Biomedical subjects

S Li

Publications and source records attributed to S Li.

At least 379 records · Page 21Linked to original sources

PubMed2001

[Imitative restenosis after percutaneous transluminal coronary angioplasty prevented by buyang huanwu decoction in rabbits].

OBJECTIVE: To examine the preventive effect of Buyang Huanwu Decoction (BYHWD) on imitative restenosis after percutaneous transluminal coronary angioplasty (PTCA) in diet-induced atherosclerotic rabbits. METHODS: Diet-induced atherosclerotic rabbits were randomly allocated into group 1 (n = 24, fed with BYHWD one week before and 4 weeks after the operation, 2 ml/kg per day, containing herbal drug 8.4 g/ml) and group 2 (n = 20, as control). Balloon angioplasty was performed in the abdominal arota to mimic coronary angioplasty. RESULTS: Sixty days after operation: (1) Incidence of hyperplasia of the intima was 7/24 (29.2%) in group 1 vs 17/20 (85.0%) in group 2, P < 0.01; (2) Comparison of area of hyperplastic intima was (0.54 +/- 0.21) mm2 vs (1.67 +/- 0.75) mm2, P < 0.01; (3) Area of hyperplastic intima/area of lumen (limited by the internal elastic membrane was (18.0 +/- 7.2)% vs (56.0 +/- 17.1)%, P < 0.01; (4) Intact lumen/dilated lumen was (0.74 +/- 0.03) vs (0.35 +/- 0.07), P < 0.01; (5) Effect of serum taken from group 1 on cultured smooth muscle cells showed by 3H-TdR method was (4110.14 +/- 1977.01) cpm, which was significantly less than that of serum taken from group 2 [(7960.14 +/- 2802.59) cpm, P < 0.05]. CONCLUSION: BYHWD has significant preventive effect on the imitative post PTCA restenosis in diet-induced atherosclerotic rabbits.

Angioplasty, Balloon, Coronary↗

PubMed2001

[3D-QSAR of antiinflammatory activities of 5,6-diaryl-2,3-dihydro-1-pyrrolizinone derivatives].

AIM: To study the SARs of 5,6-diaryl-2,3-dihydrol-1-pyrrolizinone derivatives to provide information for the design of new structural compounds. METHODS AND RESULTS: Three dimensional quantitative structure-activity relationship (3D-QSAR) model was constructed by Apex-3D. CONCLUSION: The antiinflammatory activities of 5, 6-diaryl-pyrrolizinones were related to the global hydrophobicity and volume, the properties of the group at 1-position of pyrrolizinone ring and the two secondary sites; improved the pi-electronic density of the group at 1-position of pyrrolizinone ring and lowered the global hydrophobicity and the volume of p-substituent of the phenyl ring at 6-position of pyrrolizinone contributed to the antiinflammatory activities of the title compounds.

Animals↗

PubMed2001

[Studied on docking of 5,6-diaryl-2,3-dihydro-1-pyrrolizinone derivatives with cyclooxygenase].

AIM: To theoretically explore the mechanism of action of 5,6-diaryl-2, 3-dihydro-1-pyrrolizinone derivatives. METHODS: The interactions of the compound ZZ-122 with cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) were modeled by docking method. RESULTS: According to the binding pattern, intermolecular energy and capacity to form H-bond, it was easy for ZZ-122 to bind to COX-2 and not easy to COX-1. CONCLUSION: Compound ZZ-122 may be a selective COX-2 inhibitor, which has to be confirmed by experiment.

Cyclooxygenase 1↗

PubMed2001

[Sequences of 5S-rRNA gene spacer region and comparison of alkaloid content in Fritillaria thunbergii from different habitats].

OBJECTIVE: To study the genetic basis of the formation of indigenous Chinese medicine materials. METHODS: The 5S-rRNA gene spacer regions in F. thunbergii from different habitats were amplified with AS and AS-1 as primers, and then sequenced. Total alkaloid contents were assayed by acid dye colorimetry, and 2 main alkaloid contents were assayed by pre-column derivatization and gas chromatographic method. RESULT: The sequenues of 5S-rRNA gene spacer regions in F. thunbergii from different habitats were same, and the length of them was 588 bp. They had same content total alkaloid. The results of gas chromatography showed that they had same kinds of monomer alkaloids, but the contents of different monomer alkaloids were different. CONCLUSION: The difference of alkaloid content in F. thunbergii from various habitats isn't resulted from base sequence variation, but from microenvironment.

Alkaloids↗

PubMed2001

[The effect of fluid shear stress on the proliferation of rat primary osteoblast-like cells in vitro].

