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Biomedical subjects

J Summers

Publications and source records attributed to J Summers.

At least 127 records · Page 7Linked to original sources
PubMed1978

Hepatitis B virus DNA in primary hepatocellular carcinoma tissue.

Tumour, cirrhotic, and metastatic tissues from four patients with primary hepatocellular carcinoma have been investigated for the presence of hepatitis B viral DNA by nucleic acid hybridization. Tumours from two of three patients with a current HBV infection contained 1--2 genomes per cell of unintegrated viral DNA, while tumours from the third HBs antigen-positive patient contained less than one genome equivalent per ten cells. A tumour from one patient with anti-HBs contained no detectable HBV DNA. A variety of models involving HBV as an etiologic agent may be advanced to explain the statistical correlation of HBV infection with primary hepatocellular carcinoma (PHC). The data presented here argue against the model that HBV DNA integrated into every cell is required to maintain the oncogenic transformation of hepatocytes, but they do not rule out other models.

Adult↗
PubMed1977

Association of e antigen with Dane particle DNA in sera from asymptomatic carriers of hepatitis B surface antigen.

Sera containing hepatitis B surface antigen from 30 asymptomatic blood donors were assayed for e antigen (HBeAg) and antibody to e antigen (anti-HBe) by rheophoresis,. Fourteen samples (47%) had detectable HBeAg, ten (33%) had anti-HBe, and six (20%) had neither. DNA was extracted from 26 of these sera and assayed for its ability to anneal to a [32P]-DNA probe that is a copy of Dane particle DNA. All 10 HBeAg-positive samples tested contained DNA that formed specific hybrids with the DNA probe, as did one of 10 anti HBe-positive samples. Hybridization was not detected in nine sera containing anti-HBe and six sera without HBeAg or anti-HBe. Because the Dane particle is thought to be the hepatitis B virus, this association between HBeAg positivity and Dane particle DNA strongly supports the hypothesis that e antigen is a marker of the presence of the virus and, consequently, potential infectivity.

Antibodies, Viral↗
PubMed1976

Efficeint transcription of RNA into DNA by avian sarcoma virus polymerase.

The DNAase digestion end-product of calf thymus DNA contains oligonucleotides that will function as primers for the efficient transcription into DNA of many naturally-occurring RNA's by purified avian sarcoma virus RNA-directed DNA polymerase. The labeled DNA transcripts so obtained are valuable as probes for molecular hybridization studies. Typical applications of the method include the efficient transcription into DNA of 18 and 28 S rRNA as well as the RNA's of avian sarcoma virus, polio virus, influenza virus, satellite tobacco necrosis virus and tobacco mosaic virus. In addition, when these primers are added to avian sarcoma virus particles that have been partially-disrupted with non-ionic detergent there is 6-fold stimulation of the endogenous RNA-directed DNA synthesis.

Alpharetrovirus↗
PubMed1975

Rat cell line 3y1 and its virogenic polyoma- and sv40- transformed derivatives.

Cell lines were established from cultures derived from Fischer rat embryos according to the transfer schedule described by Todaro and Green (1963) for mouse 3T3 cells where cell crowding and serum exhaustion were kept to a minimum. Cell growth rate did not decline greatly during the course of successive 3-day transfers. Like 3T3 cells the rat cell lines possess very low saturation desities under standard culture conditions. A clonal cell line with a relatively high plating efficiency as obtained from one of the cell lines, 3YL. In these cloned cultures, virus growth was not detectable upon infection with SV40, while a small amount of virus was produced upon infection with polyoma virus. Morphological transformation of the cloned 3Y1 cells by SV40 and polyoma virus could be assayed with single-hit kinetics and with effieiencies comparable to those of the previously available transformation systems for each virus. Independent cell lines transformed by SV40 were consistently virus-free and all the lines tested produced SV40 upon fusion with permissive monkey cells. Most of the independent transfromed cell lines isolated after polyoma infection appeared to be virus-free, although the cultures of some lines produced a small amount of polyoma virus spontaneously after a prolonged cultivation. Most of the virus-free polyoma-transformed lines produced virus upon fusion with permissive mouse cells.

Animals↗
PubMed1975

Genome of hepatitis B virus: restriction enzyme cleavage and structure of DNA extracted from Dane particles.

