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Biomedical subjects

A Burger

Publications and source records attributed to A Burger.

At least 145 records · Page 8Linked to original sources
PubMed1976

Effect of amiodarone on serum triiodothyronine, reverse triiodothyronine, thyroxin, and thyrotropin. A drug influencing peripheral metabolism of thyroid hormones.

2-n-Butyl-3-(4'-diethylaminoethoxy-3',5'-diiodobenzoyl)-benzofurane (amiodarone), a drug used in arrythmias and angina pectoris, contains 75 mg of organic iodine/200 mg active substance. Four studies were performed to test its effect on thyroid hormone metabolism: (a) nine male subjects were treated with 400 mg of amiodarone for 28 days; (b) five male subjects received, for the same period of time, 150 mg of iodine in the form of Lugol's solution; (c) five subjects received 300 mug L-thyroxine (T4) for 16 days; from the 10th to the 16th day, 400 mg of amiodarone was added; and (d) five euthyroid subjects received 300 mug L-T4 for 16 days. The changes in serum thyroid-stimulating hormone (TSH), serum total T4, 3,5,3'-triiodothyronine (T3), free T3, and 3,5',3'-triiodothyronine (reverse T3, rT3) were measured, and the pituitary reserve in TSH was evaluated by a thyrotropin-releasing hormone (TRH) test. The results show that amiodarone induced a decrease in serum T3 (28+/-5.1 ng/100 ml, mean+/-SEM, P less than 0.0S and 82.7+/-9.3 ng rT3/100 ml, P less than 0.01). The control study with an equal amount of inorganic iodine did not induce these opposite changes but slightly lowered serum rT3, T3, and T4. In the third study, serum rT3 increased as under amiodarone treatment, thereby proving that these changes were peripheral. It is suggested that amiodarone changes thyroid hormone metabolism, possibly by reducing deiodination of T4 to T3 and inducing a preferential production of rT3. Amiodarone also increased the response of TSH to TRH. The maximal increment of serum TSH above base line was 32+/-4.5 muU/ml under treatment and 20+/-3 muU/ml before treatment (P less than 0.01). During this test, the serum T3 increase was more pronounced than during the control period (83+/-13 and 47+/-7.4 ng/100 ml, P less than 0.05).

Adult↗
PubMed1976

Radioimmunoassay for 3,3',5'-triiodo-L-thyronine in unextracted serum: method and clinical results.

Serum 3,3',5'-triiodothyronine (rT3) was measured with a radioimmunoassay in unextracted serum. The assay was specific and reproducible. The coefficients of variation for 3 different sera known for high, normal, and low rT3 concentrations between assays were 4, 6, and 9% within assays 4, 9, and 7%, respectively. In euthyroid subjects 20 to 60 years old, rT3 was 450 +/- 200 pg/ml (mean +/- 2 SD.n = 83). Serum rT3 was found to be increased in hyperthyroidism (range: 762-2581 pg-ml; n = 11) but also in acute and chronic illness (up to 2400 pg/ml; n = 24) and in anorexia nervosa (536-1058 pg/ml; n = 7). In the latter two situations there was mostly an inverse change in serum 3,5,3'-triiodothyronine (T3) which was in the low normal range or decreased. These findings suggest a metabolic control of thyroxine deiodination. A low serum rT3 was found in 9 of 12 hypothyroid patients and in the serum of 1 chronically ill patient. Long-term treatment (1-7 years) with lithium carbonate slightly reduced serum rT3, although the changes were inside the normal range. Kidney function was not found to be necessary for its production as anephric patients had normal rT3 values. In addition, hemodialysis increased serum rT3, which is probably due to the heparin therapy.

Adolescent↗
PubMed1976

The failure of physiologic doses of reverse T3 to effect thyroid-pituitary function in man.

