The effect of alpha-fetoprotein on the growth of placental cells in vitro.

Cell cultures of early mouse placentae were studied in the presence of mouse amniotic fluid or isolated alpha-fetoprotein (AFP). Four cell types were observed: polygonal cells, giant cells, small round cells and fibroblasts. The number of polygonal cells increased in placental cultures in the presence of amniotic fluid or AFP, suggesting de novo formation and proliferation in vitro.

Structural and microspectrofluorometric studies on glial cells from the periventricular and arcuate nuclei of the rat hypothalamus.

Fluorescence spectroscopy and electron microscopic techniques have been employed to investigate a class of glial cells that is characterized by the presence in their cytoplasm of large fluorescing inclusions that stain with paraldehyde-fuchsin or chrome-hematoxyline-alum. In the periventricular nucleus the cells have been identified as a population of astrocytes whose inclusions emit an orange-red fluorescence. In the arcuate nucleus there are, in addition to an overwhelming majority of such astrocytes, also some microglial cells with similar characteristics.

A new method for measuring radioactivity in select areas of intact tissue sections.

A new technique is described for measuring radioactivity in select areas of intact tissue sections. The method, which makes use of a liquid scintillation counter, also makes possible identification of the studied zones by prestaining.

Energy absorbing capacity of rat tail tendon at various ages.

Fibres from tail tendons of male rats aged 1--18 months were stretched to breaking point by an 'Instron' tensile apparatus. The energy absorbed during stretching of the tendon was calculated. A sharp increase was found in the energy value during the first 6 months of postnatal life.

Changes in the mechanical properties or rat tail tendon during postnatal ontogenesis.

The ultimate tensile strength, elasticity modulus and ultimate elongation of tail tendon in rats age 1-18 months were measured with an Instron tensile apparatus. An increase in all these parameters was observed during the period of maturation, with a later levelling off of the tensile strength and the ultimate elongation. The value of the elasticity modulus attained a maximum during sexual maturation, and then decreased and stabilized.

Identification of Gomori-positive glia in autoradiographs.

Unstained Gomori or paraldehyde fuchsin or chrome-haematoxylin-alum positive granules in the perikaria of so-called Gomori-positive glia of the periventricular zone of the rat hypothalamus, fixed with Bouin's or Carnoy's fluids, have been found to produce a positive chemographic (blackening) effect on autoradiographic emulsion. Similar action was produced by some granules in ependymal cells localized in the ventral part of the third ventricle between optical chiasma and median eminence. It is suggested that this positive chemographic effect can be employed for the identification and characterization of Gomori-positive glia in autoradiographic studies.

Non-diffusional distribution of radioactivity in the rat median eminence after intraventricular injection of 3H-LH-RH.

The distribution of radioactivity in the rat hypothalamus after intraventricular injection of tritiated luteinizing hormone-releasing hormone (LH-RH) was studied by autoradiography and compared with that expected from Fick's second law which defines the character of ordinary diffusion. The results suggest that LH-RH penetrates through the ependyma and thin subependymal layer in the median eminence and into the suprachiasmatic area by ordinary diffusion. By contrast, concentration of radioactivity in outer layers of the median eminence is increased and, therefore, can not be explained by the diffusion law.

Studies on the structure and function of Gomori-positive glial cells in the rat hypothalamus.

Electron-microscopic, histochemical and endocrinologic study of aldehyde-fuchsin-positive (Gomori-positive; GP) grains of rat brain periventricular glia (GP glia) was carried out. GP structures appear as a population of osmiophilic particles, which is heterogeneous in both shape and size. Laminar structures interspersed with fine granular material were seen in the GP granules.