共查询到20条相似文献,搜索用时 8 毫秒
1.
《Electromagnetic biology and medicine》2013,32(4):331-341
The comparative study of the effects of 5.8mW/cm2 Millimeter Waves (MMW) and near Infrared (IR) irradiation on thermal properties, specific adsorption rate (SAR), specific electrical conductivity (SEC) and hydrogen peroxide (H2O2) content of distilled water (DW), and physiological solutions (PS) was performed. The thermal effect of MMW irradiation appeared only after the first minute of irradiation, while the IR heating started from the first minute of irradiation. The heat fusion of frozen MMW-treated DW and PS was significantly less than sham and IR-treated DW and PS. MMW irradiation had time-dependent elevation effect on water SEC and SAR, which was accompanied by the increase of H2O2 formation in it. We suggest that the MMW-induced vibration of water dipole molecules caused the non thermal changes of physicochemical properties of DW and PS, which promote the formation of H2O2 in water. 相似文献
2.
Anesthetic Gases and Water Structure : The effect of xenon on tritiated water flux across the gut 下载免费PDF全文
Eugene Y. Berger F. Rene Pecikyan Grace Kanzaki 《The Journal of general physiology》1968,52(6):876-886
Pauling and Miller have independently proposed that the presence of an anesthetic gas in tissue induces a cage-like arrangement of hydrogen-bonded water molecules. The theories recognize that most gas-hydrate crystals would not form at the temperature and pressure that exist during anesthesia and propose that other components of tissue such as protein should have a stabilizing effect. Measurements of the behavior of water, rather than the anesthetic agent, would provide alternative information about the likelihood of hydrate crystal formation and this information could be such as to be applicable to body temperature and to pressures used for anesthesia. If the number of hydrogen-bonded water molecules in tissue is increased, then the movement of an average water molecule should be hindered. Movement of water through the tissue may be measured by tagging it with tritium and the anesthetic gas should then slow the movement of tritiated water through the tissue. The flux of tritiated water through rat cecum is indeed slowed when the cecum is exposed to the anesthetic gas, xenon, which can participate biochemically only by virtue of its van der Waals interaction. The decrement in water flux is in reasonable agreement with what could be expected theoretically from calculations based on the activation energy for the self-diffusion of water and the degree of hypothermia necessary to produce narcosis. 相似文献
3.
The close association between marine invertebrates, zooxanthellae, and numerous bacteria gives rise to the question of the identity of the actual producer of secondary metabolites. In fall of 2005, a widespread bleaching event occurred throughout the Caribbean Sea in which some colonies of the gorgonian coral Plexaurella fusifera bleached. This study investigated whether zooxanthellae play a key role in the biosynthesis of secondary metabolite terpenes from P. fusifera. The extent of bleaching was examined by chlorophyll A analysis and also by zooxanthellae isolation and cell counting. The bleached and unbleached colonies were found to contain similar concentrations of eremophilene as the major terpene, and both exhibited similar biosynthetic capability as evaluated by the transformation of [C(1)-(3)H]-farnesyl diphosphate to the sesquiterpenes. Differences in bacterial communities between the bleached and unbleached colonies were analyzed using molecular techniques, and preliminary indications are that unbleached and bleached corals are dominated by low G + C firmicutes and gammaproteobacteria, respectively. It therefore appears that terpene biosynthesis can proceed independently of the zooxanthellae in P. fusifera, suggesting that the coral or a bacterium is the biosynthetic source. 相似文献
4.
Pier Luigi Luisi 《化学与生物多样性》2012,9(11):2635-2647
The general framework of the origin of life on Earth is outlined, emphasizing that the so‐called prebiotic ‘RNA world’ is as yet on shaky scientific ground, and that one should any way ask the question of the structure of the first protocellular compartments capable of the initial forms of metabolism. This question is the basis of the research project on the minimal cells, containing the minimal and sufficient complexity capable of leading to life. Such research is briefly summarized, highlighting experiments with liposome‐based semisynthetic cells which are capable of ribosomal protein synthesis with a very minimal number of enzymes. The most recent finding in this area of research is the unexpected observation that the formation and closure of liposomes in situ acts as an attractor for the solute molecules in solution, bringing about a very high local concentration in some of the liposomes. It is argued that this spontaneous overcrowding, which permits reactions which are not possible in the original dilute solution, might be the origin of cellular metabolism for the origin of life on Earth. 相似文献
5.
