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Biomedical subjects

X Meng

Publications and source records attributed to X Meng.

At least 199 records · Page 11Linked to original sources
PubMed1996

Inhibition of restriction endonuclease activity by DNA binding fluorochromes.

Activity of type II restriction endonuclease is affected by many common factors including buffer composition and sequences flanking the recognition site (Brabec et al., Eur.J. Biochem. 216, 183, 1993). The successful development of Optical Mapping (Schwartz et al., Science, 262, 110, 1993; Meng et al., Nature Genet. 9, 432, 1995; Wang and Schwartz, PNAS, 1995 Cai et al., PNAS, 92, 5164, 1995) relied on optimization of light microscope-based imaging of fluorescently labeled DNA molecules during restriction endonuclease digestion. Little was known about the effects of commonly used DNA-fluorochromes on restriction endonuclease activity. Thus, we developed an enzyme activity assay using lambda bacteriophage DNA or adenovirus-2 DNA to evaluate the effects of five DNA binding fluorochromes (4'-6-daimidine-2-phenylindole (DAPI), ethidium bromide (EtdBr), ethidium bromide homodimer (EthD-1), bis-benzimide (H33258) and benzothiazolium-4-quinolinium dimer (TOTO-1)) on the enzymatic activities of eleven type II restriction endonucleases (Asc I, Csp I, Dra I, EcoR I, Hha I, Hind III, Not I, Rsr II, Sfi I, SgrA I and Sma I). We found that the minor groove binding fluorochrome, DAPI, did not measurably inhibit activity of this group, with the exception of Dra I. Similarly, another minor groove binding fluorochrome H33258 inhibited Dra I and Not I (slightly). The three intercalating fluorochromes EtdBr, EthD-1 and TOTO-1, however, variably inhibited the other enzymes. Since Beta-mercaptoethanol (Beta-ME) is used to discourage photodamage of stained DNA molecules, we also assessed its effect on restriction endonuclease activity. Interestingly, Dra I, Hind III, Sfi I and Sma I retained full activities at high concentration of Beta-ME (5%), but Asc I, Csp I, Not I, Rsr II and SgrA I showed varying sensitivities to the Beta-ME. Isoschizomers Csp I and Rsr II behaved differently to both fluorochromes and Beta-ME. The results presented here should provide a basis for further development of new Optical Mapping-based techniques requiring fluorescence labeling of other actively imaged enzymatic reactions.

Binding Sites↗
PubMed1996

A novel keratin K5 gene mutation in Dowling-Meara epidermolysis bullosa simplex.

We examined keratin K14 and K5 genes mutation in a Japanese Dowling-Meara epidermolysis bullosa simplex patient with severe generalized blistering and erosions at birth. The patient had a C to T transition at the first position of codon 174 in the keratin K5 gene, which resulted in a Leu->Phe substitution at the highly conserved 1A domain in keratin K5. Thus, our results revealed a novel mutation in the helix initiation peptide of keratin K5.

Amino Acid Sequence↗
PubMed1996

Normal range estimation for repeated immunologic measures.

A method for estimating a normal range from a set of immunologic measurements on control subjects when there may be more than one observation per subject is described. The method is nonparametric, makes efficient use of all observations, and is very simple to apply. It is illustrated on a set of 152 CD38 measurements from 58 healthy men.

ADP-ribosyl Cyclase↗
PubMed1996

Endotoxin induces cardiac HSP70 and resistance to endotoxemic myocardial depression in rats.

Endotoxin (bacterial lipopolysaccharide, LPS) depresses myocardial function. However, heat shock and sublethal LPS can confer cardiac resistance to postischemic dysfunction. We hypothesized that a prior exposure to LPS stress induces the expression of cardiac heat shock protein 70 (HSP70) and resistance to endotoxemic myocardial depression. Moreover, induction of HSP70 by hyperthermia should also increase cardiac resistance to LPS toxicity. LPS (500 micrograms/kg ip) depressed rat left ventricular developed pressure (LVDP) maximally at 6 h (58.4 +/- 3.72 vs. 101 +/- 1.46 mmHg in saline control, P < 0.01), and myocardial contractile function recovered at 24 h. In rats pretreated with LPS 24 h earlier, subsequent LPS exposure did not depress LVDP (97.0 +/- 3.53 mmHg at 6 h, P < 0.01 vs. single exposure). Both LPS and hyperthermia (42 degrees C, 15 min) induced HSP72 mainly in the cardiac interstitial cells, including macrophages at 24 h after treatment. When hyperthermia-pretreated animals were similarly challenged with LPS, myocardial depression at 6 h was partially abrogated (LVDP 80.1 +/- 5.67 vs. 62.2 +/- 4.91 mmHg in sham+LPS group, P < 0.01). We conclude that LPS induces HSP70 in rat heart and that an exposure to LPS or heat stress confers cardiac resistance to endotoxemic myocardial depression.

