Biomedical subjects

M Zhu

Publications and source records attributed to M Zhu.

At least 181 records · Page 10Linked to original sources

PubMed1998

Endothelium-dependent relaxation induced by hawthorn extract in rat mesenteric artery.

The extract prepared from hawthorn (Crataegus fruit) was examined for its relaxant effect in rat isolated mesenteric arteries. Hawthorn extract induced concentration-dependent relaxation of the U46619-precontracted artery with an IC50 of 0.22 +/- 0.02 mg/ml. Removal of the functional endothelium reduced by approximately 85% the maximum relaxant response to hawthorn extract. Pretreatment of the arterial tissues with N(G)-nitro-L-arginine methyl ester (3-10 microM) or methylene blue (3-10 microM) inhibited the relaxation induced by hawthorn extract, while indomethacin (10 microM) had no effect. L-arginine (3 mM) did not affect the relaxation induced by hawthorn extract but partially reversed the effect of 10 microM N(G)-nitro-L-arginine methyl ester. Iberiotoxin (100 nM) slightly but significantly inhibited the relaxant effect of hawthorn extract whilst glibenclamide (3 microM) was ineffective. Glibenclamide at 3 microM reversed the relaxation induced by pinacidil. N(G)-nitro-L-arginine methyl ester and methylene blue markedly inhibited acetylcholine-induced relaxation in endothelium-intact arteries. Hawthorn extract also reduced the contraction induced by phenylephrine (1 microM) or high Ki (60 mM) with respective IC50 values of 0.13 +/- 0.01 mg/ml and 0.11 +/- 0.01 mg/ml. In high K+-contracted arteries, hawthorn extract induced only 55% of relaxation while it caused a complete inhibition of the U46619- or phenylephrine-induced contraction. These results suggest that hawthorn contains active components which cause vasorelaxation in rat isolated mesenteric arteries. Nitric oxide but not other endothelium-derived vasoactive factors was probably involved in the relaxation induced by hawthorn extract.

Animals↗

PubMed1998

A role of nicotinamide-induced increase in pancreatic beta-cell mass on blood glucose control after discontinuation of the treatment in partially pancreatectomized OLETF rats.

Otsuka Long-Evans Tokushima Fatty (OLETF) rat, a model of NIDDM, is normoglycemic at a young age. However, they become hyperglycemic, even at a young age as a result of a 70% pancreatectomy, which is associated with insufficient proliferation of beta-cells. Administration of nicotinamide ameliorates the sustained hyperglycemia by increasing beta-cell proliferation. In order to further understand its mode of action, we studied how long nicotinamide is effective, in terms of ameliorating hyperglycemia, as evidenced by an increase in beta-cell mass, after its administration, in partially pancreatectomized OLETF rats. Male rats, 6 weeks of age, were allocated at random to two groups, 70% pancreatectomy (Px) and sham-pancreatectomy (sham). The Px group was divided into three subgroups, based on treatment with either nicotinamide (350 mg/kg), phlorizin (400 mg/kg) or saline, which continued until 4 weeks after surgery, and were sacrificed at 4, 6, or 8 weeks after surgery. A 70% Px resulted in sustained hyperglycemia in the saline-treated Px rats, which was ameliorated by administration of either phlorizin or nicotinamide, showing the non-fasting blood glucose levels reached to or near the levels found in the sham rats. After cessation of phlorizin injection, non-fasting blood glucose level increased rapidly, reaching the level of the saline-treated Px rats at the end of the experiment, whereas after cessation of nicotinamide injection, non-fasting blood glucose increased gradually to a level which was significantly lower than that observed in the saline-treated Px rats. An increased beta-cell mass, 62.7 +/- 7.8% of total beta-cell mass induced by nicotinamide at 4 weeks, decreased gradually, reaching the level of pretreatment, 30.3 +/- 4.0% 4 weeks after cessation of the treatment. The findings in this study suggest that ameliorated hyperglycemia as a result of proliferated beta-cells during the administration of nicotinamide may results in showing beta-cell exhaustion (a majority of beta-cell degranulation) once stopping injection, as compared with phlorizin treated group in this model rat.

Animals↗

PubMed1998

Methods to reduce the variability of EMG power spectrum estimates.

