Strength indices of the proximal femur and shaft in prepubertal female gymnasts

Introduction/Purpose: The role of impact loading activity on bone mass is well established; however, there are little data on the effects of exercise on bone geometry and indices of bone strength. The primary purpose of this study was to compare indices of bone strength at the proximal femur (PF) between elite premenarcheal gymnasts (N = 30) and age-matched controls (N = 30). Methods: Structural properties of the proximal femur were derived from the hip analyses program and included measurement of subperiosteal width, endosteal diameter, cross-sectional area, bone mineral density, cross-section moment of inertia (CSMI), and section modulus (Z). These parameters were measured for two regions of the PF: the narrow neck (NN), and the shaft (S). In addition, a strength index (S-SI) was calculated at the shaft by dividing the Z at the shaft by the femur length. A secondary purpose was to compare bone mineral content (BMC) values at the total body, lumbar spine, and three sites at the PF (neck, trochanter, and total) between the groups. All dependent values were compared adjusting for height and weight using an ANCOVA procedure and for relative lean body mass post hoc. Results: The gymnasts had significantly greater size-adjusted strength indices (CSMI, Z, and SI) at the NN and S. Gymnasts also had significantly greater size-adjusted BMC at all sites investigated. However, these differences disappeared when adjusted for relative lean body mass. Conclusion: When adjusted for body size, gymnasts had significantly greater indices of both axial strength and bending strength at the NN region of the PF and S, as well as a greater bone SI at the femoral shaft. These differences may be related to greater relative lean body mass attained in gymnastics training.

Erythropoietin protects against ischaemic acute renal injury

Erythropoietin (EPO) has recently been shown to exert important cytoprotective and anti-apoptotic effects in experimental brain injury and cisplatin-induced nephrotoxicity. The aim of the present study was to determine whether EPO administration is also renoprotectivein both in vitro and in vivo models ofischaemic acute renal failure Methods. Primary cultures of human proximal tubule cells (PTCs) were exposed to either vehicle or EPO (6.25–400 IU/ml) in the presence of hypoxia (1% O2), normoxia (21% O2) or hypoxia followed by normoxia for up to 24 h. The end-points evaluated included cell apoptosis (morphology and in situ end labelling [ISEL], viability [lactate dehydrogenase (LDH release)], cell proliferation [proliferating cell nuclear antigen (PCNA)] and DNA synthesis (thymidine incorporation). The effects of EPO pre-treatment (5000 U/kg) on renal morphology and function were also studied in rat models of unilateral and bilateral ischaemia–reperfusion (IR) injury. Results. In the in vitro model, hypoxia (1% O2) induced a significant degree of PTC apoptosis, which was substantially reduced by co-incubation with EPO at 24 h (vehicle 2.5±0.5% vs 25 IU/ml EPO 1.8±0.4% vs 200 IU/ml EPO 0.9±0.2%, n = 9, P

Synaptology of the proximal segment of pyramidal cell basal dendrites

Pyramidal neurons are covered with dendritic spines, the main postsynaptic targets of excitatory (asymmetrical) synapses. However, the proximal portion of both the apical and basal dendrites is devoid of spines, suggesting a lack of excitatory inputs to this region. In the present study we used electron microscopy to analyse the proximal region of the basal dendrites of supra- and infragranular pyramidal cells to determine if this is the case. The proximal region of 80 basal dendrites sampled from the rat hindlimb representation in the primary somatosensory cortex was studied by electron microscopy A total of 317 synapses were found within this region of the dendrites, all of which were of the symmetrical type. These results suggest that glutamate receptors, although present in the cytoplasm, are not involved in synaptic junctions in the proximal portion of the dendrites. These data further support the idea that inhibitory terminals exclusively innervate the proximal region of basal dendrites.

Are interactions in Gray's Reinforcement Sensitivity Theory proximal or distal in the prediction of religiosity: a test of the joint subsystems hypothesis

Gray's Reinforcement Sensitivity Theory (RST) consists of the Behavioural Activation System (BAS) which is the basis of Impulsivity, and Behavioural Inhibition System (BIS) which is the basis of Anxiety. In this study, Impulsivity and Anxiety were used as distal predictors of attitudes to religion in the prediction of three religious dependent variables (Church attendance, Amount of prayer, and Importance of church). We hypothesised that Impulsivity would independently predict a Rewarding attitude to the Church and that Anxiety would independently predict an Anxious attitude to the church, and that these attitudes would be proximal predictors of our dependent variables. Moreover, we predicted that interactions between predictors would be proximal. Using structural equation modelling, data from 400 participants supported the hypotheses. We also tested Eysenck's personality scales of Extraversion and Neuroticism and found a key path of the structural equation model to be non-significant. (C) 2003 Elsevier Ltd. All rights reserved.

