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Biomedical subjects

R Vohra

Publications and source records attributed to R Vohra.

At least 37 records · Page 2Linked to original sources
PubMed1992

Purification and kinetics of extracellular phospholipase A of Salmonella newport.

Attempts were made to purify and study the kinetics of extracellular phospholipase A of Salmonella newport (6,8, eb; 1,2). The enzyme was purified by salt precipitation followed by gel filtration, using different grades of Sephadex. The enzymically active purified preparation was found to be a protein, having molar mass ranging between 43 and 67 kDa. The enzyme had a pH optimum at 7.5, giving 18.2 micrograms of lysophosphatidylcholine per mg protein. Its activity was enhanced by all metal ions except potassium, by solvents and surfactants except sodium dodecyl sulfate. It hydrolyzed the membrane phospholipids of red blood cells and was inhibitory to the growth of other microorganisms.

Chromatography, Gel↗
PubMed1992

Management of neutropenic colitis.

Neutropenic colitis is recognized as a rare complication of chemotherapy in haematological malignancies. By contrast, the complication is less well known in relationship to chemotherapy for solid malignancies. There are very few examples reported and this paper adds three further cases and reviews the literature. We emphasize that although some cases of neutropenic colitis may be managed medically, full thickness involvement of the bowel wall may lead to perforation and require surgery. The pathogenesis of this progression is discussed and it is concluded that clinical awareness is important in the diagnosis. The signs of peritonitis or septicaemia are indications for excisional surgery with the formation of a temporary ileostomy.

Adrenal Gland Neoplasms↗
PubMed1992

Fibronectin binding to gelatin-impregnated Dacron (Gelseal) prostheses.

Endothelial cell adherence to uncoated gelatin-impregnated Dacron (Gelseal) is poor but can be significantly improved by precoating with a suitable basement membrane such as fibronectin. To assess the suitability of fibronectin-coated Gelseal for endothelial cell seeding, fibronectin binding to Gelseal and its dissociation kinetics were investigated. Fibronectin binding was quantified by radiolabeling human fibronectin with iodine 125, concentrations of 10, 25, 50, 150, and 250 micrograms/ml being used to coat Gelseal at 30, 60, and 90 min of incubation. The amount of fibronectin bound was directly proportional to the concentration used and increased with time of incubation (p < 0.05). However, the percentage attachment decreased with increasing concentration (p < 0.001). The number of molecules bound per centimeter squared of graft was calculated. In the first 30 min, 75% of bound fibronectin was lost after exposure to a flow rate of 200 ml/min in a pulsatile artificial circulation; thereafter, the fibronectin-Gelseal bond was stable for up to 2 h.

Blood Vessel Prosthesis↗
PubMed1992

The response of rapidly formed adult human endothelial-cell monolayers to shear stress of flow: a comparison of fibronectin-coated Teflon and gelatin-impregnated Dacron grafts.

Endothelial cells labeled with indium 111-oxine were seeded in supraconfluent densities onto fibronectin-coated expanded polytetrafluoroethylene (ePTFE) and gelatin-impregnated Dacron graft segments. These grafts with rapidly formed endothelial-cell monolayers were then exposed to varying shear stresses at flow rates of 200 and 300 ml/min, using tissue culture medium in an artificial flow circuit. As the loss of radioactivity represented endothelial-cell loss, cell retention was calculated by the ratio of counts recorded at different time points during 2 hours of flow to initial counts. Although initial cell adherence to gelatin-impregnated Dacron graft segments was poor compared to ePTFE, once cells were attached they resisted shear stress of flow better at 200 ml/min and equally well at 300 ml/min. The cell retention on fibronectin-coated ePTFE was 55.4 +/- 12.9% at 200 ml/min and 56.5 +/- 15.2% at 300 ml/min; cell retention for gelatin-impregnated Dacron graft segments was 69.0 +/- 6.0% and 66.5 +/- 5.5%, respectively. Qualitatively scanning electron microscopy of both ePTFE and gelatin-impregnated Dacron graft segments showed patchy coverage of grafts with cells. There was preferential attachment of endothelial cells to the nodes on ePTFE, although on gelatin-impregnated Dacron graft segments, cells conformed to the Dacron fibers at different levels and directions with evidence of bridging in the gaps between individual fibers. This study shows conclusively that rapidly formed endothelial-cell monolayers on ePTFE and gelatin-impregnated Dacron graft segments resisted a shear stress of flow equal to that seen in a femoropopliteal vein graft with significant cell retention at 2 hours.

Blood Vessel Prosthesis↗
PubMed1991

Comparison of different vascular prostheses and matrices in relation to endothelial seeding.

