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.     

Effects of NO2 and O3 Alone or in Combination on Kidney Bean Plants (Phaseolus vulgaris L.): Growth, Partitioning of Assimilates and Root Activities

Ten-day old kidney bean plants (Phaseolus vulgaris L. cv. Shin-edogawa)were exposed to 2.0 and 4–0 parts 10^–6 NO2, and0.1, 0.2, and 0.4 parts 10^–6 O3 alone or in combinationfor 2, 4, and 7 d. The effects of these air pollutants wereexamined with respect to the growth, partitioning of assimilates,nitrogen uptake, soluble sugar content, and root respiration. Decreased dry matter production was significant with all treatmentsexcept 2.0 parts 10^–6 NO₂ and 0.1 parts 10^–6 O₃.Exposure to mixtures of the gases produced more severe suppressionof growth than exposure to the single gases. Root/shoot ratiowas significantly lowered at 7 d by the gas treatments otherthan 2.0 parts 10^–6 NO₂ and 0.1 parts 10^–6 O₃. Thetotal nitrogen content of plants was increased by all treatments;the higher percent of nitrogen found with O₃ exposure will resultfrom the growth retardation which increases the concentrationof nitrogen in the plants because the absorption of nitrogenby roots was unaffected. The combination of O₃ with NO₂ significantlydecreased the assimilation of NO₂ by the plants. The concentration of soluble sugars in roots was decreased bythe gas treatments. There was a strong positive correlationbetween soluble sugar content and dry weight of the roots harvestedat 7 d. Root respiration was relatively unchanged until 5 dand then decreased significantly at 7 d by 2.0 parts 10^–6NO₂ and 0–2 parts 10^–6 O₃. Retarded growth of theroots and the decreased root respiration may be due to diminishedtranslocation of sugars from leaves to roots caused by exposureto air pollutants. The uptake of soil nitrogen was not closelyrelated with root respiration in the case of O₃ exposure. Key words: NO₂, O₃, Phaseolus vulgaris, Growth, Sugars, Root respiration     

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.     

INHIBITORY EFFECT OF THIOURACIL ON GERMINATION OF LEAF MUSTARD SEED AND ITS REVERSAL BY PYRIMIDINE DERIVATIVES

1. Investigations were carried out to examine the effects of certainnucleic acid antimetabolites upon the germination of leaf mustardseed. Antimetabolites tested were 2 barbituric acid, variousuracil analogues, azaadenine, azaxanthine, azaguanine and benzimidazol.
2. Among the antimetabolites tested, only 2-thiouracil showedastrong inhibitory action on the germination of Brassica junceavar. foliosa (BAILEY) Corn. "Akatirimen".
3. This inhibitionby 2-thiouracil was relieved markedly by suchpyrimidine derivativesas uracil, thymine, orotic acid, uridylicacid and cytidylicacid, though these compounds did not showany promotive effecton the germination by themselves. On the other hand, sucha relieving effect was not shown bypurine derivatives suchas adenine, hypoxanthine and xanthine.
4. Among other kinds ofcole-wort seeds tested, a similar thiouracilinhibition on seedgermination was observed only in a limitednumber of speciesor varieties.

(Received November 10, 1962; )     

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.     

Growth models and the expected distribution of fluctuating asymmetry

Multiplicative error accounts for much of the size-scaling and leptokurtosis in fluctuating asymmetry. It arises when growth involves the addition of tissue to that which is already present. Such errors are lognormally distributed. The distribution of the difference between two lognormal variates is leptokurtic. If those two variates are correlated, then the asymmetry variance will scale with size. Inert tissues typically exhibit additive error and have a gamma distribution. Although their asymmetry variance does not exhibit size-scaling, the distribution of the difference between two gamma variates is nevertheless leptokurtic. Measurement error is also additive, but has a normal distribution. Thus, the measurement of fluctuating asymmetry may involve the mixing of additive and multiplicative error. When errors are multiplicative, we recommend computing log  E ( l ) − log  E ( r ), the difference between the logarithms of the expected values of left and right sides, even when size-scaling is not obvious. If l and r are lognormally distributed, and measurement error is nil, the resulting distribution will be normal, and multiplicative error will not confound size-related changes in asymmetry. When errors are additive, such a transformation to remove size-scaling is unnecessary. Nevertheless, the distribution of l  −  r may still be leptokurtic.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80, 57–65.     

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.     

A global molecular phylogeny of the fern genus Trichomanes (Hymenophyllaceae) with special reference to stem anatomy

To establish a basis for future taxonomic revisions and to infer the evolutionary traits of Trichomanes s.l. , one of two large filmy fern genera, molecular phylogenetic analyses were conducted using chloroplast rbcL sequences. Sampling covered most of the global distribution range of this genus throughout the tropical and temperate zones, as well as all taxonomically significant species by the addition of 51 samples principally from Asia. The evolution of eight selected characters, which were adopted as taxonomic keys and/or putatively reflect morphological regression, was optimized on the retrieved most parsimonious rbcL trees, together with new observations on the stem anatomy of 45 species. The eight robust clades retrieved within Trichomanes in the rbcL phylogeny conflict with the existing classifications. Our results also suggest that the cup-shaped sorus, the primary diagnostic character of the genus, appears in parallel in the Hymenophyllum lineage, as demonstrated by Pleuromanes (typified by Trichomanes pallidum ) included in the lineage. The suggestion that the regressive character states are homoplastic apomorphies in the evolution of the frond size, stem thickness, root system, and stem anatomy (stele and cortex) probably illustrates a strong tendency towards adaptive evolutionary transition in Trichomanes . © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 155 , 1–27.