Search PubMed⌕ Search

Biomedical subjects

G Zhou

Publications and source records attributed to G Zhou.

At least 145 records · Page 8Linked to original sources
PubMed1999

[An experimental study on effect of methazolamide on decreasing intraocular pressure in rabbits].

OBJECTIVE: To study the therapeutic effect of methazolamide on glaucoma. METHODS: Various doses of methazolamide were orally administered in rabbits, their effects on high intraocular pressures and on recovery of low intraocular pressures were observed. RESULTS: The high intraocular pressures were significantly decreased and the maintenance of low intraocular pressure was significantly prolonged by the oral administration of 40, 20, 10 mg/kg of methazolamide. A dose-effect relationship that is the reduction of intraocular pressure increases with the increase of the dosage administration of methazolamide could be observed. CONCLUSION: This study indicates that methazolamide might play an effective therapeutic role in glaucoma.

Animals↗
PubMed1999

[Determination of isofraxidin in Sarcandra glabra (Thunb.) Nakai by HPLC].

OBJECTIVE: To establish a method for the determination of isofraxidin in Sarcandra glabra. METHOD: Using HPLC with mu-Bondapak C18 column, acetonitrile -0.1% phosphoric acid solution(20:80) as mobile phase and detection wavelength at 344 nm. RESULT: The recovery and RSD were 98.1% and 1.9% (n = 5) respectively. CONCLUSION: This method is rapid, simple and accurate, thus may be used for the quality control of this drug.

Chromatography, High Pressure Liquid↗
PubMed1999

[A study on the quality criteria for wushicha capsules].

OBJECTIVE: To build up the quality criteria for Wushicha capsules. METHOD: Rhizoma Atractylodis, Cortex Magnoliae Officinalis, Rhizoma Chuanxiong, Herba Pogostemonis in Wushicha capsules were identified by TLC. The contents of magnolol in the preparation were determined by GC. RESULT: These methods are simple and accurate. CONCLUSION: These methods can be used for the quantitative analysis of Wushicha capsules.

Asteraceae↗
PubMed1999

[Expression of P53 protein in premalignant lesion and carcinoma of larynx].

To investigate the expression of P53 protein in the premalignant lesion and carcinoma of laryngeal epithelium, the authors used DO-7, an antibody to wild and mutant type P53 protein. Eleven cases of simple hyperplasia of epithelium (SHE), 32 cases of atypical hyperplasia of epithelium (AHE) and 42 cases of laryngeal squamous cell carcinoma (LSCC) were examined by ABC technique. The results showed that the overexpression of P53 protein were 0%, 31.25% and 52.38% in SHE, AHE and LSCC, respectively. The positive rate of P53 protein were 0%, 33.33% and 75.00% in mild, moderate and severe AHE, respectively. In well, moderately and poorly differentiated carcinomas of larynx, the positive rates were 62.50%, 76.92% and 15.39%, respectively. There were highly significant differences (P < 0.01). No correlation was found between the P53 protein overexpression and the clinical stages, neck lymph node metastasis, local recurrence and, survival of LSCC. The results suggest that the overexpression of P53 protein may play a role in the pathogenesis and development of LSCC.

Carcinoma, Squamous Cell↗
PubMed1999

[Complete nucleotide sequence of the nonstructural gene of alphavirus YN87448 strain isolated in China and its relationship to other Sindbis viruses].

OBJECTIVE: To determine the complete nucleotide sequence of the nonstructural gene of YN87448 virus stain which was firstly isolated from a female patient with fever in Yunnan Province in 1986, and identified as a member of Alphavirus by the serological method. METHODS: The complete nucleotide sequence of the nonstructural region gene of YN87448 virus strain was determined with nine clones, which were obtained by using reverse transcription and polymerase chain reaction (RT-PCR), and by linking nine overlapping fragments into pGEM-T vector respectively. RESULTS: The complete nucleotide sequence of nonstructural gene of YN87448 virus strain was 7,613 nucleotides long exclusive of the 5' cap, encoding four nonstructural proteins, nsP1, nsP2, nsP3, nsP4, and contained one initiator(ATG) and two stop codons (TGA). In comparison with the consensus sequence of S.A.AR86, the homogeneity of the nucleotide sequence between YN87448 virus strain and sindbis-like virus isolate S.A.AR86 was 98.8%. YN87448 virus strain can not produce a fatal disease in adult mice. In comparison with the consensus sequence of S.A.AR86, there is a 54 nucleotide insertion from 5,256 bp to 5,309 bp, 3 nucleotide (AGT) deletion at 5,603 bp in nsP3 region, and an opal termination codon between the nsP3 and the nsP4 genes in YN87448. virus strain. This sequence has been put into Gene Bank and No. is AF103734. CONCLUSION: YN87448 is a new sindbis-like virus strain.

