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T Li

Publications and source records attributed to T Li.

At least 55 records · Page 3Linked to original sources
PubMed2003

Both stress experience and age determine the impairment or enhancement effect of stress on spatial memory retrieval.

It has been documented that stress or glucocorticoids have conflicting effects on memory under different conditions. However, it is not fully understood why stress can either impair or enhance memory. Here, we have examined the performance of six age groups of Wistar rats in a water maze spatial task to evaluate the effects of stress under different conditions. We found that the impairment or enhancement effect of an 'elevated platform' (EP) stress on memory was dependent on previous stress experience and on age. EP stress impaired memory retrieval in water maze naive animals, but enhanced rather than impaired memory retrieval in young water maze stress-experienced animals. Furthermore, exogenously applied corticosterone or foot shock stress before water maze training prevented the impairment of memory retrieval that should be induced by treatment with corticosterone or foot shock before the 'probe trial'. Again, memory retrieval was enhanced in young animals under these conditions, and this enhancement can be prevented by the glucocorticoid receptor antagonist RU 38486. Thus, glucocorticoid receptor activation not only induced impairment of memory but also increased the capacity of young animals to overcome a later stress. The present findings suggest that the effect of stress on memory can be switched from impairment to enhancement dependent on both stress experience and age.

Aging↗
PubMed2003

Crystallization of the N-terminal domain of DFF45: the mutual chaperone mechanism is challenged.

DNA fragmentation factor 45 (DFF45) regulates DNase DFF40 as its inhibitor and chaperone. It was reported that the N-terminal domain (NTD) of DFF45 alone is disordered and DFF40 is necessary as a mutual chaperone for the folding of NTD. However, here we reported the crystallization of DFF45 NTD. These crystals diffract to 9A using a synchrotron radiation source. In spite of the low resolution, the demonstration of crystal formation indicates that DFF45 NTD itself is not unstructured, which strongly questions the mutual chaperone speculation about DFF45 and DFF40.

Apoptosis Regulatory Proteins↗
PubMed2003

Superior mesenteric arterial embolism: a retrospective study of local thrombolytic treatment with urokinase in West China.

Embolism of the superior mesenteric artery (SMA) is a rare disorder. To explore the selective criteria of local thrombolysis, evaluate its efficacy and discuss the therapeutic protocol of SMA embolism, a retrospective case control study was undertaken. Sixteen cases were divided into two groups: nine cases (group A) from May 1995 to April 1999 were given traditional treatment, while seven cases (group B) from November 1999 to June 2002 received comprehensive therapy including local thrombolysis. The local thrombolytic treatment was performed without procedure-related complications and the embolus was successfully lysed in four patients. The time between admission and diagnosis (or treatment) was shorter in group B than in group A (2.3 +/- 1.2 vs 12.3 +/- 9.2 hr, p = 0.013). Gangrenous bowel segments in group A were much longer than in group B (159.4 +/- 87.7 vs 45.7 +/- 61.6 cm, p = 0.009). However, mortality between the two groups was the same (p = 0.282, OR = 0.32, 95% CI = 0.039, 2.618) perhaps because of the small sample size. Angiography could shorten the duration from the onset of SMA embolism to therapy and certainly lowers the risk of mortality. Local fibrinolytic infusion may be an effective alternative to embolectomy in patients with SMA embolism but without intestinal infarction.

Adult↗
PubMed2003

Antioxidant enzyme gene expression in congestive heart failure following myocardial infarction.

