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Biomedical subjects

K D Murphy

Publications and source records attributed to K D Murphy.

15 recordsLinked to original sources
PubMed2002

Grazing instabilities and post-bifurcation behavior in an impacting string.

A theoretical and experimental investigation of the nonlinear dynamic response of a periodically excited string subject to a knife-edge amplitude restraint is presented. The amplitude restraint creates an impact condition as the amplitude of the response grows. The focus of this work is on the influence of a grazing instability; this zero-velocity impact event leads to complicated, post-bifurcation behavior ranging from multifrequency, periodic motion to chaos. In addition to looking at the response numerically, parameter combinations leading to an incidence of grazing are clearly identified in the excitation force excitation frequency parameter space using a multiple scales perturbation analysis. Modeling issues, numerical difficulties, and experimental limitations are also discussed.

Motion↗
PubMed1996

Aortoiliac aneurysms: management with endovascular stent-graft placement.

PURPOSE: To evaluate endovascular stent-graft placement for management of aortoiliac aneurysms. MATERIALS AND METHODS: Balloon-expandable stents covered with polytetrafluoroethylene were placed in 11 aortoiliac lesions in nine male non-surgical candidates (mean age, 63.5 years). There were six abdominal aortic aneurysms, four iliac artery aneurysms, and one acute pseudoaneurysm from a ruptured iliac artery. Stent-grafts were dilated up to 14 mm (iliac) and 24 mm (aorta). Patients underwent follow-up computed tomography and angiography. RESULTS: Stent-grafts were successfully placed in all 11 cases. There were two complications: a ruptured iliac artery treated with placement of an additional covered stent and a lower-extremity vessel embolization and bowel infarction resulting in death. All stent-grafts remained patent without increased aneurysmal diameter. Three leaks (27%) were detected. Two leaks were treated with placement of additional covered stents. One still is asymptomatic. CONCLUSION: Endovascular treatment of aortoiliac aneurysms with stent-graft devices may be an alternative to surgery.

Aged↗
PubMed1995

Role of the eosinophil in chronic vascular rejection of renal allografts.

Obiliterative arteriopathy in chronic renal allograft rejection is caused by intimal smooth muscle proliferation accompanied by infiltration of lymphocytes, monocytes, and eosinophils. We investigated the role of the eosinophil in chronic rejection. Twenty-four allograft nephrectomies were examined for the presence of eosinophils on hematoxylin-eosin-stained sections and using epifluorescence on Fisher-Giemsa-stained sections. Among 15 cases with chronic rejection, eosinophils were detected in 14 cases (93%) with epifluorescence compared with only six cases (40%) with hematoxylin-eosin staining (P = 0.005). With epifluorescence, eosinophils were identified in the intimal, adventitial, and tubulointerstitial compartments in 73%, 80%, and 87% of cases, respectively. To examine the pathogenic relevance of the eosinophils in the vessel wall, we investigated the effect of eosinophil-conditioned medium on DNA synthesis in cultured vascular smooth muscle cells. Autofluorescent eosinophils were isolated from atopic human donors using a fluorescence-activated cell sorter. Supernatant was collected from eosinophils (1 x 10(6)/mL) cultured overnight in medium with 0.5% fetal bovine serum. Incorporation of 3H-thymidine into DNA was measured in rat and human vascular smooth muscle cells treated for 24 hours with eosinophil-conditioned medium at 1:20, 1:10, 1:5, and 1:2 dilutions. Eosinophil-conditioned medium had a significant dose-dependent stimulatory effect on DNA synthesis in both cell lines. Our results indicate that eosinophil involvement in chronic renal allograft rejection is more common than previously recognized. The stimulatory effect of eosinophil-conditioned medium on vascular smooth muscle cell DNA synthesis suggests that eosinophils may be involved in the pathogenesis of the obliterative arteriopathy characteristically seen in chronic vascular rejection of renal allografts.

Animals↗
PubMed1991

Effects of rearing diet, age at freshening, and lactation feeding system on performance.