Alphavirus↗
PubMed1998

Transition state structure of arginine kinase: implications for catalysis of bimolecular reactions.

Arginine kinase belongs to the family of enzymes, including creatine kinase, that catalyze the buffering of ATP in cells with fluctuating energy requirements and that has been a paradigm for classical enzymological studies. The 1.86-A resolution structure of its transition-state analog complex, reported here, reveals its active site and offers direct evidence for the importance of precise substrate alignment in the catalysis of bimolecular reactions, in contrast to the unimolecular reactions studied previously. In the transition-state analog complex studied here, a nitrate mimics the planar gamma-phosphoryl during associative in-line transfer between ATP and arginine. The active site is unperturbed, and the reactants are not constrained covalently as in a bisubstrate complex, so it is possible to measure how precisely they are pre-aligned by the enzyme. Alignment is exquisite. Entropic effects may contribute to catalysis, but the lone-pair orbitals are also aligned close enough to their optimal trajectories for orbital steering to be a factor during nucleophilic attack. The structure suggests that polarization, strain toward the transition state, and acid-base catalysis also contribute, but, in contrast to unimolecular enzyme reactions, their role appears to be secondary to substrate alignment in this bimolecular reaction.

Animals↗
PubMed1998

A reduction-pyrolysis-catalysis synthesis of diamond

Diamond powder was synthesized through a metallic reduction-pyrolysis-catalysis route with the reaction of carbon tetrachloride and sodium at 700 degreesC, in which the sodium was used as reductant and flux. This temperature is much lower than that of traditional methods. The x-ray powder diffraction patterns showed three strong peaks of diamond. The Raman spectrum showed a sharp peak at 1332 inverse centimeters, which is characteristic of diamond. Although the yield was only 2 percent, this method is a simple means of forming diamond.

Journal Article↗
PubMed1998

A common requirement for the catalytic activity and both SH2 domains of SHP-2 in mitogen-activated protein (MAP) kinase activation by the ErbB family of receptors. A specific role for SHP-2 in map, but not c-Jun amino-terminal kinase activation.

The ErbB family of receptors, which include the epidermal growth factor receptor (EGFR), ErbB2, ErbB3, and ErbB4 mediate the actions of a family of bioactive polypeptides. EGF signals through EGFR, whereas heregulin (HRG) signaling is initiated through binding to either ErbB3 or ErbB4. In this report we studied the role of protein-tyrosine phosphatase SHP-2 in ErbB-mediated activation of mitogen-activated protein kinase (MAPK) by overexpressing SHP-2 mutants in COS-7 cells. We demonstrate that enzymatic activity and both NH2- and COOH-terminal SH2 domains of SHP-2 are required for EGF-induced MAPK activation, but not for c-Jun amino-terminal kinase stimulation or MAPK activation which occurred in response to myristoylated son of sevenless, activated Ras, or phorbol ester. Dominant-negative forms of SHP-2 had no effect on EGF-stimulated interaction of GRB2 with EGFR or SHC, nor did they influence phosphorylation of SHC and SHC/EGFR association. The same mutant SHP-2 structures that inhibited EGF-mediated stimulation of MAPK also blocked HRG alpha/beta-induced MAPK activation. EGF or HRG beta caused SHP-2 SH2 domains to engage multiple phosphotyrosine proteins, and mutation of either domain disrupted these associations. These results demonstrate that SHP-2 performs a common and essential function(s) in ligand-stimulated MAPK activation by the ErbB family of receptors.

Animals↗
PubMed1998

Wild-type p53-mediated induction of rat mdr1b expression by the anticancer drug daunorubicin.

The expression of P-glycoproteins encoded by the mdr gene family is associated with the emergence of the multidrug resistance phenotype in animal cells. mdr expression can be induced by many extracellular stimulants including cytotoxic drugs and chemical carcinogens. However, little is known about the mechanisms involved. Here, we report that the expression of the rat mdr1b can be induced by anticancer drug daunorubicin. Further analysis identified a bona fide p53-binding site spanning from base pairs -199 to -180 (5'-GAACATGTAGAGACATGTCT-3') in the rat mdr1b promoter that is essential for basal and daunorubicin-inducible promoter activities. In addition, our results show that wild-type p53 can up-regulate not only the promoter function but also endogenous expression of the rat mdr1b. To the best of our knowledge, this is the first report showing that a specific p53-binding site is involved in the transcriptional regulation of mdr gene by wild-type p53. Since p53 is a sensor for a wide variety of genotoxic stresses, our finding has broad implications for understanding the mechanisms involved in the inducible expression of mdr gene by anticancer drugs, chemical carcinogens, UV light, and other DNA-damaging agents.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Three high mobility group-like sequences within a 48-base pair enhancer of the Col2a1 gene are required for cartilage-specific expression in vivo.

