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C Azevedo

Publications and source records attributed to C Azevedo.

46 records · Page 3Linked to original sources
PubMed1987

Ultrastructure of a microsporidian hyperparasite, Unikaryon legeri (Microsporida), of trematode larvae.

Unikaryon legeri (Dollfus, 1912) Canning and Nicholas, 1974, has been reexamined by electron microscopy from material collected in Portugal. It parasitises metacercariae of Meigymnophallus sp. in Cardium edule. A sporophorous vesicle forms around the sporonts, arising as a blister that separates from the electron-dense surface coat of the sporont. Sporogony is disporoblastic, giving rise to 2 spores that are retained in pairs within the sporophorous vesicle. Unikaryon piriformis, which is the type species of the genus and is also hyperparasitic in platyhelminth larvae, has not been examined by electron microscopy, and it is not known whether this species also produces sporophorous vesicles. If it does, then all that will be required is a simple addition of this character to the definition; if not, U. legeri will have to be transferred to a new genus and reclassified with other disporoblastic genera that sporulate in sporophorous vesicles.

Eukaryota↗
PubMed1987

Ultrastructural and cytochemical observations of the spherites in a parasite trematoda larva.

Concentric laminated concretions, termed 'spherites', were found in the parenchymal cells and in the lumen of the collecting vessels of the trematode Meigymnophallus minutus, parasite of a lamellibranch mollusc. In the initial stage, the spherites are surrounded by a membrane and located in close proximity to the endoplasmic reticulum and Golgi complexes, increasing in size with age and by deposit of concentric layers. Later, they migrate and are released into the lumen of the collecting vessels. These structures contain high concentrations of calcium and phosphorus. The organic matrix is mainly composed of protein, lipids, acid phosphatase and glycoproteins as demonstrated by several cytochemical staining methods. It is possible that these calcareous concretions play an important role in the excretory system of the adult trematode, the life cycle of which takes place within the mantle of the host mollusc.

Animals↗
PubMed1985

Prognosis in colorectal carcinoma. A reassessment of the pathologist's role.

The prognostic significance of some pathologic features was evaluated in a series of 177 patients with colorectal carcinoma consecutively treated by curative resection in a department of Surgery from 1960 to 1981. There were 90 men and 87 women with a mean age of 59.2 +/- 12.8 and a range from 23 to 88 years. Current follow-up information was obtained in 92.7% of the patients. Pathologic staging as classified according to a modification of Dukes' original scheme was found to be the most important prognostic factor. Evaluation of lymphatic and venous invasion, histologic differentiation, and site of tumors also provided valuable prognostic information. Size, configuration, mucin-producing ability and the morphologic evaluation of the so-called "host immunologic response" were found to be irrelevant for the prognosis when the influence of the other indices was controlled.

Adult↗
PubMed1976

Intranuclear membranous inclusions in oocytes of a viviparous teleost (Xiphophorus helleri).

Intranuclear inclusions were observed in oocytes of Xiphophorus helleri during prophase I. In osmium-fixed leptotene nuclei, the inclusions were made up of groups of membrane-limited vesicles or tubules with pale contents, situated near the inner nuclear membrane with which some of them exhibited apparent continuities. In zygotene nuclei, larger vesicles also appeared bounded by two or three membranes and containing tubules apparently invaginated from their walls. In pachytene-dictyate nuclei most vesicular bodies had a wall formed by stratified membranes, or were entirely made up of membranous whorls. In glutaraldehyde-osmium fixed material some of these myeline-like bodies showed a peculiar arrangement, consisting of concentric bands each containing thick inner dense lamellae 2-0-3-0 nm thick and a 5-0 nm outer lamella. It is suggested that these inclusion bodies arise from the inner nuclear membrane of oocytes when cells start to grow intensely during prophase I. The bodies seem to become more complex at late prophase, probably by association of individual vesicles and the occurrence of multiple membrane invaginations, which may be related to active metabolic phenomena taking place at this stage in oocytes.

Animals↗
PubMedDate not supplied

Enzyme cytochemistry of the alveolar sacs and golgian-like cisternae in the ciliate Ichthyophthirius multifiliis.

In the cell cortex of the parasitic ciliate Ichthyophthirius multifiliis different kinds of cisternae were observed: the alveolar sacs, thick membrane cisternae and the endoplasmic reticulum. The thick membrane cisternae possess coated dilated rims and sometimes could be observed close to the endoplasmic reticulum. Using cytochemical techniques acid phosphatase, thiamine pyrophosphatase and nucleoside diphosphatase activities were detected in the thick membrane cisternae and in the alveolar sacs of trophozoites. In the endoplasmic reticulum acid phosphatase activity was not detected and only very small amounts of thiamine pyrophosphatase and nucleoside diphosphatase reaction product were observed. After exit from the host, a reduction in acid phosphatase activity was evident in the alveolar sacs. At theront stage acid phosphatase activity is absent from these structures. However, high thiamine pyrophosphatase and nucleoside diphosphatase activities remain in the alveolar sacs during the whole life cycle. On the other hand, acid phosphatase, thiamine pyrophosphatase and nucleoside diphosphatase activities were detected in thick membrane cisternae of theronts. Based on the morphological aspects and enzymatic content the thick membrane cisternae of the cell cortex are designated as golgian-like cisternae. The cytochemical results point out a relationship between the alveolar sacs and the Golgi complex.

