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Biomedical subjects

J A Robb

Publications and source records attributed to J A Robb.

At least 55 records · Page 3Linked to original sources
PubMed1979

Differentiation between SV40 large-T and U antigenic sites.

Radioimmune precipitation, SDS-polyacrylamide slab gel electrophoresis and fluorography were used to investigate the SV40 large-T and U antigenic sites on species of proteins synthesized during wild type and tsA58 mutant infections in TC7 monkey cells. Wild type infection at 33 and 41.5 degrees C and the A58 infection at 33 degrees C produced similar profiles of three species ranging in mol. wt. from 84000 to 94000, all of which had both the large-T and U antigenic sites. The A58 infection at 41.5 degrees C, however, produced an additional four discrete species ranging in mol. wt. from 60000 to 74000 that contained the large-T site(s), but not the U site(s). A subpopulation of the 74000 mol. wt. species contained both sites. Therefore, the region of the A58 mutant 94000 mol. wt. species containing the U antigenic site(s), the COOH-terminal region, appears to be more sensitive to processing, probably proteolytic cleavage, than does the region containing the large-T antigenic site(s).

Animals↗
PubMed1977

Transformation of human cystinotic fibroblasts by SV40: characteristics of transformed cells with limited and unlimited growth potential.

Human skin fibroblasts derived from patients with nephropathic cystinosis were transformed with SV40 virions, cloned and permitted to enter the degenerative stage of growth termed "crisis," characteristic of SV40 transformed human cells. Nephropathic cystinosis is an autosomal recessively inherited metabolic disorder resulting in the intracellular accumulation of the amino acid cystine. A transformed cystinotic cell line which was recovered from the crisis stage was indistinguishable from its transformed precrisis parental cell strain in growth rate in media containing either 1% or 10% serum, cloning efficiency on plastic, in semisolid media, or upon confluent monolayers of normal skin fibroblasts, expression of SV40 T antigen, or production of virus. However, the modal DNA content of the recovered postcrisis transformed cystinotic cell line was different from that of the cloned parental precrisis transformed cell strain, suggesting that the postcrisis line was derived from a small subpopulation of the precrisis strain. The DNA content of the established cystinotic cell line continued to be unstable during subsequent subculturing and gave rise to subclones with both more and less DNA per cell. This line now has an apparently infinite growth potential and still has the hallmark of the cystinotic parental line, the storage of abnormally large amounts of intracellular nonprotein cystine.

Antigens, Viral↗
PubMed1977

Identification of simian virus 40 tumor and U antigens.

The synthesis and identity of the tumor and U antigens of simian virus 40 (SV 40) have been examined during productive infection in monkey cells, abortive infection in mouse cells, and in SV40-transformed mouse cells by using sodium dodecyl sulfate/polyacrylamide slab gel electrophoresis to analyze [35S]methionine-labeled radioimmune precipitates. The following observations were made: (i) the tumor and U antigenic sites are on the same 94,000, 89,000, and 84,000 molecular weight species detected during productive infection; a 94,000 species made during abortive infection; and a 94,000 species found in transformed cells. (ii) The 94,000 species is relatively unstable compared to the relatively stable 89,000 and 84,000 species produced during productive infection. (iii) The stable 89,000 and 84,000 molecular weight species are differentially extracted from productively infected cells, which suggests an intracellular compartmentation and/or different affinities of these species for cellular substrates. (iv) The 94,000 species synthesized during abortive infection is more stable than the comparable 94,000 species synthesized in transformed cells. (v) Three tsA group mutants overproduce several unstable species of tumor antigen at restrictive temperature.

Antigens, Neoplasm↗
PubMed1977

Skeletal scintimaging and radiography in the diagnosis and management of Paget's disease.

