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Biomedical subjects

M L Chen

Publications and source records attributed to M L Chen.

At least 163 records · Page 9Linked to original sources
PubMed1989

[Estrogen and progesterone receptors in human ovary and ovarian tumors].

Ovarian specimens from 159 different patients were analyzed for estrogen and progesterone receptor (ER and PR) content with the Dextran-coated Charcoal method. The results indicated that the contents of ER and PR in malignant ovarian tumors were not correlated with the menstrual cycle of the patient, clinical stage and differentiation of the tumor. Among malignant ovarian tumors, the mean ER and PR concentrations in sex-cord stromal tumors and endometrioid carcinomas were higher than those in other malignant ovarian tumors (P less than 0.05, P less than 0.025). This suggests the possibility of endocrine therapy for these patients with the hope for a better prognosis.

Adenocarcinoma↗
PubMed1989

[Comparative study on human chorionic gonadotropin receptor in normal human ovary with ovarian tumors].

Human Chorionic Gonadotropin (HCG) is major physiological luteotropic factors for the human corpus luteum. The observations strongly suggest that the human ovary possesses a gonadotropin receptor in the cell membrane. We studied the HCG receptor in normal human ovary and ovarian tumors. Twenty-three human ovarian specimens and 16 ovarian tumor specimens were obtained from women patients having gynecological surgery. Ovaries were homogenized and sonicated. The homogenates were centrifuged at 2000 g for 15 min. After sucrose density gradient ultracentrifugation (78,000 g, 4 h), two fractions were collected from layer of 33% and interface between 33% and 37%. Thirty micrograms of ovarian protein, 8 ng 125I-HCG and unlabeled HCG in a final volume of 0.5 ml of 0.05 mol/L Tris buffer were incubated at 30 degrees C for 2 h. The results were shown in the table.

Binding Sites↗
PubMed1988

Metallothionein metabolism in the liver and kidney of the streptozotocin-diabetic rat.

1. Elevated levels of metallothionein (MT)-I and -II were identified in the liver and kidney of insulin-deficient diabetic rats. 2. The relative rate of MT synthesis and the turnover of cytoplasmic MT were both accelerated in the liver of diabetic rats. 3. The rate of synthesis of MT, but not its cytoplasmic turnover, was increased in diabetic kidney. 4. Maximal relative rates of MT synthesis in liver and kidney were first observed at 4 and 10 days, respectively, after inducing the diabetic condition. 5. The altered metabolism of hepatic MT in diabetic rats was attributed primarily to disturbances in endocrine status, while the altered metabolism of renal MT was largely due to accumulation of excessive dietary copper in the kidney.

Animals↗
PubMed1988

High-level production of hepatitis B viral X protein in Escherichia coli using gene II promoter of bacteriophage M13.

Region X is one of the four open reading frames (ORFs) of hepatitis B virus (HBV) and encodes a polypeptide of 154 amino acids (aa). A 584-bp BamHI-BglII fragment of the HBV DNA containing the major part of ORF X which encodes 145 aa was inserted into the BglII site within the gene II of bacteriophage M13. The insertion resulted in an in-phase gene II-X fused protein of 174 aa under the control of the gene II promoter. Cells harboring plasmids (pML alpha X.59 and pMLX.12d) derived from the above construct overproduced the 19-kDa fused protein in Escherichia coli at a level of 10%-20% of total cellular protein. The fused protein was recognized by the anti-X antibodies. This is the first demonstration of using gene II promoter of M13 to express a foreign gene efficiently.

Bacteriophage lambda↗
PubMed1988

Iron metabolism in genetically obese (ob/ob) mice.

Several reports in the clinical literature suggest that obese children may be at risk for developing iron deficiency. Here the absorption, retention, tissue distribution and tissue levels of iron were compared in lean (+/?) and obese (ob/ob) C57BL/6J mice to examine the impact of obesity on the iron status of this animal model. Obese mice absorbed and retained approximately twice as much 59Fe as lean mice after receiving a solution containing 1 mumol iron per os. This difference was independent of age, severity of obesity and mass of the gastrointestinal tract. Obese mice fed ad libitum had higher levels of 59Fe in blood and fat pads, but lower amounts of 59Fe in the skeletal-muscular system, than lean mice 6 d after subcutaneous injection of 1 mumol of the metal. At least 30% of carcass 59Fe was present in the liver of obese and lean mice 6 d after injection. Despite significantly lower concentrations of iron in liver and bone, blood hemoglobin and hematocrit were significantly higher in obese mice fed ad libitum than in lean mice at 10 wk of age. Plasma iron and transferrin were not affected by chronic obesity. Although several characteristics of iron metabolism differed in obese and lean mice, the results indicate that ob/ob mice were not iron deficient when fed a diet containing an adequate level of this micronutrient. The increased absorption of iron by obese mice probably represents an adaptive response that is required to supply additional micronutrient for the expanded blood volume in these animals.

