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Biomedical subjects

D G Thomas

Publications and source records attributed to D G Thomas.

At least 163 records · Page 9Linked to original sources
PubMed1989

Application of CT-directed stereotaxy in the determination of functional neurosurgical targets in the diencephalon and cerebral hemisphere.

The descriptions of two techniques allowing for CT target determination in functional neurosurgery are presented, the first for thalamic and peri-thalamic explorations in the treatment of dyskinesiae and chronic pain, the second for the implantation of multiple hemispheric depth electrodes in the assessment of chronic drug-resistant epilepsy.

Cerebral Ventricles↗
PubMed1988

Effect of 2-mercaptoethanol on the electrophoretic behavior of rat and dogfish metallothionein and chromatographic evidence of a naturally occurring metallothionein polymerization.

1. Metallothionein behavior in SDS-PAGE has been characterized. 2. It has been found that metallothionein behavior in this electrophoretic system depends upon the reducing environment. Migration as a well-defined protein band is only achieved in the presence of 2-100 mM 2-mercaptoethanol. 3. Within those 2-mercaptoethanol levels, both rat and dogfish metallothionein migrate as a protein with a molecular weight several times higher than that expected by amino acid analyses. This is not due to molecule oxidations, since this effect is promoted by the presence of 2-mercaptoethanol. 4. No effect of 2-mercaptoethanol on metallothionein behavior is found in conventional PAGE. 5. The present results suggest that to study the effect of 2-mercaptoethanol in SDS-PAGE is a simple and accurate way to identify a protein as metallothionein. 6. It has also been found that metallothionein aggregates naturally in the absence of ionic strength.

Acetates↗
PubMed1988

A comparison of real-time ultrasonography with intravenous urography in the follow-up of patients with spinal cord injury.

Patients with spinal cord damage require an expert urological assessment at regular intervals. Seventy-five patients with neurogenic bladder dysfunction associated with spinal paralysis attending for routine assessment of the upper urinary tract had both intravenous urography (IVU) and renal ultrasonography. The combination of a plain radiography of the abdomen and an ultrasound scan of the kidneys was found to be a cheap, safe and reliable alternative to intravenous urography for the regular follow-up of these patients.

Adolescent↗
PubMed1988

Experience with the Brindley anterior sacral root stimulator.

Brindley anterior sacral root stimulators have been implanted into 22 spinal cord injured patients from the spinal injury units in Cardiff and Sheffield. The group comprised 20 men and 2 women (15 paraplegics and 7 tetraplegics); 16 patients are using the implant, of whom 11 (68%) are continent. Of the remaining 5, 4, who empty completely, are incontinent because of inability to use the implant with sufficient frequency; 6 patients are not using their implant, though 4 are continent. Of 11 patients with detrusor/sphincter dyssynergia, sphincterotomy was necessary in 3 patients before implantation and in a further 3 after implantation. Of 4 patients with abnormal upper tracts prior to implantation, 2 resolved and 2 deteriorated, in the presence of dyssynergia; 1 patient developed hydronephrosis after implantation, having previously had normal upper tracts. Although erectile function with the stimulator was clinically adequate in 6 patients, in no patient has intercourse been achieved because of concurrent lower limb spasm.

Adult↗
PubMed1988

Long-term follow-up of selective sacral neurectomy.

Between 1976 and 1981, 22 patients underwent selective, complete sacral root section as a treatment for severe detrusor overactivity. Eighteen were followed up for more than 4 years (mean 6.2). Thirteen of the 22 patients had significant symptomatic improvement lasting for more than 4 years post-operatively (59%), 8 of whom had stable bladders. It was concluded that this operation still has a place in the treatment of detrusor overactivity.

Adolescent↗
PubMed1988

Urological abnormalities in young women with severe constipation.

