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Biomedical subjects

S Chen

Publications and source records attributed to S Chen.

At least 289 records · Page 16Linked to original sources
PubMed2001

Identification of an SAS (Sp1c adjacent site)-like element in the distal 5'-flanking region of the rat lutropin receptor gene essential for cyclic adenosine 3',5'-monophosphate responsiveness.

One of the hallmarks of the differentiation of granulosa cells is the estradiol and FSH/cAMP-dependent induction of the LH receptor (LHR). Previous studies using granulosa cells isolated from diethylstilbestrol-pretreated immature rats identified a novel cAMP-responsive element termed the SAS site (Sp1c adjacent site) in the promoter region of the rat (r) LHR gene. The studies presented herein show that there is an additional distal site located at nucleotide (nt) -933/-924 that appears to interact with the same transcription factor that binds to the promoter SAS site. Similar to the SAS site, the complex formed between granulosa cell nuclear extracts and this distal site is enhanced by cAMP treatment of the granulosa cells. The core sequence required for the formation of the DNA/protein complex at this distal rLHR site was determined to be AGTGG(A)GGGG. With the exception of adenine at -928, substitution of any residue within this sequence prevented formation of this complex. The core sequence of this distal site differs from that of the proximal SAS site, which is GGGGG, and hence the distal site has been termed a SAS-like site. Reporter gene assays using constructs containing the -2,109/-1 region of the rLHR demonstrate that mutation of the distal SAS-like site abolishes the cAMP-induced transcription of the rLHR gene in rat granulosa cells, underscoring the functional significance of this site. Given the lack of sequences in the 5'-flanking region of the rLHR gene consistent with known cAMP-responsive elements, the identification of the novel SAS and SAS-like sites in the rLHR gene provides important clues toward understanding the mechanisms by which the rLHR gene is induced by FSH/cAMP.

Animals↗
PubMed2001

Aromatase p450 expression in a feminizing adrenal adenoma presenting as isosexual precocious puberty.

A 7-yr-old girl presented with isosexual precocious puberty secondary to a feminizing adrenal adenoma. The adrenal tumor was found to express aromatase messenger ribonucleic acid. Enzyme kinetic studies revealed a high level of aromatase activity in the adrenal tumor, with a K(m) of 45 nmol/L and a maximum velocity of 25.6 pmol/mg.h. Aromatase activity was approximately 500-fold higher in the tumor than in adjacent normal adrenal tissue. Although histopathological examination of the tumor was most consistent with a benign adenoma, the aromatase transcripts present in the tumor corresponded to those previously associated with malignant as well as benign tumors. We consider the pattern of aromatase expression sufficient to warrant continued follow-up for tumor recurrence. Our case demonstrates that isosexual precocious puberty secondary to a feminizing adrenal tumor can be due to estrogen synthesis from the tumor itself rather than peripheral aromatization as had been previously theorized.

Adenoma↗
PubMed2001

Presence of antibody against the inducible Hsp71 in patients with acute heat-induced illness.

Antibodies against heat shock or stress proteins (Hsps) have been reported in a number of diseases in which they may be involved in the pathogenesis of the disease or may be of use for prognosis. Heat-induced diseases, such as heat cramps, heat exhaustion, or heat stroke, are frequent in hot working or living environments. There are still few investigations on the presence and possible significance of autoantibodies against Hsps in heat-induced illnesses. Using an immunoblotting technique with recombinant human Hsps, we analyzed the presence and titers of antibodies against Hsp60, Hsp71, and Hsp90alpha, and Hsp90beta in a group of 42 young male patients who presented with acute heat-induced illness during training. We also examined the presence of antibody against Hsp71 in a second group of 57 patients with acute heat-induced illness and measured the changes in titers of anti-Hsp71 antibodies in 9 patients hospitalized by emergency physicians. In the first group of young persons exercising in a hot environment, the occurrence of antibodies against Hsp71 and Hsp90alpha was significantly higher among individuals with symptoms of heat-induced illness (P < 0.05) than in the matched group of nonaffected exercising individuals. Moreover titers of antibody against Hsp71 were higher in individuals of the severe and mild heat-induced illness groups, the highest titer being found in the most severe cases. The results from the second group of 57 heat-affected patients exposed to extreme heat were similar. Again, patients with the more severe heat-induced symptoms showed a significantly higher incidence of antibodies to Hsp71 than controls and the titer of anti-Hsp71 was higher in the severely affected group. Finally, in a study of 9 patients, it was observed that the titer of anti-Hsp71 decreased during recovery from severe heat symptoms. These results suggest that measurement of antibodies to Hsps may be useful in assessing how individuals are responding to abnormal stress within their living and working environment and may be used as one biomarker to evaluate their susceptibility to heat-induced diseases.

