SYNCHRONIZATION OF CHLOROPLAST DIVISION IN THE ULTRAMICROALGA CYANIDIOSCHYZON MEROLAE (RHODOPHYTA) BY TREATMENT WITH LIGHT AND APHIDICOLIN

A system of highly synchronized chloroplast divisions was developed in the unicellular red alga Cyanidioschyzon merolae De Luca, Taddei, & Varano. Chloroplast divisions were examined by epifluorescence microscopy following treatments with light and inhibitors. When the cells during stationary phase were transferred into a new medium under a 12:12 h LD cycle, chloroplasts, mitochondria, and cell nuclei divided synchronously in that order soon after the initiation of dark periods. More than 40% of the cells contained dividing chloroplasts. To obtain a system of highly synchronized cell division and chloroplast division, the cells synchronized by a 12:12 h LD cycle were treated with various inhibitors. Nocodazole and propyzamide did not affect cell and organelle divisions, whereas aphidicolin markedly inhibited cell-nuclear divisions and cytokinesis and induced a delay in chloroplast division. More than 80% of the cells contained dividing chloroplasts when cells synchronized by light were treated with aphidicolin for 12 h. This synchronized system will be useful for studies of the molecular and cellular mechanisms of organelle divisions .     

Inhibition of soybean lipoxygenase-1 by n-alcohols and n-alkylthiols.

A series of n-alcohols and n-alkylthiols with carbon chains from 2 to 12 were examined for the inhibition of soybean lipoxygenase-1 (L-1). The alcohol produces a competitive inhibition, the extent of which increases with an increase in the carbon number of alkyl chain up to 8. Whereas the inhibition of the alkylthiol is noncompetitive, the extent of which is almost independent from the carbon number. From the behavior of pKi dependence on the carbon number of the alcohol, the decyl group appears to be optimum to bind to L-1. The thermodynamic analysis for the inhibition based upon van 't Hoff equation indicates positive enthalpy and entropy changes for the binding of the alcohol to the enzyme and negative enthalpy and positive to negative entropy changes for that of the alkylthiol. These observations suggest that the alcohol inhibits L-1 by binding of the hydrophobic alkyl tail to the catalytic site of the enzyme by a hydrophobic interaction. The alkylthiol inhibits by binding of the nucleophilic sulfhydryl head to a polarizable region of the enzyme and the alkyl tail to a hydrophobic region of the enzyme free from the steric hindrance as an anchor.     

Polarographic Behavior of Thiolated Natural and Synthetic Polymers

Polarographic protein waves were studied by using model samples. Two samples were prepared by thiolation of natural and synthetic polymers which show no catalytic wave in the ammoniacal cobalt buffer. The one was made from bacterial α-amylase by thiolation with N-acetylhomocysteine and the other was made from polyvinylalcohol by esterification with thioglycolic acid. These thiolated polymers showed typical double waves similar to protein waves both in cobaltous and cobaltic media though minute differences were present between the waves of thiolated polyvinylalcohol and those of proteins.     

Grayanoside C,a new diterpene glucoside from Leucothoe grayana

A new diterpene glucoside has been isolated from Leucothoe grayana. Its structure was elucidated by X-ray diffraction analysis of a dehydrated product of the aglycone and conversion of the same to leucothol A.     

Purification of 7-Keto-8-aminopelargonic Acid-7,8-Diaminopelargonic Acid Aminotransferase,an Enzym Involved in Biotin Biosynthesis,from Brevibacterium divaricatum

Vitamin B₆ is synthesized by green Cytisus scoparius callus and green Phellodendron amurense callus cultured on Linsmaier and Skoog Agar-medium with 10^?5m of ±-naphthaleneacetic acid (NAA) and 10^?6 m of 6-benzyladenine (BA). Even when thiamine and inositol were omitted from this medium, the growth and vitamin B₆ content of Cytisus scoparius callus did not change. Vitamin B₆ contents of clones of the calluses varied and were unstable during long-term subculture. Clonal selection was repeated to obtain stable strains with high vitamin B₆ content, and the vitamin B₆ content of one strain of green Cytisus scoparius callus became 4-times higher than that of the green leaves.     

