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Biomedical subjects

W Tang

Publications and source records attributed to W Tang.

At least 37 records · Page 2Linked to original sources
PubMed2003

Genetic transformation of conifers and its application in forest biotechnology.

Genetic modification of conifers through gene transfer technology is now an important field in forest biotechnology. Two basic methodologies, particle bombardment and Agrobacterium-mediated transformation, have been used on conifers. The use of particle bombardment has produced stable transgenic plants in Picea abies, P. glauca, P. mariana, and Pinus radiata. Transgenic plants have been produced from Larix decidua, Picea abies, P. glauca, P. mariana, Pinus strobus, P. taeda, and P. radiata via Agrobacterium-mediated transformation. Agrobacterium-mediated transformation has advantages over particle bombardment such as a simpler integration pattern and a limited rearrangement in the introduced DNA. At present, genetic transformation of conifers has been directed toward improving growth rate, wood properties and quality, pest resistance, stress tolerance, and herbicide resistance, which will drive forestry to enter a new era of productivity and quality.

Agrobacterium tumefaciens↗
PubMed2003

Association of histochemical expression of Maackia amurensis leukoagglutinin-positive glycoconjugates with behaviour of human gastric cancer.

AIMS: To investigate the relationship between sialylation of glycoconjugates and clinicopathological characteristics of gastric cancer. METHODS AND RESULTS: Sialylation of glycoconjugates was examined histochemically in 71 gastric cancers using Maackia amurensis leukoagglutinin (MAL), a lectin that recognizes the trisaccharide sequence NeuAc alpha 2,3Gal beta 1,4GlcNAc/Glc. Positive staining with MAL was observed in the tumour region of all of the samples, but the populations of MAL-positive tumour cells in the tumour region varied among the samples. In the corresponding non-cancerous regions, however, no positive staining was observed. Calculating the percentage of MAL-positive tumour cells as part of the total tumour cells with respect to the MAL-staining index (MI) allowed the gastric cancer to be classified into two distinct groups: high and low levels of MI, with a cut-off level of 40% of MI. Furthermore, statistical analyses using the MI level and clinicopathological characteristics of the tumour indicated that a high MI level in gastric tumour tissues is related to a poorer prognosis. CONCLUSIONS: The appearance of MAL-positive glycoconjugates in gastric tumour cells is associated with the behaviour of gastric cancer.

Adult↗
PubMed2003

Amino acid conjugates: metabolites of 2-propylpentanoic acid (valproic acid) in epileptic patients.

In this study, spectroscopic and chromatographic evidence is presented for the identification and characterization of the metabolites, valproyl glutamate (2-propylpentanoyl glutamate, VPA-GLU) and valproyl glutamine (2-propylpentanoyl glutamine, VPA-GLN) in the urine, serum, and cerebrospinal fluid (CSF) of patients on valproic acid (VPA) therapy. Moreover, the identification of valproyl glycine (2-propylpentanoyl glycine, VPA-GLY) in the serum and urine of patients on VPA, albeit in trace concentrations, is also reported here. The three amino acid conjugates excreted in urine accounted for about 1% of the VPA dose in four patients who were on VPA therapy chronically and had reached steady state. VPA-GLU was quantitatively the most prominent metabolite (0.66-13.1 microg/mg creatinine) compared with VPA-GLN (0.78-9.93 microg/mg creatinine) and VPA-GLY (trace-1.0 microg/mg creatinine) in overnight urine samples of all patients studied (n = 29). The relatively low serum concentrations of the three amino acid conjugates of VPA in six patients suggest that the metabolites are readily excreted once formed. In contrast, whereas VPA GLY was absent in the CSF of one patient on VPA, the concentrations of VPA-GLU and VPA-GLN in this CSF sample were 9 and 5 times, respectively, their corresponding serum concentrations.

Adolescent↗
PubMed2002

Additional virulence genes and sonication enhance Agrobacterium tumefaciens-mediated loblolly pine transformation.

