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Biomedical subjects

A E Walker

Publications and source records attributed to A E Walker.

At least 73 records · Page 4Linked to original sources
PubMed1977

Histological reaction to various conductive and dielectric films chronically implanted in the subdural space.

Thirty different test patches of various thin film materials were chronically implanted in the subdural space of cats to determine their suitability as components for proposed neuroprosthetic devices. In particular, materials employed by the microelectronics industry were screened, and reactions were found to be quite dependent on specific formulations or surface preparations of otherwise similar materials. A nonspecific but severe complication of pressure necrosis under thin films that spontaneously roll and curl in vivo was noted.

Animals↗
PubMed1977

Sedative drug surveys in coma: how reliable are they?

Routine blood tests of comatose patients for drugs that depress the CNS are highly desirable, but techniques of analysis are not well standardized and the results do not correlate well with clinical condition. Determining the role of sedative drugs in coma requires a high degree of suspicion and sound clinical judgment.

Adolescent↗
PubMed1976

Immunological mechanisms in the pathogenesis of vinyl chloride disease.

Vinyl chloride (VC) disease is a multisystem disorder incorporating Raynaud's phenomenon, acro-osteolysis, thrombocytopenia, portal fibrosis, and hepatic and pulmonary dysfunction. Immunological and immunochemical investigations showed the presence of circulating immune complexes in 19 out of 28 patients with the disease and in a further two out of 30 workers exposed to VC. The immunological data were reviewed in relation to the clinical picture of the disease and to the available evidence on the metabolism of VC. The results suggest that VC disease is an immune complex disorder and that the immune response is initiated by the adsorption of VC or a metabolite on to tissue or plasma protein.

Autoantibodies↗
PubMed1976

Respirator brain. Report of a survey and review of current concepts.

Because of renewed public and scientific interest in the concept of brain death and its diagnostic criteria, an opinion survey was undertaken, polling the membership of the American Association of Neuropathologists, regarding the definition, gross and microscopical features, and pathogenesis of the syndrome popularly designated the "respirator brain." Of the 191 respondents who completed the questionnaire, 174 (91%) indicated that the term respirator brain is properly used to describe a specific pathological entity, and 160 (84%) considered the characteristics of respirator brain to be distinct from those of late fixation. Of the 174 respondents who accepted the designation, 148 (85%) regarded a history of respiratory dependency as essential, and a vast majority (95%) agreed that extensive tissue necrosis occurs with little inflammatory cell reaction; other criteria were more controversial. Microscopical changes that suggest a pathogenetic mechanism attracted a number of informative, limiting, or qualifying remarks. Nonetheless, 54% thought that impaired cerebral blood flow contributed to pathogenesis.

Brain↗
PubMed1976

Bullous transient acantholytic dermatosis.

We have been three cases of a bullous variant of transient acantholytic dermatosis. Skin biopsy specimens showed histopathologic changes identical to pemphigus foliaceus, but immunofluorescent studies showed no tissue-fixed or circulating antibodies to intercellular antigens. The bullous eruption lasted a few weeks to several months and healed without scarring or recurrence. The lesions healed with topical and/or systemic corticosteroid therapy.

Acantholysis↗
PubMed1975

DC potentials of temporal lobe seizures in the monkey.

In 8 monkeys, made epileptic by alum or penicillin injection into temporal lobe structures, 40 seizures were studied by both DC cortical potential and subcortical EEG recordings. Eighteen seizures of lateral temporal origin had an abrupt negative DC potential shift of 0.5 to 2.0 mV in and around the focus. The frontal, parietal and occipital cortices did not develop DC potential changes, perhaps due to the limited propagation of the neocortical seizures. Twenty-two seizures of medial temporal origin showed a negative shift of the anterior, inferior or lateral temporal cortex in 85% of seizures. The other 15% had a positive or no shift. In hippocampal seizures, a positive displacement was sometimes seen prior to the main negative shift in the lateral temporal cortex. The remote cortex developed only a minimal positive shift in 30% of the mediotemporal seizures. A marked negative shift in the frontocentral cortex was the first sign of impending generalization, which may result from a series of chain reactions with seizure propagation, involving more and more structures of the brain. Registration of DC potentials in temporal lobe seizures may give insight into the nature of abnormal EEG activities and to some extent into the origin of seizures.

