Effect of sunlight on the survival of Salmonella on surfaces

AIMS: To investigate the effect of simulated full-spectrum tropical sunlight on the survival of Salmonella in droplets on surfaces. MATERIALS AND RESULTS: The survival on surfaces of three Zambian strains of Salmonella enterica serovars Enteritidis and Heidelberg was compared with that of a strain of S. enterica serovar Enteritidis phage type (PT) 4 with known characteristics which had been isolated from poultry in the UK. Samples were taken from surfaces every hour for 3 h and after 24 h exposure in either dark or 12 h light/12 h dark cycle conditions. Differences were analysed for significance using a one-way analysis of variance (anova). Results show that there were a significantly higher number of cells surviving on surfaces after 24 h in the dark when compared with populations exposed to a 12 h light/12 h dark cycle. Significantly more cells also survived exposure to sunlight under dirty than clean conditions. CONCLUSIONS: Exposure to sunlight results in a significant decrease in numbers of Salmonella on surfaces. SIGNIFICANCE AND IMPACT OF THE STUDY: Under field conditions exposure of contaminated surfaces to sunlight could be used in place of chemical methods of control as a cheaper way to reduce Salmonella contamination of surfaces.     

Fertiliser response of vegetation on ultrabasic terraces on Rhum

Summary

The application of fertilisers to sparse vegetation on unstable ultrabasic soil on a ridge of extreme exposure on the Isle of Rhum, Inner Hebrides, resulted in a marked increase of vegetation cover and a change in species composition. On this site, nutrient deficiency appears to be a major factor limiting the development of closed plant communities.     

Influence of cations on the mode of action of miconazole on yeast cells

The influence of the antifungal agent miconazole nitrate on yeast plasma membranes was studied in a concentration range 0-100 microM. The reaction of 100 microM miconazole with the plasma membranes lead to a rapid breakdown of the transmembrane pH gradient and to an efflux of metabolites from the cytoplasm of the cells. This effect of miconazole could be reversed by mono-, di- and most effectively by trivalent cations due to the formation of miconazole-cation complexes. At a ratio of trivalent cation/miconazole (1:3) the effect was completely reversed. X-Ray diffraction studies indicated a crystalline structure of the aluminium-miconazole complex.     

基于右旋糖酐蔗糖酶转糖基作用的槲皮素葡萄糖苷的合成研究

右旋糖酐蔗糖酶是一种以蔗糖为唯一底物,将蔗糖分子中D-葡萄糖基催化转移到受体分子上的葡萄糖基转移酶。利用右旋糖酐蔗糖酶的转糖基作用,以蔗糖为葡萄糖糖基供体,槲皮素为糖基受体,对槲皮素糖苷的酶法合成进行了探索。通过对该酶催化反应体系、催化反应条件及产物分析的研究,结果表明：在25℃下,右旋糖酐蔗糖酶能够在30％DMSO-70％乙酸-乙酸钙（0.02 mol/L,pH值5.4）的反应体系中催化合成一种槲皮素葡萄糖苷,在这个反应体系下,以10％的蔗糖作为糖基供体,槲皮素为糖基受体,右旋糖酐蔗糖酶活力为40 U/mL,转速为150 r/min,槲皮素糖苷的转化率最高,可达39.5％。通过质谱分析确定是一种槲皮素单糖苷,分子量为464。该研究结果为黄酮类物质的糖基化修饰奠定了基础。     

Experiments on effects of phosphorus on the manganese nutrition of plants

Summary Monocalcium phosphate (MCP), the salt of concentrated superphosphate, applied to a Buganda soil increased the amount of manganese taken up by ryegrass. To investigate the cause of this effect the derivatives of MCP hydrolysis, dicalcium phosphate (DCP) and triple-point solution (TPS) were separated and applied independently. Both derivatives, and a synthetic dicalcium phosphate dihydrate, increased the concentration of manganese in ryegrass showing that dissolution of soil manganese by TPS (pH 1.48) was not a unique cause.DCP derived by hydrolysis of MCP supplied little phosphorus to early crops of ryegrass but a larger proportion of its P was taken up by later crops; TPS supplied more of its P to earlier than to later crops. During 42 weeks the proportions of P taken up from DCP and TPS were similar to the proportions of phosphorus in these forms when MCP hydrolyzes.Phosphorus in DCP derived by hydrolysis of MCP was more available to ryegrass than phosphorus in a synthetic dicalcium phosphate dihydrate, showing that results may be misleading when synthetic materials are used to simulate the compounds that form from fertilizers in soil. re]19760401     

