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Biomedical subjects

C C Chen

Publications and source records attributed to C C Chen.

At least 541 records · Page 30Linked to original sources
PubMed1990

EDRF-release and Ca+(+)-channel blockade by magnolol, an antiplatelet agent isolated from Chinese herb Magnolia officinalis, in rat thoracic aorta.

Magnolol is an antiplatelet agent isolated from Chinese herb Magnolia officinalis. It inhibited norepinephrine (NE, 3 microM)-induced phasic and tonic contractions in rat thoracic aorta. At the plateau of the NE-induced tonic contraction, addition of magnolol caused two phases (fast and slow) of relaxation. These two relaxations were concentration-dependent (10-100 micrograms/ml), and were not inhibited by indomethacin (20 microM). The fast relaxation was completely antagonized by hemoglobin (10 microM) and methylene blue (50 microM), and disappeared in de-endothelialized aorta while the slow relaxation was not affected by the above treatments. Magnolol also inhibited high potassium (60 mM)-induced, calcium-dependent (0.03 to 3 mM) contraction of rat aorta in a concentration-dependent manner. 45Ca(+)+ influx induced by high potassium or NE was markedly inhibited by magnolol. Cyclic GMP, but not PGI2, was increased by magnolol in intact, but not in de-endothelialized aorta. It is concluded that magnolol relaxed vascular smooth muscle by releasing endothelium-derived relaxing factor (EDRF) and by inhibiting calcium influx through voltage-gated calcium channels.

Animals↗
PubMed1990

Enhancement of the critical current density in single-crystal Bi2Sr2CaCu2O8 superconductors by chemically induced disorder.

The effect of metal substitution on the critical current densities of single-crystal PbxBi2-xSr2CaCu2O8 (x = 0 or x = 0.7) superconductors has been investigated. Substitution of lead was found to increase the average critical current density from 1 x 10(5) A/cm2 to 2 x 10(6) A/cm2 at 5 K in an applied magnetic field of 10 kilooersteds (1 oersted = 80 A/m). The order of magnitude increase in the critical current density was observed for temperatures up to the flux vortex lattice melting point; the flux lattice melting point was also found to increase to 30 K (from 22 K) in the lead-substituted materials. Diffraction and microscopy investigations of the structural parameters indicate that the fundamental atomic lattices are virtually the same for both materials. Scanning tunneling microscopy images demonstrate, however, that lead substitution causes significant disorder (or defects) in the one-dimensional superstructure found in Bi2Sr2CaCu2O8. Since crystal defects can increase the critical current density by pinning the motion of flux vortices, it is likely that this lead-induced disorder enhances vortex pinning. The lead-induced disorder is specific to the nonsuperconducting Bi-O layers, and thus our results suggest that chemical substitutions may be utilized to control selectively flux pinning and the critical current density in these materials.

Journal Article↗
PubMed1990

Filter and leak penetration characteristics of a dust and mist filtering facepiece.

The filtering facepiece, also referred to as a disposable respirator, is an extensively used type of respirator without an officially accepted fit testing method. This study describes an aerosol generator and a sampling train, which have been developed for investigating the aerosol penetration characteristics through the filter element and the face seal. Electrostatic attraction and impaction are the two primary filtration mechanisms for micrometer- and supermicrometer-sized aerosols, respectively. Filtration and flow dynamics were found to affect aerosol penetration in distinct ways that allow for the differentiation of the face seal leakage from the filter penetration. The slope of the aerosol size-dependent penetration curve potentially may differentiate the face seal leakage from filter penetration.

Aerosols↗
PubMed1990

Extralobar pulmonary sequestration of the left retroperitoneum.

This paper presents an extralobar pulmonary sequestration in the left retroperitoneum in an eight year old girl. The clinical and diagnostic features included abdominal pain, an abdominal mass, elevated VMA, and radiological manifestations simulating a left adrenal mass. A laparatomy was performed. Extralobar pulmonary sequestration of the left retroperitoneum is fairly uncommon. An eight year old girl was admitted with abdominal pain, elevated urinary VMA and an abdominal mass. The radiological manifestations simulated a left adrenal mass. At surgery an extralobar pulmonary sequestration was detected.