Anorectal and urodynamic studies were carried out in 10 young women with severe constipation and the results compared with those obtained in controls. The lowest volumes that provoked a desire to defecate (constipated 200 +/- 50 v controls 110 +/- 10 [mean +/- SEM] ml: p less than 0.05), and a desire to micturate (constipated 560 +/- 40 v controls 295 +/- 15 [mean +/- SEM] ml: p less than 0.001), were significantly greater in constipated patients compared with controls. The maximum tolerable rectal volume (380 +/- 30 v 290 +/- 20 [mean +/- SEM] ml: p less than 0.05) and the bladder capacity (720 +/- 50 v 540 +/- 10 [mean +/- SEM] ml: p less than 0.001) were also increased in the constipated subjects compared with controls. Electromyographic studies show failure of relaxation of the external anal sphincter (EAS) on attempted defecation in all 10 patients; and eight of these patients actually contracted their EAS when they strained to defecate, causing a functional outlet obstruction. Urodynamic studies showed normal urinary flow rates, normal detrusor pressures and normal radiology during voiding. Thus, these studies suggest that constipated patients have an increase in capacity and a reduction in sensitivity in the urinary bladder as well as in the rectum, but showed no evidence of obstruction to urine flow.

Adult↗
PubMed1988

Computer-directed stereotactic biopsy of intrinsic brain stem lesions.

Despite advances in the neuro-imaging of the brain stem, an accurate diagnosis of intrinsic lesions in this region requires tissue sampling and histological verification. We have performed a series of computer-directed stereotactic procedures in 12 patients with intrinsic brain stem lesions. A positive diagnosis was obtained in 11 cases and therapeutic intervention was possible in four. There was no operative mortality. Because of the importance of an accurate diagnosis in order to avoid inappropriate therapy, together with the relative safety of the technique, computer-directed stereotactic biopsy should be considered in all patients harbouring an intrinsic brain stem mass.

Adolescent↗
PubMed1988

Neurophysiological studies of human cognitive development in premature infants: an approach to the study of maturational brain processes.

In normal cerebral development, language function typically becomes lateralized in the left hemisphere in most individuals. It is theorized that disturbances in the development of this cerebral asymmetry may result in language dysfunction such as dyslexia and dysphasia. Recently, it has been reported that language disturbances occur in many children who were born prematurely and who have suffered insults such as asphyxia and hyperbilirubinemia. Premature infants have also been shown to have a high incidence of abnormalities associated with auditory reception. Thus, it is possible that perinatal insults could lead to disturbances in the development of normal central nervous system (CNS) functional organization which result in later learning disabilities. The extent to which such learning impairments are related to nervous system development and to the subsequent limitations placed by neonatal insults upon cognitive capacities, is unknown. The purpose of this study was to examine the relationships among neurophysiological indices of CNS function, language development, and general infant competence over the first two years of life in order to provide information concerning the ontogenesis of higher cognitive functioning in both preterm and full term infants. In this report we will present an overview of the relevant issues in the area and focus on some of the neurophysiological data obtained to date. The approach discussed might prove useful in the study of any group of infants at risk for cognitive and/or developmental disorders related to a variety of perinatal insults.

Brain↗
PubMed1987

Enzyme-linked immunosorbent assay (ELISA) for metallothionein.

A heterogeneous, double-antibody, fluorometric enzyme-linked immunosorbent assay (ELISA) is described for the detection and quantitation of metallothionein(MT) The protocol uses the same immunological reagents as the radioimmunoassay(RIA) developed previously in this laboratory; fluorescence replaces radioactivity for detection of the reference antigen in the specific binding reaction. Present results indicate that the developed ELISA has approximately the same range of capability in detecting and quantitating MT as is characteristic of the RIA. The ELISA has the advantage that the time required to perform a typical assay is significantly less than that required for the RIA.

Animals↗
PubMed1987

The function of metallothionein in cell metabolism.

Rat hepatocytes were obtained and cultured in media containing 65Zn in the presence or absence of insulin and hepatocyte growth factors. Cells were also grown in a pulse-chase type of experiment. After varying periods of incubation the cells were harvested and assayed for zinc, protein and metallothionein. Although the amount of intracellular zinc (Zn/cell protein) was constant, the amount of metallothionein (MT/cell protein) in the cells exposed to zinc alone increased to a level approximately five times higher than the cells cultured in the presence of the growth factors. Chromatographs established that for cell cultured in the absence of hepatocyte growth factors all the 65Zn coeluted with metallothionein whereas for cultures maintained in the presence of these factors the zinc was associated with higher molecular weight components in addition to being present in the 10,000 dalton peak.

Animals↗
PubMed1987

Metallothionein gene expression and cadmium toxicity in freshwater fish.