OBJECTIVE: To inquire into the cellular mechanism by which mechanical stress regulates bone remodeling and make an attempt at establishing the most suitable physiological stress to stimulate bone formation. METHODS: The isolated rat primary osteoblast-like cells were exposed to fluid shear stress 2, 4, 8, 12, 14, 17 and 19 dyn/cm2 for 60 min respectively in the flow chamber. The ability of proliferation of cells was studied by flow cytometry. RESULTS: After exposed to fluid shear stress, the cells rearranged and the cells' axes were elongated following the flow direction. The proliferation indexes (PI) of the cells went up with the gradual increase of shear stress. When fluid stress reached 12 dyn/cm2, the PI of cells increased significantly (P < 0.05), compared with the control. But the PI of cells began to decrease when the fluid stress continued to increase, and when fluid stress reached 14 dyn/cm2, the PI of cells decreased significantly (P < 0.01), compared with the control. CONCLUSION: The mechanism by which mechanical stress regulates bone remodeling is related to the proliferation of the osteoblast cells stimulated by stress-induced fluid flow. Low shear stress has no marked influence on the proliferation of cells. Medium shear stress (12 dyn/cm2) can stimulate cells significantly. Major shear stress (14 dyn/cm2) can inhibit cells significantly.

Animals↗

PubMed2001

[The effects of leptin on proliferation and function of human osteoblast].

OBJECTIVE: To observe the effect of leptin on osteoblast. METHODS: Human osteoblast primary culture was carried out, and the morphology and function of osteoblast were observed. The effects of different levels of leptin on osteoblast in different days were assessed by MTT colorimetry. Osteocalcin production was measured also. RESULTS: Human osteoblasts were fusiform in shape and were positive for alkaline phosphatase by histochemical staining, positive for osteocalcin by immunofluorescence staining, and positive by Alizarin Reds staining after mineralized upon supplementation with ascorbate and beta-glycerophosphate. On the first, second and third days, the proliferation of osteoblast, cultured with different concentrations of leptin, had no changes. The leptin-stimulated synthesis of osteocalcin of cells was found to be dose-dependent (P < 0.05), but not time-dependent (P > 0.05). CONCLUSION: The above data indicated that there were no evidences for the effects of leptin on the proliferation of human osteoblast, but leptin could enhance the function of human osteoblast.

Ascorbic Acid↗

PubMed2001

[The effects of streptomycin on the calcium influx in SGCs during depolarization].

OBJECTIVE: To examine the effect of streptomycin on the calcium influx in spiral ganglion cells (SGCs) during depolarization and the differences among different concentrations of streptomycin and SGCs sources with the aim of exploring the mechanism of acute streptomycin ototoxicity. METHODS: The SGCs of guinea pig cochlea were isolated using an enzyme-machine method and loaded with 10 mumol/L Fluo-3/AM for 30 min at 37 degrees C. Dissociated SGCs loaded with Fluo-3 were examined with a confocal microscope (ACAS Ultima, USA) using a 20 x objective lens and linear scan mean. The fluorescent images collected every 5-sec for a total of 300 sec were stored in a computer. The fluorescent intensity of the images was analyzed by a software cooperated with the confocal microscope, and a curve of fluorescent intensity changes against time was obtained. RESULTS: The [Ca2+]i of SGCs was steady under the perfusion with standard extracellular solution. The [Ca2+]i of SGCs increased in 12/14 cells under the perfusion with 150 mmol/L high potassium solution, but increased in only 1/10 cells induced by the high potassium calcium free solution. After treating with 1 mmol/L, 0.1 mmol/L, 0.01 mmol/L streptomycin, the [Ca2+]i of the SGCs perfused with the potassium solution was increased in 0/9, 6/14, 7/13 cells, respectively. After the SGCs were treatment with 0.02 mmol/L streptomycin, the [Ca2+]i of the SGCs perfused with the high potassium solution was increased in 5/10 SGCs from the apical turn and in 0/15 SGCs from the basal turn. CONCLUSION: Perfusion with high potassium media can result in obviously increased [Ca2+]i of the SGCs, and the increase of the [Ca2+]i in the SGCs may originate from the extracellular calcium influx. The calcium influx can be blocked by streptomycin and such effects depend on streptomycin concentrations and SGCs sources.

Animals↗

PubMed2001

[Study of Newcastle disease virus in the treatment of human laryngeal squamous carcinoma].

