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Biomedical subjects

C G Thomas

Publications and source records attributed to C G Thomas.

At least 37 records · Page 2Linked to original sources
PubMed1987

Current management of the patient with autonomously functioning nodular goiter.

Autonomously functioning thyroid nodules (AFTNs) are presumably independent of TSH for growth and function and appear "hot" on scintiscan because they selectively concentrate radionuclide to a greater extent than the remaining thyroid gland, which is controlled by the normal TH-TSH feedback mechanism. Such autonomously functioning tissue may occur in "patchy" areas, as a solitary nodule, or as multiple nodules (classic Plummer's disease), with the mass of hyperfunctioning tissue and the related secretion of thyroid hormones determining whether the patient is euthyroid or hyperthyroid. Important diagnostic tests include a 99mTc thyroid scan, T4 RIA, T3 uptake, FTI, TSH RIA, and occasionally T3 RIA ("T3 thyrotoxicosis"). Solitary autonomous nodules in adult patients characteristically progress slowly over many years, with toxicity rarely developing in nodules less than 2.5 cm in diameter and occurring primarily in nodules 3 cm or larger and in older patients. The decision to treat a solitary nodule depends upon the size and degree of function of the nodule and the patient's age. Surgery and radioactive iodine are effective therapies. Hyperfunctioning thyroid nodules in children and adolescents (under age 18) have a more rapidly progressive course than those in adults and should be treated by thyroid lobectomy at the time of diagnosis. Subtotal thyroidectomy is the preferred treatment for most patients with toxic multinodular goiter, because it achieves prompt control of the hyperthyroidism and removes the goiter. Radioiodine therapy and long-term antithyroid drug therapy are alternative forms of treatment for patients who are poor surgical risks or who develop recurrent hyperthyroidism following thyroid surgery.

Adenoma↗
PubMed1987

Evaluation and redesign of a system to rank applicants for surgical residencies.

The present paper is a report of the evaluation and subsequent revision of a selection system for surgical house officers. The authors conducted a series of studies to determine the content validity, concurrent validity, and predictive validity of the system used by the surgery department prior to 1982. The results did not support the validity of that ranking system. In particular, the system was found not to evaluate candidates on criteria considered important by the faculty. Based on these findings, the department adopted a new ranking system organized around a multimethod-multitrait matrix (that is, using multiple methods to assess multiple traits) and based on a new set of traits that had been identified as important in the earlier validity studies. The new system has been used for five years, since 1982, with acceptance and favorable evaluation by the faculty. During that period, the median and mean rank of candidates who were matched to the residency program improved.

Educational Measurement↗
PubMed1987

Characterization of the subunit structure of the thyrotropin receptor in the FRTL-5 rat thyroid cell line.

Radioiodinated TSH was covalently cross-linked to monolayers of FRTL-5 rat thyroid cells using the homobifunctional cross-linking agent disuccinimidyl suberate. Analysis of the cross-linked samples by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions demonstrated the presence of three specifically labeled complexes with apparent mol wt of 68,000, 85,000, and 145,000, in addition to the TSH alpha-beta dimer and its alpha- and beta-subunits. When bound [125I]iodo-TSH was cross-linked with increasing concentrations of disuccinimidyl suberate, the formation of the 68,000 and 85,000 mol wt complexes was sequential, with the 68,000 complex appearing first. These two complexes were also observed after labeling with radioiodinated TSH hybrid molecules (alpha-beta or alpha-beta), in which the label is in only one subunit, or immuno-precipitation with antibodies against either the alpha- or beta-subunit of TSH. Similar complexes (65,000, 82,000, and 145,000 mol wt) were also formed after cross-linking with the alkaline-cleavable cross-linker (bis-[2-(succinimidooxycarbonyloxy)ethyl]sulfone. Again, the appearance of these three complexes was sequential and dependent on the cross-linker concentration. At low concentrations and under reducing conditions, the 65,000 mol wt complex was the major band. However, at high concentrations, especially under nonreducing conditions, most of the radioactivity was present in the 145,000 mol wt complex. Alkaline cleavage of these three complexes followed by electrophoresis in a second dimension resulted in the release of three components with approximate mol wt of 31,000, 17,000, and 63,000 in addition to the TSH alpha-beta dimer and its alpha- and beta-subunits. Reduction by dithiothreitol followed by electrophoresis in a second dimension resulted in the release of only the 17,000 and 63,000 components. Taken together, these results suggest that 1) both the 65,000 and 82,000 complexes are formed after incremental cross-linking of TSH alpha-beta dimer to receptor subunits; and 2) the TSH receptor may be an oligomer composed of three different subunits, 31,000, 17,000, and 63,000, of which only the 31,000 subunit binds TSH.

