Cytochemical demonstration of acid phosphatase activity in the pineal organ of the rainbow trout,Salmo gairdneri

Summary Activity of acid phosphatase (ACP) was investigated cytochemically in the pineal organ of the rainbow trout, Salmo gairdneri. Intense reaction product for ACP activity was observed (1) in lysosomes varying in size and shape and (2) in endoplasmic reticulum associated with the Golgi complex of (i) the pineal photoreceptor and supporting cells, (ii) vascular endothelial cells, and (iii) macrophages inhabiting pineal lumen, parenchymal epithelium and perivascular spaces. This localization of ACP is discussed with particular reference to the capacity for lysosomal digestion in a pineal organ combining photoreceptive and secretory functions, and lacking a blood-brain barrier, as holds true for the pineal of the rainbow trout. Taking advantage of its capacity for endocytotic uptake and lysosomal digestion, the pineal organ of the rainbow trout may serve as a barrier between the blood circulation and the cerebrospinal-fluid compartment. Furthermore, the macrophages may be considered as an essential component in pineal function of fish.Fellow of the Alexander von Humboldt Foundation.Fellow of the Alexander von Humboldt Foundation.     

Leishmania donovani: Surface membrane acid phosphatase activity of promastigotes

Subcellular fractionation of Leishmania donovani promastigotes yielded plasma membranes, which were enriched in acid phosphatase (E.C.3.1.3.2.) activity. Cytochemically, the enzyme displayed a uniform distribution over the surface of intact protozoa. The enzyme was also visualized on the external face of the isolated plasma membranes, as indicated by the distribution of subpellicular microtubules. Various parameters of the membrane-bound enzyme were also determined including pH and temperature optima and substrate specificity. The results suggest that these organisms are adapted for existence in a hydrolytic environment.     

Entamoeba histolytica: ultrastructural localization of Ca2+-dependent nucleotidases

Localization of nucleotidases dependent on Ca²⁺ was investigated cytochemically in axenically cultivated trophozoites of Entamoeba histolytica, strain HM-1:IMSS, with an electron microscope. Ca²⁺-dependent ATPase (EC 3.6.1.3) activity was found on the plasma membrane and on the inner surface of the limiting membrane of a few cytoplasmic vacuoles. Ca²⁺-dependent ADPase, Ca²⁺-dependent thiamine pyrophosphatase, and acid phosphatase (EC 3.1.3.2) activities were detected on the inner surface of the limiting membrane of most of the cytoplasmic vacuoles but not on the plasma membrane. Cytoplasmic vacuoles with these enzymatic activities seemed similar in morphological characteristics. Moreover, the reaction product formed by Ca²⁺-dependent ADPase, Ca²⁺-dependent thiamine pyrophosphatase and acid phosphatase was demonstrable on the inner surface of the limiting membrane of vacuoles containing ingested red blood cells. The reaction product formed by these enzymes was also observed on the periphery of ingested red blood cells. The findings suggest that cytoplasmic vacuoles with these enzymatic activities are lysosomal in nature, probably phagolysosomes; therefore, the enzymes appear to be at least partially associated with primary lysosomes of E. histolytica.     

Leishmania donovani: action of excreted factor on hydrolytic enzyme activity of macrophages from mice with genetically different resistance to infection

The effect of purified excreted factor from promastigotes of Leishmania donovani upon the activity of four enzymes from lysed peritoneal exudate cells of mice (C3H and C57BL) was determined. There was no demonstrable effect on acid phosphatase (EC3.1.3.2), β-glucuronidase (EC3.2.1.21), and N-acetyl-β-glucosaminidase (EC3.2.1.29), but β-galactosidase (EC3.2.1.23) was inhibited up to 72% after 3 hr of incubation at 37 C. Inhibition of C57BL mouse enzymes was not significantly different from that of C3H mice. Protamine sulfate combined with the highly negatively charged excreted factor of L. donovani to migrate as a single positively charged band on immunoelectrophoresis. Protamine sulfate also reversed the β-galactosidase inhibition, though this was without direct effect on the enzyme. The excreted factor did not change or lose its charge or antigenicity with regard to precipitating antibody, when incubated with extracts of mouse peritoneal exudate cells, splenocytes, or liver homogenate—irregardless of whether the mice had been infected with leishmaniasis for 1 or 2 weeks or were uninfected.