Biomedical subjects

X Nie

Publications and source records attributed to X Nie.

At least 19 recordsLinked to original sources

PubMed2006

Improvement of peripheral nerve regeneration by a tissue-engineered nerve filled with ectomesenchymal stem cells.

Ectomesenchymal stem cells (EMSCs) originate from the cranial neural crest. They are a potential source of neuronal and Schwann cells (SCs) of the peripheral nervous system (PNS) during embryonic development. The third passage of EMSCs enzymatically isolated from the mandibular processes of Sprague-Dawley rats were cultured in forskolin and bovine pituitary extract for 6 days to generate functional Schwann cell phenotypes. Next, 10-mm defects in the sciatic nerves were bridged with an autograft, tissue-engineered nerve filled with differentiated cells in collagen, or a PLGA conduit alone in 18 rats, and the nerve defects of another four rats were left untreated. The regenerated nerves were evaluated by the sciatic functional index (SFI) monthly and by histological analysis 4 months after grafting. The recovery index of the sciatic nerve improved significantly in the autograft and tissue-engineered nerve groups, both of which were superior to the PLGA group. In animals transplanted with the EMSCs, there was greater regeneration than with conduit alone during the same period of implantation. These results show that when EMSCs are transplanted to a peripheral nerve defect they differentiate into supportive cells that contribute to the promotion of axonal regeneration.

Absorbable Implants↗

PubMed2006

FGF signalling in craniofacial development and developmental disorders.

The Fgf signalling pathway is highly conserved in evolution and plays crucial roles in development. In the craniofacial region, it is involved in almost all structure development from early patterning to growth regulation. In craniofacial skeletogenesis, the Fgf signal pathway plays important roles in suture and synchondrosis regulation. Mutations of FGF receptors relate to syndromatic and non-syndromatic craniosynostosis. The Fgf10/Fgfr2b signal loop is critical for palatogenesis and submandibular gland formation. Perturbation of the Fgf signal is a possible mechanism of palatal cleft. Fgf10 haploinsufficiency has been identified as the cause of autosomal dominant aplasia of lacrimal and salivary glands. The Fgf signal is also a key regulator of tooth formation: in the absence of Fgfr2b tooth development is arrested at the bud stage. Fgfr4 has recently been identified as the key signal mediator in myogenesis. In this review, these aspects are discussed in detail with a focus on the most recent advances.

Cleft Palate↗

PubMed2005

The genome of the social amoeba Dictyostelium discoideum.

The social amoebae are exceptional in their ability to alternate between unicellular and multicellular forms. Here we describe the genome of the best-studied member of this group, Dictyostelium discoideum. The gene-dense chromosomes of this organism encode approximately 12,500 predicted proteins, a high proportion of which have long, repetitive amino acid tracts. There are many genes for polyketide synthases and ABC transporters, suggesting an extensive secondary metabolism for producing and exporting small molecules. The genome is rich in complex repeats, one class of which is clustered and may serve as centromeres. Partial copies of the extrachromosomal ribosomal DNA (rDNA) element are found at the ends of each chromosome, suggesting a novel telomere structure and the use of a common mechanism to maintain both the rDNA and chromosomal termini. A proteome-based phylogeny shows that the amoebozoa diverged from the animal-fungal lineage after the plant-animal split, but Dictyostelium seems to have retained more of the diversity of the ancestral genome than have plants, animals or fungi.

ATP-Binding Cassette Transporters↗

PubMed2002

Magnetization-direction-dependent local electronic structure probed by scanning tunneling spectroscopy.

Scanning tunneling spectroscopy (STS) of thin Fe films on W(110) shows that the electronic structure of domains and domain walls is different. This experimental result is explained on the basis of first-principles calculations. A detailed analysis reveals that the spin-orbit induced mixing between minority d(xy+xz) and minority d(z(2)) spin states depends on the magnetization direction and changes the local density of states in the vacuum detectable by STS. As a consequence nanometer-scale magnetic structure information is obtained even by using nonmagnetic probe tips.

Journal Article↗

PubMed2002

Sodium sulphite inhibition of potato and cherry polyphenolics in nucleic acid extraction for virus detection by RT-PCR.

