Biomedical subjects

Min Chen

Publications and source records attributed to Min Chen.

At least 163 records · Page 9Linked to original sources

PubMed2004

Brain-derived neurotrophic factor and trkB signaling in parasympathetic neurons: relevance to regulating alpha7-containing nicotinic receptors and synaptic function.

Parasympathetic neurons do not require neurotrophins for survival and are thought to lack high-affinity neurotrophin receptors (i.e., trks). We report here, however, that mRNAs encoding both brain-derived neurotrophic factor (BDNF) and its high-affinity receptor tropomyosin-related kinase B (trkB) are expressed in the parasympathetic chick ciliary ganglion (CG) and that BDNF-like protein is present in the ganglion and in the iris, an important peripheral target of ciliary neurons. Moreover, CG neurons express surface trkB and exogenous BDNF not only initiates trk-dependent signaling, but also alters nicotinic acetylcholine receptor (nAChR) expression and synaptic transmission. In particular, BDNF applied to CG neurons rapidly activates cAMP-dependent response element-binding protein (CREB), and over the long-term selectively upregulates expression of alpha7-subunit-containing, homomeric nAChRs (alpha7-nAChRs), increasing alpha7-subunit mRNA levels, alpha7-nAChR surface sites, and alpha7-nAChR-mediated whole-cell currents. At nicotinic synapses formed on CG neurons in culture, brief and long-term BDNF treatments also increase the frequency of spontaneous EPSCs, most of which are mediated by heteromeric nAChRs containing alpha3, alpha5, beta4, and beta2 subunits (alpha3*-nAChRs) with a minor contribution from alpha7-nAChRs. Our findings demonstrate unexpected roles for BDNF-induced, trk-dependent signaling in CG neurons, both in regulating expression of alpha7-nAChRs and in enhancing transmission at alpha3*-nAChR-mediated synapses. The presence of BDNF-like protein in CG and iris target coupled with that of functional trkB on CG neurons raise the possibility that signals generated by endogenous BDNF similarly influence alpha7-nAChRs and nicotinic synapses in vivo.

Animals↗

PubMed2004

Genetic background (C57BL/6J versus FVB/N) strongly influences the severity of diabetes and insulin resistance in ob/ob mice.

We studied the effects of genetic background on the phenotype of ob/ob mice, a model of severe obesity, insulin resistance, and diabetes caused by leptin deficiency. Despite a comparable degree of obesity and hyperinsulinemia, C57BL/6J ob/ob mice had much milder hyperglycemia and, surprisingly, normal circulating adiponectin levels despite still-prominent signs of insulin resistance. Hyperinsulinemic-euglycemic clamp revealed relatively less whole-body and muscle insulin resistance in C57BL/6J ob/ob mice, whereas liver insulin resistance tended to be more severe than in FVB/N ob/ob mice. C57BL/6J ob/ob mice had also more rapid clearance of circulating triglycerides and more severe hepatic steatosis. We suggest that strain-related distinction in lipid handling is the most important player in the differences in diabetic phenotype and insulin sensitivity, whereas the impact of circulating adiponectin levels on the overall phenotype of ob/ob mice is less important.

Adipose Tissue↗

PubMed2004

Poly(ADP-ribose) polymerase contributes to the development of myocardial infarction in diabetic rats and regulates the nuclear translocation of apoptosis-inducing factor.

