Elucidation of fragmentation mechanisms involving transfer of three hydrogen atoms using a quadrupole time-of-flight mass spectrometer.
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Letter↗
Biomedical subjects
X Yu
Publications and source records attributed to X Yu.
Neurotoxicity of 2-bromopropane and 1-bromopropane, alternative solvents for chlorofluorocarbons.
To clarify the neurotoxicity of 2-bromopropane (2-BP) in comparison with 1-bromopropane (1-BP), 36 Wistar strain male rats were divided into 4 groups of 9 and exposed daily to 100-ppm 2-BP, 1000-ppm 2-BP, 1000-ppm 1-BP, or fresh air for 8 h a day. Exposure to 1000 ppm of 1-BP was discontinued after 5 or 7 weeks' exposure because of the unexpected appearance of incomplete hindlimb paralysis followed by serious emaciation. The other groups were sacrificed at the end of 12 weeks' exposure. Exposure to 1000 ppm of 2-BP resulted in significant decreases in body weight and motor nerve conduction velocity (MCV) and elongation in distal latency (DL). A ball-like enlargement of myelin sheaths was observed. Significant reductions in the number of erythrocytes, platelets, and leukocytes, testicular germ cell loss, and seminiferous atrophy were also observed in this group, but not in 100-ppm 2-BP group. Exposure to 1000 ppm of 1-BP for 5 or 7 weeks caused a significant decrease in body weight and MCV and elongation in DL. Linearly arranged ovoid- or bubble-like debris of the axons and myelin sheaths in the teased tibial nerves and axonal swelling in gracilis nucleus were found in this group. No significant changes in hematological indices or histopathological findings of the testis were found in this group. In conclusion, 2-BP is neurotoxic to the peripheral nerves in addition to its toxic effects on the reproductive and hematopoietic systems at 1000 ppm. No noticeable changes were found in the rats exposed to 100 ppm of 2-BP. 1-BP is a potent neurotoxicant at 1000 ppm for 5 or 7 weeks, while testicular and hematopoietic toxicity was not found.
Animals↗
Electron microscopic studies of the translin octameric ring.
Translin is thought to participate in a variety of cellular activities including chromosomal translocations, translational regulation of mRNA expression, and mRNA transport. It forms an octameric ring structure capable of sequence-specific binding of both DNA and RNA substrates. We have used electron microscopy and single-particle image analysis to generate a three-dimensional reconstruction of the Translin ring. The subunits appear to have two distinct domains that assemble to form an open channel with diameter of approximately 30 A at one end and approximately 50 A at the opposite end. In the presence of either DNA or RNA containing consensus binding sequences, the largest opening into the central cavity is filled with density. Strikingly, although Translin shows significant sequence homology to only one other protein, Translin-associated factor X, the quaternary organization and the dimerization of subunits in the ring are very similar to those observed for hexameric ring helicases. This suggests that many of the structures in DNA and RNA metabolism may have similar quaternary organization.
Algorithms↗
Lack of nigral pathology in transgenic mice expressing human alpha-synuclein driven by the tyrosine hydroxylase promoter.
alpha-Synuclein has been identified as a major component of Lewy body inclusions, which are one of the pathologic hallmarks of idiopathic Parkinson's disease. Mutations in alpha-synuclein have been found to be responsible for rare familial cases of Parkinsonism. To test whether overexpression of human alpha-synuclein leads to inclusion formation and neuronal loss of dopaminergic cells in the substantia nigra, we made transgenic mice in which the expression of wild-type or mutant (A30P and A53T) human alpha-synuclein protein was driven by the promoter from the tyrosine hydroxylase gene. Even though high levels of human alpha-synuclein accumulated in dopaminergic cell bodies, Lewy-type-positive inclusions did not develop in the nigrostriatal system. In addition, the number of nigral neurons and the levels of striatal dopamine were unchanged relative to non-transgenic littermates, in mice up to one year of age. These findings suggest that overexpression of alpha-synuclein within nigrostriatal dopaminergic neurons is not in itself sufficient to cause aggregation into Lewy body-like inclusions, nor does it trigger overt neurodegenerative changes.
