bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of vasoconstrictor responses to histamine in the hindlimb vascular bed of the rabbit
Authors: Champion Hunter C. , Bivalacqua Trinity J. , Lambert David G. , Abassi Rasheed A. , Kadowitz Philip J.
Published: December 2017

Hemodynamic responses to histamine were investigated in the anesthetized rabbit. Intravenous injections of histamine induced dose-dependent decreases in systemic arterial pressure that were blocked by the H1-receptor antagonist pyrilamine but not the H2 antagonist cimetidine. Injections of histamine and the H1 agonist 6-[2-(4-imidazolyl)ethylamine]- N-(4-trifuormethylphenyl)-heptanecardoxamide dimaleate (HTMT) into the hindlimb perfusion circuit increased hindlimb perfusion pressure, whereas the H2agonist dimaprit decreased perfusion pressure and the H3-receptor agonist R-(−)-α-methylhistamine did not alter perfusion pressure. Pyrilamine reduced hindlimb vasoconstrictor responses to histamine and HTMT but did not alter vasodilator responses to dimaprit. Cimetidine reduced the response to dimaprit but did not alter vasoconstrictor responses to histamine or HTMT. The H3-receptor antagonist thioperamide was without effect on responses to the histamine agonists. These data suggest the presence of H1 and H2 receptors and that histamine for the most part acts by stimulating H1 receptors to produce vasoconstriction in the hindlimb vascular bed of the rabbit. Responses to histamine, HTMT, and norepinephrine were significantly enhanced by a nitric oxide synthase inhibitor at a time when vasodilator responses to dimaprit were unaltered and responses to acetylcholine were significantly reduced. Responses to histamine and the H1 and H2 agonists were not affected by the cyclooxygenase inhibitor meclofenamate or by ATP-sensitive K+ channel, α-adrenergic, or angiotensin AT1 receptor antagonists. The present data suggest that H1 receptors mediate both systemic vasodepressor and hindlimb vasoconstrictor responses to histamine.
Focal delivery during direct infusion to brain: role of flow rate, catheter diameter, and tissue mechanics
Authors: Morrison Paul F. , Chen Michael Y. , Chadwick Richard S. , Lonser Russell R. , Oldfield Edward H.
Published: December 2017

Direct interstitial infusion is a technique capable of delivering agents over both small and large dimensions of brain tissue. However, at a sufficiently high volumetric inflow rate, backflow along the catheter shaft may occur and compromise delivery. A scaling relationship for the finite backflow distance along this catheter in pure gray matter ( x m) has been determined from a mathematical model based on Stokes flow, Darcy flow in porous media, and elastic deformation of the brain tissue: x m = constant Q o 3 R 4 r c 4 G −3μ−1( Q o = volumetric inflow rate, R = tissue hydraulic resistance, r c = catheter radius, G = shear modulus, and μ = viscosity). This implies that backflow is minimized by the use of small diameter catheters and that a fixed (minimal) backflow distance may be maintained by offsetting an increase in flow rate with a similar decrease in catheter radius. Generally, backflow is avoided in rat gray matter with a 32-gauge catheter operating below 0.5 μl/min. An extension of the scaling relationship to include brain size in the resistance term leads to the finding that absolute backflow distance obtained with a given catheter and inflow rate is weakly affected by the depth of catheter tip placement and, thus, brain size. Finally, an extension of the model to describe catheter passage through a white matter layer before terminating in the gray has been shown to account for observed percentages of albumin in the corpus callosum after a 4-μl infusion of the compound to rat striatum over a range of volumetric inflow rates.
Regulation of in vitro renin secretion by ANG II feedback manipulation in vivo in the ovine fetus
Authors: Giammattei Carlos E. , Strandhoy Jack W. , Rose James C.
Published: December 2017

The renin-angiotensin system is critically important to fetal cardiovascular function and organ development. The feedback regulation of renin secretion by ANG II develops early in gestation yet does not linearly progress from fetal life to adulthood. Renin secretion is elevated in late gestation compared with earlier or postnatal time periods, which suggests that some component of the negative feedback regulation of renin secretion is less sensitive in late gestation. We examined in fetal sheep the age-related consequence of chronic in vivo manipulation of ANG II on renal renin secretion measured in vitro. Immature (101–103 days of gestation) and mature (130–133 days of gestation) fetuses were treated for 72 h with enalaprilat, ANG II or vehicle. Content and basal and isoproterenol-stimulated secretion of prorenin (PR) and active renin (AR) from fetal kidney cortical slices were determined. Enalaprilat pretreatment in vivo increased renal renin content and basal and stimulated secretion of PR and AR in vitro even in immature animals. Immunohistochemical localization showed that enalaprilat treatment caused an age-related recruitment of renin-containing juxtaglomerular cells. Conversely, ANG II pretreatment decreased basal and stimulated PR and AR secretion from immature fetal kidneys, but only inhibited PR secretion from mature kidneys. It also caused an age-related decrease in the percentage of renin-containing juxtaglomerular cells. These results suggest that ANG II feedback modulates not only the synthesis and content of renin, but the sensitivity of the coupling between stimulus and secretion. A critical observation of our study is that the higher renal tissue concentrations of prorenin and active renin in late gestation may be a consequence of reduced sensitivity to ANG II feedback; this is consistent with the increased plasma concentrations of renin found in near-term mammals.
Hemodynamic effects of platelet-activating factor in nonpregnant and pregnant sheep
Authors: Greenberg Suzanne G. , Clark Kenneth E.
Published: December 2017

