Functional morphology of adult female Culex quinquefasciatus midgut during blood digestion

The adult female Culex quinquefasciatus midgut comprises a narrow anterior and a dilated posterior region, with epithelia composed of a monolayer of adjacent epithelial cells joined at the apical portion by septate junctions. Densely packed apical microvilli and an intricate basal labyrinth characterise each cell pole. Our morphological studies suggest that, during blood digestion, the anterior midgut region also participates in an initial absorptive stage which is probably related to the intake of water, salts and other small molecules. This activity peaked by 6h after bloodmeal feeding (ABF) and ended approximately 18 h ABF, when the peritrophic membrane was already formed. After this time, absorption only occurred in the posterior region, with morphologic and biochemical evidence of high synthetic activity related to the secretion of proteases. Chymotrypsin, elastase, aminopeptidase, and trypsin reached their maximum activity at around 36 h ABF. Digestion products were apparently absorbed and transported to the basal labyrinth, from where they should be released to the hemolymph. At 72 h ABF, proteolysis had already ended and protein levels had returned to those observed before blood meal. The epithelium of the posterior region, however, did not return to its initial morphology, appearing quite disorganised. Additionally, from 48 h ABF onwards some epithelial cells showed morphological signals of apoptosis.

A monoclonal antibody to Trypanosoma cruzi trypomastigotes recognizes a myosin tail epitope

A monoclonal antibody, 1E7, raised against tissue culture-derived trypomastigotes of Trypanosoma cruzi reacted with proteins located at the perinuclear region of the parasite as detected by immunofluorescence and immunogold electron microscopy. The antibody also recognized antigens in all trypanosomatids tested, including T. cruzi epimastigotes, as well as in many mammalian cells. Five principal antigens of 140-270 kDa soluble in 1 M NaCl were recognized by the monoclonal antibody, suggesting that the epitope may belong to more than one polypeptide since the same bands appeared even when the samples were treated with high concentrations of denaturing agents. The antibody reacted in Western blots with muscle myosin. Bacterial clones expressing fast skeletal muscle myosin head or tail cDNAs upon IPTG induction were used to demonstrate that 1E7 monoclonal antibody recognizes an epitope present in the tail region of the myosin heavy chain. This result adds to the on-going discussion related to the possible existence of an auto-immune component in the immunopathogenesis of Chagas' disease due to cross-reactive epitopes shared by the parasite and cardiac myosin.

Procathepsin and acid phosphatase are stored in Musca domestica yolk spheres

Yolk spheres present in mature invertebrate oocytes are composed of yolk proteins and proteolytic enzymes. In the fly Musca domestica, yolk proteins are degraded during embryogenesis by a cathepsin-like proteinase that is stored as a zymogen. An acid phosphatase is also active in the yolk spheres during Musca embryogenesis. In this paper we show that procathepsin and acid phosphatase are initially stored by a different pathway from the one followed by yolk protein precursors. Both enzymes are taken up by the oocytes and transitorily stored into small vesicles (lysosomes) surrounding the early yolk spheres. Fusion of both structures, the early yolk spheres and lysosomes, creates the mature yolk spheres.

Morphological and biochemical analyses of the salivary glands of the malaria vector, Anopheles darlingi

Adult Anopheles darlingi salivary glands are paired organs located on either side of the esophagus. The male glands consist of a single small lobe. The female gland is composed of two lateral lobes, with distinct proximal and distal portions, and a medial lobe. The lobes are acinar structures, organized as a unicellular epithelium that surrounds a salivary canal. The general cellular architecture is similar among the lobes, with secretory material appearing as large masses that push the cellular structures to the periphery of the organ. Cells of the proximal-lateral lobes show asynchronous cycles of secretory activity and contain secretory masses with finely filamentous aspect. In the distal-lateral lobes, cells display synchronous cycles of activity, and have a dense secretory product with mottled pattern. Cells of the medial lobe have secretory masses uniformly stained and highly electrondense. Biochemical analysis of the adult female salivary glands revealed apyrase, alpha-glucosidase and lysozyme activities. Alpha-glucosidase and lysozyme activities are detected mostly in the proximal lobes while apyrase is mainly accumulated in the distal lobes. This differential distribution of the analyzed enzymes reflects a specialization of different regions for sugar and blood feeding. Thus, the morphological differences observed in the lobes correlate with functional ones.

