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Biomedical subjects

A M Burke

Publications and source records attributed to A M Burke.

At least 19 recordsLinked to original sources
PubMed1998

Estrogen replacement attenuates effects of scopolamine and lorazepam on memory acquisition and retention.

A multiple-trial passive avoidance paradigm was used to examine and compare the ability for estrogen replacement to attenuate learning and memory deficits produced by the muscarinic antagonist scopolamine and the benzodiazepine lorazepam. The multiple-trial paradigm was used in order to distinguish effects on acquisition from effects on retention. Estrogen replacement significantly attenuated a scopolamine-induced deficit on passive avoidance acquisition, but not retention. The ability for estrogen to attenuate the effect of scopolamine on acquisition was observed only when the analysis was limited to animals with serum levels of estradiol <200 pg/ml, suggesting that higher levels of estradiol were ineffective. This observation is consistent with at least one recent study showing dose-related effects of estrogen on ChAT-like immunoreactivity in the basal forebrain and supports the hypothesis that effects of estrogen on basal forebrain cholinergic neurons can help to reduce cognitive deficits associated with cholinergic impairment. Estrogen replacement was also observed to protect against a lorazepam-induced impairment on passive avoidance retention. This effect was observed specifically in animals that received estrogen prior to and during training and was not due to any effect of estrogen on serum levels of lorazepam following acute lorazepam administration. Collectively, these data demonstrate the ability for estrogen replacement to attenuate specific pharmacologically induced impairments in learning and retention and provide additional clues as to potential mechanisms by which estrogen replacement may help to reduce cognitive deficits associated with aging and Alzheimer's disease in postmenopausal women.

Animals↗
PubMed1997

Enhanced plasma DHEAS, brain acetylcholine and memory mediated by steroid sulfatase inhibition.

Steroid sulfatase inhibitors can alter the metabolism of neurosteroids which modulate brain function. Administration of the non-steroidal steroid sulfatase inhibitor (p-O-sulfamoyl)-N-tetradecanoyl tyramine (DU-14) to rats for 15 days increased plasma dehydroepiandrosterone sulfate (DHEAS) concentrations by 88.2%, decreased plasma dehydroepiandrosterone (DHEA) concentrations by 84.6%, increased hippocampal acetylcholine (ACh) release determined via in vivo microdialysis by almost 3-fold, and produced a significant blockade of scopolamine-induced amnesia as measured by a passive avoidance test. These results suggest DHEAS rather than DHEA enhances brain cholinergic function and that steroid sulfatase inhibition may become an important tool for enhancing neuronal functions, such as memory, mediated by excitatory neurosteroids.

Acetylcholine↗
PubMed1997

Memory enhancement mediated by the steroid sulfatase inhibitor (p-O-sulfamoyl)-N-tetradecanoyl tyramine.

The intent of this study was to determine whether altering the metabolism of neurosteroids via blockade of the enzyme, steroid sulfatase, could enhance memory retention in rats. The steroid sulfatase inhibitor p-O-(sulfamoyl)-N-tetradecanoyl tyramine (DU-14) was administered alone and in combination with the neurosteroid dehydroepiandrosterone sulfate (DHEAS) to rats which were then tested for the reversal of scopolamine-induced amnesia. A single 30 mg/kg IP dose of DU-14 produced a significant inhibition of steroid sulfatase activity in both brain (14.8%), and liver (85.2%) tissues, 24 hours following administration. In a passive avoidance test, DU-14 enhanced the reversal of amnesia by DHEAS. These results suggest that steroid sulfatase inhibition can potentiate the memory enhancing properties of DHEAS.

Adjuvants, Anesthesia↗
PubMed1991

Non-neoplastic pineal cysts.

We identified 53 patients with non-neoplastic cysts of the pineal gland. In contrast to patients with pineal neoplasms, pineal cysts are usually asymptomatic. They infrequently obstruct the aqueduct to cause hydrocephalus or compress the tectum to produce the neuro-ophthalmologic signs of dorsal midbrain dysfunction. Obstructive hydrocephalus was present in only five patients (9.4%); three of them showed clinical signs of Parinaud's syndrome. CT and MRI typically reveal a cystic mass that averages 1.6 cm in anteroposterior (A-P) diameter with calcification at the periphery and faint rim-like contrast enhancement. Sagittal MRI is the most useful diagnostic test because it shows the anatomic relationship of the cyst to the aqueduct. The mass may compress the tectum and distort the proximal aqueduct; occasionally a large cyst may occlude the aqueduct. All patients with obstructive hydrocephalus had cysts greater than 2.0 cm in A-P diameter. Nine patients had suboccipital craniotomy. In all of them, the cysts contained clear fluid and were easily removed. We advocate conservative management with clinical observation of these benign lesions that may be developmental variants of normal pineal gland.

Adolescent↗
PubMed1991

Sedation for paediatric computerized tomography--a double-blind assessment of rectal midazolam.

This double-blind study investigated the rectal administration of midazolam as an alternative to general anaesthesia for elective computerized tomography (CT) of the brain. Thirty children were randomly allocated to receive either midazolam 0.3 mg kg-1 (Group 1) or midazolam 0.6 mg kg-1 (Group 2) by the rectal route. Sedation was obtained in 13 children in Group 1 and 12 in Group 2 but this was only satisfactory for scanning in seven children in Group 1 and eight in Group 2. We concluded that although the technique produced sedation, it did not reliably produce satisfactory conditions for CT scanning.

