CYTOKINE- AND NEUROPEPTIDE-MEDIATED DIFFERENTIATION IN RETINAL PIGMENT EPITHELIAL CELLS IN VITRO

To determine the mechanism of growth and differentiation of retinal pigment epithelial (RPE) cells it is important to understand the pathogenesis of several retinal diseases. Recently it has been reported that several cytokines and neuropeptides regulate the growth of RPE cells. In this study, the role of cytokines and neuropeptides in melanin synthesis, which is one indication of the RPE cell differentiation, was examined using chick RPE cells in vitro IL-1β, TNF-α, substance P, β-endorphin and methionine-enkephalin stimulated the melanin synthesis of RPE cells in a dose-dependent manner. The most effective concentrations of these agents on RPE cell melanin synthesis were not the same as that for RPE cell proliferation. These results indicate that cytokines and neuropeptides play an important role not only for the growth but also for the differentiation of RPE cells.     

Isolation of Zn2+ as an Endogenous Agonist of GPR39 from Fetal Bovine Serum

We attempted to determine natural agonists of GPR39 in fetal bovine serum (FBS). FBS was conditioned to extract peptides and fractionated by two types of HPLC. The activity of each fraction was monitored by intracellular calcium mobilization. Then the purified active ingredient was analyzed by inductively coupled plasma mass spectrometry. In this fashion, Zn^{2 +} ion was identified as an agonist of GPR39, though no peptidergic molecules were found. The calcium-mobilizing activity of Zn^{2 +} was not abolished by pertussis toxin but was by a phospholipase C (PLC) inhibitor, U73122, indicating that the activity of GPR39 is mediated through the G_qα -PLC pathway. In addition, Zn^{2 +} also activated mouse and rat GPR39, showing that the function of GPR39 as a Zn^{2 +} receptor is conserved across species. This study is the first exploration of GPR39 agonists in FBS and indicates that GPR39 functions as a Gq-coupled Zn^{2 +}-sensing receptor.     

Food web structure of the fungivorous insect community on bracket fungi in a Bornean tropical rain forest

1. If fungivorous insect diversity is maintained by host specialisation on particular fungi, it should be higher in the tropics than in temperate or boreal regions owing to high macrofungus species diversity. 2. To reveal the community and food web structure of fungivorous insects on bracket fungi, fungivorous insects were collected from 427 fruiting bodies belonging to 22 genera throughout the development and deterioration process in a 3‐ha plot of lowland dipterocarp tropical rain forest on Borneo Island. 3. Eight hundred and twenty‐nine individuals of 82 coleopteran species in 13 families from 111 fruiting bodies of 15 fungal genera were collected. Tenebrionidae and Staphylinidae were most common. Fifty‐three and 19 insect species were observed on Ganoderma and Phellinus, respectively. The numbers of insect species and individuals on a particular fungal genus were positively correlated with the abundance of that fungal genus. 4. Quantitative food web analysis revealed a high degree of specialisation at the whole‐community level. At least 65% of insect individuals were observed on Ganoderma at every stage of development and deterioration. Diverse insects coexist on one dominant fungal genus, Ganoderma, in contrast to our hypothesis. 5. The high abundance of Ganoderma fruiting bodies, which lack obvious defences against insect feeding, probably influences the bracket fungus–insect food web in this tropical rainforest.     

Effects of four-week feed restriction on toxicological parameters in beagle dogs

This study was conducted to examine any changes caused by feed restriction in dogs tocontribute to safety evaluation in toxicity studies. Two male 7-month-old beagledogs/group were fed 300 (control), 150 (50% of control), or 70 g/animal of diet daily (23%of control) for 4 weeks. Effects of feed restriction, except for clinical signs, werenoted depending on the feed dosage in almost all examinations. The principal outcomeswere: decreased body weight and water consumption, ECG changes (decreased heart rate andprolonged QTc), and hematopoietic and lymphopoietic suppression (decreased reticulocyteratio or white blood cell count in hematology, decreased nucleated cell count in bonemarrow, decreased erythroid parameters in myelography, and hypocellularity of bone marrowand thymic atrophy in histopathology). In addition, some changes were noted in urinalysis(decreased urine volume and sodium and potassium excretion), blood chemistry (decreasedALP and inorganic phosphorus and increased creatinine), organ weights, and gastrichistopathology. These results provide important reference data for distinguishing theprimary effects of test compounds from secondary effects of decreased food consumption intoxicity studies in beagle dogs.     

Ultrastructural Studies on Development of the Tail Gland of a Cuttlefish, Sepiella japonica

Hatching glands in embryos of teleosts and amphibians have been reported to be indispensable for hatching of the embryos. The cephalopod has capsuled eggs, so we expected to find some exocrine organ in the embryos that functioned as a hatching gland. The tail gland (Hoyle's organ) has been suspected to be a hatching gland in the cephalopod, and therefore we examined it during the course of development of cuttlefish embryos. Cells in the tail gland appeared similar to the hatching gland cells (HGCs) of teleosts and amphibians, and contained a number of secretion granules that also resembled the hatching enzyme granules (HEGs) in HGCs of teleosts and amphibians in size, electron density and distribution in the cells. However, a few of these granules were discharged one after another from an early stages, whereas most of them were retained up to the stage just before hatching, and then discharged all at once. The former process of trickling discharge was similar to that in amphibians and the latter process of abrupt discharge resembled that in teleosts.     

