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Biomedical subjects

P Barnes

Publications and source records attributed to P Barnes.

118 records · Page 7Linked to original sources
PubMedDate not supplied

Visual electrophysiological effect of a GABA transaminase blocker.

Vigabatrin is an antiepileptic drug for the treatment of partial seizures. The anticonvulsant effect is achieved by irreversible inhibition of the enzyme GABA-transaminase which catalyses the inactivation of GABA. Vigabatrin has been associated with visual field loss and electrophysiological abnormalities. The purpose of the study was to determine any alterations in normal volunteers of the visual field and the visual electrophysiology resulting from a short exposure to vigabatrin. A three-way, double-blind study of placebo, carbamazepine and vigabatrin was undertaken at baseline and on days two, four and nine. Seven subjects completed all three cycles and 14 subjects (six females and eight males; mean age 27.3 years SD 6.7) completed at least one cycle. Static threshold automated perimetry comprised Humphrey Visual Field Analyzer Programs 30-2 and 30/60-2. Electro-oculography and electroretinograms were performed with undilated pupils using the Medelec Ganzfeld stimulator GS2000. The visual field was unaffected by placebo, carbamazepine or vigabatrin. The group mean amplitudes and latencies for the scotopic ERG, 30 Hz flicker ERG and the oscillatory potentials remained unchanged for any cycle. The group mean photopic ERG b-wave latency increased from baseline (p<0.05); no significant change occurred with carbamazepine or placebo. The group mean Arden Index for vigabatrin decreased from baseline to day 9 (p<0.01); no significant differences were present for carbamazepine or placebo. Vigabatrin has a rapid effect on both the photopic ERG and the EOG; however, the changes merely reflect alterations in retinal GABA levels secondary to concomitant blocking of GABA transaminase by existing vigabatrin therapy.

4-Aminobutyrate Transaminase↗
PubMedDate not supplied

A survey and evaluation of human genetic traits used in classroom laboratory studies.

Twenty-six selected introductory biology and genetics laboratory manuals were examined and were found to include 57 human "inherited" traits as examples for classroom study. Forty-three of these 57 traits are included in McKusick's catalog of human inherited characteristics, Mendelian Inheritance in Man. Of these 43 traits, 26 are annotated with an asterisk, indicating that their modes of inheritance are well documented, while 17 traits are not so annotated, suggesting uncertain mechanisms of inheritance. Fourteen of the 57 traits are not found in McKusick's catalog, implying that they may not be inherited traits at all or that their modes of inheritance may be polygenic. Current literature also suggest that certain traits included in the McKusick catalog may, in fact, not have a genetic basis. Notable examples of such questionable traits are handedness, hand clasping, and tongue rolling. Clearly, a need exists for reliable morphological and easily detected biochemical human genetic traits for use in classroom instruction. Authors preparing instructional manuals for introductory biology and genetics laboratory studies should carefully select the traits with which they illustrate human inheritance. A first requisite for selection of such characteristics must be conclusive evidence that the trait does, indeed, have an established genetic basis. Additional criteria for selection of such traits are also discussed.

Bibliographies as Topic↗
PubMedDate not supplied

Fast spin-echo imaging of intracranial neoplasms.

Our goal was to compare dual echo fast SE (FSE) T2-weighted MRI of intracranial neoplasms with conventional SE (CSE) images. In phase 1 of the study, CSE and FSE dual echo MR studies of 33 patients with intracranial neoplasms and 26 normal controls were separately interpreted by three neuroradiologists blinded to clinical history to ascertain differences in lesion conspicuity. The CSE and FSE images were read independently, in random order, with at least a 3 week interval between readings. In phase 2 of the study, CSE and FSE sequences were compared side by side by three neuroradiologists independently to evaluate lesion conspicuity and artifacts and to determine whether FSE would be an acceptable replacement for CSE imaging. Lesion detection was equivalent in 111 of 117 interpretations (94.9%). The CSE and FSE sequences were equivalent in detecting lesion-associated abnormalities (hemorrhage, calcium, mass effect, edema, and hydrocephalus) and in characterizing lesion size, margins, and signal intensity. Nonspecific T2 white matter hyperintensities were detected more often with CSE, while susceptibility artifacts were less conspicuous on FSE. Ventricular catheters, postoperative soft tissue and bony changes, and postradiation therapy changes were detected equally well on both sequences. In phase 2 of the study, lesion conspicuity and presence of artifacts were felt to be equivalent with the two sequences. The FSE sequences can serve as a rapid, feasible alternative to conventional CSE sequences for intracranial tumor detection.