Administration, Rectal↗
PubMed1987

Regional variation in cerebral perfusion during acute hypertension.

Regional cerebral blood flow (rCBF) was measured in rats to define the autoregulatory response at different levels of hypertension. Mean arterial blood pressure (MABP) was raised with IV metaraminol. rCBF was measured using 14C-iodoantipyrine. Autoregulation was intact in normotensive animals and those with MABP of 152 to 158 mm Hg. At higher pressures, autoregulation was abnormal and heterogeneous. Hyperperfusion was most prominent in cerebellum, parietal gray matter, thalamus, striatum, and pons. These anatomic sites are recognized sites of hypertensive hemorrhage in humans.

Animals↗
PubMed1984

Computed tomography in the diagnosis of iliopsoas abscesses.

Two cases in which patients presented with lower back pain and bacteraemia, and in which the diagnosis of iliopsoas abscess was made by computed tomography, are reported. Before the introduction of computed tomography, this diagnosis was difficult to establish by means of clinical and radiological investigations. Computed tomography makes it possible to obtain a clear view of the retroperitoneum.

Abscess↗
PubMed1984

Strongyloides stercoralis hyperinfection masquerading as cerebral vasculitis.

Strongyloides stercoralis hyperinfection is a unique opportunistic infection in which the nematode disseminates widely to cause a multisystem illness. We treated a patient with systemic lupus erythematosus in whom ileus and fever developed and who later lapsed into coma. A xenon Xe 133 cerebral blood flow study showed a global reduction in flow, compatible with CNS vasculitis. The patient's condition failed to improve with high-dose steroid therapy, but he recovered rapidly after Strongyloides larvae were found in stool and sputum and treatment with thiabendazole was begun. We believe that hyperinfection explained the patient's symptoms and should be considered as a cause of diminished cerebral perfusion and mentation in immunosuppressed patients.

Brain Diseases↗
PubMed1983

Ileopopliteal fistula in Crohn's disease.

A patient with Crohn's disease is reported, in whom a fistula, which originated in the terminal ileum, ultimately reached the skin behind the right knee.

Crohn Disease↗
PubMed1983

Occurrence of oligoclonal bands in multiple sclerosis and other CNS diseases.

The results of cerebrospinal fluid agarose gel electrophoresis in 300 consecutive patients were correlated with neurological examinations and diagnoses, other cerebrospinal fluid studies, and the results of evoked potential examinations. The presence of oligoclonal bands was the most sensitive test for multiple sclerosis (MS); bands were present in from 100% (11/11) of patients with definite MS to 82% (27/33) of those with possible MS (classified by McAlpine criteria). The visual evoked response was the next most sensitive study. Thirty-eight patients without MS or related disorders had bands in the IgG region. Three patients had plasma cell dyscrasias. Seven patients had thick single bands. Single bands did not correlate with chronic polyneuropathy but appeared to be an artifact of storage. Twenty-eight patients had active neurological disease, including cerebral infarction (in 5), viral infection (in 4), remote effect of carcinoma (in 4), and acute and chronic polyneuropathies (in 6). In acute illnesses (i.e., vascular insults), repeat electrophoresis showed disappearance of bands. In continually active disease, bands persisted. These results indicate that the presence of oligoclonal bands provides sensitive supporting evidence for the diagnosis of MS but that bands may be present in other disorders, including those not directly related to infection or abnormal immune response. The data suggest that oligoclonal bands may represent an immune response to neurological injury that is prominent in disorders with a particularly intense or continuous antigenic stimulus.

Central Nervous System Diseases↗
PubMed1983

Aortocaval fistula associated with ruptured aortic aneurysm.

Seven cases of rupture of an abdominal aortic aneurysm into the inferior vena cava are reported. In the management of this rare condition it is important to make the diagnosis preoperatively. Most cases show evidence of a large arteriovenous fistula which can, on occasions, dominate the clinical picture, e.g. cyanosed lower extremities or cardiac failure, but abdominal pain is the major feature. Careful examination of all patients with a ruptured aneurysm, particularly listening for an abdominal bruit, will usually allow the diagnosis of aortocaval rupture to be made.

Aged↗
PubMed1983

Traumatic gastric ulceration.

A case of acute gastric ulceration is described which resulted from direct blunt trauma to the stomach. This produced significant haemorrhage ten days after the injury which was successfully managed by conservative means.

Adolescent↗
PubMed1981

The effects of mannitol on blood viscosity.

To determine the effect of mannitol on blood viscosity, serial measurements were carried out on venous blood in patients undergoing craniotomies for intracranial aneurysms. Blood samples were drawn immediately prior to, and 30 minutes, 2, and 4 hours after administration of mannitol. Complete blood counts, serum osmolarities, and erythrocyte microsieving studies were also performed on each sample. Whole-blood viscosity decreased at 30 minutes and 2 hours, but not at 4 hours after mannitol administration. This decreased appeared at high shear rates only, where erythrocyte deformability is critical viscosity. This effect was independent of the hematocrit. Removal of mannitol from the suspension returned red cell deformability to preadministration values indicating that the increased erythrocyte deformability required the presence of mannitol and the relative hyperosmolarity induced by this agent. The reduced erythrocyte rigidity and subsequent decreased whole-blood viscosity should enhance tissue perfusion in the microcirculation.

Blood Viscosity↗