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Biomedical subjects

O H Clark

Publications and source records attributed to O H Clark.

At least 199 records · Page 11Linked to original sources
PubMed1984

Do the prognoses of papillary and follicular thyroid carcinomas differ?

Our 44 patients with follicular thyroid carcinoma had a survival rate similar to patients of the same age and sex with papillary carcinoma. By matching our patients by age and sex, this study appears to show that the biologic behavior of differentiated thyroid carcinomas is better correlated with the age and sex of the patients than with the pathologic classification of papillary carcinoma or follicular carcinoma; therefore, it is unnecessary to distinguish between patients with papillary carcinoma and follicular carcinoma from a prognostic standpoint. A classification considering all well-differentiated thyroid carcinomas as one disease with behavioral variability due to constitutional factors such as age and sex should be adopted.

Adenocarcinoma↗
PubMed1984

Magnetic resonance imaging of the neck. Part I: Normal anatomy.

Magnetic resonance (MR) images of the neck were obtained in 24 patients using a specially designed radio-frequency coil, standard and high-resolution imaging techniques, and a variety of spin echo and inversion recovery pulse sequences. Cervical vascular structures were more easily identified with MR than with CT because of the inherent contrast of flowing blood. The laryngeal skeleton, paralaryngeal tissues, trachea, thyroid, esophagus, and muscles were identified in all cases by MR using morphologic criteria comparable with CT criteria. The spatial resolution of high-resolution MR was slightly inferior to high-resolution CT. However, streak artifacts due to motion and x-ray beam hardening often limited CT, but did not affect MR. Anatomic resolution was best using high-resolution spin echo images obtained with TR = 2.0 seconds and TE = 28 msec because this imaging technique offered excellent contrast between normal tissues and had the highest signal-to-noise ratio. With further improvements in spatial resolution MR is likely to become an important technique for imaging the neck.

Adolescent↗
PubMed1984

Magnetic resonance imaging of the neck. Part II: Pathologic findings.

Magnetic resonance (MR) images of the neck were obtained in 14 patients with thyroid, parathyroid, lymph node, or laryngeal lesions. Tumors and lymph nodes were more easily differentiated from muscle and blood vessels with MR than with CT because of the superior soft tissue contrast of MR. Tissue characterization allowed MR differentiation of thyroid nodules, thyroid cysts, and parathyroid tumors from normal thyroid tissue; however, nonspecifically increased T1 and T2 relaxation times overlapped for a variety of neoplastic and inflammatory conditions. Thyroid cyst fluid had the greatest water content and longest T1 and T2 times of all tissues studied. Parathyroid hyperplasia could not be differentiated from parathyroid adenoma; however, parathyroid tumors had slightly longer T1 and T2 times than thyroid nodules or lymph nodes. With further experience, MR tissue characterization may become a useful technique for evaluating neck masses.

Adolescent↗
PubMed1984

Magnetic resonance imaging of the thyroid, thymus, and parathyroid glands.

Magnetic resonance (MR) images of the neck were obtained in 16 patients with use of a variety of spin echo and inversion recovery pulse sequences. Anatomic resolution was best with high-resolution spin echo images obtained with the pulse sequence repetition rate equal to 2.0 seconds and the echo delay equal to 28 msec because this imaging technique offered excellent contrast between normal tissues and had the highest signal noise ratio. The spatial resolution of MR was nearly as good as state of the art computerized tomography (CT). However, streak artifacts caused by motion and x-ray beam hardening often limited CT but did not affect MR. Tumors and lymph nodes were more easily differentiated from muscle and blood vessels with MR than with CT because of the superior soft-tissue contrast of MR. Tissue characterization allowed MR differentiation of thyroid nodules, thyroid cysts, and parathyroid tumors from normal thyroid tissue. Thyroid cyst fluid had the greatest water content and longest T1 and T2 relaxation times of all tissues studied. However, nonspecifically increased T1 and T2 relaxation times overlapped for a variety of neoplastic and inflammatory conditions. With further experience, MR imaging is likely to become a useful technique for the evaluation of neck masses.

Adenoma↗
PubMed1983

Milk alkali syndrome. Does it exist and can it be differentiated from primary hyperparathyroidism?

Four patients with milk-alkali syndrome (MAS) presented with many of the characteristics of primary hyperparathyroidism including hypercalcemia, low or normal serum phosphorus levels, normal or increased urinary calcium levels, and inappropriately high or elevated serum parathyroid hormone levels. These laboratory findings differ from those classically described in MAS, i.e., hypercalcemia without hypercalciuria and a normal or high plasma phosphate level. Because the serum calcium level failed to return to normal after two weeks of hydration and a low calcium diet, and because of the inability to distinguish this syndrome from primary hyperparathyroidism, two of the four patients underwent neck exploration. Four normal parathyroid glands were histologically proven in each, and at autopsy in a third patient, there was no evidence of parathyroid hyperplasia or adenoma. Hypercalcemia eventually resolved in all patients with a low-calcium diet for as long as six months. Of the several features of MAS, hypercalcemia, alkalosis in the presence of azotemia, a history of increased calcium and alkali intake, and a response to dietary calcium restriction are helpful in differentiating this syndrome from primary hyperparathyroidism. Laboratory tests in patients with MAS may be confusing and the return to normocalcemia in response to a calcium deficient diet may be delayed.

