Biomedical subjects

G Wu

Publications and source records attributed to G Wu.

At least 199 records · Page 11Linked to original sources

PubMed2000

The experimental charge-density approach in the evaluation of intermolecular interactions. Application of a new module of the XD programming package to several solids including a pentapeptide.

A new module interfaced to the XD programming package has been used in the evaluation of intermolecular interactions and lattice energies of the crystals of p-nitroaniline, L-asparagine monohydrate and the pentapeptide Boc-Gln-D-Iva-Hyp-Ala-Phol (Boc = butoxycarbonyl, Iva = isovaline = ethylalanine, Phol = phenylalaninol). The electrostatic interactions are evaluated with the atom-centered distributed multipoles from KRMM (kappa'-restricted multipole model) refinements, using the Buckingham expression for non-overlapping charge densities. Results for p-nitroaniline are compared with Hartree-Fock (HF), density functional (DFT) and Moller-Plesset (MP2) supermolecular calculations and with HF and DFT periodic calculations. The HF and DFT methods fail to predict the stability of the p-nitroaniline crystal but the results of the experimental charge-density approach (ECDA) are in good agreement with both MP2 interaction energies and the experimental lattice energy. ECDA results for L-asparagine monohydrate compare well with those from DFT supermolecular and periodic HF calculations. The disorder of the terminal group in the pentapeptide, which persists at the experimental temperature of 20 K, corresponds to an energy difference of only 0.35 kJ mol(-1), which is too small to be reproduced with current methods.

Aniline Compounds↗

PubMed2000

Diffusion-convection equation solved in parallel regions of the lung.

The single path model of airway gas transport was incorporated into each of Cruz (Cruz, J. C. Respir. Physiol. 86:1-14, 1991). Thus, the effect of time on the predicted gas fractions in and out of the lung could be evaluated. Two experimental maneuvers were simulated: (1) fast inhalation of an argon-oxygen mixture from a functional residual capacity and fast exhalation to residual volume, including inspiratory breath holdings of 5-20 s, and (2) the standard single-breath nitrogen washout test. Expired argon and nitrogen are predicted within a +3% error of the experimental data with no breath holding. Breath holding predictions were at variance with experimental results because the solution of the diffusion-convection equation produced even mixing in the alveoli at the end of inspiration. The minimum square of the difference between the experimental data (standard single-breath nitrogen washout test) and those provided by the model was 0.0016. This model is capable of generating a nitrogen expirogram with four phases when a vital capacity of oxygen is inhaled. However, the model failed to produce a sharp distinction between phase 3 and phase 4. Thus, we conclude that uneven emptying of parallel regions generates any expirogram (a fast or slow expiratory maneuver). The alveolar gas stratification that is created during inspiration disappears at the end of the inspiratory maneuver. As a result, breath holding maneuvers cannot be predicted in the anatomical model used.

Biomedical Engineering↗

PubMed2000

Isoproterenol and cAMP regulation of the human brain natriuretic peptide gene involves Src and Rac.

Brain natriuretic peptide (BNP) gene expression and chronic activation of the sympathetic nervous system are characteristics of the development of heart failure. We studied the role of the beta-adrenergic signaling pathway in regulation of the human BNP (hBNP) promoter. An hBNP promoter (-1818 to +100) coupled to a luciferase reporter gene was transferred into neonatal cardiac myocytes, and luciferase activity was measured as an index of promoter activity. Isoproterenol (ISO), forskolin, and cAMP stimulated the promoter, and the beta(2)-antagonist ICI 118,551 abrogated the effect of ISO. In contrast, the protein kinase A (PKA) inhibitor H-89 failed to block the action of cAMP and ISO. Pertussis toxin (PT), which inactivates Galpha(i), inhibited ISO- and cAMP-stimulated hBNP promoter activity. The Src tyrosine kinase inhibitor PP1 and a dominant-negative mutant of the small G protein Rac also abolished the effect of ISO and cAMP. Finally, we studied the involvement of M-CAT-like binding sites in basal and inducible regulation of the hBNP promoter. Mutation of these elements decreased basal and cAMP-induced activity. These data suggest that beta-adrenergic regulation of hBNP is PKA independent, involves a Galpha(i)-activated pathway, and targets regulatory elements in the proximal BNP promoter.

