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Biomedical subjects

R J Quigg

Publications and source records attributed to R J Quigg.

At least 19 recordsLinked to original sources
PubMed1992

Inhibition of the alternative pathway of complement by glomerular chondroitin sulphate proteoglycan.

Cultured rat glomerular epithelial cells (GEC) synthesize and secrete a complement inhibitory chondroitin sulphate B proteoglycan (termed GCRF). As proteoglycans and their component glycosaminoglycans may affect several different steps of complement activation, the functional properties of GCRF were investigated in this study. GCRF inhibited preformed alternative pathway convertases (C3bBbP), but did not substantially accelerate their decay. In contrast to other polyanions, GCRF did not affect the activity of human or rat factor H, nor did it inhibit the terminal complement proteins. GCRF inhibited the effect of decay-accelerating factor (DAF) on C3bBbP when the two were incubated together and DAF was in excess, but it did not affect the decay of DAF of classical pathway convertases. However, when DAF was first incorporated into the erythrocyte membrane, the effect of GCRF on C3bBbP was additive to that of DAF. Thus, GCRF inhibits the activity of C3bBbP and blocks the action of DAF, but not that of factor H, perhaps by binding to factor B in the alternative pathway convertase.

Animals↗
PubMed1991

Effect of nephritogenic antibody on complement regulation in cultured rat glomerular epithelial cells.

In passive Heymann nephritis, a rat model of membranous nephropathy, antibody (anti-Fx1A) activates C on the surface of the glomerular epithelial cell (GEC), leading to GEC injury and proteinuria. In this study, we examined C activation by anti-Fx1A in cultured rat GEC. In addition to anti-Fx1A IgG, anti-Fx1A F(ab')2 and Fab' led to GEC injury in the presence of rat or human sera as sources of C. Cytotoxicity was Mg2+ and factor B dependent, but Ca2+ independent, indicating that anti-Fx1A activated the C alternative pathway (AP). Furthermore, in the presence of Mg2+ and factor B, anti-Fx1A enhanced 125I-C3b deposition on GEC in the absence of classical pathway activation. AP C3 and C5 convertases formed on GEC (GEC-C3bBbP) were inactivated over time, probably due to binding of GEC C regulatory proteins. This inactivation was prevented when GEC-C3bBbP were incubated with anti-Fx1A IgG. An antibody raised against cultured GEC that binds to GEC in vitro and in vivo had no effect on C3 and C5 convertases, suggesting that stabilization of C3bBbP is unique to anti-Fx1A. Anti-Fx1A Fab' also stabilized GEC-C3bBbP, indicating that cross-linking of membrane Ag was not required. C3bBbP on E were not affected by anti-Fx1A, excluding direct stabilization of convertases by anti-Fx1A. Therefore, anti-Fx1A inhibits C regulation on GEC, which can account for its ability to activate the AP. This represents a potentially powerful mechanism of producing disease in vivo.

Animals↗
PubMed1991

Acute glomerulonephritis in a patient with Rocky Mountain spotted fever.

It is generally assumed that acute tubular necrosis is the etiology of renal failure that can occur during the course of Rocky Mountain spotted fever (RMSF). However, histologic examination of kidneys has been mainly limited to autopsy cases of fulminant infections. Acute glomerulonephritis due to glomerular immune complex deposition has not been reported in RMSF. We describe a case of acute oliguric renal failure that developed more than 2 weeks following the onset of RMSF. Renal biopsy showed acute glomerulonephritis with inflammatory cell infiltration and subendothelial immune deposits. Thus, acute glomerulonephritis should be in the differential diagnosis of acute renal failure that occurs in RMSF.

Acute Kidney Injury↗
PubMed1991

Isolation of a novel complement regulatory factor (GCRF) from glomerular epithelial cells.

