Dystrophin-deficient muscular dystrophy in a Weimaraner

A 2-year-old, male Weimaraner with muscular dystrophy was presented with generalized muscle atrophy of the limbs; hypertrophy of the neck, infraspinatus, and lingual muscles; dysphagia; and regurgitation. Unilateral cryptorchidism, unilateral renal agenesis, and hiatal hernia were also detected. Spontaneous muscle activity was identified on myography. Serum creatine kinase was markedly elevated. Immunohistochemical staining for dystrophin was restricted to suspected revertant (characteristics of immaturity) fibers. Histologically, skeletal myofiber degeneration, endomysial fibrosis, and mineralization were present. Following euthanasia, necropsy revealed hypertrophy of the diaphragm and cardiac muscle fibrosis. This case of muscular dystrophy represents a slowly progressive form with organ agenesis.

Evaluation of the success of medical management for presumptive thoracolumbar intervertebral disk herniation in dogs

OBJECTIVE

To determine the success of medical management of presumptive thoracolumbar disk herniation in dogs and the variables associated with treatment outcome.

STUDY DESIGN

Retrospective case series.

ANIMALS

Dogs (n=223) with presumptive thoracolumbar disk herniation.

METHODS

Medical records from 2 clinics were used to identify affected dogs, and owners were mailed a questionnaire about success of therapy, recurrence of clinical signs, and quality of life (QOL) as interpreted by the owner. Signalment, duration and degree of neurologic dysfunction, and medication administration were determined from medical records.

RESULTS

Eighty-three percent of dogs (185/223) were ambulatory at initial evaluation. Successful treatment was reported for 54.7% of dogs, with 30.9% having recurrence of clinical signs and 14.4% classified as therapeutic failures. From bivariable logistic regression, glucocorticoid administration was negatively associated with success (P=.008; odds ratio [OR]=.48) and QOL scores (P=.004; OR=.48). The duration of cage rest was not significantly associated with success or QOL. Nonambulatory dogs were more likely to have lower QOL scores (P=.01; OR=2.34).

CONCLUSIONS

Medical management can lead to an acceptable outcome in many dogs with presumptive thoracolumbar disk herniation. Cage rest duration does not seem to affect outcome and glucocorticoids may negatively impact success and QOL. The conclusions in this report should be interpreted cautiously because of the retrospective data collection and the use of client self-administered questionnaire follow-up.

CLINICAL RELEVANCE

These results provide an insight into the success of medical management for presumptive thoracolumbar disk herniation in dogs and may allow for refinement of treatment protocols.

Evaluation of the Success of Medical Management for Presumptive Cervical Intervertebral Disk Herniation in Dogs

OBJECTIVE

To determine the success of medical management of presumptive cervical disk herniation in dogs and variables associated with treatment outcome.

DESIGN

Retrospective case series.

ANIMALS

Dogs (n=88) with presumptive cervical disk herniation.

METHODS

Dogs with presumptive cervical and thoracolumbar disk herniation were identified from medical records at 2 clinics and clients were mailed a questionnaire related to the success of therapy, clinical recurrence of signs, and quality of life (QOL) as interpreted by the owner. Signalment, duration and degree of neurologic dysfunction, and medication administration were determined from medical records.

RESULTS

Ninety-seven percent of dogs (84/87) with complete information were described as ambulatory at initial evaluation. Successful treatment was reported for 48.9% of dogs with 33% having recurrence of clinical signs and 18.1% having therapeutic failure. Bivariable logistic regression showed that non-steroidal anti-inflammatory drug (NSAID) administration was associated with success (P=.035; odds ratio [OR]=2.52). Duration of cage rest and glucocorticoid administration were not significantly associated with success or QOL. Dogs with less-severe neurologic dysfunction were more likely to have a successful outcome (OR=2.56), but this association was not significant (P=.051).

CONCLUSIONS

Medical management can lead to an acceptable outcome in many dogs with presumptive cervical disk herniation. Based on these data, NSAIDs should be considered as part of the therapeutic regimen. Cage rest duration and glucocorticoid administration do not appear to benefit these dogs, but this should be interpreted cautiously because of the retrospective data collection and use of client self-administered questionnaire follow-up.

CLINICAL RELEVANCE

These results provide insight into the success of medical management for presumptive cervical disk herniation in dogs and may allow for refinement of treatment protocols.

