bluuebunny/crossref_metadata_2025 huggingface dataset:
The vasa vasorum in diseased and nondiseased arteries
Authors: Mulligan-Kehoe Mary Jo
Published: November 2009

The vasa vasorum form a network of microvasculature that originate primarily in the adventitial layer of large arteries. These vessels supply oxygen and nutrients to the outer layers of the arterial wall. The expansion of the vasa vasorum to the second order is associated with neovascularization related to progression of atherosclerosis. Immunohistological analysis of human plaques from autopsied aortas have defined plaque progression and show a significant correlation with vasa vasorum neovascularization. Recent technological advances in microcomputed tomography have enabled investigation of vasa vasorum structure and function in nondiseased large arteries from pigs and dogs. Smaller mammals, particularly mice with genetic modifications that enable disease development, have been used extensively to study the vasa vasorum in diseased vessels. Despite the fact that most mouse models that are used to study atherosclerosis are unable to develop plaque to the extent found in humans, studies in both humans and mice underscore the importance of angiogenic vasa vasorum in progression of atherosclerosis. Those who have examined the vasa vasorum in occluded vessels of nondiseased pigs and dogs find that inhibition of the vasa vasorum makes the animals atheroprone. Atherosclerosis is a multifactorial disease. There is increasing evidence that factors, produced in response to changes in the arterial wall, collaborate with the vasa vasorum to enhance the disease process.
Inhibition of cytochrome c release by 10-N-nonyl acridine orange, a cardiolipin-specific dye, during myocardial ischemia-reperfusion in the rat
Authors: Zhang Guo-Xing , Kimura Shoji , Murao Koji , Obata Koji , Matsuyoshi Hiroko , Takaki Miyako
Published: November 2009

The release of cytochrome c from the mitochondria to the cytosol is a critical step for downstream caspase-mediated apoptotic signal transduction in ischemia-reperfusion (I/R)-induced myocardial tissue injury. 10- N-nonyl acridine orange (NAO), a cardiolipin-specific dye, has been shown to inhibit Bid-mediated cytochrome c release from isolated mitochondria in vitro; however, the possible protective effects of NAO and the mechanisms underlying the protection from myocardial I/R-induced tissue injury in a rat model are unknown. Male Sprague-Dawley rats were subjected to a 30-min coronary arterial occlusion followed by reperfusion. All rats received either vehicle or NAO (100 μg/kg iv) 10 min before the occlusion. The infarct size in the heart at 24 h after reperfusion was significantly reduced in NAO-treated rats compared with vehicle-treated rats. NAO treatment significantly reduced the cytosolic cytochrome c contents and caspase-9 activity in the ischemic region but did not affect caspase-8 activity. Furthermore, NAO treatment markedly suppressed the translocation of truncated Bid, a proapoptotic Bcl-2 family member, to the mitochondrial fraction. NAO also suppressed the mitochondrial swelling and oxygen uptake stimulated by calcium overload. The results suggest that NAO possesses protective effects against myocardial I/R injury, which may be due to the suppression of cytochrome c release through blockade of truncated Bid translocation to mitochondria and inhibition of the opening of mitochondrial permeability transition pores.
Gastric leptin: a novel role in cardiovascular regulation
Authors: Sartor D. M. , Verberne A. J. M.
Published: November 2009

Gastric-derived leptin affects satiety and gastrointestinal function via vagal mechanisms and has been shown to interact with the gut hormone cholecystokinin (CCK). CCK selectively inhibits splanchnic sympathetic nerve discharge (SND) and the activity of a subset of presympathetic vasomotor neurons in the rostroventrolateral medulla (RVLM). The present study sought to examine the effects of gastric leptin on arterial pressure (AP), heart rate (HR), SND, and RVLM neuronal activity to determine whether its effects on cardiovascular regulation are dependent on CCK1receptors and vagal afferent transmission. To mimic gastric leptin, leptin (15–30 μg/kg) was administered close to the coeliac artery in anesthetized, artificially ventilated Sprague-Dawley rats. Within 5 min, leptin selectively decreased the activity of RVLM neurons also inhibited by CCK (−27 ± 4%; P < 0.001; n = 15); these inhibitory effects were abolished following administration of the CCK1receptor antagonist lorglumide. Leptin significantly decreased AP and HR (−10 ± 2 mmHg, P < 0.001; and −8 ± 2 beats/min, P < 0.01; n = 35) compared with saline (−1 ± 2 mmHg, 3 ± 2 beats/min; n = 30). In separate experiments, leptin inhibited splanchnic SND compared with saline (−9 ± 2% vs. 2 ± 3%, P < 0.01; n = 8). Bilateral cervical vagotomy abolished the sympathoinhibitory, hypotensive, and bradycardic effects of leptin ( P < 0.05; n = 6). Our results suggest that gastric leptin may exert acute sympathoinhibitory and cardiovascular effects via vagal transmission and CCK1receptor activation and may play a separate role to adipose leptin in short-term cardiovascular regulation.
Adrenergic stimulation promotes T-wave alternans and arrhythmia inducibility in a TNF-α genetic mouse model of congestive heart failure
Authors: Shusterman Vladimir , McTiernan Charles F. , Goldberg Anna , Saba Samir , Salama Guy , London Barry
Published: November 2009

