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71.
Li P Akimoto T Zhang M Williams RS Yan Z 《American journal of physiology. Cell physiology》2006,290(6):C1461-C1468
Skeletal muscle undergoes active remodeling in response to endurance exercise training, and the underlying mechanisms of this remodeling remain to be defined fully. We have recently obtained evidence that voluntary running induces cell cycle gene expression and cell proliferation in mouse plantaris muscles that undergo fast-to-slow fiber-type switching and angiogenesis after long-term exercise. To ascertain the functional role of cell proliferation in skeletal muscle adaptation, we performed in vivo 5-bromo-2'-deoxyuridine (BrdU) pulse labeling (a single intraperitoneal injection), which demonstrated a phasic increase (5- to 10-fold) in BrdU-positive cells in plantaris muscle between days 3 and 14 during 4 wk of voluntary running. Daily intraperitoneal injection of BrdU for 4 wk labeled 2.0% and 15.4% of the nuclei in plantaris muscle in sedentary and trained mice, respectively, and revealed the myogenic and angiogenic fates of the majority of proliferative cells. Ablation of resident stem cell activity by X-ray irradiation did not prevent voluntary running-induced increases of type IIa myofibers and CD31-positive endothelial cells but completely blocked the increase in muscle mass. These findings suggest that resident stem cell proliferation is not required for exercise-induced type IIb-to-IIa fiber-type switching and angiogenesis but is required for activity-dependent muscle growth. The origin of the angiogenic cells in this physiological exercise model remains to be determined. endurance exercise; adaptation 相似文献
72.
Huang X Xu H Sha MM Zhao L Ohkusu K Kawamura Y Ezaki T 《Microbiology and immunology》2006,50(4):273-279
The use of biosafety level 3 pathogens is an essential element of education and training at medical schools. We previously reported on invasion-defective strains of Salmonella enterica serovar Typhi, GTC 3P408 (DeltainvA, DeltasipB) and GTC 3P409 (DeltainvA, DeltasipB, and DeltaviaB), as candidates for use in educational programs. Vi negative strains of S. enterica serovar Typhi became extremely sensitive to complement attack but showed increased invasiveness. Therefore, this study was conducted to construct two virulencedefective strains, GTC 3P460 (DeltainvA, DeltasipB, and DeltarpoS) and GTC 3P461 (DeltainvA, DeltasipB, DeltaviaB, and DeltarpoS), of S. enterica serovar Typhi by deleting rpoS from the GTC 3P409 and GTC 3P408 strains. Stress tests demonstrated that GTC 3P460 and GTC 3P461 are sensitive to conditions of starvation, acid stress and oxidative stress. These results suggest that these virulence-defective strains have difficulty surviving in the gastric environment and in macrophages, characteristics that make them ideal candidates for education at level 2 facilities. Colony morphology and conventional biochemical features of these strains are identical to the parent strain S. enterica serovar Typhi GIFU 10007. 相似文献
73.
74.
Using a combination of atomic force, scanning and transmission electron microscopy, we found that avian erythrocytes infected with the avian malaria parasite Plasmodium gallinaceum develop 60 nm wide and 430 nm long furrow-like structures on the surface. Furrows begin to appear during the early trophozoite stage of the parasite’s development. They remain constant in size and density during the course of parasite maturation and are uniformly distributed in random orientations over the erythrocyte surface. In addition, the density of furrows is directly proportional to the number of parasites contained within the erythrocyte. These findings suggest that parasite-induced intraerythrocytic processes are involved in modifying the surface of host erythrocytes. These processes may be analogous to those of the human malaria parasite P. falciparum, which induces knob-like protrusions that mediate the pathogenic adherence of parasitized erythrocytes to microvessels. Although P. gallinaceum-infected erythrocytes do not seem to adhere to microvessels in the host chicken, the furrows might be involved in the pathogenesis of P. gallinaceum infections by some other mechanism involving host-pathogen interactions. 相似文献
75.
- A field study was carried out on the population dynamics of a thistle-feeding lady beetle, Henosepilachna pustulosa (Kôno ) living in a cool temperature climax forest in northern Kyoto Prefecture, central Japan.
- Intensive marking, release and recapture program was carried out to estimate the adult population parameters by usingJolly-Seber method.
- Sampling ratio was around 50%. Marking ratio rapidly rised as the census progressed and approached to 100%.
- Sex ratio (% ♀) was 63–69% in both overwintered and new adults.
- Daily survival rate was as high as 0.95 or more and constant throughout the season. Adult longevity in the spring was longer than 40 days.
- Reproductive rate i. e., the ratio of the number of newly emerged adults in a given generation to that of overwintered adults in the preceding generation, is very small, ranging 1–3, whereas winter survival is higher than 50%, consequently the size of populations in the study area remain in a remarkably constant size and it never reached a level where intraspesific competition occurred.
