Blood pressure control, proteinuria, and the progression of renal disease. The Modification of Diet in Renal Disease Study

OBJECTIVE

To examine the relations among proteinuria, prescribed and achieved blood pressure, and decline in glomerular filtration rate in the Modification of Diet in Renal Disease Study.

DESIGN

2 randomized trials in patients with chronic renal diseases of diverse cause.

SETTING

15 outpatient nephrology practices at university hospitals.

PATIENTS

840 patients, of whom 585 were in study A (glomerular filtration rate, 25 to 55 mliters/min.1.73 m2) and 255 were in study B (glomerular filtration rate, 13 to 24 mliters/min.1.73 m2). Diabetic patients who required insulin were excluded.

INTERVENTIONS

Patients were randomly assigned to a usual blood pressure goal (target mean arterial pressure, < or = 107 mm Hg for patients < or = 60 years of age and < or = 113 mm Hg for patients > or = 61 years of age) or a low blood pressure goal (target mean arterial pressure, < or = 92 mm Hg for patients < or = 60 years of age and < or = 98 mm Hg for patients > or = 61 years of age).

MAIN OUTCOME MEASURES

Rate of decline in glomerular filtration rate and change in proteinuria during follow-up.

RESULTS

The low blood pressure goal had a greater beneficial effect in persons with higher baseline proteinuria in both study A (P = 0.02) and study B (P = 0.01). Glomerular filtration rate declined faster in patients with higher achieved blood pressure during follow-up in both study A (r = -0.20; P < 0.001) and study B (r = -0.34; P < 0.001), and these correlations were stronger in persons with higher baseline proteinuria (P < 0.001 in study A; P < 0.01 in study B). In study A, the association between decline in glomerular filtration rate and achieved follow-up blood pressure was nonlinear (P = 0.011) and was stronger at higher mean arterial pressure. In both studies, the low blood pressure goal significantly reduced proteinuria during the first 4 months after randomization. This, in turn, correlated with a slower subsequent decline in glomerular filtration rate.

CONCLUSIONS

Our study supports the concept that proteinuria is an independent risk factor for the progression of renal disease. For patients with proteinuria of more than 1 g/d, we suggest a target blood pressure of less than 92 mm Hg (125/75 mm Hg). For patients with proteinuria of 0.25 to 1.0 g/d, a target mean arterial pressure of less than 98 mm Hg (about 130/80 mm Hg) may be advisable. The extent to which lowering blood pressure reduces proteinuria may be a measure of the effectiveness of this therapy in slowing the progression of renal disease.

Integrated case studies and medical decision making: a novel, computer-assisted bridge from the basic sciences to the clinics

This article describes a novel course that was designed to bridge the gap between the basic science years and clinical experiences in medical school by using information science and computer technology as major components of problem-based learning (PBL) sessions. The course, Integrated Case Studies and Medical Decision Making, was first given to second-year students at the University of Pittsburgh School of Medicine in the spring of 1994. It consists of 13 PBL exercises, each of which explores a clinical case. The cases, including images and gated access to information, are housed on a computer. Using one of 16 networked terminals in specially designed small-group rooms, groups of nine students progress through the cases with a faculty facilitator. The responses of students and faculty to the initial year of the course were favorable. In comparison with traditional PBL sessions, enhanced quality of and access to images and accountability for accessing case information in sequential fashion were cited as major strengths of the course. Juxtaposition of basic science and clinical material and utility in reviewing for the United States Medical Licensing Examination were also cited as strengths. The diversity of the basic science material involved in completing the cases drew overwhelming enthusiasm from students and facilitators alike. In conclusion, the course successfully employs computer and information science technology, which will be of increasing importance to future physicians. The course also serves as an effective bridge to the clinical years of medical school and as a study adjunct for the USMLE.