A niche for neutrality

Ecologists now recognize that controversy over the relative importance of niches and neutrality cannot be resolved by analyzing species abundance patterns. Here, we use classical coexistence theory to reframe the debate in terms of stabilizing mechanisms (niches) and fitness equivalence (neutrality). The neutral model is a special case where stabilizing mechanisms are absent and species have equivalent fitness. Instead of asking whether niches or neutral processes structure communities, we advocate determining the degree to which observed diversity reflects strong stabilizing mechanisms overcoming large fitness differences or weak stabilization operating on species of similar fitness. To answer this question, we propose combining data on per capita growth rates with models to: (i) quantify the strength of stabilizing processes; (ii) quantify fitness inequality and compare it with stabilization; and (iii) manipulate frequency dependence in growth to test the consequences of stabilization and fitness equivalence for coexistence.

Imaging diagnosis--bacterial diskospondylitis in a goat

A 3-year-old intact male Boer goat was evaluated for paraplegia. Computed tomography (CT) indicated the presence of diskospondylitis, which had previously not been reported in this species, and significant compressive myelopathy. Chronic bacterial pneumonia, epididymitis, nephritis, and soft-tissue abscesses were believed to result in hematogenous spread of bacteria to the affected disk spaces. Staphylococcus spp. and Archanobacterium pyogenes were both identified from postmortem cultures of the vertebral column.

Climate variability has a stabilizing effect on the coexistence of prairie grasses

How expected increases in climate variability will affect species diversity depends on the role of such variability in regulating the coexistence of competing species. Despite theory linking temporal environmental fluctuations with the maintenance of diversity, the importance of climate variability for stabilizing coexistence remains unknown because of a lack of appropriate long-term observations. Here, we analyze three decades of demographic data from a Kansas prairie to demonstrate that interannual climate variability promotes the coexistence of three common grass species. Specifically, we show that (i) the dynamics of the three species satisfy all requirements of "storage effect" theory based on recruitment variability with overlapping generations, (ii) climate variables are correlated with interannual variation in species performance, and (iii) temporal variability increases low-density growth rates, buffering these species against competitive exclusion. Given that environmental fluctuations are ubiquitous in natural systems, our results suggest that coexistence based on the storage effect may be underappreciated and could provide an important alternative to recent neutral theories of diversity. Field evidence for positive effects of variability on coexistence also emphasizes the need to consider changes in both climate means and variances when forecasting the effects of global change on species diversity.

Association between various physical factors and acute thoracolumbar intervertebral disk extrusion or protrusion in Dachshunds

OBJECTIVE

To determine whether body weight, body condition score, or various body dimensions were associated with acute thoracolumbar intervertebral disk extrusion or protrusion and whether any of these factors were associated with severity of clinical signs in Dachshunds.

DESIGN

Cross-sectional clinical study.

ANIMALS

75 Dachshunds with (n = 39) or without (36) acute thoracolumbar intervertebral disk extrusion or protrusion.

PROCEDURES

Signalment, various body measurements, body weight, body condition score, and spinal cord injury grade were recorded at the time of initial examination.

RESULTS

Mean T1-S1 distance and median tuber calcaneus-to-patellar tendon (TC-PT) distance were significantly shorter in affected than in unaffected dogs. A 1-cm decrease in T1-S1 distance was associated with a 2.1-times greater odds of being affected, and a 1-cm decrease in TC-PT distance was associated with an 11.1-times greater odds of being affected. Results of multivariable logistic regression also indicated that affected dogs were taller at the withers and had a larger pelvic circumference than unaffected dogs, after adjusting for other body measurements. Results of ordinal logistic regression indicated that longer T1-S1 distance, taller height at the withers, and smaller pelvic circumference were associated with more severe spinal cord injury.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that certain body dimensions may be associated with acute thoracolumbar intervertebral disk extrusion or protrusion in Dachshunds and, in affected dogs, with severity of neurologic dysfunction.

Plant-soil feedbacks and invasive spread

Plant invaders have been suggested to change soil microbial communities and biogeochemical cycling in ways that can feedback to benefit themselves. In this paper, we ask when do these feedbacks influence the spread of exotic plants. Because answering this question is empirically challenging, we show how ecological theory on 'pushed' and 'pulled' invasions can be used to examine the problem. We incorporate soil feedbacks into annual plant invasion models, derive the conditions under which such feedbacks affect spread, and support our approach with simulations. We show that in homogeneous landscapes, strong positive feedbacks can influence spreading velocity for annual invaders, but that empirically documented feedbacks are not strong enough to do so. Moreover, to influence spread, invaders must modify the soil environment over a spatial scale larger than is biologically realistic. Though unimportant for annual invader spread in our models, feedbacks do affect invader density and potential impact. We discuss how future research might consider the way landscape structure, dispersal patterns, and the time scales over which plant-soil feedbacks develop regulate the effects of such feedbacks on invader spread.

