Search PubMed⌕ Search

Biomedical subjects

A M Lawrence

Publications and source records attributed to A M Lawrence.

At least 109 records · Page 6Linked to original sources
PubMed1982

TSH in the rat and monkey brain. Distribution, characterization and effect of hypophysectomy.

Characterization of the molecular, immunological and biological properties of a thyrotropin-stimulating hormone (TSH)-like peptide in rodent brain tissue showed similarities to its pituitary counterpart. The distribution of immunoreactivity in rodent brain was determined by radioimmunoassay in both intact and hypophysectomized animals. Easily detectable but smaller quantities of immunoassayable TSH were present in formalin fixed, acetone-stored brains from Macaca mullata. No change in the level of this TSH-like peptide was observed in most rat brain parts, although the hypothalamus did show a significant drop in hormone level after removal of the pituitary. Extracts of brain containing TSH-like material restored thyroid histology to normal when administered to hypophysectomized rats. Tissue cultured neural cells from both intact and hypophysectomized rats released a TSH-like material into the medium over a 30-day time period. Sodium l-thyroxine suppressed TSH release from pituitary monolayers but did not alter TSH release from brain derived cells that were similarly cultured. Surgical thyroidectomy resulted in a striking rise in serum TSH concentrations with no alteration in the content of brain TSH.

Animals↗
PubMed1982

Simultaneous primary hyperparathyroidism and nodular thyroid disease.

Of 351 patients treated for primary hyperparathyroidism from 1966 to 1981, 70 (20%) had grossly evident nodular thyroid disease at the time of subtotal parathyroidectomy. These patients have been reviewed to determine if prior radiation exposure may play a role in their coexistence and if combined subtotal parathyroidectomy and thyroidectomy are safe and efficacious. Thirty-three of the 70 patients (47%) had received prior radiation therapy for benign conditions of the head and neck. Nine of 15 patients with nonmedullary thyroid carcinoma had received previous irradiation. In addition to subtotal parathyroidectomy, 28 patients underwent total thyroidectomy, 14 underwent bilateral subtotal thyroidectomy, and 28 underwent unilateral lobectomy. There were no deaths and no permanent recurrent laryngeal nerve injury from combined subtotal parathyroidectomy and thyroidectomy. Two patients in whom parathyroid tissue was not autotransplanted required calcium and vitamin D supplementation. This study shows that (1) primary hyperparathyroidism and nodular thyroid disease occur simultaneously with sufficient frequency to warrant careful preoperative and intraoperative evaluation of both glands, (2) radiation probably does play a role in the pathogenesis of coexistent primary hyperparathyroidism and nodular thyroid disease, and (3) in experienced hands combined subtotal parathyroidectomy and thyroidectomy can be safely performed.

Adenoma↗
PubMed1982

Castration induces a marked reduction in the incidence of thyroid cancers.

Although thyroid disease in humans predominates in females, the prognosis of thyroid cancer in males is much less favorable. To further explore the role of male sex hormones, we utilized the experimental model of radiation-induced follicular cancer in the rat, studying the effects of castration on tumor development. Microscopic evidence of tumor formation was correlated with the biochemical parameters serum thyroxine (T4), thyrotropin (TSH), and thyrocalcitonin (TC) at 24 months. The incidence of follicular carcinomas in intact males ws 58%, compared to 28% in comparable females. Castration of males caused a reduction in the incidence to 22%. Mean circulating levels of TSH were markedly elevated in all three irradiated groups. Mean T4 levels were reduced significantly only in irradiated castrated animals. TC levels were reduced in all irradiated groups. We conclude that although elevated levels of TSH probably play a significant role in the development of radioactive iodine-triggered follicular thyroid neoplasms in the rat, male sex hormone may also play an important role beyond their known effect on basal and thyrotropin-releasing hormone-stimulated TSH.

Adenocarcinoma↗
PubMed1981

Subtotal parathyroidectomy: normalization of circulating parathormone.

