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.     

Base-line susceptibility of the oriental latrine fly, Chrysomya megacephala (Diptera: Calliphoridae), to five insecticides

Susceptibility to five insecticides was assessed on seven colonies of the oriental latrine fly, Chrysomya megacephala (Fabricius), originating from Japan, Hong Kong, Philippines, Indonesia and Papua New Guinea, and on C. saffranèa (Bigot) from PNG. All the colonies were susceptible to fenitrothion, diazinon, dichlorvos, permethrin and gamma-HCH, although the Jakarta, Manila and Tokyo colonies of C.megacephala were least susceptible (most tolerant) to diazinon, dichlorvos and permethrin. Feral forms of both Chrysomya species were 4-5-fold more susceptible to permethrin at the LD50 level than were all six colonies of the synanthropic form of C.megacephala.     

Different responses to photoperiod in non-diapausing colonies of the flesh fly, Boettcherisca peregrina

Abstract.  The effect of photoperiod on pupariation time and the ability to secrete ecdysteroids by the larval ring gland of the flesh fly, Boettcherisca peregrina , are compared among three tropical non-diapausing colonies, Bp (forest), Bp (Luwuk) and Bp (NC) and one temperate diapausing colony of Bp (Tokyo). Non-diapausing colonies do not enter diapause under any photoperiod at 20°C, whereas the Bp (Tokyo) diapausing colony enters diapause at the pupal stage under a short-day photoperiod. The times required for 50% pupariation of Bp (forest), Bp (Luwuk) and Bp (Tokyo) are 34 h, 36 h 20 min and 34 h 40 min under short days (SD), respectively. However, Bp (NC) pupariates in a much shorter time (26 h 10 min) compared with the others. The 50% pupariation times of Bp (NC), Bp (forest) and Bp (Tokyo) under long days (LD) are 27 h, 25 h 50 min and 26 h 40 min, respectively. However, it is much longer in Bp (Luwuk) at 53 h 20 min. The rates of secretion of ecdysteroids by the larval ring glands in vitro in Bp (Tokyo) and Bp (forest) are six- to ten-fold higher under SD (6.00 and 3.69 ng) than under LD (0.60 ng), whereas the ring glands of Bp (Luwuk) and Bp (NC) secrete 3.06 and 8.25 ng ecdysteroids under LD and 5.18 and 10.53 ng under SD, respectively. These results suggest there are at least three different physiological types among non-diapausing colonies of B. peregrina : Bp (forest), Bp (Luwuk) and Bp (NC).     

Geographic variation in the incidence of pupal diapause in Asian and Oceanian species of the flesh fly Boettcherisca (Diptera: Sarcophagidae)

ABSTRACT. The incidence of pupal diapause was examined in nine species of the genus Boettcherisca Rohdendorf ( B.peregrina, B.javanica, B.nathani, B.septentrionalis, B. karnyi, B. koimani, B. timorensis, B. formosensis and B.invaria ) collected from various localities in East Asia and Oceanian islands.
Colonies of B.septenrionalis, B. nathani and B.peregrina obtained from temperate regions of Asia and those of B. formosensis and B.peregrina from the continental subtropics entered pupal diapause in response to photoperiod at 20C.
The incidence of pupal diapause showed a geographic gradient in B.peregrina. No photoperiodically induced diapause was observed in the other five species which are indigenous to the tropical or subtropical habitats.
Different species of Boettcherisca seem to have evolved their pupal diapause independently of one another as an ecophysiological mechanism which enabled those species to expand from the tropical to temperate region.