Biomedical subjects

W Sun

Publications and source records attributed to W Sun.

At least 127 records · Page 7Linked to original sources

PubMed2000

[Application of autotransfusion hemodilution in laryngectomy].

OBJECTIVE: To study the application and clinical significance of autotransfusion hemodilution in laryngectomy. METHOD: Autotransfusion hemodilution was adopted in 30 patients with III or IV stage laryngeal carcinoma during operation as the experimental group, and the blood transfusion only was adopted in the patients with excessively blood loss. The other 30 patients with the same stages of disease and the same kinds of operation were performed as the control group, without autotransfusion hemodilution and the blood transfusion was adopted if necessary. RESULT: Blood transfusion was necessary to be performed only in 8 patients of the experimental group, on the contrary, it was necessary in 19 of 30 patients of the control group (P < 0.01). There were no complications during the operations, and the postoperative complications were no significance (P > 0.05) between two groups. CONCLUSION: The application of autotransfusion hemodilution may be of help to a plenty of patients with laryngeal carcinoma in advanced stage to keep off the blood transfusion during laryngectomy.

Adult↗

PubMed2000

[Nasal cavity volume and nasopharyngeal cavity volume in adults measured by acoustic rhinometry].

OBJECTIVE: To investigate the range of normal value of total nasal cavity volume(NV) and total nasopharyngeal cavity volume (NPV) of healthy adults. METHOD: Six hundred and fifty-nine healthy adults and eighty-two adults of chronic rhinitis were measured with acoustic rhinometry. RESULT: The range of NV was 29.922-37.481 cm3 and NPV was 29.369-44.159 cm3. Comparing healthy adults with adults of chronic rhinitis, there was a significant difference in NV. CONCLUSION: Acoustic rhinometry suited for objective assessment of the nasal airways in adults. It was demonstrated that these data could provide available information for the study of nasal physiology and pathophysiology, as well as for the diagnosis and judgement of therapeutic effectiveness of nasal diseases.

Adolescent↗

PubMed1999

Differential expression of hepatocyte growth factor and its receptor, c-Met in the rat retina during development.

Hepatocyte growth factor (HGF) is a pleiotrophic factor with mitogenic, motogenic, and morphogenic activities. Recent evidence has suggested that HGF plays an important role in the development and maintenance of the nervous system. In this study, we examined spatial and temporal expression of HGF and its receptor, c-Met, during retinal development at RNA or protein levels. Competitive RT-PCR revealed that HGF and c-met mRNA expressions were up-regulated during the development and sustained at high levels in adulthood. By immunohistochemical analysis, we demonstrated that c-Met-immunoreactivity (IR) was present in the major classes of retinal neurons after their differentiation. In the adult, c-Met-IR was predominantly present in the photoreceptors. In contrast, HGF-IR was observed from P7 and thereafter in ganglion cells and the inner nuclear layer, but not in other layers. Differential or co-localization of HGF and c-Met indicates the autocrine or paracrine action of HGF depending on the cell types and developmental stages. Moreover, dynamic regulation of HGF and c-Met implicates their multiple roles in the development, maintenance and modification of retinal system.

Animals↗

PubMed1999

High susceptibility of a human breast epithelial cell type with stem cell characteristics to telomerase activation and immortalization.