Studies on the immobilization of trypsin on sand

Trypsin was immobilized on sand using five different methods. Attempts were made to attach amino-functional groups onto sand using 3-aminopropyltriethoxysilane, hexamethylenetetramine, hexamethylenediamine, and melamine. Glutaraldehyde was used as a bifunctional agent in all the methods. Methods for the estimation of the proteolytic 1activity and protein content of immobilized trypsin were standardized. The maximum retained activity was observed for trypsin immobilized on sand via 3-aminopropytriethoxysilane and glutaraldehyde. Immobilized trypsin showed a shift in the pH optimum toward the acidic side over that of soluble trypsin in all five cases. The optimum temperature for both native and immobilized trypsin prepared by the silane-glutaraldehyde method was found to be 45°C. However, the pH and thermal stabilities of immobilized trypsin were observed to be better than that of the native enzyme.     

Studies on the effects of structure on the behavior of enzyme systems

The effects of structural features on various properties of enzyme systems are studied. Some of the effects are: in a homogeneous reaction, enzyme compartmentalization decreases the rate; in a heterogeneous reaction, compartmentalization increases the rate. The steady-state concentration of intermediates is larger in a non-uniform than in uniform systems. Periodicities do not generally occur in the common kinetic systems; they do occur in autocatalytic systems, but compartmentalization reduces their probability of occurrence. The conditions for overshoot are different for uniform and non-uniform systems. Multiple stable steady states are not a common occurrence among biologically typical reactions; they do occur in combined autocatalytic and surface systems (a mechanism for the gener position effect is suggested by this property). The local pH is affected by the enzyme aggregation as well as by the geometry of the enzyme structure. A 2-step system can give rise to the characteristic rate vs. pH curve, where the optimum is not necessarily at isoelectric point. The expression for the osmotic pressure inside a spherical particle is deduced. The pressure is shown to be dependent on the radius. The rate inside a cell particle is shown to be determined by the shape of the particle.     

Influence of renin on the effects of electric stimulation on the ventromedial hypothalamus

The influence of intraventricular injection of different doses of renin on the effects of electrical stimulation of the ventromedial hypothalamus was studied. Injection of renin (10 micrograms/kg) into the lateral ventricles of the brain of experimental animals elicited a prolonged elevation of arterial pressure and a decrease of the heart rate, while given in doses of 20 and 30 micrograms/kg it also provoked arrhythmias and ventricular extrasystoles, and a lowering of the threshold of ventromedial hypothalamus stimulation. It was found that under the central action of renin, a short-term stimulation of the ventromedial hypothalamus provoked ventricular extrasystoles.     

Computational study on effect of stenosis on primary thrombus formation

The purpose of this study was to evaluate the effects of stenosis geometry on primary thrombogenesis with respect to the dynamics of the blood flow. A two-dimensional computer simulation was carried out to simulate the formation of a primary thrombus under blood flow in two geometrically different blood vessels: one straight and the other stenosed. In the simulation, blood was modeled by particles that have characteristics of plasma and of platelets. Plasma and platelet flow was analyzed using the Moving Particle Semi-implicit (MPS) method, while the motion of adhered and aggregated platelets was expressed by mechanical spring forces. With these models, platelet motion in the flowing blood and platelet aggregation and adhesion were successfully coupled with viscous blood flow. The results of the simulation demonstrated that the presence of a stenosis induced changes in blood flow and thereby altered the formation, growth, and destruction of a thrombus. In particular, whereas in the absence of stenosis, the thrombus evenly covered the injured site, in the presence of a stenosis, thrombus formation was skewed to the downstream side. The number of platelets that adhered to the injured site increased earlier as the stenosis became more severe. These results suggest that dynamic changes in blood flow due to the presence of a stenosis affect primary thrombogenesis.     

