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Biomedical subjects

R Garza

Publications and source records attributed to R Garza.

At least 19 recordsLinked to original sources
PubMed1990

Influence of soluble environmental factors on the development of fetal brain acetylcholinesterase-positive neurons cultured in a chemically defined medium: comparison with the effects of L-triiodothyronine (L-T3).

In cerebral hemisphere neuronal cultures derived from 15-day-old rat embryos, the addition of L-triiodothyronine (L-T3) or nerve growth factor (NGF) enhanced the expression of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities in a dose-dependent manner. When cultures were supplemented with both agents at maximal effective concentrations, the stimulation in ChAT and AChE activities was significantly greater than the sum of the individual effects. Conversely, when the cultures were exposed to astrocyte conditioned medium grown in the presence or absence of L-T3 (CM + L-T3 or CM-L-T3). laminin and fibroblast growth factor (FGF), ChAT and AChE activities were not stimulated above those of control cultures when added alone or in combination with L-T3. Furthermore, L-T3, NGF, CMs, laminin and FGF did not affect AChE+ cell survival, but significantly increased neurite outgrowth and branching with NGF and L-T3 being the most powerful agents followed by CMs, laminin and FGF. Additionally, the simultaneous addition of L-T3 with either laminin or FGF in culture, caused an additive effect of L-T2 in the neurite density of AChE+ cells with both agents. This study shows that (1) thyroid hormones do not act through the regulation of soluble neurotrophic factors produced by astroglial cells, (2) thyroid hormones interact with the effect of NGF on ChAT and AChE activities, (3) the regulation of ChAT and AChE activities and the neurite outgrowth are independently regulated. and (4) the regulation of ChAT and AChE activities is very specific compared with that of neurite outgrowth.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholinesterase↗
PubMed1990

Extended en bloc resection of a primary mediastinal parathyroid carcinoma.

Parathyroid carcinoma is a rare endocrine tumor infrequently seen in the mediastinum. This report describes a patient who underwent en bloc resection of a primary mediastinal parathyroid carcinoma. The tumor originated from the thymus and extended from the aortic arch to the thyroid; local invasion suggested malignancy. En bloc resection of this carcinoma with all surrounding tissue provided local control of the tumor and relief of symptomatic hypercalcemia.

Carcinoma↗
PubMed1990

Immunocytochemical localization of thyroid hormone nuclear receptors in cultured acetylcholinesterase-positive neurons: a correlation between the presence of thyroid hormone nuclear receptors and L-tri-iodothyronine morphological effects.

A monoclonal antibody against the rat liver L-tri-iodothyronine nuclear receptor and acetylcholinesterase cytochemistry were used for the localization of thyroid hormone nuclear receptors in acetylcholinesterase-positive cell nuclei in fetal rat cerebral hemisphere neuronal cultures. After 3 days in vitro, the ratio of acetylcholinesterase-positive cells that were immunoreactive for the thyroid hormone nuclear receptor to those not stained for this receptor (74-26%, respectively) remains unchanged despite an increase in the number of acetylcholinesterase-positive cells with time (from day 3 to day 21) in culture. Furthermore, the addition of 3 X 10(-8) L-tri-iodothyronine in culture did not modify this ratio or have an effect on the number of acetylcholinesterase-positive cells, but significantly increased the neurite density in those acetylcholinesterase-positive cells that were immunoreactive for the thyroid hormone receptor. Conversely, no difference in the neurite densities of those acetylcholinesterase-positive cells not stained for this receptor was observed when cultured in the presence or absence of thyroid hormone. In other experiments with the same fetal brain cultures, treatment of cultures for 8 days with L-tri-iodothyronine, beginning on culture day 20, demonstrated the presence of a critical period which occurs in vitro around day 20, since the stimulatory effect of L-tri-iodothyronine on immunoreactive acetylcholinesterase-positive cell neurite density is lost after 20 days in vitro. These results demonstrate, for the first time, the presence of L-tri-iodothyronine nuclear receptors in fetal rat acetylcholinesterase-positive neurons and the existence of a cellular heterogeneity in the distribution of the thyroid hormone receptor. The presence of these receptors in fetal brain acetylcholinesterase-positive neurons suggests that some effects of L-tri-iodothyronine on the maturation of a subpopulation of acetylcholinesterase-positive neurons may result from a direct effect of this hormone through an interaction with its specific nuclear receptors.

Acetylcholinesterase↗
PubMed1988

Influence of triiodothyronine (L-T3) on the morphological and biochemical development of fetal brain acetylcholinesterase-positive neurons cultured in a chemically defined medium.