Adolescent↗
PubMed2001

Association of plasma antibodies against the inducible Hsp70 with hypertension and harsh working conditions.

Autoantibodies against certain stress or heat shock proteins (Hsps) may play a role in the pathogenesis and/ or prognosis of some diseases. Using immunoblotting with human recombinant Hsps and univariate and multivariate logistic regression models, we have investigated the presence of antibodies against Hsp70, the inducible member of the 70-kDa family of heat shock proteins, and analyzed its possible association with hypertension and working conditions. Plasma and serum were collected from 764 steel mill workers from 6 work sites exposed to (1) severe noise; (2) severe noise and dust; (3) noise, dust, and heat; (4) noise and heat; (5) severe noise and heat; and (6) office conditions (control). Workers with prolonged exposure to stresses such as noise, dust, and high temperature and a combination of these in the workplace had a high incidence (26.6% to 40.2%) of antibodies to Hsp70 compared to the lowest incidence (18.6%) of antibodies to Hsp70 in the control group of office workers. Moreover, there was a statistical association of antibodies against Hsp70 with hypertension. The statistical correlation between the presence of antibodies to Hsp70 and hypertension is higher in the group of workers with blood pressure of 160/95 mmHg than in the 140/90-mmHg group after excluding possible effects of the workplace stresses. These results suggest that harsh workplace conditions can increase the production of antibodies against Hsp70 and that the presence of antibodies to this stress protein may be associated with hypertension. The precise mechanism for the elevation of antibodies against Hsps by environmental and workplace stresses and their relation to hypertension remains to be established.

Autoantibodies↗
PubMed2001

Spectroscopic studies and photodynamic actions of hypocrellin B in liposomes.

Hypocrellin B (HB), a lipid-soluble natural pigment of perylenequinone derivative, is considered as potential photosensitizer for photodynamic therapy. Liposomes loaded with HB can constitute a simple model system, appropriate for better understanding the photodynamic action of HB in vivo. The steady-state absorption and emission spectra, quantum yield and lifetime of fluorescence of HB incorporated into egg L-a-phosphatidyl-choline (EPC) liposome were examined. The photochemical properties (Type I and/or Type II) of HB have also been studied in aqueous dispersions of small unilamellar liposomes of EPC using electron paramagnetic resonance and spectrophotometric methods, respectively. The quantum yield of 1O2 generated by HB is ca 0.76 in chloroform solution and it did not change upon the incorporation of HB into liposomes of EPC. The superoxide anion radical was generated by the electron transfer from the anion radical of HB (HB.-) to oxygen. The disproportionation of O2.- can generate H2O2 and ultimately the highly reactive .OH via the Fenton reaction. It could be that the disproportionation proceeded too fast, so we could not detect O2.- directly in aqueous dispersions of liposome EPC. Moreover, the self-sensitized photooxygenation of HB embedded in liposomes was studied, and almost fully (87%) inhibiting this reaction of HB by p-benzoquinone (as the quencher of O2.-) in aqueous dispersion of liposome EPC indicated that the radical mechanism (Type I) might be mainly involved in this oxygenation. All these findings suggested that the photodynamic action of HB proceeded via both Type-I and -II mechanisms, but Type-I mechanism might play a more important role in the aqueous dispersion.

Electron Spin Resonance Spectroscopy↗
PubMed2001

Photobleaching of hypocrellin B and its butylamino-substituted derivative in solutions.

