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Biomedical subjects

R S Lord

Publications and source records attributed to R S Lord.

At least 73 records · Page 4Linked to original sources
PubMed1996

Acute platelet deposition after carotid endarterectomy in sheep: vein patch compared with gelatin-sealed Dacron and polytetrafluoroethylene patch closure.

PURPOSE: Patch angioplasty is commonly used to close the arteriotomy after carotid endarterectomy is performed. The purpose of this study was to determine whether any significant variations were present in platelet deposition for different patch sizes and materials. METHOD: The study measured 111-indium-labeled uptake in the sheep to compare thrombus deposition for three different patch materials: autologous vein, gelatin-sealed Dacron, and polytetrafluoroethylene and for 6- and 12-mm patch widths. Platelet uptake was measured on the patch itself and on the artery wall that was opposite to the patch and that had undergone endarterectomy. Scanning electron microscopy was used to confirm the localization of the labeled platelets on the patch and on the surface that had undergone endarterectomy. RESULTS: Although considerable variation was seen among animals, platelet accumulation was lowest in the vein patches compared with the prosthetic patches (p < 0.01), but the deposition on the gelatine-sealed Dacron was not significantly different from that on polytetrafluoroethylene patches. Platelet deposition on the artery wall that had undergone endarterectomy was considerably less than on the patch but was higher when a synthetic patch was used rather than a vein patch (p < 0.05). CONCLUSIONS: Acute thrombus deposition after carotid endarterectomy was considerably less for vein patch closure than for synthetic patches. A 6-mm patch width caused less thrombus deposition both on the patch itself and on the artery wall compared with a 12-mm patch, but the difference was proportional to the patch width.

Animals↗
PubMed1996

No additional benefit from laser in balloon angioplasty of the superficial femoral artery.

OBJECTIVES: To evaluate the efficacy of the addition of plaque ablation by hot-tip laser to balloon angioplasty. DESIGN: Prospective randomised clinical trial. MATERIALS AND METHODS: Patients with either occlusion orf > 50% diameter stenosis less than 3 cm in length in the superficial femoral artery, and with two or three calf vessel run-off were eligible and randomised to receive either balloon angioplasty alone or with laser assistance. Treatment failure in follow-up was defined as reocclusion or recurrence of greater that 50% stenosis at the site of angioplasty. RESULTS: Ninety limbs (82 patients) were entered into the study. Forty-four patients had mild claudication, 32 more severe symptoms and 6 rest pain or ulceration. More patients with diabetes (5 of 5, p = 0.04, Fisher's exact test) and occlusions (16 of 22, p < 0.05, chi(2)) were randomised to the laser group. Initial technical success was obtained in all lesions. The median duration of follow-up was 1 year. Failure occurred in 40 limbs during follow-up. Three segments, all with initial occlusions and undergoing laser angioplasty re-occluded within 2 days, one requiring immediate thrombectomy. Another 20 limbs underwent further intervention. Overall success (+/- S.D.) (Kaplan-Meier) at 1 year was 67% (+/- 5%) and at 2 years 43% (+/- 7%). Only increased age, initial occlusion, female sex, and not smoking were significantly (p < 0.05, Cox's proportional hazards) associated with failure; on multivariate analysis, age and occlusion were the best independent predictors. There was no significant difference (p > 0.05) in outcome between limbs undergoing laser assisted balloon angioplasty and balloon alone either overall of within the stenosis or occlusion subgroups. CONCLUSIONS: This study found no significant benefit was gained by the addition of laser to balloon angioplasty and that the long term success was modest for lesions considered to be suitable for angioplasty.

Aged↗
PubMed1996

Vascular dendritic cells and atherosclerosis.

CD1a positive cells of dendritic shape were detected in the intima of human arteries by immunohistochemical investigation. Analysis of contiguous parallel sections showed that the CD1a positive cells also stained with S-100 and expressed HLA-DR. The CD1a+/S-100+/HLA-DR+ vascular dendritic cell is a type of dendritic cell which participates in atherosclerotic lesion formation. This finding has important implications for understanding atherogenesis and offers a link between immune mechanisms and atherosclerotic lesion formation.

Adult↗
PubMed1996

Structural heterogeneity and contacting interactions of vascular dendritic cells in early atherosclerotic lesions of the human aorta.

