Biomedical subjects

S Zhang

Publications and source records attributed to S Zhang.

At least 523 records · Page 29Linked to original sources

PubMed1999

Reduction of Listeria monocytogenes and Escherichia coli O157:H7 numbers on vacuum-packaged fresh beef treated with nisin or nisin combined with EDTA.

Nisin or nisin combined with EDTA was used to treat fresh beef. Beef cubes (2.5 by 2.5 by 2.5 cm) that were inoculated with approximately 7 log CFU/ml of Listeria monocytogenes Scott A or Escherichia coli O157:H7 505 B were dipped in the following solutions: (i) H2O, (ii) HCl, (iii) nisin, (iv) EDTA, or (v) nisin combined with EDTA, respectively, for 10 min each, with an exception of one set of control beef samples without treatment. Beef samples were then drip-dried for 15 min, vacuum packaged, and stored at 4 degrees C for up to 30 days. The pH on beef after different treatments was not a key factor in preventing bacterial growth. Treatment with nisin or with nisin combined with EDTA reduced the population of L. monocytogenes by 2.01 and 0.99 log CFU/cm2 as compared to the control, respectively, under the conditions of vacuum package and storage at 4 degrees C for up to 30 days. However, the effect of nisin and nisin combined with EDTA against E. coli O157:H7 505 B was marginal at 1.02 log CFU/cm2 and 0.8 log CFU/cm2 reductions, respectively.

Animals↗

PubMed1999

Metabolic acidosis-induced retinopathy in the neonatal rat.

PURPOSE: Carbon dioxide (CO2)-induced retinopathy (CDIR) in the neonatal rat, analogous to human retinopathy of prematurity (ROP), was previously described by our group. In this model, it is possible that CO2-associated acidosis provides a biochemical mechanism for CDIR. Therefore, the effect of pure metabolic acidosis on the developing retinal vasculature of the neonatal rat was investigated. METHODS: A preliminary study of arterial blood pH was performed to confirm acidosis in our model. In neonatal rats with preplaced left carotid artery catheters, acute blood gas samples were taken 1 to 24 hours after gavage with either NH4Cl 1 millimole/100 g body weight or saline. In the subsequent formal retinopathy study, 150 newborn Sprague-Dawley rats were raised in litters of 25 and randomly assigned to be gavaged twice daily with either NH4Cl 1 millimole/100 g body weight (n = 75) or saline (n = 75) from day 2 to day 7. After 5 days of recovery, rats were killed, and retinal vasculature was assessed using fluorescein perfusion and ADPase staining techniques. RESULTS: In the preliminary pH study, the minimum pH after NH4Cl gavage was 7.10+/-0.10 at 3 hours (versus 7.37+/-0.03 in controls, mean +/- SD, P < 0.01). In the formal retinopathy study, preretinal neovascularization occurred in 36% of acidotic rats versus 5% of controls (P < 0.001). Acidotic rats showed growth retardation (final weight 16.5+/-3.0 g versus 20.2+/-2.6 g, P < 0.001). The ratio of vascularized to total retinal area was smaller in acidotic rats (94%+/-4% versus 96%+/-2%, P < 0.001). CONCLUSIONS: Metabolic acidosis alone induces neovascularization similar to ROP in the neonatal rat. This suggests a possible biochemical mechanism by which high levels of CO2 induce neovascularization and supports the suggestion that acidosis may be an independent risk factor for ROP.

Acidosis↗

PubMed1999

[A preliminary study of human Y chromosome specific short tandem repeat loci].

OBJECTIVE: To understand the allele structure and reveal genetic polymorphism of Y chromosome specific short tandem repeat (Y-specific STR) loci in Chinese Han population. METHODS: The authors used a set of five Y-specific STR loci which were tetrameric tandem repeat loci chosen from the Genome Database. EDTA-blood specimens were collected from the unrelated individuals. DNA was extracted by Chelex method and amplified by the polymerase chain reaction (PCR). The PCR products were analyzed using both the PAGE horizontal electrophoresis with discontinuous buffer system and the automated fluorescence detection approach. RESULTS: The authors observed that the alleles at the five Y-specific STR loci were composed of some complex repeat structures. They successfully prepared a set of human allele ladders for the typing of the five Y-specific STRs and demonstrated the polymorphisms at the five Y-specific STR loci in Chinese Han population. CONCLUSION: Y-specific STRs are good genetic markers for the purpose of analysis of genetic relationship between populations. This preliminary study not only reveals allele frequencies and haplotype distribution of Y-specific STR in Chinese Han population, but also indicates a reference population for detecting male migration events and for reconstructing paternal history.

