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Biomedical subjects

W Yu

Publications and source records attributed to W Yu.

At least 91 records · Page 5Linked to original sources
PubMed2000

Identification of novel purine and pyrimidine cyclin-dependent kinase inhibitors with distinct molecular interactions and tumor cell growth inhibition profiles.

Substituted guanines and pyrimidines were tested as inhibitors of cyclin B1/CDK1 and cyclin A3/CDK2 and soaked into crystals of monomeric CDK2. O6-Cyclohexylmethylguanine (NU2058) was a competitive inhibitor of CDK1 and CDK2 with respect to ATP (Ki values: CDK1, 5 +/- 1 microM; CDK2, 12 +/- 3 microM) and formed a triplet of hydrogen bonds (i.e., NH-9 to Glu 81, N-3 to Leu 83, and 2-NH2 to Leu 83). The triplet of hydrogen bonding and CDK inhibition was reproduced by 2,6-diamino-4-cyclohexylmethyloxy-5-nitrosopyrimidine (NU6027, Ki values: CDK1, 2.5 +/- 0.4 microM; CDK2, 1.3 +/- 0.2 microM). Against human tumor cells, NU2058 and NU6027 were growth inhibitory in vitro (mean GI50 values of 13 +/- 7 microM and 10 +/- 6 microM, respectively), with a pattern of sensitivity distinct from flavopiridol and olomoucine. These CDK inhibition and chemosensitivity data indicate that the distinct mode of binding of NU2058 and NU6027 has direct consequences for enzyme and cell growth inhibition.

Antineoplastic Agents↗
PubMed2000

Electron acceleration by a short relativistic laser pulse at the front of solid targets.

Acceleration of electrons in a low-density plasma in front of a solid target by a propagating short ultraintense laser pulse is studied. When the laser is reflected at the target surface the accelerated electrons, with energy scaling as the laser intensity, continue to move forward inertially and thus escape from the pulse. Electrons accelerated backwards by the reflected light can attain even higher energies due to their longer acceleration length and their high initial momentum from a relativistic return current.

Journal Article↗
PubMed2000

Two-photon microscopy of aorta fibers shows proteolysis induced by LDL hydroperoxides.

Oxidatively modified LDL mimics several aspects of atherogenesis. In this disease, degradation of the matrix proteins' network also occurs. By a new morphological ex vivo approach, not requiring sample processing, we explored the relationship between the degradation of matrix protein and oxidatively modified LDL. Two-photon excitation fluorescence microscopy images of fresh cross-section rings of rat aorta, acquired while the sample was maintained in a glucose- and oxygen-supplemented buffer, showed straight, parallel, thick, long extracellular matrix proteins. Traditional microscopic examination, requiring sample fixation and staining, shows smaller and curved fibers. Instead, we observed curved and broken fibers after a 30-min incubation of aorta with either LDL containing lipid hydroperoxides, or tert-butyl-hydroperoxide. The adhesion of LDL to the endothelium and its internalization was directly visualized by using a lipid fluorophore. The damage to aorta matrix proteins induced by LDL and tert-butyl-hydroperoxide was fully prevented by antioxidants, such as ascorbate or Trolox C, or inhibitors of proteases. The image spectroscopy of the fibers' autofluorescence (polarization and lifetime) revealed an increased mobility of the fluorescent cross-link in fibers. Damaged matrix proteins were also imaged in aorta samples from apolipoprotein E knock-out mice. Our ex vivo images directly visualized the activation of a fast redox-sensitive proteolytic process in the arterial wall triggered by lipid hydroperoxides in LDL.

Animals↗
PubMed2000

Immunogenicity of porcine transmissible gastroenteritis virus spike protein expressed in plants.

Transgenic plants expressing recombinant proteins from pathogenic microorganisms provide an inexpensive edible vaccine for induction of local immunity. Three transgenic plant lines were generated expressing the spike (S) protein of transmissible gastroenteritis virus (TGEV), a protein crucial for establishing mucosal immunity. All three of them were driven by a strong plant promoter. One construct contained the 3.7 kb 5' end of the native S gene sequence. In the second construct part of the S gene, from nucleotide 49 to 1785, was modified for optimal plant recognition and was fused to a plant signal peptide coding sequence. The third construct contained the D epitope-coding region of the S gene, from nucleotide 1201 to 1591, which was fused to the alfalfa beta-amylase gene. The S gene products were detected by enzyme-linked immunosorbent assay (ELISA) and Western blotting. Antigens from all three transgenic plant lines induced TGEV-specific immune responses in pigs as determined by virus neutralization and ELISA, and the resultant antibody titers for all three constructs were similar.

