 2) to specify alterations in activity, HR, and Tdb regulation that signal imminent death, and 3) to test the hypothesis that the decay in homeostasis associated with imminent death incorporates the coincident disintegration of multiple physiological systems. To achieve these goals, the circadian regulation of activity, HR, and Tdbwas assessed using radiotelemeters implanted in AKR/J ( n = 17) inbred mice at ∼190 days of age. During a 12:12-h light-dark cycle, weekly measurements were obtained at 30-min intervals for 48-h periods until each animal's natural death. The average (±SE) life span of surgically treated animals did not differ from untreated controls (319 ± 12 vs. 319 ± 14 days). Cardiac and thermal stability were characterized by a circadian periodicity, which oscillated around stable daily averages of 640 ± 14 beats/min in HR and 36.6 ± 0.1°C in Tdb. Stable HR and Tdb responses were compared with extreme conditions 3 days before death, during which a disintegration of circadian periodicity was coincident with a fall in the daily average HR and Tdb of ∼29 and ∼13% lower (i.e., 456 ± 22 beats/min and 31.7 ± 0.6°C), respectively. The results further suggested that multiple predictors of cardiac and thermal instability in AK mice, including significant bradycardia, hypothermia, and a loss of circadian periodicity, forecast life span 5–6 wk before expiration.
Guanylyl cyclase mediates ANP-induced vasoconstriction of murine splenic vessels
Authors: Andrew Peter S. , Kaufman Susan
Published: March 2015

We have previously shown that ANP causes differential constriction of the splenic vasculature of the rat (veins greater than arteries), which may be inhibited by blocking the production of cGMP with A7195. In this paper, we report experiments done on vessels derived from guanylyl cyclase (GC)-A knockout mice. Small splenic arteries (∼150-μm diameter) and veins (∼250-μm diameter) were dissected from male GC-A-deficient 129sv mice or age-matched wild-type controls and mounted in a wire myograph. In the wild-type mice, ANP exhibited higher potency in the veins than in the arteries (EC50 values wild-type mice: artery, 8 ± 3 × 10−9 M, n = 5 vs. vein, 6 ± 4 × 10−10 M, n = 5; P < 0.05). The concentration-response curve for ANP-induced vasoconstriction was also shifted leftward in denuded compared with intact arteries (EC50 values: denuded artery: 5 ± 3 × 10−10 M, n = 5 vs. intact artery, 8 ± 3 × 10−9 M, n = 5; P < 0.05), i.e., the denuded vessels were more reactive. By contrast, ANP caused no significant change in tension from baseline in intact splenic arteries, intact splenic veins, or denuded splenic arteries derived from the GC-A-deficient mice, although these vessels did show normal concentration-dependent increases in tension to phenylephrine. We conclude that ANP causes vasoconstriction in the splenic vasculature by an endothelium-independent mechanism, mediated via guanylyl cyclase.
Photoperiod effects on gene expression for hypothalamic appetite-regulating peptides and food intake in the ram
Authors: Clarke Iain J. , Rao Alexandra , Chilliard Yves , Delavaud Carole , Lincoln Gerald A.
Published: March 2015

Relationship between voluntary food intake (VFI) and gene expression for appetite-regulating peptides was examined in the brains of Soay rams under contrasting photoperiods. Two groups ( n = 8) were subjected to alternating block long-day (LD) and short-day photoperiods (SD) over a period of 42 wk to entrain long-term cycles in VFI. Five animals from each group were killed 18 wk into LD or SD, and the brains were collected for in situ hybridization studies. VFI was fourfold higher under LD compared with SD. Body weight, abdominal fat, or plasma leptin levels were similar under LD and SD. LD animals were in positive energy balance and sexually inactive, and SD animals were in negative energy balance and sexually active. Neuropeptide Y (NPY) mRNA levels were higher in the arcuate nucleus (ARC) under LD, and pro-opiomelanocortin expression was lower under LD. Leptin receptor (Ob-Rb) was higher in the ARC under LD. We conclude that photoperiod-induced increase in VFI correlates with expression of NPY, but not with expression of genes for other putative orexigenic peptides. Ob-Rb gene expression is regulated by photoperiod.
Short-chain fatty acids stimulate colonic transit via intraluminal 5-HT release in rats
Authors: Fukumoto Satoshi , Tatewaki Makoto , Yamada Tadanori , Fujimiya Mineko , Mantyh Chris , Voss Miranda , Eubanks Steve , Harris Mary , Pappas Theodore N. , Takahashi Toku
Published: March 2015

We studied whether physiological concentration of short-chain fatty acids (SCFAs) affects colonic transit and colonic motility in conscious rats. Intraluminal administration of SCFAs (100–200 mM) into the proximal colon significantly accelerated colonic transit. The stimulatory effect of SCFAs on colonic transit was abolished by perivagal capsaicin treatment, atropine, hexamethonium, and vagotomy, but not by guanethidine. The stimulatory effect of SCFAs on colonic transit was also abolished by intraluminal pretreatment with lidocaine and a 5-hydroxytryptamine (HT)3 receptor antagonist. Intraluminal administration of SCFAs provoked contractions at the proximal colon, which migrated to the mid- and distal colon. SCFAs caused a significant increase in the luminal concentration of 5-HT of the vascularly isolated and luminally perfused rat colon ex vivo. It is suggested that the release of 5-HT from enterochromaffin cells in response to SCFAs stimulates 5-HT3 receptors located on the vagal sensory fibers. The sensory information is transferred to the vagal efferent and stimulates the release of acetylcholine from the colonic myenteric plexus, resulting in muscle contraction.
An evolutionary approach for identifying potential transcription factor binding sites: the renin gene as an example
Authors: Mrowka Ralf , Steinhage Karola , Patzak Andreas , Persson Pontus B.
Published: March 2015

