Biomedical subjects

J Xiong

Publications and source records attributed to J Xiong.

At least 19 recordsLinked to original sources

PubMed2001

Disruption of BRCA1 LXCXE motif alters BRCA1 functional activity and regulation of RB family but not RB protein binding.

The tumor suppressor activity of the BRCA1 gene product is due, in part, to functional interactions with other tumor suppressors, including p53 and the retinoblastoma (RB) protein. RB binding sites on BRCA1 were identified in the C-terminal BRCT domain (Yarden and Brody, 1999) and in the N-terminus (aa 304-394) (Aprelikova et al., 1999). The N-terminal site contains a consensus RB binding motif, LXCXE (aa 358-362), but the role of this motif in RB binding and BRCA1 functional activity is unclear. In both in vitro and in vivo assays, we found that the BRCA1:RB interaction does not require the BRCA1 LXCXE motif, nor does it require an intact A/B binding pocket of RB. In addition, nuclear co-localization of the endogenous BRCA1 and RB proteins was observed. Over-expression of wild-type BRCA1 (wtBRCA1) did not cause cell cycle arrest but did cause down-regulation of expression of RB, p107, p130, and other proteins (e.g., p300), associated with increased sensitivity to DNA-damaging agents. In contrast, expression of a full-length BRCA1 with an LXCXE inactivating mutation (LXCXE-->RXRXH) failed to down-regulate RB, blocked the down-regulation of RB by wtBRCA1, induced chemoresistance, and abrogated the ability of BRCA1 to mediate tumor growth suppression of DU-145 prostate cancer cells. wtBRCA1-induced chemosensitivity was partially reversed by expression of either Rb or p300 and fully reversed by co-expression of Rb plus p300. Our findings suggest that: (1) disruption of the LXCXE motif within the N-terminal RB binding region alters the biologic function of BRCA1; and (2) over-expression of BRCA1 inhibits the expression of RB and RB family (p107 and p130) proteins.

Amino Acid Motifs↗

PubMed2001

[Protective effect of epidural cooling upon ischemic spinal cord injury].

OBJECTIVE: To evaluate the protective effect of epidural cooling on ischemic spinal cord injury. METHODS: Fourteen healthy hybrid dogs were randomly divided into two groups: control group (n = 8) and experimental group (n = 6). Spinal cord injury was induced by double aortic cross-clamping for 40 minutes. Before the clamping, the cerebrospinal fluid temperature of the animals in experimental group was decreased to 30 degrees C +/- 1 degrees C by epidural cooling until the aorta was unclamped for 5 minutes. Three days after the operation, the function of the hind limbs of the animals was evaluated by Tarlov's scale and histological examination of the spinal cord was made. RESULTS: Six dogs showed complete paraplegia (grade 0) and two showed paresis (grade 1) in the control group. The neurological outcome of the experimental group was much better than that in the control group (H = 10.68, P = 0.001). The neurological function of 4 dogs in the experimental group was in grade 4, and one in grade 3. Histological examination revealed hemorrhage of gray matter, degeneration and necrosis of neurons, and severe demyelination of myelinated nerve fibers in the spinal cord from T10 to sacral segments in dogs with paraplegia. The changes in spinal cord were slight in the dogs without severe neurological injury. CONCLUSION: Local hypothermia of spinal cord by epidural cooling provides effective protection against ischemic spinal cord injury in dog.

Animals↗

PubMed2001

Occurrence of a new metallo-beta-lactamase IMP-4 carried on a conjugative plasmid in Citrobacter youngae from the People's Republic of China.

During the course of an antimicrobial resistance surveillance programme in Guangzhou, the People's Republic of China, single strains of Citrobacter youngae and Pseudomonas aeruginosa were identified which were resistant to imipenem and found to carry the carbapenemase gene bla(IMP). PCR screening of the citrobacter strain with specific primers for the bla(IMP) type genes gave a 587-bp product which when sequenced gave 100% homology with the bla(IMP-4) sequence reported recently from Acinetobacter spp. The determinant in the C. youngae strain was found to be located on a 156-kb plasmid capable of transfer to Escherichia coli UB1637 by conjugation. Sequencing of the bla(IMP-4) open reading frame in the C. youngae strain and adjacent sequences not only confirmed the presence of bla(IMP-4) but also identified that a conserved core site found within the 59-bp element of integrons was present and the same as the one described in the only other occurrence of bla(IMP-4) in Acinetobacter spp. isolated from an intensive care unit in Hong Kong. This is the second report of transferable carbapenemase genes in Enterobacteriaciae outside of Japan and the first in the People's Republic of China. Under the selective pressure of carbapenems and extended spectrum cephalosporins use we might expect this gene to spread and widespread surveillance should be instituted.