Animals↗
PubMed2000

Phosphatidylinositide 3-kinase localizes to cytoplasmic lipid bodies in human polymorphonuclear leukocytes and other myeloid-derived cells.

Phosphatidylinositide 3-kinase (PI3K) is a key enzyme implicated in intracellular signaling of diverse cellular responses including receptor-mediated responses and neutrophil activation. Several PI3K subunits have been cloned and shown to be localized to plasma membrane receptors, the cytosol, or intracellular vesicles or caveolae. We report the localization of PI3K to a distinct intracellular site, cytoplasmic lipid bodies, in leukocytes. In U937 monocyte cells, PI3K p85 regulatory and p110beta catalytic subunits were localized to lipid bodies by immunocytochemistry and/or immunoblotting and enzyme assays of subcellular fractions. In RAW murine macrophages, p55, p85alpha, and p85beta PI3K subunits were present at isolated lipid bodies. PI3K p85 was also shown to colocalize and, by co-immunoprecipitation, to be physically associated with phosphorylated Lyn kinase in lipid bodies induced to form in human polymorphonuclear leukocytes. These findings, therefore, indicate a novel site for PI3K compartmentalization and suggest that PI3K-mediated signaling is active within cytoplasmic lipid bodies in leukocytes.

Animals↗
PubMed2000

Two-photon autofluorescence microscopy and spectroscopy of Antarctic fungus: new approach for studying effects of UV-B irradiation.

We combined two-photon fluorescence microscopy and spectroscopy to provide functional images of UV-B (280-315 nm) induced stress on an Antarctic fungus. Two-photon excitation microscopy was used to characterize the distribution of autofluorescence inside the spore and the hyphae of the fungus. The imaging analysis clearly shows that the autofluorescence response of spores is higher than that of hyphae. The imaging analysis at different depths shows that, strikingly enough, the spore autofluorescence originates from the cell wall and membrane fluorophores. The spectroscopic results show moreover that the fluorescence spectra of spores are redshifted upon UV-B irradiation. Tentative identification of the chromophores involved in the autofluorescence response and their biological relevance are also discussed on the basis of a previous steady-state fluorescence spectroscopic study performed on both whole spore suspension and organic-soluble extracts.

Image Processing, Computer-Assisted↗
PubMed2000

Development of a mouse model of neuropathic pain following photochemically induced ischemia in the sciatic nerve.

A mouse model of neuropathic pain was developed by a photochemically induced ischemic nerve injury in normal male C57/BL6 mice. The ischemia was induced by unilateral irradiation of the sciatic nerve with an argon ion laser after intravenous administration of a photosensitizing dye, erythrosin B. The nerve injury resulted in a significant decrease in withdrawal threshold of the hindpaws to mechanical stimulation with von Frey hairs, as well as increased responsiveness to cold and heat stimulation. The mice, however, did not exhibit overt spontaneous pain-like behaviors. The evoked pain-related behaviors were observed bilaterally, although the ipsilateral changes were greater than on the contralateral side. The extent and time course of the behavioral changes were related to the duration of laser irradiation, with 1-min exposure producing the most consistent effect. Morphological examination at the light microscopic level revealed partial demyelination and axonal degeneration of the large myelinated fibers at the epicenter of the lesion 1 week postirradiation. The extent of the damage was correlated with the duration of irradiation. Injury and loss of unmyelinated fibers were also observed at the electronmicroscopic level. We conclude that an intravascular photochemical reaction leading to ischemia results in graded damage to the sciatic nerve in mice. Moreover, the nerve injury is associated with the development of abnormal pain-related behaviors. Both the behavioral and the morphological changes are correlated with the duration of irradiation. These results establish a mouse model of partial nerve injury with neuropathic pain-like behaviors which may be useful in studies using genetically modified mice.

Animals↗
PubMed2000

Altered baroreflex responses in alpha7 deficient mice.

