Left ventricular mass index increase in early renal disease: impact of decline in hemoglobin

Cardiovascular disease occurs in patients with progressive renal disease both before and after the initiation of dialysis. Left ventricular hypertrophy (LVH) is an independent predictor of morbidity and mortality in dialysis populations and is common in the renal insufficiency population. LVH is associated with numerous modifiable risk factors, but little is known about LV growth (LVG) in mild-to-moderate renal insufficiency. This prospective multicenter Canadian cohort study identifies factors associated with LVG, measured using two-dimensional-targeted M-mode echocardiography. Eight centers enrolled 446 patients, 318 of whom had protocol-mandated clinical, laboratory, and echocardiographic measurements recorded. We report 246 patients with assessable echocardiograms at both baseline and 12 months with an overall prevalence of LVH of 36%. LV mass index (LVMI) increased significantly (>20% of baseline or >20 g/m2) from baseline to 12 months in 25% of the population. Other than baseline LVMI, no differences in baseline variables were noted between patients with and without LVG. However, there were significant differences in decline of Hgb level (-0.854 v -0.108 g/dL; P = 0.0001) and change in systolic blood pressure (+6.50 v -1.09 mm Hg; P = 0.03) between the groups with and without LVG. Multivariate analysis showed the independent contribution of decrease in Hgb level (odds ratio [OR], 1.32 for each 0.5-g/dL decrease; P = 0.004), increase in systolic blood pressure (OR, 1.11 for each 5-mm Hg increase; P = 0.01), and lower baseline LVMI (OR, 0.85 for each 10-g/m2; P = 0.011) in predicting LVG. Thus, after adjusting for baseline LVMI, Hgb level and systolic blood pressure remain independently important predictors of LVG. We defined the important modifiable risk factors. There remains a critical need to establish optimal therapeutic strategies and targets to improve clinical outcomes.

Cardiovascular disease in patients with chronic kidney disease: getting to the heart of the matter

The high prevalence of cardiovascular disease (CVD) in patients with kidney disease is well described. This Canadian, multicenter, observational cohort study reports the prevalence and risk factors of CVD associated with kidney disease, in a cohort of patients with established chronic kidney disease (CKD), who are followed-up by nephrologists. This analysis sought to answer 2 questions: (1) in patients with established CKD, are the prevalence and progression of CVD accounted for by conventional or uremia-related risk factors, and (2) to what extent can progression to renal replacement therapy (RRT) be explained by CVD versus traditional risk factors for kidney disease? This study population consists of 313 patients (predominantly men) who had a mean age of 56 years and a mean creatinine clearance of 36 mL/min. Thirty percent were diabetic. The overall prevalence of CVD was 46%, and was independent of severity of kidney dysfunction (P = 0.700). The median follow-up time was 23 months, for a total of 462 patient years. We note the overall incidence of CVD events (new CVD or worsening of CVD) was 47/244 (20%). The best predictors of new CVD events among those without preexisting CVD were diabetes (odds ratio [OR] = 5.35, P = 0.018) and age (OR = 1.26, P = 0.08). In those with preexisting CVD, low diastolic pressure (DP) (OR =.72, P = 0.004) and high triglycerides (OR = 1.48, P = 0.019) at baseline were independent predictors of progression of CVD. We could not determine an independent impact of kidney function on CVD in the overall cohort. Furthermore, we determined that the presence of CVD itself confers an increased risk for progression to RRT (relative risk [RR] = 1.58, P = 0.047), adjusted for kidney function. This is the first in-depth analysis of CVD in a cohort of patients with established chronic kidney disease who are not on dialysis. The question regarding the impact of the altered biology of uremia in contributing to CVD progression remains unanswered, and clearly needs further study. However, the findings do raise the issue of whether aggressive treatment of CVD and risk factors might, in fact, reduce progression to RRT. Further large-scale, observational studies as well as interventional studies are needed to more clearly understand the complex biology of cardiovascular and kidney disease progression.

