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Biomedical subjects

Gang Li

Publications and source records attributed to Gang Li.

At least 217 records · Page 12Linked to original sources
PubMed2003

[Record, analysis and application of EGG].

Electrogastrography (EGG) is the cutaneous recording of the myoelectrical activity of the stomach using surface electrodes and it is more and more attractive due to its noninvasiveness. It has been used in medical research and clinical diagnosis. It is evident that with the use of this noninvasive measurements of gastric electrical activity(GEA) that we can diagnose gastric dysfunction. In this article, record, analysis, application and trend of EGG are reviewed.

Electrodiagnosis↗
PubMed2003

Age-dependent changes in beta-adrenoceptor function in human detrusors and possible mechanisms.

OBJECTIVE: To study age-dependent changes in beta-adrenergic responsiveness and their possible mechanisms. METHODS: Responsiveness to the beta-adrenergic agonists isoprenaline, BRL37344, forskolin, and dibutyryl cyclic AMP (DBcAMP) was examined in samples from 10 older patients by using a cellular function test. A radioligand binding assay was performed using the non-selective beta-adrenergic receptor ligand [3H]-dihydroalprenolol ([3H]-DHA). Specimens from 10 young men were used as controls. RESULTS: There were no age-dependent changes in contractile response to KCl. The relaxation responses to isoprenaline, BRL37344, and forskolin decreased in the aged group by 15.0%, 17.6%, and 12.6%, respectively (P < 0.001). The pD2 values for isoprenaline and BRL37344 also declined significantly. There was no difference in the responsiveness to dibutyryl cyclic AMP (DBcAMP) between the two groups; the maximum binding site decreased significantly with increasing age, but the equilibrium-dissociation constant did not change. CONCLUSIONS: There is an age-related decline in beta-adrenergic responsiveness which might be one of the causative factors of reduced bladder compliance in the elderly. A decrease in cAMP level caused by reduced receptor density and adenylyl cyclase activity might be the underlying molecular mechanism of the changes in beta-adrenergic responsiveness.

Adrenergic beta-Agonists↗
PubMed2003

[Study of X-irradiation to enhance the functional and structural recovery of the injured spinal cord of rat].

OBJECTIVE: To explore whether X-irradiation can enhance the functional and structural recovery of the injured spinal cord of rats. METHODS: Seventy Sprague-Dawley rats received spinal cord injury by clip compression at the T2 level were randomly divided into two groups. The experimental group received X-irradiation at 14 days after injury, the control group did not receive X-irradiation. The functional tests were performed at day 3, 7, 14, 21, 28, 35, and 42 after irradiation including open field movement, inclined plane and pain withdrawal test. All injured rats were sacrificed at 43 days after injury and the injured spinal cords were taken out for histological tests. RESULTS: Sixty-two rats met the experimental requirements among 70 injured rats, 32 rats in experimental group and 30 rats in control group. Statistically significant difference was achieved between two groups in open field movement and inclined plane (P < 0.01), but not for the pain withdrawal test. The edema and necrosis area of injured spinal cords of experimental group were less than those in control group, and the number of axons of experimental group were more than those in control group. CONCLUSIONS: X-irradiation can enhance the functional recovery by improving and restoring structural integrity of the injured spinal cord.

Animals↗
PubMed2003

[Investigation on the sperm quality of 549 college students in Chengdu area].

OBJECTIVE: To evaluate the sperm quality of college students in Chengdu area. METHODS: A computer assisted sperm analysis (CASA) was made of the sperm concentration, grade A sperm, grade B sperm, sperm viability rate and movement parameters (VCL, VAP, VSL, LIN, STR) of 549 volunteers from 14 colleges in Chengdu area. The volunteers were divided into normal and abnormal groups according to the criteria (sperm concentration > or = 20 x 10(6)/ml, grade A and B sperm > or = 50% or grade A sperm > or = 25%). The results were compared with the data reported in China. RESULTS: Among the 549 volunteers, the sperm concentration was (50.90 +/- 27.31) x 10(6)/ml, grade A and B sperm was (42.21 +/- 15.38)%, grade A sperm was (29.48 +/- 13.71)%, and the sperm viability rate was (56.40 +/- 14.77)%. The volunteers with normal sperm accounted for 62.84% (345/549) in contrast with abnormal (37.16%, 204/549). Among the 204 volunteers with abnormal sperms, there were 187 (90.67%) with abnormal motility, 39 (19.21%) with abnormal concentration, 22 (10.78%) with both abnormal concentration and abnormal motility. There were no volunteers without sperm. Among the 345 volunteers with normal sperm, the VCL, VAP and VSL were above 25 microns/s, and the VCL, VAP, VSL, LIN and STR were significantly higher than those of the abnormal group (P < 0.01). Moreover, the sperm concentration and the sperm viability rate in 549 volunteers, including 345 volunteers with normal sperm, were lower than the data reported in China. CONCLUSIONS: Due attention should be paid to the sperm quality of the college students in Chengdu area, whose sperm concentration and sperm viability rate have a tendency to decrease.

