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Biomedical subjects

L J DeGroot

Publications and source records attributed to L J DeGroot.

At least 163 records · Page 9Linked to original sources
PubMed1985

Anti-thyroid peroxidase antibody in patients with autoimmune thyroid disease: possible identity with anti-microsomal antibody.

Thyroid microsomal antigen and peroxidase (TPO) have a close intracellular anatomical relationship, especially in exocytotic vesicles. We considered that antibodies to microsomal antigen might react with TPO and therefore looked for the presence of antibodies against TPO in the serum of patients with autoimmune thyroid disease (AITD). TPO was prepared from Graves' thyroid glands, solubilized by n-octyl glucoside, and its activity was assayed by the guaiacol method. Control sera and sera with a positive microsomal hemagglutination test (MCHA(+) ) were assayed for their ability to precipitate TPO activity by incubation of sera with TPO and protein A. We identified MCHA(+) sera which caused precipitation of TPO activity, and the extent of precipitation was related to the amount of serum added. A significant correlation was present between this anti-peroxidase activity and microsomal antibodies titers, measured by a micro-ELISA method. Affinity columns prepared from immunoglobulins of MCHA(+) sera, coupled to Reacti-Gel (6X), bound TPO activity, whereas using control IgG the recovery in the unbound fraction was high. These data provide evidence of antibodies against thyroid peroxidase in the serum of patients with AITD and suggest a close link between microsomal antigen and thyroid peroxidase.

Antibodies↗
PubMed1985

Thyrotropin (TSH) binding activities in bovine thyroid tissue: possible role of adenosine 3',5'-monophosphate dependent phosphorylation of thyroid plasma membranes in TSH receptor degradation.

The relationship between thyroid plasma membrane phosphorylation and thyrotropin (TSH) receptor degradation was investigated by using bovine thyroid tissues. By fractionation of thyroid cytosol (105,000 X g supernatant of thyroid homogenate) in a continuous sucrose density gradient centrifugation, three different TSH binding activities were separated. During the incubation of thyroid plasma membranes, TSH binding activities were spontaneously released in vitro. By fractionation of the fraction containing released TSH binding activities in the same sucrose density gradient centrifugation, three different TSH binding activities were isolated. These peaks of TSH binding activity corresponded to the peaks of TSH binding activity obtained in cytosol fraction. Adenosine 3',5'-monophosphate (cyclic AMP) enhanced the release of TSH binding activities from the plasma membranes in vitro. After fractionation on a sucrose density gradient centrifugation of the supernatant of the plasma membranes which were preincubated with cyclic AMP, three different peaks of TSH binding activity were identified. These peaks corresponded to the peaks obtained in spontaneously released TSH binding activity. In this case, however, the amount of small molecule TSH binding activities was predominant compared to that of large molecule TSH binding activity. During the incubation of the plasma membranes with [r-32P]-ATP and with cyclic AMP, phosphorylated soluble proteins were released. The profile of the phosphorylated soluble proteins in the sucrose density gradient centrifugation showed three different peaks which corresponded to the peaks of binding activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Early effect of thyroid hormone on cytosolic protein phosphorylation in rat anterior pituitary.

The effect of T3 was studied on phosphorylation of cytosolic proteins in rat anterior pituitary. Cytosols obtained from hypothyroid (H) and T3 (50 micrograms/100 g body weight) injected H rats (T) were phosphorylated in vitro. Although total incorporation of 32P into proteins did not differ between H and T, analysis of phosphoproteins by SDS polyacrylamide gel electrophoresis and autoradiography revealed that T3 injection significantly increased phosphorylation of 2 proteins within 1 h. These results and our previous demonstration of T3 effects on phosphorylation in rat liver cytosol and cultured human skin fibroblasts suggest that protein phosphorylation is an important early intracellular process in T3 action.

Animals↗
PubMed1985

Cold reactive lymphocytotoxic activity in autoimmune thyroid disease.

An increased incidence of cold-reactive lymphocytotoxic activity (LCTA) has been demonstrated in the sera of patients with autoimmune thyroid disease. Twenty-six of 79 (33%) patients with Graves' disease and 9 of 21 (43%) patients with Hashimoto's thyroiditis had cold-reactive LCTA detected by microcytotoxicity assay compared to 6 of 42 (14%) normal controls. There was no correlation between LCTA and age, sex, MCHA titre or TGHA titre. A positive correlation with FTI and LCTA in Hashimoto's patients was demonstrated, but no such correlation was demonstrable in Graves' patients. The lymphocytotoxic activity was directed preferentially against B cells. There was no preferential lysis of T-cell subsets as defined by monoclonal antibodies, and the lymphocytotoxins were equally reactive with normal lymphocytes and toxic Graves' lymphocytes. The significance of cold-reactive lymphocytotoxic activity in the pathogenesis of autoimmune thyroid disease remains to be determined.

