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31.
S. Zielinski H. O. Pörtner 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(8):492-500
The intertidal wormSipunculus nudus was exposed to various temperatures for an analysis of the integrated changes in energy and acid-base status. Animals were
incubated in sea water or maintained for up to 8 days at 4 and 0°C while dwelling in the sediment. Cannulation of the animals
prior to experimentation allowed the analysis of blood gas parameters (
,
and pH).
fell to 0 torr within 8 days at 0°C. A simultaneous reduction of ventilatory activity was derived from measurements of the
pattern of coelomic fluid pressure changes associated with ventilatory movements. The increase in
and an onset of anaerobic metabolism, indicated by the accumulation of end products like acetate and propionate both in the
coelomic fluid and the body wall musculature, led to the development of a progressive acidosis and a deviation from the alphastat
regulation of intracellular pH seen in unburied animals. The drop in intracellular pH together with the depletion of the adenylates
and the phosphagen, phospho-l-arginine, reflect a significant decrease in the Gibb's free-energy change of ATP hydrolysis. These changes are interpreted
to indicate lethal cold injuries, because recovery was not possible when the animals were returned to 12°C after more than
2 days of exposure to 0°C. A low critical temperature indicating the onset of cold-induced anaerobiosis is concluded to exist
below 4°C owing to the insufficient response of the ventilatory system to the developing hypoxia. 相似文献
32.
具有中等毒性的马氏钳蝎神经毒素的纯化和初步晶体学研究 总被引:1,自引:0,他引:1
运用柱层析技术对产自淅川和常德的马氏钳蝎毒素进行分离纯化,得到8种哺乳动物神经毒素。运用制备型等电聚焦电泳技术,对常德样品中具有中等毒性的蝎神经毒素(BmK5)进一步纯化,获得了高纯度样品。两个产地的蝎毒素BmK5均已经成功地获得了大晶体。空间群均为P212121,晶胞参数分别为:a=38.46埃,b=37.28埃,c=36.97埃(淅川);a=38.44埃,b=37.55埃,c=36.83埃(常德)。对两个产地的晶体分别收集了2.1埃(淅川)和1.62埃(常德)分辨率的衍射数据。 相似文献
33.
The microsomal epoxide hydrolase (mEH)-catalyzed hydrolysis of cis-4,4′–dimethylstilbene oxide ( 1a ), cis-4,4′-diethylstilbene oxide ( 1b ), cis-4,4′-diisopropylstilbene oxide ( 1c ), and cis-4,4′-dichlorostilbene oxide ( 1d ) have been investigated using rabbit liver microsomal preparations. The kinetic parameters, Km and Vmax, and the absolute stereochemistry of the reactions have been determined and compared with those of cis-stilbene oxide ( 1e ). All epoxides 1a – d are hydrolyzed by mEH with high product enantioselectivity to give (R,R)-(+)-diols with ee ≥ 90%. The presence of the substituents on the phenyl rings markedly reduces the rates of mEH catalyzed hydrolysis with respect to cis-stilbene oxide, by increasing Km and reducing Vmax in the cases of 1a , 1b , and 1d , or reducing only the Vmax in the case of 1c . The very low Vmax, together with a persistent ability to fit into the mEH active site, make all these epoxides, and particularly 1c , inhibitors of cis-stilbene oxide hydrolysis. The kinetic and stereochemical results are interpreted on the basis of the proposed topology of the mEH active site. © 1994 Wiley-Liss, Inc. 相似文献
34.
35.
A relatively drought tolerant cultivar of maize ( Zea mays L. cv. Pioneer 3950) and a drought tolerant line of sorghum ( Sorghum bicolor [L.] Moench cv. ICSV 112) were grown hydroponically for 11 days. Treatments for non-ionic osmotic and salt stresses were started at the 8th day by addition of polyethylene glycol 6000 and NaCl, respectively, at 200 mOsm equivalent concentrations in the presence or absence of 0. 1 μ M abscisic acid. Relative growth rate was depressed by both stress factors, more severely for maize than sorghum. Abscisic acid increased the growth rate and reverted the negative effect of NaCl in maize, while sorghum was only slightly affected. In general, sorghum had higher levels of K+ and lower levels of Na+ and the K+ /Na+ ratio was further increased by abscisic acid treatment. From the pressure-volume curves, osmotic potential, the water potential at turgor loss point, bulk elastic modulus and the water saturation deficit at initial turgor loss were estimated. Most significantly, sorghum had a higher elastic modulus than maize and it decreased under osmotic treatment, while in maize it increased under NaCl stress. The results suggest that bulk tissue turgor was not limiting growth under these conditions and underscores the possible implications of changes in the elastic condition of the cell walls in stress responses. 相似文献
36.
