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Biomedical subjects

D Wicks

Publications and source records attributed to D Wicks.

11 recordsLinked to original sources
PubMed1998

A follow-up study of actigraphic measures in home-residing Alzheimer's disease patients.

This article reports cross-sectional and follow-up data with actigraphic measures of nocturnal sleep and rest/activity in 61 Alzheimer's disease (AD) patients as well as the relation of actigraphic measures to levels of behavioral disturbance across different stages of the disease. Over the course of approximately 1.5 years' follow-up, patients showed significant deterioration of nocturnal sleep parameters, but no significant change in rest/activity circadian rhythm parameters. There were also significant correlations among nocturnal sleep, rest/activity circadian rhythm, and behavioral disturbance measures, but only in relatively early stages of AD. It is argued that study of nocturnal sleep and circadian rhythm in relation to behavioral disturbance in AD requires longitudinal data and analyses that take into account the stage of disease at which patients are assessed.

Aged↗
PubMed1997

Disruptive behavior and actigraphic measures in home-dwelling patients with Alzheimer's disease: preliminary report.

The purpose of this preliminary report was to explore overall level and diurnal patterning of caregiver reports of abnormal behavior and to explore relationships with actigraphic measures of sleep/wake activity in Alzheimer's disease (AD) patients. Our primary behavioral measure was the Time-based Behavioral Disturbance Questionnaire (TBDQ). The overall score on this measure was shown to have adequate test-retest reliability and convergent validity with another behavioral measure. Significant correlations were obtained between the TBDQ overall score and actigraphically scored sleep efficiency (r = -.35, P < .05) and wake after sleep onset (r = .43, P < .01) in 41 subjects. The data suggest a moderate relationship between actigraphic measures of sleep/wake and disturbed behavior in home-dwelling AD patients.

Aged↗
PubMed1995

Cross-linked hemoglobin increases fractional reabsorption and GFR in hypoxic isolated perfused rat kidneys.

We compared the ability of human red blood cells (RBC) and a cell-free oxygen carrier to maintain isolated perfused kidney function under moderately hypoxic conditions. Recirculating perfusate was gassed initially with 93% air-7% CO2, and, after 30 min, the gas was changed to 12 O2-7 CO2-81% N2. Oxygen content of the perfusate was increased with RBC (30 g/l Hbg) or highly purified human hemoglobin Ao (HbAo) polymerized with O-raffinose (o-R-poly-Hb, 30 g/l Hbg). For comparison, kidneys were perfused with 60 g/l of bovine serum albumin (BSA) alone. The effects of unmodified hemoglobin were examined by adding 5 g/l of nonpolymerized HbAo to the BSA perfusate after 20 min. The effect of increasing oxygen delivery without hemoglobin was examined by switching to 93% O2 after 20 min during some BSA perfusions (BSA-HiO2). Vascular resistance decreased progressively in o-R-poly-Hb- and BSA-HiO2-perfused kidneys but remained constant in other experiments. Nitro-L-arginine methyl ester (L-NAME) prevented vasodilation and increased the filtration fraction of o-R-poly-Hb-perfused kidneys with no change in other functions. L-NAME also prevented the formation of methemoglobin. After a 70-min perfusion with BSA, Na reabsorption was 82 +/- 3% (means +/- SD), and inulin clearance [glomerular filtration rate (GFR)] was 0.66 +/- 0.33 ml.min-1.g-1. RBC increased reabsorption to 95% (85-98%) (median, 25th-75th percentile) but did not alter GFR (0.52 +/- 0.26 ml.min-1.g-1). o-R-poly-Hb increased Na reabsorption proportionately more than GFR, so that, while GFR was doubled to 1.04 +/- 0.40 ml.min-1.g-1, Na reabsorption increased to 98% (92-99.5%). HbAo increased GFR to 1.07 +/- 0.44 ml.min-1.g-1 and increased reabsorption to 89 +/- 6%.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1993

Reduction of cortical volume in schizophrenia on magnetic resonance imaging.