Adult↗

PubMed2001

Determination of arsenic species by capillary zone electrophoresis with large-volume field-amplified stacking injection.

Determination of arsenic species by large-volume field amplified stacking injection-capillary zone electrophoresis (LV-FASI-CZE) is reported in this paper. Whole column injection was employed. The optimum buffer pH for the separation of weak acids was discussed. It was found that the optimum buffer to analyze the stacked arsenate (As(V)), monomethylarsonate (MMA), and dimethylarsinate (DMA) was 25 mM phosphate at pH 6.5. However, the optimum buffer to analyze the concentrated arsenite (As(III)) was 20 mM phosphate - 10 mM borate at pH 9.28. The limits of detection of the method developed were 0.026 mg/L for As(III), 0.023 mg/L for As(V), 0.043 mg/L for MMA, and 0.018 mg/L for DMA. An enrichment factor of 34-100 for several arsenic species was obtained. In the end, this method was applied to determine the arsenic concentration in the environmental reference materials to show the usefulness of the method developed.

Arsenates↗

PubMed2001

Tagged Transcriptome Display (TTD) in indica rice using Ac transposition.

We have developed a population of transgenic indica rice lines containing the autonomous Activator transposon (Ac) from maize. A transposon excision assay using as the reporter the green fluorescent protein (GFP) gene driven by the ubiquitin promoter was used to monitor Ac excision in various tissues. Our results, based on Ac excision and re-insertion events in 289 independent rice transformants, provide an insight into transposon biology in this heterologous model cereal system. Twenty percent of the transformed calli displayed uniform GFP activity, indicating very early Ac excision, while later excision in another 40% of calli was revealed by mosaic GFP activity. Both phenotypes were confirmed by molecular analysis. Progeny analysis revealed active transposition, with some lines displaying transposition to unlinked positions. Amplification of the Ac copy number was observed in approximately 30% of the lines, thus tagging multiple sites. We developed a "transposon insertion display" procedure, involving the use of CpG methylation-sensitive enzymes and a macroarray-based approach with cDNA as a complex hybridization probe, to selectively detect transposon insertions in transcribed sequences. Sequencing of tagged sites identified by hybridization to leaf cDNA revealed that all the hybridizing tags were homologous to genes or ESTs present in databases. Extrapolation from these data suggests that 12% of all amplified tags display homology to genes or ESTs - five times more than would be expected on the basis of random transpositional insertion. This Tagged Transcriptome Display (TTD) technique, using a population of Ac insertion-tagged lines, therefore represents a convenient approach for the identification of tagged genes involved in specific processes, as revealed by their expression patterns.

Base Sequence↗

PubMed2001

Cerebral hemodynamic response in Chinese (first) and English (second) language processing revealed by event-related functional MRI.

Comparative functional neuroimaging studies using the block design paradigm have previously demonstrated that there are no significant differences in the location of areas of cerebral activation when native Chinese speakers independently process single words or sentences in both the Chinese (first) and English (second) languages. While it has also been documented that significant domains of brain response include the inferior to middle left frontal lobe, the latency, amplitude and duration of the associated hemodynamic changes during isolated neural processing of Chinese and English languages still remain unknown. The aim of this study, therefore, was to examine the characteristics of the hemodynamic alterations in the above-mentioned regions with event-related functional MRI (ER-fMRI) when native Chinese speakers performed verb generation tasks in both the Chinese (first) and English (second) languages. Our results demonstrate the presence of a similar neural activity-induced hemodynamic response in the inferior to middle left frontal lobe during both tasks. Further, there were also no statistically significant differences among the variables that described the hemodynamic response curves. These findings strongly imply that the underlying neural mechanism for Chinese (first) and English (second) language processing may be similar in native Chinese speakers.

Adult↗

PubMed2001

[Generation of Mx-cre transgenic mice].

To generate the transgenic mice expressing cyclization recombination enzyme, the recombinant gene, in which the coding region of cre gene is derived by the promoter of mouse Mx gene, was microinjected into pronuclei of fertilized mouse eggs. Founders of transgenic mice harbouring the recombinant gene were screened by polymerase chain reaction (PCR) at genomic DNA level and confirmed by Southern blot. One line of Mx-cre transgenic mice was obtained. Then, the Mx-cre transgenic mouse line was cultured and propagated.

Animals↗

PubMed2001

Amygdalar and hippocampal volumetry in control participants: differences regarding handedness.

