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Competing Interests: Disclosure The authors report no conflicts of interest in this work.

Thieno[3,2-c]quinoline-4-yl-amines - synthesis and investigation of activity against malaria pH-Dependant reduction of the methyl 2-(2-nitrophenyl)thiophene-3-carboxylate 3, formed by Suzuki coupling of methyl 2-iodothiophene-3-carboxylate (2) with 2-nitrophenylboronic acid, yielded the cyclic hydroxamic acid 4 and the lactam 5, respectively. The 4-chlorothieno[3,2-c]quinoline 6 was formed from the lactam 5 by heating with POCI3/PCI5s. Melting of 6 with the novaldiamine base in phenol gave the chloroquine analogue 7, whereas the amodiaquine and the pyronaridine analogues 8 and 9 were obtained using phenol Mannich bases. The reaction of 6 with putrescine and N,N'-bis(3-aminopropyl)piperazine as spacer formed the bisquinoline derivatives 10 and 11 as well as the monosubstituted quinoline 12. In the same manner the isomeric 4-chlorothieno[2,3-c]quinoline 13 reacted to yield the quinoline-4-yl-amines 14-16. The compounds 7-12 and 14-16 were tested for in vitro growth inhibition of the malaria parasite Plasmodium falciparum. As most active compound the pyronaridine derivative 9 displayed an IC50 value of 210 nM with the chloroquine sensitive P. falciparum strain 3D7 and 750 nM with the chloroquine resistant P. falciparum strain Dd2. The N,N'-bis(3-aminopropyl)piperazine derivative 11 displayed in vivo activity in Plasmodium vinckei infected mice with an ED50 value of 30 mg/kg after i.p. administration.

The synthesis of 1,3-oxazino-anellated 4-amino-5-hydroxy-quinolines has been investigated. Cyclisation to 2,3-dihydro[1,3]oxazino[4,5,6-de]quinoline-2-ones/-2-thiones (2/3) was achieved by reaction with 1,1'-carbonyldiimidazole or 1,1'-thiocarbonyldiimidazole. Cyclocondensation with aldehydes yielded 2,3-dihydro[1,3]oxazino[4,5,6-de]quinoline-derivatives (5). All new tricyclic compounds exhibited weak antiprotozoal activity against Plasmodium falciparum.

History and Admission Findings: A 54-year-old man was admitted because of intermittent fever for 2 days. Ten days earlier he had returned from Kenya. He had not taken any antimalarial drugs prophylactically., Investigations: Initial blood smears showed Plasmodium falciparum in 10.4% of erythrocytes. Laboratory tests indicated hyponatremia and disseminated intravascular coagulation. Also, laboratory markers of infection and hemolysis were clearly positive and accompanied by a low-grade normocyticanaemia. Chest radiograph showed the heart size to be at the upper limit of normal and no signs of congestion, pleural effusion or inflammatory infiltrates. Sonography demonstrated hepatosplenomegaly with diffusely increased echogenicity of the liver., Treatment and Course: Falciparum malaria [corrected] with quartan fever was diagnosed and treatment with quinine and doxycycline was initiated. Despite the successful elimination of parasites and a negative fluid balance the patient died two days after admission from pulmonary edema and heart failure., Conclusions: A negative fluid balance failed to prevent acute pulmonary edema in this case of severe malaria,supporting the view that fluid imbalance is not an essential feature in malaria-induced lung injury and that cytokines play and important role.

Malaria is the most prevalent parasite-transmitted infectious disease in humans, with 300-500 million people infected and 3-5 million persons dying from the disease each year [1]. There is, however, surprisingly little knowledge of the parasite's biology and its evolutionary adaptations to cope with a life as an intracellular parasite within its vertebrate host. This article gives an overview of the parasite's developmental cycle and highlights aspects of the immune response in infected humans and the parasite's mechanisms of immune evasion. In addition, special features of the life cycle of the parasite are presented, especially the invasion process of merozoites into red blood cells. Putative mechanisms of drug action of synthetic antimalaria drugs are discussed as well as hypotheses explaining the development of drug resistance in a variety of parasite strains.

