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Biomedical subjects

X Hua

Publications and source records attributed to X Hua.

At least 37 records · Page 2Linked to original sources
PubMed1998

Synergistic cooperation of TFE3 and smad proteins in TGF-beta-induced transcription of the plasminogen activator inhibitor-1 gene.

Members of the TGF-beta superfamily influence a broad range of biological activities including stimulation of wound healing and inhibition of cell growth. TGF-beta signals through type I and II receptor serine/ threonine kinases and induces transcription of many genes including plasminogen activator inhibitor-1 (PAI-1). To identify proteins that participate in TGF-beta-induced gene expression, we developed a novel retrovirus-mediated expression cloning strategy; and using this approach, we established that transcription factor microE3 (TFE3) is involved in TGF-beta-induced activation of the PAI-1 promoter. We showed that TFE3 binds to an E-box sequence in PE2, a 56-bp promoter fragment of the PAI-1 promoter, and that mutation of this sequence abolishes both TFE3 binding as well as TGF-beta-dependent activation. TFE3 and Smad3 synergistically activate the PE2 promoter and phosphorylated Smad3 and Smad4 bind to a sequence adjacent to the TFE3-binding site in this promoter. Binding of both TFE3 and the Smad proteins to their cognate sequences is indispensable for TGF-beta-inducible activation of the PE2 promoter. Hence, TFE3 is an important transcription factor in at least one TGF-beta-activated signal transduction pathway.

Basic Helix-Loop-Helix Leucine Zipper Transcriptio↗
PubMed1998

Cloning and expression of phenylalanine ammonia lyase cDNA in Escherichia coli.

The phenylalanine ammonia lyase (PAL) cDNA was amplified from Petroselinum crispum RNA by using the RT-PCR technique. The amplified 2.2 kb DNA fragment was sequenced and inserted into expression vector pET23b. The resulting plasmid pET23bPAL was then transformed into E. coli JM109DE3. The expressed PAL protein in JM109DE3 (pET23bPAL) accounted for more than 15% of total proteins in the engineering E. coli cells. The activity and specificity of the expressed PAL was identified and tested by using HPLC technique. The results indicated that the PAL activity was good enough for application to enzymatic therapy of phenylketonurea (PKU).

Apiaceae↗
PubMed1997

[Distribution of 70kDa heat shock protein in rabbit brains after heat stress and heat stroke].

OBJECTIVE: Evaluation of the relationship between the induction of 70kDa heat shock protein in rabbit brains and heat stress. METHODS: HSP70 was detected using monoclonal antibody by ABC method in rabbit hypothalamus, hippocampus and cerberal cortex. RESULTS: Intense HSP70 staining was displayed in rabbit brains of the heat stroke group (rectal temperature 43 degrees C to death). Positive cells were distributed mainly in the CA1, CA2 regions of the hippocampus; granular cell layer I and pyramidal layer (II) of the cerebral cortex; and the periventricular area of hypothalamus. HSP70-psoitive substances were localized in the cytoplasm and neuronal processes, a few neurons exhibited dark staining nucle. Hosever, the rabbit brains of the general heat stress group (rectal temperature 42.0 degrees C, 30 minutes) had much weaker staining. CONCLUSION: Hyperthermia causes neuronal expression of HSP70, particularly under strong heat stress, and may be sustained till death.

Animals↗
PubMed1997

Clinical therapeutic effect of drug-separated moxibustion on chronic diarrhea and its immunologic mechanisms.

In the present paper it was reported that 24 cases of ulcerative colitis and 23 cases of chronic colitis were treated by drug-separated moxibustion and the total effective rates were 95.83% and 95.65% respectively, which were markedly superior to that of western medicine group. Observation in 15 cases of ulcerative colitis showed that drug-separated moxibustion could inhibit humoral immunity and elevate cellular immune function. The therapy possibly regulated the abnormal ratio of T-lymphocyte subgroups and corrected the abnormal state of autoimmunity of patients, so that pathological changes of intestinal mucosa were corrected effectively.