Introduction
There is increasing interest in the control and elimination of schistosomiasis. Little is known, however, about the likely effects of increasing water-body temperatures on transmission.Methods
We have developed an agent-based model of the temperature-sensitive stages of the Schistosoma and intermediate host snail life-cycles, parameterised using data from S. mansoni and Biomphalaria pfeifferi laboratory and field-based observations. Infection risk is calculated as the number of cercariae in the model, adjusted for their probability of causing infection.Results
The number of snails in the model is approximately constant between 15–31°C. Outside this range, snail numbers drop sharply, and the snail population cannot survive outside the range 14–32°C. Mean snail generation time decreases with increasing temperature from 176 days at 14°C to 46 days at 26°C. Human infection risk is highest between 16–18°C and 1 pm and 6–10 pm in calm water, and 20–25°C and 12–4 pm in flowing water. Infection risk increases sharply when temperatures increase above the minimum necessary for sustained transmission.Conclusions
The model suggests that, in areas where S. mansoni is already endemic, warming of the water at transmission sites will have differential effects on both snails and parasites depending on abiotic properties of the water-body. Snail generation times will decrease in most areas, meaning that snail populations will recover faster from natural population reductions and from snail-control efforts. We suggest a link between the ecological properties of transmission sites and infection risk which could significantly affect the outcomes of interventions designed to alter water contact behaviour – proposing that such interventions are more likely to reduce infection levels at river locations than lakes, where infection risk remains high for longer. In cooler areas where snails are currently found, increasing temperatures may significantly increase infection risk, potentially leading to new, high-intensity foci of infection. 相似文献6.
Biophysics - The formation of ice microparticles during freezing of aqueous cryoprotective solutions has been studied. The shapes and sizes of particles depend on the composition of the solution.... 相似文献
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To elucidate the structural basis of the diversity and universality in protein-protein interactions, an exhaustive all-against-all structural comparison of all known protein interfaces in the Protein Data Bank was performed at atomic resolution. After similar interfaces were clustered, approximately 20,000 structural motifs with at least two members were identified, out of which 3678 motifs consisted of at least 10 interfaces. Except for some trivial interfaces involving single α helices, almost all motifs were found to be confined within single protein families. Furthermore, the interaction partners of each motif were found to be very limited, and, accordingly, the interaction networks of the motifs tend to be small and are much more restricted than the binding sites for small ligand molecules. These findings suggest that, at the level of atomic structures, protein-protein interactions are precisely designed; hence, protein interfaces with multiple interacting partners should involve incompletely overlapping multiple interfaces and/or accommodate structural changes upon binding to their targets. 相似文献
9.
Sylvaine Boissinot Monique Erdinger Baptiste Monsion Véronique Ziegler-Graff Véronique Brault 《PloS one》2014,9(4)
Cucurbit aphid-borne yellows virus (CABYV) is a polerovirus (Luteoviridae family) with a capsid composed of the major coat protein and a minor component referred to as the readthrough protein (RT). Two forms of the RT were reported: a full-length protein of 74 kDa detected in infected plants and a truncated form of 55 kDa (RT*) incorporated into virions. Both forms were detected in CABYV-infected plants. To clarify the specific roles of each protein in the viral cycle, we generated by deletion a polerovirus mutant able to synthesize only the RT* which is incorporated into the particle. This mutant was unable to move systemically from inoculated leaves inferring that the C-terminal half of the RT is required for efficient long-distance transport of CABYV. Among a collection of CABYV mutants bearing point mutations in the central domain of the RT, we obtained a mutant impaired in the correct processing of the RT which does not produce the RT*. This mutant accumulated very poorly in upper non-inoculated leaves, suggesting that the RT* has a functional role in long-distance movement of CABYV. Taken together, these results infer that both RT proteins are required for an efficient CABYV movement. 相似文献
10.
Cladograms, phylogenetic trees that depict evolutionary relationships among a set of taxa, are one of the most powerful predictive
tools in modern biology. They are usually depicted in one of two formats—tree or ladder. Previous research (Novick and Catley
2007) has found that college students have much greater difficulty understanding a cladogram’s hierarchical structure when it
is depicted in the ladder format. Such understanding would seem to be a prerequisite for successful tree thinking. The present
research examined the effect of a theoretically guided manipulation—adding a synapomorphy on each branch that supports two
or more taxa—on students’ understanding of the hierarchical structure of ladder cladograms. Synapomorphies are characters
shared by a group of taxa due to inheritance from a common ancestor. Thus, their depiction on a cladogram may facilitate the
understanding of evolutionary relationships. Students’ comprehension was assessed in terms of success at translating relationships
depicted in the ladder format to the tree format. The results indicated that adding synapomorphies provided powerful conceptual
scaffolding that improved comprehension for students with both weaker and stronger backgrounds in biology. For stronger background
students, the benefit of adding synapomorphies to the ladders was comparable to that of approximately two hours of instruction
in phylogenetics that emphasized the ladder format. 相似文献
11.
