Biomedical subjects

F C Cheng

Publications and source records attributed to F C Cheng.

At least 55 records · Page 3Linked to original sources

PubMed1996

Effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and 5,7-dihydroxytryptamine on the locomotor activity and striatal amines in C57BL/6 mice.

The present study examined the effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 5,7-dihydroxytryptamine (5,7-DHT) on striatal levels of dopamine (DA), 5-hydroxytryptamine (5-HT), and their metabolites homovanillic acid (HVA) and 5-hydroxyindole-3-acetic acid (5-HIAA), respectively, as well as their influence on locomotor activity in conscious C57BL/6 mice. High doses (s.c., 35-45 mg/kg per day for 10 days) of MPTP resulted in a significant (P < 0.05) increase in locomotor activity and a marked decrease of striatal DA levels. Concomitantly, the ratios of HVA to DA and 5-HIAA to 5-HT increased significantly, the latter reflecting increased 5-HIAA levels. In contrast, i.c.v. administration of the serotonergic neurotoxin 5,7-DHT, either alone or following high doses (40 mg/kg per day for 10 days) of MPTP, decreased locomotor activity. Furthermore, striatal levels of 5-HT and 5-HIAA as well as the 5-HIAA/5-HT ratio decreased significantly. Thus, the increased locomotor activity induced by chronic high doses of MPTP might be due to increased striatal 5-HT levels which appear to compensate for the loss of DA. Furthermore, the locomotor hypoactivity induced by 5,7-DHT may be secondary to the striatal 5-HT deficiency.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed1996

New dual electrochemical detector for microbore liquid chromatography. Determination of dopamine and serotonin in rat striatum dialysates.

A new type of liquid chromatographic (LC) dual thin-layer amperometric detector for the simultaneous measurement of trace levels of dopamine and serotonin in microdialysates is described. The concentrations of these analytes in rat dialysates are usually in the sub-nanomolar concentration range (typically, 0.10-5.00 pg in 5-microl dialysates). With this dual electrode, a glass-lined microbore column provides excellent sensitivity, selectivity, and separation. In addition, a three- to five-fold improvement in anodic current or cathodic responses over conventional dual electrodes in microbore LC can be achieved. Due to the irreversible electrochemical properties of some interference peaks, this dual electrode provides reliable measurement of dopamine based on the cathodic signal. The detection limit (signal-to-noise ratio = 3) of this assay is 0.02 pg per injection for dopamine or serotonin. This new dual electrode allows the simultaneous measurements of basal dopamine and serotonin in rat striatum dialysates without the use of re-uptake inhibitors in perfusion medium.

Animals↗

PubMed1996

The dorsal facial area of the medulla in cats: inhibitory action of serotonin on glutamate release in regulating common carotid blood flow.

Whether glutamate and serotonin would release and interact in the dorsal facial area (DFA) of cat medulla to regulate common carotid arterial (CCA) blood flow was explored by placing a microdialysis probe in DFA and employing high performance liquid chromatographic technique. Glutamate concentration was dose-dependently decreased by perfusion with serotonin, or alaproclate, a serotonin reuptake inhibitor. Serotonin and glutamate concentrations were increased by perfusion with KCl, a depolarizing agent. Furthermore, CCA blood flow was decreased when glutamate concentration was reduced by serotonin or alaproclate perfusion, and conversely increased when glutamate concentration was increased by KCl perfusion. In conclusion, glutamate and serotonin releases in DFA that involve regulation of CCA blood flow are tonically mediated by nerve terminals. The glutamate release is depressed by the serotonin release.

Alanine↗

PubMed1996

Elevated 5-S-cysteinyldopamine/homovanillic acid ratio and reduced homovanillic acid in cerebrospinal fluid: possible markers for and potential insights into the pathoetiology of Parkinson's disease.

