An enzyme-linked immunosorbent assay for the detection of Entamoeba histolytica antigens in faecal material

This paper describes a method for the detection of Entamoeba histolytica antigens in stool samples using a multi-layer ELISA. The method is sensitive and specific, showing no interference with other intestinal parasites, e.g. E. coli, E. hartmanni, Endolimax nana, Iodamoeba buetschlii, Hymenolepis nana, Giardia lamblia, Trichomonas and Ascaris. The method provides a rapid and simple screening assay for E. histolytica infections and should assist in diagnosis and epidemiological studies of the disease.     

The effect of combinations of qinghaosu (artemisinin) with standard antimalarial drugs in the suppressive treatment of malaria in mice

Artemisinin is a novel antimalarial drug isolated in China from the wormwood plant Artemisia annua L. Studies with rodent malaria were carried out to detect antagonism and synergism with a variety of antimalarial drugs. Isobolograms of drug interaction were plotted at the ED90 level. With a normally susceptible strain of Plasmodium berghei, marked potentiative synergism was found with mefloquine, tetracycline and spiramycin. There was some synergism also with primaquine. Combinations of artemisinin with dapsone, sulfadiazine, sulfadoxine, pyrimethamine, pyrimethamine/sulfadoxine and cycloguanil showed antagonism. A high degree of potentiation was shown between artemisinin and primaquine with a primaquine-resistant strain, whilst the combination with mefloquine showed enhanced potentiation with a mefloquine-resistant strain. Combinations of artemisinin with mefloquine, primaquine, tetracycline or clindamycin showed marked potentiation with an artemisinin-resistant strain. The mechanisms underlying the drug interactions observed are discussed.     

A cAMP-activated chloride channel in the plasma membrane of cultured human gastric cells (HGT-1)

Hydrochloric acid (HCl) secretion by gastric parietal cells involves an apical Cl^– conductance, the properties of which have not been defined. In the present study, forskolin and histamine [agonists that increase intracellular cyclic adenosine monophosphate (cAMP)], and dibutyryl cAMP, activated channels in previously quiescent cell-attached membrane patches on cultured human gastric cells (HGT-1). In the cell-attached configuration (Cl^–149 mmol/ 1 in bath and pipette), channels exhibited outward rectification, voltage dependence, inward current (–0.7 pA) at zero holding potential and a reversal potential of +24 mV, consistent with the presence of a Cl^– conductive pathway. In excised inside-out patches, channels (i) exhibited degrees of outward rectification and voltage dependence that were comparable to those seen in cell-attached patches, (ii) demonstrated a –21 mV shift of their reversal potential when bath Cl^– was decreased from 149 mmol/l to 53 mmol/l (calculated Cl^–:cation permeability ratio 171), and (iii) were highly sensitive to the Cl^– channel blocker diphenylamine-2-carboxylic acid (DPC, 10^–3 mol/l). This cAMP-activated Cl^– channel bears many similarities to other Cl^– channels within intestinal epithalia, and may represent the apical Cl^– channel operating in HCl-secreting gastric parietal cells.     

Efficacy of artesunate plus pyrimethamine-sulphadoxine for uncomplicated malaria in Gambian children: a double-blind, randomised, controlled trial

This double-blind, randomized, controlled study investigated the efficacy, safety and tolerability of artesunate plus pyrimethamine-sulphadoxine for uncomplicated malaria among Gambian children. Combined use of artesunate and pyrimethamine-sulphadoxine was hypothesized to delay or prevent resistance, which proved to be effective in reducing childhood mortality in sub-Saharan Africa. A total of 600 children with acute uncomplicated Plasmodium falciparum malaria, 6 months to 10 years old, were randomly administered pyrimethamine-sulphadoxine (25 mg/500 mg) with placebo, 4 mg/kg body weight pyrimethamine-sulphadoxine plus 1 dose of artesunate, or pyrimethamine-sulphadoxine plus 4 mg/kg body weight artesunate for 3 days. Results indicate that combined treatment was well tolerated. On day 1, 178 of 381 children treated with artesunate were still parasitemic compared with 157 of 195 children in the pyrimethamine-sulphadoxine group. On the other hand, failure rates on day 14 were 3.1% in the pyrimethamine-sulphadoxine group and 3.7% in the 1-dose artesunate group and 1.6% in the 3-dose group. Insignificant differences were found among children administered 1-dose and 3-dose artesunate, and were found less likely to be gametocytemic after treatment. In conclusion, this study confirms the safety and efficacy of a combined treatment, which eventually results in lower gametocyte rates and lower transmission rates.     

The chemotherapy of rodent malaria, XXIX DNA relationships within the subgenus Plasmodium (Vinckeia).

The relationships between rodent malarias were examined by means of DNA buoyant density determinations and DNA--DNA hybridization data. Current views of the existence in this group of four species: Plasmodium berghei, P. yoelli, P. vinckei and P. chabaudi were confirmed. The identity of two chloroquine-resistant lines derived from P. berghei N strain was established. One of these, the NS line, was found to be a subspecies of P. yoelii; the implications of this finding are discussed.     

