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

Four types of ß-galactoside     

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 .     

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.     

Membrane lipid biosynthesis in Acholeplasma laidlawii B: Investigations into the in vivo regulation of the quantity and hydrocarbon chain lengths of de novo biosynthesized fatty acids in response to exogenously supplied fatty acids

The regulation of the nature and quantity of the fatty acids produced in vivo by Acholeplasma laidlawii B in the presence of various exogenous fatty acids has been investigated. In the presence of exogenous medium- or long-chain fatty acids, the organism appears to reduce the amounts of de novo biosynthesized fatty acids in its cellular lipid pool by two distinct mechanisms: an excretion of biosynthesized fatty acids to the growth medium as free fatty acids, and a reduction in total de novo biosynthetic output. These two mechanisms do not suffice to maintain constant total membrane lipid levels, but they do appear to significantly moderate the effect of exogenous fatty acids on the level of membrane lipid. In the presence of short-chain fatty acids, total membrane lipid levels are not elevated. Exogenous fatty acids can cause shifts in the average chain length of de novo biosynthesized fatty acids; the magnitudes and directions of these shifts can be correlated with the specificity of the exogenous species for esterification to the 1- or the 2-position of the glycerol moiety of membrane glycerolipids. As the various endogenously synthesized fatty acids differ in their positional specificity for glycerolipid esterification, we propose that the competition of an exogenous species with significant specificity for a particular position with the endogenously derived fatty acids specific for that position can selectively depress the synthesis of such endogenously derived species, thereby altering the overall product spectrum of de novo fatty acid biosynthesis in vivo.     

Purification and characterisation of β-N-acetylhexosaminidase from the butter clam, saxidomus purpuratus

A β-N-acetylhexosaminidase [EC 3.2.1.30] has been purified ～98-fold from an extract of the digestive organs of Saxidomus purpuratus by using ammonium sulfate fractionation, and chromatography on Toyopearl HW-50, CM-cellulose, and Sepharose 4B. The purified enzyme, the molecular weight of which was estimated to be ～66,000 by gel filtration, was composed of two sub-units of molecular weight 30,000 as determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The purified enzyme had a pH optimum of 3.8 and an optimum temperature of 55°, and its activity was enhanced ～2-fold in the presence of 0.1m sodium chloride. The Michaelis constants toward p-nitrophenyl 2-acetamido-2-deoxy-β-d-glucoside and -galactoside were 1.2 × 10^?4 and 1.3 × 10^?4m, respectively.     

Secondary Echinococcus multilocularis infection in severe combined immunodeficient (scid) mice: biphasic growth of the larval cyst mass.

E. multilocularis infection was suppressed in C.B-17 mice after intraperitoneal inoculation of protoscoleces, with larval cysts weighing no more than 1.0 g. In scid mice, which are genetically identical to C.B-17 except for a deficiency in functional lymphocytes, infection progressed and larval cysts reached a mass of 17.5 g at 15 weeks post-infection. The growth of the larval cyst mass in scid mice was similar to that in other susceptible mouse strains, with a biphasic pattern. Histological observations revealed giant cells and granulomatous inflammation in the C.B-17, but not in the scid mice. These results led to the conclusion that suppression of the growth of the larval cyst mass in the initial stage of infection in susceptible mice strains is caused by factors other than the host's lymphocytic immune response.