bluuebunny/crossref_metadata_2025 huggingface dataset:
Dual-frequency addressed hybrid-aligned nematic liquid crystal
Authors: Lu Yan-Qing , Liang Xiao , Wu Yung-Hsun , Du Fang , Wu Shin-Tson
Published: October 2004

Dual-frequency addressed hybrid-aligned nematic (HAN) liquid crystal cell is demonstrated as a variable optical attenuator at 1.55μm wavelength. By controlling the low- and high-frequency electric field, the dual-frequency liquid crystal (DFLC) molecules can be reoriented parallel or perpendicular to the substrates so that the maximum obtainable phase modulation is doubled. In comparison to a homogeneous cell, the DFLC HAN cell shows a lower operating voltage and faster response time. Furthermore, the DFLC HAN cell exhibits three stable states that have some applications such as ternary photonic devices.
The relationship between regional and local species diversity in marine benthic communities: A global perspective
Authors: Witman Jon D. , Etter Ron J. , Smith Franz
Published: October 2004

The number of species coexisting in ecological communities must be a consequence of processes operating on both local and regional scales. Although a great deal of experimental work has been devoted to local causes of diversity, little is known about the effects of regional processes on local diversity and how they contribute to global diversity patterns in marine systems. We tested the effects of latitude and the richness of the regional species pool on the species richness of local epifaunal invertebrate communities by sampling the diversity of local sites in 12 independent biogeographic regions from 62°S to 63°N latitude. Both regional and local species richness displayed significant unimodal patterns with latitude, peaking at low latitudes and decreasing toward high latitudes. The latitudinal diversity gradient was represented at the scale of local sites because local species richness was positively and linearly related to regional species richness. The richness of the regional species pool explained 73-76% of local species richness. On a global scale, the extent of regional influence on local species richness was nonrandom—the proportion of regional biota represented in local epifaunal communities increased significantly from low to high latitudes. The strong effect of the regional species pool implies that patterns of local diversity in temperate, tropical, and high-latitude marine benthic communities are influenced by processes operating on larger spatiotemporal scales than previously thought.
Formation of deletions during double-strand break repair in
Drosophila
DmBlm mutants occurs after strand invasion
Authors: McVey Mitch , LaRocque Jeannine R. , Adams Melissa D. , Sekelsky Jeff J.
Published: October 2004

Bloom syndrome is a rare disorder associated with cancer predisposition and genomic instability and is caused by loss of the RecQ helicase BLM. The
Drosophila
ortholog of BLM (DmBlm) is required for accurate repair of DNA double-strand gaps by homologous recombination. Repair products from DmBlm mutants have shorter repair synthesis tract lengths compared to wild type and are frequently associated with deletions flanking the break site. To determine the mechanisms responsible for deletion formation in the absence of DmBlm, we characterized repair after excision of the
P
{
w
a
} element in various genetic backgrounds. Flies lacking DmRad51 do not have an elevated deletion frequency. Moreover, loss of DmRad51 suppresses deletion formation in DmBlm mutants. These data support a model in which DmBlm acts downstream of strand invasion to unwind a D-loop intermediate to free the newly synthesized strand. In the absence of DmBlm, alternative pathways of D-loop disassembly result in short repair synthesis tracts or flanking deletions. This model explains how RecQ helicases can promote homologous recombination while preventing illegitimate recombination.
A reexamination of the evidence for the somatic marker hypothesis: What participants really know in the Iowa gambling task
Authors: Maia Tiago V. , McClelland James L.
Published: October 2004

Bechara, Damasio, and coworkers [Bechara, A., Damasio, H., Tranel, D. & Damasio, A. R. (1997)Science275, 1293–1295] have reported that normal participants decide advantageously before knowing the advantageous strategy in a simple card game designed to mimic real-life decision-making. Becharaet al. have used this result to support their view that nonconscious somatic markers can guide advantageous behavior. By using more sensitive methods, we show that participants have much more knowledge about the game than previously thought. In fact, participants report knowledge of the advantageous strategy more reliably than they behave advantageously. Furthermore, when they behave advantageously, their verbal reports nearly always reveal evidence of quantitative knowledge about the outcomes of the decks that would be sufficient to guide such advantageous behavior. In addition, there is evidence that participants also have access to more qualitative reportable knowledge. These results are compatible with the view that, in this task, both overt behavior and verbal reports reflect sampling from consciously accessible knowledge; there is no need to appeal to nonconscious somatic markers. We also discuss the findings of other studies that similarly suggest alternative interpretations of other evidence previously used to support a role for somatic markers in decision-making.
PSORTb v.2.0: Expanded prediction of bacterial protein subcellular localization and insights gained from comparative proteome analysis
Authors: Gardy J. L. , Laird M. R. , Chen F. , Rey S. , Walsh C. J. , Ester M. , Brinkman F. S. L.
Published: October 2004

Motivation: PSORTb v.1.1 is the most precise bacterial localization prediction tool available. However, the program's predictive coverage and recall are low and the method is only applicable to Gram-negative bacteria. The goals of the present work are as follows: increase PSORTb's coverage while maintaining the existing precision level, expand it to include Gram-positive bacteria and then carry out a comparative analysis of localization.

Results: An expanded database of proteins of known localization and new modules using frequent subsequence-based support vector machines was introduced into PSORTb v.2.0. The program attains a precision of 96% for Gram-positive and Gram-negative bacteria and predictive coverage comparable to other tools for whole proteome analysis. We show that the proportion of proteins at each localization is remarkably consistent across species, even in species with varying proteome size.

Availability: Web-based version: http://www.psort.org/psortb. Standalone version: Available through the website under GNU General Public License.