Additional virulence (vir) genes in Agrobacterium tumefaciens and sonication were investigated for their impact on transformation efficiency in loblolly pine (Pinus taeda L.). Mature zygotic embryos of loblolly pine were co-cultivated with disarmed A. tumefaciens strain EHA105 containing either plasmid vector pCAMBIA1301 or vector pCAMBIA1301 with an additional 15.8-kb fragment carrying extra copies of the Vir B, Vir C, and Vir G regions from the supervirulent plasmid pTOK47. pCAMBIA1301 contains hygromycin resistance and the beta-glucuronidase (GUS) reporter gene. Expression of GUS was observed after 3-6 days of co-cultivation, with peak expression at approximately 21 days. The highest numbers of GUS-expressing areas were visible up to 21 days after co-cultivation, declining rapidly thereafter. Both transient and stable transformation efficiencies increased when the explants were sonicated before co-cultivation and/or the additional virB, virC, and virG genes were included with the pCAMBIA1301 plasmid T-DNA. Use of the plasmid with additional vir genes and sonication dramatically enhanced the efficiency of Agrobacterium-mediated gene transfer not only in transient expression but also in the recovery of hygromycin-resistant lines. Stably transformed cultures and transgenic plants were produced from embryos transformed with A. tumefaciens EHA105 carrying pCAMBIA1301 or pCAMBIA1301+pTOK47 in the three families of loblolly pine. The presence of the introduced GUS and hygromycin phosphotransferase genes in the transgenic plants was confirmed by polymerase chain reaction and Southern hybridization analyses.

Agrobacterium tumefaciens↗
PubMed2001

Zinc fingers and thiol-disulfide oxidoreductase activities of chaperone DnaJ.

Chaperone DnaJ is a homodimer with each subunit containing 10 cysteine residues and two Zn(II) ions, which have been identified to form two zinc fingers, C(144)DVC(147)Zn(II)C(197)NKC(200) (Zn1) and C(161)PTC(164)Zn(II)C(183)PHC(186) (Zn2), with C(265) and C(323) in reduced form. Guanidine hydrochloride at 6.4 M destroys only Zn1, which does not reform after refolding. p-Hydroxymercuriphenylsulfonate acid, but not ethylenediaminetetraacetic acid (EDTA) even at high concentrations, can remove two Zn(II) ions from DnaJ, but only Zn2 can be reconstituted. After removal of Zn(II) ions, only C(144) and C(147) in Zn1 are oxidation-resistant, and the other six cysteines are easily oxidizable. DnaJ shows reductase activity and oxidase activity but little, if any, isomerase activity. The reductase activity is reversibly inhibited by EDTA. Zn2 is important for the enzymatic activity, and only -C(183)PHC(186)- among the four motifs of -CXXC- functions as the active site of the enzyme. A C-terminal (Q(181)-R(376)) fragment shows a zinc finger of C(183)PHC(186)Zn(II)C(197)NKC(200) and full enzymatic activity of DnaJ. The N-terminal half sequence (M(1)-Q(180)) and Zn1 are not required for the enzymatic activity but are important for the chaperone activity of DnaJ.

Aprotinin↗
PubMed2001

A comparison of myocardial function after primary cardiac and primary asphyxial cardiac arrest.

Although myocardial dysfunction after resuscitation from ventricular fibrillation (VF) has been extensively investigated, less is known of the function of the myocardium after asphyxial cardiac arrest. The present experimental study was designed to compare postresuscitation left ventricular (LV) function after cardiac arrest caused by asphyxia with that of cardiac arrest induced by dysrhythmia. Four groups of Sprague-Dawley rats, which included eight animals in each group, were investigated. In the first two groups, cardiac arrest followed asphyxia produced by neuromuscular blockade with and without airway obstruction. In a third group, cardiac arrest was induced by electrical fibrillation of the ventricle. The fourth group represented animals in which the duration of asphyxial cardiac arrest was maintained for a time interval corresponding to that of the VF group. The fourth group received approximately the same number of electrical shocks as the third (VF) group. All animals were successfully resuscitated with precordial compression and mechanical ventilation. Postresuscitation measurements, including cardiac output, LV end-diastolic pressure (LVEDP), rate of pressure rise at LV pressure of 40 mm Hg (LV dP/dt40), and negative LV dP/dt, demonstrated decreased myocardial function in each group. No differences in cardiac function were observed between the animals with primary respiratory arrest whether or not the airway was obstructed. However, disproportionate and consistently greater impairment in myocardial function followed primary cardiac arrest due to VF when compared with equal duration of asphyxial cardiac arrest. We conclude that in this healthy animal model, asphyxial cardiac arrest resulted in significantly lesser impairment of postresuscitation myocardial function when compared with cardiac arrest caused by VF.