We have recently characterized two types of normal human breast epithelial cells (HBECs) from reduction mammoplasty. Type I cells express estrogen receptor, luminal epithelial cell markers, and stem cell characteristics (i.e., the ability to differentiate into other cell types and to form budding/ductal structures on Matrigel), whereas Type II cells show basal epithelial cell phenotypes. In this study, we have examined whether Type I HBECs are more susceptible to telomerase activation and immortalization after transfection with SV40 large T-antigen. The results show that both types of cells acquire extended life span [(EL); i.e., bypassing senescence] at a comparable frequency. However, they differ significantly in the ability to become immortal in continuous culture, ie., 11 of 11 Type I EL clones became immortal compared with 1 of 10 Type II EL clones. Both parental Type I and Type II cells as well as their transformed EL clones at early passages [approximately 30 cumulative population doubling level (cpdl)] showed a low level of telomerase activity as measured by the telomeric repeat amplification protocol assay. For all 11 of the Type I EL clones and the single Type II EL clone that became immortal, telomerase activities were invariably activated at middle passages (approximately 60 cpdl) or late passages (approximately 100 cpdl). For the four Type II EL clones randomly selected from the nine Type II clones that did not become immortal, the telomerase activities were found to be further diminished at mid-passage, before the end of the life span. Thus, normal HBECs do have a low level of telomerase activity, and Type I HBECs with stem cell characteristics are more susceptible to telomerase activation and immortalization, a basis on which they may be major target cells for breast carcinogenesis.

Breast↗

PubMed1999

No braiding of Holliday junctions in positively supercoiled DNA molecules.

The Holliday junction is a prominent intermediate in genetic recombination that consists of four double helical arms of DNA flanking a branch point. Under many conditions, the Holliday junction arranges its arms into two stacked domains that can be oriented so that genetic markers are parallel or antiparallel. In this arrangement, two strands retain a helical conformation, and the other two strands effect the crossover between helical domains. The products of recombination are altered by a crossover isomerization event, which switches the strands fulfilling these two roles. It appears that effecting this switch from the parallel conformation by the simplest mechanism results in braiding the crossover strands at the branch point. In previous work we showed by topological means that a short, parallel, DNA double crossover molecule with closed ends did not braid its branch point; however, that molecule was too short to adopt the necessary positively supercoiled topology. Here, we have addressed the same problem using a larger molecule of the same type. We have constructed a parallel DNA double crossover molecule with closed ends, containing 14 double helical turns in each helix between its crossover points. We have prepared this molecule in a relaxed form by simple ligation and in a positively supercoiled form by ligation in the presence of netropsin. The positively supercoiled molecule is of the right topology to accommodate braiding. We have compared the relaxed and supercoiled versions for their responses to probes that include hydroxyl radicals, KMnO4, the junction resolvases endonuclease VII and RuvC, and RuvC activation of KMNO4 sensitivity. In no case did we find evidence for a braid at the crossover point. We conclude that Holliday junctions do not braid at their branch points, and that the topological problem created by crossover isomerization in the parallel conformation is likely to be solved by distributing the stress over the helices that flank the branch point.

Bacterial Proteins↗

PubMed1999

Electrophysiological effects of dronedarone (SR33589), a noniodinated benzofuran derivative, in the rabbit heart : comparison with amiodarone.

BACKGROUND: To overcome the side effects of amiodarone (AM), its noniodinated analogue, dronedarone (SR), was synthesized. In this study, its electrophysiological effects were compared with those of AM in rabbit hearts. METHODS AND RESULTS: Five animal groups (n=7 each) for 3 weeks received daily oral treatment of 1 of these regimens: (1) control, vehicle only; (2) AM 50 mg/kg (AM50); (3) AM 100 mg/kg (AM100); (4) SR 50 mg/kg (SR50); and (5) SR 100 mg/kg (SR100). ECGs were recorded before drug and at 3 weeks of drug before euthanasia. Action potentials were recorded from isolated papillary muscle and sinoatrial node by microelectrode techniques. The short-term effects were studied in controls (n=5) at various concentrations of SR (0 to 10 micromol/L) in tissue bath. Action potential duration at 50% (APD(50)) and 90% (APD(90)) repolarization and upstroke dV/dt (V(max)) at various cycle lengths were compared by ANOVA with repeated measures. Compared with control, AM and SR increased RR, QT, and QTc intervals (P<0.0001 for all). Ventricular APD(50) and APD(90) were lengthened by 20% to 49% as a function of dose (P<0.005 to <0.0001) and cycle length (P<0.001). SR100 effects were greater than those of AM100 (P<0.002). V(max) was decreased by both AM100 (P<0.0001) and SR100 (P<0.01). Sinoatrial node automaticity was slowed in treated groups compared with that of the control group (P<0.0001 for all). CONCLUSIONS: The electrophysiological effects of dronedarone are similar to those of AM but more potent, despite deletion of iodine from its molecular structure, a finding of importance for the development of future class III antiarrhythmic compounds.

