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W Haas

Publications and source records attributed to W Haas.

At least 37 records · Page 2Linked to original sources
PubMed2002

[Memory disorders after unilateral cerebral lesions].

In contrast to the amnestic syndrome, unilateral hemispheric lesions are mostly connected with selective memory deficits, which are related to either verbal or visual-spatial information. Clinical studies concerning this are mostly about patients with temporal lobe epilepsy. Almost all studies found that significantly worse verbal memory deficits appeared before or after left temporal lobectomy. In contrast to these outcomes, the results concerning right temporal lobectomy (RTL) are nonuniform. There are studies that cannot prove figurative memory deficits before or after RTL and others that ascertain a correlation between RTL and figurative memory deficits. Mean values are always compared with random samples of left and right hemispheric patients. In contrast, the presented study assumes a clinical isolated case and analyses a random sample of neurological patients with different genesis with a standardized memory test (Berlin Amnesia Test, or BAT). As a result, a significant correlation between left hemispheric lesions and verbal memory deficits as well as right hemispheric lesions and visual-spatial memory deficits can be proven. Possible reasons for these differing results with visual-spatial memory deficits are still under discussion.

Adult↗
PubMed2002

Recognition and invasion of human skin by Schistosoma mansoni cercariae: the key-role of L-arginine.

The attachment of Schistosoma mansoni cercariae to mammalian skin is specifically stimulated by L-arginine. As L-arginine is an unsuitable signal for a specific identification of mammalian skin we examined the following 5 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, and this could enable the cercariae to avoid attachments to already infected mice. However, the infection did not reduce the arginine concentration in the skin and the cercarial attachment responses to it. (2) Creeping cercariae showed chemotactic orientation specifically along increasing L-arginine gradients. L-arginine could act as a pheromone which could guide cercariae towards common penetration sites. However, the cercarial acetabular gland contents were not attractive and they did not (in contrast to previous reports) contain much arginine. (3) Schistosomula (transformed cercariae) could use L-arginine to produce nitric oxide (NO) for blood vessel dilation during their migration in the host. However, in vitro the transformed cercariae did not convert L-arginine into citrulline and NO. (4) Schistosomula could bind L-arginine from the surrounding tissues and so escape the cellular immune attack (which needs L-arginine as the precursor of NO). However, transformed cercariae bound no more L-arginine than L-serine and L-lysine. (5) Schistosomula, migrating parallel to the surface in the mammalian epidermis, are dependent on information on their position between the inner and the surface layers of the skin. In the mouse skin, they adjusted their body axis with the ventral side toward the deeper (arginine-residue rich) epidermis layers. When migrating in agar, they showed chemo-orientation toward serum, and D-glucose and L-arginine were the stimulating compounds therein. The burrowing schistosomula adjusted their body axis (as in the epidermis) with the ventral side toward the higher concentration of L-arginine and not of glucose. We argue that the sensitivity for L-arginine has its primary function in orientation within mammalian skin and in location of blood vessels.

Animals↗
PubMed2001

Completion of the nucleotide sequence of the Enterococcus faecalis conjugative virulence plasmid pAD1 and identification of a second transfer origin.

pAD1 is a 59.3-kb plasmid in Enterococcus faecalis that has been the subject of intense investigation with regard to its pheromone-inducible conjugation behavior as well as its contribution to virulence. Approximately two-thirds of the pAD1 nucleotide sequence has been previously reported. Here we report on an analysis of the final approximately 22 kb, a significant portion of which is believed to encode structural genes associated with conjugation. The conjugation-related region was also found to contain a new (second) origin of conjugative transfer (oriT). A list of open reading frames covering the entire plasmid is presented.

Conjugation, Genetic↗
PubMed2001

Recognition of cattle skin by cercariae of Orientobilharzia turkestanica.

The cercariae of Orientobilharzia turkestanica attached to isolated cattle skin and penetrated it. The attachment was stimulated by warmth and by hydrophilic and lipophilic chemical cues of skin surface extracts. The enduring contact with the skin was also stimulated by the chemical cues, but not by warmth. Penetration of the cercariae into agar substrates was triggered by skin surface lipids, and free fatty acids were identified as the exclusively active compounds of the lipids. That the cercariae attach and remain on the skin by responding to at least two different chemical host cues is unique among the schistosomatids studied so far. It might reflect an adaptation to invade the hosts in clear water or near the water surface where chemical mud compounds will not interfere with host recognition.

Animals↗
PubMed2001

Prevalence of cercariae from Lymnaea stagnalis snails in a pond system in Southern Germany.

