Survey of the crayfish plague pathogen presence in the Netherlands reveals a new Aphanomyces astaci carrier.

North American crayfish species as hosts for the crayfish plague pathogen Aphanomyces astaci contribute to the decline of native European crayfish populations. At least six American crayfish species have been reported in the Netherlands but the presence of this pathogenic oomycete with substantial conservational impact has not yet been confirmed in the country. We evaluated A. astaci prevalence in Dutch populations of six alien crustaceans using species-specific quantitative PCR. These included three confirmed crayfish carriers (Orconectes limosus, Pacifastacus leniusculus, Procambarus clarkii), two recently introduced but yet unstudied crayfish (Orconectes cf. virilis, Procambarus cf. acutus), and a catadromous crab Eriocheir sinensis. Moderate levels of infection were observed in some populations of O. limosus and P. leniusculus. Positive results were also obtained for E. sinensis and two Dutch populations of O. cf. virilis. English population of the latter species was also found infected, confirming this taxon as another A. astaci carrier in European waters. In contrast, Dutch P. clarkii seem only sporadically infected, and the pathogen was not yet detected in P. cf. acutus. Our study is the first confirmation of crayfish plague infections in the Netherlands and demonstrates substantial variation in A. astaci prevalence among potential hosts within a single region, a pattern possibly linked to their introduction history and coexistence.

Dynamic training of skeletal muscle ventricles. A method to increase muscular power for cardiac assistance.

BACKGROUND: Skeletal muscle can be used for cardiac assistance after electrical stimulation over a period of several weeks. This will adapt it to do chronic work with no resulting fatigue. The result of this procedure, however, is a reduction of 80% in muscle power, > 60% in muscle mass, and approximately 85% in contractile speed. To minimize these disadvantages, the following study was done to develop and test a method to dynamically train skeletal muscle ventricles (SMVs). METHODS AND RESULTS: Barrel-shaped SMVs were tested in 15 Jersey calves. They were made from the latissimus dorsi muscle, which was wrapped around an elastic silicone training device. Six SMVs were used extrathoracically in a single layer and nine intrathoracically in a double layer. With dynamic training preserving contractile speed, the output increased to approximately 5 L/min, the systolic pressure increased to > 200 mm Hg, and power developed to approximately 10 W after 3 months of dynamic training. The contractile speed of dynamically trained SMVs was between 250 and 700 mm/s. The diameter of the latissimus dorsi muscle increased to three times that of the corresponding contralateral muscle. CONCLUSIONS: The combination of electrical conditioning with dynamic training of the SMVs resulted in a strong muscle pump that did not develop fatigue. Dynamic training for skeletal muscle represents a new and promising method for providing powerful autologous cardiac assist.

Development and training of skeletal muscle ventricles with low preload.

One-layered skeletal muscle ventricles (SMV) were constructed from latissimus dorsi (LD) muscles extrathoracally in six calves and trained under electrical stimulation on totally implanted mock circulation systems. These ventricles had low preloads of about 5 mmHg. The results showed that training against a resistance similar to the human aorta does not create an effective blood pump. But conditioning against a highly complaint workload makes them six times more effective. Therefore, further research on this observation is mandatory. After a conditioning of 16 to 63 days, all implanted mock circulations became infected due to perforated skin, so these experiments had to be terminated. To avoid these infections, we developed and tested an intrathoracic implantable mock circulation system with a highly compliant workload. With a double-layered muscle pump, systolic pressure 120-140 mmHg was generated and an output of more than 31/min was obtained. SMVs with a low end-diastolic pressure seem to be suitable for construction of an effective blood pump between the left atrium and the aorta as a left heart assist device.