Biomedical subjects

C Y Chu

Publications and source records attributed to C Y Chu.

At least 37 records · Page 2Linked to original sources

PubMed1999

Inhibitory effect of 12-O-tetradecanoylphorbol-13-acetate-caused tumor promotion in benzo[a]pyrene-initiated CD-1 mouse skin by baicalein.

The effects of topical application of baicalein on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced promotion of skin tumors, hyperplasia, ornithine decarboxylase activity, and inflammation were evaluated in female CD-1 mice. Topical application of baicalein (0.08, 0.16, or 0.2 mumol) with TPA (5 nmol) twice weekly for 24 weeks to mice previously initiated with benzo[a]pyrene inhibited the number of TPA-induced tumors per mouse significantly. Preapplication of the same amount of baicalein also afforded significant protection against TPA-induced hyperplasia in the ear skin. Topical application of baicalein inhibited tumor promoter-caused induction of epidermal ornithine decarboxylase activity by TPA (5 nmol). The topical application of baicalein (0.008, 0.016, or 0.02 mumol) inhibited TPA-induced edema of mouse ears by 88%, 96%, or 97%, respectively. Pretreatment of mouse skin with various amounts of baicalein caused inhibition of H2O2 and myeloperoxidase formation by TPA. These results indicate that baicalein can be a potential cancer-chemopreventive agent against tumor promotion.

Animals↗

PubMed1998

Individual sex preferences and the population sex ratio of newborns.

This paper proposes the hypothesis that countries with stronger sex preferences are more likely to have a negative relationship between crude birth rates and male/female ratios of newborn babies. Conversely, the existence of a significantly negative relationship in any country may also be a supportive evidence of its preferences for sons. Our hypothesis is both behavioral and biological: on the behavioral side, parents with strong sex preferences are inclined to continue to bear children if the existing sex ratio of children is less than desirable. On the biological side, parents with many girls are more likely to be "girl producers", who with individual-specific biological characteristics tend to generate higher female births. We use the macro data in the United Nations Demographic Yearbook to verify and test our hypothesis. For developing countries which do not have reliable micro data on fertility, our approach using macro data is a useful and interesting alternative.

Female↗

PubMed1998

Inhibitory effect of Hibiscus protocatechuic acid on tumor promotion in mouse skin.

Hibiscus protocatechuic acid (PCA), a phenolic acid isolated from Hibiscus sabdariffa L., was evaluated for its ability to inhibit the 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced promotion in skin tumors of female CD-1 mice. Topical application of PCA (5, 10 or 20 micromol) 5 min prior to TPA (15 nmol) treatment twice weekly for 20 weeks to mice which were initiated with benzo[a]pyrene (B[a]P) inhibited the incidence of tumors in mice to 81.3, 62.5 and 56.3%, respectively, while all mice in the TPA-treated group developed tumors. The average number of tumors in mice pretreated with PCA was 2-4 and that of mice treated only with TPA was 6.6. The protection effects of PCA were also presented by its significant suppression on the TPA-induced hyperplasia in the skin and edema of mouse ears by 65 and 73% at doses of 10 and 20 micromol, respectively. When it was applied to the dorsal surface of CD-1 mice before TPA application, PCA (5, 10 or 20 micromol) inhibited the induction of epidermal ornithine decarboxylase (ODC) activity by 5 nmol TPA and myeloperoxidase (MPO) activity by 6.5 nmol TPA. The same doses of PCA also reduced the formation of hydrogen peroxide in the mouse skin to an inhibition of 61, 84 and 89%, respectively, when compared with that of the TPA-treated group. These results indicate that PCA possesses potential as a cancer chemopreventive agent against tumor promotion.

Animals↗

PubMed1997

Protective effects of dried flower extracts of Hibiscus sabdariffa L. against oxidative stress in rat primary hepatocytes.