Cultured rat glomerular epithelial cells (GEC) are able to prevent both antibody-directed and spontaneous (alternative pathway) complement activation. In this study, a novel complement regulatory factor (GCRF) was isolated from GEC. The ability to accelerate the decay of alternative pathway C3/C5 convertases formed on sheep erythrocytes (EC3bBbP) was used to guide purification. GEC were solubilized in Triton X-114 and GCRF was recovered in the aqueous phase. Complement inhibitory material also was present in the culture supernatant, which likely represented GCRF. By Mono Q anion exchange chromatography, GCRF eluted at greater than or equal to 0.6 M NaCl and by Superose 6 size-exclusion chromatography, it had a Kav less than or equal to 0.3. GCRF reduced the t1/2 of EC3bBbP from 128 minutes in buffer alone to 41 minutes in 3 micrograms/ml GCRF protein, and also prevented formation of EC3bBbP in a dose-dependent fashion. Digestion with chondroitinase ABC, neuraminidase, or trypsin, but not with heparitinase or chondroitinase AC significantly reduced the activity and size of GCRF, demonstrating that it is a sialic acid-containing dermatan sulfate proteoglycan. Thus, cultured rat GEC synthesize and secrete into the medium, GCRF, a dermatan sulfate proteoglycan with complement inhibitory activity.

Animals↗
PubMed1991

Limb vascular responsiveness to beta-adrenergic receptor stimulation in patients with congestive heart failure.

BACKGROUND: In patients with congestive heart failure, the chronotropic and inotropic responses to beta-adrenergic agonists are reduced. It is not known whether desensitization of peripheral beta-adrenoceptors accounts for impaired limb vasodilation in these patients. Accordingly, we studied 14 normal subjects and 13 age-matched patients with congestive heart failure. METHODS AND RESULTS: To distinguish vasodilation mediated by beta-adrenoceptors and adenylate cyclase from that mediated by stimulation of guanylate cyclase, each subject received intrabrachial artery infusions of isoproterenol (1-100 ng/min) and sodium nitroprusside (0.3-10 micrograms/min), respectively. Forearm blood flow was determined by venous occlusion plethysmography. Maximal vasodilative potential, determined during reactive hyperemia, was reduced in the patients with congestive heart failure. The maximal forearm blood flow response to isoproterenol was comparable in patients with heart failure and in normal subjects (8.0 +/- 1.1 versus 9.2 +/- 1.2 ml/100 ml of tissue/min, respectively, p = NS). Furthermore, the dose-response relation to isoproterenol was similar in both groups. Likewise, the forearm vasodilative response to sodium nitroprusside was preserved in the heart failure group. Plasma concentration of norepinephrine was higher in the patients with heart failure (436 +/- 34 versus 201 +/- 74 pg/ml, p less than 0.01). When both groups were considered, there was no correlation between norepinephrine levels and the maximal forearm blood flow response to isoproterenol (r = 0.10, p = NS). CONCLUSIONS: We conclude that beta-adrenoceptor desensitization does not occur in the limb vessels of patients with congestive heart failure.

Adrenergic beta-Agonists↗
PubMed1990

Cytosolic calcium and protein kinase C reduce complement-mediated glomerular epithelial injury.

In rat membranous nephropathy, protein-uria is due to formation of the C5b-9 membrane attack complex of complement (C), and is associated with morphological evidence of glomerular epithelial cell (GEC) injury. Analogous morphological changes are induced by C5b-9 in cultured GEC. In addition, in cultured GEC C5b-9 induces Ca2+ influx, as well as Ca2+ mobilization and increased 1,2-diacylglycerol due to the activation of phospholipase C. In this study we investigated how this GEC activation pattern might influence C-mediated GEC injury. We demonstrate that the C5b-9-induced increase in cytosolic Ca2+ concentration ([Ca2+]i) did not impair ATP generation by mitochondria, suggesting that it does not contribute to cytotoxicity. Moreover, this increase in [Ca2+]i protected GEC from C-mediated cytolysis. However, a large increase in [Ca2+]i (produced by the Ca2+ ionophore A23187) impaired ATP generation and aggravated C-mediated cytotoxicity, suggesting that intact mitochondrial activity is necessary for GEC to withstand C attack. Activation of protein kinase C (PKC) by phorbol myristate acetate (PMA) also decreased C-mediated cytolysis. Conversely, C lysis was enhanced in GEC that had been pretreated for 18 hours with a high dose of PMA to deplete PKC, and following PKC inhibition with H-7. Therefore, PKC activation, possibly resulting from C5b-9-induced increase in 1,2-diacylglycerol, triggered mechanisms that protected GEC from C-mediated injury. Thus, as a consequence of C5b-9-induced phospholipase activation, the amount of C-induced GEC injury is diminished.

