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C C Lai

Publications and source records attributed to C C Lai.

At least 37 records · Page 2Linked to original sources
PubMed2000

Analysis of phospholipase A2 glycosylation patterns from venom of individual bees by capillary electrophoresis/electrospray ionization mass spectrometry using an ion trap mass spectrometer.

A method based on tryptic digestion, ultrafiltration and capillary electrophoresis/mass spectrometry (CE/MS) has been developed for the analysis of the glycosylation pattern in the phospholipase A2 (PLA) of individual honeybees. Without reducing the disulfide bonds, PLA was digested with trypsin and filtered with a 3 kDa molecular weight (MW) cut-off membrane. With this procedure, the glycopeptides could be isolated from the nonglycosylated peptides. After tryptic digestion and ultrafiltration, the disulfide bonds were reduced before analysis by CE. To reduce the adsorption, CE separation was performed on successive multiple ionic-polymer (SMIL) polybrene (PB) coated capillary columns. The SMIL-PB columns allowed partial separation of the glycopeptides and eight glycopeptides were identified by on-line coupling of CE with electrospray ionization (ESI) mass spectrometry. The analysis of phospholipase A2 from the venom of individual bees indicated that the variation and relative abundances of different glycopeptides were similar between the younger and the older bees.

Aging↗
PubMed2000

The platelet-derived growth factor beta receptor as a target of the bovine papillomavirus E5 protein.

The 44-amino acid E5 protein of bovine papillomavirus is a homo-dimeric, transmembrane protein that transforms cells by activating the platelet-derived growth factor ss receptor in a ligand-independent fashion. The E5 protein induces receptor activation by forming a stable complex with the receptor, thereby inducing receptor dimerization, trans-phosphorylation of tyrosine residues in the cytoplasmic domain of the receptor, and recruitment of cellular SH2 domain-containing proteins into a signal transduction complex. Direct interactions between specific transmembrane and juxtamembrane amino acids in the E5 protein and the PDGF ss receptor appear to drive complex formation and dimerization of the receptor. Further analysis of this unique mechanism of viral transformation promises to yield new insight into the regulation of growth factor receptor activity and cellular signal transduction pathways.

Amino Acid Sequence↗
PubMed2000

Regulation of endothelial heme oxygenase activity during hypoxia is dependent on chelatable iron.

The regulation of heme oxygenase (HO) activity and its dependence on iron was studied in bovine aortic endothelial cells (BAEC) subjected to hypoxia-reoxygenation (H/R). HO activity was induced by hypoxia (10 h) and continued to increase during the reoxygenation phase. HO-1 protein levels were strongly induced by hypoxia from undetectable levels and remained elevated at least 8 h postreoxygenation. Addition of the Fe(3+) chelator desferrioxamine mesylate (DFO) or the Fe(2+) chelator o-phenanthroline during hypoxia alone or during the entire H/R period inhibited the induction of HO activity and HO-1 protein levels. However, DFO had no effect and o-phenanthroline had a partial inhibitory effect on HO activity and protein levels when added only during reoxygenation. Loading of BAEC with Fe(3+) enhanced the activation of the HO-1 gene by H/R, whereas loading with L-aminolevulinic acid, which stimulates heme synthesis, had little effect. These results suggest that chelatable iron participates in regulating HO expression during hypoxia.

Acetylcysteine↗
PubMed2000

Nociceptin inhibits rat sympathetic preganglionic neurons in situ and in vitro.

In vitro and in situ experiments were conducted to evaluate the hypothesis that the nonclassical opioid peptide nociceptin acting on sympathetic preganglionic neurons (SPNs) inhibits spinal sympathetic outflow. First, whole cell patch recordings were made from antidromically identified SPNs from immature (12-16 day old) rat spinal cord slices. Nociceptin (0.1, 0.3, and 1 microM) concentration dependently suppressed the excitatory postsynaptic potentials (EPSPs) evoked by focal stimulation and hyperpolarized a population of SPNs; these effects were naloxone insensitive. L-Glutamate-induced depolarizations were not significantly changed by nociceptin. Results from this series of experiments indicate that nociceptin inhibits the activity of SPNs by either a presynaptic or postsynaptic site of action, whereby the peptide reduces, respectively, the amplitude of EPSPs or the excitability of SPNs. Second, intrathecal injection of nociceptin (3, 10, and 30 nmol) to urethan-anesthetized rats dose dependently reduced the mean arterial pressure and heart rate; these effects were not prevented by prior intravenous administration of naloxone (1 mg/kg). Physiological saline given intrathecally was without appreciable effects. These results, together with earlier observations of the detection of nociceptin-immunoreactive nerve fibers and nociceptin receptor immunoreactivity in the rat intermediolateral cell column, raise the possibility that the opioid peptide, which may be released endogenously, reduces spinal sympathetic outflow by depressing the activity of SPNs.

