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Biomedical subjects

S Wallace

Publications and source records attributed to S Wallace.

At least 523 records · Page 29Linked to original sources
PubMedDate not supplied

Treatment of experimentally induced atherosclerosis in swine iliac arteries: a comparison of self-expanding and balloon-expanded stents.

Atherosclerosis was induced in 20 Hanford miniature swine. Subsequently, one iliac artery lesion in each of 16 pigs was stented with either a self-expanding (8 pigs) or a balloon-expanded (8 pigs) stent. Immediately after stent placement, 4 animals in each group were taken off the atherogenic diet and continued on normal chow for the remainder of the study. Four months after stents were placed, atherosclerosis and the mural changes associated with the stent were more clearly evident in the arteries of the pigs continued on the atherogenic diet. These pigs also exhibited significantly more neointimal proliferation. In addition, the arteries containing the balloon-expanded stents showed more extensive and complex intimal changes when compared with arteries with self-expanding stents. Although both stent designs were equally effective in maintaining vascular patency, the balloon-expanded stent was more traumatic to the vessel wall which resulted in a significantly greater neointimal thickness.

Animals↗
PubMedDate not supplied

Magnetic resonance imaging of malignant fibrous histiocytoma.

The magnetic resonance imaging (MRI) changes in 39 patients with malignant fibrous histiocytoma (MFH) were reviewed retrospectively. Twenty-one sarcomas were in the lower extremity, five each in the upper extremity and trunk, two each in the neck and heart, and one each in the maxillary sinus, sella turcica, tongue, and spermatic cord. The examinations were performed with spin-echo sequences on a 1.5 Tesla Signa Scanner (GE, Milwaukee WI). Twenty-two tumors exhibited intermediate signal intensity on T1-weighted images and 23 were of high signal intensity on T2-weighted images. There was no significant differences in signal intensity of 12 preoperative and 13 recurrent neoplasms. Twelve of 13 patients were correctly diagnosed as having postoperative changes. The MR sensitivity and specificity for detecting a neoplasm were 96% and 83% respectively, but the signal changes were nonspecific for MFH. When compared to CT in 14 patients, MR better defined the extent of the MFH, its relationship to surrounding tissues and vessels, and best differentiated residual or recurrent disease from postoperative changes when examined at least 3 months after surgery.

Adolescent↗
PubMedDate not supplied

Magnetic resonance imaging and computed tomography appearance of asymptomatic paravaginal cysts.

The magnetic resonance imaging (MRI) and computed tomography (CT) appearance of 18 paravaginal cysts was reviewed. On MRI, serious cysts were hypointense on T1-weighted and hyperintense on T2-weighted images. Cysts presumed to contain proteinaceous material were hyperintense on T1-weighted and T2-weighted sequences while hemorrhagic cysts exhibited varying stages of hemorrhage. On CT, a high attenuation cyst was presumed to contain proteinaceous material or hemorrhage. MRI and CT examination may reveal paravaginal cysts; their varied appearance must be recognized to avoid confusion with other lesions.

Adult↗
PubMedDate not supplied

Serological similarities between hyperreactive malarial splenomegaly and splenic lymphoma in west Africa.

In West Africa hyperreactive malarial splenomegaly (HMS) and splenic lymphoma with villous lymphocytes (SLVL) are demographically and clinically indistinguishable. Determination of lymphocyte clonality is needed to differentiate clearly between these 2 disorders. To obtain evidence to support our hypothesis that HMS and SLVL are aetiologically related we studied the serological profile of malaria-related antibodies in HMS and SLVL in West Africa. We found that in SLVL total immunoglobulin M and antimalarial antibody levels were markedly raised, a combination which is characteristic of HMS. These findings strongly support a developmental relationship between HMS and SLVL in tropical Africa and implicate malaria in this process.

Adolescent↗
PubMedDate not supplied

Preliminary study of cardiac accumulation of F-18 fluorotamoxifen in patients with breast cancer.