Miyakawa Shin Cleaves H. James Miller Stanley L. 《Origins of life and evolution of the biosphere》2002,32(3):209-218
A wide variety of pyrimidines and purineswere identified as products of a dilute frozen ammoniumcyanide solution that had been held at –78°C for 27 years.This demonstrates that both pyrimidines and purines couldhave been produced on the primitive earth in a short time byeutectic concentration of HCN, even though the concentrationof HCN in the primitive ocean may have been low. We suggestthat eutectic freezing is the most plausible demonstratedmechanism by which HCN polymerizations could have producedbiologically important prebiotic compounds. 相似文献
12.
This study explored event-related potential (ERP) correlates of common fractions (1/5) and decimal fractions (0.2). Thirteen subjects performed a numerical magnitude matching task under two conditions. In the common fraction condition, a nonsymbolic fraction was asked to be judged whether its magnitude matched the magnitude of a common fraction; in the decimal fraction condition, a nonsymbolic fraction was asked to be matched with a decimal fraction. Behavioral results showed significant main effects of condition and numerical distance, but no significant interaction of condition and numerical distance. Electrophysiological data showed that when nonsymbolic fractions were compared to common fractions, they displayed larger N1 and P3 amplitudes than when they were compared to decimal fractions. This finding suggested that the visual identification for nonsymbolic fractions was different under the two conditions, which was not due to perceptual differences but to task demands. For symbolic fractions, the condition effect was observed in the N1 and P3 components, revealing stimulus-specific visual identification processing. The effect of numerical distance as an index of numerical magnitude representation was observed in the P2, N3 and P3 components under the two conditions. However, the topography of the distance effect was different under the two conditions, suggesting stimulus specific semantic processing of common fractions and decimal fractions. 相似文献
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14.
N. G. Zemlianskykh 《Biophysics》2018,63(1):66-76
The aim of this study was to examine the effects of sucrose, dextran, polyethylene glycol, glycerol, and mannitol, which possess cryoprotective properties to various degrees, on the mechanical stability and the geometric parameters of human erythrocytes. All substances, except mannitol, contributed to a decrease in hemolysis, which was caused by the movement of small beads. Glycerol and polyethylene glycol, which provide the highest level of protection of erythrocytes during cryopreservation, also showed the maximum efficiency under mechanical stress. Changes in cell resistance may be associated with the transformation of their geometric parameters. According to the cytometry data, 5% solutions of all the substances, except mannitol, caused similar changes in the geometric parameters of the cell. The relationship between changes in the mechanical stability and the geometric parameters of erythrocytes under the influence of cryoprotective agents may be caused by the modification of the membrane?cytoskeleton protein complex, which controls the mechanoelastic properties and morphology of erythrocytes. 相似文献
15.
《Bioscience, biotechnology, and biochemistry》2013,77(3):544-549
To provide a molecular explanation of the role of the disulfide (SS) bridge in the thermostability and structural integrity of ovalbumin (OVA), we prepared SS-mutated OVAs in which SS-forming residues were replaced by Ala or Ser (C73A, C73S, C120A, and C73/120A), and compared the conformation, thermostability, susceptibility to elastase, and formation of heat-stable OVA (S-OVA) with those of the wild-type. The circular dichroism (CD) and tryptophan fluorescence spectra revealed that the SS-mutated OVAs assumed a native-like conformation similar to the wild-type. The thermal denaturation temperature for the SS-mutated OVAs was significantly lower than that for the wild-type. C73S, C120A, and C73/120A mutants converted to S-OVA on alkaline treatment. Analyses for elastase digestion fragments showed that a non-native SS bridge was generated in all SS-mutated OVAs, but non-native SS-pairing did not contribute to thermostability. Hence, we concluded that the presence of the original SS bridge in OVA contributes to conformational stability but is not directly related to the conversion to S-OVA. 相似文献
16.
Biophysics - The effects of viscous media with glycerol and sucrose (10–40%) on the kinetics of the bacterial bioluminescent reaction have been investigated by stopped-flow technique.... 相似文献
17.
