Biomedical subjects

C Azevedo

Publications and source records attributed to C Azevedo.

At least 19 recordsLinked to original sources

PubMed2006

Ultrastructural aspects of hepatic coccidiosis caused by Goussia lusca n. sp. (Apicomplexa: Coccidia) infecting Trisopterus luscus (Gadidae) from the NE Atlantic Ocean.

Goussia lusca n. sp. is described from the liver of pouting Trisopterus luscus from the NE Atlantic Ocean in Ibero-Atlantic Portuguese and Spanish waters. Mature oocysts were 31.7 (28.8 to 35.4) microm in diameter. Each oocyst contained 4 ellipsoidal sporocysts arranged in an aleatory position, and measuring approximately 13.7 x 9.2 microm. Each sporocyst contained 2 sporozoites. Ultrastructurally, the sporocyst wall consisted of a dense inner layer 115 nm thick, transversely striated, regularly intercalated by thin grooves with electron-lucent spaces, and separated from the outer layer by a thin, light (electron-lucent) space. The outer layer was multilamellated and consisted of parallel dense bands alternating with light spaces. These lamellae formed filamentous extensions of the wall. The dehiscence suture, a characteristic feature of the genus, was present in the sporocysts. No external clinical signs were observed in the host fish. Parasites observed in the liver tissue were often enveloped in a yellowish-brown matrix, generally known as 'yellow bodies'. Sometimes sporocysts were observed in direct contact with the liver cells. Parasites in degeneration and aggregations of amylopectin granules were frequently observed surrounded by host inflammatory cells. In severe infections, we observed large agglomerations of oocysts encapsulated by layers of concentrically arranged connective tissue forming large granulomas, which caused significant replacement of the host liver parenchyma by the parasite.

Animals↗

PubMed2006

Unidentified extracellular prokaryotes within the byssal threads of the deep-sea vent mussel Bathymodiolus azoricus.

Bacterial symbiosis and/or parasitism is widespread in hydrothermal bivalves, and is typically developed in gills, with a lower incidence in mantle and digestive glands, while it has never been described in byssus. Using ultrastructural examination, we provide evidence for the existence of a potentially new group of filamentous prokaryotic organism in Bathymodiolus azoricus byssus, with putative parasitic influence. Additionally, a cystic, undefined organism was found with an unclear physiological role within the spongy net of the byssus plaque. Our results indicate that in spite of its antibacterial protective sheath, byssus gives access to prokaryotic organisms becoming prone to failure through damaged collagen fibres.

Animals↗

PubMed2006

Inositol pyrophosphates: metabolism and signaling.

Inositol pyrophosphates belong to the diverse family of inositol polyphosphate species that have a range of signaling functions. Since the discovery of inositol pyrophosphates in the early 1990s, enormous progress has been achieved in characterising this class of molecules, linking their biological presence to a wide range of cellular functions, including vesicular trafficking, apoptosis, telomere maintenance and protein phosphorylation. The activity of inositol pyrophosphates appears to be related to their rapid turnover in cells and also to their pyrophosphate groups, which are considered to contain high-energy bonds. Together, these observations suggest that inositol pyrophosphates may represent a class of cellular messengers with basic and not yet fully characterised functions. This review aims at summarising the recent progress of our knowledge of this exciting class of molecules, from inositol pyrophosphate discovery to the description of their physiological functions.

Animals↗

PubMed2005

Ultrastructure of Goussia cruciata (Apicomplexa: Coccidia) infecting the liver of horse mackerel, Trachurus trachurus (L.), from Ibero-Atlantic waters.

