Biomedical subjects

L Mathews

Publications and source records attributed to L Mathews.

26 records · Page 2Linked to original sources

PubMed1985

Metabolic epidemiology of colon cancer: fecal mutagens in healthy subjects from rural Kuopio and urban Helsinki, Finland.

Fecal mutagenic activity and dietary pattern of rural and urban Finnish population groups with distinct risk for the development of colon cancer were studied in a low-risk population in rural Kuopio and an intermediate-risk population in urban Helsinki. The average daily intake of protein and fat was the same in the two groups but the frequency of consumption of whole-grain cereals and whole-grain bread, as well as the amount of fiber from the bread were higher in Kuopio as compared to Helsinki. Fecal samples collected for 2 days were incubated under anaerobic conditions at 37 degrees C for 96 h, extracted with hexane: peroxide-free diethyl ether, partially purified on a silica Sep-Pak cartridge, and assayed for mutagenic activity using the Salmonella typhimurium/mammalian microsome system. The fecal mutagenic activity was observed with the tester strains TA98 and TA100 with and without microsomal activation in both the population groups. The percentage of samples showing fecal mutagenic ratio greater than 3 with TA98 and TA100 with microsomal activation, was higher in volunteers from Helsinki than in Kuopio.

Adult↗

PubMed1984

Effect of Japanese seaweed (Laminaria angustata) extracts on the mutagenicity of 7,12-dimethylbenz[a]anthracene, a breast carcinogen, and of 3,2'-dimethyl-4-aminobiphenyl, a colon and breast carcinogen.

Animal model studies suggest that diets containing Laminaria angustata, a brown seaweed commonly eaten in Japan, inhibit breast carcinogenesis. In order to identify the compound(s) in the seaweed responsible for tumor-inhibiting activity, we used Ames/mammalian microsome assay system to determine the antimutagenic (or anticarcinogenic) effect of various solvents and water extracts of Laminaria angustata. The antimutagenic effects of acetone, ether, chloroform, chloroform + methanol, hot water and cold water extracts on the mutagenicity induced by 7,12-dimethylbenz[a]anthracene (DMBA), a breast carcinogen, and 3,2'-dimethyl-4-aminobiphenyl (DMAB), a colon and breast carcinogen, was studied using the Salmonella typhimurium strains TA98 and TA100. All extracts were nonmutagenic in both bacterial tester strains. The addition of 10-100 mg solvent extracts of seaweed/plate greatly inhibited DMAB-induced mutagenicity in both tester strains (80-96% inhibition) and DMBA-induced mutagenicity in TA100 (about 82%), whereas hot and cold water extracts produced a moderate inhibition in a dose-related manner in both strains.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1984

Fecal mutagens from subjects consuming a mixed-western diet.

Because of potential significance of fecal mutagens (presumptive carcinogens) in the pathogenesis of colon cancer, feces from 99 healthy subjects from the New York metropolitan area were studied. The diet histories indicate that all participants were consuming a mixed-western diet which is high in total fat and low in fiber. Fecal samples that were incubated under anaerobic conditions at 37 degrees C for 96 h or frozen without incubation, were extracted with hexane: peroxide-free diethyl ether (1:1), partially purified on a silica Sep-pak cartridge and assayed for mutagenicity using the Salmonella typhimurium/mammalian microsome system. Aliquots of fecal samples incubated anaerobically showed a higher frequency of mutagenic activity (per cent samples showing activity) in strains TA98 and TA100 with and without microsomal (S9) activation. In addition, the mutagens requiring S9 activation, were more frequently inactivated when the fecal samples were frozen immediately after defecation and transported to the laboratory. Compared with hexane: ether, extraction of fecal samples with acetone increased the mutagenic activity mostly with TA98 with S9 activation. The HPLC fractionation of hexane: ether extract with methanol: water gradient using reverse phase C-18 column and UV detector at 254 nm indicated that the mutagenic activity (TA98 with S9 activation) is concentrated in several peaks. This is the first demonstration of HPLC profile of fecal samples that are active in TA98 with S9 activation. HPLC profile of fecal extracts and mutagenic activity of these extracts in strains TA98 and TA100 suggest the presence of several types of mutagens in the feces of healthy subjects consuming a high-fat, low-fiber mixed-western diet.

Biotransformation↗

PubMed1983

Effect of micronutrients, antioxidants and related compounds on the mutagenicity of 3,2'-dimethyl-4-aminobiphenyl, a colon and breast carcinogen.

