Development of a colorimetric dosimeter for quality control of blood units and irradiators

The development is reported of a reproducible colorimetric irradiation dosimeter that is easy to prepare as well as to interpret. Optimal chloroform, dithizone, and paraffin concentrations to produce a distinctive color change at > 1500 cGy (optimized for 3000 cGy) were determined by combining various concentrations of each component at 65 degrees C. The melted dosimetric material was poured into molds, allowed to solidify, and irradiated with doses ranging from 0 to 3000 cGy. Color change was evaluated visually and spectrophotometrically to determine reproducibility. Twenty-percent chloroform (wt/wt) and a dithizone concentration of 5.0 × 10(-5) M combined in paraffin (TP-2) produced optimal color change from pink to green after > 1500 cGy. The change was reproducible, and 50 individuals were able to distinguish between irradiated and nonirradiated dosimeters. Additionally, five of five of these individuals correctly ranked five dosimeters in order of increasing irradiation from 0 to 3000 cGy, in increments of 750 cGy. This dosimeter is easy to make and easy to read and may allow blood banks to show unit-by-unit quality assurance for irradiated blood components and quality control of the irradiator itself.     

Acetylcholinesterase inhibition in patients with orthostatic intolerance.

The efficacy of current therapeutic measures in orthostatic intolerance (OI) varies among patients and is oftentimes unsatisfactory. New approaches to alleviate symptoms of OI are therefore clearly needed. Recent reports have demonstrated that acetylcholinesterase inhibition is effective in the treatment of orthostatic hypotension with the presumed mechanism of enhancing sympathetic ganglionic transmission. Based on the hypothesis that acetylcholinesterase inhibition, by improving the safety factor of cholinergic transmission, will result in enhanced vascular adrenergic tone and a vagal shift in cardiac sympathovagal balance, we evaluated the role of acetylcholinesterase inhibition in the treatment of patients with OI. We monitored heart rate (HR), blood pressure, and indexes for cardiac output, end-diastolic volume, and systemic resistance continuously in 18 patients with OI during supine rest and during 5 minutes of 70 degrees head-up tilt before and 1 hour after oral administration of 60 mg pyridostigmine. Plasma catecholamines and baroreflex sensitivity were determined for the supine and upright position before and after medication. Patients scored orthostatic symptoms for both tilt studies. The excessive HR response to orthostatic stress was significantly blunted after pyridostigmine administration. HR was significantly lower in the supine and more so in the upright position. Baroreflex sensitivity in the upright position was significantly higher after pyridostigmine. Norepinephrine was increased in both supine and upright position. These changes were associated with significant improvement of orthostatic symptoms. We conclude that pyridostigmine improves orthostatic tolerance in patients with OI. Our findings support the suggested mechanisms of enhanced sympathetic ganglionic neurotransmission and a vagal shift in cardiac sympathovagal balance. Acetylcholinesterase inhibition could be a new useful concept in the treatment of OI.     

Origins of cementum

There are diverging opinions about the role of Hertwig's epithelial root sheath in the formation of cementum. In the present review this role is discussed. There is increasing evidence that Hertwig's epithelial root sheath is actively involved in the formation of both acellular and cellular cementum. The development of acellular cementum seems to be associated with secretion of enamel-related proteins by cells of the epithelial root sheath. Formation of the matrix for cellular cementum appears to be induced by exposure of the inner layer of the epithelial root sheath to the mesenchymal cells in the dental follicle. Experimental studies with I-hydroxyethylidene-I, I-bisphosphonate (HEBP) indicate that the formation of acellular cementum must be preceded by mineralization of the mantle dentin. If the mineralization is inhibited by means of HEBP, there is precocious separation of the two layers of the epithelial root sheath after which matrix for a cellular type of cementum is formed.     

CD antigens 1993: an updated nomenclature for clusters of differentiation on human cells

The 5th International Workshop on Human Leukocyte Differentiation Antigens (Boston, USA, 3-7 November 1993) recommended the adoption of 48 new CD clusters and subclusters and the redefinition of 14 previously established clusters. The additions and changes made to the existing CD nomenclature are summarized in a Table.