Clinical characteristics, management and long-term outcome of suspected rapid eye movement sleep behaviour disorder in 14 dogs

OBJECTIVE

To describe the clinical characteristics, management and long-term outcome in dogs with suspected rapid eye movement sleep behaviour disorder.

METHOD

Medical records and video recordings of 14 dogs with suspected rapid eye movement sleep behaviour disorder were reviewed and the owners were contacted via telephone or email for further information.

RESULTS

Clinical signs included episodes of violent limb movements, howling, barking, growling, chewing, or biting during sleep. Episodes occurred at night and during daytime naps. The age at onset ranged from 8 weeks to 7·5 years with a median of 6 years but 64% of dogs were one year or less. There was no apparent sex or breed predisposition. Rapid eye movement sleep behaviour disorder events were reduced in severity and frequency in 78% of the dogs treated with 40 mg/kg/day oral potassium bromide. One dog was euthanized within 3 months of the onset of signs because of their severity. The duration of the disorder in the 13 surviving dogs ranged from 1·5 to 9 years. None of the dogs spontaneously recovered.

CLINICAL SIGNIFICANCE

Rapid eye movement sleep behaviour disorder is suspected to occur in dogs, as it does in human beings. It causes concern to the owners and disrupts the home environment. Unlike human beings, rapid eye movement sleep behaviour disorder of dogs often has a juvenile onset.

Radiosurgery using a stereotactic headframe system for irradiation of brain tumors in dogs

Radiation therapy of brain tumors in dogs typically involves administration of multiple fractions over several weeks. Fractionation is used to minimize damage to normal tissue. Radiosurgery uses multiple non-coplanar stereotactically focused beams of radiation in a series of arcs to deliver a single dose to the target with extreme accuracy. The large number of beams facilitates a high degree of conformation between the treatment area and the target tumor and allows for a steep dose gradient; the use of nonintersecting arcs minimizes exposure of normal tissue. Computed tomography with a stereotactic localizer secured to the skull allows generation of a 3-dimensional image of the target and provides accurate spatial coordinates for computerized treatment planning and delivery. Three dogs were treated with radiosurgery, using 1,000 to 1,500 cGy. A linear accelerator mounted on a rotating gantry was used to generate and deliver the radiation. Two dogs with meningiomas survived 227 and 56 weeks after radiosurgery. A dog with an oligodendroglioma survived 66 weeks. No complications were observed following the use of this technique.

Magnetic resonance imaging of cerebral cortical necrosis (polioencephalomalacia) in a dog

A 3-year-old neutered female mixed breed dog was examined because of severe, generalized seizure activity, tetraparesis, and encephalopathic signs. Cerebrospinal fluid (CSF) evaluation was unremarkable except for a mild increase in protein. Serum and CSF titers for infectious diseases were negative. Magnetic resonance (MR) imaging examination of the brain was performed and lesions were found within the cerebral gray matter of the temporal and parietal lobes. The lesions had increased signal intensity on T1, T2, and proton density-weighted images. There was mild inhomogeneous enhancement following intravenous contrast medium administration. Neurologic status improved and the seizures were well controlled, but the dog never regained normal mentation and euthanasia was performed 10 weeks after initial evaluation. At necropsy, severe cerebral cortical necrosis was found in the regions corresponding to the lesions seen on MR imaging examination. Large numbers of fat-containing macrophages (gitter cells) were found within these areas, and are thought to be responsible for the characteristic hyperintensity seen on the MR images.

Magnetic resonance imaging of spongy degeneration of the central nervous system in a Labrador Retriever

A 7-month-old, neutered female Labrador Retriever was evaluated for tetraparesis and subtle cerebellar dysfunction. Clinical signs progressed over a period of 6 weeks to severe ataxia, hypermetria, intention tremors, and finally non-ambulatory tetraparesis. On magnetic resonance imaging of the brain there were large, bilaterally symmetrical, ovoid lesions in the region of the deep cerebellar nuclei that were hyperintense on T2-weighted and proton density images and hypointense on T1-weighted images. There were similar but smaller bilaterally symmetrical lesions present within the thalamus. Euthanasia was performed and lesions consistent with the previously described spongy degeneration of Labrador Retrievers were identified. This disease and its relation to similar human heritable leukodystrophies are discussed.

