Biomedical subjects

V Salih

Publications and source records attributed to V Salih.

23 records · Page 2Linked to original sources

PubMed1993

The lining of textured surfaces in implantable left ventricular assist devices. An immunocytochemical and electronmicroscopic study.

OBJECTIVE: The aim was to examine and identify some components of biological linings developed upon the textured surfaces of a circulatory assist device. The development of biological linings upon a textured surface circulatory assist device was evaluated in patients implanted for periods ranging from 84 to 132 days. METHODS: Explanted devices were examined macroscopically. Light microscopy, transmission electron microscopy and immunocytochemistry techniques were employed to evaluate the histogenesis of the tissue deposits upon the device surfaces. Visible material was essentially limited to focal areas upon the static housing and the periphery of the pusher-plate diaphragm (Biomer). RESULTS: Microscopy of the linings showed fibrin-rich areas with platelets, monocytes and few spindle-shaped surface cells. Central areas were composed of multiple layers of spindle-shaped cells separated, mainly, by collagen. Giant-cell foreign-body reaction to Biomer fibrils was seen. CONCLUSION: Transmission electron microscopy and immunocytochemistry indicated the presence of at least two cell populations: fibroblasts and smooth muscle-like cells, or 'myofibroblasts'. There was no evidence of endothelial cell presence.

Adult↗

PubMed1992

The development of an in-vitro perfusion system for studies on cultured cells.

The design and use of a perfusion system, using a modified flow chamber for studies on cultured animal cells, is described. Rat thoracic aorta smooth muscle cells were isolated by an explant method and grown on Thermanox coverslips. These were introduced into the flow chamber. A flow rate of 25ml/min and a shear stress of 14.6 dynes/cm2 (12 dyne = 10 microN) (both within physiological limits) were maintained. Cells remained attached to the coverslips after 8h of perfusion with culture medium. The effect of exposing rat smooth muscle cells to the cardiovascular toxin, allylamine, is also described. The components of the system are routinely available, simple to clean, easy to assemble and sterilize. The incorporation of an in-line sensor that monitors pH, PO2, PCO2 and temperature ensures that the perfusion conditions remain within physiological limits. Automation means that minimal supervision is required. This system provides a potential mechanism in which cultured vascular cells may be perfused under controlled haemodynamic conditions, and their response to a cytotoxin may be evaluated.

Allylamine↗

PubMed1990

Neo-intimal development on textured biomaterial surfaces during clinical use of an implantable left ventricular assist device.

Implantable left ventricular assist systems are being developed for long term clinical use. Prototype devices are currently used as extended mechanical bridges to cardiac transplantation. The Thermo Cardiosystems Inc. (TCI) pneumatic pusher plate left ventricular assist device (LVAD) features textured blood contacting surfaces to encourage the formation of an adherent fibrin-cellular coagulum. This serves as the foundation for the development of a neo-intimal lining. The TCI LVAD was implanted in 6 male patients (age range 22-53 years) between 1986 and 1988. The duration of implantation ranged from 1-41 days. No clinical thromboembolic events or pump-related thromboembolism occurred and none was evident at necropsy. The six device linings have been fully evaluated. Explanted devices were free of thrombus and calcification. Lining samples for light and electron microscopy were collected from areas of the diaphragm identical for flex and blood shear conditions and from high and low shear areas on the static housing. Islands of collagenous tissue were deposited on the static housing amongst compact fibrin. By day 13, cells populated the surface of the developing neo-intima overlying the diaphragm. By 41 days, the surface cell density increased and the cells became spindle shaped and relatively orientated in the high shear/flex area. Immunohistochemical techniques suggest that these cells are of mesenchymal origin. Textured blood contacting surfaces appear satisfactory in the preliminary clinical use of this device.

Adult↗

PubMedDate not supplied

Effects of therapeutic ultrasound on osteoblast gene expression.

Ultrasound (US) is commonly used as a physiotherapy aid for a number of types of injury to soft connective tissues and for fracture healing. However, the precise effects of therapeutic US on tissue healing processes are not clearly understood, although they are likely to involve changes in key cellular functions. The present study has therefore examined the effects of several US intensity levels on the activity of two bone-associated proteins, alkaline phosphatase (ALP) and osteopontin (OP) in a human cell line, MG63, using RT-PCR. ALP showed progressively higher expression with increasing US intensities, whereas OP responded differently, showing down-regulation at 120 mW/cm2, the lowest US exposure. OP expression was considerably less affected overall compared with the relative response of ALP to the same US doses. The results show that there is a differential response to therapeutic levels of US, since ALP and OP clearly exhibited gene-specific response profiles. These findings suggest that modifying the parameters of US exposure could be used to improve repair and regeneration processes and enhance the clinical efficacy of implanted biomaterials for tissue engineering.

Journal Article↗

PubMedDate not supplied

Development of a polyurethane percutaneous access device for long-term vascular access.

The percutaneous placement of intravascular devices creates a portal for microbial invasion that can result in local infections or septicemia. In nature, resistance to "exist site" infection in percutaneous organs, such as teeth, is prevented by a dense collagen/epithelial barrier. A new percutaneous access device has been developed that incorporates a porous polyurethane "button" at the subdermal level. This device promotes the development of a collagen/epithelial interface, thus inhibiting sinus formation. Twelve percutaneous access devices (PCADS) were implanted in calves; eight devices were utilized for venting of, and hard wire passage to, an implantable left ventricular assist device (LVAD) and served as controls. Four devices were utilized for long-term vascular access. The PCADS remained in situ for 2-127 days (mean 70). Excellent healing was apparent in all cases, and no exit site or catheter related infections occurred. Histologic examination demonstrated fibroblastic in-growth and collagen deposition within the porous polyurethane, which provides a barrier to epithelial migration and firmly anchors the device. These PCADS appear to reduce exit site infections and may improve upon currently available long-term vascular access catheters.

Animals↗