Phenolic compounds from plant tissues inhibit reverse transcription-polymerase chain reaction (RT-PCR). Multiple-step protocols using several additives to inhibit polyphenolic compounds during nucleic acid extraction are common, but time consuming and laborious. The current research highlights that the inclusion of 0.65 to 0.70% of sodium sulphite in the extraction buffer minimizes the pigmentation of nucleic acid extracts and improves the RT-PCR detection of Potato virus Y (PVY) and Potato leafroll virus (PLRV) in potato (Solanum tuberosum) tubers and Prune dwarf virus (PDV) and Prunus necrotic ringspot virus (PNRSV) in leaves and bark in the sweet cherry (Prunus avium) tree. Substituting sodium sulphite in the nucleic acid extraction buffer eliminated the use of proteinase K during extraction. Reagents phosphate buffered saline (PBS)-Tween 20 and polyvinylpyrrolidone (PVP) were also no longer required during RT or PCR phase. The resultant nucleic acid extracts were suitable for both duplex and multiplex RT-PCR. This simple and less expensive nucleic acid extraction protocol has proved very effective for potato cv. Russet Norkotah, which contains a high amount of polyphenolics. Comparing commercially available RNA extraction kits (Catrimox and RNeasy), the sodium sulphite based extraction protocol yielded two to three times higher amounts of RNA, while maintaining comparable virus detection by RT-PCR. The sodium sulphite based extraction protocol was equally effective in potato tubers, and in leaves and bark from the cherry tree.

Flavonoids↗

PubMed2001

Effects of solution pH and electrical parameters on hydroxyapatite coatings deposited by a plasma-assisted electrophoresis technique.

Hydroxyapatite (HA) coatings can be deposited using a hybrid process of plasma electrolysis and electrophoresis, called plasma-assisted electrophoretic deposition (PEPD). HA aqueous suspensions with various pH values were prepared using a modified ultrasonic cleaning bath as an agitator/stirrer. Both DC and unbalanced AC power supplies were used to bias the titanium alloy substrate materials employed in this work. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and Fourier transform infrared spectroscopy (FTIR) were used to observe and analyze coating morphology and microstructure. It was shown that the morphology and composition of the calcium phosphate coatings were significantly influenced by solution pH values; the level of "pure" HA in the coatings' composition corresponded to both solution pH and the type of power supply employed. Loss of hydroxyl radials (i.e., dehydroxylation), which degrades the performance of the hydroxyapatite coating in terms of long-term chemical and mechanical stability, can be virtually eliminated by a combination of high pH and unbalanced AC plasma power. In addition, the underlying TiO2 coatings used to support the HA layer (preproduced by plasma electrolysis process) have a nanoscaled (10-20 nm) polycrystalline structure. TEM studies also revealed a dense, continuous amorphous titania layer (10 nm in thickness) at the interface between the Ti alloy substrate and the TiO2 layer, which may play a role in improving the corrosion resistance of the substrate. Such a nanophase TiO2 layer (if used as a coating alone) may also provide a further improvement in osteoinductive properties, compared to a conventional TiO2 coating on the Ti alloy substrate.

Alloys↗

PubMed2001

Hepatocyte growth factor is a mitogen for olfactory ensheathing cells.

Hepatocyte growth factor (HGF) is a potent mitogen for mature hepatocytes, and it has multi-functional effects in a variety of cells in various organs. HGF stimulates DNA synthesis and promotes cell migration and morphogenesis in several cell types including the olfactory system. To characterize the potential mitogenic activity of HGF that might contribute to olfactory ensheathing cell (OEC) proliferation, we tested the ability of HGF to stimulate OEC division in vitro. OECs were obtained from adult rat olfactory bulbs and cultured in serum-free medium, and were identified by double immunostaining for p75 and S-100 antibodies. DNA synthesis assayed by pulsing BrdU for 24 hr showed that HGF at the concentration of 5-100 ng/ml elicited a 5-10-fold increase of OEC proliferation. By immunocytochemical analysis, we demonstrated that c-Met-immunoreactivity was present in cultured OECs, and c-Met anti-serum significantly sequestered the activity of HGF on OECs proliferation, suggesting that HGF-induced proliferation of OECs is mediated by the c-Met receptor. The mitogenic activity of HGF was potentiated by addition of heregulin (HRG), but inhibited by addition of forskolin. These results demonstrate that HGF is a novel mitogen for rat OECs in vitro, and HGF/c-Met system is involved in regulating OECs growth and development.

Animals↗

PubMed2001

Structure and functionality of a designed p53 dimer.