The present study was designed to assess the dose-related effects of platelet-activating factor (PAF) on systemic, renal, and uterine hemodynamics in nonpregnant sheep and to evaluate how pregnancy might alter these responses. Nonpregnant and pregnant (110 ± 5 days gestation) ewes were instrumented for conscious measurements of maternal mean arterial pressure (MAP), renal blood flow (RBF), uterine blood flow (UBF), hematocrit, and urinary protein concentration. After recovery, dose-response curves to PAF were generated by systemic infusion at 10, 30, and 100 ng ⋅ kg−1⋅ min−1(15 min/dose) into the maternal femoral vein. The above parameters were measured, and renal and uterine vascular resistances (RVR and UVR, respectively) were calculated. In pregnant sheep, PAF increased MAP, RVR, UVR, and urinary protein concentration. We also observed increases in hematocrit, indicative of reduced blood volume secondary to increased systemic microvascular protein permeability. These responses were similar in nonpregnant sheep, with the exception of UVR in nonpregnant ewes being decreased (and thus UBF was increased), whereas in pregnant sheep, UVR was increased, which resulted in decreased UBF. This suggests that pregnancy alters the mechanism of action of PAF within the uterine vasculature in a way that can reduce UBF and thereby potentially compromise placental perfusion.
Gastric and duodenal features of meals mediate controls of liquid gastric emptying during fill in rhesus monkeys
Authors: Moran Timothy H. , Knipp Susan , Schwartz Gary J.
Published: December 2017

To study the dynamics of liquid gastric emptying in rhesus monkeys under conditions that simulated gastric fill during a meal, we measured the gastric emptying of liquid glucose at various concentrations and volumes when administered intragastrically at rates ranging from 12.5 to 37.5 ml/min. Glucose gastric emptying was faster during than following the period of gastric fill. At a single glucose concentration, volume infused rather than the rate of filling determined the volume emptied. Lower glucose concentrations emptied more slowly than physiological saline. As glucose concentration increased, emptying during fill slowed. Duodenal glucose infusions greatly slowed the rate of saline emptying during fill, demonstrating duodenal feedback control. Although casein hydrolosate emptied more rapidly than glucose, the dynamics of volume and concentration dependency and the role of duodenal feedback were similar. These data reveal that both gastric volume and duodenal negative feedback controls important in gastric emptying following stomach filling also contribute to its control during fill.
Role of steroid hormones in Trichinella spiralis infection among voles
Authors: Klein Sabra L. , Gamble H. Ray , Nelson Randy J.
Published: December 2017

Males are generally more susceptible to parasite infection than females. This sex difference may reflect the suppressive effects of testosterone and enhancing effects of estradiol on immune function. This study characterized the role of circulating steroid hormones in sex differences after infection with the nematode Trichinella spiralis. Because testosterone suppresses immune function and because polygynous males have higher circulating testosterone concentrations than monogamous males, sex differences in parasite burden were hypothesized to be exaggerated among polygynous meadow voles compared with monogamous prairie voles. As predicted, sex differences in response to T. spiralis infection were increased among meadow voles; males had higher worm numbers than females. Male and female prairie voles had equivalent parasite burden. Overall, prairie voles had higher worm numbers than meadow voles. Contrary to our initial prediction, differences in circulating estradiol concentrations in females, testosterone concentrations in males, and corticosterone concentrations in both sexes were not related to the observed variation in T. spiralisinfection. Taken together, these data suggest that not all sex differences in parasite infection are mediated by circulating steroid hormones and that adaptive-functional explanations may provide new insight into the causes of variation in parasite infection.
Mechanism of branchial apical silver uptake by rainbow trout is via the proton-coupled Na+channel
Authors: Bury Nicolas R. , Wood Chris M.
Published: December 2017

The branchial uptake mechanism of the nonessential heavy metal silver from very dilute media by the gills of freshwater rainbow trout was investigated. At concentrations >36 nM AgNO3, silver rapidly entered the gills, reaching a peak at 1 h, after which time there was a steady decline in gill silver concentration and a resulting increase in body silver accumulation. Below 36 nM AgNO3, there was only a very gradual increase in gill and body silver concentration over the 48-h exposure period. Increasing water sodium concentration ([Na+]; 0.05 to 21 mM) significantly reduced silver uptake, although, in contrast, increasing ambient [Ca2+] or [K+] up to 10 mM did not reduce silver uptake. Kinetic analysis of silver uptake at varying [Na+] showed a significant decrease in maximal silver transport capacity (173 ± 34 pmol ⋅ g−1⋅ h−1at 0.1 mM [Na+] compared with 35 ± 9 at 13 mM [Na+]) and only a slight decrease in the affinity for silver transport ( Km; 55 ± 27 nM at 0.1 mM [Na+] compared with 91 ± 47 nM at 13 mM [Na+]). Phenamil (a specific blocker of Na+channels), at a concentration of 100 μM, blocked Na+uptake by 78% of control values (58% after washout), and bafilomycin A1(a specific blocker of V-type ATPase), at a concentration of 2 μM, inhibited Na+uptake by 57% of control values, demonstrating the presence of a proton-coupled Na+channel in the apical membrane of the gills. Phenamil (after washout) and bafilomycin A1also blocked silver uptake by 62 and 79% of control values, respectively, indicating that Ag+is able to enter the apical membrane via the proton-coupled Na+channel.
Mice deficient in interleukin-1β converting enzyme resist anorexia induced by central lipopolysaccharide
Authors: Yao Jian-Hua , Ye Shi-Ming , Burgess William , Zachary James F. , Kelley Keith W. , Johnson Rodney W.
Published: December 2017

