PubMed Health⌕ Search

Biomedical subjects

R Armitage

Publications and source records attributed to R Armitage.

48 records · Page 3Linked to original sources
PubMed1993

Digital period analysis of EEG in depression: periodicity, coherence, and interhemispheric relationships during sleep.

1. Interhemispheric EEG differences were compared between 12 symptomatic depressed outpatients, 12 asymptomatic patients and 12 normal controls during two consecutive nights in the Sleep Study Unit. 2. EEG was quantified using digital period analysis (DPA), a time-domain analysis of successive polarity changes (zero-cross) and instances of zero slope (first derivative), yielding percent-time in each frequency band. 3. The degree of hemispheric asymmetry (L-R) was computed for delta, beta and theta percentages from REM, Stage 2 and Slow-Wave (SW) sleep. 4. Normals showed small asymmetries throughout sleep with largest differences in SW, with no consistent relationship between right and left activity and sleep stage. 5. Both depressed groups showed largest asymmetries in REM sleep, with significantly more beta, theta and delta in the right hemisphere consistently. None of the 24 depressed patients showed greater left hemisphere activity throughout sleep.

Adult↗
PubMed1992

Digital period analysis of sleep EEG in depression.

The period-analyzed sleep electroencephalogram (EEG) was compared in a group of 9 depressed outpatients and 9 age-matched normal controls. Both groups showed rhythms in beta, delta, and theta activity with an approximately 90-min period. The phase and coherence between fast and slow frequency EEG measures, however, differed significantly in the two groups. Beta and delta rhythms were less coherent in the depressed outpatient sample. The control group showed higher coherence and a strong coupling of beta and delta activity. These preliminary data suggest that depression may be associated with some degree of ultradian rhythm disturbances though periodicity is unaffected.

Activity Cycles↗
PubMed1992

Comparison of the delta EEG in the first and second non-REM periods in depressed adults and normal controls.

The distribution of period-analyzed delta activity in the first and second non-rapid eye movement (NREM) periods was compared in nine symptomatic depressed outpatients and nine normal controls. The groups did not differ in ratios of delta zero-cross or delta power in the first to the second NREM periods. Further, neither group showed a systematic change in delta count or delta power across the first two NREM periods. Our findings suggest that ratios of delta activity in the first two NREM periods may not systematically differentiate depressed adults from normal subjects.

Adult↗
PubMed1992

Distribution of period-analyzed delta activity during sleep.

The distribution of delta EEG activity was evaluated during sleep in eight healthy adults. Digital period analysis, including an amplitude measurement, was used to quantify delta activity. The average percentages of delta half- and full-wave zero-crosses, mean delta power, and mean total power were computed for each nonrapid eye movement (NREM) period. The distribution of these delta measures was examined across NREM periods (NREMPs). No significant linear trends were evident in the zero-cross or power measures. Four subjects showed the highest delta power and greatest incidence of delta in the second rather than first NREMP. Regression analyses of individual delta incidence data revealed that only 62.5% of recording nights could be described with an exponential equation. Exponential regressions described 81% of delta amplitude cases. Further, delta activity in some subjects could be described by either linear or exponential regression. The findings suggest that the temporal changes of delta activity may not be entirely systematic across NREMPs and are variable across subjects.

Adult↗
PubMed1990

Asymmetrical auditory probe evoked potentials during REM and NREM sleep.

Two experiments were conducted to evaluate interhemispheric differences in late auditory evoked potentials (AEPs) during rapid-eye-movement (REM), Stage 2, and Stage 4 sleep. In the first study, 1,000-Hz stimuli [80 db (SPL)] were presented binaurally at a rate of 1/1.1 s. Analyses of variance were computed on the absolute difference in the amplitude of right and left evoked responses. N1 AEPs were significantly more asymmetrical in Stage 4 sleep compared to either REM or Stage 2 sleep. A second study was conducted with a wider topographical electrode distribution. This study used both a long and a short interstimulus interval with 500-Hz 80-db SPL tone pips. The absolute difference in the amplitude of right and left AEPs was compared across sleep stage. Asymmetries were larger in Stage 4 sleep than in either REM or Stage 2. Examination of these data indicated relative hemispheric balance in REM and Stage 2 sleep with largest asymmetries in Stage 4. The results do not support the view that REM and non-REM sleep stages are associated with differential activation of the two cerebral hemispheres. Rather, they suggest that the sleep cycle is characterized by variations in the degree of asymmetry. Asymmetries in Stage 4 sleep were not consistently in favor of the left hemisphere.

Adolescent↗
PubMed1989

Human IL-7: a novel T cell growth factor.

