PubMed Health⌕ Search

Biomedical subjects

R Hoermann

Publications and source records attributed to R Hoermann.

51 records · Page 3Linked to original sources
PubMed1992

Immunoreactive human chorionic gonadotropin and its free beta subunit in serum and ascites of patients with malignant tumors.

Human chorionic gonadotropin (hCG) is a clinically relevant marker of trophoblastic and nontrophoblastic malignancies. In the present studies, in addition to determining serum hCG, we investigated the presence and properties of hCG immunoreactivity in ascites of patients with nontrophoblastic malignant tumors and, for comparison, in ascites caused by cirrhotic liver disease. Total hCG immunoreactivity [hCG (+hCG-beta)] was found to be elevated above the reference value (greater than 5 IU/liter) in the serum of 2 of 20 patients with cirrhosis and 11 of 20 patients with malignant tumors. For comparison, in ascites, hCG (+hCG-beta) concentrations were frequently higher than in the corresponding serum samples and exceeded 10 IU/liter in 0 of 20 cirrhotic samples and in 16 of 20 malignant samples. In order to elucidate the nature of the hCG immunoreactive material, all samples were then assessed by immunoradiometric assays specific for the intact hCG molecule (holo-hCG) and the free hCG-beta subunit, respectively. In the holo-hCG assay, elevated values were detected in 0 of 20 (0 of 20) cirrhotic ascites (serum) samples and 0 of 20 (1 of 20) malignant ascites (serum) samples. In the free hCG-beta assay, on the other hand, no positive results were obtained in the ascites or serum of 20 patients with liver cirrhosis; however, 8 of 20 serum samples and 16 of 20 ascites samples derived from tumor patients were positive. In accord with the immunological data, gel chromatographical studies of malignant ascites revealed the abundance of free hCG-beta subunit rather than that of holo-hCG. In contrast to malignancy-related ascites, in ascites of patients receiving hCG injections for treatment of infertility, holo-hCG was more abundant than free hCG-beta immunoreactivity. Incubation experiments of purified holo-hCG in ascites for 24 h at -20, 20, or 37 degrees C showed no substantial dissociation of the hCG molecule and release of free hCG-beta immunoreactivity, thus arguing against production of free hCG-beta by degradation of holo-hCG and in favor of its tumor-related secretion. In conclusion, hCG-beta immunoreactivity is frequently elevated in malignancy-related ascites and appears to be related to the presence of free beta subunit of hCG rather than that of the intact hCG molecule. Interestingly, hCG-beta determination in ascites proved to be clearly superior to serum measurement in discriminating between tumor and cirrhosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Antagonists of the human TSH receptor: in vitro and in vivo studies of their functional and immunological effects.

We have developed and characterized a prototype of a TSH receptor antagonist derived from the hCG molecule. This may be used to block human TSH receptor both functionally and immunologically, particularly in the study of Graves' disease. Our hCG derived TSH receptor blocker compares favorably with other substances (e.g. deglycosylated forms of TSH, synthetic peptides of the alpha or beta subunit of TSH) that hare been reported to inhibit bTSH binding or bTSH-stimulated cAMP response (Joshi et al., 1981; Morris et al., 1988). It has a much higher affinity for human TSH receptor than the TSH subunit peptides and it is the only substance an efficacy of which has been proven in vivo so far. Recent progress in the synthesis of recombinant glycoprotein hormones should permit to biosynthetically produce this or a similar TSH receptor antagonist. With respect to Graves' disease, the data suggest that TSH receptor, in addition to its role in maintaining thyroid hyperfunction, plays also a role in propagating the thyroid autoimmune disease itself. Stimulation of TSH receptor by bTSH as well as TSAb enhances the expression of HLA class II antigens on the surface of thyrocytes, and a blockade of TSH receptor results in a substantial inhibition of this immunological key event. This could possibly explain why suppression of TSH by administering levothyroxine was found in a recent study by Hashizume and coworkers (1991) to decrease TSAb titers and to reduce relapse rate in patients with Graves' hyperthyroidism.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Asialoagalacto-human chorionic gonadotropin, a carbohydrate-modified variant of human chorionic gonadotropin, antagonizes the stimulatory actions of bovine thyroid-stimulating hormone on thyroid function and HLA-DR expression in human thyroid in vitro and in vivo.