Interleukin-1β (IL-1β) is expressed in the mouse brain after intracerebroventricular injection of lipopolysaccharide (LPS) and is thought to be responsible for many of the behavioral and neuroendocrine changes that occur during inflammation. In this study we show that LPS in the brain also induces expression of interleukin-1β converting enzyme (ICE) and that ICE is important for the characteristic anorectic response of mice to intracerebroventricular LPS. Specifically, mice that were deficient in ICE (ICE−/−) resisted the anorexia caused by intracerebroventricular injection of LPS but were sensitive to the anorectic properties of recombinant IL-1β. The typical anorectic response seen in wild-type (WT) mice after LPS was restored in ICE−/−mice by intracerebroventricular administration of the ICE analog cathepsin G. Conversely, anorexia induced by intracerebroventricular injection of LPS in WT mice was blocked by prior intracerebroventricular injection of the ICE antagonist YVAD.CMK. Furthermore, in situ hybridization immunohistochemistry revealed intense expression of ICE mRNA in the hippocampus and dorsomedial hypothalamus of WT mice after intracerebroventricular injection of LPS. Thus ICE mRNA is expressed in brain after intracerebroventricular injection of LPS and is important for induction of anorexia, presumably because it generates mature IL-1β. These results suggest that preventing generation of mature IL-1β can inhibit anorexia induced by LPS in the brain and, therefore, reveal ICE as a potential target for regulating food intake during brain inflammation.
Chronic orall-DOPA increases dopamine and decreases serotonin excretions
Authors: García Néstor H. , Berndt Theresa J. , Tyce Gertrude M. , Knox Franklyn G.
Published: December 2017

Given the common pathways for uptake and synthesis for dopamine and serotonin, enhanced renal dopamine synthesis in response to increased substrate 3,4-dihydroxyphenylalanine (l-DOPA) is postulated to decrease renal serotonin synthesis. The present study compared the effects of chronic oral administration ofl-DOPA on dopamine and serotonin excretion in vivo, with the effects of enhanced dopamine synthesis per nephron due to adaptation to reduced renal mass (RRM). Four groups of rats were studied: sham-operated rats and rats with RRM in the absence and presence of chronic orall-DOPA.l-DOPA (2 mg ⋅ 100 g body wt−1⋅ day−1) for 6–14 days increased calculated dopamine synthesis per nephron in sham-operated rats from 2.0 ± 0.3 ( n = 7) to 13.6 ± 1.8 pg ⋅ day−1⋅ nephron−1( n = 7, P < 0.05) and in rats with RRM from 6.1 ± 1.3 ( n = 7) to 39.3 ± 5.2 pg ⋅ day−1⋅ nephron−1( n = 7, P < 0.05). Chronic orall-DOPA concomitantly decreased serotonin synthesis per nephron in sham-operated rats (1.6 ± 0.1 to 1.0 ± 0.1 pg ⋅ day−1⋅ nephron−1, n = 7, P < 0.05) and in rats with RRM (5.6 ± 0.9 to 2.6 ± 0.4 pg ⋅ day−1⋅ nephron−1, n = 7, P < 0.05). Both serotonin and dopamine synthesis per nephron were increased in rats with RRM. In conclusion, chronic oral administration ofl-DOPA enhances dopamine excretion and decreases serotonin excretion in normal rats and in rats with reduced renal mass. Both dopamine and serotonin excretions per nephron were elevated by renal mass reduction.
Regional wall motion and strain of transplanted hearts in pediatric patients using magnetic resonance tagging
Authors: Donofrio Mary T. , Clark Bernard J. , Ramaciotti Claudio , Jacobs Marshall L. , Fellows Kenneth E. , Weinberg Paul M. , Fogel Mark A.
Published: December 2017

Abnormal ventricular systolic torsion is present during histological rejection in adult cardiac transplant patients. Because biomechanical properties of transplanted hearts in the baseline state have not been studied in children, pediatric patients were evaluated to quantify ventricular wall motion and strain. Eight transplant studies and eight normal controls were evaluated. Magnetic resonance tagging was performed to determine radial shortening, twist, and strain in four ventricular anatomic areas at two short-axis levels. Controls had counterclockwise twist. Six transplant studies had clockwise twist, six had akinetic regions, and all had regions of no twist. One demonstrated paradoxical motion of the septum. A comparison between transplant patients and controls revealed strain to be similar in all regions except one (superior wall at the atrioventricular valve level) and strain distribution to be different only in two of eight regions. Pediatric transplant patients demonstrate regional wall motion abnormalities in the absence of rejection. Compared with normal controls, the transplanted left ventricle maintains normal strain in the presence of abnormal twist. This may be a compensatory mechanism and have clinical implications.
Rainbow trout (Oncorhynchus mykiss) possess two somatostatin mRNAs that are differentially expressed
Authors: Moore Craig A. , Kittilson Jeffrey D. , Ehrman Melissa M. , Sheridan Mark A.
Published: December 2017

Previously, we isolated a 624-bp cDNA encoding for a 115-amino acid preprosomatostatin containing [Tyr7,Gly10]-somatostatin (SS)-14 (now designated PPSS-II′) obtained from the endocrine pancreas (Brockmann bodies) of rainbow trout. In this study we have characterized a second cDNA obtained from trout pancreas that is 600-bp in length and encodes for a 111-amino acid precursor containing [Tyr7,Gly10]-SS-14 (PPSS-II′′). The nucleotide and amino acid identity between the two cDNAs is 82.3 and 80.5%, respectively. Both PPSS-II′ and PPSS-II′′ mRNA were present in esophagus, pyloric ceca, stomach, upper and lower intestine, and pancreas, whereas only SS-II′′ mRNA was present in brain. PPSS-II′′ mRNA was more abundant than PPSS-II′ mRNA in pancreas, whereas PPSS-II′ mRNA was more abundant than PPSS-II′′ mRNA in stomach. Fasting increased pancreatic PPSS-II′′ mRNA levels but had no effect on the levels of PPSS-II′ mRNA. These results indicate the existence of two nonallelic pancreatic SS-II genes that are differentially expressed, both in terms of distribution among tissues and in terms of relative abundance within the tissues.
Purification, structural characterization, and myotropic activity of endothelin from trout,Oncorhynchus mykiss
Authors: Wang Yuqi , Olson Kenneth R. , Smith Michael P. , Russell Michael J. , Conlon J. Michael
Published: December 2017