Dried flower extracts of Hibiscus sabdariffa L., a local soft drink material and medical herb, was found to possess antioxidant activity in the present study. In the preliminary studies, antioxidant potential of three fractions of the ethanol crude extract (HS-C: chloroform-soluble fraction; HS-E: ethyl acetate soluble fraction; HS-R: residual fraction) obtained from the dried flowers of Hibiscus sabdariffa L. were evaluated by their capacity of quenching 1,1 -diphenyl-2-picrylhydrazyl (DPPH) free radical and inhibiting xanthine oxidase (XO) activity. HS-E showed the greatest capacity of scavenging free radical (EC50=0.017mg/ml), and HS-C showed the strongest inhibitory effect on XO activity (EC5o=0.742 mg/ml). Furthermore, antioxidant bioactivities of these crude extracts were investigated using a model of tert-butyl hydroperoxide (t-BHP)-induced oxidative damage in rat primary hepatocytes. All fractions were found to inhibit significantly the unscheduled DNA synthesis (UDS) induced by t-BHP at a concentration of 0.20 mg/ml. HS-C and HS-E also decreased the leakage of lactate dehydrogenase (LDH) and the formation of malondialdehyde (MDA) induced by t-BHP (1.5 mM) considerably at a concentration of 0.10 and 0.20 mg/ml in the rat primary hepatocyte cultures. These results indicated that the dried flower extracts (HS-C and HS-E) of H. sabdariffa L. protect rat hepatocytes from t-BHP-induced cytotoxicity and genotoxicity by different mechanisms.

Animals↗

PubMed1997

Nucleus accumbens dopaminergic mediation of protection against gastric mucosal ulcerations by cold-restraint stress in the male hyperprolactinemic rats.

An investigation was undertaken to study the relationship between change in gastric lesion induced by cold-restraint stress and brain dopamine (DA) activity in male rat with chronic hyperprolactinemia. Male rats of Wistar strain were divided into two groups: one received extra two pieces of anterior pituitary (AP) from its littermates, the other grafted with several pieces of muscle served as control. Experiment I: From the 5th day to 40th day after transplantation, the levels of serum prolactin (PRL) in the AP-grafted group were higher than those of control (p < 0.05 or p < 0.01). Experiment II: On the 40th day after transplantation, AP-grafted and control rats were restrained and placed supine in a ventilated refrigerator with an ambient temperature of 5 degrees C for 3 hrs. Although gastric mucosal ulceration was observed in both groups, the ulcer index (including total number and length of gastric mucosal ulceration) was lower in AP-grafted group than that in control group (p < 0.05 or p < 0.01). Experiment III: On the 40th day after transplantation, all rats were divided into AP-grafted and muscle-grafted rats. Subsequently, they were allowed to expose to cold-plus-restraint stress and unstress (room temperature: 24 +/- 1 degrees C) respectively. After stress and unstress, all animals were immediately sacrificed by decapitation, the brains were dissected with Palkovits' micropunch technique. DA and its metabolites, DOPAC content in Nucleus accumbens (NAc) area of brain were assayed by HPLC with electrochemical detection. These results showed that concentrations of DA, DOPAC and their ratios (DOPAC/DA) in the NAc area of brain, were not statistically different under room temperature condition between muscle-grafted and AP-grafted rats. The DOPAC/DA ratio in both groups showed significant increase in the brain's NAc area under cold-restraint stress condition as compared with unstress condition. But AP-grafted rats exhibited significantly higher DOPAC content in the brain's NAc area when compared with muscle-grafted rats under cold-restraint stress condition (171.7 +/- 22.1 versus 101.5 +/- 14.2 ng/mg protein, p < 0.05). According to these findings, we suggest that reduced effect of chronic high serum PRL level from extra pituitary grafts on gastric mucosal ulceration produced by cold-restraint stress is probably mediated via Nucleus accumbens dopaminergic neuronal mechanism.

Animals↗

PubMed1997

Age-distribution dynamics and aging indexes.

I analyze the dynamics of the age distribution as some vital rates change. When the fertility or mortality rate declines, the age distribution often manifests a dynamic stochastic-dominance relationship. I also propose some alternative indexes for measuring population aging. These indexes are closely connected with the age-distribution dynamics and contain more refined information about the distribution of age among the old.