Increased oxidative stress and reduction in antioxidant enzymes have been suggested to be involved in the pathophysiology of congestive heart failure subsequent to myocardial infarction (MI). The objective of the present study was to characterize changes in the mRNA abundance and protein levels for the enzymatic antioxidants, superoxide dismutase (SOD), glutathione peroxidase (GSHPx) and catalase during the sequelae of congestive heart failure in rats. MI was produced by the ligation of the left coronary artery and hearts from controls and 1, 4 and 16 week PMI groups were analyzed. Losartan treatment (2 mg/ml in drinking water, daily) was started at 4 weeks and continued for 12 weeks. The mRNA levels for SOD were reduced by about 40% at 1-week PMI, were near to the control levels at 4-week PMI and at 16 weeks PMI, the levels were reduced by about 73% below the controls. GSHPx mRNA levels remained unchanged at all time points. The mRNA levels for catalase remained unchanged at 1 and 4 weeks PMI and were significantly reduced by about 44% at 16 weeks PMI as compared to the controls. The protein levels for MnSOD, CuZnSOD, GSHPx at 1 and 16 weeks remained unchanged in treated and untreated PMI groups. However, the protein levels for catalase was significantly increased in the control and PMI groups treated with Losartan. It is concluded that changes in the SOD and catalase activities during severe heart failure correlated with changes in mRNA for these enzymes. The precise mechanism/s for the improvement in antioxidant reserve and protein levels after Losartan treatment is/are unclear at this time.

Animals↗
PubMed2002

Single-nucleotide polymorphisms in the lipoprotein lipase gene associated with coronary heart disease in Chinese.

Coronary heart disease is a complex disease reflecting the interaction of multiple genes with the environment (e.g. diet, life style). Lipoprotein lipase (LPL) plays an important role in lipid metabolism and the pathogenesis of coronary atherosclerosis. Recent associations between single-nucleotide polymorphisms in the LPL gene and heart disease have been reported, but little is known in Chinese. The LPL gene spans >26 kb, with an mRNA of 3549 bp. In the present study, we screened 5155 bp (565 bp of 5' flanking region, nine exons and donor- and acceptor-splice sites, and some intronic bases) in 160 Chinese patients with confirmed coronary heart disease and 150 age- and gender-matched controls. Thirteen of the sixteen single-nucleotide polymorphisms that we found have not been previously reported. In males, significant (P<0.05) differences between the coronary heart disease patients and controls were found for five single-nucleotide polymorphisms: -421G>A (5' flanking region); +13,577C>A (intron 2); +16,052G>A, R192Q (exon 5); +16,173C>G and +16,177T>C (intron 5). In females, significant differences between the patients with coronary heart disease and controls were found for only the -421G>A and +16,052G>A (R192Q) mutations. Among the coronary heart disease males, significant (P<0.05) associations were found between the low-HDL high-triglyceride (LHDL/HTG) phenotype and the non-LHDL/HTG trait for the 5' flanking-421G, the intron 2+13,577C, and the exon 5+16,052G mutations, with odds-ratios (ORs)[confidence intervals] of 3.90[1.12-13.66], 3.38[1.22-9.40], and 3.22[1.04-10.01], respectively; no corresponding associations were found in females. There were 69, 51, 57 and 41 unphased haplotype patterns in male coronary heart disease, male control, female coronary heart disease and female control groups, respectively; the computer program PM-Plus found the heterogeneity model by far the best fit (P<0.0001 in males, >0.01 in females). These data show that some single-nucleotide polymorphisms in the LPL gene among Chinese are associated with abnormal lipid and lipoprotein profiles and predisposition to coronary heart disease, a genetically heterogeneous complex disease, and that they are gender-specific.

Adult↗
PubMed2002

A high efficient approach used for BAC-contig extension of Oryza sativa with PCR screening the BAC clone pools.

To extend 8 BAC contigs, which were previously located in the 56.1-68 cM region of the chromosome 4 of the Oryza sativa indica GuangLuAi4, 14 pairs of primers were designed according to the terminal sequences of the existing seed BACs and were deliberately divided into 3 groups. With the 3 groups of primer mixtures, 233 pools of BAC DNA that represent 22 368 BAC clones from O.sativa indica GuangLuAi4 genomic library were screened. 65 positive clones corresponding to the 8 contigs were isolated and 29 clones of them were confirmed to be extended to the seed BACs by end-sequencing and fingerprinting. The protocol greatly enhanced the efficiency of the contig extension and was also superior for its specificity, sensitivity and reusability to the colony in situ hybridization which is a conventional method employed in contig extension and physical map construction.

