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Biomedical subjects

D G Thomas

Publications and source records attributed to D G Thomas.

At least 235 records · Page 13Linked to original sources
PubMed1983

Stratified trend and homogeneity analyses of proportions and life table data.

Tests for linear trend and homogeneity among proportions and analogous time adjusted tests for life table data are programmed for stratified data. For proportions, the maximum likelihood estimator of the common logistic slope and its approximate standard error is given. This parameter is related to the relative risk for the factor under test. The model is a simpler and more relevant subcase of the general linear multiple logistic model. Tests of fit include a chi-square test of departure from trend for both types of data, and, for proportions, a test for the equality of slopes among groups of strata. The program is particularly useful for large prospective studies in epidemiology, but may also prove helpful for case-control studies, clinical trials, and combining animal studies. Several optional analyses are included. The program generalizes most aspects of a previously published program by Thomas, Breslow, and Gart (Trend and homogeneity analyses of proportions and life table data. Comp. Biomed. Res. 10, 373 (1977)). A FORTRAN card deck with documentation is available upon request.

Actuarial Analysis↗
PubMed1983

The use of a control or baseline condition in electrophysiological studies of hemispheric specialization of function.

Asymmetries in event-related potential (ERP) measures between the two cerebral hemispheres in humans may not be apparent when the absolute values of left and right hemisphere recordings are only considered within the context of one experimental condition. ERP asymmetries may only emerge when results obtained during experimental conditions designed to differentially activate the two cerebral hemispheres are compared to a baseline or control condition involving low-level cognitive demands. Both theoretical and empirical considerations of such a baseline condition are discussed.

Adult↗
PubMed1983

Cell lines (VMDk) derived from a spontaneous murine astrocytoma. Morphological and immunocytochemical characterization.

Three cell lines (VMDk) derived from a spontaneous, murine astrocytoma, which produce tumours when injected either subcutaneously or intracranially into syngeneic mice, have been examined in vitro. Ultrastructurally, the cells show astrocytic features but each line differs in its degree of differentiation. Treatment with both dexamethasone and dibutyryl adenosine 3',5'-cyclic monophosphate (dbcAMP) increases intracytoplasmic differentiation and causes surface structural changes. The addition of dbcAMP also induces a statistically significant increase in the length and number of cell processes. All three cell lines express the astrocyte-specific markers, glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS), by indirect immunofluorescence, with two lines showing an increased propensity to stain for GFAP following dbcAMP treatment. The cell surface antigen fibronectin is also detected in all lines. Thus these VMDK cell lines exhibit both the morphological and antigenic characteristics of astrocytes and respond to dexamethasone and dbcAMP and may be used to provide a suitable in vivo-in vitro model system for the study of astrocytoma.

Animals↗
PubMed1983

Multicellular tumour spheroids derived from human brain tumours.

Multicellular tumour spheroids were prepared from a total of 46 human brain tumour biopsies by collagenase digestion and plating into agar coated flasks. Both primary malignant and secondary tumours formed spheroids with some correlation between the malignancy of tumour and the ability to undergo spheroid formation. The spheroids were capable of progressive growth, the rate of which was dependent, to some extent, on environmental conditions and was reflected by an increase in cell number within the spheroids. Spheroids prepared in this way may prove to be useful models for in vitro chemosensitivity and the general biology of brain tumours.

Adult↗
PubMed1983

A comparison of the accumulation and protein binding of environmental cadmium in the gills, kidney and liver of rainbow trout (Salmo gairdneri Richardson).

Rainbow trout were exposed to cadmium in their aquarium water for different lengths of time and at different concentrations. More than 99% of the total body loads accumulated under all such conditions of exposure was found in the liver, kidney and gills. Comparison of the metal-binding proteins in these organs indicated that two low mol. wt proteins sequestered the cadmium while zinc was bound to metallothionein. Cadmium was not found in association with metallothionein unless artificially high concentrations were introduced either by intraperitoneal injection of the fish or by dialysis of tissue extracts in vitro.

