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Biomedical subjects

D Wu

Publications and source records attributed to D Wu.

At least 307 records · Page 17Linked to original sources
PubMed1998

[Determination of ascorbic acid and its stability of Fructus Hippophae fruit by the method of high-valence iron reduction].

The high-valence iron reduction method was used to determine the ascorbic acid of fructus hippophae fruit. The reduction method had simple, high sensitivity and accuracy in comparison with fluorospectrophotometry or indophenol titration method. Its limit of detection was 0.01 microg/mL, the relative standard deviation and the average recovery was 0.83% (n = 8) and 95.6% (n = 6) respectively. We also researched the influence of the environment factors (temperature, storage period and condition, pH value) on the stability of ascorbic acid in fructus hippophae fruit. The ascorbic acid in fructus hippophae fruit was more stable than thepure ascorbic acid on the same condition of heating (80 C,1 hour), in pH neutral or storing in the refrigerator.

Ascorbic Acid↗
PubMed1998

In vivo disposition of dermorphin analog (DALDA) in nonpregnant and pregnant sheep.

Although synthetic opioid peptide analogs have been used extensively to study the functional roles of opioid receptors, little is known about their in vivo disposition. Our goal was to develop novel opioid drugs with limited transfer across the placenta. DALDA (Tyr-D-Arg-Phe-Lys-NH2) is a potent and highly selective mu agonist that is quite polar because of its 3+ charge at physiological pH. It can therefore be expected that the distribution of DALDA across the placenta would be highly restricted. In this study, we determined the pharmacokinetics and placental transfer of DALDA after systemic administration in sheep. DALDA was infused intravenously to four nonpregnant and four pregnant sheep at a dose of 0.6 mg/kg/hr for 4 hr. Steady state plasma levels of DALDA were 5436 +/- 464 ng/ml in nonpregnant sheep and 5214 +/- 661 ng/ml in pregnant sheep. A one-compartment open model provided an excellent fit for nonpregnant and pregnant plasma data. The apparent volume of distribution was estimated to be 45.6 +/- 4.4 and 59.2 +/- 7.9 ml/kg in nonpregnant and pregnant animals, respectively. There was no difference in the elimination half-life of DALDA in nonpregnant (1.4 +/- 0.1 hr) and pregnant (1.7 +/- 0.2 hr) animals, and clearance was also similar in nonpregnant (23.1 +/- 1.7 ml/kg/hr) and pregnant (23.7 +/- 1.3 ml/kg/hr) animals. These data suggest that the distribution of DALDA is restricted to plasma volume and that its disposition is not altered in pregnancy. DALDA was not detected in any of the fetal plasma samples (< 50 ng/ml), indicating that fetal plasma concentration is < 1% of maternal concentration. The highly restricted placental distribution of DALDA suggests that it may be a promising opioid drug for obstetrical use.

Analgesics↗
PubMed1998

Antioxidant modulation of cytokines and their biologic function in the aged.

The oxidant/antioxidant balance is an important determinant of immune cell function, including maintaining integrity and functionality of membrane lipids, cellular proteins, nucleic acids, and for control of signal transduction and gene expression in immune cells. Optimal levels of antioxidants are needed for maintenance of the immune response across all age groups. This need might be more critical, however, in the aged. Age-associated dysregulation of immune response, particularly of cytokine production and T-cell-mediated function, is well documented. The well-known age-related increase in free radical formation and lipid peroxidation contributes, at least in part, to this phenomenon. This review will summarize animal and human studies undertaken by the authors as well as those by other investigators on the effect of antioxidants, vitamin E, beta-carotene, and glutathione on cytokine production and T-cell-mediated function in the aged.

Aged↗
PubMed1998

Sex and electroencephalographic synchronization after photic stimulation predict signal changes in the visual cortex on functional MR images.