The photobleaching of hypocrellin B (HB) and its derivative butylamino-substituted hypocrellin B (BAHB), both of which are potent sensitizers for photodynamic therapy (PDT), were investigated by studies of absorption spectra and quenching experiments and by the determination of photoproducts. Control experiments indicated that the sensitizer, oxygen and light were essential for the photobleaching of HB and BAHB, which suggested that it was a photodynamic process, e.g. the photobleaching processes of both HB and BAHB were mainly self-sensitized photooxidations. The illumination of HB with visible light in oxygenated nonpolar solvents generated singlet oxygen efficiently [phi(1O2) = 0.76] which in turn attacked the sensitizer HB with the subsequent formation of an endoperoxide product. The endoperoxide of HB is unstable at room temperature and undergoes loss of singlet oxygen with regeneration of the parent HB. The singlet oxygen released from the endoperoxide of HB was detected with chemical trapping experiments. The quenching experiments indicated that in increasingly polar solvents the superoxide anion mechanism (type I) as well as the singlet oxygen mechanism (type II) contributed to the photobleaching of HB. The introduction of the electron-donating butylamino group not only enhanced the yield of the superoxide anion generation but also altered the position of attack in the BAHB molecule by the activated oxygen species. No endoperoxide product was observed, and no singlet oxygen released from the photobleaching process of BAHB was detected. The photobleaching process of BAHB was more complex. Both the singlet oxygen and superoxide anion mechanism played important roles in the photobleaching of BAHB in all organic solvent used here, even in aerobic nonpolar solvents such as CHCl3.

Electron Transport↗
PubMed2001

t(8;21;8)(p23;q22;q22): a new variant form of t(8;21) translocation in acute myeloblastic leukemia with maturation.

The complex variants of t(8;21) involving chromosomes 8 and 21 as well as a variable chromosome account for 1.1-5% of acute myeloid leukemia (AML) patients. This paper reports a case of AML-M2 with t(8;21;8) translocation for the first time. The patient was a female, aged 47 years. Her myelogram was compatible with AML-M2. Chromosome study using R-banding technique revealed a karyotype 46, XX, t(8;8)(p23;q22). Dual-color FISH assay with two probes P1 164(green signal) and YAC 225B8 (red signal) both of which closely located on the 8q showed that one yellow signal consisting of a green signal and a red signal and one red signal appeared on the long and the short arm of the same der(8) chromosome, respectively, further confirming this translocation occurred between both homologous chromosomes 8. RT-PCR analysis detected the AML1/ETO fusion transcript in our patient, thus indicating that this chromosomal aberration was, in fact, a complex three-way rearrangement t(8;21;8)(p23;q22;q22). In conclusion, combining conventional karyotype, FISH or RT-PCR analyses is a rational strategy for identification of the complex variants of t(8;21) translocation.

Bone Marrow Cells↗
PubMed2001

[Polymorphisms of the CYP1A1 and GSTM1 genes and their combined effects on individual susceptibility to lung cancer in a Chinese population].

OBJECTIVE: To investigate the polymorphisms of CYP1A1 and GSTM1 genes as well as their separate and combined effects on individual susceptibility to lung cancer. METHODS: In the matched 106 pairs of patients with lung cancer and non-cancer control persons, genomic DNA were prepared from peripheral blood samples. The genotypes of CYP1A1 Ile/Val and GSTM1+/0 polymorphisms were detected by the allele-specific(AS)-PCR and multidifferential(MD)-PCR. RESULTS: Individuals with genotype Val/Val of CYP1A1, genotype 0/0 of GSTM1, combined genotypes GSTM1 0/0 and CYP1A1 Val/Val, or combined genotypes GSM1 0/0 and CYP1A1 Ile/Val had higher relative risk than those with the corresponding common genotypes and combined genotypes; their odds ratios were 4.02(P=0.03), 1.92(P=0.019), 9.38(P=0.04) and 3.27(P=0.01), respectively. CONCLUSION: There is a synergy of susceptible genotypes GSTM1 0/0 and CYP1A1 Val/Val or CYP1A1 Ile/Val to enhance the individual susceptibility to lung cancer.

Adult↗
PubMed2001

Systemic administration of phenyl-N-tert-butylnitrone protects the retina from light damage.

