Radiological case of the month. Neonatal alloimmune thrombocytopenia.
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Cerebral Hemorrhage↗
Biomedical subjects
S Morrison
Publications and source records attributed to S Morrison.
Immunomorphologic studies of macrophages and MHC class II-positive dendritic cells in the iris and ciliary body of the rat, mouse, and human eye.
PURPOSE: To establish the presence of distinct populations of macrophages and MHC class II (Ia)-positive dendritic cells (DC) in the iris and ciliary body of the rat, mouse, and human eye. METHODS: Iris-ciliary body wholemounts from a variety of rat strains, balb/c mice, and human eyes were investigated by single and double immunohistochemistry, immunoelectron microscopy, and confocal microscopy to determine the phenotype, density, distribution, and location of macrophage and DC populations. RESULTS: Dendritiform and pleiomorphic macrophages were distributed in a regular array within the rat iris and ciliary body stroma (600 to 700 cells/mm2 or 7000 cells per iris). Ia+ DC were distributed in a similar regular network (400 cells/mm2 or 5500 cells per iris) within the iris stroma and ciliary epithelium. In the rat, a strain-dependent variation in the numbers of DC was noted, F344 rats displaying highest numbers of DC (962 +/- 398 cells/mm2) and WAG strain the lowest numbers (285 +/- 218 cells/mm2). Double color immunoperoxidase staining using anti-Ia and anti-pan specific macrophage monoclonal antibodies revealed that macrophages and Ia+ DC are distinct populations with only 5% to 15% overlap. Single immunoperoxidase of mouse iris and ciliary body using anti-pan macrophage and anti-Ia antibodies produced findings identical to those in rat. Preliminary studies of human tissue using confocal microscopy of immunostained whole irides also revealed a regular array of macrophages and MHC class II (HLA-DR)+ dendritiform cells. CONCLUSIONS: The mammalian iris contains rich networks of dendritiform-pleiomorphic macrophages and MHC class II+ DC. These findings suggest that the DC in the tissues lining the anterior chamber represent a rich network of putative antigen presenting cells and are the most likely candidates for transmitting antigen-specific signals from the anterior chamber in vivo and in experimental models such as ACAID: These observations have wide implications for the understanding of the pathogenesis of anterior and posterior uveitis.
Animals↗
Reproducibility of fluorine-18-6-fluorodopa positron emission tomography in normal human subjects.
UNLABELLED: Fluorine-18-6-fluorodopa (FD) positron emission tomography (PET) is established for measuring nigrostriatal dopaminergic function. This is despite the absence of data on the reproducibility of results. METHODS: With an ECAT 953B/31 tomograph, we performed two or three repeated FD PET scans in 10 normal subjects to measure the scan-to-scan variation in the total striatal uptake rate constant (Ki). RESULTS: We found a scan-to-scan standard deviation (s.d.) of 8.7% of the mean. The between-subject s.d. was 26% of the mean, resulting in a reliability coefficient of 90%. Analysis of the variation in the components contributing to Ki showed a reliability varying from 77% to 86% (depending on the different time points analyzed) for emission data measured by the PET camera. The reliability of the blood radioactivity time course, as reflected by the stretch time, varied from 43% to 81%. The overall reliability for the correction of the blood time course for metabolites of FD was 71%. Variation in the blood radioactivity contributed to the variability of Ki by 50% more than the metabolite correction and by 200% more than the emission data. CONCLUSION: The striatal Ki is a reliable measurement; it has a 95% chance of lying within +/- 18% of its value for an individual normal subject.
Adult↗
Concurrent validity of the Cognitive Levels Test with measures of achievement for a sample of referred children and youth.
The present investigation compared the Cognitive Levels Test (CLT) with the Woodcock Reading Mastery Test (WRMT) and Wide Range Achievement Test-Revised (WRAT-R) for 55 children and youth who were referred for remedial/special education services. A comparison of the correlations for the criterion measures for the WRMT and WRAT-R showed a consistent significant positive relationship with the CLT. A repeated measures analysis of variance that compared standard scores of the CLT with those of the WRMT and WRAT-R indicated that significant differences existed between the test scores. Implications with respect to the concurrent validity of the CLT are discussed.