Bronchopulmonary Sequestration↗
PubMed1990

Patients at high risk for renal artery stenosis: a simple method of renal scintigraphic analysis with Tc-99m DTPA and captopril.

Fifty patients with suspected renal artery stenosis (RAS) were studied with renal scintigraphy before and after administration of captopril. Twenty-three patients had RAS (greater than or equal to 75% RAS or greater than or equal to 50% RAS with poststenotic dilatation) and 27 had normal renal arteries at angiography. Angiotensin-converting enzyme inhibitors were discontinued 24 hours prior to renal scintigraphy; all other medications were continued. Each patient was evaluated with a simplified captopril renal scintigraphic protocol: renal imaging after administration of 12 mCi (444 MBq) of technetium-99m diethylenetriaminepentaacetic acid (DTPA), a 3-hour wait, oral administration of 50 mg of captopril, a 1-hour wait, and another scintigram obtained after administration of 12 mCi (444 MBq) of Tc-99m DTPA. Times of peak renal activity (Tmax) were determined from renal time-activity curves, and glomerular filtration rates (GFRs) were calculated with the Gates technique. A Tmax greater than or equal to 11 minutes after injection or a GFR ratio (larger GFR/smaller GFR) greater than 1.5 enabled detection of RAS with 91% sensitivity, 93% specificity, and 92% accuracy. Renal scintigraphy without captopril had only 43%-68% sensitivity in detecting RAS, depending on the criteria used.

Captopril↗
PubMed1990

Usefulness of echocardiography in the prediction of early results of catheter balloon mitral valvuloplasty.

Catheter balloon mitral valvuloplasty (BMV) was performed in 50 patients and 32 of them undergoing BMV with double balloon technique were studied to evaluate the usefulness of echocardiography in the prediction of early results of BMV. Five echocardiographic variables including mitral valve motion, mitral valve thickness, subvalvular change, commissural calcification and left atrial dimension were evaluated. Each variable was divided into mild, moderate and severe subgroups. Before valvuloplasty there were no differences in mitral valve area among any subgroup for any variable. After valvuloplasty, variables associated with a greater increase in mitral valve area from mild and moderate subgroups than from severe subgroup included mitral valve motion, mitral valve thickness, and subvalvular change, but not commissural calcification or left atrial dimension. We scored the former 3 variables as 0, 1 and 2 points in the mild, moderate and severe subgroups, respectively. The sums of individual scores in these 3 variables were further divided into 3 groups: 12 patients had a lower score (less than 2), 10 patients had a score of 3-4 and 10 patients had a higher score (greater than 5). Patients with lower scores tended to have greater increases in mitral valve areas after valvuloplasty than those with higher scores. Thus, mitral valve motion, mitral valve thickness and subvalvular change may be useful to predict a greater increase in mitral valve area after valvuloplasty. A lower score of echocardiographic variables anticipates successful balloon mitral valvuloplasty, which may be helpful in patient selection.

Adult↗
PubMed1990

Additivity of cytotoxic damage due to dimethylbenz(a)anthracene and X rays.

7,12-Dimethylbenz(a)anthracene is one of a group of polycyclic aromatic hydrocarbons that are known to be indirectly acting carcinogens. As a product of the incomplete combustion of complex hydrocarbons, dimethylbenzanthracene is present in the environment and may therefore act on living systems in conjunction with ionizing radiation. We have studied the cytotoxic effects of dimethylbenzanthracene by itself, together with other polycyclic aromatic hydrocarbons, and combined with X radiation. Pre- or postirradiation treatment of mouse C3H 10T1/2 cells with dimethylbenzanthracene progressively removes the shoulder of the X-ray survival curve and, consistent with that observation, the survival sparing from dose fractionation is progressively lost. The cotreatment of cells with 3-methylcholanthrene and dimethylbenzanthracene largely abrogates the killing due to the latter compound alone and, accordingly, returns the shoulder to the survival curve. The application of dimethylbenzanthracene, or similar compounds, between X-ray dose fractions, separated by 4 h, is without effect quite likely because of the need for metabolic activation of the compound for effectiveness. Dimethylbenzanthracene is believed to be genotoxic because, after it is activated, it forms bulky adducts with DNA. Hence these results suggest that bulky adducts are a form of DNA damage operationally equivalent to sublethal X-ray damage.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

Myocardial Na+-K+-ATPase activity and [3H]ouabain binding sites in hypertensive rats.

