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Biomedical subjects

C A Magee

Publications and source records attributed to C A Magee.

At least 19 recordsLinked to original sources
PubMed2006

Transgastric endoscopic splenectomy: is it possible?

BACKGROUND: We have previously reported the feasibility of diagnostic and therapeutic peritoneoscopy including liver biopsy, gastrojejunostomy, and tubal ligation by an oral transgastric approach. We present results of per-oral transgastric splenectomy in a porcine model. The goal of this study was to determine the technical feasibility of per-oral transgastric splenectomy using a flexible endoscope. METHODS: We performed acute experiments on 50-kg pigs. All animals were fed liquids for 3 days prior to procedure. The procedures were performed under general anesthesia with endotracheal intubation. The flexible endoscope was passed per orally into the stomach and puncture of the gastric wall was performed with a needle knife. The puncture was extended to create a 1.5-cm incision using a pull-type sphincterotome, and a double-channel endoscope was advanced into the peritoneal cavity. The peritoneal cavity was insufflated with air through the endoscope. The spleen was visualized. The splenic vessels were ligated with endoscopic loops and clips, and then mesentery was dissected using electrocautery. RESULTS: Endoscopic splenectomy was performed on six pigs. There were no complications during gastric incision and entrance into the peritoneal cavity. Visualization of the spleen and other intraperitoneal organs was very good. Ligation of the splenic vessels and mobilization of the spleen were achieved using commercially available devices and endoscopic accessories. CONCLUSIONS: Transgastric endoscopic splenectomy in a porcine model appears technically feasible. Additional long-term survival experiments are planned.

Animals↗
PubMed2000

Pregnancy outcomes among U.S. women Vietnam veterans.

BACKGROUND: Since the 1965-1975 Vietnam War, there has been persistent concern that women who served in the U.S. military in Vietnam may have experienced adverse pregnancy outcomes. METHODS: We compared self-reported pregnancy outcomes for 4,140 women Vietnam veterans with those of 4,140 contemporary women veterans who were not deployed to Vietnam. As a measure of association, we calculated odds ratios (OR) and 95% confidence intervals (CI) using logistic regression adjusting for age at conception, race, education, military nursing status, smoking, drinking and other exposures during pregnancy. RESULTS: There was no statistically significant association between military service in Vietnam and index pregnancies resulting in miscarriage or stillbirth, low birth weight, pre-term delivery, or infant death. The risk of having children with "moderate-to-severe" birth defects was significantly elevated among Vietnam veterans (adjusted OR = 1.46, 95% CI = 1.06-2.02). CONCLUSIONS: The risk of birth defects among index children was significantly associated with mother's military service in Vietnam.

Abortion, Spontaneous↗
PubMed2000

Illnesses among United States veterans of the Gulf War: a population-based survey of 30,000 veterans.

Despite numerous studies on veterans of the 1990 to 1991 Gulf War, the fundamental questions of how healthy they are and how their health compares with that of their military peers who were not deployed to the Gulf have not been fully answered. We conducted a health survey in which the health outcomes of a population-based sample of 15,000 Gulf veterans representing various military branches and unit components (regular, reserve, National Guard) were compared with those of 15,000 non-Gulf veterans who were randomly sampled to mirror the number in the same military strata in the Gulf veteran group. In comparison with their peers, Gulf veterans had a higher prevalence of functional impairment, health care utilization, symptoms, and medical conditions and a higher rate of low general health perceptions. A longitudinal follow-up of the health of these veterans will be needed to detect changes in health status and to detect diseases with a long latency period.

Adult↗
PubMed2000

Prevalence of gynecologic cancers among female Vietnam veterans.

