Comparative evaluation of two density gradient preparations for sperm separation for medically assisted conception. (1/455)

To evaluate and optimize the sperm separation efficiency of a novel silane-coated silica bead (Puresperm), serial studies were carried out to compare the various sperm parameters between: (i) three-layer (90%-70%-40%) Puresperm and three-layer (90%-70%-40%) conventional polyvinylpyrrolidone (PVP)-coated silica bead (Percoll) gradients; (ii) three-layer (90%-70%-40%) and two-layer (90%-45%) Puresperm gradients and separately the same for Percoll; and (iii) large (3.0 ml) and small (0.75 ml) semen loading volumes on three-layer Puresperm gradients. Normozoospermic semen samples were treated and analysed in 12 replicates for each experiment. Manual evaluation of concentration, percentage motility, percentage vitality, percentage normal morphology; computer-assisted semen analysis evaluation of concentration, percentage motility, grade of motility, motion characteristics (curvilinear velocity, linearity, amplitude of lateral head velocity, beat cross frequency, percentage hyperactivation); and yields from the initial semen samples were compared. Percoll was found to be superior to Puresperm in concentration, percentage motility, percentage vitality and yields after three-layer density gradient centrifugation. There were no significant differences in sperm parameters between two- and three-layer Percoll gradients, but three-layer Puresperm gradients behaved significantly better than two-layer gradients. Large semen volume loads on three-layer Puresperm gradients resulted in greater sperm concentrations, percentage motility, percentage vitality and percentage normal morphology, but small semen volume loads produced greater yields of good-quality spermatozoa. In the light of Percoll being withdrawn from the shelf for the use of assisted reproduction because of the presence of PVP, three-layer Puresperm gradients with large semen loading volumes appear to be an attractive alternative for sperm separation in medically assisted conception.  (+info)

Cationic silanes stabilize intermediates in DNA condensation. (2/455)

In vitro condensation of DNA has been widely studied to gain insight into the mechanisms of DNA compaction in biological systems such as chromosomes and phage heads and has been used to produce nanostructured particles with novel material and functional properties. Here we report on the condensation of DNA in aqueous solutions by cationic silanes, which combine the condensing properties of polyamines with the cross-linking chemistry of silanes. DNA can be reversibly condensed into classical toroidal and rod-shaped structures with these agents. At low silane concentrations DNA forms a variety of looped structures with well-defined characteristics, including flower- and sausage-shaped forms. These structures suggest that at low silane concentrations a DNA-DNA contact in which the strands are at very large angles to each other is stabilized. Changes in these structures observed as a function of silane concentration suggest possible pathways for the formation of toroids and rods.  (+info)

Factors affecting the shear bond strength of orthodontic brackets to porcelain. (3/455)

The aim of this investigation was to establish a regime for orthodontic bonding to feldspathic porcelain, which ensures adequate bond strength (6-8 MPa) with minimal damage on debond and consisted of an ex vivo investigation measuring the effects of porcelain surface preparation and thermocycling on shear bond strength of orthodontic brackets. One-hundred-and-twenty feldspathic porcelain bonded crown surfaces were divided into 12 equally-sized groups to assess the effects of: (1) glaze removal, (2) application of hydrofluoric acid, phosphoric acid, or omission of acid treatment, and (3) silane priming upon the bond strength of premolar brackets bonded with Right-on (TM) composite resin adhesive. Specimens were subjected to thermocycling and then to shear debonding forces on an Instron machine. Removal of the porcelain glaze, or use of hydrofluoric acid, prior to bonding were found to be unnecessary to secure the target bond strength. Hydrofluoric acid application was associated with increased porcelain surface damage. Thermocycling caused a significant reduction in shear bond strength to porcelain (P < 0*001). The best regime for orthodontic bonding to feldspathic porcelain was to apply phosphoric acid for 60 seconds, and prime with silane prior to bonding. Usually the porcelain surfaces could be repolished. Refereed Paper  (+info)

Relationships among cell attachment, spreading, cytoskeletal organization, and migration rate for anchorage-dependent cells on model surfaces. (4/455)

Many research and commercial applications use a synthetic substrate which is seeded with cells in a serum-containing medium. The surface properties of the material influence the composition of the adsorbed protein layer, which subsequently regulates a variety of cell behaviors such as attachment, spreading, proliferation, migration, and differentiation. In this study, we examined the relationships among cell attachment, spreading, cytoskeletal organization, and migration rate for MC3T3-E1 osteoblasts on glass surfaces modified with -SO(x), -NH(2), -N(+)(CH(3))(3), -SH, and -CH(3) terminal silanes. We also studied the relationship between cell spread area and migration rate for a variety of anchorage-dependent cell types on a model polymeric biomaterial, poly(acrylonitrile-vinylchloride). Our results indicated that MC3T3-E1 osteoblast behavior was surface chemistry dependent, and varied with individual functional groups rather than general surface properties such as wettability. In addition, cell migration rate was inversely related to cell spread area for MC3T3-E1 osteoblasts on a variety of silane-modified surfaces as well as for different anchorage-dependent cell types on a model polymeric biomaterial. Furthermore, the data revealed significant differences in migration rate among different cell types on a common polymeric substrate, suggesting that cell type-specific differences must be considered when using, selecting, or designing a substrate for research and therapeutic applications.  (+info)

The use of silane-coated silica particles for density gradient centrifugation in in-vitro fertilization. (5/455)