Subtotal parathyroidectomy was performed in 52 consecutive patients with primary hyperparathyroidism. The postoperative results, 6-24 months following the operation, were evaluated according to a calcium-parathormone normogram. In 48 patients the values returned to the normal zone. Two patients had persistent hypercalcemia. The other two patients remained in the hyperparathyroid zone of the normogram, with moderate elevations of serum parathormone, in spite of normocalcemia. The significance of the failure to achieve normal circulating parathormone levels in patients with postoperative eucalcemia is discussed. The importance of serum parathormone and calcium relationship in the evaluation of patients following parathyroidectomy is emphasized.

Calcium↗
PubMed1981

Unexpected parathyroid disease discovered at thyroidectomy in irradiated patients.

Eight of 23 patients undergoing total thyroidectomy for radiation-associated nodular thyroid disease were found to have unsuspected parathyroid hyperplasia or adenoma at operation. The total serum calcium level was normal preoperatively in each patient. Serum ionized calcium and parathyroid hormone levels were measured in five patients preoperatively and were normal in each case. These pathologic findings in normocalcemic patients may represent a preclinical form of hyperparathyroidism, which would be further evidence linking radiation to the pathogenesis of hyperparathyroidism. The parathyroid glands should be evaluated both pre-operatively and at operation in all patients who have a history of radiation and require thyroidectomy.

Adenoma↗
PubMed1981

Preservation of glucose tolerance and insulin secretory response to repeated glucose levels by the feeding of minimal glucose during prolonged fasting.

The facilitation of glucose disposal (Staub-Traugott effect) and potentiation of serum insulin (IRI) concentration normally occurring after closely spaced intravenous glucose loads, are known to disappear after prolonged starvation. To study the effects of minimal amounts of glucose during fasting upon the insulin response and disposal of repeated intravenous glucose tolerance tests, obese volunteers were fasted for a mean of 25 +/- 2 days, while receiving either 8 or 16 gm of oral glucose every 6 hr, and compared to totally fasted subjects without glucose supplementation. Weight loss rate and the fall in basal IRI and glucose levels were similar to those of totally fasted subjects. However, the Staub-Traugott effect and insulin secretory dynamics after stimulation by repetitive intravenous glucose loading were preserved by this glucose modified fast, while baseline serum glucagon levels (IRG) were significantly lower, and the basal IRI/IRG ratios were thus unchanged from the fed state. IRG and free fatty acid suppression were similar in the fed and glucose modified fasted states. Lactic acid levels increased as expected after the repeated glucose injections in the fed state, but failed to do so after the prolonged modified fast until the second and third repetitive glucose loads, in which a significant rise coincided with accelerated glucose disposal. It is suggested that minimal amounts of carbohydrate during fasting preserve the insulin potentiating action of glucose, preferentially sparing a delayed releasable pool of insulin, while protecting the glucose utilization mechanisms, including increased glycolysis, responsible for the Staub-Traugott effect.

Adult↗
PubMed1981

Hypothalamic LH may play a role in control of pituitary LH release.

We have recently reported immunoassayable luteinizing hormone (LH) in several areas of the rat brain and conspicuously present in the hypothalamus. In this report, we focus on the presence of LH in the hypothalamus and its potential role in regulation of pituitary LH release. In adult female rats, examined during the course of the estrous cycle, a significant fall in hypothalamic LH coincides with the surge in pituitary and serum LH at the time of proestrus, signaling ovulation. Ovariectomized adult rats show no change in hypothalamic LH at a time when there is a dramatic rise in both anterior pituitary and serum LH. These data support the concept that hypothalamic LH is not of pituitary origin and that it may play a role in the short-loop negative feedback system controlling the surge in anterior pituitary LH release, and event initiating ovulation.

Animals↗
PubMed1981

Basilar artery aneurysm simulating pheochromocytoma.

Stimulation of sympathetic vasomotor centers by lesions in the posterior fossa has been described in humans and animals. We describe a patient with a pheochromocytoma-like syndrome and a basilar artery aneurysm. Repair of the aneurysm was followed by disappearance of hypertensive episodes. Posterior fossa lesions must be considered in patients with hypertensive crises when diagnostic procedures do not indicate an adrenal or extra-adrenal pheochromocytoma.

