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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
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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
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Guengerich FP 《Archives of biochemistry and biophysics》2005,433(2):369-378
Mechanisms of toxicity continue to be important in developing rational strategies to deal with chemicals present in the environment. Understanding and predicting toxicity have also become a critical step in the process of drug development. Covalent binding of chemicals to macromolecules is one aspect of toxicity, and the principles and outcomes of the process are considered. Two examples of chemicals for which several aspects of metabolism and reactions are understood are aflatoxin B(1) and polyhalogenated olefins. Ethylene dibromide is a compound that is activated to genotoxic half-mustards by conjugation with glutathione or the DNA repair protein O(6)-alkylguanine DNA alkyltransferase (AGT). The AGT reaction is unusual, in that crosslinking of the protein to DNA increases mutagenicity. One of the involved mechanisms is formation of N(7)-guanyl crosslinks and depurination to produce G-->T transversions; other reactions appear to yield the additional mutagenic events. The phenomenon of thiol conjugation to increase mutagenicity is widespread among bis-electrophiles. 相似文献
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The involvement of the carbohydrate components of the Azospirillum brasilense Sp245 capsules in bacterial protection from the action of extreme factors was investigated. The survival of encapsulated and non-encapsulated azospirilla exposed to elevated (46-48 degrees C) and below-freezing (-20 and -70 degrees C) temperatures, extreme pH values (2 and 10), and to drying was studied. High-molecular-weight carbohydrate-containing complexes (lipopolysaccharide-protein complex and polysaccharide-lipid complex) were isolated from the capsular material of azospirilla. It was shown that the addition of these complexes to the suspension of decapsulated cells before exposing them to extreme factors enhanced their survival rates by 15 to 51%. 相似文献
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The degree of deacetylation (DDA) of chitosan determines the biopolymer's physico-chemical properties and technological applications. pH-Potentiometric titration seems to offer a simple and convenient means of determining DDA. However, to obtain accurate pH-potentiometric DDA values, several factors have to be taken into consideration. We found that the moisture content of the air-dry chitosan samples can be as high as 15%, and a reasonable fraction of this humidity cannot be removed by ordinary drying. Corrections have to be made for the ash content, as in some samples it can be as high as 1% by weight. The method of equivalence point determination was also found to cause systematic variations in the results and in some samples extra acid as high as 1 mol% of the free amino content was also identified. To compensate for the latter effect, the second equivalence point of the titration has to be determined separately and the analytical concentration of the acid be corrected for it. All the corrections listed here are necessary to obtain DDA values that are in reasonable agreement with those obtained from (1)H NMR and IR spectroscopic measurements. The need for these corrections severely limits the usefulness of pH-metry for determining accurate DDA values and thus potentiometry is hardly able to compete with other standard spectroscopic procedures, that is, (1)H NMR spectroscopy. 相似文献
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Dermatoglyphic investigations conducted by the authors made it possible to demonstrate a genetic predisposition to occupational diseases, in particular, to silicosis and silicotuberculosis. Methods based on the mathematical theory of pattern recognition were used for multifactor analysis of the data. It was shown that complex evaluation of 10 dermatoglyphic indices gave a reliable prognosis of the risk of the above two kinds of disease due to silica dust. The dermatoglyphic patterns which predict predisposition to simple silicosis or to silicotuberculosis were found to differ significantly. 相似文献
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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
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目的:探讨输卵管炎性不孕症通水试验的诊断及治疗的临床意义。方法:回顾分析对268例输卵管炎性不孕患者行输卵管通水术后的疗效。结果:来我院进行通水试验治疗的268例输卵管炎性不孕症患者,其中原发性不孕症67例,占发病总数的25%;继发性不孕201例,占75%。经通水反复局部药物治疗,严重者加全身治疗后,输卵管完全通畅者244例,成功率91.04%,术后随访宫内妊娠238例,有效治愈率达88.81%;发生异位妊娠3例,占1.12%。仅有24例经通水治疗无效后行输卵管碘油造影,术后宫内妊娠4例。输卵管通水治疗当月受孕占14.2%。结论:输卵管通水术是诊断和治疗输卵管炎性不孕症的有效方法,早期性生活是否有利于输卵管功能的恢复,有待进一步探讨。 相似文献
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Insulin (Ins) and various other hormones and growth factors have been shown to be rapidly internalized and translocated to
the cell nucleus. This review summarizes the mechanisms that are involved in the translocation of Ins to the nucleus, and
