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Biomedical subjects

M Chen

Publications and source records attributed to M Chen.

At least 793 records · Page 44Linked to original sources
PubMed1991

Overlap syndrome of progressive systemic sclerosis and polymyositis: report of 40 cases.

Forty cases of overlap syndrome of progressive systemic sclerosis and polymyositis (OS PSS-PM) are reported in this paper. All of these cases had manifestations of both PSS and PM as well as Raynaud's phenomenon. The sclerodermatous skin changes were diffused over the whole body in most cases. All cases had muscular weakness, elevated skeletal muscle enzyme levels and muscle damage as seen on the electromyogram. Histopathologic changes showed characteristics of myositis. There was noticeable systemic involvement, especially with the digestive and circulatory systems. Serologic examination frequently revealed autoantibodies. The patients responded well to traditional Chinese medicines and corticosteroids.

Adolescent↗
PubMed1991

[Preparation of monoclonal antibodies against chorionic gonadotropin receptor and study of its characteristics].

We reported the production of monoclonal antibodies (McAbs) against chorionic gonadotropin hormone (CG) receptor by fusing spleen cells of BALB/c mice which had been immunized by purified bacteria (Pseudomonas maltophilia) CG receptor with mouse myeloma line SP2/0. Four hybridoma cell lines secreting CG receptor McAbs were obtained (ED490 DG390, AB890 and GE590). The titers of specific antibodies of both mice ascites and culture supernatant were 10(-2)-10(-6) and 1-10(-2) respectively, by solid phase ELISA. Double-Immunodiffusion test showed that the McAb GE590 was IgG1, and the McAbs ED490, DG390 and AB890 were IgG2b Immunoprecipitation indicated that 125I-HCG could bind the HCG receptor which had reacted with McAbs ED490, AB890 and DG390, suggesting that they may recognize the receptor with different antigenic determinant. Interaction of McAb GE590 with the receptor showed that the increased concentration of GE590 was in inverse proportion to the amount of 125I-HCG binding receptor, indicating that both the McAb and 125I-HCG could recognize a common site of receptor and that increased concentration of McAb GE590 may induce some change in conformation and structure of the receptor. Our study suggested that these McAbs may be used for studying structure of CG receptor.

Animals↗
PubMed1991

[Sedative chemical constituents of leaves of Apocynum venetum Linn].

Eight constituents were isolated from the ether solvent fraction of leaves of Apocynum venetum and identified as triacontanol, beta-sitosterol, quercetin, hyperin, long-chain fatty acids (C28-C34), lupeol, scopoletin and isofraxidin. Isofraxidin and hyperin were effective sedative components.

Alkaloids↗
PubMed1991

[Studies on the chemical constituents of Flemingia philippinensis].

Two new prenylated flavonoids, flemiphilippinin C (I) and flemiphilippinin D (II) have been isolated from the root of Flemingia philippinensis (Merr. et Rolfe) Li along with four known compounds. The structure of I and II were elucidated as 7-(.4'-hydroxy-3'-methoxyphenyl)-5-hydroxy-2, 2-dimethyl-10-prenyl-2H,6H-benzo-[1,2-b:5,4-b']dipyran-6-one and 5,7,2',4'-tetrahydroxy-6,8-diprenylisoflavanone, respectively, on the basis of chemical and spectroscopic data. The four known compounds were identified as 5,7,3',4'-tetrahydroxy-6,8-diprenylsilflavone (III), flemichin D (IV), beta-sitosterol (VI) and lupeol (VII), and a mixture of n C22-C30 aliphatic acid (V). Compounds III and IV showed significant cytotoxic activities against P388 cell cultures.

Animals↗
PubMed1991

Comparative efficacy of levo-praziquantel and praziquantel in treatment of schistosomiasis japonica at a single dose.

The result of a randomized double blind comparison of therapeutic efficacy of single doses of levo-praziquantel (L-PZQ) and praziquantel (PZQ) in the treatment of 139 matched pairs of proved cases of schistosomiasis japonica was reported, 268 were chronic early cases and 10 were late cases. The dosage of L-PQZ was 20 mg/kg, and that of PZQ was 40 mg/kg. Four and 6 months after treatment the stool-ova negative conversion rates were 94.8% and 96.3% for the L-PZQ group, and 97.1% and 94.0% for the PZQ group respectively (P greater than 0.05).

Adolescent↗
PubMed1991

[Use DNA techniques to detect tetracycline resistance genes in clinical strains].

Our purpose in the present report was to use DNA techniques to analyse the distribution of Tetracycline resistance determinants among Gram negative bacteria and different location in our country. 306 clinical isolates, 102 out of which were isolated from nosocomial infections in Beijing Union Medical College Hospital from 1981-1986, were identified by fifteen kinds of biochemical reaction. According to sensibility test results, the percentage of resistant to antibiotics was that: Tetracycline 100%, Ampicillin 81.4%, Cefazolin 28.4%, Gentamycin 56.9%, Chloramphenicol 59.8%, TMP-SMZ 57.2%, Erythromycin 91.5%. The result of colony hybridization was that TetB (on R222) occurred at 31.4%, followed by TetD (on RA1) at 25.2%, TetA (on RP1) at 12.4% and TetC (on pSC101) at 10.5%, 36.6% of isolates failed to hybridize to any of the probes, while 51.3% harbored one determinant, 7.5% harbored two, 2.9% three and 1.6% four. Strains from some location contained TetB and TetD were slightly higher than TetC and TetA. At high stringency conditions of hybridization, we were able to show cross reaction of determinant C with TetA DNA, but no reaction with TetB and TetD DNA.

