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N Bank

Publications and source records attributed to N Bank.

At least 19 recordsLinked to original sources
PubMed2000

Inhibition of nitric oxide synthase ameliorates cellular injury in sickle cell mouse kidneys.

BACKGROUND: In previous studies of transgenic sickle cell mice, increased renal expression of inducible nitric oxide synthase (iNOS) and endothelial cell isoform of NOS (EcNOS) was found by Western blot and immunohistochemistry. In addition, putative evidence of peroxynitrite (ONOO-) formation was found in the form of positive immunostaining and immunoblot for nitrotyrosine. Apoptosis was also detected by DNA strand breakage and TUNEL assay. The present study was carried out to examine the role of NO/ONOO- in mediating renal tubular cell apoptosis in sickle cell mouse kidneys. METHODS: Mercaptoethylguanidine (MEG), a compound that selectively inhibits iNOS and also is a scavenger of ONOO-, was administered intraperitoneally over a five-day period to control and betas mice. Immunohistochemistry of iNOS and nitrotyrosine, DNA electrophoresis, ApoTACS assay for apoptosis, and Western blot of poly(ADP-ribose) polymerase (PARP) were carried out. RESULTS: MEG administration virtually eliminated renal immunostaining of iNOS and nitrotyrosine and prevented DNA strand breakage. In addition, Western blot analysis of PARP, a nuclear DNA-reparative enzyme activated in response to DNA strand breakage, was found to be cleavaged in hypoxic betas mice, but was partially protected in MEG-treated betas hypoxic mice. Finally, apoptosis was markedly reduced by MEG in betas hypoxic mice. CONCLUSIONS: These observations provide evidence that NO and/or ONOO- are responsible for initiating cell damage, which leads to apoptosis in sickle cell mouse kidneys.

Alanine Transaminase↗
PubMed1998

Peroxynitrite formation and apoptosis in transgenic sickle cell mouse kidneys.

BACKGROUND: In a previous study, nitric oxide synthases (NOS) were found to be strongly expressed in the tubular epithelium of kidneys of a transgenic mouse model of sickle cell disease (alphaHbetaS[betaMDD]). Because NOS activity is often associated with peroxynitrite formation when superoxide radical (.O-2) is present in abundance, we examined the kidneys of sickle cell mice for nitrotyrosine, considered to be a footprint of ONOO-. METHODS: Western blot and immunohistochemistry for nitrotyrosine was carried out. Since peroxynitrite and other reactive oxygen radicals are capable of causing apoptosis, we also performed agarose gel electrophoresis of kidney DNA and TUNEL staining of nuclei, indicators of apoptosis. RESULTS: Nitration of tyrosine residues of three proteins (kD 66, 57 and 22) was found on Western blot of kidney protein extracts of the sickle cell mice. The degree of tyrosine nitration of the 66 kD protein was not significantly different in the control versus transgenic mice, whereas tyrosine nitration of the 57 and 22 kD proteins was clearly increased in transgenic mice. Strong immunostaining for nitrotyrosine was seen in tubular epithelial cells of the sickle cell mice, in close proximity to positive immunostaining of iNOS. Neither iNOS nor nitrotyrosine was expressed in the control mice. DNA "laddering" was found localized to the same zones of the kidney as nitrotyrosine and iNOS immunostaining. TUNEL assay on mouse kidney tissue sections showed minimal tubular cell apoptosis in normal mouse with hypoxia, mild tubular cell apoptosis in sickle cell mouse in room air, and moderate tubular cell apoptosis in sickle cell mouse with hypoxia. CONCLUSIONS: The observations suggest that ONOO- and perhaps other reactive oxygen species are being produced in the sickle cell kidney. The mechanism may be ischemia/reperfusion due to intermittent vascular occlusion by sickle cells. The resulting hypoxia could result in iNOS activation, superoxide radical and peroxynitrite formation. Two consequences of these reactions appear to be nitration of tyrosine residues of some renal proteins and enhanced apoptosis.

Anemia, Sickle Cell↗
PubMed1996

Immunohistochemical localization of hepatic nitric oxide synthase in normal and transgenic sickle cell mice: the effect of hypoxia.