Certain species of fish e.g. rainbow trout, are particularly susceptible to poisoning by cadmium in their aquatic environment whereas others e.g. roach and stone loach, are much more resistant. It is postulated that the vulnerability of the salmonids arises because 1) existing metallothionein (MT) in the tissues of these fish is unable to bind cadmium and 2) the toxic metal (in contrast to zinc) cannot switch on the gene(s) for apo-thionein production de novo. Consequently, cadmium is sequestered in the liver, kidney and gills of these fish by two low mol.wt. non-metallothionein proteins for which no excretion mechanism appears to exist.

Animals↗
PubMed1987

MRI-directed stereotactic biopsy of cerebral lesions.

Using a modified CT-directed stereotactic system we have performed MRI-directed biopsies in five patients whose intracerebral lesions were not clearly shown by CT. Tissue sampling from targets defined on the MR image enabled a histological diagnosis to be made in four of the five cases.

Adult↗
PubMed1987

An experimental trial of cyclic nucleotides on multicellular spheroids derived from human brain tumours.

The effects of cyclic nucleotides, dibutyryl cyclic adenosine monophosphate and dibutyryl cyclic guanosine monophosphate (db-cAMP and db-cGMP), on the growth rate of multicellular tumour spheroids were evaluated by comparing the growth delay and colony forming efficiency in vitro. Multicellular tumour spheroids were derived directly from human brain tumours. To compare the chemotherapeutic effect of cyclic nucleotides, CCNU was used as a known effective cytotoxic drug on malignant gliomas. Significant growth delay was obtained by db-cAMP (p less than 0.001) while CCNU was tumouricidal rather then producing a delay in growth of the tumour spheroids. Db-cGMP found not to be effective in decreasing the growth rate of the tumour spheroids in vitro (p greater than 0.2). The role of cyclic nucleotides in brain tumours is discussed on a review basis.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1987

A cultured human oligodendroglioma cell line and herpes simplex virus-infected cells share antigenic determinants.

Cell cultures derived from 60 different human brain tumors were screened for the presence of HSV infected cell antigens by indirect immunofluorescence using a polyclonal rabbit antiserum reacting with herpes simplex virus (HSV), 3 monoclonal antibodies recognising different HSV-specified proteins, and one monoclonal antibody T181 reacting with a DNA binding protein present in HSV-infected cells. Only one tumor (IN/157), derived from an oligodendroglioma, stained with the polyclonal antiserum. T181 but none of the other monoclonal antibodies used also specifically reacted with IN/157 cells. High levels of the T181-defined protein were detected using immunoblotting in HSV-1 infected BHK/21 cells but not in IN/157 cells. T181 may react with either an epitope shared between two different molecules in HSV-1 infected and IN/157 cells or a cell-specified polypeptide that is upregulated after HSV-1 infection.

Antigens, Viral↗
PubMed1987

Auditory event-related potentials in waking infants and adults: a developmental perspective.

Auditory event-related potentials (AERPs) were recorded in waking 1 month olds, 3 month olds, 6 month olds and adults in order to study the morphology and development of the wave form in the waking subject. Previous data were generally obtained in sleeping or drowsy infants. The findings indicated that there were 3 quantitative changes in the AERP over the first 6 months of life in waking infants: an increase in the latency of peaks, an increase in peak amplitude, and a decrease in intersubject variability. Adult peak latencies were generally shorter than those for 3 month olds and 6 month olds. Further, latencies of earlier AERP peaks for 1 and 6 month olds, in the present study, were comparable to those reported in previous investigations with sleeping infants. However, latencies of later AERP peaks differed from those of previous reports and were closer to those reported for waking adults. With respect to the amplitude, the 6 month olds, in general, had the highest amplitudes, the 1 month olds the lowest, and the 3 month olds and adults fell in between the two groups. Some differences were present between early and late components. The findings of this study are significant in that the AERPs were quantitatively different from those reported in earlier work with sleeping or drowsy infants. If cognitive and perceptual development is to be studied, it is necessary to obtain data on waking subjects. The data presented in this report are consistent with behavioral studies of biobehavioral shifts that are associated with changes in responsivity of the organism to stimuli during the first 6 months of life.

Adult↗