Effect of ephemeral stepping stones on metapopulations on fragmented landscapes

In both percolation models and metapopulation (habitat patch) models, habitat pattern is assumed to be fixed and binary (matrix is unsuitable). In percolation models movement (dispersal) is strictly to neighbors whereas in metapopulation models movement is not explicitly considered but is factored into the colonization coefficients. Models with explicit dispersal also typically treat habitat as binary. Disturbance, if considered, is usually assumed to affect only preferred habitat. In this study, a dispersal kernel is assumed with spatially explicit populations and habitat, and the matrix is assumed to be affected by disturbances or fluctuating environmental conditions that open sites for dispersers (e.g., seeds) on a temporary basis. These ephemeral habitat patches are shown to act as stepping stones between preferred habitat. The consequence of stepping stones in this case is an increase in persistence when remnant preferred habitat is rare, and the conversion of extinction scenarios into persistence scenarios in some cases. The utilization of stepping stones by a species leads to nonintuitive relationships between observed abundance and habitat preference that could cause conservation strategies to backfire.     

Reflections on the origin of optical asymmetry on earth

The importance of optical purity, which was stressed in an earlier review, is reassessed in the light of recent evidence concerning the optical configuration of amino acids in biological systems. The most significant fact to emerge in recent years that bears on the origin of optical asymmetry is the experimental evidence for the Salam-Weinberg theory. However, the problem remains: is the effect of PNC-interactions too small to be detectable, and if it is so small, can it be of any significance? In view of the contradictory and confusing nature of the evidence on the induction of optical activity, it is suggested that the Bremen Symposium should agree on some experimental protocols.     

Studies on immobilization of lipase on alumina for hydrolysis of ricebran oil

The immobilization of lipase from Candida lipolytica on alumina by adsorption for the hydrolysis of ricebran oil is described. Some of the factors which influence the activity of immobilizate and the stability of immobilizate are discussed. About 69% of the initially added enzyme activity is found in the biocatalyst when immobilized at pH 7.2. The stability of the immobilized enzyme to different pH and temperature conditions has also been studied.List of Symbols DE Dextrose equivalent. One DE is reducing sugar equivalent to one milligram of glucose - NE Nitrogen equivalent. One NE is one milligram of nitrogen     

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.     

Effect of quinolinate on aminotransferases

Quinolinate inhibits several aminotransferases (ornithine, alanine, and aspartate). However, it is considerably more potent as an inhibitor of liver and heart cytoplasmic aspartate aminotransferase. It is a much less potent inhibitor of mitochondrial aspartate aminotransferases. Quinolinate is bound to the active site of cytoplasmic aspartate aminotransferase. It has a much greater affinity for the pyridoximine-P than the pyridoxal-P form of the enzyme. According to kinetic results, the inhibition or dissociation constant of quinolinate is 0.2 and 20 mm, respectively, for the pyridoxamine-P and the pyridoxal-P forms of the enzyme. Since quinolinate is mainly bound to the pyridoxamine-P form: (a) it is a potent competitive inhibitor of α-ketoglutarate but has little effect when α-ketoglutarate is saturating even if the level of aspartate is low; (b) it decreases the effect of α-ketoglutarate on the absorption spectrum of the pyridoxamine-P form; and (c) it enhances the effect of glutamate on the absorption spectrum of the pyridoxal-P form. Quinolinate is also apparently bound to the apoenzyme since it inhibits reconstitution by either pyridoxamine-P or pyridoxal-P. Since quinolinate is a competitive inhibitor of α-ketoglutarate, it is possible that part of the inhibitory effect of quinolinate on hepatic gluconeogenesis could result from quinolinate inhibiting the conversion of aspartate to oxalacetate by the cytoplasmic aspartate aminotransferase. Quinolinate has no effect on either rat or bovine liver glutamate dehydrogenase or on kidney glutamate dehydrogenase.     

A comment on Bobisud's paper on evolution of cannibalism

One of Bobisud's (1976) models for the evolution, of cannibalism is discussed. His analysis is criticised for not being based on the principle of individual selection. Assuming the operation of that principle, we show by simulating his model that cannibals may establish themselves in a noncannibal population. This will happen both in cases where Bobisud concluded cannibalism to be optimal and in cases where he concluded cannibalism not to be optimal.     

A physicochemical investigation on the effects of ozone on blood

Ozonation of either human whole blood or saline-washed erythrocytes causes considerable damage to the latter and this result has opened a controversy. With the benefit of hindsight, it appears logical that once erythrocytes are deprived of the potent antioxidants of plasma, they become very sensitive to the oxidant effects of ozone. The aim of the present work was to perform a physical–chemical evaluation of some critical parameters able to clarify this issue. We have ascertained that when whole blood is exposed to the appropriate ozone doses used in human therapy, no damage ensues while saline-washed erythrocytes undergo conspicuous haemolysis. The dogma that ozone is always toxic is incorrect because its reactivity below the concentration of 80 μg/mL can be controlled by the plasmatic antioxidant system.     