Evolutionary pressure has resulted in the conservation of certain nucleotide sequences. These conserved regions are potentially important for certain functions. Here we give an example of a comparison between noncoding sequences combined with other independent database information to shed light onto the regulation of the renin gene, a gene that has great importance for cardiovascular and renal homeostasis. To combine the information regarding conservation and weight matrices of transcription factor (TF) binding sites, an algorithm was developed (TFprofile). Notably, a local peak in the resulting binding profile coincides with a previously experimentally identified regulatory region for the renin gene. The existence of further peaks in the binding profile in the conserved 3.9-kb-long hRENc DNA block upstream of the renin gene suggests additional regions of potential importance for gene regulation. The algorithm TFprofile may be used to integrate information on cross-species evolutionary conservation and aspects of TF binding characteristics to provide putative regulatory DNA regions for experimental verification.
COX-2 and prostanoid expression in micturition pathways after cyclophosphamide-induced cystitis in the rat
Authors: Hu V. Y. , Malley S. , Dattilio A. , Folsom J. B. , Zvara P. , Vizzard M. A.
Published: March 2015

The purpose of this study was to determine the role of cyclooxygenase-2 (COX-2) and its metabolites in lower urinary tract function after induction of acute (4 h), intermediate (48 h), or chronic (10 day) cyclophosphamide (CYP)-induced cystitis. Bladders were harvested from euthanized female rats for analyses. Conscious cystometry was used to assess the effects of a COX-2-specific inhibitor, 5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl2(5 H)-furanone (DFU, 5 mg/kg sc), a disubstituted furanone, in CYP-induced cystitis. COX-2 mRNA was increased in inflamed bladders after acute (12-fold) and chronic (9-fold) treatment. COX-2 protein expression in inflamed bladders paralleled COX-2 mRNA expression. Prostaglandin D2-methoxime expression in the bladder was significantly ( P ≤ 0.01) increased in acute (3-fold) and chronic (5.5-fold) cystitis. Prostaglandin E2 was significantly ( P ≤ 0.01) increased (2-fold) in the bladder with intermediate (1.7-fold) and chronic (2.6-fold) cystitis. COX-2-immunoreactive cell profiles were distributed throughout the inflamed bladder and coexpressed histamine immunoreactivity. Conscious cystometry in rats treated with CYP + DFU showed increased micturition intervals 4 and 48 h after CYP treatment and decreased intravesical pressures during filling and micturition compared with rats treated with CYP + vehicle. These studies suggest an involvement of urinary bladder COX-2 and its metabolites in altered micturition reflexes with CYP-induced cystitis.
PACAP release from the canine adrenal gland in vivo: its functional role in severe hypotension
Authors: Lamouche Stéphane , Yamaguchi Nobuharu
Published: March 2015

This study was to investigate if endogenous pituitary adenylate cyclase-activating polypeptide (PACAP) can be released during direct splanchnic nerve stimulation in vivo and to determine whether PACAP in the adrenal gland can modulate the medullary response to sympathoadrenal reflex. The output of adrenal catecholamine and PACAP-38-like immunoreactivity (PACAP-38-ir) increased in a frequency-dependent manner after direct splanchnic nerve stimulation (0.2–20 Hz). Both responses were highly reproducible, and PACAP-38-ir output closely correlated with catecholamine output. Sodium nitroprusside (SNP; 0.1 mg/kg iv bolus) caused a severe hypotension resulting in marked increases in catecholamine secretion. In the presence of local PACAP-27 (125 ng), the maximum catecholamine response to SNP was significantly potentiated in a synergistic manner compared with that obtained in the group receiving SNP or PACAP-27 alone. The study indicates that endogenous PACAP-38 can be released particularly when the sympathoadrenal system is highly activated and that the local exogenous PACAP-27 enhanced the reflex-induced catecholamine release, suggesting collectively a facilitating role of PACAP as neuromodulator in the sympathoadrenal function in vivo.
Increased albumin plasma efflux contributes to hypoalbuminemia only during early phase of sepsis in rats
Authors: Ruot Benoît , Papet Isabelle , Béchereau Fabienne , Denis Philippe , Buffière Caroline , Gimonet Johan , Glomot Francoise , Elyousfi Mimoun , Breuillé Denis , Obled Christiane
Published: March 2015

The mechanisms leading to hypoalbuminemia in sepsis were explored by measuring plasma volume, albumin distribution, plasma albumin transcapillary escape rate (TER), and efflux (TER × albumin intravascular pool). These parameters were quantified in infected rats, injected intravenously with live Escherichia coli, and pair-fed and well-fed rats using an injection of35S-albumin and measuring plasma and whole body albumin concentrations. Animals were studied on days 1, 6, and 10 after infection. In pair-fed rats, neither albumin distribution nor exchange rate between the intra- and extravascular compartments was modified. The increase of plasma volume after infection partly explained hypoalbuminemia. Infection resulted in a reduction of the total albumin pool of the body all along the experimental period, indicating a net loss of the protein. Albumin TER (%/day) was significantly increased 1 and 6 days after infection, but the absolute efflux was increased only on day 1. Normal values were observed on day 10. Therefore, an accelerated plasma efflux contributes to hypoalbuminemia only during the early period of sepsis. During this phase, the protein was retained in the extravascular space where it was probably catabolized. Later on, other factors are probably involved.
Sleep of transgenic mice producing excess rat growth hormone
Authors: Hajdu I. , Obal F. , Fang J. , Krueger J. M. , Rollo C. D.
Published: March 2015

