An EPHB4-RASA1 signaling complex inhibits shear stress-induced Ras-MAPK activation in lymphatic endothelial cells to promote the development of lymphatic vessel valves.

EPHB4 is a receptor protein tyrosine kinase that is required for the development of lymphatic vessel (LV) valves. We show here that EPHB4 is necessary for the specification of LV valves, their continued development after specification, and the maintenance of LV valves in adult mice. EPHB4 promotes LV valve development by inhibiting the activation of the Ras-MAPK pathway in LV endothelial cells (LEC). For LV specification, this role for EPHB4 depends on its ability to interact physically with the p120 Ras-GTPase-activating protein (RASA1) that acts as a negative regulator of Ras. Through physical interaction, EPHB4 and RASA1 dampen oscillatory shear stress (OSS)-induced Ras-MAPK activation in LEC, which is required for LV specification. We identify the Piezo1 OSS sensor as a focus of EPHB4-RASA1 regulation of OSS-induced Ras-MAPK signaling mediated through physical interaction. These findings contribute to an understanding of the mechanism by which EPHB4, RASA1 and Ras regulate lymphatic valvulogenesis.

PYY-Dependent Restoration of Impaired Insulin and Glucagon Secretion in Type 2 Diabetes following Roux-En-Y Gastric Bypass Surgery.

Roux-en-Y gastric bypass (RYGB) is a weight-reduction procedure resulting in rapid resolution of type 2 diabetes (T2D). The role of pancreatic islet function in this restoration of normoglycemia has not been fully elucidated. Using the diabetic Goto-Kakizaki (GK) rat model, we demonstrate that RYGB restores normal glucose regulation of glucagon and insulin secretion and normalizes islet morphology. Culture of isolated islets with serum from RYGB animals mimicked these effects, implicating a humoral factor. These latter effects were reversed following neutralization of the gut hormone peptide tyrosine tyrosine (PYY) but persisted in the presence of a glucagon-like peptide-1 (GLP-1) receptor antagonist. The effects of RYGB on secretion were replicated by chronic exposure of diabetic rat islets to PYY in vitro. These findings indicate that the mechanism underlying T2D remission may be mediated by PYY and suggest that drugs promoting PYY release or action may restore pancreatic islet function in T2D.

Striving to be in the profession and of It: the African American experience in physical education and kinesiology.

This study analyzes the experiences of African Americans in the physical education and kinesiology profession since the late 1850s. Using a variety of primary and secondary source material, we place special emphasis on the experiences of African American physical educators in higher education and in the American Alliance for Health, Physical Education, Recreation and Dance and its southern, regional, and state chapters. Apparent from this examination is that African Americans have experienced various forms of racially discriminatory practices in physical education and kinesiology and have found it extraordinarily difficult to assume leader ship positions in the profession and be acknowledged for their scholarly and academic accomplishments.

Pressure frequency characteristics of the pericardial space and thorax during subxiphoid access for epicardial ventricular tachycardia ablation.

BACKGROUND: Nonsurgical subxiphoid pericardial access may be useful in ventricular tachycardia ablation and other electrophysiologic procedures but has a risk of right ventricular puncture. OBJECTIVE: The purpose of this study was to identify a signature pressure frequency that would help identify the pericardial space and guide access. METHODS: The study consisted of 20 patients (8 women and 12 men; mean age 59.1 +/- 14.2 years; left ventricular ejection fraction 25.2% +/- 12.2%; failed 1.8 +/- 0.5 endocardial ablations; unresponsive to 2.0 +/- 1.0 antiarrhythmic drugs; 6 ischemic cardiomyopathy, 12 nonischemic cardiomyopathy, 2 normal heart; 4 previous sternotomy) undergoing epicardial ventricular tachycardia ablation. After pericardial access was obtained, a 10Fr long sheath was used to record pressure inside the pericardium and pleural space. Pressures were analyzed using a fast Fourier transform to identify dominant frequencies in each chamber. RESULTS: Mean pressures in the pleural space and the pericardium were not different (7.7 +/- 1.9 mmHg vs 7.8 +/- 0.9 mmHg, respectively). However, the pericardial space in each patient demonstrated two frequency peaks that correlated with heart rate (1.16 +/- 0.21 Hz) and respiratory rate (0.20 +/- 0.01 Hz), whereas the pleural space in each patient had a single peak correlating with respiratory rate (0.20 +/- 0.01 Hz). CONCLUSION: The pericardial space demonstrates a signature pressure frequency that is significantly different from the surrounding space. This difference may make minimally invasive subxiphoid pericardial access safer for nonsurgeons and may have important implications for electrophysiologic procedures.

Gender and Racial Characteristics of Patients Referred to a Tertiary Atrial Fibrillation Center.