Follicle-stimulating hormone regulates oocyte growth by modulation of expression of oocyte and granulosa cell factors

Oocyte-granulosa cell communication is essential for oocyte development. The aims of this study were: 1) to determine the effect of FSH on expression of Kit ligand (KL), growth/differentiation factor-9, bone morphogenetic protein (BMP)-15, and Kit during growth of oocyte-granulosa cell complexes (OGCs) in vitro; 2) to investigate the role of BMP-15 in regulation of KL expression; and 3) to correlate mRNA expression with oocyte growth. OGCs from 12-d-old mice were cultured for up to 7 d in the presence of FSH [0.05 ng/ml (low), 5 ng/ml (high)] or BMP-15 (10 or 100 ng/ml). Transcripts were quantified using real-time RT-PCR, and oocyte and OGC diameters were measured. FSH regulated KL expression in a biphasic manner, with low FSH decreasing the KL-1/KL-2 ratio, and high FSH increasing the KL-1/KL-2 ratio, compared with controls (P < 0.05). The decrease in KL-1/KL-2 ratio with low FSH was due to increased KL-2 mRNA expression. Both FSH concentrations increased OGC diameter (P < 0.05), but only low FSH promoted oocyte growth (P < 0.05). High FSH also decreased BMP-15 expression (P < 0.05). FSH-stimulated oocyte growth was inhibited by Gleevec, an inhibitor of Kit activity. BMP-15 increased both KL-1 and KL-2 mRNA levels in a dose-dependent manner (P < 0.05) but did not alter the KL-1/KL-2 ratio or promote oocyte growth. When the KL-1/KL-2 ratio was increased by exogenous KL-1, FSH-stimulated oocyte growth was suppressed (P < 0.05), suggesting that lowered KL-1/KL-2 ratio is important for oocyte growth. In summary, the correct concentration of FSH is crucial for appropriate modulation of KL and BMP-15 to promote oocyte growth.

Animal models of ovarian cancer

Ovarian cancer is the most lethal of all of the gynecological cancers and can arise from any cell type of the ovary, including germ cells, granulosa or stromal cells. However, the majority of ovarian cancers arise from the surface epithelium, a single layer of cells that covers the surface of the ovary. The lack of a reliable and specific method for the early detection of epithelial ovarian cancer results in diagnosis occurring most commonly at late clinical stages, when treatment is less effective. In part, the deficiency in diagnostic tools is due to the lack of markers for the detection of preneoplastic or early neoplastic changes in the epithelial cells, which reflects our rather poor understanding of this process. Animal models which accurately represent the cellular and molecular changes associated with the initiation and progression of human ovarian cancer have significant potential to facilitate the development of better methods for the early detection and treatment of ovarian cancer. This review describes some of the experimental animal models of ovarian tumorigenesis that have been reported, including those involving specific reproductive factors and environmental toxins. Consideration has also been given to the recent progress in modeling ovarian cancer using genetically engineered mice.

Roles of activin and its signal transduction mechanisms in reproductive tissues

Activins were identified initially as gonadal proteins having a stimulating effect on FSH production by the pituitary gland. Strong evidence has accumulated that activins are important regulating factors for many reproductive processes. Activin may have paracrine or autocrine roles rather than solely an endocrine action on FSH secretion. Activins together with their signalling molecules must be shown to be produced locally in a particular tissue to provide support for their paracrine or autocrine action in that tissue. The discovery of the activin receptors, the intracellular signalling mediators (Smads) and some transcription co-factors involved in activin responses has helped to unravel the activin-transforming growth factor beta signalling mechanism. However, few reports have clearly demonstrated the presence of all of the activin signalling molecules in reproductive tissues, despite the important roles of activin in these tissues. Several activin receptor types and Smad molecules have been identified, indicating either a redundancy in signalling molecules or different signalling pathways. At present, it is not clear which particular subset of these signalling molecules is important in reproductive processes. The aim of this review is to collate the information available on activin actions, as well as on the signalling molecules, to understand how activins may transduce their paracrine or autocrine signals in reproductive tissues.

Expression of activin receptors, follistatin and betaglycan by human endometrial stromal cells; consistent with a role for activins during decidualization

Decidualization of the human endometrium is critical for implantation, but the mechanisms involved are largely unknown. Activin subunits are expressed in endometrium during decidualization. From its known actions in cell differentiation and tissue remodelling, we hypothesized that activin A is involved in the paracrine regulation of decidualization. We examined the expression of activin receptors (ActRs) by semi-quantitative and real-time RT-PCR. mRNA for all ActR subtypes (Ia, Ib, IIa and IIb) was detected in endometrium, with maximal expression in the early secretory phase and in early pregnancy. ActR protein was localized exclusively to stromal and endothelial cells. This expression pattern was confirmed by in-situ hybridization. Activin bioavailability is locally regulated by its binding protein, follistatin, and also by the antagonist, inhibin. Inhibin competition for ActRII binding is enhanced by the binding protein, betaglycan. Follistatin and betaglycan were also detected in the endometrium, localized to stromal and epithelial cells. This co-expression of activin subunits, receptors and binding proteins indicates that stromal cells are capable of responding to activin, and that there is tight local regulation of activin action within the endometrium. As activin production is up-regulated in decidual cells, this provides further evidence for an involvement of activins during stromal cell decidualization.