The undergraduate medical curriculum: centralized versus departmentalized

The authors describe the advantages and disadvantages of central governance of the undergraduate medical curriculum as contrasted with traditional departmental approaches, based upon their school's experience with a new centrally governed curriculum during the preceding four years. Central governance has more advantages, but also more costs, compared with traditional departmental approaches. Central governance does what it was intended to do: it provides rational and integrative mechanisms for ensuring a broad general education in medicine focusing on the doctor-patient relationship. It also provides an effective mechanism for dealing with "turf" and time issues in the curriculum while allowing for and encouraging changes and providing mechanisms for evaluating those changes. However, as the allocation of resources and rewards remains more departmentally than centrally based, a major challenge of central governance has been to help faculty resolve a "conflict of loyalty" (the sense of serving two masters) between school and department, particularly in the evaluation and reward of teaching. On balance, central governance provides a powerful means of introducing broad-based reforms into all elements of the undergraduate medical curriculum, but it requires ongoing collaboration with faculty and chairs to assist them in negotiating competing pressures and priorities as they strive to become excellent teachers.

Complement regulation in the rat glomerulus: Crry and CD59 regulate complement in glomerular mesangial and endothelial cells

The complement regulators, decay accelerating factor, membrane cofactor protein, and CD59 are present in human glomeruli. Crry is the rodent analogue to the former two proteins. In this study, we examined complement regulation in cultured rat glomerular endothelial cells (GEnC) and mesangial cells (MES). Immunoprecipitation of 125I-labeled membrane proteins and Western blotting studies were performed with anti-Crry and anti-CD59. In both GEnC and MES, Crry was present as 53, 65, and 78 kD proteins. The 20 kD CD59 was apparent in GEnC. CD59 was also present in MES, but in relatively smaller quantities. By Northern analyses, 1.8 kb CD59 mRNA was present in GEnC as well as in RNA from isolated rat glomeruli. mRNA for Crry was present in both GEnC and MES as 2.2 kb species. The functional significance of these proteins was evaluated next. Anti-Thy 1.1 IgG was used to activate the complement classical pathway in MES. To inhibit the function of the complement regulators, anti-CD59 and/or anti-Crry F(ab')2 antibodies were added with anti-Thy 1.1. Inhibition of Crry function led to enhanced cytotoxicity, while there was no effect when CD59 function was inhibited. The complement alternative pathway was studied by adding complement in Mg-EGTA buffer. Inhibition of Crry led to productive alternative pathway activation, which was accentuated by anti-CD59 when Crry was incompletely inhibited. Alternative pathway regulation was also evaluated in GEnC. Inhibition of CD59 function alone had no effect in GEnC, while inhibition of Crry led to significant cytotoxicity from alternative pathway activation. Under conditions in which Crry was inactive, inhibition of CD59 further enhanced cytotoxicity. Therefore, Crry is present in both GEnC and MES and restricts the complement alternative pathway in both cell types. Crry also regulates the classical pathway in MES. CD59 is present and functionally active in GEnC, while it appears to have a minor role in MES.

[Vaso-occlusive crises in sickle-cell anemia]

HISTORY AND FINDINGS

Severe pain suddenly occurred in the shaft of the right thigh in a 21-year-old patient of Turkish descent with known homozygotic sickle cell anaemia. He also had marked scleral jaundice and anaemia (haemoglobin 9.1 g/dl). An X-ray film of the lower leg pointed to a bone infarct. Type of pain, partial pressure of oxygen in blood (70 mm Hg), concentration of lactate dehydrogenase and the bilirubin level (4,5 mg/dl) as signs of haemolysis, as well as the fall in haemoglobin, indicated a vascular occlusive crisis in sickle cell anaemia.

TREATMENT AND COURSE

The symptoms regressed within 8 days of the patient receiving fluids, analgesics and oxygenation by nasal tube. A few weeks later he developed a fever, productive cough and severe pain in joints and abdomen. Blood p02 was 54 mm Hg. Pneumonia in the right lung base was the cause of this renewed life-threatening crisis, which was again associated with haemolysis. Klebsiella having been found in sputum he was treated with cefotaxim (1 g twice daily intravenously) and oxygen insufflation via nasal tube (7 l/min). His condition quickly improved.

CONCLUSIONS

In patients with sickle cell anaemia it is important (1) to regard crises as potentially life-threatening conditions, (2) to detect and treat infections as possible causes early and (3) to provide sufficient oxygen insufflation quickly, especially in pulmonary infections.

