Ovine Hemisection Model of Spinal Cord Injury.

INTRODUCTION: We are developing ovine models of spinal cord injury to test novel neuromodulation-based methods on spasticity. The hemisection has been reported in a number of large animal studies. Our aim is to duplicate a hemisection injury in the sheep. Our effort is explored here. Methods and Results: Three sheep underwent hemi-sectioning of the spinal cord. Quantitative gait analysis was completed both pre- and post-injury. While measurable differences in most of the 20 gait metrics were observed, relatively few were above the predicted thresholds based on error levels expected from the data. Variations in severity of injury across the three sheep were observed. Conclusions: The hemisection ovine model of spinal cord injury shows promise as a large-animal platform for developing new therapies for treating spinal cord injuries. While variability in injury severity was observed across animals, as has been observed with weight drop-based SCI models, the hemi-section approach has the advantages of procedural ease and reduced technical complexity.

The Hemisection Approach in Large Animal Models of Spinal Cord Injury: Overview of Methods and Applications.

Introduction: Translating basic science research into a safe and effective therapy for spinal cord injury (SCI) requires suitable large animal models for testing both implantable devices and biologic approaches to better approximate human anatomy and function. Hemisection lesions, routinely used for investigational purposes in small animals, are less frequently described in large animals that might be appropriate for translational studies. Size constraints of small animals (mice and rats) limits the predictability of the findings when scaled up. Our goal is to review the status of hemisection SCI in large animals across species and time to prepare for the testing of a novel intradural spinal cord stimulation device for control of spasticity in an ovine model. Methods and Results: We surveyed the literature on hemisection in quadrupeds and nonhuman primates, and catalogued the species, protocols and outcomes of the experimental work in this field. Feline, lapine, canine, simian, porcine, ovine and bovine models were the primary focal points. There is a consistent body of literature reporting use of the hemisection approach in large animals, but with differences in surgical technique depending on the goals and nature of the individual studies. While the injuries are not always consistent, the experimental variability is generally lower than that of the contusion-based approach. In general, as the body size of the animal increases, animal care requirements and the associated costs follow. In most cases, this is inversely correlated with the number of animals used in hemisection models. Conclusions: The hemisection approach to modeling SCI is straightforward compared with other methods such as the contusive impact and enables the transection of isolated ascending and descending tracts and segment specific cell bodies. This has certain advantages in models investigating post-injury axonal regrowth. However, this approach is not generally in line with the patho-physiologies encountered in SCI patients. Even so, the ability to achieve more control over the level of injury makes it a useful adjunct to contusive and ischemic approaches, and suggests a useful role in future translational studies.

Properties and mechanisms of drug release from matrix tablets containing poly(ethylene oxide) and poly(acrylic acid) as release retardants.

The interactions between poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) in aqueous medium at pH 6.8 were investigated in the current study. We have also studied the effect of interpolymer interactions and various formulation variables, including the molecular weight of PEO, the ratio between PEO and PAA, the crystallinity of PEO, and the presence of an acidifying agent, on the release of theophylline from matrix tablets containing both PEO and PAA as release retardants. At pH 6.8, the synergy in solution viscosity between PEO and PAA as the result of ion-dipole interaction was observed in this study. The release of theophylline from the matrix tablets containing physical mixtures of PEO and PAA was found to be a function of dissolution medium pH because of the pH-dependent interactions between these two polymers. Because of the formation of water insoluble interpolymer complex between PEO and PAA in aqueous medium at pH below 4.0, the release of theophylline was independent of PEO molecular weight and was controlled by Fickian diffusion mechanism in 0.01N hydrochloric acid solution. In comparison, the drug release was a function of PEO molecular weight and followed the anomalous transport mechanism in phosphate buffer pH 6.8. The presence of PAA exerted opposite effects on the release of theophylline in phosphate buffer pH 6.8. In one aspect, theophylline release was accelerated because the erosion of PAA was much faster than that of PEO at pH6.8. On the opposite aspect, theophylline release was slowed down because of the formation of insoluble complex inside the gel layer as the result of the acidic microenvironment induced by PAA, and the increase in the viscosity of the gel layer as the result of the synergy between PEO and PAA. These two opposite effects offset each other. As a result, the release of theophylline remained statistically the same even when 75% PEO in the formulation was replaced with PAA. In phosphate buffer pH 6.8, the release of theophylline was independent of the crystalline form of PEO. The release profile remained identical whether PEO was present as a semicrystalline powder blend with PAA or an amorphous complex with PAA in the matrix tablets. It has also been observed that the presence of citric acid as an acidifying agent had negligible effect on the drug release rate.

