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C F Lo

Publications and source records attributed to C F Lo.

At least 37 records · Page 2Linked to original sources
PubMed1999

A new picorna-like virus, PnPV, isolated from ficus transparent wing moth, Perina nuda (Fabricius).

Two viruses, Perina nuda nucleopolyhedrovirus and a new picorna-like virus, were previously isolated from P. nuda larvae with flacherie. In this study the new picorna-like virus was characterized using physical and biochemical methods. This small virus appears to belong to the family Picornaviridae and we propose the name PnPV. PnPV can be propagated in its homogenous cell line, NTU-PN-HH. PnPV purified from the cell line resembles PnPV isolated from insects: under electron microscopy, it exhibits icosahedral symmetry, measures 30 nm in diameter, and has no envelope and no distinct surface structure in negatively stained preparations. In addition, we show here that PnPV has a buoyant density of 1.381 g/ml in cesium chloride, the viral genome was composed of one single-stranded RNA molecule with a length of 10 kb, and poly(A) tract and polyacrylamide gel electrophoresis of purified viral particles revealed three major (31.5, 29.7, and 28.4 kDa) and three minor (27. 0, 24.5, and 4.0 kDa) structural proteins.

Animals↗
PubMed1998

Independent and exclusive modulation of cardiac delayed rectifying K+ current by protein kinase C and protein kinase A.

Expression of minK in Xenopus oocytes results in a current similar to the cardiac slow delayed rectifying K+ (IKs) current. Modulation of the IKs current in cardiac myocytes has been studied extensively because of its role in shaping the cardiac action potential. The human and cat minK cDNA have been cloned, but their regulation by protein kinases has not been characterized. We report here on the complex modulation of human and cat IKs currents by protein kinase C (PKC) and protein kinase A (PKA). Activation of PKC by phorbol ester (100 nmol/L phorbol 12,13-didecanoate [PDD]) produces an increase in IKs current that peaks after 20 minutes and then subsequently decreases to approximately 50% of the control level after 1 hour. PKA activation only produces a sustained increase in IKs current. Interestingly, premodulation by PKC prevents IKs current modulation by PKA, and PKC has no effect on IKs current after potentiation by PKA. This shows that the IKs current is modulated by PKC and PKA in a mutually exclusive manner and suggests that multiple interacting phosphorylation sites are involved. Activation of PKC by diacylglycerol analogues only produces a slow decrease in IKs current. The biphasic effects of PKC on IKs current activated by PDD can also be separated by dose and duration. Low doses of PDD (5 nmol/L) or brief applications (5 minutes) of 100 nmol/L PDD only produces IKs current activation. These data suggest that there are at least 2 independent PKC phosphorylation sites in the minK-KvLQT1 channel. Additionally, long-term activation of PKC strongly attenuates the IKs current expression even when the corresponding changes in capacitance are taken into account.

Animals↗
PubMed1997

Characterization of C3-binding proteins on mouse neutrophils and platelets.

In the mouse, MCR1 and MCR2 on B lymphocytes are encoded by alternatively spliced Cr2 gene transcripts. Immune adherence receptors that bind C3 are present on mouse platelets and unstimulated neutrophils, yet they are not MCR1 or MCR2. To examine C3b- and C3d-binding proteins on mouse platelets and neutrophils, we performed C3b and C3d affinity chromatography as well as immunoprecipitation studies using previously described Ab to MCR1/MCR2 (mAb clones 8C12, 7G6, and 7E9 and polyclonal Ab BRN-1). Mouse neutrophils contained a 190-kDa membrane protein that specifically bound to C3b-Sepharose. Preabsorption of neutrophil proteins with anti-MCR1/MCR2 Ab did not affect the recovery of the 190-kDa C3b-binding protein by subsequent C3b affinity chromatography. Thus, this protein is immunologically distinct from the previously described MCR1 and MCR2 proteins. By virtue of its size and C3b-binding capacity, the 190-kDa protein was named C3bR-190. C3bR-190 was also apparent on platelets, but in reduced amounts. BRN-1 anti-MCR1/MCR2 Ab immunoprecipitated proteins of 125 and 150 kDa from surface-radiolabeled mouse platelets, which specifically bound to C3d-Sepharose. However, these proteins were not identified by mAb to MCR2, thus distinguishing them from previously described MCR2. These proteins were named C3dR-125 and C3dR-150. Therefore, we have identified a 190-kDa C3b-binding protein on mouse neutrophils and 125- and 150-kDa C3d-binding proteins on mouse platelets. These appear to be distinct from the heretofore identified mouse B lymphocyte MCR1 and MCR2. The identity of these C3b- and C3d-binding proteins on mouse neutrophils and platelets awaits further study.

