Biomedical subjects

D Wu

Publications and source records attributed to D Wu.

At least 271 records · Page 15Linked to original sources

PubMed1998

High throughput liquid chromatography/mass spectrometry bioanalysis using 96-well disk solid phase extraction plate for the sample preparation.

The 96 well solid phase extraction (SPE) operated by robot in the LC/MS/MS bioanalysis offered rapid sample preparation for drugs and metabolites in biological matrices, based on simultaneous extraction of 96 samples. The use of a disk as sorbent in the 96 well plate further improved the performance of SPE and allowed for small elution volumes, making it possible to 'dilute and shoot" after SPE elution. In this study, a 96 well plate (Empore) was developed, characterized and optimized for several pharmaceutical compounds. In addition, a robot (MultiProbe) was modified to automate the 96 well plate operation. Examples were given to illustrate the major differences of using 96 well disk plate SPE in the method development as compared to the traditional SPE. This technology has been successfully used to support many clinical studies. Typically, a batch of 96 samples were prepared in 1-1.5 hours unattended (except for the replacement of a collection plate). Considerable savings in disposable supplies were also noted.

Anti-Asthmatic Agents↗

PubMed1998

Brain activation during silent word generation evaluated with functional MRI.

This is a study of word generation during functional MRI (fMRI). Eleven normal healthy subjects were instructed to generate words covertly, (i.e., silently) that began with particular letters. Images were acquired on a conventional 1.5T scanner at three contiguous axial planes encompassing language-related areas of the temporal and frontal lobe. The data were analyzed at the level of a Talairach box, after individually fitting the proportional Talairach grid system to each slice. The main variable of interest was the number of activated pixels within a Talairach box. Boxes with a significant increase in the proportion of activated pixels were located in three regions of the left neocortex: (1) Brodmann areas 44 and 45 in the dorsolateral frontal cortex (Broca's area), (2) areas 21 and 37 in the temporal cortex, (3) and the striate/extrastriate cortex (areas 17 & 18). The results are discussed in terms of a cognitive model of word generation and are compared, in detail, with the results of prior relevant imaging studies.

Adolescent↗

PubMed1998

Evidence for the presence of a Na+-H+ exchanger in the endolymphatic sac epithelium of guinea-pigs.

The intracellular pH (pHi) of epithelial cells from the endolymphatic sac (ES) of the guinea-pig was measured microfluorometrically with the pH-sensitive fluorescent dye, 2', 7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) to examine the presence of a Na+-H+ exchanger (NHE) in the ES epithelial cells. pHi recovery from acid loading with an NH4+-prepulse in a nominally HCO3-free solution was dependent on extracellular Na+ ([Na+]o) and was inhibited by amiloride and its analogue ethylisopropylamiloride (EIPA), suggesting that a decreased pHi induced by an acute acid load may be equilibrated by a NHE. In the steady-state, amiloride had no effect on pHi, indicating that the NHE activity is low at the resting pHi. However, the intracellular acidification induced by the removal of [Na+]o was inhibited by the simultaneous application of amiloride. H+-efflux rate (JH, mean activity of NHE), which was calculated as the product of the recovery rate (dpHi/dt) from the acid loading and the intrinsic buffering capacity (betai) at the corresponding pHi, was decreased as pHi was increased. The concentration/response curve for the inhibition of initial JH by EIPA revealed an apparent 50% inhibitory constant (Ki ) of 0.85 microM. Kinetic analysis of initial JH as a function of [Na+]o revealed a Michaelis-Menten constant (Km) of 24.14 mM for Na+-dependent H+ efflux. The results indicate that NHE in the ES epithelium belongs to an amiloride-sensitive subtype.

Amiloride↗

PubMed1998

Late coronary artery stenting in patients with acute myocardial infarction.