The effects of chronic excess of growth hormone (GH) on sleep-wake activity was determined in giant transgenic mice in which the metallothionein-1 promoter stimulates the expression of rat GH (MT-rGH mice) and in their normal littermates. In the MT-rGH mice, the time spent in spontaneous non-rapid eye movement sleep (NREMS) was enhanced moderately, and rapid eye movement sleep (REMS) time increased greatly during the light period. After a 12-h sleep deprivation, the MT-rGH mice continued to sleep more than the normal mice, but there were no differences in the increments in NREMS, REMS, and electroencephalogram (EEG) slow-wave activity (SWA) during NREMS between the two groups. Injection of the somatostatin analog octreotide elicited a prompt sleep suppression followed by increases in SWA during NREMS in normal mice. These changes were attenuated in the MT-rGH mice. The decreased responsiveness to octreotide is explained by a chronic suppression of hypothalamic GH-releasing hormone in the MT-rGH mice. Enhancements in spontaneous REMS are attributed to the REMS-promoting activity of GH. The increases in spontaneous NREMS are, however, not consistent with our current understanding of the role of somatotropic hormones in sleep regulation. Metabolic, neurotransmitter, or hormonal changes associated with chronic GH excess may indirectly influence sleep.
Trigeminal reflex regulation of the glottis depends on central glycinergic inhibition in the rat
Authors: Dutschmann Mathias , Paton Julian F. R.
Published: March 2015

In an unanesthetized decerebrate in situ arterially perfused brain stem preparation of mature rat, strychnine (0.05-0.2 μM) blockade of glycine receptors caused postinspiratory glottal constriction to occur earlier, shifting from early expiration to inspiration. This resulted in a paradoxical inspiratory-related narrowing of the upper airway. Stimulation of the trigeminal ethmoidal nerve (EN5; 20 Hz, 100 μs, 0.5–2 V) evoked a diving response, which included a reflex apnea, glottal constriction, and bradycardia. After strychnine administration, this pattern was converted to a maintained phrenic nerve discharge and a reduced glottal constriction that was interrupted intermittently by transient abductions. The onset of firing of postinspiratory neurons shifted from early expiration into neural inspiration in the presence of strychnine, but neurons maintained their tonic activation during EN5 stimulation, as observed during control. Inspiratory neurons that were hyperpolarized by EN5 stimulation in control conditions were powerfully excited after loss of glycinergic inhibition. Thus the integrity of glycinergic inhibition within the pontomedullary respiratory network is critical for the coordination of cranial and spinal motor outflows during eupnea but also for protective reflex regulation of the upper airway.
Troglitazone induces a cellular acidosis by inhibiting acid extrusion in cultured rat mesangial cells
Authors: Welbourne Tomas , Su Gan , Coates Greg , Routh Robert , McCarthy Kevin , Battarbee Harold
Published: March 2015

We studied the effect of troglitazone on cellular acid-base balance and alanine formation in isolated rat mesangial cells. Mesangial cells were grown to confluency in RPMI 1640 media on 30-mm chambers used to monitor both cellular pH using the pH-sensitive dye 2′7′-bis(2-carboxyethyl)-5,6-carboxyfluorescein and metabolic acid production as well as glutamine metabolism. Troglitazone (10 μM) induced a spontaneous cellular acidosis (6.95 ± 0.02 vs. 7.47 ± 0.04, respectively; P < 0.0001) but without an increase in lactic acid production. Alanine production was reduced 64% ( P < 0.01) consistent with inhibition of the glutamate transamination. These findings pointed to a decrease in acid extrusion rather than an increase in acid production as the underlying mechanism leading to the cellular acidosis. To test their acid extrusion capabilities, mesangial cells were acid loaded with NH[Formula: see text] and then allowed to recover in Krebs-Henseleit media or in Krebs-Henseleit media minus bicarbonate (HEPES substituted), and the recovery response (ΔpHi/min) was monitored. In the presence of 10 μM troglitazone, the recovery response to the NH[Formula: see text] acid load was virtually eliminated in the bicarbonate-buffered media (0.00 ± 0.001 vs. 0.06 ± 0.02 pHi/min, P < 0.0001 vs. control) and reduced 75% in HEPES-buffered media (0.01 ± 0.01 vs. 0.04 ± 0.02 pHi/min, P < 0.002 vs. control). These results show that troglitazone induces a spontaneous cellular acidosis resulting from a reduction in cellular acid extrusion.
The kallikrein-kinin and the renin-angiotensin systems have a multilayered interaction
Authors: Schmaier Alvin H.
Published: March 2015

Understanding the physiological role of the plasma kallikrein-kinin system (KKS) has been hampered by not knowing how the proteins of this proteolytic system, when assembled in the intravascular compartment, become activated under physiological conditions. Recent studies indicate that the enzyme prolylcarboxypeptidase, an ANG II inactivating enzyme, is a prekallikrein activator. The ability of prolylcarboxypeptidase to act in the KKS and the renin-angiotensin system (RAS) indicates a novel interaction between these two systems. This interaction, along with the roles of angiotensin converting enzyme, cross talk between bradykinin and angiotensin-( 1 – 7 ) action, and the opposite effects of activation of the ANG II receptors 1 and 2 support a hypothesis that the plasma KKS counterbalances the RAS. This review examines the interaction and cross talk between these two protein systems. This analysis suggests that there is a multilayered interaction between these two systems that are important for a wide array of physiological functions.
Angiotensin II attenuates the natriuresis of water immersion in humans
Authors: Schou Morten , Gabrielsen Anders , Bruun Niels Eske , Skøtt Peter , Pump Bettina , Dige-Petersen Harriet , Frandsen Erik , Bie Peter , Warberg Jørgen , Christensen Niels Juel , Norsk Peter
Published: March 2015

