Statistical fluctuations in processes of gene expression regulation: consideration of the problem from point of view of statistical mechanics

The regulation of gene expression is a basic problem of biology. In some cases, the gene activity is regulated by specific binding of regulatory proteins to DNA. In terms of statistical mechanics, this binding is described as the process of adsorption of ligands on the one-dimensional lattice and has a probability nature. As a random physical process, the adsorption of regulatory proteins on DNA introduces a noise to the regulation of gene activity. We derived equations, which make it possible to estimate this noise in the case of the binding of the lac repressor to the operator and showed that these estimates correspond to experimental data. Many ligands are able to bind nonspecifically to DNA. Nonspecific binding is characterized by a lesser equilibrium constant but a greater number of binding sites on the DNA, as compared with specific binding. Relations are presented, which enable one to estimate the probability of the binding of a ligand on a specific site and on nonspecific sites on DNA. The competition between specific and nonspecific binding of regulatory proteins plays a great role in the regulation of gene activity. Similar to the one-dimensional "lattice gas" of particles, ligands adsorbed on DNA produce "one-dimensional" pressure on proteins located at the termini of free regions of DNA. This pressure, an analog of osmotic pressure, may be of importance in processes leading to changes in chromatin structure and activation of gene expression.     

Production and Robustness of a Cacao Agroecosystem: Effects of Two Contrasting Types of Management Strategies

Ecological intensification, i.e. relying on ecological processes to replace chemical inputs, is often presented as the ideal alternative to conventional farming based on an intensive use of chemicals. It is said to both maintain high yield and provide more robustness to the agroecosystem. However few studies compared the two types of management with respect to their consequences for production and robustness toward perturbation.In this study our aim is to assess productive performance and robustness toward diverse perturbations of a Cacao agroecosystem managed with two contrasting groups of strategies: one group of strategies relying on a high level of pesticides and a second relying on low levels of pesticides. We conducted this study using a dynamical model of a Cacao agroecosystem that includes Cacao production dynamics, and dynamics of three insects: a pest (the Cacao Pod Borer, Conopomorpha cramerella) and two characteristic but unspecified beneficial insects (a pollinator of Cacao and a parasitoid of the Cacao Pod Borer). Our results showed two opposite behaviors of the Cacao agroecosystem depending on its management, i.e. an agroecosystem relying on a high input of pesticides and showing low ecosystem functioning and an agroecosystem with low inputs, relying on a high functioning of the ecosystem. From the production point of view, no type of management clearly outclassed the other and their ranking depended on the type of pesticide used. From the robustness point of view, the two types of managements performed differently when subjected to different types of perturbations. Ecologically intensive systems were more robust to pest outbreaks and perturbations related to pesticide characteristics while chemically intensive systems were more robust to Cacao production and management-related perturbation.     

Biology of gastrointestinal nematodes of ruminants

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.     

Calibration of measured center of pressure of a new stairway design for kinetic analysis of stair climbing

A stairway that allows the collection of kinetic data is essential for biomechanical studies on stair climbing. There is a need to validate the measured center of pressure (COP) on the surface of a stair in order to verify the accuracy of the calculation of joint kinetics. The purpose of this study was to validate a new stairway design for kinetic analysis of stair climbing through a calibration and error analysis of the COP obtained from this system. The new stairway design allows the collection of kinetic data for multiple steps without any constraint to foot placement. Known vertical forces were applied to known locations on the surface of each stair and each force plate. Multiple regression analyses were conduced to determine the distribution pattern of the error in the measured COP. It was found that the error in the COP was a function of location on the stair or force plate. The magnitude of the vertical force had no significant effect on the error in the measured COP. The distribution pattern of the error in the measured COP on the force plates used in this study matched the results in the literature. A healthy female subject was used as the subject in a stair climbing test. The error in the measured COP had a significant effect on the calculated joint resultant moments, especially the abduction-adduction and internal-external rotation moments. The correction of these errors should make the kinetic calculation in stair climbing more accurate.     

