Biomedical subjects

R Zhao

Publications and source records attributed to R Zhao.

At least 55 records · Page 3Linked to original sources

PubMed2001

Abnormal DNA-binding of transcription factors in minimal change nephrotic syndrome.

The activation of transcription factors such as nuclear factor kappaB (NF-kappaB) and activator protein 1 (AP-1) plays an important role in regulating the expression of target genes, including those for cytokines involved in pathogenesis of minimal change nephrotic syndrome (MCNS). The therapeutic effects of glucocorticoids depend on the glucocorticoid receptor (GR) acting on gene transcription and interacting with certain transcription factors. To explore the role of transcription factors in the pathogenesis of MCNS and the therapeutic effects of glucocorticoids, we examined the DNA-binding abilities of NF-kappaB, AP-1, and GR in peripheral blood mononuclear cells (PBMC) from 6 children with MCNS and 6 healthy controls by electrophoretic mobility shift assay (EMSA). NF-kappaB and AP-1 DNA-binding abilities were significantly increased both at baseline and after stimulation by phorbol 12-myristate 13-acetate (TPA) in PBMC from MCNS patients compared with controls, but declined to normal levels after treatment with dexamethasone (DEX). GR DNA-binding abilities were significantly reduced at baseline and after treatment with TPA, but were enhanced markedly by DEX. There were strong correlations between urinary protein and the baseline DNA binding ability of NF-kappaB or AP-1, or GR. These results suggested that the abnormal activation of NF-kappaB and AP-1 and the reduction of GR DNA-binding abilities may be involved in the pathogenesis of MCNS. Inhibition of NF-kappaB and AP-1 and enhancement of GR DNA-binding abilities by DEX may form the molecular basis of the effects of glucocorticoids in MCNS.

Child↗

PubMed2001

Relationship between dopamine-stimulated phospholipid methylation and the single-carbon folate pathway.

In a previous study we demonstrated the ability of dopamine (DA) to stimulate phospholipid methylation (PLM) via a novel mechanism involving the D4 dopamine receptor (D4R) in which single-carbon folates appeared to be the primary source of methyl groups. To further understand the relationship between D4R-mediated PLM and folate metabolism, we examined the effect of several folate pathway interventions on the level of basal and DA-stimulated incorporation of [14C]-labeled formate into phospholipids in cultured SH-SY5Y neuroblastoma cells. These interventions included: (i) Overexpression of methenyltetrahydrofolate synthetase (MTHFS). (ii) Treatment with 5-formylTHF. (iii) Treatment with the MTHFS inhibitor 5-formyltetrahydrohomofolic acid (5-formylTHHF). (iv) Growth in nucleoside-free media. 31P-NMR was also used to follow DA-induced changes in cell phospholipid composition. MTHFS overexpression and 5-formylTHHF treatment, both of which lower 5-methylTHF levels, each reduced basal PLM and its stimulation by DA. In contrast, 5-formylTHF, which increases 5-methylTHF, caused a dose-dependent increase in both basal and DA-stimulated PLM. Growth in nucleoside-free media caused time-dependent changes in PLM, which were due to the absence of purine nucleosides. While basal PLM was maintained at a reduced level, DA-stimulated PLM was initially increased followed by a later decrease. Together, these findings indicate a close functional relationship between single-carbon folate metabolism and DA-stimulated PLM, consistent with a role for 5-methylTHF as the methyl donor for the D4R-mediated process.

Carbon Radioisotopes↗

PubMed2001

Mutational analysis of the functional role of conserved arginine and lysine residues in transmembrane domains of the murine reduced folate carrier.