Comments on optimization of glycolysis

A recently proposed function for optimization of anaerobic glycolysis is analysed. The maximum value of this optimization function is shown in general to lead to a conserved energy yield of 50% for any coupled reaction. Maximization of the optimization function is shown to correspond to maximizing the product of two variables, the sum of which is constant. The maximum value of the product is always obtained when the two variables have the same size.     

论心理对生理的影响和作用

本文阐述了心理对生理的能动作用。在一定的条件下,人的心理可影响其生理功能,两者互为因果、相互影响。生理是心理活动的物质基础,心理是其生理的驱动力和标志。本文论述了精神、情绪、意念、信念、暗示等心理活动对生理的影响和作用及中医论心理对生理的作用,中医利用情志疗法的理论达到心理对生理趋向健康的作用。同时论证了肠道菌群通过心理间接影响生理功能,通过微生态制剂调节肠道菌群的微生态平衡,可改善患者的神经症状,使之心理活动达到最佳状态,进而使人的生理趋向健康。     

Effect of viscoelasticity on the analysis of single-molecule force spectroscopy on live cells

Single-molecule force spectroscopy is used to probe the kinetics of receptor-ligand bonds by applying mechanical forces to an intermediate media on which the molecules reside. When this intermediate media is a live cell, the viscoelastic properties can affect the calculation of rate constants. We theoretically investigate the effect of media viscoelasticity on the common assumption that the bond force is equal to the instantaneous applied force. Dynamic force spectroscopy is simulated between two cells of varying micromechanical properties adhered by a single bond with a constant kinetic off-rate. We show that cell and microvilli deformation, and hydrodynamic drag contribute to bond forces that can be 28-90% lower than the applied force for loading rates of 10(3)-10(7) pN/s, resulting in longer bond lifetimes. These longer bond lifetimes are not caused by changes in bond kinetics; rather, they are due to the mechanical response of the intermediate media on which the bonds reside. Under the assumption that the instantaneous bond force is equal to the applied force--thereby ignoring viscoelasticity--leads to 14-39% error in the determination of off-rates. We present an approach that incorporates viscoelastic properties in calculating the instantaneous bond force and kinetic dissociation parameter of the intermolecular bond.     

Effects of traces of rare earth elements on the protozoanBlepherisma and on mice

The growth of the protozoanBlepherisma is stimulated by Lanthanum (La) at concentrations as low as 0.32 ppm. In mice Yttrium (Y) and Ytterbium (Yb) are absorbed, accumulated, and metabolized. Both rare earth elements (RE) exhibit a high affinity for teeth and bones, accumulation occurs and metabolism is slow. In the livers of RE-exposed mice, concentrations are variable. The liver is apparently capable of absorbing and discharging RE in a manner depending on metabolic activity. The main route of discharge for ingested REs is the alimentary canal. Exposure of pregnant mice to RE leads to rapid placental transfer of RE; 14.1% of the total amount of RE administered was detected in newborn mice. Young, developing organisms appear to be especially susceptible to RE accumulation.     

Investigation on Fertilization of Cephalotaxus

The structure of spermatogenous cell of Cephalotaxus is unique among the gymnosperms. While towards the mature stage, its nucleus is close to one side of the spermatogenous cell, and on the other side there is abundant and prominent . cytoplasm, which contain a group of the aggregate cytoplasms of radial arrangement similar to blepharoplast of spermatogenous cell of Ginkgo. But, there are two opposite blepharoplasts at either side of the nucleus in Ginkgo, and while there is only one blephareplast at one side in Cephalotaxus. This is one feature of the sexual process in Cephalotaxus. When the pollen tubes approach the top of the archegonia, the division of the spermatogenous cell takes place and there are two almost similar sperm cells both in size and morphology. It is interesting to note that the cytoplasm of the sperm cell contains certain granules of nucleolus-like structure, which appears to be a rare phenomenon among the gymnosperms. This is another feature of the sexual process in Cephalotaxus. These two features are the important characters of Cephalotaxaceae. The egg morphology of Cephalotaxus is also unique among the conifers, its outline looks like a carrot. The upper part of the egg is rather wide and is about 85 to 108 μm in width. On the other hand, the opposite end is gradually becoming narrow and about 910 to 1100 μm in total length. So the ratio of the length and width in the egg of Cephalotaxus is about 10:1. The structure of the egg in Celhalotaxus fortunei and C. oliveri have the following common feature: 1. When their eggs mature the cytoplasm of the egg at lower part of the nucleus possesses deep- staining and fine granules of 2 to 3 groups of aggregate cytoplasm. 2. During maturation of the egg, some of the granules of nucleolus-like structure are scattered in the cytoplasm. As fer- tilization takes place the number of these granules reaches the peak. This condition has been encountered in the egg of Amentotaxus argotaenia. Therefore we could conclude that they are closely related between Cephloraxaceae and Taxaceae. The fertilization of Cephalotaxus fortunei occured on May 10 to 24 (1983), and that of C. oliveri took place on May 28 to June 13 (1983). The fertilization of the genus belong to the type of undergoing mitosis prior to complete fuse of both male and female nuclei. This type of fertilization has been found only in Pinaceae and Cephalotaxaceae. After fertilization the structure of fertilized egg becomes prominent in polar organization. In other words, the cytop- lasm at upper part of the fertilized egg becomes highly vacuolated and that at lower portion, conversely, is rich in abundant proteinous vacuoles and certain granules of nucleolus-like structure dispersed in the cytoplasm. Because the division and differentiation of the proembryo are proceeding at the base of the archegonium, the large inclusions and the nucleolus-like granules may be involved in the nourishing and development of the proembryo.     