Three methods that can significantly reduce the variability of the EMG power density spectrum (PDS) variable by eliminating artifactual components are described. Two methods, one that allows the subtraction of power line noise in the time domain and one which allows the subtraction of system noise in the frequency domain from the EMG, were shown to be effective in helping to accurately estimate the median frequency (MF) of the PDS, and especially during low level contractions (0-25% maximal voluntary contraction, MVC) when the signal-to-noise ratio is unfavorable. The techniques eliminate the artifactual effects of system and power line noises from the EMG recordings throughout the force range (0-100% MVC) while preserving the native EMG power at all frequencies. It was also shown that if a technique to train subjects to produce their true MVC is employed, the absolute force/torque produced could be as much as 30% higher than in untrained MVC. The effect of true MVC production was also shown to be significant when interpretation of PDS variables are correlated to the processes which produce contraction.

Algorithms↗

PubMed1998

Collagenase-1 complexes with alpha2-macroglobulin in the acute and chronic wound environments.

The purpose of this study was to examine the appearance and activation of collagenase-1 (MMP-1) in the wound environment. We found that MMP-1 accumulates in the fluid phase of the burn wound environment within 2 d of injury and reaches maximal levels by day 4. Two forms of the enzyme were evident; one that corresponded to proMMP-1 and another that corresponded to a group of high molecular mass (approximately 200 kDa and >200 kDa doublet) MMP-1 containing complexes. ProMMP-1 and MMP-1 containing complexes also occurred in wound fluid from venous stasis ulcers, but neither was detected in mastectomy fluid or in plasma. Levels of the proteinase inhibitor alpha2-macroglobulin in burn fluid and chronic ulcer wound fluid were almost as high as in plasma, and the high molecular mass MMP-1 containing complexes in burn fluid appeared to result from binding between alpha2-macroglobulin and activated MMP-1. These observations provide direct evidence that active MMP-1 in the fluid phase of the wound environment becomes complexed to alpha2-macroglobulin.

Acute Disease↗

PubMed1998

Isolation, culture and characteristics of human foetal and adult retinal pigment epithelium.

BACKGROUND: Current methods for the isolation and culture of adult retinal pigment epithelium (RPE) provide successful primary culture. However, most methods result in contamination with other cell types and low cell yields. The isolation and culture of human foetal RPE presents further problems associated with the limited size of the eye cup and adherence among cells. Reliable methods are necessary for the culture of human RPE and subsequent functional studies. METHODS: The present procedure is based on mechanical peeling of the whole RPE layer under the dissecting microscope. Dissected pieces are subsequently explanted to a 35 mm culture dish and are cultured with Dulbecco's modified Eagle's medium containing 10% foetal bovine serum. Peroxidase immunohistochemical methods were used to investigate cell phenotypes. RESULTS: Primary cultures were obtained within 10-14 days with high yields, good viability and purity in subsequent culture. Cultured cells were vimentin and cytokeratin positive and CD31 negative. CONCLUSIONS: This mechanical dissection technique is recommended for the isolation of foetal and young adult RPE cells, while the enzyme digestion method is preferred for aged adult tissue.

Adolescent↗

PubMed1998

A cellular protein binds vaccinia virus late promoters and activates transcription in vitro.

Available evidence indicates that the transcription of the late class of vaccinia virus genes requires the participation of several virus-encoded proteins in addition to the viral RNA polymerase. In this report we describe the identification of a protein present in extracts of uninfected HeLa cells that binds avidly to viral late promoter DNA. The protein bound specifically to several different vaccinia virus late promoters but not an early nor an intermediate promoter. DNase I footprinting localized the protein's binding site to nucleotides surrounding the transcriptional start site of the I1L promoter. Optimal promoter binding required sequences in the highly conserved TAAAT motif at the transcriptional start site as well as sequences immediately upstream; however, one variation on the motif's sequence did not affect promoter binding by the protein. Partially purified late promoter binding protein (LPBP) was capable of stimulating the transcription activity of extracts depleted of LPBP on a late promoter-driven template, establishing LPBP as a transcription activator in vitro. These results suggest that a cellular protein is responsible for targeting vaccinia virus late promoters for initiation of transcription.

Binding Sites↗

PubMed1998

Assessment of presystemic factors on the oral bioavailability of rifampicin following multiple dosing.