Adult↗

PubMed1996

Hepatotoxicity of 1,3,5-trinitro-2-acetyl pyrrole derived from nitrosation of Maillard reaction product in BALB/C mouse.

1,3,5-Trinitro-2-acetyl pyrrole (TNAP) is a product derived from the reaction of 2-acetyl pyrrole with nitrite in the model of Maillard browning systems. This compound is moderately mutagenic to the Salmonella strains TA98 and TA100 and is markedly cytotoxic to mouse C3H10T1/2 cells. Experiments are performed to investigate the effects of TNAP on the hepatic toxicity in mouse. Male BALB/C mice were subjected to a dose of 7.2 mg/kg body weight twice a week by i.p. injection for 24 weeks, then followed by a feeding diet for 21 weeks. TNAP-treated mice showed an increase in mortality and time-dependent appearance of lesions in the liver. TNAP is hepatotoxic as demonstrated by a marked increase in the activities of serum alanine transaminase (ALT) and aspartic transaminase (AST). TNAP-related lesions observed histologically in mice, included hapatic atrophy, mild fatty metamorphosis with multilocular cysts in the liver. In conclusion, TNAP was considered to be a toxic compound in mice as evidenced by increased incidences of mortality, and lesions of liver.

Alanine Transaminase↗

PubMed1996

Promotion of colon carcinogenesis through increasing lipid peroxidation induced in rats by a high cholesterol diet.

To examine the influence of hypercholesteremia on 1,2-dimethylhydrazine (DMH)-induced rat colon cancer, Sprague-Dawley rats received dietary cholesterol (CH, 0-2%) and cholic acid (CA, 0.25%) with or without DMH (20 mg/kg, s.c. injection) for 18 weeks. The rats receiving dietary cholesterol and cholic acid all significantly increased total serum cholesterol and lipids but only a high cholesterol diet (2% CH plus 0.25% CA) decreased the activity of glutathione peroxidase (GSH-Px) and increased the formation of peroxides in the colon (P < 0.01). The rats that received the combination of DMH and high cholesterol diet enhanced these effects. At the end of the experiment, the diet group administered DMH and high cholesterol (2% CH plus 0.25% CA) developed colon adenoma at 50% of incidence in pathological examination, but no colon adenoma formed in the rats treated with high cholesterol alone. It is supposed that a non-carcinogenic agent like cholesterol may potentiate the carcinogenicity of DMH in rats via an increase of lipid peroxidation and decrease in the activity of peroxidase in the target organ.

1,2-Dimethylhydrazine↗

PubMed1996

Inhibitory effect of atractylon on tert-butyl hydroperoxide induced DNA damage and hepatic toxicity in rat hepatocytes.

Atractylon, a main sesquiterpenic constituent of Atractylodes rhizomes, was studied for the mechanism of its inhibitory effects on the tert-butyl hydroperoxide (t-BHP)-induced cytotoxicity and lipid peroxidation in primary culture of rat hepatocytes. In the preliminary study, atractylon showed an effective antioxidant property tested by its capacity for quenching 1,1-diphenyl-2-picrylhydrazyl radical (DPPH). Further investigations showed that atractylon at the concentrations of 0.01, 0.1 and 1.0 mg/ml decreased the formation of malondialdehyde (MDA), leakage of lactate dehydrogenase (LDH) and alanine aminotransferase (ALT) and repair synthesis of DNA induced by 30-min treatment of t-BHP (1.5 mM) in primary cultured rat hepatocytes. Addition of atractylon also attenuated the genotoxicity of t-BHP evaluated by unscheduled DNA synthesis. The sum of the results suggested that the protective effect of atractylon against oxidative stress induced by t-BHP is via its ability to quench free radicals.

Animals↗

PubMed1996

The effect of fissure morphology and pretreatment of the enamel surface on penetration and adhesion of fissure sealants.

