L-thyroxine and L-triiodothyronine in the cerebral tissues of the adult rat. Effect of hypothyroidism]

The L-thyroxine and L-triiodothyronine concentrations in several brain areas (cerebral cortex, brain stem, hypothalamus, total brain and hypophysis) in normal and hypothyroid rats have been studied. Results show that L-thyroxine values at tissue level are inferior in the hypothyroid group, although non-significant with respect to the control group, whereas L-triiodothyronine presents values similar to the hypothyroid group and its control in all the brain regions studied with the exception of hypophysis. These results show that in hypothyroid situations exist a compensatory mechanism for maintaining the adequate L-triiodothyronine levels in several brain areas, although the serum levels are strongly decreased in hypothyroid animals.     

Effect of strontium and magnesium on blood calcium]

Twenty four male Wistar rats weighing 250 +/- 10 g, in three groups of 8 rats each, were used. Group A was used as control and the content of its drinking water was 6.5 mg/l Ca; 2.4 mg/l Mg. The drinking water of groups B and C was supplemented with 20 mM (SrCl2) and 20 mM (MgCl2), respectively. Once the 20 days of mineral supplementation had passed, arterial blood was extracted by puncture in the abdominal aorta. In the serum obtained after centrifugation, Ca, Mg, Sr and the total proteins (TP) were determined. Afterwards the serum was subjected to ultrafiltration. Concentrations of Ca, Mg and TP were measured in the obtained ultrafiltrates (u), with the above described techniques. The pH was measured before and after the ultrafiltration. The TP decreased significantly both in group B (supplemented with Sr), and in group C (supplement with Mg). Increases in Ca were found in group B and in Mg in group C. The Mg/Ca ratio increased 10% after the supplementation with Mg. At the ultrafiltrate a significant increase in Cau after supplementation with Sr and with Mg was observed. The Mgu/Cau ratio decreased 14% in the group supplemented with Sr and 38% after the supplementation with Mg. In conclusion, the supplementation with Sr (20 mM) in rats increases the Cau and could have the effect of reducing protein synthesis. These facts should be borne in mind when Sr is used for therapeutical purposes.     

Comparison of two techniques for quantifying environmental contaminants in human serum

Peak area matching and linear regression were used to quantify eight chlorinated pesticides and polychlorinated biphenyls (as Aroclor 1260) in human serum. There are no statistically significant differences in data obtained by these two quantifying techniques which were indicated by the paired t-test. For chlorinated pesticides, p = 0.053-0.62, and for polychlorinated biphenyls (as Aroclor 1260), p = 0.64. Analyte residues for the chlorinated pesticides ranged from 0.5 ppb for hexachlorobenzene (HCB) to 186 ppb for dichlorodiphenyldichloroethylene (DDE). Analyte residues for the polychlorinated biphenyls (as Aroclor 1260) ranged from 5-114 ppb. The absolute mean percent difference between the two quantifying techniques ranged from 0.06% for DDE to 8.06% for dieldrin (HEOD) among the chlorinated pesticides. The absolute mean percent difference between the two quantifying techniques for the polychlorinated biphenyls (as Aroclor 1260) was 3.4%. Peak area matching and linear regression were found to be comparable for quantifying these environmental residues in serum when the following conditions apply: 1) the concentration of the chlorinated pesticides is greater than or equal to 0.5 ppb (e.g., HCB, hexachlorocyclohexane (HCCH), oxychlordane (OC), heptachlor epoxide (HE), transnonachlor (TN), HEOD, and dichlorodiphenyltrichloroethane (DDT); 2) the concentration of the chlorinated pesticide is greater than or equal to 3 ppb (e.g., DDE); and 3) the total concentration of polychlorinated biphenyls (e.g., as Aroclor 1260) is greater than or equal to 5 ppb.     

The effect of storage on the frequency of dominant lethals in Drosophila melanogaster

Summary Ethylenimine, ethyl methanesulfonate and formaldehyde have been shown to produce a storage effect in dominant lethality in Drosophila melanogaster.