Abscisic acid both promotes and inhibits photoperiodic flowering of Pharbitis nil

Abscisic acid (ABA) has been reported to have diverse effects on photoperiodic flowering. Activity of a natural ABA, (+)-( S )-abscisic acid (S-ABA), was recently suggested to be somewhat different from that of racemic ABA, which has been used in previous work. Use of S-ABA might enable clarification of the role of ABA in flowering. S-ABA inhibited flowering of the short-day plant Pharbitis nil (cv. Violet) when given before or 4 h after the start of a 14-h inductive dark period, and promoted flowering when given 12 h after the start of the dark period or later. The flower-promoting effect was observed when ABA was applied to the shoot apex. These results indicate that ABA has a dual effect on photoperiodic flowering of P. nil : it may inhibit the time-measuring process as well as promote some processes that proceed after generation of the flowering stimulus.     

Intercellular Localization of Acid Invertase in Tomato Fruit and Molecular Cloning of a cDNA for the Enzyme

The localization of acid invertase (AI, EC 3.2.1.26 [EC] ) in tomatofruits was studied. AI was localized in the intercellular fraction(cell wall fraction). A cDNA encoding a wall-bound form of AIfrom tomato fruits was cloned and its nucleotide sequence wasdetermined. The cloned cDNA was 2363 base pairs long and containedan open reading frame of 1908 base pairs which encoded a polypeptideof 636 amino acids. RNA blot analysis indicated that the mRNAfor the acid invertase was about 2.5 kb in length. The levelsof the mRNA were low at the mature green stage but increasedduring ripening of fruit. (Received July 13, 1992; Accepted December 3, 1992)     

Lung tissue behavior in the mouse during constriction induced by methacholine and endothelin-1

Nagase, Takahide, Hirotoshi Matsui, Tomoko Aoki, YasuyoshiOuchi, and Yoshinosuke Fukuchi. Lung tissue behavior in the mouseduring constriction induced by methacholine and endothelin-1. J. Appl. Physiol. 81(6):2373-2378, 1996.Recently, mice have been extensively used toinvestigate the pathogenesis of pulmonary disease because appropriatemurine models, including transgenic mice, are being increasinglydeveloped. However, little information about the lung mechanics of miceis currently available. We questioned whether lung tissue behavior andthe coupling between dissipative and elastic processes, hysteresivity(), in mice would be different from those in the other species. Toaddress this question, we investigated whether tissue resistance (Rti)and  in mice would be affected by varying lung volume, constrictioninduced by methacholine (MCh) and endothelin-1 (ET-1), andhigh-lung-volume challenge during induced constriction. From measuredtracheal flow and tracheal and alveolar pressures in open-chest ICRmice during mechanical ventilation [tidal volume = 8 ml/kg,frequency (f) = 2.5 Hz], we calculated lung resistance(RL), Rti, airway resistance(Raw), lung elastance (EL),and  (=2fRti/EL). Underbaseline conditions, increasing levels of end-expiratory transpulmonarypressure decreased Raw and increased Rti. The administration ofaerosolized MCh and intravenous ET-1 increasedRL, Rti, Raw, andEL in a dose-dependent manner.Rti increased from 0.207 ± 0.010 to 0.570 ± 0.058 cmH₂O ^· ml^{1 ·} safter 10⁷ mol/kg ET-1(P < 0.01). After inducedconstriction, increasing end-expiratory transpulmonary pressuredecreased Raw. However,  was not affected by changing lung volume,constriction induced by MCh and ET-1, or high-lung-volume challengeduring induced constriction. These observations suggest that1)  is stable in mice regardlessof various conditions, 2) Rti is animportant fraction of RL andincreases after induced constriction, and3) mechanical interdependence mayaffect airway smooth muscle shortening in this species. In mammalianspecies, including mice, analysis of  may indicate that both Rti andEL essentially respond to asimilar degree.

     

Computational 3-D modeling and site-directed mutation of an antibody that binds Neu2en5Ac, a transition state analogue of a sialic acid.

