Pathway of mannitol formation during photosynthesis in brown algae

Eisenia bicyclis, Arame, was allowed to photosynthesize in seawatercontaining H¹⁴CO₃^–, and ¹⁴C-mannitol was isolated fromits fronds. The ratio of ¹⁴C-total/¹⁴C₁ + ¹⁴C₆ in the ¹⁴C-mannitolwas found to be about 8.0 at 1 min-illumination, but graduallydecreased with time to 3.0, showing uniform radioactivity distribution.Mannitol therefore seems to be formed in brown algae throughthree carbon compounds. Enzymes which may be involved in the possible biosynthetic pathwayof mannitol, i.e. aldolase, hexose diphosphatase, mannitol-1-phosphataseand glucosephosphate isomerase were present in extracts fromseveral brown algae. Some of their properties are discussed. ¹Contribution from the Shimoda Marine Biological Station ofTokyo Kyoiku University, No. 187. ²Present address: Reseach Institute, Seikagaku Kogyo Co., Ltd.,Yamato-machi, Kitatama-gun, Tokyo, Japan. (Received December 13, 1968; )     

A Cell Kinetic and Cytological Study on the Asymmetric Cell Division of Thymic Lymphoblasts of the Embryonic Rat

Cell division of thymus lymphoid cells from embrynonic and young rats was investigated cytologically on cell smears, focusing attention on asymmetric cell division. Some of thymic lymphoblasts displayed features implicating asymmetric cell division. At the telophase of such cells, two immature daughter cells looked dissimilar: one of them was smaller in size and possessed a more condensed nucleus, compared with the counterpart cell. Furthrmore, in most cases the cytoplasm of the smaller daughter cell was stained with Giemsa more deeply. It was suggested that the asymmetry of the nucleus emerges at anaphase and telophase probably due to some polarized situation of the cytoplasm. Asymmetrically-dividing cells were relatively frequently observed during the developmental period when large lymphoblasts actively transform into smaller lymphocytes :16% to 17% of whole dividing cells were under asymmetric cell division on days 16 and 17 of gestation, while less than 5% on day 19 or thereafter. In correlation with this observation, asymmetrically-dividing cells were more frequently observed among large lymphoblasts than among other smaller cell fractions. These results support the view that the asymmetric cell division may play some essential role in the transformation of large lymphoblasts into smaller lymphocytes.     

Development of microsatellite markers for the Manila clam Ruditapes philippinarum

We isolated nine polymorphic microsatellites from the Manila clam Ruditapes philippinarum. These loci provide one class of highly variable genetic marker as the number of alleles ranged from six to 22, and the observed and expected heterozygosity ranged from 0.136 to 0.909 and from 0.553 to 0.954, respectively. We consider that these loci are potentially useful for detailing the genetic structure and gene flow among R. philippinarum populations.     

THIS ARTICLE HAS BEEN RETRACTEDDevelopment of microsatellite markers in the noxious red tide‐causing dinoflagellate Heterocapsa circularisquama (Dinophyceae)

We isolated 15 polymorphic microsatellites from one of the most noxious red tide‐causing dinoflagellate species, Heterocapsa circularisquama. These loci provide one class of highly variable genetic markers, as the number of alleles ranged from two to six, and the estimate of gene diversity was from 0.205 to 0.684 across the 15 microsatellites. These loci have the potential to reveal genetic structure and gene flow among H. circularisquama populations.     

Development of microsatellite markers for the crown‐of‐thorns starfish Acanthaster planci

We isolated nine polymorphic microsatellites from the crown‐of‐thorns starfish, Acanthaster planci. These loci provide one class of highly variable genetic marker as the number of alleles ranged from three to 12 and the observed and expected heterozygosities ranged from 0.130 to 0.783 and from 0.163 to 0.862, respectively. We consider that these loci are potentially useful for detailing the genetic structure and gene flow among A. planci populations.     

Gene flow of Acanthaster planci (L.) in relation to ocean currents revealed by microsatellite analysis

Population outbreaks of the coral-eating starfish, Acanthaster planci , are hypothesized to spread to many localities in the Indo-Pacific Ocean through dispersal of planktonic larvae. To elucidate the gene flow of A. planci across the Indo-Pacific in relation to ocean currents and to test the larval dispersal hypothesis, the genetic structure among 23 samples over the Indo-Pacific was analysed using seven highly polymorphic microsatellite loci. The F -statistics and genetic admixture analysis detected genetically distinct groups in accordance with ocean current systems, that is, the Southeast African group (Kenya and Mayotte), the Northwestern Pacific group (the Philippines and Japan), Palau, the North Central Pacific group (Majuro and Pohnpei), the Great Barrier Reef, Fiji, and French Polynesia, with a large genetic break between the Indian and Pacific Oceans. A pattern of significant isolation by distance was observed among all samples ( P =  0.001, r  = 0.88, n  = 253, Mantel test), indicating restricted gene flow among the samples in accordance with geographical distances. The data also indicated strong gene flow within the Southeast African, Northwestern Pacific, and Great Barrier Reef groups. These results suggest that the western boundary currents have strong influence on gene flow of this species and may trigger secondary outbreaks.     

