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Biomedical subjects

L Shen

Publications and source records attributed to L Shen.

At least 91 records · Page 5Linked to original sources
PubMed2000

A metabolite of equine estrogens, 4-hydroxyequilenin, induces DNA damage and apoptosis in breast cancer cell lines.

Estrogen replacement therapy has been correlated with an increased risk of developing breast or endometrial cancer. 4-Hydroxyequilenin (4-OHEN) is a catechol metabolite of equilenin which is a minor component of the estrogen replacement formulation marketed under the name of Premarin (Wyeth-Ayerst). Previously, we showed that 4-OHEN autoxidizes to quinoids which can consume reducing equivalents and molecular oxygen, are potent cytotoxins, and cause a variety of damage to DNA, including formation of bulky stable adducts, apurinic sites, and oxidation of the phosphate-sugar backbone and purine/pyrimidine bases [Bolton, J. L., Pisha, E., Zhang, F., and Qiu, S. (1998) Chem. Res. Toxicol. 11, 1113-1127]. All of these deleterious effects could contribute to the cytotoxic and genotoxic effects of equilenin in vivo. In the study presented here, we examined the relative toxicity of 4-OHEN in estrogen receptor (ER) positive cells (MCF-7 and S30) compared to that in breast cancer cells without the estrogen receptor (MDA-MB-231). The data showed that 4-OHEN was 4-fold more toxic to MCF-7 cells (LC(50) = 6.0 +/- 0. 2 microM) and 6-fold more toxic to S30 cells (LC(50) = 4.0 +/- 0.1 microM) than to MDA-MB-231 cells (LC(50) = 24 +/- 0.3 microM). Using the single-cell gel electrophoresis assay (comet assay) to assess DNA damage, we found that 4-OHEN causes concentration-dependent DNA single-strand cleavage in all three cell lines, and this effect could be enhanced by agents which catalyze redox cycling (NADH) or deplete cellular GSH (diethyl maleate). In addition, the ER(+) cell lines (MCF-7 and S30) were considerably more sensitive to induction of DNA damage by 4-OHEN than the ER(-) cells (MDA-MB-231). 4-OHEN also caused a concentration-dependent increase in the amount of mutagenic lesion 8-oxo-dG in the S30 cells as determined by LC/MS-MS. Cell morphology assays showed that 4-OHEN induces apoptosis in these cell lines. As observed with the toxicity assay and the comet assay, the ER(+) cells were more sensitive to induction of apoptosis by 4-OHEN than MDA-MB-231 cells. Finally, the endogenous catechol estrogen metabolite 4-hydroxyestrone (4-OHE) was considerably less effective at inducing DNA damage and apoptosis in breast cancer cell lines than 4-OHEN. Our data suggest that the cytotoxic effects of 4-OHEN may be related to its ability to induce DNA damage and apoptosis in hormone sensitive cells in vivo, and these effects may be potentiated by the estrogen receptor.

Apoptosis↗
PubMed2000

Inhibition of LDL oxidation and oxidized LDL-induced cytotoxicity by dihydropyridine calcium antagonists.

PURPOSE: The antioxidant activity of dihydropyridine calcium channel antagonists was evaluated based on LDL oxidation kinetics, oxidative cell injury associated with reactive species generation, and increases in free intracellular calcium (Ca2+) levels. Interactions with ascorbic acid were studied under conditions representative of LDL oxidation in plasma and tissue. METHODS: Analysis of antioxidant activity utilized measurements of one-electron oxidation potentials and scavenging of peroxy radical-mediated oxidation. LDL antioxidant potency was determined spectrophotometrically using copper-mediated oxidation kinetics in the absence and presence of 100 microM ascorbic acid. Prevention of oxidant-induced endothelial cell injury was determined from the formation of reactive oxygen species generation and increases in intracellular free calcium concentrations following addition of oxidized LDL or linoleic acid hydroperoxide. RESULTS: Felodipine and amlodipine effectively inhibit peroxyl radical-mediated oxidation in lipoproteins and cells that is markedly enhanced in the presence of ascorbic acid. In the presence of ascorbic acid, inhibition of LDL oxidation is over four times greater than in LDL treated without antioxidants, and oxidized LDL and linoleic acid hydroperoxide-induced reactive oxygen species formation is effectively suppressed in cells. Inhibition of intracellular calcium increases was achieved using nM concentrations of felodipine or amlodipine. CONCLUSIONS: The additive effect for ascorbic acid and the calcium channel antagonist is postulated to involve a combination of peroxide-degrading and peroxyl radical scavenging reactions, demonstrating the importance of lipid peroxides during LDL oxidation and oxidized LDL-induced cytotoxicity. Cytoprotection is associated with inhibition of oxidant-induced increases in intracellular free calcium. Both the cytoprotective and LDL antioxidant activity for these compounds is manifested at concentrations approaching the therapeutic levels found in plasma.

