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Biomedical subjects

J R Stephenson

Publications and source records attributed to J R Stephenson.

248 records · Page 14Linked to original sources
PubMed1971

Induction of colonies of hemoglobin-synthesizing cells by erythropoietin in vitro.

A culture method has been developed in which erythroid colonies are produced in vitro from hemopoietic cells from the livers of 13-day fetuses of C3H(f)/Bi mice. Heme synthesis by the cultures was correlated with the presence of these colonies, and the hemoglobin produced was shown to be electrophoretically normal. The individual colonies were identified as erythroid since they were erythropoietin-dependent, positively stained by the histochemical "Lepehne" procedure for hemoglobin, and labeled by (59)Fe radioautography. Evidence is presented that the development of these colonies is under separate control from that of granulocytic colonies found in the same cultures.

Animals↗
PubMedDate not supplied

Antigenic analysis of tick-borne encephalitis complex viruses by time-resolved fluoroimmunoassay with monoclonal antibodies.

The antigenic structure of 5 strains of tick-borne encephalitis (TBE) virus and 7 other viruses of the TBE complex was examined by the highly sensitive and specific technique of time-resolved fluoroimmunoassay (TR-FIA). A collection of 8 monoclonal antibodies to the Austrian strain. Neudörfl, was used in this study. The findings demonstrate the uniformity of the antigenic structure of TBE viruses from different geographic regions of the USSR. In addition, an epitope was detected which is characteristic of western variants of TBE virus, and another epitope was detected which permits the differentiation of the east-Siberian strain, Aina, from other TBE virus strains. The unique nature of Skalica virus was confirmed, and its similarity, but not identity, to Langat TP-21 virus was shown. Substantial variability in the antigenic structure of some TBE complex viruses was also demonstrated.

Animals↗
PubMedDate not supplied

Homology between phosphotyrosine acceptor site of human c-abl and viral oncogene products.

The human homologues of several independent viral oncogenes, each of which encodes tyrosine-specific protein kinases, have been identified. Of these, three (v-src, v-yes and v-fes/fps) are known to exhibit considerable sequence homology, particularly in the regions of their phosphorylation acceptor sites. In the present study, sequences encoding the tyrosine phosphorylation acceptor sites of the Abelson murine leukaemia virus oncogene, v-abl, and its human cellular homologue, c-abl, have been identified and their nucleic acid sequences determined. Our results establish extensive homology between this region of c-abl and acceptor domains of the v-src, v-yes and v-fes/fps family of viral oncogenes, as well as more distant relatedness to the catalytic chain of the mammalian cyclic AMP-dependent protein kinase. These findings suggest that, of the homologues of retroviral oncogenes with tyrosine protein kinase activity examined to date, all were probably derived from a common progenitor and may represent members of a diverse family of cellular protein kinases.

Amino Acid Sequence↗
PubMedDate not supplied

Localization of the c-ab1 oncogene adjacent to a translocation break point in chronic myelocytic leukaemia.

The human c-ab1 oncogene maps within the region (q34-qter) of chromosome 9 which is translocated to chromosome 22, the Philadelphia (Ph') chromosome, in chronic myelocytic leukaemia (CML). The position of the Ph' chromosomal break point is shown to be variable and, in one CML patient, has been localized immediately 5' of, or within, the c-ab1 oncogene. A DNA restriction fragment corresponding to this site has been molecularly cloned and shown to represent a chimaeric fragment of DNA from chromosomes 9 and 22.

Abelson murine leukemia virus↗
PubMedDate not supplied

Genetic factors influencing endogenous type-C RNA viruses of mouse cells: control of viral polypeptide expression in the C57BL/10 strain.

Type-C viral polypeptides are expressed at very low levels in C57BL/10 liver and embryo cells as compared to cells of other mouse strains. The 12,000-mol. wt. polypeptide in C57BL/10 cells was purified and shown to possess type-specific antigenic determinants indistinguishable from those of a previously described class of endogenous virus. The very low levels of endogenous virus-specific RNA in cells of C57BL/10 as compared to other strains suggests control of this endogenous virus at the level of transcription. Analysis of viral antigen expression F1 hybrids of C57BL/10 with strains characterized by intermediate and high levels of viral antigen expression indicates that the restriction of this endogenous virus by C57BL/10 cells is not due to simple dominance by a repressor of virus expression.

Animals↗
PubMedDate not supplied

Displaced fractures of the os calcis involving the subtalar joint: the key role of the superomedial fragment.

Fourteen displaced intra-articular fractures of the os calcis are reviewed following open reduction and internal fixation using a lateral approach with an average follow-up of 22 months (range, 12 to 44 months). Postoperative management consisted of early subtalar motion with delayed weightbearing. Twelve of 14 fractures were considered good results on the basis of no pain, 50% normal subtalar motion, and near-normal anatomy. Pain correlated with incomplete reduction of the superomedial fragment and, thus, incongruent reduction of the posterior facet in two cases. The importance of effecting a reduction of the superomedial border of the os calcis is emphasized.

Ankle Injuries↗
PubMedDate not supplied

[Antigenic analysis of tick-borne encephalitis virus group using monoclonal antibodies and immunofluorescence].

The study included 18 monoclonal antibodies (MAb) to E- or NS1-antigens tested by immunofluorescence with tick-borne encephalitis (TBE) complex viruses. MAb were induced to 3 strains of TBE virus: the pathogenic 4072 strain isolated from a patient; the Skalica strain of low pathogenicity; and the Neidorf strain isolated from ticks. According to their reactivity to complex viruses, MAb comprised 3 groups: monospecific for TBE virus (T6, T15) which detected tick-borne encephalitis virus alone; widely cross-reactive with 4-6 viruses of the complex (NEK, KEN, T7, T9); and partially complex-reactive (T11, T12, T13, T33/3) and bound to 2-3 viruses of the complex. T13 and T33/3 MAb reacted with the Omsk hemorrhagic fever virus to the same degree or stronger than with TBE virus. The cross-reactivity was more marked in anti-E-than in anti-NS1 MAb. The similarity of the Langat viruses and the Skalica strain was confirmed. Using anti-NS1 MAb in tests with non-fixed cells, the release of NS1-antigen was found to begin at hour 18 (time of observation). The results of the study may be useful for improvement of laboratory diagnosis of TBE and evaluation of the capacity of a vaccine to induce cross immunity to viruses of the TBE complex.

Animals↗