Chromosomes, Artificial, Bacterial↗
PubMed2001

No association between T102C polymorphism of serotonin-2A receptor gene and clinical phenotypes of Chinese schizophrenic patients.

Serotonin dysfunction has been implicated in the pathogenesis of schizophrenia. Previous studies have shown an association between the T102C polymorphism of the 5HT2a receptor gene and schizophrenia. However, negative findings have also been reported. One possible explanation for such discrepancy is disease heterogeneity due to the current limitations in the diagnosis of schizophrenia. We conducted a case-control study of the T102C polymorphism with detailed characterisation of the clinical phenotypes to investigate the possible association with schizophrenia not only at the diagnostic level, but also with reference to other clinical phenotypes potentially related to serotonin dysfunction. Four hundred and seventy-one biologically unrelated schizophrenic patients and 523 unrelated healthy controls of Han Chinese descent in Hong Kong were compared for genotypes and allele frequencies of the T102C polymorphism by PCR amplification and restriction analysis. No evidence of association was detected at the diagnostic level and various clinical phenotypes. However, we found a trend association with small effect size between genotype 102T/102C and patients with better verbal fluency and less motor co-ordination soft neurological signs. There is a need for future large-scale studies on the possible associations between genetic polymorphisms and neurocognitive function impairments in schizophrenia.

Adolescent↗
PubMed2001

Cysteinyl-tRNA synthetase is not essential for viability of the archaeon Methanococcus maripaludis.

The methanogenic archaea Methanocaldococcus jannaschii and Methanothermobacter thermautotrophicus contain a dual-specificity prolyl-tRNA synthetase (ProCysRS) that accurately forms both prolyl-tRNA (Pro-tRNA) and cysteinyl-tRNA (Cys-tRNA) suitable for in vivo translation. This intriguing enzyme may even perform its dual role in organisms that possess a canonical single-specificity cysteinyl-tRNA synthetase (CysRS), raising the question as to whether this latter aminoacyl-tRNA synthetase is indeed required for cell viability. To test the postulate that all synthetase genes are essential, we disrupted the cysS gene (encoding CysRS) of Methanococcus maripaludis. The knockout strain was viable under normal growth conditions. Biochemical analysis showed that the pure M. maripaludis ProCysRS was capable of forming Cys-tRNA, implying that the dual-specificity enzyme compensates in vivo for the loss of CysRS. The canonical CysRS has a higher affinity for cysteine than ProCysRS, a reason why M. maripaludis may have acquired cysS by a late lateral gene transfer. These data challenge the notion that all twenty aminoacyl-tRNA synthetases are essential for the viability of a cell.

Amino Acyl-tRNA Synthetases↗
PubMed2001

SRY interacts with and negatively regulates androgen receptor transcriptional activity.

This study investigated interactions between SRY, the Y chromosome encoded male sex determining factor, and the androgen receptor (AR). Coexpression of AR and SRY caused marked repression of AR transcriptional activity on a series of androgen-responsive reporter genes. Mammalian one- and two-hybrid experiments demonstrated an AR-SRY interaction mediated by the AR DNA binding domain. Precipitations with glutathione S-transferase fusion proteins indicated that AR-SRY interactions were direct and mediated by the AR DNA binding domain and the SRY high mobility group box DNA binding domain. Transient expression of SRY in LNCaP prostate cancer cells repressed expression of an androgen-dependent prostate-specific antigen (PSA) reporter gene and stable SRY expression repressed the endogenous PSA gene. SRY protein expression was increased by proteosome inhibitors and by the androgen-liganded AR in transient and stable transfectants. AR transcriptional activity was also repressed by DAX1, and the effects of SRY and DAX1 on the AR were additive. These findings indicate that interactions between the AR, SRY, and DAX1 contribute to normal male development and function and suggest a general role for protein-protein interactions between high mobility group box proteins and steroid hormone receptors in regulating tissue-specific gene expression.

Base Sequence↗
PubMed2001

Electrochemical investigation of the rate-limiting mechanisms for trichloroethylene and carbon tetrachloride reduction at iron surfaces.