PURPOSE: This study was conducted to test the hypothesis that phenyl-N-tert-butylnitrone (PBN), a spin-trapping agent known to cross the blood-brain barrier and protect the brain from ischemia-reperfusion injury, is incorporated into the retina after intraperitoneal injection and protects photoreceptor cells from the damaging effects of constant visible light. METHODS: Albino rats were injected intraperitoneally with PBN (aqueous solution) or water, or were not injected, and then were placed in constant light (2700 lux) for 24 hours. The incorporation of PBN into the retina was determined by high-performance liquid chromatography. Electroretinograms (ERGs) were recorded before light treatment and 1 and 15 days after the cessation of exposure to constant light. Eyes were taken for histology at each time point and outer nuclear layer (ONL) thickness determined. RESULTS: PBN was incorporated into the retina after intraperitoneal injection. Both control (water-injected and uninjected) groups exposed to constant light maintained only 28% of ONL thickness and 20% of retinal function, compared with the unexposed control group. In contrast, the PBN-treated animals maintained 80% of ONL thickness and exhibited 87% of retinal function. CONCLUSIONS: PBN protects the albino rat retina from the damaging effects of constant light stress. That light-induced and hereditary retinal degenerations share certain morphologic hallmarks and follow a similar apoptotic mechanism of degeneration raises the possibility of pharmacologic therapy for hereditary and environmentally induced neurodegenerative disorders.

Animals↗
PubMed2001

[A 40 Hz event-related potential detecting system based on correlation-threshold method].

A 40 Hz event related potential(ERP) detecting system is introduced here. The system employs the elliptic--type filters which have excellent edge features to extract signals of narrow-band frequency. It exploits the correlation--threshold method proposed by us to cancel the muscle artifacts. We also realizes the automatic control of experiment procedure and statistical data processing in microcomputer.

Algorithms↗
PubMed2001

Radioimmunotherapy of a human lung cancer xenograft with monoclonal antibody RS7: evaluation of (177)Lu and comparison of its efficacy with that of (90)Y and residualizing (131)I.

UNLABELLED: Tumor targeting and therapeutic efficacy of (177)Lu-labeled monoclonal antibody (mAb) RS7 (antiepithelial glycoprotein-1) was evaluated in a human nonsmall cell lung carcinoma xenograft model. The potential of (177)Lu-labeled RS7 was compared with that of RS7 labeled with (90)Y and a residualizing form of (131)I. METHODS: A 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid (DOTA) conjugate of RS7 was used for radiolabeling with (177)Lu-acetate or (88/90)Y-acetate. Biodistribution and therapy studies were conducted in nude mice with subcutaneous Calu-3 xenografts. Therapy studies were performed using the maximal tolerated doses (MTDs) of (90)Y-DOTA-RS7 (3.9 MBq [105 microCi]) and (177)Lu-DOTA-RS7 (10.2 MBq [275 microCi]) and compared with the data obtained using the MTD (13.0 MBq [350 microCi]) of a residualizing form of (131)I-RS7. RESULTS: Radiolabeling of RS7-DOTA conjugate with (177)Lu-acetate was facile. (177)Lu-DOTA-RS7 displayed biodistribution results that were nearly identical to that of the (88)Y analog in a paired-label study. The mean percentage injected doses per gram (%ID/g) for (177)Lu-RS7 and (88)Y-RS7 (in parentheses) in tumor were 38.3 %ID/g (39.1 %ID/g), 63.0 %ID/g (66.0 %ID/g), 63.0 %ID/g (65.8 %ID/g), and 34.0 %ID/g (34.9 %ID/g) on days 1, 3, 7, and 14, respectively. Elimination of established tumors, with an initial mean tumor volume of 0.24 cm(3), was shown using doses of (177)Lu-DOTA-RS7 ranging from 5.6 to 9.3 MBq (150--250 microCi) per nude mouse, with no significant difference in response rate noted between the doses in this range. Specificity of the therapeutic effect was shown in an isotype-matched control experiment, in which (177)Lu-DOTA-RS7 was markedly more effective than the (177)Lu-DOTA control antibody. A comparison of the therapeutic efficacies of (177)Lu-DOTA-RS7 and (90)Y-DOTA-RS7, using mice with established tumors with an initial mean tumor volume of 0.85 cm(3), indicated similar tumor growth inhibition and similar tumor regrowth profiles. The therapy data were similar to those obtained with residualizing (131)I-RS7 obtained at the same time. CONCLUSION: (177)Lu-RS7 is an effective radioimmunoconjugate for radioimmunotherapy. With its radiophysical properties similar to those of (131)I, coupled with its facile and stable attachment to mAb, (177)Lu promises to be an alternative to (131)I, and a complement to (90)Y, in radioimmunotherapy.

Animals↗
PubMed2001

[Effect of Cordyceps militaris on the damage of rats induced by n-hexane].