Polyneuropathies of cats

Polyneuropathies of cats have a variety of clinical presentations. Areflexic flaccid quadriparesis, or quadriplegia, progressing over a 24- to 48-hour period, may be associated with polyneuropathies, as can chronic insidiously progressive tremors and muscle weakness that wax and wane or progress slowly over weeks or months, and which can go undiagnosed for years. In addition, these neurological signs may be due to spinal cord, neuromuscular junction or muscle disorders, so the diagnosis of polyneuropathy can be a challenge even for the most astute of clinicians. Polyneuropathies may have congenital, inherited, inflammatory, metabolic and toxic causes. Sometimes the underlying aetiology is not found and a diagnosis of idiopathic polyneuropathy is made. Since the treatment and prognosis of polyneuropathies in cats vary, the purpose of this review is to assist the veterinary practitioner to recognise, appropriately manage and provide an accurate prognosis for these challenging cases.

Comparison of plasma benzodiazepine concentrations following intranasal and intravenous administration of diazepam to dogs

OBJECTIVE

To determine whether plasma concentrations of benzodiazepines (BDZ) in dogs following intranasal (IN) administration of diazepam are comparable to concentrations following IV administration.

ANIMALS

6 (4 male, 2 female) healthy adult Greyhounds.

PROCEDURE

Dogs were randomly assigned to 2 groups of 3 dogs in a crossover design. Diazepam (0.5 mg/kg of body weight) was administered intravenously to dogs in group 1 and intranasally to dogs in group 2. Blood was collected from the jugular vein of each dog into tubes containing lithium heparin before and 3, 6, 9, 12, 15, 20, 30, 60, 120, 240, and 480 minutes following diazepam administration. After a 4-day washout period, dogs in group 1 received diazepam intranasally, dogs in group 2 received diazepam intravenously, and blood was again collected. Plasma concentration of BDZ was determined by use of a fluorescence polarization immunoassay.

RESULTS

Mean (+/- SD) peak plasma concentration of BDZ following IV administration (1,316 +/- 216 microg/L) was greater than that following IN administration (448 +/- 41 microg/L). Time to peak concentration was < or = 3 minutes following IV administration and 4.5 +/- 1.5 minutes following IN administration. Mean bioavailability of BDZ following IN administration was 80 +/- 9%.

CONCLUSIONS AND CLINICAL RELEVANCE

Diazepam is rapidly and efficiently absorbed following IN administration of the parenteral formulation. Plasma concentrations match or exceed the suggested therapeutic concentration (300 microg/L). Intranasal administration of diazepam may be useful for treatment of seizures in dogs by owners or when intravenous access is not readily available.

Electrodiagnostic evaluation of peripheral nerve function in rheas and barred owls

OBJECTIVE

To establish reference values for electrodiagnostic evaluation of peripheral nerve function in birds.

ANIMALS

6 rheas and 6 barred owls.

PROCEDURE

Birds were anesthetized with propofol or isoflurane in oxygen. Using a computer-based electromyograph system and needle electrodes for stimulation and recording, electromyography (EMG) was performed on the pectoral, biceps brachialis, and gastrocnemius muscles, and evoked EMG was performed on the tibial and ulnar nerves. Motor nerve conduction velocity (MNCV) was calculated. Repetitive stimulation was performed on these 2 nerves. Late F waves were recorded for each nerve, when possible.

RESULTS

Activity was evident during insertion of the electrodes, but muscles tested were electrically quiescent after spontaneous EMG. Motor nerve conduction velocity was faster in the tibial nerve than ulnar nerve but did not differ significantly between species. Mean +/- SEM MNCV was 132.3+/-7.8 m/s for the tibial nerve and 59.7+/-7.8 m/s for the ulnar nerve. A significant difference was not observed in responses at the fourth or ninth stimulation during repetitive stimulation. Subsequent to the initial stimulation, amplitudes were +/-22.7% of the initial motor potential amplitude. Recorded F waves were inconsistent, which may have been associated with technique.

CONCLUSIONS AND CLINICAL RELEVANCE

Reference range (mean +/-2 SEM) for MNCV was 34.1 to 75.3 m/s for the ulnar nerve and 116.7 to 147.9 m/s for the tibial nerve in barred owls and rheas. After repetitive stimulation, motor potential amplitudes may be +/-22.7% of the initial amplitude response.