The mechanisms involved in reductive dechlorination of carbon tetrachloride (CT) and trichloroethylene (TCE) at iron surfaces were studied to determine if their reaction rates were limited by rates of electron transfer. Chronoamperometry and chronopotentiometry analyses were used to determine the kinetics of CT and TCE reduction by a rotating disk electrode in solutions of constant halocarbon concentration. Rate constants for CT and TCE dechlorination were measured as a function of the electrode potential over a temperature range from 2 to 42 degrees C. Changes in dechlorination rate constants with electrode potential were used to determine the apparent electron-transfer coefficients at each temperature. The transfer coefficient for CT dechlorination was 0.22 +/- 0.02 and was independent of temperature. The temperature independence of the CT transfer coefficient is consistent with a rate-limiting mechanism involving an outer-sphere electron-transfer step. Conversely, the transfer coefficient for TCE was temperature dependent and ranged from 0.06 +/- 0.01 at 2 degrees C to 0.21 +/- 0.02 at 42 degrees C. The temperature-dependent TCE transfer coefficient indicated that its reduction rate was limited by chemical dependent factors and not exclusively by the rate of electron transfer. In accord with a rate-limiting mechanism involving an electron-transfer step, the apparent activation energy (Ea) for CT reduction decreased with decreasing electrode potential and ranged from 33.0 +/- 1.6 to 47.8 +/- 2.0 kJ/mol. In contrast, the Ea for TCE reduction did not decline with decreasing electrode potential and ranged from 29.4 +/- 3.4 to 40.3 +/- 3.9. The absence of a potential dependence for the TCE Ea supports the conclusion that its reaction rate was not limited by an electron-transfer step. The small potential dependence of TCE reaction rates can be explained by a reaction mechanism in which TCE reacts with atomic hydrogen produced from reduction of water.

Carbon Tetrachloride↗
PubMed2001

Performance of batch membrane reactor: Glycerol-3-phosphate synthesis coupled with adenosine triphosphate regeneration.

Glycerol-3-phosphate (G3P) was synthesized from glycerol using glycerol kinase (GK). This reaction requires adenosine triphosphate (ATP) and was coupled with the ATP regeneration reaction using acetate kinase (AK) in a batch-operated ultrafiltration hollow-fiber reactor. By taking into consideration the dynamic nature of the bioreactor performance under non-steady-state conditions, a model for the performance of a batch membrane reactor for G3P synthesis coupled with ATP regeneration was developed and studied. The simulation results showed good agreement with the experimental results. The simulation studies have provided some insight into the process dynamics of the coupled reactions in the reactor system studied. For the reactor operational model used, in which the enzymes are retained in the shell side and the substrates are also initially placed in the shell side, it was found that the substrate concentration in the lumen side increased to a level higher than that in the shell side, and a backdiffusion occurred from the lumen side to the shell side during reactor operation. The ratio of the reaction rate to diffusion rate goes through a sharp peak during the time that the direction of diffusion is reversed. For another reactor operational model, in which the substrates were initially placed in the lumen side and enzymes were retained in the shell side, it was found that the rate-controlling step between the reaction and diffusion was switched during the reactor operation. Initially, the reaction rate increased while the diffusion rate was high and the substrate concentrations increased in the shell side. The ratio of reaction rate to diffusion rate increased to a maximum and remained at a constant level as the diffusion rate decreased to a low level due to the nonlinear characteristics of mass transfer process. This study provides information that is useful for optimization of batch membrane enzyme reactor operation and for a fed-batch-type process with an intermittent feeding strategy for efficient use of substrates.

Acetate Kinase↗
PubMed2001

Divergent evolution in M6P/IGF2R imprinting from the Jurassic to the Quaternary.

