RESUMEN
The present study aimed to describe F. pedrosoi propagules capable of causing chronic murine disease. Several changes in F. pedrosoi hyphae were identified in fungal cells cultured for a long period. Optical microscopy found many rounded cells with double-rigid melanin-rich walls. Terminal and intercalary chlamydoconidia were also frequently observed. Analyses of images from transmission electron microscopy (TEM) revealed several cells with walls composed of at least three layers and an outer layer enriched with melanin. Two groups of twenty BALB/c mice were subcutaneously infected in their footpads with F. pedrosoi cells at an inoculum concentration of approximately 1 x 10(4) cells/mL. In one group, long-term cultured F. pedrosoi cells were inoculated in one footpad, whereas in the other group, both footpads were infected. Active lesions were observed up to seven months post-infection, particularly in mice inoculated at two sites. After this period, animals were killed. Histological sections revealed characteristics bearing a strong resemblance to the human form of the disease such as tissue hyperplasia, granulomas with microabscesses and sclerotic cells. Based on this study, we identified fungal cells from old cultures capable of provoking chronic chromoblastomycosis under experimental conditions, especially when more than one site is infected.
Asunto(s)
Animales , Masculino , Ratones , Cromoblastomicosis , Hongos/aislamiento & purificación , Ratones Endogámicos BALB C , MurinaeRESUMEN
Summary The aim of this study was to describe and localize the intercellular junctions in the ora serrata region of albino and pigmented rabbit eyes. Eyes of albino and pigmented rabbits were fixed and processed for transmission electron microscopy. Light and electron microscope examination was carried out on semithin and ultrathin sections. The ora serrata region showed adherens, gap and tight junctions in the retinal and ciliary margins of albino and pigmented rabbit eyes. In the retinal margin, zonulae adherens between Müller cells and photoreceptors are associated with tight junctions. In the ciliary margin, epithelial cells are joined by adherens, gap and tight junctions localized between apical and apicolateral cell membranes. Tight junctions appear as zonulae occludens in the non-pigmented apicolateral cell membranes and as tight focal junctions between pigmented and non-pigmented apical cell membranes. Between the ciliary and retinal margins there are adherens and tight focal junctions which attach pigmented apical cell membranes to adjacent cells. There were no differences in the distribution of intercellular junctions between albino and pigmented rabbits.
Asunto(s)
Cuerpo Ciliar/ultraestructura , Ojo/ultraestructura , Uniones Intercelulares/ultraestructura , Epitelio Pigmentado Ocular/ultraestructura , Conejos , Animales , Ojo/anatomía & histología , Microscopía Electrónica de Transmisión/métodos , Microscopía Electrónica de Transmisión/veterinaria , Conejos/anatomía & histología , Retina/ultraestructuraRESUMEN
The process of vascularization of the enamel organ, a unique epithelial structure, occurs when the tooth germ is fully developed, i.e., at the onset of dentinogenesis. Although the three-dimensional organization of the capillaries has been previously investigated, the structural features underlying the formation of the new capillaries remains poorly understood. Thus, in the hope of better understanding the mechanism of formation of the stellate reticulum capillaries, upper first molar tooth germs of newborn and 3-day-old rats were fixed in glutaraldehyde-formaldehyde and processed for light and electron microscopy. Our results showed that blood capillaries are initially in close proximity to the outer enamel epithelium. Between and intercalated with the capillaries are round/ovoid clusters of cells, some of which are vacuolated, closely apposed to the outer enamel epithelium. The outer enamel epithelium is not a continuous layer, but exhibits gaps between the cells. This suggests that the capillaries penetrate the enamel organ through these gaps, since no invagination of the epithelium was observed. The presence of a cluster of cells containing vacuoles suggests that vasculogenesis is taking place. Images showing loss of the basal lamina, proliferation of endothelial cells, presence of filopodia and lateral sprouting suggests that angiogenesis is also occurring. Thus, neoformation of capillaries of the molar enamel organ of rat seems to occur simultaneously by mechanisms of vasculogenesis and angiogenesis.