The concept of using thyroid-stimulating hormone (TSH) receptor antagonists in the management of Graves' disease is intriguing. Therefore, we investigated a TSH receptor antagonist derived from human chorionic gonadotropin (hCG) with respect to TSH receptor binding, adenylate cyclase activity, thyroid hormone release, and HLA class II antigen expression in vitro and in an in vivo model. A variant of hCG, asialoagalacto-hCG, like asialo-hCG and unlike hCG itself, inhibited both 125I-bTSH binding and cAMP response to bTSH in human thyroid membranes. However, like intact or deglycosylated hCG and unlike asialo-hCG, asialoagalacto-hCG displayed a limited affinity for hepatic asialoglycoprotein receptors, a likely marker for its in vivo turnover rate. It proved capable of inhibiting bTSH-stimulated thyroid hormone release in human thyroid slices as well as in the nude mouse bearing human thyroid transplants. It also prevented bTSH induced hypertrophy of transplanted thyrocytes. Further, HLA-DR expression induced by bTSH in the presence of gamma-interferon on human thyrocytes was inhibited. In conclusion, we present evidence that asialogalacto-hCG antagonizes bTSH actions on thyroid function and HLA-DR expression in human thyroid in vitro and, more importantly, in an in vivo model. Hence, the hCG variant described here or similar agents should warrant further exploration in the study and treatment of Graves' disease.

Adenylyl Cyclases↗
PubMed1991

Carbohydrate modifications transform human chorionic gonadotropin into a potent stimulator of adenosine 3',5'-monophosphate and growth responses in FRTL-5 thyroid cells.

To delineate the role of carbohydrate moiety in the expression of in vitro thyrotropic activity of hCG, its variants that lacked sialic acid residues or the entire carbohydrate moiety on one or both subunits were prepared. They along with intact hCG were then tested for the abilities to bind to TSH receptor and stimulate cAMP production and growth responses in FRTL-5 cells. The removal of sialic acid from either one or both subunits sharply increased the [125I]bovine TSH binding-inhibiting activity of hCG in the receptor assay. Among the variants tested, desialylated hCG (as-hCG) was the most potent inhibitor, followed by alpha-as-beta, as-alpha-beta, and hCG in that order. With respect to their abilities to stimulate cAMP generation in the cells, the activities of all desialylated hCG variants were markedly higher than that of hCG itself, and as in the receptor assay, as-hCG was the most potent stimulator tested. At the same concentration (100 micrograms/ml), as-alpha-beta, alpha-as-beta, and hCG were approximately only 57%, 46%, and 27% as active as as-hCG in activating cAMP production. The findings in the growth assay were entirely consistent with those noted in the cAMP response assay. Among the deglycosylated hybrids examined, alpha-dg-beta was the most effective in activating cAMP release. An equivalent dose (200 micrograms/ml) was about 1.7, 2.7, and 3.8 times as active as dg-hCG dg-alpha-beta, and hCG, respectively. The deglycosylated variants of hCG showed a similar pattern of activity in growth response and cAMP accumulation assays. In both cases, alpha-dg-beta was the most potent stimulator, while hCG was the least active. No significant difference between the potencies of dg-alpha-beta and alpha-dg-beta was discerned in the receptor assay; however, deglycosylated hCG (dg-hCG) was sharply more active. Results of these studies strongly suggest that the optimal expression of in vitro thyrotropic activity of hCG variants in FRTL-5 cells may require an alpha-subunit, with intact carbohydrate, in combination with the deglycosylated beta-subunit. Further, they demonstrate that modification of the hCG carbohydrate moiety alone can transform it from a weak agonist to a potent stimulator of in vitro thyrotropic bioactivity. These results also provide further evidence to support the notion that the degree of expression of thyrotropic activity is strongly affected by the species in which the studies are performed.

Animals↗
PubMed1991

Course of thyroid iodine concentration during treatment of endemic goitre with iodine and a combination of iodine and levothyroxine.