BACKGROUND AND PURPOSE: Amygdalar and hippocampal volume measurements indicate a right-greater-than-left asymmetry for right-handed normal participants in most studies. The purpose of this study was to compare amygdalar and hippocampal volume ratios between right- and left-handed participants. METHODS: Amygdalar and hippocampal volume measurements were performed in 34 (20 right-handed and 14 left-handed) normal participants. All participants completed a 10-item handedness questionnaire. The MR imaging sequence was a 3D T1-weighted gradient-echo acquisition of the whole brain (24/6 [TR/TE]; flip angle, 25 degrees). MR images were spatially normalized, and volumes were painted with a 1.0-mm(3) resolution cursor on an SGI workstation. RESULTS: In right-handed participants, the amygdala and hippocampus (P <.001 for both) were significantly larger on the right side than on the left. The left-handed group did not show a significant difference between right- and left-sided structures. Right-to-left volume ratios differed significantly between right- and left-handed participants for both amygdalar (P <.02) and hippocampal (P <.01) structures. Gender did not affect right-to-left amygdalar and hippocampal volume ratios in right- or left-handed participants. CONCLUSION: Handedness, but not gender, seems to affect right-to-left amygdalar and hippocampal volume ratios.

Adult↗

PubMed2001

[Detection of Cre recombinase activity in Mx-Cre transgenic mice induced by INF in vitro].

The Cre recombinase and its activity in C57-TgN(Mx-Cre) transgenic mice is studied by polymerase chain reaction (PCR), Western blot, immunohistochemistry, immunogold electron microscopy and Southern blot. C57-TgN(Mx-Cre) transgenic mice harbouring cre gene in genomic DNA is demonstrated by PCR, and these mice which are induced by INF-alpha 1b could express Cre recombinase, which is confirmed by Western blot. With immunohistochemistry, we find that the Cre recombinase expresses in hepatocyte cytoplasm and nuclear of C57-TgN(Mx-Cre) transgenic mice. Cre recombinase expressed in hepatocyte cytoplasm and nuclear is further confirmed by immunogold electon microscopy. And it is supported that the Cre recombinase which is created from C57-TgN(Mx-Cre) transgenic mice induced by INF-alpha 1b can direct DNA recombination reaction in vitro. All evidence leads us supporting the view that the Cre recombinase expressed in C57-TgN(Mx-Cre) transgenic mice has activity. Thus we find a method to detect the activity of Cre recombinase in vitro.

Animals↗

PubMed2001

[The presentation of neo gene in chimeric mice obtained from ES cells].

To explore the potentiality of the mouse ES cell line which is employed in our laboratory were transfected with neo gene and selected with G418. Some ES cell clones expressing neo gene were obtained. After ES clones were picked up and expanded, the ES cells were mircoinjected into blastocysts and implanted miceuterus. 60 blastocysts were implanted into 5 mice. Finally, 3 chimeric mice with neo gene were born. PCR was carried out to analyze the presentation of neo gene in tissues of chimeric mice. The results showed that many tissues harbored the neo gene, including skin, liver and blood et al.

Animals↗

PubMed2001

[Expression of cell cycle associated proteins cyclin D1 and P16 in endometrial carcinoma and the correlation between their expression status].

OBJECTIVE: To study the expression of cell cycle associated proteins Cyclin D1, P16 in endometrial carcinoma and their correlation to clinical parameters, and to assess the correlation between their expression status. METHODS: Immunohistochemical method was used to detect Cyclin D1 and P16 expressions in 64 cases of endometrial carcinoma. RESULT: The positive rate of Cyclin D1 was 54.68%. The Cyclin D1 expression was significantly associated with FIGO stage (P < 0.05). The positive rate of P16 was 53.13% and its expression was related to age, histological grade and FIGO stage (P < 0.05). There was an inverse correlation between Cyclin D1 and P16, r = -0.4007 (P < 0.01). CONCLUSION: Cyclin D1 and P16 had cooperative effect and may play an important role in the development and progression of endometrial carcinoma.

Adenocarcinoma↗

PubMed2000

Molecular evidence for the early evolution of photosynthesis.