Estrogenic activity of RU 486 (mifepristone) in rat uterus and cultured uterine myocytes

OBJECTIVE

Our purpose was to determine whether RU 486 (mifepristone) has direct estrogenic activity in uterine myocytes.

STUDY DESIGN

Ovariectomized adult rats were treated with RU 486, and its effect on uterine oxytocin receptor concentration, as a marker of estrogenic activity, was measured. Results were compared with the induction by RU 486 of an estrogen-responsive reporter gene in a cultured Syrian hamster uterine myocyte cell line.

RESULTS

Baseline oxytocin receptor concentration was 58.8 +/- 7.2 fmol/mg protein (mean +/- SEM) and increased to 227 +/- 49 fmol/mg with 17 beta-estradiol (2.5 micrograms/kg) and to 145 +/- 18 fmol/mg after RU 486 (5 mg/kg) treatment, an effect that was inhibited by the antiestrogen ICI 182,780 (1.5 mg/kg). In the cultured Syrian hamster uterine myocyte cell line cells RU 486 (10(-6) mol/L) caused a 2.17 +/- 0.17-fold increase in the expression of the reporter gene versus 113.0 +/- 7.4-fold with 17 beta-estradiol (10(-8) mol/L). The estrogenic activity of RU 486 was dependent on the presence of both estrogen receptor and the promoter's estrogen response element.

CONCLUSION

RU 486 has a weak estrogen-like activity in uterine myocytes. This activity may partly explain the therapeutic effects of RU 486 on this target organ.

Crinkling of epicardial defibrillator patches. A common and serious problem

The durability and reliability of the implantable cardioverter-defibrillator epicardial patch systems have not been reported. In 128 consecutive patients such systems manufactured by Cardiac Pacemakers, Inc. (St. Paul, Minn.) or Medtronic, Inc. (Minneapolis, Minn.) were implanted with 100% follow-up to investigate the rate of patch crinkling and its consequences. A total of 122 patients survived the operation (operative mortality, 6 patients: 4.7%). Ninety-four patients received Cardiac Pacemakers, Inc. AICD patches and 28 received Medtronic PCD patches. Patients had chest x-ray studies every 3 to 6 months and function of the defibrillator was checked every 3 months. Late mortality occurred in 17 patients (13%) leaving a total of 105 long-term survivors (82%) to the present. Among 122 survivors, severe crinkling of the patches occurred in 48 patients--33 in the Cardiac Pacemakers, Inc. AICD group (36%) and 15 in the PCD group (54%)--within 2 years of the implant. Crinkling of patches caused not only malfunction of the system, but also cardiac pain in three patients. Crinkling occurred as early as 2 months after implant and progressed throughout the period of observation. Fourteen patients later required implant of an additional transvenous defibrillator because of failure of the epicardial system. The percentage of transvenous implantable cardioverter-defibrillator systems needed was higher for the Medtronic group (28%) than for the Cardiac Pacemakers, Inc. AICD group (6.3%). Both systems have shown an unacceptably high rate of patch crinkling that occurs in a relatively short time. There is no difference whether a thoracotomy or midline sternotomy is used or whether the patches are implanted intrapericardially or extrapericardially. The quest should continue for a better patch system design.

Effect of rapid correction of hyponatremia on the blood-brain barrier of rats

Brain demyelination sometimes follows rapid correction of hyponatremia, especially if the hyponatremia is chronic. During correction brain water decreases and the brain shrinks. The present study examined whether such shrinkage might be sufficient to disrupt the tight junctions of the blood-brain barrier. Barrier intactness was evaluated using magnetic resonance imaging and intravenous gadolinium contrast administration. Hypertonic saline infusion rapidly increased the plasma sodium concentration and caused barrier disruption more frequently in chronic than in acute hyponatremic rats. Similar increases in plasma sodium concentration did not disrupt the barrier in normonatremic rats. The disruption appeared to be due to altered plasma osmolality since infusion of hypertonic mannitol, which raised plasma osmolality without changing the plasma sodium concentration, disrupted the barrier in hyponatremic but not normonatremic rats. Moreover, the osmotic threshold for barrier disruption was lowest in chronic hyponatremia, intermediate in acute hyponatremia, and highest in normonatremia. The greater susceptibility to osmotic disruption in chronic hyponatremia suggests that blood-brain barrier disruption may play a significant role in causing the demyelination sometimes found following too rapid correction of hyponatremia, possibly through exposure of oligodendrocytes to plasma macromolecules such as complement.

