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Biomedical subjects

D S Shewach

Publications and source records attributed to D S Shewach.

59 records · Page 4Linked to original sources
PubMed1983

Molecular cloning of human adenosine deaminase gene sequences.

Using a mixture of synthetic 17-mer oligonucleotides encoding the 64 possible sequences for a peptide of adenosine deaminase as probe, we have isolated a clone for adenosine deaminase mRNA sequences from a collection of T-cell cDNA recombinants. This cDNA clone, phADA-1, contains an insert of 0.8 kilobase. In addition to the peptide chosen for synthesis of the oligonucleotide probe, the complete DNA sequence predicts 16 other experimentally determined peptides. Mapping of total cellular human DNAs with several restriction enzymes revealed relatively simple patterns of hybridization with phADA-1 as probe, including a polymorphism for PvuII cleavage. In agreement with previous studies, the adenosine deaminase gene was localized by blot hybridization to chromosome 20 in a hybrid cell mapping panel. Using the cDNA as probe, an 18-kilobase EcoRI fragment of human cellular DNA was also cloned in bacteriophage Charon 4A. These adenosine deaminase clones will prove valuable in the full characterization of the cellular gene, molecular analysis of inherited enzyme deficiency associated with immunodeficiency, and regional mapping of human chromosome 20.

Adenosine Deaminase↗
PubMed1982

Characterization of Sertoli cell RNA synthetic activities in vitro at selected times during sexual maturation.

In this study, Sertoli cell RNA synthetic activity in vitro was characterized at selected times during sexual maturation. Sertoli cells, isolated from rat testes undergoing the first wave of spermatogenesis and placed in culture for 4 days, exhibited 2-fold increases in soluble ribonucleotide pools and in total RNA concentrations over the age span of 18-35 days. High performance liquid chromatographic analysis of the ribonucleotide pools in Sertoli cells cultured from 18- and 33- to 34-day-old rats revealed that, in addition to the overall age-related doubling of concentrations, uridine triphosphate (UTP) and cytidine triphosphate (CTP) pools were disproportionately increased 4- and 6-fold, respectively. In general, Sertoli cell contained relatively small amounts of UTP in comparison to several other cell types, but exhibited a high ADP:ATP ratio. A uniform 2-fold increase in the base composition of Sertoli cell RNA per mg DNA was observed over the age span of 18-35 days, with no preferential increase in any one specific nucleotide. There was no change in [3H]uridine incorporation (2 h) into RNA per cell (pmol/mg DNA), but decreased specific activity of the RNA (pmol/mg RNA) in Sertoli cells cultured from 35-day-old rats as compared to those from 18- to 19-day-old rats. Similar differences were noted in the specific activity of label incorporated into specific RNA bases. In contrast, the specific activity of the UTP-CTP soluble pool/mg DNA was only slightly increased. These data indicate that processes related to RNA synthesis in the Sertoli cell undergo a number of changes during the period of sexual maturation.

Animals↗
PubMed1982

Correlation of cytotoxicity with total intracellular exposure to 9-beta-D-arabinofuranosyladenine 5'-triphosphate.

The mechanism by which 9-beta-D-arabinofuranosyladenine produces cell death has been studied extensively, but the details remain controversial. The results presented here describe an evaluation of 9-beta-D-arabinofuranosyladenine-induced cytotoxicity in terms of the product of the total amount of the active 5'-triphosphate metabolite, 9-beta-D-arabinofuranosyladenine 5'-triphosphate (ara-ATP), which accumulated in the cells, and the duration of the exposure expressed in units of ara-ATP microM-hr. It was demonstrated that a strong correlation exists between these parameters which was not affected by the rate of accumulation of ara-ATP. In addition, inhibition of 9-beta-D-arabinofuranosyladenine deamination by 2'-deoxycoformycin did not alter the relationship between cell death and total intracellular exposure to ara-ATP. The consistency of this relationship both within and between experiments indicates that the quantitation of the total cellular exposure to ara-ATP is useful in predicting cytotoxicity.

Animals↗