Studies on the influence of nutria on carp growth

Summary Data from 9 experiments with nutria growing on fish ponds were studied. In the cases when no carry-over effect occured from prolonged nutria breeding, the following results were obtained:The statistical analysis showed the high significance of these results and their close fit to the curve of the function of the increase in carp yield in dependence on nutria density.Breeding of nutria on a fish pond during a year leaves a carry-over effect which increases the yield of carp in the next year by 0.7–0.8 kg per nutria. In two cases of prolonged breeding of nutria, the yield increase per one nutria grew from 1.6 to 2.3 and from 1.7 to 2.5 kg.     

Studies on micronuclei time response and on the effects of multiple treatments of mutagens on induction of micronuclei

Micronuclei time response and the effects of multiple treatments of mutagens on induction of micronuclei were studied. In the time-response investigation, mice were treated once with each of 5 mutagens, then killed at various times. The bone marrow was examined for the presence of micronucleated erythrocytes (MNEs). The maximal frequencies for MNEs occurred around 30 h post treatment for all mutagens tested. To examine the effects of multiple treatments, the frequencies of MNEs observed after a single- or a 5-treatment schedule were compared for 9 mutagens. Both treatment schedules were equally sensitive in detecting alkylating agents and spindle poisons, whereas the 5-treatment schedule was more sensitive for anti-metabolites. The 5-treatment schedule was particularly effective for detecting the anti-metabolites 5-fluorouracil and methotrexate, which require longer than 30 h to induce micronuclei (Maier and Schmid, 1976). These results suggest that it is practicable to sample at 30 h in the single-treatment schedule, and seem to support the usefulness of the 5-treatment schedule in screening tests.     

Effect of aggregating behavior on population recovery on a set of habitat islands

We consider a single-species model which is composed of several patches connected by linear migration rates and having logistic growth with a threshold. We show the existence of an aggregating mechanism that allows the survival of a species which is in danger of extinction due to its low population density. Numerical experiments illustrate these results.     

Conservation of mammals on a tobacco farm on the Highlands of Malawi

The natural vegetation of the Shire Highlands of Malawi has become fragmented because of human activities. As a consequence, some species of mammals have become locally extinct and the population numbers and geographical ranges of other species have declined. This study investigated the species richness of mammals on a commercial tobacco farm, and the importance of remnants of natural vegetation on farms for the conservation of mammals. The farm covered 180 ha and supported 44 species of mammals (equivalent to 66% of the species known to occur in the Shire Highlands at a similar altitude, and 24% of the total mammalian fauna of Malawi). Most of the species were bats (22 species) and rodents (13 species). The largest remnants of natural 'miombo' woodland supported more species and more individuals than smaller remnants. The high species richness was due, in part, to the variety of different habitats on the farm ('miombo' woodland, riverine forest, grassland, swamp, streams and dams), as well as to good conservation practices. The farm is especially important for the conservation of 13 species which are rare and/or have limited geographical ranges in Malawi. It is suggested that well-managed farms which contain remnants of natural vegetation can play a significant role in the conservation of mammals, and other vertebrates, in Central Africa.     

Influence of latitude factor on organism of adolescences residing on North

Complex investigations of adolescences (14-15 years) residing on the European North at 62 and 65 degrees latitudes have been carried out. It was shown that the latitude factor on the North affected on mature organism of adolescences already at a difference of residence place on 3 degrees. The decrease of tolerance to hypoxemia, quality of hemodynamic regulation at short-term physical activity, physical health level, nervous processes rate (switching of attention) and the increase of plasma lactate level (attribute of hypoxia) were shown in adolescences residing at higher latitudes. The sexual distinctions and features of northerner organism on a lot of parameters in adolescences were revealed.     

The effect of spatial heterogenity on the aggregation of ticks on white-footed mice

Parasites are often aggregated on a minority of the individuals in their host populations. Although host characteristics are commonly presumed to explain parasite aggregation on hosts, spatio-temporal aggregation of parasites during their host-seeking stages may have a dominant effect on the aggregation on hosts. We aimed to quantify, using mixed models, repeatability and autocorrelation analyses, the degree to which the aggregation of blacklegged ticks (Ixodes scapularis) on white-footed mice (Peromyscus leucopus) is influenced by spatio-temporal distributions of the host-seeking ticks and by heterogeneity among mice. Host-seeking ticks were spatially aggregated at both the larval and nymphal life-stages. However, this spatial aggregation accounted for little of the variation in larval and nymphal burdens observed on mice (3% and 0%, respectively). Conversely, mouse identity accounted for a substantial proportion of the variance in tick burdens. Mouse identity was a significant explanatory factor as the majority of ticks parasitized a consistent set of mice throughout the activity seasons. Of the characteristics associated with mouse identity investigated, only gender affected larval burdens, and body mass and home range sizes in males were correlated with nymphal burdens. These analyses suggest that aggregation of ticks on a minority of mice does not result from the distribution of host-seeking ticks but from characteristics of the hosts.     

