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Biomedical subjects

M M Salpeter

Publications and source records attributed to M M Salpeter.

105 records · Page 6Linked to original sources
PubMed1968

The incorporation of radioactive proline into cultured cells. Interpretations based on radioautography and electron microscopy.

Cultured carrot explants, stimulated to grow rapidly in a medium containing coconut milk, were labeled with radioactive proline. After an initial period of absorption (8 hr for proline-(3)H; 24 hr for proline-(14)C) the tissue was allowed to grow for a further period of 6 days in a similar medium free from the radioactivity. Samples were prepared for electron microscopy and radioautography at the end of the absorption period and also after the further growth. The distribution of the products from the radioactive proline in the cells is shown by high-resolution radioautography and is rendered quantitative for the different regions of the cells. The results show that the combined label, which was present in the form of proline and the hydroxyproline derived from it, was all in the protoplasm, not in the cell walls. Any combined label that appeared to be over the cell walls is shown to be due to scatter from adjacent cytoplasmic sites. Initially the radioactivity was concentrated in nuclei, even more so in nucleoli, but it subsequently appeared throughout the ground cytoplasm and was also concentrated in the plastids. The significance of these observations for the general concept of a plant cell wall protein and for the special problem of growth induction in otherwise quiescent cells is discussed.

Autoradiography↗
PubMed1968

The surface coat of chylomicrons: electron microscopy.

Electron microscope studies were performed on thoracic duct lymph and on washed chylomicrons from dogs fed corn oil. High-resolution electron micrographs showed the presence of a surface coat that differed from the core material and did not resemble a plasma membrane. This was true for both chylomicrons in whole lymph and those that had been subjected to repeated washing. Apparently, the chylomicrons, while passing from the intracellular to the extracellular space, do not acquire their surface coat from pinched off cellular membrane.

Animals↗
PubMed1967

Electron microscope radioautography as a quantitative tool in enzyme cytochemistry. I. The distribution of acetylcholinesterase at motor end plates of a vertebrate twitch muscle.

Tritiated diisopropylfluorophosphate (DFP) was used to phosphorylate acetylcholinesterase (AChase) in the motor end plate of mouse sternomastoid muscle, and its distribution within the end plate was evaluated quantitatively by electron microscope radioautography. With the use of emulsion layers whose sensitivity to tritium had been calibrated, the density of AChase in different components of the end plate was calculated. The AChase was primarily localized (85%) in the junctional fold region. The concentration of AChase there was more than 20,000 active sites per cubic micron of tissue. The resolution of the technique was not sufficient to determine whether there was some AChase in the nerve end bulb; however, if there is any there, the concentration must be less than 10% of that at the junctional fold region.

Acetylcholinesterase↗
PubMed1967

Absolute sensitivity of electron microscope radioautography.

A calibration method is described for measuring absolute radioautographic sensitivities under various experimental conditions. Sensitivities to (3)H and (35)S radiation, i.e. ratio of developed grains to radioactive decays in the specimen, were determined with Ilford L4 and Kodak NTE emulsions. The highest values obtained in monolayers of emulsion were (1/8) for (3)H and 1/21 for (35)S. The influence of various experimental parameters on sensitivity is described, and the possibilities for quantitative electron microscope radioautography are discussed.

Autoradiography↗