DNA Probes↗
PubMed1990

Protein-protein interactions between adenovirus DNA polymerase and nuclear factor I mediate formation of the DNA replication preinitiation complex.

The in vitro adenovirus (Ad) DNA replication system provides an assay to study the interaction of viral and host replication proteins with the DNA template in the formation of the preinitiation complex. This initiation system requires in addition to the origin DNA sequences 1) Ad DNA polymerase (Pol), 2) Ad preterminal protein (pTP), the covalent acceptor for protein-primed DNA replication, and 3) nuclear factor I (NFI), a host cell protein identical to the CCAAT box-binding transcription factor. The interactions of these proteins were studied by coimmunoprecipitation and Ad origin DNA binding assays. The Ad Pol can bind to origin sequences only in the presence of another protein which can be either pTP or NFI. While NFI alone can bind to its origin recognition sequence, pTP does not specifically recognize DNA unless Ad Pol is present. Thus, protein-protein interactions are necessary for the targetting of either Ad Pol or pTP to the preinitiation complex. DNA footprinting demonstrated that the Ad DNA site recognized by the pTP.Pol complex was within the first 18 bases at the end of the template which constitutes the minimal origin of replication. Mutagenesis studies have defined the Ad Pol interaction site on NFI between amino acids 68-150, which overlaps the DNA binding and replication activation domain of this factor. A putative zinc finger on the Ad Pol has been mutated to a product that fails to bind the Ad origin sequences but still interacts with pTP. These results indicate that both protein-protein and protein-DNA interactions mediate specific recognition of the replication origin by Ad DNA polymerase.

Adenoviruses, Human↗
PubMed1990

Replication of an adenovirus type 34 mutant DNA containing tandem reiterations of the inverted terminal repeat.

A mutant of human adenovirus type 34 (Ad34) has been isolated which contains DNA molecules with tandem reiterations of from two to eight copies of a 131-bp sequence within the right-sided inverted terminal repetition. Terminal heterogeneity was not eliminated by repeated plaque purifications indicating that the population of DNA molecules with various numbers of reiterations could rapidly evolve from the DNA of a single virus particle. These enlarged DNA molecules were capable of replication both in vivo and in vitro. The nucleotide sequence of the mutant Ad34 inverted terminal repetitions contained most of the essential features of the Ad origin of DNA replication. These features include the ATAATATACC sequence which is present between the highly conserved bases 9-18 in all human adenoviruses, as well as the consensus sequences for the binding of nuclear factor I and nuclear factor III. However, the reiterated sequences lacked a dG appropriately placed on the template strand to serve as a potential site for internal initiation. It appears that the rapid amplification of two to eight copies of the reiterated terminal sequences does not arise from internal initiation during replication but probably from homologous recombination.

Adenoviruses, Human↗
PubMed1990

Hydrocephalus in developing cats: physiological properties of visual cortex cells.

We have studied electrophysiologically by single cell recording in the visual cortex, whether modification of the visual system in developing and in adult cats by hydrocephalus has an effect on processing of visual information. One of our cats (H1) had developed a complete hydrocephalus and the others partial, as proved by either complete or partial dilation of the lateral ventricles, respectively and by the thinning of the cortex. Despite this, the horizontal lamination and the vertical organization of the cortex were fully preserved. Except for the optic radiation and the corpus callosum which was remarkably modified, the optic tract, chiasm, nerve and retina were morphologically and histologically normal. The visual behavior of the hydrocephalic cats was normal. This was also reflected, by and large, in the physiological properties of the visual cortex. However, in cat H1 there were many more visually unresponsive cortical cells in comparison to its matched controls (C1) and the normal cats. A reduced responsiveness was also found in cat H2 with partial hydrocephalus but not in the other partial hydrocephalic cats. Similarly, the ocular dominance distribution of the cells was affected in cat H1 in comparison to the control cats as indicated by the changes found in the relative proportions of contralaterally and ipsilaterally driven cells in the two hemispheres. No change was, however, found in the partially hydrocephalic cats. Most of the cells in the hydrocephalic cats were orientation specific, similarly to the result of their matched controls. Direction specific cells were much smaller in proportion in cat H1 but not in the other cats, in comparison with their matched controls. In keeping with this, a large increase was found in the receptive field area of cat H1, a smaller one in cat H2 and none in the other hydrocephalic cats in comparison to the matched controls. The eccentricity distribution of the receptive fields in the hydrocephalic cats was the same as expected under normal conditions. It was concluded that in the way hydrocephalus had modified the brain of several of our cats, a quantitative effect was induced in visual cortex cells leading to some degradation of function; this change, however, did not interfere with their basic visual properties.