DNA extracted from Dane particles has been characterized by gel electrophoresis and restriction enzyme cleavage with endonuclease R-HaeIII (from Hemophilus aegyptius). Dane particle DNA is proposed to be a double-stranded circular DNA approximately 3600 nucleotides in length containing a single-stranded gap of 600-2100 nucleotides. The endogenous DNA polymerase (DNA nucleotidyl-transferase; deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase; EC 2.7.7.7) reaction appears to repair this single-stranded gap.

DNA Nucleotidyltransferases↗
PubMed1975

Physical map of polyoma viral DNA fragments produced by cleavage with a restriction enzyme from Haemophilus aegyptius, endonuclease R-HaeIII.

Digestion of polyoma viral DNA with a restriction enzyme from Haemophilus aegyptius generates at least 22 unique fragments. The fragments have been characterized with respect to size and physical order on the polyoma genome, and the 5' to 3' orientation of the (+) and (-) strands has been determined. A method for specific radiolabeling of adjacent fragments was employed to establish the fragment order. This technique may be useful for ordering the fragments produced by digestion of complex DNAs.

Autoradiography↗
PubMedDate not supplied

Changes of hepatitis B virus DNA in liver and serum caused by recombinant leukocyte interferon treatment: analysis of intrahepatic replicative hepatitis B virus DNA.

Twenty patients with HBeAg-positive chronic liver disease were given large doses of recombinant leukocyte interferon for 4 weeks. Changes of hepatitis B virus DNA in livers and sera were analyzed by the molecular hybridization technique in paired biopsies obtained before and 2 weeks after treatment. Serum hepatitis B virus DNA was examined before, during and after the treatment until 4 weeks post-interferon. Analysis of hepatic hepatitis B virus DNA revealed species that appeared to represent various forms of replicative hepatitis B virus DNA, i.e., relaxed circular, linear, supercoiled and single-stranded hepatitis B virus DNA, respectively. No evidence of integration of hepatitis B virus DNA in genomic DNA was obtained. Of 15 cases which were positive for hepatic hepatitis B virus DNA before treatment and in which paired biopsies were obtained, hepatic hepatitis B virus DNA became negative in 4, decreased in 5 and unchanged in 6. Among several types of replicative viral DNA in liver tissue, supercoiled hepatitis B virus DNA tended to remain after other forms were reduced. A close correlation between hepatic and serum hepatitis B virus DNA was found in 37 liver biopsy samples and corresponding sera. These results indicate that interferon treatment reduces serum hepatitis B virus levels by inhibiting viral replication in the liver and that persistence or reappearance of hepatitis B virus in serum after interferon is associated with replication.

Adult↗
PubMedDate not supplied

Antiviral activity of magnesium and magnesium/poly r(A-U) combinations against two RNA viruses.

Magnesium (Mg2+) potentiated the anti-vesicular stomatitis virus (VSV) activity of poly r(A-U) or poly r(G-C) and the anti-HIV-1 activity of poly r(A-U). Mg2+ did not affect the anti-VSV activity of poly (rI).poly (rC), poly (dA-dT).poly (dA-dT) or poly (dG-dC).poly (dG-dC). Modulation of one or more nuclear (nucleolar) processes of the host cell may be responsible for the synergistic antiviral activity.

Antiviral Agents↗
PubMedDate not supplied

Boranophosphate nucleic acids--a versatile DNA backbone.

Important chemical and biochemical properties of boranophosphate DNA and RNA oligonucleotides are reviewed. Stereoregular boranophosphate oligomers can be synthesized enzymatically and form stable duplexes with DNA. Fully boronated, non-stereoregular oligothymidylates, synthesized chemically, form hybrids with poly(A) that have lower melting points than oligothymidylate:poly(A), yet they nevertheless can support the RNase H mediated cleavage of RNA.

Boron Compounds↗
PubMedDate not supplied

The influence of HIV-related support groups on survival in women who lived with HIV. A pilot study.

To determine the effect of support groups on survival, the authors retrospectively studied 21 HIV-seropositive women who died during the course of participation in a natural history study of HIV. Groups were composed of women who self-selected HIV support groups before death (n = 11) and a comparison group (n = 10). Survival analysis found group participation to be associated with increased longevity (73 months vs. 45 months; P = 0.011). Proportional-hazards regression demonstrated that HIV-related support groups and smaller family size significantly influenced survival (P = 0.0002). Factors related to group participation and ways in which support groups might promote longevity are discussed.

Adaptation, Psychological↗