The ultrastructure of developmental stages of Goussia cruciata and the pathology they cause in the liver of Trachurus trachurus (Teleostei: Carangidae) caught off the Galician (North-West Spain) and Portuguese North Atlantic coasts are described. Each oocyst contained four ellipsoidal sporocysts, with two sporozoites. The sporocyst wall consisted of a thick and dense inner layer with transverse striations and a multi-lamellated outer layer formed by parallel dense internal bands alternating with lighter areas. The lamellae formed filamentous extensions of the wall. The sporocyst wall striation period was smaller than that observed in G. clupearum, which has a similar habitat. The dehiscence suture, characteristic of the genus, was present in the sporocysts of G. cruciata. The sporocysts were arranged in a symmetrical and characteristic cross shape. A large number of sporocysts with sporozoites were observed in direct contact with host liver cells. No macroscopic lesions were observed. In heavily infected fish, aggregations of oocysts were often enveloped in a 'yellow body' composed of amylopectin granules derived from the parasite and necrotic or aggregated host cells. Degenerating parasites were frequently observed in liver tissue. Host inflammatory cells were accumulated near some oocysts. The ultrastructure of the parasite, together with its strict host specificity, confirmed G. cruciata as a separate and valid species.

Animals↗

PubMed2005

Ultrastructural description of an unidentified apicomplexan oocyst containing bacteria-like hyperparasites in the gill of Crassostrea rizophorae.

Oocysts of an unidentified coccidian are reported in this study to parasitize the gills of the oyster Crassostrea rizophorae (Mollusca, Bivalvia) collected near the city of Recife (Itamaracá Island, 07 degrees 38' 00" S, 34 degrees 48' 06" W), Brazil. Oocysts appeared as light and dense forms, both containing rod-shaped, bacteria-like hyperparasites (BL). Both light and dense oocysts were spherical, 4.3 to 4.7 pm in diameter, but denser oocysts had irregular contours. Both forms consisted of a thick dense wall (approximately 165 nm thick) consisting of 3 layers. The outermost, a dense and irregular layer about 25 nm thick, possessed numerous bead-like structures and some slender conical projections (up to 1.5 microm long). The inner layer of the wall was formed by a dense and homogenous layer about 125 nm thick. Between these 2 layers, a thin light layer about 12 nm thick was present. Uninucleated sporocysts occupied the internal space of the oocyst and contained some rod-shaped BL and mitochondria surrounded by numerous ribosome-like particles. The dense forms of the oocysts showed the same structures described in the lighter forms and appeared to be the final maturation form of the oocysts. Free sporozoites were occasionally observed among oocysts.

Animals↗

PubMed2004

Investigation of Nematopsis spp. oocysts in 7 species of bivalves from Chonburi province, Gulf of Thailand.

This is the first detailed report of Nematopsis spp. in Thai bivalves. A monthly survey was conducted on 7 species of commercial bivalves from Chonburi province, on the eastern seaboard of Thailand, from November 2000 to November 2001 to investigate the prevalence of the apicomplexan parasite Nematopsis Schneider, 1892. Nematopsis spp. sporozoites were found in the cultivated bivalves Arcuatula arcuatula, Anadara granosa and Perna viridis as well as the locally harvested Paphia undulata. They were not found in Donax faba, Meretrix meretrix or Saccostrea cucullata. Using light microscopy, we were able to identiby 4 oocyst morphotypes of the gregarine Nematopsis spp. Prevalence of Nematopsis spp. during the 13 mo sampling period was highest in A. arcuatula (91.8%; n = 110) and lowest in A. granosa (59.2%; n = 130). The morphology of the oocysts differed between hosts, with an average (x +/- SD) length/width of 16.28 +/- 0.64/12.01 +/- 0.35 microm (n = 50) for A. arcuatula, 16.90 +/- 0.71/12.69 +/- 0.33 microm (n = 50) for A. granosa, 17.61 +/- 0.69/12.72 +/- 0.36 microm (n = 50) for P. viridis, and 11.21 +/- 0.62/8.55 +/- 0.52 microm (n = 50) for P. undulata. Identification of oocysts of these apicomplexan gregarines to species was not attempted. The prevalence of infection in relation to habitat and time of sampling is discussed.

Animals↗

PubMed2003

Ultrastructural details of the xenoma of Loma myrophis (phylum Microsporidia) and extrusion of the polar tube during autoinfection.