Animals↗
PubMed1987

Autonomously functioning thyroid nodules in childhood and adolescence.

Autonomously functioning thyroid nodules (AFTNs) in children and adolescents (under age 18) are unusual but are not as rare as earlier reports suggested. These lesions have a significantly different biologic potential than similar lesions in older patients. In the younger age group there is a more rapid progression toward toxicity and a higher incidence of thyroid carcinoma. Our experience with 12 patients is combined with those previously reported for identification of a total of 61 children and adolescents with AFTNs, of whom 53 have undergone operation. Hyperthyroidism was present in 15 patients (24.6%), and in six patients (11.3%) the AFTN was due to a well-differentiated thyroid carcinoma. Surgical treatment is advisable for all children and adolescents with AFTNs because of the risks of hyperthyroidism and thyroid carcinoma. Surgical excision (lobectomy is preferred) results in rapid restoration of a euthyroid state for the toxic AFTN and allows histopathologic diagnosis. Therapy with radioiodine is not advisable for treatment of AFTNs in this age group. Thyroid-stimulating hormone suppression should be used for all patients with a diagnosis of thyroid carcinoma.

Adolescent↗
PubMed1986

Further characterization of the low and high affinity binding components of the thyrotropin receptor.

Following cross-linking with disuccinimidyl suberate and analysis by SDS-PAGE and autoradiography, both the high- and low-affinity TSH binding components exhibited two similar 125I-TSH-labeled bands, with Mr values of 80,000 and 68,000. IgG fractions from patients with Graves' disease inhibited 125I-TSH binding to both components, while normal IgG had no effect. Although not entirely conclusive, these results suggest that the high- and low-affinity components share similar subunit composition and antigenic determinants.

Animals↗
PubMed1986

Characterization of the guinea pig adipocyte thyrotropin receptor.

125I-TSH binding to porcine thyroid and guinea pig fat resulted in curvilinear Scatchard plots with similar dissociation constants for the high and low affinity binding components. Antibodies from the sera of patients with Graves' disease inhibited binding to the high and low affinity binding components of both tissues. Covalent cross-linking of 125I-TSH to membranes from each tissue resulted in the specific labeling of two protein bands. The guinea pig fat receptor subunits have Mr values of 52,000 and 38,000, whereas the porcine thyroid receptor subunits have values of 46,000 & 35,000. The labeling of the receptor subunits was inhibited by preincubation with Graves' autoantibodies. Despite possessing a different subunit composition, the receptors from these tissues exhibit similar affinity for TSH and share similar antigenic determinants for Graves' autoantibodies.

Adipose Tissue↗
PubMed1986

Hirschsprung's disease in young adults.