Atrial Fibrillation Centers (AFCs) are becoming increasingly common and are often developed at institutions to provide comprehensive evaluation and management for patients with atrial fibrillation (AF) including catheter and surgical ablation. Studies have shown that women and racial minority patients are less likely to be offered aggressive or invasive therapies. The University of Virginia (UVA) AFC was opened in 2004. We analyzed data collected during initial visits to our AFC from 2004-2008 to determine the gender and racial characteristics of a tertiary AFC population. Multivariable regression analysis was used to compare clinical characteristics. There were a total of 1664 consecutive initial patient visits. Cardiologists referred 61% and primary care physicians referred 37% of patients. Twice as many men were referred as women (570 vs. 1094; P<0.0001). Women were older (68.0±11.9 vs. 62.4±13.0 years; P<0.0001) and more symptomatic with palpitations (80% vs. 73%; P=0.008), but otherwise were not substantially different from men. Our referring physicians treated the majority of both men and women with anticoagulant and rate-controlling medications. African American patients accounted for 2.8% of AFC initial visits. In contrast, they accounted for 7.4% of patients seen for a primary diagnosis of AF at all other UVA outpatient clinics (P<0.0001). In conclusion, the demographics of a tertiary AFC are different than those of the general population. Women and racial minority patients are underrepresented, and the women have few comorbidities and symptoms than the known epidemiology would lead us to expect.

Catheter ablation of atrial fibrillation without fluoroscopy using intracardiac echocardiography and electroanatomic mapping.

BACKGROUND: Catheter ablation of atrial fibrillation is currently guided by x-ray fluoroscopy. The associated radiation risk to patients and medical staff may be significant. We report an atrial fibrillation ablation technique using intracardiac echocardiography (ICE) and electroanatomic mapping without fluoroscopy. METHODS AND RESULTS: Twenty-one patients with atrial fibrillation (age, 42 to 73 years; 14 male; 14 paroxysmal, 7 persistent; body mass index, 26 to 38) underwent ablation. A decapolar catheter was advanced through the left subclavian vein until stable coronary sinus electrograms appeared on all electrodes. Two 9F sheaths were advanced transfemorally over a guide wire to the right atrium. A rotational ICE catheter was advanced through a deflectable sheath. Double transseptal puncture was performed with ICE guidance and facilitated by electrocautery. A 3D MRI left atrial image was registered to the ostia of the pulmonary veins using ICE. Catheter ablation was performed using ICE and electroanatomic mapping navigation. In 19 cases, no fluoroscopy was used and the staff did not wear protective lead. In 2 cases, 2 to 16 minutes of fluoroscopy was used to assist transseptal puncture. Median procedure time was 208 (188 to 221) minutes; coronary sinus cannulation took 5 (2 to 26) minutes; double transseptal took 26 (17 to 40) minutes; left atrial ablation time was 103 (90 to 127) minutes. All patients underwent circumferential pulmonary vein ablation and 8 patients underwent additional left atrial ablation. There were no procedure-related complications. CONCLUSIONS: Catheter ablation of atrial fibrillation without fluoroscopy is feasible and merits further attention. This technique may be especially helpful in preventing x-ray exposure in children, pregnant women, and obese patients undergoing left atrial ablation.

Peroxisome proliferator-activated receptor alpha deficiency abolishes the response of lipogenic gene expression to re-feeding: restoration of the normal response by activation of liver X receptor alpha.

The mRNA expression of lipogenic genes Scd-1 and Fas is regulated partly by the insulin-sensitive transcription factor SREBP-1c and liver X receptor alpha (LXRalpha). Compared with normal mice, the increase in the mRNA expression of hepatic Scd-1, Fas, and Srebp-1c was severely attenuated in peroxisome proliferator-activated receptor alpha (PPARalpha)-deficient mice during the transition from the starved to the re-fed states. The concentration of the membrane-bound form of SREBP-1c was also lower in the livers of the PPARalpha-deficient mice during re-feeding but there was little difference in the concentration of the active, nuclear form, or in the abundance of Insig-2a mRNA. The response of plasma insulin to starvation and re-feeding was normal in the PPARalpha-deficient mice. Rat hepatocytes transfected with an adenovirus encoding a dominant negative form of PPARalpha were resistant to the stimulatory effects of insulin on Fas and Scd-1 mRNA expression in vitro. When LXRalpha was activated in vivo by inclusion of a non-steroidal ligand in the diet, the expression of the mRNA for hepatic Srebp-1c, Fas, and Scd-1 was increased severalfold in mice of both genotypes and resistance associated with PPARalpha deficiency was abolished during re-feeding. However, although re-feeding the LXRalpha ligand induced the immature form of SREBP-1c equally in the livers of both genotypes, the concentration of the nuclear form remained relatively low in the livers of the PPARalpha-deficient mice. We conclude that intact PPARalpha is required to mediate the response of Scd-1 and Fas gene expression to insulin and that this is normally achieved directly by activation of LXRalpha.

