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Biomedical subjects

W C Ko

Publications and source records attributed to W C Ko.

69 records · Page 4Linked to original sources
PubMed1996

Determination of Z-butylidenephthalide in plasma by high-performance liquid chromatography.

An HPLC assay is described for the determination of Z-butylidenephthalide (Z-Bdph) in plasma. Plasma samples were cleaned up by extraction with 2% chloroform in n-hexane. Z-Bdph was separated on a normal-phase silica column with a mobile phase of chloroform-n-hexane (1:1). The limit of quantitation with UV detection at 254 nm for Z-Bdph in plasma was 0.01 microgram/ml. The recovery of Z-Bdph by organic solvent extraction of plasma was 99.5%. The intra-day and inter-day coefficients of variation and relative errors for Z-Bdph determination in plasma were both less than 10%. The present method was applied to pharmacokinetic studies of Z-Bdph in plasma after intravenous administration to rabbits.

Animals↗
PubMed1996

Increasing antibiotic resistance in clinical isolates of Aeromonas strains in Taiwan.

A total of 234 clinical isolates of Aeromonas, primarily A. hydrophila, were collected for the present study. Most were isolates from blood. By the agar dilution method, more than 90% of the Aeromonas strains were found to be susceptible to moxalactam, ceftazidime, cefepime, aztreonam, imipenem, amikacin, and fluoroquinolones, but they were more resistant to tetracycline, trimethoprim-sulfamethoxazole, some extended-spectrum cephalosporins, and aminoglycosides than strains from the United States and Australia.

Aeromonas↗
PubMed1996

Hemorrhagic fever with renal syndrome: first imported case of hantavirus infection in Taiwan.

A patient infected with hantavirus, with resultant hemorrhagic fever with renal syndrome (HFRS), is reported. The patient was a 38-year-old man, living in Tainan, Taiwan, who had been visiting Mainland China for 3 months when he suddenly developed fever and chills, generalized myalgia, abdominal pain and petechiae on his chest. He sought treatment in Mainland China. His clinical course progressed through febrile, hypotensive, oliguria and polyuria phases. Supportive care included one course of hemodialysis. He returned to Tainan in partial defervescence. Serologic studies undertaken in Taiwan confirmed Hantaan virus infection, with one of the currently identified hantavirus strains. Hospitalization with supportive care produced further clinical improvement. Clinicians should be alert to the possibility of HFRS when examining patients who have been in endemic areas and complain of fever associated with renal dysfunction, hemorrhage or abdominal pain or both.

Adult↗
PubMed1995

Aeromonas bacteremia: review of 59 episodes.

Fifty-nine episodes of bacteremia due to Aeromonas species occurred within a 5-year period in one medical center in southern Taiwan. Underlying diseases in the 58 patients included hepatic cirrhosis (36%) and cancer (24%). Patients with aeromonas bacteremia more often had underlying hepatic cirrhosis than did those with bacteremia due to other gram-negative bacilli. Males (67%) outnumbered females. The cases appeared to cluster in the summer and fall months. Thirty-two percent were polymicrobial infections; often the Aeromonas pathogens were accompanied by other gram-negative bacilli. Aeromonas hydrophila was the most common species isolated (69%). In addition to fever, hypotension and jaundice were the common clinical manifestations of aeromonas sepsis. In cirrhotic patients, spontaneous bacterial peritonitis, altered mental status, and jaundice were most common, and aeromonas bacteremia in such patients was monomicrobial and community-acquired more often than in noncirrhotic patients. In vitro aeromonads were generally susceptible to aminoglycosides, cefuroxime, the third-generation cephalosporins, and quinolones. The overall crude fatality rate was 36%. Predictors of fatal outcome for cirrhotic patients included spontaneous bacterial peritonitis, hypotension on admission, diabetes mellitus, and high Pugh scores.

Adolescent↗
PubMed1991

Inhibition of platelet aggregation by some flavonoids.

