Search PubMed⌕ Search

Biomedical subjects

H Yao

Publications and source records attributed to H Yao.

At least 55 records · Page 3Linked to original sources
PubMed2001

[YAG laser-induced reperfusion of photothrombotic middle cerebral artery occlusion in rats].

The laser-driven photochemical occlusion of middle cerebral artery(MCA) is much easier, and less traumatic than standard electrocautery or even clip methods, while the infarct size is fairly reproducible. This study aimed to establish the system for YAG laser-induced reperfusion of photothrombotic MCA occlusion. Male spontaneously hypertensive rats(5-7 months old, 350-450 g) were anesthetized with halothane, endotracheally intubated, and mechanically ventilated. The photosensitizing dye rose bengal(20 mg/kg body weight) was administered intravenously over 90 sec starting simultaneously with 3 min of krypton laser irradiation(568 nm, 20 mW). The irradiated middle cerebral artery was completely occluded by an intraluminal thrombus. A YAG laser operating at 355 nm(16 mW, 15 Hz) was focused with a cylindrical lens and positioned with a mirror onto the occluded distal MCA. This YAG laser irradiation for approximately 3 min caused reperfusion of the thrombosed distal MCA. We demonstrated a novel method of reperfusion in the photothrombotic MCA occlusion model. This reperfusion model should facilitate study of the therapeutic window for reversibility in thrombotic stroke.

Animals↗
PubMed2001

Computational fluid dynamics study of a protruded-hinge bileaflet mechanical heart valve.

BACKGROUND AND AIM OF THE STUDY: Following clinical experience with the Medtronic Parallel bileaflet mechanical heart valve, considerable interest has been shown in investigating fluid mechanics inside the hinge socket. Most of these studies involved hinges that are recessed into the valve housing, such as the St. Jude Medical (SJM), CarboMedics, Sorin and On-X bileaflet mechanical heart valves. The aim of this study was to investigate the flow fields of a protruded hinge under steady flow conditions, with the occluder in its fully open position. Computational fluid dynamics (CFD) simulation using the Fluent 4.4.7 commercial solver was applied in this investigation. This protruded hinge mechanism for pivoting the occluder is an in-house design from the Cardiovascular Dynamics Laboratory, Nanyang Technological University. METHODS: The Fluent 4.4.7 code was run on a Silicon Graphic Inc. computer (4-CPUx185 MHz) in the CFD simulation. A body-fitted coordinates (BFC) grid was generated to cover the entire valvular flow domain, including the interior of the hinge and leaflet. Clearance between the leaflet and pivot housing was 50-70 microm. In the vicinity of the protruded hinge, mesh cells were small compared with hinge dimensions. A power law distribution of grid points was applied to optimize the number of cells used to cluster the entire flow field. The overall computational flow domain of the valve channel, including the floating leaflet and immersed hinge, was approximately 170,000 cells in total. Inside the hinge socket, approximately 10,000 cells were generated. A comparative model with recessed hinge that resembled the SJM valve hinge design was modeled. Due to geometric difficulties, an unstructured grid scheme was applied. Great attention was focused within the hinge pocket, in particular to the clearance between the hinge pivot and leaflet. A total of 2 million cells was generated for the whole computational flow domain. RESULTS: Under steady flow conditions, with the leaflet fixed in an open position, the protruded hinge design yielded a pair of small vortices that formed behind the stoppers. A low-magnitude velocity was observed inside the hinge clearance. Vortices developed behind the protruded stopper. Migrating flow was noted beneath the leaflet clearance as a result of pressure difference across the leaflet. For the recessed hinge design, reverse flow dominated the inside of the hinge socket, and developed into a pair of vortices at high Reynolds number. CONCLUSION: The protruded hinge mechanism was designed to expose the overall hinge region to the mainstream flow for a positive washing effect. Flow in this protruded hinge design is, in general, found to be three-dimensional. Initial results under steady flow conditions showed low laminar and turbulent shear stress, while the hinge clearance was well washed.

Computer Simulation↗
PubMed2001

Erythrocyte membrane protein abnormalities in beta-thalassemia of the Li nationality in Hainan.

