Strangeness suppression of qq creation observed in exclusive reactions.

We measured the ratios of electroproduction cross sections from a proton target for three exclusive meson-baryon final states: ΛK(+), pπ(0), and nπ(+), with the CLAS detector at Jefferson Lab. Using a simple model of quark hadronization, we extract qq creation probabilities for the first time in exclusive two-body production, in which only a single qq pair is created. We observe a sizable suppression of strange quark-antiquark pairs compared to nonstrange pairs, similar to that seen in high-energy production.

Tensor correlations measured in 3He(e,e' pp)n.

We have measured the 3He(e,e' pp)n reaction at an incident energy of 4.7 GeV over a wide kinematic range. We identified spectator correlated pp and pn nucleon pairs by using kinematic cuts and measured their relative and total momentum distributions. This is the first measurement of the ratio of pp to pn pairs as a function of pair total momentum p(tot). For pair relative momenta between 0.3 and 0.5 GeV/c, the ratio is very small at low p(tot) and rises to approximately 0.5 at large p(tot). This shows the dominance of tensor over central correlations at this relative momentum.

Measurement of single- and double-spin asymmetries in deep inelastic pion electroproduction with a longitudinally polarized target.

We report the first measurement of the transverse momentum dependence of double-spin asymmetries in semi-inclusive production of pions in deep-inelastic scattering off the longitudinally polarized proton. Data have been obtained using a polarized electron beam of 5.7 GeV with the CLAS detector at the Jefferson Lab (JLab). Modulations of single spin asymmetries over the azimuthal angle between lepton scattering and hadron production planes ϕ have been measured over a wide kinematic range in Bjorken x and virtual photon squared four-momentum Q2. A significant nonzero sin2ϕ single spin asymmetry was observed for the first time indicating strong spin-orbit correlations for transversely polarized quarks in the longitudinally polarized proton.

Absorption of the ω and ϕ mesons in nuclei.

Because of their long lifetimes, the ω and ϕ mesons are the ideal candidates for the study of possible modifications of the in-medium meson-nucleon interaction through their absorption inside the nucleus. During the E01-112 experiment at the Thomas Jefferson National Accelerator Facility, the mesons were photoproduced from 2H, C, Ti, Fe, and Pb targets. This Letter reports the first measurement of the ratio of nuclear transparencies for the e+e- channel. The ratios indicate larger in-medium widths compared with what have been reported in other reaction channels. The absorption of the ω meson is stronger than that reported by the CBELSA-TAPS experiment and cannot be explained by recent theoretical models.

Genetic evidence against a morphologically suggestive conspecificity of Dermacentor reticulatus and D. marginatus (Acari:Ixodidae).

International Journal for Parasitology 25: 1413-1419. Dermacentor reticulatus and D. marginatus exhibit overlapping phenotypes. The possibility of conspecificity was investigated on the nucleotide level by comparing DNA sequences of the second internal transcribed spacer (ITS 2) of the rDNA gene. The inter-specific polymorphism was more than 20-times greater than the intra-specific polymorphism of 3 D. reticulatus strains of different geographic origins. Furthermore, the degree of polymorphisms between D. reticulatus and D. marginatus was found to be of the same order of magnitude as that between D. andersoni and D. variabilis, for which separate species status is accepted. These genomic findings do not support a possible conspecificity of D. reticulatus and D. marginatus.

Genetic evidence suggests that Psoroptes isolates of different phenotypes, hosts and geographic origins are conspecific.

The second internal transcribed spacer of the rRNA gene was characterised in 15 Psoroptes isolates collected from the ears or bodies of rabbits, goats, sheep and cattle originating from four continents. Morphologically, the isolates were differentiated as Psoroptes cuniculi, Psoroptes ovis and Psoroptes cervinus. Genotypically, the isolates were highly homogeneous, except for the existence of different rDNA classes. In view of previous phenotypic data, a possible conspecificity of these species is proposed.

Molecular analyses suggest monospecificity of the genus Sarcoptes (Acari: Sarcoptidae).