The possibility of a gender-specific health problem associated with the Vietnam War has been a concern since the war. We targeted 4140 female Vietnam veterans and 4140 veteran controls to complete a structured telephone interview that included questions regarding any history of gynecologic cancer. As a measure of association between the risk of cancer and military service in Vietnam, odds ratios and 95% confidence intervals were calculated using multiple logistic regression models that yielded estimates of potential cofounders. Although 8% of Vietnam veterans and 7.1% of non-Vietnam veterans reported a history of gynecologic cancers, namely, breast, ovary, uterus, or cervix, the difference was not statistically significant either for the individual site or for the gynecologic cancers as a group. Female Vietnam veterans have not experienced a higher prevalence of gynecologic cancer in the 30 years since the conflict.

Adult↗
PubMed2000

Local tumor recurrence following hepatic cryoablation: radiologic-histopathologic correlation in a rabbit model.

PURPOSE: To use radiologic-histopathologic correlation in an animal model to distinguish normal postoperative findings from evidence of residual tumor after cryoablation of malignant hepatic tumors. MATERIALS AND METHODS: Hepatic cryoablation was performed in 12 rabbits with VX2 tumors and in two healthy rabbits. Nonenhanced and dynamic contrast material-enhanced computed tomography (CT) and magnetic resonance (MR) imaging and power and color Doppler flow ultrasonography (US) were performed 7-8 days after cryoablation. Histopathologic findings were correlated with imaging findings. RESULTS: Twenty tumors of 5-20 mm (mean, 10 mm) and seven areas of normal liver were treated with cryolesions of 11-21 mm (mean, 15 mm). All cryolesions exhibited arterial phase rim enhancement at CT and MR imaging, and 13 (57%) of 23 lesions demonstrated peripheral flow at US because of granulation tissue. There was macroscopic recurrence in 15 (75%) of 20 treated tumors; 14 (93%) appeared as peripheral nodularity with low-grade enhancement. Necrotic tissue did not enhance. Intact vessels extended up to 6 mm inside cryolesion margins and caused focal internal enhancement and Doppler flow. Areas of high signal intensity on T2-weighted MR images correlated with liquefaction necrosis, granulation tissue, and tumor. CONCLUSION: In this animal model, recurrent tumor typically appeared as focal nodules at the cryolesion periphery. Rim and central foci of enhancement, Doppler flow, and increased signal intensity on T2-weighted MR images can be normal findings after hepatic cryoablation.

Animals↗
PubMed2000

1999 ARRS Executive Council Award. Contrast-enhanced CT of small hypovascular hepatic tumors: effect of lesion enhancement on conspicuity in rabbits. American Roentgen Ray Society.

OBJECTIVE: The purpose of this study was to evaluate the effect of lesion enhancement on the conspicuity of small hypovascular hepatic tumors in an animal model. MATERIALS AND METHODS: Seven VX2 hepatic tumors in five rabbits were imaged. Dynamic contrast-enhanced CT was performed at a single level centered over the lesions at 5-sec intervals for 119 sec after injection of 2 ml/kg i.v. contrast material at 2 ml/sec. Attenuation was measured over time within regions of interest in the tumor and normal liver, aorta, inferior vena cava, and portal vein. Lesion conspicuity, defined as the difference between the attenuation of the uninvolved liver and neoplasm, was calculated. RESULTS: The mean diameter of the tumors on CT was 10 mm (range, 6-15 mm). The tumors appeared as low-attenuation lesions with progressive enhancement during the arterial phase and early portal phase. Peak mean lesion attenuation was 60 +/- 27 H (enhancement, 23 H) at 64 sec. Peak mean lesion conspicuity was 80 +/- 18 H at 39 sec, occurring 10 sec before the peak mean hepatic attenuation of 135 +/- 15 H (enhancement, 67 H) at 49 sec. Relative lesion conspicuity paralleled relative enhancement of the liver throughout the imaging period. CONCLUSION: Although low-level tumor enhancement during the arterial phase and early portal phase reduced the conspicuity of small hypovascular tumors in this animal model, our results support the use of maximum liver enhancement as a marker for peak lesion conspicuity.

Animals↗
PubMed1999

Endoscopic cryotherapy: experimental results and first clinical use.

