Platelet surface charge heterogeneity: characterization of human platelet subpopulations separated by high voltage continuous flow electrophoresis

Washed formol-fixed normal human platelets have been separated into surface charge-dependent subpopulations using high voltage continuous flow electrophoresis. The procedure is highly reproducible and the heterogeneity profile extends over 20-25 fraction tubes on the anodal side of the entry port to the separation chamber. Fractions have been subdivided into subpopulation pools A, B and C which have mean mobilities by analytical cytopherometry extending over the range 0.81-0.91 micron/s/V/cm from the least (C) to the most (A) electronegative cells. Coulter volume differences across the profile from 5.0 to 12.8 fl correlated well with electrophoretic mobilities whereas buoyant density appeared to be an independent parameter. Analysis of surface neuraminidase-labile sialic acid of the platelets in pools A and C correlated well with differences in electrophoretic mobility, whereas a similar relationship for the alkaline phosphatase-labile phosphate moieties (also believed to be contributory to cell surface electrokinetic properties) could not be established even though in both cases the profiles of the enzyme-treated platelets showed significant shifts towards the cathode when compared with untreated cells. Titration of surface DTNB-reactive sulphydryl (-SH) groups revealed an inverse relationship between electronegativity and membrane -SH group status. This electrophoretic expression of subpopulation heterogeneity within the circulating platelet pool may have advantages in studying clinical conditions where the profiles may reflect cell surface interactions 'in vivo'.     

Paediatric day surgery.

An in-depth study of the experience of 10 children admitted for day surgery revealed that parents received little information before the admission and that this was not compensated for by the information given on admission. Most of the children underwent excessively long pre-operative fasts and only three out of the 10 children were actually discharged on the day of their operation.     

Atrioventricular pacing in congenital heart disease.

We have attempted to optimize cardiac performance in patients with congenital heart disease requiring artificial pacing by using pacemakers capable of both sensing and pacing both the atrium and the ventricle (DDD). We reviewed our results with 88 patients receiving DDD devices to determine the safety and dependability of these devices in children. Age ranged from 1 hour to 25 years. Endocardial leads were used in 68 patients, whereas epicardial leads were used in 20 patients. Previous cardiac procedures had been done in 30 patients. There were nine deaths but none due to pacemaker malfunction. Endocardial leads functioned better than epicardial leads. Ninety-eight percent of patients with endocardial leads and 62% of patients with epicardial leads were maintained in the DDD mode. Complications were infrequent and all were corrected without long-term sequelae. The DDD mode may offer considerable benefits to children who require artificial pacing. Our data allow us to conclude that most children can be paced safely and dependably in the DDD mode.     

Minimum scan speeds for suppression of motion artifacts in CT.

Cardiac and ventilatory motions cause artifacts at chest computed tomography (CT). To determine how short the scan times on third-generation units must be to avoid such artifacts, motion was measured with fast and ultrafast CT scans. Minimum detectable motion was then determined. The longest scan time that avoided a barely perceptible artifact was calculated by dividing the minimum detectable motion by the peak physiologic velocity. The posterior left ventricular wall moved at a maximum velocity of 52.5 mm/sec, necessitating a scan time of 19.1 msec or less to avoid artifact. Lung vessels near the heart moved at 40.5 mm/sec for a scan time of 24.7 msec or less. During quiet breathing, pulmonary vessels moved at 10.7 mm/sec for a scan time of 93.5 msec or less. The authors conclude that the shortest scan time on third-generation units (0.6 second) cannot prevent all artifacts arising from motion in the chest. Even ultrafast scan times (50 msec) are not short enough to eliminate artifacts on these units. Thus, reduction of motion artifacts will require techniques other than fast scanning.     

Long chain polyunsaturated fatty acids and fetal growth

Long chain polyunsaturated fatty acid composition of plasma choline phosphoglycerides has been measured at birth in 22 preterm infants. Positive correlations were found between both n-6 and n-3 fatty acids and measurements of growth and maturation. 20:4(n-6) and the sum of 20:3(n-6) + 20:4(n-6) correlated most strongly with weight and head circumference, while 22:6(n-3) showed strongest correlation with length of gestation. These findings are of relevance to understanding the role of nutrition in fetal growth and in establishing the group of infants most at risk of postnatal deficiency of essential fatty acids.     

Neurofilament distribution and organization in the myelinated axons of the peripheral nervous system

The nature of neurofilament organization within the axonal cytoskeleton has been the subject of controversy for many years. Previous reports have suggested that neurofilaments are randomly distributed in the radial dimension of the myelinated axon. Randomness of distribution implies that there is no interaction between neurofilaments, while order in distribution suggest the presence of forces between neurofilaments. To address the issue of randomness vs. order, we evaluated neurofilament distribution by two different statistical approaches—nearest-neighbor distance and the Poisson tile-counting method. Neurofilament nearest-neighbor distances in a myelinated axon differ from nearest-neighbor distances of a set of random points with similar density (40.6 ± 7.0nm vs.30.7 ± 12.9nm, P < 0.0001). The Poisson tile-counting method also indicated that neurofilament distribution is different from a random distribution, under conditions of appropriate tile size and masking of other organelles. To further characterize the distribution of neurofilaments, we compared the relationship between nearest-neighbor distance and density for three sets of data: evenly spaced points, randomly distributed points and measured neurofilament coordinates. Neurofilaments do not conform to either evenly spaced or random distribution models. Instead, neurofilament distribution falls into an intermediate position between evenly spaced and random distributions. This study also demonstrates that the nearest-neighbor distance method of assessing neurofilament distribution offers several technical and theoretical advantages to the Poisson tile-counting method.     

Massive extracapsular hemorrhage from a parathyroid cyst

A 32-year-old man had a giant cervical mass, dysphagia, dyspnea, and severe hypercalcemia. A computed tomographic scan showed the mass to extend from the left mandible to the level of the aortic arch. Exploratory surgery of the neck revealed a ruptured parathyroid cyst complicated by massive hemorrhage into the cervical tissues and mediastinum. The postoperative course was uncomplicated with prompt resolution of the hypercalcemia. Although a rare occurrence, extracapsular parathyroid hemorrhage should be considered in the differential diagnosis of all rapidly evolving cervical and mediastinal masses, especially when hypercalcemia is present.