The pigmentary system of the planaria, Dugesia gonocephala s.l. (Platyhelminthes, Turbellaria, Tricladida), has been studied by light and electron microscopy. The system consists of granules contained in chromatophore-like cells embedded in the parenchyma. The cell processes penetrate between the muscle layers and extend to the sub-epidermal basal lamina. The nature of the pigment and the comparative anatomical significance of the chromatophore structure is discussed.
Photosensitization phenomena may be induced in planarias by eosin and hematoporphyrin, and as a result, dopamine agonistic behavior ("screw-like hyperkinesia") is set up in the animal. Histochemical, ultrastructural and pharmacological investigations have shown that this hyperkinesia is of post-synaptic origin in eosin photosensitization, and of pre-synaptic origin in hematoporphyrin photosensitization. The authors suggest an hypothesis to explain the different activity of the two photosensitizers, and discuss the validity of the experiment with regard to human porphyria.
Initial maturative arrest, thickening of the tubular wall, and involution-degeneration of the Leydig cells are the most frequent lesions observed in contralateral testis in men affected by monolateral varicocele. Alterations observed in the Leydig cells at the electron microscope appear to support the hypothesis of hyperstimulation of the cells with rapid degeneration.
The pigmentary system of the planaria, Dugesia gonocephala s.l. (Platyhelminthes, Turbellaria, Tricladida), consists of granules contained in chromatophore cells distributed in the parenchyma tissue. The administration of MSH release-inhibiting Factor (M.I.F.) leads to an easily observable general decolouration of the animal due to the migration of the pigment granules towards the deeper-lying cell nucleus. In planarians bisected transversely through the pharyngeal region, the decolouration occurs only in the cephalic segment, and the caudal segment remains dark. When, however, the decapitated caudal segment regenerates a head region, a decolouration response occurs when exposed to M.I.F. The significance of these results is discussed, and an hypothesis on the hormonal regulation of the pigmentary system is proposed.
Several human cell lines (normal and neoplastic glia, cerebral metastases from adenocarcinoma, fibroblasts) were incubated with sera from patients with well and poorly differentiated glioma and with sera from healthy donors and then stained with PAP complex to define and localize the antibody reaction with cell surface antigens by means of electron microscopy. The sera of glioma patients proved to contain antibodies which bound the tumor-associated antigenic determinants on the cell membranes of gliomas and of cerebral metastases from adenocarcinoma in tissue cultures. Further, absorption testing of the reactive sera on normal brain, well-differentiated astrocytoma and cultured glioblastoma cells, together with cross-reactivity experiments suggests that at least two antigens or groups of antigens are expressed on the glioma cell surface: one shared by well and poorly differentiated glioma cells and the other by poorly differentiated glioma cells and the cells of cerebral metastases from adenocarcinoma.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.