The clinical meaning of cardiac uptake of [18F]fluorotamoxifen was assessed. Tamoxifen, a nonsteroidal antiestrogenic drug for treatment and prevention of breast cancer, has a cardioprotective, estrogen-like effect in postmenopausal women. We conducted a pilot study of [18F]fluorotamoxifen to evaluate its clinical usefulness in patients with breast cancer. Significant cardiac uptake of [18F]fluorotamoxifen in five patients was found in the pilot study. We performed positron emission tomography (PET) with [18F]fluorotamoxifen. The intracardiac distribution of [18F]fluorotamoxifen was observed and compared with the patients' clinical symptoms, past history, and results of the electrocardiogram (ECG). None of the patients had a prior history of ischemic heart disease. Various patterns of [18F]fluorotamoxifen distribution were seen in the heart: one patient showed homogeneous distribution; two had defects in the lateral wall; one had patchy distribution; and in one the uptake was questionable. Non-uniform cardiac uptake may be related to myocardial damage. Cardiac uptake of tamoxifen suggests that its cardioprotective benefits may be related not only to serum cholesterol reduction but also to a direct cardioprotective action. Further experimental studies are required to elucidate the pathophysiological mechanism of cardiac uptake of [18F]fluorotamoxifen.

Adult↗
PubMedDate not supplied

Preliminary experimental evaluation of temporary segmental hepatic venous occlusion: angiographic, pathologic, and scintigraphic findings.

PURPOSE: Pigs were used to evaluate temporary segmental hepatic venous occlusion as a means of improving the selective delivery of therapeutic agents within the liver. MATERIALS AND METHODS: Hepatic angiography and scintigraphy were performed alone and in combination with hepatic venous occlusion. RESULTS: Arteriograms obtained during venous obstruction demonstrated a greater number of peripheral arterial branches in the occluded area compared with the nonoccluded areas. A prolonged hepatogram showing hepatofugal opacification of the portal branches was observed in the occluded area. Microscopically, mild congestion of the sinusoids and central veins was seen immediately after 60-minute occlusion, but these changes were not evident 2 hours after balloon deflation. Severe congestion and focal hemorrhage were found in the occluded segment of the liver 2 hours after 90-minute venous occlusion. When the right or left hepatic vein was occluded during hepatic arterial infusion of technetium-99m macroaggregated albumin, there was a significant (P < or = .05) increase in the amount of radioactivity measured in the obstructed segment and a significant (P < or = .05) decrease in that found in the nonoccluded regions. CONCLUSION: These results indicate that temporary segmental hepatic vein occlusion is safe for up to 60 minutes and may be clinically applicable as a means of improving the therapeutic index of agents within the liver when they are administered via concomitant hepatic arterial infusion.

Angiography↗
PubMedDate not supplied

Placement of covered self-expanding metallic stents in the common bile duct: a feasibility study.

PURPOSE: Gianturco self-expanding metallic stents have been useful in cases of benign biliary stenoses; however, the stents have not worked well in the presence of intraluminal tumor because of tumor growth between the wire struts. Stents were covered with polymeric membranes, which may prevent tumor ingrowth, and the feasibility of using these covered stents in the common bile duct was studied in healthy adult dogs. MATERIALS AND METHODS: Initially, stents (10 x 6 mm) covered with polycaprolactone (PCL), segmented polyether polyurethane (SPP), and silicone were placed in the common bile duct of dogs and were followed up for 3-12 months. Subsequently, four types of modified silicone-covered stents were evaluated. Rough-surface, small-diameter (3-mm), half-covered, and tapered stents were placed and followed up for 3 months. RESULTS: In the initial study, the SPP and silicone membranes remained intact, but the PCL covering broke in all dogs. In all but two dogs, luminal narrowing caused by varying degrees of papillary mucosal hyperplasia at both ends of the stent was observed. In the subsequent study, mucosal hyperplasia was considerably reduced by using half-covered stents and was virtually eliminated with tapered stents. All small-diameter stents migrated into the bowel. CONCLUSION: These studies suggest that tapered Gianturco self-expanding stents covered with silicone may be useful in the biliary tract in cases of intraluminal tumor.

Animals↗
PubMedDate not supplied

Sinusoidal embolization: impact of iodized oil on hepatic microcirculation.