Nitric oxide (NO) generated from L-arginine and molecular oxygen by nitric oxide synthase (NOS) has been shown to influence hepatocellular function and pathology in response to ischemia and certain hepatotoxins. In the present study, we examined the liver of a transgenic line of sickle cell mice for hepatocellular injury and localization of two isoforms of NOS, the endothelial constitutively expressed isoform (EcNOS) and the inducible isoform (iNOS) by immunohistochemistry. Diffuse expression of EcNOS was observed in hepatocytes of control and sickle cell animals maintained under room air conditions. In contrast, iNOS was observed only in the sickle cell mice, well-localized to hepatocytes surrounding the central veins of the lobules. When normal mice were exposed to hypoxic conditions for 4 to 5 days, iNOS immunostaining appeared de novo in a patchy distribution throughout the liver lobules. In the sickle cell mice, hypoxia appeared to increase the subjective intensity of pericentral staining of iNOS. Liver histology was normal in the sickle cell mice maintained under room air conditions, but showed multifocal areas of necrosis when sickling was exacerbated by chronic hypoxic conditions. However, a pericentral zone of preserved architecture was present, corresponding to the region of iNOS staining. We postulate that pericentral induction of iNOS under ambient conditions occurs in transgenic sickle cell mice in response to particularly intense hypoxic conditions near the central veins of the liver. Increases in NO synthesis may occur in this region, which would serve to protect these cells from ischemic damage either directly or by maintaining blood flow. These findings could be relevant to liver pathophysiology in patients with sickle cell disease.

Anemia, Sickle Cell↗
PubMed1996

Renal nitric oxide synthases in transgenic sickle cell mice.

The alpha H beta S [beta MDD] mouse is a useful model for studying renal functional abnormalities in sickle cell disease. We previously reported that these mice develop a urine concentrating defect when chronically exposed to a low oxygen environment. In the present study, we measured glomerular filtration rate (GFR), urinary excretion of NO2 s+ NO3, the stable products of nitric oxide (NO), and the abundance of endothelial constitutive nitric oxide synthase (NOS III) and inducible nitric oxide synthase (NOS II) in the kidneys by Western blot. Immunohistochemistry was also carried out. We found that GFR is significantly higher in the transgenic mice than in controls. The urinary NO2 + NO3/creatinine ratio was also higher. The Western blots revealed that both NOS III and NOS II are markedly increased in the kidneys of transgenic mice as compared to normal control mice. Immunohistochemistry localized NOS III reactivity in proximal convoluted cells in the cortex of control and alpha H beta S [beta MDD] mice. NOS II immunostaining was not seen in control mice but was clearly evident in glomeruli and distal nephron segments of the alpha H beta S [beta MDD] mice. These observations suggest that NOS II is induced in glomeruli and distal nephrons of the alpha H beta S [beta MDD] mice. An increase in synthesis of NO may occur in the glomeruli as a result of NOS II induction, and this may contribute to the hyperfiltration in these mice.

Anemia, Sickle Cell↗
PubMed1995

Interpretation of positive edrophonium (Tensilon) test in patients with end-stage renal disease.

Many patients with end-stage renal disease (ESRD) have signs and symptoms of easy fatigability, fluctuating weakness, apathy, dry mouth, and blurring of vision. These symptoms can be confused with disorders of neuromuscular transmission. When present, the physician may want to determine whether the patient has myasthenia gravis--the commonest of all neuromuscular disorders--and administer the edrophonium (Tensilon) test. An unequivocally positive response to the test must be interpreted with caution in ESRD. However, the exact mechanism of a positive response is unclear but may be explained by metabolic abnormalities related to end-stage renal disease, i.e., uremic toxins, disordered calcium metabolism, abnormal neuromuscular mechanism, associated neurological disorders, or myopathic processes in uremia, all of which can affect neuromuscular transmission.

Aged↗
PubMed1994

Mechanism of vasoconstriction induced by chronic inhibition of nitric oxide in rats.