Lymnaea stagnalis snails were collected from 174 individual ponds of an extensive pond system in South Germany; 43,441 snails collected during 1980 2000 were examined for shedding cercariae. The species richness (at least 18 species of cercariae) and the high cercarial prevalence (at least 44.9%) may result from the high abundance and diversity of vertebrate and invertebrate hosts in the area. The mean prevalence (% +/- SEM) of most cercarial species increased from May-June to August-October, e.g. in Diplostomum spathaceum from 4.1% to 18.6%, in all echinostomatids from 5.6% to 18.0%, in Pseudechinoparyphium echinatum from 3.0% to 11.2%, in Xiphidiocercariae from 2.2% to 13.4%, and the overall prevalence shifted from 13.7% to 53.5%. There was no change in the prevalence of the different cercarial species over the last 20 years. The agents of cercarial dermatitis showed a constant low prevalence, 0.17% in Trichobilharzia ocellata (43,441 L. stagnalis examined) and 0.24% in other Trichobilharzia species (4,245 Radix examined). Such low prevalences seem to be normal in areas where cercarial dermatitis occurs in humans.

Animals↗
PubMed2001

Photo- and geo-orientation by Echinostome cercariae results in habitat selection.

The effect of light and gravity on orientation was studied in cercariae of 4 echinostome species: Pseudechinoparyphium echinatum, Echinostoma revolutum, Hypoderaeum conoideum, and Isthmiophora melis. The cercariae were placed into vertical and horizontal cuvettes, illuminated with 2 different light intensities from various directions, and their distribution recorded for 6 hr Each species showed its individual pattern of horizontal photo-orientation and geo-orientation, with distinct changes during the time after emerging. The geo-orientation was controlled differently in each species by the intensity and the direction of light radiation. The different orientation patterns suggest functions such as leaving the habitats of the host-snails emitting the cercariae, dispersal, and frequenting the microhabitats of potential hosts. The high diversity of orientation patterns among the species that originated from the same first intermediate host Lymnaea stagnalis in the same ponds and that invade similar host spectra suggests adaptations to different ecological conditions.

Animals↗
PubMed2000

Snail host finding by Fasciola hepatica and Trichobilharzia ocellata: compound analysis of "miracidia-attracting glycoproteins".

The glycoconjugates from snail-conditioned water of Lymnaea truncatula and L. stagnalis which elicit typical host finding behavior in miracidia of Fasciola hepatica and Trichobilharzia ocellata were separated by anion-exchange chromatography and a two-step size-exclusion chromatography. We obtained fractions attractive for the parasites with MW of about 10(6) Da in both snail species. These fractions still contained species-specific information since miracidia responded only to molecules from their respective host snail. Analysis of the amino acid composition from the protein backbone revealed a similar composition in the effective fractions of both snails. Amounts of serine and threonine were higher than 30 mol %, which is typical for mucin-type glycoproteins. The carbohydrate moieties consisted mainly of galactose and fucose, but nine different other monosaccharides also were identified in smaller amounts. The heterogeneity of the molecules was also confirmed by the binding of six different lectins. Because of these characteristics, the effective molecules were termed "miracidia-attracting glycoproteins" (MAGs). MAGs may play an important role for parasite transmission, as they may increase the chance of an encounter between parasite and host and enable the miracidia to discriminate between their specific intermediate host and other unsuitable snail species.

Amino Acids↗
PubMed2000

Host-finding in Echinostoma caproni: miracidia and cercariae use different signals to identify the same snail species.

The snail host signals releasing host-finding responses in miracidia and cercariae of Echinostoma caproni were analysed by fractionation of snail-conditioned water (SCW). Cercariae responded non-specifically to organic and hydrophilic, low molecular weight components of SCW showing their typical turning response. Hydrolysis of peptides in SCW had no effect on cercarial responses. An artificial mixture of amino acids in concentrations determined from SCW as well as glycine alone in a concentration corresponding to the total concentration of amino acids in SCW showed nearly the same efficacy as SCW itself. Miracidia responded to a high molecular weight glycoprotein fraction, which could be isolated from SCW by ion-exchange and size-exclusion chromatography. In contrast to an Egyptian Schistosoma mansoni strain, the echinostome miracidia were not able to differentiate between different snail species. The results show for the first time that miracidia and cercariae of the same species may use different signals to identify the same snail host species. This indicates an independent evolution of host-finding mechanisms in the two parasite stages.

Animals↗
PubMed2000

Ligand-binding properties of the carboxyl-terminal repeat domain of Streptococcus mutans glucan-binding protein A.

