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Biomedical subjects

L Gaber

Publications and source records attributed to L Gaber.

At least 19 recordsLinked to original sources
PubMed2001

Carbamoylation of glomerular and tubular proteins in patients with kidney failure: a potential mechanism of ongoing renal damage.

BACKGROUND: Cyanate formed spontaneously from urea carbamoylates non-protonated amino groups of protein, irreversibly altering function, charge and structure. Carbamoylated proteins in renal tissue have not been examined hitherto. OBJECTIVES: To identify homocitrulline (epsilon-amino-carbamoyl-lysine), a result of in vivo carbamoylation by urea-derived cyanate, from patients with renal disease or in newly transplanted kidneys by immunohistochemistry. To evaluate enzymatic activity of carbamoylated and non-carbamoylated matrix metalloproteinase-2 and correlate this with renal tissue carbamoylated in vivo. DESIGN: Anti-homocitrulline antibody is specific for homocitrulline and was used to identify carbamoylation of epsilon-amino-lysine in renal biopsies from patients with elevated BUN, with isolated proteinuria, and as controls, from normal donors at time of transplantation. Enzymatic activity of matrix metalloproteinase-2 carbamoylated in vitro was evaluated. RESULTS: Homocitrulline was present in glomerular basement membrane (8/10), mesangium (8/10), tubular epithelium and cytoplasm (7/10) and Bowman's capsule (1/10) in patients with elevated BUN. The discordant patterns of glomerular and tubular localization of homocitrulline versus immune complexes indicated that the carbamoylated proteins were not a component of immune deposits but were modified proteins in renal tissue. No homocitrulline was found in transplanted kidneys (14/15) or in proteinuric patients (2/2). Enzymatic activity of both human and rat matrix metalloproteinase-2 was strongly inhibited in a dose-dependent fashion when incubated with cyanate. CONCLUSIONS: In situ carbamoylation in proteins occurred in kidneys of patients with renal dysfunction but not in normal newly transplanted kidneys. Decreased enzymatic activity of carbamoylated enzymes may alter specific renal regulatory mechanisms. Carbamoylated proteins with altered function and charge may represent a previously underestimated mechanism in renal pathophysiology.

Amino Acids↗
PubMed2001

Blocking pulmonary ICAM-1 expression ameliorates lung injury in established diet-induced pancreatitis.

OBJECTIVE: To determine whether blocking the cell surface expression of intracellular adhesion molecules (ICAM-1) in established severe acute pancreatitis (AP) would ameliorate pulmonary injury. SUMMARY BACKGROUND DATA: Lung injury in AP is in part mediated by infiltrating leukocytes, which are directed to lung tissue by ICAM-l. The authors' laboratory has previously demonstrated that AP results in overproduction of inflammatory cytokines, upregulation of pulmonary ICAM-1 expression, and a concomitant infiltration of neutrophils, which results in lung injury. METHODS: Young female mice were fed a choline-deficient/ethionine-supplemented diet to induce AP and were treated with a blocking dose of monoclonal antibody specific to the ICAM-1 receptor. Antibody treatment was administered at 72, 96, and 120 hours after beginning the diet, and all animals were killed at 144 hours. The degree of pancreatitis was evaluated by serum biochemical and tumor necrosis factor alpha levels as well as histology. The dual radiolabeled monoclonal antibody method was used to quantitate ICAM-1 cell surface expression in pulmonary tissue. Lung injury was assessed histologically and by determining lung microvascular permeability by measuring accumulated 125I-radiolabeled albumin. Pulmonary neutrophil sequestration was determined by the myeloperoxidase assay. RESULTS: All mice developed severe AP, and pancreatic injury was equally severe in both treated and untreated groups. Pulmonary ICAM-1 expression was significantly upregulated in animals with AP compared with controls. Treatment with a blocking dose of anti-ICAM-1 antibody after the induction of AP resulted in inhibited ICAM-1 cell surface expression to near control levels. Compared to untreated animals with AP, mice treated with anti-ICAM-1 mice had significantly reduced histologic lung injury and neutrophil sequestration, and a decreased microvascular permeability by more than twofold. CONCLUSIONS: These results demonstrate for the first time that treatment targeting the cell surface expression of ICAM-1 after the induction of AP ameliorates pulmonary injury, even in the face of severe pancreatic disease.

