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Biomedical subjects

L M Weiss

Publications and source records attributed to L M Weiss.

395 records · Page 22Linked to original sources
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Brachiola vesicularum, n. g., n. sp., a new microsporidium associated with AIDS and myositis.

Brachiola vesicularum, n. g., n. sp., is a new microsporidum associated with AIDS and myositis. Biopsied muscle tissue, examined by light and electron microscopy, revealed the presence of organisms developing in direct contact with muscle cell cytoplasm and fibers. No other tissue types were infected. All parasite stages contain diplokaryotic nuclei and all cell division is by binary fission. Sporogony is disporoblastic, producing 2.9 x 2 microns diplokaryotic spores containing 8-10 coils of the polar filament arranged in one to three rows, usually two. Additionally, this microsporidium produces electron-dense extracellular secretions and vesiculotubular appendages similar to Nosema algerae. However, the production of protoplasmic extensions which may branch and terminate in extensive vesiculotubular structures is unique to this parasite. Additionally, unlike Nosema algerae, its development occurred at warm blooded host temperature (37-38 degrees C) and unlike Nosema connori, which disseminates to all tissue types, B. vesicularum infected only muscle cells. Thus, a new genus and species is proposed. Because of the similarities with the genus Nosema, this new genus is placed in the family Nosematidae. Successful clearing of this infection (both clinically and histologically) resulted from treatment with albendazole and itraconozole.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

Intracellular Ca2+ homeostasis in trypomastigotes of Trypanosoma cruzi.

Trypomastigotes of Trypanosoma cruzi maintain an intracellular Ca2+ concentration ([Ca2+]i) of 64 +/- 30 nM. Equilibration of trypomastigotes in an extracellular buffer containing 0.5 mM [Ca2+]o (preloaded cells) increased [Ca2+]i < 20 nM whereas total cell Ca2+ increased by 1.5 to 2.0 pmole/cell. This amount of Ca2+ would be expected to increase [Ca2+]i to > 10 microM suggesting active sequestration of Ca2+. We tested the hypothesis that maintenance of [Ca2+]i involved both the sequestration into intracellular storage sites and extrusion into the extracellular space. Pharmacological probes known to influence [Ca2+]i through well characterized pathways in higher eukaryotic cells were employed. [Ca2+]i responses in the presence or absence of [Ca2+]o were measured to asses the relative contribution of sequestration or extrusion processes in [Ca2+]i homeostasis. In the presence of 0.5 mM [Ca2+]o, the ability of several agents to increase [Ca2+]i was magnified in the order ionomycin >>> nigericin > thapsigargin > monensin > valinomycin. In contrast, preloading markedly enhanced the increase in [Ca2+]i observed only in response to monensin. Manoalide, an inhibitor of phospholipase A2, enhanced the accumulation of [Ca2+]i due to all agents tested, particularly ionomycin and thapsigargin. Our results suggest that sequestration of [Ca2+]i involved storage sites sensitive to monensin and ionomycin whereas extrusion of Ca2+ may involve phospholipase A2 activity. A Na+/Ca2+ exchange mechanism did not appear to contribute to Ca2+ homeostasis.

Animals↗
PubMedDate not supplied

Polar tube proteins of microsporidia of the family encephalitozoonidae.

Encephalitozoonidae are microsporidia associated with human infections including hepatitis, encephalitis, conjunctivitis, and disseminated disease. Microsporidia produce a small resistant spore containing a polar tube which serves as a unique vehicle of infection. Polar tube proteins (PTPs) from Encephalitozoon hellem. Encephalitozoon (Septata) intestinalis, and Encephalitozoon cuniculi were purified to homogeneity by HPLC. By SDS-PAGE, the Mr of E. hellem PTP was 55 kDa, while the Mr of E. intestinalis and E. cuniculi PTP was 45 kDa. Polyclonal rabbit antiserum to these purified PTPs localized to polar filaments by immunogold electron microscopy and immunofluorescence, and demonstrated cross-reactivity by both immunoblotting and immunogold electron microscopy. These PTPs have similar solubility properties, hydrophobicity, and proline content to a 43-kDa PTP we have previously purified from Glugea americanus, a fish microsporidium. As the polar tube is critical in the transmission of this organism, further study of PTPs may lead to the development of new therapeutic strategies and diagnostic tests.

Animals↗
PubMedDate not supplied

Polyamine synthesis and interconversion by the Microsporidian Encephalitozoon cuniculi.

