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排序方式: 共有75条查询结果,搜索用时 78 毫秒
1.
The dynamics of the sympathoadrenal function and the specific features of heart rhythm regulation were studied in female students and clothing factory female workers during their adaptation to academic and work conditions. Periods of the strongest functional tension in test systems were found in first-year students: the beginning of an academic year, the end of the first semester, and a period after winter examinations, all characterized by an increase in the central-circuit and sympathetic effects on sinus rhythm, acceleration of the heart rate, activation of sympathoadrenal mechanisms, and a decrease in sympathoadrenal reserves. The comparative analysis allowed us to disclose general trends typical of females of this age group such as the relative maturity of the sympathoadrenal system (SAS) and optimum correlation between autonomic and centralized heart rhythm regulation and to reveal the differences in the character and dynamics of functional shifts caused by a specific effect of academic load and work conditions. The degree of correlation between the indices characteristic of hormonal and mediator SAS mechanisms and the statistical characteristics of heart rhythm was proposed as the criteria for estimating the functional tension of the human body. 相似文献
2.
DIDIER FOURGON IGOR EECKHAUT DEVARAJEN VAÏTILINGON MICHEL JANGOUX 《Invertebrate reproduction & development.》2013,57(3):155-165
Summary The larval development of the ophiocomid ophiuroid Ophiomastix venosais described using SEM. The gastrula transforms into a uniformly ciliated early larva which progressively changes into a lecithotrophic late premetamorphic larva with a continuous bilateral ciliated band. This stage is short-lived and equivalent to a highly reduced ophiopluteus. Comparisons between O. venosa and other ophiuroid species whose development has been investigated suggest that, whatever the developmental mode (lecithotrophic or planktotrophic), a pluteus stage always occurs in ophiuroids with planktonic development. Two metamorphic stages were identified, the late metamorphic larva differing from the early one by the closure of the larval mouth. The appearance of the permanent mouth marks the end of the metamorphosis. The postlarva still possesses remnants of larval features. The transformation of the reduced ophiopluteus into a barrel-shaped metamorphic larva with transverse ciliated bands, a vitellaria larva, is followed. The possible occurrence of a unique type of metamorphic larva in non-brooding ophiuroids is discussed. Verification of this, however, needs further SEM investigations on metamorphic larva from species having “regular” planktotrophic development. 相似文献
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4.
Victor A. Sorokin Olga A. Antonova Vladimir A. Valeev 《Journal of inorganic biochemistry》1984,20(4):299-311
The effect ot Cu2+ and Ca2+ ions, on the ultraviolet differential (UVD) spectra of single-stranded poly I was studied and the coordination (Δεb) and conformation (Δεc) conponents of the spectra calculated The comparison of Δεb and the UVD spectrum of protonated IMP leads to the conclusion that N(7) ot inosine-5'-monophosphate (IMP) is a coordinating site tor Ca2+ and Cu2+ ions on the polymer bases. The binding ot Ca2+ and Cu2+ ions causes differently directed displacements of the four absorption bands of poly I, which are observed in the wavenumber range (50-34) × 103 cm−1 The calculation of concentration dependencies tor the association constants (K“) ot Ca2+ and Cu2+ ions binding to poly I bases shows that the binding is cooperative The K“ values for the poly I + Ca2+ complex are two orders of magnitude lower than those for the poly 1 + Cu2+ complex At low ion concentrations, binding to the poly I phosphates predominates and increases the degree of the polynucleotide helicity. At higher concentrations the spectra are mainly affected by the ion binding to bases, which results in melting of the helical parts of poly I At Ca2+ concentrations exceeding 10−3 M light-scattering aggregates are formed. The degree of monomer order in them is close to that observed in multistranded helices of poly I 相似文献
5.
V A Sorokin Y P Blagoi V A Valeev S V Kornilova G O Gladchenko I D Reva V I Sokhan 《Journal of inorganic biochemistry》1987,30(2):87-99
The formation of Cu2+ complexes with native and denatured DNA is studied by the methods of differential UV spectroscopy, CD spectroscopy, and viscometry. On ion binding to the bases of native DNA the latter transforms into a new conformation. This transition is accompanied with a sharp increase in UV absorption and a decrease in the intrinsic viscosity though the high degree of helicity persists. Possible sites of Cu2+ ion binding on DNA of various conformations are found along with corresponding constants of complex formation. 相似文献
6.