The hypothesis was tested that suppression of generation of ANG II is one of the mechanisms of the water immersion (WI)-induced natriuresis in humans. In one protocol, eight healthy young males were subjected to 3 h of 1) WI (WI + placebo), 2) WI combined with ANG II infusion of 0.5 ng · kg−1· min−1(WI + ANG II-low), and 3) a seated time control (Con). In another almost identical protocol, 7–10 healthy young males were investigated to delineate the tubular site(s) of action of ANG II by the lithium clearance method (CLi) and were on an additional fourth study day subjected to infusion of ANG II at a rate of 1.5 ng · kg−1· min−1(WI + ANG II-high). During WI + placebo, plasma concentration of ANG II decreased from 16 ± 2 to 8 ± 1 pg/ml ( P < 0.05) and renal sodium excretion increased from 104 ± 15 to 294 ± 27 μmol/min ( P < 0.05). During WI + ANG II-low, plasma ANG II was not suppressed by WI, and the natriuresis was blunted by 52 ± 13% ( P < 0.05). During WI + ANG II-low and WI + ANG II-high, an increase in CLiwas prevented that was otherwise observed during WI, and fractional distal reabsorption of sodium was facilitated. In conclusion, maintaining plasma concentration of ANG II unchanged at the level of control attenuates the natriuresis of WI considerably in humans. Therefore, suppression of generation of ANG II is an important mechanism of the natriuresis of WI in humans. Furthermore, infusion of ANG II during WI prevents an otherwise induced increase in CLiand facilitates the fractional distal reabsorption of sodium, probably via an effect on aldosterone release.
Estrogen decreases biglycan mRNA expression in resistance blood vessels
Authors: Rodrigo Manoj C. , Martin Douglas S. , Eyster Kathleen M.
Published: March 2015

This study was designed to identify new gene targets of estrogen in the mesenteric arteries and to determine whether the soy phytoestrogens could mimic estrogen effects. Ovariectomized rats were treated with estradiol, genistein, or daidzein for 4 days. The mesenteric arteries were harvested, total RNA was extracted, mRNA was reverse transcribed in the presence of[33P]dCTP, and the labeled probes were hybridized with DNA microarrays. Analysis of the microarray data identified biglycan as a target of estrogenic regulation. Semiquantitative RT-PCR was used to confirm and quantitate the decrease in biglycan gene expression in response to estrogen (-37%), genistein (-15%), and daidzein (-10%). Treatment with the pure estrogen receptor antagonist ICI-182,780 reversed the inhibition of biglycan gene expression. The decrease in biglycan gene expression in response to estrogens was paralleled with a decrease in biglycan protein expression. Biglycan protein was localized to the media of the mesenteric arteries by immunohistochemistry. Collectively, these data suggest that biglycan is a vascular protein regulated at the genomic level by estrogens.
Early osmoregulatory stimulation of neurohypophyseal hormone secretion and thirst after gastric NaCl loads
Authors: Stricker Edward M. , Callahan John B. , Huang Wan , Sved Alan F.
Published: March 2015

Cerebral osmoreceptors mediate thirst and neurohypophyseal secretion stimulated by increases in the effective osmolality of plasma (Posmol). The present experiments determined whether an intragastric load of hypertonic saline (ig HS; 0.5 M NaCl, 4 ml) would potentiate these responses before induced increases in Posmol in the general circulation could be detected by cerebral osmoreceptors. Adult rats deprived of water overnight and then given intragastric HS consumed much more water in 15–30 min than rats given either pretreatment alone, even though systemic Posmol had not yet increased significantly because of the gastric load. In other rats pretreated with an intravenous infusion of 1 M NaCl (2 ml/h for 2 h), plasma levels of vasopressin and oxytocin were considerably elevated 15 and 25 min after intragastric HS treatment, whereas systemic Posmol was not increased further. These and other findings are consistent with previous reports that hepatic portal osmoreceptors (or Na+ receptors) stimulate thirst and neurohypophyseal hormone secretion in euhydrated rats given gastric NaCl loads and indicate that these effects are potentiated when animals are dehydrated.
Sympathoinhibitory pathway from caudal midline medulla to RVLM is independent of baroreceptor reflex pathway
Authors: Potas J. R. , Dampney R. A. L.
Published: March 2015

Glutamate stimulation of the caudal midline medulla (CMM) causes profound sympathoinhibition due to GABAergic inhibition of presympathetic neurons in the rostral ventrolateral medulla (RVLM). We investigated whether the sympathoinhibitory pathway from CMM to RVLM, like the central baroreceptor reflex pathway, includes a glutamatergic synapse in the caudal ventrolateral medulla (CVLM). In pentobarbital sodium-anesthetized rats, the RVLM on one side was inhibited by a muscimol microinjection. Then the response evoked by glutamate microinjections into the CMM or by baroreceptor stimulation was determined before and after 1) microinjection of the GABA receptor antagonist bicuculline into the RVLM on the other side or 2) microinjections of the glutamate receptor antagonist kynurenate bilaterally into the CVLM. Bicuculline in the RVLM greatly reduced both CMM- and baroreceptor-evoked sympathoinhibition. Compared with the effect of vehicle solution, kynurenate in the CVLM greatly reduced baroreceptor-evoked sympathoinhibition, whereas its effect on CMM-evoked sympathoinhibition was not different from that of the vehicle solution. These findings indicate that the output pathway from CMM sympathoinhibitory neurons, unlike the baroreceptor and other reflex sympathoinhibitory pathways, does not include a glutamatergic synapse in the CVLM.
ATP-stimulated Ca2+-activated K+ efflux pathway and differentiation of human placental cytotrophoblast cells
Authors: Clarson L. H. , Roberts V. H. J. , Greenwood S. L. , Elliott A. C.
Published: March 2015

