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Biomedical subjects

H Zong

Publications and source records attributed to H Zong.

12 recordsLinked to original sources
PubMed2001

The insert region of RhoA is essential for Rho kinase activation and cellular transformation.

RhoA is involved in multiple cellular processes, including cytoskeletal organization, gene expression, and transformation. These processes are mediated by a variety of downstream effector proteins. However, which effectors are involved in cellular transformation and how these proteins are activated following interaction with Rho remains to be established. A unique feature that distinguishes the Rho family from other Ras-related GTPases is the insert region, which may confer Rho-specific signaling events. Here we report that deletion of the insert region does not result in impaired effector binding. Instead, this insert deletion mutant (RhoDeltaRas, in which the insert helix has been replaced with loop 8 of Ras) acted in a dominant inhibitory fashion to block RhoA-induced transformation. Since RhoDeltaRas failed to promote stress fiber formation, we examined the ability of this mutant to bind to and subsequently activate Rho kinase. Surprisingly, RhoDeltaRas-GTP coprecipitated with Rho kinase but failed to activate it in vivo. These data suggested that the insert domain is not required for Rho kinase binding but plays a role in its activation. The constitutively active catalytic domain of Rho kinase did not promote focus formation alone or in the presence of Raf(340D) but cooperated with RhoDeltaRas to induce cellular transformation. This suggests that Rho kinase needs to cooperate with additional Rho effectors to promote transformation. Further, the Rho kinase catalytic domain reversed the inhibitory effect of RhoDeltaRas on Rho-induced transformation, suggesting that one of the downstream targets of Rho-induced transformation abrogated by RhoDeltaRas is indeed Rho kinase. In conclusion, we have demonstrated that the insert region of RhoA is required for Rho kinase activation but not for binding and that this kinase activity is required to induce morphologic transformation of NIH 3T3 cells.

3T3 Cells↗
PubMed2001

Glucose toxicity and the development of diabetes in mice with muscle-specific inactivation of GLUT4.

Using cre/loxP gene targeting, transgenic mice with muscle-specific inactivation of the GLUT4 gene (muscle GLUT4 KO) were generated and shown to develop a diabetes phenotype. To determine the mechanism, we examined insulin-stimulated glucose uptake and metabolism during hyperinsulinemic-euglycemic clamp in control and muscle GLUT4 KO mice before and after development of diabetes. Insulin-stimulated whole body glucose uptake was decreased by 55% in muscle GLUT4 KO mice, an effect that could be attributed to a 92% decrease in insulin-stimulated muscle glucose uptake. Surprisingly, insulin's ability to stimulate adipose tissue glucose uptake and suppress hepatic glucose production was significantly impaired in muscle GLUT4 KO mice. To address whether these latter changes were caused by glucose toxicity, we treated muscle GLUT4 KO mice with phloridzin to prevent hyperglycemia and found that insulin-stimulated whole body and skeletal muscle glucose uptake were decreased substantially, whereas insulin-stimulated glucose uptake in adipose tissue and suppression of hepatic glucose production were normal after phloridzin treatment. In conclusion, these findings demonstrate that a primary defect in muscle glucose transport can lead to secondary defects in insulin action in adipose tissue and liver due to glucose toxicity. These secondary defects contribute to insulin resistance and to the development of diabetes.

Adipose Tissue↗
PubMed2001

[The impact of early diagnosis and thrombolytic-anticoagulant therapies on outcome of pulmonary embolism].

OBJECTIVE: To investigate the effect of early diagnosis and thrombolytic followed by anticoagulant therapy in pulmonary embolism (PE). METHODS: 46 patients diagnosed as PE were retrospectively analyzed. All the patients were treated with thrombolytic followed by anticoagulant therapy. Therapeutic effect was compared between two groups of patients with symptoms more or less than two weeks before establishment of diagnosis. RESULT: 36 patients were documented as PE by lung scan, 13 of 46 patients (28.3%) were misdiagnosed as other heart or lung diseases. All the patients had accompanying diseases, including leg deep vein thrombosis (DVT) (33/46, 71.7%) heart or lung diseases other than PE(23/46, 50%), and history of surgery (6/46, 3%). 93.1% of the patients with clinical history less than 2 weeks showed improvement, whereas only 52.9% of those with clinical history exceeding 2 weeks improved. There was significant difference between them. CONCLUSION: In order to diagnose PE early, we should pay more attention to the risk factors of PE, especially DVT. The success of thrombolysis appears to depend on the interval between the onset of symptoms and start of thrombolytic therapy. Patients with clinical symptoms less than 2 weeks show better improvement.

Adult↗
PubMed2000

Structure and chromosomal localization of the human glycogenin-2 gene GYG2.

Glycogenin-2 is one of two self-glucosylating proteins involved in the initiation phase of the synthesis of the storage polysaccharide glycogen. Cloning of the human glycogenin-2 gene, GYG2, has revealed the presence of 11 exons and a gene of more than 46 kb in size. The structure of the gene explains much of the observed diversity in glycogenin-2 cDNA sequences as being due to alternate exon usage. In some cases, there is variation in the splice junctions used. Over regions of protein sequence similarity, the GYG2 gene structure is similar to that of the other glycogenin gene, GYG. A genomic GYG2 clone was used to localize the gene to Xp22.3 by fluorescence in-situ hybridization. Localization close to the telomere of the short arm of the X chromosome is consistent with mapping information obtained from glycogenin-2 STS sequences. Glycogenin-2 maps between the microsatellite anchor markers AFM319te9 (DXS7100) and AFM205tf2 (DXS1060), and its 3' end is 34.5 kb from the 3' end of the arylsulphatase gene ARSD. GYG2 is outside the pseudoautosomal region PAR1 but still in a region of X-Y shared genes. As is true for several other genes in this location, an inactive remnant of GYG2, consisting of exons 1-3, may be present on the Y chromosome.

