bluuebunny/crossref_metadata_2025 huggingface dataset:
Letters to the Editor
Authors: Rothe Carl F.
Published: May 2004

The following is the abstract of the article discussed in the subsequent letters:

The National Research Council-sponsored report, BIO 2010: Transforming Undergraduate Education for Future Research Biologists, describes a number of significant changes that should be made to the undergraduate biology curriculum if we are to adequately train students to become the researchers of the 21st century. What should be of concern to the physiology community is the lack of identifiable physiology in the proposed revisions. This article describes the report and suggests some steps that physiologists can take to enhance our discipline in the undergraduate biology curriculum.
Pedagogical effectiveness of innovative teaching methods initiated at the Department of Physiology, Government Medical College, Chandigarh
Authors: Nageswari K. Sri , Malhotra Anita S. , Kapoor Nandini , Kaur Gurjit
Published: May 2004

Modern teaching trends in medical education exhibit a paradigm shift from the conventional classroom teaching methods adopted in the past to nonconventional teaching aids so as to encourage interactive forms of learning in medical students through active participation and integrative reasoning where the relationship of the teacher and the taught has undergone tremendous transformation. Some of the nonconventional teaching methods adopted at our department are learning through active participation by the students through computer-assisted learning (CD-ROMs), Web-based learning (undergraduate projects), virtual laboratories, seminars, audiovisual aids (video-based demonstrations), and “physioquiz.”
Progesterone in milk: a simple experiment illustrating the estrous cycle and enzyme immunoassay
Authors: Rioux Pierre , Rajotte Denis
Published: May 2004

Experiments designed for students in reproductive physiology are rare. Here, we describe a simple experiment concerning a physiological aspect of the reproductive system. Milk samples are obtained from cows in estrus, in midcycle, 21 days after insemination, and in gestation. With these samples, the gestation or estrous stage is determined according to the progesterone level in milk that is measured using enzyme immunoassay. This experiment can therefore be used to demonstrate assay techniques and to illustrate the variations in progesterone concentrations during an estrous cycle and gestation. This exercise should be given after the reproduction section of the animal physiology course so that students can apply their knowledge concerning hormonal profiles during an estrous cycle.
Isoform switching from SM-B to SM-A myosin results in decreased contractility and altered expression of thin filament regulatory proteins
Authors: Babu Gopal J. , Pyne Gail J. , Zhou Yingbi , Okwuchukuasanya Chris , Brayden Joseph E. , Osol George , Paul Richard J. , Low Robert B. , Periasamy Muthu
Published: May 2004

We previously generated an isoform-specific gene knockout mouse in which SM-B myosin is permanently replaced by SM-A myosin. In this study, we examined the effects of SM-B myosin loss on the contractile properties of vascular smooth muscle, specifically peripheral mesenteric vessels and aorta. The absence of SM-B myosin leads to decreased velocity of shortening and increased isometric force generation in mesenteric vessels. Surprisingly, the same changes occur in aorta, which contains little or no SM-B myosin in wild-type animals. Calponin and activated mitogen-activated protein kinase expression is increased and caldesmon expression is decreased in aorta, as well as in bladder. Light chain-17b isoform (LC17b) expression is increased in aorta. These results suggest that the presence or absence of SM-B myosin is a critical determinant of smooth muscle contraction and that its loss leads to additional changes in thin filament regulatory proteins.
Autocrine effects of IGF-I-induced VEGF and IGFBP-3 secretion in retinal pigment epithelial cell line ARPE-19
Authors: Slomiany Mark G. , Rosenzweig Steven A.
Published: May 2004

Hypoxia-induced physiological stress plays a central role in various neovascular diseases of the eye. Increased expression of hypoxia-inducible factor 1α (HIF-1α) and subsequent formation of HIF-1 dimers active at the vascular endothelial growth factor (VEGF) promoter lead to expression of this potent angiogenic factor in the retina, including retinal pigment epithelial (RPE) cells. We previously demonstrated that insulin-like growth factor I (IGF-I) stimulates VEGF and IGF binding protein (IGFBP)-3 secretion in RPE cells. In this study we examined IGF-I-induced HIF-1α expression, VEGF and IGFBP-3 secretion, and the autocrine actions of VEGF and IGFBP-3 on these processes in the spontaneously transformed RPE cell line ARPE-19. Cells were treated with CoCl2, IGF-I, recombinant human (rh)IGFBP-3, and rhVEGF. Immunoblot analysis revealed IGF-I-induced upregulation of total HIF-1α protein, whereas luciferase reporter assays of HIF-1 transcriptional activity demonstrated accumulation of HIF-1α correlated with the formation of functional HIF-1 heterodimers. Western and ligand blot analyses of RPE cell conditioned medium confirmed that IGF-I stimulated VEGF and IGFBP-3 secretion. rhVEGF stimulated IGFBP-3 secretion in an IGF-I- and HIF-1α-independent manner, whereas rhIGFBP-3 attenuated IGF-I-induced VEGF secretion. These findings demonstrate the multifaceted autocrine regulation of IGF-I-induced VEGF secretion by IGFBP-3 secreted in response to both IGF-I and, to a lesser extent, VEGF. These results provide evidence for HIF-1-dependent and -independent mechanisms by which IGF-I regulates VEGF and IGFBP-3 secretion.
Minimal model estimation of glucose absorption and insulin sensitivity from oral test: validation with a tracer method
Authors: Dalla Man Chiara , Caumo Andrea , Basu Rita , Rizza Robert , Toffolo Gianna , Cobelli Claudio
Published: May 2004

