Search PubMed⌕ Search

Biomedical subjects

P Aman

Publications and source records attributed to P Aman.

At least 91 records · Page 5Linked to original sources
PubMed1992

Effect of oat bran on plasma cholesterol and bile acid excretion in nine subjects with ileostomies.

A higher excretion of dry matter, fat, nitrogen, energy, and total bile acids in ileal effluents; a lower plasma low-density-lipoprotein (LDL) and total cholesterols (12.1% and 9.0% lower respectively); but no change in plasma high-density-lipoprotein (HDL) cholesterol or apolipoproteins A-I and B were observed in nine subjects with ileostomies when they consumed an oat-bran, bread-based, high-fiber diet (HFD) as compared with a wheat-flour, bread-based, low-fiber diet (LFD) for 3 wk with a crossover design. Of the nine subjects only the subjects with a low daily excretion of bile acids had an elevated excretion of total bile acids during the HFD compared with the LFD. Total cholesterol, LDL cholesterol, and apolipoprotein B in plasma also decreased by 11.3%, 15.3%, and 10.7%, respectively, after consumption of the HFD for 3 wk.

Adult↗
PubMed1992

The EBNA2-related resistance towards alpha interferon (IFN-alpha) in Burkitt's lymphoma cells effects induction of IFN-induced genes but not the activation of transcription factor ISGF-3.

Transfection of a plasmid encoding the Epstein-Barr virus (EBV) nuclear antigen 2 (EBNA2) gene confers resistance to the antiproliferative effect of alpha interferon (IFN-alpha) in EBV-negative U968 cells (P. Aman and A. von Gabain, EMBO J. 9:147-152, 1990). We studied the expression of IFN-stimulated genes (ISGs) in two pairs of Burkitt's lymphoma cell lines, differing in the expression of the putative immortalizing gene of EBV, EBNA2. In EBNA2-expressing cells, the induction of four ISGs by IFN-alpha was strongly reduced or, in some cases, abolished. Chloramphenicol acetyltransferase reporter gene constructs containing different IFN-stimulated response elements were transfected into EBNA2-negative and EBNA2-positive cells. Induction of chloramphenicol acetyltransferase activity by IFN was impaired in EBNA2-positive cells. Also, a reporter gene construct driven by an IFN-gamma-sensitive promoter element was affected. However, as revealed by gel shift assays, EBNA2-positive and EBNA2-negative cells exhibited a nearly identical pattern of IFN-stimulated response element-binding proteins. Most important, activation of the factor ISGF-3, which previously has been shown to be required and sufficient for transcriptional activation of IFN-induced genes, was not inhibited in IFN-resistant cells expressing EBNA2. The mechanism of the EBNA2-related IFN resistance seems to be distinct both from the resistance mediated by hepatitis virus and adenovirus gene products and from the IFN resistance in Daudi cell variants. In these three cases, the transcriptional block of IFN-induced genes is due to inhibition of ISGF-3 activation and binding. Our data suggest that the EBNA2-related IFN resistance in Burkitt's lymphoma cells acts downstream of the activation of ISGF-3.

Antigens, Viral↗
PubMed1991

[Molecular genetics methods discovering the mechanisms of neoplasm etiology].

The rapid advance in our understanding of cancer biology during the past decade, as exemplified by the discovery of oncogenes and tumour suppressor genes and their interactions in tumourigenesis, has revolutionized cancer research. This rapid progress has largely been due to the use of molecular genetics techniques. However, despite the wealth of available information as to the genetic basis of carcinogenesis, its clinical applicability remains limited. The review is a summary of the general principles and methods currently used to detect genetic alterations in neoplastic cells, with special emphasis on clinical applications.

Animals↗
PubMed1991

Biological characterization of infectious molecular clones derived from a human immunodeficiency virus type-1 isolate with rapid/high replicative capacity.

In order to molecularly characterize rapidly and slowly replicating HIV-1 variants, molecular clones were obtained from a rapid/high virus isolate. This isolate, 4803, had only been passaged in peripheral blood mononuclear cells (PBMC) prior to cloning. Molecular cloning was done in bacteriophage lambda-dash using high molecular weight DNA of isolate 4803 infected PBMC. Seven recombinant phages were identified. The clones were found to be related to each other and differed only at 1 or 2 restriction sites (out of 28). The molecular clones were transfected into various cell types by electroporation. The phenotype of progeny viruses was found to be dependent on the cell type used for transfection. Progeny viruses produced by PBMC cultures differed from the parental isolate in that they did not form syncytia and lacked the capacity to replicate in cell lines. Since transfection of PBMC yielded progeny viruses within 1 week, this phenotype is considered to be the true phenotype of the clones. Transfection of the T-lymphoid HUT-78 cell line and of the monocytoid U937-2 cell line yielded progeny viruses after considerable delay (more than 1 month). Progeny viruses from HUT-78 cells were similar to the parental isolate in that they formed syncytia in PBMC and replicated in all cell lines tested. Progeny viruses from U937-2 cells showed an intermediate phenotype in that they replicated in U937-2 but not in T-lymphoid cell lines. These results indicate that molecular clones of a rapid/high virus may have a restricted replicative capacity compared to the parental, genetically heterogenous virus isolate.