Chromosome Mapping↗

PubMed1999

Growth factors secreted by bronchial epithelial cells control myofibroblast proliferation: an in vitro co-culture model of airway remodeling in asthma.

Remodeling of the bronchial wall is a major determinant of morbidity in asthma. An increased number of myofibroblasts beneath the bronchial epithelial basement membrane has been described in asthma. The production of mediators by epithelial cells in close proximity to myofibroblasts during epithelial repair after repeated damage is one of the possible mechanisms for airway remodeling. In this study, we established a three-dimensional co-culture system in which myofibroblasts derived from human bronchial wall were maintained in collagen gels and a human bronchial epithelial cell line, 16HBE14o-, was grown on the surface of the gels. The epithelial cells were chemically injured by exposure to poly-L-arginine as a surrogate for eosinophil granule cationic protein and the proliferative response of the fibroblasts was examined. Conditioned medium from mechanically damaged epithelial cells was also tested for its effect on fibroblast proliferation. Myofibroblasts in the co-cultures showed significantly enhanced proliferation after poly-L-arginine-induced epithelial damage. Conditioned medium from mechanically damaged epithelial cells also increased fibroblast-proliferation. After epithelial perturbation, basic fibroblast growth factor, platelet-derived growth factor, IGF-1, transforming growth factor-beta2, and endothelin-1 levels increased in culture supernatants. Blockade of these growth factors inhibited fibroblast proliferation by 76% after epithelial injury. This study demonstrates that epithelial cells are an important regulator of airway remodeling by means of paracrine control of bronchial myofibroblasts in response to cell damage and repair.

Asthma↗

PubMed1999

Retinopathy associated with enterococcus enteropathy in the neonatal rat.

PURPOSE: Preretinal neovascularization has been previously observed in neonatal rats with spontaneously occurring diarrhea. This neovascularization appears analogous to retinopathy of prematurity (ROP), which occurs in human neonates. A new enterococcus species, designated Enterococcus rattus, has been isolated from the duodenum of these rats. In the present controlled study, the effect of the enteropathy induced by this organism on the retinal vasculature in the neonatal rat was further investigated. METHODS: One hundred fifty newborn Sprague-Dawley rats were randomly assigned to 6 expanded litters (n = 25). On the second day of life, animals were gavaged with either 100 microl of E. rattus suspension (1.0 X 10(7) colony forming units, inoculated group, n = 100 rats) or 100 microl saline (control group, n = 50 rats). All rats were raised in room air and were killed on day 13 of life. Duodenal and blood samples were cultured. The retinal vasculature was assessed using fluorescent microscopy and ADPase staining in a masked manner. Two additional inoculated litters and one control litter were studied for evaluation of arterial blood gases and validation of the grading method for preretinal neovascularization. RESULTS: One hundred percent of rats in the inoculated group developed severe diarrhea and had duodenal cultures positive for E. rattus compared with 0% in the control group. Preretinal neovascularization similar to ROP occurred in 55% of rats in the inoculated group compared with 2% in the control group (P = 0.001). Retinal vascular areas were reduced in the inoculated group (mean +/- SD, 89% +/- 5% versus 96% +/- 2%; P < 0.001). Rats in the inoculated group demonstrated severe growth retardation (final weight, 9.7 +/- 2.2 versus 16.7 +/- 2.7 g, P < 0.001). Inoculated animals also experienced acidosis (pH 7.31 +/- 0.06 versus 7.39 +/- 0.06 control, P = 0.04). CONCLUSIONS: A previously undescribed enterococcal enteropathy was associated with preretinal neovascularization similar to ROP in the neonatal rat. This supports an independent role for factors other than inspired oxygen in the development of ROP.