Measuring insulin sensitivity during the physiological milieu of oral glucose perturbation, e.g., a meal or an oral glucose tolerance test, would be extremely valuable but difficult since the rate of appearance of absorbed glucose is unknown. The reference method is a tracer two-step one: first, the rate of appearance of glucose (Ra mealref) is reconstructed by employing the tracer-to-tracee ratio clamp technique with two tracers and a model of non-steady-state glucose kinetics; next, this Ra mealref is used as the known input of a model describing insulin action on glucose kinetics to estimate insulin sensitivity (SIref). Recently, a nontracer method based on the oral minimal model (OMM) has been proposed to estimate simultaneously the above quantities, denoted Ra meal and SI, respectively, from plasma glucose and insulin concentrations measured after an oral glucose perturbation. This last method has obvious advantages over the tracer method, but its domain of validity has never been assessed against a reference method. It is thus important to establish whether or not the “nontracer” Ra meal and SI compare well with the “tracer” Ra mealref and SIref . We do this comparison on a database of 88 subjects, and it is very satisfactory: Ra meal profiles agree well with the Ra mealref and correlation of SIref with SI is r = 0.86 ( P < 0.0001). We conclude that OMM candidates as a reliable tool to measure both the rate of glucose absorption and insulin sensitivity from oral glucose tests without employing tracers.
Nocturnal ghrelin pulsatility and response to growth hormone secretagogues in healthy men
Authors: Koutkia Polyxeni , Canavan Bridget , Breu Jeff , Johnson Michael L. , Grinspoon Steven K.
Published: May 2004

The physiological importance of endogenous ghrelin in the regulation of growth hormone (GH) secretion is still unknown. To investigate the regulation of ghrelin secretion and pulsatility, we performed overnight ghrelin and GH sampling every 20 min for 12 h in eight healthy male subjects [age 37 ± 5 (SD) years old, body mass index 27.2 ± 2.9 kg/m2]. Simultaneous GH and ghrelin levels were assessed to determine the relatedness and synchronicity between these two hormones in the fasted state during the overnight period of maximal endogenous GH secretion. Pulsatility analyses were performed to determine simultaneous hormonal dynamics and investigate the relationship between GH and ghrelin by use of cross-approximate entropy (X-ApEn) analyses. Subjects demonstrated 3.0 ± 2.1 ghrelin pulses/12 h and 3.3 ± 0.9 GH pulses/12 h. The mean normalized ghrelin entropy (ApEn) was 0.93 ± 0.09, indicating regularity in ghrelin hormone secretion. The mean normalized X-ApEn was significant between ghrelin and GH (0.89 ± 0.12), demonstrating regularity in cosecretion. In addition, we investigated the ghrelin response to standard GH secretagogues [GH-releasing hormone (GHRH) alone and combined GHRH-arginine] in separate testing sequences separated by 1 wk. Our data demonstrate that, in contrast to GHRH alone, which had little effect on ghrelin, combined GHRH and arginine significantly stimulated ghrelin with a maximal peak at 120 min, representing a change of 66 ± 14 pg/ml ( P = 0.001 by repeated-measures ANOVA and P = 0.02 for GHRH vs. combined GHRH-arginine by MANOVA). We demonstrate relatedness between ghrelin and GH pulsatility, suggesting either that ghrelin participates in the pulsatile regulation of GH or that the two hormones are simultaneously coregulated, e.g., by somatostatin or other stimuli. Furthermore, the differential effects of GHRH alone vs. GHRH-arginine suggest that inhibition of somatostatin tone may increase ghrelin. These data provide further evidence of the physiological regulation of ghrelin in relationship to GH.
NF-κB activation is required for the development of cardiac hypertrophy in vivo
Authors: Li Yuehua , Ha Tuanzhu , Gao Xiang , Kelley Jim , Williams David L. , Browder I. William , Kao Race L. , Li Chuanfu
Published: May 2004

In the present study, we examined whether NF-κB activation is required for cardiac hypertrophy in vivo. Cardiac hypertrophy in rats was induced by aortic banding for 1, 3, and 5 days and 1–6 wk, and age-matched sham-operated rats served as controls. In a separate group of rats, an IκB-α dominant negative mutant (IκB-αM), a superrepressor of NF-κB activation, or pyrrolidinedithiocarbamate (PDTC), an antioxidant that can inhibit NF-κB activation, was administered to aortic-banded rats for 3 wk. The heart weight-to-body weight ratio was significantly increased at 5 days after aortic banding, peaked at 4 wk, and remained elevated at 6 wk compared with age-matched sham controls. Atrial natriuretic peptide and brain natriuretic peptide mRNA expressions were significantly increased after 1 wk of aortic banding, reached a maximum between 2 and 3 wk, and remained increased at 6 wk compared with age-matched sham controls. NF-κB activity was significantly increased at 1 day, reached a peak at 3 wk, and remained elevated at 6 wk, and IKK-β activity was significantly increased at 1 day, peaked at 5 days, and then decreased but remained elevated at 6 wk after aortic banding compared with age-matched sham controls. Inhibiting NF-κB activation in vivo by cardiac transfection of IκB-αM or by PDTC treatment significantly attenuated the development of cardiac hypertrophy in vivo with a concomitant decrease in NF-κB activity. Our results suggest that NF-κB activation is required for the development of cardiac hypertrophy in vivo and that NF-κB could be an important target for inhibiting the development of cardiac hypertrophy in vivo.
Contribution of Akt and endothelial nitric oxide synthase to diazoxide-induced late preconditioning
Authors: Wang Yigang , Ahmad Nauman , Kudo Mitsuhiro , Ashraf Muhammad
Published: May 2004