Contact:  psort-mail@sfu.ca, brinkman@sfu.ca

Supplementary information:  http://www.psort.org/psortb/supplementaryinfo.html
Comparison of different melting temperature calculation methods for short DNA sequences
Authors: Panjkovich Alejandro , Melo Francisco
Published: October 2004

Motivation: The overall performance of several molecular biology techniques involving DNA/DNA hybridization depends on the accurate prediction of the experimental value of a critical parameter: the melting temperature Tm. Till date, many computer software programs based on different methods and/or parameterizations are available for the theoretical estimation of the experimental Tm value of any given short oligonucleotide sequence. However, in most cases, large and significant differences in the estimations of Tm were obtained while using different methods. Thus, it is difficult to decide which Tm value is the accurate one. In addition, it seems that most people who use these methods are unaware about the limitations, which are well described in the literature but not stated properly or restricted the inputs of most of the web servers and standalone software programs that implement them.

Results: A quantitative comparison on the similarities and differences among some of the published DNA/DNA Tm calculation methods is reported. The comparison was carried out for a large set of short oligonucleotide sequences ranging from 16 to 30 nt long, which span the whole range of CG-content. The results showed that significant differences were observed in all the methods, which in some cases depend on the oligonucleotide length and CG-content in a non-trivial manner. Based on these results, the regions of consensus and disagreement for the methods in the oligonucleotide feature space were reported. Owing to the lack of sufficient experimental data, a fair and complete assessment of accuracy for the different methods is not yet possible. Inspite of this limitation, a consensus Tm with minimal error probability was calculated by averaging the values obtained from two or more methods that exhibit similar behavior to each particular combination of oligonucleotide length and CG-content class. Using a total of 348 DNA sequences in the size range between 16mer and 30mer, for which the experimental Tm data are available, we demonstrated that the consensus Tm is a robust and accurate measure. It is expected that the results of this work would be constituted as a useful set of guidelines to be followed for the successful experimental implementation of various molecular biology techniques, such as quantitative PCR, multiplex PCR and the design of optimal DNA microarrays.

Availability: A binary software distribution to calculate the consensus Tm described in this work for thousands of oligonucleotides simultaneously for the LINUX operating system is freely available upon request to the authors or from our website http://protein.bio.puc.cl/melting-temperatures.html

Contact:  fmelo@bio.puc.cl

Supplementary information: The large set of oligonucleotides, the detailed results of the comparative and accuracy benchmarks, and hundreds of comparative graphs generated during this work are available at our website http://protein.bio.puc.cl/melting-temperatures.html
ATP Depletion Of Tubular Cells Causes Dissociation of the Zonula Adherens and Nuclear Translocation of β-Catenin and LEF-1
Authors: Price Valerie R. , Reed Christine A. , Lieberthal Wilfred , Schwartz John H.
Published: October 2004

This study examined the events associated with the reversible disruption of the structural and functional integrity of the zonula occludens (ZA) induced by ATP depletion of renal tubular cells. It shows that loss of the ZA after ATP depletion is associated with the withdrawal of E-cadherin, α-catenin, and β-catenin, probably as intact cadherin-catenin complexes from the basolateral membrane of tubular cells. The relative amounts of all three proteins increased in the Triton X-100–insoluble fraction of cell lysates and decreased in the Triton X-100–soluble pool. These changes were reversed with repletion of cell ATP. It is additionally shown that ATP depletion induces nuclear translocation of β-catenin and T cell factor (TCF)/lymphoid enhancer factor–1 (LEF-1), a transcriptional factor with which β-catenin associates. The redistribution of the ZA proteins as intact E-cadherin-catenin complexes from the plasma membrane facilitates the rapid recovery of the ZA after sublethal ischemic injury. The translocation of β-catenin and TCF/LEF-1 to the nucleus indicates that ATP depletion may activate the wnt/wingless signal transduction pathway. Thus, entirely novel evidence is provided that both of the known roles of β-catenin, as a structural part of the ZA and as a component of the wnt/wingless pathway, play a role after sublethal ischemic injury to tubular cells. It is also speculated that the nuclear translocation of β-catenin and TCF/LEF-1 modulates gene expression after ischemic injury and may contribute to events necessary for renal regeneration and repair after ischemic injury.
The Hypertrophic Effect of Transforming Growth Factor-β is Reduced in the Absence of Cyclin-Dependent Kinase-Inhibitors p21 and p27
Authors: Monkawa Toshiaki , Hiromura Keiju , Wolf Gunter , Shankland Stuart J
Published: October 2004

Transforming growth factor-β (TGF-β) has both antiproliferative and hypertrophic effects on mesangial cells (MC). However, it is not known if these processes are independent or if they share common signaling pathways. Proliferation and hypertrophy are regulated by specific cell-cycle regulatory proteins, where the cyclin-dependent kinase (CDK) inhibitors inhibit target cyclin-CDK complexes. This study examined whether the growth regulatory effects of TGF-β were determined by the CDK inhibitors p21 and p27. Accordingly, cultured MC from wild type (+/+) and single and double null (−/−) p21 and p27 mice were grown in 5% serum in the presence or absence of TGF-β1 (2 ng/ml). Proliferation ([3H]-thymidine incorporation, cell number, cell cycle) and hypertrophy ([3H]-leucine incorporation, total protein content, forward light scatter) were measured after 24 h, 48 h, and 96 h. TGF-β inhibited proliferation in +/+ and p21/p27 double −/− MC to a similar extent. TGF-β induced hypertrophy in +/+ MC (18.0% increase at 48 h), and to lesser extent in p21 −/− (12.8%) and p27 −/− MC (11.5%) measured by forward light scatter analysis. In p21/p27 double −/−, the hypertrophic effects of TGF-β were significantly reduced (3.9% at 48 h). Similar results were obtained by measuring hypertrophy by total protein and [3H]-leucine incorporation. In conclusion, the CDK inhibitors p21 and p27 are not required for the antiproliferative effects of TGF-β. However, the hypertrophic growth effects of TGF-β are reduced in the absence of both p21 and p27. These data suggest that the regulation of the antiproliferative and hypertrophic effects of TGF-β may be distinct processes.
Trends in Anemia Management among US Hemodialysis Patients
Authors: Coladonato Joseph A. , Frankenfield Diane L. , Reddan Donal N. , Klassen Preston S. , Szczech Lynda A. , Johnson Curtis A. , Owen William F.
Published: October 2004

