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Biomedical subjects

S Wallace

Publications and source records attributed to S Wallace.

At least 541 records · Page 30Linked to original sources
PubMedDate not supplied

Malignant cardiac fibrous histiocytomas and angiosarcomas: MR features.

Primary tumors of the heart are rare, and one-third of them are malignant. The magnetic resonance (MR) features, their specificity, and significance in two patients with malignant fibrous histiocytoma and three patients with angiosarcoma are presented and the literature briefly reviewed. Malignant fibrous histiocytoma occurred in the left atrium and demonstrated slightly heterogeneous intermediate signal intensity on T1-weighted images and high signal intensity on T2-weighted images. The angiosarcomas involving primarily the right heart were more varied in MR appearance with heterogeneous signals. The extensive angiosarcomas almost circumferentially involving the epicardium and pericardium showed the "cauliflower" appearance with focal areas of increased signal intensity probably related to thrombosis or hemorrhage. Magnetic resonance provided detailed anatomic information and characterization of malignant cardiac tumors.

Adult↗
PubMedDate not supplied

MR imaging of liposarcomas: correlation of MR features and histology.

The magnetic resonance (MR) imaging features of liposarcoma were correlated with histology in 15 patients. The MR findings for liposarcoma were not specific. The six myxoid liposarcomas and two atypical lipomatous tumors, however, had distinctive MR features, i.e., nodular masses of slightly heterogeneous intermediate to high signal intensity (SI), intermingled with high SI septa on T1-weighted images. The T2-weighted images demonstrated the relative reversal of these regional SI characteristics. Additionally, MR correctly identified the presence of fat in all eight cases in which it was pathologically present. The fat in two atypical lipomatous tumors was inseparable on MR from the subcutaneous fat. Magnetic resonance appears useful for preoperative staging and follow-up studies of liposarcomas. It may be helpful in identifying patients with myxoid liposarcoma and atypical lipomatous tumors who have longer survival times.

Adult↗
PubMedDate not supplied

MR imaging of extracranial nerve sheath tumors.

We retrospectively reviewed MR images of 32 histologically proven extracranial nerve sheath tumors (NSTs). There were 23 benign (10 neurofibromas, 13 schwannomas) and 9 malignant NSTs. On T1-weighted images (T1WIs) tumors were isointense or slightly hyperintense to muscle. On T2-weighted images (T2WIs) (11 lesions) and enhanced T1WIs (1 intraspinal lesion), a target pattern with peripheral hyperintense rim and central low intensity was seen in 12 of 23 (52%) benign NSTs (5 of 10 neurofibromas and 7 of 13 schwannomas). This pattern corresponded histologically to peripheral myxomatous tissue and central fibrocollagenous tissue. The pattern was absent in lesions with cystic, hemorrhagic, or necrotic degeneration. These tumors were hyperintense and variably inhomogenous on T2WIs. Malignant NSTs were hyperintense and variably inhomogenous on T2WIs and mimicked benign variably inhomogeneous lesions unless involvement of contiguous structures was visualized. A target pattern was not visible in malignant lesions. Magnetic resonance imaging cannot distinguish schwannomas from neurofibromas, and benign tumors may mimic malignant NSTs when cystic, hemorrhagic, and necrotic degeneration is present. A target pattern may be visualized in some benign NSTs, and evaluation of this sign with assessment of location and growth along nerves may help to avoid confusion with other lesions.

Adult↗
PubMedDate not supplied

Primary hepatic lymphoma in a patient with chronic hepatitis C.

The case is presented of a woman with chronic active hepatitis C who developed primary hepatic lymphoma. The possible roles of viral hepatitis and therapeutic interferon in the pathogenesis and progression of this unusual malignancy are discussed. In addition, the importance of accurate tissue diagnosis to identify potentially treatable hepatic tumours is emphasized.

Female↗
PubMedDate not supplied

Acanthamoeba healyi n. sp. and the isoenzyme and immunoblot profiles of Acanthamoeba spp., groups 1 and 3.

Two strains of Acanthamoeba isolated from human brain tissue and a strain of Acanthamoeba isolated from a fish were compared with 10 species of Acanthamoeba belonging to groups 1, 2 and 3 based on their isoenzyme profiles and antigenic characteristics. A total of 12 enzymes were studied. The isoenzymes and antigens were electrophoretically separated on polyacrylamide gradient gels, and the patterns obtained were compared after appropriate staining for particular enzymes and reactivities with homologous and heterologous rabbit anti-Acanthamoeba antisera. One of the human strains (CDC:1283:V013) was identified as A. healyi n. sp. because of its unique isoenzyme profiles for 11 of the 12 enzymes tested. The other human isolate was reidentified as A. culbertsoni because its isoenzyme profiles for 10 of 12 enzymes resembled those of A. culbertsoni, Lilly A-1 strain. Since the isoenzyme profiles and the antigenic patterns of the fish isolate as well were remarkably similar to those of A. royreba, it was considered as a strain of A. royreba. Polyacrylamide gradient gel electrophoresis appears to be a powerful technique for the study of isoenzymes and antigens of Acanthamoeba.