BACKGROUND: Cryotherapy or the application of extreme cold has many potential applications in gastroenterology including tissue destruction and hemostasis but until now its development has been prevented by the lack of a delivery device suitable for use through the endoscope. We report here our experience with prototype devices using both liquid nitrogen driven by a cryosurgical system and cryogenic refrigerants (nitrous oxide and carbon dioxide) at or near ambient temperature. METHODS: Cryotherapy was applied to the distal esophageal mucosa of dogs via a flexible catheter passed through an upper endoscope. In other dogs, cryotherapy was used for hemostasis in a bleeding ulcer model. The procedure was also used for palliation in a 58-year-old man with unresectable adenocarcinoma of the stomach with pyloric channel obstruction. RESULTS: Freezing of the superficial mucosa was nearly instantaneous. All dogs survived the procedure and appeared to thrive. Histologic evaluation revealed significant necrosis of the superficial epithelial layer accompanied by a fibrinocellular infiltrate on the surface. These markers of acute injury subside by the fourth to sixth day and are replaced by regenerating epithelium, a process that is virtually complete by day 10. In the hemostasis experiments, bleeding ceased immediately after cryospraying of the lesions but resumed on thawing in most cases. Application of cryotherapy in the patient resulted in reduction of the pyloric mass with no immediately apparent adverse effects. CONCLUSIONS: These data, although preliminary, demonstrate the feasibility of endoscopic cryotherapy using a simple hand-held device. This device has broad potential for use in gastroenterology including ablation of superficial epithelium, debulking of large tumors and hemostasis.

Adenocarcinoma↗
PubMed1999

Ablation of renal tumors in a rabbit model with interstitial saline-augmented radiofrequency energy: preliminary report of a new technology.

OBJECTIVES: To evaluate the efficacy of interstitial saline radiofrequency energy for reproducibly ablating nonmalignant (control) and malignant (the VX-2 tumor) renal tissue in a rabbit model, and to determine the ability of conventional gray-scale and power sonography to image the tumor and ablative process in real time before, during, and after treatment. METHODS: The VX-2 tumor was implanted beneath the renal capsule in 18 rabbit kidneys. Twelve days after implantation, 50 W of 500-kHz radiofrequency energy was delivered into the surgically externalized renal tumor and contralateral control kidney for 30 or 45-second treatment intervals using an interstitial saline-augmented radiofrequency probe (the virtual electrode). Localization of the tumor and response to treatment were imaged with gray-scale and power Doppler ultrasonography. The effect of radiofrequency and extent of the destructive process on benign and malignant renal tissue were evaluated histologically. RESULTS: Mean tumor size was 1.3 x 0.7 cm. Both 30 and 45-second treatment intervals provided marked tissue/tumor ablation. Gross anatomic and histologic analysis showed time-dependent ablated lesions averaging 1.4+/-0.3 x 1.0+/-0.3 cm (30-second treatment) and 1.8+/-0.4 x 1.5+/-0.3 cm (45-second treatment), with clear demarcation of the surrounding parenchyma. Conventional gray-scale sonography allowed visualization of the ablative process, and power Doppler ultrasound demonstrated changes in the vascular pattern of the tumor both before and after ablation. No immediate treatment-related complications were observed. CONCLUSIONS: These preliminary studies in a rabbit model demonstrate the feasibility of using the interstitial saline-augmented electrode to ablate small renal tumors and the ability to simultaneously visualize the ablative process using real-time ultrasonography. This technology may have the potential to treat small renal tumors in a minimally invasive manner in the clinical setting.

Animals↗
PubMed1999

Placement of a flexible endovascular stent across the femoral joint: an in vivo study in the swine model.

