Mononuclear phagocytes in the blood of turtles characterized by ultrastructural and cytochemical analyses and by phagocytic activity.

Ultrastructural and cytochemical characteristics of mononuclear phagocyte cells in turtles are not well described in the literature, especially in Phrynops hilarii. Thus, the aim of this study was to evaluate these characteristics in the mononuclear phagocyte cells and their phagocytic activity "in vitro" using the turtle P. hilarii as an experimental animal model. The six turtles used in the study were observed in two seasons, spring and summer. Results showed that mononuclear phagocytes incubated only in diluted solution or with colloidal charcoal have cytoplasm phagolysosomes. The cells incubated with colloidal charcoal and further exposed to the cytochemical reaction for acid beta-glycerophosphatase, showed cytoplasm phagolysosomes filled by charcoal particles being digested and some positively stained lysosomes. Acid beta-glycerophosphatase positive reaction was present in lysosomes and inside the phagolysosomes, while acid cytidine 5-monophosphatase staining occurred in lysosome surroundings. A positive reaction for trimetaphosphatase was also found inside phagolysosomes. In conclusion, the presence of lysosomal enzymes like trimetaphosphatase and cytidine-5'-sodium monophosphate, in the circulating blood of P. hilarii indicate that mononuclear phagocytes participate in the phagocytic process by gathering many phagocytic cells and forming multinucleated giant cells, which probably have a role in the blood "clearance" process.

Catabolism of Ap4A and Ap5A by rat brain synaptosomes

Adenosine 5',5'''-P1,P4-tetraphosphate (Ap4A) and adenosine 5',5'''-P1,P5-pentaphosphate (Ap5A) are stored in and released from rat brain synaptic terminals. In the present study we investigated the hydrolysis of dinucleotides (Ap4A and Ap5A) in synaptosomes from the cerebral cortex of adult rats. Ap4A and Ap5A, but not Ap3A, were hydrolyzed at pH 7.5 in the presence of 20 mM Tris/HCl, 2.0 mM MgCl2, 10 mM glucose and 225 mM sucrose at 37oC. The disappearance of the substrates measured by FPLC on a mono-Q HR column was both time and protein dependent. Since synaptosome integrity was at least 90 percent at the end of the assay, hydrolysis probably occurred by the action of an ecto-enzyme. Extracellular actions of adenine dinucleotides at central nervous system terminate due to the existence of ecto-nucleotidases which specifically cleave these dinucleotides. These enzymes in association with an ATP diphosphohydrolase and a 5'-nucleotidase are able to promote the complete hydrolysis of dinucleotides to adenosine in the synaptic cleft

Cytochemical demonstration of lysosomes in skeletal and cardiac striated muscle of fish and turtles.

Skeletal and cardiac striated muscle from two species of fish and turtles were incubated for the cytochemical detection of trimetaphosphatase (TMPase) activity. The results showed that striated muscle from these animals has TMPase-positive structures, which are presumed to be lysosomes.

Extensive networks of TMPase positive basal lysosomes are present in fetal rat gastric epithelium before overt differentiation.

The rat gastric epithelium of 17 to 19 days of intrauterine life changes from a pseudostratified epithelium to a simple columnar epithelium. From a flat epithelium at 17-18 days, groups of epithelial cells begin to invaginate towards a cellularly rich mesenchyma and foveolae appear at 19 fetal days. Ultrastructural differentiation of the first cells of gastric glands occurs at 19 days. The ultrastructure of the undifferentiated cells at 17-18 fetal days shows extensive distribution of granules in the basal cytoplasm, near the basal lamina. To investigate the nature of these structures, enzyme cytochemistry was carried out. Acid phosphatase and trimetaphosphatase activities were demonstrated cytochemically in the gastric epithelium of the fetal rat. Whereas acid phosphatase positive lysosomes were observed mainly in typical round lysosomes, near the Golgi, a strong positive reaction for trimetaphosphatase, at 17 and 18 fetal days, was present in granules and tubular structures located in the basal cytoplasm. This reaction was coincident with the observed basal granules. At 19 days, the number of basal TMPase positive lysosomes was diminished, but other lateral tubular and vesicular positive structures were seen. The presence of coated pits in the basal membrane and microtubules and coated vesicles between tubular lysosomes, at 17-18 days, just before overt differentiation, reinforces the possibility of the association of this kind of lysosome with endosomes and the internalization of receptors.