Endothelin (ET) from a nontetrapod species has never been characterized, either structurally or biologically. A single molecular form of trout ET with 21-amino-acid residues was isolated in pure form from an extract of the kidney of the steelhead trout, Oncorhynchus mykissand its primary structure established as Cys-Ser-Cys-Ala-Thr-Phe-Leu-Asp-Lys-Glu10-Cys-Val-Tyr-Phe-Cys-His-Leu-Asp-Ile-Ile20-Trp. This amino acid sequence shows only three substitutions (Ala4→Ser, Thr5→Ser, and Phe6→Trp) compared with human ET-2, demonstrating that the structure of the peptide has been well conserved during evolution and that the pathway of posttranslational processing of preproendothelin in the trout is probably similar to that in mammals. Synthetic trout ET produced concentration-dependent constrictions of isolated rings of vascular tissue from trout efferent branchial artery (EBA; pD2= 7.90 ± 0.06, n = 5), caeliacomesenteric artery (pD2= 8.03 ± 0.04, n = 4), anterior cardinal vein (ACV; pD2= 8.57 ± 0.25, n = 4), and rat abdominal aorta (AO; pD2= 8.86 ± 0.08, n = 7). Trout and rat vessels were more sensitive to mammalian ET-1 than to trout ET (pD2for human ET-1 in: EBA = 9.12 ± 0.14; ACV = 9.90 ± 0.15; AO = 8.86 ± 0.08), but there was no significant difference in the maximum tension produced by either peptide in these vessels.
Role of metallothionein against oxidative stress in the musselMytilus galloprovincialis
Authors: Viarengo Aldo , Burlando Bruno , Cavaletto Maria , Marchi Barbara , Ponzano Enrica , Blasco Julián
Published: December 2017

Metallothionein (MT) is a sulfhydryl-rich protein involved mainly in heavy metal homeostasis and detoxification. In this study, the use of the mussel as an experimental model allowed us to test MT antioxidant properties at the molecular, cellular, and organism level. MT induction was achieved by mussel exposure to Cd (200 μg/l) in aquaria for 7 days followed by detoxification in the sea for 28 days. Cd-preexposed and nonexposed mussels were then treated with Fe (300–600 μg/l) in aquaria for 3 days. Biochemical assays on digestive gland tissue showed that treatment with Fe led to a significant increase in oxyradical production and malondialdehyde level only in mussels not preexposed to Cd. The Cd-dependent resistance to oxidative stress was ascribed to MT induction, as Cd produced no significant variation of reduced glutathione and major antioxidant enzymes. Digital imaging of isolated digestive gland cells showed lower oxyradical rise and higher viability in cells from Cd-preexposed mussels after treatments with 0.5–5 mM H2O2. Analyses on whole organisms showed that anoxic survival was lowered in mussels that had been treated with Fe, but such an effect was less pronounced in Cd-preexposed mussels compared with nonpreexposed ones. In conclusion, data suggest an antioxidant role for MT, which seems to occur through oxyradical scavenging and is able to protect both isolated cells and the entire organism from oxidative stress.
Measurement of force and both surface and deep M wave properties in isolated rat soleus muscles
Authors: Harrison A. P. , Flatman J. A.
Published: December 2017

In isolated soleus muscles of 4-wk-old rats, M wave parameters were recorded with surface and deep recording electrodes and examined in relation to both twitch and tetanic force. Addition of ouabain (10−5 M for 16 min) to isolated muscles caused an ∼40% decrease in twitch amplitude and area ( P < 0.01) that was associated with a 98% decrease in surface M wave amplitude, a 78% decrease in deep M wave amplitude (both P< 0.001), a 98% decrease in surface M wave area ( P < 0.01), 48% of which occurred within 60 s of addition of ouabain ( P< 0.05), and a 55% decrease in deep M wave area ( P < 0.05). The decrease in twitch parameters on addition of ouabain was most closely correlated with deep M wave area ( r = 0.92). Direct tetanic stimulation at a frequency of 30 Hz resulted in an initial potentiation of M waves, which was not seen at a frequency of 90 Hz. Instead, 90 Hz stimulation resulted in a prompt decrease in tetanic force that was correlated with a decrease in both deep M wave amplitude ( r = 0.94; P < 0.01) and deep M wave area ( r = 0.96; P < 0.01). It is concluded that simultaneous surface and deep recordings involving area and amplitude are fundamental to analysis of the effects of pharmacological agents on muscle performance and the use of M waves as predictors of muscle excitability.
Control of pulmonary surfactant secretion from type II pneumocytes isolated from the lizardPogona vitticeps
Authors: Wood Philip G. , Lopatko Olga V. , Orgeig Sandra , Codd Jonathan R. , Daniels Christopher B.
Published: December 2017

Pulmonary surfactant, a mixture consisting of lipids and proteins and secreted by type II cells, functions to reduce the surface tension of the fluid lining of the lung, and thereby decreases the work of breathing. In mammals, surfactant secretion appears to be influenced primarily by the sympathetic nervous system and changes in ventilatory pattern. The parasympathetic nervous system is not believed to affect surfactant secretion in mammals. Very little is known about the factors that control surfactant secretion in nonmammalian vertebrates. Here, a new methodology for the isolation and culture of type II pneumocytes from the lizard Pogona vitticeps is presented. We examined the effects of the major autonomic neurotransmitters, epinephrine (Epi) and ACh, on total phospholipid (PL), disaturated PL (DSP), and cholesterol (Chol) secretion. At 37°C, only Epi stimulated secretion of total PL and DSP from primary cultures of lizard type II cells, and secretion was blocked by the β-adrenoreceptor antagonist propranolol. Neither of the agonists affected Chol secretion. At 18°C, Epi and ACh both stimulated DSP and PL secretion but not Chol secretion. The secretion of surfactant Chol does not appear to be under autonomic control. It appears that the secretion of surfactant PL is predominantly controlled by the autonomic nervous system in lizards. The sympathetic nervous system may control surfactant secretion at high temperatures, whereas the parasympathetic nervous system may predominate at lower body temperatures, stimulating surfactant secretion without elevating metabolic rate.
Mode of activation of salt secretion by C-type natriuretic peptide in the shark rectal gland
Authors: Silva Patricio , Solomon Richard J. , Epstein Franklin H.
Published: December 2017

