Search PubMed⌕ Search

Biomedical subjects

R G Thomson

Publications and source records attributed to R G Thomson.

At least 55 records · Page 3Linked to original sources
PubMed1982

The pulmonary clearance of Pasteurella haemolytica in calves infected with bovine virus diarrhea or Mycoplasma bovis.

Based on current literature which commonly associates bovine virus diarrhea virus and Mycoplasma bovis with "pneumonic pasteurellosis," an investigation was conducted into the effect of these two pathogens on the capacity of bovine lung to clear inhaled Pasteurella haemolytica. There was no significant effect (p less than 0.05) of either bovine virus diarrhea virus or M. bovis on the mean clearance rate of P. haemolytica, nor did the time interval of three, five or seven days between the first inoculation and exposure to P. haemolytica and adversely affect the lung clearance rates. However, it was found that the left lungs and a higher bacterial retention (p less than 0.05) than the right lungs.

Animals↗
PubMed1981

Involution abnormalities in the postpartum uterus of the bitch.

Of 95 reproductive tracts from postpartum bitches, 20 had subinvolution of the placental sites. Grossly, the placental sites were hemorrhagic and about twice the size of normal sites at the same time after parturition. Microscopically, large masses of collagen, hemorrhage and dilated endometrial glands were in the endometrial sites. The myometrium was invaded in many areas by trophoblast-like cells from the endometrium. Variations in the size of placental sites in the same uterus were found in eight cases, and histological variations in the involution process in five. Invasion of the myometrium by trophoblast-like cells four days after parturition was seen in one bitch.

Animals↗
PubMed1981

A review of the lesions in shipping fever of cattle.

A review of literature concerning the information published on the macroscopic and microscopic lung lesions in "shipping fever" of cattle is presented as reported in naturally occurring cases as well as the experimental disease.

Animals↗
PubMed1981

Spontaneous cardiomyopathy: histopathologic and ultrastructural alterations of turkey heart tissue.

Twelve turkeys poults, 4 to 5 weeks of age, were selected from a farm chosen for the study of spontaneous cardiomyopathy (SC) because of repeated outbreaks in successive flocks. An augmented myocardial mass accompanied the characteristic gross features of cardiomegaly and biventricular dilatation in SC-affected birds. Histologic alterations in myocardium were attributed to artifacts, resulting from unopposed cardiac muscle contraction prior to formalin fixation; specific pathologic lesions were not detected. Ultrastructural artifacts were minimized by perfusion fixation. Salient ultrastructural changes were mild when compared with the changes in the myocardium of nonaffected poults and consisted mainly of Z-band abnormalities. Virus-like particles were identified within sarcoplasmic reticulum of 2 SC-affected birds. The pathogenesis of SC, including acquired and inherited etiologic factors, is discussed.

Animals↗
PubMed1981

Normal postpartum involution of the uterus in the dog.

Ninety-eight reproductive tracts from dogs at different postpartum time periods were used to investigate stages of normal involution. Seventy-eight reproductive tracts were obtained from the field, and 20 obtained surgically for gross and microscopic examination. Plasma progesterone was measured in 22 dogs at various times postpartum. The uterine horns during the first week postpartum were dilated and edematous. The placental sites were 1.5-3 cm in width, rough, granular and covered with mucus and a few blood clots. By the fourth week the placental sites were thick, grayish-tan and nodular with a few blood clots within nodules. The uterine horns during the seventh week were greatly contracted and the placental sites were narrow and light in color. A few nodules were still present on the surface. By the ninth week the uterine horns were uniform in shape and contracted with a narrow lumen. The placental sites appeared as a narrow brown band. Histologically the placental sites during the first week postpartum were covered by an eosinophilic staining necrotic mass and a few intact epithelial cells scattered on the surface as an interrupted single layer. Under the necrotic mass, large eosinophilic staining cells in moderate number were scattered throughout the lamina propria of the placental site. These cells were considered to be decidual cells. By the fourth week the placental sites were covered by a large lobulated mass of collagen fibers. The uterine glands were greatly dilated and degenerate, and mononuclear cell infiltration in the lamina propria was pronounced. By the seventh week, large masses of collagen fibers were detached from the surface, and endometrial glands were normal in size and shape. By the ninth week surface sloughing was completed. However, regeneration and replacement of the endometrial lining from the mouth of the uterine glands continued until the end of the twelfth week when the involution process was completed. The progesterone levels were very low for eight weeks postpartum.

Animals↗
PubMed1980

A perspective on respiratory disease in feedlot cattle.

The etiological factors causing acute pneumonia in feedlot cattle are complex in terms of their interactions with the host to cause clinical disease or death. The most significant agent is Pasteurella hemolytica, but it may be acting relatively late in the overall sequence of events.It is necessary to develop an overall strategy to determine the pathogenesis of the disease in the field. Approaches to this objective are discussed, with the emphasis on the role of the epidemiologist.

Animal Feed↗
PubMed1980

Factors associated with mortality in feedlot cattle: the Bruce County Beef Cattle Project.

