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Biomedical subjects

M Liu

Publications and source records attributed to M Liu.

At least 523 records · Page 29Linked to original sources
PubMed1995

Specificity of lecithin:cholesterol acyltransferase and atherogenic risk: comparative studies on the plasma composition and in vitro synthesis of cholesteryl esters in 14 vertebrate species.

To determine whether the specificity of lecithin: cholesterol acyltransferase (LCAT) influences the susceptibility to atherosclerosis, we compared the composition and in vitro synthesis of cholesteryl ester (CE) in the plasmas of 14 vertebrate species with varying predisposition to atherosclerosis. The susceptible species (Group I) had significantly higher ratios of 16:0 CE/20:4 CE in their plasma than the resistant species (Group II). The in vitro formation of labeled CE species in native plasma from labeled cholesterol correlated highly with the mass composition, showing that the LCAT reaction is the predominant source of plasma CE in all the animal species examined. Isolated LCATs from Group I species also synthesized CE with higher ratios of 16:0/20:4 than LCATs from Group II when egg phosphatidylcholine (PC) was used as the acyl donor. In addition, the Group I LCATs exhibited lower specificity towards sn-2-20:4 and sn-2-22:6 PCs, and higher specificity towards sn-2-18:2 PC species than Group II LCATs. With 16:0-20:4 PC as the substrate, all Group I LCATs synthesized more 16:0 CE than 20:4 CE, whereas all Group II LCATs, with the exception of dog enzyme, synthesized predominantly 20:4 CE, showing that the two types of LCAT have different positional specificities towards this PC. These results suggest that there are two classes of LCAT in nature that differ from each other in their substrate and positional specificities, possibly because of differences in their active-site architectures. We propose that the presence of one type of LCAT, which cannot efficiently transfer certain long chain polyunsaturated acyl groups and which consequently synthesizes more saturated CE, may increase the risk of atherosclerosis.

Animals↗
PubMed1995

[Hypocrellin B-ethanolamine (HB-E) sensitized photodamage on rat mitochondria].

The Hypocrellin B-Ethanolamine (HB-E) sensitized photodamage on lipid peroxidation, sulfhydryl oxidation and ATPase inactivation of rat liver mitochondria was studied under illumination of 640 nm, The HB-E sensitized photodamage of lipid peroxidation is less than sulfhydryl photooxidation, when HB-E concentration is 50 mumol/L. To elucidate the mechanism of photodamage of HB-E, antioxidant: BHT, Vit E, oxygen radical quencher: L-His, beta-Cart, were investigated. The results showed that HB photodamage of mitochondria is not only by oxygen radical, but also by HB-E radical as well. From compared tests among HB, HA, Hp, MB and HB-E, we found that HB-E had higher ability to photodamage lipid peroxidation, sulfhydryl oxidation and tryptophan than other photosensitizers. The experiments showed that the superoxide generated may be by HB-E radical.

Adenosine Triphosphatases↗
PubMed1995

[Detection of neck lymph node metastasis in the patients with supraglottic cancer].

Histo-pathologic materials from 115 cases of supraglottic squamous cell carcinoma were studied by retroSpective analysis. Each set of laryngeal specimens was reviewed with attention to the following factors: 1. Site of the primary lesion. 2. Size of the primary lesion. 3. Histologic grade of the primary tumor. 4. Histologic pattern at the tumor periphery. 5. Clinical and pathological stage. The features would reliably assist the laryngologist in identifying the laryngeal cancer with high probability of lymph node metastasis, so they can be used as the data for arranging the operation or treatment of the neck.

Adult↗
PubMed1995

[Analysis of 1116 strains of pathogens isolated from infected burn wounds].

We report the analysis of 1,116 strains of pathogens isolated from infected burn wounds of 536 patients hospitalized from 1989 to 1991. From the 1,116 strains of pathogens, 39 species of aerobes and fungi were found, including 217 strains of staphylococcus aureus, 208 strains of Pseudomonas aeruginosa and 119 strains of Acinetobacter calcoaceticus. The positive rates of the above three bacteria were 19.4%, 18.6% and 10.6% respectively. Some opportunistic pathogens, such as bacillus cercus, aerococcus virdans and aspergillus etc. were also isolated from the burn wounds as well as the ward environments. The drug sensitivity of some of the common bacterial was determined.

