The surface electromyography-force relationship during isometric dorsiflexion in males and females

This study evaluated sex-related differences in the tibialis anterior (TA) surface electromyography (EMG) to force relationship. One-hundred participants (50 males and 50 females) performed three isometric contractions at 20, 40, 60, 80, and 100% of maximal voluntary contraction (MVC) in an apparatus designed to isolate the action of the dorsiflexors. The surface EMG signal was amplified (lOOOx), band-pass filtered (10-500Hz), and sampled at 2048 Hz. The load cell signal was low-passed filtered at 100 Hz and sampled at the same rate. Males were stronger than females {P <0.05). However, there was no significant difference in root-mean-square (RMS) values between sexes {P <0.05). Both sexes exhibited a quadratic increase in RMS across force levels (P <0.05). The mean power frequency (MNF) for males was greater than for females {P <0.05). Males and females exhibited a linear increase in both frequency measures up to 80% of MVC (P <0.05). Between 80 and 100% MVC, the frequency values for the females plateaued while males showed a decrease {P <0.05). The magnitude of the difference in MNF between males and females was consistent with sex-specific TA physiology. In general, the pattern of means for RMS and MNF between males and females revealed no sex-related differences in the surface EMG/force relationship. We therefore conclude that there are no sex-related differences in the gradation of muscle force.

Isolation and partial characterization of host cell wall surface glycoproteins: their involvement in agglutination, attachment and appressorium formation by piptocephalis virginiana

Cell surface proteins obtained by alkaline extraction from isolated cell walls of Mortierella pusilla and M. candelabrum, host and nonhost, respectively, to the mycoparasite, Piptocephalis virginiana, were tested for their ability to agglutinate mycoparasite spores. The host cell wall protein extract had a high agglutinating activity (788 a.u. mg- t ) as compared with the nonhost extract (21 a.li. mg- t ). SDS-polyacrylamide gel electrophoresis of the cell wall proteins revealed four protein bands, a, b, c, and d (Mr 117, 100, 85 and 64 kd, respectively) at the host surface, but not at the nonhost surface, except for the faint band c. Deletion of proteins b or c from the host cell wall protein extract significantly reduced its agglutinating activity. Proteins band c, obtained as purified preparations by a series of procedures, were shown to be two glycoproteins. Carbohydrate analysis by gas chromatography demonstrated that glucose and Nacetylglucosamine were the major carbohydrate components of the glycoproteins. It was further shown that the agglutinating activity of the pure preparation containing both band c was 500-850 times that of the single glycoproteins, suggesting the involvement of both glycoproteins in agglutination. The results suggest that the glycoproteins band c are the two subunits of agglutinin present at the host cell surface. The two glycoproteins band c purified from the host cell wall protein extract were further examined after various treatments for their possible role in agglutination, attachment and appressorium formation by the mycoparasite. Results obtained by agglutination and attachment tests showed: (1) the two glycoprotein-s are not only an agglutinin responsible for the mycoparasite spore agglutination, but may also serve as a receptor for the specific recognition, attachment and appressorium formation by the mycoparasite; (2) treatment of the rnycoparasite spores with various sugars revealed that arabinose, glucose and N-acetylglucosamine inhibited the agglutination and attachment activity of the glycoproteins, however, the relative percentage of appressorium formation was not affected by the above sugars; (3) the two glycoproteins are relatively stable with respect to their agglutinin and receptor functions. The present results suggest that the agglutination and attachment may be mediated directly by certain sugars present at the host and mycoparasite cell surfaces while the appressorlum formation may be the response of complementary combinations of both sugar and protein, the two parts of the glycoproteins at the interacting surfaces of two fungi.

Isolation and partial characterization of a complementary protein from the mycoparasite, Piptocephalis virginiana, which specifically binds to two glycoproteins b and c of the host cell surface

