EFFECT OF LIGHT ON AUXIN TRANSPORT AND ELONGATION OF AVENA MESOCOTYL

The present work was undertaken to find if there are relations between light and auxin action on elongation of coleoptilar node and mesocotyl with Avena seedlings. Red light inhibited the elongation of mesocotyl and simultaneously decreased the rate of transport of diffusible auxin through the node. Red light also inhibited the transport of exogenously given IAA through the nodal region. The light inhibition of IAA transport was closely related to the increase of IAA immobilization. As the age proceeds, the ability of IAA immobilization increased with the decrease in the rate of mesocotyl elongation, even if the seedling was grown in complete darkness. The nature of radioactive substances found in the IAA-C¹⁴ treated tissue was examined by paper chromatography. The above results strongly suggested that the increase of IAA immobilization might result in the inhibition of mesocotyl elongation.     

Circadian Motile Activity of Erythrophores in the Red Abdominal Skin of Tetra Fishes and Its Possible Significance in Chromatic Adaptation

The red abdominal skin of the neon tetra Paracheirodon innesi and the cardinal tetra P. axelrodi was found to blanch at night or in the dark. Melatonin added to the bathing medium caused blanching of the red skin. Microscopic observations of the erythrophores indicated that the erythrosomes aggregated in response to norepinephrine, melanin-concentrating hormone (MCH), and melatonin. Of these compounds, melatonin was the most effective. By contrast, many erythrophores were refractory to MCH. Alpha-melanophore-stimulating hormone, isoproterenol, adenosine, and ATP each caused dispersal of the pigment to some extent. Isoproterenol dispersed the pigment only when an alpha-adrenergic blocker, tolazoline, was present. It appears that the change in color of the abdominal skin is primarily due to increased secretion during the night of the pineal hormone melatonin, while other hormonal and nervous factors may modify the distribution of the pigment in the erythrophores.     

The ultrastructure of anionic sites in rat articular cartilage as revealed by different preparation methods and polyethyleneimine staining

The ultrastructure of anionic sites in the middle layer of rat articular cartilages was studied by two methods, the quick-freezing and deep-etching method, and the quick-freezing and freeze-substitution method. The anionic sites were visualized with a cationic tracer, polyethyleneimine. They were also compared with those revealed in tissues subjected to conventional fixation, such as pre-embedding or post-embedding. With the deep-etching method, three-dimensional meshwork structures were observed more clearly in the extracellular matrix compared with those seen in conventional ultrathin sections. In combination with polyethyleneimine staining, in which no chemical contrast was needed for visualization of anionic sites, numerous stained particles were detected around filaments in the extracellular matrix, indicating that they were anionic sites consisting mainly of proteoglycans. With the pre-embedding method and polyethyleneimine staining, the shapes of aggregated stained particles varied with different preparation procedures, including chemical fixation and contrasting. The fine meshworks were also observed with the post-embedding method and polyethyleneimine staining. It is suggested that such images of anionic sites, as revealed by the deep-etching method and the post-embedding polyethyleneimine-staining method with low-temperature dehydration, are probably closer to native states than those revealed by the conventional pre-embedding polyethyleneimine-staining method. © 1998 Chapman & Hall     

The status of donor cancer tissues affects the fate of patient-derived colorectal cancer xenografts in NOG mice

Patient-derived xenografts (PDXs) of tumors are increasingly becoming important tools for translational research in oncology. The NOD.Cg-Prkdc^scid Il2rg^tm1Sug/Jic (NOG) mouse is an efficient host for PDXs. Thus as a basis for future development of methods to obtain PDXs from various disease types, we have studied the factors that affect the outcome of transplantation of human colorectal cancer in NOG mice. Of the original donor cases examined, 73% had successful engraftment. The outcome of donor-matched tissues was consistent in most cases, and was thought to show that the condition of the host did not affect engraftment. Next we analyzed the tumor aggressiveness in terms of histology grade of the original tumor and found that they were related to engraftment. Detailed histopathological examination of the transplanted tissues strongly indicated that lymphocytes engrafted with the tumor cells affect engraftment. As a factor related to transplantation of lymphocytes, we studied the human IgG concentration in the serum of tumor-bearing mice, but there was no tendency for higher concentrations to result in unsuccessful engraftment. Finally, we studied the type, density and location of T cells in the original donor tissue to determine the immune contexture and found that the unsuccessful engraftment cases tended to have an adequate or coordinated immune contexture compared to successful engraftment cases. From these results, we concluded that the aggressiveness and the T cell infiltration of the original tumor affect the outcome of transplantation in the NOG mouse.     

CHANGES IN THE LEVELS OF NICOTINAMIDE NUCLEOTIDES AND IN ACTIVITIES OF NADP-DEPENDENT DEHYDROGENASES AFTER A BRIEF ILLUMINATION OF RED LIGHT

A brief red irradiation caused an immediate rise of NADPH level and an immediate drop of NADP level in coleoptilar node of etiolated Avena seedling. With the duration of the dark incubation after the red irradiation, the level of NADPH gradually fell, and the NADP level rose higher than in non-irradiated materials. Such NADP-dependent dehydrogenases as glucose-6-phosphate, isocitrate and 6-phosphogluconate dehydrogenases were activated immediately after the red irradiation.     

