Elasticity and energy dissipation in the double network hydrogel adhesive of the slug Arion subfuscus.

The slug Arion subfuscus produces a mucus-based defensive secretion that is remarkably tough. This glue appears to be a double network hydrogel, gaining its toughness through the synergistic actions of two networks of polymers, a relatively stiff network and a relatively deformable network. The double network mechanism has great potential to guide the development of synthetic adhesives. Mechanical tests were performed to analyse key predictions of the mechanism. Stress relaxation tests and tensile tests support the presence of stable cross-links. Cyclic stress-strain tests demonstrate that the glue dissipates a great deal of energy through the failure of these cross-links as sacrificial bonds. Energy dissipation by failure of sacrificial bonds rather than viscous processes is supported by the minimal effect of the time course of the experiments on the measured properties. These sacrificial bonds appear able to reform within minutes after failure. Finally, the glue's stiffness decreases at pH values below 5.5, whereas magnesium and calcium rapidly dissociate from the glue at all pH values tested. Thus, these ions may not be the primary cross-linkers generating the glue's stiffness. This article is part of the theme issue 'Transdisciplinary approaches to the study of adhesion and adhesives in biological systems'.

Can visual distraction decrease the dose of patient-controlled sedation required during colonoscopy? A prospective randomized controlled trial.

BACKGROUND AND STUDY AIMS: We previously demonstrated that audio distraction using relaxation music could lead to a decrease in the dose of sedative medication required and improve patient satisfaction during colonoscopy. This prospective randomized controlled trial was designed to test the hypotheses that visual distraction may also decrease the requirement for sedatives and that audio and visual distraction may have additive beneficial effects when used in combination. PATIENTS AND METHODS: 165 consecutive patients who underwent elective colonoscopy were randomly allocated into three groups to receive different modes of sedation: group 1 received visual distraction and patient-controlled sedation (PCS); group 2 received audiovisual distraction and PCS; group 3 received PCS alone. A mixture of propofol and alfentanil, delivered by a Graseby 3300 PCA pump, was used for PCS in these groups. Each bolus of PCS delivered 4.8 mg propofol and 12 micro g alfentanil. Measured outcomes included the dose of PCS used, complications, recovery time, pain score, satisfaction score, and willingness to use the same mode of sedation if the procedure were to be repeated. RESULTS: Eight patients were excluded after randomization. The mean+/-SD dose of propofol used in group 2 (0.81 mg/kg +/- 0.49) was significantly less than the dose used in group 1 (1.17 mg/kg +/- 0.81) and that used in group 3 (1.18 mg/kg +/- 0.60) ( P < 0.01, one-way analysis of variance). The mean +/- SD pain score was also lower in group 2 (5.1 +/- 2.5), compared with the pain scores in group 1 (6.2 +/- 2.2) and group 3 (7.0 +/- 2.4) ( P < 0.01, one-way analysis of variance). The mean +/- SD satisfaction score was higher in groups 1 (8.2 +/- 2.4)) and 2 (8.4 +/- 2.4), compared with the score in group 3 (6.1 +/- 2.9) ( P < 0.01, one-way analysis of variance). A majority of patients in groups 1 (73 %) and 2 (85 %) said that they would be willing to use the same mode of sedation again, compared with only 53 % in group 3 ( P < 0.01, chi-squared test). CONCLUSIONS: Visual distraction alone did not decrease the dose of sedative medication required for colonoscopy. When audio distraction was added, both the dose of sedative medication required and the pain score decreased significantly. Both visual and audiovisual distraction might improve patients' acceptance of colonoscopy.

A randomised placebo-controlled trial of vaginal misoprostol for cervical priming before hysteroscopy in postmenopausal women.

OBJECTIVE: To investigate the effectiveness of misoprostol given vaginally for cervical priming before hysteroscopy in postmenopausal women. DESIGN: Double-blind randomised controlled study. SETTING: Regional hospital, Hong Kong. PARTICIPANTS: One hundred women with postmenopausal bleeding scheduled for hysteroscopy from October 1998 to September 2001 were randomly assigned to receive either misoprostol or placebo vaginally before the operation. MAIN OUTCOME MEASURES: The number of women requiring cervical dilatation, outcome of hysteroscopy and side effects of the medication were assessed. RESULTS: Forty-eight women receiving misoprostol and 48 women receiving placebo were compared. The mean degree of endocervical diameter estimated by Hegar's dilator was similar between the treatment group and the control group. A similar number of women in the treatment group and the control group required cervical dilatation. The operative times for both groups were similar. The incidence of side effects was comparable in both groups. The most common side effects for misoprostol were febrile episodes and diarrhoea. There was no cervical tear nor uterine perforation encountered in both groups. The mean duration of hospital stay in both groups were similar. Subanalysis of results were similar in women receiving vaginal medication at least five hours before the operation. CONCLUSION: Vaginal misoprostol was not shown to reduce the need for cervical dilatation in postmenopausal women. It cannot convert diagnostic hysteroscopy from a hospital procedure into an office one in postmenopausal women with tight cervical os.

Early clinical outcomes after subfascial endoscopic perforator surgery (SEPS) and saphenous vein surgery in chronic venous insufficiency.

BACKGROUND: Subfascial endoscopic perforator surgery (SEPS) has recently become popular as a minimally invasive way to treat chronic venous insufficiency (CVI) of the lower extremities. We report the early clinical outcomes of SEPS and saphenous vein surgery in a prospective series of Chinese patients who presented with severe CVI. METHODS: All patients referred to our hospital for the management of severe CVI (class IV disease or above) after January 1998 underwent SEPS using an ultrasonic scalpel in conjunction with saphenous vein surgery. All patients were followed up prospectively to assess ulcer healing, ulcer recurrence, and symptoms after SEPS. Clinical outcome was evaluated by the scoring system suggested by the Consensus Committee of the American Venous Forum on Chronic Venous Disease. RESULTS: Over a 24-month period, we performed 36 SEPS on 31 patients. Nineteen lower extremities (53%) had active or healing ulcers. Sapheno-femoral ligation was also performed in 33 limbs (92%). Four limbs (11%) developed superficial wound infection, and two (6%) had saphenous nerve dysesthesia. The mean clinical score and disability score decreased from 8.42 to 3.42 and 1.45 to 0.31 respectively, after a median follow-up of 14 months (range, 6-22) (p < 0.005). Eleven ulcers (58%) healed within 6 weeks after surgery. At 1-year follow-up, ulcer recurrence was found in two legs (11%). CONCLUSION: SEPS is safe and feasible. Early clinical results have shown a promising outcome in patients with severe chronic venous insufficiency.