Biomedical subjects
Publications and source records attributed to B J Witrak.
A 7-month-old male presented with a 2 X 3 cm soft tissue mass overlying the right mastoid bone. An underlying bony defect was palpable. Plain skull films, CT scan and cerebral arteriogram showed the classic radiologic findings of a sinus pericranii. This rare vascular anomaly is briefly discussed.
Intracranial tuberculosis is often insidious, may be difficult to diagnose clinically, and is neurologically devastating if untreated. The advent of computerized tomography has permitted earlier detection of the structural abnormalities associated with intracranial tuberculosis than was possible with older techniques. Correct radiologic interpretation can heighten the index of suspicion for what is often an overlooked diagnosis and can lead to earlier treatment, with decreased morbidity and mortality. We present four cases that cover the spectrum of abnormalities of intracranial tuberculosis shown by CT.
Here we report a highly sensitive and convenient ligand binding assay for the determination of 1,25(OH)2D3 in small volumes of human plasma. This method involves: (1) extraction of vitamin D3 and its metabolites using methanol-methylene chloride with separation of phases by centrifugation; (2) gel chromatography and high pressure liquid chromatography for the quantitative isolation of 1,25-(OH)2D3; and (3) a sensitive ligand binding assay for 1,25-(OH)2D3 employing cytosol receptor from the intestinal mucosa of rachitic chicks. Using modified rachitogenic chick diets allows early (less than 4 wks) harvesting of active receptor for 1,25-(OH)2D3 in high yield. The method includes a rapid and effective procedure for stable and long-term storage of the active cytosol receptor. A convenient dextran-charcoal means is used for the separation of receptor bound from free 1,25-(OH)2D3 resulting in the achievement of a lower (less than 5%) background (i.e., nonspecific binding) than reported for other 1,25-(OH)2D3 assays. Analysis of this receptor shows it to be a saturable, single class of binding sites with a dissociation constant (Kd) of approximately 3.7 x 10-11. The final recovery of 1,25-(OH)2D3 following extraction and chromatography is 80 +/- 3% and triplicate determinations can be made on a 3 ml plasma sample. The ligand binding assay routinely detects less than or equal to 5pg of 1,25-(OH)2D3 per assay tube and the inter- and intraassay variation, based on repeated determinations of 1,25-(OH)2D3 in pooled normal human plasma, is less than 5%. Preliminary studies indicate that our methodology will permit measurement of plasma 1,25-(OH)2D3 levels in all normal subjects and in pathophysiologic states where 1,25-(OH)2D3 levels may be below or above normal values. 1,25-(OH)2D3 values (pg/ml +/- SEM) in human plasma obtained from both normals and patients with various untreated calcium homeostatic disorders were: normals = 33.5 +/- 1.8; end-stage chronic renal failure = 5.1 +/- 1.2; primary hypoparathyroidism = 18.3 +/- 2.8; primary hyperparathyroidism = 61.4 +/- 7.1; and hyperthyroidism with associated hypercalcemia = 42.1 +/- 8.4.