Novel green surface modification of metallocene polyethylene by steam to enhance its hemocompatible properties

Steam treatment is a green surface modification technique that was used to improve the surface characteristics and hemocompatibility of metallocene polyethylene (mPE). In this study, a sharp decrease in the mean contact angle of steam‐exposed mPE compared to that of untreated mPE showed enhanced hydrophilicity. The increased surface roughness was demonstrated by atomic force microscopy, scanning electron microscopy, and Hirox three‐dimensional microscopy. The average roughness of the control mPE (2.757 nm) was enhanced to 8.753 nm by steam treatment. Fourier transform infrared spectroscopy analysis illustrated no chemical changes, but the changes in the absorbance intensity ensured morphological changes. Blood compatibility studies were assessed by coagulation assays, hemolysis, and platelet adhesion tests. The mean number of platelets adhered to the steam‐treated sample (11) was half of the number of platelets adhered to the untreated mPE surface (22). The clotting time on the steam exposed surface was delayed, hemolysis and platelet adhesion were significantly reduced. The green surface modification of mPE with steam enhanced its surface properties and hemocompatibility. The improved blood compatibility of mPE may help in the efficient designing of hemocompatible biomaterials such as cardiovascular implants. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43395.     

Mechanical and barrier properties of carbon nanotube reinforced PCL‐based composite films: Effect of gamma radiation

Carbon nanotube (CNT) reinforced (0.05–0.5% by wt) polycaprolactone (PCL)‐based composites were prepared by compression molding. Addition of 0.2% CNT caused a 131% improvement of tensile strength (TS) of PCL films. The tensile modulus (TM) and elongation at break (Eb) of PCL were also significantly improved with the addition of CNT. The water vapor permeability of PCL was 1.51 g·mm/m²·day but 0.2% CNT containing PCL films showed 1.08 g·mm/m²·day. Similarly, the oxygen transmission rate (OTR) of PCL films was found to decrease with the addition of CNT. But, carbon dioxide transmission rate (CO₂TR) of PCL film was improved due to incorporation of CNT. Effect of gamma radiation on PCL films and CNT reinforced PCL‐based composites were also studied. The TS of the irradiated (10 kGy) PCL films gained to 75% higher than control sample. The TS of the 0.2% CNT reinforced composite film was reached to 41 MPa at 15 kGy dose. The barrier properties of non‐irradiated and irradiated (10 kGy) PCL films and composites (0.2% CNT reinforced) were also measured. Both PCL films and composites showed lower values of WVP upon irradiation and indicated better water vapor barrier. The OTR and CO₂TR of the irradiated (10 kGy) PCL films and composites were decreased compared to their counterparts. Surface and interface morphologies of the composites were studied by scanning electron microscopy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Rheometric study of the gelation and fusion processes of poly(vinyl chloride‐co‐vinyl acetate) plastisols with different commercial plasticizers

Evolution of the complex viscosity of pastes of PVC‐VA (vinyl chloride‐vinyl acetate copolymer) plasticized with different commercial plasticizers has been studied. Knowledge of the rheological behavior of the formulations allows for better understanding of the gelation and fusion processes. Twenty commercial plasticizers of different types and with different functional groups have been studied and are grouped into five families: phthalate esters with linear chains, phthalate esters with branched chains, adipates (normal and polymeric), citrates, and rest of the plasticizers (carboxylates, alkylsulfonates, and pentaerythritol ester derivatives). Interesting relationships among the observed rheologies and the nature and molecular weight of the plasticizer have been observed. The evolution of the complex viscosity with temperature—at the temperatures where the blowing agents normally used in PVC plastisol foaming processes generate the main amount of gas—has been newly discussed with regard to the chemical structure and molecular weight of all of the plasticizers used. It was found that several different dynamic processes must be synchronized in order to understand the relationships among the chemical structure, plasticization, plasticizer compatibility, rheological properties, and foaming process of such materials. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Effects of gallotannin treatment on attachment, growth, and survival of Escherichia coli O157:H7 and Listeria monocytogenes on spinach and lettuce

Food-borne illness outbreaks are increasingly associated with fresh produce. Their high prevalence may reflect the lack of methods to effectively remove pathogenic bacteria from the surface of fruits and vegetables. This study evaluated the effect of antimicrobial gallotannins on attachment, growth, and survival of food-borne pathogens on green leafy vegetables. Spinach leaves and interior leaves of lettuce harboring high and low cell counts of background microbiota, respectively, were washed with tap water with and without added gallotannins. To account for the variability among organisms, green leafy vegetables were inoculated with strain cocktails of Escherichia coli O157:H7 and Listeria monocytogenes. Cell counts of L. monocytogenes were significantly reduced by the gallotannin treatment. Lower cell counts after storage for 8?days at 4?°C demonstrated antimicrobial effects of gallotannins retained on the surface of green leafy vegetables. Gallotannin treatments with 1?g/L did not inhibit E. coli O157:H7 but hindered their attachment to filter paper by up to 94?%. The addition of gallotannin-containing extracts from mango (Mangifera indica L.) kernels to the washing water did neither alter color nor texture of bagged fresh-cut products. In conclusion, gallotannin treatment significantly reduced surface contamination of green leafy vegetables with L. monocytogenes and reduced the attachment of cells of E. coli O157:H7.     

