Nuclear medicine-important advances in clinical medicine: the role of nuclear and ultrasonic thyroid imaging

The Scientific Board of the California Medical Association presents the following inventory of items of progress in nuclear medicine. Each item, in the judgment of a panel of knowledgeable physicians, has recently become reasonably firmly established, both as to scientific fact and important clinical significance. The items are presented in simple epitome and an authoritative reference, both to the item itself and to the subject as a whole, is generally given for those who may be unfamiliar with a particular item. The purpose is to assist busy practitioners, students, research workers or scholars to stay abreast of these items of progress in nuclear medicine that have recently achieved a substantial degree of authoritative acceptance, whether in their own field of special interest or another.The items of progress listed below were selected by the Advisory Panel to the Section on Nuclear Medicine of the California Medical Association and the summaries were prepared under its direction.     

Modulation of endogenous prostaglandins by thymosin-α1 in lymphocytes

The effects of thymosin-α₁ on the stimulation of specific release of prostaglandin E₂ (PGE₂) from splenic lymphocytes and thymocytes were studied. Experiments were also performed to study in parallel the absolute levels of thymosin-α₁ in the blood and the induction of serum FTS activity and of azathioprine sensitivity of spleen cells from adult thymectomized (ATx) mice. A significant difference in the release of PGE₂ between normal splenocytes and splenocytes from ATx mice was observed. Thymosin-α₁ at certain concentrations was able to stimulate PGE₂ release from lymphocytes of ATx mice while inhibiting release in lymphocytes of normal mice. Also, thymocytes were stimulated to release PGE₂ after incubation with α₁ in a manner similar to that seen in spleen cells of ATx mice. Approximately the same concentration of α₁ was found to also correct the low azathioprine sensitivity of splenocytes from ATx mice. Determinations of FTS-like activity in the blood and the pharmacokinetics of α₁ after administration of this synthetic molecule show a clear dissociation. A maximum peak of α₁ activity was obtained after 1 hr, while maximal FTS-like activity was observed after 24 hr. The inhibition of the induction by α₁ of FTS-like activity and of Thy 1.2 antigen by indomethacin suggests that the action of α₁ requires prostaglandin biosynthesis.     

The stimulation of glycogenolysis and gluconeogenesis in isolated hepatocytes by opioid peptides.

The opioid agonists [leucine]enkephalin, [D-Ala2,D-Leu5]enkephalin and dynorphin-(1-13)-peptide, but not morphine, stimulated the conversion of [2-14C]pyruvate into glucose and glycogenolysis when added directly to isolated hepatocytes. Naloxone produced a small but significant inhibition of both the basal and stimulated rate of incorporation of label into glucose but had no effect on the total glucose output by the cells. The effects of the opioid peptides were mediated by a cyclic AMP-independent mechanism.     

Stable isotope-labeled vitamin D, metabolites and chemical analogs: synthesis and use in mass spectrometric studies

Methods for the measurement of vitamin D and its metabolites using stable isotope-labeled internal standards and mass spectrometry are reviewed. The synthesis of both labeled and unlabeled standards is illustrated, and details of the synthesis of (26,26,27,27,27(-2)H5)-25,26-dihydroxyvitamin D3 and (28,28,28(-2)H3)-24,25-dihydroxyvitamin D2 are given. The use of in vitro biologic systems for the production of further metabolites of deuterated 25-hydroxyvitamin D3 is discussed. Use of deuterated 25-hydroxydihydrotachysterol3 as a substrate in the isolated perfused rat kidney has provided valuable data for the assignment of structure to a number of metabolites of 25-hydroxydihydrotachysterol3 formed in this system.