Threshold change in forest understory vegetation as a result of selective fuelwood extraction in Nairobi, Kenya     

Takuya Furukawa  Kazue Fujiwara 《Forest Ecology and Management》2011,262(6):962-969

We examined whether heavy fuelwood collection can cause threshold change in understory forest community and evaluated how selective wood extraction might lead to delayed forest recovery in an urban forest of Nairobi, Kenya. Piecewise regression which represents strongest support for threshold change provided the best fit for the relationships between understory floristic composition (i.e. DCA axis 1) and human disturbance gradients (i.e. canopy cover, and distance from the slum), where threshold changes were detected at c.a. 350 m from the slum and c.a. 30% canopy cover. Only one tree species significantly indicated communities beyond the threshold while an aggressive invasive alien plant (IAP) Lantana camara was strongly represented. Total species diversity along the two human disturbance gradients peaked before the threshold was reached, suggesting that decline in species diversity along the prevailing disturbance gradient might be able to forecast threshold change. Tree species richness in the understory rapidly declined as the threshold was surpassed while other growth forms (i.e. shrubs, herbs and climbers) were relatively unaffected. The effect of selective tree cutting was indirectly impacting the forest understory as species richness pattern of preferred and non-preferred species paralleled that of trees and shrubs, respectively. Thickets of L. camara can negatively affect indigenous flora and its establishment was favored under selective fuelwood extraction removing certain tree species while leaving the IAP untouched. Shading can readily eliminate the IAP, but weak tree regeneration beyond the threshold suggested forest recovery might be delayed for longer than expected because of the interaction between selective fuelwood use and the IAP.  相似文献   

First report of Helleborus net necrosis virus isolated from hellebores with black death syndrome in Japan     

Takuya Shiraishi  Hideo Hoshi  Koki Eimori  Takeshi Kawanishi  Ken Komatsu  Masayoshi Hashimoto  Kensaku Maejima  Yasuyuki Yamaji  Shigetou Namba 《Journal of General Plant Pathology》2011,77(4):269-272

Helleborus net necrosis virus (HeNNV) in hellebores (Helleborus spp.) has been detected for the first time in Japan. Infected plants had black streaks on fresh leaves and black spots on sepals, which resembled the symptoms of black death disease. The morphology of the virus particles isolated from infected plants was comparable to that of carlaviruses. RT-PCR analysis showed that the entire HeNNV genomic sequence isolated in Japan shared 99% identity with that of HeNNV previously reported in the United States.  相似文献   

Effect of simulated acid rain on the growth of soybean     

Yoshishisa Kohno  Takuya Kobayashi 《Water, air, and soil pollution》1989,43(1-2):11-19

Soybean seedlings (Glycine max) grown in a glasshouse were exposed to simulated acid rain using a solution of deionized water containing sulfate, nitrate and chloride in concentrations and proportions equivalent to those in ambient rain water. Plants were subjected to acid rain treatment twice a week during the growing season, for a 1 hr period at a rate of 5 mm hr^?1. When the acid rain was below pH 3.0, visible symptoms developed in the young trifoliate leaves. However, at a pH above 3.0 there was no evidence of visible leaf injury; also tissue dry weights and leaf areas were not affected even after 7 weeks of exposure. The number of root nodules in plants exposed to acid rain at pH 4.0 tended to be higher than those of control plants maintained at pH 5.6, but decreased subsequently with decreasing pH. Based on our results current ambient levels of rain acidity in Japan should not have an adverse impact on seedling growth in soybean.  相似文献   

Effects of long-term administration of carprofen on healing of a tibial osteotomy in dogs     

Ochi H  Hara Y  Asou Y  Harada Y  Nezu Y  Yogo T  Shinomiya K  Tagawa M 《American journal of veterinary research》2011,72(5):634-641

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Can stumps tell what people want: Pattern and preference of informal wood extraction in an urban forest of Nairobi, Kenya     

Takuya Furukawa  Kazue Fujiwara  Samuel K. Kiboi  Patrick B. Chalo Mutiso 《Biological conservation》2011,144(12):3047-3054

Detailed patterns and preferences of informal wood extraction were investigated in an urban forest used by slum inhabitants of Nairobi, Kenya, as such information determines the sustainability of resource use. Instead of asking the people what they had secretly cut, a survey was conducted of the stumps and trees left in the forest to (i) evaluate how accessibility and patrolling affected spatial patterns of resource use, and to (ii) estimate a broad spectrum of species and species-specific size preferences. Both probability and size of cutting increased with better accessibility (represented by distance from the slum), and stump size exceeded that of living stem size around 1.7 km from the slum, which suggested magnified impact of tree cutting near the slum. Patrolling (represented by distance from ranger stations) had little effect in reducing the probability of cutting but was effective in reducing cut size. With the use of random effect models, a broad species preference spectrum (including less abundant and non-preferred species) was estimated, which indicated trends in vegetation change. Smaller stems were preferred for most species presumably used for domestic fuelwood, but major exploitation of large Brachylaena huillensis stems traded in the woodcarving industry was also revealed. Such detailed information on informal wood use can help forest managers to understand threats to the forests as well as the needs of local communities. This is a first step to redefining ‘acceptable’ resource use by the local community for their increased role and responsibility in sustainable forest management, especially when conventional controls of informal activities (i.e. exclusion and penalty) are not functioning well.  相似文献   

Stimulatory effect of peat on spore germination and hyphal growth of arbuscular mycorrhizal fungus Gigaspora margarita     

Nan MA  Kazuhira YOKOYAMA  Takuya MARUMOTO 《Soil Science and Plant Nutrition》2006,52(2):168-176

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Effect of activation treatments on actin filament distribution and in vitro development of miniature pig somatic cell nuclear transfer embryos     

