Biomedical subjects

M Bakker

Publications and source records attributed to M Bakker.

77 records · Page 5Linked to original sources

PubMedDate not supplied

Immunodominant B-cell clones responsive to an HIV-1 neutralization and cell fusion inhibition epitope in chimpanzee-to-chimpanzee passages of HTLV-IIIB and LAV-1.

Chimpanzees infected with the HIV-1 strains HTLV-IIIB or LAV-1 in primary, secondary or tertiary passages developed neutralizing antibodies binding to variable domain V3 in the carboxyl terminal half of the external envelope (amino acids 309-317). Nonapeptide antigens reflecting either the HTLV-IIIB/LAV-1 neutralization epitope (IQRGPGRAF, designated 3B) or peptide analogues (ITKGPGRVI, designated RF; IQRGPGRVI, designated 3B/RF; ITKGPGRAF, designated RF/3B) were previously shown to be able to distinguish antibody populations in a polyclonal response of rabbits to these peptides. Sera from chimpanzees infected with the HIV-1 strains HTLV-IIIB and LAV-1 were tested for the presence of antibodies reactive to these nonapeptides. Sera from 3 chimpanzees infected with a primary LAV-1 or HTLV-IIIB passage, 2 chimpanzees infected with blood from the primary infected chimpanzees and from 1 chimpanzee infected with blood from a secondary passage animal, all bound peptides 3B and 3B/RF, sharing the sequence IQRGPGR, in equally high tires. In 2 primary passage animals and in 1 secondary passage animal, the capacity to bind to peptides 3B and 3B/RF was equally high, indicating clonality of these B-cell responses. Contrasting results were obtained with the sera from 1 primary, 1 secondary and 1 tertiary passage animal, showing stronger binding to the 3B/RF peptide than to the 3B peptide. The animals with antibodies binding strongly to the 3B peptide had an early HTLV-IIIB-induced cell-fusion-inhibiting (CFI) antibody response, while the animals with antibodies binding strongly to the 3B/RF peptide had a late HTLV-IIIB-induced CFI antibody response. This difference in binding to the 3B peptide might result from antigenic variation in the neutralization domain of the inoculum virus(es). The conservation of the antibody specificity for the neutralization epitope of the inoculum strain might open the way to type circulating virus strains by antibody specificity for a panel of peptide analogues derived from the V3 domain of the external envelope of distinct HIV-1 strains.

Amino Acid Sequence↗

PubMedDate not supplied

Antibody recognition of amino acid divergence within an HIV-1 neutralization epitope.

Antibodies elicited by HIV-1 strains, and which neutralize such strains in vitro, bind to synthetic peptides of 5-8 amino acids in length. These amino acids, although variable, have a fixed location between two cysteines in the carboxyl terminus of the HIV-1 external envelope. Nine peptides of 9 amino acids corresponding to the gp120 domains of European and American (LAV-1, NY5, CDC4, SF2), Haitian (RF) and African (ELI, MAL, Z3, Z6) HIV-1 strains, were synthesized using LAV-1 and RF neutralization epitopes as models. Serum of chimpanzees infected with LAV-1, HTLV-IIIB or HTLV-IIIRF reacted predominantly with the homologous peptide, although cross-reactivity with heterologous peptides occurred: 8 out of 11 human sera with HTLV-IIIB-neutralizing activity bound the LAV-1/HTLV-IIIB peptide, and 6 out of 7 sera with HTLV-IIIRF-neutralizing activity bound the RF peptide. African sera reacted most frequently with the Z3 peptide (78%) while only 35% (p = 0.0001) of European and 20% (p less than 0.0001) of American sera recognized it. Recognition patterns of children from the USA and Europe were different. Although multiple reactivities were observed, blocking experiments favoured cross-reactivity as the explanation. Based on the antibody profiles of nonapeptide recognition, peptides LAV-1, RF and SF2 were clustered, as were NY5 and CDC4, and so were Z6, MAL and ELI. This antigenic relatedness of HIV-1 strains could not entirely be explained by the physico-chemical characteristics of the nonamers per se. Resemblance was observed with the clustering of HIV-1 strains based on the divergence of the nucleotide sequence of entire HIV-1 envelopes. This implies a role of peripheral envelope residues, in the context of infectious particles or infected cells, in determining the specificity of antibodies reactive to the V3 domain. Therefore, the neutralization domain in this variable region may be considered part of a conformational structure involving several envelope regions which appear distinct from each other in the primary sequence.

