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Biomedical subjects

M Yang

Publications and source records attributed to M Yang.

At least 451 records · Page 25Linked to original sources
PubMed1993

[The distribution of normal oral flora in 49 healthy children and juvenile].

The frequencies and proportions of predominant cultiv ableoral bacteria associated with 49 healthy children and juvenile (6-25 yr old) were studied. A total of 72 bacterial species belonging to 28 genus were detected in 195 samples of saliva, fissure plaque, supragingival plaque, and subgingival plaque. The predominant bacteria were Oral streptococci, Neisseria, Actinomyces, Capnocytophaga, Bacteroides and Fusobacterium in the normal oral cavity of healthy children and juvenile. There were differences in the distribution of the predominant flora, e.g. Fusobacterium and Bacteroides had higher incidence and proportion in the subgingival plaque than in the fissure plaque.

Adolescent↗
PubMed1993

Human very low density lipoprotein structure: interaction of the C apolipoproteins with apolipoprotein B-100.

Very low density lipoproteins (VLDL) are a heterogenous population of particles differing in size and composition. Heparin-Sepharose chromatography yields three VLDL subfractions. Two subfractions, VLDLNR-1 and VLDLNR-2, which are not retained by heparin, contain little or no detectable apolipoprotein (apo)E. According to negative stain electron microscopy, VLDLNR-1 is slightly larger than VLDLNR-2. The third fraction, VLDLR, is composed of smaller particles that are retained by the heparin-Sepharose and contain apoE. The C apolipoproteins of the respective VLDL subfractions transfer to 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC) single bilayer vesicles giving three subfractions designated VLDLNR-1-C, VLDLNR-2-C, and VLDLR-C. The protein, phospholipid, and cholesterol (free + esterified) contents decrease in the order VLDLR > VLDLNR-2 > VLDLNR-1. Triglyceride content decreases in the opposite order. POPC treatment of each VLDL subfraction increases the phospholipid and decreases the protein, triglyceride, and cholesteryl ester contents, while free cholesterol remains unchanged. According to immunological analysis of each subfraction with well-characterized monoclonal antibodies, the accessibility of some epitopes of apoB-100 on VLDL is changed by POPC treatment. Electron-microscopic analysis of POPC-treated VLDL subfraction reveals vacancies on the surfaces of each particle. VLDLNR-1, VLDLNR-2, and VLDLR are resistant to thrombin cleavage, whereas the lipoproteins lacking C apolipoproteins are not. Thrombin cleavage (8 h) of apoB-100 of VLDLNR-2-C and VLDLR-C gives two fragments, T1 and T2, that are converted to smaller fragments only after prolonged treatment. In contrast, apoB-100 of VLDLNR-1-C is converted into small fragments after 8 h thrombin treatment. These results suggest that removal of apoCs affects the accessibility and conformation of apoB-100 in the individual VLDL subfractions in the region near residue 3249, which is the primary thrombin cleavage site and the epitope of monoclonal antibody 4C11.

Apolipoprotein B-100↗
PubMed1993

Effects of intermediate metabolites of 37 xenobiotics on the catalytic activities of reconstituted cytochrome P-450IIB1 and P-450IA1 enzyme systems.

Direct effects of intermediate metabolites of 37 different xenobiotics on the catalytic activities of both reconstituted cytochrome P-450IIB1 and P-450IA1 enzyme systems were studied by determination of NADPH oxidation at various intervals after initiation of the reaction. The results showed that cytochrome P-450IIB1 isozyme was much more likely than cytochrome P-450IA1 isozyme to be attacked by the reactive intermediates formed by some xenobiotics with smaller molecular weight and lose its catalytic activities. These xenobiotics were carbon tetrachloride, chloroform, carbon disulfide, benzene, parathion, methylparathion, methyldursban and dimethylnitrosamine. In contrast, however, steadily increasing metabolic activities were observed towards benzo(a)pyrene, 3-methylcholanthrene and polychlorinated biphenyls in reconstituted cytochrome P-450IA1 enzyme system as the reaction time prolonged within 4 min. The method discussed in this paper could be used as a simple and convenient way to observe directly the autocatalytic destruction of P-450 enzymes by some chemical agents.

