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Biomedical subjects

K S Cohen

Publications and source records attributed to K S Cohen.

16 recordsLinked to original sources
PubMed1998

Enteric beta-defensin: molecular cloning and characterization of a gene with inducible intestinal epithelial cell expression associated with Cryptosporidium parvum infection.

A growing body of evidence suggests that endogenous antibiotics contribute to the innate defense of mammalian mucosal surfaces. In the cow, beta-defensins constitute a large family of antibiotic peptides whose members have been previously isolated from the respiratory and oral mucosa, as well as circulating phagocytic cells. A novel bovine genomic clone with beta-defensin-related sequence [corrected] related to those of these alpha-defensins was isolated and characterized. The corresponding cDNA was isolated from a small intestinal library; its open reading frame predicts a deduced sequence of a novel beta-defensin, which we designate enteric beta-defensin (EBD). Northern blot analysis of a variety of bovine tissues revealed that EBD mRNA is highly expressed in the distal small intestine and colon, anatomic locations distinct from those for previously characterized beta-defensins. EBD mRNA was further localized by in situ hybridization to epithelial cells of the colon and small intestinal crypts. Infection of two calves with the intestinal parasite Cryptosporidium parvum induced 5- and 10-fold increases above control levels of EBD mRNA in intestinal tissues. An anchored-PCR strategy was used to identify other beta-defensin mRNAs expressed in the intestine. In addition to that of EBD, several low-abundance cDNAs which corresponded to other beta-defensin mRNAs were cloned. Most of these clones encoded previously characterized beta-defensins or closely related isoforms, but two encoded a previously uncharacterized prepro-beta-defensin. Northern blot evidence supported that all of these other beta-defensin genes are expressed at levels lower than that of the EBD gene in enteric tissue. Furthermore, some of these beta-defensin mRNAs were abundant in bone marrow, suggesting that in enteric tissue their expression may be in cells of hematopoietic origin. Extracts of small intestinal mucosa obtained from healthy cows have numerous active chromatographic fractions as determined by an antibacterial assay, and one peptide was partially purified. The peptide corresponded to one of the low-abundance cDNAs. This study provides evidence of beta-defensin expression in enteric tissue and that the mRNA encoding a major beta-defensin of enteric tissue, EBD, is inducibly expressed in enteric epithelial cells. These findings support the proposal that beta-defensins may contribute to host defense of enteric mucosa.

Amino Acid Sequence↗
PubMed1991

Nucleotide sequence of murine PCNA: interspecies comparison of the cDNA and the 5' flanking region of the gene.

Proliferating cell nuclear antigen (PCNA) RNA levels are regulated by transcription as well as changes in stability, in growing cells. We have cloned the murine PCNA cDNA and a fragment of the murine PCNA gene flanking the transcription initiation site. Comparison of the murine deduced amino acid sequence with the PCNA sequence from rat, human, Drosophila, Saccharomyces cerevisiae, and higher plants, reveals extensive homology between species. The homology is likely to be related to the fundamental role of PCNA as an auxiliary protein for DNA replication. Consensus sequences for transcriptional regulatory factors identified within 520 bp 5' of the cap site of the murine PCNA gene include: an inverted CCAAT site, an enhancer core element (EBP-1), three cAMP-response elements (CRE-BP), one AP-2 site, three Sp1 sites, and two octamer sequences. The first 20 bp of the transcriptional unit are homologous to an initiator element, which may direct transcription from RNA polymerase II in the absence of a TATAA box. The consensus elements in the murine PCNA gene are similar in sequence and/or location to elements identified in the genes for human, Drosophilia, and yeast PCNA.

Amino Acid Sequence↗
PubMed1990

Interleukin 2-induced expression of proliferating cell nuclear antigen is regulated by transcriptional and post-transcriptional mechanisms.

Proliferating cell nuclear antigen (PCNA) is an auxiliary protein required for leading strand DNA synthesis by polymerase delta. Steady-state levels of PCNA RNA increase during interleukin 2 stimulated G1 activation of cloned T cells (L2 cells) and correlate with expression of the PCNA protein. We demonstrate that the initial (G1) rapid rise in PCNA RNA levels is predominantly related to increased transcription. The slower rate of increase in PCNA RNA at the initial G1-S transition is related to transcription as well as increased stability of the PCNA message and partially requires protein synthesis. These data provide a foundation for further investigation of the mechanisms of increased stability and transcription of PCNA.

Animals↗
PubMed1978

Techniques to improve the seating of castings.

A convergence of 20 degrees for full crowns is the most likely to be seen clinically, as determined by random measurements taken at a dental laboratory. Castings did not seat without cement, by an average of 215 micron at 10 degrees of convergence, or by 99 micron at 20 degrees of convergence. Biting forces will seat a casting approximately 150 micron, but will cause random concentrations of force against tooth structure, thus compressing it. All castings tend to rebound from this position. Zinc phosphate and polycarboxylate cemented crowns seated to 33 micron and 20 micron respectively when relieved, but each were elevated to 112 micron when not relieved. A silicophosphate cement displaced crowns with 20 degrees of convergence 122 micron under "ideal" clinical conditions, even when relieved; and with CBA 9080 cement, more than 500 micron. A die relief method was found to be the most suitable of the three casting compensation techniques. Casting retention, after cementation, was increased by 25%.

Cementation↗