Amino Acid Sequence↗
PubMed2000

Photocatalytic degradation of AZO dyes by supported TiO2 + UV in aqueous solution.

The photocatalytic degradation performance of photocatalysts TiO2 supported on 13-X, Na-Y, 4A zeolites with different loading content was evaluated using the photocatalytic oxidation of dyes direct fast scarlet 4BS and acid red 3B in aqueous medium. The results showed that the best reaction dosage of TiO2-zeolite catalysts is about 2 g/l and the photocatalytic kinetics follows first order for all supported catalysts. The photocatalytic activity order of the three series catalysts is 13X type >Y type >4A type. The physical state of titanium dioxide on the supports is evaluated by X-ray photoelectron spectra (XPS), powder X-ray diffraction (XRD), BET, and FTIR.

Azo Compounds↗
PubMed1999

Loop 6 of RhoA confers specificity for effector binding, stress fiber formation, and cellular transformation.

Rho family GTPases regulate multiple cellular processes, including cytoskeletal organization, gene expression, and transformation. These effects are achieved through the interaction of GTP-bound proteins with various downstream targets. A series of RhoA/Rac1 and Rho/Ras chimeras was generated to map the domain(s) of RhoA involved in its association with two classes of effector kinase, represented by PRK2 and ROCK-I. Although the switch 1 domain was required for effector binding, the N terminus of Rho (residues 1-75) was interchangeable with that of Rac. This suggested that the region of Rho that confers effector binding specificity lay further C-terminal. Subsequent studies indicated that the "insert domain"(residues 123-137), a region unique to Rho family GTPases, is not the specificity determinant. However, a determinant for effector binding was identified between Rho residues 75-92. Rac to Rho point mutations (V85D or A88D) within loop 6 of Rac promoted its association with PRK2 and ROCK, whereas the reciprocal Rho(D87V/D90A) double mutant significantly reduced effector binding capacity. In vivo studies showed that microinjection of Rac(Q6IL/V85D/A88D) but not Rac(Q6IL) induced stress fiber formation in LLC-PK epithelial cells, suggesting that loop 6 residues conferred the ability of Rac to activate ROCK. On the other hand, the reciprocal Rho (Q6IL/D87V/D90A) mutant was defective in its ability to transform NIH 3T3 cells. These data suggest that although Rho effectors can utilize a Rho or Rac switch 1 domain to sense the GTP-bound state of Rho, unique residues within loop 6 are essential for determining both effector binding specificity and cellular function.

3T3 Cells↗
PubMed1999

[Studies on immunoprotection of monoclonal antibodies against Cryptosporidium parvum].

AIM: To explore the immune protection of the monoclonal antibody (McAb) against Cryptosporidium parvum. METHODS: On the basis of Madin-Darby canine kidney (MDCK) cell culture, the immunoprotection of McAb against C. parvum was screened by means of neutralization test in vitro, and verified by rat model and transmission electron microscopy of infected MDCK cells. RESULTS: The number of C. parvum sporozoites recovered on the surface of rat intestinal epithelial cells and the mean output of oocyst were significantly reduced by McAb Z3D2 (P < 0.001, P < 0.05). The decreased Cryptos poridium at each development phase within infected MDCK cells and less damage of cell ultrastructure caused by Cryptosporidium were found in Z3D2 treated group. CONCLUSION: McAb Z3D2 possesses highly effective protection against C. parvum.

Animals↗
PubMed1998

[Preparation and characterization of monoclonal antibodies against Cryptosporidium parvum].

AIM: To develop and characterize the monoclonal antibodies(McAbs) against Cryptosporidium parvum (C. parvum). METHODS: BALB/c mice were immunized with purified oocyst antigens of C. parvum from human isolates and McAbs against C. parvum were prepared by using hybridoma technique. The characterization of McAbs was studied by means of indirect immunofluorescent assay (IFA) and Western blot analysis. RESULTS: Four clones of hybridoma cell lines secreting McAbs against oocyst antigens of C. parvum were obtained. The immunoglobulin subclasses of these four McAbs were identified as IgM (Z4C8,Z3D7) and IgG1(Z2B6,Z3D2) and their light chains were kappa chain. IFA results showed that three McAb (Z4C8, Z3D7 and Z3D2) conjugates produced a diffuse fluorescence in the Cryptosporidium sporozoites (CSP) and one (Z2B6) produced local fluorescence in the oocyst wall of C. parvum. Four McAbs could recognize 4 of 42 polypeptide antigen bands of CSP with molecular weights of 20.5 kDa, 33 kDa, 60.5 kDa and 95 kDa, among which both Z4C8 and Z3D7 could recognize 20.5 kDa band that was defined as a principal antigenic protein of CSP. CONCLUSION: These four McAbs possess their own characteristics of recognizing antigenic epitopes on CSP, but react specifically against antigens of C. parvum.

Animals↗
PubMed1995

[Non-radioactive detection of dinucleotide repeat polymorphisms and its application to genetic diagnosis].

We have developed a rapid and non-radioactive procedure for detecting dinucleotide repeat polymorphisms. Specific primers flanking the repeats were used in the polymerase chain reaction (PCR). The generated allelic fragments were resolved by thin-layer denaturing polyacrylamide gel electrophoresis and visualized by improved silver staining. This method is simple, fast and without labelling of PCR products. Resolution of 1 bp can be easily obtained. It can also be used in multiplex PCR analysis of (CA)n loci. This method will be a valuable tool for linkage analysis and DNA diagnosis as demonstrated by its successful application to the CA dinucleotide repeat haplotying of a DMD family.

Base Sequence↗