共查询到20条相似文献,搜索用时 31 毫秒
1.
In experiments on Black Sea skates (Raja clavata), the potential of the receptor epithelium of the ampullae of Lorenzini and spike activity of single nerve fibers connected to them were investigated during electrical and temperature stimulation. Usually the potential within the canal was between 0 and –2 mV, and the input resistance of the ampulla 250–400 k. Heating of the region of the receptor epithelium was accompanied by a negative wave of potential, an increase in input resistance, and inhibition of spike activity. With worsening of the animal's condition the transepithelial potential became positive (up to +10 mV) but the input resistance of the ampulla during stimulation with a positive current was nonlinear in some cases: a regenerative spike of positive polarity appeared in the channel. During heating, the spike response was sometimes reversed in sign. It is suggested that fluctuations of the transepithelial potential and spike responses to temperature stimulation reflect changes in the potential difference on the basal membrane of the receptor cells, which is described by a relationship of the Nernst's or Goldman's equation type.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. I. M. Sechenov, Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Pacific Institute of Oceanology, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 67–74, January–February, 1980. 相似文献
2.
E. V. Rozengart N. B. Basova 《Journal of Evolutionary Biochemistry and Physiology》2003,39(5):511-518
Taking into account the phenomenon of non-productive binding of substrate, kinetic parameters of hydrolysis of acetylcholine (ACh) and its 13 derivatives with different structures of ammonium group by cholinesterase (ChE) of human erythrocytes, ChE of horse blood serum, and ChE of optic ganglia of the Pacific squid Todarodes pacificus are determined. A dependence is revealed of values of parameters of their enzymatic hydrolysis and parameters of the non-productive binding on the substrate structure and ChE nature. Effects of salts, LiCl, NaCl, KCl, MgCl2, CaCl2 and BaCl2, on various kinetic parameters, including parameters of the non-productive binding of substrate, of enzymatic hydrolysis of iodides of ACh and N-acetoxyethylene-N-ethylpiperidinium under action of horse blood serum ChE are studied. Addition of the salts to the reaction mixture produced different effects on values of the catalytic center activity (a
c) and the Michaelis constant (K
M), depending on the cation nature and the substrate structure. At the same time, values of the a
c/K
M ratio that characterize to a degree the substrate affinity to the enzyme are equal to each other for two substrates differing in structure, regardless of the presence and nature of the studied cations. Parameters of the non-productive binding of N-acetoxyethylene-N-ethylpiperidinium iodide also depended on the salt nature; however, in that case, a question arises as to the correctness of the comparative analysis, when at determinations of the parameters the non-productive binding of ACh is ignored. 相似文献
3.
The significance of variability of biological properties of lipopolysaccharides (LPS) is discussed in the paper within the pathogenesis of infectious process. On the basis of an analysis of published data and of results of independent research of two microorganisms (Yersinia pestis and Francisella tularensis) a conclusion is made on that a biologically inert LPS form (with a weak cytokine-inducing ability, apirogenicity and non-toxicity etc.) is typical of highly pathogenic bacteria. It is suggested that the above phenomenon is biologically expedient. Presumably, the inert LPS transforms to the active form inside a sensitive host and, according to an infection stage, each of them being functionally significant. It is the inert status of LPS that enables the pathogens, at the initial stages, to surmount freely the humoral and cell barriers of host. As the infection progressively aggravates and the proliferation of bacteria modifies itself due to LPS micro- and macroorganisms, its chemical structure and biopolymer conformation change. Both modification mechanisms enhance the LPS toxic potential. In case of a sensitive host, such variations transform the biologically inert LPS into a toxically active form with its function of endotoxin being realized. There is no LPS modification in a host insensitive to such infection, which entails either recovery or prolonged persistence of the pathogen inside the microorganism. 相似文献
4.
