Thyrotropin Releasing Hormone (TRH) suppresses stress induced eating

Thyrotropin releasing hormone (TRH) administered both intraventricularly and parenterally suppressed stress induced eating (using the mild tail pinch model) in a dose related manner. This suppression was partially reversed by intraventricular administration of the long acting synthetic enkephalin analog, D-Ala-Met-Enkephalin (p < 0.01). Preliminary data suggests that the naturally occurring metabolic breakdown product of TRH, histidyl-proline-diketopiperazine, may be the active substance with TRH acting as a pro-hormone. The TRH effect was present in hypophysectomized animals showing that the TRH-induced decrease in food ingestion was not secondary to an increase in thyrotropin or thyroid hormones. TRH did not alter blood glucose levels. Our data is compatible with a possible physiological role for TRH, as a peptidergic mediator of satiety acting as a direct antagonist of the lateral hypothalamic of satiety acting as a direct antagonist of the lateral hypothalamic enkephalin-mediated feeding center.     

Methods for study of mutations and mutagenesis in human lymphocytes

Detailed methods are presented for measurement and study of in vivo mutations and in vitro mutagenesis in human lymphocytes. The methods described include preparation of conditioned medium containing interleukin-2, enumeration of mutant clones, in vitro mutagenesis, and expansion of mutant clones for further study.     

Lanthanide probes in biological systems: characterization of luminescence excitation spectra of terbium complexes with proteins

Upon irradiation in the ultraviolet region aromatic chromophores may transfer energy to a nearby Tb³⁺, which in turn emits a green phosphorescence. This paper reports the characterization of the ultraviolet excitation spectra of aromatic chromophores capable of transferring energy to Tb³⁺ by monitoring of the green Tb³⁺ emission in the 540-550 nm region. Results are included for complexes containing phenyl, hydroxyphenyl, indole. and catechol chromophores. Characteristic excitation spectra are presented for the aromatic chromophores occurring as side chains in proteins. Though it is preferable to compare entire excitation spectra, the ratio of intensities at 292 to 276 nm, R, is suggested as a useful diagnostic criterion. Numerical R values are indicative of the following aromatic side chains as the energy donor to Tb³⁺: R <0.2, unionized tyrosine; R = 0.5 to 1.0, tryptophan; and R > 1.8. ionized tyrosine. Tlie phenylalanyl chromophore displays a definitive excitation spectrum at shorter wavelengths. For ovotransferrin R = 0.9 and comparison of the full excitation spectra suggests that it contains comparable contributions from both ionized tyrosine and tryptophan side chains. Some difficulties in obtaining reliable excitation spectra are described. An analysis of inner-filtering of incident light reveals that for an absorbance less than 0.8 the excitation spectrum is broadened and flattened compared to the absorption spectrum. At maximum absorbances greater than 0.8 false maxima may appear to both sides of a real maximum. Two spurious maxima in an excitation spectrum were generated in a Tb³⁺ complex and compared to the correct excitation spectrum of the same complex obtained at lower absorbance.     

Molecular basis of X-ray-induced mutation at the HPRT locus in human lymphocytes

Human lymphocytes lacking functional HPRT enzyme after a dose of 300 rad X-radiation were cloned and the monoclonal populations expanded so that sufficient genomic DNA was obtained for Southern analysis. A total of 33 mutant clones were analysed. Wild-type clones showed no evidence of changes to the HPRT gene resolvable by Southern banding patterns whereas 17 of 33 mutant clones showed changes. The alterations observed included total gene deletions (3 clones) and partial gene deletions with or without the appearance of novel bands (12 clones). Two clones showed the appearance of novel bands only. There were no changes observed in 16 of the 33 mutant clones. Three clones showed changes inconsistent with deletion of portions of the gene. In these clones inversion seems to have been the most likely cause of the mutation. The spectrum of gene alterations following ionizing radiation appears different to that previously observed for spontaneous mutations. Consequently, ionizing radiation or radiomimetic agents would appear to be aetiologic, at the most, for only a minor proportion of in vivo somatic mutations.     

Novel inhibitors of the αvβ3 integrin—lead identification strategy

A novel approach to inhibition of the αvβ3 integrin is described, which uses compounds designed to generate nM potency without using the arginine binding site.