NMR imaging of water sorption into poly(hydroxyethyl methacrylate-co-tetrahydrofurfuryl methacrylate)

The diffusion of water into a series of hydroxyethyl methacrylate, HEMA, copolymers with tetrahydrofurfuryl methacrylate, THFMA, has been studied over a range of copolymer compositions using NMR imaging analyses. For polyHEMA the diffusion was found to be consistent with a Fickian model. The mass diffusion coefficient of water in polyHEMA at 37 degreesC was determined from the profiles of the diffusion front to be 1.5 x 10(-11) m(2) s(-1), which is less than the value based upon mass uptake, 2.0 x 10(-11) m(2) s(-1). The profiles of the water diffusion front obtained from the NMR images showed that stress was induced at the interface between the rubbery and glassy regions which led to formation of small cracks in this region of the glassy matrix of polyHEMA and its copolymers with mole fractions of HEMA greater than 0.6. Water was shown to be able to enter these cracks forming water pools. For copolymers of HEMA and THFMA with mole fractions of HEMA less than 0.6 the absence of cracks was attributed to the ability of the THFMA sequences to undergo stress relaxation by creep.

An ESR study of irradiated poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (PFA)

Poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (PFA) with 2 mol% perfluoropropyl vinyl ether (PPVE) was exposed to gamma -irradiation in vacuum at both 77 K and room temperature and the ESR spectra recorded. Both the main chain, similar to CF2-(CF)-F-.-CF(2)similar to, and end chain, similar to (CF2CF2)-F-. radicals were identified at both temperatures and their thermal stabilities measured, No radicals unique to the radiolytic cleavage at the PPVE units were observed at room temperature, either due to the low concentration of the comonomer or beta -scission to form a chain end radical and a nonradical species. G-values for radical formation at room temperature and 77 K were found to be 0.93 and 0.16, respectively. (C) 2001 Elsevier Science Ltd. All rights reserved.

Operative treatment of ankle fractures: A minimum ten-year follow-up

The long-term outcome of 25 patients with bimalleolar fractures of the ankle was assessed ten to fourteen years following their fractures using the Phillips scoring system. All patients had undergone open reduction and anatomical internal fixation (as described in their operative notes in the medical records). 52 % of patients had a good or excellent overall outcome while 24% had a poor overall outcome. This study has the longest follow-up period (10 to 14 years) to date on the outcomes of internal fixation of bimalleolar ankle fractures and demonstrates a higher percentage of poorer outcomes than has been previously described. This trend appears to be predictable as other studies with shorter term follow-up have already established a trend of increasing radiological evidence of post-traumatic arthritis with successively longer-term outcome reports.

Effects of concentrated viral communities on photosynthesis and community composition of co-occurring benthic microalgae and phytoplankton

Marine viruses have been shown to affect phytoplankton productivity; however, there are no reports on the effect of viruses on benthic microalgae (microphytobenthos). Hence, this study investigated the effects of elevated concentrations of virus-like particles on the photosynthetic physiology and community composition of benthic microalgae and phytoplankton. Virus populations were collected near the sediment surface and concentrated by tangential flow ultrafiltration, and the concentrate was added to benthic and water column samples that were obtained along a eutrophication gradient in the Brisbane River/Moreton Bay estuary, Australia. Photosynthetic and community responses of benthic microalgae, phytoplankton and bacteria were monitored over 7 d in aquaria and in situ. Benthic microalgal communities responded to viral enrichment in both eutrophic and oligotrophic sediments. In eutrophic sediments, Euglenophytes (Euglena sp.) and bacteria decreased in abundance by 20 to 60 and 26 to 66%, respectively, from seawater controls. In oligotrophic sediments, bacteria decreased in abundance by 30 to 42% from seawater controls but the dinoflagellate Gymnodinium sp. increased in abundance by 270 to 3600% from seawater controls, The increased abundance of Gymnodinium sp. may be related to increased availability of dissolved organic matter released from lysed bacteria. Increased (140 to 190% from seawater controls) initial chlorophyll a fluorescence measured with a pulse-amplitude modulated fluorometer was observed in eutrophic benthic microalgal incubations following virus enrichment, consistent with photosystem II damage. Virus enrichment in oligotrophic water significantly stimulated carbon fixation rates, perhaps due to increased nutrient availability by bacterial lysis. The interpretation of data from virus amendment experiments is difficult due to potential interaction with unidentified bioactive compounds within seawater concentrates. However, these results show that viruses are capable of influencing microbial dynamics in sediments.