OBJECTIVE: To determine the composition of abnormal red cell membrane skeleton. METHODS: By sodium dodecyl sulphate polyacrylamide gel electrophoresis of ghostcorpuscles, we quantified the amount of protein by densitometric evaluation. RESULTS: The results showed that in beta-thalassemia, the amount of spectrin, 4.5 protein and globin significantly increased compared with the controls (26.05 +/- 1.46, 21.69 +/- 1.86; 22.87 +/- 5.61, 12.99 +/- 2.33; 15.23 +/- 3.31 and 4.97 +/- 2.73, respectively, P < 0.05). CONCLUSION: These data suggest that the erythrocyte membrane protein composition matched with globin in patients with beta-thalassemia of the racial Li minority are different from the normal control. These factors increase rigidity but decrease deformability of the beta-thalassemic red cell membrane, which may lead to hemolytic anemia.

China↗
PubMed2001

[Assembly and evaluation of tissue engineered human cellular alveolar bony implanting materials in vitro].

OBJECTIVE: To assembly human cellular alveolar bony implanting materials in vitro and evaluate their osteogenic activities. METHODS: Human alveolar bone cells were separated from alveolar bone around the third impacted teeth of 3 patients by enzyme digestion and cultured in alpha-MEM containing beta-glycerophosphate and Dexamethasone at 5% CO2, 37 degrees C for 21-28 days. Confirmed osteoblasts-like cells were then seeded onto 3 kinds of degradable biomaterials of polyglycolic acid scaffold, collagen sponge, and L-lactic acid/epsilon-caprolactone to form the cell-scaffold complexes. The 3 types of complexes were continued to culture for 21-28 days at the same conditions. The cell proliferation, morphological changes, ALPase activity and mineral nodule formation on scaffolds were measured and observed at 3 days intervals. RESULTS: The results indicated that the cultured human alveolar bone origin cells from 3 patients could successfully express the osteoblasts phenotype in single layered culturing after stimulated by beta-glycerophosphate and Dexamethasone. The cultured osteoblast-like cells seeded on PGAS matrix had the highest attachment, proliferative and osteogenic activities, suggesting a good bio-affinity between the human alveolar osteoblast-like cells and the PGAS matrix. The statistical analysis (ANOVA) showed that there were significant differences between PGAS- osteoblasts complex and CLGS or LACT complexes on osteogenic activities (P < 0.05). CONCLUSION: PGAS-osteoblast complex is worth to be further developed into a tissue-engineered cellular artificial bony implant for reconstructing the oral-maxillofacial bony defects.

Absorbable Implants↗
PubMed2001

[Research of ultra-structural pathological changes of nervous, endocrine and immune system in heroin addicts].

OBJECTIVE: To investigate ultrastructural pathological changes of Heroin-Addicts. METHODS: Heroin-Addicts' central nervous system, endocrine system, immune system and reproductive system in 4 cases are observed by using transmission electron microscope(TEM). RESULTS: The changes of central nervous system are mitochondrion swelling, crista fragmentation and disappear. Endoplasmic reticulum dilation, nervous fibres and cell organelles reduction; mitochondrion swelling, Partial crista fragmentation and endoplasmic reticulum dilation are also found in endocrine system; Lymphocytes reduction, cytoplasm ingredient reduction and dead lymphocytes increase in immune system; in reproductive system, spermatogenic cells and cell organelles are reduced in the male and follicle disappeared in the female. CONCLUSION: Ultra-structural pathological changes of heroin-addicts are presented acute, chronic oxygen deficiency degeneration and necrosis.

Central Nervous System↗
PubMed2001

[Analysis of olanzapine in human plasma with reversed-phase high performance liquid chromatography].

