Andriy Lytvynets

Novel composite hyaluronan/type I collagen/fibrin scaffold enhances repair of osteochondral defect in rabbit knee.

A new composite scaffold containing type I collagen, hyaluronan, and fibrin was prepared with and without autologous chondrocytes and implanted into a rabbit femoral trochlea. The biophysical properties of the composite scaffold were similar to native cartilage. The macroscopic, histological, and immunohistochemical analysis of the regenerated tissue from cell-seeded scaffolds was performed 6 weeks after the implantation and predominantly showed formation of hyaline cartilage accompanied by production of glycosaminoglycans and type II collagen with minor fibro-cartilage production. Implanted scaffolds without cells healed predominantly as fibro-cartilage, although glycosaminoglycans and type II collagen, which form hyaline cartilage, were also observed. On the other hand, fibro-cartilage or fibrous tissue or both were only formed in the defects without scaffold. The new composite scaffold containing collagen type I, hyaluronan, and fibrin, seeded with autologous chondrocytes and implanted into rabbit femoral trochlea, was found to be highly effective in cartilage repair after only 6 weeks. The new composite scaffold can therefore enhance cartilage regeneration of osteochondral defects, by the supporting of the hyaline cartilage formation.

Fibrin/hyaluronic acid composite hydrogels as appropriate scaffolds for in vivo artificial cartilage implantation.

Hydrogels prepared from a mixture of fibrin and high-molecular weight (MW) hyaluronic acid (HA) were found to be suitable scaffolds for chondrocyte seeding and pig knee cartilage regeneration. Collagen in the hydrogels is not necessary for the formation of biomechanically stable tissue. Regenerated cartilage showed very good biomechanical and histological properties only 6 months after implantation. Notably, the quality of the healing process was dependent on the initial chondrocyte concentration of the scaffolds. These experiments were performed according to good laboratory practice (GLP).

A perivascular system releasing sirolimus prevented intimal hyperplasia in a rabbit model in a medium-term study

The main complication of aortocoronary reconstruction with vein grafts is restenosis in the course of time. The aim was to assess the effect of a periadventitial polyester mesh releasing sirolimus on intimal hyperplasia of autologous grafts. We implanted v. jugularis ext. into a. carotis communis in rabbits. The vein graft was either intact, or was wrapped with a pure polyester mesh, or with a sirolimus-releasing mesh. Three and six weeks after surgery, the veins were subjected to standard histological staining and the thicknesses of the tunica intima, the media and the intima-media complex were measured. Wrapping the vein with a mesh releasing sirolimus or with a pure mesh decreased the thickness of the intima in comparison with a vein graft by 73 ± 11% or 73 ± 8% after 3 weeks, and by 73 ± 9% or 59 ± 12% after 6 weeks, respectively. Sirolimus-releasing meshes reduced the thickness of the media by 65 ± 9% and 20 ± 12% after 3 and 6 weeks. The thickness of the intima-media complex in grafts with sirolimus-releasing meshes decreased by 60 ± 6% and 30 ± 13% in comparison with pure PES meshes, after 3 and 6 weeks, respectively. A periadventitial polyester mesh releasing sirolimus has the potential to become an effective device in preventing vein graft restenosis.

Arrested development of sheep strongyles: onset and resumption under field conditions of Central Europe

Two tracer tests were conducted between August 2004 and March 2007 at an ecological farm in western Bohemia. The first tracer test was performed for the summer–autumn grazing period (onset of arrested development), the second for spring (resumption of arrested development). In the first tracer test, the percentage of nematodes arresting development over the winter months reached 87.7% for Teladorsagia circumcincta, 66.7% for Haemonchus contortus, 89.9% for Nematodirus filicollis, 21.6% for Trichostrongylus axei, and 23.9% for both Trichostrongylus vitrinus and Trichostrongylus colubriformis. None of the arrested larvae were observed with species Cooperia curticei, Nematodirus battus, and Oesophagostomum venulosum. In the second tracer test, a significant increase of adult worms was discovered in March of species T. circumcincta and N. filicollis and Trichostrongylus spp. in February. Redundancy analysis and generalized linear models analyses have confirmed that environmental conditions play a crucial role in hypobiosis of sheep strongyles in the Czech Republic. The analysis of influences of various environmental factors revealed that the number of arrested larvae was negatively influenced by light—day length, sunshine, or daylight decrease (p < 0.01).

The contribution to the epidemiology of gastrointestinal nematodes of sheep with special focus on the survival of infective larvae in winter conditions

Tracer tests conducted over a 3-year period were aimed at measuring the level and species nematode composition of survival on pastures with a special focus on winter months. The survival of infective larvae in chilly conditions is not significantly affected by Trichostrongylus axei, Trichostrongylus colubriformis, Trichostrongylus vitrinus and Chabertia ovina. On the contrary, the number of Teladorsagia circumcincta and Nematodirus filicollis significantly increased in milder winter conditions. The results confirmed an epidemiological strategy of overwintering in the arrested stage for Teladorsagia circumcincta and Nematodirus filicollis; the epidemiological strategy of genus Trichostrongylus used both strategies—in particular the tolerance of free-living stages to cold conditions. Part of the population overwintered in the arrested stage as well.

