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121.
XOSÉ ANXELU G. MORÁN ÁNGEL LÓPEZ‐URRUTIA ALEJANDRA CALVO‐DÍAZ WILLIAM K. W. LI 《Global Change Biology》2010,16(3):1137-1144
The macroecological relationships among marine phytoplankton total cell density, community size structure and temperature have lacked a theoretical explanation. The tiniest members of this planktonic group comprise cyanobacteria and eukaryotic algae smaller than 2 μm in diameter, collectively known as picophytoplankton. We combine here two ecological rules, the temperature–size relationship with the allometric size‐scaling of population abundance to explain a remarkably consistent pattern of increasing picophytoplankton biomass with temperature over the ?0.6 to 22 °C range in a merged dataset obtained in the eastern and western temperate North Atlantic Ocean across a diverse range of environmental conditions. Our results show that temperature alone was able to explain 73% of the variance in the relative contribution of small cells to total phytoplankton biomass regardless of differences in trophic status or inorganic nutrient loading. Our analysis predicts a gradual shift toward smaller primary producers in a warmer ocean. Because the fate of photosynthesized organic carbon largely depends on phytoplankton size, we anticipate future alterations in the functioning of oceanic ecosystems. 相似文献
122.
I.B. ZABALA DÍAZ C.A. FROELICH S.C. RICKE 《Journal of Rapid Methods and Automation in Microbiology》2002,10(4):217-229
A rapid microtiter methionine assay was developed using a methionine auxotroph E. coli strain. The bacterial strain was first grown on rich media to promote extensive bacterial growth and the cells were depleted to exhaust all endogenous methionine. After depletion, cells were transferred to minimal media with increasing concentrations of methionine and microtiter plates were incubated at 37C for 6 h. Methionine microtiter standard curves yielded linear growth responses to increasing concentrations of methionine in the range of 0 to 26.8 μM. Addition of different antibiotic and antifungal agents to the media did not significantly alter the linear growth response observed in the microtiter assay. This microtiter plate E. coli methionine assay has potential as a rapid in vitro assay method for quantifying methionine. 相似文献
123.
D. F. Rakhmatullina L. Kh. Gordon A. A. Ponomareva T. I. Ogorodnikova A. Yu. Alyab’ev V. S. Iyudin A. A. Obynochnyi 《Russian Journal of Plant Physiology》2011,58(1):100-108
The effects of nitric oxide (NO) on oxygen consumption, heat generation, and cell ultrastructure were investigated in the
seedlings of wheat (Triticum aestivum L.). The experiments were conducted with the excised roots of 5-day-old seedlings grown in the solution of CaCl2 (2.5 × 10−4 M). The source of NO was NaNO2 (5 × 10−3 M) where the roots were incubated. Production of NO was determined by means of EPR, respiration — gasometrically, heat generation
— using a microcalorimeter. The results showed that NO was formed in the presence of NaNO2. This was accompanied by a decrease in the respiration rate by about 30%, which lasted for 5–6 h. Apparently, NO inhibited
mitochondrial oxidation because stimulation of oxygen consumption induced by 2,4-DNP was completely removed in the presence
of NaNO2. When the cells were affected by succinic acid in the presence of NaNO2, respiration was strongly inhibited. The effects of succinic acid and NaNO2 were negated by ascorbic acid. A decrease in the rate of respiration was accompanied by a reduction in heat generation. Moreover,
the efflux of potassium ions to the root incubation medium was stimulated, which may point to changes in ionic membrane permeability.
The observed changes in energy exchange were accompanied by disturbances in the cell ultrastructure. Nitric oxide induced
a clarification of the mitochondrial matrix and a reduction in the number of cristae. It was concluded that NO excess in plant
tissues brings about a deceleration of energy exchange, disturbance of the ultrastructural organization, and cell death. 相似文献
124.
Adiga U Taylor D Bell B Ponomareva L Kanzlemar S Kramer R Saldanha R Nelson S Lamkin TJ 《Journal of biomolecular screening》2012,17(3):401-408
This article presents a methodology for acquisition and analysis of bright-field amplitude contrast image data in high-throughput screening (HTS) for the measurement of cell density, cell viability, and classification of individual cells into phenotypic classes. We present a robust image analysis pipeline, where the original data are subjected to image standardization, image enhancement, and segmentation by region growing. This work develops new imaging and analysis techniques for cell analysis in HTS and successfully addresses a particular need for direct measurement of cell density and other features without using dyes. 相似文献
125.
L B Tarasova A K Bo?kov S P Bo?kova N N Kvitko T I Ponomareva 《Biulleten' eksperimental'no? biologii i meditsiny》1989,107(5):627-629
An experiment on 6 green monkeys and on 286 cotton newly born rats was made with the aim of studying the lung during experimental adenovirus infection. All the animals during different terms of infection (from 6 hours and up to 40 days) have been studied. Several morphological changes were discovered in the lungs of monkeys and rats after 6 hours of infection and were retained up to the 10-th day of infection. All the components of air-blood barrier and basal membranes were involved in the process, but after 20 day of the experimental adenovirus infection the entire restoration of cellular structure occurred. 相似文献
126.
Combined action of rotenone and malonate, inhibitors of complexes I and II of the mitochondrial electron transport chain (ETC), on wheat cut-off root seedlings was studied after 6 h of incubation. Intensity of oxygen consumption and release of potassium ions into incubation medium were determined simultaneously with the study of changes in cell ultrastructure. Malonic acid was added 1 h after the root incubation in the rotenone solution and produced inhibition of respiration, as well as a greater release of K+ into the incubation solution as compared with effect of rotenone alone. After 2 h of the combined action of these inhibitors, many mitochondria acquired a toroidal shape, thereby increasing the outer surface. For the ensuing hours, stimulation of oxygen consumption by the roots and a decrease of K+ content in the incubation medium were observed. Mitochondria once again acquired a round or oval shape and compensation-reparation processes took place. Contacts of endoplasmic reticulum channels with mitochondria were observed, which seems to be due to the synthesis of the enzyme splitting malonate to acetyl-CoA, which in turn can be included both into the Krebs cycle and into lipogenesis. It is suggested that the toroidal form of mitochondria is associated with the activation of the external NAD(P)H-dehydrogenase of the inner mitochondrial membrane, as under these conditions, at the inhibition of the ETC complexes I and II, the activity of other dehydrogenises is blocked. Thus, the use of the external NAD(P)H allows the activity of the ETC mitochondria to be restored, which facilitates the course of the reparation processes and allows cells to be adapted to this action. 相似文献
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130.
S. M. Ponomareva P. Yu. Malkov V. V. Dubatolov S. E. Chernyshev A. V. Barkalov A. A. Legalov S. V. Chesnokov 《Contemporary Problems of Ecology》2008,1(5):555-563
The major spatial changes in the communities of invertebrates in the grass cover of the Northeastern Altai and the factors determining these changes are revealed on the basis of multi-year accounts. The strength and general character of the connection between nonhomogeneity of population and environment are estimated. 相似文献