Reaction of N-(3-pyrene)maleimide with thiol groups of reticulocyte ribosomes

The reaction of N-(3-pyrene)maleimide with thiol groups of rabbit reticulocyte ribosomes offers a possible fluorescent probe for studying ribosomal structure and conformation. At relatively low concentrations of N-(3-pyrene)maleimide a group of 30-40 readily reactive sulfhydryl residues is derivatized. The major ribosomal proteins containing these thiol groups are identified as S2 + S3, S5, S7, S8, S29, S31, S32, L1, L5, L6, L10 + L14, L15, L18 + L19, and L36. Ribosomal activity, as measured by the nonenzymic binding of phenylalanyl-tRNA and polyphenylalanine synthesis, is inhibited by this degree of reaction with N-(3-pyrene)maleimide. The inhibition is relieved by the prior binding of polyuridylic acid to the ribosomes while the extent of derivatization by N-(3-pyrene)-maleimide is diminished only slightly. The average relative polarization of the fluorescence of the ribosomal bound N-(3-pyrene)maleimide changes significantly with the degree of derivatization of ribosomal thiol groups or with the binding of polyuridylic acid, indicating the value of such a fluorescent thiol-derivatizing agent as a probe of ribosomal structure.

N-Isopropyl derivatives of dopamine and 5,6-dihydroxy-2-aminotetralin

Secondary and tertiary amino homologs of the title compounds have been prepared, bearing an N-isopropyl group. In peripheral evaluation, certain members of the series exhibited beta-adrenergic agonist effects of lower activity than isoproterenol. N-Methyl-N-isopropyl-5,6-dihydroxytetralin exhibited marked properties consistent with its being an alpha agonist, and it is concluded that introduction of considerable bulk about the nitrogen of a catecholamine does not a priori destroy alpha-agonist effects. The compounds qualitatively paralleled the effects of dopamine in assays based upon direct intrastriatal administration in rats, although they were less potent than dopamine.

Trans-2-Acetoxycyclobutyltrimethylammonium iodide, a cyclobutane analog of "trans-ACTM"

The (+/-) title compound was prepared to evaluate prior observations that certain acetylcholine congeners derived from cyclobutane are devoid of muscarinic effects. It was prepared by a multistep sequence from trans-2-carbomethoxycyclobutyl methyl ketone. In a guinea pig ileum assay, it was 0.02 times as active as AcCh, and in a dog blood pressure assay, it was 0.09 times as active. In these assays, its (+/-)-cyclopropane congener and AcCh were equally active. This is the first cyclobutane-derived AcCh congener possessing significant muscarinic effect.

Cellular phosphorylation of 1-beta-D-arabinofuranosylcytosine 5-azacytidine with intact fibrosarcoma and leukemic cells

The phosphorylation of 1-beta-D-arabinofuranosylcytosine (ara-C) and 5-azacytidine (5-aza-C) by A(T1)C1-3 hamster fibrosarcoma cells and L5178Y murine leukemic cells was studied, using intact cells. The cellular phosphorylation of both these nucleoside analogs appears to follow Michaelis-Menton kinetics. The apparent Km value for ara-C in the fibrosarcoma and leukemic cells was about 40 muM, whereas the apparent Km values for 5-aza-C in these cells were about 1.3 and 0.41 mM, respectively. Deoxycytidine and cytidine were found to be potent competitive inhibitors of the phosphorylation of ara-C and 5-aza-C, respectively, ara-C and 5-aza-C were found to be weak competitive inhibitors of the phosphorylation of deoxycytidine and cytidine, respectively. A clone isolated from the fibrosarcoma cells that was partially resistant to the cytotoxic effects of ara-C exhibited a higher Km value for both ara-C and deoxycytidine than the wild-type fibrosarcoma cells.

The acute and chronic effects of alcohol on the human immune system

The immunologic status of 24 male patients admitted for acute alcoholic detoxification was evaluated by in vivo and in vitro parameters. In vivo reactivity, as measured by skin testing with a denovo antigen, dinitrochlorobenzene, as well as a recall antigen, tuberculin, was inact. However, both qualitative and quantitative defects were seen in vitro in the thymus-derived lymphocyte population. These defects were not seen in recovered alcoholics, that is, they appear reversible. The defects seen in the cell-mediated immunity of alcoholics may, in part, be responsible for the high incidence of head and neck cancer observed in this patient population.

Antipsychotic drugs: direct correlation between clinical potency and presynaptic action on dopamine neurons

Neuroleptic (antipsychotic) drugs inhibited the electrically stimulated release of [3-H] dopamine from rat striatal slices. The concentrations for 50 percent inhibition (ranging from 11.5 nanomolar for spiroperidol to 800 nanomolar for thioridazine) correlated closely with the average daily dosages of 25 neuroleptic drugs used clinically for schizophrenia. The correlation includes butyrophenones, phenothiazines, reserpine, pimozide, clozapine, and (plus)- butaclamol. Clinically inactive isomers [trans-thiothixene, trans-flupenthixol, and (minus)-butaclamol] required 20 to 1000 times higher concentrations than the active isomers to inhibit release. Compared to the inhibition of [3-H] dopamine release, much higher neuroleptic concentrations were needed to inhibit the electrically stimulated release of other neurotransmitters--[3-H] acetylcholine, [3-H-a1 (gamma-aminobutyric acid). The neuroleptic drugs may block the presynaptic coupling between impulse and neurosecretion.

Enhanced binding of chlorpromazine to cholesterol-depleted synaptosome fractions

Brain synaptosome fractions were treated by Murphy's method in order to deplete the membrane cholesterol. The binding of 35S-chlorpromazine to these treated membranes was measured. It was found that the membrane/buffer partition coefficient of the drug was threefold greater in the treated synaptosome-rich fractions compared with the untreated fractions. The results suggest that cholesterol may not be a part of the membrane hydrophobic binding site for tranquilizers.