Influence of Shading on the Gross Composition of Cuscuta Species on Medicago sativa

A study was made of the alterations in growth characteristics of Cuscuta Campestris, Cuscuta indecora and Cuscuta reflexa on Medicago sativa as a consequence of a limitation in light intensity. There was a decrease in the content of dry solids, protein and total phosphorus in the filament mass. A decrease in these parameters occurred also in the tissues of the host, but was less pronounced that in the parasite. The response by the host to parasite growth was not always the same in the shade as in light. Phosphorus showed a distinct tendency toward firm retention in the infection complex in the dark.     

Effects of terrestrial buffer zones on amphibians on golf courses

A major cause of amphibian declines worldwide is habitat destruction or alteration. Public green spaces, such as golf courses and parks, could serve as safe havens to curb the effects of habitat loss if managed in ways to bolster local amphibian communities. We reared larval Blanchard's cricket frogs (Acris blanchardi) and green frogs (Rana clamitans) in golf course ponds with and without 1 m terrestrial buffer zones, and released marked cricket frog metamorphs at the golf course ponds they were reared in. Larval survival of both species was affected by the presence of a buffer zone, with increased survival for cricket frogs and decreased survival for green frogs when reared in ponds with buffer zones. No marked cricket frog juveniles were recovered at any golf course pond in the following year, suggesting that most animals died or migrated. In a separate study, we released cricket frogs in a terrestrial pen and allowed them to choose between mown and unmown grass. Cricket frogs had a greater probability of using unmown versus mown grass. Our results suggest that incorporating buffer zones around ponds can offer suitable habitat for some amphibian species and can improve the quality of the aquatic environment for some sensitive local amphibians.     

《生物多样性公约》研究知识图谱:基于CiteSpace的文献计量分析

《生物多样性公约》(简称《公约》)作为保护地球生物资源的国际性公约,与生态文明建设、构建人类命运共同体息息相关.对《公约》进行不同角度的研究,分析当前生物多样性保护进展中的热点与趋势能为科学制定"2020年后框架"提供参考,也能为推动生态文明建设提供智力支持.本文以CNKI中的论文为研究对象,通过CiteSpace软件...     

Studies on adsorption of amyloglucosidase on ion-exchange resins

Highly charged water-soluble conjugates of amyloglucosidase with a copolymer of ethylene-maleic acid or styrene-maleic acid were prepared and adsorbed on DEAE-cellulose and other cationic resins. Negatively charged enzyme conjugates were also obtained by means of succinylation. The polyanionic conjugates of amyloglucosidase adsorbed on the cationic carriers show higher temperature stability than the native enzyme adsorbed on the same carriers under the same experimental conditions. The insoluble enzyme conjugate-carrier complexes could be reused and retained their full activity while working continuously for three weeks. The application of the insoluble enzyme preparations with the above characteristics which could possibly satisfy the requirements for industry are discussed.     

A simple formalism on dynamics of proteins on potential energy landscapes

We present a simple formalism for the dynamics of proteins on a potential energy landscape, using connectedness of configurational domains as an order parameter. This formalism clearly shows that the energy bias required to form a unit correct contact toward the native configuration of a two-state folder, to overcome Levinthal's paradox, is E(bias) congruent with RT ln 2. This result agrees well with earlier studies and indicates that the bias is mainly due to hydrophobic interaction. Further investigations have shown that the landscape funnel could be experimentally mapped onto a two-dimensional space formed by denaturant concentration and the connectedness of configurational domains. The theoretical value of the depth-of-folding funnel in terms of denaturant concentration has been calculated for a model protein (P450cam), which agrees well with the experimental value. Using our model, it is also possible to explain the turnover nature of heat-capacity change upon unfolding of proteins and the existence of enthalpy and entropy convergence temperatures during unfolding without any strict assumptions as proposed in earlier studies.