Animals↗
PubMed1983

The failure of human leukocyte interferon to influence the growth of human glioma cell populations: in vitro and in vivo studies.

Five high-grade (3 grade III and 2 grade IV) astrocytoma tumour cell populations were treated with a preparation of Human Leukocyte Interferon either in monolayer cell culture or as multicellular spheroids in vitro or as xenografts growing in immune-deprived mice in vivo. A moderate and transient sensitivity was seen in one grade III tumour when tested in both of the in vitro assays, but no inhibition of growth was seen in vivo. Two tumours which were apparently resistant to Interferon treatment responded to orthodox chemotherapy. When used in conjunction with BCNU, Interferon was not effective in prolonging delay in tumour growth. It is concluded that Interferon is unlikely to be an effective agent in the treatment of malignant brain tumours.

Adult↗
PubMed1983

Assay of anticancer drugs in tissue culture: cell cultures of biopsies from human astrocytoma.

A method has been developed for measuring the drug sensitivity of human gliomas in short-term culture, using scintillation counting or autofluorography. Cell cultures prepared from malignant astrocytomas were treated with anticancer drugs whilst in exponential growth in microtitration plates. After drug treatment and a recovery period, residual viability was measured by [3H] leucine incorporation followed by scintillation counting or by [35S] methionine incorporation and autofluorography in situ. In 5 glioma cell lines tested against 6 drugs, the microtitration method correlated well with monolayer cloning. Although replicate samples of the same tumour showed little variation in chemosensitivity, there was marked variation between the chemosensitivities of cultures derived from the tumours of different patients. However, as variability between replicates was apparent during drug exposure or shortly after, it is important to allow the assay to run as long as possible after drug removal. It is hoped that this assay may provide the basis of a method for the prediction of in vivo chemosensitivity or the screening of potential chemotherapeutic drugs.

Antineoplastic Agents↗
PubMed1983

The effect of anteromedian sphincterotomy on penile erections in patients with neuropathic bladder.

In a series of 94 patients with neuropathic bladder undergoing anteromedian urethral sphincterotomy, 20 had no penile erections prior to surgery. In the remaining 74 cases, seven (9 X 5 per cent) had diminished erections postoperatively and three (4 per cent) no erections. It is considered that the risk of this complication is less with anteromedian sphincterotomy than with bilateral 3 and 9 o'clock sphincterotomy.

Adolescent↗
PubMed1983

Alterations in the cellular immune response of patients with cerebral glioma, benign intracranial tumour, and spontaneous subarachnoid haemorrhage measured in vitro by the leucocyte migration inhibition test.

Leucocyte migration inhibition in response to ubiquitous antigens was studied in 104 patients as an in vitro indicator of cell-mediated immunity. Patients with cerebral glioma, benign intracranial tumours, and subarachnoid haemorrhage demonstrated impaired inhibition of leucocyte migration compared with control subjects. The greatest impairment occurred in patients with subarachnoid haemorrhage, while the least impairment was seen in patients with glioma. Significant rises in inhibition of leucocyte migration in response to antigen preparations from glioma and normal brain were seen in the early post-operative period in patients with glioma and subarachnoid haemorrhage. Impaired cellular immunity, together with sensitivity of lymphocytes to brain-derived antigens, are features of cerebral disease in general and not specific for glioma.

Adenoma↗
PubMed1983

An intracranial metastasis from a PRL secreting pituitary tumour.

A 70-year-old man developed panhypopituitarism and was found to have hyperprolactinaemia and a locally invasive pituitary tumour. The visual fields were unaffected and therefore the patient was treated with hormone replacement only. After 3.5 years during which time the pituitary tumour had not enlarged further, the patient developed a mass in the left cerebello-pontine angle. This mass was subsequently shown to be entirely separate from, but histologically identical to, the pituitary tumour and the cells of both contained PRL. Evidence was obtained to show that the tumour had spread by a vascular route. This is the second reported case of a malignant prolactinoma.

