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Biomedical subjects

S J Martin

Publications and source records attributed to S J Martin.

At least 127 records · Page 7Linked to original sources
PubMed1985

Repair of nonreplicating UV-irradiated DNA: cooperative dark repair by Escherichia coli uvr and phr functions.

The system previously used to study recombination of nonreplicating UV-irradiated phage lambda DNA was adapted to study UV repair. Irradiated phages infected undamaged homoimmune lysogens. Pyrimidine dimer content (by treatment with Micrococcus luteus UV endonuclease and alkaline sucrose sedimentation) and a biological activity endpoint (infectivity in transfection of uvrB recA recB spheroplasts) were followed. Unless room light was excluded during DNA extraction procedures, photoreactivation (Phr function) was significant. In uvr delta phr bacteria, repair, by both assays, was very low but not zero. Even when light was totally excluded, Phr function appeared to play a role in Uvr-mediated excision repair: both dimer removal and restoration of infectivity were two to five times as efficient in uvr+ phr+ bacteria as in uvr+ delta phr bacteria. Similarly, UV-irradiated phages plated with higher efficiencies on phr+ than delta phr bacteria even under totally dark conditions. In uvr phr+ repressed infections, removal of dimers from nonreplicating DNA did not increase infectivity as much as in uvr+ infections, suggesting a requirement for repair of nondimer photoproducts by the uvrABC system.

Bacteriophages↗
PubMed1985

The generation of small-plaque mutants during undiluted passage of canine distemper virus.

A culture of Vero cells persistently infected with undiluted-passage, large-plaque canine distemper virus was found to release small-plaque virus (SPV). This suggested that SPV could be generated by large-plaque virus (LPV). However, attempts to induce small-plaque mutants from LPV with 5-fluorouracil resulted in the production of virus that expressed a variable plaque type and induced a spectrum of disease in hamsters. In contrast, small-plaque mutants, shown to arise during undiluted passage of LPV, retained their small-plaque characteristic and resembled our original SPV isolate in their cytopathogenicity, immunogenicity, and neurovirulence for hamsters.

Animals↗
PubMed1985

A survey of serum antibodies to eight common viruses in psychiatric patients.

Serum antibody titres to eight neurotropic viruses were measured by enzyme immunoassay in 450 psychiatric in-patients and 143 controls. A seasonal variation in schizophrenic births was observed, with a peak incidence between March and April. Both herpes simplex virus and cytomegalovirus antibody titres correlated with age and, when this was controlled for, no significant differences emerged between any patient group and the controls. Mumps antibody titres were significantly lower in patients with mental subnormal and neurosis or personality disorder; measles and rubella antibody titres were lower in male but not female mentally handicapped patients; males had lower antibody titres to mumps, cytomegalovirus and Epstein-Barr virus than females in all groups. A decrease in mumps antibody titres was also found in schizophrenics if the medication factor was excluded. These low antibody titres may indicate an impaired immune response. Thus perinatal or childhood subclinical viral infections of the central nervous system, particularly of mumps, might lead to a range of possible psychiatric outcomes in later life.

Adolescent↗
PubMed1985

Serum and CSF antibody titres to seven common viruses in schizophrenic patients.

CSF and matched serum antibody titres to seven common viruses were measured in 20 chronic schizophrenic patients, and 17 of these were age and sex-matched with orthopaedic controls. CT scans were carried out in patients and age and sex-matched radiological controls. There was a trend for CSF viral antibody titres (except CMV, HSV and VZV) to be decreased in the patients compared to controls, statistically significant for mumps and IgG. The CSF/serum ratios showed a reduction in the patients, compared to controls, statistically significant for measles and rubella as well as mumps and IgG. Cerebral ventricular size was significantly increased in the patients compared to controls, but did not correlate with any of the antibody data. These findings suggest that there is a reduced immune response to certain common viruses in the CNS of schizophrenic patients, but possible effects of institutionalisation or current medication could only be adequately excluded by further prospective studies.

Adult↗
PubMed1983

An immunological study of infection of hamsters with large and small plaque canine distemper viruses.