Acute Disease↗
PubMed2000

Quantitative measurement of P- and E-selectin adhesion molecules in acute pancreatitis: correlation with distant organ injury.

OBJECTIVE: To determine whether expression of P- and E-selectin molecules is associated with the development of systemic organ manifestations in acute pancreatitis (AP). SUMMARY BACKGROUND DATA: Overproduction of inflammatory cytokines in AP induces expression of adhesion molecules, which may lead to increased leukocytic infiltration and tissue damage. Understanding the temporal expression of these molecules could afford better measures for therapeutic intervention. METHODS: Acute pancreatitis was induced in 30-day-old female C57/ bI/6J mice by feeding a choline-deficient/ethionine-supplemented diet (n = 95). Mice were divided into three groups. Group I (n = 35) was used to study the biochemical and histologic manifestations of AP and to evaluate the neutrophilic infiltration by myeloperoxidase activity and immunofluorescence. Groups II (n = 35) and III (n = 25) were used to evaluate expression of P- and E-selectin by the dual radiolabeled monoclonal antibody technique. RESULTS: Biochemical and histologic evidence of AP developed in all mice. The inflammatory cytokine tumor necrosis factor-alpha gradually increased in serum as early as 18 hours, reaching more than 800-fold background levels by 72 hours. Biphasic P-selectin expression in the lung was seen with peaks at 24 and 48 hours; E-selectin expression peaked at 48 hours. CD18-positive leukocytes and increased myeloperoxidase activity in the lung were demonstrated at 24 hours, correlating with the onset of selectin upregulation. Histologic scoring of lung tissue demonstrated mild damage at 24 hours, with progressive injury occurring from 48 to 72 hours. CONCLUSIONS: In AP, the production of inflammatory cytokines precedes up-regulation of P- and E-selectin, whose expression coincided with the increased infiltration of CD18-positive cells and neutrophil sequestration in lung tissue. Temporally, these events correlate with evidence of histologic pulmonary injury and underscore the role of adhesion molecules as mediators of pathophysiologic events. This mechanistic pathway may afford novel therapeutic interventions in clinical disease by using blocking agents to ameliorate the systemic manifestations of AP.

Acute Disease↗
PubMed2000

Trypsin stimulates production of cytokines from peritoneal macrophages in vitro and in vivo.

Acute pancreatitis (AP) is characterized by release of proteolytic enzymes from the pancreas and a powerful inflammatory cytokine cascade that mediates the systemic manifestations and contributes to the mortality of the disease. The purpose of this study was to examine a potential link between pancreatic proteolytic enzymes, which are increased in AP, and cytokine production. To evaluate this, we incubated rat peritoneal macrophages (PMO) with increasing concentrations of trypsin and measured cytokine production. Supernatants from the cell cultures were assayed for TNF-alpha and IL-1beta, and the PMO were collected for the evaluation of cytokine mRNA by polymerase chain reaction (PCR). Further to evaluate the role of pancreatic proteases in triggering the cytokine cascade in AP, trypsin was injected into the peritoneal cavity of Sprague-Dawley rats, and the production of cytokines was measured in the peritoneal fluid. Controls included injection of inactivated trypsin. Incubation of PMO with trypsin in vitro resulted in a dose-dependent increase in TNF-alpha production with maximal response (2,660.5+/-748.8 pg/mL) at 10 microg/mL protease. Peak TNF-alpha and IL-1beta release was noted 16 h after stimulation of the PMO (2,759.5+/-698.0 pg/mL and 160,596+/-4,065 cpm, respectively). Trypsin-induced TNF-alpha production was not due to release of cell-associated cytokine, inasmuch as activation of PMO with this protease causing an increase in TNF-alpha mRNA by 30 minutes, reaching a 14-fold increase at 4 h. Trypsin-injected animals produced TNF-alpha-containing ascitic fluid in a dose-dependent manner with peak TNF-alpha at 2 h (371.3+/-180 pg/mL) versus control (53.8+/-11.2 pg/mL; p < 0.022). No TNF-alpha was found in ascites of rats injected with heat-inactivated trypsin. Histologic examination of trypsin-injected animals revealed evidence of pulmonary inflammation at 2 and 4 hours. We conclude that the proteolytic enzyme trypsin stimulates cytokine production from macrophages in vitro and in vivo. This model demonstrates for the first time that trypsin is a potential mediator of the cytokine response seen during AP.

