RESUMEN
The National Research Council of Argentina (CONICET) was founded in 1958, and the Research Career opened officially two years later (1960). Originally, 214 scientists belonged to this Career, increasing slowly to 3642 members in 1999. There are 5 categories of investigators, besides the Clinical Investigator class for the area of Medical Sciences. Investigators comprise 46
, while Technicians (34
) and Fellows (20
) account for the rest of CONICET research personnel. The low number of Fellows is a matter of worry, although Fellows from universities, local councils and private foundations contribute to increase their total number. There is an irregular regional distribution of Investigators, most of whom work in the Federal Capital and Province of Buenos Aires (61
). Increasing the salary of those living outside the metropolitan area did not solve the problem. Input to the Research Career has been erratic and not well planned, while mechanisms for personnel output due to low productivity or retirement age has had variable and erratic policies. The problem the Research Career is facing is similar to that of other areas of CONICET, due to an extremely low budget. Hopefully, new CONICET authorities will be active scientists considering Science and Technology as a Matter of State, just as important for the country as health, education or recovery of the Malvinas Islands.
RESUMEN
We have studied the cytosolic estrogen receptor in uterus of rats after castration and diabetes induction with Streptozotocin, and the relationship of estradiol (E2) binding with phosphatase activities. Ovariectomy (OVX) and diabetes produced a significant reduction in Type I and II binding sites, but did not affect the equilibrium dissociation constants. The reduction of receptor levels was partially reversed by homogenization and incubation with 20 mM molybdate (MoO4) and also by chronic treatment with E2. Considering the possibility that the increase in E2 binding in the presence of MoO=4 was due to phosphatase inhibition, the activities of these enzymes hypothetically involved in receptor dephosphorylation and inactivation were determined in uterine homogenate and cytosol from intact, OVX, and diabetic rats with and without E2 treatment. Chronic OVX and diabetes induced stimulation of alkaline, acid and neutral phosphatase activities. On the contrary, the increment of estrogenic receptors due to E2 treatment was not correlated with changes in phosphatase activity. It is possible that this effect was due to the protection of the receptor or to the induction of receptor synthesis by E2. Molybdate inhibited acid and neutral phosphatases and increased alkaline phosphatase, which suggest that neutral and acid phosphatases are identical and that they were responsible for the receptor inactivation. However, it is unclear at present the relationship between the increment of alkaline phosphatase and the reduction of receptors.
RESUMEN
Short and prolonged administration of ACTH was used to study the effects of the hormone on protein synthesis in two subcellular fractions obtained from rat adrenals incubated in the presence of a (14C)-labelled amino acid mixture. Acute treatment with ACTH produced an increased labelling of the proteins of the post-mitochondrial (POST-MIT) fraction only. On the other hand, treatment with ACTH for 4-28 days, significantly increased the specific activity of proteins in the mitochondrial (MIT) fraction, without change in the radiolabelling of the POST-MIT fraction. The incorporation of (14C)-labelled amino acids into the proteins of the MIT and POST-MIT fractions, from control or ACTH-treated adrenals, was reduced by inhibitors of cytoplasmic protein synthesis (puromycin and cycloheximide). This suggests that the increased labelling of the MIT fraction after prolonged ACTH might be related to a translocation of cytoplasmic proteins to the mitochondrion.
RESUMEN
Binding of cortisol and corticosterone by serum proteins is well established, but discrepancies exist regarding aldosterone. We have observed that approximately 1
of 3H-aldosterone incubated with rat serum was bound in a time-dependent process, although it was not competed by a large excess of non-radioactive aldosterone, assessed by Florisil separation or gel filtration on Sephadex G-50 columns. After electrophoresis on cellulose acetate of rat serum incubated with 3H-aldosterone, specific or non-specific binding to protein fractions was not obtained. Further, a 10 000-fold molar excess of aldosterone (10 microM) displaced only 34
of the bound 3H-aldosterone to rat serum, preventing the calculation of the IC50 value. Increasing concentrations of aldosterone (3-83 nM) did not displace 3H-corticosterone bound in rat serum to presumably corticosterone binding globulin (CBG). In contrast, inhibition of this binding by 3-83 nM corticosterone was concentration dependent, showing an IC50 value of 10(-8) M. In normal human serum, binding of 3H-aldosterone demonstrated competition by a 100 and 1 000-fold excess of aldosterone. Displacement curves of 3H corticosterone bound to human serum by 1.7-75 nM corticosterone or 0.05-8.8 microM aldosterone yielded IC50 values in the range of 10(-8) M for corticosterone and 10(-6) M for aldosterone. With horse serum, aldosterones binding affinity was three orders of magnitude lower than that of corticosterone. These studies suggest that in the rat aldosterone was loosely and weakly bound to a high capacity binder, possibly albumin. In agreement with the work of others, in humans aldosterone may be bound to both CBG and albumin. The current data do not substantiate for the presence of specific aldosterone binding proteins in serum.