T-wave alternans (TWA) is a proarrhythmic repolarization instability that is common in congestive heart failure (CHF). Although transgenic mice are commonly used to study the mechanisms of arrhythmogenesis in CHF, little is known about the dynamics of TWA in these species. We hypothesized that TWA is present in a TNF-α model of CHF and can be further promoted by adrenergic stimulation. We studied 16 TNF-α mice and 12 FVB controls using 1) in vivo intracardiac electrophysiological testing and 2) ambulatory telemetry during 30 min before and after an intraperitoneal injection of isoproterenol. TWA was examined using both linear and nonlinear filtering applied in the time domain. In addition, changes in the mean amplitude of the T wave and area under the T wave were computed. During intracardiac electrophysiological testing, none of the animals had TWA or inducible arrhythmias before the injection of isoproterenol. After the injection, sustained TWA and inducible ventricular tachyarrhythmias were observed in TNF-α mice but not in FVB mice. In ambulatory telemetry, before the isoproterenol injection, the cardiac cycle length (CL) was longer in TNF-α mice than in FVB mice (98 ± 9 and 88 ± 3 ms, P = 0.04). After the injection of isoproterenol, the CL became 8% and 6% shorter in TNF-α and FVB mice ( P < 10−4); however, the 2% difference between the groups in the magnitude of CL changes was not significant. In TNF-α mice, the magnitude of TWA was 1.5–2 times greater than in FVB mice both before and after the isoproterenol injection. The magnitude of TWA increased significantly after the isoproterenol injection compared with the baseline in TNF-α mice ( P = 0.003) but not in FVB mice. The mean amplitude of the T wave and area under the T wave increased 60% and 80% in FVB mice ( P = 0.006 and 0.009) but not in TNF-α mice. In conclusion, TWA is present in a TNF-α model of CHF and can be further promoted by adrenergic stimulation, along with the enhanced susceptibility for ventricular arrhythmias.
Acute attenuation of glycocalyx barrier properties increases coronary blood volume independently of coronary flow reserve
Authors: Brands Judith , Spaan Jos A. E. , Van den Berg Bernard M. , Vink Hans , VanTeeffelen Jurgen W. G. E.
Published: November 2009

Vascular endothelium is covered with an extensive mesh of glycocalyx constituents, which acts like an effective barrier up to several micrometers thick that shields the luminal surface of the vasculature from direct exposure to flowing blood. Many studies report that various enzymatic and pharmaceutical challenges are able to increase glycocalyx porosity, resulting in farther permeation of plasma macromolecules and greater access of red blood cells into glycocalyx domain. Attenuation of glycocalyx barrier properties therefore potentially increases the amount of blood that effectively occupies available microvascular volume. We tested in the present study whether attenuation of coronary glycocalyx barrier properties actually increases coronary blood volume and whether such changes would be noticeable during measurements of coronary flow reserve using adenosine. In anesthetized goats ( n = 6) with cannulated left main coronary artery that were perfused under controlled pressure, coronary blood volume was measured via the indicator-dilution technique using high-molecular-weight (2,000 kDa) dextrans as plasma tracer and labeled red blood cells as red blood cell tracer. Coronary blood volume was determined at baseline and during intracoronary infusion of adenosine causing maximal vasodilation (0.2–0.6 mg·kg−1·h−1) before and after intracoronary hyaluronidase treatment (170,000 units) of the glycocalyx. With an intact glycocalyx, coronary blood volume was 18.9 ± 1.1 ml/100 g heart tissue at baseline, which increased to 26.3 ± 2.7 ml/100 g after hyaluronidase treatment of the coronary glycocalyx. Maximal vasodilation by administration of adenosine further increased coronary blood volume to 33.9 ± 6.8 ml/100 g, a value not different from the maximal coronary blood volume of 33.2 ± 5.3 ml/100 g obtained by administration of adenosine in the absence of hyaluronidase treatment. Adenosine-induced increases in coronary conductance were not affected by hyaluronidase treatment. We conclude that acute attenuation of glycocalyx barrier properties increases coronary blood volume by ∼40%, which is of similar magnitude as additional changes in coronary blood volume during subsequent maximal vasodilation with adenosine. Furthermore, maximal coronary blood volume following administration of adenosine was similar with and without prior hyaluronidase degradation of the glycocalyx, suggesting that adenosine and hyaluronidase potentially increase glycocalyx porosity to a similar extent. Hyaluronidase-mediated changes in coronary blood volume did not affect baseline and adenosine-induced increases in coronary conductance, demonstrating that measurements of coronary flow reserve are insufficient to detect impairment of coronary blood volume recruitment in conditions of damaged glycocalyx.
Altered lymphocyte trafficking and diminished airway reactivity in transgenic mice expressing human MMP-9 in a mouse model of asthma
Authors: Mehra Divya , Sternberg David I. , Jia Yuxia , Canfield Stephen , Lemaitre Vincent , Nkyimbeng Takwi , Wilder Julie , Sonett Joshua , D'Armiento Jeanine
Published: November 2009

Matrix metalloproteinase-9 (MMP-9) is hypothesized to facilitate leukocyte extravasation and extracellular remodeling in asthmatic airways. Careful descriptive studies have shown that MMP-9 levels are higher in the sputum of asthmatics; however, the consequence of increased MMP-9 activity has not been determined in this disease. We induced asthma in transgenic mice that express human MMP-9 in the murine lung tissue macrophage to determine the direct effect of human MMP-9 expression on airway inflammation. Transgenic (TG) and wild-type (WT) mice were immunized and challenged with ovalbumin. Forty-eight hours after the ovalbumin challenge, airway hyperresponsiveness (AHR) was measured, and inflammatory cell infiltration was evaluated in bronchoalveolar lavage fluid (BALF) and lung tissue. Baseline levels of inflammation were similar in the TG and WT groups of mice, and pulmonary eosinophilia was established in both groups by sensitization and challenge with ovalbumin. There was a significant reduction in AHR in sensitized and challenged trangenics compared with WT controls. Although total BALF cell counts were similar in both groups, the lymphocyte number in the lavage of the TG group was significantly diminished compared with the WT group (0.25 ± 0.08 vs. 0.89 ± 0.53; P = 0.0032). In addition, the draining lymphocytes were found to be larger in the TG animals compared with the WT mice. Equal numbers of macrophages, eosinophils, and neutrophils were seen in both groups. IL-13 levels were found to be lower in the sensitized TG compared with the WT mice. These results demonstrate an inverse relationship between human MMP-9 and AHR and suggest that MMP-9 expression alters leukocyte extravasation by reducing lymphocyte accumulation in the walls of asthmatic airways.
Pregnancy impairs baroreflex control of heart rate in rats: role of insulin sensitivity
Authors: Brooks Virginia L. , Mulvaney Julia M. , Azar Afaf S. , Zhao Ding , Goldman Robert K.
Published: November 2009

