A novel approach to evaluate the mechanical responses of elastin-like bioresorbable poly(glycolide-co-caprolactone) (PGCL) suture.

Poly(glycolide-co-caprolactone) (PGCL) has become a novice to the bioresorbable suture owing to the synergistic properties taken from the homo-polyglycolide (PGA) and polycaprolactone (PCL) such as excellent bioresorption and flexibility. In addition to under conventional monotonic loading, the understanding of mechanical responses of PGCL copolymers under complex loading conditions such as cyclic and stress relaxation is crucial for its application as a surgical suture. Consequently, the present work focuses on evaluating the mechanical responses of PGCL sutures under monotonic, cyclic, and stress relaxation loading conditions. Under monotonic loading, the stress-strain behavior of the PGCL suture was found to be non-linear with noticeable strain-rate dependence. Under cyclic loading, inelastic responses including stress-softening, hysteresis and permanent set were observed. During cyclic loading, both stress-softening and hysteresis were found to increase with the maximum strain. In multi-step stress relaxation, the PGCL sutures were observed to exhibit a strong viscoelastic response. In an attempt to describe the relationship between the stress-relaxation and strain-induced crystallization (SIC) occurring during the loading and relaxation processes, a schematic illustration of the conformational change of polymer chains in PGCL sutures was proposed in this work. Results showed that SIC was dependent on the strain level as well as the loading and relaxation durations. The inelastic phenomena observed in PGCL sutures can be thus correlated to the combined effect of stress relaxation and SIC.

Mechanical Response of Glass-Epoxy Composites with Graphene Oxide Nanoparticles.

Graphene-based fillers possess exceptional properties that encourage researchers toward their incorporation in glass-epoxy (GE) polymer composites. Regarding the mechanical and wear properties of glass-epoxy composites, the effect of graphene oxide (GO) reinforced in glass-epoxy was examined. A decrease in tensile modulus and increase in tensile strength was reported for 1 wt. % of GO. A shift in glass transition temperature Tg was observed with the addition of GO. The cross-link density and storage modulus of the composite decreased with the addition of GO. The decrease in dissipation energy and wear rate was reported with the increase in GO concentration. A simple one-dimensional damage model of nonlinear nature was developed to capture the stress-strain behavior of the unfilled and filled glass-epoxy composite. Tensile modulus E, Weibull scale parameter σo, and Weibull shape parameter ß were considered to develop the model. Finally, to understand the failure mechanisms in GO-filled composites, a scanning electron microscopic (SEM) examination was carried out for tensile fractured composites.

An assessment of electronically captured data in the patient care enhancement system (PACES) for syndromic surveillance.

INTRODUCTION: A common approach to the surveillance of emerging infectious diseases and agents of bioterrorism is to analyse electronically captured data for disease syndromes. The Patient Care Enhancement System (PACES) is a form of electronic medical records presently in service in the Singapore Armed Forces (SAF). We assess the feasibility of PACES data for surveillance, describe time-trends, and identify methods of sub-analysis which could improve performance. MATERIALS AND METHODS: Medical consults from July 2000 to June 2003 were extracted. Diagnosis codes were mapped to 7 infectious disease syndromes according to the categorisation in the Electronic Surveillance System for the Early Notification of Community-based Epidemics (ESSENCE): gastrointestinal (GI), fever (FEVER), respiratory, (RESP), coma (COMA), neurological (NEURO), dermatologic-haemorrhagic (DERMHEM) and dermatologic- infectious (DERM-INF). RESULTS: A total of 732,233 episodes of care were analysed. Weekly periodicity was observed, with decreased weekend consults; there were no obvious seasonal trends in any of the syndromes. RESP, FEVER and GI syndromes were common events. Sub-analyses, either by restricting to cases with a repeated consultation, or grouping the data by medical centres, could dramatically lower thresholds used to flag outbreaks. CONCLUSION: In spite of the level of background noise inherent in a system consisting mainly of primary care consults, sub-analysis by medical centre, or restriction to cases with repeated consults were able to yield sensitive thresholds for outbreak detection.

Bed rest decreases whole-body protein turnover in post-absorptive man.

1. Whole-body protein turnover was measured using the [15N]glycine tracer technique in 10 post-absorptive healthy volunteers during normal daily activities and a period of bed rest. 2. Bed rest reduced whole-body protein turnover (25%), synthesis (26%) and breakdown (25%), but short-term urinary nitrogen excretion remained unchanged.