Yamanaka K  Sugimura S  Wakai T  Shoji T  Kobayashi J  Sasada H  Sato E 《The Journal of reproduction and development》2007,53(4):791-800

In the present study, we investigated the effect of activation treatments on the actin filament distribution and in vitro development of somatic cell nuclear transfer (SCNT) embryos in miniature pigs. We combined three activation methods, ionomycin (ION), electrical stimulation (ES), and cycloheximide treatment (CH), to prepare seven activation treatments (ION, ES, CH, ION + CH, ION + ES, ES + CH and ION + ES + CH). First, we investigated the activation rate of oocytes and in vitro development of parthenotes. The activation rates of the oocytes in the ION, ES, CH, ION + CH, ION + ES, ES + CH, and ION + ES + CH groups were 42.9, 51.3, 0.0, 82.1, 80.6, 78.1 and 78.6%, respectively, showing that the rates of the combined treatment groups were significantly higher (P<0.05) than those of the single treatment groups. Although there were no significant differences in the activation rates of the combined treatment groups, the developmental rate to blastocysts in the ION + CH treatment group (36.1%) was significantly higher (P<0.05) than the other combined treatment groups (14.6-24.7%). Subsequently, we investigated the in vitro development and distribution of microfilaments in SCNT embryos. The developmental rate to blastcysts of the SCNT embryos in the ION + CH treatment group (11.3%) was significantly higher (P<0.05) than in the ES and ION + ES + CH treatment groups (4.5 and 5.2%, respectively). The rate of normal actin filament distribution in the SCNT embryos activated with ION + CH was significantly higher (P<0.05) than those activated with ES or ION + ES + CH treatment (63.3 vs. 46.8 or 46.4%). In addition, the fragmentation rate of the SCNT embryos activated with ION + CH was significantly lower (P<0.05) than those activated with ION + ES + CH (14.9 vs. 26.1%). The present results suggest that an activation treatment of ionomycin combined with cycloheximide may avoid physical damage to microfilaments and result in improved subsequent development of miniature pig SCNT embryos.  相似文献   

Arrhythmogenic right ventricular cardiomyopathy coincided with the cardiac fibrosis in the inner muscle layer of the left ventricular wall in a boxer dog     

Naoaki YAMADA  Takashi KITAMORI  Fumiyo KITAMORI  Kanako ISHIGAMI  Koji IWANAGA  Taiki ITOU  Ryosuke KOBAYASHI  Shino KUMABE  Takuya DOI  Junko SATO  Yumi WAKO  Minoru TSUCHITANI 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2015,77(10):1299-1303

A 7-year-old female boxer dog died suddenly without any clinical signs. It was suspected that the dog had arrhythmogenic right ventricular cardiomyopathy (ARVC) due to ventricular premature complexes and ventricular tachycardia at 3 years of age. The final diagnosis of ARVC was confirmed by histological characteristics, such as loss of cardiocytes and fibrofatty replacement, occurring in the right and left ventricular walls. In the cardiocytes, non-lipid vacuoles were observed. Cardiac fibrosis and intimal thickening of the small arteries occurred without fatty replacement in the inner muscle layer including the papillary muscles of the left ventricular wall. This paper describes the pathomorphological details of an ARVC case with coincidental cardiac fibrosis in the inner muscle layer of the left ventricular wall.  相似文献   

Intracerebroventricular administration of chicken glucagon‐like peptide‐2 potently suppresses food intake in chicks          下载免费PDF全文

Kazuhisa Honda  Takaoki Saneyasu  Tomohiko Shimatani  Koji Aoki  Takuya Yamaguchi  Kiwako Nakanishi  Hiroshi Kamisoyama 《Animal Science Journal》2015,86(3):312-318

Glucagon‐related peptides, such as glucagon‐like peptide (GLP)‐1, GLP‐2 and oxyntomodulin (OXM), are processed from an identical precursor proglucagon. In mammals, all of these peptides are suggested to be involved in the central regulation of food intake. We previously showed that intracerebroventricular administration of chicken OXM and GLP‐1 significantly suppressed food intake in chicks. Here, we show that central administration of chicken GLP‐2 potently suppresses food intake in chicks. Male 8‐day‐old chicks (Gallus gallus domesticus) were used in all experiments. Intracerebroventricular administration of chicken GLP‐2 significantly suppressed food intake in chicks. Plasma glucose concentration was significantly decreased by chicken GLP‐2, whereas plasma nonesterified fatty acid concentration was significantly increased. Intracerebroventricular administration of chicken GLP‐2 did not affect plasma corticosterone concentration. In addition, the anorexigenic effect of GLP‐2 was not reversed by the corticotropin‐releasing factor (CRF) receptor antagonist α‐helical CRF, suggesting that CRF is not a downstream mediator of the anorexigenic pathway of GLP‐2 in chicks. Intracerebroventricular administration of an equimolar amount of GLP‐1 and GLP‐2, but not OXM, significantly suppressed food intake in both broiler and layer chicks. All our findings suggest that GLP‐2 functions as a potent anorexigenic peptide in the brain, as well as GLP‐1, in chicks.  相似文献   

Immunohistochemical analysis of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxicity on the developmental dentate gyrus and hippocampal fimbria in fetal mice     

Yoshihiro KOBAYASHI  Tetsushi HIRANO  Takuya OMOTEHARA  Rie HASHIMOTO  Yuria UMEMURA  Hideto YUASA  Natsumi MASUDA  Naoto KUBOTA  Kiichi MINAMI  Shogo YANAI  Mitsuko ISHIHARA-SUGANO  Youhei MANTANI  Toshifumi YOKOYAMA  Hiroshi KITAGAWA  Nobuhiko HOSHI 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2015,77(11):1355-1361

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