To clarify the taxonomic status of mites of the genus Sarcoptes, the second internal transcribed spacer (ITS-2) of the rRNA gene, as well as phenotypic characters, were investigated in 23 isolates from nine host species in four continents. Phenotypic differences among isolates were observed, but the range of variation within each isolate precluded the differentiation of individual mites. Genotypically, there was no delimitation between distinct genotypic groups and no correlation with host species or geographic origin was evident. These results support the conspecificity of the mites investigated and confirm the view that the genus Sarcoptes consists of a single, heterogenous species.

The mutagenicity of chloroethylene oxide, chloroacetaldehyde, 2-chloroethanol and chloroacetic acid, conceivable metabolites of vinyl chloride.

Previous investigations have shown that the carcinogen vinyl chloride causes base-pair substitution in the bacterium Salmonella typhimurium. The ability of four conceivable metabolites-chloroethylene oxide, chloroacetaldehyde, 2-chloroethanol and chloroacetic acid-to cause base-pair substitution directly in Salmonella typhimurium TA1535 has been compared. The main comparison was performed at initial concentrations from 0.1 to 1.5 mM. In this region, however, a mutagenic effect was observed only with chloroethylene oxide and chloroacetaldehyde, the former being approximately 20 times more effective than the aldehyde when compared on a molar basis.2-Chloroethanol and chloroacetic acid were studied also at higher concentration (1 mM-1 M), and a weak mutagenic response was found with 1 M 2-chloroethanol solution. With chloroacetic acid no enhancement of the mutation frequency could be detected. Chloroethylene oxide was found to be approximately 450 times more effective as a mutagen than chloroacetaldehyde when the comparison is based on exposure doses, defined as the time-dependent concentrations of the compounds in the treatment solutions, integrated between the times of onset and termination of treatment. Similarly, chloroethylene oxide was 10,000-15,000 times more effective as a mutagen than ethylene oxide, used as a positive control.

The life cycle of Argas (Argas) africolumbae under constant abiotic and biotic conditions.

The developmental and reproduction pattern as well as the nondiapause behaviour of Argas (Argas) africolumbae, reared on domestic chickens and held at 27 degrees C and 90% RH, indicate that there may be 2-3 generations annually. The minimum incubation period of eggs requires 16.2 days (mean), irrespective of the day of oviposition. Larvae feed for 5-6 days and moult 10.2 days after detaching to N1. Generally, there are only 2 nymphal instars. All N1 develop to N2 13.7 days after feeding. After repletion, N2 moult to males and females within 28.3 days with a ratio of 1.12:1.0. Female determined N1 and N2 are always heavier (1.13 mg and 3.81 mg, respectively) and imbibe larger bloodmeals (4.19 mg and 17.45 mg, respectively) than male N1 and N2 (0.9 mg and 2.71 mg unfed weight and 3.04 mg and 12.33 mg bloodmeal size, respectively). Fed females begin to oviposit 9.5 days after engorgement and produce 102.9 eggs during a 14-day oviposition period.

Eimeria infections of sheep in northwest Germany.

To investigate the incidence of ovine Eimeria spp. and seasonal dynamics in oocyst output, fecal samples of sheep from three different management systems were collected monthly over a 1-year period and examined for oocysts. A total of 10 species of Eimeria were observed. The most frequent species were E. bakuensis, E. ovinoidalis, E. weybridgensis/crandallis, E. parva and E. ahsata whereas E. faurei, E. granulosa, E. intricata and E. pallida were found less often. Lambs passed larger numbers of oocysts in their feces than either ewes or yearlings.

Detection of a new pathogenic Babesia microti-like species in dogs.

Small babesiae in dogs are generally considered to belong to Babesia gibsoni. Here we describe the genotypic characterisation of small piroplasms found in the blood of a dog which suffered from clinical babesiosis. Pairwise identities as well as distance, parsimony and maximum likelihood analyses of the 18S rDNA clearly demonstrated that this isolate was only distantly related to the other canine piroplasms characterised genetically so far, including B. gibsoni. It was more closely related to B. microti, B. rodhaini, and Theileria equi. It is concluded that the small canine piroplasms described in this study represent a hitherto unknown species and that the fauna of piroplasms occurring in dogs is more diverse than assumed so far.

