Search PubMed⌕ Search

Biomedical subjects

P Aman

Publications and source records attributed to P Aman.

At least 109 records · Page 6Linked to original sources
PubMed1988

Surface marker characterization of EBV-carrying cells in blood of healthy seropositive individuals.

We have determined the phenotype of EBV-carrying cells in human blood by establishing spontaneous LCLs from populations selected according to three B cell markers, B1, B2, and 35.1C5. LCLs grew from the B1-positive, B2-positive, B2-negative and 35.1C5-positive population. Thus, EBV-carrying cells in blood of seropositive individuals are restricted to the B cell lineage. These B cells may or may not express the B2 epitope, and they may be derived from the lymph node mantle zone or the splenic marginal zone. These in vivo EBV-carrying cells could enter the viral productive cycle and transform coresident B cells during the initial 3 days in vitro. The characteristic of the LCLs with regard to these 3 B cell markers did not correspond to the original B cell population from which they were derived.

Adult↗
PubMed1988

Buoyant density characterization of neoplastic cell populations in patients with chronic B-lymphocytic leukemia.

Leukemic cells from a series of patients with chronic B-lymphocytic leukemia (CLL) were analyzed for their buoyant density on discontinuous Percoll gradients. The density profile varied markedly between different patients and also between samples from different body compartments within the same patient. A good correlation was observed between buoyant density and maturation stage of the leukemic clones as judged by Ig-expression and their reactivity with a panel of monoclonal antibodies. Phorbol-ester-induced changes in the leukemic cells were found to be accompanied by a general decrease in their buoyant density. No correlation between density and clinical parameters such as cell counts, clinical stage and survival could be noted. Buoyant density characterization of leukemic B-cell populations is seen as a useful, rapid and simple marker of compartmentalization within the B-lymphocyte maturation spectrum but its clinical relevance remains to be established.

Antigens, Surface↗
PubMed1987

Conversion of the lymphoma line "BJAB" by Epstein-Barr virus into phenotypically altered sublines is accompanied by increased c-myc mRNA levels.

The steady-state level of c-myc proto-oncogene mRNA was investigated in the EBV-negative human B-lymphoma line BJAB and 2 sublines that have been converted by EBV into stable EBV-genome-carrying and EBNA-positive status. The EBV-converted sublines expressed c-myc at a 2- to 6-fold higher level than the original BJAB during exponential growth. The EBV-positive BJAB lines are known to differ from the parent line in several phenotypic characteristics, including increased agarose clonability, lower serum requirement and, in one case, increased tumorigenicity in nude mice. The pattern of increased c-myc expression accompanying EBV conversion was not observed in the myc/Ig translocation-carrying Burkitt lymphoma line RAMOS or in 2 of its EBV-converted sublines.

Actins↗
PubMed1987

Characterization of EBV-carrying B-cell populations in healthy seropositive individuals with regard to density, release of transforming virus and spontaneous outgrowth.

Peripheral or tonsil lymphocyte populations of EBV-seropositive donors give rise to EBV-carrying LCLs upon in vitro explantation. Such lines can arise either by a 2-step mechanism, namely release of virus from some of the explanted cells followed by infection of previously uninfected B cells, or by direct outgrowth of virus-harboring B cells (Rickinson et al., 1974; Dalens et al., 1975; Hinuma and Katsuki 1978; Katsuki et al., 1979). We observed that cells responsible for both the 2-step mechanism and for direct outgrowth are found in the purified B-cell compartment. Virus release was more frequent than direct outgrowth. The majority of virus-releasing cells were found in the low-density fraction that contains large, activated B blasts. Cells that were capable of spontaneous outgrowth in the presence of the viral inhibitor PFA and of virus-neutralizing antibody gave rise to cell lines that carried the sex chromosome marker of the original donor, rather than that of admixed cord blood lymphocyte of the opposite sex. Such cells were found in both the low- and the high-density fractions. The majority of the EBV-carrying B cells in vivo are thus low-density blasts. Rare small B cells of high density harboring EBV were capable of spontaneous outgrowth. This may be indicative of a host control mechanism that is removed upon cultivation in vitro.