Animals↗
PubMed1992

A mutation generating a stop codon in the alpha-L-fucosidase gene of a fucosidosis patient.

Fucosidosis is an autosomal recessive, lysosomal storage disease featured by deficient activity of alpha-L-fucosidase. Lymphoid cell lines from a fucosidosis patient (JT) and a healthy individual (control) contained alpha-L-fucosidase mRNA of the same size, 2.3 Kb, as determined by Northern blot analysis. cDNA was prepared from alpha-L-fucosidase mRNA of JT and control cells and each cDNA was amplified by the polymerase chain reaction. Direct DNA sequencing of the amplified products revealed a single mutation in JT, a G1141-->T transition. This changed the codon (GAA) for Glu-375 to a stop codon (UAA). Amplification and sequencing of the area containing the G1141-->T transition in genomic DNA of JT and control cells demonstrated that the mutation was homozygous in JT. Analysis of cDNA and genomic DNA derived from lymphoid cells of mother JT revealed her to be heterozygous (G and T) at position 1141. The G1141-->T mutation is probably responsible for disease in JT.

B-Lymphocytes↗
PubMed1992

Priority among air pollution factors for preventing chronic obstructive pulmonary disease in Shanghai.

The problems that city environmental protection planners face are how important the air pollution exposures are in relation to chronic obstructive pulmonary disease (COPD) in local residents and which factor should be controlled most urgently. The purpose of our study is to determine the control priority among ambient sulphur dioxide (SO2) inhalable particulates (IP) and indoor use of coal to prevent COPD in residents of the city. Ambient air pollution is mainly from SO2 and IP(< 10 nm). Indoor air pollution is mainly from the use of coal for heating and/or cooking. Distribution of ambient SO2, and IP concentrations were described using a quartic trend surface simulation. When stratified by two extreme levels of ambient SO2 and IP and types of fuel used indoors, eight local area populations in four communities with different combinations of exposure levels were selected. In each community a local area population mostly using coal and one mostly burning gas was chosen. Chronic obstructive pulmonary diseases (COPD, ICD 490-493) including chronic bronchitis, asthma and emphysema, are a major cause of death in residents of Shanghai. The relationship between the three air pollution factors and their health effects were analyzed at the level of mortality (1978-1987, 232,459 person-years), prevalence of symptoms (12,037 persons) of COPD, lung function and non-specific immunologic function (514 women). The results show that indoor use of coal has stronger associations with health than estimated exposure to ambient SO2 or IP.

Adult↗
PubMed1992

Localization and retention in vitro of fluorescently labeled aortic baroreceptor terminals on neurons from the nucleus tractus solitarius.

The anterograde fluorescent tracer DiA was used to visualize baroreceptor fibers and synaptic terminals both in living and fixed tissue. Baroreceptor fibers labeled with DiA terminated as a dense synaptic field in the medial nucleus tractus solitarius (NTS), making synaptic contact on the soma, as well as processes of neurons that they innervated. A similar distribution and morphology was observed in baroreceptor fibers and terminals labeled with horseradish peroxidase. DiA also identified baroreceptor terminals and the neurons receiving these synaptic contacts in vitro. NTS neurons were dissociated from their surrounding tissue and identified by attached baroreceptor terminals that retained the fluorescent dye. These results will enable us to study the electrophysiological properties of dispersed neurons that receive identified baroreceptor synaptic terminals.

Animals↗
PubMed1992

Glucagon administration to the rat via eye drops.

