The p53 tumour-suppressor gene is mutated in 60% of human tumours, and the product of the gene acts as a suppressor of cell division. It is thought that the growth-suppressive effects of p53 are mediated through the transcriptional transactivation activity of the protein. Overexpression of the p53 protein results either in arrest in the G1 phase of the cell cycle or in the induction of apoptosis. Both the level of the protein and its transcriptional transactivation activity increase following treatment of cells with agents that damage DNA, and it is thought that p53 acts to protect cells against the accumulation of mutations and subsequent conversion to a cancerous state. The induction of p53 levels in cells exposed to gamma-irradiation results in cell cycle arrest in some cells (fibroblasts) and apoptosis in others (thymocytes). Cells lacking p53 have lost this cell cycle control and presumably accumulate damage-induced mutations that result in tumorigenesis. Thus, the role of p53 in suppressing tumorigenesis may be to rescue the cell or organism from the mutagenic effects of DNA damage. Loss of p53 function accelerates the process of tumorigenesis and alters the response of cells to agents that damage DNA, indicating that successful strategies for radiation therapy may well need to take into account the tissue of origin and the status of p53 in the tumour.

No abstract

A cross-sectional survey was made in 56 exceptionally healthy males, ranging in age from 20 to 84 years. Measurements were made of selected steroidal components and peptidic hormones in blood serum, and cognitive and physical tests were performed. Of those blood serum variables that gave highly significant negative correlations with age (r > ؊0.6), bioavailable testosterone (BT), dehydroepiandrosterone sulfate (DHEAS), and the ratio of insulinlike growth factor 1 (IGF-1) to growth hormone (GH) showed a stepwise pattern of age-related changes most closely resembling those of the age steps themselves. Of these, BT correlated best with significantly age-correlated cognitive and physical measures. Because DHEAS correlated well with BT and considerably less well than BT with the cognitive and physical measures, it seems likely that BT and͞or substances to which BT gives rise in tissues play a more direct role in whatever processes are rate-limiting in the functions measured and that DHEAS relates more indirectly to these functions. The high correlation of IGF-1͞GH with age, its relatively low correlation with BT, and the patterns of correlations of IGF-1͞GH and BT with significantly age-correlated cognitive and physical measures suggest that the GH-IGF-1 axis and BT play independent roles in affecting these functions. Serial determinations made after oral ingestion of pregnenolone and data from the literature suggest there is interdependence of steroid metabolic systems with those operational in control of interrelations in the GH-IGF-1 axis. Longitudinal concurrent measurements of serum levels of BT, DHEAS, and IGF-1͞GH together with detailed studies of their correlations with agecorrelated functional measures may be useful in detecting early age-related dysregulations and may be helpful in devising ameliorative approaches.

The first U.S. nationwide food sampling with measurement of dioxins, dibenzofurans, and coplanar, mono-ortho and di-ortho

The relation of the reproductive endocrine system to impotence in older men was examined by measuring the concentrations of testosterone (T), bioavailable testosterone (BT), LH, and PRL and body mass index (BMI) in 57 young controls (YC), 50 healthy potent older controls attending a health fair (HF), and 267 impotent patients (SD). The SD and HF had markedly reduced mean T and BT values compared to YC. When adjusted for age and BMI there was no difference in BT between potent and impotent older men. The percent BT was much higher in YC than in the older groups. While the percent BT rose significantly with increased T in YC, it was inversely related to T in the older subjects, suggesting that increased sex hormone-binding globulin binding was a primary event leading to a low BT. Forty-eight percent of HF and 39% of SD were hypogonadal, as defined by a mean BT of 2.5 SD or more below the mean of YC (less than or equal to 2.3 nmol/L). Ninety percent of these had LH values in the normal range, suggesting hypothalamic-pituitary dysfunction. Thirty-four SD and six each of YC and older control volunteers (OC) underwent GnRH testing. Older subjects showed impaired responsiveness to GnRH compared to YC. A low basal LH level correlated very highly with hyporesponsiveness to GnRH. Thus, secondary hypogonadism and impotence are two common, independently distributed conditions of older men.