Sorption immobilization of glycerol on disperse silica and its interaction with the surface of bovine reproductive cells, seminal plasma and sperm]

The binding of hydroxylated disperse silica (I) surface and surface, modified by glycerol (II), with components of above-membrane matrix of bovine reproductive cell and seminal plasma was investigated. It was found that structure of inorganic support defined the character of binding SiO2 with proteins and glycoproteins, including those with hexose and N-acetylneuraminic acid as terminal residue. Value of binding depends on concentration of disperse silica contacting with biomaterial.     

Effect of the nature of the surface of disperse silica on its interaction with the reproductive cells and seminal plasma of cattle]

The interaction of various disperse silica of I, II, III kind possessing various structure of surface groups (-OH; -O-CH2-CH2-O-CH2-CH2OH; -O-CH2-CH2-NH2 respectively) was investigated with some above membrane matrix polymers of bovine reproductive cells and seminal plasma (namely the surface proteins and carbohydrate polymers containing the N-acetyl-neuraminic acid (NANA) as terminal residue). Protein binding was preferentially observed for silica surface modified by aminoethoxy--and ethylene glycol groups and depended on concentration of silica in the mixture. It was found that biopolymers containing carbohydrate groups had larger affinity to I than to II or III. The binding value of I-III was 12-16% with respect to plasma proteins. Silicas I and II with -OH-groups on the surface absorb 17-21% N-ANA-containing polymers of bovine seminal plasma.     

Fouling of nanostructured insect cuticle: adhesion of natural and artificial contaminants

The adhesional properties of contaminating particles of scales of various lengths were investigated for a wide range of micro- and nanostructured insect wing cuticles. The contaminating particles consisted of artificial hydrophilic (silica) and spherical hydrophobic (C(18)) particles, and natural pollen grains. Insect wing cuticle architectures with an open micro-/nanostructure framework demonstrated topographies for minimising solid-solid and solid-liquid contact areas. Such structuring of the wing membranes allows for a variety of removal mechanisms to contend with particle contact, such as wind and self-cleaning droplet interactions. Cuticles exhibiting high contact angles showed considerably lower particle adhesional forces than more hydrophilic insect surfaces. Values as low as 3 nN were recorded in air for silica of ~28 nm in diameter and <25 nN for silica particles 30 μm in diameter. A similar adhesional trend was also observed for contact with pollen particles.     

Fouling of nanostructured insect cuticle: adhesion of natural and artificial contaminants

The adhesional properties of contaminating particles of scales of various lengths were investigated for a wide range of micro- and nanostructured insect wing cuticles. The contaminating particles consisted of artificial hydrophilic (silica) and spherical hydrophobic (C₁₈) particles, and natural pollen grains. Insect wing cuticle architectures with an open micro-/nanostructure framework demonstrated topographies for minimising solid–solid and solid–liquid contact areas. Such structuring of the wing membranes allows for a variety of removal mechanisms to contend with particle contact, such as wind and self-cleaning droplet interactions. Cuticles exhibiting high contact angles showed considerably lower particle adhesional forces than more hydrophilic insect surfaces. Values as low as 3 nN were recorded in air for silica of ～28 nm in diameter and <25 nN for silica particles 30 μm in diameter. A similar adhesional trend was also observed for contact with pollen particles.     

Towards using of new and safety material against tomato leafminer,Tuta absoluta (Mayrick)