Lithium poisoning treated by high-performance continuous arteriovenous and venovenous hemodiafiltration

Intermittent hemodialysis is considered the modality of choice when enhanced lithium removal is indicated. However, postdialysis rebound in serum lithium concentration is frequently observed after the dialysis sessions and results from incomplete intracellular removal. Continuous renal replacement therapy could provide a more gradual and complete lithium removal since it is performed over longer time periods, thus avoiding rebound following therapy. Seven patients presenting with symptomatic lithium intoxication were treated by continuous renal replacement therapy (continuous arteriovenous and venovenous hemodiafiltration [CAVHDF and CVVHDF]). For CAVHDF, the dialysate flow rate was increased to 4 L/hr to optimize solute clearances. Five intoxicated patients (four acute and one chronic) were treated by high dialysate flow rate (HDFR) (4 L/hr) CAVHDF and two patients with chronic poisoning were treated by CVVHDF, one with a dialysate flow rate of 1 L/hr and one with a dialysate flow rate of 2 L/hr. Serum lithium concentrations for the four acute poisoning cases were 4.0, 4.6, 4.4, and 3.2 mEq/L, at initiation of HDFR CAVHDF, and decreased respectively to 1.2, 0.8, 1.2, and 1.1 mEq/L after 15, 19, 35, and 21 hours of treatment. No lithium rebound was observed over 24 to 36 hours following CAVHDF. For the three chronic intoxication cases, serum lithium concentrations dropped from 1.7, 2.2, and 3.8 mEq/L to 0.7, 0.17, and 0.4 mEq/L, respectively, after 18, 42, and 44 hours of HDFR CAVHDF or CVVHDF. The chronic case treated for only 18 hours presented a slight rebound in lithium level (0.3 mEq/L), whereas no significant rebound was observed for the two other cases treated for longer periods. Mean +/- SEM dialyser urea, lithium, and creatinine clearance during HDFR CAVHDF were 50.5 +/- 5.0, 41.4 +/- 4.6, and 37.6 +/- 3.7 mL/min, respectively (number of measurements = 41). Dialyser lithium clearance during CVVHDF was 48.4 +/- 1.4 mL/min (n = 10) and 61.9 +/- 2.3 mL/min (n = 7), with dialysate flow rates of 1 and 2 L/hr, respectively. Mean dialyzer lithium removal for the seven cases was 106.4 mEq, while mean renal lithium removal was 21.5 mEq during the same period. We conclude that HDFR CAVHDF and CVVHDF are effective alternatives to intermittent hemodialysis for treatment of lithium poisoning. They provide excellent lithium clearances (60 to 85 L/d); in addition, because of their continuous nature, they prevent posttherapy lithium rebound by allowing a more gradual and complete removal from intracellular compartments, and they may be particularly useful in chronic poisoning in which intracellular lithium accumulation is more extensive.

