PubMed Health⌕ Search

Biomedical subjects

C Cao

Publications and source records attributed to C Cao.

At least 19 recordsLinked to original sources
PubMed2001

Heterologous dimerization domains functionally substitute for the double-stranded RNA binding domains of the kinase PKR.

The protein kinase PKR (dsRNA-dependent protein kinase) phosphorylates the eukaryotic translation initiation factor eIF2alpha to downregulate protein synthesis in virus-infected cells. Two double-stranded RNA binding domains (dsRBDs) in the N-terminal half of PKR are thought to bind the activator double-stranded RNA, mediate dimerization of the protein and target PKR to the ribosome. To investigate further the importance of dimerization for PKR activity, fusion proteins were generated linking the PKR kinase domain to heterologous dimerization domains. Whereas the isolated PKR kinase domain (KD) was non-functional in vivo, expression of a glutathione S-transferase-KD fusion, or co-expression of KD fusions containing the heterodimerization domains of the Xlim-1 and Ldb1 proteins, restored PKR activity in yeast cells. Finally, coumermycin-mediated dimerization of a GyrB-KD fusion protein increased eIF2alpha phosphorylation and inhibited reporter gene translation in mammalian cells. These results demonstrate the critical importance of dimerization for PKR activity in vivo, and suggest that a primary function of double-stranded RNA binding to the dsRBDs of native PKR is to promote dimerization and activation of the kinase domain.

3T3 Cells↗
PubMed2001

Ethanol-induced swelling in neonatal rat primary astrocyte cultures.

We tested the hypothesis that astrocytes swell in response to ethanol (EtOH) exposure. The experimental approach consisted of an electrical impedance method designed to measure cell volume. In chronic experiments, EtOH (100 mM) was added to the culture media for 1, 3, or 7 days. The cells were subsequently exposed for 15 min to isotonic buffer (122 mM NaCl) also containing 100 mM EtOH. Subsequently, the cells were washed and exposed to hypotonic buffer (112 mM NaCl) containing 100 mM mannitol. Chronic exposure to EtOH led to a marked increase in cell volume compared with control cells. Specific anion cotransport blockers, such as SITS, DIDS, furosemide, or bumetanide, when simultaneously added with EtOH to hyponatremic buffer, failed to reverse the EtOH-induced effect on swelling. In acute experiments, confluent neonatal rat primary astrocyte cultures were exposed to isotonic media (122 mM NaCl) for 15 min, followed by 45-min exposure to hypotonic media (112 mM NaCl, mimicking in vivo hyponatremic conditions associated with EtOH withdrawal) in the presence of 0-100 mM EtOH. This exposure led to a concentration-dependent increase in cell volume. Combined, these studies suggest that astrocytes exposed to EtOH accumulate compensatory organic solutes to maintain cell volume, and that in response to hyponatremia and EtOH withdrawal their volume increases to a greater extent than in cells exposed to hyponatremia alone. Furthermore, the changes associated with EtOH are osmotic in nature, and they are not reversed by anion cotransport blockers.

Animals↗
PubMed2001

Coexpression of microsomal-type prostaglandin E synthase with cyclooxygenase-2 in brain endothelial cells of rats during endotoxin-induced fever.

Fever is triggered by an elevation of prostaglandin E(2) (PGE(2)) in the brain. However, the mechanism of its elevation remains unanswered. We herein cloned the rat glutathione-dependent microsomal prostaglandin E synthase (mPGES), the terminal enzyme for PGE(2) biosynthesis, and examined its induction in the rat brain after intraperitoneal injection of pyrogen lipopolysaccharide (LPS). In Northern blot analysis, mPGES mRNA was weakly expressed in the brain under the normal conditions but was markedly induced between 2 and 4 hr after the LPS injection. In situ hybridization study revealed that LPS-induced mPGES mRNA signals were mainly associated with brain blood vessels, especially vein or venular-type ones, in the whole brain area. Immunohistochemical study demonstrated that mPGES-like immunoreactivity was expressed in the perinuclear region of brain endothelial cells, which were identified as von Willebrand factor-positive cells. Furthermore, in the perinuclear region of the endothelial cells, mPGES was colocalized with cyclooxygenase-2 (COX-2), which is the enzyme essential for the production of the mPGES substrate PGH(2). Inhibition of cyclooxygenase-2 activity resulted in suppression of both PGE(2) level in the CSF and fever (Cao et al., 1997), suggesting that the two enzymes were functionally linked and that this link is essential for fever. These results demonstrate that brain endothelial cells play an essential role in the PGE(2) production during fever by expressing COX-2 and mPGES.

