Search PubMed⌕ Search

Biomedical subjects

S Yao

Publications and source records attributed to S Yao.

At least 109 records · Page 6Linked to original sources
PubMed1999

[Effect of long-term experimental stress on blood glucose level in mice with diabetes-prone: the age difference and its mechanism].

OBJECTIVE: To compare the effects of long-term experimental stressors on blood glucose level and insulin secretion in the aged and young mice with diabetes-prone and to explore the mechanism. METHODS: Diabetes-prone was induced by streptozotocin (STZ) in 40 1.5-month-old mice and 40 15-month-old mice. The young and the aged STZ mice were divided randomly into the stress group and the control group, respectively. Each group contained 20 mice. Both the aged and the young stress mice were exposed to multiple stressors (restrain, rotation, crowding) for 6 weeks. Fasting blood glucose (FBG), fasting plasma insulin (FINS), pancreas lipid peroxidase (LPO) and the metabolic products of nitric oxide (NO2-, NO3-) levels and superoxide dismutase (SOD) activity were measured. The grade of insulitis in STZ mice was also evaluated. RESULTS: After 6-week stress, FBG level, pancreatic tissue LPO and NO2-, NO3- contents were significantly higher while FINS level and SOD activity lower in the aged stress mice than those in the youngs. The insulitis malignization in the aged stress group was severer than that in the young stress group. There were correlativities among the above variables. CONCLUSION: The effects of long-term stress in promoting hyperglycemia exacerbating insulitis, and inhibiting insulin secretion are more significant in the aged STZ mice than in the young ones. This difference may result from the excessive NO and the peroxide injury to the pancreas.

Aging↗
PubMed1999

[The development and clinical application of a multipurpose neuroendoscope].

The multipurpose rigid neuroendoscope MGE-4 has been developed with the application of the self-focussing lens technology. We have been using it to examine and treat 10 neurosurgical patients who suffered from tumours, hydrocephalus, intracerebral haematomas of head injury and hypertensive cerebral haemorrhage. The short-term effect was satisfactory and there was no operative complications. It is considered that Model MGE-4 with the accessories can be used safely for the brain functional subcortical lesion or the deep-seated cystic lesions and haematomas.

Adult↗
PubMed1999

[Development and clinical application of dental spot weld & heat-treat tri-uses device].

A spot weld & heating treatment tri-uses device based on modern mechanical-electric technique, was developed for dental spot weld, stainless steel orthodontic wire heating-reversion and Ni-Ti orthodontic wire heating-overload metamorphism. The device will be very helpful instrument in orthodontic clinic. The paper not only described the operating methods of the device, but also discussed the Performance-improved principles of stainless steel orthodontic wire and the principles of heating overload metamorphism of Ni-Ti orthodontic wire.

Dental Soldering↗
PubMed1999

[Study on laser flash spectroscopy of laser-induced interaction of DNA and polynucleotides with SO4*-].

The interactions of DNA and polynucleotides (poly[G],poly[A] and poly[C]) with SO4*- were investigated by 248 nm laser flash photolysis. The results show that, the reactions of poly[G] or poly[A] with SO4*- yield predominantly the corresponding one-electron-oxidated base radicals. With poly[C], it is suggested that SO4*- radical reacts predominantly by addition to the base moiety to produce C5-yl and C6-yl sulphate radical adducts,and subsequently H-abstraction yields C2'-sugar radical. The predominant species resulting from the reaction of DNA with SO4*- is DNA guanyl radical.

DNA↗
PubMed1999

[Study on laser flash spectroscopy of processes of photoionization of tyrosine: pH effects].

The processes of photoionization of tyrosine on three different pH value solutions were investigated by 248 nm laser flash photolysis. The results showed that the processes of photoionization of tyrosine were affected by pH value of the solution. With pH value increasing, the molecule number of photoionization increases via a monophotonic process, and decreases via a biphotonic process. Furthermore, the pH effect of photoionization of tyrosine resulting from deprotonation of phenolic hydroxyl group in alkaline solution was demonstrated.

Hydrogen-Ion Concentration↗
PubMed1998

Selective amplification by auto- and cross-catalysis in a replicating peptide system.

Self-replication has been demonstrated in synthetic chemical systems based on oligonucleotides, peptides and complementary molecules without natural analogues. However, within a living cell virtually no molecule catalyses its own formation, and the search for chemical systems in which both auto- and cross-catalysis can occur has therefore attracted wide interest. One such system, consisting of two self-replicating peptides that catalyse each other's production, has been reported. Here we describe a four-component peptide system that is capable of auto- and cross-catalysis and allows for the selective amplification of one or more of the products by changing the reaction conditions. The ability of this system selectively to amplify one or more molecules in response to changes in environmental conditions such as pH or salt concentration supports the suggestions that self-replicating peptides may have played a role in the origin of life.

