Experimental assessment of the effects of sublethal salinities on growth performance and stress in cultured tra catfish (Pangasianodon hypophthalmus).

The effects of a range of different sublethal salinities were assessed on physiological processes and growth performance in the freshwater 'tra' catfish (Pangasianodon hypophthalmus) juveniles over an 8-week experiment. Fish were distributed randomly among 6 salinity treatments [2, 6, 10, 14 and 18 g/L of salinity and a control (0 g/L)] with a subsequent 13-day period of acclimation. Low salinity conditions from 2 to 10 g/L provided optimal conditions with high survival and good growth performance, while 0 g/L and salinities >14 g/L gave poorer survival rates (p < 0.05). Salinity levels from freshwater to 10 g/L did not have any negative effects on fish weight gain, daily weight gain, or specific growth rate. Food conversion ratio, however, was lowest in the control treatment (p < 0.05) and highest at the maximum salinities tested (18 g/L treatment). Cortisol levels were elevated in the 14 and 18 g/L treatments after 6 h and reached a peak after 24-h exposure, and this also led to increases in plasma glucose concentration. After 14 days, surviving fish in all treatments appeared to have acclimated to their respective conditions with cortisol levels remaining under 5 ng/mL with glucose concentrations stable. Tra catfish do not appear to be efficient osmoregulators when salinity levels exceed 10 g/L, and at raised salinity levels, growth performance is compromised. In general, results of this study confirm that providing culture environments in the Mekong River Basin do not exceed 10 g/L salinity and that cultured tra catfish can continue to perform well.

Liver hydrolysate assists in the recovery from physical fatigue in a mouse model.

It is reported that liver hydrolysate (LH) enhances liver function. However, the effects of LH on physical fatigue are unknown. The aim of this study was to investigate the effect of LH on alterations in locomotor activity and energy metabolism such as 5'-AMP-activated protein kinase (AMPK), glycogen content, and blood lactic acid, after forced walking. Adult male ddY mice were used. Locomotor activity, AMPK phosphorylation, and glycogen content in the liver and soleus muscle, as well as blood lactic acid were determined following LH treatment before and/or after forced walking. The locomotor activity significantly decreased after forced walking for 3 h. Two administrations of LH (30 or 100 mg/kg) significantly increased the locomotor activity, while a single administration either before or after forced walking did not show any specific effect. Administering LH twice activated AMPK in the liver and soleus muscle. Glycogen levels significantly decreased in both the liver and soleus muscle after forced walking, whereas the blood lactate level significantly increased. In contrast, administering LH twice increased muscle glycogen and decreased blood lactic acid. These findings indicate that LH produced an anti-fatigue effect and that this effect appears to involve the efficient glycogen utilization through activation of AMPK.

An in vitro release study of indomethacin from nanoparticles based on methyl methacrylate/glycidyl methacrylate copolymers.

Indomethacin was coupled onto some macromolecular nanostructures based on methyl methacrylate copolymers with glycidyl methacrylate and tested as a model drug. The polymeric matrices were synthesized by radical emulsion copolymerization with and without the presence of a continuous external magnetic field of 1500 Gs intensity. Mathematical analysis of the release data was performed using Higuchi, Peppas-Korsmeyer equations. NIR chemical imaging (NIR-CI) was used to provide information about the spatial distribution of the components in the studied nanostructures. This opportunity was used to visualize the spatial distribution of bioactive substances (indomethacin) into the polymeric matrix, as well as to evaluate the degree of chemical and/or physical heterogeneity of the bioactive samples. The release rate dependence on the synthesis conditions as well as on the chemical compositions of the tested polymeric systems, it was also evidenced.

Ultrastructural evaluation of in vitro mineralized calcium phosphate phase on surface phosphorylated poly(hydroxy ethyl methacrylate-co-methyl methacrylate).

The in vitro functionality of surface phosphorylated poly(hydroxy ethyl methacrylate-co-methyl methacrylate), poly(HEMA-co-MMA) to induce bioinspired mineralization of calcium phosphate phase is evaluated. The primary nucleation of calcium phosphate on the surface phosphorylated copolymer occurs within 3 days of immersion when immersed in 1.5x simulated body fluid and the degree of mineralization is proportional to the hydroxy ethyl methacrylate content in the copolymer. The calcium phosphate phase is identified as hydroxyapatite by X-Ray diffraction analysis. The transmission electron microscopic evaluation combined with selected area diffraction pattern and energy dispersive analysis exemplified that the primary nuclei of amorphous calcium phosphate transforms to crystalline needle like calcium rich apatite, within a period of 3 days immersion in simulated body fluid. The atomic force microscopic results corroborate the c-axis growth of the crystals within 3 days immersion in SBF.

