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Biomedical subjects

G F Combs

Publications and source records attributed to G F Combs.

118 records · Page 7Linked to original sources
PubMedDate not supplied

Effects of aurothioglucose and dietary Se on glutathione S-transferase activities and glutathione concentrations in chick tissues.

Experiments were conducted to determine whether the increased glutathione S-transferase (GSH-T) activity associated with selenium (Se) deficiency is necessarily related to losses in the activity of Se-dependent glutathione peroxidase (SeGSHpx) in chicks. Nutritional Se status was altered in two ways: by treatment with an antagonist of Se utilization, aurothioglucose (AuTG), and by feeding diets containing excess Se. Chicks given AuTG (10-30 mg AU/kg, sc) had growth rates and hepatic GSH concentrations that were comparable to those of saline-treated controls; however, their plasma GSH levels exceeded those of either Se-deficient (6-fold) or -adequate (3-fold) saline-treated chicks. Hepatic SeGSHpx activities of AuTG-treated chicks were half those of controls under conditions of Se-adequacy; however, this effect was not detected when Se was deficient. Hepatic GSH-TCDNB (assayed with 1-chloro-2,4-dinitrobenzene) activities of AuTG-treated chicks were significantly greater than those of controls when Se was deficient (i.e., when SeGSHpx activity was 12% of the Se-adequate level); however, deprivation of Se did not affect GSH-TCDNB activity in the absence of AuTG. Chicks fed excess Se (6-20 ppm as Na2SeO3) in diets containing either low (2 IU/kg) or adequate (100 IU/kg) VE, showed hepatic GSH-TCDNB activities and GSH concentrations greater than those of Se-adequate (0.2 ppm Se) chicks by 100% and 40%, respectively. That increased hepatic GSH-TCDNB activity can occur because of either AuTG or excess Se status under conditions wherein SeGSHpx activity is not affected indicates that the transferase response is not directly related to changes in the peroxidase.

Animals↗
PubMedDate not supplied

Ascorbate interacts with sodium selenite to increase glutathione peroxidase activity in selenium-deficient chick duodena cultured in vitro.

Duodena from Selenium (Se)/vitamin E-depleted 19 d chick embryos were cultured in vitro for 0-30 h. The addition of sodium selenite to the culture medium was associated with increased selenium-dependent glutathione peroxidase (SeGSHpx) activity after 24 h of incubation. In the absence of Se or in the presence of sodium ascorbate supplementation alone, SeGSHpx activity showed a gradual decline over the same time period. When ascorbate was added, along with sodium selenite, SeGSHpx activity was increased earlier and to a greater extent than in the presence of Se alone. These observations show that ascorbate can influence the metabolism of sodium selenite, resulting in increased SeGSHpx activity.

Animals↗
PubMedDate not supplied

Plasma selenium concentration predicts the prevalence of colorectal adenomatous polyps.

The objective of this cross-sectional study was to determine whether plasma selenium concentration predicts the prevalence of adenomatous polyps of the colon and rectum. The source population for the study was 101 patients undergoing sequential colonoscopies at the Veterans Affairs Medical Center, Tucson, AZ. The study population was then limited to the 48 patients (all male) undergoing their initial colonoscopy who did not have a diagnosis of colorectal cancer. For each of these patients, a prediagnostic fasting plasma selenium concentration was determined. The data from this study suggest that fasting plasma selenium concentrations may be an important risk factor for colorectal adenomas. Patients with fasting plasma selenium concentrations below the median (< 128 mcg/liter) were significantly more likely to have one or more adenomatous polyps (prevalence odds ratio 4.2) and more adenomatous polyps (3.5 times) per patient. There was also a suggestion of a more proximal distribution of adenomatous polyps in the patients with a lower level of selenium. These associations were not confounded by age or smoking. The results of this study are consistent with the experimental animal studies, geographic mortality studies, and prospective cohort studies of selenium and colorectal cancer.

Adenoma↗