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Biomedical subjects

D Barnes

Publications and source records attributed to D Barnes.

At least 181 records · Page 10Linked to original sources
PubMed1987

The Self Care Assessment Schedule (SCAS)--I. The purpose and construction of a new assessment of self care behaviours.

The Self Care Assessment Schedule (SCAS) is a new questionnaire which measures the frequency of ten behaviours during a period of fourteen days. Data are presented for five patient samples and a group of non consulting controls and the distributions of scores between groups show expected differences. In some groups scores are significantly greater for male subjects and those with the most chronic disorders but scores are not related to age. It is tentatively suggested that the SCAS may be used to determine the severity of aspects of disability based on percentile scores.

Activities of Daily Living↗
PubMed1987

The Self Care Assessment Schedule (SCAS)--II. Reliability and validity.

Evaluation of the SCAS in three groups of patients demonstrates high levels of test-retest reliability and satisfactory internal consistency. Multiple investigations of validity support the use of the SCAS as a measure of self care deficit which is related to social disability. The potential uses of the SCAS in clinical work and research are discussed.

Activities of Daily Living↗
PubMed1987

Quantitative nuclear magnetic resonance imaging: characterisation of experimental cerebral oedema.

Magnetic resonance imaging (MRI) has been used quantitatively to define the characteristics of two different models of experimental cerebral oedema in cats: vasogenic oedema produced by cortical freezing and cytotoxic oedema induced by triethyl tin. The MRI results have been correlated with the ultrastructural changes. The images accurately delineated the anatomical extent of the oedema in the two lesions, but did not otherwise discriminate between them. The patterns of measured increase in T1' and T2' were, however, characteristic for each type of oedema, and reflected the protein content. The magnetisation decay characteristics of both normal and oedematous white matter were monoexponential for T1 but biexponential for T2 decay. The relative sizes of the two component exponentials of the latter corresponded with the physical sizes of the major tissue water compartments. Quantitative MRI data can provide reliable information about the physico-chemical environment of tissue water in normal and oedematous cerebral tissue, and are useful for distinguishing between acute and chronic lesions in multiple sclerosis.

Animals↗
PubMed1987

Accuracy and precision in the measurement of relaxation times from nuclear magnetic resonance images.

The accuracy (proximity to the true value) and precision (reproducibility) of relaxation times derived from nuclear magnetic resonance images were investigated. Two methods of deriving relaxation times were considered. A patient scanning protocol in which the minimum number of scans necessary for the calculation (three) were performed. Calculated T1 and T2 images were then formed. An animal (cat) protocol in which many more scans were performed. The data were read from the display and fitted by computer to the theoretical curves. The accuracy of the measurements was determined by an empirical method. A series of bottles with different concentrations of MnCl2 and CuSO4 in water were prepared and their relaxation times determined using the imager as a simple pulsed spectrometer. These values were compared with those derived from images. Over the normal range of tissue values (T1 less than 700 ms, T2 less than 200 ms) the animal protocol gave values of T1 up to 1% shorter than the true values. The T2 values were up to 5% shorter. Patient protocol values were up to 7% shorter for T1 and up to 20% shorter for T2. There was some difference between results for MnCl2 and for CuSO4 (particularly for patient T2s), suggesting that the results depend to a small extent on the T1/T2 ratio. The precision of the values was investigated by considering the standard deviations (SDs) of brain tissue measurements over populations of cats (animal protocols) and normal control subjects and multiple sclerosis patients (patient protocols). These were compared with the SDs of measurements of calibration bottles scanned with the patients. Standard deviations of 3% for T1 and 6% for T2 were found over 19 cats using the animal protocols; SDs of 7% for T1 and 14% for T2 were found over 15 normal control subjects using the patient protocols. Standard deviations of bottle measurements were similar to these figures. There are also variations between different subjects and different regions of the brain. There was no significant change between readings on the same patient in follow-up studies. Other sources of variation in the measurements made with the patient protocols were investigated by scanning phantoms. Noise in T1 and T2 images is about 2%. Spatial non-uniformity within slices is about 1% for T1 and 10% for T2. Non-uniformity between slices in multislice sets is 4% for T1 and 14% for T2. There is no long-term variation in measured values over 9 months; short-term variation is approximately 1%.

Adolescent↗
PubMed1986

Disruption of corticospinal plasticity by 6-hydroxydopamine as measured by intracortical microstimulation in rats.

Intracortical microstimulation in normal, adult rats evoked low-threshold contralateral and high-threshold ipsilateral forelimb movements. In comparison, stimulation of the intact cortex in adult rats that sustained unilateral cortical lesions at birth evoked ipsilateral movements at abnormally low-threshold levels in addition to normal contralateral movements. Depletion of cortical and spinal cord noradrenaline levels by treatment with 6-hydroxydopamine prior to the placement of neonatal cortical lesions eliminated the low-threshold ipsilateral movements when tested at maturity. These findings suggest that the noradrenergic system may influence corticospinal plasticity.