Silane-coated silica particles (PureSperm) were evaluated as an alternative to Percoll for gradient separation of spermatozoa, for use in assisted reproduction. Recovery of motile and morphologically normal spermatozoa after using a four-layer Percoll and a two- and four-layer PureSperm gradient respectively was recorded. In-vitro fertilization (IVF) results after using PureSperm for the sperm preparation were also evaluated. No difference in sperm recovery or sperm motility was found when comparing the use of Percoll and the four-layer gradient of PureSperm. When using a two-layer PureSperm gradient, motility was significantly decreased (P < 0.05) compared to Percoll. Normal sperm morphology increased from 8-17.2% after using Percoll and to 12.7% and 11.4% after using a four-layer and a two-layer PureSperm gradient respectively. All gradient preparations showed a significant decrease in the teratozoospermia index compared to the ejaculate (P < 0.01). No significant differences in IVF results regarding fertilization and pregnancy rates were found when PureSperm or the swim-up technique were used for the sperm preparation. PureSperm seems to be an acceptable alternative to Percoll but although the percentage of sperm recovery was higher after PureSperm we still recommend the swim-up technique to be the first choice, as a higher percentage of progressive motile spermatozoa is obtained without using other chemicals than IVF culture medium.  (+info)

Photodynamic therapy with the phthalocyanine photosensitizer Pc 4 of SW480 human colon cancer xenografts in athymic mice. (6/455)

Photodynamic therapy (PDT) using the silicon phthalocyanine photosensitizer Pc 4 [HOSiPcOSi(CH3)2(CH2)3N-(CH3)2] is an oxidative stress associated with induction of apoptosis in various cell types. We assessed the effectiveness of Pc 4-PDT on SW480 colon cancer xenografts grown in athymic nude mice. Animals bearing xenografts were treated with 1 mg/kg body weight Pc 4 and 48 h later were irradiated with 150 J/cm2 672-nm light from a diode laser delivered at 150 mW/cm2. Biochemical studies were performed in xenografts resected at various time points up to 26 h after Pc 4-PDT treatment, whereas tumor size was evaluated over a 4-week period in parallel experiments. In the tumors resected for biochemical studies, apoptosis was visualized by activation of caspase-9 and caspase-3 and a gradual increase in the cleavage of the nuclear enzyme poly(ADP-ribose) polymerase (PARP) to a maximum of approximately 60% of the total PARP present at approximately 26 h. At that time all Pc 4-PDT-treated tumors had regressed significantly. Two signaling responses that have previously been shown to be associated with Pc 4-PDT-induced apoptosis in cultured cells, p38 mitogen-activated protein kinase and p21/WAF1/Cip1, were examined. A marked increase in phosphorylation of p38 was observed within 1 h after Pc 4-PDT without changes in levels of the p38 protein. Levels of p21 were not altered in the xenografts in correspondence with the presence of mutant p53 in SW480 cells. Evaluation of tumor size showed that tumor growth resumed after a delay of 9-15 days. Our results suggest that: (a) Pc 4-PDT is effective in the treatment of SW480 human colon cancer xenografts independent of p53 status; (b) PARP cleavage may be mediated by caspase-9 and caspase-3 activation in the Pc 4-PDT-treated tumors; and (c) p38 phosphorylation may be a trigger of apoptosis in response to PDT in vivo in this tumor model.  (+info)

Silanized nucleic acids: a general platform for DNA immobilization. (7/455)

We have developed a method for simultaneous deposition and covalent cross-linking of oligonucleotide or PCR products on unmodified glass surfaces. By covalently conjugating an active silyl moiety onto oligonucleotides or cDNA in solutions we have generated a new class of modified nucleic acids, namely silanized nucleic acids. Such silanized molecules can be immobilized instantly onto glass surfaces after manual or automated deposition. This method provides a simple and rapid, yet very efficient, solution to the immobilization of prefabricated oligonucleotides and DNA for chip production.  (+info)

Tethered polymer-supported planar lipid bilayers for reconstitution of integral membrane proteins: silane-polyethyleneglycol-lipid as a cushion and covalent linker. (8/455)

There is increasing interest in supported membranes as models of biological membranes and as a physiological matrix for studying the structure and function of membrane proteins and receptors. A common problem of protein-lipid bilayers that are directly supported on a hydrophilic substrate is nonphysiological interactions of integral membrane proteins with the solid support to the extent that they will not diffuse in the plane of the membrane. To alleviate some of these problems we have developed a new tethered polymer-supported planar lipid bilayer system, which permitted us to reconstitute integral membrane proteins in a laterally mobile form. We have supported lipid bilayers on a newly designed polyethyleneglycol cushion, which provided a soft support and, for increased stability, covalent linkage of the membranes to the supporting quartz or glass substrates. The formation and morphology of the bilayers were followed by total internal reflection and epifluorescence microscopy, and the lateral diffusion of the lipids and proteins in the bilayer was monitored by fluorescence recovery after photobleaching. Uniform bilayers with high lateral lipid diffusion coefficients (0.8-1.2 x 10(-8) cm(2)/s) were observed when the polymer concentration was kept slightly below the mushroom-to-brush transition. Cytochrome b(5) and annexin V were used as first test proteins in this system. When reconstituted in supported bilayers that were directly supported on quartz, both proteins were largely immobile with mobile fractions < 25%. However, two populations of laterally mobile proteins were observed in the polymer-supported bilayers. Approximately 25% of cytochrome b(5) diffused with a diffusion coefficient of approximately 1 x 10(-8) cm(2)/s, and 50-60% diffused with a diffusion coefficient of approximately 2 x 10(-10) cm(2)/s. Similarly, one-third of annexin V diffused with a diffusion coefficient of approximately 3 x 10(-9) cm(2)/s, and two-thirds diffused with a diffusion coefficient of approximately 4 x 10(-10) cm(2)/s. A model for the interaction of these proteins with the underlying polymer is discussed.  (+info)