Maria Fernanda Falcone-Dias Daniela Centrón Fernando Pavan Adriana Candido da Silva Moura Felipe Gomes Naveca Victor Costa de Souza Adalberto Farache Filho Clarice Queico Fujimura Leite 《PloS one》2015,10(3)
Several differences concerning bacterial species, opportunistic pathogens, elements of the resistome as well as variations concerning the CFU/mL counts were identified in some of the five most marketed bottled mineral water from Araraquara city, São Paulo, Brazil. Two out of five brands tested were confirmed as potential source of opportunistic pathogens, including Mycobacterium gordonae, Ralstonia picketti and Burkholderia cepacia complex (Bcc). A total of one hundred and six isolates were recovered from four of these bottled mineral water brands. Betaproteobacteria was predominant followed by Alphaproteobacteria, Gammaproteobacteria and Firmicutes. Ninety percent of the bacteria isolated demonstrated resistance to seventeen of the nineteen antimicrobials tested. These antimicrobials included eight different classes, including 3rd and 4th generation cephalosporins, carbapenems and fluoroquinolones. Multidrug resistant bacteria were detected for fifty-nine percent of isolates in three water brands at counts up to 103 CFU/ml. Of major concern, the two bottled mineral water harboring opportunistic pathogens were also source of elements of the resistome that could be directly transferred to humans. All these differences found among brands highlight the need for continuous bacteriological surveillance of bottled mineral water. 相似文献
18.
Sara C. Campbell Paul J. Wisniewski Michael Noji Lora R. McGuinness Max M. H?ggblom Stanley A. Lightfoot Laurie B. Joseph Lee J. Kerkhof 《PloS one》2016,11(3)
Background
The gut microbiota is now known to play an important role contributing to inflammatory-based chronic diseases. This study examined intestinal integrity/inflammation and the gut microbial communities in sedentary and exercising mice presented with a normal or high-fat diet.Methods
Thirty-six, 6-week old C57BL/6NTac male mice were fed a normal or high-fat diet for 12-weeks and randomly assigned to exercise or sedentary groups. After 12 weeks animals were sacrificed and duodenum/ileum tissues were fixed for immunohistochemistry for occludin, E-cadherin, and cyclooxygenase-2 (COX-2). The bacterial communities were assayed in fecal samples using terminal restriction fragment length polymorphism (TRFLP) analysis and pyrosequencing of 16S rRNA gene amplicons.Results
Lean sedentary (LS) mice presented normal histologic villi while obese sedentary (OS) mice had similar villi height with more than twice the width of the LS animals. Both lean (LX) and obese exercise (OX) mice duodenum and ileum were histologically normal. COX-2 expression was the greatest in the OS group, followed by LS, LX and OX. The TRFLP and pyrosequencing indicated that members of the Clostridiales order were predominant in all diet groups. Specific phylotypes were observed with exercise, including Faecalibacterium prausnitzi, Clostridium spp., and Allobaculum spp.Conclusion
These data suggest that exercise has a strong influence on gut integrity and host microbiome which points to the necessity for more mechanistic studies of the interactions between specific bacteria in the gut and its host. 相似文献19.
20.
Dimitris Missirlis 《PloS one》2014,9(5)
Substrate mechanical properties have emerged as potent determinants of cell functions and fate. We here tested the hypothesis that different forms of endocytosis are regulated by the elasticity of the synthetic hydrogels cells are cultured on. Towards this objective, we quantified cell-associated fluorescence of the established endocytosis markers transferrin (Tf) and cholera toxin subunit B (CTb) using a flow-cytometry based protocol, and imaged marker internalization using microscopy techniques. Our results demonstrated that clathrin-mediated endocytosis of Tf following a 10-minute incubation with a fibroblast cell line was lower on the softer substrates studied (5 kPa) compared to those with elasticities of 40 and 85 kPa. This effect was cancelled after 1-hour incubation revealing that intracellular accumulation of Tf at this time point did not depend on substrate elasticity. Lipid-raft mediated endocytosis of CTb, on the other hand, was not affected by substrate elasticity in the studied range of time and substrate elasticity. The use of pharmacologic contractility inhibitors revealed inhibition of endocytosis for both Tf and CTb after a 10-minute incubation and a dissimilar effect after 1 hour depending on the inhibitor type. Further, the internalization of fluorescent NPs, used as model drug delivery systems, showed a dependence on substrate elasticity, while transfection efficiency was unaffected by it. Finally, an independence on substrate elasticity of Tf and CTb association with HeLa cells indicated that there are cell-type differences in this respect. Overall, our results suggest that clathrin-mediated but not lipid-raft mediated endocytosis is potentially influenced by substrate mechanics at the cellular level, while intracellular trafficking and accumulation show a more complex dependence. Our findings are discussed in the context of previous work on how substrate mechanics affect the fundamental process of endocytosis and highlight important considerations for future studies. 相似文献