Adolescent↗
Parametric imaging of the rate constant Ki using [18Fluoro]-L-dopa positron emission tomography in progressive supranuclear palsy.
Positron emission tomography (PET) studies using [18F]-L-dopa were carried out in 9 patients with supranuclear palsy and 13 controls. For quantification of PET data a rate constant Ki was calculated for the radiotracer using a graphical method. Corrections for nonspecific activity were performed in both arterial plasma and brain tissue. The purpose of this study was to test the hypothesis that parametric images of the rate constant K mapping can be obtained on a pixel-by-pixel basis using an appropriate mathematical algorithm. Ki values from these parametric images and the graphical approach were compared. Both correlated closely, with y = 0.013 + 0.947*x, r = 0.992 and y = -0.052 + 1.018*x, r = 0.965 in patients and controls, respectively. Contrast measurements were also performed and showed a striking increase in contrast on parametric images. K mapping offers several advantages over the graphical approach, since parametric images are time-independent, i.e. one image represents the quantitative result of the study. In addition, parametric images of the rate constant are normalized to arterial plasma radioactivity and corrected for tissue metabolites. Thus, parametric images of Ki in different individuals can be compared directly without further processing in order to assess the nigrostriatal integrity.
Aged↗
Safety, tolerance, and pharmacokinetics of systemic ribavirin in children with human immunodeficiency virus infection.
Eleven pediatric patients, aged 1 to 10 years and with symptomatic human immunodeficiency virus infection, were treated with 6 or 10 mg of oral ribavirin per kg of body weight daily for 60 days. Safety and pharmacokinetic parameters were monitored; five children had comprehensive pharmacokinetic evaluations. The children tolerated the drug well, and treatment was not associated with any clinically significant adverse effects. Peak concentrations in plasma of 2.5 and 3.0 microM were reached at 90 min after single oral doses of 6 and 10 mg/kg, respectively. The mean systemic availability of oral ribavirin was 42.3%. After 60 days of ribavirin administration, mean trough concentrations in plasma of 2.6 and 4.1 microM were obtained. Ribavirin penetrated well into the cerebrospinal fluid, achieving 70% of the concentration in plasma at steady state.
Acquired Immunodeficiency Syndrome↗
Contribution of water condensation in endotracheal tubes to contamination of the lungs.
We postulated that water condensate in endotracheal tubes (ETTs) transports bacteria in the ETTs into the lungs during mechanical ventilation. Thirty-two ETTs obtained from freshly extubated patients were studied under wet and dry conditions using a physiologic lung model. All bacteria expelled from the ETTs were collected on culture plates positioned beneath the ETT. The lung model was ventilated with saturated air at 37 degrees C over two time periods (60 min each), one in which condensation formation was prevented and the second in which condensation formed within the ETT. A mean of 457.6 colony-forming units (CFU)/h were expelled with condensation compared to a mean of 2.4 CFU/h without condensation. We concluded that bacteria were continuously transported from the ETT into the lungs during mechanical ventilation in water droplets. Prevention of water condensation abolishes this constant bacterial inoculation in a lung model.
Air Microbiology↗
Frontal, temporal, and striatal proton relaxation times in schizophrenic patients and normal comparison subjects.
Spin-lattice (T1) and spin-spin (T2) magnetic resonance relaxation times were examined in frontal, temporal, and striatal regions of 24 patients with schizophrenia and 10 normal comparison subjects. The schizophrenic patients had more prolonged T2 values than did the comparison subjects, particularly in the left temporal cortex and white matter, suggesting tissue pathology.
Adult↗
A comparison of generalization functions and frame of reference effects in different training paradigms.