The autonomic nervous system controls and coordinates several cardiovascular functions, including heart rate, arterial pressure, blood flow and vasomotor tone. Neuronal nicotinic acetylcholine receptors (nAChRs) are the interface between the nervous system and the cardiovascular system, but it is not known which nAChR subtypes regulate autonomic function in vivo. Nicotinic AChRs containing the alpha7 subunit are a candidate subtype in autonomic ganglia. Stimulation of these nAChRs can increase neurotransmitter release via presynaptic mechanisms, as well as mediate fast synaptic transmission via postsynaptic mechanisms. To investigate the role of the alpha7 nAChR subunit in cardiac autonomic function, we measured baroreflex-mediated responses in alpha7 null mice. Here we show that the alpha7 null mice have impaired sympathetic responses to vasodilatation, as sodium nitroprusside infusion triggered a 48% heart rate increase in wild type mice but only a 21% increase in the alpha7 nulls (P < 0.001). The mutant mice developed supersensitivity to adrenergic agonists, although norepinephrine release from sympathetic nerve terminals could be elicited through mechanisms alternative to nAChR stimulation. Baroreflex-mediated parasympathetic responses were normal in alpha7 null mice. The decreased baroreflex-mediated tachycardia in alpha7 mutant mice indicates that alpha7-containing nAChRs participate in the autonomic reflex that maintains blood pressure homeostasis. The alpha7 mutant mice may serve as a model of baroreflex impairment arising from autonomic dysfunction.

Animals↗
PubMed2000

Regulation of RAG expression in developing lymphocytes.

Proper expression of products of the recombination-activating genes (RAGs) is essential for the development of the adaptive immune system. A major advance in the past year toward understanding RAG regulation is the establishment of green fluorescent protein (GFP)-RAG indicator mouse strains. In vivo visualization of RAG expression in single cells has helped to define the cells that express RAGs in secondary lymphoid organs and revealed differential cis requirements for stage- and lineage-specific RAG expression.

Animals↗
PubMed2000

Effect of intragastric pH on control of peptic ulcer bleeding.

BACKGROUND: We have performed series studies to investigate the effect of intragastric pH on control of peptic ulcer bleeding. In laboratory and animal studies, both platelet aggregation and gastric mucosal bleeding time were shown to be extremely sensitive to different pH levels. Platelet aggregation decreased significantly at pH > or = 6.8 and gastric mucosal bleeding time fell significantly at pH > or = 6.4. In a prospective clinical trial, primed infusions of different dosages of omeprazole (8 or 4 mg/h) after a bolus (40 mg) produced consistently high intragastric pH values in patients with bleeding duodenal ulcer. These results were not significantly different from that obtained from omeprazole 40 mg bolus treatment every 12 h (P > 0.05). However, primed injection with cimetidine (800 mg/12 h) was less effective (P < 0.05). METHODS: In a retrospective analysis, 303 patients with bleeding peptic ulcer who were treated with cimetidine and 326 patients who were treated with omeprazole were compared. RESULTS: The emergency surgery (4.91%) and mortality rates (1.84%) in the omeprazole group were not significantly different (P > 0.05) from those (7.28 and 1.99%) in the cimetidine group. However, the standardized emergency surgery rate of the omeprazole group (3.28%) was significantly lower than that (9.28%) of the cimetidine group (P < 0.05). CONCLUSION: We conclude that increased intragastric pH to at least 6.4 with omeprazole is helpful in controlling peptic ulcer bleeding. Chinese patients require a lower dose of omeprazole than their Western counterparts to control ulcer bleeding.

Adolescent↗
PubMed2000

Intensive care unit use and mortality in the elderly.

OBJECTIVE: To examine utilization and outcomes of intensive care unit (ICU) use for the elderly in the United States. DESIGN: We used 1992 data from the Health Care Financing Administration to examine ICU utilization and mortality by age and admission reason for hospitalizations of elderly Medicare beneficiaries. MAIN RESULTS: Use of the ICU was least likely for the oldest elderly overall (85+ years, 21.1% of admissions involved ICU; 75-84 years, 27.9%; 65-74 years, 29.7%), but more likely during surgical admissions. Eighty-three percent of the Medicare patients who received intensive care survived at least 90 days. Of the oldest elderly, 74% survived. Even among the 10% most expensive ICU hospitalizations, 77% of all patients and 62% of those 85 years and older survived at least 90 days. CONCLUSIONS: The likelihood of ICU use among these elderly decreased with age, especially among those 85 years or older. Diagnostic mix importantly influenced ICU use by age. The great majority of the elderly, including those 85 years and older and those receiving the most expensive ICU care, survived at least 90 days.

Aged↗
PubMed2000

Photochemically-induced ischemic injury of the rat sciatic nerve: a light- and electron microscopic study.

