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S Halpern

Publications and source records attributed to S Halpern.

At least 73 records · Page 4Linked to original sources
PubMed1989

[Quantitation of iodine by analytical ion microscopy (AIM)].

AIM allows imaging and quantification of all elements on a biological tissue section. However quantification is limited by physical parameters which are difficult to assess and which intervene for a given element in the relation between its concentration and the measured signal. Thus, to quantify iodine in thyroid follicles, an iodine standard was prepared. Homogeneity in its atomic iodine distribution was tested by surface and depth analyses. Then, a standard curve was generated to be used as a reference for quantification of iodine on histological preparation by AIM.

Iodine↗
PubMed1989

Application of the pyroantimonate method and electron probe microanalysis to the study of glycogen metabolism in liver.

Glycogen distribution in the liver of mouse under different metabolic conditions was studied by the pyroantimonate (PA) method combined with semi-quantitative electron probe microanalysis (EPMA). In the liver of animals subjected to a sugar-rich diet, glycogen granules were abundant and electron transparent. In fasted animals, they were less numerous and stained by PA, which indicates the presence of a complexed cation. This cation was identified as calcium by EPMA. In both cases, adjacent cytoplasmic areas contained "masked" calcium not revealed by PA but detected by EPMA, which is characteristic of a neutral complexed form; but in the case of the fasted animals, the calcium concentration was significantly lower. If the liver of fasted animals was dissected in 0.2% glucose-containing medium, the glycogen areas dramatically released calcium and lost their stainability by PA, whereas mitochondria and adjacent cytoplasm contained many PA precipitates rich in calcium and sodium, suggesting a sudden increase of intracellular [Ca2+]. In mitochondria, the sodium:calcium ratio was relatively constant, which suggests a process involving a coupling between these two elements. Our results could be explained in the light of physiological and biochemical data. We particularly noted that diffusible cations as calcium and sodium did not appear to be displaced over long distances from their likely source. This observation agrees with recent theories on the state of water and ion mobility in the cell.

Animals↗
PubMed1988

Localization of cations by pyroantimonate. II. Electron probe microanalysis of calcium and sodium in skeletal muscle of mouse.

A new formulation of the pyroantimonate (PA) method for localization of calcium and sodium is proposed and evaluated in mouse skeletal muscle. This study, performed at the ultrastructural level by means of transmission electron microscopy (TEM) and electron probe microanalysis (EPMA), completes a previous work done at the optical level with analytical ion microscopy (AIM), which enabled us to define the appropriate composition of fixatives. In our present experiments, calcium and sodium were shown localized in various cell structures, e.g., T-tubules, glycogen, granules, nuclei. For AIM, the best fixatives were characterized by PA supersaturation, which resulted in smaller crystals and a high rate of penetration in the presence of paraformaldehyde and either phenol or collidine. Contrary to the findings at the optical level, collidine did not give satisfactory results at the ultrastructural level. The method of floating sections on the microtome trough was an important cause of cation displacement. We found that alkalinization of the floating medium significantly decreased ion loss. The technique also provided an indication of the form of these elements: free or easily liberated cations were precipitated into coarse PA deposits; electron-positive chelates were "stained" by PA; neutral chelates were not stained, but some of them could be detected by EPMA. This PA method should make possible more precise localization of cellular calcium, such as in glycogen metabolism, and perhaps detection of movements of cytoplasmic calcium and sodium.

Animals↗
PubMed1988

Changes in iodine mapping in rat thyroid during the course of iodine deficiency: imaging and relative quantitation by analytical ion microscope.

The analytical ion microscope (AIM) makes possible imaging and relative quantitation of multiple stable or labeled elements on an even tissue section, according to their mass. The purpose of this work was to follow at the rat thyroid follicle level the changes in 127I mapping during low iodine diet (LID) in relation to the ability of thyroid to pick up radioiodine (129I) and to synthesize Tg from its precursor, 2H-labeled leucine. The overall picture of images and countings of 127I shows a progressive decrease of the luminal iodine concentration which on day 80 was 10-fold lower than that of control value. In control rat thyroid cell, concentration was 10-fold lower than that of follicular lumina and was unchanged until 35 days, but the size of the cytoplasmic compartment increased, suggesting a redistribution of iodine stores between thyroid cells and follicular lumina. 129I was always found in colloid as well as in cells at all stages. After 35 days of LID, cytoplasmic and luminal radioiodine concentrations decreased. In control rats, [2H]leucine was found mainly in the cells. During LID its localization was evidenced progressively in most of the lumina. The most striking fact was the presence up to 35 days of some large residual follicles with high 127I concentration and low 129I and 2H incorporation. These data demonstrate the follicular heterogeneity of thyroid response to progressive chronic TSH stimulation induced by LID.

Animals↗