A strain of Babesia divergens was propagated by inoculation of 1.5 x 10(7) parasitized erythrocytes in 30 passages under same conditions on altogether 150 jirds. The developmental stages of Babesia divergens revealed pleomorphism in the erythrocytes of the jird. Single parasites were observed as being pyriform, globular, budding, ring-like or amoebid. The shape of dividing parasites varied between the spherical and the pyriform. The stages in the erythrocytes were localized predominantly intermedia. The reduction of the number of dividing forms and the increase of single forms occurred with increasing numbers of passages. Length and breadth of double pyriforms increased by approximately 20%.

Human proto- and metazoa, which spend a part of their life-cycle within erythrocytes or extracellularly in human blood or in monocyte-derived macrophages, are considered as blood parasites. In spite of their individually widely differing habitat, they elicit a common hematological syndrome essentially consisting in hemolytic anemia and splenomegaly. Furthermore, some basic factors of host/parasite interaction are very similar: (1) Specific cell attachment through receptor/ligand mechanisms such as the integrin/RGD-oligopeptide system, (2) competition for essential nutrients such as iron, which may be influenced therapeutically to the disadvantage of the parasite by the use of iron chelators, and (3) provocation of host defense through T-cell dependent, cytokine-mediated macrophage activation.

A procedure is described for the elucidation of the glycolytic flux rate of red blood cells infected with the malarial parasite Plasmodium berghei. It is based on the titration of the protons originating from the glycolytic lactate accumulation. Compared with traditional methods of biochemical measurements of glucose consumption or accumulation of lactate the proposed procedure shows the following advantages: continuously measurement is possible; constancy of the pH-value during the measurement; lower amounts of biological material are necessary (increased sensitivity) increased accuracy; The method can also be applied to studies on other cells and species with normal or increased glycolytic flux rate.

The fine structure of trophozoites and especially of merozoites of Babesia herpailuri is described before and after treatment with Imidocarb (Wellcome). The mostly piriform to oval merozoites possess an outer membrane and a supporting membrane below. The intratorium consists of a polar ring, rhoptries micronemes and the sperical body which lies beside the big nucleus and next to mitochondria. The endoplasmic reticulum and invaginations are not clearly formed. The cellular changes of Babesia herpailuri, observed one hour after drug treatment in trophozoites and six hours later in merozoites, concern the form and function of the parasite: widening of the subpellicular endoplasmic reticulum and of the perinuclear space; sporadic dilatation of the endoplasmic reticulum of the merozoites (9 fig.). Damaged membranes, dissolution of the cellular membrane, disintegration of the nuclei as are known effects of the Berenil treatment to Babesia herpailuri, are not noted results after the Imidocarb treatment. The original membrane systems of trophozoites as well as of merozoites, remain unaffected by the drug as long as investigations were carried on (24 h). The satisfying prophylactic effect of Imidocarb as well as the insignificant cellular damages on merozoites may be due to the small feeding of hemoglobin.

The in vitro-invasion of mouse erythrocytes by Toxoplasma gondii could be detected and analysed by electron microscopy. The sequence of events observed during erythrocyte invasion led to the assumption of an actively penetrating parasite into the non-phagocytic host cell.

After arriving in Austria a 10 month old Nigerian infant fell sick with malaria tropica and survived after specific antiparasitic therapy. Early diagnosis and immediate begin of treatment are stressed.

The glutathione status of Plasmodium vinckei parasitized erythrocytes of mice was determined in correlation to the intraerythrocytic stage of maturation of the parasite. The different stages of blood schizogony were separated by discontinuous Dextran-density-centrifugation. The changes of protein content, glutathione concentration (reduced/oxidized and bound/free glutathione) and in the specific activities of the following enzymes: gamma-glutamyl-cysteine-synthetase (GC-synthetase), glutathione-reductase (GR), glucose-6-phosphate dehydrogenase (Gl-DH), glutathione-peroxydase (G-POD) and catalase were investigated in dependence of the intraerythrocytic stage of development. The following changes of the investigated metabolic parameters were observed during the schizogony: - the protein content decreased to about one half, - the glutathione concentration increased about 10-fold, while the relations reduced/oxidized and free/bound glutathione remained constant, - Gl-DH activity appeared and increased steeply, - the specific activities of GC-synthetase and of GR increased more than 2-fold, while G-POD remained almost constant, - and the activities of G-6-PDH and catalase showed a significant, strong decrease to about 25% of the original values. It is tried to relate the observed changes to the growing parasite or to the host cell. The significance of the results for the metabolism of malaria parasites and for a possible adaptation to the mosquito by a GSH mediated protection of the malaria parasite against an enzymatic defence-reaction of the mosquito, is discussed.

