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Biomedical subjects

W Levin

Publications and source records attributed to W Levin.

At least 235 records · Page 13Linked to original sources
PubMed1978

Peritoneoscopy in the management of breast cancer.

Peritoneoscopy has been recommended by the Combined Breast Clinic at the Provincial Hospital, Port Elizabeth, since 1975, mainly to confirm or exclude metastatic involvement of the liver. Experience with 27 procedures is reviewed. Peritoneoscopy is shown to be a useful aid in the staging and management of selected cases of breast cancer. Positive findings, confirmed by histological examination, were recorded for 5 patients. Negative findings in 22 patients were equally helpful, and were found to be reliable, in that none of these patients had evidence of liver involvement during the follow-up period, while in 5 patients there was evidence of metastases elsewhere.

Breast Neoplasms↗
PubMed1978

Hepatic microsomal epoxide hydrase. Involvement of a histidine at the active site suggests a nucleophilic mechanism.

The effects of a wide variety of chemical modification reagents on the activity of purified rat liver microsomal epoxide hydrase have been investigated. Alkylating agents, such as the phenacyl bromides and benzyl bromide are potent inhibitors of epoxide hydrase. 2-Bromo-4'-nitroacetophenone (p-nitrophenacyl bromide) specifically and irreversibly inactivates epoxide hydrase. Pseudo-first order kinetics of inhibition is observed at higher inhibitor/enzyme ratios. The rate of inactivation is controlled by a group on the enzyme with an apparent pKa of 7.6. Inactivation of the enzyme with 14C-labeled 2-bromo-4'-nitroacetophenone leads to the incorporation of approximately 1 mol of radioactive inhibitor/mol of protein. Epoxide hydrase can be protected against this inactivation by the substrate phenanthrene-9,10-oxide. These results are consistent with the interpretation that 2-bromo-4'-nitroacetophenone acts as an active site-directed inhibitor. The site of alkylation by 2-bromo-4'-nitroacetophenone is a histidine residue of epoxide hydrase. The N-alkylated histidine derivative has been identified as 1-(p-nitrophenacyl)-4-histidine. A possible mechanism for the enzymatic hydration catalyzed by epoxide hydrase is discussed which involves a histidine residue of the enzyme serving as a general base catalyst for the nucleophilic addition of water.

Amino Acids↗
PubMed1978

Binding of benzo[a]pyrene 7,8-diol-9,10-epoxides to DNA, RNA, and protein of mouse skin occurs with high stereoselectivity.

The formation, stereostructure, and cellular reactions of the 7,8-diol-9,10-epoxide metabolites of the carcinogen benzo[a]pyrene have been examined after topical application of benzo[a]pyrene to the skin of mice. In this known target tissue, polymer adducts from diastereomeric diol epoxides, (+)-(7S, 8R, 9R, 10R) and (+)-(7R, 8S, 9R, 10R), were formed stereospecifically from their corresponding 7,8-dihydrodiols. Both diol epoxides bind with proteins, RNA, and DNA in vivo. For the nucleic acids, binding occurs preferentially at the 2-amino group of guanine in cellular RNA and DNA in vivo. Methods for establishing the structure of the cellular adducts as well as the possible biological implications of their formation are discussed.

Animals↗
PubMed1978

Chemotherapy of small cell carcinoma of the lung with V.P. 16-213.

A Phase II study of V.P. 16-213 administered to 47 patients suffering from small cell carcinoma of the bronchus. V.P. 16-213 was given as an intravenous infusion over 15 minutes daily for five consecutive days using 60 mg/m2/d at 14-day intervals. Oral V.P. in 100 mg doses was given twice a week between the intravenous courses. Objective response rate for this drug compared favourably with that of other single agents reported. All but two patients showed a degree of response to treatment and 24 of 47 patients showed a true objective response to treatment. The overall median survival of these patients was 225 days and localized disease 278 days. The quality of survival was such that responders lived relatively normal lives up to the latter stages of their disease. The majority of patients had a marked response in performance status, 37 out of 47 showing an improvement. Three patients are alive and well at more than 27 months. In all cases the side effects were minimal. Alopecia was common and reversible haematological complications occurred. Severe toxicity was not encountered and the drug was well tolerated with supportive antiemetic therapy at onset of treatment.

Bone Marrow↗
PubMed1978

Formation of a thiomethyl metabolite of phenacetin and acetaminophen in dogs and man.

Conjugates of 3-methylthio-4-hydroxyactanilide were found in the urine of dogs and humans treated with phenacetin (4-ethoxyacetanilide) or acetaminophen (4-hydroxyacetanilide). About 1% to 3% of the administered dose was excreted as this thiomethyl metabolite after administration of phenacetin or acetaminophen to dogs. An average of 0.39% of the dose was excreted in the urine as 3-methylthio-4-hydroxyacetanilide conjugates after administration of phenacetin to several subjects, and an average of 0.66% of the dose was excreted as this metabolite in the urine after administration of acetaminophen to humans. The possibility that the thiomethyl metabolite is derived from a mercapturic acid conjugate or an N-hydroxy derivative of phenacetin or acetaminophen is discussed.