discusses its possible role in Ins action, based on observations by the authors and others. Ins is internalized to endosomes
by both receptor-mediated and fluid-phase endocytosis, the latter occurring only at high Ins concentrations. The authors recently
demonstrated the caveolae are the primary cell membrane locations responsible for initiating the signal transduction cascade
induced by Ins. Once Ins is internalized, Ins dissociates from the Ins receptor in the endosome, and is translocated to the
cytoplasm, where most Ins is degraded by Ins-degrading enzyme (IDE), although how the polypeptides cross the lipid bilayer
is unknown. Some Ins escapes the degradation and binds to cytosolic Ins-binding proteins (CIBPs), in addition to IDE. IDE
and some CIBPs are known to be binding proteins for other hormones or their receptors, and are involved in gene regulation,
suggesting physiological relevance of CIBPs in the signaling of Ins and other hormones. Ins is eventually translocated through
the nuclear pore to the nucleus, where Ins tightly associates with nuclear matrix. The role of Ins internalization and translocation
to the nucleus is still controversial, although there is substantial evidence to support its role in cellular responses caused
by Ins. Many studies indicate that nuclear translocation of various growth factors and hormones plays an important role in
cell proliferation or DNA synthesis. It would be reasonable to suggest that tial for the regulation of nuclear events by Ins. 相似文献
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T Iu Lipskaia T A Borisova M E Trofimova N Iu Kedishvili 《Biokhimii?a (Moscow, Russia)》1987,52(9):1512-1522
Using isoelectrofocusing in three pH gradients differing in the initial pH value of the ampholyte gel mixture and in gradient pH range, the isoelectric points for the dimeric and octameric forms of mitochondrial creatine kinase from bovine heart and pigeon breast muscle were determined. The isoelectric points for the dimer and octamer are equal to 9.67 +/- 0.01 and 8.93 +/- 0.05 for the heart enzyme and to 9.56 +/- 0.08 and 8.91 +/- 0.23 for the skeletal muscle enzyme. The correctness of identification of the oligomeric forms of mitochondrial creatine kinase was confirmed by ultracentrifugation in a sucrose density linear gradient. Since creatine kinase is known to bind to mitochondrial membrane cardiolipin by electrostatic forces, it can be assumed that both oligomeric forms of the enzymes can bind to the membranes. However, the properties of the creatine kinase dimer suggest its greater ability to bind to mitochondrial membranes. 相似文献
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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
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The inhibitory effect of xenobiotics known to damage cell surface structures was studied. The sensitivity of suspended cells of the two fungi Candida maltosa and Fusarium proliferatum was compared with that of artificial or natural biofilms of these fungi. The results obtained indicate that the resistance of attached cell populations to model xenobiotics is increased compared with suspended cells. Only the attached fungal cells had the capacity to degrade acetone and phenol and to adapt to increasing concentrations of these substances, so they seem ideally suited for bioremediation of waste water. 相似文献
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Manfredi MT 《Parassitologia》2006,48(3):397-401
The development and survival of free-living stages of gastro-intestinal nematodes of small ruminants are influenced by several abiotic and biotic factors. Within the abiotic factors, most important are the environmental temperature and humidity. They regulate the development of larvae from eggs dispersed on the pasture by the animals faeces. Each parasite species that infect ruminants requires a different time to development, depending on temperature and humidity. Among trichostrongylids, Ostertagia, Teladorsagia and Nematodirus show a strong adaptation to low temperatures. Nematodirus larvae are able to survive to winter inside the egg shell. Temperature and humidity influence the distribution and survival of larvae on pasture. The larval third stage can migrate from faeces to pasture vegetation and they accumulate at the basis of vegetation where stay during the day or in the soil to avoid the desiccation. The forage species affects the migration of larvae on herbage too. Many biological factors contribute to disperse the larvae on the pasture. Dung burying beetles, coprophagous beetles and earthworms can greatly reduce the larvae of some trichostrongylids on pasture. They contribute to the spread of the faecal material on the pasture and allow the larval death as a consequence of drying. 相似文献