Recent studies in rabbits suggest that insulin resistance and reduced brain insulin contribute to impaired baroreflex control of heart rate (HR) during pregnancy; however, the mechanisms are unknown. The rat model is ideal to investigate these mechanisms because much is known about rat brain baroreflex neurocircuitry and insulin receptor locations. However, it is unclear in rats whether pregnancy impairs the HR baroreflex or whether insulin resistance is involved. Therefore, this study tested the hypothesis that in rats pregnancy decreases HR baroreflex sensitivity (BRS) and that this decrease is related to concurrent decreases in insulin sensitivity (IS). BRS was quantified before, during, and after pregnancy using complementary methods: 1) spontaneous BRS (sBRS) derived from sequence method analysis of telemetric, continuous arterial pressure recordings; and 2) maximal BRS of complete sigmoidal baroreflex relationships. IS was measured (hyperinsulinemic euglycemic clamp) to determine whether BRS and IS change in parallel. sBRS was reduced at midgestation [pregnancy day 10 (P10)], returned to nonpregnant (NP) levels on P18, and fell again at late gestation (P20) (sBRS in ms/mmHg: NP, 1.66 ± 0.04; P10, 1.17 ± 0.11; P18, 1.55 ± 0.12; P20, 1.31 ± 0.05; n = 5; P < 0.05). Similar triphasic patterns were observed for both maximal BRS [in beats·min−1·mmHg−1: NP, 4.45 ± 0.52 ( n = 10); P11–12, 2.76 ± 0.11 ( n = 7); P17–18, 3.79 ± 0.14 ( n = 5); P19–20, 2.32 ± 0.40 ( n = 8); P < 0.0001] and previous and current measurements of IS (in mg glucose·kg−1·min−1: NP, 32 ± 2; P19–20, 15 ± 1; P < 0.0005). Furthermore, during pregnancy, the standard deviation (SD) of MAP increased, and the SD of HR decreased, indirectly suggesting baroreflex impairment. sBRS increased transiently during parturition, and sBRS, maximal BRS, and IS normalized 3–4 days postpartum. In conclusion, pregnancy decreases HR BRS in rats. The parallel temporal changes in BRS and IS suggest a mechanistic link.
Development of K+ and Na+ conductances in rodent postnatal semicircular canal type I hair cells
Authors: Li Gang Q. , Meredith Frances L. , Rennie Katherine J.
Published: November 2009

The rodent vestibular system is immature at birth. During the first postnatal week, vestibular type I and type II hair cells start to acquire their characteristic morphology and afferent innervation. We have studied postnatal changes in the membrane properties of type I hair cells acutely isolated from the semicircular canals (SCC) of gerbils and rats using whole cell patch clamp and report for the first time developmental changes in ionic conductances in these cells. At postnatal day (P) 5 immature hair cells expressed a delayed rectifier K+ conductance ( GDR) which activated at potentials above approximately −50 mV in both species. Hair cells also expressed a transient Na+ conductance ( GNa) with a mean half-inactivation of approximately −90 mV. At P6 in rat and P7 in gerbil, a low-voltage activated K+ conductance ( GK,L) was first observed and conferred a low-input resistance, typical of adult type I hair cells, on SCC type I hair cells. GK,L expression in hair cells increased markedly during the second postnatal week and was present in all rat type I hair cells by P14. In gerbil hair cells, GK,L appeared later and was present in all type I hair cells by P19. During the third postnatal week, GNa expression declined and was absent by the fourth postnatal week in rat and the sixth postnatal week in gerbils. Understanding the ionic changes associated with hair cell maturation could help elucidate development and regeneration mechanisms in the inner ear.
Changes in angiotensin type 1 receptor binding and angiotensin-induced pressor responses in the rostral ventrolateral medulla of angiotensinogen knockout mice
Authors: Chen Daian , Hazelwood Lisa , Walker Lesley L. , Oldfield Brian J. , McKinley Michael J. , Allen Andrew M.
Published: November 2009

ANG II, the main circulating effector hormone of the renin-angiotensin system, is produced by enzymatic cleavage of angiotensinogen. The present study aimed to examine whether targeted deletion of the angiotensinogen gene ( Agt) altered brain ANG II receptor density or responsiveness to ANG II. In vitro autoradiography was used to examine the distribution and density of angiotensin type 1 (AT1) and type 2 receptors. In most brain regions, the distribution and density of angiotensin receptors were similar in brains of Agt knockout mice ( Agt−/−) and wild-type mice. In Agt−/−mice, a small increase in AT1receptor binding was observed in the rostral ventrolateral medulla (RVLM), a region that plays a critical role in blood pressure regulation. To examine whether Agt−/−mice showed altered responses to ANG II, blood pressure responses to intravenous injection (0.01–0.1 μg/kg) or RVLM microinjection (50 pmol in 50 nl) of ANG II were recorded in anesthetized Agt−/−and wild-type mice. Intravenous injections of phenylephrine (4 μg/kg and 2 μg/kg) were also made in both groups. The magnitude of the pressor response to intravenous injections of ANG II or phenylephrine was not different between Agt−/−and wild-type mice. Microinjection of ANG II into the RVLM induced a pressor response, which was significantly smaller in Agt−/−compared with wild-type mice (+10 ± 1 vs. +23 ± 4 mmHg, respectively, P = 0.004). Microinjection of glutamate into the RVLM (100 pmol in 10 nl) produced a robust pressor response, which was not different between Agt−/−and wild-type mice. A diminished response to ANG II microinjection in the RVLM of Agt−/−mice, despite an increased density of AT1receptors suggests that signal transduction pathways may be altered in RVLM neurons of Agt−/−mice, resulting in attenuated cellular excitation.
Restricted feeding-induced sleep, activity, and body temperature changes in normal and preproghrelin-deficient mice
Authors: Szentirmai Éva , Kapás Levente , Sun Yuxiang , Smith Roy G. , Krueger James M.
Published: November 2009