E V Iashchuk 《Genetika》1985,21(11):1909-1917
A hypothesis claiming that the total phenotypes of finger patterns are controlled by three independent two-allele loci A, L and W with the complete dominance in each was analysed in this work. By means of the population genetics methods, non-accordance of the hypothesis examined to the observed distributions of total phenotypes A, L, W, AL, LW, ALW was revealed on the material of five populations (3060 men). On the basis of the segregation analysis method applied to 210 complete families (the total number of children-532), the hypothesis of one-locus heredity with the complete dominance of total phenotypes A and W was rejected, the reliability of this conclusion being 0.999 and 0.95, respectively. The hypothesis of the L pattern being genetically controlled by one locus with the complete dominance gave, when examined, the contradictory results, due to monomorphism of the character. 相似文献
5.
6.
Dietary intakes of tomatoes and tomato products containing lycopene have been shown to be associated with decreased risk of chronic diseases such as cancer and cardiovascular diseases in numerous studies. Serum and tissue lycopene levels have also been inversely related to the risk of lung and prostate cancers. Lycopene functions as a very potent antioxidant, and this is clearly a major important mechanism of lycopene action. In this regard, lycopene can trap singlet oxygen and reduce mutagenesis in the Ames test. However, evidence is accumulating for other mechanisms as well. Lycopene at physiological concentrations can inhibit human cancer cell growth by interfering with growth factor receptor signaling and cell cycle progression specifically in prostate cancer cells without evidence of toxic effects or apoptosis of cells. Studies using human and animal cells have identified a gene, connexin 43, whose expression is upregulated by lycopene and which allows direct intercellular gap junctional communication (GJC). GJC is deficient in many human tumors and its restoration or upregulation is associated with decreased proliferation. The combination of low concentrations of lycopene with 1,25-dihydroxyvitamin D3 exhibits a synergistic effect on cell proliferation and differentiation and an additive effect on cell cycle progression in the HL-60 promyelocytic leukemia cell line, suggesting some interaction at a nuclear or subcellular level. The combination of lycopene and lutein synergistically interact as antioxidants, and this may relate to specific positioning of different carotenoids in membranes. This review will focus on the growing body of evidence that carotenoids have unexpected biologic effects in experimental systems, some of which may contribute to their cancer preventive properties in models of carcinogenesis. Consideration of solubility in vitro, comparison with doses achieved in humans by dietary means, interactions with other phytochemicals, and other potential mechanisms such as stimulation of xenobiotic metabolism, inhibition of cholesterogenesis, modulation of cyclooxygenase pathways, and inhibition of inflammation will be considered. This review will point out areas for future research where more evidence is needed on the effects of lycopene on the etiology of chronic disease. 相似文献
7.
A sensitive method for the detection of small quantities of hydrophobic antioxidant free radical scavengers such as butylatedhydroxytoluene (BHT) and butylatedhydroxyanisole (BHA) in aqueous samples is described. The procedure involves extraction of the hydrophobic free radical scavenger into an organic solvent phase, followed by the subsequent reaction of an aliquot of this extract with the stable cation radical tris(p-bromophenyl)amminium hexachloroantimonate (TBACA). In experiments with BHT and BHA, the loss of TBACA absorbance at 730 nm was found to be linearly proportional to the amount of antioxidant added, with quantities of BHT as small as 200 pmol being easily detectable. In aqueous suspensions of dimyristoylphosphatidylcholine vesicles, assays of the aqueous BHT concentration showed that BHT partitioned strongly into the membrane phase, achieving very high BHT/phospholipid ratios. For a given concentration of BHT, partitioning into the membrane phase was greater in large, multilamellar liposomes than in either small, single-walled vesicles or in purified rat brain synaptic vesicle membranes. Direct assay of BHT and BHA in phospholipid membranes, however, was complicated by a nonspecific interaction between TBACA and the phospholipid. 相似文献
8.
The antibiotic resistance and lipid composition of rhodococci grown in rich organic media with gaseous or liquid n-alkanes were studied. Hydrocarbon-grown rhodococci exhibited an increased resistance to a wide range of antibiotics (aminoglycosides, linkosamides, macrolides, beta-lactams, and aromatic compounds). The enhanced antibiotic resistance of rhodococci grown on n-alkanes correlated with an increased content of total cell lipids (up to 14-28%) and saturated straight-chain fatty acids (C16:0, C18:0, C21:0) and was accompanied by the appearance of cardiolipin and phosphatidylglycerol in cells. These lipid compounds were supposed to promote the formation of nonspecific antibiotic resistance in rhodococci by decreasing the permeability of their cell envelope to antibiotics. 相似文献
9.
