Biomedical subjects

A Witte

Publications and source records attributed to A Witte.

61 records · Page 4Linked to original sources

PubMed1981

Absence of thyroid-stimulating antibody and long acting thyroid stimulator in relatives of Graves' disease patients.

None of the 76 euthyroid relatives of patients with Graves' disease had detectable LATS in their serum nor was thyroid-stimulating antibody (TSAb), assessed by an increment of cAMP in human thyroid slices, detected in any of the 60 sera tested. Seven of 41 were slightly positive for TSH binding-inhibiting immunoglobulin (TBII). Nineteen of 73 sera were positive (greater than 1:1600) for antibody to thyroid antimicrosomal antigen, of which 4 were also positive (greater than 1:400) for antibody to thyroglobulin; 3 of the 19 had a slightly elevated basal TSH which rose excessively after TRH. Thus, although these euthyroid relatives had evidence of thyroid immunological defects, a thyroid-stimulating antibody was not found.

Antibodies↗

PubMed1980

Thyrotropin binding to rat thyroid membranes: reduced capacity associated with goitrogenesis.

To investigate a possible role of TSH in the regulation of its own receptor, a sensitive assay of [125I]TSH tropin binding to rat thyroid membranes was used. With 1 mM MgCl2 in the buffer, Scatchard analysis of displacement of TSH gave a curvilinear plot with a high affinity, low capacity (K1, 3.4 nM; Q1, 3.1 pmol/microgram) and a low affinity, high capacity binding site (K2, 0.54 microM; Q2, 1.2 X 0.1 nmol/microgram). Feeding rats propylthiouracil led to a decrease in [125I]TSH binding (expressed either per U protein or per wet wt of tissue) that was related to the duration of treatment. Evaluation by Scatchard analysis showed that this was due to a loss of binding sites, e.g. a 50-60% decrease after 1 month of propylthiouracil treatment; affinity was actually slightly increased in the goitrous tissue. This change in the number of TSH-binding sites was readily reversed in association with the suppression of TSH in vivo either by injections of T3 for 3 days or more by feeding a normal diet for 1 month. Thus, the data are compatible with TSH, that is in high concentration in the serum of rats fed propylthiouracil, exerting a downregulatory influence on its own receptors.

Adenylyl Cyclases↗

PubMed1980

Influence of cholera toxin on in vitro refractoriness to thyrotropin of thyroids from rats fed propylthiouracil.

Using an increase in the concentration of cAMP as an index of stimulation, we previously reported that in vitro thyroid tissue of rats fed a goitrogenic diet (0.1% propylthiouracil in Purina) were unresponsive to TSH. We now show that the addition of cholera toxin (0.1-1.0 microM) to fragments of normal thyroid enhanced the concentration of cAMP. Subsequent exposure of the tissue to TSH resulted in a further increase in the concentration of cAMP, and there was statistical evidence of interaction or potentiation between the effects of TSH (20 mU/ml) and cholera toxin (1.0 microM). With fragments of thyroid from animals fed propylthiouracil (i.e. unresponsive in vitro to TSH), an increase in the concentration of cAMP was effected by 1 or 9 microM cholera toxin, and prior exposure to 9 microM toxin caused the tissue to be responsive to TSH. Unresponsiveness of the goitrous tissue was associated with a reduced capacity of the membrane to bind [125I]iodo-TSH although the affinity of the binding sites was unaffected. Cholera toxin at 0.1 microM enhanced and at 1 microM diminished the binding of [125I]iodo-TSH to membranes from either normal or goitrous glands, and these effects also reflected influences on the capacity rather than on the affinity of the binding sites. It is postulated that the unresponsiveness to TSH of thyroid tissue from rats fed propylthiouracil represents a down-regulation of receptor capacity, and this is effected by the binding sites becoming relatively inaccessible, rather than nonexistent.

Adenylyl Cyclases↗

PubMed1980

Synthesis of methotrexate polyglutamates by bone marrow cells from patients with leukemia and lymphoma.

Bone marrow cells from children with lymphoblastic leukemia, myeloblastic leukemia and non-Hodgkin's lymphoma were incubated with tritium-labelled methotrexate in short-term cultures. Cells obtained both during disease activity as well as during remission synthesized large quantities of methotrexate polyglutamates. Synthesis was time- and dose-dependent and occurred with concentrations of methotrexate regularly achieved during conventional treatment with this drug.

Bone Marrow↗

PubMedDate not supplied

Iodine contamination as a cause of hyperthyroidism or lack of TSH response to TRH stimulation (results based on a screening investigation).

The sera of all patients with completely suppressed TSH response to TRH obtained during one year (n = 668), and of those with diminished TSH response (n = 153) were screened for total serum iodine content. The ratio between serum iodine and thyroxine iodine below 1.5 indicates none or only a minor degree of iodine contamination, whereas a ratio above 1.5 is a clear index of exogenous iodine contamination. Eighty-four (21.3%) of 395 patients with overt hyperthyroidism were iodine contaminated. No prevalence of hyperthyroidism with hyperthyroxinemia could be detected as compared to T3-hyperthyroidism in the contaminated groups. Surprisingly, the iodine contamination rate was twice as high in 273 patients with suppressed TSH response to TRH but normal thyroid hormone levels and not fully explained thyroidal diseases. A high incidence of multifocal autonomous adenomas of the thyroid is the most probable explanation for the TSH suppression in iodine contaminated patients with normal thyroid hormone levels.

Angiocardiography↗

PubMedDate not supplied

The transposable element IS4712 prevents S-layer gene (sbsA) expression in Bacillus stearothermophilus and also affects the synthesis of altered surface layer proteins.

Cell surface (S)-layer protein synthesis in Bacillus stearothermophilus PV72/p6 is blocked when cells are grown at elevated temperature. From a culture exhibiting the S-layer-negative phenotype, the S-layer deficient mutant T5 (SbsA-) was isolated. Genetic analysis of the S-layer-encoding gene (sbsA) of mutant T5 revealed an insertion element (IS4712) integrated into the upstream regulatory region of the S-layer gene, thereby blocking sbsA transcription. The insertion element consists of 1371 base pairs which are flanked by two perfect inverted terminal repeats. Sequence similarity to other transposases of the IS4 family was detected. DNA-DNA hybridizations demonstrated that multiple homologues of IS4712 were also present within the genomes of several other thermophilic bacillus isolates. Attempts to isolate SbsA+ revertants failed. Instead, cells with altered surface proteins were detected. The synthesis of the altered S-layer proteins was correlated with the presence of IS4712 along with the occurrence of deletions in the sbsA coding region. Furthermore imprecise excision of IS4712 was detected. This work demonstrated that B. stearothermophilus is able to express at least four different S-layer proteins and that blocking of sbsA transcription by the insertion element IS4712 is associated with the expression of altered surface proteins.

5' Untranslated Regions↗

PubMedDate not supplied

Phi X174 protein E-mediated lysis of Escherichia coli.

Bacteriophage PhiX174 encodes a single lysis gene, E, the function of which is necessary and sufficient to induce lysis of Escherichia coli. Here we present a novel model for E-lysis: physiological, genetic and biochemical data are presented which suggest that a transmembrane tunnel penetrating the inner and outer membrane is formed during the lytic action of protein E. Moreover, using high magnification scanning and transmission electron microscopy in this study, it was possible to visualize the transmembrane lysis structure directly.

Bacteriolysis↗