Production and actions of inhibin and activin during folliculogenesis in the rat

Evidence to enhance the premise that inhibin and activin are local regulators of ovarian folliculogenesis is presented in this review. Granulosa cells (GC) have been identified as the source of inhibin/activin in the ovary on the basis of mRNA and protein localisation and the measurement of the inhibin forms in GC conditioned media. Expression of the subunit mRNAs changed with follicular development, being maximal in the ovaries of 8-day-old rats, where secondary follicles predominate. The expression of beta subunit mRNAs by GC isolated from diethylstilboestrol (DES)-treated immature rats, was reduced in the absence of any change in alpha subunit mRNA expression. Dimeric inhibin-A, -B and free alpha subunit were produced by ovarian cell cultures prepared from 4- to 12-day-old rats. Inhibin-A production by these cultures was responsive to FSH and TGF-beta, with preantral follicles of day 8 ovaries exerting effects so profound that the inhibin A/alpha subunit ratio increased, most likely due to a stimulation of beta(A) subunit production. In contrast, inhibin-B was not stimulated by TGF-beta until day 8 and FSH until day 12. Fractionation of GC conditioned media revealed a prominence of free alpha subunit and inhibin-A, but little inhibin-B, suggesting that inhibin-B production declines with follicular development. Activin receptor types I and II, Smads 1-8 and betaglycan (beta-glycan) mRNAs were present in the rat ovary and showed distinct patterns of expression between postnatal days 4 and 12. Oocytes and GC localised activin receptor, Smad and beta-glycan proteins, with beta-glycan also present in theca cells (TC). These data indicate that activin/TGF-beta signalling machinery and factors which influence these pathways, are present in the postnatal rat ovary. Our hypothesis that inhibin and activin play important and changing autocrine/paracrine roles in the growth and differentiation of follicles, including the oocyte, has been supported by these studies.

Activin betaC-subunit heterodimers provide a new mechanism of regulating activin levels in the prostate

Activins are formed by dimerization of beta-subunits and, as members of the TGF-beta superfamily, have diverse roles as potent growth and differentiation factors. As the biological function of the activin C homodimer (betaC-betaC) is unknown, we sought to compare activin A (betaA-betaA), B (betaB-betaB), and C homodimer bioactivities and to investigate the consequences of activin betaC-subunit overexpression in prostate tumor cells. Exogenous activin A and B homodimers inhibited cell growth and activated activin-responsive promoters. In contrast, the activin C homodimer was unable to elicit these responses. We previously showed that the activin betaC-subunit heterodimerized with activin betaA in vitro to form activin AC. Therefore, we hypothesize that the activin betaC-subunit regulates the levels of bioactive activin A by the formation of activin AC heterodimers. To test this hypothesis, we measured activin AC heterodimer production using a novel specific two-site ELISA that we developed for this purpose. In the PC3 human prostate tumor cell line, activin betaC-subunit overexpression increased activin AC heterodimer levels, concomitantly reduced activin A levels, and decreased activin signaling. Overall, these data are consistent with a role for the activin betaC-subunit as a regulatory mechanism to reduce activin A secretion via intracellular heterodimerization.

Bovine SRY gene locus: cloning and testicular expression

The bovine SRY gene was cloned by a combination of anchored polymerase chain reaction (PCR) amplification of genomic restriction fragments and reverse transcription-PCR (RT-PCR) of testicular RNA. We report 1800 bp of combined genomic and cDNA sequences including 911 bp of 5' upstream sequences, an open reading frame of 687 bp, and 202 bp of sequences corresponding to the 3' end of the mRNA. The bovine SRY gene encodes a deduced (predicted on the basis of a cDNA sequence) protein product of 229 amino acids, with sequence conservation between species, notably in the region of the high-mobility group (HMG) domain or HMG box. Outside of the HMG box, the bovine SRY structure shows greater resemblance to the human SRY than to the mouse Sry. As with human SRY promoter sequences, putative binding sites for Sp1 and for SRY itself are seen in the bovine SRY promoter region. Unlike the human SRY promoter, CAAT and TATA box motifs are present in the bovine sequences. Southern analysis and PCR amplification of male and female bovine genomic DNA show that the described sequences are specific to the Y chromosome. Northern analysis of bull testicular RNA demonstrated low levels of expression of the bovine SRY gene in adult testes with a major poly(A) species at 1.9 kb. RT-PCR amplification of bull testicular RNA revealed multiple sites of polyadenylation, but sequencing showed no consensus polyadenylation signal.

Veno-venous continuous renal replacement therapy for burned patients with acute renal failure

