Haematology of experimental Trypanosoma brucei rhodesiense infection in vervet monkeys

Haematological aberrations associated with human infective trypanosomes were investigated in the vervet monkey model of the Rhodesian sleeping sickness. Four monkeys were infected intravenously with 104 Trypanosoma brucei rhodesiense and monitored for changes in the blood profile using a haematological analyser. A chronic infection lasting between 48 and 112 days was observed. Microcytic hypochromic anaemia, which was characterized by a decline in packed cell volume (PCV), red blood cell (RBC) numbers, mean corpuscular volume (MCV) and mean corpuscular haemoglobin concentration (MCH) developed at an early stage, and persisted throughout the infection. The mean platelet counts declined significantly from 3 x 105/μl (day 0 post infection) to 6.8 x 104/μl (day 7 post infection) and remained low in all the animals. However, the mean platelets volume rose during the course of the infection. An initial decline in total white blood cell (WBC) counts occurred between day 0 and 7 (3.1 x 106/μl) and remained low up to day 35 post infection (3.5 x 106/μl). This was followed by an increase in WBC counts, principally associated with increased lymphocyte numbers. It is concluded that microcytic hypochromic anaemia, thrombocytopaenia and an initial leucocytopaenia are the most important haematological changes associated with a chronic infection of T.b. rhodesiense infection in vervet monkeys. African Journal of Health Sciences Vol. 13 (3-4) 2006: pp. 59-6

Effect of Aflatoxin B-1 on Course of Infection of Trypanosoma congolense in Mice

Mycotoxins as secondary metabolites are known to be common contaminants of both human food and animal feed. If ingested in minute but regular doses, they are known to cause suppression of the immune system and therefore, alter pathogenesis of many infectious diseases. Trypanosoma congolense an intravascular parasite is the most important cause of African animal trypanosomosis. The aim of this work was to investigate the effect of aflatoxin B-1, a common mycotoxin on progression and response of T. congolense to chemotherapy. Female Swiss white mice were intra-peritoneally injected with 0.05mg/kg body weight aflatoxin B-1 every after 3 days upto 10 times and on the 21st day were infected with T. congolense. Parasitological parameters including weight, packed cell volume and parasitaemia levels of aflatoxin B-1-injected-T. congolense-infected mice were compared with those of T. congolense-infected mice. ANOVA and mean separation were used to determine differences between the test and control mice. It was observed that there was significant difference (p?0.05) in body weight and mean death time but no significant difference in packed cell volume. It was concluded that aflatoxin B-1 has an effect on pathogenesis of T. congolense. Key words: Trypanosoma congolense, Aflatoxin B-1, progression, chemotherap

Pharmacology of DB844, an orally active aza analogue of pafuramidine, in a monkey model of second stage human African trypanosomiasis

Novel drugs to treat human African trypanosomiasis (HAT) are still urgently needed despite the recent addition of nifurtimox-eflornithine combination therapy (NECT) to WHO Model Lists of Essential Medicines against second stage HAT, where parasites have invaded the central nervous system (CNS). The pharmacology of a potential orally available lead compound, N-methoxy-6-{5-[4-(N-methoxyamidino) phenyl]-furan-2-yl}-nicotinamidine (DB844), was evaluated in a vervet monkey model of second stage HAT, following promising results in mice. DB844 was administered orally to vervet monkeys, beginning 28 days post infection (DPI) with Trypanosoma brucei rhodesiense KETRI 2537. DB844 was absorbed and converted to the active metabolite 6-[5-(4-phenylamidinophenyl)-furanyl-2-yl]-nicotinamide (DB820), exhibiting plasma C(max) values of 430 and 190 nM for DB844 and DB820, respectively, after the 14th dose at 6 mg/kg qd. A 100-fold reduction in blood trypanosome counts was observed within 24 h of the third dose and, at the end of treatment evaluation performed four days post the last drug dose, trypanosomes were not detected in the blood or cerebrospinal fluid of any monkey. However, some animals relapsed during the 300 days of post treatment monitoring, resulting in a cure rate of 3/8 (37.5%) and 3/7 (42.9%) for the 5 mg/kg×10 days and the 6 mg/kg×14 days dose regimens respectively. These DB844 efficacy data were an improvement compared with pentamidine and pafuramidine both of which were previously shown to be non-curative in this model of CNS stage HAT. These data show that synthesis of novel diamidines with improved activity against CNS-stage HAT was possible