B-Lymphocytes↗
PubMed1986

B cell activation by the nontransforming P3HR-1 substrain of the Epstein-Barr virus (EBV).

The P3HR-1 substrain of Epstein-Barr virus does not transform B cells. This defect is known to be determined by the loss of the coding sequence for the nuclear antigen EBNA-2. The virus can attach to and enter resting B cells. The initial events after EBV infection are reminiscent of those induced by polyclonal B cell activators. Similar to the effect of these, P3HR-1 virus lowers membrane IgD expression on B cells and abrogates the transient elevation of activation markers BB-1 and LB-1 induced by the culture conditions. An important event of B cell activation is the acquisition of competence to respond to specific growth factors produced by T cells. This was induced by the P3HR-1 virus. The infected B cells had elevated [3H]thymidine incorporation when exposed to the supernatant of PHA-treated T cells. The EBV receptor is identical with the complement receptor CR2. Ligand binding to CR2 has been shown both with mouse and human B cells to deliver certain activation signals. Therefore, it is possible that the early step of activation by EBV is initiated through the binding to the receptor and is thus a cell surface event.

Antigens, Surface↗
PubMed1986

Production of chemokinetic inhibitory factor (CIF) by normal blood and spleen B lymphocytes.

We have recently reported the partial purification and characterization of of a new lymphokine, the heat-labile chemokinetic inhibitory factor (CIF) which inhibits neutrophil movement. We have also shown that this lymphokine is produced and secreted by cultured B-chronic lymphocytic leukaemia (CLL) cells in vitro. The present study shows that highly purified resting normal B lymphocytes from blood and spleen have the capacity to produce CIF spontaneously. After activation with anti-IgM or EBV-infection the lymphocytes produced a number of other factors, heat-stable chemokinetic inhibitory factors and heat-labile chemokinetic enhancing factors. Supernatants from a collection of human B-cell lines representing different stages of B-cell differentiation were also investigated. None of these cell lines produced CIF. The present results show that the production of CIF is not restricted to the malignant B-CLL cell but is also produced by a subset of normal blood and spleen B cells.

B-Lymphocytes↗
PubMed1986

The influence of wheat bran and sugar-beet pulp on the digestibility of dietary components in a cereal-based pig diet.

The influence of added wheat bran or dried sugar-beet pulp on the apparent digestion of dietary components was examined in pigs fitted with duodenal and terminal ileal cannulas. The pigs were fed a basal cereal-based diet alone or substituted at a level of 33% by wheat bran or beet pulp. Neither fibrous component influenced the digestibility of starch, but inclusion of beet pulp decreased dry matter content and digestibility of ash, protein and fat in the ileum and fecal digestibility of fat. Between 11 and 37% of the nonstarch polysaccharides were degraded anterior to the ileum, and the percentage of beet pulp diet nonstarch polysaccharides that was soluble increased from 11% in the feed to 35% at the ileum. Xylose and glucose were the least degraded nonstarch polysaccharide residues in all three diets, and the non-starch polysaccharide residues varied in susceptibility to breakdown within and between diets, depending on the composition of the fiber. Almost 50% of the beet pulp, but less than 20% of the wheat bran, was degraded in the large intestine. The inclusion of wheat bran and beet pulp increased fecal output by 127 and 56%, respectively.

Animal Feed↗
PubMed1985

Capacity of B-lymphocytic lines of diverse tumor origin to produce and respond to B-cell growth factors: a progression model for B-cell lymphomagenesis.

