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Biomedical subjects

M Liu

Publications and source records attributed to M Liu.

At least 487 records · Page 27Linked to original sources
PubMed1996

Pulmonary surfactant given prophylactically alleviates an asthma attack in guinea-pigs.

BACKGROUND: Previous studies have indicated that the increased airway resistance that develops in asthma may partly be due to a surfactant dysfunction. If so, it might be possible to alleviate the acute signs following an allergen challenge by prophylactically instilling into the airways a well functioning pulmonary surfactant. OBJECTIVE: The study was planned and enacted to test the above hypothesis. METHODS: The lung function (airway resistance, tidal volume, minute ventilation, and dynamic compliance) of 22 immunized guinea-pigs was studied for 30 min following a challenge. Ten of the animals had received a tracheal instillation of 0.5 mL calf lung surfactant extract (CLSE, 35 mg/mL) prior to the challenge. RESULTS: The animals receiving the dose of 17.5 mg surfactant were less affected by the challenge than were the controls. Only one of them died following the challenge, whereas four of the 12 controls succumbed. Lung function was significantly less affected among the nine surviving animals treated with surfactant prior to the challenge than among the eight surviving controls (P < 0.01) and also their blood gases (pCO2 and pO2) were less influenced (P < 0.05). CONCLUSION: The study indicated that the symptoms developing after a challenge, which to some extent simulate those of asthma, can be alleviated by a prophylactic airway instillation of pulmonary surfactant.

Animals↗
PubMed1996

[Studies on the mechanisms of immunoregulatory effects of ginsenoside Rg1 in aged rats].

Using methods of fluorescence flow cytometry and Western blot analysis, Rg1 was found to enhance the expression of IL-2 receptor alpha chain and inhibit the release of soluble IL-2 receptor. In in vitro experiment, Rg1 showed no influence on Con A-induced increase of cytoplasmic free calcium concentration, but significantly increased the levels of intracellular cAMP and cGMP in aged animals. In view of the important role of cAMP and cGMP as second messengers in the regulation of immune system, the results of the present studies suggest that one of the mechanisms by which Rg1 enhances immune function in old rats might be mediated by increase of cAMP and cGMP contents, resulting in IL-2 gene expression and splenocyte proliferation.

Adjuvants, Immunologic↗
PubMed1996

Comparative studies on the substrate specificity of lecithin:cholesterol acyltransferase towards the molecular species of phosphatidylcholine in the plasma of 14 vertebrates.

Comparative studies indicate that plasma cholesteryl ester (CE) composition is correlated with susceptibility to atherosclerosis. We previously showed that the lecithin:cholesterol acyltransferases (LCATs) of susceptible species such as rabbit, pig, and chicken (group I) differ in their substrate and positional specificities from the LCATs of resistant species such as rat and mouse (group II). However, the relative importance of enzyme specificity and substrate phosphatidylcholine (PC) composition in determining the CE composition is not known. To address this, we analyzed the molecular species composition of plasma PC in the same 14 vertebrates in which we previously studied the CE composition and LCAT specificity. The utilization of native PC species by LCAT was studied by determining the loss of each PC after incubation of plasma at 37 degrees C. The major contributor for LCAT reaction was either 16:0-18:2 PC or 18:0-18:2 PC in all species except dog, in which it was 18:0-20:4 PC. The formation of 20:4 CE correlated more with the consumption of 18:0-20:4 PC in group I, and with the consumption of 16:0-20:4 PC in group II. The group II enzymes exhibited higher selectivity for sn-2-20:4 PCs, whereas the group I enzymes showed preference for sn-2-18:2 PCs. The synthesis of high percentage of 20:4 CE in dog plasma was found to be due to the presence of unusually high concentration of 18:0-20:4 PC, rather than due to enzyme selectivity. These results show that the PC molecular species composition, especially the concentrations of sn-2-20:4 phosphatidylcholines has profound influence on plasma CE composition, and possibly on atherogenic risk.

Animals↗
PubMed1996

Dengue vector mosquitos at a tourist attraction, Ko Samui, in 1995.

