Biomedical subjects

X Y Liu

Publications and source records attributed to X Y Liu.

At least 55 records · Page 3Linked to original sources

PubMed2000

Quantitative affinity chromatographic studies of mitochondrial cytochrome c binding to bacterial photosynthetic reaction center, reconstituted in liposome membranes and immobilized by detergent dialysis and avidin--biotin binding.

In order to study the affinity binding of c-type cytochromes to the photosynthetic reaction center (RC) by quantitative affinity chromatography (QAC), RC from Rhodobacter sphaeroides was reconstituted into liposomes composed of egg phosphatidylcholine (EPC) and 2 mol% of biotinyl phosphatidylethanolamine simultaneously as the liposomes were formed and immobilized in (strept)avidin-coupled gel beads by rotary detergent dialysis. The immobilized amount was up to 80 nmol of RC and 33 micromol of lipid/g of moist gel in streptavidin-coupled Sephacryl S-1000 gel. By QAC frontal runs, retardation of mitochondrial cyt c on immobilized RC liposome columns was demonstrated. The dissociation constant for the RC-cyt c interaction was determined to be 0.20-0.57 microM. QAC studies also allowed evaluation of the orientation of reconstituted RC in immobilized liposomes by comparison of the total amount of cyt c binding sites with the amount of available binding sites obtained by QAC. It seems that the RC proteoliposomes immobilized in Sephacryl S-1000 gel exposed the cyt c binding sites on the outer surface of the liposomes due to effects of the gel network pore size and the resulting liposomal size.

Animals↗

PubMed2000

Combined heterozygosity of factor V leiden and the G20210A prothrombin gene mutation in a patient with cerebral cortical vein thrombosis.

Cerebral venous thrombosis (CVT) is a rare type of stroke with a variety of causes. Several reports have suggested that either factor V Leiden or G20210A prothrombin gene mutation is associated with an increased risk of CVT. The genetic thrombophilias are typically associated with other predisposing factors. We report a unique case of CVT in a patient with both the factor V Leiden and the G20210A prothrombin gene mutations without other identifiable precipitating factors in a 28-year-old white male in good health. MRI and cerebral arterial angiography showed cerebral cortical venous thrombosis. This case suggests that combined heterozygous individuals may be particularly prone to spontaneous thrombosis, like CVT.

Adult↗

PubMed2000

Analgesic effect of interferon-alpha via mu opioid receptor in the rat.

Using the tail-flick induced by electro-stimulation as a pain marker, it was found that pain threshold (PT) was significantly increased after injecting interferon-alpha (IFN alpha) into the lateral ventricle of rats. This effect was dosage-dependent and abolished by monoclonal antibody (McAb) to IFN alpha. Naloxone could inhibit the analgesic effect of IFN alpha, suggesting that the analgesic effect of IFN alpha be related to the opioid receptors. Beta-funaltrexamine (beta-FNA), the mu specific receptor antagonist could completely block the analgesic effect of IFN alpha. The selective delta-opioid receptor antagonist, ICI174,864 and the kappa-opioid receptor antagonist, nor-BNI both failed to prevent the analgesic effect of IFN alpha. IFN alpha could significantly inhibit the production of the cAMP stimulated by forskolin in SK-N-SH cells expressing the mu-opioid receptor, not in NG108-15 cells expressing the delta-opioid receptor uniformly. The results obtained provide further evidence for opioid activity of IFN alpha and suggest that this effect is mediated by central opioid receptors of the mu subtype. The evidence is consistent with the hypothesis that multiple actions of cytokines, such as immunoregulatory and neuroregulatory effects, might be mediated by distinct domains of cytokines interacting with different receptors.

Analgesia↗

PubMed2000

Long-term phenotypic correction of rodent hemiparkinsonism by gene therapy using genetically modified myoblasts.

Rat myoblasts were genetically modified to express tyrosine hydroxylase (TH) and produce dopamine in culture. Implanting TH gene-transfected myoblasts into the denervated striatum of 6-OHDA-lesioned rats significantly decreased rotational asymmetry by 50 to approximately 60%. Improvement persisted for up to 13 months. Genetically modified cells could survive and express transgene in the striatum as demonstrated by RT-PCR and immunohistochemical stain-ing. The dopamine content in the striatum tissue of the gene therapy group recovered to 49% of the normal level and was 25-fold higher than that of a control group receiving parental cells. Neither tumor formation nor immunorejection was observed in this study. These results show that myoblasts may be useful as gene carriers for ex vivo gene therapy in the CNS. Gene Therapy (2000) 7, 445-449.

