Search PubMed⌕ Search

Biomedical subjects

A Adams

Publications and source records attributed to A Adams.

At least 181 records · Page 10Linked to original sources
PubMed1978

Integration of Epstein-Barr virus DNA.

The application to herpesviruses of different standard methods fo measuring tumour-virus integration is discussed. The evidence for the presence of integrated virus DNA in EBV-transformed cells is summarized.

Cell Transformation, Neoplastic↗
PubMed1977

Human lymphoblastoid cell lines derived from individuals without lymphoproliferative disease contain the same latent forms of Epstein-Barr virus DNA as those found in tumor cells.

The physical state of the intracellular Epstein-Barr virus DNA was characterized in four human lymphoblastoid cell lines, F-265, NC-37, U-303 L, and PG-1, derived from individuals without lymphoproliferative disease. For comparison, a previously investigated Burkitt lymphoma line, Raji, and a more recently established cell line of that origin, Rael, were also studied. The techniques employed were CsCl density gradient centrifugation, glycerol gradient centrifugation, and ethidium bromide-CsCl density gradient centrifugation in combination with nucleic acid hybridization, as well as electron microscopy contour length measurements of purified circular EBV DNA. All six cell lines contained multiple copies of covalently closed circular EBV DNA-molecules of the same size, as well as viral DNA with the properties of integrated DNA. No differences could be detected between the forms of EBV DNA present in cell lines derived from non-malignant sources and those present in lymphoma lines.

Burkitt Lymphoma↗
PubMed1977

Circular Epstein-Barr virus genomes of reduced size in a human lymphoid cell line of infectious mononucleosis origin.

Circular Epstein-Barr virus (EBV) DNA molecules have been purified and characterized from a human lymphoid cell line derived from a case of heterophile antibody-positive, blood transfusion-induced infectious mononucleosis, 883L. The circular EBV DNA in three cell lines obtained by transformation of human umbilical cord blood leukocytes with a strain of EBV originally derived from 883L was also studied. As estimated from sedimentation velocity data and electron microscopy, the circular EBV DNA molecules are 10 to 15% smaller than either the circular EBV DNA previously found intracellularly in several other types of EBV-transformed cells or the linear EBV DNA present extracellularly in virus particles. In addition, the EBV-transformed cord blood cell lines studied here differed from other EBV-transformed cells in that integrated virus DNA sequences could not be detected.

Burkitt Lymphoma↗
PubMed1977

The pathophysiologic basis for the angiographic signs of vascular ectasias of the colon.

Three reliable diagnostic signs were identified on angiograms from 25 patients with ectasias of the right colon: (a) a slowly emptying dilated, tortuous, intramural vein; (b) a vascular tuft; and (c) an early filling vein. The frequency of these signs and the order of their occurrence reflect the different stages in the evolution of ectasias. The earliest and most frequent sign, the slowly emptying vein, reflects ectatic changes in a submocosal vein resulting from chronic intermittent partial obstruction. The vascular tuft represents more advanced lesions and corresponds to extension of the degenerative process to the venules in the mucosa. An early filling vein reflects an arteriovenous communication through a dilated arteriolar-capillary-venular unit-a mucosal ectasia.

Aged↗
PubMed1977

On the nature and etiology of vascular ectasias of the colon. Degenerative lesions of aging.

Vascular lesions of the right colon are being diagnosed increasingly as a cause of lower intestinal bleeding, but their nature and occurrence, primarily in the elderly, remains unexplained. Colons from patients with clinical and angiographic diagnoses of cecal vascular lesions were studied by injection and clearing, and by histological sections. In all injected specimens one or more mucosal vascular ectasias were identified. The mucosal lesions appeared to be secondary to dilated tortuous submucosal veins which were the more prominent feature and were often present without the mucosal ectasia. This suggests that ectasias are caused by chronic, intermittent, low grade obstruction to submucosal veins with dilation and tortuosity initially of submucosal veins, then of venules, capillaries, and arteries of the mucosal vascular unit. Ultimately, precapillary sphincters lose their competency, producing small arteriovenous communications. The concept that ectasias are degenerative lesions was evaluated by studying 15 right colons resected for carcinoma with no history of bleeding. Mucosal ectasias were identified in four colons and submucosal ectasias in eight. These investigations suggested that these lesions: (1) are vascular ectasias developing as a degenerative process of aging, (2) are present with or without bleeding in a significant portion of the population over 60 years of age, (3) are multiple more often than single, and (4) may represent the commonest cause of major lower intestinal bleeding in the elderly.