The MRI scans of 48 schizophrenic patients, fulfilling RDC criteria, were compared to those of 34 healthy controls matched for age, ethnicity and parental social class. The volume of the frontal and anterior parietal lobes was significantly reduced in the schizophrenic group as a result of a selective decrease in cortical volume, with a corresponding increase in the volume of sulcal fluid. Reduction in the volume of the temporal grey matter was more marked on the right, but was not in excess of the loss of volume observed in other areas of the cortex. MRI abnormalities correlated poorly with clinical parameters, although both unemployment and poor pre-morbid adjustment predicted reduced cerebral volume and increased sulcal volume. These results question whether the medial temporal lobes are the only site of structural pathology in schizophrenia.

Adult↗
PubMed1991

Major differences in the dynamics of primary and secondary progressive multiple sclerosis.

In patients with primary and secondary progressive multiple sclerosis (MS), major differences in the pattern and extent of abnormality on cerebral magnetic resonance imaging (MRI) between the two groups have recently been demonstrated. In the present study, 24 patients, matched for age, sex, duration of disease, and disability, had serial gadolinium diethylenetriaminepentaacetic acid-enhanced MRI over a 6-month period. The 12 patients in the secondary progressive group had a total of 109 new lesions over this time (18.2 lesions per patient per year) and 87% of these enhanced. Enhancement also occurred within and at the edge of preexisting lesions. In contrast, only 20 new lesions were seen in the primary progressive group (3.3 lesions per patient per year) and only one of these enhanced. There was no difference in the degree of clinical deterioration between the two groups over the 6-month period. These findings may indicate a difference in the dynamics of disease activity between the two forms of progressive MS, particularly in relation to the inflammatory component of the lesions, and have important implications for the selection of patients and the monitoring of disease activity in therapeutic trials.

Adult↗
PubMed1990

Implications of mainstream classrooms for adolescents with spina bifida.

This study examined the social and academic implications of mainstream, mainstream and special (combined) or special-class education for 31 adolescents with spina bifida, and for their primary caretakers. The Peabody Picture Vocabulary Test and the UCLA Loneliness Scale (adolescents) and the Personality Inventory for Children (caretakers) were administered. Adolescents in mainstream classes had the most normal scores for academic and social skills, those in combined classes had intermediate scores and those in special classes had the lowest scores. Paradoxically, adolescents in combined classes reported the least loneliness. This study suggests that even among students with relatively good social skills, mainstream placement is associated with greater subjective experience of loneliness than is combined placement.

Adolescent↗
PubMed1986

Volume flow measurement of pulsatile flow by digitised cine angiography.

The validation, by phantom experiments, of a method of measuring volumetric, pulsatile blood flow in vessels of about 4 mm calibre is described. 'Instantaneous' as well as integrated flow is obtained from cine angiograms by digitisation of the images and densitometric analysis in an advanced computer vision analysis system. From 48 frames per second cine, pulsatile flow at any moment between 0 and about 400 ml/min was calculated within about 10 per cent of the electromagnetic flow meter reading. Further improvement is expected. It is proposed to advance to 3D and have the methodology available for clinical use in due course.

Angiography, Digital Subtraction↗
PubMedDate not supplied

Using greyscale voxel databases for improved shading and segmentation.

Many different data representations are possible in computer graphics. Originally, in the medical field, simplified methods were used in order to reduce computation times on small computer systems. Currently a wider range of techniques is developing as costs of hardware continue to fall. In this paper we review a number of possible representations and explain the advantage of one that is greyscale, volumetric and random access. Different segmentation techniques can be used, as well as shading algorithms that give greatly improved appearances. A quantitative analysis of shading methods is derived in terms of the degree of sampling of the 'pseudo-normal' vectors that estimate the direction of the tangent to a surface. The application to a study of multiple sclerosis lesions in the brain using nuclear magnetic resonance data is shown.

Brain↗