Either acute or chronic inhibition of nitric oxide synthesis by L-arginine analogues results in increases in mean arterial pressure and reductions in renal blood flow. The role of endogenous vasoconstrictors in mediating these effects is not entirely clear. In the present study, nitric oxide was inhibited in male Sprague-Dawley rats by oral administration of nitro-L-arginine for 3 weeks. At the end of this time, mean arterial pressure was 30 to 40 mm Hg higher than in normal controls, renal blood flow and glomerular filtration rate were 25% to 30% lower, and renal vascular resistance was markedly increased. Intravenous infusion of receptor antagonists for angiotensin II, thromboxane, epinephrine, and endothelin-1 had no significant effect on the hypertension. Inhibition of prostaglandin synthesis and furosemide-induced diuresis in the presence of angiotensin blockade also had no effect on blood pressure. Renal vascular resistance was also unaffected by these interventions, except that saralasin did reduce renal resistance in both control and nitric oxide-inhibited groups. However, the absolute level of renal vascular resistance remained higher in the latter group. Calcium channel blockade partially corrected blood pressure and renal resistance, but the levels remained significantly higher than in control animals. The findings are consistent with the view that the increase in vascular smooth muscle tone caused by inhibition of nitric oxide synthesis cannot be accounted for by overexpression of common endogenous vasoconstrictors. Rather, the generalized increase in vascular smooth muscle tone appears to be due to a direct effect of reduced nitric oxide availability, which may lead to an increase in intracellular calcium concentration or sensitivity.

Animals↗
PubMed1994

An adult patient with hyperimmunoglobulemia E (Job's) syndrome, end-stage renal disease and repeated episodes of peritonitis.

We report the first case of an adult patient with hyperimmunoglobulemia E (Job's) syndrome, end-stage renal disease and repeated episodes of Staphylococcus peritonitis. A 42-year-old black female with end-stage renal disease was treated with hemodialysis, and later switched to peritoneal dialysis because of severe vascular access problems. On CAPD, she had numerous (> 15) episodes of staphylococcal peritonitis. Past history included chronic atopic eczema and repeated sinopulmonary infections since childhood. She was found to have serum IgE levels greater than 10,000 units/ml. This combination of repeated infections, chronic skin condition and phenomenal elevation of IgE levels establish the diagnosis of hyperimmunoglobulemia E (Job's) syndrome. The cause of repeated episodes of Staphylococcal peritonitis are presumed to be related to impaired host defense mechanisms known to be present in patients with this disorder. As nephrologists, we should be aware that patients with impaired host defense mechanisms are highly susceptible to peritonitis in the presence of an indwelling peritoneal catheter.

Adult↗
PubMed1993

Role of EDRF (nitric oxide) in diabetic renal hyperfiltration.

In order to study the role of EDRF in diabetic hyperfiltration, the concentrations of NO2-/NO3-, the stable products of nitric oxide (NO), were measured in arterial plasma, urine, and renal venous blood in streptozotocin diabetic rats and normal control rats. In additional experiments, the renal hemodynamic and blood pressure responses to graded doses of an inhibitor of NO synthesis (Nitro-L-arginine; NLA) were measured. We found that plasma and urinary levels of NO2/NO3 are significantly higher in STZ diabetic rats (10 to 15 days) than in normal rats. Renal blood flow and GFR fell comparably in diabetic and normal rats in response to NLA infusion, although the absolute levels of RBF and GFR remained significantly higher in the diabetic rats at all doses of the inhibitor. Mean arterial blood pressure (MAP) rose in response to NLA administration, but the increase in the diabetic rats was significantly blunted as compared with the normal rats. Similarly, renal vascular resistance (RVR) increased less in the diabetic than in the normal rats at comparable doses of NLA. The blunted vasoconstrictor responses to NLA were accompanied by a smaller reduction in the levels of NO2-/NO3- in the urine of the diabetic versus the normal rats. These findings suggest that NO synthesis is increased in diabetic rats manifesting hyperfiltration and are consistent with the view that excess NO synthesis contributes to renal hyperfiltration.

Animals↗
PubMed1993

Renal hemodynamic consequences of hyperlipidemia.

Short-term dietary induced hypercholesterolemia in animals has been found to cause either increased vascular tone in various blood vessels, such as coronary arteries and renal vasculature, or impaired relaxation to endothelial-dependent vasodilators. In the kidney, renal blood flow, glomerular filtration rate and ultrafiltration coefficient are decreased whereas glomerular capillary pressure is elevated. These findings indicate pre- and post-glomerular constriction and mesangial cell contraction. Most evidence indicates that oxidized low density lipoprotein (ox-LDL) is responsible for initiating these functional abnormalities, and that it affects the endothelium rather than vascular smooth muscle cells. Nitric oxide (NO) and prostaglandin production are increased, probably due to the effects of ox-LDL on endothelial cell membranes. Vasoconstrictor prostaglandins and accelerated inactivation of NO by reactive oxygen species appear to play important roles in the impaired relaxation response. These endothelial abnormalities are postulated to contribute to progressive glomerulosclerosis via local hemodynamic changes and/or direct effects on mesangial cell proliferation and matrix synthesis.

