Effect of posttranslational modification on the Na+, K+ ATPase kinetics

The Na+, K+ ATPase is an essential membrane protein in eukaryotic cells, which transports Na+ out of the cell in exchange for K+ into the cell. For this transport it hydrolyses one molecule of ATP for each cycle. The partial reactions of the ATPase cycle and the effects of posttranslational modifications on ATPase activity have been studied extensively. However, amalgamation of the reported rate constants for the partial reactions along with the effect of posttranslational modifications have never been attempted. We have designed a simplified four-state mathematical model of the Na+, K+ ATPase using published results for the partial reactions. We have incorporated the effect of the Na+ allosteric site and poise dependent glutathionylation and attempted to replicate K+ activated transient currents reported in voltage clamped cardiomyocytes. Our voltage clamped cardiomyocyte results indicate the K+ activated transient is an effect of poise dependent glutathionylation rather than the Na+ subsarcolemmal space. These results can be replicated to some extent by the proposed kinetic model. This is the first kinetic model of the Na+, K+ ATPase that incorporates both partial rate constants and a reported posttranslational modification which is able to reproduce voltage clamped cardiomyocyte data

Making and breaking order via clothing Clothing regulation, cross-dressing, and the ordering mentality in later medieval and early modern England

Following the events which disrupted social stability in fourteenth and fifteenth-century England, individuals from a variety of social contexts demonstrated a particular necessity to see order visibly displayed in society. This thesis examines sumptuary regulations and cross-dressing side by side to demonstrate clothing's relationship to both making and breaking order. In the act of revealing this relationship, this thesis will argue that the two cases demonstrate clothing’s importance in creating a visible confirmation of social order which ultimately brings to the surface an underlying collective ordering mentality that equated a sense of security with arranging everyone in society in their rightful place

Depictions of Thailand in Australian and Thai writings:Reflections of the Self and Other

This thesis offers both an examination of the depiction of Thailand in Australian novels, short stories and poems written in the 1980s and after, and an analysis of modern Thai novels and short stories that reflect similar themes to those covered in the Australian literature. One Australian film is also examined as the film provides an important framework for the analysis of some of the short stories and novels under consideration. The thesis establishes a dialogue between Thai and Australian literatures and demonstrates that the comparison of Australian representations of Thailand with Thai representations challenges constructively certain dominant political and social ideologies that enhance conservatism and the status quo in Thailand. The author acknowledges that the discussion of the representations of Thailand in contemporary Australian novels and short stories needs to take into account the colonial legacy and the discourse of Orientalism that tends to posit the ‘East’ as the ‘West’’s ‘Other’. Textual analysis is thus informed by post-colonial and cross-cultural theories, starting from Edward Said’s powerful and controversial critique of Western representation of the East in Orientalism. The first part of the thesis examines Australian crime stories and shows how certain Orientalist images and perceptions persist and help reinforce the image of the East and its people as the antithesis of the West. From Chapters Three through Six, however, more literary works by Australian authors are examined. The important finding is that most of the Australian authors under consideration attempt, though not always successfully, to resist and challenge the Eurocentric stereotypes of Asia and Asians that dominated Australian literature in earlier periods. This difference between contemporary Australian authors and their predecessors seems to reflect modern Australia’s endeavor to distinguish itself from the rest of the Western world and to redefine its relationship with Asia. As literary representations cannot be separated from socio-political contexts, the thesis also includes discussion of the Thai social and political history and, where appropriate, shows how colonialism and neo-colonialism exert their impact on modern Thailand

TRPC6 single nucleotide polymorphisms and progression of idiopathic membranous nephropathy

Background: Activating mutations in the Transient Receptor Potential channel C6 (TRPC6) cause autosomal dominant focal segmental glomerular sclerosis (FSGS). TRPC6 expression is upregulated in renal biopsies of patients with idiopathic membranous glomerulopathy (iMN) and animal models thereof. In iMN, disease progression is characterized by glomerulosclerosis. In addition, a context-dependent TRPC6 overexpression was recently suggested in complement-mediated podocyte injury in e.g. iMN. Hence, we hypothesized that genetic variants in TRPC6 might affect susceptibility to development or progression of iMN. Methods & Results: Genomic DNA was isolated from blood samples of 101 iMN patients and 292 controls. By direct sequencing of the entire TRPC6 gene, 13 single nucleotide polymorphisms (SNPs) were identified in the iMN cohort, two of which were causing an amino acid substitution (rs3802829; Pro15Ser and rs36111323, Ala404Val). No statistically significant differences in genotypes or allele frequencies between patients and controls were observed. Clinical outcome in patients was determined (remission n = 26, renal failure n = 46, persistent proteinuria n = 29, follow-up median 80 months {range 51-166}). The 13 identified SNPs showed no association with remission or renal failure. There were no differences in genotypes or allele frequencies between patients in remission and progressors. Conclusions: Our data suggest that TRPC6 polymorphisms do not affect susceptibility to iMN, or clinical outcome in iMN

The von Hippel-Lindau gene is required to maintain renal proximal tubule and glomerulus integrity in zebrafish larvae