The possible antimutagenic effects of butylated hydroxytoluene (BHT), ethoxyquin, disulfiram, indole-3-carbinol, indole-3-acetonitrile, sodium selenite and alpha-tocopherol on 3,2'-dimethyl-4-aminobiphenyl-induced mutagenicity were studied using the Ames Salmonella/mammalian microsome assay system with strains TA98 and TA100. All seven compounds were nonmutagenic in both bacterial tester strains. The addition of or 50-250 micrograms of sodium selenite, 5-50 mg of alpha-tocopherol or 50-250 microgram of BHT per plate inhibited DMAB-induced mutagenicity in TA98 and/or TA100. Ethoxyquin, disulfiram and indole-3-carbinol increased DMAB-induced mutagenicity in TA100, whereas these compounds had little or no effect in TA98-3-acetonitrile had very little effect in either strain.

Aminobiphenyl Compounds↗

PubMed1983

Effect of butylated hydroxytoluene and butylated hydroxyanisole on the mutagenicity of 3,2'-dimethyl-4-aminobiphenyl.

This study was undertaken to investigate the possible antimutagenic effects of butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) on 3,2'-dimethyl-4-aminobiphenyl (DMAB)-induced mutagenicity, using the Ames Salmonella/mammalian microsome system. The addition of 100-250 micrograms of BHT or 25-500 micrograms of BHA/plate was found to inhibit DMAB-induced mutagenicity in Salmonella strains TA 98 and TA 100. In TA 100, the mutagenicity was further inhibited with the addition of S9 prepared from the livers of rats fed a 0.6% BHT diet as compared to S9 from the animals fed a diet containing no BHT.

Aminobiphenyl Compounds↗

PubMed1982

Fecal sterols and bacterial beta-glucuronidase activity: a preliminary metabolic epidemiology study of healthy volunteers from Umea, Sweden, and metropolitan New York.

The dietary pattern, fecal bile acid and neutral sterol concentrations, and the bacterial beta-glucuronidase activity of 2 population groups with a varied risk for colon cancer development (i.e., a high-risk population in the metropolitan New York area and an intermediate-risk population in Umea, Sweden) were investigated. The average daily intake of dietary protein was the same in the 2 groups, but the fat intake was higher in Umea than in New York. The daily total fiber intake was also higher in Umea, as was the daily total stool output. The concentration of fecal secondary bile acids and beta-glucuronidase activity was lower in Umea than in New York, but the total daily excretion of these constituents was the same in both groups. The data suggest that one of the factors contributing to the lower risk of colon cancer in Umea, despite the high dietary fat intake, is the high intake of dietary whole grain and cereal fiber, which leads to an increase in stool bulk, thus diluting and/or binding promoters.

Bacteria↗

PubMed1980

Effect of high-fat, high-beef diet and of mode of cooking of beef in the diet on fecal bacterial enzymes and fecal bile acids and neutral sterols.

The effect of a high-fat, high-beef diet and of method of preparation of beef in the diet on the fecal bile acids and neutral sterols and on the activities of fecal bacterial beta-glucuronidase, cholesterol dehydrogenase and 7 alpha-dehydroxylase was studied in healthy men and women, 24-41 years old, who were consuming a customary mixed-western diet. The experimental diets were high in fat and beef, which was cooked rare, medium or well-done. The sequence of dietary regimen was selected at random and each diet phase lasted for 4 weeks. Individual 24-hour fecal specimens were collected from each volunteer for the final 3 days during each dietary period, including pre- and post-experimental periods while they were consuming a customary mixed-western diet. The mode of cooking beef in the high-fat, high-beef experimental diets had no influence on the fat and protein content of the diets but the fat content of experimental diets was high compared to customary mixed-western diet. Fecal bacterial beta-glucuronidase activity and fecal secondary bile acid and cholesterol metabolite levels were significantly higher during the experimental diet periods but the fecal bacterial activities of 7 alpha-dehydroxylase and cholesterol dehydrogenase were unaffected. The mode of cooking beef in experimental diets had no influence on the fecal bacterial enzymes and on the excretion of fecal bile acids and cholesterol metabolites.

Adult↗

PubMedDate not supplied

An intervention technique for children with autistic spectrum disorder: joint attentional routines.

Virtually all children with autism are deficient in joint attentional skills. The impact of this deficit may be understood in the context of pragmatically based explanations of language acquisition. In this view, each step in the ontongeny of joint attention is consequential for language development. Thus, it is important that speech-language pathologists understand the developmental course of joint attention so that intervention may start at the earliest step possible. In this article, we review the literature on joint attention and its relationship with other rule systems of language. We discuss the ontogeny of joint attention in typical children. Finally, we describe the developmental course of joint attention as a framework for language intervention through the study of one case.

Attention↗