This study was undertaken to describe the relationship between hematocrit (Hct) and changes in the prescribed dose of erythropoietin (EPO) as well as selected patient and process care measures across annual national samples of hemodialysis patients from 1994 to 1998. This study uses the cohorts identified in the ESRD Core Indicators Project, random samples of 6181, 6241, 6364, 6634, and 7660 patients, stratified by ESRD Networks drawn for each year from 1994 to 1998. Patient demographic and clinical information was collected from October to December for each year. Surrogates of iron stores and patterns of iron and EPO administration were profiled from 1996 to 1998. Multivariable stepwise linear regression analyses were performed to adjust for potential confounding variables and to identify independent variables associated with Hct and EPO dose. Mean Hct and EPO dose increased each year from 31.1 ± 5.2% to 34.1 ± 3.7% and from 58.2 ± 41.8 U/kg to 68.2 ± 55.0 U/kg, respectively (P = 0.0001). Increasing Hct was positively associated with male gender, more years on dialysis, older age, higher urea reduction ratio and transferrin saturation, prescription of intravenous iron, and lower ferritin and EPO dose in multivariable models (all P = 0.0001). Male gender, older age, diabetes, higher Hct, and increasing weight, urea reduction ration, and transferrin saturation were associated with lower EPO doses (all P < 0.01). Conversely, intravenous EPO and iron were associated with higher prescribed EPO doses (all P = 0.0001). Although increasing Hct is associated with decreasing EPO dose at the patient level, the increase in Hct seen across years among the cohorts of hemodialysis patients in the United States has been associated with increasing doses of EPO at the population level.
Preemptive Kidney Transplantation
Authors: Kasiske Bertram L. , Snyder Jon J. , Matas Arthur J. , Ellison Mary D. , Gill John S. , Kausz Annamaria T.
Published: October 2004

It remains unclear whether preemptive transplantation is beneficial, and if so, who benefits. A total of 38,836 first, kidney-only transplants between 1995 and 1998 were retrospectively studied. A surprising 39% of preemptive transplants were from cadaver donors, and the proportions of cadaver donor transplants that were preemptive changed little, from 7.3% in 1995 to 7.7% in 1998. Preemptive transplants using cadaver donors were more likely among recipients aged 0 to 17 yr versus 18 to 29 yr (odds ratio [OR], 2.48; 95% confidence interval [CI], 1.94 to 3.17), white versus black (OR, 2.33; 95% CI, 2.03 to 2.68), able to work versus unable to work (OR, 1.42; 95% CI, 1.26 to 1.61), covered by private insurance versus Medicare (OR, 4.77; 95% CI, 4.26 to 5.32), or recipients with a college degree versus no college degree (OR, 1.34; 95% CI, 1.17 to 1.54). Preemptive transplants were less likely for Hispanics versus non-Hispanics (OR, 0.57; 95% CI, 0.50 to 0.67), patients with type 2 versus type 1 diabetes (OR, 0.76; 95% CI, 0.61 to 0.96), and for 2 to 5 HLA mismatches compared with 0 HLA mismatches (OR range, 0.77 to 0.82). In adjusted Cox proportional hazards analysis, the relative risk of graft failure for preemptive transplantation was 0.75 (0.67 to 0.84) among 25,758 cadaver donor transplants and 0.73 (0.64 to 0.83) among 13,078 living donor transplants, compared with patients who received a transplant after already being on dialysis. Preemptive transplantation was associated with a reduced risk of death: 0.84 (0.72 to 0.99) for cadaver donor transplants and 0.69 (0.56 to 0.85) for living donor transplants. Thus, preemptive transplantation, which is associated with improved patient and graft survival, is less common among racial minorities, those who have less education, and those who must rely on Medicare for primary payment. Alterations in the payment system, emphasis on early referral, and changes in cadaver kidney allocation could increase the number of patients who benefit from preemptive transplantation.
Increased Oxidative Damage to Peripheral Blood Leukocyte DNA in Chronic Peritoneal Dialysis Patients
Authors: Tarng Der-Cherng , Wen Chen Tzen , Huang Tung-Po , Chen Chiu-Lan , Liu Tsung-Yun , Wei Yau-Huei
Published: October 2004