Differential positive and negative transcriptional regulation by tamoxifen

Tamoxifen, a nonsteroidal antiestrogen and breast cancer chemotherapeutic, exhibits both estrogen agonist and antagonist properties. Rat GC3 cells grown under estrogen-free conditions were analyzed for the expression of model luciferase reporter genes, either positively or negatively regulated by estrogens. Expression assays adding tamoxifen alone or in combination with 17 beta-estradiol were performed to determine agonist or antagonist activities. In rat GC3 cells, tamoxifen acts as an estrogen antagonist for gene activation, but as an agonist for repression. Regulation by tamoxifen is mediated by estrogen receptor (ER), not via nonreceptor tamoxifen effects. Evaluation of human ER shows that although the wild-type receptor behaves similarly to the rat receptor, the Gly400 to Val400 mutant receptor does not. Tamoxifen, an effective agonist for gene repression with rat and wild-type receptor, shows no agonist activity using this mutated Val400 receptor. Yet, 17 beta-estradiol and clomiphene, another mixed agonist/antagonist, are effective agonists for gene repression with all three receptors. In this model system, tamoxifen functions as antagonist or agonist, depending on whether the ER acts to activate or repress its gene target. In other systems regulated by estrogens, functional analyses of ER action might also serve to predict the agonist or antagonist activity of tamoxifen.

Multiple-sensor systems for physiologic cardiac pacing

PURPOSE

To review the status of artificial sensors in cardiac pacemakers and the rationale for developing pacing systems that use multiple sensors.

DATA SOURCES

Journal articles published between 1982 and 1993 indexed in MEDLINE using the keywords pacemakers, sensors, and rate-adaptive, as well as abstracts and articles in the authors' personal files.

STUDY SELECTION

Articles describing clinical experience with or clinical evaluation of cardiac pacing systems using multiple artificial sensors.

DATA SYNTHESIS

Artificial sensors were created to adjust pacing rate reliably in response to changes in levels of physical exertion for patients with sinoatrial disease in whom exercise heart rate response is inadequate (for example, chronotropic incompetence in sinoatrial disease). To achieve this, various artificial sensors were developed and many reports confirm improved exertional tolerance. More recently, sensors have assumed a greater role in cardiac pacemakers. For example, sensors are used to permit automatic adjustment of certain programmable pacemaker settings, such as the atrioventricular interval. In the future, they may also be used to maximize pacemaker longevity by automatically optimizing energy output (voltage, pulse width). No single sensor is ideal for all potential applications, and investigators have advocated using two or more sensors. Several pacemakers that use multiple sensors with different but complementary operating characteristics are already commercially available outside the United States. Although preliminary findings are encouraging, additional clinical experience with these pacemakers is needed to determine their ultimate role in clinical practice.

CONCLUSION

Simultaneous use of multiple complementary artificial sensors may permit development of cardiac pacemakers that operate more physiologically yet require less specialized medical follow-up.

Structure-function relationships associated with extracellular matrix alterations in diabetic glomerulopathy

Proteinuria and progressive renal insufficiency are the primary manifestations of diabetic nephropathy. Accumulating evidence suggests that these clinical features can be linked, at least in part, to pathologic changes in the glomerular extracellular matrix. Most evidence suggests that glomerular basement membrane thickening and mesangial matrix expansion consist of at least three elements. These are (1) an accumulation of normal extracellular components; (2) an increase in the novel peptide chains of the normal components of Type IV collagen; and (3) an increase in matrix elements not normally expressed in the glomerulus. The pathogenetic features underlying these changes include increased synthesis and decreased degradation of matrix. Abnormal physico-chemical interactions among these matrix elements likely contribute to alterations in three-dimensional structure, leading to proteinuria and loss of glomerular basement membrane filtering surface area. Many of these changes may be explained in whole or in part by direct or secondary effects of hyperglycemia, as well as by hemodynamic changes.

