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Biomedical subjects

R Israeli

Publications and source records attributed to R Israeli.

At least 37 records · Page 2Linked to original sources
PubMed1979

Effect of dibromochloropropane on human testicular function.

Severe impairment of spermatogenesis was found in 18 (78%) of 23 workers after exposure to 1,2-dibromo-3-chloropropane (DBCP). Azoospermia associated with elevated plasma follicle-stimulating hormone was diagnosed in 12 workers whose exposure time to DBCP varied from 100 to greater than 6,000 h. Oligospermia and normal plasma follicle-stimulating hormone were found in six employees with exposure times between 34 and 95 h. Plasma luteinizing hormone, testosterone and thyroxine were within the normal range. Testicular biopsy showed selective atrophy of the germinal epithelium, intact Sertoli cells and normal appearance of Leydig cells. The mechanism and potential reversibility of these testicular changes are still to be evaluated.

Adult↗
PubMed1978

Suppressive effect of 1,2-dibromo-3-chloropropane on human spermatogenesis.

Azoospermia was diagnosed in six factory workers who had been chronically exposed to 1,2-dibromo-3-chloropropane. Infertility was the presenting symptom in two patients and a decrease in libido or impotence characterized the others. Hormone studies revealed elevated plasma follicle-stimulating hormone levels and normal plasma luteinizing hormone and testosterone concentrations. Testicular biopsy showed selective atrophy of the germinal epithelium, intact Sertoli cells, and a normal appearance of a relatively increased number of Leydig cells.

Adult↗
PubMed1978

Specific binding of messenger RNA and methionyl-tRNAfMet by the same initiation factor for eukaryotic protein synthesis.

Affinity chromatography on columns containing globin mRNA, R17 phage mRNA, or double-stranded RNA linked to cellose is used to demonstrate unequivocally that the eukaryotic initiation factor (eIF-2) that forms a ternary complex with Met-tRNAf and GTP also binds tightly to these RNA species. Affinity chromatography of reticulocyte ribosomal wash yields over 100-fold purification of Met-tRNAf-binding factor. This factor is eluted as one of the most tightly bound proteins, and is active in protein synthesis even after passage over a column of double-stranded RNA-cellulose. eIF-2 binds mRNA and double-stranded RNA in distinctly different modes, protecting essentially all sequences in double stranded RNA, but very few in mRNA, against digestion with ribonuclease. Apparently, eIF-2 recognized the A conformation of double-stranded RNA, but not its sequence. By contrast, globin, Mengo virus, R17 and vesicular stomatitis virus mRNA are shown to possess a high-affinity binding site for eIF-2 that is absent in negative-strand RNA of vesicular stomatitis virus, an RNA that cannot serve as messenger. The results support the concept that eIF-2, the initiation factor that binds Met-tRNAf, recognizes an internal sequence in mRNA essential for protein synthesis.

Base Sequence↗
PubMed1978

Translational control: recognition of the methylated 5' end and an internal sequence in eukaryotic mRNA by the initiation factor that binds methionyl-tRNAfMet.

Structural analogs of the methylated 5' end (cap) of eukaryotic mRNA, such as 7-methylguanosine 5'-monophosphate, specifically inhibit both GTP-dependent binding of Met-tRNAfMet and binding of globin mRNA to eukaryotic initiation factor 2 (eIF-2). Addition of purified eIF-2 effectively relieves the cap analog-induced inhibition of globin mRNA translation. The analog competitively inhibits the function of eIF-2 and of mRNA in protein synthesis. Binding to eIF-2 of capped mRNA as well as noncapped mRNA, such as Mengo virus RNA, can be inhibited completely by free cap molecules, but much more cap is needed to inhibit binding of Mengo virus RNA. mRNA, whether or not it is capped, competitively inhibits the binding of Met-tRNAfMet to eIF-2. These results provide compelling evidence that eIF-2 recognizes mRNA. It is shown that binding of mRNA to eIF-2 is primarily at an internal sequence, and secondarily through the cap. A model for the function of eIF-2 is presented that can account for all these properties. This model can provide a molecular basis for the differential translation of mRNA species, whether or not they are capped.

Eukaryotic Cells↗