Functional abnormalities of experimental autogenous vein graft neoendothelium.

When a vein is grafted into the arterial circulation, the endothelium of the graft is damaged. Regeneration of an intact neoendothelium occurs, but the functional properties of this surface have not been clarified. In this study, the functional integrity of the neoendothelium of veins grafted into the carotid artery of the rabbit was assessed through the use of acetylcholine and histamine to stimulate the production of the important endothelium-derived relaxing factor (EDRF). Control veins, precontracted with norepinephrine [10(-5) M], relaxed after exposure to acetylcholine [( 10(-7) M], 42.4% +/- 6.4%, p = 0.008) and histamine [( 10(-6) M], 30.6% +/- 4.3%, p = 0.03). This relaxation response was abolished after mechanical removal of the endothelium. By contrast, neither acetylcholine nor histamine caused an endothelium-dependent relaxation in the vein grafts, even though scanning electron microscopy demonstrated the presence of a morphologically intact endothelium. However, addition of stabilized EDRF purified from cultured endothelial cells induced relaxation of the vein grafts (35.8% +/- 3.6%, p = 0.002). These data indicate that vein graft endothelium is unable to produce EDRF in response to exposure to acetylcholine or histamine. The inability to produce this potent smooth muscle cell relaxing factor and anti-aggregatory substance may be a predisposition to vein graft failure.     

Meniscal suture: a simple method

A simple technique of meniscal suture is described. It avoids the main problem with most other outside-to-inside suture techniques, which is that knots either have to be left inside the joint or have to be pulled out through the meniscus. These knots often come undone or damage either the joint surface or meniscus. Essentially, a suture is inserted from outside to inside through the meniscus, using a cannulated needle. The end of this suture is then pulled back out through a separate hole in the meniscus, using a suture loop inserted with another cannulated needle. The two ends of the first suture are then tied together.     

General practitioners'' views on continuing medical education.

BACKGROUND. The 1990 contract for general practitioners altered the provision of continuing medical education. AIM. This study set out to examine doctors' experiences of postgraduate education before and after the contract and their preferences for the provision of postgraduate education. METHOD. In 1991 a structured questionnaire was sent to 1959 doctors registered on the database held by the west of Scotland postgraduate office. RESULTS. An 82% response rate was obtained. Eighty eight questionnaires had to be excluded. Of 1523 respondents, 74% were entitled to study leave under the terms of their practice agreement, an increase of 15% since the introduction of the contract. When attending courses 11% reported that they always employed a locum (32% occasionally). Those who did so were more likely to be general practitioners in rural areas than in urban or mixed areas. Almost all respondents (1485, 98%) had participated in postgraduate education since April 1990. Lectures remained popular (47% of respondents indicated it was their preferred or most preferred choice) while distance learning and practice based learning were least preferred. Evening meetings and afternoon meetings were the most popular, and Wednesday and Thursday were reported to be the most suitable days for educational meetings. CONCLUSION. Organizing education for a large number of people is difficult, but individuals' preferences and difficulties have emerged which must be taken into account when doing so. In terms of attendance, postgraduate education seems to have been a success although its value in influencing quality of care is more doubtful. Perhaps the development of personal education plans may make learning more useful and relevant.     

Laser-generated acoustic emission in urological and arterial surgery

Acoustic emission from renal calculi irradiated by a pulsed dye laser was observed in vivo and investigated in vitro. A number of acoustic frequency spectra were recorded from laser exposure of ureteric calculi, calcified arterial wall and bladder tissue. Although differences were observed between spectra, these did not depend on target material. Investigations with model targets suggested that variations in acoustic emission were caused by fluctuations in the strength of the laser plasma, due to changes in the local surface absorption of laser light, and by alterations in the relative orientation of laser fibre, target and transducer. Interaction between lasers and stones is reviewed and discussed.     

Long-term effects of physiologic concentrations of dexamethasone on human bone-derived cells

Bone cells derived from human trabecular explants display osteoblastic features. We examined the modulation of alkaline phosphatase activity and cAMP production as the result of exposing trabecular explants to physiologic concentrations of dexamethasone for 4 weeks during cellular outgrowth and subculture. Cells treated with dexamethasone were observed to grow generally more slowly than control cells. Cells appeared larger and more polygonal, and staining for alkaline phosphatase was more intense in the dexamethasone-exposed cultures. There was a progressive increase in cellular PTH responsiveness with increasing duration of exposure of cells to dexamethasone. Cells grown for 6 weeks in 3 x 10(-8) M dexamethasone had a 10-fold increase in PTH-stimulated cyclic AMP accumulation. Dexamethasone-treated cells also had a significantly increased alkaline phosphatase activity. 1,25-(OH)2D3-stimulated alkaline phosphatase activity was increased approximately 20-fold. cAMP responses were significantly increased to PTH (21.7-fold), PGE1 (2.67-fold), and forskolin (4.81-fold), but not to cholera toxin. Dexamethasone-treated cells also had a mean decrease in 1,25-(OH)2D3-stimulated osteocalcin production to 26.2% of control values (p less than 0.001). Hydrocortisone treatment gave rise to similar effects but of smaller magnitude than those of dexamethasone. Testosterone did not have a significant effect on alkaline phosphatase activity or cAMP production. Skin fibroblasts showed a significant enhancement of alkaline phosphatase activity in response to dexamethasone, but of a much smaller magnitude than in bone cells. The phenotypic changes induced by long-term culture in dexamethasone are consistent with the promotion of a more differentiated osteoblastic phenotype.