Biomedical subjects
Publications and source records attributed to W A Maier.
Plasmodium falciparum strains from different malaria-endemic regions were grown in continuous culture without human serum. The medium was complemented with Nutridoma-SR instead of serum. All parasite strains developed well in serum-free medium. Two strains were thawed without serum and showed good multiplication in subsequent continuous culture.
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Several components were tested for their ability to replace human serum in cultures of Plasmodium falciparum set up for the development of gametocytes. Besides a serum-free medium, A*I*M*V (Gibco BRL), RPMI medium supplemented with commercially available serum substitutes was used to culture gametocytes. The following substances served as serum replacements: Basal Medium Supplement (Biochrom), Ultroser G (Gibco BRL) and Nutridoma-SR (Boehringer Mannheim). All serum-free additives supported some parasite growth, but only in RPMI supplemented with Nutridoma-SR were morphologically mature gametocytes obtained. The asexual forms developed almost as well as in RPMI with human serum added.
To examine possible effects of hormones on the gametocytogenesis of Plasmodium falciparum in vitro, insulin, progesterone, 17-beta-estradiol and testosterone were added in different concentrations to the culture medium. The medium containing RPMI was free of human serum but complemented with BMS (Basal-Medium-Supplement, Biochrom), a semidefined serum replacement. As controls, cultures were grown either with BMS supplemented RPMI without hormones, or with human serum complemented RPMI. Only addition of insulin increased the parasitemia. All tested steroid hormones added to the medium enhanced the number of gametocytes.
Entamoeba histolytica, Giardia lamblia, Cryptosporidium parvum, Isospora belli, Balantidium coli, and Microsporidia spp. are cosmopolitan parasites. They often cause diarrheal diseases. The waterborn transmission of all these parasites is possible (41). Surface water supplies used for drinking water are potential sources of contamination. Giardia lamblia and Cryptosporidium spp. have received great attention in industrialized countries during the last years because they are the etiological agents of waterborne diseases. The life cycles of Giardia lamblia and Cryptosporidium are described with a special reference to drinking water technologies aimed at removing these parasites.
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.
Experimental simultaneous infections of Anopheles stephensi (Diptera: Culicidae) with Nosema algerae (Microsporida: Nosematidae) and Plasmodium yoelii nigeriensis under standardized laboratory conditions showed partial suppression of the malaria parasite. At 9 days after an infective bloodmeal, the oocysts in the midgut were counted; 12.1%-66.6% of the double-infected mosquitoes exhibited no oocysts, whereas only 4.5%-12% of the control group showed no oocysts. The mean reduction in oocyst numbers under the influence of Nosema was 84.68%. At 14 days after infection with Plasmodium, the amount of sporozoites was examined; their mean reduction in eight experiments was 70%.
The activity of chloroquine, halofantrine and pyrimethamine against the gametocytes and sporogonic stages of Plasmodium falciparum (strain NF54) was tested. Five-day-old gametocytes (stages I and II) from in vitro cultures were exposed to the drugs for 48 hours. The effect of the drugs on gametocyte development was assessed by counting gametocytes on days nine and 15 of culture and determining the infectivity of the drug-treated gametocytes to mosquitoes. Gametocytogenesis was partially inhibited by all three drugs; there were 71% of the number of gametocytes in drug-free control cultures in cultures with 3 x 10(-8) M chloroquine, 51% with 5 x 10(-8) M chloroquine, 78% with 5-7 x 10(-9) M halofantrine, and 48% with 10(-7) M pyrimethamine. Halofantrine- and pyrimethamine-treated gametocytes were found to be more infective to Anopheles stephensi than untreated controls. The three drugs were also administered to the mosquitoes, either in the first bloodmeal, which contained gametocytes from in vitro cultures, or in the second, parasite-free bloodmeal, given four days after infection. The sporontocidal activity of the drugs was evaluated by counting the number of oocysts on the midgut seven or eight days after infection, or the number of sporozoites in the salivary glands 15 days after infection. A sporontocidal effect was observed only when pyrimethamine was administered with the infective bloodmeal. Neither chloroquine nor halofantrine had any marked effect on sporogony at the concentrations tested.