New silica formulations offer expanded possibilities for use in horticultural crops. However, many crop pests are found on the leaf underside, and this is especially challenging when using silica because the substance must have direct contact with the insect to be effective. Silica a new and safety material was used against the second instar larvae of tomato leafminer, Tuta absoluta (Mayrick) alone and combined with other pesticides (chlorfenapyr, spinetoram and chlorantraniliprole). The results showed that when silica was used alone, the percents of mortalities were 51.7, 26.7 and 13.3%. The results showed also chlorantraniliprole was the most toxic compared with the other compounds. The per cents of mortalities were 90, 65 and 30% with the first, second and third concentrations, respectively. When silica was used in a combination with the tested pesticides, the mixture of silica and chlorfenapyr was the most toxic against the second instar larvae of T. absoluta, the percents of mortalities were 100, 76.7 and 60% with the first, second and third concentrations, respectively. The results recommended that silica was moderate toxic to the second instar larvae of T. absoluta when it used alone, so it can be used when this pest under the economic threshold or with integrated pest management programme. Silica has an activation action on the tested pesticides. Although silica was combined with one-fifth of the field rate of the tested pesticides, the toxicity of these pesticides was increased.     

Rhodamine B isothiocyanate-modified Ag nanoaggregates on dielectric beads: a novel surface-enhanced Raman scattering and fluorescent imaging material

Rhodamine B isothiocyanate (RhBITC) is a prototype dye molecule that is widely used as a fluorescent tag in a variety of biological applications. We report in this work that once RhBITC is adsorbed onto Ag on silica or polystyrene beads, it exhibits not only a strong surface-enhanced Raman scattering (SERS) signal but also a measurable amount of fluorescence. The RhBITC-modified Ag-deposited silica or polystyrene beads disperse well in ethanol, and they are also readily coated in water with polyelectrolytes for their further derivatization with biological molecules of interest that can bind to target molecules. The application prospects of these materials are thus expected to be very high especially in the areas of biological sensing and recognition that rely heavily on optical and spectroscopic properties. For instance, on the basis of the nature of the SERS peaks of RhBITC, those Ag-deposited silica or polystyrene beads were confirmed, after attaching biotin groups over RhBITC, to selectively recognize streptavidin molecules down to concentrations of 10(-13)M based on a signal-to-noise ratio of 3. The biotin-streptavidin interaction was also confirmed from the photoluminescence of RhBITC.     

Application of response surface methodology to optimization of glutaraldehyde activation of a support for enzyme immobilization

Summary We have studied the influence of several parameters (glutaraldehyde concentration, pH and contact time) on the activation of an amine silica with glutaraldehyde. In order to take interactions between parameters into consideration, we have used the Response Surface Methodology which allows us to obtain an equation (not a single estimation). The optimal conditions for glutaraldehyde activation of amine Spherosil beads were as follow: the porous silica was activated for 1 h at 25°C with an 8% (V/V) solution of glutaraldehyde at pH 6.4 these conditions were the same with RNA or CMP used as substrates.     

Effect of Soil Texture on the Distribution and Infectivity of Neoaplectana carpocapsae (Nematoda: Steinernematidae)

The vertical migration of N. carpocapsae infective juveniles applied to the soil surface or introduced 14 cm below the soil surface was studied in four different soil types (pure silica sand, coarse sandy loam, silty clay loam, and clay). The percentage of juveniles able to migrate and infect wax moth pupae placed in the soil decreased as the percentage of clay and silt increased. Most nematodes placed on the soil surface remained within 2 cm of the surface, but some penetrated to a depth of 10 cm in pure silica sand and coarse sandy loam to infect pupae. Some pupae at the same depth were also infected with nematodes in silty clay loam soil. In pure silica sand and coarse sandy loam, nematodes introduced 14 cm below the soil surface were able to infect wax moth pupae located between 4 and 24 cm. Movement was least in clay soil and limited in silty clay loam. Nematodes showed a tendency to disperse upwards from the point of application. In all cases the number of migrating nematodes was greatest when wax moth pupae were present.     