Acinetobacter Infections↗
PubMed1995

[Percutanous transluminal coronary angioplasty for unstable angina].

Percutanous transluminal coronary angioplasty (PTCA) was performed in 190 patients with 250 diseased vessels and 278 lesions from Dec. 1987 to Feb. 1994. All the patients had unstable angina (UA). There were 52 (18.7%) type A lesions, 175 (62.9%) type B lesions and 51 (18.3%) type C lesions. Of the 190 patients undergoing PTCA, 134 (70.5%) patients had dilatation of a single vessel, 46 (24.2%) of two vessels and 10 (5.3%) of three or more vessels. In 121 patients with multivessel disease, 98 (81.0%) had incomplete revascularization of the ischemia-related vessel (the culprit vessel) and only 23 (19.0%) had complete vessel revascularization. Kissing balloon technique was used in six patients and autoperfusion balloon in five. There were four patients undergoing directional coronary atherectomy (DCA) and four intracoronary stent. The clinical (patient) success rate was 94.7% (180/190) and technical (vessel) success rate 95.2% (238/250). The average degree of vessel stenosis was 88.7% +/- 8.3% before PTCA and the residual tenosis was 17.9% +/- 9.2% after PTCA. Acute vascular complications occurred in 18 (6.5%) lesions. 15 were managed successfully, two developed Q wave myocardial infarct and one died. None needed emergency coronary bypass operation. PTCA was not successful in 10 patients. In 180 patients with successful PTCA, 165 (91.7%) were free from UA, 15 (8.3%) patients had symptoms improved and oxygen need reduced. During a six-month follow-up, 26 patients had chest pain again with confirmed restenosis, repeated PTCA was performed successfully.

Adult↗
PubMed1995

Morphometric evaluation on myocardial protection of cold crystalloid versus warm blood cardioplegia.

Twenty patients undergoing open-heart valve replacement were divided randomly into two groups in this study; intermittent perfusion of cold crystalloid (St. Thomas Hospital solution) with hypothermic cardiopulmonary bypass (CPB) (hypothermic group) and continuous administration of warm blood cardioplegia with normothermic CPB (normothermic group) respectively. Tissue samples were taken from the right atrium before weaning from CPB and from the right appendage 30 minutes after removal of the cross-clamp. The results of pathological study in these two groups were as follows: the structural alterations were most severe during the ischemic period in the hypothermic group. Damages of the myocardial mitochondria examined with transmission electron microscope were found more severe in the hypothermic group than in the normothermic group, and in the reperfusion period than in the ischemic period. Loss of integrity of the mitochondrial membrane could be noted during reperfusion in the hypothermic group. The surface to volume ratios of mitochondria of each period of the two groups were calculated by computerizing the microphotographs of the myocardium. It was shown that the average of the surface to volume ratios was smallest in the reperfusion period in the normothermic group. It seemed that the volumes of the mitochondria were larger in the warm group than in the cold one. Probably the results were due to more severe damages of the mitochondrial membranes in the hypothermic group, which led to the release of the contents out of the mitochondria while in the normothermic group, the sodium-pump was disordered and it made the mitochondria swell. Pathologically, blood cardioplegic perfusion with the use of normothermic CPB is a feasible method for myocardial protection in open-heart surgery.

Bicarbonates↗
PubMed1995

[Analysis of causes of accidental deaths in several districts of Sichuan province].

The causes of accidental deaths from 1981 to 1988, including drowning, traffic accident, poisonning, child asphyxia, hitting, electric shock, fire and explosion in two cities and six districts of Sichuan Province were analysed. The average mortality from accidental death was 35. 58/10(5). Drowning and traffic death stood first and constituted 65.55% of the accidental deaths. Drowning, traffic death, poisoning and hitting death were more frequent in the male (P < 0.05). The mortality from traffic accident in the city was higher than that in the countryside. The mortality from drowning, child asphyxia and hitting in the city was lower than that in the countryside (P < 0.05).

Accidents↗
PubMed1995

[Chemical components of decoction of radix Paeoniae and radix Glycyrrhizae].