M6P/IGF2R imprinting first appeared approximately 150 million years ago following the divergence of prototherian from therian mammals. Although M6P/IGF2R is clearly imprinted in opossums and rodents, its imprint status in humans remains ambiguous. It is also still unknown if M6P/IGF2R imprinting was an ancestral mammalian epigenotype or if it evolved convergently. We report herein that M6P/IGF2R is imprinted in Artiodactyla, as it is in Rodentia and Marsupialia, but that it is not imprinted in Scandentia, Dermoptera and Primates, including ringtail lemurs and humans. These results are most parsimonious with a single ancestral origin of M6P/IGF2R imprinting followed by a lineage-specific disappearance of M6P/IGF2R imprinting in Euarchonta. The absence of M6P/IGF2R imprinting in extant primates, due to its disappearance from the primate lineage over 75 million years ago, demonstrates that imprinting at this locus does not predispose to human disease. Moreover, the divergent evolution of M6P/IGF2R imprinting predicts that the success of in vitro embryo procedures such as cloning may be species dependent.

Animals↗
PubMed2001

Polyquinanes by [4 + 4] cycloaddition-transannular cyclization.

[reaction: see text] Photocycloaddition of 2-pyridones yields a rigid polycyclic product containing a 1,5-cyclooctadiene. The cis isomer, with the alkenes in close proximity, undergoes a transannular reaction when treated with chlorine to give a polyquinane product. The chlorination reaction involves migration of an amide nitrogen and forms a single isomer, generating eight stereogenic centers in two steps.

Alkenes↗
PubMed2001

[Expression and significance of CD44 and angiogenic growth factor in nasal NK/T cells lymphoma].

OBJECTIVE: To investigate the molecular basis of the high aggressiveness of nasal NK/T cells lymphoma. METHODS: Immunohistochemical study was used on 17 cases of nasal NK/T cells lymphoma to examine CD20, CD43/CD45RO, CD3, CD56, TIA-1, and CD44. In situ hybridization was used to examine Epstein-Barr virus (EBV) infection, VEGF, and bFGF. RESULTS: The positive rates of CD20, CD43/CD45RO, CD3, CD56, TIA-1, and CD44 were 0%, 88.2%, 70.6%, 88.2%, 100%, and 41.2%. Fifteen cases (88.2%) were positive in EBER1 (EBV infection). VEGF was expressed in 11 cases (64.7%). VEGF expression was negative in 2 out of 4 cases with angioinvasion, and negative in 4 cases out of 7 cases who died of tumor. bFGF was weakly expressed in 3 cases (17.6%) and was not expressed in 2 out of 4 cases with angioinvasion and 6 out of 7 cases who died of tumor. CD44 expression was negative in all 3 cases with dysplasia, and in 4 out of the 7 cases who died of tumor. CONCLUSION: CD44 can not predict the potentiality of NK/T cells lymphoma in invasion, and does not correlate with prognosis. The expression of VEGF is far more frequent than that of bFGF in NK/T cells lymphoma. The significance of VEGF and bFGF expression remains to be investigated.

Angiogenesis Inducing Agents↗
PubMed2001

[Short-term and long-term effectiveness of endovascular embolization in treating intracranial aneurysms].

OBJECTIVE: To study the short-term and long-term effectiveness of endovascular embolization with Guglielmi detachable coil (GDC) or mechanical detachable spiral (MDS) intreating intracranial aneurysms. METHODS: 362 patients with cerebral aneurysms were treated by endovascular embolization with GDC or MDS. Follow-up interviews in the form of correspondence or hospital visit were conducted to 173 of those patients 3 approximately 24 months after the treatment. DSA cerebral artery angiography was made to 84 patients. RESULTS: The clinical symptoms disappeared gradually after the treatment among all of the interviews. No subarchnoid hemorrhage was found. All of the 56 cases with ocular paralysis recovered, 1 case in a week, 52 in a year, and 3 in 18 months. Visual acuity improved to different degrees among 10 cases with visual disturbance in 6 months. Five of the 84 patients who received DSA angiography showed recurrence of aneurysm. Then cause of recurrence was absorption of MDS coils in 2 cases and shifting of the coil in 3 case. CONCLUSIONS: Endovascular embolization is an effective method in treating the intracranial aneurysms with minimal invasiveness and few complications.

Adult↗