Animals↗
PubMed2001

The ARG tyrosine kinase interacts with Siva-1 in the apoptotic response to oxidative stress.

The Abl family of mammalian nonreceptor tyrosine kinases consists of c-Abl and ARG (Abl-related gene). Certain insights are available regarding the involvement c-Abl in the response of cells to stress. ARG, however, has no known function in cell signaling. The present studies demonstrate that ARG associates with the proapoptotic Siva-1 protein. The functional significance of the ARG-Siva-1 interaction is supported by the finding that ARG is activated by oxidative stress and that this response involves ARG-mediated phosphorylation of Siva-1 on Tyr(48). The proapoptotic effects of Siva-1 are accentuated in cells stably expressing ARG and are inhibited in ARG-deficient cells. Moreover, the proapoptotic effects of Siva-1 are abrogated by mutation of the Tyr(48) site. We also show that the apoptotic response to oxidative stress is attenuated in ARG-deficient cells and that this defect is corrected by reconstituting ARG expression. These findings support a model in which the activation of ARG by oxidative stress induces apoptosis by a Siva-1-dependent mechanism.

Animals↗
PubMed2001

Localization of an insulin-like peptide in brains of two flies.

A nucleotide sequence (GenBank AI134194) was identified in the database of the Berkeley Drosophila Genome Project based on the similarity of its translated sequence to insulin-like peptides known for other insects. The putative A chain of the Drosophila peptide was synthesized and used to produce an antiserum for immunocytochemistry. Medial neurosecretory cells and their axons were immunostained in whole brains of Drosophila larvae and adults. In larvae, immunostained axons from these cells extended to the corpus cardiacum in the ring gland and the hypocerebral ganglion and along the aorta in the head. In adults, axons from these cells extended along the aorta to the corpus cardiacum-hypocerebral ganglion complex near the cardiac valve and branched along the midgut and crop. In contrast, two clusters of lateral neurosecretory cells and their axons were immunostained weakly in brains of female mosquitoes, Aedes aegypti. No other cells were stained in the nervous systems or midguts of Drosophila larvae and adults or Ae. aegypti females. These specific localizations substantiate the existence of an endogenous insulin-like peptide in Drosophila and suggest that a similar peptide is present in the distantly related mosquitoes.

Aedes↗
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

Computer simulation of temperature changes in a wheat storage bin.

A mathematical model describing the transient temperature distribution of grain in a cylindrical storage bin with mixed boundaries is presented and solved using the finite element method. Using the typical meteorological data of a region such as temperate China, temperature changes of wheat in a storage bin are simulated and analysed in detail. Simulated results indicate that high temperature accumulation areas of the grain are in the bin centre and near the bin bottom or at the top surface of the grain throughout the whole year and ventilation under appropriate weather conditions is necessary. This method can be used to develop and evaluate aeration control strategy and reduce the need for chemical treatments of grain during storage.

Journal Article↗
PubMed2001

Medial axis reformation: a new visualization method for CT angiography.

RATIONALE AND OBJECTIVES: The authors performed this study to evaluate a new method (medial axis reformation [MAR]) for visualizing three-dimensional vascular data at electron-beam computed tomographic (CT) angiography. MATERIALS AND METHODS: MAR was performed automatically with a personal computer-based workstation. After the region of interest was edited, voxels were divided into groups according to their path lengths. Centroids of groups were connected to form the medial axis. Then, the medial axis was refined with multiscale medial response. Bifurcations were also detected and refined. Finally, curved sections were generated through the branches and laid out onto a single image by using a splitting method. The authors performed MAR during electron-beam CT angiography of coronary arteries, common carotid arteries, and iliac arteries. RESULTS: MAR displayed curved sections of branched vessels on one image, cut through the axis of vessels to show the vessel diameter objectively, and allowed the viewing direction to be altered arbitrarily. CONCLUSION: Results of preliminary applications demonstrate that MAR is a valuable new visualization method for CT angiography.

