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Biomedical subjects

R T Howell

Publications and source records attributed to R T Howell.

At least 37 records · Page 2Linked to original sources
PubMed1988

Dicentric chromosome in the bone marrow of a child with megakaryoblastic leukaemia and Down's syndrome.

A two year old girl with Down's syndrome (constitutional karyotype: 47 + 21), presenting with pancytopenia, developed acute megakaryoblastic leukaemia (AMKL). Her bone marrow contained an abnormal clone with a novel dicentric chromosome derived from chromosomes 5 and 7 (karyotype 46, XX, -5, -7, +dic (5;7) (p 13; p 11.2), +21. This case provides further evidence for a connection between chromosome 21 and this unusual form of childhood leukaemia, and raises questions about the loss of short arm material from chromosomes 5 and 7 compared with the more usual monosomy or long arm loss.

Bone Marrow↗
PubMed1986

Terminal deletion of the long arm of chromosome 10.

A de novo chromosome abnormality interpreted as a terminal deletion of chromosome 10, del(10)(pter----q25.2:), was ascertained in a newborn female with multiple malformations. The clinical features observed at birth and on follow up at 10 months of age are described and compared with previously reported cases.

Adolescent↗
PubMed1984

Down's syndrome with a recombinant tandem duplication of chromosome 21 derived from a maternal ring.

An account is given of the cytogenetic investigations of a girl with Down's syndrome found to have a dicentric duplication of chromosome 21. This tandem type of rearrangement was interpreted as a recombinant derived from a single meiotic crossover between a maternal ring 21 and its normal homologue. A population of cells was also found in which breakage of the dicentric resulted in a chromosome 21 with a small terminal deletion. The mother and the proband's younger brother, who was also a ring 21 heterozygote, were both clinically normal.

Adult↗
PubMed1983

Fragile X chromosome: clinical and cytogenetic studies on cases from seven families.

Results of detailed clinical and cytogenetic studies on 13 mentally retarded males and two heterozygous females (one normal and one retarded) are reported. Reference is made to technical modifications to enhance the incidence of expression of the fragile X. The addition of excess methionine to the fibroblast cultures (final concentration of 115 mg/l medium TC 199) was found to be particularly valuable, increasing the incidence of expression up to four-fold, and enabling the demonstration of the fragile X in fibroblasts when it could not be demonstrated in blood cultures in at least one case. Studies on replication patterns of the X chromosomes in the two heterozygous females showed that the fragile X chromosome was genetically active in a significantly greater proportion of cells (74%) in the mentally retarded female, whereas the normal X was active in a similar proportion (72%) in the carrier with normal intelligence.

Adult↗
PubMed1982

Replication status of the fragile X chromosome, fra(X)(q27), in three heterozygous females.

Investigation of lymphocyte cultures from three females heterozygous for fra(X)(q27) shows widely differing proportions of early and late replicating X chromosomes having the fragile site, and suggests that the replication status of the fragile X may be related to the mental capacity of the patient. The study has utilised a sequential staining technique to reduce ascertainment bias, and evidence is presented to suggest that the expression of the fragile site is independent of the differential incorporation of BUdR into the early and late replicating X chromosomes.

Adult↗
PubMed1980

Identification of Salmonella typhi in faecal specimens by an antiserum-agar method.

An antiserum-agar technique was evaluated as a method for detecting Salmonella typhi in faeces. Thirty-one laboratory strains of S. typhi produced immunoprecipitate haloes during overnight growth on SS agar and blood-agar-base infusion agar (BAB) containing donkey antiserum to a vaccine strain of S. typhi. Other salmonella species sharing O serogroup antigens with S. typhi also produced haloes when streaked in pure culture on SS-antiserum agar but not on BAB-antiserum agar. One hundred and forty-one consecutive faecal specimens were cultured on SS-antiserum agar. Results with this method were concordant with those of established isolation techniques on specimens from six of seven suspected carriers of S. typhi. Ten other salmonellas were isolated from the faecal specimens but only S. javiana, like S. typhi a serogroup-D organism, yielded false-positive haloes on antiserum agar. The antiserum-agar technique offers promise as a means of screening for S. typhi in faecal cultures.

Agar↗
PubMed1977

A fragile secondary constriction on chromosome 2 in a severely mentally retarded patient.

A case is presented of an eighteen-year-old girl suffering from severe mental retardation associated with a fragile secondary constriction on the long arm of chromosome 2. The question of the relationship between the phenotypic and chromosomal abnormalities is discussed. We acknowledge the co-operation of Dr M. E. Elsarag and Dr K. M. Laurence in allowing this investigation to be made.

Adolescent↗
PubMed1977

Stable dicentric autosome, tdic (8:22)(p23:p13), in a mentally retarded girl.

A dicentric autosome, tdic(8:22)(p23:p13), was found in all metaphase cells examined from the peripheral blood of a mentally retarded girl. It is suggested that the centromere of chromosome 22 was inactive, allowing the dicentric to behave as a monocentric element. The involvement of acrocentric chromosomes in the stable dicentric autosomes of man is discussed.

Child↗
PubMed1976

Dicentric X isochromosomes in man.

Four cases of Turner's syndrome are presented in which an apparent X isochromosome i(Xq) has been found to possess two regions of centromeric heterochromatin. It is suggested that these chromosomes were isodicentric structures capable of functioning as monocentric elements as a result of the inactivation of one centromere. The prevalence of mosaicism is believed to be a consequence of the dicentric nature of these chromosomes, and it is considered possible that a high proportion of X isochromosmes are structurally dicentric. Banding patterns showed that the exchange site involved in the formation of the dicentric chromosome was different in at least three of the cases.

Adolescent↗
PubMed1973

Salmonellosis.

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Animals↗