Organochlorines in polar bears (Ursus maritimus) at Svalbard

A comprehensive survey on organochlorine (OC) contaminants in polar bears at Svalbard has been undertaken. Subcutaneous tissue, blood and milk have been sampled from anesthetized free-ranging bears of both sexes and different ages in the period from 1990 to 1994. A number of sexually mature females have been fitted with satellite transmitters which make it possible to follow their reproductive behaviour pattern. We report on contamination levels and pattern of PCB congeners, chlordanes, DDT-compounds, HCB and HCH-isomers in the various tissues. The relation of age, sex and reproductive status to OC contamination has been described, and the capacity of polar bears in metabolising OCs has been discussed from the isomer/metabolite composition of residues. Finally, the possible association between OC contamination and reproduction success has been assessed. The PCB levels present in polar bears at Svalbard are extremely high. Especially high levels of higher chlorinated PCBs are found, and they accumulate with age, particularly in males. With females, considerable amounts of OCs are transferred to the offspring via milk. However, more efficient OC transfer between subcutaneous depot lipid and circulatory lipids than from the circulatory system to milk is found particularly for the most lipophilic compounds. The OC pattern in suckling yearlings reflects the low transfer of the highest chlorinated PCBs into maternal milk. The levels of most other OCs, however, are higher in depot lipid of yearlings than in that of their mothers. The polar bears have high capacity to metabolise several OCs. This may protect them against toxic action of the contaminants. No relation between OC levels in females and their ability to get pregnant is found in this preliminary investigation on OC effects on the polar bears at Svalbard.     

Quality assurance of multivariate analytical measurements by principal components analysis

The use of principal components analysis for the quality control of a mass spectrometer is demonstrated and commented upon.     

Can the Earth's magnetic field be simulated in the laboratory?

Today it is generally accepted that the Earth's magnetic field, as well as that of many other planets, is generated by buoyancy driven convection in the electrically conducting liquid cores of these rotating celestial bodies. The conversion of mechanical energy into electromagnetic energy is known as the dynamo effect. In contrast to technical dynamos, which utilize the rotational motion of a complex arrangement of wire coils and other materials of different electrical and magnetic properties, the geodynamo is based on a freely developing spiral flow in a practically homogeneous, electrically conducting liquid core domain, and is therefore termed a homogeneous dynamo. This report outlines some fundamental properties of the Earth's magnetic field. The structure of the spiral flow in the liquid interior of planets is explained with the help of some model experiments in rapidly rotating spherical shells, which were carried out by Busse and Carrigan (1974). Based on the main ideas of electromagnetism it is shown that spiral motion in well-conducting fluids, like liquid metals, can amplify seed magnetic fields to generate dynamo action. Starting from the conjectured flow structure in the Earth's interior, a conceptional and engineering design is described for a laboratory dynamo experiment. Some details of the construction of the test facility and first experimental results are presented and discussed.     

Early prenatal diagnosis of short rib-polydactyly (SRP) syndrome type I (Majewski) by ultrasound in a case at risk

Short rib-polydactyly (SRP) syndrome Type I was diagnosed accurately in an at-risk fetus at 16 weeks of gestation by real-time sonography. The most important findings were a narrow thorax, significant shortening of the long bones, particularly the tibiae, and–by directed search–the polydactyly.     

Determinants of mating success in the golden hamster (Mesocricetus auratus) IV. Sperm competition

Summary This study was designed to clarify several aspects of sperm competition in the golden hamster (Mesocricetus auratus). By mating females homozygous for a recessive coat color gene with two males, one homozygous for the dominat gene (agouti) and one homozygous for the recessive (cream), paternity of the resulting young could be determined by day 2 postpartum. When females received 5 consecutive ejaculations from a male of one strain followed by 5 ejaculations from a male of the other strain, there was a significant advantage with respect to litter composition for the male ejaculating first. A mechanism for the first male mating advantage was suggested by the results of an experiment in which the time interval between first and second males was varied. Delays of 30 min between first and second males significantly increased the proportion of young sired by the first male. With a delay of 8 h, the first male sired all of the young. Delays between matings by males of the two strains had greater effects when mating tests began around the time of ovulation, rather than several hours before. Ejaculations in excess of those required for pregnancy initiation were shown to have a two-fold effect. They afforded the first male a measure of protection against displacement by a subsequent male. Conversely, prolonged copulation by the second male resulted in significant displacement of the sperm of a predecessor. The protective effects of multiple ejaculations by the first male were mediated by two mechanisms: the delay in introduction of competing sperm and an increase in the relative concentration of the first male's sperm. Prolonged copulation by the second male also appeared to function through its effect on relative sperm concentrations. Males of these genotypes differed with respect to the relative fertilizing capacity of their cjaculates. When ejaculations from males of the two strains were alternated (thus minimizing mating order effects), agouti males sired over 90% of the young. The time during which mating tests were conducted (relative to the occurrence of ovulation) had no effect on the relative performance of the strains. The effects of prolonged copulation and first male mating advantage demonstrated in this study are consistent with observations of mating behavior under semi-natural conditions. Thus, it appears that patterns of sperm allocation and manipulation, male and female mating strategies, and mating systems have coevolved.