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Biomedical subjects

A Marston

Publications and source records attributed to A Marston.

At least 19 recordsLinked to original sources
PubMed1992

An immunohistochemical study of mesothelial cell seeding for knitted Dacron.

Six greyhounds underwent bilateral femoral artery replacement with knitted Dacron, one side seeded with omental digest at graft preclotting, the other acting as an unseeded control. Grafts were removed at 24 hours and two months. Tissue was examined using a monoclonal antibody (MNF116) directed against a broad range of human cytokeratins to differentiate mesothelial cells (MC) from microvascular endothelial cells (MEC), which stained only with a polyclonal antibody directed against von Willebrand Factor (anti-vWF). Cells released from omentum by collagenase stained with MNF116 and reacted poorly with anti-vWF. Identical cells were observed to be within the interstices of seeded but not control knitted Dacron. Few remained in seeded grafts (n = 2) removed at 24 hours and none at two months (n = 4).

Animals↗
PubMed1989

Laser angioplasty with a pulsed NdYAG laser: early clinical experience.

Since December 1986, 40 laser angioplasty procedures have been performed using the energy from a pulsed NdYAG laser, delivering near infrared light (1064 nm) in 100-microseconds pulses of approximately 300 mJ per pulse, directly through a transparent sapphire tipped device. All patients had total occlusion of the superficial femoral artery and symptoms severe enough to warrant surgery, with ulceration or gangrene in eight, rest pain in 14 and severe claudication interfering with life-style in the others. The device was introduced through an antegrade puncture of the superficial or common femoral artery and laser recanalization was followed by attempted balloon angioplasty in all cases. Occlusions were a median length of 15 cm (range 2-35 cm); ten patients had previously undergone failed attempts at conventional balloon angioplasty and four had occluded femoropopliteal grafts. Thirty-seven legs of 34 patients were treated with an average of 60 J (range 10-235 J) with successful recanalization in 27 and immediate reocclusion in seven. The 20 successful recanalizations have been followed up for up to 24 months (median 7 months) with only one late occlusion at 5 months. Failed recanalization was due to poor transmission by the delivery device in the early part of the series (five cases), repeated passage of the device down a collateral branch (four cases), dissection at the site of previous surgery (two cases) or no apparent reason (two cases). Immediate reocclusion was due to very poor run off in patients with severely ischaemic limbs (three cases) or technical difficulties with balloon dilatation (two cases). Complete symptomatic relief was obtained in all the cases of radiologically successful laser angioplasty. Early surgery was required in one case following reocclusion of the artery when an angioplasty balloon failed to deflate, and one patient suffered a skin reaction thought to be due to inadequate removal of the sterilizing solution. A different sterilizing procedure is now followed. Laser angioplasty can reduce the number of patients requiring bypass surgery and improvements in the device and access methods may reduce the number of untreatable cases.

Adult↗
PubMed1989

Assessment of a new device for laser angioplasty.

Experimental work has shown that a transparent laser device delivering pulsed energy to an artery results in a smaller area of surrounding damage than does an opaque device with a continuous wave laser. The combination of a transparent ball-tipped device with a pulsed Nd-YAG laser has been investigated. The system delivers pulses of 100 microseconds at a rate of 10 Hz and average energy of 0.5 J per pulse with an energy loss of 5-10% between the output at the laser rail and the fibre tip. The dose/response was measured and showed that on normal aorta under saline the device produces craters with a depth of 5 microns/J and 1.5 mm radius. There is a 100% increase in dose response with diseased aorta and a 50% increase when exposure is carried out under blood. The effect of a varying angle of incidence upon the arterial wall has been measured. Angulation of the device at 10 degrees from the perpendicular reduces the crater depth to 50%, as compared with a 50% reduction at 60 degrees using a bare fibre. As estimated with a thermal camera in air, the device heats up to a maximum of 50 degrees C during a 50 J exposure, compared to 110 degrees C after 5 J for the sapphire device. Artificial circulation experiments were carried out using diseased femoral vessels occluded by a ligature. The new system recanalised 100% of occlusion in straight vessels, and 40% of occlusions in curved vessels at a radius of 2.5 cm.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Management of the ischaemic leg. The modern approach.

Atheroma leading to blockage of the leg arteries is on the increase, throughout the world. Its commonest manifestation is intermittent claudication, a symptom which usually improves without treatment, provided that the patient takes regular exercise and does not smoke. It follows, that claudication on its own does not usually need further investigation. If the patient deteriorates, or develops rest-pain, then some form of arterial reconstruction will be required, and at this point an arteriogram becomes necessary, in order to decide the best method. Available techniques include endarterectomy, balloon and laser angioplasty, and bypass surgery, and the respective roles of these are discussed. If surgery becomes necessary, the best bypass is the patient's own long saphenous vein. In the event of this not being available, a synthetic tube is used. There is nothing to suggest that the more expensive synthetics have any advantage over the cheaper ones.

Humans↗
PubMed1978

Blood pressure changes in the marginal artery of the colon following occlusion of the inferior mesenteric artery.

The perfusion pressure in the marginal artery of the descending colon was measured continuously at laparotomy in eight patients and the effect of sudden occlusion of the inferior mesenteric artery recorded. Three patients with ulcerative colitis, all in their early 30s, and five elderly patients with colonic or rectal carcinoma were studied. In all patients occlusion caused an initial and marked pressure drop, which remained reduced at a critically low level in two of the elderly patients. Such a reduction in perfusion pressure is probably still insufficient to interfere with the nourishment of the terminal part of the colon provided that the systemic pressure is kept at a normal level. However, since in many patients there is a sharp drop in systemic blood pressure during the recovery phase after surgery, it appears likely that the perfusion pressure in the marginal artery may in those cases be insufficient to maintain an adequate blood flow to the colon despite the inherent tendency of "auto-regulation" in this vascular bed. The results of the present study indicate that, contrary to previous belief, ligation of the inferior mesenteric artery may increase the risk of ischaemia in the terminal part of the descending colon, leading to anastomotic dehiscence after anterior resection, or sloughing after a "pull-through" operation. This complication could probably be prevented by a more generous resection of the sigmoid and descending colon, thus reducing the length of the anastomosis formed by the arc of Riolan and by careful maintenance of an adequate blood pressure during the recovery phase.

Adult↗