This study focuses on the extent of oxidative DNA damage in peripheral blood leukocytes of chronic peritoneal dialysis (CPD) patients. 8-Hydroxy 2′-deoxyguanosine (8-OHdG) contents in peripheral leukocyte DNA were measured by an HPLC-electrochemical detection method in 24 age- and sex-matched healthy subjects, 22 nondialyzed patients with advanced renal failure, and 42 CPD patients. Mean 8-OHdG content was the highest in CPD patients, followed by the nondialyzed patients, and then by the healthy subjects (19.4 versus 11.9 versus 8.3/106 dG; ANOVA P < 0.001). In nondialyzed subjects, peripheral leukocyte 8-OHdG contents inversely correlated with renal creatinine clearance (r = −0.772; P < 0.001). Deficiency of blood antioxidants in CPD and nondialyzed patients was expressed by the lower plasma levels of ascorbate, cholesterol-standardized α-tocopherol and whole-blood reduced glutathione, and the higher levels of whole-blood oxidized glutathione as compared with healthy subjects (ANOVA P < 0.05). Mean serum ferritin and iron levels and transferrin saturation were higher in the CPD patients than those in the nondialyzed patients and controls (ANOVA P < 0.05). Flow cytometric analyses of intracellular reactive oxygen species production of peripheral leukocytes showed that spontaneous production by granulocytes, as well as phorbol-12-myristate-13-acetate (PMA)–induced production by granulocytes, lymphocytes and monocytes, were the highest from CPD patients, followed by nondialyzed patients, and then by the healthy subjects (ANOVA P < 0.05). Forward stepwise multiple regression disclosed that uremia, PD treatment, spontaneous and PMA-induced reactive oxygen species production in leukocytes, and serum iron were the independent determinants of peripheral leukocyte 8-OHdG content (R2
= 0.769; P < 0.001). In conclusion, profound increased 8-OHdG levels in peripheral leukocyte DNA occur in the course of chronic renal failure, gradually increase with its progression, and are further exacerbated by PD treatment.
Transcription Factor IRF-1 in Kidney Transplants Mediates Resistance to Graft Necrosis during Rejection
Authors: Afrouzian Marjan , Ramassar Vido , Urmson Joan , Zhu Lin-Fu , Halloran Philip F.
Published: October 2004

In many circumstances kidney transplants remain viable despite extensive inflammation, permitting rejection episodes to be reversed. The mechanisms by which the kidney resists host effector mechanisms are not known. In mouse kidney transplants, resistance requires interferon-γ (IFN-γ), which acts on the graft to protect the graft from necrosis during the first days of rejection as well as inducing major histocompatibility complex (MHC) expression. Because some effects of IFN-γ are mediated by transcription factor IRF-1, the role of IRF-1 in the donor tissue early phases of rejection of mouse kidney allografts was studied. H-2b kidneys were transplanted from mice with wild-type IRF-1 genes (WT) or mice with disrupted IRF-1 genes (IRF-1KO) into CBA (H-2k) recipients. At day 5 and day 7, IRF-1KO and WT kidneys were functioning despite typical rejection pathology: interstitial infiltration and tubulitis. However, function deteriorated rapidly in rejecting IRF-1KO allografts, associated with widespread epithelial necrosis, peritubular capillary congestion, glomerulitis, and fibrin thrombi in small veins by day 7. At day 21, WT kidneys were viable despite severe tubulitis and arteritis, whereas IRF-1KO kidneys showed massive necrosis of the epithelium despite patent large vessels. Compared with WT kidneys, rejecting IRF-1KO kidneys showed less induction of donor MHC yet had similar mRNA levels of perforin, granzyme B, and Fas ligand and evoked host alloantibody responses. Thus in rejecting kidney transplants, IRF-1 in the graft mediates MHC induction, but it also mediates resistance to necrosis, an effect that could be crucial to permit success in interventions against rejection.
Refining Predictive Models in Critically Ill Patients with Acute Renal Failure
Authors: Mehta Ravindra L. , Pascual Maria T. , Gruta Carmencita G. , Zhuang Shunping , Chertow Glenn M.
Published: October 2004

Mortality rates in acute renal failure remain extremely high, and risk-adjustment tools are needed for quality improvement initiatives and design (stratification) and analysis of clinical trials. A total of 605 patients with acute renal failure in the intensive care unit during 1989-1995 were evaluated, and demographic, historical, laboratory, and physiologic variables were linked with in-hospital death rates using multivariable logistic regression. Three hundred and fourteen (51.9%) patients died in-hospital. The following variables were significantly associated with in-hospital death: age (odds ratio [OR], 1.02 per yr), male gender (OR, 2.36), respiratory (OR, 2.62), liver (OR, 3.06), and hematologic failure (OR, 3.40), creatinine (OR, 0.71 per mg/dl), blood urea nitrogen (OR, 1.02 per mg/dl), log urine output (OR, 0.64 per log ml/d), and heart rate (OR, 1.01 per beat/min). The area under the receiver operating characteristic curve was 0.83, indicating good model discrimination. The model was superior in all performance metrics to six generic and four acute renal failure-specific predictive models. A disease-specific severity of illness equation was developed using routinely available and specific clinical variables. Cross-validation of the model and additional bedside experience will be needed before it can be effectively applied across centers, particularly in the context of clinical trials.
Proteomics and the Kidney
Authors: Knepper Mark A.
Published: October 2004

Proteomics can be defined as “the systematic analysis of proteins for their identity, quantity, and function.” The central concept is “multiplexing,” i.e., simultaneous analysis of all proteins in a defined protein population, rather than investigation of one protein at a time, as in traditional biochemistry. Two major approaches have been described: (1) mass spectrometry-based approaches and (2) protein micro-array approaches. The purpose of this Science Watch article is to describe the fundamental features of these two approaches and to speculate on how proteomics will be useful in nephrology and nephrology research in the coming years.
Purinergic Receptor Signaling at the Basolateral Membrane of Macula Densa Cells
Authors: Liu Ruisheng , Bell P. Darwin , Peti-Peterdi Janos , Kovacs Gergly , Johansson Alf , Persson A. Erik G.
Published: October 2004