PURPOSE: To determine the effects of iodized oil, which is used in chemoembolization of liver cancer, on hepatic microcirculation and to measure the time required for recovery of microcirculation. MATERIALS AND METHODS: Iodized oil was injected in 0.1-, 0.2-, and 0.4-mL/kg doses into the hepatic artery in three groups of rats (n = 63). In vivo microscopy was performed during and immediately after the procedure and on days 1, 3, 7, 15, 30, and 60. A control group of rats underwent identical microscopy procedures. RESULTS: Changes in microcirculation occurred after injections with iodized oil. Oil injected into the hepatic artery entered the portal vein and flowed into the sinusoids to create an incomplete sinusoidal embolization. Recovery of the sinusoidal circulation occurred 3, 7, and 30 days after injections of 0.1, 0.2, and 0.4 mL/kg of oil, respectively. CONCLUSIONS: The liver tolerated oil embolization well. Despite the changes in microcirculation and a nonlinear recovery time, the microcirculation completely recovered, even with a 0.4-mL/kg dose.

Animals↗
PubMedDate not supplied

Anchoring coil embolization in a high-flow arterial model: a pilot study.

PURPOSE: To devise and test an occluding coil anchoring system to improve the safety of coil embolization. MATERIALS AND METHODS: The anchoring system was attached to Gianturco embolization coils and investigated in 15 pigs. In the short-term studies, one 0.035-inch anchored coil (15-18 cm in length and 7-10 mm in diameter) was placed in the infrarenal portion of the abdominal aorta in each of 12 pigs with use of an 8-F catheter from the carotid approach. Aortography was performed before and up to 4 hours after coil placement. In the long-term studies, 0.028-inch anchored coils (8 cm in length and 5 mm in diameter) were placed in the left femoral and the right carotid arteries in each of three pigs with use of a 6-F catheter positioned from the right femoral approach. One week later, the animals were evaluated angiographically for coil migration and vascular occlusion. RESULTS: Radiographically, the coils created a compact conglomerate on placement in all but one of the animals. No coil migration was noted during follow-up. Necropsy confirmed compact arrangement of the coils within the vessels and revealed effective anchoring of the device in all cases. CONCLUSIONS: The anchoring coil has proved effective in making coil embolization safer, especially in a high-flow arterial model.

Animals↗
PubMedDate not supplied

Poly(ethylene glycol)-conjugated anti-EGF receptor antibody C225 with radiometal chelator attached to the termini of polymer chains.

Several biological barriers, including significant liver uptake, limit the clinical application of radiolabeled antibodies in radioimmunoscintigraphy. Here, a general approach is described for radiolabeling of monoclonal antibodies conjugated with poly(ethylene glycol) (PEG). This strategy is demonstrated with C225, a monoclonal antibody directed against epidermal growth factor (EGF) receptor. We synthesized a heterofunctional PEG with one end attached to a radiometal chelator, diethylenetriaminepentaacetic acid (DTPA), and the other end to a protected thiol group, S-acetylthioacetate. After a deprotection step, the resulting DTPA-PEG-SH was conjugated to maleimide-activated C225 to yield DTPA-PEG-C225 conjugate. Characterization of DTPA-PEG-C225 with immunoprecipitation and Western blot analysis revealed that the conjugate was biologically active in binding to the EGF receptor in A431 cells. Competitive EGF receptor binding assay in MDA-MB-468 cells showed that DTPA-PEG-C225, with up to 60% of the amino groups in C225 substituted, retained 66% of C225's binding affinity. Moreover, DTPA-PEG-C225 with increasing degrees of NH(2) substitution from 20% to 70% retained the activity of C225 to induce apoptosis in DiFi cells. More importantly, DTPA-PEG-C225 demonstrated less nonspecific interaction than DTPA-C225. Pharmacokinetic analysis using (111)In-labeled compounds revealed narrower steady-state distribution of (111)In-DTPA-PEG-C225 than (111)In-DTPA-C225, probably due to reduced nonspecific binding of PEG-modified antibody to tissues. The terminal half-life (t(1/2,)(gamma)) of (111)In-DTPA-PEG-C225, 21.1 h, was shorter than that of (111)In-DTPA-C225, 52.9 h. These data suggest that (111)In-DTPA-PEG-C225 may provide better imaging characteristics than (111)In-DTPA-C225, and that using PEG as a linker between the monoclonal antibody and DTPA may be a promising strategy in optimizing the imaging characteristics of immunoscintigraphic agents.

