Inhibitory effect of corticoids on the proliferative pattern in mouse palatal processes.

The formation of the secondary palate in mice is accompanied by intensive mitotic activity, which is mainly concentrated at the medial edges of the palatal processes. In control H-Velaz randombred fetuses the mitotic activity culminated approximately 24 h before palatal-shelf horizontalization, so that the period of intensive cell proliferation coincided with the period when cleft palate could be induced by cortisone administration. Effects of teratogenic doses of corticoids, injected directly into amniotic sac of embryos on day 13 (0.3 mg hydrocortisone) or im to pregnant females on day 12 (7.5 mg cortisone acetate), on the proliferative peak in palatal processes were studied using intraamniotic injection of colchicine. Counts of colchicine-blocked mitoses in histological serial sections revealed both a significant decrease in overall mitotic density and a posterior shift of the proliferative peak in the palatal processes of fetuses treated with doses of corticoids producing cleft palate.     

白介素-6对NMDA诱导的小脑神经元放电活动的抑制作用及其机制

目的：观察白介素-6（IL-6）对N-甲基-D-天冬氨酸（NMDA）激发的神经元放电活动的影响及其可能的作用机制。方法：用含IL-6、NMDA和JAK抑制剂ACA90的人工脑脊液（ACSF）灌流小脑脑片,利用离体脑片神经元单位放电细胞外记录技术,记录药物对小脑间位核神经元放电的影响。用Western blot法测定间位核神经元NMDA受体亚单位1（NRI）的磷酸化水平。结果：单独用12．5μmol／L和25μmol／LNMDA灌流,神经元放电频率均较基础放电频率增加;用不同浓度IL-6（50,100,200μg／ml）联合NMDA作用后,神经尤的放电频率出现浓度依赖性地降低;AG490可部分阻断IL-6对NMDA兴奋神经元放电的抑制作用。与单独NMDA处理组比较,用IL-6联合NMDA处理神经元后,神经元的NR1磷酸化水平出现浓度依赖性地降低。AG490可阻断IL-6所致的神经元NR1磷酸化水平的降低。结论：IL-6可抑制NMDA激发的小脑间位核神经元的放电兴奋活动;并同时下调神经元的NR1磷酸化水平。     

Inhibitory effect of ursolic acid derivatives on hydrogen peroxide- and glutathione-mediated degradation of hemin: A possible additional mechanism of action for antimalarial activity

Compounds obtained by the condensation of ursolic acid (UA) with 1,4-bis(3-aminopropyl)piperazines have previously been shown as cytocidal to Plasmodium falciparum strains. Preliminary results indicated that the inhibition of β-hematin formation (one of the possible mechanisms of action of antimalarial drugs) was achieved by a few of these molecules with varying efficiencies. To gain further insight in the antimalarial action of UA derivatives, we report here the results of additional pathways that may explain their in vitro cytocidal activity such as inhibition of hemin degradation by H₂O₂ or glutathione (GSH). H₂O₂-mediated hemin degradation was drastically reduced by hydroxybenzyl-substituted UA derivatives while UA and intermediate compounds displayed weaker inhibitory actions. The results of GSH-mediated hemin degradation inhibition did not parallel those of H₂O₂ degradation as hydroxybenzyl-substituted UA only proved to be a weak inhibitor. As H₂O₂ interaction with the iron moiety of hemin is the first step towards its degradation, we assume that the interaction of our products with the ferric ion in the hemin structure is of upmost importance in inhibiting its peroxidative degradation. A two-step mechanism of action implying (1) stacking of the acetylursolic acid structure to hemin and (2) additive protection of hemin ferric iron from H₂O₂ by hydroxyphenyl groups through steric hindrance and/or trapping of oxygen reactive species in the direct neighborhood of ferric iron can be put forward. For GSH degradation pathway, grafting of UA structure with a piperazine structure gave the best inhibition, pleading for the implication of this latter moiety in the inhibitory process.     

Immunomodulating effect of cyclophosphamide on cytotoxic activity of rat and mouse splenocytes

The goal of this work consisted in study of the immunomodulating action of the cytostatic drug cyclophosphamide (CP) on the natural cytotoxic activity of rat and mice splenocytes. The cytotoxicity of effector cells (EC) with respect to monolayer cell lines of the Zajdela rat hepatoma and the HTC rat hepatoma and of the MH-22a mouse hepatoma was determined with the aid of morphometric analysis. CP at a dose of 100 mg/kg 48 h after administration to animals has been shown to produce an immunomodulating effect on cytotoxicity of splenocytes—a suppressive one with respect to cell-targets (CT) of Zajdela hepatoma and an immunopotentiating one with respect to CT of HTC and MH-22 hepatomas. Possible mechanisms of the CP immunopotentiating action are discussed.     