This study was carried out to elucidate the possible mechanism(s) responsible for reduced oral rifampicin bioavailability after multiple dosing. In addition to autoinduction, the relative contribution of the two possible controlling factors, e.g., intestinal metabolism and microbial degradation, was investigated using a rat model. Pharmacokinetic studies were carried out to assess the absolute rifampicin bioavailability by both oral and intravenous drug administration before and after 8 daily doses of 25 mg/kg. To estimate the possible involvement of microbial degradation, rifampicin kinetics were also assessed in rats on day 8 after receiving multiple oral dosing and concurrent administration of nonabsorbable triple antibiotics for gut sterilization 3 days prior to the study day. Pharmacokinetic parameters were generated by noncompartmental analysis. The results revealed a significant decrease in rifampicin levels for rats after multiple exposure, compared to single dosing; the mean clearance determined by intravenous dosing increased by 43% from 3.7 ml/min/kg and the half-life decreased by 24% from 238 min. However, the extent of decrease in rifampicin exposure following multiple dosing was substantially greater for rats dosed orally than intravenously; estimated absolute oral bioavailability decreased by 15% from 0.89 on day 1 to 0.76 on day 8. No apparent alterations in any of the pharmacokinetic parameters were observed after gut sterilization, suggesting minimal contribution of microbial degradation to the reduction in oral rifampicin absorption after multiple dosing. In addition to hepatic enzyme autoinduction, these results strongly suggest the involvement of enhanced intestinal metabolism as a contributing factor to the decrease in oral rifampicin bioavailability following prolonged exposure.

Absorption↗

PubMed1998

Identification of a quantitative trait locus influencing plasma insulin levels after 70% pancreatectomy using the OLETF rat.

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is an animal model for obese-type non-insulin-dependent diabetes mellitus (NIDDM) in humans. The OLETF rat has poor capacity for proliferation of pancreatic beta-cells after partial pancreatectomy, which may be the critical pathogenetic event in NIDDM development. The poor pancreatic beta-cell proliferation in this model is characterized by reduction in beta-cell mass and decrease in insulin content in the remnant pancreas. Our investigation was designed to identify quantitative trait loci (QTLs) responsible for beta-cell mass and plasma insulin levels after partial pancreatectomy by performing a genome-wide scan in an F2 intercross obtained by mating the OLETF and the Fischer-344 (F344) rats. We have identified a suggestive QTL for the plasma insulin levels, near D20Mgh5 on rat chromosome 20, with a maximum lod score of 3.75 which accounts for 20% of the total variance, while no QTLs were detected for beta-cell mass. This chromosome 20 QTL, whose OLETF allele is associated with low plasma insulin levels through acting in an incompletely recessive manner, may affect insulin secretion itself rather than beta-cell proliferation.

Animals↗

PubMed1998

[Protective effect of tea on immune function in mice].

OBJECTIVE: To study the mechanism of preventive effect of tea on cancer by immune regulation. METHODS: A tumor model was induced in mice using carcinogen, 4-methyl-nitrosoamino-1-(3-pyridyl)-1-butanone (NNK), to examine their changes in immune function and the effects of green tea, mixed tea and polyphenol on protection from tumor. RESULTS: During the four weeks of observation after injection of NNK into mice, their immunological indicators, such as cytophagocytosis of macrophage in the abdominal cavity, chemiluminescence of peripheral leukocyte, delayed allergic reaction, count of antibody-forming spleen cells and activity of spleen nature killer cells, etc. increased or decreased to various extent, as compared with those in normal controls. It was found that whether green tea, mixed tea or polyphenol all showed significant protection from adverse changes in immune functions. CONCLUSION: Tea and its components had significant protection from early adverse changes in immune function in tumorgenesis induced by NNK.

Adjuvants, Immunologic↗

PubMed1998

Expression of calmodulin-binding domain of neuronal nitric synthase and its binding activity to calmodulin.

To facilitate the study of associations of nNOS functions with its calmodulin (CaM) binding domain and to prepare nNOS specific inhibiting peptides from phage peptide library, we have amplified the coding gene of nNOS CaM-binding domain (nNOS 2544-2988 bp) and expressed it in E.coli. The recombinant product in the size of 22 kDa was purified (over 90% in pure) by His.Tag-Sepharose column and its obvious CaM-binding activity was detected with CaM overlay assay. Since it possesses the sequence specificity and effective calmodulin-binding activity, the protein was considered an ideal target for screening nNOS specific peptides from peptide library and also an antigen for marking nNOS antibody.

