Untersuchungen an Salamanderlarven über das Regenerationsvermögen der Urniere und ihre Anpassungsveränderungen nach partieller Ektomie

Ohne ZusammenfassungD 7.     

Trehalose preserves DDA/TDB liposomes and their adjuvant effect during freeze-drying

Disaccharides are well-known reagents to protect biostructures like proteins and phospholipid-based liposomes during freezing and drying. We have investigated the ability of the two disaccharides trehalose and sucrose to stabilize a novel, non-phospholipid-based liposomal adjuvant composed of the cationic dimethyldioctadecylammonium (DDA) and trehalose 6,6′-dibehenate (TDB) upon freeze-drying. The liposomes were freeze-dried using a human dose concentration containing 2.5 mg/ml DDA and 0.5 mg/ml TDB with varying concentrations of the two sugars. The influence on particle size upon rehydration was investigated using photon correlation spectroscopy (PCS) and the gel to fluid phase transition was examined by differential scanning calorimetry (DSC). Data revealed that concentrations above 211 mM trehalose protected and preserved DDA/TDB during freeze-drying, and the liposomes were readily rehydrated. Sucrose was less efficient as a stabilizer and had to be used in concentrations above 396 mM in order to obtain the same effect. Immunization of mice with the tuberculosis vaccine candidate Ag85B-ESAT-6 in combination with the trehalose stabilized adjuvant showed that freeze-dried DDA/TDB liposomes retained their ability to stimulate both a strong cell-mediated immune response and an antibody response. These findings show that trehalose at isotonic concentrations protects cationic DDA/TDB-liposomes during freeze-drying. Since this is not the case for liposomes based on DDA solely, we suggest that the protection is facilitated via direct interaction with the headgroup of TDB and a kosmotropic effect, whereas direct interaction with DDA plays a minor role.     

Bacteriophage-mediated interference of the c-di-GMP signalling pathway in Pseudomonas aeruginosa

C-di-GMP is a key signalling molecule which impacts bacterial motility and biofilm formation and is formed by the condensation of two GTP molecules by a diguanylate cyclase. We here describe the identification and characterization of a family of bacteriophage-encoded peptides that directly impact c-di-GMP signalling in Pseudomonas aeruginosa. These phage proteins target Pseudomonas diguanylate cyclase YfiN by direct protein interaction (termed YIPs, YfiN Interacting Peptides). YIPs induce an increase of c-di-GMP production in the host cell, resulting in a decrease in motility and an increase in biofilm mass in P. aeruginosa. A dynamic analysis of the biofilm morphology indicates a denser biofilm structure after induction of the phage protein. This intracellular signalling interference strategy by a lytic phage constitutes an unexplored phage-based mechanism of metabolic regulation and could potentially serve as inspiration for the development of molecules that interfere with biofilm formation in P. aeruginosa and other pathogens.     

Comparative support for the expensive tissue hypothesis: Big brains are correlated with smaller gut and greater parental investment in Lake Tanganyika cichlids

The brain is one of the most energetically expensive organs in the vertebrate body. Consequently, the energetic requirements of encephalization are suggested to impose considerable constraints on brain size evolution. Three main hypotheses concerning how energetic constraints might affect brain evolution predict covariation between brain investment and (1) investment into other costly tissues, (2) overall metabolic rate, and (3) reproductive investment. To date, these hypotheses have mainly been tested in homeothermic animals and the existing data are inconclusive. However, there are good reasons to believe that energetic limitations might play a role in large-scale patterns of brain size evolution also in ectothermic vertebrates. Here, we test these hypotheses in a group of ectothermic vertebrates, the Lake Tanganyika cichlid fishes. After controlling for the effect of shared ancestry and confounding ecological variables, we find a negative association between brain size and gut size. Furthermore, we find that the evolution of a larger brain is accompanied by increased reproductive investment into egg size and parental care. Our results indicate that the energetic costs of encephalization may be an important general factor involved in the evolution of brain size also in ectothermic vertebrates.     