Adult↗
PubMed2001

Pyrogenic cytokines injected into the rat cerebral ventricle induce cyclooxygenase-2 in brain endothelial cells and also upregulate their receptors.

Peripheral immunological insults induce interleukin (IL)-1 beta and IL-6 in the brain. To elucidate the mechanism(s) of fever evoked by these brain-derived cytokines, and possible interactions between them, we examined in rats: (i) whether cyclooxygenase-2 is responsible for fever evoked by central injection of these cytokines; (ii) if so, where in the brain cyclooxygenase-2 is induced; (iii) where the receptors for these cytokines are located; and (iv) how the expression of these receptors is influenced by the cytokines. Intracerebroventricular injection of these cytokines evoked fever that was suppressed by a cyclooxygenase-2 inhibitor. Brain endothelium was the site of cyclooxygenase-2 induction by these cytokines. IL-1 receptor (IL-1R) was constitutively expressed in brain endothelium, and its mRNA was further upregulated by either cytokine. IL-6R mRNA was constitutively expressed in the cerebral cortex, and was newly induced in as yet unidentified cells in brain blood vessels by either cytokine. Messenger RNAs for cyclooxygenase-2, IL-1R, and IL-6R were often observed in the same blood vessels. These results suggest that COX-2 induced in brain endothelium is, at least in part, involved in the fever evoked by these cytokines, and that one possible interaction between these two cytokines is mutual upregulation of their receptors in the endothelium or perivascular cells, resulting in augmentation of their actions.

Animals↗
PubMed2001

Expression of Streptococcus mutans wall-associated protein A gene in Chinese hamster ovary cells: prospect for a dental caries DNA vaccine.

The Streptococcus mutans strain GS-5 wall-associated protein A (Wap-A) is a precursor to the extracellular antigen A (AgA), a recognized candidate dental caries vaccine. The full-length wapA gene (wapA-E) and a C-terminal truncated version (wapA-G) encoding the AgA were cloned into the mammalian expression vector pcDNA 3.1/V5/His-TOPO. The resulting constructs were propagated in the Escherichia coli Top10. To investigate the expression of the S. mutans genes in mammalian cells, the above constructs were used to transfect Chinese hamster ovary (CHO) cells in the presence of the cationic lipid pfx-8. Transient expression of the wapA-E and wapA-G genes was observed at 24 h post-transfection, as shown by Western immunoblot analysis using a rabbit antiserum to S. mutans cell wall. Immunochemical staining of the transfected CHO cells showed expression of WapA mainly in the cells and budding vesicles, whereas AgA was found mainly in the transfected cells and extracellular medium. The expression of S. mutans proteins in CHO cells, in either vesicles or soluble form, suggested an antibody response to the above DNA constructs. Work is under way to test the efficacy of these as DNA vaccines against S. mutans.

Animals↗
PubMed2001

Duration and specificity of humoral immune responses in mice vaccinated with the Alzheimer's disease-associated beta-amyloid 1-42 peptide.

