Preferred conformations of RGDX tetrapeptides to inhibit the binding of fibrinogen to platelets

The conformational study on Arg-Gly-Asp (RGD)-containing tetrapeptides in the unhydrated and hydrated states has been carried out using the force field ECEPP/3 and the hydration shell model. The tetrapeptides studied here are H-RGDX-OH (X = Trp, Tyr, Phe, Leu, Val, Cys, Gln, and Ser), which show the inhibitory activity for binding of fibrinogen to platelets in the order of RGDW approximately equal to RGDY approximately equal to RGDF approximately equal to RGDL > RGDV > or = RGDC > or = RGDQ > or = RGDS. The backbone conformations with two C(7) backbone-to-backbone hydrogen bonds between Asp and Arg residues and between Xaa and Gly residues are in common most probable for the RGD sequence of RGDX tetrapeptides in the hydrated state. The dominant beta-turns for RGDX are found to be the types V' and IV at Gly-Asp and Asp-Xaa sequences, respectively, which are quite similar to the types II' and I (or II), respectively. However, it cannot be ruled out that the extended conformations are also remarkably feasible for RGDX tetrapeptides in water by peering the distributions of backbone conformations. These calculated results are consistent with the experimental results on RGD-containing proteins and conformationally constrained RGD-containing peptides. The reason why the RGDX becomes more potent as the side chain of the X residue is more hydrophobic may be ascribed to that the more hydrophobic is the residue X, the more populated are beta-turn structures for the Gly-Asp sequence. The hydrophobic side chain of X residue exposed to water is likely to interact with the hydrophobic region of receptor easily.     

Applications of Biocatalysis to Biotechnology

β-lactam antibiotics (e.g. penicillins, cephalosporins) are of major clinical importance and contribute to over 40% of the total antibiotic market. These compounds are produced as secondary metabolites by certain actinomycetes and filamentous fungi (e.g. Penicillium, Aspergillus and Acremonium species). The industrial producer of penicillin is the fungus Penicillium chrysogenum. The enzymes of the penicillin biosynthetic pathway are well characterized and most of them are encoded by genes that are organized in a cluster in the genome. Remarkably, the penicillin biosynthetic pathway is compartmentalized: the initial steps of penicillin biosynthesis are catalyzed by cytosolic enzymes, whereas the two final steps involve peroxisomal enzymes. Here, we describe the biochemical properties of the enzymes of β-lactam biosynthesis in P. chrysogenum and the role of peroxisomes in this process. An overview is given     

Biogeochemical approaches to assessment of East Asian ecosystem sensitivity to acid depositon

We used the critical load (CL) concept to calculate ecosystem response to acid deposition in East Asia. The calculation of critical loads to assess the sensitivity of ecosystems to acidic deposition was made using a biogeochemical approach, which took into consideration both rates of biogeochemical cycling and temperature responses. On the basis of these data the soil-biogeochemical mapping has been carried out for the area of East Asia and the CL values for acid-forming compounds have been calculated using modified steady-state mass balance (SSMB) equations. In the north-eastern ecosystems of the Asian part of Russia these values of critical loads for N [CL(N)] and S [CL(S)] compounds are shown to be less than in Europe due to peculiarities of climate, soil and vegetation. The minimum values of both CL(N) and CL(S) are <50 eq/ha/yr (which occur in 8.3% and 40.5% of this area for N and S, correspondingly) and the maximum values are >300 eq/ha/yr. These values are occasionally lower than for corresponding European ecosystems. For the south-eastern ecosystems of the northern part of Thailand the minimum values are <200 eq/ha/yr and maximum values are >700 eq/ha/yr. The minimum CL values (<200 eq/ha/yr) occur in more than 75% of the studied Thai area.     

Comparison of Stimulus Energies Required to Elicit the ERG in Response to X-Rays and to Light

The retina of Rana pipiens, the leopard frog or grass frog, is shown to be an extremely sensitive detector of x-rays. Its sensitivity to x-rays equals in some respects its sensitivity to visible light. The energy required for the response to visible light is so low that the reaction has long been known as one of the most sensitive in biological systems. An exact comparison is made of the amount of energy required in the stimulus to elicit an electroretinogram (ERG) in response to x-rays and in response to light. ERG's from threshold responses to maximal responses obtainable with x-rays and with light are reproduced. The rods of the retina are shown to be responsible for the production of the ERG. The actual amount of energy absorbed in the rhodopsin from x-ray and from light stimulation over a wide range of intensities and durations has been determined and has been related to the amplitude of the ERG. To the question whether light or x-rays are more efficient in eliciting an ERG, no simple or unequivocal answer can be given. The three dimensional relationship of amplitude of response, intensity of stimulus, and duration of stimulus shows rather unexpectedly that in certain regions light is more efficient while in other regions x-rays are more efficient.     