Reverse T3 (3,3',5'-triiodothyronine, rT3), a major product of the peripheral monodeiodination of thyroxine (T4), was administered to normal male volunteers in doses sufficient to sustain an elevated serum rT3 concentration similar to that frequently observed in patients with nonthyroidal illness. No changes in basal serum T4, T3, TSH and prolactin concentrations, nor in the T3, TSH and prolactin responses to iv TRH were observed during rT3 administration. These findings suggest that physiologic increases in serum rT3 concentration probably do not inhibit T4 to T3 conversion or the anterior pituitary TSH and prolactin responses to thyrotropin-releasing hormone (TRH).

Adult↗
PubMed1976

Changes of circulating thyroxine, triiodothyronine and reverse triiodothyronine after radiographic contrast agents.

Thyroid function was studied for 42 days in 58 patients, 28 of whome had euthyroid goiter, after urography (diatrizoic acid), cholangiography (ioglycamic acid), and cholecystography (Naiopanoate). After urography and cholangiography short-lived increases of the serum thyroxine occurred in a few patients, but the mean thyroxine and triiodothyronine concentration did not change. By contrast, 7 days after oral cholecystography serum thyroxine had risen consistently by 22% with a concomittant rise of the free thyroxine, while triiodothyronine declined by 15%. The thyroxine metabolite 3,3',5'-triiodo-1-thyronine (reverse T3) rose by 50% and serum thyrotropin concentration doubled. After 42 days thryoxine and triiodothyronine had returned to baseline, and none of the 58 patients developed clinical hyperthyroidism. In patients with severe myxoedema kept on a constant replacement dose with 1-thyroxine NA-iopanoate produced similar changes with the exception of the rise of the serum thyroxine. The primary event after Na-iopanoate seems to be a fall of the serum triiodothyronine, which in turn augments thyrotropin and indirectly thyroxine secretion. the marked and sometimes sustained rose of serum thyroxine after cholecystography may lead to the erroneous diagnosis of hyperthyroidism.

Adult↗
PubMed1975

High-affinity binding of tetraiodothyroacetic acid by a prealbumin in normal rabbit serum.

A protein that binds tetraiodothyroacetic acid (tetrac) with high specificity has been detected in normal rabbit serum. Scatchard plots revealed the protein to have a principal binding site with both high capacity and high affinity for tetrac (KA 4.8 X 10(10) M-1. Binding of tetrac by the protein is partially inhibited by barbital. During polyacrylamide gel electrophoresis at pH 8.0, the tetrac binding protein has a mobility characteristic of a prealbumin. As judged from competitive binding studies, the protein also binds tetraiodothyropropionic acid (tetraprop) firmly, but less so than tetrac. The apparent affinity of the protein for the triiodinated analogues of tetrac and tetraprop is only about 1% that for tetrac, and that for thyroxine (T4) only 0.6% that for tetrac; 3,5,3'-triiodothyronine is not bound at all. The protein can be utilized in a competitive protein binding assay for tetrac in human serum, after removal of cross-reacting T4.

Animals↗
PubMed1975

Diversion of peripheral thyroxine metabolism from activating to inactivating pathways during complete fasting.

In 9 euthyroid obese volunteers, as previously reported, 4 weeks of total caloric deprivation resulted in a striking decrease in serum 3,5;3'-triiodothyronine (T3) concentration. The present studies reveal that this decrease in serum T3 is accompanied by a proportionately similar increase in the serum concentration of 3,3',5' -T3 (reverse T3; rT3). In four additional obese volunteers given suppressive doses of sodium-Lthyroxine (T4) for 1 month prior to fasting, serum T3 concentration declined sharply during a 6-11 day period of fast, while rT3 concentration increased strikingly. Concentrations of both T3 and rT3 returned to control values during a 5 day period of refeeding. The findings indicate that caloric deprivation results in an alteration in peripheral T4 metabolism away from generation of T3 and toward the generation of rT3. Since the former is more active than T4, and the latter is essentially inactive, caloric deprivation appears to shunt peripheral T4 metabolism from activating to inactivating pathways.

Adult↗
PubMed1975

Detection of human anti-thyroxine and anti-triiodothyronine antibodies in different thyroid conditions.