Using the thermal denaturation method the effect of bivalent copper of (4-10(-6)-10(-3)) M concentrations on the helix-coil transition of DNA was studied in the solution of Na+ concentrations 10(-3)-10(-1) M. Unlike the previous studies, this paper makes allowance for the effect of impurity ions present in DNA and deionized water. It has been shown that in the region of low Cu2+ and Na+ concentrations, thermal stability increases, the melting range extends and the denaturation curves become asymmetric. At concentrations more than approximately 3-10(-5) M Cu2+, melting temperature starts to fall, and the range reduces to 1-1.5 degrees at [Cu2+] greater than or equal to 2-10(-4) M. As [Cu2+] reaches these values, the denaturation curve asymmetry and melting range increase again, which is due to the inversion of the relative stability of AT- and GC-pairs. Employing experimental and phase-transition-theory data for homopolymers, the constants of Cu2+ binding with phosphates and DNA bases were calculated. The concentration dependence of the DNA denaturation parameters was shown to be governed by the superposition of binding Cu2+ with phosphates and nucleic acid bases. 相似文献
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The effect of lincocin (a plastid protein synthesis inhibitor) treatment on the greening process of bean (Phaseolus vulgaris L.) leaves have been studied. In comparison with control leaves treated ones had a decreased rate of chloroplast development. They had a marked chlorophyll deficiency and a decreased chlorophyll a/b ratio. Some long and short wavelength forms of chlorophyll a were lacking as evidenced from the absorption spectra at 25°C and the fluorescence spectra at 77°K. The –14CO2 fixation was inhibited by 80–90% in treated leaves. The fluorescence induced by the measuring light was greater in the treated leaves than in the control ones, and the kinetics of the decline of the relative fluorescence intensity were also different. Electron microscopic studies showed macrogranum-like structures and incomplete membrane vesicles in the treated plastids. After longer treatment a destruction of membranes was observed. The results indicate some structural and functional membrane deficiencies and instability of the membranes. 相似文献
9.
The influence of Cd2+ ions on the conformational equilibrium of single-stranded (poly(U), poly(A), poly(I)) and triple-stranded polyribonucleotides (A2I, A2U) in aqueous solutions (0.1 M Na+ pH 7) has been investigated using difference UV spectroscopy and thermal denaturation. Analysis of the shape and intensity of the DUV spectra of poly(A), poly(I), and A2I has revealed the presence of two types of complex formed as a result of (i) interaction between Cd2+ and the N7 atoms of purines, producing macrochelates; and (ii) binding of Cd2+ to the N1 atoms of poly(A) and poly(I). Since Cd2+ ions are not bound to heteroatoms of the bases in A2U, the conformation of the structure remains stable up to 0.02 M Cd2+. There is a critical Cd2+ concentration (~1.5?10?4 M) above which A2I assumes a new helical conformation with lower thermal stability. It is supposed that, upon the formation of the “metallized” A2I triplex, the Cd2+ ions are located inside the triple helix and form bridges between the hypoxanthine and adenine of the homopolynucleotide strands. 相似文献
10.
I. V. Maksimov A. Sh. Valeev E. A. Cherepanova L. G. Yarullina 《Applied Biochemistry and Microbiology》2009,45(4):433-438
The effect of two strains of the phytopathogenic fungus Septoria nodorum Berk. of different virulence on the intensity of local generation of hydrogen peroxide in common wheat leaves and the role of oxidoreductases in this process was studied. Differences in the pattern of hydrogen peroxide production in wheat plants infected with high- and low-virulence pathogen strains have been found. The low-virulent S. nodorum strain caused a long-term hydrogen peroxide (H2O2) generation in the infection zone, whereas the inoculation of leaves with the highly virulent strain resulted in a transient short-term increase in the H2O2 concentration at the initial moment of contact between the plant and the fungus. It was shown that the low level of H2O2 production by plant cells at the initial stages of pathogenesis facilitates S. nodorum growth and development. The decrease in the H2O2 concentration induced by the highly virulent S. nodorum strain is determined by inhibition of the oxalate oxidase activity in plant tissues and by the ability of the fungus to actively synthesize an extracellular catalase. The pattern of hydrogen peroxide generation at the initial stages of septoriosis may serve as an index of virulence of S. nodorum population. 相似文献