Animals↗
PubMed2000

Endogenous Klebsiella pneumoniae endophthalmitis associated with prostate abscess: case report.

A young alcoholic and heavy smoker was admitted because of Klebsiella pneumoniae bacteremia. The abdominal and pelvic computed tomography with enhancement revealed an abscess in the right prostate. He experienced blurred vision of his left eye on the third day during admission. Initial ocular examination revealed mild reaction in the anterior chamber and vitreous as well as multiple Roth's spots in the retina. The administration of empirical antibiotics including cefazolin and gentamicin intravenously was changed to ceftriaxone and amikacin after ophthalmologic consultation. After parenteral antibiotics for 3 weeks, the systemic condition was controlled, and the vision remained stable. During the past decades, many cases of endogenous Klebsiella pneumoniae endophthalmitis associated with liver abscess were reported in Taiwan. However, documented reports of this condition associated with a prostate abscess are rare. This case, classified as posterior focal endogenous endophthalmitis, had good prognosis under appropriate antibiotic treatment. Early diagnosis and prompt therapy are important for control of sepsis and restoration of vision.

Abscess↗
PubMed2000

Local immunosuppression prolongs survival of RPE xenografts labeled by retroviral gene transfer.

PURPOSE: To determine whether local immunosuppression with Cyclosporin A can influence the survival of human fetal retinal pigment epithelium (RPE) xenografts in the rabbit's subretinal space. METHODS: Cultured human fetal RPE cells were transduced with the gene for green fluorescent protein (GFP) using a lentiviral vector. The RPE was transplanted into the subretinal space of rabbits that received intravitreal cyclosporine either by weekly injections (0. 25-0.5 mg) or by slow release (approximately 2 microg/d) from a capsule sutured into the vitreal cavity after prior cryopexy. The transplanted RPE was followed by GFP fluorescence scanning laser ophthalmoscopy and by histology of the transplant site. RESULTS: RPE xenografts in eyes receiving intravitreal cyclosporine survived longer (several months) than they did in control eyes without cyclosporine. Survival was as long with slow release capsules as it was with weekly intravitreal injections at much higher concentrations of cyclosporine. CONCLUSIONS: Local immunosuppression of the eye with cyclosporine prolongs the survival of RPE xenografts in the subretinal space of rabbits, implying that rejection involves activated T lymphocytes. Local immunosuppression with slow release capsules is as effective as weekly injections at much higher concentrations.

Animals↗
PubMed2000

Bilateral endogenous Klebsiella pneumoniae endophthalmitis associated with meningitis-useful vision regained after treatment: case report.

Endogenous endophthalmitis is a rare but devastating complication of bacteremia. Klebsiella pneumoniae is reported to be the leading organism of endogenous endophthalmitis in Taiwan, and the prognosis of endogenous Klebsiella pneumoniae endophthalmitis is extremely poor. A 46-year-old male patient was hospitalized because of fever, chills, and consciousness disturbance for 1 day. Meningitis was the impression by clinical presentation and findings of cerebrospinal fluid analysis. Parenteral ceftriaxone (4 g/day) and gentamicin (180 mg/day) were given, and his consciousness gradually cleared. On hospital day 6, he complained of blurred vision in both eyes and floaters in the left eye for 1 day. After ophthalmic examination, bilateral endogenous endophthalmitis was diagnosed. After aggressive treatment with intravitreal antibiotics and trans pars plana vitrectomy, the visual outcome of both eyes was better than those of other reported cases.

Endophthalmitis↗
PubMed2000

Dietary oxidized oil influences the levels of type 2 T-helper cell-related antibody and inflammatory mediators in mice.