The aim of this study was to determine whether extracellular ATP ([ATP]o) stimulated a Ca2+-activated K+ efflux in trophoblast cells that was dependent on extracellular Ca2+([Ca2+]o). Cytotrophoblast cells, isolated from human placenta, were examined following 18 h (relatively undifferentiated) and 66 h (multinucleate cells) of culture. Potassium efflux was measured using 86Rb as a trace marker. Intracellular Ca2+ ([Ca2+]i) was examined by microfluorometry using fura 2. [ATP]osignificantly increased 86Rb efflux to a peak that declined to control (18-h cells) or an elevated plateau (66-h cells) and was inhibited by 100 nM charybdotoxin. Removing [Ca2+]o significantly reduced86Rb efflux in both groups as did application of 150 μM GdCl3. [ATP]o significantly increased [Ca2+]i in both groups of cells. The response was reduced by removing [Ca2+]o and applying 150 μM GdCl3. For both 86Rb efflux and microfluorometry experiments, the response to [ATP]o was more dependent on [Ca2+]o in 66-h cells compared with 18-h cells (∼70% greater). Cytotrophoblast cells exhibit an [ATP]o-stimulated Ca2+-activated K+ efflux. The dependency of this pathway on [Ca2+]o is greater in the 66-h multinucleate syncytiotrophoblast-like cells, suggesting that the mechanism for Ca2+ entry may be altered during differentiation of trophoblast cells.
The role of hypothalamic input on corticotroph maturation in fetal sheep
Authors: Young Sharla F. , Tatter Stephen B. , Valego Nancy K. , Figueroa Jorge P. , Thompson Jalonda , Rose James C.
Published: March 2015

Corticotropin-releasing hormone receptor type 1 (CRH-R1) expression 1 and vasopressin type 1b (V1b) receptor protein decrease in late-gestation fetal sheep. Because hypothalamo-pituitary disconnection (HPD) has been demonstrated to prevent the morphological maturation of corticotrophs, we hypothesized that hypothalamic input is necessary for the maturational changes in CRH-R1 and V1b receptor levels. We measured CRH-R1 and V1b receptor expression in the anterior pituitaries of fetuses at 140 days gestational age (dGA) that underwent HPD or sham surgery at 120 dGA. CRH-R1 mRNA decreased similarly in HPD and sham-operated fetuses compared with 120 dGA naive fetuses. However, CRH-R1 protein levels were elevated in HPD fetuses compared with sham and were not different from 120 dGA values. V1b protein levels decreased similarly in HPD and sham-operated fetuses compared with 120 dGA naive fetuses. We conclude that hypothalamic input to the pituitary is necessary for the decrease in CRH-R1 receptor protein levels in late-gestation fetal sheep. However, hypothalamic input is not necessary for the decrease in V1b receptor expression seen in late gestation.
NKCC activity restores muscle water during hyperosmotic challenge independent of insulin, ERK, and p38 MAPK
Authors: Gosmanov Aidar R. , Schneider Edward G. , Thomason Donald B.
Published: March 2015

In isosmotic conditions, insulin stimulation of PI 3-K/Akt and p38 MAPK pathways in skeletal muscle inhibits Na+-K+-2Cl−cotransporter (NKCC) activity induced by the ERK1,2 MAPK pathway. Whether these signaling cascades contribute to NKCC regulation during osmotic challenge is unknown. Increasing osmolarity by 20 mosM with either glucose or mannitol induced NKCC-mediated86Rb uptake and water transport into rat soleus and plantaris skeletal muscle in vitro. This NKCC activity restored intracellular water. In contrast to mannitol, hyperosmolar glucose increased ERK1,2 and p38 MAPK phosphorylation. Glucose, but not mannitol, impaired insulin-stimulated phosphorylation of Akt and p38 MAPK in the plantaris and soleus muscles, respectively. Hyperosmolarity-induced NKCC activation was insensitive to insulin action and pharmacological inhibition of ERK1,2 and p38 MAPK pathways. Paradoxically, cAMP-producing agents, which stimulate NKCC activity in isosmotic conditions, suppressed hyperosmolar glucose- and mannitol-induced NKCC activity and prevented restoration of muscle cell volume in hyperosmotic media. These results indicate that NKCC activity helps restore muscle cell volume during hyperglycemia. Moreover, hyperosmolarity activates NKCC regulatory pathways that are insensitive to insulin inhibition.
Leptin secretion and hypothalamic neuropeptide and receptor gene expression in sheep
Authors: Sorensen Annette , Adam Clare L. , Findlay Pat A. , Marie Michel , Thomas Louise , Travers Maureen T. , Vernon Richard G.
Published: March 2015