Systemic absorption of glucagon from eye drops containing an emulsant caused an elevation in blood D-glucose concentrations in anesthetized rats. Glucagon (0.03 mg) delivered to the eye in buffered saline had no significant hyperglycemic action. However, delivery of glucagon in eye drops containing 0.25% saponin caused a rapid, dose-dependent increase in blood D-glucose values. Maximal absorption was observed 20 minutes after eye drop administration and values returned to baseline after 60 minutes. Immunoreactive glucagon levels measured 20 minutes after administration of eye drops containing saponin plus glucagon were increased by 2.4-fold compared to basal values. Glucagon administration via eye drops was ineffective when 0.5% Brij78 or BL-9 was substituted for saponin. These results demonstrate that in the rat, systemic absorption of glucagon delivered in eye drops is possible, but the choice of an emulsant may be critical.

Absorption↗
PubMed1992

The accuracy of catheter-tip pressure transducers for the measurement of intrauterine pressure in labour.

OBJECTIVE: To assess the reliability of intrauterine pressure measurements in labour with transducer tipped catheters. DESIGN: Prospective clinical study. SETTING: Delivery ward, National University Hospital, Singapore. SUBJECTS: 20 women admitted in early labour were randomly allocated to two groups. INTERVENTIONS: Women in the first group had two catheters that had been tied together introduced transcervically into the same amniotic fluid pocket. The second group had two catheters introduced in different directions so that each catheter tip was in a different pocket of amniotic fluid. MAIN OUTCOME MEASURE: The contraction to contraction pressure difference recorded by the two catheters in the same uterus. In addition, the cumulative uterine active pressure generated by one catheter was compared with that of the other. RESULTS: There were differences in peak pressure of up to 4-5.3 kPa (30-40 mmHg) during some contractions. The difference in pressure recordings between the two catheters could not be explained by effects of loculation of amniotic fluid. However, the pressures recorded were not systematically higher in one catheter than in the other. Cumulative uterine activity was very similar when assessed by each catheter in the same uterus. CONCLUSION: Intrauterine pressure measurements using transducer tipped catheters provide reliable information on the cumulative pressure wherever the catheter tip was sited in the uterus, but there are variations in pressures recorded during individual contractions.

Catheterization↗
PubMed1992

Identification of the promoter region of the Escherichia coli major cold shock gene, cspA.

The major cold shock protein of Escherichia coli, CS7.4, is produced at a level of 13% of total protein synthesis upon a temperature shift from 37 to 10 degrees C. The transcription of its gene (cspA) was found to be tightly regulated and induced only at low temperature. In addition, the cspA mRNA was extremely unstable at 37 degrees C, so that CS7.4 production was hardly detected when the culture temperature was shifted from 15 degrees C to 37 degrees C. The transcription initiation site (+1) was identified. In vivo footprinting demonstrated that the region from bases -35 to -73 was protected from chemical modification, and gel mobility shift analysis showed that a cold-shocked cell extract contained a factor(s) specifically bound to the fragment containing the sequence between bases -63 and -92. This factor was synthesized de novo only at low temperature, and its synthesis was inhibited by chloramphenicol. Possible functions of this factor are discussed.

Amino Acid Sequence↗
PubMed1992

Identification of a genetically distinct subspecies of Mycobacterium kansasii.

To assess the usefulness of a specific DNA probe for Mycobacterium kansasii, 105 isolates from Australia, Belgium, Japan, South Africa, and Switzerland were collected and analyzed. Twenty of these isolates were probe negative, of which 18 were from Belgium and Switzerland. Analysis of all isolates by Southern blot hybridization indicated a lack of variability among probe-positive isolates, while probe-negative isolates were clearly distinct and showed greater diversity. Sequence analysis of the 250 nucleotides at the 5' end of the 16S rRNA gene revealed that 19 of the 20 probe-negative isolates had a sequence different from that of M. kansasii. A total of five nucleotide differences were present in a cluster consisting of two nucleotide deletions and three nucleotide substitutions. These results suggest the existence of a genetic subspecies of M. kansasii.

Base Sequence↗
PubMed1992

Gadolinium and mechanotransduction of rat aortic baroreceptors.

