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Biomedical subjects

G T Liu

Publications and source records attributed to G T Liu.

At least 109 records · Page 6Linked to original sources
PubMed1992

Antioxidant activity of two dibenzocyclooctene lignans on the aged and ischemic brain in rats.

The effects of two dibenzocyclooctene lignans on peroxidative damage of aging and ischemic rat brain were studied. Incubation of eight-month-old rat brain mitochondria and membrane suspension with Fe(2+)-cysteine resulted in the formation of malondialdehyde (MDA) and decrease of ATPase activity. Schisanhenol (Sal) (10(-4) M) completely inhibited the peroxidative damages of brain mitochondria and membrane of rats. The swelling and disintegration of brain mitochondria, as well as the reduction of brain membrane fluidity induced by Fe(2+)-cysteine were also prevented by Sal. The results of imitative experiment of ischemia and reperfusion of brain mitochondria and membrane in vitro indicated that Sal significantly impeded production of MDA and loss of ATPase activity induced by reoxygenation following anoxia. Oral administration of Sal induced increase of cytosol glutathione-peroxidase of brain in mice under the condition of reoxygenation following anoxia. The other compound schizandrin (Sin B) also has similar activity. But its potency is weaker than that of Sal. All these results indicate that Sal and Sin B have protective action against oxidative stress.

Adenosine Triphosphatases↗
PubMed1992

Protection by salvianolic acid A against adriamycin toxicity on rat heart mitochondria.

It was found that salvianolic acid A (Sai A) has potent antioxidant activity. The effects of Sai A on adriamycin-induced heart mitochondrial toxicity of rats in vitro and on adriamycin antitumor activity are investigated in this article. Malondialdehyde (MDA) formation and membrane rigidification of rat heart mitochondria intoxicated with adriamycin were significantly reduced by Sai A. In the electron spin resonance (ESR) studies, Sai A has no significant effect on the formation of adriamycin semiquinone radicals (AQ.), while hydroxyl radicals generated by electron transfer from AQ. to H2O2 were scavenged by Sai A dose-dependently. On the other hand, Sai A was shown to have no effects on the antitumor activity of adriamycin in cultured L1210 ascitic tumor cells and in mice with P388 ascite tumor. These results indicate that Sai A protects against adriamycin induced heart mitochondrial toxicity of rats, while Sai A has no antagonizing effect on the antitumor activity of adriamycin.

Animals↗
PubMed1992

Anti-oxidant activity of dibenzocyclooctene lignans isolated from Schisandraceae.

The anti-oxidant activity of nine dibenzocyclooctene lignans isolated from Schisandra chinensis, S. rubriflora, and Kadsura longipedunculata, respectively, was studied. Seven of the 9 lignans (1 mM) inhibited iron/cysteine-induced lipid peroxidation (malondialdehyde, MDA, formation) of rat liver microsomes as well as superoxide anion production in the xanthine/xanthine oxidase system. The actions of the 7 lignans were much more potent than vitamin E at the same concentration of 1 mM. Among the lignans, schisanhenol was the most active one. This compound also prevented the decrease of membrane fluidity of liver microsomes induced by iron/cysteine. The results indicated that seven of the lignans such as schisanhenol have anti-oxidant activities.

Animals↗
PubMed1992

Dissociated perceptual-sensory and exploratory-motor neglect.

A patient with a right sided parietal lobe infarction manifested left sided sensory extinction in the visual, auditory, and tactile modalities but had only mild exploratory-motor neglect. In contrast, another patient with a right frontal haemorrhage demonstrated only left sided exploratory-motor hemispatial neglect. Tasks that combined perceptual and exploratory features elicited varying degrees of neglect in each patient. These two cases with dissociated neglect behaviour lend further evidence for behavioural specialisation within components of a cortical network for directed attention: sensory-representational aspects mediated primarily by the parietal component, motor-exploratory primarily by the frontal component. These cases also highlight the need to include and distinguish among several different measures of neglect in the clinical investigation of patients with hemispatial inattention.