Peripheral and hypothalamic mechanisms underlying the hyperphagia of lactation have been investigated in sheep. Sheep were fed ad libitum and killed at 6 and 18 days of lactation; ad libitum-fed nonlactating sheep were killed as controls. Despite increased food intake, lactating ewes were in negative energy balance. Lactation decreased plasma leptin and adipose tissue leptin mRNA concentrations. OB-Rb gene expression, determined by in situ hybridization, was increased in the hypothalamic arcuate nucleus (ARC) and ventromedial hypothalamic nucleus (VMH) at both stages of lactation. Neuropeptide Y (NPY) was increased by lactation in both the ARC and dorsomedial hypothalamus (DMH), although increased gene expression in the DMH was only apparent at day 18 of lactation. Gene expression was decreased for cocaine- and amphetamine-regulated transcript (CART) in the ARC and VMH and for proopiomelanocortin in ARC during lactation. Agouti-related peptide gene expression was increased in the ARC, and melanocortin receptor expression was unchanged in both the ARC and VMH with lactation. Thus the hypoleptinemia of lactation may activate NPY orexigenic pathways and attenuate anorexigenic melanocortin and CART pathways in the hypothalamus to promote the hyperphagia of lactation.
Length-dependent regulation of basal myosin phosphorylation and force in detrusor smooth muscle
Authors: Ratz Paul H. , Miner Amy S.
Published: March 2015

Urinary bladder (detrusor) smooth muscle is active in the absence of an external stimulus. Tone occurs even “at rest” during the filling phase, and it is elevated in patients with overactive bladder. This study examined the role of muscle length on tone and the level of basal myosin light chain phosphorylation (MLC20P). MLC20Pwas 23.9 ± 1% ( n = 58) at short lengths (zero preload; Lz). An increase in length from Lzto the optimal length for contraction ( Lo) caused a reduction in MLC20Pto 15.8 ± 1% ( n = 49). Whereas 10 μM staurosporine reduced MLC20Pat Lz, 1 μM staurosporine, a Ca2+-free solution, and inhibitors of MLC kinase, protein kinase C (PKC) and RhoA kinase (ROK) did not. However, 1 μM staurosporine and inhibitors of ROK inhibited MLC20Pand tone at Lo. These data support the hypothesis that a Ca2+-independent kinase, possibly ZIP-like kinase, regulates MLC20Pat Lz, whereas in detrusor stretched to Lo, additional kinases, such as ROK, participate.
β-Adrenergic modulation of muscarinic cholinergic receptor expression and function in developing heart
Authors: Garofolo M. C. , Seidler F. J. , Auman J. T. , Slotkin T. A.
Published: March 2015

Imbalances of β-adrenoceptor (β-AR) and muscarinic ACh receptor (mAChR) input are thought to underlie perinatal cardiovascular abnormalities in conditions such as sudden infant death syndrome. Administration of isoproterenol, a β1/β2-AR agonist, to neonatal rats on postnatal days (PN) 2– 5 caused downregulation of cardiac m2AChRs and a corresponding decrement in their control of adenylyl cyclase activity. Terbutaline, a β2-selective agonist that crosses the placenta and the blood-brain barrier, was also effective when given either on PN 2– 5 or during gestational days 17– 20. Terbutaline failed to downregulate brain m2AChRs, even though it downregulated β-ARs; β-ARs and m2AChRs are located on different cell populations in the brain, but they are on the same cells in the heart. Destruction of catecholaminergic neurons with neonatal 6-hydroxydopamine upregulated cardiac but not brain m2AChRs. These results suggest that perinatal β-AR stimulation shifts cardiac receptor production away from the generation of m2AChRs so that the development of sympathetic innervation acts as a negative modulator of cholinergic function. Accordingly, tocolytic therapy with β-AR agonists may compromise the perinatal balance of adrenergic and cholinergic inputs.
High-frequency oscillations of phrenic activity in eupnea and gasping of in situ rat: influence of temperature
Authors: St.-John Walter M. , Leiter J. C.
Published: March 2015

We hypothesized that the in situ perfused preparation of the juvenile rat exhibits patterns of ventilatory activity comparable to eupnea and gasping in vivo. To evaluate this hypothesis, we examined high-frequency oscillations of activity of the phrenic nerve at 27–34°C. The peak frequency of these high-frequency oscillations was defined from power spectral analysis. In situ, recordings were obtained in hyperoxic normocapnia, during ventilatory cycles in which the peak of integrated phrenic activity was achieved late in the burst, as in eupnea in vivo. Recordings were also obtained in hypoxic hypercapnia, when the peak of integrated phrenic activity occurred in the first half of the burst, as in gasping in vivo. In situ, peak frequencies in the power spectra were significantly higher in gasping than during eupnea. Frequencies during eupnea and gasping were progressively elevated as the temperature of the in situ preparation was increased. The shift in peak frequencies between eupnea and gasping and the temperature sensitivity of frequencies in situ were the same as in vivo. Results provide additional support for the conclusion that the in situ preparation demonstrates distinctly different patterns of automatic ventilatory activity, comparable to eupnea and gasping in vivo.
Physiological and pathophysiological roles of oxygen radicals in the renal microvasculature
Authors: Schnackenberg Christine G.
Published: March 2015

