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Scanning electron microscopical observations on the shedding of the tegument of adult Schistosoma mattheei
Internotional Journal for Prrnred in Great Brifoin
Parasitology
Vol.
20, No.
7. pp.
965-967,
/ 990
RESEARCHiVOTE
SCANNING ELECTRON MICROSCOPICAL OBSERVATIONS ON THE SHEDDING OF THE TEGUMENT OF ADULT SCHISTOSUA4A ~ATTH~~I F. J. KRUGER
and P. H. JOUBERT
Research Institute for Diseases in a Tropical Environment of the South African Medical Research Council, P.O. Box 634, Nelspruit 1200, Republic of South Africa (Received 8 June 1990; accepted 2 July 1990) Abstract-KRUGER
F. J. and JOUBERTP. H. 1990. Scanning electron microscopical observations on the shedding of the tegument of adult Sclnstosoma mattheei. International Journalfir Parasitology 20: 965-967. In search of indications of membrane turnover the teguments of male Schistosoma mattheei from cattle and laboratory rodents were studied by means of scanning electron microscopy. A number of slightly elevated circular patches of tegument which appeared to peel off on the edges were seen on the outer membrane of a limited number of specimens from both rodents and cattfe. It is suggested that this phenomenon may represent limited rapid turnover of the outer layer in response to host immunological action. INDEX KEY WORDS: Schistosoma mattheei; scanning electron microscopy; tegument shedding. methods by which adult schistosomes evade the immune response of the host. It was previously believed that this is a continuous process. More recently, Saunders, Wilson & Co&son (1987) studied the turnover rate of the outer membrane of Schistosoma mansoni and found this not to be the case. Using
ACCORDING to transmission electron microscopical studies, the outer membrane of schistosomes has a multilaminate structure which is continually replaced from the tegumental matrix by means of membranous bodies (Hockley, 1973). Shedding of the outer layer of the tegument has been suggested as one of the
FIG. 1. Circular membrane patches on the spined tubercules of a male S. martheei maintained in M. coucha. 965
966
F. J. KRUGERand P. H. JOUBERT
FIG. 2. Aspinous dorsal tegument of a male S. marfheei from M. coucha with circular patches which appe ,ared to become detached from the outer membrane.
FIG. 3. Circular membrane patches on the dorsal tegument of a male S. mnuheei from cattle
Research Note an immunoradiometric assay method to measure turnover rate, they made the following deduction:
the
In conclusion, the normal rate of turnover of the outer bilayer appears to be much lower than would probably be necessary to evade immune attack. However, the parasite possesses the capacity for rapid, but limited, repair to tegumental damage; a capacity which may be overwhelmed under some circumstances, and which may have been mistaken for constant rapid turnover. By means of scanning electron microscopy @EM) Kruger, F.J. (unpublished D. SC. thesis, Potchefstroom University for CHE, 1989) studied the tegument of a large number of South African male Schistosoma mattheei from naturally infected cattle and laboratory infected Mastomys coucha. One of the objectives of the study was to characterize the tegument of the species. However, it also enabled the description of possible membrane turnover by the parasite. Although considerable polymorphism occurred (Kruger, 1989, thesis cited above), the tegument of most paired adult male S. mattheei from both cattle and laboratory rodents did not reveal an indication of tegumental shedding. However, a small number of male schistosomes exhibited circular membrane patches of variable size which seemed elevated in relation to the outer layer (Fig. 1). In some specimens from both M. coucha (Fig. 2) and cattle (Fig. 3) the circular patches appeared to become detached from the outer membrane.
967
It must be emphasized that the observed phenomenon was only evident on a limited number of schistosomes; since it was not possible to study the complete tegument of each and every schistosome, the prevalence of the phenomenon could not be determined. The patches were dissimilar to artifacts caused by osmotic or mechanical damage (Weisberg, Carlisle & Bentley, 1983). If it can be proved that the presence of the circular patches is associated with tegumental turnover in response to immunological induced damage, this may well be the type of turnover suggested by Saunders et al. (1987). In this case humoral factors would be involved, since no cellular reaction to the patches was noticed. ~c~~o~~e~ge~~~~~-We
are
thankful
to
Dr
V.
L.
Hamilton-Attwell who assisted with the SEM, Prof. C. H. J. Schutte who edited the manuscript and the South African Medical Research Council for permission to publish. REPRICE HOCKLEY D. J. 1973. Ultrastructure of the tegument nf Schistosoma. Advances in Parasitology 11: 233-505. ._ -_ SAUNDERSN.. WILSON R. A. & COULSON S. 1987. The c-l+,_.__ bilayer of the adult schistosome tegument surface has a low turnover rate in vitro and in vivo. ,~o~e~lar and BioiogicaI Parasitology 25: 123-131. WEISBERG L. S., CARLISLE S. & BENTLEY A. G. 1983. Schisrosomn mansoni: evaluation of selected preparative procedures for transmission and scanning electron microscopy. fournal ~~~e~minthology 69: 335-345.