High-performance liquid chromatography with electrochemical detection has been employed to analyze ultrafiltrates of cerebrospinal fluid of Parkinson's Disease (PD) patients and age-matched controls for the dopamine (DA) metabolites homovanillic acid (HVA) and 5-S-cysteinyldopamine (5-S-CyS-DA). The mean level of HVA in the CSF of PD patients, measured 5 days after withdrawal from L-DOPA therapy, was significantly lower than that measured in controls. By contrast, mean levels of 5-S-CyS-DA were not significantly different in the CSF of PD patients taking L-DOPA (PD-LT patients) the same patients 5 days after discontinuing this drug (PD-LW patients) or controls. However, the mean 5-S-CyS-DA/HVA concentration ratio was significantly (p < 0.05) higher in the CSF of PD-LW patients compared to controls. Although the PD patient population employed in this study had been diagnosed with the disease several years previously and had been treated with L-DOPA for prolonged periods of time the results of this study suggest that low CSF levels of HVA and a high 5-S-CyS-DA/HVA ratio together might represent useful markers for early diagnosis of PD. The high 5-S-CyS-DA/HVA ratio observed in the CSF of PD-LW patients also provides support for the hypothesis that the translocation of glutathione or L-cysteine into neuromelanin-pigmented dopaminergic cell bodies in the substantia nigra might represent an early event in the pathogenesis of PD.

Aged↗

PubMed1996

A micro liquid chromatographic assay for the determination of plasma-unbound atenolol.

An improved high performance liquid chromatographic assay for plasma-unbound atenolol is described. The assay has a wide range (10-5000 ng ml-1) of linearity and a detection limit of 5 ng ml-1 (or 0.1 ng per injection) with acceptable intra- and inter-assay reproducibilities using small volumes of plasma (100 microliters). Following administration of a single dose of atenolol to the rat, nine blood samples were collected over a period of 8 h. These samples were analyzed for atenolol concentrations by a sensitive and specific microbore high performance liquid chromatograph with a photodiode-array detector. This multi-channel detector was used to acquire spectral information on atenolol and demonstrated a superior performance in comparison to all other techniques in that both qualitative and quantitative information were acquired with the system. Because of it sensitivity and applicability to plasma analysis, the assay can be used for pharmacokinetic studies and is valuable in therapeutic drug monitoring.

Animals↗

PubMed1996

Effect of quinapril therapy on blood pressure and serotonin change in patients with mild to moderate hypertension.

BACKGROUND: Previous studies have shown that serotonin plays an important role in hypertension because of its vasoconstrictive effect, mediated through serotonergic receptors. Angiotensin-II is a potent vasopressor which facilitates the aggregation of platelets, subsequently releases serotonin. Because quinapril is an angiotensin-converting enzyme inhibitor and could result in a decrease of angiotensin-II, Quinapril was used to treat patients with mild or moderate hypertension in order to observe the change of plasma serotonin. METHODS: Twenty-two patients, (10 males, 12 females, mean age 45 yrs) without other major medical diseases and secondary causes of hypertension, were selected for this study. High performance liquid chromatography (HPLC) with electrochemical detection was used to detect the plasma serotonin. These patients were given placebos for two weeks before the first dose of quinapril (5 mg). Thereafter, the dosage was adjusted according to the response of blood pressure to a desired value (BP < 140/90 mmHg). At about 14:00 hours on the first day, after the patient had rested for an hour and was in a quiet condition, blood was drawn by venipuncture with heparin as anti coagulant; the plasma serotonin concentration was determined for the baseline value. The plasma serotonin level was rechecked eight weeks later. RESULTS: It was found that systolic blood pressure began to decrease significantly two weeks after quinapril therapy, and then reached a constant state. Blood pressure decreased from 174/107 mmHg to 134/87 mmHg. Among these 22 patients, there were 14 (65%) whose blood pressure reduced to a normal range. Plasma serotonin also decreased significantly from 4.69 +/- /3.67 ng/ ml to 2.89 +/-2.64 ng/ml (p < 0.05). According to this data, 15 in 22 patients (68%) had reduction of plasma serotonin. There was little correlation between change in blood pressure and change of plasma serotonin; the correlation co-efficiency is only 0.019. CONCLUSIONS: This study shows that quinapril has an antihypertensive property and serotonin-lowering effect. Since there was no correlation between the change of serotonin and blood pressure, these two actions of quinapril might have been mediated through different mechanisms.

