Immunofluorescence studies of neurofilaments in the rat and human peripheral and central nervous system

Localization of antisera to neurofilament antigens derived from rat peripheral nerve was carried out in tissues of rat and human peripheral and central nervous systems by indirect immunofluorescence. Unfixed and chloroform-methanol-fixed frozen sections of tissues were incubated in purified IgG of the experimental rabbit antisera and subsequently exposed to goat anti-rabbit IgG conjugated with fluorescein isothiocyanate. Control studies were conducted on identical tissue preparations incubated in the same concentrations of nonspecific rabbit IgG or in experimental rabbit IgG absorbed with extracts of rat peripheral nerve containing neurofilament antigen. Extensive immunofluorescence was observed in rat and human peripheral and central nervous systems. The distribution and configuration of immunofluorescence corresponded to neurofilament-rich structural components of these tissues. Prominent immunofluorescence was also noted in neuronal cell bodies of spinal sensory ganglia, especially in perikarya of the large neuronal type. Immunofluorescence of the central nervous system was located predominantly in myelinated axons of the white matter in cerebrum, cerebellum, brain stem, and spinal cord. Less intense immunofluorescence was also seen in neuronal perikarya and in short thin linear processes of grey matter.     

The Upper Tremadocian (Ordovician) graptolite Bryograptus: taxonomy, biostratigraphy and biogeography

Abstract:  The taxonomy, biostratigraphical and palaeogeographical distribution of the Lower Ordovician graptolite genus Bryograptus is evaluated. Bryograptus is recognized as a distinct triradiate anisograptid with a multiramous, pendent rhabdosome. The species of the genus Bryograptus can be interpreted as shallow water faunal elements with a strongly limited biogeographical distribution to the Atlantic Faunal Realm. Bryograptus is restricted to a narrow interval in the Upper Tremadocian, the Bryograptus Biozone of Scandinavia and South America (Argentina), making it a taxon with a high potential for precise biostratigraphical correlations. The proximal end development can be used to differentiate the genus Bryograptus from other pendent multiramous graptoloid genera with a homoplastic rhabdosome development. Characteristics of the proximal end development and structure easily differentiate these genera in relief specimens, but not in flattened material.     

Cyclic AMP Phosphodiesterase in Leydig Cell Preparations of the Rat Testis

Enzymatic digestion of the interstitial tissue of early juvenile and adult rat testes resulted in an enrichment of the Leydig cell population. The cells of the intertubular preparation from adult testes were separated by centrifugal elutriation, according to differences in sedimentation velocity, a counter-flow centrifugation technique leading to 70% Leydig cell purity. Using this approach, it was possible to demonstrate that Leydig cells from adult testes contain only low affinity isoenzymes of cyclic AMP phosphodiesterase (PDE; E.C.: 3.1.4.17), an intracellular regulator of cAMP. Starch gel electrophoresis showed that the isozyme of cAMP PDE of Leydig cells is masked in crude testis homogenates due to the relatively low level of these cells in the total population. In Leydig cells, there are two different electrophoretic forms expressed which resemble two of eleven different molecular forms of cAMP PDE demonstrated for comparison in 21 different organs of the adult rat.
An interstitial cell preparation from early juvenile testes, with a Leydig cell content of up to 20%, was also investigated electrophoretically with regard to molecular forms of cAMP PDE, the properties of which were characterized by kinetic analysis of cAMP hydrolysis. The results presented are discussed in relation to the onset of testosterone synthesis in Leydig cells of prepubertal rats leading to the initiation of male puberty.