PURPOSE: We evaluated factors that influence MR signal changes during photic stimulation of the visual cortex. We also tested the hypothesis that functional MR imaging response corresponds to electroencephalographic (EEG) synchronization after photic stimulation. METHODS: Thirty-eight healthy subjects, 20 men and 18 women, underwent photic stimulation of the visual cortex. They were studied with a 1.5-T MR unit, and photic stimulation was induced via 8-Hz LED goggles. Seven subjects with and seven without detectable functional MR imaging response to photic stimulation underwent further studies with 16-channel EEG after 2- to 30-Hz stroboscopic stimulation. RESULTS: Thirteen men and 18 women had a significant increase in MR signal in the visual cortex; seven men showed no visual cortex activation during more than two repeated studies. Six of seven volunteers with increased functional MR imaging signal after photic stimulation also showed signs of EEG synchronization when an 8-Hz stroboscopic flash was used; six of seven subjects with no functional MR imaging lacked EEG synchronization at 8-Hz stimulation. CONCLUSIONS: Men were more likely than women to have undetectable MR signal changes after photic stimulation. This finding should be considered when interpreting results of functional MR imaging studies. EEG with stroboscopic examination is a good predictor of functional MR imaging sensitivity to changes in regional cerebral blood flow induced by sensory stimulation.

Adult↗
PubMed1998

CT findings in splenic tuberculosis.

Splenic tuberculosis is rare and delay in diagnosis is common. We present two cases of splenic tuberculosis with their appearance on CT. The CT findings were multiple, round or ovoid, low-density lesions without calcification. Except for non-specific lymphadenopathy no abnormality nor history suggestive of tuberculosis was revealed prior to laparotomy. Although CT does not confirm a diagnosis of splenic tuberculosis, it would be a valuable examination to define the extent of disease and guide aspiration biopsy.

Abscess↗
PubMed1998

Enhanced endocytosis in cultured human breast carcinoma cells and in vivo biodistribution in rats of a humanized monoclonal antibody after cationization of the protein.

For monoclonal antibody therapeutics to access target antigen in extravascular compartments, an antibody drug delivery technology is required that has the dual properties of 1) transendothelial migration of the antibody and 2) endocytosis of the antibody into the target cell. These two objectives may be achieved with antibody cationization, and the present studies examine the feasibility of cationizing the humanized 4D5 monoclonal antibody directed against the p185HER2 oncogenic protein. The cationized antibody binds to the p185HER2 extracellular domain with an ED50 of 35 micrograms/ml and inhibits SK-BR3 cell proliferation similar to the native antibody. Confocal microscopy showed that although there was binding of the native 4D5 antibody to the plasma membrane of SK-BR3 cells, this antibody was confined to the periplasma membrane space with minimal endocytosis into the cell. In contrast, robust internalization of the cationized 4D5 antibody by the SK-BR3 cells was demonstrated by confocal microscopy. The systemic volume of distribution of the cationized 4D5 antibody was 11-fold greater than that of the native antibody. In summary, these studies show that a humanized monoclonal antibody may be cationized with retention of antibody affinity for the target antigen and biological activity, yet with a marked alteration in the cellular distribution and pharmacokinetics in vivo.

Animals↗
PubMed1998

Pharmacokinetics and blood-brain barrier transport of an anti-transferrin receptor monoclonal antibody (OX26) in rats after chronic treatment with the antibody.

Monoclonal antibodies (MAbs) directed against cell surface receptors (e.g. the transferrin receptor or the insulin receptor) on the brain capillary endothelium, which makes up the blood-brain barrier (BBB) in vivo, are brain drug-delivery vectors. When cells are chronically exposed to MAbs in tissue culture, there is often down-regulation of the cell surface receptors. To examine whether similar down-regulation occurs in vivo, rats were chronically treated either with the OX26 murine MAb to the rat transferrin receptor or with a mouse IgG2a isotype control (0.25 mg/kg sc daily for 1 week), and the BBB transport of the OX26 MAb was then measured for both rat brain and liver in vivo. Although this treatment regimen resulted in a 41% increase in the permeability-surface area product for 125I-OX26 MAb transport into rat liver in vivo, there was no significant change in the BBB permeability-surface area product for the OX26 MAb. These studies indicate that repetitive administration of cell surface-specific MAbs does not necessarily result in down-regulation of BBB receptors.

Animals↗
PubMed1997

Adenosine-sensitive ventricular tachycardia from the anterobasal left ventricle.