Adult↗
PubMed1997

[Three-dimensional finite element stress analysis of magnetical retaining and bar retaining in overdenture implants].

The purpose of this study was to determine which type of denture retaining implants can produce better biomechanical effect on the bone tissue. Two mechanical models of magnetically retained complete overdenture supported by osseo-integrated implant and bar-retained complete over denture supported by osseo-integrated implant were made. The peak stress in mandibular peri-implant bone tissue of the models were studied under the same loading conditions vertically and horizontally by three-dimensional FEM stress analysis. The results were as follows: (1) Both types of dentures retention can produce significant stress effect on the peri-implant and other regions of the jaw bone and (2) Magnetical retention is more beneficial to maintenance both of peri-implant bone tissue and long-term success of denture supported by osseo-integrated implant than bar retention does.

Dental Implantation, Endosseous↗
PubMed1996

Recurrent G-to-A substitution in a single codon of SREBP cleavage-activating protein causes sterol resistance in three mutant Chinese hamster ovary cell lines.

Oxygenated sterols such as 25-hydroxycholesterol kill Chinese hamster ovary cells because they inhibit the proteolytic processing of sterol regulatory element binding proteins (SREBPs), a pair of membrane-bound transcription factors that activate genes controlling cholesterol synthesis and uptake from lipoproteins. The unprocessed SREBPs remain membrane-bound, they cannot activate the cholesterol biosynthetic pathway, and the cells die of cholesterol deprivation. Several sterol-resistant hamster cell lines have been isolated previously by chemical mutagenesis and selection for resistance to killing by 25-hydroxycholesterol. We recently identified the defect in one such cell line (25-RA cells) as a point mutation in a newly discovered membrane protein of 1276 amino acids, designated SREBP cleavage-activating protein (SCAP). The mutation in the 25-RA cells resulted from a G-to-A transition in codon 443 of the SCAP gene, changing aspartic acid to asparagine. Wild-type SCAP, when overexpressed by transfection, stimulates the proteolytic processing of both SREBPs. The D443N substitution is an activating mutation that increases the activity of SCAP and renders it resistant to inhibition by 25-hydroxycholesterol. We here report the identical G-to-A transition in two additional lines of Chinese hamster ovary cells that were mutagenized and isolated by a similar protocol. The three mutations occurred independently as indicated by haplotype analysis of the mutant genes using two intragenic sequence polymorphisms. All three cell lines were mutagenized with alkylating agents (nitrosoethylurea or ethylmethane sulfonate) that favor G-to-A transitions. Nevertheless, the finding of the same nucleotide substitution at the same location in all three cell lines indicates that SCAP may be unique in its ability to stimulate SREBP cleavage, and residue 443 is a crucial determinant of the protein's ability to be inhibited by 25-hydroxycholesterol.

Adenine↗
PubMed1996

Sterol resistance in CHO cells traced to point mutation in SREBP cleavage-activating protein.

Through expression cloning we have isolated a cDNA-encoding SREBP cleavage-activating protein (SCAP), which regulates cholesterol metabolism by stimulating cleavage of transcription factors SREBP-1 and -2, thereby releasing them from membranes. The cDNA was isolated from Chinese hamster ovary cells with a dominant mutation that renders them resistant to sterol-mediated suppression of cholesterol synthesis and uptake. Sterol resistance was traced to a G-->A transition at codon 443 of SCAP, changing aspartic acid to asparagine. The D443N mutation enhances the cleavage-stimulating ability of SCAP and renders it resistant to inhibition by sterols. SCAP has multiple membrane-spanning regions, five of which resemble the sterol-sensing domain of HMG CoA reductase, an endoplasmic reticulum enzyme whose degradation is accelerated by sterols. SCAP appears to be a central regulator of cholesterol metabolism in animal cells.

Amino Acid Sequence↗
PubMed1996

Sterol-regulated release of SREBP-2 from cell membranes requires two sequential cleavages, one within a transmembrane segment.

