A Similar Expression Pattern of Adhesion Molecules between Intermediate TCR Cells in the Liver and Intraepithelial Lymphocytes in the Intestine

Two major populations of extrathymically differentiated T cells exist in the liver and intestine. Such T cells in the liver have TCR of intermediate intensity (i.e., intermediate TCR cells) and constitutively express IL-2 receptor β-chain (IL-2Rβ), whereas those in the intestine, especially intraepithelial lymphocytes, have TCR of bright intensity, consisting of a mixture of IL-2Rβ⁺ and IL-2Rβ^–. All mature thymocytes and thymus-derived T cells seen in the peripheral immune organs are TCR-bright⁺IL-2Rβ^– under resting conditions. When the expression pattern of adhesion molecules, including CD44, L-selectin, LFA-1 and ICAM-1, was compared among these T-cell populations, they displayed quite unique patterns of expression. All extrathymic T cells in the liver, intestine, and even other organs were CD44⁺L-selectin^– LFA-1⁺⁺ICAM-1⁺, whereas thymocytes and thymus-derived T cells were CD44^– L-selectin⁺LFA-1⁺ICAM-1^–. This inverted expression of adhesion molecules between extrathymic T cells and thymus-derived T cells might be associated with their unique tissue-localization.     

Phylogenetic place of guinea pigs: no support of the rodent-polyphyly hypothesis from maximum-likelihood analyses of multiple protein sequences

Graur et al.'s (1991) hypothesis that the guinea pig-like rodents have an evolutionary origin within mammals that is separate from that of other rodents (the rodent-polyphyly hypothesis) was reexamined by the maximum-likelihood method for protein phylogeny, as well as by the maximum-parsimony and neighbor-joining methods. The overall evidence does not support Graur et al.'s hypothesis, which radically contradicts the traditional view of rodent monophyly. This work demonstrates that we must be careful in choosing a proper method for phylogenetic inference and that an argument based on a small data set (with respect to the length of the sequence and especially the number of species) may be unstable.      

Physical Characterization of the Chromosomal DNA of the Yeast Saccharomyces exiguus

The number of chromosomes in the yeast Saccharomyces exiguuswas determined to be thirteen by two-dimensional pulsed-fieldgel electrophoresis. The thirteen chromosomes ranged in DNAsize from 520 to 2,600 kbp, with a total length of approximately14 Mbp. Numbers I to XIII were assigned to the chromosomes indecreasing order of DNA length. Southern hybridization analysisusing total DNAs from S. exiguus and S. cerevisiae as probesshowed that there was no significant homology between the chromosomalDNAs of the two species, except in the case of the chromosomalDNA that included rDNA. When rDNA and genes LEU2, TRP1, URA3and HO of S. cerevisiae were used as hybridization probes, itwas apparent that S. exiguus had DNA sequences homologous tothe rDNA and to the LEU2 and HO genes. In S. exiguus, rDNA-likeand LEU2-like DNAs were located on chromosomes I and IX, respectively,and HO-like DNA was located on chromosome VI or VII. (Received May 17, 1993; Accepted July 15, 1993)     

The giant panda is closer to a bear,judged by α- and β-hemoglobin sequences

Summary Using - and -hemoglobin sequences, we made a maximum likelihood inference as to the phylogenetic relationship among carnivores, including the two pandas, giant and lesser. Molecular phylogenetic studies up to 1985 had consistently indicated that the giant panda is more closely related to the bear than to the lesser panda. In 1986, however, a contradictory tree was constructed, using hemoglobins and so on, in which the two pandas link together (Tagle et al. 1986). In contrast to that tree, our conclusion supports the close relationship between bear and giant panda. The surface impression of a close relationship between the two pandas drawn from pairwise amino acid differences is explained by a rapid rate of hemoglobin evolution in the bear compared to that in the two pandas.Offprint requests to: T. Hashimoto     

Visual prey discrimination of queen and worker ants by a generalist lizard

Laboratory experiments were conducted to test the hypothesis that widelyforaging generalist lizard,Eumeces okadae, visually discriminates palatable queen ants from unpalatable worker ants. The workers ofCamponotus japonicus andLasius niger were rejected on sight, while the queens of both species were eaten with little prior chemical examination by tongue flicks or licks. Comparison of the lizards' responses towards the workers and wingless queens of similar size indicated that neither body size nor presence or absence of wings accounted for difference in responses toward the 2 ant castes. The lizards probably discriminated different ant castes by body proportions.     