On Ko Samui, Thailand there were two epidemics of dengue hemorrhagic fever (DHF) in 1966 and 1967, followed by endemics up to 1994. Aedes aegypti and Aedes albopictus were the vectors. From January to July 1995, 51 cases of DHF were reported, out of these were many foreigners who still suffer from dengue fever and return home with negative impression. We carried out an entomological survey around the island and collected the mosquitos to detect dengue virus by digoxigenin-cDNA probe. The data revealed that Aedes aegypti and Aedes albopictus still were abundant and some were infected with dengue virus. Visual larval survey indices (HI, CI and BI) were 90.4, 61.3 and 301.3 respectively. Biting rate (BR) of Aedes mosquitos was high, the average indoor and outdoor BR were 9.7 and 100.8 mosquitos/man-hour. From 13 pools of mosquitos, 8 strains of dengue virus were detected (61.5%). The results may encourage the local authorities to improve vector surveillance and control before the famous island becomes an unpleasant island.

Aedes↗
PubMed1996

A one-hand operation gun for transrectal prostate biopsy.

OBJECTIVE: To develop a new automatic biopsy device (ABD) that enables a radiologist to obtain multiple samples with one hand and free the other hand to handle the ultrasonic scanner for continuous monitoring. MATERIALS AND METHODS: The new ABD developed by us in April 1994 enabled a radiologist to complete all the biopsy procedures including loading and reloading the spring system, firing the device, emptying the specimen, selecting the depth of needle advancement, and multiple sampling, simply by pressing 3 buttons in turn with his/her right thumb. Using this new ABD, transrectal prostate biopsy under the guidance of transrectal ultrasonic imaging was performed in 60 consecutive cases of prostate diseases. Each biopsy procedure was completed by a single radiologist, who was able to obtain multiple specimens with one biopsy needle, using only one hand and freeing the other hand for the manipulation of the ultrasonic scanner for guidance. RESULTS: A total of 265 satisfactory core tissue specimens of 285 needle passes (93%) were obtained from the 60 patients. Definite pathologic diagnoses were made for all the 60 patients (100%). No serious biopsy-related complications were observed. The main complications were hematuria in 24 of 60 (40%) patients and fever in 5 (8.3%). CONCLUSION: On the basis of our experience with the 60 patients, this new ABD can be operated smoothly and effectively with the right hand, while the left hand is freed to handle the ultrasonic transducer for continuous monitoring.

Biopsy, Needle↗
PubMed1996

Experimental study of right ventricular assist in acute right ventricular failing.

The efficacy of right atrial-pulmonary artery (RA-PA) bypass during acute right ventricular failure (RVF) produced by pulmonary artery constriction in dogs was examined in this study Control group (n = 7) was supported with conventional volume loading and inotropic therapy. In the experimental animals (n = 8), RA-PA bypass was initiated 5 min, after the onset of severe RVF. Three control animals died from refractory ventricular fibrillation within one hour of RVF. No animals in the experimental group died within two hours of RA-PA bypass, but the histological study of the lungs in these animals demonstrated peribronchial, perivascular and intraalveolar hemorrhage. Light microscopic and electron microscopic examination of the myocardial specimens of the right ventricular free wall displayed the myocardial structures and ultrastructures were maintained effectively with RA-PA bypass while irreversible myocardial injuries occurred in the control animals after two hours of RVF with conventional therapy. During the 2 hours of RA-PA bypass, the hemodynamic indices were also maintained better when compared to the control animals. It may be concluded, a roller pump right ventricular assist device effectively unloads the acute failing right ventricle, maintains systemic cardiac output, and significantly reverses the myocardial ischemia during right ventricular failure, but RA-PA bypass may induce pulmonary hypertension due to increased pulmonary vascular resistance secondary to pulmonary edema and interstitial hemorrhage.

Animals↗
PubMed1996

[High efficiency eukaryotic expression of rhIL-12 in COS-7 cells].

In this study, two high-efficiency eukaryotic expression vectors, PED35 and PED40 containing p35 and p40 cDNA of rhIL-12 respectively, were co-transfected into COS-7 cells by modified DEAE-Dextran method. The COS-7 cell culture supernatant had been certified to contain high level of expressed rhIL-12 protein, nearly 600 IU/ml. Furthermore, in the two biological assays, the expressed rhIL-12 protein can cause the proliferation of human PHA-activated lymphoblasts and augmentation of NK cells mediated cytotoxic activity. This study, therefore, could help further exploration of biological activities and potential usage of rhIL-12.

