Gibberellins and pea seed development

The gibberellin (GA)-biosynthesis mutations, lh ⁱ , ls and Ie ⁵⁸³⁹ have been used to investigate the role(s) of the GAs in seed development of the garden pea (Pisum sativum L.). Seeds homozygous for lh ⁱ possess reduced GA levels, are more likely to abort during development, and weigh less at harvest, compared with wild-type seeds due to expression of the lh ⁱ mutation in the embryo and/ or endosperm. Compared with wild-type seeds, the lh ⁱ mutation reduces endogenous GA₁ and gibberellic acid (GA₃) levels in the embryo/endosperm a few days after anthesis and fertilizing lh ⁱ plants with wild-type pollen dramatically increases GA₁ and GA₃ levels in the embryo/ endosperm and restores normal seed development. By contrast, the ls and le ⁵⁸³⁹ mutations do not appear to reduce GA levels in the embryo/endosperm of seeds a few days after anthesis, and do not affect embryo or endosperm development. However, both the ls and lh ⁱ mutations substantially reduce endogenous GA levels in embryos at contact point (the first day the liquid endosperm disappears). Levels of GAs in seeds from crosses involving the ls and lh ⁱ mutations suggest that GAs are synthesised in both the embryo/endosperm and testa and that the expression of ls depends on the tissue and developmental stage examined. These results suggest that GAs (possibly GA₁ and/or GA₃) play an important role early in pea seed development by regulating the development of the embryo and/or endosperm. By contrast, the high GA levels found in wild-type seeds at contact point (and beyond) do not appear to have a physiological role in seed development.Abbreviations GA_n gibberellin A_n - DAA days after anthesis - WT wild-type We thank Noel Davies, Katherine McPherson and Peter Bobbi for technical assistance, Professor L. Mander (ANU, Canberra) for dideuterated GA standards, and the Australian Research Council and Frontier Research Program, The Institute of Physical and Chemical Research (RIKEN, Japan), for financial support.     

Mouse {beta}-galactoside {alpha}2,3-sialyltransferases: comparison of in vitro substrate specificities and tissue specific expression

Four types of ß-galactoside     

Relations Between the Extracellular Concentrations of Choline and Acetylcholine in Rat Striatum

Abstract: Changes in extracellular levels of acetylcholine (ACh) and choline (Ch) in the striatum of rats were examined by in vivo microdialysis after intraperitoneal injections of drugs. A dopamine D₂ antagonist, sulpiride (20 mg/kg), and a muscarinic antagonist, atropine (3.5 mg/kg), increased ACh levels and decreased Ch levels. On the contrary, the D₂ agonist (±)-2-( N -phenylethyl- N -propyl)amino-5-hydroxytetralin (N-434; 5 mg/kg) and an anesthetic, pentobarbital (50 mg/kg), decreased ACh levels and increased Ch levels. Perfusion of 10 µ M hemicholinium-3 (HC-3), a Ch uptake inhibitor, through the striatum induced a complete inhibition of ACh release and increased Ch levels in all drug-treated groups. The degree of relative increase in the level of Ch induced by HC-3 differed among the drug-pretreated groups; compared with the control group, the relative increase was larger in the sulpiride- and atropine-treated groups and smaller in the N-434 and pentobarbital-treated groups. Thus, we demonstrated reciprocal relations between extracellular concentrations of Ch and ACh after treatments by drugs. The data suggest that in the striatum, which is rich in cholinergic innervation, the extracellular Ch concentration is to a large extent determined by activity of the cholinergic transmission reflected in high-affinity choline uptake.     