Animals↗
PubMed1992

High expression of human beta S- and alpha-globins in transgenic mice: erythrocyte abnormalities, organ damage, and the effect of hypoxia.

A line of transgenic mice with two cointegrated transgenes, the human beta S- and alpha 2-globin genes, linked to the beta-globin locus control region was produced and bred with mice carrying a deletion of the mouse beta major-globin gene. In transgenic mice homozygous for the beta major deletion (alpha H beta S[beta MDD]; where alpha H is human alpha-globin and MD is mouse deletion), 72.5 +/- 2.4% (mean +/- SD) of the beta-chains are beta S and the ratio of alpha H- to beta S-globin was 0.73. Introduction of a heterozygous mouse alpha-globin deletion into mice homozygous for the beta major deletion (alpha H beta S[alpha MD beta MDD]) resulted in 65.1 +/- 8.5% beta S and a human alpha/beta ratio of 0.89 +/- 0.2. Sickling occurs in 95% of erythrocytes from alpha H beta S[beta MDD] mice after slow deoxygenation. Transmission electron microscopy revealed polymer fiber formation but not fascicles of fiber. Increased organ weight was noted in lung, spleen, and kidney of transgenic mice vs. controls that may be due to hypertrophy or increased blood volume in the lungs and/or increased tissue water content. The hemoglobin content of lung, spleen, and kidney was also elevated in transgenic animals due to trapped hemoglobin and/or increased blood volume. When transgenic and control mice were examined by magnetic resonance imaging at 9.4 tesla, some transgenic animals had enlarged kidneys with prolonged relaxation time, consistent with increased organ weight and water content. The glomerular filtration rate was elevated in transgenic animals, which is characteristic of young sickle cell patients. Furthermore, exposure to hypoxia resulted in significantly decreased hematocrit, increased erythrocyte density, and induced a urine-concentrating defect. We conclude that the transgenic mouse line reported here has chronic organ damage and further hematological and organ dysfunction can be induced by hypoxia.

Anemia, Sickle Cell↗
PubMed1992

Reduced glomerular thromboxane receptor sites and vasoconstrictor responses in diabetic rats.

Glomerular thromboxane production and urinary thromboxane excretion are increased in early diabetes, but in spite of this renal blood flow and glomerular filtration rate are significantly higher than in control animals. To study the possibility of a defect in thromboxane actions in the kidney, we have measured glomerular thromboxane receptors and the renal hemodynamic response to the administration of a stable thromboxane analog in diabetic rats. Glomerular thromboxane receptors were studied in hyperglycemic diabetic rats 7 to 10 days after injection of streptozotocin (65 mg/kg, i.v.) and in normal controls. Scatchard analysis of equilibrium binding using the thromboxane antagonist, [3H]-SQ29548, demonstrated one class of high affinity thromboxane receptor sites in control (Kd = 19.9 +/- 2.6 nM, N = 16) and diabetic rats (Kd = 19.8 +/- 2.1 nM, N = 8, P = NS). The number of thromboxane receptors was reduced by 44% in diabetic rats (control, 374 +/- 20 vs. diabetic, 210 +/- 21 fmol/mg, P less than 0.01). Thromboxane binding in diabetic rats was not restored to normal levels by thromboxane synthetase inhibition with OKY046. Diabetic rats had higher renal blood flow (diabetic, 7.03 +/- 0.18 vs. control, 6.33 +/- 0.13 ml/min, P less than 0.05) and glomerular filtration rate (2.42 +/- 0.10 vs. 1.96 +/- 0.07 ml/min, P less than 0.05). Infusion of the stable thromboxane agonist, U46619 (0.1 micrograms/kg/min), reduced renal blood flow and glomerular filtration rate in all animals, but the constrictor responses were blunted by 50% in hyperglycemic diabetic rats compared with normal controls or euglycemic diabetic rats (P less than 0.05). Control of blood glucose with insulin normalized the number of glomerular thromboxane receptor sites, reversed hyperfiltration and restored glomerular responses to thromboxane agonist. The abnormalities of glomerular thromboxane receptors are similar to changes in angiotensin II receptors, and suggest a generalized defect in vasoconstrictor receptors in the diabetic kidney.

