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Biomedical subjects

P C Su

Publications and source records attributed to P C Su.

11 recordsLinked to original sources
PubMed2001

Metabolic changes following subthalamotomy for advanced Parkinson's disease.

We studied 6 advanced-stage Parkinson's disease patients with [18F] fluorodeoxyglucose/positron emission tomography before and 3 months after unilateral ablation of the subthalamic nucleus performed with microelectrode mapping. Operative changes in glucose metabolism were assessed by comparing baseline and postoperative scans. We also quantified operative changes in the activity of an abnormal Parkinson's disease-related metabolic network that we had identified in previous [18F] fluorodeoxyglucose/positron emission tomography studies. Following unilateral subthalamic nucleus ablation, a highly significant reduction in glucose utilization was present in the midbrain ipsilateral to the lesion site, most pronounced in the vicinity of the substantia nigra pars reticularis. Significant metabolic reductions were also present in the ipsilateral internal globus pallidus, ventral thalamus, and pons. Operative changes in Parkinson's disease network activity differed significantly for the lesioned and unlesioned hemispheres. In the lesioned hemisphere, network activity declined significantly following surgery, but was unaltered in the contralateral, unlesioned hemisphere. These results suggest that subthalamotomy reduces basal ganglia output through internal globus pallidus/substantia nigra pars reticularis and also influences downstream neural activity in the pons and ventral thalamus. This procedure also reduces the activity of abnormal Parkinson's disease-related metabolic brain networks, suggesting a widespread modulation of motor circuitry.

Adult↗
PubMed1996

Cutaneous electromyographic silent period findings in brachial dystonia.

In this study we investigated the physiologic mechanisms in primary brachial dystonia by analyzing the cutaneous EMG silent period during isometric contraction of the opponens pollicis muscle. Results from the affected and unaffected arms of 11 patients with dystonia were compared to 7 patients with Parkinson's disease and 16 age-matched normal individuals (controls). The silent period onset latency, degree of EMG suppression during the silent period, and EMG rebound at the end of the silent period did not differ significantly between patients with dystonia and any other group. The duration of the silent period (the S-X interval), however, was significantly prolonged in dystonia (p<0.005) and in Parkinson's disease (p<0.001) in both affected and unaffected arms compared with controls. These findings suggest that mechanisms responsible for the initiation of the cutaneously induced silent period and the subsequent suppression depth of EMG activity are not affected in brachial dystonia, but the abnormally prolonged S-X intervals may reflect dysfunctional basal ganglia timing influences over spinal circuitry common to both dystonia and Parkinson's disease.

Adult↗
PubMed1989

Pharmacokinetics and systemic effects of tissue-type plasminogen activator in normal subjects.

Pharmacokinetics and systemic effects of recombinant tissue-type plasminogen activator (rt-PA) were studied in 18 healthy male volunteers after 30-minute intravenous infusions of placebo, 0.25 mg/kg rt-PA, and 0.5 mg/kg rt-PA. Highly comparable pharmacokinetic parameters were obtained after analysis of rt-PA as both an antigen and an activity. Mean clearance (antigen) was 620 +/- 70 (SD) ml/min, volume of distribution at steady state was 8.1 +/- 0.8 L, initial volume of distribution was 4.4 +/- 0.6 L, and dominant half-life was 4.4 +/- 0.3 minutes. The pharmacokinetics of rt-PA were linear, showed low interindividual variation, and are compatible with rapid hepatic elimination of the protein. Systemic plasminogen activation was minimal as assessed by hemostatic assays of plasma samples treated with anti-rt-PA Immunoglobulin G (IgG) to inhibit in vitro fibrinogenolysis. Circulating fibrinogen levels, clotting times, and coagulation factors were unchanged; plasminogen and alpha 2-antiplasmin decreased maximally to 85% and 65% of baseline values, respectively. The data are consistent with the fibrin specificity of t-PA, which is derived from its role in physiologic fibrinolysis.

Adult↗
PubMed1979

Combined myelopathy and radiculoneuropathy with malignant lymphoproliferative disease.

Clinicopathological findings for two similar patients in whom myelopathy and radiculoneuropathy developed in association with malignant lymphoma were reviewed. This pattern of neurological disease has not been reported in association with the malignant lymphoproliferative disorders, and it provides ground for speculation concerning lymphocyte function and viral infection in cases of neurological disease in association with remote neoplasm.

Adult↗
PubMed1979

Pre- and postsynaptic effects of pancuronium at the neuromuscular junction of the mouse.

The dose-effectiveness of pancuronium as it relates to membrane potentials, action potentials, electrical membrane constants, miniature endplate potentials, endplate potentials, and quantal release was studied in murine phrenic nerve-diaphragm preparations in vitro. Emphasis was placed on comparison of presynaptic with postsynaptic effects of pancuronium under similar experimental conditions. At low concentrations of pancuronium (5 X 10(-8) g/ml or less), no presynaptic effect was found. At high concentration (5 X 10(-7) g/ml), pancuronium depressed quantal release to 26 per cent of control in cut-fiber preparations and 40 per cent of control in high-magnesium preparations. Postsynaptic effects as measured by the amplitude of miniature endplate potentials and relative depolarization induced by 20 microns carbachol, revealed depression to 16 and 22 per cent of control, respectively, at a pancuronium concentration of 5 X 10(-7) g/ml. Pancuronium had no effect on directly elicited action potentials and electrical membrane constants. The authors conclude that presynaptic as well as postsynaptic effects of pancuronium in paralytic doses are essential in contributing to the total efficacy of neuromuscular depression.

Action Potentials↗
PubMedDate not supplied

Generation of 5-fluorouracil from 5-fluorocytosine by monoclonal antibody-cytosine deaminase conjugates.

Cytosine deaminase (CDase) catalyzes the conversion of cytosine to uracil and is also able to convert the clinically used antifungal agent 5-fluorocytosine (5FC) into the anticancer drug 5-fluorouracil (5FU). The enzyme was purified from bakers' yeast in a six-step procedure. Studies indicated that bakers' yeast CDase had a molecular weight of approximately 32 kDa and was composed of two subunits of equal molecular weights. Monoclonal antibodies were covalently attached to CDase, forming conjugates that could bind to antigens on tumor cell surfaces. The combination of L6-CDase and 5FC was equivalent in cytotoxic activity to 5FU when tested against the H2981 human lung adenocarcinoma cell line (L6 positive, 1F5 negative). 5FC alone was noncytotoxic. The activation of 5FC was immunologically specific since 1F5-CDase did not enhance 5FC activity.

Adenocarcinoma↗