The inhibitory effects of five flavonoids on the aggregation and secretion of platelets were studied. These flavonoids inhibited markedly platelet aggregation and ATP release of rabbit platelets induced by arachidonic acid or collagen, and slightly those by platelet-activating factor. ADP-induced platelet aggregation was also suppressed by myricetin, fisetin and quercetin. The IC50 on arachidonic acid-induced platelet aggregation was: fisetin, 22 microM; kaempferol, 20 microM; quercetin, 13 microM; morin, 150 microM less than IC50 less than 300 microM. The thromboxane B2 formations were also inhibited by flavonoids in platelets challenged with arachidonic acid. Fisetin, kaempferol, morin and quercetin antagonized the aggregation of washed platelets induced by U46619, a thromboxane A2/prostaglandin endoperoxides mimetic receptor agonist. In human platelet-rich plasma, quercetin prevented the secondary aggregation and blocked ATP release from platelets induced by epinephrine or ADP. These results demonstrate that the major antiplatelet effect of flavonoids tested may be due to both the inhibition of thromboxane formation and thromboxane receptor antagonism.

Adenosine Triphosphate↗
PubMed1988

Cyclic GMP affecting the tracheal nonadrenergic noncholinergic inhibitory system.

An association between guanosine 3',5'-monophosphate (cyclic GMP) and the nonadrenergic noncholinergic inhibitory system (NANCIS) has been demonstrated in the isolated bovine tissue (Bowman and Drummond, 1984). In order to investigate this association in the guinea pig trachea, we used cyclic GMP derivatives, guanylate cyclase activators (N-methylhydroxylamine (NMH) and nitroglycerin (NG)] and inhibitors [oxyhemoglobin (HbO2) and methylene blue (MB)]. Under general anesthesia paralysis, the animals were ventilated and hourly injected with atropine (0.2 mg/kg) and propranolol (1 mg/kg). Cervical segment of the trachea was converted to a closed tracheal pouch and then filled with Kreb's solution augmented with atropine (1 microM) and propranolol (3.5 microM). A decrease in the pouch pressure (Pp) reflected NANCIS nerve transmural stimulation (TS)--or drug-induced relaxation. Pharmacological agents were applied intravenously. At 2-11 min after injection, NMH and NG decreased baseline Pp and reduced TS-induced relaxation. NMH, which is more potent than NG in activating particulate guanylate cyclase activity, potentiated the TS-induced relaxation at high frequencies, but NG did not. HBO2 inhibited the TS-induced relaxation at high but not at low frequencies. In contrast, MB inhibited the relaxation at low but not high frequencies. The results suggest that activation of particulate or membrane bound guanylate cyclase potentiates NANCIS-induced decrease in Pp. Therefore, there is a possible association between cyclic GMP and the NANCIS in the guinea pig trachea.

Animals↗
PubMed1988

The tracheal nonadrenergic noncholinergic inhibitory system during antigen challenge.

This study was undertaken to test the hypothesis that malfunction of the nonadrenergic noncholinergic inhibitory system (NANCIS) induces hyperreactive airways. Antigen sensitized guinea pigs were divided into four groups: (1) antigen challenge (n = 6), (2) 2 min oxyhemoglobin (HbO2) + antigen challenge (n = 5), (3) 27 min HbO2 + antigen challenge (n = 4), and (4) 2 min HbO2 + transmural stimulation (TS) + antigen challenge (n = 6). These animals were sensitized with ovalbumin 10 days before the study. In addition, 12 normal control animals without antigen sensitization were used for comparison. Under artificial ventilation, the anesthetized-paralyzed animals were hourly injected with atropine (0.2 mg/kg) and propranolol (1 mg/kg). Cervical segment of the trachea was converted to a closed tracheal pouch filled with Krebs solution containing also atropine (1 microM) and propranolol (3.5 microM). A change in the pouch pressure (Pp) reflected NANCIS TS- or antigen (5 micrograms) challenge-induced relaxation and/or constriction. HbO2 was used to inhibit NANCIS transmitter. There was no significant difference between normal and sensitized animals in the NANCIS TS-induced relaxation. Antigen challenge resulted in biphasic alteration in Pp, an initial increase and then a decrease after about 7 min. HbO2 pretreatment alone did not potentiate antigen-induced increase in Pp. HbO2 + TS, however, significantly abolished the late relaxation phase after antigen challenge.