Polyamines are small cationic molecules necessary for growth and differentiation in all cells. Although mammalian cells have been studied extensively, particularly as targets of polyamine antagonists, i.e. antitumor agents, polyamine metabolism has also been studied as a potential drug target in microorganisms. Since little is known concerning polyamine metabolism in the microsporidia, we investigated it in Encephalitozoon cuniculi, a microspordian associated with disseminated infections in humans. Organisms were grown in RK-13 cells and harvested using Percoll gradients. Electron microscopy indicated that the fractions banding at 1.051-1.059/g/ml in a microgradient procedure, and 1.102-1.119/g/ml in a scaled-up procedure were nearly homogenous, consisting of pre-emergent (immature) spores which showed large arrays of ribosomes near polar filament coils. Intact purified pre-emergent spores incubated with [1H] ornithine and methionine synthesized putrescine, spermidine, and spermine, while [14C]spermine was converted to spermidine and putrescine. Polyamine production from ornithine was inhibitable by DL-alpha-difluoromethylornithine (DFMO) but not by DL-alpha-difluoromethylarginine (DFMA). Cell-free extracts from mature spores released into the growth media had ornithine decarboxylase (ODC), S-adenosylmethionine decarboxylase (AdoMetdc), and spermidine/spermine N1-acetyltransferase (SSAT) activities. ODC activity was inhibited by DFMO, but not by DFMA. AdoMetdc was putrescine-stimulated and inhibited by methylglyoxal-bis(guanylhydrazone); arginine decarboxylase activity could not be detected. It is apparent from these studies that Encephalitozoon cuniculi pre-emergent spores have a eukaryotic-type polyamine biosynthetic pathway and can interconvert exogenous polyamines. Pre-emergent spores were metabolically active with respect to polyamine synthesis and interconversion, while intact mature spores harvested from culture supernatants had little metabolic activity.

Acetyltransferases↗
PubMedDate not supplied

Cytology of angiosarcoma in effusions.

The cytologic and immunocytochemical findings in pleural effusions from three cases of angiosarcoma are presented. In two of the cases, the primary lesion was on the scalp; in the third case, an angiosarcoma of the small intestine developed after radiotherapy for Hodgkin's disease. Single malignant cells and small clusters of cells were seen in cytologic preparations from two cases while only single cells were seen in preparations from one case. The malignant cells had delicate, finely vacuolated cytoplasm with distinct borders. No specific morphologic features were noted. Immunoperoxidase studies revealed binding of Ulex europaeus and reactivity for vimentin in all three cases and expression of Factor VIII-related protein in two of the cases but no expression of epithelial markers. The clinical history and immunoperoxidase studies are necessary to distinguish angiosarcoma from metastatic adenocarcinoma and other malignancies in effusions.

Aged↗
PubMedDate not supplied

Disseminated histoplasmosis diagnosed by fine needle aspiration biopsy of the adrenal gland. A case report.

A case of disseminated histoplasmosis diagnosed by fine needle aspiration (FNA) biopsy of the adrenal gland is reported for a 60-year-old man who presented with a 40-pound weight loss and abdominal computed tomography showing bilateral adrenal enlargement. FNA biopsy of the adrenal gland revealed clusters of macrophages with abundant cytoplasm containing the yeast forms of Histoplasma capsulatum. This case emphasizes that FNA is effective in diagnosing infectious as well as neoplastic conditions of the adrenal glands.

Adrenal Glands↗
PubMedDate not supplied

Graft coronary disease in pediatric heart and combined heart-lung transplant recipients: a study of fifteen cases.

Graft coronary disease (GCD) has emerged as the most important deterrent to long-term survival in adult heart transplant recipients. The incidence, natural history, and pathobiology of GCD is less well understood in the pediatric transplant population. This study evaluated the histopathologic and immunohistochemical features of GCD in the Stanford pediatric heart and heart-lung group. Eighty-eight patients, ages 1 week to 18 years, received heart transplants between 1974 and 1992, and 15 patients, ages 1 month to 18 years received heart-lung transplants between 1981 and 1992 at Stanford University Hospital. There were 50 males and 38 females in the heart transplant group; 39 (11%) had idiopathic cardiomyopathy, 26 (30%) had congenital heart disease, 13 (15%) had viral cardiomyopathy, seven (8%) had familial cardiomyopathy, two (2%) had cardiomyopathy resulting from doxorubicin therapy, and one other case was not further delineated. In the heart-lung transplant group, there were eight males and seven females; pretransplantation diagnoses included nine (60%) with congenital heart disease and Eisenmenger's physiology, three (20%) with primary pulmonary hypertension, and one (7%) each with cystic fibrosis, bronchopulmonary dysplasia, and congenital lymphangiectasia. Fifteen (17%) of the heart transplant recipients and three (20%) of the heart-lung transplant recipients had GCD on angiographic or pathologic examination. Histopathologic samples were available on 14 cases (11 heart transplants and three heart-lung transplants).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Epstein-Barr virus-associated gastric adenocarcinoma among Japanese Americans in Hawaii.

This study confirms the observation that some gastric adenocarcinomas contain Epstein-Barr viral (EBV) sequences in their carcinoma cells. EBV sequences were detected by polymerase chain reaction and in situ hybridization in the tumors of 19 of 187 (10.2%) Japanese-American men and women living in Hawaii. The EBV-associated gastric cancers were more frequently present in men than in women: 14 of 99 (14.3%) men versus 5 of 88 (5.7%) women (P = 0.046). EBV type A was found in 17 of the 19 EBV-associated cancers, a finding consistent with the type A predominance in Japanese populations. Intestinal and diffuse-type tumors were both EBV-positive, and moderate to marked inflammation was usually present. The virus was not found in adjacent normal nonneoplastic mucosal cells or in mucosa showing intestinal metaplasia. EBV-associated tumors were found at stages 1 or 2 in 53% of cases, compared with 36% of the EBV-negative cancers (P = 0.13). The presence of EBV did not appear to influence survival. The relatively high incidence of gastric cancer compared to other EBV-associated tumors makes EBV-associated gastric cancer potentially one of the most common EBV-related tumors in the United States.

Adenocarcinoma↗