Nucleic acids within urinary exosomes/microvesicles are potential biomarkers for renal disease

Urinary exosomes or microvesicles are being studied intensively to identify potential new biomarkers for renal disease. We sought to identify whether these microvesicles contain nucleic acids. We isolated microvesicles from human urine in the same density range as that previously described for urinary exosomes and found them to have an RNA integrity profile similar to that of kidney tissue, including 18S and 28S rRNA. This profile was better preserved in urinary microvesicles compared with whole cells isolated from urine, suggesting that microvesicles may protect RNA during urine passage. We were able to detect mRNA in the human urinary microvesicles encoding proteins from all regions of the nephron and the collecting duct. Further, to provide a proof of principle, we found that microvesicles isolated from the urine of the V-ATPase B1 subunit knockout mice lacked mRNA of this subunit while containing a normal amount of the B2 subunit and aquaporin 2. The microvesicles were found to be contaminated with extraneous DNA potentially on their surface; therefore, we developed a rapid and reliable means to isolate nucleic acids from within urine microvesicles devoid of this extraneous contamination. Our study provides an experimental strategy for the routine isolation and use of urinary microvesicles as a novel and non-invasive source of nucleic acids to further renal disease biomarker discovery.

Modeling digits. Digit patterning is controlled by a Bmp-Sox9-Wnt Turing network modulated by morphogen gradients

During limb development, digits emerge from the undifferentiated mesenchymal tissue that constitutes the limb bud. It has been proposed that this process is controlled by a self-organizing Turing mechanism, whereby diffusible molecules interact to produce a periodic pattern of digital and interdigital fates. However, the identities of the molecules remain unknown. By combining experiments and modeling, we reveal evidence that a Turing network implemented by Bmp, Sox9, and Wnt drives digit specification. We develop a realistic two-dimensional simulation of digit patterning and show that this network, when modulated by morphogen gradients, recapitulates the expression patterns of Sox9 in the wild type and in perturbation experiments. Our systems biology approach reveals how a combination of growth, morphogen gradients, and a self-organizing Turing network can achieve robust and reproducible pattern formation.

The normal kidney filters nephrotic levels of albumin retrieved by proximal tubule cells: retrieval is disrupted in nephrotic states

The origin of albuminuria remains controversial owing to difficulties in quantifying the actual amount of albumin filtered by the kidney. Here we use fluorescently labeled albumin, together with the powerful technique of intravital 2-photon microscopy to show that renal albumin filtration in non-proteinuric rats is approximately 50 times greater than previously measured and is followed by rapid endocytosis into proximal tubule cells (PTCs). The endocytosed albumin appears to undergo transcytosis in large vesicles (500 nm in diameter), identified by immunogold staining of endogenous albumin by electron microscopy, to the basolateral membrane where the albumin is disgorged back to the peritubular blood supply. In nephrotic rats, the rate of uptake of albumin by the proximal tubule (PT) is decreased. This is consistent with reduced expression of clathrin, megalin, and vacuolar H(+)-ATPase A subunit, proteins that are critical components of the PT endocytotic machinery. These findings strongly support the paradigm-shifting concept that the glomerular filter normally leaks albumin at nephrotic levels. Albuminuria does not occur as this filtered albumin load is avidly bound and retrieved by PTCs. Dysfunction of this retrieval pathway leads to albuminuria. Thus, restoration of the defective endocytotic and processing function of PT epithelial cells might represent an effective strategy to limit urinary albumin loss, at least in some types of nephrotic syndrome.

The progression of coronary artery calcification in predialysis patients on calcium carbonate or sevelamer

Coronary artery calcification is more prevalent in dialysis patients than in patients without kidney disease and this is associated with high serum phosphorus. In this study, we evaluate the effect of calcium carbonate or sevelamer treatments on the progression of calcification in 90 predialysis patients. Inclusion criteria were stable serum calcium, phosphorus, parathyroid hormone, and a similar baseline total calcium score (TCS). These patients were not treated by phosphate binder, vitamin D, or statin. They were given low-phosphorus diets without or with daily calcium carbonate or sevelamer throughout the study that averaged 2 years. Baseline demographic or clinical characteristics along with biochemical parameters were not different among the three groups. The TCS significantly increased in patients on the low-phosphorus diet alone, to a lesser extent in calcium carbonate-treated patients, and not at all in sevelamer-treated patients. The progression of coronary calcification paralleled that of the calcium score. Our study shows that sevelamer treatment should not be restricted to dialysis patients; however, a larger study should be undertaken to confirm these results.