37.
温度对麦长管蚜种群存活率的特征参数的影响 总被引:2,自引:0,他引:2
在测定麦长管蚜种群存活率基础上,本提出反S型曲线模型来描述种群存活率,探讨了麦长管蚜种群存活率过程变化的特征参数,并得到不同的特征值. 相似文献
38.
Aspects of the biology of Pantinonemertes californiensis,a high intertidal nemertean 总被引:3,自引:3,他引:0
Pamela Roe 《Hydrobiologia》1993,266(1-3):29-44
I studied the distribution, feeding biology, and reproductive biology of Pantinonemertes californiensis, described as a semi-terrestrial nemertean, along the central California coast. At the sites used in this study, maximal
tidal height is about 2 m, and P. californiensis typically occurred under boulders between 1.3 and 1.7 m tidal height. Worms fed primarily on the semi-terrestrial amphipod
Traskorchestia traskiana. Distribution of nemerteans was similar to that of the prey, although prey extended higher on the beach than did the worms.
Nemerteans were largest and most abundant at the site with highest abundance of T. traskiana and smallest and least abundant at the lowest prey abundance site. In laboratory feeding trials, nemerteans from the site
with lowest prey abundance fed most readily. Non-reproductive nemerteans lived for at least a week when submerged in sea water;
some prey died within a week of being submerged. Nemerteans only lived minutes when submerged in fresh water; 50% of prey
lived 4.5 h. Eggs are approximately 90–100 μm in diameter and hundreds to thousands are shed per female. Larvae are planktonic
and apparently planktotrophic, and are morphologically similar to other marine hoplonemertean larvae. At the sites studied
life history characteristics of P. californiensis provided little evidence of adaptations to terrestrial life in these worms and were not helpful in elucidating the role of
semi-terrestrial nemerteans in the evolution of terrestrial nemerteans. 相似文献
39.
Isha Gupta Devender Singh Sitender Singh Pawan Kumar Shri Bhagwan Vinod Kumar Harish Kumar Sunil Kumar Chhikara 《Luminescence》2023,38(5):585-599
Terbium(III)-doped yttrium aluminate perovskite (YAP:xTb3+) (x = 0.01–0.08 mol) was synthesized using a simple gel-combustion method. Structural elucidations were performed using X-ray diffraction (XRD) and Rietveld analysis. Fourier-transform infrared spectral studies validated the efficient synthesis of designed doped samples. Transmission electron microscopic images showed the agglomerated irregular dimensions of the synthesized nanocrystalline materials. When excited at 251 nm, a strong emissive line attributed to 5D4 → 7F5 electronic transition was observed at 545 nm (green emission). The maximum luminescence was found at the optimized concentration (0.05 mol) of Tb3+ ions; this emission was quenched by dipolar–dipolar (d–d) interactions. Chromaticity (x and y) and correlated colour temperature parameters were obtained by analysing the emission profiles. Finally, the colour coordinates of nanophosphors were closer to the National Television Standards Committee green coordinates, which replicates their potency in the design and architecture of R-G-B-based white LEDs. 相似文献
40.
Two-month old Wistar rats of both sexes received, as sole drinking liquid, an aqueous solution of ammonium metavanadate (AMV) at a concentration of 0.01 or 0.05 mg V cm–3 (0.2 or 1.0 mM) for a period of 4 weeks. It was calculated that the animals took up doses of 1.5 and 5–6 mg V kg body weight–1 24 h–1, respectively. Food and AMV solution consumption in the experimental groups was similar to food and water consumption in the control group. A statistically significant decrease of consumption of AMV solution at a concentration of 0.05 mg V cm–3 was noted only in males. Hematological examination demonstrated a decrease in the erythrocyte count, hemoglobin level and hematocrit index. This decrease in the erythrocyte count was associated with an increased percentage of reticulocytes in the peripheral blood of the animals drinking the solution with a higher vanadium content. Biochemical analyses demonstrated a decrease of l-ascorbic acid levels in the plasma and erythrocytes of animals drinking the AMV solutions. A distinct tendency for the malonyldialdehyde level to increase in the blood was also observed. Among the enzymes examined in the erythrocytes (catalase, glucose-6-phosphate dehydrogenase, lactate dehydrogenase and -aminolevulinic acid dehydratase [ALA-D]) only ALA-D activity was depressed. 相似文献