The aim of this present study was to investigate the effect of amount and degree of oxidation of dietary oil on type 2 T-helper cell (TH)-related immune responses. Four groups of BALB/c mice were fed either 50 g soyabean oil/kg (50-S), 50 g oxidized oil/kg (50-O), 150 g soyabean oil/kg (150-S) or 150 g oxidized oil/kg (150-O). After 14 weeks consuming the experimental diets, the mice were immunized with ovalbumin (OVA) plus Al and antigen-specific immunoglobulin (Ig)E, IgG1 and IgG2a, inflammatory mediators such as prostaglandin (PG) E2 and leukotriene (LT)B4 were determined. Higher hepatic microsomal cytochrome P450 was noted in mice fed 150 g oxidized oil/kg compared with those of other groups. OVA-specific IgG1 and IgE were higher in mice fed 150 g oxidized oil/kg compared with those of the other groups. The data suggested the interleukin (IL)-4: interferon (IFN)-gamma ratio was higher in mice fed 50 g dietary oxidized oil/kg compared with that of the 50-S group. The IL-5:IFN-gamma ratios were higher in the 150-S and 150-O groups than in the 50-S and 50-O groups. PGE2 and LTB4 produced by macrophages stimulated by lipopolysaccharide were highest in mice in the 150 g oxidized oil/kg group. The data suggested that an increased intake of oxidized oil might exert an unfavourable effect on the TH2 response involved in allergic disease.

Animals↗
PubMed1999

Constitutive hsp70 attenuates hydrogen peroxide-induced membrane lipid peroxidation.

Thermal pretreatment improves cardiac recovery from subsequent ischemia/reperfusion. Induction of heat shock proteins (hsps) may contribute to this protection. We have demonstrated that augmentation of the constitutive hsp70 (hsc70) in H9c2 heart myoblasts promotes oxidative resistance. We employed a model oxidant to explore potential target(s) of protection by hsc70. Upon exposure to 54 microM of hydrogen peroxide (H(2)O(2)), hsc70-overexpressing cells exhibited a lower lipid peroxidation than the sham-transfected control. Constitutive hsc70 overexpression, however, did not protect against H(2)O(2)-induced depletion of ATP and glutathione (GSH). Lipid protection also occurred in cells preconditioned at 39 degrees C (selectively induces hsc70) during H(2)O(2) exposure. Interestingly, the protection conferred by hsc70 was comparable in magnitude to that provided by alpha-tocopherol, and was followed with a reduced release of lactate dehydrogenase and a unaltered calcium uptake during H(2)O(2) challenge. Collectively, our observations suggest that hsc70 may preserve membrane function via attenuation of lipid peroxidation during oxidative insult.

Animals↗
PubMed1999

Induction of heat-shock protein 72 in rat skeletal muscle does not increase tolerance to ischemia-reperfusion injury.

Ischemia-reperfusion injury is implicated in the failure of free flap and replant surgeries and is associated with the pathogenesis of a wide variety of clinical diseases including stroke, myocardial infarction, spinal injury, and compartment syndromes. We used a skeletal muscle flap model to test if the induction of heat-shock protein 72 (HSP72) by mild hyperthermia provides tolerance against ischemia-reperfusion injury. Immunocytochemistry and Western blot analysis verified increased production of HSP72 in the gracilis muscle of globally heated rats. Neutrophil accumulation in the microvasculature and postischemic muscle survival after ischemia-reperfusion were unaltered by preischemic hyperthermia, indicating HSP72 induction is not sufficient to provide resistance against severe injury in skeletal muscle.

Adaptation, Physiological↗
PubMed1999

A physiologically relevant hyperthermia selectively activates constitutive hsp70 in H9c2 cardiac myoblasts and confers oxidative protection.

