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Biomedical subjects

S Wan

Publications and source records attributed to S Wan.

82 records · Page 5Linked to original sources
PubMed1982

Platelet-compatible hydrophilic segmented polyurethanes from polyethylene glycols and cyclohexane diisocyanate.

A new type of segmented polyurethane (SPU) was synthesized from alpha, omega polyethylene oxide diols (PEG) of MW varying from 600 to 4500, by end capping with 1,4 trans cyclohexane diisocyanate (CHDI) and chain extending with ethylene diamine (ED) in toluene with dibutyl tin dilaurate as catalyst. These SPU are cast as films and coatings from hexafluroisopropanol (HFIP). Depending on PEG MW, these SPU swell two- to tenfold in water. Examined by an in vitro platelet retention test, these SPU are more bland (platelet retention -rho around 0.05) than most other polymers, whereas an alternating copolymer of CHDI and ED shows -rho around 0.80 (very active); x-ray photoelectron spectroscopy shows that the surfaces of these SPU to a depth of about 40 Ao are nearly pure PEO, unlike SPU synthesized from aromatic diisocyanates TDI and MDI.

Biocompatible Materials↗
PubMed1981

Analytical modeling for the optical properties of the skin with in vitro and in vivo applications.

Analytical modeling that interrelates the optical properties of multilayered structures is applied to the skin. The mathematical approach is based on relations of diffuse reflectance and transmittance of a multilayered system and the diffuse reflectance and transmittance of each component layer. The formula can also be derived from the Kubelka-Munk theory of radiation transfer. Using both collimated and diffuse incident irradiance, the applicability of the model to human epidermis over the UV and visible region has been verified. The model has been applied to calculate to absorption and scattering coefficients of human epidermis in vitro, and to estimate the epidermal transmittance under simulated in vivo condition.

Humans↗
PubMedDate not supplied

Does external stenting reduce porcine vein-graft occlusion via an action on vascular nerves?

BACKGROUND: Neural reorganization occurs in porcine vein grafts and placement of an external stent reduces graft occlusion. AIM OF THE STUDY: To determine the effect of external stenting on the innervation of porcine vein grafts. METHODS: Saphenous vein into carotid artery grafting (with and without external stents) was performed in 16 pigs. After one and six months, grafts were removed, nerves were counted, and neointima was assessed. RESULTS: In vein graft compared to ungrafted vein, there was a significant (p < 0.05) decrease in medial perivascular nerves, but a dramatic increase in paravascular nerves in the adventitia (p < 0.05). In stented vein grafts there was also a reduction of perivascular nerves and the paravascular nerve proliferation observed in vein grafts at one month was inhibited (p < 0.05). Neointima formation and the appearance of large paravascular nerve bundles in the adventitia of vein grafts were abolished by external stenting. CONCLUSIONS: Neural reorganization plays a role in vein-graft failure, possibly through the local release of mitogens; the prevention of this reorganization contributes to the inhibitory effect of the external stent on neointima formation.

Animals↗
PubMedDate not supplied

Giant pulmonary bulla.

The present report describes a case of a giant pulmonary bulla in a 32-year-old man that progressed to occupy almost the entire left hemithorax. This report is unique in documenting the natural history of progression of this condition. Bullectomy was performed using the video-assisted thoracoscopic surgery approach.

Adult↗
PubMedDate not supplied

Factors associated with sexually transmitted diseases among prostitutes in Singapore.

From June to December 1990, 806 prostitutes registered with the STD programme in Singapore for regular screening for sexually transmitted diseases (STD) were investigated for factors associated with STD incidence in the preceding year. The majority were foreigners (92.7% Malaysians and 3.1% Thais). Anal sex (0.4%) and intravenous drug use (0.9%) were rare. The overall STD incidence rate was 47.7 per 100. None was human immunodeficiency virus (HIV) positive. The crude and age-adjusted risk of STD was found to increase significantly with client load. An inverse relationship between condom use and STD risk was also observed. Mean condom use among clients was reported as 56.1% for spontaneous use and estimated as 75.4% following negotiation for condom use by prostitutes. Although the prostitutes negotiated for condom use with majority of the clients (85.5%) who did not use condoms spontaneously, they were successful with only about half of them (54.4%). Health education should be targeted at clients on the protective effects of condom use and at the prostitutes on skills in negotiating condom use.

Adult↗