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Biomedical subjects

B Haberl

Publications and source records attributed to B Haberl.

9 recordsLinked to original sources
PubMed1996

Schistosoma mansoni miracidial host-finding: species specificity of an Egyptian strain.

The effect of snail-conditioned water (SCW) from Biomphalaria alexandrina, a pigmented and an albino strain of B. glabrata, and Lymnaea stagnalis on the host-finding behavior of miracidia of two Brazilian and one Egyptian strain of Schistosoma mansoni was studied. Miracidia of the Egyptian strain significantly preferred their suitable host B. alexandrina versus the other snail species with their behavior patterns of host location and their responses after contact with the host. However, miracidia of both Brazilian strains did not differentiate between SCW from three of the snail species; only the pigmented B. glabrata elicited weaker responses. The releasing cues of SCW for miracidial host-finding phases are macromolecular glycoconjugates. An analysis of SCW by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), blotting, and subsequent carbohydrate detection showed that the band patterns of glycoconjugates differed significantly among the four snail strains. Therefore, differing chemical characteristics of the signaling glycoconjugates could be the basis for the observed host specificity in miracidial host-finding.

Agar↗
PubMed1995

Schistosoma mansoni and S. haematobium: miracidial host-finding behaviour is stimulated by macromolecules.

The miracidia of Schistosoma mansoni and S. haematobium approach their host snails by increasing their rate of change of direction (RCD) in increasing gradients of snail-conditioned water (SCW), and they perform a turnback response in decreasing gradients. After contact with the host "repeated investigation" is the typical host-specific response. Both species show no significant directed chemotactical orientation towards their snail hosts. All three host-finding responses (increased RCD, turnback response, and "repeated investigation") seem to be stimulated in both species by a similar component of SCW, a macromolecular glycoconjugate with a molecular weight > 30,000. The saccharide chains seem to be O-glycosidically linked via serine and N-acetylgalactosamine. The glycoconjugate is sensitive to lysozyme which may suggest that muramic acid as a gastropod-specific component is involved in the recognition process. Small molecular components of SCW, as well as magnesium chloride offered as pure chemical, may cause a moderate increase in the RCD. Therefore a minor contribution of these components to the host-finding response of schistosome miracidia cannot be excluded. That schistosome miracidia respond to complex macromolecules as host cues may indicate an adaptation to avoid interference of the host-finding with ubiquitous small molecular mud components and it might enable the miracidia to achieve a high degree of host-specificity in their host-finding.

Animals↗
PubMed1995

Finding and recognition of the snail intermediate hosts by 3 species of echinostome cercariae.

Finding and recognition of snail second intermediate hosts was studied in cercariae of 3 echinostome species. The cercariae of the 3 species accumulated in snail-conditioned water (SCW) with 2 types of orientation mechanisms and responded to different small molecular weight ( < 500 Da) components of SCW. Pseudechinoparyphium echinatum and Echinostoma revolutum cercariae returned by swimming an arc, when swimming in decreasing concentration gradients of SCW (turn-back swimming). The stimulating cues of SCW were identified as hydrophilic organic molecules, probably possessing amino groups. Amino acids contributed to the attractivity of SCW, at least in P. echinatum, but they could not account for the complete attractivity of SCW. Hypoderaeum conoideum were directed chemotactically and swam along increasing concentration gradients of small peptides within SCW, but in decreasing SCW gradients they showed no turn-back swimming. Chemotactic orientation in H. conoideum only started 1 h after emission, which may assist the cercariae to leave the immediate area of their first intermediate host snails and to disperse. Attachments occurred specifically to snail hosts in the 3 species and were stimulated by macromolecular mucus compounds, probably mainly by viscoelastic properties of the mucus. The results of this study show, that host-finding mechanisms and the stimulating host cues of snail invading echinostome cercariae differ considerably from those of schistosome miracidia.

Animals↗
PubMed1994

Schistosoma haematobium cercarial host-finding and host-recognition differs from that of S. mansoni.

Schistosoma haematobium cercarial host-finding responses differ from those of Schistosoma mansoni. The attachment response to warm substrata is more sensitive and intense and is inhibited by unphysiologically warm substrata. Attachment is also stimulated by L-arginine as the exclusive chemical cue of the human skin surface (threshold 3 microM); however, the response is drastically lower than that of S. mansoni cercariae. No chemical host stimulus could be identified for an enduring contact with the host after attachment. After attachment, the cercariae creep in a temperature gradient toward heat source; their response is, however, more sensitive than that of S. mansoni (threshold 0.03 vs. 0.15 C/mm). Creeping S. haematobium cercariae orientate in chemical gradients in the same way as S. mansoni cercariae toward L-arginine as the exclusive chemical signal of the human skin surface. The selective benefit of this behavior is not yet understood. The penetration of both species is stimulated by free fatty acids from the human skin surface, not by heat. Thus, S. haematobium responds more to thermal host signals, whereas S. mansoni prefers chemical host signals.

Animals↗
PubMed1992

Miracidium of Schistosoma mansoni: a macromolecular glycoconjugate as signal for the behaviour after contact with the snail host.

1. The behaviour of the miracidium of Schistosoma mansoni after contact with agar blocks containing Biomphalaria glabrata snail conditioned water (SCW) or its components, was studied. 2. "Repeated investigation" was the most specific response at contact with the snail host. 3. Fractionation and specific chemical treatment of SCW revealed that this response was stimulated by a lysozyme sensitive glycoconjugate with a mol. wt greater than 300,000. 4. Low molecular weight components of SCW had no stimulatory effect on the miracidia, although MgCl2 offered as pure chemical did so.

Animals↗
PubMed1991

Miracidia of Schistosoma japonicum: approach and attachment to the snail host.

Schistosoma japonicum miracidia swim directed along a chemical gradient toward the snails Oncomelania hupensis and Biomphalaria glabrata, and they turn back when the concentration of attractive chemicals decreases. The host signal for this chemotactic response has a molecular weight of more than 30,000. When swimming miracidia encounter the surface of O. hupensis or agar containing O. hupensis snail-conditioned water (SCW) they perform the host-specific responses "contact with return," "repeated investigation," and "attachment," but they do not exhibit such behavior when encountering B. glabrata surface or agar containing B. glabrata SCW. Thus S. japonicum miracidia respond to different host signals when they approach snails than when they attach to snails.

Animals↗