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Biomedical subjects

Q Wu

Publications and source records attributed to Q Wu.

At least 307 records · Page 17Linked to original sources
PubMed1997

[Application of ultrasound biomicroscopy in diagnosis of anterior segment vitreoretinal disorders].

PURPOSE: To investigate the diagnostic value of ultrasound biomicroscopy(UBM) in anterior segment vitreoretinal disorders(ASVD). METHODS: 60 eyes of 58 sequential patients were examined with UBM. The ultrasound biomicroscopic images were compared with the results of clinic examination, B-scan ultrasonography and the finding during surgery to evaluate the reliability of UBM for ASVD. RESULTS: UBM allows structural details of the conjunctiva, rectus muscle, sclera, uvea, retina and vitreous to be visualized at microscopic resolution in living eye. The area of UBM may cover from cornea to vitreous base, partially to the equator of eye. A variety of the changes of ASVD were imaged in 60 eyes, including retinal detachment in 43 eyes, retinal circumferential contraction in 29 eyes, retinal anterior displacement in 24 eyes, vitreous opacities or fibrosis in 57 eyes, ciliary orchoroidal detachment in 26 eyes, ciliary nonpigmented epithelial detachment in 6 eyes, proliferative tissue at the sclerotomy site in 9 eyes, retinal neoplasm in 2 eyes, ciliary cyst in 6 eyes, proliferation of peripheral silicone oil in 8 eyes, silicone oil emulsification in 7 eyes and vitreous foreign body in 2 eyes, respectively. CONCLUSIONS: Our studies showed the feasibility of UBM for ASVD not visible by current techniques UBM can be used for the diagnosis, differential diagnosis and the instructive treatments of ASVD.

Adult↗
PubMed1997

[Effect of human neutrophil defensins on subgingival flora].

40 teeth of 18 patients with moderate or severe adult periodontitis were examined for evaluating the effect of defensins on subgingival flora. The period of experiment was 11 days. Defensins fibers were put in the periodontal pockets deeper than 5 mm for 3 days and discarded on the fourth day. Each of the pockets was applied one fiber containing about 8 micrograms defensins. The clinical parameters (GI,BI) and the density of subgingival flora were reduced (P < 0.05). The increase of coccoid cells, and the decrease of spirochetes and rods were indicated in the relative ratio (P < 0.05). This study indicated that defensins could reduce the density of the subgingival flora and change their ratio towards the periodontal healthy flora level.

Adult↗
PubMed1997

[A mathematical model of heat exchange between astronaut and environmental medium on the Lunar surface].

To maintain thermal balance of astronaut, and avoid injuries by heats of the solar radiation and radiation from the Moon, a detailed analysis of heat exchange between the astronaut and the environment medium was made and a mathematical model was established. It indicates that the Lunar surface temperature and the thermal current transmitted to the astronaut change with the incident angle of the solar radiation. The thermal balance of the astronaut is affected by absorption coefficient, radiation coefficient and thermal resistance.

Astronauts↗
PubMed1997

[Studies on sultamicillin hydrolysis].

Sultamicillin is an oral mutual pro-drug composed of double esters of formaldehyde hydrate in which one of the hydroxyl groups is esterified with ampicillin and the other with sulbactam. It is hydrolyzed fast in neutral or weakly alkaline condition. When hydrolyzed, it forms ampicillin and hydroxylmethyl sulbactam or sulbactam and hydroxylmethyl ampicillin by different routes. Usually, the former has priority as the two ester bonds have different activities. The ratio of ampicillin to sulbactam in the products is about 3:1. Both the hydroxylmethyl sulbactam and the hydroxylmethyl ampicillin can be further catalyzed by esterase to produce formaldehyde.

Ampicillin↗
PubMed1997

Splicing of a divergent subclass of AT-AC introns requires the major spliceosomal snRNAs.

