Biomedical subjects

G Margos

Publications and source records attributed to G Margos.

21 records · Page 2Linked to original sources

PubMed1992

The effect of nosematosis on the development of Plasmodium falciparum in Anopheles stephensi.

To quantify the effect of Nosema algerae (Microsporidia, Nosematidae) on the development of Plasmodium falciparum in Anopheles stephensi (Diptera, Culicidae), we carried out infection experiments under standardized laboratory conditions. Apart from a mean reduction of 69% in oocyst development, smaller numbers of oocysts and fewer sporozoites were found in the Nosema-infected mosquitoes. In addition, nosematosis resulted in higher mortality. The potential role of Nosema algerae as a biological control agent is discussed.

Animals↗

PubMed1992

Experiments on cryopreservation of Plasmodium falciparum.

A comparative study was carried out in order to assess the effectivity of the deep-freezing conditions for P. falciparum cultures: 1. by plunging them into liquid nitrogen, 2. by use of an established freezing program for lymphocytes. After thawing in a waterbath at 37 degrees C, samples were diluted with equal volumes of 3.5% sodium chloride solution or 15% phosphate-buffered saline supplemented glucose solution. Other samples were not diluted after thawing, but the medium was replaced twice during the first day in culture. Survival was evaluated by counting the parasites in Giemsa-stained smears taken on day 3 after thawing. We obtained the best survival rate using NaCl solution, whereas replacing the medium twice resulted in the lowest level of survival. In synchronized cultures we studied survival rates of the different developmental stages of the intraerythrocytic parasites: young trophozoites (ring stages) and schizonts. The results indicate that irrespective of the freezing technique used, the survival level of young trophozoites was high (40 and 60%). The more sensitive stages (late trophozoites and schizonts) were better protected by using the freezing program designed for lymphocytes.

Animals↗

PubMedDate not supplied

The mosquito transmission of malaria: the effects of atovaquone-proguanil (Malarone) and chloroquine.

Despite its recognized importance, the prevention of patients with malaria from continuing to infect mosquitoes after treatment is not always achieved in practice. An inevitable consequence of the prolonged life-span and relative metabolic stasis of the mature gametocytes of Plasmodium falciparum is that they are not cleared by most antimalarials, and few antimalarials block infection in the mosquito vector. Previous research on the constituents of Malarone, a new 'combined antimalarial', suggested that the active components, atovaquone and proguanil, might inhibit infectivity of gametocytes to mosquitoes. We contrast here the impact of atovaquone-proguanil and chloroquine on the transmission of P. falciparum and P. berghei. While chloroquine enhanced infectivity of P. falciparum, atovaquone-proguanil caused a significant reduction. Surprisingly, sporontocidal activity against the rodent parasite persisted long after the levels of the constituent drugs would have been expected to have fallen below effective plasma concentrations on the basis of the established pharmacokinetics of atovaquone and proguanil. The P. berghei model may thus have provided a sensitive bioassay, detecting drug(s) at levels below that normally found with the usual chemical assays.

Animals↗