Sterol regulatory element binding proteins (SREBPs) are transcription factors attached to the endoplasmic reticulum. The NH2-segment, which activates transcription, is connected to membranes by a hairpin anchor formed by two transmembrane sequences and a short lumenal loop. Using H-Ras-SREBP-2 fusion proteins, we show that the NH2-segment is released from membranes by two sequential cleavages. The first, regulated by sterols, occurs in the lumenal loop. The second, not regulated by sterols, occurs within the first transmembrane domain. The liberated NH2-segment enters the nucleus and activates genes controlling cholesterol synthesis and uptake. Certain mutant Chinese hamster ovary cells are auxotrophic for cholesterol because they fail to carry out the second cleavage; the NH2-segment remains membrane-bound and transcription is not activated.

Amino Acid Sequence↗
PubMed1996

Regulated cleavage of sterol regulatory element binding proteins requires sequences on both sides of the endoplasmic reticulum membrane.

Sterol regulatory element binding proteins (SREBP-1 and SREBP-2) are attached to the endoplasmic reticulum (ER) and nuclear envelope by a hairpin domain consisting of two transmembrane regions connected by a short lumenal loop of approximately 30 hydrophilic amino acids. In sterol-depleted cells, a protease cleaves the protein in the region of the first transmembrane domain, releasing an NH2-terminal fragment of approximately 500 amino acids that activates transcription of genes encoding the low density lipoprotein receptor and enzymes of cholesterol synthesis. In sterol-overloaded cells, proteolysis does not occur, and transcription is repressed. Through mutational analysis in transfected cells, we identify two segments of SREBPs that are required for proteolysis, one on either side of the ER membrane. An arginine in the lumenal loop is essential. A tetrapeptide sequence (DRSR) on the cytosolic face adjacent to the first transmembrane domain is also required for maximal cleavage. Both of these elements are conserved in the human and hamster versions of SREBP-1 and SREBP-2. Sterol-mediated suppression of cleavage of SREBP-1 was found to be dependent on the extreme COOH-terminal region (residue 1034 to the COOH terminus), which exists in two forms as a result of alternative splicing. The form encoded by the "a" class exons (exons 18a and 19a) undergoes sterol-regulated cleavage. The form encoded by the "c" class exons (18c and 19c) is cleaved less efficiently and is not suppressed by sterols. These studies were made possible through use of a vector that achieves low level expression of epitope-tagged SREBPs under control of the relatively weak thymidine kinase promoter from herpes simplex virus. In contrast to SREBPs overproduced by high level expression vectors, the SREBPs produced at low levels were subject to the same regulated cleavage pattern as the endogenous SREBPs. These results indicate that sterol-regulated proteolysis of SREBPs is a complex process, requiring sequences on both sides of the ER membrane.

Alternative Splicing↗
PubMed1996

[Regulation on ACTH, beta-EP and immune function by moxibustion on different acupoints].

The experimental results displayed that the cellular immune functions of tumor-bearing mice in control group were significantly lower than that the normal control group. The cellular immune functions of those groups accepting moxibustion treatment were maintained at a relatively higher level. Among them the Guanyuan group seemed to be best in immune regulation. The data further demonstrated that an instant elevation of serum ACTH and beta-EP could be caused by moxibustion. But the bariations of serum ACTH and beta-EP are not paralleled. A remarkable increase of serum beta-EP was seen in Guanyuan group but not of serum ACTH. The experimental results hinted that the regulation of beta-EP and ACTH was related to the immune regulation induced by moxibustion.

Acupuncture Points↗
PubMed1995

Hairpin orientation of sterol regulatory element-binding protein-2 in cell membranes as determined by protease protection.