Filthy or fashionable? Young people's perceptions of smoking in the media.

Research has shown that the media over-estimates smoking rates and often associates smoking with favorable attributes or situations. Given that the media plays a large role in influencing youth culture, portrayal of smoking in the media is of concern. In order to explore young people's perceptions of smoking imagery in the media, 16 focus groups were conducted with 117 school students. Participants were asked to rate smoking images selected from audio-visual and print media, and to discuss their perceptions of these images. The results showed that young people perceived smoking in these media selections to be normal and acceptable. They identified with the stress-relieving and social aspects of smoking, despite being well aware of the harmful health effects. Its acceptability as part of a 'cool' image was also noted. Positive images of smoking in the media have the potential to down-play the serious health consequences of smoking by portraying it in a way that young people interpret as a normal part of everyday life. They may also encourage a more neutral or tolerant attitude towards smoking among young people and therefore act to counteract other health promotion efforts to reduce teenage smoking.

Improved high resolution MR imaging for surface coils using automated intensity non-uniformity correction: feasibility study in the orbit.

This study examined the effects of a recently developed automated intensity non-uniformity correction on surface coil images using the orbit as an exemplar. Images were obtained using a standard head coil and a range of surface coils. Slices through the optic nerve head and cavernous sinus were subjected to the correction algorithm. Blind forced-choice rankings of the subjective image quality were performed. Quantitative measurements were taken of the similarity between vitreous humor at two depths from the coil, and of the conspicuity between orbital fat and temporalis muscle intensities. The combined qualitative ranks for corrected surface coil images were higher than for the equivalent uncorrected images in all cases. Intensity non-uniformity correction produced statistically significant improvements in orbital surface coil images, bringing their intensity uniformity in homogeneous tissue to the level of head coil images. The subjective quality of the corrected surface coil images was superior to head coil images, due to increased spatial resolution combined with improved signal to noise ratio across the image.

The effect of hyperoxia on cerebral blood flow: a study in healthy volunteers using magnetic resonance phase-contrast angiography.

A small decrease in cerebral blood flow (approximately 10%) in response to 100% oxygen (O2) administration is well recognized. This observation was based on human volunteer studies, which employed a nitrous oxide washout method for the measurement of cerebral blood flow. Because this method is now appreciated to be subject to potential errors we have examined the cerebral blood flow response to 100% oxygen using a magnetic resonance imaging technique to quantify changes in carotid and basilar artery flow. The study, was performed in 12 normal male subjects aged 23-42 years. We report decreases in cerebral blood flow ranging from 9 to 31% with a mean value of over 20%. The decrease in cerebral blood flow was greater in seven young subjects (aged 23-26 years) with decreases in cerebral blood flow of 19.3-31.4% (mean 26.8%). In five older subjects (aged 32-42 years), decreases in CBF were smaller (mean 16. 2%). The administration of 100% O2 was accompanied by a small decrease in end-tidal CO2 (3.7-7.1%), insufficient to explain the changes in cerebral blood flow. We conclude that the decrease in cerebral blood flow in response to O2 administration is greater than previously described and appears to be greater in young adults.

