Redistribution of fallout radionuclides in Enewetak Atoll lagoon sediments by callianassid bioturbation

The lagoon sediments of Enewetak Atoll in the Marshall Islands contain a large selection of fallout radionuclides as a result of 43 nuclear weapon tests conducted there between 1948 and 1958. Studies of the burial of fallout radionuclides have been conducted on the islands and in several of the large craters, but studies of their vertical distribution have been limited to about the upper 20 cm of the lagoon sediments. We have found elevated fallout radionuclide concentrations buried more deeply in the lagoon sediments and evidence of burrowing into the sediment by several species of callianassid ghost shrimp (Crustacea: Thalassinidea) which has displaced highly radioactive sediment. The burrowing activities of callianassids, which are ubiquitous on the lagoon floor, facilitate radionuclide redistribution and complicate the fallout radionuclide inventory of the lagoon.     

The peritoneal fluid cytology of the adult female rhesus monkey

Résumé Le % de distribution des cellules de fluide péritonéal d'une femelle adulte de singe rhésus fut enregistré dans des échantillons de fluide cytologique extraits par la paratomie. Les données sond comparées à celles qui ont obtenues précédemment chez la femme.     

Block of Na current and intramembrane charge movment in myelinated nerve fibres poisoned with a vegetable toxin

In nerve membrane, the non-linear capacity current (displacement current) is assumed to reflect the movement of intrinsic membrane charges which control the opening of specific pathways for sodium ions (Na channels). However, various discrepancies have been reported between the effects of pharmacological agents on sodium and displacment currents (for a review see ref. 1). It is generally supposed that the opening and closing of Na channels constitutes one step of multi-step system in which each configuration change may or not give rise to a measurable charge movement. New drugs affecting either sodium or displacement currents may elucidate the relationship between charge movement and the control of sodium conductance. We therefore now report a comparison of the effects of a vegetable toxin (oenanthotoxin or OETX) on both sodium current (INa) and intra-membrane charge movement (Q) in Ranvier nodes. We show that OETX reversibly blocks both sodium and displacement current. Studies of INa and Q during partial supression by the toxin reveal differences in the effects of OETX on the remaining INa and Q. The findings are discussed in relation to recent models for the Na-channel gating process and for Na-channel block by local anaesthetics.     

Polyunsaturated fatty acids and cardiovascular disease

Replacing saturated with polyunsaturated (PUFAs) rather than monounsaturated fatty acids or carbohydrates results in cardiovascular prevention over a wide range of intakes. The mechanisms by which PUFAs reduce cardiovascular risk are manifold, and the extent and precise nature of their activities is the subject of several investigations, spanning from in vitro mechanistic studies to human intervention trials. This article reviews the most up-to-date evidence of the association between PUFA consumption and reduced cardiovascular mortality.     

A superfamily of variant genes encoded in the subtelomeric region of Plasmodium vivax

The malarial parasite Plasmodium vivax causes disease in humans, including chronic infections and recurrent relapses, but the course of infection is rarely fatal, unlike that caused by Plasmodium falciparum. To investigate differences in pathogenicity between P. vivax and P. falciparum, we have compared the subtelomeric domains in the DNA of these parasites. In P. falciparum, subtelomeric domains are conserved and contain ordered arrays of members of multigene families, such as var, rif and stevor, encoding virulence determinants of cytoadhesion and antigenic variation. Here we identify, through the analysis of a continuous 155,711-base-pair sequence of a P. vivax chromosome end, a multigene family called vir, which is specific to P. vivax. The vir genes are present at about 600-1,000 copies per haploid genome and encode proteins that are immunovariant in natural infections, indicating that they may have a functional role in establishing chronic infection through antigenic variation.