Effect of opioids on oral Salmonella infection and immune function.
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3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
Biomedical subjects
A C Wan
Publications and source records attributed to A C Wan.
Fabrication of poly(phosphoester) nerve guides by immersion precipitation and the control of porosity.
Immersion precipitation was employed as a method for the fabrication of polymeric conduits from P(BHET-EOP/TC), a poly(phosphoester) with an ethylene terephthalate backbone, to be applied as guidance channels for nerve regeneration. Coatings of various porosities could be obtained by immersing mandrels coated with a solution of the polymer in chloroform into non-solvent immersion baths, followed by freeze or vacuum-drying. The porosity of the coatings decreased with an increase in polymer molecular weight, drying time before precipitation and concentration of polymer solution. The effects of these parameters can be rationalized by employing ternary phase diagrams, where porosity is directly related to the degree of phase separation available to the system before gelation occurs. To afford improved porosity control, a new system was developed which employed the contrasting phase-separation behavior of P(BHET-EOP/TC)/chloroform solution in methanol and water. As water is essentially a non-solvent for the polymer, the demixing boundary of the P(BHET-EOP/TC)-CHCl3-H2O system is located close to the polymer-solvent edge of the phase diagram, while that of the P(BHET-EOP/TC)-CHCl3-MeOH system is located further away. A mixture of methanol and water allows the demixing boundary to be shifted to intermediate coordinates. By immersing P(BHET-EOP/TC) coatings in immersion baths containing different ratios of water and methanol, then gradually titrating the bath with methanol to a concentration of 70% (v/v) methanol, surface porosities ranging from 2 to 58% could be achieved.
Biocompatible Materials↗
A new nerve guide conduit material composed of a biodegradable poly(phosphoester).
There is a resurgence of interest in the development of degradable and biocompatible polymers for fabrication of nerve guide conduits (NGCs) in recent years. Poly(phosphoester) (PPE) polymers are among the attractive candidates in this context, in view of their high biocompatibility, adjustable biodegradability, flexibility in coupling fragile biomolecules under physiological conditions and a wide variety of physicochemical properties. The feasibility of using a biodegradable PPE, P(BHET-EOP/TC), as a novel NGC material was investigated. Two types of conduits were fabricated by using two batches of P(BHET-EOP/TC) with different weight-average molecular weights (Mw) and polydispersity indexes (PI). The polymers as well as conduits were non-toxic to all six types of cells tested, including primary neurones and neuronally differentiated PC12 cells. After in situ implantation in the sciatic nerve of the rat, two types of conduits triggered a similar tissue response, inducing the formation of a thin tissue capsule composed of approximately eight layers of fibroblasts surrounding the conduits at 3 months. Biological performances of the conduits were examined in the rat sciatic nerve model with a 10 mm gap. Although tube fragmentation, even tube breakage, was observed within less than 5 days post-implantation, successful regeneration through the gap occurred in both types of conduits, with four out of 10 in the Type I conduits (Mw 14,900 and PI 2.57) and 11 out of 12 in the Type II conduits (Mw 18,900 and PI 1.72). The degradation of conduits was further evidenced by increased roughness on the tube surface in vivo under scanning electron microscope and a mass decrease in a time-dependent manner in vitro. The Mw of the polymers dropped 33 and 24% in the Type I and II conduits, respectively, in vitro within 3 months. Among their advantages over other biodegradable NGCs, the PPE conduits showed negligible swelling and no crystallisation after implantation. Thus, these PPE conduits can be effective aids for nerve regeneration with potential to be further developed into more sophisticated NGCs that have better control of the conduit micro-environment for improved nerve regeneration.
Animals↗
Acid-base complex reactions in resin-modified and conventional glass ionomer cements.
Resin-modified glass ionomer cements are a recent development in which the desirable properties of glass ionomer cements and resin-composites are combined. The presence of resin may, however, retard the acid-base reaction of the ionomer component. This has led to a debate regarding the classification of resin modified materials as true glass ionomer cements, and the actual duration of the acid-base reaction after initial setting via light polymerization has taken place. To investigate this issue, a novel method employing FT-IR spectrophotometry was used to monitor the acid-base complexation reaction in a resin-modified glass ionomer cement (Fuji II LC) and a conventional, chemically cured cement (Fuji II Cap). This method involved subtraction of the background "resin" spectrum from the Fuji II LC spectra and subsequent application of a baseline to obtain the plot of absorbance area ratio in the range of 1685 to 1510 cm(-1) (complexed carboxyls) to that in the range of 1750 to 1685 cm(-1) (free carboxyls). This study demonstrates evidence of a delayed acid-base reaction for the resin-modified cement, which levels off after 168 hours of cement mixing. In contrast, the complexation reaction of the conventional glass ionomer cement was essentially complete after 24 hours.
