An atomic force microscopy investigation of bioadhesive polymer adsorption onto human buccal cells.

Atomic force microscopy (AFM) was used to examine the buccal cell surface in order to image the presence of adsorbed bioadhesive polymers identified from previous work. Isotonic saline solution (5 ml) containing either polycarbophil (pH 7.6), chitosan (pH 4.5) or hydroxypropyl methylcellulose (pH 7.6) (0.5% w/v) was exposed to freshly collected buccal cells (ca. 48x10(4) cells/test) for 15 min at 30 degrees C. The cells were then rinsed with a small volume of double distilled water, allowed to air-dry on a freshy cleaved mica surface and imaged using contact mode AFM. Untreated cells showed relatively smooth surface characteristics, with many small 'crater-like' pits and indentations spread over cell surfaces. Cells that had been treated with all the investigated polymers appeared to have lost the crater and indentation characteristic and gained a higher surface roughness. These results suggest that polymer chains had adsorbed onto the cell surfaces. Quantitative image analysis of cell topography showed significant increases (P<0.05) in arithmetic roughness average (R(a)) for all the investigated polymer treated cells surfaces with respect to untreated control specimens. The changes in surface topography indicate the presence of adsorbed polymer, confirming previous work. This study demonstrates the suitability of AFM as a powerful and sensitive technique for detecting and imaging bioadhesive polymers present on mucosal cell surfaces.

An in vitro mucosal model predictive of bioadhesive agents in the oral cavity.

The formulation of a drug/carrier complex that can be distributed and retained for extended periods within the oral cavity would be advantageous in the treatment of local conditions. In this study, an in vitro system was developed to investigate the binding of bioadhesive macromolecules to buccal epithelial cells, without having to alter their physicochemical properties by the addition of 'marker' entities. In this innovative approach a lectin binding inhibition technique, involving an avidin-biotin complex and a colourmetric detection system, was used to evaluate polymer binding. 0.5% w/v polymer solutions in saline (pH 7.6) were left in contact with a standardized number of freshly collected human buccal cells for 15 min. The cells were then exposed to 10 mg L(-1) biotinylated lectin from Canavalia ensiformis followed by 5 mg L(-1) streptavidin peroxidase. The inhibition of lectin binding (i.e. by 'masking' of the binding site on the cell surface by the attached bioadhesive polymer) was measured and expressed as a percentage reduction in the rate of o-phenylenediamine oxidation over 1 min. From the wide range of polymer solutions screened, chitosan gave the greatest inhibition of lectin binding to the surface of buccal cells, while methylcellulose, gelatin, Carbopol 934P and polycarbophil also produced a substantial reduction. Lectin binding inhibition was also observed for a selected number of polymer solutions when screened at pH 6.2. The presence of bound chitosan, polycarbophil and Carbopol 934P on the buccal cell surface was confirmed using direct staining techniques. It was concluded that this assay can be used to detect polymer binding to the cells present on the buccal mucosa, and the information gained used in the development of retentive drug/polymer formulations.

Manual de biossegurança para o laboratório / Laboratory biosafety manual

Trata dos seguintes assuntos: normas para o plano básico do laboratório, o equipamento e o procedimento, nos diferentes níveis de biossegurança, com inclusão das instalações para os animais de laboratório; técnicas e procedimentos microbiológicos; equipamento laboratorial e seu uso; segurança em relação aos produtos químicos, ao fogo e à eletricidade; organização das medidas de segurança e treinamento; lista de controle das medidas de segurança

Infections in British clinical laboratories, 1988-1989.

During 1988-89 this continuing survey showed 18 infections in the staff of laboratories reporting from 166 centres, representing 21,756 person-years of exposure. Shigella and other bowel infections (one caused by S typhi) predominated, affecting 11 microbiology medical laboratory scientific officers. Three shigella infections originated from quality control samples. Pulmonary tuberculosis affected four workers, including two mortuary technicians, but without detected occupational exposure to Mycobacterium tuberculosis. Other infections included one caused by Brucella melitensis. Hepatitis was not reported. The sustained low level of hepatitis is encouraging and suggests a low risk to staff of bloodborne infections such as human immunodeficiency virus.

A cumulative review of studies on travellers, their experience of illness and the implications of these findings.

A cumulative review of illness experienced by 13,816 travellers returning to Scotland since 1977, shows an overall attack rate of 36%. Alimentary complaints predominated; 18% of travellers had these alone and a further 10% had other symptoms as well as their gastro-intestinal disorder. Higher attack rates were noted in those taking package holidays. Inexperience of travel, smoking, more southerly travel and younger age (particularly those between 20- and 29-years-old) were other contributing factors. A similar pattern emerged from a I year study of hospital in-patients with travel related admissions. Serological studies of 470 travellers showed that 20% had incomplete immunity to poliomyelitis; 25% of those tested (312 travellers) had serological evidence of typhoid immunisation, I.9% (of 760 travellers) had antibodies to Legionella pneumophila, 64% (5II travellers tested) had antibodies to hepatitis A, 87% (288 tested) had adequate levels of tetanus antitoxin but only 40% of the 225 travellers tested had adequate levels of diphtheria antitoxin. Amongst a subgroup of 645 travellers the travel agent was the most frequently consulted source of pre-travel health advice. This carries particular significance for the dissemination of relevant advice in view of the inadequacies found from study of the health information in travel brochures. These findings, viewed against the perspective of the continuing growth in international travel, means that travellers, the medical profession, the travel trade, health educators, global health agencies and health authorities in those countries accepting and encouraging tourists, will be required to recognise the health implications of further tourism development if this problem of illness associated with travel is to be brought under control.

Infections in British clinical laboratories, 1986-87.

During 1986-87 this continuing survey showed 15 specific infections in the staff of 235 laboratories, representing 28,524 person years of exposure. The community was the probable source of four of the five cases of tuberculosis and one of the five cases of salmonellosis. Occupational exposure was the probable cause of four infections by Shigella flexneri, three by Salmonella typhimurium, and one by S typhi, all affecting medical laboratory scientific officers (MLSOs) in microbiology. Occupational exposure was also the probable cause of one case of tuberculosis in a mortuary technician and one of probable non-A, non-B hepatitis in a medical laboratory scientific officer haematology worker. The overall incidence of reported infections was 52.6/100,000 person years (35/100,000 for infections of probable occupational origin). The highest rates of laboratory acquired infections related to MLSO microbiology workers and mortuary technicians. No additional infections were seen as a result of extending the survey to forensic laboratories.