The origin and evolution of photosynthesis have long remained enigmatic due to a lack of sequence information of photosynthesis genes across the entire photosynthetic domain. To probe early evolutionary history of photosynthesis, we obtained new sequence information of a number of photosynthesis genes from the green sulfur bacterium Chlorobium tepidum and the green nonsulfur bacterium Chloroflexus aurantiacus. A total of 31 open reading frames that encode enzymes involved in bacteriochlorophyll/porphyrin biosynthesis, carotenoid biosynthesis, and photosynthetic electron transfer were identified in about 100 kilobase pairs of genomic sequence. Phylogenetic analyses of multiple magnesium-tetrapyrrole biosynthesis genes using a combination of distance, maximum parsimony, and maximum likelihood methods indicate that heliobacteria are closest to the last common ancestor of all oxygenic photosynthetic lineages and that green sulfur bacteria and green nonsulfur bacteria are each other's closest relatives. Parsimony and distance analyses further identify purple bacteria as the earliest emerging photosynthetic lineage. These results challenge previous conclusions based on 16S ribosomal RNA and Hsp60/Hsp70 analyses that green nonsulfur bacteria or heliobacteria are the earliest phototrophs. The overall consensus of our phylogenetic analysis, that bacteriochlorophyll biosynthesis evolved before chlorophyll biosynthesis, also argues against the long-held Granick hypothesis.

Bacteria↗

PubMed2000

The O(2) binding pocket of myohemerythrin: role of a conserved leucine.

A conserved O(2) binding pocket residue in Phascolopsis gouldii myohemerythrin (myoHr), namely, L104, was mutated to several other residues, and the effects on O(2) association and dissociation rates, O(2) affinity, and autoxidation were examined. The L104V, -F, and -Y myoHrs formed stable O(2) adducts whose UV-vis and resonance Raman spectra closely matched those of wild-type oxymyoHr. The L104V mutation produced only minimal effects on either O(2) association or dissociation, whereas the L104F and -Y mutations resulted in 100-300-fold decreases in both O(2) association and dissociation rates. These decreases are attributed to introduction of steric restrictions into the O(2) binding pocket, which are not present in either wild-type or L104V myoHrs. The failure to observe increased O(2) association or dissociation rates for L104V indicates that the side chain of leucine at position 104 does not sterically "gate" O(2) entry into or exit from the binding pocket in the rate-determining step(s). L104V myoHr autoxidized approximately 3 times faster than did wild type, whereas L104T autoxidized >10(6) times faster than did wild type. The latter large increase is attributed to increased side chain polarity, thereby increasing water occupancy in the oxymyoHr binding pocket. These results indicate that L104 contributes a hydrophobic barrier that restricts water entry into the oxymyoHr binding pocket. Thus, a leucine at position 104 in myoHr appears to have the optimal combination of size and hydrophobicity to facilitate O(2) binding while simultaneously inhibiting autoxidation.

Amino Acid Sequence↗

PubMed2000

A hemerythrin-like domain in a bacterial chemotaxis protein.

Hemerythrin (Hr) is an O(2)-carrying protein found in some marine invertebrates. A conserved sequence motif in all Hrs provides five histidine and two carboxylate ligands to an oxo-/hydroxo-bridged diiron active site, as well as a hydrophobic O(2) binding pocket. Database searches located a previously unrecognized Hr-like sequence motif at the 3' end of the gene, dcrH, from the anaerobic sulfate-reducing bacterium, Desulfovibrio (D.) vulgaris (Hildenborough). This gene encodes a putative methyl-accepting chemotaxis protein, DcrH. We have established by immunoblotting that a full-length DcrH, including the Hr-like domain, is expressed in D. vulgaris (Hildenborough). The C-terminal domain of DcrH, when expressed separately in recombinant form in Escherichia coli, was found to fold into a stable protein, DcrH-Hr. The UV-vis absorption and resonance Raman spectra of DcrH-Hr, and of its azide adduct, provide clear evidence for an oxo-bridged diiron(III) site very similar to that found in Hr. Based on UV-vis absorption spectra, exposure of the reduced (colorless, presumably diferrous) DcrH-Hr to air resulted in formation of an O(2) adduct also very similar to that of Hr. Unlike that of Hr, the O(2) adduct of DcrH-Hr autoxidized within a few minutes at room temperature. The O(2) binding pocket of DcrH-Hr appears to be larger than that of Hr. Given the air-sensitive nature of D. vulgaris and the putative chemotactic function of DcrH, one possible role for the Hr-like domain of DcrH is O(2)-sensing. DcrH-Hr is the first characterized example of a Hr-like protein from any microorganism.

Amino Acid Sequence↗

PubMed2000

The human red nucleus and lateral cerebellum in supporting roles for sensory information processing.

