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G Hennemann

Publications and source records attributed to G Hennemann.

At least 109 records · Page 6Linked to original sources
PubMed1981

Inherited thyroxine excess: a serum abnormality due to an increased affinity for modified albumin.

Further analysis of sera from euthyroid subjects with dominantly-inherited, elevated serum total thyroxine (T4) and free T4 index but with normal free T4 levels was performed as an extension of a previous study (Hennemann et al., 1979a). Scatchard analysis and isoelectric focusing of whole sera and purified serum fractions suggest that this T4 excess is due to increased T4 binding by modified serum albumin. Recognition of this syndrome and appreciation that the free T4 index does not reflect the free T4 levels is important to protect patients from the consequences of an incorrect diagnosis of thyrotoxicosis.

Humans↗
PubMed1980

Solubilization and partial characterization of rat liver iodothyronine deiodinases.

Rat liver cells contain iodothyronine deiodinating enzymes (iodothyronine-5 and 5'-deiodinases), which are associated with the endoplasmic reticulum. In the present study, the iodothyronine deiodinases have been solubilized from the microsomal fraction of rat liver with 1.0% cholate and 0.25% of the polyoxyethylene ether W-1. Cholate can be effectively removed from the cholate extract with a mixture of the polystyrene beads XAD-2 and XAD-7. However, after some time, aggregation of proteins occurred. Cholate solubilized iodothyronine-5'-deiodinase has an apparent molecular weight of 65,000 and a Stokes radius of 36-37 A. The sedimentation coefficient is 4.3 S in 0.4-0.6% cholate, 7.6 S in 0.05% W-1 ether and 12.8 S in the absence of detergent. The enzyme solubilized with W-1 ether has an apparent molecular weight of approx. 200,000 and a Stokes radius of 52-56 A in 0.025% W-1 ether. In the latter extract, the sedimentation coefficient of the deiodinase is 4.3-5.2 S under different conditions. On DEAE-Sepharose chromatography, 70% of the bound deiodinases eluted with 0.1 M NaCl. The purification of this fraction was only 2-fold. Covalent chromatography, using activated thiol-Sepharose, resulted in approximately 3-fold purification of the deiodinases solubilized with W-1 ether, whereas in case of the cholate extract, no purification at all was obtained. Glutathione-Sepharose affinity chromatography resulted in no enrichment of the deiodinases.

Animals↗
PubMed1980

The role of dietary fat in peripheral thyroid hormone metabolism.

Short term changes in serum 3,3',5-triiodothyronine (T3) and 3,3'5-triiodothyronine (reverse T3, rT3) were studied in four healthy nonobese male subjects under varying but isocaloric and weight maintaining conditions. The four 1500 kcal diets tested during 72 hr, consisted of: I, 100% fat; II, 50% fat, 50% protein; III, 50% fat, 50% carbohydrate (CHO), and IV, a mixed control diet. The decrease of T3 (50%) and increase of rT3 (123%) in the all-fat diet equalled changes noted in total starvation. In diet III (750 kcal fat, 750 kcal CHO) serum T3 decreased 24% (NS) and serum rT3 rose significantly 34% (p < 0.01). This change occurred in spite of the 750 kcal CHO. This amount of CHO by itself does not introduce changes in thyroid hormone levels and completely restores in refeeding models the alterations of T3 and rT3 after total starvation. The conclusion is drawn that under isocaloric conditions in man fat in high concentration itself may play an active role in inducing changes in peripheral thyroid hormone metabolism.

Adult↗
PubMed1980

Thyrotrophin binding inhibiting immunoglobulins in Graves' disease before, during and after antithyroid therapy, and its relation to long-acting thyroid stimulator.