Background: von Hippel-Lindau (VHL) disease is characterized by the development of benign and malignant tumours in many organ systems, including renal cysts and clear cell renal cell carcinoma. It is not completely understood what underlies the development of renal pathology, and the use of murine Vhl models has been challenging due to limitations in disease conservation. We previously described a zebrafish model bearing inactivating mutations in the orthologue of the human VHL gene. Methods: We used histopathological and functional assays to investigate the pronephric and glomerular developmental defects in vhl mutant zebrafish, supported by human cell culture assays. Results: Here, we report that vhl is required to maintain pronephric tubule and glomerulus integrity in zebrafish embryos. vhl mutant glomeruli are enlarged, cxcr4a+ capillary loops are dilated and the Bowman space is widened. While we did not observe pronephric cysts, the cells of the proximal convoluted and anterior proximal straight tubule are enlarged, periodic acid schiff (PAS) and Oil Red O positive, and display a clear cytoplasm after hematoxylin and eosine staining. Ultrastructural analysis showed the vhl–/– tubule to accumulate large numbers of vesicles of variable size and electron density. Microinjection of the endocytic fluorescent marker AM1–43 in zebrafish embryos revealed an accumulation of endocytic vesicles in the vhl mutant pronephric tubule, which we can recapitulate in human cells lacking VHL. Conclusions: Our data indicates that vhl is required to maintain pronephric tubule and glomerulus integrity during zebrafish development, and suggests a role for VHL in endocytic vesicle trafficking

Characterization of the gene encoding human sarcolipin (SLN), a proteolipid associated with SERCA1: Absence of structural mutations in five patients with brody disease

Sarcolipin (SLN) is a low-molecular-weight protein that copurifies with the fast-twitch skeletal muscle sarcoplasmic reticulum Ca2+ ATPase (SERCA1). Genomic DNA and cDNA encoding human sarcolipin (SLN) were isolated and characterized and the SLN gene was mapped to chromosome 11q22-q23. Human, rabbit, and mouse cDNAs encode a protein of 31 amino acids. Homology of SLN with phospholamban (PLN) suggests that the first 7 hydrophilic amino acids are cytoplasmic, the next 19 hydrophobic amino acids form a single transmembrane helix, and the last 5 hydrophilic amino acids are lumenal. The cytoplasmic and transmembrane sequences are not well conserved among the three species, but the lumenal sequence is highly conserved. Like SERCA1, SLN is highly expressed in rabbit fast-twitch skeletal muscle, but it is expressed to a lower extent in slow-twitch muscle and to an even lower extent in cardiac muscle, where SERCA2a and PLN are highly expressed. It is expressed in only trace amounts in pancreas and prostate. SLN and PLN genes resemble each other in having two small exons, with their entire coding sequences lying in exon 2 and a large intron separating the two segments. Brody disease is an inherited disorder of skeletal muscle function, characterized by exercise-induced impairment of muscle relaxation. Mutations in the ATP2A1 gene encoding SERCA1 have been associated with the autosomal recessive inheritance of Brody disease in three families, but not with autosomal dominant inheritance of the disease. A search for mutations in the SLN gene in five Brody families, four of which were not linked to ATP2A1, did not reveal any alterations in coding, splice junction or promoter sequences. The homozygous deletion of C438 in the coding sequence of ATP2A1 in Brody disease family 3, leading to a frameshift and truncation following Pro147 in SERCA1, is the fourth ATP2A1 mutation to be associated with autosomal recessive Brody disease

The phenotype of Floating-Harbor syndrome: Clinical characterization of 52 individuals with mutations in exon 34 of SRCAP

Background: Floating-Harbor syndrome (FHS) is a rare condition characterized by short stature, delays in expressive language, and a distinctive facial appearance. Recently, heterozygous truncating mutations in SRCAP were determined to be disease-causing. With the availability of a DNA based confirmatory test, we set forth to define the clinical features of this syndrome. Methods and results. Clinical information on fifty-two individuals with SRCAP mutations was collected using standardized questionnaires. Twenty-four males and twenty-eight females were studied with ages ranging from

Inherited forms of renal hypomagnesemia: an update.

Item does not contain fulltextThe kidney plays an important role in ion homeostasis in the human body. Several hereditary disorders characterized by perturbations in renal magnesium reabsorption leading to hypomagnesemia have been described over the past 50 years, with the most important of these being Gitelman syndrome, familial hypomagnesemia with hypercalciuria and nephrocalcinosis, familial hypomagnesemia with secondary hypocalcemia, autosomal dominant hypomagnesemia with hypocalciuria, and autosomal recessive hypomagnesemia. Only recently, following positional cloning strategies in affected families, have mutations in renal ion channels and transporters been identified in these diseases. In this short review, I give an update on these hypomagnesemic disorders. Elucidation of the genetic etiology and, for most of these disorders, also the underlying pathophysiology of the disease, has greatly increased our understanding of the normal physiology of renal magnesium handling. This is yet another example of the importance of studying rare disorders in order to unravel physiological and pathophysiological processes in the human body

Molecular and cellular defects in nephrogenic diabetes insipidus

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