Possible intraspinal metastasis of a canine spinal cord nephroblastoma

A 2-year-old Basset Hound was admitted to the University of Florida Veterinary Medical Teaching Hospital with progressive spastic paraparesis. At necropsy, intradural extramedullary tumors produced areas of spinal cord swelling and softening in spinal cord segments T11-T12 and L4-L6. Histologic examination of the masses revealed sheets of polygonal blastemal cells, epithelial cells forming tubules and rosettes, and embryonal glomeruloid-like structures in the thoracic mass. Cells in the lumbar mass were less differentiated, forming rare tubules and no glomeruloid-like structures. The occurrence of two tumors in the spinal cord along with the less differentiated appearance of the lumbar tumor raises the possibility that the lumbar mass arose as a result of intraspinal metastasis. To our knowledge, this is the first report of multifocal or metastatic canine spinal nephroblastoma. In addition, the vimentin and cytokeratin immunohistochemical staining characteristics of these spinal cord nephroblastomas are described.

Partial surgical removal of an intramedullary epidermoid cyst from the spinal cord of a dog

An intramedullary space-occupying lesion in the form of an epidermoid cyst was diagnosed in a one-and-a-half-year-old flat-coated retriever. Dorsal laminectomy and durotomy were performed in order to establish the diagnosis followed by excision of one third of the cyst. The remaining cystic tissue that was intimately attached to the spinal cord parenchyma was left in place in order to avoid further damage to the nervous tissue. The dog's neurological status improved dramatically after the surgery, but deteriorated four months later due to recurrence of the cyst.

Canine intracranial epidermoid cyst

A 7-year-old intact male pitbull presented with a 2-month history of progressive dysequilibrium. Cerebrospinal fluid analysis was indicative of a central inflammatory or neoplastic disorder. A cerebellar cystic structure was identified on magnetic resonance imaging which was found to be an epidermoid cyst on histopathology.

Magnetic resonance imaging and ultrasonography in the diagnosis of a malignant peripheral nerve sheath tumor in a dog

A 9-year-old male neutered mixed breed dog had a two-month history of progressive left thoracic limb lameness. There was electromyographic evidence of denervation potentials in all muscles of this limb. In magnetic resonance images a multilobulated, hyperintense mass was visible caudal to the middiaphysis of the left humerus on T-2 weighted images. The mass, which was isointense with surrounding tissue on T1 weighted images, extended proximally towards the brachial plexus. The mass was also visible as a fusiform structure of mixed echogenicity sonographically, although fine-needle aspiration performed at this time was nondiagnostic. A malignant peripheral nerve sheath tumor was diagnosed histopathologically.

Sensory polyganglioradiculoneuritis in a dog

Generalized reduction of nociception and conscious and unconscious proprioception were found in an approximately eight-year-old, male, Maltese mixed-breed dog presented for difficulty prehending food and experiencing ataxia of three months duration. Results of needle electromyogram, motor nerve conduction velocity, and cerebrospinal fluid analysis were normal. A diagnosis of sensory polyneuropathy was suspected. No underlying cause could be determined. Neurological signs progressed to quadriparesis over the following four months despite treatment attempts with prednisone and procarbazine. Necropsy confirmed a sensory polyganglioradiculoneuritis, but no inciting cause could be established.

Peripheral neuropathy in a turkey vulture with lead toxicosis

Clinical, electromyographic, and pathologic findings characteristic of lead toxicosis were detected in a turkey vulture (Cathartes aura). The bird had generalized lower motor neuron dysfunction that progressed over 5 days. Electromyography revealed diffuse denervation potentials and a presumed decrement in the sciatic-tibial nerve conduction velocity. Histologic examination of peripheral nerves obtained at necropsy revealed changes that could be compatible with lead-induced neuropathy. Lead toxicosis was confirmed by determination of blood lead concentrations. Lead toxicosis causing neurologic disorders in birds has been described. However, this report emphasizes the effects of lead on the peripheral nervous system and demonstrates the use of electromyography for diagnosis of peripheral neuropathy in birds.

Secondary hypoadrenocorticism associated with craniocerebral trauma in a dog

An 11-month-old, neutered female miniature schnauzer presented with a severe head injury. The dog was treated for the acute effects of craniocerebral trauma and was hospitalized for just over a week. Several weeks later, she became weak and lethargic. A diagnosis of hypoadrenocorticism was confirmed with an adrenocorticotropin hormone (ACTH) stimulation test. An endogenous ACTH assay confirmed secondary hypoadrenocorticism. The dog was tested for hypopituitarism with canine thyroid-stimulating hormone and thyroxine serum assays and an insulin-like growth factor assay. These tests could not confirm panhypopituitarism in this dog. The hypoadrenocorticism was treated with prednisone, and the dog remains controlled adequately three years later.