Adrenergic beta-Agonists↗

PubMed2000

Enhanced intestinal synthesis of polyamines from proline in cortisol-treated piglets.

This study was conducted to determine a role for cortisol in regulating intestinal ornithine decarboxylase (ODC) activity and to identify the metabolic sources of ornithine for intestinal polyamine synthesis in suckling pigs. Thirty-two 21-day-old suckling pigs were randomly assigned to one of four groups with eight animals each and received daily intramuscular injections of vehicle solution (sesame oil; control), hydrocortisone 21-acetate (HYD; 25 mg/kg body wt), RU-486 (10 mg/kg body wt, a potent blocker of glucocorticoid receptors), or HYD plus RU-486 for two consecutive days. At 29 days of age, pigs were killed for preparation of jejunal enterocytes. The cytosolic fraction was prepared for determining ODC activity. For metabolic studies, enterocytes were incubated for 45 min at 37 degrees C in 2 ml of Krebs-bicarbonate buffer (pH 7.4) containing 1 mM [U-(14)C]arginine, 1 mM [U-(14)C]ornithine, 1 mM [U-(14)C]glutamine, or 1 mM [U-(14)C]proline plus 1 mM glutamine. Cortisol administration increased intestinal ODC activity by 230%, polyamine (putrescine, spermidine, and spermine) synthesis from ornithine and proline by 75-180%, and intracellular polyamine concentrations by 45-83%. Polyamine synthesis from arginine was not detected in enterocytes of control pigs but was induced in cells of cortisol-treated pigs. There was no detectable synthesis of polyamines from glutamine in enterocytes of all groups of pigs. The stimulating effects of cortisol on intestinal ODC activity and polyamine synthesis were abolished by coadministration of RU-486. Our data indicate that an increase in plasma cortisol concentrations stimulates intestinal polyamine synthesis via a glucocorticoid receptor-mediated mechanism and that proline (an abundant amino acid in milk) is a major source of ornithine for intestinal polyamine synthesis in suckling neonates.

Animals↗

PubMed2000

A cortisol surge mediates the enhanced polyamine synthesis in porcine enterocytes during weaning.

This study was conducted to determine whether a cortisol surge mediates the enhanced expression of intestinal ornithine decarboxylase (ODC) in weanling pigs. Piglets were nursed by sows until 21 days of age, when 40 pigs were randomly assigned into one of four groups (10 animals/group). Group 1 continued to be fed by sows, whereas groups 2-4 were weaned to a corn and soybean meal-based diet. Weanling pigs received intramuscular injections of vehicle solvent (sesame oil), RU-486 (a potent blocker of glucocorticoid receptors; 10 mg/kg body wt), and metyrapone (an inhibitor of adrenal cortisol synthesis; 5 mg/kg body wt), respectively, 5 min before weaning and 24 and 72 h later. At 29 days of age, pigs were used to prepare jejunal enterocytes for ODC assay and metabolic studies. To determine polyamine (putrescine, spermidine, and spermine) synthesis, enterocytes were incubated for 45 min at 37 degrees C in 2 ml Krebs-bicarbonate buffer containing 1 mM [U-(14)C]arginine, 1 mM [U-(14)C]ornithine, 1 mM [U-(14)C]glutamine, or 1 mM [U-(14)C]proline plus 1 mM glutamine. Weaning increased intestinal ODC activity by 230% and polyamine synthesis from ornithine, arginine, and proline by 72-157%. Arginine was a quantitatively more important substrate than proline for intestinal polyamine synthesis in weaned pigs. Administration of RU-486 or metyrapone to weanling pigs prevented the increases in intestinal ODC activity and polyamine synthesis, reduced intracellular polyamine concentrations, and decreased villus heights and intestinal growth. Our results demonstrate an essential role for a cortisol surge in enhancing intestinal polyamine synthesis during weaning, which may be of physiological importance for intestinal adaptation and remodeling.

Animals↗

PubMed2000

Arginase I: a limiting factor for nitric oxide and polyamine synthesis by activated macrophages?