Animals↗
PubMed1997

Characterization of the human and rat phospholemman (PLM) cDNAs and localization of the human PLM gene to chromosome 19q13.1.

Previous reports have demonstrated that the phospholemman (PLM), a 72-residue plasma-membrane protein enriched in skeletal muscle and heart, is a major substrate phosphorylated in response to insulin and adrenergic stimulation. Here we describe the isolation and characterization of human and rat PLM cDNA from the heart. Both PLM proteins share significant nucleotide and amino acid sequence and structural similarities with the previously published canine PLM and, to a lesser degree, with Na+/K(+)-ATPase gamma subunit, Mat-8 protein, and CHIF protein. Despite the functional diversity, all these proteins are quite small and possess a single transmembrane domain. Human PLM appears to be a unique gene localized on chromosome 19q13.1. The PLM mRNA is widely distributed in human tissues, with the highest expression in skeletal muscle and heart, suggesting a functional role in muscle contraction. Like canine PLM, both human and rat PLM induce a hyperpolarization-activated chloride current when expressed in Xenopus oocytes. The high degree of sequence and functional conservation among the mammalian PLM proteins indicates that this gene is conserved throughout evolution.

Amino Acid Sequence↗
PubMed1997

Endothelium-dependent higenamine-induced aortic relaxation in isolated rat aorta.

The pharmacological action of higenamine in isolated rat aorta was investigated. Although the beta-adrenoceptor antagonist propranolol (1 x 10(-5) M) completely blocked the beta-adrenoceptor agonist higenamine in inducing a positive chronotropic activity in isolated mouse atria, the higenamine-induced aortic relaxation was not completely antagonized by this concentration of propranolol. The present data also demonstrate that the higenamine-induced aortic relaxation was attenuated in the absence of endothelium. These findings suggest that the beta-adrenoceptor specificity to higenamine in aorta is different from that of beta-1 in atria; moreover, the beta-adrenoceptors sensitive to higenamine are mainly located in the endothelial layer.

Adrenergic beta-Agonists↗
PubMed1996

Pharmacokinetics of higenamine in rabbits.

The pharmacokinetics of higenamine were investigated in rabbits by IV bolus, PO route, and IV infusion. Plasma higenamine concentration declined rapidly in a biexponential pattern, with a terminal half-life of 22 min. The AUC increased proportionally with increasing dose, whereas the percentage of unchanged higenamine excreted from urine remained constant when dose was increased. The means of total body clearance, mean residence time, volume of distribution at steady state, and fraction of urinary excretion were 127.7 mL min-1 kg-1, 9.28 min, 1.44 kg-1, and 5.48%, respectively. The mean percentage of protein binding of higenamine in plasma was 54.8% at steady state after IV infusion. The results from post-infusion also confirmed that higenamine followed a two-compartment open model in animals. After oral administration, higenamine was rapidly absorbed to reach peak concentration within 10 min. Interestingly, the plasma concentration-time profiles revealed two distinguishable groups with different Cmax, extent of absorption, and urinary excretion. The average absolute bioavailabilities of higenamine calculated by AUCs and accumulated urinary excretion were 21.86 and 2.84% versus 20.19 and 5.50% for the two groups, respectively. Upon hydrolysis of urine samples with beta-glucuronidase, urinary concentrations of higenamine were greatly enhanced in both groups.