Eleven compounds were isolated from the water extract of the decoction of Radix Paeoniae and Radix Glycyrrhizae, namely benzoic acid, formononetin, isoliguiritigenin, liquiritigenin, 4',7-dihydroxyflavone, formononetin-7-glucoside, liquiritin, gallic acid, paeoniflorin, isoliquiritin and glycyrrhizin acid.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1995

[Protective effects of ginsenoside Rb1 and Rg1 on cultured hippocampal neurons].

It has been well documented that ginsenoside Rb1 and Rg1 are important active principles of ginseng. In the present studies, Rb1 and Rg1 were found to prolong the duration of neuronal life and provided partial protection against the excitotoxic effect of glutamate in primary hippocampal cultures. Since excitotoxic neuronal injury of glutamate is considered to be caused by the increase of intracellular Ca2+ concentrations, the effects of Rb1 and Rg1 on [Ca2+]i elevated by glutamate were measured in cultured hippocampal cells using Fura-2/AM as a calcium indicator. The results showed that Rb1 and Rg1 could selectively inhibit the high level glutamate (500 mumol.L-1) induced increase of [Ca2+]i, suggesting that the neuroprotective activities of Rb1 and Rg1 were mediated by blocking calcium over-influx into neuronal cells.

Animals↗
PubMed1995

[Immunoregulatory effects of ginsenoside Rg1 in aged rats].

It has been well documented that the immune function declines with age in the human and animals. The possible causes for the decline are the inability of lymphocytes to proliferate in response to mitogenic stimulation and the decrease of IL-2 production. In the present studies, Rg1 was shown to selectively enhance the proliferation of lymphocytes and the production of IL-2 in aged rats. Using Northern blot and Western blot analyses, Rg1 was found to promote IL-2 gene expression which showed increase of IL-2 mRNA and IL-2 protein contents. Interestingly, under the same conditions, studies were carried out on the effect of Rg1 on the immune function of young adult rats, but no marked influence was observed. According to these results, it is reasonable to consider Rg1 an immunoregulator rather than a purely "immunopotentiating agent".

Adjuvants, Immunologic↗
PubMed1995

[Immunohistochemical study of 5-HT on gunshot wound of human skin].

Fourty antemortem and 30 postmortem gunshot wound samples of human skin were studied by immunohistochemical method. The 5-HT was seen mainly in wound edge, papillary layer, hypodermis and surrounding tissue of all antemortem gunshot wounds. The 5-HT was also discovered on the postmortem gunshot wounds which occurred within 8 minutes after death. The result showed that immunohistochemical staining of 5-HT be useful for diagnosing the antemortem gunshot wound. It also demonstrated that the mast cells of human do not contain 5-HT. We also studied the rate of mast cell degranulation of gunshot wounds of human skin by toluidine blue staining. The rate of mast cell degranulation of antemortem gunshot wounds increased (50%), and it was higher than that of postmortem gunshot wounds, suggesting that the rising of degranulation rate is a sign of antemortem injury.

Cell Degranulation↗
PubMed1994

Calcium-calmodulin modulation of the olfactory cyclic nucleotide-gated cation channel.

Although several ion channels have been reported to be directly modulated by calcium-calmodulin, they have not been conclusively shown to bind calmodulin, nor are the modulatory mechanisms understood. Study of the olfactory cyclic nucleotide-activated cation channel, which is modulated by calcium-calmodulin, indicates that calcium-calmodulin directly binds to a specific domain on the amino terminus of the channel. This binding reduces the effective affinity of the channel for cyclic nucleotides, apparently by acting on channel gating, which is tightly coupled to ligand binding. The data reveal a control mechanism that resembles those underlying the regulation of enzymes by calmodulin. The results also point to the amino-terminal part of the olfactory channel as an element for gating, which may have general significance in the operation of ion channels with similar overall structures.

Amino Acid Sequence↗
PubMed1994

Substrate and positional specificities of human and mouse lecithin-cholesterol acyltransferases. Studies with wild type recombinant and chimeric enzymes expressed in vitro.

