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M A Block

Publications and source records attributed to M A Block.

At least 55 records · Page 3Linked to original sources
PubMed1982

Age-related probability of development of hereditary medullary thyroid carcinoma.

Hereditary medullary thyroid carcinoma is inherited as an autosomal dominant trait; at birth each child of an affected parent has a 50% chance of developing the disease. Measurement of plasma calcitonin concentrations after provocative calcium or pentagastrin stimulation has proved useful in the early diagnosis of this disease. To determine the age-related risk of conversion from a negative to a positive provocative test, 445 members of 11 kindreds were studied with sequential tests. Of 159 family members with a 50% risk at birth of developing medullary thyroid carcinoma 38 converted from a negative to a positive test result (mean age of conversion was 15 years). By means of methods previously described for determining the age-related probability for developing Huntington chorea, we present a method for determining the probability of development of medullary thyroid carcinoma. An individual at risk whose test result was negative had the following probability of converting to a positive test result at a later date: age (years)/probability, 0/0.5; 5/0.49; 10/0.41; 15/0.25; 20/0.16; 25/0.10, 30/0.05; and 35/0. We conclude that hereditary medullary thyroid carcinoma is regularly detectable in the pediatric age group and that screening should begin by age 5 years and be continued at regular intervals until age 35.

Adolescent↗
PubMed1982

Probable clonal origin of aldosteronomas versus multicellular origin of parathyroid "adenomas".

Adrenocortical adenomas causing hyperaldosteronism in two women heterozygous at the X chromosome-linked glucose-6-phosphate dehydrogenase (G-6-PD) locus exhibited only one G-6-PD isoenzyme. This finding suggests a clonal development for these benign tumors and contrasts with the multicellular origin of parathyroid adenomas reported in three patients from our institution in 1977 and found subsequently in seven other hyperparathyroid women whose cases are reported here. One of these seven patients had hereditary hyperparathyroidism. In this case each of three glands removed showed both A and B G-6-PD isoenzymes in similar ratios as were found in normal tissues. The multicellular origin of hereditary hyperparathyroidism is compatible with the concept of parathyroid lesions being manifestations of the first genetic event in Knudson's two-mutational-event theory for the initiation of cancer. The multicellular origin of sporadic parathyroid tumors suggest that they are caused by some factors stimulating many cells in the parathyroid glands. The young average age of onset of eight cases of parathyroid cancer from five families with hereditary hyperparathyroidism in the literature is also compatible with Knudson's theory. G-6-PD studies of other aldosteronomas, parathyroid tumors, and other endocrine neoplasms may provide important information about the pathogenesis of these conditions.

Adenoma↗
PubMed1981

Primary treatment of well-differentiated thyroid cancer.

Operations for well-differentiated thyroid carcinoma should be individualized on the basis of the pathologic variety and clinically demonstrated extent of carcinoma. Although precise studies have not been carried out specifically to provide treatment plans for various clinical situations, experience does provide management policies to follow currently. The basic operation is thyroid lobectomy. This appears adequate for minimal carcinoma, small (under 1.5 cm diameter) carcinoma, and low grade encapsulated follicular carcinomas of the thyroid. Extent of operation for other clinical patterns of well-differentiated thyroid carcinoma is indivualized to permit control of the disease in the neck. If well-differentiated carcinoma is recognized only postoperatively, a decision for reoperation can relate to evidence of multicentricity. Improvements in autotransplantation of parathyroid tissue and diagnostic needle biopsy have permitted improvements in therapy in recent years.

Adenocarcinoma↗
PubMed1981

Effects of sphincter of Oddi bypass on bile acid metabolism in fed and fasted intact and cholecystectomized dogs.

The effects of cholecystectomy and sphincter of Oddi bypass on bile acid (BA) metabolism in dogs have been studied. Cholecystectomy and sphincter bypass decreased the BA pool half-life and increased the percent of taurodeoxycholic acid in the pool. A 48-hour fast had no effect on total BA pool size of intact and intact sphincter-of-Oddi-bypassed dogs but caused a marked decrease in cholecystectomized dogs. It was concluded that while the sphincter of Oddi is unnecessary to maintain bile acid pool size in fasting dogs, the gallbladder is. Alimentation is necessary to maintain pool size in cholecystectomized dogs.

