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Biomedical subjects

D G Thomas

Publications and source records attributed to D G Thomas.

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

Endoscopic bladder transection for detrusor instability.

Eighteen patients with intractable detrusor instability were treated by endoscopic bladder transection. In two patients there was complete symptomatic relief. Two more were rendered continent but continued to complain of urgency and nocturia. The remaining 14 patients were not improved by the procedure. These results have caused us to abandon this operation as a treatment for detrusor instability.

Adult↗
PubMed1987

Surgical management of benign intractable pain.

A multidisciplinary approach to chronic pain will usually obtain reasonable results, but in some selected patients with nonmalignant disease a surgical solution may be sought with benefit. A variety of techniques used are described in detail, including the treatment of trigeminal neuralgia, post-herpetic neuralgia, and the pain associated with avulsion injury of the brachial plexus.

Aged↗
PubMed1987

Dorsal column stimulation (DCS) in chronic pain: report of 31 cases.

Thirty-one patients of chronic pain treated with dorsal column stimulation (DCS) are reported. All of them had been treated previously with drugs and multiple procedures including injections and frequently several operations. After a trial of percutaneous DCS, permanent implantations were carried out. The patients have been followed for up to eight years. Overall, sixty per cent of patients had good to fair relief of pain with DCS. Some of them had a good response for five years and more.

Adult↗
PubMed1986

Fluorometric ELISA for the detection and quantitation of metallothionein.

The development of a heterogeneous fluorometric ELISA for the detection and quantitation of metallothionein (MT) is described. A radioimmunoassay (RIA) previously developed in our laboratory is used as a reference assay to characterize the performance of the ELISA. The standard curves (logit-log regressions) that are typical of either assay have similar ranges (customarily from 20 000 to 100 pg of competing antigen); both assays are capable of quantitating MT in unknowns with 5-10% accuracy. Aspects of MT measurement in cytosols and physiological fluids are discussed.

Animals↗
PubMed1986

Gliomyosarcoma. Report of a case of rhabdomyosarcoma arising in a malignant glioma.

The development of sarcoma within a glioblastoma is a well recognised complication: in the majority of cases it is a fibro-sarcoma originating in the tissues of the proliferating hyperplastic blood vessels. In the case described here the tumour is a rhabdomyosarcoma, apparently derived from abnormal prolific vascular mesenchyme. Only one comparable example has been recorded previously.

Brain Neoplasms↗
PubMed1986

Studies on regional cerebral haematocrit and blood flow in patients with cerebral tumours using positron emission tomography.

Regional cerebral haematocrit has been measured in seven patients with brain tumours, and in one normal subject, using positron emission tomography (PET). Red cell and plasma volumes of distribution were assessed using 11CO and [methyl-11C]albumin, respectively. Haematocrit values were compared with values of regional cerebral blood flow (rCBF) measured using steady-state inhalation of C15O2. Only two of the seven cerebral tumours studied showed any increase in uptake of [methyl-11C]albumin over 45 min. Values of r, the regional ratio of cerebral small-to-large vessel haematocrit, varied from 0.52 to 0.84 for the seven tumours studied. No correlation between r and tumour blood flow was observed. The normal subject yielded an r value of 0.69 for the mean whole brain small-to-large vessel haematocrit ratio. No significant difference between gray and white matter r values was found. The contralateral hemispheres of the seven tumour patients studied yielded an overall mean r value of 0.71 +/- 0.05. We conclude that it is reasonable to assume an r value of 0.7 in tomographic calculations of regional cerebral blood volume (rCBV) from red cell or plasma volumes of distribution in normal brain. Such an assumption for tumours, however, may lead to errors of 35% in estimated rCBV.

Blood Volume↗
PubMed1986

A comparison of the differential accumulation of cadmium in the tissues of three species of freshwater fish, Salmo gairdneri, Rutilus rutilus and Noemacheilus barbatulus.

Roach and stone loach were exposed to cadmium dissolved in their aquarium water at 500 and 1250 micrograms/l, respectively, and the distribution of the metal accumulated in the major body organs was determined. The pattern of distribution for each species was somewhat different and was distinct in each case from that observed previously with rainbow trout. The total body loads of cadmium accumulated by the three species were assessed during the period of exposure and found not to correlate directly with the concentration of cadmium to which the individual species had been exposed. An alternative comparator was devised which as the quotient of the total body cadmium accumulation (microgram/100 g body wt) and the notional cadmium dose (microgram/l) X weeks was described as a fractional retention coefficient for cadmium. The coefficient was constant for each species at different periods of exposure to cadmium alone. The values of the coefficient for roach and stone loach were however much lower than that for rainbow trout. When rainbow trout were preexposed to zinc (100 micrograms/l, 5 days) before being exposed to cadmium, the fractional retention coefficient for cadmium fell to a value similar to those seen with roach and stone loach exposed to cadmium alone. The significance of these observations in relation to the nature of the intracellular proteins to which cadmium is bound in the three species is discussed in the light of their differential susceptibility to the toxic effects of cadmium.

Animals↗
PubMed1986

Glucose transport across the blood-brain barrier in normal human subjects and patients with cerebral tumours studied using [11C]3-O-methyl-D-glucose and positron emission tomography.

