Quantitative coronary arteriography: design and validation

The authors assessed the performance of an automatic and rapid coronary quantification method by evaluating its accuracy in a stenosis phantom. Measurements were obtained with a lucite phantom with 2-, 3-, and 4-mm vessel diameters and concentric stenoses of 33%, 50%, 67%, and 75%. Direct digital angiographic images as well as 10 X 10 spot films and 35-mm cine angiography films were acquired with and without structural noise and mask subtraction. The films were digitized with magnification factors of one and two. An interactive analysis program was used to automatically determine the vessel edges with a Gaussian fit to the cross-sectional density profiles perpendicular to the center line of the vessel. Relative changes of the densitometric cross-sectional area along the vessel were used to assess the percentage of stenosis. Densitometric measurements were comparable in both digital and cine angiograms (r = .99 and r = .98, respectively); however, diameter measurements showed a higher variability and were dependent on the amount of magnification applied to the images.     

Long-Latency Evoked Potentials and Reaction Time

Tone pips separated by a constant 1 sec interval were delivered to 12 subjects. The pips were of three pitches given in a random sequence. The 400 and 1600 Hz pips each had a probability of 0.1 and the 800 Hz pips had a probability of 0.8. For each subject, either the 400 or 1600 Hz pips were designated as targets in a reaction time (RT) task. Stimulus-synchronized averages (SSAs) to infrequent tones contained two prominent waves: a P3 and a slow wave (SW). SW and P3 amplitudes were larger, and P3 latency was 15 msec shorter, to targets than to non-targets. SSAs were computed for RT quartiles (Q1–Q4) of each subject. Between Q1 and Q4, P3 amplitude decreased, while SW amplitude increased, demonstrating behavioral and dissociation of the two waves. Between Q1 and Q4, RTs increased from 366 to 540 msec, while P3 latency at C_z increased from 328 to 359 msec. Response-synchronized averages computed for each RT quartile showed no response-related deflections that could explain the effects in the SSAs.     

Human EEG response to beta-endorphin.

Beta-endorphin, morphine, and saline were given intravenously to a single schizophrenic subject on separate occasions in a double-blind design. EEG spectral analyses performed on data collected before and after drug injection demonstrated that beta-endorphin and morphine produced similar increases in alpha power within 5 to 15 minutes after injection. This effect could be distinguished from two placebo (saline) injections. These data suggest that intravenous beta-endorphin can produce changes in the central nervous system in humans.     

The effects of methamphetamine and secobarbital on the contingent negative variation amplitude

The amplitude of the contingent negative variation (CNV) was studied in twelve male subjects given oral doses of methamphetamine (10 mg), secobarbital (50 mg), and placebo on the three testing days separated by one week. Orders were balanced across subjects and testing conditions were double-blind. The mean amplitudes of the CNV elicited with methamphetamine were significantly greater than those obtained with secobarbital and placebo. Comparing secobarbital with placebo yielded no significant results, possibly due to the low secobarbital dosage. The sensitivity of the CNV amplitude to methamphetamine suggests that the CNV may be a sensitive measure of arousal and attention and could provide a reliable index for assessing the relative arousal effects of complex drugs on humans.     

Methamphetamine and diphenhydramine effects on the rate of cognitive processing

Three cognitive tasks in which performance depends primarily on the rate of cognitive processing were given to 24 male subjects before and after oral doses of methamphetamine (10 mg), diphenhydramine hydrochloride (100 mg), and placebo. Each subject was tested on Monday, Wednesday, and Friday of one week with drug orders balanced across subjects. Compared with placebo and diphenhydramine, methamphetamine increased the rate at which a visual display was scanned for a target stimulus. Methamphetamine affected neither a time-production task nor a divided attention task that required the subject to perform two cognitive tasks in a limited amount of time. This suggests that methamphetamine can increase cognitive processing speed on tasks involving familiar cognitive operations but that an increase is not likely in tasks involving more complicated decision processes. Compared with placebo and methamphetamine, diphenhydramine caused subjects no experience geophysical time as passing more slowly, but the drug had no significant effects on the visual search or divided-attention tasks. This suggests that time perception is more likely to be altered by diphenhydramine than is performance on tasks requiring short periods of rapid cognitive processing.     

Amino acid immunoreactivity in normal human retina and after brachytherapy

We localised amino acids in the mid‐peripheral aged human retina and a retina that had undergone radiation treatment 10 years earlier. The distribution pattern of glutamate, γ‐amino butyric acid (GABA), glycine, glutamine and taurine, reflected patterns established in the primate retina. The retina that had undergone radiation exposure displayed both anatomical and neurochemical remodelling. The proximal retina comprised around 40 to 45 per cent of the total retina and neuronal kinesis and aberrant neuronal projections were also present. Amino acid neurochemistry was strikingly different with Müller cells displaying GABA loading, glycinergic neurons displaced and displaying a very high level of glycine labelling. We conclude that radiation exposure triggered these changes in the human retina and likely reflects general remodelling of structure and function following ischaemic damage to endothelial cells.