Impact of toxic cyanobacterial blooms on Eurasian perch (Perca fluviatilis): experimental study and in situ observations in a peri-alpine lake.

Due to the importance of young-of-the-year (YOY) perch in the peri-alpine regions where they are consumed, the microcystin (MC) contamination of YOY perch was analysed both in field (Lake Bourget, France) and experimentally using force-feeding protocols with pure MCs. In-situ, schools of YOY perch present in the epilimnion of the lake were never found in direct contact with the P. rubescens blooms that were present in the metalimnion. However, MCs were detected in the muscles and liver of the fish and were thus assumed to reach YOY perch through dietary routes, particularly via the consumption of MC-containing Daphnia. Force-feeding experiment demonstrates the existence of MC detoxification/excretion processes and suggests that in situ, YOY perch could partly detoxify and excrete ingested MCs, thereby limiting the potential negative effects on perch populations under bloom conditions. However, because of chronic exposure these processes could not allow for the complete elimination of MCs. In both experimental and in situ studies, no histological change was observed in YOY perch, indicating that MC concentrations that occurred in Lake Bourget in 2009 were too low to cause histological damage prone to induce mortality. However, Deoxyribonucleic acid (DNA) damages were observed for both the high and low experimental MC doses, suggesting that similar effects could occur in situ and potentially result in perch population disturbance during cyanobacterial blooms. Our results indicate the presence of MCs in wild perch, the consumption of this species coming from Lake Bourget is not contested but more analyses are needed to quantify the risk.

Fungal rhinosinusitis caused by Scedosporium apiospermum in a cat.

A 3-year-old neutered male Bengal cat with a history of chronic mucopurulent bilateral nasal discharge and sneezing was diagnosed with severe fungal rhinosinusitis. A diagnosis was obtained after computer tomography imaging, histopathological examination and fungal culture. The mold Scedosporium apiospermum was identified as the aetiological agent. To our knowledge, this case is the first description of a rhinitis or sinusitis caused by this agent in a cat. Aggressive surgical debridement combined with topical and systemic antifungal therapy was performed. Unfortunately, the treatment resulted only in a partial remission of signs.

Effects of Madagascar yam extracts, Dioscorea antaly, on embryo-larval development of medaka fish, Oryzias latipes.

The yams edible starchy tubers, are of cultural, economic and nutritional importance in tropical and subtropical regions. The present study concerns the analysis at different levels of Dioscorea antaly toxicity to medaka embryo-larval development. The incubation of medaka fish embryos in a medium containing Dioscorea antaly extract resulted in a dose dependent reduction in survival rate. Survival rates were reduced up to 100% with extract concentrations of 4mg mL(-1). The LD(50) was estimated to be 0.86mg mL(-1)Dioscorea antaly. Anatomopathological studies did not show any caustic effects, irritation to mouth, throat or intestinal tract in surviving embryos but rather an inflammatory reaction in the liver. The data presented in this paper thus extends the use of medaka embryos as a valuable model to analyze the effects of food toxins.

Effects of Rhodocodon madagascariensis extracts on embryo-larval development of medaka fish, Oryzias latipes.

Rhodocodon madagascariensis, also named Urginea mascarenensis, is a malagasy plant belonging to the Hyacinthaceae family. As for the other members of the endemic malagasy genus Rhodocodon, the chemical and toxicological properties of this species have not yet been studied. The present study concerns the analysis of the toxicity of R. madagascariensis to medaka embryo-larval development. The incubation of medaka fish embryos or larvae in a medium containing R. madagascariensis extract resulted in a dose dependent reduction in development of embryos leading to lethality and a drastic reduction in survival rate of exposed larvae. Survival rates were reduced up to 100% with an extract concentration of 4 mg mL(-1). The LD(50) was estimated to be 1 mg mL(-1). Anatomopathological studies did show some neuro-embryonal modifications in the encephalic region. The data presented in this paper thus extends the use of medaka embryos as a valuable model to detect and analyse the effects of plant toxins.

Dendritic cell-mediated-immunization with xenogenic PrP and adenoviral vectors breaks tolerance and prolongs mice survival against experimental scrapie.