Impaired tubular uptake explains albuminuria in early diabetic nephropathy

Understanding the pathogenesis of albuminuria in diabetic nephropathy is important to improve methods for early diagnosis and treatment. In this study, we addressed whether albuminuria in diabetes results from altered glomerular filtration and/or altered processing of filtered albumin by the proximal tubule. Type 1 diabetic Munich Wistar rats developed albuminuria after 12 wk of diabetes. Intravital two-photon microscopy revealed similar glomerular permeability in the diabetic and control animals, assessed using both albumin-Alexa568 and 69-kD FITC-dextran; however, diabetic animals demonstrated significantly less filtered fluorescent albumin in renal proximal tubule (PT) cells compared with control animals. We also observed increased albumin-derived urinary peptide excretion in diabetic animals, and hyperglycemia modulated this peptideuria. In conclusion, in the early stages of diabetic nephropathy, the PT plays a major role in the development of albuminuria, which may be preceded by peptideuria.

Renal handling of albumin: a critical review of basic concepts and perspective

Biochemical and physiological processes that underlie the mechanism of albuminuria are completely reassessed in this article in view of recent discoveries that filtered proteins undergo rapid degradation during renal passage and the resulting excreted peptide fragments are not detected by conventional urine protein assays. This means that filtered protein and/or albumin levels in urine have been seriously underestimated. The concept that albuminuria is a result of changes in glomerular permeability is questioned in light of these findings and also in terms of a critical examination of charge selectivity, shunts, or large-pore formation and hemodynamic effects. The glomerulus appears to function merely in terms of size selectivity alone, and for albumin, this does not change significantly in disease states. Intensive albumin processing by a living kidney occurs through cellular processes distal to the glomerular basement membrane. Failure of this cellular processing primarily leads to albuminuria. This review brings together recent data about urinary albumin clearance and current knowledge of receptors known to process albumin in both health and disease states. We conclude with a discussion of topical and controversial issues associated with the proposed new understanding of renal handling of albumin.

Disease-dependent mechanisms of albuminuria

The mechanism of albuminuria is perhaps one of the most complex yet important questions in renal physiology today. Recent studies have directly demonstrated that the normal glomerulus filters substantial amounts of albumin and that charge selectivity plays little or no role in preventing this process. This filtered albumin is then processed by proximal tubular cells by two distinct pathways; dysfunction in either one of these pathways gives rise to discrete forms of albuminuria. Most of the filtered albumin is returned to the peritubular blood supply by a retrieval pathway. Albuminuria in the nephrotic range would arise from retrieval pathway dysfunction. The small quantities of filtered albumin that are not retrieved undergo obligatory lysosomal degradation before urinary excretion as small peptide fragments. This degradation pathway is sensitive to metabolic factors responsible for hypertrophy and fibrosis, particularly molecules such as angiotensin II and transforming growth factor-beta1, whose production is stimulated by hyperglycemic and hypertensive environments. Dysfunction in this degradation pathway leads to albuminuria below the nephrotic range. These new insights into albumin filtration and processing argue for a reassessment of the role of podocytes and the slit diaphragm as major direct determinants governing albuminuria, provide information on how glomerular morphology and "tubular" albuminuria may be interrelated, and offer a new rationale for drug development.

