Under barrier condition and with ad lib access to food and water, 20 Fischer-344 rats were chronically treated for 10 months with the benzodiazepine (BDZ) antagonist, flumazenil (FL; 4 mg/kg/day in drinking water acidified to pH = 3.0), beginning at the age of 13 months, while the group of 20 control age-matched rats received plain acidified water. The life span of the first 8 deceased rats treated with FL was significantly longer than that of the first 8 deceased rats in the age-matched control group. In tests for spontaneous ambulation and exploratory behavior in the Holeboard apparatus, conducted during the 3rd and the 8th month of treatment, the FL group, relative to controls, had significantly higher scores for the ambulation and exploratory behavior. In tests for unrewarded spontaneous alternation in the T maze, conducted at days 7, 39, 42, and 47 through 54 after drug withdrawal, i.e., at the age of 24-25 months, the FL-exposed group, compared to age-matched controls, showed a significantly higher percent of alternating choices, a behavior that was statistically comparable to that of the "young" 6-month-old controls. In the Radial Maze tests conducted 2 months after drug withdrawal, the FL group made significantly less "working memory" errors and "reference memory" errors, relative to the age-matched 25-month-old control group, a performance that was comparable to that of the young 7-month-old control group. In conclusion, chronic FL significantly protected rats from age-related loss of cognitive functions. It is postulated that the age-related alterations in brain function may be attributable to the negative metabolic/trophic influences of the "endogenous" benzodiazepine (BDZ) ligands and/or those ingested with food. A BDZ/GABAergic hypothesis of brain aging has been formulated which assumes that age-related and abnormally strong BDZ/GABAergic influences promote neurodegeneration by suppressing trophic functions of the aminergic and peptidergic neurons through opening of chloride channels in soma membrane and axon terminals, causing excessive hyperpolarizing and depolarizing inhibition, respectively. The review of human clinical and animal data indicates that FL has nootropic actions by enhancing vigilance cognitive and habituation processes.

Aging↗

PubMedDate not supplied

Phorbol ester promotes growth and transformation of carcinogen-exposed nonhuman primate cells in vitro.

Kidney cells established in vitro from a white-lipped marmoset (106) were exposed to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) alone or in combination with 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Low (0.1 micrograms/ml, 4 times), intermediate (1 microgram/ml) and high (1 microgram/ml, 4 times) doses of MNNG resulted in 100%, 50% and 2.8% of cell survival, respectively. High and low doses of MNNG had no effect on cell transformation. Upon exposure of cells to an intermediate dose of MNNG, 106 cells ecquired immortality and evolved into permanent cell line, 106-1M. However, the cells retained normal morphology and anchorage dependence. Chronic applications of TPA (0.1 micrograms/ml, 13 times) promoted 106-1M cells to morphological transformation and anchorage-independent growth but not to tumorigenicity in nude mice (106-1MT cell line). Chromosome analysis revealed only numerical changes in 106 cells and both numerical and structural aberrations in transformed 106-1MT cells. These changes in marmoset cells usually reflected cell culture instability leading to either senescence or to longer survival of cells in vitro. Chronic treatment with TPA did not result in downregulation of protein kinase C (PKC) in transformed 106-1MT cells. Instead, an additional species of PKC appeared in these cells.

Animals↗

PubMedDate not supplied

Transformation of primate cells by chemicals and oncogenes: requirements for multiple factors.

Although several chemical carcinogenes have been shown to induce malignant transformation in human cells in culture, the molecular events involved in conversion of normal cells to malignant cells remain unknown at present. Normal human cells seem to be resistant to transformation by a single oncogene unless these cells have been immortalized by chemical carcinogens or DNA tumor virus genes. In some human cell systems, malignant phenotype is expressed after activation of protooncogenes probably through the mechanism of point mutations. Our results represent the first induction of KRAS gene rearrangement in cells of patients with familiar polyposis coli (FPC) treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and 12-0-tetradecanoyl-phorbol-13-acetate (TPA). Whether or not KRAS rearrangement is a prerequisite for transformation in these cells is unknown. The contrast between the response of the FPC cells following treatment with these chemicals compared with that of normal fibroblasts suggests that KRAS gene rearrangement in FPC cells may be considered as a genetic marker for the disease. Studies of transformation with chemicals and oncogenes extended to nonhuman primate--marmoset cells have shown that two viral oncogenes, v-src and v-sis, converted marmoset cells to altered morphology, anchorage independence and immortality in cell culture. The transformed cells, however, lacked tumorigenicity in allogeneic and xenogeneic hosts. In v-src transformed cells additional changes associated with mutations of transforming virus and chromosome rearrangements were necessary for induction of tumorigenicity in allogeneic marmosets. Transformation of marmoset cells by chemical carcinogens depended on the type of target cells. Skin fibroblasts treated with MNNG acquired transformed morphology, anchorage independence and random chromosome aberrations. Kidney cells treated with the same carcinogen remained untransformed, but attained the same characteristics of transformation when exposed to TPA. Neither skin nor kidney transformed cells showed true tumorigenic potential in nude mice.

Adenomatous Polyposis Coli↗