Adolescent↗
PubMedDate not supplied

Dyspnea management in alpha-1 antitrypsin deficiency: effect of oxygen administration.

BACKGROUND: A deficiency of alpha-1 antitrypsin (AAT) can lead to pulmonary disease in middle-aged adults in whom dyspnea management can be a significant issue. OBJECTIVE: The research addressed whether short-term oxygen (O2) administration during activities might decrease dyspnea and improve exercise performance in nonhypoxemic patients with emphysema caused by a deficiency of alpha-1 antitrypsin. METHOD: This was a double-blind, randomized crossover study of 31 subjects with a deficiency of AAT (mean + SD, age = 47 +/- 7), moderate emphysema and a resting PaO2 > 70 mm Hg. Oxygen saturation (SpO2), 6-minute walk distance, and end of walk dyspnea were measured during three practice walks and during walks with nasal cannula administration of O2 (intervention) and compressed air (control). RESULTS: Repeated measures analysis of variance (ANOVA) showed significant differences across the walks for SpO (F= 18.9, p = 0.0001), 6-minute walk distance (F= 6.07, p = 0.004), and dyspnea (F= 4.44, p = 0.016). Using post hoc contrasts, SpO2 was the only variable that differed between 20, and compressed air (p < 0.0001). There was, however, an interaction effect of gender with O2 for dyspnea (F= 9.85, p = 0.004). Mean values showed that men did not benefit from O2 (p = 0.87). However, women experienced less dyspnea when receiving O2 as compared with compressed air (p = 0.0025), and although not statistically significant, the lower dyspnea with O2 corresponded with an increased walk distance of 79 feet. CONCLUSIONS: O2 administration may be useful for reducing dyspnea during exercise in selected populations.

Adult↗
PubMedDate not supplied

Symptomatic haemodynamically significant carotid occlusion treated by posterior circulation revascularization.

Haemodynamic cerebral ischaemic symptoms secondary to occlusive atheromatous disease of the internal carotid artery may resolve with revascularization. We describe a case of symptomatic internal carotid artery occlusion and ipsilateral subclavian stenosis with duplex and angiographically demonstrated vertebrobasilar steal and a patent ipsilateral posterior communicating artery with flow towards the steal. The patient suffered frequent ipsilateral middle cerebral artery territory transient ischaemic attacks and one minor stroke. Transcranial Doppler demonstrated markedly impaired ipsilateral carbon dioxide reactivity (13.8%, lower-limit normal range >32.6%). Percutaneous angioplasty to the subclavian artery stenosis resulted in resolution of symptoms and an improvement in reactivity to near the lower limit of the normal range (33.5%). This case demonstrates that normalization of vertebral artery steal by subclavian artery revascularization may benefit anterior circulation haemodynamic symptoms in the presence of a functioning posterior communicating artery. The measurement of middle cerebral artery reactivity using transcranial Doppler can identify such cases of haemodynamic impairment and monitor the effect of therapy.

Angiography↗
PubMedDate not supplied

Return to work after rehabilitation following traumatic brain injury.

The relationship of medical variables and discharge functional status to vocational and educational outcomes was examined in 79 closed head-injured patients who were consecutively admitted to an inpatient rehabilitation hospital during a two-year period. A follow-up study, conducted after hospital discharge (median, 16.5 months), found that 66% (n = 52) of the patients had returned to work or school, while 34% (n = 27) did not. Patients were divided into return and non-return to work groups. Traditional variables included age, severity of brain-damage as characterized by CT head scan, duration of post-traumatic amnesia, duration of coma, length of stay and acute inpatient rehabilitation program. Discharge functional scores were analysed by t-tests and chi-square analysis. Results suggest that traditional factors of younger age, shorter length of coma, minimal CT head scan findings and shorter length of stay were significant contributors to educational/vocational outcome. Their significance was enhanced by discharge functional profile measurement of medical, physical and psychological/neuropsychological integrity. Those functional measures not significant were in social, vocational, recreational and communication areas. These factors may continue to improve over a longer period of time and should be tracked in the post-acute rehabilitation phase for their significance in return to work/school.

Activities of Daily Living↗
PubMedDate not supplied

Courage to change.

Explore the source record for details and available documents.

Education, Nursing, Continuing↗
PubMedDate not supplied

MR in idiopathic central diabetes insipidus of childhood.

We present the cases of two children with presumed idiopathic central diabetes insipidus whose follow-up MR studies eventually revealed hypothalamic tumors. Thin-section sagittal T1-weighted MR with gadolinium administration is important in the evaluation of these children, and serial examinations are probably necessary.

Child↗