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Biomedical subjects

G C Hunter

Publications and source records attributed to G C Hunter.

At least 91 records · Page 5Linked to original sources
PubMed1988

Assessment of the role of pancreatic proteases in human abdominal aortic aneurysms and occlusive disease.

Previous studies on the pathogenesis of abdominal aortic aneurysms have shown both elastase-like activity in the aortic wall and a decreased elastin content. The present study, using specific radioimmunoassays for pancreatic elastase 2 (IRE2) and cationic trypsin(ogen) (IRCT), investigates the concentrations of these proteases which are known to circulate in blood, in abdominal aortic aneurysms. Aortic specimens were obtained from 32 patients with aneurysms and 21 patients with atherosclerotic occlusive disease. Aortic tissue, obtained at autopsy from young adults, served as controls. Elastase-like activity was 300% and 800% higher, respectively, in aortic homogenates from aneurysms in comparison to occlusive disease and control aortic tissue. This was associated with 1.4-fold higher level of IRE2 and 2.7-fold higher levels of IRCT as compared to occlusive disease. Although there was no significant difference in the aortic collagen concentration among all 3 groups, the elastin content of aneurysmal aorta was 85% and 74% lower, respectively, in comparison to control and occlusive aorta. The results of this investigation demonstrate the presence of pancreatic elastase 2 and cationic trypsin(ogen) in abdominal aortic aneurysmal tissue and suggest that circulating pancreatic proteases contribute to the pathophysiology of aneurysms of the infrarenal aorta.

Adult↗
PubMed1988

Peripheral nerve conduction abnormalities in lower extremity ischemia: the effects of revascularization.

Peripheral nerve conduction studies were performed on 32 limbs in 25 patients to determine the incidence of peripheral nerve conduction defects and prospectively evaluate the influence of revascularization in patients with lower extremity ischemia. Ankle pressure indices improved from a mean preoperative value of 0.43 +/- 0.12 to 0.81 +/- 0.26 in patients with aortoiliac disease and 0.40 +/- 0.13 +/- 0.84 +/- 0.19 in the limbs of patients with femoropopliteal disease, P less than 0.001. When compared to controls, there were significant nerve conduction abnormalities detected in the common peroneal and posterior tibial nerves of patients with aortoiliac and femoropopliteal disease preoperatively, P less than 0.02. Postoperatively, there was no improvement in nerve conduction, amplitudes, or velocities in the common peroneal or posterior tibial nerves when compared to preoperative values. However, distal latency in the sural nerve in patients with aortoiliac disease was prolonged indicating deterioration in function. Nerve conduction abnormalities in patients with aortoiliac and femoropopliteal occlusive diseases are often present in patients with lower extremity ischemia and are not significantly improved by revascularization. These observations may indicate nonreversible changes as a result of chronic ischemia.

Adult↗
PubMed1988

Venous complications of sclerotherapy for esophageal varices.

Although endoscopic sclerotherapy is effective in controlling bleeding from esophageal varices, the effects of sclerosing agents on the extrahepatic portal and splenic veins have not previously been investigated. This study of 21 men with portal hypertension and variceal bleeding compares the morphology of the portal and splenic veins in 11 who had received endoscopic sclerotherapy versus 10 patients who did not. The mean number of injections per patient was 11 +/- 5, the mean volume of 1.5 percent sodium tetradecyl injected was 23 +/- 15 ml, and the interval between the last injection and surgery was 15 +/- 6.5 days. Among the 11 patients who had endoscopic sclerotherapy, portal vein thrombosis occurred in 4 (36 percent). Two of these patients died from acute liver failure; the other two had shunt procedures. Histologic changes included intimal thickening and medial fibrosis in seven patients, thrombus in four patients, and destruction of the venous architecture in two patients. Of the 10 patients with portal hypertension who did not have endoscopic sclerotherapy, all had medial fibrosis of the portal vein, with thrombus and intimal thickening present in only 1. These findings suggest that endoscopic sclerotherapy for esophageal varices should be used cautiously in patients who may later require a shunt. Moreover, further studies are necessary to evaluate the long-term effects of injecting sclerosing agents into the portal circulation before widespread use of prophylactic sclerotherapy can be recommended.

Adult↗
PubMed1988

Mesenteric ischemia.