Adolescent↗
PubMed1984

Long-term follow-up study of compensated low-dose 131I therapy for Graves' disease.

We treated 187 patients who had Graves' disease with low-dose radioactive iodide (131I), using a protocol that included a compensation for thyroid size. The incidence of early hypothyroidism (12 per cent) was acceptably low in the first year after 131I treatment, but we found a cumulative high incidence (up to 76 per cent) at the end of the 11th year. In contrast, the incidence of permanent hypothyroidism was relatively stable in 166 surgically treated patients, increasing from 19 to 27 per cent at the end of 11 years. Among 122 medically treated patients, only 40 per cent entered remission, and hypothyroidism developed in 2 per cent during the same period of follow-up. The long-term incidence of hypothyroidism in our patients treated with low-dose 131I therapy was much higher than that found in earlier studies using a comparable dose. Our study suggests that it will be difficult to modify therapy with 131I alone to produce both early control of thyrotoxicosis and a low incidence of hypothyroidism.

Adult↗
PubMed1984

Use of isotope bone scans and skeletal survey X-rays in the follow-up of patients with thyroid carcinoma.

We have evaluated the utility of isotope bone scans and skeletal survey X-rays in the periodic evaluation of patients known to have had thyroid carcinoma. Patient data were evaluated in 29 patients with known metastatic disease and 79 patients without known metastatic disease who were followed over a period of 3-12 years and who had coincident 131Iodide whole body scans, technetium pyrophosphate bone scans, chest X-rays, and skeletal surveys, at periodic intervals. The information gained for each patient, at a time when two or three of the major survey procedures were conducted coincidentally, was evaluated retrospectively for its impact on classification and management of the patients. Metastatic tumor was detected in most instances by 131I RAIU in the lungs or by chest X-rays. Six patients had proven bone metastasis. Four of these patients had positive 131Iodide RAIU in bones, and two were positive and two negative by pyrophosphate bone scan. Only one was positive by skeletal survey X-rays at the time metastases were first detected by bone scans. Nine of the patients with metastatic disease displayed abnormal bone scans, but six of these were determined to be false positives. Bone scans detected one poorly differentiated metastatic tumor which did not accumulate 131I. Bone scans were more sensitive than skeletal survey X-rays. Physical exam, chest X-ray, and I131 whole body scans detected all instances of metastatic carcinoma.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Alterations in hepatic protein kinase activity induced by triiodothyronine.

Quantitative and qualitative alterations in protein kinase (PK) activity in preparations of rat liver from hypothyroid (H) and T3-treated hypothyroid animals (T) were analyzed in comparison to enzyme from normal (N) animals. Qualitative variations in type of protein kinase were assessed by chromatography of cytosol preparations on DE-52 cellulose columns. Cytosol kinases resolved into a small fraction I containing a catalytic subunit, fraction II containing a type 1 holoenzyme, fraction III containing a cyclic-AMP independent PK, and fraction IV containing a type 2 holoenzyme. A cytosolic kinase active with casein as substrate was also identified. In H the type 1 holoenzyme was reduced in comparison to N. There were no other qualitative changes. Nuclear PKs were extracted with solvents containing 0.3 M KCl. Qualitative changes were evaluated by chromatography on phosphocellulose columns, but available methodology did not give reproducible evidence of changes in individual PKs. H had significantly more cytosolic PK active with protamine substrate than did normal animals, and by administration of T3, the H level was reduced progressively over 48 h to the N level. The activation ratio of total PK in cytosol was higher in H, and was also reduced to the N level by T3 administration. This suggests a higher steady state level of cyclic-AMP may be present in H rat liver cytosol. Cytosolic protein kinase reactive with casein as substrate increased gradually over 48 h after T3 administration from the H to the higher N level. It was significantly elevated to 110% of the H value by 48 h after T3 administration. The behavior of nuclear PK was entirely different. Nuclear PK reactive with protamine as substrate was increased within 1-1/2 h after T3 administration, reaching a peak of 130% of the control value at 5 h and returning to the normal level by 48 h. In contrast, nuclear PK reactive with casein as substrate also increased by 1-1/2 h after T3 administration and remained elevated at 110-115% of the control value throughout 48 h after T3 administration. The early changes in nuclear PK activity were prevented by administration of cycloheximide or alpha-amanitin. The observed changes in cytosolic PK, including the increment induced by T3 in type 1 enzyme, reduction in

Animals↗
PubMed1984

cAMP-independent casein kinase mediates phosphorylation of many T3-dependent phosphoproteins in rat liver cytosol.

