Carbamazepine inhibits NMDA-induced depolarizations in cortical wedges prepared from DBA/2 mice.

There is some doubt as to the mechanism of action of the widely-used anticonvulsant drug, carbamazepine. In cortical wedges prepared from genetically epilepsy-prone DBA/2 mice, carbamazepine at therapeutic concentrations (1-10 microM) markedly reduced the depolarization produced by N-methyl-D-aspartate (NMDA). The NMDA sub-type of glutamate receptor has been implicated in the pathogenesis of epilepsy and the inhibitory action of carbamazepine on this response suggests that the anticonvulsant action of the drug may be due to its blockade of NMDA receptor-mediated events.     

4-Aminopyridine and barium chloride attenuate the anti-epileptic effect of carbamazepine in hippocampal slices

Summary The exact mode of action of the anti-epileptic agent carbamazepine is unknown. In hippocampal slices in which epileptiform discharges were induced by addition of penicillin to the perfusion medium, the depressant effect of carbamazepine was attenuated by the potassium-channel blockers barium chloride (0.1 mM) and 4-aminopyridine (200 M), which suggested that potassium fluxes might be involved in the mechanism of action of carbamazepine.     

The anticonvulsant effects of propranolol and β-adrenergic blockade

Summary The anticonvulsant activity of racemic and (+)-propranolol was studied in rats. Neither drug changed the current to produce a minimal seizure in 50% of animals. Both drugs were effective in the maximal electroshock seizure test, the (+) isomer being more potent than the racemic form. Since the (+) isomer is practically devoid of -adrenergic blocking activity, the anticonvulsant effects of propranolol do not result from -adrenergic blockade.We wish to thank Hana Boucek for skilful technical assistance. Propranolol and (+)-propranolol were obtained through the courtesy of Ayerst Laboratories Ltd, in Montreal. This research was supported by the Medical Research Council of Canada, grant MA-4754.     

Molecular mechanisms of glutamate-dependent neurodegeneration in ischemia and traumatic brain injury

Stroke and neurotrauma mediate neuronal death through a series of events that involve multiple interdependent molecular pathways. It has been suggested that these pathways are triggered following elevations in extracellular excitatory amino acids, primarily glutamate [1]. This report outlines mechanisms involving glutamate-mediated excitotoxicity with specific focus on (i) the role of Ca²⁺ in neurotoxicity, (ii) The concept of source specificity of neurotoxicity, (iii) the role of the ionotropic N-methyl-D-aspartate (NMDA)-subtype glutamate receptor and its associated submembrane molecules that may give rise to signaling specificity in excitotoxicity and (iv) the role of glutamate-mediated free-radical generation and associated cell death pathways. We also highlight a novel, peptide-based approach for uncoupling NMDA receptors from excitotoxicity in the rat central nervous system subjected to focal ischemia, thereby reducing stroke infarct volume and improving neurological functioning.Received 11 August 2003; received after revision 15 September 2003; accepted 17 September 2003     

The discovery of antidepressants: A winding path

Summary Modern treatment of mental depression started with the availability of monoamine oxidase (MAO) inhibitors and tricyclic antidepressants. These drugs also contributed to the early development of psychopharmacology. Attempts to improve the anti-tuberculous action of the hydrazine derivative isoniazid by developing derivatives thereof led to the synthesis of iproniazid. Its introduction as the first modern antidepressant was based on three unexpected actions of the drug: MAO-inhibition, reversal of reserpine-induced sedation, and the presence of psychostimulation as a clinical side effect in man. However, the initial success of iproniazid and other MAO inhibitors, hydrazides and non-hydrazides, was curtailed by the occurrence of undesirable side effects such as potentiation of the blood-pressure elevating action of food amines. The tricyclic antidepressants were a development of the class of antihistamines, one of which, chlorpromazine, showed neuroleptic activity. A congener of this compound, imipramine, was discovered by clinical observation to have unexpected antidepressant effects. The clinical success of this drug (which is still in use) led to the development of a successful series of other tricyclic and non-tricyclic antidepressants. Progress in the elucidation of possible mechanisms of the action of the tricyclic compounds has helped this development. Recent advances in basic research have also induced a revival of MAO-inhibitors since, due to the discovery of MAO-subtypes, inhibitors with higher specificity and fewer undesirable side effects are now available.     

