Showing papers by "World Health Organization published in 1968"

Hemagglutination by Rabies Virus

Abstract: Goose erythrocytes were agglutinated by five strains of rabies virus grown in monolayer cell cultures at pH 6.4 and at 0 to 4 C. Hemagglutination was not affected by the cell type in which the virus was grown. Prerequisites for occurrence of hemagglutination are absence of hemagglutination inhibitors (such as those contained in bovine serum) and a relatively high virus concentration (> 10(6) plaque-forming units of virus per ml). "Soluble" hemagglutinin was not present in crude preparations of extracellular virus. Treatment of purified preparations of extracellular virus with Tween 80 and ether did not result in release of a "soluble" hemagglutinin. The hemagglutinating property of extracellular virus seemed to be conditioned by the integrity of its coat. Preparations of infectious intracellular virus exhibited about 15 times lower hemagglutinating activity than extracellular virus. This decreased hemagglutinating activity did not seem to be caused by binding of hemagglutination inhibitors to the virus particles. Rabies virus can be quantitatively adsorbed onto and eluted from erythrocytes. Erythrocytes pretreated with rabies virus retained their ability to be agglutinated by the same virus strain. The reaction with rabies virus of erythrocytes treated with the receptor-destroying enzyme or KIO(4) was the same as that of nontreated erythrocytes. The hemagglutinating component of rabies virus, therefore, does not exhibit neuraminidase activity. Treatment of extracellular virus by various agents indicated that the hemagglutinating component consists of protein or lipoprotein. Sulfhydryl groups present in the viral hemagglutinin are essential for hemagglutination.

Some improved techniques for the study of rhinoviruses using HeLa cells.

Abstract: It has been confirmed that plaque assays of rhinoviruses may be performed using M-HeLa cells and 30 mM MgCl2. Eighty-seven pools of rhinoviruses grown in human diploid cell strains (HDCS) or organ cultures or as human nasal washings were inoculated into HDCS and M-HeLa cells with 30 mM additional MgCl2 in the medium. Cytopathic effects were produced in HDCS and in M-HeLa cells by 78 pools, in HDCS only by one, in M-HeLa only by one, and in neither cell type by seven pools. A micro metabolic inhibition test was developed which was satisfactory for the titration of rhinoviruses and neutralizing antibody and for identifying rhinovirus strains with specific antisera. Preliminary observations show that rhinovirus type 2 multiplies in suspension cultures of M-HeLa cells. It is concluded that the use of M-HeLa cells with additional MgCl2 instead of HDCS should facilitate the laboratory diagnosis of rhinovirus infections.

Fundamental Theorem of Natural Selection

Abstract: FISHER'S fundamental theorem of natural selection has recently been discussed1,2. Edwards2 observes that the theorem V′ − V ≥ 0, where V and V′ represent, in successive discrete generations, the mean fitness at a single diallelic locus in a random mating diploid population, has already been proved by Moran3. He notes further that the more general result involving a multiple allelic system was actually established some years ago, and comments that the reason for this curiosity is that the validity of the theorem for two alleles was simply assumed to follow immediately from the work of Sewall Wright.

Sarcomas in Afghanistan.

Abstract: SARCOMAS in general receive much less attention than carcinomas. There are two reasons for this: first, sarcomas are considerably outnumbered by carcinomas in most populations and, second, environmental, that is, avoidable, factors have been more often aetiologically related to carcinomas than to sarcomas. For these reasons I have made this investigation. In Afghanistan, sarcomas are not greatly outnumbered by carcinomas and I shall suggest that there may be an aetiological relationship between some sarcomas and an environmental factor, namely, arthropod vectors.