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.     

Metapopulations of moths on islands: a test of two contrasting models

1. We describe a generalized mainland-island metapopulation model which includes migration among the island populations. We test model predictions with quantitative data on more than 200 species of moths in two contrasting networks of small islands. The data include a direct measure of migration rate, based on trapping of moths on rocky skerries with no local populations of the vast majority of species.
2. We predicted that moths which are strong fliers but uncommon on the islands have a higher incidence on scattered islands than on islands in a group, because the latter 'compete' for immigrants from the mainland. In contrast, we predicted that weakly flying species with potentially large local populations on the islands occur more frequently on islands in a group due to enhanced colonization rate.
3. Both predicted patterns were observed. Island occupancy increased significantly with the number of individuals caught on the rocky skerries, which is our measure of migration rate from the mainland, supporting the basic assumption that the species occur on the islands in a balance between colonizations and extinctions.
4. These results demonstrate that the moth metapopulations on islands represent a mixture of Levins's and mainland-island metapopulations, and that the mixture is different for different species in the same landscape.     

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.     

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.     

A Mechanism of Action of Neurotransmitters on the Regeneration of the Planarian Worm Dugesia tigrina. Role of Acetylcholine as a Negative Feed-back

By means of histochemical and pharmacological analysis it is shown that acetylcholine has an inhibitive effect on regeneration in the planaria Dugesia tigrina. It seems that serotonin and adrenaline on the one hand, and acetylcholine on the other hand, play a role in a mechanism of regulation in which the latter plays a role in a negative feed-back process.     

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.     

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.     

Kinetic study of seita-fitting

We have already presented two studies of the traditional carrier frame, the seita. In our first study, we reported on seita users supporting loads not on the lumbar vertebrae but on the sacrum. In the second study, we showed that carrying a load on the sacrum was efficient in terms of metabolic rate, muscle activity, cadence and subjective responses. The purpose of this study was to verify the effect of carrying a load on the sacrum in terms of gait pattern. We compared the kinetic parameters produced while carrying a load on the sacrum (LOS) with those produced while carrying a load on the lumbar vertebrae (LOLV). Maximum propulsive force and medial impulse were significantly larger in LOS than in LOLV. These results suggested that a normal gait pattern was maintained more in LOS conditions than in LOLV conditions. This indicated that seita-fitting was efficient for carrying and transporting loads.     

Effect of carbon sources upon the mycelial growth of Phytophthora citrophthora

In order to study the effect of carbon originating from different sources on the growth ofP. citrophthora, a modified Christie's formula was used as the basic nutrient medium. Carbon in various forms was then substituted for glucose in equivalent amounts. The fungus grew to a limited extent on glucose as the carbon source, but grew quite well on a maltose medium and less extensively on a sucrose medium. Fungus growth was most profuse on soluble starch, even more so than on potato dextrose and oatmeal medium. No sporangia were found in any of the media.     

The effect of electromagnetic waves of very high frequency of molecular spectra of radiation and absorption of nitric oxide on the functional activity of platelets

A study was made of the effect of electromagnetic EMI MMD-fluctuation on the frequencies of molecular spectra of radiation, and nitric oxide absorption under in vitro conditions on the functional activity of platelets in patients with unstable angina pectoris, with the help of a specially created generator. At amplitude-modulated and continuous modes of EMI MMD-irradiation of platelet-rich plasma for 5, 15 and 30 min the platelet functional activity decreases, which was shown up in reduction of their activation and fall of aggregative ability. The degree, to which platelet functional activity was inhibited, depended on the mode of irradiation and on duration of EMI MMD effect. The most obvious changes in platelet activation and in their readiness to aggregative response were observed at a continuous mode of irradiation within a 15 min interval.     

The spreading of monolayers of myosin

The spreading of the muscle proteins myosin and actomyosin depends both on the salt solution in which the proteins are dissolved and on the solution on which they are spread. The spreading is more complete the lower the concentration of the salt solution in which the proteins are dissolved and the higher the salt concentration of the solutions on which the proteins are spread. This effect seems to be due partially to the difference in density allowing the spread droplets a longer life on the surface, and partially to the effect of salt on the charge of the protein. A change in the pH of the substrate has a smaller effect than a change in the salt concentration. Heavy metals like Cu⁺⁺ or Zn⁺⁺, inhibit spreading almost completely. The dependence of spreading on these salts and on time was investigated in detail.The effect of the different salts was also compared with the effect of different phosphate compounds. It was noted that the above substances, including the different salts, phosphate compounds, and heavy metals, affect the mechanism of spreading but not films already spread. The viscosity of these fibrillar proteins was compared with other proteins in the monomolecular film state and in myosin an unusually high viscosity was found.     

