Biomedical subjects
Publications and source records attributed to H M Seitz.
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.
Immune responses to Borrelia burgdorferi and their influence on spirochete transmission to Ixodes ricinus were analyzed in the natural European reservoir hosts; i.e., the mouse species Apodemus flavicollis (yellow-necked mouse) and Apodemus sylvaticus (wood mouse) and the vole species Clethrionomys glareolus (bank vole), and, in addition, in the laboratory mouse strain NMRI. Naive and preimmunized rodents were infected either by artificially infected I. ricinus larvae or by intradermal injection of spirochetes. Independent of the species, all animals developed antibodies to various spirochetal antigens. However, antibodies to the outer surface proteins A (OspA) and B (OspB) were not found in recipients infected via ticks. Rodents of the genus Apodemus and of the NMRI strain showed higher levels of B. burgdorferi-specific antibodies than those of the species C. glareolus. The rate of spirochete transmission to noninfected ticks correlated with both the quality and quantity of spirochete-specific antibodies generated in the various species: high levels of spirochete-specific immunoglobulins correlated with low transmission rates. Furthermore, lower transmission rates were observed with rodents expressing antibodies to OspA and OspB (i.e., intradermally infected or immunized) than with those lacking these specificities (i.e., infected via ticks). The study provides evidence that transmission of B. burgdorferi from natural hosts to ticks is controlled by the specificity and quantity of spirochete-reactive antibodies and suggests that immunity to B. burgdorferi in natural reservoir hosts is an important regulatory factor in the horizontal transmission of B. burgdorferi in nature.
During a field investigation in Rhino Camp at Albert Nile in northern Uganda, 77.8% of 636 persons excreted Schistosoma mansoni ova that were detected by the Kato-Katz method. Six patients, 8-17 years of age, had terminally spined schistosome eggs in their stools. These findings were confirmed when preserved specimens were examined at the Institute of Medical Parasitology in Bonn using a concentration technique. The mean +/- SD length of 36 terminally spined eggs was 156 +/- 6 microns and the mean +/- SD width was 59 +/- 3.6 microns. Urine filtration in the study patients revealed no schistosome eggs in the urine. It is concluded that these findings provide evidence for the occurrence of S. intercalatum at Albert Nile in northern Uganda.
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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.
The frequency, presentation, diagnosis and clinical course of Pneumocystis carinii infections (PCI) were studied during aerosolized pentamidine prophylaxis (AP) and its impact on the spectrum of AIDS-related and other pulmonary infections in HIV-infected hemophiliacs. We conducted an open study on primary (PP) and secondary (SP) AP. Breakthrough P. carinii infections (BPCI) and other infectious complications were analyzed retrospectively. Hemophiliacs without prior P. carinii pneumonia (PCP) who had been reluctant to any prophylaxis and who developed PCP served as control group. Statistical analysis of the efficacy of prophylaxis was performed by calculating confidence intervals of binomial p. Of 73 hemophiliacs (56 on PP and 17 on SP) 10 developed BPCI (7 in PP and 3 in SP) during a mean observation time of 14.9 months (range 0.5-30); total 13.6% (6.7%; 23.7%), PP 12.5% (5.1%; 24%), SP 17.6% (3.7%; 43.4%), confidence intervals at a level of 95%. Three BPCI presented atypically with cavitation (1), pneumothorax (2), Pneumocystis pleuritis (1), dissemination (2) as compared to none in the control group. Sensitivity of bronchoalveolar lavage (BAL) was 88.9%, specificity 100% (both 100% in the control group). PCP was the leading AIDS manifestation (21.3%), CNS manifestations taken together were more frequent (36.2%). Bacterial pneumonia was the most frequent respiratory infection. One patient of the study group with recurrent pneumothorax possibly died of BPCI as compared to no BPCI-related deaths in the control group. Efficacy of prophylaxis in hemophiliacs was comparable to other risk groups. AP alone may be insufficient for the control of PCI in patients with long-term profound immunodeficiency, especially in SP. 30% of BPCI presented atypically.(ABSTRACT TRUNCATED AT 250 WORDS)
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.
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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.
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