Plasmodium berghei parasites (strain K173) in mice with developing immunity changed to a variant type with increased resistance against antibodies and enhanced invasion of mature erythrocytes; on passages in normal mice this variant type retransformed to the normal type (Kretschmar 1964). On detailed study, parasites of the variant type showed a markedly decreased predilection for polychromatophilic erythrocytes, leading to slowed multiplication during prepatency, increased invasion of mature erythrocytes and rapidly fatal course of the infection. Avoidance of parasitized immature erythrocytes remained unaltered in the variant type. In presence of antibodies many parasites invaded mature erythrocytes even in blood with high concentrations of immature erythrocytes. --Plasmodium yoelii (strain 17X) showed very high predilection for polychromatophilic erythrocytes, only slight lowering of immature erythrocyte concentration and low parasitization of mature erythrocytes. Parasites with altered preference for polychromatophilic erythrocytes were not observed in animals with parasitemia relapsing after spontaneous disappearance of the primary parasitemia or after injection of antiserum. It is suggested that in a variant of Plasmodium yoelii with high invasion of mature erythrocytes (Yoeli et al. 1975), the decisive virulence factor might be a lowered predilection for polychromatophilic erythrocytes. Avoidance of parasitized immature erythrocytes is less marked in Plasmodium yoelii than in Plasmodium berghei. In presence of antibodies more parasites invade mature erythrocytes. --Plasmodium chabaudi showed an appreciable preference for invasion of immature erythrocytes. Moreover, significantly more multiply parasitized mature and immature erythrocytes were found than would have been produced by random invasion of erythrocytes.

Invasion of immature and mature erythrocytes by merozoites of Plasmodium berghei seems to obey the following rules: Merozoites prefer unparasitized immature erythrocytes. Multiple infections of immature erythrocytes occur in conditions of high merozoite production and low concentration of unparasitized immature erythrocytes, when frequently repeated contacts between merozoites and unparasitized or freshly parasitized immature erythrocytes become increasingly probable. Mature erythrocytes are invaded when the relative density of unparasitized immature erythrocytes drops below 0.2--0.5%, in other words, when merozoites do not meet unparasitized immature erythrocytes in 200--500 erythrocytes. Failure to invade mature erythrocytes is obviously not due to inability of the merozoites to penetrate the erythrocyte membranes.--Merozoites of Plasmodium vinckei, on the other hand, show random invasion of parasitized and unparasitized mature erythrocytes, leading to frequencies of unparasitized and singly or multiply parasitized erythrocytes approaching a Poisson distribution.--The Plasmodium berghei infection regularly leads to a lowered density of polychromatophilic erythrocytes in the peripheral blood. This depression of polychromatophilic erythrocytes uses to be of very different duration, form and intensity. The relative density of immature erythrocytes may show pronounced fluctuations in this phase. As has been seen in one animal, even monocytes and polymorphonuclear leucocytes may, alongside with the immature erythrocytes, for some time totally disappear from the peripheral blood. The depression of polychromatophilic erythrocytes evidently goes along with pronounced alterations of the erythropoesis in spleen and bone marrow. Leucocytes in the peripheral blood generally show rather uncharacteristic alterations of their concentration, they may form very high concentration peaks.

