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[en] Radioenzymatic assays are widely used for the quantification of a number of biogenic amines. All previous procedures have utilized methyltransferases derived from mammalian tissues. In this assay for the quantification of the trace aralkylamines, p-tyramine (p-tym) and phenylethylamine (PEA), an enzyme, tyramine N-methyltransferase isolated from sprouted barley roots was used. The enzyme was specific for phenylethylamines. Of 26 structurally-related compounds, only p-tym, PEA, m-tym and amphetamine were substrates in vitro. Theoretic maximal methylation of substrates occurred at 10-20⁰C. When TLC was used to separate the radiolabeled reaction products, a specific method was developed for p-tym and PEA. The assay had a sensitivity of 0.8 and 2.8 pg/tube with a C.V. < 5% and was applicable to human plasma and urine. Assay throughput is similar to that of other TLC based radioenzymatic assays

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[en] Various species of rodents are distinguished by their radiosensitivity (increasing): bank vole < Wistar rat < wild mouse < CC₅₇Br mouse < golden hamster < BALB mouse < guinea pig. There is a positive correlation between radiosensitivity of these species and catecholamines content in the adrenals, urea and blood; and negative correlation between radiosensitivity and adrenaline and noradrenaline concentrations in liver and spleen cells. Presumable causes of this correlation, and the possibility of application of the index under study for predicting the organism radiosensitivity and forecasting the outcome of radiation damage are discussed

[en] A spectro fluorometric method was developed for determination of brassinosteroids plant hormones based on the reaction between brassinolide and m-dansylaminophenylboronic acid. 90 μM of m-dansylaminophenylboronic acid solution was chosen as the optimal concentration of the reagent. The temperature of the reaction was 30 degree Celsius (room temperature) for 20 min duration in 5 mM phosphate buffer solution, pH 7. The excitation and emission wavelengths were 380 nm and 505 nm, respectively. Under optimal condition, linearity was found in the range 1-50 μM. Standard addition was used for the brassinosteroids determination in bio-extract samples, without any sample preparation. Limit of detection (3SD, n=10) of 0.24 μM and limit of quantitation (10SD, n=10) of 0.48 μM were obtained using sample blank with this standard addition method. Result was demonstrated to be a suitable semi-quantitative technique and was applied successfully for the determination of total brassinosteroids plant hormones equivalent to brassinolide. (author)

[en] After intra-aortic administration of ³H-angiotensin II in the rat, the radioactivity rapidly concentrates within the kidney. It was of interest to see where in the kidney this radioactivity was localized. The autographic experiments have shown that there exists a specific interaction between angiotensin II and the glomerular mesangial cells, but the presence of true biological receptors for the hormone in these mesangial cells was not demonstrated

[en] The purpose of this work was to demonstrate the presence of α-adrenoceptors in a crude membrane preparation made from rabbit bladder base and urethra. This was achieved by radioligand binding studies, using ₃H-dihydro-α-ergocryptine (₃H-DHE) as the radioligand. The specific binding, i.e. the binding that could be inhibited by 10^-₅ M phentolamine, was saturable with 73 fmol ₃H-DHE bound per mg membrane protein. Binding was at steady state after 60 min., and reversible. Rate constants for association and dissocation were 3x10₇ M^-₁ min.^-₁, and 2x10^-₂ min.^-₁, respectively. A number of compounds were tested for their abilities to complete with ₃H-DHE for the binding sites. The relative affinity of some adrenoceptor agonists was (-)-adrenaline>(-)-noradrenaline much larger than (+-)-isoprenaline. Steroselectivity was shown, since (-)-noradrenaline had 42 times higher affinity than (+)-noradrenaline. Adrenoceptor antagonists inhibited ₃H-DHE binding in the following order of potency: DHE>phentolamine much larger than (+-)-propranolol. The dissociation constant, Ksub(D), for DHE to the binding sites was estimated in three different ways. The constants were derived from saturation, competition, and kinetic studies, and gave Ksub(D) values of 1.1,1.4 and 0.7 nM, respectively. The results suggest that α-adrenoceptors were labelled by ₃H-DHE in the tissue homogenates. (author)