Biomedical subjects

P Telleman

Publications and source records attributed to P Telleman.

7 recordsLinked to original sources

PubMed2000

The role of the Brambell receptor (FcRB) in liver: protection of endocytosed immunoglobulin G (IgG) from catabolism in hepatocytes rather than transport of IgG to bile.

The Brambell receptor (FcRB) mediates functions of both immunoglobulin G (IgG) transport, transmitting immunity from mother to young, and IgG protection, making IgG the longest surviving of all plasma proteins. Reflecting its role as transport receptor (termed FcRn, for neonatal rat intestine, the tissue from which it was first cloned), FcRB is expressed antenatally in the rabbit, mouse and rat fetal yolk sac and in human placental syncytiotrophoblasts, and neonatally in the intestinal epithelium of mice and rats. Reflecting its role as protection receptor (FcRp), FcRB is expressed in the vascular endothelium throughout life, where it protects IgG from the on-going catabolic activities of this tissue. FcRB detected in hepatocytes was hypothesized to mediate transport of IgG from serum to bile, thus potentially extending the transport expression (FcRn) of this receptor beyond the perinatal period. Our results show serum-to-bile transport of IgG to be unaffected in mice functionally deleted for FcRB. Accordingly, the hypothesis is rejected that FcRB functions as transport receptor (FcRn) in liver. The default conclusion is that FcRB in hepatocytes functions as FcRp, serving to protect IgG from catabolism in hepatocytes that accompanies the endocytic activity of these cells. We conclude that there remains to date no evidence of an FcRn-like transport function of the Brambell receptor beyond the perinatal period, after which the FcRp function of the receptor predominates, paralleling the endocytic activities of the associated tissues.

Animals↗

PubMed1997

An optimized method for cell-based phage display panning.

BACKGROUND: Traditional methods of phage display panning, bind purified antigen to plates or other solid phases to which libraries are then applied, followed by vigorous washings in detergent-supplemented buffers to select for specific phage Fab. These methods are not directly applicable to antigens in their native environment on cell surfaces or in settings where the target antigen is unknown. OBJECTIVES: To develop a model antigen system employing whole cells rather than purified protein immobilized on a substrate; to optimize methods for phage display panning using a cell-based system. RESULTS: Specificity of binding of phage Fab to antigen on cells was demonstrated by output titer and by flow cytometry. Output titers showed a plateau and binding advantage, after four washes, corresponding to removal of most non-specifically bound phage. Enrichment advantage was independent of input phage number. Longer incubation times, to cell tolerance, improved specific binding. Temperature had modes impact as a variable in the panning and washing. An increase in output titers paralleled enrichment for specific phage Fab. CONCLUSION: An optimized method applied to whole cells can productively enrich specific phage Fab in mixtures with large excesses of non-specific phage Fab over several rounds of panning.

Animals↗

PubMed1996

Spectrum of spontaneously occurring mutations in the HPRT gene of the Chinese hamster V79 cell mutant V-H4, which is homologous to Fanconi anemia group A.

The mitomycin C (MMC)-hypersensitive Chinese hamster V79 cell mutant V-H4 has a cellular phenotype similar to Fanconi anemia (FA), and has been shown to be homologous to FA group A. To examine consequences of the defect in V-H4 cells on spontaneous mutagenesis, we studied the frequency and nature of spontaneous mutations at the hypoxanthine phosphoribosyltransferase (HPRT) locus in this mutant and the parental V79 cells. The mutation rates expressed as the number of mutations per cell per generation were 8.7 x 10(-7) and 3.7 x 10(-7) for V-H4 and V79 cells respectively. The molecular spectrum of 42 spontaneous hprt mutants of V-H4 cells was determined and compared with the previously described spectrum of spontaneous mutations at the HPRT locus of Chinese hamster V79 cells. The spectra of spontaneous mutations in the hprt gene of both cell lines are predominated by base pair substitutions and splice mutations. Among the base changes, V-H4 shows a larger frequency of transitions (13/42; 31%) than transversions (3/42; 7%), whereas in V79 transversions are observed more often than transitions (P < 0.001; Wilcoxon test). The frequency of splice mutations in V-H4 (17/42; 40%), which affects exon 4 almost exclusively, is not significantly different from V79. The fraction of deletions in V-H4 is low (6/42; 14%), and comparable to the level in V79. This is in contrast with the published molecular spectrum of spontaneous hprt mutants in FA (group D) cells, which consists predominantly of deletions.

Animals↗

PubMed1995

A new complementation group of mitomycin C-hypersensitive Chinese hamster cell mutants that closely resembles the phenotype of fanconi anemia cells.