Activity of recombinant dengue 2 virus NS3 protease in the presence of a truncated NS2B co-factor, small peptide substrates, and inhibitors

Recombinant forms of the dengue 2 virus NS3 protease linked to a 40-residue co-factor, corresponding to part of NS2B, have been expressed in Escherichia coli and shown to be active against para-nitroanilide substrates comprising the P6-P1 residues of four substrate cleavage sequences. The enzyme is inactive alone or after the addition of a putative 13-residue co-factor peptide but is active when fused to the 40-residue co-factor, by either a cleavable or a noncleavable glycine linker. The NS4B/NS5 cleavage site was processed most readily, with optimal processing conditions being pH 9, I = 10 mm, 1 mm CHAPS, 20% glycerol. A longer 10-residue peptide corresponding to the NS2B/NS3 cleavage site (P6-P4') was a poorer substrate than the hexapeptide (P6-P1) para-nitroanilide substrate under these conditions, suggesting that the prime side substrate residues did not contribute significantly to protease binding. We also report the first inhibitors of a co-factor-complexed, catalytically active flavivirus NS3 protease. Aprotinin was the only standard serine protease inhibitor to be active, whereas a number of peptide substrate analogues were found to be competitive inhibitors at micromolar concentrations.

Co-activation of the abdominal and pelvic floor muscles during voluntary exercises

The response of the abdominal muscles to voluntary contraction of the pelvic floor (PF) muscles was investigated in women with no history of symptoms of stress urinary incontinence to determine whether there is co-activation of the muscles surrounding the abdominal cavity during exercises for the PF muscles. Electromyographic (EMG) activity of each of the abdominal muscles was recorded with fine-wire electrodes in seven parous females. Subjects contracted the PF muscles maximally in three lumbar spine positions while lying supine. In all subjects. the EMG activity of the abdominal muscles was increased above the baseline level during contractions of the PF muscles in at least one of the spinal positions. The amplitude of the increase in EMG activity of obliquus externus abdominis was greatest when the spine was positioned in flexion and the increase in activity of transversus abdominis was greater than that of rectus abdominis and obliquus externus abdominis when the spine was positioned in extension. In an additional pilot experiment. EMG recordings were made from the pubococcygeus and the abdominal muscles with fine-wire electrodes in two subjects during the performance of three different sub-maximal isometric abdominal muscle maneuvers. Both subjects showed an increase in EMG activity of the pubococcygeus with each abdominal muscle contraction. The results of these experiments indicate that abdominal muscle activity is a normal response to PF exercise in subjects with no symptoms of PF muscle dysfunction and provide preliminary evidence that specific abdominal exercises activate the PF muscles. Neurourol. Urodynam. 20:31-42, 2001. (C) 2001 Wiley-Liss, Inc.

Accuracy of frozen section for the operative management of endometrial cancer

Objective To assess the accuracy of intra-operative frozen section reports at identifying the features of high risk uterine disease compared with final histopathology. Design Retrospective study. Methods The records, of 460 patients with uterine cancer registered with the Queensland Centre for Gynaecological Cancer between January 1, 1996 and December 31, 1998 were reviewed. Intra-operative frozen section was undertaken in 260 patients with endometrial adenocarcinoma. Frozen section pathology was compared with the final histopathology reports. Inter-observer reliability was assessed using percentage agreement and kappa statistics. Clinical notes were also reviewed to determine if errors resulted in sub-optimal patient care. Results Respectively, tumour grade and depth of myometrial invasion were accurately reported in 88.6% of cases (expected 61.5%, Kappa 0.70) and 94.7% (expected 53.8%, Kappa 0.89). Errors were predominantly attributable to difficulties with respect to the interpretation of tumour grade. The error resulted in the patient receiving sub-optimal surgical management in only I I cases (5.3%) Conclusion Frozen section is accurate at identifying the features of high risk uterine disease in the setting of endometrial cancer and can play an important role in directing primary operative management.