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by overproduction of beta-amyloid (Abeta), which is formed from amyloid precursor protein (APP), with the subsequent pathologic deposition of Abeta in regions of the brain important for memory and cognition. Recently, vaccination of murine models of AD that exhibit Abeta deposition has halted or delayed the usual progression of the pathology of AD. Our group has demonstrated that vaccination of a doubly transgenic mouse model (expressing mutant APP and presenilin-1) with the Abeta 1-42 peptide protects these mice from the memory deficits they would ordinarily develop. This report further characterizes the Abeta 1-42 peptide vaccine in mice. Anti-Abeta response time course analysis indicated that at least three vaccinations (each 100 microg) were necessary to elicit a significant anti-Abeta titer. Subsequent vaccinations resulted in half-maximal antibody titers of at least 10,000, and these titers were maintained for at least 5 months after the final boost. Peptide binding competition studies indicated that the highest humoral responses are generated against the N terminus of the Abeta peptide. Also, measurement of specific murine Ig isotypes in Abeta-vaccinated mice demonstrated a predominant IgG(1) and IgG(2b) response, suggesting a type 2 (Th2) T-helper cell immune response, which drives humoral immunity. Finally, lymphocyte proliferation assay experiments using Abeta peptides and splenocytes from vaccinated mice demonstrated that the vaccine specifically stimulates T-cell epitopes present within the Abeta peptide.

Amino Acid Sequence↗
PubMed2001

Association of vitamin D receptor gene polymorphism with periodontal diseases in Japanese and Chinese.

We examined whether polymorphisms in the vitamin D receptor (VDR) gene are associated with the incidence of adult periodontitis (AP) and early-onset periodontitis (EOP) in case-controlled studies of Japanese and Chinese subjects. Restriction fragment length polymorphisms in the VDR gene detected by digestion with Taq I were found to be significantly associated with the occurrence of AP or EOP, suggesting that the VDR genotype a risk factor for periodontitis.

Adult↗
PubMed2001

Diagnosing primary and metastatic renal cell carcinoma: the use of the monoclonal antibody 'Renal Cell Carcinoma Marker'.

The diagnosis of primary or metastatic renal cell carcinoma (RCC) can be difficult, especially in small biopsies, because of the wide variety of histologic appearances and clinical presentations that RCC can assume. An immunomarker specific for RCC is currently not available. We tested the relevant diagnostic use of the Renal Cell Carcinoma Marker (RCC Ma), a monoclonal antibody, against a normal human proximal tubular brush border antigen. Immunostaining using RCC Ma and the avidin-biotin-peroxidase complex technique was performed on archival tissues from primary and metastatic tumors of renal or nonrenal origin. A total of 122 of 153 primary RCCs (79.7%) were positive [clear cell (84%), papillary (96%), chromophobe (45%), sarcomatoid (25%), and collecting duct (0%)], with > or =10% of tumor cells stained in 93% of cases. None of the 64 primary renal tumors other than RCC, including 15 oncocytomas, was positive. Fifteen of 146 (10.2%) nonrenal primary tumors were positive (5 of 17 breast tumors, 8 of 8 parathyroid adenomas, and 2 of 7 embryonal carcinomas). Forty-two of 63 (67%) metastatic RCCs were positive with > or =10% of cells being stained in 83% of them. Two of 108 (2%) metastases from tumors other than RCCs were positive, both of which were metastatic breast carcinomas; however, only 10% (2 of 19) of metastatic breast carcinomas were positive. RCC Ma is an excellent marker for primary RCC, which should facilitate its diagnosis in a small biopsy. Although RCC Ma remains highly specific (98%) for metastatic RCC, a negative result may not rule out metastatic RCC because of a rather low sensitivity and a focal staining pattern in some of the positive cases. RCC Ma may also facilitate the differential diagnosis between oncocytoma and other types of RCC when they are composed mostly of eosinophilic cells.

Antibodies, Monoclonal↗
PubMed2001

A four-day study to evaluate the anti-plaque efficacy of an experimental triclosan-containing dentifrice.

Four-day, non-brushing studies have been used successfully to demonstrate the anti-plaque efficacy of triclosan-containing dentifrices. The treatment effects observed are variable, likely due to differences in formulation, study design and measurement techniques. This randomized, double-blind crossover study was conducted to evaluate the anti-plaque efficacy of an experimental, multiple-benefit, triclosan-containing dentifrice versus two currently marketed sodium fluoride dentifrices in a four-day, lingual-brushing model on subjects in Beijing. People's Republic of China. Subjects brushed the lingual surfaces for 30 seconds, and before expectorating, swished the saliva/dentifrice slurry over the buccal surfaces for an additional 30 seconds. This procedure was repeated. Subjects performed their assigned brushing regimen twice daily for four days under supervision. On Day 5, plaque was measured using the Turesky Modification of the Quigley-Hein Plaque Index. There were highly significant treatment effects in favor of the experimental triclosan-containing dentifrice for whole mouth, buccal and lingual sites when compared to either of the sodium fluoride dentifrices (p < 0.0001).