Parasitology
Vol.
20, No.
7. pp.
965-967,
/ 990
RESEARCHiVOTE
SCANNING ELECTRON MICROSCOPICAL OBSERVATIONS ON THE SHEDDING OF THE TEGUMENT OF ADULT SCHISTOSUA4A ~ATTH~~I F. J. KRUGER
and P. H. JOUBERT
Research Institute for Diseases in a Tropical Environment of the South African Medical Research Council, P.O. Box 634, Nelspruit 1200, Republic of South Africa (Received 8 June 1990; accepted 2 July 1990) Abstract-KRUGER
F. J. and JOUBERTP. H. 1990. Scanning electron microscopical observations on the shedding of the tegument of adult Sclnstosoma mattheei. International Journalfir Parasitology 20: 965-967. In search of indications of membrane turnover the teguments of male Schistosoma mattheei from cattle and laboratory rodents were studied by means of scanning electron microscopy. A number of slightly elevated circular patches of tegument which appeared to peel off on the edges were seen on the outer membrane of a limited number of specimens from both rodents and cattfe. It is suggested that this phenomenon may represent limited rapid turnover of the outer layer in response to host immunological action. INDEX KEY WORDS: Schistosoma mattheei; scanning electron microscopy; tegument shedding. methods by which adult schistosomes evade the immune response of the host. It was previously believed that this is a continuous process. More recently, Saunders, Wilson & Co&son (1987) studied the turnover rate of the outer membrane of Schistosoma mansoni and found this not to be the case. Using
ACCORDING to transmission electron microscopical studies, the outer membrane of schistosomes has a multilaminate structure which is continually replaced from the tegumental matrix by means of membranous bodies (Hockley, 1973). Shedding of the outer layer of the tegument has been suggested as one of the
FIG. 1. Circular membrane patches on the spined tubercules of a male S. martheei maintained in M. coucha. 965
966
F. J. KRUGERand P. H. JOUBERT
FIG. 2. Aspinous dorsal tegument of a male S. marfheei from M. coucha with circular patches which appe ,ared to become detached from the outer membrane.
FIG. 3. Circular membrane patches on the dorsal tegument of a male S. mnuheei from cattle
Research Note an immunoradiometric assay method to measure turnover rate, they made the following deduction:
the
In conclusion, the normal rate of turnover of the outer bilayer appears to be much lower than would probably be necessary to evade immune attack. However, the parasite possesses the capacity for rapid, but limited, repair to tegumental damage; a capacity which may be overwhelmed under some circumstances, and which may have been mistaken for constant rapid turnover. By means of scanning electron microscopy @EM) Kruger, F.J. (unpublished D. SC. thesis, Potchefstroom University for CHE, 1989) studied the tegument of a large number of South African male Schistosoma mattheei from naturally infected cattle and laboratory infected Mastomys coucha. One of the objectives of the study was to characterize the tegument of the species. However, it also enabled the description of possible membrane turnover by the parasite. Although considerable polymorphism occurred (Kruger, 1989, thesis cited above), the tegument of most paired adult male S. mattheei from both cattle and laboratory rodents did not reveal an indication of tegumental shedding. However, a small number of male schistosomes exhibited circular membrane patches of variable size which seemed elevated in relation to the outer layer (Fig. 1). In some specimens from both M. coucha (Fig. 2) and cattle (Fig. 3) the circular patches appeared to become detached from the outer membrane.
967
It must be emphasized that the observed phenomenon was only evident on a limited number of schistosomes; since it was not possible to study the complete tegument of each and every schistosome, the prevalence of the phenomenon could not be determined. The patches were dissimilar to artifacts caused by osmotic or mechanical damage (Weisberg, Carlisle & Bentley, 1983). If it can be proved that the presence of the circular patches is associated with tegumental turnover in response to immunological induced damage, this may well be the type of turnover suggested by Saunders et al. (1987). In this case humoral factors would be involved, since no cellular reaction to the patches was noticed. ~c~~o~~e~ge~~~~~-We
are
thankful
to
Dr
V.
L.
Hamilton-Attwell who assisted with the SEM, Prof. C. H. J. Schutte who edited the manuscript and the South African Medical Research Council for permission to publish. REPRICE HOCKLEY D. J. 1973. Ultrastructure of the tegument nf Schistosoma. Advances in Parasitology 11: 233-505. ._ -_ SAUNDERSN.. WILSON R. A. & COULSON S. 1987. The c-l+,_.__ bilayer of the adult schistosome tegument surface has a low turnover rate in vitro and in vivo. ,~o~e~lar and BioiogicaI Parasitology 25: 123-131. WEISBERG L. S., CARLISLE S. & BENTLEY A. G. 1983. Schisrosomn mansoni: evaluation of selected preparative procedures for transmission and scanning electron microscopy. fournal ~~~e~minthology 69: 335-345.