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  • 1
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The distribution of the NADPH diaphorase activity was studied in mouse Leydig cells by means of light and electron microscopy. When observed by the light microscope, most Leydig cells appeared intensely stained; a few cells (about 10%) showed a slightly positive or apparently negative reaction. The inhibitory effects of NG-nitro-l-arginine and iodonium diphenyl on frozen sections suggest the colocalisation of NADPH diaphorase reaction with nitric oxide synthase. The ultrastructural study revealed that all the Leydig cells were positively stained for NADPH diaphorase; however, a small number of cells displayed weak enzymatic activity. The reaction product was located in the mitochondria, smooth endoplasmic reticulum and lipidic vacuoles, and the nuclear envelope was also stained. The possible meaning of the NADPH diaphorase activity in the Leydig cells of mice was discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1615-6102
    Keywords: Cellular evolution ; Epixenosomes ; Eukaryotes ; Prokaryotes ; Symbiosis ; In situ hybridization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Epixenosomes live on the dorsal surface of their ciliate host,Euplotidium itoi. They lack a nuclear envelope and divide like prokaryotes. On the other hand they have a morphological and functional cell compartmentalization and possess tubules that are sensible to tubulin inhibitors and positively react with different antitubulin antibodies. In the present paper, as a first step to investigate their real nature, the in situ hybridization technique was applied at the ultrastructural level. Different prokaryotic and eukaryotic probes suitable for detecting rRNA genes were used. An additional test was performed with the gene encoding for β tubulin in the ciliateEuplotes crassus. Positive results, evidenced by a precise localization of gold particles, were obtained with all the eukaryotic probes used. These probes were obtained from organisms belonging to three different kingdoms (Protista, Animalia, Plantae). On the contrary, no hybridization was obtained with prokaryotic probes, not even when the probe used was an oligonucleotide complementary to all bacterial 16S rRNA so far sequenced. On the basis of these results and of the other observations so far accumulated, the possible eukaryotic nature of epixenosomes is discussed.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1615-6102
    Keywords: Adrenalin ; Cyclic AMP ; Ejecting process ; Epixenosomes ; Membrane receptors ; Cytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The extrusive apparatus is the most prominent and complex structure of epixenosomes. In the present paper the mechanisms activating its ejecting process were investigated by means of in vivo treatments and cytochemical procedures at the ultrastructural level. The results obtained clearly demonstrated that the ejecting process in epixenosomes is triggered by the detection of external signals through membrane receptors and the consequent activation of the adenylate cyclase-cyclic AMP system as a transduction mechanism. The membrane receptors coming into play have an affinity for soybean agglutinin and have a precise localization at the top of the organism, just where a membrane interruption appears as a first step in the whole process. The factors that trigger ejection in nature are still unknown. In the laboratory, ejection was obtained in the presence of adrenalin, which has been proved to bind to the same receptors shown to have affinity for soybean agglutinin. So epixenosomes appear to possess specific binding molecules for a mammalian hormone in the appropriate location, i.e., in the plasma membrane, and this hormone induces a precise biological response. These results are particularly interesting if we consider that epixenosomes are enigmatic organisms in which prokaryotic and eukaryotic characteristics appear to coexist.
    Type of Medium: Electronic Resource
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