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X Cai

Publications and source records attributed to X Cai.

At least 145 records · Page 8Linked to original sources
PubMed1997

APOE is linked to Alzheimer's disease in a large pedigree.

Although previous association studies have demonstrated that the APOE4 allele is a risk factor for Alzheimer's disease (AD), its value for the prediction of AD in individuals is <100%. The limited predictive value of epsilon4 is also seen in multiply affected families where the epsilon4 allele is not tightly linked to AD. We analyzed a large pedigree multiply affected with AD by lod score linkage analysis at the known loci associated with AD. In this pedigree, the APOE/APOCI gene area was linked to the development of AD, while no linkage was detected to any of the other loci known to be associated with the disease. In this family, then, the inheritance of an epsilon4 allele is highly associated with the early development of the disease (mean age of onset, 62 years), and is a good predictor of disease. However, given the wealth of evidence for association, but not linkage, of APOE4 to AD, we believe this finding suggests that another factor (or factors) interact(s) with APOE to precipitate early disease, and produce positive linkage results. The nature of this factor presently remains unknown.

Age of Onset↗
PubMed1997

Interactions of the amino-terminal noncollagenous (NC1) domain of type VII collagen with extracellular matrix components. A potential role in epidermal-dermal adherence in human skin.

Type VII collagen, the major component of anchoring fibrils, consists of a central collagenous triple-helical domain flanked by two noncollagenous domains, NC1 and NC2. The NC1 domain contains multiple submodules with homology to known adhesive molecules including fibronectin type III-like repeats and the A domain of von Willebrand factor. In this study, we produced the entire NC1 domain of human type VII collagen in the stably transfected human kidney 293 cell clones and purified large quantities of the recombinant NC1 protein from serum-free culture media. The recombinant NC1 formed interchain disulfide-bonded dimers and trimers and was N-linked glycosylated. Tunicamycin inhibited the cellular secretion of NC1, suggesting that N-linked glycosylation may play a role in NC1 secretion. The recombinant NC1 was indistinguishable from the authentic NC1 obtained from human amnions or WISH cells with respect to N-linked sugar content, electrophoretic mobility, rotary shadow imaging, and binding affinity to type IV collagen. Purified recombinant NC1, like authentic NC1, also bound specifically to fibronectin, collagen type I, and a laminin 5/6 complex. Both monomeric and trimeric forms of NC1 exhibited equal affinity for these extracellular matrix components, suggesting that the individual arms of NC1 can function independently. The multiple interactions of NC1 with other extracellular matrix components may support epidermal-dermal adhesion.

Amnion↗
PubMed1997

Use of arsenic trioxide (As2O3) in the treatment of acute promyelocytic leukemia (APL): I. As2O3 exerts dose-dependent dual effects on APL cells.

Recent clinical studies in China showed that As2O3 is an effective and relatively safe drug in the treatment of acute promyelocytic leukemia (APL). We found previously that As2O3 can trigger apoptosis of APL cell line NB4 cells, which is associated with downregulation of bcl-2 gene expression and modulation of PML-RAR alpha chimeric protein. To further understand the mechanisms of this alternative therapy for APL, we investigated in this report the effects of a wide range of concentrations of As2O2 on cultured primary APL cells, all-trans retinoic acid (ATRA)-susceptible (NB4 cells) and ATRA-resistant (MR2 subclone) APL cell lines. The results indicated that As2O3 had dose-dependent dual effects on APL cells: inducing preferentially apoptosis at relatively high concentrations (0.5 to 2 micromol/L) and inducing partial differentiation at low concentrations (0.1 to 0.5 micromol/L). The rapid modulation and degradation of PML-RAR alpha proteins, which was induced by As2O3 at 0.1 to 2 micromol/L, could contribute to these two effects. Bone marrow and peripheral blood examination showed that myelocyte-like cells, probably as a result of partial in vivo differentiation, and degenerative cells increased after 2 to 3 weeks of continuous in vivo As2O3 treatment when leukemic promyelocytes decreased. In conclusion, combination of induction of apoptosis and partial differention could be the main cellular mechanisms of As2O3 in the treatment of APL, and PML-RAR alpha could play an important role in determining the specific effects of As2O3 on APL cells.

Antineoplastic Agents↗
PubMed1997

No association between the intronic presenilin-1 polymorphism and Alzheimer's disease in clinic and population-based samples.