T cell epitope analysis with peptides simultaneously synthesized on cellulose membranes: fine mapping of two DQ dependent epitopes

Several MHC class II restricted, CD4+ human T cell clones from three donors were induced with soluble matrix protein of influenza virus. The epitopes recognized by these clones were mapped using a complete set of overlapping 15-mer peptides synthesized with the newly developed SPOT method which allows the simple simultaneous synthesis of numerous peptides on cellulose membranes. Fine analysis of two clones by truncation of the stimulatory peptide by single subsequent amino acids from either the NH2- or the COOH-terminus revealed the minimal stimulatory determinants of two DQ dependent T cell epitopes.

Brain buffering is restored in hyponatremic rats by correcting their plasma sodium concentration

Previous studies from this laboratory showed that both acute and chronic hyponatremia impaired active brain buffering. These studies were performed to determine whether correcting the plasma sodium restored normal buffering in hyponatremic rats. Acute (1- and 2-day) and chronic (7- and 14-day) hyponatremia was induced in male Sprague-Dawley rats by constant desmopressin administration combined with a liquid diet. Plasma sodium was corrected by stopping desmopressin for 6 h, substituting solid chow, and allowing free access to water. Studies were performed 24 h later. Uncorrected hyponatremic rats who continued to receive desmopressin and liquid diet served as controls. Brain pH was determined by [31P]NMR in rats anesthetized with N2O and paralyzed with pancuronium. Brain buffering was determined by the response to CO2 loading. Resting brain pH was the same in corrected and uncorrected rats, but the two groups responded differently to CO2 loading. Thus, 55 min after ventilation with 20% CO2, corrected rat brain pH was 0.13 pH units higher than in uncorrected rats despite statistically similar changes in CO2 tension and arterial pH in both groups. Moreover, 15 min into recovery from CO2 exposure, brain pH in corrected rats overshot resting pH by 0.07, whereas no overshoot occurred in uncorrected rats. Buffering in corrected rats was identical to that shown previously in normonatremic rats. The complete restoration of late-phase buffering achieved by normalizing the plasma sodium of hyponatremic rats indicates that at least some portion of active hydrogen ion transport is sodium dependent in the brain.

Chronotherapy with 5-fluorouracil and folinic acid in advanced colorectal carcinoma. Results of a chronopharmacologic phase I trial

BACKGROUND

Chronotherapy with antineoplastic drugs is a rather new strategy of reducing cytotoxic side effects. Because the circadian timing of 5-fluorouracil (5-FU) was reported to result in a higher efficacy and lower toxicity, the authors conducted a chronopharmacologic Phase I trial with 5-FU and folinic acid (FA).

METHODS

Eight patients with advanced colorectal cancer received 5-FU (initial dose of 500 mg/m2/day) and FA (20 mg/m2/day) as a continuous intravenous infusion over 5 consecutive days. Using a portable, ambulatory drug delivery system, 75% of the daily dose of 5-FU and FA were given from Oh00-7h00, and the remaining 25% from 7h00-24h00. Treatment courses were repeated after 28 days. Dose escalations of 250 mg/m2/day of 5-FU and 10 mg/m2/day of FA per course were performed in the absence of any toxicity greater than WHO (World Health Organization) grade 2.

RESULTS

Dose-limiting toxicity WHO grade 3 was observed at a dose of 750 mg/m2/day of 5-FU and 30 mg/m2/day of FA in five, and 1000 mg/m2/day of 5-FU and 40 mg/m2/day of FA in two patients, respectively. One patient tolerated 1000 mg/m2/day of 5-FU and 40 mg/m2/day of FA, but the treatment was stopped before further dose escalation because of rapid disease progression. Mucositis was the dose-limiting toxicity in seven patients and diarrhea in two. Disease stabilization occurred in three patients and disease progression in five. Compared with conventional Phase I/II trials using a 5-day infusion regimen, the maximal tolerated dose of 5-FU and FA was slightly higher but significantly lower than in a chronotherapeutic trial that used a different, sinusoidal mode of drug application.