A P Khokhryakov 《Biology bulletin of the Academy of Sciences of the USSR》1979,6(4):476-486
For classifying life forms of plants a proposal was made to use the principle of parallel divergence based on the hypothesis that life forms diverging to any degree preserve further the potential of evolving in a similar way, that is, in parallel series. Life forms of plants are divided into thirteen types corresponding to the nature of their basic metameres. Further, every type is divided into subtypes and sections according to the character of these metameres and then into smaller grades (classification units of the system of living forms corresponding to one trait and its evolutionary level) according to categories of traits: ramification, vegetative flexibility, rate of changes of metameres, types of habitat and environment. On the basis of the principle of parallel divergence scales of traits were constructed for each category. Corresponding to 26 paires of alternative traits 26 degrees of hierarchic classification were devised and within the limits of every type of life form there were 2(26) grades at the lowest rank. Separate systems were developed for single-celled and colonial forms. 相似文献
10.
目的:分析激光联合注射曲安奈德治疗婴幼儿血管瘤的疗效。方法:将120例处于增殖期血管瘤患儿分成观察组和对照组各60例,观察组给予激光联合注射曲安奈德治疗,对照组采用激光治疗,比较两组患者的治疗疗效。结果:观察组和对照组的总有效率分别为96.7%和66.7%,两组比较具有显著差异,P〈0.05;对于表浅病灶,观察组治疗的有效率为96.8%,对照组为84.8%,两组之间无差异,P〉0.05;对于深部病灶,观察组和对照组的总有效率分别为96.6%和44.4%,具有显著差异(P〈0.05)。结论:激光联合注射曲安奈德治疗婴幼儿血管瘤具有较好的疗效,尤其对深部增殖期的血管瘤具有较好的效果,适合在临床推广应用。 相似文献
11.
O. N. Mukhametova 《Journal of Ichthyology》2010,50(8):660-670
Ichthyoplankton surveys are made in lagoon water bodies of the south-eastern part of Sakhalin (the Vavai-Chibisan system of
lakes, Lake Tunaicha, Lake Izmenchivoe) from April until November 2002–2007. Comparative characteristics of ichthyoplankton
complexes in the ice-free period is given. In the investigated lagoon lakes, differences in the species composition of the
ichthyoplankton by the number and time of appearance of the maxima of abundance of eggs and larvae are noted, and also related
to morphological structure and hydrological conditions of water bodies. In lagoon lake Izmenchivoe with a salinity not less
than 26‰, the eggs and larvae of marine fishes only takes place while, in Vavai-Chibisan lakes, that of freshwater fishes
only takes place. In brackish lake Tunaicha, the lowest number of fish species reproduce. In the Vavai-Chibisan system and
in Lake Izmenchivoe, one maximum of abundance of ichthyoplankton in June is recorded and, in Lake Tunaicha, two maxima (the
highest in June and less expressed in August) are recorded. Irrespective of the species composition, the ichthyoplankton complexes
of lagoon lakes have general traits determined by hydrological conditions of water bodies and by their general origin and
geographic situation: prevalence of eggs and larvae of low boreal fish species, the maximum species diversity in the late
spring-early summer, and decrease of abundance in cooler years. 相似文献
12.
The levels of endogenous phytohormones and respiratory rate in nine sorts of flowers such as Cymbidium faberi Rolfe, Nopalxochia ackermannii Kunth and others were investigated both at full bloom and senescence and meanwhile the effect of exogenous phytohormones on prolonging the blossoms and promoting ethylene production were tested. There is a high content of endogenous ethylene in all the long-lived flowere, about 3–16 folds higer than the short-lived ones. There is a high level of ABA at full blooming flowers of short-lived flowers, in which there is no or only some cytokinins in it, but the ratio of CTK (6BA+zeatin)/ABA is smaller(l.7). The endogenous ABA reached a much higher level at senescence in all nine sorts of flowers, so it is reasonable to consider that it is ABA which plays an important role of regulation in controlling flower's senescence. There is a much higher level of GA3 and zeatin in the long-lived flowers which is not demonstrated in the shortlived ones. The respiratory rate is one of the factors controtling the longevity of flowers, but it does not play a decided role. Application of 6BA and zeatin prolongs distinctly orchid’s longevity, however exogenous IAA through the promotive action on ethylene production, evidently extends the longevity of the flowers of the Nopalxochia ackermannii Kunth. 相似文献
13.
