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Biomedical subjects

J Letarte

Publications and source records attributed to J Letarte.

At least 73 records · Page 4Linked to original sources
PubMed1976

TSH measurements from blood spots on filter paper: a confirmatory screening test for neonatal hypothyroidism.

A sensitive radioimmunoassay for the measurement of TSH in the eluate of blood spotted on filter paper has been developed. The method is consistently sensitive to 0.1 to 0.25 muU of TSH and enables the detection of values equivalent to 6 to 15 muU/ml of serum. The measurement of TSH in the filter paper spot in all infants with low filter paper spot T4 has permitted rapid confirmation of 10 cases of neonatal hypothyroidism. However, cases of hypothalamic hypothyroidism with low or normal filter paper spot TSH concentrations would have been missed using only this method. Since these patients represent approximately 10% of our neonatal hypothyroid population, we do not recommend this method as a primary screening procedure, but rather as a confirmatory test which will accelerate the diagnosis and therefore the onset of therapy.

Filtration↗
PubMed1976

Catecholamines metabolism in thyroid diseases. I. Epinephrine secretion rate in hyperthyroidism and hypothyroidism.

We have measured the secretion rate of epinephrine in 6 euthyroid, 6 hyperthyroid, and 6 hypothyroid subjects infused at a constant rate for a one hour period with tritiated epinephrine (.01 muc/kg/min) (New England Nuclear Inc.). Plasma and urinary levels of epinephrine were measured by modifying the fluorometric method of Anton and Sayre. Plasma levels of epinephrine were 3.0 +/- 3.0 ng/100 ml (mean +/- SD) in normal subjects, compared to 4.4 +/- 3.5 ng/100 ml (mean +/- SD) in hyperthyroid subjects. In urine, epinephrine values ranged from 1.3 mug/day to 6.1 mug/day in normal subjects. Mean value observed in hyperthyroidism was 4.9 +/- 2.6 mug/day and 3.8 +/- 1.0 mu/day in hypothyroidism. Plasma secretion rates averaged 48 +/- 27 mug/kg/day in normal subjects, compared to 54 +/- 18 mu/kg/day in hyperthyroidism and 43 +/- 20 mug/kg/day in hypothyroidism. Likewise, the mean urinary secretion rate was 55 +/- 27 mug/kg/day in normal subjects compared to 60 +/- 22 mug/kg/day in hyperthyroidism and 50 +/- 28 mug/kg/day in hypothyroidism. There is no statistical difference between the values found in the three groups of subjects (plasma and urine). Therefore, these results would indicate that the signs and symptoms encountered in hyperthyroidism are not secondary to a high secretion rate of epinephrine.

Epinephrine↗
PubMed1975

Preliminary report on a mass screening program for neonatal hypothyroidism.

We have recently developed an immunoassay that can measure thyroxine rapidly and accurately in the eluate of 40 mul of dried blood spotted on filter paper at the fifth day of life. The method is completely automated and by using the samples received by the Central Laboratory of the Quebec Network for Genetic Medicine and their follow-up facilities, we are now screening every newborn in the province of Quebec for neonatal hypothyroidism. To date, from 47,000 measurements, three newborn infants with abnormally low TBG and seven hypothyroid infants have been detected. From these data we conclude that the frequency of congenital hypothyroidism is about one in 7,000 births and that our method is effective in detecting thyroid hormone abnormalities with an acceptable percentage of false positive measurements; no false negative results have occurred to our knowledge.

Blood Specimen Collection↗
PubMed1975

Inhibition of pentobarbital-induced release of growth hormone by thyrotropin releasing hormone.

TRH antagonized the GH releasing effect of pentobarbital anesthesia as well in normal as in thyroidectomized rats, and significantly increased plasma B levels in normal animals. This effect was also observed when TRH was administered into a lateral ventricle of the brain in ug amounts, and was suppressed by the beta-adrenergic receptor blocker propranolol. T3 also antagonized the pentobarbital-induced release of GH; however, plasma B levels were not modified, and the effect on plasma GH levels was not suppressed by propranolol.

Animals↗
PubMed1975

Endocrine effects of chronic administration of psychoactive drugs to prepubertal male rats. II. LSD.

The endocrine effects of chronic D-lysergic acid diethylamide (LSD) administration to prepubertal animals were studied by injecting intraperitoneally three times a week for a month either 100 mug or 500 mug of the psychoactive drug per kilogram or the vehicle to groups of Sprague-Dawley male rats starting at 21 days of age. Animals injected with either dosage of LSD had smaller body weights than controls and tail length was significantly reduced in the high dosage group, plasma levels of growth hormone (GH) were decreased in the high dosage group, and pituitary levels in the low dosage group. Plasma levels and pituitary concentrations of luteinizing hormone and follicle stimulating hormone were not significantly modified by the drug. The low dosage of LSD decreased the brain levels of noradrenaline and increased those of dopamine, while the high dosage decreased those of 5-hydroxyindoleacetic acid. These data suggest that LSD, when administered chronically to developing animals, can inhibit body growth probably by altering the secretion of GH through modifications of its neuroendocrine control.

Animals↗
PubMed1975

Endocrine effects of pimozide, a specific dopaminergic blocker.

Pimozide, a specific blocker of dopaminergic receptors, was administered orally to 10 adult male volumteers for 4 days. Half of the subjects received 4 mg/day and the other half 2 mg/day. Blood samples were obtained the day before, the 4th day of Pimozide, and 4 days after the last dose of the drug for the determination of LH, FSH, GH, PRL, TSH, cortisol and testosterone levels. Twenty-four h urinary collections were obtained for the determination of LH and FSH levels. Plasma LH levels decreased and plasma PRL levels increased in the combined groups during Pimozide. Plasma TSH levels decreased during treatment in the 4 mg group only. Urinary LH and plasma testosterone levels decreased in the post-treatment period in the combined groups. These data support the concept of a dopaminergic control of the secretion of several hormones in the human.

Adult↗
PubMed1975

[Chronic hyperammonemia with orotic aciduria: evidence of pyrimidine pathway stimulation (author's transl)].

We have investigated a 3 year old girl with mental and physical retardation, chronic hyperammonemia and orotic aciduria. Plsma glutamine, alanine and proline concentrations were high. Alanine was present in her urine. She excreted only half the urea of control subjects on a similar protein intake. Raising protein intake induced NH4 intoxication with convulsion. Orotic aciduria was present (max: 693 mg/day) and was related to NH4 levels. Red blood cell orotate phosphoribosyl transferase and orotidine decarboxylase activieé were normal, eliminating congenital orotic aciduria, with induction of activity seen on repeated assay during protein load (form 1.37 to 7.5 nmole/109 RBC/hr). Blood ammonia rose with ornithine load, while ornithine levels were twice that of controls. Citrulline was normally metabolized. Although lacking liver assay, we have provided evidence of partial ornithine carbamyl transferase deficiency. The importance of orotic aciduria for ammonia detoxication in partial OCT deficiency is shown, and its possible effect on liver lipoprotein synthesis discussed. Our investigation also confirmed that OCT activity is not present in normal leukocytes rendering them useless for OCT deficiency diagnosis.

Alanine↗