The opening of mitochondrial ATP-sensitive K+ (mitoKATP) channels has a significant role in delayed ischemic preconditioning, and nitric oxide (NO) is a well-known trigger for its activation. However, the source of NO remains unknown. Phosphorylation of endothelial NO synthase (eNOS) increases NO production and reduces apoptosis through the Akt signaling pathway. To elucidate the Akt signaling pathway involved in the opening and antiapoptotic effect of mitoKATP channel during delayed pharmacological preconditioning, the mitoKATP channel opener diazoxide (DE, 7 μg/kg ip) alone or DE plus Nω-nitro-l-arginine methyl ester (l-NAME, 30 μg/kg iv), an inhibitor of NOS, or wortmannin (WTN, 15 μg/kg iv), an inhibitor of phosphatidylinositol 3′-kinase (PI3 kinase), was administered to wild-type (WT) or eNOS−/− mice during DE treatment. Twenty-four hours later, hearts were isolated and subjected to 40 min ischemia and 30 min reperfusion (I/R). The effect of DE and other interventions on hemodynamic, terminal dUTP nick-end labeling staining and biochemical changes during I/R was assessed in mouse hearts. Treatment with DE resulted in a 2.2-fold increase in phosphorylation of Akt and a significant increase in eNOS and inducible NOS (iNOS) proteins. Akt is upstream of NOS and the mitoKATP channel as simultaneous pretreatment of WTN with DE abolished phosphorylation of Akt, which was not affected by l-NAME and 5-hydroxydecanoate. In hearts treated with DE, cardiac function was significantly improved after I/R, and apoptosis was also significantly decreased. WTN abolished the antiapoptotic effect of DE. Similarly, S-methylisothiourea, a specific iNOS inhibitor, when given to eNOS−/− mice that were pretreated with DE completely abolished the beneficial effects of DE on reduction of apoptotic death. DE was partially effective in eNOS−/− mice against the ischemic injury. It is concluded that DE activates Akt through the PI3 kinase signaling pathway and iNOS and eNOS is downstream of Akt.
Computer model of action potential of mouse ventricular myocytes
Authors: Bondarenko Vladimir E. , Szigeti Gyula P. , Bett Glenna C. L. , Kim Song-Jung , Rasmusson Randall L.
Published: May 2004

We have developed a mathematical model of the mouse ventricular myocyte action potential (AP) from voltage-clamp data of the underlying currents and Ca2+ transients. Wherever possible, we used Markov models to represent the molecular structure and function of ion channels. The model includes detailed intracellular Ca2+ dynamics, with simulations of localized events such as sarcoplasmic Ca2+ release into a small intracellular volume bounded by the sarcolemma and sarcoplasmic reticulum. Transporter-mediated Ca2+ fluxes from the bulk cytosol are closely matched to the experimentally reported values and predict stimulation rate-dependent changes in Ca2+ transients. Our model reproduces the properties of cardiac myocytes from two different regions of the heart: the apex and the septum. The septum has a relatively prolonged AP, which reflects a relatively small contribution from the rapid transient outward K+ current in the septum. The attribution of putative molecular bases for several of the component currents enables our mouse model to be used to simulate the behavior of genetically modified transgenic mice.
Effects of aging on the cardiac remodeling induced by chronic high-altitude hypoxia in rat
Authors: Chouabe C. , Ricci E. , Amsellem J. , Blaineau S. , Dalmaz Y. , Favier R. , Pequignot J.-M. , Bonvallet R.
Published: May 2004

Effects of chronic high-altitude hypoxia on the remodeling of right ventricle were examined in three age groups of rats: 2, 6, and 18 mo. The extent of right ventricular (RV) hypertrophy (RVH) showed an age-associated diminution. RV cell size and pericellular fibrosis showed a significant increase in the 2- and 6-mo-old exposed rats but not in the 18-mo-old exposed rats compared with control. A hyperplasic response was underscored in the three exposed age groups but appeared less pronounced in the 18-mo-old rats. A significant decrease in the transient outward potassium current ( Ito) density was observed in RV cell only in the 2-mo-old exposed group compared with the control group. In the control group, there was a clear tendency for Ito density to decrease as a function of age. The sustained outward current density was modified neither by the hypoxia condition nor by the age. Neither the cytochrome c oxidase activity nor the heat shock protein 72 content in the RV was altered after hypoxic exposure regardless of age. The norepinephrine content in the RV was significantly decreased in each age group exposed to hypoxia when compared with their age-matched control group. Our findings indicate that the remodeling (at morphological and electrophysiological levels) induced by chronic hypoxia in the RV can be decreased by the natural aging process.
Neutral sphingomyelinase inhibitor scyphostatin prevents and ceramide mimics mechanotransduction in vascular endothelium
Authors: Czarny Malgorzata , Schnitzer Jan E.
Published: May 2004

Recently, we showed that neutral sphingomyelinase (N-SMase) is concentrated at the endothelial cell surface in caveolae and is activated to produce ceramide in an acute and transient manner by increase in flow rate and pressure in rat lung vasculature (Czarny M, Liu J, Oh P, and Schnitzer JE, J Biol Chem 278: 4424–4430, 2003). Here, we report further on our investigations of this new acute mechanotransduction pathway. We employed three experimental models to explore the role of N-SMase and ceramides in mechanosignaling: 1) a cell-free, in vitro model using isolated luminal plasma membranes of rat lung endothelium; 2) a fluid shear stress model using monolayers of intact bovine aorta endothelial cell in culture; and 3) an in situ model using controlled perfusion of the rat lung vasculature. Scyphostatin, which specifically inhibited N-SMase but not acid SMase activity, prevented mechanoactivation of N-SMase as well as downstream tyrosine and mitogen-activated protein kinases. Cell-permeable ceramide analogs ( N-acetylsphingosine, C2-ceramide, and N-hexanoylsphingosine, C6-ceramide) but not the inactive dihydroderivatives D2-ceramide and D6-ceramide ( N-acetylsphinganine and N-hexanoylsphinganine, respectively) mimic rapid mechano-induced tyrosine phosphorylation of cell surface proteins as well as mechanoactivation of Src-like kinases and the extracellular regulated kinase pathway. The responses common to ceramide and mechanical stress were inhibited by genistein, herbamycin A, and PP2, but not PP3, which suggests an obligate role of Src-like kinases in ceramide-mediated mechanotransduction. Ceramides also induced serine/threonine phosphorylation to activate the Akt/endothelial nitric oxide synthase pathway. Thus N-SMase at the plasma membrane in caveolae may be an upstream initiating mechanosensor, which acutely triggers mechanotransduction by generation of the lipid second messenger ceramide.
A comparison of oxidized LDL-induced collagen secretion by graft and aortic SMCs: role of PDGF
Authors: Absood Afaf , Furutani Akira , Kawamura Tsutomu , Graham Linda M.
Published: May 2004