The cellular mechanisms enabling baroreceptors to transduce wall distortion into axonal discharge are unknown but might involve stretch-activated ion channels. Gadolinium (Gd3+, 10 microM) blocks stretch-activated channels in several preparations. Here we tested Gd3+ effects on discharge responses of 15 single-fiber baroreceptors in vitro. We simultaneously measured discharge, pressure, and aortic diameter at Gd3+ concentrations from 0.001 to 400 microM. High levels of Gd3+ added to a bicarbonate-buffered perfusate (Krebs) slightly shifted the pressure-discharge relation (less than 4 mmHg, n = 3, P = 0.01) without affecting slope or discharge frequency at threshold. Gd3+ in Krebs variably altered the pressure-diameter relation. Because 500 microM Gd3+ produced visible precipitate in Krebs, we tested Gd3+ in a simpler perfusate using N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES). Gd3+ in HEPES (n = 10) induced minor, but statistically significant, average increases in threshold (less than +5-7%) and no changes in gain. However, prolonged HEPES exposure alone (n = 2) produced similar shifts. Electron microscopy verified that Gd3+ diffused from the lumen to reach extracellular locations near baroreceptor endings. We conclude that 1) HEPES perfusate alone reversibly depresses baroreceptor discharge and 2) Gd3+ has no direct effects on baroreceptors. Thus it appears that aortic baroreceptor mechanotransduction must utilize a different class of stretch-activated ion channels.

Animals↗
PubMed1992

Smooth muscle tone and rapid resetting of rat aortic baroreceptors.

Changes in conditioning mean arterial pressure (cMAP) selectively alter the set point of arterial baroreceptors and baroreflexes without affecting gain. Changes in smooth muscle tone at constant cMAPs shift the pressure-discharge curves of aortic baroreceptors in a similar manner. Using an in vitro preparation of the rat aortic arch, we tested whether near maximal changes in smooth muscle tone affect rapid resetting in single regularly discharging aortic baroreceptors. Discharge, pressure, and aortic diameter were simultaneously measured. By using vasoactive drugs (phenylephrine, angiotensin II, Bay K 8644, and nitroprusside), rapid resetting to cMAP changes was tested during different smooth muscle tone conditions (control, constricted, and dilated). Baroreceptor discharge-response curves were periodically assessed with slow ramps of increasing pressure at each of three different cMAP levels (10-15 minutes each). Rapid resetting relations were constructed for pressure threshold (Pth) and diameter threshold (Dth) plotted against cMAP and conditioning diameter (cD), respectively. Vasoconstriction decreased Pth in all baroreceptors (n = 13, p less than 0.05). Baroreceptor resetting ability as indicated by the slopes of the resetting relations (pressure- or diameter-resetting ratios, delta Pth/delta cMAP or delta Dth/delta cD, respectively) was unaffected by large increases in smooth muscle tone (p greater than 0.12). Vasoconstriction, however, offset the pressure-resetting relation, shifting the linear relation in a parallel manner to higher Pth values. In contrast, Dth values during vasoconstriction were not offset but instead fell along a single diameter-resetting relation coincident with the control relation for each baroreceptor. This last result suggests that acute alteration of vessel mechanics by vasoconstriction does not alter the basic rapid resetting process.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

[Cytological observation on culture of embryo in vitro of Tripterygium hypoglaucum (level.) Hutch].

This paper for the first time reports the embryo culture in vitro of Tripterygium hypoglaucum. Callus, adventitious roots and adventitious protuberances were induced from the cultured embryos in vitro. Multi-buds at the excised embryo tip were also observed at the same time. Cytohistological examination showed (1) callus was histologically easy to be induced to form adventitious roots; (2) callus on the cotyledons was originated from the epidemical and subepidemical cells of the cotyledons, and the adventitious roots were originated from the disperse meristematic tissue or vascular tissue in the callus obtained from cultured excised embryos.

Culture Techniques↗
PubMed1992

Comparative study of 99mTc-HM-PAO SPECT brain imaging, EEG and CT scanning in epileptic patients during the interictal period.