Aged↗
PubMed1983

Parathyroid scanning by computed tomography.

Conventional parathyroid computed-tomographic scanning detected 51% (29/57) of tumors averaging 1.5 X 1.0 X 0.8 cm in size at surgery. Forty-six per cent (7/43) of the scans were uninterpretable due to shoulder-streak artifacts. Using a specially designed patient positioning device and a new imaging protocol involving dynamic scanning and the intravenous administration of a bolus of contrast material, 14 patients were scanned; 78% (18/23) of tumors averaging 1.4 X 1.0 X 0.8 cm in size were detected. All 14 scans were interpretable, and image quality was markedly improved.

Contrast Media↗
PubMed1983

Characterization of the thyrotropin receptor-adenylate cyclase system in neoplastic human thyroid tissue.

Experiments were performed to determine whether the TSH receptor-adenylate cyclase (AC) system in benign and malignant thyroid neoplasms differs from the TSH receptor-AC system in normal thyroid tissue removed from the same patients. TSH binding and AC assays were performed using the same in vitro conditions. TSH binding was rapid, reversible, saturable, and hormone specific in particulate fractions from both normal and neoplastic thyroid tissue. A positive correlation existed between the equilibrium constants for [125I]bovine ([125I]bTSH) TSH binding and the concentration of TSH required to activate AC, suggesting that binding sites were coupled to AC in neoplastic thyroid tissue. Mean values for dissociation constants (Kd1 and Kd2), capacity (site 2), as determined by Scatchard analysis, and nonspecific binding (NSB) for the TSH receptors were lower in neoplastic thyroid. Some normal thyroid tissue appeared to lack a high affinity site, and some tumors lacked a low affinity binding site. Hormone specificities (bTSH, human (h) TSH, hLH, hFSH, hGH, hACTH, and glucagon) in normal thyroid and neoplastic tissue were virtually identical. hFSH, hACTH, hGH, and glucagon failed to inhibit [125I]bTSH binding or stimulate AC in either normal or neoplastic thyroid tissue, whereas hLH inhibited [125I]bTSH binding and stimulated AC, but required 10- to 100-fold higher concentrations than hTSH or bTSH. The specific binding and NSB of [125I]bTSH in both normal and neoplastic thyroid tissue was highest at pH 7.0 and lowest at pH 8.3. In contrast to bTSH binding, TSH stimulation of AC was lowest at pH 7.0 in both normal and neoplastic tissues and highest at pH levels of 7.5-8.0. TSH binding and TSH stimulation of AC activity were highest in the absence of NaCl and decreased progressively as the salt concentration was increased in both normal and neoplastic thyroid tissues. Increasing the sucrose concentration and, thus, the osmolarity of the system had a minimal effect on the binding of [125I]bTSH. Preincubation with ammonium sulfate did not significantly influence binding. Basal AC activity and the AC response to TSH were greater in neoplastic thyroid than in normal tissues. These studies demonstrate that changes in salt concentration and pH affect the TSH receptor-cyclase system in a comparable fashion in normal and neoplastic thyroid tissues. The discriminatory properties of the TSH receptor are also maintained in thyroid neoplasms. Thyroid tumors, however, have a higher affinity for TSH and display a greater AC response to TSH than normal thyroid tissue.

Adenylyl Cyclases↗
PubMed1983

Parathyroid imaging: comparison of high-resolution CT and high-resolution sonography.

Parathyroid computed tomographic (CT) scanning using a specially designed patient positioning harness, bolus contrast administration, and dynamic scanning significantly improved localization of parathyroid tumors from 45% (19/42) to 76% (35/46) (p less than 0.01) over conventional CT scanning. High-resolution sonography with a 10 MHz transducer localized 65% (57/88) of these tumors. Average tumor size was 15 X 10 X 9 mm. Patients undergoing reoperation for hyperparathyroidism had similarly small tumors localized by CT in 63% (12/19) and high-resolution sonography in 47% (9/19) of cases. High-resolution sonographic equipment suitable for parathyroid imaging is not widely available. Since high-resolution CT is more generally available and more effective, it is recommended as the procedure of choice for localizing cervical parathyroid tumors.

Adenoma↗
PubMed1983

High-resolution ultrasonography and computed tomography of thyroid lesions in patients with hyperparathyroidism.

High-resolution ultrasonography and computed tomography examinations of the thyroid gland were compared with surgical inspection of the thyroid gland at the time of parathyroid surgery in 65 patients with hyperparathyroidism. Twenty-six patients (40%) had one or more nonpalpable thyroid lesions. Thirty benign thyroid lesions averaged 7 mm in size. A 5 mm follicular carcinoma and a 20 mm recurrent medullary carcinoma were also identified. Ultrasonography detected 88% (28/32), computed tomography detected 59% (19/32), and surgical inspection detected 84% (27/32) of the thyroid lesions. Preoperative ultrasonography with a 10 MHz small-parts real-time scanner is suited ideally to complement surgical inspection of the thyroid for delineation of small thyroid lesions in order to determine whether the lesions are solid or cystic and whether they are single or multiple. This information may be important to determine whether biopsy is necessary.