Animals↗
PubMed1990

Riboflavin intakes and status of morbidly obese females during the first postoperative year following gastroplasty.

Eighteen women participated in a prospective study to assess the need for supplemental riboflavin after gastroplasty. Three groups of five patients received either a placebo or 0.6 or 1.2 mg riboflavin daily for up to 12 months, except during months 4 and 7 when all participants were given a "one-a-day" supplement containing 1.7 mg riboflavin. Dietary intakes of riboflavin decreased from 1.43 +/- 0.17 mg before the operation to 0.70 +/- 0.07 mg at 3 months, and then increased to 1.02 +/- 0.17 mg by 6 months. Even at 12 months, only 33% of the subjects had dietary intakes greater than or equal to 1.2 mg. All those with total intakes less than or equal to 1.7 mg at 3 months had impaired riboflavin status, as indicated by an erythrocyte gluthatione reductase activity coefficient greater than 1.40 and an erythrocyte riboflavin concentration less than 372 nmol/L. In contrast, 62% of the same subjects had urinary riboflavin excretion in the acceptable range. Supplemental intake of 1.7 mg riboflavin appeared to prevent tissue depletion in all subjects.

Adult↗
PubMed1990

Preventive dentistry in Texas, USA.

This paper presents the results of a 1985 survey of 1000 Texas dentists regarding three major types of preventive measures--educational services, preventive procedures, and diagnostic services. The results show that among several given educational services, respondents tended most to instruct on correct brushing or flossing and tended least to counsel on diet. Among preventive procedures, most dentists removed plaque or calculus. A very small portion applied occlusal sealants on patients under the age of 15. As for diagnostic services, most performed oral cancer screening exams. Most performed dental X-rays, but many did not use leaded protection on their patients while taking X-rays. A large number did not check their patients' blood pressure. Income, attendance of continuing education programs, and number of dental hygienists were strong, positive predictors of provision of all three types of preventive measures. Dentists who practiced in more populous areas, or had practiced for fewer years, more likely provided patients with educational services and preventive procedures. Dentists delivered more preventive procedures if they attended more professional dental meetings. Dentists who worked more hours were more likely to provide educational services and preventive procedures. Patient load correlated negatively with dentists' delivery of preventive procedures.

Adult↗
PubMed1990

Acantholytic variant of seborrheic keratosis.

From among 524 histologic specimens of seborrheic keratosis (SK), 29 showed acantholysis, not related to pemphigus, Darier's disease, actinic keratosis or acantholytic squamous cell carcinoma. Acantholysis was found in 24 (23.3%) of the irritated type of SK, almost exclusively in the squamous cell nests showing dyskeratosis and spongiosis between and around squamous eddies or horn cysts. Clinically, 65.5% of the lesions were located on the face and scalp, 20.7% on the trunk and 13.8% on the limbs. It was speculated that dyskeratotic, degenerative changes of the keratinocytes together with spongiosis were responsible for the acantholysis.

Acantholysis↗
PubMed1990

Simple medium that preserves low concentrations of Escherichia coli for use in the water bacteriology proficiency test.

A medium containing (per liter) 6.8 g of sodium acetate trihydrate, 3.4 g of potassium dihydrogen phosphate, and 0.1 g of magnesium sulfate heptahydrate (medium pH, 5.85 plus/minus 0.05) was developed for use in a water bacteriology proficiency test. The medium maintained 80 to 100 % viability of inoculated Escherichia coli at temperatures up to 31 degrees C for at least 12 days, while the concentrations of bacteria in the medium were as low as 20 bacteria per 100 ml. The medium remained stable after a year of storage. It has been used successfully to preserve bacteria in nine statewide bacteriology proficiency tests for potable and nonpotable water and has also been used in a nationwide pilot test. This report presents the results of these tests.

Culture Media↗
PubMed1990

Role of primary and secondary maternal viremia in transplacental guinea pig cytomegalovirus transfer.

The modulation of the outcome of intrauterine guinea pig cytomegalovirus (GPCMV) infection by maternal viremia was investigated in the guinea pig model. Virus assay and in situ hybridization were used to study GPCMV infection of maternal blood, placentas, and fetuses following inoculation of pregnant guinea pigs by the subcutaneous, intracardiac, or intranasal route. Animals were inoculated in early gestation and were evaluated every 7 to 10 days throughout pregnancy. Although placental and fetal infections occurred in all groups examined, transfer of GPCMV to placentas and fetuses was most efficient in mothers inoculated subcutaneously. Primary viremia was followed by virus clearance from blood and by an episode of secondary viremia in the three groups of mothers examined. Placental and fetal infections in animals infected subcutaneously or intracardially were first detected at the time of primary viremia, persisted throughout gestation, and increased during secondary viremia. In contrast, placental and fetal infections in animals inoculated intranasally were demonstrated primarily during secondary viremia. Fetal infection was detected in all mothers with detectable primary and secondary viremia but in only 33% of mothers that experienced only primary viremia. These results suggest that secondary maternal viremia is associated with increased placental and fetal GPCMV infections.

Abortion, Spontaneous↗