Mutations in the Presenilin 1 (PS1) gene on chromosome 14 cause most early-onset familial Alzheimer's disease (AD). An intronic polymorphism in the PS1 gene was recently identified and reported to be associated with late-onset AD [Wragg et al., Lancet 347: 509-512, 1996]. The authors found an excess of homozygotes for the more common allele (allele 1) in AD cases, associated with an approximate doubling of risk. In the present study, we report the PS1 polymorphism distributions in clinic and population-based samples. We were not able to replicate the findings of Wragg et al. [1996]. Our results are consistent with those of other researchers and do not support the conclusion that the PS1 polymorphism is associated with late-onset AD.

Alleles↗
PubMed1997

Modulation of type VII collagen (anchoring fibril) expression by retinoids in human skin cells.

We examined the effects of retinoids on the expression of type VII collagen, a major component of anchoring fibrils, in human keratinocytes and amnion cells (WISH). All-trans retinoic acid (RA) (5 X l0(-6) M) decreased the steady-state levels of type VII collagen mRNA by at least 80% after 18 h. The inhibition was evident within 6 h after the addition of RA, maximal at 18 h, and was dose-dependent. Reduction of type VII mRNA expression also occurred when cell cultures were incubated with retinol, retinal, and 13-cis RA. Retinoid-mediated inhibition of type VII collagen mRNA expression was observed in keratinocytes growing in either serum-free keratinocyte growth medium (KGM) or KGM supplemented with 1.4 mM Ca2+. Cycloheximide blocked RA-mediated inhibition of type VII collagen mRNA, demonstrating the need for de novo protein synthesis. The mRNA levels for fibronectin and glyceraldehyde phosphate dehydrogenase were not affected by the retinoids, suggesting selective inhibition on type VII collagen expression. In addition, the decrease in type VII collagen mRNA was accompanied by a parallel decrease in secretion of the 290 kDa, type VII collagen alpha chains.

Amnion↗
PubMed1997

Expression cloning of a mammalian amino acid transporter or modifier by complementation of a yeast transport mutant.

A cDNA clone named L21 was isolated from L6 rat muscle cells by complementation of a yeast proline transport mutant. L21 cDNA has 2,268 bp and codes for a peptide of 228 amino acids with four potential transmembrane domains. The amino acid sequence of L21 shows no homology to any known proteins. Expression of L21 cDNA enables the mutant yeast to grow in proline as the sole nitrogen source and to transport proline, alpha-aminoisobutyric acid (AIB) and leucine. The Km for proline is about 1.0 mM. The substrate specificity of L21 expressed in yeast shows no striking similarity to known mammalian amino acid transporters.

Amino Acid Sequence↗
PubMed1997

No association between the very low density lipoprotein receptor gene and late-onset Alzheimer's disease nor interaction with the apolipoprotein E gene in population-based and clinic samples.

It is now commonly known that possession of one of the three common alleles of the apolipoprotein E (APOE) gene (allele epsilon 4) confers an increased risk for both familial and sporadic Alzheimer's disease (AD), and that this risk is dose-dependent. Other genes that may play a role in AD, either through independent association with the disease or through modification of the existing APOE risk, are under investigation. One such gene, the very low density lipoprotein receptor (VLDL-R) gene, was reported by Okuizumi et al. to be independently associated with AD in a Japanese population, but not interactive with the APOE4 conferred risk. Their clinic-based data set demonstrated a 2-fold increased risk conferred by the 5-repeat allele of a polymorphism in VLDL-R. As recruitment from a clinic rather than a population-based sample may result in a distortion of allele frequencies, as has been shown with APOE allele frequencies, it is important to investigate this association in a population-based study. We have genotyped both population and clinic-based AD data sets at this VLDL-R polymorphism, and we find no independent association between the VLDL-R gene and the occurrence of AD in either sample. Further, despite the biochemical relationship between the VLDL-R and APOE proteins, we find no significant statistical interaction between the alleles at these loci.

Age of Onset↗
PubMed1997

Characterization of colorectal-cancer-related cDNA clones obtained by subtractive hybridization screening.