Animals↗
PubMed2001

Requirement of ceramide for adhesion of Helicobacter pylori to glycosphingolipids.

Direct adhesion of Helicobacter pylori to immobilized glycosphingolipids (GSLs) was compared to that of their corresponding oligosaccharide-conjugated neoglycoconjugates in order to clarify the roles of the carbohydrate and lipid portions of GSLs in H. pylori adhesion. These bacteria were found to adhere to sulfatide, GM3, GalCer and LacCer, but not to ceramide, sphingomyelin, or polyacrylamides conjugated with beta-galactose, lactose, 3'-sialyllactose or 3'-sulfo-beta-galactose. Furthermore, neoglycolipids or bovine serum albumin derivatives with corresponding oligosaccharides were unable to serve as the ligands. H. pylori adhesion to GalCer with alpha-hydroxyl fatty acid was much stronger than GalCer with the non-hydroxyl fatty acid. These results suggest that H. pylori recognize the conformation of GSL with alpha-hydroxyl fatty acid on solid phase.

Bacterial Adhesion↗
PubMed2001

Induction of immune responses and safety profiles in rhesus macaques immunized with a DNA vaccine expressing human prostate specific antigen.

Prostate specific antigen (PSA) is a widely used marker for prostate cancer, which is secreted by normal prostate cells at low levels, but is produced more substantially by cancer cells. We have previously reported on the use of a DNA vaccine construct that encodes for human PSA gene to elicit host immune responses against cells producing PSA. DNA immunization strategy delivers DNA constructs encoding for a specific immunogen into the host, who becomes the in vivo protein source for the production of antigen. This antigen then is the focus of the resulting immune response. In this study, we examine the induction of immune responses and safety profiles in rhesus macaques immunized with DNA-based PSA vaccine. We observed induction of PSA-specific humoral response as well as positive PSA-specific lymphoproliferative (LPA) response in the vaccinated macaques. We also observed that the stimulated T cells from the PSA-immunized rhesus macaques produced higher levels of Th1 type cytokine IFN-gamma than the control vector immunized animals. On the other hand, DNA immunization did not result in any adverse effects in the immunized macaques, as indicated by complete blood counts, leukocyte differentials and hepatic and renal chemistries. The macaques appeared healthy, without any physical signs of toxicity throughout the observation period. In addition, we did not observe any adverse effect on the vaccination site. The apparent safety and immunogenecity of DNA immunization in this study suggest that further evaluation of this vaccination strategy is warranted.

Animals↗
PubMed2001

Renal cortical mitochondrial dysfunction upon cadmium metallothionein administration to Sprague-Dawley rats.

