Light cells, thyroid

The infusion of calcitonin to rats induces increased calcium deposition in the bone and hypocalcemia. Thus, the hormone has properties antagonistic to those of parathormone. Fluorescent antibody techniques have demonstrated that the hormone is secreted by the C cells of the thyroid gland. A light cell hyperplasia outside the follicular walls of the thyroid has been observed in mice with hereditary hypocalcemia. 

PNP-DTP has been used to photoaffinity label the thyroid hormone nuclear receptors in intact cells by preparing a derivative of 3,5,3 -triiodo-L-thyronine with the crosslinker (Pascual et al., 1982 Casanova et al., 1984). Effective photoreactive conjugation was found to occur after irradiation with UV light at 254 or 310 nm. 

Differences in enantiomers become apparent in their interactions with other chiral molecules, such as enzymes. Still, we need a simple method to distinguish between enantiomers and measure their purity in the laboratory. Polarimetry is a common method used to distinguish between enantiomers, based on their ability to rotate the plane of polarized light in opposite directions. For example, the two enantiomers of thyroid hormone are shown below. The (5) enantiomer has a powerful effect on the metabolic rate of all the cells in the body. The (R) enantiomer is useless. In the laboratory, we distinguish between the enantiomers by observing that the active one rotates the plane of polarized light to the left. 

Seven-week-old Wistar rats at normal iodine baseline were divided into four different groups and fed on water with normal, 1.5-fold high, 3-fold high and 6-fold high iodine levels for 8 months. Thyroid follicular epithelial cells were observed using a light microscope, the height of epithelium... 

Potassium Iodide Kl K+ -H P P Is rapidly taken up from gut, actively transported Into thyroid cells and used for synthesis of thyroid hormone Under air slow oxidation to f and loss by evaporation, enhanced by humidity and exposure to light. Used to Iodize salt... 

Fig 1. Effect of incubation meditun and excess hormone on L-T and L-T/, uptake by mouse neuroblastoma cells (NBATA3) After 45 min preincubation confluent cells were incubated at 37°C for 2 h with 10 pM labeled thyroid hormone in the absence or presence of lOpM unlabeled hormone. Wells measuring 28.2 cm contained 4 ml of culture medium (RPMI 1640) or Hank s balanced salt solution. After washing with phosphate buffered saline +0.1% serum albumin, the cells were harvested and their radioactivity measured. Mean SEM of 3 experiments performed in duplicate. Experiments were performed under diminished light to avoid spontaneous deiodination especially of T, in RPMI due to riboflavin and folic acid. 

For light microscopy, the fetal thyroid gland was fixed in 10% buffered formalin solution after weighing. Tissue blocks were embedded in paraffin. Sections were stained with HE and PAS. Frozen sections were stained for peroxidase activity. In addition to the routine microscopic examination, the maximal diameter of the follicles and the heights of the epithelial cells and their nuclei were measured by micrometer. In each case, 100 cells were randomly measured, the average values were obtained and the nucleus-cytoplasm index (N/C) was calculated. 

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