Acid Anhydride Hydrolases↗
PubMedDate not supplied

Ultrastructural and cytochemical identification of peroxisomes in the ciliate Ichthyophthirius multifiliis.

The peroxisomes of the parasitic ciliate Ichthyophthirius multifiliis were studied, using ultrastructural and cytochemical techniques. In this ciliate most peroxisomes possess a circular or oval section less than 0.6 micron in diameter. However, some dumbbell-shaped and elongated peroxisomes could also be observed. These organelles were frequently associated with the mitochondria and were more abundant in the cell cortex than in the center of the ciliate. Small vesicles and dense nucleoids were usually present in the ultrathin sections of these peroxisomes. Peroxisomal vesicles and tubular structures were selectively impregnated with osmium tetroxide. Catalase was detected by cytochemical techniques in I. multifiliis peroxisomes.

Animals↗
PubMedDate not supplied

Henneguya adherens n. sp. (Myxozoa, Myxosporea), parasite of the Amazonian fish, Acestrorhynchus falcatus.

A new species of myxosporean from the gill filaments of the freshwater teleost fish, Acestrohynchus falcatus collected in the Amazon river is described from light and transmission electron microscope observations. The mature spores (total length 32.3 [30.7-35.1] micron) and all developmental stages were found in the same sporogonic plasmodium. The ellipsoidal spore body consists of 2 unequal shell valves adhering together along the suture lines. Each valve, tapering as a caudal projection, forms a long tail (length 20.5 [18.0-21.7] micron). The tail was surrounded by a homogeneous sheath on its length. The polar capsules measuring 3.1 x 1.2 micron contain 3-4 coils of the polar filament. All surfaces of the immature and mature spores were surrounded by a closely adherent homogenous structural sheath, mainly thicker around the tails. The taxonomic affinities of this parasite to other species are discussed.

Animals↗
PubMedDate not supplied

New ultrastructural aspects of the spermatozoon of Aplysia depilans (Gastropoda, Opisthobranchia).

The spermatozoon of the sea hare Aplysia depilans was studied under scanning (SEM) and transmission electron microscopy (TEM). Previous descriptions of this sperm and related species, both from light and electron microscopy, were inconsistent with each other. These descriptions include A. depilans, A. punctata, A. fasciata, A. kurodai and Bursatella leachiplei. Several detailed micrographs provide a new ultrastructural model and reveal new aspects such as the presence of acrosome and the absence of a glycogen piece, therefore the modified dense ring is the terminal structure. Results also show that previous models are incorrect in many aspects. The spermatozoon is a long slender uniflagellated cell with a complex helical structure and a length of approximately 165 microm. Observed in SEM the spermatozoon has an undifferentiated head and tail. The nucleus is cord-shaped and helically intertwined with the axoneme/mitochondrial derivative complex. The mitochondrial derivative has only one glycogen helix. Glycogen presence was demonstrated by Thiéry's method. Typical heterobranchia spermatozoa features are recognised. From bibliographic analysis, a high degree of similarity was found with the sperm of Pleurobranchea maculata (Notaspidea).

Acrosome↗
PubMedDate not supplied

Evidence for the generation of specific T suppressor lymphocytes by Streptococcus intermedius.

Crude extracellular products of the Streptococcus intermedius "CEP-Si" were able to strongly decrease the in vitro proliferation of stimulated human peripheral blood mononuclear cells (HPBMC) when evaluated by (3H)-thymidine and (3H)-leucine uptake. On the other hand, CEP-Si only slightly decreased this proliferation when HPBMC were either not stimulated or cultured in poor conditions or immature cells, i.e. thymocytes were used as target instead. Also in vivo CEP-Si was ineffective when target cells were not highly reactive. Both in vivo and in vitro, the effect of CEP-Si was proportional to the time of contact with the target cells. The dynamics of the effects of CEP-Si suggest the generation of "something" ("suppressor cells") which cause an abrupt drop in the values of (3H)-thymidine uptake rather than a progressive decrease of the values, which could indicate a loss effector or helper cells. On the other hand, CEP-Si suppressed the in vitro primary immunization of human HPBMC against SRBC and, furthermore, human HPBMC incubated with CEP-Si were able to suppress the primary immune response against SRBC of, CEP-Si untreated, HPBMC. In some instances of insufficient time of contact of CEP-Si with the target cells, an enhancement of the immune response was observed both in vivo and in vitro. Moreover, the histological pattern of the spleens of C57 BL/6 mice injected with semipurified products of CEP-Si were consistent with an adjuvant-like effect. Finally, the target HPBMC for the semipurified products of CEP-Si acquired the ultrastructural and antigenic characteristics of suppressor T lymphocytes.

Animals↗