Animals↗
PubMed1992

Role of thromboxane in impaired renal vasodilatation response to acetylcholine in hypercholesterolemic rats.

Short-term cholesterol feeding has been shown to cause impaired vasodilatation in response to acetylcholine. The present study of renal hemodynamics was carried out to examine the role of thromboxane/PGH2 in mediating this abnormal response. In normal rats (ND), infusion of acetylcholine into the suprarenal aorta caused marked increases in renal blood flow, GFR, single nephron glomerular filtration rate, single nephron afferent plasma flow, and ultrafiltration coefficient, accompanied by a fall in preglomerular resistance. In cholesterol fed rats (CSD), the response to acetylcholine was markedly blunted. Infusion of L-arginine, the precursor to nitric oxide (NO), caused comparable renal vasodilatation in ND and CSD rats, implying that the ability to synthesize NO from its precursor was not severely impaired in the CSD animals. The observations do not exclude, however, the possibility of impaired synthesis of NO from endogenous precursor. In additional experiments, we infused a TxA2/PGH2 receptor antagonist in CSD rats and then administered acetylcholine. Renal vasodilatation occurred to a degree indistinguishable from that in ND rats given acetylcholine alone. When ND rats were infused with the same combination of the TxA2/PGH2 receptor antagonist and acetylcholine, renal vasodilatation was also significantly greater than with acetylcholine alone. This suggests that acetylcholine initiates release of vasoconstrictor prostanoids as well as NO from vascular endothelium. This was observed in ND as well as in CSD animals. Because LDL increases the supply of arachidonic acid for prostaglandin synthesis, we postulate that greater amounts of PGH2/TxA2 are synthesized via calcium activation of phospholipase A2 when acetylcholine is administered to CSD animals. This may account in large measure for the blunted vasodilatation to acetylcholine.

Acetylcholine↗
PubMed1991

Acid-base balance and acute renal failure.

In several models of acute renal failure (ARF) in animals, acidosis has been found to worsen the renal failure, whereas alkalosis may ameliorate it. Most evidence points to a reduction in the degree of tubular obstruction by casts as the explanation for the beneficial effects of bicarbonate administration. However, alkalinization of the urine is effective only in some experimental conditions but not in others. The reason for these differences is not known but may relate to the nature of the obstructing casts. Alkalinization of the urine could decrease cast formation in Bence-Jones protein and hemoglobinuric ARF by increasing the negative charge on these molecules, thereby diminishing precipitation with anionic Tamm-Horsfall protein. In contrast, release of tubular cell contents into the urine, as occurs in renal ischemia, could lead to complex casts not responsive to alterations in urine pH. In aminoglycoside ARF, the beneficial effects of urine alkalinization may be due primarily to reduced uptake of the antibiotic by tubular epithelium, resulting in less cellular damage. Because tubular obstruction reduces net filtration pressure, new approaches to therapy which include efforts to raise net glomerular filtration pressure may improve the therapeutic efficacy of alkali administration.

Acid-Base Imbalance↗
PubMed1990

Progressive increases in luminal glucose stimulate proximal sodium absorption in normal and diabetic rats.

The effect of progressive increases in intraluminal glucose concentration on proximal tubule sodium absorption was studied in normal and streptozotocin diabetic rats by microperfusion. Each tubule was perfused twice, with and without glucose added to the perfusion fluid. Net sodium and water absorption were markedly enhanced by 300-500 mg% intraluminal glucose in both normal and diabetic rats. Substituting the transported but nonmetabolized glucose analogue, alpha-methyl D-glucoside for glucose also resulted in marked stimulation of sodium absorption, whereas substituting bicarbonate and acetate for chloride in the perfusion solution inhibited the effect of glucose. These observations suggest that the stimulation of sodium absorption by glucose was mediated by the brush border Na/glucose cotransporter. Sodium concentration and osmolality were found to fall markedly to hypotonic levels when high glucose concentrations were in the perfusion fluid. This luminal hypotonicity may be an important driving force for proximal fluid absorption. In poorly controlled diabetes, high filtered glucose concentrations may lead to enhanced proximal sodium and water absorption, which could in turn contribute to volume expansion, hypertension, and renal hypertrophy.

