In vitro evaluation of erythromycin in chloroquine resistant brazilian P. falciparum freshly isolates: modulating effect and antimalarial activity evidence.
(49/2261)
Erythromycin, a reversal agent in multidrug-resistant cancer, was assayed in chloroquine resistance modulation. The in vitro microtechnique for drug susceptibility was employed using two freshly isolates of Plasmodium falciparum from North of Brazil. The antimalarial effect of the drug was confirmed, with an IC50 estimates near the usual antimicrobial therapy concentration, and a significant statistical modulating action was observed for one isolate. (+info)
The glycosphingolipid sulfatide in the islets of Langerhans in rat pancreas is processed through recycling: possible involvement in insulin trafficking.
(50/2261)
In previous studies we have shown that sulfatide (galactosylceramide-3-O-sulfate), in various species, is present in the insulin-producing cells in pancreatic islets of Langerhans. In this study the synthesis of sulfatide in the islets has been investigated by pulse chase labeling at varying glucose levels and in the presence or absence of the glycosphingolipid synthesis inhibitory agents, Brefeldin A, fumonisin B1 and chloroquine and the distribution of sulfatide by immune-electronmicroscopy. The data showed that (1) sulfatide was produced in islets of Langerhans, (2) the main pathway for synthesis was through recycling involving partial degradation in the lysosome, and that (3) high glucose levels, although not primarily reflected in an increased synthesis of sulfatide, lead to an increased expression of mRNA for the UDP-galactose:ceramide galactosyltransferase, producing the immediate precursor of sulfatide. Furthermore, mass spectrometry analyses revealed a high proportion of short chain fatty acids, C16:0 (50%) and no hydroxylated forms and thus special physicochemical properties, indicating important differences between pancreatic and brain/neural sulfatide. Immune electron microscopy revealed an intracellular expression of sulfatide in the secretory granules, the Golgi network and the lysosomes of the islets. These results indicate that sulfatide follows the same intracellular route as insulin and suggest a functional association between these molecules. We have raised the hypothesis that sulfatide possibly plays a role in the trafficking of insulin in the islets of Langerhans in rat pancreas. (+info)
A community perspective on the efficacy of malaria treatment options for children in Lundazi district, Zambia.
(51/2261)
In 1996, Zambia's Ministry of Health made sulfadoxine-pyrimethamine (SP) available as a second-line antimalarial. SP differs from chloroquine (CQ) in ways that might affect parents' acceptance of the drug, resulting in possible delays in seeking treatment if parents perceive SP as less efficacious. A multifaceted study consisting of a rapid community ethnographic assessment to examine local attitudes and perceptions toward malaria, a 14-day in vivo drug efficacy study comparing clinical and parasitological efficacy of CQ, SP, and SP with paracetamol (PCM) in children under five, and a qualitative study examining caretakers' perceptions of drug efficacy helped to guide implementation of the new drug policy. The rapid ethnographic study indicated that the community was aware of malaria as an illness best treated with modern medicines, particularly CQ. The drug efficacy study demonstrated a 25% level of clinical failures compared to none with SP, and 30% of the children treated with CQ had either RIII or RII parasitological failures whereas none occurred in children treated with SP. Most parents perceived that their children were improving and that the drugs were working. Parents in the SP groups were most pleased and readily accepted SP as a new drug. The addition of PCM did not improve perceptions of SP efficacy, contradicting conventional wisdom regarding the need for direct antipyretic action for parents to perceive a drug as efficacious. The combined results reflected a community that was in the beginning stages of evaluating a new malaria therapy mostly unknown to them. Perceptions of efficacy of CQ were beginning to shift, indicating a readiness for accepting a new drug based on its shown biological efficacy. Parasitological and clinical failure rates reinforced the need to fully implement the changed national policy as soon as possible, and to consider a change in first-line therapy. (+info)
Regulated trafficking of the human dopamine transporter. Clathrin-mediated internalization and lysosomal degradation in response to phorbol esters.
(52/2261)
The dopamine transporter plays an essential role in the modulation of dopaminergic neurotransmission by mediating the reuptake of dopamine into presynaptic neurons. In cells expressing the dopamine transporter, activation of protein kinase C by phorbol esters results in a significant reduction in dopamine uptake. This phorbol ester-mediated inhibition of dopamine transport is associated with a decrease in V(max), although the apparent affinity of the transporter for dopamine remains unchanged. Using a green fluorescent protein-tagged dopamine transporter stably expressed in Madin-Darby canine kidney cells, we show in live cells that the decrease in transporter activity is caused by the rapid internalization of carriers from the plasma membrane. This redistribution of the transporter is specific to phorbol ester activation and is unaffected by the presence of either substrates or inhibitors of the carrier. Upon the addition of phorbol esters, transporters at the cell surface are rapidly endocytosed through a clathrin-mediated and dynamin-dependent mechanism into early endosomes, where they colocalize with transferrin. The internalized carrier is targeted to the endosomal/lysosomal pathway and is completely degraded within 2 h of protein kinase C activation. Phorbol ester-mediated alterations in the trafficking of the dopamine transporter may serve as a mechanism for controlling extracellular dopamine levels in the central nervous system. (+info)
Anti-malarial drug use among preschool children in an area of seasonal malaria transmission in Kenya.
