Autoradiographic detection of mucopolysaccharide accumulation in single fibroblasts

Ice crystal damage in frozen thin sections: freezing effects and their restoration

Thin sections of unfixed kidney, fast frozen without cryoprotectants, were fixed in osmium tetroxide vapour directly after freeze drying or after 30 min in a moist atmosphere. Dry sections fixed in vapour showed ice crystal damage characteristic for the freezing procedure. This was demonstrated with freeze fracture replicas from the same preparation. Ice crystal holes were obscured in serial sections which were freeze dried and allowed to rehydrate in a moist atmosphere. The same ultrastructural appearance was observed in frozen sections brought to room temperature immediately after cutting. Frozen thin sections from unfixed tissue, if freeze dried, are very sensitive to atmospheric conditions and need some form of stabilization (e.g. osmium vapour fixation, sealing with an evaporated carbon film) before electron microscope images can be interpreted as representative for the frozen state. Restoration of ice crystal damage can occur by melting frozen sections or by rehydration of freeze dried frozen sections. Restoration phenomena will impair studies aimed at the localization of diffusible substances by autoradiography or X-ray microanalysis.

Hybridization studies of fibroblasts from Hurler, Scheie, and Hurler/Scheie compound patients: support for the hypothesis of allelic mutants

Heterokaryons were made by fusion of alpha-L-iduronidase-deficient fibroblasts from patients with the Hurler, Scheie, or Hurler/Scheie compound syndrome. The fused cell populations remained alpha-L-iduronidase deficient and accumulated 35S-labeled glycosaminoglycans (35S-GAG) to the same extent as the parental cells strains. Also, when 35S-GAG accumulation was studied by autoradiography at the level of single bi- and multinuclear hybrid cells, no evidence was found for genetic complementation. The results support the hypothesis that the mutations in the Hurler and Scheie syndromes are allelic, and they are compatible with the view that patients with intermediate phenotypes represent genetic compounds.

Freeze-drying of unfixed monolayer cultures for electron microscopic autoradiography

A method has been developed for freezing, drying and embedding of unfixed monolayer cultures for electron microscopic autoradiography (EM ARG). Experimental results showed: a) Aclar 33 C was a more suitable substrate than the plastic of petri dishes, b) cultures pressed rapidly against the polished face of a large copper cylinder chilled in liquid nitrogen had better cellular morphology than did cultures dipped in Freon 12 chilled in liquid nitrogen, and c) cultures embedded in Epon alone had finer extracellular ice spaces and lower background grain densities than did cultures embedded in Epon with 1% silicone. This method has been used to evaluate the effect of fixation on the localization of the neurotransmitter, 3H-gamma-aminobutyric acid (3H-GABA), in neurons of dispersed cell cultures. EM ARG results showed that the neuronal cell bodies and vesicle elements were present in similar numbers in both glutaraldehyde fixed and freeze-dried cultures.