Structural heterogeneity and contact interactions of vascular dendritic cells (VDCs) in early atherosclerotic lesions of the human aortic intima were studied using electron microscopy. VDCs were identified through their ultrastructural features which were typical of dendritic cells. From their morphological characteristics, two phenotypes of VDCs (types I and II) were distinguished. VDCs were found to be distributed throughout atherosclerotic lesions, and through their processes were seen to be in contact with each other and with other intimal cells. VDCs developed multiple contacts with intimal macrophages, smooth muscle cells and foam cells. Smooth muscle cells contacting VDCs were mainly of synthetic phenotype suggesting the involvement of VDCs in the regulation of cell phenotypes. Occasionally, contacts between VDCs and lymphocyte-like cells were also observed. We speculate that through cell-to-cell contacts, VDCs are involved in immune reactions in atherosclerotic lesions.

Adolescent↗
PubMed1995

Selective inhibition of nitric oxide production during cardiac allograft rejection causes a small increase in graft survival.

Nitric oxide production is increased in allograft rejection and may have both beneficial and deleterious effects on graft function and survival. In animal models, conventional immunosuppressive agents have been shown to decrease nitric oxide production. The aim of our study was to determine what effect augmentation and selective inhibition of nitric oxide production may have on graft survival by using the model of heterotopic cardiac transplantation in the rat. L-Arginine, the naturally occurring substrate for nitric oxide production, was administered subcutaneously at 200 mg/kg/day. L-NG-monomethyl-L-arginine (L-NMMA) is a selective inhibitor of nitric oxide synthase and was administered at 500 mg/kg/day to allograft recipients from the day of operation. Endogenous nitric oxide production was quantified by analysis of urinary nitrate excretion, and time to rejection was determined by graft palpation. L-Arginine did not significantly alter urinary nitrate excretion by iso- or allografts, suggesting that nitric oxide production is not a substrate-limited process in this model. Graft survival in this group was unchanged. L-NMMA produced a small increase in graft survival from 5.1 +/- 0.1 to 6.3 +/- 0.3 days compared with control allografts (P = 0.001) and abolished the rise in urinary nitrate excretion seen with control allografts. Lower doses of L-NMMA produced dose-related decrements in urinary nitrate excretion, but did not alter graft survival. We found that allograft rejection can proceed to graft loss despite complete inhibition of the increase in nitric oxide production that occurs during untreated rejection. The small increase in graft survival suggests that nitric oxide plays a minor role as a cytotoxic effector molecule in this model of acute rejection.

Animals↗
PubMed1995

Complex abdominal and thoracoabdominal aortic aneurysm reconstruction.

Complex reconstructions of the abdominal aorta are required for aneurysms that require visceral or splanchnic revascularization, when the aorta is inflammatory or infected, when a fistula to the vena cava or bowel is present, and when the aneurysm involves the juxtarenal, pararenal segments, or the full length of the abdominal aorta. The technique for full-length abdominal and thoracoabdominal aortic reconstructions has been modified to separate the visceral and spinal cord revascularization from the body of the main graft. The visceral, renal, and intercostal arteries are not directly reimplanted into the aortic graft but rather into sidearm grafts using a patch inclusion technique. The reconstruction commences distally by anastomosing the main graft to the aortic bifurcation or to the iliac arteries as appropriate. The main graft is then anastomosed to the proximal aorta after which the aortic clamps are released to perfuse the lower limbs. The intercostal arteries are reimplanted into a posterior sidearm graft followed by visceral and renal artery reimplantation into an anterior sidearm graft. This technique reimplantation into an anterior sidearm graft. This technique reduces the period of left ventricular strain to the time taken to complete the upper aortic anastomosis. It also allows separate control of the visceral and intercostal implantations should bleeding occur, without the necessity to reclamp the main body of the graft.

Aorta, Abdominal↗
PubMed1995

Calcified deposit formation in intimal thickenings of the human aorta.

The formation of calcified deposits in intimal thickenings of human aorta was studied by electron microscopy. Microzones of calcification were detected in about 20% of fatty streaks and were located predominantly in the deep musculoelastic layer of the intima. Calcified deposits formed only on previously existing structures including extracellular vesicles and unesterified cholesterol. Calcified deposits in the musculoelastic layer of the intima localised inside altered elastin fibres, but initiating the calcification of of elastin required the prior accumulation of cholesterol esters inside elastin fibres. Co-localization of calcified deposits and elastin fibres was followed by destruction of elastin. The present study suggests that at an early stage of development is atherosclerotic lesions, calcified deposits are formed by a physicochemical process which is not strongly controlled by the intimal cells. The recognition of calcified deposits in intimal thickenings support the hypothesis that a subset of fatty streaks might progress to fibrous plaques in human atherosclerosis.

Adolescent↗
PubMed1995

Carotid-subclavian bypass and the carotid steal phenomenon.