Animals↗
PubMed1996

[Causes of death of pancrease hemorrhage. Report of 35 autopsy cases].

The causes of death of 35 cases of pancreas hemorrhage have been analysed. The pancreas hemorrhage was seen not only in acute hemorrhagic pancreatitis, but also in poisoning, mechanical injury, mechanical asphyxia, and heart disease. The diagnosis and pathogenesis of acute hemorrhagic pancreatitis were discussed.

Acute Disease↗
PubMed1996

[Immunohistochemical study on morphine in human tissues from opiate associated death].

The morphine distribution in human tissues was studied by immunohistochemical method. Four cases of opiate associated death were examined. Morphine was demonstrated not only in some neuronal cytoplasma of cerebral cortex, hippocampus, basal ganglia thalamus, brainstem, and cerebellum, but also found in some nervous fibers and some capillary walls in the central nervous system. Besides, it was also found in the capsule and mesenchyma of heart, liver, spleen, lung, kidney, adrenal gland, pancreas, thymus, thyroidea and testis. Morphine was not seen in the parenchyma of these organs. It was suggested that the postmortem redistribution was not in the central nervous system, but in other organs. We considered that immunohistochemical staining of morphine is useful in the diagnosis of death from opiate addiction.

Adult↗
PubMed1996

[Early result comparison following mitral valve replacement with partial or entire subvalvular structure preservation].

21 patients after mitral valve replacement with partial subvalvular structure preservation and 20 patients with entire subvalvular structure preservation were compared with 26 patients after mitral valve replacement with entire subvalvular structure excision. We found that patients after mitral valve replacement with partial or entire subvalvular structure preservation had a more uneventful postoperative course with less inotropic therapy and more decreased left atrial dimension when compared to those with conventional mitral valve replacement. But the patients after mitral valve replacement with entire mitral structure preservation had more decreased left ventricular dimension and short hospital stay when compared to those of the other two groups. The authors suggest that mitral subvalvular structure should be preserved, and we especially recommend the procedure of intravalvular implantation of mitral prosthesis with entire mitral subvalvular structure preservation.

Adult↗
PubMed1996

[Studies on the anti-aging and nootropic effects of ginsenoside Rg1 and its mechanisms of actions].

It has been well documented that ginsenoside Rg1 is one of the important active principles of ginseng and shares many pharmacological effects of this drug, such as facilitating learning and memory and alleviating many ailments associated with aging. In the present studies, Rg1 was found to selectively enhance the deteriorated immune function in aged animals, ameliorate age-related alterations in both behavior and motor response, promote hippocampal neuronal function of aged rats, and provide partial protection against the excitotoxic effect of glutamate. All of these provide several aspects of explanation to elucidate Rg1's anti-aging and nootropic mechanisms.

Aging↗
PubMed1996

Effects of ginsenoside Rg1 on c-fos gene expression and cAMP levels in rat hippocampus.

AIM: To study the mechanisms of Rg1 antiaging and nootropic function. METHODS: Using Northern and Western blot analyses, the levels of c-fos mRNA and fos protein were determined in the hippocampus of young and old rats treated with or without ginsenoside Rg1. RESULTS: The expression of c-fos gene and protein was decreased in the hippocampus of aged rats, but dose-dependently increased in young and aged rats after the administration of Rg1. Furthermore, Rg1 increased the level of cAMP in the hippocampus of both young and old rats. CONCLUSION: The changes at the genomic and protein levels, arisen from the increase of cAMP, provide an explanation of the mechanisms of Rg1 nootropic and antiaging function. The c-fos proto-oncogene is the prototype of the early-response class of genes. It encodes for a nuclear phosphoprotein, which after forming a complex with the protein product of another oncogene c-jun, binds to the AP-1 sites of DNA, and acts as a regulatory factor for gene transcription. The c-fos gene expression can be considered as a marker for neuronal activity. Moreover, fos protein is believed to be involved in processes related to neuronal plasticity. Ginsenoside Rg1 is one of the important pharmacological principles of ginseng and shares many pharmacological effects of this plant, such as, facilitating learning and memory, and alleviating many ailments, especially those associated with aging. Since the c-fos gene expression might be of crucial importance for neuronal activity and cAMP is a factor regulating gene expression. The present work was to study the effects of Rg1 on c-fos mRNA and protein expression as well as cAMP and cGMP levels.