Fissure sealants have been used successfully as a means of preventing fissure caries. This effectiveness is directly related to sealant retention and retention is dependent upon a meticulous method of application. The aims of this study were to determine if sealant adhesion and penetration were affected by the variation in preparation of the enamel surface, or by pretreatment of the enamel surface with dentine adhesive systems, in fissures of varying morphology. Non-carious posterior teeth were visually examined and sorted according to fissure type, classified as shallow, deep or intermediate. Occlusal fissures were sealed using one of six methods, thermocycled for 200 cycles between 5 and 55 degrees C, in artificial saliva, then placed in a 1.5% procion orange dye for 3 min. Teeth were sectioned bucco-lingually and examined with a light microscope for (i) penetration of the sealant into the fissure pattern and (ii) adhesion of the sealant. All sealant techniques employed in this study adapted well to the enamel surface as the 1.5% procion Reactive orange dye failed to penetrate any of the sealed tooth sections. Shallow fissures were well obturated in both lateral and vertical dimensions. Sealants adapted well to the vertical walls at the orifice of deep fissures but generally failed to penetrate into the deeper aspects. Reducing the etching period with 37% phosphoric acid resulted in increased voids between the sealant and enamel surface and poorer adaptation to the vertical walls. The addition of dentine adhesive systems, Scotchbond Multi-Purpose and All-Bond 2, enhanced the vertical penetration of the sealant, particularly in deep fissures. It is proposed that the dentine adhesive systems may improve the retention rate of sealants in deep fissures particularly if the fissure is not completely dry prior to resin placement.

Acid Etching, Dental↗

PubMed1996

Terbutaline nebulization and epinephrine injection in treating acute asthmatic children.

Ninety children with acute asthma, equally divided into two study groups, were studied to compare the efficacy and safety of nebulized terbutaline with injected epinephrine in the treatment of acute exacerbation. The terbutaline group received 2 ml (5,0 mg) terbutaline solution diluted with 2 ml 0.9% saline for inhalation over 10 minutes; the epinephrine group received 0.01 ml/kg of 1:1000 epinephrine (maximum 0,3 ml) through subcutaneous injection at deltoid area. Spirometry, pulse oximetry, and clinical severity scoring system were evaluated at baseline and again 15 minutes after treatment. The baseline data of the two groups were not significantly different. The clinical severity score and spirometry of both groups were significantly improved after treatment. Compared with the terbutaline group, the epinephrine group had better mean oxygen saturation (SaO2; p < 0.001), frequency of oxygen desaturation (p = 0.0028) and forced expiratory flow 25-75% (FEF25-75%, p = 0.027). For those patients with initial forced expiratory volume in one second (FEV1) lower than 60% of predicted value, epinephrine treatment was more effective in the improvement of FEV1, FEF25-75%, and oxygen saturation (SaO2) (p = 0.011, 0.012, and 0.006, respectively). A Significantly higher rate of adverse effects occurred in patients given epinephrine (47% vs 11%, p = 0.0002); these included pallor, tremor, dizziness, headache, palpitation, soreness of legs, numbness of extremities, cold sweating, general weakness and nausea. Considering the general trend to noninvasive therapy in children and the more frequent adverse effects after epinephrine injection, such nebulized beta-2 agonists as terbutaline appear preferable for initial therapy of acute asthma if oxygen is supplemented to prevent possible hypoxemia. However, parenteral epinephrine still is worth trying, particularly in any severe, life-threatening attack.

Administration, Inhalation↗

PubMed1995

Crocetin protects against oxidative damage in rat primary hepatocytes.