Behavioral and physiological rhythms can be entrained by daily restricted feeding (RF), indicating the existence of a food-entrainable oscillator (FEO). One manifestation of the presence of FEO is anticipatory activity to regularly scheduled feeding. In the present study, we tested if intact ghrelin signaling is required for FEO function by studying food anticipatory activity (FAA) in preproghrelin knockout (KO) and wild-type (WT) mice. Sleep-wake activity, locomotor activity, body temperature, food intake, and body weight were measured for 12 days in mice on a RF paradigm with food available only for 4 h daily during the light phase. On RF days 1–3, increases in arousal occurred. This response was significantly attenuated in preproghrelin KO mice. There were progressive changes in sleep architecture and body temperature during the subsequent nine RF days. Sleep increased at night and decreased during the light periods while the total daily amount of sleep remained at baseline levels in both KO and WT mice. Body temperature fell during the dark but was elevated during and after feeding in the light. In the premeal hours, anticipatory increases in body temperature, locomotor activity, and wakefulness were present from RF day 6 in both groups. Results indicate that the preproghrelin gene is not required for the manifestation of FAA but suggest a role for ghrelinergic mechanisms in food deprivation-induced arousal in mice.
Sex differences in endothelin-1-mediated vasoconstrictor tone in middle-aged and older adults
Authors: Stauffer Brian L. , Westby Christian M. , Greiner Jared J. , Van Guilder Gary P. , DeSouza Christopher A.
Published: November 2009

The prevalence of cardiovascular disease is lower in middle-aged and older women than men. Increased endothelin-1-mediated vasoconstriction has been linked to the etiology of a number of cardiovascular diseases, including atherosclerosis, heart failure, and hypertension. It is unknown whether a sex difference in endothelin-1-mediated vasoconstrictor tone exists in middle-aged and older adults. Therefore, we tested the hypothesis that middle-aged and older men would demonstrate greater ET-1-mediated vasoconstrictor tone than age-matched women. Forearm blood flow in response to intra-arterial infusions of endothelin (ET)-1, BQ-123 (a selective ETA receptor antagonist), and BQ-788 (a selective ETB receptor antagonist) was assessed by venous occlusion plethysmography in 21 women (age: 58 ± 1 yr; body mass index: 26.0 ± 1.0 kg/m2) and 25 men (age: 57 ± 2 yr; body mass index: 26.8 ± 0.7 kg/m2). In response to BQ-123, the increase in forearm blood flow from baseline was significantly higher in the men than the women (24 ± 5% vs. 9 ± 5%; P < 0.05). In contrast, the increase in forearm blood flow in response to BQ-123 coinfused with BQ-788 was greater in the women than the men, such that the maximum vasodilation to dual endothelin receptor blockade was similar between men and women (∼25%). There was no difference in the vasoconstrictor response to ET-1 between the sexes. These results indicate that middle-aged and older men are under greater ETA receptor-mediated vasoconstrictor tone than age-matched women. Since the ETA receptor is the predominant receptor subtype in the coronary vasculature, this sex difference in vasoconstrictor tone may be a mechanism contributing to the sex difference in the prevalence of coronary heart disease in middle-aged and older adults.
Rapid EEG desynchronization and EMG activation induced by intravenous cocaine in freely moving rats: a peripheral, nondopamine neural triggering
Authors: Kiyatkin Eugene A. , Smirnov Michael S.
Published: November 2009

Many important physiological, behavioral, and psychoemotional effects of intravenous (IV) cocaine (COC) are too fast and transient compared with pharmacokinetic predictions, suggesting a possible involvement of peripheral neural mechanisms in their triggering. In the present study, we examined changes in cortical electroencephalogram (EEG) and neck electromyogram (EMG) induced in freely moving rats by IV COC administration at low, reinforcing doses (0.25–1.0 mg/kg) and compared them with those induced by an auditory stimulus and IV COC methiodide, which cannot cross the blood-brain barrier. We found that COC induces rapid, strong, and prolonged EEG desynchronization, associated with decrease in alpha and increase in beta and gamma activities, and EMG activation and that both begin within 2–6 s following the start of a 10-s injection; immediate components of this effect were dose independent. The rapid COC-induced changes in EEG and EMG resembled those induced by an auditory stimulus; the latter effects had shorter onset latencies and durations and were fully blocked during urethane anesthesia. Although urethane anesthesia completely blocked COC-induced EMG activation and rapid components of EEG response, COC still induced EEG desynchronization that was much weaker, greatly delayed (∼60 s), and associated with tonic decreases in delta and increases in alpha, beta, and gamma activities. Surprisingly, IV saline delivered during slow-wave sleep (but not quite wakefulness) also induced a transient EEG desynchronization but without changes in EMG activity; these effects were also fully blocked during anesthesia. Peripherally acting COC methiodide fully mimicked rapid EEG and EMG effects of regular COC, but the effects at an equimolar dose were less prolonged than those with regular COC. These data suggest that in awake animals IV COC, like somato-sensory stimuli, induces cortical activation and a subsequent motor response via its action on peripheral neural elements and involving rapid neural transmission. By providing a rapid neural signal and triggering transient neural activation, such an action might play a crucial role in the sensory effects of COC, thus contributing to the learning and development of drug-taking behavior.
Gene expression profiling of the short-term adaptive response to acute caloric restriction in liver and adipose tissues of pigs differing in feed efficiency
Authors: Lkhagvadorj Sender , Qu Long , Cai Weiguo , Couture Oliver P. , Barb C. Richard , Hausman Gary J. , Nettleton Dan , Anderson Lloyd L. , Dekkers Jack C. M. , Tuggle Christopher K.
Published: November 2009