Oxyresveratrol and hydroxystilbene compounds. Inhibitory effect on tyrosinase and mechanism of action

Tyrosinase is responsible for the molting process in insects, undesirable browning of fruits and vegetables, and coloring of skin, hair, and eyes in animals. To clarify the mechanism of the depigmenting property of hydroxystilbene compounds, inhibitory actions of oxyresveratrol and its analogs on tyrosinases from mushroom and murine melanoma B-16 have been elucidated in this study. Oxyresveratrol showed potent inhibitory effect with an IC(50) value of 1.2 microm on mushroom tyrosinase activity, which was 32-fold stronger inhibition than kojic acid, a depigmenting agent used as the cosmetic material with skin-whitening effect and the medical agent for hyperpigmentation disorders. Hydroxystilbene compounds of resveratrol, 3,5-dihydroxy-4'-methoxystilbene, and rhapontigenin also showed more than 50% inhibition at 100 microm on mushroom tyrosinase activity, but other methylated or glycosylated hydroxystilbenes of 3,4'-dimethoxy-5-hydroxystilbene, trimethylresveratrol, piceid, and rhaponticin did not inhibit significantly. None of the hydroxystilbene compounds except oxyresveratrol exhibited more than 50% inhibition at 100 microm on l-tyrosine oxidation by murine tyrosinase activity; oxyresveratrol showed an IC(50) value of 52.7 microm on the enzyme activity. The kinetics and mechanism for inhibition of mushroom tyrosinase exhibited the reversibility of oxyresveratrol as a noncompetitive inhibitor with l-tyrosine as the substrate. The interaction between oxyresveratrol and tyrosinase exhibited a high affinity reflected in a K(i) value of 3.2-4.2 x 10(-7) m. Oxyresveratrol did not affect the promoter activity of the tyrosinase gene in murine melanoma B-16 at 10 and 100 microm. Therefore, the depigmenting effect of oxyresveratrol works through reversible inhibition of tyrosinase activity rather than suppression of the expression and synthesis of the enzyme. The number and position of hydroxy substituents seem to play an important role in the inhibitory effects of hydroxystilbene compounds on tyrosinase activity.     

Decoding the signaling of a GPCR heteromeric complex reveals a unifying mechanism of action of antipsychotic drugs

Atypical antipsychotic drugs, such as clozapine and risperidone, have a high affinity for the serotonin 5-HT(2A) G protein-coupled receptor (GPCR), the 2AR, which signals via a G(q) heterotrimeric G protein. The closely related non-antipsychotic drugs, such as ritanserin and methysergide, also block 2AR function, but they lack comparable neuropsychological effects. Why some but not all 2AR inhibitors exhibit antipsychotic properties remains unresolved. We now show that a heteromeric complex between the?2AR and the G(i)-linked GPCR, metabotropic glutamate 2 receptor (mGluR2), integrates ligand input,?modulating signaling output and behavioral changes. Serotonergic and glutamatergic drugs bind the mGluR2/2AR heterocomplex, which then balances Gi- and Gq-dependent signaling. We find that the mGluR2/2AR-mediated changes in Gi and Gq activity predict the psychoactive behavioral effects of a variety of pharmocological compounds. These observations provide mechanistic insight into antipsychotic action that may advance therapeutic strategies for disorders including schizophrenia and dementia.     

Inhibitory effect of [6]-gingerol on melanogenesis in B16F10 melanoma cells and a possible mechanism of action

[6]-Gingerol is an active component of ginger that shows antipyretic and anti-inflammation activities. To find a novel skin-whitening agent, the melanogeneis inhibitory effects and action mechanisms of [6]-gingerol were investigated. In the present study, the effects of [6]-gingerol on mushroom tyrosinase, tyrosinase activity, and melanin content were determined spectrophotometrically, and the expression of tyrosinase and related proteins in B16F10 murine melanoma cells was evaluated by Western blotting. Furthermore, a possible signaling pathway involved in [6]-gingerolmediated depigmentation was investigated by means of specific inhibitors. The results revealed that [6]-gingerol (25-100 μM) effectively suppresses murine tyrosinase activity and decreases the amount of melanin in a dose-dependent manner. Additionally, it also effectively decreased the intracellular reactive oxygen species (ROS) level in a dose-dependent pattern in the same dose range. Our results indicate that [6]-gingerol inhibits melanogenesis of B16F10 melanoma and can function as a good skinwhitening agent.     

Hypnotic action of benzodiazepines: a possible mechanism

The objective of this investigation was to determine whether the effects of muscimol on benzodiazepine receptor binding relate to the hypnotic activity of nine benzodiazepines (clonazepam, triazolam, diazepam, flurazepam, nitrazepam, oxazepam, temazepam, clobazam, and chlordiazepoxide) and CL 218,872. There was no correlation between the basal receptor binding affinities of the drugs tested and their hypnotic potencies, whereas the benzodiazepine receptor agonists whose receptor bindings are strongly modulated by muscimol possess potent hypnotic activity. These results indicate that benzodiazepine receptors that couple to GABA receptors are involved in the hypnotic activity of the benzodiazepines.     