Hirschsprung's disease is rarely seen in the young adult, and presents unique problems in management because of the massive dilatation and hypertrophy that occur proximal to the aganglionic rectum or the rectosigmoid colon. The diagnosis, which may be suspected by barium enema, is confirmed by suction or full-thickness biopsy of the rectum that may be complemented by anal manometry. Based on our experience with eight patients, a two-stage surgical reconstruction is recommended, with a preliminary sigmoid colostomy through the normally innervated colon and an associated defunctionalized stoma constituting the initial operation. The distal colonic stoma permits cleansing of the caudal colon while the normally innervated proximal colon reverts to near normal caliber, usually within 2 to 6 months. This approach is in accord with the recommendation of Fairgrieve. Reconstruction using a Duhamel or Soave procedure has given good results. The Duhamel procedure seems preferable when a considerable discrepancy remains between the ganglionic and aganglionic segments of rectum.

Adolescent↗
PubMed1986

Mesothelial cysts of the round ligament simulating inguinal hernia. Report of four cases and a review of the literature.

Cysts of the mesothelial investment of the round ligament are rare and occur in women in their late third or fourth decades. They are relatively painless, mobile, may be perceived to be reducible, and should be included in the differential diagnosis of groin masses in women. Differentiation of these cysts from a small indirect inguinal hernia, with which they are frequently associated, is difficult and may be made only at the time of operation. They are likely to be less symptomatic than inguinal hernias. Cysts should not change in size with the Valsalva maneuver, although they may become more conspicuous with coughing. The clinical manifestations of cysts of the round ligament in four patients are described, along with a discussion of their embryologic and pathologic characteristics and a summary of the world literature. An embryologic mechanism of cyst formation is proposed and diagnostic criteria are presented. Symptomatic cysts of the inguinal ligament should be excised and the inguinal canal should be explored for possible associated indirect inguinal hernias. In the absence of symptoms or of a progressive increase in size, surgical removal of a cyst of the round ligament is not mandatory.

Adult↗
PubMed1986

Covalent crosslinking of thyrotropin to thyroid plasma membrane receptors: subunit composition of the thyrotropin receptor.

The subunit composition of the thyrotropin (TSH) receptor has been characterized using the bifunctional crosslinking agent, disuccinimidyl suberate (DSS), to covalently link [125I]TSH to its receptor. Purified thyroid membranes were labeled with [125I]TSH, and the hormone-receptor complex was crosslinked by incubation with 0.1 mM DSS. Analysis of this crosslinked complex by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing conditions indicated the presence of a specifically labeled hormone-receptor complex, corresponding to a Mr of 68,000 +/- 3000 before correction for the relative molecular mass of TSH. When reducing agents were absent during SDS solubilization, the mobility of the band increased slightly, suggesting the presence of intramolecular disulfide bonds. The labeling of the 68,000 band was specifically inhibited by TSH, but not by other glycoprotein hormones. Specific labeling occurred only in thyroid, and not in liver or muscle plasma membranes. Protease-free immunoglobulin G, isolated from sera of patients with Graves' disease and capable of competing with TSH for binding to its receptor, inhibited the labeling of the 68,000 complex. When the hormone-receptor complex was crosslinked with higher concentrations of DSS (greater than 0.3 mM), a second specifically labeled band was observed, with a Mr of 80,000 +/- 5000. This complex exhibited hormone, tissue, and immunologic specificities similar to those of the 68,000 band. Continuous sucrose density gradient analysis indicated that the intact solubilized receptor possessed a sedimentation coefficient of 10.5 S prior to correction for detergent binding. However, this value increased to 16 S when determined under conditions which took into account the change in hydrodynamic properties attributable to bound Triton X-100. These data suggest that the 80,000 and 68,000 bands represent binding components of the TSH receptor and that the receptor molecule most likely contains multiple subunits, linked by noncovalent forces.

Animals↗
PubMed1986

Pseudotumor of the supraclavicular fossa.

Minor musculoskeletal variants of the upper thoracic spine or of the ribs can cause effacement of the supraclavicular fossa, simulating a mass ("pseudotumor"). These variants may occur singly or in combination, and include unilateral prominence or asymmetry of the first rib, unilateral prominence or asymmetry of a cervical rib, and mild upper thoracic scoliosis causing prominence of the first rib on one side. The detection of variants by physical examination or more easily by review of the chest x-ray film may in selected instances obviate the need for costly diagnostic procedures and unnecessary biopsies. We call attention to this condition and describe our experience with four patients.

