Colored polydimethylsiloxane micropillar arrays for high throughput measurements of forces applied by genetic model organisms

Measuring forces applied by multi-cellular organisms is valuable in investigating biomechanics of their locomotion. Several technologies have been developed to measure such forces, for example, strain gauges, micro-machined sensors, and calibrated cantilevers. We introduce an innovative combination of techniques as a high throughput screening tool to assess forces applied by multiple genetic model organisms. First, we fabricated colored Polydimethylsiloxane (PDMS) micropillars where the color enhances contrast making it easier to detect and track pillar displacement driven by the organism. Second, we developed a semiautomated graphical user interface to analyze the images for pillar displacement, thus reducing the analysis time for each animal to minutes. The addition of color reduced the Young's modulus of PDMS. Therefore, the dye-PDMS composite was characterized using Yeoh's hyperelastic model and the pillars were calibrated using a silicon based force sensor. We used our device to measure forces exerted by wild type and mutant Caenorhabditis elegans moving on an agarose surface. Wild type C. elegans exert an average force of similar to 1 mu N on an individual pillar and a total average force of similar to 7.68 mu N. We show that the middle of C. elegans exerts more force than its extremities. We find that C. elegans mutants with defective body wall muscles apply significantly lower force on individual pillars, while mutants defective in sensing externally applied mechanical forces still apply the same average force per pillar compared to wild type animals. Average forces applied per pillar are independent of the length, diameter, or cuticle stiffness of the animal. We also used the device to measure, for the first time, forces applied by Drosophila melanogaster larvae. Peristaltic waves occurred at 0.4Hz applying an average force of similar to 1.58 mu N on a single pillar. Our colored microfluidic device along with its displacement tracking software allows us to measure forces applied by multiple model organisms that crawl or slither to travel through their environment. (C) 2015 AIP Publishing LLC.

Meiosis in flowering plants and other green organisms.

Sexual eukaryotes generate gametes using a specialized cell division called meiosis that serves both to halve the number of chromosomes and to reshuffle genetic variation present in the parent. The nature and mechanism of the meiotic cell division in plants and its effect on genetic variation are reviewed here. As flowers are the site of meiosis and fertilization in angiosperms, meiotic control will be considered within this developmental context. Finally, we review what is known about the control of meiosis in green algae and non-flowering land plants and discuss evolutionary transitions relating to meiosis that have occurred in the lineages giving rise to the angiosperms.

Improved Procedure on the Microscopic Approach to Determine Colloidal Stability

We present an improved procedure on the approach to determine the stability of polystyrene spheres at microscopic particle levels by means of artificially induced particle collisions with the aid of optical tweezers [J.Chem.Phys. 119, 2399(2003)]. The basic consideration on this new development is that the major contribution to the sticking probability for a particle pair caught into the optical trap for a short period is from its single collision; therefore, if the trapping duration for the pair is taken to be short, the accumulated sticking probability will be a good approximation for the single collision. The experimental procedure associated with this approximation does not resort to exactly controlling the short trapping duration or request the trapping duration correction as previously reported and therefore it is more practical and applicable for broader range of the stability ratio. The experimental results under different electrolyte concentrations by the new procedure are consistent with those from the turbidity measurements.

Measurement of Microscopic Deformation in a Cualni Single Crystal Alloy by Nanoindentation with a Heating Stage

Thermally induced recovery of nanoindents in a CUAINi single crystal shape memory alloy was studied by nanoindentation in conjunction with a heating stage. Nanoindents formed by a Berkovich indenter at room temperature were heated to 40, 70 and 100 degrees C. Partial recovery was observed for the nanoindents. The recovery ratio depended on the heating temperature. Indentation of CuAlNi can induce inelastic deformation via dislocation motion and a stress-induced matensitic transformation. The percentages of dislocation-induced plastic strain would affect the thermal deformation of CuAlNi, because the induced dislocations could stabilize stress-induced martensite plates even when the temperature above austenite finish temperature, A(f). When the applied indentation load is low (less than 10,000 mu N), the shape recovery strain is predominant, compared with the dislocation-induced plastic strain. Therefore, the degree of indent recovery in the depth direction, delta(D), is high (about 0.7-0.8 at 100 degrees C).

