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921.
美洲黑杨(Populus deltoids)是一种重要的商业用材树种, 在我国多用作胶合板和纸浆原料, 其速生性的特点也很早为人们所认识。众所周知, 树木次生维管组织的发育具有内在的节律性, 与此同时维管组织的细胞内含物也会发生动态变化。利用电镜技术及细胞化学方法, 研究了美洲黑杨次生维管组织的发育以及细胞内含物分布的变化, 发现次生维管组织的发育具有内在节律性, 在年周期中表现为分化期和休眠期交替出现; 次生韧皮部与次生木质部交替分化形成。在维管组织发育过程中, 早期蛋白质和脂类物质首先减少, 然后淀粉粒解体消失, 发育期内维管组织的蛋白质、脂类和淀粉的积累最少, 休眠期内维管组织细胞内最早出现淀粉的积累, 然后蛋白质和脂类物质积累大大增加。杨树维管组织发育过程的内在节律性与细胞内含物的动态变化密切相关。 相似文献
922.
Effects of elevated atmospheric CO2 on soil enzyme activities at different nitrogen application treatments
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It has been predicted that elevated atmospheric CO2 will increase enzyme activity as a result of CO2-induced carbon entering the soil. The objective of this study was to investigate the effects of elevated atmospheric CO2 on soil enzyme activities under a rice/wheat rotation. This experiment was conducted in Wuxi, Jiangsu, China as part of the China FACE (Free Air Carbon Dioxide Enrichment) Project. Two atmospheric CO2 concentrations (580±60) and (380±40) μmol·mol-1) and three N application treatments (low-150, normal-250 and high-350 kg N·hm-2) were included. Soil samples (0-10 cm) were collected for analysis of β-glucosidase, invertase, urease, acid phosphates and β-glucosaminidase activities. The results revealed that with elevated atmospheric CO2 β-glucosidase activity significantly decreased (P < 0.05) at low N application rates; had no significant effect with a normal N application rate; and significantly increased (P < 0.05) with a high N application rate. For urease activity, at low and normal N application rates (but not high N application rate), elevated atmospheric CO2 significantly increased (P < 0.05) it. With acid phosphatase elevated atmospheric CO2 only had significant higher effects (P < 0.05) at high N application rates. Under different CO2 concentration, effects of N fertilization are also different. Soil β-glucosidase activity at ambient CO2 concentration decreased with N fertilization, while it increased at elevated CO2 concentration. In addition, invertase and acid phosphatase activities at elevated CO2 concentration, significantly increased (P < 0.05) with N treatments, but there was no effect with the ambient CO2 concentration. For urease activity, at ambient CO2 concentration, N fertilization increased it significantly (P < 0.05), whereas at elevated CO2 concentration it was not significant. Additionally, with β-glucosaminidase activity, there were no significant effects from N application. In general, then, elevated atmospheric CO2 increased soil enzyme activity, which may be attributed to the following two factors: (1) elevated atmospheric CO2 led to more plant biomass in the soil, which in turn stimulated soil microbial biomass and activity; and (2) elevated atmospheric CO2 increased plant photosynthesis, thereby increasing plant-derived soil enzymes. 相似文献
923.
Various ionic and molecular activities in the extracellular environment are vital to plant cell physiological processes. A noninvasive microsensing system (NMS) based on either the scanning ion-selective electrode technique (SIET) or the scanning polarographic electrode technique (SPET) is able to obtain information regarding the transportation of various ions/molecules in intact samples under normal physiological conditions. The two-probe simultaneous test system (2STS) is an integrated system composed of SIET,SPET, and a Xu-Kunkel sampling protocol. In the present study, 2STS was able to simultaneously measure fluxes of H+ and O2 of the lily (Lilium Iongiflorum Thunb. cv. Ace) pollen tube while avoiding interference between the two probes. The results indicate that the proton fluxes were effluxes, whereas the oxygen fluxes were influxes, and they were closely correlated to each other surrounding the constitutive alkaline band region. Specifically, when the proton effluxes increased, the oxygen influxes also increased. Therefore,the hypothesis of condensed active mitochondria existing in the alkalized area of the pollen tube proposed by Hepler's group is supported. 相似文献
924.