Lipid storage myopathy in a cocker spaniel

A six-year-old male cocker spaniel was presented to the Veterinary Medical Teaching Hospital, University of Florida, with a three-week history of generalised weakness and myalgia. Electrodiagnostic evaluation, cerebrospinal fluid analysis and thoracolumbar myelography were unremarkable. Biopsies from vastus lateralis and triceps muscles revealed numerous large lipid droplets within type 1 fibres and to a lesser degree within type 2 fibres. The resting plasma lactate was mildly increased and there was elevated urinary excretion of lactic, pyruvic and acetoacetic acids, increased urinary excretion of carnitine esters, and increased plasma alanine. This pattern of metabolite excretion is consistent with an, as yet undefined, block in oxidative metabolism.

Primary encephalic plasma cell tumor in a dog

A 5-year-old female spayed Spitz dog had a 5-week history of right head tilt, seizures, and progressive quadriplegia. Analysis of cerebrospinal fluid revealed 27,600 white blood cells per microliter with 63% mononuclear phagocytes, 27% lymphocytes, 6% neutrophils, 3% plasmacytoid cells, and 1% eosinophils, and over 2000 mg/dl protein. On contrast-enhanced magnetic resonance images, a focal 1-cm oval lesion was identified in the right ventral brainstem. There was also marked contrast enhancement of the meninges in the following areas: surrounding the brainstem, outlining cerebellar folia, along the ventral floor of the brain and extending to the falx cerebri, and partially outlining the left frontal lobe. At necropsy, the areas of contrast enhancement corresponded to the presence of compact cellular sheets of pleomorphic, anisocytotic, oval to polygonal neoplastic cells with plasmacytoid differentiation. The smaller of these plasmacytoid cells stained predominantly for cytoplasmic immunoglobulin A using immunoperoxidase methodology. Ultrastructurally, the neoplastic cells had morphologic features typical of plasma cells, with large amounts of predominantly rough endoplasmic reticulum with variably prominent Golgi formation. This is the first report of a canine primary intracranial malignant plasma cell tumor.

Neurologic examination of sea turtles

OBJECTIVE

To determine whether neurologic examination techniques established for use on dogs and cats could be adapted for use on sea turtles.

DESIGN

Prospective controlled observational study.

ANIMALS

4 healthy Green Turtles (Chelonia mydas), 1 healthy Kemp's ridley sea turtle (Lepidochelys kempi), and 6 Green Turtles suspected to have neurologic abnormalities.

PROCEDURE

Neurologic examinations were performed while sea turtles were in and out of the water and in ventral and dorsal recumbency. Mentation, general activity, head and body posture, movement and coordination, thoracic and pelvic limb movement, strength and muscle tone, and tail movement were observed. Thoracic and pelvic limb flexor reflexes and nociception, righting response, cranial nerve reflexes, clasp and cloacal reflexes, and neck, dorsal scute, cloacal and tail nociception were tested.

RESULTS

Results of neurologic evaluations were consistent for healthy sea turtles. Sea turtles suspected to have neurologic abnormalities had abnormal results.

CLINICAL IMPLICATIONS

Many of the neurologic examination techniques used to evaluate dogs and cats can be adapted and used to evaluate sea turtles. A standardized neurologic examination should result in an accurate assessment of neurologic function in impaired sea turtles and should help in evaluating effects of rehabilitation efforts and suitability for return to their natural environment.

Acute, flaccid quadriplegia in three cats with suspected coral snake envenomation

Three cats were evaluated for acute, ascending, flaccid quadriplegia; depression; and reduced nociception. Complete or partial neuromuscular junction blockade was found on nerve stimulation studies during electromyographic examinations. Two of the cases had wounds on the chin or paw compatible with coral snake bites. Although a coral snake was found in only one case, coral snake envenomation was suspected because potential for exposure, clinical signs, and electrodiagnostic findings were similar to dogs reported with this condition and to cats with tiger snake envenomation. Only one case received coral snake antivenin. All cases recovered within seven-to-10 days.