北半球500hPa高度场遥相关指数对我国草地螟成虫物候期与幼虫发生面积的影响

北半球500hPa高度场的遥相关指数(遥相关指数)是一个综合了气温,降水以及气压等众多气象因素的气候变化指数,很多生物学现象都与其有关;为了探究遥相关指数是否对我国的草地螟的发生危害有影响,作者分析了我国草地螟Loxostege sticticalisL.成虫物候期及幼虫发生面积的变化趋势及两者与遥相关指数的相关关系,结果表明:我国草地螟成虫始见期年际间有显著提前的趋势,平均每年提前0.40d,与1—5月极地-欧亚型遥相关指数均值(POL1-5)相关性最大;终见期有显著延后的趋势,平均每年延后1.31d,与6—10月东太平洋型遥相关指数均值(EP-NP6-10)相关性最大;全国草地螟幼虫发生面积年际间有显著增长的趋势,平均每年增长57.07khm2,与1—10月东大西洋型遥相关指数均值(EA1-10)相关性最大。     

On meta-analytic assessment of surrogate outcomes

We discuss the strengths and weaknesses of the meta-analytic approach to estimating the effect of a new treatment on a true clinical outcome measure, T, from the effect of treatment on a surrogate response, S. The meta-analytic approach (see Daniels and Hughes (1997) 16, 1965-1982) uses data from a series of previous studies of interventions similar to the new treatment. The data are used to estimate relationships between summary measures of treatment effects on T and S that can be used to infer the magnitude of the effect of the new treatment on T from its effects on S. We extend the class of models to cover a broad range of applications in which the parameters define features of the marginal distribution of (T, S). We present a new bootstrap procedure to allow for the variability in estimating the distribution that governs the between-study variation. Ignoring this variability can lead to confidence intervals that are much too narrow. The meta-analytic approach relies on quite different data and assumptions than procedures that depend, for example, on the conditional independence, at the individual level, of treatment and T, given S (see Prentice (1989) 8, 431-440). Meta-analytic calculations in this paper can be used to determine whether a new study, based only on S, will yield estimates of the treatment effect on T that are precise enough to be useful. Compared to direct measurement on T, the meta-analytic approach has a number of limitations, including likely serious loss of precision and difficulties in defining the class of previous studies to be used to predict the effects on T for a new intervention.     

Integration of the effects of estradiol and progesterone in the modulation of gonadotropin secretion

Estradiol secreted by the maturing follicle is the primary trigger for the surge of gonadotropins leading to ovulation. Progesterone has stimulatory or inhibitory actions on this estrogen-induced gonadotropin surge depending upon the time and dose of administration. The administration of progesterone to immature ovariectomized rats primed with a low dose of estradiol induced a well-defined LH surge and prolonged FSH release, a pattern similar to the proestrus surge of gonadotropins. A physiological role of progesterone is indicated in the normal ovulatory process because a single injection of the progesterone antagonist RU 486 on the day of proestrus in the adult cycling rat and on the day of the gonadotropin surge in the pregnant mare's serum gonadotropin stimulated immature rat resulted in an attenuated gonadotropin surge and reduced the number of ova per ovulating rat. Progesterone administration brought about a rapid LHRH release and an decrease in nuclear accumulation of estrogen receptors in the anterior pituitary but not the hypothalamus. The progesterone effect was demonstrated in vitro in the uterus and anterior pituitary and appears to be confined to occupied estradiol nuclear receptors. In in vivo experiments the progesterone effect on estradiol nuclear receptors appeared to be of approximately 2-h duration, which coincided with the time period of progesterone nuclear receptor accumulation after a single injection of progesterone. During the period of progesterone effects on nuclear estrogen receptors, the ability of estrogens to induce progesterone receptors was impaired. Based on the above results, a model is proposed for the stimulatory and inhibitory effects of progesterone on gonadotropin secretion.     