Animals↗
PubMed2000

Contribution of Ras GTPase/MAP kinase and cytochrome P450 metabolites to deoxycorticosterone-salt-induced hypertension.

We recently reported that norepinephrine and angiotensin II activate the Ras/mitogen-activated protein (MAP) kinase pathway through generation of a cytochrome P450 (CYP450) and lipoxygenase metabolites. The purpose of this study was to determine the contribution of Ras/MAP kinase to deoxycorticosterone acetate (DOCA)-salt-induced hypertension in rats. Administration of DOCA and 1% saline drinking water to uninephrectomized rats for 6 weeks significantly elevated mean arterial blood pressure (MABP) (166+/-5 mm Hg, n=19) compared with that of normotensive controls (95+/-5 mm Hg, n=7) (P<0.05). The activity of Ras and MAP kinase measured in the heart was increased in DOCA-salt hypertensive rats. Infusion of the Ras farnesyl transferase inhibitors FPT III (138 ng/min) and BMS-191563 (694 ng/min) significantly (P<0.05) attenuated MABP to 139+/-4 mm Hg (n=14) and 126+/-1 mm Hg (n=4), respectively. Moreover, infusion of MAP kinase kinase inhibitor PD-98059 (694 ng/min) also reduced MABP in hypertensive rats. Morphological studies of the kidney showed that treatment of rats with FPT III, which reduced Ras activity, minimized the hyperplastic occlusive arteriosclerosis and fibrinoid vasculitis observed in untreated hypertensive rats. In addition, the rise in CYP450 activity and MABP in hypertensive rats was prevented by the CYP450 inhibitor aminobenzotriazole (50 mg/kg) and was associated with a decrease in Ras and MAP kinase activity in the heart. These data suggest that the Ras/MAP kinase pathway contributes to DOCA-salt-induced hypertension and associated vascular pathology consequent to activation of CYP450.

Alkyl and Aryl Transferases↗
PubMed2000

Angiotensin II-induced hypertension: contribution of Ras GTPase/Mitogen-activated protein kinase and cytochrome P450 metabolites.

We reported that norepinephrine and angiotensin II (Ang II) activate the Ras/mitogen-activated protein (MAP) kinase pathway primarily through the generation of cytochrome P450 (CYP450) metabolites. The purpose of the present study was to determine the contribution of Ras and CYP450 to Ang II-dependent hypertension in rats. Infusion of Ang II (350 ng/min for 6 days) elevated mean arterial blood pressure (MABP) (171+/-3 mm Hg for Ang II versus 94+/-5 for vehicle group, P<0.05). Ras is activated on farnesylation by farnesyl protein transferase (FPT). When Ang II was infused in combination with FPT inhibitor FPT III (232 ng/min) or BMS-191563 (578 ng/min), the development of hypertension was attenuated (171+/-3 mm Hg for Ang II plus vehicle versus 134+/-5 mm Hg for Ang II plus FPT III and 116+/-6 mm Hg for Ang II plus BMS-191563, P<0.05). Treatment with the MAP kinase kinase inhibitor PD-98059 (5 mg SC) reduced MABP. The CYP450 inhibitor aminobenzotriazole (50 mg/kg) also diminished the development of Ang II-induced hypertension to 113+/-8 mm Hg. The activities of Ras, MAP kinase, and CYP450 measured in the kidney were elevated in hypertensive animals. The infusion of FPT III, BMS-191563, or aminobenzotriazole reduced the elevation in Ras and MAP kinase activity. Morphological studies of the kidney showed that FPT III treatment ameliorated the arterial injury, vascular lesions, fibrinoid necrosis, focal hemorrhage, and hypertrophy of muscle walls observed in hypertensive animals. These data suggest that the activation of Ras and CYP450 contributes to the development of Ang II-dependent hypertension and associated vascular pathology.