Adolescent↗
PubMed2001

[A study on affecting factors on dental care demands by logistic regression model].

OBJECTIVE: To develop probability model for dental visits based on analysis of the factors affecting people's dental services utilization in urban area of Beijing, thus providing some evidence for forecasting further demanded dental care and building the more efficient oral health care delivery system. METHODS: A cross-sectional survey was conducted amnog 1,517 subjects of all age groups in Beijing selected by stratified, clustering, random sampling. The first model of dental care demand--probability model for dental visits was established with logistic regression. RESULTS: Awareness of oral health showed the most important relationship. Different social background and economic factors also had great effects on demand. Higher demand for care were existed among those who suffered from a disease that was painful or resulted in poor oral function. CONCLUSIONS: It is suggested that dental care has different characters from general health service. Utilization of dental service is largely determined by people's awareness, income and insurance system. So oral health education should be extended in order to promote the effective demands and reduce the potential demands. Rational oral health insurance system should be set up to provide some priority to certain people, thus stimulating the supply of dental care and improving the utilization of dental service. Since raising price for care will restrain the low-incomer's basic demand, and it will neither add the profit nor improve people's oral health, the price decision should be considered carefully. At last, oral health care should be emphasized on children and adolescent as priority age groups based on the conclusion from demand model.

Dental Care↗
PubMed2001

[A study on the bioavailability of fluoride added into milk].

OBJECTIVE: To assess the bioavailability of fluoride added into milk. METHODS: Eight subjects were studied by testing fluoride levels in blood and urine samples collected after drinking fluoridated milk and fluoridated water respectively, according to pharmacokinetics and cross control method. RESULTS: The bioavailability of fluoride in fluoridated milk reached 80.2% in blood analysis and 84.8% in urine analysis. The result was about 20.0% lower as compared with fluoridated water. CONCLUSION: Fluoride bioavailability in fluoridated milk is still high and sufficient.

Adult↗
PubMed2001

[The efficacy of the chlorhexidine chip following scaling and root planing (SRP) and compared to SRP alone].

OBJECTIVE: To evaluate the clinical efficacy and safety of the adjunctive use of Chlorhexidine Chip (CHX; commercial name, Perio Chip) following scaling and root planing (SRP) in periodontitis. METHODS: One center, blinded, randomized, split-mouth and active control study was designed. Sixty-five adult periodontitis patients were enrolled into the baseline after SRP. Each subject had at least one tooth with pocket depth of 5 mm or more and bleeding on probing (BOP) in each side of the mouth. Then the tooth was selected as a target and its parameters of probing depth (PD), attachment loss (AL), BOP, gingival index (GI), plaque index (PI) and staining index (SI) were recorded. Each side of mouth was randomly assigned to one of two treatments--drug placement after SRP or SRP alone. All the adverse events and parameters were recorded at time of 3-month, 6-month and meanwhile the patients received oral hygiene instruction and scaling. The same was conducted at 6-week, 4.5-month except for recording of parameters and scaling of the target teeth. RESULTS: Reduction of PD and gain of attachment at 6-month in group of SRP plus CHX (1.32 mm, 0.94 mm) were significantly higher than those in group of SRP alone (0.77 mm, 0.40 mm) (P < 0.001). Forty-four point six percent (44.6%) of patients reflected adverse reactions related to drug placement. Toothaches, the main reactions, were mild to moderate in nature and spontaneously resolved within 2-4 days. CONCLUSIONS: The chlorhexidine chip is indeed a safe and effective control-delivered drug for topical use when patient in his supportive periodontal therapy.

Adult↗