An investigation of the interactions of E-selectin with fuco-oligosaccharides of the blood group family

This investigation is concerned with assignments of Lewis(a) (Le(a)) and Le(x) analogs on linear and branched di- to hexasaccharide backbones as components of the recognition motifs for E-selectin. The influence of the location of fucose residue(s) was investigated using 14 structurally defined and variously fucosylated oligosaccharides in biotinylated form or as neoglycolipids in static binding assays, in microwells, and on thin-layer chromatograms. Results of the two assay systems were in agreement overall and showed that the recognition motifs for E-selectin include 4-fucosyl-lacto (Le(a)) and 3-fucosyl-neo-lacto (Le(x)) sequences strictly at capping positions and not Le(x) at an internal position as a part of VIM-2 antigen sequence. There is greater potency of the Le(a) over the Le(x) series. Additional fucose residues alpha1-2-linked to neighboring galactoses or alpha1-3-linked to inner N-acetyglucosamines or to reducing-terminal glucose residues of the tetrasaccharide backbone had little or no effect on the selectin binding. E-selectin binding to the Le(a) or Le(x )capping motif on a 3-linked branch was equivalent to the binding on the corresponding linear backbone. A lack of E-selectin binding to the Le(x) motif capping a 6-linked branch and to the Le(x) trisaccharide linked to biotin via a nine-carbon spacer indicates that the -GlcNAcbeta1-3Gal- sequence on the oligosaccharide backbone adjoining the Le(x) is a part of recognition motif for E-selectin. These findings contribute to understanding the molecular basis of E-selectin recognition and could influence future designs of selectin antagonists as possible therapeutic substances.     

烟粉虱对寄主植物叶背的定向行为

烟粉虱Bemisia tabaci(Gennadius)成虫在自然条件下总是能够准确定位到寄主的叶片背面进行取食和产卵,这是一种本能的定向行为。以扶桑和油麦菜为寄主材料,通过非选择性和选择性实验,研究和评价光照、叶面物理性状和重力3个环境因子在烟粉虱成虫定向行为中的作用。结果显示,重力在定向行为中起主导作用,寄主叶片正反面的物理性状差异也能够使烟粉虱成虫定位到寄主叶片的背面,但是存在时滞效应。说明烟粉虱成虫在定向到寄主叶片背面的过程中存在2个系统,一个是以重力为线索的垂直方向感作为导航系统,另一个则是以叶面物理性状为线索的行为调节作为校正系统,二者的相互协作使得烟粉虱成虫能够精确定位到寄主叶片的背面。     

Chromogenicity of Streptomyces

A simplified technique to detect polyphenol oxidase and melanin formation by Streptomyces culture filtrates was developed. The procedure involves the direct assay of pigment formation by the culture filtrate with 3-(3,4-dihydroxyphenyl)-L-alanine (L-dopa) as a substrate. Among cultures of the International Streptomyces Project, 34 failed to produce a diffusible dark brown pigment on peptone-yeast extract-iron-agar and synthetic tyrosine-agar and gave a negative reaction to the melanin formation test. Sixteen cultures produced a diffusible dark brown pigment on both peptone-yeast extract-iron-agar and synthetic tyrosine-agar and gave positive reactions to the test with either L-tyrosine or L-dopa as substrate. Twenty-one cultures produced a diffusible dark brown pigment on peptone-yeast extract-iron-agar, but failed to do so on synthetic tyrosine-agar. Most of these cultures gave a positive reaction to the test when L-dopa was used as the substrate. The correlation between chromogenicity on complex organic media and melanin formation was more clearly established with L-dopa as substrate than with synthetic tyrosine-agar in the present test. The melanin formation test by the present technique, instead of chromogenicity on complex organic media, is recommended as a key feature for the classification of Streptomyces.     

Effects of the perinatal exposure of Gum Arabic on the development,behavior and biochemical parameters of mice offspring