We studied the modes of activation of the salt-secreting rectal gland of the spiny dogfish, Squalus acanthias, by the native cardiac peptide CNP. The stimulatory action of CNP in isolated perfused glands is inhibited by 10 mM procaine, presumably by blocking release of vasoactive intestinal peptide (VIP) from nerves. Procaine reduces the slope of the dose-response curve of human CNP and that of shark CNP (each P < 0.0001). CNP increases short-circuit current in cultured rectal gland cells from 4.8 ± 1.6 to 27.0 ± 7.8 μA/cm2. It also stimulates the secretion of chloride in isolated perfused glands in the presence of 10 mM procaine from 72 ± 31 to 652 ± 173 μeq ⋅ h−1⋅ g−1. These results suggest that CNP has a direct cellular action not mediated by the neural release of VIP. The residual stimulation of perfused glands in the presence of procaine was almost completely inhibited by staurosporine [10 nM; an inhibitor of protein kinase C (PKC)] from 652 ± 173 to 237 ± 61 μeq ⋅ h−1⋅ g−1. Although CNP stimulates guanylyl cyclase in shark rectal gland, chloride secretion of perfused glands was not elicited by 8-bromoadenosine-cGMP (8-BrcGMP) alone nor by the activator of PKC phorbol ester. The combination of PKC activation and 8-BrcGMP infusion, however, stimulated chloride secretion in perfused glands from 94 ± 30 to 506 ± 61 μeq ⋅ h−1⋅ g−1, a level comparable to that observed in glands blocked with procaine. Several parallel pathways appear to be synergistic in activating chloride secretion stimulated by CNP in the rectal gland.
PGE2suppresses mitogen-induced Ca2+mobilization in T cells
Authors: Choudhry Mashkoor A. , Hockberger Philip E. , Sayeed Mohammed M.
Published: December 2017

PGE2-mediated suppression of T cell proliferation during sepsis could result from altered Ca2+signaling. The present study evaluated the effects of PGE2on Ca2+release from intracellular stores and its influx through the plasma membrane in splenic T cells from Sprague-Dawley rats. Intracellular Ca2+concentration ([Ca2+]i) responses in individual T cells were assessed using the Ca2+imaging technique, and the release of Ca2+from intracellular stores and Ca2+influx were spectrofluorometrically quantified in T cell suspensions. Under unstimulated conditions, nearly 85% of T cells exhibited [Ca2+]i≤50 nM. After stimulation with concanavalin A (Con A), an increase in [Ca2+]iwas recorded in ∼60% of the cells. The pretreatment of T cells with PGE2had no apparent effect on [Ca2+]iin resting cells; it significantly suppressed the Con A-induced increase in [Ca2+]iin all of the Con A-responsive cells. Ca2+release from the intracellular stores contributed to the early spike in [Ca2+]i, and the late phase of elevation in [Ca2+]iwas dependent on Ca2+influx through the plasma membrane. Our data suggest that PGE2causes an overall suppression of the Con A-induced [Ca2+]ielevation in T cells via inhibiting both Ca2+influx and its release from the intracellular stores.
Determinants of the natriuresis after acute, slow sodium loading in conscious dogs
Authors: Bie Peter , Sandgaard Niels C. F.
Published: December 2017

The relative importance of systemic volume, concentration, and pressure signals in sodium homeostasis was investigated by intravenous infusion of isotonic (IsoLoad) or hypertonic (HyperLoad) saline at a rate (1 μmol Na+⋅ kg−1⋅ s−1), similar to the rate of postprandial sodium absorption. IsoLoad decreased plasma vasopressin (−35%) and plasma ANG II (−77%) and increased renal sodium excretion (95-fold), arterial blood pressure (ΔBP; +6 mmHg), and heart rate (HR; +36%). HyperLoad caused similar changes in plasma ANG II and sodium excretion, but augmented vasopressin (12-fold) and doubled ΔBP (+12 mmHg) without changing HR. IsoLoad during vasopressin clamping (constant vasopressin infusion) caused comparable natriuresis at augmented ΔBP (+14 mmHg), but constant HR. Thus vasopressin abolished the Bainbridge reflex. IsoLoad during normotensive angiotensin clamping (enalaprilate plus constant angiotensin infusion) caused marginal natriuresis (9% of unclamped response) despite augmented ΔBP (+14 mmHg). Cessation of angiotensin infusion during IsoLoad immediately decreased BP (−13 mmHg) and increased glomerular filtration rate by 20% and sodium excretion by 45-fold. The results suggest that fading of ANG II is the cause of acute “volume-expansion” natriuresis, that physiological ANG II deviations override the effects of modest systemic blood pressure changes, and that endocrine rather than hemodynamic mechanisms are the pivot of normal sodium homeostasis.
Synthesis of gill Na+-K+-ATPase in Atlantic salmon smolts: differences in α-mRNA and α-protein levels
Authors: D'Cotta Helena , Valotaire Claudiane , le Gac Florence , Prunet Patrick
Published: December 2017

