Cells, Cultured

BACKGROUND: Clinical studies suggest that midazolam and propofol interact synergistically to induce hypnosis, but these drugs do not interact synergistically to prevent movement in response to noxious stimuli. The mechanisms underlying these interactions are not certain but may occur at the level of the gamma-aminobutyric acid A (GABA(A)) receptor. METHODS: The authors evaluated the interactions between propofol and midazolam in modulating GABA(A) receptor activity in embryonic hippocampal neurons.

The antimalarial compound qinghaosu (artemisinin) was tested in vitro for the ability to inhibit plaque formation by Toxoplasma gondii in fibroblasts. Qinghaosu at 0.4 microgram/ml for 5 days eliminated all plaques and microscopic foci of T. gondii. At 1.3 micrograms/ml for 14 days, qinghaosu completely eliminated T. gondii. Pretreatment of host cells or T. gondii with qinghaosu had no effect on T. gondii growth. There was no apparent toxicity to human fibroblasts in long-term studies.

The susceptibility of Pneumocystis carinii to artemisinin (qinghaosu) was determined in short-term primary culture. In untreated cultures, trophozoites increased an average of fivefold over 4 days. Inhibition of parasite growth in cultures treated with artemisinin at concentrations as low as 0.5 microM was seen. In contrast, artemisinin concentrations up to 100 microM had no effect on feeder layer cells.

The sesquiterpene endoperoxide antimalarial agents arteether and artemether have been reported to cause neurotoxicity with a discrete distribution in the brain stems of rats and dogs after multiple doses. The nature and distribution of the brain lesions suggest a specific neuronal target, the identity of which is unknown.

AIM: To study the effect of artemisinin (Art) on outward rectifier potassium current in ventricular myocytes. METHODS: In isolated guinea pig ventricular myocytes, the effects of Art on the two components of delayed outward rectifier K+ current (IK), the rapidly activating inward K+ current (IKr), and the slowly rectifying outward K+ current (IKs) were observed by the whole cell patch-clamp technique. RESULTS: Art decreased IK in a concentration-dependent manner.

We recently described a screening system designed to detect neurotoxicity of artemisinin derivatives based on primary neuronal brain stem cell cultures (G. Schmuck and R. K. Haynes, Neurotoxicity Res. 2:37-49, 2000). Here, we probe possible mechanisms of this brain stem-specific neurodegeneration, in which artemisinin-sensitive neuronal brain stem cell cultures are compared with nonsensitive cultures (cortical neurons, astrocytes). Effects on the cytoskeleton of brain stem cell cultures, but not that of cortical cell cultures, were visible after 7 days.

Three antimalarial drugs, artesunate, pyrimethamine, and pamaquine, were evaluated for their growth-inhibitory effects against Babesia equi and Babesia caballi in in vitro culture. B. equi was more resistant to pyrimethamine than B. caballi. B. equi was also found to be more sensitive to artesunate and pamaquine than B. caballi. Of the three compounds, pyrimethamine gave the most promise for in vivo effectiveness.

Sera collected at various time intervals from healthy Thai male subjects after the administration of the three oral formulations of dihydroartemisinin (Cotecxin) manufactured in the People's Republic of China, a formulation manufactured by Arenco n.v. Pharmaceutica in Belgium, and a formulation manufactured by the Faculty of Pharmacy of Mahidol University in Thailand) were investigated for their ex vivo blood schizontocidal activities against the K1 strain of Plasmodium falciparum.

AIM: To study the immunosuppressive activity of SM735 {[3-(12-beta-artemisininoxy)] phenoxyl succinic acid}, a synthetic artemisinin derivative with nonsteroidal anti-inflammatory drug structure, with the aim of finding potential immunosuppressive agents. METHODS: Concanavalin A (ConA), lipopolysaccharide (LPS), and mixed lymphocyte reaction (MLR), were used to induce the proliferation of splenocytes, and [3H]-thymidine incorporation was used to evaluate the proliferation of splenocytes.

Toxoplasmosis, caused by the protozoan Toxoplasma gondii, is medically important and distributed worldwide. Currently available medications are limited in terms of efficacy and side effects. We synthesized novel, nonacetal, hydrolytically stable derivatives of artemisinin and showed that they inhibit the replication of Toxoplasma gondii in cell culture.