Induction of secondary antibody responses to Plasmodium chabaudi in vitro

Spleen cells and peripheral blood mononuclear cells (PBMC) from mice, which had recovered from infection with Plasmodium chabaudi, were induced to produce anti-P. chabaudi antibody by incubating the cells with P. chabaudi parasitized red cells in Marbrook cultures. The anti-malarial antibody was assayed using the indirect fluorescent antibody test. Spleen cells and PBMC from mice infected 2-4 months previously gave higher antibody titres in culture than similar cells from mice infected a year previously. There was a good correlation between the ability of spleen cells or PBMC to be stimulated to produce antibody in vitro and the ability of mice similar to the cell donors to resist a challenge infection. Some immunity can be adoptively transferred with both spleen cells and PBMC.

Suppression of primary and secondary antibody responses and inhibition of antigen priming during Babesia microti infections in mice

The antibody response to sheep red blood cells (SRBC) has been measured in C57Bl mice infected with the intra-erythrocytic piroplasm Babesia microti. The primary antibody response is severely reduced or abolished when antigen is administered at the time of maximum parasitaemia. The secondary antibody response of infected mice, which had been primed with SRBC, is reduced but retains the characteristics of a secondary response. Mice injected with SRBC at maximum parasitaemia failed to become primed to that antigen: these mice gave a primary antibody response to a second injection of SRBC given after the infection had become sub-patent. B. microti, therefore, can completely prevent the induction of memory, but only partially inhibit the expression of memory.

Ligand effects on the limited proteolysis of phenylalanine hydroxylase: evidence for multiple conformational states

The effects of phenylalanine and tetrahydrobiopterin on the limited proteolysis of rat liver phenylalanine hydroxylase by chymotrypsin have been examined. The presence of tetrahydrobiopterin inhibits the proteolytic activation of native phenylalanine hydroxylase. In contrast, phenylalanine causes a stimulation of proteolytic activation under these conditions. Neither phenylalanine nor tetrahydrobiopterin affect the rate of hydrolysis of a synthetic substrate by chymotrypsin. Both tetrahydrobiopterin and phenylalanine inhibit the release of soluble radioactivity from [32P]phosphorylated phenylalanine hydroxylase. These results confirm the existence of multiple conformational states of phenylalanine hydroxylase.

Dopamine-B-hydroxylase: suicide inhibition by the novel olefinic substrate, 1-phenyl-1-aminomethylethene

Dopamine-B-hydroxylase [E.C.1.14.17.1] plays a key role in the biosynthetic interconversion of neurotransmitters. It is now demonstrated for the first time that dopamine-B-hydroxylase also catalyzes the oxygenation of an olefinic substrate, 1-phenyl-1-aminomethylethene, producing 2,3-dihydroxy-2-phenylpropylamine after acid workup. This reaction gives the normal oxygenase stoichiometry of electrons to O2 to product of 2:1:1, and is kinetically comparable to other oxygenase activities of dopamine-B-hydroxylase, with a kcat value of 10 sec-1 and a KM of 8.3 mM. 1-Phenyl-1-aminomethylethene is also a time-dependent, first-order inactivator of dopamine-B-hydroxylase. The inactivation process exhibits the characteristics of mechanism-based, irreversible inactivation, giving a KI value of 13 mM and a kinac of 0.04 min-1. The central role of dopamine-B-hydroxylase in catecholamine metabolism suggests possible pharmacological uses for olefinic inhibitors of this enzyme.

Use of sorbitol in the cryopreservation of babesia

Blood collected from mice infected with Babesia microti was frozen at two different rates to -196 degrees C using 19 per cent (w/v) glycerol as cryoprotectant. Survival of the parasites was measured by recording the parasitaemias of mice inoculated with thawed blood. Parasite survival was increased by using a solution of sorbitol in saline rather than Hanks' balanced salt solution as the diluent for the glycerol and for washing the recovered blood.

Ovarian myxoma

A case of primary ovarian myxoma is reported. The tumor is rare as there are only two previously reported cases in the literature.

Increase in non-specific antibody mediated cytotoxicity in malarious mice

The K cell activity in the spleens of mice infected with Plasmodium chabaudi has been investigated. Chicken red cells coated with antibody were the target cells used. Increased K cell activity was found 6 to 15 days, but not 3 days, after infection with the malaria parasites.

Differentiation of gametocytes in microcultures of human blood infected with Plasmodium falciparum

Gametocytes differentiated from ring-stage parasites in microcultures of human blood infected with Plasmodium falciparum. Immature gametocytes could be distinguished morphologically from late asexual trophozoites after approximately 40 h of culture. Differentiation into crescentic forms took several days and the incorporation of [3H]-isoleucine by developing gametocytes was demonstrated. About 1% of red cells contained gametocytes at the maxiumum densities attained. Differentiation of gametocytes occurred either directly from rings placed in culture or from the progeny of subsequent cycles of schizogony and invasiton in vitro. The latter occurrence was confirmed by the development of gametocytes in marker fetal red cells added to cultures, although fetal red cells provide a less favorable environment than those with HbA for growth of the parasites.

Plasmodium chabaudi in mice. Adoptive transfer of immunity with enriched populations of spleen T and B lymphocytes

Thymectomized NIH and C57BL mice were more susceptible to Plasmodium chabaudi than controls, indicating a role for T cells in acquired immunity to the parasite. Enriched populations of T and B cells were prepared from the spleens of immune mice using nylon-wool columns, and were adoptively transferred to syngeneic non-irradiated mice or mice irradiated with 600 or 800 rad. Some immunity could usually be transferred with immune T, B and glass-wool (g.w.) filtered spleen cell populations. In the heavily irradiated mice g.w. filtered immune spleen cells gave the best protection and the immune T cells the least. Preliminary attempts to show synergistic activity between immune T and B cells in irradiated mice were not successful.