Ultrastructure of the eyes of the larva of Neoheterocotyle rhinobatidis (Platyhelminthes, Monopisthocotylea), and phylogenetic implications.

The oncomiracidium of Neoheterocotyle rhinobatidis (Monogenea, Monopisthocotylea, Monocotylidae) has two pairs of eyes, each eye with a lens and pigment cup. The anterior eyes have a single rhadomere; the posterior ones, two rhadomeres. Lenses are part of the pigment cup cells, as indicated by cytoplasmic connections between them and the pigment cups, and they are of mitochondrial origin because mitochondrial cristae are present in the periphery of the lenses. This is the first time that mitochondrial lenses have been shown to exist in a neodermatan. Such lenses may be a synapomorphy of a large taxon comprising the Neodermata and its turbellarian sister groups, or they may have evolved convergently in several not closely related groups as a result of strong selection pressure to find a suitable habitat or host.

Mentoring today--the students' views. An investigative case study of pre-registration nursing students' experiences and perceptions of mentoring in one theory/practice module of the Common Foundation Programme on a Project 2000 course.

The study reported in this paper investigated the mentoring experiences and perceptions of pre-registration nursing students in one organization, on a theory/practice nursing module. It considered the extent to which students' understanding and expectations matched their actual experiences. Interviews were conducted with 35 students on a Common Foundation Programme, and 15 allocated mentors, using a semi-structured interview guide. These were done within the clinical setting of the wards on which the students were placed as part of their requirements for completion of the module. A distortion of the actual meaning of mentoring appears to be present because of the lack of clarity provided, both internally by organizations and by the English National Board (ENB) who have provided loose guidelines. The implications of this distortion are discussed. The application of a mentoring role in practice needs to be re-examined, with the provision of a clear structured guide internally and externally, with regard to the needs of students and staff who are expected to act as mentors. The study was small scale and cannot be generalized. Mentoring, however, is now widely used within pre-registration nursing education, even though it is generally considered that its use may not be appropriate. Follow-up studies need to be undertaken on an ongoing basis, to examine what actually happens in practice, and to consider ways of ensuring that the benefits for staff and students are enhanced.

Symbioses in Amphipholis squamata (Echinodermata, Ophiuroidea, Amphiuridae): geographical variation of infestation and effect of symbionts on the host's light production.

Populations of the polychromatic and bioluminescent species Amphipholis squamata from eight locations were examined for internal and external symbionts. At three locations (two in the United Kingdom and one in Papua New Guinea), no symbionts were present, while four species were recovered from the remaining locations: Cancerilla tubulata and Parachordeumium amphiurae (copepods), Rhopalura ophiocomae (orthonectid) and an undescribed species of rhabdocoel turbellarian. No ophiuroid individual hosted more than one symbiont species, despite the presence of two or more within a population. Symbiont presence and prevalence varied with location, and with colour variety, but with no apparent pattern or trends. Light-production characteristics of the host were affected by the presence of all symbionts except C. tubulata. These effects, however, did not vary between colour varieties or between geographical locations, but were specific to the symbiont species: the presence of P. amphiurae resulted in enhanced intensity of light production, while that of R. ophiocomae and the turbellarian species resulted in reduced intensity. The kinetics of light production (time until maximum output) were altered only by the presence of the turbellarian. Changes in the light-production characteristics are discussed in relation to morphological, energetical and physiological effects of the symbioses.

Supradiaphragmatic middle aorta syndrome--MR and angiographic imaging.

We describe the case of an asymptomatic 24-year-old man with hypertension who was investigated for aortic coarctation but found on MR scanning to have narrowing of the distal thoracic aorta. Stenosis of the thoracolumbar aorta--the Middle Aorta Syndrome--is rare and is usually found below the diaphragm. The MRI and angiographic findings are presented.

The effect of post-injury spinal position on canal occlusion in a cervical spine burst fracture model.