Alkyl and Aryl Transferases↗
PubMed1994

Amelioration of the physiologic and biochemical changes of acute pancreatitis using an anti-TNF-alpha polyclonal antibody.

Tumor necrosis factor (TNF) is an inflammatory cytokine that may be an important mediator in the development of the systemic sequelae associated with severe acute pancreatitis. The purpose of this study was to determine whether the neutralization of TNF-alpha with a polyclonal antibody could ameliorate selected biochemical parameters of severe pancreatitis in a rat model. Pancreatitis was induced by an antegrade injection of artificial bile into the bile duct. Forty rats were randomized into 4 groups: no surgery (controls), saline infusion to bile duct (sham), placebo treatment in animals with pancreatitis (placebo + Px), and pretreatment with a polyclonal antibody (PAb) in animals with pancreatitis (PAb + Px). Serum TNF-alpha, amylase, calcium, hematocrit, glucose, and ascites volume were measured 2 hours after bile duct infusion. Pretreatment with the PAb produced a significant improvement in all parameters when compared with pancreatitis animals treated with placebo (p < 0.001). In addition, TNF-alpha, which was elevated in animals with pancreatitis, was reduced significantly in treated animals (p < 0.001). These results suggest that TNF-alpha may be an important mediator in the evolution of the systemic manifestations of severe acute pancreatitis.

Acute Disease↗
PubMed1994

Effects of different antihypertensive treatments on morphologic progression of diabetic nephropathy in uninephrectomized dogs.

We previously reported the renal hemodynamic effects of different antihypertensive regimens in uninephrectomized, alloxan-induced, diabetic (DM) beagle dogs following one year of treatment. Dogs were prospectively randomized to one of five groups (N = 26): nondiabetic controls, Group I; dogs with DM on no antihypertensive drugs, Group II; dogs on a converting enzyme inhibitor, lisinopril (L), Group III; dogs on a calcium antagonist, TA3090 (diltiazem-like), Group IV; and dogs on a combination of each drug, in reduced doses, Group V. The current paper extends our previous studies by describing the morphologic changes that occurred within each group of dogs studied. More than 100 glomeruli from the renal cortex of each dog were evaluated for increases in mesangial volume fraction (Vv), glomerulosclerosis (GS) and ateriolar hyalinosis. The interstitium was also evaluated for associated changes. Increases in Vv were attenuated in all treated groups (0.28 +/- 0.04, DM alone versus 0.16 +/- 0.05 L; 0.21 +/- 0.07, TA-3090; 0.19 +/- 0.06 micron 2/micron 2, L+TA 3090; P < 0.05) compared to untreated DM. An attenuated increase in Vv also correlated with a blunted rise in proteinuria in Groups III (r = 0.79) and V (r = 0.81) but not Group IV (r = 0.29). Development of focal GS was blunted in all treated groups; however, global GS was fourfold greater in Group IV compared to untreated DM. The degree of interstitial fibrosis also correlated with the degree of global GS. These data support the concept that both a converting enzyme inhibitor and heart rate lowering calcium antagonist attenuate morphologic progression of diabetic renal disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Induction of tumor necrosis factor in severe acute pancreatitis and its subsequent reduction after hepatic passage.