Absorption↗
PubMed1988

Laboratory and field assessment of molluscicidal activity of B-2 against Oncomelania hupensis, the vector snail of schistosomiasis in China.

Molluscicidal activity of B-2 (sodium 2,5-dichloro-4-bromophenol; called as Phebrol and registered in WHO as OMS 3012) was evaluated in a laboratory and the field trials were performed in two different localities in Yueyang city, China, for control of Oncomelania hupensis. B-2 was effective against O. hupensis both in the laboratory and in the field. A dosage of 50 g/m2 in 10% granular form or 20 ml/m2 in 25% liquid form of B-2 would be recommendable as a standard mollusciciding dose for control of O. hupensis.

Animals↗
PubMed1988

Morphologic, immunohistochemical, and ultrastructural studies of the production of hepatitis B virus in vitro.

Well differentiated human hepatoblastoma Hep G2 cells after transfection with cloned hepatitis B virus (HBV) genomes produce replicative HBV DNA intermediates, high levels of HBsAg, HBeAg and HBcAg as well as mature Dane particles. To analyze the replication cycle of HBV, we studied the expression of HBV antigens with monoclonal antibodies by immunomorphologic methods in the transfected cells at various time intervals after plating. HBcAg and HBeAg were detected in the cytoplasm and less frequently in the nuclei of transfected cells. The percentage of positive cells increased with time after plating and reached a plateau of about 50% positive cells at 10 days. HBsAg and the large and middle HBsAg polypeptides were observed in the cytoplasm of transfected cells and a maximum of 20 to 30% positive cells was reached during the 3rd week after plating. Examination of viable cells in suspension revealed HBcAg/HBeAg and HBsAg expression on the cell surface. Electron microscopy demonstrated characteristic core particles in the nuclei and cytoplasm and Dane particles in cytoplasmic vesicles and culture media of transfected cells. The HBV producing cells did not show any evidence of a cytopathic effect. These observations demonstrate significant similarities between the HBV DNA transfected cells and infected human hepatocytes which support active HBV replication in vivo. Taken together, the results suggest that the cultured cells may serve as a model to elucidate a number of unsolved problems of the molecular and cellular pathobiology of hepatitis B.

Carcinoma, Hepatocellular↗
PubMed1987

Effect of phencyclidine on post-tetanic twitch tension of the mouse diaphragm preparation.

The effects of phencyclidine(PCP) on the post-tetanic potentiation(PTP) of twitch tension were studied on the isolated mouse phrenic nerve diaphragm preparation. Phencyclidine increased directly elicited twitch tension while it decreased post-tetanic potentiation of the indirectly elicited twitch tension. The maximal depression effect of the PTP was found after higher frequencies and longer durations of stimulation. After repetitive stimulation, the amplitude of endplate potential was potentiated. Phencyclidine decreased the post-tetanic potentiation of the amplitude of endplate potential while the quantal content of the endplate potential was not affected. 4-Aminopyridine increased both directly and indirectly elicited twitch tension while it did not inhibit the post-tetanic potentiation of the twitch tension. It is concluded that phencyclidine suppressed the post-tetanic potentiation of the indirectly elicited twitch tension. The depressant effect may be mainly due to its effect on the acetylcholine receptor-ionic channel complex of the motor endplate.

Action Potentials↗
PubMed1987

Application of moment analysis in assessing rates of absorption for bioequivalency studies.

Moment analysis was utilized in the evaluation of equivalency between test and reference formulations with respect to the rate of absorption for four drugs having different pharmacokinetic characteristics. A confidence interval technique was applied to compare the three relevant absorption parameters, that is, peak plasma concentration (Cmax), time to peak plasma concentration (tmax), and mean absorption time (MAT). Equivalence in the absorption rate of drugs was found to be best evaluated by the combined use of MAT, tmax, and Cmax. Use of these parameters for assessing equivalency requires careful interpretation of the results of statistical analysis as well as appropriate consideration of efficacy and safety issues for individual drugs. In addition, the statistical moment method proves to be useful in the assessment of bioequivalency, particularly for drugs with multiple absorption maxima.