OBJECTIVE: To explore the biological value of newcastle disease virus in the therapy of human laryngocarcinoma. METHODS: Nude mice model bearing laryngocarcinoma were established using human laryngeal squamous carcinoma cell line (Hep-2). Large amounts of Newcastle disease virus(NDV) were injected into the tumor. Changes in carcinoma administrated with the NDV were observed under light and electron microscopes. Isolation of NDV was attempted and sera were examined using the method of enzyme-linked immunosorbent assay (ELISA). RESULTS: The difference between experimental and control groups was statistically significant, including the average weight of the mice: t' = 2.397 (P < 0.05), the average weight of the tumor tissue: t' = 2.852 (P < 0.05) and the average volume of the tumor tissue: t' = 6.058 (P < 0.01). In the experimental group, the NDV was isolated in the tumor tissue and ELISA was positive. The necrosis of the tumor cell and inflammatory cellular infiltration were found under light and electron microscopes. CONCLUSION: These results indicated that NDV was effective in the treatment of laryngocarcinoma and had no damage to normal tissue.

Animals↗

PubMed2001

[Clinical study of the sentinel lymph node of patients with laryngeal and hypopharyngeal carcinomas].

OBJECTIVE: To investigate the methods of detecting the sentinel lymph node of laryngeal and hypopharyngeal carcinomas and its predictive value in the cervical metastasis of the carcinoma. METHODS: In 29 patients who suffered from laryngeal or hypopharyngeal carcinoma with NO neck, the patent blue was injected into the surrounding tissue of the tumor during the operation to identify the sentinel lymph nodes. The sentinel lymph nodes were dyed blue. The frozen histopathology was done during the operation, the lymph nodes at the ipsilateral side of the neck were dissected completely, and the routine histopathology was done as the gold standard to study the predictive value of the sentinel lymph node in the metastasis of the cervical node. RESULTS: Of 29 patients, 28 patients' sentinel lymph nodes were detected successfully during operation. There was an average of 2.5 lymph nodes per side per patient. Most of the sentinel lymph nodes were in the level II and level III regions of the ipsilateral side of the neck, and there were bilateral sentinel nodes in patients suffered from superglottic carcinoma. Three patients' sentinel lymph nodes were found to be positive in the frozen inspection, and the routine histopathology confirmed the result. The micrometastasis rate was 10.7% (3/28). There were no metastatic lymph nodes found in patients who were negative for the sentinel lymph nodes during the operative frozen histopathology. The predicted value of the sentinel lymph nodes to the cervical lymph node metastasis was 100 per cent. CONCLUSION: There is a very important predicted value of sentinel lymph nodes in the cervical metastasis of patients suffered from laryngeal and hypopharyngeal carcinomas. It could reduce the neck dissection in patients with laryngeal and hypopharyngeal carcinomas.

Adult↗

PubMed2001

[Determination of deoxyribonucleic acid with rosaniline by a resonance light scattering method].

The resonance light scattering (RLS) spectra of Rosaniline with DNA have been studied. The RLS of Rosaniline is greatly enhanced by DNA in pH range of 10.5-10.8. There is a resonance light scattering peak ofat 485 nm, and the enhanced intensity of RLS at this wavelength is proportional to the concentration of DNA. The linear range of the calibration graph is 0-1.00 mg.L-1 with the correlation coefficient of 0.9980. The detection limit is 14.2 ng.mL-1. The relative standard deviation(n = 10) was within 2.1%. This method is simple, rapid and has been applied to the determination of DNA in mixed samples with satisfactory results.

Attention↗

PubMed2000

Pyrogenic signaling via vagal afferents: what stimulates their receptors?

Although there is good evidence that pyrogenic messages may be conveyed from the periphery to the brain via vagal afferents, the exact nature of the factors that activate their sensory terminals is unclear. Since IL-1beta and PGE2 have established roles in fever production and since their receptors have been identified on or near vagal nerves, they are potential candidate mediators. A difficulty, however, is that (1) IL-1beta is not expressed constitutively in mononuclear phagocytes, their presumed cell source upon stimulation by exogenous pyrogens, e.g. endotoxin, and (2) similarly, the isoform of the enzyme that selectively mediates the production and release of PGE2 by endotoxin-stimulated macrophages, COX-2, is also not constitutively expressed in these cells. Since the transcription and translation of these factors significantly lags the onset of fever induced by endotoxin administered intravenously, in particular, it is possible that a secondary, quickly-acting mediator evoked in almost immediate reaction to the presence of endotoxin excites, directly or indirectly, the sensory neurons. We have evidence that the complement component C5 contributes importantly to the initiation of the febrile response to endotoxin. This article briefly reviews the prevailing concepts of pyrogen sensing and signaling, examines their shortcomings particularly in terms of the temporal discrepancy between the very rapid onset of the febrile response to intravenously administered endotoxin and the significant delay in the elaboration of the putative mediators of fever, and presents newer data that may help to integrate the various preposed mechanisms.