From 1995 to 1998, 12 burned patients with acute renal failure (ARF) were treated by veno-venous continuous renal replacement therapy (CRRT) at the Burn Unit of Hôtel-Dieu de Montréal. Their mean (+/-SD) age was 51+/-12 years, and the mean burned surface covered 48.6+/-15.8% of total body surface area. All patients were mechanically ventilated and presented evidence of sepsis. The mean delay before occurrence of ARF was 15+/-6 days and ARF was mainly related to sepsis and hypotension. Main reasons for CRRT initiation were azotemia and fluid overload. A total of 15 CRRT modalities were applied (12 continuous veno-venous hemodiafiltration, CVVHDF; two continuous veno-venous hemofiltration, CVVH; and one continuous veno-venous hemodialysis, CVVHD) over 14+/-13 days. For CRRT, nine patients received heparin and three were not anticoagulated. Mean values for dialysate and reinjection flow rates were 1134+/-250 ml/h and 635+/-327 ml/h, respectively. Admission weight was 78.8+/-12.7 kg with a mean weight gain before CRRT initiation of 10.0+/-5.8 kg and a mean weight loss during CRRT of 8.9+/-5.5 kg. Nine patients received enteral plus parenteral nutrition, and three, parenteral nutrition only; the total caloric intake was 31.5+/-7.0 kcal/kg/day and protein intake, 1.8+/-0.4 g/kg/day. The normalized protein catabolic rate (nPCR) was evaluated at 2.28+/-0.78 g/kg/day during CRRT. The mortality rate was 50%. The six survivors all recovered normal renal function with four of them requiring intermittent hemodialysis for short periods. In conclusion, veno-venous CRRT is particularly well suited for this selected population allowing smooth fluid removal and aggressive nutritional support.

A unified structural/terminological interoperability framework based on LexEVS: application to TRANSFoRm

OBJECTIVE

Biomedical research increasingly relies on the integration of information from multiple heterogeneous data sources. Despite the fact that structural and terminological aspects of interoperability are interdependent and rely on a common set of requirements, current efforts typically address them in isolation. We propose a unified ontology-based knowledge framework to facilitate interoperability between heterogeneous sources, and investigate if using the LexEVS terminology server is a viable implementation method.

MATERIALS AND METHODS

We developed a framework based on an ontology, the general information model (GIM), to unify structural models and terminologies, together with relevant mapping sets. This allowed a uniform access to these resources within LexEVS to facilitate interoperability by various components and data sources from implementing architectures.

RESULTS

Our unified framework has been tested in the context of the EU Framework Program 7 TRANSFoRm project, where it was used to achieve data integration in a retrospective diabetes cohort study. The GIM was successfully instantiated in TRANSFoRm as the clinical data integration model, and necessary mappings were created to support effective information retrieval for software tools in the project.

CONCLUSIONS

We present a novel, unifying approach to address interoperability challenges in heterogeneous data sources, by representing structural and semantic models in one framework. Systems using this architecture can rely solely on the GIM that abstracts over both the structure and coding. Information models, terminologies and mappings are all stored in LexEVS and can be accessed in a uniform manner (implementing the HL7 CTS2 service functional model). The system is flexible and should reduce the effort needed from data sources personnel for implementing and managing the integration.

Porcine and bovine steroidogenic acute regulatory protein (StAR) gene expression during gestation

We have generated complete complementary DNA (cDNA) sequences for the porcine steroidogenic acute regulatory protein (StAR) gene, using a combination of genomic PCR amplification and reverse transcription-PCR amplification of pig ovarian cDNA. Porcine StAR cDNA consists of 855 bp and shares 90.2%, 87.3%, 84.3%, and 83.9% homologies with bovine, human, mouse, and rat StAR cDNA at the nucleotide level, and 89.1%, 88.8%, 86.7%, and 86.3% homologies with bovine, human, mouse, and rat StAR protein at the deduced amino acid level. Northern analysis of porcine StAR showed that it is expressed in adult and fetal steroidogenic tissues, including adult testes and ovaries and adult adrenal glands as well as steroidogenic tissues of pregnancy, including developing fetal testes, corpus luteum, and pregnancy, but not the fetal ovary. Major hybridizing bands of 1.8 and 1.1 kilobases were demonstrated. In contrast to human StAR, porcine StAR was not expressed in adult or fetal kidneys. Expression of porcine StAR by the pig placenta is in contrast to human StAR, which is not expressed by the human placenta. Northern analysis of bovine cotyledons using a homologous probe for bovine StAR showed that StAR is also expressed by the placenta in the bovine animal. With respect to placental expression of StAR, variations may exist among mammalian species.

