Biomedical subjects
S Carmichael
Publications and source records attributed to S Carmichael.
Trimethoprim-sulphonamide hypersensitivity in dogs.
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Flurbiprofen warning.
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Familial cerebellar ataxia with hydrocephalus in bull mastiffs.
A family of bull mastiff pups in which 16 animals developed certain neurological signs is described. It is probable that the disease is inherited in an autosomal recessive manner. Clinical and pathological examination of six animals revealed ataxia, behavioural abnormalities and a visual defect associated with symmetrical lesions in the cerebellar nuclei, lateral vestibular nucleus and inferior colliculus together with a communicating hydrocephalus. The cerebellar lesions consisted of vacuolation, gliosis and axonal degeneration. Evidence for both axonal and oligodendroglial abnormalities was present and these probably result from a genetically determined metabolic disturbance in the affected neurones.
Polyradiculoneuritis in two dogs presenting as neuritis of the cauda equina.
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The relationship of glucose utilization and morphological change in the visual system in hexacarbon neuropathy.
A reduction in local glucose utilization occurs in the superficial layer of the superior colliculus of rats following exposure to 0.5% 2,5-hexanedione in drinking water for 3 weeks. Axonal pathology, with increased neurofilaments and swelling, is seen at about 5 weeks in the distal portions of the optic pathways to the superior colliculus. These lesions in the optic system occur earlier and are more marked than those in the peripheral nerves and dorsal columns. The results suggest that the functional abnormality, as implied by the decreased glucose utilization, precedes the morphological changes in hexacarbon neuropathy.
Case of isolated sensory trigeminal neuropathy in a dog.
A two-year-old rough collie bitch with a five-week history of excess salivation, coughing and dysphagia was examined. The dog had bilateral sensory loss over the whole trigeminal field while motor function of the fifth cranial nerve was preserved. No other neurological abnormalities were detected. The dog was observed over 18 months during which the condition did not progress. It was destroyed 18 months after the onset of trigeminal signs following development of a systemic illness, refractory to treatment and unrelated to the neurological signs. Pathological abnormalities were limited to the three major branches of both fifth nerves and the gasserian ganglia. There was partial loss of myelinated nerve fibres in each branch and also in the spinal tract of the fifth nerve in the brain stem. It was considered that the primary abnormality was in the gasserian ganglion and that the fibre loss was secondary to the neuronal lesion in the ganglia. The motor nucleus of the fifth nerve was normal. No cause could be found for this isolated sensory neuropathy of the trigeminal nerve.
Tumours involving the brachial plexus in seven dogs.
Seven cases with tumours localised in the brachial plexus are described. The main clinical features were a progressive lameness in one forelimb with marked muscle atrophy and very obvious but non-localizable pain. A palpable lump in the axilla was present in less than half the cases. Ancillary aids contributed little in the diagnosis except for electrophysiology which gave evidence of neural damage at an early stage of the disease and as such may be the most useful aid to an early diagnosis. Two different pathological entities were observed, the first where the tumour, primarily of neural origin (usually a neurofibrosarcoma), arose within the nerves themselves and the second where the tumours arose in adjacent tissue and involved the plexus by local infiltration. In all cases the prognosis was hopeless because of local infiltration of the tumour and metastases. In the early stages accurate diagnosis can be difficult in the absence of a mass but the possibility should be considered in any case where chronic lameness with obvious non-localizable pain is present in one forelimb.
Some aspects of the aetiology, diagnosis and treatment of infertility in the bitch.
The nature of the infertility in 19 bitches was investigated: 10 animals were considered to be normal on the basis of their sexual behaviour, vaginal cytology and plasma oestrogen and progesterone concentrations. Successful conception and whelping occurred for 6 of the 10 bitches. The previous apparent infertility was probably attributable to defective mating management by the owners. Although follicular development and ovulation occurred in 4 of the remaining bitches, oestrus was not exhibited: AI resulted in 3 conceptions. The other 5 animals exhibited only some of the normal characteristics of pro-oestrus. Another group of 10 anoestrous bitches (normal and pathological) was treated with PMSG or stilboestrol. PMSG induced follicular development in 5 of 6 bitches treated. The magnitude of the induced plasma oestrogen peak varied considerably. Delay in the initiation of oestrous behaviour occurred relative to the plasma gonadal steroid pattern in 2 of the 3 bitches that showed oestrus. Stilboestrol induced a sequence of behavioural changes and plasma steroid concentrations and patterns similar to those found in the normal oestrous bitch, but none conceived.