Purinergic receptors are important in the regulation of renal hemodynamics; therefore, this study sought to determine if such receptors influence macula densa cell function. Isolated glomeruli containing macula densa cells, with and without the cortical thick ascending limb, were loaded with the Ca2+ sensitive indicators, Fura Red (confocal microscopy) or fura 2 (conventional video image analysis). Studies were performed on an inverted microscope in a chamber with a flow-through perfusion system. Changes in cytosolic calcium concentration ([Ca2+]i) from exposed macula densa plaques were assessed upon addition of adenosine, ATP, UTP, ADP, or 2-methylthio-ATP (2- MeS-ATP) for 2 min added to the bathing solution. There was no change in [Ca2+]i with addition of adenosine (10−7 to 10−3 M). UTP and ATP (10−4 M) caused [Ca2+]i to increase by 268 ± 40 nM (n = 21) and 295 ± 53 nM (n = 21), respectively, whereas in response to 2MesATP and ADP, [Ca2+]i increased by only 67 ± 13 nM (n = 8) and 93 ± 36 nM (n = 14), respectively. Dose response curve for ATP (10−7 to 10−3 M) added in bath showed an EC50 of 15 μM. No effect on macula densa [Ca2+]i was seen when ATP was added from the lumen. ATP caused similar increases in macula densa [Ca2+]i in the presence or absence of bath Ca2+ and addition of 5 mM ethyleneglycotetraacetic acid (EGTA). Suramin (an antagonist of P2X and P2Y receptors) completely inhibited ATP-induced [Ca2+]i dynamics. Also, ATP-Ca2+ responsiveness was prevented by the phospholipase C inhibitor, U-73122, but not by its inactive analog, U-73343. These results suggest that macula densa cells possess P2Y2 purinergic receptors on basolateral but not apical membranes and that activation of these receptors results in the mobilization of Ca2+.
Hepatitis C and Renal Transplantation in the Era of Modern Immunosuppression
Authors: Abbott Kevin C. , Bucci Jay R. , Matsumoto Cal S. , Swanson S. John , Agodoa Lawrence Y.C. , Holtzmuller Kent C. , Cruess David F. , Peters Thomas G.
Published: October 2004

Kidneys from donors who are positive for hepatitis C virus (DHCV+) have recently been identified as an independent risk factor for mortality after renal transplantation. However, it has not been determined whether risk persists after adjustment for baseline cardiac comorbidity or applies in the era of modern immunosuppression. Therefore, a historical cohort study was conducted of US adult cadaveric renal transplant recipients from January 1, 1996, to May 31, 2001; followed until October 31, 2001. A total of 36,956 patients had valid donor and recipient HCV serology. Cox regression analysis was used to model adjusted hazard ratios for mortality and graft loss, respectively, adjusted for other factors, including comorbid conditions from Center for Medicare and Medicaid Studies Form 2728 and previous dialysis access-related complications. It was found that DHCV+ was independently associated with an increased risk of mortality (adjusted hazard ratio, 2.12, 95% confidence interval, 1.72 to 2.87; P < 0.001), primarily as a result of infection. Mycophenolate mofetil was associated with improved survival in DHCV+ patients, primarily related to fewer infectious deaths. Adjusted analyses limited to recipients who were HCV+, HCV negative, or age 65 and over, or by use of mycophenolate mofetil confirmed that DHCV+ was independently associated with mortality in each subgroup. It is concluded that DHCV+ is independently associated with an increased risk of mortality after renal transplantation adjusted for baseline comorbid conditions in all subgroups. Recipients of DHCV+ organs should be considered at high risk for excessive immunosuppression. E-mail: kevin.abbott@ na.amedd.army.mil
Urea Restrains Aldosterone-Induced Development of Peanut Agglutinin–Binding on Embryonic Renal Collecting Duct Epithelia
Authors: Schumacher Karl , Strehl Raimund , Minuth Will W.
Published: October 2004

Peanut agglutinin (PNA) represents a commonly used marker for β-type intercalated (IC) cells and their distribution in the corticomedullary course of the collecting duct (CD) in the mature rabbit kidney. It has been shown that aldosterone is able to generate >90% of PNA-binding cells in an embryonic CD epithelium in vitro. In adult kidney, a maximum of only 25% PNA-positive cells is found in the cortical segment of the CD, and PNA-binding completely disappears in the inner-medullary CD. Molecules that regulate the gradual development of CD-specific cells during organ growth are unknown. In the present experiments, it was found that addition of physiologic concentrations of urea to the culture medium is able to restrain the action of aldosterone in embryonic CD epithelia. Urea antagonizes in a concentration-dependent manner the action of aldosterone finally leading to only 10% of PNA-binding cells. The data point to a urea-specific effect, because osmolytes such as NaCl and mannitol did not affect PNA binding. In addition, urea did not influence expression of principal-cell typical markers such as AQP2 and 3. The findings may explain that a higher number of PNA-positive cells is found in the cortical region of the kidney correlated with a low concentration of urea as compared with only few PNA-binding cells in the medullary CD, where a high concentration of urea occurs. Thus, an increasing concentration of urea may trigger the number of PNA-positive cells in the cortical-medullary course of the CD during organ development. E-mail: karl.schumacher@vkl.uni-regensburg.de
Gene Expression Profiles of Podocyte-Associated Molecules as Diagnostic Markers in Acquired Proteinuric Diseases
Authors: Schmid Holger , Henger Anna , Cohen Clemens D. , Frach Karin , Gröne Hermann-Josef , Schlöndorff Detlef , Kretzler Matthias
Published: October 2004

