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Biomedical subjects

W M Howell

Publications and source records attributed to W M Howell.

101 records · Page 6Linked to original sources
PubMed1976

Inclusion of satellites in an 18/21 translocation chromosome shown by ammonical-silver staining (sat-banding) in case of partial trisomy 18.

A male infant with a partial trisomy 18 and a 46,XY, --21, t(18;21)(18qter replaced by 18q12::21 p13 replaced by 21 qter) chromosome complement is described. The translocation chromosome is of special interest because it includes the satellites of chromosome 21. This was shown by differential satellite staining with the ammoniacal-silver technique.

Ammonia↗
PubMed1975

Umbra limi: a model for the study of chromosome aberrations in fishes.

Due to the lack of information available on the effect of various clastogenic agents on the chromosomes of fishes, an in vivo cytogenetics model system was developed. The central mudminnow, Umbra limi, was chosen fro this study because of its ideal karyotype consisting of 22 large meta- and submetacentric chromosomes. Various organs of the fish were investigated to determine their suitability for chromosome preparations. The tissues of the intestines, stomach, kidneys, and gills were found to be the most suitable for clastogenic studies. Phase contrast observations were made on the chromosomes of control mudminnows and mudminnows exposed to 325 R of X-radiation. The control rate of spontaneous chromosome aberrations was found to be low (about 0.03%). In contrast, fish exposed to 325 R of X-rays had aberrations in approximately 30% of the metaphases per fish examined. An apparent increase in clumping and a decrease in the mitotic index were also noted. It was concluded that the chromosomes of Umbra limi displayed typical responses to low level radiation exposure and that this fish would be an ideal cytogenetics model for this study of induced chromosome aberrations in fishes.

Animals↗
PubMed1975

Centromeric and telomeric staining regions in the chromosomes of cattle (Bos taurus).

Two new types of staining regions exist aftet treatment with a modified version of the ammoniacal-silver technique (Howell et al., 1975), in addition to findings by many other researchers working on the chromosomal complement of Bos taurus. Densely stained regions appear to be associated with the centromeres of many of the 29 pairs of acrocentric chromosomes, but there are also 4-6 of the same acrocentric chromosomes bearing telomeric staining regions (TSRs) at the ends of their long arms. In many metaphases examined, actual physical connectives were observed between both types of these ammoniacal-silver staining regions.

Animals↗
PubMedDate not supplied

Mitochondrial sequence variants in patients with schizophrenia.

To investigate whether mitochondrial mutations underly susceptibility to schizophrenia, we sequenced the mtDNAs of two unrelated Swedish patients with schizophrenia and low cytochrome oxidase activity and two maternally related Scottish patients from a family with suspected maternal inheritance of the disease. We found five substitutions in coding regions that have not previously been described as polymorphisms. These new substitutions were studied in 81 schizophrenic patients and five control groups from Sweden and Scotland and found to differ in frequency between populations, emphasizing the importance of using large and well-defined control materials for evaluating the association of mtDNA mutations with disease. The results do not lend strong support to the association of a particular mtDNA substitution with increased risk for schizophrenia. However, the trend towards a higher frequency of substitutions in the patients deserves further attention.

Conserved Sequence↗