Prolactin-producing pituitary adenoma and carcinoma with neuronal components--a metaplastic lesion.

Recent studies indicate that cells of various epithelial tumors are capable of transformation to neurons. Observing both neurons and neuropil in two prolactin-producing adenohypophyseal tumors, one benign and one malignant, we sought to assess their cellular differentiation, the presence of nerve growth factor receptor, and expression of the dopamine receptor gene using immunocytochemistry, electron microscopy, and in situ hybridization. Light and electron microscopy clearly revealed cells morphologically transitional between adenoma/carcinoma cells and neurons. Large neurons lacked proliferative activity. Neurons in varying number showed immunoreactivity for pituitary hormones including prolactin, growth hormone and alpha subunit in the adenoma and prolactin alone in the carcinoma. The distribution of nerve growth factor receptor staining was similar. In both tumors, in situ hybridization showed mRNAs for prolactin and dopamine receptor within adenohypophyseal cells and neurons. Our results indicate that the occurrence of neurons and neuropil in growth hormone and prolactin-producing pituitary tumors appears to be the result of metaplasia. The process is not limited to benign tumors and may be due to the production of tropic substances by the adenohypophysial cells, which by paracrine/autocrine mechanisms result in transformation of adenoma cells to nerve cells.

Reduced storage VQ via secondary quantization.

This paper introduces methods for reducing the table storage required for encoding and decoding with unstructured vector quantization (UVQ) or tree-structured vector quantization (TSVQ). Specifically, a low-storage secondary quantizer is used to compress the code vectors (and test vectors) of the primary quantizer. The relative advantages of uniform and nonuniform secondary quantization are investigated. A Linde-Buzo-Gray (LBG) like algorithm that optimizes the primary UVQ codebook for a given secondary codebook and another that jointly optimizes both primary and secondary codebooks are presented. In comparison to conventional methods, it is found that significant storage reduction is possible (typically a factor of two to three) with little loss of signal-to-noise ratio (SNR). Moreover, when reducing dimension is considered as another method of reducing storage, it is found that the best strategy is a combination of both. The method of secondary quantization is also applied to TSVQ to reduce the table storage required for both encoding and decoding. It is shown that by exploiting the correlation among the test vectors in the tree, both encoder and decoder storage can be significantly reduced with little loss of SNR--by a factor of about four (or two) relative to the conventional method of storing test vectors (or test hyperplanes).

Concurrent Cushing's and Zollinger-Ellison syndromes in a patient with islet cell carcinoma. Case report and review of the literature.

This report documents the simultaneous occurrence of Cushing's and Zollinger-Ellison syndromes in a patient with islet cell carcinoma. The clinical concurrence of these two syndromes has been recorded in only three previous case studies, while three other case reports record evidence suggesting the presence of both gastrin and ACTH within the tumor but without clinical sequelae. In the present report, evidence based on multiple clinical and biochemical data supports the concept that both syndromes are a result of "ectopic" hormone production by the tumor.

Single dose captopril as a diagnostic test for primary aldosteronism.

Most diagnostic tests for primary aldosteronism use maneuvers to expand the extracellular fluid volume, thereby suppressing the renin-angiotensin system. This results in a decline in plasma aldosterone concentrations in normal subjects and essential hypertension (EH) patients, but not in patients with primary aldosteronism. Captopril blocks angiotensin II synthesis and might be used as a diagnostic test for primary aldosteronism. We have measured plasma aldosterone concentrations 2 h after the administration of 25 mg captopril in 9 normotensive subjects, 10 patients with EH, and 12 patients with primary aldosteronism while they were ingesting an unrestricted diet. The plasma aldosterone concentration decreased to less than 15 ng/dl in all normotensive subjects and in 9 of 10 patients with EH, but remained greater than 15 ng/dl in 4 of 5 patients with idiopathic hyperaldosteronism and in all patients with an aldosterone-producing adenoma. The aldosterone to renin ratio was greater than 50 in 4 of 5 patients with idiopathic hyperaldosteronism and in all adenoma patients, but less than 50 in all normotensive subjects and EH patients. A nomogram comparing the plasma aldosterone concentration with the aldosterone to renin ratio clearly separated primary aldosteronism patients from EH patients.

Captopril stimulation of differential renins in renovascular hypertension.

Twenty-six patients being evaluated for renovascular hypertension were studied to assess the diagnostic value of enhancing the differential between renal venous renins (PRA) by a single 25 mg oral dose of converting enzyme inhibitor (CEI, captopril). Antihypertensive medications were not discontinued prior to the study, and renal venous effluent was sampled before and 30 minutes after CEI. Eight patients without stenosis who did not have surgery had post-CEI ratios of less than 3.0. The other 18 patients had operative intervention, with 14 subsequently having improved blood pressure control. Of these 14, seven patients with unilateral stenosis, four patients with bilateral stenosis, and one patient without overt stenosis but with other evidence of reduced renal blood flow had 30-minute PRA ratios of 3.0 or greater. Five of these 14 patients had prestimulation ratios of less than 1.5 and might not be considered operative candidates by conventional criteria. Four other patients unimproved by surgery had post-CEI ratios of less than 3.0 despite a baseline ratio of greater than 1.5 in two of four. Only two patients with post-CEI ratios of less than 3.0 were improved with surgery. We conclude that a 30-minute post-CEI renal venous ratio of 3.0 or greater enhances the probability that patients with renovascular disease, and hypertension will respond to surgical intervention with improved blood pressure control.