In prion diseases, PrP(c), a widely expressed protein, is transformed into a pathogenic form called PrP(Sc), which is in itself infectious. Antibodies directed against PrP(c) have been shown to inhibit PrP(c) to PrP(Sc) conversion in vitro and protect in vivo from disease. Other effectors with potential to eliminate PrPSc-producing cells are cytotoxic T cells directed against PrP-derived peptides but their ability to protect or to induce deleterious autoimmune reactions is not known. The natural tolerance to PrP(c) makes difficult to raise efficient adaptive responses. To break tolerance, adenovirus (Ad) encoding human PrP (hPrP) or control Ad were administered to wild-type mice by direct injection or by transfer of Ad-transduced dendritic cells (DCs). Control Ad-transduced DCs from Tg650 mice overexpressing hPrP were also used for immunization. DC-mediated but not direct administration of AdhPrP elicited antibodies that bound to murine native PrP(c). Frequencies of PrP-specific IFNgamma-secreting T cells were low and in vivo lytic activity only targeted cells strongly expressing hPrP. Immunohistochemical analysis revealed that CD3(+) T cell infiltration was similar in the brain of vaccinated and unvaccinated 139A-infected mice suggesting the absence of autoimmune reactions. Early splenic PrP(Sc) replication was strongly inhibited ten weeks post infection and mean survival time prolonged from 209 days in untreated 139A-infected mice to 246 days in mice vaccinated with DCs expressing the hPrP. The efficacy appeared to be associated with antibody but not with cytotoxic cell-mediated PrP-specific responses.

Progressive myelopathy due to a spontaneous intramedullary hematoma in a dog: pre- and postoperative clinical and magnetic resonance imaging follow-up.

A 4-year-old, male Jack Russell terrier was presented for a 6-month history of progressive right hemiparesis with episodic cervical hyperesthesia. The neurological examination showed a right-sided, upper motoneuron syndrome and partial Horner's syndrome. Two magnetic resonance imaging (MRI) examinations were performed 3 months apart and revealed a persistent cervical intramedullary hematoma. A dorsal myelotomy was performed. A subacute hematoma was confirmed histologically without underlying lesions. Eighteen months later, the dog's clinical signs were minimal. Two MRI examinations were performed 2 weeks and 5 months after surgery and revealed regressing signal abnormalities at the surgical site, consistent with a surgical scar.

Clinical and pathologic manifestation of oesophagostomosis in African great apes: does self-medication in wild apes influence disease progression?

Nodular worms (Oesophagostomum spp.) are common intestinal parasites found in cattle, pig, and primates including humans. In human, they are responsible for serious clinical disease called oesophagostomosis resulting from the formation of granulomas, caseous lesions or abscesses in intestinal walls. In wild great apes, the fecal prevalence of this parasite is high, but little information is available concerning the clinical signs and lesions associated. In the present study, we describe six cases of multinodular oesophagostomosis in free-ranging and ex-captive chimpanzees and captive gorillas caused by Oesophagostomum stephanostomum. While severe clinical signs associated with this infection were observed in great apes raised in sanctuaries, nodules found in wild chimpanzees do not seem to affect their health status. One hypothesis to explain this difference would be that in wild chimpanzees, access to natural environment and behavior such as rough leaves swallowing combined with ingestion of plants having pharmacological properties would prevent severe infection and decrease potential symptoms.

Effects of cyanobacterial crude extracts from Planktothrix agardhii on embryo-larval development of medaka fish, Oryzias latipes.

Embryonic toxicity from exposure to microcystins, cyclic hepatotoxic heptapeptides from cyanobacteria, receives increasing attention as a public human health biohazard. Using a microinjection technology, we have introduced cyanobacterial extracts from Planktothrix agardhii directly into the vitellus of late neurula embryos (stage 19) of medaka (Oryzias latipes). Microinjection (2 nL) of P. agardhii PMC 75.02 extract containing microcystins (MC) resulted in a dose-dependent mortality of embryos. Survival rates were reduced up to 81% with extract concentrations of 10 mg mL(-1) (EC(50)=7.8 microg mL(-1)). On the other hand, injection of P. agardhii PMC 87.02 extract in which no microcystin could be detected resulted in much less embryonal toxicity (EC(50)=460 microg mL(-1)). In addition, advanced embryonic hatching processing was limited with PMC 75.02 crude extract and less obvious than had been described with pure MC-LR injections. In agreement with the known hepatotoxic effects of microcystin, embryos injected with PMC 75.02 extract consistently displayed hepatobiliary abnormalities. Loss of glycogen content of the hepatocytes and hepatic haemorrhage were evidenced in surviving post-hatching juveniles. Thus, the methodology presented in this paper should be a valuable tool to analyse the effects of crude extracts of cyanobacterial toxins on the development of aquatic vertebrate embryos.

Toxicity to medaka fish embryo development of okadaic acid and crude extracts of Prorocentrum dinoflagellates.