Activation of the nuclear enzyme poly(ADP-ribose) polymerase (PARP)-1 by oxidant-mediated DNA damage is an important pathway of cell dysfunction and tissue injury during myocardial infarction. Because diabetes mellitus can substantially alter cellular signal transduction pathways, we have now investigated whether the PARP pathway also contributes to myocardial ischemia/reperfusion (MI/R) injury in diabetes mellitus in rodents. Myocardial ischemia/reperfusion in control and streptozotocin-diabetic rats was induced by transient ligation of the left anterior descending coronary artery. PARP activation was inhibited by the isoindolinone derivative PARP inhibitor INO-1001. In diabetic rats, a more pronounced degree of myocardial contractile dysfunction developed, which also was associated with a larger infarct size, and significant mortality compared with nondiabetic rats. Inhibition of PARP provided a similar degree of myocardial protective effect in diabetic and nondiabetic animals and reduced infarct size and improved myocardial contractility. In diabetic rats, PARP inhibition reduced mortality during the reperfusion phase. There was marked activation of PARP in the ischemic/reperfused myocardium, which was blocked by INO-1001. In addition, there was a significant degree of mitochondrial-to-nuclear translocation of the cell death effector apoptosis-inducing factor (AIF) in myocardial infarction, which was blocked by pharmacological inhibition of PARP. The role of PARP in regulating AIF translocation in myocytes also was confirmed in an isolated perfused heart preparation. Overall, the current results demonstrate the importance of the PARP pathway in diabetic rats subjected to myocardial infarction and demonstrate the role of PARP in regulating AIF translocation in MI/R.

Animals↗

PubMed2004

Tissue-specific imprinting of the G protein Gsalpha is associated with tissue-specific differences in histone methylation.

The G protein Gsalpha is imprinted in a tissue-specific manner, being primarily expressed from the maternal allele in some tissues, such as renal proximal tubules. The Gsalpha promoter is unmethylated, but is downstream of a differentially methylated region [the exon 1A differentially methylated region (DMR)] that is methylated on the maternal allele. Maternal Gsalpha null mutations or loss of maternal-specific exon 1A methylation leads to pseudohypoparathyroidism types 1A or 1B, respectively. We now have examined the chromatin state of each parental allele within the exon 1A-Gsalpha promoter region by chromatin immunoprecipitation of samples derived from mice with heterozygous deletions within the region using antibodies to covalently modified histones. The exon 1A DMR had allele-specific differences in histone acetylation and methylation, with histone acetylation and H3 lysine 4 (H3K4) methylation of the paternal allele, and H3 lysine 9 (H3K9) methylation of the maternal allele. Both parental alleles had similar levels of histone acetylation and H3K4 methylation within the Gsalpha promoter and first exon, with no H3K9 methylation. In liver, where Gsalpha is biallelically expressed, both parental alleles had similar levels of tri- and dimethylated H3K4 within the Gsalpha first exon. In contrast, in renal proximal tubules there was a greater ratio of tri- to dimethylated H3K4 of Gsalpha exon 1 in the more transcriptionally active maternal as compared with the paternal allele. These results show that allele-specific differences in Gsalpha expression correlate in a tissue-specific manner with allele-specific differences in the extent of H3K4 methylation, and are the first demonstration that chronic transcriptional activation in mammals is correlated with trimethylation of H3K4.

Animals↗

PubMed2004

Genetic and functional analyses of the øX174 DNA binding protein: the effects of substitutions for amino acid residues that spatially organize the two DNA binding domains.

The øX174 DNA binding protein contains two DNA binding domains, containing a series of DNA binding basic amino acids, separated by a proline-rich linker region. Within each DNA binding domain, there is a conserved glycine residue. Glycine and proline residues were mutated and the effects on virion structure were examined. Substitutions for glycine residues yield particles with similar properties to previously characterized mutants with substitutions for DNA binding residues. Both sets of mutations share a common extragenic second-site suppressor, suggesting that the defects caused by the mutant proteins are mechanistically similar. Hence, glycine residues may optimize DNA-protein contacts. The defects conferred by substitutions for proline residues appear to be fundamentally different. The properties of the mutant particles along with the atomic structure of the virion suggest that the proline residues may act to guide the packaged DNA to the adjacent fivefold related asymmetric unit, thus preventing a chaotic packaging arrangement.

Amino Acid Sequence↗

PubMed2004

Pilot study on the midsecond trimester examination of fetal nasal bone in the Chinese population.