A bolus dose of cadmium metallothionein (CdMT) produces renal proximal tubular dysfunction because it accumulates in the tubular epithelial cells and undergoes rapid degradation, releasing Cd. Morphologically, mitochondria appear to be the target organelle. The present study examined changes in renal cortical mitochondrial function following CdMT administration and investigated whether some of these effects could be ascribed to Cd2+ accumulation in the mitochondria. Sprague-Dawley rats were injected ip with 0.3 mg Cd as CdMT/kg and the animals were sacrificed after 6, 8, or 12 h. Two- to threefold increases in urinary protein excretion and LDH activity were evident at 8 h, with marked elevations (11- and 29-fold) thereafter. Renal cortical mitochondria were swollen and rounded at 12 h. The mitochondrial Cd level was 399 pmol/mg protein at 6 h and did not change significantly during the next 6 h; however, mitochondrial respiratory function declined with time. At 12 h, state 3 oxygen consumption, respiratory control ratio (RCR), and ADP:O (P/O) ratio were 48, 49, and 76% of control values, respectively, indicating inhibition of electron transfer and oxidative phosphorylation. The direct effect of Cd on mitochondrial function was examined by incubating mitochondria from untreated rats with 0.1-2 microM CdCl2. Rapid uptake of Cd resulted in concentration-dependent effects on respiration. After 1 min of incubation with 2 microM Cd, the mitochondria contained 262 microgCd/mg protein and state 3 respiration and RCR values were 75 and 33% of control levels, respectively. Thus, renal proximal tubular cell damage following a bolus dose of CdMT involves perturbations in mitochondrial respiration, brought on by the accumulation of Cd.

Analysis of Variance↗
PubMed2001

Critical sites for the interaction between IL-2Rgamma and JAK3 and the following signaling.

JAK3 is the only known protein tyrosine kinase associating with IL-2Rgamma. This interaction is supposed to be very important to IL-2 signaling. In order to identify the critical residues for these two molecular interactions and the following signal events, various mutants of gammac and JAK3 were constructed on the basis of computer analysis. The direct interaction was determined via the yeast two-hybrid system, while the signaling was analyzed with reporter genes under the control of the c-fos, c-myc, or tnf-beta promoters, respectively. Results showed that there are two key sites on gammac involved in this interaction and the following signal transduction: the critical one is E327 via electrostatic interaction, the other is L293 via hydrophobic interaction. As to JAK3, the data indicated that Y100 is important for the interaction with gammac. These results also document that the requirement for interaction between gammac and JAK3 is different to activate different signaling pathways mediated by gammac, such as c-fos, c-myc, and JAK-STAT.

Animals↗
PubMed2001

Carboxy ester hydrolysis promoted by a zinc(II) 2-[bis(2-aminomethyl)amino]ethanol complex: a new model for indirect activation on the serine nucleophile by zinc(II) in zinc enzymes.

A complexation study on the new Zn(II) complexes of asymmetric tripodal ligand 2-[bis(2-aminoethyl)amino]ethanol (L) has revealed that the alcoholic OH group of complex ZnL exhibits remarkable acidity with a very low pK(a) value of 7.7 at 25 degrees C. Both the monomeric complex [ZnH(-0.25)L(H(2)O)](ClO(4))(1.75) (I) and the dimeric alkoxide-coordinating complex [Zn(2)(H(-1)L)(2)](ClO(4))(2) (II) were synthesized, and their structures were determined by X-ray diffraction. The Zn(II)-bound alkoxide, as the reactive nucleophile toward the hydrolysis of esters, has shown a second-order rate constant of 0.13 +/- 0.01 M(-1) s(-1) in 10% (v/v) CH(3)CN at 25 degrees C in 4-nitrophenyl acetate (NA) hydrolysis, which is almost the same as the corresponding value for the very reactive alcohol-dependent [12]aneN(3)-Zn complex. Present work shows for the first time that Zn(II) complexes of the asymmetric tripodal polyamine bearing an ethoxyl pod can also serve as good models of Zn(II)-containing enzymes.

Chelating Agents↗
PubMed2001

Characterization and cloning of a Tenebrio molitor hemolymph protein with sequence similarity to insect odorant-binding proteins.