Spinal meningeal sarcoma in a rottweiler puppy

An 11-week-old rottweiler puppy was presented for evaluation of progressive paraparesis, urinary and faecal incontinence. Radiography and myelography revealed widening of the vertebral canal and remodelling of several lumbar vertebrae associated with an intramedullary spinal mass. Magnetic resonance imaging revealed an extensive, heterogeneous mass involving the lumbosacral spinal cord. Histopathological examination indicated a meningeal sarcoma with very varied cytological architecture.

Diagnostic and prognostic importance of chromosomal aberrations identified in 61 dogs with lymphosarcoma

To determine the diagnostic and/or prognostic importance of chromosomal aberrations identified in dogs with malignant (non-Hodgkin's) lymphoma, clinical stages for 61 dogs with lymphosarcoma were determined, the lymph node(s) were histopathologically graded, and the malignant tissue lymphocytes were karyotyped. The results from life table survival curve analysis demonstrated that first remission length and survival time were significantly longer in 15 of 61 (25%) dogs that had a trisomy of chromosome 13 as the primary chromosomal aberration than in those dogs (46/61, 75%) with other primary chromosomal aberrations (P < 0.05). Sex, age, weight, histopathologic subtype and grade, World Health Organization (WHO) clinical stage, WHO and modified Karnofsky performance status, chromosomal modal number, and treatment protocol were of no prognostic importance in predicting first remission length or survival time (P > 0.05). Multivariate analysis did not identify a significant correlation between the prognostic groups or within the various prognostic subsets (P > 0.05). The pathogenesis of canine and human non-Hodgkin's lymphoma, as observed cytogenetically, differs.

An auricular acupuncture treatment for idiopathic canine epilepsy: a preliminary report

A new canine auricular acupuncture point for the treatment for epilepsy is introduced. The new acupoint was used with a previously reported canine auricular acupoint (van Neikerk and Eckersley, 1988) for the treatment of epilepsy in five dogs. The testimonial results of these five cases indicate that the technique is worthy of scientific investigation, and controlled research is proposed. Only testimonial evidence currently supports its application, yet this innocuous treatment is recommended for use in all cases of canine epilepsy. The traditional Chinese medical explanation for the treatment is described, and hypothetical Western physiology is presented.

Analysis of aphidicolin-induced chromosome fragility in the domestic pig (Sus scrofa)

Aphidicolin (APC)-sensitive fragile sites were identified in chromosome preparations from peripheral lymphocyte cultures of 12 four-way crossbred pigs. A chi 2 analysis demonstrated that aphidicolin-induced breakage events and previously reported in vivo chromosome rearrangement events were not independent. Comparison of expected Poisson and negative binomial distributions to observed breakage patterns indicated that the negative binomial distribution provided a better fit to experimental data. The negative binomial distribution is consistent with a distribution of breakage rates, i.e., non-constant rates of breakage at chromosomal loci across the genome.

Integration, expression and germ-line transmission of foreign growth hormone genes in medaka (Oryzias latipes)

Gene constructs consisting of human growth hormone (hGH) gene driven by promoter/regulatory sequence of mouse metallothionein (mMT), viral thymidine kinase (vTK), rat cholecystokinin (rCCK), or chicken beta-actin (cBA) gene were injected into the cytoplasm of fertilized medaka eggs via the micropyle. More than 49% of the injected embryos survived at hatching. Up to 26% of the survivors showed integration of the introduced gene construct, as determined by polymerase chain reaction analysis and subsequent confirmation by Southern blot hybridization of the genomic DNA. A significant fraction of F1 progeny, derived from crosses between transgenic founders and the nontransgenic individuals, inherited the transgene. Expression of hGH gene was also observed in some of the P1 founders and F1 transgenic progeny carrying mMT-hCG or cBA-hGH gene. Furthermore, the growth performance of the P1 mMT-hGH and cBA-hGH transgenic founders and F1 cBA-hGH F1 transgenic progeny was significantly greater than their full sibling, nontransgenic individuals. In addition to the microinjection experiment, a gene construct containing the long-terminal repeat (LTR) sequence of avian Rous sarcoma virus (RSV) and rainbow trout (rt) GH2 cDNA was introduced into embryos of medaka by electroporation using an exponential decay electroporator. Approximately 70% of the electroporated embryos survived at hatching, and 20% of the survived individuals integrated RSVLTR-rtGH2 cDNA into their genomes. These two techniques will greatly enhance the ability to study regulation of gene expression in transgenic animals during differentiation and development.