Animals↗
PubMed2000

Down-regulation of macaque gammadelta + T cells in lymphoid compartments after rectal infection with SIVsmmPBj14.

The dynamics of T cells expressing the gammadelta T-cell receptor in mucosae and other compartments during the course of human immunodeficiency virus (HIV)-1 infection are poorly understood. To examine the impact of an acquired immunodeficiency syndrome virus on the gammadelta + T-cell population, rectal inoculation of macaques with simian immunodeficiency virus (SIV)-PBj14 was used as a model. After rectal inoculation, five macaques were sacrificed on days 4, 5, or 7 and then assessed for changes in the gammadelta T-cell receptor repertoire in different lymphoid compartments. There was decreased representation of gammadelta + T cells in the intestinal mucosae, blood, and spleens. Overall, the reduced number of total gammadelta + T cells was consistent with decreases in the Vgamma or Vdelta T-cell sub-populations. Nevertheless, there was no consistent deletion or expansion of a selected Vdelta + or Vdelta + cell sub-population. These results demonstrate that SIV-PBj14 replication and dissemination after mucosal inoculation resulted in a decline of detectable gammadelta + T cells, suggesting that macaque gammadelta + T cells are susceptible to down-regulation or destruction during acute SIV-PBj14 infection.

Animals↗
PubMed2000

Prolonged dominance of clonally restricted CD4(+) T cells in macaques infected with simian immunodeficiency viruses.

The repertoire of functional CD4(+) T lymphocytes in human immunodeficiency virus type 1-infected individuals remains poorly understood. To explore this issue, we have examined the clonality of CD4(+) T cells in simian immunodeficiency virus (SIV)-infected macaques by assessing T-cell receptor complementarity-determining region 3 (CDR3) profiles and sequences. A dominance of CD4(+) T cells expressing particular CDR3 sequences was identified within certain Vbeta-expressing peripheral blood lymphocyte subpopulations in the infected monkeys. Studies were then done to explore whether these dominant CD4(+) T cells represented expanded antigen-specific cell subpopulations or residual cells remaining in the course of virus-induced CD4(+) T-cell depletion. Sequence analysis revealed that these selected CDR3-bearing CD4(+) T-cell clones emerged soon after infection and dominated the CD4(+) T-cell repertoire for up to 14 months. Moreover, inoculation of chronically infected macaques with autologous SIV-infected cell lines to transiently increase plasma viral loads in the monkeys resulted in the dominance of these selected CDR3-bearing CD4(+) T cells. Both the temporal association of the detection of these clonal cell populations with infection and the dominance of these cell populations following superinfection with SIV suggest that these cells may be SIV specific. Finally, the inoculation of staphylococcal enterotoxin B superantigen into SIV-infected macaques uncovered a polyclonal background underlying the few dominant CDR3-bearing CD4(+) T cells, demonstrating that expandable polyclonal CD4(+) T-cell subpopulations persist in these animals. These results support the notions that a chronic AIDS virus infection can induce clonal expansion, in addition to depletion of CD4(+) T cells, and that some of these clones may be SIV specific.

Animals↗
PubMed2000

Gene therapy applications in gastroenterology and hepatology.

Advantages and disadvantages of viral vectors and nonviral vectors for gene delivery to digestive organs are reviewed. Advances in systems for the introduction of new gene expression are described, including self-deleting retroviral transfer vectors, chimeric viruses and chimeric oligonucleotides. Systems for inhibition of gene expression are discussed, including antisense oligonucleotides, ribozymes and dominant-negative genes.