Because arginase hydrolyzes arginine to produce ornithine and urea, it has the potential to regulate nitric oxide (NO) and polyamine synthesis. We tested whether expression of the cytosolic isoform of arginase (arginase I) was limiting for NO or polyamine production by activated RAW 264.7 macrophage cells. RAW 264.7 cells, stably transfected to overexpress arginase I or beta-galactosidase, were treated with interferon-gamma to induce type 2 NO synthase or with lipopolysaccharide or 8-bromo-cAMP (8-BrcAMP) to induce ornithine decarboxylase. Overexpression of arginase I had no effect on NO synthesis. In contrast, cells overexpressing arginase I produced twice as much putrescine after activation than did cells expressing beta-galactosidase. Cells overexpressing arginase I also produced more spermidine after treatment with 8-BrcAMP than did cells expressing beta-galactosidase. Thus endogenous levels of arginase I are limiting for polyamine synthesis, but not for NO synthesis, by activated macrophage cells. This study also demonstrates that it is possible to alter arginase I levels sufficiently to affect polyamine synthesis without affecting induced NO synthesis.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed2000

Frequency and Markov chain analysis of amino acid sequences of mouse p53.

The amino acid sequence of mouse p53 was measured according to two- and three-amino-acid sequences. The measured frequency and probability were compared with predicted frequency and probability. Of 389 two-amino-acid sequences in mouse p53,85 (21.851%) and 27 (6.941%) sequences can be explained by the predicted frequency and probability according to a purelyrandom mechanism. Of 188 non-appearing two-amino-acid sequences in mouse p53, 86 (45.745%) and 32 (17.021%) can be explained by the predicted frequency and probability according to a purely random mechanism; no more than two-amino-acid sequences in mouse p53 can be explained by a purely random mechanism.

Amino Acid Sequence↗

PubMed2000

Infection by bacterial pathogens expressing type III secretion decreases luciferase activity: ramifications for reporter gene studies.

Pathogenic microbes influence gene regulation in eukaryotic hosts. Reporter gene studies can define the roles of promoter regulatory sequences. The effect of pathogenic bacteria on reporter genes has not been examined. The aim of this study was to identify which reporter genes are reliable in studies concerning host gene regulation by bacterial pathogens expressing type III secretory systems. Human intestinal epithelial cells, T84, Caco-2 and HT-29, were transfected with plasmids containing luciferase (luc), chloramphenicol acetyltransferase (CAT) or beta-galactosidase (beta-gal) as reporter genes driven by the inducible interleukin-8 (IL-8) or constitutively active simian virus 40 (SV40) promoter. Cells were infected with enteropathogenic E. coli or Salmonella typhimurium, and the reporter activity was assessed. Luc activity significantly decreased following infection, regardless of the promoter. The activity of recombinant luc was nearly ablated by incubation with either EPEC or Salmonella in a cell-free system. Activity was partially preserved by protease inhibitors, and immunoblot analysis showed a decreased amount and molecular weight of recombinant luc, suggesting protein degradation. Neither beta-gal nor CAT activity was altered by infection. Disruption of type III secretion prevented the loss of luc activity. We conclude that CAT or beta-gal, but not luc, can be used as reliable reporter genes to assess the impact of pathogenic microbes, especially those expressing type III secretion on host cell gene regulation.

Cell Line↗

PubMed2000

Postnatal changes of plasma amino acids in suckling pigs.