The kinetics of the regional cerebral uptake of [11C]3-O-methyl-D-glucose ([11C]MeG), a competitive inhibitor of D-glucose transport, have been studied in normal human subjects and patients with cerebral tumours using positron emission tomography (PET). Concomitant measurement of regional cerebral blood volume and blood flow enabled corrections for the contribution of intravascular tracer signal in PET scans to be carried out and regional unidirectional cerebral [11C]MeG extractions to be determined. A three-compartment model containing an arterial plasma and two cerebral compartments was required to produce satisfactory fits to experimental regional cerebral [11C]MeG uptake data. Under fasting, resting conditions, normal controls had mean unidirectional whole-brain, cortical, and white matter [11C]MeG extractions of 14, 13, and 17%, respectively. Mean values of k1 and k2, first-order rate constants describing forward and back transport, respectively, of tracer into the first cerebral compartment, were similar for [11C]MeG and [18F]2-fluoro-2-deoxy-D-glucose (18FDG), a second competitive inhibitor of D-glucose transport. k3, a rate constant describing FDG phosphorylation, was 20 times higher for cortical FDG uptake than the k3 fitted for [11C]MeG cortical uptake. Glioma [11C]MeG extractions ranged from normal levels of 12% to raised levels of 30%. Transport of [11C]MeG in and out of contralateral cortical tissue was significantly depressed in patients with gliomas. It is concluded that under fasting, resting conditions, regional cerebral glucose extraction remains relatively uniform throughout normal brain tissue. Gliomas, however, may have raised levels of glucose extraction. The nature of the second cerebral compartment required to describe [11C]MeG uptake is unclear, but it could represent either a useless phosphorylation-dephosphorylation cycle or nonspecific tracer uptake by a cerebral subcompartment.

3-O-Methylglucose↗
PubMed1986

Studies on regional cerebral pH in patients with cerebral tumours using continuous inhalation of 11CO2 and positron emission tomography.

Regional cerebral pH (rpH) was measured in 12 patients with cerebral tumours and in 5 normal subjects using continuous inhalation of 11CO2 and positron emission tomography (PET). Cerebral tumours with a disrupted blood-brain barrier (BBB) on computed tomography scanning had a similar rpH to that of equivalent regions of contralateral brain tissue (mean tumour rpH, 6.98; mean contralateral brain pH, 6.99). Cerebral tumours with an intact BBB were consistently found to be more alkaline than contralateral brain tissue (mean tumour rpH, 7.09). There was no significant difference between the mean rpH values obtained for peripheral cortical gray and central white matter in normal subjects (7.02 and 6.98, respectively). It is concluded that in spite of reports of raised levels of aerobic glycolysis in neoplastic tissue, there is no evidence that cerebral tumour rpH values are depressed.

Blood-Brain Barrier↗
PubMed1986

Studies on cerebral oxygen metabolism, blood flow, and blood volume, in patients with hydrocephalus before and after surgical decompression, using positron emission tomography.

Cortical oxygen utilization, oxygen extraction, blood flow, and blood volume, have been measured in patients with hydrocephalus before and after surgical decompression using positron emission tomography (PET). The hydrocephalus subjects fell into two categories: patients with recent-onset obstructive hydrocephalus and symptoms of raised intracranial pressure due to obstruction of cerebrospinal fluid (CSF) drainage by posterior fossa or third ventricular cerebral tumours, and patients with hydrocephalus of more insidious onset that was associated either with congenital abnormalities, or which was idiopathic. The hydrocephalus subjects had a significantly reduced level of mean cortical oxygen utilization (rCMRO2) and mean cortical blood flow (rCBF) compared with age-matched normal controls. Patients with recent-onset obstructive hydrocephalus associated with cerebral neoplasia had inappropriately low levels of cortical blood flow compared with their levels of cortical oxygen utilization, all having elevated levels of cortical oxygen extraction (rOER). Levels of cortical blood flow in the group of patients with more insidious-onset hydrocephalus matched levels of cortical rCMRO2, all these subjects having normal levels of rOER. All those hydrocephalus subjects who had a raised cortical oxygen extraction preoperatively increased their cortical blood flow following cerebral decompression. No improvement, however, was noted in their mean cortical oxygen utilization. By contrast, those hydrocephalus subjects with normal baseline levels of cortical extraction showed no improvement in mean cortical blood flow, oxygen utilization, or cognitive function after surgical intervention. It is concluded that if cortical oxygen extraction is elevated, hydrocephalic patients are likely to improve their cortical blood flow following cerebral decompression.

Adult↗
PubMed1986

Penile erections in myelomeningocele patients.

Of 52 post-pubertal male myelomeningocele patients, 36 (70%) appeared to have penile erections. In relation to spinal neurology, erections occurred in all of those with a positive anocutaneous reflex, 64% of those with a negative anocutaneous reflex and a level at or below the sympathetic outflow and 14% of those with a negative anocutaneous reflex and a level above the sympathetic outflow. The physiological implications of these findings are discussed.

Adolescent↗
PubMed1986

The in-vitro chemosensitivity of three cell lines derived from the VM/DK spontaneous murine astrocytoma.

Three cell lines, VM/Dk P497 P540 and P560 derived from the VM spontaneous murine astrocytoma have previously been fully characterised and found to differ in their degree of astrocytic differentiation. The in vitro chemosensitivity of the three lines has been investigated using the 35S-methionine uptake assay. Differential chemosensitivity was found to exist between the cell lines. The pattern of chemosensitivity in relation to astrocytic differentiation was complex but the least differentiated cell line, P497, tended to be the least chemosensitive.

Animals↗