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Biomedical subjects

T Wang

Publications and source records attributed to T Wang.

At least 109 records · Page 6Linked to original sources
PubMed2001

[The influence of load changes and ischemia on canine left ventricular diastolic blood flow].

OBJECTIVE: To find the relation between left ventricular diastolic function and left ventricular diastolic blood flow. METHODS: At control, load change and ischemic states, left ventriculer relaxation time constant (T) was measured by catheter and echocardiographic indexes were measured at dogs. Echocardiographic indexes included mitral peak flow velocity E at mitral tip level (E(0)) and at 1 cm and 2 cm below the mitral tip toward the apex (E(1) and E(2)) and the interval from ECG peak of R to the peak of velocity E (R-E(0), R-E(1), R-E(2)). RESULTS: The left ventricular diastolic blood flow decreased nonlinearly at every states, and interval indexes were independent of the changes of loads but both kinds of indexes were affected markedly by myocardial ischemia. CONCLUSION: Ischemia decreases left ventricular diastolic function and increases left ventricular diastolic blood flow attenuation.

Animals↗
PubMed2001

Stereocontrolled total synthesis of alkaloid G via the oxy-anion Cope rearrangement and improved total synthesis of (+)-ajmaline.

[figure: see text] The oxy-anion Cope rearrangement followed by protonation of the enolate which resulted under conditions of kinetic control has been employed to generate the key asymmetric centers at C(15), C(16), and C(20) in alkaloid G (1) and (+)-ajmaline (2) in a highly stereocontrolled fashion. The aldehyde 7b from this process has been converted into alkaloid G (1) and (+)-ajmaline (2) in 36% and 13% overall yields (11 reaction vessels from 3), respectively.

Ajmaline↗
PubMed2001

Interactions of the human T-cell leukemia virus type-II integrase with the conserved CA in the retroviral long terminal repeat end.

Retroviral integrases (INs) interact with termini of retroviral DNA in the conserved 5'-C(A/G)T. For most integrases, modifications of critical moieties in the major and minor grooves of these sequences decrease 3'-processing. However, for human immunodeficiency virus type-2 (HTLV-2) IN, the replacement of the guanine with 6-methylguanine or hypoxanthine not only reduced 3'-processing, but also promoted cleavage at a second site. This novel cleavage activity required an upstream ACA, unique to the HTLV-2 U5 end. 3'-Processing assays with additional isosteric modifications at Gua and filter binding experiments revealed that the mechanism of the second site cleavage differed among the major groove, minor groove, and mismatch modifications. Importantly, the decrease in 3'-processing activity noted with the minor groove and mismatch modifications were attributed to a decrease in binding. Major groove modifications, however, decreased the level of 3'-processing, but did not affect binding. This suggests that integrase binds the viral end through the minor groove, but relies on major groove contacts for 3'-processing. Several modifications were also examined in strand transfer and disintegration substrates. HTLV-2 IN showed reduced activity with strand transfer and disintegration substrates containing major groove, but not minor groove modifications. This suggests major groove interactions at guanine also provide an important role in these reactions.

Base Sequence↗
PubMed2001

Nonreplication of association between mu-opioid-receptor gene (OPRM1) A118G polymorphism and substance dependence.

In the present investigation we hypothesized the A118G (Asn40Asp) polymorphism of the mu-opioid receptor gene (OPRM1) as a particular vulnerability factor for heroin and alcohol dependence. Therefore, we tested this hypothesis in two independent large samples by two different methods: a case-control sample (comprising n = 287 heroin and n = 221 alcohol study subjects versus n = 365 nondependent controls) and a family-controlled sample of 111 parent-offspring trios of heroin-dependent study subjects and 75 parent-offspring trios of alcohol-dependent study subjects to avoid stratification artifacts. In both patient samples and by both methods we were unable to corroborate the hypothesis of OPRM1 A118G polymorphism as a particular risk factor for any kind of substance dependence including opioid addiction. In addition, there was no significant association between the endophenotype of the individuals under study (e.g., comorbidity, severity of illness) and a particular genotype of OPRM1.

Adenine↗
PubMed2001

Expression of legumin and vicilin genes in pea mutants and the production of legumin in transgenic plants.