Gastroenterology↗
PubMed2000

New beta-blocker: prolonged reduction in high blood pressure with beta(1) antisense oligodeoxynucleotides.

beta-Blockers are widely used for hypertension treatment but must be taken daily. We have developed a novel beta-blocker by targeting beta(1)-adrenergic receptor (beta(1)-AR) mRNA with antisense oligodeoxynucleotides (beta(1)-AS-ODN). A single intravenous injection of beta(1)-AS-ODN significantly reduced cardiac contractility and blood pressure (38+/-5 mm Hg, P<0.05) in spontaneously hypertensive rats for 3 weeks. In the present study, we improved the antihypertensive effect of beta(1)-AS-ODN by delivery with the cationic liposomes DOTAP/DOPE and studied its impact on the peripheral renin-angiotensin system. Five charge ratios (+/-) of liposome/ODN from 0 to 3.5 were tested to deliver 0. 5 mg/kg beta(1)-AS-ODN intravenously in spontaneously hypertensive rats (n=30). On the basis of the magnitude and duration of hypotension, 2.5 was determined to be the optimal charge ratio, which decreased blood pressure by up to 35 mm Hg for 20 to 33 days (P<0.05). The effects were specific for beta(1)-AR, because radioligand binding assay and quantitative autoradiography showed a 35% reduction in beta(1)-AR levels in kidney but no change in beta(2)-AR. beta(1)-AS-ODN diminished the preprorenin mRNA levels in renal cortex by 37% 4 days after administration. This transient effect was followed by a delayed yet marked diminution of plasma renin activity and plasma angiotensin II levels on days 10 and 17 (P<0.01). The results show that beta(1)-AS-ODN has an effective long-term antihypertensive effect up to 33 days with a single intravenous injection. The mechanism appears to be through reduced beta(1)-AR number specifically and reduced cardiac contractility. The inhibition of the renin-angiotensin system is probably a second mechanism to produce the sustained antihypertensive effect of beta(1)-AS-ODN.

Adrenergic beta-Antagonists↗
PubMed2000

Data mining in brain imaging.

Data mining in brain imaging is proving to be an effective methodology for disease prognosis and prevention. This, together with the rapid accumulation of massive heterogeneous data sets, motivates the need for efficient methods that filter, clarify, assess, correlate and cluster brain-related information. Here, we present data mining methods that have been or could be employed in the analysis of brain images. These methods address two types of brain imaging data: structural and functional. We introduce statistical methods that aid the discovery of interesting associations and patterns between brain images and other clinical data. We consider several applications of these methods, such as the analysis of task-activation, lesion-deficit, and structure morphological variability; the development of probabilistic atlases; and tumour analysis. We include examples of applications to real brain data. Several data mining issues, such as that of method validation or verification, are also discussed.

Algorithms↗
PubMed2000

Differentiation-associated expression and intracellular localization of cyclin-dependent kinase inhibitor p27KIP1 and c-Jun co-activator JAB1 in neuroblastoma.

Neuroblastoma is a unique pediatric cancer, which spontaneously regress in some infants and undergo maturation in older children. The cyclin-dependent kinase inhibitor p27KIP1 negatively control cell cycle progression and its expression is reported to be associated with differentiation and prognosis of some human cancers. To examine whether p27KIP1 is involved in differentiation of neuroblastomas, expression and localization of p27KIP1 in 30 cases of neuroblastic tumors were determined with immunohistochemistry. p27KIP1 was expressed in all cases, but staining intensity and intracellular localization varied in association with tumor differentiation. Primitive small round neuroblasts showed negative or only weak nuclear staining, while differentiating tumor cells displayed a novel, intense cytoplasmic positivity besides the nuclear staining, and mature ganglion cells showed intense positive reaction confined to the nucleus. A neuroblastoma cell line TGW was also immunostained positively for p27KIP1 in the cytoplasm after differentiation induction, and western blot analysis revealed an increase of p27KIP1 in these cells, corroborating the in vivo observations. JAB1, which is thought to bind p27KIP1 and transport it from the nucleus to the cytoplasm for proteasome/ubiquitin-mediated degradation, was found to be localized both in the cytoplasm and the nucleus in undifferentiated and differentiating tumors whereas located predominantly in the nucleus of differentiated tumor cells. These data indicate that the cytoplasmic localization of p27KIP1 in the process of differentiation is due to upregulation of p27KIP1 synthesis and subsequent degradation and suggest a role of p27KIP1 in differentiation of neuroblastoma.

Blotting, Western↗
PubMed2000

[Clinical diagnosis of apical hypertrophic cardiomyopathy].