Adult↗

PubMed1995

High-performance liquid chromatographic analysis with electrochemical detection of biogenic amines using microbore columns.

High-performance liquid chromatography with electrochemical detection (HPLC-ED) is a popular method for measuring biogenic amines, owing to its simplicity, versatility, sensitivity, and specificity. Recent developments in microbore column HPLC-ED have been facilitated by miniaturization of solvent delivery, column packing, sample injection and micro-flow cell construction. The aim of this paper is to present an overview of recent developments in microbore column HPLC-ED, in terms of advantages and limitations. This paper covers the recent advancements and important factors of HPLC-ED analysis of biogenic amines using microbore columns. Particular emphasis is placed on applying this technique to microdialysis, for which great sensitivity is required. Its potential in future biomedical applications is also discussed.

Animals↗

PubMed1995

Studies of dementia, depression, electrophysiology and cerebrospinal fluid monoamine metabolites in patients with Parkinson's disease.

Twenty-two patients with Parkinson's disease (PD) were studied by clinical evaluation, assessments of dementia and depression, as well as electrophysiologic examinations for blink reflex (BR), cortical somatosensory evoked potentials (CSEP), brain stem, and long-latency auditory evoked potentials (BAEP, and LAEP), and cerebrospinal fluid (CSF) assays for monoamine metabolites. Results show that PD patients have a significant decrease of Mini-Mental State Examination (MMSE) scores (p < 0.05) and an increase of Hamilton Depression Scale (HDS) scores (p < 0.01), as well as a longer latencies of R2 in BR, N19 and P22 in CSEP, W4 and W5 in BAEP and P300 in LAEP (p < 0.01), and lower CSF levels of HVA and MHPG (p < 0.05). The findings suggest a correlation between dementia/depression and mesocorticolimbic and mesostriatocortic dysfunction with dopaminergic and noradrenergic deficiencies in PD patients. Furthermore, parkinsonian dementia parallels the length of duration of the disease, but not the severity of motor disability. Parkinsonian depression parallels both the length of duration of the disease and the severity of motor disability.

Aged↗

PubMed1995

Determination of human plasma biogenic amines and their metabolites using liquid chromatography with a dual-channel electrochemical detector.

BACKGROUND: Measurement of biogenic amines and their metabolites in plasma has been used for decades to explore the pathophysiology of neuropsychiatric disorders or to examine the mode of action of psychotropic medications. Many advantages of ultrafiltration and high-performance liquid chromatography (HPLC) in assaying human plasma content have been described in our previous study. METHODS: The present HPLC assay, applying a dual-channel electrochemical detector, provides an additional reliable measurement or confirmation of peaks by identifying each peak retention capacity factor and its current ratio in the dual-channel detector. Simultaneous measurements of plasma serotonin, catecholamines and their metabolites by ultrafiltration and microbore HPLC technique is applied to evaluate moclobemide and fluoxetine therapy in patients with major depression. RESULTS: This present HPLC method provides highly specific detection, free from interference by the large offscale peak of plasma ultrafiltrates. Isocratic separation of all analytes by a microbore column is achieved within 15 mins. The detection limit (signal-to-noise ratio = 3) of this method is about 0.2-0.5 pg per injection for all analytes. In addition, the required volume of plasma samples is only 100 microliters. CONCLUSIONS: This rapid, simple and sensitive method for the measurement of human plasma serotonin, catecholamines and their metabolites can be used as a clinical or biomedical research tool. Blood loss is minimal in the present assay, especially in repeated blood sampling for pharmacokinetic studies.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1995

Pressor effects elicited from the periaqueductal grey, and dorsal and ventrolateral medulla in cats are independent from cerebellar mechanisms.

