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Biomedical subjects

J Horowitz

Publications and source records attributed to J Horowitz.

32 records · Page 2Linked to original sources
PubMed1978

Replacement of pseudouridine in transfer RNA by 5-fluorouridine does not affect the ability to stimulate the synthesis of guanosine 5'-triphosphate 3'-diphosphate.

The requirement for ribothymidine and pseudouridine in the TpsiCG loop of tRNA for its activity in the ribosome and tRNA-stimulated synthesis of guanosine 5'-triphosphate 3'-diphosphate (pppGpp) by stringent factor has been tested by the use of a purified tRNAPhe (883 pmol of phenylalanine incorporated/A260 unit) in which 92% of the pseudouridine, 98% of the ribothymidine, 98% of the dihydrouridine, and 88% of the uridines were substituted by 5-fluorouridine. This tRNA was quantitatively as active as control tRNA in inducing pppGpp synthesis. With loose-couple ribosomes, the concentration of tRNA needed to give half-maximal reaction was 0.07 micrometer for both normal and fluorouridine-substituted tRNA, with vacant tight-couple ribosomes it was 0.05 micrometer, and with tight couples carrying poly(Phe)-tRNA at the P site the value was 0.02 micrometer. These results show that at the level of intact tRNA there is no special requirement for modified bases in the TpsiCG loop of tRNA in the synthesis of pppGpp.

Escherichia coli↗
PubMed1977

19F nuclear magnetic resonance of 5-fluorouridine-substituted tRNA1Val from Escherichia coli.

The 19F NMR spectrum of Escherichia coli tRNA1Val in which [5-19F]uridine replaces 93% of all uridine and uridine-derived residues has been examined at 93.6 and 235 MHz. The resolution of 11 peaks and visibility of two additional shoulders at either frequency for the 14 FUra residues in the molecule attests to the excellence of 19F as a probe for the structure of tRNA1Val in solution. No significant gain in resolution was attained at the higher frequency. A comparison of the relative areas in the different regions of the 19F spectrum of mixed [FUra]tRNAs with that of [FUra]tRNA1Val suggests that the three single resonances at lowest field in the region 86.5 to 88.5 ppm upfield from trifluoroacetate correspond to the three invariant bases which form tertiary hydrogen bonds in all tRNAs, namely, 8 (U or s4U), 54 (T), and 55 (phi) in unsubstituted tRNAs.

Escherichia coli↗
PubMed1975

Norepinephrine-induced depolarization of skeletal muscle cells.

I.v. administration of norepinephrine to anesthetized hamsters was followed by a significant depolarization of the cell membranes of skeletal muscle (gracilis anticus and sartorius). The occurrence of this depolarization in consistent with the suggestion that changes in ionic distribution across the cell membrane are associated with activation of non-shivering thermogenesis in muscle cells as has been proposed for brown adipocytes.

Animals↗
PubMedDate not supplied

Dead Sea bath salts for the treatment of rheumatoid arthritis.

Thirty patients with classical or definite rheumatoid arthritis were randomly divided into two groups of fifteen patients each of similar age, sex, duration and severity of disease, and medical treatment. All patients were treated once a day with bath salts heated to 35 degrees C for twenty minutes. Group I received Dead Sea bath salts and Group II, the control group, received sodium chloride (NaCl). The study was double-blind and of two weeks' duration. All patients were evaluated by one rheumatologist both before treatment, and two weeks later at the end of the treatment period. Follow-up evaluations were made one and three months after conclusion of the treatments. The clinical parameters evaluated included duration of morning stiffness, fifteen meter walk time, hand-grip strength, activities of daily living, circumference of proximal interphalangeal joints, number of active joints, Ritchie index and the patient's own assessment of disease activity. The laboratory parameters evaluated included erythrocyte sedimentation rate and serum levels of amyloid A, rheumatoid factor, sodium, potassium, calcium and magnesium. A statistically significant improvement (p less than 0.01 or p less than 0.05) was observed in Group I only, in most of the clinical parameters assessed. Maximal therapeutic effect was obtained at the end of the treatment and lasted up to one month.

Arthritis, Rheumatoid↗