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Biomedical subjects

M Liu

Publications and source records attributed to M Liu.

At least 559 records · Page 31Linked to original sources
PubMed1994

Oxygenation of human tumor xenografts in nude mice by a perfluorochemical emulsion and carbogen breathing.

Human solid tumors (prostate carcinomas PC-3 and DU-145, breast carcinoma MX-1, cervical carcinoma ME-180, small cell lung carcinoma SW2, and glioblastoma T98G) were grown as xenografts in nude mice. Using the Eppendorf pO2 histograph microelectrode system, the oxygen profiles of the tumors were determined while the animals breathed air or carbogen (95% O2/5% CO2), and after administration of the perfluorochemical emulsion Oxygent-CA (8 ml/kg) under air breathing and carbogen breathing conditions. Under normal air breathing with or without Oxygent-CA administration the mean oxygen tensions were between 4.9 and 9.3 mmHg and each tumor had severely hypoxic regions where the pO2 was less than 5 mmHg. The severely hypoxic regions comprised 41-71% of the oxygen tension measurements under normal air breathing conditions. Carbogen breathing alone increased the mean oxygen tensions to 10.9-23.9 mmHg. Administration of Oxygent-CA and carbogen breathing increased the mean oxygen tensions over the levels of carbogen breathing alone to varying degrees. The highest mean oxygen tensions were 40.8 mmHg in the T98G glioblastoma and 24.5 mmHg in the ME-180 cervical carcinoma. Investigation of the use of Oxygent-CA/carbogen to increase the oxygenation of clinical tumors is warranted.

Administration, Inhalation↗
PubMed1994

Effects of dietary supplementation on the function of alveolar macrophages of silicosis rats, on the blastogenic response of lymphocytes and on the peroxidase activity in blood of silicosis patients.

We studied the effects of a nutrient supplemented diet on the function of alveolar macrophages of silicosis rats and on the blastogenic response of lymphocytes, glutathione peroxidase (GSH-PX) activity, and lipid peroxidase (LPO) activity in the blood of silicosis patients. The results showed that a nutrient supplemented diet increased the phagocytosis rate (p < 0.01) and index (p < 0.05) of alveolar macrophages of silicosis rats. A nutrient supplemented diet also enhanced significantly the GSH-PX activity (p < 0.001) and the blastogenic response of lymphocytes (p < 0.01), and decreased substantially the LPO content (p < 0.05) in the blood of silicosis patients. We conclude that a nutrient supplemented diet may play an important role in antilipid peroxidation, decreased free radical reaction, stabilizing cell membrane, delaying lung fibrosis, and enhancing immune functions of the body.

Animals↗
PubMed1994

[Immunohistochemical study on fibrin in brain traumas].

The fibrin formation in brain traumas was studied by immunohistochemical method. Eleven cases of brain trauma were examined. The fibrin was demonstrated not only in the areas of brain contusion and the neuronal cytoplasm of hypothalamus, thalamus, brainstem, and cerebellum, but also on the membrane of endothelial cells and red blood cells within some capillaries. The fibrin was also found around capillaries and the areas far from the brain trauma. It was suggested that injuries to the brain occurred not only in the local areas of the brain subjected to the violence, but also in the areas far from the local injury. It meant that the brain injuries were not local, but diffuse. The fibrin observed in the neuronal cytoplasm, and on the membrane of endothelial cells and red blood cells within some capillaries was a sign of ante mortem brain traumas. The combined HE staining and immunohistochemical staining of the fibrin is useful in the demonstration of simple brainstem traumas.

Brain Chemistry↗
PubMed1994

[Practical value of IgG index and IgG synthesis rate in multiple sclerosis].