Whole body hyperthermia (42-43 degrees C for 15-20 min) elicits the formation of heat shock proteins (hsps) and improves cardiac recovery from subsequent ischemia/reperfusion. However, the beneficial effects of this response are compromised by initial tissue injury, which limits its clinical applicability. Using a simplified myocardial model (rat heart-derived H9c2 myoblasts) a hypothesis was tested that chronic, mild hyperthermia is as effective as acute heat shock in inducing the heat shock response. Our results indicate that 39 degrees C pre-conditioning evoked thermotolerance and oxidative resistance, but caused no detectable adverse effects. An improved survival after hydrogen peroxide (H2O2) exposure (40-54 microm for 3 h) was first observed in cells pre-conditioned at 39 degrees C for 24 h. As the duration of thermal pre-incubation increased, cells became more resistant than the control (37 degrees C) to a greater toxicity of H2O2(68 microm). An optimal oxidative protection developed by;4 days at 39 degrees C and this persisted for as long as the cells were incubated at this temperature. Three hsps are known to modulate cellular antioxidant defenses: the constitutive-hsp70 (hsc70), its inducible counterpart (hsp70), and hsp27. The authors found that mild hyperthermia selectively induced only hsc70, which demonstrates a lower temperature threshold for activation of hsc70. The initial protection against the milder H2O2challenge correlated with a homogenous distribution of pre-existing hsc70. The subsequent optimal protection was associated with an identical distribution pattern and a moderate increase of hsc70. These observations suggest that mild hyperthermia induces a beneficial adaptive response, in which hsc70 plays a critical role.

Adaptation, Physiological↗
PubMed1999

Tracking RPE transplants labeled by retroviral gene transfer with green fluorescent protein.

PURPOSE: To determine whether human retinal pigment epithelium (RPE) can be modified by retroviral-mediated gene transfer and to monitor the human RPE cells in the subretinal space of living rabbits with scanning laser ophthalmoscopy (SLO). METHODS: Cultured human fetal retinal pigment epithelium (HFRPE) was exposed to green fluorescent protein (GFP)-transducing retroviral vectors, Moloney murine leukemia virus, and lentivirus. The cultured cells were followed by fluorescence microscopy. Suspensions of GFP-expressing HFRPE were transplanted into the subretinal space of pigmented rabbits, and the transplant sites were examined by SLO for fluorescence, including fluorescein and indocyanine green angiography. The rabbits were euthanatized at different times after transplantation, and the retinas were studied histologically. RESULTS: Retroviral gene transfer can introduce a foreign gene such as GFP into cultured HFRPE. Gene expression is maintained in cultured RPE for at least 3 months. The lentiviral vector transduced both nondividing and dividing cells; the Moloney vector only transduced the latter. GFP-expressing cells can be followed in the living retina. Their changes reflect the rejection response followed histologically. CONCLUSIONS: Cultured HFRPE could be transduced to express GFP for long periods of time by retroviral gene transfer. GFP allowed retinal transplants and gene expression to be monitored in vivo. These results provide a model for potential ex vivo gene therapy in the subretinal space.

Animals↗
PubMed1999

Rapidly resorptive exudative retinal detachment in a patient with renogenic hypertension: case report.

We present an 18-year-old woman who developed rapidly resorptive exudative retinal detachment (ERD) due to chronic renal failure and renogenic hypertension. In July 1998, the patient came to our clinic because of a 2-month-history of progressively deteriorating visual acuity. Initially examination of the fundi revealed typical hypertensive retinopathy. Two weeks later, the patient was admitted due to hypertension and consulted our ophthalmic department again. In addition to hypertensive retinopathy, the fundi showed high bullous ERD, involving the temporal retinas in both eyes. Intensive medical therapy was begun, including blood pressure control and maintenance of body fluid and electrolyte balance, resulting in almost complete regression of retinal detachment within two days. The visual acuity improved during the following 2 weeks. The clinical features and treatment response in this rare case indicate that multiple factors, including fluids overload, hypertension, and possibly renal failure, contributed to the development of ERD. Blood pressure control and the balance of fluids are important in patients with renal failure, and may help to prevent the occurrence of ERD.

Adolescent↗
PubMed1999

Evaluation of peribulbar anesthesia in encircling scleral buckle surgery and its postoperative pain course.