Olanzapine is a novel antipsychotic drug. Recently it has been applied to clinical research. For the determination of olanzapine in plasma a reversed-phase HPLC method has been established. An aqueous solution of 0.25% ascorbic acid was added into the plasma sample and kept at -20 degrees C. Olanzapine can be separated on a Zorbax ODS column with a mobile phase of 50 mmol/L sodium phosphate (pH 7.2)-methanol-acetonitrile(12:10:3, volume ratios) and detected at 270 nm. The flow rate was 1.0 mL/min. The linear range was 15 micrograms/L-1,200 micrograms/L, r = 0.9988. The limited concentration of detection was 3 micrograms/L. The average recovery was (97.02 +/- 3.11)%. The intra-day and inter-day coefficients of variation were 3.86% (n = 15) and 4.12% (n = 15) respectively. The method has been used to determine olanzapine concentration in patient's plasma. The data obtained show that the sensitivity and selectivity of this method are adequate for drug monitoring in clinical research.

Antipsychotic Agents↗
PubMed2000

Acetylation of adenovirus E1A regulates binding of the transcriptional corepressor CtBP.

Adenovirus E1A mediates its effects on cellular transformation and transcription by interacting with critical cellular proteins involved in cell growth and differentiation. The amino terminus of E1A binds to CBP/p300 and associated histone acetyltransferases such as P/CAF. The carboxyl terminus binds to the carboxyl-terminal binding protein (CtBP), which associates with histone deacetylases. We show that 12S E1A can be acetylated by p300 and P/CAF and map one of the acetylation sites to Lys-239. This Lys residue is adjacent to the consensus CtBP binding motif, PXDLS. Mutation of Lys-239 to Gln or Ala blocks CtBP binding in vitro and disrupts the E1A-CtBP interaction in vivo. Peptide competition assays demonstrated that the interaction of E1A with CtBP is also blocked by Lys-239 acetylation. Supporting a functional role for Lys-239 in CtBP binding, mutation of this residue to Ala decreases the ability of E1A to block cAMP-regulated enhancer (CRE)-binding protein (CREB)-stimulated gene expression. Finally, we demonstrate that Lys-239 is acetylated in cells by using an antibody directed against an acetyl-Lys-239 E1A peptide. CtBP interacts with a wide variety of other transcriptional repressors through the PXDLS motif, and, in many instances, this motif is followed by a Lys residue. We suggest that acetylation of this residue by histone acetyltransferases, and the consequent disruption of repressor complexes, might be a general mechanism for gene activation.

Acetylation↗
PubMed2000

Calcium and cAMP signals differentially regulate cAMP-responsive element-binding protein function via a Rap1-extracellular signal-regulated kinase pathway.

Two major intracellular signals that regulate neuronal function are calcium and cAMP. In many cases, the actions of these two second messengers involve long term changes in gene expression. One well studied target of both calcium and cAMP signaling is the transcription factor cAMP-responsive element-binding protein (CREB). Multiple signaling pathways have been shown to contribute to the regulation of CREB-dependent transcription, including both protein kinase A (PKA)- and mitogen-activated protein (MAP) kinase/extracellular signal-regulated kinase (ERK)-dependent kinase cascades. We have previously described a mechanism by which cAMP and calcium influx may stimulate ERKs in neuronal cells. This pathway involves the PKA-dependent activation of the Ras-related small G-protein, Rap1, and subsequent stimulation of the neuronal Raf isoform, B-Raf. In this study, we examined the contribution of the Rap1-ERK pathway to the control of gene transcription by calcium influx and cAMP. Using the PC12 cell model system, we found that both calcium influx and cAMP stimulated CREB-dependent transcription via a Rap1-ERK pathway, but this regulation occurred through distinct mechanisms. Calcium-mediated phosphorylation of CREB through the PKA-Rap1-ERK pathway. In contrast, cAMP phosphorylated CREB via PKA directly but required a Rap1-ERK pathway to activate a component downstream of CREB phosphorylation and CREB-binding protein recruitment. These data suggest that the Rap1/B-Raf signaling pathway may have an important role in the regulation of CREB-dependent gene expression.

3T3 Cells↗
PubMed2000

Synthesis and evaluation of hydroxylated polyamine analogues as antiproliferatives.