Animals↗

PubMed2000

Mutations of the second extracellular loop of the human lutropin receptor emphasize the importance of receptor activation and de-emphasize the importance of receptor phosphorylation in agonist-induced internalization.

Alanine scanning mutagenesis of the second extracellular loop of the human lutropin receptor (hLHR) showed that mutation of most of the residues present in this region either enhance or impair the internalization of agonist. A more complete analysis of four mutants, two that enhanced internalization (F515A and T521A) and two that impaired internalization (S512A and V519A), showed that the two mutants that impaired internalization also show a decrease in the sensitivity for agonist-induced cAMP accumulation, whereas the two mutants that enhanced internalization show an increase in the sensitivity for agonist-induced cAMP accumulation. None of these mutants had an effect on the agonist-induced phosphorylation of the hLHR, however. We conclude that, in contrast to the prevailing view of the relative importance of receptor phosphorylation in the internalization of G protein-coupled receptors, the phosphorylation of the hLHR is less important than the agonist-induced activation of the hLHR in the process of internalization.

Cell Line↗

PubMed2000

Reactivity and regulatory properties of human anti-idiotypic antibodies induced by T cell vaccination.

Immunization with irradiated autoreactive T cells (T cell vaccination) induces anti-idiotypic T cell responses that preferentially recognize complementarity-determining region 3 sequences, contributing to clonal depletion of autoreactive T cells. However, it remains unknown whether T cell vaccination elicits anti-idiotypic humoral responses and whether the anti-idiotypic Abs play a similar role in the regulatory mechanism induced by T cell vaccination. In this study we examined the occurrence, the reactivity pattern, and the regulatory role of anti-idiotypic Abs elicited by T cell vaccination in patients with multiple sclerosis. We demonstrated for the first time that B cells producing anti-idiotypic Abs could be isolated from vaccinated patients. These EBV-transformed B cell lines were selected for specific reactivity to a 20-mer TCR peptide incorporating a common complementarity-determining region 3 sequence of the immunizing T cell clones. The resulting anti-idiotypic Abs were found to react with the original immunizing T cell clones and exhibit an inhibitory effect on their proliferation. The findings suggest that anti-idiotypic Ab responses can be induced by T cell vaccination in humans and that their regulatory properties are likely to contribute to the suppression of myelin basic protein-reactive T cells in vaccinated patients. The study has important implications in our understanding of the regulatory role of the anti-idiotypic humoral responses induced by T cell vaccination.

Adoptive Transfer↗

PubMed2000

Activation of fibroblast collagenase-1 expression by tumor cells of squamous cell carcinomas is mediated by p38 mitogen-activated protein kinase and c-Jun NH2-terminal kinase-2.

Collagenase-1 [matrix metalloproteinase (MMP)-1] is expressed by stromal fibroblasts of various invasive malignant tumors. Here, we have examined the molecular mechanisms of tumor-induced expression of MMP-1 by stromal fibroblasts. Treatment of fibroblasts with conditioned media of tumor cells derived from squamous cell carcinomas (SCCs) of the oral cavity and larynx resulted in activation of fibroblast MMP-1 expression at the transcriptional level. The induction of MMP-1 expression correlates with activation of c-Jun NH2-terminal kinase (JNK) and p38 mitogen-activated protein kinase and phosphorylation of c-Jun and activating transcription factor-2 (ATF-2) and is dependent on the activity of p38 mitogen-activated protein kinase. Furthermore, using fibroblasts derived from JNK2-/- mice, we show that JNK2 is required for induction of fibroblast collagenase-3 expression in response to conditioned SCC tumor cell medium. Together, these results provide evidence that stress-activated p38 and JNK pathways play a crucial role in paracrine regulation of collagenolytic capacity of stromal fibroblasts in SCCs and suggest JNK2 as a novel target for inhibition of MMP-1 expression and tumor invasion.

Activating Transcription Factor 2↗

PubMed2000

The tuberous sclerosis-1 (TSC1) gene product hamartin suppresses cell growth and augments the expression of the TSC2 product tuberin by inhibiting its ubiquitination.