COMPARATIVE MORPHOLOGY, CROSSABILITY, AND TAXONOMY WITHIN THE CALOGLOSSA CONTINUA (DELESSERIACEAE, RHODOPHYTA) COMPLEX FROM THE WESTERN PACIFIC

Systematic studies were undertaken on the Caloglossa continua ( Okamura) King et Puttock complex from Japan, Singapore, and Australia, based on morphology and reproductive compatibility. Specimens from Japan had two to six cell rows derived from a nodal axial cell, at the margin opposite the branch, whereas those from Australia possessed only a single cell row. Specimens from Singapore formed one to four cell rows per nodal axial cell and always contained at least one single cell row on any one thallus. These differences were maintained in cultured materials over a range of temperatures or salinities. Type material of C. continua had the same morphology as the Japanese specimens in this study. Carpospores discharged from the Japanese isolate germinated at 10°C, whereas those from Singapore and Australia died at this temperature. In hybridization experiments, the Japanese entity was completely nonfertile with both the Singaporean and Australian isolates. Many pseudocystocarps were produced in the crossing between the male from Australia and the female from Singapore, although the reciprocal combination did not produce any such structures. On the basis of the discontinuous morphology coupled with the complete reproductive isolation, the entities from Singapore and Australia are described here as C. monosticha sp. nov. The entities with multiple cell rows likely expanded their geographic range from tropical regions, where the majority of Caloglossa species are now distributed, to high-latitude regions, and such an expansion would be associated with acquiring low-temperature tolerance .     

Control of the rate of phosphocreatine resynthesis after exercise in trained and untrained human quadriceps muscles

We examined the effect of differences in exercise intensity on the time constant (t _c) of phosphocreatine (PCr) resynthesis after exercise and the relationships betweent _c and maximal oxygen uptake (VO_2max) in endurance-trained runners (n = 5) and untrained controls (n = 7) (average VO_2max = 66.2 and 52.0 ml · min^–1 · kg^–1, respectively). To measure the metabolism of the quadriceps muscle using phosphorus nuclear magnetic resonance spectroscopy, we developed a device which allowed knee extension exercise inside a magnet. All the subjects performed four types of exercise: light, moderate, severe and exhausting. The end-exercise PCr: [PCr + inorganic phosphate (P_i)] ratio decreased significantly with the increase in the exercise intensity (P < 0.01). Although there was little difference in the end-exercise pH, adenosine diphosphate concentration ([ADP]) and the lowest intracellular pH during recovery between light and moderate exercise, significant changes were found at the two higher intensities (P < 0.01). These changes for runners were smaller than those for the controls (P < 0.05). The _c remained constant after light and moderate exercise and then lengthened in proportion to the increase in intensity (P < 0.05). The runners had a lowert _c at the same PCr and pH than the controls, particularly at the higher intensity (P < 0.05). There was a significant correlation betweent _c and [ADP] in light exercise and betweent _c and both end-exercise PCr and pH in severe and exhausting exercise (P < 0.05). The threshold of changes in pH andt _c was a PCr: (PCr + P_i) ratio of 0.5. There was a significant negative correlation between the VO_2max andt _c after all levels of exercise (P<0.05).However, in the controls a significant correlation was found in only light and moderate exercise (P < 0.05). These findings suggest the validity of the use oft _c at an end-exercise PCr:(PCr + P_i) ratio of more than 0.5 as a stable index of muscle oxidative capacity and the correlation between local and general aerobic capacity. Moreover, endurance-trained runners are characterized by the faster PCr resynthesis at the same PCr and intracellular pH.     

Production of L-aspartic acid from fumaric acid by a fumaric acid-assimilating obligate thermophile,Bacillus stearothermophilus KP 1041

Summary A fumaric acid-assimilating obligate thermophile having a high aspartase activity was isolated from soil. The isolate (KP 1041) that grew at 45 to 68 °C was assigned to a strain of Bacillus stearothermophilus. The cell suspensions produced L-aspartate from fumarate and ammonium ion, with the rapidest initial rate at 65 °C and pH 9.5. The Michaelis constant for fumarate was 0.2 M. The cellular aspartase was relatively stable for 18 h at and below 50 °C over a pH range 6.7–8.3 in the presence of ammonium fumarate; this substance protected the enzyme from heat inactivation. The best yield in L-aspartic acid production was achieved at 6 h incubation at 53 °C and pH 8.5, using 0.88 M fumarate, 3.1 M ammonium ion, and the cells at 53 mg dry weight per ml. In this case, 85% of fumarate added was converted into aspartic acid. The structure of the product was determined from its infrared spectrum, specific rotation, melting point and ultimate analysis.Presented at the Annual Meeting of the Agricultural Chemical Society of Japan, Yokohama, April 2, 1977     