通过对6种藓类植物,即褶叶青藓(Brachythecium salebrosum(Web.et Mohr.)B.S.G.)、湿地匐灯藓(Plagiomnium acutum(Lindb.)Kop.)、侧枝匐灯藓(Plagiomnium maximoviczii(Lindb.)Kop.)、大凤尾藓(Fissidensnobilis Griff.)、大羽藓(Thuidium cymbifolium(Doz.et Molk.)B.S.G.)和大灰藓(Hypnum plumaeforme Wils.)嫩茎和老茎的石蜡切片和显微观察发现,同一藓类植株的嫩茎和老茎,茎结构稳定,不同种藓类植物茎横切面具有不同特征.植物体茎横切面形状、表层细胞的层数、细胞大小和细胞壁厚薄、皮层细胞大小和形状、中轴的有无以及比例等特征可以作为藓类植物的分科分类依据之一. 相似文献
14.
The alpha-chain of the fourth component of complement (C4) contains tyrosine sulfate (Karp, D.R. (1983) J. Biol. Chem. 258, 12745-12748). Here we have determined the site and stoichiometry of sulfation of C4 secreted by the human hepatoma-derived cell line Hep G2. C4 was labeled with [35S]sulfate and isolated from culture medium by immunoprecipitation. C4 digested with trypsin and chymotrypsin and analyzed by reverse-phase high-performance liquid chromatography contained a single sulfate-labeled peptide. Digestion of C4 with trypsin alone yielded two major sulfate-labeled peptides, suggesting that there may be some sequence variability in C4 near the site of sulfation. Sequential Edman degradation of tryptic peptides labeled with [3H]tyrosine and [35S]sulfate detected tyrosine residues at positions 5, 13, 16, and 18. Chymotrypsin cleaved 5 residues off the NH2-terminal end of tryptic peptides, yielding a peptide with tyrosine at positions 8, 11, and 13. Comparison of the position of tyrosine residues with the reported sequence of C4 identified the sites of sulfation as tyrosine residues at positions 738, 741, and 743 in the alpha-chain of C4. All 3 of these tyrosine residues appeared to be sulfated. When sulfation of C4 was partially inhibited by addition of catechol to culture medium, three different forms of the peptide were resolved by high-performance liquid chromatography, consistent with peptides containing 1, 2, or 3 sulfates. Comparison of the quantities of tyrosine and tyrosine sulfate in C4 which had been labeled with [3H]tyrosine and digested with Pronase also indicated that C4 contained an average of 2-3 residues of tyrosine sulfate/molecule. These results suggest that the biologically active form of the protein is sulfated. 相似文献
15.
16.
Henry B. F. Dixon 《The Biochemical journal》1973,131(1):149-154
A simple case is considered in which the rate of a two-step reaction depends on pH because the intermediate formed in the first step has to gain (or lose) a proton before it can react in the second step, and in which the rate-determining step therefore changes with pH. The curves of reaction rate against pH are shown to be symmetrical, and the sharpest peak possible has a width at half its height of 1.53pH units, i.e. of 2log(3+2 radical2). Any particular curve for this situation proves to be identical with a curve that could be generated for the pH-dependence of a single-step reaction in which the rate is proportional to the concentration of a particular ionic form of a reactant. Curves for the latter situation, however, can have forms impossible for the former case in which the rate-determining step changes, but only if the protonations that activate and deactivate the reactant are co-operative. The peak can then become even sharper, and its width at half its height can fall to 1.14pH units, i.e. to 2log(2+ radical3). 相似文献
17.
18.