Ampulla of Vater↗
PubMed1981

Treatment of well-differentiated thyroid carcinoma.

Improved selection of thyroid nodules for surgery and greater individualization of surgery for well-differentiated thyroid carcinoma are emphasized. Thyroid nodules are common but infrequently are manifestations of carcinoma. Needle biopsy permits better selection of patients with thyroid nodules for surgery by identifying those which are malignant or are likely to become malignant. Experience in performing diagnostic needle biopsies and in cytologic and histologic interpretation is essential. The majority of well-differentiated thyroid carcinomas are well-localized papillary carcinomas controlled by surgery, usually a lobectomy or partial thyroidectomy. Well-differentiated thyroid carcinomas include papillary and follicular types and their subsets. The extent of surgery should be individualized based on gross extent of disease, histologic variety, and age of the patient. The prognosis is reduced for patients more than 40 years of age. With appropriate early surgical treatment, the outlook is excellent. Metastatic disease can frequently also be controlled by large doses of thyroid hormone and the use of radioactive iodine.

Adenocarcinoma↗
PubMed1980

Site of synthesis of geranylgeraniol derivatives in intact spinach chloroplasts.

Chloroplasts isolated from fully developed spinach leaves and incubated in the presence of isopentenyl pyrophosphate were able to synthesize rapidly geranylgeranyl chlorophyll alpha and geranylgeraniol. The biosynthesis of the geranylgeraniol derivatives from isopentenyl pyrophosphate is a compartimentalized process. The membrane fractions (thylakoid and envelope membranes) were essentially unable to synthesize geranylgeraniol, geranylgeranyl pyrophosphate and geranylgeranyl chlorophyll alpha. When stromal and thylakoid fractions were combined the capacity to synthesize geranylgeranyl chlorophyll alpha and geranylgeraniol was restored. When stromal and envelope membrane fractions were combined the capacity to synthesize gernylgeranyl pyrophosphate and geranylgeraniol was restored. The products of the reaction were discharged inside the lipid phase of the membranes.

Cell Compartmentation↗
PubMed1980

Clinical characteristics distinguishing hereditary from sporadic medullary thyroid carcinoma. Treatment implications.

Distinctive differences between the hereditary and sporadic varieties of medullary thyroid carcinoma include the uniform bilaterality, consistent association of C cell hyperplasia, and the frequent association with other endocrine lesions as characteristics of the hereditary type. Total thyroidectomy is required for hereditary medullary thyroid carcinoma. Lateral cervical lymph node dissections do not appear necessary for the hereditary type when not palpable, detected only by family screening, and when biopsy of midjugular lymph nodes shows no evidence of metastasis. For palpable medullary thyroid carcinoma, the eradication of all cervical locations is unlikely to result in normal or undetectable levels of serum calcitonin postoperatively, even though such appears more likely for the sporadic variety.

Adrenal Gland Neoplasms↗
PubMed1980

Hyperparathyroidism following head and neck irradiation.

A history of head and neck irradiation in childhood or adolescence was found in 22 of 130 patients with primary hyperparathyroidism compared with only 12 of 400 control patients, a significant difference (P less than .025). Among 200 patients with a known history of childhood irradiation, biochemical or surgical evidence of hyperparathyroidism was found in ten, a prevalence of 5%. This is at least 30 times the prevalence of hyperparathyroidism in the general population (P less than .025). The data indicate that head and neck irradiation should be regarded as an important risk factor in the subsequent development of hyperparathyroidism.

Adenoma↗
PubMed1979

The two-mutational-event theory in medullary thyroid cancer.

Comparisons are presented of the ages of onset of 20 cases of hereditary medullary carcinoma of the thyroid (MCT) and of 22 sporadic cases of this same type of cancer. These data are compatible with what might be expected by the two-mutational-event theory of the initiation of cancer postulated by Knudson. It had been previously postulated that C-cell hyperplasia of the thyroid was a premalignant change resulting from the first or genetic mutational event in the initiation of this type of cancer. The finding of C-cell hyperplasia in thyroid glands of each of the 10 patients with the hereditary condition and in none of the 10 sporadic patients is compatible with this theory. The C-cell hyperplasia is believed to be the expression of the genetic mutation, which requires a subsequent somatic mutation to transform the initially mutated cell into a cancer cell.

Adolescent↗