Adult↗
PubMed2002

p33(ING1) enhances UVB-induced apoptosis in melanoma cells.

The biological functions of the tumor suppressor ING1 have been studied extensively in the past few years since it was cloned. It shares many biological functions with p53 and has been reported to mediate growth arrest, senescence, apoptosis, anchorage-dependent growth, chemosensitivity, and DNA repair. Some of these functions, such as cell cycle arrest and apoptosis, have been shown to be dependent on the activity of both ING1 and p53 proteins. Two recent reports by Scott and colleagues demonstrate that p33(ING1) (one of the ING1 isoforms) translocates to the nucleus and binds to PCNA upon UV irradiation. Here we report that p33(ING1) mediates UV-induced cell death in melanoma cells. We found that overexpression of p33(ING1) increased while the introduction of an antisense p33(ING1) plasmid reduced the apoptosis rate in melanoma cells after UVB irradiation. We also demonstrated that enhancement of UV-induced apoptosis by p33(ING1) required the presence of p53. Moreover, we found that p33(ING1) enhanced the expression of endogenous Bax and altered the mitochondrial membrane potential. Taken together, these observations strongly suggest that p33(ING1) cooperates with p53 in UVB-induced apoptosis via the mitochondrial cell death pathway in melanoma cells.

Apoptosis↗
PubMed2002

Total synthesis of epothilone a through stereospecific epoxidation of the p-methoxybenzyl ether of epothilone C.

The total synthesis of epothilone A is described by the coupling four segments 4-7 a. Three of the segments, 4, 5 and 7 a, have only one chiral center; all other chiral centers were introduced by simple asymmetric catalytic reactions. The key steps are the ring opening of epoxide 5 with acetylide 8 for the construction of the C12-C13 cis double bond and a practical hydrolytic kinetic resolution (HKR) developed by Jacobsen group for the introduction the chiral center at C3. Especially, the stereospecific epoxidation of 3-O-PMB epothilone C 3 b through long-range effect of 3-O-PMB protecting group gave high yields of the C12-C13 alpha-epoxide for the synthesis of target molecule.

Antineoplastic Agents↗
PubMed2002

Fusion of alphaviruses with liposomes is a non-leaky process.

It has been reported that low-pH-induced fusion of influenza virus with liposomes results in rapid and extensive release of both low- and high-molecular-weight substances from the liposomes [Günther-Ausborn et al., J. Biol. Chem. 270 (1995) 29279-29285; Shangguan et al., Biochemistry 35 (1996) 4956-4965]. Here, we demonstrate retention of encapsulated water-soluble compounds during fusion of Semliki Forest virus (SFV) or Sindbis virus with liposomes at low pH. Under conditions allowing complete fusion of the liposomes, a limited fluorescence dequenching of liposome-encapsulated calcein was observed, particularly for SFV. Also, radioactively labeled inulin or sucrose were largely retained. Freezing and thawing of the viruses in the absence of sucrose resulted in an enhanced leakiness of fusion. These results support the notion that the alphavirus fusion event per se is non-leaky and may well involve a discrete hemifusion intermediate.

Fluoresceins↗
PubMed2002

The p53 stabilizing compound CP-31398 induces apoptosis by activating the intrinsic Bax/mitochondrial/caspase-9 pathway.

p53 is considered the guardian of the genome and has a number of biological functions, including cell cycle arrest, DNA repair, and apoptosis. In a recent study by Foster and colleagues, the pharmacological compound CP-31398 was found to stabilize wild-type p53 to enhance its transcriptional activity and inhibit tumor growth in mice. We hypothesize that CP-31398 induces apoptosis by stabilizing the p53 protein and activating the mitochondrial-mediated pathway. Using the wild-type p53 HCT116+/+ and the p53-deficient HCT116-/- colon carcinoma cell lines, we demonstrate here that CP-31398 induces apoptosis in a dose-, time-, and p53-dependent manner. CP-31398 dramatically elevated p53 and p21(Waf1) protein levels in HCT116+/+, while a smaller p53-independent p21(Waf1) induction by CP-31398 in HCT116-/- cells was also observed. Moreover, we also found that CP-31398 increased Bax expression, altered mitochondrial membrane potential causing the release of cytochrome c, and induced the cleavage of caspases-9 and -3. Taken together, our results indicate that CP-31398 induces p53-dependent apoptosis by activating the Bax/mitochondrial/caspase-9 pathway. Elucidating the mechanism by which CP-31398 induces cell death may establish it as an anticancer agent.

