High-Speed Electron Microscope Autoradiographic Studies of Diffusible Compounds,

Abstract

Three important factors are necessary for successful electron microscope autoradiography (EM-ARG): good resolution, proper preparation of the radioactive isotope (RI) labeled diffusible compounds, and shortened exposure time for ARG. The resolution problem is fundamental to EM-ARG. However, unless the diffusible RI compounds have been fixed correctly in the tissues during preparation, good resolution is useless. It is also necessary to shorten the exposure time for ARG. As yet, a high-speed ARG method for electron microscopy has not been reported, although scintillation ARG methods have been applied to macro-and micro-ARG since 1960. High specific activity, a large amount of radioactivity per unit exposure for radio incorporation (incubation), and careful selection of labeled compounds that concentrate in the DNA or RNA of cell organelles may increase the sensitivity of the emulsion and shorten the exposure time for ARG. For example, labeled thymidine accumulates in nuclear DNA, `H-SPG (Schizophyllan-produced polyglucan) is incorporated into lysosomal granules, and labeled iodine concentrates in thyroid follicles, often increasing the sensitivity of the emulsion and shortening the exposure time. High-speed ARG yields good data in a very short time, but high-resolution ARG continues to be necessary, even though it requires 4 weeks or more of exposure time. Scintillation autoradiography using tritium seems unstable. We propose a new way to shorten exposure time for EM-ARG, by combining overdevelopment with coating both sides of the grid with emulsion. This method is approximately 100 times more sensitive than the conventional method, and only 4 days of exposure time are required, in contrast to the 1 month usually needed.

New tissue fixation method for cytochemistry using migrowave irradiation. I. General remarks.

“…In conventional immersion fixation, the aldehyde penetrates gradually into the tissue block from the periphery to the center, proceeding together with the cross-linking. Tannic acid can accelrate the cross-linking process (75,79). Our results showed that the MWI method yields excellent fixation effects, equivalent to those of the rapid frozen fixation method (42,43).…”

Autoradiographic Studies on the Binding Sites of 125I-Adrenomedullin in Rat Tissues.

“…Proteins and peptides have been found to be more effectively fixed when tannic acid is present in the aldehyde fixative solution [8,11]. In our in vitro test, we added 0.1% tannic acid, 2% formaldehyde and 0.5% glutaraldehyde to the 125I-AM solution.…”

Histological and cytochemical studies on the distribution of schizophyllan glucan (SPG) in cancer-inoculated animals. I. Differences in distribution and antitumor activity of 3H-SPG in sarcoma-180 inoculated females between ICR and DBA mice.

“…However, most of these investigators used cytotoxic and seroimmunological techniques, without a histopathological and histochemical background. Mizuhira (25) and Fujioka (11) and Mizuhira et al (26,28) reported on the antitumor action of PS-K from a morphological standpoint. Therefore, most of the investigators explained the host-mediated antitumor activity as the result of adjuvant immunological or cytotoxic functions.…”