Osteological and histological comparison of the development of the interphalangeal intercalary skeletal element between hyloid and ranoid anurans

Some frog species have a unique skeletal element, referred to as the intercalary element (IE), in the joints between the terminal and subterminal phalanges of all digits. IEs are composed of cartilage or connective tissue and have a markedly differ shape than the phalanges. IEs are highly related to the arboreal lifestyle and toe pads. The IE is found only in neobatrachian frogs among anurans, suggesting that it is a novelty of Neobatrachia. IEs are widely distributed among multiple neobatrachian lineages and are found in the suborders Hyloides and Ranoides (the two major clades in Neobatrachia). However, it is unclear whether the IEs found in multiple linages resulted from convergent evolution. Therefore, in this study, we aimed to examine how similar or different the developmental trajectories of the IEs are between Hyloides and Ranoides. To that end, we compared the osteological and histological developmental processes of the IEs of the hyloid frog Dryophytes japonicus and the ranoid frog Zhangixalus schlegelii. Both species shared the same IE-initiation site and level of tissue differentiation around the IE when it began to form in tadpoles, although the IE developments initiated at different stages which were determined by external criteria. These results suggest that similar mechanisms drive IE formation in the digits of both species, supporting the hypothesis that the IEs did not evolve convergently.     

β-Glucosidase activities and HCN liberation in unimbibed and imbibed seeds, and the induction of cocklebur seed germination by cyanogenic glycosides

In many seed species, the major source of HCN evolved during water imbibition is cyanogenic glycosides. The present investigation was performed to elucidate the role of endogenous cyanogenic glycosides in the control of seed germination and to examine the involvment of β-glucosidase in this process. All seed species used here contained some activities of β-glucosidase already in the dry state before imbibition. in the decreasing order of Malus pumila, Daucus carota, Hordeum vulgare, Chenopodium album and so on. β-Gluosidase activity in upper and lower seeds of cocklebur (Xanthium pennsylvanicum Wallr.) decreased with imbibition, and in lower seeds the activity disappeared when they germinated. On the contrary, in caryopses of rice (Oryza sativa L. cv. Sasanishiki) β-glucosidase increased during imbibition, and this increase continued even after germination. β-Glucosidase in cocklebur seeds was more active in the axial than in the cotyledonary tissue. Amygdalin, prunasin and linamarin could all serve as substrattes for the β-glucosidase(s) from both cocklebur and rice. Amygdalin, prunasin and linamarin as well as KCN, were effective in stimulating the germination of upper cocklebur seeds. The seeds evolved much more free HCN gas when they were exposed to the cyanogenic glycosides than when the glycosides were absent. Moreover, the application of the cyanogenic glycosides or of KCN caused accumulation of bound HCN in the seeds. Carbon monoxide, which stimulated cocklebur seed germination only slightly, did not cause accumulation of bound HCN. We suggest that a balance between the cytochrome and the alternative respiration pathways, which is adequate for germination (Esashi et al. 1987. Plant Cell Physiol. 28: 141–150), may be brought about by the action of endogenous HCN; a large portion of which is liberated from cyanogenic glycosides via the action of β-glucosidase. In addition to the partial suppression of the cytochrome path and unlike carbon monoxide, the HCN thus produced may act to supply cyanide group(s) to unknown compounds necessary for germination.     

Phototropism in hypocotyls of radish. VI. No exchange of endogenous indole-3-acetic acid between peripheral and central cell layers during first and second positive phototropic curvatures

Using a physicochemical method, the distribution of endogenous indole-3-acetic acid (IAA) was measured in the peripheral and central cell layers, as well as in the illuminated and shaded sides of phototropically stimulated radish hypocotyls (Raphanus sativus var. hortensis f. gigantissimus Makino). The IAA was evenly distributed over the illuminated and shaded sides in the first and second positive phototropic curvatures induced by a pulse or a continuous unilateral illumination with blue light. Also, no net exchange of the IAA between the peripheral and central cell layers was observed during these curvatures. These results suggest that phototropism of radish hypocotyls cannot be described by the Cholodny-Went theory.