Maximal oxygen deficit of sprint and middle distance runners

Anaerobic energy capacity was evaluated by maximal oxygen deficit (MOD) as well as by blood gas and muscle biopsy variables during short exhausting running in six recreational (RR) and eight competitive sprint and middle distance runners (SMDR). On 3 days runs to exhaustion were executed. Two runs were performed at a treadmill gradient of 15% at speeds which resulted in exhaustion after approximately 1 (R_{15%, 1min}) and 2–3 min (R_{15%, 2–3min}), respectively. On the 3rd day, the subjects ran with the treadmill at a gradient of 1% at a speed which caused exhaustion after 2–3 min (R_{1%, 2–3min}). The runner performance was assessed from 400 m [RR, median 64.8 (range 62.2–69.6) s; SMDR, median 49.4 (range 48.5–52.0) s] and 800 m [RR, median 158.8 (range 153.3–170.2) s; SMDR, median 115.2 (range 113.3–123.3) s] track times. Muscle biopsies from gastrocnemius muscle were obtained before and immediately after R_{15%, 2–3min}, from which muscle lactate and creatine phosphate (CP) concentrations, fibre type distribution, capillaries per fibre, total lactate dehydrogenase (LDH) activity and the LDH isoenzyme pattern were determined. The MOD increased with the treadmill gradient and duration. During both treadmill and track runs, SMDR performance was superior to that of RR, but no significant differences were observed with respect to MOD, muscle fibre type distribution, total LDH activity, its iso-enzyme pattern, changes in muscle lactate or CP concentrations. However, after treadmill runs, peak venous lactate concentration and partial pressures of carbon dioxide were higher, and pH lower in SMDR. Also the number of capillaries per muscle fibre and the maximal oxygen uptake were larger in SMDR. These findings would suggest that the superior performance of SMDR depended more on their aerobic than on their anaerobic capacity.     

Reduced use of antimicrobials after vaccination of pigs against porcine proliferative enteropathy in a Danish SPF herd

The present study explored whether the use of group medication with antibiotics in a Danish pig herd was reduced after vaccination of the pigs against proliferative enteropathy (PE) caused by Lawsonia intracellularis. 7900 pigs originating from a single commercial sow herd were vaccinated against L. intracellularis, whereas 7756 pigs were kept as non-vaccinated controls. The pigs were included batch-wise in the study with every second batch being vaccinated. In the vaccinated batches, the consumption of oxytetracykline to treat PE was reduced by 79%, with a significantly lower number of pigs being treated (P < 0.0001). Vaccination also resulted in a highly significant improvement of average daily weight gain (+ 46 g/day; P = 9.55 × 10^-31) and carcase weight (+ 1.25 kg; P = 4.54 × 10^-05) as well as a shortened fattening period (-8 days; P = 2.01 × 10^-45).     

Dissection of Francisella-Host Cell Interactions in Dictyostelium discoideum

Francisella bacteria cause severe disease in both vertebrates and invertebrates and include one of the most infectious human pathogens. Mammalian cell lines have mainly been used to study the mechanisms by which Francisella manipulates its host to replicate within a large variety of hosts and cell types, including macrophages. Here, we describe the establishment of a genetically and biochemically tractable infection model: the amoeba Dictyostelium discoideum combined with the fish pathogen Francisella noatunensis subsp. noatunensis. Phagocytosed F. noatunensis subsp. noatunensis interacts with the endosomal pathway and escapes further phagosomal maturation by translocating into the host cell cytosol. F. noatunensis subsp. noatunensis lacking IglC, a known virulence determinant required for Francisella intracellular replication, follows the normal phagosomal maturation and does not grow in Dictyostelium. The attenuation of the F. noatunensis subsp. noatunensis ΔiglC mutant was confirmed in a zebrafish embryo model, where growth of F. noatunensis subsp. noatunensis ΔiglC was restricted. In Dictyostelium, F. noatunensis subsp. noatunensis interacts with the autophagic machinery. The intracellular bacteria colocalize with autophagic markers, and when autophagy is impaired (Dictyostelium Δatg1), F. noatunensis subsp. noatunensis accumulates within Dictyostelium cells. Altogether, the Dictyostelium-F. noatunensis subsp. noatunensis infection model recapitulates the course of infection described in other host systems. The genetic and biochemical tractability of the system allows new approaches to elucidate the dynamic interactions between pathogenic Francisella and its host organism.