Animals↗

PubMed1999

The use of human hepatocyte cultures to study the induction of cytochrome P-450.

We have previously reported that paclitaxel (Taxol) is a potent inducer of cytochrome P-450 (CYP) 3A protein and CYP3A mRNA in human hepatocyte cultures. Here we report that Taxol increased CYP3A-dependent testosterone 6beta-hydroxylation in intact hepatocytes. This effect was concentration-dependent, with maximal increase in enzyme activity being observed at 10 microM Taxol. Treatment of hepatocyte cultures with concentrations of Taxol higher than 10 microM caused a dose-dependent decrease in testosterone 6beta-hydroxylase activity, amount of CYP3A protein, and total protein synthesis. The maximal CYP3A activity detected after treatment with Taxol or rifampicin was similar in six separate human hepatocyte cultures, suggesting that the cultures have achieved a limit of maximally inducible CYP3A. The fold increase in enzyme activity, however, was different and was inversely related to the level of expression in untreated hepatocytes, with the greatest increases being observed in the hepatocytes that expressed the lowest basal level of CYP3A. Pretreatment of hepatocytes with triacetyloleandomycin resulted in a 90% inhibition of testosterone 6beta-hydroxylase activity. Our results demonstrate the use of human hepatocyte cultures to investigate the induction of cytochrome P-450 by xenobiotics in intact cells and stress the importance of large dose-response studies as well as the need to assess toxicity in these investigations. The response to inducers of CYP3A activity were very consistent among different hepatocyte donors. Absolute values of testosterone 6beta-hydroxylase activity did not vary more than 2- and 5-fold in induced and untreated hepatocytes, respectively.

Antibiotics, Antitubercular↗

PubMed1999

[Cloning of the idiopathic azoospermia related genes with mRNA differential display method].

OBJECTIVE: Defect of some genes related to spermatogenesis may result in male infertility with azoospermia. This study aimed to clone some of the genes. METHODS: Testis tissues from a patient with idiopathic azoospermia and from a normal fathered man were investigated with an improved mRNA differential display approach. RESULTS: Significant difference was observed between the two tissues in gene expression. Five differential expressed sequence-tags (ESTs) were cloned and sequenced. Homology analysis with software advanced BLAST 2.0 showed that one EST shared 100% homology with cosmid L27h9, which located in Huntington's disease region on 4p16.3; the other 4 showed very low homology with sequences in GenBank. CONCLUSION: Azoospermia has complex genetic heterogeneity. A gene located in Huntington's disease region on 4p16.3 is expressed in human testis during the spermatogenesis, and a loss of its function may associate with azoospermia.

Cloning, Organism↗

PubMed1999

[Genetic polymorphisms of five STR loci in a Chinese Han population].

OBJECTIVE: To understand the allele structure and genetic polymorphism at five STR loci in Chinese Han population, and construct a preliminary database. METHODS: EDTA-blood specimens were collected from the unrelated individuals. The DNA samples were extracted with Chelex method and were amplified by PCR technique. The PCR products were analyzed using both the PAGE horizontal electrophoresis with discontinuous buffer system and the automated fluorescence detection approach. RESULTS: Four STRs consist of simple repeat motifs, while one STR contains a complex repeat structure. The STR polymorphisms at all of the five loci have been observed in Chinese Han population. CONCLUSION: The obtained data are beneficial to understanding the population genetics of the five STR loci in Chinese Han population. As a simple approach, the PAGE horizontal electrophoresis can be employed for typing the five STR markers.

Alleles↗

PubMed1999

Effects of acupuncture on the levels of endothelin, TXB2, and 6-keto-PGF1 alpha in apoplexy patients.

