Interaction between neutrophils and Schistosoma mansoni larvae in vivo: a transmission electron-microscopic study

Schistosoma mansoni cercariae were inoculated into the peritoneal cavity of naive mice and recovered 30 minutes later. Ultrastructural studies showed that neutrophils adhere to the larval surface and participate in the removal of glycocalyx by phagocytosis. This finding suggests that the neutrophils can play a role on the cercaria-schistosomulum transformation process.

Experimental paracoccidioidomycosis in hamster: transmission electron microscopy of inoculation site lesion

Interaction between Paracoccidioides brasiliensis (Pb) and inflammatory cells in hamster testis was studied sequentially by transmission electron microscopy. In early lesions (six hours after inoculation), polymorphonuclear neutrophils (PMNs) were the major and mononuclear cells and eosinophils were the minor constituents of the inflammatory cells. PMNs were later replaced by mononuclear cells. Viable Pb cells were phagocytosed or surrounded by inflammatory cells. Preserved Pb cells usually had broad host-parasite interphases, whereas dying ones had narrow interphases. The outer layer of the fungus wall was sometimes broken by PMN in some focal points, broken pieces being peeled off and phagocytosed. Small Pb cells were uninuclear, and were often related to broad interphase. Large Pb cells were multinucleated with irregularly shaped wall, and sometimes had lomasome and/or myelin like structures. Different interaction patterns of Pb with inflammatory cells may be due to functionally different host cell flow to the inoculation site or due to the age of Pb cells or both.

Rapid detection by transmission electron microscopy of mycoplasma contamination in sera and cell cultures

Transmission electon microscopy has been employed for the rapid detection of mycoplasma in sera and cell cultures. High speed centrifugation of sera or low speed centrifugation of cell debris, followed by negative staining of the resuspended pellet, detected mycoplasma contamination more frequently than a culture method followed by direct fluorescence (DAPI), which was used as a control procedure. The appearance of the mycoplasma cell border and content gives some information about particle viability.

Scanning and transmission electron microscopy of the tegument of Paranaella luquei Kohn, Baptista-Farias & Cohen, 2000 (Microcotylidae, Monogenea), parasite of a Brazilian catfish, Hypostomus regani

The surface topography and ultrastructure of the tegument of Paranaella luquei Kohn, Baptista-Farias & Cohen, 2000, a microcotylid monogenean parasite from the gills of Hypostomus regani (Ihering, 1905) (Loricariidae) was studied by scanning (SEM) and transmission electron microscopy (TEM). By SEM, it was observed that the tegument presents transversal ridges, forming folds in the ventral and dorsal surfaces and microvillous-like tegumental projections in the anterior and median regions of body. These projections were also observed by TEM. The tegument is made up of a syncytium delimited by apical and basal plasma membranes, containing inclusion bodies and mitochondria, connected to the nucleated region by means of cytoplasmatic processes. The tegumental cells present a well developed nucleus and cytoplasm containing inclusion bodies, similar to those found on the external layer, mitochondria, rough endoplasmatic reticulum and free ribossomes.

The transmission of suprapylarian Leishmania by bite of experimentally infected sand flies (Diptera: Psychodidae)

Lutzomyia furcata transmitted Leishmania chagasi to a hamster 10 days after being experimentally fed on an infected spleen. An individual female Psychodopygus carrerai carrerai that had fed on a hamster lesion caused by Leishmania mexicana amazonensis transmitted this parasite 6 days later to another hamster. Transmission electron microscopy of this fly's head revealed a small number of degenerate promastigotes in the foregut, but only a few were attached.

External morphology of sensory structures of fourth instar larvae of neotropical species of phlebotomine sand flies (Diptera: Psychodidae) under scanning electron microscopy

In the present study, some morphological structures of antennae, maxillary palps and caudal setae of fourth instar larvae of laboratory-reared phlebotomine sand flies (Lutzomyia longipalpis, L. migonei, L. evandroi, L. lenti, L. sericea, L. whitmani and L. intermedia) of the State of Ceará, Brazil, were examined under scanning electron microscopy. The antennal structures exhibited considerable variation in the morphology and position. A prominent digitiform distal segment has been observed only on the antenna of species of the subgenus Nyssomyia. The taxonomic relevance of this and other antennal structure is discussed. The papiliform structures found in the maxillae and the porous structures of the caudal setae of all species examined may have chemosensory function. Further studies with transmission electron microscopy are needed to better understand the physiological function of these external structures.