Study of the surface structure of butterfly wings using the scanning electron microscopic moire method

Scanning electron microscopic (SEM) moire method was used to study the surface structure of three kinds of butterfly wings: Papilio maackii Menetries, Euploea midamus (Linnaeus), and Stichophthalma how-qua (Westwood). Gratings composed of curves with different orientations were found on scales. The planar characteristics of gratings and some other planar features of the surface structure of these wings were revealed, respectively, in terms of virtual strain. Experimental results demonstrate that SEM moire method is a simple, nonlocal, economical, effective technique for determining which grating exists on one whole scale, measuring the dimension and the whole planar structural character of the grating on each scale, as well as characterizing the relationship between gratings on different scales of each butterfly wing. Thus, the SEM moire method is a useful tool to assist with characterizing the structure of butterfly wings and explaining their excellent properties. (c) 2007 Optical Society of America.

Microscopic theory of chemical-reaction rate

In this paper we deduce the formulae for rate-constant of microreaction with high resolving power of energy from the time-dependent Schrdinger equation for the general case when there is a depression on the reaetional potential surface (when the depression is zero in depth, the case is reduced to that of Eyring). Based on the assumption that Bolzmann distribution is appropriate to the description of reactants, the formula for the constant of macrorate in a form similar to Eyring's is deduced and the expression for the coefficient of transmission is given. When there is no depression on the reactional potential surface and the coefficient of transmission does not seriously depend upon temperature, it is reduced to Eyring's. Thus Eyring's is a special case of the present work.

Factors to consider when using native biological control organisms to manage exotic plants

Biological control of exotic plant populations with native organisms appears to be increasing, even though its success to date has been limited. Although many researchers and managers feel that native organisms are easier to use and present less risk to the environment this may not be true. Developing a successful management program with a native insect is dependent on a number of critical factors that need to be considered. Information is needed on the feeding preference of the agent, agent effectiveness, environmental regulation of the agent, unique requirements of the agent, population maintenance of the agent, and time to desired impact. By understanding these factors, researchers and managers can develop a detailed protocol for using the native biological control agent for a specific target plant. . We found E. lecontei in 14 waterbodies, most of which were in eastern Washington. Only one lake with weevils was located in western Washington. Weevils were associated with both Eurasian ( Myriophyllum spicatum L.) and northern watermilfoil ( M. sibiricum K.). Waterbodies with E. lecontei had significantly higher ( P < 0.05) pH (8.7 ± 0.2) (mean ± 2SE), specific conductance (0.3 ± 0.08 mS cm -1 ) and total alkalinity (132.4 ± 30.8 mg CaCO 3 L -1 ). We also found that weevil presence was related to surface water temperature and waterbody location ( = 24.3, P ≤ 0.001) and of all the models tested, this model provided the best fit (Hosmer- Lemeshow goodness-of-fit = 4.0, P = 0.9). Our results suggest that in Washington State E. lecontei occurs primarily in eastern Washington in waterbodies with pH ≥ 8.2 and specific conductance ≥ 0.2 mS cm -1 . Furthermore, weevil distribution appears to be correlated with waterbody location (eastern versus western Washington) and surface water temperature.

Effects and impacts of physical stress on entrained organisms.

Environmental studies of power plants have recently shifted their emphasis from examination of the effects of heated discharges to studies of the impacts of entire cooling systems. One of the major impacts arises when planktonic organisms are carried into and through a plant with the cooling water. Because of their relatively immobile, free-floating character, planktonic organisms are highly vulnerable to being "entrained" or passively drawn into the cooling water condenser systems of power plants. More than 70% of estuarine animals have planktonic eggs and larvae. The environmental impact of entrainment is related to the composition and abundance of affected organisms, the numbers of organisms in the adjacent waters, survival rates during entrainment as related to natural survival, the ecological roles of entrained organisms, and their reproductive strategies.

