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Biomedical subjects

Wei Liang

Publications and source records attributed to Wei Liang.

At least 37 records · Page 2Linked to original sources
PubMed2004

Excluded volume effect of rat intestinal mucin on taurocholate/phosphatidylcholine mixed micelles.

The interaction of bile salt/phospholipid mixed micelles with an intestinal mucin has been investigated to provide the foundation for the transport of ingested fat and poorly water-soluble drugs through the intestinal mucous layer. Egg phosphatidylcholine (PC) was equilibrated with sodium taurocholate (TC) to generate several series of solutions, which had different intermicellar concentrations of TC. Within each series, each solution had the same IMC and thereby micelle sizes, but varied with respect to micelle concentration. These solutions were combined with isolated rat intestinal mucin, equilibrated, and then separated by centrifugation. The supernatant and mucin pellet were assayed for PC and TC, and the diffusion coefficient of PC was measured in the supernatant by PFG-SE NMR spectroscopy. For each series, four linear relationships were found; TC supernatant concentration plotted as a function of PC supernatant concentration; TC pellet concentration plotted as a function of PC pellet concentration; TC pellet concentration plotted as a function of TC supernatant concentration; and PC pellet concentration plotted as a function of PC supernatant concentration. Theoretical analysis of these results indicated that mucin excludes from 25 to 80% of the bile salt/phospholipid mixed micelles with greater exclusion observed with larger micelle size. There is preferential association of the taurocholate with intestinal mucin, when present in the mixed micelle region of the phase diagram. The association coupled with exclusion would allow mucin to modulate the concentration of bile salt at the epithelial surface.

Animals↗
PubMed2004

Differences in endosomal targeting of human (beta)1- and (beta)2-adrenergic receptors following clathrin-mediated endocytosis.

The beta(2)-adrenergic receptor (beta(2)AR) undergoes agonist-mediated endocytosis via clathrin-coated pits by a process dependent on both arrestins and dynamin. Internalization of some G protein-coupled receptors, however, is independent of arrestins and/or dynamin and through other membrane microdomains such as caveolae or lipid rafts. The human beta(1)AR is less susceptible to agonist-mediated internalization than the beta(2)-subtype, and its endocytic route, which is unknown, may be different. We have found that (i) co-expression of arrestin-2 or -3 enhanced the internalization of both subtypes whereas co-expression of dominant-negative mutants of arrestin-2 or dynamin impaired their internalization, as did inhibitors of clathrin-mediated endocytosis. (ii) Agonist stimulation increased the phosphorylation of beta(2)AR but not beta(1)AR. (iii) In response to agonist, each subtype redistributed from the cell surface to a distinct population of cytoplasmic vesicles; those containing beta(1)AR were smaller and closer to the plasma membrane whereas those containing beta(2)AR were larger and more perinuclear. (iv) When subcellular fractions from agonist-treated cells were separated by sucrose density gradient centrifugation, all of the internalized beta(2)AR appeared in the lighter endosomal-containing fractions whereas some of the internalized beta(1)AR remained in the denser plasma membrane-containing fractions. (v) Both subtypes recycled with similar kinetics back to the cell surface upon removal of agonist; however, recycling of beta(2)AR but not beta(1)AR was inhibited by monensin. Based on these results, we propose that the internalization of beta(1)AR is both arrestin- and dynamin-dependent and follows the same clathrin-mediated endocytic pathway as beta(2)AR. But during or after endocytosis, beta(1)AR and beta(2)AR are sorted into different endosomal compartments.

Adrenergic beta-1 Receptor Agonists↗
PubMed2004

Interaction of bile salts with gastrointestinal mucins.