Asunto(s)
Capilares/anatomía & histología , Órgano del Esmalte/irrigación sanguínea , Órgano del Esmalte/ultraestructura , Diente Molar , Germen Dentario/irrigación sanguínea , Animales , Animales Recién Nacidos , Órgano del Esmalte/crecimiento & desarrollo , Femenino , Masculino , Ratas , Ratas WistarRESUMEN
In amphibia, steroidogenesis remains quiescent in distinct seasonal periods, but the mechanism by which spermatogenesis is maintained under low steroidogenic conditions is not clear. In the present study, testosterone location in the testes of Rana catesbeiana was investigated immunohistochemically during breeding (summer) and nonbreeding (winter) periods. In winter, the scarce interstitial tissue exhibited occasional testosterone immunopositivity in the interstitial cells but the cytoplasm of primordial germ cells (PG cells) was clearly immunopositive. By contrast, in summer, PG cells contained little or no immunoreactivity whereas strong immunolabelling was present in the well-developed interstitial tissue. These results suggest that PG cells could retain testosterone during winter. This androgen reservoir could be involved in the control of early spermatogenesis in winter and/or to guarantee spermiogenesis and spermiation in the next spring/summer. The weak or negative immunoreaction in the summer PG cells might reflect consumption of androgen reservoir by the intense spermatogenic activity from spring to summer. Thus, besides acting as stem cells, PG cells of R. catesbeiana could exert an androgen regulatory role during seasonal spermatogenesis.
Asunto(s)
Rana catesbeiana/metabolismo , Espermatozoides/química , Testículo , Testosterona/análisis , Animales , Citoplasma/química , Inmunohistoquímica/métodos , Células Intersticiales del Testículo/química , Masculino , Estaciones del Año , Espermatogénesis/fisiología , Espermatozoides/fisiologíaRESUMEN
Some anurans have a peculiar casqued head with the skin co-ossified with the underlying bones. This type of skull usually is associated with phragmosis, a protective behaviour in which the animal enters a hole and closes it with the head. Although co-ossification of the head in lissamphibians frequently has been associated with water economy, recent studies of Corythomantis greeningi, a casque-headed tree frog from semi-arid areas in north-eastern Brazil, suggest that cranial co-ossification contributes little to conservation of water in the frog. Instead, during phragmotic behaviour, the co-ossified head protects the animal against predators and indirectly enhances water balance. Thus, the primary role of co-ossification is defence, a hypothesis that is the focus of this study, which describes the morphology of the head of C. greeningi with an emphasis on the co-ossification and the venom glands. We report on behavioural features and on the toxicity of the cutaneous secretion produced by the abundant venom glands that are associated with large spicules on the skull.
Asunto(s)
Animales , Anuros/anatomía & histología , Anuros/clasificaciónRESUMEN
PURPOSE: To evaluate the potential of photodynamic therapy using indocyanine green for occlusion of choroidal neovascularization, the authors studied efficiency and collateral damage of photodynamic therapy-induced photothrombosis in the rabbit choriocapillary layer. METHODS: Fundus photography, fluorescein angiography, and light and transmission electron microscopy were used to study the efficiency of photodynamic therapy-induced photothrombosis using indocyanine green as the photosensitizer, and to assess the resultant collateral damage. The delivery system consisted of a modified infrared diode laser tuned to 810 nm, near the maximum absorption peak of indocyanine green. RESULTS: Choriocapillary occlusion was achieved at indocyanine green doses of 10 and 20 mg/kg and a radiant as low as 6.3 J/cm(2). When photodynamic therapy was performed with indocyanine green doses of 10 mg/kg, damage to the neural retina was minimal. Only inner photoreceptor segments showed degeneration, probably secondary to choroidal ischemia. Bruch membrane remained intact. Retinal pigment epithelium was invariably damaged, as seen with other photosensitizers. Temporary occlusion of large choroidal vessels occurred at both dye doses. CONCLUSIONS: In this experimental study, photodynamic therapy using indocyanine green and 810-nm light irradiation produced endothelium-bound intraluminal photothrombosis, with preservation of the retinal architecture and minimal loss of visual cells. Membrane targetability, hydrophilic and fluorescent properties, and activation at 805 nm suggest indocyanine green as a potential photosensitizer for choroidal neovascularization. These combined considerations point toward further study of photodynamic therapy using indocyanine green for the treatment of choroidal vascular disease.
Asunto(s)
Coroides/irrigación sanguínea , Neovascularización Coroidal/tratamiento farmacológico , Verde de Indocianina/uso terapéutico , Fotoquimioterapia , Fármacos Fotosensibilizantes/uso terapéutico , Animales , Barrera Hematorretinal , Coroides/ultraestructura , Neovascularización Coroidal/patología , Angiografía con Fluoresceína , Fondo de Ojo , Luz , Conejos , Retina/lesiones , Retina/ultraestructuraRESUMEN
The pathogenic mechanisms of enteroaggregative Escherichia coli (EAEC) are not well defined. We investigated the interaction of EAEC strain 236 (serotype O111:H12) with polarised Caco-2 and T84 human intestinal epithelial cells lines, and with human jejunal and colonic mucosa. Strain 236 adhered to both polarised cell lines and to both intestinal tissue types, but caused severe damage and was invasive only in T84 cells and colonic mucosa. In contrast, prototype EAEC strain 042, which also adhered to the cultured intestinal cell lines, did not adhere to or invade jejunal or colonic tissue. These observations suggest a heterogeneity of virulence properties within the EAEC category of diarrhoea-causing E. coli.