Human lecithin-cholesterol acyltransferase (LCAT) preferentially attacks sn-1 position of 16:0-20:4 phosphatidylcholine (PC), producing more 16:0 cholesteryl ester (CE) than 20:4 CE. In contrast, rat and mouse LCATs produce mostly 20:4 CE from the same PC. To understand the structural basis for this difference in positional specificity, we studied the specificities of recombinant mouse and human LCATs and several chimeric constructs of the two. The rLCATs retained the substrate and positional specificities of the plasma enzymes when expressed in COS-1 cells. Human and mouse LCAT cDNAs were each cleaved into three fragments, recombined in various combinations, and the chimeric products were analyzed for their specificities. When the N-terminal, or (and) C-terminal segments of human LCAT were replaced by the corresponding mouse LCAT segments, the chimeric products exhibited the specificity of intact human enzyme. However, when the middle segment, containing the residues 130-306 was replaced by the corresponding mouse LCAT segment, the enzyme exhibited the specificity of mouse LCAT. Similarly, the mouse rLCAT exhibited the specificity of human enzyme when its central segment, but not its N-terminal or C-terminal segment was replaced by the corresponding segment from human LCAT. These results show that the substrate and positional specificities of LCAT are controlled by the central domain of LCAT protein, corresponding to the amino acid residues 130-306.

Amino Acid Sequence↗
PubMed1994

Role of sn-2 acyl group of phosphatidylcholine in determining the positional specificity of lecithin-cholesterol acyltransferase.

Although human plasma lecithin-cholesterol acyltransferase (LCAT) is believed to be specific for the sn-2 position of phosphatidylcholine (PC), our recent studies showed that it derives a significant percent of acyl groups from the sn-1 position of certain PC species. To understand the physicochemical basis for this altered positional specificity, we determined the effect of sn-2 acyl group of PC on the enzyme activity and utilization of 16:0 from the sn-1 position by purified human and rat LCATs. Positional isomers of PC containing 16:0 at sn-2 were better substrates for human LCAT than the corresponding sn-1-16:0 isomers, whereas the reverse was true for rat LCAT. The positional specificity of human LCAT varied greatly depending on the nature of the acyl group at sn-2. The sn-1 contribution from various sn-1-16:0-2-acyl PCs for cholesteryl ester (CE) synthesis was 1.0% from 16:0-16:0, 1.4% from 16:0-20:5, 7.3% from 16:0-18:1, 47.0% from 16:0-20:3, 49.9% from 16:0-20:4, 54.9% from 16:0-22:6, and 72.3% from 16:0-18:0. There was a linear relationship between the percentage of 16:0 CE formed (from sn-1 position) and the acyl chain length at sn-2 position (r = 0.94). Rat LCAT also transferred some 16:0 from sn-1 position of 16:0-22:6, 16:0-20:3, and 16:0-18:0 PCs, but not from the other natural PCs tested. The phospholipase A activity of both LCATs in the presence of 16:0-20:4 PC showed the same positional specificity as CE synthesis, indicating that the specificity is determined at the formation of acyl-enzyme intermediate. These results show that the positional specificity of LCAT is influenced by the structure of PC, especially the chain length of the sn-2 acyl group.

Acylation↗
PubMed1994

Functional transfer RNAs with modifications in the 3'-CCA end: differential effects on aminoacylation and polypeptide synthesis.

The trinucleotide CCA sequence is present at the 3' terminus of all mature tRNAs. Despite this high degree of conservation, we have been able to prepare in vitro transcripts of Escherichia coli tRNA(Val) with altered 3' termini that are readily aminoacylated and can function in polypeptide synthesis. Replacement of the 3'-terminal adenosine with either cytidine or uridine yields a tRNA(Val) variant that retains almost full aminoacylation activity, having specificity constants (Vmax/Km) 40-50% that of wild-type tRNA(Val). The tRNA(Val) variant with a 3'-terminal guanosine remains fully chargeable but is a poor substrate for valyl-tRNA synthetase, largely as the result of a decrease in the catalytic constant. End-group analysis revealed the absence of adenosine at the 3' end of the tRNA(Val) mutants and identified the nucleotide expected from the sequence of the DNA template as the predominant 3'-terminal residue; Val-cytidine was isolated from the aminoacylated C76 mutant. Val-tRNA(Val) with 3'-CCG is active in poly(U,G)-directed (Val, Phe) copolypeptide synthesis, whereas the tRNA(Val) mutants terminating in 3'-CCC and 3'-CCU, which are readily aminoacylated, are inactive. The differential effects of nucleotide substitution on aminoacylation and polypeptide synthesis suggest that the universally conserved 3'-CCA end of tRNAs is monitored at two or more steps in protein synthesis that have different nucleotide recognition specificities.

Base Sequence↗