PURPOSE: To investigate the effects of joint motion on the structural integrity of periarticular stents and on the development of neointimal hyperplasia within these devices. MATERIALS AND METHODS: In four juvenile farm swine, Wall-stents were implanted in the common femoral arteries and contralateral common femoral veins, centered at the point of maximal conformational change during passive hip flexion. Control stents were placed in the aortae and iliac veins. Angiography and transcatheter blood pressure measurements were obtained across each stent, with periarticular stents studied in flexion and extension. Two animals underwent repeated evaluation after 1 month, the others after 3 months. Findings were correlated with gross and histopathologic findings in the harvested stents. RESULTS: No stent fractures occurred. One femoral vein was injured during stent placement and was occluded 1 month later at follow-up. Hemodynamically significant stenoses were identified in one arterial stent and one venous stent at 3 months. The amount of neointimal hyperplasia was greater in periarticular stents than in controls and greater in animals studied at 1 month than in those studied at 3 months. The pattern of neointimal hyperplasia within mobile arteries was circumferentially asymmetric and thicker at the distal ends of the stents. Venous neointimal hyperplasia was thicker and markedly different in character than that seen in arterial stents from the same animals. CONCLUSIONS: Periarticular Wallstents and the underlying vascular anatomy remained structurally intact despite the stresses of repetitive motion during a 3-month period. Stents deployed across joints or in venous locations may be at greater risk for neointimal hyperplasia development and eventual occlusion than those deployed in immobile vessels and arteries. Neointimal hyperplasia may decrease in thickness after an initial period of exuberant development. Additional studies are necessary to determine long-term outcomes.

Analysis of Variance↗
PubMed1995

'Microgastria--limb reduction' complex with congenital heart disease and twinning.

We report a newborn, the second of male twins, with multiple abnormalities, including microphthalmia, a complex cardiovascular malformation, asplenia, anomalous lobation of the lungs, oesophageal atresia, microgastria, intestinal malrotation, anal atresia, multicystic dysplastic kidneys, and reduction defects of the upper extremities. These defects fit into the so-called 'microgastria-limb reduction' complex. Two of twelve previously reported patients with this complex were from discordant twin pairs. The occurrence of twinning in three out of 13 cases suggests that the origin of the 'microgastria-limb reduction' complex may be related to the process of twinning itself.

Abnormalities, Multiple↗
PubMed1994

Quantitative proton spectroscopy of canine brain: in vivo and in vitro correlations.

Quantitative, single-voxel proton NMR spectroscopy of normal brain was performed in five adult beagle dogs using the cerebral water signal as an internal intensity reference. The same brain regions were then rapidly isolated and frozen using a pneumatic biopsy drill, perchloric acid extracted, and analyzed by biochemical assay and high-resolution NMR spectroscopy. The concentrations of the major resonances in the in vivo and in vitro spectra were compared, and good agreement was found between the different measurements. The in vivo spectra contained three peaks at 3.21, 3.04, and 2.02 ppm, which are usually assigned to trimethylamines (TMA), creatines, and N-acetyl derivatives (NAc), which corresponded to be the following metabolite concentration values: 1.7 +/- 0.6, 7.7 +/- 2.1, and 10.9 +/- 2.7 mumol/g wet weight respectively. In vitro, the following metabolite concentrations were measured: glycerophosphocholine (GPC) 1.3 +/- 0.2, phosphocholine (PC) 0.5 +/- 0.1, phosphocreatine (PCr) 2.6 +/- 0.4, creatine (Cr) 5.9 +/- 1.4, and N-Acetyl aspartate (NAA) 8.9 +/- 1.8 mumol/g wet weight. Therefore, the 3.21 ppm resonance observed in the in vivo spectrum is predominantly GPC and PC in a ratio of 2.6:1, the 3.04 ppm resonance is Cr and PCr in a ratio of 2.3:1, and the 2.02 ppm resonance is predominantly (approximately 80%) NAA with small contributions from N-acetylaspartylglutamate (NAAG) and glutamate. The data presented here validate the technique of water referencing as a simple and convenient means of quantitating single-voxel in vivo proton NMR spectra of the brain.

Animals↗
PubMed1994

Palmaz stent in the treatment of central venous stenosis: safety and efficacy of redilation.