Host immune rejection of TA3 ascites carcinoma cells following administration of a water soluble carbodiimide

Summary Regression of TA3 ascites carcinoma tumors occurred following i.p. injection of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide\HCl. An immunological mechanism of drug action was indicated by the fact that no significant antitumor activity was demonstrable in mice that had previously received an immunosuppressive 700 rad dose of⁶⁰Co radiation.Research support received from United States Atomic Energy Commission Contract No. W-7405-eng-48 with the Lawrence Berkeley Laboratory.     

Effects of diethylstilbestrol on the production of various extracellular products of Staphylococcus aureus

Summary The synthetic estrogen diethylstilbestrol at a subinhibitory level of 1.75 g/ml diminished the production of staphylococcal alpha toxin, coagulase, deoxyribonuclease and penicillinase. Thus, the reported host beneficial effects of diethylstilbestrol may be partially related to its retardive action of certain toxins, or enzymes of S. aureus.Acknowledgments. This work was supported by United States Public Health Service, grant AI 06618, a grant in aid from Loyola University, United States Public Health Service, grant GRSG PRO 5368, and grants from Eli Lilly, Upjohn, Syntex, and G. D. Searle drug companies.     

Effect of tingenone,a quinonoid triterpene,on growth and macromolecule biosynthesis inTrypanosoma cruzi

Summary Tingenone and horminone, two natural quinonoid substances, inhibited the in vitro growth ofTrypanosoma cruzi, 30 M drug concentration producing total inhibition of growth. Tingenone inhibited total uptake and incorporation of [³H]thymidine, [³H]uridine, L-[³H]leucine into parasite macromolecules. Other quinonoids assayed were either less effective (abruquinone A) or even quite inactive (visminone B and ferruginin B). Investigation of several mechanisms for the cytotoxic action of tingenone pointed to the interaction with DNA as the most likely factor involved. Tingenone also inhibited the growth ofCrithidia fasciculata, but the drug was significantly less active on this organism than onT. cruzi.This work was supported by grants of UNDP/World Bank/World Health Organization Special Programme for Research and Training in Tropical Diseases, Organization of American States (Multinational Programme of Biochemistry) and Programa Nacional de Enfermedades Endémicas (SECYT), República Argentina. A preliminary account was given at the Workshop on Oxidative Damage and Related Enzymes, Frascatti (Italy), 1983.     

Disruption of mitochondrial function as the basis of the trypanocidal effect of trifluoperazine onTrypanosoma cruzi

Summary The tricyclic anti-calmodulin drug trifluoperazine (TFP) inhibited growth and motility of epimastigotes ofTrypanosoma cruzi, at concentrations lower than 100 M, and motility and infectivity of the bloodstream trypomastigote form at 200 M. Electron microscopy of TFP-treated epimastigotes showed that the major effect was at the mitochondrial level, with gross swelling and disorganization. The oligomycin-sensitive, mitochondrial ATPase was completely inhibited by 20 M TFP, and the same drug concentration caused a 60% decrease in intracellular ATP content. The results suggest that the trypanocidal effect of TFP may be related more to mitochondrial damage than to the well-known anticalmodulin effect of the drug.     

4-aminopyridine and barium chloride attenuate the anti-epileptic effect of carbamazepine in hippocampal slices

The exact mode of action of the anti-epileptic agent carbamazepine is unknown. In hippocampal slices in which epileptiform discharges were induced by addition of penicillin to the perfusion medium, the depressant effect of carbamazepine was attenuated by the potassium-channel blockers barium chloride (0.1 mM) and 4-aminopyridine (200 microM), which suggested that potassium fluxes might be involved in the mechanism of action of carbamazepine.     

Hemmung der experimentellen,testosteron-bedingten Epidermisproliferation an der weiblichen Ratte durch ein synthetisches Phenanthrenderivat mit antiandrogener Wirkung

Summary In the female rat, testosterone propionate-induced proliferation of the epidermis (acanthosis and mitotic activation) is inhibited in proportion to dosage by a phenanthrene derivative with antiandrogenic action.     