Sterol regulatory element-binding proteins (SREBP-1 and SREBP-2) are proteins of approximately 1150 amino acids each that are attached to membranes of the endoplasmic reticulum (ER). In sterol-depleted cells, a protease releases an NH2-terminal fragment of approximately 500 amino acids that contains a basic helix-loop-helix leucine zipper motif. This fragment enters the nucleus and stimulates transcription of genes encoding the low density lipoprotein receptor and enzymes of cholesterol biosynthesis. Prior evidence indicates that the SREBPs are attached to membranes by virtue of an 80-residue segment located approximately 80 amino acids to the COOH-terminal side of the leucine zipper. This segment contains two long hydrophobic sequences separated by a short hydrophilic sequence of approximately 30 amino acids. We have proposed a hairpin model in which the two hydrophobic sequences span the membrane, separated by the short hydrophilic sequence which projects into the lumen of the ER (the "lumenal loop"). The model predicts that the NH2- and COOH-terminal segments face the cytosol. To test this model, we constructed a cDNA encoding human SREBP-2 with epitope tags at the NH2 terminus and in the lumenal loop. The COOH-terminal region was visualized with a newly developed monoclonal antibody against this region. Sealed membrane vesicles were isolated from cells expressing the epitope-tagged version of SREBP-2. Trypsin treatment of these vesicles destroyed the NH2- and COOH-terminal segments and reduced the lumenal epitope to a size consistent with protection of the lumenal sequence plus the two membrane-spanning segments. The lumenal epitope tag contained two potential sites for N-linked glycosylation. The size of the trypsin-protected fragment was reduced by treatment with N-Glycanase and endoglycosidase H, indicating that this segment was located in the lumen of the ER where it was glycosylated. These data provide strong support for the hairpin model.

Amino Acid Sequence↗
PubMed1995

Structure of the human gene encoding sterol regulatory element binding protein-1 (SREBF1) and localization of SREBF1 and SREBF2 to chromosomes 17p11.2 and 22q13.

Sterol regulatory element binding protein-1 (SREBP1) and SREBP2 are structurally related proteins that control cholesterol homeostasis by stimulating transcription of sterol-regulated genes, including those encoding the low-density lipoprotein (LDL) receptor and 3-hydroxy-3-methylglutaryl CoA synthase. SREBP1 and SREBP2 are 47% identical, and they share a novel structure comprising a transcriptionally active NH2-terminal basic helix-loop-helix-leucine zipper (bHLH-Zip) domain followed by a membrane attachment domain. Cleavage by a sterol-regulated protease frees the bHLH-Zip domain from the membrane and allows it to enter the nucleus. SREBP1 exists in several forms, possibly as a result of alternative splicing at both the 5' and the 3' ends of the mRNA. The genes for SREBP1 (SREBF1) and SREBP2 (SREBF2) have not been studied. In this paper we describe the cloning and characterization of the human SREBF1 gene. The gene is 26 kb in length and has 22 exons and 20 introns. The 5' and 3' sequences that differ between the two SREBP1 cDNAs are encoded by discrete exons, confirming the hypothesis that they result from alternative splicing. The chromosomal locations of human SREBF1 and SREBF2 were determined by analysis of human-rodent somatic cell hybrids and fluorescence in situ hybridization. The SREBF1 gene mapped to the proximal short arm of chromosome 17 (17p11.2), and the SREBF2 gene was localized to the long arm of chromosome 22 (22q13).

Alternative Splicing↗
PubMed1995

Oxidative metabolism in Rett syndrome: 2. Biochemical and molecular studies.

In an attempt to identify a possible defect of mitochondrial metabolism in Rett syndrome we studied 9 girls with typical Rett syndrome using a clinical protocol designed to identify disorders of oxidative metabolism. One girl, (RO) had marked lactic acidemia. Biochemical studies on samples from these patients included leukocyte pyruvate carboxylase assay, serum biotinidase and skin fibroblast pyruvate production, pyruvate dehydrogenase, citrate synthetase and 2-oxoglutarate dehydrogenase assay. Muscle electron transport activities were studied on samples from 4 typical Rett patients including RO. Mitochondrial DNA (mtDNA) mutational analysis for the np3243 MELAS mutation, the np8993 NARP mutation, the np8344 MERFF mutation and the 4977 kb common deletion found in Kearns-Sayre syndrome and aged tissues were tested for in 1 of the muscle samples and 2 blood samples from typical Rett patients. Western blotting of electron transport complex III was performed on mitochondrial samples obtained from autopsy brain tissue in 2 Rett patients and compared to pediatric control brain samples. No abnormalities were found in blood biotinidase or pyruvate carboxylase. Western blotting of 2 Rett brain mitochondrial samples for complex III appear normal. Pyruvate consumption in medium from 8 Rett fibroblast lines grown with and without dichloroacetate (DCA) showed a normal fall in pyruvate suggesting normal pyruvate dehydrogenase activity in these cells, however the fibroblasts from patient RO had a high pyruvate production in culture. Pyruvate dehydrogenase, 2-oxo-glutarate dehydrogenase and citrate synthetase activities in 8 Rett fibroblast lines were normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Blotting, Western↗
PubMed1995