Animals↗

PubMed2000

Interleukin-2: structural and biological relatedness to opioid peptides.

Interleukin (IL)-2 is not only an immunoregulatory factor, but also an analgesic molecule. There are distinct domains of immune and analgesic functions in the IL-2 molecule. The analgesic domain is located around the 45th Tyr residue of human IL-2 in tertiary structure. Antiopioid (beta-endorphin, Leu-enkephalin, Met-enkephalin and dynorphin A1-13) sera partially neutralized the analgesic activity of IL-2. Monoclonal antibody against the IL-2 receptor alpha subunit (Tac) could not block the analgesic activity of IL-2. There existed cross-reactivity between IL-2 and antiopioid sera by indirect ELISA. These studies show strong structural and biological similarities between IL-2 and opioid peptides. The tertiary structure around the 45th residue of IL-2 composes the analgesic domain that is similar to that of endogenous opioids. These results are consistent with the hypothesis that multiple domains of cytokines serve as the structural bases for the immunoregulatory and neuroregulatory effects of cytokines.

Analgesics↗

PubMed2000

[Multiplication of the shrimp baculovirus HHNBV with primary cell cultures from lymphoid organ of Penaeus chinensis].

The hypodermal and hematopoietic necrosis baculovirus HHNBV has been confirmed to be the causative agent for the explosive epidermic disease of farmed shrimp Penaeus chinensis since 1993. The virus was isolated and multiplied successfully in the primary cell cultures from the lymphoid organ of the shrimp. A cell monolayer was formed in three days in the medium MPS and could be maintained for 1-3 months as the medium replaced every 4-5 days. The cytopathic effect occurred in 5 days after inoculation of the tissue extract from the diseased shrimp. The transmission electron microscopy showed many rod-shaped virions of HHNBV in the nuclei of infected cells.

Animals↗

PubMed2000

[Design of reaction canister in a solid amine carbon dioxide removal system].

Objective. To design a reaction canister using in solid amine carbon dioxide removal system for long-duration spaceflight. Method. On consideration of system demand and properties of solid amine, key problems must be solved were found out: 1) the rated resistance limit tends to shorten the length of the canister while absorption and concentration require to increase the length of the canister; 2) limited quantity of heat for keeping the temperature of the canister; 3) inflation or contraction of the solid amine under micro-gravity. Result. After appropriate measures were taken, effective adsorption and desorption, as well as concentration of CO2 were achieved, the concentration of CO2 in the space cabin could be controlled below 0.5%; and the concentration of the concentrated CO2 was as high as 98% so that it could be directly send to the CO2 reduction system; and that the resistance of the canister was below 160 mm H2O; moreover, the energy consumption was decreased to below 650 W. Conclusion. The designed reaction canister could meet the requirements of the solid amine carbon dioxide (correction of bioxide) removal system under microgravity.

Adsorption↗

PubMed2000

[The changes in the heart and erythrocyte L-arginine transport of spontaneously hypertensive rats].

Changes of L-arginine/nitric oxide pathway in heart and of L arginine transport in erythrocytes and their relationship were investigated in spontaneously hypertensive rats (SHR). 12 and 16 weeks old SHR, 16 weeks old SHR with captopril treatment for 4 weeks and 16 weeks old Wistar-Kyoto (WKY) rats were used. L arginine transport of myocardial ventricular tissue and erythrocytes, total nitric oxide synthase (tNOS) activity, nitrite and nitrate (NO(2) + NO(3)) and cyclic GMP (cGMP) content in myocardium were measured. The result showed that in myocardial ventricular tissue of SHR L-arginine transport decreased significantly with V(max) of the high-affinity transport being decreased by 24.3% (P<0.05, 12W group), 36.4% (P<0.01, 16W group) as compared with WKY group. Michaelis constant (K(m)) of low affinity transport was significantly lower than that of WKY group. NO(2) + NO(3) and cGMP content were respectively decreased by 24.6%, 19.8% (P>0.05, P<0.05, 12W group), 52.5%, 60.4% (P<0.05, P<0.01, 16W group) and 14.8%, 23% (P>0.05, P<0.05, SHR+C group) as compared with WKY group. But the K(m) of L-arginine high-affinity transport and the V(max) of low affinity transport and tNOS activity were not significantly changed. In erythrocytes, the changes of L-arginine transport coincided with those of myocardial tissue. The V(max) had significant positive correlation with the V(max) of high-affinity transport in myocardial tissue, r=0.5606, P=0.01 and had negative correlation with left ventricular weight to body weight radio, r=0.6231,P<0.01. These results indicate that the activity of L-arginine/nitric oxide pathway inhibited in myocardial tissue of SHR. The correlation between the inhibitory degree of L-arginine/nitric oxide pathway and the degree of ventricular hypertrophy is negative. The changes of L-arginine transport in erythrocytes coincide with those in myocardium.