Xenomas of the recently described new microsporidian species Loma myrophis parasitizing the gut tissue of the Amazonian fish Myrophis platyrhynchus (family Ophichthidae) were described by light- and transmission-electron microscopy. The xenoma consisted of a thin fibrillar wall that surrounded a hypertrophic host cell cytoplasm containing numerous microsporidian developmental stages and spores. Several spores showed different stages of natural extrusion of the polar tube. Numerous longitudinal and transverse sections of the extruded polar tubes were observed in developing life-cycle stages (spores excepted), the nucleus of hypertrophic host cell, the xenoma wall and surrounding fibroblasts. The extruded polar tubes were projected in all directions with no preferential orientation. These aspects suggested that autoinfection occurred within this xenoma.

Animals↗

PubMed2003

Biflagellate spermatozoon structure of the hermaphrodite fish Satanoperca jurupari (Heckel, 1840) (Teleostei, Cichlidae) from the Amazon River.

The ultrastructural features of the sperm were studied in the hermaphroditic teleost Satanoperca jurupari HECKEL, 1840 from Amazon River. Spermatocytes, spermatids and sperm develop in the testicular cysts among the different oocyte stages. Different stages of early spermatocyte development, mainly the ones with synaptonemal complexes were often observed. The mature spermatozoa belong to the introsperm type, with a short head (approximately 3 microns long and 1.3 microns wide) without acrosome, short midpiece (approximately 1.2 microns long and 1.8 microns wide) containing several mitochondria surrounding two centrioles and forming a mitochondrial collar. They have two flagella (each approximately 15 microns long) each of which has a common 9 + 2 microtubular pattern. Each flagellum has two opposite lateral cytoplasmic extensions that begin about 3 microns the midpiece still close to the end piece of flagellum.

Animals↗

PubMed2003

Ultrastructural aspects of the myxosporean Henneguya astyanax n. sp. (Myxozoa: Myxobolidae), a parasite of the Amazonian teleost Astyanax keithi (Characidae).

This study reports light and electron microscopical aspects of a myxosporean found in the gills of the freshwater teleost Astyanax keithi Géry, Planquete & Le Bail, 1996 (family Characidae), collected from the estuarine region of the Amazon River, near Belém, Brazil. The prevalence of infection was 23%. In interlamellar spaces of the gills, ellipsoidal whitish cyst-like plasmodia structures were present, which contained spores. The spores had a spermatozoa-like appearance (47.8 +/- 0.71 microm in total length) with a fusiform body (15.2 +/- 0.77 pm in length, 5.7 +/- 0.71 microm in width and 4.2 +/- 0.31 microm in thickness), and each of the 2 valves presented a tapering tail (32.6 +/- 1.11 microm in length). The valves surrounded a binucleate sporoplasm cell and 2 polar capsules (5.0 +/- 0.13 microm in length, 1.5 +/- 0.07 microm in width) that contained 8 to 9 coils of the polar filament. In the sporoplasm, several unique sporoplasmosomes were visible. A synoptic table of spore measurements of known Brazilian Henneguya species is presented. The spores differed from those of previously described species. Based on spore morphology, it is concluded that this species belongs to the family Myxobolidae, genus Henneguya, and that it constitutes a new species: H. astyanax n. sp.

Animals↗

PubMed2003

Light and electron microscopic study of the myxosporean, Henneguya friderici n. sp. from the Amazonian teleostean fish, Leporinus friderici.

A new histozoic species of myxosporean was found to infect the gill filaments, gut, kidney and liver of the freshwater teleost Leporinus friderici, collected from the estuarine region of the Amazon, near the city of Belém, Brazil. The plasmodia show asynchronous development, at any one time composed of mature spores and all sporogonic stages. The ellipsoidal spore body, measuring 10.4 microm long and 5.7 microm wide, consists of 2 equal shell valves adhering together along the straight suture line. Each valve has a caudal process measuring 23.3 microm in length. There are 2 symmetric polar capsules, without intercapsular appendix, measuring 5.0 microm x 2.1 microm, and each has a polar filament with 7-8 coils. In general, ultrastructural details of sporoblast and spore development are in agreement with previously described myxosporeans. Some ultrastructural aspects such as cellular alterations of the pericyte in the different organs infected and characterization of the sporoplasmosomes during the sporoplasm maturation are described. This parasite was studied under light and electron microscope and compared with others species of the genus Henneguya, considering also host specificity. From our observations we propose the creation of a new species, Henneguya friderici n. sp.