Pea seeds contain two major storage proteins, legumin and vicilin, in proportions that are genetically and environmentally determined. They are synthesized from at least 40 genes and at least 10 different genetic loci. Mutant alleles at loci involved in starch synthesis, which result in perturbations in starch accumulation, also affect the expression of legumin genes, thereby influencing the legumin: vicilin ratio within the total seed protein. Examples of such alleles include r (starch-branching enzyme) and rb (ADP-glucose pyrophosphorylase), both of which result in a reduction in legumin synthesis; double mutants (rrb) show a particularly severe reduction in the amount of legumin. The effects of such mutations are specific to legumins. The amounts of vicilin are unaffected by mutations at r or rb. One of the consequences of the production of legumin from many genes is structural heterogeneity that is believed to preclude the purification of homogeneous legumin for crystallization and 3D-structure determination. Expression of cloned legumin cDNA in E. coli can result in sequence homogeneity, but E. coli is unable to carry out the normal proteolytic processing of legumin precursors and consequently such material is different from that produced in pea seeds. This paper describes the high-level synthesis, processing and assembly of pea legumin in transgenic wheat seeds, leading to the spontaneous in vitro formation of paracrystalline arrays of legumin, which may be attributed to the fact that the legumin consists of a single type of subunit. Such material might be used as a source of single-sequence, processed and assembled pea legumin for structural investigation.

Gene Expression Regulation, Plant↗
PubMed2001

A deletion/insertion mutation in the BRCA2 gene in a breast cancer family: a possible role of the Alu-polyA tail in the evolution of the deletion.

Patients with breast and/or ovarian cancer were screened for gross rearrangements in the BRCA2 gene by Southern hybridization, with exon 10 and a fragment of exon 11 used as probes. One breast cancer patient with a positive family history had a 6.2-kb deletion including exons 12 and 13. The deletion breakpoint in intron 11 was in the 3' polyA tail of an Alu element, where a track of approximately 60 adenine nucleotide residues was inserted. Expansion of the Alu-polyA tail may have resulted from polymerase slippage during replication, representing a novel mechanism in which Alu elements mediate deletion/insertion mutations.

Adult↗
PubMed2001

A deletion mutation in GJB6 cooperating with a GJB2 mutation in trans in non-syndromic deafness: A novel founder mutation in Ashkenazi Jews.

A deletion of at least 140 kb starting approximately 35kb upstream (telomeric) to the GJB2 (CX26) gene was identified in 7 patients from 4 unrelated Jewish Ashkenazi families with non-syndromic hearing loss. These patients were heterozygous for one of the common mutations 167delT or 35delG in the GJB2 gene in trans to the deletion. The deletion started at 5' side of the GJB6 (CX30) gene including the first exon and it did not affect the integrity of the GJB2 gene. The deletion mutation segregated together with the hearing loss, and was not found in a control group of 100 Ashkenazi individuals. We suggest that the deletion is a recessive mutation causing hearing loss in individuals that are double heterozygous for the deletion and for a mutation in the GJB2 gene. The effect of the deletion mutation could be due to a digenic mode of inheritance of GJB2 and GJB6 genes that encode two different connexins; connexin 26 and connexin 30, or it may abolish control elements that are important in the expression of the GJB2 gene in the cochlea. Regardless which of the options is valid, it is apparent that the deletion mutation provides a new insight into connexin function in the auditory system. The deletion mutation was on the same haplotypic background in all the families, and therefore is a founder mutation that increases the impact of GJB2 in the etiology of prelingual recessive non-syndromic hearing loss in the Ashkenazi population.

Alleles↗
PubMed2001

Rapid quantitative lung (1)H T(1) mapping.

In this contribution, a rapid and robust technique for quantitative T(1) mapping of the human lung is presented. Based on a series of Snapshot FLASH tomograms acquired after a single inversion pulse, high quality and quantitative T(1) parameter maps acquired in under five seconds were obtained from six healthy volunteers. The measured T(1) values are in good agreement with previously reported literature values. T(1) maps were also acquired with the volunteers breathing room air or 100% O(2). The T(1) difference between breathing room air and 100% O(2) is statistically significant at P < 0.0001.

Adult↗
PubMed2001

Mass-directed fractionation and isolation of pharmaceutical compounds by packed-column supercritical fluid chromatography/mass spectrometry.

An automated packed-column semi-preparative supercritical fluid chromatography/mass spectrometry (SFC/MS) system incorporating mass-directed fraction collection has been designed and implemented as an alternative to preparative HPLC and preparative HPLC/MS (PrepLC/MS) for the purification of pharmaceutical compounds. The system incorporates a single quadrupole mass spectrometer and a supercritical fluid chromatograph. Separations were achieved using a binary solvent system consisting of carbon dioxide and methanol. Purification of SFC-separated compounds was achieved incorporating mass-directed fraction collection, enabling selective isolation of the target molecular weight compound and eliminating the collection of undesired compounds (e.g., by-products, excess starting materials, etc.). Cross contamination between fractions and recoveries of the system were investigated. Mass spectrometer ionization with basic mobile additives is discussed, and examples of preparative SFC/MS chiral separations are presented. Early experiences suggest SFC will be a powerful and complementary technique to HPLC for the purification of pharmaceutical compounds.