Immobilization of type-I collagen and basic fibroblast growth factor (bFGF) onto poly (HEMA-co-MMA) hydrogel surface and its cytotoxicity study.

Type-I collagen and bFGF were immobilized onto the surface of poly (HEMA-co-MMA) hydrogel by grafting and coating methods to improve its cytotoxicity. The multi-layered structure of the biocompatible layer was confirmed by FTIR, AFM and static water contact angles. The layers were stable in body-like environment (pH 7.4). Human skin fibroblast cells (HSFC) were seeded onto Col/bFGF-poly (HEMA-co-MMA), Col-poly (HEMA-co-MMA) and poly (HEMA-co-MMA) films for 1, 3 and 5 day. MTT assay was performed to evaluate the extraction toxicity of the materials. Results showed that the cell attachment, proliferation and differentiation on Col/bFGF-poly (HEMA-co-MMA) film were higher than those of the control group, which indicated the improvement of cell-material interaction. The extraction toxicity of the modified materials was also lower than that of the unmodified group. The protein and bFGF immobilized poly (HEMA-co-MMA) hydrogel might hold great promise to be a biocompatible material.

Maternal-placental-fetal biodistribution of multimodal polymeric nanoparticles in a pregnant rat model in mid and late gestation.

Multimodal polymeric nanoparticles have many exciting diagnostic and therapeutic applications, yet their uptake and passage by the placenta, and applications in the treatment of pregnancy complications have not been thoroughly investigated. In this work, the maternal-fetal-placental biodistribution of anionic and cationic multimodal poly(glycidyl methacrylate) (PGMA) nanoparticles in pregnant rats at mid (ED10) and late (ED20) gestation was examined. Fluorescently-labelled and superparamagnetic PGMA nanoparticles functionalized with/without poly(ethyleneimine) (PEI) were administered to pregnant rats at a clinically-relevant dose and biodistribution and tissue uptake assessed. Quantitative measurement of fluorescence intensity or magnetic resonance relaxometry in tissue homogenates lacked the sensitivity to quantify tissue uptake. Confocal microscopy, however, identified uptake by maternal organs and the decidua (ectoplacental cone) and trophoblast giant cells of conceptuses at ED10. At ED20, preferential accumulation of cationic vs. anionic nanoparticles was observed in the placenta, with PGMA-PEI nanoparticles localised mainly within the chorionic plate. These findings highlight the significant impact of surface charge and gestational age in the biodistribution of nanoparticles in pregnancy, and demonstrate the importance of using highly sensitive measurement techniques to evaluate nanomaterial biodistribution and maternal-fetal exposure.

Embedding of bone samples in methylmethacrylate: an improved method suitable for bone histomorphometry, histochemistry, and immunohistochemistry.

Methylmethacrylate (MMA) embedding of undecalcified bone biopsies is a technique widely used for bone histomorphometry. However, conventional MMA embedding causes almost complete loss of enzyme activity and protein antigenicity in the tissues. Recently, an MMA embedding technique has been reported that preserves enzyme activity and antigenic determinants in bone tissue. We describe here a modification of this embedding method. For our modified MMA embedding process, commercially available methacrylates can be used without purification, and the histologic quality of bone sections is comparable to that of conventionally MMA-embedded bone specimens. The technique reported here can be employed for embedding of larger bone samples and is suitable for histochemical and immunohistological applications as well as for routine bone histomorphometry. By addition of methylbenzoate during infiltration and polymerization of the plastic, the antigenicity of the tissue was improved. As applications of this novel technique, demonstration of alkaline phosphatase and tartrate-resistant acid phosphatase as well as positive labeling of Kupffer cells and osteoclasts with the monoclonal antibody ED1 in sections of liver, tibiae, and vertebrae of 3-month-old rats was demonstrated. The method described here might be useful for the inclusion of histochemical and immunohistological methods into bone histomorphometry.

An infrared study of the interaction of polymethyl methacrylate with the protein and mineral components of bone.