BACKGROUND: The safety and efficacy of late coronary artery stenting of the infarct-related artery after acute infarction has not been evaluated previously. METHODS AND RESULTS: Coronary artery stenting was performed in 117 consecutive patients with acute infarction who were receiving ticlopidine/aspirin regimen without coumarin. There were 97 men and 18 women, aged 58+/-11 (mean +/- SD) years. A total of 136 Palmaz-Schatz stents were successfully implanted in 130 lesions 15+/-8 days after acute myocardial infarction (median 9 days) in 115 of 117 (98%) patients. The minimal luminal diameter (MLD) increased from 0.66+/-0.46 to 3.14+/-0.53 mm (P< .001), with an acute gain of 2.49+/-0.61 mm. One patient had acute thrombosis requiring further stenting and another patient received emergency bypass surgery. There was no subacute thrombosis or other complications. During a follow-up duration of 14+/-3 months, 2 patients had angina pectoris develop and 1 died suddenly. Sixty-two patients underwent a follow-up coronary angiography 195+/-36 days after stenting. Restenosis was noted in 8 patients (13%); the MLD was 2.19+/-0.73 mm, the late loss was 0.96+/-0.65 mm (P< .001), the loss index was 0.39+/-0.28, and the net gain was 1.56+/-0.79 mm (P< .001). The angiographic left ventricular ejection fraction increased from 47%+/-12% to 55%+/-12% (P< .001). CONCLUSIONS: Late coronary stenting of the infarct-related artery in patients with acute myocardial infarction is a safe and effective late reperfusion therapy and may be beneficial to the patients.

Adult↗

PubMed1998

Baroreflex-mediated bradycardia but not tachycardia is blunted peripherally by intravenous mu-opioid agonists.

OBJECTIVE: We sought to test the hypothesis that an intravenous dose of H-Tyr-D-Arg-Phe-Lys-NH2, a highly mu-receptor selective opioid peptide, suppresses baroreflex sensitivity through a peripheral mechanism. STUDY DESIGN: A transient change in mean arterial pressure was produced in chronically instrumented pregnant ewes by norepinephrine or sodium nitroprusside in the absence or in the presence of H-Tyr-D-Arg-Phe-Lys-NH2, a highly mu-selective opioid peptide. In some studies naloxone methiodide, a peripheral opioid antagonist, was infused starting 60 minutes before the administration of H-Tyr-D-Arg-Phe-Lys-NH2 and maintained for a total of 90 minutes. Linear plots were obtained when the changes in mean arterial pressure during the pressure rise were plotted against the changes in heart rate and the sensitivity of the baroreflex was derived as the slope of the linear regression line. RESULTS: We observed (1) lower baroreflex sensitivity after H-Tyr-D-Arg-Phe-Lys-NH2 administration with a hypertensive stimulus; (2) unchanged baroreflex sensitivity after H-Tyr-D-Arg-Phe-Lys-NH2 administration with a hypotensive stimulus; and (3) unchanged baroreflex sensitivity after H-Tyr-D-Arg-Phe-Lys-NH2 administration with a hypertensive stimulus in the presence of naloxone methiodide. CONCLUSION: H-Tyr-D-Arg-Phe-Lys-NH2 suppresses the hypertensive but not the hypotensive arm of the baroreflex through peripheral opioid receptors. These results suggest that mu-opioid receptors are present in the vagus nerves and that the activation of these opioid receptors inhibits reflex bradycardia in pregnant sheep.

Animals↗

PubMed1998

Cardiovascular and metabolic responses to two receptor-selective opioid agonists in pregnant sheep.

OBJECTIVE: Our purpose was to assess the effects of an intravenous dose of a highly selective mu-(DALDA) and delta-(DPDPE) opioid peptide to determine which class of peptide has the best clinical potential. STUDY DESIGN: Chronically instrumented pregnant ewes received a 0.3 mg/kg intravenous bolus of each peptide with and without opioid receptor blockade by means of a randomized prospective design. RESULTS: Intravenous DALDA produced only mild hypertension and a loss of heart rate variability, whereas DPDPE produced respiratory depression, maternal hypertension, and a fall in heart rate in both mother and fetus. Uterine blood flow, oxygen uptake, and glucose uptake were unchanged with both drugs. The effects of DALDA but not DPDPE were reversed by opioid receptor blockade. CONCLUSION: The delta-selective agonist had multiple nonopioid adverse effects, whereas the mu-selective agonist was well tolerated by the pregnant ewe, suggesting that mu-selective agonists have better potential for clinical use as an analgesic in pregnancy.

Animals↗

PubMed1998

Multiplane transesophageal echocardiography in diagnosis of anomalous origin of the left coronary artery from the pulmonary artery: a case report.