In an attempt to seek out new factors that are related to colorectal carcinogenesis at the molecular level, subtractive hybridization between cDNA of normal mucosal tissues and mRNA of colorectal carcinoma tissues was performed. Subsequent screenings of the cDNA libraries, constructed from normal mucosal tissues, using the "subtractive probes" generated a total of 46 clones that were expressed in normal mucosa but were either expressed at a significantly reduced level or not expressed at all in cancer tissues. Partial nucleotide sequences of all of these cDNA clones were determined, and sequence homology analyses were performed with the Genbank database. Of the 46 cDNA samples, 44 contained substantial sequence homologies with 32 immunoglobulin gene fragments, a helix-loop-helix basic phosphoprotein gene, an acidic ribosomal phosphoprotein P2 gene, a BLR1 gene for Burkitt's lymphoma receptor 1 gene, D5S419 DNA segment containing (C-A) repeats, a glucokinase (GCK) gene, a Na+, K+-ATPase alpha-subunit gene, a histocompatibility system HLA-DR heavy-chain gene, a dystrophic gene, a mucin (MUC2) gene, a mu-glutathione S-transferase gene, a Menkes disease protein gene, and a 40-kDa keratin intermediate filament precursor gene. The remaining two cDNA clones (now registered under GenBank accession numbers U17714 and U20428) showed few (less than 60%) sequence homologies with any known sequences in the GenBank database and, therefore, may represent novel genes whose expression was down-regulated in human colorectal carcinomas. The possible clinical significance of these findings and the involvement of these two genes in the carcinogenesis of colorectal as well as other cancers are being investigated.

Base Sequence↗
PubMed1997

Nucleic-acid immobilization, recognition and detection at chronopotentiometric DNA chips.

Wide-scale DNA testing requires the development of fast, small, easy-to-use biosensing devices. Various synthetic oligonucleotides and DNA have thus been immobilized onto microfabricated thick-film carbon transducers for performing several new nucleic-acid assay protocols. These include hybridization detection of nucleic acid sequences, determination of small molecules (drugs, pollutants) based on their collection into the dsDNA layer or via monitoring their effect upon the intrinsic DNA oxidation signal, and direct adsorptive stripping measurements of ultratrace levels of nucleic acids. Transduction of these DNA recognition processes is accomplished by a new highly-sensitive constant-current stripping chronopotentiometric operation. Comparison to traditional electrodes indicates that the biosensing performance is not compromised by the use of mass-producible disposable transducers. Such thick-film DNA biosensors have been coupled to a compact, user-friendly, hand-held analyzer. Applicability for the detection of sequences from M. tuberculosis and HIV-1 DNAs is illustrated. Such activity in the author's laboratory, aimed at developing DNA-coated screen-printed electrodes, is reviewed.

Biosensing Techniques↗
PubMed1997

Analysis of the solubilization of steroids by bile salt micelles.

Bile salt mixed micelles play an important role in the emulsification, solubilization, and absorption of cholesterol, fats, and lipid-soluble vitamins. Studies have also revealed the importance of wetting and solubilization of drugs by the bile salts; however, the capacity and specificity of bile salt simple and mixed micelles for solubilization are still undefined. Thus, in this study the aqueous solubility and the extent of solubilization in bile salt micellar solutions of a series of steroids were determined. The melting point and enthalpy of fusion were measured to determine the ideal mole fraction solubility of each steroid. From the ideal mole fraction solubility and the observed solubility of each steroid, the activity coefficient of each steroid in solution was calculated with respect to the supercooled pure liquid as the standard state. In aqueous solution, the activity coefficients decreased with increasing number of hydroxyl groups on the steroids. This trend also occurred in the bile salt solutions, although the values of the activity coefficients were smaller by about three orders of magnitude. The stereochemical position of the hydroxyl groups influenced the rank order of the activity coefficients in the aqueous and micellar solutions. Incorporation of a fluoro or methyl group resulted in an increase in the activity coefficient, whereas aromatization of the A ring of the steroid frame markedly decreased the activity coefficient. The results for the aqueous solubility are consistent with the expected interaction of the functional groups with the polar environment. The relatively small activity coefficients observed with the micellar solutions result from the nonpolar environment of the aggregates. However, the similarity of the relationship between the activity coefficient and the number of hydroxyl groups in the aqueous and micellar solutions indicates the importance of polar interactions for solubilization. These results may provide new insight into the solubilization of steroids by bile salt micellar solutions and may provide a basis for predicting solubilization of other compounds by bile salt aggregates.

Bile Acids and Salts↗
PubMed1997

Characterization of a soluble IL-6 receptor alpha mutant C277D/H280I expressed in E.coli.

