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Biomedical subjects

C T Chen

Publications and source records attributed to C T Chen.

At least 163 records · Page 9Linked to original sources
PubMed1990

[An in vitro study of lithium index in healthy Chinese].

The lithium index, a ratio of erythrocyte (intracellular) to plasma (extracellular) lithium concentrations, were studied by in vitro method in 22 healthy volunteers, 15 men and 17 women. Their mean age was 31.0 +/- 4.6 years (ranging from 26 to 41 years). In the study design, 20 ml of venous blood was taken from each subject into a test tube containing sodium citrate at the room temperature and erythrocytes were separated from plasma immediately. Then, the whole procedures for preparation and determination of lithium index were performed by using Pandey's method. Lithium levels were measured by atomic absorption spectrophotometry. Values of lithium index in vitro thus obtained were: 0.43 +/- 0.13 (range, 0.23-0.73) in men plus women; 0.37 +/- 0.10 (range, 0.23-0.57) in men; 0.49 +/- 0.13 (range, 0.26-0.73) in women. Women had a significantly higher Li+ index in vitro than men (t = 2.86, d.f. = 30, p less than 0.005). The possible reasons for the difference of the Li+ index in vitro between our result and other studies were discussed.

Adult↗
PubMed1989

Pharmacodynamics and pharmacokinetics of haloperidol and reduced haloperidol in schizophrenic patients.

Twelve male chronic schizophrenic inpatients, neuroleptic-free for at least 4 weeks, were given an oral test dose of 10 mg haloperidol (HAL) and reduced HAL (RHAL) in a random order, with a 2-week interval. Two weeks after the last test dose, the patients were given HAL, 5 mg orally twice daily for 7 days. Blood samples were drawn at baseline and between 0.5 and 24 hr after the test doses, and during HAL treatment as well. Plasma drug concentrations and homovanillic acid (HVA) levels were measured with high-performance liquid chromatography using electrochemical detection. HAL, but not RHAL, produced increments in plasma HVA (pHVA) levels at 24 hr after a test dose. pHVA levels remained higher than baseline during HAL treatment. Detectable interconversion between HAL and RHAL was observed in eight patients. The capacity of the reductive drug-metabolizing enzyme system, however, was greater than that of the oxidative processes. The plasma RHAL:HAL ratios on days 6 and 7 were higher than and positively correlated with those at Tmax after a single dose of HAL and were negatively correlated with the HAL:RHAL ratios at Tmax after a single dose of RHAL. Thus, both reductive and oxidative drug-metabolizing systems probably contribute to individual differences in plasma RHAL:HAL ratios in HAL-treated schizophrenic patients.

Adult↗
PubMed1989

Multiparameter extrapolation of biodistribution data between species.

Values of an inaccessible biological parameter in man may be predicted from values measured in animals by correlating with a parameter accessible in both species, such as body weight, energy production, excretion rate, etc. Predicting toxic effects, from environmental chemicals, of therapeutic doses for drug administration and of radiation absorbed dose from medical and environmental radioactivity depends on the rationalization of relationships between concentration and time when scaling to humans from animal data. For example, the retention of 99mTc, injected intravenously as pertechnetate, reaches 10% in the mouse at about 1 d, but this level occurs in humans at about 7 d. Making a simultaneous transformation between two species for the concentration and time variables by using a method of least-squares fitting, we have derived a series of transformation factors for several species. When correlated with a biological parameter such as body weight, these factors can be used to yield predicted values that are in good agreement with measured values. This system may be used with any related variables, making it useful for predicting other types of biological data.

Animals↗
PubMed1989

The brain: integrated three-dimensional display of MR and PET images.

Three patients with intractable epilepsy, two with brain tumors, and one with encephalitis were imaged with magnetic resonance (MR) and positron emission tomography (PET). MR data were used to construct a three-dimensional (3D) computer model of the brain surface depicting the precentral (movement), postcentral (sensation), left inferior frontal (speech), and left superior temporal (hearing) gyri. PET-derived measurements of average surface metabolism were encoded as colors and mapped onto the 3D model by means of a retrospective technique for registering the two scans. The integrated 3D model depicted the location of PET-detected metabolic abnormalities with respect to the gyral anatomy visualized with MR. In each case, the predicted relationships were confirmed intraoperatively by means of inspection of the brain and electroencephalography. Multimodality 3D displays are likely to be particularly valuable for interpreting PET studies of epileptic patients and others with normal MR anatomy.