Research progress on the effects of soil erosion on vegetation

The relationship between vegetation and soil erosion deserves attention due to its scientific importance and practical applications. A great deal of information is available about the mechanisms and benefits of vegetation in the control of soil erosion, but the effects of soil erosion on vegetation development and succession is poorly documented. Research shows that soil erosion is the most important driving force for the degradation of upland and mountain ecosystems. Soil erosion interferes with the process of plant community development and vegetation succession, commencing with seed formation and impacting throughout the whole growth phase and affecting seed availability, dispersal, germination and establishment, plant community structure and spatial distribution. There have been almost no studies on the effects of soil erosion on seed development and availability, of surface flows on seed movement and redistribution, and their influences on soil seed bank and on vegetation establishment and distribution. However, these effects may be the main cause of low vegetation cover in regions of high soil erosion activity and these issues need to be investigated. Moreover, soil erosion is not only a negative influence on vegetation succession and restoration, but also a driving force of plant adaptation and evolution. Consequently, we need to study the effects of soil erosion on ecological processes and on development and regulation of vegetation succession from the points of view of pedology and vegetation, plant and seed ecology, and to establish an integrated theory and technology for deriving practical solutions to soil erosion problems.     

Pleiotropic effects of spastin on neurite growth depending on expression levels

Hereditary spastic paraplegia (HSP) is characterized by weakness and spasticity of the lower limbs, owing to degeneration of corticospinal axons. The most common form is due to heterozygous mutations in the SPG4 gene, encoding spastin, a microtubule (MT)-severing protein. Here, we show that neurite growth in immortalized and primary neurons responds in pleiotropic ways to changes in spastin levels. Spastin depletion alters the development of primary hippocampal neurons leading to abnormal neuron morphology, dystrophic neurites, and axonal growth defects. By live imaging with End-Binding Protein 3-Fluorescent Green Protein (EB3-GFP), a MT plus-end tracking protein, we ascertained that the assembly rate of MTs is reduced when spastin is down-regulated. Spastin over-expression at high levels strongly suppresses neurite maintenance, while slight spastin up-regulation using an endogenous promoter enhances neurite branching and elongation. Spastin severing activity is exerted preferentially on stable acetylated and detyrosinated MTs. We further show that SPG4 nonsense or splice site mutations found in hereditary spastic paraplegia patients result in reduced spastin levels, supporting haploinsufficiency as the molecular cause of the disease. Our study reveals that SPG4 is a dosage-sensitive gene, and broadens the understanding of the role of spastin in neurite growth and MT dynamics.     

Overview on immobilization of enzymes on synthetic polymeric nanofibers fabricated by electrospinning

The arrangement and type of support has a significant impact on the efficiency of immobilized enzymes. 1-dimensional fibrous materials can be one of the most desirable supports for enzyme immobilization. This is due to their high surface area to volume ratio, internal porosity, ease of handling, and high mechanical stability, all of which allow a higher enzyme loading, release and finally lead to better catalytic efficiency. Fortunately, the enzymes can reside inside individual nanofibers to remain encapsulated and retain their three-dimensional structure. These properties can protect the enzyme's tolerance against harsh conditions such as pH variations and high temperature, and this can probably enhance the enzyme's stability. This review article will discuss the immobilization of enzymes on synthetic polymers, which are fabricated into nanofibers by electrospinning. This technique is rapidly gaining popularity as one of the most practical ways to fibricate polymer, metal oxide, and composite micro or nanofibers. As a result, there is interest in using nanofibers to immobilize enzymes. Furthermore, present research on electrospun nanofibers for enzyme immobilization is primarily limited to the lab scale and industrial scale is still challanging. The primary future research objectives of this paper is to investigate the use of electrospun nanofibers for enzyme immobilization, which includes increasing yield to transfer biological products into commercial applications.     