Smooth muscle cells (SMCs) from prosthetic vascular grafts constitutively secrete higher levels of collagen than aortic SMCs. Lipid oxidation products accumulate in grafts, and we postulated that they stimulate SMC production of collagen. The effect of oxidized low-density lipoprotein (oxLDL) on type I collagen secretion by aortic and graft SMCs was compared. SMCs isolated from the canine thoracic aorta or Dacron thoracoabdominal grafts ( n = 10) were incubated with native LDL or oxLDL (0–400 μg cholesterol/ml) for 72 h. Type I collagen in the conditioned medium was measured by ELISA. OxLDL increased collagen production by graft SMCs from 4.1 ± 0.3 to 11.0 ± 0.4 ng/μg DNA and by aortic SMCs from 2.3 ± 0.1 to 3.5 ± 0.2 ng/μg DNA. Native LDL had little effect. LY-83583, a superoxide generator, stimulated a dramatic increase in collagen secretion by graft SMCs and a smaller but significant elevation by aortic SMCs. OxLDL has been shown to increase PDGF production by graft SMCs, and PDGF can stimulate collagen production. Anti-PDGF antibody inhibited the increase in collagen production by graft SMCs that was stimulated by oxLDL, implicating PDGF as one mechanism of oxLDL-induced collagen production. Lipid oxidation products that accumulate in prosthetic vascular grafts can cause an oxidative stress that stimulates PDGF production by graft SMCs that in turn stimulates collagen production, contributing to the progression of intimal hyperplasia.
Myocardial O2consumption in porcine left ventricle is heterogeneously distributed in parallel to heterogeneous O2delivery
Authors: Alders David J. C. , Groeneveld A. B. Johan , de Kanter Frans J. J. , van Beek Johannes H. G. M.
Published: May 2004

Myocardial blood flow is unevenly distributed, but the cause of this heterogeneity is unknown. Heterogeneous blood flow may reflect heterogeneity of oxygen demand. The aim of the present study was to assess the relation between oxygen consumption and blood flow in small tissue regions in porcine left ventricle. In seven male, anesthetized, open-chest pigs, local oxygen consumption was quantitated by computational model analysis of the incorporation of13C in glutamate via the tricarboxylic acid cycle during timed infusion of [13C]acetate into the left anterior descending coronary artery. Blood flow was measured with radioactive microspheres before and during acetate infusion. High-resolution nuclear magnetic resonance13C spectra were obtained from extracts of tissue samples (159 mg mean dry wt) taken at the end of the acetate infusion. Mean regional myocardial blood flow was stable [5.0 ± 1.6 (SD) and 5.0 ± 1.4 ml·min−1·g dry wt−1before and after 30 min of acetate infusion, respectively]. Mean left ventricular oxygen consumption measured with the NMR method was 18.6 ± 7.7 μmol·min−1·g dry wt−1and correlated well ( r = 0.85, P = 0.02, n = 7) with oxygen consumption calculated from blood flow, hemoglobin, and blood gas measurements (mean 22.8 ± 4.7 μmol·min−1·g dry wt−1). Local blood flow and oxygen consumption were significantly correlated ( r = 0.63 for pooled normalized data, P < 0.0001, n = 60). We calculate that, in the heart at normal workload, the variance of left ventricular oxygen delivery at submilliliter resolution is explained for 43% by heterogeneity in oxygen demand.
Plasma volume expansion does not increase maximal cardiac output or VO2 max in lowlanders acclimatized to altitude
Authors: Calbet José A. L. , Rådegran Göran , Boushel Robert , Søndergaard Hans , Saltin Bengt , Wagner Peter D.
Published: May 2004

With altitude acclimatization, blood hemoglobin concentration increases while plasma volume (PV) and maximal cardiac output (Q̇max) decrease. This investigation aimed to determine whether reduction of Q̇max at altitude is due to low circulating blood volume (BV). Eight Danish lowlanders (3 females, 5 males: age 24.0 ± 0.6 yr; mean ± SE) performed submaximal and maximal exercise on a cycle ergometer after 9 wk at 5,260 m altitude (Mt. Chacaltaya, Bolivia). This was done first with BV resulting from acclimatization (BV = 5.40 ± 0.39 liters) and again 2–4 days later, 1 h after PV expansion with 1 liter of 6% dextran 70 (BV = 6.32 ± 0.34 liters). PV expansion had no effect on Q̇max, maximal O2 consumption (V̇o2), and exercise capacity. Despite maximal systemic O2 transport being reduced 19% due to hemodilution after PV expansion, whole body V̇o2 was maintained by greater systemic O2 extraction ( P < 0.05). Leg blood flow was elevated ( P < 0.05) in hypervolemic conditions, which compensated for hemodilution resulting in similar leg O2 delivery and leg V̇o2 during exercise regardless of PV. Pulmonary ventilation, gas exchange, and acid-base balance were essentially unaffected by PV expansion. Sea level Q̇max and exercise capacity were restored with hyperoxia at altitude independently of BV. Low BV is not a primary cause for reduction of Q̇max at altitude when acclimatized. Furthermore, hemodilution caused by PV expansion at altitude is compensated for by increased systemic O2 extraction with similar peak muscular O2 delivery, such that maximal exercise capacity is unaffected.
Mechanical ventilation with moderate tidal volumes synergistically increases lung cytokine response to systemic endotoxin
Authors: Altemeier William A. , Matute-Bello Gustavo , Frevert Charles W. , Kawata Yasunobu , Kajikawa Osamu , Martin Thomas R. , Glenny Robb W.
Published: May 2004