Several parameters were analyzed to determine the mechanisms responsible for the enhancement of the gill Na+-K+-ATPase activity of Atlantic salmon smolts. A major α-subunit transcript of 3.7 kb was revealed by Northern blot in both parr and smolt gills when hybridized with two distinct cDNA probes. The α-mRNA abundance demonstrated an increase to maximal levels in smolts at an early stage of the parr-smolt transformation. This was followed by a gradual rise in α-protein levels, revealed by Western blots with specific antibodies and by an increase in gill Na+-K+-ATPase hydrolytic activity, both only reaching maximum levels a month later, at the peak of the transformation process. Parr fish experienced a decrease in α-mRNA abundance and had basal levels of α-protein and enzyme activity. Measurement of the binding of [3H]ouabain to Na+-K+-ATPase was characterized in smolts and parr gill membranes showing more than a twofold elevation in smolts and was of high affinity in both groups (dissociation constant = 20–23 nM). Modulation of the enzyme due to increased salinity was also observed in seawater-transferred smolts, as demonstrated by an increase in α-mRNA levels after 24 h with a rise in Na+-K+-ATPase activity occurring only after 11 days. No qualitative change in α-expression was revealed at either the mRNA or protein level. Immunological identification of the α-protein was performed with polyclonal antibodies directed against the rat α-specific isoforms, revealing that parr, freshwater, and seawater smolts have an α3-like isoform. This study shows that the increase in Na+-K+-ATPase activity in smolt gills depends first on an increase in the α-mRNA expression and is followed by a slower rise in α-protein abundance that eventually leads to a higher synthesis of Na+-K+pumps.
Hormonal regulation of renal sodium and water excretion during normotensive sodium loading in conscious dogs
Authors: Sandgaard Niels C. F. , Andersen Jens Lundbæk , Bie Peter
Published: December 2017

.—Saline was infused intravenously for 90 min to normal, sodium-replete conscious dogs at three different rates (6, 20, and 30 μmol ⋅ kg−1⋅ min−1) as hypertonic solutions (HyperLoad-6, HyperLoad-20, and HyperLoad-30, respectively) or as isotonic solutions (IsoLoad-6, IsoLoad-20, and IsoLoad-30, respectively). Mean arterial blood pressure did not change with any infusion of 6 or 20 μmol ⋅ kg−1⋅ min−1. During HyperLoad-6, plasma vasopressin increased by 30%, although the increase in plasma osmolality (1.0 mosmol/kg) was insignificant. During HyperLoad-20, plasma ANG II decreased from 14 ± 2 to 7 ± 2 pg/ml and sodium excretion increased markedly (2.3 ± 0.8 to 19 ± 8 μmol/min), whereas glomerular filtration rate (GFR) remained constant. IsoLoad-20 decreased plasma ANG II similarly (13 ± 3 to 7 ± 1 pg/ml) concomitant with an increase in GFR and a smaller increase in sodium excretion (1.9 ± 1.0 to 11 ± 6 μmol/min). HyperLoad-30 and IsoLoad-30 increased mean arterial blood pressure by 6–7 mmHg and decreased plasma ANG II to ∼6 pg/ml, whereas sodium excretion increased to ∼60 μmol/min. The data demonstrate that, during slow sodium loading, the rate of excretion of sodium may increase 10-fold without changes in mean arterial blood pressure and GFR and suggest that the increase may be mediated by a decrease in plasma ANG II. Furthermore, the vasopressin system may respond to changes in plasma osmolality undetectable by conventional osmometry.
Suppression of food intake is linked to enteric inflammation in nematode-infected rats
Authors: Faro Constance J. , Reidelberger Roger D. , Palmer Jeffrey M.
Published: December 2017

Our aim was to investigate the cause-effect relationship between intestinal inflammation induced by infection with enteric stages of Trichinella spiralis and decreased host food intake. A suppression of food intake in T. spiralis-infected rats occurred within the first 24 h postinfection (PI) and was maximized by day 6 PI. Food intake, cumulated over an 8-day PI period, decreased by 59% compared with uninfected animals. The anti-inflammatory glucocorticoid betamethasone 21-phosphate was orally administered to rats in their drinking water to suppress T. spiralis-induced jejunal inflammation. When treated with a low dose of glucocorticoid (5.2 μg/ml), food intake in infected rats was still significantly reduced, but only by 21% compared with glucocorticoid-treated, uninfected rats. At the highest glucocorticoid dose (10.4 μg/ml) administered, infection-induced reduction in food intake was not different from that of glucocorticoid-treated, uninfected counterparts. The elevation in jejunal myeloperoxidase activity caused by infection was also significantly blunted by oral glucocorticoid treatment. Our results suggest that suppressed host food intake during enteric T. spiralis infection is directly linked to intestinal inflammation.
Myotubes originating from single fast and slow satellite cells display similar patterns of AChE expression
Authors: Boudreau-Larivière Céline , Parry David J. , Jasmin Bernard J.
Published: December 2017

Slow- and fast-contracting skeletal muscles of both rats and mice display significant differences in their patterns of acetylcholinesterase (AChE) expression. Although neural influences are known to account for a large proportion of these differences, intrinsic variations between fast and slow myogenic precursor cells have been implicated. In the present study, we have capitalized on the use of Immorto transgenic mice to obtain single myogenic precursor cells isolated from either slow or fast muscle fibers and determined whether these cells generated myotubes that produced distinct patterns of AChE expression as observed in vivo between slow and fast muscles. These two myotube populations displayed similar cell-associated and secreted AChE enzyme activity as well as comparable levels of AChE transcripts. Both myotube populations also expressed nearly identical molecular form profiles. By contrast, AChE activity and transcript levels were approximately two- and fivefold greater in fast skeletal muscles compared with slow ones. Together, these findings indicate that differences in AChE expression between fast and slow muscles are not due to inherent differences in myogenic precursor cells, thereby suggesting that other factors, such as innervation, play a predominant role in establishing the distinct patterns of AChE expression in these muscle types.
Role of hypothermia induced by tumor necrosis factor on apoptosis and function of inflammatory neutrophils in mice
Authors: Mizuno Toshiko , Kannan Yukiko , Tokunaga Midori , Moriyama Mitsuaki , Kiso Yasuo , Kusakabe Ken , Yamate Jyoji , Kiyomiya Kenichi , Sugano Tsukasa
Published: December 2017