Linear distribution of nematodes in the gastrointestinal tract of tracer lambs.

Forty-eight tracer lambs were killed in 2004–2007. The abomasum, duodenum, small intestine (jejunum and ileum), colon and caecum were collected and processed for parasites enumeration and identification—mucosal scrapings of both abomasums and intestines were digested. Out of 48 gastrointestinal tracts examined, all were found to be positive for nematode infection. Seventeen species of gastrointestinal nematodes were recovered: Bunostomum trigonocephalum, Cooperia curticei, Haemonchus contortus, Chabertia ovina, Nematodirus battus, Nematodirus filicollis, Oesophagostomum venulosum, Teladorsagia circumcincta, Trichostrongylus axei, Trichostrongylus colubriformis, Trichostrongylus vitrinus, Strongyloides papillosus, Trichuris ovis, Trichuris globulosa, Trichuris skrjabini and Skrjabinema ovis. All species were searched for in the entire gastrointestinal tract. Six species of nematodes were recovered from abnormal sites, naturally in small numbers of lambs as well as in small amounts: Nematodirus battus in the abomasums (6.67% of lambs), N. filicollis in the caecum and in the colon (%4 and 8%, respectively), T. axei in the colon (9.52%), T. colubriformis in the colon (13.89%), T. vitrinus in the caecum (16.67%), in the colon (20.00%) and in the abomasum (3.33%). T. ovis was found in one case in the small intestine.

Detection of pinworm eggs in the dust of laboratory animals breeding facility, in the cages and on the hands of the technicians

Pinworms (Nematoda: Oxyurida) are common contaminants in most laboratory rodent colonies. The aim of the study was to monitor the transmission of Syphacia muris eggs in laboratory rat breeding facilities. Dust in a breeding room was investigated using special grids (free fallout, or through the help suction chamber). Furthermore, the ventilation system, breeding cages and the hands of the laboratory technical staff were examined. In the case of free fallout, the percentage of positive grids increased slightly over time: from 5.5% (after 24 h) to 8.2% (72 h). Similar values were also found when using the suction chamber (7.6%). Many more pinworm eggs were found in samples collected every second month from suction holes of the ventilation system (28.7%). One-half of the samples taken from the breeding cages (before washing) exhibited pinworm eggs (50.8%). Examination of the hands of technical staff showed positive detection in 37.9% of cases. In this study, certain transmission factors (dust, unclean cages and technicians) were proved to be significant in the distribution of pinworm infection in laboratory rodent facilities.

Drinking water ivermectin treatment for eradication of pinworm infections from laboratory rat colonies

SummaryThe effects of ivermectin were studied in laboratory rats naturally infected with the pinworm Syphacia muris. Ivermectin was administered over four 5-days periods in drinking water; the ivermectin dose was 2.5 mg/kg of body weight per day. All the rats were weighed every five days and their ova production was monitored by a cellophane — tape test. Every fifth day six males and six females from the experimental group were euthanized and examined for adult pinworms and larvae. The rats’ health condition, behaviour and consumption of food and water were monitored every day. The aim of this study was to investigate the effectiveness of orally administered ivermectin as a treatment against adult pinworms and their larvae in laboratory rat colonies.

The influence of desiccation and UV radiation on the development and survival of free-living stages of cyathostomins under field and laboratory conditions

SummaryThe present work describing both laboratory and field experiments was performed to assess the effects of desiccation and UV radiation on the development and survival of free-living stages of equine cyathostomins.Cyathostomin larvae in horse faeces did not develop to the infective stage when faecal humidity levels dropped below 23 %, nonetheless solitary preinfective larvae were still recovered after 151 days (humidity 19.5 %). The development to infective stage after remoistening occurred for the last time after 54 days following desiccation.Preinfective stages are susceptible to the effects of the direct desiccation stage. The preinfective larvae were rapidly killed within one minute, the cyathostomin eggs within 5 hours. The numerous normal mobile infective larvae were encountered after 35 days of the desiccated period. The preinfective stage of cyathostomins also showed very little tolerance to direct sun radiation: most eggs were killed by the exposure within 3 hours and the preinfective larvae within 1 hour. The survival of infective larvae was, on the other hand, unaffected by sun radiation after 7 days (P < 0.05). However, desiccated infective larvae were then found to be susceptible to UV radiation, resulting in total mortalities after 5 days.

Peptidases of pinworms Syphacia muris and Passalurus ambiguus

In this first report about pinworms peptidases we primarily characterize peptidases released during in vitro maintenance of two common pinworms of laboratory animals -Syphacia muris and Passalurus ambiguus. The peptidase activity obtained using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed the presence of peptidases from S. muris with a wide range of molecular size (25-110 kDa), which degrades gelatin and mucin at alkaline pH levels. P. ambiguus released serine and aspartyl peptidases degrading gelatin at all tested pH (3, 5, 7, and 9) and at acidic pH Passalurus released aspartyl and cysteine peptidases which are active against mucin.