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Biomedical subjects

K G Thompson

Publications and source records attributed to K G Thompson.

84 records · Page 5Linked to original sources
PubMed1976

Enzyme replacement therapy--an experiment of nature in a chimeric mannosidosis calf.

Enzyme replacement therapy was studied in a chimeric mannosidosis calf which had received a natural transplacental transplant of normal lymphocytes from its co-twin. There was considerable reduction in the pathology of certain organs and in the amount of storage oligosaccharides, but the clinical course of this neurologic disease was not significantly altered. It was postulated that if this disease had been purely visceral the transplant would have been relatively effective.

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PubMedDate not supplied

Selective depletion of beta cells affects the development of alpha cells in cat retina.

The results of previous studies suggest that class-specific interactions contribute to the development of the different classes of retinal ganglion cells. We tested this hypothesis by examining the morphologies and distributions of alpha (alpha) cells in regions of mature cat retina selectively depleted of beta (beta) cells as a result of visual cortex lesions at birth. We find that alpha cells in regions of central retina depleted of beta cells are abnormally large while alpha cells in regions of peripheral retina depleted of beta cells are abnormally small. The normal central-to-peripheral alpha cell soma-size gradient is absent in hemiretinae depleted of beta cells. The dendritic fields of alpha cells in the border of beta-cell-depleted hemiretina extend preferentially into the beta-cell-poor hemiretina. In spite of this, alpha cell bodies retain their normal retinal distribution and remain distributed in a nonrandom mosaic-like pattern. Thus, it appears that the development of alpha retinal ganglion cells is influenced by interactions both with other alpha cells (class-specific interactions) and with surrounding beta cells (nonclass-specific interactions).

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PubMedDate not supplied

Direction-sensitive X and Y cells within the A laminae of the cat's LGNd.

Drifting sinusoidal gratings, moving bars, and moving spots were employed to study the direction sensitivity of 425 neurons in the A laminae of the cat's LGNd. Thirty-two percent of X- and Y-type LGNd relay cells exhibit significant direction sensitivity when tested with drifting sinusoidal gratings. X and Y cells exhibit the same degree of direction sensitivity. Moving spots and bars elicit direction specific responses from LGNd cells that are consistent with those elicited when drifting sinusoidal gratings are employed. For cells that are both orientation and direction sensitive, the preferred direction tends to be orthogonal to the preferred orientation. In general, direction sensitivity is strongest at relatively low spatial frequencies, well below the spatial-frequency cutoff for the cell. The presence of significant numbers of direction-sensitive LGNd cells raises the possibility that subcortical direction specificity is important for the generation of this property in the visual cortex.

Animals↗
PubMedDate not supplied

Stimulus dependence of orientation and direction sensitivity of cat LGNd relay cells without cortical inputs: a comparison with area 17 cells.

The cortical contribution to the orientation and direction sensitivity of LGNd relay cells was investigated by recording the responses of relay cells to drifting sinusoidal gratings of varying spatial frequencies, moving bars, and moving spots in cats in which the visual cortex (areas 17, 18, 19, and LS) was ablated. For comparison, the spatial-frequency dependence of orientation and direction tuning of striate cortical cells was investigated employing the same quantitative techniques used to test LGNd cells. There are no significant differences in the orientation and direction tuning to relay cells in the LGNd of normal and decorticate cats. The orientation and direction sensitivities of cortical cells are dependent on stimulus parameters in a fashion qualitatively similar to that of LGNd cells. The differences in the spatial-frequency bandwidths of LGNd cells and cortical cells may explain many of their differences in orientation and direction tuning. Although factors beyond narrowness of spatial-frequency tuning must exist to account for the much stronger orientation and direction preferences of cells in area 17 when compared to LGNd cells, the evidence suggests that the orientation and direction biases present in the afferents to the visual cortex may contribute to the orientation and direction selectivities found in cortical cells.

Animals↗
PubMedDate not supplied

Thromboembolic meningocephalitis caused by Haemophilus somnus infection in a bull calf-a new disease in New Zealand.

Thromboembolic meningoencephalitis (TEME) caused by Huemophilus somnus infection was diagnosed for the first time in New Zealand in an eight month old bull calf. Clinical signs included pyrexia, excessive salivation, recumbency, opisthotonus and rigidity of the front legs. Multiple red, malacic foci (1-10 mm in diameter) were visible grossly on the surface of the cerebrum and cerebellum, and were scattered throughout the brain parenchyma. Histologically these lesions consisted of focal haemorrhage, necrosis and neutrophilic infiltration. Fibrin thrombi and colonies of gram negative bacteria were present in many small blood vessels within necrotic foci. An organism with the morphological and biochemical characteristics of Haemophilus somnus was cultured from the brain. Although TEME is an important disease of feedlot cattle in North America and Europe it is relatively uncommon in cattle grazing pasture and is therefore unlikely to become a major problem in New Zealand.

Journal Article↗
PubMedDate not supplied

Rickets in yearling steers wintered on a swede (Brassica napus) crop.

Rickets was diagnosed in a group of 80 yearling Angus steers wintered for three months on a crop of swedes (Brassica napus) in the Kimbolton area. Growth rate was poor and several steers developed lameness during the final three weeks on the crop. Five animals were euthanased after developing bone fractures. Necropsy of two animals revealed soft ribs, enlarged costochondral junctions and irregularly thickened growth plates in long bones. Histologically there were islands of hypertrophic cartilage within metaphyses and disruption of metaphyseal trabeculae. Thickened, irregular, trabeculae were sometimes lined by wide osteoid seams. Phosphorus deficiency was considered to be the most likely aetiology of the osteodystrophy. The dry matter content of the swedes was only six percent, and in order to satisfy their phosphorus requirements each steer would have had to ingest approximately 330 kg of swedes per day. Rickets is an uncommon disease of grazing animals in New Zealand and to our knowledge this is the first report of its occurrence in cattle.

Journal Article↗