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Biomedical subjects

S G Barker

Publications and source records attributed to S G Barker.

At least 19 recordsLinked to original sources
PubMed1995

The influence of the adventitia on the presence of smooth muscle cells and macrophages in the arterial intima.

OBJECTIVE: To test the hypothesis that atherosclerosis may be initiated by hypoperfusion or thrombotic occlusion of the adventitial vasa vasonum. DESIGN: In a new model of atherogenesis, an early atherosclerotic lesion may be initiated by removal of the adventitia from the carotid artery of the New Zealand White rabbit, wherein lie the vasa vasorum. SETTING: Animal laboratory, University Department of Surgery and Medicine. CHIEF OUTCOME MEASURES: Immunocytochemistry was undertaken to demonstrate the presence of smooth muscle cells and macrophages within the intimal lesions. Smooth muscle cells were labelled with a monoclonal antibody designated HHF35 and macrophages were labelled with a rabbit specific, macrophage specific antibody, RAM11. CHIEF RESULTS: In rabbits fed a normal diet, at day 14, the intimal lesion was composed exclusively of smooth muscle cells. By day 28, such lesions had regressed. In rabbits fed a high cholesterol diet, at day 14, the intimal lesion was composed of a mixture of macrophages and smooth muscle cells. By day 42, the pattern of cellular distribution was such that macrophages (present as foam cells) were predominant. In the presence of persistent hypercholesterolaemia these lesions did not regress. CONCLUSIONS: This new model can produce two different cellular responses that may mimic the intimal lesions seen with re-stenosis after angioplasty or in hypercholesterolaemic man and as such, might be useful in separating out these two different pathophysiologies.

Animals↗
PubMed1995

Sporting 'groin strains': not always muscular!

A gluteal artery pseudoaneurysm presenting as a 'groin strain' following minor trauma is reported. Diagnosis was made by CT scan and arteriography. Treatment was with superselective catheterization and microcoil embolization.

Adolescent↗
PubMed1994

The adventitia and atherogenesis: removal initiates intimal proliferation in the rabbit which regresses on generation of a 'neoadventitia'.

Removal of the carotid artery adventitia from rabbits induced the formation of an intimal hyperplastic lesion. In rabbits fed a normal diet, the lesion (measured as the intimal:medial ratio) was maximal by day 14 (0.456 +/- 0.079, n = 5, P < 0.01) and thereafter, regressed towards control dimensions (0.037 +/- 0.003, n = 14) by day 28 (0.080 +/- 0.025, n = 7, P = 0.14). In rabbits fed a high cholesterol diet, the lesion was again maximal by day 14 (0.376 +/- 0.056, n = 8, P < 0.01). Although some regression was seen, the lesion persisted to day 42 (0.272 +/- 0.052, n = 8, P < 0.01). Electron microscopy and immunocytochemistry showed two types of lesion, (a) smooth muscle cell predominant on normal diet and, (b) macrophage predominant on high cholesterol diet. Smooth muscle cell predominant lesions underwent almost complete regression, whereas macrophage predominant lesions persisted. We propose that lesion formation may be initiated following the development of arterial wall hypoxia, secondary to excision of the adventitial vasa vasorum. Furthermore, we have devised a novel method to restore a highly vascular 'neoadventitia' to an artery whose adventitia has previously been removed, using loosely placed PVC tubing. We suggest this 'neoadventitia' was able to inhibit the formation of an intimal hyperplastic lesion and to promote regression of an already established lesion by restoring arterial wall oxygenation.

Animals↗
PubMed1993

[125I]-endothelin-1 binding to vasa vasorum and regions of neovascularization in human and porcine blood vessels: a possible role for endothelin in intimal hyperplasia and atherosclerosis.

The distribution of [125I]-endothelin-1 (ET-1) binding sites on human and porcine vessels was studied with in vitro receptor autoradiography. Binding to normal human saphenous veins was compared to atheromatous veins used as coronary artery bypass grafts. Binding to porcine vessels, from an experimental model of intimal hyperplasia, was also studied. There was dense binding of [125I]-ET-1 to smooth muscle of all vessels examined, as well as to the vasa vasorum and regions of neovascularization of diseased vessels. Binding to microvasculature (vasa vasorum and regions of neovascularization) is of particular interest, because ET-1 has been shown to have mitogenic activity on vascular smooth-muscle cells in culture and microvessels are extremely sensitive to the constrictor effect of ET-1. Binding of [125I]-ET-1 to vasa vasorum of normal blood vessels and to regions of neovascularization of atheromatous vessels suggests that ET-1 plays a pathophysiologic role in atherosclerosis.