In the treatment of endemic goitre, the concept of giving levothyroxine in combination with iodine offers a promising therapeutic approach by influencing not only TSH secretion but also intrathyroidal iodine content. However, little is known about the doses of iodine necessary to correct intrathyroidal iodine deficiency. To get more information on this important issue, we conducted a prospective, double-blind study on the effect of a monotherapy with 500 micrograms iodide/day and a combined treatment with 100 micrograms levothyroxine and 100 micrograms iodide/day on thyroid iodine concentration as measured by fluorescence scintigraphy. In a group of 12 patients, a 4-month treatment with 100 micrograms levothyroxine and 100 micrograms iodide/day did not significantly affect thyroid iodine concentration (0.35 +/- 0.14 vs 0.37 +/- 0.11 mg/g). The application of 500 micrograms iodide/day in these patients during a second 4-month period resulted in a sharp increase in thyroid iodine concentration from 0.37 +/- 0.11 to 0.61 +/- 0.14 mg/g (p less than 0.01). Another group of 8 patients first treated with 500 micrograms iodide/day also showed a significant increase in iodine concentration from 0.35 +/- 0.14 to 0.65 +/- 0.20 mg/g (p less than 0.01). After switching to the combination regimen during a second 4-month period, thyroid iodine concentration slightly decreased, particularly in those patients with high iodine concentrations after monotherapy with iodide (0.65 +/- 0.20 vs 0.50 +/- 0.12 mg/g, p less than 0.05). In conclusion, treatment with 500 micrograms iodide/day could sharply increase thyroid iodine concentration in patients with endemic goitre. In contrast, a combination of 100 micrograms levothyroxine and 100 micrograms iodide/day had no significant effect on thyroid iodine concentration.

Adult↗
PubMed1990

Evaluation of the ratio of T3 release stimulating antibodies to TSH-binding inhibiting antibodies during the course of Graves' disease.

The mechanisms leading to a remission of Graves' hyperthyroidism are still unknown. One possibility would be that autoantibodies raised during the course of disease could change the composition of the autoantibody spectrum in such a way to counterbalance the action of stimulatory autoantibodies, thereby resulting in an induction of remission. Therefore, in the present study using a rigorous methodological approach we have characterized the portion of T3 release stimulating autoantibodies among the total body of TSH receptor antibodies, i.e. the TSAb/TBII ratio, over the course of a 12 month antithyroid therapy in 25 patients with Graves' hyperthyroidism. Further, we have evaluated the relation of the alteration of the antibody spectrum to the course of disease. The TSAb/TBII ratio was indeed found to be subject to considerable changes. The observed shift in the antibody composition was more often in favor of a relative increase in stimulatory inactive TBII. Nevertheless, the clinical course of patients showing a persistence of TBII despite the decline or even absence of TSAb proved to be variable. In conclusion, our data indicate that the spectrum of autoantibodies may change over the course of antithyroid therapy owing mostly to a relative rise in stimulatory less active autoantibodies. This phenomenon, however, is apparently not closely related to the course of disease.

Adult↗
PubMed1990

Evidence for the presence of human chorionic gonadotropin (hCG) and free beta-subunit of hCG in the human pituitary.