Amino acids, ammonia, urea, orotate, and nitrate plus nitrite (stable oxidation products of nitric oxide) were determined in plasma of 1- to 21-d-old suckling pigs. Jugular venous blood samples were obtained from pigs at 1, 3, 7, 14, and 21 d of age for analysis of plasma amino acids and metabolites by HPLC and enzymatic methods. Plasma concentrations of arginine and its immediate precursors (citrulline and ornithine) decreased (P < 0.01) progressively (20 to 41%) with increasing age from 3 to 14 d. Plasma concentrations of glutamine declined (P < 0.01) progressively (10 to 31%) during the 1st wk of life. Plasma concentrations of branched-chain amino acids, threonine, and alanine decreased (P < 0.01) (5 to 12%) in 14- and 21-d-old pigs, compared with 1- and 3-d-old pigs. There were no postnatal changes (P > 0.05) in plasma concentrations of other amino acids. Plasma concentrations of ammonia increased (P < 0.01) by 18 and 46%, whereas those of nitrate plus nitrite decreased (P < 0.01) by 16 and 29%, in 7- and 14-d-old pigs, respectively, compared with 1- to 3-d-old pigs. Because arginine plays a crucial role in ammonia detoxification via the hepatic urea cycle and is the physiological substrate for nitric oxide synthesis, our results of the decreased plasma concentrations of arginine and nitrate plus nitrite, as well as the increased plasma ammonia concentration, indicate a hitherto unrecognized deficiency of arginine in 7- to 21-d-old suckling pigs. Arginine is an essential amino acid for piglets and has a great potential to enhance neonatal growth; therefore, further studies are necessary to elucidate the mechanism responsible for arginine deficiency in sow-reared piglets and to identify hormonal and metabolic means for improving neonatal arginine nutrition and growth.

Amino Acids↗

PubMed2000

Regulation of glial cell line-derived neurotrophic factor expression by electroacupuncture after transient focal cerebral ischemia.

The present study was designed to investigate whether electroacupuncture (EA) is able to regulate glial cell line-derived neurotrophic factor (GDNF) expression following transient middle cerebral artery occlusion (MCAO) using reverse transcriptase polymerase chain reaction and immunohistochemistry in rats. The results indicate that after 2 h MCAO, GDNF mRNA and immunoreactivity profoundly increased in peri-infarct cerebral cortex, with peaks at 2 h after reperfusion, then declined dramatically at 12 and 24 h after reperfusion. Although EA given immediatelly after MCAO couldn't elevate the peaks of GDNF expression, it obviously raised the GDNF mRNA and immunoreactivity levels at 12 h after reperfusion, delayed the declining trends of GDNF mRNA and immunoreactivity levels. These results suggest that EA could upregulate GDNF expression after ischemic insult, elongating the duration of upregulated GDNF expression. This may be one of the mechanisms of EA anti-ischemic injury by augmenting endogenous protective mechanism.

Animals↗

PubMed2000

Mechanisms of impaired beta-adrenergic receptor signaling in G(alphaq)-mediated cardiac hypertrophy and ventricular dysfunction.

Targeted cardiac overexpression of the alpha-subunit of the heterotrimeric G protein G(q) in transgenic mice evokes hypertrophy and depressed stimulation of cardiac inotropy and chronotropy by beta-adrenergic receptor (betaAR) agonists in vivo, which is a hallmark of many forms of experimental and human heart failure. The molecular basis of this betaAR dysfunction was explored in transgenic mice overexpressing G(alphaq) approximately 5-fold over background. Isoproterenol-stimulated adenylyl cyclase activities in myocardial membranes were significantly depressed in G(alphaq) mice compared with nontransgenic controls (19.7 +/- 2.6 versus 43.7 +/- 5. 6 pmol/min/mg) without a decrease in betaAR expression levels. Functional coupling of both betaAR subtypes was impaired. Similarly, in whole-cell patch-clamp studies, betaAR stimulation of L-type Ca(2+) channel currents was depressed approximately 75% in the G(alphaq) mice. Cardiac betaAR from these mice showed decreased formation of the active high-affinity conformation (R(H) = 29% versus 62% for nontransgenic littermates), confirming a receptor-G(s)-coupling defect. Of the three candidate kinases that might impose this uncoupling by receptor phosphorylation (protein kinase A, betaAR kinase, protein kinase C), only protein kinase C activity was elevated in G(alphaq) mouse hearts. Type V adenylyl cyclase was decreased approximately 45% in these mice, consistent with decreased basal, NaF, and forskolin-stimulated enzyme activities. Although cellular G(s) levels were unaltered, G(i2) and G(i3) were increased in G(alphaq) mice. Pertussis toxin treatment of isolated G(alphaq) myocytes resulted in an improvement in betaAR, but not that of forskolin or NaF, stimulation of adenylyl cyclase. Thus three distinct mechanisms contribute to impaired betaAR function by in vivo G(q) signaling cross-talk in myocytes. Because many elements of hypertrophy and/or failure in cellular and animal models can be initiated by increased G(alphaq) signaling, the current work may be broadly applicable to interfaces whereby modification of heart failure might be considered.