AT-AC introns constitute a minor class of eukaryotic pre-mRNA introns, characterized by 5'-AT and AC-3' boundaries, in contrast to the 5'-GT and AG-3' boundaries of the much more prevalent conventional introns. In addition to the AT-AC borders, most known AT-AC introns have highly conserved 5' splice site and branch site sequence elements of 7-8 nt. Intron 6 of the nucleolar P120 gene and intron 2 of the SCN4A voltage-gated skeletal muscle sodium channel are AT-AC introns that have been shown recently to be processed via a unique splicing pathway involving several minor U snRNAs. Interestingly, intron 21 of the same SCN4A gene and the corresponding intron 25 of the SCN5A cardiac muscle sodium channel gene also have 5'-AT and AC-3' boundaries, but they have divergent 5' splice site and presumptive branch site sequences. Here, we report the accurate in vitro processing of these two divergent AT-AC introns and show that they belong to a functionally distinct subclass of AT-AC introns. Splicing of these introns does not require U12, U4atac, and U6atac snRNAs, but instead requires the major spliceosomal snRNAs U1, U2, U4, U5, and U6. Previous studies showed that G --> A mutation at the first position and G --> C mutation at the last position of a conventional yeast or mammalian GT-AG intron suppress each other in vivo, suggesting that the first and last bases participate in an essential non-Watson-Crick interaction. Our results show that such introns, hereafter termed AT-AC II introns, occur naturally and are spliced by a mechanism distinct from that responsible for processing of the apparently more common AT-AC I introns.

Base Sequence↗
PubMed1997

Membrane-associated carbonic anhydrase in cultured rabbit nonpigmented ciliary epithelium.

PURPOSE: To measure the activity of membrane-associated carbonic anhydrase (CA) in cultured rabbit nonpigmented epithelial (NPE) cells, determine its identity and its sensitivity to extracellular trypsin, and compare the ability of acetazolamide and a cell-impermeant dextran-bound CA inhibitor to change cytoplasmic pH. METHODS: Studies were conducted using a cell line derived from rabbit NPE. The cells were lysed and separated into soluble and insoluble fractions by differential centrifugation. CA activity in these fractions was determined using a CO2 hydration assay. In studies with intact cells, a membrane-impermeable high-molecular-weight dextran-bound inhibitor (DBI) was synthesized and used to selectively bind and inhibit the extracellular-facing membrane-bound CA. Measurements of CA activity in intact red blood cells were conducted to confirm DBI remains extracellular. Acetazolamide, a membrane-permeable CA inhibitor, was used to inhibit total CA activity. Intracellular pH was determined using the pH-dependent absorbance of the fluorescent dye BCECF-AM. RESULTS: A low-speed pellet enriched with plasma membrane material accounted for 22.3 +/- 6.1% (n = 18) of the total CA activity in the cultured NPE. When intact cells were exposed to trypsin-EDTA, a 28% reduction of membrane-associated CA activity was observed; DBI inhibited this CA activity loss. Cytosolic CA activity was inhibited by 0.2% sodium dodecyl sulfate (SDS). In contrast, membrane-associated CA was SDS resistant, a characteristic of the CA-IV isozyme. By Western blot, CA-IV immunoreactive polypeptide was detected in the cultured cells and also in native rabbit and porcine ciliary epithelium. Inhibition of total CA activity with acetazolamide and inhibition of extracellular-facing membrane-associated CA with DBI caused an identical intracellular pH decrease in intact NPE cells. CONCLUSIONS: Expression of the CA-IV isozyme could account for the significant fraction of CA activity in the cultured NPE, which is membrane associated and SDS resistant. Sensitivity to tryptic hydrolysis suggests the membrane-associated CA partially faces extracellularly. As judged by responses to an extracellular CA inhibitor, the membrane-associated CA has a functional role in maintaining cytoplasmic pH.

Acetazolamide↗
PubMed1997

Automated biodosimetry using digital image analysis of fluorescence in situ hybridization specimens.