Effect of Soil Texture on the Distribution and Infectivity of Neoaplectana glaseri (Nematoda: Steinernematidae)

The vertical migration of infective juveniles of Neoaplectana glaseri applied to the soil surface or introduced 16 cm below the soil surface was studied in pure silica sand, coarse sandy loam, silty clay loam, and clay. The number of juveniles that migrated and infected wax moth pupae placed in the soil decreased as the proportion of clay and silt increased. The majority of nematodes moved downwards 2-6 cm from the surface, but some penetrated to a depth of 14 cm in pure silica sand and coarse sandy loam. In pure silica sand and coarse sandy loam, nematodes introduced 16 cm below the soil surface were able to infect wax moth pupae located at depths of 0-4 cm and 28-32 cm. Nematodes showed a greater tendency to disperse downwards from the point of application. Movement of the nematode was least in clay soil and limited in silty clay loam soil. The number of migrating nematodes was greatest when wax moth pupae were present.     

Dispersal of Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) on potted greenhouse chrysanthemum

Dispersal of natural enemies through a crop is a key component of biological control. The release strategy should optimize the number of predators that are released, the release frequency and number of release sites throughout a crop with regards to the distance that natural enemies can disperse from their release point. In this study, dispersal rate and behaviour of Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) was investigated in potted greenhouse chrysanthemums in the presence or absence of prey (Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). Results demonstrate that A. swirskii did not disperse far from the release site. Presence of prey did not influence dispersal, but had an effect on predator survival in one experiment. Only a quarter of the A. swirskii eventually attempted to disperse by going down to the ground. The presence of inter-plant contact greatly improved movement of A. swirskii between plants. It is concluded that good coverage with predators of the crop is needed when using A. swirskii in a biological control program. Having a continuous crop canopy will promote dispersal.     

Degradation of fenitrothion byBacillus stearothermophilus adhering to silica

B. stearothermophilus strain AG-49, when cultivated in mineral medium in the presence of silica (SA), adhered to SA. Adhesion depended on age of culture, contact time and glucose concentration of the culture medium. Mid-exponential phase culture (5 h) required minimum contact time (30 min) for maximum adhesion. 0.6% glucose concentration was optimum. Quantitative variation in protein and saccharide extractable in sodium chloride and sodium dodecyl sulfate (SDS) was observed. Five % degradation of fenitrothion by adherentB. stearothermophilus could be achieved in 4 d.     

Tolerance assessment of Cistus ladanifer to serpentine soils by developmental stability analysis

Developmental instability is the result of random environmental perturbations during development. Its absence (developmental stability) depends on an organism's ability to buffer environmental disturbances. Both genotype and environment influence the phenotypic expression of developmental instability and it is susceptible to selection pressure. We studied developmental instability (as indicated by increased within-individual asymmetry of repeated traits) in vegetative and reproductive structures of three populations of Cistus ladanifer L. living in different soil substrates (serpentine, siliceous and contact zone) to detect tolerance to serpentine soils. Serpentine soils, characterized by high concentrations of heavy metals (Ni, Cr, and Co), low levels of Ca/Mg ratio and high water deficit, can adversely affect plant performance. In this study we demonstrated that asymmetry and within-plant variance were higher in the contact zone population than either the silica or serpentine populations, proving the adaptation of C. ladanifer to serpentine soils. Within-population estimates of developmental instability were concordant for both vegetative and reproductive traits. There was little or no within-individual correlation among estimates of developmental instability based on different structures, i.e., plants that had highly asymmetric leaves always had high developmental instability in translational symmetry. Radial asymmetry of petals was negatively correlated with petal size, especially in silica soil plants, providing evidence of selection for symmetric and large petals. While leaf size was positively correlated with absolute fluctuating asymmetry, suggesting selection for small or intermediate size leaves. Serpentine soils presented the largest foliar and floral traits, as well as shoot elongation, while silica soil plants had the smallest scores. On the contrary, aboveground plant biomass was larger in silica soil plants, while the contact zone plants had the lowest biomass.     