- The population characteristics of H. pustulosa are compared with those of the two closely related species, H. vigintioctopunctata and H. vigintioctomaculata, which are the pests of Solanaceous crops. Hp is more K-strategic than the two pest species.
76.
Kenji Kato Su-wan Oh Hiroyuki Yamamoto Takayuki Hanazato Ikuko Yasuda Akira Otuki Masayuki Takahashi 《Ecological Research》1992,7(3):267-276
In order to understand the control mechanisms of a large, stable bacterial standing stock, enclosure experiments were conducted
in a eutrophic lake, where both bacterial productivity and grazing pressure were very high. Total bacterial number in the
different enclosures ranged from 1.2 to 2.7×107 cells mL−1 throughout the experiment. The average bacterial cell production rate estimated from a grazer eliminating experiment was
6.3×105 cells mL−1 h−1. Difference in the bacterial cell production rate between shaded and unshaded enclosures was not apparent. Bacteria showed
a reduction in standing stock of only about 25–30% even after the supply of light was cut to 1%. Bacteria in the shaded enclosures
then recovered their production rate in the first 12 days of perturbation. Grazing pressure in the shaded enclosures was not
less than that for the control. Thus, it was considered a control mechanism of bacterial stable standing stock that the bacteria
shifted their organic substrate from extracellular dissolved organic carbon freshly released from phytoplankton to that already
stocked in the water column, though it is not known whether the dominant bacteria were the same. 相似文献
77.
Masaki Uchida Takayuki Nakatsubo Takao Horikoshi Kaneyuki Nakane 《Ecological Research》1998,13(1):17-26
In order to clarify the role of micro-organisms in the carbon cycle of the boreal forest ecosystem, the vertical distribution of soil carbon, soil microbial biomass and respiratory activity was studied in a black spruce forest near Candle Lake in Saskatchewan, Canada. The total amount of carbon contained in moss and soil layers (to the depth of 50cm beneath the mineral soil surface) was 7.2kgm–2, about 47% of which was in the L and FH horizons of the soil. Soil microbial biomass per dry weight of soil was largest in the L horizon, while the biomass per ground area was largest in the FH horizon. Soil respiration rate, measured using a portable infrared gas analyzer, was highest in the FH horizon, exceeding 50% of the total soil respiration. Low but significant CO2 emission was detected even in deeper soil horizon (E horizon). We also examined the respiration rate of cut roots and the effect of root excision on respiration. The contribution of root respiration to total soil respiration, calculated from root biomass and respiration rate of cut roots, was about 54%. The amount of carbon evolved through microbial respiration during the snow-free season (June–October) was estimated as 221gCm–2. Micro-organisms in the L horizon showed high respiratory activity as compared with those in deeper soil horizons. 相似文献
78.
Murakami C Yamazaki T Hanashima S Takahashi S Takemura M Yoshida S Ohta K Yoshida H Sugawara F Sakaguchi K Mizushina Y 《Biochimica et biophysica acta》2003,1645(1):72-80
Sulfo-glycolipids in the class of sulfoquinovosyl diacylglycerol (SQDG) including the stereoisomers are potent inhibitors of DNA polymerase alpha and beta. However, since the alpha-configuration of SQDG with two stearic acids (alpha-SQDG-C(18)) can hardly penetrate cells, it has no cytotoxic effect. We tried and succeeded in making a permeable form, sulfoquinovosyl monoacylglycerol with a stearic acid (alpha-SQMG-C(18)) from alpha-SQDG-C(18) by hydrolysis with a pancreatic lipase. alpha-SQMG-C(18) inhibited DNA polymerase activity and was found to be a potent inhibitor of the growth of NUGC-3 cancer cells. alpha-SQMG-C(18) arrested the cell cycle at the G1 phase, and subsequently induced severe apoptosis. The arrest was correlated with an increased expression of p53 and cyclin E, indicating that alpha-SQMG-C(18) induced cell death through a p53-dependent apoptotic pathway. 相似文献
79.
80.
Suhara Y Kittaka A Kishimoto S Calverley MJ Fujishima T Saito N Sugiura T Waku K Takayama H 《Bioorganic & medicinal chemistry letters》2002,12(22):3255-3258
The 2alpha-methyl-, 2alpha-(3-hydroxypropyl)-, and 2alpha-(3-hydroxypropoxy)-derivatives of the 'double side chain' analogue of 1alpha,25-dihydroxyvitamin D(3) were synthesized using Trost A-ring/CD-ring connective strategy. Regarding the requisite A-ring building blocks, a new, high yield and stereoselective route to the 2alpha-methyl compound starting from D-glucose was developed. All three new analogues showed potent HL-60 cancer cell differentiation activity. 相似文献