Atsushi Nakamoto

Analysis of Cellular Response and Gamma Interferon Synthesis in Bronchoalveolar Lavage Fluid and Lung Homogenate of Mice Infected with Pneumocystis carinii

The cellular and cytokine responses in the lungs of mice infected with Pneumocystis carinii were examined on both lung homogenates and bronchoalveolar lavage (BAL) fluids. In the lungs of infected mice, the number of P. carinii cysts rapidly decreased by day 7, then started to increase with a peak on day 14, and thereafter decreased gradually. When the presence of P. carinii was examined at the DNA level by dot blot hybridization, a similar clearance curve was obtained, and the organisms were shown to be completely eliminated on day 28. In the late phase of infection, leukocytes, mainly lymphocytes, increased in number when analyzed on lung homogenates, while no significant increase of inflammatory cells was observed in BAL fluids. An accumulation of both CD4+ and CD8+ T cells and an increase of activated T cells expressing IL‐2Rα were observed in lung homogenates of the infected mice. In addition, a considerable amount of IFN‐γ was detected in lung homogenates, but not in BAL fluids. These data indicate that lung homogenates are more suitable than BAL fluids for the analysis of cellular and cytokine responses in the lungs of mice infected with P. carinii. To define the involvement of IFN‐γ in host defense against P. carinii, the effect of this cytokine on the killing activity of macrophages against P. carinii was examined in vitro. IFN‐γ was found to augment this activity by increasing nitric oxide synthesis of the macrophages. Thus, it is suggested that IFN‐γ plays an important role in the protection of mice from P. carinii infection.

Food habits of Orii's flying-fox, Pteropus dasymallus inopinatus, in relation to food availability in an urban area of Okinawa-jima Island, the Ryukyu Archipelago, Japan

ABSTRACT The diet of the Oriis flying-fox, Pteropus dasymallus inopinatus, a subspecies of the Ryukyu flying-fox, was investigated on Okinawa-jima Island, Japan. The Oriis flying-fox is a generalist forager that feeds on 78 plant species from 62 genera and 43 families. They consume fruits of 53 species, flowers of 20 species, and leaves of 18 species. Cultivated or naturalized plants composed almost half of the diet. Diversity in the diet may be an adaptation to unstable food conditions on this small subtropical island. The number of individual Oriis flying-foxes fluctuated greatly corresponding to monthly changes in food availability, especially that of Ficus microcarpa, which was the animals main food resource throughout the year. Oriis flying-foxes may adapt to an urban environment by intensively using areas with abundant planted trees.

Feeding behavior of the Orii's flying-fox, Pteropus dasymallus inopinatus, on Mucuna macrocarpa and related explosive opening of petals, on Okinawajima Island in the Ryukyu Archipelago, Japan

Abstract. The role of the Oriis flying-fox, Pteropus dasymallus inopinatus, in the reproduction of Mucuna macrocarpa was investigated through captive and wild observations on Okinawajima Island in the Ryukyu Archipelago, Japan. When Oriis flying-fox fed on flowers of M. macrocarpa, it pushed its nose to the basal portion of the flowers to feed on nectar. This caused the hard petals of flowers to explode and consequently opened the carina. When a flying-foxs face pointed in the same direction as a flower, there was a significantly higher explosive opening rate compared with approaches from the side or the opposite direction (&khgr;2 test; P < 0.001). In total, in the captive setting, 32.2% of the flowers exhibited explosive opening. During such events, stamens with pollen and pistils emerged and attached to the throat and forehead of the flying-fox. Other main flower visitors were the brown-eared bulbul, the Japanese white-eye, the Japanese bush warbler, and the honeybee, but they did not stimulate explosive opening. These observations demonstrate that the Oriis flying-fox is the only explosive opener and the primary pollinator of this flower. On the other hand, flying-foxes sometimes damaged flowers. However, this does not appear to be a serious problem for M. macrocarpa, which has a large number of flowers.