IL-7 is a hemopoietic growth factor that induces the proliferation of early B lineage cells. In the course of studies to determine its effect on human bone marrow cells, we noted a marked outgrowth of mature T cells. When T cells from the circulation were cultured with IL-7, a dose-dependent proliferative response was observed. The target cells included both the CD4+ and CD8+ subpopulations of T cells, but the memory T cells (CD45R-) were better responders than unprimed T cells (CD45R+). IL-7 induced the expression of receptors for IL-2 and transferrin and higher levels of the 4F2 activation Ag. Although T cell responses to suboptimal concentrations of IL-7 were enhanced by the addition of IL-2, the proliferative response to IL-7 was not inhibited by neutralizing antibody to the IL-2R (Tac), nor was IL-2 secretion detected in this response. This response pattern of mature T cells suggests an important role for IL-7 in normal T cell physiology in humans.

Adult↗
PubMed1989

Variations in period-analysed EEG asymmetry in REM and NREM sleep.

Monopolar EEG was recorded from lateral frontal and parietal sites with linked ear reference during sleep in 24 adults. Electrode placement followed the 10-20 International system. EEG was quantified using digital period analyses. The absolute difference in interhemispheric EEG parameters was compared for Stage 2, REM, and a slow wave sleep measure. The absolute difference measures reflect the degree of symmetry or asymmetry, regardless of the hemisphere of origin. Theta and delta activity in slow wave sleep was more asymmetrical than in either Stage 2 or REM. REM sleep was associated with the smallest asymmetries. These results do not support a right hemisphere REM, left hemisphere NREM relationship. Rather they suggest that REM sleep is associated with relative hemispheric symmetry whereas asymmetries are most prominent in slow wave sleep. Stage 2 sleep was significantly less asymmetrical than slow wave on a number of theta and delta measures. The significant differences between slow wave and Stage 2 sleep may denote functional differences within NREM sleep stages.

Adolescent↗
PubMed1988

Recognition memory for words and event-related potentials: a comparison of normal and disabled readers.

Visual event-related potentials elicited during a word-recognition memory task were examined for groups of normal and disabled readers (RD). The strong association of reading ability with recognition memory performance endorsed the appropriateness of this signal detection paradigm as a reading-related task. Enhanced amplitude of the P200 component for the RD group was evident during both the acquisition and recognition series and it is indicative of differences at an early sensory stage of item encoding and retrieval. Normal readers displayed greater N400 amplitude than the RD group during both the acquisition and recognition series, an effect which is consistent with more extensive semantic evaluation or memory search that is attributed to that component. In the absence of any remarkable differences in P300 amplitude between groups, the poorer recognition memory performance for the RD group may not be attributable to attentional deficits.

Child↗
PubMed1983

An indirect rosette technique for the identification and separation of human lymphocyte populations by monoclonal antibodies: a comparison with immunofluorescence methods.

A simple indirect rosette technique is described which allows the rapid enumeration, morphological identification and separation of monoclonal-antibody (MoAb)-defined human lymphocyte populations. The method is based on the binding to MoAb-stained cells of marker ox red blood cells coated with anti-mouse immunoglobulin. When compared with indirect immunofluorescence staining assessed by microscopy, the rosette method is quicker, shows greater sensitivity and is less subjective. Purification of helper (OKT4), suppressor (OKT8) or B-cell (BA1) subpopulations by positive or negative enrichment of rosetted cells gives purity and recoveries comparable with that of the fluorescence-activated cell sorter (FACS). Such purification is readily performed without loss of viability or function and is more easily done sterilely than with the FACS.

Animals↗
PubMed1980

A new primary screening test for anthelmintics utilizing the parasitic stages of Nippostrongylus brasiliensis, in vitro.

A new in vitro test suitable for the large scale screening of chemical compounds for anthelmintic activity is described. The test which utilizes the fourth larval and adult stages of Nippostrongylus brasiliensis in a medium capable of supporting the growth and development of the parasite, detects selectively those compounds which possess either broad spectrum anthelmintic or specific anti-trichostrongyle activity. The screen is easy to operate requiring only minute quantities of experimental compound. It renders fully reproducible results which furthermore can be interpreted objectively. This is the first reported in vitro test directed against the parasitic stages of a nematode that is capable of detecting reliably the activity of a wide range of anthelmintics including thiophanate and all the benzimidazoles.

Animals↗
PubMed1979

Rhythms in human performance: 1 1/2-hour oscillations in cognitive style.

Performance on verbal and spatial matching tasks was assessed every 15 minutes for 8 hours. Significant 60- to 100-minute oscillations were observed for each task. These oscillations were 180 degrees out of phase, supporting the hypothesis that in humans the basic rest activity cycle involves alternating activation of processing systems residing in the two cerebral hemispheres.

Behavior↗