Amino Acid Sequence↗
PubMed1998

NS398, a selective cyclooxygenase-2 inhibitor, induces apoptosis and down-regulates bcl-2 expression in LNCaP cells.

Cyclooxygenase (COX)-2, an inducible enzyme that catalyzes the formation of prostaglandins and other eicosanoids from arachidonic acid, is constitutively expressed in LNCaP human prostate cancer cell line. To evaluate the potential role of COX-2 in prostate cancer, LNCaP cells were treated with NS398, a selective COX-2 inhibitor, and the effects on cell viability and apoptosis were determined. NS398 treatment induced apoptosis in LNCaP cells in a time- and dose-dependent fashion. Treatment with 100 microM NS398 caused a down-regulation in bcl-2 protein expression, followed by chromatin condensation, chromosomal DNA fragmentation, and changes in nuclear morphology detected by 4,6-diamidino-2-phenylindole staining, DNA fragmentation assay, and terminal deoxynucleotidyl transferase-mediated UTP-biotin nick end-labeling assay. In contrast, NS398 treatment had no effect on either cell viability or nuclear function and morphology in human fetal prostate fibroblasts. These results demonstrate that NS398 induces apoptosis in LNCaP cells but not in human fetal prostate fibroblasts, and that this induction is associated with a decreased level of bcl-2 protein.

Apoptosis↗
PubMed1998

[Effects of cadmium on 3H-leucine incorporation and cell growth of cultured myocardiocytes].

The effects of cadmium on 3H-leucine incorporation and cell growth of cultured cardiac myocytes were investigated by measuring the incorporation quantity of radioisotope labelled amino-acid and the cell volume on cultured myocardiocytes in neonatal Wistar rats. The results showed that 3H-leucine incorporation was decreased significantly in 1 x 10(-4) mmol/L CdCl2 for 24 h, and was gradually reduced with prolongation. The cell volume was decreased after exposed to Cd for 48 h. The volume was from (2053 +/- 189) microns 3 to (1847 +/- 176) microns 3. There was no significant difference in cell number between the treated group and the control group. These data indicated that cadmium can inhibit the synthesis of protein and the growth on cultured myocardiocytes.

Animals↗
PubMed1998

Topotecan lactone selectively binds to double- and single-stranded DNA in the absence of topoisomerase I.

We report the first experimental observation that a clinically important camptothecin [CPT; topotecan (TPT), a water-soluble CPT] binds directly and noncovalently to double-stranded DNA and single-stranded DNA structures in the absence of topoisomerase I, but only in the lactone form. We observed clear DNA sequence specificity of the TPT lactone binding to duplex DNA, which was comprised of alternating purine-pyrimidine sequences that contained dT. These structural studies of direct TPT lactone-DNA binding support several important considerations involving possible mechanism(s) of anticancer activity of CPT-type drugs containing a 20(S) lactone moiety.

Antineoplastic Agents↗
PubMed1998

Mutation of a gene encoding a protein with extracellular matrix motifs in Usher syndrome type IIa.

Usher syndrome type IIa (OMIM 276901), an autosomal recessive disorder characterized by moderate to severe sensorineural hearing loss and progressive retinitis pigmentosa, maps to the long arm of human chromosome 1q41 between markers AFM268ZD1 and AFM144XF2. Three biologically important mutations in Usher syndrome type IIa patients were identified in a gene (USH2A) isolated from this critical region. The USH2A gene encodes a protein with a predicted size of 171.5 kilodaltons that has laminin epidermal growth factor and fibronectin type III motifs; these motifs are most commonly observed in proteins comprising components of the basal lamina and extracellular matrixes and in cell adhesion molecules.

Amino Acid Sequence↗
PubMed1998

Endothiopeptide inhibitors of HIV-1 protease.

Endothiopeptide inhibitors of HIV-1 protease were synthesized by chemical and enzymatic methods to individually replace each backbone amide bond in 1 with a thioamide-linkage. Interestingly, agent 7, which contains a thioamide-linkage between the P2' and P3' positions of 1, was the most potent, competitive inhibitor of HIV-1 protease with a Ki of 3.4 microM.

