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Biomedical subjects

L M Liu

Publications and source records attributed to L M Liu.

At least 19 recordsLinked to original sources
PubMed2006

Increased glycophorin A somatic cell variant frequency in arsenic-exposed patients of Guizhou, China.

Exposure to arsenic through domestic burning arsenic-containing coal causes various tumors in a population of Guizhou, China. The glycophorin A (GPA) assay is a human mutation assay detecting somatic variation in erythrocytes expressing the MN blood type, and was used to assess genotoxicity of arsenic-exposed patients. Peripheral blood was collected from 18 adult healthy subjects and 40 arsenic-exposed patients in heparin-treated tubes. Erythrocytes were isolated, fixed in formalin and immuno-labeled with fluorescent antibodies against GPA, followed by flow cytometry analysis. Arsenic exposure increased the variant frequency (expressed as the number of variant red cells per 10(6) erythrocytes): NN, 3.7 in healthy subjects versus 21.2 in arsenic-exposed patients; N phi, 12.6 versus 33.1; MM, 13.1 versus 110; and M phi, 5.2 versus 20.3. The total GPA variant frequency was increased about five-fold (34.7 in healthy subjects versus 185 in arsenosis patients). Furthermore, the variant frequency was significantly higher in skin tumor-bearing patients: NN, 19.4 in arsenic-exposed non-tumor patients versus 31.5 in tumor-bearing patients; N phi, 29.5 versus 54.5; MM, 102 versus 159; M phi, 15.9 versus 45.1. Total GPA variant frequency in arsenic-exposed patients bearing skin tumors was significantly increased compared to patients without skin tumors (167 versus 290). The relationship between arsenic exposure history and GPA variant frequency was less evident. These data demonstrate that arsenic exposure is associated with mutations at the GPA locus, an effect exaggerated in patients bearing arsenic-induced skin tumors. The variant frequency of GPA could be a useful biomarker for arsenic exposure and arsenic carcinogenesis.

Adult↗
PubMed2006

Identifying an O2 supply pathway in CO oxidation on Au/TiO2(110): a density functional theory study on the intrinsic role of water.

Au catalysis has been one of the hottest topics in chemistry in the last 10 years or so. How O2 is supplied and what role water plays in CO oxidation are the two challenging issues in the field at the moment. In this study, using density functional theory we show that these two issues are in fact related to each other. The following observations are revealed: (i) water that can dissociate readily into OH groups can facilitate O2 adsorption on TiO2; (ii) the effect of OH group on the O2 adsorption is surprisingly long-ranged; and (iii) O2 can also diffuse along the channel of Ti (5c) atoms on TiO2(110), and this may well be the rate-limiting step for the CO oxidation. We provide direct evidence that O2 is supplied by O2 adsorption on TiO2 in the presence of OH and can diffuse to the interface of Au/TiO2 to participate in CO oxidation. Furthermore, the physical origin of the water effects on Au catalysis has been identified by electronic structure analyses: There is a charge transfer from TiO2 in the presence of OH to O2, and the O2 adsorption energy depends linearly on the O2 charge. These results are of importance to understand water effects in general in heterogeneous catalysis.

Journal Article↗
PubMed2006

Increasing glycolytic flux in Torulopsis glabrata by redirecting ATP production from oxidative phosphorylation to substrate-level phosphorylation.

AIMS: This study aimed at further increasing the pyruvate productivity of a multi-vitamin auxotrophic yeast Torulopsis glabrata by redirecting ATP production from oxidative phosphorylation to substrate-level phosphorylation. METHODS AND RESULTS: We examined two strategies to decrease the activity of F0F1-ATPase. The strategies were to inhibit F0F1-ATPase activity by addition of oligomycin, or to disrupt F0F1-ATPase by screening neomycin-resistant mutant. The addition of 0.05 mmol l(-1) oligomycin to the culture broth of T. glabrata CCTCC M202019 resulted in a significantly decreased intracellular ATP level (35.7%) and a significantly increased glucose consumption rate (49.7%). A neomycin-resistant mutant N07 was screened and selected after nitrosoguanidine mutagenesis of the parent strain T. glabrata CCTCC M202019. Compared with the parent strain, the F0F1-ATPase activity of the mutant N07 decreased about 65%. As a consequence, intracellular ATP level of the mutant N07 decreased by 24%, which resulted in a decreased growth rate and growth yield. As expected, glucose consumption rate and pyruvate productivity of the mutant N07 increased by 34% and 42.9%, respectively. Consistently, the activities of key glycolytic enzymes of the mutant N07, including phosphofructokinase, pyruvate kinase and glyceraldehyde-3-phosphate dehydrogenase, increased by 63.7%, 28.8% and 14.4%, respectively. In addition, activities of the key enzymes involved in electron transfer chain of the mutant N07 also increased. CONCLUSIONS: Impaired oxidative phosphorylation in T. glabrata leads to a decreased intracellular ATP production, thereby increasing the glycolytic flux. SIGNIFICANCE AND IMPACT OF THE STUDY: The strategy of redirecting ATP production from oxidative phosphorylation to substrate-level phosphorylation provides an alternative approach to enhance the glycolytic flux in eukaryotic micro-organisms.