Three Mitomycin C (MMC)-hypersensitive mutants (CL-V1B, CL-V5B, and CL-V101B) were isolated from Chinese hamster V79B cells by the replica plating technique. In comparison to the parental cell line, CL-V1B, CL-V5B, and CL-V101B show about a 22-, 32-, and 13-fold increased sensitivity to MMC, respectively (judged by the D10). These mutants are also sensitive to other DNA cross-linking agents, such as 1,2,3,4-diepoxybutane (9-, 19-, and 12-fold, respectively) and cis-diamminedichloroplatinum(II) (17-, 12-, and 6-fold, respectively). CL-V5B and CL-V101B display an exclusive sensitivity to DNA cross-linking agents, whereas CL-V1B also shows an increased sensitivity to monofunctional alkylating agents, such as methyl methanesulfonate (3-fold) and ethyl methanesulfonate (2-fold), and UV254mm (2-fold). Approximately 2-3-fold higher levels of spontaneous chromosomal aberrations are found in these three mutants in comparison to wild-type V79B cells. At a MMC survival level of 80%, CL-V5B demonstrates a 16-fold higher level of MMC-induced chromosomal damage than V79B. Despite phenotypical heterogeneity within this group of mutants, hybrid clones derived after fusion remained MMC sensitive, indicating that these mutants belong to the same complementation group. To determine whether the mutants represent a new complementation group among other Chinese hamster cell mutants that also display hypersensitivity to MMC, CL-V1B cells were fused with mutants representing different complementation groups i.e., irs1, irs3, irs1SF, UV20, UV41, V-H4, and V-C8 cells. In all cases, the derived hybrids regained MMC sensitivity similar to wild-type cells, indicating that the CL-V1B mutant represents a new complementation group. The phenotype of CL-V1B, CL-V5B, and CL-V101B cells closely resembles the phenotype of Fanconi anemia cells, suggesting that these hamster mutants could be defective in a gene that is involved in this disorder.

Alkylating Agents↗

PubMed1994

Mutagenic response and repair of cis-DDP-induced DNA cross-links in the Chinese hamster V79 cell mutant V-H4 which is homologous to Fanconi anemia (group A).

Previously, it has been shown that the V-H4 mutant of Chinese hamster V79 cells is homologous to Fanconi anemia (FA) group A cells. This hamster cell mutant shows a specific sensitivity to DNA cross-linking agents; therefore, the induction and repair of DNA cross-links were studied in V-H4 and wild-type V79 cells after cis-DDP treatment by the DNA alkaline elution technique. A significant difference in repair of these lesions in V-H4 and wild-type cells was observed. After the cis-DDP treatment (24 h) about 3 times more cross-links remained in V-H4 cells in comparison to the parental V79 cells. These results indicate that the process of cross-link repair in V-H4 cells is hampered when compared to that of wild-type cells. To assess the effect of slower removal of DNA cross-links on the mutability of V-H4, the induction of mutants at the hypoxanthine-guanine phosphoribosyltransferase locus (HPRT) by cis-DDP was studied in V-H4 and V79 cells. Despite the increased cytotoxicity of cis-DDP to V-H4 cells, the mutation induction at the HPRT locus was not significantly different in both cell lines, but when the frequency of the hprt mutants was plotted against survival, hypomutability was observed in V-H4 cells after the cis-DDP treatment.

Animals↗

PubMed1993

Genetic diversity of mitomycin C-hypersensitive Chinese hamster cell mutants: a new complementation group with chromosomal instability.

A Chinese hamster cell mutant (V-C8) isolated previously, which is approximately 100 fold more sensitive to mitomycin C (MMC) than its parental wild-type V79 cells (judged by D10 values), was further characterized. V-C8 cells exhibit an increased sensitivity towards other cross-linking agents, such as cis-DDP (approximately 40-fold), DEB (approximately 30-fold), and also to adriamycin (approximately 5-fold), and the monofunctional alkylating agents: MMS (approximately 5-fold) and EMS (approximately 6-fold). V-C8 cells show a higher level induction of chromosomal aberrations by cross-linking agents (MMC, cis-DDP, and DEB) and an increased level of spontaneous chromosomal aberrations in comparison to the wild-type V79 cells. To determine whether the V-C8 mutant represents a new complementation group among Chinese hamster cell mutants that also display the extreme sensitivity to MMC, V-C8 cells were fused with irs1, irs1SF, UV20, UV41, and V-H4 cells. In all cases, the derived hybrids regained the MMC sensitivity similar to wild-type cells, indicating that the V-C8 mutant belongs to a new sixth complementation group.

Animals↗

PubMed1992

Effect of ploidy on transcription levels in cultured rat aortic smooth muscle cells.

Aging and hypertension increase the number of polyploid smooth muscle cells (SMC) in a blood vessel. We assessed the effect of ploidy on the transcription of several genes in SMC cultures derived from newborn and adult rats. In diploid and tetraploid subcultures of SMC from newborn rats, RNA expression of the genes assayed is linked with ploidy. However, when phenotypically different SMC cultures derived from newborn and adult rats were compared, transcription levels varied from gene to gene and not linked with the ploidy. Thus, differences in gene expression due to polyploidy are superimposed on those due to other phenotypical features.

Actins↗