Routine chest roentgenograms and electrocardiograms. Usefulness in the hypertensive workup.

We reviewed the records of all patients entering the hypertension Clinic in 1974. One hundred sixteen met the criteria for hypertension and had a routine chest roentgenogram and/or ECG obtained for the evaluation of hypertension, Routine chest films and ECGs led to therapeutic or diagnostic interventions in only two instances, were not useful as baseline examinations, were never used for prognostic purposes, and not once influenced hypertensive management. We conclude that the value of routine chest roentgenograms and ECGs cannot be defended on the basis of their contribution to the workup of hypertension.

Serum cholesterol levels in American (Pima) Indian children and adolescents.

Serum cholesterol levels from birth to adulthood in a population of North American (Pima) Indians are described and compared to those of Caucasian populations. Cholesterol levels at birth (mean +/- SEM, 87 +/- 2.6 mg/100 ml) were similar in Pimas and Caucasians, but levels in Pimas from 5 to 16 years (148 +/- 4.6 mg/100 ml) were 20 to 30 mg/100 ml lower than among most white populations. The levels showed little rise with age from 5 to 16, then rose significantly in both sexes from ages 17 to 25. Cholesterol levels in adult Pimas (190 +/- 1.5 mg/100 ml) were up to 50 to 60 mg/100 ml lower than in American whites, and showed little increase after age 25. Two cohorts of children followed prospectively for six years indicated that the prevalence data reflect sequential changes in the population. Cholesterol levels of those subjects were significantly correlated at the first and last examinations. The Pima, in contrast to Caucasian American populations, have relatively low levels of serum cholesterol and low rates of coronary heart disease, but evidence of a causal relationship with the latter remains to be established.

Control of rabbit nictitating membrane movements. I. A computer model of the retractor bulbi muscle and the associated orbital mechanics.

Our objective in this study is to synthesize existing experimental data by constructing a realistic neuromechanical control model of rabbit nictitating membrane (NM) movements. We model the retractor bulbi muscle at the motor unit level because this is the level of nervous system control and also facilitates comparison with experimental data. Our motor unit model is derived from an earlier model of muscle activation based on calcium kinetics and includes a post-activation potentiation mechanism. Motor units are combined into a model of whole muscle that includes length-tension and force-velocity effects. Finally, we incorporate the muscle model into a biomechanical model in which the globe and NM are represented as a system of inertial, viscous, and elastic elements. The model takes patterns of neural signals (in the form of impulses) as input and produces movement of the NM as output. Our muscle model quantitatively accounts for data on isometric force development and decay for twitch, double shock, and tetanic stimulation. The complete model may be used for analysis of the relationship of motoneuron activity to behavior or as a realistic response generator in models of NM conditioning. This study also highlights gaps in the experimental data on the rabbit NM effector system.

Control of rabbit nictitating membrane movements. II. Analysis of the relation of motoneuron activity to behavior.

The objective of this study is to understand more precisely the relationship of motoneuron activity to movements of the rabbit nictitating membrane (NM). We use a model of the oculomotor plant to investigate what NM movements are generated by a given pattern of neural input and what inputs are required to generate particular NM movements. Simulated peak NM extensions can occur well over 50 ms after the end of motoneuron activity. The neural input required for the model to generate full amplitude NM extension responses is more consistent with single accessory abducens unit recordings from awake rabbits than recordings from anesthetized rabbits. An initial high frequency burst of neural activity followed by a rapid decay is required for simulations of conditioned responses (CRs) trained at a 125 ms interstimulus interval (ISI). For CRs trained with a 250 ms ISI, a more slowly rising and decaying neural activity is required. Model simulations show that the linear correlation between the shape of histogrammed motoneuron activity and the shape of NM movements can be high for long duration responses (> 400 ms) but is low for short duration responses (< 200 ms). Simulations are also consistent with the hypothesis that NM retraction is generally passive.

Basecalling with LifeTrace.

A pivotal step in electrophoresis sequencing is the conversion of the raw, continuous chromatogram data into the actual sequence of discrete nucleotides, a process referred to as basecalling. We describe a novel algorithm for basecalling implemented in the program LifeTrace. Like Phred, currently the most widely used basecalling software program, LifeTrace takes processed trace data as input. It was designed to be tolerant to variable peak spacing by means of an improved peak-detection algorithm that emphasizes local chromatogram information over global properties. LifeTrace is shown to generate high-quality basecalls and reliable quality scores. It proved particularly effective when applied to MegaBACE capillary sequencing machines. In a benchmark test of 8372 dye-primer MegaBACE chromatograms, LifeTrace generated 17% fewer substitution errors, 16% fewer insertion/deletion errors, and 2.4% more aligned bases to the finished sequence than did Phred. For two sets totaling 6624 dye-terminator chromatograms, the performance improvement was 15% fewer substitution errors, 10% fewer insertion/deletion errors, and 2.1% more aligned bases. The processing time required by LifeTrace is comparable to that of Phred. The predicted quality scores were in line with observed quality scores, permitting direct use for quality clipping and in silico single nucleotide polymorphism (SNP) detection. Furthermore, we introduce a new type of quality score associated with every basecall: the gap-quality. It estimates the probability of a deletion error between the current and the following basecall. This additional quality score improves detection of single basepair deletions when used for locating potential basecalling errors during the alignment. We also describe a new protocol for benchmarking that we believe better discerns basecaller performance differences than methods previously published.