The synthesis of four hydroxylated polyamine analogues, (2R, 10R)-N(1),N(11)-diethyl-2,10-dihydroxynorspermine, (2S,10S)-N(1), N(11)-diethyl-2,10-dihydroxynorspermine, (3S,12S)-N(1), N(14)-diethyl-3,12-dihydroxyhomospermine, and (3R,12R)-N(1), N(14)-diethyl-3,12-dihydroxyhomospermine, is described along with their impact on the growth and polyamine metabolism of L1210 murine leukemia cells. Four different synthetic approaches are set forth, two each for the hydroxylated norspermines and for the hydroxylated homospermines. The key step in the assembly of the norspermines was the coupling of either N-[(2R)-2,3-epoxypropyl]-N-ethyl p-toluenesulfonamide or N-[(2S)-2,3-epoxypropyl]-N-ethyl trifluoromethanesulfonamide to N,N'-dibenzyl-1,3-diaminopropane. The key step with homospermines employed alkylation of putrescine with (3S)-N-(benzyloxycarbonyl)-N-ethyl-3,4-epoxybutylamine or of N, N'-bis(mesitylenesulfonyl)-1,4-butanediamine with (2R)-2-benzyloxy-4-[N-(mesitylenesulfonyl)ethylamino]-O-tosyl-1-++ +butan ol. All of the hydroxylated analogues were active against L1210 cells with 96-h IC(50) values of </=2 microM, and they also effectively reduced putrescine and spermidine, although the effect on spermine pools ranged from moderate to insignificant. Interestingly, the impact of the hydroxylated analogues on ornithine decarboxylase (ODC) was significantly less than that of unhydroxylated parent drug (e.g., N(1),N(11)-diethylnorspermine [DENSPM]) at 1 microM; however, S-adenosylmethionine decarboxylase (AdoMetDC) depletion was nearly identical to what was observed in cells treated with parent drug. The most notable difference between the parent and hydroxylated analogues was seen with spermidine/spermine N(1)-acetyltransferase (SSAT) upregulation in the DENSPM series. The hydroxylated analogues, especially (R, R)-(HO)(2)DENSPM, were much less effective at upregulation than the parent DENSPM. Finally, a comparison of the toxicity of (R, R)-(HO)(2)DENSPM with that of DENSPM at subchronic doses revealed that the neurological effects seen with DENSPM were now absent.

Animals↗
PubMed2000

Microbial Biomass and Community Structure in a Sequence of Soils with Increasing Fertility and Changing Land Use.

The microbial biomass and community structure of eight Chinese red soils with different fertility and land use history was investigated. Two community based microbiological measurements, namely, community level physiological profiling (CLPP) using Biolog sole C source utilization tests and phospholipid fatty acid (PLFA) profiles, were used to investigate the microbial ecology of these soils and to determine how land use alters microbial community structure. Microbial biomass-C and total PLFAs were closely correlated to organic carbon and total nitrogen, indicating that these soil microbial measures are potentially good indices of soil fertility in these highly weathered soils. Metabolic quotients and C source utilization were not correlated with organic carbon or microbial biomass. Multivariate analysis of sole carbon source utilization patterns and PLFAs demonstrated that land use history and plant cover type had a significant impact on microbial community structure. PLFAs showed these differences more than CLPP methods. Consequently, PLFA analysis was a better method for assessing broad-spectrum community differences and at the same time attempting to correlate changes with soil fertility. Soils from tea orchards were particularly distinctive in their CLPP. A modified CLPP method, using absorbance readings at 405 nm and different culture media at pH values of 4.7 and 7.0, showed that the discrimination obtained can be influenced by the culture conditions. This method was used to show that the distinctive microbial community structure in tea orchard soils was not, however, due to differences in pH alone.

Journal Article↗
PubMed2000

Effect of optical purity on the critical heat capacity at the smectic-A-(chiral)-smectic-C transition in an antiferroelectric liquid crystal

High resolution ac calorimetric measurements have been carried out near the smectic-A-chiral-smectic-C phase transition in the antiferroelectric liquid crystal 4-(1-methylheptyloxycarbonyl)phenyl 4(')-octyloxybiphenyl-4-carboxylate (MHPOBC). Data on samples with different optical purities have been analyzed in detail using a renormalization-group expression with corrections-to-scaling terms. The chiral-smectic-C(alpha)-chiral-smectic-C phase transition is first order, while the smectic-A-chiral-smectic-C(alpha) phase transition is second order. A direct smectic-A-chiral-smectic-C phase transition, which occurs in near-racemic mixtures, was found to be quasitricritical and weakly first order. This implies that the smectic-A-smectic-C transition in the racemate locates at a special point where four critical lines intersect.