Aged↗
PubMed1992

Induction of liver microsomal cytochrome P-450 2B1 by dimethyl diphenyl bicarboxylate in rats.

Dimethyl diphenyl bicarboxylate (dimethyl-4,4'-dimethyloxy-5,6,5',6'-dimethylene-dioxy-di phe nyl-2,2'- bicarboxylate, DDB), a synthetic mimic of the natural product schizandrin C, is used in China as a hepatoprotective agent to improve the liver functions of patients with hepatitis or under cancer chemotherapy. In this study, we investigated the effects of DDB on liver microsomal drug-metabolizing enzymes. When male Sprague-Dawley rats were treated with a daily intragastric dose of DDB (200 mg.kg-1) for 3 d, the microsomal pentoxyresorufin dealkylase activity and P-450 2B1 protein levels were markedly increased. The fold increase was lower than that by phenobarbital (75 mg.kg-1, ip once daily x 3 d). The level of P-450 2B1 mRNA was elevated by DDB but the magnitude of the elevation was much less than that caused by phenobarbital. DDB also increased the rates of testosterone hydroxylation at positions 16 beta, 16 alpha, 6 beta, and 2 beta as well as the rate of ethoxyresorufin dealkylation, suggesting moderate increases in the levels of P-450 3A and P-450 1A1 in addition to the huge increase in P-450 2B1. The level of glutathione S-transferase was also slightly increased, but the levels of P-450 2E1 and NAD(P)H: quinone oxidoreductase were not changed. The results indicate that DDB is an inducer of P-450 2B1.

Animals↗
PubMed1992

Effect of schisandrin B on lipoperoxidative damage to plasma membrane of rat liver in vitro.

The effect of schisandrin B (Sin B) on oxygen free radicals--induced lipoperoxidative damage to plasma membrane of rat hepatocytes was investigated. When the plasma membrane of rat hepatocytes was incubated with iron/cysteine or Vit C/NADPH, the production of malondialdehyde (MDA) and consumption of NADPH increased, while the membrane fluidity reduced. Addition of Sin B (3-25 micrograms.ml-1) to the incubation mixture inhibited all these alterations of the plasma membrane induced by iron/cysteine and Vit C/NADPH. The results indicated that Sin B could maintain membrane stability of rat hepatocytes under oxidative stress.

Animals↗
PubMed1992

Etiological role of Alternaria alternata in human esophageal cancer.

In this paper, the mutagenicity and carcinogenicity of alternariol monomethyl ether (AME), alternariol (AOH), and their relevance to the etiology of human esophageal cancer were studied. These mycotoxins were produced by Alternaria alternata which was the main contaminating fungi isolated from the grain in Linxian County, an area with high incidence of esophageal cancer. This study demonstrated that: 1. AME and AOH might cause cell mutagenicity and transformation; 2. AME and AOH could combine with the DNA isolated from human fetal esophageal epithelium, activate the oncogens, c-H-ras and c-mys in it, and promote proliferation of human fetal esophageal epithelium in vitro; 3. squamous cell carcinoma of the fetal esophagus could be induced by AOH. According to the results of the studies of AME and AOH mentioned above, we consider that Alternaria alternata plays an important role in the etiology of human esophageal cancer.

Alternaria↗
PubMed1992

Reflex blink to visual threat.

The requisite visual modalities for the reflex blink to visual threat have not been thoroughly studied. We identified five patients with different focal cerebral lesions documented on computerized tomography scan who had abnormal blink-to-threat reflexes. One had a homonymous hemianopia secondary to posterior cerebral artery occlusion; another had a unilateral parietal neglect; and a third had a frontal neglect. They did not blink in response to visual stimuli contralateral to their lesion. A cortically blind patient and one with Balint's syndrome did not have a blink response. Observation of these and other similar patients and animals previously reported suggests that the blink-to-threat reflex is cortically mediated and requires intact primary visual cortex as well as higher order mechanisms for visual attention mediated in the inferior parietal lobule and frontal eye fields.

