BACKGROUNDDuring the blood stage of malaria infection, parasites internalize in the host red blood cells and degrade massive amounts of hemoglobin for their development. Although the morphology of the parasite's hemoglobin uptake pathway has been clearly observed, little has been known about its molecular mechanisms.

METHODSThe recombinant proteins from Plasmodium falciparum, dynamin like protein 1 (PfDYN1) and 2 (PfDYN2) GTPase domain, were expressed in E.coli and showed GTPase activity. By using a dynamin inhibitor, dynasore, we demonstrated the involvement of PfDYN1 in the hemoglobin uptake pathway.

RESULTSThe GTPase activity of the two recombinant proteins was inhibited by dynasore in vitro. Treatment of parasite cultures with 80 micromol/L dynasore at the ring and early trophozoite stage resulted in substantial inhibition of parasite growth and in an obvious decline of hemoglobin quantum. Furthermore, reduced intracellular hemozoin accumulation and decreased uptake of the FITC-dextran were also observed, together with distinctive changes in the ultrastructure of parasites after the dynasore treatment.

CONCLUSIONSOur results show that PfDYN1 plays an important role in the hemoglobin uptake pathway of P. falciparum and suggest its possibility of being a novel target for malaria chemotherapy.

Animals ; Antimalarials ; pharmacology ; Dynamins ; antagonists & inhibitors ; GTP Phosphohydrolases ; genetics ; metabolism ; Hemoglobins ; metabolism ; Hydrazones ; pharmacology ; Malaria, Falciparum ; metabolism ; Microscopy, Electron, Transmission ; Plasmodium falciparum ; drug effects ; metabolism ; ultrastructure ; Protozoan Proteins ; genetics ; metabolism ; Recombinant Proteins ; genetics ; metabolism

Nitric oxide synthases (NOSs) play complex roles in the regulation of cardiac excitation contraction coupling under basal and stressed conditions. Herein, using the recording approach for intracellular calcium transient and synchronous myocyte contraction, the potential mechanism for NOSs-mediated cardiomyocyte contraction was explored. We found that selective inhibition of neuronal NOS (nNOS) with 100 µmol/L spermidine markedly enhanced the cardiomyocyte twitch [control: (10.5 ± 0.21)%; nNOS inhibition: (12.4 ± 0.18)%] and calcium transient [control: (0.27 ± 0.03)%; nNOS inhibition: (0.42 ± 0.01)%], but slowed the relengthening of twitch [control: (25.2 ± 1.3) ms; nNOS inhibition: (53 ± 2.8) ms] and the calcium transient decay [control: (129 ± 4.3) ms; nNOS inhibition: (176 ± 7.1) ms], which was similar to that by dynamin inhibition with 30 µmol/L dynasore. The nNOS inhibition- or dynasore-mediated effects could be rescued by an NO donor, S-Nitroso-N-acetylpenicillamine (SNAP). Our data suggest that the selective nNOS-mediated regulation of cardiac contractile activity may partly involve the dynamin-mediated endocytic mechanism.
Animals ; Biological Transport ; Calcium Signaling ; Dynamins ; antagonists & inhibitors ; physiology ; Endocytosis ; physiology ; Female ; Hydrazones ; pharmacology ; Male ; Myocardial Contraction ; physiology ; Nitric Oxide Synthase Type I ; physiology ; Rats ; Rats, Sprague-Dawley ; Spermidine ; pharmacology ; Transport Vesicles ; physiology

Animals ; Body Water ; metabolism ; Capillary Permeability ; Hydrazones ; pharmacology ; Lung ; metabolism ; pathology ; MAP Kinase Signaling System ; Male ; Phosphorylation ; Rats ; Rats, Sprague-Dawley ; Respiratory Distress Syndrome, Adult ; etiology ; p38 Mitogen-Activated Protein Kinases ; physiology

BACKGROUND: Acinetobacter baumannii is one of the most important pathogens capable of colonization in burn patients, leading to drug-resistant wound infections. This study evaluated the distribution of the AdeABC efflux system genes and their relationship to ciprofloxacin resistance in A. baumannii isolates collected from burn patients. METHODS: A total of 68 A. baumannii clinical strains were isolated from patients hospitalized in Motahari Burns Center in Tehran, Iran. Ciprofloxacin susceptibility was tested by the disk diffusion and agar dilution methods. PCR amplification of the adeRS-adeB drug efflux genes was performed for all resistant and susceptible isolates. To assess the role of the drug efflux pump in ciprofloxacin susceptibility, carbonyl cyanide 3-chlorophenylhydrazone (CCCP) was used as an efflux pump inhibitor (EPI). RESULTS: Approximately 95.6% of the Acinetobacter isolates were resistant to ciprofloxacin, with minimum inhibitory concentration (MIC) values ranging from 4 to > or =128 microg/mL. The susceptibility of 86.1% of the resistant isolates increased by factors of 2 to 64 in the presence of CCCP. All resistant isolates were positive for the adeRS-adeB genes, and 73.2% of them had mutations in the AdeRS regulatory system. CONCLUSIONS: The results showed that AdeABC genes are common in A. baumannii, which might be associated with ciprofloxacin non-susceptibility, as indicated by the observed linkage to the presence of the genes essential for the activity of the AdeABC, several single mutations occurring in the adeRS regulatory system, and an increase of ciprofloxacin susceptibility in the presence of a CCCP EPI.
ATP-Binding Cassette Transporters/antagonists & inhibitors/genetics/*metabolism ; Acinetobacter Infections/diagnosis/microbiology ; Acinetobacter baumannii/*drug effects/genetics/isolation & purification ; Anti-Bacterial Agents/*pharmacology ; Bacterial Proteins/antagonists & inhibitors/genetics/*metabolism ; Base Sequence ; Ciprofloxacin/*pharmacology ; DNA, Bacterial/chemistry/genetics/metabolism ; Drug Resistance, Bacterial ; Humans ; Hydrazones/pharmacology ; Microbial Sensitivity Tests ; Mutation ; Polymerase Chain Reaction