The author investigated 4,853 specimens of wild living small mammals (43 species: Insectivora, Chiroptera, Lagomorpha, Rodentia, Carnivora) from Czechoslovakia for blood parasites. Trypanosomes were found in Talpa europaea, Sorex alpinus, Crocidura suaveolens, Myotis myotis, Apodemus sylvaticus, Apodemus flavicollis, Mus musculus, Rattus norvegicus, Clethrionomys glareolus and Microtus agrestis. Babesia was detected in Myotis emarginatus, Myotis myotis, Clethrionomys glareolus, Microtus arvalis and Microtus agrestis. Grahaemella was found in Talpa europaea, Sorex araneus, Neomys fodiens, Neomys anomalus, Myotis emarginatus, Myotis myotis, Apodemus sylvaticus, Apodemus flavicollis, Apodemus microps, Apodemus agrarius, Mus musculus, Clethrionomys glareolus, Arvicola terrestris, Pitymys subterraneus, Microtus arvalis, Microtus agrestis, and Microtus oeconomus. Spontaneous Bartonella-infection was ascertained in one Microtus arvalis and, in erythrocytes of one Sorex araneus, parasitic organisms very similar to Bartonella were found.

A decreased chloroquine (Resochin) sensitivity of strains of Plasmodium falciparum in certain areas of East Africa has given rise to an inappropriate change of chemoprophylaxis to pyrimethamine-sulfadoxine (Fansidar). Falciparum malaria occurred in five tourists during or after Fansidar prophylaxis. A therapeutic chloroquine-R2-resistance was observed in one seriously ill patient. In some patients the course of disease was prolonged to such an extent that the diagnosis could be established only after as much as 4 months after the end of the journey. This was in part surely caused by intake of anti-plasmodial drugs such as sulfonamides, tetracyclines and co-trimoxazol. The high mortality of falciparum malaria of nearly 10% in this country does not depend on the choice of drug prophylaxis or on problems of resistance, but still on a missed or delayed diagnosis.

By using the model of infection with plasmodium berghei in white mice the attempt was made to explain the oxidative damages of red blood cells as a cause for haemolysis. In addition to a diminished new formation of erythrocytes there was an increased cell lysis under the impact of infection. Without any changes of the Met-Hb-percentage and of Heinz bodies an increase of GSH and GSSG could be measured. The conclusion was drawn that a damage of red blood cells caused by oxidation may occur by changing the relation of reduced tripeptides to oxidised ones.

This is a report about the monoxenic cultivation of Entamoeba histolytica in Asami culture medium. The culture amebae serve as material for antigen preparation, for intrahepatic infections in golden hamsters and also for microscopical observation, s. Figs. 2 and 3.

DNA-, RNA-, and lipidsynthesis, glucose-6-phosphate-dehydrogenase, glucose-6-phosphatase and succinate-dehydrogenase were studied in the different morphologic stages of blood schizogony of Plasmodium vinckei. For the separation of these stages of the maturation cycle a discontinuous Ficoll-density gradient was developed. By this method the morphologic stages were separated and obtained in sufficient amounts. DNA-, RNA- and lipidsynthesis was not continuous in the intraerythrocytic cycle of the parasite. The glucose-6-phosphate dehydrogenase activity of the infected erythrocytes decreases whereas that of the glucose-6-phosphatase increases in the maturation cycle of P. vinckei.

After 25 massive passages of a Plasmodium yoelii-population (strain 17X) in the phase of high parasitization of mature erythrocytes, parasites with markedly lowered preference for immature erythrocytes could be isolated. Of 3 isolates in 3 independent experiments, one showed a distinctly lower preference than the other two. With very high infecting doses, the isolates caused in most mice high parasitization of mature erythrocytes and death. The original strain had been kept in mice by passage of a few parasites every 1--2 weeks for several months; on testing it exhibited a somewhat lower preference for immature erythrocytes and less polyparasitization of immature erythrocytes for a given multiplicity. Polyparasitization seemed to be unaltered in the 3 isolates. Antiserum against Plasmodium yoelii inhibited 2 tested isolates more than the modified original strain. These observations suggest that Plasmodium yoelii merozites may exist in several types differing in their relative affinity for mature erythrocytes, antibodies and parasitized immature erythrocytes. Different types should become predominant under different selective pressures. The different types are probably formed by mutations determining alterations in molecules of the merozoite surface.