The small plaque virus (SPV), derived from the Onderstepoort strain of canine distemper virus (CDV) does not cause a lethal encephalitis in weanling hamsters. When we immunosuppressed hamsters infected with this virus they developed an acute disease, similar to that produced by the large plaque virus (LPV). Passive transfer of maternal antibody from SPV infected mothers to their offspring was effective in preventing acute disease following LPV infection. Co-infection of animals with both LPV and SPV resulted in increased hamster survival, associated with high titres of serum antibody. Similarly, heat inactivated SPV, present during infection with LPV, increased the survival rate. Heat inactivated LPV did not inhibit acute disease, although hamsters had high titres of neutralizing antibody. A small number of animals developed a delayed or recurring paralysis after immunosuppression, exposure to maternal antibody or co-infection. It would appear that the neurovirulence of CDV for hamsters can be modified by altering the levels of circulating antibody early in infection.

Animals↗
PubMed1983

Comparison of morbillivirus proteins by limited proteolysis.

Proteins of a number of measles and SSPE virus strains have been compared by limited proteolysis and they appear to be largely conserved amongst the various strains. Viruses derived from SSPE cannot be distinguished from other measles viruses by this technique. Small differences in the digest patterns of the M proteins have been observed between the Edmonston and other measles virus strains. Furthermore, in some strains where the M proteins migrate slower in SDS-PAGE the limited proteolysis patterns are slightly different from those in other MV and SSPE virus strains. The limited proteolysis pattern of some canine distemper virus (CDV) proteins have been determined and nucleocapsid breakdown products have been identified in infected cells. Comparisons of proteins of four strains of CDV have shown that these, too, are largely conserved, although the digest of proteins of CDV appear to show more pronounced differences than those present in the MV and SSPE virus group. Limited proteolysis can be used readily to distinguish MV from CDV isolates.

Chemical Phenomena↗
PubMed1983

A simple method for the removal of mycoplasma contamination from paramyxovirus stocks.

A simple and quick method of detecting mycoplasmas in virus stocks using the fluorochrome Hoechst 33258 is described. Different methods of removal of mycoplasmas from stocks are discussed. The simple but effective method using gentamicin (0.2 mg/ml) or chloramphenicol (5 micrograms/ml) is demonstrated and chosen as the most efficient as judged using both the Hoechst stain and the direct assessment of mycoplasma RNA species labelled with [5-3H]uridine.

Animals↗
PubMed1981

The isolation of large and small plaque canine distemper viruses which differ in their neurovirulence for hamsters.

Large and small plaque-forming viruses were isolated from the Onderstepoort strain of canine distemper virus (CDV). Small plaque virus, which was released more slowly from infected cells than large plaque virus, readily established persistent infections in Vero cells, whereas large plaque virus required undilute passage to do so. All persistently infected cultures eventually released small plaque virus. No difference was found in the size of polypeptides induced by either plaque-purified viruses or virus released from persistent cultures. Both dilute and undilute passage, large plaque virus produced an acute neurological illness in weanling hamsters. whereas small plaque virus failed to produce any clinical signs of disease for 3 months after inoculation. After this period 50% of the animals infected with small plaque virus showed a general deterioration in their condition and lesions were observed in the brain which resembled those found in cases of large plaque virus infection. Serum-neutralizing antibody titres to CDV rapidly increased after infection with small plaque virus, whereas animals infected with large plaque virus had low or undetectable levels. All hamsters infected with small plaque virus and a small number which survived large plaque virus infection had elevated titres of antibody over a test period of 15 months.

Animals↗
PubMed1981

A study of phosphorylation of the measles membrane protein.

A polypeptide (designated X) which migrates with a mobility similar to the membrane protein (M) of measles virus has been found in virus-infected cells. This polypeptide appears to be phosphorylated. However, limited proteolysis has shown that this protein is not a phosphorylated form of the M protein, but appears related to the P protein of measles virus.

Animals↗
PubMed1980

Polypeptide synthesis i mumps virus-infected cells.

The synthesis of polypeptides in infected Vero cells has been studied with two tissue culture adapted strains of mumps virus. Minor differences between the strains are found in the mobilities of the virus-specific polypeptides in SDS-PAGE. Eight virus-induced polypeptides have been identified with mol. wt. of 180K, 80K, 71K, 69K, 45 K, 39K, 23K and 17K. These may correspond to the L, HN, N, Fo, P, M, C and S polypeptides identified in other paramyxoviruses. The 69K F0 glycoprotein is probably a precursor for glycopolypeptides F1 and F2 with mol. wt. 61K and 14K, respectively.

Animals↗
PubMed1980

A comparison of measles and canine distemper virus polypeptides.