Binding of Ions to Oligopeptides

A model for the binding of ions to oligopeptides, in which nearest neighbor interactions are considered is developed. Equations for the titration curves are derived The apparent association constants are determined as a function of the degree of polymerization and of the interactions between nearest neighbors.     

Coral bleaching is linked to the capacity of the animal host to supply essential metals to the symbionts

Massive coral bleaching events result in extensive coral loss throughout the world. These events are mainly caused by seawater warming, but are exacerbated by the subsequent decrease in nutrient availability in surface waters. It has therefore been shown that nitrogen, phosphorus or iron limitation contribute to the underlying conditions by which thermal stress induces coral bleaching. Generally, information on the trophic ecology of trace elements (micronutrients) in corals, and on how they modulate the coral response to thermal stress is lacking. Here, we demonstrate for the first time that heterotrophic feeding (i.e. the capture of zooplankton prey by the coral host) and thermal stress induce significant changes in micro element concentrations and isotopic signatures of the scleractinian coral Stylophora pistillata. The results obtained first reveal that coral symbionts are the major sink for the heterotrophically acquired micronutrients and accumulate manganese, magnesium and iron from the food. These metals are involved in photosynthesis and antioxidant protection. In addition, we show that fed corals can maintain high micronutrient concentrations in the host tissue during thermal stress and do not bleach, whereas unfed corals experience a significant decrease in copper, zinc, boron, calcium and magnesium in the host tissue and bleach. In addition, the significant increase in δ⁶⁵Cu and δ⁶⁶Zn signature of symbionts and host tissue at high temperature suggests that these isotopic compositions are good proxy for stress in corals. Overall, present findings highlight a new way in which coral heterotrophy and micronutrient availability contribute to coral resistance to global warming and bleaching.     

Application of input to state stability to reservoir models

Reservoir models play an important role in representing fluxes of matter and energy in ecological systems and are the basis of most models in biogeochemistry. These models are commonly used to study the effects of environmental change on the cycling of biogeochemical elements and to predict potential transitions of ecosystems to alternative states. To study critical regime changes of time-dependent, externally forced biogeochemical systems, we analyze the behavior of reservoir models typical for element cycling (e.g., terrestrial carbon cycle) with respect to time-varying signals by applying the mathematical concept of input to state stability (ISS). In particular, we discuss ISS as a generalization of preceding stability notions for non-autonomous, non-linear reservoir models represented by systems of ordinary differential equations explicitly dependent on time and a time-varying input signal. We also show how ISS enhances existing stability concepts, previously only available for linear time variant (LTV) systems, to a tool applicable also in the non-linear case.     

Functional dynamics of plant growth and photosynthesis--from steady-state to dynamics--from homogeneity to heterogeneity

Plants are much more dynamic than we usually expect them to be. This dynamic behaviour is of paramount importance for their performance under natural conditions, when resources are distributed heterogeneously in space and time. However, plants are not only the cue ball of their physical and chemical environment. Endogenous rhythms and networks controlling photosynthesis and growth buffer plant processes from external fluctuations. This review highlights recent evidence of the importance of dynamic temporal and spatial organization of photosynthesis and of growth in leaves and roots. These central processes for plant performance differ strongly in their dependence on environmental impact and endogenous properties, respectively. Growth involves a wealth of processes ranging from the supply of resources from external and internal sources to the growth processes themselves. In contrast, photosynthesis can only take place when light and CO2 are present and thus clearly requires 'input from the environment'. Nevertheless, growth and photosynthesis are connected to each other via mechanisms that are still not fully understood. Recent advances in imaging technology have provided new insights into the dynamics of plant-environment interactions. Such processes do not only play a crucial role in understanding stress response of plants under extreme environmental conditions. Dynamics of plants under modest growth conditions rise from endogenous mechanisms as well as exogenous impact too. It is thus an important task for future research to identify how dynamic external conditions interact with plant-internal signalling networks to optimize plant behaviour in real time and to understand how plants have adapted to characteristic spatial and temporal properties of the resources from their environment, on which they depend on.     

