In vitro anti trypanosomal activity of some medicinal plants used in the treatment of trypanosomosis in Northern Nigeria

The in vitro trypanocidal activity of 13 medicinal plants used by local herdsmen in Northern Nigeria for the treatment of trypanosomosis was investigated. Forty-four different extracts prepared from the 13 plants were screened for in vitro activity against Trypanosoma brucei brucei. Four of the extracts showed activity against the parasite at minimum concentration of 8.3 mg/ml of blood. Key Words: Medicinal plants, Trypanosomosis, Trypanosoma brucei brucei African Journal of Biotechnology Vol.3(9) 2004: 481-48

Physico-chemical characteristics of immobilized polygalacturonase from Aspergillus niger (SA6)

Polygalacturonase (PG) was isolated from Aspergillus niger (A. niger) (SA6), partially purified, characterized and immobilized by entrapment using calcium alginate. The polygalacturonase showed two bands on sodium dodecyl sulfate polyacryamide gel electrophoresis (SDS-PAGE) suggesting an “endo and exo” polygalacturonase with apparent molecular weights of 35 and 40 KDa, respectively. The enzyme was purified 9 fold with a yield of 0.18% and specific activity of 246 μmole/min/mg. The apparent KM and Vmax of the immobilized polygalacturonase were11.1 mg/ml and 1.65 μmole/min/mg, respectively. The optimum pH and optimum temperature of the immobilized polygalacturonase were 4.5 and 40°C, respectively. Immobilized polygalacturonase exhibited more stability to changes in pH than the temperature. The activity of the immobilized polygalacturonase reduced to 34.56 and 14.81% of the initial activity in the second and third catalytic cycles, respectively. The half life of the enzyme and theactivity lost per minute on thermal storage were 10 min and 0.0213 μMole of D-galacturonic acid.Keywords: Polygalacturonase, Aspergillus niger, pectinases, enzyme

Production and regulation of lignin degrading enzymes from Lentinus squarrosulus (mont.) Singer and Psathyrella atroumbonata Pegler

The influence of metal ions on the production and regulation of ligninase and mycelia extension of two type Basidiomycetes (Lentinus squarrosulus and Psathyrella atroumbonata) cultivated on lignocellulose waste was investigated. Mn2+ and Ca2+ ions stimulated growth of both fungi and mycelia extension significantly. Ligninase production increased two to twelve fold under the influence of Mn2+ and Ca2+ ions at concentrations of 20 to 80 mM. Mg2+ and K+ ions did not stimulate growth and extension of fungal mycelia, rather fungal cultures became deactivated after six days. The importance of mycelia extension and enhanced enzyme production has biotechnological applications in wood and pulp, textile and tanning, as well as in oil industries. Key words: Basidiomycetes, Lentinus squarrosulus, Psathyrella atroumbonata, ligninase, cofactors. African Journal of Biotechnology Vol.2(11) 2003: 444-44

Studies on the degraduation of wood sawdust by Lentinus squarrosulus (Mont.) Singer

Lentinus squarrosulus (Mont.) Singer, a basidiomycete also known as a white rot fungi, was immobilized on sodium alginate and tested for the effectiveness to degrade wood sawdust (WSD). Untreated and 0.1 M HCl-pretreated WSD samples were separately reacted in a micro-carrier bioreactor (mCBR) and the extent of degradation to form protein, glucose and ethanol was investigated. Pretreatment enhanced the production of both proteins and ethanol by average value of 72.0% over untreated WSD samples, after hydraulic retention time of 72 h. The maximum production of protein observed was 0.94 mg/ml-reaction volume and that of ethanol was 6.6 mg/ml-reaction volume, whereas glucose concentration fluctuated due to interconversion to ethanol. This report shows that L. squarrosulus (Mont.) Singer have the potentials of degrading WSD samples to important chemical compounds that are not hazardous to the environment. Key words: Lentinus squarrosulus, wood sawdust, sodium alginate, bioreactor, ethanol. African Journal of Biotechnology Vol.3(8) 2004: 395-39

Role of sialic acids in the midguts of Trypanosoma congolense infected Culex pipense pipiense mosquitoes

Free and total sialic acid concentrations were determined in the midgut extract of Culex pipiense pipiense mosquitoes infected with Trypanosoma congolense. The mean total sialic acid concentrations were found to be 1.5 to 2 fold higher than the mean free sialic acid concentrations in the midgut extracts of all the groups of the T. congolense infected C.p. pipiense. Infusion of 10 mg/ml galactose and 10 mg/ml lactose did not change the pattern of this difference but resulted to 1.3 to 1.4 fold decrease in the total sialic acid concentration. The relevance of these findings to the role of sialic acids in the midgut of T. congolense infected C.p. pipiense mosquitoes is discussed in this paper. Key Words: Trypanosoma congolense, Culex pipiense pipiense, sialic acid, midgut. African Journal of Biotechnology Vol.3(8) 2004: 405-40

In vitro trypanocidal effect of methanolic extract of some Nigerian savannah plants

