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Biomedical subjects

M Sun

Publications and source records attributed to M Sun.

At least 109 records · Page 6Linked to original sources
PubMed1998

Hepatocyte injury in tyrosinemia type 1 is induced by fumarylacetoacetate and is inhibited by caspase inhibitors.

Tyrosinemia type 1, caused by mutations in the fumarylacetoacetate hydrolase gene (Fah), is characterized by severe liver injury. We earlier developed a tyrosinemic mouse model with two genetic defects, Fah and 4-hydroxyphenylpyruvate dioxygenase (Hpd) deficiencies. Apoptosis of hepatocytes was induced and an acute onset of liver failure occurred after administration of homogentisic acid (HGA), the intermediate metabolite between the enzymes HPD and FAH. Cytochrome c was released from mitochondria prior to liver failure in the Fah-/- Hpd-/- double-mutant mice after the administration of HGA. In a cell-free system, the addition of fumarylacetoacetate induced the release of cytochrome c from the mitochondria. We also found that caspase inhibitors were highly effective in preventing the liver failure induced by HGA in the double-mutant mice. Therefore, fumarylacetoacetate apparently induces the release of cytochrome c, which in turn triggers activation of the caspase cascade in hepatocytes of subjects with hereditary tyrosinemia type 1.

Acetoacetates↗
PubMed1998

Enzyme array-amperometric detection in carbohydrate analysis.

The introduction of an enzyme array-electrochemical detection method for carbohydrate analysis is demonstrated by using two complex and one high mannose N-linked oligosaccharides. Instead of measuring the remaining uncleaved oligosaccharides in enzymatic digestion, released monosaccharides are directly quantified by pulsed amperometric detection at a gold electrode. The measured monosaccharide concentrations in combination with the enzyme array analysis provide structural characterization of oligosaccharides. The enzyme array-electrochemical detection method does not require any separation procedure or any prior labeling of oligosaccharides. However, this method is limited by the use of purified oligosaccharide samples and the nature of the enzyme array. The development of more sophisticated enzyme arrays relies upon the introduction of a bank of highly specific (bond, arm, aglycon) exoglycosidases.

Carbohydrate Metabolism↗
PubMed1998

Purification and properties of soman-hydrolyzing enzyme from human liver.

A soman-hydrolyzing enzyme (somanase) was purified from human liver. The human somanase is capable of hydrolyzing pinacolyl methylphosphonofluoridate (soman), diisopropylphosphorofluoridate (DFP), and ethyl-N-dimethyl phosphoramidocyanidate (Tabun) with P-F or P-CN bonding, but not ethyl (S-2-diisopropylaminoethyl) methylphosphonothiolate (VX) and diethyl-p-nitro-phosphenylphosphate (paraoxon) with P-S or P-O bonding. The somanase has been purified 1570-fold with a specific activity of 41.4 mumol/min/mg protein. Its molecular weight is around 58 kDa determined by SDS-PAGE. The somanase could be stimulated by the divalent cations Mn+2, Mg+2, and Co+2, where CO+2 activation is the highest. The requirement of disulfide bonds for the enzyme activity was demonstrated by the inhibition effect of DTT.

Catalysis↗
PubMed1998

Total energy expenditure and physical activity in prepubertal children: recent advances based on the application of the doubly labeled water method.

The prevalence of obesity in children has continued to increase despite a general increased awareness of health and fitness. Epidemiologic data show that the prevalence of obesity in children is approximately 25%, with a higher prevalence in some subgroups of the population. In addition, the incidence of obesity-related diseases is dramatically increasing in children. For example, the incidence of type 2 diabetes in children and adolescents has increased 10-fold over the past decade, and this increase is more pronounced in obese persons. The etiology of the development of childhood obesity and subsequent disease is poorly understood, but is likely to be explained by alterations in the regulation of energy balance between energy expenditure and energy intake. It is not known whether obesity is caused by an increase in energy intake relative to energy needs, a decrease in energy expenditure relative to energy needs, or the effect of both. This review will focus on recent studies that have attempted to elucidate the etiology of childhood obesity and have increased our understanding of the regulation of energy balance in prepubertal children by using the doubly labeled water method for estimating total energy expenditure and physical activity-related energy expenditure. This review serves as a brief summary and general update of recent reviews of this topic.

Body Water↗
PubMed1998

Cellular specificity of interleukin-1beta-stimulated expression of type-2 prostaglandin H synthase in human amnion cell cultures.