Cell Line↗
PubMed1991

The leukemic B-cell population of patients with monoclonal lymphocytosis of undetermined significance (MLUS) are functionally distinct from the chronic lymphocytic leukemia (CLL) derived cell population.

Some patients with CLL survive for decades with a stable lymphocytosis without other signs of progression of the disease. This condition has been termed monoclonal lymphocytosis of undetermined significance (MLUS). The aim of the present study was to search for functional differences between the monoclonal B-cell population of CLL (n = 3) and MLUS (n = 5) patients. MLUS derived B-cell populations were susceptible to Epstein-Barr virus (EBV) infection measured as the production of EB nuclear antigen (EBNA) whereas CLL derived cells were resistant. In 4 out of 5 MLUS patients, lymphoblastoid cell line (LCL) like cell-clumps were formed, but not in CLL. The clonal B-cell population from 2 of 5 MLUS patients was immortalized by EBV (LCL restricted to the expression of one Ig light chain) while no cell line emerged from the CLL patients. Phorbol esters induced cell to cell adhesion of MLUS and normal B cells but not of CLL derived cells. This study further enlarges previous observations and strengthens the assumption that MLUS clonal B cells are functionally close to normal B cells while CLL B cells display various functional abnormalities.

Antigens, Surface↗
PubMed1991

Brewer's spent grain, serum lipids and fecal sterol excretion in human subjects with ileostomies.

A crossover design studying lipid and apoprotein levels in serum and excretion of sterol, nitrogen and fat in ileostomy effluent was performed in 10 subjects fed diets with or without supplementation with brewer's spent grain, which is the residue of barley after the brewing of beer. More cholesterol, nitrogen, fat and energy were excreted in the ileostomy effluents when the subjects consumed a brewer's spent grain supplemented, high fiber diet than when they consumed a low fiber diet. No significant change was found in the daily net sterol excretion. The six subjects with low daily excretion of bile acids (less than 1000 mg/24 h) had increased cholesterol and net cholesterol and decreased bile acid excretion per day, and lowered serum LDL-cholesterol and apoprotein B levels after supplementation with brewer's spent grain. We propose that subjects with low daily bile acid excretion are suitable models for studying the effect of dietary changes on sterol excretion and serum lipid levels. Increased fecal cholesterol excretion is suggested to be the primary mechanism for the serum LDL-cholesterol lowering effect of brewer's spent grain.

Adult↗
PubMed1990

Effect of the EBNA-2 gene on the surface antigen phenotype of transfected EBV-negative B-lymphoma lines.

Two EBV-negative B-lymphoma cell lines with different phenotypes were transfected with the Epstein-Barr virus EBNA-2 gene. The effects on the expression of 8 B-cell surface markers were analyzed by immunofluorescence methods. In one of the EBNA-2 transfected cell lines, the expression of the CR2 receptor CD21 was induced and the expression of CD23 was enhanced. The results suggest that the EBNA-2 gene is involved in the regulation of CD21 and CD23 in EBV-carrying cells.

Antibodies, Monoclonal↗
PubMed1990

An Epstein-Barr virus immortalization associated gene segment interferes specifically with the IFN-induced anti-proliferative response in human B-lymphoid cell lines.

Immortalization of human B-lymphocytes by Epstein-Barr virus (EBV) is associated with a decreased anti-proliferative response to interferon (IFN). In the present investigation we show that the resistance to the anti-proliferative effect of IFN class I on certain EBV-carrying Burkitt lymphoma cell lines is connected to the presence of the EBNA-2 gene and parts of the EBNA-5 gene of the EBV genome. Transfection of the genomic segment comprising these open reading frames into an IFN-sensitive lymphoma cell line demonstrated that it is sufficient to make cells resistant towards the antiproliferative effect of IFN class I. Expression of the EBNA-2 gene seems to be correlated with the IFN-resistant phenotype. The antiviral function of IFN, as tested by inhibition by vesicular stomatitis virus (VSV) infection, and the IFN-receptor binding are not suppressed. The present results suggest that the neutralization of the anti-proliferative effect of IFN-alpha is involved in the EBV-mediated immortalization of B-cells and that the anti-proliferative action of IFN class I does not necessarily recruit the same mechanism as the antiviral effect.