Presence of surface glycoprotein in Piptocephalis virginiana that recognizes the host glycoproteins band c, reported earlier from our laboratory, was detected by immunofluorescence microscopy. Germinated spores of P. virginiana treated with Mortierella pusilla cell wall protein extract, primary antibodies prepared against glycoproteins band c and FITC-goat anti-rabbit IgG conjugate showed fluorescence. This indicated that on the surfaces of the biotrophic mycoparasite P. virginiana , there might be a complementary molecule which recognizes the glycoproteins band c from M. pusilla. Immunobinding analysis identified a glycoprotein of Mr 100 kDa from the mycoparasite which binds with the host glycoproteins band c, separately as well as collectively. Purification of this glycoprotein was achieved by (i) 60% ammonium sulfate precipitation, (ii) followed by heat treatment, and (iii) Sephadex G-IOO gel filtration. The glycoprotein was isolated by preparative polyacrylamide gel electrophoresis by cutting and elution. The purity of the protein ·was ascertained by SDS-PAGE and Western blot analysis. Positive reaction to periodic acid-Schiff reagent revealed the glycoprotein nature of this 100 kDa protein. Mannose was identified as a major sugar component of this glycoprotein by using a BoehringerMannheim Glycan Differentiation Kit. Electrophoretically purified glycoprotein was used to raIse polyclonal antibody in rabbit. The specificity of the antibody was determined by dot-immunobinding test and western-blot analysis. Immunofluorescence mIcroscopy revealed surface localization of the protein on the germ tube of Piptocephalis virginiana. Fluorescence was also observed at the surfaceJ of the germinated spores and hyphae of the host, M. pusilla after treatment with complementary protein from P. virginiana, primary antibody prepared against the complementary protein and FITC-goat anti-rabbit IgG conjugate.

Surface effect ferromagnetism in pure and reduced strontium titanate

A room temperature ferromagnetic hysteresis is observed in single crystal strontium titanate substrates as purchased from several manufacturers. It was found that polishing all sides of the substrates removed this observed hysteresis, suggesting that the origin of the ferromagnetic behavior resides on the surface of the substrates. X-ray diffraction and energy dispersive x-ray spectra were measured however they were unable to detect any impurity phases. In similar semiconducting oxides it was previously suggested that ferromagnetism could originate in oxygen vacancies or from disorder within the single crystal. To this end substrates were annealed in both air and vacuum in a range of temperatures (600°C to 1100°G) to both create bulk oxygen vacancies and to heal surface damage. Annealing in vacuum was found to create a measureable number of oxygen vacancies however their creation could not be correlated to the ferromagnetic signal of the substrate. Annealing in air was found to effect the remnant moment of the substrate as well as the width of the x-ray diffraction peaks on the unpolished face, weakly suggesting a relation between surface based disorder and ferromagnetism. Argon ion bombardment was employed to create a layer of surface disorder in the polished crystal, however it was not found to induce ferromagnetism. It was found that acid etching was sufficient to remove the ferromagnetism from as purchased samples and similarly simulated handling with stainless steel tweezers was sufficient to re-create the ferromagnetism. It is suggested that the origin of this ferromagnetism in SrTi03 is surface contaminants (mainly iron).

The analysis of Metarhizium robertsii potential as endophytic plant root coloniser, plant growth enhancer and antagonist to bean root pathogen Fusarium solani f. sp. phaseolis.

The soil-inhabiting insect-pathogenic fungus Metarhizium robertsii also colonizes plant roots endophytically, thus showing potential as a plant symbiont. M robertsii is not randomly distributed in soils but preferentially associates with the plant rhizosphere when applied in agricultural settings. Root surface and endophytic colonization of switchgrass (Panicum virgatum) and haricot beans (Phaseolus vulgaris) by M robertsii were examined after inoculation with fungal conidia. Light and confocal microscopies were used to ascertain this rhizosphere association. Root lengths, root hair density and emergence of lateral roots were also measured. Initially, M robertsii conidia adhered to, germinated on, and colonized, roots. Furthermore, plant roots treated with Metarhizium grew faster and the density of plant root hairs increased when compared with control plants. The onset of plant root hair proliferation was initiated before germination of M robertsii on the root (within 1-2 days). Plants inoculated with M robertsii AMAD2 (plant adhesin gene) took significantly longer to show root hair proliferation than the wild type. Cell free extracts of M robertsii did not stimulate root hair proliferation. Longer term (60 days) associations showed that M robertsii endophytically colonized individual cortical cells within bean roots. Metarhizium appeared as an amorphous mycelial aggregate within root cortical cells as well as between the intercellular spaces with no apparent damage to the plant. These results suggested that not only is M robertsii rhizosphere competent but displays a beneficial endophytic association with plant roots that results in the proliferation of root hairs. The biocontrol of bean (Phaseolis vulgaris) root rot fungus Fusarium solani f. sp. phaseolis by Metarhizium robertsii was investigated in vitro and in vivo. Dual cultures on Petri dishes showed antagonism of M robertsii against F. solani. A relative inhibition of ca. 60% of F. solani growth was observed in these assays. Cell free culture filtrates of M robertsii inhibited the germination of F. solani conidia by 83% and the inhibitory metabolite was heat stable. Beans plants colonized by M robertsii then exposed to F. solani showed healthier plant profiles and lower disease indices compared to plants not colonized by M robertsii. These results suggested that the insect pathogenic/endophytic fungus M robertsii could also be utilized as a biocontrol agent against certain plant pathogens occurring in the rhizosphere.