Cerebrospinal fluid analysis

Accurate interpretation of cerebrospinal fluid (CSF) changes can only be made in the context of the differential diagnosis for each case. The routine analysis of CSF cell number and type as well as CSF total protein can provide information that suggests a specific mechanism or disease, but is often inconclusive. Further information obtained from CSF protein electrophoresis and immunoglobulin determination and calculation of an albumin quota and IgG index can lend additional support for the suspected mechanism of disease. Paired serum and CSF antibody titers for specific organisms can be useful to confirm the presence of a systemic or nervous system infection. Current research on detecting antibodies against nervous tissue components in CSF should result in better diagnostic capabilities and understanding of the pathophysiology of certain disorders in the future.

Tissue-specific expression of the human neuropeptide Y gene in transgenic mice

Neuropeptide Y (NPY) is the most abundant neuropeptide detected in the mammalian brain, and is found throughout the central and peripheral nervous system. This peptide is a proposed regulator of appetite, blood pressure, and pituitary hormone release. Previous experiments have demonstrated the ability of 5' sequences within the human NPY gene to promote transcription in cultured neuronal cells. To identify sequences in this gene that regulate tissue-specific expression, a NPY/CAT fusion gene, containing approximately 850 bp of NPY sequences, was microinjected into fertilized mouse ova. Five lines of transgenic mice were derived from these ova and several tissues from mice of each line were tested for transgene expression using the CAT assay. One line demonstrated X-chromosome-linked transmission of the transgene while the other lines demonstrated autosomally-linked transmission. Three lines demonstrated transgene expression with significant levels of CAT activity detectable only in tissues which have been shown to express endogenous NPY. One autosomally-linked line did not demonstrate significant levels of transgene activity because the transgene appeared to have undergone structural alteration during genomic integration. No transgene activity was detected in either male of female mice from the X-linked line, suggesting a positional regulation of the transgene locus other than X-inactivation in this line. The present research demonstrated the NPY regulatory sequences included in pCATNPY delta 796 sufficiently directed tissue-appropriate gene expression in transgenic mice.

Analysis of post-implantation mouse embryos after maternal heat stress during meiotic maturation

The effects of heat stress during oocyte maturation were studied in post-implantation mouse embryos. Virgin ICR mice were exposed to 35 +/- 1 degree C and 65 +/- 3% RH for 12.5 h beginning immediately after synchronization of ovulation with PMSG and hCG. Embryos of heat-stressed dams were developmentally heterogeneous and showed significant delays in development with as much as 48 h delayed development. Nearly 6% of these embryos were triploid, and another 2% were hyper-diploid. Development of triploid embryos was delayed more than 24 h. Nine embryos with severe developmental delay had heterogeneous chromosome constitutions. Embryo mortality before and after implantation was higher in heat-stressed dams than in controls.

Effects of dexamethasone and chlorpromazine treatment on X-Y dissociation and multinucleated giant cell formation in hyperthermic mice

The effects of anti-stress drugs on X-Y dissociation and multinucleated giant cell formation in the testes of hyperthermic mice were determined for the possible use of such drugs in animal production. Mice were injected with dexamethasone 1 mg/kg or 2 mg/kg, chlorpromazine 1 mg/kg or 4 mg/kg, or 0.85% saline, and heat stressed for 4 d at 35 +/- 1 C and 65 +/- 1 % relative humidity. Mice were killed 5 d after stress, and the testes processed for observation of meiotic chromosomes and testicular histology. Heat stress caused a significant increase in X-Y bivalent dissociation in diakinesis-metaphase I spermatocytes and a significant increase in formation of multinucleated giant cells. Drug treatment increased X-Y dissociation but had no significant effect on giant cell formation.

A leukoencephalomyelopathy of rottweiler dogs

Two adult rottweiler dogs were evaluated for slowly progressive ataxia and paresis of all four limbs of over seven months duration. On neurologic examination, signs referable to a lesion in the cervical spinal cord affecting motor and sensory white matter tracts were found. Both dogs were necropsied and were found to have demyelinating lesions in the spinal cord, brain stem, and deep cerebellar white matter. Primary morphologic alterations were intact naked axons and thinly myelinated axons accompanied by reactive astrogliosis. The spinal cord lesions tended to have bilateral symmetry and were found in the lateral funiculi and occasionally in the dorsal funiculi. The cause and pathogenesis of the lesion were not determined.