The reduced folate carrier (RFC1) plays a major role in the delivery of folates into mammalian cells. RFC1 is an anion exchanger with seven conserved positively charged amino acid residues within 12 predicted transmembrane domains. This article explores the role of these residues in transport function by the development of cell lines in which arginines and lysines in RFC1 were replaced with leucine by site-directed mutagenesis. Three cell lines transfected with R131L, R155L, or R366L all lacked activity, despite high levels of protein expression in the plasma membrane, suggesting the crucial role of these amino acid residues in RFC1 function. In several mutant carriers, R26L, R42L, and K332L, there was little or no change in the influx K(t) value for MTX or influx K(i) value for folic acid. However, the R26L, R42L, and K332L carriers had decreased affinity for reduced folates. This was most prominent for K404L, which had 11- and 4-fold increases in influx K(i) for 5-methyl-THF and 5-formyl-THF, respectively, compared with L1210 cells. The marked influx stimulation observed with wild-type carrier when extracellular chloride was decreased was significantly diminished when influx was mediated by the K404L carrier, but was only slightly decreased with the R26L, R42L, and K332L mutants. This suggested that the K404 residue may be a major site of inhibition by chloride in the wild-type carrier. These studies indicate the important role that some positively charged residues within transmembrane domains of RFC1 play in RFC1 function.

Animals↗

PubMed2001

Expression and characterization of the anion transporter homologue YNL275w in Saccharomyces cerevisiae.

A search of the yeast Saccharomyces cerevisiae genome has revealed an open reading frame, YNL275w, which encodes a 576-amino acid protein that shows sequence similarity to the family of mammalian Cl-/HCO3- anion exchangers and Na+/HCO3- cotransporters. This yeast protein also has a very similar hydropathy profile to the mammalian HCO3- transporters, indicating a similar membrane topology and structure. A V5 epitope and His6-tagged version of Ynl275wp was expressed in yeast and was localized to the plasma membrane by subcellular fractionation and immunofluorescence labeling. The protein was purified by nickel affinity chromatography and was found not to be N-glycosylated. The protein's mobility on SDS-PAGE gels was not altered by treatment with N-glycanase F, alpha-mannosidase, or by mutation of each of the five consensus N-glycosylation sites. The protein did not bind to concanavalin A by lectin blotting or lectin affinity chromatography. The expressed protein bound specifically to a stilbene disulfonate inhibitor resin (SITS-Affi-Gel), and this binding could be competed by certain anions (HCO3-, Cl-, NO3-, and I-) but not by others (SO4(2-) and PO4(3-)). These results suggest that the yeast gene YNL275w encodes a nonglycosylated anion transport protein, localized to the plasma membrane.

Amino Acid Sequence↗

PubMed2001

Expression of the reduced folate carrier SLC19A1 in IEC-6 cells results in two distinct transport activities.

Intestinal absorption of folates has been characterized as a facilitative process with a low pH optimum. Studies with intestinal epithelial cells have suggested that this activity is mediated by the reduced folate carrier (RFC1). In this paper, we report on folate transport characteristics in an immortalized rat IEC-6 cell line that was found to exhibit the predominant influx activity for methotrexate (MTX) at pH 5.5 with a low level of activity at pH 7.4. Transfection of this cell line with an RFC1 construct resulted in clones exhibiting increased MTX uptake at both the pHs and high folic acid uptake only at the low pH. For the two clones with the highest level of transport activity, relative MTX influx at the two pHs was reversed. Moreover, the low pH MTX influx activity ([MTX](e) = 0.5 microM) was markedly inhibited by 20 microM folic acid while influx at neutral pH was not. Furthermore, in the presence and absence of glucose at low pH, MTX and folic acid influx activity was inhibited by azide, while MTX influx at pH 7.4 was stimulated by azide in the absence of glucose but was unchanged in the presence of glucose and azide. This was contrasted with the results of transfection of the same RFC1 construct into an L1210 murine leukemia cell line bearing a nonfunctional endogenous carrier. In this case, the activity expressed was only at pH 7.4. These data indicate that RFC1 can exhibit two distinct types of folate transport activities in intestinal cells that must depend on tissue-specific modulators.

Animals↗

PubMed2001

Expression of prostaglandin D synthase in ovarian cancer.

Lipocalin-type prostaglandin D synthase (L-PGDS) has recently been shown to be expressed in human brain tumors and breast tumors. However, L-PGDS expression has not been investigated in ovarian cancer. The objective of this study was to determine whether L-PGDS is expressed in human ovarian cancer. Lipocalin prostaglandin D synthase mRNA was cloned and sequenced by RT-PCR. Using in situ hybridization (ISH) technique, the expression of L-PGDS mRNA in 54 ovarian cancer was investigated. Expression of L-PGDS mRNA was found in tumor cells of all various types of ovarian cancers. Patterns of staining of tumor cells varied among different histological types of ovarian cancer. Significant discrepancy between the intensity of the staining and histological types of ovarian cancer could be established (p<0.01). It is reported for the first time that the expression of mRNA of L-PGDS exists in the ovarian cancer, and is related to the cancer type. This may have significance for the progress of ovarian cancer.