(53/2261)
The aims of this study were to estimate the proportion of asymptomatic Kenyan preschool children using anti-malarial drugs, to identify factors associated with chloroquine use, and to assess the validity of frequency of febrile episodes and drug use reported by mothers or carers. Of 318 children studied, 38% (95% confidence interval [CI] = 30-47%]) tested positive for chloroquine or sulfadoxine. Of chloroquine-positive children, 15% had concentrations exceeding the estimated minimum therapeutically effective values. Among those testing negative for sulfadoxine, chloroquine-positive children were more frequently parasitemic (odds ratio = 2.6, 95% CI = 1.3-5.2), and had lower mean hemoglobin concentrations (6.1 g/L, 95% CI = 2.1-10.1) than chloroquine-negative children. Mothers over-reported the frequency of malaria or fever episodes as usually defined in medical studies, and underreported anti-malarial drug use. We conclude that anti-malarials are frequently given for treatment of malaria or malaria-associated illness, rather than prophylactically or for symptoms unrelated to malaria. Questionnaire surveys cannot replace biochemical markers to obtain information on anti-malarial drug use. (+info)
Analysis of mefloquine resistance and amplification of pfmdr1 in multidrug-resistant Plasmodium falciparum isolates from Thailand.
(54/2261)
Resistance to quinoline-containing compound has been associated with the Plasmodium falciparum multidrug resistance 1 (pfmdr1) gene. We analyzed wild P. falciparum isolates with high levels of chloroquine and mefloquine resistance for their macrorestriction maps of chromosome 5 and sequence of pfmdr1. Two types of chromosome 5 amplification were found. Eleven of 62 resistant isolates displayed Bgl 1 fragments larger than 100 kb. Twenty-nine isolates possessed multiple copies of the fragments. We failed to detect any amplification of this region on chromosome 5 in 22 mefloquine-resistant isolates, suggesting that other mechanisms can mediate the mefloquine-resistant phenotype. There was no direct association between pfmdr1 mutations and chloroquine sensitivity. Resistant lines could have Asn-86 and Tyr-184 or Phe-184, the predicted sequence of those chloroquine-sensitive isolates. No mutation at Asn-1042 and Asp-1246 was detected among these chloroquine-resistant isolates. Therefore, a few base substitutions in the pfmdr1 gene may not be sufficient to account for all chloroquine-resistant phenotypes. (+info)
Molecular epidemiology of malaria in Yaounde, Cameroon V. analysis of the omega repetitive region of the plasmodium falciparum CG2 gene and chloroquine resistance.
(55/2261)
A novel Plasmodium falciparum gene, denoted cg2 gene, has been recently discovered, and a distinct genotype, characterized by 12 point mutations and 3 size polymorphisms, has been shown to be associated with chloroquine resistance in laboratory-adapted parasite strains. One of the polymorphic regions, denoted the omega region, consists of 16 tandem repeat units in chloroquine-resistant strains, while the chloroquine-sensitive strains have either < or = 15 or > or = 17 repeat units. In this study, the in vivo and in vitro responses were compared with the number of repeat units in the omega region of the cg2 gene for 75 Cameroonian isolates determined either by DNA sequencing or agarose gel electrophoresis. The 16-repeat units that characterize the resistant strains were found in 10 chloroquine-sensitive isolates (50% inhibitory concentration [IC50] < 100 nM) and 30 chloroquine-resistant isolates (IC50 > or = 100 nM). Thirty-five isolates (28 chloroquine-sensitive isolates and 7 chloroquine-resistant isolates) displayed < or = 15 or > or = 17 repeat units. Of the 18 patients responding with treatment failure, 15 were infected with parasites carrying 16 repeat units. Twenty-eight patients (11 with isolates carrying 16 repeat units and 17 with isolates carrying < or = 15 or > or = 17 repeat units) showed an adequate clinical response. The sensitivity, specificity, and predictive value were 81% (83%), 74% (61%), and 75% (58%), respectively compared with in vitro (or in vivo) responses. Neither the level of IC50 nor the key P. falciparum multidrug resistance gene 1 (pfmdr 1) allele at position 86 was associated with the number of omega repeat units. Although in vitro and in vivo resistance to chloroquine was statistically associated with the presence of 16 repeat units in the omega region (P < 0.05), the number of omega repeat units did not adequately discriminate patients infected with chloroquine-resistant parasites from those infected with chloroquine-sensitive parasites. Further studies on the cg2 gene are needed to determine whether cg2 gene is a reliable genetic marker for chloroquine resistance. (+info)
Initial events in infectious salmon anemia virus infection: evidence for the requirement of a low-pH step.
(56/2261)
We have investigated the initial steps in the interaction between infectious salmon anemia virus (ISAV) and cultured cells from Atlantic salmon (SHK-1 cell line). Using radioactively or fluorescently labelled viral particles we have studied the binding and fusion kinetics and the effect of pH on binding, uptake, and fusion of ISAV to SHK-1 cells and liposomes. As pH in the medium was reduced from 7.5 to 4.5, the association of virus to the cells was nearly doubled. The same effect of pH was observed when fusion between ISAV and liposomes was analyzed. In addition, the binding of ISAV to intact SHK-1 cells and to cell membrane proteins blotted onto filters was neuraminidase sensitive. However, the increased binding induced by low pH was not neuraminidase sensitive, probably reflecting activation of a fusion peptide at low pH. By using confocal fluorescence microscopy, the increased fusion of fluorescently labelled ISAV with the plasma membrane due to low pH could be demonstrated. When vacuolar pH in the cells was raised during inoculation with chloroquine or ammonium chloride, both electron and confocal microscopy showed accumulation of ISAV in endosomes and lysosomes. Production of infectious virus could be increased by lowering the extracellular pH during infection. Furthermore, chloroquine present during virus inoculation also caused a reduction in the synthesis of viral proteins in ISAV-infected cells as well as in the production of infective virus. These results indicate that ISAV binds to sialic acid residues on the cell surface and that the fusion between virus and cell membrane takes place in the acid environment of endosomes. This provides further evidence for a high degree of similarity between ISAV and influenza virus and extends the basis for the classification of this virus as a member of the Orthomyxoviridae family. (+info)