Matrix metalloproteinase-9 activity in the cerebrospinal fluid and serum of dogs with acute spinal cord trauma from intervertebral disk disease

OBJECTIVE

To detect matrix metalloproteinase (MMP)-9 in serum and CSF and determine relationships between MMP activity and severity of disease, duration of clinical signs, and duration of hospitalization in dogs with acute intervertebral disk disease (IVDD).

ANIMALS

35 dogs with acute IVDD and 8 clinically normal control dogs.

PROCEDURE

CSF and serum were collected from affected and control dogs. Zymography was used to detect MMP-9.

RESULTS

Activity of MMP-9 in CSF was detected in 6 of 35 dogs with IVDD; activity was significantly more common in dogs with duration of signs < 24 hours. Paraplegic dogs were more likely to have MMP-9 activity in the CSF than non-paraplegic dogs. No significant difference in hospitalization time was detected in dogs with IVDD between those with and without activity of MMP-9 in the CSF. Serum MMP-9 was detected more frequently in dogs with IVDD than in control dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Data were consistent with results of experimental rodent spinal cord injury studies that indicate that MMP-9 is expressed early during secondary injury.

Evaluation of the association between spondylosis deformans and clinical signs of intervertebral disk disease in dogs: 172 cases (1999–2000)

OBJECTIVE

To evaluate the association between spondylosis deformans and clinical signs of intervertebral disk disease (IVDD) in dogs.

DESIGN

Retrospective case series.

ANIMALS

210 dogs.

PROCEDURE

Records of 172 dogs with clinical signs of IVDD and 38 dogs with other neurologic disorders were reviewed. Signalment, sites of spondylosis, severity of associated osteophytosis, type of disk herniation, and duration of signs were recorded.

RESULTS

Dogs with IVDD had significantly fewer sites of involvement and lower grades of spondylosis deformans, compared with those in the non-IVDD group. When groups were adjusted for age and weight via multivariate linear regression, there were no differences in severity of osteophytosis or number of affected sites. Dogs with type II disk disease had higher numbers of affected sites and more severe changes, compared with dogs with type I disk herniation. There was no difference between groups in the rate at which IVDD was diagnosed at sites of spondylosis, compared with the rate at which IVDD was diagnosed in unaffected disk spaces. Areas of spondylosis were closer to sites of IVDD that elicited clinical signs than to randomly chosen intervertebral spaces, and distances between sites of spondylosis and sites of IVDD had a bimodal appearance.

CONCLUSIONS AND CLINICAL RELEVANCE

An association may exist between radiographically apparent spondylosis and type II disk disease; type I disk disease was not associated with spondylosis. Spondylosis in radiographs of dogs with suspected type I disk disease is not clinically important. Spatial associations among sites of spondylosis and sites of IVDD may be coincidental or associated with vertebral column biomechanics.

Myasthenia Gravis and Hypothyroidism in a Dog With Meningomyelitis

A 12-year-old, spayed female miniature poodle was evaluated because of a 4-day history of paraparesis, dysuria, and tenesmus. Neurological assessment suggested peripheral nervous system dysfunction, predominantly pelvic limb weakness with a possible concurrent sixth lumbar (L6) to second sacral (S2) myelopathy. Further studies supported the diagnoses of myasthenia gravis, hypothyroidism, and meningomyelitis. To the authors’ knowledge, this is the first reported case of concurrent myasthenia gravis and meningomyelitis in the dog. It was unclear whether the identified conditions evolved from a shared etiopathogenesis or were merely coincidental.

Effects of Temporal Variability on Rare Plant Persistence in Annual Systems

Traditional conservation biology regards environmental fluctuations as detrimental to persistence, reducing long-term average growth rates and increasing the probability of extinction. By contrast, coexistence models from community ecology suggest that for species with dormancy, environmental fluctuations may be essential for persistence in competitive communities. We used models based on California grasslands to examine the influence of interannual fluctuations in the environment on the persistence of rare forbs competing with exotic grasses. Despite grasses and forbs independently possessing high fecundity in the same types of years, interspecific differences in germination biology and dormancy caused the rare forb to benefit from variation in the environment. Owing to the buildup of grass competitors, consecutive favorable years proved highly detrimental to forb persistence. Consequently, negative temporal autocorrelation, a low probability of a favorable year, and high variation in year quality all benefited the forb. In addition, the litter produced by grasses in a previously favorable year benefited forb persistence by inhibiting its germination into highly competitive grass environments. We conclude that contrary to conventional predictions of conservation and population biology, yearly fluctuations in climate may be essential for the persistence of rare species in invaded habitats.