The yellow mealworm beetle, Tenebrio molitor, produces a number of moderately abundant low molecular weight hemolymph proteins ( approximately 12 kDa) which behave in a similar manner during purification and share antigenic epitopes. The cDNA sequence of the major component (THP12) was determined and the deduced protein sequence was found to be similar to those of insect odorant-binding proteins. Southern blot analysis suggests that at least some of the diversity in this family of proteins is encoded at the gene level. Both northern and western blot analysis indicate that THP12 is present in a variety of developmental stages and both sexes. THP12 was originally classified as an antifreeze protein, but the lack of antifreeze activity in the recombinant protein, as well as the clear separation of the antifreeze activity from THP12 following HPLC purification, has ruled out this function. The abundance of THP12, the similarity of THP12 to insect odorant-binding proteins, and the presence of hydrophobic cavities inside the protein (Rothemund et al., A new class of hexahelical insect proteins revealed as putative carriers of small hydrophobic ligands. Structure, 7 (1999) 1325-1332.) suggest that THP12 may function to carry non-water soluble compounds in the hemolymph. THP12 is also similar, particularly in structurally important regions, to other insect proteins from non-sensory tissues, suggesting the existence of a large family of carrier proteins which may perform diverse functions throughout the insect.

Amino Acid Sequence↗
PubMed2001

Diacylglycerol kinase epsilon regulates seizure susceptibility and long-term potentiation through arachidonoyl- inositol lipid signaling.

Arachidonoyldiacylglycerol (20:4-DAG) is a second messenger derived from phosphatidylinositol 4,5-bisphosphate and generated by stimulation of glutamate metabotropic receptors linked to G proteins and activation of phospholipase C. 20:4-DAG signaling is terminated by its phosphorylation to phosphatidic acid, catalyzed by diacylglycerol kinase (DGK). We have cloned the murine DGKepsilon gene that showed, when expressed in COS-7 cells, selectivity for 20:4-DAG. The significance of DGKepsilon in synaptic function was investigated in mice with targeted disruption of the DGKepsilon. DGKepsilon(-/-) mice showed a higher resistance to electroconvulsive shock with shorter tonic seizures and faster recovery than DGKepsilon(+/+) mice. The phosphatidylinositol 4,5-bisphosphate-signaling pathway in cerebral cortex was greatly affected, leading to lower accumulation of 20:4-DAG and free 20:4. Also, long-term potentiation was attenuated in perforant path-dentate granular cell synapses. We propose that DGKepsilon contributes to modulate neuronal signaling pathways linked to synaptic activity, neuronal plasticity, and epileptogenesis.

Animals↗
PubMed2001

alpha-Methylnorepinephrine, a selective alpha2-adrenergic agonist for cardiac resuscitation.

OBJECTIVES: The purpose of this study was to investigate the effects of a selective alpha2-adrenergic agonist, alpha-methylnorepinephrine (alphaMNE) as an alternative vasopressor agent during cardiopulmonary resuscitation (CPR). BACKGROUND: For more than 40 years, epinephrine has been the vasopressor agent of choice for CPR. Its beta- and alpha1-adrenergic effects increase myocardial oxygen consumption, magnify global myocardial ischemia and increase the severity of postresuscitation myocardial dysfunction. METHODS: Ventricular fibrillation (VF) was induced in 20 Sprague-Dawley rats. After 8 min of untreated VF, mechanical ventilation and precordial compression began. AlphaMNE, epinephrine or saline placebo was injected into the right atrium 2 min after the start of precordial compression. As an additional control, one group of animals was pretreated with alpha2-receptor blocker, yohimbine, before injection of alphaMNE. Defibrillation was attempted 4 min later. Left ventricular pressure, dP/dt40, negative dP/dt and cardiac index were measured for an interval of 240 min after resuscitation. RESULTS: Except for saline placebo and yohimbine-treated animals, comparable increases in coronary perfusion pressure were observed after each drug intervention. All animals were successfully resuscitated. Left ventricular diastolic pressure, cardiac index, dP/dt40 and negative dP/dt were more optimal after alphaMNE; this was associated with significantly better postresuscitation survival. Pretreatment with vohimbine abolished the beneficial effects of alphaMNE. CONCLUSIONS: The selective alpha2-adrenergic agonist, alphaMNE, was as effective as epinephrine for initial cardiac resuscitation but provided strikingly better postresuscitation myocardial function and survival.

Adrenergic alpha-Antagonists↗