Adrenal Gland Neoplasms↗
PubMed1981

Operative and chemotherapeutic management of malignant glucagon-producing tumors.

Glucagon-producing tumors of the pancreas are among the rarest forms of islet cell tumors. Two patients are described in whom the characteristic dermatitis, glucose intolerance, weight loss, and anemia of the glucagonoma syndrome were due to a metastasizing islet cell carcinoma. In both, removal of the primary tumor with a distal pancreatectomy brought marked relief of all clinical symptoms for 1- and 2-year periods. Because streptozocin, the usual chemotherapeutic agent for these tumors, is quite toxic and frequently unsuccessful dimethyltriazenoimidazole carboximide (DTIC) was used for recurrence after operation. The first patient began taking DTIC when his rash reappeared and his immunoreactive glucagon (IRG) level rose to 6,000 pg/ml (normal, less than 200 pg/ml). Within 3 months, his rash was gone, and IRG level was 75 pg/ml. The second patient developed a neoplastic gastrocolic fistula and was extremely emaciated. With DTIC, the fistula healed, and he gained weight and returned to work. His IRG level has decreased from 2,975 to 200 pg/ml. No side-effects were noted during chemotherapy. Temporary palliation of malignant glucagon-producing neoplasms can be achieved by cytoreductive surgery. When the life-threatening symptoms of this syndrome recur, DTIC chemotherapy seems indicated because of its safety and effectiveness.

Adenoma, Islet Cell↗
PubMed1981

Clinical aspects of glucagon-producing islet cell tumors.

Review of the 55 reported cases of glucagon-producing tumors reveals that a distinctive clinical syndrome consisting of diabetes, a peculiar dermatitis termed necrolytic migratory erythema, weight loss and an increased tendency for thrombosis is associated with these neoplasms. Normochromic normocytic anemia, hypocholesterolemia, hypoproteinemia and generalized hypoaminoacidemia are frequent laboratory findings. Definitive diagnosis of a glucagonoma requires elevation of the fasting serum glucagon level. Selective arteriography of the pancreas has been the best method for localizing these neoplasms preoperatively, but the noninvasive technics of ultrasound and CAT scanning can also be helpful. When the tumor is benign, complete surgical excision can completely reverse all the clinical manifestations of the glucagonoma syndrome and result in lasting cure. Since, however, approximately three-fourths of these tumors are malignant, palliative therapy is frequently required. Cytoreductive surgery can decrease the amount of hormone-producing tissue and can improve or even temporarily reverse the clinical symptomatology. For disseminated disease, chemotherapy is necessary. The best results have been obtained with DTIC although streptozotocin has also been used.

Adenoma, Islet Cell↗
PubMed1981

Hyperparathyroid crisis. Successful treatment of ten comatose patients.

Hyperparathyroid crisis is a rare disease manifested by elevated serum calcium, weakness, nausea and vomiting, altered states of consciousness, and elevated circulating parathormone. This hypercalcemic state is noted for a frequently acute presentation and associated high mortality rate, approaching 60% in some series. Ten patients in parathyroid crisis were observed in a consecutive personal series of 325 cases of operatively proved hyperparthyroidism. All 10 patients were successfully treated. Each patient remained or lapsed into persistent coma despite extensive medical management and normalization of serum calcium in some instances. An emergency parathyroidectomy was performed in all cases. Reversal of the comatose state was noted in all patients within 24 hours, followed by gradual normalization of serum calcium. Serum calcium ranged from 15 to 19.6 mg/dl. The blood urea nitrogen level was elevated in six patients. A single adenoma was found in nine patients and multiglandular disease involving the neck and the mediastinum in one. All patients survived. The successful treatment of this disease demands prompt and accurate diagnosis coupled with vigorous medical therapy and emergency parathyroidectomy if the patient's status continues to deteriorate.

Acute Disease↗