P53 is a homotetrameric tumor suppressor protein involved in transcriptional control of genes that regulate cell proliferation and death. In order to probe the role that oligomerization plays in this capacity, we have previously designed and characterized a series of p53 proteins with altered oligomeric states through hydrophilc substitution of residues Met340 or Leu344 in the normally tetrameric oligomerization domain. Although such mutations have little effect on the overall secondary structural content of the oligomerization domain, both solubility and the resistance to thermal denaturation are substantially reduced relative to that of the wild-type domain. Here, we report the design and characterization of a double-mutant p53 with alterations of residues at positions Met340 and Leu344. The double-mutations Met340Glu/Leu344Lys and Met340Gln/Leu344Arg resulted in distinct dimeric forms of the protein. Furthermore, we have verified by NMR structure determination that the double-mutant Met340Gln/Leu344Arg is essentially a "half-tetramer". Analysis of the in vivo activities of full-length p53 oligomeric mutants reveals that while cell-cycle arrest requires tetrameric p53, transcriptional transactivation activity of monomers and dimers retain roughly background and half of the wild-type activity, respectively.

Binding Sites↗

PubMed2001

A novel usage of random primers for multiplex RT-PCR detection of virus and viroid in aphids, leaves, and tubers.

A multiplex reverse transcription polymerase chain reaction (m-RT-PCR) was developed for the simultaneous detection of five potato viruses and a viroid. The synthesis of cDNAs used for amplification was primed by hexanucleotides (random primers, RP). An RNA extraction procedure employing DNase I, is routinely used to isolate potato viruses and viroid (Potato virus S, PVS; Potato leafroll virus, PLRV; Potato virus X, PVX; Potato virus A and Y, PVA, PVY; and Potato spindle tuber viroid, PSTVd) from infected tissues. This extraction method produced deoxy-oligonucleotides, which in turn were used to prime the reverse transcription of RNA templates of all the viruses and the viroid. A time-course study from 15 s to 30 min showed optimal oligonucleotide generation by DNase I occurred at 10 min, an incubation time already incorporated in the extraction protocol. The presence of oligonucleotides capable of priming cDNA synthesis was also demonstrated in RNA preparations from aphids, leaves, and tubers. In order to duplicate the priming of templates by oligonucleotides, commercially available hexanucleotides were used as RP. When fragments were amplified from 5'- and 3'-ends of the random primed cDNA of PVY genome, bands of similar intensity were observed. In contrast, when two fragments (short and long) from the P1 gene region of the PVA genome were amplified, the yield of the short fragment was significantly higher in intensity than that of the long fragment in random primed cDNA. Irrespective of the origin of the primers (generated during extraction vs. commercially purchased), single or multiple viruses or the viroid were detected by amplification of random primed cDNAs present individually in the reaction or in a cDNA pool consisting of five viruses and the viroid. The cDNA produced by RP or virus specific primers (SP) was used to detect PLRV and PVY from infected tubers in a duplex reverse transcription polymerase chain reaction (d-RT-PCR). The RP cDNA gave increased detection. Comparison of RP primed cDNAs from dormant or sprouted tubers and leaves showed that for some cultivars, such as 'Shepody', leaves were more reliable for PVY and PLRV detection than the tubers, in both the d- and m-RT-PCR.

Animals↗

PubMed2001

[Study on polymorphism of D gene exons among RhD-negative Chinese Han population].

OBJECTIVE: To explore the genomic structure of 8 exons in D gene of RhD(-) Chinese Han population. METHODS: Polymerase chain reaction-sequence specific primers(PCR-SSP) were used to study genomic DNA from 50 samples of RhD(-) Chinese Han donors. Exons 2, 3, 4, 5, 6, 7, 9, 10 of RHD gene and exons 1, 2, 4, 5 of RHCE gene were specifically amplified, also intron 4 of them was amplified. RESULTS: Phenotypes of the 50 RhD(-) donors were: 22 ccdee, 22 Ccdee, 3 CcdEe, 3 CcdEe. The 8 exons of RHD gene were completely absent in 25 donors with ccdee or ccdEe phenotype, while polymorphisms of D gene exons were found in 25 donors with Ccdee or CcdEe phenotype: the presence of all 8 exons of D gene in 9 donors, the absence of the 8 exons in 7 donors, the presence of exon 2 in 5 donors, the presence of exon 6 in 3 donors and the presence of exons 2, 6, 10 in 1 donor were demonstrated. CONCLUSION: Polymorphisms of RHD gene exons were present among RhD(-) Chinese Han blood donors. The 8 exons of RHD gene were completely absent in donors with Rhesus cc phenotype, while 5 polymorphisms of RHD gene exons were found in donors with Rhesus Cc phenotype. The discrepancy of the RHD gene in RhD(-) individuals between Chinese Hans and Caucasians indicates that care should be exercised by clinicians in the use of the RhD genotyping results.