Journal Article↗
PubMed2000

Effect of extracellular HCO(3)(-) on Na(+) channel characteristics in hippocampal CA1 neurons.

The effect of HCO(3)(-)/CO(2) on membrane properties of isolated hippocampal CA1 neurons was studied with the use of the whole cell configuration of the patch-clamp technique. Neurons were acutely dissociated from 21- to 30-day-old mice. In the current-clamp mode, HCO(3)(-)/CO(2) significantly hyperpolarized CA1 neurons by more than 10 mV and decreased their input resistance. In addition, the overall excitability of these neurons was lower in the presence of HCO(3)(-)/CO(2) than in HEPES. Spontaneous and evoked action potential firing frequency was lower in the presence of HCO(3)(-)/CO(2) than in its absence. In the voltage-clamp mode, both activation and steady-state inactivation of a fast Na(+) current were shifted in the hyperpolarized direction in such a way that the window currents were smaller in HCO(3)(-)/CO(2) than in HEPES. Recovery from inactivation and deactivation from the open state of the fast Na(+) current was slower in HCO(3)(-)/CO(2) than in HEPES. We conclude that HCO(3)(-)/CO(2) decreases the intrinsic excitability of CA1 neurons by altering not only the passive properties of the neuronal membranes but also by changing several characteristics of the fast Na(+) current, including activation and inactivation kinetics as well as the recovery from inactivation and deactivation.

Action Potentials↗
PubMed2000

Ovariectomy exacerbates and estrogen replacement attenuates photothrombotic focal ischemic brain injury in rats.

BACKGROUND AND PURPOSE: We previously reported the infarct volumes in female spontaneously hypertensive rats (SHR) to be significantly smaller than those in male SHR. The purpose of the present study was to determine whether estrogen is responsible for the sex difference in ischemic vulnerability in SHR. METHODS: In experiment 1, 1 week (short-term) or 4 weeks (long-term) after the ovariectomy (OVX), female SHR (5 months old) were randomly subjected to photothrombotic occlusion of the middle cerebral artery, and the infarct volumes were determined. In experiment 2, the rats were randomly assigned to 3 groups (ie, the sham-ovariectomized, ovariectomized, and estrogen replacement groups). In the replacement group, estradiol valerate (200 microgram/kg) was subcutaneously injected once a week after the OVX. Four weeks after the OVX or sham-OVX, all rats were subjected to middle cerebral artery occlusion. Changes in regional cerebral blood flow were determined by laser-Doppler flowmetry. RESULTS: In experiment 1, the infarct volume produced 1 week after the OVX was not different from that of the sham-ovariectomized group. In contrast, the infarct volume produced 4 weeks after the OVX was significantly larger than that of the sham-ovariectomized group (82.4+/-11.6 versus 54.5+/-16.0 mm(3), P=0.0058). In experiment 2, estradiol replacement after the OVX was observed to attenuate the infarct volume compared with the ovariectomized group (55.6+/-18.8 versus 78.5+/-21.0 mm(3), P=0.0321). The degrees of regional cerebral blood flow reduction did not differ among the sham-ovariectomized, ovariectomized, and estrogen replacement groups. CONCLUSIONS: Chronic estrogen depletion was thus found to increase the infarct size, which was attenuated by estradiol replacement. These findings indicate that estrogen contributes to the sex difference in ischemic vulnerability and that endogenous estrogen also has a neuroprotective effect against ischemic brain damage.

Animals↗
PubMed2000

Deep white matter lesions on MRI, and not silent brain infarcts are related to headache and dizziness of non-specific cause in non-stroke Japanese subjects.