Adenosine Triphosphate↗
PubMed1990

Extracellular matrix regulates proliferation and phospholipid turnover in glomerular epithelial cells.

To understand how glomerular epithelial cell (GEC) growth might be regulated in health and disease, we studied the effects of growth factors and extracellular matrix on proliferation and membrane phospholipid turnover in cultured rat GECs. In GECs adherent to type I collagen matrix, epidermal growth factor (EGF), insulin, and serum stimulated DNA synthesis and increased cell number. In addition, GECs proliferated when adherent to type IV collagen, but not to laminin or plastic substrata. Attachment of GECs to the substrata that facilitated proliferation (types I or IV collagen) produced increases in 1,2-diacylglycerol (DAG), an activator of protein kinase C (PKC). Increased DAG was associated with hydrolysis of inositol phospholipids and an increase in inositol trisphosphate and was not dependent on the presence of growth factors. After PKC downregulation (by preincubation with a high dose of phorbol myristate acetate), DNA synthesis was enhanced in GECs adherent to collagen. Thus contact of GECs with collagen matrices is required for serum, EGF, or insulin to induce proliferation. Collagen matrix also activates phospholipase C. As a result, the DAG-PKC signaling pathway desensitizes GECs to the mitogenic effects of growth factors and might promote cell differentiation. Understanding the interaction between GECs, growth factors, and extracellular matrix may elucidate the mechanisms of proliferation during glomerular injury.

Animals↗
PubMed1989

Decay accelerating factor regulates complement activation on glomerular epithelial cells.

Epithelial cells of the glomerular capillary are the site of C5b-9 mediated injury in rat membranous nephropathy. We investigated the regulation of C activation by cultured glomerular epithelial cells (GEC). Rat and human GEC were more resistant to C injury by homologous C than heterologous C. In human GEC homologous C cytotoxicity was enhanced by antiserum to decay accelerating factor (DAF) indicating that homologous C activation was, at least in part, restricted by membrane DAF. Anti-DAF immunoprecipitated a 67-kDa protein from human glomeruli. In rat GEC, pronase and phosphatidylinositol-specific phospholipase C (which are known to inactivate human DAF) enhanced cytotoxicity by homologous C. Thus, DAF is present on human GEC in culture and in human kidney glomeruli, and a DAF-like protein is present on cultured rat GEC. These proteins regulate C activation in vitro and may play a role in controlling C activation on GEC in vivo.

Animals↗
PubMed1989

Mechanism of the attenuated peak heart rate response to exercise after orthotopic cardiac transplantation.

The mechanism responsible for attenuation of the peak heart rate response to exercise in patients after cardiac transplantation was studied. Because the donor heart is believed to be surgically denervated, the peak heart rate response to exercise is dependent primarily on 1) an increase in the circulating levels of the catecholamines norepinephrine and epinephrine at peak exercise, and 2) the end-organ responsiveness of the sinoatrial (SA) node to beta-adrenergic stimulation. To assess the former mechanism, the levels of plasma nonepinephrine and epinephrine were measured at rest and at peak exercise on a cycle ergometer in 23 transplant recipients an average of 7 +/- 1 months after transplantation and in 23 normal subjects matched for age. To assess the latter mechanism, the heart rate response to a graded infusion of isoproterenol was determined in six normal subjects with and without atropine pretreatment and in eight transplant recipients. In transplant recipients, both the absolute plasma levels of nonepinephrine and epinephrine at peak exercise and the increments from baseline to peak exercise were comparable with or greater than those in normal subjects. In transplant recipients, the isoproterenol dose that increased heart rate by 25 beats/min over baseline was not different from that in atropine-treated normal subjects (normal subjects 9 +/- 2 ng/kg per min; transplant recipients 11 +/- 1 ng/kg per min; p = NS). These data show that after cardiac transplantation, there is a normal or slight elevation of circulating catecholamines at peak exercise, and that the responsiveness of the SA node to beta-adrenergic stimulation is normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Complement C5b-9 complex activates phospholipases in glomerular epithelial cells.