Administration, Oral↗
PubMed1996

Characterization of Perina nuda nucleopolyhedrovirus (PenuNPV) polyhedrin gene.

The Perina nuda nucleopolyhedrovirus (PenuNPV) polyhedrin gene was located in EcoRI-G (6.3 kilobase pairs; kbp) and PstI-G (4.3 kbp) fragments of its genomic DNA. A portion of 1333 nucleotides (nt) containing this gene was sequenced. An open reading frame of 735 nt encoded a 245-amino-acid-long polyhedrin. A conserved TAAG motif which is associated with transcriptional start sites was identified 51 nt upstream of the translation initiation codon of PenuNPV polyhedrin gene. A putative polyadenylation signal, AATAAA, was found 116 nt downstream of the termination codon (TAA). Comparison of the amino acid sequences of PenuNPV polyhedrin with those of other NPVs showed that PenuNPV polyhedrin was most closely related to Orgyia pseudotsugata multiple NPV (OpMNPV) polyhedrin.

Amino Acid Sequence↗
PubMed1996

The bamboo skewer: airway management in a patient with penetrating injury of the floor of mouth.

PURPOSE: To report a safe airway management option in patients with penetrating injury of the floor of the mouth, reinforcing the similar experience of others and illustrating the importance of proper assessment and planning before airway negotiation. CLINICAL FEATURES: A 23-yr-old man was admitted with a penetrating injury of the floor of mouth caused by falling on bamboo and with the foreign body in situ. The extent of penetration could not be assessed clinically but computerized tomography (CT) was used to assist in preoperative evaluation of the airway. After atropine iv, fentanyl iv, topical cocaine and lidocaine spray, awake fibreoptic guided nasal intubation was performed successfully and the patients airway secured before induction of anaesthesia. Elective tracheostomy was performed postoperatively which was removed on day 5. Post-operative recovery was uneventful. CONCLUSION: Awake fibreoptic guided nasal intubation was useful in managing the airway of a patient with a penetrating injury of the floor of mouth and foreign body in situ. Thorough previous evaluation of the patients airway by CT scan, careful topicalisation of the airway, and judicious use of iv sedation and anti-sialogue contributed to the safe and successful airway management.

Adult↗
PubMed1995

Molecular characterization of rat Crry: widespread distribution of two alternative forms of Crry mRNA.

The rat complement regulator 5I2 antigen/Crry is present in a widespread distribution as at least two discrete proteins of Mr 65000-70000 and 75000-85000. The molecular basis for the different proteins has not been determined. We screened a cDNA library derived from cultured rat glomerular epithelial cells with a polymerase chain reaction (PCR)-generated nucleotide probe for CR1 and Crry. Two identical clones with 1.8 kilobase inserts were obtained. Clone 6.1 consisted of 1811 nucleotides. The sequence was identical to nucleotides 42-1666 of the cDNA for rat 5I2 antigen/Crry except for 11 nucleotides at the extreme 5' and 3' ends and an exact duplication of 186 bases that would encode an additional complete short consensus repeat (SCR). By reverse transcription PCR, we show that the two forms of Crry mRNA exist in all rat cells/tissues examined. It is likely that these two Crry mRNA species differ by the absence or presence of a 186 base repeat that encodes a complete SCR. These are translated into Crry proteins, containing six and seven SCRs, respectively, which explains the different sizes of Crry proteins. The role of the SCR duplication remains to be defined.

Alternative Splicing↗
PubMed1995

Cellular chloride depletion inhibits cAMP-activated electrogenic chloride fluxes in HT29-18-C1 cells.