Methanol extracts from twenty three plants harvested from the Savannah vegetation belt of Nigeria were analyzed in vitro for trypanocidal activity against Trypanosoma brucei brucei and Trypanosoma congolense at concentrations of 4 mg/ml, 0.4 mg/ml and 0.04 mg/ml. Extracts of Khaya senegalensis, Piliostigma reticulatum, Securidaca longepedunculata and Terminalia avicennoides were strongly trypanocidal to both organisms while extracts of Anchomanes difformis, Cassytha spp, Lannea kerstingii, Parkia clappertioniana, Striga spp, Adansonia digitata and Prosopis africana were trypanocidal to either T. brucei brucei or T. congolense. These findings provide evidence of the effects of some plants in the traditional management of trypanosomiasis. Key words: Savannah, medicinal plants, trypanocidal effects, trypanosomiasis, trypanosome, in vitro model. African Journal of Biotechnology Vol.2(9) 2003: 317-32

Purification and partial characterization of laccase from Lachnocladium sp.

Laccase, a multicopper oxidase that catalyzes the oxidation of various aromatics, particularly phenolic substrates, e.g. hydroquinones guaiacol, 2,6-dimethoxyphenol or phenylene diamine, was purified and partially characterised from culture filtrates of a white rot fungus, Lachnocladium sp. This enzyme was purified by anion exchange and gel filtration chromatography. Laccase activity was determined using ABTS (2, 2’-azinobis-(3-ethylbenzthiazoline)-6-sulphonic acid) substrate. The culture filtrate had maximum laccase activity of 1.62 U/ml after 14 days of incubation. The purified laccase had an optimum temperature of 50oC and its optimum pH was 6 for ABTS. The activity of this enzyme was enhanced by Fe2+, Cu2+, Zn2+ and Ca2+, and was inhibited by EDTA and sodium iodide. Laccase from Lachnocladium sp. had a Km of 0.119 mM and a Vmax of 0.313 U.Keywords: Lachnocladium sp., anion exchange chromatography, gel filtration chromatography, ABTS, DM

Mechanisms controlling anaemia in Trypanosoma congolense infected mice.

Trypanosoma congolense are extracellular protozoan parasites of the blood stream of artiodactyls and are one of the main constraints on cattle production in Africa. In cattle, anaemia is the key feature of disease and persists after parasitaemia has declined to low or undetectable levels, but treatment to clear the parasites usually resolves the anaemia. The progress of anaemia after Trypanosoma congolense infection was followed in three mouse strains. Anaemia developed rapidly in all three strains until the peak of the first wave of parasitaemia. This was followed by a second phase, characterized by slower progress to severe anaemia in C57BL/6, by slow recovery in surviving A/J and a rapid recovery in BALB/c. There was no association between parasitaemia and severity of anaemia. Furthermore, functional T lymphocytes are not required for the induction of anaemia, since suppression of T cell activity with Cyclosporin A had neither an effect on the course of infection nor on anaemia. Expression of genes involved in erythropoiesis and iron metabolism was followed in spleen, liver and kidney tissues in the three strains of mice using microarrays. There was no evidence for a response to erythropoietin, consistent with anaemia of chronic disease, which is erythropoietin insensitive. However, the expression of transcription factors and genes involved in erythropoiesis and haemolysis did correlate with the expression of the inflammatory cytokines Il6 and Ifng. The innate immune response appears to be the major contributor to the inflammation associated with anaemia since suppression of T cells with CsA had no observable effect. Several transcription factors regulating haematopoiesis, Tal1, Gata1, Zfpm1 and Klf1 were expressed at consistently lower levels in C57BL/6 mice suggesting that these mice have a lower haematopoietic capacity and therefore less ability to recover from haemolysis induced anaemia after infection

Pentamidine Is Not a Permeant but a Nanomolar Inhibitor of the Trypanosoma brucei Aquaglyceroporin-2

The chemotherapeutic arsenal against human African trypanosomiasis, sleeping sickness, is limited and can cause severe, often fatal, side effects. One of the classic and most widely used drugs is pentamidine, an aromatic diamidine compound introduced in the 1940s. Recently, a genome-wide loss-of-function screen and a subsequently generated trypanosome knockout strain revealed a specific aquaglyceroporin, TbAQP2, to be required for high-affinity uptake of pentamidine. Yet, the underlying mechanism remained unclear. Here, we show that TbAQP2 is not a direct transporter for the di-basic, positively charged pentamidine. Even though one of the two common cation filters of aquaglyceroporins, i.e. the aromatic/arginine selectivity filter, is unconventional in TbAQP2, positively charged compounds are still excluded from passing the channel. We found, instead, that the unique selectivity filter layout renders pentamidine a nanomolar inhibitor of TbAQP2 glycerol permeability. Full, non-covalent inhibition of an aqua(glycero)porin in the nanomolar range has not been achieved before. The remarkable affinity derives from an electrostatic interaction with Asp265 and shielding from water as shown by structure-function evaluation and point mutation of Asp265. Exchange of the preceding Leu264 to arginine abolished pentamidine-binding and parasites expressing this mutant were pentamidine-resistant. Our results indicate that TbAQP2 is a high-affinity receptor for pentamidine. Taken together with localization of TbAQP2 in the flagellar pocket of bloodstream trypanosomes, we propose that pentamidine uptake is by endocytosis