Cerebrospinal fluid from a dog with neurologic collapse

A 3-year-old Staffordshire Terrier was presented to the Texas Veterinary Medical Center with a short progressive history of anorexia, weight loss, and weakness that had progressed to ataxia and collapse with empirical treatment. The dog was tetraparetic and obtunded. Results of a complete neurologic evaluation were consistent with severe, multifocal to diffuse disease involving the forebrain, spinal cord, and brainstem. Cerebrospinal fluid, obtained via cerebellomedullary cisternal puncture, was highly cellular and contained large atypical round cells with small numbers of nondegenerate neutrophils and large mononuclear cells. Rare eosinophils and small lymphocytes were noted. The atypical round cells were approximately 15-25 micro m in diameter with a single nucleus set in a small amount of cytoplasm. The nuclei were typically round to slightly ovoid; however, occasional notched, lobulated, and reniform nuclei were observed. These cells were interpreted as malignant lymphocytes. Owing to a grave prognosis, the animal was euthanized and a necropsy was performed. No gross lesions were found in the central nervous system. Multiple sections of cerebellum, medulla, and spinal cord contained a diffuse neoplastic infiltrate that was predominantly meningeal with rare superficial neuropil invasion. The neoplastic cells were arranged in sheets, cords, and rosettes. Immunohistochemical staining for vimentin, pancytokeratin, CD3, CD79a, synaptophysin, S-100, and neuron-specific enolase was negative; glial fibrillary acidic protein (GFAP) staining was equivocal. Based on histologic findings, a diagnosis of medulloblastoma was made. This case documents the rare occurrence of a canine medulloblastoma and illustrates the difficulty in distinguishing between some embryonal brain tumors and lymphoma.

Use of an ankle-foot orthosis in a dog with traumatic sciatic neuropathy

Traumatic unilateral sciatic neuropathy secondary to a gunshot wound was diagnosed in a seven-month-old, intact male golden retriever. Findings on neurological assessment, performed after cardiovascular stabilisation, were incompatible with a return to normal limb function. An ankle-foot orthosis was used to correct excessive flexion of the digits and tarsus. This device greatly improved the dog's willingness to ambulate and could serve as an alternative to amputation in companion animals with severe sciatic axonotmesis or neurotmesis. Complications associated with chronic tibiotarsal hyperflexion necessitated a pantarsal arthrodesis one year after initial presentation; the dog also developed cranial cruciate disease in the affected limb three years after the gunshot injury.

Mechanisms underlying the impacts of exotic plant invasions

Although the impacts of exotic plant invasions on community structure and ecosystem processes are well appreciated, the pathways or mechanisms that underlie these impacts are poorly understood. Better exploration of these processes is essential to understanding why exotic plants impact only certain systems, and why only some invaders have large impacts. Here, we review over 150 studies to evaluate the mechanisms underlying the impacts of exotic plant invasions on plant and animal community structure, nutrient cycling, hydrology and fire regimes. We find that, while numerous studies have examined the impacts of invasions on plant diversity and composition, less than 5% test whether these effects arise through competition, allelopathy, alteration of ecosystem variables or other processes. Nonetheless, competition was often hypothesized, and nearly all studies competing native and alien plants against each other found strong competitive effects of exotic species. In contrast to studies of the impacts on plant community structure and higher trophic levels, research examining impacts on nitrogen cycling, hydrology and fire regimes is generally highly mechanistic, often motivated by specific invader traits. We encourage future studies that link impacts on community structure to ecosystem processes, and relate the controls over invasibility to the controls over impact.

The glial precursor proteoglycan, NG2, is expressed on tumour neovasculature by vascular pericytes in human malignant brain tumours

Glial precursor cells express NG2 and GD3 in the developing brain. These antigens are both over-expressed during neoplasia, which suggests they may have specific functions in the malignant progression of human brain tumours. This study describes the expression of NG2 and GD3 in 28 paediatric and adult brain tumours. Glioblastoma biopsy spheroids were also implanted into nude rats to assess the regional distribution of the molecules within the tumour. These xenografts showed extensive infiltration and growth that mimicked the growth patterns of human gliomas in situ. NG2 was identified in 20 out of 28 brain tumours, where the expression was confined to the main mass of the tumour, and was reduced towards the tumour periphery. NG2 was mainly associated with blood vessels on both the pericyte and basement membrane components of the tumour vasculature. Ki67 (MIB-1) labelling indicated that NG2 expression was associated with areas of high cellular proliferation. Conversely, all the tumours expressed GD3, which was present both in the tumour main mass and throughout the periphery. Thus, the expression of NG2 may be indicative of tumour progression and might be an amenable target for future therapeutic interventions.