The polypeptides induced by canine distemper virus (CDV) strains have been characterized by polyacrylamide slab gel electrophoresis of infected cell lysates labelled with 35S-methionine, 14C-amino acids, 3H-glucosamine and 3H-mannose, or 32P-orthophosphate. Seven virus-induced polypeptides have been asigned the following nomenclature and mol. wt.: a large polypeptide L (180,000); a large glycoprotein G (77,000); a nucleocapsid-associated protein P (73,000); the nucleocapsid protein N (60,000); the smaller glycoprotein F0 (59,000); a membrane protein M (35,000) and a small polypeptide S (15,000). During pulse-chase experiments with 3H-glucosamine and 14C-amino acids the intensity of the F0 band decreases and that of the F1 and F2 bands increases; the H polypeptide band becomes more diffuse and the S-protein disappears. The N- and P- but not the M-proteins have been found to be phosphorylated. The polypeptide pattern of the Onderstepoort strain of CDV has been compared with that of two other CDV and with 17 measles and subactue sclerosing panencephalitis (SSPE) strains. Differences in the mobilities of various polypeptides have been observed between CDV and measles and SSPE strains; however, the only consistent difference is the mol. wt. of the M-protein of CDV strains which is smaller by 2000 than that of MV and this may be a biochemical marker to distinguish CDV from measles and SSPE virus strains.

Animals↗
PubMed1979

A comparison of polypeptides in measles and SSPE virus strains.

The polypeptide patterns of twelve subacute sclerosing panencephalitis (SSPE) and measles viruses have been compared by slab gel electrophoresis. The polypeptide patterns of nine strains of SSPE and measles virus were identical. Differences in the NP protein and the HA protein of the Oddo strain, the P protein of the large plaque variant of the Lec strain of SSPE and in the M protein of the Hu 2 measles strain could not be correlated with biological characteristics such as plaque morphology, origin or haemagglutination properties.

Electrophoresis, Polyacrylamide Gel↗
PubMed1979

Studies of the replication of a bovine enterovirus RNA.

Replicative intermediate (RI), replicative form (RF) and single-stranded (SS) RNA have been isolated from BHK cells infected with a bovine enterovirus by salt precipitation and gel filtration techniques. Kinetic experiments showed that at no time up to 16 h post-infection (p.i.) did the amount of RF exceed that of RI or SS RNA. Electrophoresis of RF on 1.5% polyacrylamide-agarose gels showed that at least three species of double-stranded RNA were present, one of which was associated with an accessible poly(A)-containing tract. All of the RF was denatured by 99% dimethylsulphoxide (DMSO), although reannealling occurred rapidly when samples were returned to aqueous conditions. No evidence for circular structures in the RF molecular population was found by use of caesium sulphate density gradients containing ethidium bromide. Treatment of RI with ribonuclease produced double-stranded RNA molecules, some of which were smaller in size than intact RF. Denaturation with DMSO and analysis on 99% DMSO sucrose gradients showed that the RI did not contain single strands of greater length than virion RNA. A portion of the RI bound to poly(U)-Sepharose 4B columns. The poly(A) tracts involved were present only in the nascent RNA strands with greatest sedimentation coefficients (30 to 35S). Bovine enterovirus induced SS RNA was heterogeneous with regard to both sedimentation through sucrose gradients and mobility on acrylamide gels compared to purified virion RNA. The reason for this difference has never been satisfactorily resolved. Sedimentation through 99% DMSO-sucrose gradients showed that the heterogeneity was due to aggregation rather than any variation in chain length or conformational differences. Our results support the single-stranded template model rather than a circular model for picornavirus RNA replication.

Animals↗
PubMed1979

Effect of undiluted passage on the polypeptides of measles virus.

Measles virus induces a large polypeptide (L; mol. wt. 180 K), a large glycopolypeptide (H; mol. wt. 80 K), a nucleocapsid associated polypeptide (P; mol. wt. 70 K), a nucleocapsid polypeptide (N; mol. wt. 60 K), a second glycopolypeptide (F0; mol. wt. 60 K), a matrix or membrane polypeptide (M; mol. wt. 37 K) and a small polypeptide (S; mol. wt. 15 K). The second glycopolypeptide (F0) appears to be cleaved in purified measles virus. Defective interfering particles accumulate during passage of measles virus leading to a decrease in the amounts of virus-specific protein synthesized in infected cells. Even in the best preparations of purified measles virus, host proteins are always detected and these become more predominant in preparations with low infectivity.

Carcinoma, Squamous Cell↗