Malondialdehyde (MDA) is a well known inducer of carbonyl stress in a variety of human cells, however, its effects on human
bone marrow mesenchymal stem cells (hMSCs) have not been documented. In this study, the effects of MDA concentration on the
growth rate and proliferation of hMSCs in vitro were assessed. Under high concentrations of MDA, the cell count was decreased and the population doubling time (PDT) was
lengthened. Flow cytometry (FCM) demonstrated that MDA triggered cells to undergo apoptosis, in parallel with the findings
in MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay which showed that it can also impair cellular
viability. Surprisingly, FCM also determined that the percentage of hMSCs in G2/M-and S-phases also increased in a dose-dependent manner with respect to MDA concentration. These results strongly suggest
that even though hMSCs were severely impaired by high concentrations of MDA, they were still able to send signals that resulted
in accelerated cellular proliferation process. This study provided important insights on how carbonyl stress affects cell
cycle and proliferation of hMSCs.
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Translated from Journal of Natural Science of Hunan Normal University, 2005, 28 (2) [译自: 湖南师范大学自然科学报, 2005,28(2)] 相似文献
925.
Zhang D Zhou W Yin C Chen W Ozawa R Ang LH Anandan L Aigaki T Hing H 《Genesis (New York, N.Y. : 2000)》2006,44(4):189-201
Despite the identification of a number of guidance molecules, a comprehensive picture has yet to emerge to explain the precise anatomy of the olfactory map. From a misexpression screen of 1,515 P{GS} lines, we identified 23 genes that, when forcibly expressed in the olfactory receptor neurons, disrupted the stereotyped anatomy of the Drosophila antennal lobes. These genes, which have not been shown previously to control olfactory map development, encode novel proteins as well as proteins with known roles in axonal outgrowth and cytoskeletal remodeling. We analyzed Akap200, which encodes a Protein Kinase A-binding protein. Overexpression of Akap200 resulted in fusion of the glomeruli, while its loss resulted in misshapen and ectopic glomeruli. The requirement of Akap200 validates our screen as an effective approach for recovering genes controlling glomerular map patterning. Our finding of diverse classes of genes reveals the complexity of the mechanisms that underlie olfactory map development. 相似文献
926.
927.
928.
Yuelan Yin Chenju Zhang Hui Dong Zhongwei Niu Zhiming Pan Jinlin Huang Xinan Jiao 《Microbiology and immunology》2010,54(4):175-183
Listeria monocytogenes is a food‐borne pathogen able to cause serious disease in human and animals. Listeriolysin O (LLO), a major virulence factor secreted by this bacterium, is a vacuole‐specific lysin that facilitates bacterial entrance into the host cytosol. Thus, LLO plays a key role in the translocation and intracellular spread of L. monocytogenes. To study the effect of LLO on virulence and immunopotency, a LLO‐deficient L. monocytogenes mutant was constructed using a shuttle vector followed by homologous recombination. The mutant strain had lost hemolytic activity, which resulted in an extremely reduced virulence, 5 logs lower than that of the parent strain, yzuLM4, in BALB/c mice. The number of bacteria detected in the spleens and livers of mice infected with the mutant was greatly reduced, and the bacteria were rapidly eliminated by the host. Kinetics studies in this murine model of infection showed that the invasion ability of the mutant strain was much lower than that of the parent strain. Moreover, immunization with the mutant strain conferred protective immunity against listerial infection. In particular, stimulation with Ag85B240‐259, strong specific Th1 type cellular immunity was elicited by vaccination C57BL/6 mice with hly deficient strain delivering Mycobacterium tuberculosis fusion antigen Ag85B‐ESAT‐6 via intravenous inoculation. These results clearly show that highly attenuated LLO‐deficient L. monocytogenes is an attractive vaccine carrier for delivering heterologous antigens. 相似文献
929.
930.