In cerebral hemisphere cultures initiated from 15-day-old rat embryos, the number of acetylcholinesterase-positive (AChE+) cells increased from 6.8 +/- 1.6 cells/well on day 3 to 112 +/- 16 cells/well on day 15. With time in culture, AChE+ cells increased both in size of the perikarya and neurite length. The addition of L-triiodothyronine (L-T3) at a concentration of 3 x 10(-8) M at the initiation of the culture had no effect on the number of AChE+ cells but significantly increased the size and neurite length of AChE+ neurons after 5 days in vitro. These morphological effects are associated with biochemical effects. L-T3 increased AChE activity in both a dose- and time-dependent manner (the stimulatory effect of L-T3 becomes significant between day 8 and day 15). Since a major part of AChE+ cells may be cholinergic neurons, we have also measured the effect of L-T3 on ChAT activity. L-T3 also increased ChAT activity in a dose and time dependent manner. Furthermore, treatment of cultures with L-T3 at different times in culture demonstrated the presence of a critical period which occurs in vitro around day 20, since the stimulatory effect of L-T3 on ChAT activity is lost after 20 days in vitro. Studies of the time necessary for L-T3 to increase both ChAT and AChE activities show that 2 days and 15 days, respectively, are required for L-T3 to significantly stimulate both enzyme activities. This in vitro analysis demonstrated the morphological effect of L-T3 on the size and the neurite length of AChE+ cells. These effects are associated with biochemical effects on ChAT and AChE activities. Thus, it appears that thyroid hormones regulate several steps of neuronal maturation.

Acetylcholinesterase↗
PubMed1981

Lactate oxidation and sodium reabsorption by dog kidney in vivo.

Lactate uptake (Qlact) and oxidation (QCO2lact), oxygen consumption (QO2) and net tubular Na+ reabsorption (TNa), were estimated in pentobarbital-anesthetized dogs under control conditions and following unilateral intrarenal injection of ouabain or intravenous infusion of acetazolamide, ethacrynic acid, or furosemide. QCO2lact accounted for approximately half of simultaneous Qlact and for about one-third of QO2 in control periods. Ouabain injection resulted in significant decreases in several functions of the injected kidney: TNa, 46%; TNa/FNa, 36%; QO2, 40%; Qlact, 59%; and QCO2lact, 70%. Acetazolamide infusion decreased TNa, 33%; TNa/FNa, 12%; QO2, 10%; and QCO2lact, 38%; but did not change Qlact. Ethacrynic acid diminished TNa, 60%; TNa/FNa, 36%; QO2, 45%; Qlact, 31%; and QCO2lact, 73%. Furosemide lowered TNa, 37%; TNa/FNa, 28%; QO2, 25%; and Qlact, 48%; but did not change QCO2lact, 2%. Results indicate that decarboxylation is a major pathway of renal lactate metabolism, that lactate oxidation is a substantial source of aerobic energy for the kidney, and that QCO2lact is probably functionally related to sodium reabsorption. This relationship appears to be closer for a fraction of TNa associated with ouabain- and ethacrynic acid-sensitive mechanisms.

Absorption↗
PubMed1977

Liposarcoma of the larynx: a multicentric or a metastatic malignancy.

The third case of liposarcoma of the larynx, this one arising from the preepiglottic space, is presented. The report is unique in so far as the patient previously had been treated for a liposarcoma in another anatomic region. The diagnosis in this case was in doubt until electron microscopic studies were done. Since the histopathology of the laryngeal and the previous liposarcoma were different, the question of metastasis versus multicentricity was raised. Other discussions of liposarcomas over the past three decades have not resolved this aspect of their behavior completely. In this instance, after considering avenues of metastatic spread in conjuction with the histopathology, it would appear that the laryngeal lesion was a second primary and not a metastasis.

Aged↗
PubMed1976

Serum cortisol and 11-desoxycortisol levels in hirsute premenopausal women.

It has been postulated that hirsute patients may have a relative deficiency in 11beta-hydroxylase activity of the adrenal cortex. In order to test this postulate, we have measured the serum levels of cortisol (Cp F) and 11-desoxycortisol (Cp S) and estimated the Cp S/Cp F ratio in 9 nonhirsute and 34 hirsute premenopausal women. As a group, the hirsute patients had significantly elevated (P less than 0.05) mean Cp F and Cp S levels but the mean Cp S/Cp F ratio was not significantly different from normal. Considered individually, only 3 hirsute patients had a Cp S/Cp F ratio greater than 2 SD above the mean normal levels. These ratios were 0.0218, 0.0139, and 0.023. If there is indeed an 11beta-hydroxylase deficiency in these 3 patients, it must be relatively minor, since a patient with documented 11beta-hydroxylase deficiency had Cp S levels of 218 ng/ml and a Cp S/Cp F ratio of 0.7. Our data suggest that 11beta-hydroxylase deficiency is not a common cause of hirsutism.

17-Hydroxycorticosteroids↗
PubMed1975

Combined radioimmunoassay of four steroids in one ml of plasma: I. Progestins.

Using partially specific antisera combined with a 1 step celite microcolumn chromatography, progesterone (P), 20alpha-hydroxypregn-4-ene-3-one (20alpha-P), 17-hydroxyprogesterone (17-P), and 16alpha-hydroxyprogesterone (16alpha-P) could be measured in the same 1 ml aliquot of plasma. The chromatographic step removed known interfering steroids and conferred specificity to the assay. After correction for recovery the sensitivities, expressed as ng/ml of plasma, were respectively: 0.04 for P, 0.03 for 20alpha-P, 0.02 for 17P, and 0.01 for 16alpha-P. Recovery experiments, using steroid-free plasma to which various amounts of each steroid were added and then measured in the assay in 12 replicates, confirmed adequate accuracy and precision. The ability to measure multiple progestogens in small volumes of plasma should permit comprehensive evaluation of the role of these steroids in health and disease.

20-alpha-Dihydroprogesterone↗