Amiodarone↗

PubMed1999

Design and synthesis of novel alpha(1)(a) adrenoceptor-selective antagonists. 1. Structure-activity relationship in dihydropyrimidinones.

Dihydropyrimidinones such as compound 12 exhibited high binding affinity and subtype selectivity for the cloned human alpha(1a) receptor. Systematic modifications of 12 led to identification of highly potent and subtype-selective compounds such as (+)-30 and (+)-103, with high binding affinity (K(i) = 0.2 nM) for alpha(1a) receptor and greater than 1500-fold selectivity over alpha(1b) and alpha(1d) adrenoceptors. The compounds were found to be functional antagonists in human, rat, and dog prostate tissues. Compound (+)-103 exhibited excellent selectively to inhibit intraurethral pressure (IUP) as compared to lowering diastolic blood pressure (DBP) in mongrel dogs (K(b)(DBP)/K(b)(IUP) = 40) suggesting uroselectivity for alpha(1a)-selective compounds.

Adrenergic alpha-1 Receptor Antagonists↗

PubMed1999

Design and synthesis of novel alpha(1)(a) adrenoceptor-selective antagonists. 2. Approaches to eliminate opioid agonist metabolites via modification of linker and 4-methoxycarbonyl-4-phenylpiperidine moiety.

We have previously described compound 1a as a high-affinity subtype selective alpha(1a) antagonist. In vitro and in vivo evaluation of compound 1a showed its major metabolite to be a mu-opioid agonist, 4-methoxycarbonyl-4-phenylpiperidine (3). Several dihydropyrimidinone analogues were synthesized with the goal of either minimizing the formation of 3 by modification of the linker or finding alternative piperidine moieties which when cleaved as a consequence of metabolism would not give rise to mu-opioid activity. Modification of the linker gave several compounds with good alpha(1a) binding affinity (K(i) = < 1 nM) and selectivity (>300-fold over alpha(1b) and alpha(1d)). In vitro analysis in the microsomal assay revealed these modifications did not significantly affect N-dealkylation and the formation of the piperidine 3. The second approach, however, yielded several piperidine replacements for 3, which did not show significant mu-opioid activity. Several of these compounds maintained good affinity at the alpha(1a) adrenoceptor and selectivity over alpha(1b) and alpha(1d). For example, the piperidine fragments of (+)-73 and (+)-83, viz. 4-cyano-4-phenylpiperidine and 4-methyl-4-phenylpiperidine, were essentially inactive at the mu-opioid receptor (IC(50) > 30 microM vs 3 microM for 3). Compounds (+)-73 and (+)-83 were subjected to detailed in vitro and in vivo characterization. Both these compounds, in addition to their excellent selectivity (>880-fold) over alpha(1b) and alpha(1d), also showed good selectivity over several other recombinant human G-protein coupled receptors. Compounds (+)-73 and (+)-83 showed good functional potency in isolated human prostate tissues, with K(b)s comparable to their in vitro alpha(1a) binding data. In addition, compound (+)-73 also exhibited good uroselectivity (DBP K(b)/IUP K(b) > 20-fold) in the in vivo experiments in dogs, similar to 1a.

Adrenergic alpha-1 Receptor Antagonists↗

PubMed1999

Design and synthesis of novel alpha(1)(a) adrenoceptor-selective antagonists. 3. Approaches to eliminate opioid agonist metabolites by using substituted phenylpiperazine side chains.