OBJECTIVE: Silent or asymptomatic cerebrovascular disease is believed to be an important risk factor for symptomatic stroke and vascular dementia. Although non-specific complaints such as mild to moderate headache and/or dizziness may also be caused by silent stroke, which remains a topic of controversy. METHODS: To investigate the relationship between silent brain infarcts and non-specific complaints, we assessed findings on magnetic resonance images using a common protocol in the following three groups of subjects; Group 1:78 subjects with non-specific complaints, Group 2:47 subjects with vascular risk factors, and Group 3:75 normal subjects without any subjective complaints or vascular risk factors. In addition to silent stroke, deep white matter lesions on MRI were also evaluated. All subjects were recruited from 12 institutes of the study group located at various parts of Japan. RESULTS: Silent brain infarcts were demonstrated in 44%, 43%, and 20% of subjects in Groups 1, 2, and 3, respectively. In Group 1, the average number of infarcts per individual who had silent brain infarction was 1.8, which was significantly fewer than 3.8 in Group 2 or 3.5 in Group 3 (p<0.0167). White matter lesions were found in 68%, 49%, and 11% in Groups 1, 2, and 3, respectively, indicating that non-specific complaints are more closely related to deep white matter lesions than to silent infarct lesions. Such white matter lesions were found more frequently in subjects with depressive state than in non-depressed subjects (67% vs. 39%, p=0.0155). CONCLUSION: The present results suggest that deep white matter lesions, rather than silent brain infarcts, appear to be important in producing headache and/or dizziness of non-specific cause and also to be related to the depressive state.

Aged↗
PubMed2000

[Necessity of permanent anticoagulant therapy for isolated mitral valve replacement with bioprosthetic heart valve to prevent the postoperative thromboembolic complications].

One hundred fifty four patients underwent isolated mitral valve replacement with bioprosthetic heart valve at Hyogo Medical College Hospital from November 1973 to December 1998. A porcine bioprosthetic valve was replaced in 82 patients (Hancock 43, Carpentier-Edwards 26, Hancock II 13) and pericardial bioprosthetic valve in 72 patients (Ionescue-Shiley 39, Carpentier-Edwards 33) with a mean follow-up of 1,410 patients-years. Their thromboembolism rates were also analyzed in linear and actuarial term over the 15-year period. The incidence of thromboembolism rate was 2.5%/pt.yr. Thromboembolic free rates for patients with anticoagulant therapy were significantly decreased for patients without therapy. Thromboembolic free rates for patients with atrial fibliration were also were significantly decreased for patients with sinus rhythm because the patients with sinus rhythm were not on anticoagulant therapy. In conclusion, it is necessary for the all patients to be on anticoagulant therapy after mitral valve replacement with bioprosthetic valves, even though patients with sinus rhythm.

Adult↗
PubMed2000

Gastric rupture caused by acute gastric distention in non-neonatal children: clinical analysis of 3 cases.

OBJECTIVE: To study gastric rupture, a progressive, rapid and high mortality condition, caused by acute gastric distention (GRAGD) and its appropriate diagnosis and treatment. METHODS: The etiology, pathology, clinical manifestations and experiences in 3 children with GRAGD were reviewed. RESULTS: Case 1: After diagnosing GRAGD and stabilizing her shock with massive fluid replacement, gastrostomy was performed. Her postoperative course was uneventful because of fasting, suction, fluid infusion, correction of acidosis and supporting nutrition. Case 2: After diagnosing gastric distention which subsided with conservative therapy for 9 days, she suddenly had gastric rupture when she had not eaten for 6 days. She died of shock and had no chance for surgery. Case 3: The patient had sudden abdominal pain, distention and vomiting with severe shock for 4 days. Emergency surgery found gastric rupture and the method was the same as Case 1. The patient survived but has brain impairment. Case 1 and 3 showed multifocal transmural necrosis. CONCLUSIONS: Symptoms like overeating, bulimia, changes in kind of food, X-ray showing large distended stomach and massive pneumoperitoneum were seen after gastric rupture and can help to diagnose this condition. Clinical course of gastric distention with toxic shock progresses rapidly, however subsequent gastric rupture exacerbates the shock and makes the treatment difficult treatment. It is extremely important that a laparotomy be performed at once after stabilizing shock with massive fluid replacement. Postoperative nutritional support and fluid replacement will increase survival. It is very important that when gastric distention disappears after conservative therapy, the doctor should assess carefully whether the gastric wall recovery is under way by using effective methods of examination.

Abdominal Pain↗