Massively parallel sequencing of human urinary exosome/microvesicle RNA reveals a predominance of non-coding RNA

Intact RNA from exosomes/microvesicles (collectively referred to as microvesicles) has sparked much interest as potential biomarkers for the non-invasive analysis of disease. Here we use the Illumina Genome Analyzer to determine the comprehensive array of nucleic acid reads present in urinary microvesicles. Extraneous nucleic acids were digested using RNase and DNase treatment and the microvesicle inner nucleic acid cargo was analyzed with and without DNase digestion to examine both DNA and RNA sequences contained in microvesicles. Results revealed that a substantial proportion (∼87%) of reads aligned to ribosomal RNA. Of the non-ribosomal RNA sequences, ∼60% aligned to non-coding RNA and repeat sequences including LINE, SINE, satellite repeats, and RNA repeats (tRNA, snRNA, scRNA and srpRNA). The remaining ∼40% of non-ribosomal RNA reads aligned to protein coding genes and splice sites encompassing approximately 13,500 of the known 21,892 protein coding genes of the human genome. Analysis of protein coding genes specific to the renal and genitourinary tract revealed that complete segments of the renal nephron and collecting duct as well as genes indicative of the bladder and prostate could be identified. This study reveals that the entire genitourinary system may be mapped using microvesicle transcript analysis and that the majority of non-ribosomal RNA sequences contained in microvesicles is potentially functional non-coding RNA, which play an emerging role in cell regulation.

cAMP stimulates apical V-ATPase accumulation, microvillar elongation, and proton extrusion in kidney collecting duct A-intercalated cells

Kidney proton-secreting A-intercalated cells (A-IC) respond to systemic acidosis by accumulating the vacuolar ATPase (V-ATPase) in their apical membrane and by increasing the length and number of apical microvilli. We show here that the cell-permeant cAMP analog CPT-cAMP, infused in vivo, results in an almost twofold increase in apical V-ATPase accumulation in AE1-positive A-IC within 15 min and that these cells develop an extensive array of apical microvilli compared with controls. In contrast, no significant change in V-ATPase distribution could be detected by immunocytochemistry in B-intercalated cells at the acute time point examined. To show a direct effect of cAMP on A-IC, we prepared cell suspensions from the medulla of transgenic mice expressing EGFP in IC (driven by the B1-subunit promoter of the V-ATPase) and exposed them to cAMP analogs in vitro. Three-dimensional reconstructions of confocal images revealed that cAMP induced a time-dependent growth of apical microvilli, starting within minutes after addition. This effect was blocked by the PKA inhibitor myristoylated PKI. These morphological changes were paralleled by increased cAMP-mediated proton extrusion (pHi recovery) by A-IC in outer medullary collecting ducts measured using the ratiometric probe BCECF. These results, and our prior data showing that the bicarbonate-stimulated soluble adenylyl cyclase (sAC) is highly expressed in kidney intercalated cells, support the idea that cAMP generated either by sAC, or by activation of other signaling pathways, is part of the signal transduction mechanism involved in acid-base sensing and V-ATPase membrane trafficking in kidney intercalated cells.

Independent prognostic role of circulating chromogranin A in prostate cancer patients with hormone-refractory disease

The presence of neuroendocrine (NE) differentiation in the context of predominantly exocrine prostate cancer may play a key role in androgen-independent tumor growth. The prognostic significance of plasma chromogranin A (CgA) was assessed in a series of consecutive prostate cancer patients with hormone-refractory disease. One hundred and eight patients with newly diagnosed hormone-refractory prostate cancer entered the study. Plasma CgA levels and other biochemical parameters, such as serum prostate specific antigen, serum alkaline phosphatase, serum lactate dehydrogenase, serum albumin and hemoglobin concentration, were measured at baseline (i.e. when hormone refractoriness occurred) and their prognostic role was evaluated together with patient performance status, Gleason score (at diagnosis of prostate cancer) and the presence of visceral metastases. Furthermore, plasma CgA was prospectively evaluated in 50 patients undergoing chemotherapy. At baseline, 45 patients (43.3%) showed elevated CgA values. Plasma CgA negatively correlated with survival, either in univariate analysis (P=0.008) or in multivariate analysis, after adjusting for previously mentioned prognostic parameters (P<0.05). In the patient subset undergoing chemotherapy, median CgA (range) values were 13.3 (3.0-141.0) U/l at baseline, 19.1 (3.0-486.0) U/l after 3 months, 20.8 (3.0-702.0) U/l after 6 months and 39.4 (3.0-414.0) U/l after 9 months (P<0.01). The corresponding supranormal rates were 17/50 (34%), 23/50 (46%), 26/50 (52%) and 34/50 (68%) respectively (P<0.005). Elevated plasma CgA levels are frequently observed in prostate cancer patients with hormone-refractory disease and correlate with poor prognosis. NE differentiation in hormone-refractory patients is a time-dependent phenomenon and is not influenced by conventional antineoplastic treatments.