Paracetamol versus paracetamol-codeine in the treatment of post-operative dental pain: A randomized, double-blind, prospective trial

Background: Codeine is frequently added to paracetamol to treat post-operative dento-alveolar pain; studies have shown effectiveness in relief of post-operative pain at high doses but at the expense of central nervous and gastrointestinal side effects. There has been no trial to compare the efficacy and safety of paracetamol 1000mg with paracetamol 1000mg combined with codeine 30mg. Method. A randomized, single centre, double-blind prospective parallel group trial was performed to compare paracetamol 1000mg with paracetamol 1000mg with codeine 30mg for the relief of pain following surgical removal of impacted third molars, and analysed on an intention-to-treat (ITT) basis. Eighty-two patients were assigned randomly to receive either drug for a maximum of three doses. Patients recorded their pain intensity one hour after surgery and hourly thereafter for 12 hours. Results: The average increase in pain intensity over 12 hours was significantly less in patients receiving paracetamol plus codeine than in those receiving paracetamol alone (p=0.03) -1.81cm/h compared with 0.45cm/h - a difference of 1.13cm/h (95 per cent Cl: 0.18 to 2.08). Of the patients who received the paracetamol codeine combination, 62 per cent used escape medication compared with 75 per cent of those on paracetamol alone (p=0.20). There was no significant difference between the two groups in the proportion of patients experiencing adverse events (P=0.5). Conclusion: A combination of 1000mg paracetamol and 30mg codeine was significantly more effective in controlling pain for 12 hours following third molar removal, with no significant difference of side effects during the 12 hour period studied.

H-1 NMR study of the states of water in equilibrium Poly(HEMA-co-THFMA) hydrogels

The spin-spin relaxation times, T-2, of hydrated samples of poly(hydroxymethyl methacrylate), PHEMA, poly(tetrahydrofurfuryl methacrylate),PTHFMA, and the,corresponding HEMA-THFMA copolymers have been examined to probe the states of,the imbibed water in these polymers. The decay in the transverse magnetization of water. in fully hydrated samples of PHEMA, PTHFMA, and copolymers of HEMA and THFMA was described by a multiexponential function. The short component of T-2 was interpreted as water molecules that were strongly interacting with the polymer chains. The intermediate component of T-2 was assigned to water residing in the porous structure of the samples. The long component of T-2 was believed to arise from water residing in the remnants of cracks formed in the polymer network during water sorption.

Copolymers obtained by the radiation-induced grafting of styrene onto poly(tetrafluoroethylene-co-perfluoropropylvinyl ether) substrates. 1. Preparation and structural investigation

A study has been made to investigate the radiation grafting of styrene onto poly(tetrafluoroethylene-co-perfluoropropylvinyl ether) (PFA) substrates, using the simultaneous irradiation method. Two PFA polymers of different comonomer perfluoropropyl vinyl ether (PPVE) content and degree of crystallinity were used. Effects of grafting conditions such as monomer concentrations, type of solvent, dose rate, and irradiation dose on the grafting yield were investigated. Of the six different solvents used, the most efficient in terms of increasing grafting yield were dichloromethane, benzene, and methanol. The degree of grafting increased with increasing radiation dose up to 500 kGy, stabilizing above this dose. However, the grafting yield decreased with an increase in the dose rate. The grafting of styrene onto the PFA substrates was confirmed by FTIR-ATR and micro-Raman spectroscopy, The increase in the overall grafting yield was accompanied by a proportional increase in the penetration depth of the grafts into the substrate.

PFG-NMR measurements of the self-diffusion coefficients of water in equilibrium poly(HEMA-co-THFMA) hydrogels

The self-diffusion coefficients for water in a series of copolymers of 2-hydroxyethyl methacrylate, HEMA, and tetrahydrofurfuryl methacrylate, THFMA, swollen with water to their equilibrium states have been studied at 310 K using PFG-NMR. The self-diffusion coefficients calculated from the Stejskal-Tanner equation, D-obs, for all of the hydrated polymers were found to be dependent on the NMR storage time, as a result of spin exchange between the proton reservoirs of the water and the polymers, reaching an equilibrium plateau value at long storage times. The true values of the diffusion coefficients were calculated from the values of D-obs, in the plateau regions by applying a correction for the fraction of water protons present, obtained from the equilibrium water contents of the gels. The true self-diffusion coefficient for water in polyHEMA obtained at 310 K by this method was 5.5 x 10(-10) m(2) s(-1). For the copolymers containing 20% HEMA or more a single value of the self-diffusion coefficient was found, which was somewhat larger than the corresponding values obtained for the macroscopic diffusion coefficient from sorption measurements. For polyTHFMA and copolymers containing less than 20% HEMA, the PFG-NMR stimulated echo attenuation decay curves and the log-attenuation plots were characteristic of the presence of two diffusing water species. The self-diffusion coefficients of water in the equilibrium-hydrated copolymers were found to be dependent on the copolymer composition, decreasing with increasing THFMA content.