A. J. de Craen P. J. Roos A. Leonard de Vries J. Kleijnen 《BMJ (Clinical research ed.)》1996,313(7072):1624-1626
OBJECTIVE: To assess the impact of the colour of a drug''s formulation on its perceived effect and its effectiveness and to examine whether antidepressant drugs available in the Netherlands are different in colour from hypnotic, sedative, and anxiolytic drugs. DESIGN: Systematic review of 12 published studies. Six studies examined the perceived action of different coloured drugs and six the influence of the colour of a drug on its effectiveness. The colours of samples of 49 drugs affecting the central nervous system were assessed using a colour atlas. MAIN OUTCOME MEASURES: Perceived stimulant action versus perceived depressant action of colour of drugs; the trials that assessed the effect of drugs in different colours were done in patients with different diseases and had different outcome measures. RESULTS: The studies on perceived action of coloured drugs showed that red, yellow, and orange are associated with a stimulant effect, while blue and green are related to a tranquillising effect. The trials that assessed the impact of the colour of drugs on their effectiveness showed inconsistent differences between colours. The quality of the methods of these trials was variable. Hypnotic, sedative, and anxiolytic drugs were more likely than antidepressants to be green, blue, or purple. CONCLUSIONS: Colours affect the perceived action of a drug and seem to influence the effectiveness of a drug. Moreover, a relation exists between the colouring of drugs that affect the central nervous system and the indications for which they are used. Research contributing to a better understanding of the effect of the colour of drugs is warranted. 相似文献
19.
Summary MAO of the brain was investigated histochemically in mice, rats, guinea pigs and rabbits. Fresh frozen sections were subjected to the tryptamine-tetrazolium method by Glenner, Burtner and Brown (1957).MAO activity of the brain of 4 animal species is generally similar with respect to its pattern of distribution. However, the intensity of enzyme action of the brain as a whole differs somewhat in animal species, being highest in guinea pigs, intermediate in rats and lowest in mice and rabbits. The enzyme action occurs mainly in the neuropil of the cerebral grey matter, while weak or negative activity is generally observed in the white matter excepting the tractus retroflexus of Meynert.The marked activity is encountered in the interpeduncular nucleus, locus coeruleus, area postrema, dorsal nucleus of the vagus nerve, hypothalamus, habenular nuclei and midline nuclear group of the thalamus, nucleus of the brachium conjunctivum, and central grey matter. The enzyme activity is weak or negative in the neocortex, striatum, mamillary body, thalamic nuclei (excepting the habenula and midline nuclear group), subthalamic nucleus, substantia nigra, red nucleus and nuclei of the somatic cranial nerves.The possible function and significance of MAO in the brain were discussed particularly by comparing the sites of this enzyme with those of succinic dehydrogenase and cytochrome oxidase, and the inverse relation between these enzymes was suggested. 相似文献
20.
Ying Tsun-Shen 《植物分类学报:英文版》1989,27(1):27-38
Nine of 10 genera and 119 of approximately 240 species of the Pinaceae occur
in China, including 67 endemic species and two endemic genera.
In this paper, the distributional maps of all the genera of the Pinaceae are presented (fig.
1-8). The horizontal and vertical distributions of species in each genus are discussed.
The analysis of the distribution patterns of the genera indicates that some genera, such as
Keteleeria, Tsuga, Pseudotsuga, Cathaya and Pseudolarix, are restricted to the area south of the
Qinling Mountains and the Huaihe River, and the others, i. e. Picea, Abies, Larix and Pinus,
extend northward to northeastern China. However, all of the genera except Keteleeria and Pinus
are not found in very dry areas and tropical mountainous regions of China.
The monotypic genera, Cathaya and Pseudolarix, are distributed in eastern and central
China. The genus Keteleeria consists of 10 species, 7 of which are concentrated in southern
Guizhou, northern Guangxi, southwestern Hunan and easternmost Yunnan. The distribution of
the remaining 6 genera shows the maximum concentration in western Sichuan and northwestern
Yunnan. (Figs. 2-8). Furthermore, more than third of species of the Pinaceae (37.8%) are
also concentrated in western Sichuan and northwestern Yunnan. where a great variety of habitats and different topographic features occur. It is apparent that to conduct our systematic and
evolutionary studies on this family in these region is especially needed.
The relations between the areal size and the tolerance of species are discussed. The distributions of macrofossils and microfossils of the genera of the Pinaceae ia China are given, and
it has been proved that areas of most genera of the family were considerably larger in the past.
than at present. 相似文献