IgG index and IgG synthesis rate were determined in 40 patients with multiple sclerosis (MS) (including 21 patients treated with corticosteroid), 20 patients with other neurological diseases (OND) and 22 normal controls, by Beckman Immunochemistry system II made in USA. The practical value of IgG index and IgG synthesis rate were evaluated by means of the method of clinical epidemiology. The results showed that in the diagnosis of MS the sensitivity, specificity and positive result likelihood ratio (PRLR) of IgG index were 63%, 65% and 1.80, respectively; those of IgG synthesis rate were 50%, 65% and 1.43, respectively. In the further observation, however, it was found that the sensitivity and PRLR were 84% and 2.4 in IgG index, 79% and 2.26 in IgG synthesis rate, after the influence of corticosteroid was excluded. In addition, in judging whether there was organic damage in central nervous system, the specificities and PRLRs of IgG index and IgG synthesis rate were 100% and infinitely great, respectively. The above results are discussed in this article.

Adolescent↗
PubMed1994

[Application of multilocus enzyme electrophoresis in studies of taxonomy and population genetics of S. typhi in Xinjiang].

Multilocus enzyme electrophoresis (MEE) was employed to study the genotype taxon and population genetics of 154 isolates of S. typhi from Xinjiang in recent 11 years. Seven kinds of enzymes were examined and determined. One hundred and fifty-four strains of S. typhi were classified into 69 electroretic types (ETs) and 10 clones (CLa-CLj). Among those 154 strains 80 epidemic isolates belonged to 21 ETs and 3 clones (CLe, f, j). ET17, 20, 21, 24, 26, 27 were the main ETs (61.30%), and CLf was the dominant clone (95.00%). Seventy-four non-epidemic isolates belonged to 48 ETs and 9 clones (CLa, b, c, d, f, g, h, i, j), no obvious dominant ET was found in them, and the main clone CLh accounted for 43.30%. It demonstrated that both outbreak and sporadic epidemics could be caused by many strains of ETs and clones, but the distribution of the former ETs was more concentrated and the preponderance of clones was more obvious. The analyses on structure of population genetics indicated that all of 7 enzymes were polymorphic. Genetic diversity among the enzyme loci was quite high, with an average of 0.35 per locus (H). The average number of alleles per locus (h) was 6.14. There was no significant difference in h or H between the isolates of different sources (P > 0.05). It was clear that S. typhi of different sources in Xinjiang were originated from the same population. The results also showed that there was a dominant allele in every enzyme locus. Natural selection was the main role in the evolution of S. typhi.

Alleles↗
PubMed1993

Role of sphingomyelin in the regulation of cholesterol esterification in the plasma lipoproteins. Inhibition of lecithin-cholesterol acyltransferase reaction.

In order to determine whether sphingomyelin (SPH) affects the rate of cholesterol esterification by plasma lecithin-cholesterol acyltransferase (LCAT), we studied the effects of its incorporation in to defined proteoliposome substrates containing phosphatidyl choline (PC), unesterified cholesterol, and apoprotein A-I, on the activity of purified LCAT. Cholesterol esterification was inhibited by up to 90% in the presence of SPH, and this inhibition was reversed by treatment with bacterial sphingomyelinase. The inhibition could be overcome by increasing the concentration of PC, but not unesterified cholesterol or apoprotein A-I, in the substrate. The effect of SPH was not related to the alterations in the size of the substrate particle and was not dependent on the type of acyl donor or apoprotein activator employed. The lysolecithin acyltransferase and phospholipase reactions carried out by LCAT were also inhibited by SPH. Kinetic studies suggested that: 1) LCAT binds better to substrate vesicles which contain SPH; 2) SPH competes with PC in binding to the active site of the enzyme; and 3) SPH is a more powerful competitive inhibitor than a diether analog of PC. The ability of various lipoproteins to act as substrates for purified LCAT varied inversely with the SPH/PC ratio. Treatment of the lipoproteins with sphingomyelinase activated the LCAT reaction, the percent activation being directly proportional to the SPH concentration in the native lipoprotein. Enrichment of high density lipoproteins with SPH inhibited cholesterol esterification in them by 50%, and this inhibition could be reversed by the degradation of SPH. These results show that SPH is a physiological inhibitor of cholesterol esterification in the plasma, by virtue of its competition with PC, the acyl donor for the reaction.