Carbon Dioxide↗
PubMed2001

Cloning and expression of a putative common cytokine receptor gamma chain (gammaC) gene in rainbow trout (Oncorhynchus mykiss).

A full length cDNA of a putative common cytokine receptor gamma chain (gammaC) gene of rainbow trout (Oncorhynchus mykiss) has been cloned and sequenced. The contiguous cDNA contained 2291 nucleotides, consisting of an ORF of 1029 bp, with a 72 bp 5' UTR and a 1190 bp 3' UTR. The coding region showed 44-46% identity to mammalian gammaC genes. The ORF translated into a 343 amino acid protein, with some 28-30% amino acid identity to the coding region of mammalian sequences. A predicted signal peptide and transmembrane domain were identified, giving a 206 amino acid extracellular domain and a 98 amino acid intracellular domain in the trout molecule. Five potential glycosylation sites were present in the extracellular domain, as were six conserved cysteine residues and the W-S-X-W-S motif typical of haemopoietin receptors. One of the most interesting differences between the trout and mammalian sequences was the lack of tyrosines in the trout intracellular domain. RT-PCR studies revealed a wide tissue distribution of gammaC expression, with detectable transcript in blood, spleen, gill, kidney, brain and liver. Low levels of gammaC transcript were detectable in unstimulated macrophage cultures and expression was increased by stimulation of the cells with recombinant trout interleukin-1beta (IL-1beta) or LPS. Similarly, in the RTG cell line which exhibited even lower level constitutive expression, stimulation with IL-1beta increased gammaC transcript levels but LPS had no effect.

Amino Acid Sequence↗
PubMed2001

Src family kinase and adenosine differentially regulate multiple MAP kinases in ischemic myocardium: modulation of MAP kinases activation by ischemic preconditioning.

Recent studies suggest that ischemia activates Src and members of the mitogen-activated protein (MAP) kinase superfamily and their downstream effectors, including big MAP kinase 1 (BMK1) and p90 ribosomal S6 kinase (p90RSK). It has also been reported that adenosine is released during ischemia and involved in triggering the protective mechanism of ischemic preconditioning. To assess the roles of Src and adenosine in ischemia-induced MAP kinases activation, we utilized the Src inhibitor PP2 (4-Amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine) and the adenosine receptor antagonist 8-(p-sulfophenyl) theophylline (SPT) in perfused guinea pig hearts. PP2 (1 microm) inhibited ischemia-induced Src, BMK1 and JNK activation but not JAK2 and p38 activation. SPT inhibited ischemia-mediated p38 and JNK activation. These results demonstrate that Src family kinase and adenosine regulate MAP kinases by parallel pathways. Preconditioning significantly improved both recovery of developed pressure and dp/dt in isolated guinea pig hearts. Since the protective effect of preconditioning was blocked by PP2 (1 microm) and SPT (50 microm), we next investigated the regulation of Src, MAP kinases and p90RSK during preconditioning. The activity and time course of ERK1/2 was not changed, but p90RSK activation by reperfusion was completely inhibited by preconditioning. In contrast, the activation by ischemia of Src, BMK1, p38 and JNK was significantly faster in preconditioned hearts. Maximal BMK1 activation by ischemia was also significantly enhanced by preconditioning. These data suggest important roles for Src family kinases and adenosine in mediating preconditioning, and suggest specific roles for individual MAP kinases in preconditioning.

Adenosine↗
PubMed2001

Gene analysis of free fetal DNA in maternal plasma.

To investigate the feasibility of using free fetal DNA from maternal plasma as the source of fetal material in non-invasive prenatal diagnosis, SRY gene of free DNA in maternal blood of 65 samples were analyzed by using primer extension preamplication (PEP) and probe microplate hybridization techniques. The results showed that the detection rate of SRY gene in maternal blood from women carrying male fetuses detected by probe microplate hybridization alone and probe microplate hybridization with PEP were 76.09% (35/46) and 95.65% (44/46) respectively, and there was a significant difference between them. The non-detection rate of SRY gene in blood samples from women carrying female fetus was 100% (19/19). It is indicated that probe microplate hybridization was an effective method in detecting trace fetal DNA from maternal plasma and the sensitivity could be substantially improved by combined use of the two techniques. Analysis of fetal DNA in maternal plasma can serve as an alternative for non-invasive prenatal diagnosis.