Relationships between species of the Rhipicephalus sanguineus group: a molecular approach.

The biosystematic status of species belonging to the Rhipicephalus sanguineus group is difficult to determine by phenotypic methods and has been subject to frequent revisions and ongoing debate. Yet, the differentiation of species within this complex is of clinical importance especially in veterinary medicine due to different host specificities of the transmitted pathogens. In order to generate quantifiable and comparable data independent of environmental influences, a section of the second internal transcribed spacer (ITS2) of the rRNA gene was sequenced for 6 species belonging to the Rhipicephalus sanguineus complex: Rhipicephalus sanguineus sensu stricto, R. turanicus, R. rossicus, R. pumilio, R. pusillus, and R. camicasi. Rhipicephalus sanguineus s. str. and R. turanicus as well as R. pumilio and R. rossicus were found to have a close genetic relationship compatible with possible conspecificities. Conversely, R. pusillus was found to have the most distant relationship to the other species.

Close genotypic relationship between Enterocytozoon bieneusi from humans and pigs and first detection in cattle.

The reservoirs and the routes of transmission of Enterocytozoon bieneusi are still unknown. In humans, it is the most commonly found microsporidial species. It has also been found repeatedly in pigs, too. The first detection of E. bieneusi in cattle is reported herein. Two distinct genotypes were characterized and compared with 4 other genotypes from humans, 6 from pigs, and 1 from a cat. From these 13 E. bieneusi genotypes known to date, 25 polymorphic sites could be identified in the internal transcribed spacer of the rRNA gene. The spectrum of polymorphisms within and between each of the 4 host species indicates a close relationship between E. bieneusi strains from humans and pigs, whereas those from cattle are more distantly related. The data suggest the absence of a transmission barrier between pigs and humans for this pathogen.

Isolation of a neurotoxin from the salivary glands of female Rhipicephalus evertsi evertsi.

A quantitative study of the changes in the protein pattern of the salivary glands of female Rhipicephalus evertsi evertsi during the entire repletion process was undertaken. These results, in conjunction with the previously determined toxic phase, indicated the presence of a toxic protein. The development of a sensitive in vitro assay using a Xenopus nerve-muscle preparation, made it possible to identify toxic phases during feeding and to assay fractions of salivary gland extracts during toxin isolation. Sufficient amounts of electrophoretically and chromatographically homogeneous toxin could be obtained through the use of chromatofocusing, enabling its characterization with respect to molecular weight (68 kDa; determined by gel permeation chromatography), pI (6.00), and amino acid composition. The toxin was inactivated by pronase digestion as well as by antiserum.

Tick pheromones.

According to their activity profiles tick pheromones can be characterized as assembly pheromones, aggregation/attachment pheromones, pre-attachment or pre-feeding pheromones, attractant sex pheromones, contact sex pheromones, fecundity-reducing pheromone and various ungrouped pheromones. This paper gives a short review of the chemical characteristics, biological roles, and activity periods as well as the sites of production and release of tick pheromones.

Studies on the critical water mass, rehydration capability and potential, acute chill tolerance and supercooling point of Argas (Persicargas) walkerae (Acari: Argasidae).

