Biomedical subjects

K M Ko

Publications and source records attributed to K M Ko.

At least 37 records · Page 2Linked to original sources

PubMed1998

Structure-activity relationship of schisandrins in enhancing liver mitochondrial glutathione status in CCl4-poisoned mice.

AIM: To explore whether the methylenedioxy group and cyclooctadiene ring of the dibenzocyclooctadiene skeleton of schisandrins (Sch) play a role in the liver mitochondrial glutathione status enhancing activity. METHOD: The effects of three dibenzocyclooctadiene derivatives, Sch A, Sch B, Sch C, and a synthetic intermediate of Sch C, (dimethyl biphenyl dicarboxylate, DBD) on carbon tetrachloride (CCl4)-hepatotoxicity and liver mitochondrial glutathione status were examined in mice. RESULTS: Pretreating mice with intragastric Sch B, Sch C, or DBD 1.mmol.kg-1.d-1 for 3 d protected against CCl4-hepatotoxicity. The hepatoprotection afforded by Sch B or Sch C pretreatment was associated with increases in liver mitochondrial reduced glutathione (mtGSH) level and glutathione reductase (mtGRD) activity, an indication of enhanced mitochondrial glutathione status. In contrast, the hepatoprotective action of DBD was not accompanied by any detectable changes in mtGSH level and mtGRD activity. CONCLUSION: Both the methylenedioxy group and the cyclooctadiene ring of the dibenzocyclooctadiene molecule are important structural determinants in the enhancement of liver mitochondrial glutathione status.

Animals↗

PubMed1997

Methylenedioxy group as determinant of schisandrin in enhancing hepatic mitochondrial glutathione in carbon tetrachloride-intoxicated mice.

As a preliminary approach to exploring whether the methylenedioxy group of the dibenzocyclooctadiene skeleton of schisandrins plays an important role in hepatic mitochondrial-reduced glutathione (GSH) stimulatory activity, we examined the effects of three schisandrins, namely schisandrin A (Sch A), schisandrin B (Sch B), and schisandrin C (Sch C), on carbon tetrachloride (CCl4) hepatotoxicity and hepatic mitochondrial GSH status in mice. Pretreating mice with Sch A at a daily oral dose of 1 mmol/kg for 3 days did not protect against CCl4 hepatotoxicity, whereas pretreatment with Sch B or Sch C at the same dosage regimen produced almost complete protection. The hepatoprotection afforded by Sch B or Sch C pretreatment was associated with significant increases in the hepatic mitochondrial GSH level and glutathione reductase (EC 1.6.4.2) activity. Our results indicate that the methylenedioxy group of the dibenzocyclooctadiene skeleton of schisandrin is an important structural determinant in the stimulation of hepatic mitochondrial GSH, particularly under conditions of CCl4 intoxication.

Alanine Transaminase↗

PubMed1997

Alterations in susceptibility to carbon tetrachloride toxicity and hepatic antioxidant/detoxification system in streptozotocin-induced short-term diabetic rats: effects of insulin and Schisandrin B treatment.

The streptozotocin-induced short-term (2 week) diabetic rats showed an increase in susceptibility to carbon tetrachloride (CCl4)-induced hepatocellular damage. This diabetes-induced change was associated with a marked impairment in the hepatic glutathione antioxidant/detoxification response to CCl4 challenge, as indicated by the abrogation of the increases in hepatic reduced glutathione (GSH) level, glucose-6-phosphate dehydrogenase and microsomal glutathione S-transferases (GST) activities upon challenge with increasing doses of CCl4. While the hepatic GSH level was increased in diabetic rats, the hepatic mitochondrial GSH level and Se-glutathione peroxidase activity were significantly reduced. Insulin treatment could reverse most of the biochemical alterations induced by diabetes. Both insulin and schisandrin B (Sch B) pretreatments protected against the CCl4 hepatotoxicity in diabetic rats. The hepatoprotection was associated with improvement in hepatic glutathione redox status in both cytosolic and mitochondrial compartments, as well as the increases in hepatic ascorbic acid level and microsomal GST activity. The ensemble of results suggests that the diabetes-induced impairment in hepatic mitochondrial glutathione redox status may at least in part be attributed to the enhanced susceptibility to CCl4 hepatotoxicity. Sch B may be a useful hepatoprotective agent against xenobiotics-induced toxicity under the diabetic conditions.