Antigens, Viral↗
PubMed1990

Epstein-Barr virus-carrying B cells in the blood during acute infectious mononucleosis give rise to lymphoblastoid lines in vitro by release of transforming virus and by proliferation.

In accordance with earlier studies, we detected higher numbers of Epstein-Barr virus (EBV)-carrying lymphocytes (B-EBV) in the blood of acute infectious mononucleosis (IM) patients and higher amounts of transforming EBV particles in the saliva compared to healthy seropositive individuals. B cells grew in cultures seeded with the low and high density IM lymphocytes. The majority of B cells which grew acquired the infection in vitro (2-step outgrowth), because addition of virus neutralizing antibodies considerably reduced the emergence of lymphoblastoid cell lines (LCLs). Only the minority of the explanted B-EBV cells proliferated. The antiviral drug phosphonoformate (PFA) did not influence the frequency of 2-step LCLs in the IM cultures. This may indicate that a large proportion of EBV carrying B cells have already entered the viral productive cycle in vivo and passed the PFA-sensitive stage at the time of explantation. Earlier experiments with blood of healthy seropositive individuals showed an inhibitory effect of PFA on the generation of LCLs. One healthy individual who entered this study as a control, probably had a reactivated EBV infection as judged by the anti-EA activity in his serum and the high level of virus in his saliva. He had antibodies against EBV nuclear antigens (EBNA), and therefore he did not have a primary infection at the time of the test. Judged by the number of wells with B cell growth, the frequency of virus-carrying B cells in his blood was low. It seems that anti-EBV immunity can control the number of infected B cells in the blood, but does not influence the virus load in the epithelial cells.

Acute Disease↗
PubMed1990

Microfilament-disrupting Clostridium difficile toxin B causes multinucleation of transformed cells but does not block capping of membrane Ig.

The effects of Clostridium difficile toxin B on some actin-dependent cellular functions were studied. A three-day incubation of intoxicated B-lymphocytes and transformed 3T3 fibroblasts resulted in dose-dependent multinucleation. Using vimentin-negative Daudi cells we showed that this effect of toxin B does not involve vimentin. As DNA and protein syntheses are not impaired in the cells used, the results suggest that toxin B has an effect on the actin-containing contractile ring during mitosis, in a manner similar to that of the microfilament-disrupting agent cytochalasin B. Toxin B is the first bacterial toxin shown to have this effect. It was also found that the capping of surface IgM on B-lymphocytes was not inhibited by toxin B, whereas cytochalasin B did inhibit capping. These results suggest that capping is dependent on a specific membrane-associated actin structure, which is not affected by toxin B.

Actin Cytoskeleton↗
PubMed1989

Inhibition of polyamine synthesis in human B lymphocytes during primary infection with Epstein-Barr virus (EBV) blocks cellular DNA synthesis but not the expression of EBV-encoded nuclear antigens (EBNA).

Inhibition of polyamine synthesis by 2-difluoromethylornithine (DFMO) treatment had no apparent effect on the initial manifestation of Epstein-Barr virus (EBV) infection in human B lymphocytes, because the expression of EBV-encoded nuclear antigens (EBNA) occurred normally. However, many subsequent steps in the transformation process were inhibited by DFMO treatment. These include cellular DNA synthesis and immunoglobulin (IgM, IgG and IgA) synthesis and secretion. Consequently, DFMO treatment blocked the progression of the transformation process of EBV-infected B lymphocytes. EBV-carrying marmoset B lymphocytes (B95-8 cells) were also blocked in their DNA synthesis when treated with DFMO. At variance with other DNA synthesis inhibitors, which induce virus production very effectively in B95-8 cells, DFMO caused no increase in the number of cells expressing the early antigens associated with the lytic cycle.

Antigens, Viral↗
PubMed1989

Enzyme supplementation of a poultry diet containing rye and wheat.

A total of 360 1-d-old broiler chickens were fed on a diet based on rye and wheat in equal proportions without or with supplementation of increasing levels (0.11, 0.22, 0.44 and 0.88 g/kg) of a technical enzyme preparation containing pentosanase and beta-glucanase activities. In vitro investigations revealed that the enzyme preparation solubilized pentosans, increasing the relative viscosity of buffer extracts from enzyme-supplemented diets. Enzyme supplementation generally improved body-weight by approximately 27% at day 15 and 15% at day 27, increased feed intake by 15 and 8% respectively, and improved feed conversion efficiency by 10 and 5% respectively. There was also a decreased occurrence of sticky droppings. Enzyme supplementation increased the digestibility of organic matter, crude protein (nitrogen x 6.25) and starch measured in the last third of the small intestine, and of organic matter and crude fat measured in excreta. Solubilization of insoluble pentosans by the enzyme included led to negative digestibility values for soluble pentosans in the small intestine at the higher levels of supplementation. Most of the dietary fibre degradation observed occurred before the middle section of the small intestine, with some degradation of soluble fibre in the caeca and colon. The solubilization and disruption of feed endosperm cell walls by enzyme supplementation probably was primarily responsible for the observed improvements in digestibility and production results.

