An extract of Hydrilla verticillata and associated epiphytes induces avian vacuolar myelinopathy in laboratory mallards

Avian vacuolar myelinopathy (AVM) is a neurological disease affecting bald eagles (Haliaeetus leucocephalus), American coots (Fulica americana), waterfowl, and other birds in the southeastern United States. The cause of the disease is unknown, but is thought to be a naturally produced toxin. AVM is associated with aquatic macrophytes, most frequently hydrilla (Hydrilla verticillata), and researchers have linked the disease to an epiphytic cyanobacterial species associated with the macrophytes. The goal of this study was to develop an extraction protocol for separating the putative toxin from a hydrilla-cyanobacterial matrix. Hydrilla samples were collected from an AVM-affected reservoir (J. Strom Thurmond Lake, SC) and confirmed to contain the etiologic agent by mallard (Anas platyrhynchos) bioassay. These samples were then extracted using a solvent series of increasing polarity: hexanes, acetone, and methanol. Control hydrilla samples from a reference reservoir with no history of AVM (Lake Marion, SC) were extracted in parallel. Resulting extracts were administered to mallards by oral gavage. Our findings indicate that the methanol extracts of hydrilla collected from the AVM-affected site induced the disease in laboratory mallards. This study provides the first data documenting for an "extractable" AVM-inducing agent.

Vacuolar myelinopathy in waterfowl from a North Carolina impoundment

Vacuolar myelinopathy was confirmed by light and electron microscopic examination of mallards (Anas platyrhynchos), ring-necked ducks (Aythya collaris), and buffleheads (Bucephala albeola) collected during an epizootic at Lake Surf in central North Carolina (USA) between November 1998 and February 1999. Clinical signs of affected birds were consistent with central nervous system impairment of motor function (incoordination, abnormal movement and posture, weakness, paralysis). This is the first report of this disease in wild waterfowl (Anseriformes).

Experimental vacuolar myelinopathy in red-tailed hawks

Avian vacuolar myelinopathy (AVM) was recognized in 1994 as a cause of wild bird mortality when 29 bald eagles (Haliaeetus leucocephalus) succumbed to the disease at DeGray Lake, Arkansas (USA). The cause of AVM and its source remain undetermined despite extensive diagnostic and research investigations. Two years later, when AVM killed 26 eagles in the same area in Arkansas, it became apparent that American coots (Fulica americana) had identical neurologic signs and lesions, and it was hypothesized that eagles acquired AVM via ingestion of affected coots. In order to test this hypothesis, we fed coot tissues (brain, liver, kidney, muscle, fat, and intestinal tract) to rehabilitated, non-releasable red-tailed hawks (Buteo jamaicensis). Five hawks received tissues from coots with AVM lesions, and one hawk received tissues from coots without brain lesions that had been collected at a site where AVM never has been documented. All hawks received 12-70 g/day (mean = 38 g) of coot tissues for 28 days. All six hawks remained clinically normal during the study. The birds were euthanatized on day 29 and microscopic lesions of AVM were found in all hawks that received tissues from affected coots, but not in the hawk that received tissues from unaffected coots. This marks the first time that AVM has been produced in birds under laboratory conditions and proves that birds of prey can acquire AVM via ingestion of tissues from affected coots.

Treatment with 6-hydroxydopamine in planaria (Dugesia gonocephala s.l.): morphological and behavioral study

Morpho-functional and behavioral effects of exposure to 6-hydroxydopamine (OHDA)-HCI (24 microg/ml per day for 24 h and 7 days) were studied in planarias (Dugesia gonocephala s.l.). Exposure to 6-OHDA-HC1 for 24 h produced hypokinesia of the specimens. These behavioral changes were more pronounced, leading to complete immobility, after 7 days of exposure to the neurotoxin. Moreover, specimens exposed to 6-OHDA-HCI for 24 h and 7 days failed to show any behavioral response to nomifensine, thus furnishing evidence of the damage of presynaptic dopamine terminals. Exposure to 6-OHDA-HCl for 24 h significantly reduced cathecolamine content in neuropil region, as demonstrated by histochemistry, and electron-dense presynaptic vesicles, as observed on electron microscopy examination. All these alterations were significantly more pronounced and were accompanied by swelling and strong increase of electron-density in cytoplasm of numerous neurons after exposure to the neurotoxin for 7 days. This appears to be the first demonstration of the neurotoxic effects of 6-OHDA-HCI in flatworms.

Clinoidal meningioma arising from falciforme process of optic canal: case report and review

A 56-year-old female with an initial symptom of unilateral progressive visual disturbance presented with a clinoidal meningioma arising from a falciforme process of the optic canal. Magnetic resonance images with gadolinium-diethylenetriaminepenta-acetic acid demonstrated marked enhancement of a small mass, approximately 1 cm in diameter, roofing the right optic nerve at the intracranial opening of the optic canal. The clinoidal meningioma is rarely reported and the precise originating location of the neoplasm has not been clarified. This is the first case of clinoidal meningioma, which is confirmed by the operative observation as the origin of the neoplasm is a falciforme process of the optic canal. Magnetic resonance images with enhancement are useful for the diagnosis of such a small neoplastic lesion adjacent to bone structure and total removal without a deterioration of visual function is achieved by careful microsurgical procedure.

Behavioural and neurohistological changes in aging Sepia

The life cycle of the cuttlefish in the English Channel is characterized by a succession of homogeneous population cohorts. These conditions provide an excellent opportunity for the study of aging in this cephalopod. In a first longitudinal study, we considered the oldest animals and compared their success rates at the first capture attempt. During the first weeks of the study, the results remained constant and then, during the weeks immediately preceding the natural death, a dramatic drop was observed. This deterioration may be due to defects of visuomotor coordination. In a second study, we used an associative learning protocol with negative reinforcement and the performances of young and old animals were compared. The most striking results showed that the performances of the oldest animals during the retention test were very mediocre. Such results suggest that the long-term memory process is affected. Finally, a modification of the Fink-Heimer silver stain enabled us to draw a map of spontaneous terminal degeneration in the central nervous system of the oldest animals. The structures which are characterized by the presence of multimodal inputs (the spine of the peduncle lobe and the basal lobes) present the most obvious signs of degeneration.