Na+-K+-ATPase activity and [3H]ouabain binding were studied in cardiac ventricles of single wrapped kidney and DOCA-NaCl hypertensive rats. It was found that the total Na+-K+-ATPase activity decreased in the DOCA-NaCl and kidney wrapped hypertensive rats. The decrease of enzyme activity in DOCA-NaCl hypertensive rats was due to extracellular fluid expansion induced by NaCl loading, as DOCA itself had no effect on the enzyme. All these alterations were specific for Na+-K+-ATPase, since Mg2+-ATPase and 5'-nucleotidase activities were unaffected. Binding studies with [3H]ouabain showed that the decrease in Na+-K+-ATPase activity was due to a reduction in the number of binding sites for ouabain rather than to a change of binding affinity. The reduced myocardial Na+-K+-ATPase activity observed in these two types of low renin hypertension, coupled with the observation of reduced vascular Na+ pump activity by others, suggests a common underlying defect in the cardiovascular Na+-K+ transport system of these hypertensive rats.

5'-Nucleotidase↗
PubMed1989

Pharmacokinetic and pharmacodynamic comparison of conventional and controlled release formulations of metoprolol [correction of motoprolol] in healthy Chinese subjects.

A double-blind, crossover comparison of the pharmacokinetics and pharmacodynamics of controlled-release metoprolol (CR) 100 mg and 200 mg, metoprolol plain tablet 100 mg, metoprolol Durules 200 mg, and placebo was carried out in 10 healthy Chinese subjects. Standardized treadmill exercise tests according to the Bruce protocol were performed at a steady state of medication, before and 2, 6, 12, and 24 hours after the dose, and multiple blood samples were collected for determination of the metoprolol concentration. The plasma metoprolol levels over 24 hours were more uniform after metoprolol CR than Durules and the plain tablet. The mean peak concentrations for CR 100 mg, 200 mg, Durules, and the plain tablets were 231, 426, 790, and 1105 nmol/l, respectively. The corresponding fluctuation incides were 1.1, 1.5, 2.2, and 5.0. The effects on exercise heart rate (EHR) were investigated at steady state. Metoprolol CR produced more even reduction in EHR over 24 hours than Durules and plain tablets. All four treatments gave similar maximal reduction in EHR of about 20% at 2 hours after the dose. In conclusion, once daily metoprolol CR showed almost even blood levels and provided relatively constant levels of beta1 blockade over 24 hours in healthy Chinese subjects.

Adult↗
PubMed1989

Hypermedia in radiology: computer-assisted education.

Hypertext is a new computer-based method of presenting information that provides greater flexibility than conventional methods of continuing education. With a hypertext system, an individual using the computer can acquire more information on a word or concept that needs to be pursued in depth. Hypermedia is an expanded concept which uses the computer's ability to incorporate images, sounds, and video images in addition to text. This interactive, multimedia approach customizes information for more effective learning. The authors devised a prototype hypermedia textbook of nuclear medicine using a personal computer with hypermedia software that contains text, graphs, tables, figures, literature citations, and an easily persuable image database. All the information is organized with multiple cross-references, allowing instant branching to relevant facts, in different levels of detail. The system's applications and the ease of expansion or modification by the user are described.

Computer-Assisted Instruction↗
PubMed1989

The role of computerized modeling and simulation in the development of life support system technologies.

Using conventional means of process development, it would take decades and hundreds of millions of dollars to develop technology for recycling of water and solid waste for lunar missions within the next thirty years. Since we anticipate neither that amount of time nor level of funding, new methodologies for developing life support systems (LSS) technologies are essential. Computerized modeling and simulation (CMAS) is a tool that can greatly reduce both the time and cost of technology development. By CMAS, we refer to computer methods for correlating, storing and retrieving property data for chemical species and for solving the phenomenological equations of physical/chemical processes (i.e., process conditions based on properties of materials and mass and energy balances, equipment sizing based on rate processes and the governing equations for unit operations). In particular, CMAS systems can be used to evaluate a LSS process design with minimal requirements for laboratory experimentation. A CMAS model using ASPEN PLUS is presented for a vapor compression distillation (VCD) system designed for reclaiming water from urine.