Adult↗
PubMed2001

Effects of extracellular ATP on survival of sensory neurons in the dorsal root ganglia of rats.

ATP was added to the cultured sensory neurons obtained from the dorsal root ganglia of the neonatal rats and PBS was added to serve as control. MTT assays were conducted to evaluate the survival and activity of the cultured neurons. And the silicone regenerative chamber was used after the sciatic nerve incision of the mature SD rat. 1 mmol/L ATP was injected into the left chamber and 0.09% natrium chloride was injected into the right chamber as controls. The changes of nitric oxide synthase (NOS) activity in the corresponding dorsal root ganglia were measured histochemically and image analysis was also performed 4 days after the sciatic nerve injury. The results showed that extracellular ATP could enhance the survival of the neurons and the number of NOS positive neurons were significantly different between the ATP and control groups (P < 0.05). It was suggested that extracellular ATP had neurotrophic effect on neurons survival and could inhibit the NOS activity of the sensory neurons after the peripheral nerve incision, hence exerting the protective effect on the neurons, which was valuable for nerve regeneration after nerve injury.

Adenosine Triphosphate↗
PubMed2001

Y specific sequence gene analysis of single fetal nucleated erythroblasts from the peripheral blood of pregnant women.

The single cell isolation technique was used to detect fetal nucleated erythroblasts (FNRBCs) at a single cell level from the peripheral blood of pregnant women in order to investigate the feasibility of this method for noninvasive prenatal diagnosis. Single fetal nucleated erythroblasts were isolated from the peripheral blood samples from 51 pregnant women (14 to 26 weeks of gestation) by micromanipulation techniques after density gradient centrifugation. Nested polymerase chain reaction method was used to amplify the SRY gene. It was found that the concordance rate of amplification results with real fetal sex was 82.61%. The sensitivity and specificity were 80% and 87.50% respectively. It was suggested that it is feasible and promising in non invasive prenatal diagnosis to detect fetal nucleated erythroblasts at a single cell level by using micromanipulation techniques.

Adult↗
PubMed2001

Shear strength and fatigue properties of human cortical bone determined from pure shear tests.

Shear properties of bone have been inferred from torsion tests. However, torsion often causes spiral fracture planes that correspond to tensile rather than shear failure. We measured the shear properties of human cortical bone in both longitudinal and transverse directions using pure shear tests. Shearing applied transverse to the bone long axis caused fracture along a 45 degrees plane that coincided with maximum tension. This fracture pattern is similar to spiral fractures caused by torsion. Shear strength along the bone axis was 51.6 MPa or about 35% less than that determined using torsion tests. Fatigue tests of human cortical bone in pure shear were conducted. The results agreed well with previous measurements of cortical bone fatigue life in tension and compression, when normalized to strength. Using tibial shear strain magnitudes measured previously for human volunteers, we estimated the fatigue life of cortical bone for different activities, and speculate that shear fatigue failure is a probable cause of tibial stress fractures resulting from impact loading.

Aged↗
PubMed2001

Pulmonary receptors in reptiles: discharge patterns of receptor populations in snakes versus turtles.

This study examines the effects of lung inflation/deflation with and without CO2 on the entire population of pulmonary receptors in the vagus nerve in two species of snakes and two species of turtles. We asked the question, "how does the response of the entire mixed population of pulmonary stretch receptors (PSR) and intrapulmonary chemoreceptors (IPC) in species possessing both differ from that in species with only PSR"? This was studied under conditions of artificial ventilation with the secondary goal of extending observations on the presence/absence of IPC to a further three species. Our results indirectly illustrate the presence of IPC in the Burmese python and South American rattlesnake but not the side necked turtle, adding support to the hypothesis that IPC first arose in diapsid reptiles. In both species of snake, CO2-sensitive discharge (presumably from IPC) predominated almost to the exclusion of CO2-insensitive discharge (presumably arising from PSR) while the opposite was true for both species of turtle. The data suggest that for animals breathing air under conditions of normal metabolism there is little to distinguish between the discharge profiles of the total population of receptors arising from the lungs in the different groups. Interestingly, however, under conditions of elevated environmental CO2 most volume-related feedback from the lungs is abolished in the two species of snakes, while under conditions of elevated metabolic CO2, it is estimated that volume feedback from the lungs would be enhanced in these same species.

Animals↗