Superior mesenteric artery embolism or thrombosis and nonocclusive ischemia are the most frequent causes of mesenteric ischemia. Symptoms out of proportion to the physical findings, leucocytosis, and metabolic acidosis suggest the diagnosis. A high index of suspicion, aggressive resuscitation and correction of metabolic derangements, early angiography, and operative intervention are necessary if the current high mortality rates are to be reduced.

Humans↗
PubMed1987

The etiology of symptoms in patients with recurrent carotid stenosis.

We performed 33 carotid endarterectomies in 29 patients for recurrent carotid stenosis. The interval between the initial and second operations ranged from six weeks to 11 years with a mean of 56 months. Three types of pathologic lesions were identified: (1) recurrent atherosclerosis (RA), (2) neointimal fibromuscular hyperplasia (NFH), and (3) lesions with elements of both RA and NFH (complex lesions). Histologic examination of early-recurring lesions (less than three years) revealed NFH in 17 patients and one complex lesion. Late-recurring lesions (three years or later) were due to atherosclerosis in eight vessels, NFH in four, and both RA and NFH in three. Focal neurologic symptoms occurred in 25 (76%) of 33 vessels, and an embolic source could be identified in 16 (64%) of 25 patients. Embolic events rather than reduced blood flow due to progressive stenosis are more frequent causes of symptoms in patients with recurrent carotid stenosis than was formerly believed.

Aged↗
PubMed1987

Aortic ascorbic acid, trace elements, and superoxide dismutase activity in human aneurysmal and occlusive disease.

Altered trace elements and ascorbic acid metabolism have been implicated in the pathogenesis of atherosclerotic cardiovascular disease. However, their role in the disease process, or the effect of atherosclerosis on their tissue levels within plaque, is poorly understood. The present study analyzes the concentrations of Fe, Cu, Zn, and Mn, and ascorbic acid and superoxide dismutase (SOD) activity in tissue samples from 29 patients with abdominal aortic aneurysms (AAA) and 14 patients with atherosclerotic occlusive disease (AOD). It was observed that the Fe and Mn concentrations in AAA and AOD tissue were higher than the levels in nondiseased control aorta, whereas Cu and Zn levels in AAA and AOD tissue were similar to the levels in controls. The Zn:Cu ratio was significantly lower in the AAA tissue in comparison to both AOD and control tissue. In addition, AAA and AOD tissue had low ascorbic acid levels and low Cu,Zn-SOD activity with Cu,Zn-SOD:Mn-SOD ratios of 0.27 and 0.19, respectively, compared to a ratio of 3.20 in control aorta. These data indicate that aorta affected by aneurysms and occlusive disease have altered trace element and ascorbic acid concentrations, as well as low Cu,Zn-SOD activity. Although these observations do not directly support the hypothesis that AAA is associated with aortic Cu deficiency they do suggest a role for oxygen radicals or increased lipid peroxidation in occlusive and aneurysmal disease of the aorta.

Adult↗
PubMed1986

Anesthetic, preoperative and postoperative considerations for liver transplantation in swine.

Perioperative care and anesthetic management of donor and recipient animals are crucial factors in studies involving experimental liver transplantation in the pig. Prevention of unacceptably high morbidity and mortality in the transplant recipients requires meticulous attention to anesthesia, preoperative and postoperative care. Liver transplant surgeries were performed using 15 pairs of pigs. Six of the transplant recipients were anesthetized with halothane plus 50% nitrous oxide (N2O) and oxygen (O2), and nine with isoflurane plus 50% N2O in O2. Arterial blood pressure, total anesthetic time, time of interruption of vena cava blood flow, and fluids administered, as well as length of survival were among the parameters measured and compared for the two groups. No deaths were attributed to either anesthetic technique. However, the isoflurane group had slightly higher blood pressure intraoperatively, better long range survival, and relatively rapid recoveries when compared to the halothane group. Because of these findings and the reported low rate of isoflurane metabolism and low resultant potential for formation of toxic metabolites when compared to halothane metabolism, we have elected to use the isoflurane-50% N2O regimen for this procedure.

Anesthesia↗
PubMed1985

Orthotopic porcine liver transplantation: operative technique.

Considerable interest in experimental liver transplantation has been generated recently due to improvements in the results of clinical liver transplantation efforts. An operative technique for orthotopic porcine liver transplantation is presented which represents modifications of and improvements to previously published techniques. Salient features of the technique include (1) use of a diaphragmatic cuff for the suprahepatic inferior vena cava anastomosis, (2) use of a splenojugular shunt, (3) omission of caval shunts, and (4) use of isoflurane as the primary anesthetic agent. This operative technique has provided excellent survival rates in our transplanted animals.