Lesion of presumably ischemic origin of the rat sciatic nerve was induced photochemically by laser irradiation combined with systemic administration of a photosensitizing organic dye, erythrosin B. We have studied the pathologic features of the nerve after the photochemical insult with light- and electronmicroscopy and related them to behavioral signs of neuropathic pain. At the irradiated nerve site, occlusion of blood vessels was seen and the vessels were packed with aggregated thrombocytes, fibrins and deformed erythrocytes, supporting the notion that photochemical reaction caused intraneural ischemia. The degree of the nerve injury at the center of irradiation was related to the duration of the laser exposure. Brief irradiation (30 seconds) only caused identifiable injury to myelinated fibers, whereas longer irradiation (2 minutes) caused greater injury to myelinated and unmyelinated fibers, characterized by extensive axonal degeneration and demyelination. The rats irradiated for 2 minutes, but not 30 seconds, exhibited neuropathic pain-like behaviors, expressed as mechanical and cold allodynia. The nerve injury was most severe 7 days after ischemia and regeneration of both myelinated and unmyelinated fibers was observed 3 months later. The nerve caudal to the irradiation exhibited Wallerian degeneration 7 days after the insult, whereas at 10 mm proximal to the irradiation the nerve was largely normal. It is thus concluded that photochemically induced intraneural ischemia caused injury to both myelinated and unmyelinated fibers, with myelinated fibers being more susceptible. However, the development of neuropathic pain-like behaviors may require injury to the unmyelinated fibers.

Animals↗
PubMed2000

Gender differences in the treatment of cerebrovascular disease.

OBJECTIVE: Previous studies have shown that women receive fewer invasive procedures for the treatment of coronary artery disease than men, but gender differences in cerebrovascular disease have not been well studied. Our objective was to explore differences in the treatment of stroke between men and women. DESIGN: Secondary database analyses. STUDY PARTICIPANTS: We examined the use of carotid endarterectomy in a nationally representative sample of Medicare enrollees aged 65 to 84, hospitalized for a principal diagnosis of stroke in 1992, the "all strokes group". We also studied a subgroup of patients, the "carotid disease subgroup", admitted with a principal diagnosis of precerebral arterial occlusion and stenosis or transient cerebral ischemia. MEASUREMENTS: We determined rates of carotid endarterectomy for the all strokes group within gender and age groups and calculated corresponding female-to-male relative risks (RR) and 95% confidence intervals (CI). We also performed similar analyses for the carotid disease subgroup. We then used logistic regression to estimate the relative risk of use of carotid endarterectomy for women, controlling for age and comorbidity. RESULTS: The all-strokes group consisted of 3,356 women and 2,927 men, of whom 1,009 women and 990 men were in the carotid disease subgroup. The overall age-adjusted female-to-male relative risk of undergoing carotid endarterectomy for those aged 65 to 84 was 0.69 (95% CI, 0.64-0.74) in the all strokes group and 0.77 (95% CI, 0.72-0.82) in the carotid disease subgroup. In both analyses, the RR became more pronounced with increasing age. In the all strokes group, for example, the RR was 0.80 (0.70-0.92) for those aged 65 to 69 and 0.39 (0.32-0.48) for those aged 80 to 84. The RR for the all strokes group remained similar in magnitude even after controlling for comorbidity (RR, 0.63 and 95% CI, 0.59-0.70). CONCLUSION: We conclude that women hospitalized for strokes undergo fewer carotid endarterectomies than men. Further studies are needed to examine the reasons for and implications of this gender difference.

Aged↗
PubMed2000

Retigabine, a novel anti-convulsant, enhances activation of KCNQ2/Q3 potassium channels.

Retigabine [N-(2-amino-4-[fluorobenzylamino]-phenyl) carbamic acid; D-23129] is a novel anticonvulsant, unrelated to currently available antiepileptic agents, with activity in a broad range of seizure models. In the present study, we sought to determine whether retigabine could enhance current through M-like currents in PC12 cells and KCNQ2/Q3 K(+) channels expressed in Chinese hamster ovary cells (CHO-KCNQ2/Q3). In differentiated PC12 cells, retigabine enhanced a linopirdine-sensitive current. The effect of retigabine was associated with a slowing of M-like tail current deactivation in these cells. Retigabine (0.1 to 10 microM) induced a potassium current and hyperpolarized CHO cells expressing KCNQ2/Q3 cells but not in wild-type cells. Retigabine-induced currents in CHO-KCNQ2/Q3 cells were inhibited by 60.6 +/- 11% (n = 4) by the KCNQ2/Q3 blocker, linopirdine (10 microM), and 82.7 +/- 5.4% (n = 4) by BaCl(2) (10 mM). The mechanism by which retigabine enhanced KCNQ2/Q3 currents involved large, drug-induced, leftward shifts in the voltage dependence of channel activation (-33.1 +/- 2.6 mV, n = 4, by 10 microM retigabine). Retigabine shifted the voltage dependence of channel activation with an EC(50) value of 1.6 +/- 0.3 microM (slope factor was 1.2 +/- 0.1, n = 4 to 5 cells per concentration). Retigabine (0.1 to 10 microM) also slowed the rate of channel deactivation, predominantly by increasing the contribution of a slowly deactivating tail current component. Our findings identify KCNQ2/Q3 channels as a molecular target for retigabine and suggest that activation of KCNQ2/Q3 channels may be responsible for at least some of the anticonvulsant activity of this agent.