Residual feed intake (RFI) is a measure of feed efficiency, in which low RFI denotes improved feed efficiency. Caloric restriction (CR) is associated with feed efficiency in livestock species and to human health benefits, such as longevity and cancer prevention. We have developed pig lines that differ in RFI, and we are interested in identifying the genes and pathways that underlie feed efficiency. Prepubertal Yorkshire gilts with low RFI ( n = 10) or high RFI ( n = 10) were fed ad libitum or fed at restricted intake of 80% of maintenance energy requirements for 8 days. We measured serum metabolites and hormones and generated transcriptional profiles of liver and subcutaneous adipose tissue on these animals. Overall, 6,114 genes in fat and 305 genes in liver were differentially expressed (DE) in response to CR, and 311 genes in fat and 147 genes in liver were DE due to RFI differences. Pathway analyses of CR-induced DE genes indicated a dramatic switch to a conservation mode of energy usage by down-regulating lipogenesis and steroidogenesis in both liver and fat. Interestingly, CR altered expression of genes in immune and cell cycle/apoptotic pathways in fat, which may explain part of the CR-driven lifespan enhancement. In silico analysis of transcription factors revealed ESR1 as a putative regulator of the adaptive response to CR, as several targets of ESR1 in our DE fat genes were annotated as cell cycle/apoptosis genes. The lipid metabolic pathway was overrepresented by down-regulated genes due to both CR and low RFI. We propose a common energy conservation mechanism, which may be controlled by PPARA, PPARG, and/or CREB in both CR and feed-efficient pigs.
CLC-5 and KIF3B interact to facilitate CLC-5 plasma membrane expression, endocytosis, and microtubular transport: relevance to pathophysiology of Dent's disease
Authors: Reed Anita A. C. , Loh Nellie Y. , Terryn Sara , Lippiat Jonathan D. , Partridge Chris , Galvanovskis Juris , Williams Siân E. , Jouret Francois , Wu Fiona T. F. , Courtoy Pierre J. , Nesbit M. Andrew , Rorsman Patrik , Devuyst Olivier , Ashcroft Frances M. , Thakker Rajesh V.
Published: November 2009

Renal tubular reabsorption is important for extracellular fluid homeostasis and much of this occurs via the receptor-mediated endocytic pathway. This pathway is disrupted in Dent’s disease, an X-linked renal tubular disorder that is characterized by low-molecular-weight proteinuria, hypercalciuria, nephrolithiasis, and renal failure. Dent's disease is due to mutations of CLC-5, a chloride/proton antiporter, expressed in endosomes and apical membranes of renal tubules. Loss of CLC-5 function alters receptor-mediated endocytosis and trafficking of megalin and cubilin, although the underlying mechanisms remain to be elucidated. Here, we report that CLC-5 interacts with kinesin family member 3B (KIF3B), a heterotrimeric motor protein that facilitates fast anterograde translocation of membranous organelles. Using yeast two-hybrid, glutathione- S-transferase pull-down and coimmunoprecipitation assays, the COOH terminus of CLC-5 and the coiled-coil and globular domains of KIF3B were shown to interact. This was confirmed in vivo by endogenous coimmunoprecipitation of CLC-5 and KIF3B and codistribution with endosomal markers in mouse kidney fractions. Confocal live cell imaging in kidney cells further demonstrated association of CLC-5 and KIF3B, and transport of CLC-5-containing vesicles along KIF3B microtubules. KIF3B overexpression and underexpression, using siRNA, had reciprocal effects on whole cell chloride current amplitudes, CLC-5 cell surface expression, and endocytosis of albumin and transferrin. Clcn5Y/− mouse kidneys and isolated proximal tubular polarized cells showed increased KIF3B expression, whose effects on albumin endocytosis were dependent on CLC-5 expression. Thus, the CLC-5 and KIF3B interaction is important for CLC-5 plasma membrane expression and for facilitating endocytosis and microtubular transport in the kidney.
Renin-angiotensin system activation in renal adipogenesis
Authors: Sui Yi , Zhao Hai-Lu , Fan Rong-Rong , Guan Jing , He Lan , Lee Heung Man , Chan Juliana C. N. , Tong Peter C. Y.
Published: November 2009

The kidney is one of the major organs involved in whole-body homeostasis while chronic renal impairment usually leads to fat redistribution and hyperlipidemia. The aim of this study was to elucidate the role of tissue renal renin-angiotensin system (RAS) components, lipogenic peroxisome proliferator-activated receptor-γ (PPARγ), and cytokine TNF-α in the development of ectopic adipogenesis and lipid deposition. Adult male Sprague-Dawley rats were randomized into three groups: untreated uninephrectomized (UNX) rats, UNX rats treated with an angiotensin-converting enzyme inhibitor (ACEI), lisinopril, and sham-operated rats. All animals were euthanized at 10 mo postoperation. The untreated UNX rats showed increased protein expression of renin, angiotensinogen, PPARγ, and the angiotensin II type 2 receptor (AT2R) but reduced protein expression of AT1R and TNF-α in their remnant kidneys. Immunofluorescence staining revealed increased reactivity of angiotensinogen and angiotensin I/II in renal tubular cells and adipocytes of the untreated UNX rats. ACEI treatment largely prevented these disorders in association with restored normolipidemia and normalized renal adipogenesis and lipid deposition. These findings support the notion that tissue RAS, PPARγ, and TNF-α collectively play an important role in the renal adipogenesis and lipid metabolism.
OCRL1 function in renal epithelial membrane traffic
Authors: Cui Shanshan , Guerriero Christopher J. , Szalinski Christina M. , Kinlough Carol L. , Hughey Rebecca P. , Weisz Ora A.
Published: November 2009

