Formamidines interact withDrosophila octopamine receptors,alter the flies' behavior and reduce their learning ability

Summary We have studied the effect of formamidines onDrosophila melanogaster. Low concentrations of formamidines are toxic to adultDrosophila. A mutant with reduced cAMP synthesis displays increased resistance to the toxin. Formamidines also reduce viability ofDrosophila eggs and retard imago eclosion. At sublethal concentrations, formamidines markedly affect the flies' behavior. Upon injection, the compounds increase muscle activity. Upon feeding, formamidines induce motor excitation, reduce phototaxis and impair olfactory learning without affecting the ability to recognize an olfactory cue. In vitro, two formamidines were found to inhibit octopamine-stimulated adenylate cyclase without affecting the basal activity of the enzyme, while a third one was found to stimulate adenylate cyclase; this stimulation was blocked by phentolamine and to a lesser degree by propranolol, thus resembling the effect of octopamine. The binding of [³H]octopamine toDrosophila head membranes was also inhibited. Taken together, our results indicate that formamidines interact with octopaminergic systems inDrosophila, exert both peripheral and central effects in the fly, and could be used to dissect the roles of octopamine in development and behavior, including behavioral plasticity. The results also suggest that formamidines could be used to select mutants in aminergic transmission and in the cAMP cascade.Abbreviations CDMF chlordimeform - DMPF N,N-dimethyl-N2-(2,4-dimethylphenyl) formamidine     

The gene for trypsin inhibitor CMe is regulated in trans by the lys 3a locus in the endosperm of barley (Hordeum vulgare L.)

Summary A cDNA encoding trypsin inhibitor CMe from barley endosperm has been cloned and characterized. The longest open reading frame of the cloned cDNA codes for a typical signal peptide of 24 residues followed by a sequence which is identical to the known amino acid sequence of the inhibitor, except for an Ile/Leu substitution at position 59. Southern blot analysis of wheat-barley addition lines has shown that chromosome 3H of barley carries the gene for CMe. This protein is present at less than 2%–3% of the wild-type amount in the mature endosperm of the mutant Risø 1508 with respect to Bomi barley, from which it has been derived, and the corresponding steady state levels of the CMe mRNA are about I%. One or two copies of the CMe gene (synonym Itc1) per haploid genome have been estimated both in the wild type and in the mutant, and DNA restriction patterns are identical in both stocks, so neither a change in copy number nor a major rearrangement of the structural gene account for the markedly decreased expression. The mutation at the lys 3a locus in Risø 1508 has been previously mapped in chromosome 7 (synonym 5H). A single dose of the wild-type allele at this locus (Lys 3a) restores the expression of gene CMe (allele CMe-1) in chromosome 3H to normal levels.     

Cannibalism as a life boat mechanism

Under certain conditions a cannibalistic population can survive when food for the adults is too scarce to support a non-cannibalistic population. Cannibalism can have this lifeboat effect if (i) the juveniles feed on a resource inaccessible to the adults; and (ii) the adults are cannibalistic and thus incorporate indirectly the inaccessible resource. Using a simple model we conclude that the mechanism works when, at low population densities, the average yield, in terms of new offspring, due to the energy provided by one cannibalized juvenile is larger than one.     

Tritiated borohydride reduction of carbohydrates: reduction of individual monosaccharides, alone or in groups, results in highly divergent specific activities.

Reduction of carbohydrates by tritiated borohydride resulted in the production of alditols or glycosides with characteristically divergent specific radioactivities. Simultaneous reduction of individual sugars in the presence of a reference standard, talose, permitted the assignment of a unique specific radioactivity with respect to talitol as 100%. A variety of structures was examined, including neutral hexoses, free and acetylated aminosugars, ketohexoses and glycosides containing a fixed pyranose ring adjacent to a carbonyl group. In the latter case, the resulting steric hindrance severely restricted the incorporation of tritium. In both of the ketohexoses tested, the minor product of the two epimeric alditols exhibited the higher specific radioactivity. In all cases, reduction produced a characteristic and reproducible specific activity in which the values varied from 51 to 182% of that found for talose. These results are interpreted on the basis of generalizations concerning mechanism and predictive value.     