OBJECTIVE: To evaluate the clinical features of apical hypertrophic cardiomyopathy (AHCM) and the value of ECG for a reliable clinical diagnosis as compared with two-dimensional echocardiography. METHODS: 29 cases with AHCM were studied by with clinical features, ECG, echocardiography, myocardial scanning, coronary angiography and left ventriculography (LVG). RESULTS: The major clinical feature of AHCM was myocardial ischemia; ECG showed increased R amplitude and inverted T in chest leads. The increase of R amplitude was in such a pattern that RV(4)>or=RV(5) > RV(3). Thickening of left ventricular apical wall was found with echocardiography and radionuclide myocardial scanning. Exercise electrocardiogram showed myocardial ischemia in 20 cases. LVG and coronary angiography demonstrated apical hypertrophic cardiomyopathy with normal coronary arteries in 16 cases. CONCLUSION: The characteristic inverted T waves and increased R wave amplitude with RV(4)>or=RV(5 > RV3) in the ECG are the important signs for clinical diagnosis of AHCM.

Adult↗
PubMed2000

[A computer-aided analysis system for counting the synaptic numerical density based on disector technique].

The change in the numbers of synapse is of importance in various kinds of physiological and pathological processes. The numerical density is the structural parameter measuring up the numbers of the particles in the space. A new stereological technique, the disector technique, has been described to count the number of particles in a given volume of tissue. It is a technique for counting the number of arbitrary particles in 3-dimensional space using adjacent parallel sections at known distance apart. In this article also discussed is the software for computer assisted count of the synaptic numerical density based on the physical director technique with Visual Basic 4.0.

Algorithms↗
PubMed2000

[Studies on human cytokine responses before and after praziquantel chemotherapy in an endemic area of schistosomiasis japonica].

OBJECTIVE: To observe the cellular immune responses in a population of an endemic area of schistosomiasis japonica and the influence of praziquantel treatment. METHODS: Blood was taken from 129 residents (64 cases were egg-positive, 65 cases were egg-negitive) of an endemic area of Poyang Lake before and 45 days after praziquantel treatment. Cytokines induced by the schistosome soluble egg antigen (SEA) and soluble worm antigen preparations (SWAP) in the peripheral blood cells including IL-5, IL-10 and IFN-gamma were measured. RESULTS: Among 129 cases, the cytokine levels were found much higher in egg negative individuals than in egg-positive individuals. The cytokine levels induced by both antigens were increased significantly after praziqantel treatment especially IL-5 and IFN-gamma. CONCLUSION: The cellular immune responses in the population in schistosomiasis japonica endemic area exhibited a general trend of down-regulation and were elevated significantly after praziquantel treatment.

Adolescent↗
PubMed2000

[Gene cloning and characterization of mitochondria-related protein of Schistosoma japonicum].

OBJECTIVE: To subclone and characterize a cDNA clone coding for Schistosoma japonicum (S.j.) mitochondria-related protein. METHODS: The open reading frame of the fragment(Sj338/24) obtained from an adult worm cDNA library of S.j. was analysed, at the upstream and downstream of the open reading frame(ORF) the primers A and B were designed, respectively, and the cDNA fragment was used as PCR template. The Sj338 gene fragment obtained was amplified by PCR method and then subcloned into pGEM-T vector for sequencing. The gene sequence was analyzed and the target fragment was restrictedly digested and subcloned into expression vector pGEX-6P-1. The expressed recombinant protein was purified and characterized. RESULTS: The cloned Sj338 gene was demonstrated to be 487 bp long containing one 459 bp ORF, encoding a protein with a molecular weight of 17 kDa. The nucleotide sequence of the cloned gene Sj338 had higher homology with those genes coding for mitochondrial outer membrane protein of Homo sapiens and Rattus norvegicus. The recombinant construct of pGEX-6P-1/Sj338 could be expressed efficiently and the antigenicity of its product rSj338 has been demonstrated by Western blotting. CONCLUSION: Sj338 may be the gene coding for S.j. mitochondria-related protein and the recombinant protein may be used as a new vaccine candidate.

Amino Acid Sequence↗
PubMed2000

[Human parasite antigen-specific IFN-gamma response in schistosomitsis japonica endemic area].

