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Biomedical subjects

D Whitley

Publications and source records attributed to D Whitley.

18 recordsLinked to original sources
PubMed2001

Mutual exclusion of apoptosis and hsp70 in human vein intimal hyperplasia in vitro.

BACKGROUND: Apoptosis of vascular smooth muscle cells (VSMC) plays a role in physiological vascular remodeling, as well as in disease states such as atherosclerosis and restenosis after angioplasty. Heat shock protein 70 (hsp70) may protect the cell against apoptosis and/or necrosis. In this study, we examined hsp70 expression and its temporal relationship to cell survival or death in a model of intimal vein hyperplasia in vitro. METHODS: Segments of human saphenous veins were placed into culture. At different days vein segments were serum-starved or exposed to heat shock. Apoptosis and hsp70 expression were analyzed by Western blot, immunohistochemistry, and TUNEL assay. RESULTS: A marked intimal vein hyperplasia developed after 14 days of culture when compared with baseline. hsp70 was present at baseline and disappeared during culture. Heating during culture could not up-regulate hsp70. The apoptotic markers were absent at baseline and present during normal culture. Conversely, serum starvation stimulated strong hsp70 expression coincidental with the disappearance of apoptotic markers. CONCLUSIONS: Stimulation of veins during culture with serum resulted in hyperplasia, apoptosis, and inhibition of hsp70 expression. Down-regulation of hsp70 may permit apoptosis and vessel wall remodeling in this model.

Apoptosis↗
PubMed2000

Psychological distress in grandmother kinship care providers: the role of resources, social support, and physical health.

OBJECTIVE: The purpose of the present study was to investigate predictors of psychological distress in grandmother kinship care providers. More specifically, it was hypothesized that social support, family resources, and physical health would predict psychological distress in grandmothers raising grandchildren. METHOD: One hundred and two grandmothers raising grandchildren in parent-absent homes completed the Brief Symptom Inventory, Short Health Form-36, Family Resource Scale, Family Support Scale, and a questionnaire requesting background and demographic data. RESULTS: Results indicated that psychological distress was predicted by family resources, participants' physical health, and to a lesser extent, social support. CONCLUSION: The findings indicate that family resources, social support, and physical health affected psychological distress in grandmothers raising grandchildren. Grandmothers who reported fewer resources, less social support, and poorer physical health tended to experience higher levels of psychological distress. This study suggests that greater attention be given to interventions aimed to decrease psychological distress and improve the financial resources and physical health of grandmothers raising grandchildren.

Adult↗
PubMed2000

Editorial Introduction.

There is exciting news! The International Society for Genetic Algorithms (ISGA) and Genetic Programming, Inc. have joined efforts, recombined, and organized a new society: The International Society for Genetic and Evolutionary Computation (ISGEC). This follows the merger of the International Conference on Genetic Algorithms and the Genetic Programming Conference into a single conference: The Genetic and Evolutionary Computation Conference (GECCO). This is exciting because the new society will have dues that include a subscription to Evolutionary Computation as well as the new journal Genetic Programming and Evolvable Machines. This will help to link Evolutionary Computation more directly to the community that founded it and to associate the journal with a large body of researchers and application developers that would appear to be its natural readership. The journal Evolutionary Computation was founded as a grassroots effort and with a spirit of cooperation that embraced all aspects of the field. The new society builds on this theme.

Journal Article↗
PubMed1999

Predicting epistasis from mathematical models.

Classically, epistasis is either computed exactly by Walsh coefficients or estimated by sampling. Exact computation is usually of theoretical interest since the computation typically grows exponentially with the number of bits in the domain. Given an evaluation function, epistasis also can be estimated by sampling. However this approach gives us little insight into the origin of the epistasis and is prone to sampling error. This paper presents theorems establishing the bounds of epistasis for problems that can be stated as mathematical expressions. This leads to substantial computational savings for bounding the difficulty of a problem. Furthermore, working with these theorems in a mathematical context, one can gain insight into the mathematical origins of epistasis and how a problem's epistasis might be reduced. We present several new measures for epistasis and give empirical evidence and examples to demonstrate the application of the theorems. In particular, we show that some functions display "parity" such that by picking a well-defined representation, all Walsh coefficients of either odd or even index become zero, thereby reducing the nonlinearity of the function.

Algorithms↗
PubMed1998

Cell-free hemoglobin preserves renal function during normothermic ischemia.