Previous studies have indicated that the pituitary gland may produce free alpha-subunit and small quantities of hCG in addition to other glycoprotein hormones. Since synthesis of holo-hCG requires the presence of both subunits, we have investigated the occurrence in human pituitary of free beta-subunit of hCG, in addition to intact holo-hCG. We processed a pituitary extract by fractionated ammonium sulfate precipitation followed by sequential chromatography on Sephadex G-100 and Ultrogel AcA 44. The fractions obtained were assessed for their reactivities with a panel of polyclonal and monoclonal antibodies specific for holo-hCG, beta-subunit of hCG, alpha-subunit, or hCG/LH. In addition to the expected LH and alpha-subunit, we detected materials which eluted from the column in positions very similar to those of cochromatographed 125I-hCG tracer and hCG-beta (NIH CR123-beta), and which showed immunoreactivity in specific immunoradiometric assays for holo-hCG and hCG-beta, respectively. Holo-hCG and hCG-beta material derived from the urine of a postmenopausal woman showed behaviors on the column similar to the pituitary forms. Both the pituitary holo-hCG- and free hCG-beta-subunit activity could be enriched (approximately 500 times) by affinity chromatography on an hCG antibody-coupled Sepharose column. When subjected to isoelectric focusing in granulated gel holo-hCG and hCG-beta-subunit of pituitary origin were focused in the pI-range of pregnancy hCG and pregnancy hCG-beta-subunit, respectively. Like pregnancy hCG, most (75%) of the pituitary hCG was bound to a column of Con A-Sepharose; however, the Con A-nonbinding hCG fraction (approximately 25%) was much higher than that found in pregnancy hCG. On the basis of immunoreactivities, the content of holo-hCG in our pituitary extract was estimated to be 60 micrograms/g, and that of free beta-subunit 45 micrograms/g; for comparison, LH was approximately 20 mg/g, and free alpha-subunit 1.6 mg/g. In addition, we could demonstrate the presence of both holo-hCG- and free hCG-beta-subunit-like immunoreactivity in NaCl-extracts from single pituitaries of two postmenopausal women. In these studies a second hCG-beta-immunoreactive material eluting far behind the hCG-beta-position was found. Chromatography of purified LH-beta-subunit, which crossreacts 1.56% in the hCG-beta IRMA, yielded an elution pattern clearly distinguishable from that of the hCG-beta-immunoreactive substances.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1989

Insulin and insulin-like growth factor (IGF I) modulate the effects of bTSH on 3H-thymidine incorporation in human thyroid cells in primary culture.

The role of TSH in thyroid cell growth and the pathogenesis of goiter has become a matter of recent debate, since many investigators have failed to demonstrate a growth-promoting effect of TSH in human thyroid cells in culture. While those studies have focused on the action of TSH in human thyroid cells, the influence of assay conditions and cofactors has received scant attention. In the present study, we have therefore undertaken to elucidate the effects of insulin and insulin-like growth factor (IGF I) on 3H-thymidine uptake in human thyroid cells, particularly with respect to their relation to the actions of bTSH. We could demonstrate a considerable, dose-dependent stimulation of 3H-thymidine incorporation in the cells by bTSH that was dependent on the presence of insulin or IGF I; bTSH alone was ineffective in that respect. The concentrations of insulin and IGF I required to facilitate the TSH response were of a magnitude at which both peptides were totally ineffective by themselves. At concentrations of insulin or IGF I that produced a maximum stimulation of 3H-thymidine incorporation, the addition of bTSH did result in a slight decrease rather than a further increase of that stimulation. We conclude from these findings, first, that TSH appears to be a growth factor for human thyroid cells under the conditions described, and, second, the effects of TSH on thyroid cell proliferation are under the control of cofactors like insulin and IGF I.

Cell Division↗
PubMed1989

Design of a long-lived thyrotropin antagonist from derivatives of human chorionic gonadotropin.

Previous studies have revealed that desialylated forms of hCG have a high potency to inhibit both the binding of bovine TSH (bTSH) to human thyroid membranes and the bTSH-stimulated adenylate cyclase activity therein. The biological activities of these desialylated forms, however, are greatly reduced in vivo due to the high affinity of asialo-glycoproteins for hepatic receptors and their consequent rapid clearance from the circulation. Intact purified hCG (hCGp), on the other hand, has little affinity for hepatic receptors and has a relatively long half-life in vivo, but displays only negligible inhibitory potency in the human thyroid. In the present studies, we have sought to obtain one or more compounds derived from hCG that are able to inhibit binding to TSH to the high affinity receptor in human thyroid membranes, and, consequently, could inhibit the stimulatory effect of TSH and Graves' immunoglobulin G and which also display a relatively low affinity for the hepatic asialoglycoprotein receptor and, as a consequence, have a reasonable survival in the circulation. Two hCG forms isolated by sequential chromatography of crude hCG on DEAE-52 and Sephadex G-100 were of interest, since they displayed some degree of selectivity in binding to thyroid and liver receptors. The first form (hCGv), whose isolation we described previously, was comprised of partially desialylated variant forms of intact hCG. The second material, as judged from its immunoreactivity, elution behavior on Bio-Gel P-100, and migration during sodium dodecyl sulfate-polyacrylamide gel electrophoresis, contained a fragment of the beta-subunit (BF), similar to the beta-core fragment described by others. However, BF differed from the beta-core fragment in having a higher sialic acid content. Interestingly, we found that BF as well as the enzymatically desialylated form of BF displayed a much lower affinity for mouse liver receptors than did asialo-hCGp or the free asialo-beta- and asialo-alpha-subunits. Further, the activity of BF to inhibit the binding of [125I]bTSH to human thyroid membranes exceeded that of the desialylated subunits of hCGp as well as that of intact hCGp, but was only exerted at the low affinity binding site and was not accompanied by inhibition of TSH-stimulated adenylate cyclase. In an attempt to shift the locus of BF action from the low to the high affinity TSH receptor, we recombined BF with either an intact alpha-subunit of hCG or an asialo-alpha-subunit. This led to the creation of two novel forms of hCG with properties of the type that we were seeking.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Evidence that partially desialylated variants of human chorionic gonadotropin (hCG) are the factors in crude hCG that inhibit the response to thyrotropin in human thyroid membranes.