Porcine SRY gene locus and genital ridge expression

Porcine SRY gene locus was cloned through use of a strategy of anchored polymerase chain reaction (PCR) amplification from a male pig genomic DNA size-selected library constructed in a plasmid vector as well as 3' reverse transcription (RT)-PCR amplification of porcine genital ridge SRY transcripts. In total, 1664 bp of genomic DNA and 106 bp of 3' cDNA are presented. The open reading frame of porcine SRY consists of 624 bp representing 208 amino acids (aa) with a centrally located HMG box domain of 79 aa, an amino-terminal region of 59 aa, and a carboxy terminal of 70 aa. Structurally, porcine SRY resembles human and bovine SRY more closely than it does mouse Sry, and it lacks the carboxy-terminal activation domain seen in the mouse Sry molecule. Similar to human and bovine testicular SRY transcripts, the porcine SRY genital ridge transcript has a relatively short 3' untranslated region (UTR), in contrast to the extended UTR of the mouse genital ridge Sry transcript. The porcine SRY gene is expressed within the cells of the genital ridge of the developing male pig embryo between Days 21 and 26 (e21-e26) of gestation, during which time the primitive gonads are bipotential, but not on Day e31, by which time male testis determination is histologically evident.

Transforming growth factor-beta modulates inhibin A bioactivity in the LbetaT2 gonadotrope cell line by competing for binding to betaglycan

Activin stimulates expression of GnRH receptor (GnRHR) and FSH beta-subunit in gonadotropes. Inhibin antagonizes activin actions on the gonadotropes, but its molecular mechanism of action remains poorly understood. It has been suggested that inhibin exerts its antagonistic effects by competing with activin for the binding of the activin receptor complex. Betaglycan has recently been identified as an inhibin-binding accessory protein in this process. Because both inhibin and TGFbeta bind betaglycan, we examined whether TGFbeta can modify inhibin's antagonism of activin-induced transcription in gonadotrope cells. Two activin-responsive reporter constructs were used, the first containing 5.5 kb of the ovine FSHbeta promoter (oFSHbetaluc), and the second containing three copies of the activin-responsive sequence of the GnRHR promoter (3XGRAS-PRL-lux). These constructs were transfected into the gonadotrope cell line LbetaT2. The oFSHbetaluc and 3XGRAS-PRL-lux activities stimulated by 0.5 nM activin A were decreased by up to 50% in a dose-dependent manner by inhibin A. TGFbeta(1) and TGFbeta(2) (0-4 nM), alone or in the presence of activin A, did not significantly affect the promoter elements. However, with increasing doses of TGFbeta(1) or TGFbeta(2), inhibin A antagonism of activin A activity was partly or completely reversed. Competition studies with radiolabeled inhibin A showed that TGFbeta(1) and TGFbeta(2) competed with [(125)I]inhibin for the binding to LbetaT2 cells (IC(50) = 280 pM and 72 pM, respectively). Immunoprecipitation studies of [(125)I]inhibin A cross-linked receptor complexes confirmed that TGFbeta(1) and TGFbeta(2) competed with inhibin A for the binding of betaglycan. These results suggest that TGFbeta competition with inhibin for binding to betaglycan interferes with inhibin's suppression of activin-induced FSHbeta and GnRHR promoters in LbetaT2 cells. We propose that under certain circumstances, TGFbeta may facilitate activin biological activity by hindering the access of inhibin to its coreceptor betaglycan.

Topological analysis and role of the transmembrane domain in polar targeting of PilS, a Pseudomonas aeruginosa sensor kinase

In Pseudomonas aeruginosa, synthesis of pilin, the major protein subunit of the pili, is regulated by a two-component signal transduction system in which PilS is the sensor kinase. PilS is an inner membrane protein found at the poles of the bacterial cell. It is composed of three domains: an N-terminal hydrophobic domain; a central cytoplasmic linker region; and the C-terminal transmitter region conserved among other sensor kinases. The signal that activates PilS and, consequently, pilin transcription remains unknown. The membrane topology of the hydrophobic domain was determined using the lacZ and phoA gene fusion approach. In this report, we describe a topological model for PilS in which the hydrophobic domain forms six transmembrane helices, whereas the N- and C-termini are cytoplasmic. This topology is very stable, and the cytoplasmic C-terminus cannot cross the inner membrane. We also show that two of the six transmembrane segments are sufficient for membrane anchoring and polar localization of PilS.