Spectroscopic study of the penetration depth of grafted polystyrene onto poly (tetrafluoroethylene-co-perfluoropropylvinylether) substrates. 1. Effect of grafting conditions

This study concerns the radiation grafting of styrene onto poly(tetrafluoroethylene-co-perfluoropropylvinylether) (PFA) substrates and the penetration depth of the graft. Grafting was obtained by the simultaneous irradiation method, and the spectroscopic analysis was made with the micro-Raman technique. Effects of grafting conditions such as the type of solvent, dose rate, and irradiation dose on the grafting yield were investigated. Of the different solvents used, the most efficient in terms of increasing grafting yield were dichloromethane, benzene, and methanol, respectively. A mixture of methanol and dichloromethane used as a solvent for styrene achieved a higher degree of grafting and concentration of grafted polystyrene onto the surface of PFA substrates than solutions of the monomer in the separate solvents. The degree of grafting increased with increasing radiation dose up to 500 kGy, stabilizing above this dose. However, the grafting yield decreased with an increase in the dose rate. The increase in the overall grafting yield was accompanied by a proportional increase in the penetration depth of the grafts into the substrate. (C) 2002 Wiley Periodicals, Inc.

Co-crystallization of sucrose at high concentration in the presence of glucose and fructose

Co-crystallization of sucrose from a highly concentrated sucrose syrup (less than or equal to 7% moisture, w/w) at 131 degreesC with 0, 5, 10, 15, and 20% of fructose, glucose, or a mixture of fructose and glucose was investigated. The crystallization of sucrose was delayed in presence of these lower molecular weight sugars. The DSC melting endotherm of cocrystallized samples exhibited a decrease in crystalline sucrose in the sample as a function of increased level of glucose and fructose. The mechanical strength of co-crystallized granules was found to be related to the moisture content and the amount of glucose or fructose content in the sample. The samples containing 10, 15, and 20% glucose in co-crystallized product demonstrated crystallization of glucose in its monohydrate form during 1 mo of storage.

Postural control and movement performance during upper limb tasks in children with developmental co-ordination disorder (DCD)

At least 6% of primary school aged children present with DCD, where co-ordination is substantially below the normal range for the child’s age and intelligence. Motor skill difficulties negatively affect academic achievement, recreation and activities of daily living. Poor upper-limb co-ordination is a common difficulty for children with DCD. A possible cause of this problem is deviant muscle timing in proximal muscle groups, which results in poor postural and movement control. While studies have been published investigating postural control in response to external perturbations, detail about postural muscle activity during voluntary movement is limited even in children with normal motor development. No studies have investigated the relationship between muscle timing, resultant arm motion and upper-limb coordination deficits. Objectives: To investigate the relationship between functional difficulties with upper-limb motor skills and neuromuscular components of postural stability and coordination. Specifically, to investigate onset-timing of muscle activity, timing of arm movement, and resultant three-dimensional (3D) arm co-ordination during rapid, voluntary arm movement and to analyse differences arising due to the presence of DCD. This study is part of a larger research program investigating postural stability and control of upper limb movement in children. Design: A controlled, cross-sectional study of differences between children with and without DCD. Methods: This study included 50 children aged eight to 10 years (25 with DCD and 25 without DCD). Children participated in assessment of motor skills according to the Movement ABC Test and a laboratory study of rapid, voluntary arm movements. Parameters investigated included muscle activation timing of shoulder and trunk muscles (surface electromyography), arm movement timing (light sensor) and resultant 3D arm motion (Fastrak). Results: A MANOVA is being used to analyse between-group differences. Preliminary results indicate children with DCD demonstrate altered muscle timing during a rapid arm raise when compared with the control group of children. Conclusion: Differences in proximal muscle timing in children with DCD support the hypothesis that altered proximal muscle activity may contribute to poor proximal stability and consequently poor arm movement control. This has implications for clinical physiotherapy.