Secretory phenomenon of the adenohypophyseal cells viewed with the scanning electron microscope

Summary Exocytosis from rat adenohypophyseal cells, probably somatotrophic, was studied in the scanning electron microscope after freeze fracturation of the glands. This technique permitted the distinguishing of a clearly delimited exoplasm interrupted by the passage of the secretory granules. It was postulated that the exoplasm could be involved in the control of the release of secretory granules in the endocrine cells studied. At the basal cell surface a simultaneous discharge of several secretory granules has been detected.With the technical assistance of Mr P.-A. Milliquet.     

Scanning electron microscope observations of the canaliculi in the rat pineal gland.

The scanning electron microscope has shown rich ramifications of the parenchymal canaliculi forming a three-dimensional network of anastomosing intercellular spaces in the rat pineal gland. Every pineal cell seems to be in contact with this channel system. An abundance of cellular processes can be found within the canaliculi which may play an important role in the histophysiology of the pineal body.     

A novel xanthone as secondary metabolite fromCentaurium cachanlahuen

Summary From the plantCentaurium cachanlahuen, swertiaperenine1, swercherine2, decusatine4, oleanolic acid5 and the xanthone 1,8-dihydroxy-2,3,4,6-tetramethoxy-9H-xanthone3 were isolated and characterized.     

Estradiol-induced changes in TSH-like immunoreactivity of pituitary cells in female rats

Beta-thyrotropin (TSH)-producing cells in the pituitary pars distalis of female rats were studied using rabbit anti-rat beta-thyrotropin (TSH) serum and a peroxidase-antiperoxidase (PAP) immunohistochemical procedure. Animals were neonatally treated with 1 mg estradiol-dipropionate (EDP) and sacrificed at different stages of development up to adulthood. Intact females of the corresponding age served as the controls. Morphometry and stereology were used to evaluate the changes in TSH-cell number and volume densities of the cells and nuclei. All morphometric parameters examined in estradiol-treated animals showed a significant decrease in comparison with immunoreactive TSH cells of age-matched controls. The most prominent EDP-induced changes were evident in peripubertal 38-day-old rats, the number and volumetric densities of both TSH cells and their nuclei being reduced by about 90% compared to intact pituitary. This decrease in the number and volume densities of TSH cells in EDP-treated rats explicitly demonstrated that this hormone, applied neonatally, has an inhibitory effect on TSH-immunoreactive cells up to adulthood, in accordance with our earlier data obtained by light and electron microscopy.     

A belt of moonlets in Saturn's A ring

The origin and evolution of planetary rings is one of the prominent unsolved problems of planetary sciences, with direct implications for planet-forming processes in pre-planetary disks. The recent detection of four propeller-shaped features in Saturn's A ring proved the presence of large boulder-sized moonlets in the rings. Their existence favours ring creation in a catastrophic disruption of an icy satellite rather than a co-genetic origin with Saturn, because bodies of this size are unlikely to have accreted inside the rings. Here we report the detection of eight new propeller features in an image sequence that covers the complete A ring, indicating embedded moonlets with radii between 30 m and 70 m. We show that the moonlets found are concentrated in a narrow 3,000-km-wide annulus 130,000 km from Saturn. Compared to the main population of ring particles (radius s < 10 m), such embedded moonlets have a short lifetime with respect to meteoroid impacts. Therefore, they are probably the remnants of a shattered ring-moon of Pan size or larger, locally contributing new material to the older ring. This supports the theory of catastrophic ring creation in a collisional cascade.