Apolipoprotein A-I↗
PubMed1993

Activation of plasma lysolecithin acyltransferase reaction by apolipoproteins A-I, C-I and E.

The lysolecithin acyltransferase (LAT) activity of lecithin-cholesterol acyltransferase (LCAT) converts lysophosphatidylcholine (lyso PC) to PC, and requires low-density lipoproteins (LDL). To determine whether LDL can be replaced by defined substrates, we tested proteoliposomes containing egg PC, labeled lyso PC and apoprotein (apo) A-I at molar ratios of 250:12.5:0.8, as substrate for purified enzyme. A significant percent of lyso PC in this substrate was acylated to PC, indicating that apo A-I can substitute for apo B in LAT reaction, and that PC is the acyl donor in the reaction. Apo C-I and apo E were, respectively, 70% and 40% as effective as apo A-I. When both lyso PC and free cholesterol (FC) were incorporated into the same proteoliposome, they competed with each other for the acyl groups, with 72% of the total acylation being directed to FC and 28% to lyso PC, at equimolar concentrations. With the native lipoproteins, the esterification of lyso PC was dominant in LDL, whereas FC esterification was dominant in high-density lipoproteins (HDL). Albumin inhibited LAT and activated LCAT in both lipoproteins, but its effects were more pronounced in HDL. These results indicate that the esterification of lyso PC and FC involve the same mechanism, and that the relative predominance of LAT on LDL is due to higher affinity of lyso PC to LDL, compared to HDL.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1993

Coupling of cellular energy state and ion homeostasis during recovery following brain ischemia.

The present experiments were undertaken to explore the relationship between recovery of cerebral energy state following transient ischemia, and resumption of Na+/K+ transport, as this is reflected in changes in extracellular K+ concentration ([K+]c). Cerebral energy state was evaluated by measurements of cerebral cortical concentrations of phosphocreatine (PCr), ATP, ADP, and AMP at the end of 15 min of severe, incomplete ischemia, as well as after 2 and 5 min of recirculation. Derivation of intracellular pH (pHi) allowed calculation of 'free' ADP (ADPf) and AMP (AMPf) concentrations. Changes in [K+]e were measured by an ion-sensitive microelectrode. The results showed that tissue ATP concentration, which was close to zero after 15 min of ischemia, rose to 30% of control after 2 min, and to 60% of control after 5 min of recirculation. However, since the adenine nucleotide pool was reduced by the ischemia the latter value represents extensive or complete phosphorylation of that pool, as reflected in a normalized ATP/ADPf ratio. During recirculation, the concentration of pyruvate rose, but the lactate content remained unchanged, suggesting that the substrate for oxidative metabolism was exogenous glucose. Resumption of Na+/K+ transport, as reflected in the [K+]e began after 2-3 min, and a normal [K+]e was attained within 5 min. The results demonstrate that transport of Na+ and K+ is resumed at tissue ATP concentrations which are only 30-40% of control. It is discussed whether this reflects relatively extensive rephosphorylation of the remaining adenine nucleotide pool, or if compartmentation of adenine nucleotides exists during recirculation.

Adenosine Diphosphate↗
PubMed1993

Physical mapping of buzura suppressaria nuclear polyhedrosis virus genome.

A physical map of the genome of buzura suppressaria singly-enveloped nuclear polyhedrosis virus (BsSNPV) was determined using six restriction endonucleases (RE), singly or in pairs, and Southern hybridizations of cloned or gel-purified DNA fragments. The maps of the genomes of BsSNPV and autographa californica multiply-enveloped nuclear polyhedrosis virus (AcMNPV) were different.

Animals↗
PubMed1993

Muscle damage progression in Duchenne muscular dystrophy evaluated by a new quantitative computed tomography method.

