A trans-dominant mutational strategy was used to down-regulate trypanothione reductase (TR) activity levels in Leishmania donovani, the causative agent of visceral leishmaniasis in humans. TR, regarded as an ideal drug target against trypanosomatid infections, is a homodimeric f lavoprotein oxidoreductase unique to these organisms that plays a central role in the enzymatic regeneration of the thiol pool. Extrachromosomal, heterologous expression of a transdominant mutant version of the Trypanosoma cruzi enzyme in L. donovani resulted in the formation of inactive cross-species heterodimers and in a dramatic decrease of endogenous TR activity levels. Recombinant cells depleted of up to 85% of TR activity were significantly impaired in their ability to regenerate dihydrotrypanothione from trypanothione disulfide following oxidation with diamide. Nonetheless trans-dominant mutant recombinants were still capable of maintaining a reduced intracellular environment during cell growth in culture and were able to metabolize hydrogen peroxide at wildtype rates in vitro. Importantly, however, cells expressing the trans-dominant mutant enzyme displayed a decreased ability to survive inside activated macrophages in a murine model of Leishmania infection. The apparent inability of Leishmania to modulate the expression of active TR homodimers in response to the expression of trans-dominant mutant protein suggests that specific inhibitors of this enzyme should be useful anti-leishmanial agents.

No abstract

Unselected, disposable acupuncture needles from various manufacturers and retail suppliers were taken from a pool of donated and bought samples. Three needles of each type were prepared for electron-microscopy. The needle tips were inspected at two magnifications (x39.37 and x612.5): 52 electron-micrographs were taken of 31 individual needles from 11 different types. No needle-tip looked perfect and significant faults were seen in most; some appeared seriously deformed. The faults noted were: scratch marks along or across the needle, metallic scuff, lumps and irregularities in the needle surface, needle-tip stubbed or malformed, and needle point off-centre. An additional test made was to wipe a number of needles firmly on white paper tissue. Some left grey lines, and these were regarded as evidence of metallic or oily residue from the needle surface which could have been deposited in the patient. These unexpected findings, in a variety of popularly used needles from well-respected suppliers, suggest that most manufacturers need to reassess their quality control procedures.