Marked Amplification and Diversification of Products of ras Genes from Rat Brain,Rab GTPases,in the Ciliates Tetrahymena thermophila and Paramecium tetraurelia

ABSTRACT. Small GTPase Rab (products of ras genes from rat brain) is a widely conserved molecular switch among eukaryotes and regulates membrane trafficking pathways. It is generally considered that the number of Rab encoded in the genome correlates with multicellularity; however, we found that unicellular ciliates Tetrahymena thermophila (Tt) and Paramecium tetraurelia (Pt) possess many more Rab genes in their genome than the 64 HsRab genes in the human genome. We succeeded in isolating 86 cDNA clones of 88 TtRab genes in the Tetrahymena genome. By comparing the amino acid sequence of Rab in humans and the budding yeast Saccharomyces cerevisiae, 42 TtRab belonged to subfamilies functionally characterized and designated as conventional Rab, while the remaining 44 TtRab were considered to be species‐specific. To examine the diversity of Rab in ciliates, we searched for Rab genes in the genome database of P. tetraurelia. Overall, 229 PtRab genes were found and categorized as 157 conventional and 72 species‐specific PtRab, respectively. Among them, nine PtRab genes showed high homology to seven TtRab, suggesting the conservation of ciliate‐specific Rab. These data suggested that the range of Rab is markedly amplified and diversified in ciliates, which may support the elaborate cellular structures and vigorous phagocytosis of those organisms.     

Trypanosoma cruzi: Flow Cytometric Analysis of Developmental Stage Differences in DNA

Flow cytometry and DNA binding-specific fluorescent reagents were used to compare the total DNA, G-C, and A-T content of the epimastigote and trypomastigote stages of Trypanosoma cruzi stocks. Significant total DNA differences of 2–12% between epimastigotes and trypomastigotes were found in three of six stocks studied. The epimastigote G-C content of five of six stocks was 4–8% higher than trypomastigotes, whereas the trypomastigote A-T content was 2.5–13% higher than the epimastigote A-T content. Although no obvious developmental stage association between total DNA and base composition was found, intrastage associations do exist. These observations were unaffected by nucleoprotein extraction implying that the observed differences between trypomastigotes and epimastigotes are not a consequence of nucleoprotein interference with DNA-binding fluorochromes. The nuclei and kinetoplasts of four T. cruzi stocks were isolated and analyzed. Developmental stage differences in nuclear and kinetoplast DNA are stock-dependent and base composition-dependent; both organelles contribute to the observed differences in DNA of intact cells. We found a nearly linear association between the percentage of total kinetoplast DNA, G-C, and A-T content. During metacyclogenesis, the G-C content decreases by approximately 7% as epimastigotes transform into metacyclic trypomastigotes. The decrease in G-C content precedes changes in morphology or in complement resistance. If the DNA changes are causally connected to developmental stage transformations in T. cruzi remains to be determined. However, our results could facilitate studies of the molecular genetic processes the parasite uses to successfully complete various phases of its life cycle and, consequently, the disease process it evokes.     

DOES COLCHICINE AFFECT AGGREGATION OF NORMAL AND TRANSFORMED BHK CELLS DIFFERENTLY?

The effect of colchicine and vinblastine on cell aggregation was studied, using BHK cells and their transformed derivatives (pyBHK cells). When cells were dissociated with EDTA and the assay was made in a Ca²⁺-containing medium, the aggregation of transformed cells was prevented by colchicine and vinblastine, whereas the aggregation of normal cells was unaffected. When a Ca²⁺-free medium was used for aggregation, neither type of cell was influenced by these drugs. BHK and pyBHK cells, dissociated by trypsin in the presence of Ca²⁺, can aggregate only in the Ca²⁺-containing medium and the aggregation of both cell types was equally prevented by colchicine and vinblastine. Based on these results, it was concluded that colchicine and vinblastine inhibited the Ca²⁺-dependent mechanism of cell adhesion, but not the Ca²⁺-independent one which occurs in the Ca²⁺-free aggregation medium.