Fast-to-slow conversion following chronic low-frequency activation of medial gastrocnemius muscle in cats. I. Muscle and motor unit properties

This study of cat medial gastrocnemius (MG) muscle and motor unit (MU) properties tests the hypothesis that the normal ranges of MU contractile force, endurance, and speed are directly associated with the amount of neuromuscular activity normally experienced by each MU. We synchronously activated all MUs in the MG muscle with the same activity (20 Hz in a 50% duty cycle) and asked whether conversion of whole muscle contractile properties is associated with loss of the normal heterogeneity in MU properties. Chronically implanted cuff electrodes on the nerve to MG muscle were used for 24-h/day stimulation and for monitoring progressive changes in contractile force, endurance, and speed by periodic recording of maximal isometric twitch and tetanic contractions under halothane anesthesia. Chronic low-frequency stimulation slowed muscle contractions and made them weaker, and increased muscle endurance. The most rapid and least variable response to stimulation was a decline in force output of the muscle and constituent MUs. Fatigue resistance increased more slowly, whereas the increase in time to peak force varied most widely between animals and occurred with a longer time course than either force or endurance. Changes in contractile force, endurance, and speed of the whole MG muscle accurately reflected changes in the properties of the constituent MUs both in extent and time course. Normally there is a 100-fold range in tetanic force and a 10-fold range in fatigue indexes and twitch time to peak force. After chronic stimulation, the range in these properties was significantly reduced and, even in MU samples from single animals, the range was shown to correspond with the slow (type S) MUs of the normal MG. In no case was the range reduced to less than the type S range. The same results were obtained when the same chronic stimulation pattern of 20 Hz/50% duty cycle was imposed on paralyzed muscles after hemisection and unilateral deafferentation. The findings that the properties of MUs still varied within the normal range of type S MUs and were still heterogeneous despite a decline in the variance in any one property indicate that the neuromuscular activity can account only in part for the wide range of muscle properties. It is concluded that the normal range of properties within MU types reflects an intrinsic regulation of properties in the multinucleated muscle fibers.     

Lack of type 2 T cell-independent B cell responses and defect in isotype switching in TNF-lymphotoxin alpha-deficient mice

TNF is implicated in in vitro Ig production, but its role in vivo is not clearly defined. Our previous studies had shown that TNF-LT alpha double-deficient mice have defective IgM and IgG primary Ab responses to the T cell-dependent (TD) Ag SRBC. We now extend these studies to secondary responses and to T cell-independent (TI) B cell responses. Injections of the TD Ag SRBC did not induce germinal center formation in the spleen of TNF-LT alpha-deficient mice. Associated with the morphologic defect, there was a defective IgG Ab response and a secondary hyper-IgM response to the TD Ag in TNF-LT alpha-deficient mice. The response to the TI Ag type 2 DNP-alanyl-glycyl-glycyl-Ficoll was essentially absent in TNF-LT alpha-deficient mice, while that to the TI Ag type 1 TNP-LPS was significantly reduced only for IgG2b isotype. Transplantation of bone marrow cells from wild-type mice into irradiated TNF-LT alpha-deficient mice restored the formation of splenic germinal centers and corrected the IgM and IgG responses to both TD and TI Ags. These data suggest that TNF and/or LT alpha signaling are critically required for germinal center formation and for the IgM and IgG responses to both TD and TI type 2 Ags.     

The neurophysiological and biochemical mechanisms of the dose-dependent amphetamine modulation of the sensorimotor cortex neurons in developing animals

The resulting data give evidences, that after injection of the low doses of amphetamine the decrease of amplitudes both negative (NC-3), and positive components (PC-3) of the thalamo-cortical responses (TCR) of the sensorimotor cortex (SMC) takes place in 2nd-3d-weeks-old rabbits of their postnatal life. At the same time the amplitudes of these phases in 45-50-days-old animals change to greatly less extent, without any system, with low level of statistical significance. After injection of medium doses of amphetamine in 2nd-3d-weeks-old rabbits, the increase in amplitudes of both components of TCR SMC in observed, at the same time in definitive animals the amplitudes of these responses decrease greatly. After injection of the high doses of amphetamine in 2nd-3d-weeks-old rabbits the further increase in amplitude PC-3 and NC-3 is displayed, at the same time the growth of amplitude parameters of TCR SMC appears for elder animals under this concentration of amphetamine only. Neurophysiological and neurochemical analyses of these phenomena are developed. Neuro-ontogenesis hypothesis of causes of high vulnerability of the nervous system in young animals and children during critical period of increased risk under the exposure to both psychotropic drugs and endogenous psychopathogenic factors being proposed, that can simplify search for adequate psychopharmacology protector, etc.     

Preventing the cardiotoxic effects of anthracyclines with Cardioxane]

An immune response to heparin, which is clinically manifested by the development of thrombocytopenia with or without thrombosis, is stimulated by a complex of heparin with platelet factor 4 (PF4). The primary thrombotic events in patients with heparin-induced thrombocytopenia (HIT) are more frequently venous than arterial. The development of antibodies, however, does not always result in thrombocytopenia or in catastrophic events. The antibodies, which are of the IgG, IgM, and IgA isotypes, can be easily measured by an ELISA that contains a complex of heparin-platelet factor 4 (PF4). Initial antibody formation can be greatly reduced by limiting the exposure to unfractionated heparin or by the use of low-molecular-weight heparin. For those patients who require anticoagulation and who have antibodies to heparin-PF4, danaparoid (Orgaran), a low-molecular weight heparinoid that does not react with the antibodies, is now commercially available; argatroban, a thrombin-specific inhibitor, can also be obtained for compassionate use. The use of these agents during anticoagulation with warfarin is preferable to the simple discontinuation of heparin and intitiation of warfarin, because the latter treatment can result in ongoing thrombosis.