Axenic cultivation and partial characterization of Leishmania braziliensis amastigote-like stages

Leishmania braziliensis strain M2903 was adapted for growth and serially maintained as amastigotes at 34 degrees C in modified UM-54 medium, with growth curves exhibiting typical log and stationary phases. In late passages, amastigote growth took place in the absence of supplementary haemin and was unaffected when the initial medium pH was adjusted between 5.4 and 6.3. In contrast to promastigotes, which were elongated and exhibited very long free flagella endowed with the paraflagellar rod (PFR), axenic amastigotes were rounded to ovoid and displayed a short flagellum restricted to the pocket area. The absence of PFR in axenic amastigotes was confirmed in Western blots and confocal immunofluorescence microscopy, by lack of reactivity with mAb 1B10. The antibody, which specifically labelled the paraflagellar structure, recognized a 70/72 kDa doublet in Trypanosoma cruzi epimastigotes and two 70/74 kDa related proteins in L. braziliensis promastigotes. Surface 125I-labelling experiments identified promastigote-specific components (> 100, 74, 45/47 and 28 kDa) and at least 1, a 76 kDa polypeptide was specific for the amastigote stage. While axenic amastigotes were agglutinated by both peanut (PNA) and Lens culinaris (LCA) agglutinins, respectively at 50 and 12.5 micrograms/ml, promastigotes were not agglutinated by PNA and agglutinated in the presence of LCA at concentrations of 100 micrograms/ml and higher. Axenic amastigotes infected rat bone marrow-derived macrophages and were avidly taken up by J774 cells, from which numerous organisms, able to proliferate at 34 degrees C in UM-54 medium, could be recovered 48 h later.

Trypanosoma cruzi: monoclonal antibody to cytoskeleton recognizes giant proteins of the flagellar attachment zone

Cytoskeletal preparations of Trypanosoma cruzi trypomastigotes and epimastigotes contain a protein recognized by a monoclonal antibody (2G4) which is connected to the flagellar attachment zone of both stages of the parasite. Western blot analysis revealed that the antibody was able to recognize protein bands of molecular masses higher than 700 kDa up to 2500 kDa. These giant proteins do not seem to share sequences with beta-connectin since an anti-beta-connectin antibody did not recognize the T. cruzi proteins nor did the 2G4 monoclonal antibody recognize authentic beta-connectin. Immunofluorescence and immunogold electron microscopy provided evidence that this protein is located inside the cell body of the parasite, closely related to a corset of four microtubules known as subpellicular microtubule quartet. Immunogold labeling shows that the protein accompanies the flagellar attachment zone as long as the flagellum adheres to the cell body. It is proposed that these microtubule-associated proteins recognized by the 2G4 monoclonal antibody exist only in trypanosomatid forms having a junctional complex between the flagellum and the cell body and may act as transmembrane elements connecting the subpellicular microtubular quartet with the flagellum at the desmosome region.

Leishmania mexicana: proteinase activities and megasomes in axenically cultivated amastigote-like forms

Proteinase activities and megasomes were examined in axenically cultivated amastigote-like forms, freshly isolated lesion amastigotes, and promastigotes. Megasomes were absent in promastigotes and present in both amastigote stages, but they seemed to be less numerous and more homogeneous in cultured amastigote-like forms. Contrasting with the poor detection of proteinase activities in promastigote lysates, both types of amastigotes shared multiple proteinases, which were classified in two groups: (a) 60 to > 100 kDa, o-phenanthroline-sensitive activities; and (b) 23- to 40-kDa cysteine proteinases, of which those resolving as 35- to 40-kDa bands in gelatin gels were more clearly visualized in lysates of cultured amastigote-like forms. Incubation of both kinds of amastigotes with 0.25 to 1.0 microM of either Z-Phe-AlaCHN2 or Z-Tyr-AlaCHN2 selectively inactivated cysteine proteinases, but not the 35- to 40-kDa activities, which, again, were detected with higher intensity in cultured amastigote-like forms. The expression of the 35- to 40-kDa proteinases progressively increased when promastigotes were allowed to transform into amastigote-like forms or when lesion amastigotes were incubated at 34 degrees C for different time periods prior to exposure to Z-Phe-AlaCHN2; activities comparable to those of amastigote-like forms were attained within 24 to 48 hr. The activities resistant to Z-Phe-AlaCHN2 in vivo were fully inhibited by E-64 or Z-Phe-AlaCHN2 during gelatin digestion, suggesting that the 35- to 40-kDa proteinases were mainly inactive before cell lysis. The presence of cycloheximide (at 10, 50, and 100 micrograms/ml) during the pulse with Z-Phe-AlaCHN2 abolished the 35- to 40-kDa activities of lesion amastigotes and significantly reduced gelatin digestion by the similar enzymes of cultured amastigote-like forms. In the latter, the 35- to 40-kDa proteinases were no more detected when cycloheximide was given 60 min prior to Z-Phe-AlaCHN2. The results indicate higher rates of synthesis of the 35- to 40-kDa enzymes, and the existence of a more representative pool of inactive enzyme precursors, in cultured amastigote-like forms.