The design of and the analysis of data from the Bruch County Beef Cattle Project, particularity the field study, are presented and discussed. A major value of the study may lie in its ability to relate laboratory findings to events in the field. The factor most strongly related to mortality was ration, with cattle on hay based rations having a much lower mortality on average than cattle on corn based rations. In general, management activities associated with growing cattle (as opposed to fattening) over the first winter were sparing for mortality. Groups of cattle given prophylactic vaccines or drugs within two days of arrival tended to experience higher mortality (not statistically higher) than those cattle not receiving those measures, or cattle groups recieving the same prophylactics more than 48 hours after arrival. However, these results require validation in the remaining years of the study. Fibrinous pneumonia was the most frequent diagnosis in the calves on postmortem examination.

Animal Feed↗
PubMed1979

Effects of prolonged cyanide and thiocyanate feeding in rats.

Male weaning rats were fed a semipurified diet containing 10% casein; this diet restricted in methionine, vitamin B12, and iodine; or the complete and restricted diets supplemented with either 1500 ppm potassium cyanide or 2240 ppm potassium thiocyanate for 11.5 mo. There were no deaths or clinical signs of toxicity. Cyanide, but not thiocyanate, caused a consistent reduction in weight gain in the complete and restricted groups. Both cyanide and thiocyanate caused decreased thyroid gland activity in young rats, particularly in the restricted groups. Plasma thyroxine concentrations were maintained in the mature cyanide-treated rats, even though secretion rates were decreased. However, the mature thiocyanate-treated animals showed decreased plasma thyroxine concentrations, despite thyroid gland enlargement. Modest primary myelin degeneration in the spinal cord white matter was found in the restricted group and in rats receiving this diet supplemented with either cyanide or thiocyanate. The lesions did not resemble those of a vitamin B12 deficiency in appearance or those of acute cyanide intoxication in distribution. Because of tissue autolysis, it could not be determined whether these changes resulted from histotoxic anoxia or an alteration of oligodendroglial myelin metabolism.

Animals↗
PubMed1979

Pathological studies of "Sudden death syndrome" in broiler chickens.

Sudden death syndrome usually occurs in heavy, fast-growing and healthy-looking broilers. Most of the affected birds are males. The characteristic necropsy changes are seen in well-fleshed broilers with edema and generalized pulmonary congestion, recently ingested feed in the crop and gizzard, distended intestine with creamy content and empty gall bladder. The liver and kidneys are slightly enlarged and the latter have patchy areas of subcapsular hemorrhage. The heart contains clotted blood in the atria but the ventricles are often empty and the left ventricle in particular assumes a hypertrophied appearance. Microscopic examination of heart muscle reveals degeneration of fibers, separation of cardiac muscle fibers by edema and infiltration of heterophils. The lungs have severe vascular congestion, inflammatory cell infiltration in the mucosa of the secondary bronchi and edema fluid in the tertiary bronchi and interlobular connective tissue. The liver has moderate bile duct hyperplasia, periportal hepatitis and mononuclear cell infiltration adjacent to bile ducts which possibly leads to bile duct constriction. The kidneys have subcapsular and parenchymatous hemorrhage.

Animals↗
PubMed1979

Studies on effect of lighting on "Sudden death syndrome" in broiler chickens.

Broiler chicken flocks were studied to determine the mortality from sudden death syndrome occurring in the flocks. The difference in the incidence of the syndrome in pullets and cockerels, and the age at which the most birds are affected were also studied. The weight of sudden death syndrome birds was compared with the flock average and the effect of continuous lighting as opposed to intermittent lighting was examined. The results suggest that; continuous lighting produces more sudden death syndrome deaths than intermittent lighting; that the incidence of sudden death syndrome is higher in cockerels than pullets; that the highest death rate occurred during the third and fourth weeks of life, and that sudden death syndrome birds on the average were heavier than the flock average.

Animals↗
PubMed1979

Atypical interstitial pneumonia in cattle.

Atypical interstitial pneumonia is described as two clinical syndromes in young cattle. One syndrome occurs in animals which have clinical evidence of pneumonic pasteurellosis, responds initially to treatment for one to two days and then develops acute signs of atypical interstitial pneumonia. The second syndrome involves acute respiratory distress in young calves due to atypical interstitial pneumonia with antecedents of enzootic pneumonia. The postmortem lesions are described along with discussion of the possible pathogenesis of the condition and treatment.

Animals↗
PubMed1979

Subchronic toxicity test for two thermotolerant filamentous fungi used for single cell protein production.

Safety evaluations of two thermotolerant filamentous fungi, Cephalosporium eichhorniae 152 (C. 152) and Rhizopus chinensis 180 (R. 180), grown on a sugar-salts medium were carried out through feeding the biomases to rats at 20% or 40% dietary levels for 90 days. There was a control group fed soybean meal. Weight gain and feed consumption for rats fed 20% C. 152 were equal to those for the control animals, but were depressed in the other three groups, especially the rats fed R. 180. All animals appeared normal and healthy except that transient alopecia was found for a short duration in the fungi-treated rats in the initial period. The cause of this lesion is not clear. At the end of the feeding trial, clinical determinations of constituents in blood and urine samples were conducted. The animals were autopsied and weights for four organs were taken. Histopathological examinations for 26 different tissues were carried out. Mild changes were found in both C. 152 and R. 180-treated rats but most of the these were not considered to be related to treatment.

Acremonium↗