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Biomedical subjects

H T Imai

Publications and source records attributed to H T Imai.

34 records · Page 2Linked to original sources
PubMed1982

X-Y chromosome dissociation in wild derived Mus musculus subspecies, laboratory mice, and their F1 hybrids.

The frequencies of X and Y chromosome dissociation in primary spermatocytes of wild-caught specimens of six Mus musculus subspecies, fifteen inbred mouse strains, and their F1 hybrids were examined. Three different types (I, II, and III) of X-Y dissociation were identified. Type I was found in inter-subspecies hybrids (BALB/c X M. m. molossinus, M. m. bactrianus, M. m. castaneus, or M. m. urbanus), in which the X-Y dissociation was less than 20% in each subspecies but 60-80% in the f1 hybrids. Type II was seen in the DBA/2J and DDK strains, in which the dissociation frequency was about 30% in the homozygous condition and increased up to 50% in inter-strain hybrids (C57BL/6J X DBA/2J or DDK). Type III found in the WB/Re strain also showed high dissociation frequency (51.1%) in the homozygous condition but the value was remarkably lower (11.3%) in C57BL/6J X WB/Re)F1s. Some asian wild mice seem to have type II or III as well as type I.

Animals↗
PubMed1981

High frequency fo X-Y chromosome dissociation in primary spermatocytes of F1 hybrids between Japanese wild mice (Mus musculus molossinus) and inbred laboratory mice.

In the hybrids between Japanese wild mice (Mus musculus molossinus) and inbred laboratory mice (BALB/c and B10.BR, which were probably derived from M. m. domesticus), the X and Y chromosomes dissociated precociously at the first meiotic metaphase in some 70% of spermatocytes; that percentage was only 8.9% in inbred laboratory mice and 21.1% in wild mice. X-Y dissociation began at least at early diakinesis and continued during metaphase I (MI). Some autosomes of the hybrid (10.1%) and BALB/c (10.6%) mice also dissociated precociously, but there was no distinctive correlation between X-Y and autosomal dissociation. In B10 or B6 congenic lines with a Y chromosome from wild M. m. molossinus, there was an apparent tendency for the percentage of precocious X-Y dissociation to decrease with an increasing number of back cross generations. Based on these observations we concluded that: 1. the X-Y dissociation found is genetically controlled, perhaps by multiple genes; 2. these genes are located on autosomes and are active only when they are heterozygous; 3. the frequent dissociation of the sex chromosomes neither affects male fertility nor induces non-disjunction of the X and Y chromosomes, though it significantly reduces testes weight.

Animals↗