The effects of N-substitution of chitosan and the physical form of the products on the rate of hydrolysis by chitinase from Streptomyces griseus

N-Formyl, N-chloroacetyl, N-glycyl, N-isobutyryl, and N-pentanoyl derivatives of chitosan have been prepared. N-Acetylchitosan was the derivative most susceptible to chitinase from Streptomyces griseus and lysozyme from chicken egg-white, but the susceptibility was not restrictive. The relative rates of hydrolysis by chitinase with respect to R in the RCONH group were CH₃ > CH₃CH₂ > H > CH₃CH₂CH₂ > (CH₃)₂CH > NH₂CH₂ > ClCH₂. Neither enzyme hydrolysed chitosan or its N-methylene, N-benzylidene, N-benzoyl, N-nicotinyl, and N-fatty acyl (C₅C₁₈) derivatives, and lysozyme did not hydrolyse N-butyrylchitosan. N-Acetylhexanoyl-chitosans, which had d.s. ratios of ~0.7: ~0.3 and ~0.3; ~0.7, were hydrolysed at ~0.75 and ~0.04 of the rate of N-acetylchitosan (powder) by chitinase. O-Acylation of N-acylchitosans caused a decrease in the rates of hydrolysis by chitinase. N-Acetylchitosan gels were hydrolysed at 8–13 times the rate for crab-shell chitin. These results indicate that not only N- and O-substituents but also the physical form of the substrates influence the rates of hydrolysis by these enzymes.     

Transformation of straight flagella and recovery of motility in a mutant Escherichia coli.

The non-motile strain W3623 ha-177 of Escherichia coli (Kondoh &; Ozeki, 1976) is known to produce straight flagella as a result of a mutation in the structural gene for the flagellin. Under physiological conditions, however, flagella of this mutant undergo straight-to-helical transformation with small changes of pH. Evidence for this came from dark-field light microscope observations of reconstituted flagella. At pH values lower than 6.6 in the presence of 0.1 m-NaCl, the flagella were straight. When, however, the pH was raised above 7.3, they were transformed into left-handed helices with a pitch of 2.05 μm. The transformation was rapid and reversible. In the pH range between 6.6 and 7.3, straight and transformed flagella co-existed but no stable forms other than the two were found.Bacterial motility also depended on the pH of the medium: at pH values above 7.0, bacteria swam by means of the transformed flagella. Therefore, helically transformed flagella of the mutant strain were similar in morphology and function to normal-type flagella of the parent strain. The significance of this similarity is discussed on the basis of general considerations of polymorphism in bacterial flagella.     

Studies on contraction rhythm of the plasmodial strand III. Role of endoplasmic streaming in synchronization of local rhythms

Summary Two separate segments of plasmodial strands (Physarum polycephalum) generally contract and relax with different periods, but if the two are bridged with another small strand segment to make into a single system, the contraction cycles of the two previously separate segments become gradually unified under isometric as well as isotonic conditions. To clarify the possible role of the streaming endoplasm as the information carrier for synchronization, we stopped the streaming between two halves of a single strand either by cutting it or by using the double-chamber method without cutting it. When the endoplasm is prevented from flowing between the two halves of the same continuous system, which had been in good synchrony, their contraction-relaxation rhythms become out of phase with each other. After the endoplasm in the strand is allowed to stream freely again, the synchrony of their cyclic contraction is reestablished. It was concluded that endoplasm flowing back and forth in a plasmodial strand must carry a factor(s) which coordinates the period and phase of the contraction-relaxation cycle but does not control the amplitude of the cycle.The present work was supported in part by grants-in-aid from the Mitsubishi Foundation and the Japanese Ministry of Education, Science, and Culture.