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Biomedical subjects

G Leadbetter

Publications and source records attributed to G Leadbetter.

10 recordsLinked to original sources

Hepatitis B virus genes and their expression in E. coli.

A composite DNA sequence of regions of hepatitis B virus, determined from a series of recombinant plasmids, reveals the genes for the surface antigen and the core antigen of the virus. The sequence of the core antigen shows it to be a DNA binding protein. The core antigen gene is expressed in Escherichia coli and when injected into rabbits the bacterial product induces antibodies which react with core antigen isolated from human sources.

Amino Acids

Incipient germ cell tumor in a cryptorchid testis.

A 13-year-old male who had bilateral cryptorchid testes since birth underwent testicular biopsies and subsequent left orchiectomy following a diagnosis of malignant germ cell tumor. No tumor mass was noted although the malignant cells were seen within the seminiferous tubules and the interstitium. Five recorded cases of in-situ or incipient germ cell neoplasms of the testes are reviewed; three were infertile, another had a cryptorchid testis, and the fifth was both infertile and cryptorchid. Two of these patients have developed frank carcinoma, which would suggest that the process represents an early phase of invasive germ cell neoplasia.

Adolescent

Rapid detection of hepatitis B surface antigen by double antibody radioimmunoassay.

HBsAg and anti-HBs can be detected by double-antibody radioimmunoassay in a reliable routine overnight assay of sensitivity approaching that of solid-phase immunoradiometric assay. The test requires careful standardisation and regular preparation of I125-HBsAg of appropriate quality, but otherwise uses only small quantities of commercially available reagents. In this paper, the reaction kinetics of the first incubation (test sample + limiting amount of rabbit anti-HBs), second incubation (reaction mixture + I125 -HBsAg) and precipitation reaction (reaction mixture + antirabbit globulin) were examined, to determine the minimum time required for the assay compatible with adequate sensitivity and user convenience; in addition, in order to reduce the time of radioactive counting, the maximum amount of I125-HBsAg per test compatible with a satisfactory assay was examined. It was concluded that, by terminating each reaction before equilibrium was reached, results could be obtained in 2--3 hours with a detection limit similar to the standard overnight procedure. To allow routine examination of large numbers of samples, the possibilities of complete automation of this liquid-phase type of assay were discussed.

Hepatitis B Antibodies

Prevalence of antibody to hepatitits B surface antigen among staff in an Edinburgh hospital.

Antibody to hepatitis B surface antigen was detected by radioimmunoprecipitation in 74 (5-5%) of 1336 staff members in a large general hospital in Edinburgh, in 14 (2-9%) of 480 volunteer blood donors in the area, and in 12 (6-1%) of 197 pregnant women attending for the first time at the ante-natal clinic in the hospital. Rates of antibody prevalence rose with age in the sample of hospital staff and in that of the blood donors, particularly among males. On the other hand, in the ante-natal patients antibody prevalence declined with age. The rates in hospital staff were higher than those in blood donors of comparable age and sex, and high titres of antibody were more common in the staff group. However, no association was found between antibody prevalence and a history of clinical hepatitis, blood transfusion, or recognized contact with cases of hepatitis. Staff who had previously worked in an infectious disease hospital did not show increased antibody prevalence, indicating that simple isolation measures have been adequate to minimize exposure to hepatitis B. No particular prevalence of infection was seen in physicians and surgeons, in the nursing staff, or in workers in clinical diagnostic laboratories, hospital administration or other areas. One group clearly showing increased antibody prevalence was staff currently working, or who had worked, in the Haemodialysis Unit; this correlated with the outbreak of dialysis-associated hepatitis in 1969--70. However, no evidence suggested that significant dissemination of infection had occurred to other defined groups of hospital staff. Elevated rates were also observed in a small sample of kitchen and portering staff, and in obstetric medical and nursing staff; the latter observation indicate a need for further investigation to identify unsuspected exposure to hepatitis B virus.

Adolescent

Mitomycin antibiotics. Synthesis and activity of 1,2-disubstituted mitosenes.

cis-1-Acetamido-2-acetoxy-7-methoxy-N-methylmitosene was prepared in 11 steps from 7-methoxy-6-methyl-2,3-dihydro-1H-pyrrolo[1,2-a]indol-1-one by a route involving bromination of the pyrrolidineenamine or trimethylsilyl enol ether of starting material, displacement of bromide by acetate, oxime formation, and reductive acetylation, followed by elaboration of the quinone and methyl carbamate functions according to previously established methods. An unsubstituted carbamate could not be prepared. The mitosene thus synthesized differs from previously reported 1,2-disubstituted mitosenes, which are derived from the solvolysis of mitomycins, in that it has the opposite arrangement of oxygen and nitrogen substituents at the 1 and 2 positions. It showed antibacterial activities in disk-plate assays superior to those of cis-diacetylapomitomycin A and equivalent to those of certain 1-substituted mitosenes; however, it was less active than mitomycin A in these assays. It was inactive in inducing lambda-bacteriophage in Escherichia coli and inactive against P388 leukemia in mice. In contrast, certain 1-substituted mitosenes were active in prophage induction and 2b and mitomycin A were active in both assays.

Animals

Tryptic cleavage of antibody binding sites from hepatitis B surface antigen particles.

The sedimentation of radiolabelled 22 nm hepatitis B surface antigen particles was unaffected by treatment with either trypsin or SDS alone, but combined treatment disrupted the particulate nature of the radiolabelled material. Considerable antibody binding activity by the group-specific determinant (a) was preserved after combined SDS and trypsin treatment but was released from the bulk of the radiolabelled protein; gel filtration indicated an approximate mol. wt. of 5000 to 15000 for the released antibody binding material. This material was precipitated by concanavalin A, suggesting the presence of carbohydrate. Its serological activity was remarkably resistant to boiling and to proteolytic digestion, but was partially sensitive to treatment with 0-01 M-periodate or with mixed carbohydrases and neuraminidase, and was greatly reduced by treatment with reducing agent. These data suggest that the stability of the a determinant is due to the structure of the antibody binding site itself, rather than to involvement in the quaternary structure of the particle, and that intact disulphide bonds and carbohydrate, closely related to the antibody binding site, are necessary for the full expression of serological acitivity.

Binding Sites, Antibody