Antineoplastic Agents↗
PubMed2002

A draft sequence of the rice genome (Oryza sativa L. ssp. indica).

We have produced a draft sequence of the rice genome for the most widely cultivated subspecies in China, Oryza sativa L. ssp. indica, by whole-genome shotgun sequencing. The genome was 466 megabases in size, with an estimated 46,022 to 55,615 genes. Functional coverage in the assembled sequences was 92.0%. About 42.2% of the genome was in exact 20-nucleotide oligomer repeats, and most of the transposons were in the intergenic regions between genes. Although 80.6% of predicted Arabidopsis thaliana genes had a homolog in rice, only 49.4% of predicted rice genes had a homolog in A. thaliana. The large proportion of rice genes with no recognizable homologs is due to a gradient in the GC content of rice coding sequences.

Arabidopsis↗
PubMed2002

Cancer chemoresistance: the relationship between p53 and multidrug transporters.

Extensive studies indicate that both p53 and multidrug transporters play important roles in chemoresistance. Since the initial reports a decade ago demonstrating a transcriptional dependence of the ABCB1 gene (MDR) promoter by p53, much data have been accumulated. However, despite being the subject of intense study, this p53-MDR relationship remains unclear in human cancers. The data are confounded by variable and contrasting results when considering the in vitro regulation and attempting to draw parallels in tissue specimens. The original model suggested that wild-type p53 downregulates the ABCB1 promoter, whereas mutant p53 increases expression of ABCB1. This review summarizes the data for and against this hypothesis. What emerges from these studies is a complex picture, where data have been obtained in support of this hypothesis, but there are also many circumstances where it is not supported. Taken together, these data suggest that the relationship between p53 and multidrug transporters is conditional. It is dependent on cellular environment, the drug used, and the nature of the p53 mutation.

Apoptosis↗
PubMed2002

Ku86 is essential in human somatic cells.

Ku86 plays a key role in nonhomologous end joining in mammals. Functional inactivation in rodents of either Ku86 or Ku70, which form the heterodimeric DNA end-binding subunit of the DNA-dependent protein kinase complex, is nevertheless compatible with viability. In contrast, no human patient has been described with mutations in either Ku86 or Ku70. This has led to the hypotheses that either these genes are performing an additional essential role(s) and/or redundant pathways exist that mask the phenotypic expression of these genes when they are mutated in humans. To address this issue, we describe here the construction of human somatic cell lines containing a targeted disruption of the Ku86 locus. Human HCT116 colon cancer cells heterozygous for Ku86 were haploinsufficient with an increase in polyploid cells, a reduction in cell proliferation, elevated p53 levels, and a slight hypersensitivity to ionizing radiation. Functional inactivation of the second Ku86 allele resulted in cells with a drastically reduced doubling time. These cells were capable of undergoing only a limited number of cell divisions, after which they underwent apoptosis. These experiments demonstrate that the Ku86 locus is essential in human somatic tissue culture cells.

Antigens, Nuclear↗
PubMed2002

DNA cleavage by aromatic amines.

A series of aryl amines was found to induce cleavage of DNA. Subsequent refinement led to an efficient family of dimeric derivatives capable of cleavage at low concentration. Initial investigations suggest this is an unprecedented mode of DNA cleavage, which may be ultimately applied to the development of sequence-specific agents.

Amines↗
PubMed2002

Bone consolidation is enhanced by rhBMP-2 in a rabbit model of distraction osteogenesis.