Previous studies have revealed that pure unmodified hCG (hCGp) has little potency to inhibit the binding of bovine TSH (bTSH) to human thyroid membranes and to either stimulate adenylate cyclase or inhibit TSH-stimulated adenylate cyclase therein. On the other hand, preparations of crude hCG (hCGc) as well as enzymatically desialylated hCGp (asialo-hCGp) are relatively potent inhibitors of bTSH binding (TBI activity) and bTSH-stimulated adenylate cyclase activity in human thyroid membrane preparations. In the present studies we have sought to identify and characterize the inhibitory moieties in crude hCG that are responsible for these inhibitory activities and to elucidate the properties of their interaction with the TSH receptor in human thyroid membranes. Preparations of hCGc were processed by DEAE-52 chromatography; this separated components of interest, which were not adsorbed, from intact hCGp, which was adsorbed to the column. The former were then subjected to gel filtration on Sephadex G-100, and the earliest eluting fractions, which proved to have the greatest TBI activity, were pooled, rechromatographed, and designated as variant hCG (hCGv). Three different preparations of hCGv were studied. All displayed a lower sialic acid content, by about half, than that in hCGp. Though their potencies varied somewhat, all had significant TBI activity, which was less than that of asialo-hCGp, but more than that of hCGc. Saturation studies revealed that the TBI activities of hCGv and asialo-hCGp were due to a competitive inhibition of bTSH binding at both the high and low affinity bTSH-binding sites, whereas the inhibitory activity of hCGc was exerted primarily at the low affinity binding site. Preparations of hCGv were also capable of inhibiting the adenylate cyclase response to TSH in human thyroid membranes, and Lineweaver-Burk analysis revealed this inhibition to be competitive in nature. As with its TBI activity, the potency of hCGv to inhibit the adenylate cyclase response was intermediate between that of asialo-hCGp and hCGc. Among the three batches of hCGv, their inhibitory effects on bTSH binding and adenylate cyclase activation appeared to vary inversely with with their sialic acid content. Enzymatic desialylation of hCGv increased its potency to that of asialo-hCGp. Several lines of evidence, as follows, indicate that the moieties that comprise hCGv are modified forms of hCGp itself. 1) On a unit weight basis, hCGv was at least as potent as hCGp in its ability to inhibit the binding of [125I]hCG to rat testicular membranes.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenylyl Cyclases↗
PubMed1986

Similar triiodothyronine releasing activity of thyroid stimulating antibodies in human and porcine thyroid slices.

In an approach to addressing species specificity of thyroid stimulating antibodies (TSAb) stimulation of T3 release by Graves' sera was comparatively studied in human and porcine thyroid slices. A high sensitivity and specificity was found for the T3 bioassay independently on the use of human or porcine thyroid. Moreover, activity indices of the individual sera in both tissues were significantly correlated to each other and to circulating hormone levels in untreated disease. In conclusion, we suppose a lack of functionally relevant differences between target antigens, brought about probably by the TSH receptor itself and other membrane components, in human and porcine thyroid. Thus, for clinically applicable T3 releasing bioassay porcine thyroid may be alternatively used. In addition, this bioassay renders the advantage of reflecting the activity of disease.

