ABSTRACT
Objective: To understand the relationship between chloroquine resistance and the virulence of Plasmodium berghei. Met hods: Dynamic changes of histopathologic features of livers, spleens, brains, hearts, lungs and kidneys of mice infected with the chloroquine-sensitive (N) and the chloroquine-resistant (RC) strains of P. berghei were compared. Results: In mice infected with the N strain, deposition of heavy hemoz oin in livers and spleens, congestive edema in lungs, and congestion and embolis m in the brain capillaries were observed. The histopathologic features revealed ac ute inflammatory reaction. In mice infected with the RC strain, histopathologic variations of livers and spleens were associated with changes of parasitemia. In terstitial pneumonia was displayed in lungs. There were chronic histopathologic changes of the organs in the mice infected with RC strain. Conclusion: The mice infected by the N strain with potent virulence die due to adher ence of the erythrocytes to microvascular endothelia and embolism of the microva scula, especially in their brain. Immune responses of the mice infected by the R C strain with poor virulence may be a delayed-type hypersensitive inflammation a ssociated with CD4+Th1 at an early stage of the infection, but may become anti body-dependent immune response assisted with CD4+Th2, which play a key role in elimination of the malaria parasites at later stage of the infection.
ABSTRACT
Objective: To investigate virulence differences of the malaria parasites and responses of their hosts to the malaria infection between chloroquine sensitive (N) and resistant (RC) strains of Plasmodium berghei . Methods: Ultrastructural pathological alterations of liver, kidney and lungs of ICR mice infected with the N or the RC strains were investigated. Results: Congestion and more parasite infected red blood cells in hepatic sinusoids, renal interstitium, capillaries of the liver, kidney and lungs in late period of the infection with the N strain were observed. Necrosis of hepatic cells in liver, juxtaglomerular cells and epithelial cells of renal tubules in kidney, type Ⅰ and type Ⅱ alveolar cells in lungs occurred. Membranes of these cells were broken, resulting in cytoplasm missing and mitochondria swelling infected with the N strain. While degeneration of some hepatic cells of liver, epithelial cells of renal tubules, alveoli cells of lungs appeared during late period of the infection with the RC strain of P. berghei . It was observed that some hepatic cells recoved, the glomeruli basement membrane and mesangial cells contained electron dense deposits,alveoli septa were undergoing the proliferation and infiltration of lymphocytes, macrophages and neutrophilic granulocytes. Conclusion: The N strain is more virulent than the RC strain of P. berghei . Ultrastructures of the liver, kidney and lungs of the mice infected with the N strain show cellular necrosis, while those infected with the RC strain mainly reveal cellular degeneration.
ABSTRACT
Objective: To investigate the feature of crisis at asexual stages of chloroqine resistant strain (RC) of Plasmodium berghei . Methods: By means of optical microscope,transmission electron microscope and agarose electrophoresis, microscopic and ultramicroscopic architectures, and genomic DNA electrophoresis at asexual stages of the RC and chloroquine sensitive (N) strains of P. berghei with rising parasitemia and the RC strain of the parasite with declining parasitemia were observed in ICR mice. Results: Under microscope, different developmental stages asexual parasites with normal forms were found in blood smears from the mice infected by the N and RC strains with rising parasitemia, whereas there were a few of the asexual parasites most of which were contracted and vacuolated from the mice recovered from infection by the RC strain. Using electron microscope, intact cytoplasm membranes of the parasites paralleling with parasitophrous membrane of erythrocytes, nuclear laterad, obvious metabilic window and mitochondrions, ribosomes, endoplasmic reticulum in cytoplasm were recognized in erythrocytic stages of the RC and N strains with rising parasitemia. There were rhoptries in merozoites and food vacuoles in trophozoites of the N strain. Erythrocytic parasites of the RC strain from recovered mice with declining parasitemia were spherical or elliptical, with intact cytoplasm membrane, contracted nuclei and concentrated cytoplasm, without mitochondrion membranaceous structure and metabolic windows. The genomic DNA electrophoretogram of the RC strain parasites in the recovered mice showed a ladder pattern, which differed evidently from the parasites of the RC strain with rising parasitemia and the N strain which showed a single band. Conclusion: It is confirmed that crisis form of asexual stages of the RC strain is apoptosis.
ABSTRACT
Objective: To understand the morphologic foundation for differences in drug-resistance, virulence and immunity between chloroquine-sensitive (N) and chloroquine-resistant (RC) strains of Plasmodium berghei. Methods: The RC strain and the N strain were compared concerning the formation and morphologic features of digestive vacuoles and haemozoin with transmission electron microscope. Results: There was a single large digestive vacuole and multiple micro-single-mem-braned vacuole-like structures in the trophozoites of the N strain, and haemozoins centralized and fused during their schizo-gony were situated under the plasma membrane. Whereas there were few digestive vacuoles in the trophozoites of the RC strain, but with multiple micro-single-membraned vacuole-like structures instead. The RC strain formed obviously less hemo-zoins than that of the N strain and the hemozoins were not centralized and fused during the schizogony. Conclusion: The RC strain forms multiple single-membraned food vacuole-like structures in the trophozoites, and has different mechanism for detoxifying free heme with N strain and the features may be the foundation for the difference in drug-resistance, virulence, immunity between RC strain and N strain of Plasmodium berghei.