Dihydropyrimidinones, such as 1, represent a novel class of alpha(1a) adrenoceptor antagonists with potential for the treatment of benign prostatic hyperplasia (BPH) (see part 1 of this series). Analysis of the metabolites of 1 revealed that 4-methoxycarbonyl-4-phenylpiperidine is formed as the major metabolite and is an agonist at the mu-opioid receptor. To circumvent any potential liability resulting from the metabolite, we decided to identify alternate templates devoid of agonist activity at the mu-opioid receptor to replace the 4-methoxycarbonyl-4-phenylpiperidine moiety. The present study describes the synthesis and SAR of dihydropyrimidinones linked to substituted 4-phenylpiperazine containing side chains. Compound (+)-38 was identified as a lead compound with a binding and functional profile comparable to that of 1. The putative metabolite 2-carboxamidophenylpiperazine has negligible affinity for the mu-opioid receptor.

Adrenergic alpha-Antagonists↗

PubMed1999

Design and synthesis of novel alpha(1)(a) adrenoceptor-selective antagonists. 4. Structure-activity relationship in the dihydropyrimidine series.

We have previously disclosed dihydropyridines such as 1a,b as selective alpha(1a) antagonists as a potential treatment for benign prostatic hyperplasia (BPH). The propensity of dihydropyridines toward an oxidation led us to find suitable replacements of the core unit. The accompanying papers describe the structure-activity relationship (SAR) of dihydropyrimidinones 2a,b as selective alpha(1a) antagonists. We report herein the SAR of dihydropyrimidines such as 4 and highlight the similarities and differences between the dihydropyrimidine and dihydropyrimidinone series of compounds.

Administration, Oral↗

PubMed1999

Learning induces a CDC2-related protein kinase, KKIAMRE.

To elucidate molecular mechanisms in learning and memory, we analyzed expression of mRNAs in brains of rabbits undergoing eyeblink conditioning. Infusion of the transcription inhibitor actinomycin D into the cerebellar interpositus nucleus reversibly blocked learning but not performance of the conditioned response. Differential display PCR analysis of cerebellar interpositus RNAs from trained and pseudotrained rabbits identified a 207 bp band that was induced with learning. The fragment was used to isolate a cDNA from a lambdagt11 rabbit brain library containing a 1698 bp open reading frame. The deduced amino acid sequence contains the KKIAMRE motif, which is conserved among cell division cycle 2 (cdc2)-related kinases. These results suggest that there is a new category of cdc2-related kinases in the brain whose function may be important in learning and memory.

Acoustic Stimulation↗

PubMed1999

VIP and PACAP differentially regulate the costimulatory activity of resting and activated macrophages through the modulation of B7.1 and B7.2 expression.

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating polypeptide (PACAP), two structurally related neuropeptides produced and/or released within the lymphoid microenvironment, modulate numerous immune functions. Although primarily antiinflammatory in nature, VIP and PACAP also affect resting macrophages. In this study, we report on in vitro and in vivo dual effects of VIP/PACAP on the expression of B7.1 and B7.2 and on the costimulatory activity for T cells in unstimulated and LPS/IFN-gamma-activated macrophages. VIP and PACAP up-regulate B7.2, but not B7.1, expression and induce the capacity to stimulate the proliferation of naive T cells in response to soluble anti-CD3 or allogeneic stimulation. In contrast, both neuropeptides down-regulate B7.1/B7.2 expression on LPS/IFN-gamma-activated macrophages and inhibit the endotoxin-induced costimulatory activity for T cells. Interestingly, both the stimulatory and the inhibitory effects of VIP/PACAP are mediated through the specific receptor VPAC1 and involve the cAMP/protein kinase A transduction pathway. The dual effect on B7.1 and B7.2 expression occurs at both mRNA and protein level and correlates with the VIP/PACAP regulation of the macrophage costimulatory activity. Through their regulatory role for resting and activated macrophages, VIP and PACAP act as endogenous participants in the control of immune homeostasis. Their effects depend not only on the timing of their release, but also on the activation and differentiation state of the neighboring immune cells.