Tracer diffusion coefficients of proteins by means of holographic relaxation spectroscopy: application to bovine serum albumin

Holographic relaxation spectroscopy has been used to measure tracer diffusion coefficients for photochromically labeled bovine serum albumin in solutions having total bovine serum albumin concentrations in the range 3.25 to 257 g/liter. In the limit of zero concentration, the diffusion coefficient (20 degrees C, 0.1 M NaCl, 0.05 M Tris, pH 8.0) was found to be (5.9 +/- 0.1) X 10(-7) cm2/s and the initial slope was zero. The concentration dependence of the diffusion coefficient was not significantly affected by the fraction of protein molecules which were labeled. Holographic relaxation spectroscopy permits rapid, accurate determination of tracer diffusion coefficients for proteins in mixtures.     

Ion-pair reverse-phase high-performance liquid chromatography. Application to the study of chicken liver NAD+ kinase

An ion-pair, reverse-phase, high-performance liquid chromatography method of assay was developed and used in a series of rate studies carried out with the enzyme chicken liver NAD+ kinase (ATP:NAD+ 2'-phosphotransferase, EC 2.7.1.23). Complete separation of all products and reactants was achieved within 15 min. ATP, NAD+, ADP, and NADP+ were monitored at 260 nm as they eluted from a Zorbax (Dupont) ODS (4.6 X 250-mm) column using an acetonitrile and 0.01 mM NH4(H2PO4)/0.005 M tetrabutylammonium phosphate (pH 7.0) gradient. The enzyme shows a marked preference for ATP (and dATP) and Mg2+ (or Mn2+) relative to other trinucleotides and divalent metal ions. It exhibits residual adenylate kinase and ATPase activity, but no NADH kinase activity. When polyphosphate replaced ATP, NADP+ production dropped to 2.5%. The addition of Ca2+ and/or bovine brain calmodulin did not significantly enhance the rate of NADP+ production.     

Potentiation of direct antitumor cytotoxicity and production of tumor cytolytic factors in human blood monocytes by human recombinant interferon-gamma and muramyl dipeptide derivatives

Summary We investigated whether human peripheral blood monocytes isolated by centrifugal elutriation from healthy donors could be acitivated to become tumoricidal and release tumor cytolytic factor (TCF) subsequent to incubation with recombinant human interferon-gamma (r-IFN-) or a derivative of muramyl dipeptide (nor-MDP), or both. Blood monocytes incubated in endotoxin-free medium containing up to 1000 U/ml of r-IFN- or in medium containing less than 1 g/ml of nor MDP were not activated to lyse radiolabeled allogeneic human tumor cells. In contrast, the incubation of monocytes with various dose combinations of r-IFN- and nor-MDP generated significant direct cytotoxic activity as well as production of TCF. Preincubation of the r-IFN- and nor-MDP mixture with polymyxin B did not inhibit the synergism, thus ruling out the possibility that the process was due to endotoxin contamination. TCF harvested from monocyte culture supernatants was cytolytic against five allogeneic tumor targets, but not against a nontumorigenic cell line. Collectively, the data demonstrate that r-IFN- can prime human blood monocytes to allow their activation by synthetic nor-MDP.On leave from the Department of Internal Medicine, The University of Tokushima School of Medicine, Kuramoto-cho, Tokushima 770, Japan     

Dimethylsulfoxide action on dark- and light-induced leaflet movements and its necrotic effects on excised leaves of Cassia fasciculata

Dimethylsulfoxide (DMSO) acts on dark- and light-induced movements exhibited by leaflets of isolated leaves of Cassia fasciculate Michx. The closing movement (scotonasty), induced when the leaves are placed in darkness during the normal period of daylight, was inhibited, whereas the opening movement (photonasty), when the leaves arc transferred to light during the normal period of darkness, was promoted. The concentration for significant effects of DMSO was 1% (v/v) when applied over a 3-h period. After five days, a necrosis of the leaflets was observed for DMSO concentrations as small as 0.1%, applied over a 6-h period. Complete abscission took place if 3% DMSO was applied for more than 30 min.     

A cDNA clone containing the entire coding sequence of a mouse H-2Kd histocompatibility antigen

We have isolated a cDNA clone carrying a 1560 bp long insert which contains the entire coding and 3' untranslated regions of an H-2K(d) mouse histocompatibility antigen. Its sequence and overal features are described. They point to the existence of unique properties of DNA sequences associated with the H-2K(d) antigen.