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Biomedical subjects

A C Johnstone

Publications and source records attributed to A C Johnstone.

17 recordsLinked to original sources
PubMed1990

The pathology of an inherited hyperlipoproteinaemia of cats.

The gross and histological features of congenital lipoprotein lipase deficiency are described in eight cats. The main histological features could be directly related to the presence of the chylomicronaemia. They consisted of lipid accumulation within clear vacuoles or ceroid accumulation within residual bodies in parenchymatous organs such as the liver, spleen, lymph nodes, kidney and adrenal gland. Xanthomata were seen in various sites, probably arising either from frank haemorrhage or the leakage of lipid-rich plasma perivascularly. As in human lipoprotein lipase deficiency there was no evidence of the formation of atherosclerotic plaques. Focal degenerative changes were, however, present within arteries and this may indicate blood vessel weakness and explain the tendency to haemorrhage and xanthomata/granulomata formation. The degeneration and fibrous replacement of glomeruli and nephrons possibly arises from pressure necrosis of adjacent xanthomata and alterations in renal blood flow.

Animals↗
PubMed1989

The ultrastructural pathology of five lipoprotein lipase-deficient cats.

The ultrastructural pathology of cats suffering from familial lipoprotein lipase deficiency is described. There were large numbers of lipid vacuoles within hepatocytes, epithelial cells of the proximal convoluted tubule of kidney and macrophages of the liver, spleen and lymph node. The older cats tended to have larger quantities of ceroid within hepatocytes and macrophages, and all stages of development of ceroid were observed. Chylomicron emboli were seen within the glomerular capillaries and interlobular blood vessels. There was podocyte foot fusion and thickening of basement membranes of glomeruli, Bowman's capsule and some proximal convoluted tubules, similar to that seen in diabetes mellitus. These changes represent a non-specific reaction of the kidney to noxious insults such as hypoxia caused by emboli. Transformation of smooth muscle cells from a contractile to a synthetic state was seen in the splenic trabeculae and, to a lesser extent, in blood vessels. Dilatations of the nuclear membrane of the lymphocytes were noted, the significance of which is unknown.

Animals↗
PubMed1987

Congenital vascular tumours in the skin of horses.

Congenital vascular tumours in the skin of the legs of two horses showed histological features at biopsy which were consistent with capillary haemangioma but, at necropsy, one tumour had invaded the superficial digital flexor tendon and was therefore classified as a haemangiosarcoma.

Animals↗
PubMed1987

The effects of gamma-irradiation on haemopoiesis and red blood cell destruction in hamsters infected with Leptospira interrogans serovar ballum.

Irradiated hamsters were infected with Leptospira interrogans serovar ballum in order to study the effects of impairment of the reticulo-macrophage system on the progression of the disease and the development of haemoglobinaemia. Infected and irradiated hamsters were compared with infected controls, irradiated controls and untreated controls. Red blood cells (RBCs) from untreated controls were biconcave disks while those from irradiated controls were echinocytes. Red blood cells from animals of both infected groups which were severely affected and moribund were in the form of pitted spherocytes and were associated with increased icteric indices and haemoglobinaemia. Red blood cells from less severely affected animals were echinocytic. Pitted spherocytes, however, were seen in some irradiated-infected hamsters before increased icteric indices and haemoglobinaemia were present. Both irradiated-infected and irradiated hamsters showed severe depletion of haemopoietic cells and lymphoid cells, with regeneration occurring in those animals which survived for longer. Red cell sequestration and erythrophagocytosis were present in infected-only hamsters. In irradiated-infected animals, severe anaemia was caused by both persistence of fixed macrophages, RBC sequestration and erythrophagocytosis, and haemorrhage due to vascular damage and renal papillary necrosis. A severe leucopaenia affected the irradiated hamsters' ability to suppress leptospiral multiplication resulting in the presence of larger numbers of organisms.

Animals↗
PubMed1986

Peripheral neuropathy in cats with inherited primary hyperchylomicronaemia.

Primary hyperlipoproteinaemia (hyperchylomicronaemia) with a slight increase in very low density lipoprotein) is described in 20 cats. Fasting hyperlipaemia, lipaemia retinalis and peripheral neuropathies were the most frequently detected clinical signs. The disease is thought to be inherited as an autosomal recessive trait but the exact mode of inheritance has not been determined. Affected cats showed reduced lipoprotein lipase activity measured after heparin activation compared with the response in normal cats. Plasma triglyceride and cholesterol were increased in all the cats with the major proportion of triglyceride and cholesterol being present in chylomicrons. The peripheral nerve lesions were caused by compression of nerves by lipid granulomata. It is probable that the lipid granulomata result from trauma because the nerves most often affected were at sites like the spinal foraminae where they were susceptible to trauma.

Animals↗
PubMed1985

Investigations into the association of retroviruses with ovine lymphoma.