Animals↗
PubMed2000

Vitamin E succinate induces apoptosis in human prostate cancer cells: role for Fas in vitamin E succinate-triggered apoptosis.

The apoptosis-triggering properties of vitamin E succinate (VES, RRR-alpha-tocopheryl succinate) for human LNCaP and PC-3 prostate carcinoma cells and normal PrEC human prostate epithelial cells were investigated. LNCaP and PC-3 cells were sensitive to VES-induced apoptosis, with 100% and 60% of cells undergoing apoptosis after three days of treatment with 10 micrograms of VES/ml, respectively. PrEC cells were resistant to VES-induced apoptosis. Treatment of prostate cells with agonistic anti-Fas antibody triggered apoptosis in approximately 50% of PC-3 cells within 48 hours, whereas LNCaP and PrEC cells were resistant. Prostate cells simultaneously treated with VES and agonistic anti-Fas antibodies revealed 1) no effect on PrEC cells, 2) an additive effect on Fas-sensitive PC-3 cells, and 3) a synergistic effect on LNCaP cells. VES treatment of LNCaP cells caused depletion of cytosolic 43-kDa Fas, enhanced membrane levels of 43-kDa Fas, and induced Fas sensitivity. PC-3 cells expressed high levels of membrane 43-kDa Fas that were enhanced by VES treatments. Fas ligand expression by LNCaP cells was enhanced by VES treatments. In summary, VES triggers apoptosis in human prostate carcinoma cells but not normal prostate cells in vitro, and VES modulates Fas signaling.

Apoptosis↗
PubMed2000

Synergism of protein kinase A, protein kinase C, and myosin light-chain kinase in the secretory cascade of the pancreatic beta-cell.

Protein phosphorylation by myosin light-chain kinase (MLCK), protein kinase A, and protein kinase C (PKC) plays a positive role in insulin secretion from the pancreatic beta-cell. To investigate the underlying mechanisms, we examined intracellular distribution of the insulin granules and MLCK by immunofluorescence and immunoelectron microscopies and also investigated intracellular traffic of the granules in cultured beta-cells (MIN6) by video microscopy. Considerable parts of MLCK immunoreactivity were colocalized with the insulin granules. Subcellular fractionation of MIN6 cell extracts revealed that myosin light chain (MLC) may be distributed with the insulin-rich fractions, and immunofluorescence staining using specific antibodies against mono- and diphosphorylated MLCs depicted presence of phosphorylated MLCs in the cytoplasm, in part, with colocalization with the insulin granules. Activation of PKC by 12-O-tetradecanoyl-phorbol 13-acetate (TPA) caused a shift of both insulin granules and MLCK to the cell periphery, which was not reproduced by the adenylate cyclase activator, forskolin. In contrast, forskolin, but not TPA, increased the granule movement. Costimulation of the beta-cell by TPA and forskolin induced drastic translocation of insulin granules and MLCK to the cell periphery, resulting in enormous potentiation of insulin release. These findings suggest that these protein kinases increase insulin granules in the ready-releasable pool by acting on different steps in the secretory cascade.

Cell Line↗
PubMed2000

Cardiac angiosarcoma: two cases and a review of the literature.

BACKGROUND: Primary cardiac tumours are rare, and primary malignant cardiac tumours even rarer. Of these, cardiac angiosarcomas are uncommon and, until recently, almost invariably diagnosed at the time of autopsy, primarily because the symptoms are initially nonspecific and do not become manifest until the tumour is advanced. METHODS: Two patients, who presented in quite different manners and were diagnosed at autopsy and at open surgical biopsy, are presented. The literature on cardiac angiosarcomas is reviewed critically, with emphasis on presentation and morphology. RESULTS: This review of the literature shows that, with increasing availability of newer diagnostic tools, especially noninvasive ones, diagnosis of this rare lesion can be made at an early stage and confirmed at cardiac biopsy or cardiac surgery. Unfortunately, so far, the results remain virtually uniformly poor, though occasionally survival at up to 53 months has been reported.

Adult↗