Antibodies, Monoclonal↗
PubMedDate not supplied

Functional polymeric microspheres based on 2-hydroxyethyl methacrylate for immunochemical studies.

Co gamma irradiation of 2-hydroxethyl methacrylate in the presence or in the absence of other acrylic monomers was found to constitute an effective technique for the synthesis of hydrophilic functional microspheres in the size range of approxumately 0.3 to 3 mu in diameter. The effect of monomer concentration, steric stabilization, and electrostatic interaction on the particle size was investigated. Experimental conditions were determined to obtain desired particle sizes of relatively narrow distribution. It was shown that particles may be formed without intermediate micelles, i.e., by homogeneous nucleation, and the rate of particle formation is affected primarily by the rate of particle coalescence in the initial stages of the reaction. When covalently bound to antibodies these microspheres were successfully used to label murine and human lymphocytes.

Acrylates↗
PubMedDate not supplied

Utility of lymphangiography in the prediction of lymph node metastases in patients with cervical cancer.

Our objective was to assess the value of lymphangiography in selecting patients for surgical staging of locally advanced cervical cancer. We reviewed our computerized database to identify patients with cervical cancer who had abnormal findings on lymphangiography and underwent retroperitoneal lymph node dissection between September 1991 and January 1996. The records of these patients were retrospectively reviewed, and the following data were retrieved: clinical tumor stage and findings on lymphangiography at surgery, and on pathologic examination of resected lymph nodes. The lymphangiograms were reviewed and reinterpreted in blinded fashion by two of the authors. The positive and negative predictive values of lymphangiography for the presence of lymph node metastases were calculated, with findings on pathologic examination of lymph nodes used as the gold standard. The positive and negative predictive values of surgeons' clinical assessments at surgery were also calculated. Fifty patients met the selection criteria and constituted the study population. Fourteen patients (28%) had histologically negative nodes, and 36 patients (72%) had lymph node metastases. Thirty-three patients had metastases to pelvic nodes, 1515 patients had metastases to common iliac nodes, and 1616 patients had metastases to para-aortic nodes. The positive predictive value of lymphangiography for lymph node metastases was 74% for pelvic nodes, 73% for common iliac nodes, and 88% for para-aortic nodes. The negative predictive value of lymphangiography for lymph node metastasis was 76% for common iliac nodes and 77% for para-aortic nodes. Overall, 46% of the patients selected for surgical exploration had histologic findings of either common iliac or para-aortic lymph node metastases; these findings led clinicians to extend radiation fields to cover the para-aortic lymph nodes. Lymphangiography is helpful in selecting patients with cervical cancer who have a high risk of common iliac or para-aortic lymph node metastasis. However, more accurate and more readily available noninvasive methods of evaluating cervical patients for the presence of regional disease continue to be needed.

Adenocarcinoma↗
PubMedDate not supplied

The virtual mole clinic: preliminary results from the Plymouth skin cancer screening study using telemedicine.

This study evaluated a skin cancer screening service between primary and secondary care in Plymouth using a store and forward telemedicine system. The primary objective was to minimize the time from a patient presenting to a GP with a suspicious lesion to the lesion being assessed and diagnosed by a plastic surgeon. This study retrospectively assessed the practical, technical and operational aspects of incorporating telemedicine into everyday practice and patient satisfaction. Both the GP practice and plastic surgeons were equipped with the appropriate technology for creating, transmitting and accessing an electronic telemedicine record (ETR) via an ISDN 2 line. Patients with suspicious lesions accessed the GP via Mole Check Clinics. The GP captured and transmitted an ETR consisting of digital images and relevant clinical data. In a virtual mole clinic, the plastic surgeon accessed and reviewed the ETR. The expert opinion was entered directly into the ETR and transmitted to the GP within 48 hours. All patients were offered a face-to-face consultation at a real mole clinic within 7 days. Outcomes demonstrated patient and clinician satisfaction and the ability to deliver high quality diagnostic images and resulting expert opinion. This study informed a larger study for future applications of telemedicine.

Humans↗
PubMedDate not supplied

Infectious complications of hepatic artery catheterization procedures in patients with cancer.