The effects of the perinatal oral exposure to Gum Arabic (GA) on mice offspring was examined. GA was added to the drinking water of pregnant female Swiss–Webster strain mice at doses of 1 and 4 g/kg body weight, starting from the first day of pregnancy. The treatment continued until the fifteenth day after delivery, after which mothers were switched to plain tap water. A number of tests were carried out on offspring starting one day after birth and extending up to postnatal day 30 (PD30). Pups showed a reduced gain of body weight and delayed opening of the eyes in comparison to the control group and only pups exposed to 1 g/kg body weight GA had a faster appearance of hair. Sensory motor reflex tests carried out during the weaning period (from day of birth to PD21) showed enhanced motor reflexes in pups exposed to GA. During the adolescent period (from PD22 to PD30), offspring showed dose-dependent enhanced motor activity (on PD22), reduced anxiety and fear (on PD27) and slightly enhanced memory and learning abilities (on PD30). Biochemical tests of a number of blood parameters were conducted during and after the weaning period (on PD15 and PD30, respectively). Our results indicated that GA might have a hypoglycemic and a beneficial effect on red and white blood cell counts. This study gives a first insight on the effect of GA consumption on offspring, providing a starting point for further studies.     

Reciprocal modulation of regulatory action of prolactin and somatotropin on DNA synthesis in granulosa cells of cows

A comparative analysis of the individual and joint influence of bovine prolactin (BPRL) and bovine somatotropin (BST) on DNA synthesis in cultured bovine granulosa cells from follicles of 3-5 mm in diameter was conducted, and a possibility for regulation of BPRL binding to receptors on the cells by BST was examined. Despite a unidirectional growth-promoting action of BPRL and BST on granulosa cells, their joint mitogenic effect on the cells was not additive at low concentrations of BPRL. The addition of BST to the culture medium did not alter the biphasic character of dependence of DNA synthesis in the cells on BPRL concentration, but increased the maximum effective concentration of the latter. When culturing granulosa cells with BST, the absence of its influence on the level of BPRL specific binding to the cells was shown. This fact suggests that BST modulating action on the mitogenic effect of BPRL is not a result of a change in the number of free receptors for PRL on granulosa cells. The results obtained are discussed in relation to the notion of similarity of receptor functional properties and intracellular signal ways for PRL and ST.     

Mechanism of secretion of the contents of the mandibular glands of Plodia interpunctella larvae

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.     

Mathematical model of the dynamics of psychotherapy

The success of psychotherapy depends on the nature of the therapeutic relationship between a therapist and a client. We use dynamical systems theory to model the dynamics of the emotional interaction between a therapist and client. We determine how the therapeutic endpoint and the dynamics of getting there depend on the parameters of the model. Previously Gottman et al. used a very similar approach (physical-sciences paradigm) for modeling and making predictions about husband–wife relationships. Given that this novel approach shed light on the dyadic interaction between couples, we have applied it to the study of the relationship between therapist and client. The results of our computations provide a new perspective on the therapeutic relationship and a number of useful insights. Our goal is to create a model that is capable of making solid predictions about the dynamics of psychotherapy with the ultimate intention of using it to better train therapists.     

Effects of Additional Support on the Maintenance of Human Vertical Posture

Effects of contact of a hand or fingertip with an additional support on human balance on stationary and movable surfaces were studied. Contact with a fixed or free vertical bar was established either by a handgrip or a touch with the tip of the index finger. Amplitudes and lengths of posturograms under conditions of free standing and standing with additional proprioceptive information were compared. It was shown that contact with an additional support during standing on a stationary surface with closed eyes decreases the amplitude of sagittal sway of the center of gravity by 1.3- to 2-fold as compared to standing without such a contact, independently of the contact type and the degree of bar mobility. During standing on a movable platform (which resulted in a three- to fourfold increase in the amplitude of sway as compared to standing on the floor), the grasp of the fixed bar decreased the amplitude of sagittal sway by five- to ninefold and the touch led to a three- to fourfold decrease. The sway of the common center of gravity upon contact with the movable bar during standing on the unstable platform was reduced by half on both planes independently of the contact type. The results suggest that sensory information from receptors of the hand contacting with a stationary or movable support substantially supplements the current neural representation of the spatial position of the body, correcting and changing the direction of postural reactions and the perception of the location of external objects, which ensures the ability of the CNS to maintain the balance under complicated conditions and to provide highly stable standing.     