Effects of laminin glycopeptides on metastasis—related behaviors of cancer cells

Our previous reports have shown that lamininglycopeptides (LN-GPs),the total glycopeptides prepared from laminin (LN),can prevent the experimental lung metastasis and liver metastasis of mouse cancer cells.In order to explore the anti-metastatic mechanism of LN-GPs,we studied the effects of LN-GPs on metastasisrelated behaviors of cancer cells in vitro.LN-GPs did not affect cell survival.However,LN-GPs inhibited cell attachment and spreading of S180 cells on LN-and Matrigelsubstrate in dose-dependent and time-dependent manners.Moreover,inhibition of cell attachment and spreading on Matrigel substrates were much greater on Matrigel substrate than on LN substrate.In the gresence of LN-GPs,S180 cells on LN substrate changed from a flattened polygonal shape to a round one,the migration of S180 cells on LN substrate decreased,and the number of a highly invasive human pulmonary giant carcinoma PG cells invading Matrigel filter in a Boyden chamber was reduced.LN-GPs thus have multiple inhibitory effects on cancer metastasisrelated behaviors.     

An iron-dependent mutant of Listeria monocytogenes of attenuated virulence

Abstract A bank of Tn 917 -insertional mutants from the facultative intracellular pathogen Listeria monocytogenes was screened by an original method based on bacterial growth on synthetic medium under iron-limiting conditions. One mutant, whose in vitro growth in synthetic medium was specifically dependent upon the availability of iron in its environment, was isolated and characterized. The insertional event occurred in a non-coding region, upstream of a rrn operon and located within a 1100-kb Not I fragment of the physical map, where the virulence genes already identified in L. monocytogenes were also present. Protein analysis by SDS-PAGE revealed a pleiotropic effect of the insertional event on cell-associated proteins, suggesting a polar effect of the transposon on adjacent unknown gene(s). The virulence in the mouse of this mutant was strongly impaired, although it was capable in vitro of growing intracellularly and of spreading from cell to cell, as shown by the production of lytic plaques on cell culture.     

The influence of upstream predation on the expression of fish effects in downstream patches

1. Enclosures were installed in a fishless stream and divided transversely into upstream and downstream sections. Downstream sections were further divided longitudinally, and one of the downstream sections in each enclosure was stocked with juvenile coho salmon ( Oncorhynchus kisutch ), and the other side was left as a fishless control. Densities of juvenile coho were then manipulated in upper sections of enclosures to determine the effect of upstream predation intensity on fish predation effects in downstream sections.
2. Significantly fewer mayflies (primarily Ameletus sp.) were observed grazing on unglazed ceramic tiles in lower enclosure sections with fish present. There was no detectable effect of fish density in upstream enclosure sections on the number of mayflies observed grazing on ceramic tiles in lower sections of the enclosures.
3. There was a significant positive effect of both fish presence and upstream density on chlorophyll a concentrations on ceramic tiles in lower enclosure sections, but not on chlorophyll a on natural gravel substratum.
4. Behavioural experiments with mayflies and coho in streamside troughs suggest that Ameletus sp. responds primarily to mechanical rather than chemical cues from coho parr.     

Modulation of protein synthesis and secretion by substratum in primary cultures of rat hepatocytes

Hepatocytes isolated by perfusion of adult rat liver and cultured on substrata consisting of one or more of the major components of the liver biomatrix (fibronectin, laminin, type IV collagen) have been examined for the synthesis of defined proteins. Under these conditions, tyrosine amino transferase, a marker of hepatocyte function, is maintained at similar levels in response to dexamethasone over 5 days in culture on each substratum, and total cellular protein synthesis remains constant. By contrast, there is a rapid decrease in synthesis and secretion of albumin and a 3-7-fold increase in synthesis and secretion of alpha-fetoprotein which are most marked on a laminin substratum, but least evident on type IV collagen, and an increased synthesis of fibronectin and type IV collagen. The newly synthesized matrix proteins are present in the cell layer as well as in cell secretions. The enhanced synthesis of fibronectin is less in cells seeded onto a fibronectin substratum than on laminin or type IV collagen substrata, and its synthesis by hepatocytes seeded onto a mixed substratum of laminin and fibronectin is down-regulated by fibronectin in a dose-related manner. Similarly, type IV collagen synthesis is less when the cells are seeded on the homologous matrix protein substratum than on heterologous substrata. These results indicate that hepatocytes cultured in serum-free medium on substrata composed of components of the liver biomatrix maintain certain functions of the differentiated state (tyrosine amino transferase), lose others (albumin secretion) and switch to increased synthesis of matrix components as well as fetal markers such as alpha-fetoprotein. The magnitude of these effects depends on the substratum on which the hepatocytes are cultured.     