To determine whether retroviruses are associated with sporadic ovine lymphoma, suspension cell cultures of four lymphomas and one control lymph node were labelled with tritiated uridine. Following differential and sucrose density gradient ultracentrifugation of their media a peak of radioactivity was found at a density of 1.15 to 1.18 g ml-1 in preparations from the cell cultures of two lymphomas and the normal lymph node. Sedimentation velocity centrifugation of the sodium dodecyl sulphate-treated radiolabelled material found an approximate sedimentation value of 7S. The assay for RNA directed DNA polymerase in ultracentrifuged pellets of media from cultures of 15 lymphomas and one control lymph node found activity in material from four lymphomas and the control node cultures. However, little variation in incorporation kinetics occurred with changes in assay conditions and activities were not associated with particles of density 1.15 g ml-1. It was concluded that the detected activities were not retroviral in origin.

Animals↗
PubMed1984

An immunological classification of ovine lymphomas.

Sporadic ovine lymphoma cells were identified as T or B lymphocytes with a T cell-specific antiserum or by detecting surface immunoglobulin. Lymphomas were classified as being of T or B cell origin if 60 per cent, or more, of the cells were of the respective type. Of 16 lymphomas, 6 were T cell and 6 were B cell derived. In one lymphoma more than 60 per cent of the cells were identified as both T and B cells. In the other 3 lymphomas neither T nor B cells reached this value; 2 of these had negligible T and B cell numbers and were classified as null cell lymphomas. A relationship was seen between the immunological and anatomical classifications of the lymphomas in that all the T cell lymphomas were of multicentric distribution while 4 of the 6 B cell neoplasms were confined to the alimentary tract and its associated lymphoid tissue. In contrast, there was no relationship between the immunological and histological classifications of the lymphomas.

Animals↗
PubMed1979

Persistent lymphocytosis and virus-like particles in lymphocytes of sheep inoculated with cell-free extracts derived from ovine malignant lymphomas.

White cell counts of sheep inoculated in utero or at birth with cell-free extracts of ovine malignant lymphomas have been monitored for 5 yr. Of 28 inoculated sheep which have survived, 19 have shown persistent lymphocytosis. After 5 yr, no lymphomas had developed in the inoculated sheep. Electron-microscopic examination of short-term cultures of phytohaemaglutinin-stimulated lymphocytes from the sheep with persistent lymphocytosis has revealed virus-like particles in five of nine animals examined but none in similar cultures from 11 uninoculated sheep. The density of particles recovered from these cultures has been determined by centrifugation on caesium chloride isopycnic density as being 1.14--1.145 gm/microliter. These particles are not typical of oncornavirus as reported from sheep and cattle elsewhere and may represent a different type of virus or indeed be non-viral.

Animals↗
PubMed1979

Lymphocyte sensitization in sheep inoculated with extracts of spontaneously occurring malignant lymphomas.

A macrophage migration inhibition test showed that the blood lymphocytes of 15 of 27 sheep inoculated in utero or at birth with disrupted cells from ovine malignant lymphomas responded in culture to antigens derived from three other lymphomas. A close association was seen between animals whose lymphocytes were antigen-sensitive and those which developed lymphocytosis. This association and the specificity of reaction between the various tumour antigens employed in the tests is interpreted as further evidence toward a viral aetiology in ovine malignant lymphoma.

Animals↗
PubMed1978

The pathology of spontaneously occurring malignant lymphoma in sheep.

The most common locations of tumours in 22 sheep with malignant lymphoma were the lymph nodes (19 sheep), spleen (14), liver (13), kidney (10), small intestine (9) and heart (9). The distribution of the lesions could be classified as multicentric (14 sheep, alimentary (6), skin (1) and thymic (1). Histological examination of malignant lymphomas from 40 sheep showed there were three reticulum cell sarcomas, and 37 lymphosarcomas. The lymphosarcomas were further classified on the basis of cytological features as lymphoblastoid, lymphocytic/prolymphocytic, prolymphocytic and lymphocytic in 14, 6, 11 and six cases, respectively. Viruses were not detected by electron microscopy in tumourous tissue from 10 sheep with malignant lymphoma.

Animals↗
PubMedDate not supplied

Evaluation of the risk of potential bacteraemia in carcasses from very young slaughter calves with localized navel ill.

In the absence of gross pathological and bacteriological indicators, histopathology was used as the most sensitive technique to determine the risk of potential bacteraemia in the very young slaughter calves with and without lesions of localized navel ill (omphalophlebitis). The positive predictive value (ability to detect truly diseased cases) of routine post-mortem meat inspection for the detection of localized navel ill was 87.4% and the negative predictive value (ability to detect truly non-diseased cases) was 98.1%. The probability of histopathological lesions suggestive of bacteraemia in the kidneys and/or liver of calves with localized navel ill (319 cases) was 0.29 [0.24, 0.34] whereas that in control carcasses (319 cases) was 0.21 [0.17, 0.25]. There was no statistically significant difference in the proportion of cases graded as having severe compared with moderate periportal hypercellularity of the liver in each group. The risk of potential bacteraemia in carcasses passed at routine post-mortem meat inspection according to two different judgement regimes for localized navel ill (condemnation vs trimming of localized lesions) was virtually identical (251 vs 254 per 1000 carcasses passed respectively) and was not sensitive to changes in the prevalence of localized navel ill.

Animals↗