Adenosine Triphosphate↗
PubMed2001

Characterization of the gene EPAC2: structure, chromosomal localization, tissue expression, and identification of the liver-specific isoform.

The liver-specific protein cAMP-GEFII (also known as Epac2) belongs to a family of cyclic adenosine monophosphate (cAMP) binding proteins having guanine nucleotide exchange factor (GEF) activity (the cAMP-GEF family). Here we clone the gene EPAC2, encoding cAMP-GEFII, from a human liver cDNA library. Human EPAC2 has at least 31 exons and is mapped to human chromosome 2q31. Analyses by primer extension, reverse transcriptase-polymerase chain reaction, and in situ hybridization revealed the presence of three transcription start sites of liver-specific Epac2: two major sites located in exon 10 and a minor site in intron 9. The same translation start site is used in all three transcripts. Liver-specific cAMP-GEFII protein, which lacks the first cAMP-binding domain and the Dishevelled/Egl-10/Pleckstrin domain, was detected at 79 kDa by immunoblot analysis, confirming the presence of the short form of cAMP-GEFII in the liver. Liver-specific cAMP-GEFII also has GEF activity toward Rap1. These results demonstrate the presence of liver-specific cAMP-GEFII. Together with the previous finding that cAMP-GEFII is responsible for cAMP-dependent exocytosis in secretory cells, our study suggests that cAMP-GEFII may have a distinct role in liver.

Amino Acid Sequence↗
PubMed2001

Neonatal surgical emergencies.

Improvements in the diagnosis and treatment of congenital disorders have resulted in a change in surgical practice. Many conditions that formerly required corrective surgery immediately after birth are no longer surgical emergencies. Most babies with congenital anomalies that can be corrected by surgery are now stabilized and optimized before the procedure. This article focused on the more common conditions that require semi-elective or urgent surgery in the neonatal period. Salient features of each of these disorders were described. Factors unique to each of these conditions that can affect the anesthetic course of these children were discussed. Methods and techniques that may aid in the anesthetic management of these children were delineated.

Anesthesia↗
PubMed2001

[Use of intraoperative red blood cell salvage in the anterior stabile operation of spinal fracture].

OBJECTIVE: To observe the clinical results in the anterior stabile operation of spinal fracture using red blood salvage. METHODS: Nineteen cases with spinal fracture were performed the anterior decompress operation. Blood cell salvage were used during operation. Other 20 cases were also reviewed as control group, who were received the same operation without blood cell salvage. RESULTS: In the 19 cases, average volume of autologous transfusion was 536 ml. Only two cases had homologous transfusion requirements. In the control group, all cases needed homologous transfusion (averaged 947 ml). CONCLUSION: In the anterior decompress operation, the intraoperative blood salvage is highly effective in reducing transfusion and also improves the security of operation.

Adolescent↗
PubMed2001

[Intracellular potential changes in crucian carps Mauthner cells evoked by vagal sensory inputs].

In the present experiments, microelectrode recording technique was used to explore the electrophysiological properties of Mauthner cells (M-cells) with stimuli applied to the right vagus. Direct stimulation of the right vagus evoked short-latency, long-lasting, graded, and complex postsynaptic potentials (PSPs) on both Mauthner cell bodies in crucian carp, which are stimulus strength- and frequency- dependent. The evoked PSPs reduced the amplitudes of the antidromic action potentials. After intramuscular injection of strychnine, both amplitude and averaged duration of the PSPs increased, on which two or more action potentials were superimposed. The results suggest that the afferent pathways from vagus to M-cells are mediated by several neuron chains with different numbers of relayed synapses, and they may be excitatory and/or inhibitory in nature. Therefore vagus input would modulate the excitability of the M-cells.

Action Potentials↗
PubMed2001

[Hemorrhagic shock induces changes in large-conductance Ca(2+) dependent K+ channel activity in mesenteric arterial smooth muscle cells of rats].