Twelve patients with patent carotid-subclavian bypass grafts were investigated by colour flow duplex imaging to look for a carotid steal. Centre-stream peak systolic flow velocities in the common carotid arteries distal to the take-off of the bypass graft were equivalent to those in the contralateral common carotid artery. On the side of the bypass, common carotid flow proximal to the graft was almost double that on the distal side. Steal phenomena were not identified in the carotid artery either with the arm at rest or during hyperaemia. However, in two instances arm hyperaemia caused reversal of flow in the ipsilateral vertebral artery, suggesting the induction of a subclavian steal. The method of centre-stream peak systolic velocity as an index of flow confirmed that carotid-subclavian bypass can be safely carried out without depriving the cerebral circulation of the normal carotid inflow.

Aged↗
PubMed1995

Informed consent in Australia.

Recent decisions in Australian courts affirm three important principles relating to consent to therapy. First, patients must be appropriately and adequately informed. Second, the scope and detail of the information supplied should be based on the reasonable patient's need to know rather than on the actions of the reasonable doctor. Third, the doctor must take care to ensure that the information imparted is understood by the patient. This publication reviews the basis of informed consent and traditional beneficent-style consent. The occasions when beneficence is more appropriate are outlined.

Adult↗
PubMed1995

Ultrastructural recognition of cells with dendritic cell morphology in human aortic intima. Contacting interactions of Vascular Dendritic Cells in athero-resistant and athero-prone areas of the normal aorta.

Analysis of serial ultrathin sections of the human aortic intima detected a new cell yet to be described in the literature. These cells, which we have designated Vascular Dendritic Cells, appeared in contact with each other and with other intimal cells. Vascular dendiritic cells are characterised by ultrastructural features similar to those of dendritic cells, including a well developed smooth endoplasmic reticulum and the presence of several processes which were 3-5 or more times in excess of the size of the cell body. In areas of the normal aorta resistant to atherosclerosis, vascular dendritic cells were mainly localised in the subendothelial layer where they contacted both endothelial cells and smooth muscle cells. In areas of the normal aorta predisposed to atherosclerosis, vascular dendritic cells were distributed throughout the intima and the cellular interactions were altered with the vascular dendritic cells, developing multiple contacts with monocyte/macrophages and lymphocyte-like cells. Aortic areas predisposed to atherosclerosis showed the destruction of some vascular dendritic cell processes where they apposed endothelial cells. We speculate that vascular dendritic cells (VDCs) are a variety of dendritic cell and are involved in the maintenance of homeostasis in normal arterial intima. Vascular dendritic cells may be important in the development of atherosclerotic lesions, possibly through an immune mechanism.

Adolescent↗
PubMed1995

S-100 positive cells in human arterial intima and in atherosclerotic lesions.

OBJECTIVE: The presence of previously unrecognised cells has been detected during ultrastructural investigations of normal and atherosclerotic human aortic intima. These cells show many of the morphological features of dendritic cells. Because dendritic cells can be stained positively for S-100, the aim of this study was to determine whether S-100 immunoreactive cells can be detected in the arterial wall, and if so, how they are distributed in normal intima and in atherosclerotic lesions. METHODS: Paraffin sections of human aorta and carotid artery were stained with S-100 antibody, using an immunoperoxidase technique. RESULTS: In areas of the arterial wall without histological signs of atherosclerosis, S-100 positive cells were found but they were relatively few compared with the much greater numbers of S-100 positive cells showing dendritic cell morphology in atherosclerotic lesions. Different atherosclerotic lesions were found to contain different numbers of S-100 positive cells. In fatty steaks and in uncomplicated atheromatous plaques, many S-100 positive cells were present, but in complicated atherosclerotic lesions fewer such cells were found. CONCLUSIONS: Although the nature of these S-100 positive dendritic cells needs further clarification, the results suggest that these cells play an important role in the development of atherosclerotic lesions, and may represent antigen presenting dendritic cells in human arteries. If the S-100 positive cells prove to be part of the family of antigen presenting dendritic cells, the findings have important implications for understanding atherogenesis and offer a link between immune mechanisms and atherosclerotic lesion formation.

Adult↗
PubMed1994

Urinary nitrate excretion is a noninvasive indicator of acute cardiac allograft rejection and nitric oxide production in the rat.