Adenylyl Cyclases↗

PubMed2000

[Modification of surface of Dacron materials by UV irradiation for prevention of microbial adhesion].

UV irradiation grafting method was used to modify the surface of Prosthetic Valve materials (Dacron) for prevention of bacteria-adhesion, and PEG was introduced to the surface of Dacron by this method. The result showed that the chemical magnifying effect of PEG improved the grafting of heparin on the material surface. This method can obviously reduce the number of adherent bacteria.

Bacterial Adhesion↗

PubMed2000

[Researches on surface modification for prevention of bacterial adhesion to implanting biomaterials].

The failure of operation caused by biomaterials centered infections (BCI) has seriously restricted the clinical application of biomaterials. Two mechanisms of bacterial adhesion and the relationship between surface free energy of bimaterials and bacterial adhesion are introduced and discussed in this paper. Increasing the surface free energy can improve (decrease) the adhesion of some kinds of bacteria. At last, some methods of the surface modification are reviewed.

Bacterial Adhesion↗

PubMed2000

Prediction of two- and three-amino-acid sequences of Citrobacter Freundii beta-lactamase from its amino acid composition.

The repeated amino-acid sequences in Citrobacter Freundii beta-lactamase may be indispensable for its function, because such repetitions cannot be simply attributed to a chance. In order to fully explore the functional units in Citrobacter Freundii beta-lactamase, it may need to analyse all the amino acid pairs, triplets, etc. along Citrobacter Freundii beta-lactamase from one terminal to the other terminal, to count their frequencies and calculate their probabilities. The amino-acid sequence of Citrobacter Freundii beta-lactamase was counted according to two-, three- and four-amino-acid sequences. The counted frequency and probability were compared with the predicted frequency and probability. The amino acid sequences, which appear in Citrobacter Freundii beta-lactamase and can be predicted from its amino acid composition according to a purely random mechanism, should not be deliberately evolved and conserved. By contrast, the amino acid sequences, which appear in Citrobacter Freundii beta-lactamase but cannot be predicted from its amino acid composition according to a purely random mechanism, should be deliberately evolved and conversed. Accordingly 99 (26.053%) and 33 (8.684%) of 380 two-amino-acid sequences can be predicted by the frequency and probability according to a purely random mechanism. Some kinds of amino acid sequences, which absent in Citrobacter Freundii beta-lactamase and can be predicted from its amino acid composition according to a purely random mechanism, should not be deliberately excluded from Citrobacter Freundii beta-lactamase. By contrast, some kinds of amino acid sequences, which absent in Citrobacter Freundii beta-lactamase and cannot be predicted from its amino acid composition according to a purely random mechanism, should be deliberately excluded from Citrobacter Freundii beta-lactamase. Accordingly 89 (48.370%) and 41 (22.283%) of 184 kinds of absent two-amino-acid sequences can be predicted by the frequency and probability according to a purely random mechanism, and 7236 (99.848%) of 7247 kinds of absent three-amino-acid sequences can be predicted by the frequency according to a purely random mechanism. The amino acids, whose probabilities in following certain preceding amino acids can be predicted from Citrobacter Freundii beta-lactamase amino acid composition according to a purely random mechanism, should not be deliberately evolved and conversed, accordingly 2 (0.526%) of 380 counted first order Markov transition probabilities for the second amino acid in two-amino-acid sequences match the predicted conditional probabilities.

Citrobacter↗

PubMed2000

[Study of differential expressed genes in vascular endothelial cell line ECV304 induced by low density lipoprotein].