Evidence for a role of transforming growth factor (TGF)-beta1 in the induction of postglomerular albuminuria in diabetic nephropathy: amelioration by soluble TGF-beta type II receptor

Transforming growth factor-beta (TGF-beta) has previously been implicated in the progression of diabetic nephropathy, including the onset of fibrosis and albuminuria. Here we report for the first time the use of a high-affinity TGF-beta1 binding molecule, the soluble human TGF-beta type II receptor (sTbetaRII.Fc), in the treatment of diabetic nephropathy in 12-week streptozotocin-induced diabetic Sprague-Dawley rats. In vitro studies using immortalized rat proximal tubule cells revealed that 50 pmol/l TGF-beta1 disrupted albumin uptake (P < 0.001 vs. control), an inhibition significantly reversed by the use of the sTbetaRII.Fc (1,200 pmol/l). In vivo studies demonstrated that treatment with sTbetaRII.Fc reduced urinary albumin excretion by 36% at 4 weeks, 59% at 8 weeks (P < 0.001), and 45% at 12 weeks (P < 0.01 for diabetic vs. treated). This was correlated with an increase in megalin expression (P < 0.05 for diabetic vs. treated) and a reduction in collagen IV expression following sTbetaRII.Fc treatment (P < 0.001 for diabetic vs. treated). These changes occurred independently of changes in blood glucose levels. This study demonstrates that the sTbetaRII.Fc is a potential new agent for the treatment of fibrosis and albuminuria in diabetic nephropathy and may reduce albuminuria by reducing TGF-beta1-induced disruptions of renal proximal tubule cell uptake of albumin.

The influence of menopause and hormonal replacement therapy on body cell mass and body fat mass

OBJECTIVE

Our purpose was to determine the efficacy of dietary calcium augmentation in the prevention of early postmenopausal bone density loss in comparison with hormonal replacement therapy and placebo.

STUDY DESIGN

A three-arm parallel randomized trial comparing the influence of placebo, dietary calcium augmentation, and estrogen-progesterone-calcium in 118 women who were within 6 years of menopause was conducted. Dual photon absorptiometry was performed annually to measure lean and fat mass. In addition, the ratio of fat in the trunk/extremities was measured.

RESULTS

Body weight increased in each group. The increase was statistically significant in the hormone replacement group (0.8 kg/year). The percent of body fat increased in each group from baseline measurements, with the greatest increase in the hormonal replacement group. There was a decline in the extremity/trunk ratio in the hormonal replacement group as a result of a relatively greater increase in the trunk fat mass. There was a rapid rate of loss in lean body mass that was equal among groups.

CONCLUSIONS

Menopause is associated with a gain in fat mass and a loss of lean body mass, but these changes in body composition are not prevented by hormone replacement therapy.

The effect of teriparatide compared with risedronate on reduction of back pain in postmenopausal women with osteoporotic vertebral fractures

The effect of teriparatide and risedronate on back pain was tested, and there was no difference in the proportion of patients experiencing a reduction in back pain between groups after 6 or 18 months. Patients receiving teriparatide had greater increases in bone mineral density and had fewer vertebral fractures.

INTRODUCTION

This study aimed to understand the effect of teriparatide in reducing back pain in patients with prevalent back pain and vertebral fracture compared to risedronate.

METHODS

In an 18-month randomized, double-blind, double-dummy trial, we investigated the effects of teriparatide (20 μg/day) vs. risedronate (35 mg/week) in postmenopausal women with back pain likely due to vertebral fracture. The primary objective was to compare the proportion of subjects reporting ≥30% reduction in worst back pain severity from baseline to 6 months as assessed by a numeric rating scale in each treatment group. Pre-specified secondary and exploratory outcomes included assessments of average and worst back pain at additional time points, disability and quality of life, bone mineral density, incidence of fractures, and safety.