Glass↗
Rigid videosigmoidoscopy vs conventional sigmoidoscopy. A randomized controlled study.
BACKGROUND: Not only is rigid sigmoidoscopy uncomfortable for patients, but visualisation of the rectosigmoid junction and sigmoid colon is successful in only 40-70% of examinations. A novel fine-bore rigid videosigmoidoscope is described and then compared with a rigid conventional sigmoidoscope for patient discomfort and length of insertion. METHOD: A total of 58 patients were examined with both sigmoidoscopes in a random order. Discomfort was scored on a visual analogue scale; length of insertion was scored by the surgeon. Patients were blinded to which sigmoidoscope was being used. The images from the video examination were transmitted in real time for a second opinion in a different hospital. RESULTS: The mean (SD) insertion distance of the videosigmoidoscope was 23.2 (5.9) cm, which was significantly further than with the conventional sigmoidosocpe 16.5 (3.8) cm (p < 0.01). The discomfort on a visual analogue score for the videosigmoidoscope was 3.0 (1.8), which was significantly less than for the conventional sigmoidoscope 5.5 (2.7) (p < 0.01). The five users of the equipment (four surgeons and one colorectal nurse practitioner) preferred the videosigmoidoscope for image quality and ease of examination. CONCLUSIONS: A thinner, longer, rigid videosigmoidoscope is a more effective means of looking at the proximal sigmoid colon. Despite being inserted further, it caused less discomfort than the conventional sigmoidoscope. High-quality video images can be recorded or transmitted for real-time teleconsultation.
Humans↗
Undergraduate surgical teaching utilizing telemedicine.
OBJECTIVES: To evaluate the concept of a new telemedicine orientated educational application by exposing junior medical students to surgical teaching via video-conferencing from the operating theatre and comparing this to the traditional method currently employed, which requires the presence of students in the operating room. To determine student satisfaction with this novel method and identify deficiencies associated with traditional surgical teaching. DESIGN: Students were connected by video-conferencing equipment 2 Mbit/s permanent virtual circuits that provided two-way picture and voice communication. Traditional tutoring involved students attending the operating theatre in set numbers. Video recordings were made during the telemedicine transmission for highlighting important factors relevant to the operative procedure. A questionnaire was used to assess the quality of time spent and information obtained by the students. SETTING: Telemedicine centre and operating theatre, St Mary's Hospital, London. SUBJECTS: Junior clinical students. RESULTS: The median score for surgical teaching utilizing video-conferencing was 9 (scale 0-10) compared to 5 for traditional operating theatre surgical teaching. All 46 (100%) subjects indicated a willingness to return for the telemedicine influenced method of tutoring compared to 65% of students exposed to the conventional method. CONCLUSIONS: Our early experience with telemedicine assisted surgical teaching indicate high acceptance and satisfaction rates by clinical students. Further studies to evaluate the objective gain in knowledge associated with this method is required prior to its implementation in any future medical curriculum.
Consumer Behavior↗
Sigmoidoscopy in a nurse-practitioner community clinic using telemedicine.
We evaluated the feasibility of remote endoscopy in a community setting. Realtime teleconsultation and telesigmoidoscopy were carried out by a nurse practitioner at a community clinic while a colorectal specialist was present at the main hospital. Rigid video-sigmoidoscopes were used and the images were transmitted via ISDN lines at 384 kbit/s. Over three months, 32 patients (mean age 35 years; 19 men and 13 women) with bleeding per rectum took part in the study. Evaluation was carried out using satisfaction questionnaires for the patients, the nurse practitioner and the clinicians. The mean grade for clarity of intraluminal views was 3.5 (1 poor, 4 excellent). Only two cases had views graded less than 3, due to the presence of excessive faecal residue. All the patients were satisfied with the teleconsultation and video-endoscopy and would return for a similar visit. User satisfaction was also high on the part of the nurse practitioner and the clinician.
Adult↗
Realtime remote consultation in the outpatient clinic--experience at a teaching hospital.
We used an outpatients' telemedicine clinic to evaluate remote consultation in a London hospital practice. Video-images were relayed by ISDN at 384 kbit/s between the main hospital site and the sister hospital. Teleconsultation was evaluated in three different specialties: pain management, orthopaedics and general surgery. Medical personnel involved in the consultation consisted of a resident or senior house officer at the remote site and a senior registrar or consultant at the main hospital. A total of 146 consultations was held over a six-month period in the three clinical specialties involved. Questionnaires were completed by 58% of patients and over 90% of the medical personnel involved. The mean scores (on a five-point Likert scale) for physician satisfaction at the main and distant site were 3.6 and 3.8, respectively. On a scale of 0-10, 92% of patients rated the consultation 8-10 and 90% indicated that they would return for a similar consultation. Seventy-three per cent felt that a similar consultation from their referring doctor would have been appropriate. Confidence in the diagnosis was high among the specialists at the main hospital site.