Nedd4-2 functionally interacts with ClC-5 - Involvement in constitutive albumin endocytosis in proximal tubule cells

Constitutive albumin uptake by the proximal tubule is achieved by a receptor-mediated process in which the Cl- channel, ClC-5, plays an obligate role. Here we investigated the functional interaction between ClC-5 and ubiquitin ligases Nedd4 and Nedd4-2 and their role in albumin uptake in opossum kidney proximal tubule (OK) cells. In vivo immunoprecipitation using an anti-HECT antibody demonstrated that ClC-5 bound to ubiquitin ligases, whereas glutathione S-transferase pull-downs confirmed that the C terminus of ClC-5 bound both Nedd4 and Nedd4-2. Nedd4-2 alone was able to alter ClC-5 currents in Xenopus oocytes by decreasing cell surface expression of ClC-5. In OK cells, a physiological concentration of albumin (10 mug/ml) rapidly increased cell surface expression of ClC-5, which was also accompanied by the ubiquitination of ClC-5. Albumin uptake was reduced by inhibiting either the lysosome or proteasome. Total levels of Nedd4-2 and proteasome activity also increased rapidly in response to albumin. Overexpression of ligase defective Nedd4-2 or knockdown of endogenous Nedd4-2 with small interfering RNA resulted in significant decreases in albumin uptake. In contrast, pathophysiological concentrations of albumin (100 and 1000 mug/ml) reduced the levels of ClC-5 and Nedd4-2 and the activity of the proteasome to the levels seen in the absence of albumin. These data demonstrate that normal constitutive uptake of albumin by the proximal tubule requires Nedd4-2, which may act via ubiquitination to shunt ClC-5 into the endocytic pathway.

High glucose transactivates the EGF receptor and up-regulates serum glucocorticoid kinase in the proximal tubule

Background. Serum glucocorticoid regulated kinase (SGK-1) is induced in the kidney in diabetes mellitus. However, its role in the proximal tubule is unclear. This study determined the expression and functional role of SGK-1 in PTCs in high glucose conditions. As the epidermal growth factor (EGF) receptor is activated by both EGF and other factors implicated in diabetic nephropathy, the relationship of SGK-1 with EGFR activity was assessed. Methods. mRNA and protein expression of SGK-1 and mRNA expression of the sodium hydrogen exchanger NHE3 were measured in human PTCs exposed to 5 mmol/L (control) and 25 mmol/L (high) glucose. The effects of SGK-1 on cell growth, apoptosis, and progression through the cell cycle and NHE3 mRNA were examined following overexpression of SGK-1 in PTCs. The role of EGFR activation in observed changes was assessed by phospho-EGFR expression, and response to the EGFR blocker PKI166. SGK-1 expression was then assessed in vivo in a model of streptozotocin-induced diabetes mellitus type 2. Results. A total of 25 mmol/L glucose and EGF (10 ng/mL) increased SGK-1 mRNA (P < 0.005 and P < 0.002, respectively) and protein (both P < 0.02) expression. High glucose and overexpression of SGK-1 increased NHE3 mRNA (P < 0.05) and EGFR phosphorylation (P < 0.01), which were reversed by PKI166. SGK-1 overexpression increased PTC growth (P < 0.0001), progression through the cell cycle (P < 0.001), and increased NHE3 mRNA (P < 0.01), which were all reversed with PKI166. Overexpression of SGK-1 also protected against apoptosis induced in the PTCs (P < 0.0001). Up-regulation of tubular SGK-1 mRNA in diabetes mellitus was confirmed in vivo. Oral treatment with PKI166 attenuated this increase by 51%. No EGF protein was detectable in PTCs, suggestive of phosphorylation of the EGFR by high glucose and downstream induction of SGK-1. Conclusion. The effects of high glucose on PTC proliferation, reduced apoptosis and increased NHE3 mRNA levels are mediated by EGFR-dependent up-regulation of SGK-1.

NaSi-1 and Sat-1: structure, function and transcriptional regulation of two genes encoding renal proximal tubular sulfate transporters

Sulfate (SO42-) is an important anion regulating many metabolic and cellular processes. Maintenance Of SO42- homeostasis occurs in the renal proximal tubule via membrane transport proteins. Two SO42- transporters that have been characterized and implicated in regulating serum SO42- levels are: NaSi- 1, a Na+-SO4 (2-) cotransporter located at the brush border membrane and Sat-1, a SO4 (2-) -anion exchanger located on the basolateral membranes of proximal tubular cells. Unlike Sat-1, for which very few studies have looked at regulation of its expression, NaSi- 1 has been shown to be regulated by various hormones and dietary conditions in vivo. To study this further, NaSj- I (SLC13A1) and Sat- I (SLC26A1) gene structures were determined and recent studies have characterized their respective gene promoters. This review presents the current understanding of the transcriptional regulation of NaSj- I and Sat- 1, and describes possible pathogenetic implications which arise as a consequence of altered SO(4)(2-)homeostasis. (c) 2005 Elsevier Ltd. All rights reserved.