Acanthamoeba↗
PubMedDate not supplied

Inhibition of the spore polar filament extrusion of the microsporidium, Encephalitozoon hellem, isolated from an AIDS patient.

Spores of the microsporidian parasitic protozoan Encephalitozoon hellem were purified and incubated at 37 degrees C in a solution with an electrolyte composition similar to that of mammalian extracellular fluid, and in solution in which the calcium had been replaced with 0.2 mM EGTA. Polar filament extrusion (germination) was monitored by both scanning electron microscopy and light microscopy. Germination was pH-dependent, with optima at pH 7.4 and 9.5, and was significantly greater in the presence of medium calcium. Hydrogen peroxide caused a concentration-dependent increase in germination that was also reduced in a calcium-free medium. Four agents were found to inhibit spontaneous and H2O2-stimulated polar filament extrusion: the microfilament disrupter, cytochalasin D; the microtubule disrupter, demecolcine; the calcium channel blocker, nifedipine; and the antifungal agent, itraconazole. These results are consistent with the existence of a calcium-channel-mediated step, and requirements for an F-actin- and for a tubulin-containing element in the germination process of the spore of this parasite. Nifedipine, cytochalasin D and itraconazole all have different sites of action and were therefore able to potentiate one another when used in paired combination to inhibit germination.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

Calcium and hydrogen ion concentrations in the parasitophorous vacuoles of epithelial cells infected with the microsporidian Encephalitozoon hellem.

Microsporidia of the genus Encephalitozoon undergo merogony and sporogony in a parasitophorous vacuole within the host cell. Cultured green monkey kidney cells infected with Encephalitozoon hellem were loaded with the fluorescent dyes fura-2 or BCECF in order to measure intracellular concentrations of calcium and hydrogen ions respectively. Both the parasitophorous vacuole calcium concentration and pH values resembled those of the host cell cytoplasm in infected cells. Calcein entered the parasitophorous vacuole but not other host cell vacuoles or parasite stages within the parasitophorous vacuole. The lack of a pH or calcium concentration gradient across the parasitophorous vacuole membrane and the permeability of this membrane to a large anion such as calcein suggest that the vacuole membrane surrounding E. hellem resembles that surrounding some other intracellular parasites such as Toxoplasma gondii. A potential role is discussed for the parasitophorous vacuole calcium concentration in germination in situ.

Animals↗
PubMedDate not supplied

Short-term in vitro culture and molecular analysis of the microsporidian, Enterocytozoon bieneusi.

The microsporidium, Enterocytozoon bieneusi, causes a severe, debilitating, chronic diarrhea in patients with the acquired immunodeficiency syndrome. Specific diagnosis of intestinal microsporidiosis, especially due to Enterocytozoon, is difficult and there is no known therapy that can completely eradicate this parasite. Preliminary studies indicate that a short term (about 6 months) in vitro culture of this parasite yielding low numbers of spores, may be established by inoculating human lung fibroblasts and/or monkey kidney cell cultures with duodenal aspirates and or biopsy from infected patients. The cultures may subsequently be used for the isolation and molecular analysis of parasite DNA.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

Microcapsules for arterial chemoembolization: appearance and in vitro drug release characteristics.

Microcapsules made of eight different capsular materials and containing floxuridine (FUDR) were formulated and evaluated with regard to physical properties (size and structure) and in vitro drug release characteristics. Capsules averaged 100, 150 and 200 micron in diameter and appeared as either round or 'crystalline' particles. The degree and pattern of drug release was dependent on the capsular material used. Alteration in the molecular architecture of a specific material produced changes in the percentage of total encapsulated drug released per unit of time, but not in the pattern of release. Changing capsular size or amount of drug contained within the capsules failed to alter either the pattern of drug release or the percentage of encapsulated drug released per unit of time. However, changes in either parameter did affect the total amount of drug released per unit of time.

Capsules↗
PubMedDate not supplied

Cell-killing by paclitaxel in a metastatic murine melanoma cell line is mediated by extensive telomere erosion with no decrease in telomerase activity.