Effects of piperaquine, chloroquine, and amodiaquine on drug uptake and of these in combination with dihydroartemisinin against drug-sensitive and -resistant Plasmodium falciparum strains

Piperaquine is being developed as a long-acting component in artemisinin combination therapies. It was highly active in vitro and drug interaction studies showed that dihydroartemisinin combinations with piperaquine, chloroquine, and amodiaquine were indifferent tending toward antagonism. Competitive uptake of radiolabeled chloroquine and dihydroartemisinin in combination with other antimalarials was observed.     

Correlation of in vivo-resistance to chloroquine and allelic polymorphisms in Plasmodium falciparum isolates from Uganda

The efficacy of chloroquine in the treatment of uncomplicated falciparum malaria in Africa is heavily compromised by high levels of drug resistance. The occurrence of active site mutations in the Plasmodium falciparum multi drug resistance-gene 1 (pfmdr1) has been associated with development of resistance to chloroquine. This study investigates the occurrence of several mutations at codons 86, 1042 and 1246 of the pfmdr1-gene in infected blood samples taken from Ugandan children before treatment with chloroquine and their relationship to clinical and parasitological resistance. Even though a clear association of CQR to one certain pfmdr1 single point mutation could not be substantiated, the frequency of resistance was consistently higher for samples revealing any of the mutations than among wild type samples, and 90% of the clinically resistant samples did present a mutation. Thus detection of these allelic pfmdr1 polymorphisms is not a decisive factor for prediction of clinical chloroquine resistance, but an interplay of the different mutations with unknown cofactors is to be assumed and the possible role of other genetic alterations remains to be investigated.     

The chemotherapy of rodent malaria, XXXVIII. Studies on the activity of three new antimalarials (WR 194,965, WR 228,258 and WR 225,448) against rodent and human malaria parasites (Plasmodium berghei and P. falciparum)

In addition to their blood schizontocidal action on Plasmodium berghei in vivo, two Mannich bases WR 194,965 and 228,258 are also active against chloroquine-sensitive and chloroquine-resistant lines of P. falciparum in vitro. The response of the lines to each drug differs but shows no correlation in either case with response to chloroquine. The 8-aminoquinoline WR 225,448 is also active against P. falciparum in vitro but at much higher concentrations than the Mannich bases. Application of the 'chloroquine-induced pigment clumping (CIPC) test' and the study of ultrastructural changes induced in P. berghei in drug-treated mice indicate that WR 194,965 has a mode of action somewhat resembling that of quinine. WR 228,258 in vitro shows a chloroquine-like effect, but not in vivo, suggesting that its mode of action in vivo is different from that of chloroquine. WR 225,448 has no action in the CIPC in vitro and affects primarily mitochondria of the parasites in vivo. It probably acts through a metabolite. Both pre-erythrocytic and erythrocytic stages of rodent malaria parasites are affected by WR 225,448.     

Interferon γ induces differential upregulation of α and β chemokine secretion in colonic epithelial cell lines

Background—Production of chemoattractant factorsby the intestinal epithelium may contribute to mucosal infiltration byinflammatory cells in inflammatory bowel disease. Secretion of the α chemokine interleukin 8 (IL-8), a neutrophil chemoattractant, has beenwidely studied, but little is known about epithelial secretion of β chemokines, which are preferentially involved in recruiting monocytes.
Aims—To investigate the profiles of α and β chemokine secretion in colonic cell lines and their differentialmodulation by interferon γ (IFN-γ), a product of activated Tlymphocytes and natural killer cells.
Methods and results—HT29-19A, a model of theCl secretory crypt cell, exhibited a parallel secretionof the α chemokines IL-8 and GROα, which could be markedlyupregulated by tumour necrosis factor α (TNF-α) and IL-1β. Thesecells showed no significant expression of the β chemokines RANTES(regulated upon activation T cell expressed and secreted), MIP-1α(macrophage inflammatory protein 1α), and MCP-1 (monocyte chemotacticprotein 1) under these conditions, but IFN-γ in combination withTNF-α caused a dose dependent induction of RANTES and MCP-1secretion. This was accompanied by a marked increase of RANTES mRNA. Incontrast, IFN-γ had no significant effect on TNF-α stimulated IL-8secretion. Caco-2 cells, with features more typical of villusabsorptive cells, were relatively poor secretors of α chemokines butsecreted high levels of MCP-1 in response to IL-1β. IFN-γ did notinfluence α or β chemokine secretion in these cells.
Conclusions—These studies suggest that intestinalepithelial cells may produce chemokines capable of attracting bothneutrophils and monocytes. The ability of IFN-γ to activate theexpression of β chemokines preferentially could facilitate thedevelopment of chronic inflammatory infiltrates.

Keywords:inflammatory bowel disease; RANTES; interferongamma; chemokine