Medicine and contemporary cultism.
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Inherited canine giant axonal neuropathy.
To date, a single case of canine giant axonal neuropathy (GAN) has been recorded. The present report describes the disease in 3 more dogs from the second litter produced by the parents of the original case. Regular clinical and electrophysiological examinations were carried out on all 11 dogs of the second litter. At 14--16 months of age, 3 dogs developed slight posterior ataxia which progressed to a severe lower motor neuron disturbance involving only the hind legs. During this period, each dog began to regurgitate food as a result of megaesophagus. From 12 months of age, there was a progressive reduction in the amplitude of the evoked muscle action potential. Biopsy of the tibial fascicular nerve at 16 months of age confirmed that all 3 dogs had GAN, with numerous swollen unmyelinated fibers and less frequent enlarged myelinated fibers containing accumulated neurofilaments.
The effect of post-spin drawing on spider silk microstructure: a birefringence model.
Measurements of optical birefringence have been used to characterise the effect of mechanical history on supramolecular structure in major ampullate silk from Nephila clavipes (golden orb weaver) spiders. Birefringence modelling is demonstrated to be a powerful technique for obtaining quantitative information on supramolecular rearrangement in response to macroscopic strain. Temporary and permanent birefringence changes measured as a function of strain and strain rate are interpreted in terms of two types of microstructural response: increased molecular alignment in all the microstructural phases present is accompanied by decreased lateral register within crystallographically ordered phases. Significant implications of these studies for the commercial processing of silks and silk-like biopolymers are discussed.
Further studies of the central nervous system in canine giant axonal neuropathy.
The CNS of three further cases of canine giant axonal neuropathy (GAN) were examined. The axonal swellings were present in the distal portions of the spinal long tracts and their terminations in the cerebellar vermis; in the distal optic pathways; the nuclei of the habenulo-interpeduncular tract; certain thalamic relay nuclei and the cerebral cortex. The swellings were present both paranodally and internodally with the myelin sheath being attenuated or even absent. Excessive numbers of disordered 10 nm neurofilaments were the main constituent although mitochondria, membranous bodies, glycogen bodies and amorphous electron dense material also accumulated, particularly in the fasciculus gracilis. The neurotubules tended to form small subaxolemmal or intra-axonal islands. Complex interdigitations of oligodendroglia and axolemma were found in the affected areas. A small number of fibres in the rostral fasciculus gracilis showed marked proliferation of the smooth endoplasmic reticulum which may represent abortive attempts at regeneration. A small proportion of astrocytic processes were markedly enlarged with excessive whorling of the glial filaments. The accumulation of these various organelles in the non-terminal axon in the absence of mechanical obstruction suggests a defect in axoplasmic transport which may result from an energy failure as suggested in toxic neuropathies. The significance and pathogenesis of the glial filamentous changes and those reported in other cells in human GAN is at present uncertain.
Vertebral plasma cell tumors in 8 dogs.
The case histories of 8 dogs with spinal pain and neurologic deficits associated with vertebral plasma cell tumor are reviewed. Four dogs had solitary plasmacytoma, 3 had multiple myeloma, and 1 dog had 2 vertebral lesions with no evidence of disseminated disease. Four dogs were treated: 2 with multiple myeloma received chemotherapy only and survived 17 and 26 months, respectively. Two dogs with solitary plasmacytomas of the spine had chemotherapy and radiotherapy: the 1st survived 4 months and was euthanized after developing radiation myelopathy; the 2nd survived 65 months before developing multiple myeloma. The diagnosis of solitary plasmacytoma of the spine versus multiple myeloma is discussed.