The pleiotropic cytokine interleukin-6(IL-6) triggers the formation of a high affinity receptor complex constituted by the ligand-binding subunit IL-6 receptor alpha (IL-6R alpha) and the signal transducer gp130. To construct the antagonist of IL-6, a DNA segment encoding the soluble human IL-6R alpha (shIL-6R alpha) mutant with two substitutions C277D/H280I was generated by overlap extension polymerase chain reaction. The DNA segment was then subcloned into vector pET-3b and expressed in E.coli at a high level. The refolded and purified recombinant protein, which was designated as DM650, exhibited an increased IL-6-binding capability by 8-fold. DM650 antagonized IL-6 perfectly, resulting in the growth-inhibition of human myeloma AF-10 cells. DNA fragmentation assay proved that the growth of AF-10 cells was inhibited through the induction of apoptosis suppressed by IL-6.

Antigens, CD↗
PubMed1997

Development of an ELISA for rapid detection of anti-type VII collagen autoantibodies in epidermolysis bullosa acquisita.

Epidermolysis bullosa acquisita (EBA) is an acquired blistering skin disease characterized by the presence of IgG autoantibodies to type VII collagen. EBA autoantibodies recognize four major immunodominant epitopes localized within the amino-terminal, noncollagenous (NC1) domain. In this study, we developed a rapid, quantitative enzyme-linked immunosorbent assay (ELISA) to detect autoantibody activity against the complete NC1 domain of type VII collagen with the use of an eukaryotic-expressed, recombinant human NC1 antigen. With the ELISA, we tested serum from patients with EBA (n = 24), bullous systemic lupus erythematosus (BSLE) (n = 3), bullous pemphigoid (n = 16), pemphigus (n = 11), and normal controls (n = 12). All EBA and BSLE serum, including four sera that were negative by indirect immunofluorescence, demonstrated reactivity with immobilized NC1 in the ELISA. In contrast, none of the sera from healthy control subjects or patients with unrelated blistering skin diseases reacted with NC1. The EBA sera also reacted with recombinant NC1 by immunoblot analysis but with less sensitivity. Thus, the newly developed ELISA using recombinant NC1 is a sensitive, specific assay and a useful tool for rapidly screening EBA and BSLE serum.

Autoantibodies↗
PubMed1997

Polyomavirus major capsid protein VP1 is capable of packaging cellular DNA when expressed in the baculovirus system.

Using the p2Bac dual multiple cloning site transfer vector, the polyomavirus major capsid protein gene VP1 was cloned for expression in the baculovirus-insect cell expression system. The 5-day-infected cellular lysate from this recombinant preparation was purified by cesium chloride density gradient centrifugation. Capsid-like particles were observed in the resulting preparation. The purified particle preparation was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and was shown to have accurately expressed the polyomavirus VP1 protein as cloned. It was found that the preparation revealed the presence of host histones in the stained gels, which is indicative of DNA packaging. To determine if cellular DNA was being packaged in the particles, Sf9 insect cells were prelabeled with [3H] thymidine. The label was removed, and the cells were subsequently infected with a recombinant Autographa californica multiple nuclear polyhedrosis virus (AcMNPV) carrying the polyomavirus VP1 gene. Upon purification through three cesium chloride gradients and DNase I treatment, capsid-like particles, containing [3H]thymidine-labeled DNA, were isolated which were found to coincide with hemagglutination activity. Studies have indicated that the AcMNPV appears to have the ability to fragment Sf9 cellular DNA. When infected with the recombinant AcMNPV carrying the VP1 gene of polyomavirus, these host DNA fragments are being packaged by the VPI major capsid protein; further, these DNA fragments have been shown to be approximately 5 kb in size, which corresponds to the size of the native polyomavirus genome. These studies demonstrate that the recombinant polyomavirus VP1 protein has the ability to package DNA in the absence of the minor structural proteins VP2 and VP3 and independently of the polyomavirus T antigens.

Animals↗
PubMed1997

[Inhibition effect of p53 antisense RNA on malignant phenotype of colorectal cancer cells].