RESUMEN
Binding parameters of type I and type II sites for (3H)-estradiol were studied in cytosol of the rat uterus using the Scatchard method and a computer program based on the analysis of Rodbard et al. The data showed that type II sites present low binding capacity, in addition to low affinity, in contrast to the previously reported high capacity for this binding molecule. These results suggest that type II sites may not be crucial in the action of estradiol at the uterine level.
RESUMEN
The effect of corticosteroids on electrolyte movement was studied in an everted sac model from distal rat colon. Corticosterone had a significant stimulatory effect on sodium and fluid transfer in a dose-related manner. At the low dose of 10(-9) M corticosterone increased sodium absorption by 29.4 microEq X g-1 X h-1, a value that was statistically greater than the effect of 10(-9) M dexamethasone. At the higher concentration of 10(-7) M the effect of corticosterone on sodium movement was twice that of aldosterone or dexamethasone in equimolar concentrations. By contrast, the effect of corticosterone on potassium movement was biphasic: at lower concentration (10(-9) M) a significant net secretion occurred, whereas potassium absorption was observed at 10(-7) M corticosterone. Dexamethasone significantly increased net potassium secretion, meanwhile the effect of aldosterone on potassium movement was not significantly different from controls. These data suggest that the native glucocorticoid, corticosterone, exerts regulatory control of colonic fluid and electrolyte function.
RESUMEN
Short and prolonged administration of ACTH was used to study the effects of the hormone on protein synthesis in two subcellular fractions obtained from rat adrenals incubated in the presence of a (14C)-labelled amino acid mixture. Acute treatment with ACTH produced an increased labelling of the proteins of the post-mitochondrial (POST-MIT) fraction only. On the other hand, treatment with ACTH for 4-28 days, significantly increased the specific activity of proteins in the mitochondrial (MIT) fraction, without change in the radiolabelling of the POST-MIT fraction. The incorporation of (14C)-labelled amino acids into the proteins of the MIT and POST-MIT fractions, from control or ACTH-treated adrenals, was reduced by inhibitors of cytoplasmic protein synthesis (puromycin and cycloheximide). This suggests that the increased labelling of the MIT fraction after prolonged ACTH might be related to a translocation of cytoplasmic proteins to the mitochondrion.
RESUMEN
Free nuclear receptors were measured in anterior pituitaries from ovariectomized-adrenalectomized rats after extraction of purified nuclei with 0.4 M KC1 and incubation of the extract with 2.5 nM (3H)-estradiol (E2) during 1.5 h at 0-4 degrees C. High affinity, low capacity binding was present in untreated rats; receptor concentration doubled after E2 was given for 4 days, whereas acute (60 min) treatment was without effect. Prolonged exposure to diethylstilbestrol (3 months) down-regulated free as well as total nuclear receptors. Tamoxifen increased free nuclear receptors, induced the progestin receptor in cytosol, and inhibited E2-stimulated serum prolactin but not E2 stimulation of free nuclear receptors. Progesterone and testosterone had no effect on basal or E2-stimulated free nuclear sites, whereas dexamethasone reduced the former but not the latter. Furthermore, from 33 to 36
of free nuclear receptors bound to (3H)-E2, were retained in DNA-cellulose columns whether incubation with ligand was performed at low (0-4 degrees C) or high temperature (25 degrees C); DNA-cellulose binding was unchanged after short E2 but increased after 4 days of E2. These data suggest ligand as well as antiestrogen and corticoid regulation of free nuclear receptors for E2 in anterior pituitary. Free nuclear sites may be a fraction of total cell receptors which are in the transformed state and which bind more tightly to nuclei in vivo, as indicated by the results of DNA-cellulose binding in vitro.
RESUMEN
The specific uptake of tritiated 18-hydroxycorticosterone (18-OH-B) by purified cell nuclear fractions and cytosol of medulla oblongata, pons, amygdala, anterior pituitary, hypothalamus, hippocampus, preoptic-area and lung from adrenalectomized animals was investigated after incubation of tissue sections with radioactive ligand. We found that 18-OH-B was taken up mainly by nuclei obtained from pons and medulla oblongata; this profile differs from previous observations with the closely related steroids corticosterone and aldosterone, which are mostly concentrated by the limbic system. Based on this finding, as well as on former studies with 18-OH-B, we suggest that this steroid may exert its action on renal excretion of protons as well as on central nervous system structures involved in respiratory regulation, related to that excretion.
RESUMEN
The specific uptake of tritiated 18-hydroxycorticosterone (18-OH-B) by purified cell nuclear fractions and cytosol of medulla oblongata, pons, amygdala, anterior pituitary, hypothalamus, hippocampus, preoptic-area and lung from adrenalectomized animals was investigated after incubation of tissue sections with radioactive ligand. We found that 18-OH-B was taken up mainly by nuclei obtained from pons and medulla oblongata; this profile differs from previous observations with the closely related steroids corticosterone and aldosterone, which are mostly concentrated by the limbic system. Based on this finding, as well as on former studies with 18-OH-B, we suggest that this steroid may exert its action on renal excretion of protons as well as on central nervous system structures involved in respiratory regulation, related to that excretion.