Crocetin is a major component in the fruit of Gardenia jaminoides Ellis, a Chinese herbal medicine. Its protective action and mechanism against oxidative damage were investigated and mechanism against oxidative damage were investigated. Reactive oxygen species (ROS) were generated enzymatically in the xanthine-xanthine oxidase (X/XO 5 microM/0.01 u/ml) system and non-enzymatically in the paraquat (PQ 5 mM) system. Both systems increased leakage of lactate dehydrogenase (LDH) and alanine transaminase (ALT) in rat primary hepatocytes, but the hepatotoxicity was significantly suppressed on pretreatment with crocetin (10, 20 microM). Crocetin decreased formation of malondialdehyde (MDA) as an index of lipid peroxidation induced by ROS. The oxyradical generation by X/XO or PQ caused DNA damage evaluated with unscheduled DNA synthesis (UDS) in rat primary hepatocytes. The addition of crocetin decreased genotoxicity evaluated with UDS in both systems. The data showed that crocetin also inhibited the formation of superoxide anion in the X/XO system and bleached the free radical 1, 1-diphenyl-2- picrylhydrazyl (DPPH). The protective action of crocetin operated via quenching of the superoxide anion and/or free radical.

Animals↗

PubMed1995

Toward a general analysis of endogenous Easterlin cycles.

Easterlin believed that there were two features associated with the birth cycles he observed: the cycles were related to the labor market, and they might be self-generating. This paper tries to set up a model that contains both of these two features. The authors suppose that the welfare of various age-specific cohorts are determined by their respective marginal productivity, and that the underlying technology which puts together labor force of various age-specific cohorts can be characterized by a general production function. Under these weak assumptions, they show that the well-analyzed cohort and period models along the lines of Lee (1974) are restricted versions of the general setting. Given that both the cohort model and the period model were rejected by statistical tests, the authors adopt the coefficient values obtained from the estimation of the unrestricted version to perform the bifurcation analysis. They go beyond the previous study which focused upon the possible existence of limit cycles, and show that the US fertility limit cycle solution is unstable. Therefore the population trajectory will never converge to that limit cycle.

Americas↗

PubMed1994

Famine, revolt, and the dynastic cycle: population dynamics in historic China.

"Historians have long noticed that population declines in ancient China often coincided with dynasty changes, and that most of these declines were the result of internecine wars which, in turn, were often initiated by famine or density pressure. Since the interactions between density pressure, internecine wars, and dynasty changes cannot be explained by the traditional age-specific density-dependent population structure, we propose to use a bandit/peasant/ruler occupation-specific population model to interpret the dynamic socio-economic transitions of ancient Chinese population, and provide econometric support to our model. We also highlight the rich dynamics of the composition of human population, a factor which was often neglected in previous research on general populations."

Asia↗

PubMed1994

Modulatory effect of piperine on benzo[a]pyrene cytotoxicity and DNA adduct formation in V-79 lung fibroblast cells.

Piperine, a major component of black pepper and long peppers, has been reported previously to have an effect on the activation and deactivation of some exogenous substances. In the present study, piperine was found to promote DNA damage and cytotoxicity induced by benzo[a]pyrene (B[a]P) in cultured V-79 lung fibroblast cells. The V-79 cells were treated with a non-toxic dose of piperine (1-20 microM) plus 10 microM B[a]P, or pretreated with piperine for 30 min or 2 hr prior to the administration of 10 microM B[a]P. B[a]P cytotoxicity was potentiated significantly by piperine under each experimental condition. The relative plating efficiency (RPE) was 71% when V-79 cells were exposed to 10 microM B[a]P alone. When the culture was exposed to B[a]P plus piperine or pretreated with piperine for 30 min prior to the administration of B[a]P, the RPE values were 63 and 44% (P < 0.001), respectively. Pretreatment with piperine for 2 hr had no significant effect (P > 0.05). Furthermore, the lowest activities (P < 0.05) of glutathione S-transferase (GST) and uridine diphosphate glucuronyl transferase (UDP-GTase) of piperine-treated V-79 cells occurred 30 min to 1 hr after the piperine pretreatment. Pretreatment of V-79 cells with piperine also caused an increase in the covalent binding of B[a]P-diol-epoxide to DNA, 2.3 times greater than that of the V-79 cells without piperine treatment. These results suggest that the promotion by piperine of B[a]P-induced cytotoxicity in V-79 lung fibroblast cells is due to mechanisms that decrease the activities of GST and UDP-GTase and increase the formation of a B[a]P-DNA adduct.