Alanine Transaminase↗

PubMed1996

Effects of Schisandrin B and alpha-tocopherol on lipid peroxidation, in vitro and in vivo.

Effects of Schisandrin B (Sch B) and alpha-tocopherol (alpha-TOC) on ferric chloride (Fe3+) induced oxidation of erythrocyte membrane lipids in vitro and carbon tetrachloride (CCl4) induced lipid peroxidation in vivo were examined. While alpha-TOC could produce prooxidant and antioxidant effect on Fe(3+)-induced lipid peroxidation, Sch B only inhibited the peroxidation reaction. Pretreatment with alpha-TOC (3 mmol/kg/day x 3) did not protect against CCl4-induced lipid peroxidation and hepatocellular damage in mice, whereas Sch B pretreatment (0.3 mmol/3.0 mmol/kg/day x 3) produced a dose-dependent protective effect on the CCl4-induced hepatotoxicity. The ensemble of results suggests that the ability of Sch B to inhibit lipid peroxidation, while in the absence of pro-oxidant activity, may at least in part contribute to its hepatoprotective action.

Animals↗

PubMed1996

The crucial antioxidant action of schisandrin B in protecting against carbon tetrachloride hepatotoxicity in mice: a comparative study with butylated hydroxytoluene.

A comparison between the effects of schisandrin B (Sch B) and butylated hydroxytoluene (BHT) treatments on hepatic antioxidant status was made to identify the critical antioxidant action of Sch B involved in hepatoprotection in mice. Whereas Sch B treatment (3 mmol/kg/day x 3, p.o.) increased the hepatic mitochondrial-reduced glutathione (GSH) level, BHT treatment at the same dosage regimen decreased it. However, both Sch B and BHT increased, albeit to a different extent, the activity of mitochondrial glutathione reductase. The differential effect of Sch B and BHT treatment on hepatic mitochondrial glutathione status became more apparent after carbon tetrachloride (CCl4) challenge. Pretreatment with Sch B could sustain the hepatic mitochondrial GSH level in CCl4-intoxicated mice and protect against CCl4 hepatotoxicity. BHT pretreatment did not produce any protective effect on CCl4-induced GSH depletion in mitochondrion and hepatocellular damage. Although both Sch B and BHT treatments increased hepatic ascorbic acid (VC) level in control animals, only Sch B pretreatment sustained a high hepatic VC level in CCl4-intoxicated mice. Moreover, Sch B pretreatment prevented the CCl4-induced decrease in the hepatic alpha-tocopherol (VE) level. However, Sch B inhibited NADPH oxidation in mouse liver microsomes incubated with CCl4 in vitro, whereas BHT stimulated this oxidation. The ensemble of results suggests that the ability to sustain the hepatic mitochondrial GSH level and the hepatic VC and VE levels may represent the crucial antioxidant action of Sch B in protection against CCl4 hepatotoxicity. The possible inhibition of CCl4 metabolism by Sch B may also contribute to its hepatoprotective action.

Alanine Transaminase↗

PubMed1996

Alterations in tissue glutathione antioxidant system in streptozotocin-induced diabetic rats.

Changes in tissue glutathione antioxidant system in streptozotocin-induced diabetic rats for a period of 15 weeks were examined. Total glutathione level was significantly increased in kidney tissue, but were slightly decreased and increased in liver and heart tissues, respectively. The small changes in total glutathione level in the liver and heart, though not statistically significant, were associated with reciprocal alterations in the activity of gamma-glutamylcysteine synthetase (GCS). While the GCS activity was not changed in kidney tissue, the activity of gamma-glutathione peroxidase was significantly increased in kidney tissue. Insulin treatment could completely or partly normalize almost all of these changes induced by diabetes. However, the decrease in hepatic glutathione S-transferases activity in diabetic rats was not reversed by the insulin treatment. The ensemble of results suggests that the diabetes-induced alterations in tissue glutathione antioxidant system may possibly reflect an inter-organ antioxidant response to a generalized increase in tissue oxidative stress associated with diabetes.