Streptococcus mutans glucan-binding protein A (GbpA) has sequence similarity in its carboxyl-terminal domain with glucosyltransferases (GTFs), the enzymes responsible for catalyzing the synthesis of the glucans to which GbpA and GTFs can bind and which promote S. mutans attachment to and accumulation on the tooth surface. It was predicted that this C-terminal region, comprised of what have been termed YG repeats, represents the GbpA glucan-binding domain (GBD). In an effort to test this hypothesis and to quantitate the ligand-binding specificities of the GbpA GBD, several fusion proteins were generated and tested by affinity electrophoresis or by precipitation of protein-ligand complexes, allowing the determination of binding constants. It was determined that the 16 YG repeats in GbpA comprise its GBD and that GbpA has a greater affinity for dextran (a water-soluble form of glucan) than for mutan (a water-insoluble form of glucan). Placement of the GBD at the carboxyl terminus was necessary for maximum glucan binding, and deletion of as few as two YG repeats from either end of the GBD reduced the affinity for dextran by over 10-fold. Interestingly, the binding constant of GbpA for dextran was 34-fold higher than that calculated for the GBDs of two S. mutans GTFs, one of which catalyzes the synthesis of water-soluble glucan and the other of which catalyzes the synthesis of water-insoluble glucan.

Bacterial Proteins↗
PubMed1999

Host-odour recognition in two tick species is coded in a blend of vertebrate volatiles.

The questing behaviour of ixodid ticks serves for identification and localisation of approaching hosts and is evoked by carbon dioxide, vibrations, visual and odour stimuli. In an olfactometer, we examined the specificity of the questing response of larvae of Boophilus microplus, a one-host tick which develops mainly on cattle, and Ixodes ricinus, a three-host tick with a broader host spectrum. While all mammalian odours tested were equally stimulatory for I. ricinus, B. microplus was clearly more activated by bovine odours. A phenolic fraction of bovine odour stimulated B. microplus only. Attractive components of the host odours were identified by exposing the ticks to single chemicals and mixtures. Single chemicals stimulated questing responses only at levels higher than the levels detected in the bovine odour. However, an artificial odour blend of 37 pure chemicals, diluted to concentrations at which the individual components were inactive, proved to be as effective as natural host odour for both tick species. Further fractionation of the blend revealed that the combinatory effect was achieved by only 7 compounds in both species. Although B. microplus responded to the same synergistic mixture of volatiles as I. ricinus, it showed significant higher sensitivity to the cattle-associated compounds 1-octen-3-ol and 2-nitrophenol and this might contribute to its host-specificity.

Animals↗
PubMed1999

Semisynthetic derivatives of madurahydroxylactone and their antibacterial activities.

Madurahydroxylactone is a secondary metabolite from Nonomuria rubra (former Actinomadura rubra) with in vitro activity against gram-positive bacteria and belongs to the family of benzo[a]naphthacenequinones. A series of derivatives of madurahydroxylactone were synthesized to investigate the effect on the antibacterial activity. Reaction with alcohols and amines gave cyclic acetals or aminals derived from the lactone form, whereas other amino reagents like hydroxylamines and acyl or sulfonyl hydrazides led to the corresponding imine derivatives of the aldehyde. Hydrazine, alkyl and aryl hydrazines react with madurahydroxylactone under cyclization to give compounds of the new heterocyclic basic structure naphthaceno[1,2-g]phthalazine. Some new compounds strongly inhibit gram-positive bacteria, in part stronger than the parent compound.

Actinomycetales↗
PubMed1998

Circular dichroism analysis of the glucan binding domain of Streptococcus mutans glucan binding protein-A.

The glucan binding domain (GBD) of the glucan binding protein-A (GBP-A) from the cariogenic bacterium Streptococcus mutans was studied using circular dichroism (CD) analysis, Chou-Fasman-Rose secondary structure prediction, and absorption and fluorescence spectroscopy. Our data show that the binding domain undergoes a conformational shift upon binding to the ligand dextran. The CD spectrum shows two positive bands at 280 nm and 230 nm which were assigned to aromatic residues. The 230-nm band was seen at 20 degrees C and 30 degrees C, lost intensity at 40 degrees C, and was eliminated at 45 degrees C coinciding with complete denaturation. The protein was stable at physiological pH, but precipitated at pH 5. A pH of 10 changed the secondary structure but had no effect on the 230-nm band. Analysis of the CD data in the far UV using the SELCON computer program revealed a high content of beta-sheets and a lack of alpha-helical structures. Secondary structure prediction based on the amino acid sequence of GBD agreed with the CD analysis. The fluorescence emission maximum at 339 nm suggested that the majority of the tryptophans were located in the interior of the protein. This maximum shifted to higher energy upon binding to the ligand dextran.

Amino Acid Sequence↗
PubMed1998

Invasion of the vertebrate skin by cercariae of Trichobilharzia ocellata: penetration processes and stimulating host signals.

