2 results
Sperm-egg fusion in the sea urchin is blocked in Mg2+-free seawater
- Hideo Mohri, Yukihisa Hamaguchi, Miyako S. Hamaguchi, Kiyoshi Sano, Hideki Shirakawa, Ken Nakada, Shunichi Miyazaki
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Magnesium ions as well as calcium ions are required for successful fertilisation in sea urchins. In the absence of Mg2+ spermatozoa attached to the egg plasma membrane, their acrosomal processes passing through the vitelline envelope, but could not enter the egg cytoplasm (Sano et al, Dev. Growth Differ. 22, 531–41,1980). Such an individual spermatozoon was observed microscopically to resume entry into the egg immediately after the addition of a sufficient amount of Mg2+ to the surrounding medium. Neither any change in membrane potential nor an increase in intracellular Ca2+ concentration of the egg was observed after insemination in the absence of Mg2+, although both could be observed after the addition of Mg2+. The sperm heads did not show fluorescence when attached to the surface of an egg previously microinjected with mithramycin A in Mg-free seawater, indicating that there was no connection between the sperm and the egg. Therefore, occurrence of fertilisation potential must be a post-fusional event. These results suggest that Mg2+ are indispensable for fusion between the sperm acrosomal membrane and the egg plasma membrane.
15 - Analysis of genes associated with hypercholesterolaemia in the Japanese population
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- By Hideo Hamaguchi, University of Tsukuba, Yuka Watanabe, University of Tsukuba, Yasuko Yamanouchi, University of Tsukuba, Hisako Yanagi, University of Tsukuba, Tadao Arinami, University of Tsukuba, Ryunosuke Miyazaki, Kudanzaka Hospital, Shigeru Tsuchiya, University of Tsukuba, Kimiko Kobayashi, University of Tsukuba
- Edited by Derek F. Roberts, University of Newcastle upon Tyne, N. Fujiki, Department of Internal Medicine and Medical Genetics, Fukui Medical School, Japan, K. Torizuka, Fukui Medical School, Japan
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- Isolation, Migration and Health
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- 05 March 2012
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- 10 September 1992, pp 154-166
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Summary
Genes associated with hypercholesterolaemia have been detected and characterised at the loci for low density lipoprotein (LDL) receptor, apolipoprotein B, apolipoprotein E, and apolipoprotein (a) (Goldstein & Brown, 1989; Soria et al., 1989; Mahley & Rail, 1989; Utermann, 1989). Among them, genes at the loci for apolipoprotein E and apolipoprotein (a) are polymorphic and act as polymeric genes for multifactorial hypercholesterolaemia. These polymorphic genes have been identified by the analysis of proteins using electrophoretic methods. It is interesting to examine whether these polymorphic and seemingly deleterious genes are identical at the DNA and amino acid sequence levels among different ethnic groups. On the other hand, deleterious genes detected at the loci for LDL receptor and apolipoprotein B are not polymorphic but act as major genes which cause autosomal dominant hypercholesterolaemia. These genes have been shown to be a cause of premature coronary heart disease (Goldstein & Brown, 1989; Soria et al., 1989). The data obtained by the analysis of DNA suggest the same mutational origin for some of these deleterious genes (Goldstein & Brown, 1989) and their subsequent spread in populations.
This communication reports the results of molecular genetic studies on the phenotype E4 determined by the alleles at the locus for apolipoprotein E and on familial hypercholesterolaemia caused by the mutant LDL receptor gene in the Japanese population.
Apolipoprotein E4 in the Japanese population
Apolipoprotein E is a protein constituent of plasma lipoproteins and plays an important role in lipoprotein metabolism (Mahley, 1988). The genetic polymorphism of apolipoprotein E is under the control of three common alleles (ε2, ε3, ε4) that specify isoforms apolipoprotein E2, E3 and E4 respectively (Mahley & Rail, 1989).