Animals↗

PubMed2002

Ultrastructural data on the spore of Myxobolus maculatus n. sp. (phylum Myxozoa), parasite from the Amazonian fish Metynnis maculatus (Teleostei).

Light and electron microscopy studies of a myxosporean, parasitic in the intertubular interstitial tissue of the kidney of the freshwater teleost fish Metynnis maculatus Kner, 1860 (Characidae) from the lower Amazon River (Brazil), are described. We observed polysporic histozoic plasmodia delimited by a double membrane and with several pinocytic channels and containing several life cycle stages, including mature spores. The spore body was of pyriform shape and was 21.0 microm long, 8.9 microm wide and 7.5 microm thick. Elongated-pyriform polar capsules were of equal size (12.7 x 3.2 microm) and contained a polar filament with 14 or 15 coils. The spore features fit those of the genus Myxobolus. Densification of the capsular primordium matrix, which increased in density from the inner core outwards, differentiating at the periphery into small microfilaments measuring 45 nm each, and tubuli arranged in aggregates and dispersed within the capsular matrix of the mature spores, are described. Based on the morphological differences and specificity of the host, we propose the creation of a new species named Myxobolus maculatus n. sp.

Animals↗

PubMed2001

Ultrastructural aspects of a new species, Vavraia mediterranica (Microsporidia, Pleistophoridae), parasite of the French Mediterranean shrimp, Crangon crangon (Crustacea, Decapoda).

The life cycle stages of a new species of the genus Vavraia (Microsporidia, Pleistophoridae), which parasitizes the shrimp Crangon crangon (Crustacea, Decapoda), were examined by light and electron microscopy. This parasite was monomorphic with polysporous sporogony and developed in the skeletal muscle of the host. The multinucleate sporogonial plasmodium divided by plasmotomy and multiple division into uninucleate sporoblasts. All stages were surrounded by a thick and amorphous dense coat external to the plasmalemma. This structure gradually became a merontogenetic sporophorous vacuole (MSV) where the sporonts developed into sporoblasts. The MSV was filled with episporontal granular secretory products and eventually contained up to 50 uninucleate spores. During spore morphogenesis, these episporontal granular products within the MSV became organized as episporontal tubular-like structures. In transverse sections, these structures showed a mean diameter of 1.0 microm, but disappeared during the final phase of the spore maturation. Mature spores were ellipsoidal to slightly pyriform and measured 2.30 x 1.41 microm. The polar filament was anisofilar and consisted of a single coil with six to seven turns (rarely five). This new species is named Vavraia mediterranica n. sp.

Animals↗

PubMed2001

Fine structure of sporogonic stages of Goussia clupearum (Apicomplexa: Eimeriidae) in the liver of infected fish (Belone belone L.), using light and electron microscopy.

A coccidian species, Goussia clupearum (L.) is reported to parasitize the liver of a new host, Belone belone (Teleostei: Belonidae), caught on the Atlantic coast at the north of Portugal. The parasitophorous vacuole containing oocysts was attached to the host's liver cells. Spherical oocysts (approximately 21.2 microm diameter), each containing four ellipsoidal elongated sporocysts (10.5 x 6.3 microm), were enclosed in the parasitophorous vacuole. Each sporocyst contained two sporozoites. The micropyle was absent, but a polar granule (without Stieda body) was present. Each sporozoite possessed four refractile bodies. During sporoblastogenesis and sporogenesis, one or two dense polar bodies were found within the oocysts. They were composed of a dense homogeneous core, surrounded by a ring of dense granular material. On occasion, we observed some sporocysts in direct contact with host cells. This paper describes the morphology and ultrastructural details of the oocysts, sporocysts and sporozoites of G. clupearum. This species seems to represent the only coccidium described in fish from this Atlantic coast.

Animals↗

PubMed2001

The U-box protein family in plants.

The U-box is a highly conserved domain recently identified at the C terminus of yeast UFD2, an E4 ubiquitination factor. In yeast, UFD2 is the only U-box-containing protein, but there are two UFD2 homologs and several other proteins containing a U-box domain in humans. Intriguingly, a database search revealed 37 predicted proteins containing a U-box in Arabidopsis. The plant U-box (PUB) proteins form five distinct subclasses, suggesting that they play diverse roles. The ARC1 gene from Brassica, required for self-incompatibility, is currently the only PUB gene functionally characterized. Here, we discuss the characteristics and possible functions of the PUB gene family.