A total of 353 hepatic artery catheterization procedures were carried out in 211 patients with cancer over a 1-year period (January-December 1988). The procedures included 49 embolizations in 32 patients, 123 chemoembolizations in 73 patients, and 181 chemoinfusions in 106 patients. The overall infection rate was 3.4%. Infectious complications occurred in 3.1% of patients undergoing hepatic artery embolization alone, 1.9% of patients undergoing hepatic artery chemoinfusion, and 4.1% of patients undergoing hepatic artery embolization followed by chemoinfusion. Four patients had infectious complications that included four episodes each of cholangitis, liver abscess, and septicemia. One patient developed a subphrenic abscess in addition to a liver abscess. Enteric gram-negative bacilli (aerobic and anaerobic) were isolated from all four patients. None of the patients had received prophylactic antibiotics. All patients responded to antimicrobial therapy and percutaneous drainage of abscesses.

Bacteremia↗
PubMedDate not supplied

Infections associated with biliary drainage procedures in patients with cancer.

A total of 170 therapeutic biliary drainage procedures were carried out in 90 patients with cancer over a 1-year period (January-December 1988). There were 129 percutaneous transhepatic biliary drainage procedures done in 61 patients and 41 endoprostheses were placed in 29 patients. The overall infection rate related to these procedures was 60.6%, the rate being similar for the two procedures. Infectious complications were experienced by 50% of patients undergoing a biliary drainage procedure. The most common manifestation was cholangitis followed by bacteremia. Other infections included liver abscess, gallbladder abscess, and subphrenic abscess. The most common isolates were enteric gram-negative bacilli, followed by Enterococcus species, Candida species, and Staphylococcus epidermidis. The use of prophylactic antibiotics in 76% of infected patients failed to prevent biliary catheter-related infections. Two patients died of complications related to biliary sepsis. All other infected patients responded to antimicrobial therapy, which included various regimens of beta-lactam agents (third-generation cephalosporin, extended-spectrum penicillin, imipenem-cilastatin, and aztreonam) that were used in combination with an aminoglycoside in 15 patients.

Abscess↗
PubMedDate not supplied

Experimental transcatheter intraarterial infusion-occlusion chemotherapy.

Dogs were used to develop transcatheter vascular techniques to improve local tissue accumulation of a radiolabeled chemotherapeutic agent. A double lumen balloon catheter was used for short term (10 minute) intraarterial infusions of 14C labeled Fluorouracil (5-FU) during temporary vascular occlusion with the balloon. Local tissue (hind limb musculature) as well as venous blood concentrations of 5-FU draining the area of infusion were compared to those obtained following intraarterial infusion alone or following intravenous administration of the drug. Combining intraarterial infusion with temporary vascular occlusion increased (7 to 9 times) the local tissue concentration of the 5-FU when compared to intraarterial infusion alone. The local tissue levels of the drug during intraarterial infusion and temporary vascular occlusion were 30 to 50 times greater than those obtained by intravenous administration. Levels of 5-FU were also significantly higher in the venous blood draining the infusion area when the combined intraarterial infusion-occlusion technique was employed.

Animals↗
PubMedDate not supplied

An animal model of occlusion-hyperthermia of the liver.

An animal model of partial hepatic artery occlusion and radiofrequency (RF)-induced hepatic hyperthermia was developed in the New Zealand white rabbit. Seventy-seven percent (10/13) of animals survived partial hepatic artery occlusion, 82% (41/50) survived RF-induced hepatic hyperthermia, and 66% (24/36) survived combined occlusion-hyperthermia. Mesenteric infarction secondary to inadvertent embolization of intestinal arteries was the principal cause of death in animals undergoing partial hepatic artery occlusion. Extrahepatic thermal toxicity appeared to be the major cause of death in animals subjected to hepatic hyperthermia or occlusion hyperthermia although some animals showed evidence of hepatic necrosis as well. Recent developments in our laboratory hold the promise that extrahepatic thermal toxicity can be eliminated by selectively focusing heat into the liver allowing exploration of the efficacy of occlusion-hyperthermia in controlling VX-2 tumors implanted in the rabbit liver.

Animals↗