Adjuvants, Immunologic↗

PubMed1999

Disabled-2 inactivation is an early step in ovarian tumorigenicity.

Disabled-2 (Dab2) functions in mitogenic signal transduction pathway, and is frequently activated by homozygous gene deletion in tumors, suggesting that Dab2 is a candidate tumor suppressor. Here, we surveyed the expression of Dab2, and report that Dab2 is expressed in a variety of tissues, and the level of expression is particularly high in ovary and breast. Dab2 expression was also detected in immortalized breast and ovarian epithelial cells. However, in more than a dozen established tumor cell lines derived from breast and ovarian epithelial tumors examined by Western blotting, Dab2 expression was undetectable in 90% of these cell lines. Histological staining of human ovarian tissues with specific anti-Dab2 antibodies indicated that Dab2 is highly expressed in the surface epithelial layer. In an immunohistological study of 26 ovarian carcinomas, 22 (85%) of the tumors were found to lose the expression of Dab2 in the tumor cells, which are epithelial origin. Loss of Dab2 expression is not correlated with tumor grade, suggesting that Dab2 is lost in an early stage of tumorigenicity. Indeed, loss of Dab2 correlates closely with morphological transformation of the surface epithelial cells. Additionally, loss of Dab2 protein occurs in hyperproliferative, but histological benign ovarian epithelium, suggesting that loss of Dab2 occurs in pre-malignant lesions. Thus, this study indicates that the loss of Dab2 expression is correlated with tumorigenicity of the cells disregarding the grade of the tumors, and loss of Dab2 expression is an early event in ovarian malignancies.

Adaptor Proteins, Signal Transducing↗

PubMed1999

A nanomechanical device based on the B-Z transition of DNA.

The assembly of synthetic, controllable molecular mechanical systems is one of the goals of nanotechnology. Protein-based molecular machines, often driven by an energy source such as ATP, are abundant in biology. It has been shown previously that branched motifs of DNA can provide components for the assembly of nanoscale objects, links and arrays. Here we show that such structures can also provide the basis for dynamic assemblies: switchable molecular machines. We have constructed a supramolecular device consisting of two rigid DNA 'double-crossover' (DX) molecules connected by 4.5 double-helical turns. One domain of each DX molecule is attached to the connecting helix. To effect switchable motion in this assembly, we use the transition between the B and Z forms of DNA. In conditions that favour B-DNA, the two unconnected domains of the DX molecules lie on the same side of the central helix. In Z-DNA-promoting conditions, however, these domains switch to opposite sides of the helix. This relative repositioning is detected by means of fluorescence resonance energy transfer spectroscopy, which measures the relative proximity of two dye molecules attached to the free ends of the DX molecules. The switching event induces atomic displacements of 20-60 A.

Biomechanical Phenomena↗

PubMed1999

Bacterial expression and characterization of functional recombinant triosephosphate isomerase from Schistosoma japonicum.

The dimeric enzyme triosephosphate isomerase (TPI) converts glyceraldehyde-3-phosphate to dehydroxyacetone phosphate, a key reaction in glycolysis. Previous studies of the native enzyme in the human blood-flukes belonging to the genus Schistosoma have indicated that TPI is a promising anti-schistosome vaccine antigen. However, a recombinant form of the enzyme is required as an alternative to the impractical option of using biochemically purified TPI obtained from worm tissue for large-scale vaccine use. We previously cloned and sequenced a full-length cDNA encoding the TPI of the Asian (Chinese strain) schistosome Schistosoma japonicum (SjcTPI). We now report very high level bacterial expression of this cDNA and the subsequent purification of the recombinant protein to >98% homogeneity under nondenaturing conditions. The recombinant SjcTPI (re-SjcTPI) was shown to be enzymatically active with a specific activity of 7687 units/mg protein, an activity higher than that of commercially obtained porcine TPI tested concurrently under the same assay conditions. The K(m) value for the re-SjcTPI using glyceraldehyde-3-phosphate as substrate was 406.7 microM, which is similar to the K(m) values reported for the yeast enzyme and various mammalian TPIs. With the availability of substantial amounts of enzymatically active and readily purified re-SjcTPI made in bacteria we can now test whether the recombinant protein can induce a similar level of protection in vaccination/challenge experiments as the native, biochemically purified enzyme.

