Biomedical subjects
Publications and source records attributed to E Boyd.
The gene for the human glucocorticoid receptor, previously mapped to chromosome 5, has been further localised to 5q31 by in situ hybridisation using a biotinylated 4.3-kb cDNA probe.
Between 40 years and 43 years of age, a woman had three consecutive pregnancies with different prenatally diagnosed autosomal trisomies. This is compatible with the view that the predisposition to non-disjunction is not chromosome-specific.
Thirteen single-copy, chromosome-21-specific DNA probes were isolated from a recombinant library made from flow-sorted chromosome 21 DNA and regionally mapped using a panel of somatic cell hybrids. Five probes mapped in the 21q21-q22.1 region, six to the 21q22.1-qter region, and one to each of the regions 21q22.1-q22.2 and 21q22.3. Two of these probes, one of which maps in the critical region for Down syndrome, have recently been shown to be expressed at high levels in Down syndrome brain tissue (Stefani et al. 1988). Following preliminary screening for restriction fragment length polymorphisms (RFLPs), five polymorphisms were discovered with four of the chromosome 21 DNA probes. A frequent MspI polymorphism detected by one of the probes was used in conjunction with four previously described polymorphic chromosome 21 probes to analyse the origin of nondisjunction in 33 families with a child or fetus with trisomy 21. The parental origin of the additional chromosome 21 was determined in 12 cases: in 9 (75%) of these it was derived from the mother and in the other 3 cases (25%) it was of paternal origin. Cytogenetic analysis of Q-banding heteromorphisms was informative in three of five families tested, and in each case the RFLP results were confirmed. The meiotic stage of nondisjunction was defined with confidence in five families, the results being obtained with pericentromeric RFLP or cytogenetic markers. Recombination between two nondisjoined chromosomes was demonstrated in one family and is consistent with the view that a lack of recombination between chromosome 21 homologues or failure of their conjunction is not the invariable cause of trisomy 21.
A gene for tRNAGlu has been assigned to human chromosome 1p36 by in situ hybridisation using a [3H]-labelled or biotinylated 2.4-kb (human) DNA fragment containing a tRNAGlu gene as a probe. With the biotinylated DNA probe a secondary statistically significant site of hybridisation was observed at 1q21-22 which might represent a pseudogene or related sequence. In fibroblasts from gorilla (Gorilla gorilla) using biotin labelling, a single site of hybridisation occurred at 1qter which provides further support for homology of 1q in the higher apes and human 1p.
In an attempt to resolve conflicting evidence from the literature concerning the existence of a paternal age effect in 46,X,i(Xq) Turner's syndrome, we have analysed data on all known cases ascertained in the main population centres of Scotland and on others ascertained in England, using population controls matched for year of birth. There was a significant (P = 0.02) increase of 2.3 years in the mean paternal age of the Scottish cases, and a smaller and non-significant increase in their mean maternal age. Logistic regression analysis confirmed that the primary association was with paternal, rather than maternal, age. For the English cases, however, there were small and non-significant decreases in their mean maternal and paternal ages. The differences between the two groups were also significant, but cannot be explained by any likely source of ascertainment bias. We therefore conclude that there is no evidence for a universal paternal age effect in this condition, but that at least one mechanism of origin, occurring with variable frequency, may be associated with increased paternal age. Using data from this and earlier published studies, we estimate the incidence of individuals with a 46,X,i(Xq) cell line to be between 3.3 and 13 per 10(5) female livebirths.
We report a 16 year old boy with the abnormal karyotype 46,XY,del(2)(q32.2q33.1) who has mental retardation, microcephaly, epilepsy, craniofacial dysmorphism, distinctive scalloped skin pigmentation, and normal levels of isocitrate dehydrogenase.
We report male and female siblings with extreme microcephaly and mental retardation, growth retardation, and multiple chromosome mosaicism. Mental retardation associated with chromosome mosaicism does not always carry a low recurrence risk.
The assessment of dental pulp vitality is an important part of oral diagnosis. Conventional tests stimulate the nerves in the pulp and rely on a subjective response from the patient. The use of an optical method for assessment of pulp vitality has been investigated. Fibre optic light guides were used to transmit light to and from the tooth and signal processing was employed to enhance the resulting signal. Valid pulse signals were differentiated from artefactual signals by analysis of signal parameters. Artefactual signals were found to have coefficients of variability that are greater than 40% for amplitude and greater than 25% for phase. With this technique it has been possible to recognize a pulse signal from over 70% of healthy teeth. Further work is in progress to develop the technique to a state where it can be used as a routine clinical tool.