Animals↗
PubMed1996

Neutrophil depletion attenuates endotoxin-induced dysfunction of cGMP-mediated pulmonary vasorelaxation.

The effect of neutrophil depletion on endotoxin-induced dysfunction of guanosine 3',5'-cyclic monophosphate (cGMP)-mediated pulmonary vasorelaxation was studied in rats. Two mechanisms of neutrophil depletion were used: vinblastine (0.75 mg/kg iv) and rabbit anti-rat neutrophil antiserum (0.15 ml iv). Concentration-response curves were generated (10(-9) to 10(-6) M) for acetylcholine (ACh), A-23187, and sodium nitroprusside (SNP) in isolated pulmonary arterial rings preconstricted with phenylephrine 6 h after endotoxin (20 mg/kg ip). Absolute neutrophil count was significantly lowered from 1,050 +/- 206 (neutrophils/ml; mean +/- SE) in controls to 100 +/- 41 by vinblastine and to 50 +/- 29 by antiserum. Endotoxin produced histological evidence of pulmonary vascular endothelial damage and significantly increased lung neutrophil accumulation (myeloperoxidase assay, 5.1 +/- 0 vs. 1.2 +/- 0.1 in controls; 0.1 +/- 0.1 and 0.8 +/- 0.0 U/g lung wt after endotoxin in neutrophil-depleted rats by vinblastine and antiserum, respectively). Endotoxin produced significant impairment of endothelium-dependent cGMP-mediated pulmonary vasorelaxation by receptor-dependent (ACh) and -independent (A-23187) pathways as well as endothelium-independent relaxation (SNP). Neutrophil depletion significantly attenuated the endotoxin-induced impairment of all three of these mechanisms. We conclude that neutrophils contribute to endotoxin-induced impairment of GMP-mediated pulmonary vasorelaxation.

Acetylcholine↗
PubMed1996

Mutational analysis of Hsp90 alpha dimerization and subcellular localization: dimer disruption does not impede "in vivo' interaction with estrogen receptor.

The molecular chaperone Hsp90 has been found ubiquitously as a predominantly cytoplasmic dimer. By interacting with cytoplasmic or nuclear proteins such as pp60v-src or steroid receptors, Hsp90 helps its targets to become competent for full biological activity. Mutational deletion analysis of some properties of chicken Hsp90 alpha was undertaken after transient transfection of the constructs in COS7 cells. First, Hsp90 mutants were analyzed for their ability to behave as cytosolic dimers. We confirmed that the C-terminal Hsp90 region (amino acids 446-728) was sufficient for dimerization, and found that deletion of three small subregions in the 200 C-terminal residues precluded Hsp90 dimer formation. Moreover, we demonstrated that the N-terminal region of the protein (1-442) was not involved in dimerization. Second, the subcellular localization of the wild-type (WT) protein and mutants was analyzed by specific immunodetection and confocal microscopy. Most of the mutants were cytoplasmic like Hsp90WT, a nuclear localization being barely detectable in the WT protein or in mutants with a C-terminal truncation equal to or shorter than 286 residues. Surprisingly a mutant encoding the N-terminal region (1-285) was nuclear localized. In addition, the in vivo interaction between the cytoplasmic Hsp90 and the nuclear ER was documented after coexpression of both proteins in the same cells: some Hsp90 was shifted into the nucleus via its interaction with ER. From an analysis of dimeric or monomeric cytoplasmic Hsp90 mutants, we found that disruption of Hsp90 dimer did not systematically impede its interaction with ER. Finally, Hsp90WT and cytoplasmic mutants were tested for their ability to rescue from lethality a yeast strain deleted of both Hsp90 genes. Interestingly, the delta 661-677 mutant that showed an impaired dimerization but interacted with ER was able to confer viability, while the mutant deleted of the 30 C-terminal residues (NC6) was monomeric, did not confer viability and did not interact with ER. We therefore suggest that Hsp90 properties analyzed here are not necessarily interdependent.

Animals↗
PubMed1996

Omniplane transesophageal echocardiography imaging planes exploration.

One hundred and twenty-four patients with heart disease were examined by omniplane TEE in order to systematically research every views of omniplane TEE, and further explore anatomy and image feature of each view. The result showed that omniplane TEE transducer can be rotated in probe from 0 degree to 180 degrees, obtain many views at various angles behind the heart and fully demonstrate the structure and pathology of the heart and great vessels. It was useful for clinical diagnosis because of getting more information about the heart and great vessels. As omniplane TEE probe was little rotated in esophagus, it lessened esophagus stimulation. Meanwhile, it was suitable for three-dimensional reconstruction of left ventriculum.