OBJECTIVES: Hypoplasia of the nasal bone of fetuses affected by trisomy 21 and other aneuploidies could be detected by prenatal ultrasound examination and was an important new marker in the detection of Down syndrome in the second trimester. Racial differences in fetal nasal bone length have been reported. However, there was no reference range for the fetal nasal bone length (NBL) in the Chinese population. We conducted a pilot study to investigate the reproducibility of the measurement of fetal NBL in the mid second trimester and to determine whether there is any difference in NBL between the Chinese and the Caucasian population. METHODS: From June 2002 to February 2003, 198 Chinese women were examined. Ultrasound measurements of NBL were performed on a strictly midsagittal plane in normal singleton fetuses at 15 to 23 weeks' gestation. RESULTS: The mean difference in the NBL between the two investigators was small (mean = 0.043 mm; 95% CI, -0.033 to 0.12), and there was substantial agreement between the measurements for each observer. Limits of agreement were -0.48 to 0.35 and -0.29 to 0.22 mm in the two investigators respectively. It was found that the median length of the nasal bones increased from 3.5 mm at 15 weeks to 6.7 mm at 23 weeks' gestation. There was a linear relationship between the length of the nasal bone and the gestational age. CONCLUSION: It was demonstrated that the measurement of nasal bone length was feasible and reproducible in the second trimester. The fetal nasal bone length in Chinese population appeared shorter than that of Caucasian and African-Americans. There is a need to establish a reference range of fetal NBL for the Chinese population.

Adolescent↗

PubMed2004

Ultrasound screening of fetal structural abnormalities at 12 to 14 weeks in Hong Kong.

OBJECTIVE: Ultrasound screening for fetal abnormalities is conventionally performed at 18 to 20 weeks of gestation. Recent data suggested that many fetal structural abnormalities could be detected by ultrasound examination at 12 to 14 weeks of pregnancy. In this study, we investigated the effectiveness of early ultrasound examination in the detection of fetal abnormalities in women aged 35 years or older. METHODS: From February 1998 to March 2001, pregnant women aged 35 or above were examined by transabdominal and transvaginal sonography between 12 and 14 weeks of gestation. If the anatomical survey was normal, the women underwent routine 16- to 20-week ultrasound examination. Pregnancy outcome was obtained from the hospital records or by contacting the subjects. RESULTS: Twenty-six of the 1609 fetuses had structural abnormalities. Fourteen were detected at the ultrasound examination at 12 to 14 weeks. Detection rate was 53.8% (14/26; 95% CI 44, 64) with a false-positive rate of 0.3% (5/1583; 95% CI 0.16, 0.44). Six additional abnormalities (23.1%, 6/26) were detected at 16- to 20-week ultrasound examination. The overall detection rate of structural abnormalities was 76.9% (20/26; 95% CI 68.6, 85.2). CONCLUSIONS: The effectiveness of ultrasound examination at 12 to 14 weeks to screen for fetal abnormalities approached that achieved at 20 weeks and can be a good adjunct to the conventional examination.

Adult↗

PubMed2004

Raman properties of chlorophyll d, the major pigment of Acaryochloris marina: studies using both Raman spectroscopy and density functional theory.

The Raman spectroscopy of purified chlorophyll (Chl) d extracted from Acaryochloris marina has been measured over the wide region of 250-3200 cm(-1) at 77 K following excitation of its Soret band at 488 nm and analyzed with the aid of hybrid density-functional vibrational analyses. A Raman peak specific to Chl d, which arises from the formyl group 3(1) C=O stretching, was clearly observed at 1659 cm(-1) with medium intensity. Peaks due to other C=O stretching vibrations of the 13(1) keto-, 13(3) ester- and 17(3) groups were also observed. Four very strong peaks were observed in the range of 1000-1600 cm(-1), assigned to the CC stretching and mixtures of the CH3 bend and CN stretching. CCC and NCC bending contribute to medium intensity peaks at 986 and 915 cm(-1). Out-of-plane CH bending at Chl d methine sites 10, 5 and 20 contribute to observed peaks at 885, 864 and 853 cm(-1), respectively. A few modes involving the MgN stretching and MgNC bending motions were observed in the very low frequency range. Density functional theory (DFT) calculations have been used to make assignments on the observed Raman spectrum and the DFT results have been found to be in good agreement with the experimental results.