The properties of three mucins were examined to identify the structural features responsible for their functional difterences. Bovine submaxillary mucin (BSM), porcine gastric mucin (PGM), and rat intestinal mucin (RIM) were each characterized, and high carbohydrate contents were found for RIM and PGM. The amino acid compositions were typical of mucin glycoproteins, with over half comprising small, neutral amino acids. Thereafter, each mucin was equilibrated with three different series of concentrations of the bile salts sodium taurocholate, sodium taurodeoxycholate, and sodium taurochenodeoxycholate. Following multiple centrifugations, the supernatant and mucin pellet concentrations of the bile salts were measured. The bile salt pellet concentration was plotted as a function of supernatant concentration, and from the slopes, the excluded volumes were calculated as 25, 29-44, and 28 55 mL/g for BSM, RIM, and PGM, respectively. The intercepts were 8-10, 2-3, and 1-3 mM for BSM, RIM, and PGM, respectively, which represents an estimate of the bound concentration of bile salt. Differences among the bile salts were observed in the excluded volume and amount bound, but no trends were evident. The bile salts may interact as aggregates with the hydrophobic areas and carbohydrate side chains of the mucins, providing favorable sites for association. The binding at low concentrations with exclusion at high concentrations is significant for modulating the absorption of lipid aggregates from the intestine. Finally, the differences among the mucins reflect the unique structure function relationship of these gastrointestinal mucins.

Amino Acids↗
PubMed2004

Lung distribution of the chemopreventive agent difluoromethylornithine (DFMO) following oral and inhalation delivery.

The inhalation delivery of difluoromethylornithine (DFMO) was evaluated to determine its feasibility for use in lung cancer chemoprevention. Aerosol droplets of DFMO were produced, and the solvent was removed by a reflux drying column. Equivalent doses of DFMO (40 mg/kg) were given over 10 minutes by inhalation and by gavage, and the serum and tissue levels were determined. Inhalation of DFMO resulted in a peak lung concentration 80 times higher and area under the curve (AUC) that was 35 times higher than oral dosing. The estimated pharmacokinetic advantage based on serum and lung AUCs was 13 in favor of inhalation.

Administration, Inhalation↗
PubMed2004

Estrogen receptor genotypes and their association with the 10-year changes in bone mineral density and osteocalcin concentrations.

We conducted a 10-yr prospective study of peak bone mass and its change in 604 women, aged 24-44 yr at study initiation, and related changes in bone mineral density (BMD) and osteocalcin (OCN) concentrations to estrogen receptor (ER) alpha gene polymorphisms in 442 of these women. We examined the association of ER alpha PvuII and XbaI polymorphisms with the 10-yr change in lumbar spine (LS) and femoral neck (FN) BMD, measured by densitometry, as well as serum OCN levels, after accounting for weight and menstrual status change. The women were members of the Michigan Bone Health Study, a population-based longitudinal study of BMD. There was a linear loss of LS BMD and curvilinear loss of FN BMD from peak bone mass over a 10-yr period. Women homozygous for the ER alpha gene variant without an XbaI restriction site (XbaI -/- genotype) had higher FN BMD and less change in LS over time. Women homozygous for the ER alpha gene variant without a PvuII restriction site (PvuII -/- genotype) had less LS BMD change over time as well as higher FN BMD. However, this higher FN BMD was dependent upon the rate of bone turnover as estimated from serum OCN change over time. The ER alpha genotype associations were statistically significant in explaining the rate of perimenopausal bone loss and its turnover; however, BMI or becoming postmenopausal contributed more to the magnitude of the difference in bone change.

Adult↗
PubMed2004

Loss optimization of transverse Bragg resonance waveguides.

Coupled-mode theory was used to analyze guiding in a transverse Bragg resonance (TBR) waveguide structure composed of a GaAs substrate with air holes. This analysis predicts that propagation loss will be minimized for discrete widths of the waveguide core. Although the coupled-mode theory is normally applied to structures with small index perturbations, two-dimensional finite-difference time-domain simulations of the TBR waveguide show good quantitative agreement with the coupled-mode predictions, and these results corroborate the previously predicted existence of discrete core widths for low-loss propagation.

Journal Article↗
PubMed2004

ATP-containing immunoliposomes specific for cardiac myosin.

The application of ATP-loaded liposomes has been shown effective against ischemic damage in several tissues. In this study, we have prepared ATP-containing liposomes capable of specific recognition of component (myosin) specific for ischemic myocardium. ATP-containing immunoliposomes specific towards cardiac myosin were obtained by the attachment of the monoclonal anti-cardiac myosin 2G4 antibody to the surface of ATP-containing PEGylated liposomes prepared by the freezing-thawing method. Since intracellular myosin is exposed only in the areas containing ischemically compromised cells with damaged plasmic membranes, such liposomes are expected to target these areas both in vitro and in vivo. The attachment of the antibody did not provoke their ATP release from the liposomes and only minimally influenced liposome size and size distribution. Liposome-attached anti-myosin 2G4 antibody preserved its specific activity; and anti-myosin antibody-bearing, ATP-loaded liposomes bound efficiently to the monolayer of myosin in ELISA. The preparation of myosin-specific ATP-loaded immunoliposomes represented an important step in the development of targeted delivery systems capable of providing energy support to ischemic myocardium in vivo.