Animals↗
Agarose gel stiffness determines rate of DRG neurite extension in 3D cultures.
The optimization of scaffold mechanical properties for neurite extension is critical for neural tissue engineering. Agarose hydrogels can be used to stimulate and maintain three-dimensional neurite extension from primary sensory ganglia in vitro. The present study explores the structure-function relationship between dorsal root ganglion (DRG) neurite extension and agarose gel mechanical properties. A range of agarose gels of differing concentrations were generated and the corresponding rate of E9 DRG neurite extension was measured. Rate of neurite extension was inversely correlated to the mechanical stiffness of agarose gels in the range of 0.75-2.00% (wt/vol) gel concentrations. In addition, we postulate a physical model that predicts the rate of neurite extension in agarose gels, if gel stiffness is a known parameter. This model is based on Heidemann and Buxbaum's model of neurite extension. These results, if extended to scaffolds of other morphological and chemical features, would contribute significantly to the design criteria of three-dimensional scaffolds for neural tissue engineering.
Animals↗
Dipyridamole stress ultrasonic myocardial tissue characterization in patients with Kawasaki disease.
Dipyridamole stress integrated backscatter (IBS) was used for evaluation of myocardial ischemia or damage in 31 children with coronary artery lesions caused by Kawasaki disease, in comparison with thallium-201 myocardial imaging. All patients underwent echocardiography at rest and after dipyridamole stress at the anterior interventricular septum, posterior wall (PW), and inferior wall (INF). At rest, no significant difference was seen in cyclic variation (CV) of IBS in the regions with normal or abnormal distribution on Tl-201 imaging. But in the regions showing abnormal distribution after stress, CV decreased significantly. A delayed study after stress showed the recovery of CV to the level at rest in all patients. Sensitivity of abnormal cyclic variation integrated backscatter was 75% in the PW and 91% in the INF, and specificity was 91% in the PW and 90% in the INF, compared with the results of thallium-201 imaging. Dipyridamole stress IBS can provide sensitive detection of myocardial ischemia or damage in Kawasaki disease.
Adolescent↗
Detection of bacterial DNA by PCR and reverse hybridization in the 16S rRNA gene with particular reference to neonatal septicemia.
AIM: The clinical diagnosis of sepsis is difficult, particularly in neonates. It is necessary to develop a rapid and reliable method for detecting bacteria in blood and cerebrospinal fluid (CSF). Polymerase chain reaction (PCR) and reverse hybridization of the 16S rRNA gene would permit fast and sensitive determination of the presence of bacteria and differentiate gram-positive bacteria from gram-negative ones in clinical specimens. METHODS: We developed a pair of primers according to the gene encoding 16SrRNA found in all bacteria. DNA fragments from different bacterial species and from clinical samples were detected with PCR, and with reverse hybridization using a universal bacterial probe, a gram-positive probe and a gram-negative probe. RESULTS: A 371 bp DNA fragment was amplified from 20 different bacterial species. No signal was observed when human DNA and viruses were used as templates. The sensitivity could be improved to 10(-12) g. All 26 culture-positive clinical samples (22 blood samples and 4 CSF samples) were positive with PCR. The gram-negative and gram-positive probes hybridized to clinical samples and to known bacterial controls, as predicted by Gram's stain characteristics. CONCLUSIONS: Our results suggest that the method of PCR and reverse hybridization is rapid, sensitive and specific in detecting bacterial infections. This finding may be significant in the clinical diagnosis of sepsis in neonates.
Bacteremia↗
Computer-aided dynamic simulation of microwave-induced thermal distribution in coagulation of liver cancer.
