Entamoeba histolytica - Cell Press

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Bednets revisited I - what a fascinating and wide-ranging article, which I read with great enjoyment. Stimulated by it, I have come up with the following additional ...

Parasitology Today, voL"5, no. I, 1989

Bednets: the Cannabis Connection Bednets revisited I - what a fascinating and wide-ranging article, which I read with great enjoyment. Stimulated by it, I have come up with the following additional information. Although the term 'canopis' for bednet may be plausibly derived from the Greek 'kunopestis' (= venomous insect), there is possibly a more convincing origin in 'cannabis', meaning hemp or canvas, from which the earliest nets were apparently made. In the Revised Medieval Latin Word List 2, for example, the meaning of'can0peum' or 'conopeum' is given as canopy, veil or pyx, and in the supplement'canibis' is interpreted as hunting net or 'toil' (cf. present-day haute couture 'toile'), and these are reported to be derived from 'cannab', hemp. This is itself derived from the Latin 'Canna' or Greek 'Kanna' meaning reed. It is interesting to note that in Smith's Smaller Latin-English Dictionary 3 the only meaning given for 'conopeum' or 'conopium' is 'a net of fine gauze to keep off mosquitoes, etc.'. For those like me who wondered what 'Canopic jars' found in ancient Egyptian tombs and used to store the organs of mummies have to do with canopies the answer at first sight appears to be nothing. The jars with lids shaped like human heads were one of the major products of the ancient Egyptian town of Canopus, near modern Aboukir, north of Alexandria. However, the town was at one of the mouths of the Nile, where many reeds may have grown... David Warhurst

Department of MedicalParasitology London Schoolof Hygieneand Tropical Medicine KeppelStreet London WC I E7HT, UK References

I Lindsay,S.W. and Gibson, M. (1988) Parasitology Today 4, 270-272 2 Latham,R.E.,ed. (1983) RevisedMedieval Latin Word-list from British and Irish Sources Oxford University Press 3 Smith,W., ed. (1947) Smaller Latin~English Dictionary John Murray

9 Even more intriguingly, the French word 'canape' is derived from the same root, 'konaps '2. In modern French it means a sofa, as well as the cocktail snack which we in England know as a canape- presumably by extension, due to the sofa-like shape of the little bit of bread, toast, etc. on which the small savoury lies3. So take your choice: when you eat your next canape, you can imagine that you are

Entamoeba histolytica: Evasion and Invasion Denis and Chadee excellently described the cellular immune dysfunctions facilitating amoebic invasion and immunopathology during invasive amoebiasisk However, I should like to give some additional information about the evasion of the host's immune response by E. histolytica. Complement-mediated cytolysis of E. histolytica, both by the classicaland the alternative pathways, has been described in vitro. In viva, however, a considerable number of amoebae survive and apparently escape the harmful effects of antibodies and cam plement. One way of circumventing the effect of specific antibodies bound to the surface is 'capping' and subsequent release of surface molecules into the extracellular environment. However, internalization has been shown to constitute an important mechanism for modulation of the amoebic surface membrane. The internalized antibodies then become harmless by degradation, and are later recovered in the medium as peptide fragments2. The ability to survive complement-mediated killing is particularly pertinent when considering the invasion of the liver by the parasite. Reed et al. 3 have demonstrated in amoeba-bacteria cultures that pathogenic strains are resistant to lysis by normal human serum and thus potentially invasive. Non-pathogenic strains are susceptible to lysis but can survive in the intestinal lumen where they are not exposed to complement. Serum-resistant parasites may fail to activate the classicalor alternative complement pathways, so that C3b is not deposited on the parasite surface. Complement resistance may also result despite effective complement activation through C3b. In this instance, either a C5b-9


Editorial Comment David Warhurst's intriguing letter stimulated me to do a little etymological research also. According to my etymological dictionary I , 'canopy' is derived from the Latin 'conapeum', a net over a bed, which itself came, via the G reek 'konopeion' (an Egyptian bed with mosquito curtain), ultimately from the Greek word for a mosquito, 'konops'.

Diagnostic D N A Amplification - Not the Complete Answer? Let us congratulate you on the timely article by Dr de Bruijn pon the uses of the polymerase chain reaction (PCR) technique in the field of parasitology. Although we agree that this technology will have an important role in the general analysis of the

eating either cannabis or a mosquito, accordingto taste (literally). John Baker References

I Onions, C.T., ed. (1966) The Oxford Dictionary of English Etymology Clarendon Press 2 Dauzat, A. et al. (n.d.) Nouveau Dictionnaire Etyrnologique et Histonque Larousse 3 Sykes,J.B., ed. (1976) The Concise Oxford Dictionary(6th edn) Clarendon Press

complex is not formed, orthe C5b-9 complex that is assembled does not become attached to a lethal site in the parasite membrane. Trypomastigotes of Trypanosoma cruzi produce an inhibitor of C3 convertase formation that limits complement activation at a step before C3b deposition, and metacyclic promastigotes of Leishmania major resist complement lysis because the C5b-9 complex that forms does not become inserted into the membrane and is shed 4, Direct complement activation by E. histolytica trophozoites does not seem to be an effective host defence mechanism, since inactivation of large amounts of complement is necessary to produce relatively poor lysis of amoebaes. It seems reasonable to consider a pathogenic strain as one that has, or can adopt, protective mechanisms against the attack of complement as well as of oxygen reduction products; the latter may form when the parasite faces a high concentration of oxygen du ringlihe invasive stage6, ~ K . Mehlotra

Divisionof Biochemistry Central Drug ResearchInstitute Lucknow 22600 I India References

I Denis, M. and Chadee, K. (1988) Parasitology Today 4, 247-252 2 Kettis, A.A. and Utter, G. (1984) Am. J. Trap. Meal Hyg. 33,569-577 3 Reed, S.L., Sargeaunt, P.G. and Brande, A.I. (1983) Trans. R. Sac. Trap. Meal Hyg. 77, 248-253 4 Tait, A. and Sacks, D.L. (1988) Parasitology Today 4, 228-234 5 Stemberger, H., Widermann, G. and Meingassner, G. (1979) tmmunobiology 156, 240 6 Mehlotra, R.K. (1988) Parasitology Today 4, 235-236

parasite genomic DNA, we seriously doubt that it will have a central role in parasitic disease diagnosis. Furthermore, we worry that overemphasizing its virtues may have the effect of limiting support for other promising approaches. Here we would like to play the devil's advocate and suggest that the nature of parasitic diseases has not been taken into consideration, as we detail below. It is known that clinical recovery from parasitic infection is not necessarily associated with complete removal of the parasite from the host. In fact, in some cases immunity may