Cellular Aspects of the Control of Physiological Color Changes in Fishes

SYNOPSIS. Recent advances in the cellular aspects of chromatophoricactivities in fishes are reviewed, special emphasis being laidon the black pigment-containing cells, the melanophores. A fewrecent electron-microscopic studies have disclosed the finestructure of melanophores. They are enclosed with a single cellmembrane, within which melanosomes and other cell organellesare found. All observations favor the view that melanosomesare selectively moved through the cellular processes, leavingthe cell contour rather fixed. In regard to these findings,current ideas about the mechanisms of pigment movements arediscussed. Particular attention is directed to the possibleintervention of microtubules and the theory of migration ofpigment by intracellular electrophoresis. The regulatory mechanismsof pigment cells are then dealt with. The adrenergic natureof transmission is affirmed in the peripheral melanin-aggregatingnervous system. The mode of nervous supply to a melanophoreis also analyzed. Investigations of the antagonistic, melanin—dispersing,nervous system are also considered, with special reference torecent physiological studies and to the finding of synapticvesicles by electron microscopy. On the basis of these results,a new interpretation of the so-called Parker effect is proposed.     

Analysis and understanding of butterfly community composition based on multivariate approaches and the concept of generalist/specialist strategies

We analyzed butterfly community composition using multivariate analyses. The results of principal components analysis showed that the butterfly community was composed mainly of two species groups. This species grouping was also supported by the results of the cluster analysis (unweighted pair‐group method using arithmetic average). Comparing the present results with species classification based on the generalist/specialist concept, the butterfly community was found to be composed of five species groups differing from each other in their ecological characteristics: a specialist group, two intermediate groups and two generalist groups. By comparison of their characteristics, it was suggested that, in the butterfly community, the positions of the specialist group and one of the generalist groups are the endpoints on the generalist/specialist selection spectrum, and the three other groups are positioned between these two extremes. The multivariate analyses showed that the species grouping with the generalist/specialist concept based only on voltinism and larval diet breadth was not sufficient to classify both intermediate and generalist groups, and also succeeded in extracting a typical generalist group from the butterfly community. From these results, we propose and recommend the synergetic application of the generalist/specialist concept and multivariate approaches to the detailed analysis and deeper understanding of community structure and composition.     

PHYTOCHROME ACTION IN ORYZA SATIVA L. III. THE SEPARATION OF PHOTOPERCEPTIVE SITE AND GROWING ZONE IN COLEOPTILES, AND AUXIN TRANSPORT AS EFFECTOR SYSTEM

• 1 In 4-day-old etiolated rice seedlings, 3 mm of the coleoptile tip did mainly perceive the photostimulus to cause the phytochrome-dependent inhibition of coleoptile elongation. At this age, cell elongation occurred most in the middle portion of coleoptiles in the dark, and was reversibly controlled by a brief exposure of the tip to red and far-red light. Thus, the photoperceptive site was evidently separated from the growing zone in intact rice coleoptiles.
• 2 The red-light-induced inhibition of coleoptile elongation was nullified by the removal of tip followed by the exogenous application of IAA. The sensitivity of thus treated coleoptiles to IAA was gradually lost during intervening darkness between the irradiation and the decapitation, and a 50% loss was obtained at ca. 6th hour at 26°C.
• 3 Polar auxin transport from coleoptile tips was remarkably prevented at the period between, at least, 2nd and 4th hour after red irradiation, and it recovered to the level of dark control by the 6th hour. Far-red light given immediately after red irradiation reversed the yield of diffusible auxin up to that of far-red control.

     

PHOTOCONTROL OF DEVELOPMENT OF EXCISED ERAGROSTIS EMBRYOS

• 1 Both the germination of intact seeds and the development of excised embryos depend on their after-ripening. Shortly after the harvest, the intact seeds of Eragrostis ferruginea are in dormancy and germinate neither in the light nor in the dark. The ability of seeds to germinate under both conditions, however, gradually increases with the progress of after-ripening. The development of excised embryos, on the other hand, is readily induced in the light and dark even shortly after the harvest. As the after-ripening proceeds, however, the ability of excised embryos to develop gradually decreases and is finally lost 18 months after the harvest. The after-ripened embryos whose ability to develop is completely reduced become light sensitive again when they are supplied with the yeast extract of a low concentration, and develop readily even in darkness at a high concentration of the extract.
• 2 The photorequirement for development of excised embryos is scarcely affected by oxygen concentrations, and the embryo growth can take place equally in both light and darkness in the atmosphere containing 100 to 10 percent of air, while it can not be induced in pure nitrogen.
• 3 The promotion of embryo development by light is observed at the time when the ability of embryos to develop declines. The effectiveness of the irradiation is very similar to that in intact seed germination.