A number of patients with paradoxical sex chromosome complements (so-called XY females, XX and XO males) have been investigated with a series of 19 Yp and 4 Yq DNA probes to establish which region of the Y is essential for male sexual differentiation. Of the 23 XX males, 18 possessed one or more Yp probe sequences with only 5 lacking such sequences. Of 9 XY females examined, only one showed evidence of a deletion in Yp occurring either as a result of X-Y interchange or interstitial deletion. This suggests that the majority of XY females are not commonly deleted for those Y sequences which are found to be transferred to the X in XX males. The DNA of two XO males both contained different portions of the Y. From a comparison of the patterns of Yp sequences in these patients, it has been possible to elaborate a model of Yp in terms of the order of probe sequences and to suggest a location for the testis determining region in distal Yp.
Chromosomes from the mother, father, and child of nine families were stained with ethidium bromide and analysed in flow. These flow karyotypes on average resolved separately the homologues of 4.8 of the offspring's chromosomes. A homologue's relative DNA content (calculated from the flow karyotype) was found to be an accurate marker which could be used to trace that chromosome in a family. In this way the parental origin of 74.4% of the offspring's resolved homologues was determined. In the karyotypically normal families studied no chromosome was found in a child which was clearly different from a homologue present in one of the parents. Using parental flow karyotypes to identify familial heteromorphisms, a number of dysmorphic children were studied in an attempt to detect small "de novo" abnormalities. Although no chromosome abnormality was detected in these cases, the usefulness of family studies was illustrated. In one family a large chromosome 4 homologue was found in the child and this was shown to be similar to one found in the father, suggesting an inherited heteromorphism rather than a clinically significant duplication. Flow analysis of the parents of a patient diagnosed cytogenetically as having an interstitial deletion of the X chromosome revealed the abnormality to be a "de novo" 3;X translocation. It is suggested that flow karyotype analysis in families has potential for the detection of chromosome rearrangements at the limits of resolution of conventional cytogenetics.
Cytogenetic examination of a dysmorphic infant with multiple congenital abnormalities revealed a possible de novo interstitial deletion in the long arm of chromosome 16. Conclusive proof of the deletion was obtained by flow karyotype analysis of the patient and both parents, which showed that the deleted segment was approximately 7000 kb in size.
A series of Y recombinants have been isolated from Y-specific DNA libraries and regionally located on the Y chromosome using a Y deletion panel constructed from individuals carrying structural abnormalities of the Y chromosome. Of twenty recombinants examined twelve have been assigned to Yp and eight to Yq. Five of the Yp recombinants map between Yp11.2 and Ypter and one can only be assigned to Yp. Of the former, four detect homologies on the X chromosome between Xq13 and Xq24 and the latter one between Xp22.3 and Xpter. The sixth recombinant detects autosomal homologous sequences. The six remaining Yp probes are located between Ycen and Yp11.2. One of these detects a homology on the X chromosome at Xq13-Xq24 and a series of autosomal sequences, two detect uniquely Y-specific sequences and three a complex pattern of autosomal homologies. The remaining eight recombinants have been assigned to three intervals on Yq. Of three recombinants located between Ycen and Yq11.21 two detect only Y sequences and one additional autosomal homologies. Two recombinants lie in the interval Yq11.21-Yq11-22, one of which detects only Y sequences and the other an Xp homology between Xp22.3 and Xpter. Finally, the three remaining Yq recombinants all detect autosomal homologies and are located between Yq11.22 and Yq12. The divergence between homologies on different chromosomes has been examined for three recombinants by washing Southern Blots at different levels of stringency. Additionally, Southern analysis of DNA from flow sorted chromosomes has been used to identify autosomes carrying homologies to two of the Y recombinants.
We have developed and characterised a variant of the human T-cell tumour, MOLT-4F, which is resistant to both 8-azaguanine and 6-thioguanine. This new cell line, M4HS2, is suitable for the efficient production of lymphokine-secreting human T-cell hybrids and is available for distribution.
