Search

This review addressed the adverse effects of the frequently-used recreational drug, ketamine through using mice and monkey models. Our laboratory has documented initially that ketamine can induce the formation of hyperphosphorlated tau (hypertau), which is a hallmark of Alzheimers disease (AD), in the cerebral cortex of both mice and monkeys as well as apoptosis in neurons in these species. Besides the cerebral cortex, other centers in the central nervous system (CNS) and peripheral nervous system (PNS) are also influenced by ketamine. Cerebellum was found to be down-regulated in both mice and humans after long-term of ketamine administration and it was caused by the apoptosis of Purkinje cells. Deleterious effects in other organs reported in long-term ketamine users include of kidney dysfunction leading to proteinuria, fibrosis of the urinary bladder and reduction in size of the urinary bladder leading to frequent urination, increase of liver fibrosis and cardiac problems such as premature ventricular beats. Moreover, ketamine is usually co-administrated with other chemicals such as caffeine or alcohol. It has been reported increased harmful effects when ketamine was used in combination with the above substances. Mechanisms of damages of ketamine might be due to 1) up-regulation of NMDA receptors leading to overestimation of glutamatergic system or 2) the metabolite of ketamine which was a hydroquinone exerted toxicity.

The tumor suppressor p53 plays a key role in regulating apoptosis and cell cycle progression. In addition, p53 is implicated in control of cell differentiation in muscle, the circulatory system, ocular lens and various carcinoma tissues. However, the mechanisms by which p53 controls cell differentiation are not fully understood. Here we present evidence that p53 directly regulates c-Maf and Prox1, two important transcription factors controlling differentiation in the ocular lens. First, human and murine c-Maf and Prox1 gene promoters contain authentic p53 DNA binding sites. Second, p53 directly binds to the p53 binding sites found in the promoter regions. Third, exogenous p53 induces dose-dependent expression of the luciferase report gene driven by both c-Maf and Prox1 promoters, and p53 binds to both promoters in the ChIP assays. Fourth, in the in vitro differentiation model, knockdown of p53 significantly inhibits lens differentiation which is associated with downregulated expression of c-Maf and Prox1. Finally, in p53 knockout mice, the expression of c-Maf and Prox1 are significantly altered. Together, our results reveal that p53 regulates lens differentiation through modulation of two important transcription factors, c-Maf and Prox1, and through them p53 thus controls expression of various differentiation-related downstream crystallin genes.

Chinese medicine has a long history of several thousand years. The main form of Traditional Chinese Medicine (TCM) is composite, i.e. a mixture of up to 10 medicinal products. Thus a composite prescription of 4-5 kinds of Chinese medicinal products may contain several hundred kinds of chemical composition. The active ingredients and clinical efficacy of which are difficult to characterize. We aim to review the Chinese literature of TCMs with neuroprotective effects. We illustrate with our study on Pien Tze Huang (PZH) the use of in vivo tests in the study of composite TCM. Our results show evidence that PZH might have neuropreventive effects in rats.

The analytic models for size-dependent Curie temperature Tcand saturation magnetization at room temperature Msof Fe3O4nanoparticles have been proposed in terms of the size-dependent melting temperature. The Tc(r) and Ms(r) values decrease with a decreasing of the particle radius r. Agreement between model predictions and the corresponding experimental results can be found, which enable us to determine the size dependences of the thickness of nonmagnetic surface layer (r) and t(r) in respectively describing Tc(r) and Ms(r) functions. It is found that both (r) and t(r) increase with a decreasing of rand t(r) is always twice as large as (r). Moreover, the surface layer should be an intrinsic property of ferromagnetic crystals since the nonmagnetic surface layer exists in the whole size range rather than vanishes as rapproaches infinite.

A model for size-dependent surface energy of elemental nanocavities is proposed in terms of size-dependent cohesive energy. It is found that the surface energy of elemental nanocavities increases with decreasing of the cavity size to several nanometers. The newly built model is validated to be in agreement with that based on some other theories. Moreover, an analytic model is developed to describe the size-dependent melting temperature of elemental nanocavities for the first time. The analytic results show that the melting temperature increases with decreasing of the size of nanocavities. The theoretical predictions confirm well to the available data of argon obtained by molecular dynamics simulations.

