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Biomedical subjects

D R Armstrong

Publications and source records attributed to D R Armstrong.

12 recordsLinked to original sources
PubMed2001

Outcome of liver transplantation for hepatitis B: report of a single center's experience.

Results of liver transplantation (LT) for hepatitis B have improved significantly with the use of hepatitis B immune globulin (HBIG) and/or lamivudine. The aim of this study is to review the long-term outcome of patients who underwent LT for hepatitis B. Records of 41 patients who underwent LT for hepatitis B and survived 3 months or longer post-LT were reviewed. Twenty patients were administered no immunoprophylaxis or short-term intramuscular HBIG, whereas 21 patients were administered high-dose intravenous (IV) HBIG. Median post-LT follow-up in these 2 groups was 76 months (range, 4 to 155 months) and 25 months (range, 4 to 68 months), respectively. Hepatitis B recurred in 15 (75%) and 4 patients (19%) who underwent LT in the pre-HBIG and post-HBIG eras, respectively. Cumulative rates of recurrent hepatitis B at 1 and 3 years post-LT in these 2 groups were 66% and 77% and 20% and 20%, respectively (P <.001). Recurrent hepatitis B in the post-HBIG era correlated with antibody to hepatitis B surface antigen titer less than 100 IU/L. Nine patients with recurrent hepatitis B were administered lamivudine for 13 to 49 months (median, 28 months); 6 patients continued to have stable or improved liver disease, whereas 3 patients developed virological breakthrough with slow deterioration of liver disease. Long-term IV HBIG is effective in preventing recurrent hepatitis B. The risk for recurrent hepatitis B is negligible after the first year post-LT. Among patients with no virological breakthrough, lamivudine can stabilize or improve liver disease for up to 4 years in patients with recurrent hepatitis B post-LT.

Adult↗
PubMed1998

The uptake of radionuclides by beans, squash, and corn growing in contaminated alluvial soils at Los Alamos National Laboratory.

Pinto beans (Phaselous vulgaris), sweet corn (Zea mays), and zucchini squash (Cucurbita pepo) were grown in a field pot study using alluvial floodplain soils contaminated with various radionuclides within Los Alamos Canyon (LAC) at Los Alamos National Laboratory, New Mexico. Soils as well as washed edible (fruit) and nonedible (stems and leaves) crop tissues were analyzed for tritium (3H), cesium (137Cs), strontium (90Sr), plutonium (238Pu and 239,240Pu), americium (241Am), and total uranium (totU). Most radionuclides, with the exception of 3H and totU, in soil and crop tissues from LAC were detected in significantly higher concentrations (p < 0.05) than in soil or crop tissues collected from regional background locations. Significant differences in radionuclide concentrations among crop species (squash were generally higher than beans or corn) and plant parts (nonedible tissue were generally higher than edible tissue) were observed. Most soil-to-plant concentration ratios for radionuclides in edible and nonedible crop tissues grown in soils from LAC were within default values in the literature commonly used in dose and risk assessment models. Overall, the maximum net positive committed effective dose equivalent (CEDE)--the CEDE plus two sigma for each radioisotope minus background and then all positive doses summed--to a hypothetical 50-year resident that ingested 352 lb ([160 kg]; the maxiumum ingestion rate per person per year) of beans, corn, and squash in equal proportions was 74 mrem y-1 (740 microS y-1). This upper bound dose was below the International Commission on Radiological Protection permissible dose limit of 100 mrem y-1 (1000 microS y-1) from all pathways and corresponds to a risk of an excess cancer fatality of 3.7 x 10(-5) (37 in a million), which is also below the U.S. Environmental Protection Agency's guideline of 10(-4).

Environmental Health↗
PubMed1989

Absence of electrographic seizures after transient forebrain ischemia in the Mongolian gerbil.

EEG was continuously recorded from Mongolian gerbils for 4 days after transient bilateral forebrain ischemia, to determine whether ischemic brain damage in this species is necessarily associated with seizures. Gerbils were chronically implanted with EEG recording electrodes in hippocampal area CA1, striatum and frontal neocortex and were subjected to a 5-10 min occlusion of both common carotid arteries. During the first few hours after the occlusion, the EEG was dominated by slow waves similar to those recorded from human brain after a damaging episode of cerebral ischemia. Amplitudes of the hippocampal and striatal EEG declined markedly with time, presumably as a result of neuronal degeneration. Ictal activity was never recorded, even from animals that suffered extreme damage to the hippocampal formation and striatum. Therefore ischemic brain damage in the gerbil does not result from seizure activity.

Animals↗
PubMed1986

Baclofen suppresses bursting activity induced in hippocampal slices by differing convulsant treatments.

Epileptiform activity was induced in area CA3 of hippocampal slices by superfusion of medium containing 50 microM bicuculline and 3.5 mM K, 50 microM bicuculline and 5 mM K, 50 nM kainic acid and 3.5 mM K, or 7 mM K. Burst potentials were recorded at rates between 5 and 44/min, depending on the convulsant treatment. Baclofen reduced the frequency of burst firing in all slices tested in a dose-dependent manner, with little change in the morphology of individual bursts. Thus baclofen primarily affected the initiation of epileptiform discharges. IC50 values varied between 27 and 500 nM and were positively correlated with the rate of bursting. These experiments indicate that baclofen, at concentrations present in the CSF of patients treated for spasticity, has an anticonvulsant-like effect in the hippocampal formation and suggest that its mode of action is to reduce the excitability of pyramidal cells.

Action Potentials↗
PubMed1986

Comparison of seizures and brain lesions produced by intracerebroventricular kainic acid and bicuculline methiodide.

Intracerebroventricular kainic acid produces in rats brain lesions similar to Ammon's horn sclerosis in humans. To test the hypothesis that these lesions result indirectly from prolonged seizure activity and not from a direct action of kainic acid on the neurons that are destroyed, the effects of intracerebroventricular kainic acid and bicuculline methiodide were compared. Although bicuculline methiodide seizures differed dramatically from kainic acid seizures, both electrographically and behaviorally, the resulting brain lesions were similar for a given total limbic seizure duration. These results, in combination with other data, support the view that lesions made by intracerebroventricular administration of convulsants are indeed caused by prolonged limbic seizures. The total duration of seizure activity appears to be one important variable.

Animals↗
PubMed1986

Efficacy of baclofen and phenobarbital against the kainic acid limbic seizure-brain damage syndrome.

Baclofen and phenobarbital were tested for anticonvulsant efficacy against limbic seizures produced by i.c.v. infusion of kainic acid (KA) in unanesthetized rats. All rats treated with KA alone developed a prolonged status epilepticus associated with extensive neuronal degeneration. When administered immediately after the KA infusion, baclofen (5 mg/kg i.p.) protected five of six animals against the development of status epilepticus and did not alter the behavioral expression of the residual discrete electrographic seizures. Phenobarbital (40 mg/kg i.p.) given 15 min before KA also prevented the development of status epilepticus in five of six rats, but blocked the behavioral expression of the residual electrographic seizures. In two of five additional rats, baclofen prevented or reversed status epilepticus when administered 50 to 60 min after the end of the KA infusion. The ability of these drugs to prevent KA-induced neuronal degeneration correlated with their anticonvulsant action.

Animals↗