OBJECTIVES: This study demonstrates that exercise-provocable tachycardia resembling right ventricular outflow tract tachycardia may originate from the anterobasal left ventricle. BACKGROUND: Reentry is the operative mechanism of idiopathic left ventricular tachycardia, with a QRS complex of right bundle branch block and superior axis that is responsive to verapamil but not adenosine. Whether some mechanism other than reentry is operative in some idiopathic left ventricular tachycardias is unclear. METHODS: In 4 of 53 consecutive patients with idiopathic left ventricular tachycardia, the tachycardia was sensitive to adenosine. These four patients were women 63, 61, 61 and 31 years old and were the subjects of the present study. RESULTS: In all four patients, spontaneous tachycardia was related to exercise or emotional stress. The tachycardia displayed atypical left (one patient) or right (three patients) bundle branch block with an inferior axis and marked variation in cycle length. An intravenous bolus of adenosine triphosphate (10 to 20 mg) terminated tachycardia in all four patients. Tachycardia was terminated or prevented in three patients given intravenous or oral verapamil. Atrial or ventricular incremental or extrastimulus testing induced tachycardia in all four patients (three with, one without isoproterenol infusion). Electrically induced tachycardia also demonstrated marked variation in cycle length, which ranged from 230 to 390 ms. Entrainment was not demonstrable with overdrive pacing from multiple sites. Endocardial mapping during tachycardia revealed that the earliest activations were registered 25, 40, 35 and 50 ms before onset of the QRS complex, respectively, from the anterior aspect of the left ventricle just below the mitral annulus, adjacent to the left ventricular outflow tract. High frequency Purkinje spikes were not recorded at this site. Radiofrequency current delivered to this site successfully ablated the tachycardia in three of the four patients. CONCLUSIONS: Exercise-provocable, catecholamine-mediated, verapamil-responsive, adenosine-sensitive ventricular tachycardia may arise from the anterobasal left ventricle adjacent to the outflow tract.

Adenosine↗
PubMed1997

Midgut-specific immune molecules are produced by the blood-sucking insect Stomoxys calcitrans.

We have cloned and sequenced two defensins, Smd1 and Smd2, from anterior midgut tissue of the blood-sucking fly Stomoxys calcitrans. The DNA and N-terminal protein sequences suggest both are produced as prepropeptides. Smd1 differs from the classic defensin pattern in having an unusual six-amino acid-long N-terminal sequence. Both Smd1 and Smd2 have lower pI points and charge than insect defensins derived from fat body/hemocytes. Northern analysis shows both of these defensin molecules are tissue specific; both are produced by the anterior midgut tissue and, unlike the other insect defensins reported to date, neither appears to be expressed in fat body or hemocytes. Northern analysis also shows that mRNAs for both defensins are constitutively produced in the anterior midgut tissues and that these transcripts are up-regulated in response to sterile as well as a lipopolysaccharide-containing blood meal. However, anti-Gram-negative biological activity in the midgut is substantially enhanced by lipopolysaccharide. These findings suggest that the insect midgut has its own tissue-specific immune mechanisms and that this invertebrate epithelium is, like several vertebrate epithelia, protected by specific antibacterial peptides.

Amino Acid Sequence↗
PubMed1997

Two basic amino acids in the second inner loop of the interleukin-8 receptor are essential for Galpha16 coupling.

The involvement of basic residues of interleukin(IL)-8 receptors in coupling to the Gi and G16 proteins was investigated by using a series of IL-8 receptor mutants. Substitution of the basic amino acids in the third inner loop of the receptor does not alter the abilities of the receptor mutants to activate recombinant Galpha16 or phosphoinositide-specific phospholipase C (PLC) beta2 expressed in COS-7 cells. However, an IL-8 receptor mutant with double mutations at residues Lys158 and Arg159 of the second inner loop loses its abilities to activate Galpha16 but retains its ability to activate PLC beta2. The activation of PLC beta2 by an IL-8 receptor that is sensitive to pertussis toxin has been previously demonstrated to be mediated through Gbetagamma. Surprisingly, the IL-8 receptor mutants with substitution of Ala for either residue Lys158 or Arg159 can still activate Galpha16, which suggests that either of the two basic residues in the second inner loop of the IL-8 receptor is sufficient for Galpha16 coupling.