The role of P-glycoprotein in secretion of indinavir metabolites produced by CYP3A4 was evaluated in Caco-2 cells expressing CYP3A4. Metabolism of indinavir by CYP3A4 expressing Caco-2 cells grown on filters resulted in the formation of N-dealkylation products (M5 and M6) and hydroxylation of indinavir, which were preferentially secreted into the apical compartment. Apical secretion of the metabolites was inhibited by cyclosporin A (CsA) with all three classes of metabolites showing similar sensitivity to CsA, suggesting that they are all secreted by the same pathway. M6 stimulated P-glycoprotein (Pgp)-ATPase activity in a concentration-dependent manner. This stimulation was inhibited by the Pgp-specific monoclonal antibody C219. A method was developed to specifically inhibit Pgp using the monoclonal antibody UIC2 to determine whether Pgp efflux accounts for a significant proportion of the apical secretion of indinavir metabolites. UIC2 recognizes an extracellular transient conformational epitope that is stabilized by some Pgp substrates or by ATP depletion. Incubation of Caco-2 cells with UIC2 in the presence of 1 microM CsA resulted in 50 to 80% inhibition of Pgp-mediated vinblastine efflux, with no significant inhibition observed by UIC2 or CsA alone. Inhibition of Pgp in CYP3A4-expressing Caco-2 cells by UIC2 and 1 microM CsA resulted in a significant decrease in the apical secretion of M6, M5, and OH-indinavir and an increase in the amount of the metabolites secreted in the basolateral compartment and retained in the cytosol. These results are consistent with a role of Pgp in elimination of CYP3A4-generated metabolites and indicate that even relatively polar metabolites may be secreted from the cell by Pgp.

Most cytochrome P450 (P450 or CYP)-catalyzed reactions are adequately described by classical Michaelis-Menten kinetic parameters (e.g., Km and Vmax), which are usually determined by a saturation profile of velocity of product formation versus substrate concentration. In turn, these parameters may be used to predict pharmacokinetics. However, some P450 enzymes exhibit atypical or non-Michaelis-Menten kinetics, due largely to substrate inhibition at higher concentrations of substrate. Although the mechanism of substrate inhibition is unknown, ignoring it and truncating the data can lead to erroneous estimates of kinetic parameters. In the present study, 13 P450 marker substrates were examined with 10 recombinant P450 proteins, and 6 were found, to varying degrees, to exhibit substrate inhibition. To understand the nature of the inhibition, a kinetic model was proposed (assuming that two binding sites exist on the enzyme) and used to fit the experimental data. The derived data indicated that 1) the K(I) values (substrate inhibition) were approximately 1.2- to 10-fold greater than the respective K(S) values; 2) both K(S) and K(I) values may be affected by the interaction of the two bound substrates within the enzyme, exhibited by a factor alpha (alpha = 5.1-23.3); and 3) enzyme activity was inhibited markedly (39-97%) at excess concentrations of the substrates (beta = 0.03-0.61). These findings suggest that substrates have access to both the inhibitory site and catalytic site simultaneously (K(I) > K(S)). Furthermore, the two sites, in the presence of substrate, can interact with each other. Therefore, the degree of inhibition of the enzyme is dependent on the concentration of the substrate (usually >K(I)) that sufficiently occupies the inhibitory site.

Methylation at the 2-position of the imidazole ring of IBN (I), a 1, 5-substituted imidazole-containing compound, was carried out to minimize its inhibition of rat cytochrome P450 (CYP)3A activity. The resulting analog 2-MIBN (II) exhibited an inhibitory potency 70-fold weaker (K(i) = 25 microM) than that of I (K(i) = 0.3 microM) toward CYP3A, the major rat liver microsomal P450 isoform(s) for the metabolism of I and II by rat liver microsomes in the presence of NADPH. The structural modification did not switch the major metabolic pathways for I and II, but significantly decreased the affinity of II to the metabolizing enzyme(s) as reflected by the difference in their K(i) values for CYP3A. Enzyme kinetic studies also demonstrated that I had a lower apparent K(m) (0.3 microM) than than II (18 microM), but an apparent V(max) 14 times lower than II. This finding indicates that methylation at the imidazole ring reduced the affinity of the compound to CYP3A, but increased the catalytic capacity, turning I as a substrate of low K(m) value but low capacity into a compound of high K(m) but high capacity for the metabolism. Our results suggest the significance of substrate concentration in comparing the metabolic stability of compounds with different kinetic parameters. Although higher intrinsic clearance is implied for I when the substrate concentration is below or close to its K(m) value, higher metabolic rate was constantly seen with II over micromolar range. The different kinetic parameters of I and II may also explain the observation that no significant difference in pharmacokinetic behavior was seen after an i.v. administration of I and II to the rat.