The progression of muscle damage was studied in the lower extremity and trunk muscles of patients with Duchenne muscular dystrophy (DMD) with a new quantitative computed tomography (CT) method. The degree of muscle fiber loss and fat tissue replacement was quantified using the indices of percent cross-sectional area (%CSA) of muscle and fat, or the percentages of the area having the CT numbers of normal muscle and fat. A cross-sectional study in 71 patients showed that as the disability stage progressed, both CT number and %CSA of muscle decreased while %CSA of fat increased. The rate of progression was different for each muscle, and the order of involvement was clarified. The CT findings were also significantly correlated with muscle strength, indicating validity of our method. Our findings of the natural course of muscle involvement would be useful in providing appropriate rehabilitative care as well as assessing the efficacy of therapeutic interventions.

Adolescent↗
PubMed1993

Excision products of TCR V alpha recombination contain in-frame rearrangements: evidence for continued V(D)J recombination in TCR+ thymocytes.

Cortical thymocytes that express a TCR on their surface continue to express mRNA for the recombination activating genes RAG-1 and RAG-2. As the expression of these genes appears to be necessary and sufficient for V(D)J recombination to occur, this finding suggests that productive TCR gene rearrangement may not by itself terminate TCR recombination. To further study this question, we have utilized a polymerase chain reaction-based strategy to isolate and sequence excision products of secondary TCR alpha gene rearrangement events. Our data shows that TCR alpha excision products from TCR+ thymocytes contain in-frame V-J joints and thus support the concept that V(D)J recombinatorial activity may continue even in thymocytes which have undergone productive TCR gene rearrangement.

Base Sequence↗
PubMed1993

Restoration of T-cell function in HIV infection by reduction of intracellular cAMP levels with adenosine analogues.

OBJECTIVE AND DESIGN: The impaired function of T cells is characteristic of HIV infection. It contributes to disease pathogenesis and is associated with disease prognosis. Our aim was to describe a biochemical basis for this impairment and a pharmacological way of restoring function. METHODS: Measurement of intracellular cAMP, protein kinase A (PKA) activity and proliferative capacity of T cells to recall antigens. RESULTS: HIV-seropositive individuals without AIDS showed significant increases in intracellular cAMP levels and PKA activity (inhibitors of lymphocyte function). The proliferative capacity of T cells to recall antigens correlated inversely with initial cAMP levels: poor proliferation was associated with high cAMP level in HIV infection. Moreover, drugs that reduced intracellular cAMP levels led to significant restoration of specific T-cell proliferation and cytotoxicity. CONCLUSIONS: Our findings indicate that high intracellular cAMP concentrations contribute to pathogenesis of T-cell anergy in HIV infection and that drugs that decrease intracellular cAMP levels may be beneficial in the treatment of AIDS.

Adenosine↗
PubMed1993

Prospective comparison of diagnostic peritoneal lavage, computed tomographic scanning, and ultrasonography for the diagnosis of blunt abdominal trauma.

From January through December 1990, a prospective study comparing the accuracy of diagnostic peritoneal lavage (DPL), abdominal computed tomographic (CT) scanning, and abdominal ultrasonographic (US) scanning was carried out. Patients with stable vital signs following their initial resuscitation coupled with equivocal physical examination findings received both CT and US scanning. A DPL was then done. If any of these three examinations produced positive findings, a laparotomy was done and the surgical findings were compared with the results of the diagnostic studies. Fifty-five patients were studied (44 men, 11 women), with a mean age of 43 years and a mean ISS of 18.5 +/- 10.5. The sensitivity, specificity, and accuracy were 100%, 84.2%, and 94.5% for DPL, 97.2%, 94.7%, and 96.4% for CT scanning, and 91.7%, 94.7%, and 92.7% for US scanning. Problems do exist in identifying isolated small intestinal perforations with ultrasonography. Since more and more trauma centers are using ultrasonography in the emergency department as a screening method in the management of patients with blunt abdominal trauma, it is important to avoid overestimating its capability. Frequent re-evaluation of the patient's condition, repeat ultrasonographic scans, diagnostic peritoneal lavage, and CT scanning are complementary and important in the diagnosis of blunt abdominal trauma.

Abdominal Injuries↗