Anti-thyroxine (T4) and anti-triiodothyronine (T3) antibodies have been demonstrated in man. It was assumed that antibodies were at least partially saturated in vivo by the hormones. The initial step of the method therefore consisted in a dissociation of the postulated antigen-antibody complex by a 45% ammonium sulfate precipitation. The second part of the method consisted in incubating the euglobulins with trace amounts of 125I-T3 and 131I-T4. The hormones bound to the gammaglobulins were then separated from the free hormones by a column of DEAE Sephadex A-50 in ammonium acetate 0.05 M pH 7.6. The amounts of 125I and 131I bound to the gammaglobulin fraction were then measured. The results in any unknown sample were compared to those obtained when an equal amount of standard serum was identically treated, and the results were expressed as unknown/standard ratios of bound 125I and bound 131I, respectively. The mean binding ratios for T3 and T4 found in sera obtained from 42 normal subjects were 0.7 +/- 0.4 SD and 0.8 +/- 0.5, respectively. Elevated binding ratios for both T3 and T4 were found in sera obtained from 5 out of 43 cases of primary hypothyroidism and in 2 out of 34 cases of hyperthyroidism. The binding ratios were elevated for only T3 in 10 cases of primary hypothyroidism and in 5 cases of hyperthyroidism. Antibodies against T4 were detected in one case of primary hypothyroidism. High binding ratios for T3 were also observed in one patient with secondary hypothyroidism who had received treatment with dessicated thyroid for several years. In most of the positive sera, anti-thyroglobulin antibodies, as measured by passive hemagglutination, could also be detected. For one serum containing anti-T3 antibody and another containing anti-T4 antibody, the binding affinity and capacity were estimated by Scatchard plot analysis; affinity constants were 5.4 x 10(8) L/mol and 1.3 x 10(9) L-mol, respectively; capacities 1.4 ng/ml and 1.2 ng/ml, respectively. The presence of anti-T3 and anti-T4 antibodies in serum may result in an apparent lowering of the serum T3 and T4 concentrations, respectively.

Animals↗
PubMed1975

Radioimmunoassays of 3,5,3'-triiodo-L-thyronine with and without a prior extraction step.

Two radioimmunoassays for triiodothyronine (T3) are described, one of which includes an extraction step, while the other does not. To raise antibodies, two carrier proteins and different coupling agents were used, namely haemocyanin and diazotized benzidine or human serum albumin and carbodiimide. In the case of T3 coupled to haemocyanin by diazotized benzidine, evidence of covalent binding of the hapten to the protein was obtained. In the case of T3 coupled to human serum albumin, little evidence of covalent linkage was available. Nevertheless immunization was successful in both cases. The radioimmunoassay in unextracted serum was highly reproducible and precise (intra-assay variability 5.2% inter-assay variability 8.1%). Normal values were determined which clearly indicate a fall in the serum T3 concentration with increasing age. In men the fall occurs in the fifth decade. In women the T3 starts to fall only after 70 years of age. In 31 cases of hyperthyroidism the serum T3 concentration ranged from 2.26 to 10.4 ng T3/ml. In 10 cases of hypothyroidism the values ranged from 0 to 0.8 ng T3/ml. The radioimmunoassay using an extraction procedure was less extensively used since it was found to be less reproducible (intra-assay variability 7.5%, inter-assay 12.25%). The normal values were determined with a mixed population aged 20-50. The mean +/- 2 SD was 0.9 /- .36 ng T3/ml (n = 52). In 17 cases of hypothyroidism the values ranged from 0 to 0.6 ng T3/ml and in 22 cases of hyperthyroidism from 2 to 14.4 ng T3/ml.

Adult↗
PubMed1975

Dissolution and polymorphism of metolazone.

The solubility and dissolution rate of five different solid forms of 7-chloro-1,2,3,4-tetrahydro-2-methyl-4-oxo-o-tolyl-6-quinazoline-sulfonamide (metolazone) in n-butanol, water and 0.01 n HCl are investigated and thermodynamic values have been computed. The amorphous metolazone dissolves about 8 times faster than the stable modification I (mp. 267-270 degrees C) in 0.01 n HCl at 37 degrees C.

Butanols↗