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is a differentiation factor which has been shown to induce bone formation and heal bony defects in a variety of animal models. A possible application of rhBMP-2 is to accelerate bone regeneration during distraction osteogenesis. which clinically is a long procedure, often involving significant complications. In this study we tested the ability of rhBMP-2 to accelerate the consolidation phase of distraction osteogenesis in a rabbit model of leg lengthening. Tibiae were lengthened 2 cm over a period of ten days. rhBMP-2 was administered at the end of the lengthening phase. Two modes of rhBMP-2 application were tested: surgical implantation of rhBMP-2/ACS (absorbable collagen sponge) into the regenerate (50 microl of 1.5 mg/ml rhBMP-2, total dose = 75 microg rhBMP-2), and percutaneous injection of rhBMP-2/buffer (0.1 ml of 0.75 mg/ml rhBMP-2. total dose = 75 microg rhBMP-2) into three sites within the regenerate. Also, there were three groups of control animals: (1) no surgical intervention, (2) surgical implantation of buffer/ACS and (3) percutaneous injection of buffer. Rabbits were sacrificed at 5, 14 and 28 days after the interventions. Radiographic evaluation indicated a significant increase in bony union of the distraction regenerate in the rhBMP-2 treated groups compared with the untreated groups at 5 and 14 days. At 28 days, formation of a cortex and reestablishment of the medullary canal was evident only in the rhBMP-2 treated groups. The bone mineral content (BMC) of the regenerate was significantly higher in the rhBMP-2 treated groups at 5 and 14 days. However, at 28 days, BMC of the regenerate was similar in all groups. The average volumetric density of the regenerate was significantly higher in the rhBMP-2 injection group at day 14. In Summary, both injection of rhBMP-2/buffer and implantation of rhBMP-2/ACS enhanced the consolidation stage of distraction osteogenesis in this rabbit model.

Animals↗
PubMed2002

The inhibition of lung cancer cell growth by intracellular immunization with LC-1 ScFv.

A monoclonal antibody, LC-1, recognizing lung cancer associated common antigens was obtained in authors' laboratory. Its single chain Fv fragment (ScFv) named LC-1 ScFv was constructed based on recombinant phage displayed techniques. For expression on cell membrane, LC-1 ScFv was cloned into pDisplay vector, which directed the cloned gene to express as cell membrane bound protein. The resulting plasmid was sequenced and then introduced by the lipofectin method into a lung adenocarcinoma cell line SPC-A-1. G418 resistant cells were obtained by G418 selection. After transfection, LC-1 ScFv expression was observed by Western blot analysis and the expression of cognate antigens was down-regulated as shown in ELISA assay. SPC-A-1-pDisplay-ScFv cells grew in vitro at lower speed than the control intact cells and the cells transfected with vacant vector. Flow cytometry analysis detected a substantial increase in G1 phase and decrease in S phase in population of SPC-A-1-pDisplay-ScFv cells compared to SPC-A-1 and SPC-A-1-pDisplay cells. Semi-quantitative RT-PCR analysis showed that c-myc expression was down-regulated in SPC-A-1-pDisplay-ScFv cells. It seems that the antigens recognized by LC-1 may be in some way involved in a growth stimulating pathway and the antibody blocking of the function of the antigens shut down the pathway and thus down-regulate the expression of c-myc and growth of the cells.

Adenocarcinoma↗
PubMed2002

The intracellular mechanism of alpha-fetoprotein promoting the proliferation of NIH 3T3 cells.

AIM: The existence and properties of alpha-fetoprotein (AFP) receptor on the surface of NIH 3T3 cells and the effects of AFP on cellular signal transduction pathway were investigated. METHODS: The effect of AFP on the proliferation of NIH 3T3 cells was measured by incorporation of 3H-TdR. Receptor-binding assay of 125I-AFP was performed to detect the properties of AFP receptor in NIH 3T3 cells. The influences of AFP on the [cAMP]i and the activities of protein kinase A (PKA) were determined. Western blot was used to detect the change of K-ras P21 protein expression. RESULTS: The proliferation of NIH 3T3 cells treated with 0-80 mg/L of AFP was significantly enhanced. The Scatchard analysis indicated that there were two classes of binding sites with KD of 2.722 x 10(-9)M (Bmax=12810 sites per cell) and 8.931 x 10(-8)M (Bmax=119700 sites per cell) respectively. In the presence of AFP (20 mg/L), the content of cAMP and activities of PKA were significantly elevated . The level of K-ras P21 protein was upregulated by AFP at the concentration of 20 mg/L. The monoclonal antibody against AFP could reverse the effects of AFP on the cAMP content, PKA activity and the expression of K-ras p21 gene. CONCLUSION: The effect of AFP on the cell proliferation was achieved by binding its receptor to trigger the signal transduction pathway of cAMP-PKA and alter the expression of K- ras p21 gene.

3T3 Cells↗
PubMed2002

On sample size calculation based on odds ratio in clinical trials.

Sample size calculation formulas for testing equality, noninferiority, superiority, and equivalence based on odds ratio were derived under both parallel and one-arm crossover designs. An example concerning the study of odds ratio between a test compound (treatment) and a standard therapy (control) for prevention of relapse in subjects with schizophrenia and schizoaffective disorder is presented to illustrate the derived formulas for sample size calculation for various hypotheses under both a parallel design and a crossover design. Simulations were performed to assess the adequacy of the sample size calculation formulas. Simulation results were given at the end of the paper.

Algorithms↗