PARATI – a dynamic model for radiological assessments in urban areas

The structure and mathematical model of PARATI, a detailed computer programme developed for the assessment of the radiological consequences of an accidental contamination of urban areas, is described with respect to the scenarios used for the estimation of exposure fields in a village or town, the models for the initial and secondary contamination with the radionuclide ¹³⁷Cs, the concepts for calculating the resulting radiation exposures and the changes with time of the contamination and radiation fields. Kerma rates at various locations in tropical urban areas are given, and the contribution of different contaminated surfaces to these rates after dry or wet deposition are discussed. Received: 12 April 1996 / Accepted in revised form: 30 August 1996     

Oocyte growth and development in teleosts

Oocyte growth and development is an important issue in fish and fisheries biology. This paper reviews the information available on oocyte growth patterns and the rates and dynamics of oocyte growth in teleosts. In synchronous spawners, the weight of the gonad may represent as much as 40% of the overall body weight of the fish. In asynchronous spawners, the weight of the mature ovary is considerably less than in synchronous ovulators, but the ovary shows a more regular periodicity and may grow repeatedly many times during the breeding season. There is a huge variability in egg size in teleosts, with the largest known measuring up to 8 cm in diameter. Within the limits of variance set by genetic constraints, egg size may vary between populations of the same species. Oocytes in all teleosts undergo the same basic pattern of growth: oogenesis, primary oocyte growth, cortical alveolus stage, vitellogenesis, maturation and ovulation. The mechanisms that control oocyte growth are addressed in this review, albeit that the available information, as in all other vertebrates, is very limited. The main hormones that have been shown to affect ovarian growth are gonadotrophin, thyroid hormones, growth hormone, insulin and insulin-like growth factors. An overview of the determinants of fecundity, with particular reference to oocyte recruitment and atresia, is the focus of the second part of the paper. Genetics and nutrition have major effects on fecundity, and studies so far suggest that the determinants of fecundity usually operate during the early part of gametogenesis. The role of atresia in determining fecundity is less clear. The final part of this review highlights some areas of study that are priorities for research on ovarian development in fish.     

Response to treatment in hereditary metabolic disease: 1993 survey and 10-year comparison.

Knowledge about cause, pathogenesis, and manifestations of hereditary metabolic diseases puts them among the best known of all human diseases. On the other hand, outcomes of treatment are cause for uncertainty and concern. In 1985, Hayes et al. analyzed efficacy of treatment up to 1983 in 65 of these diseases selected randomly from the McKusick catalogs. Disease scores were calculated for seven parameters: longevity; reproductive capability; somatic and cognitive development; and handicaps affecting schooling, work, and cosmetic appearance. Scores of the untreated and treated phenotypes were then compared. We have now measured progress over the past decade by calculating scores on the same 65 diseases from data in several hundred new reports published since 1983. All seven parameters in the 1993 survey reflect improved efficacy of treatment in the 10-year interval. However, the percent of diseases for which all manifestations of the disease were removed by treatment has not changed (12% in 1983; 12% in 1993). The group in which manifestations were untouched by treatment has become smaller (48% in 1983; 31% in 1993), and the group partially ameliorated by treatment had increased reciprocally (40% in 1983; 57% in 1993). Progress in the treatment of hereditary metabolic disease is thus better than it was, but it is still only a partial success. The advances are attributable to greater success with organ and tissue transplantation, better pharmacotherapy, and better support systems. Restoration of normal homeostasis, the key to successful treatment, remains an elusive challenge and is a logical, major focus for research in human genetics.