BACKGROUND: Retrobulbar anesthesia is considered effective in ocular surgery but it can give rise to serious complications. We used peribulbar anesthesia with sub-Tenon's irrigation to perform encircling scleral buckling for retinal detachment, as it could reduce the complications caused by retrobulbar anesthesia. We also recorded the course of pain for 72 hours after surgery. METHODS: Thirty patients who were diagnosed with rhegmatogenous retinal detachment were treated with an encircling scleral buckle. The surgery was performed with peribulbar anesthesia with occasional sub-Tenon's irrigation. We evaluated the patient's pain with a visual analogue scale after surgery at 30 minutes, 1 hour, 2 hours, 4 hours, 6 hours, 12 hours, 24 hours, 48 hours, and 72 hours. RESULTS: In 24 cases (80%), the anesthesia was complete with the peribulbar block. Only 6 patients (20%) needed sub-Tenon's irrigation and four of them felt no pain after augmentation. Although all the surgical procedures proceeded without problem, two of the patients felt pain and were uncomfortable during the surgery. No serious complications occurred. The course of pain peaked 6 hours after surgery when 26 patients (86.7%) felt pain and 12 patients (40%) were uncomfortable (pain score > or = 5). Forty-eight hours after surgery, 9 patients (30%) still felt pain but no one felt uncomfortable. CONCLUSION: Peribulbar anesthesia can be used safely in encircling scleral buckling for retinal detachment. The postoperative pain is maximal 6 hours after surgery and becomes mild (pain score < or = 4) after 48 hours.

Adolescent↗
PubMed1998

Bovine papillomavirus E5 protein induces oligomerization and trans-phosphorylation of the platelet-derived growth factor beta receptor.

The bovine papillomavirus E5 protein is a 44-aa transmembrane protein that forms a stable complex with the cellular platelet-derived growth factor (PDGF) beta receptor and induces constitutive tyrosine phosphorylation and activation of the receptor, resulting in cell transformation. The E5 protein does not resemble PDGF, but rather activates the receptor in a ligand-independent fashion, thus providing a unique system to examine activation of receptor tyrosine kinases. Here, we used a variety of approaches to explore the mechanism of receptor activation by the E5 protein. Chemical cross-linking experiments revealed that the E5 protein activated only a small fraction of the endogenous PDGF beta receptor in transformed fibroblasts and suggested that this fraction was constitutively dimerized. Coimmunoprecipitation experiments using extracts of cells engineered to coexpress full-length and truncated PDGF beta receptors confirmed that the E5 protein induced oligomerization of the receptor. Furthermore, in cells expressing the E5 protein, a kinase-active receptor was able to trans-phosphorylate a kinase-negative mutant receptor but was unable to catalyze intramolecular autophosphorylation. These results indicated that the E5 protein induced PDGF beta receptor activation by forming a stable complex with the receptor, resulting in receptor dimerization and trans-phosphorylation.

Amino Acid Substitution↗
PubMed1998

Constitutive and inducible hsp70s are involved in oxidative resistance evoked by heat shock or ethanol.

Improved cardiac post-ischemic recovery after whole-body hyperthermia is correlated with an increased expression of the heat shock proteins (hsps). The inducible hsp70 (hsp70i) has a known cardioprotective effect against ischemia/reperfusion injury. Here, we studied whether other hsps are also involved in cardioprotection. Using rat heart-derived H9c2 myocytes, we observed that preheating at 43 degreesC for 20 min conferred resistance to hydrogen peroxide (H2O2). The resistance to mild H2O2 toxicity (3-5 micro mol/10(7) cells) appeared early and persisted, whereas the resistance to moderate H2O2 toxicity (6-9 micro mol/10(7) cells) was detectable only at 20-44 h post heat shock. No resistance was observed at higher doses of hydrogen peroxide (10-12 micro mol/10(7) cells), indicating that severe toxicity exceeds the capacity of the induced protective mechanism. Coincidentally, this thermal regimen elicited a rapid and prolonged increase in the cellular level of hsp70i, and a delayed and transient induction of the constitutive hsp70 (hsp70c). Nuclear translocations of hsp70i and hsp70c also occurred upon heat stimulation. A homogeneous distribution of the accumulated hsp70i and hsp70c throughout the nuclei and cytoplasm paralleled the development of heat-induced resistance to moderate H2O2 challenge. Application of another hsp inducer, ethyl alcohol, evoked a similar pattern of H2O2 resistance, and hsp induction and distribution. Our results suggest that induction and subcellular distribution of hsp70s contribute importantly to cellular antioxidant defenses, and that a co-operation between hsp70i and hsp70c may improve cardiac preservation during oxidative insult.

Animals↗