Cyclic AMP-activated chloride fluxes have been analyzed in HT29-18-C1 cells (a clonal cell line derived from a human colon carcinoma) using measurements of cell volume (electronic cell sizing), cell chloride content (chloride titrator) and intracellular chloride activity (6-methoxy-N-(3-sulfopropyl)quinolinium; SPQ). HT29-18-C1 was shown to mediate polarized chloride transport. In unstimulated cells, the apical membrane was impermeable to chloride and net chloride flux was mediated by basolateral furosemide-sensitive transport. Forskolin (10 microM) increased furosemide-insensitive chloride permeability of the apical membrane, and decreased steady-state intracellular chloride concentration approximately 9%. Cellular chloride depletion (substitution of medium chloride by nitrate or gluconate), caused greater than fourfold reduction in cellular chloride concentration. When chloride-depleted cells were returned to normal medium, cells regained chloride and osmolytes via bumetanide-sensitive transport, but forskolin did not stimulate bumetanide-insensitive chloride uptake. The inhibition of cAMP-activated chloride reuptake was not explained by limiting cation conductance, cell shrinkage, choice of substitute anion, or decreased generation of cAMP in chloride-depleted cells. When cells with normal chloride content were depolarized (135 mM medium potassium + 10 microM valinomycin), cAMP activated electrogenic chloride uptake permselective for Cl- approximately Br- > NO3- > I-. The electrogenic transport pathway was inhibited in chloride-depleted cells. Results suggest that chloride depletion limits activation of electrogenic chloride flux.

Anions↗
PubMed1995

Complement regulation in the rat glomerulus: Crry and CD59 regulate complement in glomerular mesangial and endothelial cells.

The complement regulators, decay accelerating factor, membrane cofactor protein, and CD59 are present in human glomeruli. Crry is the rodent analogue to the former two proteins. In this study, we examined complement regulation in cultured rat glomerular endothelial cells (GEnC) and mesangial cells (MES). Immunoprecipitation of 125I-labeled membrane proteins and Western blotting studies were performed with anti-Crry and anti-CD59. In both GEnC and MES, Crry was present as 53, 65, and 78 kD proteins. The 20 kD CD59 was apparent in GEnC. CD59 was also present in MES, but in relatively smaller quantities. By Northern analyses, 1.8 kb CD59 mRNA was present in GEnC as well as in RNA from isolated rat glomeruli. mRNA for Crry was present in both GEnC and MES as 2.2 kb species. The functional significance of these proteins was evaluated next. Anti-Thy 1.1 IgG was used to activate the complement classical pathway in MES. To inhibit the function of the complement regulators, anti-CD59 and/or anti-Crry F(ab')2 antibodies were added with anti-Thy 1.1. Inhibition of Crry function led to enhanced cytotoxicity, while there was no effect when CD59 function was inhibited. The complement alternative pathway was studied by adding complement in Mg-EGTA buffer. Inhibition of Crry led to productive alternative pathway activation, which was accentuated by anti-CD59 when Crry was incompletely inhibited. Alternative pathway regulation was also evaluated in GEnC. Inhibition of CD59 function alone had no effect in GEnC, while inhibition of Crry led to significant cytotoxicity from alternative pathway activation. Under conditions in which Crry was inactive, inhibition of CD59 further enhanced cytotoxicity. Therefore, Crry is present in both GEnC and MES and restricts the complement alternative pathway in both cell types. Crry also regulates the classical pathway in MES. CD59 is present and functionally active in GEnC, while it appears to have a minor role in MES.

Animals↗
PubMed1994

Determination of higenamine in plasma and urine by high-performance liquid chromatography with electrochemical detection.

A method for the determination of higenamine in plasma and urine based on high-performance liquid chromatography (HPLC) with electrochemical detection was developed. The plasma or urine sample was treated by adsorption with acidic alumina and then higenamine was released by acid treatment. HPLC was performed on an ODS column with a mobile phase of acetonitrile-0.1% phosphoric acid (9:91) and an electrochemical detector at an oxidation potential of 0.75 V. The lower limits of the assay for higenamine in plasma and urine were 2.645 and 10.58 ng/ml, respectively. The recoveries of higenamine after alumina treatment in rabbit plasma and urine were ca. 77.5 and 84.4%, respectively. Intra- and inter-day precision and accuracy reported as coefficients of variation in plasma and urine were less than 7%. The application of the assay was demonstrated successfully by the determination of the concentration of higenamine in rabbit plasma and urine samples after doses of higenamine hydrochloride at 20 mg/kg intravenously and 50 mg/kg orally.