INTRODUCTION: The purpose of this study is to determine whether an infusion of polymerized hemoglobin solution is capable of suppressing the tubular damage and loss of renal function normally seen during a clinically relevant period of warm ischemia. METHODS: Male rats (350-450 g) were randomized to treatment with control (5% human serum albumin, HSA, n = 6) or test solution (9% polymerized hemoglobin, PHB, n = 6). Following a right nephrectomy, the left renal artery was perfused with 4 ml of HSA or PHB at 37 degreesC. The left renal artery was temporarily occluded for 50 min. At 72 h, creatinine (Cr), blood urea nitrogen (BUN), and percentage hemoglobin (Hb) were measured and the kidney was removed. Stained kidney sections were graded for ischemic injury (0-4, 0 = normal and 4 = necrosis of the proximal tubule). All results were expressed as means +/- SEM and statistical analysis was performed by t test. RESULTS: Treatment with PHB resulted in lower Cr (1.2 +/- 0.23 mg/dl vs 3.26 +/- 0.60 mg/dl, P < 0.01) and BUN (60.5 +/- 12.7 mg/dl vs 151 +/- 20.2 mg/dl, P < 0.01) at 72 h compared to HSA controls. Total hemoglobin was not significantly different at 72 h. The weight of all treated kidneys increased; however, the increase was significantly less in the PHB-treated group (34 +/- 9.1% vs 70 +/- 7. 4%, P < 0.01). PHB-treated kidneys had less evidence of histologic damage compared to those in the HSA group (0.75 +/- 0.11 vs 2.50 +/- 0.64, P < 0.05). CONCLUSIONS: During normothermic renal ischemia, renal artery infusion of PHB resulted in preservation of renal function and histologic architecture. PHB solutions may be useful in preserving organ function during prolonged periods of in vivo ischemia.

Animals↗
PubMed1997

Midaortic pseudoaneurysm complicating extensive endovascular stenting of aortic disease.

We report a case of successful surgical management of a potentially life-threatening complication of aortoiliac stent placement. A 59-year-old man who had Leriche syndrome underwent bilateral iliac artery and infrarenal aortic stent placement at another institution. His history was significant for retroperitoneal lymph node dissection at 19 years of age for testicular cancer. One week after stent placement, the patient was readmitted with abdominal pain, poor oral intake, and diffuse intermittent tenderness. Evaluation with computed tomographic scanning and endoscopy was unremarkable, and the patient was discharged. He was admitted to our institution 1 week later with persistent abdominal pain. A computed tomographic scan of the abdomen revealed a large pseudoaneurysm of the abdominal aorta. The patient underwent urgent exploration, and exclusion of his infrarenal aorta was achieved with aortobifemoral bypass grafting. After the operation, the patient's course was complicated by a large paraduodenal hematoma, which resulted in a gastric outlet obstruction, which was managed without operation. This case illustrates a potential life-threatening complication of extensive stent placement for aortoiliac occlusive disease. Injury to the abdominal aorta must be considered in a symptomatic patient after the placement of stents in the aortoiliac region, beyond the immediate periprocedural period.

Abdominal Pain↗
PubMed1997

To grandmother's house we go ... and stay. Children raised in intergenerational families.

An increased incidence in child abuse and neglect has resulted in a dramatic rise in the number of grandparents raising grandchildren and great-grandchildren. Grandchildren raised by grandparents often suffer from emotional and behavioral problems due to prior abuse, neglect, and abandonment. Grandparent caregivers experience increased health problems, psychological distress, and social isolation related to their roles as primary caregivers of children. Grandparents who become caregivers of grandchildren face increased financial responsibilities at a time in their lives, close to or at retirement, when income is dramatically decreased.

Aged↗
PubMed1997

Critical pathways and cost-effective practice.

With increasing pressure by third-party payers and federal reimbursement systems to reduce health care expenditures, cost-effective means to care for the resource intensive vascular surgical population must be explored. The challenge of meeting these cost-saving priorities while maintaining or improving quality of care can result in conflicting demands on surgeons, particularly in academic practices. The adaptation of an industrial management tool-the critical pathway method-to health care delivery is an attempt to reduce length of stay and improve efficiency. Utilization of vascular nurse practitioners, concentration of vascular patients into a dedicated unit, reduction in angiography through more aggressive use of the vascular laboratory, and optimal use of rehabilitation units and skilled nursing facilities are important adjuncts to reduce length of stay without sacrificing quality of care. This report describes the critical pathway method as implemented in a university teaching hospital, and the integration of other modalities in the care of vascular patients that has reduced length of stay by as much as 40% for some vascular surgical procedures.