In order to delve into the mechanism governing the treatment of apoplexy by acupuncture at yangming channel points as main points, we observed the changes in the endothelin (ET) level in plasma, TXB2 and 6-Keto-PGF1 alpha levels in urine in convalescent apoplexy patients during acupuncture treatment. The results showed that the ET level in plasma in convalescent apoplexy patients was significantly higher than that in healthy subjects (P < 0.05), and the ET level in plasma in patients was decreased after one course of acupuncture treatment. It was found that before treatment the TXB2 level in urine in apoplexy patients was significantly higher than in healthy subjects, and the 6-Keto-PGF1 alpha level in urine in the patients was significantly lower than that in healthy subjects, with an increased ratio of TXB2 to 6-Keto-PGF1 alpha. After acupuncture treatment, the TXB2 level in urine was lowered with a decrease in the ratio of TXB2 to 6-Keto-PGF1 alpha. All this indicated that one of the mechanisms governing acupuncture treatment of apoplexy acupuncture at yangming channel points as main points was that acupuncture could produce therapeutic effects by adjusting the imbalance of important vaso-active substances, ET, TXA2, and PGI2.

6-Ketoprostaglandin F1 alpha↗

PubMed1999

Troglitazone increases cytochrome P-450 3A protein and activity in primary cultures of human hepatocytes.

Troglitazone (TRO) is an insulin sensitizer used in the treatment of type II diabetes. TRO is known to increase the activity of cytochrome P-450 (CYP) 3A in vivo. We have investigated the effect of TRO on CYP3A protein content and the activity of CYP3A (as measured by the formation of 6beta-hydroxytestosterone formation) in primary cultures of human hepatocytes in comparison with rifampicin (RIF). Hepatocytes were isolated from four human livers by perfusion with collagenase, plated on collagen-coated plates, and maintained in William's E medium. After 48 h in culture, cells were exposed to RIF (10 microM) or TRO (0-50 microM) twice, each over a period of 24 h, and the activity of CYP3A was measured. TRO increased the activity of CYP3A in a concentration-dependent manner, reaching a maximal response at 5 microM. Pretreatment of the hepatocytes with 10 microM TRO or 10 microM RIF resulted in a 4- to 15-fold increase in the activity of CYP3A. Maximum increase in CYP3A protein was observed at 5 microM TRO. There was a significant correlation (R(2) = 0.89) between the content of immunoreactive CYP3A protein in the hepatocytes and the rate of formation of 6beta-hydroxytestosterone. These results indicate that TRO is a potent inducer of CYP3A and is similar to RIF in inducing CYP3A in human hepatocytes. At concentrations of 25 microM and above, TRO was toxic to the cells, as determined by a decrease in the activity of CYP3A, a reduction in the amount of immunoreactive protein, and changes in the morphology of the cells.

Aryl Hydrocarbon Hydroxylases↗

PubMed1999

[Double-strand-primered polymerase chain reaction].

OBJECTIVE: To develop a simple and reliable method for DNA amplification. METHODS: Double-strand-primers of fragile X mental retardation 1 gene (FMR1) were generated and used to amplify DNAs that were roughly extracted from human peripheral blood. RESULTS: All products from 15 DNA samples by double-strand-primered polymerase chain reaction (DSP-PCR) were more specific than those amplified by routine PCR. CONCLUSION: The double-strand-primers reported here may increase the specificity of PCR amplification.

Humans↗

PubMed1999

[Detection of methylation status of tumor suppressor gene p16 by methylation specific polymerase chain reaction].

OBJECTIVE: To introduce a new method for studies on methylation status of CpG island: methylation specific polymerase chain reaction (MSP) with some modifications. METHODS: Target DNA was modified by sodium bisulfite, converting all unmethylated, but not methylated, cytodines to uracil, and subsequent amplification with primers specific for methylated versus unmethylated DNA. The status of 5'CpG island of tumor suppressor gene p16 in maxilliofacial squamous cell carcinoma (MSCC) was analyzed by modified MSP assay. RESULTS: To get single strand DNA, the authors denatured the target DNA by heating instead of alkaline treatment. DNA purification kit was also replaced by dialysis. A cheaper restriction enzyme Taq I was used in place of BstU I to distinguish methylated fragment from unmethylated fragment. The 5'CpG island of p16 gene was methylated in some MSCC tumors. CONCLUSION: MSP is a simple, sensitive, and specific method for detecting the methylation status of any CpG-rich region and the modifications make it more simple to perform.

CpG Islands↗

PubMed1999

Purification and properties of genetic expressing product of thermostable protease from Bacillus stearothermophilus HY-69.