China↗

PubMed2000

A meanfield approach to the thermodynamics of a protein-solvent system with application to the oligomerization of the tumor suppressor p53.

The thermodynamic stability and oligomerization status of the tumor suppressor p53 tetramerization domain have been studied experimentally and theoretically. A series of hydrophilic mutations at Met-340 and Leu-344 of human p53 were designed to disrupt the hydrophobic dimer-dimer interface of the tetrameric oligomerization domain of p53 (residues 325-355). Meanfield calculations of the free energy of the solvated mutants as a function of interdimer distance were compared with experimental data on the thermal stability and oligomeric state (tetramer, dimer, or equilibrium mixture of both) of each mutant. The calculations predicted a decreasing stability and oligomeric state for the following amino acids at residue 340: Met (tetramer) > Ser Asp, His, Gln, > Glu, Lys (dimer), whereas the experimental results showed the following order: Met (tetramer) > Ser > Gln > His, Lys > Asp, Glu (dimers). For residue 344, the calculated trend was Leu (tetramer) > Ala > Arg, Gln, Lys (dimer), and the experimental trend was Leu (tetramer) > Ala, Arg, Gln, Lys (dimer). The discrepancy for the lysine side chain at residue 340 is attributed to the dual nature of lysine, both hydrophobic and charged. The incorrect prediction of stability of the mutant with Asp at residue 340 is attributed to the fact that within the meanfield approach, we use the wild-type backbone configuration for all mutants, but low melting temperatures suggest a softening of the alpha-helices at the dimer-dimer interface. Overall, this initial application of meanfield theory toward a protein-solvent system is encouraging for the application of the theoretical model to more complex systems.

Amino Acid Substitution↗

PubMed2000

Real-space imaging of two-dimensional antiferromagnetism on the atomic scale

A two-dimensional antiferromagnetic structure within a pseudomorphic monolayer film of chemically identical manganese atoms on tungsten(110) was observed with atomic resolution by spin-polarized scanning tunneling microscopy at 16 kelvin. A magnetic superstructure changes the translational symmetry of the surface lattice with respect to the chemical unit cell. It is shown, with the aid of first-principles calculations, that as a result of this, spin-polarized tunneling electrons give rise to an image corresponding to the magnetic superstructure and not to the chemical unit cell. These investigations demonstrate a powerful technique for the understanding of complicated magnetic configurations of nanomagnets and thin films engineered from ferromagnetic and antiferromagnetic materials used for magnetoelectronics.

Journal Article↗

PubMed2000

Duplex RT-PCR: reagent concentrations at reverse transcription stage affect the PCR performance.

Test conditions for the simultaneous detection of potato leafroll virus (PLRV) and potato virus Y (PVY) in dormant tubers and leaves by reverse transcription-polymerase chain reaction (RT-PCR) were optimized. Various factors optimized at the reverse transcription (RT) stage rather than at the amplification (PCR) stage affected the outcome. In the simplex RT-PCR a onefold dNTPs concentration (0.5 mM) was sufficient in yielding a PLRV or PVY band. In contrast, the duplex RT-PCR required a minimum twofold dNTPs concentration (1.0 mM) during RT to produce distinct bands in PCR. Similarly, various proportions of antisense primers of PLRV and PVY used during RT affected subsequent duplex RT-PCR. Optimal amplification of both viruses were obtained at a ratio of 0.90:0.49 microM of PLRV:PVY antisense primers. An interaction of dNTPs and RNA template concentration was observed. A higher concentration of RNA was required at onefold dNTPs concentration than at twofold dNTPs. Dilutions down to 1:300 of RNA template yielded distinct bands of both viruses at twofold dNTPs concentration. At optimized conditions of the duplex RT-PCR both viruses were reliably detected in composite samples at a ratio of one part infected sap mixed with 399 parts of sap from healthy tubers. Application of optimized conditions to singly- and doubly-infected tubers detected both viruses from naturally infected field-grown tubers. A nearly perfect correlation (r(2)=0.99) was observed between visible plant symptoms and the virus detection from leaves and tubers by the duplex RT-PCR.

DNA Primers↗

PubMed2000

Detection of multiple potato viruses using an oligo(dT) as a common cDNA primer in multiplex RT-PCR.