Adenosine Triphosphate↗
PubMed2004

Interaction of a novel peptoid enhancer--arginine oligomer with bovine submaxillary mucin.

AIM: To determine the thermodynamics of binding reaction of arginine oligomer (R8) to bovine submaxillary mucin (BSM) in order to provide the foundation for understanding the influence of mucin on transport of macromolecules through mucosa mediated by arginine oligomer. METHODS: Ultracentrifugation sedimentation was employed to investigate the interaction of BSM-R8. The mixtures of R8 with variable concentration and constant volume of BSM were placed on a shaker under oscillation at 25 degrees C to achieve equilibriums of binding reaction, and then centrifuged. The fluorescence intensity of the supernatant was measured by spectrofluorometer. The data were described by two types of binding sites model, the binding parameters of BSM-R8 were obtained by Scatchard plots. RESULTS: At the low pH values < or = 4.5 and ionic strength > or = 0.2 mol x L(-1), the BSM-R8 interaction was principally electrostatic interaction, the five primary binding sites (n1) predominantly were supplied by sulfate groups, the secondary binding sites apparently depended on pH, in that percent ionization of sialic acid residues (n2) in BSM. At the low ionic strength < or = 0.2 mol x L(-1) and pH 7.0, the BSM-R8 interaction was exceedingly complex, hydrogen bonds, hydrophobic interaction and electrostatic forces were involved in the interaction between R8 and BSM, the binding sites of BSM bound R8 were markedly increased. CONCLUSION: There existed evidence that R8 interacted with BSM. The pH and the ionic strength of the binding solution strongly affected the interaction of BSM with R8. The results suggested that the enhancing efficacy of the arginine oligomer for the transport of macromolecules through different site mucosa in body might be variable.

Arginine↗
PubMed2003

High-quality-factor Bragg onion resonators with omnidirectional reflector cladding.

We propose to approximate a spherically symmetric Bragg resonator in an onionlike geometry. We develop a transfer-matrix theory for calculation of the quality factors and analyze the effect of the onion stem on cavity Q factors. We find that it is possible to achieve significant inhibition of spontaneous emission in an onion resonator with omnidirectional cladding layers.

Journal Article↗
PubMed2003

Engineering transverse Bragg resonance waveguides for large modal volume lasers.

We recently analyzed a new class of laser amplifier based on transverse Bragg reflection. We show that the unique properties of Bragg confinement make it possible through modal loss discrimination to achieve single-transverse-mode operation with transverse modal size that is an order of magnitude larger than in lasers that depend on total internal reflection for transverse confinement.

Journal Article↗
PubMed2003

Resistance of the human beta 1-adrenergic receptor to agonist-mediated down-regulation. Role of the C terminus in determining beta-subtype degradation.

Prolonged agonist stimulation results in down-regulation of most G protein-coupled receptors. When we exposed baby hamster kidney cells stably expressing the human beta1-adrenergic receptor (beta 1AR) to agonist over a 24-h period, we instead observed an increase of approximately 30% in both beta 1AR binding activity and immune-detected receptors. In contrast, beta 2AR expressed in these cells exhibited a decrease of > or =50%. We determined that the basal turnover rates of the two subtypes were similar (t(1/2) approximately 7 h) and that agonist stimulation increased beta 2AR but not beta 1AR turnover. Blocking receptor trafficking to lysosomes with bafilomycin A1 had no effect on basal turnover of either subtype but blocked agonist-stimulated beta 2AR turnover. As beta 1AR mRNA levels increased in agonist-stimulated cells, beta 1AR up-regulation appeared to result from increased synthesis with no change in degradation. To explore the basis for the subtype differences, we expressed chimeras in which the C termini had been exchanged. Each chimera responded to persistent agonist stimulation based on the source of its C-tail; beta 1AR with a beta 2AR C-tail underwent down-regulation, and beta 2AR with a beta 1AR C-tail underwent up-regulation. The C-tails had a corresponding effect on agonist-stimulated receptor phosphorylation and internalization with the order being beta 2AR > beta 1AR with beta 2AR C-tail > beta 2AR with a beta 1AR C-tail > beta 1AR. As internalization may be a prerequisite for down-regulation, we addressed this possibility by co-expressing each subtype with arrestin-2. Although beta 1AR internalization was increased to that of beta 2AR, down-regulation still did not occur. Instead, beta 1AR accumulated inside the cells. We conclude that in unstimulated cells, both subtypes appear to be turned over by the same mechanism. Upon agonist stimulation, both subtypes are internalized, and beta 2AR but not beta 1AR undergoes lysosomal degradation, the fate of each subtype being regulated by determinants in its C-tail.