Pneumocystis carinii抗原に対するヒト単核球のリンパ球増殖反応とIFN-γ産生

In vitro proliferative response and gamma-interferon (IFN-gamma) production to Pneumocystis carinii antigen were investigated in peripheral blood mononuclear cells (PBMC) from healthy volunteers and cord blood mononuclear cells (CBMC) from umbilical cords after delivery. Twenty three of 25 samples of PBMC had strong proliferative response, and 15 of 25 samples of PBMC produced IFN-gamma. In the samples showing strong proliferative response, CD4 lymphocytes expressed interleukin 2 receptors. None of the 3 CBMC samples had proliferative response nor production of IFN-gamma. When CD4 lymphocytes were depleted in PBMC, the proliferative response was markedly decreased and IFN-gamma production was abolished. In conclusion, the lymphocytes of healthy adults are activated and produce IFN-gamma by stimulation with P. carinii antigen, and these two response are both induced by CD4 lymphocytes.

Ranging Patterns and Habitat Use of a Solitary Flying Fox (Pteropus dasymallus) on Okinawa-jima Island, Japan

Most flying fox species (genus Pteropus) exhibit strong coloniality. They are highly mobile animals and commonly forage over vast areas. Only a small number of species are solitary, and their foraging and roosting patterns are not well understood. Here, we examined ranging patterns and habitat use of Oriis flying fox, Pteropus dasymallus inopinatus, a solitary fruit bat, using radiotracking from April 2002 to January 2006 on Okinawa-jima Island, Ryukyu Archipelago, Japan. The daily home range size for this species was very small (mean 52.5 ha) compared to other Pteropus species, although home range size was highly variable among individuals and seasons. The distance between a day roost and feeding trees was 621 m on average, with a maximum of 6,875 m. Day roost site shifted frequently (every 1.6 ±0.8 days) to a nearby site in the current foraging area. The distance between consecutive day roost sites was 792 m on average, with a maximum of 6,000 m. These bats favored forest habitats for roosting sites, whereas they often used residential areas as feeding sites. Our results suggest that they regularly shifted the location of their personal activity range, a small home range with roost switching, probably to track changes in food availability and to avoid local competition for food. The solitary roosting system of this species links to its flexible foraging system, which likely provides an advantage for using limited food resources on a small island, even when food is patchily distributed in urbanized habitats.

Activity patterns of the Ryukyu flying fox on a subtropical island: responses to seasonal changes in night length

Almost all chiropteran species are nocturnal, but some species are occasionally active during the daytime. We conducted radio-tracking surveys and direct observations of the Ryukyu flying fox, Pteropus dasymallus, in two different habitats—urbanized and forested areas—on a subtropical island from April 2002 to January 2006. We recorded the departure time and return time from/to day roosts as well as behavioral time budgets during the night. The departure and return times shifted in correspondence with seasonal changes in sunset and sunrise times. The Ryukyu flying fox tended to depart earlier in summer when the night length was shorter, suggesting that it adjusts its active period by departing earlier. On the contrary, the amount of foraging performed by the bats in urbanized areas decreased in the summer when fruits of Ficus microcarpa were more abundant, suggesting that the bats adjust their behavioral time budgets in line with local food availability. Daytime activity was observed only in the forested area. In conclusion, the duration of Ryukyu flying fox activity was found to primarily depend on seasonal changes in the light–dark cycle, and this bat may adjust its behavioral time budget according to local food availability and the intensity of human activities.

Home Range, Habitat Selection, and Activity of Male Asian House Shrews, Suncus murinus, on Okinawa-Jima Island

Abstract. The Asian house shrew (Suncus murinus) is a commensal species whose has become widespread across the Old World due to human activities. This species has been well studied in captivity as a laboratory animal; however, in the wild, its ecological habits are not well investigated. We conducted radio-telemetry surveys to determine home range, habitat selection, and activity patterns of the Asian house shrew over 1 week in September 2012 on Okinawa-jima Island, Japan. The home range size of male shrews was 2,556 m2 on average. The shrews were nocturnal, and they exhibited repetitive cycles of active and inactive during the night. The shrews did not move from dens during the daytime, although a few brief activities were observed near dens. Shrews favored grassland habitat as a nocturnal activity place (presumable foraging sites), whereas they favored under floors of artificial constructions as den sites. Our results suggest that Asian house shrews live in near human residential area to obtain the favorable den sites, and they do not absolutely need food resources from human activities for their settlement.