Base Sequence↗

PubMed2001

p16 gene methylation in colorectal cancers associated with Duke's staging.

AIM: To explore the association of methylation of the CpG island in the promotor of the p16 tumor suppressor gene with the clinicopathological characteristics of the colorectal cancers. METHODS: Methylation-specific PCR (MSP) was used to detect p16 methylation of 62 sporadic colorectal cancer specimens. RESULTS: p16 methylation was detected in 42% of the tumors.Dukes'staging was associated with p16 methylation status.p16 methylation occurred more frequently in Dukes'C and D patients (75.9%) than in Dukes'A and B patients (12.1%). CONCLUSION: p16 methylation plays a role in the carcinogenesis of a subset of colorectal cancer, and it might be linked to poor prognosis.

Colorectal Neoplasms↗

PubMed2001

[Study on the effects of DNA damage induced by cigarette smoke in male mice testicular cells using comet assay].

The mainstream whole smoke was collected using atmosphere collector-U shape glass plate absorption tube with poly-hole, and both dimethyl sulfoxide(DMSO) and phosphate buffer solution (PBS) were used as absorbents respectively. Comet assay was used to detect the effects of DNA damage of the two solutions of cigarette smoke in male mice testicular cells. The results showed that both the two solutions of cigarette smoke contained some DNA damage agents that could induce the DNA single strand breakage in male mice testicular cells. Besides, the solution of cigarette smoke absorbed by DMSO had stronger cytotoxicity and genotoxicity than the solution of cigarette smoke absorbed by PBS. The research also suggested that collecting cigarette smoke like this paper and detecting DNA damage effects using comet assay might be an ideal measure in studying male reproducible toxicity.

Animals↗

PubMed2001

[Effects of homocysteine on post-implantation rat embryo cultured in vitro].

In order to investigate the effect of homocysteine(HCY) on the development of rat embryos, the post-implantation whole embryo culture(WEC) technique was used. Neural plate stage(GD9.5) rat embryos were explanted in rat serum medium(immediately centrifugal serum, ICS) with D,L-HCY(0,0.15, 1.5,2.0,4.0,6.0,8.0,10.0 mmol/L), and cultured for 48 hours. The results showed that HCY did cause damage to embryonic development and the damages of HCY on embryos were characterized in a significant dose-response pattern. The minimum teratogenic dose of D,L-HCY was 0.15 mmol/L, the incidence of dysmorphogenic embryos was 8.33%. Significant inhibiting effects of HCY on yolk sac(including reduced yolk sac diameter, shriveled surface, small or defective yolk sac vessels) and embryonic growth and morpholological differentiation were apparent with increased HCY, while HCY were 4 mmol/L or more (P < 0.05). The abnormalities included neural tube defects, delayed cardiac tube formation, pericardial effusion, incomplete flexion, small or missing forelimb buds and irregular somites, etc. These findings suggested that HCY might exert a direct effect on embryos and a "double effect" both on yolk sac and embryos.

Animals↗

PubMed2001

Effect of pneumoperitoneal pressure on tumor dissemination and tumor recurrence at port-site and midline incisions.

Over the past several years numerous cases of port site tumor recurrence after laparoscopic resection of a cancerous tissue have been reported. Possible mechanisms for tumor seeding include tumor removal, contaminated instruments, pneumoperitoneum, and aerosolization of tumor cells. This experiment examined the relationship among trocar contamination, aerosolization, and tumor recurrence with increasing pneumoperitoneal pressure using a hamster model. Increased pneumoperitoneal pressure significantly increased both instrument contamination and tumor recurrence at midline and port site incisions. Interestingly, increasing pneumoperitoneal pressure had no significant effect on the number of aerosolized tumor cells. The results reaffirm that the use of a reduced pneumoperitoneum or gasless laparoscopy may significantly lower port site tumor recurrence.

Animals↗

PubMed2001

[Effect of pH on copper sorption by the loess and its species].