Chromatography, High Pressure Liquid↗
PubMed1998

Uncoiling c-Jun coiled coils: inhibitory effects of truncated Fos peptides on Jun dimerization and DNA binding in vitro.

c-Jun is an oncoprotein that comprises a portion of the AP-1 transcription factor and belongs to the basic-leucine zipper (bZIP) DNA binding protein family. Using peptides derived from the leucine zipper region of Fos, we have developed agents that inhibit Jun's DNA binding in the low micromolar range. Fos peptides that were effective inhibitors in the DNA binding assay were also found to inhibit cellular Jun binding to an AP-1 site in a luciferase reporter plasmid in MCF-7 cells. Size exclusion studies confirmed that peptides that inhibit the DNA binding of Jun also inhibit its dimerization. These peptides were found to have a cytotoxic effect on the MCF-7 cell line when delivered with the transfecting agent Tfx-50, possibly due to their role as transcription factor regulators.

Amino Acid Sequence↗
PubMed1998

Solution structure of peptides from HIV-1 Vpr protein that cause membrane permeabilization and growth arrest.

Vpr, one of the accessory gene products encoded by HIV-1, is a 96-residue protein with a number of functions, including targeting of the viral pre-integration complex to the nucleus and inducing growth arrest of dividing cells. We have characterized by 2D NMR the solution conformations of bioactive synthetic peptide fragments of Vpr encompassing a pair of H(F/S)RIG sequence motifs (residues 71-75 and 78-82 of HIV-1 Vpr) that cause cell membrane permeabilization and death in yeast and mammalian cells. Due to limited solubility of the peptides in water, their structures were studied in aqueous trifluoroethanol. Peptide Vpr59-86 (residues 59-86 of Vpr) formed an alpha-helix encompassing residues 60-77, with a kink in the vicinity of residue 62. The first of the repeated sequence motifs (HFRIG) participated in the well-defined alpha-helical domain whereas the second (HSRIG) lay outside the helical domain and formed a reverse turn followed by a less ordered region. On the other hand, peptides Vpr71-82 and Vpr71-96, in which the sequence motifs were located at the N-terminus, were largely unstructured under similar conditions, as judged by their C(alpha)H chemical shifts. Thus, the HFRIG and HSRIG motifs adopt alpha-helical and turn structures, respectively, when preceded by a helical structure, but are largely unstructured in isolation. The implications of these findings for interpretation of the structure-function relationships of synthetic peptides containing these motifs are discussed.

Amino Acid Sequence↗
PubMed1998

Improved Estimation of Protein Rotational Correlation Times from 15N Relaxation Measurements

In the study of protein backbone dynamics by 15N relaxation measurements, an initial estimation of the isotropic global correlation time, taum, is usually obtained from the average T1/T2 ratio of nuclear spins that do not exhibit slow internal motion and with T2 values not significantly shortened by chemical or conformational exchange processes. Different methods have been used for identification of the rates of internal motion. However, the number of nuclear spins included in the taum estimation is often larger than the number that ultimately can be fitted to a single-order parameter, S2, implying that some nuclear spins involved in the initial taum estimation actually have an effective internal correlation time, taue, not as fast as assumed. As a consequence, taum is underestimated, since internal motion reduces the T1/T2 ratio. This situation becomes more obvious if the molecule has a large taum value because the reduction in T1/T2 ratio arising from internal motion is more significant than for molecules with smaller taum and the same degree of internal motion. This Communication describes a more reliable method for identifying nuclear spins which should be excluded from the taum estimation because of insufficiently rapid internal motion. This results in an improved taum value, giving a much better agreement between the number of nuclear spins fitted successfully to a single-order parameter, S2, and those used in the taum estimation. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

A rapid method for determination of in vitro susceptibility to antibiotics with a bulk acoustic wave bacterial growth biosensor.

A novel bulk acoustic wave (BAW) bacterial growth biosensor was developed to study in vitro susceptibility by continuous monitoring of disturbances of bacterial growth at low antibiotic concentrations, followed by the accurate and rapid estimation of growth kinetic parameters and minimum inhibitory concentrations (MICs). The susceptibilities of bacteria, e.g. Escherichia coli, Staphylococcus aureus, Proteus vulgaris, Pr. morganii and Pr. mirabilis, to various antibiotics, e.g. penicillin, streptomycin, gentamicin and cefotaxime, were investigated, respectively, and the MICs were rapidly determined with a higher reproducibility than the conventional broth micro-dilution technique (BMDT). The effects of cell constant of conductivity electrode, pH and temperature on bacterial growth and biosensor signals were discussed in detail. The proposed method offers an effective alternative to the conventional methods.

Acoustics↗