Whole-body protein turnover in response to hyperinsulinemia in humans postabsorptively with [15N]glycine as tracer.

Studies using stable isotopes to determine the effect of insulin on whole-body protein turnover have given conflicting results. The precursor approach to studying healthy subjects in a postabsorptive state shows reductions in breakdown and oxidation; with end product methods in parenterally fed patients no such changes are seen. To explain these discrepancies, we measured protein turnover with and without euglycemic hyperinsulinemic clamping postabsorptively in nine healthy subjects by using single-dose [15N]glycine with calculations based on ammonia and urea end product excretion. With and without clamping, respectively, insulin reduced nitrogen (22.1 and 48.2 mg.kg-1.9 h-1, P < 0.01) and urea (15.8 and 37.5 mg.kg-1.9 h-1, P < 0.05) but increased ammonia (7.7 and 5.0 mg.kg-1.9 h-1, P < 0.05) excretion. Although the urea end product method suggested that insulin tended to reduce both protein breakdown and synthesis, the protein metabolism changes detected with the ammonia end product method tended to be in the opposite direction. The [15N]glycine ammonia end-product method may be inappropriate for studies during insulin infusion because of insulin's effect on ammonia excretion.

Lipid fuel metabolism after abdominal surgery.

The work investigated fuel interrelationships in surgical patients infused with saline (Group I) or glucose (Group II) (13 patients in each group) on the day of surgery and subsequently maintained solely on saline until the fifth postoperative day. Blood concentrations of non-esterified fatty acids (NEFA) and ketone bodies were markedly increased in response to surgical stress on the day of surgery only in patients who were not administered carbohydrate. Increased concentrations of lactate and glucose were observed on the day of surgery in patients infused with either saline or glucose. As both fatty acid and ketone body concentrations were decreased by glucose infusion, impaired glucose utilization immediately after surgery is not a simple consequence of increased oxidation of lipid fuels. Glucose and lactate concentrations declined after the day of surgery. Despite a progressive fall in plasma non-esterified fatty acid concentrations from the first to fifth post-operative days, blood ketone body concentrations were strikingly elevated in both groups of patients. The findings emphasize the role of the liver in post-operative fatty acid turnover.

Perfluorocarbon liquids (perfluorodecalin) in vitreoretinal surgery--a local experience.

A low viscosity perfluorocarbon liquid (perfluorodecalin) known commercially as DKLine was used intraoperatively as a temporary vitreous substitute in 20 patients undergoing vitrectomy surgery for a variety of complicated vitreoretinal conditions. The indications for its use included giant retinal tears (9), proliferative vitreoretinopathies (2), dislocated lenses (2), dislocated posterior chamber implant (1), endophthalmitis with retinal detachment (2), traction retinal detachment (1), pseudophakic retinal detachment (2) and exudative retinal detachment (1). In all cases with retinal detachment, perfluorodecalin was successful in flattening the retina intraoperatively. It was also successful in permitting the safe removal of dislocated lenses that were lying on the retina. In all except four cases, removal of perfluorodecalin was complete. We observed no toxic effects from remnant bubbles of perfluorocarbon in the eye.

Ophthalmic screening for diabetics: the importance of physician-ophthalmologist collaboration in the prevention of blindness.

Diabetes mellitus as a disease is a dragon with many heads. To cope with it, each manifestation must be deftly handled by family physician and specialists in unison. Similarly, the spectre of diabetic retinopathy is best exorcised before it manifests - by effective prophylactic screening. This programme can only be successful through a co-ordinated effort of both physicians and ophthalmologists. In this paper, we present one such agenda which we have adopted, The result indicate that a fifth of diabetics have retinopathy, and that sight threatening disease affects 7% of those screened. More critically, it also establishes that a cost-effective method of screening can be achieved through a synergetic endeavour of primary care physician and specialist.

Idiopathic subretinal neovascularization.

Idiopathic subretinal neovascularization is a potentially blinding condition and often strikes patients in their prime of life. It appears to be seen in more females, at an earlier age than males. Treatment is possible by photoablation of the subretinal new vessel by Argon or Yag laser. There is a clinical impression that Argon laser is more effective than the Yag laser for this purpose.

Implantation and diabetes: analysis of 525 cases.

