Surgical treatment of a traumatic intracranial epidural haematoma in a dog.

A 10-month-old Czech wolf dog was unconscious after being kicked in the head by a horse. The following day, the dog was ataxic and collapsed after several steps. The level of consciousness was decreased. Cranial nerve examination was normal and right postural reactions were decreased. Spinal reflexes were intact in all limbs. The diagnostic work-up included a computed tomography (CT) scan of the head with IV contrast. A lenticular shaped, hyperdense, non-enhancing lesion was observed in the left fronto-parietal region. A diagnosis of intracranial epidural haematoma was made. Two craniotomies were performed on a different day and most of the haematoma was removed. Corticosteroids and antimicrobial therapy were administered. Fifteen days after the surgery, the clinical examinations were unremarkable. Fifteen months later, the owners considered the dog normal. Intracranial subdural or intraparenchymal haematomas have been described in the veterinary literature. To the authors' knowledge, this is the first report of the successful management of an intracranial epidural haematoma in the dog. In humans, these lesions are well described. Common locations are temporal, parietal and frontal regions or a combination of these regions. Patients can be asymptomatic, present with varying clinical signs, or be unconscious. Based on the human literature, following trauma to the head, a CT scan should be performed even if the patient is asymptomatic. Some authors believe that there are not any absolute indications for conservative management versus surgical management.

Computed tomography study of implantation corridors in canine vertebrae.

OBJECTIVES: To define the characteristics of optimum implantation corridors in vertebral bodies C2 to C7 and T10 to S1, using computed tomography examination. METHODS: Measurements were taken from 207 vertebrae from 35 different adult dogs. RESULTS: Implantation corridors of the cervical vertebrae are narrow. The width preserving the transverse hole is less than 2.5 mm in 68.6 per cent of the 86 vertebrae C2 to C6. Dorsal implantation corridors of the last four thoracic vertebrae are narrow, and major anatomical structures are very close to their emergence point. In 63 per cent of the 40 thoracic vertebrae, the right azygos vein is at a distance less than or equal to 1 mm from the vertebral body. The first six lumbar vertebrae have broader corridors. Furthermore, vascular structures are far from the emergence point. The last lumbar vertebra and the sacrum have a broad pedicle, which provides an alternative site for implant placement. CLINICAL SIGNIFICANCE: For the vertebrae L1 to S1, the dorsal implantation can be performed. For the cervical vertebrae, the risk of laceration of the vertebral artery is high. For the last four thoracic vertebrae, the dorsal implantation should not be used.

Effects of soman inhibition and of structural differences on cholinesterase molecular dynamics: a neutron scattering study.

Incoherent elastic neutron scattering experiments on members of the cholinesterase family were carried out to investigate how molecular dynamics is affected by covalent inhibitor binding and by differences in primary and quaternary structure. Tetrameric native and soman-inhibited human butyrylcholinesterase (HuBChE) as well as native dimeric Drosophila melanogaster acetylcholinesterase (DmAChE) hydrated protein powders were examined. Atomic mean-square displacements (MSDs) were found to be identical for native HuBChE and for DmAChE in the whole temperature range examined, leading to the conclusion that differences in activity and substrate specificity are not reflected by a global modification of subnanosecond molecular dynamics. MSDs of native and soman-inhibited HuBChE were identical below the thermal denaturation temperature of the native enzyme, indicating a common mean free-energy surface. Denaturation of the native enzyme is reflected by a relative increase of MSDs consistent with entropic stabilization of the unfolded state. The results suggest that the stabilization of HuBChE phosphorylated by soman is due to an increase in free energy of the unfolded state due to a decrease in entropy.

The influence of solvent composition on global dynamics of human butyrylcholinesterase powders: a neutron-scattering study.

A major result of incoherent elastic neutron-scattering experiments on protein powders is the strong dependence of the intramolecular dynamics on the sample environment. We performed a series of incoherent elastic neutron-scattering experiments on lyophilized human butyrylcholinesterase (HuBChE) powders under different conditions (solvent composition and hydration degree) in the temperature range from 20 to 285 K to elucidate the effect of the environment on the enzyme atomic mean-square displacements. Comparing D(2)O- with H(2)O-hydrated samples, we were able to investigate protein as well as hydration water molecular dynamics. HuBChE lyophilized from three distinct buffers showed completely different atomic mean-square displacements at temperatures above approximately 200 K: a salt-free sample and a sample containing Tris-HCl showed identical small-amplitude motions. A third sample, containing sodium phosphate, displayed highly reduced mean-square displacements at ambient temperature with respect to the other two samples. Below 200 K, all samples displayed similar mean-square displacements. We draw the conclusion that the reduction of intramolecular protein mean-square displacements on an Angstrom-nanosecond scale by the solvent depends not only on the presence of salt ions but also on their type.

Involvement of deacylation in activation of substrate hydrolysis by Drosophila acetylcholinesterase.

Insect acetylcholinesterase (AChE), an enzyme whose catalytic site is located at the bottom of a gorge-like structure, hydrolyzes its substrate over a wide range of concentrations (from 2 microm to 300 mm). AChE is activated at low substrate concentrations and inhibited at high substrate concentrations. Several rival kinetic models have been developed to try to describe and explain this behavior. One of these models assumes that activation at low substrate concentrations partly results from an acceleration of deacetylation of the acetylated enzyme. To test this hypothesis, we used a monomethylcarbamoylated enzyme, which is considered equivalent to the acylated form of the enzyme and a non-hydrolyzable substrate analog, 4-oxo-N,N,N-trimethylpentanaminium iodide. It appears that this substrate analog increases the decarbamoylation rate by a factor of 2.2, suggesting that the substrate molecule bound at the activation site (K(d) = 130 +/- 47 microm) accelerates deacetylation. These two kinetic parameters are consistent with our analysis of the hydrolysis of the substrate. The location of the active site was investigated by in vitro mutagenesis. We found that this site is located at the rim of the active site gorge. Thus, substrate positioning at the rim of the gorge slows down the entrance of another substrate molecule into the active site gorge (Marcel, V., Estrada-Mondaca, S., Magné, F., Stojan, J., Klaébé, A., and Fournier, D. (2000) J. Biol. Chem. 275, 11603-11609) and also increases the deacylation step. This results in an acceleration of enzyme turnover.