Detecting long-range interactions between migrating cells.

Chemotaxis enables cells to systematically approach distant targets that emit a diffusible guiding substance. However, the visual observation of an encounter between a cell and a target does not necessarily indicate the presence of a chemotactic approach mechanism, as even a blindly migrating cell can come across a target by chance. To distinguish between the chemotactic approach and blind migration, we present an objective method that is based on the analysis of time-lapse recorded cell migration trajectories: For each movement step of a cell relative to the position of a potential target, we compute a p value that quantifies the likelihood of the movement direction under the null-hypothesis of blind migration. The resulting distribution of p values, pooled over all recorded cell trajectories, is then compared to an ensemble of reference distributions in which the positions of targets are randomized. First, we validate our method with simulated data, demonstrating that it reliably detects the presence or absence of remote cell-cell interactions. In a second step, we apply the method to data from three-dimensional collagen gels, interspersed with highly migratory natural killer (NK) cells that were derived from two different human donors. We find for one of the donors an attractive interaction between the NK cells, pointing to a cooperative behavior of these immune cells. When adding nearly stationary K562 tumor cells to the system, we find a repulsive interaction between K562 and NK cells for one of the donors. By contrast, we find attractive interactions between NK cells and an IL-15-secreting variant of K562 tumor cells. We therefore speculate that NK cells find wild-type tumor cells only by chance, but are programmed to leave a target quickly after a close encounter. We provide a freely available Python implementation of our p value method that can serve as a general tool for detecting long-range interactions in collective systems of self-driven agents.

Differentiation of Pasteurella multocida subspecies multocida isolates from the respiratory system of pigs by using polymerase chain reaction fingerprinting technique.

PCR fingerprinting technique was applied to subtype 44 Pasteurella multocida subspecies multocida (P.m.sp.m.) isolates from the respiratory system of pigs. Two single primers were tested for their abilities to generate individual fingerprints by using PCR. Primer 1 (core sequence of the M13 phage) grouped the 44 P.m.sp.m. strains into five distinct fingerprinting profiles, while primer 2 ((GACA)4) grouped them into seven profiles. The results suggest that PCR fingerprinting is an efficient technique to detect DNA polymorphism in the species P.m.sp.m. This technique could be used to differentiate P.m.sp.m. strains of the same capsular serotype.

[Electron microscopic detection of spirochetes in dermatitis digitalis of cattle]. / Zum elektronenmikroskopischen Spirochäten-Nachweis bei der Dermatitis digitalis des Rindes.

In typical Dermatitis digitalis (D.d.) lesions, spirochaete-like bacteria with variations in spiralization were revealed by electron microscopy. While, in the early stages of the disease, these are found to be associated with fibrillar material of keratocytes, they occur massively in vacuoles at more advanced stages. The spirochaetes carry one pair of endoflagella, originating with a hook from the poles of the bacteria. These flagellae are composed of coiled flagellating fibrils in the pole region, merging towards the centre of the bacterium. A coat of fibrils was found in association with the cytoplasmatic membrane. The winding of this coat follows and may influence the coiling of the protoplast, and is probably involved in the rapid motility of this spirochaetes, together with the flagella. Immuno-electronmicroscopy revealed an antigenic relationship with Borrelia burgdorferi, at least with regard to the regions of flagella and undulating membrane. The paper discusses: 1. The possible classification of these spirochaetes with the genus Treponema; 2. The layer of peptidoglycan occurring on the outer membrane; and 3. The keratolytic activity of spirochaetes in D.d.

[The lipopolysaccharide structure of Haemophilus parasuis strains in SDS-PAGE]. / Untersuchungen zur Lipopolysaccharidstruktur von Haemophilus parasuis-Stämmen in der SDS-PAGE.

The LPS patterns of 231 H.p. strains were studied by using SDS-PAGE. The strains were isolated from the nasal mucous membrane of clinical healthy animals, from animals with GK and from animals with pneumonia without any symptoms of GK. The LPS patterns of H.p. strains consists of 2 to 4 bands of high electrophoretical mobility. In all it was possible to distinguish seven different LPS electrophoretic profiles. The distribution of the H.p. isolates from clinically healthy animals and animals with GK or pneumonia to the 7 LPS electrophoretic profiles shows a similar picture. Variation in the growth conditions showed a process of a standardization of the LPS structure as a result of an increased CO2 atmosphere or lack of O2 respectively.

[Detection of atypical toxin-producing Pasteurella strains on the nasal mucosa of calves and their differential diagnostic limits for Pasteurella haemolytica and Pasteurella multocida]. / Nachweis atypischer toxinbildender Pasteurella-Stämme auf der Nasenschleimhaut von Kälbern und ihre differentialdiagnostische Abgrenzung zu Pasteurella haemolytica und Pasteurella multocida.