Animals↗
PubMed1984

Arterial wall thromboxane: dominance after surgery predisposes to thrombosis.

Ibuprofen reduces early occlusion and surface thrombogenicity of small-diameter polytetrafluoroethylene (PTFE) grafts in sheep. The following experiments were designed to determine the effects of cyclooxygenase inhibition by ibuprofen on long-term patency and arterial wall and graft neointima prostaglandin synthesis. Crossover PTFE grafts (internal diameter 4 mm) were interposed between the carotid arteries of 18 sheep. Nine animals were used as controls, and nine received ibuprofen, 10 mm/kg intravenously, 1 hour prior to surgery and then every 8 hours for the duration of the experiment. Grafts were removed either when they became occluded or routinely at 60 days. Arterial segments adjacent to anastomoses were removed at graft insertion and at graft removal for assay of arterial wall production of the prostaglandins 6-keto-PGF1 alpha and thromboxane B2 (TxB2). There was no difference in patency between control animals (four out of nine) and ibuprofen-treated (five out of nine) animals. Arterial segments removed before the administration of ibuprofen produced 2.59 +/- 1.48 nM/mg protein/20 min of 6-keto-PGF1 alpha and 2.59 +/- 1.38 nM/mg protein/20 min of TxB2. A single dose of ibuprofen reduced the levels of 6-keto-PGF1 alpha to 0.30 +/- 0.12 nM/mg protein/20 min and the levels of TxB2 to 0.78 +/- 0.41 nM/mg protein/20 min (p less than 0.01). When the grafts were removed, control animals showed a reduction of 6-keto-PGF1 alpha to 1.69 +/- 0.86 nM/mg protein/20 min, whereas TxB2 levels remained unchanged at 2.54 +/- 1.23 nM/mg protein/20 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Recurrence of femoral anastomotic aneurysms.

Forty-two noninfected femoral anastomotic aneurysms that occurred after aortobifemoral bypass were repaired during a 7 year period. Twenty of these were recurrent aneurysms. In an attempt to define the cause of recurrence, a number of factors were studied including infection, suture failure, graft deterioration, defective graft manufacture, graft dilatation, and arterial degeneration. Five grafts in the primary group failed because of inherent defects in the graft structure. Two lightweight Dacron grafts showed generalized graft dilatation, and three unwrapped expanded polytetrafluoroethylene grafts had linear tears at the anastomosis. We believe that such graft degeneration does not represent a current problem because the polytetrafluoroethylene grafts now used are reinforced, and lightweight Dacron grafts are no longer made. Two primary femoral anastomotic aneurysms resulted from broken polypropylene suture. No infections were found in the primary or recurrent groups of aneurysms. Arterial degeneration adjacent to the anastomosis, consisting of a decrease in wall thickness due to loss of smooth muscle with proliferation of elastic fibers and disruption of elastic laminae, was a consistent finding in the remaining 15 primary femoral anastomotic aneurysms and all recurrent femoral anastomotic aneurysms. In many instances of primary femoral anastomotic aneurysm and in all instances of recurrent aneurysms dilatation of the Dacron graft with secondary arterial degeneration was believed to be the cause of aneurysm formation. Graft dilatation without fiber deterioration is an inherent problem in Dacron grafts and reportedly varies from 10 to 50 percent of the original graft diameter. This dilatation plus the use of initial graft diameters larger than the host artery leads to increased tension at the anastomotic site with subsequent arterial degeneration. For the aforementioned reasons, our current practice and recommendation is that repair of all anastomotic aneurysms be with expanded polytetrafluoroethylene grafts sized to approximate the host artery since its dilatation at sites of arterial pressure is minimal.

Adult↗
PubMed1982

Vascular manifestations in patients with Ehlers-Danlos syndrome.

Ehlers-Danlos syndrome (EDS) is clinically and genetically a heterogenous disorder of connective tissue synthesis. Seven clinical types of this disease have been identified and the underlying biochemical defects defined in types IV through VII. Unfortunately, most patients with major vascular complications of EDS have few, if any of the commonly recognized musculoskeletal and cutaneous abnormalities. Recognition of the correct diagnosis and the application of accepted vascular surgical techniques may improve the morbidity and mortality for these patients.

