The influence of gene flow on latitudinal clines of photoperiodic adult diapause in the Drosophila auraria species-complex

Temperate species belonging to the Drosophila auraria species complex, D. auraria Peng, D. biauraria Bock & Wheeler, D. triauraria Bock & Wheeler and D. subauraria Kimura, enter reproductive diapause to pass the winter in response to short daylengths. These species from Japan showed latitudinal clines in critical daylength which is longer in populations from higher latitudes. The slopes of these clines coincided well with that of the cline which is approximately predicted from climatic data, suggesting that these clines result from adaptation of the species to the latitudinal gradient of climatic conditions. Between the mainlands and the surrounding islands of Japan, the slopes of clines did not differ significantly, but the deviation from the regression line was usually smaller in mainland populations. It is assumed that gene flow reduces the genetic variation among mainland populations and results in the development of smooth clines. In the plain of east China, D. triauraria did not show clinal variation in critical daylength, although the development of the cline is expected from climatic data. Extensive gene flow among Chinese populations is considered to prevent the development of a cline.     

Selection for rapid and slow recovery from chill‐ and heat‐coma in Drosophila melanogaster

To assess the trade‐offs associated with cold and heat tolerance, selection experiments were conducted on the rate of recovery from chill‐ and heat‐coma using Drosophila melanogaster. Flies were treated with cold and heat to induce coma, and those that showed rapid or slow recovery from coma were selected. The lines selected for rapid (or slow) recovery from chill‐coma also showed rapid (slow) recovery from heat‐coma, although such a correlation was not observed in the lines selected for the rate of recovery from heat‐coma. On the other hand, survival after cold was enhanced in both lines selected for rapid and slow recovery from chill‐coma, and survival after heat was enhanced in both lines selected for rapid and slow recovery from heat‐coma. It was assumed that cold and heat treatments to induce coma caused some damages to flies and those that were tolerant to cold or heat were unintentionally selected in the present coma‐based selection. Only a weak trade‐off was observed between survival‐based cold and heat tolerance. On the other hand, developmental time was prolonged and desiccation resistance, walking speed, and longevity were reduced in the lines selected for rapid and slow recovery from chill‐ and/or heat‐coma, suggesting that these resistance and life‐history traits are under trade‐offs with cold and/or heat tolerance. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 72–80.     

Possible Involvement of ERK 1/2 in UVA‐Induced Melanogenesis in Cultured Normal Human Epidermal Melanocytes

UV‐induced melanogenesis is a well known physiological response of human skin exposed to solar radiation; however, the signaling molecules involved in the stimulation of melanogenesis in melanocytes following UV exposure remain unclear. In this study we induced melanogenesis in vitro in normal human epidermal melanocytes using a single irradiation with UVA at 1 kJ/m² and examined the potential involvement of mitogen‐activated protein kinases (MAPK) as UVA‐responsive signaling molecules in those cells. UVA irradiation did not affect the proliferation of melanocytes, but it did increase tyrosinase mRNA expression, which reached a maximum level 4 hr after UVA irradiation. The amount of tyrosinase protein, as quantitated by immunoblotting, was also increased at 24 hr following UVA irradiation. Among the MAPK examined, extracellular signal‐related kinase (ERK) 1/2 was phosphorylated within 15 min of UVA irradiation, but no such phosphorylation was observed for c‐Jun N‐terminal kinases (JNK) or p38. Accordingly, the activity of ERK1/2 was also increased shortly after UVA irradiation. These responses of ERK1/2 to UVA irradiation were markedly inhibited when cells were pre‐treated with N‐acetyl‐l ‐cysteine, an antioxidant, or with suramin, a tyrosine kinase receptor inhibitor. The formation of (6‐4)photoproducts or cyclobutane pyrimidine dimers was not detected in cellular DNA after UVA irradiation. These findings suggest that a single UVA irradiation‐induced melanogenesis is associated with the activation of ERK1/2 by upstream signals that originate from reactive oxygen species or from activated tyrosine kinase receptors, but not from damaged DNA.     