Interleukin-1beta (IL-1beta) has been shown in numerous studies to increase prostaglandin output by cultures of human amnion cells. This is due to an increase in the expression of type-2 prostaglandin H synthase (PGHS-2), the inducible form of the enzyme, in these cultures. Amnion consists of an epithelial layer of cells and a subepithelial mesenchymal layer of cells. The purpose of the present study was to determine the cell-type(s) responsible for the IL-1beta-induced PGHS-2 expression in amnion cultures. Amnion was obtained at term after elective Cesarean section or vaginal delivery. Tissues were dispersed with collagenase, and cells were plated in multichamber culture slides and cultured for 7 days in media supplemented with 10% fetal bovine serum. Cell types were characterized with antisera to keratin (epithelial cells) and vimentin (mesenchymal cells). Cultures contained both cell types, and the proportion of these varied considerably from one culture to another. Cells were treated with various concentrations of IL-1beta for 6 or 24 h and were then fixed in 4% paraformaldehyde. The fixed cells were permeabilized with Triton and examined by immunohistochemistry for PGHS-2 protein using specific antisera, and PGHS-2 mRNA was localized by in situ hybridization using a specific oligonucleotide probe. The cell type(s) expressing PGHS-2 was characterized using double labeling with antisera to keratin (epithelial cell marker) and vimentin (mesenchymal cell marker). IL-1beta was found to increase expression of immunoreactive PGHS-2 and PGHS-2 mRNA. This increased expression was found to occur only in the vimentin-positive cells and not the epithelial cells. These results highlight the potential importance of the subepithelial cells in the mesenchymal layer of amnion in the formation of prostaglandins during pregnancy and possibly in preterm labor with infection.

Amnion↗
PubMed1998

Total, resting, and activity-related energy expenditures are similar in Caucasian and African-American children.

There is some evidence to suggest that ethnic differences in energy expenditure in adults may modulate different propensities for obesity. However, there is lack of data for the components of energy expenditure in young children of different ethnic backgrounds. In this study, we examined total energy expenditure (TEE), resting energy expenditure (REE), and physical activity-related energy expenditure (AEE) in healthy prepubertal Caucasian (18 girls, 21 boys) and African-American (29 girls, 30 boys) children. TEE was measured over 14 days under free-living conditions with the doubly labeled water technique, REE was from indirect calorimetry after an overnight fast, and AEE was estimated from the difference between TEE and REE after reducing TEE by 10% to account for the thermic effect of feeding. Fat mass (FM) and fat-free mass (FFM) were measured by dual-energy X-ray absorptiometry. There were no significant effects of ethnicity or gender on TEE after adjustment for FFM or for both FFM and FM. For REE, there was no effect of ethnicity, but a significant effect of gender, with a higher REE in boys after adjustment for FFM and FM (P < 0.001). For AEE, there were no significant effects of ethnicity or gender after adjustment for FFM or for FFM and FM. In conclusion, ethnicity was not a significant determinant for any of the components of energy expenditure. TEE, REE, and AEE were similar in Caucasian and African-American prepubertal children after adjustment for FFM or for FFM and FM.

Basal Metabolism↗
PubMed1998

[Effects of lotensin and nitrendipine on plasma fibrinogen and platelet aggregation in hypertensive patients].

Plasma fibrinogen and platelet aggregation were measured by turbidimetric immunoassay, turbidimetry in 47 hypertensive patients and 20 normotensive control subjects. Among the 47 hypertensives, 24 cases were received lotensin and 23 nitrendipine. The plasma fibrinogen was increased and platelet aggregation enhanced in hypertensive patients before treatment. Platelet aggregation decreased after 8 weeks of treatment with lotensin or nitrendipine respectively. Lotensin decreased plasma fibrinogen whereas nitrendipine did not. It was concluded that both lotensin and nitrendipine decreased platelet aggregation; lotensin decreased plasma fibrinogen but nitrendipine did not.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1998

[Effect of mifepristone on the expression of progesterone receptor messenger RNA and protein in uterine leiomyomata].

OBJECTIVE: To determine the expression of progesterone receptor (PR) mRNA and PR protein levels in the myometrium and leiomyomata from untreated and mifepristone pretreated women with leiomyoma and to examine the mechanism of mifepristone treatment on uterine leiomyomata. METHODS: Expression of PR mRNA and PR protein were determined by Northern blot and HAP of single-dose saturated analysis in myometrium and leiomyomata (center and marginal area) from 27 untreated and 6 mifepristone pretreated women with leiomyomata. RESULTS: PR mRNA abundance and PR protein levels in both myomatous center and marginal area were significantly greater than those in corporal myometrium (P < 0.01) in both follicular and luteal phases, but similar between myomatous center and marginal area (P > 0.05). 6 cases pretreated with mifepristone 25 mg/day for 3 months were operated, all but one patient displayed a decrease in leiomyomata volume. PR mRNA abundance in both myometruim and leiomyomata (center and marginal area) was significantly decreased in 4 patients continuing mifepristone treatment before the operation but not in the other 2 patients stopping RU486 1 month before operation. PR protein levels in these tissues showed significant decrease in all 6 cases. CONCLUSION: There are overexpression of PRmRNA and PR protein in leiomyomata. One of the mechanism of mifepristone action on decreasing leiomyomata volume may be related to suppression on expression of PR gene. It seems that suppression on transcription of PR gene is reversible, but on translation of PR gene may maintain in a relatively longer period.