In vitro studies were conducted to identify the cytochromes P450 (CYP) involved in the oxidative metabolism of celecoxib. The hydroxylation of celecoxib conformed to monophasic Michaelis-Menten kinetics (mean +/- S.D., n = 4 livers, K(m) = 3.8 +/- 0.95 microM, V(max) = 0.70 +/- 0.45 nmol/min/mg protein) in the presence of human liver microsomes, although substrate inhibition was significant at higher celecoxib concentrations. The treatment of a panel of human liver microsomal samples (n = 16 subjects) with antibodies against CYP2C9 and CYP3A4 inhibited the formation of hydroxy celecoxib by 72 to 92% and 0 to 27%, respectively. The presence of both antibodies in the incubation suppressed the activity by 90 to 94%. In addition, the formation of hydroxy celecoxib significantly correlated with CYP2C9-selective tolbutamide methyl hydroxylation (r = 0.92, P <. 001) and CYP3A-selective testosterone 6beta-hydroxylation (r = 0.55, P <.02). In contrast, correlation with activities selective for other forms of CYP was weak (r

Acetonitrile is an organic solvent commonly used to increase the solubility of lipophilic substrates for in vitro studies. In this study, we examined its effect on four reactions (diclofenac hydroxylation, tolbutamide methyl hydroxylation, phenytoin hydroxylation, and celecoxib methyl hydroxylation) catalyzed by human liver microsomes and by the recombinant CYP2C9. In both cases, the effect of acetonitrile on activity was found to be substrate-dependent. Namely, it increased diclofenac 4'-hydroxylase and tolbutamide methyl hydroxylase activities, but decreased celecoxib methyl hydroxylase activity in a concentration-dependent manner. By comparison, hydroxylation of phenytoin was resistant to its effect. The presence of acetonitrile (3%, v/v) gave rise to a lower K(m) and a higher V(max) for diclofenac hydroxylase in both liver microsomes and recombinant CYP2C9 preparations (87 and 52% increase in V(max)/K(m) ratio, respectively). On the other hand, the inhibitory effect of the solvent (1%, v/v) toward celecoxib hydroxylase was characterized by a decrease in V(max) (human liver microsomes) or a change in both K(m) and V(max) (rCYP2C9), leading to 25 and 46% decrease in V(max)/K(m) for both systems. The results of this study underscore the need for careful evaluation of solvent effects before initiation of inhibition or cytochrome P450 reaction phenotyping studies.

The theoretical analysis for sulfur K-edge near-edge X-ray adsorption fine structure of SO₂ adsorbed on Ag(110) at half monolayer has been performed by using the multiple-scattering cluster method. The resonance located between π* and σ* is proved to arise from transitions into an antibonding orbital induced by the interaction between SO₂ and the substrate and its unclear polarisation dependence is found to be caused by the slight tilt of SO₂ molecular plane away from the surface normal. Compared to gas phase SO₂, the O–S intramolecular bond length is elongated by 0.17±0.03 Åand the OSO bond angle is reduced by 15°±5° after adsorption. It is concluded that SO₂ is adsorbed on Ag(110) with the S atom sitting in a hollow site and the two O atoms being in asymmetric geometry, that the adsorption height is 1.8±0.1 Åand that the molecular plane rotates about 52° from the [001] azimuth and tilts slightly away from the surface normal.

Cytochrome P-450 (CYP) 3A4 is an inordinately important CYP enzyme that catalyzes the metabolism of a vast array of clinically used drugs. Microsomal proteins of Spodoptera frugiperda (Sf21) insect cells infected with recombinant baculoviruses encoding CYP3A4 cDNA were used to immunize mice and to develop a monoclonal antibody (mAb(3A4a)) specific to CYP3A4 through the use of hybridoma technology. The mAb is both a potent inhibitor and a strong binder of CYP3A4. One and 5 microl (0.5 and 2.5 microM IgG(2a)) of the mAb mouse ascites in 1-ml incubation containing 20 pmol of CYP3A4 strongly inhibited the testosterone 6beta-hydroxylation by 95 and 99%, respectively, and, to a lesser extent, cross-inhibited CYP3A5 and CYP3A7 activity. mAb(3A4a) exhibited no cross-reactivity with any of the other recombinant human CYP isoforms (CYP1A1, CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP2E1) in the course of CYP reaction phenotyping and Western immunoblot analyses. The potency of mAb-induced inhibition is insensitive to substrate concentration in human liver microsomes. Therefore, mAb(3A4a) was used to assess the quantitative role of CYP3A4/5 to the metabolism of testosterone and diazepam in five human liver microsomes. The results showed that CYP3A4 and CYP3A5 contribute >95% to both testosterone 6beta-hydroxylation and diazepam 3-hydroxylation and 52 to 73% to diazepam N-demethylation, respectively. In addition, mAb(3A4a) significantly inhibited testosterone 6beta-hydroxylase activity in rhesus monkey liver microsomes to a degree equal to that observed with CYP3A4 in human liver microsomes. By comparison, no inhibition of testosterone 6beta-hydroxylase activity was observed in the presence of dog, rat, and mouse liver microsomes. The selectivity of ketoconazole, a chemical inhibitor of CYP3A4, was probed with mAb(3A4a) and was shown to be highly concentration dependent in the diazepam N-demethylation by human liver microsomes. The results demonstrate that inhibitory and immunoblotting mAb(3A4a) can offer a precise and useful tool for quantitative identification of CYP3A4/5 in the metabolism of drugs in clinical use and drugs in development.