Cats were anesthetized with chloralose (35 mg/kg, i.p.) and urethane (350 mg/kg, i.p.). In 5 cats, the pressor regions of periaqueductal grey (PAG) of the midbrain were stimulated electrically (rectangular pluses, 80 Hz, 0.5 ms, 100-150 microA). In another 6 cats, the pressor regions of both dorsal medulla (DM) and ventrolateral medulla (VLM) previously located by electrical stimulation in the same cat were stimulated by sodium glutamate (Glu, 0.25 M, 100 nl). After control stimulation, the superior, middle and inferior cerebellar peduncles on both sides were transected while the stimulating electrodes were maintained in the same position. Changes of systemic arterial pressure (SAP) and plasma norepinephrine (NE) and epinephrine (EP) following stimulations of the PAG, DM or VLM were compared before and after transections. It was found that the transection did not cause significant changes in the resting SAP and plasma NE and EP and also the induced pressor responses, namely the increases of above parameters. Findings suggest that the sympathetic vasomotor effect and adrenomedullary secretion resulted from stimulations of both DM and VLM and possibly PAG are independent from the cerebellar mechanism.

Animals↗

PubMed1994

Pharmacokinetics of honokiol after intravenous administration in rats assessed using high-performance liquid chromatography.

A simple and sensitive high-performance liquid chromatographic method for the identification and determination of honokiol in rat plasma has been developed. Up to 0.1 ml of plasma containing honokiol was deproteinized with acetonitrile, which contained an internal standard (paeonol). The supernatant was injected onto a reversed-phase C18 column using acetonitrile-water (70:30, v/v, adjusted to pH 2.5-2.8 with orthophosphoric acid) as the mobile phase and ultraviolet detection at 290 nm, followed by UV spectrum identification (between 220 and 380 nm) with a photodiode-array detector. The method was applied to pharmacokinetic studies of honokiol in rat following 5 or 10 mg/kg intravenous administration. A biphasic process consisting of a rapid distribution phase followed by a slower elimination phase was observed from the plasma concentration-time curves. Compartmental analysis yielded a two-compartment model.

Animals↗

PubMed1994

Rapid measurement of the monoamine content in small volumes of rat plasma.

A method for the simultaneous measurement of serotonin, catecholamines, and their metabolites, 5-hydroxy-indoleacetic acid, homovanillic acid, and 3, 4-dihydroxyphenylacetic acid, by ultrafiltration and microbore high-performance liquid chromatography with dual electrochemical detection in small plasma volumes was established. Unlike the traditional assays which require at least 1-2 ml of plasma for each measurement, the present method uses only a 20-microliters sample volume. Since blood loss is minimal, repeated blood sampling from a single animal as a rat becomes practicable. The present microassay provides low detection limits (signal-to-noise ratio = 3) for all analytes (0.2-0.5 pg per 5-microliters injection or 50-120 pg/ml plasma). Isocratic separation of these analytes on a microbore column is achieved within 15 min. This rapid and sensitive method can be used as a routine research tool in various physiological or pharmacokinetic studies especially in small animals.

Animals↗

PubMed1994

Rapid assay of the monoamine content in small volumes of rat plasma.

A method for the simultaneous measurement of serotonin catecholamines, and their metabolites in rat plasma by ultrafiltration and microbore liquid chromatography with electrochemical detection (LC-ED) in small volumes is established. Prior to the LC assay, sixteen plasma ultrafiltrates are readily prepared within 30 min in the present study. The present method, applying a dual-electrode detection technique, provides an additional reliable assignment or measurement of peaks by identifying the peaks on the basis of their redox ratios. In addition, the important early-eluting peaks and interfering peaks are eliminated in the cathodic chromatogram resulting in a reliable measurement of norepinephrine, epinephrine, and 3,4-dihydroxyphenylacetic acid. Isocratic separation of serotonin, catecholamines, and their metabolites by a microbore column is achieved within 15 min. Hence, theoretically, over 90 analyses can be performed in a working day. The limit of detection (signal-to-noise ratio = 3) of this method is ca. 0.2-0.5 pg per injection for all analytes. The required volume of the plasma samples can be less than 100 microliters. Hence, the remainder of the plasma sample can be analysed for other substances. This rapid, simple, and sensitive method can thus be used as a research tool in the simultaneous measurement of rat plasma serotonin, catecholamines, and their metabolites.

