Biomedical subjects
Publications and source records attributed to M Bobrow.
Parents of patients with Down's syndrome show dermatoglyphic features intermediate between the affected and the normal population. Dermatoglyphs were studied on the parents of 19 cases of trisomy 18, but no similar "intermediate" traits were discovered. The number of cases studied needs to be enlarged before it can definitely be stated that trisomies 18 and 21 differ in this respect.
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Raised levels (greater than or equal to 4.5 munits/ml) of acetylcholinesterase (AChE) activity in amniotic fluid at 14--23 weeks of pregnancy were significantly associated with open fetal neural-tube defects. Out of 72 pregnancies correctly classified by the amniotic-fluid alpha-fetoprotein (A.F.P.) test, 2 of 56 without neural-tube defects and all 16 with open neural-tube defects (8 with anencephaly and 8awith open spina bifida) had raised levels of AChE. Out of 5 pregnancies misclassified by the A.F.P. test (4 without neural-tube defects and 1 with open spina bifida), only 1 was misclassified by the AChE test--namely, one of those without a neural-tube defect. Thus, only 3 of the 77 pregnancies tested were misclassified by the quantitative AChE test. A qualitative test for an isoenzyme of AChE found in cerebrospinal fluid correctly classified these 3 pregnancies. These findings suggest that the analysis of AChE in amniotic fluid may be a useful test in the diagnosis of open neural-tube defects.
The BB isozyme of creatine kinase is consistently present in cultured human fibroblasts and shows great variation in activity in long-term lymphoid lines. One mouse line tested, PG 19, had strong activity, but all other rodent lines tested did not express CK BB. Human and mouse CK BB can be expressed independently of each other in human--rodent somatic cell hybrids. There is some evidence that the structural locus for CK BB may be on chromosome 14, but the involvement of other chromosomes, expecially no.17, cannot be excluded. The MM and MB isozymes of creatine kinase were not seen in any human cultured cells.
Between May 1975 and the end of 1977, 6443 antenatal patients were screened mainly between 16 and 22 weeks of pregnancy for neural tube defects (NTDs) at the John Radcliffe Hospital, Oxford, by maternal serum alpha-fetoprotein (AFP) measurement; a take-up of 72 per cent. Seventeen out of 18 (94 per cent) patients with open NTD pregnancies (9 out of 9 with anencephaly and 8 out of 9 with open spina bifida) had positive screening tests, and all except one were offered and accepted a termination of pregnancy. Two hundred and forty-five (3.8 per cent) patients with unaffected pregnancies also had positive screening tests, although only 1.4 per cent had an amniocentesis. Following ultrasonography, about 50 per cent of patients with unaffected pregnancies with positive screening tests were not offered an amniocentesis because they had a multiple pregnancy or their gestational age had been underestimated. The odds of having a fetus with an NTD among the women who had an amniocentesis was about 1 to 6 (1 to 11 for open spina bifida alone). Two apparently normal pregnancies were terminated. A survey of the acceptability of the screening programme among a consecutive sample of 73 patients who knew that they had a positive screening test revealed that all except one had no objection to screening in general, and 68 (93 per cent) wanted to be tested again in a future pregnancy. The approximate direct cost of the programme was 2 pounds to 3 pounds per patient screened, or about 1000 pounds per NTD detected (about 2200 pounds per open spina bifida detected).
Eight case histories are presented which demonstrate clinical problems associated with the antenatal screening for and diagnosis of neural tube defects. It is suggested how some of these problems might be avoided in future.
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Prospective observations on 442 consecutive samples have confirmed that pregnancies with CNS malformations are regularly associated with an abnormal cellular content of amniotic fluid. A crude semiquantitative test of the cell content can give valuable clinical information in relation to borderline amniotic fluid alpha-fetoprotein values, and help to detect false positive AFP's.
We show that individual men are polymorphic for the amount of two different repeated DNA sequences. The amount of one of these sequences is proportional to the length of the brightly fluorescent heterochromatin on the Y chromosome. There are no detectable alterations in sequence between polymorphic individuals. Female DNA contains sequences complementary to those found on the Y, but at a much reduced level.
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Human/rodent hybrid cell cultures were examined for the presence of DIA1 and other marker enzymes. Many of these hybrids were also analysed for human chromosomes. Complete concordance was found only with chromosome 22.
Human fibroblasts containing a translocation between the X chromosome and chromosome 15 were fused with the 6-thioguanine-resistant mouse cell line, IR. Resulting hybrids, selected in HAT medium, retained the X/15 chromosome. Hybrids which were counterselected in 6-thioguanine lost this chromosome. The X-linked markers glucose-6-phosphate dehydrogenase (G6PD), phosphoglycerate kinase (PGK), and hypoxanthine phosphoribosyl transferase (HPRT), and the non-X-linked markers pyruvate kinase (PKM2) mannose phosphate isomerase (MPI), N-acetyl hexosaminidase A (HEXA) and beta2-microglubulin (beta2-m) all segregated in concordance with the X/15 translocation chromosome. The latter markers have been assigned to chromosome 15. Selection against the X/15 chromosome was done using antihuman beta2-m serum. Electrophoretic and immunochemical analyses of the N-acetyl hexosaminidases A and B in these hybrids were performed.