Our previous studies demonstrated that huperzine A, a reversible and selective acetylcholinesterase inhibitor, exerts beneficial effects on memory deficits in various rodent models of amnesia. To extend the antiamnesic action of huperzine A to nonhuman primates, huperzine A was evaluated for its ability to reverse the deficits in spatial memory produced by scopolamine in young adult monkeys or those that are naturally occurring in aged monkeys using a delayed-response task. Scopolamine, a muscarinic receptor antagonist, dose dependently impaired performance with the highest dose (0.03 mg/kg, i.m.) producing a significant reduction in choice accuracy in young adult monkeys. The delayed performance changed from an average of 26.8/30 trials correct on saline control to an average of 20.2/30 trials correct after scopolamine administration. Huperzine A (0.01-0. 1 mg/kg, i.m.) significantly reversed deficits induced by scopolamine in young adult monkeys on a delayed-response task; performance after an optimal dose (0.1 mg/kg) averaged 25.0/30 correct. In four aged monkeys, huperzine A (0.001-0.01 mg/kg, i.m.) significantly increased choice accuracy from 20.5/30 on saline control to 25.2/30 at the optimal dose (0.001 mg/kg for two monkeys and 0.01 mg/kg for the other two monkeys). The beneficial effects of huperzine A on delayed-response performance were long lasting; monkeys remained improved for about 24 h after a single injection of huperzine A. This study extended the findings that huperzine A improves the mnemonic performance requiring working memory in monkeys, and suggests that huperzine A may be a promising agent for clinical therapy of cognitive impairments in patients with Alzheimer's disease.

OBJECTIVE: To compare the rates and predictors of smoking uptake between adolescents speaking English and those speaking a language other than English (LOTE) at home. DESIGN: A cross-sectional survey of year 7 and 8 students (aged 12 and 13 years) was conducted in 1994 and repeated 12 months later. A cohort of students was identified with respondents at baseline matched at follow up. chi 2 and logistic regression were used for analysis. SETTING: 38 schools in southern, east, and northern Sydney, Australia. SUBJECTS: Year 7 and 8 students in the schools were included and examined on two occasions, with complete data for 5947 (80%) students at baseline and 6177 (98%) students at a 12-month follow up. Records were able to be matched perfectly for 3513 respondents (59%). MAIN OUTCOME MEASURES: Smoking rates and predictors of smoking uptake among students speaking English or a LOTE at home. RESULTS: At baseline, 6.1% of students surveyed were smokers. Twelve months later, 15.8% of student surveyed were smokers. There were significantly lower smoking rates among students speaking a LOTE at home compared with those speaking English at home at baseline and at 12 months. Using matched data, for students speaking English at home, five variables were significant predictors of smoking uptake: thinking it acceptable to smoke, perceived benefits of smoking, and having a brother, sister, or close friend who smokes. For students speaking a LOTE, the only predictor was the smoking status of close friends. CONCLUSIONS: Despite the higher smoking prevalence among men with a non-English-speaking background, and the reported strong association between fathers' smoking status and smoking onset of their children, adolescents speaking a LOTE at home were significantly less likely to be smokers than their English-speaking counterparts. Thus, there would seem to be a delay of smoking onset among students speaking a LOTE at home. The smoking rates among respondents speaking a LOTE at home in this study are lower than those obtained from the studies conducted in Europe and the United States. Effective smoking prevention interventions need to be implemented at an early stage of adolescence.