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Colon/microbiología , Escherichia coli/patogenicidad , Mucosa Intestinal/microbiología , Adhesión Bacteriana , Células CACO-2 , Línea Celular , Niño , Escherichia coli/clasificación , Humanos , Yeyuno/microbiología , Microscopía Electrónica , Serotipificación , VirulenciaRESUMEN
Some species of anuran amphibians possess a calcified dermal layer (the Eberth-Kastschenko layer) located between the "stratum spongiosum" and the "stratum compactum." This layer consists of calcium phosphate deposits, proteoglycans, and glycosaminoglycans. Although regarded as a protective layer against desiccation, a calcium reservoir, or possibly a remnant of a dermal skeleton present in anuran ancestors, very little is known about its origin, structure, and function. Thus, we studied the structure and composition of the mineralized dermal layer of Corythomantis greeningi, a peculiar hylid from the Brazilian semiarid region (caatinga), using conventional and cryosubstitution methods combined with transmission, scanning, and analytical electron microscopy. Results show that the dermal layer consists of dense, closely juxtaposed, globular structures. Although the electron opacity of the globules was variable, depending on the type of preparation, crystal-like inclusions were present in all of them, as confirmed by dark field microscopy. Electron probe X-ray microanalysis showed calcium, phosphorus, and oxygen, and electron diffraction revealed a crystalline structure comparable to that of a hydroxyapatite.
Asunto(s)
Anuros/anatomía & histología , Piel/anatomía & histología , Piel/citología , Piel/ultraestructura , Animales , Brasil , Microanálisis por Sonda Electrónica , Microscopía Electrónica , Microscopía Electrónica de Rastreo , Coloración y Etiquetado , Difracción de Rayos XRESUMEN
In trypanosomes transcription occurs as large polycistronic units, with trans-splicing and polyadenylation generating each individual mRNA. There are no defined RNA polymerase II promoters and mRNA stabilisation is most likely the process controlling levels of differentially expressed mRNAs, since no selective modulation of gene activity has even been reported at the transcriptional level. Here, we show a large decrease in the transcription rates by RNA polymerases I and II when proliferative forms of Trypanosoma cruzi (epimastigotes and amastigotes) transform into non-proliferative and infective forms (trypomastigotes). We also show that these changes in transcription occur in parallel with modifications in the nuclear structure. While nuclei of proliferative forms are round, contain small amounts of peripheral heterochromatin and a large nucleolus, nuclei of trypomastigotes are elongated, the nucleolus disappears and the heterochromatin occupies most of the nuclear compartment. The decrease in the transcription parallels the nucleolus disassembly, as seen by the dispersion of nucleolar antigens. As T. cruzi cycles continuously through proliferative and infective forms, the molecular mechanisms involved in the control of nuclear organisation and chromatin remodelling can be revealed by this system.
Asunto(s)
Núcleo Celular/ultraestructura , Enfermedad de Chagas/parasitología , Regulación del Desarrollo de la Expresión Génica , Transcripción Genética , Trypanosoma cruzi/crecimiento & desarrollo , Animales , Línea Celular , Medios de Cultivo , Técnica del Anticuerpo Fluorescente , Immunoblotting , Estadios del Ciclo de Vida , Microscopía Electrónica , ARN Polimerasa I/genética , ARN Polimerasa I/metabolismo , ARN Polimerasa II/genética , ARN Polimerasa II/metabolismo , Trypanosoma cruzi/genética , Trypanosoma cruzi/metabolismoRESUMEN
Some species of anuran amphibians possess a calcified dermal layer (the Eberth-Kastschenko layer) located between the "stratum spongiosum" and the "stratum compactum". This layer consists of calcium phosphate deposits, proteoglycans, and glycosaminoglycans. Although regarded as a protective layer against desiccation, a calcium reservoir, or possibly a remnant of a dermal skeleton present in anuran ancestors, very little is known about its origin, structure, and function. Thus, we studied the structure and composition of the mineralized dermal layer of Corythomantis greeningi, a peculiar hylid from the Brazilian semiarid region (caatinga), using conventional and cryosubstitution methods combined with transmission, scanning, and analytical electron microscopy. Results show that the dermal layer consists of dense, closely juxtaposed, globular structures. Although the electron opacity of the globules was variable, depending on the type of preparation, crystal-like inclusions were present in all of them, as confirmed by dark field microscopy. Electron probe X-ray microanalysis showed calcium, phosphorus, and oxygen, and electron diffraction revealed a crystalline structure comparable to that of a hydroxyapatite.