Fluorescence in situ hybridization (FISH) of metaphase chromosome spreads is valuable for monitoring the radiation dose to circulating lymphocytes. At low dose levels, the number of cells that must be examined to estimate aberration frequencies is quite large. An automated microscope that can perform this analysis autonomously on suitably prepared specimens promises to make practical the large-scale studies that will be required for biodosimetry in the future. This paper describes such an instrument that is currently under development. We use metaphase specimens in which the five largest chromosomes have been hybridized with different-colored whole-chromosome painting probes. An automated multiband fluorescence microscope locates the spreads and counts the number of chromosome components of each color. Digital image analysis is used to locate and isolate the cells, count chromosome components, and estimate the proportions of abnormal cells. Cells exhibiting more than two chromosomal fragments in any color correspond to a clastogenic event. These automatically derived counts are corrected for statistical bias and used to estimate the overall rate of chromosome breakage. Overlap of fluorophore emission spectra prohibits isolation of the different chromosomes into separate color channels. Image processing effectively isolates each fluorophore to a single monochrome image, simplifying the task of counting chromosome fragments and reducing the error in the algorithm. Using proportion estimation, we remove the bias introduced by counting errors, leaving accuracy restricted by sample size considerations alone.

Automation↗
PubMed1997

[Association of pregnancy induced hypertension with human leucocyte antigen system].

OBJECTIVE: To examine whether pregnancy induced hypertension (PIH) is correlated with a polymorphism of human leucocyte antigen (HLA)-DRB1 in the Shanghai population. METHODS: We determined the HLA-DRB1 types of 17 PIH families and 14 normotension families by DNA typing utilizing the polymerase chain reaction (PCR) and hybridization of Dig-labeled sequence specific oligonucleotide (PCR-SSO). RESULTS: The antigens frequency and feto-material sharing of HLA-DR4 in PIH were increased and relative to that of the controls, and furthermore the 0405 allele occurred more often in PLH patients. CONCLUSION: These results suggest that a PIH susceptibility gene is associated with HLA-DRB1 0405. We therefore propose the following working hypothesis; 0405 allele is presumably due to linkage disequilibrium or the possibility that it acts directly as an immune response gene; PIH is correlated with DR4 compatibility between PIH mother and fetus which leads to failure of the mother's nonresponsiveness to fetal antigen. Lack of blocking factor increases the risk for PIH.

Adult↗
PubMed1997

[Human leucocyte antigen-DQA1, -DQB1 polymorphism distribution in Shanghai Chinese women with pregnancy induced hypertension].

OBJECTIVE: To explore the mechanism of correlation between human leucocyte antigen (HLA) and pregnancy induced hypertension (PIH). METHODS: Oligotyped HLA-DQA1, -DQB1 locus in 30 Shanghai Chinese PIH families and 14 control families were analysed by polymerase chain reaction-sequence specific oligonucleotide (PCR-SSO) hybridization method (probes labelled by nonradioactive technique). RESULTS: Compared with the control group, the allelic frequency of HLA-DQB1 * 0502 was significantly higher in PIH couples, and their sharing of HLA-DQA1 increased. No difference was found in HLA-DQA1 allelic frequency or HLA-DQB1 sharing in couples of the two groups. Analysis of HLA-DQA1 and DQB1 allelic frequency in PIH patients and their neonates showed no positive results. CONCLUSION: HLA-DQB1 * 0502 may be the marker of susceptibility to PIH. The increase of compatibility in HLA-D region resulted in decrease of producting blocking antibody. The unbalance of maternal-fetal immunity will induce PIH.

Adult↗
PubMed1997

Alterations in renal function in patients with obstructive sleep apnea syndrome and effects of continuous positive airway pressure.