Giardia muris and Giardia duodenalis groups: ultrastructural differences between the trophozoites

Trophozoites of the Giardia muris group from hamsters, domestic rats and mice and of the Giardia duodenalis group from hamsters and domestic rats were examined by transmission electron microscopy. The basic ultrastructure of the trophozoites was similar. Differences were shown in the morphology of the ventrolateral flange of the trophozoites of Giardia muris and Giardia duodenalis groups. Marginal plates are less developed in the species of the Giardia duodenalis group. In this group, the distal extremity of the lateral flange is short and thick and the marginal plate does not penetrate into the distal extremity of the flange. In the Giardia muris group, the ventro-lateral flange is well developed and narrow and the marginal plate penetrates the distal extremity of the flange. The osmiophilic lamella, which accompanies the dorsal surface of the marginal plate is seen only in the Giardia muris group.

Clinical and diagnostic aspects of intestinal microsporidiosis in HIV-infected patients with chronic diarrhea in Rio de Janeiro, Brazil

The objectives of this study were to determine both the prevalence of microsporidial intestinal infection and the clinical outcome of the disease in a cohort of 40 HIV-infected patients presenting with chronic diarrhea in Rio de Janeiro, Brazil. Each patient, after clinical evaluation, had stools and intestinal fragments examined for viral, bacterial and parasitic pathogens. Microsporidia were found in 11 patients (27.5%) either in stools or in duodenal or ileal biopsies. Microsporidial spores were found more frequently in stools than in biopsy fragments. Samples examined using transmission electron microscopy (n=3) or polymerase chain reaction (n=6) confirmed Enterocytozoon bieneusi as the causative agent. Microsporidia were the only potential enteric pathogens found in 5 of the 11 patients. Other pathogens were also detected in the intestinal tract of 21 patients, but diarrhea remained unexplained in 8. We concluded that microsporidial infection is frequently found in HIV infected persons in Rio de Janeiro, and it seems to be a marker of advanced stage of AIDS.

ULTRASTRUCTURAL CHANGES IN Schistosoma mansoni MALE WORMS AFTER in vitro INCUBATION WITH THE ESSENTIAL OIL OF Mentha x villosa Huds

Introduction: The essential oil Mentha x villosa (MVEO) has a wide range of actions, including antibacterial, antifungal, antiprotozoal and schistosomicidal actions. The present study aimed to investigate the ultrastructural changes of MVEO on the tegument of adult Schistosoma mansoni. Materials and Methods: Different concentrations of MVEO were tested on S. mansoni adult worms in vitro. Ultrastructural changes on the tegument of these adult worms were evaluated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results: The MVEO caused the death of all worms at 500 μg mL-1 after 24 h. After 24h of 500 μg mL-1 MVEO treatment, bubble lesions were observed over the entire body of worms and they presented loss of tubercles in some regions of the ventral portion. In the evaluation by TEM, S. mansoni adult worms treated with MVEO, 500 μg mL-1, presented changes in the tegument and vacuoles in the syncytial matrix region. Glycogen granules close to the muscle fibers were visible. Conclusion: The ability of MVEO to cause extensive ultrastructural damage to S. mansoni adult worms correlates with its schistosomicidal effects and confirms earlier findings with S. mansoni.

Removal of Trypanosoma cruzi by white cell-reduction filters: an electronmicroscopic study

White cell (WBC)-reduction filters have been shown to be effective in removing infectious agents from infected blood products. In this study, the mechanisms of Trypanosoma cruzi (T. cruzi) retention by WBC-reduction filters were assessed. Human packed red blood cell (PRBC) and platelet concentrate (PC) samples were contaminated with T. cruzi organisms (Y strain; 3.4 x 10(6)/ml), and then filtered using WBC-reduction experimental filters that provided about 3 log10 WBC removal. Transmission electron microscopy sections showed that T. cruzi parasites were removed from contaminated PRBC and PC samples primarily by mechanical mechanism without interacting with filter fibbers or blood cells. In addition, we found that T. cruzi parasites were also removed by a direct fibber adhesion. These data indicate that T. cruzi parasites are removed from infected blood not only by mechanical mechanism but also by biological mechanism probably mediated by parasite surface proteins.