Effect of (+)-catechin on renal and intestinal transport

Summary The ability of dog renal cortex slices to accumulate -methyl-glucoside or glycine is enhanced by the flavonoid (+)-catechin at a concentration of 3.5 mM. This stimulatory effect is apparently due to a decreased rate of efflux of either substrate. On the other hand, the uptake of p-amino-hippuric acid and N¹-methyl-nicotinamide is inhibited by (+)-catechin. The drug at the same concentration is without action on amino-acid transport by guineapig intestine in vitro.This study was supported by grants from Zyma S.A., Nyon. We are grateful to MmesH. Capt andP. Ganguillet and MlleD. Mettraux for their skilful technical assistance.     

Identification of swelling-activated Cl<Superscript>-</Superscript> current in rabbit cardiac Purkinje cells

The presence and functional role of the swelling-activated Cl^- current (I_Cl(swell)) in rabbit cardiac Purkinje cells was examined using patch-clamp methodology. Extracellular hypotonicity (210 or 135 mOsm) activated an outwardly rectifying, time-independent current with a reversal potential close to the calculated Cl^- equilibrium potential (E_Cl). The magnitude of this current was related to tonicity of the superfusate. The current was blocked by 0.5 mM 4,4-diisothiocyanostilbene-2,2-disulfonic acid (DIDS). These features are comparable to those of I_Cl(swell) found in sinoatrial nodal, atrial, and ventricular myocytes. I_Cl(swell) activation at 210 and 135 mOsm depolarized the resting membrane potential with 6 and 10 mV and shortened the action potential by 18 and 33%, respectively. DIDS partially reversed I_Cl(swell)-induced action potential changes. We conclude that I_Cl(swell) is present in Purkinje cells and its activation leads to action potential shortening and resting membrane potential depolarization, both of which can promote the development of reentrant arrhythmias.Received 20 January 2004; received after revision 17 February 2004; accepted 25 February 2004     

Antitumor effect of β-elemene in non-small-cell lung cancer cells is mediated via induction of cell cycle arrest and apoptotic cell death

-Elemene is a novel anticancer drug, which was extracted from the ginger plant. However, the mechanism of action of -elemene in non-small-cell lung cancer (NSCLC) remains unknown. Here we show that -elemene had differential inhibitory effects on cell growth between NSCLC cell lines and lung fibroblast and bronchial epithelial cell lines. In addition, -elemene was found to arrest NSCLC cells at G2-M phase, the arrest being accompanied by decreases in the levels of cyclin B1 and phospho-Cdc2 (Thr-161) and increases in the levels of p27^kip1 and phospho-Cdc2 (Tyr-15). Moreover, -elemene reduced the expression of Cdc25C, which dephosphorylates/activates Cdc2, but enhanced the expression of the checkpoint kinase, Chk2, which phosphorylates/ inactivates Cdc25C. These findings suggest that the effect of -elemene on G2-M arrest in NSCLC cells is mediated partly by a Chk2-dependent mechanism. We also demonstrate that -elemene triggered apoptosis in NSCLC cells. Our results clearly show that -elemene induced caspase-3, –7 and –9 activities, decreased Bcl-2 expression, caused cytochrome c release and increased the levels of cleaved caspase-9 and poly(ADP-ribose) polymerase in NSCLC cells. These data indicate that the effect of -elemene on lung cancer cell death may be through a mitochondrial release of the cytochrome c-mediated apoptotic pathway.Received 12 January 2005; accepted 5 February 2005     

Über «therapeutische» und «toxische» Digitoxigeninwirkungen auf elektrophysiologische Messgrössen des Meerschweinchenvorhofs

Summary Therapeutic concentrations of digitoxigenin (10^–7–3× 10^–7 g/ml), producing positive inotropic effects, did not alter resting and action potentials of electrically driven guinea-pig auricles. However, toxic concentrations of digitoxigenin (5 × 10^–7–10^–8 g/ml), producing arrhythmias and contracture of the myocardium, had a marked influence upon resting and action potentials and conduction velocity.     