The X-linked disorder Lowe syndrome arises from mutations in OCRL1, a lipid phosphatase that hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2). Most patients with Lowe syndrome develop proteinuria very early in life. PIP2dynamics are known to modulate numerous steps in membrane trafficking, and it has been proposed that OCRL1 activity regulates the biogenesis or trafficking of the multiligand receptor megalin. To examine this possibility, we investigated the effects of siRNA-mediated OCRL1 knockdown on biosynthetic and postendocytic membrane traffic in canine and human renal epithelial cells. Cells depleted of OCRL1 did not have significantly elevated levels of cellular PIP2but displayed an increase in actin comets, as previously observed in cultured cells derived from Lowe patients. Using assays to independently quantitate the endocytic trafficking of megalin and of megalin ligands, we could observe no defect in the trafficking or function of megalin upon OCRL1 knockdown. Moreover, apical delivery of a newly synthesized marker protein was unaffected. OCRL1 knockdown did result in a significant increase in secretion of the lysosomal hydrolase cathepsin D, consistent with a role for OCRL1 in membrane trafficking between the trans-Golgi network and endosomes. Together, our studies suggest that OCRL1 does not directly modulate endocytosis or postendocytic membrane traffic and that the renal manifestations observed in Lowe syndrome patients are downstream consequences of the loss of OCRL1 function.
Renoprotective effects of paricalcitol on gentamicin-induced kidney injury in rats
Authors: Park Jeong Woo , Bae Eun Hui , Kim In Jin , Ma Seong Kwon , Choi Chan , Lee JongUn , Kim Soo Wan
Published: November 2009

Vitamin D is thought to exert a protective effect on renal disease progression, but the underlying molecular mechanism remains unclear. We investigated whether paricalcitol ameliorates tubular dysfunction and fibrosis in gentamicin (GM)-induced renal injury. Two groups of rats were treated with GM (100 mg·kg−1·day−1), one of which was cotreated with paricalcitol (0.3 μg·kg−1·day−1) for 14 days and the other was not. The control group was treated with vehicle only. HK-2 cells were cultured with GM in the absence or presence of paricalcitol. Paricalcitol restored impaired renal function and the downregulated renal sodium transporters and aquaporin-1 expression caused by GM. ED-1-expressing monocyte/macrophage accumulation induced by GM was attenuated by paricalcitol treatment. Paricalcitol prevented upregulated inflammatory cytokines (TNF-α, IL-1β, INF-γ) and adhesion molecules (monocyte chemoattractant protein-1, ICAM-1, VCAM-1) induced by GM. In addition, paricalcitol effectively reversed TGF-β1-induced epithelial-to-mesenchymal transition (EMT) process and extracellular matrix accumulation in GM-induced nephropathy. Increased collagen deposition and fibrosis in GM-treated kidney were ameliorated by paricalcitol. Paricalcitol also attenuated the upregulated NF-κB and phosphorylated ERK1/2 expression in HK-2 cells cultured with GM. In conclusion, paricalcitol prevents GM-induced renal injury by inhibiting renal inflammation and fibrosis, the mechanism of which is the interruption of NF-κB/ERK signaling pathway and preservation of tubular epithelial integrity via inhibiting EMT process.
Renal potassium transport: the pioneering studies of Gerhard Giebisch
Authors: Stanton Bruce A.
Published: November 2009

This essay looks at the historical significance of six APS Classic Papers that are freely available on line:

Malnic G, Klose RM, Giebisch G. Micropuncture study of renal potassium excretion in the rat. Am J Physiol 206: 674–686, 1964 ( http://ajplegacy.physiology.org/cgi/reprint/206/4/674 ).

Malnic G, Klose RM, Giebisch G. Micropuncture study of distal tubular potassium and sodium transport in rat nephron. Am J Physiol 211: 529–547, 1966 ( http://ajplegacy.physiology.org/cgi/reprint/211/3/529 ).

Malnic G, Klose RM, Giebisch G. Microperfusion study of distal tubular potassium and sodium transfer in rat kidney. Am J Physiol 211: 548–559, 1966 ( http://ajplegacy.physiology.org/cgi/reprint/211/3/548 ).

Duarte CG, Chomety F, Giebisch G. Effect of amiloride, ouabain, and furosemide on distal tubular function in the rat. Am J Physiol 221: 632–640, 1971 ( http://ajplegacy.physiology.org/cgi/reprint/221/2/632 ).

Malnic G, De Mello Aires M, Giebisch G. Potassium transport across renal distal tubules during acid-base disturbances. Am J Physiol 221: 1192–1208, 1971 ( http://ajplegacy.physiology.org/cgi/reprint/221/4/1192 ).