A novel usage of multiplex reverse transcription polymerase chain reaction (m-RT-PCR) for simultaneous detection of multiple viruses is reported. By use of an oligo(dT), as a common primer, nearly full-length cDNAs can be synthesized. Furthermore, combining an oligo(dT) primer with a specific antisense primer can be used to simultaneously prime reverse transcription of both polyadenylated and non-polyadenylated RNAs. Four viral genera including five potato viruses [(carlavirus (PVS), polerovirus (PLRV), potexvirus (PVX), potyvirus (PVA and PVY))] and a viroid genus including a viroid genome (pospiviroid (PSTVd)) were used to develop various formats of m-RT-PCR. In artificially created viral RNA mixtures, all six RNA pathogens were detected successfully by uniplex- and m-RT-PCR. In naturally infected field grown tubers, m-RT-PCR detected infection of two to three viruses, which were present in the tubers.

DNA, Complementary↗

PubMed2000

Expression of Glut-4 and Glut-1 transporters in rat diaphragm muscle.

Glucose transporters (Gluts) are a family of membrane proteins responsible for the transport of glucose across cellular membranes. Generally, alterations of Gluts expression in limb skeletal muscle have been reported. However, the changes of Glut isoforms in respiratory muscle which contracts with a duty cycle have rarely been studied. This study was performed to evaluate at the light microscopy level the expression of Glut-4 and Glut-1 transporters in normal and denervated diaphragm by immunohistochemistry method with specific Gluts antibodies. The results showed Glut-4 immunoreactivity in both the cell periphery and the interior of myocytes. Glut-1 was also present in the cell border and in the interior of myocytes in control diaphragm. However, Glut-4 staining was stronger than Glut-1 staining in control diaphragm. In denervated hemidiaphragm, the Glut-4 immunolabelling decreased and Glut-1 increased. These data indicated that (1) Glut-4 and Glut-1 transporters were observed in diaphragm; and (2) there were alterations in the expression of both glucose transporters after denervation. These alterations in Glut isoforms after denervation may be associated with the removal of innervation itself, and/or may partly result from passive stretch imposed by inspiratory activation of the contralateral side.

Animals↗

PubMed2000

Effects of morphine on rheological properties of rat red blood cells.

To evaluate the effect of morphine on red blood cells, in vivo and in vitro rat models of morphine dependence were established. Rheological properties of rat red cells were measured by ektacytometry; the biophysical changes in the membrane of rat red cells were measured by the Fourier-Transformed Infrared technique (FT-IR) and the fluorescence depolarization method. The results show that the membrane fluidity of red cells was greatly reduced by morphine and the secondary structure of membrane proteins was changed. This suggests that morphine affects the rat red cell membrane directly, rather than through opioids-receptors.

Animals↗

PubMed1999

A model system of primary murine hepatocytes infected by murine cytomegalovirus.

In order to establish a model system of the murine hepatocyte infection by murine cytomegalovirus (MCMV), the primary cultured murine hepatocytes were obtained in a modified low-serum medium system by a non-perfusion method, and then infected by Smith strain MCMV. Infected hepatocytes showed characteristic cytopathic effect (CPE) at 30 h after infection, in which a large number of viral particles was found and ultrastructures were destroyed (as revealed by disappearance of bile canalicula and organelles) under the electron microscope and MCMV immediate-early genes were detected by in situ hybridization. Meanwhile, infected cells produced albumin significantly less than corresponding uninfected controls. On the contrary, uninfected controls simultaneously cultured under the same conditions showed normal function and ultrastructure (glycogen rosettes, bile canalicula, wheel-like mitochondria and well-developed rough and smooth endoplasmic reticula). These results demonstrated that a model system of primary cultured murine hepatocytes infected by MCMV was successfully set up.

Animals↗

PubMed1999

The clinical study and HLA genotyping of 112 familial myasthenia gravis patients.

One hundred and twelve cases of familial myasthenia gravis (MG) from 44 families selected from 2100 patients with MG diagnosed since 1983 in the Department of Neurology were studied. The clinical pictures and immunological features of the patients showed a great resemblance to those of sporadic cases. The pedigree analysis disclosed that the hereditary patterns of familial patients were basically Mendellian autosomal inheritance. Many predisposing factors such as fever, infection, use of aminoglycoside or vaccines, played an important role in presenting the phenotype of subclinical cases. The HLA genotyping suggested that the complement polymorphism C4A * 4, the complotype S42, and the genes 0901 and 1301 of DRB1 allele, were related to the pathogenesis of MG. It was concluded that the phenotype of MG may be the result of interaction between hereditary defects and environmental factors.

Alleles↗