An evaluation of semiautomatic approaches to contour segmentation applied to fungal hyphae

Semiautomatic image analysis techniques are particularly useful in biological applications, which commonly generate very complex images, and offer considerable flexibility. However, systematic study of such methods is lacking; most research develops fully automatic algorithms. This paper describes a study to evaluate several different semiautomatic or computer-assisted approaches to contour segmentation within the context of segmenting degraded images of fungal hyphae. Four different types of contour segmentation method, with varying degrees and types of user input, are outlined and applied to hyphal images. The methods are evaluated both quantitatively and qualitatively by comparing results obtained by several test subjects segmenting simulated images qualitatively similar to the hyphal images of interest. An active contour model approach, using control points, emerges as the method to be preferred to three more traditional approaches. Feedback from the image provider indicates that any of the methods described have something useful to offer for segmentation of hyphae.     

防治甘草萤叶甲生物源农药筛选及其对生物多样性的影响

为了筛选出防治甘草萤叶甲Diorhbda tarsalis Weise的生物药剂,采用多种生物源药剂,通过室内、田间试验,进行综合分析。室内毒力测定结果表明,甘草萤叶甲对0.5%黎芦碱SL的敏感性最高,LD50为0.139mg/L,0.3%印楝素EC、L2、1%苦参碱SL、L1依次递减,LD50分别为0.457,1.352,2.014和2.251mg/L,均高于其他药剂。田间防效结果表明,黎芦碱药后21d对甘草萤叶甲的防效最高,为100%,苦参碱、印楝素次之,均为86.67%,L2、L1的分别为66.67%和40%;对非靶标害虫小绿叶蝉也有较好的控制作用,药后21d防效L1较低,为56.67%,其他防效均高于68.89%;对田间天敌多异瓢虫和中华草蛉的安全性,除黎芦碱外,印楝素、苦参碱、L2、L1均较好,药后21d校正虫口减退率最高为57.14%;另外,苦参碱药后各期生物多样性指数平均最高,为2.93,印楝素次之,为2.88,藜芦碱、L1、L2依次递减,分别为2.45,2.43和2.07。因此,印楝素、苦参碱是防治甘草萤叶甲的理想药剂。     

Legal obligation of physicians to disclose information to patients.

Obtaining a patient''s consent is a routine daily process for physicians, although many are unaware of the scope of this legal obligation. In 1980 the Supreme Court of Canada changed the law relating to informed consent; promotion of patient autonomy shifted the focus from a standard of professional disclosure to one of a "reasonable patient." Physicians have a legal obligation to disclose to patients specific information, the scope of which is determined by a court on the basis of a reasonable patient''s expectation and the circumstances of the case. This gives rise to many controversies in the practice of clinical medicine. It is difficult for physicians to know which treatment risks require disclosure, since this is decided by a court in a retrospective analysis of the evidence. Will the court recognize exceptions to the duty of disclosing information? If several health care professionals are involved in a patient''s care who has the duty to disclose information? Can this duty be delegated? This paper provides physicians with guidelines that are consistent with the promotion of patient autonomy and comply with the doctrine of informed consent. In addition, it suggests ways of improving awareness of the doctrine and procedures to ease its application.     

On the failure of two butterfly species to respond to the presence of conspecific eggs prior to oviposition

Abstract. 1. The eggs of Euptychiine butterflies are laid singly, but their distributions tend to be contagious. However, these insects do not discriminate between egg-laden and egg-free plants.
2. Response to conspecific eggs is not part of the mechanism responsible for clumped egg distribution.     