Animals↗
PubMed1993

Arterial intimal hyperplasia after occlusion of the adventitial vasa vasorum in the pig.

Oxygenation of the arterial wall is provided by diffusion of oxygen outward from the main vessel lumen and inward from the adventitial vasa vasorum. In a group of four Yucatan miniature pigs the oxygenation profiles across the superficial femoral arteries were recorded by polarographic oxygen microelectrodes. The profiles obtained suggested a relatively poorly oxygenated media (a trough value of approximately 25% that of the intimal oxygenation) with a progressive rise in oxygenation toward the intimal and adventitial surfaces. In four other survival experiments, occlusion of the adventitial vasa vasorum by flush ligation of the arterial branches that supply them resulted in the production of a focal, intimal hyperplastic lesion that was absent in control vessels (intimal to medial ratios [mean +/- SEM] of 0.053 +/- 0.008, n = 8, p < 0.001 and 0.013 +/- 0.001, n = 8, respectively). By electron microscopy this lesion was seen to be composed mainly of smooth muscle cells. This evidence would support the hypothesis that arterial wall hypoxia may be involved in the initiation of intimal hyperplasia. It is proposed that human atherosclerosis may be initiated by occlusion of the vasa vasorum and concomitant hypoxia.

Animals↗
PubMed1992

The vasa vasorum of the rabbit carotid artery.

The anatomy of the vasa vasorum of the carotid arteries was assessed by light and electron microscopy in a series of 25 New Zealand White male rabbits. The low viscosity acrylic resin, LR White, was used to cast the microvasculature. The carotid artery was found to have an endothelial monolayer placed directly upon a broad fenestrated internal elastic lamina. The media consisted of 12-18 laminae comprised of smooth muscle cells, elastin, collagen and ground substance. Vasa vasorum were confined to the adventitial layer, with no penetration into the media. They arose directly from the lumen of the carotid artery in addition to the arterial branching points. The potential role of the vasa vasorum in the aetiology of atherosclerotic plaques is discussed.

Animals↗
PubMed1991

Small bowel function after aortic surgery.

One cause of post-operative morbidity in the elective repair of abdominal aortic aneurysms is the development of a paralytic or 'adynamic' ileus. In a series of 20 consecutive patients undergoing such a procedure, the maintenance of small bowel motility and absorptive capacity in the immediate post-operative period was assessed using barium sulphate and xylose passed down a naso-duodenal tube sited at the time of surgery. This simple study demonstrated that small bowel function was preserved in all cases, and hence that patients could be fed enterally via naso-duodenal tube (in particular using very low residue formulae) rather than using costly parenteral regimens, should an ileus persist.

Aorta, Abdominal↗
PubMed1990

Self protection in surgery: the use of double gloves.

This study assesses the perforation rate of single and double gloves and thus the extent to which double gloving protects the surgeon from diseases transmissible from the patient. We have also investigated whether double gloving offers the patient extra protection by reducing wound sepsis. Two hundred adult hernia repairs were performed, the first 100 single gloved and the second 100 double gloved. Glove perforation rates were not significantly different between single gloves and the outer of the double gloves. Although 46 of 400 outer gloves were perforated there were only 15 inner glove perforations and only eight of these matched the outer perforations. The percentage of operations in which the latex protective barrier was breached was reduced from 31 per cent when the surgeon wore single gloves to 8 per cent with double gloves. Wound sepsis was not increased by glove perforation nor reduced by double gloving. While careful technique remains mandatory we conclude that double gloving offers increased protection to the surgeon operating on high risk infectious cases.

General Surgery↗
PubMed1988

Surgical glove perforation.

In a study to investigate the incidence and significance of surgical glove perforation, bacterial contamination of surgeons' hands and gloves before and after operation was measured and the gloves tested for damage. Perforations were found in 74 of 582 gloves (12.7 per cent) and occurred in 34.5 per cent of operations. Glove perforation did not influence bacterial counts on the surgeons' hands or on the outside of their gloves. A separate clinical study of 100 adult hernia repairs gave no evidence that perforation increased wound sepsis. After standard pre-operative hand preparation, glove perforations are of no clinical significance to the patient, but their high incidence should alert surgeons to the need for protection against pathogens transmissible during surgery, such as hepatitis B and the human immunodeficiency virus. Protection of the surgeon is the main indication for preoperative change of damaged gloves.

Equipment Contamination↗