Browsing by Author "TELLEZ, R"

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    A PREPUBERTAL SURGE OF THYROTROPIN PRECEDES AN INCREASE IN THYROXINE AND 3,5,3'-TRIIODOTHYRONINE IN NORMAL-CHILDREN
    (ENDOCRINE SOC, 1991) MICHAUD, P; FORADORI, A; RODRIGUEZPORTALES, JA; ARTEAGA, E; LOPEZ, JM; TELLEZ, R
    The variations in plasma levels of TSH, T4, T3, and rT3, during the pubertal period, were studied in 647 school students from the urban area of Santiago in Chile (47% males and 53% females) with ages ranging between 7.5 and 15 yr. The subjects were grouped by age in consecutive intervals of 6 months each, and pubertal development was determined in every subject. TSH showed a significant increase, reaching a peak in the 9- to 9.5-yr interval. The same was found for T3 and T4, which reached a peak by 10 and 11 yr. The T4/T3 ratio did not show any significant variation with age. After 9.5 yr, a decrease in rT3 and increase in the T4/rT3 ratio was found. The TSH peak preceded the onset of clinical pubertal development, while the T3 and T4 peaks coincided with this onset. The variations in rT3 suggest an increase of peripheral conversion of T4 to T3. These transient events, not described until now, could be termed thyroidarche and could have a significant effect on pubertal growth and development.
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    THE PH-DEPENDENCE OF RAT-LIVER RNA POLYMERASE-I AND POLYMERASE-II
    (1980) BULL, P; MARTIAL, J; TELLEZ, R; VENEGAS, A; VALENZUELA, P
    The effect of pH on the stability and activity of rat liver RNA polymerases I (A) and II (B) was studied. Both enzymes are irreversibly inactivated in buffer solutions below pH 5.0. Km values of the 2 enzymes are constant between pH 6.5 and 8.7, but a 2- to 3-fold increase is observed between pH 8.7 and 9.7. The Vmax vs. pH profiles are bell-shaped curves indicating the participation of 2 ionizing groups with apparent pKa values of 6.5 and 9.8 for enzyme I and 6.7 and 9.9 for enzyme II. Both enzymes are inactivated by photooxidation in the presence of Rose Bengal. The above pKa corresponds to the imidazole of a histidine residue and an amino group of a lysine residue.