Parasitology and pathology of marine organisms of the world ocean

The Symposium in which the communications, as they were called during the meeting, comprising this volume were presented was held at the Zoological Institute of the Academy of Sciences of the U.S.S.R. in Leningrad during 13 to 16 October 1981. Conducted as part of the cooperative program of the U.S.A.-U.S.S.R. Working Group on Biological Productivity and Biochemistry of the World Ocean, the Leningrad meeting was sponsored by the Academy of Sciences of the U.S.S.R. (the Zoological Institute) and the Ministry of Fisheries of the U.S.S.R. (The Scientific Council on Fish Diseases of the Ichthyological Commission). It was an extremely interesting and successful Symposium, offering all participants the opportunity to describe the results of their studies and reviews during the course of the formal presentations and direct interchange between scientists during breaks in the program and the organized and casual social activities. The facilities provided by the Zoological Institute were quite adequate and the assistance offered by its Director, O. A. Scarlato and his staff in organization,logistics, and translation was excellent. Several of our Soviet colleagues presided over the proceedings, as did I. All were businesslike and efficient, yet graceful and accommodating. To O. N. Bauer Jell the brunt of programmatic detail and follow-up. He bore his burdens well and, with Director Scarlato and his staff, including A. V. Gussev and others of the professional and technical staffs of the Zoological Institute, helped make our stay pleasant and the Symposium productive. These organizations and individuals deserve much credit and praise as well as the thanks of their American and British colleagues. (PDF file contains 141 pages.)

Aquatic insects as target organisms for the study of effects of projected climate change in the British Isles

One of the objectives of the Terrestrial Initiative in Global Environmental Research is to assess the sensitivity of British plant and animal species to climate change. The first phase of the program involved the identification of criteria for selecting species suitable for the study of effects of projected climate change in the British Isles. Apart from shallow ponds, annual temperature ranges of 0 to 25 C in temperate freshwater habitats are narrower than those in most temperate terrestrial habitats. Although freshwater organisms have to exist within a narrower range than their terrestrial equivalents, few species can survive throughout their life cycle over the whole temperature range. Field studies on the effects of natural and artificial thermal discharges into streams and rivers have shown that increases in water temperature affect aquatic insects at both the species and community level. Although field data provide valuable information, a more productive approach is to determine experimentally the requirements of different species. Although there are just over 1850 species of aquatic insects in the British Isles, detailed quantitative information on the relationship between temperature and development of eggs, larvae and pupa is available for relatively few species. One exception is the egg stage of stoneflies (Plecoptera). The range for egg hatching in stoneflies clearly show that some species could be threatened while others could benefit from a defined increase in water temperature as a result of climate change. A critical review of the available data on this group would produce a set of equations that could be used to predict the ecological effects of climate change on this group of indicator species.

Microscopic Model Of Nano-Scale Particles Removal In High Pressure Co2-Based Solvents

A physical model is presented to describe the kinds of static forces responsible for adhesion of nano-scale copper metal particles to silicon surface with a fluid layer. To demonstrate the extent of particle cleaning, Received in revised form equilibrium separation distance (ESD) and net adhesion force (NAF) of a regulated metal particle with different radii (10-300 nm) on the silicon surface in CO2-based cleaning systems under different pressures were simulated. Generally, increasing the pressure of the cleaning system decreased the net adhesion force between spherical copper particle and silicon surface entrapped with medium. For CO2 + isopropanol cleaning system, the equilibrium separation distance exhibited a maximum at temperature 313.15 K in the Equilibrium separation distance regions of pressure space (1.84-8.02 MPa). When the dimension of copper particle was given, for example, High pressure 50 nm radius particles, the net adhesion force decreased and equilibrium separation distance increased with increased pressure in the CO2 + H2O cleaning system at temperature 348.15 K under 2.50-12.67 MPa pressure range. However, the net adhesion force and equilibrium separation distance both decreased with an increase in surfactant concentration at given pressure (27.6 or 27.5 MPa) and temperature (318 or 298 K) for CO2 + H2O with surfactant PFPE COO-NH4+ or DiF(8)-PO4-Na+. (C) 2008 Elsevier B.V. All rights reserved.

