Folia Morphologica (Praha)

The validity of von Baer's "laws" on the general and the specific in vertebrate morphogenesis (especially organogenesis) was varified. The author starts from the hypothesis that the rudiments of traits newly acquired during morphogenesis are not rigid, not immovable, during morphogenesis, but that the action of protracted stabilizing selection during the geological ages causes them to spread and pushes them back to the perfected and stabilized in adulthood, thereby shortening the recapitulation of ancestral traits, which may eventually disappear below the threshold of detectable morphogenesis...

The authors describe ultrastructural changes in and around rat brain capillaries after hypoxia. The experimental animals breathed a mixture of 5% oxygen and 95% nitrogen for two or for three hours; a third group, which spent three hours in this atmosphere, was treated 24 h later. Cytoplasm processes and vesicles were observed on the luminal side in the endothelial cells, while the cytoplasm contained vacuoles and altered mitochondria. The basement membrane of the brain capillaries was uneven and longitudinal clear zones were formed in it...

In the regenerating optic lobe of Bufo regularis larvae, secondary ependymas were formed in both the dorsal part (optic tectum) and ventral region (tegmentum) of the lobe concerned. These secondary ependymas were frequently observed in the rostral and caudal tectal regions after complete excision of the tectum. Most of the multiple ependymal structures were formed by self-organization of groups of undifferentiated cells migrating from the primary ependyma lining the optic tectum. Others split off from the primary ependyma, but remained in contact with it...

The pituitary gland of Puntius sarana is of the leptobasic type and has three subdivisions--a proximal pars distalis (PPD), a rostral pars distalis (RPD) and a pars intermedia (PI) arranged vertically one below the other. The gonadotrophs (GTH cells) of the PPD were identified by their PAS, ATh, AF, aniline blue and alcian blue positivity and by their immunoreactivity to ovine anti-LH beta-subunit, anti-salmon GTH and anti-silver carp GTH. The testes of Puntius sarana have been classified as the "unrestricted type"...

The structure of the components of the Haversian canals of the osseous tissue of the adult human mandible was studied in celloidin sections stained with haematoxylin and eosin. Fine blood vessels - mostly profiles of postcapillary venules, precapillaries and occasional capillaries - were demonstrated in osteons with Haversian canals 60-80 microns in diameter. Neither lymph capillaries nor vessels were observed, even in wider Haversian canals with larger blood vessels. The intraosseal spaces with rich blood vessel plexuses likewise did not contain any lymphatics with a characteristic form...

Accumulation of cadmium in the liver was demonstrated by X-ray microanalysis in every type of experiment, i.e. after injecting Cd into the ligated intestine and after the peroral acute single and combined, subchronic and chronic administration of Cd. Half an hour after its injection, Cd was localized diffusely in the liver; one hour after injection its increased accumulation in the cells caused generalized changes in the endoplasmic reticulum, mitochondria and nuclei. In acute and chronic peroral tests, the hepatocytes of the intermedial and peripheral zone of the lobes were the main storage region...

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