The thermostable metal protease gene from Bacillus stearothermophilus HY-69 had been cloned and expressed in Bacillus subtilis MI113. The genetic expressing product of the enzyme was purified by CM-cellulose chromatography. The product shows homogeneity on PAGE. Its molecular weight is 27,000 +/- 1000 by SDS-PAGE and Sephadex G100 filtration, respectively. The alpha-helix content of the protease is estimated to be about 66%, the beta-turn about 28%, the random coil about 6%, but not beta-sheet, calculated from the circular dichroism data. The optimal temperature of the enzyme was 70 degrees C. When the enzyme was denatured in 3 mol/L of Gdn--HCl in phosphate buffer pH6.0 for 20 min, it remained about 40% of original activity. It shows that it is rather resistant to heat and Gdn-HCl denaturation. Its conformational variety coursed by Gdn-HCl was investigated by the far UV circular dichroism and fluorescence spectra. The results show that the enzyme has more compact conformation and internal hydrophobility.

Amino Acids↗

PubMed1999

Systemic and coronary hemodynamic effects of JTV-506, a novel potassium channel opener, in conscious dogs: comparison with cromakalim and nicorandil.

We compared the coronary and systemic hemodynamic effects of JTV-506, a novel potassium channel opener, with those of cromakalim and nicorandil in chronically instrumented conscious dogs. Experiments were performed in 7 dogs which had undergone the implantation of flow probes on the ascending aorta and left circumflex coronary artery, and of catheters into the descending thoracic aorta and left ventricular cavity, respectively. On different days at least 10 days after the implantation, dogs were randomly assigned to the doses of JTV-506 (2, 5 or 10 microg/kg), cromakalim (10 microg/kg), nicorandil (0.2 mg/kg) or glibenclamide (5 mg/kg) plus JTV-506 (5 microg/kg). Each dose of the three drugs produced dose-related increases in heart rate, coronary blood flow, cardiac output, dP/dt(max) and %SS, and produced decreases in arterial blood pressure, left ventricular systolic pressure, and coronary and systemic vascular resistance. JTV-506 at doses of 2 and 5 microg/kg reduced arterial blood pressure only slightly as compared to its significant coronary vasodilating effect. An increase in myocardial oxygen consumption (as estimated by pressure-work index) was also observed in response to each dose of three drugs. At doses that reduced coronary vascular resistance by 75%, JTV-506 produced a greater increase in coronary blood flow, as compared with cromakalim and nicorandil. JTV-506 has the longest duration of action as compared with cromakalim and nicorandil. Glibenclamide pretreatment completely abolished the effects of JTV-506 on coronary and systemic hemodynamics. These results suggest that JTV-506 is relatively more potent in the coronary bed with minimal systemic influence, and exerts a longer time course of action.

Animals↗

PubMed1999

Cloning and sequencing of sialyltransferase gene from human fetal liver.

Based on sequences of the highly conserved segments in the previously cloned sialyltransferases, 150 bp fragments were amplified and sequenced using human fetal liver mRNA as template. One of them (s38) showed 57%-97% identities with the active domains of previously cloned sialyltransferases. Based on the sequence of s38, an oligonucleotide was synthesized and labeled to screen human fetal liver cDNA library. A cDNA encoding alpha 2, 3-sialyltransferase has been isolated. The cDNA sequence included an open reading frame coding for 340 amino acid residues, and the deduced amino acid sequence showed 100% identity with that of human submaxillary gland Gal beta 1, 3GalNAc alpha 2, 3-sialyltransferase, 83.2% identity with that of pig submaxillary gland alpha 2, 3-sialyltransferase. These results suggested that the protein encoded by the cDNA from human fetal liver cDNA library was a Gal beta 1, 3GalNAc alpha 2, 3-sialyltransferase.

Base Sequence↗

PubMed1999

[Clinical study on transvaginal hysterectomy for moderate enlarged uterus].