Animals↗

PubMed1996

Schisandrin B protects against carbon tetrachloride toxicity by enhancing the mitochondrial glutathione redox status in mouse liver.

Previous studies in our laboratory have demonstrated the effect of Schisandrin B (Sch B),an active ingredient of the fruit of Schisandra chinensis, on enhancing the hepatic glutathione antioxidant system in mice, as evidenced by the hepatoprotection against carbon tetrachloride (CCl4) toxicity. In the present study, the mechanism involved in the hepatoprotection afforded by Sch B treatment was investigated. Treating female Balb/c mice with 1, 3-bis(2-chloroethyl)-1-nitrosourea, an inhibitor of glutathione reductase (GRD), at a dose of 2 mmol/kg (i.p.) did not abrogate the hepatoprotective action of Sch B in CCl4-treated mice. The result indicates that the increased activity of hepatic GRD is not ascribable to the hepatoprotective action of Sch B. In control mice, the same Sch B treatment regimen caused an enhancement in hepatic mitochondrial glutathione redox status, as indicated by the significant increase and decrease in reduced and oxidized glutathione levels, respectively. While the CCl4 intoxication greatly impaired mitochondrial glutathione redox status, the beneficial effect of Sch B treatment became more evident after CCl4 challenge. Our results strongly suggest that the mechanism of hepatoprotection afforded by Sch B treatment may involve the enhancement of mitochondrial glutathione redox status.

Alanine Transaminase↗

PubMed1996

Effect of a lignan-enriched extract of Schisandra chinensis on aflatoxin B1 and cadmium chloride-induced hepatotoxicity in rats.

Treatment of rats with a lignan-enriched extract of the fruit of Schisandra chinensis could enhance hepatic antioxidant/detoxification system, as indicated by increases in hepatic reduced glutathione (GSH) level as well as hepatic glutathione reductase and glutathione S-transferase activities. The hepatoprotective action was evident after aflatoxin beta 1 or cadmium chloride (Cd) challenge. Schisandra chinensis pretreatment protected against aflatoxin B1-or Cd-induced hepatocellular damage in rats. However, pretreating rats with alpha-tocopherol acetate (vitamin E) did not protect against hepatic damage induced by both toxins. Results from the present as well as our previous studies demonstrate that the hepatoprotection afforded by Schisandra chinensis pretreatment is not hepatotoxin specific. Schisandra chinensis seems to be more effective than vitamin E in protecting against aflatoxin B1 and Cd toxicity. The mechanism of hepatoprotection afforded by Schisandra chinensis pretreatment may involve facilitation of both antioxidant and detoxification processes in the liver.

Aflatoxin B1↗

PubMed1996

Schisandra chinensis-dependent myocardial protective action of sheng-mai-san in rats.

Sheng-Mai-San (SMS), a traditional Chinese formulation used for the treatment of coronary heart disease, is comprised of Radix Ginseng, Fructus Schisandrae and Radix Ophiopogonis. Pretreatment with a lignan-enriched SMS (17 g/kg/day x 3, p.o.) was found effective in protection against isoproterenol-induced myocardial injury in rats, and in ischemia-reperfusion injury in isolated perfused hearts prepared from pretreated animals. Results obtained from pretreatment studies using extracts prepared by mixing various combinations of the three component herbs indicate that the major myocardial protective component in SMS is the lignan-enriched extract of Fructus Schisandrae.

Animals↗

PubMed1996

Video-assisted thoracoscopic anatomic lung resections. The initial Hong Kong experience.