Phage M13Ko7 Detection With Biosensor Based On Imaging Ellipsometry And Afm Microscopic Confirmation

A rapid detection and identification of pathogens is important for minimizing transfer and spread of disease. A label-free and multiplex biosensor based on imaging ellipsometry (BIE) had been developed for the detection of phage M13KO7. The surface of silicon wafer is modified with aldehyde, and proteins can be patterned homogeneously and simultaneously on the surface of silicon wafer in an array format by a microfluidic system. Avidin is immobilized on the surface for biotin-anti-M13 immobilization by means of interaction between avidin and biotin, which will serve as ligand against phage M13KO7. Phages M13KO7 are specifically captured by the ligand when phage M13KO7 solution passes over the surface, resulting in a significant increase of mass surface concentration of the anti-M13 binding phage M13KO7 layer, which could be detected by imaging ellipsometry with a sensitivity of 10(9) pfu/ml. Moreover, atomic force microscopy is also used to confirm the fact that phage M13KO7 has been directly captured by ligands on the surface. It indicates that BIE is competent for direct detection of phage M13KO7 and has potential in the field of virus detection. (C) 2008 Elsevier B.V. All rights reserved.

Gene enrichment using antibodies to DNA/RNA hybrids : mapping the ribosomal DNA of slime mold and rat

A novel method for gene enrichment has been developed and applied to mapping the rRNA genes of two eucaryotic organisms. The method makes use of antibodies to DNA/RNA hybrids prepared by injecting rabbits with the synthetic hybrid poly(rA)•poly(dT). Antibodies which cross-react with non-hybrid nucleic acids were removed from the purified IgG fraction by adsorption on columns of DNA-Sepharose, oligo(dT)-cellulose, and poly(rA)-Sepharose. Subsequent purification of the specific DNA/RNA hybrid antibody was carried out on a column of oligo(dT)-cellulose to which poly(rA) was hybridized. Attachment of these antibodies to CNBr-activated Sepharose produced an affinity resin which specifically binds DNA/RNA hybrids.

In order to map the rDNA of the slime mold Dictyostelium discoideum, R-loops were formed using unsheared nuclear DNA and the 178 and 268 rRNAs of this organism. This mixture was passed through a column containing the affinity resin, and bound molecules containing R- loops were eluted by high salt. This purified rDN A was observed directly in the electron microscope. Evidence was obtained that there is a physical end to Dictyostelium rDN A molecules approximately 10 kilobase pairs (kbp) from the region which codes for the 268 rRNA. This finding is consistent with reports of other investigators that the rRNA genes exist as inverse repeats on extra-chromosomal molecules of DNA unattached to the remainder of the nuclear DNA in this organism.

The same general procedure was used to map the rRNA genes of the rat. Molecules of DNA which contained R-loops formed with the 188 and 288 rRNAs were enriched approximately 150- fold from total genomal rat DNA by two cycles of purification on the affinity column. Electron microscopic measurements of these molecules enabled the construction of an R-loop map of rat rDNA. Eleven of the observed molecules contained three or four R-loops or else two R-loops separated by a long spacer. These observations indicated that the rat rRNA genes are arranged as tandem repeats. The mean length of the repeating units was 37.2 kbp with a standard deviation of 1.3 kbp. These eleven molecules may represent repeating units of exactly the same length within the errors of the measurements, although a certain degree of length heterogeneity cannot be ruled out. If significantly shorter or longer repeating units exist, they are probably much less common than the 37.2 kbp unit.

The last section of the thesis describes the production of antibodies to non-histone chromosomal proteins which have been exposed to the ionic detergent sodium dodecyl sulfate (SDS). The presence of low concentrations of SDS did not seem to affect either production of antibodies or their general specificity. Also, a technique is described for the in situ immunofluorescent detection of protein antigens in polyacrylamide gels.