This two-phase trial involved 83 Holstein heifers. The rearing phase consisted of two diets (alfalfa silage plus corn grain for ad libitum intake vs. corn silage plus urea for ad libitum intake) and two breeding age groups (13 vs. 16 mo). The lactation phase compared the above treatments plus two lactation feeding systems: concentrate fed individually to production versus a TMR. The heifers were assigned randomly to the rearing phase at 7 wk of age and fed their respective diets until 14 d prepartum. They were placed on preassigned lactation diets 14 d prepartum and remained on the lactation phase for 550 consecutive d. Daily gains and height at the withers were similar between forage groups during the first half of the rearing phase; in the second half, the heifers fed alfalfa silage were taller at the withers. Those fed corn silage consumed less DM and CP throughout the rearing phase and gained more BW than the heifers fed alfalfa in the latter half. There were no differences in daily gain or DMI between the breeding age groups. In the lactation phase, the group fed alfalfa for ad libitum intake consumed more DM and gave more milk during the first 90 d of lactation than heifers fed corn silage. However, after 90 d the difference in cumulative milk production was not significant. There were no differences in milk production. FCM, or DMI between breeding age groups. The cows fed concentrate consumed more DM and gave more milk during the first 90 d of lactation. By 550 d, there were no differences. Feeding high levels of corn silage can cause heifers to have lower DMI in early lactation. These differences tend to disappear during the second lactation.

Age Factors↗
PubMed1991

Compatibility of packed erythrocytes and Ringer's lactate solution.

Packed erythrocytes are frequently reconstituted with crystalloid during rapid infusion. Dilution of whole blood with calcium containing solutions, such as Ringer's lactate has been cautioned against, citing possible clot formation because of chelation of the citrate anticoagulant. We studied the compatibility of Ringer's lactate solution and citrate phosphate dextrose (CPD)-preserved packed erythrocytes to evaluate the safety of using Ringer's lactate solution as a diluent in the emergency setting. Aliquots of CPD-preserved packed erythrocytes were diluted with either Ringer's lactate or normal saline solutions in ratios between 5:1 to 1:20 (packed erythrocyte to crystalloid), incubated at room temperature or 37 degrees centigrade and examined for clot formation at intervals up to two hours. Although clotting occurred at dilutions of 1:1 (packed erythrocytes to Ringer's lactate solution) and beyond, no clot formation occurred in the clinically relevant dilutions between 5:1 and 2:1. Thirty-two additional units of CPD-preserved packed erythrocytes were diluted to hematocrit values of 35, 45, 55 or 65 per cent and passed through a 170 micron filter. Flow rates of packed erythrocytes diluted with Ringer's lactate and normal saline solutions were compared. There was no difference in flow rates between packed erythrocytes diluted with Ringer's lactate compared with normal saline solutions. Ringer's lactate solution can be safely used as a packed erythrocyte diluent in patients requiring rapid blood transfusions.

Anticoagulants↗
PubMedDate not supplied

Progestogens and Cushing's syndrome.

We report 3 patients where Medroxyprogesterone Acetate (MPA = Provera) and Megestrol Acetate (Megace) in doses used for therapy of breast cancer, caused clinical hypercortisolism and Cushing's syndrome. Studies of the toxicity of Medroxyprogesterone Acetate list the commonest adverse events at 500 mg/day as weight gain, water retention, increased blood pressure, tremor, moon face, sweating, muscle cramps, vaginal bleeding and increased appetite. Glucocorticoid-like effects are seen in up to 30% of patients treated for longer than 6 weeks with mostly large doses of the order of 1500 mg/day but Cushing's syndrome has been reported in patients taking 400 mg/day. Neither the glucocorticoid-like effects or Cushing's syndrome have been previously observed with Megestrol Acetate. In the elderly female population receiving progestogens for neoplastic disease the progestogen itself could be an appreciable cause of morbidity both by causing glucocorticoid-like effects and Cushing's syndrome but also by lack of awareness of the danger of sudden withdrawal of these compounds when the hypothalmic-pituitary-adrenal (HPA) axis is suppressed. The signs and symptoms could be easily overlooked unless appropriate testing for Cushing's syndrome is carried out. While the progestogen may have to be continued indefinitely a dose decrease may be feasible with reduction of morbidity.

Adrenocortical Hyperfunction↗
PubMedDate not supplied

Conjoined gastric and mediastinal benign cystic teratomas. Case report of a rare occurrence and review of literature.

Teratomas are embryonal neoplasms which arise from totipotential cells and contain elements from all three germ layers (ectoderm, mesoderm, and the endoderm). Simultaneous occurrence of mediastinal and gastric teratomas in infants has not been reported, although gastric teratomas extending into the mediastinum have been reported twice in literature. We report here a case in which a gastric cystic teratoma was connected to its mediastinal counterpart with a pedicle. The pertinent literature is reviewed.

Diagnostic Imaging↗
PubMedDate not supplied

Use of stents covered with polytetrafluoroethylene in experimental abdominal aortic aneurysm.