OBJECTIVE: Inhibition effect of p53 antisense RNA on malignant phenotype of colorectal cancer cells was studied. METHODS: For the purpose of inhibiting tumorigenecity of mutant p53 gene in colorectal cancer cells, a 2.1 kb human p53 full length cDNA was inserted into a mammalian expression vector pREP9 to make a p53 antisense RNA expression vector pREP9-p53 (AS). pREP9-p53 (AS) was then introduced into human colorectal cancer cell line SW1116 (with mutated endogenous p53). MTT method and FCM analysis were performed to measure the effect of p53 antisense RNA expressed by pREP9-p53 (AS) on SW1116 cell cycle progression. RESULTS AND CONCLUSION: It was shown that the growth rate of SW1116 cells with pREP9-p53 (AS) was significantly suppressed by the expression of p53 antisense RNA as compared to the control SW1116 cells and SW1116 cells with pREP9 vector alone. FCM analysis showed that SW1116 cells with pREP9-p53 (AS) were arrested at G0/1 phase, whereas no significant influence can be observed on control SW1116 cells with pREP9.

Cell Division↗
PubMed1997

[Assignment of a novel colorectal cancer-associated gene HSU17714 gene to human chromosome band 22q13 by in situ hybridization].

OBJECTIVE: To identify the chromosomal localization of novel colorectal cancer-related gene HSU17714. METHODS: Enhanced fluorescence in situ hybridization technique was applied with tyramine as the enhancer. RESULTS: 80%(128/160) interphase and 60% (104/174) metaphase cells showed obvious hybridization signals of HSU17714. 85%(40/47) metaphase cells showed hybridization signals at 22q13 in the fluorescence R-banding assay. CONCLUSION: HSU17714 is assigned to human chromosome 22q13.

Chromosomes, Human, Pair 22↗
PubMed1997

[Determination of minor flavor components in Chinese spirits by direct-injection technique with capillary columns].

Chinese spirits are among the best-known distilled alcoholic beverages in the world. Because of the longer multiple-strain fermentation, Chinese spirits are richer than yeast fermented western liquors in fragrance and mellow. The complex nature of Chinese spirits often makes it difficult to separate, identify and quantify major and minor flavor components. Among the several analytical methods for flavor components in Chinese spirits developed in recent years, the direct-injection technique using capillary columns is by far the best. In this study of direct injection with crosslinked PEG 20M, HP-INNOWax and bonded SGE BP21 columns, up to 68 flavor components including alcohols, organic acids, esters, acetals, carbonyl and heterocyclic compounds were identified with fine-tuning separation and followed by GC/MS to identify. The gas chromatographic separation of flavour components of Maotai Liquor by the method on PEG 20M, SGE BP21 and HP-INNOWax are shown. The compounds of the numbered peaks in the chromatograms are listed. Three compounds of, ie., amyl acetate, t-pentanol and 2-ethyl butyric acid, were used as internal standards to minimize discrimination in quantitative determination. The operation procedures for these tests were provided. The application identities of three capillary columns for the analysis of minor flavor components with direct injection were summarized respectively.

Flavoring Agents↗
PubMed1997

Screening and identification of down-regulated genes in colorectal carcinoma by subtractive hybridization: a method to identify putative tumor suppressor genes.

OBJECTIVE: To search for new putative tumor suppressor genes in colorectal carcinoma. METHODS: Subtractive hybridization technologies were applied to screen and select genes, the expression of which was down-regulated in colorectal carcinoma. mRNAs uniquely expressed in normal cells but not in colorectal carcinoma were recovered as cDNA (sub-cDNA) after two rounds of subtractive hybridization with mRNA prepared from colorectal carcinoma. The sub-cDNAs were then used as probes to screen a normal human colon cDNA library constructed in lambda-Zap II phage. The DNAs of positive clones were in vivo excised, and partial DNA sequences were analyzed and compared with DNA sequence database Genbank. RESULTS: A total of 46 different clones with an average of about 1 kilobases in transcript size was recovered. Among these 46 down-regulated genes in colorectal carcinoma were genes encoding immunoglobulin (n = 32), 40-kDa keratin intermediate filamentous protein or IFP (n = 1), major histocompatibility complex-related protein (n = 1), unrelated structural proteins (n = 10) and gene products yet to be identified (n = 2). RNA dotblot hybridizations confirmed that all 46 clones contained genes that were down-regulated and have not been reported before in colorectal carcinoma. CONCLUSION: The results of this study suggested that the 46 clones were down-regulated in colorectal carcinoma, they should be further studied as new putative tumor suppressor genes and could be used as new tumor markers of colorectal carcinoma.

Colorectal Neoplasms↗