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Biomedical subjects

J Letarte

Publications and source records attributed to J Letarte.

At least 55 records · Page 3Linked to original sources
PubMed1982

Specific detection of circulating DNA:anti-DNA immune complexes in human systemic lupus erythematosus sera using murine monoclonal anti-DNA antibody.

The presence of DNA-anti-DNA immune complexes in sera from patients with systemic lupus erythematosus (SLE) was investigated by a new solid phase radioimmunoassay (RIA). This assay used murine monoclonal anti-double stranded DNA (dsDNA) antibody to recognize DNA present in the complexes and 125I-rabbit anti-human gamma globulin as a tracer. DNA-anti-DNA immune complexes were found in certain SLE sera but not in sera from patients with other immune complex diseases and from healthy blood donors. The presence of circulating DNA-anti-DNA complexes was associated with low C4 levels. It was not related to the presence of immune complexes detected by the polyethylene glycol assay suggesting either that the assay did not detect all DNA-anti-DNA complexes or that other antigen-antibody systems constitute the major immune complex components in SLE sera. The clinical significance of circulating DNA-anti-DNA complexes in SLE sera as well as the potential use of this solid phase RIA using various monoclonal antibodies to detect specific antigen-antibody systems is discussed.

Antibodies, Antinuclear↗
PubMed1981

Ammonia metabolism in a family affected by hyperargininemia.

A French-Canadian family, with a 14-year old mentally retarded girl, was investigated for hyperargininemia. The girl showed a fasting plasma ammonia N concentration of 100 micrograms/dl (normal : 50.5 +/- 13 micrograms/dl), and a two-hour post protein load level of 183 micrograms/dl (normal : 51.6 +/- 17.6 micrograms/dl). Plasma urea N was lower than normal in the post-load sample. Arginine concentrations were 11 times normal in the plasma, 47 times normal in the urine and 4 times normal in erythrocytes. Measurement of erythrocyte arginase showed only 1% activity in the propositus, and 52-54% in the parents and a sibling as compared to controls. In heterozygous members of the family, the Km (arginine) was similar to controls. Column chromatography of serum amino acids in the propositus showed arginine to be 17.6 S.D. higher than the normal mean. A characteristic cystine-lysinuria pattern of urinary amino acids was also seen. Measurement of other urinary nitrogenous metabolites showed low urinary urea and excessive orotic aciduria. On "normal" food intake, the patient excreted 122 mg of orotic acid/24 h, as against 3.7 mg by the sibling and 3.9 mg by the mother. It is postulated that the level of ornithine in hepatocyte mitochondria is critical to the disposal of carbamyl phosphate. The lack of normal regeneration of ornithine by liver arginase, and an excessive urinary excretion may be responsible for its low mitochondrial concentration. This would cause diversion of unmetabolised carbamyl phosphate towards orotic acid synthesis or ammonia production.

Adolescent↗
PubMed1980

Lack of influence of thyroid antibodies on thyroid function in the newborn infant and on a mass screening program for congenital hypothyroidism.

Data regarding the incidence and effect of maternal thyroid antibodies on neonatal thyroid function are conflicting. In order to elucidate this aspect, antimicrosomal thyroid antibodies were measured: (1) in cord serum of a normal populations, (2) in the eluate of blood spots of infants with normal filter paper spot T4 and TSH, (3) in the eluate of blood spots from our recalled population (low T4 and normal TSH), and (4) in serum of detected hypothyroid infants. The incidence of MCA with titer greater than 1/40 in cord sera was 8% (115 of 1.383). There was no statistical difference in cord serum T4' T3' or TSH concentrations in these newborn infants compared to the MCA negative population. In 1,000 spots with normal T4 and TSH, 11 or 1.1% were positive for MCA. In 1,630 spots with low T4' 18 positive cases were discovered, or 1.1%. There was excellent correlation between maternal MCA titers and newborn infant titers either in sera or spots when paired samples were available. Finally, only one of 104 detected infants with primary hypothyroidism had detectable MCA. These results indicate a high incidence (8%) of MCA in our presumed normal newborn population, MCA does not decrease serum T4' T3' and TSH concentration or filter paper spot T4 and TSH, and thyroid autoimmunity is not a frequent cause of congenital hypothyroidism.

Autoantibodies↗
PubMed1980

Thyroxine-binding globulin capacity and concentration evaluated from blood spots on filter-paper in a screening program for neonatal hypothyroidism.

We describe a simple method for evaluating thyroxine-binding globulin capacity and concentration from a single 1-cm blood spot on filter-paper used in a screening program for neonatal hypothyroidism. This method permits prompt diagnosis of about 90% of the infants with thyroxine-binding globulin deficiency in our abnormal low-thyroxine, low-thyrotropin population. There was excellent equivalence between results obtained by our method and by the method of Chopra et al. (J. Clin. Endocrinol. Metab. 35:565, 1972), and minimal overlap between the population with low thyroxine-binding globulin and the low-thyroxine, normal thyrotropin population. We recommend this method to all programs in which a primary thyroxine measurement is used in screening for congenital hypothyroidism.

Blood Specimen Collection↗
PubMed1980

Lack of protective effect of breast-feeding in congenital hypothyroidism: report of 12 cases.