Wright FS, Strieder N, Fowler NB, Giebisch G. Potassium secretion by distal tubule after potassium adaptation. Am J Physiol 221: 437–448, 1971 ( http://ajplegacy.physiology.org/cgi/reprint/221/2/437 ).
Effect of episodic hypoxia on the susceptibility to hypocapnic central apnea during NREM sleep
Authors: Chowdhuri Susmita , Shanidze Irina , Pierchala Lisa , Belen Daniel , Mateika Jason H. , Badr M. Safwan
Published: November 2009

We hypothesized that episodic hypoxia (EH) leads to alterations in chemoreflex characteristics that might promote the development of central apnea in sleeping humans. We used nasal noninvasive positive pressure mechanical ventilation to induce hypocapnic central apnea in 11 healthy participants during stable nonrapid eye movement sleep before and after an exposure to EH, which consisted of fifteen 1-min episodes of isocapnic hypoxia (mean O2 saturation/episode: 87.0 ± 0.5%). The apneic threshold (AT) was defined as the absolute measured end-tidal Pco2 (PetCO2) demarcating the central apnea. The difference between the AT and baseline PetCO2 measured immediately before the onset of mechanical ventilation was defined as the CO2 reserve. The change in minute ventilation (V̇I) for a change in PetCO2 (ΔV̇I/ ΔPetCO2) was defined as the hypocapnic ventilatory response. We studied the eupneic PetCO2, AT PetCO2, CO2 reserve, and hypocapnic ventilatory response before and after the exposure to EH. We also measured the hypoxic ventilatory response, defined as the change in V̇I for a corresponding change in arterial O2 saturation (ΔV̇I/ΔSaO2) during the EH trials. V̇I increased from 6.2 ± 0.4 l/min during the pre-EH control to 7.9 ± 0.5 l/min during EH and remained elevated at 6.7 ± 0.4 l/min the during post-EH recovery period ( P < 0.05), indicative of long-term facilitation. The AT was unchanged after EH, but the CO2 reserve declined significantly from −3.1 ± 0.5 mmHg pre-EH to −2.3 ± 0.4 mmHg post-EH ( P < 0.001). In the post-EH recovery period, ΔV̇I/ΔPetCO2 was higher compared with the baseline (3.3 ± 0.6 vs. 1.8 ± 0.3 l·min−1·mmHg−1, P < 0.001), indicative of an increased hypocapnic ventilatory response. However, there was no significant change in the hypoxic ventilatory response (ΔV̇I/ΔSaO2) during the EH period itself. In conclusion, despite the presence of ventilatory long-term facilitation, the increase in the hypocapnic ventilatory response after the exposure to EH induced a significant decrease in the CO2 reserve. This form of respiratory plasticity may destabilize breathing and promote central apneas.
Leucine modulates contraction- and insulin-stimulated glucose transport and upstream signaling events in rat skeletal muscle
Authors: Iwanaka Nobumasa , Egawa Tatsuro , Satoubu Nozomi , Karaike Kouhei , Ma Xiao , Masuda Shinya , Hayashi Tatsuya
Published: November 2009

Leucine has profound effects on glucose metabolism in muscle; however, the effects of leucine on glucose transport in muscle have not been well documented. We investigated the effects of leucine on contraction- and insulin-stimulated glucose transport in isolated rat epitrochlearis muscle in vitro. In the absence of insulin, tetanic contraction increased 3- O-methyl-d-glucose (3-MG) transport and Thr172phosphorylation of the catalytic α-subunit of 5′-AMP-activated protein kinase (AMPK), a signaling intermediary leading to insulin-independent glucose transport. Leucine (2 mM, 30 min) significantly enhanced contraction-stimulated 3-MG transport and AMPK phosphorylation, accompanied by increased phosphorylation of p70 S6 kinase (p70S6K) Thr389. The stimulatory effects of leucine on 3-MG transport and AMPK phosphorylation were canceled by STO-609 blockade of Ca2+/calmodulin-dependent protein kinase kinase (CaMKK) or rapamycin blockade of p70S6K. On the other hand, leucine blunted insulin-stimulated 3-MG transport and reduced insulin-stimulated Akt Thr473phosphorylation. Leucine increased insulin-stimulated p70S6K Thr389phosphorylation and enhanced the inhibitory phosphorylation of the insulin receptor substrate 1 (IRS1) Ser636/639. Furthermore, the effects of leucine on insulin-stimulated 3-MG transport and IRS phosphorylation were abolished by rapamycin. These results indicate that leucine activates contraction-stimulated glucose transport and inhibits insulin-stimulated glucose transport in skeletal muscle by activating mammalian target of rapamycin (mTOR)/p70S6K signaling. Enhanced increases in contraction-stimulated AMPK Thr172phosphorylation and insulin-stimulated IRS1 Ser636/639phosphorylation might be responsible for these opposing effects of leucine, respectively.
Airway responses to methacholine and exercise at high altitude in healthy lowlanders
Authors: Pellegrino Riccardo , Pompilio Pasquale , Quaranta Marco , Aliverti Andrea , Kayser Bengt , Miserocchi Giuseppe , Fasano Valter , Cogo Annalisa , Milanese Manlio , Cornara Giuseppe , Brusasco Vito , Dellacà Raffaele
Published: November 2009

Peribronchial edema has been proposed as a mechanism enhancing airway responses to constrictor stimuli. Acute exposure to altitude in nonacclimatized lowlanders leads to subclinical interstitial pulmonary edema that lasts for several days after ascent, as suggested by changes in lung mechanics. We, therefore, investigated whether changes in lung mechanics consistent with fluid accumulation at high altitude within the lungs are associated with changes in airway responses to methacholine or exercise. Fourteen healthy subjects were studied at 4,559 and at 120 m above sea level. At high altitude, both static and dynamic lung compliances and respiratory reactance at 5 Hz significantly decreased, suggestive of interstitial pulmonary edema. Resting minute ventilation significantly increased by ∼30%. Compared with sea level, inhalation of methacholine at high altitude caused a similar reduction of partial forced expiratory flow but less reduction of maximal forced expiratory flow, less increments of pulmonary resistance and respiratory resistance at 5 Hz, and similar effects of deep breath on pulmonary and respiratory resistance. During maximal incremental exercise at high altitude, partial forced expiratory flow gradually increased with the increase in minute ventilation similarly to sea level but both achieved higher values at peak exercise. In conclusion, airway responsiveness to methacholine at high altitude is well preserved despite the occurrence of interstitial pulmonary edema. We suggest that this may be the result of the increase in resting minute ventilation opposing the effects and/or the development of airway smooth muscle force, reduced gas density, and well preserved airway-to-parenchyma interdependence.
Comparison of exogenous adenosine and voluntary exercise on human skeletal muscle perfusion and perfusion heterogeneity
Authors: Heinonen Ilkka , Kemppainen Jukka , Kaskinoro Kimmo , Peltonen Juha E. , Borra Ronald , Lindroos Markus M. , Oikonen Vesa , Nuutila Pirjo , Knuuti Juhani , Hellsten Ylva , Boushel Robert , Kalliokoski Kari K.
Published: November 2009