To understand the molecular mechanisms by which mesenchymal cells differentiate into chondrocytes, we have used the gene for an early and abundant marker of chondrocytes, the mouse pro-alpha1(II) collagen gene (Col2a1), to delineate a minimal sequence needed for chondrocyte-specific expression and to identify the DNA-binding proteins that mediate its activity. We show here that a 48-base pair (bp) Col2a1 intron 1 sequence specifically targets the activity of a heterologous promoter to chondrocytes in transgenic mice. Mutagenesis studies of this 48-bp element identified three separate sites (sites 1-3) that were essential for its chondrocyte-specific enhancer activity in both transgenic mice and transient transfections. Mutations in sites 1 and 2 also severely inhibited the chondrocyte-specific enhancer activity of a 468-bp Col2a1 intron 1 sequence in vivo. SOX9, an SRY-related high mobility group (HMG) domain transcription factor, was previously shown to bind site 3, to bend the 48-bp DNA at this site, and to strongly activate this 48-bp enhancer as well as larger Col2a1 enhancer elements. All three sites correspond to imperfect binding sites for HMG domain proteins and appear to be involved in the formation of a large chondrocyte-specific complex between the 48-bp element, Sox9, and other protein(s). Indeed, mutations in each of the three HMG-like sites of the 48-bp element, which abolished chondrocyte-specific expression of reporter genes in transgenic mice and in transiently transfected cells, inhibited formation of this complex. Overall our results suggest a model whereby both Sox9 and these other proteins bind to several HMG-like sites in the Col2a1 gene to cooperatively control its expression in cartilage.

Animals↗
PubMed1998

A systematic and effective supervised learning mechanism based on Jacobian rank deficiency.

Most neural network applications rely on the fundamental approximation property of feedforward networks. Supervised learning is a means of implementing this approximate mapping. In a realistic problem setting, a mechanism is needed to devise this learning process based on available data, which encompasses choosing an appropriate set of parameters in order to avoid overfitting, using an efficient learning algorithm measured by computation and memory complexities, ensuring the accuracy of the training procedures as measured by the training error, and testing and cross-validation for generalization. We develop a comprehensive supervised learning algorithm to address these issues. The algorithm combines training and pruning into one procedure by utilizing a common observation of Jacobian rank deficiency in feedforward networks. The algorithm not only reduces the training time and overall complexity but also achieves training accuracy and generalization capabilities comparable to more standard approaches. Extensive simulation results are provided to demonstrate the effectiveness of the algorithm.

Algorithms↗
PubMed1998

Determination of the relative precision of atoms in a macromolecular structure.

Several real-space indices and temperature factors are compared with respect to their correlation with atomic positional error and their ability to indicate atoms and residues with the worst of subtle errors. The best index, rED, is a correlation coefficient between model and map electron densities, similar to one proposed earlier, but incorporating two improvements. Firstly, resolution is accounted for explicitly by calculating the model electron density by Fourier transformation of resolution-truncated scattering factors. Secondly, the deviation between model and map electron densities is assigned to neighboring atoms according to their contribution to the electron density of each grid point. With maps of various qualities, rED is the single index with best correlation to atomic error with grouped or individual atoms, and it is the most reliable indicator of poor residues. With poorer omit maps, imprecision of individual atoms is best diagnosed by a combination of low rED or high B factor. With the improved methods, 60-70% of the least precise atoms can detected in a fully refined structure. Similarly, 40-80% of the least precise atoms of an unrefined model can be detected by comparison with an isomorphous replacement map. This is useful in assessing and improving the quality of a model, but not sufficient to confidently validate all atoms of a structure at sub-atomic resolution.

Electrons↗
PubMed1998

Genetic dissection of retinal development.

Retinal development depends on complex interactions between products of thousands of genes and numerous cellular and environmental factors. We are using novel quantitative genetic methods to map and characterize genes that are responsible for the pervasive quantitative differences in the architecture of the eye and the retina. These genes, known as quantitative trait loci (QTLs), may also determine susceptibility to common eye diseases. To map QTLs that generate variation among normal individuals we have analyzed several traits in a wide variety of mice, including standard inbred strains, recombinant inbred strains, wild mice, F1 hybrids and intercross progeny. Here we review this approach and give three specific examples of how genes with well-defined functions in retinal development are being mapped and characterized.