We report here that overexpression of the tuberous sclerosis-1 (TSC1) gene product hamartin results in the inhibition of growth, as well as changes in cell morphology. Growth inhibition was associated with an increase in the endogenous level of the product of the tuberous sclerosis-2 (TSC2) gene, tuberin. As overexpression of tuberin inhibits cell growth, and hamartin is known to bind tuberin, these results suggested that hamartin stabilizes tuberin and this contributes to the inhibition of cell growth. Indeed, transient transfection of TSC1 increased the endogenous level of tuberin, and transient co-transfection of TSC1 with TSC2 resulted in higher tuberin levels. The stabilization was explained by the finding that tuberin is highly ubiquitinated in cells, while the fraction of tuberin that is bound to hamartin is not ubiquitinated. Co-expression of tuberin stabilized hamartin, which is weakly ubiquitinated, in transiently transfected cells. The amino-terminal two-thirds of tuberin was responsible for its ubiquitination and for stabilization of hamartin. A mutant of tuberin from a patient missense mutation of TSC2 was also highly ubiquitinated, and was unable to stabilize hamartin. We conclude that hamartin is a growth inhibitory protein whose biological effect is likely dependent on its interaction with tuberin.

Animals↗

PubMed2000

Lessons learned from BRCA1 and BRCA2.

BRCA1 and BRCA2 are breast cancer susceptibility genes. Mutations within BRCA1 and BRCA1 are responsible for most familial breast cancer cases. Targeted deletion of Brca1 or Brca2 in mice has revealed an essential function for their encoded products, BRCA1 and BRCA2, in cell proliferation during embryogenesis. Mouse models established from conditional expression of mutant Brca1 alleles develop mammary gland tumors, providing compelling evidence that BRCA1 functions as a breast cancer suppressor. Human cancer cells and mouse cells deficient in BRCA1 or BRCA2 exhibit radiation hypersensitivity and chromosomal abnormalities, thus revealing a potential role for both BRCA1 and BRCA2 in the maintenance of genetic stability through participation in the cellular response to DNA damage. Functional analyses of the BRCA1 and BRCA2 gene products have established their dual participation in transcription regulation and DNA damage repair. Potential insight into the molecular basis for these functions of BRCA1 and BRCA2 has been provided by studies that implicate these two tumor suppressors in both the maintenance of genetic stability and the regulation of cell growth and differentiation.

Animals↗

PubMed2000

Identification and characterization of estrogen receptor variants in prostate cancer cell lines.

A sensitive semi-nested reverse transcriptase-polymerase chain reaction (RT-PCR) amplification was performed to evaluate estrogen receptor-alpha (ER-alpha) mRNA expression in prostate cancer cell lines. We demonstrated the presence of wild-type ER-alpha (wt ER-alpha) and five ER-alpha variants, designated ER-alphaA, B, C, D, and E. Unlike ER-alphaA and D, ER-alphaB, C, and E were not previously reported in normal or cancerous mammalian cells. DNA sequencing analysis of these ER-alpha variants revealed the genetic changes to be either in-frame or out-of-frame deletions. The expression of each ER-alpha variant differs significantly depending on the androgen responsiveness, tumorigenic and metastatic potentials of each prostate cancer cell line. The potential functional significance of ER-alpha variants was assessed in yeast two-hybrid and ERE promoter-reporter mammalian transcription assay systems. The results of these studies indicated that none of the ER-alpha variants can form homo- or heterodimers either with wt ER-alpha or among themselves in vivo, and that these ER-alpha variants have no demonstrable transcriptional or dominant-negative activity, as assessed in vitro.

Amino Acid Sequence↗

PubMed2000

A strategically positioned cation is crucial for efficient catalysis by chorismate mutase.

Combinatorial mutagenesis and in vivo selection experiments previously afforded functional variants of the AroH class Bacillus subtilis chorismate mutase lacking the otherwise highly conserved active site residue Arg(90). Here, we present a detailed kinetic and crystallographic study of several such variants. Removing the arginine side chain (R90G and R90A) reduced catalytic efficiency by more than 5 orders of magnitude. Reintroducing a positive charge to the active site through lysine substitutions restored more than a factor of a thousand in k(cat). Remarkably, the lysine could be placed at position 90 or at the more remote position 88 provided a sterically suitable residue was present at the partner site. Crystal structures of the double mutants C88S/R90K and C88K/R90S show that the lysine adopts an extended conformation that would place its epsilon-ammonium group within hydrogen-bonding distance of the ether oxygen of bound chorismate in the transition state. These results provide support for the hypothesis that developing negative charge in the highly polarized transition state is stabilized electrostatically by a strategically placed cation. The implications of this finding for the mechanism of all natural chorismate mutases and for the design of artificial catalysts are discussed.

Binding Sites↗