Previous animal studies have identified a role for activation of innate immunity in the pathogenesis of ventilator-associated lung injury. These studies have used large tidal volume ventilation to study the effect of alveolar overdistension on induction of inflammatory pathways. We hypothesized an alternative mechanism for the pathogenesis of lung injury in which moderate tidal volume ventilation does not independently cause clinical inflammation but rather interacts with innate immune activation by bacterial products, resulting in an enhanced inflammatory response. We measured cytokine expression and lung injury in normal and lipopolysaccharide (LPS)-treated anesthetized rabbits randomized to either spontaneous respiration or mechanical ventilation. Outcome parameters were analyzed by two-way factorial analysis of variance to identify synergism between ventilation and systemic LPS. Mechanical ventilation alone resulted in minimal cytokine expression in the lung but did enhance LPS-induced expression of tumor necrosis factor-α, the CXC chemokines interleukin-8 and growth-related protein-α, and the CC chemokine monocyte chemoattractant protein-1. Increased mRNA expression and activation of the transcription factors nuclear factor-κB and activator protein-1 accompanied the cytokine responses. We conclude that moderate volume ventilation strategies augment the innate immune response to bacterial products in the lung and may play a role in the development of acute lung injury in patients with sepsis.
Leptin augments alveolar macrophage leukotriene synthesis by increasing phospholipase activity and enhancing group IVC iPLA2(cPLA2γ) protein expression
Authors: Mancuso Peter , Canetti Claudio , Gottschalk Andrew , Tithof Patricia K. , Peters-Golden Marc
Published: May 2004

Leptin is a hormone secreted by adipocytes in correlation with total body fat mass. In addition to regulating energy homeostasis, leptin modulates immune functions such as macrophage phagocytosis and cytokine synthesis. Previously, we reported defective leukotriene synthesis in macrophages from leptin-deficient mice that could be restored with exogenous leptin. In the present study, we utilized macrophages from normal rodents to explore the mechanism by which leptin could enhance cellular leukotriene synthesis. Leptin pretreatment of either rat alveolar or murine peritoneal macrophages for 16 h dose dependently increased the synthesis of leukotriene B4and cysteinyl leukotrienes in response to calcium ionophore or the particulate zymosan. Leptin also enhanced calcium ionophore-stimulated release of free arachidonic acid. Calcium-dependent and -independent arachidonoyl-selective phospholipase activities in macrophage lysates were likewise increased following leptin treatment. Immunoblot analysis of leptin-treated cells revealed that group IVC iPLA2(cPLA2γ) protein expression increased ∼80%. These data demonstrate for the first time that phospholipase A2activity and cPLA2γ protein levels in alveolar macrophages represent targets for upregulation by leptin and provide previously unrecognized mechanisms by which this hormone can promote inflammatory responses.
Prenatal blockade of estradiol synthesis impairs respiratory and metabolic responses to hypoxia in newborn and adult rats
Authors: Doan V. D. , Gagnon S. , Joseph V.
Published: May 2004

We tested the hypothesis that estradiol modifies respiratory control in pregnant rats and participates in the development of respiratory chemoreflexes in fetuses. Pregnant rats ( n = 12) received daily subcutaneous injections of vehicle (Veh, n = 6) or 4-androsten-4-ol-3,17-dione acetate (ATD; inhibitor of estradiol synthesis; n = 6; 5 mg/day in vehicle) from gestational day 16 (G16) to delivery. Baseline ventilation (whole body plethysmography) and metabolic rate [oxygen consumption (V̇o2)] were determined at G14 and G20, in pups [on postnatal day 3 (P3) and P20] and in adult rats (on P70) born to Veh- or ATD-treated mothers. Hypoxic chemoreflex was assessed in P3 rats by acute exposure to 60% O2 and in P20 or P70 rats by moderate hypoxia (12% O2, 30 min). ATD treatment reduced circulating estradiol in pregnant dams at G20 without producing changes in the circulating level of estradiol precursors (testosterone and androstenedione). ATD-treated dams showed impaired respiratory adjustment to late gestation. Pups born to ATD mothers had higher resting V̇o2 (+23% at P3, +21% at P20), respiratory frequency (+15% at P3, +12% at P20), and minute ventilation (+11% at P3, +18% at P20) than pups from Veh mothers. Respiratory decrease during acute hyperoxic exposure at P3 was −9.7% in Veh ( P < 0.05 vs. room air) and only −2.6% ( P = not significant) in ATD pups. In P20 ATD rats, hypoxic ventilatory response was attenuated compared with Veh. In P20 and P70 rats, the drop of V̇o2 in hypoxia (−31% in P70, P < 0.0001) was not observed in ATD rats. We conclude that estradiol secreted during late gestation is necessary for respiratory adjustment to pregnancy and is required for adequate development of respiratory and metabolic control in the offspring.
Regulation of an inwardly rectifying K+channel by nitric oxide in cultured human proximal tubule cells
Authors: Nakamura Kazuyoshi , Hirano Junko , Kubokawa Manabu
Published: May 2004