Adolescent↗
PubMed1996

[Immunohistochemical double labelling studies on liver tissues superinfected with hepatitis C virus and hepatitis B virus].

OBJECTIVE: To explore the relatiship between hepatitis C virus (HCV) and hepatitis B virus (HBV) replication in liver tissue of patients superinfected with HCV and HBV. METHODS: The expresion and distribution of HCVAg and HBVAg in paraffin-embeded liver tissue from 25 autopsy cases were studied with immunohistochemical double labelling techniques using monoclonal anti-HCV NS3 and anti-HCV NS5 as well as polyclonal anti-HBs and anti-HBc. RESULTS: HBsAg and HCV NS3 or NS5 antigen were detected at the same section in 11 and 12 cases, and HBcAg and HCV NS3 or NS5 antigen in each 10 cases, respectively. Nearly all of the specimens with single labelling stained positive tissue for HC-VAg or HBVAg were also those positive with double labelling studies for HCVAg and HBVAg. The distribution of HCV and HBV infected hepatocytes was characterized as diffuse and single or cluster scattered in liver lobular. There were no differences in expression related to replication such as membranous, cytoplasmic type of HBsAg or cytoplasmic type of HBcAg and the cases positive for HCV NS3Ag or HCV NS5Ag between the group of HCV superinfected with HBV and the group infected with single HCV or HBV (chi 2 = 0.154 and 0.198, P > 0.05). CONCLUSION: The results suggested that there was no interference or suppression each other in liver tissues superinfected with HCV and HBV.

Hepacivirus↗
PubMed1996

Clinical application of Omniplane transesophageal echocardiography.

One hundred and twenty-four patients with heart disease (75 cases of rheumatic heart disease, 26 cases of congenital heart disease, 13 cases of aortic disease and 10 cases of other disease) were examined by Omniplane transesophageal echocardiography (TEE). The result showed that Omniplane TEE transducer can be rotated from 0 degree to 180 degrees in probe and had the advantages of broader scope, obtaining more information, less stimulation to esophagus and easy to manipulate. It suggests that Omniplane TEE is a efficient technique in clinical diagnosis and can be extensively used in the future.

Adolescent↗
PubMed1996

[Normal spinal changes of bone mineral density in 445 individuals: assessment by quantitative computed tomography].

Spinal BMD was measured by QCT in 445 normal individuals aged 10-80 including 190 males and 255 females, which were divided into age-groups by every ten years. Statistic results showed that peak bone mass reached at 10-19 age-group for both male and female and that BMD assessed by QCT in females was not lower than that in males and BMD declined with increasing age. In females, BMD results in this study were different from those in USA. An acceleration bone loss was predominantly shown in the period after 40-49 age group. Among many factors related to bone loss, we consider that estrogen change may play a most important role for the remarkable bone loss in our country.

Absorptiometry, Photon↗
PubMed1996

[The angiographic classification and endovascular therapy of the vein of Galen aneurysmal malformation].

We treated 11 cases of the vein of Galen aneurysmal malformation, one of which was diagnosed by MRI only, and 10 underwent CAG diagnostic procedure. Among the 10 CAG diagnosed cases, 5 were classified as the vein of Galen aneurysmal malformation (VGAM) with the AV shunt directing to the vein of Galen. The other 5 were classified as the vein of Galen aneurysmal dilitation (VGAD) secondary to parenchymal AVM or dural AVF. 8 cases underwent endovascular treatment. For VGAM, the shunts in the wall of the vein were embolized. For VGAD, the primary AVM or AVF were embolized. The pathphysiology, angiographic characteristics, classification and the principle of endovascular therapy of the vein of Galen aneurysmal malformation were discussed.

Adolescent↗
PubMed1996

[Dynamic effects of sulphuric gentamicin on vestibular function in guinea pigs].

Sinusoidal rotation and rotational stimulation tests were used to examine vestibular function in guinea pigs. The results showed that there was no statistically significant difference in the mean number of nystagmus of semi-cycle sinusoidal rotation test and the duration of nystagmus of rotational stimulation test for both the control and test groups before treatment in albinos and pigmented guinea pigs. Meantime, daily subcutaneous injection of gentamicin 125 mg/kg body weight for 12 days in albinos and pigmented guinea pigs showed no significant change in vestibular function until the 7th day of treatment. Significant impairment of vestibular function was noticed on the 10th treatment day. At 5 days after treatment vestibular impairment reached its maximum and minimal recovery was seen at 14 days after treatment. No Further improvement of vestibular function was noticed three months after treatment. The methods are feasible and reliable.

