N-Acetyl-L-cysteine serves as an efficient substrate for the rat liver microsomal glutathione transferase with 1-chloro-2,4-dinitrobenzene as second substrate (8.8 +/- 0.37 mumol/min mg). The activity is actually higher than that obtained with glutathione (2-4 mumol/min mg). In examining the activity of liver subcellular fractions, no activity with N-acetyl-L-Cys could be detected in dialyzed or N-ethylmaleimide-treated (in order to remove endogenous glutathione) cytosol. The activity in rat liver microsomes was 0.11 +/- 0.007 mumol/min mg, which is accounted for by the content of microsomal glutathione transferase. Thus, N-acetyl-L-Cys can be used as a specific substrate for determining the conjugating activity of microsomal glutathione transferase. N-Acetyl-L-Cys was also shown to function as a substrate for the enzyme when other second substrates than 1-chloro-2,4-dinitrobenzene (with varying electrophilicity) are used. The pH dependence of microsomal glutathione transferase was studied. The kcat/Km(1-chloro-2,4-dinitrobenzene) was dependent on pH with an apparent pKa of 6, > or = 9, and > or = 8 with saturating glutathione, gamma-L-Glu-L-Cys, and N-acetyl-L- cysteine, respectively. Apparently the enzyme has the ability to lower the pKa of glutathione by 3 orders of magnitude. The kcat/Km(thiol) did not vary appreciably with pH (except for N-acetyl-L-cysteine), indicating that no rate-determining deprotonation occurs on the enzyme itself between pH 5.5 and 9. The abilities of histidine-, lysine-, and arginine-selective reagents to inactivate the enzyme when N-acetyl-L-cysteine and gamma-L-Glu-L-Cys were used as substrates were investigated. The activity toward N-acetyl-L-cysteine was decreased considerably less after treatment with the arginine-selective reagent phenylglyoxal, as compared to the activity toward GSH and gamma-L-Glu-L-Cys. This indicates that an arginine makes contact with gamma-L-Glu residue in GSH. With the other reagent/substrate combinations tested the enzyme was inactivated almost completely. The ability of microsomal glutathione transferase to stabilize the Meisenheimer complex formation between 1,3,5-trinitrobenzene and various glutathione analogues, including non-substrate thiols, has been examined. It is shown that, in general, substrates exhibited higher formation constants (approaching 50 mM-1) than non-substrates (4.5 +/- 1.7 mM-1, n = 7), whereas simpler thiols did not yield enzyme-bound complexes. The fact that the enzyme can stabilize Meisenheimer complexes from non-substrate thiol analogues of glutathione offers new possibilities for examining the substrate interactions of glutathione transferases.

Acetylcysteine↗

PubMed1994

Successful engraftment of autologous and allogeneic islets into the porcine thymus.

Work in rodents has shown that injection of pancreatic islets of Langerhans into the thymus can induce donor-specific unresponsiveness to islets subsequently transplanted to extrathymic sites. The overall objective of our investigation is to test this in a large animal (pig) model. In the current study we examined whether autologous and allogeneic adult or fetal islets survive in the porcine thymus. Collagenase-digested adult and fetal porcine islets were injected into the thymic lobes of 5- to 13-month-old, normal pigs. Pigs receiving allografts were given either a standard triple regimen of oral cyclosporine, azathioprine, and prednisone or intravenous anti-lymphocyte globulin (ALG) for immunosuppression. Two pigs of each group that received an allograft or autograft were given no immunosuppression. Biopsies of the grafts were taken at 4, 6, or 12 weeks for examination. Islet survival was assessed by histology with hematoxylin and eosin and insulin staining and by measurement of tissue insulin content using acid alcohol extraction and radioimmunoassay. The insulin content of control thymus was found to be 0.71 +/- 0.29 microU/mg (n = 5). The insulin content of the islet-grafted thymic tissues ranged from 1.57 to 10.65 microU/mg. Since the amounts of injected islets were not equal and not distributed evenly, and only a part of the graft site was used for determination of tissue insulin, thymic insulin contents higher than 1.4 microU/mg (twice that of the control value) were considered to demonstrate the presence of viable islets. With this criterion, we concluded that islets were found to be viable in seven of nine pigs and two pigs which were treated with ALG were shown to be marginally positive. On histological examination, islets were found in the thymus as well as under the thymic capsule, except for the above two pigs. These results demonstrate that the pig thymus supports fetal and adult islet transplants.

Animals↗

PubMed1994

Traditional herbal remedies used for the treatment of urinary schistosomiasis in Zimbabwe.

A total of 286 traditional healers, 85% of them registered with the Zimbabwe National Traditional Healers' Association (ZINATHA), in five administrative provinces of Zimbabwe, were interviewed to assess their knowledge about the signs and symptoms of urinary schistosomiasis. Information on the names of plants used to treat Schistosoma haematobium infections was solicited. Haematuria was mentioned by 99% of the traditional healers to be the most obvious sign of S. haematobium infection. General body weakness, increased urinary frequency and pain on micturition also were reported to be some of the signs of infection. Eight plant materials were identified as the most commonly used for the treatment of S. haematobium. The plants were identified and parts collected to investigate their antischistosomal properties. The plant materials were prepared according to the guidelines of the traditional healers and their efficacy determined by administering the crude extracts orally to hamsters infected with S. haematobium cercariae. The results obtained suggested that plant extracts from Abrus precatorius (Leguminosae), Pterocarpus angolensis (Leguminosae) and Ozoroa insignis (Anacardiaceae) were lethal to adult schistosomes.

Adult↗

PubMed1994

Penile gangrene associated with chronic renal failure: report of 7 cases and review of the literature.

Distal penile gangrene associated with renal failure is a rare entity with only 3 cases reported in the literature. Certain physiological abnormalities are commonly found in association with this condition, including secondary hyperparathyroidism, diabetes and peripheral vascular disease. We report our experience with 7 patients who presented with this condition. All patients had end stage renal disease with 5 on hemodialysis, 1 on peritoneal dialysis and 1 with a functioning cadaveric renal transplant. Six patients had diabetes mellitus and all had derangements of the calcium and phosphate metabolism, with the calcium-phosphorus product being greater than 70. Five patients were treated expectantly with resolution of gangrene in 2 and stable disease in 3. Three of the 5 patients managed expectantly and both patients treated with penectomy died of unrelated causes within 3 months. We conclude that there is no advantage to aggressive surgical treatment of penile gangrene associated with renal failure, since the outcome is the same. The overall mortality for this group is high due to associated co-morbid disease regardless of the type of treatment. Furthermore, subtotal parathyroidectomy is not indicated, since spontaneous improvement and mortality rates reported in our series were similar to those of previously reported cases. Expectant management of affected patients affords the best treatment.

Aged↗

PubMed1994

Linear facial skin defects associated with microphthalmia and other malformations, with chromosome deletion Xp22.1.

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Abnormalities, Multiple↗