We investigated the effects of nitric oxide (NO) on activity of the inwardly rectifying K+channel in cultured human proximal tubule cells, using the cell-attached mode of the patch-clamp technique. An inhibitor of NO synthases, Nω-nitro-l-arginine methyl ester (l-NAME; 100 μM), reduced channel activity, which was restored by an NO donor, sodium nitroprusside (SNP; 10 μM) or 8-bromo-cGMP (8-BrcGMP; 100 μM). However, SNP failed to activate the channel in the presence of an inhibitor of soluble guanylate cyclase, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (10 μM). Similarly, the SNP effect was abolished by a protein kinase G (PKG)-specific inhibitor, KT-5823 (1 μM), but not by a protein kinase A-specific inhibitor, KT-5720 (500 nM). Another NO donor, S-nitroso- N-acetyl-d,l-penicillamine (10 μM), mimicked the SNP-induced channel activation. In contrast to the stimulatory effect of SNP at a low dose (10 μM), a higher dose of SNP (1 mM) reduced channel activity, which was not restored by 8-BrcGMP. Recordings of membrane potential with the slow whole cell configuration demonstrated that l-NAME (100 μM) and the high dose of SNP (1 mM) depolarized the cell by 10.1 ± 2.6 and 9.2 ± 1.0 mV, respectively, whereas the low dose of SNP (10 μM) hyperpolarized it by 7.1 ± 0.7 mV. These results suggested that the endogenous NO would contribute to the maintenance of basal activity of this K+channel and hence the potential formation via a cGMP/PKG-dependent mechanism, whereas a high dose of NO impaired channel activity independent of cGMP/PKG-mediated processes.
Developmental expression and biological activity of gastrin-releasing peptide and its receptors in the kidney
Authors: Dumesny Chelsea , Whitley Jane C. , Baldwin Graham S. , Giraud Andrew S. , Shulkes Arthur
Published: May 2004

Mammalian gastrin-releasing peptide (GRP) has a widespread distribution and multiple stimulating effects on metabolism, release of regulatory peptides, gastrointestinal and pancreatic secretions, and behavior. GRP is a potent mitogen for a number of tumor types, including colon and lung. Although GRP is known to stimulate the growth of renal tumors, little is known of its synthesis, distribution, and receptors in the developing and mature kidney. Both Northern blot analysis and RT-PCR revealed the presence of GRP mRNA in ovine kidney from midgestation through to adulthood. GRP mRNA was detected in rat kidney from embryonic day 19 to postnatal day 30 by RT-PCR. Sequence-specific radioimmunoassay demonstrated the presence of substantial amounts of fully processed amidated GRP in the ovine renal cortex and medulla. The mRNA for the major receptor subtype, GRP-R, was present in fetal and adult sheep and rat kidneys. The mRNA for the low-affinity GRP receptor, bombesin receptor subtype-3 (BRS-3), was only detected in the rat kidney. In the ovine kidney, immunohistochemistry localized GRP predominantly to the thick ascending limb of the loop of Henle. mRNAs for GRP, GRP-R, and BRS-3 were detected in the human embryonic kidney cell line HEK293, and radioimmunoassay of cell extracts and conditioned media revealed the presence of proGRP but not the amidated form. However, amidated GRP did stimulate the proliferation of these cells. These studies demonstrate that the developing and mature kidney may be previously unidentified sites of autocrine or paracrine action for GRP.
Effects of 10-day confinement on the immune system and psychological aspects in humans
Authors: Shimamiya Tamiyasu , Terada Nobuyuki , Hiejima Yoshimitsu , Wakabayashi Sonoe , Kasai Hirotake , Mohri Motohiko
Published: May 2004

We investigated the changes in percentages of leukocyte subpopulations, natural killer (NK) cells, CD69-expressing lymphocytes, and psychological aspects in 10 subjects who participated in a 10-day confinement study. Suppression of lymphocyte proliferative reaction and changes in leukocyte distribution are known to occur in space. These responses are similar to those induced by psychological stress. Ground-based confinement studies are suitable for validating the effects of stress arising only due to confinement. Two groups, consisting of five male subjects (ages 20–27 yr, mean 22.8 yr) each, participated in a 10-day confinement study. Blood samples were taken once before, three times during, and once after the confinement and activated with an anti-CD2 agonistic antibody cocktail. The percentages of leukocyte subpopulations, NK (CD45+CD56+) cells, and activated lymphocytes (CD45+CD69+) were measured by flow cytometric assay. The face scale test was used to measure psychological aspects. The percentage of CD69+lymphocytes decreased during the period of confinement. This was mostly caused by changes in the ratio between NK and non-NK lymphocytes. The face scale showed that the subjects' moods improved toward the postconfinement period. Consistent with the face scale, the percentages of innate immune cells, such as NK cells and granulocytes, increased during the postconfinement period. We concluded that the changes in the distribution of immune cells caused by stress plays an important role in suppression of proliferative reactivity. The observed physiological reactions were specific to the confined environment, and the stress caused by confinement plays a role in the immune changes observed in space.
Autonomic control of the cardiovascular system during acclimatization to high altitude: effects of sildenafil
Authors: Cornolo Jérémy , Mollard Pascal , Brugniaux Julien V. , Robach Paul , Richalet Jean-Paul
Published: May 2004