Changes in body temperature and cell infiltration, mediated by cytokines including tumor necrosis factor-α (TNF-α), occur during inflammation, but a role of body temperature on inflammatory responses remains obscure. Intraperitoneal injection of 10% casein to mice resulted in transient hypothermia followed by neutrophil accumulation in peritoneal cavities. Peritoneal TNF-α was rapidly raised, and pretreatment of mice with an anti-TNF-α antibody promoted temperature restoration and partially inhibited neutrophil accumulation. To investigate direct effects of body temperature on neutrophils, peritoneal or peripheral blood neutrophils were cultured at 35°C or 37°C with or without recombinant murine TNF-α (100 ng/ml) or a protein synthesis inhibitor cycloheximide (1 μg/ml). Significant inhibition of spontaneous and TNF-α-induced apoptosis was obtained at 35°C compared with 37°C, an effect that was not altered by the addition of cycloheximide. Moreover, phagocytic ability of peritoneal neutrophils was significantly enhanced by incubating them at the lower temperature. These results indicate that mild hypothermia induced by endogenous TNF-α has enhancing roles on neutrophil survival and function during peritoneal inflammation.
Volume expansion natriuresis during servo control of systemic blood pressure in conscious dogs
Authors: Andersen Jens Lundbæk , Andersen Lars Juel , Sandgaard Niels C. F. , Bie Peter
Published: December 2017

.—The importance of arterial blood pressure (BP) and ANG II for the renal natriuretic response (NaEx) to volume expansion (3.5% body wt) was investigated during converting enzyme blockade (enalaprilate, 2 mg/kg). In separate experiments, BP was clamped either 30 mmHg above or a few millimeters mercury below baseline by servo-controlled infusion of ANG II or sodium nitroprusside, respectively, so that volume expansion did not change BP. Enalapril decreased BP by 8 mmHg. Without clamping, volume expansion returned BP to that of preenalapril control and increased NaEx 10-fold (40 ± 10 to 377 ± 69 μmol/min). During high pressure clamping (133 ± 2 mmHg), peak NaEx after volume expansion was 6% of control experiments. During low pressure clamping, NaEx was 68% of control experiments (45 ± 15 to 256 ± 64 μmol/min). The results show that 1) in absence of ANG II, volume expansion elicited pronounced natriuresis without increases in BP beyond baseline, 2) in the presence of hypertensive amounts of ANG II, the volume expansion-induced natriuresis was almost eliminated, and 3) nitroprusside prevented the increase in BP but not sodium excretion during volume expansion. ANG II appears to dominate the control of NaEx; however, when absent, volume expansion may still induce marked natriuresis even at constant BP, possibly via nitric oxide-mediated mechanisms.
Short-term and long-term blood pressure and heart rate variability in the mouse
Authors: Janssen Ben J. A. , Leenders Peter J. A. , Smits Jos F. M.
Published: December 2017

Knowledge on murine blood pressure and heart rate control mechanisms is limited. With the use of a tethering system, mean arterial pressure (MAP) and pulse interval (PI) were continuously recorded for periods up to 3 wk in Swiss mice. The day-to-day variation of MAP and PI was stable from 5 days after surgery. Within each mouse ( n = 9), MAP and PI varied by 21 ± 6 mmHg and 17 ± 4 ms around their respective 24-h averages (97 ± 3 mmHg and 89 ± 3 ms). Over 24-h periods, MAP and PI were bimodally distributed and clustered around two preferential states. Short-term variability of MAP and PI was compared between the resting (control) and active states using spectral analysis. In resting conditions, variability of MAP was mainly confined to frequencies <1 Hz, whereas variability of PI was predominantly linked to the respiration cycle (3–6 Hz). In the active state, MAP power increased in the 0.08- to 3-Hz range, whereas PI power fell in the 0.08- to 0.4-Hz range. In both conditions, coherence between MAP and PI was high at 0.4 Hz with MAP leading the PI fluctuations by 0.3–0.4 s, suggesting that reflex coupling between MAP and PI occurred at the same frequency range as in rats. Short-term variability of MAP and PI was studied after intravenous injection of autonomic blockers. Compared with the resting control state, MAP fell and PI increased after ganglionic blockade with hexamethonium. Comparable responses of MAP were obtained with the α-blocker prazosin, whereas the β-blocker metoprolol increased PI similarly. Muscarinic blockade with atropine did not significantly alter steady-state levels of MAP and PI. Both hexamethonium and prazosin decreased MAP variability in the 0.08- to 1-Hz range. In contrast, after hexamethonium and metoprolol, PI variability increased in the 0.4- to 3-Hz range. Atropine had no effect on MAP fluctuations but decreased those of PI in the 0.08- to 1-Hz range. These data indicate that, in mice, blood pressure and its variability are predominantly under sympathetic control, whereas both vagal and sympathetic nerves control PI variability. Blockade of endogenous nitric oxide formation by N G-nitro-l-arginine methyl ester increased MAP variability specifically in the 0.08- to 0.4-Hz range, suggesting a role of nitric oxide in buffering blood pressure fluctuations.
Developmental stage modifies diet-induced peripheral insulin resistance in rats
Authors: Pagliassotti Michael J. , Gayles Ellis C. , Podolin Deborah A. , Wei Yuren , Morin Catherine L.
Published: December 2017