RESULTS

At 6 months, 59% of teriparatide and 57% of risedronate patients reported ≥30% reduction in worst back pain and there were no differences between groups in the proportion of patients experiencing reduction in worst or average back pain at any time point, disability, or quality of life. There was a greater increase from baseline in bone mineral density at the lumbar spine (p = 0.001) and femoral neck (p = 0.02) with teriparatide compared to risedronate and a lower incidence of vertebral fractures at 18 months (4% teriparatide and 9% risedronate; p = 0.01). Vertebral fractures were less severe (p = 0.04) in the teriparatide group. There was no difference in the overall incidence of adverse events.

CONCLUSIONS

Although there were no differences in back pain-related endpoints, patients receiving teriparatide had greater skeletal benefit than those receiving risedronate.

Prevention of albuminuria by aminoguanidine or ramipril in streptozotocin-induced diabetic rats is associated with the normalization of glomerular protein kinase C

This study examined whether the prevention of diabetes-related albuminuria by aminoguanidine (AG) or ramipril (RAM) may be mediated by a common post-glomerular basement membrane renal intracellular mechanism involving protein kinase C (PKC). The renal handling of albumin was examined over 24 weeks in control and streptozotocin (STZ)-induced diabetic rats. A radioimmunoassay (RIA) that measures intact albumin, and intravenously injected tritium-labeled rat serum albumin, was used to assess the proportion of intact albumin and albumin fragments in urine. Diabetes was induced in male Sprague-Dawley rats by the intravenous administration of STZ at a dose of 50 mg/kg. Age-matched control rats received buffer alone. Diabetes was characterized by an increase in blood glucose (>15 mmol/l), an increase in GHb (means at 24 weeks 29.3+/-1.1%; control 6.1+/-0.1%, P<0.005), an increase in glomerular filtration rate (GFR) (4.13+/-0.15 ml/min; control 3.54+/-0.19 ml/min, P<0.005), an increase in intact albumin excretion rate (expressed as geometric mean 11.64 times/divided by 2.11 mg/24 h; control 0.74 times/divided by 1.57 mg/24 h, P<0.005) as measured by RIA, and an increase in glomerular PKC activity (26.83+/-2.38 pmol x mg(-1) x min(-1); control 14.6+/-2.99 pmol x mg(-1) x min(-1), P<0.005). Treatment of diabetic rats with either AG or RAM prevented the rise in intact albuminuria and glomerular PKC activity. Renal lysosomal cathepsin activity decreased in diabetic rats and this was not prevented by AG or RAM. Neither drug affected glycemic control or GFR, but RAM reduced systolic blood pressure (BP), whereas AG did not. These data indicate that urinary excretion of intact albumin and albumin-derived fragments in diabetes may be modulated independently of glycemic control (AG and RAM) and systolic BP (RAM). While both drugs are known for their different mechanisms of action, the fact that both prevent diabetes-related increases in glomerular PKC activity and albuminuria supports the hypothesis that PKC plays a central role in the development of diabetic nephropathy.

Brain in eclampsia: MR imaging with clinical correlation

Cranial magnetic resonance (MR) imaging was performed on eight consecutive patients with generalized tonic-clonic seizures caused by eclampsia. Each patient underwent serial neurologic examinations until all symptoms resolved. Six of those eight patients underwent follow-up MR imaging. These patients were compared with those in previous case reports of MR imaging abnormalities of the brain in eclampsia. MR imaging typically demonstrates bilateral hyperintense lesions on T2-weighted images and iso- to hypointense lesions on T1-weighted images. MR imaging abnormalities are most commonly located in the distribution of the posterior cerebral circulation and are associated with visual disturbances. Basal ganglia and deep white matter lesions are less common and are associated with mental status changes. Most lesions seen at MR imaging in patients with eclampsia are reversible.

Acquired and inherited risk factors for developing venous thromboembolism in cancer patients receiving adjuvant chemotherapy: a prospective trial

BACKGROUND

Acquired and inherited risk factors for venous thromboembolism (VTE) and the incidence of symptomatic VTE were investigated in patients on adjuvant chemotherapy for breast or gastrointestinal cancer (GI).