Asunto(s)
Animales , Anuros/anatomía & histología , PielRESUMEN
The effects of gonadal steroids or tamoxifen over the synaptic density of the CA1 region of the hippocampus was investigated in ovariectomized (OVX) rats. Chronic oral administration of conjugated equine estrogen, conjugated equine medroxyprogesterone, a combination of both or tamoxifen was performed in ovariectomized (OVX) rats over a period of 60 days. Synaptic density of the stratum radiatum of the CA1 region was evaluated by means of electron microscopy. Significant increases in the range of 34-49% were found for treated animals as compared to OVX controls not subject to hormonal replacement. Our results confirm previously reported effects of estradiol over synaptic density in this region and reports for the first time an effect of medroxyprogesterone (alone or in combination with estrogen) and tamoxifen. Our findings support the notion that hormonal replacement therapy and tamoxifen might have beneficial effects for cognitive function.
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Estrógenos/administración & dosificación , Hipocampo/efectos de los fármacos , Medroxiprogesterona/administración & dosificación , Sinapsis/efectos de los fármacos , Tamoxifeno/administración & dosificación , Administración Oral , Animales , Recuento de Células , Esquema de Medicación , Antagonistas de Estrógenos/farmacología , Femenino , Hipocampo/ultraestructura , Ovariectomía , Congéneres de la Progesterona/farmacología , Ratas , Ratas Wistar , Sinapsis/ultraestructuraRESUMEN
Development of the periodontium involves a series of complex steps that result in the formation of root dentine, cementum, bone and fibres of the ligament. These precisely controlled and timed events require the participation of the enamel organ derived epithelial cells of Hertwig's (HRS) and ectomesenchymal cells of the dental follicle. These events involve rapid turnover of the tissues and cells, including disappearance of epithelial cells of HRS. Thus, it seemed likely to us that programmed cell death (apoptosis) may play a role in the development of the periodontium. Fragments of first molars, obtained from 14- and 29-day-old rats, were fixed in glutaraldehyde-formaldehyde and processed for light and electron microscopy. For the TUNEL method for detection of apoptosis, specimens were fixed in 4% formaldehyde and embedded in paraffin. Results confirmed that epithelial cells of HRS maintain a close relationship with the forming dentine root, and that they may become trapped in the dentino-cemental junction. Some of the epithelial cells exhibited ultrastructural features which are consistent with the interpretation that they were undergoing programmed cell death, i.e. apoptosis. Periodontal fibroblast-like cells showed typical images of apoptosis and engulfed apoptotic bodies. TUNEL positive structures were present in all corresponding regions. It seems therefore that apoptosis of epithelial cells of HRS and fibroblast-like cells of the periodontal ligament constitutes an integral part of the developmental process of the tissues of the periodontium.
Asunto(s)
Apoptosis , Diente Molar/crecimiento & desarrollo , Periodoncio/crecimiento & desarrollo , Envejecimiento , Animales , Esmalte Dental/citología , Esmalte Dental/crecimiento & desarrollo , Etiquetado Corte-Fin in Situ , Microscopía Electrónica , Diente Molar/citología , Periodoncio/citología , Periodoncio/ultraestructura , Ratas , Ratas WistarRESUMEN
The femoral or cloacal region of many species of lizards and amphisbaenians exhibits epidermal glands. The pores of these glands are plugged with holocrine solid secretions that serve as semiochemical sources. Many authors assume that these glands are mainly associated with reproduction and demarcation of territory. The structure of precloacal glands in Amphisbaena alba was previously studied by Antoniazzi et al. (Zoomorphology 113:199-203, 1993; J. Morphol. 221:101-109, 1994). These authors suggested that as the animal moves inside tunnels, the secretion plugs are abraded against the substrate, releasing a secretion trail. Some aspects of the plug were difficult to interpret in fine sections due to the dense and brittle nature of the plug. The morphology of the trail, and the manner of deposition on the substrate, have never been reported. This study presents a primarily scanning electron microscopic description of A. alba precloacal glands and of the secretion plugs. It also demonstrates experimentally the formation of the trail and its fine morphology. The results show that when the plugs scrape against the substrate, their constitution helps them to fragment into tiny pieces, which are spread on the ground, thus forming a trail. Each one of the fragments corresponds to a secretion granule of the precloacal gland's secretory cells. In this way, the trail might have an extensive area for volatilization of semiochemicals, constituting an efficient means of intraspecific communication inside the tunnels.