To develop a method of dynamic three-dimensional (3-D) simulation of thermal distribution in ultrasound-guided microwave coagulation therapy of liver cancer and to verify its accuracy. The specific absorption rate (SAR) values were established by measuring the temperature in equivalent phantom tests. Those values were different under different power output condition. Dynamic 3-D temperature distributions were reconstructed with a finite-element model. Testing and rectification were performed through animal experiments and clinical trials, respectively. The temperature curves in the experiments corresponded well with simulated ones in vitro--91.4% and 88.9% using single and double electrodes, respectively. The measured coagulated boundary and simulated temperature boundary had a good correspondence in 85.7% of the specimens. In both in vivo experiments and clinical trials, blood perfusion influenced the rise in temperature significantly. Temperature curves between the simulations and actual measured results showed good correspondence--67.8% (19/28) in the patients with hepatocellular carcinoma. Distance between electrodes and combined thermal distributions were both optimized with computer-aided simulation during simultaneous two-electrode coagulation. The results demonstrated that computer-aided simulation of microwave thermal distribution is an accurate and reliable method which provides a theoretical and technical basis for controlling coagulated tissue volume and placement of the electrodes during microwave coagulation therapy of liver cancer.
Animals↗
Critical roles of nuclear receptor response elements in replication of hepatitis B virus.
Functional analysis of the roles of the nuclear receptor response elements (NRREs) in the transcription and replication of hepatitis B virus (HBV) in the context of its whole genome has been hampered by the extensive overlapping of the NRREs with the regions encoding viral proteins. We introduced point mutations that inactivate the NRREs individually without altering the open reading frames of viral proteins. These mutations in the context of a plasmid containing 1.2 copies of the HBV genome were transiently transfected into the human hepatoma cell line Huh7. Inactivation of the NRRE in either the preC promoter (NRRE(preC)) or enhancer I (NRRE(enhI)) led to moderate reductions in synthesis of viral RNAs. Concurrent inactivation of both NRREs led to 7- to 8-fold reductions in synthesis of the preC, pregenomic, and preS RNAs and a 15-fold reduction in synthesis of the S RNA. The accumulation of viral DNA in the cytoplasmic nucleocapsids and virion particles in the culture medium was also reduced seven- to eightfold. These results suggest that these NRREs are critical for the efficient propagation of HBV in hepatocytes. In cotransfection experiments we also found that overexpression of PPARalpha-RXRalpha in the presence of their respective ligands led to a fourfold increase in pregenomic RNA synthesis and a four- to fivefold increase in viral DNA synthesis, while it had little or no effect on synthesis of the other viral RNAs. Similar effects were observed with overexpression of PPARgamma-RXRalpha in the presence of their respective ligands. This activation was dependent on NRRE(preC), because the increase in synthesis of viral RNA and DNA was not observed when this site was mutated. Likewise, no activation of synthesis of pregenomic RNA and viral DNA by PPARalpha-RXRalpha was observed in a naturally occurring NRRE(preC)(-) mutant of HBV. Our results suggest that interactions between nuclear receptors and NRREs present in the HBV genome may play critical roles in regulating its transcription and replication during HBV infection of hepatocytes.
Base Sequence↗
Inhibition of androgen receptor-mediated transcription by amino-terminal enhancer of split.
A yeast two-hybrid assay has identified an androgen-dependent interaction of androgen receptor (AR) with amino-terminal enhancer of split (AES), a member of the highly conserved Groucho/TLE family of corepressors. Full-length AR, as well as the N-terminal fragment of AR, showed direct interactions with AES in in vitro protein-protein interaction assays. AES specifically inhibited AR-mediated transcription in a well-defined cell-free transcription system and interacted specifically with the basal transcription factor (TFIIE) in HeLa nuclear extract. These observations implicate AES as a selective repressor of ligand-dependent AR-mediated transcription that acts by directly interacting with AR and by targeting the basal transcription machinery.
Androgen Receptor Antagonists↗
Degradation and drug delivery properties of poly(1,4-cyclohexanedicarboxylic anhydride).
Polyanhydrides for drug-controlled release systems from cis- and trans-1,4-cyclohexanedicarboxylic acid (1,4-CHDA) were synthesized by melt polycondensation. The degradation of polymers was estimated by weight loss in 0.1 mol l(-1), pH 7.4 phosphate buffer at 37 degrees C. The drug delivery was conducted in the same buffer. The results show that the different polymers lost weight over 150-360 h, and fine surface erosion was investigated. The different conformation of CHDA has an obvious influence on the degradation of polyanhydrides due to their different crystallinity, with higher crystallinity samples degrading much more slowly. The incorporation of adipic acids into the poly(CHDA) can obviously accelerate the degradation and the introduction of -CH2- segments increased the flexibility of polyanhydride backbone and accelerated the degradation rate. In vitro delivery experiments show that Bruffen was completely released in about 10 days from a melting mold disk with a fine linear delivery curve.