Anomalous origin of the left coronary artery from the pulmonary artery in adults is difficult to identify reliably by transthoracic echocardiography (TTE). We describe a 32-year-old woman with this coronary anomaly mimicking a coronary artery fistula on conventional TTE study. This anomaly was suggested by multiplane transesophageal echocardiography (TEE) and subsequently confirmed by coronary angiography. Multiplane TEE thus may serve as a first-line diagnostic tool for detecting anomalous origin of coronary arteries.

Adult↗

PubMed1998

Regulation of the cholinergic gene locus.

DNase I hypersensitive site mapping of the human cholinergic gene locus has been used to detect cholinergic specific potential regulatory sites. Analysis of mutant PC12 cell lines provides evidence that protein kinase A II is required and coordinately regulates basal expression of both the ChAT and VAChT genes.

Adenocarcinoma↗

PubMed1998

Camptothecin-20-PEG ester transport forms: the effect of spacer groups on antitumor activity.

An improved synthesis of the hindered PEG-camptothecin diester transport form has been achieved using the Mukaiyama reagent. We have also assessed the effect of changing the electronic configuration of the (d-position of PEG-camptothecin transport forms on the rates of hydrolysis of the pro-moiety, and attempted to correlate these differences to efficacy in two animal models. In addition to the simple substitution of N for O, other synthetic modifications of these atoms were accomplished by employing heterobifunctional linker groups. The half lives by disappearance (rates of hydrolysis) of the transport forms in buffer and rat plasma were determined. It was established that anchimeric assistance to hydrolytic breakdown of the pro-moiety occurs in a predictable manner for some of these compounds. Results for the new derivatives in a P388 murine leukemic model and HT-29 human colorectal xenograft study are also presented. The use of a glycine linker group was found to provide similar efficacy in rodent models to that of simple camptothecin 20-PEG ester, and displayed enhanced pharmacokinetics.

Animals↗

PubMed1998

Effects of L-NAME and L-arginine on diaphragm contraction in a septic animal model.

The effects of nitric oxide on diaphragm contraction after endotoxin administration were studied in Wistar rats. The animals were divided into seven treatments: a saline-injected group as control, three groups injected with L-NAME (0.01, 0.1, 1 mg/kg) and three groups injected with L-arginine (1, 10, 100 mg/kg). Escherichia coli endotoxin was injected into the peritoneal cavity 15 min later. Twitch kinetics and force-frequency curves were measured 0, 2, and 4 hr after endotoxin injection. In the control group, the force-frequency curves significantly decreased from 0 hr to 4 hr. In the L-NAME group, the force-frequency curves at 4 hr showed significant increases in a dose-dependent manner. In the L-arginine group, the force-frequency curve with 100 mg/kg at 4 hr showed a significant increase. There was no consistent change in the contraction time, half relaxation time, or fatiguability. NADPH diaphorase histochemistry performed on diaphragm muscle samples 4 hr after endotoxin injection showed positive in the control and L-arginine group, but was only weakly observed in L-NAME group. These data suggest that nitric oxide contributes to the endotoxin induced diaphragm contractile deterioration.

Animals↗

PubMed1998

Combined use of carboxyl-directed protein pegylation and vector-mediated blood-brain barrier drug delivery system optimizes brain uptake of brain-derived neurotrophic factor following intravenous administration.

PURPOSE: Peptide drug delivery to the brain requires optimization of (a) plasma pharmacokinetics and (b) blood-brain barrier (BBB) permeability. In the present studies, plasma pharmacokinetics are improved with protein pegylation and BBB transport is facilitated with the use of vector-mediated drug delivery using the OX26 monoclonal antibody (MAb) to the rat transferrin receptor, which undergoes receptormediated transcytosis through the BBB in vivo. METHODS: A conjugate of OX26 and streptavidin (SA), designated OX26/SA, was prepared in parallel with the carboxyl-directed pegylation of brain-derived neurotrophic factor (BDNF). A novel bifunctional polyethyleneglycol (PEG) was used in which a hydrazide (Hz) was attached at one end and a biotin moiety was attached to the other end. This allowed for conjugation of BDNF-PEG-biotin to OX26/SA. RESULTS: The brain uptake of BDNF-PEG-biotin was increased following conjugation to OX26/SA to a level of 0.144 +/- 0.004% injected dose per g brain and a BBB permeability-surface area product of 2.0 +/- 0.2 microL/min/g. CONCLUSIONS: These studies demonstrate that peptide drug delivery to the brain can be achieved with advanced formulation of protein-based therapeutics. The formulation is intended to (a) minimize rapid systemic clearance of the peptide, and (b) allow for vector-mediated drug delivery through the BBB in vivo. Following this dual formulation, the brain uptake of a neurotrophin such as BDNF achieves a value that is approximately 2-fold greater than that of morphine, a neuroactive small molecule.