We used Fourier transform infrared (FT-IR) microscopic mapping techniques to investigate the infiltration of polymethyl methacrylate (PMMA), a widely used medium for embedding biological tissues, into rat femur sections. Monitoring of the infrared absorbances of the PMMA carbonyl stretch, the protein amide I, and the apatite mineral phosphate stretch over a 225 x 975-microns region of the epiphyseal growth plate region of the rat femur enabled comparison of the relative amount of each component in distinct regions of the tissue. It was found that PMMA penetrates less into regions of greater mineral density and that the frequency of the PMMA carbonyl absorbance from the embedded tissue, 1729 cm-1, is identical to the free PMMA carbonyl frequency. This is consistent with a diffusion mechanism of infiltration of the PMMA, with no specific chemical interaction between the PMMA and the tissue components.

Adsorption of proteins from artificial tear solutions to contact lens materials.

A series of polymers and copolymers of 2-hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) were synthesized in order to find surfaces that would adsorb minimal amounts of protein. The adsorption of albumin, lysozyme and immunoglobulin G from a three-way mixture of these proteins in isotonic buffered saline to the polymers was measured using 125I-labeled proteins. Apparently high protein uptake on copolymers rich in HEMA was found to be due to sorption of unbound 125I by the polymers. 125I sorption by the polymers was minimized by dialysis of the protein solution to remove unbound 125I iodide and inclusion of 0.01 M sodium iodide to block uptake of residual 125I iodide. Using these improved protocols, minimal total protein uptake was observed on copolymers containing 50% or more HEMA. The majority of adsorbed protein on all p(MMA-HEMA) polymers was albumin. Total protein uptake was greatest on pMMA. Commercial contact lenses composed of copolymers of HEMA and N-vinyl pyrrolidone (NVP) or acrylamide (AAm) adsorbed small amounts of all proteins whereas copolymers of methacrylic acid (MAAc) and HEMA adsorbed much larger quantities of lysozyme. These results indicate that protein uptake by contact lens materials varies greatly with polymer composition. Artifactually high "adsorption" can occur if precautions are not taken to prevent uptake of unbound 125I.

Local antibacterial therapy for the management of orthopaedic infections. Pharmacokinetic considerations.

Bone infection has long been a formidable foe of orthopaedic surgeons. The standard method of treating osteomyelitis generally consists of irrigation and debridement supplemented by pre- and postoperative antibiotics and intraoperative antimicrobial solutions. In the 1970s, Buchholz introduced the concept of local antibacterial therapy in the form of antibiotic impregnated bone cement to treated infected arthroplasties. From this, antibiotic impregnated beads were developed to treat local infections of bone and soft tissue. The advantage of these beads compared with parenteral therapy is that they deliver a high concentration of antibacterial locally while avoiding high systemic concentrations, thus avoiding adverse effects that are often associated with parenteral antibacterial therapy. Additionally, methylmethacrylate bone cement does not significantly affect the immune response of the body. This makes the use of antibiotic-impregnated polymethylmethacrylate (PMMA) beads highly effective either as an alternative to, or in conjunction with, systemic antibiotic treatment of infected arthroplasties, and localised bone and soft tissue infection. This article explores the indications for the use of local therapy as well as any advantages or disadvantages it may have over systemic antibacterial treatment. Additionally, there are important pharmacokinetic considerations for the optimal use of antibacterial agents in the treatment of osteomyelitis.

Nuclear magnetic resonance spectroscopic studies of the interaction of methyl methacrylate and ethylene dimethacrylate with phosphatidylcholine liposomes as a model for biomembranes.

The interaction of methyl methacrylate (MMA) and ethylene dimethacrylate (EDMA) with dipalmitoyl phosphatidylcholine (DPPC) liposomes was studied by 1H and 13C nuclear magnetic resonance spectroscopy (NMR). It was found that the changes in the 1H chemical shift of EDMA were larger than those of MMA when comparing membrane-bound state with free state and that the amount of EDMA incorporated into DPPC liposomes was approximately 74%, whilst MMA was approximately 41%. The major changes in chemical shifts of EDMA appeared to be due to its interaction with the acyl chains of DPPC liposomes.

Swelling/deswelling of anionic copolymer gels.

Studies of dynamic and equilibrium swelling of ionic gels are important in understanding the diffusion of physiologically important fluids in materials for site-specific controlled drug delivery applications. The dynamic and equilibrium swelling properties of dry glassy poly(2-hydroxyethyl methacrylate-co-methacrylic acid) and poly(2-hydroxyethyl methacrylate-co-acrylic acid) polymeric networks were studied as a function of pH, ionic strength, nature of the counterion and buffer composition. The mechanism of water diffusion in these gels became more anomalous as the pH of the swelling medium increased and as the ionic strength decreased at a constant pH > or = pKa,gel. The mechanism of water diffusion was Fickian in all unbuffered swelling media at pH 4.0, which is lower than the pKa,gel. The pKa,gel of these gels was between 5.5 and 6. At pH 4.0, the diffusion mechanism was independent of ionic strength. This swelling behaviour is explained in terms of the concept of ion osmotic swelling pressure and ion exchange kinetics.