Adult↗
PubMed1998

[Relationship between sex hormone levels and blood lipids/immunity in perimenopausal women].

To investigate the relationship between sex hormone levels and blood lipids/immunity and to evaluate the therapeutical effects of nylestriol, 96 women without coronary heart disease(CHD) were studied during their perimenopausal period. The estimation of serum biochemical components included serum 17 beta-estradiol(E2), testosterone(T), total cholesterol(TC), triglyceride (TC), high density lipoprotein cholesterol(HDL-C), low density protein cholesterol(LDL-C), apolipoprotein A-I(ApoAI), apolipoprotein B(ApoB), lipoprotein (a)[Lp(a)], immunoglobulin G(IgG), and IgG antibody against cardiolipin(ACAIgG). Thirty-six postmenopausal volunteers were divided into two groups and randomized to treat with either 2 mg nylestriol or placebo. In postmenopausal women, serum levels of E2, E2/T, HDL, and ApoAI decreased, while those of T, TC, TG, LDL, ApoB, Lp(a), IgG, and ACAIgG increased. Serum level of E2 was positively correlated to HDL-C and negatively correlated to TC, ApoB, LDL, IgG, and ACAIgG. Serum level of T was positively correlated to LDL, IgG, and ACAIgG and negatively correlated to HDL. In the nylestriol group, as compared with the results before treatment, serum levels of TG, TC, LDL, IgG, and ACAIgG decreased and that of HDL-C increased after treatment. We conclude that estradiol is a protective factor of CHD, whereas testerone is a dangerous factor. After menopause, the imbalance of the estradiol/testosterone ratio increases the incidence of CHD. Nylestriol is an effective substitute for estradiol to prevent CHD in post menopausal women.

Cholesterol↗
PubMed1998

[Changes of plasma endothelin-1 in patients with congestive heart failure and the influence of metoprolol].

To investigate the alterations of plasma endothelin-1(ET-1) in patients with congestive heart failure(CHF) and the effects of metoprolol on it, plasma ET-1 and norepinephrine(NE) were measured in 43 patients using radioimmunoassay and high-performance liquid chromatography methods. Twenty-four patients were treated with metoprolol plus the routine therapy while the others were received the routine therapy only. The findings were that levels of plasma ET-1 and NE increased before the treatment, and decreased after the treatment with metoprolol for 1 month. There was no alteration of plasma ET-1 or NE in the control group.

Adrenergic beta-Antagonists↗
PubMed1998

[Expression of inducible nitric oxide synthase in atherosclerotic rabbits].

Atherosclerotic lesions contain vascular smooth cells and thus may have an increased capacity for generation of nitric oxide (NO) by inducible NO synthase (iNOS). Rabbits (n = 8) were raised for eight weeks by the atherogenic diet, then the aortic rings were captured. Contractive responsiveness to norepinephrine, changes of CGMP, expression of iNOS of aortic rings were examined in vitro. There was a substantial decrease in contractile responsiveness to norepinephrine (NE) (P < 0.05), a decrease of CGMP (P < 0.01) and an increase of expression of iNOS (P < 0.05), after L-arginine or sodium nitroprusside treatment. The contractile responsiveness to NE was attenuated (P < 0.01). The CGMP was increased ((P < 0.01). After NG-nitric arginine (L-NNA) treatment, those reaction were reversed. It implied that L-arginine/NO pathway obstructure might likely be another mechanism of atherosclerosis and atherosclerotic arteries and had an increased capacity for generation of NO by iNOS.

Animals↗
PubMed1998

[Effect of Gengnianjian on up regulated estrogen receptor mRNA to substance P and beta-endorphin in hypothalamus of aging female rats].