Animals↗

PubMed1998

The use of DNase I hypersensitivity site mapping to identify regulatory regions of the human cholinergic gene locus.

The DNase I hypersensitive sites of the human cholinergic gene locus, where both the choline acetyltransferase gene and the vesicular acetylcholine transporter gene are located, were analyzed to detect potential regulatory elements involved in cholinergic-specific transcriptional activation. From this analysis, seven cholinergic cell line-specific DNase I hypersensitive sites were found. The majority of these sites correspond to active promoter regions of the gene, including the promoter region of the vesicular acetylcholine transporter gene and the R, N, and M exons of the choline acetyltransferase gene. Two DNase I hypersensitive sites were identified in two noncholinergic cell lines, HeLa and MCF-7. One corresponds to a previously observed non-cell-specific enhancer, whereas the other corresponds to a previously described neuronal restrictive silencer element, NRSE. The NRSE has been shown to repress expression of various neuron-specific genes, not restricted to cholinergic-specific genes, in nonneuronal cells. This element can account for repression of the cholinergic gene locus in nonneuronal cells but does not account for repression in noncholinergic neurons. In addition, the chromatin boundary domain of the cholinergic gene locus, which possibly corresponds to the end of the transcription unit, was identified.

Carrier Proteins↗

PubMed1998

The cholinergic gene locus is coordinately regulated by protein kinase A II in PC12 cells.

The vesicular acetylcholine transporter (VAChT) gene and the choline acetyltransferase (ChAT) gene comprise the cholinergic gene locus. We have studied the coordinate regulation of these genes by cyclic AMP-dependent protein kinase (PKA) in the rat pheochromocytoma cell line PC12 and PC12 PKA-deficient mutants. Both ChAT and VAChT mRNA increased approximately fourfold after treatment of PC12 cells with dibutyryl cyclic AMP (dbcAMP). ChAT and PKA activity were also increased by dbcAMP. The basal levels of ChAT and VAChT mRNAs in the PKA-deficient cell lines were both about six times lower than in wild-type PC12 cells, and were induced less than twofold by addition of dbcAMP. H-89 and H-9, specific inhibitors for PKA, reduced ChAT and VAChT mRNA levels to approximately one-third that of untreated cells and ChAT activity to approximately one-fourth that of untreated PC12 cells. Activation of PKA type II, but not PKA type I, increased ChAT activity approximately threefold. Analysis of reporter gene constructs indicates that PKA affects gene transcription at an upstream site in the cholinergic gene locus. These results demonstrate that the expression of the ChAT and VAChT genes is regulated coordinately at the transcriptional level, and a signaling pathway specifically involving PKA II plays an important role in this process.

Animals↗

PubMed1998

n-3 polyunsaturated fatty acids and immune function.

n-3 PUFA have been shown to reduce the risk of cardiovascular and inflammatory diseases. However, they have also been shown to suppress T-cell-mediated immune function, an undesirable effect, especially in immuno-suppressed individuals. Studies have thus far suggested that this immuno-suppression may be in part attributable to increased lipid peroxidation and decreased antioxidant (especially vitamin E) levels, which can be prevented by appropriate vitamin E supplementation. Further well-designed human studies are needed to determine the appropriate levels of n-3 PUFA and vitamin E supplementation to optimize the beneficial anti-inflammatory effect of n-3 PUFA and minimize their suppressive effect on T-cell function.

Animals↗

PubMed1998

Membrane potential in isolated epithelial cells of the endolymphatic sac in the guinea-pig.

