Biomedical subjects

X L Xie

Publications and source records attributed to X L Xie.

16 recordsLinked to original sources

PubMed2003

Wear performance of ultrahigh molecular weight polyethylene/quartz composites.

Ultrahigh molecular weight polyethylene (UHMWPE)/quartz composites were compression molded in the presence of organosiloxane, and then hydrolyzed. The used organosiloxane is vinyl tri-ethyloxyl silane. The gelation, the melting behavior, the crystallinity, the mechanical properties and the wear resistance of UHMWPE/quartz composites were investigated. The results showed that organosiloxane can act as a cross-linking agent for UHMWPE matrix and serve as a coupling agent for improving the bonding between the quartz particles and the UHMWPE matrix. The correlation between the various properties and the morphology of the composites has been discussed. At about 0.5phr organsiloxane while the degree of crystallinity of the composite is at the peak value of 57%, the mechanical properties and the wear resistance of UHMWPE/quartz composites reaches their maximum.

Biocompatible Materials↗

PubMed2002

Enhanced wear performance of ultra high molecular weight polyethylene crosslinked by organosilane.

Ultra high molecular weight polyethylene (UHMWPE) crosslinked by organosilane was thermal compression molded. The organosilane used was the tri-ethyloxyl vinyl silane. Its gelation, melting behavior, crystallinity, mechanical and wear-resisting properties were systematically investigated. The results showed that the gel ratio of UHMWPE increases with the incorporation of organosilane. At a low content of organosilane, the melting point and crystallinity of the crosslinked UHMWPE increase, and hence the mechanical and wear-resisting properties are improved. However, at a high content of organosilane, these performances of the crosslinked UHMWPE become worse. At 0.4 phr silane, the wear resistance of crosslinked UHMWPE reaches its optimum value.

Journal Article↗

PubMed2000

[The medium optimization of xylitol fermentation based on neural networks and genetic algorithms].

Using genetic algorithms(GA) for medium optimization of xylitol fermentation, and coupling neural networks model for predicting xylitol concentration is introduced. The medium compose determined by GA is as input data of the neural networks, while the output data predicted by neural networks is as suitable value of GA for predicting. The optimum medium is further validated by experimentation. The good result, which save the experimental workload and charge, enhance the level of xylitol fermentation as well as reduced the medium consume is obtained.

Algorithms↗

PubMed1993

Effects of rhynchophylline on motor activity of mice and serotonin and dopamine in rat brain.

Rhynchophylline (Rhy) reduced the spontaneous motor activity and enhanced the sedative and hypnotic effects of sodium pentobarbital in mice. The effects of Rhy on serotonin (5-HT) and dopamine (DA) concentrations in rat brain, and the release of 5-HT and DA from the regional brain slices were studied by a fluorescence detector. Rhy increased the 5-HT content in the hypothalamus and cortex, but reduced the DA concentrations in the cortex, amygdala, and spinal cord. Rhy promoted the release of endogenous DA from 4 brain regions. The release of 5-HT was increased in 2 brain regions and decreased in hypothalamus slice. However, Rhy inhibited the release of both 5-HT and DA evoked by high potassium.

Alkaloids↗

PubMed1991

Protein conformational relaxation following photodissociation of CO from carbonmonoxymyoglobin: picosecond circular dichroism and absorption studies.

Picosecond time-resolved polarization spectroscopy is used to study relaxation dynamics in myoglobin following photoelimination of CO from carbonmonoxymyoglobin. Evolution of the transient circular dichroism signal of the N band of myoglobin (probed at 355 nm) to that characteristic of equilibrium myoglobin requires approximately 300 ps. This time scale is significantly longer than that corresponding to the photoinitiated bond cleavage. Transient linear dichroism of the Soret band and picosecond time-resolved magnetic circular dichroism measurements of the Q band demonstrate that the circular dichroism kinetics do not result from either time-dependent changes in the orientation of the transition moments of the heme ring or the doming of the heme that accompanies the out-of-plane motion of the iron. Finally, transient absorption data of the near-IR optical transition of photogenerated myoglobin suggest that the circular dichroism data are not a measure of the tilting of the proximal histidine. The circular dichroism data are discussed in terms of a relaxation in the tertiary structure of the protein following dissociation.