Effect of Aflatoxin B-1 on Transmissibility of Trypanosoma Congolense in Mice

Mycotoxins as secondary metabolites are known to be common contaminants of both human food and animal feed. If ingested in minute but regular doses, they are known to cause suppression of the immune system and therefore, alter pathogenesis of many infectious diseases. Trypanosoma congolense an intravascular parasite is the most important cause of African animal trypanosomosis. The aim of this work was to investigate the effect of aflatoxin B-1, a common mycotoxin on transmissibility of T. congolense. Female Swiss white mice were intra-peritoneally injected with 0.05mg/kg body weight aflatoxin B-1 every after 3 days upto 10 times and on the 21st day were infected with T. congolense. Parasitological parameters including weight, packed cell volume and parasitemia levels of aflatoxin B-1-injected-T. congolense-infected mice were compared with those of T. congolense-infected mice. In a separate study, aflatoxin B-1-injected-T. congolense-infected and T. congolense-infected mice (12 each) were fed on by 400 tsetse flies. Some of these flies were used to cyclically infect 100 uninfected mice. ANOVA and mean separation were used to determine differences between the test and control mice. It was observed that there was significant difference (p?0.05) in body weight but no significant difference in packed cell volume, establishment of infection within the tsetse flies and subsequent transmission to uninfected mice. It was concluded that aflatoxin B-1 has an effect on pathogenesis and hence transmissibility of T. congolense. Keywords: Aflatoxin B-1, Trypanosoma congolense, pathogenesis, transmissibilit

Pharmacology of DB844, an Orally Active aza Analogue of Pafuramidine, in a Monkey Model of Second Stage Human African Trypanosomiasis

Novel drugs to treat human African trypanosomiasis (HAT) are still urgently needed despite the recent addition of nifurtimox-eflornithine combination therapy (NECT) to WHO Model Lists of Essential Medicines against second stage HAT, where parasites have invaded the central nervous system (CNS). The pharmacology of a potential orally available lead compound, N-methoxy-6-{5-[4-(N-methoxyamidino) phenyl]-furan-2-yl}-nicotinamidine (DB844), was evaluated in a vervet monkey model of second stage HAT, following promising results in mice. DB844 was administered orally to vervet monkeys, beginning 28 days post infection (DPI) with Trypanosoma brucei rhodesiense KETRI 2537. DB844 was absorbed and converted to the active metabolite 6-[5-(4-phenylamidinophenyl)-furanyl-2-y​l]-nicotinamide(DB820), exhibiting plasma Cmax values of 430 and 190 nM for DB844 and DB820, respectively, after the 14th dose at 6 mg/kg qd. A 100-fold reduction in blood trypanosome counts was observed within 24 h of the third dose and, at the end of treatment evaluation performed four days post the last drug dose, trypanosomes were not detected in the blood or cerebrospinal fluid of any monkey. However, some animals relapsed during the 300 days of post treatment monitoring, resulting in a cure rate of 3/8 (37.5%) and 3/7 (42.9%) for the 5 mg/kg×10 days and the 6 mg/kg×14 days dose regimens respectively. These DB844 efficacy data were an improvement compared with pentamidine and pafuramidine both of which were previously shown to be non-curative in this model of CNS stage HAT. These data show that synthesis of novel diamidines with improved activity against CNS-stage HAT was possible.This investigation received financial support from the Bill and Melinda Gates Foundation through the Consortium for Parasitic Drug Development

Analysis of the Yellow Bean Corridor in Tanzania

The yellow bean value chain in Tanzania was necessary to understand value chain. The objective of the survey was to characterize and explore trade of yellow bean grain and potential seed. The survey collected data and grain samples from 298 grain traders (including wholesalers, exporters, aggregators, and retailers) and 64 potential seed traders (large and retail traders) from 12 regions across four administrative zones in Tanzania. The grain samples collected were for DNA analyses. Results show existence of an established yellow bean corridor across Tanzania and the region at large (Burundi, DRC, Kenya, Rwanda, Uganda, Zambia) and demonstrated a huge market pull in the Eastern and Southern Africa regions. There are also strong perceptions on the organoleptic quality of various yellow bean grains and varieties that are traced to their sources

El Conocimiento Didáctico del Contenido en ciencias: estado de la cuestión

This paper gives a descriptive overview of the literature related to Pedagogical Content Knowledge - PCK - in the sciences. It is expected that this review can contribute to a better understanding of PCK, pointing out what has been investigated about this concept. Specifically, we analyze: a) how PCK is defined, what are its main features and how it has been appropriated by teachers; b) the relationship between PCK, knowledge of the contents to be taught and students learning; c) how PCK was actually used in teachers' training and teachers' evaluation; and, d) the scientific areas in which PCK has been studied. It concludes that PCK is an essential tool for improving the quality of teacher training

A Competitive Enzyme Linked Immunosorbent Assay For The Determination Of Diminazene Residues In Animal Tissues