Anhydrides↗
Neutrophils and mononuclear cells express vascular endothelial growth factor in acute Kawasaki disease: its possible role in progression of coronary artery lesions.
Kawasaki disease (KD) is a syndrome of systemic vasculitis of unknown etiology that is complicated by coronary artery lesions (CAL), leading occasionally to cardiac ischemic sequelae. To examine whether vascular endothelial growth factor (VEGF) is responsible for CAL in KD, we determined serum VEGF levels by ELISA and peripheral blood mononuclear cell (PBMC) and neutrophil VEGF expression by immunoblot analysis. Significantly increased levels of VEGF were demonstrated in acute KD as well as in other vasculitis syndromes (p < 0.0001). In the 10 KD patients with CAL, serum VEGF levels were maximal approximately 2 wk post-onset when CAL generally develops and were significantly higher than in 20 patients without CAL (mean, 474 and 241 pg/mL, respectively; p = 0.00015). During the same period, immunoblot analysis revealed maximal VEGF expression in PBMC, corresponding to serum VEGF levels in most patients and being particularly marked in patients with CAL (p < 0.01). Neutrophils expressed VEGF only in the early stage of acute KD and declined rapidly in the majority of KD patients regardless of the presence of CAL, showing a strikingly different expression pattern than that for PBMC. Predominant VEGF expression by PBMC was also demonstrated in patients with other vasculitis syndromes and only faintly in normal controls. The results suggest that VEGF is generated dynamically in KD, presumably reflecting its disease activity. Neutrophil-derived VEGF may play a role in regulating early vascular responses, whereas PBMC-derived VEGF may contribute to later vascular injury and remodeling.
Adolescent↗
Differential expression and functional analysis of Pitx2 isoforms in regulation of heart looping in the chick.
Pitx2, a bicoid-related homeobox gene, plays a crucial role in the left-right axis determination and dextral looping of the vertebrate developing heart. We have examined the differential expression and function of two Pitx2 isoforms (Pitx2a and Pitx2c) that differ in the region 5' to the homeodomain, in early chick embryogenesis. Northern blot and RT-PCR analyses indicated the existence of Pitx2a and Pitx2c but not Pitx2b in the developing chick embryos. In situ hybridization demonstrated a restricted expression of Pitx2c in the left lateral plate mesoderm (LPM), left half of heart tube and head mesoderm, but its absence in the extra-embryonic tissues where vasculogenesis occurs. RT-PCR experiments revealed that Pitx2a is absent in the left LPM, but is present in the head and extra-embryonic mesoderm. However, ectopic expression of either Pitx2c or Pitx2a via retroviral infection to the right LMP equally randomized heart looping direction. Mapping of the transcriptional activation function to the C terminus that is identical in both isoforms explained the similar results obtained by the gain-of-function approach. In contrast, elimination of Pitx2c expression from the left LMP by antisense oligonucleotide resulted in a randomization of heart looping, while treatment of embryos with antisense oligonucleotide specific to Pitx2a failed to generate similar effect. We further constructed RCAS retroviral vectors expressing dominant negative Pitx2 isoforms in which the C-terminal transcriptional activation domain was replaced by the repressor domain of the Drosophila Engrailed protein (En(r)). Ectopic expression of Pitx2c-En(r), but not Pitx2a-En(r), to the left LPM randomized the heart looping. The results thus demonstrate that Pitx2c plays a crucial role in the left-right axis determination and rightward heart looping during chick embryogenesis.
Amino Acid Sequence↗
Urinary 8-oxo-7, 8-dihydro-2'-deoxyguanosine and biopyrrins levels among construction workers with asbestos exposure history.
