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Biomedical subjects

H Tamir

Publications and source records attributed to H Tamir.

At least 91 records · Page 5Linked to original sources
PubMed1979

Localization of a highly specific neuronal protein, serotonin binding protein, in thyroid parafollicular cells.

A highly specific serotonin binding protein (SBP) has been found in serotonergic neurons in both brain and gut. This protein has an extremely high affinity for serotonin and may be a storage protein. Serotonin is found in many endocrine cells, including parafollicular cells of the sheep thyroid, as well as in neurons. SBP is also present in sheep thyroid. The present study was done to localize the protein in the gland. Thyroid glands were divided into five segments. Concentrations of serotonin and SBP, as well as parafollicular cell volume were measured in each. Serotonin was assayed by enzymatic conversion to melatonin using tritiated S-adenosylmethionine. SBP was assayed by molecular sieve chromatography on sephadex G-50. The relative volume of parafollicular cells was obtained by stereological analysis of electron micrographs. Experiments were also done to demonstrate these cells by histofluorescence and radioautography following incubation with tritiated 5-hydroxytryptophan. Good correlations were found between serotonin and SBP concentrations, and parafollicular cell volume. These peaked in the rostro-central portion of the gland and were minimal at the poles. We conclude that thyroid SBP is probably localized in parafollicular cells.

Animals↗
PubMed1976

Is the serotonin binding protein (SBP) a soluble storage form for serotonin?

The binding of serotonin to a soluble, high affinity binding protein (SBP) present in synaptosomes and assoicated with serotonergic tracts, has now been studied for the effect of drugs and, in particular, drugs interacting with contractile proteins. Vincristine, vinblastine, and cytochalasin B were found to cause 50% inhibition of serotonin binding to SBP at 1.5 X 10(-6)M, 7.5 X 10(-6)M and 50 X 10(-6)M, respectively. Colchicine did not affect the binding at 1 X 10(-3)M. When vinblastine was injected intraventricularly, the binding capacity of SBP isolated from brain 20 and 26 hours after injection was decreased 42% and 60% respectively. It is concluded that SBP is an actin-like contractile protein, distinct from microtubulin, and not associated with membranes. The storage of serotonin through binding to a protein with such properties suggests that this compartment is in some way involved in the translocation or transfer of serotonin from one part of the cell to another.

Animals↗
PubMed1970

Studies of the mechanism of anthranilate synthase reaction.

The enzyme anthranilate synthase catalyzes the formation of anthranilate form either chorismate and glutamine or chorismate and ammonia. In the aromatization of chorismate, a hydroxyl group and an enolpyruvyl group must be eliminated. Elimination of the enolpyruvyl group of chorismate is accompanied by protonation to form pyruvate. The source of this proton was investigated by performing the enzymatic reaction in 99.7 per cent D(2)O. The isolated pyruvate contained close to an atom of deuterium in the methyl group. High resolution mass spectra also revealed that about 6 per cent of the deuterio pyruvate contains a -CHD(2) species. Thus, the results obtained conclusively demonstrate that in the formation of the pyruvate, the third hydrogen of the methyl group arises from water and not by intramolecular shift of a hydrogen from the ring of chorismate.

Chemical Phenomena↗