To study the effect of pH on copper sorption and species, loess was taken as sorbent in this research, and control experiments were conducted with quartz. All the curves of sorption amount-pH showed three regions, namely, sorption amount increased slowly at low pH, then increased quickly with the rise of pH, and reached the maximum amount at high pH. Copper of sorbed, exchangeable and bound to carbonate decreased with the increase in sediment concentration at constant Cu concentration, and increased with the increase in Cu concentration at constant sediment concentration. The MINTEQA2 model results showed that the proportions of precipitates and their compositions were different for loess and quartz, and the proportions of precipitates decreased with the concentrations of loess.

Adsorption↗

PubMed2001

Enhancing cytotoxic T cell responses with altered-peptide ligands.

Interest in class I MHC-mediated immunotherapy is growing rapidly. In order to fight a virus or cancer effectively, a successful immunotherapeutic must activate a large number of specific CD8+ T cells and also generate immunological memory. Attempts to generate immune responses towards tumor- or virus-derived peptides have frequently been frustrated by the nature of the peptide antigen itself. Either the peptide does not bind well to its cognate MHC, or the T cells directed towards it have been functionally inactivated in vivo. Altered-peptide ligands (APL) are an effective way to circumvent these problems. However, generating enhanced binding of altered peptides to class I MHC while still maintaining recognition of the wild-type peptide is not straightforward. Many groups design enhanced binding peptides by substituting the observed anchor residues with those that are most preferred by the class I MHC molecule. For many antigenic peptides, this approach does not work. Furthermore, if a higher affinity peptide is designed, the substitutions may result in reduced recognition by CD8+ T cells. Therefore, the design of APL requires careful testing of each candidate therapeutic in terms of affinity for class I MHC and immunological reactivity. Lastly, immunotherapy using class I MHC must also take into account the large genetic heterogeneity in the population. A therapeutic that is only effective for 5-10% of the population is not as attractive as one that works for over 90% of the population. The use of MHC supertypes (groups of class I MHC allotypes that share similar peptide-binding characteristics) shows great promise in overcoming this problem.

Amino Acid Sequence↗

PubMed2001

Intracranial aneurysms: experience in treating 500 patients.

OBJECTIVE: To summarize the experience in surgical treatment of patients with intracranial aneurysms. METHODS: The measures used in the treatment of 500 patients with intracranial aneurysms were retrospectively reviewed with regard to timing of surgery, induced-hypotensive anesthesia, brain protection combined with temporal occlusion of the feeding artery, dynamically monitoring of transcranial Doppler ultrasound, antivasospasm treatment, techniques of direct surgery, and endovascular embolization. RESULTS: In 465 patients undergoing surgery, intraoperative rupture was observed in 27(6.2%), postoperative death in 13 (2.7%), hemipalsy in 8(2.2%), and vegetative state in 2 (5.0%). The operative mortality was 3.8% in 210 patients before 1990, while 1.9% in 255 patients after 1990. CONCLUSION: The outcome of patients with intracranial aneurysms can be markedly improved by comprehensive measures.

Adult↗

PubMed2001

Histochemical study of transmyocardial laser channels in dogs.

OBJECTIVE: Laser-induced myocardial injury was investigated in a canine transmyocardial laser revascularization model. METHODS: A total of 23 channels were created in the left ventricles of 5 animals with a CO2 laser. Four animals were sacrificed immediately and one at week 2. Lactate dehydrogenase and succinate dehydrogenase in channel regions were examined with a Nitro-BT method staining. RESULTS: Immediately after the procedure, laser channels and surrounding injured myocardium could be stratified from the center to the border into 5 concentric zones, i.e., vaporized zone, carbonized zone, enzyme-disappeared zone, enzyme-decreased zone and enzyme-concentrated zone. Two weeks later, the phenomenon disappeared. CONCLUSIONS: Immediately after transmyocardial revascularization, there is a ring of enzyme-concentrated zone at the outermost region of injured myocardium. Two weeks later, enzyme activities of reversibly injured myocytes appear to have recovered.

Animals↗

PubMed2001

[Effects of aluminum intake on the content of aluminum, iron, zinc and lipid peroxidation in the hippocampus of rats].