Adrenergic beta-Agonists↗
PubMed2003

Data communication between brain implants and computer.

Recent advances in neuroscience, microelectronics, and information technology have allowed construction of miniature, but highly intelligent, devices to be implanted within the brain to perform in vitro diagnostic and therapeutic functions. However, there exists a significant problem in establishing an effective wireless data communication link between brain implants and external computer. This communication investigates this link and presents a new design using the mechanism of volume conduction of biological tissues. A theoretical model of volume conduction of the head is utilized to compute signal strength in data communication and the result is evaluated by a physical model. The two-way data communication sensitivity of the volume conduction channel is found to be symmetric, as suggested by the reciprocity theorem. A high-performance, x-shaped volume conduction antenna has been designed. Experiments are performed on animals which demonstrate the effectiveness of this volume conduction approach.

Animals↗
PubMed2003

Application of autologous tumor cell vaccine and NDV vaccine in treatment of tumors of digestive tract.

AIM: To treat patients with stage I-IV malignant tumors of digestive tract using autologous tumor cell vaccine and NDV (Newcastle disease virus) vaccine, and observe the survival period and curative effect. METHODS: 335 patients with malignant tumors of digestive tract were treated with autologous tumor cell vaccine and NDV vaccine. The autologous tumor cell vaccine received were assigned for long-term survival observation. While these failed to obtain the autologous tumor tissue were given with NDV vaccine for a received short-term observation on curative effect. RESULTS: The colorectal cancer patients treated with autologous tumor cell vaccine were divided into two groups: the controlled group (subjected to resection alone) (n=257), the vaccine group (subjected to both resection and immunotherapy) (n=310). 25 patients treated with NDV immunotherapy were all at stage IV without having resection. In postoperation adjuvant therapy patients, the 5, 6 and 7-year survival rates were 66.51 %, 60.52 %, 56.50 % respectively; whereas in patients with resection alone, only 45.57 %, 44.76 % and 43.42 % respectively. The average survival period was 5.13 years (resection alone group 4.15 years), the median survival period was over 7 years (resection alone group 4.46 years). There were significant differences between the two groups. The patients treated with resection plus vaccine were measured delayed-type hypersensitivity (DTH) reactions after vaccination, (indurative scope >5 mm). The magnitude of DTH was related to the prognosis. The 5-year survival rate was 80 % for those with indurations greater than 5 mm, compared with 30 % for those with indurations less than 5 mm. The 1-year survival rate was 96 % for 25 patients treated with NDV immunotherapy. The total effective rate (CR+PR) was 24.00 % in NDV immunotherapy; complete remission (CR) in 1 case (4.00 %), partial remission (PR) in 5 cases (20.00 %), stabilizedin in 16 cases (64.00 %), progression (PD) in 1 case (4.00 %). After NDV vaccine immunotherapy, the number of NK cell increased and immune function imporved obviously. CONCLUSION: The autologous tumor cell vaccine and NDV vaccine can prolong the patients' life. NDV vaccine is notably effective for short-term with promotion of quality of life and can be used whenever necessary with good prospects.

Cancer Vaccines↗
PubMed2003

[A study on the lingual shape and position of the teeth in Chinese with normal occlusion].