PATIENTS AND METHODS

In a prospective observational study (January 2003 and February 2006), 199 GI (82 women/117 men; age range, 26-84 years) and 182 breast (180 women/2 men; age range, 29-85 years) cancer patients were enrolled and followed-up for symptomatic VTE during adjuvant chemotherapy. The effect of acquired (i.e. age, chemotherapy, tumour histotype, history of thrombosis, body mass index and smoking) and inherited risk factors [i.e. antithrombin, protein C (PC), protein S, homocysteine, activated PC resistance, factor V Leiden (FVL) and prothrombin (PT) mutations) was prospectively evaluated.

RESULTS

Overall, 30 VTE events (7.87%) were recorded: 28 (7.35%) during treatment and 2 (0.52%) during the subsequent follow-up. Among all the 381 cancer patients, FVL was detected in 14 cases (3.67%) and PT mutation in 10 cases (2.62%). Multivariate analysis showed a significant association between the development of VTE and both thrombocytosis [hazard ratio (HR) 1.65; 95% confidence interval (CI), 1.04-2.637, P <0.0341] and a prior episode of thrombosis (HR 7.6; 95% CI, 1.77-33.1, P <0.006). FVL and PT mutations were not associated with the risk for VTE.

CONCLUSION

The present data indicate thrombocytosis and history of thrombosis as risk factors for development of a thrombotic event during adjuvant chemotherapy in patients with malignant diseases.

Modulation of nephrin in the diabetic kidney: association with systemic hypertension and increasing albuminuria

OBJECTIVE

Nephrin, a cytoskeletal protein which localizes to the slit pore of podocytes, may play a role in proteinuria. This study examines the possible relationship between nephrin expression and albuminuria in normotensive and hypertensive diabetic rats.

METHODS

Streptozotocin diabetes was induced in both Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. Diabetic and control animals were sacrificed and the kidneys obtained after 8, 16 and 24 weeks. The glomerular filtration rate (GFR) and albuminuria were also measured. Glycaemic control was assessed by measurement of plasma glucose and glycated haemoglobin (HbA1c). Nephrin gene expression was quantitated by real-time polymerase chain reaction (PCR) and localized by in situ hybridization. Nephrin protein expression was localized by immunohistochemistry and quantitated.

RESULTS

Following a transient rise at 8 weeks in the diabetic SHR (P < 0.05 versus control SHRs), nephrin gene expression, as determined by real-time PCR, was significantly decreased at 16 and 24 weeks (P < 0.05 versus control SHRs). In situ hybridization confirmed similar changes in nephrin gene expression, which were confined to the glomeruli. This reduction in glomerular nephrin gene expression was associated with increasing albuminuria at 16 and 24 weeks in diabetic SHRs. There were no significant changes in nephrin gene expression, either by real-time reverse transcription polymerase chain reaction or in situ hybridization, observed in normotensive diabetic WKY rats, in the context of much less albuminuria in this group. Immunohistochemistry for nephrin protein revealed a greater depletion in renal nephrin content in SHR than in WKY rats after 24 weeks of diabetes.

CONCLUSION

Reduction in renal nephrin gene and protein expression is closely associated with the development of albuminuria, as observed in an experimental model of diabetes and hypertension.

Controlled trial of long term oral potassium supplements in patients with mild hypertension

A 15 week randomised double blind placebo controlled trial of oral potassium supplements (48 mmol daily) was conducted in 37 patients who had mildly increased blood pressure and a normal dietary intake of sodium. After a two month run in and a one week baseline period the patients were randomly assigned to receive either potassium supplements (n = 18) or placebo (n = 19). By the third week of treatment blood pressure in the actively treated group had decreased significantly compared with that in the placebo group, though the decrease reached its maximum after 15 weeks. Urinary potassium excretion increased significantly in the group who received potassium supplements, but no significant changes were found in plasma sodium and potassium concentrations or in urinary sodium excretion. In a subgroup of 13 patients who underwent a further nine weeks of treatment with oral potassium supplements at half of the previous dose (24 mmol daily) their blood pressure, at the end of this second study period, was still significantly lower compared with their baseline value but not with that of the placebo group. These results show that moderate oral potassium supplements are associated with a long term reduction in blood pressure in patients who have mild hypertension.

