The embryonic cell lineage of the nematode Halicephalobus gingivalis (Nematoda: Cephalobina: Panagrolaimoidea)

A

Stem Cells Propagate Their DNA by Random Segregation in the Flatworm Macrostomum lignano

Adult stem cells are proposed to have acquired special features to prevent an accumulation of DNA-replication errors. Two such mechanisms, frequently suggested to serve this goal are cellular quiescence, and non-random segregation of DNA strands during stem cell division, a theory designated as the immortal strand hypothesis. To date, it has been difficult to test the in vivo relevance of both mechanisms in stem cell systems. It has been shown that in the flatworm Macrostomum lignano pluripotent stem cells (neoblasts) are present in adult animals. We sought to address by which means M. lignano neoblasts protect themselves against the accumulation of genomic errors, by studying the exact mode of DNA-segregation during their division

Measurement of S-phase duration of adult stem cells in the flatworm Macrostomum lignano by double replication labelling and quantitative colocalization analysis

Platyhelminthes are highly attractive models for addressing fundamental aspects of stem cell biology in vivo. These organisms possess a unique stem cell system comprised of neoblasts that are the only proliferating cells during adulthood. We have investigated T-s (S-phase duration) of neoblasts during homoeostasis and regeneration in the flatworm, Macrostomum lignano. A double immunohistochemical technique was used, performing sequential pulses with the thymidine analogues CldU (chlorodeoxyuridine) and IdU (iododeoxyuridine), separated by variable chase times in the presence of colchicine. Owing to the localized nature of the fluorescent signals (cell nuclei) and variable levels of autofluorescence, standard intensity-based colocalization analyses could not be applied to accurately determine the colocalization. Therefore, an object-based colocalization approach was devised to score the relative number of double-positive cells. Using this approach, T-s (S-phase duration) in the main population of neoblasts was similar to 13 h. During early regeneration, no significant change in T-s was observed

Different levels of anthelmintic resistance in the facultative parasitic nematode Halicephalobus gingivalis

In recent years many studies have proven that most equine parasites have some form of resistance to all main classes of anthelmintic drugs. However, studies on anthelmintic resistance in equine parasites only include obligatory parasites, not facultative parasites. Halicephalobus gingivalis is a free-living bacteriovorous nematode and a known facultative parasite of horses. In all reported infections the horses were regularly treated with common anthelmintics, strongly indicating the possibility that H. gingivalis has some form of resistance to these anthelmintic drugs. We present the results of an in vitro study on the resistance of several isolates of H. gingivalis, both free-living and parasitic. All were tested in vitro for the extent of their resistance to two different anthelmintic drugs, ivermectine and thiabendazole, using an adaptation of the micro-agar larval development test and focusing on egg hatching and larval development. Main conclusion is that the anthelmintic resistance of H. gingivalis was considerably higher than that of closely related panagrolaimid nematode species, with the parasitic isolates having a higher resistance than the free-living ones

Anthelmintic resistance in facultative parasitic nematodes: different levels of resistance in free-living and parasitic isolates of Halicephalobus gingivalis (Panagrolaimidae)

In recent years many studies have proved that most equine parasites have some form of resistance to all main classes of anthelmintic drugs. However, studies on anthelmintic resistance in equine parasites only include obligatory parasites, not facultative parasites. Halicephalobus gingivalis is a free-living bacteriovorous nematode and a known facultative parasite of horses. In all reported infections the horses were regularly treated with common anthelmintics, strongly indicating the possibility that H. gingivalis has some form of resistance to these anthelmintic drugs. We present the results of an in vitro study on the resistance of several isolates of H. gingivalis, both free-living and parasitic. All were tested in vitro for the extent of their resistance to two different anthelmintic drugs, ivermectine and thiabendazole, using an adaptation of the micro-agar larval development test and focusing on egg hatching and larval development. Main conclusion is that the anthelmintic resistance of H. gingivalis was considerably higher than that of closely related panagrolaimid nematode species, with the parasitic isolates having a higher resistance than the free-living ones