It has been suggested that oxidative stress is associated with the cancers caused by asbestos. Since construction workers are sometimes exposed to low levels of asbestos, we investigated whether oxidative stress was elevated in construction workers who had been exposed to low levels of asbestos. The subjects were 48 Japanese construction workers. The defined asbestos-exposed group consisted of subjects who had the history of suspected exposure to asbestos and were diagnosed to have irregular opacities or pleural plaques. We measured the amount of 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxodG) and biopyyrins in the urine of the subjects. The results showed that 8-oxodG and biopyyrins levels in the defined asbestos-exposed group were higher, although they were not statistically significant, than those in the control group. In addition, the urinary 8-oxodG levels tended to correlate positively with the duration of suspected exposure to asbestos. These results suggest that even low-level asbestos exposure may induce oxidative stress and that the resulting's the oxidative stress might be related to lung cancer in construction workers.
8-Hydroxy-2'-Deoxyguanosine↗
Quantification of benzoic, phenylacetic, and phenylbutyric acids from filter-paper blood spots by gas chromatography--mass spectrometry with stable isotope dilution.
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Amino Acid Metabolism, Inborn Errors↗
Identification and characterization of a novel OCA-B isoform. implications for a role in B cell signaling pathways.
OCA-B is a B lymphocyte-specific transcription coactivator that mediates tissue- and stage-restricted transcription of immunoglobulin genes. Earlier genetic studies revealed that OCA-B is essential for germinal center formation and production of secondary immunoglobulin isotypes. Biochemically purified OCA-B contains p35 and p34 isoforms, and a further analysis has now revealed that p35 is derived from a newly found isoform, p40. More importantly, it has been found that p35 is myristoylated in vivo and that this leads to dramatic changes (including localization to membrane compartments) in its properties. These results suggest that the p35 isoform of OCA-B has functions distinct from those of the nuclear p34 and that it might be a component of a signaling pathway that is required for late-stage B cell development.
3T3 Cells↗
[The sieving performance of a new polyethersulfone hollow fiber plasma fractionation membrane].
Plasma fractionation membrane is very important in double filtration plasmapheresis. We studied a new polyethersulfone hollow fiber membrane plasma fractionator and evaluated the effect of time, transmembrane pressure (TMP) and mean shear rate on the sieving coefficient (SC) during membrane plasma fractionation. The sieving coefficients of various proteins reached their maximum values at 40 min at the plasma flow rate QI = 30 ml/min and plasma filtrated flow rate QF = 20 ml/min. The QF increased with the increase of TMP, and the point of the intersection of the curve of the QF vs. TMP and the SC vs. TMP was regarded as the ideal condition for plasma fractionation. The plasma filtrated rate PFR = QF/QI = 0.6-0.7. The TMP changed with the change of the mean shear rate, and the mean shear rate had little effect on the SC. The data is of significance to the application of plasma fractionation membrane.
Membranes, Artificial↗
[Quantitative analysis of cell fusion caused by glycoprotein of paramyxoviruses with reporter gene method].
OBJECTIVE: To establish a kind of quantitative assay method for analyzing the reporter gene assay for fusion was established. METHODS: Two populations of BHK21 cells were infected with vTF-7 recombinant and wild-type vaccinia viruses respectively and transfected with paramyxovirus F and HN cDNA and plasmid pG1NT7 beta-gal respectively. After 16 h, the two cell populations were removed from the wells by trypsinization. Equal numbers of the two populations were mixed in wells of a 96-well flat-bottom plate after washing and pelleting. After 15 hours' incubation at 37 degrees C, the cells were lysed with Nonidet P-40 and A values were read at 570 nm with an ELISA reader supported by SOFTMAX software. RESULTS: Reporter gene method had a close relationship with cell count method, r = 0.9890(P < 0.01). Positive and negative coincidence rates were 100%. The best main reaction conditions are as follows: substrate concentration, 16 mmol/L; color reaction time, 20-25 min; amount of DNA for transfection, 1 microgram; cell numbers for each population, 1 x 10(5). CONCLUSION: Reporter gene method is a kind of very sensitive, specific and repeatable quantitative analysis for cell fusion and can be used in the studies on membrane fusion caused by any viruses.
Cell Fusion↗