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The in vitro perfused rectal gland of the dogfish shark (Squalus acanthias) and filter-grown monolayers of primary cultures of shark rectal gland (SRG) epithelial cells were used to analyze the signal transduction pathway by which C-type natriuret

Contains fulltext : 125569.pdf (publisher's version ) (Closed access)

Contains fulltext : 109339.pdf (publisher's version ) (Open Access), Large outbreaks of Q fever in the Netherlands from 2007 to 2009 were monitored using notification data of acute clinical Q fever. However, the notification system provides no information on infections that remain subclinical or for which no medical attention is sought. The present study was carried out immediately after the peak of the 2009 outbreak to estimate the ratio between Coxiella burnetii infections and Q fever notifications. In 23 postcode areas in the high-incidence area, notification rates were compared with seroconversion rates in blood donors from whom serial samples were available. This resulted in a ratio of one Q fever notification to 12.6 incident infections of C. burnetii. This ratio is time and place specific and is based on a small number of seroconversions, but is the best available factor for estimating the total number of infections. In addition, as subclinical C. burnetii infection may lead to chronic Q fever, the ratio can be used to estimate the expected number of chronic Q fever patients in the coming years and as input for cost-benefit analyses of screening options.

Background & Aims: Diarrhea results from reduced net fluid and salt absorption caused by an imbalance in intestinal absorption and secretion. The bulk of sodium and water absorption in the intestine is mediated by Na+/H+exchanger 3 (NHE3), located in the luminal membrane of enterocytes. We investigated the effect of lysophosphatidic acid (LPA) on Na+/H+exchanger activity and Na+-dependent fluid absorption in the intestine. Methods: We analyzed the effects of LPA on fluid absorption in intestines of wild-type mice and mice deficient in Na+/H+exchanger regulatory factor 2 (NHERF2; Nherf2-/-) or LPA2(Lpa2-/-). Roles of LPA5and NHERF2 were determined by analysis of heterologous expression. Results: Under basal conditions, LPA increased fluid absorption in an NHE3-dependent manner and restored the net fluid loss in a mouse model of acute diarrhea. Expression of the LPA receptor LPA5was necessary for LPA-induced stimulation of NHE3 activity in colonic epithelial cells. Stimulation of NHE3 by the LPA-LPA5signaling required coexpression of NHERF2, which interacted with LPA5. LPA-mediated intestinal fluid absorption was impaired in Nherf2-/-mice, demonstrating the requirement for NHERF2 in LPA5activity. However, fluid absorption was unaltered in Lpa2-/-mice. LPA stimulated NHE3 and fluid absorption in part by increasing NHE3 protein abundance at the brush border membrane of intestinal epithelial cells. Conclusions: LPA is a potent stimulant of NHE3 and fluid absorption in the intestine, signaling through LPA5. Regulation by LPA5depends on its interaction with NHERF2. LPA might be useful in the treatment of certain diarrheal diseases.

We investigated the role of the Na+/H+ exchanger regulatory factor 1 (NHERF1) on intestinal salt and water absorption, brush border membrane (BBM) morphology, and on the NHE3 mRNA expression, protein abundance, and transport activity in the murine intestine. NHERF1-deficient mice displayed reduced jejunal fluid absorption in vivo, as well as an attenuated in vitro Na+ absorption in isolated jejunal and colonic, but not of ileal, mucosa. However, cAMP-mediated inhibition of both parameters remained intact. Acid-activated NHE3 transport rate was reduced in surface colonocytes, while its inhibition by cAMP and cGMP was normal. Immunodetection of NHE3 revealed normal NHE3 localization in the BBM of NHERF1 null mice, but NHE3 abundance, as measured by Western blot, was significantly reduced in isolated BBM from the small and large intestines. Furthermore, the microvilli in the proximal colon, but not in the small intestine, were significantly shorter in NHERF1 null mice. Additional knockout of PDZK1 (NHERF3), another member of the NHERF family of adaptor proteins, which binds to both NHE3 and NHERF1, further reduced basal NHE3 activity and caused complete loss of cAMP-mediated NHE3 inhibition. An activator of the exchange protein activated by cAMP (EPAC) had no effect on jejunal fluid absorption in vivo, but slightly inhibited NHE3 activity in surface colonocytes in vitro. In conclusion, NHERF1 has segment-specific effects on intestinal salt absorption, NHE3 transport rates, and NHE3 membrane abundance without affecting mRNA levels. However, unlike PDZK1, NHERF1 is not required for NHE3 regulation by cyclic nucleotides.

Contains fulltext : 69456.pdf (publisher's version ) (Closed access), The adaptor proteins sodium/hydrogen exchanger regulatory factor (NHERF)-1 and NHERF-2 have overlapping tissue distribution in renal cells and overlapping specificity in their binding to renal transporters and other proteins. To compare the kidney-specific differences in the function of these adaptor proteins, NHERF-1 and NHERF-2 null mice were compared with wild-type control mice. In NHERF-2 null mice, the renal proximal tubule abundance and distribution of NHERF-1 and NHERF-3 were not different from those in wild-type animals. The glomerular expression of podocalyxin and ZO-1 also did not differ. NHERF-1 null mice had increased urinary excretion of phosphate, calcium, and uric acid compared with wild-type control and NHERF-2 null mice. Because of the association between NHERF-2 and podocalyxin in glomeruli and ClC-5 in the renal proximal tubule, the urinary excretion of protein was determined. There were no differences in the urinary excretion of protein or low-molecular-weight proteins between wild-type control, NHERF-1(-/-), and NHERF-2(-/-) mice. These studies indicate that the increased urinary excretion of phosphate and uric acid are specific to NHERF-1 null mice and highlight the fact that predictions about the role of adaptor proteins such as the NHERF proteins obtained from studies of model cell systems must be confirmed in whole animals.

The adaptor proteins sodium/hydrogen exchanger regulatory factor (NHERF)-1 and NHERF-2 have overlapping tissue distribution in renal cells and overlapping specificity in their binding to renal transporters and other proteins. To compare the kidney-specific differences in the function of these adaptor proteins, NHERF-1 and NHERF-2 null mice were compared with wild-type control mice. In NHERF-2 null mice, the renal proximal tubule abundance and distribution of NHERF-1 and NHERF-3 were not different from those in wild-type animals. The glomerular expression of podocalyxin and ZO-1 also did not differ. NHERF-1 null mice had increased urinary excretion of phosphate, calcium, and uric acid compared with wild-type control and NHERF-2 null mice. Because of the association between NHERF-2 and podocalyxin in glomeruli and ClC-5 in the renal proximal tubule, the urinary excretion of protein was determined. There were no differences in the urinary excretion of protein or low-molecular-weight proteins between wild-type control, NHERF-1-/-, and NHERF-2-/-mice. These studies indicate that the increased urinary excretion of phosphate and uric acid are specific to NHERF-1 null mice and highlight the fact that predictions about the role of adaptor proteins such as the NHERF proteins obtained from studies of model cell systems must be confirmed in whole animals.