We report our combined experience on video-assisted thoracoscopic (VAT) anatomic lung resections from two major hospitals in Hong Kong over a 17-month period. From August 1993 to December 1994, 82 cases of major lung resections were attempted using the VATS approach, of which 60 were successfully completed (55 lobectomies, 2 bilobectomies, 2 pneumonectomies, and 1 segmentectomy). Of these 60 cases, there were 43 men and 17 women with a mean age of 66 years (range, 37 to 85 years). The final pathologies were 52 primary lung cancers (37 adenocarcinoma, 11 squamous cell carcinoma, 2 bronchoalveolar carcinoma, 1 adenosquamous carcinoma, and 1 undifferentiated carcinoma); 1 pulmonary metastasis (from nasopharyngeal carcinoma); and 7 benign lesions (3 tuberculosis, 1 bronchiectasis, 1 sclerosing hemangioma, 2 organizing pneumonia). There was one postoperative death (mortality rate, 1.8%). Complications include persistent air leak over 10 days (four), wound infection (two), supraventricular tachycardia (three), and recurrence of tumor over the utility thoracotomy scar (one). All the patients were followed up from 8 weeks to 19 months (mean, 10 months). The mean duration of chest drainage was 5.4 days (range, 2 to 25 days). The mean hospital stay was 7.2 days (range, 4 to 35 days). The average postoperative parenteral narcotic (meperidine hydrochloride [Pethidine]) requirement by patient-controlled analgesia was 275 mg (range, 75 to 800 mg). This compared favorably with an age- and sex-matched historic group of patients who underwent posterolateral thoracotomy and had a hospital stay of 10.4 days (statistically non-significant) and narcotic requirement of 950 mg (statistically significant by paired t test). We conclude that VAT anatomic lung resection is technically feasible. However, there are some specific complications associated with major lung resection through minimal access. Refinement of our present technique and attention to details are important to improve our results.

Adenocarcinoma↗

PubMed1996

Thoracoscopic lobectomy for benign diseases.

The few reports in the literature on thoracoscopic anatomic lung resections were almost exclusively for early primary lung cancers. We report our combined experience on video-assisted thoracoscopic (VAT) lobectomy for benign diseases from two major hospitals in Hong Kong over a 20-month period. From August 1993 to March 1995, 66 VAT lobectomies were performed; of this number, 10 cases (15%) were for benign diseases (5 tuberculosis, 2 organized pneumonia, 1 bronchiectasis, 1 sclerosing hemangioma, 1 infected bronchogenic cyst). There was no mortality or incidence of intraoperative complications. Postoperative complications occurred in one patient with tuberculosis and consisted of persistent air leak and subsequent wound infection. There were no long-term complications after a mean follow-up of 11 months. The mean duration of chest tube drainage was 6.7 days and that of hospital stay was 9.8 days. These results were not statistically different from those achieved in VAT lobectomies performed for malignant tumors (5.0 days for drainage and 6.8 days for hospital stay) despite the fact that hilar dissection was sometimes more difficult in the former because of inflammatory changes. We conclude that VAT lobectomy for benign diseases is technically feasible even though its role in thoracic surgery remains to be defined.

Adult↗

PubMed1995

Effect of a lignan-enriched fructus schisandrae extract on hepatic glutathione status in rats: protection against carbon tetrachloride toxicity.

The effect of a lignan-enriched extract of the fruits of Schisandra chinensis (FS) on hepatic glutathione (GSH) status was examined in both control and carbon tetrachloride (CCl4)-treated rats. FS treatment caused a dose-dependent enhancement in hepatic GSH status, as evidenced by significant increases in hepatic GSH level and activities of hepatic glucose-6-phosphate and glutathione reductase (GRD), as well as a decreased susceptibility of hepatic tissue homogenates to in vitro peroxide-induced GSH depletion. The beneficial effect of FS treatment on hepatic GSH status became more evident after CCl4 challenge. Pretreating rats with FS extract at increasing daily doses ranged from 0.2 to 3.2 g/kg for 3 days caused a dose-dependent protection against the CCl4-induced impairment in hepatic GSH status. The enhancement in hepatic GSH status was associated with corresponding decreases in tissue malondialdehyde levels and plasma alanine aminotransferases activities, indicating a significant reduction in the extent of oxidative hepatocellular damage. Our results indicate that the molecular mechanism of hepatoprotection afforded by FS pretreatment may involve the facilitation of GSH regeneration via the GRD-catalyzed and NADPH-mediated reaction.

