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Biomedical subjects

A Reviczky

Publications and source records attributed to A Reviczky.

8 recordsLinked to original sources
PubMed1992

Ontogeny of epidermal growth factor, transforming growth factor-alpha, epidermal growth factor receptor, and thyroid hormone receptor RNA levels in rat kidney and changes in those levels induced by early thyroxine treatment.

Ontogenic changes in the mRNA levels of epidermal growth factor (EGF), transforming growth factor-alpha, EGF receptor, and thyroid hormone receptor (r-erbA) were examined in developing rat kidneys. The mRNA levels of both EGF and thyroid hormone receptor rose dramatically during the postnatal period with the rise in thyroid hormone receptor message preceding the rise in EGF message. In addition, we examined renal mRNA levels in 1-wk-old rats treated with thyroxine (T4) from birth through d 6. Neonatal T4 treatment augmented the renal mRNA levels of EGF but decreased the levels of EGF-receptor and transforming growth factor-alpha. T4 treatment did not significantly affect the levels of renal mRNA for thyroid hormone receptor. Although the EGF and transforming growth factor-alpha peptides are similar and interact with the same receptor, our findings indicate that these homologous growth factors are regulated differently during development. In addition, hormones that influence growth and development, such as T4, may function both as positive and negative regulators of growth factor expression.

Age Factors↗
PubMed1992

Thyroxine sulfate is a major thyroid hormone metabolite and a potential intermediate in the monodeiodination pathways in fetal sheep.

T3 and rT3 production rates in the fetus account for roughly only a third of the total T4 production rate; thus, the fate of the majority of T4 produced in the fetus is unknown (the "T4 disposal gap"). We developed sensitive and specific T4 sulfate (T4S) and T3 sulfate (T3S) RIAs to investigate the roles of these compounds in fetal T4 metabolism. T3, T4, T3S, and T4S were determined in a variety of tissue fluid and/or serum samples obtained from fetal, newborn (n = 6), and adult (n = 6) sheep. Four groups of fetal animals, with gestational ages of 94 days (n = 5), 110-111 days (n = 6), 130-131 days (n = 6), and 145 days (n = 6; term = 150 days), were studied. In addition, type I 5'-monodeiodinase (5'-MDI) activity was quantified in liver and kidney tissues. 5'-MDI activities were lower in 94- to 131-day-old fetuses than in fetuses near term or in newborn animals. Mean serum T3 concentrations increased progressively from 94 days (19 ng/dl) to term (371 ng/dl), while mean T3S and T4S serum concentrations were highest at 130 days gestation (237 and 989 ng/dl), decreasing to term. Serum T3S and T4S concentrations decreased further in newborns and adult sheep. T4S and T3S levels in allantoic fluid were significantly higher than those in urine and amniotic fluid in all fetal age groups studied. T4S levels in bile were high from 94-130 days gestation (873-1006 ng/dl), decreasing by 50% at term (529 ng/dl). T4S concentrations in meconium were 46- to 83-fold higher than those in bile from 94 days gestation to term. In contrast, bile T3S levels increased progressively from 94-145 days gestation (191-605 ng/dl), while meconium T3S levels decreased during the same period (33-14 micrograms/100 g). These data demonstrate that 1) sulfated iodothyronines, particularly T4S, are major thyroid hormone metabolites in the fetus; 2) both T4S and T3S are excreted into bile and urine and concentrated in meconium and allantoic fluid; and 3) the high levels of T4S and T3S in serum and other fluids may reflect lower tissue type I 5'-MDI activities. We speculate that T4S and T3S may be further metabolized to other sulfated metabolites and may account in part for the T4 disposal gap in fetal sheep.

Allantois↗
PubMed1991

Thyrotropin-releasing hormone in ovine fetus: ontogeny and effect of thyroid hormone.