Animals↗

PubMed2000

[Distinct structural bases of the immunoregulatory and central analgesic effects of IFNalpha].

Interferon-alpha (IFNalpha), a cytokine, is also an analgesic molecule. There is significant cross reactivity between IFNalpha and anti-opioid sera, suggesting a strong antigenic relatedness between human IFNalpha molecules and opioid peptides. Different structural basis of the immunoactivity and analgesic effect of IFNalpha can be demonstrated by different reactivities of the two reactions towards different mutants of IFNalpha obtained by using the site-directed mutagenesis. When the 129th Tyr residue of human IFNalpha was mutated to Ser, the immunoactivity of the mutant almost disappeared, while the strong analgesic activity still persisted, which could be blocked by naloxone. These results indicate that there exist distinct domains in the IFNalpha molecule, which mediate immune and analgesic effects differentially, and that the receptor mechanism underlying immune and analgesic effects of IFNalpha may be different.

Adjuvants, Immunologic↗

PubMed1999

IkappaB kinase complex is an intracellular target for endotoxic lipopolysaccharide in human monocytic cells.

Endotoxic lipopolysaccharide (LPS) is a proinflammatory agonist produced by gram-negative bacteria and a contributor to the majority of the 400,000 septic shock cases recorded annually in US hospitals. The primary target cells for LPS are monocytes and macrophages. Their response consists of massive production of proinflammatory cytokines, reactive oxygen- and nitrogen-intermediates, procoagulants, and cell adhesion molecules. In turn, expression of these LPS-responsive factors contributes to collapse of the circulatory system, to disseminated intravascular coagulation, and to a 30% mortality rate. A common intracellular mechanism responsible for the expression of septic shock genes in monocytes and macrophages involves the activation of NF-kappaB. This transcription factor is regulated by a family of structurally related inhibitors including IkappaBalpha, IkappaBbeta, and IkappaBepsilon, which trap NF-kappaB in the cytoplasm. In this report, the investigators show that LPS derived from different gram-negative bacteria activates cytokine-responsive IkappaB kinases containing catalytic subunits termed IKKalpha (IKK1) and IKKbeta (IKK2). The kinetics of IKKalpha and IKKbeta activation in LPS-stimulated human monocytic cells differ from that recorded on their stimulation with tumor necrosis factor-alpha, thereby implying a distinct activation mechanism. LPS-activated IKK complexes phosphorylate all 3 inhibitors of NF-kappaB: IkappaBalpha, IkappaBbeta, and IkappaBepsilon. Moreover, LPS activates IKKbeta preferentially, relative to IKKalpha. Thus, IKK complex constitutes the main intracellular target for LPS-induced NF-kappaB signaling to the nucleus in human monocytic cells to activate genes responsible for septic shock.

Cells, Cultured↗

PubMed1999

Covalent immobilization of unilamellar liposomes in gel beads for chromatography.

For immobilized (proteo)liposome chromatography, unilamellar liposomes were covalently bound within gel beads that had been activated by CNBr, N-hydroxysuccinimide, tresyl, or chloroformate. Liposomes composed of phosphatidylcholine (PC) and 2 mol% of amino-containing lipid (phosphatidylethanolamine-caproylamine) were immobilized in the activated gels at 5-35 micromol lipid/ml gel and yields of 11-70%. The highest immobilized amount was found in chloroformate-activated TSK G6000PW gel, which contains large pore size (>100 nm). Liposomes composed of PC alone could also be attached to the chloroformate-activated gels at 33-42 micromol/ml gel and yields of 58-65%, probably by crosslinking of the phosphate moiety of phospholipid with the active group of the adsorbent. Liposomes prepared by various phospholipids with or without amino-containing lipids can generally be immobilized in the chloroformate-activated gels. The covalently bound liposomes were characterized by their high stability, unilamellarity, permeability of the membranes, and drug-membrane partition properties. A stable membrane phase was constructed for chromatographic experiments to be performed under extreme elution conditions.