Effect of long-term exposure to aluminum on the content of aluminum, iron, zinc, copper and the lipid peroxidation in hippocampus was studied. Sprague-Dawley rats were randomly divided into four groups by body weight. Aluminum chloride was added to diet at doses of Al3+ 0, 11.2, 55.9 and 111.9 mg/kg BW for successive 90 days. Neuro-behavioral tests consisted of open field and passive-avoidance conditioning were performed. SOD and GSH-Px activities and MDA levels were detected by spectrophotometry. The values of aluminum, iron, zinc and copper were measured by atomic absorption spectroscopy. The spontaneous motor ability in the open field and the latency of passive avoidance were decreased as compared with the controls. The concentration of aluminum was increased and iron and zinc were decreased copper was not changed significantly; the activities of SOD and GSH-Px were reduced, while the value of MDA was increased in hippocampus. The results suggested that long-term aluminum-exposure could lead to high accumulation of aluminum in hippocampus, which could disturb the normal distribution of iron and zinc, decrease the activities of antioxidase and increase the level of lipid peroxidation. Accumulation of aluminum and accompany with reduction of iron, zinc in hippocampus and oxidative damage to hippocampus might interpret the neurotoxicity of aluminum.

Aluminum↗

PubMed2001

[Preparation of restricted-access media--alkyl-diol silica (ADS) by an improved method].

Alkyl-diol silica (ADS) is a kind of restricted-access media, which can be used for direct injection and analysis of complex biological samples containing bio-macromolecules. A new economical procedure has been developed to prepare ADS packing. At first gamma-glycidoxypropyl group was coupled onto the surface of microporous silica gel (Develosil 60-5 mu) to form epoxy-silica. Prepared epoxy-silica can react with stearic acid in organic solvent to prepare C18 ester-bonded reversed-phase packing. The packing was packed into a column and then the solution of pancreatic lipase was pumped into the column to create enzymoloysis reaction. The stearyl groups on the surface of packing can be removed by the enzymolysis to form a hydrophilic surface. At the same time, inner surface of micropore remains hydrophobic nature due to size exclusion effect of micropore to enzyme molecules. Chromatographic evaluations were carried out and the typical ADS behavior was confirmed.

Chromatography, High Pressure Liquid↗

PubMed2001

[The effect of nitric oxide donor on the DNA content in Toxoplasma gondii tachyzoite].

OBJECTIVE: To determine the role of sodium nitroprusside (SNP) in regulating DNA synthesis of Toxoplasma gondii tachyzoites. METHODS: Hypodiploid peak of tachyzoite DNA induced by SNP was assessed according to DNA fragmentation. The effect of SNP on appearance of hypodiploid peak and the effect of Ca2+ on the growth of tachyzoites were evaluated. The intracellular Ca2+ chelator (BAPTA/AM), antagonist of Ca2+ channel (verapamil) and the extracellular Ca2+ chelator (EGTA) were used. The change of DNA content was measured by flow cytometry. RESULTS: SNP inhibited DNA synthesis of tachyzoites in a dose- and time-dependent pattern. The antiproliferative effect of SNP on tachyzoites was inhibited by verapamil, EGTA and BAPTA/AM. The inhibition of the growth of tachyzoites by SNP was associated with increased subploid peak through a Ca(2+)-dependent mechanism. CONCLUSION: SNP induced a hypodiploid peak in tachyzoites by altering the Ca2+ concentration in the plasma of tachyzoite, resulting in damages of the parasite.

Animals↗

PubMed2001

[Transposition of pedicled adrenal gland for the treatment of adrenal medullary hyperplasia].

OBJECTIVE: To investigate the operative modes for adrenal medullary hyperplasia. METHODS: 8 cases of adrenal medullary hyperplasia were treated with transposition of pedicled adrenal gland. The inferior and the medial blood vessel of adrenal gland were ligated. The superior blood vessel of adrenal gland was formed a 5.0- 6.0 cm pedicle and dragged to the subcutaneous of dorsum. RESULT: After follow-up for an average of 2 years, only 1 of the 8 patients did not recover as a result of psychosis and others had no symptoms but normal endocrine results. CONCLUSION: Transposition of the pedicled adrenal gland is a simple and satisfied way to treat patients with adrenal medullary hyperplasia.

Adrenal Glands↗