Cosmology, Particle Physics and Superfluid 3He

Many direct parallels connect superfluid 3He with the field theories describing the physical vacuum, gauge fields and elementary fermions. Superfluid $^3$He exhibits a variety of topological defects which can be detected with single-defect sensitivity. Modern scenarios of defect-mediated baryogenesis can be simulated by the interaction of the 3He vortices and domain walls with fermionic quasiparticles. Formation of defects in a symmetry-breaking phase transition in the early Universe, which could be responsible for large-scale structure formation and for microwave-background anisotropy, also may be modelled in the laboratory. This is supported by the recent observation of vortex formation in neutron-irradiated 3He-B where the "primordial fireball" is formed in an exothermic nuclear reaction.Comment: Invited talk at LT-21 Conference, 20 pages, 3 figures available at request, compressed ps file of the camera-ready format with 3 figures is at ftp://boojum.hut.fi/pub/publications/lowtemp/LTL-96006.ps.g

Selenium in reproduction

Selenium is an essential trace element of importance to human biology and health. Increasing evidence suggests that this mineral plays an important role in normal growth and reproduction in animals and humans, and selenium supplementation is now recommended as part of public health policy in geographical areas with severe selenium deficiency in soil. This review addresses the biological functions of selenium followed by a detailed review of associations between selenium status and reproductive health. In many countries, selenium dietary intake falls below the recommended nutrient intakes and is inadequate to support maximal expression of the selenoenzymes. Numerous reports implicate selenium deficiency in several reproductive and obstetric complications including male and female infertility, miscarriage, preeclampsia, fetal growth restriction, preterm labor, gestational diabetes, and obstetric cholestasis. Currently, there is inadequate information from the available small intervention studies to inform public health strategies. Larger intervention trials are required to reinforce or refute a beneficial role of selenium supplementation in disorders of reproductive health

Axonal degeneration in diphtheritic neuropathy

The purpose of this investigation was to study axonal degeneration in a neuropathy known usually to be demyelinating in type. High doses of diphtheria toxin were injected intraneurally into the sciatic nerves of 33 rabbits. At two dose levels the effects were studied histologically at various times after injection. At the higher dose level there were vascular changes from the first day after injection, accompanied between the first and the fifth day by extensive haemorrhages. Schwann cell damage and axonal degeneration which were present from the first and the third day after injection respectively, might therefore be due partly to ischaemia. A slightly lower dose produced almost no endoneurial haemorrhage. At this dose level marked axonal degeneration was present from the twelfth day onward. Reasons are given for the view that this was due to a direct effect of the toxin on the axons. The results of this investigation give further support to the view that axonal degeneration may occur in many demyelinating neuropathies if the underlying process is sufficiently severe