In vitro and in vivo analysis of murine lipoprotein lipase gene promoter: tissue-specific expression.

Lipoprotein lipase, an enzyme of central importance to lipid metabolism, is most abundant in adipose tissues, cardiac and skeletal muscle, and portions of the brain. The current work examined the murine lipoprotein lipase promoter using transient transfection, gel-retention analyses, and transgenic mice. Maximum expression of the luciferase reporter gene in transfected cells was observed with -101 bp of the promoter. Nuclear extracts from tissues expressing lipoprotein lipase contained DNA binding proteins that recognize the CCAAT box (-64 bp) and an octamer motif (-46 bp); this combination of factors was absent in nonexpressing tissues. Transgenic mice from three of five founders prepared with -1,824-bp promoter constructs expressed the luciferase reporter gene at highest levels in brown adipose tissue and brain. These findings suggest that the -1,824-bp promoter region contains sequence elements responsible for the tissue-specific transcription of lipoprotein lipase in vivo.

Animals↗
PubMed1995

[Intrapleural DDP and systemic thiosulfate rescue in the treatment of malignant pleural effusion].

One hundred twenty cases of malignant pleural effusion were treated by intrapleural administration of large doses of DDP (500-1,000 mg) followed by iv infusion of sodium thiosulfate for 3 days. Each patient received 1-4 cycles of treatment. Of 120 cases, 89 had their effusion completely disappeared and in 6 of them, it was accompanied by complete regression of tumors in the lung. Partial response was observed in 19 cases with an overall response rate of 90.0%. The median remission period was 6.4 month. Severe (grade III and IV) gastrointestinal, renal toxicity and myelosuppression occurred in 46,8 and 12 cases, respectively, Two patients died of severe intoxication.

Adenocarcinoma↗
PubMed1994

SREBP-1, a membrane-bound transcription factor released by sterol-regulated proteolysis.

Sterol regulatory element-binding protein 1 (SREBP-1), a member of the basic-helix-loop-helix-leucine zipper (bHLH-ZIP) family of transcription factors, is synthesized as a 125 kd precursor that is attached to the nuclear envelope and endoplasmic reticulum. In sterol-depleted cells, the membrane-bound precursor is cleaved to generate a soluble NH2-terminal fragment (apparent molecular mass, 68 kd) that translocates to the nucleus. This fragment, which includes the bHLH-ZIP domain, activates transcription of the genes for the LDL receptor and HMG CoA synthase. Sterols inhibit the cleavage of SREBP-1, and the 68 kd nuclear form is rapidly catabolized, thereby reducing transcription. ALLN, an inhibitor of neutral cysteine proteases, blocks the breakdown of the 68 kd form and superinduces sterol-regulated genes. Sterol-regulated proteolysis of a membrane-bound transcription factor provides a novel mechanism by which transcription can be regulated by membrane lipids.

Amino Acid Sequence↗
PubMed1994

[Regulation on beta-END in tumor-bearing mice by moxibustion on Guanyuan point].

The experimental results demonstrated that moxibustion on Guanyuan point could promote the hyperplasia of the pituitary and the adrenal gland which showed atrophy in control group. Also, the moxibustion treatment stimulated the secretion of beta-END from the pituitary and the adrenal gland, increased the level of serum beta-END significantly and kept the high level for quite a long time, that was advantageous for beta-END to carry out the immunomodulation. The data further suggested that moxibustion treatment do not cause the instant release but probably constant release of the beta-END.

Acupuncture Points↗