Thyrotrophin binding inhibiting immunoglublins (TBII) were measured in twenty-five patients with unequivocal hyperthyroid Graves' disease with a radioreceptor assay for TSH before, during and the end of treatment with antihyroid drugs and triiodothyronine. To assess the outcome of this therapy patients were followed for 10--90 months (mean 63 months). Before treatment there was significant correlation between TBII activity and serum thyroxine (r = -0.48, P less 0.05) and between TBII activated and 24 hour 131I thyroid uptake (r = -0.57, P less than 0.01). No relationship was found between TBII activated and 20 min, 4 hour and 48 hour 131I thyroid uptakes before institution of therapy. During treatment a significant correlation between TBII index and 20 min 131I thyroid uptake was found (r = -0.55, P less than 0.001). Both before and during treatment there was a significant correlation between TBII and LATS activity (r = -0.65, P less than 0.001). From the magnitude of this correlation coefficient it can be concluded that related, although not the same immunoglobulins, are measured with the two assay techniques. It is not possible to predict the occurrence of a relapse from the presence or absence of TBII activity at the end of treatment in this group of patients. The relapse rate was four out of eight for patients without TBII activity in their serum at the end of treatment and five out of nine for patients with TBII activity. From the data presented it can be concluded that although there is a significant relation between TBII activity and some indices of thyroid function before and during treatment, the correlation coefficients are too small to conclude that TBII alone is responsible for the hyperfunction of the thyroid. The same conclusion can be drawn from the fact that TBII activity has no prognostic value in relation to a possible relapse.

Adult↗
PubMed1979

Location of rat liver iodothyronine deiodinating enzymes in the endoplasmic reticulum.

The iodothyronine-deiodinating enzymes (iodothyronine-5- and 5'-deiodinase) of rat liver were found to be located in the parenchymal cells. Differential centrifugation of rat liver homogenate revealed that the deiodinases resided mainly in the microsomal fraction. The subcellular distribution pattern of these enzymes correlated best with glucose-6-phosphatase, a marker enzyme of the endoplasmic reticulum. Plasma membranes, prepared by discontinuous sucrose gradient centrifugation, were found to contain very little deiodinating activity. Analysis of fractions obtained during the course of plasma membrane isolation showed that the deiodinases correlated positively with glucose-6-phosphatase (r larger than or equal to 0.98) and negatively with the plasma membrane marker 5'-nucleotidase (r ranging between -0.88 and -0.97). It is concluded that the iodothyronine-deiodinating enzymes of rat liver are associated with the endoplasmic reticulum.

Animals↗
PubMed1979

Kinetics of enzymic reductive deiodination of iodothyronines. Effect of pH.

5'-Deiodination of thyroxine (yielding 3,3',5-tri-iodothyronine; reaction I) and of 3,3',5'-tri-iodothyronine (yielding 3,3'-di-iodothyronine; reaction II) and 5-deiodination of thyroxine (yielding 3,3',5'-tri-iodothyronine; reaction III) and of 3,3',5-tri-iodothyronine (yielding 3,3'-di-iodothyronine; reaction IV) as catalysed by rat liver microsomal fraction were studied at pH 6.5, 7.2 and 8.0 It was found that: (1) the Km of reaction I was relatively independent of pH (approx. 3 microM), whereas V was highest at pH 6.5 (63 pmol of 3,3',5-tri-iodothyronine/min per mg of protein); (2) the Km of reaction II was lowest at pH 6.5 (0.035 microM), but V was highest at pH 8.0 (829 pmol of 3,3'-di-iodothyronine/min per mg of protein); (3) thyroxine inhibited reaction II competitively; Ki values were identical at pH 6.5 and 8.0 (1 microM); (4) for both reactions III and IV Km was lowest and V was highest at pH 8.0. The results are compatible with the view that reactions I and II are mediated by a single enzyme (iodothyronine 5'-deiodinase) and that reactions III and IV are catalysed by a second enzyme (iodothyronine 5-deiodinase).

Animals↗
PubMed1979

Raised total thyroxine and free thyroxine index but normal free thyroxine. A serum abnormality due to inherited increased affinity of iodothyronines for serum binding protein.

2 people from different families had high levels of serum-thyroxine (T4) and a high free T4 (FT4) index but a normal serum triiodothyronine (T3) and serum-reverse-T3 (rT3). The abnormal serum thyroid hormone profile appeared to be inherited in an autosomal dominant manner. Serum-FT4 in affected relatives was normal. The increases in serum-T4 and FT4 index are explained on the basis of an observed increase in affinity of T4 for thyroxine-binding globulin, thyroxine-binding prealbumin, and albumin. The FT4 index did not reflect the true concentration of circulating free T4 in these cases. Thyroid function in the propositi was normal and the results of T4, T3, and rT3 kinetic studies accorded with increased binding of T4 by serum proteins and normal binding of the other iodo-thyronines. This "euthyroid high total T4, normal T3 syndrome" should be kept in mind during diagnostic evaluation of thyroid function.

Female↗
PubMed1979

Non-toxic goitre.

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Adolescent↗