Polymer surfaces derivatized with poly(vinyl-N-hexylpyridinium) kill airborne and waterborne bacteria

A facile methodology has been developed for covalently derivatizing the surfaces of common materials with a designed antibacterial polycation, poly(vinyl-N-pyridinium bromide), wherein the first, key step involves surface coating with a nanolayer of silica. Various commercial synthetic polymers derivatized in this manner become bactericidal-they kill up to 99% of deposited, from either an aerosol or an aqueous suspension, Gram-positive and Gram-negative bacteria on contact.     

Probing the silica surfaces by red blood cells

BACKGROUND: The polymorphic forms of silica (silicon dioxide; SiO(2)) interact with the cell membranes of many mammalian cells, including red blood cells (RBCs), causing hemolysis. The electrostatic factor, which is believed to be a major contributor to the silica-cell contact, might have potential interest for the study of cell surface properties. The surface properties of SiO(2) particles are also of interest. METHODS: Washed human RBCs interacted with the particles of highly dispersed fumed silica (Aerosil A-300) and silicas (nine samples) obtained from the initial A-300 by its dehydroxylation at various thermal conditions. Their light scatter (forward and side light scatter) in 0.01% silica solution was measured uninterruptedly within the first 5 min of the reaction by flow cytometry (flow erythrogram). The hemolytic effect of SiO(2) particles was evaluated by photometric measurement of hemoglobin in the supernatant 90 min after the reaction. RESULTS: Light scatter of affected RBCs and the degree of hemolysis revealed that the surface properties of SiO(2) particles had various effects on the RBCs. After thermal reduction of the surface hydroxyl groups, the membranotoxic effect of silica increased and then decreased. CONCLUSIONS: RBCs offer a convenient and informative model for examining the surface properties of silica.     

Body size determines rates of seed dispersal by giant king crickets

New Zealand is home to giant king crickets called weta, which are the only insects known to consume fleshy-fruits and disperse seeds after gut passage. Although they disperse seeds in viable condition after consumption, their importance as seed dispersers is unknown. We conducted a series of field observations and laboratory experiments to investigate intraspecific variation in the capacity of Wellington tree weta (Hemidenina crassidens) to disperse seeds of tree fuchsia (Fuchsia excorticata). We asked three questions. How frequently do weta disperse fuchsia seeds? Do seed passage rates differ between sexes and different-sized weta? Might weta select for particular seed sizes via differential seed mortality after ingestion? A total of 2,272 F. excorticata seedlings germinated from 241 scats (i.e., faecal pellets) that were collected from the field. Experimental results showed that, on average, 15% of seeds ingested by weta successfully germinated, whereas 75% germinated in control trials. Larger weta dispersed greater numbers of seeds in experimental trials, while no differences in dispersal rates were observed between sexes. Regardless of sex and size, weta preferentially dispersed larger seeds. When interpreted collectively, results indicate that (1) weta are frequent seed dispersers of F. excorticata, although many seeds are destroyed during ingestion, (2) larger-bodied weta consistently disperse greater quantities of seeds, which is unusual in seed dispersal mutualisms, and (3) weta preferentially disperse larger seeds, suggesting that they might interact evolutionarily with New Zealand plants.     

Histochemical studies of uric acid in some insects. I. Storage in the fat body of Periplaneta americana and the action of the symbiotic bacteria

An improved histochemical method for uric acid consists in precipitation as silver magnesium urate combined with fixation of the tissues in formol/glutaraldehyde followed by argentaffin reaction with silver nitrate buffered with "tris" to pH 9.5. This reveals urates both in solid deposits and in solution in the tissues. Polyphenols concerned in sclerotin formation also react. In Periplaneta, uric acid synthesized in the trophocytes is carried by intracellular and intercellular channels to form the intercellular deposits of solid spheres. The symbiotic bacteria in the mycetocytes in contact with the deposits appear to metabolize the uric acid and they disperse and eliminate the deposits.     