Bacteria↗

PubMed2004

A new geranylgeranyl diphosphate synthase gene from Ginkgo biloba, which intermediates the biosynthesis of the key precursor for ginkgolides.

Geranylgeranyl diphosphate synthase (GGPPS, EC: 2.5.1.29) catalyzes the biosynthesis of geranylgeranyl diphosphate (GGPP), which is a key precursor for ginkgolide biosynthesis. Here we reported for the first time the cloning of a new full-length cDNA encoding GGPPS from the living fossil plant Ginkgo biloba. The full-length cDNA encoding G. biloba GGPPS (designated as GbGGPPS) was 1657bp long and contained a 1176bp open reading frame encoding a 391 amino acid protein. Comparative analysis showed that GbGGPPS possessed a 79 amino acid transit peptide at its N-terminal, which directed GbGGPPS to target to the plastids. Bioinformatic analysis revealed that GbGGPPS was a member of polyprenyltransferases with two highly conserved aspartate-rich motifs like other plant GGPPSs. Phylogenetic tree analysis indicated that plant GGPPSs could be classified into two groups, angiosperm and gymnosperm GGPPSs, while GbGGPPS had closer relationship with gymnosperm plant GGPPSs.

Alkyl and Aryl Transferases↗

PubMed2004

Rapid isolation of high-quality total RNA from taxus and ginkgo.

An easy and efficient protocol was developed for isolating good-quality total RNA from various tissues including fruits, leaves, stems, and roots of ancient gymnosperm species, taxus and ginkgo. The protocol was developed based on the CTAB method with modifications, including higher-strength CTAB to help the lysis of plant cells, more PVP, and beta-mercaptoethanol to prevent oxidation of phenolic complexes, and higher-centrifugation force to get rid of most cell debris and to ensure RNA quality. In RNA isolation, chloroform/isoamyl alcohol was used to remove proteins, genomic DNA, and secondary metabolites and lithium chloride was subsequently adopted to concentrate total RNA away from most of the cytoplasmic components. Good-quality total RNA from various tissues of native taxus and ginkgo could be easily isolated within 24 hr by this protocol which avoided the limitation of plant materials and the usage of dangerous chemicals, such as phenol, and could provide total RNA for all kinds of further molecular studies.

Ginkgo biloba↗

PubMed2004

Activation of poly(ADP-ribose) polymerase in circulating leukocytes during myocardial infarction.

Myocardial ischemia-reperfusion can lead to increased oxidative stress both locally and in circulating leukocytes. Oxidant-mediated DNA single strand breaks are known to activate the nuclear enzyme poly(ADP-ribose) polymerase (PARP) in various forms of shock, inflammation, and ischemia-reperfusion injury. The aim of the current study was to investigate whether a local insult such as myocardial ischemia-reperfusion is sufficient to lead to activation of PARP in circulating leukocytes. In anesthetized rats myocardial ischemia-reperfusion was induced by transient ligation of the left anterior descending coronary artery. There was a marked increase in poly(ADP-ribosyl)ation of proteins in homogenates of leukocytes isolated from rats at the end of the reperfusion period. Poly(ADP-ribosyl)ation was inhibited by administration of the pharmacologic PARP inhibitor INO-1001 (30 mg/kg) to the rats. We conclude that local insults, such as myocardial reperfusion injury, are sufficient to activate PARP in circulating leukocytes. PARP activation in circulating cells may mediate certain systemic effects of local ischemia-reperfusion injury such as inflammatory mediator production and remote organ injury.

Animals↗

PubMed2004

Increased incidence of squamous cell carcinomas in Mastomys natalensis papillomavirus E6 transgenic mice during two-stage skin carcinogenesis.