The importance of ensuring food safety through the reduction of chemical residues in our food supply cannot be overemphasized. Food safety remains a major challenge confronting contemporary society. To ensure wholesomeness of food of animal origin, the level of drug residues must be below the maximum residue limits (MRLs) set by World Health Organization (WHO) and Food and Agriculture Organization (FAO). This calls for cost effective and efficient analytical methods for both quality assurance and monitoring. Diminazene aceturate is one of the few treatment drugs for animal trypanosomosis in the market. Because of its wide use in food producing animals, unwanted residues may be a risk to consumers. A competitive enzyme-linked immunosorbent assay (cELISA) for determination of diminazene residues in edible animal tissues after extraction in 0.1 M borax pH 9.7 is described. The assay has advantages of speed, high throughput and lower cost of analysis compared to the other conventional methods. The assay uses rabbit anti-diminazene polyclonal antibodies bound on a 96-well microtiter plate. Horseradish peroxidase-labeled diminazene and diminazene in a test sample were allowed to compete overnight at 4° C for the limited number of antibodies bound on the microtiter plate. After six washes with buffer, enzyme activity was determined by adding tetramethyl-benzidine and hydrogen peroxide as substrate. The assay detection limits for diminazene were 2.4 ng/g in muscle, 2.5 ng/g in liver and 2.2 ng/g in kidney while limits of quantification were 7.2 ng/g, 7.5 ng/g and 6.6 ng/g respectively. The recoveries for muscle liver and kidney spiked with 5 ng/g were 78%, 77% and 80% respectively while for 1,000 ng/g were 74%, 76.% and 84% respectively. The within-and between assay coefficients of variation (CV) were 2.4% and 15.5% respectively while assay specificity was above 99.9%. It is concluded that as a result of the good recoveries, high specificity and repeatability, the method could be used in the determination and monitoring of diminazene residues in tissues. These activities aimed at ensuring the safety of food of animal origin could play a major role in enhancing consumer confidence in these products which are very essential for health

Safety, pharmacokinetic, and efficacy studies of oral DB868 in a first stage vervet monkey model of human African trypanosomiasis

There are no oral drugs for human African trypanosomiasis (HAT, sleeping sickness). A successful oral drug would have the potential to reduce or eliminate the need for patient hospitalization, thus reducing healthcare costs of HAT. The development of oral medications is a key objective of the Consortium for Parasitic Drug Development (CPDD). In this study, we investigated the safety, pharmacokinetics, and efficacy of a new orally administered CPDD diamidine prodrug, 2,5-bis[5-(N-methoxyamidino)-2-pyridyl]furan (DB868; CPD-007-10), in the vervet monkey model of first stage HAT. DB868 was well tolerated at a dose up to 30 mg/kg/day for 10 days, a cumulative dose of 300 mg/kg. Mean plasma levels of biomarkers indicative of liver injury (alanine aminotransferase, aspartate aminotransferase) were not significantly altered by drug administration. In addition, no kidney-mediated alterations in creatinine and urea concentrations were detected. Pharmacokinetic analysis of plasma confirmed that DB868 was orally available and was converted to the active compound DB829 in both uninfected and infected monkeys. Treatment of infected monkeys with DB868 began 7 days post-infection. In the infected monkeys, DB829 attained a median Cmax (dosing regimen) that was 12-fold (3 mg/kg/day for 7 days), 15-fold (10 mg/kg/day for 7 days), and 31-fold (20 mg/kg/day for 5 days) greater than the IC50 (14 nmol/L) against T. b. rhodesiense STIB900. DB868 cured all infected monkeys, even at the lowest dose tested. In conclusion, oral DB868 cured monkeys with first stage HAT at a cumulative dose 14-fold lower than the maximum tolerated dose and should be considered a lead preclinical candidate in efforts to develop a safe, short course (5-7 days), oral regimen for first stage HAT

Efficacy of the Novel Diamidine Compound 2,5-Bis(4-Amidinophenyl)- Furan-Bis-O-Methlylamidoxime (Pafuramidine, DB289) against Trypanosoma brucei rhodesiense Infection in Vervet Monkeys after Oral Administration▿

Owing to the lack of oral drugs for human African trypanosomiasis, patients have to be hospitalized for 10 to 30 days to facilitate treatment with parenterally administered medicines. The efficacy of a novel orally administered prodrug, 2,5-bis(4-amidinophenyl)-furan-bis-O-methlylamidoxime (pafuramidine, DB289), was tested in the vervet monkey (Chlorocebus [Cercopithecus] aethiops) model of sleeping sickness. Five groups of three animals each were infected intravenously with 104 Trypanosoma brucei rhodesiense KETRI 2537 cells. On the seventh day postinfection (p.i.) in an early-stage infection, animals in groups 1, 2, and 3 were treated orally with pafuramidine at dose rates of 1, 3, or 10 mg/kg of body weight, respectively, for five consecutive days. The animals in groups 4 and 5 were treated with 10 mg/kg for 10 consecutive days starting on the 14th day p.i. (group 4) or on the 28th day p.i. (group 5), when these animals were in the late stage of the disease. In the groups treated in the early stage, 10 mg/kg of pafuramidine completely cured all three monkeys, whereas lower doses of 3 mg/kg and 1 mg/kg cured only one of three and zero of three monkeys, respectively. Treatment of late-stage infections resulted in cure rates of one of three (group 4) and zero of three (group 5) monkeys. These studies demonstrated that pafuramidine was orally active in monkeys with early-stage T. brucei rhodesiense infections at dose rates above 3 mg/kg for 5 days. It was also evident that the drug attained only minimal efficacy against late-stage infections, indicating the limited ability of the molecule to cross the blood-brain barrier. This study has shown that oral diamidines have potential for the treatment of early-stage sleeping sickness