BACKGROUND: Tumor necrosis factor (TNF) is rapidly gaining recognition as one of the early, critical mediators of several inflammatory conditions, most notably endotoxic shock. The purposes of this study were to determine whether TNF levels are raised in severe acute pancreatitis, thus pointing to its role as a potential mediator of the inflammatory process, and to determine the possible sites of production and uptake. METHODS: TNF levels were measured during a 2-hour period in a rat model of acute pancreatitis by using an antegrade infusion of artificial bile. TNF levels were measured with a bioassay. RESULTS: TNF levels increased proportionately with time and serum amylase level, reaching a mean value of 2700 pg/ml at 2 hours compared with sham operated rats (mean, 125 pg/ml) (p < 0.001). TNF levels in nonoperated controls were undetectable. These measurements were found to be independent of endotoxin production. In addition, selective sampling from the portal vein, hepatic vein, and femoral artery showed hepatic degradation of TNF (p < 0.005), indicating that the liver may play an important role in protecting the host from multiple organ failure. CONCLUSIONS: Our results showed that TNF levels are elevated in acute pancreatitis and may suggest a role for this cytokine in the pathogenesis of the disease.

Acute Disease↗
PubMed1993

Risk factors for postimplantation pancreatitis and pancreatic thrombosis in pancreas transplant recipients.

Reperfusion pancreatitis and pancreatic thrombosis are 2 complications of pancreatic transplantation that are associated with both an increased patient morbidity and a decrease in pancreas graft survival rates. These complications are thought to be related to donor factors, procurement and preservation variables, and postimplantation recipient management. We reviewed our experience with 41 consecutive pancreas transplant patients (18 females, 23 males) performed in association with kidney transplants (n = 34), whole (n = 5) and segmental (n = 2). The average cold ischemia time (CIT) was 11.5 hr. Donor and recipient variables were related to two outcomes: (1) postoperative pancreatitis (n = 9) and (2) postoperative pancreatic thrombosis (n = 6). Steroid administration to the donor resulted in significant reduction of postimplantation pancreatitis (P < 0.001). Also, postoperative pancreatitis was significantly less common (P < 0.02) in recipients given calcium channel blockers in the early postoperative period. Pancreatic thrombosis was significantly more common in male recipients (P < 0.04) and was also significantly related to CIT (P < 0.05). These data indicate that proper donor management and pretreatment with high-dose steroids, together with shortening of CIT and postoperative administration of calcium channel blockers, are protective against pancreatic thrombosis and pancreatitis.

Female↗
PubMed1985

Induction of graft-versus-host disease by small intestinal allotransplantation in rats.

Adult male (LewisXBrown Norway) F1 (LBNF1) rats received heterotopic small intestinal transplants from Lewis donors. Lewis-to-Lewis and LBNF1-to-LBNF1 isografts served as controls. All of the allograft recipients died after a median survival time of 16.2 days, but all isografted rats survived indefinitely. During the period of deterioration, allografted rats developed marked cutaneous erythema and became increasingly weak and cachectic. Histological changes of the skin, spleen, and grafts were characteristic of graft-versus-host disease (GVHD). There was a marked degree of relative splenomegaly. Injection of spleen cells obtained from LBNF1 rats with clinical GVHD into the foot-pad of syngeneic LBNF1 rats resulted in significant enlargement of the ipsilateral popliteal lymph node. The degree of lymph node enlargement was comparable to that induced in LBNF1 rats by injection of normal Lewis spleen cells. These results clearly demonstrate the ability of the small intestinal allograft to cause rapid and fatal GVHD in rats that are incapable of graft rejection.

Animals↗
PubMed1981

Hereditary heat-labile hexosaminidase B: its implication for recognizing Tay-Sachs genotypes.

Two pairs of alleles, at the two loci of hexosaminidase (HEX), were found to segregate in an Arab inbred family: the normal and the mutant Tay-Sachs (TSD) alleles of HEX A, and the normal and a mutant allele of HEX B. Since the mutant HEX B is heat labile, no reliable identification of TSD genotypes can be obtained in its presence, as long as the proportions of HEX A and B are estimated by the routinely used heat-inactivation method. The genotypes may be correctly identified in such cases by separation of the two isoenzymes on ion-exchange chromatography, estimating their individual activities, and calculating the ratio between them. Of the nine genotype combinations possible with these two pairs of alleles, five have been identified in the reported family by this procedure.

Adult↗