The ontogenesis of hypothalamic and extrahypothalamic thyrotropin-releasing hormone (TRH) and the effect of altered thyroid status on tissue TRH levels were studied in fetal sheep. At 62 days gestation (term = 145 days) TRH was detectable in serum and in hypothalamic, placental, and pancreatic tissues; pancreatic, placental, and serum levels exceeded hypothalamic levels two- to fivefold. Analysis of tissues obtained from 88-day gestation fetuses were comparable: TRH levels in placenta (54 +/- 15 pg/mg tissue protein), pancreas (34 +/- 5 pg/mg protein), and serum (93 +/- 9 pg/ml) exceeded those in hypothalamic extracts (15 +/- 9 pg/mg protein). By 120 days gestation, TRH values in the hypothalamus (610 +/- 52 pg/mg protein) exceeded those in extrahypothalamic sites; values were comparable at 140 days gestation. Fetal thyroidectomy resulted in a 2-fold elevation of hypothalamic TRH concentrations (1,030 +/- 139 vs. 522 +/- 29 pg/mg protein) and 2 to 20-fold elevations of TRH in the placenta (147 +/- 23 vs. 42 +/- 8 pg/mg protein), pancreas (195 +/- 11 vs. 29 +/- 7 pg/mg protein), duodenum (363 +/- 97 vs. 29 +/- 7 pg/mg protein), and serum (2,563 +/- 212 vs. 131 +/- 16 pg/ml). 3, 5, 3'-Triiodothyronine (T3) infusion in thyroidectomized fetuses resulted in elevated serum T3 values (480 +/- 80 ng/dl) and suppressed hypothalamic TRH (249 +/- 68 vs. 522 +/- 29 pg/mg protein) and serum TRH concentrations (30 +/- 4 vs. 131 +/- 156 pg/ml). Placental, pancreatic, and duodenal TRH concentrations in thyroidectomized T3-infused animals were below the level of detection of the assay (5 pg/mg tissue protein).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Nuclear thyroid hormone receptors: ontogeny and thyroid hormone effects in sheep.

To investigate the mechanism(s) responsible for the paucity of fetal thyroid hormone effects, thyroid hormone nuclear receptor (T3NR) binding characteristics were quantified in liver and brain of fetal and neonatal sheep. Maximal binding capacities [MBC; mean +/- SE fmol 3,5,3'-triiodothyronine (T3)/mg DNA] in liver increased from values of 68 +/- 14 at 80 days gestation to 684 +/- 152 at term. Liver T3NR MBC in newborn and adult sheep were comparable to values in term fetuses. Liver T3NR binding affinities were similar in all animals, averaging 1.68 +/- 0.05 X 10(9) M-1. Brain T3NR MBC were comparable at all fetal ages studied (410 +/- 55 fmol T3/mg DNA), increasing to 1,517 +/- 315 fmol T3/mg DNA during the 1st postnatal week and returning to comparable fetal values (368 +/- 37 fmol T3/mg DNA) in the 3rd week after birth. Brain T3NR binding affinities were comparable in all animals studied (7.5 +/- 2.1 X 10(9) M-1), and the mean value was significantly greater than mean liver T3NR affinity. T3NR binding of T3 analogues in six term fetal animals were qualitatively similar for both brain and liver and showed T3 = triiodothyroacetic acid greater than thyroxine greater than reverse T3. Like T3 binding affinity, T3NR analogue binding affinities in brain tissue were five- to sevenfold greater than those in liver. Fetal hypothyroidism induced by thyroidectomy at either 99-107 or 129-132 days of gestation was not associated with changes in brain or liver T3NR binding characteristics. The heterogenous ontogeny and binding characteristics of brain and liver T3NR is compatible with the hypothesis that different thyroid hormone receptors are expressed in these tissues.

Animals↗
PubMed1979

Hemoglobin Lepore Washington and hemochromatosis in a Hungarian patient.

A Hungarian family with four heterozygotes for Hb Lepore Washington is described. One, a 43-year-old male, had high levels of serum iron, saturated iron-binding capacity, and ferritin, and normal levels of folic acid and vitamin B12. Liver biopsy showed slight cirrhosis and marked iron deposition in parenchymal cells and in cells of the reticuloendothelial system. Heavy iron deposition was also found in the bone marrow. The patient is not an alcoholic and has no disease that requires blood transfusion. The hemochromatosis thus seems to be of idiopathic nature.

Adolescent↗
PubMed1977

A critical analysis of some thyroid function tests.

The results of a comparative study of thyroid function tests are reported, the assay for PBI having been used for reference. The merits and sources of error of the Bio-Rad column test, Thyopac-4 test and T3-RIA test are discussed with reference to PBI. The correlation coefficients and the sources of error being taken into consideration, PBI represents a fairly reliable indicator of T4 values and recommends itself on these grounds as a basic routine procedure, the more so as it is simple, cheap and suited for automated analysis. In case of iodine contamination or of the necessity for a selective identification of the T4 factor, the T4 column test is equally reliable. The T3-RIA test will be valuable in special diagnostic problems.

Humans↗