Distribution of 7-Keto-8-aminopelargonic Acid Synthetase in Bacteria and the Control Mechanism of the Enzyme Activity

The 7-keto-8-aminopelargonic acid (KAPA) synthetase activities of cell-free extracts from various bacteria were investigated. The experiments on the substrate specificity of KAPA synthetase, using crude cell-free extracts from bacteria having high enzyme activity, showed that l-serine and pyruvic acid could replace l-alanine, but that, when the enzyme was partially purified, these compounds were not effective. Many kinds of amino acids such as l-cysteine, l-serine, d-alanine, glycine, d-histidine, and l-histidine, inhibited the enzyme activity. This inhibition was found to be competitive with l-alanine. Pyridoxal 5′-phosphate, which is a cofactor of the enzyme, also inhibited the enzyme activity at high concentrations. The repression of KAPA synthetase by biotin occurred in Bacillus subtilis and B. sphaericus but not in Micrococcus roseus and Pseudomonas fluorescens, even at a concentration of 1000 mµg per ml of biotin.     

Thyroxine as a Mediator of Metamorphosis of Atlantic Halibut, Hippoglossus Hippoglossus

The response of morphological, histological and endocrinological development to exogenous 1-thyroxine (T₄) and to water depth during metamorphosis in Atlantic halibut, Hippoglossus hippoglossus, was investigated. Exogenous T₄ was given in daily doses of 0.1, 0.05 ppm or a control treatment to halibut larvae at 550 daydegrees (posthatch, premetamorphic) for 14 days. Water depths of 40 cm, 10 cm or 1.5 cm were used to rear halibut larvae from 590 daydegrees for 21 days. Halibut larvae given exogenous T₄ at 0.1 ppm had accelerated eye migration relative to MH in fish given 0.05 ppm and in control fish. Pigmentation was correlated with dosage after 14 days. The volume of thyroid tissue was expressed in a dose-dependent manner and exhibited a size-dependency within each treatment. However, the follicles were atypical with reduced colloid, increased lumen and low epithelial cells even in the control group. The results indicate that T₄ is a mediator in halibut metamorphosis. In the water depth experiment, only cortisol levels of larvae reared in 1.5 cm water were significantly affected after 21 days, but this was not correlated with metamorphic rate. Hormone profiles, morphological changes and size suggest the existence of a window of opportunity for metamorphosis in halibut extending from about 16 mm and tapering off about 21 mm SL. The pooled hormone profiles indicate the commencement of a hormonal cascade similar to that of other flatfishes during metamorphosis. The results indicate that growth, neural and skeletal transformation, and pigmentation are biochemically separate processes in the metamorphosis of Atlantic halibut.     

Tumor-related expression of alpha1,2fucosylated antigens on colorectal carcinoma cells and its suppression by cell-mediated priming using sugar acceptors for alpha1,2fucosyltransferase

The accumulation of alpha1,2fucosylated antigens, such as Y (Fucalpha1,2Galbeta1,4 [Fucalpha1,3]GlcNAcbeta), Le(b) (Fucalpha1,2Galbeta1,3-[Fucalpha1,4]GlcNAcbeta), and H type 2 (Fucalpha1,2 Galbeta1,4GlcNAcbeta) occurs specifically within human colorectal tumor tissues and can be detected by an antifucosylated antigen antibody, such as the YB-2 antibody. In the present investigation, we found that the expression of these antigens bearing an alpha1,2-linked fucose correlated with the resistance of the tumor cells to anticancer treatments. Addition of an exogenous sugar acceptor for alpha1,2fucosyltransferase to the cell medium resulted in suppression of alpha1,2fucosylated antigen expression on the tumor cells and increased susceptibility to anticancer treatment. The increased susceptibility may be attributed to cancer cell-mediated priming by sugar acceptors for alpha1,2fucosyltransferase added to the medium.