Papillomaviruses cause certain forms of human cancers, most notably carcinomas of the uterine cervix. In contrast to the well-established involvement of papillomavirus infection in the etiology of cervical carcinomas and in carcinomas of a rare hereditary condition, epidermodysplasia verruciformis, a causative role for cutaneous human papillomavirus types in the development of nonmelanoma skin cancer has not been proven. In order to better understand the functions of individual genes of cutaneous papillomavirus types, we generated transgenic mice carrying oncogene E6 of the Mastomys natalensis papillomavirus (MnPV), which causes keratoacanthomas of the skin in its natural host. In the present study, we demonstrate that under conditions of experimental two-stage skin carcinogenesis, fast-paced squamous cell carcinomas develop in nearly 100% of MnPV E6 transgenic mice in comparison to 10% in their nontransgenic littermates (log rank test; P < 0.0001). Therefore, we conclude that the MnPV E6 transgene favors the malignant progression of chemically induced tumors. Whereas an activating H-ras mutation is a consistent feature in benign and malignant tumors in wild-type mice, the majority of papillomas and keratoacanthomas and all squamous cell carcinomas obtained in MnPV E6 transgenic mice contain nonmutated ras alleles. These results indicate that the development of squamous cell carcinomas in MnPV E6 transgenic mice does not depend on an activated H-ras oncogene.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed2004

Preparation and characterization of pH-sensitive hydrogel of chitosan/poly(acrylic acid) co-polymer.

A pH-sensitive co-polymer hydrogel of chitosan/poly(acrylic acid) (CS/PAAc) was prepared by irradiating the aqueous solution mixture of chitosan and acrylic acid with 60Co gamma-ray irradiation. The effect of the composition of chitosan and AAc on the properties of the hydrogel, such as swelling ratio and pH-sensitivity, were determined. Fourier Transform Infrared (FT-IR) spectrometry was applied in the attenuated total reflectance (ATR) mode for analyzing the structure change of the hydrogels after the treatment in different pH buffer solutions.

Absorption↗

PubMed2004

[Study on protective effect of shenfu injection on cardiac function of patients undergoing valve replacement].

OBJECTIVE: To investigate the protective effect of Shenfu injection (SFI) on cardiac function of patients undergoing valve replacement operation under cardio-pulmonary bypass. METHODS: One hundred and twenty patients undergoing valve replacement operation under cardio-pulmonary bypass were randomly divided into the SFI group and the control group, 60 in each group. Intravenous infusion of 1 ml/kg SFI was given to the SFI group, 30 min before anesthesia, and to the control group, equal volume of normal saline was given instead. The following indices were observed: (1) the hemodynamic changes occurred in the operational period; (2) the dosage of vaso-active drugs used during and after operation; (3) the post-operational recovery time of patients. RESULTS: The mean arterial pressure and heart rate in the SFI group during operation were higher, while the central venous pressure was lower than those in the control group (P < 0.05). The dosage of vaso-active drugs, such as dopamine, dobutamine, sodium nitroprusside and lidocaine, used during and after operation was lower, and the extubation time and the intensive care unit (ICU) staying time were shorter in the SFI group when compared with those in the control group (P < 0.05). CONCLUSION: SFI has certain protective effects on the cardiac function of patients undergoing valve replacement operation under cardio-pulmonary bypass.

Adolescent↗

PubMed2004

Altered subcellular distribution of nucleolar protein fibrillarin by actinomycin D in HEp-2 cells.