Adenoma, Chromophobe↗
PubMed1983

Invited review. Nervous system antigens.

Some of the better characterized proteins (markers) of the nervous system are described. The availability of specific antibodies to these markers has allowed the localization and assay of the proteins in tissue and biological fluids. There is some evidence that autosensitization may occur. Clinical application of these markers includes the evaluation and prognostic significance after stroke and head injury. The diagnostic histopathological use of the markers in the investigation of various tumours is summarized.

Antigens↗
PubMed1983

Long term indwelling urethral catheterisation for congenital neuropathic bladder.

Long term urethral catheterisation remains an important and effective method of achieving dryness and maintaining renal function in children with congenital neuropathic bladders. Those most likely to require an indwelling catheter are girls who are severely disabled because of myelomeningocele. The management of such catheterisation and its consequences, in the light of our experience with a 100 children treated over a 12 year period, is described.

Adolescent↗
PubMed1983

Dorsal root entry zone lesions (Nashold's procedure) for pain relief following brachial plexus avulsion.

Brachial plexus avulsion is an important cause of severe intractable pain, particularly in young motor cyclists. The pain usually develops soon after the injury. In a minority of cases severe pain persists and is refractory to management. Nineteen patients are reviewed in whom dorsal root entry zone lesions have been produced for pain relief. The operative technique is described. Early post-operative motor or sensory disturbance in the ipsilateral leg have been temporary side effects, with mild persisting deficits in a minority. Sixteen cases have had significant persisting pain relief. The maximum follow-up period is 2 1/2 years.

Accidents, Traffic↗
PubMed1983

Changes in patterns of hemispheric electrophysiological activity as a function of instructional set.

Investigations of differential hemispheric functioning which have used auditory event-related potentials (AERPs) typically employ paradigms in which two or more conditions are used. In these paradigms, conditions typically differ from each other with respect to both the physical aspects of the stimuli and the operations the subject must perform on these stimuli. Because both the subject's task and the physical properties of the stimuli change from one condition to another, it is unclear whether different patterns of AERP cerebral asymmetries obtained between conditions are primarily a function of differences in the stimuli (e.g., verbal vs. musical stimuli) or of endogenous factors such as the subject's cognitive approach to the processing of the stimuli. In the present study, two conditions with identical stimuli were employed but different instructions were given about how to process these stimuli. Music and paired tones were simultaneously presented in both conditions. In the Music Condition, subjects performed a task which involved attending to the music and ignoring the tones. In the Tones Sequence Condition, subjects counted specified sequences of tones and ignored the music. The results indicated that there were different patterns of left-right hemispheric AERP relationships between the two conditions. These findings support the hypothesis that endogeneous factors play a significant role in differential hemispheric functioning and that the AERP technique employed in this paradigm is a sensitive index of changes in electrophysiological activity associated with these endogeneous factors.

Acoustic Stimulation↗
PubMed1983

Spinal cord compression due to prolapse of cervical intervertebral disc (herniation of nucleus pulposus). Treatment in 26 cases by discectomy without interbody bone graft.

Twenty-six patients who presented with spinal cord compression due to cervical disc prolapse (herniation of the nucleus pulposus) were treated by anterior discectomy. There was a high incidence of disc prolapse at the C3-4 level. The most severe degrees of preoperative disability were associated with prolapse at that level. Impairment of posterior column function, particularly in the upper limbs, played a major part in producing disability. High cervical disc prolapse can produce a clinical picture that is predominantly like that of a posterior cord syndrome. Preexisting fusion of vertebral bodies in the cervical spine and a history of cervical spinal trauma appear to be predisposing factors. Discectomy is an effective treatment of this condition. Spinal cord compression due to cervical disc prolapse should be distinguished from spondylotic myelopathy.

Adult↗