Administration of T3 (20 micrograms/100 g BW) for 3 days increases phosphorylation of several proteins in rat liver cytosol in vitro. To help elucidate the mechanism of T3-induced phosphorylation, we studied which protein kinase(s) mediate phosphorylation of endogenous cytosolic proteins. Five different protein kinases were obtained by DEAE+ cellulose column chromatographic fractionation of liver cytosol. When their ability to phosphorylate heat-inactivated cytosol was investigated, casein kinase, a cAMP independent protein kinase, showed the strongest effect. Casein kinase, purified by phosphocellulose chromatography, phosphorylated more than 10 cytosolic proteins. Several T3-dependent (and cAMP independent) phosphoproteins were included among these. One protein with Mr 39 X 10(3), of which phosphorylation is stimulated by T3 within five hours after injection, was the most active substrate for casein kinase. The results suggest that casein kinase is the enzyme responsible for phosphorylation of many rat liver cytosolic proteins and that several phosphoproteins, apparently under T3-regulation, might be phosphorylated by this enzyme.

Animals↗
PubMed1983

T-cell subsets in patients with preeclampsia.

Peripheral blood mononuclear cells from patients with preeclampsia were enumerated by means of monoclonal anti-T-cell antibodies. The percentage of total T cells was significantly decreased in this group of patients, as compared with normal term pregnant women. The low proportion of T cells was due to a proportional reduction in both helper and suppressor T cells; therefore, the ratio of helper to suppressor T cells was not different from that in normal pregnant women. There was no correlation between the degree of reduction in percentage of T cells and severity of the disease. The absolute numbers of T cells were slightly, but not significantly, decreased. Our findings support previous evidence of reduced, not increased, immune reactivity in preeclampsia.

Animals↗
PubMed1983

Binding of immunoglobulin-G from patients with thyroid autoimmune disease to normal T lymphocytes.

Sera from patients with Graves' disease and Hashimoto's thyroiditis were reacted with normal T lymphocyte preparations in an attempt to detect binding of immunoglobulin G (IgG) to T cells. Sera from normal subjects and patients with toxic adenomas served as controls. Each serum was reacted with at least three different preparations of normal T cells. Bound IgG was identified using a fluoresceinated second antibody, antihuman IgG. Positive cells were enumerated by means of epifluorescent microscopy. IgG from 57.8% of toxic Graves' patients, 30.7% of Graves' patients who were euthyroid after treatment, and 41.6% of Hashimoto's patients bound to normal T cells more than did IgG from normal controls. Reactivity of toxic adenoma sera was similar to that of normal sera. When the positive sera were reacted with helper or suppressor/cytotoxic T cell preparations (separated by negative selection technique), the binding was shown to be directed against suppressor/cytotoxic T cells but not against helper cells. These data indicate that a significant proportion of patients with autoimmune thyroid disease have IgG in their serum which react with a subset of normal T suppressor/cytotoxic cells. This phenomenon could be the expression of anti-lymphocyte antibodies, which may relate to previously recognized reductions in number and function of suppressor T cells in autoimmune thyroid disease.

Adenoma↗
PubMed1983

Inherited disorders of thyroid metabolism.

In summary, we have presented a brief survey of the current state of knowledge of inherited disorders of thyroid metabolism. Analysis of cases shows that the biochemical classification covers a wide range of abnormalities and it is likely that further biochemical studies will increase this heterogeneity as well as refining it. Genetic studies are often incomplete, and few in number compared with the classical study by Hutchison and McGirr of Scottish tinker families. Most important, this survey indicates that further research is needed to elucidate the precise molecular mechanisms of the working of the iodide pump, the oxidation and iodination and coupling mechanisms. Study of animal models and DNA sequencing and hybridization work will continue to expand our understanding of abnormalities of thyroglobulin metabolism. We urgently need to find the key to resistance of peripheral and pituitary tissues to thyroid hormone. Subtle dyshormonogenetic abnormalities may await discovery in the field of multinodular goiter and intrathyroidal calcification with goiter. Neonatal screening for hypothyroidism is likely to expand the number of cases for investigation and detailed study. There is an important relationship of dyshormonogenesis to follicular carcinoma. It is hoped that in time we will be able to transform inborn errors into areas of understanding in the realm of the thyroid gland.