AIM: To study the effects of actinomycin D on subcellular distribution of nucleolar protein fibrillarin in HEp-2 (human esophageal epithelial type 2) cells, and molecular mechanisms for maintenance of fibrillarin in nucleolus. METHODS: Indirect immunofluorescence assay was employed to investigate subcellular distribution of nucleolar protein fibrillarin and immunoblotting analysis was used to detect the total cellular amount of fibrillarin. RESULTS: Control cells with no drug treatment showed bright clumpy nucleolar staining, which indicated that fibrillarin decorated the nucleolus only. Treatment with actinomycin D caused dislocation of fibrillarin from nucleoli to nucleoplasm with numerous stained small nucleoplasmic entities. Immunoblotting showed that neither total cellular amount of fibrillarin nor the integrity of fibrillarin was changed upon the treatment. The dislocation of fibrillarin in cells treated at a lower concentration (0.05 mg/L) of actinomycin D, was totally reversible after removal of the drug from the medium. However, this reversion was not observed at a high drug concentration (1 mg/L). CONCLUSION: Actinomycin D induced dislocation of fibrillarin from nucleoli to nucleoplasm in HEp-2 cells. The retention of fibrillarin within the nucleolus was related to active RNA synthesis.

Cell Nucleolus↗

PubMed2004

[The effects of DPPH on cochlear microcirculation].

OBJECTIVE: To investigate the effects of free radical, 1, 1-Diphenyl-2-picylhydrazyl(DPPH), on cochlear blood flow. METHOD: Twenty guinea pigs were divided into 3 groups at random, 6 for control group, 6 for 1 mmol/L of DPPH group and 8 for 0.1 mmol/L of DPPH group. 2 microliters vehicle or drugs were dropped into round window membrane. Cochlear microcirculation was monitored by laser Doppler flowmeter and the mean arterial blood flow(MABP), which transferred by pressure conductor sensor and preamplifier, was simutaneously recorded by a computer. RESULT: MABP was stable throught the experiment. Cochlear blood flow increased 12.49% (P < 0.05) in 1 mmol/L group, and decreased 3.02% (P < 0.05). In control group cochlear microcirculation had no significant changes. CONCLUSION: DPPH has effects on cochlear microcirculation. The mechanism still need to be explored later.

Animals↗

PubMed2004

[The comparison of three ways for extracting nucleic acid from rats hair].

OBJECTIVE: To discuss the method of extracting nucleic acid from rat's hair. METHOD: The method with PCR buffer, SDS-proteinase K or Chelex-100 were used to extract the nucleic acid from rat's hair separately, and the isolated nucleic acid was analyzed by PCR and electrophoresis. RESULT: The success rate of antracting mt DNA from the hair gollcle, we gound the method with SDS-prot einase kis lower than the ather two methods (chi1(2) = 42.421, chi2(2) = 28.800, P<0.01). This is same as the result ot entracting nuclear DNA (chi1(2) = 49.091, chi2(2) = 30.767, P<0.01). While no alifference has been bound between the method with PCR buffer and with chelex-100 (mtDNA: chi(2) = 0.296; nuclear DNA: chi(2) = 0.048, P>0.05). The method with PCR buffer can't extract nucleic acid from hair shafts, the method with SDS-proteinase K can't extract mtDNA from one or two hairs, the method with Chelex-100 can extract mtDNA and nuclear DNA from single rat's hair or hair shafts. CONCLUSION: The method with Chelex-100 is suitable for extracting nucleic acid from hair.

Animals↗

PubMed2004

[Study on genetic diversity of herba Cistanches by RAPD].

OBJECTIVE: To determine the genetic diversity of Cistanche species. METHOD: Two populations of Cistanche deserticola and four populations of C. tubulosa were analyzed by random amplified polymorphic DNA (RAPD) markers. RESULT: A total of 76 and 87 loci were amplified using 10 random primers each other. The average percentage of polymorphic loci of C. deserticola was 47.37%. The PPL were 39.47% and 35.53% for two populations. Average Nei's gene diversity was 0.1358, Shannon' s genetic diversity was 0.2072, and Gst was 0.2546. The average PPL of C. tubulosa was 27.59%. It was 19.54% to 25.29% in different populations and Andi'er population had the highest. Average Nei's gene diversity was 0.0823, and Shannon' s genetic diversity was 0.125 8, Cst was 0.175 5. CONCLUSION: The diversity of Cistanche deserticola is higher than that of C. tubulosa, but both has differentiation among populations, C. deserticola has already separated itself into two different ecotypes.

Cistanche↗