Amino Acid Sequence↗
PubMed1997

Drug targeting of a peptide radiopharmaceutical through the primate blood-brain barrier in vivo with a monoclonal antibody to the human insulin receptor.

Peptide radiopharmaceuticals are potential imaging agents for brain disorders, should these agents be enabled to undergo transport through the blood-brain barrier (BBB) in vivo. Radiolabeled Abeta1-40 images brain amyloid in tissue sections of Alzheimer's disease autopsy brain, but this peptide radiopharmaceutical cannot be used to image brain amyloid in vivo owing to negligible transport through the BBB. In these studies, 125I-Abeta1-40 was monobiotinylated (bio) and conjugated to a BBB drug delivery and brain targeting system comprised of a complex of the 83-14 monoclonal antibody (mAb) to the human insulin receptor, which is tagged with streptavidin (SA). A marked increase in rhesus monkey brain uptake of the 125I-bio-Abeta1-40 was observed after conjugation to the 8314-SA delivery system at 3 h after intravenous injection. In contrast, no measurable brain uptake of 125I-bio-Abeta1-40 was observed in the absence of a BBB drug delivery system. The peptide radiopharmaceutical was degraded in brain with export of the iodide radioactivity, and by 48 h after intravenous injection, 90% of the radioactivity was cleared from the brain. In conclusion, these studies describe a methodology for BBB drug delivery and brain targeting of peptide radiopharmaceuticals that could be used for imaging amyloid or other brain disorders.

Alzheimer Disease↗
PubMed1997

Enhanced expression of inducible cyclooxygenase with age in murine macrophages.

Macrophages (Mphi) from old mice produce more PGE2 than those from young mice, contributing to the dysregulation of the immune and inflammatory responses with age. This study was conducted to determine the mechanisms of the age-associated increase in Mphi PGE2 production. PGE2 production is influenced by the availability of the substrate arachidonic acid and by activity of the enzyme cyclooxygenase (Cox). We demonstrate that when the substrate is not the limiting factor, Mphi from old mice have significantly higher LPS-stimulated Cox activity than young mice, indicating that the age-associated increase in PGE2 production is due to increased enzyme activity and not to changes in substrate level. Cox activity is determined by the enzyme level and requires hydroperoxide for activation. Of the two Cox isoforms, Cox 1 is constitutively expressed in nearly all cells; whereas Cox 2 is induced by a wide range of ligands. Analysis of accumulated and de novo synthesis of constitutive Cox 1 and inducible Cox 2 proteins showed no age-related difference in Cox 1 protein levels, but Mphi from old mice had higher accumulated and newly synthesized LPS-stimulated Cox 2 protein levels than young mice. Furthermore, Mphi from old mice had higher LPS-stimulated levels of Cox 2 mRNA compared with those from young mice. Clearly, the age-associated increase in LPS-stimulated PGE2 production is due to increased Cox activity resulting from higher Cox 2 protein and mRNA expression. These findings have significant implications for age-associated immune and inflammatory dysregulation as well as the development of preventive and therapeutic strategies against them.

Aging↗
PubMed1997

Interaction and regulation of the Caenorhabditis elegans death protease CED-3 by CED-4 and CED-9.

In the nematode Caenorhabditis elegans, three genes, ced-3, ced-4, and ced-9, play critical roles in the induction and execution of the death pathway. Genetic studies have suggested that ced-9 controls programmed cell death by regulating ced-4 and ced-3. However, the mechanism by which CED-9 controls the activities of CED-4 and the cysteine protease CED-3, the effector arm of the cell-death pathway, remains poorly understood. Immunoprecipitation analysis demonstrates that CED-9 forms a multimeric protein complex with CED-4 and CED-3 in vivo. Expression of wild-type CED-4 promotes the ability of CED-3 to induce apoptosis in mammalian cells, which is inhibited by CED-9. The pro-apoptotic activity of CED-4 requires the expression of a functional CED-3 protease. Significantly, loss-of-function CED-4 mutants are impaired in their ability to promote CED-3-mediated apoptosis. Expression of CED-4 enhances the proteolytic activation of CED-3. We also show that CED-9 inhibits the formation of p13 and p15, two cleavage products of CED-3 associated with its proteolytic activation in vivo. Moreover, CED-9 inhibits the enzymatic activity of CED-3 promoted by CED-4. Thus, these results provide evidence that CED-4 and CED-9 regulate the activity of CED-3 through physical interactions, which may provide a molecular basis for the control of programmed cell death in C. elegans.