A technique is described for obtaining pure gametocyte cultures of Plasmodium falciparum, using pyrimethamine at the minimum concentration for inhibition of asexual parasites. Routine cultures producing sexual stages were exposed to pyrimethamine on days 5 and 6. These cultures grew synchronously and contained gametocytes of stages II, III and V on day 7, 9 and 15 of the cultures respectively. The pyrimethamine-treated gametocytes were more infective to mosquitoes than were untreated controls. This model for the culture of pure gametocytes was used to observe the activity of chloroquine, halofantrine, pyrimethamine and quinine on the gametocyte stage III of Plasmodium falciparum strain NF54 in vitro. NF54 was shown to be sensitive to chloroquine, quinine and pyrimethamine, but the results showed that halofantrine was the most effective drug in reducing the number of gametocytes. A concentration of 3 x 10(-9) M halofantrine was lethal to both asexual parasites and gametocytes. The gametocytocidal EC90 of chloroquine (1 x 10(-6) M) and that of quinine (9 x 10(-7) M) were equal to the minimum inhibitory concentration of asexual stages of isolates of P. falciparum considered as highly resistant to these drugs. A high concentration of pyrimethamine (1 x 10(-4) M) had, in contrast, little effect on gametocytes.
The aim of this study was to find optimal conditions for the membrane feeding technique to obtain maximum infection rates of mosquitoes with Plasmodium yoelii nigeriensis. The results show that the malaria parasite Plasmodium yoelii nigeriensis is most infective to Anopheles stephensi mosquitoes on day 3 of the infection in the mice, 1 day before the peak of parasitaemia. The mortality rate of the mosquitoes fed on mice on day 3 after infection was the highest as compared to mosquitoes fed on other days after infection. Gametocytes from mice 3 days after infection were fed to mosquitoes by three different membrane feeding methods. The results indicate that feeding during the first 10 min after blood collection gave the highest infection rates. Keeping the blood meal at a pH of 7.2 yields higher infection rates than keeping it at pH of 8.5. Stirring of the blood and supplying it with CO2 is not necessary when feeding of the mosquitoes is completed within the first 10 min after collection of the blood.
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.
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Case report on a spheric duplication of the rectum in the infralevator segment. The rare incidence is underlined by an inquiry in 23 clinics in our country: 5 clinics reported about 7 cases. In a review further 17 cases are presented. In our case report we point out the differentiation between presacral rectal duplication and presacral teratoma.
The clinical and pathologic-anatomical picture of this rare lung malformation is described with reference to three cases from three different paediatric surgical hospitals. Methods of differential diagnosis against lung sequestration, pulmonary cysts, lobar emphysema, diaphragmatic hernia and pneumothorax are indicated. A definitive diagnosis and classification can be made only by means of histomorphological examinations.
The mortality rate of Anopheles stephensi increased after infection with Plasmodium berghei and correlated negatively with temperature. Development of oocysts is inhibited at temperatures above 21 degrees C. We tested the hypothesis that microorganisms were involved in killing the mosquitoes. In fact we were able to demonstrate that in our A. stephensi colony great numbers of Serratia marcescens could be found in the midgut of the insects. The highest value was 2.3 x 10(7) cfu/ml. Other bacteria were rarely seen (1 out of 30 females had flavobacteria). Serratia was neither found in larvae and pupae nor in the water of the breeding dishes. Moderate numbers were detectable in glucose solutions (for feeding of adult mosquitoes) as well as in jars where pupae emerged. Isolated Serratia strains grew faster at 25 degrees C than at 21 degrees C. In glucose solutions alone growth rates were low but they rose rapidly after the addition of blood. -In experimental infections of A. stephensi with S. marcescens (1 x 10(7) bacteria/ml glucose solution) the mortality increased at 25 degrees C. At 21 degrees C the effect of Serratia was insignificant whereas in P. berghei-infected A. stephensi the damaging effects of migrating ookinetes were obvious. Additive detrimental effects were observed at 25 degrees C in mosquitoes infected with P. berghei and Serratia concomitantly.
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