Administration, Oral↗
PubMed1994

Protein kinase-independent inhibition of muscarinic K+ channels by staurosporine.

Acetylcholine (ACh) binding to atrial muscarinic receptors activates an inwardly rectifying K+ current (IK[ACh]) via a pertussis toxin-sensitive GTP-binding protein (GK). The muscarinic K+ channel (termed GIRK1) has been cloned, and the nucleotide sequence contains nine consensus sites for protein kinase C (PKC) phosphorylation (16). Dephosphorylation of the muscarinic K+ channel has been implicated in rapid IK[ACh] desensitization in the presence of agonist (13). Staurosporine is a widely used membrane-permeant inhibitor of PKC and other protein kinases (7), including G protein-coupled receptor kinases. We investigated the role of phosphorylation in the regulation of IK[ACh] by examining the effect of a variety of protein kinase inhibitors. Staurosporine produced a rapid and reversible dose-dependent decrease in IK[ACh], activated by either GTP or guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S). Other PKC inhibitors, including calphostin C and K-252b, were without effect on GTP gamma S-activated IK[ACh]. In excised patches of atrial membrane under nonphosphorylating conditions (0 ATP, 1 mM 5'-adenylylimidodiphosphate), staurosporine reversibly reduced muscarinic K+ channel activity without altering single-channel current amplitude. These results suggest that staurosporine inhibits IK[ACh] by a mechanism independent of intracellular protein kinases.

Adenylyl Imidodiphosphate↗
PubMed1993

Purification and amplification of DNA from Penaeus monodon-type baculovirus (MBV).

The purpose of this paper was to purify and amplify the DNA fragment of Penaeus monodon-type baculovirus (MBV). Using 30-50% caesium chloride gradients, MBV virions and occlusion bodies with density parameters of 1.28-1.29 and 1.32-1.33 g/ml, respectively, were purified. Two oligonucleotide primers have been successfully designed and utilized for the amplification of a DNA fragment of MBV. After 35 amplification cycles of the MBV DNA fragment, a large amount of amplified product with an approximate molecular weight of 600 bp was obtained. This is the first successfully published work on the amplification of MBV using the polymerase chain reaction (PCR). Using the same primers, DNA extracted from MBV noninfected P. monodon, P. japonicus, and P. orientalis had a negative PCR response. However, a positive PCR response was obtained from DNA extracted from MBV-infected postlarval P. monodon. DIG-dot blot hybridization technique using PCR product obtained from the present study as a probe further confirmed that the product is originated from a portion of MBV polyhedrin gene. It is also suggested that PCR product may be beneficial for an accurate and early diagnosis of MBV infection in larval shrimp.

Animals↗
PubMed1993

Leukotriene C4 modulation of muscarinic K+ current activation in bullfrog atrial myocytes.

The effects of leukotriene C4 (LTC4) on activation of muscarinic acetylcholine receptor (mAChR)-stimulated, inwardly rectifying K+ current (IK[ACh]) were examined in single bullfrog atrial myocytes using the whole-cell patch clamp technique. LTC4 produced a reversible, concentration-dependent increase in steady-state, guanosine-gamma-thiotriphosphate (GTP gamma S)-activated IK[ACh], with a K0.5 of 3.1 microM. LTC4 also increased the rate of GTP gamma S-mediated IK[ACh] activation, both in the absence and presence of 1 nM ACh, with comparable K0.5 values of 4.7 microM under basal conditions and 4.9 microM in the presence of 1 nM ACh. LTC4 did not alter the relative affinities of the G protein, Gk, for GTP gamma S and GTP. We hypothesize that all of the effects of LTC4 on the kinetics of Gk-mediated IK[ACh] activation are produced at a common site with a K0.5 of 3-5 microM. The effects of LTC4 on IK[ACh] activation are fully reversible in the presence of GTP gamma S. Under physiological conditions (i.e., intracellular GTP), 10 microM LTC4 increased the ACh-activated peak IK[ACh]. Inhibitors of cellular LTC4 production, including 5,8,11,14-eicosatetraynoic acid, baicalein, cinnamyl-3,4-dihydroxy-alpha-cyanocinnamate, and alpha-pentyl-4-(2-quinolinylmethoxy)-benzene methanol, greatly attenuated ACh-dependent IK[ACh] activation, preventing activation of peak, and producing a lower steady-state IK[ACh] (when compared with the control response in the same cell). Addition of exogenous LTC4 was able to overcome the effects of LTC4 synthesis inhibitors, restoring both the peak and steady-state IK[ACh] responses. Although the mechanism of LTC4-mediated modulation of IK[ACh] activation is not known, our results suggest that endogenously produced lipoxygenase metabolites of arachidonic acid, specifically LTC4, are involved in the physiological process of IK[ACh] activation.