Both acute hypoxia and sildenafil may influence autonomic control through transient cardiovascular effects. In a double-blind study, we investigated whether sildenalfil (Sil) could interfere with cardiovascular effects of hypoxia. Twelve healthy men [placebo (Pla) n = 6; Sil, n = 6] were exposed to an altitude of 4,350 m during 6 days. Treatment was continuously administered from 6 to 8 h after arrival at altitude (3 × 40 mg/day). The autonomic control on the heart was assessed by heart rate variability (HRV) during sleep at sea level (SL) and between day 1–2 and day 5–6 in hypoxia. Arterial pressure (AP) and total peripheral resistances (TPR) were obtained during daytime. There was no statistical difference between groups in HRV, AP, and TPR throughout the study. Hypoxia induced a decrease in R-R interval and an increase in AP in both groups. Low frequency-to-high frequency ratio increased at day 1–2 (Pla, P = 0.04; Sil, P = 0.02) and day 5–6 (Pla and Sil, P = 0.04) vs. SL, whereas normalized high-frequency power decreased only in Pla ( P = 0.04, day 1–2 vs. SL). Normalized low-frequency power increased at high altitude (Pla and Sil, P = 0.04, day 5–6 vs. SL). TPR decreased at day 2 in Pla ( P = 0.02) and tended to normalize at day 6 ( P = 0.07, day 6 vs. day 2). Acute hypoxia induced a decrease in parasympathetic and increase in sympathetic tone, which tended to be reversed with acclimatization. Sil had no deleterious effects on the cardiovascular response to high-altitude exposure and its control by the autonomic nervous system.
Gender and ethnic differences in urinary stress hormones: the population-based Chicago Health, Aging, and Social Relations Study
Authors: Masi Christopher M. , Rickett Edith M. , Hawkley Louise C. , Cacioppo John T.
Published: May 2004

Gender and ethnic disparities in cardiovascular disease and mortality have spurred interest in the epidemiology of stress hormone production. Greater disease burden among men and blacks raises the possibility of gender and ethnic differences in stress hormone production. The purpose of this study was to determine whether urinary stress hormones were higher among men and blacks in a population-based sample. Urinary hormone analysis permits a time-integrated assessment of the stress response system. However, differences in collection and standardization strategies have led to inconsistent findings. Subjects were an ethnically diverse population-based sample of 229 men and women aged 50–67 yr who provided an overnight urine specimen. Urine concentration was standardized using a traditional creatinine-based approach as well as a new method that accounts for muscle mass. With the use of creatinine standardization, no gender or ethnic differences were noted in epinephrine or cortisol production. Norepinephrine levels were higher among women compared with men ( P = 0.001), however. After accounting for muscle mass, we found that both epinephrine ( P = 0.018) and norepinephrine ( P = 0.033) levels were higher among men compared with women. No significant differences in cortisol production were found by gender or ethnicity. The consistency of these results with previous studies of 24-h urine samples suggests muscle mass should be accounted for when comparing overnight urinary hormone values across gender and ethnicity.
Role of UCP3 in state 4 respiration during contractile activity-induced mitochondrial biogenesis
Authors: Ljubicic Vladimir , Adhihetty Peter J. , Hood David A.
Published: May 2004

In an effort to better characterize uncoupling protein-3 (UCP3) function in skeletal muscle, we assessed basal UCP3 protein content in rat intermyofibrillar (IMF) and subsarcolemmal (SS) mitochondrial subfractions in conjunction with measurements of state 4 respiration. UCP3 content was 1.3-fold ( P < 0.05) greater in IMF compared with SS mitochondria. State 4 respiration was 2.6-fold greater ( P < 0.05) in the IMF subfraction than in SS mitochondria. GDP attenuated state 4 respiration by ∼40% ( P < 0.05) in both subfractions. The UCP3 activator oleic acid (OA) significantly increased state 4 respiration in IMF mitochondria only. We used chronic electrical stimulation (3 h/day for 7 days) to investigate the relationship between changes in UCP3 protein expression and alterations in state 4 respiration during contractile activity-induced mitochondrial biogenesis. UCP3 content was increased by 1.9- and 2.3-fold in IMF and SS mitochondria, respectively, which exceeded the concurrent 40% ( P < 0.05) increase in cytochrome- c oxidase activity. Chronic contractile activity increased state 4 respiration by 1.4-fold ( P < 0.05) in IMF mitochondria, but no effect was observed in the SS subfraction. The uncoupling function of UCP3 accounted for 50–57% of the OA-induced increase in state 4 respiration in IMF mitochondria, which was independent of the induced twofold difference in UCP3 content due to chronic contractile activity. Thus modifications in UCP3 function are more important than changes in UCP3 expression in modifying state 4 respiration. This effect is evident in IMF but not SS mitochondria. We conclude that UCP3 at physiological concentrations accounts for a significant portion of state 4 respiration in both IMF and SS mitochondria, with the contribution being greater in the IMF subfraction. In addition, the contradiction between human and rat training studies with respect to UCP3 protein expression may partly be explained by the greater than twofold difference in mitochondrial UCP3 content between rat and human skeletal muscle.
Relative roles of heredity and physical activity in adolescence and adulthood on blood pressure
Authors: Hernelahti Miika , Levälahti Esko , Simonen Riitta L. , Kaprio Jaakko , Kujala Urho M. , Uusitalo-Koskinen Arja L. T. , Battié Michele C. , Videman Tapio
Published: May 2004

Part of the association between physical activity and low blood pressure (BP) may be a consequence of genetic selection. We investigated the association of genetic factors and physical activity in adolescence and adulthood with BP. BP was measured with a Finapres device in 71 monozygotic and 104 dizygotic male twin pairs using no antihypertensive medication. Subjects' mean age was 50.4 yr (range 40–72 yr). Subjects were interviewed about their lifetime exercise and other health habits. Exercise was classified as aerobic, power, or other, and these were further divided into adolescence (12–20 yr of age), the previous year, and lifetime. Genetic modeling was conducted to estimate genetic and environmental components of variance of systolic and diastolic BP. Aerobic exercise in adolescence and high-intensity aerobic exercise throughout the lifetime were associated with low diastolic BP in adulthood. Of the variance in diastolic BP, genetic factors accounted for 35% and aerobic exercise in adolescence for 5%. For systolic BP, genetic factors accounted for 39% of the variance. In turn, genetic factors accounted for 44% of the variance in aerobic exercise in adolescence. The genetic factors in part accounting for the variance in diastolic BP and those in part accounting for variance in aerobic exercise in adolescence were correlated. The association between aerobic exercise in adolescence and low diastolic BP in adulthood is a new finding, as is the observation that the factors partly share the same genes.
Serotonergic Modulation in Aplysia. I. Distributed Serotonergic Network Persistently Activated by Sensitizing Stimuli
Authors: Marinesco Stéphane , Kolkman Kristine E. , Carew Thomas J.
Published: May 2004

