Characterization of hormone-stimulated Na+ transport in a high-resistance clone of the MDCK cell line

The Madin-Darby canine kidney (MDCK) cell line forms an epithelial monolayer which expresses many of the morphological and functional properties of the renal collecting duct. The C7 subclone of the parent line forms an epithelium which expresses many of the characteristics of principal cells. The MDCK-C7 subclone forms a high-resistance epithelium that is capable of vectorial ion transport. We have found that this epithelium responds to aldosterone, antidiuretic hormone (ADH) and insulin like growth factor 1 (IGF1) with increases in amiloride-sensitive Na+ transport. The responses to aldosterone and ADH follow time-courses that are consistent with the action of these hormones in vivo. This is the first demonstration of IGF1-induced Na+ reabsorption in a mammalian model system. Interestingly, a maximal response to any one of these natriferic factors does not inhibit a subsequent response to another hormone. These studies indicate that the C7 subclone retains many of the natriferic responses of the native principal cells and is an ideal model for studying hormonal modulation of Na+ transport

Phosphatidylinositol 3-kinase activation is required for insulin-stimulated sodium transport in A6 cells

Insulin stimulates amiloride-sensitive sodium transport in models of the distal nephron. Here we demonstrate that, in the A6 cell line, this action is mediated by the insulin receptor tyrosine kinase and that activation of phosphatidylinositol 3-kinase (PI 3-kinase) lies downstream of the receptor tyrosine kinase. Functionally, a specific inhibitor of PI 3-kinase, LY-294002, blocks basal as well as insulin-stimulated sodium transport in a dose-dependent manner (IC50 approximately 6 microM). Biochemically, PI 3-kinase is present in A6 cells and is inhibited both in vivo and in vitro by LY-294002. Furthermore, a subsequent potential downstream signaling element, pp70 S6 kinase, is activated in response to insulin but does not appear to be part of the pathway involved in insulin-stimulated sodium transport. Together with previous reports, these results suggest that insulin may induce the exocytotic insertion of sodium channels into the apical membrane of A6 cells in a PI 3-kinase-mediated manner

Characterization of the ion transport responses to ADH in the MDCK-C7 cell line

The Madin-Darby canine kidney (MDCK) cell line expresses many characteristics of the renal collecting duct. The MDCK-C7 subclone forms a high-resistance, hormone-responsive model of the principal cells, which are found in distal sections of the renal tubule. The electrophysiological technique of short-circuit current measurement was used to examine the response to antidiuretic hormone (ADH) in the MDCK-C7 clone. Three discrete electrogenic ion transport phenomena can be distinguished temporally and by the use of inhibitors and effectors. Initially the cells exhibit anion secretion through the cystic fibrosis transmembrane conductance regulator (CFTR). The presence of CFTR was confirmed by immunoprecipitation followed by Western blotting. The CFTR-mediated anion secretion is transient and is followed, in time, by a verapamil- and Ba(+)-sensitive anion secretion or cation absorption and, finally, by Na+ reabsorption via epithelial Na+ channels (ENaC). In contrast to other studies of MDCK cells, we see no indication that the presence of CFTR functionally inhibits ENaC. The characterization of the various ion transport phenomena substantiates this cell line as a model renal epithelium that can be used to study the hormonal and metabolic regulation of ion transport

PPARγ agonists do not directly enhance basal or insulin-stimulated Na+ transport via the epithelial Na+ channel

Selective agonists of peroxisome proliferator-activated receptor gamma (PPARgamma) are anti-diabetic drugs that enhance cellular responsiveness to insulin. However, in some patients, fluid retention, plasma volume expansion, and edema have been observed. It is well established that insulin regulates Na(+) reabsorption via the epithelial sodium channel (ENaC) located in the distal tubule. Therefore, we hypothesized that these agonists may positively modulate insulin-stimulated ENaC activity leading to increased Na(+) reabsorption and fluid retention. Using electrophysiological techniques, dose-response curves for insulin-mediated Na(+) transport in the A6, M-1, and mpkCCD(cl4) cell lines were performed. Each line demonstrated hormone efficacy within physiological concentration ranges and, therefore, can be used to monitor clinically relevant effects of pharmacological agents which may affect electrolyte transport. Immunodetection and quantitative PCR analyses showed that each cell line expresses viable and functional PPARgamma receptors. Despite this finding, two PPARgamma agonists, pioglitazone and GW7845 did not directly enhance basal or insulin-stimulated Na(+) flux via ENaC, as shown by electrophysiological methodologies. These studies provide important results, which eliminate insulin-mediated ENaC activation as a candidate mechanism underlying the fluid retention observed with PPARgamma agonist use

The management of depressed elderly care recipients : family perspectives on the skills of professional carers

Recent studies have identified high levels of depression among older people, both those in their own homes and those in residential care. With the world\u27s population ageing, it is timely for health service providers to consider how the escalating population of depressed elderly people will be managed. Although treating general practitioners may be the health professionals most expected to detect, treat, and monitor depression among the elderly, professional carers are well placed to assist in the detection and monitoring of the disorder. This study conducted individual interviews with 15 family members of depressed aged-care recipients to determine their perceptions of the skills and knowledge of depression of professional carers. Family members reported that carers are more likely to avoid than engage with their clients about depressive symptomatology and do not communicate their concerns with managers or general practitioners (GPs). Family members believed that, in general, professional carers were undertrained in these areas. The implications of these findings for health service planning and staff training are discussed. <br /

Novel Peptide Ligands of RGS4 from a Focused One-Bead, One-Compound Library

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65605/1/j.1747-0285.2008.00687.x.pd

Depression:Diagnosis and suffering as process

The high rates of depression – as well as the widespread diagnosis of depression – are both controversial and contested in contemporary late-modern society. Issues of flawed definition have been voiced to account for the bourgeoning rates of depression and the diagnosis has been subject to criticism of medicalization and pharmaceuticalization. Others have stated that the actualization of depression is to be seen in light of societal and structural transformations. Be that as it may, depression is affecting more and more people and the diagnosis is prevalent. In this context, a more nuanced understanding of how people relate to, experience and ascribe meaning to their suffering as depression and being diagnosed as such is needed. This article draws on qualitative interviews from Denmark and Norway to explore lay accounts of depression in contemporary late-modern society. The findings reveal that lay accounts of suffering, including living with the diagnosis of depression is a dynamic process, meaning that people vacillate in and out of various perspectives of suffering and categorization to make it fit their specific life situation and prospects of the future. In this article we thus highlight the perspectives of thoroughly analyzing suffering and the diagnostic experience by applying the overall concept of process, which takes on different meanings in the course of the analysis. The final version of this research has been published in Nordic Psychology. © 2017 Taylor & Franci

Exploratory Case‐Control Analysis of Psychosocial Factors and Adult Periodontitis

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141163/1/jper1060.pd