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Biomedical subjects

J Stephen

Publications and source records attributed to J Stephen.

At least 91 records · Page 5Linked to original sources
PubMed1979

Further studies on a vaccinia virus cytotoxin present in infected cell extracts: identification as surface tubule monomer and possible mode of action.

A vaccinia virus-specific cytotoxic protein (3--10 X 10(4) daltons) had previously been detected in extracts of infected HeLa cells. In this study the protein has been shown to be a late gene product and a virion component--almost certainly the monomer of the surface tubules of the vaccinia virion. The relationship of this cytotoxin to a number of early vaccinia-induced cytopathic effects was examined: it was not the mediator of vaccinia-induced early cell rounding, did not inhibit protein or RNA synthesis in cell-free systems or intact cells (after uptake-induction by hypertonic MgSO4), or cause the release of beta-glucuronidase from a crude preparation of HeLa cell lysosomes. Its possible role in vaccinia-induced cell degeneration, late in infection, is discussed.

Cell-Free System↗
PubMed1979

Surgical management of thoracic kyphosis in adolescents.

Twenty-seven patients of a group of twenty-nine who underwent posterior spine fusion using Harrington compression instrumentation for Scheuermann's disease or postural roundback deformity were reviewed with a mean follow-up of 27.6 months. The mean curve before operation was 72 degrees and at review, 46.1 degrees. The mean loss of correction in the fusion from initial examination to final follow-up was 5.7 degrees. This procedure can achieve satisfactory correction of deformity as well as pain relief. We think that Harrington compression instrumentation and spine fusion is indicated in selected cases of roundback deformity.

Adolescent↗
PubMed1977

Vaccinia virus cytotoxin.

Extracts of vaccinia-infected HeLa cells were rendered free from infectious virus by centrifugation followed by membrane filtration and were shown to be toxic to uninfected HeLa cells in the presence of hypertonic MgSO4, used as a macromolecular uptake inducer, under conditions which did not kill control cells. Extracts from uninfected cells were nontoxic. This biological test was adapted to a semi-quantitative assay which was used to monitor the purification of the cytotoxic factor by DEAE-cellulose and Sephadex G-100 chromatography. The cytotoxic factor was purified 100-fold, shown to be of molecular weight 30 -- 100,000 daltons, acidic and completely inactivated by soluble trypsin but not by ribonuclease under conditions believed to degrade both single- and double-stranded RNA species. It was demonstrated to be virus specific by approrpiate immunosorbent chromatography. Extracts were also prepared from vaccinia-infected HEp-2, RK and W-K cells respectively. A virus-specific factor, toxic to uninfected HeLa cells, with similar chromatographic properties to that isolated from infected HeLa cells, was isolated from these three additional cell lines. The concept of virus induced cytotoxins, substances which exert their toxic effect in the host cells in which they are made, is discussed.

Antigens, Viral↗
PubMed1975

Studies on the purification of chlamydial agents grown in yolk sacs of embryonated eggs using disulphide-linked immunosorbents and enzymes.

Immunosorbents were derived from avid and non-avid sera raised in rabbits to multiple or single injections of chlamydiae passaged once or three times in HeLa cells after routine passage in eggs. Egg-derived suspensions of chlamydiae required pretreatment before application to immunosorbent columns; this was most conveniently done by fractionation on Sepharose 4B. Immunosorbents derived from avid serum had greater capacity than those from non-avid sera. However, organisms were desorbed in low yield from an avid immunosorbent, but in higher yields from non-avid immunosorbents. Even under the best conditions, the immunosorbents yielded suspensions of organisms still contaminated with egg antigens. Partially purified suspensions of chlamydiae were also treated with phospholipase C to yield suspensions of high purity.

Adsorption↗