Biomedical subjects

D Samols

Publications and source records attributed to D Samols.

58 records · Page 4Linked to original sources

PubMed1983

Isolation and characterization of the gene coding for cytosolic phosphoenolpyruvate carboxykinase (GTP) from the rat.

The gene for cytosolic phosphoenolpyruvate carboxykinase (GTP) [GTP:oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.32] from the rat was isolated from a recombinant library containing the rat genome in phage lambda Charon 4A. The isolated clone, lambda PCK1, contains the complete gene for phosphoenolpyruvate carboxykinase and approximately equal to 7 kilobases (kb) of flanking sequence at the 5' end and 1 kb at the 3' terminus. Restriction endonuclease mapping, R-loop mapping, and partial DNA sequence assay indicate that the gene is approximately equal to 6.0 kb in length (coding for a mRNA of 2.8 kb) and contains eight introns. Southern blotting of rat DNA digested with various restriction enzymes shows a pattern predicted from the restriction map of lambda PCK1. A control region at the 5' end of the gene contained in a 1.2-kb restriction fragment was isolated and subcloned into pBR322. This segment of the gene contains the usual transcription start sequences and a 24-base sequence virtually identical to the sequence found in the 5'-flanking region of the human proopiomelonocortin gene, which is known to be regulated by glucocorticoids. The 1.2-kb fragment of the phosphoenolpyruvate carboxykinase gene can be transcribed into a unique RNA fragment of predicted size by an in vitro transcription assay.

Animals↗

PubMed1979

Genomic organization in the flesh fly Sarcophaga bullata.

The genome of the flesh fly Sarcophaga bullata has been characterized both cytologically and biochemically. S. bullata has a haploid DNA level of 0.61 picograms which is five times larger than the haploid genome size of Drosophila melanogaster. Reassociation kinetics of Sarcophaga DNA shows that its sequence organization is very similar to that of D. melanogaster in having a very large proportion of single copy DNA (81%) and only small amounts of highly and moderately repetitive DNA (9% and 6%, respectively). cRNAs from all three sequence classes were prepared and their cytological distributions on biploid and polytene cells determined by in situ hybridization. The cytological distribution of the highly repetitive probe was found to be restricted to the centromeric heterochromatin of two of the five autosomes and this sequence class was also found to be markedly underreplicated in polytene foot-pad cells. No highly repetitive DNA was localized on either of the sex chromosomes, but only on the two large centromeric regions of chromosomes C and E. Moderately repetitive DNA was found uniformly distributed on all of the autosomes in both testis and polytene foot-pad squashes. As in the case of the highly repetitive sequence probe, no moderately repetitive DNA was detected on either the X or Y chromosomes. Moderately repetitive DNA in Sarcophaga was also shown to have the "Drosophila type" pattern of sequence interspersion with a moderately repetitive element of congruent to 5,000 nucleotides adjacent to a unique element of greater than 10,000 nucleotides. The Sarcophaga genome is the largest for which this type of interspersion has so far been demonstrated.

Animals↗

PubMed1979

Characterization of extrachromosomal DNA in the flesh fly Sarcophaga bullata.

The polytene pupal foot pad cells of the flesh fly Sarcophaga bullata contain numerous extrachromosomal DNA containing granules. We have determined both the origin and the nature of the DNA sequences present in these granules. Studies done with quinacrine staining of seven day old pupal foot-pad polytene nuclei showed that the granules fluoresced very brightly while the chromosomal bands to which the granules were attached did not. The only other highly fluorescent regions of the polytene karyotype were the centromeric heterochromatin of chromosomes C and E and several bands associated with the nucleolus of Chromsome A. When polytene nuclei were hybridized in situ with cRNA made from highly repetitive DNA, many of the granules positively labeled. Most of the label on these slides was concentrated on the centromeric heterochromatin of chromosomes C and E. Quinacrine staining of the foot-pad cells at very early stages of pupal development showed that when granules were present, they were always closely associated with the same two centromeric regions, those of chromosomes C and E. Since the highly repetitive DNA located in these centromeric regions is underreplicated, we conclude that the granules result from an extrusion process which takes place early during the polytenization of these cells. The chromosomal integrity of the centromeric heterochromatin of chromosomes C and E is apparently disrupted and repetitive sequences are dissociated from the chromosomes as DNA granules which then secondarily become associated with chromosomal bands throughout the nucleus.

Animals↗

PubMedDate not supplied

Expression of rabbit C-reactive protein in transgenic mice inhibits development of antigen-induced arthritis.

OBJECTIVE: C-reactive protein (CRP) is a plasma protein of hepatic origin thought to play an important role in host defences. We used transgenic mice, capable of expressing high levels of rabbit CRP (serum concentration>50 microg/mL) in response to dietary manipulation, to determine whether high levels of this acute-phase reactant can alter the course of experimentally induced monoarticular arthritis. METHOD: Arthritis was induced by a single injection of methylated bovine serum albumin (mBSA) on day 0 followed by injections of interleukin (IL)-1beta. RESULTS: In transgenic animals in which CRP expression had been suppressed (serum concentration<10 microg/mL), inflammatory arthritis began to develop by day 4 and was fully developed by 7 days after the mBSA challenge. This arthritis was characterized by marked inflammatory cell infiltrates in soft tissues, synovitis, pannus, cartilage loss, and bone erosion. By contrast, when CRP expression was induced, resulting in serum concentrations>50 microg/mL on the day of mBSA and IL-1beta injections, the inflammatory response was dramatically reduced at day 7. These mice manifested little to no evidence of joint inflammation. This anti-inflammatory effect of CRP was seen in animals with high CRP levels on days 0-1 following immunization and did not require elevated CRP levels during the period of rapid inflammatory progression, 4-7 days after challenge. CONCLUSION: CRP, expressed at the time of antigenic stimulation, effectively blocked the subsequent development of inflammatory arthritis in this model by altering the immune or inflammatory responses.

Acute-Phase Reaction↗