We report two male cousins with Duchenne muscular dystrophy (DMD) in whom cytogenetic studies have shown a small interstitial deletion at Xp21. The lesion is readily detectable in patients and carriers by flow cytometry which indicates that approximately 6000 kb of DNA are deleted in each case. The DNA markers OTC, C7, and B24 are present in the deleted X chromosome but 87-8, 87-1, and 754 are absent. Despite apparently identical deletions one affected boy has profound mental handicap while the other is only mildly retarded. The results confirm the assignment of familial DMD to Xp21 and illustrate the value of flow cytometry in improving the precision of chromosome analysis. We have also undertaken flow cytometry in a cell line from a previously reported DMD patient with a de novo Xp21 deletion who had, in addition, chronic granulomatous disease, retinitis pigmentosa, and the McLeod syndrome. The results indicate that the amount of DNA deleted from the X is similar in both families despite the striking differences in phenotype.
We studied the short-term and long-term effects of transient asymptomatic neonatal hyperammonemia on neurologic function in 21 preterm infants with normal ammonium levels and 25 with hyperammonemia (range 40 to 72 mumol/L) during the first weeks of life. The hyperammonemic infants were prospectively randomized to treatment with orally administered arginine free base 1 to 2 mmol/kg/day for 2 months (n = 13) or to a no-treatment control group (n = 12). Cortical function was assessed by auditory response and habituation during the first month of life. An auditory response was shown by 64% of the hyperammonemic infants and 43% of the normoammonemic infants (P not significant). Plasma ammonium levels at the time of examination bore no consistent relationship to whether an infant responded to an auditory stimulus. Number of trials to reach auditory habituation was also not different, and plasma ammonium level did not correlate with the presence or absence of habituation. IQ testing at 6, 12, 18, and 30 months showed no significant differences between groups. Early plasma ammonium levels did not have an effect on 30-month IQ scores. These findings suggest that transient asymptomatic hyperammonemia in premature infants is not associated with short-term or long-term neurologic deficits through 30 months of age. This study does not support the need for treatment of transient asymptomatic hyperammonemia in the premature infant.
The conventional dosage schedule for sucralfate is 1 g 4 i.d., but a dose of 2 g 2 i.d. may be equally effective in duodenal ulcer healing. We compared the efficacy of these two regimens in duodenal ulcer healing. Seventy-seven patients with endoscopically proven duodenal ulceration were entered into a double-blind, controlled study and randomized to treatment with sucralfate 2 g 2 i.d. (on waking and at bedtime) or 1 g 4 i.d. (1/2 h before meals and at bedtime). The patients were endoscoped before entry into the study, after 4 weeks, and after 8 weeks if unhealed at 4 weeks. Of the patients considered suitable for analysis at 4 weeks, 79% (26/33) of those taking 2 g 2 i.d. had healed ulcers in comparison to 72% (23/32) of those taking 1 g 4 i.d. After 8 weeks, cumulative healing rates were 85% (28/33) and 80% (24/30), respectively. The results suggest that the more convenient dosage schedule of 2 g 2 i.d. is as effective as the 1 g 4 i.d. regimen in the short-term treatment of duodenal ulcer.
The mean relative DNA content of each human chromosome was calculated from flow karyotypes of ethidium bromide-stained chromosomes obtained from healthy, normal individuals. These values were found to correlate closely with previously published data obtained by photometric scanning of stained, fixed chromosomes. Calculations of the normal variation in DNA content of each human chromosome indicated that chromosomes 1, 9, 16, and Y (chromosomes with large centric heterochromatic regions) were the most variable, followed by the acrocentrics, 13, 14, 15, 21, and 22. Chromosomes 2, 3, 18, and 19 were also found to vary significantly in DNA content. Chromosomes from a number of subjects with extreme heteromorphisms were flow karyotyped to obtain an estimate of the extent of variation in DNA content of each chromosome. The greatest difference between extreme variants was found for chromosome 1 (which differed by 0.82% of the total genomic DNA), followed by 16 and 9. The largest Y-chromosome variant was 85.9% bigger than the smallest. The precise karyotype analysis produced by flow cytometry resolved many differences between chromosome homologs, including some that cannot be readily distinguished cytogenetically. The implications of these findings for detection of chromosome abnormalities by flow karyotype analysis are discussed.
In an investigation to find the prevalence of the fragile X (Martin Bell) syndrome in a mental handicap hospital, chromosomal investigations were carried out in 196 males selected out of a total of 512, and also in 20 female patients who were related to some of the selected males. Fragile X cells were found in 41 of the males and two of the females; in 21 of the males it was associated with macro-orchidism. The overall prevalence in the hospital for males (8.0%) ranks this syndrome next in importance to Down's syndrome as a known cause for mental handicap.