Oral Sessions I Parasitology
(Suppl.) (1998) 133-281
8. Physiology-2 (Migration, Taxis) ()-0168
BEHAVIOR OF THE THIRD-
STAGE LARVAE OF STRONGnOIDES
Tobata Kudo H, Higo H, Koga M and Tada I Department of Parasitology,
OF MAMMALIAN SKIN BY SCHISTOSOMA CERCARIAE: THE PUZZLING ROLE OF THE HOST SIGNAL L-ARGININE MANSONl
Haas Stall K, Geis C, Haberl B, Fuchs M, Loy C Institute for Zoology I, University Erlangen-Nuemberg, Germany
Faculty of Medicine, Kyushu
University, Fukuoka, Japan
in the recognition
of amphids plays an important role
of the environment
and decides movement.
now accepted that chemotaxis,
in the free-living few attempts
neurons of amphid
C~eftorhabditis e~egans. However,
have been made to investigate
animal parasitic nematodes. In the present study, we analyzed the behaviors of the third-stage larvae (L.3) of Sfroqyloides by using in vitro agarose
ratti to sodium chloride (NaCl) gradient tracking assay method. When L3 of S. ratti
were placed on the gradient of NaCl in the agarose plate, they migrated to the area of lower concentrations concentration. avoidance
of C. elegans.
of NaCl in order to stay on proper
These results are similar to chemotaxis
in LS of S. ratri
It is suggested that the chemosensor recognizes
and indicates the possible involvement of chemotaxis
or osmotic avoidance.
We attempted to observe the blocking effects
of enzymes, toxic chemicals and temperature treatments which might affect on the chemosensor
activities of amphids.
RA7TI : MIGRATION STUDY OF THE THIRD STAGE LARVAE IN RATS BY WHOLE BODY AUTORADIOGRAPHY AFTER 35S-METHIONINE LABELLING STRONGYLOILJES
The attachment of Schistosmm mmsom cemariae to mammalian ski is highly specificaIIy stimulated by L-arginine. As this amino acid seems to be an unsuitable signal for a specific identification of mammalian skin we examined 4 hypotheses to explain the advantage of the cercarial sensitivity to L-arginine. (1) A Schistosoma-infection lowered the arginine concentration in the serum of mice. However, the cercarial response to Larginine was no means to avoid attachments to already infected mice, as the infection did not reduce the arginine concentration in the ski and the cercarial attachment responses to it. (2) Creeping cercariae showed chemotactic orientation specifically along increasing L-arginine gradients. However, L-arginine is no pheromone, which could guide cercariae to common penetration sites, as cercariae (in contrast to previous reports) did not secrete arginine during the Penetration processes. (3) Cercariae did not use L-arginine to produce NO and citrulline, when they were stunulated to show penetration behavior and tegument transformation. This argues against our hypothesis, that they might induce a NO mediated blood vessel dilation during their migration in the host. (4) Cercariae bound L-arginine from the surrounding medium when penetration behavior and tegument transformation were stimulated. This suggests an immune evasion strategy: cercariae may remove L-arginine (which is the precursor of the NO mediated cellular immune attack) from the invaded slun. However, there was no specialization on L-arginine, as serine and lysine were bound in sin&r quantities. Creeping cercariae orientated along mcreasmg concentratmns of human skin extracts, respondmg to a combination of L-arginine (threshold 2.5 pM) and unknown skin componenb. We suggest, that the cercarial sensitivity to L-argmine might have its prunary function m the orientation processes when cercariae migrate within the hosts tissues.
ALTERNATIVEHOST-SBARCIUNGSTRATEGIESIN AROL’LUSFOLLACEUS u M. Ning A. Tada I Department of Parasitology, Faculty of Medicine, Kyushu University. Fukuoka, In
the migration pathway of old Wistar rats were given 5,000 35S-labeled infective larvae subcutaneously and they were killed at IO, 15, 20, 25, 30 and 40h postinfection. Prior to the the labeled larvae were assessed the specific inoculation, radioactivity level by scintillation counter and were revealed to be 200.SOOcpm/L3. The specimens were prepared for whole Srrongyloides
body autoradiography. The thin sections (50Ltm) of whole rats were freeze-dried and mounted on films in darkness. The larvae were shown as dark spots. The larvae stayed at the inoculated site (lower abdomen) until 10h after infection and they were found in part in the head portion and others existed sporadically in the skin, liver and lungs at 15h. After accumulated in the head portion, 20h. the maJority of them while
skin. cavities 25h.
tissues by accumulate moved directly
ethmoid small to subcutis, or
were they them
already larvae tissues
V N.Mikheev*,E;I VaIton&‘, A.V.w udA.F.Pastua&‘*’ lA.N. 8cvertov lnshtute of Ec&y and Evoluticw Russisn Ac&&myof 8&nces, Moscow,Russia “[email protected]
of Biological and Envimmnental Sciexe, University of JywskyI8, Jyvhskyla.Finland **‘Institute of Ck.wwlo8j RA8.36 N&himov a”., 117853Moscow,Russia