OBJECTIVE: To assess renal function in patients with obstructive sleep apnea syndrome (OSAS) during two nights when they were untreated and treated with continuous positive airway pressure (CPAP). METHODS: Tubular function was estimated on the basis of the renal lithium clearance and its derived formulae, urinary osmolality, osmolal clearance and free water clearance; while glomerular function was evaluated by endogenous creatinine clearance. Twenty patients with OSAS and sixteen normal controls were studied. RESULTS: The untreated patients with OSAS had significantly lower fractional proximal tubular sodium reabsorption (59.1% +/- 7.1%, P < 0.001 vs controls), lower fractional distal tubular sodium reabsorption (93.8% +/- 1.7%, P < 0.05 vs controls) and urinary osmolality (573.0 +/- 107.9 mosm.kg-1, P < 0.05 vs controls). The absolute distal tubular reabsorption rate of sodium and osmolal clearance in the untreated patients were higher 47.0 +/- 26.0 mmol.L-1 and 25.0 +/- 4.1 ml.L-1; P < 0.01 and P < 0.05 respectively vs controls). During CPAP-treated nights all abnormal renal function indexes in the OSAS patients restored to normal control values (P > 0.05). CONCLUSIONS: The natriuresis and diuresis of OSAS patients were due to the decrease in proximal and distal tubular sodium reabsorption and in tubular concentration ability during their nocturnal sleep and were returned to normal by CPAP therapy.

Adult↗
PubMed1997

[Trends and changes in antimicrobial resistance of clinical isolates from 11 hospitals in Beijing area].

OBJECTIVE: To study the antimicrobial resistance and its changes of clinical isolates in Beijing area. METHODS: The diameters of the inhibition zones of clinical isolates around antibiotic susceptibility test discs at 12 hospitals in Beijing area were computerfiled and analysed by the software of 'WHONET' according to NCCLS published in 1994. RESULTS: A total of 10,305 isolates were collected in 1995. The percentages of resistance were as follows: (1) in E. coli: amikacin, 8%, ceftazidime, 15%, the other third generation cephalosporins, about 30%, (2) in Klebsiella spp: ofloxacin, 0%, ceftazidime, 15%, ciprofloxacin, 17%, norfloxacin, 15%, ofloxacin, 5%, (4) in Staph. aureus: norvancomycin, 0%, (5) in Strep. pneumoniae: penicillin G, 9%, (6) in Enterococcus spp: norvancomycin, 7%. The antimicrobial resistant changes over a six year period from 1990 to 1995 were surveyed and it was found that resistant percentage of the most isolates to quinolones, for example norfloxacin, increased significantly year by year and no remarkable differences of resistance to antimicrobial agents but quinolones were observed in Ps. aeruginosa. CONCLUSION: Antimicrobial resistance should be emphasised during clinical therapy with antimicrobial agents, and trends in antimicrobial resistance of isolates should be followed.

Anti-Infective Agents↗
PubMed1997

[Effect of pregnenolone sulfate on delayed rectifier K+ channel in pyramidial neuron of cerebral cortex].

Recent studies have shown that endogenous brain metabolites of steroids may exert important nongenomic modulatory effects on neuronal mechanisms. In this work the effect of pregnenolone sulfate (PS) on delayed rectifier K+ channel (IK) was studied in acutely dissociated rat cerebral cortical pyramidial neurons by means of cell-attached and inside-out patch clamp techniques. The open probability and mean open time of the IK channels were increased by PS in a concentration-dependent manner over the range of 30-100 mumol/L. but without changing the IK amplitude.

Animals↗
PubMed1996

Polyamine analogue regulation of NMDA MK-801 binding: a structure-activity study.

