Ethylene and IAA interactions in the inhibition of photoperiodic flower induction of <Emphasis Type="Italic">Pharbitis nil</Emphasis>

It has been shown that both IAA and ethylene application inhibit flower induction in the short-day plant Pharbitis nil. However application of IAA has elevated ethylene production in this plant, as well. Strong enhancement of ethylene production is also correlated with the night-break effect, which completely inhibits flowering. In order to determine what the role of IAA and ethylene is in the photoperiodic flower induction in Pharbitis nil, we measured changes in their levels during inductive and non-inductive photoperiods, and the effects of ethylene biosynthesis and action inhibitors on inhibition of flowering by IAA. Our results have shown that the inhibitory effect of IAA on Pharbitis nil flowering is not physiological but is connected with its effect on ethylene biosynthesis.     

Pharmacological studies with beta-adrenoreceptor blocking agents I. Effect on the smooth muscle of the taenia coli of the guinea pig.

The action of new beta-blockers of VUFB series (VUFB 6502, VUFB 8102, VUFB 8227, and trimepranol) (Fig. 1) was analyzed in smooth msucle of guinea pig taenia coli by the double sucrose-gap method. All the studied beta-blockers increased the spontaneous spike activity without changes in membrane potential. The amino-analogues (VUFB 8101, VUFB 8102, VUFB 8227) as well as practolol were found to be 50 to 100 times less active than the oxy-derivatives (VUFB 6502 and Trimepranol) for the inhibition of spike activity, muscle relaxation and membrane hyperpolarization evoked by isoprenaline. None of the studied compounds had a pronounced alpha-blocking activity. The structure-activity relationship of the studied compounds was discussed.     

The action of adrenoceptor agonists and antagonists on the guinea pig and dog trachea

The action of beta- and alpha-adrenoceptor agonists (isoprenaline, orciprenaline, noradrenaline, phenylephrine and ephedrine) and antagonists (propranolol, metipranolol, exaprolol, BL 445 and phentolamine) on the resting tension and cAMP level of the guinea pig and the mechanical and electrical activities of the dog trachea were studied. By activating beta 2-adrenoceptors, isoprenaline and orciprenaline relaxed the smooth muscle, elevated the membrane potential and attenuated the excitatory effect of histamine on membrane potential and muscle tension. Noradrenaline and phenylephrine, acting on alpha 1-receptors, did not affect the membrane potential and increased the basal tension of the dog trachea only insignificantly. Ephedrine, in high concentrations, however, hyperpolarized the smooth muscle membrane and relaxed the dog trachea, while it did not alter the cAMP level in the guinea pig preparations. It is, therefore unlikely that alpha 1-adrenoceptors play a major role in the excitation of the dog trachea under resting conditions whereas the participation of alpha 2-receptors in the mechanisms of adrenergic relaxation could not be ruled out. All the beta-adrenoceptor antagonists studied enhanced the action of low isoprenaline concentrations and competitively antagonized it in high concentrations. The order of their antagonistic potency in the guinea pig trachea was as follows: metipranolol greater than propranolol = exaprolol greater than or equal to BL 445. It was suggested that metipranolol and exaprolol are nonselective beta-adrenoceptor antagonists, similarly as propranolol, whereas BL 445 shown some beta 1-selectivity. In contrast to their antagonistic effects on the membrane activities and muscle tension, both histamine and isoprenaline increased the level of cAMP in smooth muscle cells and, when present simultaneously, their effect was additive. The mechanism of histamine-induced cAMP level elevation and the possible involvement of different subcellular compartments in the action of isoprenaline and histamine in relation to the contraction-relaxation cycle is discussed.     

7C female sterile mutants fail to accumulate early eggshell proteins necessary for later chorion morphogenesis in Drosophila

Seven noncomplementing female sterile mutations that affect eggshell assembly in Drosophila have been mapped to the 7C1-3 region of the X-chromosome. TEM of the mature eggshell of one of the alleles, fs(1)410, shows a lack of organization within the endochorion and an accumulation of electron dense material in the vitelline membrane of stage 14 eggchambers. SDS-PAGE of radiolabeled eggshell proteins shows that two proteins, s67 and s85, fail to accumulate in the fs(1)410 eggshell. In wild-type flies s85 is produced during stage 10 of oogenesis and then processed to s67 in stages 13 and 14. Neither s85 nor an additional stage 10 specific follicle cell protein (s130) are detected in fs(1)410 or four of the mutant alleles. Short-term labeling studies, analyses of in vitro translation products, and the simultaneous occurrence of s85 and s130 as electrophoretic variants in geographic fly strains indicate s85 is derived from s130. Although major biochemical differences appear in stage 10, mutant and wild-type eggshells are morphologically indistinguishable until stages 13-14. These results suggest that follicle cell proteins synthesized during the time of vitelline membrane deposition (stage 10) are important for proper assembly of the chorion layers during stages 13 and 14.     

Processing of the initiation methionine from proteins: properties of the Escherichia coli methionine aminopeptidase and its gene structure.

Methionine aminopeptidase (MAP) catalyzes the removal of amino-terminal methionine from proteins. The Escherichia coli map gene encoding this enzyme was cloned; it consists of 264 codons and encodes a monomeric enzyme of 29,333 daltons. In vitro analyses with purified enzyme indicated that MAP is a metallo-oligopeptidase with absolute specificity for the amino-terminal methionine. The methionine residues from the amino-terminal end of the recombinant proteins interleukin-2 (Met-Ala-Pro-IL-2) and ricin A (Met-Ile-Phe-ricin A) could be removed either in vitro with purified MAP enzyme or in vivo in MAP-hyperproducing strains of E. coli. In vitro analyses of the substrate preference of the E. coli MAP indicated that the residues adjacent to the initiation methionine could significantly influence the methionine cleavage process. This conclusion is consistent, in general, with the deduced specificity of the enzyme based on the analysis of known amino-terminal sequences of intracellular proteins (S. Tsunasawa, J. W. Stewart, and F. Sherman, J. Biol. Chem. 260:5382-5391, 1985).