Aging↗
PubMed1996

[Effects of m-Nif and Nif on left ventricle hypertrophy in rats induced by partial ligation of abdominal aorta].

Partial ligation of the abdominal aorta of rats was adopted to induce left ventricle hypertrophy (LVH). The effects of m-nifedipine (m-Nif) and nifedipine (Nif) on prevention of hypertrophy and the possible mechanism were investigated. The wet weights of the left ventricle (WWLV) of the LVH group were increased compared with those of the sham operated group. After treatment with m-Nif and Nif for 4 wks, the WWLV decreased by 25% +/- 9% and 16% +/- 9%, respectively. The pressure-volume (P-V) curve of the hypertrophied group was markedly elevated, which means that the myocardial compliance was decreased, and the stiffness coefficient of the hypertrophied group was significantly elevated than that of the sham operated group, but the groups treated with m-Nif or Nif were significantly improved. The characteristics of the left ventricular myocardial DHP binding sites were studied. The results showed that the Kd and the Bmax were similar in the m-Nif, Nif and hypertrophied groups, but the total number of the DHP receptors (TNR) of the LVH group was markly increased than that of the sham operated group, but the TNR of the m-Nif and Nif groups were the same as that of the sham operated group. These results suggest that the effects of m-Nif and Nif on preventing cardiac hypertrophy and improving myocardial compliance may be related to their depressing the TNR of DHP.

Animals↗
PubMed1995

Enzymes of B-ring-deoxy flavonoid biosynthesis in elicited cell cultures of "old man" cactus (Cephalocereus senilis).

Elicited cell cultures of the cactus Cephalocereus senilis produce a group of flavonoids with unsubstituted B-rings, including an aurone which represents a new class of phytoalexin. Preliminary enzymological studies indicated that the chalcone synthase (CHS) and chalcone isomerase (CHI) from cultures of C. senilis were active with cinnamoyl-CoA and 2',4',6'-trihydroxychalcone, respectively, probable intermediates for synthesis of flavonoids with unsubstituted B-rings. We now demonstrate that the cultures contain two isoforms of CHI, both of which are induced by elicitor treatment and are active with both 2',4,4',6'-tetrahydroxy- and 2',4',6'-trihydroxychalcone. (Hydroxy)-cinnamate:CoA ligase in the cactus cultures was active with cinnamic, 4-coumaric, caffeic, ferulic, and 4-methoxycinnamic acids, but not sinapic acid. A single form of CoA ligase, as resolved by chromatofocusing analysis, was active against both cinnamate and 4-coumarate. Cinnamic acid 4-hydroxylase (CA4H) activity was induced by elicitor treatment. Thus, elicited cultures contain the necessary enzymatic activities for synthesis of B-ring-hydroxy and -deoxy flavonoids. Synthesis of only the deoxy class in response to elicitation may result from some form of metabolic compartmentation through which the CA4H reaction is bypassed, leading to formation of cinnamoyl CoA which may then be incorporated into B-ring deoxy flavonoids via nondiscriminating CHS and CHI activities.

Acyltransferases↗
PubMed1995

IL-6 induces target cell resistance to HIV-specific cytotoxic lysis.

Interleukin-6 (IL-6) is a pleiotropic cytokine with multiple immunomodulatory functions. Although IL-6 enhances cytotoxic effector cell function in vitro, we report the paradoxical effect of IL-6-induced resistance of target cells to lysis by cytotoxic T lymphocytes (CTL). The CTL system employed autologous, Epstein-Barr virus-transformed B lymphoblastoid target cells infected with vaccinia virus vectors carrying the envelope gene from the human immunodeficiency virus (HIV). Effector cells were fresh peripheral blood mononuclear cells from HIV+ individuals. Resistance was induced by exposing B cell line targets to exogenous IL-6, or via an autocrine pathway in which IL-6 was secreted by the target cells themselves. The IL-6 effect was dose dependent and reversible by antibody to IL-6. A large proportion of B cell lines from HIV+ individuals produced IL-6, and the lysis of HIV envelope-expressing B cell targets was inversely proportional to the amounts of IL-6 produced by the cell lines. These findings have significance for the utility and interpretation of CTL assays as in vitro correlates of T cell competence and may be significant in vivo in situations such as HIV infection where IL-6 production is increased.

Adult↗