Computer Simulation↗
PubMed1989

Cloning and expression of the streptococcal C5a peptidase gene in Escherichia coli: linkage to the type 12 M protein gene.

A genomic library of Streptococcus pyogenes CS24 DNA was constructed by cloning streptococcal DNA partially digested with Sau3A into the lambda replacement vector EMBL3. The expression of streptococcal C5a peptidase (SCP) was analyzed by radioimmunoassay with hyperimmune rabbit serum. Two clones, lambda 4.1 and lambda 4.2, were found to express the desired antigen, and various DNA fragments from the hybrid bacteriophage lambda 4.1 were subcloned into the plasmid vector pUC9 in Escherichia coli. One of the recombinant plasmids, designated pTT1, contained a 5.8-kilobase (kb) streptococcal DNA insert. Analysis of total cellular protein from this E. coli clone by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western (immuno-) blotting identified a 140,000-Mr protein, similar in size to the native protein purified from S. pyogenes. Cloned SCP was functionally active, as shown by its ability to inhibit C5a-mediated chemotaxis. By deletion analysis with both restriction endonucleases and BAL 31 nuclease, the SCP gene was localized to a 4.3-kb segment of DNA. Southern hybridization experiments showed that the type 12 M protein-coding sequence is also present in the hybrid phage lambda 4.1, at approximately 2 kb upstream of the SCP structural gene. Western blot analysis indicated that the cloned streptococcal DNA in lambda 4.1 directed the expression of both SCP and M12 protein.

Adhesins, Bacterial↗
PubMed1989

Comparison of proteins and nucleic acids of Echinochloa ragged stunt and rice ragged stunt viruses.

Echinochloa ragged stunt virus (ERSV) and rice ragged stunt virus (RRSV; Reoviridae) were purified from their respective host plants and disrupted in SDS. Evidence for the double-strandedness of ERSV RNA was obtained. Electrophoresis in 10% polyacrylamide gels resolved the RNAs of each virus into 10 segments, ranging for ERSV from 0.61 x 10(6) to 2.8 x 10(6) daltons, with a sum representing the total genome of 17.89 x 10(6) daltons, and for RRSV from 0.6 x 10(6) to 2.98 x 10(6) daltons, with a sum of 18.15 x 10(6) daltons. Although the overall RNA pattern of the two viruses was similar, there were distinctive features. Using 7.5-15% polyacrylamide gels, electrophoresis of SDS-dissociated RRSV particles yielded five major proteins of 129 x 10(3), 123 x 10(3), 63 x 10(3) and 35 x 10(3) daltons, and two minor proteins of 113 x 10(3) and 88 x 10(3) daltons, respectively, while comparable samples of ERSV yielded four major proteins of 127 x 10(3), 123 x 10(3), 63 x 10(3) and 34 x 10(3) daltons, and three minor proteins of 103 x 10(3), 50 x 10(3) and 49 x 10(3) daltons, respectively. We conclude from this and other evidence that ERSV and RRSV are closely related viruses and should be classified in the same subgroup, despite reported differences in the morphology of their outer capsids.

Acridine Orange↗
PubMed1989

Beta-endorphin-like immunoreactivity in CSF of patients with acute head injury. A clinical report of 36 cases.

beta-endorphin-like immunoreactivity (beta-ELI) was measured in the cerebrospinal fluid (CSF) of 36 patients with acute head injury and 12 controls. The mean values of beta-ELI in CSF of controls and patients with moderate and severe acute head injury were 51.9 +/- 5.6 pg/ml, 110.5 pg/ml, and 173.8 +/- 20.1 pg/ml respectively, with significant difference between them (p less than 0.05). The results showed that beta-ELI increased in CSF of acute head injury patients.

Adolescent↗