The penetration of Trichobilharzia ocellata cercariae into the skin of their duck hosts was described using electron microscopy and histology. The behavior patterns of the cercariae on their exposure to human skin differed only little from those known for Schistosoma mansoni cercariae. After their attachment to living human skin the cercariae crept to wrinkles within a mean of 8 s, and full penetration was achieved within a mean of 4.0 min (83 s to 13.3 min). Tail shedding occurred as early as within a mean of 6.5 s of the first penetration attempts. It was supported by a muscular sphincter at the cercarial hindbody. The skin-surface stimuli for cercarial penetration were contained in the lipid fraction of the duck and human skin surface; hydrophilic components were effective only in some T. ocellata isolates. The penetration-stimulating components of duck-skin lipids were exclusively free fatty acids with the same chemical characteristics known to stimulate penetration of Schistosoma species. Skin-surface lipids of the abnormal human host, with their higher fatty acid contents, stimulated higher cercarial penetration rates than did skin lipids of the natural duck host. Fatty acids as penetration stimuli may offer advantages for T. ocellata cercariae by increasing the specificity for an invasion of terrestrial vertebrates, which is additionally determined by cholesterol and ceramides as signals for attachment and enduring contact behavior.

Animals↗
PubMed1998

Chemo-orientation of echinostome cercariae towards their snail hosts: the stimulating structure of amino acids and other attractants.

The cercariae of Pseudechinoparyphium echinatum and Echinostoma revolutum locate their host snails by turning back when swimming in decreasing gradients of the small molecular weight fraction (< 500) of snail conditioned water. Fractionation and chemical modifications of snail conditioned water from Lymnaea stagnalis showed that amino acids are necessary for the stimulating activity of snail conditioned water. A complete mixture of amino acids in concentrations determined from snail conditioned water had a high attraction. However, differently composed mixtures of amino acids and even single amino acids also had the same attraction as this complete mixture when used in concentrations corresponding to the total concentration of amino acids in snail conditioned water. Experiments with analogues and derivatives of amino acids showed that the primary alpha-amino group and the alpha-carboxyl group are necessary for the full effectiveness of amino acids. The highest effect was elicited by L-amino acids with a primary alpha-amino group, whereas the amino acid type and the chain length seemed to be unimportant. However, the full attraction of snail conditioned water was not achieved by amino acids alone. Chemical modifications of snail conditioned water suggested that the additional stimuli were neither inorganic ions nor organic acids or lipids. As the full attraction of snail conditioned water was obtained when the amino acid mixture of snail conditioned water was combined with its content of urea and ammonia, we conclude that the cercariae use only these excretory products as additional signals for their chemo-orientation. Chemo-orientation to amino acids, urea and ammonia seems to reflect a strategy to locate a broad spectrum of aquatic hosts.

Amino Acids↗
PubMed1998

Chemo-orientation of echinostome cercariae towards their snail hosts: amino acids signal a low host-specificity.

The cercariae of Pseudechinoparyphium echinatum and Echinostoma revolutum approach their intermediate host snails by turning back when swimming in decreasing concentration gradients of snail conditioned water. Host stimuli are small molecular amino compounds, probably amino acids. This response was inhibited reversibly when the cercariae were treated with 0.45 microM-silver nitrate. As silver nitrate binds to the ciliated papillae of the cercarial surface, papillar chemoreceptors may be involved. Snail conditioned water from different snail species stimulated different intensities of chemo-orientation in both species of digeneans. However, when the samples of water conditioned with different snail species or even fish, tadpoles and leeches were diluted to the same total amino acid concentrations, the intensities of cercarial responses were similar. Therefore, some specificity of the chemo-orientation seemed to be achieved only by the total concentration of amino acids and not by particular mixtures of amino acids. In fact, amino acid spectra released by freshwater snails varied not only among different snail species, but also within the same species.

Amino Acids↗
PubMed1998

Theronts of Ichthyophthirius multifiliis find their fish hosts with complex behavior patterns and in response to different chemical signals.

How parasites find and recognize fish hosts is best known for trematode cercariae. These multicellular organisms respond with complex behavior patterns to sequences of different chemical host signals, although these invasive stages are produced in large numbers. However, little is known on the host-finding of protozoan parasites. We therefore studied how the infective theronts of I. multifiliis find their fish hosts by offering them various fractions and chemical modifications of fish skin surface. Free swimming theronts showed at least 6 different behavior patterns, 4 of them were stimulated by fish skin components, e.g. by amino acids. Theronts approached towards solid substrates ("stop and go ahead") in response to macromolecular glycoproteins of fish skin, and they were repelled ("stop and turn away") by other macromolecular glycoconjugates. After contact with solid surfaces, they repeatedly dipped on the surface ("dipping contact") in response to glycoconjugates of fish skin and they swam along the surface ("body parallel") when it contained proteins of fish skin. The results demonstrate that also a protozoan fish-parasite without nervous system and cellular chemoreceptors may show very diverse host-finding behavior patterns (at least 11) and may respond to different chemical host cues (at least 5).

Amino Acids↗