The renal microvasculature is an important component in the regulation of kidney function. Recent studies suggest that oxygen radicals can contribute to the modulation of renal cortical and medullary microvascular function under normal conditions as well as in pathophysiological conditions such as diabetes mellitus and hypertension. This review focuses on studies that indicate oxygen radicals can cause renal vasoconstriction, mediate the vasoconstriction of other agonists, and modulate nitric oxide-dependent actions in the normal kidney. Hypertension and diabetes mellitus are associated with oxidative stress. Recent investigations suggest that oxygen radicals may contribute to the enhanced renal vascular tone, increased sensitivity to vasoconstrictors, impaired endothelium-dependent vasodilation, and enhanced tubuloglomerular feedback found in these pathophysiological conditions.
Opposite effects of iv amiodarone on cardiovascular vagal and sympathetic efferent activities in rats
Authors: Dias Da Silva Valdo Jose , Gnecchi-Ruscone Tomaso , Lavelli Barbara , Bellina Valentina , Manzella Daniela , Porta Alberto , Malliani Alberto , Montano Nicola
Published: March 2015

It is unknown whether amiodarone exerts a direct central action on the cardiovascular autonomic nervous system. This study was designed to evaluate the effects of acute amiodarone administration on vagal and sympathetic efferent nerve discharges. Experiments were carried out in 25 decerebrate unanesthetized rats. In one group, vagal activity was recorded from preganglionic fibers isolated from the cervical vagus nerve. In another group, sympathetic recordings were obtained from fibers isolated from the cervical sympathetic trunk in intact conditions or after barodenervation. Recordings were performed before and for 60 min after amiodarone (50 mg/kg iv) administration. In all groups, amiodarone induced bradycardia and hypotension. Vagal activity increased immediately, reaching a significant difference after 20 min (260 ± 131% from 16.4 ± 3.3 spikes/s) and was unmodified by the barodenervation. At difference, sympathetic activity after an initial and short-lasting increase (150 ± 83% from 24.8 ± 5.7 spikes/s) began to decrease significantly after 20 min (36 ± 17%) throughout the experiment. The initial increase in sympathetic activity was not observed in barodenervated animals. These changes in vagal and sympathetic activity could play an important role in contributing to the antiarrhythmic action of amiodarone.
Glomerulotubular balance, dietary protein, and the renal response to glycine in diabetic rats
Authors: Slomowitz Larry A. , Deng Aihua , Hammes John S. , Gabbai Francis , Thomson Scott C.
Published: March 2015

The glomerular filtration rate (GFR) normally increases during glycine infusion, which is a test of “renal reserve.” Renal reserve is absent in diabetes mellitus. GFR increases after protein feeding because of increased tubular reabsorption, which reduces the signal for tubuloglomerular feedback (TGF). Dietary protein restriction normalizes some aspects of glomerular function in diabetes. Renal micropuncture was performed in rats 4–5 wk after diabetes was induced by streptozotocin to determine whether renal reserve is lost as a result of altered tubular function and activation of TGF, whether 10 days of dietary protein restriction could restore renal reserve, and whether this results from effects of glycine on the tubule. TGF activation was determined by locating single-nephron GFR (SNGFR) in the early distal tubule along the TGF curve. The TGF signal was determined from the ionic content of the early distal tubule. In nondiabetic rats, SNGFR in the early distal tubule increased during glycine infusion because of primary vasodilation augmented by increased tubular reabsorption, which stabilized the TGF signal. In diabetic rats, glycine reduced reabsorption, thereby activating TGF, which was largely responsible for the lack of renal reserve. In protein-restricted diabetic rats, the tubular response to glycine remained abnormal, but renal reserve was restored by a vascular mechanism. Glycine affects GFR directly and via the tubule. In diabetes, reduced tubular reabsorption dominates. In low-protein diabetes, the vascular effect is enhanced and overrides the effect of reduced tubular reabsorption.
Differential evolution of blood pressure and renal lesions after RAS blockade in Lyon hypertensive rats
Authors: Bertram Delphine , Blanc-Brunat Nelly , Sassard Jean , Lo Ming
Published: March 2015

The present work aimed to assess, in Lyon hypertensive (LH) rats, whether an early and prolonged inhibition of the renin-angiotensin system (RAS) could result in a blood pressure (BP) lowering and nephroprotection that persist after its withdrawal. Male LH rats received orally from 3 to 12 wk of age either an angiotensin-converting enzyme inhibitor perindopril at the doses of 0.4 and 3 mg · kg−1· day−1or an AT1receptor antagonist losartan at the dose of 10 mg · kg−1· day−1. BP, histological changes in the kidney, and urinary protein excretion were examined during and 10 wk after cessation of the treatments. Both perindopril and losartan decreased BP, prevented renal lesions, and limited urinary protein excretion. After cessation of the treatment, BP returned to the level of never-treated LH rats in rats having received 3 mg · kg−1· day−1of perindopril while it remained slightly lower in those treated with 0.4 mg · kg−1· day−1of perindopril or with losartan. This lack of marked persistent antihypertensive effect contrasted with a durable decrease in urinary protein excretion and improvement of the renal histological lesions. In conclusion, it is possible to separate the BP-lowering effects of RAS blockade from those on glomerulosclerosis and urinary protein excretion.
Increased platelet-activating factor-induced periventricular brain microvascular constriction associated with immaturity
Authors: Hou Xin , Gobeil Fernand , Marrache Anne Marilise , Quiniou Christiane , Brault Sonia , Checchin Daniella , Bernier Sylvie G. , Sennlaub Florian , Joyal Jean-Sebastien , Abran Daniel , Peri Krishna , Varma Daya R. , Chemtob Sylvain
Published: March 2015