Experiences in sue of skeletal scintimaging, primarily with 99mTc EHDP, is reported in 108 patients with Paget's disease. The results are compared with other reports and suggest that the mean age of this sample at the time of initial diagnosis and study is somewhat younger than patients in series reported in the literature. In correlation of scintimaging with skeletal radiography only approximately 67% of lesions are seen with the latter. Lesions seen only on scintimaging primarily are associated with early symptomatic lesions and lesions seen only on radiography with older sclerotic "burned out" type lesions. Scintimaging reveals a relatively low incidence of monostotic distribution of lesions, and is superior to skeletal radiography for diagnosis of metastatic bone disease. Qualitative skeletal scintimaging is valuable for objective assessments of therapeutic management by new modes of therapy while clinical radiography is not.

Alkaline Phosphatase↗
PubMed1976

Regulation of SV40-induced cell division and tumor antigen by dibutyryl adenosine 3'-5'-monophosphate.

Simian virus 40 (SV40) induces cell division in microcultures of sparsely plated nongrowing mouse BALB/3T3 cells during acute infection at moderate multiplicities of infection (MOI = 10-100). The infected cells are killed when a MOI of 1,000 is used. SV40 tumor (T) antigen is synthesized in the infected cells, but viral DNA, virion antigen, and progeny virions are not synthesized (abortive infection). The addition of exogenous dibutyryl adenosine 3'-5'-monophosphate (dbcAMP) at the time of infection stimulates the SV40-induced cell division at all MOI and inhibits SV40-induced cell death at high MOI. The percentage of T antigen-positive cells, as monitored by immunofluorescence, is also increased by the addition of dbcAMP at the time of infection. This regulation of SV40-induced cell division and T antigen formation by exogenous dbcAMP occurs within the first 6 hr after infection at 37 degrees C and is dependent upon both the MOI and the concentration of added dbcAMP. The addition of dbcAMP to productively infected TC7 monkey cells has litte effect on the SV40-induced cell death or T antigen formation.

Antigens, Viral↗
PubMed1976

Femoral trabecular-pattern index and bone mineral content measurement by photon absorption in senile osteoporosis.

A comparative study of the usefulness of the femoral trabecular-pattern index (Singh index) and bone mineral content measurement by photon absorption in senile osteoporosis was performed in 106 white women, seventy to ninety-five years old. In 17% of the subjects adequate hip roentgenograms could not be obtained. Interpretation of the Singh index was not found to be simple and easily reproducible. A positive correlation was noted between the bone mineral content and the Singh index. The incidence of previous vertebral and non-vertebral fracture was noted to be inversely related to both bone mineral content and the Singh index, but neither method clearly separated subjects with fracture from those without fracture.

Aged↗
PubMed1974

Antigenic phenotypes and complementation groups of temperature-sensitive mutants of simian virus 40.

The antigenic phenotypes of several temperature-sensitive mutants of simian virus 40 were determined by an immunofluorescence microtechnique that allowed a very high degree of internal control for the conditions of virus infection and antigenic staining. The tumor (T), U, capsid protein (C), and virion (V) antigens were investigated. Productive infection in monkey cells and abortive infection in mouse cells were simultaneously monitored for antigen production at both permissive and restrictive temperatures. Complementation analyses of the mutants demonstrated two complementing groups (A and B) and one noncomplementing group ((*)). One of the complementing groups could be subdivided into two subgroups having very different antigenic phenotypes. The following phenotypes were observed at the restrictive temperature in monkey cells. (i) The noncomplementing group produced none of the antigens. (ii) Group A induced T antigen in moderately but consistently reduced numbers of cells. Other antigens were markedly reduced or absent. (iii) Some of the group B mutants produced T antigen but little or no U and V antigens. The C antigen appeared in the nucleolus and cytoplasm of this subgroup. (iv) In the other group B mutants, antigen synthesis was not altered. Similar phenotypes were observed in mouse cells, except that U, C, and V antigens could not be detected during either the mutant or wild-type virus infections at any temperature.

Animals↗
PubMed1974

Altered protein metabolism in infection by the late tsB11 mutant of simian virus 40.