Acetylcholine↗
PubMed1993

Platelet-activating factor receptor-dependent activation of the muscarinic K+ current in bullfrog atrial myocytes.

Platelet-activating factor (PAF), a potent signaling lipid implicated as a mediator of pathological responses, has both negative chronotropic and inotropic effects on the heart, although the mechanism(s) involved is not well defined. Because activation of the muscarinic acetylcholine-activated K+ current (IK(ACh)) also produces a negative chronotropic and inotropic response in myocardium, this study examines whether PAF has effects on IK(ACh) in isolated bullfrog atrial myocytes under whole-cell voltage-clamp conditions. We find that 2 microM PAF increases the rate of GTP-gamma-S-mediated IK(ACh) activation (from 0.30 +/- 0.01 min-1 [n = 20] to 0.73 +/- 0.07 min-1 [n = 12], p < 0.005, in the absence of acetylcholine). This effect of 2 microM PAF was blocked by the PAF antagonist CV-3988 (5 microM, 0.33 +/- 0.14 min-1 [n = 12]), suggesting the presence of specific PAF receptors coupled to IK(ACh) activation. Further support for mediation by specific G protein-coupled PAF receptors derives from the inability of PAF to modulate IK(ACh) after maximal activation in the presence of GTP-gamma-S. Eicosatetraynoic acid (ETYA, an inhibitor of 5- and 12-lipoxygenases) did not prevent the PAF-mediated increase in the rate of IK(ACh) activation (10 microM ETYA, 0.28 +/- 0.03 min-1 [n = 7]; 10 microM ETYA plus 2 microM PAF, 0.58 +/- 0.13 min-1 [n = 8]; p < 0.05), suggesting that the observed PAF effect is not mediated by increases in arachidonic acid metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1991

Expression of two forms of carp gonadotropin alpha subunit in insect cells by recombinant baculovirus.

There are two types of cDNA clones (designated alpha 1 and alpha 2) encoding the alpha subunit of carp gonadotropin. These two cDNAs are derived from different genes and encode proteins that differ by seven amino acid residues (three in the signal peptide and four in the mature polypeptide). Expression of these two cDNAs in insect cells by recombinant baculovirus revealed that the alpha 1 subunit, after noncovalent association with the beta subunit, has the same potency as the native alpha subunit purified from the pituitary. In contrast, the alpha 2 subunit can associate with the beta subunit, but only to form an inactive gonadotropin. Competition of the alpha 2 subunit with the alpha 1 subunit for association with the beta subunit decreases the gonadotropin activity of the alpha/beta complex. In addition, both alpha 1 and alpha 2 subunits are secreted into the culture medium by insect cells and have an apparent molecular mass approximately 5 kDa higher than that of the native alpha subunit. These results indicate that the insect cell-derived alpha 1 subunit is biologically active and that those four amino acid changes in the mature of alpha 2 protein affect the biological activity and thus provide valuable clues for the study of the structure-function relationship of the alpha subunit of glycoprotein hormones.

Animals↗