Acetates↗
PubMed1990

Renal vasoconstriction caused by short-term cholesterol feeding is corrected by thromboxane antagonist or probucol.

Recent studies indicate that short-term cholesterol feeding causes vascular hyperreactivity and/or increased tone in certain vascular beds. The present study in rats examined the effect of 3 wk of cholesterol-supplemented diet (CSD) on renal hemodynamics. We tested the hypothesis that LDL oxidized in vivo is causally related to increased renal vascular tone by adding the antioxidant drug probucol to the CSD (CSD + P). Micropuncture of surface nephrons in the CSD rats demonstrated that single nephron glomerular filtration rate (SNGFR) and single nephron afferent plasma flow (QA) were markedly lower than in normal rats, whereas glomerular capillary pressure (PGC), afferent arteriolar resistance (RA), and single nephron filtration fraction (SNFF) were higher. In the CSD + P animals, almost all of these hemodynamic abnormalities were absent. TXB2 and PGE2 were increased in proximal tubule fluid and urine in the CSD rats, but normal in the CSD + P group. Infusion of a TXA2 receptor antagonist into the suprarenal aorta of CSD rats caused a rapid return to normal of RBF (renal blood flow), GFR (glomerular filtration rate), SNGFR, QA, RA, PGC, and Kf (ultrafiltration coefficient). Our observations demonstrate that cholesterol feeding leads to renal vasoconstriction, which appears to be mediated largely by increased TXA2 production. The fact that probucol prevented the hemodynamic abnormalities as well as the increased TX production is consistent with the hypothesis that LDL oxidized in vivo initiates events leading to TX mediated vasoconstriction.

Animals↗
PubMed1989

Effect of long-term normalization of serum complement levels on the course of lupus nephritis.

PURPOSE: We compared the long-term outcome of patients with lupus nephritis in whom normalization of complement levels (CH50) was sustained by adjustment of immunosuppressive therapy to those patients with persistently low complement levels despite similar immunosuppression in whom therapy was adjusted solely on the basis of clinical disease activity. PATIENTS AND METHODS: Thirty-nine female patients with lupus nephritis recruited from 1972 to 1979 were prospectively studied (mean follow-up, 116.7 +/- 11 months). Entry criteria included initial renal biopsy, low CH50, and elevated anti-DNA antibody levels. A second biopsy was performed in 24 patients after an interval of 40.6 +/- 5 months. Treatment was started with prednisone (1 mg/kg/day). Azathioprine at a dose of 1.5 to 2.0 mg/kg/day was added if complement was not normalized by prednisone alone. Twenty-five of 39 patients had normal complement levels within six months (Group 1), and immunosuppressive therapy was tapered but continuously readjusted to the lowest dosage that preserved normal CH50 and maintained clinical remission. Eight of these 25 patients subsequently became persistently hypocomplementemic due to inadequate drug intake (Group 1B), whereas the complement levels continued to be controlled in the other 17 patients (Group 1A). Despite similar therapy, the remaining 14 patients did not achieve normalization of complement within the initial six months of therapy, and therefore future treatment decisions were based solely on clinical symptoms (Group 2). Renal pathologic lesions were classified according to World Health Organization criteria and a semi-quantitative chronicity index. RESULTS: During the first six months, there were no significant differences in clinical or histologic features between patients in whom complement levels were controlled and patients in whom complement levels were not controlled. After a mean observation period of 10 years, however, patients with consistent normalization of complement (Group 1A) did much better than patients with only short-term complement control (Group 1B) or persistent hypocomplementemia (Group 2). Both groups with low complement levels had a similar outcome with significantly worse kidney and patient survival. Life-table analysis demonstrated that the differences in outcome between complement-controlled and complement-uncontrolled groups became apparent only after five or more years of follow-up. Patients with a low chronicity score on initial biopsy whose complement level was controlled did uniformly well with no renal failure or death. (ABSTRACT TRUNCATED AT 400 WORDS)

Azathioprine↗