A series of analogues and homologues of spermine were synthesized, and their impact on MK-801 binding to the N-methyl-D-aspartate (NMDA) receptor was evaluated. These tetraamines encompass both linear and cyclic compounds. The linear molecules include norspermine, N1, N11-diethylnorspermine, N1,N12-bis(2,2,2-trifluoroethyl)spermine, homospermine, and N1,N14-diethylhomospermine. The cyclic tetraamines consist of the piperidine analogues N1,N3-bis(4-piperidinyl)-1,3-diaminopropane, N1,N4-bis(4-piperidinyl)-1,4-diaminobutane, N1,N4-bis(4-piperidinylmethyl)-1,4-diaminobutane, and N1,N4-bis[2-(4-piperidinyl)ethyl]-1,4-diaminobutane and the pyridine analogues N1,N3-bis(4-pyridyl)-1,3-diaminopropane, N1,N4-bis(4-pyridyl)-1,4-diaminobutane, N1,N4-bis(4-pyridylmethyl)-1,4-diaminobutane, and N1,N4-bis[2-(4-pyridyl)-ethyl]-1,4-diaminobutane. This structure-activity set makes it possible to establish the importance of charge, intercharge distance, and terminal nitrogen substitution on polyamine-regulated MK-801 binding in the NMDA channel. Four families of tetraamines are included in this set: norspermines, spermines, homospermines, and tetraazaoctadecanes. Calculations employing a SYBYL modeling program revealed that the distance between terminal nitrogens ranges between 12.62 and 19.61 A. The tetraamines are constructed such that within families cyclics and acyclics have similar lengths but different nitrogen pKa's and thus different protonation, or charge, states at physiological pH. The pKa values for all nitrogens of each molecule and its protonation state at physiological pH are described. The modifications at the terminal nitrogens include introduction of ethyl and beta,beta,beta-trifluoroethyl groups and incorporation into piperidinyl or pyridyl systems. The studies clearly indicate that polyamine length, charge, and terminal nitrogen substitution have a significant effect on how the tetraamine regulates MK-801 binding to the NMDA receptor. Thus a structure-activity basis set on which future design of MK-801 agonists and antagonists can be based is now available.

Animals↗
PubMed1996

U1-mediated exon definition interactions between AT-AC and GT-AG introns.

A minor class of metazoan introns has well-conserved splice sites with 5'-AU-AC-3' boundaries, compared to the 5'-GU-AG-3' boundaries and degenerate splice sites of conventional introns. Splicing of the AT-AC intron 2 of a sodium channel (SCN4A) precursor messenger RNA in vitro did not require inhibition of conventional splicing and required adenosine triphosphate, magnesium, and U12 small nuclear RNA (snRNA). When exon 3 was followed by the 5' splice site from the downstream conventional intron, splicing of intron 2 was greatly stimulated. This effect was U1 snRNA-dependent, unlike the basal AT-AC splicing reaction. Therefore, U1-mediated exon definition interactions can coordinate the activities of major and minor spliceosomes.

Adenosine Triphosphate↗
PubMed1996

Electrocatalytic reduction of nitric oxide at electrodes modified with electropolymerized films of [Cr(v-tpy)2]3+ and their application to cellular NO determinations.

Nitric oxide can be electrocatalytically reduced at electrodes modified with electropolymerized films of [Cr(v-tpy)2]3+. Upon further modification with a thin film of Nafion (to prevent interferences from anions, especially nitrite), these electrodes can be employed as NO sensors in solution with submicromolar detection limits and fast response. We have carried out preliminary studies of cellular NO release from Rhodobacter sphaeroides bacterial cells with excellent results.

Catalysis↗
PubMed1996

On-line microdialysis sample cleanup for electrospray ionization mass spectrometry of nucleic acid samples.

A major limitation of electrospray ionization mass spectrometry (ESI-MS) for oligonucleotide analysis arises due to sodium adduction, a problem that increases with molecular weight. Sodium adduction can preclude useful measurements when limited sample sizes prevent off-line cleanup. A novel and generally useful on-line microdialysis technique is described for the rapid (approximately 1-5 min) DNA sample cleanup for ESI-MS. Mass spectra of oligonucleotides of different size and sequence showing no significant sodium adduct peaks were obtained using the on-line microdialysis system with sodium chloride concentrations as high as 250 mM. Signal-to-noise ratios were also greatly enhanced compared to direct infusion of the original samples. By using ammonium acetate as the dialysis buffer, it was also found that the noncovalent association of double-stranded oligonucleotides could be preserved during the microdialysis process, allowing analysis by ESI-MS.

Base Sequence↗