Enzymatic basis for protection of fish embryos by the fertilization envelope

The mechanism by which the fertilization envelope (FE) is able to protect the embryo of fish until hatching is almost unknown, except for its function as a physical barrier. FE extract from activated or fertilized eggs of the fishSalmo gairdneri was demonstrated to contain enzyme activities using an agar plate enzyme assay. The enzymes apparently active were carboxymethylcellulase (cellulase; EC 3.2.1.4), laminaranase (endo-1,3(4)--glucanase; EC 3.2.1.6), carboxymethylchitinase (chitinase; EC 3.2.1.14), xylanase (endo-1,4--xylanase; EC 3.2.1.8), mannanase (mannan 1,2-(1,3)--mannosidase; EC 3.2.1.77), dextranase (EC 3.2.1.11), a protease and lysozyme (EC 3.2.1.17). The FE extract exerted an antifungal or fungicidal action on the fungusSaprolegnia parasitica, whereas an extract from the vitelline envelopes (VE) has no apparent enzyme activity nor antifungal or fungicidal action. Enzymes acquired by the FE through the cortical reaction may have an important defensive role, protecting the embryo against invaders or pathogens.     

Examen histopathologique de souris irradiées après injection de cystéamine

Summary The injection of-mercaptoethylamine to C 57 black mice before irradiation (700 r) effects a partial protection of liver and spleen. It has a strong accelerating action on regeneration in spleen, intestine and probably thymus. The experiments suggest that this action is related to a protection of glucidic metabolism.     

Alpha-crystallin: an ATP-independent complete molecular chaperone toward sorbitol dehydrogenase

-Crystallin, the major component of the vertebrate lens, is known to interact with proteins undergoing denaturation and to protect them from aggregation phenomena. Bovine lens sorbitol dehydrogenase (SDH) was previously shown to be completely protected by -crystallin from thermally induced aggregation and inactivation. Here we report that -crystallin, in the presence of the SDH pyridine cofactor NAD(H), can exert a remarkable chaperone action by favoring the recovery of the enzyme activity from chemically denaturated SDH up to 77%. Indeed, even in the absence of the cofactor, -crystallin present at a ratio with SDH of 20:1 (w:w) allows a recovery of 35% of the enzyme activity. The effect of ATP in enhancing -crystallin-promoted SDH renaturation appears to be both nonspecific and to not involve hydrolysis phenomena, thus confirming that the chaperone action of -crystallin is not dependent on ATP as energy donor.Received 28 October 2004; received after revision 22 December 2004; accepted 10 January 2005     

Chlorpromazine: A potential physiological teratogen

Summary Chlorpromazine, a drug commonly administered as an antiemetic during pregnancy, when administered prenatally to chick embryos, was associated postnatally with a curled toe anomaly (ED 50% of 88 g/egg for the 4-day-embryo).     

Snake venom action: Are enzymes involved in it?

Summary Enzymes were the first clearly recognized components of snake venoms. When several more were discovered, attempts were made to correlate venom action with enzymic functions. The last few years have seen most successful efforts in the identification, isolation and structural elucidation of highly toxic polypeptides present in snake venoms, in particular of neurotoxins and membrane-active toxins. Following this development the polypeptides were called the true toxic components and the enzymes lost their previous central position in venom pharmacology. The time, therefore, has come to re-evaluate the role of enzymes in the complex interaction between snake and prey. While highly active polypeptides indeed dominate the action of hydrophiid venoms, they appear to play a lesser role in crotalid venom action as compared with enzyme components. Enzymes are involved in many levels of venom action, e. g. by serving as spreading factors, of by producing very active agents, such as bradykinin and lysolecithins in tissues of preys or predators. Some toxins, e. g. the membrane-active polypeptides appear to participate in the interaction between membrane phospholipids and venom phospholipases. The classical neurotoxin, -bungarotoxin, has been recognized as a powerful phospholipase. Several instances are known which indicate that some enzymes potentiate the toxic action of others; the analysis of a single enzyme may, therefore, not fully reveal its biofunction. For 3 enzymes, ophidianl-amino acid oxidase, ATPpyrophosphatase, and acetylcholinesterase, some of the problems pertaining to venom toxicity are discussed.