CONCLUSION

Based on these results, the authors feel justified to caution that the circadian timing of 5-FU plus FA may not always allow the safe application of high dose levels. Future Phase I/II studies need to define whether specific drug delivery systems or schedules are necessary for chronotherapy with 5-FU and FA in patients with colorectal carcinoma.

Positive inotropic effects of the beta 2-adrenoceptor agonist terbutaline in the human heart: effects of long-term beta 1-adrenoceptor antagonist treatment

OBJECTIVES

This study was conducted to determine whether activation of cardiac beta 2-adrenoceptors increases contractility in humans and whether this is affected by long-term beta 1-adrenoceptor antagonist treatment.

BACKGROUND

Coexistence of beta 1- and beta 2-adrenoceptors in the human heart is generally accepted. The functional importance of cardiac beta 2-adrenoceptors for increases in contractility in humans, however, has not been completely established.

METHODS

We studied 1) the beta-adrenoceptor subtype mediating positive inotropic effects of the beta 2-adrenoceptor agonist terbutaline in vitro (on right atrial and left ventricular preparations from nonfailing human hearts) and increases in contractility (by measurement of systolic time intervals) in vivo in seven healthy male volunteers; and 2) in vivo whether long-term treatment of volunteers with the beta 1-adrenoceptor antagonist bisoprolol affects terbutaline-induced increases in contractility.

RESULTS

In vitro terbutaline caused a concentration-dependent increase in atrial and ventricular adenylate cyclase activity and force of contraction. Terbutaline effects were antagonized only by the beta 2-adrenoceptor antagonist ICI 118,551, indicating that they were mediated by beta 2-adrenoceptor stimulation. In vivo intravenous infusions of terbutaline (dose range 25 to 300 ng/kg body weight per min for 15 min) dose dependently increased heart rate and shortened the pre-ejection period and heart rate-corrected electromechanical systole (QS2) time. These effects are mediated predominantly by beta 2-adrenoceptor stimulation because they were only marginally affected by the beta 1-adrenoceptor antagonist bisoprolol (1 x 10 mg orally), either given 2 h before infusion or long term for 3 weeks.

CONCLUSIONS

Stimulation of cardiac beta 2-adrenoceptors in humans causes not only in vitro but also in vivo positive inotropic effects. Long-term beta 1-adrenoceptor antagonist treatment does not considerably affect beta 2-adrenoceptor-mediated in vivo increases in contractility. Thus, it may be possible to treat patients with chronic heart failure and long-term beta 1-adrenoceptor antagonist therapy with beta 2-adrenoceptor agonists if immediate inotropic support is needed.

Perfusion imaging of the rat kidney with MR

PURPOSE

To develop a technique for measurement of regional renal perfusion with magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Quantitative renal perfusion images in rats were obtained by measurement of the reduction in kidney MR image signal intensity after steady state magnetic labeling of arterial blood in the suprarenal aorta. Labeling was achieved with adiabatic fast passage inversion of arterial water.

RESULTS

Cortical renal blood flow was 4.9 mL/g/min +/- 0.15 (12 rats), which correlated well with previous measurements obtained with other techniques. Serial perfusion images obtained every 5 minutes during intravenous infusion of either acetylcholine or angiotensin II showed that one increased and the other decreased renal blood flow, respectively, also correlating with previous measurements.

CONCLUSION

Quantitative measurement of cortical renal blood flow can be obtained with proton MR imaging techniques, with use of endogenous arterial water as a tracer. This technique should be readily applicable to measurement of renal perfusion in humans.

Integrin matrix receptors in renal injury

Integrins play a major role in cell-matrix interactions. They alter cellular functions upon binding to matrix proteins or following cross linking and can in turn be regulated by other stimuli acting on the cell. In the kidney integrins may help regulate cellular proliferation and matrix turnover during renal injury, effects which could play an important role in the pathogenesis of glomerulosclerosis and the resultant loss of renal function. Alterations in cell adhesiveness may contribute to tubular epithelial cell sloughing and tubular obstruction in acute renal failure and may play a role in alterations of glomerular capillary wall permeability, leading to proteinuria. Adhesion molecules on GEC may be important targets of antibodies in several models of proteinuric renal disease and areas of GEC detachment from the GBM may be involved in the development of glomerulosclerosis. Since integrins are major links between the ECM and cells, better understanding of their function in the normal kidney and during injury is of importance to a better understanding of the pathogenesis of renal disease.