A functional MRI study compared activation in the red nucleus to that in the lateral cerebellar dentate nucleus during passive and active tactile discrimination tasks. The study pursued recent neuroimaging results suggesting that the cerebellum may be more associated with sensory processing than with the control of movement for its own sake. Because the red nucleus interacts closely with the cerebellum, the possibility was examined that activity in red nucleus might also be driven by the requirement for tactile sensory processing with the fingers rather than by finger movement alone. The red and dentate nuclei were about 300% more active (a combination of activation areas and intensities) during passive (non-motor) tactile stimulation when discrimination was required than when it was not. Thus, the red nucleus was activated by purely sensory stimuli even in the absence of the opportunity to coordinate finger movements or to use the sensory cues to guide movement. The red and dentate nuclei were about 70% more active during active tactile tasks when discrimination was required than when it was not (i.e., for simple finger movements alone). Thus, the red nucleus was most active when the fingers were being used for tactile sensory discrimination. In both the passive and active tactile tasks, the observed activation had a contralateralized pattern, with stronger activation in the left red nucleus and right dentate nucleus. Significant covariation was observed between activity in the red nucleus and the contralateral dentate during the discrimination tasks and no significant correlation between the red nucleus and the contralateral dentate activity was detected during the two non-discrimination tasks. The observed interregional covariance and contralateralized activation patterns suggest strong functional connectivity during tactile discrimination tasks. Overall, the pattern of findings suggests that the activity in the red nucleus, as in the lateral cerebellum, is more driven by the requirements for sensory processing than by motor coordination per se.

Adult↗

PubMed2000

Intersubject variability in cortical activations during a complex language task.

Intersubject variability in the functional organization of the human brain has theoretical and practical importance for basic and clinical neuroscience. In the present study, positron emission tomography (PET) and anatomical magnetic resonance imaging (MRI) were used to study the functional anatomy of language processes. Intersubject variability in task-induced activations in six brain regions was assessed in 20 normal subjects (10 men and 10 women) for frequency of occurrence, location, intensity, and extent. A complex, but well-studied task (overt verb generation) was compared to a simple baseline (visual fixation) to induce activations in brain areas serving perceptual, motoric, and cognitive functions. The frequency of occurrence was high for all selected brain areas (80-95%). The variability in response location in Talairach space, expressed as the standard deviation along each axis (x, y, z), ranged from 5.2 to 9.9 mm. This variability appears to be uniformly distributed across the brain, uninfluenced by regional differences in the complexity of gyral anatomy or mediated behavior. The variability in response location, expressed as the average Euclidean distances (averaged across subjects) about mean locations of activations, varied from 9.40 to 13.36 mm and had no significant differences by region (P>0.05, beta = 0.20). Intensity variability was also relatively small and homogenous across brain regions. In contrast, response extent was much more variable both across subjects and across brain regions (0.79 to 1.77, coefficient of variation). These findings are in good agreement with previous PET studies of intersubject variability and bode well for the possibility of using functional neuroimaging to study neural plasticity subsequent to congenital and acquired brain lesions.

Adult↗

PubMed2000

Effect of vagotomy on acute pancreatitis in rats.

One hundred and eighty-two SD rats were randomly divided into the normal control group, fast operating group and food-intake operating group. The experimental model of acute pancreatitis (AP) in rats was established by injecting 5% sodium taurocholate into the pancreatic duct of rat according to Aho's method. The sandostatin was used for positive contrast. The concentrations of serum amylase, calcium, C reaction protein (CRP) and interleukin-6 (IL-6) were assayed respectively at different time points. The pathological sections were observed. Each operating group contained 10 rats. The mortality of the operating groups was observed during the 24 h. The serum amylase level in the AP rats was reduced after receiving vagotomy (VG, P < 0.05). Although the serum calcium level in most groups was decreased, the reduction in the group with VG plus sandostatin was not obvious (P > 0.05). The increase of CRP and IL-6 was not obvious after VG (P > 0.05). The change of mortality was not significant (P > 0.05). The pathological sections showed that the AP pathological change was mild after VG. The disease condition of food-intake operating group was more serious than that of fast operating group. It was suggested that VG had some influence on the prognosis of AP in rats.

Acute Disease↗

PubMed2000

Plastic membrane electrode for the potentiometric determination of pethidine hydrochloride in pharmaceutical preparations.

A novel poly(vinyl chloride) membrane electrode with dibutyl phthalate as plasticizer based on the pethidine-tetraphenylborate ion-association complex as ion-exchange site for the determination of pethidine hydrochloride in injections and tablets was developed. A linear response for 1 x 10(-5) to 1 x 10(-2) mol/L drug with a slope of 51.77 mV/decade was established. The optimum pH range was 2-8. The lower detection limit was 2.18 x 10(-6) mol/L. There were negligible interferences from a number of inorganic and organic cations and some common drug excipients. The electrode proposed had been successfully applied to determine pethidine hydrochloride in tablets and injections. The results correlated well with those obtained by the United States Pharmacopoeia standard procedure.

Calibration↗