A common feature of arousing stimuli used as reinforcement in animal models of learning is that they promote memory formation through widespread effects in the CNS. In the marine mollusk Aplysia, sensitization is typically induced by tail-shock, an aversive reinforcer that triggers a state of defensive arousal characterized by escape locomotion and increased heart rate. Serotonin (5-HT) contributes importantly to sensitization of defensive reflexes as well as to the regulation of locomotion and heart rate. Although specific serotonergic neurons increase their firing after tail-shock, it remains unclear whether this effect is restricted to these neurons or whether tail-shock recruits a more global serotonergic system. In this study, we recorded from serotonergic neurons throughout the CNS, which were prelabeled with 5,7-dihydroxytryptamine, during an in vitro analog of sensitization training, tail-nerve shock. We found that most of the serotonergic neurons that we recorded from (80%) increased their firing rate for several minutes after nerve shock. Most serotonergic neurons in the pedal and abdominal ganglion were also excited by 5-HT and by intracellular activation of the two serotonergic neurons CB1/CC3. This interconnectivity between serotonergic neurons might contribute to spread excitation within a large proportion of the serotonergic system during sensitization training. It is also possible that serotonergic neurons could be activated by 5-HT present in the hemolymph via a neuro-humoral positive feedback mechanism. Overall, these data indicate that sensitization training activates a large proportion of Aplysia serotonergic neurons and that this form of learning occurs in a context of increased serotonergic tone.
Serotonergic Modulation in Aplysia. II. Cellular and Behavioral Consequences of Increased Serotonergic Tone
Authors: Marinesco Stéphane , Wickremasinghe Nimalee , Kolkman Kristine E. , Carew Thomas J.
Published: May 2004

Serotonin (5-HT) plays an important role in sensitization of defensive reflexes in Aplysia and is also involved in several aspects of arousal, such as the control of locomotion and of cardiovascular tone. In the preceding paper, we showed that tail-nerve shock, a noxious stimulus that readily induces sensitization, increases the firing rate of a large number of serotonergic neurons throughout the CNS. However, the functional consequences of such an increase in serotonergic tone are still poorly understood. In this study, we examined this question by using the 5-HT precursor 5-hydroxytryptophan (5-HTP) to specifically increase 5-HT release in the CNS. Increased tonic 5-HT release after 5-HTP treatment was manifested by facilitation of sensorimotor (SN-MN) synapses, increased firing rate of serotonergic neurons in the pedal and abdominal ganglia, and enhanced 5-HT release evoked by tail-nerve shock. When 5-HTP was administered to freely moving animals, it produced a strong arousal response characterized by increased locomotion and heart rate, which was reminiscent of the defensive arousal reaction triggered by noxious stimulation such as tail-shock. In contrast, 5-HTP actually inhibited the tail-induced siphon-withdrawal reflex. It is possible that 5-HT-induced facilitation of SN-MN synapses was counteracted by inhibition of polysynaptic reflex pathways between SNs and MNs, resulting in transient behavioral inhibition of the reflex, which could favor escape locomotion and/or respiration shortly after an aversive stimulus. We conclude that a major function associated with the activation of the Aplysia serotonergic system evoked by noxious stimuli is the triggering of a defensive arousal response. It is known that tail-shock-induced serotonergic activation contributes to memory encoding at least in part by facilitating SN-MN synapses. However, this effect in isolation might not be sufficient for the behavioral expression of sensitization.
Major Role For Tonic GABAA Conductances in Anesthetic Suppression of Intrinsic Neuronal Excitability
Authors: Bieda Mark C. , MacIver M. Bruce
Published: May 2004

Anesthetics appear to produce neurodepression by altering synaptic transmission and/or intrinsic neuronal excitability. Propofol, a widely used anesthetic, has proposed effects on many targets, ranging from sodium channels to GABAA inhibition. We examined effects of propofol on the intrinsic excitability of hippocampal CA1 neurons (primarily interneurons) recorded from adult rat brain slices. Propofol strongly depressed action potential production induced by DC injection, synaptic stimulation, or high-potassium solutions. Propofol-induced depression of intrinsic excitability was completely reversed by bicuculline and picrotoxin but was strychnine-insensitive, implicating GABAA but not glycine receptors. Propofol strongly enhanced inhibitory postsynaptic currents (IPSCs) and induced a tonic GABAA-mediated current. We pharmacologically differentiated tonic and phasic (synaptic) GABAA-mediated inhibition using the GABAA receptor antagonist SR95531 (gabazine). Gabazine (20 μM) completely blocked both evoked and spontaneous IPSCs but failed to block the propofol-induced depression of intrinsic excitability, implicating tonic, but not phasic, GABAA inhibition. Glutamatergic synaptic responses were not altered by propofol (≤30 μM). Similar results were found in both interneurons and pyramidal cells and with the chemically unrelated anesthetic thiopental. These results suggest that suppression of CA1 neuron intrinsic excitability, by these anesthetics, is largely due to activation of tonic GABAA conductances; although other sites of action may play important roles in affecting synaptic transmission, which also can produce strong neurodepression. We propose that for some anesthetics, suppression of intrinsic excitability, mediated by tonic GABAA conductances, operates in conjunction with effects on synaptic transmission, mediated by other mechanisms, to depress hippocampal function during anesthesia.