Intraoperative transesophageal echocardiography

A methodical, basic intraoperative transesophageal exam can be performed quickly by anesthesiologists trained in transesophagea1 echocardiography. This provides a wealth of information with minimal invasiveness that is useful for the anesthesiologist, surgeon, and internist involved in the patient's care. Transesophageal echocardiography (TEE) is particularly valuable in the intraoperative monitoring of ventricular volume, ischemia and evaluation of valve morphology. And, as TEE imaging improves it is rapidly replacing aortography as the gold standard in the rapid evaluation of aortic dissection.

Macroscopic hematuria as a presenting manifestation of oliguric acute tubular necrosis

Macroscopic hematuria associated with acute renal failure usually results from glomerulonephritis or structural abnormalities (stones, tumors, or infections). Acute tubular necrosis is rarely associated with macroscopic hematuria in the absence of other genitourinary abnormalities. We describe a patient who presented with macroscopic hematuria, in whom only acute tubular necrosis could be identified as a causative factor.

Integrin receptors and function on cultured glomerular endothelial cells

Integrin expression and function on a cloned line of rat glomerular endothelial cells (GEndoC) were studied in an effort to obtain a better understanding of the means by which these cells interact with components of the glomerular basement membrane. Cultured GEndoC adhered to fibronectin, laminin and types I and IV collagen and expressed alpha 1 beta 1, alpha 2 beta 1, alpha 3 beta 1, alpha 5 beta 1, alpha v beta 1 and alpha v beta 3 integrins. Synthetic RGDS peptides significantly decreased adhesion to fibronectin (53.1 +/- 4.7% of control). Antibody to rat beta 1 integrin strongly inhibited adhesion to laminin, fibronectin and types I and IV collagen (11.2, 19.0, 67.3 and 31.9% of control adhesion, respectively), while antibody to the rat alpha 1 integrin chain strongly inhibited adhesion to laminin (65.2% of control), but only mildly inhibited adhesion to type IV collagen (77.2% of control) and did not affect adhesion to type I collagen (97.8% of control). Affinity chromatography of GEndoC lysates on a column of immobilized type I collagen displayed predominantly binding of alpha 3 beta 1 integrin with trace amounts of alpha 1 beta 1 and alpha 2 beta 1, documenting the major role of alpha 3 beta 1 in GEndoC adhesion to collagen. Chromatography on the immobilized cell-binding fragment of fibronectin revealed the alpha 5 beta 1 integrin to be the major fibronectin receptor on these cells, but antibody to alpha v beta 3 integrin also documented a minor role for alpha v beta 1 or alpha v beta 3 in fibronectin adhesion.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of acute and chronic hyponatremia on brain buffering in rats

The present studies evaluated whether previously observed impairments in brain buffering during acute hyponatremia were maintained during chronic hyponatremia as well and whether the impairment was due in part to changes in brain water, brain perfusion, or activation of arginine vasopressin (AVP) V1 receptors. Acute (1 and 2 day) and chronic (7 and 14 day) hyponatremia was induced in male Sprague-Dawley rats by constant desmopressin administration in combination with a liquid diet. Brain pH was determined by 31P nuclear magnetic resonance (NMR) in rats anesthetized with N2O and paralyzed with pancuronium. Brain buffering was evaluated by the response to CO2 loading, and brain perfusion was evaluated by 19F-NMR using trifluoromethane washout. Compared with normonatremic controls fed the same diet, brain pH in both acute and chronic hyponatremics was 0.12 pH units lower after 55 min ventilation with 20% CO2 despite identical decreases of approximately 0.35 units in all groups during the first 15 min. Moreover, in the recovery period brain pH overshot basal levels only in normonatremic controls. Brain water content in chronic hyponatremic rats was equal to controls, and brain perfusion was identical in the five groups during CO2 exposure. These results are analogous to those reported during acute hyponatremia induced with AVP and show that the impairment of active brain buffering is maintained during chronic hyponatremia and is unrelated to brain water content, perfusion, tissue catabolism, or AVP V1 receptor activation.