The purpose of the present study was to detect changes in the activity of large-conductance Ca(2+)activated K(+) channel (BK(Ca)) during hemorrhagic shock (HS) in mesenteric arterial vascular smooth muscle cells using inside-out patches. The HS rat model was produced with withdrawing blood from the femoral artery. The results showed that the BK(Ca) activity was inhibited with decreased open probability (P(o)) and single-channel conductance. The decrease of P(o) resulted from an increase of the close time constant (tau(cs)) in the compensatory stage of HS, i.e.the term of hyperresponse of the muscle to norepinephrine (NE) (HS lasted for about 40 min). During the decompensation stage of HS, i.e. the period of hyporesponse to NE (HS developed for 3 h), the BK(Ca) activity was enhanced with the increase in single-channel conductance and P(o) which was a result of a decrease in tau(cs).

Animals↗
PubMed2000

[Effects of aprotinin on TNF-alpha levels after cardiopulmonary bypass].

OBJECTIVE: This study evaluates the anti-inflammatory activity of full-dose and pump-prime-only(low-dose) aprotinin by means of comparing tumor necrosis factor alpha(TNF-alpha) levels of both groups after CPB. METHODS: Twenty-nine adults with rheumatic heart disease were randomized into three groups: (1) full-dose aprotinin-treated group(Group A, n = 10); (2) pump-prime-only aprotinin-treated group(Group B, n = 10), and (3) control group(Group C, n = 9). Plasma concentrations of TNF-alpha were measured by enzyme-linked immunosorbent assay technique at baseline(before operation), and at 2, 24 hours after CPB termination. RESULTS: A significant(P < 0.05) increase of TNF-alpha occurred in all three groups at 2 and 24 hours after CPB termination when compared with the same group at baseline. In Group A, TNF-alpha level was significantly lower than that in group C(P < 0.05) at 24 hours after CPB, but not in group B(P > 0.05). CONCLUSIONS: Both CPB and operative stimulus induce the increase of cytokine TNF-alpha after CPB. Full-dose aprotinin has the anti-inflammatory effect by means of reducing TNF-alpha level after CPB. Low-dose aprotinin dose not reduce TNF-alpha level. So it no significant anti-inflammatory effect.

Adolescent↗
PubMed2000

Effects of MCI-154, a calcium sensitizer, on cardiac dysfunction in endotoxic shock in rabbits.

This study was designed to observe the effects of MCI-154, a calcium sensitizer, on cardiac dysfunction after endotoxic shock in rabbits. Ten hours after the rabbits were given injection of 1.0 mg/kg endotoxin (Escherichia coli, O111:B4) via marginal ear veins, 0.1 mg/kg MCI-154 was injected intravenously and then 50 mL/kg normal saline (NS) + 0.1 mg/kg MCI-154 was infused continuously at a rate of 0.7 mL/min. During this process, the parameters of cardiac function were measured. It was found that 10 h after the endotoxin injection, heart rate (HR) was increased significantly while the mean arterial blood pressure (MAP), left ventricular systolic pressure (LVSP), isovolumetric pressure (IP), myocardial contractility (MC), and the area of p-dp/dt(max) vector loop (Lo) all were markedly decreased. Treatment with 50 mL/kg NS alone had slight effects on these parameters. On the contrary, LVSP, IP, MC, and Lo all were increased significantly while HR was not obviously changed and left ventricular end-diastolic pressure (LVEDP) was reduced remarkably following MCI-154 administration in endotoxic shock rabbits. The parameters of myocardial contractility were improved nearly to the values in sham shock group and were markedly higher than that in NS alone-treated group. It can be concluded that MCI-154 can exert significant therapeutic effects on cardiac dysfunction after endotoxic shock, for it improves cardiac function, dilates peripheral blood vessels, and slightly affects HR.

Animals↗
PubMed2000

Effect of MCI-154, a calcium sensitizer, on calcium sensitivity of myocardial fibers in endotoxic shock rats.

This study was designed to investigate the effect of a calcium sensitizer on the Ca2+ sensitivity of myocardial fibers in endotoxic shock rats. Right ventricular papillary muscles from sham shock or endotoxic shock rats were skinned by incubation in saponin solution. Forces of the skinned muscles were recorded when they were activated sequentially by different pCa (-log[Ca2+]) activating solutions with or without positive inotropic agents. Tension-pCa relationship curve of skinned fibers delineated the affinity of troponin C(TnC) for Ca2+ and the medium value pCa50 (pCa required for producing 50% of maximal Ca2+-activated tension) was taken as the quantitative index of Ca2+ sensitivity of TNC. It was found that the maximal Ca2+ activated tension (Tmax) was lower, tension-pCa relationship curve was shifted rightward, and the pCa50 was reduced significantly in endotoxic shock group compared with that of sham shock group. Milrinone could not counteract the above abnormalities. However, when skinned right ventricular papillary fibers from endotoxic shock rats were dealt with activating solutions containing 1 x 10(-5) M MCI-154, the Tmax was significantly increased, the tension-pCa relationship curve was shifted leftward. The pCa50 in MCI-154 group was increased to an extent similar to that of sham shock group and markedly higher than the values of endotoxic shock group and milrinone group. Furthermore, such effects of MCI-154 were concentration dependent. It can been concluded that the sensitivity of cardiac contractile proteins to Ca2+ in endotoxic shock rats is decreased. MCI-154, a calcium sensitizer, can significantly reverse the decreased sensitivity and increase Tmax of myocardial muscles from endotoxic shock rats.

