Influence of 1 and 25 Hz, 1.5 mT magnetic fields on antitumor drug potency in a human adenocarcinoma cell line.

The resistance of tumor cells to antineoplastic agents is a major obstacle during cancer chemotherapy. Many authors have observed that some exposure protocols to pulsed electromagnetic fields (PEMF) can alter the efficacy of anticancer drugs; nevertheless, the observations are not clear. We have evaluated whether a group of PEMF pulses (1.5 mT peak, repeated at 1 and 25 Hz) produces alterations of drug potency on a multidrug resistant human colon adenocarcinoma (HCA) cell line, HCA-2/1(cch). The experiments were performed including (a) exposures to drug and PEMF exposure for 1 h at the same time, (b) drug exposure for 1 h, and then exposure to PEMF for the next 2 days (2 h/day). Drugs used were vincristine (VCR), mitomycin C (MMC), and cisplatin. Cell viability was measured by the neutral red stain cytotoxicity test. The results obtained were: (a) The 1 Hz PEMF increased VCR cytotoxicity (P < 0.01), exhibiting 6.1% of survival at 47.5 microg/ml, the highest dose for which sham exposed groups showed a 19.8% of survival. For MMC at 47.5 microg/ml, the % of survival changed significantly from 19.2% in sham exposed groups to 5.3% using 25 Hz (P < 0.001). Cisplatin showed a significant reduction in the % of survival (44.2-39.1%, P < 0.05) at 25 Hz and 47.5 microg/ml, and (b) Minor significant alterations were observed after nonsimultaneous exposure of cells to PEMF and drug. The data indicate that PEMF can induce modulation of cytostatic agents in HCA-2/1(cch), with an increased effect when PEMF was applied at the same time as the drug. The type of drug, dose, frequency, and duration of PEMF exposure could influence this modulation.

[L-thyroxine and triiodo-L-thyronine in the cerebrospinal fluid and hypothalamo-hypophyseal axis of hyper- or hypothyroid rats]. / L-tiroxina y triiodo-L-tironina en líquido cefalorraquídeo y eje hipotálamo hipofisario de ratas, hiper- e hipotiroideas.

L-thyroxine and triiodo-L-thyronine concentrations in cerebrospinal fluid (CSF), hypothalamus and pituitary gland are measured in male albino-Wistar rats under several experimental thyroid disfunction : including hyperthyroidism induced by L-T3 and L-T4 treatments and surgical hypothyroidism. Radioimmunoassay is carried out by Nejad's method modified in this work. The pattern of thyroid hormone concentrations in CSF is similar to that in serum, but the values obtained are lower. Thyroid hormone concentrations in adenohypophysis as opposed to hypothalamus or cerebral cortex, show an inverse change to functional thyroid status.

[Effect of experimental changes in thyroid function on oxidative metabolism and glutamate dehydrogenase activity in the limbic system of the rat]. / Efecto de las alteraciones experimentales de la función tiroidea sobre el metabolismo oxidativo y actividad de la glutamato deshidrogenasa en el sistema límbico de la rata.

The oxidative metabolism and GDH activity has been studied in the following regions of the brain: frontal cortex, as tissue control, adenohypophysis, hypothalamus and limbic system in adult male rats subjected to alterations of the thyroid function due to excess (by hyperthyroidism with L-thyroxine and thyrotoxicosis with Tri-iodothyronine) or defect (chronic hypothyroidism by thyroidectomy, 131-I treatment and low iodine diet). A different influence of the H.T. was observed in these animals according to the areas studied and the experimental situation induced. All this seems to indicate an oxidative metabolic pattern peculiar to each area of the brain following H.T. administration. On the other hand, the decrease of the QO2 in chronic hypothyroidism in the majority of the areas studied is remarkable. In GDH results activity increased or decreased depending on the absence or presence of thyroid hormones.