Binding Sites↗

PubMed1998

[Study on a deletion polymorphism of the angiotensin converting enzyme gene in pregnancy induced hypertension].

OBJECTIVE: To study a polymorphism and allele frequency of the angiotensin converting enzyme (ACE) gene in pregnancy induced hypertension (PIH). METHODS: Polymerase chain reaction (PCR) for detection of ACE gene polymorphism was performed to show the deletion/insertion (D/I) polymorphism in intron 16 of ACE gene. A 490 bp(I) and 190 bp(D) PCR products were identified, corresponding to the PCR amplification of the the allele with or without the insertion. RESULTS: Derived allele frequencies for insertion and deletion were the different between 35 PIH and 25 control subjects. Compared the frequency of D allele gene (0.76) and the percentage of the ACE DD genotype (65.7%) in the PIH patients with the frequency (0.28) and the percentage (8.0%) in the control population, they were significant higher in individuals with PIH (P < 0.001). CONCLUSIONS: There was an excess of DD genotype and the frequency of D allele gene in PIH, confirming the genetic variation in the ACE locus could be involved in the risk of PIH and suggesting the ACE gene may contribute to the pathogenesis of PIH.

Adult↗

PubMed1998

[The dose-response of cell proliferation and secretion of CA125 II antigen to follicle stimulating hormone in ovarian cancer cell lines].

OBJECTIVE: To study the dose-response of the proliferation and secretion of CA125 II antigen with follicle stimulating hormone (FSH) in epithelial ovarian cancer cell lines. METHODS: Two different kinds of ovarian cancer cell lines originated from different pathologic types-AO and 3AO were studied. Cancer cells were cultured in medium containing FSH in different concentrations. The proliferation rate of cells was detected by using the 3H-TdR intrusion technique. The accordant titer of CA125 II antigen in the culture medium was measured by enzyme linked immunoadsorbent assay technique. RESULTS: Proliferation rate of cancer cells (AO and 3AO) was increased apparently as increasing in the concentration of FSH in the culture medium. A positive correlation was found between them (P < 0.05). Proliferation rate of AO cells positively correlated with secreting quantity of CA125 II antigen (P < 0.05), however, no such correlation was found in 3AO cells. CONCLUSION: It suggested that FSH can stimulate the proliferation of epithelial ovarian cancer cell at high concentration and there is a accordant dose-response relationship between them. The secreting pattern of the CA125 II antigen varied by the pathological classification of the ovarian cancer.

CA-125 Antigen↗

PubMed1998

[Determination of copper, zinc, iron and calcium in wheat and maize and three nitrogen compounds in high and low risk areas of esophageal cancer].

This study reports the concentrations of copper, zinc, iron and calcium in wheat and maize from high risk area Linzhou and low risk area Yuzhou of esophageal cancer and three nitrogen compounds of four types of drinking water in Linzhou. The results showed that the concentrations of zinc and calcium in wheat and maize from Linzhou were significantly lower than these from Yuzhou, the copper concentrations in grains were higher and the iron in maize was lower. The nitrate-N concentrations in four types of drinking water from Linzhou were below the national standard but the nitrite and NH3-N concentrations were higher than the national limits. The results suggest that the low concentrations of zinc, iron and calcium and high concentrations of copper in grains as well as the high concentrations of nitrite and NH3-N may be related to the etiology of esophageal cancer.

Calcium↗

PubMed1998

[The relation between human fetal growth and the blood levels of insulin-like growth factor-I].