Chronic and subchronic toxicity following exposure to the DSP (Diarrhetic shellfish poisoning) toxin okadaic acid (OA) is receiving increasing attention as a public human health biohazard. However information on ecological impacts induced by proliferation of the OA producing dinoflagellate Prorocentrum is scarce. In order to analyse the toxicity of these substances, in vivo experiments were conducted on medaka fish (Oryzias latipes) embryos used as an experimental model. The study was focused on two strains of benthic Prorocentrum species, P. arenarium and P. emarginatum, naturally found in the Indian Ocean. Sample extracts (crude extracts, CE) were obtained from algal cultures and their toxic potential was explored. Their OA (and derivatives) content was evaluated by two methods: one based on chemical analysis using HPLC-MS, the other based on screening the inhibiting effect on protein phosphatase PP2A. P. arenarium extracts inhibit PP2A and the active toxin was confirmed as being OA by HPLC-MS. In contrast, P. emarginatum showed negative results regardless of the method used. The development of medaka fish embryos kept in medium containing pure OA or Prorocentrum CE was examined. Survival rates were reduced up to 100% depending on the concentrations used of both OA and CE of P. arenarium, while no effect was observed with CE of P. emarginatum. Anatomopathological studies of surviving embryos indicate that OA treatment resulted in significant increases in liver and digestive tract areas compared to controls. P. arenarium treated surviving embryos exhibited significant quantitative increases of global body and vitellus areas. Together, our results indicate that the toxic effects to medaka embryos development of pure OA and P. arenarium extracts containing OA are distinguishable. The differences may indicate the presence of additional toxic substance(s) (or molecules able to modulate OA impact) in the P. arenarium CE that probably are not present in P. emarginatum.

Microcystin-LR and embryo-larval development of medaka fish, Oryzias latipes. I. Effects on the digestive tract and associated systems.

The cyanobacterial hepatotoxin microcystin-LR (MC-LR) is a specific potent PP1 and PP2A protein phosphatase inhibitor. In view to obtain an integrated whole-body, understanding of the key target organs of MC-LR subsequent to embryonic exposure on the anatomy of medaka fish hatchlings, embryos at stage 19 were microinjected with a sublethal dose of MC-LR corresponding to 0.2 pg/vitellus. MC-LR-induced histo-pathological modifications of the alimentary system (i.e. digestive tract, pancreas, liver) were analysed in newly hatched embryos. Our data are indicative of an MC-LR-induced inhibition of both yolk sac resorption and gas concentrating swimbladder expansion. In contrast to control hatchlings, (i) no mucus-secreting cells in the oesophagus, (ii) a decreased folding of the stomach and intestine, (iii) a clear reduction in size of the exocrine pancreas associated with a destructuration of acinar units, and (iv) a strong decrease in the mass and size of the liver were observed in MC-LR treated embryos. Furthermore, as an indication of MC-LR-induced hepatic glycogen store depletion, unstained cytoplasmic areas present in control hatchling hepatocytes, were fully absent in all liver examined in treated embryos. Finally, as a general observation in MC-LR-treated embryos, our data clearly indicated terminal differentiation disorders in all organs associated with the digestive tract.

Effects of GSM-900 microwaves on DMBA-induced mammary gland tumors in female Sprague-Dawley rats.

The aim of this investigation was to test the hypothesis that sub-chronic whole-body exposure to GSM-900 microwaves had an effect on tumor promotion and progression. Mammary tumors were induced by ingestion of a single 10-mg dose of 7,12-dimethylbenz(a)anthracene (DMBA) in female Sprague-Dawley rats (Ico:OFA-SD; IOPS Caw). In two independent experiments, DMBA-treated animals were divided into four groups: sham-exposed (16) and exposed (three groups of 16 animals). The specific absorption rates (SARs), averaged over the whole body, were 3.5, 2.2 and 1.4 W/kg in the first experiment (May-July) and 1.4, 0.7 and 0.1 W/kg in the second experiment (September-November). Exposure started 10 days after DMBA treatment and lasted 2 h/day, 5 days/week for 9 weeks. Animals were exposed to plane waves with the electric field parallel to the long axis of the animals. Body weight and the number, location and size of the tumors were recorded at regular intervals. Rats were killed humanely 3 weeks after the end of exposure. The results are negative in terms of latency, multiplicity and tumor volume. With regard to tumor incidence, in the first experiment there was an increase in the rate of incidence at 1.4 W/kg but less at 2.2 W/kg and none at 3.5 W/kg. Overall, these results, which are rather inconsistent, do not bring new evidence of a co-promoting effect of exposure to GSM-900 signals using the DMBA rat model.