Hepatitis B virus surface antigen (HBsAg) and antibody (anti-HBs) forming immune complexes in fulminant hepatitis

This paper reports an unusual pattern of serological HBV markers and the presence of HBsAg/anti-HBs immune complexes in serum samples from two patients with fulminant hepatitis from the Brazilian Western Amazon Basin. The diagnosis was made by both serologic tests and demonstration of antigen/antibody complexes by transmission electron microscopy. Concurrent Delta virus superinfection is also discussed.

Colistin and anti-Gram-positive bacterial agents against Acinetobacter baumannii

Introduction Acinetobacter baumannii has attained an alarming level of resistance to antibacterial drugs. Clinicians are now considering the use of older agents or unorthodox combinations of licensed drugs against multidrug-resistant strains to bridge the current treatment gap. We investigated the in vitro activities of combination treatments that included colistin with vancomycin, norvancomycin or linezolid against multidrug-resistant Acinetobacter baumannii. Methods The fractional inhibitory concentration index and time-kill assays were used to explore the combined effects of colistin with vancomycin, norvancomycin or linezolid against 40 clinical isolates of multidrug-resistant Acinetobacter baumannii. Transmission electron microscopy was performed to evaluate the interactions in response to the combination of colistin and vancomycin. Results The minimum inhibitory concentrations (MICs) of vancomycin and norvancomycin for half of the isolates decreased below the susceptibility break point, and the MIC of linezolid for one isolate was decreased to the blood and epithelial lining fluid concentration using the current dosing regimen. When vancomycin or norvancomycin was combined with subinhibitory doses of colistin, the multidrug-resistant Acinetobacter baumannii test samples were eradicated. Transmission electron microscopy revealed that subinhibitory doses of colistin were able to disrupt the outer membrane, facilitating a disruption of the cell wall and leading to cell lysis. Conclusions Subinhibitory doses of colistin significantly enhanced the antibacterial activity of vancomycin, norvancomycin, and linezolid against multidrug-resistant Acinetobacter baumannii.

Antimonial drugs entrapped into phosphatidylserine liposomes: physicochemical evaluation and antileishmanial activity

Abstract: INTRODUCTION: Leishmaniasis is a disease caused by the protozoan Leishmania that resides mainly in mononuclear phagocytic system tissues. Pentavalent antimonials are the main treatment option, although these drugs have toxic side effects and high resistance rates. A potentially alternative and more effective therapeutic strategy is to use liposomes as carriers of the antileishmanial agents. The aims of this study were to develop antimonial drugs entrapped into phosphatidylserine liposomes and to analyze their biological and physicochemical characteristics. METHODS: Liposomes containing meglumine antimoniate (MA) or pentavalent antimony salt (Sb) were obtained through filter extrusion (FEL) and characterized by transmission electron microscopy. Promastigotes of Leishmania infantum were incubated with the drugs and the viability was determined with a tetrazolium dye (MTT assay). The effects of these drugs against intracellular amastigotes were also evaluated by optical microscopy, and mammalian cytotoxicity was determined by an MTT assay. RESULTS: Liposomes had an average diameter of 162nm. MA-FEL showed inhibitory activity against intracellular L. infantum amastigotes, with a 50% inhibitory concentration (IC50) of 0.9μg/mL, whereas that of MA was 60μg/mL. Sb-FEL showed an IC50 value of 0.2μg/mL, whereas that of free Sb was 9μg/mL. MA-FEL and Sb-FEL had strong in vitro activity that was 63-fold and 39-fold more effective than their respective free drugs. MA-FEL tested at a ten-times higher concentration than Sb-FEL did not show cytotoxicity to mammalian cells, resulting in a higher selectivity index. CONCLUSIONS: Antimonial drug-containing liposomes are more effective against Leishmania-infected macrophages than the non-liposomal drugs.