PURPOSE: To assess the safety and efficacy of redilation of central venous stents in a growing animal model. MATERIALS AND METHODS: Palmaz stents were placed in the inferior vena cava (IVC) in 18 newborn lambs. After 5 months, vena cavography was performed. Those animals in which growth of the IVC adjacent to the stent and/or neointimal hyperplasia had resulted in a stenosis were considered candidates for redilation. Repeat vena cavography, intravascular ultrasound, and histologic examination were performed at 2 or 6 months. RESULTS: A stenosis of > 20% was demonstrated in 13 animals. Redilation was performed, and a 50% mean increase in stent diameter was achieved. There were no immediate complications. Late complications included nonocclusive laminar clot (n = 2), and a bar of tissue dividing but not occluding the caval lumen (n = 1). Moderate neointimal hyperplasia occurred in all stents. Stent compression (unrelated to redilation) occurred in seven animals. CONCLUSION: Palmaz stents can be redilated safely and effectively in an animal model of growing central veins.

Animals↗
PubMed1993

Extrahepatic biliary atresia and associated anomalies: etiologic heterogeneity suggested by distinctive patterns of associations.

Fifty-one cases of extrahepatic biliary atresia (EHBA) with associated anomalies were found in a study of EHBA (251 cases). Analysis of segregation patterns of these anomalies in individual patients suggested the existence of 2 major groups: (1) 15 cases (29.4%) with various combinations of anomalies within the laterality sequence, and (2) 30 cases (58.8%) with one or 2 anomalies mostly involving the cardiac, gastrointestinal, and urinary systems. These latter anomalies did not follow any recognizable pattern. The third group of 6 cases all had intestinal malrotation, some with preduodenal portal vein; these cases show some similarity to the laterality sequence group and may represent a more confined phenotypic result of faulty situs determination. This previously unattempted classification of patients with EHBA and associated anomalies might enable a more targeted approach towards identification of causes in this heterogeneous disorder. EHBA within the laterality sequence might prove a suitable candidate for a major gene mutation. Teratogenic, infectious and polygenic multifactorial causes might play a more significant role in EHBA associated with "nonsyndromic" organ system anomalies.

Abnormalities, Multiple↗
PubMed1993

Quantitative proton spectroscopy and histology of a canine brain tumor model.

Quantitative, single voxel proton nuclear magnetic resonance (NMR) spectroscopy and histological analysis was performed in eight dogs implanted with the transplantable canine glioma model of Wodinsky (Proc. Am. Assoc. Cancer Res. 10, 99 (1969)). Signals from choline, creatine, N-Acetyl Aspartate (NAA) and lactate were converted to molar concentration units and correlated with the quantitative analysis of histologically determined tissue types within the localized volume selected for NMR spectroscopy. In general, compared with normal brain, the lesions were associated with reductions in all metabolite concentrations, with the exception of lactate, which was increased. NAA and creatine decreases were most significantly correlated with the total lesion volume (P < 0.01), suggesting that these compounds are present in normal brain only. Changes in choline levels did not correlate strongly with any particular tissue type. Lactate was found to increase with increasing total lesion volume (P < 0.01), but not with increasing percent tumor, suggesting that it accumulates in abnormal tissue other than the tumor. The spectra reported were similar to those observed in human glioblastomas, with the exception that elevations of choline were not observed. The transplantable canine gliosarcoma system appears to be a suitable tumor model for evaluation by clinical radiological techniques such as magnetic resonance imaging (MRI) and proton NMR spectroscopy.

Animals↗
PubMed1993

Cytochemical observations on the nervous system of adult Corrigia vitta.