OBJECTIVE: To investigate the effect of Chinese herbal formula Gengnianjian on estrogen receptor (ER), ERmRNA substance P (SP) and beta-endorphin (beta-EP) in the hypothalamus of aging female rats. METHODS: ER proteins were determined by radioligand binding assay, ER mRNA was analyzed by Northern blot analysis and the levels of beta-EP and SP were detected by immunohistochemistry. RESULTS: In aging rats, lowered ER and ER mRNA in the hypothalamus were still up-regulated by low serum E2 level, but not in rats of after the age of 21 months; Gengnianjian significantly increased ER protein level and ER mRNA expression, decreased SP and increased the level of beta-EP in the hypothalamus in aging female rats before 21 months of age, without changing of serum E2 level. In EB group, serum E2 and beta-EP levels increased and SP level decreased but ER expression suppressed in the hypothalamus except after 21 months. CONCLUSION: Enhance estrogen bioactivity can decrease the level of SP and increase the level of beta-EP in hypothalamus of aging female rats. Herbal formula Gengnianjian increase-EP level and decrease SP level by raising the level of ER and ER mRNA.

Aging↗
PubMed1998

[Transient and stable expression of human ApoE7 gene in NIH/3T3 cell lines].

OBJECTIVE: To investigate the expressing profile of h-apoE7 gene under the regulation of MT-I promoter in mouse cells. METHODS: The eukaryotic expressing plasmid pME7 was constructed through cloning human apoE7 genomic DNA(6.0 kb) into pMT at the site of Bgl II/Hind III just under the control of the mouse metallothionein-I promoter. Transfection of pME7 plasmid into NIH/3T3 cell lines by Lipo-fectamine was performed. RESULTS: The transient expression of recombinant pME7 in NIH/3T3 cells showed that the expression was not restricted to human cells; The stable expression of pME7 demonstrated that the levels of h-apoE7 mRNA was highly related to the copies of integrated h-apoE7 gene. Whereas the results of ELISA implicated that the exogenous human apoE7 gene was transcribed, processed properly, and eventually translated into functional proteins. Furthermore, heavy metal (ZnSO4) could enhance the expressing level of h-apoE7 gene in transfected cell lines. The level of human apoE7 protein arised 45%-60% while induced. CONCLUSIONS: It was suggested that MT-I promoter could modulate the expression of recombinant h-apoE7 gene correctly. Therefore, cellular studies provided the scientific basis for establishment of h-apoE7 transgenic mouse models.

3T3 Cells↗
PubMed1998

[Synthesis of hirudin variant 1 (HV1) gene and primary study of expression in yeast].

OBJECTIVE: Hirudin is an extremely efficient and specific thrombin inhibitor. It is clinically used to prevent the formation of thrombus. In this research the hirudin gene was put into yeast system for expression to evaluate the feasibility of artificially synthesized gene expressed in eukaryotic system and study the factor affecting expression level. METHODS: According to the amino acid sequence of hirudin variant 1 (HV1), the genetic code saccharomyces cerevisiae was used to design and synthesize the HV1 gene. Amplified by PCR, it was inserted into cloning vector pBS-SK(+) and sequenced. Ligation with the signal peptide gene of yeast alpha factor the correct HV1 gene was inserted into yeast expression vector pYC-DE. The recombinant plasmid was transformed into the cell of S. cerevisiae BJ1990 to carry out the primary expression experiment. RESULTS: In cultured supernatant of screened positive clone the hirudin activity was detected to be 30 ATU/ml. The expression level was higher than HV2 in yeast and HV1 in prokaryotic system. The N terminal amino acid sequence completely matches with natural hirudin. CONCLUSIONS: It was proved by this study that the synthesized hirudin gene had been expressed in yeast successfully. This result showed that it was a better way to carry out the expression in yeast using synthesized HV1 gene and a stronger promoter.

Base Sequence↗
PubMed1998

[Expression characteristic of Bacillus thuringiensis cry1 gene in Pseudomonas fluorescens Pfx-18].

The plasmids of lepidopteran-specific Bacillus thuringiensis strain from our laboratory were hybridized with RNA probe of cry 1Aa EcoR I-F fragment labelled using DIG. Cry1 gene was located in 39.3 MD plasmid. The plasmid was digested with Hind III and analysed by southern blot. It appeared both 7.1 kb and of 6.5 kb positive bands. The 7.1 kb fragment was ligated to broad-host-range vector pSUP106 and transformed into Pseudomonas fluorescens Pfx-18. The cloned strain, LZP-1 was obtained. The plasmids of LZP-1 were analysed by PCR. The results showed that gene-type is cry1Ab. SDS-PAGE analysis demonstrated that LZP-1 could express 66 kD insecticidal crystal protein and some small molecular weight peptides. Bioassay showed that motality of 1000-fold diluted fermentation broth was 33% to 3rd instar plulella xyloslelly larvae.

Animals↗