Adult↗
PubMed1983

Rapid localization of parathyroid tumors by selective venous catheterization and parathyroid hormone bioassay.

Selective venous catheterization with parathyroid hormone radioimmunoassay has been used effectively to localize parathyroid tumors in patients who have previously had failed parathyroid operations. We have analyzed our experience comparing radioimmunoassay and bioassay of parathyroid hormone for localization of parathyroid tumors by selective venous sampling. The bioassay, which uses a guanyl nucleotide-amplified adenylate cyclase assay with canine renal plasma membranes, localized the tumors in six of nine patients who had previously undergone neck operations. The radioimmunoassay localized the tumors in eight of the nine patients. The advantage of the bioassay is that it requires only 50 microliter serum per per sample and 1 day of assay time compared with the radioimmunoassay, which requires 700 microliter serum per sample and 7 days of assay time. The bioassay may be important in patients with severe hyperparathyroidism who require an urgent operation.

Biological Assay↗
PubMed1982

Total thyroidectomy: the treatment of choice for patients with differentiated thyroid cancer.

There is considerable controversy about the most appropriate treatment of patients with thyroid cancer. This report concerns the author's experience with 82 consecutive patients having total thyroidectomy from January 1977 through December 1981. The age of the patients ranged from 21 to 86 years (mean age 44 years). There were 44 women and 38 men. Twenty-four patients (29%) had had previous thyroid operations; ten patients (11%) had coexistent parathyroid adenomas removed; and seven patients (8.5%) had modified radical neck dissections. Thirty-four patients (41%) had a history of radiation to the head and neck, and 12 (35%) of the 34 irradiated patients and 51 (63%) of the entire group of 82 patients had thyroid cancer (45 papillary, five follicular, one medullary). Coexistent lesions in the patients with papillary cancer included Hashimoto's thyroiditis, five patients; parathyroid adenomas, four patients; Graves' disease, one patient; Hurthle cell neoplasm, one patient; and amyloid struma, one patient. If less than total thyroidectomy had been performed, 26 (51%) of the 51 patients with thyroid cancer would have had cancer left in the residual thyroid lobe, and focal cancers in the lobe opposite to the one containing the nodule for which the operation was performed would have been missed in five patients (10%). Five of the 20 patients with unilateral cancer had follicular cancer. Complications included one case of permanent hypoparathyroidism and two cases of transient bilateral recurrent laryngeal nerve palsy. Ninety-six per cent of the patients were discharged within four days of thyroidectomy, 94% by three days, and 79% by two days. Uptake of radioactive iodine was not above background levels in nine (26%) of the 35 patients studied after operation and was less than 1% in the remainder. These data suggest that total thyroidectomy is the treatment of choice for patients with thyroid cancer because residual cancer would persist in the remaining thyroid tissue in at least 61% of patients if only lobectomy had been performed. Total thyroidectomy can be done with minimal permanent disability in patients with benign and malignant thyroid tumors, in patients who have had previous thyroid operations, and in patients with coexistent hyperparathyroidism.

Adult↗
PubMed1982

Thyrotropin binding and adenylate cyclase activation in normal and neoplastic human thyroid tissue: lack of effect of thyroglobulin.

The effects of bovine TSH (bTSH) and bovine (bTg) and human thyroglobulin (hTg) on the binding of [125I] bTSH and the activation of adenylate cyclase (AC) were studied in both normal and neoplastic human thyroid homogenates in vitro using adenylate cyclase conditions. [125I]bTSH bound specifically and with high affinity to a particulate fraction from normal thyroid and from benign and malignant thyroid neoplasms; this binding was inhibited by unlabeled bTSH (approximate Kd = 10.0 mU/ml for normal tissue; Kd = 2.5 mU/ml for thyroid neoplasms). Half-maximal activation of AC was obtained at a TSH concentration of approximately 2.5 mU/ml for both normal and neoplastic thyroid tissue, indicating that the high affinity TSH receptors are coupled to AC, at least in the neoplastic thyroid tissue. bTg and hTg did not inhibit [125I]bTSH binding to high affinity TSH receptors in either normal or neoplastic thyroid tissue. bTSH increased AC activity up to 25-fold in neoplastic thyroid tissue and up to 4-fold in normal thyroid tissue, whereas at concentrations up to 1 mg/ml, bTg had no effect. The current study demonstrates that bTSH binds to specific, high affinity receptors and stimulates AC activity in both normal and neoplastic thyroid tissue. bTg and hTg, under the conditions used in this experiment, do not influence TSH binding to its high affinity receptor in these tissues. Since Tg does not influence high affinity TSH binding or AC activity in a particulate fraction rich in plasma membranes from normal or neoplastic thyroid tissue, it is unlikely to have a modulating role on TSH action at the thyroid plasma membrane.

Adenoma↗