Chemotactic behavior of the third-stage larvae of Strongyloides ratti

Oral Sessions I Parasitology

International47

(Suppl.) (1998) 133-281

155

8. Physiology-2 (Migration, Taxis) ()-0168

CHEMOTACIX

O-0170

BEHAVIOR OF THE THIRD-

STAGE LARVAE OF STRONGnOIDES

RATTI

Tobata Kudo H, Higo H, Koga M and Tada I Department of Parasitology,

INVASION

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

Erlangen,

University, Fukuoka, Japan

In nematode,

the chemosensor

in the recognition

of amphids plays an important role

of the environment

and decides movement.

now accepted that chemotaxis,

osmotic avoidance,

and thermotaxis

in chemosensory

are concerned

in the free-living few attempts

Soil nematode,

It is

dauer formation

neurons of amphid

C~eftorhabditis e~egans. However,

have been made to investigate

similar behaviors

in

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.

amphids

of NaCl in order to stay on proper

These results are similar to chemotaxis

in LS of S. ratri

concentrations

or osmotic

It is suggested that the chemosensor recognizes

the difference

of

of NaCl

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

O-0169

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.

O-0171

ALTERNATIVEHOST-SBARCIUNGSTRATEGIESIN AROL’LUSFOLLACEUS u M. Ning A. Tada I Department of Parasitology, Faculty of Medicine, Kyushu University. Fukuoka, In

order

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

to

Japan

elucidate

rorti.

4-week

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

some

All

skin. cavities 25h.

were

of

and

tissues by accumulate moved directly

in

in to

the the

move

through

the

through

viscera

of

no

this

remained

larvae

some

However

detected

still

the

them

larvae

were were

At ethmoid

ethmoid small to subcutis, or

the

but We

cranium rather

foramen

in in

most

intestine.

than

site

cranial the

aoy

40h.

some

of

brain other

larvae At

were they them

conclude and

occipital

injected

the

present

region.

region

the

in

found

30h.

time.

the

in

appeared

tissues

found were

the

naso-frontal

migrating magnum.

to

the

nasal

organs

had

that

of

and

at or

to still

already larvae tissues

the

head

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 “Dsp@ment of Biological and Envimmnental Sciexe, University of JywskyI8, Jyvhskyla.Finland **‘Institute of Ck.wwlo8j RA8.36 N&himov a”., 117853Moscow,Russia