Animals↗

PubMed1999

Fast reversible electron transfer for photosynthetic reaction center from wild type Rhodobacter sphaeroides re-constituted in polycation sandwiched monolayer film.

Direct reversible electron transfer for photosynthetic reaction center from wild type Rhodobacter sphaeroides re-constituted in polycation sandwiched monolayer film was observed in this work. The redox potential E0' = 0.46 V vs. NHE for first primary donor redox couple P/P+ was accurately measured from reversible CV or SWV peaks, which were quite close to those obtained from optic redox titration method. Reaction center (RC) in film was found re-constituted in such an ordered way that the orientation of RC favored the electron transfer in film. Thus, the protein electroactivity seems to be turned on in this artificial biomimic thin film. Furthermore, RC in the film features a photo-induced redox-peak fluctuation, suggesting an intact and functional state for RC in such film. Redox peaks were also found dependent of pH, implying a proton-coupled electron transfer occurring in film. Charge recombination was observed accompanied with change of electrochemical driving force. Electrochemical model assuming several classes of electroactive sites in the films on the electrode with a dispersion of standard potentials successfully fits SWV experimental data at different pulse height and frequency.

Electrochemistry↗

PubMed1999

Acquisition of fear conditioning in rats requires the synthesis of mRNA in the amygdala.

In this study, the role of mRNA synthesis in the amygdala was studied during the acquisition of conditional fear. Rats with cannulas placed in the basolateral region of the amygdala were trained with a series of noise-shock pairings in a distinctive observation chamber. One half of the rats were pretreated with the mRNA synthesis inhibitor actinomycin-D (act-D). Responding to the training context and the auditory stimulus in a novel context measured by defensive freezing was assessed. Pretreatment with act-D significantly attenuated fear responses to both stimuli. Animals receiving act-D injections exhibited normal reactions to the conditioned stimulus-unconditioned stimulus pairings in the initial training session and displayed normal learning when retrained 7 days after injections. These results indicate that the transcription of new mRNA and subsequent protein synthesis in the amygdala may be essential for neural plasticity during this form of associative learning.

Amygdala↗

PubMed1999

Characterization of an Arabidopsis thaliana receptor-like protein kinase gene activated by oxidative stress and pathogen attack.

An Arabidopsis thaliana cDNA clone that encodes a putative receptor-like protein kinase gene (At-RLK3) was characterized. The deduced 667-amino acid protein consists of an amino-terminal signal sequence, an extracellular domain, a single transmembrane domain, and a cytoplasmic domain with characteristics of serine/threonine protein kinase. Because of the original features of its extracellular domain, the At-RLK3 protein is a member of a new class of receptor-like protein kinases. The At-RLK3 gene is present as a single copy within the Arabidopsis genome and its transcripts are detected in root, stem, leaf and flower. In cultured cells, the At-RLK3 gene is activated upon oxidative stress and salicylic acid treatment. In plants, the gene appears to be differentially regulated during various plant-pathogen interactions: upon inoculation with strains of Pseudomonas syringae pv. tomato harboring or not, different avr genes, At-RLK3 transcripts accumulate transiently at similar levels during both compatible and incompatible interactions. This gene is, however, preferentially expressed during the incompatible interaction induced by the soil-borne vascular bacteria, Ralstonia solanacearum. The involvement of At-RLK3 in signal transduction pathways during pathogen attack is discussed.

Amino Acid Sequence↗