Oxidant stress contributes to the pathogenesis of hypoxic-ischemic encephalopathies. Platelet-activating factor (PAF) is generated during oxidant stress. We studied the vasomotor mode of actions of PAF on periventricular (PV) microvessels of fetal (≈75% of term), newborn (1–3 days), and adult pigs. PAF constricted PV microvessels from fetal (29.27 ± 2.6%) and newborn (22.14 ± 3.2%) pigs but was ineffective in adults (<2.5%). Specific [3H]PAF binding was greater in fetus and newborn than in adults; a concordant developmental PAF-induced inositol phosphate formation was observed. PAF-induced vasoconstriction was abrogated by thromboxane A2(TXA2) synthase and receptor inhibitors, calcium channel blockers, and by removal of endothelium; vasoconstriction to TXA2mimetic U-46619 did not differ with age. Immunoreactive TXA2synthase expression and PAF-evoked TXA2formation revealed a fetus> newborn>adult profile. Thus the greater PAF-induced PV microvascular constriction in younger subjects seems attributable to greater PAF receptor density and mostly secondary to TXA2formation from endothelium. The resulting decrease in blood flow may contribute to the increased vulnerability of the PV brain regions to oxidant stress-induced injury in immature subjects.
Myogenic reactivity is reduced in small renal arteries isolated from relaxin-treated rats
Authors: Novak Jacqueline , Ramirez Rolando J. J. , Gandley Robin E. , Sherwood O. David , Conrad Kirk P.
Published: March 2015

Administration of the ovarian hormone relaxin to nonpregnant rats vasodilates the renal circulation comparable to pregnancy. This vasodilation is mediated by endothelin (ET), the ETB receptor, and nitric oxide. Furthermore, endogenous relaxin mediates the renal vasodilation and hyperfiltration that occur during gestation. The goal of this study was to investigate whether myogenic reactivity of small renal and mesenteric arteries is reduced in relaxin-treated rats comparable to the pregnant condition. Relaxin or vehicle was administered to virgin female Long-Evans rats for 5 days at 4 μg/h, thereby producing midgestational blood levels of the hormone. The myogenic responses of small renal arteries (200–300 μm in diameter) isolated from these animals were evaluated in an isobaric arteriograph system. Myogenic reactivity was significantly reduced in the small renal arteries from relaxin-treated compared with vehicle-treated rats. The reduced myogenic responses were mediated by the ETB receptor and nitric oxide since the selective ETB receptor antagonist RES-701–1 and the nitric oxide synthase inhibitor N G-nitro-l-arginine methyl ester restored myogenic reactivity to virgin levels. The influence of relaxin was not limited to the renal circulation because myogenic reactivity was also reduced in small mesenteric arteries isolated from relaxin-treated rats. Thus relaxin administration to nonpregnant rats mimics pregnancy, insofar as myogenic reactivity of small renal and mesenteric arteries is reduced in both conditions.
The multifaceted phenotype of the knockout mouse for the KCNE1 potassium channel gene
Authors: Warth Richard , Barhanin Jacques
Published: March 2015

Mutations of the KCNE1 gene (IsK, minK) are related to hereditary forms of cardiac arrhythmias, so-called long QT syndromes (LQT). Here we review the phenotype of a mouse model for the recessive form of LQT known as Jervell and Lange-Nielsen syndrome. KCNE1 knockout mice exhibit an enhanced QT-RR adaptability, which is probably part of the pathophysiological mechanism leading to life-threatening tachyarrhythmia in patients. Like patients, knockout mice are deaf and show vestibular symptoms due to an impaired endolymph production. Knockout mice show urinary and fecal salt wasting and volume depletion. The renal phenotype is due to diminished reabsorption of Na+and glucose. The mice are hypokalemic and have increased aldosterone levels. Besides volume depletion, aldosterone is elevated via a set-point shift for sensing of extracellular K+in aldosterone-secreting glomerulosa cells, which physiologically express KCNE1. In conclusion, KCNE1 knockout leads to a complex phenotype resulting from direct loss of KCNE1 and compensatory mechanisms. Murine KCNE1 physiology could be helpful for the pathophysiological understanding and perhaps gene-specific treatment of long QT patients.
Fat depot origin affects adipogenesis in primary cultured and cloned human preadipocytes
Authors: Tchkonia Tamara , Giorgadze Nino , Pirtskhalava Tamar , Tchoukalova Yourka , Karagiannides Iordanes , Forse R. Armour , DePonte Matthew , Stevenson Michael , Guo Wen , Han Jianrong , Waloga Gerri , Lash Timothy L. , Jensen Michael D. , Kirkland James L.
Published: March 2015

Fat distribution varies among individuals with similar body fat content. Innate differences in adipose cell characteristics may contribute because lipid accumulation and lipogenic enzyme activities vary among preadipocytes cultured from different fat depots. We determined expression of the adipogenic transcription factors peroxisome proliferator activated receptor-γ (PPAR-γ) and CCAAT/enhancer binding protein-α (C/EBP-α) and their targets in abdominal subcutaneous, mesenteric, and omental preadipocytes cultured in parallel from obese subjects. Subcutaneous preadipocytes, which had the highest lipid accumulation, glycerol-3-phosphate dehydrogenase (G3PD) activity, and adipocyte fatty acid binding protein (aP2) abundance, had highest PPAR-γ and C/EBP-α expression. Levels were intermediate in mesenteric and lowest in omental preadipocytes. Overexpression of C/EBP-α in transfected omental preadipocytes enhanced differentiation. The proportion of differentiated cells in colonies derived from single subcutaneous preadipocytes was higher than in mesenteric or omental clones. Only cells that acquired lipid inclusions exhibited C/EBP-α upregulation, irrespective of depot origin. Thus regional variation in adipogenesis depends on differences at the level of transcription factor expression and is a trait conferred on daughter cells.