The critical water mass, defined as the water mass remaining in a dehydrated tick in the non-ambulatory state, differed only slightly between light and heavy mass groups of Argas walkerae and averaged 23.6% and 23.2%, respectively, in males and 28.4% and 28.0%, respectively, in females. All ticks survived dehydration to 50%, 75% or 100% of their critical water mass, and 95% of them rehydrated during their subsequent incubation at 95% relative humidity (RH) and 28 degrees C for 14 days and regained their ambulatory status. Unfed adults were able to balance water loss frequently over a period of several months. When ticks were repeatedly dehydrated at 0% RH for 14 days, females and males suffered 50% mortality after 16 and 19 cycles of de- and rehydration, respectively, over a period of 278 days and 337 days, respectively. Water itself was not attractive to either dehydrated or non-dehydrated ticks and drinking was not observed. After submergence in water for 3 days, most of the dehydrated adult ticks gained mass. Judged by 50% mortality, larvae tolerated short-term extreme chilling to -24 degrees C, nymphs 1 to -22 degrees C, nymphs II to -20 degrees C, females and males to -19 degrees C. None survived tissue freezing. At a chilling rate of 0.3 degrees C/min, mean supercooling points (SCP) ranged from -25.9 degrees C in eggs to -16.5 degrees C in unfed females. The SCP of all other stages was significantly higher than that of eggs. Mean SCPs of unfed adult ticks dehydrated to 50% or 75% of their critical water mass were significantly lower than that of fully hydrated ticks. The SCPs of ticks acclimated by several weeks exposure to 0 degrees C or to 38 degrees C were significantly lower than those of adult ticks kept constantly at 28 degrees C.

Studies on the ability of different strains or populations of female Rhipicephalus evertsi evertsi (Acarina:Ixodidae) to produce paralysis in sheep.

Simultaneous infestation of 3-6 month-old Black-head sheep with 15 South African wild strains of Rhipicephalus evertsi evertsi males and females as well as a strain from Rwanda clearly showed that all strains are capable of inducing paralysis. Assessment of the infestation-rate of engorging female ticks during the period that their mass ranged between 15 and 21 mg/kg sheep body mass indicated that toxicity is quantitatively identical and exhibits no intraspecific gradations. The period between the beginning of infestation to the manifestation of the first clinical symptoms is, however, strain dependent: 4 days for ticks from Warmbaths, and at least 5 days for all other strains.

Investigations into the volatility of female pheromones and the aggregation-inducing property of guanine in Argas (Persicargas) walkerae.

During investigations into the volatility of female pheromones of A. walkerae in a Y-shaped olfactometer, engorged conspecific male ticks responded weakly both to female-contacted filter paper discs and to intact females enclosed in nylon bags. In tests in which female-contacted filter paper discs were separated from engorged male ticks by means of a screen, no aggregation was observed. However, replete male ticks showed a vigorous response to liquefied air and hexane-trapped volatiles collected from intact females. Guanine showed a potent aggregation attraction for engorged and unfed larvae and 1st and 2nd stage nymphal ticks as well as for male and female imagines of A. walkerae over a wide concentration range. It is concluded that at least 2 pheromones, 1 volatile and 1 non-volatile, are operative in the communication system of this tick species.

Investigation into the participation of male pheromones of Rhipicephalus evertsi evertsi during infestation.

It was shown in this study that Rhipicephalus evertsi evertsi males emit pheromones in the preparasitic as well as in the parasitic phases. Conspecific unengorged male and female images exhibited a high response to water-soluble volatiles collected from unengorged males. A vigorous assembly of unfed female R. evertsi evertsi occurred on filter paper discs which had been in contact with either unfed or 5- and 9-day fed males. Progressively increasing percentages of conspecific unengorged males reacted to organic soluble volatiles obtained from 5- and 9-day fed males as well as to hexane washings of intact males which had fed for 9 days. It is concluded that R. evertsi evertsi males participate not only as pheromone receptive, but also as pheromone emitting, partners in the intraspecific communication of this tick species.

An investigation into the emission sites of the volatile pheromone produced by females of Argas (Persicargas) walkerae.

By leaving open in turn the genital orifice, coxal apertures and anus, the present study has shown that engorged female Argas walkerae release at least 1 volatile pheromone mainly, or maybe exclusively, from the genital aperture. Although this aggregation-inducing pheromone is perceived by all post-larval stages, engorged males of A. walkerae react most strongly. A possible, but only slight, emission through the anus and the coxal aperatures is also indicated. Most probably, this airborne biosubstance is the primary directing and orienting pheromone in the interrelations between members of this tick species.