Neuroaxonal dystrophy of Rottweiler dogs

Five Rottweiler dogs were examined because of progressive ataxia of thoracic and pelvic limbs of several months' to 4 years' duration. Hypermetria, especially of the thoracic limbs, and head incoordination and tremors were obvious features in the 3 older dogs. None of the dogs had evidence of weakness or loss of conscious proprioception. An electroencephalogram in 1 severely affected dog was normal. Electromyograms in 2 severely affected dogs were normal except for some positive sharp waves and fibrillation potentials in the interosseus muscles of all 4 feet. Cerebrospinal fluid evaluations of 2 severely affected dogs were normal. A reduced number of sensory nerve endings, compared with age-matched controls, was seen on histologic examination of a conjunctival biopsy specimen in 1 severely affected dog. An antemortem diagnosis of neuroaxonal dystrophy was suspected from the signalment, history, and neurologic examination findings. The diagnosis was confirmed on the basis of microscopic findings in 3 dogs necropsied.

Neurotoxicologic effects of the nonionic contrast agent iopamidol on the leptomeninges of the dog

The effect of iopamidol on the leptomeninges was tested and compared with that of metrizamide and normal saline solution in 18 dogs. Pathologic and clinical effects were evaluated at 24 hours and 14 days after cisternal injection of iopamidol, metrizamide, or normal saline solution. Pathologic changes were evaluated by microscopic examination of serial CSF samples and of sections of brain and spinal cord with the leptomeninges intact. Clinical changes were subjectively evaluated. Electromyograms and EEG were performed on each dog after physical and neurologic examination. There were no changes seen in neurologic status, electromyogram, or EEG in any of the dogs immediately after subarachnoid injection nor at 24 hours or 14 days later. Pathologic changes were limited to mild, moderate, or severe patchy hemorrhagic leptomeningitis seen at 24 hours after iopamidol or metrizamide was injected. The severity of changes were judged to be similar with both these agents. The CSF analysis and histologic evaluation of brain and spinal cord sections revealed a neutrophilic response to iopamidol and a mononuclear response to metrizamide. These findings indicate that iopamidol has minimal neurotoxicologic effect on the leptomeninges and therefore has merit as a myelographic agent.

Investigation of hyperthermia-induced dominant lethal mutations in male mice

The mutagenic potential of hyperthermia was investigated in a random-bred stock of mice to determine if this is one mechanism by which elevated ambient temperature exerts its deleterious effects on mammalian reproduction. Two dominant lethal assays were conducted to measure mutagenicity during the meiotic and post-meiotic stages of spermatogenesis following various periods of heat stress. Indirect evidence for hyperthermia-induced dominant lethality was obtained in the form of increases in the frequencies of preimplantation loss and sterile matings. However, the large number of sterile matings precluded unambiguous statistical analysis of the incidence of early embryonic mortality that would have provided direct evidence of induced dominant lethality. Control data indicated that the stock of mice used in this experiment is an excellent choice for dominant lethal studies because of the large number of implants and the low frequency of embryonic mortality.

Influence of phenylalanine and lysine deficiencies on thyroid morphology in the chick

A study was conducted to investigate the effects of dietary phenylalanine and lysine deficiencies on thyroid morphology in chicks fed crystalline amino acid diets. Both mean follicle diameter and epithelial cell height were significantly reduced in birds fed either of the deficient diets as compared with controls. These results agree with previous studies on serum T4 and T3 concentrations where the effects of an amino acid deficiency were general and not limited to precursors of thyroxine.

Cytogenic analysis of preimplantation blastocysts from prepuberal gilts treated with gonadotropins

Metaphase chromosomes were examined in 10-day-old embryos collected from prepuberal gilts that had been induced to ovulate, using a combination of 200 IU of human chorionic gonadotropin (HCG) and 400, 600, or 800 IU of pregnant mare serum gonadotropin (PMSG) followed 72 hours later by 500 IU of HCG. A repeatable, reliable method was developed for the processing of early porcine embryos in the hatched spherical blastocyst stage for cytogenetic analysis. Of 170 embryos recovered and processed from 21 gilts, 169 yielded analyzable metaphase cells for determination of somatic cell chromosome number for an overall success rate of 99.4%. All embryos were diploid (2n = 38) in chromosomal constitution, and although isolated tetraploid (4n = 76) and octaploid (8n = 152) cells were found, true triploid or other polyploid embryos were not present. The absence of these aberrations indicated that at the dosage levels tested, the hormone PMSG did not cause an increase in occurrence of polyploidy in porcine blastocysts present at day 10 of gestation. Analyses showed no significant (P less than 0.05) increase in numbers of corpora lutea or embryos at day 10 of gestation in gilts treated with these PMSG dosage levels.