Association of soluble adenylyl cyclase with the V-ATPase in renal epithelial cells

Activation of soluble adenylyl cyclase (sAC) by bicarbonate causes local cAMP generation, indicating that sAC might act as a pH and/or bicarbonate sensor in kidney cells involved in acid-base homeostasis. Therefore, we examined the expression of sAC in renal acid-base transporting intercalated cells (IC) and compared its distribution to that of the vacuolar proton pumping ATPase (V-ATPase) under different conditions. In all IC, sAC and V-ATPase showed considerable overlap under basal conditions, but sAC staining was also found in other cellular locations in the absence of V-ATPase. In type A-IC, both sAC and V-ATPase were apically and subapically located, whereas in type B-IC, significant basolateral colocalization of sAC and the V-ATPase was seen. When apical membrane insertion of the V-ATPase was stimulated by treatment of rats with acetazolamide, sAC was also concentrated in the apical membrane of A-IC. In mice that lack a functional B1 subunit of the V-ATPase, sAC was colocalized apically in A-IC along with V-ATPase containing the alternative B2 subunit isoform. The close association between these two enzymes was confirmed by coimmunoprecipitation of sAC from kidney homogenates using anti-V-ATPase antibodies. Our data show that sAC and the V-ATPase colocalize in IC, that they are concentrated in the IC plasma membrane under conditions that "activate" these proton secretory cells, and that they are both present in an immunoprecipitated complex. This suggests that these enzymes have a close association and could be part of a protein complex that is involved in regulating renal distal proton secretion.

A prospective study of hypertension and the incidence of kidney stones in men

OBJECTIVE

To examine whether hypertension predicts the incidence of kidney stone disease.

DESIGN

Prospective cohort study (the Olivetti Prospective Heart Study).

SETTING

The Olivetti factory in Southern Italy.

SUBJECTS

Five hundred and three male workers, aged 21 - 68 years, with no evidence of kidney stone disease at baseline. Follow-up 8 years.

MAIN OUTCOME MEASURES

Anthropometry, blood pressure, biochemistry and history of kidney stone disease were evaluated at the baseline examination in 1987. Occurrence of kidney stone disease was evaluated again in 1994-1995. Hypertension was defined as systolic blood pressure > or = 160 or diastolic blood pressure, > or = 95 mmHg or both, or being on drug therapy for hypertension. Occurrence of kidney stone disease was defined as radiological or echographic evidence of calculi or documented passage of one or more stones.

RESULTS

At baseline, 114/503 men (22.7%) had hypertension and 32 were on drug treatment. After 8 years, 52 (10.3%) incident cases of kidney stone disease were detected. The majority (n = 45) had a documented passage of one or more stones. The incidence of kidney stone disease was higher in hypertensive than in normotensive men (19/114 (16.7%) versus 33/389 (8.5%); P = 0.011). Hypertensive men had a greater risk of developing kidney stones than normotensive ones (RR 1.96; 95% confidence interval 1.16-3.32). The risk was unaffected by the exclusion of treated hypertensives (2.01; 1.13-3.59) and after adjustment for age (1.89; 1.12-3.18), body weight (1.78; 1.05-3.00) or height (2.00; 1.19-3.38).

CONCLUSIONS

Hypertension in middle-aged men is a significant predictor of kidney stone disease rather than a consequence of renal damage caused by the kidney stones.

Pathophysiology of the cardio-renal syndromes types 1-5: An uptodate

According to the recent definition proposed by the Consensus conference on Acute Dialysis Quality Initiative Group, the term cardio-renal syndrome (CRS) has been used to define different clinical conditions in which heart and kidney dysfunction overlap. Type 1 CRS (acute cardio- renal syndrome) is characterized by acute worsening of cardiac function leading to AKI (5, 6) in the setting of active cardiac disease such as ADHF, while type - 2 CRS occurs in a setting of chronic heart disease. Type 3 CRS is closely link to acute kidney injury (AKI), while type 4 represent cardiovascular involvement in chronic kidney disese (CKD) patients. Type 5 CRS represent cardiac and renal involvement in several diseases such as sepsis, hepato - renal syndrome and immune - mediated diseases.