Specialized hepatocyte-like cells regulate Drosophila lipid metabolism.

Lipid metabolism is essential for growth and generates much of the energy needed during periods of starvation. In Drosophila, fasting larvae release large quantities of lipid from the fat body but it is unclear how and where this is processed. Here we identify the oenocyte as the principal cell type accumulating lipid droplets during starvation. Tissue-specific manipulations of the Slimfast amino-acid channel, the Lsd2 fat-storage regulator and the Brummer lipase indicate that oenocytes act downstream of the fat body. In turn, oenocytes are required for depleting stored lipid from the fat body during fasting. Hence, lipid-metabolic coupling between the fat body and oenocytes is bidirectional. When food is plentiful, oenocytes have critical roles in regulating growth, development and feeding behaviour. In addition, they specifically express many different lipid-metabolizing proteins, including Cyp4g1, an omega-hydroxylase regulating triacylglycerol composition. These findings provide evidence that some lipid-processing functions of the mammalian liver are performed in insects by oenocytes.

Transcript and metabolite analysis of the effects of tamoxifen in rat liver reveals inhibition of fatty acid synthesis in the presence of hepatic steatosis.

Nonalcoholic steatohepatitis (NASH) is a common feature of the metabolic syndrome and toxic reactions to pharmacological drugs. Tamoxifen, (TMX) a widely used anti-breast cancer drug, can induce NASH and changes in plasma cholesterol levels through mechanisms that are unclear. We studied primary actions of TMX using a short-term treatment (5 days) that induces microvesicular hepatic steatosis and marked hypercholesterolemia in male rats. Using a combined approach of gene expression profiling and NMR-based metabolite analysis, we found that TMX-treated livers have increased saturated fatty acid content despite changes in gene expression, indicating decreased de novo lipogenesis and increased fatty acid oxidation. Our results show that TMX predominantly down-regulates FAS expression and activity as indicated by the accumulation of malonyl-CoA, a known inhibitor of mitochondrial beta-oxidation. In the face of a continued supply of exogenous free fatty acids, the blockade of fatty acid oxidation produced by elevated malonyl-CoA is likely to be the major factor leading to steatosis. Use of a combination of metabolomic and transcriptomic analysis has allowed us to identify mechanisms underlying important metabolic side effects of a widely prescribed drug. Given the broader importance of hepatic steatosis, the novel molecular mechanism revealed in this study should be examined in other forms of steatosis and nonalcoholic steatohepatitis.

A role for PPARalpha in the control of SREBP activity and lipid synthesis in the liver.

Inclusion of the PPARalpha (peroxisome-proliferator-activated receptor alpha) activator WY 14,643 in the diet of normal mice stimulated the hepatic expression of not only genes of the fatty acid oxidation pathway, but also those of the de novo lipid synthetic pathways. Induction of fatty acid synthase mRNA by WY 14,643 was greater during the light phase of the diurnal cycle, when food intake was low and PPARalpha expression was high. Hepatic fatty acid pathway flux in vivo showed a similar pattern of increases. The abundance of mRNAs for genes involved in hepatic cholesterol synthesis was also increased by WY 14,643, but was associated with a decrease in cholesterogenic carbon flux. None of these changes were apparent in PPARalpha-null mice. Mice of both genotypes showed the expected decreases in 3-hydroxy-3-methylglutaryl-CoA reductase mRNA levels and cholesterol synthesis in response to an increase in dietary cholesterol. The increase in fatty acid synthesis due to WY 14,643 was not mediated by increased expression of SREBP-1c (sterol regulatory element binding protein-1c) mRNA, but by an increase in cleavage of the protein to the active form. An accompanying rise in stearoyl-CoA desaturase mRNA expression suggested that the increase in lipogenesis could have resulted from an alteration in membrane fatty acid composition that influenced SREBP activation.

Inhibition of hepatocyte lipogenesis by nitric oxide donor: could nitric oxide regulate lipid synthesis?

Tissue lipogenesis is variably controlled by substrate supply and hormones. The possibility that nitric oxide (NO) might regulate lipogenesis derives from the action of NO on coenzyme A (CoA) to produce metabolically inactive S-nitrosoCoA. The effect of the nitric oxide donor S-nitrosoglutathione (GSNO) on long chain fatty acid and cholesterol synthesis was measured in isolated cultured rat hepatocytes. [1-14C] Butyrate was used as substrate to measure 14C incorporation into lipids as butyrate is twice as effective as acetate in hepatic lipogenesis and is ketogenic via the Lynen cycle. NO very significantly (P < 0.01) impaired long chain fatty acid and cholesterol synthesis an observation dependent upon time of exposure (3 h pre-incubation or 6 h continuous exposure) and concentration of GSNO (500 microM to 2.0 mM). Decrease in hepatic lipogenesis was paralleled by decrease in ketogenesis. ATP levels remained unchanged following short-term exposure to GSNO. Exposure of hepatocytes to GSNO together with 2.0 mM glutathione significantly diminished the inhibition of lipogenesis induced by GSNO alone. Impairment of lipogenesis by GSNO appears not to be limited by energy supply and now adduced, but not proven, to be operative via the degree of inactivation of cytosolic CoA. NO control of lipogenesis could be clinically important where NO production is increased as in demyelinating diseases, chronic arthritis or colitis and in wasting diseases such as AIDS.