Forty patients with epilepsy in the interictal period were studied with 99mTc (HM-PAO) SPECT brain imaging, EEG and CT scanning. Four cases of generalized epilepsy had normal findings on EEG, SPECT imaging and CT scanning. Two cases of childhood benign partial seizures had abnormal EEG, but the SPECT brain imagings were normal. Regional hypoperfusions of various extents were found in 20 of the 34 patients with complex partial seizures. Among the 34 patients, 17 had abnormal EEG and 8 had abnormal CT scans. A good topographic concordance between regional HM-PAO hypofixation and EEG foci was found (39.1%). Localization of the lesion by SPECT imaging and CT scan was coincident in 5 cases (27.8%). The correlation between these three examination methods is discussed.

Adolescent↗
PubMed1992

A study on genotoxicity of cooking fumes from rapeseed oil.

The present article reports the genotoxic potential of rapeseed oil cooking fume investigated by a battery of short-term tests (Ames test, SCE/V79 in vitro and mice micronucleus in vivo test). The results showed that the cooking fume contained mutagenic activity. In the presence of S9 mix, an increase in the number of the Salmonella TA98 was observed at doses ranging from 1.0 to 5.0 mg/plate, and the SCE frequencies of V79 cell were markedly raised at doses ranging from 0.05 to 0.5 mg.ml-1. The positive result was also obtained in mice micronucleus assay, the mice had inhaled the cooking fume a week earlier. The frequency of mice bone marrow MN-PCE was increased and it showed a remarkable time-dose-response relationship during the 4 weeks exposure. The results suggested that this cooking fume exposure may be a risk factor of lung cancer in Chinese women.

Animals↗
PubMed1992

Potential use of luminol-dependent chemiluminescence for estimation of free radicals produced in hepatic microsomes and reconstituted cytochrome P-450 systems.

The evaluation of luminol-dependent chemiluminescence (CL) for determination of free radicals generated during the oxidative reactions of microsomal enzymes in microsomes and reconstituted systems has been studied. The results indicated that the CL not only depended on NADPH induction but also on intact cytochrome P-450 enzymes. The light emission signal was strongly scavenged by SOD with inhibition rate of 93%. A concentration of 24 mumol.L-1 cadmium acetate and 2.5 mumol.L-1 mercuric chloride also inhibited the signal significantly as compared with the control. The study of CL in detecting free radicals formed by biotransformation of 44 xenobiotics suggested that some of the compounds known as free radicals producing agents by bioactivation increased the light emission in cytochrome P-450 enzyme system, such as carbon tetrachloride, chloroform, tetrachloroethylene etc., the others forming toxic metabolites by biotransformation induced the CL in some cases, such as carbon disulfide, benzene, methyldursban, methylparathion etc. or decreased the light emission, such as parathion, aniline and polychlorinated byphenyls etc., and still others whose toxic effects have no relationship with their biotransformation had no influence or an inhibitory effect on the CL, such as aminopyrine, TOCP, and acrylamide. CL in the cytochrome P-450 enzyme system remained unchanged during the biotransformation of carcinogens such as diethylnitrosamine, dipropylnitrosamine and benzo(a)pyrene as compared with the control. However, 3-methylcholanthrene and dimethylnitrosamine had an enhancing effect on the CL, while 2-acetylaminofluorene and 2-aminoanthracene showed an inhibition to the signals.

Acetates↗
PubMed1991

An SfiI restriction map of the Bacillus subtilis 168 genome.

A restriction map of 24 SfiI (GGCCN4/NGGCC) restriction fragments has been constructed for the Bacillus subtilis genome. The combined sizes of the fragments indicate a genome size of approx. 4.2 Mb. The SfiI fragments range in size from 7-730 kb. Genetic markers have been located on 19 of the SfiI fragments, and 69 genetic markers have been assigned to the SfiI restriction map.

Bacillus subtilis↗