In vivo incorporation of 3 H-galactose by thyroid follicular cells of the rat, as shown by electron microscopic radioautography.
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Photometric evaluation of autoradiographic grain densities can be performed according to various optical principles. In all instances the amount of light recorded should be a measure of the radioactive substance amount in the specimens. It is shown that grain densities suitable for light microscopic autoradiography are indeed linearly related to radiation exposure. Dependent on the photometric system used, there is a larger or smaller section of linear correlation of the photometric response with grain density. The advantages of incident light bright-field illumination for silver grain counting are discussed. Quantitation of substance amounts in autoradiographs depends on the use of radioactive standard sources. Two different approaches of quantitation are discussed. In 14C-autoradiography which can be applied for cell-kinetic studies, standard plates are used consisting of 14C-polymethylmethacrylate. Allowance has to be made for the different condition of radiation geometry of the cells and the standards. In 125I-autoradiography, 125I-labeled red cells are used as standards. This technique allows for quantitating the number of antibodies bound to individual cell surfaces.
Electron microscopy can resolve structures with accuracy of the order of 0.2-0.3 nm, but the radioautographic technique is able to locate radioactive label with much less certainty, at best 50 nm. This difference in resolution is what creates the problem of quantitation in electron microscope radioautographs.
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The subcellular route of incorporation of complex carbohydrates into rabbit heterophil primary granules and their subsequent intragranular distribution during granule maturation were studied with ultrastructural, cytochemical, and radioautographic methods. High iron diamine (HID) staining of sulfated glycoconjugates in primary granules was partially diminished after treatment with chondroitinase ABC or after removal of N-sulfate groups with nitrous acid, but was not altered by exposure to hyaluronidase, trypsin, or HCl. Subsequent thiocarbohydrazide-silver proteinate (TCH-SP) straining of thin sections increased the density of the HID reaction product. Golgi-derived spherules and very immature morular granules stained weakly with HID-TCH-SP and labeled intensely after a 10 min incubation with 35SO4. After a 60 min 35SO4 pulse and a 60 min chase, an increase in radiolabeling was observed in granules with HID stained, fused morular material, and some labeling was present in more mature rim stained granules. Fully mature granules lacked HID or HID-TCH-SP staining, but contained most of the 35SO4 labels after a 60 min pulse and 18 hr chase in vitro. Periodate-thiocarbohydrazide-silver proteinate (PA-TCH-SP) staining of unosmicated thin sections localized vicinal glycol-containing complex carbohydrates in Golgi-associated small vesicles. These vesicles lacked HID-TCH-SP staining and apparently contained neutral glycoprotein. They frequently bordered, in a rosette arrangement, the immature morular granules, but not the more mature primary granules. The PA-TCH-SP method localized complex carbohydrates in the rim of granules precursors and enclosed a spherule or morula, but failed to stain the sulfate-containing material in the morulas or spherules. PA-TCH-SP reactivity was diffusely distributed in moderately mature granules and was decreased in fully mature granules. These results indicate that heterophil primary granule contain several complex carbohydrates including O-sulfated and N-sulfated glycosaminoglycans, as well as vicinal glycol-containing glycoproteins. These complex carbohydrates are transported to immature primary granules by different Golgi-derived organelles. The complex carbohydrates are subsequently distributed differently within primary granules and become masked to staining as the granule matures.
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Radioautograms were made of uterine horns, cervix and vagina from guinea pigs injected with[3H]progesterone at various periods of the estrous cycle. The concentration of silver grains peaked at proestrus and estrus and then fell during metestrus, attaining a minimum at diestrus. These variations were not due to masking of binding sites by endogenous hormone since ovariectomy of guinea pigs at diestrus did not change this pattern. During proestrus and estrus, radioactivity was found in all parts of the endometrium and myometrium of the uterine horns. However, the muscle fibers and the cells of the stroma contained more silver grains than did the luminal and glandular epithelium. In the vagina, radioactivity was concentrated mostly in the nuclei of the basal layer cells of the stratified epithelium. During metestrus and diestrus, less radioactivity was present in these regions. These differences in labelling were observed simultaneously in all the uterine and vaginal cell types, suggesting that similar hormonal mechansims may control receptor variations in these different target cells.
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