Six experiments were carried out to compare go/no-go and choice paradigms for studying the effects of intradimensional discrimination training on subsequent measures of stimulus generalization in human subjects. Specifically, the purpose was to compare the two paradigms as means of investigating generalization gradient forms and frame of reference effects. In Experiment 1, the stimulus dimension was visual intensity (brightness); in Experiment 2, it was line orientation (line-angle stimuli). After learning to respond (or to respond "right") to stimulus value (SV) 4 and not to respond (or to respond "left") to SV2 (in Experiment 1) or SV1 (in Experiment 2), the subjects were tested for generalization (recognition) with an asymmetrical set of values ranging from SV1 to SV11. Go/no-go training produced peaked gradients, whereas choice training produced sigmoid gradients. The asymmetrical testing resulted in a gradual shift of the peak of responding (go/no-go group) or in the point of subjective indifference (PSI; choice group) toward the central value of the test series; thus, both paradigms revealed a frame of reference effect. The results were comparable for the quantitative (intensity) and the qualitative (line-angle) stimulus dimensions. Experiment 3 compared the go/no-go procedure with a yes/no procedure in which subjects responded "right" to SV4 and "left" to all other intensities and found no differences between these procedures. Thus the difference in gradient forms in go/no as opposed to (traditional) choice paradigms depends on whether one or two target stimuli are used in training. In Experiment 4, in which visual intensity was used, the shift in the PSI following choice training varied positively with the range of asymmetrical test stimuli employed. In Experiment 5, also with visual intensity, the magnitude of the peak shift following go/no-go training varied as a function of overrepresenting a high or a low stimulus value during generalization testing. Experiment 6, with line angles, showed that the PSI following choice training varies in a similar way. The frame of reference effects obtained in these experiments are consistent with an adaptation-level model.
Discrimination Learning↗
Towards a clinical framework for collaboration between general and complementary practitioners: discussion paper.
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Family Practice↗
[L-18F-dopa-PET in Parkinson-plus syndromes for the detection of a disordered presynaptic dopaminergic function].
PET examinations using L-18F-DOPA were performed on 14 patients with Parkinsonism-plus syndromes (PPLUS). A rate constant Ki was calculated by a graphical method using an arterial input function. Sequential PET images were obtained and no specific activity was measured both in cortical and cerebellar background regions. These results were compared with those in 20 normal controls and tested for intra- and interobserver variability. All patients with PPLUS showed reduced Ki values with a mean of 0.154 (ml/striatum/min), whereas controls exhibited Ki values with a mean of 0.690 (ml/striatum/min) using cortical background regions. The correlation coefficient was calculated to be r = 0.973 for the intraobserver variability and r = 0.879 for the interobserver variability in controls, and r = 0.989 or = 0.973 in PPLUS, resp. There was no significant difference in the Ki values for cortical and cerebellar background regions (p = 0.1). PET examinations using L-18F-DOPA can reliably assess the extent of nigrostriatal degeneration in vivo. Since this radiotracer binds irreversibly within the striatum PET examinations allow the quantification of a disturbed dopaminergic function which is observer-independent.
Aged↗
Retarded Wallerian degeneration following peripheral nerve transection in C57BL/6/Ola mice is associated with delayed down-regulation of the P0 gene.
Wallerian degeneration is markedly retarded in C57BL/6/Ola mice, the majority of axons remaining intact for up to 10 days after sciatic transections. By 5 days after axotomy in normal mice P0 mRNA is markedly down-regulated, whereas high expression is present in the mutant mice at 7 days and is not reduced by a second distal axotomy. However, dissociated Schwann cells cultured without neurons down-regulate P0 in the normal manner. The data suggest that the continued expression of P0 mRNA is probably dependent on a relatively stable axonal signal with a low turnover that does not require continuous fast anterograde or retrograde transport. This may indicate an intrinsic axolemmal molecule(s) is involved in the neuronal signal.
Animals↗
Localized phosphorus 31 magnetic resonance spectroscopy in chronic schizophrenic patients and normal controls.
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Adult↗
P0 gene expression in cultured Schwann cells.