The efficiency of close inbreeding to reduce genetic adaptation to captivity

Although ex situ conservation is indispensable for thousands of species, captive breeding is associated with negative genetic changes: loss of genetic variance and genetic adaptation to captivity that is deleterious in the wild. We used quantitative genetic individual-based simulations to model the effect of genetic management on the evolution of a quantitative trait and the associated fitness of wild-born individuals that are brought to captivity. We also examined the feasibility of the breeding strategies under a scenario of a large number of loci subject to deleterious mutations. We compared two breeding strategies: repeated half-sib mating and a method of minimizing mean coancestry (referred to as gc/mc). Our major finding was that half-sib mating is more effective in reducing genetic adaptation to captivity than the gc/mc method. Moreover, half-sib mating retains larger allelic and adaptive genetic variance. Relative to initial standing variation, the additive variance of the quantitative trait increased under half-sib mating during the sojourn in captivity. Although fragmentation into smaller populations improves the efficiency of the gc/mc method, half-sib mating still performs better in the scenarios tested. Half-sib mating shows two caveats that could mitigate its beneficial effects: low heterozygosity and high risk of extinction when populations are of low fecundity and size and one of the following conditions are met: (i) the strength of selection in captivity is comparable with that in the wild, (ii) deleterious mutations are numerous and only slightly deleterious. Experimental validation of half-sib mating is therefore needed for the advancement of captive breeding programs.     

The relationship of abnormalities of cellular immunity to antibodies to HTLV-III in homosexual men

A comprehensive evaluation of the cellular immune system (total T-cell, helper cell, suppressor cell, and natural killer cell numbers; in vitro interleukin-2 production, T-cell responses to mitogens and antigens, serum beta 2 microglobulin levels, and delayed hypersensitivity skin tests) was performed on 36 HTLV-III seronegative and 16 HTLV-III seropositive healthy homosexual men, 48 asymptomatic homosexual men with the chronic lymphadenopathy syndrome, 41 patients with AIDS, and 29 heterosexual controls without any known risk factors for AIDS. Our studies demonstrate that HTLV-III seronegative homosexual men have normal cellular immunity and are comparable to heterosexual controls. The abnormalities of lymphocyte subsets observed in HTLV-III seropositive healthy homosexual men are comparable to subjects with chronic lymphadenopathy. Assays of lymphocyte function, with the exception of delayed type hypersensitivity (DTH) skin tests, are similar in each group except patients with AIDS. Subjects with chronic lymphadenopathy were less responsive to DTH skin tests and HTLV-III seropositive healthy homosexuals were comparable to chronic lymphadenopathy subjects. We conclude that immunologic abnormalities in homosexual men are attributable to infection with HTLV-III.     

Covalent attachment of proteins to peptidoglycan

Bacterial surface proteins are key players in host-symbiont or host-pathogen interactions. How these proteins are targeted and displayed at the cell surface are challenging issues of both fundamental and clinical relevance. While surface proteins of Gram-negative bacteria are assembled in the outer membrane, Gram-positive bacteria predominantly utilize their thick cell wall as a platform to anchor their surface proteins. This surface display involves both covalent and noncovalent interactions with either the peptidoglycan or secondary wall polymers such as teichoic acid or lipoteichoic acid. This review focuses on the role of enzymes that covalently link surface proteins to the peptidoglycan, the well-known sortases in Gram-positive bacteria, and the recently characterized l,d-transpeptidases in Gram-negative bacteria.     

Benefits of Rhizobium to agriculture

Crops fixing nitrogen by means of endosymbiotic rhizobia are a major world source of protein and soil nitrogen. Interactions between the bacteria and host plant are currently being unravelled. This will enable current rhizobial biotechnology and developing plant biotechnology to be targetted towards more efficient nitrogen fixation and new nodulated, nitrogen fixing crops.     

基因差异表达研究方法的探讨--从DD-PCR到cDNA RDA

ＤＤ－ＰＣＲ和ｃＤＮＡ ＲＤＡ都是近年发展起来的新技术,它们被应用于生物及医学领域,在基因差异表达和筛选差异基因的研究中有着广泛的前景。本文论述了ＤＤ－ＰＣＲ及ｃＤＮＡ ＲＤＡ的基本技术策略,并对两者进行了比较分析。     

Applications of fractal analysis to physiology

This review describes approaches to the analysis of fractal properties of physiological observations. Fractals are useful to describe the natural irregularity of physiological systems because their irregularity is not truly random and can be demonstrated to have spatial or temporal correlation. The concepts of fractal analysis are introduced from intuitive, visual, and mathematical perspectives. The regional heterogeneities of pulmonary and myocardial flows are discussed as applications of spatial fractal analysis, and methods for estimating a fractal dimension from physiological data are presented. Although the methods used for fractal analyses of physiological data are still under development and will require additional validation, they appear to have great potential for the study of physiology at scales of resolution ranging from the microcirculation to the intact organism.