Aged↗
PubMed1986

Inhibition of thyrotropin-stimulated adenosine 3',5'-monophosphate formation in rat thyroid cells by an adenosine analog. Evidence that the inhibition is mediated by the putative inhibitory guanine nucleotide regulatory protein.

Addition of N6-(L-2-phenylisopropyl)-adenosine (PIA) to cultured FRTL-5 rat thyroid cells led to a concentration-dependent inhibition of TSH-stimulated cAMP formation. Half-maximal inhibition was attained with approximately 0.5 nM PIA. Forskolin and cholera toxin-stimulated cAMP production were also inhibited by PIA. 3-Isobutyl-methylxanthine inhibited the effect of PIA. These results are consistent with the presence of inhibitory adenosine receptors (Ri). Ri-sites were further demonstrated by the binding of 3H-cyclohexyl-adenosine to FRTL-5 plasma membranes. High (Kd = 0.50 +/- 0.07 nM) and low affinity (Kd = 5.95 +/- 2.33 nM) binding sites were observed. Pretreatment of FRTL-5 cells with pertussis, but not cholera, toxin effectively antagonized the inhibitory effects of PIA on cAMP production. ADP-ribosylation of FRTL-5 membranes with [32P]-NAD in the presence of cholera or pertussis toxin specifically labeled a 45,000 and 41,000 Mr species, respectively, which correspond to the alpha subunit of the stimulatory and inhibitory guanine nucleotide regulatory proteins. These results demonstrate that PIA inhibits TSH-stimulated cAMP production via Ri-sites on FRTL-5 thyroid cells. PIA appears to exert its inhibitory effects through the inhibitory guanine nucleotide regulatory protein.

Adenosine↗
PubMed1986

The late effect of subtotal thyroidectomy and radioactive iodine therapy on calcitonin secretion and bone mineral density in women treated for Graves' disease.

This study was designed to evaluate the effect of subtotal thyroidectomy and/or radioactive iodine therapy on plasma immunocalcitonin (iCT) levels and bone densities in patients treated for Graves' disease. Forty-eight women whose ages ranged from 29 to 79 years (mean, 55 years) were evaluated. All were at least 10 years beyond treatment. Fourteen patients had undergone subtotal thyroidectomy, 22 had received radioactive iodine therapy, and 12 had received both. Serum calcitonin levels were measured with the patient fasting and at 30 minutes and 2 hours after the ingestion of 15 mg of calcium in orange juice. Single photon absorptiometry was used to measure bone mineral density of the middle and distal radius. The mean fasting plasma levels of iCT for patients undergoing subtotal thyroidectomy was 27 +/- 2 mumol/L; women treated with radioactive iodine, 26 +/- 2; women undergoing subtotal thyroidectomy followed by radioactive iodine, 24 +/- 2, and for normal control women, 48.5 +/- 4.7. The mean stimulated iCT level of each of the patient groups was significantly lower than that of the normal controls (p = 0.01). There were no significant differences among the groups. Although there was an increased loss of bone mineral density in postmenopausal patients, with age and race as covariates, the bone densities of the distal radius in women undergoing subtotal thyroidectomy and/or receiving radioactive iodine were not significantly lower than those of normal control subjects (p greater than 0.05). These findings are consistent with other observations that patients treated by thyroidectomy and/or radioactive iodine for Graves' disease have lower basal levels of calcitonin and decreased calcitonin response to a provocative stimulus. Whether this loss of calcitonin reserve is a significant factor in development of postmenopausal osteoporosis remains unanswered.

Adult↗
PubMed1985

The role of the carbohydrate moiety in thyrotropin action.