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Cloaca , Epidermis/ultraestructura , Glándulas Perianales/ultraestructura , Reptiles/anatomía & histología , Glándulas Odoríferas/ultraestructura , Animales , Microscopía Electrónica de Rastreo , Glándulas Perianales/metabolismo , Feromonas/metabolismo , Glándulas Odoríferas/metabolismoRESUMEN
The meta 1 gene of Leishmania major is upregulated in metacyclic promastigotes and encodes an 11.5-kDa protein with no significant similarities to other proteins in the existing databases. In this paper, we characterize the homologous meta 1 genes in L. amazonensis and L. donovani. Proteins encoded by this gene in all three species present a high degree of identity. The meta 1 gene cannot be replaced by gene targeting in L. major, suggesting an essential role for the protein, at least in promastigotes. Overexpression of the meta 1 protein in L. amazonensis generates parasites that are more virulent than wild-type organisms in vivo.
Asunto(s)
Leishmania donovani/genética , Leishmania mexicana/genética , Proteínas Protozoarias/genética , Secuencia de Aminoácidos , Animales , Clonación Molecular , ADN Protozoario/química , Regulación del Desarrollo de la Expresión Génica , Leishmania donovani/química , Leishmania donovani/crecimiento & desarrollo , Leishmania donovani/patogenicidad , Leishmania major/química , Leishmania major/genética , Leishmania mexicana/química , Leishmania mexicana/crecimiento & desarrollo , Leishmania mexicana/patogenicidad , Leishmaniasis Cutánea/parasitología , Leishmaniasis Cutánea/patología , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Datos de Secuencia Molecular , Mutagénesis , Fenotipo , Proteínas Protozoarias/biosíntesis , Proteínas Protozoarias/química , ARN Protozoario/química , Alineación de Secuencia , Transfección , VirulenciaRESUMEN
Almeida-de-Faria, M., Freymüller, E., Colli, W., and Alves, M. J. M. 1999. Trypanosoma cruzi: Characterization of an intracellular epimastigote-like form. Experimental Parasitology 92, 263-274. A detailed study of transient epimastigote-like forms as intermediates in the differentiation of Trypanosoma cruzi amastigotes to trypomastigotes inside the host cell cytoplasm was undertaken using the CL-14 clone grown in cells maintained at 33 degrees C. Several parameters related to these forms have been compared with epimastigotes and other stages of the parasite. Consequently, the designation of intracellular epimastigotes is proposed for these forms. Despite being five times shorter (5.4 +/- 0.7 micrometer) than the extracellular epimastigote (25.2 +/- 2.1 micrometer), the overall morphology of the intracellular epimastigote is very similar to a bona fide epimastigote, when cell shape, position, and general aspect of organelles are compared by transmission electron microscopy. Epimastigotes from both sources are lysed by human complement and bind to DEAE-cellulose, in contrast to amastigotes and trypomastigote forms. A monoclonal antibody (3C5) reacts with both epimastigotes either isolated from axenic media or intracellular and very faintly with amastigotes, but not with trypomastigotes. Some differences of a quantitative nature are apparent between the two epimastigote forms when reactivities with lectins or stage-specific antibodies are compared, revealing the transient nature of the intracellular epimastigote. The epitope recognized by 3C5 monoclonal antibody reacts slightly more intensely with extracellular than with intracellular epimastigotes, as detected by immunoelectron microscopy. Also a very faint reaction of the intracellular epimastigotes was observed with monoclonal antibody 2C2, an antibody which recognizes a glycoprotein specific for the amastigote stage. Biological parameters as growth curves in axenic media and inhability to invade nonphagocytic tissue-cultured cells are similar in the epimastigotes from both origins. It is proposed that the epimastigote-like forms are an obligatory transitional stage in the transformation of amastigotes to trypomastigotes with a variable time of permanency in the host cell cytoplasm depending on environmental conditions.
Asunto(s)
Trypanosoma cruzi/crecimiento & desarrollo , Trypanosoma cruzi/ultraestructura , Animales , Anticuerpos Monoclonales/inmunología , Anticuerpos Antiprotozoarios/inmunología , Medios de Cultivo , Técnica del Anticuerpo Fluorescente Indirecta , Microscopía Electrónica , Microscopía Inmunoelectrónica , Orgánulos/ultraestructura , Propiedades de Superficie , Trypanosoma cruzi/inmunologíaRESUMEN
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 fibers or blood cells. In addition, we found that T. cruzi parasites were also removed by a direct fiber 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.