OBJECTIVE: To explore the characteristics of human schistosome antigen-specific IFN-gamma response in a population in an area endemic for schistosomiasis japonica. METHODS: Three neighboring villages were chosen on Nanshan Island of Poyang Lake. 65 egg-negative persons and 64 egg-positive ones were selected randomly from the residents aged 14-41 years according to the egg counts by Kato-Katz thick smear method. IFN-gamma was measured in the whole blood culture supernatant after stimulated by the schistosome soluble egg antigen (SEA) and soluble worm antigen preparations (SWAP). Serum isotype-restricted antibody was detected by ELISA. RESULTS: IFN-gamma levels induced by both SEA and SWAP were increased significantly after praziquantel treatment. The SEA-specific IFN-gamma level of the uninfected group was much higher than that of the reinfected group. A negative correlation between IFN-gamma level and IgG4 production was found, reflecting that IFN-gamma might be associated with the resistance to schistosome reinfection. CONCLUSION: The changes in IFN-gamma level might play an important role in association with the resistance to schistosome reinfection.

Adolescent↗
PubMed2000

[Wavelet transform and its application in spectral analysis].

Recently, a new mathematical technique known as wavelet transform(WT) has become the focus of many science areas. In analytical chemistry, wavelet transform has been mainly utilized for signal smoothing, de-noising and compression. In this paper, the wavelet transform theory is introduced and its applications in spectral analysis are reviewed.

Algorithms↗
PubMed1999

Purification of an EH domain-binding protein from rat brain that modulates the gating of the rat ether-à-go-go channel.

Mutations in the gene encoding ether-à-go-go (EAG) potassium channel impair the function of several classes of potassium currents, synaptic transmission, and learning in Drosophila. Absence of EAG abolishes the modulation of a broad group of potassium currents. EAG has been proposed to be a regulatory subunit of different potassium channels. To further explore this regulatory role we searched for signaling molecules that associate with EAG protein. We have purified a approximately 95-kDa protein from rat brain membranes that binds to EAG. When co-expressed in mammalian cells this protein coimmunoprecipites with EAG and alters the gating of EAG channels. Expression of this protein is regulated during neuronal differentiation. The protein is identical to the recently reported rat protein epsin, which is an EH domain-binding protein similar to the Xenopus mitotic phosphoprotein MP90. These results show that proteins of the epsin family are modulators of channel activity that may link signaling pathways, or the cell cycle, to EAG and thus to various potassium channel functions.

Adaptor Proteins, Vesicular Transport↗
PubMed1999

Gamma-chain dependent recruitment of tyrosine kinases to membrane rafts by the human IgA receptor Fc alpha R.

We show that the human IgA receptor, Fc alpha R, redistributes to plasma membrane rafts after cross-linking and that tyrosine kinases are relocated to these sites following Fc alpha R capping. We demonstrate by confocal microscopy that Fc alpha R caps in membrane rafts by a gamma-chain-independent mechanism but that gamma-chain expression is necessary for Lyn redistribution. Immunoblotting of rafts isolated by sucrose density gradient centrifugation demonstrated recruitment of gamma-chain and phosphorylated tyrosine kinases Lyn and Bruton's tyrosine kinase to membrane rafts after Fc alpha R cross-linking. Time-dependent differences in Lyn phosphorylation and Bruton's tyrosine kinase distribution were observed between cells expressing Fc alpha R plus gamma-chain and cells expressing Fc alpha R only. This study defines early Fc alpha R-triggered membrane dynamics that take place before Fc alpha R internalization.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1999

Melatonin receptor mRNA expression in human granulosa cells.

We have shown that the melatonin receptor agonist, 2-[125I] iodomelatonin, binds to high-affinity guanine nucleotide-sensitive sites on human granulosa (HG) cell membranes. In order to confirm the presence of melatonin receptors in HG cells, we have now used a reverse transcriptase-polymerase chain reaction (RT-PCR) procedure to examine receptor subtype expression. RT-PCR studies revealed the presence of the mt1 (Mel1alpha) melatonin receptor subtype in ten single or pooled HG cell samples which were obtained from 14 patients. In contrast, expression of MT2 ( Mel1b) mRNA was observed in only two of these HG samples. DNA sequencing of the mt1 PCR product confirmed its identity with the reported human mt1 melatonin receptor. The expression of mt1 and MT2 receptor mRNA in HG cells and the reported presence of melatonin in human follicular fluid indicate a potentially important role for this hormone in regulating human ovarian and reproductive function.

Cell Membrane↗