A symbiont's dispersal strategy: condition-dependent dispersal underlies predictable variation in direct transmission among hosts

Direct horizontal transmission of pathogenic and mutualistic symbionts has profound consequences for host and symbiont fitness alike. While the importance of contact rates for transmission is widely recognized, the processes that underlie variation in transmission during contact are rarely considered. Here, we took a symbiont''s perspective of transmission as a form of dispersal and adopted the concept of condition-dependent dispersal strategies from the study of free-living organisms to understand and predict variation in transmission in the cleaning symbiosis between crayfish and ectosymbiotic branchiobdellidan worms. Field study showed that symbiont reproductive success was correlated with host size and competition among worms for microhabitats. Laboratory experiments demonstrated high variability in transmission among host contacts. Moreover, symbionts were more likely to disperse when host size and competition for microhabitat created a fitness environment below a discrete minimum threshold. A predictive model based on a condition-dependent symbiont dispersal strategy correctly predicted transmission in 95% of experimental host encounters and the exact magnitude of transmission in 67%, both significantly better than predictions that assumed a fixed transmission rate. Our work provides a dispersal-based understanding of symbiont transmission and suggests adaptive symbiont dispersal strategies can explain variation in transmission dynamics and complex patterns of host infection.     

Complement fragment C3a controls mutual cell attraction during collective cell migration

Collective cell migration is a mode of movement crucial for morphogenesis and cancer metastasis. However, little is known about how migratory cells coordinate collectively. Here we show that mutual cell-cell attraction (named here coattraction) is required to maintain cohesive clusters of migrating mesenchymal cells. Coattraction can counterbalance the natural tendency of cells to disperse via mechanisms such as contact inhibition and epithelial-to-mesenchymal transition. Neural crest cells are coattracted via the complement fragment C3a and its receptor C3aR, revealing an unexpected role of complement proteins in early vertebrate development. Loss of coattraction disrupts collective and coordinated movements of these cells. We propose that coattraction and contact inhibition act in concert to allow cell collectives to self-organize and respond efficiently to external signals, such as chemoattractants and repellents.     

Adhesion dynamics, morphology, and organization of 3T3 fibroblast on chitosan and its derivative: the effect of O-carboxymethylation

Chitosan and O-carboxymethylchitosan (OCMCS) have been proved to have biocompatibility and have been extensively researched in the field of biomaterials. In this study, Confocal-reflectance interference contrast microscopy (C-RICM) in conjunction with phase contrast imaging was used to investigate the adhesion contact dynamics of 3T3 fibroblasts on chitoan and OCMCS surface-modified silica coverslips. The C-RICM results demonstrate that the weak cell contact forms on OCMCS surface while a much stronger contact area forms on the chitosan surface. 3T3 fibroblasts are found to spread randomly with spindlelike morphology on the chitosan surface, while they exhibit elongated morphology and align on the OCMCS surface. It is believed that fibroblast behaviors such as migration, spreading with an elongated morphology, and alignment on the OCMCS surface are correlated with the weak cell contact. The mechanisms to form cell adhesion contact on chitosan and OCMCS were discussed.     

Effect of Soil Texture and the Clay Component on Migration of Meloidogyne incognita Second-stage Juveniles

The vertical migration of M. incognita juveniles introduced at 20 cm from the roots was studied in five natural soils, 100% silica sand, 95% silica sand with 5% clay, 90% silica sand with 10% clay, and 95% silica sand with 5% clay as a concentrated layer. In natural soils the percentage of juveniles capable of migrating 20 cm and penetrating the roots decreased when the percentage of clay and silt increased. No migration occurred in silica sand without clay particles; when 5 or 10% of clay were mixed to silica sand, 34 and 26%, respectively, of the juveniles were able to migrate 20 cm. Clay separated from silica sand in which tomatoes were grown was attractive for juveniles. It is suggested that clay particles aid in the migration of root-knot juveniles over long distances to plant roots by absorbing and holding root exudates or bacterial by-products which form a concentration gradient enabling nematodes to locate roots.