Brain↗
PubMed1988

Effect of blood sample tubes on amiodarone and desethylamiodarone concentrations.

We have investigated the change in amiodarone and desethylamiodarone concentrations in blood sampled from three different Vacutainer tubes: (a) sodium heparin, (b) gel separator (SST), and (c) no additive (plain tube). Amiodarone and desethylamiodarone concentrations were determined by a reverse-phase high pressure liquid chromatography technique in samples from 12 subjects on chronic amiodarone therapy. Amiodarone concentrations were significantly lower in plasma compared with serum from either gel separator (11.5%, p = 0.05) or no additive (13.5%, p = 0.01) tubes. Desethylamiodarone concentrations were significantly lower in plasma compared with serum from gel separator tubes (8.5%, p = 0.04) and were slightly lower compared with no additive tubes (4.4%, p = 0.41). Serum amiodarone and desethylamiodarone concentrations from either no additive or gel separator tubes yielded similar results. We conclude that significant amiodarone and desethylamiodarone concentration differences occur between serum and plasma, and that no binding of amiodarone and desethylamiodarone to the separator gel occurs.

Amiodarone↗
PubMed1988

Isolation and properties of the pituitary gonadotropin from silver carp (Hypophthalmichthys molitrix).

The gonadotropin of silver carp (scGTH) was purified from the pituitary glands in a yield of 8.4 mg/g through extraction with 6% ammonium acetate (pH 5.1)-40% ethanol followed by 80% ethanol precipitation, DEAE-cellulose chromatography and gel filtration. The molecular weight of scGTH is about 32,000 as estimated by gel filtration. Leucine and serine were the two N-termini of scGTH. The amino acid composition of scGTH is rich in aspartic acid/asparagine, glutamic acid/glutamine, valine, proline and half cystine. Its carbohydrate content is 22.2%. Biologically, scGTH significantly stimulated the steroidogenesis in carp testis and ovary in vitro and induced the ovulation in loaches. It also stimulated the 32P-phosphate uptake into 1-day-old chicken testis. Immunologically, scGTH could cross-react with the antiserum against cGTH and vice versa. In both cases parallel displacement curves were displayed.

Amino Acids↗
PubMed1988

Retrospective geometric correlation of MR, CT, and PET images.

Magnetic resonance imaging, computed tomographic, and positron emission tomographic studies of the brain provide complementary information, and many patients undergo more than one of these studies during the course of their diagnostic workup and treatment. A new technique for quantitative geometric correlation of such studies makes it possible to create integrated multimodality images by mapping features from one image onto an image obtained with another modality. The coordinate transformation between any pair of images is found by a semiautomatic algorithm for matching models of the patient's external surface as depicted in the two data sets. The resultant hybrid images, which combine complementary features of different studies, are often more useful for diagnosis and treatment planning than are the original single-modality images. The algorithm can also be used for spatial registration of baseline studies with follow-up images created with the same modality, which allows tracking of a lesion to detect subtle interval changes in size and shape. This technique can be applied to images acquired in routine clinical practice, since it is completely retrospective and does not necessitate special positioning or landmarking of the patient.

Adolescent↗
PubMed1985

Effect of intra-alveolar meconium on pulmonary surface tension properties.

To evaluate the effect of meconium on pulmonary surface tension properties, the mechanics of 30 excised, separated canine pulmonary lobes were studied. Meconia were blended in normal saline to produce solutions of 10% and 20%. Solutions were filtered to remove large particles and instilled endobronchially into the canine lobes. The static pressure-volume deflation curve of each lobe was determined before and 4 h after instillation of either normal saline or meconium solution. In the saline control group (eight lobes), the curve was essentially unchanged before and after instillation. In the 10% meconium group (14 lobes), the curve was significantly depressed after instillation, especially at a transpulmonary airway pressure of 10 cm H2O (p less than .05) and 5 cm H2O (p less than .005). In the 20% meconium group (eight lobes), the depression of the pressure-volume curve was essentially the same as that of the 10% solution group. It is concluded that meconium depresses the surface-active properties of the alveolar linings.