Chromatography, Gel↗

PubMed1999

Partitioning of triphenylalkylphosphonium homologues in gel bead-immobilized liposomes: chromatographic measurement of their membrane partition coefficients.

Unilamellar liposomes of small or large size, SUVs and LUVs, respectively, were stably immobilized in the highly hydrophilic Sepharose 4B or Sephacryl S-1000 gel beads as a membrane stationary phase for immobilized liposome chromatography (ILC). Lipophilic cations of triphenylmethylphosphonium and tetraphenylphosphonium (TPP+) have been used as probes of the membrane potential of cells. Interaction of TPP+ and triphenylalkylphosphonium homologues with the immobilized liposomal membranes was shown by their elution profiles on both zonal and frontal ILC. Retardation of the lipophilic cations on the liposome gel bed was increased as the hydrophobicity of the cations increased, indicating the partitioning of lipophilic cations into the hydrocarbon region of the membranes. The cations did not retard on the Sepharose or Sephacryl gel bed without liposomes, confirming that the cations only interact with the immobilized liposomes. Effects of the solute concentration, flow rate, and gel-matrix substance on the ILC were studied. The stationary phase volume of the liposomal membranes was calculated from the volume of a phospholipid molecule and the amount of the immobilized phospholipid, which allowed us to determine the membrane partition coefficient (KLM) for the lipophilic cations distributed between the aqueous mobile and membrane stationary phases. The values of KLM were generally increased with the hydrophobicity of the solutes increased, and were higher for the SUVs than for the LUVs. The ILC method described here can be applied to measure membrane partition coefficients for other lipophilic solutes (e.g., drugs).

Cations↗

PubMed1999

Multiple functions of polypeptides mediated by distinct domains interacting with different receptors.

There exist multiple functions of polypeptide molecules. Both a polypeptide molecule interacting with one receptor, and distinct domains of the molecule interacting with different receptors could induce different intracellular signal transduction to elicit multiple functions. This review highlights the distinct domains of the polypeptide molecule interacting with different receptors to elicit multiple functions. It includes distinct domains, different receptor mechanisms, and different signal transduction of the polypeptide molecule.

Animals↗

PubMed1999

The gene mutated in bare patches and striated mice encodes a novel 3beta-hydroxysteroid dehydrogenase.

X-linked dominant disorders that are exclusively lethal prenatally in hemizygous males have been described in human and mouse. None of the genes responsible has been isolated in either species. The bare patches (Bpa) and striated (Str) mouse mutations were originally identified in female offspring of X-irradiated males. Subsequently, additional independent alleles were described. We have previously mapped these X-linked dominant, male-lethal mutations to an overlapping region of 600 kb that is homologous to human Xq28 (ref. 4) and identified several candidate genes in this interval. Here we report mutations in one of these genes, Nsdhl, encoding an NAD(P)H steroid dehydrogenase-like protein, in two independent Bpa and three independent Str alleles. Quantitative analysis of sterols from tissues of affected Bpa mice support a role for Nsdhl in cholesterol biosynthesis. Our results demonstrate that Bpa and Str are allelic mutations and identify the first mammalian locus associated with an X-linked dominant, male-lethal phenotype. They also expand the spectrum of phenotypes associated with abnormalities of cholesterol metabolism.

3-Hydroxysteroid Dehydrogenases↗

PubMed1999

Anterior mediastinal masses: an anaesthetic challenge.

A patient with a large anterior mediastinal mass with minimal respiratory symptoms presented for a diagnostic biopsy of the mass. A pre-operative thoracic computed tomographic scan demonstrated narrowing of the distal trachea, and right and left main stem bronchi. An awake intubation was done. Thiopentone and muscle relaxant were given and surgery commenced. High airway pressure developed and ventilation became difficult, although oxygenation remained satisfactory throughout. Anaesthetic implications are discussed. We recommend that patients with more than 50% obstruction of the airway at the level of the lower trachea and main bronchi have their femoral vessels cannulated in readiness for cardiopulmonary bypass.