Adolescent↗
PubMed1983

Thyroid hormone increases type I adenosine 3', 5'-monophosphate-dependent protein kinase and casein kinase activities in rat liver cytosol: analysis of protein kinases by polyacrylamide disc gel electrophoresis.

We investigated the action of thyroid hormone on each protein kinase in rat liver cytosol. Kinases were analyzed by polyacrylamide disc gel electrophoresis and isoelectric focusing in polyacrylamide gel. Polyacrylamide disc gel electrophoresis separated cAMP-dependent protein kinase type I (Rf = 0.35), type II (Rf = 0.44), their catalytic subunit (Rf = 0.26), and cAMP-independent protein kinase (Rf = 0.50). Casein kinase was detected at Rf = 0.37. In addition to the catalytic subunit with Rf = 0.26, another catalytic subunit was found at Rf = 0.44 when the cytosol was preincubated with cAMP. The administration of T3 (20 micrograms/100 g BW for 3 days) to hypothyroid rats increased enzyme activities of type I holoenzyme and casein kinase by 48%. Free catalytic subunit, separated from holoenzyme, had the same level of enzyme activity in both groups, suggesting greater endogenous dissociation of type I holoenzyme in hypothyroid rats. When heat-inactivated rat liver cytosol was used as substrate in the assay of protein kinase activity, the peak enzyme active in phosphorylating the cytosol corresponded to the casein kinase peak. Our data indicate that casein kinase is the main enzyme that mediates phosphorylation of endogenous proteins in rat liver cytosol, and that T3 treatment increases the activity of casein kinase and of type I cAMP-dependent protein kinase.

Animals↗
PubMed1983

Effect of hypo- and hyperthyroidism on the balance between helper and suppressor T cells in rats.

The proportion of total, helper and suppressor T lymphocytes among mononuclear cell preparations from blood and spleen of rats made hypo- and hyperthyroid was measured using three monoclonal antibodies specifically directed against total, helper and suppressor T cells. Compared to normal rats, hypothyroid (thyroidectomized or treated with 6-propyl-2-thiouracil (PTU) rats had a decreased proportion of suppressor T cells in the spleen, which produced an increase in the helper/suppressor T cells ratio. The opposite alterations (increased suppressor T cells and decreased ratio) was found in the blood of the same animals. Triiodothyronine (T3) added to PTU in the drinking water prevented these alterations. Animals treated with high doses of T3 for 17 days did not develop any alteration either in the proportions or in the ratio of helper/suppressor T cells. Our results suggest that hypothyroidism but not hyperthyroidism alters the normal balance between helper and suppressor T cells in rats.

Animals↗
PubMed1983

Pathophysiologic control of nuclear triiodothyronine receptor capacity.

Mechanisms involved in the reduced T3 receptor capacity found in a variety of pathophysiologic states were investigated by in vitro assessment of T3 receptor-nuclei interaction using tissue prepared from rats. In nuclei from immature animals, nuclear uptake of receptor was reduced, release was accelerated, and these alterations could account for the reduced nuclear receptor capacity. The functions reached the normal adult condition by 30-50 days. Nuclei from animals starved for 72 h showed no change in release of receptor, a 15% decrease in uptake, and 48% decrease in total binding capacity, indicating that the major effect is related to diminished supply of receptor, presumably due to reduced synthesis in the extranuclear compartment. Glucagon administration produced no change in receptor release, 25% decrease in receptor uptake, and nearly equivalent 33% decrease in binding capacity. Alteration in receptor uptake could account largely for changes induced by glucagon. Animals studied 24 h after hepatectomy had a 53% decrease in total binding capacity, but no change in uptake or release, indicating that reduced receptor synthesis is the primary abnormality. Administration of alpha-amanitin caused a 30% diminution in the binding capacity in the nuclei, without change in uptake and release, and cycloheximide caused an 87% decrease in binding capacity, with minimal change in uptake and no change in release. In both instances the alterations are interpretable as diminished synthesis and availability of receptor, rather than alterations in binding receptor to chromatin. The major cause of diminished receptor capacity appears to be reduced cytosolic synthesis of receptor, with reduction in retention by chromatin-associated factors playing a significant role in immature animals, and during glucagon treatment.

Age Factors↗