Adult Corrigia vitta (Trematoda: Dicrocoelidea) inhabit the pancreatic duct of the fieldmouse, Apodemus sylvaticus, where, in numbers, they may occlude the duct lumen and prevent the flow of pancreatic secretions. Enzyme histochemical and immunocytochemical techniques, in conjunction with confocal scanning laser microscopy, have been used to examine the localization and distribution of cholinergic, serotoninergic (5-HT, serotonin) and peptidergic components of the nervous system of the adult worm. All three classes of neuronal mediator showed a common pattern of staining, occurring throughout the central and peripheral nervous systems. Of the four peptide immunoreactivities (IR) demonstrated (pancreatic polypeptide (PP), peptide YY (PYY), substance P (SP), FMRFamide), PP-IR was the most predominant, occurring not only within the central ganglia and longitudinal nerve cords, but also in subtegumental plexuses and in fibres associated with the egg-forming apparatus. PYY and FMRFamide IRs were evident throughout the central and peripheral nervous systems; FMRFamide immunostaining, in particular, highlighted innervation of the ootype and immunoreactive cell bodies around the Mehlis' gland. Both SP- and 5-HT-IRs were restricted to the cerebral ganglia, ventral nerve cords and associated cell bodies. The distribution patterns of these peptides and 5-HT within the nervous system of C. vitta suggest they are likely to function as neuronal mediators. PP, PYY and FMRFamide may also serve in regulating egg production.

Animals↗
PubMedDate not supplied

Subcutaneously tethered temporary filter: pathologic effects in swine.

PURPOSE: To evaluate the histopathologic effects of the Tempo-filter, a temporary caval filter, on the caval wall and determine the feasibility of deployment and removal of the device in swine. MATERIALS AND METHODS: Filters were placed in the infrarenal inferior vena cava of 11 swine. The tethering catheter was sutured in a subcutaneous pocket near the puncture site. The original tethering catheter used in humans and a stiffer catheter designed to prevent migration in swine were evaluated. Postplacement, mid-study, and preexplant vena cavography procedures were performed. Four swine underwent in situ dissection at 3-10 weeks. Filters were removed from seven animals just before they were killed at 1-6 weeks. RESULTS: All filters were successfully placed. All seven filters were successfully removed at up to 6 weeks after placement. Cephalic migration of more than 1 cm was observed in 10 of 11 swine (100% of original catheters, 83% of stiff catheters). Other complications were more common with stiffer tethering catheters, including caval stenosis in 40% of original catheters and 100% of stiff catheters, filter cone thrombus in 0% and 67%, tethering catheter thrombus in 20% and 83%, pulmonary embolism in 0% and 50%, and death in 0% and 17%, respectively. There was mild vessel wall damage in the vena cava. CONCLUSION: Placement of the Tempofilter and removal at up to 6 weeks after placement is feasible.

Animals↗
PubMedDate not supplied

Comparison of Gianturco Z stents and Wallstents in a hemodialysis access graft animal model.

PURPOSE: To compare the primary patency of two structurally different metallic stents in an animal model of hemodialysis access grafts. MATERIAL AND METHODS: Nineteen synthetic femorofemoral arteriovenous shunts were created in 10 dogs. After a 1-month period of maturation (during which one graft thrombosed), stents were placed spanning the venous anastomosis. The grafts were divided into two treatment groups (Wallstent, n = 6, and Gianturco stent, n = 6) and a control group with no stent (n = 6). Fistulograms and pressure measurements were obtained at monthly intervals for 6 months or until thrombosis of the graft. RESULTS: Mean graft patency in the Wallstent group (112 days +/- 30) was significantly shorter than in the control (157 days +/- 32, P < .03) or Gianturco (157 days +/- 32, P < .05) groups. Patency in the Gianturco stent group was no different from that in the control group. Stenosis due to intimal hyperplasia within the stents appeared greater in the Wallstent group but did not achieve statistical significance. One Wallstent migration, three Gianturco stents shifts, and two Gianturco stent breakages occurred. Histologic examination revealed a necrotizing vasculitis in the portion of vein containing the stent in all grafts treated with the Gianturco stent but not in any other grafts. CONCLUSION: In an animal model of hemodialysis access grafts, the Gianturco stent had longer primary patency than the Wallstent when placed across the venous anastomosis. However, stent fractures and focal necrotizing inflammation may limit the use of the Gianturco stent in hemodialysis access.

Anastomosis, Surgical↗