Inhibition of cholesterol absorption associated with a PPAR alpha-dependent increase in ABC binding cassette transporter A1 in mice.

Dietary supplementation with the peroxisome proliferator-activated receptor alpha (PPAR alpha) ligand WY 14,643 gave rise to a 4- to 5-fold increase in the expression of mRNA for the ATP binding cassette transporter A1 (ABCA1) in the intestine of normal mice. There was no effect in the intestine of PPAR alpha-null mice. Consumption of a high-cholesterol diet also increased intestinal ABCA1 expression. The effects of WY 14,643 and the high-cholesterol diet were not additive. WY 14,643 feeding reduced intestinal absorption of cholesterol in the normal mice, irrespective of the dietary cholesterol concentration, and this resulted in lower diet-derived cholesterol and cholesteryl ester concentrations in plasma and liver. At each concentration of dietary cholesterol, there was a similar significant inverse correlation between intestinal ABCA1 mRNA content and the amount of cholesterol absorbed. The fibrate-induced changes in the intestines of the normal mice were accompanied by an increased concentration of the mRNA encoding the sterol-regulatory element binding protein-1c gene (SREBP-1c), a known target gene for the oxysterol receptor liver X receptor alpha (LXR alpha). There was a correlation between intestinal ABCA1 mRNA and SREBP-1c mRNA contents, but not between SREBP-1c mRNA content and cholesterol absorption. These results suggest that PPAR alpha influences cholesterol absorption through modulating ABCA1 activity in the intestine by a mechanism involving LXR alpha.

Island biogeography and the reproductive ecology of great tits Parus major.

Island biogeography theory has contributed greatly to both theoretical and applied studies of conservation biology (e.g., design of nature reserves, minimum viable population sizes, extinction risk) and community composition. However, little theoretical and empirical work has addressed how island isolation and size affect reproductive ecology. We investigated the reproductive ecology of great tits (Parus major) on one offshore and one nearshore island, as well as on the Danish mainland. Tits breeding on the offshore island bred later, laid smaller clutches, and laid larger eggs than those on the nearshore island and mainland. In addition, the level of ectoparasite infestation in nests was highest on the offshore island, intermediate on the nearshore island, and lowest on the mainland. These insular effects may occur due to lower food abundance on islands, to density-dependent effects, or to effects related to low genetic diversity within island populations. Whatever the cause, the results emphasize that future studies of forest fragmentation/population isolation should consider not only gross measures of reproductive success, but also fine-scale measures such as clutch size, timing of breeding, and parasite prevalence.

Island size, isolation, or interspecific competition? The breeding distribution of the Parus guild in the Danish archipelago.

The Parus guild (Parus spp., Sitta, Certhia, and Regulus) is distributed as a complex mosaic within the Danish archipelago, with from one to eight species on different islands. We assessed the roles of island isolation, island size, and interspecific competition in determining the breeding species compositions of this guild on 53 Danish islands. Small, isolated islands supported fewer species than larger, nearshore islands. These effects, however, were largely restricted to a few sedentary species (P. cristatus, P. palustris, S. europaea) that are known to be poor dispersers/colonizers. In some cases, these three species were also absent from large, nearshore islands with suitable habitat, suggesting that habitat availability was not always responsible for the absence of a species. Monte Carlo simulations suggested that the pattern of species presence/absence was not a result of interspecific interactions. Thus, although a number of previous studies have documented interspecific competition among members of the Parus guild, our results suggest that such competition is not responsible for the unusual pattern of species distribution within the Danish archipelago.

NATURAL SELECTION ON BODY SIZE AND LAYING DATE IN THE TREE SWALLOW.

I measured natural selection on body size and laying date in a population of tree swallows (Tachycineta bicolor) from 1986 to 1988. There was little evidence of selection on body size associated with overwinter survival. Disruptive selection on tarsus length, associated with female reproductive success, was detected in one of three years. Both repeatability and mother-daughter regression suggested that laying date was heritable. I found weak evidence of selection on laying date, associated with both overwinter survival and reproduction in females. The ecological implications of both tarsus length and laying date variation in this population could not be identified. Consequently, although I was able to identify the targets of natural selection, the ecological link between trait variation and selection remains unknown.