Animals↗

PubMed1994

Pulmonary edema and rapid transfusion: the comparison between rapid intravenous and intraarterial infusion in the severely hemorrhagic anesthesized pigs.

BACKGROUND: Patients with shock often develop pulmonary edema (PE) after rapid and massive fluid supplement and intravenous infusion. Rapid intraarterial infusion (RIA) is often used for fluid supplement in cardiac surgery, but has not yet been applied to treatment of hemorrhagic shock. However, by perfusing the ischemic peripheral organs through RIA, the fluid should flow first through the venous system to the heart and lung in less volume at lower speed. Therefore, the probability of developing PE should be less than that in rapid intravenous infusion (RIV) to the heart and lung in the same condition regarding volume and speed. Accordingly, we compared RIV and RIA in the treatment of hemorrhagic shock (HS) to determine if RIA provides any beneficial effect in reducing the development of PE. METHODS: Eleven male mini-pigs weighing 17.5-32 kg were randomly divided into two groups to have RIV and RIA. Under general anesthesia, HS was induced by shedding blood (about 35 ml/kg) through the femoral artery until the mean arterial blood pressure (MAP) fell to 50 mm Hg. This condition was maintained for three hours. Then, lactated Ringer's solution (LRS) was infused thrice by force through a femoral artery (RIA) or an external jugular vein (RIV) at a speed of 25 ml/kg/min for 3 min. Data include hemodynamics, arterial blood gases, urine output, total extravascular lung water index (ETVI), and total amount of infused LRS used to induce gross PE (endotracheal release of pinkish foamy sputum). Serum concentrations of catecholamines, platelet activating factor (PAF) and thromboxane B2 (TxB2) were measured. RESULTS: The total amount of LRS needed to induce gross PE was significantly greater in RIA than in RIV group. ETVI after rapid transfusion with a total of 225 ml/kg LRS was significantly less in RIA than in RIV group. Also, TxB2 concentrations in serum were less in RIA group. However, there was no difference in changes of hemodynamics, blood gases, acid-base, pulmonary shunting, urine output, serum concentrations of PAF or catecholamines between these two groups. CONCLUSIONS: RIA may be a better choice for fluid replacement in HS in terms of decreasing the development of PE and lessening the release of ETVI and TxB2 in severely hemorrhagic anesthetized pigs. Further human investigation is warranted.

Animals↗

PubMed1993

Rapid and reliable high-performance liquid chromatographic method for analysing human plasma serotonin, 5-hydroxyindoleacetic acid, homovanillic acid and 3,4-dihydroxyphenylacetic acid.

The simultaneous measurement of homovanillic acid, 3,4-dihydroxyphenylacetic acid, serotonin and 5-hydroxyindoleacetic acid in human plasma by an ultrafiltration and microbore high-performance liquid chromatography-electrochemical detection technique is established. Conventional preparation of blood is very tedious and time-consuming, but isocratic separation of the analytes in plasma ultrafiltrates using a microbore column could be achieved within 10 min. Hence, theoretically, over 140 analyses can be performed in a working day. The detection limit (signal-to-noise ratio = 3) of this method is about 0.1-0.5 pg per injection for all analytes. The required volume of plasma samples can be less than 100 microliters. Hence, blood loss is minimal, especially in repeated blood sampling. This rapid, simple and sensitive method can, therefore, be used as a routine clinical tool in the simultaneous measurement of plasma homovanillic acid, 3,4-dihydroxyphenylacetic acid, serotonin and 5-hydroxyindoleacetic acid.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1993

Simultaneous measurement of serotonin, catecholamines and their metabolites in mouse brain homogenates by high-performance liquid chromatography with a microbore column and dual electrochemical detection.