OBJECTIVE: To assess the feasibility and safety of performing transvaginal hysterectomy(TVH) on moderate enlarged uteri. METHODS: Twenty-five transvaginal hysterectomies were performed on enlarged myomatous uteri, with the size equivalent to 12-17 gestational week or 280-570 g. Bisection, enucleation, morcellation and combinations thereof were used to facilitate the operation by reducing the uterine volume. The operation time, blood loss, morbidity as well as complications were observed and analyzed. RESULTS: Twenty-two out of 25 vaginal hysterectomies were successfully completed with a success rate of 88%. Another 3 cases were converted to transabdominal hysterectomies, 2 of them were due to technical difficulties. One bladder injury and one severe intraoperative hemorrhage occurred. Two cases required blood transfusion. The mean operating time was (119 +/- 32) min. The mean blood loss was (231 +/- 107) ml with a range of 100-500 ml except the case with severe hemorrhage. The morbidity rate was as low as 4% and the average postoperative hospital stay was (5.5 +/- 1.1) days. The follow-up at 2-48 months after operation showed excellent recovery in all cases without any late postoperative complications. CONCLUSION: In the hands of experienced vaginal operation surgeons some of the enlarged uteri(> or = 12 weeks gestational size, i.e. > or = 280 g) with benign disease can be safely removed transvaginally through reduction of uterine volume if the uterus is mobile and obtaind more satisfactory recovery.

Adult↗

PubMed1999

[Relationship between expression of P16 protein and prognosis in carcinoma of nasopharynx].

We observed the relationship between p16 gene and the occurrence, development and prognosis of carcinoma of nasopharynx by means of LSAB immunohistochemistry method and investigated the expression of protein P16 in 73 cases of carcinoma of nasopharynx and 10 cases of epithelia of chronic inflammation of nasopharynx. The results showed that P16 positive rate was 100% for the epithelia of chronic inflammation of nasopharynx. It was significantly higher than the P16 positive rate for the carcinoma of nasopharynx (38.4%, P < 0.01). There was significant difference of P16 positive expression in differentiation of nasopharyngeal carcinoma (poor differentiation versus undifferentiation), clinical staging (I-II versus IV) and grading of tumor (T1-T2 versus T3, T4) (P < 0.01). There was no correlation between P16 expression and metastatic lymph node (P > 0.05). The 3-year survival rates were 88.9% and 72.9% in P16 expression (+) and (-) patients respectively (P < 0.05). These findings suggested that P16 might play an important role in the process of carcinogenesis and development of nasopharyngeal carcinoma, and P16 might be used as a valuable marker for assessment of the biological behavior and prognosis of nasopharyngeal carcinoma.

Adolescent↗

PubMed1999

All-trans retinoic acid reduces intimal thickening after balloon angioplasty in atherosclerotic rabbits.

OBJECTIVE: To investigate the effects of oral administration of all-trans retinoic acid (ATRA) on inhibition of intimal thickening after balloon angioplasty in the rabbit iliac artery atherosclerotic model. METHODS: Iliac atherosclerosis was induced in 24 rabbits, and balloon angioplasty was performed. At angioplasty, 24 rabbits were randomly divided into four groups (n = 6 per group): Group 1: controls not receiving oral ATRA administration; Group 2: receiving oral ATRA (0.6 mg.kg-1.d-1) administration beginning 1 week prior to angioplasty and continuing for 4 weeks; Group 3: receiving oral ATRA (0.6 mg.kg-1.d-1) administration beginning immediately after angioplasty and continuing for 4 wk; Group 4: receiving oral ATRA (0.6 mg.kg-1.d-1) administration beginning 1 wk after angioplasty and continuing for 4 wk. Values of cross-sectional area, ratio of intimal/medial area and thickness were determined by a computer-based morphometric system, and cell proliferative activity was assessed by 3H-thymidine incorporation. RESULTS: Both the cross-sectional area and the ratio of intimal/medial area and thickness were significantly reduced by ATRA administration compared with control group (P < 0.01). The inhibitory effect is less potent when ATRA is administered 1 week before angioplasty. The ATRA inhibitory effect when administered 1 week after angioplasty is not different significantly form that when administered immediately after angioplasty. The 3H-thymidine incorporation was also decreased in ATRA-treated rabbits compared with controls (P < 0.01). CONCLUSIONS: Oral ATRA administration can be effective in inhibiting intimal thickening after balloon angioplasty. It is reasonable that ATRA should be administered immediately after angioplasty.

Angioplasty, Balloon↗