Animals↗
PubMed1995

Isolation of chicken hsp90 beta gene promoter.

In order to define the mechanisms responsible for the differential expression of chicken hsp90 alpha and beta genes, a portion of the chicken hsp90 beta genomic sequence, including 3081 bp upstream from the transcription initiation site and 2718 bp of structural gene sequence which covers 7 exons and 6 introns was investigated. The transcriptional initiation site was determined by primer extension, RNAase and S1 nuclease mapping, Northern blot and cloning of 5' end of cDNA. The first intron, as in other hsp90 genes, is located just before the ATG initiation codon. Three Sp1 sites are located near the TATA box. The apparent major divergence with the hsp90 alpha promoter is that, in the hsp90 beta promoter, the only CAAT box and HSE element are located at about 3 and 2 kb upstream the TATA box, respectively. These features may explain why chicken hsp90 beta mRNA is generally less abundant than alpha and is not inducible by heat shock or serum/growth factor stimulation.

Animals↗
PubMed1995

Potential gene therapy strategies in the treatment of cardiovascular disease.

Gene therapy is the introduction of new genetic material into somatic cells to synthesize missing or defective proteins. Efficient methods for the introduction of genetic material into cells are available, both in vitro and in vivo. These strategies involve chemical, physical, and viral-mediated mechanisms of gene transfer. Application of these gene transfer techniques has led to the development of potential gene-based treatment strategies that could combat vascular and myocardial disease. Gene therapy in the treatment of cardiovascular disease promises to alter atherosclerotic risk factors, prevent vascular thrombotic disease, retard progression of disease in the peripheral vasculature, provide drug delivery systems, and prevent myocardial infarction in patients with coronary artery disease. This exciting technology will eventually become the ultimate intervention in the treatment of cardiovascular disease.

Arteriosclerosis↗
PubMed1995

Intravenous ascorbate as a tumor cytotoxic chemotherapeutic agent.

Ascorbic acid and its salts (AA) are preferentially toxic to tumor cells in vitro and in vivo. Given in high enough doses to maintain plasma concentrations above levels that have been shown to be toxic to tumor cells in vitro, AA has the potential to selectively kill tumor cells in a manner similar to other tumor cytotoxic chemotherapeutic agents. Most studies of AA and cancer to date have not utilized high enough doses of AA to maintain tumor cytotoxic plasma concentrations of AA. Data are presented which demonstrate the ability to sustain plasma levels of AA in humans above levels which are toxic to tumor cells in vitro and suggests the feasibility of using AA as a cytotoxic chemotherapeutic agent.

Animals↗
PubMed1995

Mechanisms of immature myocardial tolerance to ischemia: phenotypic differences in antioxidants, stress proteins, and oxidases.

BACKGROUND: Previous work has suggested tolerance to ischemic injury in newborn myocardium. Although various mechanisms for this protection have been proposed, a link between oxidant-antioxidant factors, stress protein expression, and protection from cardiac ischemia/reperfusion (I/R) injury has not been made in newborn myocardium. We hypothesized total newborn myocardial resistance to I/R is related to decreased oxygen radical producing potential, increased free radical scavenging capacity and augmented stress protein expression. The purposes of the study were to examine in newborn and adult rat hearts (1) functional recovery from I/R, (2) catalase and xanthine oxidase (XO) activities, and (3) heat shock protein 72 (HSP 72) expression. METHODS: Isolated rat hearts (7 to 10 days versus 60 days) were perfused on a nonworking Langendorff apparatus at 60 mm Hg (Krebs-Henseleit buffer, pH 7.4, 37 degrees C) and subjected to 20 minutes of global ischemia and 40 minutes of reperfusion. Left ventricular developed pressure was recorded by using a left ventricular catheter. Catalase and XO were measured by means of standard assays, and HSP 72 was assessed with in situ immunohistochemistry. RESULTS: Newborn rat hearts had greater percentage functional recovery of left ventricular developed pressure after I/R (66.0% +/- 4.2% versus 44.3% +/- 3.5%; p < 0.05). The newborn myocardium also had increased catalase activity (1027.9 +/- 20.6 units/gm versus 707.3 +/- 38.7 units/gm; p < 0.05), whereas the activity of XO was decreased relative to the adult (0.23 +/- 0.01 mU/gm versus 7.6 +/- 1.4 mU/gm; p < 0.05). Furthermore, the expression of HSP 72 was greater in the newborn than the adult control. CONCLUSIONS: Relative to adult hearts, newborn rat hearts are more tolerant to a global ischemic insult followed by reperfusion. This improved functional recovery is associated with decreased oxidant production potential (XO), increased scavenging capacity (catalase), and augmented stress protein expression (HSP 72).

Aging↗