Arginine Vasopressin Contents of the Hypothalamus and Pituitary during Fetal and Postnatal Development in the Mouse

The contents of arginine vasopressin (AVP) in the hypothalamus and the pituitary of the mouse during fetal and postnatal development were measured by radioimmunoassay. AVP was first detected in the hypothalamo-pituitary system at the fetal age of 14 days (FA 14). After FA 15, the pituitary levels were higher than the hypothalamic levels except on FA 16. The greater AVP content of the hypothalamus than the pituitary only on FA 16 suggests that AVP synthesis in the perikarya of AVP-producing neurons may significantly increase between FA 15 and FA 16, and that the hormonal transport to the pituitary may be characteristically activated between FA 16 and FA 17. The levels of AVP in both the hypothalamus and the pituitary increased exponentially until the postnatal age of 21 days (PA 21). After PA 30, the content in the pituitary continued to increase, while that in the hypothalamus was kept almost constant. The decrease in AVP content in the pituitary was found between PA 0 and PA 1, and PA 21 and PA 30. These results suggest that AVP might be released from the pituitary in response to significant changes in water metabolism elicited at birth and weaning.     

Identification of genes regulated by dark adaptation and far‐red light illumination in roots of Arabidopsis thaliana*

Roots in the soil are illuminated by far‐red (FR) light passed through plant tissues in the daytime, and are in complete darkness at night. To evaluate whether gene expression of roots is affected by a dark‐FR light cycle, gene expression profiles were analysed for dark‐adapted versus light‐grown plants and for FR light‐illuminated versus dark‐adapted plants using the RIKEN Arabidopsis full‐length cDNA microarray (containing approximately 7000 independent, full‐length cDNA groups). Among candidate dark‐ and FR‐regulated genes, several were further analysed. Eleven dark‐inducible and five dark‐repressed genes were characterized. Almost all the dark‐inducible and –repressed genes were oppositely regulated by FR light illumination. The functions of dark‐ and FR‐responsive genes and the significance of FR light‐regulated gene expression in roots under ground are discussed.     

THE RELATIONSHIP BETWEEN CELL-SUBSTRATE ADHESIVENESS AND CELL GROWTH: A STUDY ON CHONDROCYTES CULTURED IN VITRO WITH CONDITIONED MEDIUM

Sparsely cultured chondrocytes from the sternae of 14-day chick embryos grew vigorously with a liquid medium using Falcon tissue culture dishes, when the conditioned medium (CM) prepared from the high-density cultures of neural retinae was used as a growth medium. In CM most cells adhered to the culture substrate, while in the fresh medium, in which cell growth was very slow, many viable cells remained unattached to the substrate. Enhancement of cell growth by CM was much less marked in cultures of chondrocytes suspended in agarose. The main effect of CM in enhancing cell growth is thus considered to be related to the increase of cell adhesiveness to the substrate. The main active factor in CM is non-dialyzable and heat-stable.     

Changes in the Content of Amino acids, Carbohydrates and Adenine Nucleotides following Budding in the Hardwood Stems of Mulberry Plants (Morus alba)

Quantitative changes in the free amino acids, sugars and adeninenucleotides in the hardwood stems of mulberry plants (Morusalba L.) were followed during bud opening. Following this, thestarch and ATP content decreased rapidly. The value of the adenylateenergy charge, ATP+; ADP/ATP + ADP+AMP, or ATP/ADP ratio becamelower. Asparagine, proline and arginine existed prominentlyat the onset of budding. After budding, the content of prolineand asparagine decreased consecutively, but that of arginineincreased initially and then decreased. Thus, the fluctuationsin the carbohydrate and amino acids metabolism in the hardwoodstems caused by budding was characterized by a rapid decreasein energy and carbohydrates reserves, and a concurrent decreasein proline and asparagine. The conversion of asparagine to arginineis also presumed to have taken place at the same time. Morus alba, mulberry, amino acids, carbohydrates, adenine nucleotides     

Effects of gamma-ray irradiation on metabolic changes in potato tubers in response to cutting

Potato tubers were subjected to cobalt-60 gamma-ray irradiationand stored at room temperature for from 10 days to 4 months.Effects of this irradiation on metabolic changes in potato tubersin response to cutting were investigated. The quantities ofpolyphenols, such as chlorogenic acid and isochlorogenic acid,in the tissue increased as compared with the non-irradiatedsample. Although the polyphenol content and activities of o-diphenoloxidase, peroxidase and phenylalanine ammonialyase increasedafter cutting, increases were lower in the irradiated sample.On the other hand, in the dose range between 5,000 and 12,400rad, the irradiated sample showed a larger defense action againstinfection by the black rot fungus, Ceratocystis fimbriata thandid the non-irradiated sample. (Received April 16, 1968; )