Cultures of blood from healthy adults were irradiated 48 h after stimulation with 240 R of X-rays and fixed after various time intervals (0-2 h, 2-4 h, 4-6 h). 3HTdR was added to several cultures after irradiation. Mitotic and labelling indices were used to distinguish between two cell samples inside the irradiated G2 population: D- cells reaching mitosis without mitotic delay and a high frequency of chromatic breaks and D+ cells with mitotic delay and which, during the delay, repair most of the damage produced. After R banding 450 chromatid deletions were located in each of the two cell samples. The D+ cells showed a higher frequency of breaks than the D- cells with decreasing chromosome size, in the telomeric and centromeric region and in the junction between the R+ and R- bands. These results can be interpreted as indicative of a non-random distribution of repair processes both between and within chromosomes.

Chromosome Aberrations↗

PubMedDate not supplied

Effect of pH shifts on radiosensitivity of human lymphocytes irradiated in the G2 stage.

Experiments were carried out using human lymphocytes in order to test the effect of pH shifts on radiosensitivity of cells irradiated in the G2 stage. In our culture conditions constant variations in medium pH over the range of 7.4-6.8 were observed as a function of incubation time after PHA stimulation; in addition the pH of the medium was adjusted in parallel cultures over the range of 5.9-8.2. Then we exposed the cultures with different pH to a treatment of X-rays delivered 2 h before fixation. The pH of the medium was found to greatly affect the yield of induced chromatid aberrations.

Cell Division↗

PubMedDate not supplied

Analysis of the internal representations developed by neural networks for structures applied to quantitative structure--activity relationship studies of benzodiazepines.

An application of recursive cascade correlation (CC) neural networks to quantitative structure-activity relationship (QSAR) studies is presented, with emphasis on the study of the internal representations developed by the neural networks. Recursive CC is a neural network model recently proposed for the processing of structured data. It allows the direct handling of chemical compounds as labeled ordered directed graphs, and constitutes a novel approach to QSAR. The adopted representation of molecular structure captures, in a quite general and flexible way, significant topological aspects and chemical functionalities for each specific class of molecules showing a particular chemical reactivity or biological activity. A class of 1,4-benzodiazepin-2-ones is analyzed by the proposed approach. It compares favorably versus the traditional QSAR treatment based on equations. To show the ability of the model in capturing most of the structural features that account for the biological activity, the internal representations developed by the networks are analyzed by principal component analysis. This analysis shows that the networks are able to discover relevant structural features just on the basis of the association between the molecular morphology and the target property (affinity).

Benzodiazepines↗

PubMedDate not supplied

Biological parameters and the segregation distortion (SD) phenomenon in Drosophila melanogaster.

The relationship between some biological parameters (mortality, longevity, fertility, fecundity and sex ratio) and segregation of second chromosomes in heterozygous and homozygous SD males has been analyzed. The results obtained in SD/SD+ heterozygous males show: (1) their reduced fertility with respect to that of control males, (2) an alteration in the sex ratio in the SD+ progeny only, and (3) inversely related sex-ratio and segregation distortion values. In SDi/SDj combinations: (1) surprisingly, fertility is intermediate between that of SD/SD+ heterozygous males and that of control males, (2) the segregation ratios of the second chromosomes are normal (0.50), and (3) the sex ratio = 0.50 in both classes of SD progeny. The relationship between mortality (and therefore longevity) and fertility of the different genotypes and fecundity per male indicates that the total productivity of heterozygous males is less than that so far claimed. Indeed, their productivity depends not only on the mechanism of nonformation of the SD+ sperm, but also on their reduced longevity. The k = 0.50 and the high fecundity of SDi/SDj combinations indicated that in these males the SD phenomenon is partially suppressed, the SD chromosomes being insensitive to each other, thus implying that particular Rsp alleles are sensitive to given Sd alleles. The complementation pattern for male fertility of SD homozygous males again supports previous evidence that Sd factors from natural populations are, in effect, different Sd genes.

Animals↗

PubMedDate not supplied

Incidence, mortality and prevalence of stomach cancer in Italian regions.

The basic descriptive epidemiologic data on stomach cancer occurrence in Italian regions are presented and discussed. Incidence and prevalence were estimated from official mortality and survival data provided by four population-based Italian cancer registries. Age-adjusted mortality, incidence, and prevalence rates are presented by region for the year 1990. Time trends of incidence and their projection for the year 2000 are also presented by region and three broad age classes. Although the occurrence of stomach cancer has been decreasing in Italy and most western countries over the last decades a substantial slowing down of this decrease was evidenced in Italy, especially for women under 65 and for the regions of southern Italy. A marked tendency towards a reduction of geographic heterogeneity in stomach cancer occurrence was also shown. Such a phenomenon is consistent with the observed changes of dietary habbits in Italian regions. The regions of Umbria and The Marches seem to emerge as new areas at relatively high risk of stomach cancer incidence and mortality. About 45,000 prevalent cases were estimated in Italy by 1990, half of which have been diagnosed before 1984.

Adolescent↗

PubMedDate not supplied

Studying survival of cancer patients in different populations: its potential and role.

RATIONALE: Survival figures from a population-based study incorporate the overall practice in diagnosis, cure and clinical follow-up for a specific disease within a given health care system. Being the outcome of a number of individual, social and economical aspects, population-based survival may be thought as index for measuring the level of a country's development. DATA: The EUROCARE project, a European Cancer Registries (CR) concerted action, provided reliable information on survival for more than 800,000 cancer patients from 11 European countries. A great deal of epidemiologic information has derived from EUROCARE. Women had a longer survival than men for all studied tumour sites, except for the colon. European survival variability was fairly high for several cancers, but it was lower for cancers with a relatively good prognosis and those sensitive to treatment. The ranking of populations of cancer survival tended to be fairly stable for many cancers: CR of Switzerland and Finland ranked high and Polish CR low. Denmark, Italian and France CR did not substantially differ from the European survival average. For most cancers, prognosis improved during the studied period (years of diagnosis: 1978-1985). Survival figures for colon (r = 0.74, males; r = 0.73, women) and female breast cancer (r = 0.57) well correlated with the national health expenditure of different participating countries. The ITACARE study, a new Italian Cancer Registries collaborative project involving more than 100,000 cancer patients, was set up to study survival differences within the country. Survival of cancer patients was not homogeneous in 7 studied Italian regions (the estimated 5-year relative survival for all malignant neoplasms combined ranked from 37.8% in CR of Sicily to 42.1% in those of Emilia-Romagna). The lowest levels of regional health expenditures were accompanied by the lowest levels of prognosis for overall cancers. However, a relatively low correlation among patient cancer survival and the regional health expenditure (r = 0.21) was found, suggesting that other factors such as different efficiency in managing cancer may play a role in explaining the intracountry differences. CONCLUSIONS: Population-based survival figures may be used to study epidemiologic aspects, comparing different health systems, and may be interpreted as indexes for discussing inequalities in health in different populations.

Age Distribution↗