In the present study, the effects of age and diet on glucose disappearance and tissue-specific glucose uptake (R′g) were examined under basal or hyperinsulinemic, euglycemic conditions in male Sprague-Dawley rats. Rats were equicalorically fed either a high-starch diet (68% of kcal), high-fat diet (HFD; 45% of kcal), or high-sucrose diet (68% of kcal), beginning at either 5 (W; weanling), 10 (Y; young), 18 (M; mature), or 58 wk (O; older) of age for 5 wks ( n = 6–9 ⋅ group−1⋅ diet−1). Body weight gain was not significantly different among dietary groups within a given age. Significant ( P < 0.05) age effects were observed on basal and clamp free fatty acid concentrations. Significant diet effects were observed on basal and clamp triglyceride concentrations. There were significant diet and age effects on basal skeletal muscle R′g. This interaction was primarily due to an age-associated increase in basal R′g (μg ⋅ g−1⋅ min−1) in HFD (gastrocnemius R′g: 0.9 ± 0.2 in W, 1.1 ± 0.2 in Y, 1.8 ± 0.2 in M, 2.5 ± 0.2 in O). Both age and diet significantly decreased insulin-stimulated muscle R′g. However, whereas age-associated reductions in both glucose-6-phosphate concentration and glycogen synthase activity were observed, significant diet effects were observed on glucose-6-phosphate concentrations only. Age significantly reduced basal and clamp adipose tissue R′g when expressed per gram of tissue but significantly increased R′g when expressed per total fat pad mass. These data suggest that diet-induced changes in peripheral glucose metabolism are modulated by age.
Accelerated contractile function and improved fatigue resistance of calf muscles in newborn piglets with IUGR
Authors: Wank Veit , Bauer Reinhard , Walter Bernd , Kluge Harald , Fischer Martin S. , Blickhan Reinhard , Zwiener Ulrich
Published: December 2017

Asymmetrical intrauterine growth restriction is denoted by disproportional reduction of muscle mass compared with body weight reduction. However, effects on contractile function or tissue development of skeletal muscles were not studied until now. Therefore, isometric force output of serial-stimulated hindlimb plantar flexors was measured in thiopental-anesthetized normal weight (NW) and intrauterine growth-restricted (IUGR) 1-day-old piglets under conditions of normal, reduced (aortic cross clamping), and reestablished (clamp release) blood supply (measured by colored microspheres technique). Furthermore, muscle fiber type distribution was determined after histochemical staining, specific muscle force of the plantar flexors [quotient from absolute force divided by muscle mass (N/g)] was calculated, and glycogen content and morphometric data of the investigated muscles were estimated. Regional blood flow of hindlimb muscles was similar in NW (6 ± 2 ml ⋅ min−1⋅ 100 g−1) and IUGR piglets (8 ± 1 ml ⋅ min−1⋅ 100 g−1). Isometric muscle contractions induced a marked increase in regional blood flow of 4.1-fold in NW and 5-fold in stimulated hindlimb muscles of IUGR piglets (baseline blood flow). Specific force of NW piglet muscles (5.2 ± 0.2 N/g) was significantly lower than IUGR piglet muscles (6.1 ± 0.6 N/g; P < 0.05). Isometric muscle contractions (NW: 32.7 ± 4.7 N; IUGR: 21.7 ± 4.0 N) resulted in a higher rate of force decrease in the calf muscles of NW animals compared with IUGR piglets (8 ± 2 vs. 3 ± 1%; P < 0.01). Functional restoration of contractile performance after hindlimb recirculation was nearly complete in IUGR piglets (98 ± 1%), whereas in NW piglets a deficit of 9 ± 3% was found ( P < 0.01). Muscle fiber type estimation revealed an increased proportion of type I fibers in flexor digitalis superficialis and gastrocnemius medialis in IUGR piglets ( P < 0.05). These data clearly indicate that contractile function is accelerated in newborn IUGR piglets.
Spontaneous mutation in the db gene results in obesity and diabetes in CD-1 outbred mice
Authors: Brown Julie A. , Chua Streamson C. , Liu Shun Mei , Andrews Matthew T. , Vandenbergh John G.
Published: December 2017

Five allelic mutants of the diabetes (db) gene have been previously described in mice and rats causing obesity, infertility, and varying degrees of diabetes. We have identified a new, spontaneous mutation resulting in obesity and diabetes in a colony of CD-1 outbred mice, Mus musculus domesticus. Genetic complementation studies indicated that the new mutation was an allele of the diabeteslocus. Sequence analysis of cDNA fragments showed a deletion of one G residue located in exon 12 of the leptin receptor gene. The mutation, Lepr db-NCSU , results in a frameshift and reduces Lepr transcript levels 10-fold. Mutant mice drank up to four times more water and were up to two times heavier than wild-type mice. Blood glucose and plasma insulin and leptin concentrations were sexually dimorphic among affected mice, suggesting an effect of sex steroids. Mortality of affected males was 100% by 5 mo, whereas affected females survived up to 10 mo of age.
Aminopeptidase-A. II. Genomic cloning and characterization of the rat promoter
Authors: Jiang Qingping , Troyanovskaya Marta , Jayaraman Gomathi , Healy Dennis P.
Published: December 2017

Aminopeptidase-A (APA) has a widespread tissue distribution consistent with a role in the metabolism of circulating or locally produced ANG II or CCK-8. APA is also highly expressed in pre-B lymphocytes, but its role in lymphoid cell development is unknown. To begin to understand the basis for cell-specific regulation of APA expression, we sought to clone and characterize the rat gene promoter. Screening of a rat genomic library with a partial rat APA cDNA resulted in isolation of a 12-kb clone found to contain the first exon and >3 kb of 5′-flanking sequence. Primer extension of rat kidney mRNA indicated that the major transcription start site was 312 bp upstream of the translation start codon and 22 bp downstream from a TATA box. Constructs containing portions of the 5′-flanking region placed upstream of a chloramphenicol acetyltransferase reporter gene indicated that expression was cell specific and that high activity could be obtained with constructs containing as little as 110 bp of 5′-flanking region sequence. We further identified an upstream regulatory element between −1063 and −348 that suppressed transcription in a cell-specific manner. This element (termed upstream suppressor of APA, or USA) also suppressed transcription of a heterologous promoter. These results indicate that the organization and regulation of the rat APA is not consistent with it being a housekeeping gene and further suggest that rat APA gene transcription might be regulated through the presence of a novel strong upstream suppressor element.