Cytokine induction of calcium-independent nitric oxide synthase is associated with production of large amounts of nitric oxide (NO). NO is a free radical that is rapidly degraded to nitrite and nitrate. Measurement of plasma and urinary nitrate is an indirect marker of NO production and previous studies have demonstrated that plasma nitrate rises with allograft rejection. The purpose of this study was to examine the temporal relationship between the rise in urinary nitrate excretion and the onset of graft rejection, and to determine the effect of conventional immunosuppression on nitrate excretion. The heterotropic model of cardiac transplantation in the rat was used, with Brown-Norway to Lewis allografts and Lewis to Lewis isograft controls. Twenty-four-hour urine specimens were collected before and after transplantation. Urinary nitrate excretion was measured by gas chromatography/mass spectrometry. Each group was treated with (1) no immunosuppression, (2) dexamethasone (3 mg/kg), or (3) CsA (10 mg/kg) on days 0, 1, and 2. Time to rejection for untreated allografts was 5.1 +/- 0.1 days, extending to 8.4 +/- 0.5 and 9.6 +/- 0.4 days with dexamethasone and CsA treatment, respectively. There was a significant rise in nitrate excretion on days 4, 7, and 9 for control, dexamethasone-treated, and CsA-treated allografts, respectively, preceding evidence of rejection. Untreated allograft rejection was associated with a peak in nitrate excretion 8 times that of basal excretion by isografts. Treatment of the allografts with dexamethasone and CsA significantly attenuated peak nitrate excretion compared with untreated allografts with a only a 2- to 3-fold rise preceding rejection. Results indicate that allograft rejection is associated with a dramatic increase in peak urinary nitrate excretion that is attenuated by standard immunosuppressive therapy. An increase in nitrate excretion precedes evidence of graft rejection, and may serve as a noninvasive marker of graft rejection.

Animals↗
PubMed1994

Vascular surgery.

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Angioplasty, Balloon↗
PubMed1994

Extracranial arterial reconstruction for atheromatous stenotic disease.

Risk factors for stroke and for carotid stenosis in the Japanese population are reviewed and the variations between rates of carotid endarterectomy in different populations discussed. The evolution of carotid plaques and the involvement of intraplaque hemorrhage in embolism and hemodynamic inadequacy in causing focal cerebral ischemic events are described. The indications for operation are presented together with an assessment of fitness for operation, with particular emphasis on the influence of heart disease on perioperative morbidity and late survival. Combined carotid and coronary reconstruction is carried out when severe disease of both systems is present (138 patients). The technique of carotid endarterectomy involves minimal dissection posterior to the common and internal carotid arteries to avoid vagal nerve injury. The pathology and symptoms of disease of the proximal great vessel together with techniques for revascularization are also presented.

Angioplasty, Balloon↗
PubMed1994

Transverse abdominal incisions compared with midline incisions for elective infrarenal aortic reconstruction: predisposition to incisional hernia in patients with increased intraoperative blood loss.

PURPOSE: Both midline and transverse abdominal incisions are used for exposing the infrarenal aorta. Transverse incisions are said to cause less pulmonary and systemic complications, but the claimed advantages may be because most transverse incisions are extraperitoneal, whereas midline incisions are intraperitoneal. This study compares intraperitoneal transverse and midline incisions with respect to perioperative and late complications, especially incisional hernia. METHODS: Three hundred twenty-nine patients undergoing infrarenal aortic reconstruction (239 aneurysms; 90 occlusive disease) were analyzed retrospectively according to whether the abdominal wall incision was midline (154 patients) or transverse (175 patients). In all patients, the subsequent dissection was transperitoneal and not retroperitoneal. RESULTS: Perioperative survival rates and intraoperative blood loss were comparable, but the transverse incision tended to be followed by a shorter period of postoperative ileus (p = 0.07), perhaps because the small bowel was not always exteriorized during operation with transverse incisions. Mean time spent in the intensive care unit was not different between the groups, but those with transverse incisions remained in hospital 5 days less than those receiving midline incisions (p = 0.0005). When an aortic graft greater than 18 mm in diameter was used, survival was reduced compared with that after smaller grafts (p = 0.028). At 1 to 6 years follow-up in 235 patients (109 midline; 126 transverse), 35 (14.9%) incisional hernias were detected, with no statistical difference according to incision (16.5% midline; 13.4% transverse). Analysis by univariate and multivariate logistic regression showed that blood loss at operation exceeding 1000 ml increased the risk of later incisional hernia by a factor of 3.07. Wound infection increased the risk of hernia by 3.70. CONCLUSION: Excess blood loss and wound infection exerted this predisposition to incisional herniation independent of other variables.

Aged↗
PubMed1994

The blood supply of vagus nerve in the human: its implication in carotid endarterectomy, thyroidectomy and carotid arch aneurectomy.

The human vagus nerve is supplied by a distinct vagal artery and vein. The artery, which lies on the anterior aspect of the nerve, is reinforced by many small arterioles along its course. These small vessels often lie in the surgical fields in carotid endarterectomy, thyroidectomy and aortic arch aneurectomy. Damage to these vessels may damage the vagus nerve and account for inexplicable cases of vagal palsy following the above surgical procedures.

Aged↗