Remodeling of the mouse endometrial stroma during the preimplantation period

An ultrastructural cytochemical study of acid phosphatase activity performed in mouse endometrium on the second day of pregnancy showed that stromal cells which were heavily labeled by the cytochemical reaction had disarranged organelles. On the other hand, the cytoplasm of several stromal cells had collagen-containing phagosomes that were also labeled, indicating that the collagen fibrils were being digested by lysosomal enzymes. It is suggested that cell death and phagocytosis of collagen are events of the remodeling of the mouse endometrium that occur prior to decidualization.

Changes of the Golgi apparatus and lysosomes during decidualization in mice

The Golgi apparatus of the endometrial stromal cells of pregnant mice increases in size simultaneously with the differentiation of stromal cells into decidual cells. The activity of acid phosphatase in this organelle increases during this stage. On the other hand, the involuting decidual cells show morphological and cytochemical signs of Golgi regression (dilated cisternae, lack of enzymatic activity) together with the finding of numerous, pleomorphic lysosomes that have intense cytochemical label. These results confirm morphological data suggesting that decidual cell death occurs by autophagic degeneration.

Phagocytosis of collagen by mouse decidual cells

Collagen fibrils were present within membrane-bound vacuoles in the cytoplasm of mouse decidual cells on the 7th day of pregnancy. The space between the vacuole membranes and the fibrils was narrow and frequently filled with a granular electron-dense material. The loss of banding of the collagen fibrils, their association with lysosomelike bodies, and the demonstration of acid phosphatase activity in the vacuoles indicate that the fibrils were internalized by the decidual cells and were being digested. It is suggested that phagocytosis of collagen is a mechanism of remodeling of the mouse decidua.

Ultrastructural analysis of the interaction between host cells and Trypanosoma cruzi in experimental chagomas

The initial interaction between infective forms of Trypanosoma cruzi and host cells in vivo was studied at the ultrastructural level. In order to follow these events, T. cruzi bloodstream forms were inoculated into the cheek-pouch of hamsters--a peculiar region devoid of lymphatic vessels. This region was chosen as injection site because, unlike other regions, trypanosomes remained there and multiplied locally up to 15 days after inoculation. Parasites were detected initially outside cells or inside neutrophils. Only after the first week following inoculation were developing and multiplying trypanosomes seen inside macrophages or other resident cells. Parasites persisted until 15-20 days after inoculation, but by about the 28th day they were no longer seen.

The influence of lymphatic drainage in experimental Trypanosoma cruzi infection

The rapid disappearance of infective forms of Trypanosoma cruzi from the site of inoculation as well as the initial phase of infection produced by the parasite are not yet fully understood. To investigate this problem we used the hamster as an animal model considering the existence of the cheek pouch--a peculiar region devoid of lymphatic vessels. T. cruzi trypomastigotes were inoculated into the cheek pouch or into the footpad of animals previously infected or not with the same parasite. The results were followed from 3 up to 21 days postinoculation, by histological examination. In the cheek pouch of normal animals a large number of parasites could be seen up to 15 days post-inoculation and the inflammatory infiltrate had a focal distribution. Conversely, in the footpad the infiltrate was diffuse and no parasites could be detected. These observations indicate that the lymphatic system is the main route of T. cruzi dissemination from the site or inoculation. When hamsters were first inoculated in the footpad and 7 days later in the pouch, the inflammatory infiltrate at this point was less aggressive and no parasites could be detected.