The bacterial colonisation on nasal mucous membranes of calves at age of 3, 5 to 5 months was investigated by cotton swabs. Three Pasteurella species were found (P. multocida subspecies multocida, P. haemolytica, P. avium) as monocausal infection as well as pluricausal infection. P. avium was characterised by colonial morphology, bacterioscopy, biochemical properties, polypeptide-pattern in SDS-PAGE and by electronmicroscopic investigation and was differentiated from P. multocida and P. haemolytica. It is very interesting, that the P. avium strains possess an antigen structure, reacting with monoclonal antibodies directed against the heat labile-toxin of P. multocida subspecies multocida.

[Infection model for the reproduction of eperythrozoonosis in splenectomized SPF primary piglets]. / Beitrag zum Infektionsmodell zur Reproduktion der Eperythrozoonose bei splenektomierten SPF-Primär-Ferkeln.

Reported in this paper is an infection experiment in which whole blood infected with Eperythrozoon (Ep.) suis was applied to bacterioscopically Ep. suis negative SPF primary piglets for the purpose of doubtless diagnosis of eperythrozoonosis (EEZ) of swine. EEZ could thus be clinically, bacterioscopically, haematologically, biochemically, pathologico-anatomically, and histologically reproduced. Such experimental infection, on top of splenectomy of EEZ-suspicious store pigs, was found to be an additional step for adequate diagnosis on the basis of animal experiments. Immediate and reliable diagnosis of EEZ was found to be generally possible solely by clinical, bacterioscopic, and haematological examinations.

[The differentiation of Bordetella (B.) bronchiseptica strains. 8. The protective behavior of B. bronchiseptica strains in mice in relation to the loss of K factors]. / Untersuchungen zur Differenzierung von Bordetella-(B.-)bronchiseptica-Stämmen. 8. Mitteilung: Untersuchungen zum protektiven Verhalten von B.-bronchiseptica-Stämmen bei Mäusen in Beziehung zum Verlust der K-Faktoren.

K factors are phase-dependent, instable antigen components of B. bronchiseptica. Loss of K factors was induced by passaging on 10% horse blood agar. All K factors were not simultaneously eliminated. Cultures obtained from various passages were checked on white mice by Lienotox testing and in protectivity experiments. Culturing of B. bronchiseptica on 10% horse blood agar in Phase I probably had an adverse impact on expression of virulence-dependent factors. K factor expression in B. bronchiseptica was found to depend on both phase condition and culturing medium.

[The reproduction of eperythrozoonosis of swine by animal experiments after splenectomy]. / Reproduktion der Eperythrozoonose des Schweines mittels Tierversuchs nach Splenektomie.

An account is given in this paper of equipment, techniques, clinical tests, and investigations for laboratory diagnosis required for an animal experiment on splenectomised store pigs suspicious of eperythrozoonosis (EEZ). The clinical, bacterioscopic, haematological, and biochemical data recorded from the experiment on splenectomised store pigs with suspicion of EEZ were helpful in reproducing both symptoms indicative of EEZ and relevant parameters of laboratory diagnosis. The diagnosis of EEZ, made in the first place on the basis of clinical, bacterioscopic, and haematological findings, was thus confirmed. Conclusions of general validity for users of animal experiments for EEZ diagnosis were also drawn and will prove helpful in establishing safe diagnosis in dubious cases. The animal experiment proved useful in following up the interactions between all parameters checked, which will contribute, no doubt, to better understanding of the pathophysiological processes associated with this disease.

[Brucella titers in swine caused by Yersinia enterocolitica, serotype 0:9]. / Brucellatiter beim Schwein, hervorgerufen durch Yersinia enterocolitica Serotyp 0:9.

Antibody to Brucella abortus developed in two thirds of all gilts kept on a pig breeding station. Systematic tests taken for the purpose of detecting clinical symptoms and of isolating Brucella were negative. however, Yersinia (Y.) enterocolitica, Serotype 0:9, was cultured from rectal swab samples which had been obtained from 31 to 78 gilts. The clinical, bacteriological, and serological tests gave rise to the assumption that the Brucella titres have been caused by Yersinia enterocolitica infection. Such conclusion, however, could be drawn only as a result of a complex investigation. Detection of Yersinia enterocolitica alone is not sufficient a proof by which to rule out the possibility of concomitant Brucella infection. The question is discussed to what extent swine may be considered to be a potential source of infection of man.

[Reproduction of Brucella titers in swine using experimental infection with Yersinia enterocolitica, serotypes 0:9 and 0:6]. / Reproduktion von Brucellatitern beim Schwein mittels experimenteller Infektion mit den Yersinia-enterocolitica-Serotypen 0:9 und 0:6.

Measurable Brucella titres were produced by slow agglutination, slow agglutination at 57 degrees C (heat test), and complement fixation reaction with Brucella antigen in infection experiments with gilts in which Yersinia enterocolitica Serotypes 0:9 and 0:6 were used. Slow agglutination gave brucellosis titres up to 1:1280 and titres against Yersinia enterocolitica, Serotype 0:9, up to 1:20480. The antibody titres stayed persistent throughout the 80 days of the experiment. Yersinia enterocolitica infection was found to be transmissible between the animals. Aspects relating to the development and course of the infection as well as to pathogen detection are discussed.