Thin-walled expanded polytetrafluoroethylene (ePTFE), woven Dacron and gelatin-impregnated Dacron (Gelseal) vascular grafts were compared, the grafts being coated with three different matrices: collagen IV, fibronectin and preclot matrix. In addition, untreated ePTFE and Gelseal were examined. The graft segments, coated with these matrices, were incubated with radiolabelled adult human endothelial cells for 30, 60 and 90 min. Endothelial cell adherence was calculated from the ratio of radioactive counts in the grafts to counts in grafts plus supernatants. Endothelial cell attachment to untreated grafts was poor, but a suitable matrix significantly improved adherence. All three matrices tested gave good results, although preclot was best; 30-60 min incubation was sufficient for optimum cell attachment. Cell adherence to both Dacron and ePTFE was significantly better than to Gelseal. The type of prosthetic polymer and the substrate protein coating used to promote endothelial cell adherence are two important factors which may determine the ultimate success of endothelial seeding in the operating room.

Blood Vessel Prosthesis↗
PubMed1991

An anomalous right iliac artery presenting as iliac stenosis.

An anatomical anomaly of pre-aortic inferior vena cava and retro-psoas iliac artery in a 33-year-old female is reported. This patient presented with severe right leg claudication and was successfully managed by implantation of an aortofemoral graft.

Adult↗
PubMed1991

In vitro adherence and kinetics studies of adult human endothelial cell seeded polytetrafluoroethylene and gelatin impregnated Dacron grafts.

Lining the luminal surface of small diameter vascular prostheses with living endothelial cells reduces thrombogenicity, decreases infection and improves patency. In vitro adherence and kinetics studies of adult human endothelial cell seeded Polytetrafluoroethylene (ePTFE) and Gelatin impregnated Dacron (Gelseal) were performed. Endothelial cell adherence on ePTFE and Gelseal coated with collagen IV, fibronectin and preclot matrices was compared. Untreated ePTFE and Gelseal were also used. Ten graft segments in each group coated with these matrices were incubated with radio-labelled adult human endothelial cells for 30, 60 and 90 min. Labelled endothelial cells seeded in supra-confluent densities on fibronectin coated ePTFE and Gelseal grafts were used for kinetic studies. Resultant endothelial cell monolayers were then exposed to varying shear stress at flow rates of 200 and 300 ml/min in an artificial flow circuit. Endothelial cell attachment to untreated grafts was poor and a suitable matrix significantly improved adherence with fibronectin and preclot but less so with collagen. A 30 min incubation was sufficient for optimum cell attachment. Cell adherence to ePTFE was significantly better than Gelseal. Scanning electron micrographs (SEM) of ePTFE showed preferential attachment to the nodes whilst on Gelseal, cells conformed to Dacron fibres at different levels and directions. Rapidly formed endothelial cell monolayers on ePTFE and Gelseal grafts resisted shear stress of flow with significant cell retention at 2 h. There was patchy coverage of both grafts with evidence of bridging of gaps between individual fibres in Gelseal.

Blood Vessel Prosthesis↗
PubMed1991

The role of the perforated segment of the ventricular catheter in cerebrospinal fluid leakage into the brain.

Two cases of gross post-operative cerebrospinal fluid (CSF) leakage along an indwelling ventricular catheter are reported. The CSF appeared to leak through the perforations of the ventricular catheter, as well as at the site of penetration of the ventricular wall. A small or slit ventricle with high intraventricular pressure may thus be a predisposing factor for this localized CSF collection.

Catheters, Indwelling↗
PubMed1991

Acute aortocaval fistula in association with ruptured aortic aneurysm.

Eight cases of aortocaval fistula are described. In all of them operation was performed with repair of the fistula and replacement of the aneurysm by a prosthetic graft. In seven cases the cause was rupture of an atherosclerotic aneurysm but one case followed rupture of a re-entrant dissecting aortic aneurysm. A fistula is most easily recognized by the sensation of a palpable thrill over the aorta during operation together with systemic venous congestion and a high central venous pressure before aortic clamps are applied. Diagnosis of the fistula before surgery or its recognition during operation and before opening the aorta usually leads to a successful outcome.

Acute Disease↗
PubMed1991

Factors affecting limb salvage and mortality in patients undergoing femoral embolectomy.

The management and outcome of 131 acute femoral arterial occlusions in 126 patients over a period of 7 years is presented. The emboli were of cardiac origin in 82% of cases; 96% of the patients were treated with thromboembolectomy. The overall mortality rate was 26% with a limb salvage rate of 88% amongst the survivors. There was an increased risk of mortality in patients having both atrial fibrillation and myocardial infarction, saddle emboli and those having delayed embolectomy after 24 h. Only the latter was found to be statistically significant. One-third of the patients who died had a failed embolectomy. An early fasciotomy helped in preventing permanent neurological deficit in patients with compartment syndrome.

