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921.
Primary production of aquatic macrophytes and their epiphytes in two shallow lakes (Peipsi and Võrtsjärv) in Estonia 总被引:1,自引:0,他引:1
In shallow lakes with large littoral zones, epiphytes and submerged macrophytes can make an important contribution to the total annual primary production. We investigated the primary production (PP) of phytoplankton, submerged macrophytes, and their epiphytes, from June to August 2005, in two large shallow lakes. The production of pelagic and littoral phytoplankton and of the dominant submerged macrophytes in the littoral zone (Potamogeton perfoliatus in Lake Peipsi and P. perfoliatus and Myriopyllum spicatum in Lake Võrtsjärv) and of their epiphytes was measured using a modified 14C method. The total PP of the submerged macrophyte area was similar in both lakes: 12.4 g C m?2 day?1 in Peipsi and 12.0 g C m?2 day?1 in Võrtsjärv. In Peipsi, 84.2% of this production was accounted for by macrophytes, while the shares of phytoplankton and epiphytes were low (15.6 and 0.16%, respectively). In Võrtsjärv, macrophytes contributed 58%, phytoplankton 41.9% and epiphytes 0.1% of the PP in the submerged macrophyte area. Epiphyte production in both lakes was very low in comparison with that of phytoplankton and macrophytes: 0.01, 5.04, and 6.97 g C m?2 day?1, respectively, in Võrtsjärv, and 0.02, 1.93, and 10.5 g C m?2 day?1, respectively, in Peipsi. The PP of the littoral area contributed 10% of the total summer PP of Lake Peipsi sensu stricto and 35.5% of the total summer PP of Lake Võrtsjärv. 相似文献
922.
Chien-Chih Chen Li-Wen Hsu Li-Tung Huang Tiao-Lai Huang 《Neurochemical research》2010,35(7):1098-1104
Neurotrophins, including the brain-derived neurotrophic factor (BDNF), are essential for regulating neuronal differentiation
in developing brains. BDNF and its receptor tyrosine kinase receptor B (TrkB) are involved in neuronal signaling, survival
and plasticity. Cyclosporine A (CsA) is a potent immunosuppressive agent which prevents allograft rejection in organ transplantation
and various immunological diseases. We investigated whether chronic administration of CsA decreases BDNF gene expression in
rats, and the influence of CsA on mRNA levels of TrkB receptors was also examined. For 30 days of CsA (10 mg/kg/day) administration,
the expression of BDNF and TrkB mRNA was significantly decreased in the hippocampus and midbrain, but there was no significant
difference in the cortex. CsA (0, 1, 5 10, 15 ug/ml) down-regulated BDNF and TrkB gene expression through cultured SH-SY5Y
cells, as did all-trans retinoic acid (ATRA), and there was no effect on cell viability. These experimental results indicate
that suppression of the BDNF and TrkB mRNA, protein level of BDNF expression in the hippocampus and midbrain may be related
to altered behavior observed following chronic administration of CsA. A common mechanism of adverse effects of CsA induced
depressive symptoms may involve neurotoxicity mediated by down-regulation of brain BDNF and TrkB. 相似文献
923.
利用简便微量法定量检测肠道正常菌群中的双歧杆菌和肠杆菌,10次检测结果与常规法无显著性差异。简便微量法主要优点是简便易行,节省人力物力和时间。 相似文献
924.
Linghua Zhou Yong Shen Libo Jiang Danni Yin Jingxin Guo Hui Zheng Hao Sun Rongling Wu Yunqian Guo 《PloS one》2015,10(5)
Cells with the same genotype growing under the same conditions can show different phenotypes, which is known as “population heterogeneity”. The heterogeneity of hematopoietic progenitor cells has an effect on their differentiation potential and lineage choices. However, the genetic mechanisms governing population heterogeneity remain unclear. Here, we present a statistical model for mapping the quantitative trait locus (QTL) that affects hematopoietic cell heterogeneity. This strategy, termed systems mapping, integrates a system of differential equations into the framework for systems mapping, allowing hypotheses regarding the interplay between genetic actions and cell heterogeneity to be tested. A simulation approach based on cell heterogeneity dynamics has been designed to test the statistical properties of the model. This model not only considers the traditional QTLs, but also indicates the methylated QTLs that can illustrate non-genetic individual differences. It has significant implications for probing the molecular, genetic and epigenetic mechanisms of hematopoietic progenitor cell heterogeneity. 相似文献
925.
926.
The carotenoid synthetic genes, crtM and crtN, derived from Staphylococcus aureus, were introduced into B. subtilis, resulting in yellow pigmentation. Absorption maxima of pigments and MALDI-TOF mass spectrometry demonstrated that the pigmented
strain accumulated two C30 carotenoids, 4,4′-diapolycopene and 4,4′-diaponeurosporene. A survival test using H2O2 revealed that the pigmented strain was more resistant to oxidative stress than the strain harboring an empty-vector. These
findings indicate that B.
subtilis can produce carotenoids, and the strain accumulating the carotenoids, CarotenoBacillus, will become a basal host for production
of C30 carotenoids and evaluation of their antioxidative effects. 相似文献
927.
Georgi Z. Genchev Morten Källberg Gamze Gürsoy Anuradha Mittal Lalit Dubey Ognjen Perisic Gang Feng Robert Langlois Hui Lu 《Cell biochemistry and biophysics》2009,55(3):141-152
Efficient communication between the cell and its external environment is of the utmost importance to the function of multicellular
organisms. While signaling events can be generally characterized as information exchange by means of controlled energy conversion,
research efforts have hitherto mainly been concerned with mechanisms involving chemical and electrical energy transfer. Here,
we review recent computational efforts addressing the function of mechanical force in signal transduction. Specifically, we
focus on the role of steered molecular dynamics (SMD) simulations in providing details at the atomic level on a group of protein
domains, which play a fundamental role in signal exchange by responding properly to mechanical strain. We start by giving
a brief introduction to the SMD technique and general properties of mechanically stable protein folds, followed by specific
examples illustrating three general regimes of signal transfer utilizing mechanical energy: purely mechanical, mechanical
to chemical, and chemical to mechanical. Whenever possible the physiological importance of the example at hand is stressed
to highlight the diversity of the processes in which mechanical signaling plays a key role. We also provide an overview of
future challenges and perspectives for this rapidly developing field. 相似文献
928.
The chitosan with three-dimensional porous structure greatly increased the effective electrode surface for loading of platinum nanoparticles and promoted efficient electron transfer. The resulting biosensor had a response time (within 5 s) and a linear response from 6 μM to 4.2 mM glucose with a detection limit of 2 μM (S/N = 3). Moreover, the methodology can be applied for the immobilization of other enzymes. 相似文献
929.
930.
Athanasios Tragiannidis Zoe Dorothea Pana Theodotis Papageorgiou Emmanuel Hatzipantelis Maria Hatzistilianou Fani Athanassiadou 《Journal of medical case reports》2011,5(1):407