[Mortality among premature newborns below 32 weeks of gestational age depending on level of care and patient volume in Nordrhein-Westfalen/Germany]. / Mortalität bei Frühgeborenen < 32 Schwangerschaftswochen in Abhängigkeit von Versorgungsstufe und Patientenvolumen in Nordrhein-Westfalen.

BACKGROUND: It is an ongoing debate in Germany whether there is an association between the number of preterm infants admitted to a neonatal unit per year and neonatal mortality. Data from Germany on this topic are sparse and the generalizability of this data is questionable in face of a heterogeneous organization of perinatal care among federal states. METHODS: We used data from a state-wide quality assurance program in Nordrhein-Westfalen/Germany, encompassing 3 930 newborns below 32 completed weeks gestation p. m. admitted during the years 2004 and 2005. We hypothesized that there is an association between annually admitted premature infants below 32 completed weeks of gestation and mortality rates among these patients. RESULTS: Mortality below 28 completed weeks gestation was significantly lower in hospitals admitting more than 50 premature infants < 32 completed weeks gestation per year compared to smaller hospitals (odds ratio 0.55, 95 %-CI 0.41-0.74, p < 0.001). When lowering the critical threshold to hospitals admitting more than 40 premature infants < 32 weeks gestation, only in newborns < 25 completed weeks gestation a significant effect could be demonstrated. The level of care (level 1-3) was off less importance than patient volume. CONCLUSION: In Nordrhein-Westfalen/Germany, survival rate of immature infants is significantly higher if treated in larger neonatal intensive care units with a minimal annual volume of more than 40-50 premature infants < 32 weeks GA. Patient volume seemed to be a better indicator of performance than formal level of care.

[Assessment and outcome of perinatal and neonatal care in North Rhine area]. / Rheinische Perinatalerhebung und Neonatalerhebung.

The objective of the quality assurance program "Perinatalerhebung" and "Neonatalerhebung" is to ameliorate the perinatal and neonatal care in German hospitals. Standardised data defined by a team of experts in the early seventies are documented for more than 20 years in the North Rhine area. The documentation of more than 1.6 million deliveries created a data pool that served as a thesaurus for the improvement of medical care in obstetrical units. The same has been achieved for neonatal care on the documentation basis of more than 168,000 newborn infants admitted to a neonatal department. The results show that the approach to evaluate continuously the data monitored enables improvement in care. The support given is the anonymous collection of the documentation sheets/data sets and their evaluation by an expert committee. The results show that obstetrical management changed and the measurable results improved demonstrably. The efforts seem to be worthwhile in view of the fact that less than 1 % of the total cost of care has been spent for this project.

Pregnancy outcomes in mothers with pregestational diabetes: a population-based study in North Rhine (Germany) from 1988 to 1993.

UNLABELLED: The purpose of this study was to estimate the proportion of pregnancies with pregestational diabetes in Germany, to compare the outcome of these pregnancies to pregnancies in nondiabetic mothers and to identify risk factors for poor pregnancy outcomes in mothers with pregestational diabetes. Data of the "Perinatalerhebung Nordrhine" from 1988-1993 were analysed. The Perinatalerhebung is an ongoing quality assurance programme of prenatal and perinatal care in the region of North Rhine (South Western part of North Rhine-Westphalia). During the observation period a proportion of 93%-100% of the annual births in the region (n = approximately 100000) were included in the study. Their data had been documented by the obstetricians in a standard multiple choice questionnaire. The outcome parameters perinatal mortality, macrosomia, prematurity, and malformations were analysed in relation to several defined explanatory variables. There were 2,402 births in mothers with pregestational diabetes (0.4% of all births). The proportions of poor pregnancy outcomes in women with pregestational diabetes were 2.8% for perinatal mortality, 27.6% for macrosomia, 21.1% for prematurity and 2.1% for malformations . The respective relative risks compared to the non diabetic mothers were 4.3 (95% CI 3.4-5.5) for perinatal mortality, 3.1 (95% CI 2.9-3.3) for macrosomia, 2.7 (95% CI 2.5-2.9) for prematurity and 1.7 (95% CI 1.3-2.3) for malformations . The main risk factor for perinatal mortality in children of diabetic mothers after adjustment for maternal smoking, ethnicity, parents' professional achievement, type of obstetric hospital, and maternal age was substandard use of prenatal care. CONCLUSIONS: The prevalence of births from mothers with pregestational diabetes and their pregnancy outcomes were similar to those in other Western countries. The standard for non-diabetic mothers has not been reached yet. Further improvements may be achieved if all diabetic women are convinced to use the standard prenatal care facilities throughout pregnancy.

Life-history variation in a hybrid species complex ofDaphnia.

Life-history variation was examined among members of theDaphnia longispina group, which consists ofD. galeata, D. hyalina, D. cucullata, and hybrids. Factorial experiments were conducted at two temperatures (14° and 20° C) and two food concentrations (0.2 and 1.0 mg Cl-1). Differences in life-history features (size at maturity, age at first reproduction, size of first clutch, offspring size in first clutch) under the different environmental conditions were assessed among eightDaphnia clones, which represented members of this species complex. Significant differences between parentals and hybrids for most life-history features were observed under various treatments; generally, hybrid clones showed intermediate life-history traits when compared with parentals. When comparisons were made among clones within a given species (i.e.D. galeata, D. galeata xcucullata, D. cucullata), clonal differences were also noted for certain life-history traits. The data are discussed with reference to the formation and maintenance of hybrid species complexes in nature.

Experimental evidence for the adaptive value of sexual reproduction.

It is generally believed that recombination by sexual reproduction is unfavourable in constant environments but is of adaptive value under changing environmental conditions. To test this theory, experimental populations of yeast (Saccharomyces cerevisiae) were set up and maintained at different levels of environmental heterogeneity. Recombination was estimated by determining sporulation rates. Sporulation rates first increased in populations living in highly variable environments, but after some time began to decrease. The decrease started last and was slowest in populations which were maintained under the same conditions for a sufficiently long time, to allow some adaptation of the gene pool to the respective environment. Patterns of genotypic variability could not be interpreted in such simple terms, but there was a statistically significant correlation between sporulation rate and genotypic variability. This correlation is to be expected because recombination generates genotypic variability. Summing up, recombination by sexual reproduction is advantageous in changing environments if the population can track the changes in the environment by changing its genotypic structure.

The importance of carrying capacity, fertility, and viability for the competitive ability of populations.

A simple mathematical model is analyzed which describes the behaviour of a population under the influence of viability and fertility as well as carrying capacity and competition by another species. One locus with two alleles determining viability, fertility, and carrying capacity is considered. Throughout the analysis absolute rather than relative numbers are used. The following results have been obtained: 1. The species producing more zygotes wins the competition. 2. Absolute numbers must be used for viability and fertility in theoretical considerations, because the outcome of competition may be changed by using different absolute numbers of the same relation. 3. Differences in viability are amplified by limiting the number of individuals. 4. Differences in every parameter can be compensated by any other parameter.

Canine osteosarcoma karyotypes from an original tumor, its metastasis, and tumor cells in tissue culture.

Radiation-induced osteosarcoma, its metastasis, and cells grown in tissue culture were karyotyped. Both hypodiploid and hyperdiploid stem lines were observed. The hypodiploid line contained 45-55 chromosomes with 10-15 abnormal metacentric and submetacentric chromosomes and one subtelocentric marker. The hyperdiploid line contained 90-105 chromosomes with 20-30 abnormal metacentric and submetacentric chromosomes with two subtelocentric markers. Karyotypic analysis can be used to monitor osteosarcomas maintained in tissue culture.