Amino Acid Motifs↗

PubMed2001

Ultrastructural description of the spore maturation stages of the clam parasite Minchinia tapetis (Vilela, 1951) (Haplosporida: Haplosporidiidae).

The fine structure of maturing spores of a haplosporidian parasite found in the gill, mantle and foot tissues of Ruditapes decussatus L. (Mollusca, Bivalvia), a species of commercial importance in Portugal, is described. When observed free in suspension, immature spores exhibit one or two epispore cytoplasmic extensions (ECE) which constitute a projection of a portion of the exosporoplasm, sometimes without ultrastructural organisation, surrounded by the plasmalemma. Free spores observed by light microscopy (LM) after 3-5 days of incubation in filtered sea-water exhibit no ECE attached to the spore wall. The mature spore is ovoid to ellipsoid, operculate, uninucleate and measures c. 4.8 microm long and c. 3.9 microm wide. The spore shape and size and the identity of the host living in the same geographical region suggest that this species is the same as previously described using LM observations as Haplosporidium tapetis Vilela, 1951 and later transferred to Minchinia Labbé, 1896.

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PubMed2000

Ultrastructure of the microsporidian Inodosporus octospora (Thelohaniidae), a parasite of the shrimp Palaemon serratus (Crustacea, Decapoda).

A parasite of the muscle of the shrimp Palaemon serratus has been examined by light and electron microscopy. Development occurs among myofibrils and induces ultrastructural alterations of the muscle fibers causing white discoloration. This microsporidian is characterized by uninucleate, later diplokaryotic and di-diplokaryotic meronts. The mother cell develops by rosette-like budding into 8 uninucleate sporoblasts, each containing 3 tape-like filaments attached to the wall that is enclosed in a persistent sporophorous vacuole. Each sporoblast gives rise to a uninucleate spore that possesses 3 elongated tape-like filaments attached to the spore wall, like spore tails. The morphological characters of the spores, redescribed in the present study, suggested that the spores belonged to Inodosporous octospora. The possibility that in the future members of Inodosporus sp. may be considered a new parasite group is discussed.

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PubMed1999

A novel class of eukaryotic zinc-binding proteins is required for disease resistance signaling in barley and development in C. elegans.

Barley Rar1 is a convergence point in the signaling of resistance to powdery mildew, triggered by multiple race-specific resistance (R) genes. Rar1 is shown to function upstream of H2O2 accumulation in attacked host cells, which precedes localized host cell death. We isolated Rar1 by map-based cloning. The sequence of the deduced 25.5 kDa protein reveals two copies of a 60-amino acid domain, CHORD, conserved in tandem organization in protozoa, plants, and metazoa. CHORD defines a novel eukaryotic Zn2+-binding domain. Silencing of the C. elegans CHORD-containing gene, chp, results in semisterility and embryo lethality, suggesting an essential function of the wild-type gene in nematode development. Our findings indicate that plant R genes have recruited a fundamental cellular control element for signaling of disease resistance and cell death.

Alleles↗

PubMed1999

A revised description of Haplosporidium armoricanum, parasite of Ostrea edulis L. from Galicia, northwestern Spain, with special reference to the spore-wall filaments.

Haplosporidian spores from Ostrea edulis, previously described as Minchinia armoricana, were reexamined by light and electron microscopy. These spores were either free among host cells or enclosed in sporocysts. They contained two long epispore cytoplasm extensions (ECE), each possessing cytoskeletal structures corresponding to the filaments. After lysis and degradation of the ECE, these extensions disappeared and the spores became devoid of membrane-bound extensions. However, 2 long filaments (approximately 130 microm long) persisted that were closely attached, in opposition to the spore wall, by a bundle of 9-13 fibers each. Thus, we propose a revised description of M. armoricana (= H. armoricana) to confirm its placement in the genus Haplosporidium as H. armoricanum.

Animals↗