Alum Compounds↗
PubMed1975

Outcome of head trauma: age and post-traumatic seizures.

A series of 307 head-injured children (0-14 yr) was followed from the acute phase for up to six years with a separate group of 220 non-injured siblings as control. The neurological, EEG, psychometric and psychiatric findings were analysed. Here we discuss the influence of age at time of injury with respect to post traumatic seizures. Overall incidence of early seizures (during first week) was 15% and of late seizures (one week to six years) was 5%. Youngest children (0-2 yr), however, had a low frequency (3%) of early seizures, but 11% frequency of late seizures. The frequency of early seizures was higher and frequency of the late seizures was lower in children than in adults with either closed or penetrating injuries. Comparison of these data with those of other investigators suggested that the overall incidence of early seizures in children 2-14 yr of age is higher than in adults, whereas the late occurrence of seizures appears to be lower than that in adults. The pattern, however, in the youngest children 0-2 yr of age resembles that of adults (particularly adults with penetrating injuries).

Adolescent↗
PubMed1975

The neuropathological findings in irreversible coma. A critque of the "respirator".

1. Postmortem examinations were made on 240 of the 459 cases succumbing (52 percent of the deaths) in the Collaborative Study on Cerebral Survival; the central nervous system was examined in 226 cases. 2. The autopsy was performed on an average of 15.3 hours after death. 3. The mean weight of the brains was 1450 plus or minus 196 grams; the mean weight of the brains of patients on whom resuscitation was stopped, presumably on the basis of "cerebral death," was greater than that of the patients succumbing to cardiac failure. There was a tendency for the brain to increase in weight about 24 hours after the initiation of resuscitative measures. At that time, swelling, discoloration, softening, congestion, and brain herniations also became more prominent. 4. On the basis of a survey of American neuropathologists and the data from this study, the entity commonly termed "respirator brain" may be confirmed. This is a dynamic process that is complicated by concurrent postmortem changes. The respirator brain requires time (approximately 24 hours) for maturation; many patients die a cardiac death during the metamorphosis. If the patient survives for 3 to 4 days, the percentage dying with typical respirator brains is less, and more patients have electroencephalograms with biological activity. 5. The following clinical factors tend to be associated with an increased number of respirator brains: A. Cerebral trauma B. Subnormal body timperature C. Low systolic blood pressure D. Dilated pupils E. Pupils unresponsive to light F. Absence of cephalic reflexes G. Electrocerebral Silence (ECS) 6. The following factors have no apparent effect on the number of respirator brains or tend to be associated with fewer respirator brains: A. Severe drug intoxications B. Small reacting pupils C. Medications D. Presence of spinal reflexes E. Presence of biological activity (BA) in the electroencephalogram 7. A set of common criteria for a respirator brain was used to test the following: A. The local and consultant neuropathologist's diagnosis of respirator brain B. The significance of critical perfusion pressure and critical oxygen tension in respirator brain C. The role of cardiac output in the production of a respirator brain 8. Since a respirator brain is an imperfectly defined entity, an exact correlation with any combination of clinical and EEG findings could not be expected. The use of a standardized measurement of CBF seems a logical and promising confirmatory test for respirator brain.

Adult↗
PubMed1975

Criteria of cerebral death.

This critical survey of the current means of determining cerebral death has indicated certain shortcomings in each of the sets of criteria currently in use. It is apparent that criteria applied at a point in time and based upon a single organ system-clinical history and findings, EEG examinations or cerebral blood flow determinations - will fall short of absolute accuracy. The clinical examinations alone have an accuracy approximating 90%, the EEG findings have greater accuracy but a much smaller scope. Cerebral blood flow studies, short of four-vessel angiography, achieve about the same accuracy, but their scope is not yet determined. The combination of all three may prove to be optimal.

Brain Death↗
PubMed1974

The brain team.

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Cerebrospinal Fluid Shunts↗