Renal function recovery in end-stage renal disease

Renal function recovery (RFR) is a rare event in patients with end-stage renal disease (ESRD). Although some predictive factors have been described, there are still unresolved questions. We have analyzed the Canadian Organ Replacement Register data for the 1981 to 1989 period to assess the incidence and factors predictive of RFR in a large ESRD population as well as the outcome after recovery. Renal function recovery was defined as the interruption of renal replacement therapy (RRT) for more than 3 months. Patients on RRT for < or = 45 days were excluded. Of 14,318 registered ESRD patients, 342 (2.4%) experienced RFR after 8.9 +/- 0.5 months of RRT (mean +/- SEM); 52.3% of the recoveries occurred within 6 months of initiating RRT, while 23.7% were only observed after 12 months or more. By Cox regression, patients within the following diagnostic groups had a significantly higher rate of RFR than those with primary glomerulonephritis, who are considered to comprise the reference group: myeloma (relative rate [RR] = 6.00; P < 0.001), drug-induced disease (RR = 4.21; P < 0.001), vascular/hypertensive disease (RR = 2.60; P < 0.001), and systemic disease (RR = 2.58; P < 0.001). Inversely, patients with polycystic kidneys (RR = 0.06; P = 0.004) and diabetic patients (RR = 0.56; P = 0.024) had a lower rate of RFR than those with glomerulonephritis. Men younger than 45 years had a lower rate of RFR than older men and women of all ages (P < or = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Preliminary findings from a teleultrasound study in Alberta

BACKGROUND AND OBJECTIVES

Ultrasound practice in Alberta requires direct supervision by an ultrasound-accredited specialist physician (sonologist). This requirement limits access to ultrasound examinations in many rural communities. A prospective study was performed to evaluate the adequacy of teleultrasound service in High Level, Alberta, with remote sonologist supervision from Edmonton, Alberta.

METHODS

A total of 146 patients were evaluated in two groups. Group A (72 patients) was evaluated by both an on-site radiologist in High Level and a remote supervising radiologist in Edmonton. Group B (74 patients) was evaluated only by the remote supervising radiologist in Edmonton. The teleultrasound service included digital store-and-forward capabilities using a commercially available teleradiology system, with videoconferencing review for real-time scanning.

RESULTS

The teleultrasound service was helpful to the referring physician. It made transfer unnecessary in 42% of patients, and the results of the ultrasound assessment influenced management in 59% of patients. The sonographer on site and the remote radiologists agreed on the quality of the images. The information required for diagnosis was available from the sonographer's study in the majority of cases, with second-look scanning by the on-site radiologist or videoconferencing by the remote radiologist providing a major new diagnosis in only 1% of patients.

CONCLUSION

Teleultrasound service to High Level could be provided reliably with remote supervision, comparable to direct on-site supervision.

What is responsible for the diurnal variation in potassium excretion?

Potassium excretion exhibits a diurnal pattern, with most excretion occurring close to noon in humans. Each component of the K+ excretion rate [urinary K+ concentration ([K+]) and flow rate] was measured and back-calculated to reflect events in the cortical collecting duct (CCD). Our purpose was to determine to what extent each component contributed to this diurnal variation in each 2-h portion of the day. In humans, K+ excretion rose threefold from nadir (0600 h) to peak (1200-1400 h), 18 h after the principal intake of K+. The variation in K+ excretion was due almost exclusively to changes in [K+] in the terminal CCD ([K+]CCD) rather than via changes in flow rate. In rats, the bulk of K+ excretion occurred shortly after eating. Both components of K+ excretion rose after meals; the rise in the [K+]CCD (3.3-fold) predominated at earlier times, and the rise in flow rate occurred later and was primarily a result of a higher rate of excretion of urea. The rise in [K+]CCD did not correlate with aldosterone levels or administration. A very large rise in the [K+]CCD only occurred in the presence of bicarbonaturia; the transtubular potassium concentration gradient was now close to 15 in the morning and evening.

Bovine thyrotropin receptor cDNA is characterized by full-length and truncated transcripts

