A rapid method of following the spontaneous regression of experimental leukemias

Summary Transplantation of virus and chemically induced leukemias from C3H/He-mgxAKR/F₁ hybrid mice into C3H/He-mg males induced leukemias in the latter, which was followed by a spontaneous regression of the disease within a few days. The regression of leukemia could easily be followed by measuring the changes in the pyruvate kinase activity of para-aortic lymph node cells.     

Anchorage-dependent culture of line 10 guinea-pig hepatoma cells

Summary A simple method for the anchorage-dependent culture of line 10 guinea-pig hepatoma cells is described.     

Cloning and expression in E. coli of the malarial sporozoite surface antigen gene from Plasmodium knowlesi

The malarial sporozoite, the infective stage found in the salivary gland of the insect vector, bears highly immunogenic surface antigen(s). Repeated exposure to irradiated sporozoites induces protection against malaria in several host species, including man. Further, monoclonal antibodies that confer passive immunity react with the immunogenic surface determinants of different sporozoite species. One approach to prevent malaria, therefore, would be to produce a vaccine that induces high titres of circulating antibodies against the sporozoite surface determinant(s). However, production of such a vaccine has not been possible since sporozoites cannot be cultivated in vitro and, therefore, only limited amounts of surface antigen may be obtained. To overcome this problem, we have prepared mRNA from Plasmodium knowlesi-infected mosquitoes to construct a cDNA library. From this library we have isolated a clone that expresses the sporozoite surface antigen as a beta-lactamase fusion protein in the plasmid pBR322. This is the first potentially protective malarial antigen to be cloned by recombinant DNA technology.     

Variation in chromosome number in the sheep headflyHydrotaea irritans (Fallen) (Diptera: Muscidae)

Summary Variation in the number of chromosomes was found in sheep headflies, ranging from 12 to 15 chromosomes. Of these, five pairs were common among all individuals. Among 9 larvae no males were identified.     

The role of sialic acid in determining the life-span of circulating cells and glycoproteins

Summary The role of sialic acid in determining the life of circulating cells and glycoproteins is reviewed and an attempt is made to assess its real importance and to interpret the desialylation pathway. An overall view of factors, including desialylated glycoprotein fragments, that may regulate hepatic synthesis of glycoproteins is presented.Acknowledgments. The author wishes to thank Drs.A. Viti andG. P. Pessina for helpful discussion and comments.