OBJECTIVE: To isolate and clone the differential expressed genes induced by atherogenic factors on vascular endothelium and to understand the molecular mechanism of atherosclerosis. METHODS: The differential display reverse transcription PCR method (DDRT-PCR) was used to analyze the differential expressed cDNA in ECV304 induced by low density lipoprotein (LDL). After sequencing and homology research, the differential expressed cDNA fragments were confirmed by northern blot analysis. RESULTS: Up-regulated and down-regulated cDNAs fragments were isolated in ECV304. It was found that some cDNAs fragments were highly homologous to the known human genes, while others were fragments of novel genes. The known up-regulated genes included human 10 kD protein, FGFR1 oncogene partner, intercellular adhesion molecular-1, FK506 binding protein and rTS beta genes. The known down-regulated genes included human fb19, Apobec1-binding protein 1 and RBP2. The expression levels of different genes varied by 70%-200%. CONCLUSION: By DDRT-PCR method, our results showed that LDL could change the expression of many genes in endothelial cells. The high expression level of ICAM-1 in the endothelial cells stimulated by LDL suggested that ICAM-1 is an important adhesion molecular in atherogenesis. The down-regulated expression of Apobec 1-binding protein 1 may affect the cellular synthesis of apolipoprotein. The high expression level of FGFR1 oncogene partner is likely related to the differentiation of ECV304. The function of other differential expressed genes remains to be elucidated.

Cells, Cultured↗

PubMed2000

[Application of competition index in assessing intraspecific and interspecific spatial relations between manchurian ash and dahurian larch].

The competition among trees within a stand includes aboveground and underground parts. How to determine the zone of competition influence is important for predicting tree growth. We divide the zone into two parts: one part is defined as inside radius, the distance from nearest competitors to subject tree, in which, the competition influence is the sum of both aboveground and underground; the another part is defined as outside radius, the distance of competitors to subject tree, where the competition influence comes mostly from underground. Thus, the competition index, based upon the divided two radii, could be decomposed into different components. We used the data of manchurian ash(MA) (Fraxinus mandshurica) and dahurian larch(DL) (Larix gmelini) from pure and mixed stands to analyze the competition influence of aboveground and underground in inside and of underground in outside radius. The results show that for MA in pure stand, the competition effect was 59.06% from inside radius, and 40.94% from outside radius. For DL in pure stand, the competition effects in both radii were 71.31% and 28.69%, respectively. There was a stronger competition influence in inside than in outside radius. Underground competitions were the important issues for both species in pure stands. In a mixed stand of MA and DL, there were two species in both radii, and the effects of competition came from intraspecific and interspecific competitors. For subject tree of MA, the effect of interspecific competition was 49.55%, and that of intraspecific was 50.45%. For subject tree of DL, the effects were 81.11% and 18.89%, respectively. DL displayed a stronger interspecific competition than MA in the zone of competition influence, and was a main effect of competition on MA. For subject tree of MA, the effect of competition from inside radius was 25.33%, which was the sum of competition influence from aboveground and underground, and about 74.67% was from outside radius. For subject tree of DL, both in inside and outside radii were 55.37% and 44.64%, respectively. Comparing with the information from both species and two radii, the root-root competition from underground was an important component. DL grew well, and could reduce the impact of intraspecific competition for MA when both species mixed in a stand.

Ecosystem↗

PubMed2000

[Individual tree growth-competition model in mixed plantation of manchurian ash and dahurian larch].

Based on distance-dependent competition models and neighborhood interference models, the competition index components and competition effect coefficients were used to quantify the spatial competition among trees in the mixed plantation of ash(Fraxinus mandshurica) and larch(Larix gmelini). Taking each component of competition index as independent variables and the yearly volume growth as dependent variable, the competition-growth model was established with good regression result. The study provided a new approach to deal with the further improvement of spatial competition models and the plant competition-growth relationship ecological study.

Ecosystem↗

PubMed2000

[Comparison analysis on physical and value assessment methods for ecosystems services].

Physical assessment method (PAM) and value assessment method (VAM) for ecosystems services assessment were compared, and their strengths and weaknesses were analyzed. The comparison and analysis demonstrated that in some cases, different, even opposite results will be drawn with these two methods for the ecosystems services assessment of one ecosystem. The functions or effects of PAM and VAM are different for different assessment purposes or different spatial scales, but they will promote and complement each other to some extent.

Ecosystem↗