In rat membranous nephropathy, formation of the C5b-9 membrane attack complex (MAC) leads to proteinuria in association with glomerular visceral epithelial cell (GEC) injury. These alterations in GEC function and morphology might result from changes in intracellular free Ca2+ concentration [( Ca2+]i) and activation of phospholipases. We demonstrate that in cultured rat GEC, antibody-directed formation of noncytolytic amounts of the MAC induced a rapid and sustained increase in [Ca2+]i that was partly inhibited by ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). The MAC elevated levels of inositol bis- (IP2) and trisphosphate (IP3), as well as 1,2-diacylglycerol (DAG) and phosphatidic acid (PA). In permeabilized GEC, IP3 released Ca2+ from intracellular stores. Cellular 45Ca2+ uptake was also increased by the MAC. Thus, in GEC, the MAC induced Ca2+ mobilization from intracellular stores secondary to activation of phospholipase C and production of IP3, as well as enhanced Ca2+ influx. In addition, C5b-9 stimulated release of arachidonic acid (AA), prostaglandin F2 alpha, and thromboxane A2. Indomethacin partially inhibited the increase in DAG levels observed with the MAC, whereas the prostaglandin H2/thromboxane A2 analogue U46619 elevated DAG, suggesting that an eicosanoid product of MAC-induced AA release may enhance the activation of phospholipase C. Activation of phospholipases by the MAC may lead to altered GEC function and thereby contribute to the pathophysiological changes that characterize complement-dependent rat membranous nephropathy.

Animals↗
PubMed1989

Beta-adrenergic receptor number and adenylate cyclase function in denervated transplanted and cardiomyopathic human hearts.

To test the hypothesis that there is up-regulation of beta-adrenergic receptor density or supersensitivity of beta-adrenergic receptor-stimulated adenylate cyclase in the denervated transplanted human heart, we studied myocardium from transplanted, normal, and failing hearts. Myocardium was obtained from 10 patients 9 +/- 3 months after cardiac transplantation, from 10 patients without cardiac disease, and from eight patients with symptomatic congestive heart failure due to idiopathic cardiomyopathy. beta-Adrenergic receptor density in transplanted myocardium (15 +/- 3 fmol/mg protein, 1.20 +/- 0.14 fmol/mg DNA) was not different from that in normal myocardium (22 +/- 3 fmol/mg protein, 1.46 +/- 0.13 fmol/mg DNA; p = NS for both). In myocardium from cardiomyopathic hearts, beta-adrenergic receptor density was markedly reduced (8 +/- 2 fmol/mg protein, 0.84 +/- 0.13 fmol/mg DNA; p less than 0.05 and p less than 0.01 vs. normal myocardium, respectively). Likewise, the response of adenylate cyclase to isoproterenol in transplanted myocardium was not significantly different from that in normal myocardium, but the response was markedly depressed in cardiomyopathic myocardium. Although forskolin-stimulated adenylate cyclase activity was similar in all three groups, guanine nucleotide-stimulated adenylate cyclase activity was markedly reduced in transplanted myocardium (20 +/- 17 vs. 78 +/- 13 pmol/mg/min for normal myocardium, p less than 0.01) and to a lesser degree in cardiomyopathic myocardium (39 +/- 14 pmol/mg/min, p less than 0.03 vs. normal myocardium). Thus, there is no evidence of beta-adrenergic receptor up-regulation or supersensitivity in denervated transplanted human myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1989

Impaired chronotropic response to exercise in patients with congestive heart failure. Role of postsynaptic beta-adrenergic desensitization.