Adult↗
PubMedDate not supplied

MR angiography of the foot and ankle.

To better understand the use of magnetic resonance angiography (MRA) in evaluating peripheral vascular disease, the authors studied arteries in the foot and ankle. Twenty patients with arterial occlusive disease of the lower extremity were studied with two-dimensional time-of-flight MRA, and the results were compared with those of 10 conventional x-ray arteriograms, four digital subtraction arteriograms, and three intraoperative arteriograms. The studies were reviewed and rated by three radiologists blinded to the patients' clinical history. Also, the first 16 patients were examined with MRA before and after intravenous injection of gadopentetate dimeglumine. The mean confidence levels for the reviewers' interpretations of the MRA studies were significantly higher than those for the conventional arteriograms for the medial plantar, lateral plantar, and plantar arch arteries of the feet (P < or = .005). Postcontrast MRA images were inferior to precontrast images because of overlapping of veins and arteries. Time-of-flight MRA without gadolinium can serve as a useful complementary study for evaluating patients with peripheral vascular disease in the foot and ankle.

Aged↗
PubMedDate not supplied

Effect of chronic consumption of ethanol and vitamin E on fatty acid composition and lipid peroxidation in rat heart tissue.

Lipid peroxidation products and the fatty acid composition of phospholipids were studied in the hearts of rats chronically consuming ethanol supplemented with large amounts of vitamin E. Ethanol representing 36% of the total calories was ingested for 7 weeks in a modified Lieber-DeCarli liquid diet that contained vitamin E at 30 IU/L in the control or 172 IU/L in the supplemental dietary group. Ethanol and/or vitamin E did not change the absolute content (micrograms per mg of phospholipids) of the main fatty acids (C18:0, C18:2, and C20:4) of heart phospholipids but increased the amount of the minor C20-C22 fatty acids. Cardiac phospholipid levels increased in rats chronically consuming excess vitamin E and/or alcohol. Chronic ethanol consumption caused elevations of the relative content (percent of total fatty acids) of tri-, tetra-, and hexaenoic acids and peroxidizability index (PI) of the cardiac phospholipids. Supplementation with vitamin E blocked this ethanol-induced shift in the fatty acid profile toward unsaturation and decreased the PI. Ethanol enhanced accumulation of vitamin E in heart tissue by 30% irrespective of the vitamin E content in the diet. Enrichment of the diet with vitamin E coincided with the low levels of fluorescent products in heart lipids. A positive correlation (r = 0.36; p = 2%) was found between vitamin E and diene conjugates in the heart cells. Thus, vitamin E has a stabilizing effect on heart phospholipids by preventing changes in their fatty acid composition and peroxidative deterioration.

Alcoholism↗
PubMedDate not supplied

Correlation of ophthalmic findings with carotid artery stenosis.

Patients presenting with symptoms suggestive of amaurosis fugax, or with findings of Hollenhorst plaques on fundoscopy are frequently referred for duplex evaluation to detect possible carotid artery disease. To better determine the reliability of monocular visual loss and the presence of Hollenhorst plaques for predicting the presence or significance of carotid artery stenosis, we prospectively studied 66 patients with these ocular signs and symptoms. After evaluation, the patients were categorized as follows: 34 of 66 (52%) patients had amaurosis fugax, 23 (35%) had asymptomatic Hollenhorst plaques, 7 (11%) had retinal artery occlusion, and 2 (3%) had venous stasis retinopathy. All patients were evaluated ophthalmologically, with carotid duplex scanning and spectral analysis. A stenosis of greater than 60% was regarded as significant. The presence of risk factors including hypertension, diabetes, a history of CVA or TIA's, tobacco use and hyperlipidemia was recorded. There were no statistically significant differences (p greater than 0.05) in the incidence of atherosclerotic risk factors between the four groups. Patients with amaurosis fugax were more likely to have a significant carotid artery stenosis than those with asymptomatic Hollenhorst plaques or retinal artery occlusion (53% vs 9% vs 0% respectively) (p less than 0.006). We conclude that routine carotid duplex scanning is indicated in all patients with amaurosis fugax in view of the frequent association with significant carotid stenosis (53%). However, the presence of Hollenhorst plaques in the absence of visual symptoms appears not to have a significant association with carotid disease and may not necessarily require routine screening unless other risk factors for carotid stenosis are present.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