Idiopathic restrictive cardiomyopathy in children

OBJECTIVE

To define the natural history of idiopathic restrictive cardiomyopathy in a paediatric population and to identify any factors predictive of outcome.

DESIGN

Retrospective analysis of patients born between 1970 and 2002 were identified from the Children's Hospital of Pittsburgh cardiology database. Demographic data, mode of presentation, echocardiographic and haemodynamic findings at diagnosis, survival time, and manner of death were evaluated.

SETTING

Tertiary referral and transplant centre for paediatric patients with cardiac disease.

PATIENTS

All local and referred patients with idiopathic restrictive cardiomyopathy born after 1970 and under 21 years of age at time of diagnosis.

RESULTS

21 patients were identified. Probability of survival at 1, 5, and 10 years was 80.5% (95% confidence interval (CI) 58 to 100), 39% (95% CI 17 to 61), and 20% (95% CI 0 to 42), respectively. Median age of presentation was 3.8 years (mean (SD) 5.7 (6.1) years). Median survival without transplantation was 2.2 years (mean (SD) 4.6 (5.4) years). Age at presentation, sex, and presence or absence of heart failure symptoms at presentation were not associated with clinical course. Right (p = 0.05) and left ventricular end diastolic pressures (p = 0.04) and ratio of left atrial to aortic root dimensions (LA:Ao) (p = 0.03) at presentation had a significantly negative correlation with survival time after diagnosis.

CONCLUSIONS

Without transplantation, most children with restrictive cardiomyopathy have a very poor prognosis. Longer survival from diagnosis was correlated with lower LA:Ao and cardiac filling pressures at diagnosis. Survival time was not influenced by the symptoms present at diagnosis.

Shortened head-up tilt testing potentiated with sublingual nitroglycerin in patients with unexplained syncope

BACKGROUND

Head-up tilt testing is extensively used to determine the vasovagal origin of syncope in patients with otherwise unexplained loss of consciousness, although issues remain regarding the method of the test. The diagnostic value of a shortened head-up tilt test potentiated with sublingual nitroglycerin was assessed in patients with unexplained syncope.

METHODS

Two hundred two patients (mean age 49+/-19 years) with syncope of unknown origin and 34 subjects in a control group (mean age 45+/-17 years) were studied. The patients and the subjects in the control group were tilted upright to 60 degrees for 20 minutes. If syncope did not occur, sublingual nitroglycerin (400 microg) was administered, and observation was continued for 25 more minutes.

RESULTS

During the unmedicated phase syncope occurred in 22 (11%) patients and in one member of the control group. After nitroglycerin was administered, syncope occurred in 119 (59%) patients and in 1 (3%) member of the control group. False-positive response (exaggerated response) was observed in eight (4%) patients and in four (12%) subjects in the control group. The total positivity rate of the test was 70% with a specificity rate of 94%.

CONCLUSIONS

Short-duration head-up tilt test potentiated with sublingual nitroglycerin provides an adequate specificity and positivity rate in patients with unexplained syncope.

Epidemiology, risk and outcomes of venous thromboembolism in cancer

Cancer is associated with a fourfold increased risk of venous thromboembolism (VTE). The risk of VTE varies according to the type of malignancy (i. e. pancreatic cancer, brain cancer, lymphoma) and its disease stage and individual factors (i. e. sex, race, age, previous VTE history, immobilization, obesity). Preventing cancer-associated VTE is important because it represents a significant cause of morbidity and mortality. In order to identify cancer patient at particularly high risk, who need thromboprophylaxis, risk prediction models have become available and are under validation. These models include clinical risk factors, but also begin to incorporate biological markers. The major American and European scientific societies have issued their recommendations to guide the management of VTE in patients with cancer. In this review the principal aspects of epidemiology, risk factors and outcome of cancer-associated VTE are summarized.