Adult↗
PubMed1986

Thyrotropic activity of acidic isoelectric variants of human chorionic gonadotropin from trophoblastic tumors.

Previous studies have indicated that hCG has a weak intrinsic thyroid-stimulating activity. Differences in the molecular composition and biological activity of hCG in patients with trophoblastic diseases and pregnant women occur, but are not well defined. Therefore, we have studied the effect of serum samples and purified hCG preparations from patients with trophoblastic diseases on T3 release from human and porcine thyroid slices in vitro. We examined 30 serum samples from 13 patients with nonseminomatous testicular germ cell tumors, 3 from women with choriocarcinoma, and 5 from patients with hydatidiform moles. In all but 1 serum sample from the tumor patients, but in none of 11 serum samples of pregnant women, T3-releasing activity was found. Two patients with testicular cancer and 1 patient with molar pregnancy experienced episodes of frank hyperthyroidism. Isoelectric focusing on polyacrylamide gels of tumor sera (n = 15) revealed substantial amounts of acidic isoelectric variants, pI 3.3-3.9, which were only barely detectable in pregnancy sera. The percentage of acidic hCG variants with pI 3.3-4.0 to total hCG with pI 3.3-5.2, as determined by hCG (+hCG beta) RIA of the eluted fractions of polyacrylamide gel isoelectric focussing, varied from 12-45% in sera of tumor patients and from 0-4% in pregnant sera. We purified the acidic variants of hCG with pI 3.6-3.8 (hCGav) from the urine of our patients. The beta-subunit of purified hCGav had a slightly higher mol wt (35,750) than that of hCG CR 119 (34,190) on polyacrylamide gel electrophoresis. The hCGav showed a dose-dependant stimulation of T3 release and cAMP generation from human thyroid slices, whereas the other hCG fractions on isoelectric focussing had no thyrotropic effect in similar dose levels. The TSH-like activity of hCGav could be roughly estimated as 10 mIU TSH/IU hCGav. Anti-hCG (+hCG beta) antiserum, but not anti-hTSH antiserum, neutralized the biological activity of hCGav. These findings strongly suggest that acidic hCG variants act as functional stimulators of the human thyroid in vitro. Since these molecular variants of hCG can exist in patients with trophoblastic diseases in significant amounts, they could be responsible for some cases of hyperthyroidism in trophoblastic diseases.

Adult↗
PubMed1986

T3 releasing activity by Graves' sera from Graves' thyroid in vitro.

The insensitivity of Graves' thyroid to stimulation of cAMP formation by TSH as well as Graves' immunoglobulins in vitro is well known. The present study was performed to find out Graves' sera which may induce a final activation i.e. stimulation of T3 release in Graves' thyroid slices despite this insensitivity of tissue and to characterize determinants responsible for the efficiency of those sera. Out of 20 sera from patients with active untreated Graves' disease 6 were found to stimulate T3 release from Graves' thyroid in vitro. These 6 sera were effective in stimulating different Graves' glands, irrespective of pretreatment with propranolol, thiamazole (methimazole) or thiamazole plus iodine. In contrast, a significant response to bTSH was not observed in any Graves' gland. For comparison, 17/20 of the same sera were able to stimulate T3 release when tested on human goitrous thyroid. Sera which stimulated Graves' slices revealed no higher stimulating activities in goitrous tissue than serum samples which did not. All sera were additionally assessed for TSH binding inhibiting immunoglobulins in a radioreceptor assay. Remarkably, Graves' thyroid stimulating sera had a low or absent TSH binding inhibiting activity. Thus, hormone release from Graves' thyroid in vitro - in contrast to that from goitrous tissue - could only be activated by a minority of Graves' sera. These Graves' thyroid stimulating sera could be characterized to contain a selected spectrum of biologically active antibodies with a high TSH agonistic potency stimulating in the presence of a negligible TSH binding inhibiting activity.

Adult↗