Acetaminophen↗
PubMed1978

Tumorigenicity of benzo[alpha]pyrene 4,5-,7,8-,9,10- and 11,12-oxides in newborn mice.

Benzo[alpha]pyrene (BP) and its 4,5-,7,8-,9,10 and 11,12-oxides were tested for carcinogenicity by intraperitoneal injection into newborn mice. The mice were treated sequentially with 200, 400 and 800 nmol of hydrocarbon on days 1,8 and 15 of life, and the animals were killed at 24 weeks of age. Mice treated with BP, BP7,8-oxide and BP 11,12-oxide had a 93%, 72% and 20% incidence of pulmonary adenomas, respectively, with an average of 10.0, 2.1 and 0.32 adenomas/mouse, respectively. Eight percent of the control animals had pulmonary adenomas with an average of 0.08 adenomas per mouse. The moderate tumorigenic activity of the relatively unstable BP 7,8-oxide, together with earlier data on the strong carcinogenic activity of BP, 7,8-dihydrodiol, supports the idea that BP 7,8-oxide is a proximate carcinogenic metabolite of BP in the newborn mouse.

Adenoma↗
PubMed1978

Tumorigenicity of the optical enantiomers of the diastereomeric benzo[a]pyrene 7,8-diol-9,10-epoxides in newborn mice: exceptional activity of (+)-7beta,8alpha-dihydroxy-9alpha,10alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene.

The tumorigenicities of benzo[a]pyrene and each optical enantiomer of the diastereomeric benzo[a]pyrene 7,8-diol-9,10-epoxides derived from trans-7,8-dihydroxy-7,8-dihydrobenzol[a]pyrene were tested by sequential intraperitoneal injection of mice with 1,2, and 4 nmol, or with 2, 4, and 8 nmol of each compound on the 1st, 8th, and 15th day of life, respectively. The experiment was terminated when the animals were 34--37 weeks old. (+)-7beta, 8alpha-dihydroxy-9alpha,10alpha-epoxy-7,8,9,10-tetrahydrobenzol[a]pyrene [(+)-BP-7beta,8alpha-diol-9alpha,10alpha-epoxide 2] had exceptional tumorigenicity, whereas benzo[a]-pyrene and the other three optically pure isomers of the benzo[a]pyrene 7,8-diol,9,10-epoxides had little or no activity. These results demonstrate differences in the carcinogenic activities of optically active isomers of a polycyclic hydrocarbon diol epoxide. Eleven percent of control mice had pulmonary tumors, whereas 71% and 100% of the mice treated with a total dose of 7 or 14 nmol of (+)-BP-7beta,8alpha-diol-9alpha,10alpha-epoxide 2, respectively, had pulmonary tumors. Control mice had an average of 0.12 pulmonary tumors per mouse, whereas mice treated with a total dose of 7 or 14 nmol of (+)-BP-7beta,8alpha-diol-9alpha,10alpha-epoxide 2 had 1.72 and 7.67 pulmonary tumors per mouse, respectively. Mice treated with 14 nmol of (-)-BP-7alpha,8beta-diol-9beta,10beta-epoxide 2, (-)-BP-7beta,8alpha-diol-9beta,10beta-epoxide 1, or (+)-BP-7alpha,8beta-diol-9alpha,10alpha-epoxide 1 had 0.13, 0.25, and 0.34 pulmonary tumors per animal, respectively.

Animals↗
PubMed1978

Identification of epoxide hydrase as the preneoplastic antigen in rat liver hyperplastic nodules.

A liver microsomal protein, previously referred to as preneoplastic antigen, from hyperplastic nodules of rats fed a diet containing 2-acetylaminofluorene has been identified as the enzyme epoxide hydrase [glycol hydro-lyase (epoxideforming), EC 4.2.1.63]. Purified preneoplastic antigen from hyperplastic nodules and purified rat liver microsomal epoxide hydrase are immunochemically identical on the basis of Ouchterlony double-diffusion analysis. In addition, the purified proteins have identical minimum molecular weights in sodium dodecyl sulfate/polyacrylamide gels, and both proteins catalyze the hydration of arene oxides to dihydrodiols. Chronic feeding of 2-acetylaminofluorene to rats results in a 5- to 7-fold increase in epoxide hydrase activity in rat liver. The induced level of the enzyme is maintained in developing hyperplastic nodules and hepatomas but not in the nontumor tissue after removal of the carcinogen from the diet.

2-Acetylaminofluorene↗
PubMed1978

An improved technique for interstitial radiotherapy of the tongue.

An improvement of the plastic tube afterloading technique for interstitial radiotherapy of the tongue is described. This modification allows most of the work to be done outside the patient's mouth. The anchorage for the intra-oral ends of the polythene tubes is produced by transfixing then with a silk thread. This obvioates the need to form loops and simplifies afterloading. It provides a method for crossing the entire lingual end of the implant. All areas and volumes of lower jaw structures are accessible to this form of treatment. Removal of the implant, irrespective of position, is simple and rapid.

Humans↗