Alkaloids↗

PubMed1994

Ultrasound-guided biopsy of thoracic masses.

BACKGROUND: Fine needle aspiration cytologic examination may be sufficient for managing patients with primary lung cancer. However, the procedure is not reliable for benign lesions and metastatic lung cancers. An attempt was made to find the influence of cell type on the results of fine needle aspiration and cutting biopsy. METHODS: One hundred and sixteen patients with thoracic nodules or masses underwent chest ultrasound examination and percutaneous ultrasound-guided needle biopsy. All patients underwent ultrasound-guided fine needle aspiration biopsy (UGAB) and thirty-eight of them also underwent ultrasound-guided cutting biopsy (UGCB). Thoracic lesions were divided into seven groups. RESULTS: Using UGAB alone, the diagnostic rate varied from 56% (mediastinal tumor) to 91% (lung mass). When both methods of UGAB and UGCB were evaluated, the diagnostic rate varied from 67% (pulmonary nodule) to 100% (collapsed lung with mass and pancoast tumor). When thoracic lesions were divided into carcinomatous neoplasms (n = 88) and noncarcinomatous lesions (n = 21), a higher diagnostic rate was found in the carcinomatous group than in the noncarcinomatous group (92% versus 53%, p < 0.001). Correct histologic results between both groups had no statistical significance (64% versus 56%, p > 0.05). CONCLUSIONS: Ultrasound-guided needle biopsy has a high diagnostic yield of thoracic tumors, and carcinomatous masses can be easily diagnosed by UGCB. Noncarcinomatous masses and benign tumors frequently need UGAB to obtain a histologic diagnosis.

Adolescent↗

PubMed1993

Penta-acetyl geniposide inhibits the growth and development of C-6 glioma cells in rats.

Experimental data are provided which demonstrate the inhibitory effects of penta-acetyl geniposide, (Ac)5-GP, on the growth and development of C-6 glioma cells inoculated into rats. In the pretreatment experiments, (Ac)5-GP prolonged the latency period of T50 (time for 50% tumour incidence). At week 7, the growth inhibition was 41% with 5 mg/kg and 75% with 10 mg/kg of (Ac)5-GP. In the post-treatment experiments, growth inhibition was less. No significant hepatotoxic effects were observed in the treated group, indicated by the constant levels of serum enzymes (e.g. asparate aminotransferase). We suggest that (Ac)5-GP is a potent chemopreventive agent on glioma cells.

Animals↗

PubMed1993

Haemotoxic effect of phenylurea herbicides in rats: role of haemoglobin-adduct formation in splenic toxicity.

Three substituted phenylurea herbicides were used for the study of the haemotoxic effects on rats of chronic exposure to these compounds. Female Sprague-Dawley rats were given monuron, diuron or fenuron (250-1000 mg/kg diet) for 14 months. The final body weights were similar to those of controls. No treatment-related effects on organ weights were observed at autopsy, except for a dose-related increase in spleen weights in rats treated with monuron or diuron, but not in those treated with fenuron. The proportion of haemoglobin in the form of methaemoglobin increased in the dosed group and resulted in a secondary anaemia with changes in the morphology of erythrocytes. Haemoglobin adducts of aromatic amines released from the herbicides were present at dose-related levels in rats treated with monuron or diuron. Compound-related lesions were observed histologically in treated rats, with increased pigmentation (haemosiderin) in the spleen, reflecting the response to the haemolytic anaemia and methaemoglobinaemia induced by the herbicides. Pigment deposition consisting of golden brown granules in the cytoplasm of the tubular epithelium in the kidney and in the Kupffer cells in the liver were observed only in rats treated with monuron. The haemotoxic effects that were observed may indicate that the formation of adducts between haemoglobin and the parent aromatic amines released metabolically from these herbicides has a role in the splenic toxicity of these compounds.

Animals↗