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There is a necessary energetic linkage between ligand binding and stability in biological molecules. The critical glutamate in Site 4 was mutated to create two mutants of the C-domain of calmodulin yielding E140D and E140Q. These proteins were stably folded in the absence of calcium, but had dramatically impaired binding of calcium. We determined the stability of the mutant proteins in the absence and presence of calcium using urea-induced unfolding monitored by circular dichroism (CD) spectroscopy. These calcium-dependent unfolding curves were fit to models that allowed for linkage of stability to binding of a single calcium ion to the native and unfolded states. Simultaneous analysis of the unfolding profiles for each mutant yielded estimates for calcium-binding constants that were consistent with results from direct titrations monitored by fluorescence. Binding to the unfolded state was not an important energetic contributor to the ligand-linked stability of these mutants. 相似文献
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A formal development of the Counterion Condensation theory (CC) of linear polyelectrolytes has been performed to include specific (chemical) affinity of condensed counterions, for polyelectrolyte charge density values larger than the critical value of condensation. It has been conventionally assumed that each condensed counterion exhibits an affinity free-energy difference for the polymer, (DeltaG(aff)). Moreover, the model assumes that the enthalpic and entropic contributions to DeltaG(aff), i.e., DeltaH(aff) and DeltaS(aff), are both independent of temperature, ionic strength and polymer concentration. Equations have been derived relative to the case of the thermally induced, ionic strength dependent, conformational transition of a biopolyelectrolyte between two conformations for which chemical affinity is supposed to take place. The experimental data of the intramolecular conformational transition of the ionic polysaccharide kappa-carrageenan in dimethylsulfoxide (DMSO) have been successfully compared with the theoretical predictions. This novel approach provides the enthalpic and entropic affinity values for both conformations, together with the corresponding thermodynamic functions of nonpolyelectrolytic origin pertaining to the biopolymer backbone change per se, i.e., DeltaH(n.pol) and DeltaS(n.pol), according to a treatment previously shown to be successful for lower values of the biopolyelectrolyte linear charge density. The ratio of DeltaH(n.pol) to DeltaS(n.pol) was found to be remarkably constant independent of the value of the dielectric constant of the solvent, from formamide to water to DMSO, pointing to the identity of the underlying conformational process. 相似文献
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Gennaro Liccardi Gaetano Lobefalo Maria Russo Andrea Manzi Gennaro D'Amato 《Aerobiologia》1992,8(1):34-37
Summary In order to evaluate the age of ouset of respiratory allergic symptoms we examined 2315 patients (656 children and 1659 adults) coming to our clinic as out patients. Each patient underwent the following diagnostic tests: anamnestic and clinical examination, skin-tests for the most common allergens and, when requested, Radioallergosorbent test (RAST) and specific and non specific BPT.We selected 278 children and 673 adults for whom it was possible to establish (on the basis of precise anamnestic considerations) the age at which the respiratory symptoms first appeared.Among these, 300 reacted only toParietaria pollen, 58 only to grass pollen, 420 only to house-dust mite, and 173 were not allergic.Patients reacting to multiple allergens were excluded from the analysis.The results of our study show a significant precocity of the onset of symptoms related to allergic sensitization to mites with peak level at 5 years.On the other hand, the onset of pollen-related symptoms was later on (peak level at 20–25 years forParietaria pollen and 30–35 years for grass pollen). For non allergic patients we did not find a definite age of onset. 相似文献
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M. S. MOSSADEGH 《Physiological Entomology》1978,3(4):335-340
ABSTRACT. Larvae of Plodia interpunctella deposit droplets of mandibular gland secretion onto silk filaments connecting particles within the substrate they inhabit, and on to the substrate itself. Active participation of the mouthparts is necessary for both the formation and deposition of these droplets along the filaments and occurs as the silk is spun. Deposition of secretion directly on the substratum does not involve the mouthparts and appears to result from contact between the lower surface of the head and the substratum. Larvae from which the mandibular glands have been removed by excision neither produce droplets on silk nor deposit them on the substratum. Those which are incapable of spinning silk due to cauterization of the spinneret are still able to deposit secretion on the substratum, however. Deposition of secretion on silk webbing does not occur when the setae which regulate formation of droplets on filaments are removed by shaving. Droplets are not characteristic of a particular larval instar but are produced by larvae of all instars as a normal function which does not depend upon intraspecific encounters. Four other Lepidopteran pests, Ephestia elutella, Ephestia cautella, Anagasta kuehniella and Antigasta catolaunalis , were also found to produce droplets of mandibular gland secretion in a similar manner to larvae of P. interpunctella. 相似文献