Acute Disease↗
PubMed1991

Arterial emboli to the arm.

A review of 46 episodes of arterial emboli to the arm in 44 patients is presented. Two-thirds of cases were of cardiac origin whereas subclavian artery abnormality was responsible for 14%. Thirty-six per cent had axillary occlusion, 52% had a brachial lesion, and the lesion was distal to the elbow in 11%. Of the 36 patients treated surgically, 33 retained a viable arm with a palpable radial pulse in 26. Of the ten patients with 'failed first embolectomy', six technical failures were revised successfully, retaining a viable hand in all of them. The other four failures had evidence of organized intraluminal thrombus; one had been induced by anti-thrombin III deficiency. Three of this latter group lost limbs. Because delay leads to irreversible ischaemic changes, there seems to be an understandable bias in favour of early surgical exploration in equivocal cases.

Adult↗
PubMed1990

Long-term survival in patients undergoing resection of abdominal aortic aneurysm.

The long-term survival of patients undergoing abdominal aortic aneurysm surgery is presented. Three-hundred and thirty-eight patients who presented with elective, urgent, or emergency abdominal aortic aneurysms, have been followed retrospectively for five years. We found no statistical difference in the long-term survival in these three groups of patients. As expected patients who had successful operation survived better than patients who were not offered surgery because of their poor medical condition. Interestingly, advancing years, history of myocardial infarction or hypertension did not significantly influence long-term survival.

Adult↗
PubMed1990

Management of congenital arteriovenous malformations.

Over a 6-year period, 12 patients with 14 congenital arteriovenous malformations were considered for a staged approach to include afferent vessel ligation (AVL) and/or intra-arterial embolization (IAE) and surgical excision where possible. Patients were followed for a period ranging from 3 to 60 months. Two patients had localized lesions which were completely excised. Five patients were treated by IAE followed by excision with a successful outcome in four. One patient had a transmetatarsal amputation for failed IAE. Two patients had both IAE and AVL before excision of the lesion. In one patient AVL alone was followed by a recurrence. Two patients with multiple lesions were kept under observation. It would appear that IAE and excision of an arteriovenous malformation can achieve cure or excellent palliation in most patients.

Adolescent↗
PubMed1990

Management of urgent intact abdominal aortic aneurysms.

Fifty patients with acute and urgent but unruptured abdominal aortic aneurysms were reviewed. The mortality rate was 24.3% in 37 patients having aneurysm resection and graft replacement. The mortality rate in patients developing cardiac and renal complications after surgery was 100%. Nine patients did not receive surgery and four patients had a laparotomy but did not have their aortic aneurysms repaired. Patients presenting with urgent but stable and unruptured abdominal aortic aneurysms require careful but swift assessment before surgery, and have a higher mortality than patients undergoing elective aneurysm surgery.

Aged↗
PubMed1989

Cell seeding for small diameter ePTFE vascular grafts: a comparison between adult human endothelial and mesothelial cells.

A series of experiments was performed to compare the ability of adult human endothelial and mesothelial cells to attach and spread upon ePTFE graft material. Both cell types were harvested enzymatically and grown in culture. Two types of adhesion assay were used to assess the ability of the cultured cells to attach to ePTFE either uncoated or precoated with a variety of substrate proteins. The results showed that fibronectin, laminin, type 4 collagen and preclotted blood all greatly improve the attachment rate of endothelium to ePTFE. The extracellular matrix proteins, however, give patchy cell attachment, whereas cells seeded onto preclotted ePTFE form a virtually confluent monolayer after one hour's incubation. The matrix proteins similarly improve mesothelial attachment, although in all cases attached cells remain largely rounded up, with relatively few spreading on the surface. Mesothelial attachment to preclotted ePTFE is no better than attachment to the untreated material. It would seem that a preclotted graft seeded with endothelial cells is the combination most likely to result in a confluent monolayer within one hour.

Adult↗
PubMed1989

Vascular injury after arterial catheterization.

Twenty-three cases of arterial injury after 8,208 arterial catheterizations for diagnostic or therapeutic indications at Glasgow Royal Infirmary are reviewed. Clinical presentation included haematoma formation, development of an acutely ischaemic limb or a false aneurysm. Patients with valvular heart disease are identified as a high risk group. Nine cases were managed by simple suture of the puncture site whereas thrombectomy and vein patch closure was required in 12 patients. The incidence of late complications requiring vascular reconstruction was 9%. The early recognition of complications after arterial catheterization and prompt referral to a specialized vascular unit is essential if morbidity is to be avoided.

Aged↗