Human cell lines established from cases of acute lymphoblastic leukemia, lymphosarcoma, Burkitt's lymphoma and multiple myeloma and representing stages of B-lymphocyte development ranging from pre-B through to plasma cells, were assessed for their ability to produce and respond to B-cell growth factors (BCGF). All B-cell lines studied were found to be constitutive producers of a growth activity which assisted the S-phase entry of normal activated B-cells and provided growth support for lymphoblastoid cells transformed by Epstein-Barr virus. Furthermore, all lines responded by enhanced proliferation to supernatants from a BCGF-producing T-cell hybridoma. Not all lines, however, displayed autostimulation to their own supernatants and no tumor B-cell line appeared totally dependent on soluble factors for its growth. Non-tumorigenic B-cell lines, by contrast, revealed a strict dependency on homologous growth factor for their continued proliferation in suspension culture. The findings support a progression model of lymphomagenesis based upon the utilization, production and, ultimately, emancipation from growth-promoting soluble factors.

B-Lymphocytes↗
PubMed1985

The large sialoglycoprotein of human lymphocytes. I. Distribution on T and B lineage cells as revealed by a monospecific chicken antibody.

Chickens were immunized with highly purified large sialoglycoprotein of human lymphocytes (L-LSGP; gp 150) which was isolated from neuraminidase-treated normal peripheral blood lymphocytes by affinity chromatography to HP-Sepharose and further purified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Antibodies isolated from plasma and egg yolk were highly specific for desialylated L-LSGP (apparent molecular mass approximately 150 kDa). The antigenic sites recognized by the antibodies are probably located in the peptide moiety of the molecule since antibody binding to lymphocytes was not inhibited by a variety of different sugars or abrogated by absorption on various erythrocytes. In immunofluorescence experiments, greater than or equal to 75% of neuraminidase-treated thymocytes and peripheral blood lymphocytes, virtually all E+ cells and T4+ or T8+ T chronic lymphocytic leukemia (CLL) cells were stained by anti-gp 150. A small fraction (approximately 10%) of thymocytes and a larger fraction (greater than or equal to 30%) of T CLL cells in some patients were stained before neuraminidase treatment. Thymocytes appear to contain considerably lower amounts of a less sialylated form of L-LSGP than peripheral blood lymphocytes. In contrast to blast cells of 5-day concanavalin A or leucoagglutinin cultures (greater than or equal to 90% anti-gp150+) only about 50% of the blast cells generated in 5-day mixed leukocyte cultures were anti-gp150+. The large majority (greater than or equal to 75%) of both the anti-gp150+ and anti-gp150- cells were T3+ and T11+.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Leukocyte migration inhibitory factor production by activated lymphocytes representing immunological memory or virus-receptor interaction: response of T cell subsets to Epstein-Barr virus nuclear antigen, response of B cells to UV inactivated Epstein-Barr virus.

Both T and B lymphocytes are known to produce leukocyte migration inhibitory factor (LIF) after appropriate activation. We showed that EBV nuclear antigen (EBNA) triggered T cells for LIF production in an immunologically specific way: only T cells of seropositive individuals responded. Both Fc receptor positive and negative T cells produced LIF, and the presence of macrophages was necessary. The virus itself activated B cells independently of the serological status of the donors, thus the function was not based on immunological memory. This phenomenon was independent of the transforming capacity of the virus, because UV-inactivated virus also elicited LIF production by B lymphocytes. This triggering seems to be the consequence of the virus-receptor interaction on the cell surface.

Antigens, Viral↗
PubMed1985

Use of a nylon-bag technique for pig feed digestibility studies.

1. The use of a nylon-bag technique for pig feed digestibility determination was studied. Bags, measuring 25 x 40 mm and containing feed samples, were introduced into the pig gastrointestinal tract through a duodenal cannula, and recovered in the faeces between 23 and 69 h later. The disappearance of organic matter and crude protein (nitrogen x 6.25) from the bags was compared with in vivo apparent digestibility, determined by conventional faecal-collection methods, and neutral-detergent-fibre content for eleven feeds. The residues left in the bags after passage through the intestine from whole-crop-pea (Pisum sativum) and barley-grain samples were analysed for starch, non-starch polysaccharide residues, Klason lignin, crude protein and ash. 2. Dry matter disappearance of barley or whole-crop peas was not influenced by increasing bag pore size from 10 to 36 microns or sample weight from 250 to 1000 mg. Pepsin (EC 3.4.2.1) pretreatment had no effect on the degradation in the bags of the feeds investigated. 3. Organic matter and crude protein disappearance from the bags exceeded in vivo apparent digestibility by up to 0.10 and 0.42 units respectively. In vivo apparent organic matter digestibility could be predicted (P less than 0.001) by the organic matter disappearance from the bags and the neutral-detergent-fibre content of the feed, while in vivo apparent crude protein digestibility was highly correlated (P less than 0.001) to all these indices but poorly to crude protein disappearance from the bags. 4. Klason lignin was the least degraded component measured in the whole-crop-pea and barley residues from the bags, while starch was completely digested.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1985