Adenosine is a widely used pharmacological agent to induce a “high-flow” control condition to study the mechanisms of exercise hyperemia, but it is not known how well an adenosine infusion depicts exercise-induced hyperemia, especially in terms of blood flow distribution at the capillary level in human muscle. Additionally, it remains to be determined what proportion of the adenosine-induced flow elevation is specifically directed to muscle only. In the present study, we measured thigh muscle capillary nutritive blood flow in nine healthy young men using PET at rest and during the femoral artery infusion of adenosine (1 mgmin−1l thigh volume−1), which has previously been shown to induce a maximal whole thigh blood flow of ∼8 l/min. This response was compared with the blood flow induced by moderate- to high-intensity one-leg dynamic knee extension exercise. Adenosine increased muscle blood flow on average to 40 ± 7 ml·min−1·100 g muscle−1 with an aggregate value of 2.3 ± 0.6 l/min for the whole thigh musculature. Adenosine also induced a substantial change in blood flow distribution within individuals. Muscle blood flow during the adenosine infusion was comparable with blood flow in moderate- to high-intensity exercise (36 ± 9 ml·min−1·100 g muscle−1), but flow heterogeneity was significantly higher during the adenosine infusion than during voluntary exercise. In conclusion, a substantial part of the flow increase in the whole limb blood flow induced by a high-dose adenosine infusion is conducted through the physiological non-nutritive shunt in muscle and/or also through tissues of the limb other than muscle. Additionally, an intra-arterial adenosine infusion does not mimic exercise hyperemia, especially in terms of muscle capillary flow heterogeneity, while the often-observed exercise-induced changes in capillary blood flow heterogeneity likely reflect true changes in nutritive flow linked to muscle fiber and vascular unit recruitment.
The influence of end-expiratory lung volume on measurements of pharyngeal collapsibility
Authors: Owens Robert L. , Malhotra Atul , Eckert Danny J. , White David P. , Jordan Amy S.
Published: November 2009

Changes in end-expiratory lung volume (EELV) affect upper airway stability. The passive pharyngeal critical pressure (Pcrit), a measure of upper airway collapsibility, is determined using airway pressure drops. The EELV change during these drops has not been quantified and may differ between obese obstructive sleep apnea (OSA) patients and controls. Continuous positive airway pressure (CPAP)-treated OSA patients and controls were instrumented with an epiglottic catheter, magnetometers (to measure change in EELV), and a nasal mask/pneumotachograph. Subjects slept supine in a head-out plastic chamber in which the extrathoracic pressure could be lowered (to raise EELV) while on nasal CPAP. The magnitude of EELV change during Pcrit measurement (sudden reductions of CPAP for 3–5 breaths each minute) was assessed at baseline and with EELV increased ∼500 ml. Fifteen OSA patients and 7 controls were studied. EELV change during Pcrit measurement was rapid and pressure dependent, but similar in OSA and control subjects (74 ± 36 and 59 ± 24 ml/cmH2O respectively, P = 0.33). Increased lung volume (mean +521 ml) decreased Pcrit by a similar amount in OSA and control subjects (−3.1 ± 1.7 vs. −3.9 ± 1.9 cmH2O, P = 0.31). Important lung volume changes occur during passive Pcrit measurement. However, on average, there is no difference in lung volume change for a given CPAP change between obese OSA subjects and controls. Changes in lung volume alter Pcrit substantially. This work supports a role for lung volume in the pathogenesis of OSA, and lung volume changes should be a consideration during assessment of pharyngeal mechanics.
The 2009 Carl Ludwig Lecture: pathophysiology of the human sympathetic nervous system in cardiovascular diseases: the transition from mechanisms to medical management
Authors: Esler Murray
Published: November 2009

Sympathetic nervous system responses typically are regionally differentiated, with activation in one outflow sometimes accompanying no change or sympathetic inhibition in another. Regional sympathetic activity is best studied in humans by recording from postganglionic sympathetic efferents (multiunit or single fiber recording) and by isotope dilution-derived measurement of organ-specific norepinephrine release to plasma (regional “norepinephrine spillover”). Evidence assembled in this review indicates that sympathetic nervous system abnormalities are crucial in the development of cardiovascular disorders, notably heart failure, essential hypertension, disorders of postural circulatory control causing syncope, and “psychogenic heart disease,” heart disease attributable to mental stress and psychiatric illness. These abnormalities involve persistent, adverse activation of sympathetic outflows to the heart and kidneys in heart failure and hypertension, episodic or ongoing cardiac sympathetic activation in psychogenic heart disease, and defective sympathetic circulatory reflexes in disorders of postural circulatory control. An important goal for clinical scientists is translation of knowledge of pathophysiology, such as this, into better treatment for patients. The achievement of this “mechanisms-to-management” transition is at differing stages of development with the different conditions. Clinical translation is mature in cardiac failure, knowledge of cardiac neural pathophysiology having led to introduction of β-adrenergic blockers, an effective therapy. With essential hypertension, perhaps we are on the cusp of effective translation, with recent successful testing of selective catheter-based renal sympathetic nerve ablation in patients with resistant hypertension, an intervention firmly based on demonstration of activation of the renal sympathetic outflow. With psychogenic heart disease and postural syncope syndromes, knowledge of the neural pathophysiology is emerging, but clinical translation remains for the future.