Animals↗

PubMed1995

Effect of schisandrin B on hepatic glutathione antioxidant system in mice: protection against carbon tetrachloride toxicity.

Pretreating female Balb/c mice with schisandrin B (Sch B) at increasing daily doses (1-4 mmol/kg) for 3 days caused dose-dependent increases in hepatic glutathione S-transferase (GST) and glutathione reductase (GRD) activities. However, the activities of glucose-6-phosphate dehydrogenase (G6PDH), Se-glutathione peroxidase (GPX), and gamma-glutamylcysteine synthetase (GCS) were down-regulated to varying degrees in a dose-dependent manner. While there were biphasic changes in hepatic reduced glutathione (GSH) level as well as susceptibility of hepatic tissue homogenates to in vitro peroxide-induced GSH depletion, a gradual decrease in hepatic malondialdehyde content was observed. The beneficial effect of Sch B on the hepatic GSH anti-oxidant system became more evident after CCl4 challenge. The same Sch B pretreatment regimen caused a dose-dependent protection against carbon tetrachloride (CCl4)-induced hepatotoxicity. The hepatoprotection was associated with significant enhancement in hepatic GSH status, as indicated by the substantial increase in tissue GSH levels and the corresponding decrease in susceptibility of tissue homogenates to GSH depletion. Where the activities of GST and GRD were increased linearly over non-CCl4 control values, there was also a gradual elevation in G6PDH activity upon administration of increasing doses of Sch B. In contrast, GPX activity was moderately down-regulated. The ensemble of results suggests that the hepatoprotection afforded by Sch B pretreatment may mainly be attributed to the enhancement in the functioning of the hepatic GSH anti-oxidant system, possibly through stimulating the activities of GSH related enzymes.

Animals↗

PubMed1995

Enhancement of hepatic glutathione regeneration capacity by a lignan-enriched extract of fructus schisandrae in rats.

Exposure of liver homogenates to an in vitro tert-butyl hydroperoxide challenge can be used as a means for measuring the reduced glutathione regeneration capacity (GRC) of hepatic tissues. Pretreatment of rats with a lignan-enriched extract of Fructus Schisandrae (FS) caused a moderate enhancement of hepatic GRC in control rats, but the GRC enhancing effect of FS pretreatment on hepatic tissues was greatly exaggerated after CCl4 challenge. This in vitro bioassay can be used for investigating the hepatic GRC promoting action of orally active agents.

Animals↗

PubMed1994

Prooxidant and antioxidant effects of Trolox on ferric ion-induced oxidation of erythrocyte membrane lipids.

The prooxidant and antioxidant actions of Trolox were examined in an in vitro system measuring ferric ion-induced oxidation of erythrocyte membrane lipids. Trolox was found to produce a concentration-dependent biphasic effect on the ferric ion-stimulated lipid peroxidation, with the mode of action being similar to those produced by reducing-agent antioxidants, such as ascorbic acid and reduced glutathione, and iron chelator, such as desferrioxamine. Phytic acid, a potent iron chelator, could suppress the prooxidant actions of Trolox and desferrioxamine, but not those of ascorbic acid and reduced glutathione. The ability of Trolox to stimulate ferric ion-catalyzed ascorbate oxidation, as similar to the action produced by ethylenediaminetetraacetic acid, indicates the presence of iron-chelating activity. The ensemble of results suggests the possible involvement of iron chelation in the prooxidant action of Trolox in ferric ion-stimulated lipid peroxidation reactions.

Antioxidants↗

PubMed1993

Correlation of red cell antioxidant status and heart-lung function in swine pretreated with allopurinol (a model of heart-lung transplantation).