The mechanism responsible for the attenuated heart rate (HR) response to exercise in patients with congestive heart failure (CHF) was investigated in 46 normal subjects and 59 patients with CHF stratified by peak exercise oxygen consumption (VO2). The peak exercise HR and the increment in HR from rest to peak exercise were decreased in CHF patients, and both correlated strongly with peak VO2 (r = 0.810, p less than 0.0001; r = 0.863, p less than 0.0001, respectively). Peak exercise norepinephrine level (NE) and the increment in NE from rest to peak exercise were not attenuated in CHF patients. Resting NE was elevated in CHF patients and correlated inversely with peak VO2 (r = -0.595, p less than 0.001). However, no significant correlation occurred between peak VO2 and either peak exercise NE or the exercise increment in NE. The ratio of the exercise increments in HR and NE, and indirect index of sinoatrial node sympathetic responsiveness, was markedly reduced in CHF patients and was inversely related to the severity of exercise impairment. Likewise, the HR response to a graded isoproterenol infusion was markedly reduced in CHF patients. Age-matching of normal subjects and CHF patients did not affect the foregoing observations. Infusion of CHF patients with the phosphodiesterase inhibitor milrinone caused a significant increase in the ratio of the exercise increments in HR and NE. These data strongly suggest that the attenuated HR response to exercise in CHF patients is due, at least in part, to postsynaptic desensitization of the beta-adrenergic receptor pathway.

Adult↗
PubMed1989

Studies with antibodies to cultured rat glomerular epithelial cells. Subepithelial immune deposit formation after in vivo injection.

To investigate the role of glomerular epithelial cell (GEC) membrane proteins in the in situ formation of subepithelial immune deposits, the authors raised a rabbit antiserum against GEC that had been grown in culture (anti-GEC). By indirect immunofluorescence (IF) on normal rat kidney, anti-GEC stained proximal tubular brush border (BB). After intravenous injection into animals, granular glomerular capillary wall staining for IgG was present by IE and subepithelial immune deposits were identified by standard transmission and immunoelectron microscopy. Using the latter technique, injected anti-GEC IgG was identified beneath slit diaphragms and in endocytic-coated pits and intracellular vesicles of podocytes. Anti-GEC immunoprecipitated gp330 and two other proteins from radiolabeled BB. These proteins also were identified by sheep anti-rat Fx1A, the antiserum responsible for passive Heymann nephritis. Anti-GEC and anti-Fx1A also immunoprecipitated five identical proteins from surface-labeled GEC. Biosynthetically-labeled but not surface-labeled GEC contained immunoprecipitable gp330. Thus, injection into rats of antibodies raised against cultured GEC can produce subepithelial immune deposits, a disease process classically induced by antibodies to BB or its purified components. In addition to gp330, GEC and BB share other antigenic determinants that may contribute to the formation of these immune deposits.

Animals↗
PubMed1988

Anti-Fx1A produces complement-dependent cytotoxicity of glomerular epithelial cells.

Glomerular injury in passive Heymann nephritis (PHN) in rats is mediated by the C5b-9 membrane attack complex (MAC) and is associated with morphologic changes in glomerular visceral epithelial cells (GEC). We determined if the nephritogenic antibody of PHN (gamma 1 sheep anti-Fx1A IgG) directs insertion of the MAC into GEC plasma membranes with consequent cytotoxicity. Antibody-sensitized GEC were exposed to various sera serving as sources of complement. Loss of cell viability was determined by trypan blue uptake and/or by release of cellular lactate dehydrogenase (LDH). Incubation of antibody-sensitized primary and passaged GEC in fresh human serum (FHS) resulted in sigmoidal relationships between cytotoxicity and complement dose (r = 0.97 and 0.94, respectively) such that cytolysis approached 100% with FHS (10% vol/vol). Cytotoxicity was not evident if C8-deficient (C8D) plasma was substituted for FHS, but was restored in a dose-dependent manner by reconstitution with purified rat C8. Sublytic injury was demonstrated by wide separation between simultaneous release curves of cell-incorporated biscarboxyethyl carboxyfluorescein (BCECF; mol wt approximately equal to 520) and LDH at limiting doses of complement (at 2% FHS, BCECF release was 51.1 +/- 0.6% of maximum vs. 3.2 +/- 1.3% for LDH; N = 3) and by blebbing of the plasma membrane on electron microscopy. Thus, the pathogenic antibody of PHN produces complement-mediated sublytic as well as lytic cytotoxicity of GEC.