OBJECTIVE: To measure the lingual surfaces of the teeth in normal occlusion and obtain the data for lingual brackets' bonding and modifying for Chinese. METHODS: 50 casts of nonorthodontic subjects with ideal occlusion were examined using the YM-2115 3D measurement instrument. The data was calculated by the relevant software and analysed statistically. RESULTS: The reference values of the lingual surfaces of the teeth in normal occlusion were obtained. These include crown angulation(tip), crown inclination(torque), offset angles of molars and crown facial prominence. CONCLUSIONS: Compared with the data of foreigners, the characteristics of the lingual surface of the teeth in Chinese normal occlusion has many differences. The accurate placement of the lingual orthodontic brackets should be assisted by laboratory techniques because of the highly variable morphology of the lingual surfaces of the teeth.

Asian People↗
PubMed2003

[Study on the disabilities in aged 0-7 years children in Shenzhen, China].

OBJECTIVE: To explore the prevalence of vision, mental, audibility, language, psychiatry, extremity, and influence factors in the 0 - 7 year olds. METHODS: A total number of 77,727 0 - 7 year old children living in Shenzhen city were tested with tree phase screening under the Chinese standard of evaluation in disabilities. RESULTS: The prevalence of all disabilities was 5.59 per thousand (adjusted rate was 8.49 per thousand with a false negative of 3.1 per thousand ). The prevalence of mental disease was the highest (1.88 per thousand, with adjusted rate 3.43 per thousand ), the prevalence of language disability was 1.88 per thousand (including retarded language development, with adjusted rate 3.43 per thousand ). The prevalence rates of psychiatry, extremity and audibility disability were 1.59 per thousand, 1.56 per thousand, 1.11 per thousand respectively with of vision the lowest (0.37 per thousand ). The prevalence of all disabilities, audibility, language and mental was on the increase with age. The difference was statistically significant. Among all different age groups regarding psychiatric disease, the highest fell in the 2 - 4 year olds. The prevalence of extremity was not statistically different among age groups. The suspected agents of disease which occurred before or during pregnancy took up 45.7%. CONCLUSION: The prevalence of six kinds disabilities in Shenzhen was about 10 per thousand lower than that of the samples of the nation in 1989, but two times higher than that of similar studies in Japan. The prevalence rates of language and psychiatric disease were higher than that of the nation in 1989. The causation should be further studied.

Age Factors↗
PubMed2003

[CH4 and N2O emissions from phaeozem rice field and their mitigative measures].

Determinations on the CH4 and N2O emissions from phaeozem rice field showed that their emission amount in rice growing season was much lower than any other regions in China. There was trade-off relationship between CH4 and N2O emissions(r = -0.513, P < 0.05). Under the same fertilization, compared with continual irrigation, intermittent irrigation could reduce significantly CH4 emission and increase N2O emission, but the overall warming potential of greenhouse effect was reduced greatly, while rice yield was not affected. Therefore, intermittent irrigation was an effective irrigation measures to reduce greenhouse gas emissions from rice field. In addition, investigations on CH4 and N2O emissions and their related microbial process showed a positive relation between methanogens number and CH4 emission(R2 = 0.82, P < 0.05), and the important relationship between the numbers of nitrifiers and denitrifiers and N2O emissions.

Biodegradation, Environmental↗
PubMed2003

[Relationship between CH4 and N2O emissions and related microorganism populations in paddy soils under different water management regimes].

Methanogens, methanotrophs, nitrifiers and denitrifiers are the important microorganisms in the production and consumption of CH4 and N2O in soil. In order to understand the microbial processes related to the two greenhouse gases in paddy soil, the four bacteria groups in phaeozem (Hailun) and burozem (Shenyang) were surveyed during rice growth season by using MPN counting technique. The CH4 and N2O emissions were measured with closed chamber method. Two different water management regimes, i.e., continual irrigation and intermittent irrigation, were used for the two paddy soils. The results of multiple regression analysis showed that there was a significantly positive correlation between CH4 emission and methanogen population in both phaeozem and burozem under two water management regimes. In the soil of Shenyang, there was a significantly positive correlation between CH4 emission and methanotropli population. The N2O emission was significantly correlated to the denitrifier population in both phaeozem and burozem under intermittent irrigation, and in the soil of Shenyang, there was a significantly positive correlation between N2O emission and nitrifier population under two water managements.

Methane↗