For identifying potential diagnostic markers of proteinuric glomerulopathies, glomerular mRNA levels of molecules relevant for podocyte function (α-actinin-4, glomerular epithelial protein 1, Wilms tumor antigen 1, synaptopodin, dystroglycan, nephrin, podoplanin, and podocin) were determined by quantitative real-time RT-PCR from microdissected glomeruli. Biopsies from 83 patients with acquired proteinuric diseases were analyzed (minimal change disease [MCD; n = 13], benign nephrosclerosis [n = 16], membranous glomerulopathy [n = 31], focal and segmental glomerulosclerosis [FSGS; n = 9], and controls [n = 14]). Gene expression levels normalized to two different housekeeping transcripts (glyceraldehyde-3-phosphate-dehydrogenase and 18 S rRNA) did not allow a separation between proteinuric disease categories. However, a significant positive correlation between α-actinin-4, glomerular epithelial protein 1, synaptopodin, dystroglycan, Wilms tumor antigen 1, and nephrin was found in all analyzed glomeruli, whereas podocin mRNA expression did not correlate. Because varying amounts of housekeeper cDNA per glomerulus can confound expression ratios relevant for a subpopulation of cells, an “in silico” microdissection was performed using a podocyte-specific cDNA as a reference gene. Expression ratio of podocin to synaptopodin, the two genes with the most disparate expression, allowed a robust separation of FSGS from MCD and nephrosclerosis. Segregation of FSGS from MCD via this ratio was confirmed in an independent population of formaldehyde-fixed archival biopsies (MCD, n = 5; FSGS, n = 4) after glomerular laser capture microdissection. In addition, the expression marker was able to predict steroid responsiveness in diagnostically challenging cases of MCD versus FSGS (n = 6). As the above approach can be performed as an add-on diagnostic tool, these molecular diagnostic parameters could give novel information for the management of proteinuric diseases. E-mail: kretzler@medpoli.med.uni-muenchen.de
Role of Oxidative Stress in Endothelial Dysfunction and Enhanced Responses to Angiotensin II of Afferent Arterioles from Rabbits Infused with Angiotensin II
Authors: Wang Dan , Chen Yifan , Chabrashvili Tina , Aslam Shakil , Borrego Conde Lillian J. , Umans Jason G. , Wilcox Christopher S.
Published: October 2004

The hypothesis that O2
·− enhances angiotensin II (AngII)-induced vasoconstriction and impairs acetylcholine-induced vasodilation of afferent arterioles (Aff) in AngII–induced hypertension was investigated. Rabbits (n = 6 per group) received 12 to 14 d of 0.154 M NaCl (Sham), subpressor AngII (60 ng/kg per min; AngII 60) or slow pressor AngII (200 ng/kg per min; AngII 200). Individual Aff were perfused in vitro at 60 mmHg. AngII 200 increased mean arterial pressure (mean ± SD; 103 ± 9 versus 73 ± 6 mmHg; P < 0.01), plasma lipid peroxides (2.6 ± 0.3 versus 2.0 ± 0.3 nM; P < 0.05), renal cortical NADPH- and NADH-dependent O2
·− generation, and Aff mRNA for p22phox 5-fold (P < 0.001) but decreased that for AT1-receptor 2.4-fold (P < 0.01). AngII 60 increased only NADH-dependent O2
·− generation by renal cortex. Aff from AngII 200 rabbits had diminished acetylcholine relaxations (+50 ± 4 versus +85 ± 6%; P < 0.001), but these became similar in the presence of nitro-L-arginine (10−4 M). Aff from AngII 60 and AngII 200 rabbits had unchanged norepinephrine contractions (10−7 M) but significantly (P < 0.05) enhanced AngII contractions (10−8 M: Sham −52 ± 5 versus AngII 60 to 77 ± 5 versus AngII 200 to 110 ± 10%). The superoxide dismutase mimetic tempol (10−4 M) moderated the AngII responses of Aff from AngII 200 rabbits to levels of AngII 60 rabbits (−64 ± 7%). The AngII slow pressor response enhances renal cortical O2
·− and p22phox expression. Increased O2
·− generation in Aff mediates an impaired nitric oxide synthase–dependent endothelium-derived relaxing factor response and paradoxically enhances contractions to AngII despite downregulation of the mRNA for AT1 receptors. A subpressor dose of AngII enhances Aff responses to AngII independent of O2
·−. E-mail: wilcoxch@georgetown.edu
Obesity Is Associated with Worse Peritoneal Dialysis Outcomes in the Australia and New Zealand Patient Populations
Authors: McDonald Stephen P. , Collins John F. , Johnson David W.
Published: October 2004

Although obesity is associated with increased risks of morbidity and death in the general population, a number of studies of patients undergoing hemodialysis have demonstrated that increasing body mass index (BMI) is correlated with decreased mortality risk. Whether this association holds true among patients treated with peritoneal dialysis (PD) has been less well studied. The aim of this investigation was to examine the association between BMI and outcomes among new PD patients in a large cohort, with long-term follow-up monitoring. Using data from the Australia and New Zealand Dialysis and Transplant Registry, an analysis of all new adult patients (n = 9679) who underwent an episode of PD treatment in Australia or New Zealand between April 1, 1991, and March 31, 2002, was performed. Patients were classified as obese (BMI of ≥30 kg/m2), overweight (BMI of 25.0 to 29.9 kg/m2), normal weight (BMI of 20 to 24.9 kg/m2), or underweight (BMI of <20 kg/m2). In multivariate analyses, obesity was independently associated with death during PD treatment (hazard ratio, 1.36; 95% confidence interval, 1.14 to 1.54; P < 0.05) and technique failure (hazard ratio, 1.17; 95% confidence interval, 1.07 to 1.26; P < 0.01), except among patients of New Zealand Maori/Pacific Islander origin, for whom there was no significant relationship between BMI and death during PD treatment. A supplementary fractional polynomial analysis modeled BMI as a continuous predictor and indicated a J-shaped relationship between BMI and patient mortality rates and a steady increase in death-censored technique failure rates up to a BMI of 40 kg/m2; the mortality risk was lowest for BMI values of approximately 20 kg/m2. In conclusion, obesity at the commencement of renal replacement therapy is a significant risk factor for death and technique failure. Such patients should be closely monitored during PD and should be considered for early transfer to an alternative renal replacement therapy if difficulties are experienced. E-mail: stephenm@ anzdata.org.au
Genetic Variation in the Renin-Angiotensin System and Progression of Diabetic Nephropathy
Authors: Jacobsen Peter , Tarnow Lise , Carstensen Bendix , Hovind Peter , Poirier Odette , Parving Hans-Henrik
Published: October 2004