Ovum morphology after hyperthermic stress during meiotic maturation and ovulation in the mouse

Eggs were collected from 60 virgin ICR mice 15 1/2 h after synchronization of ovulation with PMSG and hCG from control females and those exposed for 15 1/2 h to hyperthermic conditions (35 +/- 1 degrees C, 65 +/- 3% relative humidity) immediately after the hCG injection. Eggs were classified for analysis as monocellular, bicellular, tricellular equal, tricellular, unequal, multicellular and degenerate. Egg class frequencies were affected by increasing atypical forms (P < 0.01). Stressed animals had significantly larger cells when an analysis of variance was performed on the bicellular classification, but there was no effect on ovum diameter.

Comparative karyology of the freshwater snails Bulinus tropicus and B. natalensis

Species of the subgenus Bulinus s.s. occur in a polyploid series which is of interest because of the rarity of polyploidy in animal species and because there appears to be a relation between ploidy level and ability to transmit Schistosoma haematobium, a parasite of major public health importance. We describe a technique for the preparation of standard karyotypes using cell suspensions from colchicine-treated embryos. The results for two diploid species, B. tropicus (Krauss) and B. natalensis (Küster), are presented. Both karyotypes consist of 15 metacentric and 3 submetacentric chromosomes. However, differences in centromere position are found in four pairs of chromosomes, and in the appearance of a secondary constriction. Because B. natalensis may represent a relict taxon involved in the origin of the polyploids, the results of significance for future work on the phylogeny of this group.

The effect of pregnant mare serum gonadotropin on mouse oocytes as monitored at metaphase II

Ovulated oocytes were collected from random-bred, 7-12 week old ICR mice injected with 0, 3, or 6 i.u. pregnant mare serum gonadotropin (PMSG). Analyses of 872 metaphase figures from 87 females did not show a significant increase in chromosomal imbalance with PMSG treatment. A tendency toward ovum fragmentation was noted with an increase in PMSG dose.

Hyperthermia induced dissociation of the X-Y bivalent in mice

The mutagenic potential of hyperthermia was examined employing a spermatocyte test on males heat stressed continuously for 2, 3. or 5 days. Stress conditions were 35 +/- 1 degrees C and 65 +/- 3% relative humidity. Males were sacrificed and meiotic preparations made from the testes at various intervals following removal from the stress environment. In this way, chromosome damage could be monitored in all premeiotic and early prophase I stages of spermatogenesis. Results of this study revealed a significant increase in the incidence of X and Y univalents at metaphase I. The significance of this finding is discussed.

Cytogenetic effects of diethylstilbestrol-diphosphate (DES-dp) on mouse bone marrow monitored by the micronucleus test

6 dosages of diethylstilbestrol-diphosphate (DES-dp), ranging from 0.01 to 500 mg per kg of body weight were compared to saline and phosphate buffered saline (negative controls) and two dosages of cyclophosphamide (positive control) in the micronucleus test with 115 ICR mice. DES-dp failed to generate a significant increase in micronucleated polychromatic erythrocytes over negative controls. Cyclophosphamide produced a dose-related increase in micronuclei similar to previously published reports. Iit was therefore determined that the micronucleus test did not detect the types of chromosomal changes known to be generated by DES-dp and DES.

Effect of maternal parity on aneuploidy in early mouse embryos

An attempt to evaluate the incidence of chromosomal aneuploidy in mouse blastocysts recovered from females of various ages and parity levels revealed an insignificant regression coefficient for aneuploidy on age of the female and its square, and an insignificant correlation coefficient for aneuploidy with the number of previous offspring born to the dam. However, significant regression coefficients were obtained for aneuploidy on parity of the dam and its square. These results indicate that not only does aneuploidy increase with parity level, but the rate of increase accelerates as parity level increases. Possible explanations for the increase in aneuploidy and its detrimental effect on reproductive efficiency were discussed.