Animals↗
PubMed1988

Intracoronary infusion of dobutamine to patients with and without severe congestive heart failure. Dose-response relationships, correlation with circulating catecholamines, and effect of phosphodiesterase inhibition.

We infused dobutamine into the left main coronary artery of 24 patients with severe congestive heart failure (CHF) and 8 normal subjects without hemodynamic dysfunction. The maximal +dP/dt response to intracoronary (IC) dobutamine in CHF patients was only 37% of that in normals. This decrease in maximal response was not associated with a rightshift in the EC50 for dobutamine's effect on +dP/dt, or a decrease in the affinity of myocardial beta adrenergic receptors for dobutamine determined in vitro. In nine of the CHF patients, IC dobutamine infusion was followed by IC infusion of the phosphodiesterase inhibitor milrinone, and subsequently, by a second IC infusion of dobutamine. After IC milrinone, the increase in +dP/dt caused by IC dobutamine (74 +/- 10%) was significantly greater than that caused by the first infusion of dobutamine (52 +/- 11%; P less than 0.003) or milrinone (42 +/- 6%; P less than 0.001). Resting plasma norepinephrine was markedly elevated in CHF patients (837 +/- 208 ng/liter), but not in normal subjects (142 +/- 32 ng/liter); and the increase in +dP/dt caused by IC dobutamine was inversely related to resting plasma norepinephrine levels (r = -0.653; P less than 0.001). IC dobutamine caused a dose-related decrease in plasma norepinephrine (maximal effect, -160 +/- 31 ng/liter; P less than 0.001). Thus, (a) the maximal inotropic response to dobutamine is markedly depressed in patients with severe CHF, and is significantly greater after pretreatment with the phosphodiesterase inhibitor milrinone; (b) the impairment in inotropic response to dobutamine is inversely related to circulating norepinephrine levels; and (c) myocardial stimulation by dobutamine results in withdrawal of sympathetic tone.

Catecholamines↗
PubMed1987

A role for thromboxane in complement-mediated glomerular injury.

The membrane attack complex (MAC) of complement (C) has been shown to stimulate prostaglandin (PG) and thromboxane (Tx) synthesis in nucleated cells. Because glomerular epithelial cell injury and altered permeability in rat membranous nephropathy are mediated by the MAC, the authors examined whether MAC-induced proteinuria is linked to glomerular prostanoid synthesis. In kidneys containing non-nephritogenic, non-C-fixing gamma 2 sheep anti-Fx1A (planted antigen) that were perfused in vitro with C-fixing guinea pig anti-sheep IgG and a C source (fresh human plasma, 50% vol/vol in buffered bovine albumin), heavy proteinuria developed, reaching 4.27 +/- 1.20 mg/min/g at 100-120 minutes (n = 8). Cyclooxygenase blockade with 10(-4) M indomethacin (n = 6) inhibited urinary PGE2 excretion (569 +/- 47 to 124 +/- 18 pg/min/g, P less than 0.001) and lowered proteinuria (1.06 +/- 0.42 mg/min/g, P less than 0.001). Reduced protein excretion (0.88 +/- 0.12 mg/min/g, n = 6, P less than 0.001) also occurred with inhibition of Tx synthetase by OKY-046, 10(-4) M, a dose that was shown in separate perfusions to inhibit urinary TxB2 excretion by greater than 85%. Control kidneys, without planted antigen and perfused with anti-sheep IgG and plasma, excreted 0.30 +/- 0.05 mg protein/min/g (n = 6). Because inulin clearance was reduced by indomethacin, renal hemodynamic factors may have contributed to the reduction in proteinuria observed with this drug. However, insulin clearance was not significantly affected by OKY-046, implying that inhibition of Tx synthetase reduced proteinuria independently of changes in renal hemodynamics. Thus, proteinuria in rat membranous nephropathy is due to MAC-dependent glomerular epithelial injury and is mediated, in part, by Tx.

Animals↗