Quantitation and Visualization of Ultraviolet‐Induced DNA Damage Using Specific Antibodies: Application to Pigment Cell Biology

The major types of DNA damage induced by sunlight in the skin are DNA photoproducts, such as cyclobutane pyrimidine dimers (CPDs), (6‐4)photoproducts (6‐4PPs) and Dewar isomers of 6‐4PPs. A sensitive method for quantitating and visualizing each type of DNA photoproduct induced by biologically relevant doses of ultraviolet (UV) or sunlight is essential to characterize DNA photoproducts and their biological effects. We have established monoclonal antibodies specific for CPDs, 6‐4PPs or Dewar isomers. Those antibodies allow one to quantitate photoproducts in DNA purified from cultured cells or from the skin epidermis using an enzyme‐linked immunosorbent assay. One can also use those specific antibodies with in situ laser cytometry to visualize and measure DNA photoproducts in cultured cells or in the skin, using indirect immunofluorescence and a laser‐scanning confocal microscope. This latter method allows us to reconstruct three‐dimensional images of nuclei containing DNA photoproducts and to simultaneously examine DNA photoproducts and histology in multilayered epidermis. Using those techniques, one can determine the induction and repair of these three distinct types of DNA photoproducts in cultured cells and in the skin exposed to sublethal or suberythematous doses of UV or solar simulated radiation. As examples of the utility of these techniques and antibodies, we describe the DNA repair kinetics following irradiation of human cell nuclei and the photoprotective effect of melanin against DNA photoproducts in cultured pigmented cells and in human epidermis.     

Preliminary hydrobiological survey of some Southeast Asian inland waters*

The preliminary research in some tropical inland waters of Asia is described and suggestions made concerning Phase II of this project undertaken by the International Biological Programme/ Section PF (Freshwater Productivity). Environmental factors were measured in some of the main lakes and rivers and samples taken of the plant and animal life. The stomach contents of over 80 species of fish were examined and the remains of plants and animals present compared with the numbers present in the environment as obtained by the usual hydrobiological netting techniques. Some of the important problems associated with the biological productivity of these waters is discussed in the light of the results obtained from this preliminary survey.     

Ciliate Protozoa in the Rumen of Sassaby Antelope, Damaliscus lunatus lunatus, Including the Description of a New Species and Form

ABSTRACT. Composition of rumen ciliate fauna in five Zambian, sassaby antelopes was determined. Six genera, 18 species, and four forms were identified. One new species and form, belonging to the subfamily Diplodiniinae, were found, then labeled Ostracodinium damaliscus n. sp. and Diplodinium bubalidis f. aspinosum n. f., respectively. Only ophryoscolecid species were present while isotrichids were absent. Twelve of 18 total species are commmonly found in African antelopes. Three of those 12 species, Entodinium fyferi, Enoploplastron garstangi and Opisthotrichum janus , are only found in African antelopes. Percentage composition was low in the genera ml of rumen fluid, and the average number of ciliate species per host was 17.2.     

GENERAL ACCOUNTS ON THE OÖCYTE GROWTH AND THE IDENTIFICATION OF VITELLOGENIN BY MEANS OF IMMUNOSPECIFICITY IN THE COCKROACH, BLATTELLA GERMANICA (L.)

The female Blattella germanica pushes out an oötheca 11 days after adult ecdysis and carries it for about 25 days until nymphs hatch out. The terminal oöcyte begins to accumulate yolk abruptly 4 or 5 days after adult ecdysis and grows fully on day 10 when its volume reaches 180 times as compared to that at adult ecdysis.
Vitellogenin, the vitellogenic female-specific protein, was identified by immunoelectrophoresis and Ouchterlony's test. Fluctuation of vitellogenin in the blood, ovary and embryo at various stages was analyzed. Vitellogenin appears in the female blood 3 or 4 days after adult ecdysis and disappears soon after terminal oöcytes have been released to an oötheca. In the ovary, it appears 4 or 5 days after adult ecdysis and disappears when terminal oöcytes leave the ovary. It remains in embryos until shortly before hatching, but is absent in newly hatched nymphs.