PURPOSE: To establish the effectiveness of covered stents in the treatment of aortic aneurysms, to investigate the histopathologic healing patterns of the device, and to determine the long-term endurance and integrity of modified polytetrafluoroethylene (PTFE). MATERIALS AND METHODS: Experimental aneurysms were created in dogs by enlarging the aortic lumen with a patch of abdominal fascia. After 5 months, eight animals underwent an endoluminal bypass. The bypass device consisted of a 6-cm-long stent covered with thin PTFE. After surgery, the animals were killed at 3, 6, and 12 months in groups of three, three, and two, respectively. Specimens were processed for luminal surface studies and cross-sectional histologic study. Explanted PTFE material was analyzed for its physical characteristics and performance and was compared with retained control samples. RESULTS: Before the animals were killed, aortography showed patent bypass conduits in all animals, although two of eight had leaks into the aneurysmal sac. Endothelialized neointima largely covered the luminal surface of the PTFE stent. The percentage of prosthetic surface covered by tissue did not change from 3 months to 1 year. Physical testing of the explanted PTFE material showed no structural deterioration and no change in the internodal distance. Thickness and axial tensile strength varied 12% and 17% from controls, respectively. CONCLUSION: Thin-walled PTFE seems to have physicochemical characteristics that make this material adequate for endovascular use. Though limited, this study supports the establishment of preliminary clinical evaluation of metallic stents combined with PTFE for the treatment of abdominal aortic aneurysm.

Animals↗
PubMedDate not supplied

Iliac artery stent placement with the Palmaz stent: follow-up study.

PURPOSE: The long-term efficacy of iliac artery stent placement with the Palmaz stent was evaluated for treatment of limb ischemia. PATIENTS AND METHODS: Iliac stent implantation for limb ischemia was performed on 108 limbs in 83 patients. Eighty patients (96.4%) were followed up clinically from 1 to 70 months (mean, 25.8 months), and 30 patients (37.5%) were followed up with angiography from 1 to 48 months (mean, 10.4 months). Patients were classified into six categories by using an ischemic ranking profile. Clinical success was defined as a minimum one-category improvement from preprocedure ranking. RESULTS: The clinical success rate was 98.9% immediately after the procedure and 86.2% at 48 months. Long-term success was statistically more common in patients with higher preprocedure and lower postprocedure ischemic ranking, and in patients without diabetes. Arteriography demonstrated a primary patency rate of 87.5% at latest follow-up, with five occlusions (12.5%) and only two (5.0%) restenoses. Average stenosis was 17.8% at 6 months and 24.7% at 2 years. Stent restenosis was statistically more common with a higher postprocedure pressure gradient. The complication rate was 9.7%, and 30-day mortality was 1.2%. CONCLUSION: Long-term clinical and angiographic follow-up demonstrates iliac artery stent placement with the Palmaz stent is safe and efficacious for treatment of limb ischemia.

Adult↗
PubMedDate not supplied

Heparin-induced thrombocytopenia and thrombosis syndrome.

Heparin-induced thrombocytopenia and thrombosis syndrome (HITTS) is an immune-mediated response to the administration of heparin that results in life-threatening thrombosis. The pathophysiology of HITTS remains controversial. The onset of clinical symptoms and laboratory changes is usually delayed 1-2 weeks after exposure to heparin. Thrombosis occurs in both the arterial and venous circulation with significant morbidity and mortality. Complications include deep venous thrombosis, pulmonary embolus, stroke, myocardial infarction, chronic venous insufficiency, extremity ischemia, gangrene, and death. Diagnostic criteria for HITTS include thrombocytopenia during heparin exposure, exclusion of other causes such as sepsis or medications, resolution of thrombocytopenia after withdrawal of heparin, demonstration of in vitro heparin-dependent platelet antibodies, and development of vascular thrombosis. Despite having several disadvantages, the carbon-14-serotonin release assay is the most sensitive and specific test for HITTS. Angiography as an adjunct to other imaging modalities can document the presence, location, and extent of thrombus. Optimal treatment has not yet been defined but should include immediate discontinuation of use of all heparin products and heparin-coated catheters. In addition, alternate methods of antithrombotic therapy should be considered. In severe cases, thrombolysis or thrombectomy may be warranted. Familiarity with the pathophysiology, clinical manifestations, complications, diagnostic criteria, and treatment options associated with HITTS will enable timely recognition and facilitate prompt and effective treatment.

Angiography↗