中国龙脑香科植物纪要

广义的龙脑香科是泛热带分布。中国有 5属 12种 ,其中 1种为引种栽培 ,产云南、广西、海南及西藏。本科分布北界在印度的喜马偕尔邦 ,在该地粗壮娑罗双Shorearobusta约达北纬 31°。《中国植物志》所报道见于我国的纤细龙脑香Dipterocarpusgracilis确实未见于我国。我国自然生长的东京龙脑香Dipterocarpusretusus依据毛被的多少可分为 2个变种 ,它们可能同时出现在同一林中。由于毛被多少不是区分种的可靠特征 ,因此将河内坡垒Hopeahongayanensis及多毛坡垒H mollissima两者都归并到狭叶坡垒H chinensis。鉴于雄蕊数目的不确定性 ,海南所产的Hopeaexalata与越南所产的H reticulata就视为同一种 ,而采用后者作为种名。版纳青梅Vaticaxishuangbannaensis与广西青梅V guangxiensis两者以叶脉数目来区分是不可靠的 ,也应视为同种而采用后者作为种名。经野外实地考察 ,望天树Parashoreachinensis仍应恢复其原来的学名。     

Novel paradigm on the effect of estrogen on bone

According to prevailing unitary model of involutional osteoporosis, female postmenopausal bone loss can be divided into two separate phases: the accelerated, transient phase, which is most distinct over the subsequent decade after the menopause and accounts for 20-30% of the cancellous bone loss and 5-10% of the cortical bone loss (type I osteoporosis), and the following gradual, continuous bone loss (type II osteoporosis). Estrogen deficiency is currently quite unanimously accepted as the primary cause of type I osteoporosis, as well as also a major determinant of type II osteoporosis, and quite plausibly, the quest to uncover the origin of type I (and II) osteoporosis has focused on the estrogen withdrawal-related skeletal changes at and around the menopause. However, given that the cyclical secretion of estrogen begins normally in early adolescence and continues over the entire fertile period (excluding the potential periods of pregnancy) until the eventual cessation of female reproductive capability, one could argue that this menopause-oriented approach is limited in scope. In this review, some classic findings of the pubertal effects of estrogen on female bones are presented, findings that were paramount to Fuller Albright when he first described the disease called postmenopausal osteoporosis in 1940, but studies/findings that have failed to attract the attention they deserve. When these findings are incorporated with the primary function of the axial skeleton and long bones, the locomotion, an alternative, novel explanation for the function of estrogen and accordingly, the origin of the accelerated phase of postmenopausal bone loss, is proposed: estrogen packs mechanically excess bone/mineral into the female skeleton at puberty, a bone stock that later serves as the origin of the type I postmenopausal osteoporosis.     

基于集对分析的京津冀区域可持续发展协调能力评价

区域发展的协调能力是区域可持续发展的重要表征之一。采用社会经济各相关部门的统计数据及资料,构建区域可持续发展评价指标和各级评价标准,利用集对分析中的同异反态势排序的协调发展评价模型实证分析了京津冀地区2000—2010年间的可持续发展协调能力。结果表明:(1)2000—2004年间北京和天津属于不协调发展,2006—2010年逐渐步入弱协调发展,但研究时段内河北省始终为不协调发展。(2)京、津和冀协调能力指数2010年相比2000年分别提高27.86%、8.87%和18.51%,各省域协调发展改善均不明显且步伐不一。(3)对京津冀区域各省域的发展提出了具体建议,但仍要加强各地区的合作和明确各自功能地位尤其重要。研究结果可以为京津冀整体规划的制定及实施提供科学依据和指导,也为环渤海经济圈可持续发展研究奠定了基础。     

Effect of fluid dispersion on cybernetic control of microbial growth on substitutable substrates

Many fermentation media contain two or more substrates, which a microorganism utilizes for similar purposes. Depending on the conditions prior to and during a fermentation, the substrates may be utilized in succession or simultaneously. Since it is difficult to portray this behavior through mechanistic models, a cybernetic method was proposed earlier. Here the microorganism chooses the mode of substrate utilization that maximizes its own survival, usually expressed by the growth rate. In a fully dispersed bioreactor, simultaneous utilization generates higher growth rates but leads to low biomass concentrations since this utilization pattern is preferred at low concentrations of the substrates. In this study it has been shown that by allowing less than complete dispersion in the broth it is possible to shift from sequential to simultaneous utilization at high concentrations, thereby enabling both high growth rates and large biomass concentrations. This strategy thus allows the natural incomplete dispersion in large bioreactors to be gainfully exploited.