An antibody against a transition state analog (TSA) may share some common features with an enzyme that produces such a transition state. SIC172 antibody binds specifically to Neu2en5Ac, a TSA of Neu5Ac in the sialidase reaction, but has no catalytic activity. To understand how the antibody recognizes Neu2en5Ac and to find out if it is possible to convert it to a catalytic antibody, we made and sequenced the SIC172 ScFv, and constructed a 3-D model of it. The VH-CDR3 contains a unique sequence with Cys at H95. The 3-D model showed that Cys-H95 is exposed inside the antigen-binding cavity. After affinity docking, 4 types emerged. In type I, the carboxyl group of Neu2en5Ac is located near the Cys-H95 and neighboring positively charged residues. The change of Cys-H95 to Asp by site-directed mutation decreased the binding activity, while a change to Arg did not. These and other mutation experiments, and further modeling of mutant Fv, support the 3-D model and docking type I. A comparison with sialidase indicates that SIC172 antibody appears to have some groups of residues that are conserved at the active site of the enzyme. The possibility of Neu2en5Ac-binding antibody being converted to a catalytic antibody is discussed.     

Contribution of the N-terminal and C-terminal domains of haemaphysalin to inhibition of activation of plasma kallikrein-kinin system

Haemaphysalin is a kallikrein-kinin system inhibitor from hard tick Haemaphysalis longicornis, and consists of two Kunitz type protease inhibitor domains. Each domain as well as haemaphysalin inhibited intrinsic coagulation by inhibiting activation of the kallikrein-kinin system without affecting the amidolytic activities of intrinsic coagulation factors, indicating that both domains were involved in the inhibition through a similar mechanism to that for haemaphysalin. Reconstitution experiments showed that the C-terminal domain contributed more predominantly to this inhibition. Direct binding assaying showed that the C-terminal domain could bind to the cell-binding region of high molecular weight kininogen (HK), suggesting that it also binds to the cell-binding region of factor XII. Judging from these findings, the C-terminal domain may more effectively inhibit the association of factor XII and HK with the cell surface by binding to cell-binding regions, and hence would predominantly contribute to the inhibition of activation of the kallikrein-kinin system.     

A method for direct harvest of bacterial cellulose filaments during continuous cultivation of Acetobacter xylinum

Continuous filamentation of bacterial cellulose (BC) was successfully achieved by using shallow pan for the incubation to regulate thickness of the BC gel produced by Acetobacter xylinum. The BC filament was harvested and prepared directly by picking up BC pellicles, the thin BC gel, and winding slowly from the surface of the culture medium passed through a preliminary bactericidal washing bath. The X-ray diffraction analysis and scanning electron microscopic observation of the BC filament thus obtained showed that the filament was smooth and the fairly good orientation of BC molecules.

The average tensile strength was 4.4 g denier⁻¹ for the filament prepared by hot alkaline treatment and subsequent washing with distilled water and dried under tension (Filament W): 3.4 g denier⁻¹ for washing with 10% aqueous ethylene glycol after alkaline treatment followed by drying under tension (Filament E) and 2.4 g denier⁻¹ for the treatment with 10% ethylene glycol after normal water-washing followed by drying under tension.     

Effects of high K+ concentrations on the growth and development of ciliary ganglion neurons in cell culture

Extracts prepared from embryonic eye tissue permit all of the neurons present in embryonic ciliary ganglia to survive and develop in cell culture. High K⁺ concentrations stimulate growth of the neurons in culture above the maximal levels obtained with eye extract alone. Growth in 25 mM K⁺ produced parallel increases in the levels of choline acetyltransferase activity, lactate dehydrogenase activity (a common cytoplasmic enzyme), and total protein synthesis per neuron. The K⁺ effect appears to be mediated by membrane depolarization. Intracellular recording confirmed that the neurons were chronically depolarized in 25 mM K⁺. Veratridine produced the same stimulation of growth, while tetrodotoxin blocked the veratridine effect without preventing the K⁺ effect. Ca²⁺ may also play a role in the K⁺ effect. Two drugs thought to block Ca²⁺ channels (Mg²⁺ and D600) each blocked or reduced in the increase in growth caused by 25 mM K⁺. The drugs did not interfere with neuronal growth in control cultures, indicating that eye extract and membrane depolarization influence neuronal growth by different mechanisms.