This is a retrospective study of 525 posterior chamber implants in diabetics performed by A S M Lim and B C Ang of Singapore. The patients were reviewed by visiting ophthalmologists--J E Kennedy (Sydney), M Ngui (East Malaysia) and P M Hart (Belfast). This study did not show any significant difference in the complication of post-operative visual acuity between diabetics and non-diabetics. 95% obtained 6/12 vision or better when pre-existing disease was excluded. It also showed that posterior chamber implants can be inserted in eyes with maculopathy or proliferative retinopathy if laser treatment was effectively done before or after surgery.

Eye diseases in the elderly in Singapore.

Ocular disorders in the elderly have become more important because of increased longevity and the demand for good vision. Many serious ocular conditions are age-related and they include cataract, glaucoma, diabetic retinopathy and other retinal conditions. The most important ocular disorder is cataract which fortunately is curable with excellent results when a posterior chamber implant is inserted. Angle closure glaucoma is common in the elderly Singapore Chinese and can be effectively treated with microscopic peripheral iridectomy or trabeculectomy. Blindness from diabetic retinopathy can be prevented with argon laser photocoagulation. In most cases blindness is preventable with early diagnosis e.g. in glaucoma and diabetic retinopathy. Severe visual loss in the elderly requires careful explanation and compassion by doctors and social workers.

Cryoapplication in diabetic retinopathy.

Thirty-five patients with diabetic retinopathy were treated with cryoapplication. This was used as an alternative to Argon laser or Zenon photocoagulation because the media was opaque from vitreous hemorrhage or cataract. It was difficult or impossible to treat with photocoagulation. The clinical impression indicates that cryoapplication is effective, showing adequate pigmentation and chorioretinal scarring with regression of diabetic retinopathy changes. However patients with vitreo-retinal fibrosis became frequently worse weeks later. This is considered a contraindication. The use of cryoapplication in diabetic retinopathy is recommended in situations where the ocular media is not clear, such as vitreous hemorrhage and cataract. It can also be used if there is difficulty with laser photocoagulation following lens implantation. It may be valuable in some developing countries where photocoagulation is not available. Cryomachines are frequently used in eye camps. It is inexpensive and does not necessarily require electricity.

Cardiac arrests in a geriatric unit.

The outcome of cardio-pulmonary resuscitation within an acute geriatric unit was studied in 95 patients (mean age 77 years, range 65-90) who were involved in 106 consecutive cardio-respiratory arrest calls. In 58 patients (61%), initial resuscitation was unsuccessful and a further 21 (22%) died later in hospital. Fourteen patients (15%) were alive 3 months after hospital discharge, a success rate comparable to that of published series in younger patients. The probability of successful resuscitation was greater in patients in the High-dependency Unit, and ventricular fibrillation and a short duration of arrest were confirmed as good prognostic factors. Age had no influence on outcome. Although subjective levels of psychological and physical disability of survivors at 3 months were low, their domestic and social life was often excessively restricted. Selective, but positive, use of cardio-pulmonary resuscitation within acute geriatric units will benefit a significant minority of patients, but there is also a need for further measures to reduce unnecessary disability in long-term survivors.

Argon laser photocoagulation in diabetic retinopathy: five year review of 697 treated eyes.

Diabetic retinopathy has now become a common cause of blindness in Singapore. Fortunately, laser photocoagulation has prevented blindness in the majority of patients who were treated. An analysis of 872 patients treated with argon laser photocoagulation showed that 424 patients (48.6%) were for diabetic retinopathy. Patients with adequate treatment retained useful vision. Those who lost vision frequently had associated target organ involvement besides inadequate laser treatment. Patients with proliferative diabetic retinopathy were treated with peripheral retinal photocoagulation. Patients with diabetic maculopathy especially those with focal leaks were treated with localised photocoagulation. A common cause of blindness is failure to recognise the condition early. Physicians and general practitioners must, in the management of diabetics, examine their patients periodically with the pupils dilated in a darkened room.

Indications for intraocular lens implantation: an analysis of 1033 cases.

The posterior chamber implant has increased safety in intraocular lens implantation. Implants are now inserted in one-eyed patients, in eyes with high myopia, endothelial corneal problems, senile macular degeneration, diabetic retinopathy and glaucoma. The percentage of implant from 1975-1981 was 10.3% but increased to 83.9% from 1983-1984. This is mainly because there are today fewer situations where lens implantation is contra-indicated in the hands of surgeons, skilled and experienced in posterior chamber implant surgery.