OBJECTIVE: To determine the relation between human fetal growth and the levels of insulin growth factor-I (IGF-I) in both the maternal and fetal compartments. METHODS: Serum samples were obtained from pregnant woman(n = 171) and their neonate cord blood(n = 164) between 32-42 weeks of gestation. The woman and the neonate were divided into three groups by the birth weight of newborn. In large for gestational age (LGA) group, the 77 cases were from pregnant woman and the 64 cases were from their neonate; in average for gestational age (AGA) group, the 59 cases were from pregnant woman, the 59 cases were from their neonate; and in small for gestational age (SGA) group, the 35 cases were from pregnant woman and 43 cases were from their neonate. The serum samples were analyzed by radioimmunoassay for the levels of IGF-I. RESULTS: The levels of IGF-I in the neonatal serum were lower than those in maternal blood (P < 0.01). The levels of IGF-I in SGA group were lower than those in the other groups (P < 0.05). There was significant correlation between gestational ages and the levels of IGF-I (r = 0.91-0.98), but not in SGA group (r = 0.21-0.81). There was a direct correlation between the levels of IGF-I in the cord blood and the neonatal weight (P < 0.05). CONCLUSIONS: These data demonstrate that the level of expression and regulation of IGF-I in maternal and fetal compartments were independent of each other. The IGF-I level in cord blood is shown to be adjunctively and directly associated with fetal size in pregnancies and the IGF-I plays the precise role in deviant fetal growth.

Adult↗

PubMed1998

[Study of physiological parameters of velopharyngeal function by nasopharyngeal fibroscope].

OBJECTIVE: Velopharyngeal incompetency (VPI) could be found in certain healthy people when some vowels were produced. Since neither asophia nor organic deformity do they have, it should be considered as physiological VPI. VPI which exists commonly in patients with cleft palate is also an unsatisfactory manifestation after palatoplasty. In order to distinguish between physiological VPI and pathological VPI in patient with cleft palate and establish an objective criterion, it is necessary to assess the occurrence and extent of VPI in healthy people. METHODS: The velopharyngeal function of 890 subjects with normal speech was studied dynamically by nasopharyngeal fiberscope (NPF). Two vowels /i/ and /u/ were examined. The rates of velopharyngeal incompetence (RVPI) of vowel /i/ and /u/ were analyzed. RESULTS: VPI was found in 117 (13.15%) when vowel /i/ was produced. VPI was occurred in 100 (11.24%) when /u/ was produced. The RVPI mean of vowel /i/ is 11.285% +/- 7.248 in 112 subjects, while that of /u/ is 9.066% +/- 6.162 in 96. No significant difference was obtained in age or sex. CONCLUSION: It can be used to evaluate the velopharyngeal function after palatoplasty as physiological parameters.

Adult↗

PubMed1998

[Quantitative analysis of velopharyngeal function by nasopharyngeal fibroscope (NPF)].

OBJECTIVE: To estimate the reliability of the nasopharyngeal fibroscope (NPF) for assessing velopharyngeal function. METHODS: 16 well-pronounced males were examined by NPF which was positioned in different depth. Same procedures were repeated after a week. RESULTS: The results indicated that the rate of velopharyngeal incomptence (RVPI) of NPF had no significant difference when checked in different time and various depths. CONCLUSION: RVPI can be used as a parameter of quantitative analysis for velopharyngeal function, and our results suggested that it is reliable and reproduciable.

Endoscopes↗

PubMed1998

[An analysis of curative effect of activator in treating Class II division 1 malocclusion].

OBJECTIVE: To analyze the results of class II division 1 malocclusion treated by activator. METHODS: Sixteen growing patients, who were diagnosed as class II division 1 malocclusion, were evaluated by McNamara analysis. RESULTS: The activator affects the growth of mandible positively and inhibits the growth of the maxilla. CONCLUSION: The activator can treat class II division 1 malocclusion effectively, which can be perceived by McNamara analysis directly.

Adolescent↗

PubMed1998

[Effects of biomaterials on immunoglobulins and biochemistry in serum of extracoporal circulation].

The polyvinyl chloride(PVC) tube coated with cellulose acetate(CA), polyether suffone(PES), polyurethane(PU), silicon rubber(SR) and polyester fibre(PETF) were put in contact with circular serum at 37 degrees C. According to different time-periods of exposure, the immunoglobulins (G.A.M), albumin(ALB), total protein (TP) and total cholesteral(Tch) in serum were measured by an IL-Monarch biomedical analyser. The results showed that the levels of immunoglobutins significantly decreased after the serum came in contact with CA, PETF, SR and that the levels of ALB, TP and Tch were significantly lower in the serum exposed to PETF while those in the serum exposed to other materials were normal. These changes may relate to the complement activation induced by different materials.

Biocompatible Materials↗