The relative binding affinity of deglycosylated human TSH was 6-fold higher than that of native TSH. Although deglycosylated human TSH significantly stimulated adenylate cyclase, it was less effective than the native hormone. When deglycosylated human TSH was added with bovine TSH, however, a dose-dependent antagonism was observed. In particular, submaximal and maximal concentrations of bovine TSH and deglycosylated human TSH resulted in cAMP values much lower than the sum of activities of the individual hormones. The data suggest that although the effects of TSH deglycosylation are not as dramatic as with the gonadotropins, the carbohydrates of TSH appear to be required for maximal activation of adenylate cyclase by the hormone.

Adenylyl Cyclases↗
PubMed1985

An extended Kocher incision for bilateral adrenalectomy.

The anterior approach for excision of the adrenal glands is preferred when dealing with phenochromocytoma, carcinoma, lesions greater than 6 cm in diameter, or when upper abdominal exposure is necessary for intraabdominal procedures to be performed simultaneously with adrenalectomy. We describe an extended Kocher incision for bilateral adrenalectomy and abdominal exploration. This affords excellent exposure and wound healing without incurring total denervation of the upper abdomen. We recommend it as the optimum anterior approach to the adrenal glands.

Abdomen↗
PubMed1985

Parathyroid hormone secretion from dispersed human hyperparathyroid cells: increased secretion in cells from hyperplastic glands versus adenomas.

The in vitro secretion of PTH by dispersed human parathyroid cells was examined under conditions of low and high extracellular Ca+2 using tissue from patients with primary hyperparathyroidism and hyperparathyroidism resulting from chronic renal failure (CRF). The PTH secretion rate (nanograms of PTH per 10(5) cells/h) was lower in adenomatous tissues than in either primary hyperplastic cells or CRF cells under conditions of low (0.5 mM) or high (2.0-3.0 mM) extracellular Ca+2. Among the adenomas, a wide spectrum of degree of suppressibility of PTH secretion by high Ca+2 was found, ranging from 0% (completely nonsuppressible) to 98%. Suppression of the hyperplastic tissues in general was similar. The most suppressible adenomas demonstrated 2-fold greater PTH secretion rates in low Ca+2 conditions than the least suppressible adenomas, but in high Ca+2 conditions, the two groups had similar secretory rates. We conclude that the rate of PTH secretion by cells from adenomas was substantially lower than that of cells from tissues exhibiting either primary hyperplasia or hyperplasia resulting from CRF under these in vitro conditions. Thus, in adenomas, an increase in absolute cell number as well as alterations in the degree of calcium responsiveness may prove to be important etiological factors in the expression of hyperparathyroidism.

Adenoma↗
PubMed1985

The relation of serum calcium and immunoparathormone levels to parathyroid size and weight in primary hyperparathyroidism.

This study was designed to determine whether the serum calcium or immunoparathormone (iPTH) level would be of value in predicting the size or weight of the parathyroid gland in patients with single-gland enlargement caused by primary hyperparathyroidism. Ninety-two patients who underwent parathyroidectomy with removal of a single enlarged gland at the North Carolina Memorial Hospital (1974 to 1984) were reviewed. The preoperative calcium and immunoparathormone levels were correlated to the weight and calculated volume of the removed gland. The calcium level was found to be significantly associated with parathyroid gland weight and volume (p less than 0.001), as determined by linear regression analysis. Despite the statistical association, the correlation coefficient (calculated with the Pearson correlation matrix) was low, 0.16 for the relation of calcium to gland weight and 0.25 for the relation of calcium to calculated gland volume. The calculated coefficients of correlation of iPTH (three different assays) to gland weight and volume were similarly low. These findings demonstrate a variable relationship between the preoperative serum calcium level or the iPTH level to the weight or volume of the enlarged hyperfunctioning parathyroid gland. Identification of the pathologic parathyroid gland(s) in primary hyperparathyroidism cannot be based on a perceived relation of preoperative calcium or iPTH levels to the size of the enlarged glands.

Adolescent↗