A dual electrochemical detector with two working electrodes (anode and cathode) suitable for high-performance liquid chromatography with a microbore octadecylsilica column was applied for the simultaneous measurement of norepinephrine, epinephrine, dopamine, 3,4-dihydroxyphenylacetic acid, homovanillic acid, 5-hydroxyindoleacetic acid, 3-methoxytyramine and 5-hydroxytryptamine (serotonin) in mouse brain homogenates. Microbore high-performance liquid chromatography provides very good resolution of these analytes and offers selective detection of biogenic amines and their metabolites on the basis of their retention behaviour and electrochemical reversibility. The large early-eluting peak of brain homogenates was eliminated on cathodic detection, thereby providing reliable measurements of early eluates. The detection limit of this method was ca. 0.2-0.5 pg per injection for all components, at a signal-to-noise ratio of 3. Owing to the high sensitivity, the brain tissue samples could be kept very small (less than 10 mg). Isocratic separation of these analytes was achieved within 15 min; hence over 90 analyses could be performed in a single working day. This simple, efficient and sensitive method can be used as a basic research tool for the assaying of biogenic amines and their metabolites in brain homogenates.

Animals↗

PubMed1993

Monoamines and their metabolites in plasma and lumbar cerebrospinal fluid of Chinese patients with Parkinson's disease.

Ten free monoamines and their metabolites in plasma and cerebrospinal fluid (CSF) were simultaneous measured in 6 levodopa-untreated (LU), 18 levodopa-treated (LT) and 37 levodopa-withdrawn (LW) Chinese patients with Parkinson's disease (PD) and 26 controls. We found that the levels of these substances in LW patients were not significantly different from those in LU patients. In LU- and LW-PD patients, CSF epinephrine (EPI) was higher (P < 0.05) than that of the controls. 3-methoxy-DOPA (3-OMDOPA) might not inhibit the accumulation of 3,4-dihydroxyphenylalanine (DOPA) and dopamine metabolites in CSF. Levodopa treatment might change the dopaminergic and serotoninergic neuronal systems, but not the noradrenergic or adrenergic neuronal systems, in CNS of PD patients. Benserazide (a peripheral decarboxylase inhibitor) in Madopar might decrease the levels of serotonin (5-HT) and norepinephrine (NE), but not those of DOPA and homovanillic acid (HVA), in plasma. HVA, NE and EPI in plasma were not good indices for those in CSF. Otherwise, our results were consistent with some other studies by showing a significantly lower level (P < 0.01) of HVA in CSF of LU- and LW-PD patients than that of the controls, while no difference for NE, 3-methoxy-4-hydroxyphenylglycol (MHPG), 5-hydroxyindole acetic acid (5-HIAA) or 3-OMDOPA was noted. The severity of clinical disability was related to the deficiency of CSF HVA and DOPAC in LU- and LW-PD patients; however, there was no relationship between clinical symptoms of tremor, rigidity-bradykinesia, autonomic dysfunction, dementia, depression or levodopa-induced dyskinesia and CSF monoamines or their metabolites.

Aged↗

PubMed1993

Effects of reducing sympathetic activities on acute myocardial ischemia in cats.

The importance of the sympathetic nervous system in the genesis of ventricular arrhythmias associated with acute myocardial ischemia (AMI) was assessed in urethane-chloralose anesthetized cats. AMI was created by a ligation of the left anterior descending coronary artery. All control cats developed ventricular tachyarrhythmia (VT), ventricular fibrillation (VF), bradycardia and hypotension, resulting in 50% mortality. In other groups the paramedian reticular nucleus (PRN) was intermittently stimulated to inhibit the sympathetic nervous system. Both sides of the stellate ganglia (SG) or adrenal glands (AG) were removed to exclude direct effects of cardiac sympathetic nerve or indirect effects of circulatory catecholamines from the adrenal medulla on the heart, respectively. AMI did not affect plasma norepinephrine (NE) and epinephrine (EPI) concentrations in all groups. However, NE concentration was higher in SG removed but lower in AG removed group. Removal of SG and stimulation of PRN significantly reduced arrhythmia score and the incidence of VT, VF and mortality. Removal of AG appeared to be less effective. These findings suggest that cardiac sympathetic innervation is more important than neural and adrenal catecholamine secretions in the plasma.

Acute Disease↗