Animals↗
PubMed1984

Investigation of energy responses of germanium detectors and correction of measured spectra by means of Monte Carlo simulation.

A Monte Carlo program was developed which determines the energy response of X-ray detectors of various "nested" sizes simultaneously. Twenty-one planar germanium detectors with cylindrical crystals were chosen, which are commercially available for X-ray spectrometry. The photopeak efficiency, K alpha and K beta escape fractions. Compton fraction, elastic fraction, penetration fraction, and the Compton continuum were tabulated as a function of incident X-ray energies from 12 to 300 keV in 2-keV increments. Coefficients of polynomials fitted to the Compton continua were also calculated to facilitate computer implementation of spectrum corrections. Spectrum correction methods which use the Compton continua determined by Monte Carlo calculation were compared with those approximated by rectangles. Comparison of the residual root-mean-square (RRMS) values between the incident and corrected spectra showed that the former method yielded lower RRMS values. However, the differences in these values are small, indicating that the simple rectangular approximation may be adequate for most spectral measurements.

Germanium↗
PubMed1984

Evaluation of the efficacy of Alka-Seltzer Effervescent in gastric acid neutralization.

A commercially available antacid, a mixture of sodium and potassium bicarbonates and citric acid (Alka-Seltzer Effervescent), was evaluated experimentally and clinically for its efficacy in neutralizing 0.1 N HCl and gastric contents. In an in vitro titration study, Alka-Seltzer Effervescent buffered 5-30 times the volume of HCl with a pH between 1.0 and 2.0 to above a pH of 2.5. In an isolated canine pulmonary lobe model, aspiration of the antacid or acid-antacid mixture caused only a mild increase in lobe weight and did not increase intrapulmonary shunting. In the clinical study, when the antacid was given 5-40 min before administration of general anesthesia in a group of patients for emergency surgery, the pH of the gastric contents in each patient was increased to above 4.0. This contrasts with the control group of patients, which showed 50% (P less than 0.05) of the patients were at risk when no antacid was administered. Preoperative administration of Alka-Seltzer effectively increases the pH of the gastric contents in patients undergoing emergency surgery.

Adolescent↗
PubMed1983

Evaluation of cassette performance: physical factors affecting patient exposure and image contrast.

Physical properties of four radiographic cassettes were investigated in combination with various screen/film systems. These properties included (a) transmittance of monoenergetic x rays over 14-96 keV and comparison with predictions based on attenuation coefficients; (b) relative patient exposure from 60 to 120 kV (from phantom measurements) and correlation with predictions based on measured transmittance as well as average energies and angles of incident radiation; and (c) amounts of scatter from various cassette materials and comparison with Monte Carlo calculations. The results provide a model of performance based on quantitation of cassette effects on system speed and image contrast. Carbon-fiber cassettes required the lowest patient exposure, produced the least scatter, and (in low-scatter situations) were capable of increased image contrast.

Aluminum↗
PubMed1981

The structure of methylated xanthines in relation to their effects on DNA synthesis and cell lethality in nitrogen mustard-treated cells.

The variation in cellular response to alkylated xanthines possessing different side chains has been used to evaluate more fully the effect of caffeine on both survival and DNA synthesis in cells with DNA damage. A correlation is observed between the ability of these xanthines to reverse the inhibitory effects of nitrogen mustard damage on DNA synthesis and their ability to enhance nitrogen mustard lethality in human HT-29 cells. These findings are consistent with our theory that regulation of damaged replicon initiation protects against potentially lethal damage in the form of unrepaired DNA alkylations. Enhancement of nitrogen mustard lethality is observed to have a maximum limit, which can be reduced by highly toxic xanthine concentrations. The lethal effects of xanthines alone at higher concentrations are unrelated to the effects of caffeine specific to nitrogen mustard treated cells, and appear to be related to an immediate reduction in thymidine incorporation most likely caused by inhibition of other enzyme systems influencing DNA synthesis such as de novo and salvage pathways for purine biosynthesis.

Adenocarcinoma↗