A hydrophobic interaction site for lysozyme binding to polyethylene glycol and model contact lens polymers.

Proton nuclear magnetic resonance (1H-NMR) spectroscopy is used to identify a preferred binding site for uncharged hydrophilic polymers on the surface of hen egg-white lysozyme. Chemical shift titrations show that exchangeable proton signals from amino acids Arg-61, Trp-62, Trp-63, Arg-73, Lys-96 and Asp-101 are selectively perturbed upon binding of poly(ethylene oxide), poly(ethylene glycol) and poly(ethylene-co-propylene oxide). The greatest binding-induced chemical shift changes are observed for Trp-62, Arg-61 and Arg-73 at the edge of the active site cleft of the protein, consistent with a predominantly hydrophobic interaction mode involving the polymer ethylene moieties. The more hydrophilic species poly(dihydroxypropyl methacrylate) causes similar but substantially smaller chemical shift effects than the other polymers, confirming the nature of the interaction. A dissociation constant of 76+/-5 mM is determined for the poly(ethylene glycol)-lysozyme complex. The relatively low affinity of the protein-polymer interactions compared to oligosaccharide substrate binding suggests that lysozyme activity is minimally affected by these materials.

Silicone rubber-hydrogel composites as polymeric biomaterials. VI. Transport properties in the water-swollen state.

Permeation of inorganic salts in water-swollen silicone rubber-hydrogel composites consisting of a silicone rubber matrix and lightly cross-linked particles of poly(2-hydroxyethyl methacrylate), poly(2-hydroxyethyl methacrylate-co-methacrylic acid), poly(methacrylic acid), polyacrylamide or poly(acrylamide-co-methacrylic acid) hydrogels was investigated. The results, together with earlier data on permeation of non-ionic low-molecular-weight substances through the composite materials, were evaluated in terms of the free-volume diffusion theory. It was found that the materials with water content exceeding a certain limit are highly permeable to the salts, and that, as regards permeation properties, they behave as homogeneous water-swollen hydrogels. The dependence of electrical conductivity of the water-swollen composites on the hydrogel phase content was measured, and the results are discussed in relation to other transport properties and to the structure of the materials.

Adhesion and colonisation of Candida krusei on host surfaces.

Candida krusei is an emerging pathogen, especially in immunocompromised hosts. As the adherence of this organism both to host epithelial surfaces and to catheter and prosthetic surfaces appears to be important in the pathogenesis of superficial as well as systemic candidoses, the adhesion of 20 oral isolates of C. krusei and five oral isolates of C. albicans was compared with the following substrates: cultured (HeLa) epithelial cells, buccal epithelial cells (BEC) from healthy adults and bone marrow transplant patients, and acrylic (polymethylmethacrylate) surfaces. Animal experiments in Sprague Dawley rats were also conducted to evaluate the relative oral carriage rate of the two Candida spp. C. krusei isolates adhered in far greater numbers to acrylic surfaces than to either of the cell surfaces. Significant intra-species differences in C. krusei adhesion for acrylic surfaces were noted between 74 (39%) of 190 pair comparisons in contrast to 18 (9.5%) of 190 with HeLa surfaces (p < 0.05). A positive correlation was also observed between the adhesion of C. krusei isolates to HeLa cells and acrylic surfaces. Five isolates of C. albicans showed very low adherence to HeLa surfaces when compared with BEC obtained from either healthy individuals or bone marrow transplant patients. The adherence of C. albicans to BEC from the healthy individuals was c. 12-fold greater than that of C. krusei, a figure similar to the relative murine oral carriage rate of the two Candida spp.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of intramedullary polymethylmethacrylate on healing of intercalary cortical allografts in a canine model.