Adult↗
PubMed1992

Horner's syndrome caused by intra-oral trauma.

A 7-year-old boy developed a Horner's syndrome after falling on a stick that penetrated his peritonsillar soft palate. He did not suffer from any major vascular injury, and pharmacologic testing indicated a preganglionic lesion. We review previously reported cases of oculosympathetic paresis caused by surgical and nonsurgical intra-oral trauma. Because of the proximity between sympathetic and vascular structures in the lateral and parapharyngeal space, Horner's syndrome in the setting of intra-oral trauma should prompt evaluation of the internal carotid artery. Magnetic resonance imaging may be a reasonable noninvasive method for this investigation.

Anisocoria↗
PubMed1991

Protection by schisanhenol against adriamycin toxicity in rat heart mitochondria.

The effects of schisanhenol (Sal) on Adriamycin (ADM)-induced rat heart mitochondrial toxicity in vitro were investigated. Malondialdehyde formation, lysis, disintegration and membrane rigidification in mitochondria treated with ADM were reduced significantly by Sal. In the electron spin resonance studies, Sal did not affect significantly the formation of ADM semiquinone radicals (AQ.), whereas hydroxyl radicals generated by electron transfer from AQ.to H2O2 were scavenged by Sal dose dependently. These results indicate that Sal could protect against ADM-induced rat heart mitochondrial toxicity.

Animals↗
PubMed1991

Effect of schisanhenol on the antitumor activity of adriamycin.

Schisanhenol (Sal) did not diminish the antitumor activity of adriamycin in mice bearing P388 ascites tumor. Sal did not antagonize the suppressive effect of adriamycin on DNA synthesis and cell proliferation in an L1210 ascitic tumor cell culture. Furthermore, Sal at the concentration of 0.1, 0.25, or 1 mM accelerated adriamycin-dependent DNA damage in the presence of Fe3+ in vitro. It appears that Sal was able to protect against adriamycin induced heart mitochondrial toxicity, while it did not antagonize the antitumor activity of adriamycin.

Animals↗
PubMed1991

Unilateral oculomotor palsy and bilateral ptosis from paramedian midbrain infarction.

Lesions of the oculomotor fascicles are localized clinically by associated neurologic deficits. We present two patients with bilateral ptosis, unilateral paresis of all other muscles innervated by the oculomotor nerve, and sparing of the contralateral superior rectus muscle--findings suggesting a lesion of the proximal oculomotor fascicles and the central caudal subnucleus. To our knowledge, these are the first such cases with radiologic confirmation of a lesion within the dorsal, paramedian midbrain.

Adult↗
PubMed1991

Effect of dibenzo[a,c]cyclooctene lignans isolated from Fructus schizandrae on lipid peroxidation and anti-oxidative enzyme activity.

The effect of nine dibenzo[a,c]cyclooctene lignans isolated from Fructus schizandrae on in vitro and in vivo lipid peroxidation of liver microsomes as well as on anti-oxidative enzyme activities were studied. Seven of the nine lignans (1 mM) were shown to inhibit Vit C/NADPH induced lipid peroxidation (malondialdehyde (MDA) formation) of rat liver microsomes. Of these compounds, schisanhenol (Sal), S(-)schizandrin C (S(-)sin C) and S(-)schizandrin B (S(-)sin B) were shown to be more potent than Vit E at the same concentration. Sal and Sin B were able to inhibit gossypol-induced superoxide anion generation in rat liver microsomes. In addition, oral administration of Sal and Sin B markedly reduced liver MDA formation induced by ethanol, 15 ml/kg in mice, and increased superoxide dismutase and catalase activities in rat liver cytosol. The data of this paper are in favor of the conclusion that some lignans, like Sal, have strong anti-oxidant activity. The mechanisms of anti-oxidant activity of the lignans were discussed.

Animals↗