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Biomedical subjects

C N Chen

Publications and source records attributed to C N Chen.

12 recordsLinked to original sources
PubMed1992

Folate concentration in Chinese psychiatric outpatients on long-term lithium treatment.

Among 46 Chinese and mostly manic-depressive (85%) outpatients attending a lithium clinic in Hong Kong, virtually no patients had low serum (0%) or erythrocyte (2%) folate. Their mean folate levels did not differ from lithium-free outpatients. Although serum folate correlated negatively with lithium dose (P less than 0.002) and serum level (P less than 0.01), lithium treatment probably did not by itself cause low folate. Folate level was not related to diagnosis, duration of mental illness, other drug usage or spot affective morbidity. Patients with a good response to lithium in the previous one year had a higher mean serum folate level than those with unsatisfactory response (P less than 0.05). These data suggest that folate deficiency is uncommon among Chinese psychiatric outpatients, but support recent evidence that folate at high concentrations enhances lithium prophylaxis.

Ambulatory Care↗
PubMed1992

Huntington's disease in Chinese: a hypothesis of its origin.

The period prevalence (1984-91) of Huntington's disease (HD) in Hong Kong Chinese was 3.7 per million population. HD patients in Mainland China and Hong Kong showed similar hereditary pattern, clinical and pathological features as in the West. Chinese HD patients were male predominant with a younger age of onset and death. Their ancestral origin could be traced mostly to the coastal provinces of China. It is proposed that Chinese HD patients may have a European origin and share the same gene pool as their white counterparts.

China↗
PubMed1991

Characterization of the memory gene dunce of Drosophila melanogaster.

The dunce (dnc) gene of Drosophila melanogaster encodes cAMP phosphodiesterase (PDEase) and is required for learning/memory and female fertility. The gene is structurally complex, demonstrated in part by Northern blotting experiments which detected multiple RNAs ranging in size from 4.2 to 9.6 kb (1 kb = 10(3) bases or base-pairs). To characterize these RNAs and to understand their sequence heterogeneity, we isolated and analyzed 29 new and independent cDNA clones representing the dnc RNAs. Restriction mapping, hybridization analysis and sequence determination of these cDNA clones and the corresponding genomic exons resolved these into six different classes. Exons defined by the cDNA clones are distributed over more than 148 kb of genomic DNA, with some exons being used alternatively among the RNAs. The RNAs are transcribed from at least three initiation sites: two of these were mapped by parallel S1-nuclease and primer extension experiments. In addition, some of the heterogeneity is generated by using varying lengths of a 3'-untranslated trailer sequence. Altogether, the results indicate that the size and sequence heterogeneity of dnc transcripts results from transcription initiation at multiple sites, alternative splicing, and processes which generate different 3' ends. The existence of multiple protein products is suggested by the alternative use of exons which code for portions of the open reading frame. The protein variation potentially includes N-terminal differences coded for by transcript-specific 5' exons and internal differences arising from the optional inclusion of a 39 base-pair exon and from the alternative use of two 3' splice sites separated by six base-pairs. Expression of a cDNA clone in yeast containing a large portion of the open reading frame produced cAMP PDEase activity identical in properties to the Drosophila enzyme affected by the dnc mutation. The results suggest that the remarkable structural complexity of dnc may reflect an intricate control of the spatial and/or temporal expression of various isoforms of cAMP PDEase.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1978

Pharmacokinetic model for salicyclate in cerebrospinal fluid, blood, organs, and tissues.

The developed pharmacokinetic model, an extension of the Bischoff--Dedrick model, simultaneously predicts the kinetic behavior of salicylate in cerebrospinal fluid, blood, organs, and tissues. The model, which is entirely different from conventional compartment models, is derived from basic considerations of drug distribution with biochemical and physiological meaning. The dog was studied at three different dosages of salicylate: therapeutic, moderate intoxication, and severe intoxication. The predicted kinetics of salicylate in cerebrospinal fluid, blood, plasma, liver, muscle, and adipose tissue by the model agreed well with the experimental data. The effectiveness of hemoperfusion treatment for the severely intoxicated dog by albumin-coated activated carbon and its effect on the kinetic behavior of salicylate in cerebrospinal fluid, blood, organs and tissues were studied. The model was also applied to predict the kinetic changes of salicylate in the body during and after the extracorporeal treatment. The predicted results also agreed with the experimental data.

Adipose Tissue↗
PubMed1977

Early morning migraine. Nocturnal plasma levels of catecholamines, tryptophan, glucose, and free fatty acids and sleep encephalographs.

Nocturnal plasma catecholamine, tryptophan, glucose, and free fatty acid levels have been measured in 19 subjects who regularly awoke from sleep with migraine. All-night polygraphic sleep recordings were also made. 13 subjects were studied on a second occasion allowing within-subject control as well as group comparison. Plasma total catecholamine and specifically plasma-noradrenaline levels were significantly higher in the three hours before the subjects awoke with migraine. No differences were found in plasma tryptophan, glucose, insulin, and free fatty acid levels in the migraine/no-migraine categories. Waking with migraine occurred significantly more often from rapid-eye movement (REM) sleep. There were no other differences in sleep pattern in the migraine/no-migraine categories.

Adult↗
PubMed1976

Pharmacokinetic model for simultaneous determination of drug levels in organs and tissues.

An extension of the Bischoff-Dedrick pharmacokinetic model is presented. This model is derived from basic considerations of drug distrubition with physiological and anatomical meaning. The Bischoff-Dedrick model can simultaneously predict drug distribution with time in blood, organs, and tissues of pharmacological interest. The parameters are applied to a 15-kg standard dog. The experimental kinetic data of thiopental in brain, plasma, liver, lean tissue, and adipose tissue in a dog are used to demonstrate the feasibility of the model. Allowable variations in the parameters are determined. In general, the kinetics of drug distribution in blood, organs, and tissues depend on the drug dosage, lipid solubility, partition coefficients, metabolism rate, excretion rate, protein binding, route of administration, sizes of organs and tissues, and blood flow rates through organs and tissues. These factors enter the kinetic model separately and explicitly so their effects on the kinetics of drug distribution can be studied to provide valuable information for optimal therapy.

Animals↗
PubMed1975

Isocaloric diet changes and electroencephalographic sleep.

Electroencephalographic (E.E.G.) sleep changes were studied in eight young healthy male subjects who were given a normal balanced diet or a high-carbohydrate/low-fat or low-carbohydrate/high-fat isocaloric diet, according to an experimental design. Significantly less slow-wave sleep (S.W.S.) was found after consuming a high-carbohydrate/low-fat diet than after consuming a normal balanced diet or a low-carbohydrate/high-fat diet. The latter two diets did not differ in terms of the amounts of S.W.S. Both high-carbohydrate/low-fat and low-carbohydrate/high-fat isocaloric diets, especially the former, were associated with significantly more rapid-eye-movement (R.E.M.) sleep than was the normal balanced diet. These findings emphasise the importance of daily diet for the following night's sleep.

Diet↗