Artificial surfaces as a method of studying populations of benthic micro-algae in fresh water

Most work on the ecology of communities of attached algae has involved the investigation of populations which develop on artificial surfaces exposed in the water for a known period of time. The nature and position of the surface and length of time of exposure have been shown to influence the population which develops. No studies have related the structure of these populations to populations on natural surfaces.

Microscope slides which had been exposed in a pond and a stream for two and four weeks were sampled over a period of more than one year, and natural vegetation was sampled at the same time. The populations of attached diatoms on each substrate were analysed.

The diatoms in the pond grew mainly in summer on the slides and in winter on the natural host. In the stream the main growth of the population was over the summer period in all cases. There were twice as many species of diatoms growing on natural hosts as on the slides, and the percentage importance of the species was different. The time of year at which some species grew was different on the slides and the natural vegetation. It was concluded that under these conditions the use of artificial surfaces is not a valid ecological method.     

In vitro movement of actin filaments on gizzard smooth muscle myosin: requirement of phosphorylation of myosin light chain and effects of tropomyosin and caldesmon

ATP-dependent movement of actin filaments on smooth muscle myosin was investigated by using the in vitro motility assay method in which myosin was fixed on the surface of a coverslip in a phosphorylated or an unphosphorylated state. Actin filaments slid on gizzard myosin phosphorylated with myosin light chain kinase (MLCK) at a rate of 0.35 micron/s, but did not slide at all on unphosphorylated myosin. The movement of actin filaments on phosphorylated myosin was stopped by perfusion of phosphatase. Subsequent perfusion with a solution containing MLCK, calmodulin, and Ca2+ enabled actin filaments to move again. The sliding velocities on monophosphorylated and diphosphorylated myosin by MLCK were not different. Actin filaments did not move on myosin phosphorylated with protein kinase C (PKC). The sliding velocity on myosin phosphorylated with both MLCK and PKC was identical to that on myosin phosphorylated only with MLCK. Gizzard tropomyosin enhanced the sliding velocity to 0.76 micron/s. Gizzard caldesmon decreased the sliding velocity with increase in its concentration. At a 5-fold molar ratio of caldesmon to actin, the movement stopped completely. This inhibitory effect of caldesmon was relieved upon addition of excess calmodulin and Ca2+.     

Biological activity of a fragment of insulin

Insulin controls or alters glucose, protein, and fat metabolism as well as other cellular functions. Insulin binds to a specific receptor on the cell membrane initiating a protein phosphorylation cascade that controls glucose uptake and metabolism and long-term effects such as mitogenesis. This process also initiates insulin uptake and ultimate cellular metabolism in all insulin sensitive cells. The effects of insulin on other cellular metabolic properties have not been clearly related to this mechanism. Here we show that intracellular metabolism of insulin may be related to some aspects of insulin actions, specifically control of fat metabolism. A normal intracellular degradation product of insulin has been synthesized and tested for actions on fat turnover in cultured adipocytes. This 7-peptide, B-chain fragment (HLVEALY) inhibits both basal and stimulated lipolysis as measured by glycerol release, but does not inhibit FFA release because of a lack of effect on FFA reesterification in the adipocyte. HLVEALY also enhances insulin's effects on lipogenesis. This study shows that a fragment of insulin produced by the action of the insulin-degrading enzyme has both independent biological effects and interactions with insulin. This supports a biologically important effect of insulin metabolism and insulin degradation products on insulin action on non-glucose pathways.     

Survey of the Influence of the Width of Urban Branch Roads on the Meeting of Two-Way Vehicle Flows

Branch roads, which are densely distributed in cities, allow for the flow of local traffic and provide connections between the city and outlying areas. Branch roads are typically narrow, and two-way traffic flows on branch roads are thus affected when vehicles traveling in opposite directions meet. This study investigates the changes in the velocities of vehicles when they meet on two-way branch roads. Various widths of branch roads were selected, and their influence on traffic flows was investigated via a video survey. The results show that, depending on the average vehicle velocity, branch roads require different widths to prevent a large decrease in velocity when vehicles meet. When the velocity on a branch road is not high (e.g., the average velocity without meeting is approximately 6 m/s), appropriately increasing the road width will notably increase the meeting velocity. However, when the velocity is high (e.g., the average velocity without meeting is greater than 10 m/s), there is a large decrease in velocity when meeting even if the road surface is wide (6.5 m). This study provides a basis for selecting the width of urban branch roads and the simulation of bidirectional traffic on such roads.