Experimental test of the influence of the size of shoals and density of fish on parasite infections

There is an increasing interest in the relationship between adult coral reef fishes and their parasites; however, there is almost no information concerning post larvae (i.e. newly recruited) fish and their parasites. Newly recruited and juvenile fish are highly sensitive to their environment and they have a very low survival rate. Fish grouping behavior has been studied in several ways and many studies have shown that increasing group size might be a way to share a cost linked to parasitism, via a dilution effect. To my knowledge, this hypothesis has never been tested for juveniles of fish. The potential influence of school size and density of a juvenile coral reef fish, Haemulon flavolineatum (Haemulidae), on the success of a monogenean fish parasite, Haliotrema sp., was studied. First, the fish acquired their monogeneans when they were more than 40 mm long, size corresponding also to a change in their foraging behavior. Second, there was a positive effect of fish density on the success of the establishment of the parasite on the host population. Finally, although the parasite success was not directly related to fish group size, the parasite abundance was higher for intermediate shoal size. These results are discussed in terms of the consequence parasitism may have on a fish's shoaling and to a larger extent on the fish population.     

Role of cytokinins in stress resistance of plants

The facts of both positive and negative influences of cytokinins on stress resistance of plants are known today. Without pretending to a final choice between these points of view, we have made an attempt to analyze the details of the experiments that gave rise to conclusions about the nature of the effect of cytokinins on the resistance to stress-causing influences with a focus on their intensity and duration. The review deals with the data concerning the influence of different adverse factors on the content of endogenous cytokinins and transduction of cytokinin signals, examines the influence on plant resistance of treatment with exogenous hormone, and the effects of genetic modifications causing changes in cytokinin content and signaling. Resistance is considered not only as a mean of plant survival under severe stress but also as an instrument of maintaining growth rate in plants exposed to moderate stress. Literature data and our own results make it possible to conclude that cytokinins play an important role in formation of plant resistance to adverse influences; however, the effect of these hormones depends on stress intensity. Under moderate stress, cytokinins ensure maintenance of plant growth, whereas a drop in cytokinins hampers growth under a strong influence of adverse factors, which is a prerequisite for mobilization of limited resources characteristic of severe stress and ensures preservation of plant viability.     

Comparison of population numbers of yellow-eyed penguins,

During a comprehensive survey in 1999, 2000 and 2001, we investigated the number of breeding yellow-eyed penguin pairs on Stewart Island, where cats are present, and on adjacent cat-free islands. We found 79 pairs of yellow-eyed penguin breeding in 19 discrete locations on Stewart Island (4.2 pairs per location), and 99 pairs breeding in 10 discrete locations on all cat-free islands (9.9 pairs per location). Large-scale humaninduced habitat modifications have not occurred on Stewart Island, nor on any of its adjacent offshore islands. While the extensive coastline of Stewart Island (673 km) offers potentially large areas of breeding habitat for penguins, the highest number of breeding pairs were found on the smaller, predator-free Codfish Island (25 km coastline), where a total of 61 breeding pairs were recorded. On Stewart Island, where mustelids do not occur, only feral cats can pose a serious threat to penguin offspring. Results from this study suggest that feral cats may prey on yellow-eyed penguins on Stewart Island. Further work is necessary to investigate whether the observed low numbers of yellow-eyed penguins on Stewart Island are caused by feral cat predation. If so, it may be possible to develop appropriate measures to protect this penguin species from a population decline.     

Calculation of half-lives of proteins in vivo. Heterogeneity in the rate of degradation of yeast proteins

Summary A method is given for the calculation of half-lives of proteins in vivo from the measurement of the decrease of radioactivity in pulse-labelled proteins with time. This method could be particularly useful for the study of the degradation of proteins in cells that have a low growth rate.The method applied to growing yeast indicates that there are two major classes of protein. The class with low turnover constitutes the bulk of yeast protein and has a half-life of 160 h in a medium with glucose or galactose and of 50 h in a medium with ethanol. The class of proteins with high turnover (half-life between 0.8 and 2.4 hours) represents from 1% of total protein in yeast growing on glucose to 7% in yeast growing on ethanol.It is shown that some proteins which are derepressed during growth on ethanol or induced during growth on galactose are particularly susceptible to degradation in a medium which contains glucose.It is proposed that protein degradation is regulated by a coarse control at the level of protease activity and a fine control on the susceptibility of individual proteins to proteases.