Cardiology Service, Hospital↗
PubMed1996

Effect of a femoral arteriovenous fistula on lower extremity venous hemodynamics after femorocaval reconstruction.

PURPOSE: To study the hemodynamic effects of an arteriovenous fistula (AVF) used as an adjunct to venous reconstructions and to determine the optimal size for such a fistula. METHODS: A model of limb circulation with an AVF (in vitro system) was constructed with silicon elastic tubes and 40% glycerin solution as the fluid medium. Pulsatile arterial flow and venous return was maintained with a roller pump and a centrifugal assist device. Flows and pressures were measured for three different fistula diameters (3, 4, and 5 mm). A canine model of venous hypertension with outflow obstruction was constructed in 15 adult mongrel dogs. After 7 to 13 days an externally supported 8-mm expanded polytetrafluoroethylene femorocaval graft was implanted with a distal AVF (3 mm, n = 5; 4 mm, n = 5; 5 mm, n = 5). Arterial and venous flows and venous pressures were measured proximal and distal to the fistula before and after exercise. RESULTS: In the in vitro system, flows through the venous graft increased with increasing fistula size, but venous return decreased progressively, increasing the distal venous pressure. In the canine model, flow in the venous graft increased with each AVF (p < 0.01). Only the 3-mm AVF resulted in decreased distal femoral vein pressure (p < 0.01), orthograde flow, and improved venous return with exercise. CONCLUSION: AVFs increased flow through the femorocaval grafts, yet they impeded venous return. The ideal AVF-to-graft ratio used in our study was 0.375, because it increased graft flow, permitted forward flow in the femoral vein while reducing pressure, and improved venous return with exercise.

Animals↗
PubMed1996

Urokinase treatment preserves endothelial and smooth muscle function in experimental acute arterial thrombosis.

PURPOSE: Pharmacologic lysis or balloon thrombectomy are options to treat acute arterial thrombosis; however, little is known about their effects on functional changes in the arterial wall. The aim of this study was to determine function of the endothelium and smooth muscle in canine arteries revascularized after acute thrombosis with balloon thrombectomy or lytic therapy. METHODS: Acute thrombosis was obtained by bilateral proximal and distal ligation of 8-cm. segments of the femoral arteries in dogs. After 24 hours, the ties were removed and the arteries randomized to treatment groups: group 1, balloon thrombectomy (# 4 Fogarty balloon catheter at 60 grams linear shear x 1 pass, n = 7); group 2, untreated, tie removal only (n = 6); group 3, regional intra-arterial urokinase infusion (4000 U/min x 90 min, n = 6); group 4, regional intra-arterial carrier infusion (0.43 ml/min x 90 min, n = 6); group 5, unoperated normal vessels (n = 5). After treatment, the arteries were removed and endothelial and smooth muscle responses examined in organ chambers. Endothelial loss was graded with light microscopy of vessel rings from each animal by an observer blinded to the treatment group. Findings were confirmed with scanning electron microscopy. RESULTS: Treatment with urokinase did not alter endothelium-dependent relaxations or smooth muscle contractions compared with carrier infusion or untreated alone. Balloon catheter thrombectomy significantly reduced endothelium-dependent relaxations compared with all other groups in response to acetylcholine, bradykinin, and thrombin (p < 0.001). Contractions of smooth muscle in response to potassium chloride (60 mol/L) and phenylephrine (1 x 10-6 mol/L) were also reduced (p < 0.05). Rings from balloon thrombectomized arteries contracted in response to calcium ionophore A23187 (p < 0.001); these contractions were endothelium dependent and not reduced by indomethacin or blockade of endothelin A and B receptors. No significant differences in percentage of endothelial coverage between groups were assessed by light and electron microscopy. CONCLUSION: Thrombolysis with urokinase caused no or minimal abnormalities in endothelial and smooth muscle function. Endothelium present after balloon thrombectomy produces contractile factors. Although the duration and recovery of these abnormalities in function are unknown, these findings support preferential use of urokinase over balloon thrombectomy when possible in acute arterial thrombosis or embolism.

Acute Disease↗
PubMed1996

Predictive value of carotid artery stump pressures during carotid endarterectomy.

The ideal method of monitoring cerebral perfusion during carotid endarterectomy remains controversial. This article reviews many of the larger studies in the literature that have attempted to evaluate the usefulness of carotid artery stump pressure. Topics discussed include stump pressure alone, regional anesthesia, stump pressure and EEG, and stump pressures and transcranial Doppler ultrasonography.

Blood Pressure↗