The complete coding sequence for the bovine thyrotropin (TSH) receptor was derived using a modified PCR cloning strategy. The bovine thyrotropin receptor conforms to the pattern of receptor interacting with membrane-bound G-protein already established in other species for TSH and gonadotropins receptors. The cDNA for the bovine TSH receptor consists of an open reading frame 2289 nucleotides in length, corresponding to a protein of 763 amino acids (estimated molecular mass of 86.4 kDa) which includes a 20 amino acid putative leading signal peptide. The receptor consists of a large NH2-terminal extracellular membrane domain of 417 amino acids with 5 potential N-linked glycosylation sites, a transmembrane domain (265 amino acids) consisting of 7 putative membrane alpha-helix spanning segments, and an intracytoplasmic COOH-terminal domain (82 amino acids). The bovine TSH receptor is one amino acid less than the corresponding sequence in dog, human, rat and mouse. Cysteine residues (n = 22) were conserved when compared with other TSH receptors. Three potential phosphorylation sites were found in the transmembrane domain and the COOH-terminal domain. As with other members of this receptor family, alternative splicing was observed. A transcribed but truncated TSH receptor of 1769 nucleotides was demonstrated, lacking half of the V segment of the transmembrane domain up to the COOH-terminal domain of the full length TSH receptor. Additionally, alternative transcriptional start sites were observed. Northern blot analysis using a probe (1170 bp) spanning part of the extracellular domain up to the first loop of the transmembrane domain showed specific expression in the bovine thyroid gland with major transcripts of 9.3 and 4.3 kb, and a minor transcript of 3.8 kb being detected.

Bovine activin receptor type II cDNA: cloning and tissue expression

The cDNA encoding the bovine activin type II receptor has been cloned by reverse transcription-polymerase chain reaction (RT-PCR) amplification of a bovine testicular RNA preparation. Sequence comparisons of the bovine activin type II receptor with its human, mouse and rat homologues show strong evolutionary conservation at the nucleotide level of 94.9%, 93.5%, 92.9% and at the amino acid level of 98.6%, 99.0%, 98.8%, respectively. Bovine activin type II receptor mRNA is widely but not strongly expressed in reproductive tissues, with a major RNA band at 6 kb and minor bands at 5 kb and 3 kb. The differential levels of expression observed in these tissues suggest that levels of bActRII gene expression are regulated. Furthermore, we have observed decreasing levels of the bovine activin type II receptor mRNA with testes maturation.

Cloning and tissue expression of bovine follistatin cDNA

Bovine follistatin cDNA sequences were derived using a cloning strategy based entirely on reverse transcription and polymerase chain reaction amplification of RNA derived from bovine ovarian and testicular tissues. Complete bovine follistatin cDNA coding sequences are presented including 1,029 bases of open reading frame, the 5' translational start codon, and the 3' translational stop codon. Homologies of bovine follistatin cDNA with pig, human, rat, and partial sheep sequences are 94.3%, 92.4%, 89.9%, and 98.4% at the nucleic acid level and 98.3%, 97.1%, 95.6%, and 100% at the deduced amino acid level, respectively. Northern blot analysis on a survey of bovine reproductive tissues showed strongest expression in ovaries collected from superovulated cows and major RNA species at 2.8 Kb and 1.75 Kb.

Bovine activin receptor type IIB messenger ribonucleic acid displays alternative splicing involving a sequence homologous to Src-homology 3 domain binding sites

Activins are implicated in a variety of biological effects, particularly in reproductive processes such as embryonic development and folliculogenesis. Breakthroughs in the elucidation of the activin signal transduction mechanism were achieved with the characterization of the activin receptors, and the recent identification of cytoplasmic factors apparently involved in the signaling process. The present studies were undertaken to further analyze the activin signaling pathway. The complementary DNA coding for the bovine activin receptor type IIB (bActRIIB) was amplified by RT-PCR from corpus luteum and pituitary RNA, and cloned to characterize its role in activin signal transduction. Two complementary DNA isoforms (bActRIIB2 and bActRIIB5) were detected, coding for 512 amino acids and 498 amino acids, respectively. The shortest isoform lacked a sequence encoding a 14-amino acid stretch very rich in proline residues, located between the transmembrane region and the intracellular kinase domain. Intron sequencing and ribonuclease protection assay demonstrated that alternative splicing is responsible for the generation of these bActRIIB isoforms. This alternative splicing event is unique in that it has not been observed in other species, including the mouse, in which extensive alternative splicing of the ActRIIB messenger RNA is described. Comparison of this alternative sequence with other known proline-rich sequences showed that it has characteristics of a Src-homology 3 domain (SH3) binding site. Coprecipitation experiments have identified two proteins of 69 kDa and 71 kDa from an uterine endometrial cell line, specifically interacting with the short bActRIIB alternative proline-rich sequence. These results suggest that bActRIIB could have a protein-protein interaction, through its putative SH3 binding site, with at least two intracellular SH3-containing proteins.