Computer Systems↗
Use of telemedicine in undergraduate teaching of surgery.
Telemedicine as an undergraduate teaching method was evaluated by exposing medical students to outpatient videoconferencing. Forty clinical students on a 10-week surgical rotation participated in the study. Telemedicine sessions involved videoconferencing from the general surgical outpatient department located in a sister hospital 8 km away, using a roll-about system connected by ISDN at 384 kbit/s. A questionnaire was used to assess the quality of time spent and educational information obtained by the students. On a scale of 0-10, the students gave an overall rating of 9.7 for outpatient teaching using telemedicine. All 40 students indicated a willingness to return for similar teaching sessions. Even though the results were encouraging, an objective assessment of the knowledge gained by the students is required before the inclusion of this teaching technique in an existing medical curriculum can be recommended unequivocally.
Attitude↗
Preparation of a chitin-apatite composite by in situ precipitation onto porous chitin scaffolds.
Composites of chitin with calcium phosphate were obtained by in situ precipitation of the mineral from a supersaturated solution onto chitin scaffolds. The chitin scaffolds were obtained by freeze drying to give a highly porous structure possessing a polar surface favorable for apatite nucleation and growth. THe extent and arrangement of calcium phosphate deposits on the chitin and substituted chitin scaffolds were explored. Up to 55% by mass of calcium phosphate could be incorporated into chitin scaffolds. Deposits on the chitin surface were a continuous apatite carpet nature while deposits on carboxymethylated chitin surfaces displayed a spherical morphology. Carboxymethylation of chitin exerts an overall inhibitory effect towards calcium phosphate deposition, but it provides for site-specific nucleation of the mineral phase. In situ precipitation can be an important route in the future production of various polymer-calcium phosphate composites.
Apatites↗
Hydroxyapatite modified chitin as potential hard tissue substitute material.
Calcium hydroxyapatite (HA) powder was incorporated into chitin solutions to form an intimate mixture. Upon casting of this mixture into molds of fixed dimensions with subsequent removal of solvent, HAs containing chitin flexible plates were produced. The amount of (HA) was varied from 10 to 50% by mass of HA. The elastic modulus, yield stress, and elongation to fracture, measured at a crosshead speed of 5 mm/min, of these HAs containing chitin flexible plates were evaluated. The amount of HA in the HA incorporated chitin was found to not significantly change the elastic modulus or elongation to fracture. However, a decrease in the maximum tensile stress with an increase in the HA content was found.
Biocompatible Materials↗
Promotion of calcification on carboxymethylchitin discs.
A series of water-insoluble carboxymethylchitin (CM-chitin) discs of varying degrees of substitution (d.s.) has been investigated for their interaction with calcium phosphate. Discs of d.s. 0.03, 0.11, 0.14 and 0.23 were prepared by casting from solutions of CM-chitin in 90% formic acid. Calcium uptake and calcium phosphate nucleation were found to increase with the degree of substitution of the CM-chitin discs. The results suggest that water-insoluble CM-chitin may be useful as a platform for in vivo calcification.
Analysis of Variance↗
The menisco-femoral ligaments.
The menisco-femoral ligaments were studied in 60 knees from 30 dissecting room cadavers. The anterior horns of the menisci were attached to the intercondylar area of the femur by discrete antero-medial or antero-lateral menisco-femoral ligaments, separate from the anterior cruciate ligament, in 15% of knees for each meniscus, more frequently than previously appreciated; these anterior horn ligaments may exacerbate a meniscal tear. The posterior horn of the lateral meniscus was connected with the intercondylar area of the femur in 100% of knees. In 93% of knees a ligament ran behind the posterior cruciate ligament while in 33% of knees a ligament ran in front of the posterior cruciate ligament. We propose renaming these the pre-cruciate postero-lateral menisco-femoral ligament and post-cruciate postero-lateral menisco-femoral ligament, respectively, to avoid confusion with the ligaments of the anterior horns. The menisco-femoral ligaments may function in controlling movement of the menisci, especially during rotation of the knee. The posterior horn of the medial meniscus has no direct femoral attachment and this may be a factor in the increased risk of injury to this meniscus.
Anterior Cruciate Ligament↗