Animals↗
PubMed1986

Transfection of DNA from a chloroethylnitrosourea-resistant tumor cell line (MER+) to a sensitive tumor cell line (MER-) results in a tumor cell line resistant to MNNG and CNU that has increased O-6-methylguanine-DNA methyltransferase levels and reduced levels of DNA interstrand crosslinking.

A subclone of a human glioma tumor cell strain which was deficient at O-6-alkylguanine repair was transfected with DNA from an O-6-alkylguanine DNA alkyltransferase-positive human colon tumor cell line (HT29). The transfected subclone, which was selected by its resistance to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), acquired increased resistance to chloroethylnitrosourea (CNU), contained O-6-methylguanine-DNA methyltransferase activity, and failed to accumulate interstrand crosslinks in its DNA upon treatment with CNU. The subclone morphologically resembled its CNU-sensitive parental glioma cell strain. The close correlation between the increased cellular resistance, increased O-6-alkylguanine repair activity and the absence of crosslinking suggests that the formation of DNA crosslinks is one important mechanism of cytotoxicity produced by CNU, and that repair of DNA lesions by O-6-alkylguanine DNA alkyltransferase may partially prevent CNU-induced cytotoxicity.

Cell Line↗
PubMed1986

Magnetic resonance imaging of experimental cerebral oedema.

Triethyl tin(TET)-induced cerebral oedema has been studied in cats by magnetic resonance imaging (MRI), and the findings correlated with the histology and fine structure of the cerebrum following perfusion-fixation. MRI is a sensitive technique for detecting cerebral oedema, and the distribution and severity of the changes correlate closely with the morphological abnormalities. The relaxation times, T1 and T2 increase progressively as the oedema develops, and the proportional increase in T2 is approximately twice that in T1. Analysis of the magnetisation decay curves reveals slowly-relaxing and rapidly-relaxing components which probably correspond to oedema fluid and intracellular water respectively. The image appearances taken in conjunction with relaxation data provide a basis for determining the nature of the oedema in vivo.

Animals↗
PubMed1986

Combined effects of streptozotocin and mitozolomide against four human cell lines of the Mer+ phenotype.

The majority of human tumor cell lines are proficient in the repair of guanine O6-alkylations (designated Mer+) and are thus capable of preventing the cytotoxic effects of chloroethylating agents. It has been proposed that in these cells guanine O6-chloroethylations are rapidly removed by the enzyme O6-alkylguanine DNA alkyltransferase before the formation of DNA interstrand cross-links can occur. In this study pretreatment of four Met+ human cells (A2182 lung carcinoma, A375 melanoma, HT-29 colon carcinoma, and IMR-90 normal lung fibroblasts) with the DNA methylating agent streptozotocin apparently saturates the monoadduct repair system and allows mitozolomide to form interstrand cross-links in these cells. The inhibition of the alkyltransferase results in the continued presence of guanine O6-chloroethylations which then undergo a series of reactions that lead to DNA interstrand cross-link formation. As observed by colony forming assays, streptozotocin pretreatment causes a dramatic increase in the sensitivity of these four Mer+ cell lines to the cytotoxic effects of mitozolomide. These results indicate that a combination of streptozotocin pretreatment followed by mitozolomide may be useful in the treatment of human cancer.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1986

Measurement of NMR relaxation times using the minimum number of scans.

NMR relaxation time measurements derived from a set of three multi-slice sequences (which can examine the whole brain in 30 min) have been investigated. T1 and T2 values are 5% and 20% too short, respectively. Noise in the measurements was less than 2%. Temporal instability was negligible. Spatial non-uniformity was 1% (T1) and 3% (T2) within a single slice but 4% (T1) and 14% (T2) from slice to slice. Variations in cerebral tissue measurements have also been investigated: T1 varies by 6% and T2 by 12% over a population of normal controls. There can be significant patient-patient and topographical variations.

Brain↗
PubMed1986

The NMR signal decay characteristics of cerebral oedema.

Quantitative magnetic resonance (MR) imaging has been used to characterize vasogenic and triethyltin-induced cytotoxic cerebral oedema in cats, and the findings have been compared with the ultrastructural features of the lesions. Both normal and oedematous white matter yield non-linear T2 signal decay curves. The derived biexponential functions comprised a short T2 component representing intracellular water, and a long T2 component representing oedema fluid whose T2 was increased by an increase in free water of these tissue compartments. The relative sizes of the long T2 components were compatible with the sizes of the oedema spaces as determined ultrastructurally. Quantitative MR imaging can provide information which reflects the size and relaxation behaviour of the major tissue water compartments.

Animals↗
PubMed1985

Detection of recurrent rectosigmoid carcinoma: prospective evaluation of CT and clinical factors.

Twenty-nine patients who underwent curative resection for rectosigmoid carcinoma were followed for 1-4 years by history and physical examination, computed tomography, liver function tests, and carcinoembryonic antigen levels. Recurrences occurred in 13 patients: seven asymptomatic and six symptomatic. CT scans, obtained in 10 of these 13 patients, were positive in nine. Liver function tests were not elevated in any and carcinoembryonic antigen was abnormal in six of 11 patients. CT is the most sensitive test for the detection of recurrent disease.

Aged↗