This study examines the expression of the major myelin protein gene P0 in cultured Schwann cells, grown on their own or in association with neurons. Many freshly dissociated Schwann cells from actively myelinating nerves express Po mRNA in high abundance. If neurons are not present, signal intensity falls markedly with time so that by 7 days in culture only a basal expression is evident which is negligible compared to the level in vivo. Dorsal root ganglia from embryo day 16 (E16) rats contain no significant levels of Po mRNA but when grown in full myelinating medium (containing serum and embryo extract) increasing expression is seen from 4 to 5 days onward even though myelination does not occur until after the second week. In this intervening period the intensity of P0 mRNA expression is lower than that found in the actively myelinating cell. Neurons from sympathetic ganglia are also capable of inducing P0 mRNA expression. Schwann cells in dorsal root ganglia explants grown in serum-free defined medium do not assemble a basal lamina and will not wrap or myelinate axons. Nevertheless P0 mRNA, but not protein, is expressed in levels similar to those found in full myelinating medium prior to myelination. Such Schwann cells also exhibit galactocerebroside and the sulphatide recognised by the 04 antibody. It appears that in defined medium or in myelinating medium prior to myelination axonal signals can induce P0 mRNA expression to a certain degree. However, full up-regulation is usually associated with the rapid membrane expansion accompanying myelination. Whether this augmented up-regulation is due to further axonal signalling or events in the Schwann cell is unknown, but the results suggest that P0 expression can be regulated at several stages of synthesis.
Animals↗
Peak shift revisited: a test of alternative interpretations.
In Experiment 1, 2 groups of human subjects were trained to respond to 1 of 2 light intensity stimuli, S2 or S4, and then were tested for generalization with a randomized series of increasing values from S1 to S11. Both groups, including the group trained to respond to dimmer value, showed peak shifts to a brighter more centrally located test stimulus. In Experiment 2, which used line angle stimuli, both the size of the difference between S+ and S- and the range of test stimuli that extended beyond S+ were varied. The larger the S(+)-S- separation and the larger the range, the greater was the peak shift obtained. In Experiment 3, training involved an S- (line angle) surrounded by 2 S+ values with testing symmetrical about the training values and covering either a narrow or a wide range. The wide range produced greater peak shifts in both directions from S-. All 3 experiments support an adaptation-level interpretation of intradimensional discrimination learning and generalization test performance in human subjects. Related work with animals suggests the presence of similar processes.
Adult↗
Correlation of negative symptoms in schizophrenia with frontal lobe parameters on magnetic resonance imaging.
Among 24 chronic schizophrenic patients, the 10 with high ratings for negative symptoms had significantly higher left-frontal: temporal-cortical T2 ratios. This finding was unrelated to age, dose of medication, length of illness or handedness. No T1 or T2 changes were found to be associated with positive symptoms or tardive dyskinesia in the regions examined.
Adult↗
Piliation changes in transformation-defective gonococci.
Recombination-dependent alterations of their expressed pilin gene (pilE) enable gonococci to synthesize a myriad of structurally/antigenically different pili and to reversibly switch their pilus production on and off. These changes have been ascribed both to DNA transformation and to intragenomic recombination between pilE and silent pilin genes (pilS). We examined the pilus changes in gonococci that are incompetent for transformation because of their DNA uptake deficiency (dud) mutation, pilus- (P-) phenotype, or both. Though incompetent for DNA transformation, dud cells displayed pilus antigenic variation and underwent reversible pilus variations much like their wild-type parent. Wild-type P- with a pilE nonsense mutation were also virtually nontransformable, but they reverted to P+ at high frequencies. The pilin mRNA sequence changes that accompanied pilus transitions in these nontransformable dud and P- gonococci represent insertion of pilS stretches into their respective pilE, apparently via intragenomic recombination.
Amino Acid Sequence↗
Quantitative electroencephalographic correlates of cognitive decline in normal elderly subjects.
We obtained a topographic computer analysis of the electroencephalogram in 53 normal elderly subjects. Normal aging was not associated with an increase in slow (delta) activity. However, cognitive performance correlated positively with fast (beta) activity particularly in frontal leads, even after controlling for age, education, occupation, and medication. Five subjects who showed early signs of cognitive decline, had all a marked reduction in beta activity suggesting that this may be an early indication of intellectual loss.
Aged↗