Inhibitory effect of acetazolamide on the activity of acetyl CoA carboxylase of mouse liver.

The effect of different concentrations of acetazolamide on the activities of acetyl CoA carboxylase and fatty acid synthetase was studied. Acetazolamide inhibits the activity of 100, 00 × g supernatant acetyl CoA carboxylase and that of this purified enzyme even in the presence of high concentrating of bicarbonate. It is without action on fatty acid synthetasse.     

Dynamin: possible mechanism of "Pinchase" action.

Dynamin is a GTPase playing an essential role in ubiquitous intra cellular processes involving separation of vesicles from plasma membranes and membranes of cellular compartments. Recent experimental progress (. Cell. 93:1021-1029;. Cell. 94:131-141) has made it possible to attempt to understand the action of dynamin in physical terms. Dynamin molecules are shown to bind to a lipid membrane, to self-assemble into a helicoidal structure constricting the membrane into a tubule, and, as a result of GTP hydrolysis, to mediate fission of this tubule (). In a similar way, dynamin is supposed to mediate fission of a neck connecting an endocytic bud and the plasma membrane, i.e., to complete endocytosis. We suggest a mechanism of this "pinchase" action of dynamin. We propose that, as a result of GTP hydrolysis, dynamin undergoes a conformational change manifested in growth of the pitch of the dynamin helix. We show that this gives rise to a dramatic change of shape of the tubular membrane constricted inside the helix, resulting in a local tightening of the tubule, which is supposed to promote its fission. We treat this model in terms of competing elasticities of the dynamin helix and the tubular membrane and discuss the predictions of the model in relation to the previous views on the mechanism of dynamin action.     

Microwave effect on diffusion: a possible mechanism for non-thermal effect

Abstract

In this study, we assume that microwave radiation affects hydrogen bonding between dipolar water molecules and through that diffusion in water at constant temperature. The experimental study was performed on the setup of two identical reservoirs filled with pure water and 0.9% NaCl solution and connected by a thin tube. Alterations of NaCl concentration in the reservoir initially filled with pure water were measured using the resistance of the solution as an indicator. The applied 450?MHz continuous-wave microwave field had the maximal specific absorption rate of 0.4?W/kg on the connecting tube. The standard deviation of water temperature in the setup was 0.02?°C during an experiment. Our experimental data demonstrated that microwave exposure makes faster the process of diffusion in water. The time required for reduction of initial resistance of the solution by 10% was 1.7 times shorter with microwave. This result is consistent with the proposed mechanism of low-level microwave effect: microwave radiation, rotating dipolar water molecules, causes high-frequency alterations of hydrogen bonds between water molecules, thereby affects its viscosity and makes faster diffusion.     

Inhibitory effect of galectin-3 on the cytokine-inducing activity of periodontopathic Aggregatibacter actinomycetemcomitans endotoxin in splenocytes derived from mice

Galectins, a family of animal lectins, are involved not only in development and differentiation but also in immunoregulation and host–pathogen interactions. Galectin-3 interacts with lipopolysaccharides in gram-negative bacteria such as Escherichia coli, Salmonella minnesota and Pseudomonas aeruginosa . The present study investigated whether galectin-3 inhibited the cytokine-inducing activity of periodontopathic bacterial lipopolysaccharides using splenocytes derived from mice of different ages. Lipopolysaccharides were extracted from Aggregatibacter actinomycetemcomitans Y4 and Porphyromonas gingivalis ATCC 33277, and then purified. Enzyme-linked immunosorbent assay (ELISA) analysis revealed that galectin-3 adhered to A. actinomycetemcomitans lipopolysaccharides, but not to the lipopolysaccharides of P. gingivalis . Splenocytes were prepared from 1- or 7-month-old C57BL/6 mice. Either A. actinomycetemcomitans lipopolysaccharides (200 ng mL⁻¹) alone or lipopolysaccharides and murine galectin-3 (10 μg mL⁻¹) were added to culture solutions, and the release of interleukin-6 (IL-6) and interferon-γ (IFNγ) from splenocytes was measured by ELISA after a 17-h incubation. In all mice tested, A. actinomycetemcomitans lipopolysaccharide stimulation significantly increased the production of IL-6 and IFNγ ( P <0.01). Murine galectin-3 suppressed lipopolysaccharide-induced cytokine production in the splenocytes of the 1-month-old mice ( P <0.02 for IL-6; P <0.05 for IFNγ), but not in the splenocytes of the 7-month-old mice. This suggests that responses change with age.     

DNA repair inhibition: a possible mechanism of action of co-carcinogens

Co-carcinogens with a wide diversity of chemical structure have the common property of inhibiting DNA repair replication in normal human lymphocytes. This evidence suggests that inhibition of DNA repair may be an important factor in the mechanism of action of co-carcinogens.