Animals↗
PubMed1987

Antiplatelet effect of butylidenephthalide.

Butylidenephthalide inhibited, in a dose-dependent manner, the aggregation and release reaction of washed rabbit platelets induced by collagen and arachidonic acid. Butylidenephthalide also inhibited slightly the platelet aggregation induced by PAF and ADP, but not that by thrombin or ionophore A23187. Thromboxane B2 formation caused by collagen, arachidonic acid, thrombin and ionophore A23187 was in each case markedly inhibited by butylidenephthalide. Butylidenephthalide inhibited the aggregation of ADP-refractory platelets, thrombin-degranulated platelets, chymotrypsin-treated platelets and platelets in the presence of creatine phosphate/creatine phosphokinase. Its inhibition of collagen-induced aggregation was more marked at lower Ca2+ concentrations in the medium. The aggregability of platelets inhibited by butylidenephthalide could be recovered after the washing of platelets. In human platelet-rich plasma, butylidenephthalide and indomethacin prevented the secondary aggregation and blocked ATP release from platelets induced by epinephrine. Prostaglandin E2 formed by the incubation of guinea-pig lung homogenate with arachidonic acid could be inhibited by butylidenephthalide, indomethacin and aspirin. It is concluded that the antiplatelet effect of butylidenephthalide is mainly due to an inhibitory effect on cyclo-oxygenase and may be due partly to interference with calcium mobilization.

Adenosine Diphosphate↗
PubMed1981

Effects of intracerebroventricular injection of clonidine on metabolic, respiratory, vasomotor and temperature responses in the rabbit.

1. The thermoregulatory outputs (including metabolic, respiratory and vasomotor activities) produced by an injection of clonidine or 5-hydroxytryptamine (5-HT) into the third cerebral ventricle of conscious rabbits were assessed at three different ambient temperatures (Ta) of 2, 22 and 32 degrees C. 2. When injected into the third cerebral ventricle, both clonidine and 5-HT produced a dose-dependent hypothermia in rabbits at both 2 and 22 degrees C Ta. The hypothermia was due to a decrease in metabolic heat production (M) at 2 degrees C Ta, while at 22 degrees C Ta the hypothermia was due to cutaneous vasodilatation. There were no changes in respiratory evaporative heat loss. 3. Furthermore, the clonidine-induced hypothermia was greatly reduced by pretreatment of the animals with either 5,6-dihydroxytryptamine (impairment of central 5-HT pathways) or yohimbine (alpha-adrenergic blocking agent), but not by 6-hydroxydopamine (impairment of central catecholamine pathways). 4. The results indicate that clonidine may act on the alpha-adrenergic receptors located on central 5-HT pathways to produce a hypothermic action by promoting a decrease in heat production or an increase in heat loss in the rabbit.

5,6-Dihydroxytryptamine↗
PubMed1980

A newly isolated antispasmodic--butylidenephthalide.

Butylidenephthalide (BdPh), ligustilide and butylphthalide were isolated and purified from neutral oil of Ligusticum wallichii Franch. Among these three, BdPh proved to be the most active in inhibiting rat uterine contractions induced by prostaglandin F2 alpha, oxytocin and ACh. In studies done to compare the effects of BdPh and papaverine (Pap), guinea pig ileum, vas deferens and taenia coli were used. BdPh inhibited contractile responses of the ileum to agonists including ACh, K+ and Ba2+ in normal Tyrode solution and to exogenous Ca2+ in high K+ (80 mM), Ca2+-free Tyrode solution, and also responses of vas deferens responses to norepinephrine. Thus, BdPh is a non-specific antispasmodic but weaker in potency than Pap. However, as the inhibitory effects of BdPh on phasic contraction (PC) and tonic contraction (TC) of preparations, including depolarized and non-depolarized ileum and taenia coli, were much the same, it is suggested that the action mechanism of BdPh may differ from that of Pap which inhibited TC more selectively than PC. It may be concluded that BdPh possesses an non-specific antispasmodic action like Pap, the mechanism of action being different from that of Pap.

Acetylcholine↗