Carbon Monoxide↗

PubMed1991

A picosecond circular dichroism study of photosynthetic reaction centers from Rhodobacter sphaeroides.

Picosecond transient circular dichroism spectra are reported for the primary intermediates in the photocycle of reaction centers isolated from Rhodobacter sphaeroides. The time-resolved circular dichroism spectra of the two electron transfer intermediates (BChl2) +BPh-LQA and (BChl2) +BPhLQ-A reveal a large, nonconservative, and fairly stationary CD band at 800 nm. These results suggests that mechanisms other than exciton interactions need to be included in order to explain the optical activity of this biological system.

Circular Dichroism↗

PubMed1991

[Alcohol injections for the treatment of recurrent intracerebral gliomas].

Seventeen patients with recurrent intracerebral gliomas were given alcohol injection percutaneously guided by ultrasonography. These patients suffered from supratentorial tumors and were operated on previously. The fluid of cystic lesions of 13 patients was aspirated and absolate alcohol was injected for 5-8 times. The cystic cavities soon disappeared followed by symptoms of intracerebral hypertension. Biopsies from different parts of tumor cavity showed that tumor cells were degenerated and necrotized. There was no curable effect on larger solid neoplasm and deep sited solid tumor. We conclude that percutaneous alcohol injection is effective in the treatment of recurrent gliomas.

Adolescent↗

PubMed1990

The Drosophila melanogaster z600 gene encodes a chromatin-associated protein synthesized in the syncytial blastoderm.

The Drosophila melanogaster z600 gene is zygotically expressed with gene transcripts accumulating transiently during early embryogenesis. Based on nucleotide sequence analysis, z600 is predicted to encode a small, basic, histone-like protein. Antibodies generated against a beta-galactosidase::z600 fusion protein immunoprecipitated the z600 in vitro translation product and detected a z600 protein present predominantly in 2- to 4-h embryos. We localized the z600 protein in whole-amount embryos by indirect immunofluorescence. These studies show that the protein is located in the nucleus and associated with chromatin in the syncytial blastoderm.

Animals↗

PubMed1990

cis-acting sequences required for the germ line expression of the Drosophila gonadal gene.

We have identified two DNA sequences required for the proper germ line expression of the Drosophila gonadal (gdl) gene. A 53-bp region located from -328 to -276 relative to the gdlM transcription start site was required for the expression of a gdl-lacZ gene fusion in the male germ line. This sequence resides within the upstream z600 gene; however, z600 expression was undetectable in male germ cells. A 30-bp region located from -5 to +25 relative to the gdlF transcription start site was required for the expression of gdl-lacZ gene fusion in the female germ line.

Animals↗

PubMed1990

Expression of the Drosophila gonadal gene: alternative promoters control the germ-line expression of monocistronic and bicistronic gene transcripts.

The Drosophila gonadal (gdl) gene is differentially expressed in the male and female germ lines. In males, expression in the gdlM mode results in a 1200-/1500-nucleotide RNA pair, whereas in females, expression in the gdlF mode results in a 1000-/1300-nucleotide RNA pair. Since the two expression modes are a result of alternative promoter usage, the sex-specific transcripts differ at their 5' ends. These sequence differences affect the coding capacity of the gene. A common open reading frame (ORF) of 193 codons (ORF193) is present in all four gdl transcripts; a consequence of the additional sequences at the 5' end of the gdlM transcripts is the presence of an additional ORF of 39 codons (ORF39). Translation of gdlF and gdlM cRNAs in a reticulocyte lysate reveals that these transcripts can serve as monocistronic and bicistronic mRNAs in vitro. An analysis of germ-line transformants harboring gdl-lacZ gene fusions provides information on gdl gene expression during gametogenesis. The fusion genes are transcribed and translated in the germ line; beta-galactosidase activity is detected in premeiotic and postmeiotic spermatogenic stages in males, and in nurse cells and oocytes of developing egg chambers in females. Both gdlM ORFs are used because transformant lines expressing the lacZ gene, fused in frame with either ORF39 or ORF193, are positive for beta-galactosidase activity in the testes. These studies also reveal that separable transcription control elements are responsible for gdl expression in the male and female germ lines.

Animals↗

PubMed1987