The impact of polymorphisms in the genes coding for angiotensinogen (M235T), ACE (ID), and angiotensin II type 1 receptor (A
1166→C) on decline in GFR and doubling of s-creatinine or development of ESRD in patients with type 1 diabetes and diabetic nephropathy (DN) was tested. From 1985, all patients (n = 169) who had established diabetic nephropathy and were treated with angiotensin-converting enzyme inhibition (ACE-I) were identified consecutively at Steno Diabetes Center. Patients were followed for a median of 6 yr (range, 3 to 15 yr), with nine (range, three to 29) measurements of GFR (51Cr-EDTA). In a Cox proportional hazards model corrected for other risk factors, the D allele (ACE/ID) was associated with time to doubling of s-creatinine/ESRD (rate ratio, 1.81 per allele; 95% confidence interval, 1.09 to 3.03; P = 0.02). A new interaction hypothesis was generated demonstrating that the following variables were associated with accelerated decline in GFR: albuminuria (estimate, 2.12 ml/min per yr per 10-fold increase in albuminuria; P < 0.001), mean BP (estimate, 0.88 ml/min per yr per 10 mmHg; P = 0.02), hemoglobin A1c (estimate, 0.54 min/min per yr per 1%; P = 0.02), and number of M (M235T)/D (ID)/A (A
1166→C) alleles (estimate, 0.45 ml/min per yr per allele; P = 0.049). Number of M/D/A alleles also influenced time to doubling of s-creatinine or ESRD. In this study of patients with type 1 diabetes, the D allele of the ACE/ID polymorphism in addition to nongenetic risk factors independently accelerated progression of DN during ACE-I. Interaction between polymorphisms in the renin-angiotensin system also influenced the loss of kidney function. This new genetic interaction model needs to be confirmed in future studies. E-mail: pkjacobsen@dadlnet.dk
A Cluster of Mutations in the UMOD Gene Causes Familial Juvenile Hyperuricemic Nephropathy with Abnormal Expression of Uromodulin
Authors: Dahan Karin , Devuyst Olivier , Smaers Michèle , Vertommen Didier , Loute Guy , Poux Jean-Michel , Viron Béatrice , Jacquot Christian , Gagnadoux Marie-France , Chauveau Dominique , Büchler Mathias , Cochat Pierre , Cosyns Jean-Pierre , Mougenot Béatrice , Rider Mark H. , Antignac Corinne , Verellen-Dumoulin Christine , Pirson Yves
Published: October 2004

Familial juvenile hyperuricemic nephropathy (FJHN [MIM 162000]) is an autosomal-dominant disorder characterized by abnormal tubular handling of urate and late development of chronic interstitial nephritis leading to progressive renal failure. A locus for FJHN was previously identified on chromosome 16p12 close to the MCKD2 locus, which is responsible for a variety of autosomal-dominant medullary cystic kidney disease (MCKD2). UMOD, the gene encoding the Tamm-Horsfall/uromodulin protein, maps within the FJHN/MCKD2 critical region. Mutations in UMOD were recently reported in nine families with FJHN/MCKD2 disease. A mutation in UMOD has been identified in 11 FJHN families (10 missense and one in-frame deletion)—10 of which are novel—clustering in the highly conserved exon 4. The consequences of UMOD mutations on uromodulin expression were investigated in urine samples and renal biopsies from nine patients in four families. There was a markedly increased expression of uromodulin in a cluster of tubule profiles, suggesting an accumulation of the protein in tubular cells. Consistent with this observation, urinary excretion of wild-type uromodulin was significantly decreased. The latter findings were not observed in patients with FJHN without UMOD mutations. In conclusion, this study points to a mutation clustering in exon 4 of UMOD as a major genetic defect in FJHN. Mutations in UMOD may critically affect the function of uromodulin, resulting in abnormal accumulation within tubular cells and reduced urinary excretion. E-mail: Dahan@gmed.ucl.ac.be
Molecular Analysis of the SGLT2 Gene in Patients with Renal Glucosuria
Authors: Santer René , Kinner Martina , Lassen Christoph L. , Schneppenheim Reinhard , Eggert Paul , Bald Martin , Brodehl Johannes , Daschner Markus , Ehrich Jochen H.H. , Kemper Markus , Li Volti Salvatore , Neuhaus Thomas , Skovby Flemming , Swift Peter G.F. , Schaub Jürgen , Klaerke Dan
Published: October 2004