Aged↗
PubMed1976

Developmental changes in purine phosphoribosyltransferases in human and rat tissues.

1. The hypoxanthine/guanine and adenine phosphoribosyltransferase activities in a wide variety of human tissues were studied during their growth and development from foetal life onward. A wide range of activities develop after birth, with especially high values in the central nervous system and testes. 2. Postnatal development of hypoxanthine/guanine phosphoribosyltransferase was also defined in the rat. Although there were increases in the central nervous system and testes, there was also a rise in activity in the liver, which was less marked in man. 3. A sensitive radiochemical assay method, using dTTP to inhibit 5'-nucleotidase activity, suitable for tissue extracts, was developed. 4. No definite evidence of the existence of tissue-specific isoenzymes of hypoxanthine/guanine or adenine phosphoribosyltransferase was found. Hypoxanthine/guanine phosphoribosyltransferase in testes, however, had a significantly different thermal-denaturation rate constant. 5. The findings are discussed in an attempt to relate activity of hypoxanthine/guanine phosphoribosyltransferase to biological function. Growth as well as some developmental changes appear to be related to increase in the activity of this enzyme.

Adenine Phosphoribosyltransferase↗
PubMed1976

Adenosine deaminase activity in thymus and other human tissues.

Adenosine deaminase activity (ADA) has been estimated in human tissues. Levels in the thymus during childhood were very much higher than in any of the other 6 tissues studied. Intermediate activities were obtained from spleen and lymph nodes and also skin. Cerebral cortex, liver and kidney had relatively low levels. ADA activity in lymphocytes from peripheral blood was significantly increased after antigenic stimulation by TAB immunization. The available evidence appears to be consistent with T-lymphocyte growth and development in the thymus being dependant on ADA.

Adenosine Deaminase↗
PubMed1975

Epstein-Barr virus genomes with properties of circular DNA molecules in carrier cells.

A high-density fraction of high-molecular-weight DNA was isolated from the human lymphoid cell line Raji. This cell line contains 50 to 60 virus genome equivalents of Epstein-Barr virus DNA per cell, and the high-density DNA fraction was 10-fold enriched in such viral sequences. Sedimentation analysis on neutral glycerol gradients, followed by hybridization experiments with viral complementary RNA, showed that most of the intracellular viral DNA sequences in this material did not cosediment with the cellular DNA, but were recovered as two distinct species with sedimentation coefficients of 100 S and 65 S. These two forms sediment 1.70-1.75 and 1.10-1.12 times as fast as the linear Epstein-Barr virus DNA from virus particles, and thus have the hydrodynamic properties of a covalently closed circular form and a nicked (containing single-strand breaks) circular form of the virus genome. The 100S form also behaved as a covalently closed circular EBV DNA molecule on gradient centrifugation in CsC1/propidium diiodide, It would appear that latent Epstein-Barr virus DNA has the properties of a mammalian episome, and that both nonintegrated and integrated viral DNA sequences can be isolated from carrier cells.

Base Sequence↗
PubMed1975

Sensitivity of the Epstein-Barr virus transformed human lymphoid cell lines to interferon.

The effect of interferon on expression of Epstein-Barr virus (EBV) early gene functions was investigated. The 'early antigen' synthesis which follows either EBV superinfection of established lymphoid cell lines or 5'-iododeoxyuridine activation of the intrinsic EBV genomes harboured by these cells could be suppressed with interferon. In contrast, the spontaneous early antigen expression that occurs in a few per cent of the cells in the producer cell lines could not be blocked with interferon. The lymphoid cell lines tested differed in their ability to acquire an antiviral state after exposure to interferon. Several cell lines were also growth inhibited by the interferon preparations. The antiviral and growth inhibitory activities of different interferon preparations could not be separated by a number of criteria.

Antigens, Viral↗
PubMed1975

Spontaneous interferon production and Epstein-Barr virus antigen expression in human lymphoid cell lines.

Established human lymphoid cell lines, many of which spontaneously produce interferon, differ in the efficiency by which they allow expression of Epstein-Barr virus (EBV) lytic functions. Six EBV carrying lymphoid cell lines, selected to either be extremely susceptible or very refractory to EBV superinfection, were tested for spontaneous interferon production. Only the three cell lines which were poorly superinfectable with EBV were found to produce interferon. These same three lines could not be induced to express EBV-specific early antigens from intrinsic EBV genomes. It is suggested that interferon acts as a negative control factor affecting a cell's susceptibility to EBV.

Antigens, Viral↗