Animals↗
PubMed2000

Effects of MCI-154, a calcium sensitizer, on cardiac function in endotoxemic rabbits.

AIM: To observe the effects of MCI-154, a calcium sensitizer, on cardiac function after endotoxic shock. METHODS: The rabbits were intravenously injected with MCI-154 0.1 mg.kg-1 at 10 h after the administration of endotoxin 1.0 mg.kg-1, followed by a continuous infusion of normal saline (NS) 50 mL.kg-1 + MCI-154 0.1 mg.kg-1. During this process, the parameters of cardiac function were measured. RESULTS: Ten hours after the endotoxin injection, heart rate (HR) increased noticeably while the mean arterial blood pressure (MAP), left ventricular systolic pressure (LVSP), isovolumetric pressure (IP), myocardial contractility (MC), and the area of p-dp/dtmax vector loop (Lo) were all markedly decreased. Treatment with NS 50 mL.kg-1 alone had slight effects on these parameters. LVSP, IP, MC, and Lo were all markedly increased while HR did not obviously change and left ventricular end-diastolic pressure (LVEDP) was reduced markedly following MCI-154 administration in endotoxic shock rabbits. The parameters of MC were improved nearly to the same values as in sham shock group and were markedly higher than in NS treated group. CONCLUSION: MCI-154 exerts remarkable therapeutic effects on cardiac dysfunction after endotoxic shock.

Animals↗
PubMed2000

Effect of MCI-154, a calcium sensitizer, on calcium sensitivity of myocardial contractile system in endotoxemic rats.

AIM: To investigate the effect of MCI-154 on calcium sensitivity of myocardial contractile system in endotoxemic rats. METHODS: Skinned right ventricular papillary muscles from endotoxemic rats were prepared by saponin 500 mg/L. Forces of the skinned muscles were recorded when they were activated sequentially by different concentrations of Ca2+ with or without cardiotonic agents. The tension-pCa relationship and pCa50 of the skinned fibers were taken as the index of Ca2+ sensitivity of myocardial contractile system. RESULTS: The maximal Ca(2+)-activated tension (Tmax) was lower, and pCa50 was reduced in endotoxemia group as compared with those in sham control group. Milrinone 50 mumol/L could not counteract the above abnormalities. However, after MCI-154 10 mumol/L was added, the Tmax and pCa50 were increased to an extent similar to that of sham control group and significantly higher than those of endotoxemia group and endotoxemia + milrinone group. Furthermore, such effects of MCI-154 were concentration-dependent. CONCLUSION: The Ca2+ sensitivity of cardiac contractile system in endotoxemic rats is decreased. MCI-154 can reverse the decreased sensitivity and increase Tmax of myocardial muscles from endotoxemic rats.

Animals↗
PubMed1999

Modeling the UMLS using an OODB.

The Unified Medical Language System combines many well established authoritative medical informatics terminologies in one system. Such a resource is very valuable to the healthcare industry. However, the UMLS is very large and complex and poses serious comprehension problems for users and maintenance personnel. Furthermore, the sets of concepts of semantic types are not semantically uniform and thus are difficult to study. We describe a method to represent two components of the UMLS, the Metathesaurus (META) and the Semantic Network, as an OODB. The resulting UMLS OODB schema is deeper and more refined than the Semantic Network. It offers semantically uniform classes, which improves support for comprehension and navigation of META. The UMLS OODB also exposes problems in the semantic type classifications.

Classification↗
PubMed1999

[HLA-DRB1 typing by PCR-sequence specific primers for paternity determination].

HLA-DRB1 typing by PCR-SSP technique was first used for paternity testing. The analysis of 42 paternity cases shows that this identification method is simple, fast and reliable and has high exclusion probability of paternity (66.3%). This method can also be applied to the study of transplantation, HLA associated disease and anthropogenesis.

Forensic Medicine↗