The purpose of this study was to investigate and compare the effects of paclitaxel and its water-soluble conjugates (sodium-pentetic acid-paclitaxel; polyethylene glycol-paclitaxel, and poly[L-glutamic acid]-paclitaxel) on chromosome morphology and induction of apoptosis in a metastatic murine melanoma cell line (K1735 clone X-21). For this, murine melanoma cells were treated continuously for 72 h with three concentrations (1.2 microM, 2.4 microM, and 4.8 microM) of each of paclitaxel, and conjugates. Another set of cells were pulse-treated at 2.4 microM, 4.8 microM and 9.6 microM concentrations of each of these drugs for 4 h and the recovered cells were examined after 72 h. Control cultures received only the solvents (dimethyl sulfoxide or water). Our results showed a significant increase in the frequencies of telomeric associations, chromosome aberrations, polyploidization, distorted and disintegrated chromosome morphology, and reduced telomeric signal intensity by fluorescence in situ hybridization, in treated cultures as compared to the controls. However, we detected no change in telomerase activity. In addition, the majority of interphase nuclei in treated cells showed apoptotic bodies, with chromatin condensation. These in vitro results suggest that cell death induced by paclitaxel and its water-soluble conjugates is due to the loss of telomeric repeats, as shown by reduced signal flourescence and increased telomeric associations.

Animals↗
PubMedDate not supplied

Hepatic chemoembolization: clinical and experimental correlation.

Chemoembolization has become the preferred treatment for patients with inoperable, hypervascular hepatic malignancies in the Far East, but controversial elsewhere. In vivo microscopy in addition to other experimental procedures are used in this presentation to better understand the mechanisms involved in chemoembolization. In chemoembolization Lipiodol acts as a contrast material, a vehicle for chemotherapy and an embolic agent. Although not optimal, Lipiodol injected into the hepatic artery, traverses the peribiliary plexus to the portal veins resulting in a dual embolization. Chemoembolization creates ischemia, slows arterial flow and increases the contact time between the infusate and the neoplasms, increasing the tumor cell kill. However, the vascular occlusion also produces infarction and fibrosis compounding the already existing cirrhosis frequently associated with hepatocellular carcinoma. Lipiodol/ethanol (3:1) injected into the segmental or lobar hepatic artery supplying the neoplasm also gains access to the associated portal venous branches causing focal ablation. This preoperative approach is easier to perform than direct portal vein occlusion, with less parenchymal damage and comparable hypertrophy of the remnant liver frequently necessary for adequate hepatic function following resection. Polymer-drug conjugates, e.g. PG-TXL, have considerable potential for intra-arterial delivery especially with the dramatic increase in concentration of the drug in the tumor and its efficacy. Using in vivo microscopy especially with green fluorescent protein (GFP) gene as an efficient and non-toxic tumor cell marker, the events leading to hepatic metastases can be documented which will serve to better evaluate these varied techniques of chemoembolization.

Animals↗
PubMedDate not supplied

Culture, electron microscopy, and immunoblot studies on a microsporidian parasite isolated from the urine of a patient with AIDS.

Microsporidian spores isolated from a urine sample of an HIV-positive patient were inoculated onto monolayers of six different cell cultures. The parasites (CDC:0291:V213) grew profusely in two of the cultures (HLF and E6) and extruded spores into the culture medium. The spores were Gram-positive, 2.25- to 2.8-microns long, 1.25- to 1.8-microns broad, and smooth-walled. Some of the spores had already extruded their polar tubes, which were either straight or slightly coiled. Infected host cells contained parasitophorous vacuoles filled with developing stages of the parasite, including mature spores. Each spore was surrounded by a thin, electron-dense exospore; a thick electron-lucent endospore; and a thin cell membrane. Cross-sections of six coils of the polar tube were seen inside the spore. Proteins extracted from spores of our isolate and those from Encephalitozoon cuniculi were separated on gradient sodium dodecyl sulfate-polyacrylamide gels and either silver-stained or transferred to nitrocellulose membranes. As many as 35 bands, ranging in molecular mass from 10,000 to 200,000, were visualized in the silver-stained gel. When reacted with the serum of our patient, strips cut from the membrane showed a number of bands ranging in molecular weight from 25,000 to 200,000. However, unique differences between the profiles of the two parasites were seen both in the immunoblot and the silver-stained protein profiles. Based on these findings, we conclude that our isolate belongs to the genus Encephalitozoon, but more studies are needed to identify our isolate to the species level.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Afterloading intracavitary irradiation and expanding stent for malignant biliary obstruction.

A double lumen catheter was developed as an applicator for the remote afterloading (RALS) of 60Co source for the intracavitary irradiation of an obstructed common bile duct caused by carcinoma of the gallbladder. This was followed by the placement of nylon-covered expandable metallic stents to maintain patency. This combination effectively provided palliation.

Brachytherapy↗