Assessing toxicity of nanoparticles using Brachionus manjavacas (Rotifera).

Rotifers are major components of zooplankton in freshwater and coastal marine ecosystems throughout the world and could be useful indicator species, providing valuable insight into the effects of nanoparticles on microinvertebrate grazers. Here we report initial efforts to characterize the immediate and longer-term effects of nanoparticle exposure on the reproduction of the coastal marine and salt lake rotifer Brachionus manjavacas. We used chemically unreactive fluorescent nanoparticles to probe how size and concentration affects the mode of uptake, distribution within the rotifer body, reproductive rate, feeding behavior, and offspring fitness. Population growth rate (r) was depressed 50% in rotifer populations exposed to 0.30 µg mL(-1) of 37-nm particles, and 89% in populations exposed to 1.1 µg mL(-1). Larger particles of identical chemical composition, but with diameters up to 3000 nm, caused no reduction in population growth rate. These larger particles remain confined in the gut, implicating nanoparticle size as a critical factor in the ability to penetrate the gut wall and enter tissues. Transfer of the F1 offspring from nanoparticle exposed maternal females into nanoparticle-free media demonstrated that nanoparticles are rapidly cleared from the animals with no significant residual adverse effects.

Intracranial magnetic resonance imaging artifacts and pseudolesions in dogs and cats.

Normal anatomic variation, study design, external factors, and tissue characteristics can all influence the manifestation of structures on magnetic resonance images (MRI). For the purpose of this review, imaging artifacts are considered to be nonpathologic abnormalities resulting from study design, intrinsic tissue characteristics, or external factors, while MRI pseudolesions are due to normal anatomic variation. Awareness of imaging artifacts and pseudolesions, as well as normal anatomic structures, is important when determining pathologic vs. normal or clinically insignificant abnormalities. The purpose of this report is to examine the literature to compile a review of selected artifacts and pseudolesions that are commonly encountered when imaging the canine and feline brain.

Gamma-irradiated Calvarium Allograft Cranioplasty in a cat following brain tumor removal.

A 14-year-old domestic shorthair cat was evaluated for a 3-month history of head pressing and circling. Neurological examination suggested a supratentorial problem, predominantly on the left side. An extradural mass extending from the rostral frontal lobes caudally to the level of the caudal aspect of the corpus callosum was found with magnetic resonance imaging. A bilateral rostrotentorial craniectomy combined with a frontal sinus craniectomy was performed for mass removal. A gamma-irradiated calvarial allograft was used to repair the calvarial defect. At 14 months following surgery, the cat had no neurological abnormalities, and the skull and facial appearance was normal.

Imaging diagnosis--magnetic resonance imaging pseudolesion associated with the petrous temporal bone.

Normal anatomic variation in the amount of fat within the petrous temporal bone of dogs can result in a magnetic resonance (MR) imaging pseudolesion. Focal hyperintense areas in the region of the hippocampus on T1-weighted, T1-weighted, and fluid-attenuated inversion recovery imaging sequences were noted in a dog being imaged for seizure activity. Further investigation of this region, aided by the use of cadaveric specimens, led to the identification of normal anatomic variability in the amount of fat in the substantia spongiosa of the petrous temporal bone. The presence of normal adipose tissue was confirmed histopathologically. Fat suppression MR imaging sequences can be used to differentiate whether hyperintensity ventral to the hippocampus is a result of a pathologic process, or fat in the substantia spongiosa of the petrous temporal bone.

In vitro biomechanical evaluations of screw-bar-polymethylmethacrylate and pin-polymethylmethacrylate internal fixation implants used to stabilize the vertebral motion unit of the fourth and fifth cervical vertebrae in vertebral column specimens from dogs.

OBJECTIVE: To determine the change in stiffness as evaluated by the dorsal bending moment of cervical vertebral specimens obtained from canine cadavers after internally stabilizing the vertebral motion unit (VMU) of C4 and C5 with a traditional pin-polymethylmethacrylate (PMMA) fixation implant or a novel screw-bar-PMMA fixation implant. SAMPLE POPULATION: 12 vertebral column specimens (C3 through C6) obtained from canine cadavers. PROCEDURES: A dorsal bending moment was applied to the vertebral specimens before and after fixation of the VMU of C4 and C5 by use of a traditional pin-PMMA implant or a novel screw-bar-PMMA implant. Biomechanical data were collected and compared within a specimen (unaltered vs treated) and between treatment groups. Additionally, implant placement was evaluated after biomechanical testing to screen for penetration of the transverse foramen or vertebral canal by the pins or screws. RESULTS: Treated vertebral specimens were significantly stiffer than unaltered specimens. There was no significant difference in stiffness between vertebral specimen groups after treatment. None of the screws in the novel screw-bar-PMMA implant group penetrated the transverse foramen or vertebral canal, whereas there was mild to severe penetration for 22 of 24 (92%) pins in the traditional pin-PMMA implant group. CONCLUSIONS AND CLINICAL RELEVANCE: Both fixation treatments altered the biomechanical properties of the cervical vertebral specimens as evaluated by the dorsal bending moment. There was reduced incidence of penetration of the transverse foramen or vertebral canal with the novel screw-bar-PMMA implant, compared with the incidence for the traditional pin-PMMA implant.

Intranasal malignant melanoma in a dog.

A 10-year-old, female Newfoundland-cross dog was presented for evaluation of chronic intermittent unilateral epistaxis, nasal stertor, and sneezing. Nasal magnetic resonance imaging revealed a 3 x 5-cm mass in the left nasal cavity. Histopathological evaluation of nasal biopsies determined that the mass was a malignant melanoma. The mass was surgically resected and treated with bilateral opposed photon-beam radiation. This is the first report to describe the presentation, diagnosis, and treatment of an intranasal malignant melanoma in a dog.