PKC-alpha-mediated remodeling of the actin cytoskeleton is involved in constitutive albumin uptake by proximal tubule cells

One key role of the renal proximal tubule is the reabsorption of proteins from the glomerular filtrate by constitutive receptor-mediated endocytosis. In the opossum kidney (OK) renal proximal tubule cell line, inhibition of protein kinase C (PKC) reduces albumin uptake, although the isoforms involved and mechanisms by which this occurs have not been identified. We used pharmacological and molecular approaches to investigate the role of PKC-α in albumin endocytosis. We found that albumin uptake in OK cells was inhibited by the pan-PKC blocker bisindolylmaleimide-1 and the isoform-specific PKC blockers Go-6976 and 2',3,3',4,4'-hexahydroxy-1,1'-biphenyl-6,6'-dimethanol dimethyl ether, indicating a role for PKC-α. Overexpression of a kinase deficient PKC-α(K368R) but not wild-type PKC-α significantly reduced albumin endocytosis. Western blot analysis of fractionated cells showed an increased association of PKC-α-green fluorescent protein with the membrane fraction within 10-20 min of exposure to albumin. We used phalloidin to demonstrate that albumin induces the formation of clusters of actin at the apical surface of OK cells and that these clusters correspond to the location of albumin uptake. These clusters were not present in cells grown in the absence of albumin. In cells treated either with PKC inhibitors or overexpressing kinase-deficient PKC-α(K368R) this actin cluster formation was significantly reduced. This study identifies a role for PKC-α in constitutive albumin uptake in OK cells by mediating assembly of actin microfilaments at the apical membrane.

Neonatal calyceal dilation and renal fibrosis resulting from loss of Adamts-1 in mouse kidney is due to a developmental dysgenesis

Background. A disintegrin and metalloproteinase with thrombospondin motifs 1, Adamts-1, is important for the development and function of the kidney. Mice lacking this protein present with renal lesions comprising enlarged calyces, and reduced cortex and medulla layers. Our current findings are consistent with the defect occurring due to a developmental dysgenesis. Methods. We generated Adamts-1 null mice, and further investigated their kidney phenotype in a time course study ranging from E18.5 to 12 months of age. Immunohistochemistry was used to assess the localization of type IV collagen, TGF-beta and F4/80-positive macrophages in the kidneys of Adcants-1 null mice compared to wild-type control animals. The expression of Adamts-1 mRNA was determined in metanephric kidney explants by in situ hybridization. Results. Adamts-1 null mice have a gross kidney defect. At day 18.5 of gestation, the Adcants-1 null kidney has a normal appearance but at birth when the kidney begins to function, the defect becomes evident. During development of the kidney Adamts-1 expression was specifically detected in the developing loops of Henle, as well as in the proximal and distal convoluted tubules. Expression was not detected in the ureter, ureteric bud or its derivatives as had been previously suggested. At 6 months and I year of age, the Adamts-1 null mice displayed interstitial fibrosis in the cortical and medullary regions of the kidney. At I year of age, the Adamts-1 null mice displayed mild interstitial matrix expansion associated with increased collagen type IV expression, without apparent tubular dilatation, compared to wild-type animals. Immunohistochemical analysis demonstrated TGF-beta protein localized to infiltrating macrophages and glomeruli of Adamts-1 null mice. Conclusions. Adamts-1 is required for the normal development of the kidney. The defect observed in its absence results from a dysgenic malformation affecting the medulla that becomes apparent at birth, once the kidneys start to function.

CIC-5: A chloride channel with multiple roles in renal tubular albumin uptake

CIC-5 is a chloride (Cl-) channel expressed in renal tubules and is critical for normal tubular function. Loss of function nonsense or missense mutations in CIC-5 are associated with Dent's disease, a condition in which patients present with low molecular weight (LMW) proteinuria (including albuminuria), hypercalciuria and nephrolithiasis. Several key studies in CIC-5 knockout mice have shown that the proteinuria results from defective tubular reabsorption of proteins. CIC-5 is typically regarded as an intracellular Cl- channel and thus the defect in this receptor-mediated uptake pathway was initially attributed to the failure of the early endosomes to acidify correctly. CIC-5 was postulated to play a key role in transporting the Cl- ions required to compensate for the movement of H+ during endosomal acidification. However, more recent studies suggest additional roles for CIC-5 in the endocytosis of albumin. CIC-5 is now known to be expressed at low levels at the cell surface and appears to be a key component in the assembly of the macromolecular complex involved in protein endocytosis. Furthermore, mutations in CIC-5 affect the trafficking of v-H+-ATPase and result in decreased expression of the albumin receptor megalin/cubulin. Thus, the expression of CIC-5 at the cell surface as well as its presence in endosomes appears to be essential for normal protein uptake by the renal proximal tubule. (c) 2005 Elsevier Ltd. All rights reserved.