The mechanism of 5-fluorouridine toxicity in Novikoff hepatoma cells.

The mechanism of 5-fluorouridine (FUrd) cytotoxicity in Novikoff hepatoma cells appears to vary under different experimental conditions. Continuous exposure to 1 X 10(-7) M FUrd results in a simple thymineless death that can be prevented by the addition of 1 X 10(-4) M thymidine to the culture medium. In contrast, 1 X 10(-4) M thymidine does not prevent the growth inhibition caused by a 1-hr exposure to 1 X 10(-5) M FUrd, despite the fact that it does prevent the inhibition of DNA synthesis. Although it has no effect on the inhibition of DNA synthesis, 1 X 10(-4) M uridine prevents the growth inhibition caused by a 1-hr exposure to 1 X 10(-5) M FUrd. Since 1 X 10(-4) M uridine, but not 1 X 10(-4) M thymidine, prevents the inhibition of ribosomal RNA maturation caused by a 1-hr exposure to 1 X 10(-5) M FUrd, it seems likely that the effects of the analog on RNA metabolism contribute significantly to the cytotoxic activity of the analog in this specific experimental situation.

Anxiety and the colposcopy experience.

The purpose of this study was to explore the anxiety of an abnormal Papanicolaou (Pap) result, the need for colposcopy, and the colposcopic examination experienced by first-time colposcopy clients. Spielberger's State-Trait Anxiety Inventory (STAI) and a Woman's Profile were administered to 149 women who had abnormal Pap smears necessitating colposcopy. The results confirm that this experience evokes anxiety. Younger women who knew less and had concurrent stressors in their lives were most anxious. Women identified ways that health professionals could be more helpful in alleviating their anxiety. Their suggestions included the provision of more information and an opportunity for personal contact with a health professional.

Metabolism of 5-fluorouracil in sensitive and resistant Novikoff hepatoma cells.

N1-S1/FdUrd Novikoff hepatoma cells, which lack thymidine kinase activity, are resistant to 5-fluorouracil (FUra) as well as 5-fluorodeoxyuridine (FdUrd), suggesting that the pathway, FUra leads to FdUrd leads to FdUMP, is utilized for the conversion of FUra to FdUMP. However, the inhibition of thymidylate synthetase activity, the presumed target of FdUMP, by 1 X 10(-4) M FUra in intact N1-S1 Novikoff hepatoma cells, which have significant levels of thymidine kinase activity, is completely eliminated by 5 X 10(-4) M hydroxyurea, which is a potent inhibitor of ribonucleotide reductase. These results imply that the formation of ribonucleotides and does not involve thymidine kinase. This apparent dichotomy can be explained by the fact that, in addition to the well known lack of thymidine kinase activity, [14C]FUra conversion to ribonucleotides is greatly depressed in the N1-S1/FdUrd cells. Hence, the formation of FdUMP from FUra in Novikoff hepatoma cells apparently proceeds primarily via the intermediate formation of ribonucleotides. The decreased conversion of FUra to ribonucleotides in N1-S1/FdUrd cells decreases not only the ability of the analog to inhibit DNA synthesis, but also its effect on RNA metabolism. FUra, at a concentration of 1 X 10(-5) M, inhibits rRNA maturation in N1-S1 cells, but not in N1-S1/FdUrd cells. Since N1-S1/FdUrd cells are completely resistant to 1 X 10(-5) M FUra, whereas N1-S1 cells are completely inhibited by 1 X 10(-5) M FUra, even in the presence of 1 X 10(-4) M thymidine, the effects of FUra on RNA metabolism appear to contribute significantly to the cytotoxicity of the analog at higher drug concentrations.

HLA in familial Hodgkin's disease. Results and a new hypothesis;.

A familial aggregate of seven cases of Hodgkin's disease (HD) has been investigated by HLA typing. Over 600 people in the immediate population (i.e. about half) have been HLA typed and haplotypes have been obtained for 95% of them. It was expected that the cases would share a particular HLA haplotype or at least that they would have one or two HLA antigens of the same series in common. However, this was not the case so no simple idea of association of HLA with HD cases was upheld. When antigen frequencies were examined in the whole population, it was found that HLA B18 increased progressively in incidence from 0.08 to 0.4 in successive groups of individuals each one more closely related to the HD cases. Similarly the community with the highest incidence of HD also had the highest incidence of B18. Thus B18, which in the world figures carries the highest relative risk, emerged as important in this study. Of four proposed interpretations of the data, we are most interested in the idea that the important HLA association is at a population level rather than at the level of the individual patient. A hypothesis, based on the concept of a "healthy carrier" for the HD agent, explains how such an association might operate. It is possible that B18-linked complement deficiency could be the basis for such a carrier state.

Tuberculosis associated with HLA--B8, BfS in a Newfoundland community study.

In three adjacent Newfoundland communities comprising some 1500 people, 589 people have been HLA typed. Forty-six of the typed people gave a history of previous clinical tuberculosis which required treatment. Fifty-six percent of the TB patients carried HLA B8 compared with 20% of the remainder of the population. This is a highly significant difference (P less than 0.01). In each community the frequency of B8 as an epidemiological marker correlated with the incidence of tuberculosis. B8 is associated with TB in ths study with a relative risk of 5.2 which compares with combined relative risks in the literature for coeliac disease and Addison's disease of 9.5 and 6.4, respectively, and which is greater than the risks for all the other B8-related diseases. The factor B allele, Bf S, was found on all the B8 haplotypes, but the overall Bf gene frequencies in tuberculosis patients did not deviate from expected values.