Acetaminophen↗
PubMed1987

The effect of carbamazepine on the post-tetanic twitch tension in the diaphragm of the mouse.

The effects of carbamazepine (0.084-0.25 mM) on the post-tetanic potentiation of the twitch tension, were studied on the isolated phrenic nerve diaphragm preparation of the mouse. Carbamazepine decreased the post-tetanic potentiation of the twitch tension. The maximal depressant effect was found after higher frequencies and longer durations of stimulation. After repetitive stimulation, the amplitude of the endplate potential and the frequency of miniature endplate potentials were potentiated. Carbamazepine decreased the post-tetanic potentiation of the amplitude of endplate potential and the frequency of miniature endplate potentials. The directly-elicited muscle action potential was not affected when post-tetanic potentiation of the twitch tension was decreased. It is concluded that carbamazepine suppressed the post-tetanic potentiation of the indirectly-elicited twitch tension, mainly due to its pre-synaptic inhibitory effect.

Action Potentials↗
PubMed1987

Production of hepatitis B virus particles in Hep G2 cells transfected with cloned hepatitis B virus DNA.

The hepatoblastoma cell line Hep G2 was transfected with a plasmid carrying the gene that confers resistance to G418 and four 5'-3' tandem copies of the hepatitis B virus (HBV) genome positioned such that two dimers of the genomic DNA are 3'-3' with respect to one another. Cells of one clone that grew in the presence of G418 produce high levels of hepatitis B e antigen and of hepatitis B surface antigen. HBV DNA is carried by these cells as chromosomally integrated sequences and episomally as relaxed circular, covalently closed, and incomplete copies of the HBV genome. Viral DNA was detected also in conditioned growth medium at the buoyant densities characteristic for infectious Dane and immature core particles. Finally, HBV-specific components morphologically identical to the 22-nm spherical and filamentous hepatitis B surface antigen particles as well as 42-nm Dane particles were visualized by immunoelectron microscopic analysis. Therefore, we have demonstrated that the Hep G2 cell line can support the assembly and secretion not only of several of the replicative intermediates of HBV DNA but also of Dane-like particles. This in vitro system can now be used to study the life cycle of HBV and the reaction of immunocompetent cells with cells carrying HBV.

Carcinoma, Hepatocellular↗
PubMed1987

The effects of myasthenic immunoglobulin G on neuromuscular transmission in mouse diaphragm.

The effect of immunoglobulin G (IgG) from a patient with myasthenia gravis (MG) on neuromuscular transmission of an isolated mouse diaphragm preparation was studied by using electrophysiological methods. The frequency and amplitude of miniature endplate potentials (MEPPs) of the diaphragms obtained from mice injected intraperitoneally with purified IgG from MG patient were reduced by about 13% and 20%, respectively in comparison with results from normal mouse diaphragms. The amplitude of endplate potential (EPP) and the quantal content of EPPs were also reduced by about 21% and 7%, respectively. No significant changes in EPP and MEPP amplitudes were seen in the diaphragms of mice injected with normal IgG serum. It is postulated IgG from myasthenia gravis acts to interfere with both the receptor and the nerve terminal functions.

Animals↗
PubMed1987

Effects of alpha-bungarotoxin and d-tubocurarine on the post-tetanic potentiation of the mouse diaphragm twitch tension.

Effects of alpha-bungarotoxin (alpha-BuTX, 0.037-0.062 microM) and d-tubocurarine (d-Tc, 0.7-2.2 microM) on the post-tetanic potentiation (PTP) of the twitch tension were studied on the isolated mouse diaphragm preparation. In normal physiological solution, maximum PTP was obtained after 100 Hz tetanic stimulation for 5 sec. In preparations partially blocked by alpha-BuTX, PTP was less than in control preparations if tetanically stimulated at 100-200 Hz for 5-10 sec. In contrast, in preparations partially blocked by d-Tc (1-2.2 microM), PTP was increased if a higher frequency (500 Hz) was applied. This increase of the effect was independent of the duration of tetanic stimulation. Thus, d-Tc and alpha-BuTX have a different effect on PTP. The irreversibility of alpha-BuTX may contribute to the differences in mode of action of alpha-BuTX and d-Tc on the PTP of the twitch tension of the isolated mouse diaphragm.

Animals↗