Animals↗
PubMed1997

Roles of phospholipase C beta2 in chemoattractant-elicited responses.

The physiological roles of phospholipase C (PLC) beta2 in hematopoiesis, leukocyte function, and host defense against infection were investigated using a mouse line that lacks PLC beta2. PLC beta2 deficiency did not affect hematopoiesis, but it blocked chemoattractant-induced Ca2+ release, superoxide production, and MAC-1 up-regulation in neutrophils. In view of these effects, it was surprising that the absence of PLC beta2 enhanced chemotaxis of different leukocyte populations and sensitized the in vivo response of the PLC beta2-deficient mice to bacteria, viruses, and immune complexes. These data raise questions about the roles that PLC beta2 may play in signal transduction induced by chemoattractants in leukocytes.

Animals↗
PubMed1997

Recovery of YAC-end sequences through complementation of an Escherichia coli pyrF mutation.

We have developed a genetic means to recover sequences from YAC-ends near the yeast selectable marker URA3. This strategy is based on the ability of URA3 to complement mutations in pyrF, an Escherichia coli gene required for pyrimidine biosynthesis. We have developed an E.coli strain with a non-reverting allele of pyrF that is also suitable for cloning (recA-, hsdR-). We demonstrate the utility of this complementation strategy to obtain right-end clones from three YACs containing Arabidopsis thaliana DNA.

Chromosomes, Artificial, Yeast↗
PubMed1997

Interactions of amphetamine analogs with human liver CYP2D6.

The interaction of fifteen amphetamine analogs with the genetically polymorphic enzyme CYP2D6 was examined. All fourteen phenylisopropylamines tested were competitive inhibitors of CYP2D6 in human liver microsomes. The presence of a methylenedioxy group in the 3,4-positions of both amphetamine (Ki = 26.5 microM) and methamphetamine (Ki = 25 microM) increased the affinity for CYP2D6 to 1.8 and 0.6 microM, respectively. Addition of a methoxy group to amphetamine in the 2-position also increased the affinity for CYP2D6 (Ki = 11.5 microM). The compound with the highest affinity for CYP2D6 was an amphetamine analog (MMDA-2) having both a methoxy group in the 2-position and a methylenedioxy group (Ki = 0.17 microM). Mescaline did not interact with CYP2D6. O-Demethylation of p-methoxyamphetamine (PMA) by CYP2D6 was characterized (Km = 59.2 +/- 22.4 microM, and Vmax = 29.3 +/- 16.6 nmol/mg/hr, N = 6 livers). This reaction was negligible in CYP2D6-deficient liver microsomes, was inhibited stereoselectively by the quinidine/quinine enantiomer pair, and was cosegregated with dextromethorphan O-demethylation (r = 0.975). The inhibitory effect of methylenedioxymethamphetamine (MDMA) was enhanced by preincubation with microsomes, suggesting that MDMA may produce a metabolite complex with CYP2D6. These findings suggest that phenylisopropylamines as a class interact with CYP2D6 as substrates and/or inhibitors. Their use may cause metabolic interactions with other drugs that are CYP2D6 substrates, and the potential for polymorphic oxidation via CYP2D6 may be a source of interindividual variation in their abuse liability and toxicity.

Amphetamines↗
PubMed1997

Drug quantitation on a benchtop liquid chromatography-tandem mass spectrometry system.

The specificity and selectivity of LC-MS-MS is illustrated to explain why LC-MS-MS has become the method of choice for quantitation within the pharmaceutical industry. Two assays are described that demonstrate the facility with which new ion trap technology can utilize the selectivity and sensitivity of LC-MS-MS to quantitate trace level components within complex matrices, in particular human plasma. One assay undergoes a validation procedure and demonstrates the utility of this new technology for drug quantitation within a regulated environment.

Calibration↗