Although the protection against myocardial ischemia-reperfusion injury by allopurinol has previously been attributed to inhibition of xanthine oxidase, the demonstration of protective effects in species devoid of detectable myocardial xanthine oxidase activity argues against this hypothesis. In the present study, the effects of allopurinol pretreatment in a model of heart-lung transplantation were examined in swine, a species devoid of myocardial xanthine oxidase activity. Twenty-eight experiments were performed utilizing the heart-lung transplantation model--seven controls (14 animals, 7 donors and 7 recipients) with no preoperative pharmacological intervention, and twenty-one in the experimental group (42 animals, 21 donors and 21 recipients) with donor and recipient pretreated with allopurinol 50 mg/kg/day for 3 days. The effect of allopurinol was determined on day 2 blood samples assessing red cell antioxidant status by measurement of malondialdehyde (MDA) formation in response to in vitro peroxidative challenge. The experimental group was divided into subgroups--namely, nonresponders (8 pairs of animals) and responders (13 pairs of animals) based on the range (mean +/- 2 SD) of erythrocyte MDA levels in the control group. Heart-lung transplantation was performed in the three groups (control [7], nonresponders [8], and responders [13]) on day 3 following the final dose of allopurinol administration in the experimental group. Based on postsurgical assessments of cardiac and pulmonary function integrity, animals showing the greatest red cell antioxidant response following allopurinol treatment showed significantly better recovery compared with the control group. In contrast, animals that did not respond to allopurinol pretreatment showed results similar to those of the control (i.e., untreated) group. Furthermore, red cell MDA levels in all the allopurinol-treated animals were found to correlate positively (P < 0.001) with the extent of myocardial and lung dysfunction, as indicated by cardiac index and lung water measurements, respectively. The present study suggests that allopurinol protection against ischemia-reperfusion injury may involve generalized alterations in tissue antioxidant status, and that the measurement of erythrocyte susceptibility to oxidative challenge could provide a useful approach to optimizing the effectiveness of therapeutic interventions undertaken prior to surgery in order to minimize the risk of damage resulting from postischemic tissue reperfusion.

Allopurinol↗

PubMed1991

Effects of phytic acid on the myoglobin-t-butylhydroperoxide-catalysed oxidation of uric acid and peroxidation of erythrocyte membrane lipids.

Phytic acid stimulated the myoglobin-t-butylhydroperoxide (TBHP)-catalysed oxidation of uric acid, but inhibited the peroxidation of erythrocyte membrane lipids induced by the same system. Butylated hydroxytoluene, a free radical chain reaction-terminating antioxidant, also suppressed the myoglobin-TBHP-induced lipid peroxidation. Moreover, phytic acid inhibited the hydroxyl radical-induced degradation of deoxyribose, but the extent of inhibition in this system was reduced by increasing the ferric ion concentration, suggesting that these effects of phytic acid on the myoglobin-TBHP-mediated oxidation are more likely attributable to its metal chelating properties rather than to a free radical scavenging action. The effectiveness of phytic acid, a naturally occurring antioxidant, in the inhibition of both iron- (as previously shown) and myoglobin-dependent lipid peroxidation suggests its possible therapeutic application as a non-toxic antioxidant for ameliorating the extent of oxy-radical-mediated myocardial ischemia/reperfusion damage.

Erythrocyte Membrane↗

PubMed1990

Inhibition of transition metal ion-catalysed ascorbate oxidation and lipid peroxidation by allopurinol and oxypurinol.

Allopurinol and its metabolite oxypurinol inhibited basal oxidation of ascorbate and exerted comparable concentration-dependent inhibitory effects on the oxidation of ascorbate catalysed by cupric ion, but the stimulation produced by ferric ion was affected minimally. UV spectral analysis suggested the formation of an allopurinol-ascorbate-copper ion complex. The oxidation of erythrocyte membrane lipids by ferric ion and cupric ion-t-butylhydroperoxide was also inhibited by allopurinol and oxypurinol, by the metal chelators EDTA and uric acid, and by the antioxidant butylated hydroxytoluene. The metal chelating actions of allopurinol and oxypurinol may be relevant to their protective actions against ischemia/reperfusion injury.

Allopurinol↗