Animals↗
PubMed1998

Mutations in LMX1B cause abnormal skeletal patterning and renal dysplasia in nail patella syndrome.

The LIM-homeodomain protein Lmx1b plays a central role in dorso-ventral patterning of the vertebrate limb. Targeted disruption of Lmx1b results in skeletal defects including hypoplastic nails, absent patellae and a unique form of renal dysplasia (see accompanying manuscript by H. Chen et al.; ref. 2). These features are reminiscent of the dominantly inherited skeletal malformation nail patella syndrome (NPS). We show that LMX1B maps to the NPS locus and that three independent NPS patients carry de novo heterozygous mutations in this gene. Functional studies show that one of these mutations disrupts sequence-specific DNA binding, while the other two mutations result in premature termination of translation. These data demonstrate a unique role for LMX1B in renal development and in patterning of the skeletal system, and suggest that alteration of Lmx1b/LMX1B function in mice and humans results in similar phenotypes. Furthermore, we provide evidence for the first described mutations in a LIM-homeodomain protein which account for an inherited form of abnormal skeletal patterning and renal failure.

Amino Acid Sequence↗
PubMed1998

Clinical experience with orbicularis oculi myocutaneous flaps in the temporal area.

There are many methods to repair facial skin defects in clinical practice. The desired outcome for the surgeon and the patient is the restoration of facial appearance and function. The temporal region is one of the ideal donor sites for the repair of a facial skin defect, because this area is relatively inconspicuous and the skin quality is similar to that of the face. In the past, the temporal region was always used as the donor site of the local flap for repairing the facial skin defect. Because the blood supply of the skin comes from the subjacent tissue mainly rather than from the contiguous tissue, the pedicles of the local flaps are short, limiting the use of this area as a donor site. From 1993 to 1996, the anatomy of the orbicularis oculi myocutaneous flap in five cadavers was studied; what was learned allowed for the use of this flap to repair skin defects of the face in 13 patients. In this paper, the clinical experiences using the orbicularis oculi myocutaneous flaps to repair skin defects of the face and the surgical anatomy of this myocutaneous flap are discussed.

Adolescent↗
PubMed1998

The long and the short of it: developmental genetics of the skeletal dysplasias.

The skeletal dysplasias are a large heterogeneous group of genetic conditions characterized by abnormal shape, growth, or integrity of bones. Often, there may be prominent features associated with other organ systems as part of a more encompassing skeletal malformation syndrome. Tremendous advances have been made in the clinical and molecular delineation of these conditions over the past 20-30 years. We have progressed from initial broad clinical classifications of these conditions in the first two-thirds of this century, to extensive delineation based on radiographic features in the 1970s and 1980s, to the present reconsideration and grouping of these conditions according to their molecular pathogenesis. This has in part been spurred on by advances in the understanding of the developmental pathways which govern skeletal development, as well as by the human genome sequencing effort, which has provided a plethora of positional candidate genes for many of these conditions. The pathogenetic correlations derived from such studies are often based on parallels between the human phenotype and mouse models of the human condition, and have sometimes revealed novel developmental functions.

Animals↗
PubMed1998

Antigenic characterization of Hantaan and Seoul virus nucleocapsid proteins expressed by recombinant baculovirus: application of a truncated protein, lacking an antigenic region common to the two viruses, as a serotyping antigen.

Hantaan virus (HTN) and Seoul virus (SEO) are members of the genus Hantavirus in the family Bunyaviridae and are causative agents of hemorrhagic fever with renal syndrome. The complete and truncated nucleocapsid proteins (NP) of HTN and SEO were expressed by a recombinant baculovirus system. Antigenic characterization of the NP using monoclonal antibodies (MAbs) indicated that the binding sites for the serotype-specific MAbs were located between amino acids (aa) 155 and 429. A Western blot assay indicated that the serotype-specific epitopes were conformation dependent. An indirect immunofluorescence antibody (IFA) assay with the truncated NP (aa 155 to 429) was able to distinguish convalescent-phase sera from HTN and SEO patients. However, the antibody titers with the truncated NP were lower than those with the whole NP. The truncated NP of SEO (aa 155 to 429) could be used as an enzyme-linked immunosorbent assay (ELISA) antigen, but the truncated NP from HTN lost its reactivity when used for ELISA. The IFA assay using baculovirus-expressed truncated NP as an antigen is a rapid, simple, and safe test for distinguishing between HTN and SEO infections by serotype.

Adult↗