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991.
992.
By means of the histostereometrical method, peculiarities of the thyroid gland formation have been studied in the lemming (Dicrostonyx torquatus) fetuses and newborns at the stage of the population quantity drop, as well specificity of the organ's morphofunctional state during the postnatal period. On the 14th prenatal day the thyroid gland already has the follicular structure. Up to the 19th day progressive follicular growth, accumulation of colloid and increase of its density occur. On the 19th-20th days, as well as in newborn animals, there are certain signs, demonstrating as essential activation of the thyroid gland function. In the newborn animals cavities of the completely formed follicles are devastated. During the postnatal period again growth of follicles, accumulation of colloid are observed, signs of hypersecretion of the hypophysis appear. 相似文献
993.
Jonathan D. Nickels Joseph E. Curtis Hugh O’Neill Alexei P. Sokolov 《Journal of biological physics》2012,38(3):497-505
Recent studies have discovered strong differences between the dynamics of nucleic acids (RNA and DNA) and proteins, especially at low hydration and low temperatures. This difference is caused primarily by dynamics of methyl groups that are abundant in proteins, but are absent or very rare in RNA and DNA. In this paper, we present a hypothesis regarding the role of methyl groups as intrinsic plasticizers in proteins and their evolutionary selection to facilitate protein dynamics and activity. We demonstrate the profound effect methyl groups have on protein dynamics relative to nucleic acid dynamics, and note the apparent correlation of methyl group content in protein classes and their need for molecular flexibility. Moreover, we note the fastest methyl groups of some enzymes appear around dynamical centers such as hinges or active sites. Methyl groups are also of tremendous importance from a hydrophobicity/folding/entropy perspective. These significant roles, however, complement our hypothesis rather than preclude the recognition of methyl groups in the dynamics and evolution of biomolecules. 相似文献
994.
Human long-latency auditory evoked potentials were studied during simulation with variable-amplitude pulse sequences from a sound source moving to and from the subject. The N1 peak parameters were shown to depend on an accurate estimate of the direction of the change in the distance to the sound source. Differences in the processing of signals that simulated the approaching and/or distancing of the sound source were found in the N1 and P2 component parameters of on- and off-responses as was a more pronounced long negative potential shift in the evoked response to the approaching source as compared to the distancing source. 相似文献
995.
O. V. Yagodina E. B. Nikol’skaya I. Y. Shemarova A. E. Khovanskikh 《Journal of Evolutionary Biochemistry and Physiology》2000,36(3):244-248
A comparison has been performed of catalytic properties of unicellular microorganism amine oxidases (AO) from two new enzyme
sources, the bacteriumMethanosarcina barkeri and the infusoriaTetrahymena pyriformis. It was shown that the both studied AO deaminate tyramine, serotonin, and benzylamine, but do not deaminate histamine. The
AO fromMethanosarcina barkeri catalyzes deamination of all three substrates at an identical rate, while the rate of tyramine deamination under effect of
AO fromTetrahymena pyriformis is one order higher than the rate of serotonin deamination, and about two orders higher than the rate of benzylamine deamination.
Based on the data of the substrate-inhibitor analysis, a suggestion was made about the existence of one center for the substrate
binding in the AO of the studied bacterium, while several centers in the AO of the studied infusoria. 相似文献
996.
A rapid, sensitive, assay for enzymes that degrade heparin is described. The procedure is based on the interference of heparin with color development during the interaction of protein with the dye Coomassie brilliant blue. The loss of this property when the glycosaminoglycan is degraded by heparinase can be used to quantify activity of the enzyme in pure form, or in complex biological samples such as tissue homogenates or serum. The assay is also suitable for studying dependence of heparinase activity under conditions such as varying pH and temperature. 相似文献
997.
K Scheuch W D Pietruschka E Hentschel P Winiecki G Gruber 《Activitas nervosa superior》1988,30(3):169-173
Biochemical and immunological parameters, physical and mental performance, subjective complaints and behavioural characteristics were compared before and after 14 final examinations undertaken by 64 students during a three-month examination period. A decrease in cholesterol, triglycerides, HDL-cholesterol, physical performance and an increase in LDL/HDL cholesterol quotient, lactate level, mental performance were accompanied by a lower frequency of mental complaints and higher frequency of physical complaints. From the multidimensional variance and discriminant analysis 17 of the 44 variables discriminated between the state prior to and after the examination period. The results are interpreted in terms of the psychophysiological adaptation to adequate mental stress. 相似文献
998.
Treatment of cut-throat trout broodfish Salmo clarki (Richardson) with Sulphamerazine at 220 mg/kg (10 g/100 1b) of fish/day for 14 days resulted in severe kidney histopathology and increased mortality among males. Experimental data presented showed that cut-throat trout broodfish were extremely sensitive to Sulphamerazine toxicity. Hydropic degeneration of renal tubule epithelium and haemorrhage into tubule lumens were observed in kidneys of both male and female trout, but was more severe in the former. Death, which occurred only in males, was correlated with spawning stress and impaired renal function. 相似文献
999.
1000.
Interactions between two catalytically distinct MCM subgroups are essential for coordinated ATP hydrolysis and DNA replication. 总被引:9,自引:0,他引:9
The six MCM (minichromosome maintenance) proteins are essential DNA replication factors that each contain a putative ATP binding motif and together form a heterohexameric complex. We show that these motifs are required for viability in vivo and coordinated ATP hydrolysis in vitro. Mutational analysis discriminates between two functionally distinct MCM protein subgroups: Mcm4p, 6p, and 7p contribute canonical ATP binding motifs essential for catalysis, whereas the related motifs in Mcm2p, 3p, and 5p serve a regulatory function. Reconstitution experiments indicate that specific functional interactions between these two subgroups are required for robust ATP hydrolysis. Our observations show parallels between the MCM complex and the F1-ATPase, and we discuss how ATP hydrolysis by the MCM complex might be coupled to DNA strand separation. 相似文献