The membrane potential (Em) in epithelial cells isolated from the intermediate portion of the endolymphatic sac (ES) of the guinea-pig was recorded using the whole-cell patch-clamp technique. In the steady state the Em was -53.5+/-1.5 mV (n = 74), which is similar to that in epithelial cells of other tissues. Application of 1 MM ouabain induced a depolarization of Em by approximately 10 mV (n = 6), suggesting that an active ion transport process by Na+-K+-ATPase may be present in the ES epithelial membrane. Increasing extracellular K+ concentrations from 5 to 100 mM induced a significant membrane depolarization that was close to the K+ equilibrium potential calculated by the Nernst equation, indicating that K+ may be a predominant permeable ion in the ES epithelial membrane. Total replacement of extracellular Na+ with NMDG+ led to a significant membrane hyperpolarization of 38.7+/-2.5 mV (n = 18), suggesting that Na+ may be another major permeable ion for the ES epithelial membrane. Reducing extracellular Cl- concentrations from 149.3 to 7 mM had no significant effect on Em, indicating that Cl- may be a negligible permeable ion in the ES epithelial membrane.

Animals↗

PubMed1998

Lipotrope deficiency inhibits cell growth and induces programmed cell death in human breast cancer cell line MCF-7.

To determine the effects of lipotrope modification on breast cancer cell growth and cell death, the human breast cancer cell line MCF-7 was assigned to grow in one of three lipotrope treatment media for four days. The treatment media included lipotrope-control medium (LCM), containing all required lipotropes; lipotrope-deficient medium (LDM), lacking all lipotropes but supplying homocysteine instead; and lipotrope-additive medium (LAM), containing twice as much of each lipotrope as LCM. Cell count and [3H]thymidine incorporation into DNA revealed that LDM slowed cell growth and inhibited cell proliferation in the MCF-7 cell line. Gel electrophoresis showed significant DNA degradation with the appearance of fragments in LDM-treated cells, whereas the DNA in LCM and LAM cells was largely intact. The LDM group displayed more apoptotic bodies as detected by in situ immunohistochemistry. The gene expression level of bcl-2 was lower in cells treated with LDM than in those treated with LCM and LAM, whereas p53 gene expression did not appear different among the three treatment groups. It is concluded that lipotrope deficiency inhibits cell growth and induces programmed cell death in the human breast cancer cell line MCF-7.

Amino Acids↗

PubMed1998

Clinical performance of the AMDL DR-70 immunoassay kit for cancer detection.

A clinical study using DR-70 immunoassay for the detection of 13 different cancers have been conducted with 277 healthy subjects and 136 cancer patients. The test results showed that the DR-70 immunoassay kit was capable of detecting cancers with high degree of specificity and sensitivity. At 95% specificity level, the sensitivity of the assay was 87.8%, 92.6%, 65.2% and 66.7%, respectively for lung, stomach, breast and rectum cancers. Furthermore the test kits were shown to be stable and performed reproducibly.

Adolescent↗

PubMed1998

Dietary supplementation with mushroom-derived protein-bound glucan does not enhance immune function in young and old mice.

Decline in immune response is a well-documented age-associated biological change. Protein-bound polysaccharides (PSP) are biological response modifiers and have been shown to have immunoenhancing and antitumor effects. This study was conducted to examine the effect of dietary supplementation with PSP-containing extract derived from mycelia of Coriolus versicolor on in vitro and in vivo indices of immune function of young and old mice. Young (5 mo) and old (23 mo) C57BL/6NIA mice were fed purified diets containing 0, 0.1, 0.5 or 1.0% PSP for 1 mo at which time indices of immune function were measured. PSP supplementation had no significant effect on mitogenic response to concanavalin A (Con A), phytohemagglutinin (PHA) or lipopolysaccharide (LPS), or on production of interleukin (IL)-1, IL-2, IL- 4 and prostaglandin E2 (PGE2). Of the in vivo indices of immune function tested, old mice fed 1.0% PSP had significantly higher delayed-type hypersensitivity (DTH) response than those fed 0% PSP. No significant effect of PSP was observed on the DTH response of young mice. The antibody response to sheep red blood cells was not significantly influenced by PSP in young or old mice. These results suggest that PSP-containing extract from mycelia of Coriolus versicolor might have a modest immunoenhancing effect in aged mice, but not in young mice.

Aging↗