The DNA of the temperature-sensitive mutant tsB11 is replicated at the same rate as the DNA of wild-type virus in infection at the restrictive temperature. The progeny mutant DNA cannot be distinguished from wild-type DNA by gel electrophoresis and is assembled into a nucleoprotein complex with the same velocity sedimentation characteristics as the wild-type complex. Analysis of in vivo protein synthesis by sodium dodecyl sulfate polyacrylamide gel electrophoresis and immunoprecipitation techniques demonstrated that the capsid components VP1, VP2, and VP3 of the mutant and wild-type virus are synthesized at a similar rate, but VP1 fails to accumulate within cells infected by tsB11. Furthermore, VP1 is located predominantly in the cytoplasmic rather than in the nuclear fraction of extracts from cells infected by the mutant. Immunofluorescent studies localized virion antigen within the nucleolus as well as the cytoplasm. The altered intracellular distribution and stability of VP1 suggest that it may be the mutant protein of tsB11. The synthesis of a 72,000 dalton protein is consistently induced in significant quantity in cells infected by tsB11 at the restrictive temperature. A protein of the same apparent molecular weight is present in smaller quantities in uninfected cells and is only slightly increased in quantity in cells infected by wild-type virus.

Animals↗
PubMed1974

Simian virus 40-host cell interactions. II. Cytoplasmic and nucleolar accumulation of simian virus 40 virion protein.

We have used immunofluorescence in parallel with transmission and scanning electron microscopy to characterize the unusual cytoplasmic and nucleolar accumulation of Simian virus 40 (SV40) virion protein (C antigen) at restrictive temperatures (39 to 41 C) in monkey cells infected with a temperature-sensitive mutant of SV40 defective in virion assembly, tsB11. Cytoplasmic and nucleolar accumulation of C antigen did not occur in wild-type-infected cells at any temperature. Wild-type- and tsBll-infected cells were not distinguishable at 33 C by immunofluorescence or electron microscopy. Temperature-shift experiments using metabolic inhibitors of DNA (cytosine arabinonucleoside, 20 mug/ml), RNA (actinomycin D, 5 mug/ml), and protein synthesis (cycloheximide, 2 x 10(-4) to 10 x 10(-4) M) were used to investigate the requirements for ongoing DNA, RNA, and protein synthesis in the distribution of virion protein between the nucleus, nucleolus, and cytoplasm. The transport of C antigen from the nucleolus and cytoplasm into the nucleus was complete after a temperature shift-down (41 and 39 to 33 C). Limited virus particle formation occurred after the shift-down in the presence of actinomycin D and cycloheximide, indicating some of the 39 to 41 C synthesized virion protein could be used for capsid assembly at 33 C in the absence of further virion protein synthesis. Nucleolar and cytoplasmic accumulations of C antigen occurred in the absence of drugs after a shift-up (33 to 39 C and 41 C) indicating a continuous requirement for the tsB11 mutant function. Furthermore, the virion protein synthesized at 33 C remained confined to the nucleus when the cells were shifted to 39 and 41 C in the presence of actinomycin D or cycloheximide. In the presence of cytosine arabinonucleoside, however, the virion protein accumulated in large aggregates in the nucleus and nucleolus after the shift-up, but did not migrate into the cytoplasm as it did in drug-free tsB11-infected control cells. Colchicine (10(-3) M) had no effect on the abnormal accumulation of C antigen during shift-up or shift-down experiments suggesting that microtubular transport plays little if any role in the abnormal transport of tsB11 virion protein from cytoplasm to nucleus. Although virus particles were never observed by electron microscopy and V antigen was not detected by immunofluorescence at 39 or 41 C in tsB11-infected cells, dense amorphous accumulations were formed in the nucleoli and cytoplasm. We suggest that the tsB11 function is continuously required for the normal transport of SV40 virion protein between the cytoplasm, nucleolus, and nucleus and for the assembly of capsids and virions. Several possible mechanisms for the altered tsB11 function or protein are discussed. One of the virion proteins may also be involved in some presently undetermined nucleolar function during SV40 productive infection.

Animals↗