Hypothyroid babies being breast-fed (12 cases) or bottle-fed (33 cases) have been compared. Anthropometric measurements at referral as well as biochemical values including plasma T4, T3, and thyroid-stimulating hormone were not significantly different. Bone maturation expressed as number of ossification centers or their surface were identical. Babies from both groups had similar psychologic performance at their first anniversay. It is concluded that breast-feeding does not protect against the deleterious effects of congenital hypothyroidism,.

Bone Development↗
PubMed1978

Modification of a screening program for neonatal hypothyroidism.

From our experience in the screening of 212,000 newborn infants, we have devised a flow chart for processing T4 and TSH measurements obtained from initial filter paper blood spots. To date, all infants with thyroid dysfunction or TBG deficiency have been detected. Of the population screened, 1.84% require a spot TSH determination, and 1.1% require repeat determinations of T4.

Filtration↗
PubMed1978

Effects of clofibrate on plasma tryptophan, growth hormone, and prolactin and on brain tryptophan and serotonin in prepubertal rats.

The effects of clofibrate administration (200 mg/kg, po) on somatic growth, plasma levels of lipids, tryptophan, growth hormone (GH), and prolactin (PRL), as well as on brain concentrations of tryptophan and 5-hydroxytryptamine (5-HT) were studied in prepubertal male rats. The drug did not significantly alter ponderal growth, but an appreciable reduction of tail length was observed in rats treated for 30 days. Triglyceride concentrations in plasma showed a 43% diminution after 30 days of treatment, whereas free fatty acid (FFA) levels were not modified. Clofibrate administration for 7, 15, or 30 days caused a fall in total tryptophan and a significant increase of the free fraction in plasma with no change in brain tryptophan levels. Brain 5-HT was generally unaffected but a marked elevation of this parameter was noted in rats treated for 15 days. Plasma GH and PRL concentrations remained unaltered. It may be concluded from these findings that the slight reduction of somatic growth, the diminution of triglycerides, and the increase of free tryptophan in plasma, induced by chronic clofibrate treatment, are not associated with variations in brain tryptophan and 5-HT levels or with modifications of plasma GH and PRL titers.

Animals↗
PubMed1978

Reevaluation of levodopa-propranolol as a test of growth hormone reserve in children.

The growth hormone (GH) reserve of 15 short children was evaluated with the levodopa-propranolol test (DPT) and the sequential arginine-insulin test (AIT). Four patients failed to respond to both tests and were classified as hyposomatotropic. In the other 11 children, the mean GH peak response to the DPT was significantly higher than that to the AIT, mainly because five subjects who had a normal response to the DPT failed to respond to the AIT. These children had a generally poor yearly growth increment prior to testing associated in three with an obvious emotional problem, and were found at follow-up to have resumed a normal growth pattern. These data confirm the effectiveness of the DPT as a test of GH reserve. Although hypoglycemia can occur occasionally during test, this procedure is safer and easier to perform than the widely used AIT. Finally, the DPT seems to detect a category of children who have a temporary growth failure and nonresponse to the usual GH tests but who are not hyposomatotropic and consequently do not require human GH.

Adolescent↗
PubMed1978

Study of enzyme defect in a case of ornithine transcarbamylase deficiency.

Activity of liver ornithine transcarbamylase was measured in a biopsy obtained from a seven years old girl, suffering from chronic hyperammonemia and orotic aciduria. The activity of the defective enzyme was only 17% of that of a control. pH optimum was 8.1 in the patient and the control. However, the pH curves were different between 7.0 and 8.1. Km (ornithine) of the patient's ornithine transcarbamylase was within the normal range (0.41 nM), but the Km (carbamyl phosphate) was low (0.18 mM). The girl seems to be a heterozygote carrier of ornithine transcarbamylase deficiency due to an abnormal liver enzyme.

Ammonia↗
PubMed1977

Increase in plasma growth hormone levels following thyrotropin-releasing hormone injection in children with primary hypothyroidism.

Thyrotropin-releasing hormone (TRH) induced a significant increase in plasma growth hormone (GH) levels in 4 of 8 children with primary hypothyroidism, while a slight decrease was observed in 8 control children. Base-line plasma prolactin (PRL) levels and peak responses to TRH were higher in hypothyroid children than in controls. These data may indicate the existence of dysfunction of central nervous system mechanisms of control of GH and PRL secretion in subjects with primary hypothyroidism.

Adolescent↗
PubMed1976

Thyroid function in neonatal hypothyroidism.

Various aspects of the thyroid function have been measured in 28 cases of neonatal hypothyroidism detected by means of the Quebec Screening Program for Metabolic Diseases. In all instances the T4 value in the blood of filter paper spot was below 2 SD of the mean of the day, averaging 0.39 +/- 0.04 ng/40 mul (mean +/- SEM) of eluted blood. The T4 value of a second similar sample averaged 0.22 +/- 0.04 ng/mul of eluted blood; this value was significantly lower than the first one. The serum T4 concentration was decreased in all the infants, whereas three of them had a normal serum TSH concentration. At least three groups of patients could be identified: (1) patients with primary thyroid failure, (2) those with secondary or tertiary hypothyrodism, and (3) those with abnormal synthesis of thyroid hormone.

Female↗