Adult↗

PubMed1999

[Application of repairing tibia and soft tissue defect with free fibula combined tissue grafting].

OBJECTIVE: To investigate a good method for repairing the long bone defect of tibia combined with soft tissue defect. METHODS: From 1988-1998, sixteen patients with long bone defect of tibia were admitted. There were 12 males, 4 females and aged from 16 to 45 years. The length of tibia defect ranged from 7 cm to 12 cm, the area of soft tissue defect ranged from 5 cm x 3 cm to 12 cm x 6 cm. Free fibula grafting was adopted in repairing. During operation, the two ends of fibular artery were anastomosised with the anterior tibial artery of the recipient, and the composited fibular flap were transplanted. RESULTS: All grafted fibula unioned and the flap survived completely. Followed up for 6 to 111 months, 14 patients acquired the normal function while the other 2 patients received arthrodesis of the tibial-talus joint. In all the 16 patients, the unstable ankle joint could not be observed. CONCLUSION: The modified method is characterized by the clear anatomy, the less blood loss and the reduced operation time. Meanwhile, the blood supply of the grafted fibula can be monitored.

Adolescent↗

PubMed1999

[Transposition of expanded superficial cervical artery skin flaps for the repair of cicatricial contracture of neck].

OBJECTIVE: In order to reduce the complication of the transposition of superficial cervical artery skin flap for the repair of neck defect, the method of pre-expanded skin flap was designed, and its clinical result was observed. METHODS: From March 1995 to October 1997, 12 cases with cicatricial contracture of the neck were treated by the following methods, preexpanded superficial cervical artery skin flap, and then transposed it for the reconstruction the cervical scar after burns. There were 8 males and 4 females and the age ranged from 6 to 32 years. A maximal size of flap was 35 cm x 14 cm and a minimal size was 16 cm x 7 cm. RESULTS: All the flaps were survived except one, which partial necrosis occurred in the tip. Postoperative follow-up for 6 months to 3 years showed that the physiological angle of cervico-mandibular angle was recovered and the appearance of flap was satisfactory without swelling and contracture. CONCLUSION: The preexpanded superficial cervical artery skin flap has many advantages, and it is particularly suitable for reconstruction of severe cervical contracture after extensive burns.

Adolescent↗

PubMed1998

Structures of native and complexed complement factor D: implications of the atypical His57 conformation and self-inhibitory loop in the regulation of specific serine protease activity.

Factor D is a serine protease essential for the activation of the alternative pathway of complement. The structures of native factor D and a complex formed with isatoic anhydride inhibitor were determined at resolution of 2.3 and 1.5 A, respectively, in an isomorphous monoclinic crystal form containing one molecule per asymmetric unit. The native structure was compared with structures determined previously in a triclinic cell containing two molecules with different active site conformations. The current structure shows greater similarity with molecule B in the triclinic cell, suggesting that this may be the dominant factor D conformation in solution. The major conformational differences with molecule A in the triclinic cell are located in four regions, three of which are close to the active site and include some of the residues shown to be critical for factor D catalytic activity. The conformational flexibility associated with these regions is proposed to provide a structural basis for the previously proposed substrate-induced reversible conformational changes in factor D. The high-resolution structure of the factor D/isatoic anhydride complex reveals the binding mode of the mechanism-based inhibitor. The higher specificity towards factor D over trypsin and thrombin is based on hydrophobic interactions between the inhibitor benzyl ring and the aliphatic side-chain of Arg218 that is salt bridged with Asp189 at the bottom of the primary specificity (S1) pocket. Comparison of factor D structural variants with other serine protease structures revealed the presence of a unique "self-inhibitory loop". This loop (214-218) dictates the resting-state conformation of factor D by (1) preventing His57 from adopting active tautomer conformation, (2) preventing the P1 to P3 residues of the substrate from forming anti-parallel beta-sheets with the non-specific substrate binding loop, and (3) blocking the accessibility of Asp189 to the positive1y charged P1 residue of the substrate. The conformational switch from resting-state to active-state can only be induced by the single macromolecular substrate, C3b-bound factor B. This self-inhibitory mechanism is highly correlated with the unique functional properties of factor D, which include high specificity toward factor B, low esterolytic activity toward synthetic substrates, and absence of regulation by zymogen and serpin-like or other natural inhibitors in blood.

Binding Sites↗