The role of SGLT2 (the gene for a renal sodium-dependent glucose transporter) in renal glucosuria was evaluated. Therefore, its genomic sequence and its intron-exon organization were determined, and 23 families with index cases were analyzed for mutations. In 21 families, 21 different SGLT2 mutations were detected. Most of them were private; only a splice mutation was found in 5 families of different ethnic backgrounds, and a 12-bp deletion was found in two German families. Fourteen individuals (including the original patient with ’renal glucosuria type 0′) were homozygous or compound heterozygous for an SGLT2 mutation resulting in glucosuria in the range of 14.6 to 202 g/1.73 m2/d (81 - 1120 mmol/1.73 m2/d). Some, but not all, of their heterozygous family members had an increased glucose excretion of up to 4.4 g/1.73 m2/d (24 mmol/1.73 m2/d). Likewise, in index cases with glucosuria below 10 g/1.73 m2/d (55 mmol/1.73 m2/d) an SGLT2 mutation, if present, was always detected in the heterozygous state. We conclude that SGLT2 plays an important role in renal tubular glucose reabsorption. Inheritance of renal glucosuria shows characteristics of a codominant trait with variable penetrance. E-mail: r.santer@uke.uni-hamburg.de
Hypoxia-Inducible Factors and Kidney Vascular Development
Authors: Freeburg Paul B. , Abrahamson Dale R.
Published: October 2004

Among the genes strongly induced by hypoxia-inducible factors (HIF) and highly expressed during kidney microvascular development is vascular endothelial growth factor, which encodes a potent endothelial mitogen and chemoattractant critical for embryonic vasculogenesis and angiogenesis. In developing kidney, glomerular podocytes are particularly rich sources of vascular endothelial growth factor, which probably serves to attract endothelial precursors into vascular clefts of immature glomeruli, promote their mitosis and differentiation into glomerular endothelial cells, and assist with maintenance of their highly differentiated state through maturation. This article summarizes the structure, function, and expression of HIF and discusses HIF target genes expressed during kidney vascular development. Furthermore, it is speculated that different HIF heterodimers are stabilized in different cell populations, which may lead to cell-selective induction of HIF target genes important for renal vasculogenesis/angiogenesis. E-mail: dabrahamson@kumc.edu
Inhibition of Erythrocyte Cation Channels by Erythropoietin
Authors: Myssina Svetlana , Huber Stephan M. , Birka Christina , Lang Philipp A. , Lang Karl S. , Friedrich Björn , Risler Teut , Wieder Thomas , Lang Florian
Published: October 2004

Recombinant human erythropoietin therapy is used to counteract anemia that is the result of renal insufficiency. It stimulates the formation of peripheral blood erythrocytes by inhibiting apoptosis of erythrocyte precursor cells. Mature erythrocytes have similarly been shown to undergo apoptosis. Hyperosmotic shock and Cl− removal activate a Ca2+-permeable, ethylisopropylamiloride-inhibitable cation channel. The subsequent increase of cytosolic Ca2+ activates a scramblase that breaks down cell membrane phosphatidylserine asymmetry, leading to annexin binding. Studied was whether channel activity and erythrocyte cell death are regulated by erythropoietin. Scatchard plot analysis disclosed low-abundance, high-affinity binding of 125I-erythropoietin to erythrocytes. Whole cell patch clamp experiments revealed significant inhibition of the ethylisopropylamiloride-sensitive current by 1 U/ml erythropoietin. Cl− removal triggered annexin binding, an effect abrogated by erythropoietin (1 U/ml) but not by GM-CSF (10 ng/ml). Osmotic shock (700 mOsm) stimulated annexin binding within 24 h in the majority of the erythrocytes, an effect blunted by erythropoietin (1 U/ml) but not by GM-CSF (10 ng/ml). In the nominal absence of Ca2+, the effect of osmotic shock was blunted and the effect of erythropoietin abolished. In hemodialysis patients, intravenous administration of erythropoietin (50 IU/kg) within 4 h decreased the number of annexin binding circulating erythrocytes. Erythropoietin binds to erythrocytes and inhibits volume-sensitive erythrocyte cation channels and thus the breakdown of phosphatidylserine asymmetry after activation of this channel. The effect could prolong the erythrocyte lifespan and may contribute to the enhancement of the erythrocyte number during erythropoietin therapy in dialysis patients. E-mail: florian.lang@uni-tuebingen.de
Impaired Renal Secretion of Substrates for the Multidrug Resistance Protein 2 in Mutant Transport–Deficient (TR−) Rats
Authors: Masereeuw Rosalinde , Notenboom Sylvia , Smeets Pascal H. E. , Wouterse Alfons C. , Russel Frans G. M.
Published: October 2004

Previous studies with mutant transport–deficient rats (TR−), in which the multidrug resistance protein 2 (Mrp2) is lacking, have emphasized the importance of this transport protein in the biliary excretion of a wide variety of glutathione conjugates, glucuronides, and other organic anions. Mrp2 is also present in the luminal membrane of proximal tubule cells of the kidney, but little information is available on its role in the renal excretion of xenobiotics. The authors compared renal transport of the fluorescent Mrp2 substrates calcein, fluo-3, and lucifer yellow (LY) between perfused kidneys isolated from Wistar Hannover (WH) and TR− rats. Isolated rat kidneys were perfused with 100 nM of the nonfluorescent calcein-AM or 500 nM fluo3-AM, which enter the tubular cells by diffusion and are hydrolyzed intracellularly into the fluorescent anion. The urinary excretion rates of calcein and fluo-3 were 3 to 4 times lower in perfused kidneys from TR− rats compared with WH rats. In contrast, the renal excretion of LY (10 μM, free anion) was somewhat delayed but appeared unimpaired in TR− rats. Membrane vesicles from Sf9 cells expressing human MRP2 or human MRP4 indicated that MRP2 exhibits a preferential affinity for calcein and fluo-3, whereas LY is a better substrate for MRP4. We conclude that the renal clearance of the Mrp2 substrates calcein and fluo-3 is significantly reduced in TR− rat; for LY, the absence of the transporter may be compensated for by (an)other organic anion transporter(s). E-mail: R.Masereeuw@ncmls.kun.nl