The purpose of this study was to evaluate the effect of intramedullary polymethylmethacrylate (PMMA) bone cement on the healing of intercalary allografts. Thirteen adult beagles had bilateral intercalary femoral allografts implanted. The medullary canal of one randomly assigned allograft in each dog was filled with PMMA. Healing was followed clinically and femora were evaluated radiographically, biomechanically, histologically, and histomorphometrically 9 months after surgery. There was an increased percent of eroded surface at the endosteal area of the center region of grafts containing PMMA and there was an increased percent osteoblast surface in this area in grafts not containing PMMA. There was an increased percent eroded surface at the periosteal area in the center region in grafts not containing PMMA and there was an increased percent osteoblast surface at the periosteal area in the graft adjacent to the host junction in grafts containing PMMA. There was no significant difference between PMMA-treated and untreated allografts in any other parameters measured. The results from this study suggest that, although the pattern of incorporation is altered, intramedullary PMMA does not appear to effect allograft healing adversely.

Toxicology of methyl methacrylate: the rate of disappearance of methyl methacrylate in human blood in vitro.

1. The rate of disappearance of methyl methacrylate in blood has been determined using an isotope dilution technique. 2. At a concentration of 10(-4) mol dm(-3), methyl methacrylate disappears with pseudo first order kinetics. 3. The half-life of methyl methacrylate in blood at 37 degrees C lies in the range 20--40 min. 4. The half-life showed no dependence on the age or sex of the blood donor. 5. A major, possibly the only, pathway of metabolism is by hydrolysis to methacrylic acid.

In vitro bacterial adherence to hydrogel and poly(methyl methacrylate) intraocular lenses.

PURPOSE: To compare the in vitro adherence of Staphylococcus epidermidis to poly-(hydroxyethyl methacrylate) (polyHEMA) or hydrogel intraocular lenses (IOLs) and poly(methyl methacrylate) (PMMA) IOLs. SETTING: Lions Eye Institute, Perth, Western Australia. METHODS: One-piece hydrogel lenses and one-piece PMMA lenses were suspended for 60 minutes in standardized suspensions of a well-characterized strain of S. epidermidis and then sonicated in a known quantity of balanced salt solution to remove the adherent bacteria. Quantitative cultures of the sonicates were performed and the results analyzed statistically. RESULTS: The mean bacterial adherence of S. epidermidis to the PMMA IOLs (58,400 CFU) was more than 20 times greater than that to the hydrogel IOLs (1953 CFU). The difference was statistically significant (P < .001). CONCLUSIONS: Adherence of S. epidermidis to hydrogel IOLs is significantly lower than to PMMA IOLs. This suggests that the risk of postoperative endophthalmitis after cataract extraction and IOL implantation may be lower with the use of hydrogel IOLs.

Annexin V-coated intraocular lenses.

PURPOSE: To assess whether annexin V-coated poly(methyl methacrylate) (PMMA) intraocular lenses (IOLs) prevent postoperative inflammation in rabbit eyes. SETTING: Department of Ophthalmology, Hôpital Purpan, Toulouse, France. METHODS: Thirteen IOLs coated with annexin V were implanted in 13 rabbit eyes; the contralateral eyes received uncoated IOLs. Postoperative fibrin was quantitated by daily slitlamp examination until the anterior chamber was completely clear. Results were analyzed using a Wilcoxon test. Ocular toxicity was evaluated by light and electron microscopy. RESULTS: Eyes with the annexin V-coated IOLs had less severe inflammation on the first postoperative day, and the inflammation resolved more quickly than in eyes with uncoated IOLs (P < .05). No annexin V was released postoperatively, nor were there signs of ocular toxicity. CONCLUSION: Annexin V-coated lenses effectively reduced postoperative inflammation in rabbit eyes.

Antibiotic-leaching from polymethylmethacrylate beads.

Aminoglycoside-impregnated polymethylmethacrylate beads, which are used to deliver antibiotic directly to infected sites in the musculoskeletal system, are available as a manufactured product or they can be mold-made by a pharmacy or hand-rolled by the orthopaedist in the operating suite. We investigated the leaching of antibiotic from each of these types of beads. Our hypothesis was that the elutions of antibiotic from the three types of beads are similar. Three study groups (hand-made, mold-made, and manufactured beads), each composed of four five-bead subsets, were formed so that twenty beads of each type were tested. Each bead was leached daily in a two-milliliter aliquot of normal saline solution throughout a sixty-day period, and the aminoglycoside concentration in twenty of these aliquots was determined. Analysis of variance showed no statistically significant differences when the antibiotic elutions within each subset, between the different subsets, and between the three groups were compared. The clinically important finding of this investigation is that the leaching characteristics of the three types of aminoglycoside-impregnated beads are equivalent when the beads have been fabricated out of comparable materials.