Animal Feed↗
PubMed1989

An in vitro method for studying digestion in the pig. 1. Stimulating digestion in the different compartments of the intestine.

1. An in vitro method, using duodenal and ileal digesta and faeces from pigs as inocula for the preparation of three incubation media for simulating the digestive processes in the pig, was proposed. The kinetics of degradation in these three media of three feed samples (pig-grower diet, sugar-beet pulp and wheat bran) with crude protein (nitrogen x 6.25) contents varying from 111 to 196 g/kg, starch contents from 10 to 446 g/kg and dietary fibre contents from 168 to 686 g/kg, were studied. 2. The method was investigated by incubating the feeds in the three media for up to 96 h, and determining the rate and extent of disappearance of feed components. 3. For each feed the 96 h dry matter disappearance was almost equal for all media, although the rate of disappearance varied considerably, with ileal digesta the most potent, particularly for the high-fibre feeds, and duodenal digesta the least. The patterns of disappearance of individual components were similar in all media, with the exception of crude protein which was apparently less degraded in ileal and especially faecal media. 4. Results suggest that a combination of a short (6-12 h) and a long (48-72 h) in vitro incubation could be employed to simulate digestion in the small and large intestine respectively of the pig.

Animal Feed↗
PubMed1989

An in vitro method for studying digestion in the pig. 2. Comparison with in vivo ileal and faecal digestibilities.

1. An in vitro method involving incubation of feed samples with buffered duodenal digesta for 12 h or with buffered ileal and faecal inocula for 48 h was compared with in vivo ileal or faecal apparent digestibilities in pigs. 2. The five diets investigated had crude protein (nitrogen x 6.25) contents from 164 to 185 g/kg, starch contents from 296 to 463 g/kg and dietary fibre contents from 176 to 347 g/kg. 3. In vitro disappearances with duodenal inocula were correlated (P less than 0.05) with in vivo ileal apparent digestibilities for crude protein, ash, starch, energy and dry matter, but not for dietary fibre. 4. In vitro disappearances with the ileal and faecal inocula were generally correlated (P less than 0.1) with in vivo faecal apparent digestibilities for dietary fibre, energy and dry matter, but not for ash or crude protein. The patterns of degradability of fibre polysaccharide residues in vitro and in vivo were also similar. 5. Results indicate that this in vitro method could be used to predict the availability of starch and crude protein for digestion in the small intestine, and the degradability of dietary fibre, and thus for comparing the nutritive value of pig feeds.

Animal Feed↗
PubMed1988

Activation of B lymphocytes with human serum-treated zymosan.

C3 fragments fixed on zymosan particles were presented to resting human B lymphocytes. The opsonized zymosan (Ops-Z) particles induced release of leukocyte migration inhibitory factor, a slight decrease in mIgD, and a slight increase in the activation marker Blast-2. The B cells did not proceed further along the pathway of activation: they did not respond to B cell growth factor (BCGF) and Ops-Z did not synergize with other activators for BCGF response either. Thus, we found that interaction between C3 fragments and CR2 initiates the activation of human B lymphocytes, but this is limited to the early phase.

Antigens, Surface↗
PubMed1988

Direct outgrowth of in vivo Epstein-Barr virus (EBV)-infected chronic lymphocytic leukemia (CLL) cells into permanent lines.

In the course of our efforts to characterize the EBV-carrying cells that are responsible for direct growth or the 2-step mechanism, based on virus release from the explanted cells and subsequent transformation of previously uninfected cells, we have encountered an unusual CLL patient who carried a small subpopulation of in vivo EBV-infected leukemia cells. These were predominantly present in the low-density fraction and grew into EBV-carrying lines upon explantation after a relatively short latency period, 3-4 weeks. Cytogenetic examination conclusively proved the leukemic origin of the established CLL lines. They carry a ring chromosome 15 and are trisomic for chromosome 12. The same changes are also found in the majority of the peripheral blood lymphocyte population. Taken together, our results suggest that the EBV-genome and the cytogenetic changes may have contributed to the immortalization of the CLL cells in a complementary or synergistic fashion.

Antigens, Viral↗