Amino Acids↗

PubMedDate not supplied

Moderate alcohol consumption and changes in postprandial lipoproteins of premenopausal and postmenopausal women: a diet-controlled, randomized intervention study.

Moderate alcohol consumption is associated with a reduced risk of coronary heart disease. Earlier studies in men have shown that moderate alcohol consumption affects lipoprotein metabolism and hemostasis. In this diet-controlled, randomized, crossover trial, we investigated the effect on lipoprotein metabolism of moderate consumption of red wine or red grape juice with evening dinner for 3 weeks in premenopausal women using oral contraceptives and in postmenopausal women. After 3 weeks, blood samples were collected 1 hour before dinner up to 19 hours after starting dinner at 2-hour or 4-hour intervals. Plasma triglyceride concentrations and very low density lipoprotein (VLDL) triglyceride levels peaked 3 hours after dinner with wine in both premenopausal and postmenopausal women. After wine consumption, the overall high-density lipoprotein (HDL) cholesterol level was increased in postmenopausal women (mean increase 0.17 mmol/L, or 12%, p = 0.03), and the plasma low-density lipoprotein (LDL) cholesterol level was reduced in premenopausal women (mean reduction 0.35 mmol/L, or 12%, p = 0.01) as compared with grape juice consumption. The findings suggest that postprandial lipoprotein metabolism after moderate alcohol consumption differs between oral contraceptive-using premenopausal women and postmenopausal women. The response of postmenopausal women to alcohol resembled the response found in earlier studies in men.

Adult↗

PubMedDate not supplied

A PCR-aided transcript titration assay (PATTY) to measure topoisomerase I gene expression in human tumor specimens.

UNLABELLED: Topoisomerase I (topo I) inhibitors are promising anticancer agents with demonstrated activity against a wide range of solid tumors. Quantitative information on topol mRNA levels in tumor biopsies may predict response to topo I inhibitors. MATERIALS AND METHODS: A polymerase chain reaction aided transcript titration assay (PATTY) was developed to allow quantitation of topol mRNA in small samples. Concentrations of topol mRNA in total RNA samples were estimated by RT-PCR analysis in a human small cell lung cancer (SCLC) cell line (GLC,) and its topotecan (GL2C/SK and F) and camptothecin (GL2C/Campt) resistant sublines, human non-small cell lung cancer (NSCLC) and ovarian carcinoma samples. RESULTS: Topol PATTY showed a decreased topo I mRNA level in GLC2/SK and F (4.5 pg/100 ng total RNA) and GLC,/Campt (2.2 pg/100 ng total RNA), respectively, compared to the parent cell line GLC2 (5.4 pg/100 ng total RNA). Topol protein levels as measured by Western blotting were compatible with topol mRNA levels. Median (range) topol mRNA levels were 3.23 (2.33-5.10) pg/100 ng total RNA in resected NSCLC specimen (n = 6), and 2.03 (0.54-0.95) pg/100 ng total RNA in resected ovarian cancer specimen (n = 6). CONCLUSION: We conclude that topol PATTY is a new assay that quantitates topol mRNA levels in cell lines and small tumor samples.

Blotting, Northern↗

PubMedDate not supplied

99mTc-Sestamibi scanning with SDZ PSC 833 as a functional detection method for resistance modulation in patients with solid tumours.

BACKGROUND: Our aim was to determine the value of 99mTc-Sestamibi scanning as functional detection method of P-glycoprotein (Pgp) blockade by PSC 833 in solid tumour patients. PATIENTS AND METHODS: Day 1 and day 4 after 2,200 mg orally administered PSC 833 the tumour area was scanned after intravenous (i.v.) administration of 400 MBq 99mTc-Sestamibi. In tumours with net 99mTc-Sestamibi uptake and in the hepatic region K-efflux was determined. Whole blood was analyzed for 99mTc-Sestamibi, and PSC 833 levels. RESULTS: Fourteen patients were included. In the only Pgp-positive tumour with positive 99mTc-Sestamibi scanning K-efflux of 99mTc-Sestamibi decreased significantly after PSC 833 intake. A net inhibition of liver efflux of Sestamibi after PSC 833 intake was observed in all evaluable patients. PSC 833 blood levels were all above 2 mg/L during scanning; 99mTc-Sestamibi blood levels post versus pre PSC 833 were unchanged. CONCLUSIONS: PSC 833 induced modulation of K-efflux of 99mTc-Sestamibi in a Pgp positive tumour and in all patients in the liver.

ATP Binding Cassette Transporter, Subfamily B, Mem↗