Acutely inhaling n-hexane model was adopted to study the effect of Cordyceps militaris and the damage induced by n-hexane. The results showed that Cordyceps militaris was effective on the resisting lipid peroxidation. The results also showed that acutely inhaling n-hexane could lead to or enhance the damage reaction of oxygen free radicals, which could lead to injure of lipid peroxidation. That may be one of the mechanism of n-hexane toxicity effect on living things.

Administration, Inhalation↗
PubMed2001

Signaling mechanisms underlying strain-dependent brain natriuretic peptide gene transcription.

Activation of brain natriuretic peptide (BNP) gene promoter activity represents one of the earliest and most reliable markers of ventricular cardiac myocyte hypertrophy. We recently demonstrated that mechanical strain increases immunoreactive BNP secretion, steady-state BNP mRNA levels and BNP gene transcriptional activity in neonatal rat myocyte cultures. We have also shown that strain-dependent BNP gene transcription is critically dependent on the functional integrity of a number of integrins (specfically beta1, beta3, and alpha(v)beta5 integrins) present on the surface of cardiac myocytes. When used alone, each of these antibodies resulted in a significant reduction in strain-dependent activation of a transfected hBNP-luciferase reporter and inhibition of a number of signaling pathways that have been linked to stimulation of this reporter (e.g., extracellular signal regulated kinase and c-Jun amino terminal kinase). The present study shows that combinations of these antibodies resulted in further reductions in hBNP gene promoter activity and inhibition of the relevant signaling cascades. These studies provide further support for the importance of integrin-matrix interactions in promoting strain-dependent changes in cardiac myocyte gene transcription.

Animals↗
PubMed2001

[Chromosomal aberration analyzed by comparative genomic hybridization in nasopharyngeal carcinoma].

OBJECTIVE: To identify genetic alteration in primary sporadic nasopharyngeal carcinoma(NPC) in Hunan. METHODS: Comparative genomic hybridization was applied to investigate the genomic imbalance in a series of 20 cases of primary nasopharyngeal carcinomas. RESULTS: The common chromosomal alterations included gains of chromosomes 1q, 2, 3q, 7q,8q,12 as well as losses of chromosomes 3p, 9p, 11q, 16q. CONCLUSION: There are multiple regions of chromosomes with copy number changes in NPC. The tumor suppressor genes and oncogenes on these regions may be involved in the development and progress of nasopharyngeal carcinoma.

Chromosome Aberrations↗
PubMed2001

[Genetic variation of the core and E1 region of hepatitis C virus in serum collected from patients with chronic hepatitis].

OBJECTIVE: To study the association of the core and E1 region variation of hepatitis C virus (HCV) with the chronicity of HCV infection. METHODS: Acute-phase plasma samples from two drug-injection users who acquired HCV infection during six-month follow-up and ten patients with chronic hepatitis C were obtained. A 1-kb fragment containing the 3' half of core, completed E2 and 3' half of E2 were amplified by nested reverse transcription polymerase chain reaction (RT-PCR). For each 30 cloned cDNAs were examined by a method that combined heteroduplex (HD) analysis and a single-stranded conformational polymorphism (SSCP) assay to assess quasispecies complexity and optimize selection of clones with unique gel shift patterns for sequenceing. Amino acid sequences were analyzed for signature patterns and glycosylation signals. RESULTS: There was obvious difference between the SSCP bands of cloned cDNAs representing core-E1 region, but not obvious distance between heteroduplexes and the homoduplex. There was no change in the sequence of each clonotype from acutely HCV-infected subjects, whereas the rate of nonsynonymous substitution was 1.32% in amino acid sequence of E1 from persistently HCV-infected subjects with except for functional patterns. CONCLUSIONS: The variation of the E1 gene of HCV is in the presence of quasispecies population but might not related with its immunologic escape.

Chronic Disease↗
PubMed2001

[Characteristic analysis of modulation transfer function curve of retina-brain system].

This study was aimed to find some parameters for characterizing the modulation transfer function (MTF) specific to diagnosing eye diseases. Least-square regression method was used for MTF curve (at logarithmic axis) fitting with quadratic equation so as or cubic equation to obtain the desired parameters. The data of normal and some eye diseases were fitted by quadratic and cubic equations. Three or four parameters were obtained from the curve fitting. The fitting curves were also expressed with figures along with the original data. For symmetric MTF, parameters k1, k2 and k3 were used to characterize the eye diseases. For asymmetric MTF, an additional parameter k4 was used to show the different injures of frequency channels.

Algorithms↗