Surface marker characterization of EBV target cells in normal blood and tonsil B lymphocyte populations.

Human FACS-sorted B lymphocyte subpopulations were investigated for their susceptibility to immortalization by Epstein Barr virus (EBV). Only B cells reacting with the monoclonal antibody B2 were immortalized, whereas cells reacting with anti-human IgG or the monoclonal antibody BB2 were not responding. Cells positive or negative for IgM, IgD, Burkitt's lymphoma antigen (BLA), BB1, and HB2 were all transformed by EBV.

Antigens, Surface↗
PubMed1984

Soluble factor requirements for the autostimulatory growth of B lymphoblasts immortalized by Epstein-Barr virus.

B lymphoblasts immortalized by the Epstein-Barr virus (EBV) exhibit autocrine growth stimulation--that is they release a soluble activity to which they respond by growth. A minimally supplemented serum-free medium conditioned by lymphoblastoid cells in their log phase of growth (LCL-CM) was found to contain autostimulatory activity allowing us to explore the mechanism of autocrine growth for these cell-types in defined conditions. Below cell densities capable of supporting autonomous growth, continued proliferation in serum-free medium was dependent on both added LCL-CM and transferrin. Neither activity alone was capable of sustaining growth. At higher cell densities, transferrin by itself was sufficient to maintain the autocrine loop. The action of the autostimulatory factor appeared to reside in its ability to prime cells continually for a proliferative response to transferrin by enhancing the expression of transferrin receptors at the lymphoblast surfaces. The implications of these findings for normal B cell physiology and their possible relation to oncogenesis are discussed.

B-Lymphocytes↗
PubMed1984

Epstein-Barr virus susceptibility of normal human B lymphocyte populations.

Human blood and tonsil B lymphocytes were fractionated on density gradients and tested for virus binding and penetration into the cells. Epstein-Barr Virus (EBV) transformation was detected by immunofluorescence staining for EBV-determined nuclear antigen (EBNA). EBV bound to and penetrated all B cell populations, but only the high density populations were transformed. Activated B lymphocytes were found in the low density fractions and these cells were resistant to EBV infection. Infected and noninfected B lymphocytes were density-analyzed during in vitro culture. A spontaneous, not virus-induced, density decrease was found to precede the production of EBNA. Cells remaining at high density never expressed EBNA. The results suggest that EBV can transform only small resting B lymphocytes and that a virus-independent activation of the infected cells induces the EBNA production and transformation.

Antigens, Viral↗
PubMed1984

TPA (12-O-tetradecanoyl-phorbol-13-acetate) activation and differentiation of human peripheral B lymphocytes.

The effect of the tumour-promoting phorbol ester TPA (12-O-tetradecanoyl-phorbol-13-acetate) on normal human peripheral blood and tonsil B lymphocytes was investigated. A strong DNA-synthesis response with the maximum at day 4 was detected. This response was, however, inhibited by increasing concentrations of serum in the medium. The membrane Ig expression was changed with a rapid decrease in IgD expression and a slower decrease in IgM and IgG expression. TPA-induced Ig secretion was detected in 12 out of 22 tested donors and the response was found to be independent of T cells and macrophages. The expression of four monoclonal antibody-detected B cell activation and differentiation markers, B1, B2, LB1 and BB1, was followed. The results indicate activation and differentiation of the B cells.

Antibodies, Monoclonal↗