STUDY DESIGN: The canal space of burst-fractured, human cervical spine specimens was monitored to determine the extent to which spinal position affected post-injury occlusion. OBJECTIVE: To test the null hypothesis that there is no difference in spinal canal occlusion as a function of spinal positioning for a burst-fractured cervical spine model. SUMMARY OF BACKGROUND DATA: Although previous studies have documented the effect of spinal positioning on canal geometry in intact cadaver spines, to the authors' knowledge, none has examined this relationship specifically in a burst fracture model. METHODS: Eight human cervical spine specimens (levels C1 to T3) were fractured by axial impact, and the resulting burst injuries were documented using post-injury radiographs and computed tomography scans. Canal occlusion was measured using a custom transducer in which water was circulated through a section of flexible tygon tubing that was passed through the spinal canal. Any impingement on the tubing produced a rise in fluid pressure that was monitored with a pressure transducer. Each spine was positioned in flexion, extension, lateral (and off-axis) bending, axial rotation, traction, and compression, while canal occlusion and angular position were monitored. Occlusion values for each position were compared with measurements taken with the spine in neutral position. RESULTS: Compared with neutral position, compression, extension, and extension combined with lateral bending significantly increased canal occlusion, whereas flexion decreased the extent of occlusion. In extension, the observed mechanism of occlusion was ligamentum flavum bulge caused by ligament laxity resulting from reduced vertebral body height. CONCLUSIONS: Increased compression of the spinal cord after injury may lead to more extensive neurologic loss. This study demonstrated that placing a burst-fractured cervical spine into either extension or compression significantly increased canal occlusion as compared with occlusion in a neutral position.

Spermiogenesis and sperm ultrastructure in Troglocephalus rhinobatidis, Neoheterocotyle rhinobatidis and Merizocotyle australensis (Platyhelminthes, Monogenea, Monopisthocotylea, Monocotylidae).

The ultrastructural events of spermiogenesis and the ultrastructure of nature sperm of 3 species of monocotylid monogeneans are described. Two of these species, Troglocephalus rhinobatidis and Neoheterocotyle rhinobatidis are extremely similar in all the aspects studied, and their placement in separate subfamilies is questioned. Evidence is presented in both species for extensive distalward movement during spermiogenesis of an ornamented region associated with cortical microtubules, originally located in the zone of differentiation. Spermatids of Merizocotyle australis lack this ornamentation and the mature sperm also lacks cortical microtubules. Troglocephalus rhinobatidis exhibits the highest number (128) of spermatids in an isogenic group recorded for a flatworm to date. Sperm of all 3 species have 2 normal axonemes, shifted slightly relative to one another. Comparative data are presented on sperm and spermiogenesis of all monocotylids examined to date and the phylogenetic implications are discussed.

Visually-evoked pattern and photomyoclonic responses in video game and television epilepsy: case reports.

This research paper reports a case study of two male photosensitive epileptic patients, aged 14 and 16 years old respectively, whose epileptic seizures were often triggered by the flickers from television and video games respectively. The 14-year old patient had no family history of epilepsy, while the 16 year old had a family history of epilepsy. A comprehensive electroencephalogram (EEG), including hyperventilation, intermittent photic stimulation (IPS) and pattern stimulation were carried out on them and EEG abnormalities including photoparoxysmal responses (PPR) and generalized myoclonic responses were evoked. A thorough analysis of the EEG morphology of the myclonic responses and the clinical manifestations showed evidence of two separate entitles of seizures namely: visually evoked pattern-myoclonic responses (PTMR) and visually evoked photomyoclonic responses (PMR). PTMR was independent of flash rate and occurred before a PPR and at the same time as the flash rate, while PMR occurred after the PPR and was dependent on flash rate. These findings suggest that "Video Game" epilepsy is probably a pattern sensitive epilepsy, electronic screen being the source of the triggering patterns; hence, the morphology and the family histories and the myoclonic phenomena differ from those of pure photosensitive epilepsy.