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Biomedical subjects

D A Rice

Publications and source records attributed to D A Rice.

At least 73 records · Page 4Linked to original sources
PubMed1983

Experimental models for nutritional myopathy.

Nutritional myopathy is a disease affecting young ruminants. The aetiological factors and their relative importance in disease development have been explored. A theoretical model has been developed and tested experimentally. The disease can be produced consistently using a recently developed vitamin E- and selenium-deficient diet. Disease can occur spontaneously in animals maintained on this diet alone over an extended period. Alternatively, myopathy can be induced in deficient animals by feeding polyunsaturated fatty acids such as linoleic and linolenic acid from corn and linseed oils respectively. For ruminants the oils are protected to prevent hydrogenation in the rumen. Because a similar protective mechanism appears to occur with normal ruminant forages such as grass, and the development of disease is so similar to that occurring naturally, polyunsaturated fatty acids are thought to play a major role in the development of the disease. The experimental disease reproduces extensive and consistent lesions of skeletal and cardiac myopathy. Hyaline necrosis occurs in the skeletal muscle fibres of many major muscle groups. In the heart the accumulation of droplets of lipofuscin-like pigment in Purkinje fibres is the initial lesion, followed by necrosis of Purkinje fibres and peri-Purkinje fibrosis. The accumulating pigment has been characterized by fluorescence spectroscopy and histochemical techniques. The cardiac pathology results in detectable electrocardiographic abnormalities and sudden death.

Animals↗
PubMed1983

Sound speed in pulmonary parenchyma.

The time it takes audible sound waves to travel across a lobe of excised horse lung was measured. Sound speed, which is the slope in the relationship between transit time and distance across the lobe, was estimated by linear regression analysis. Sound-speed estimates for air-filled lungs varied between 25 and 70 m/s, depending on lung volume. These speeds are less than 5% of sound speed in tissue and less than 20% of sound speed in air. Filling the lung with helium or sulfur hexafluoride, whose free-field sound speeds are 970 and 140 m/s, respectively, changed sound speed +/- 10% relative to air filling. Reducing the ambient pressure to 0.1 atm reduced sound speed to 30% of its 1-atm value. Increasing pressure to 7 atm increased sound speed by a factor of 2.6. These results suggest that 1) translobar sound travels through the bulk of the parenchyma and not along airways or blood vessels, and 2) the parenchyma acts as an elastic continuum to audible sound. The speed of sound is given by c = (B/rho)1/2, where B is composite volumetric stiffness of the medium and rho is average density. In the physiologic state B is affected by ambient pressure and percent gas phase. The average density includes both the tissue and gas phases of the parenchyma, so it is dependent on lung volume. These results may be helpful in the quantification of clinical observations of lung sounds.

Animals↗
PubMed1983

Necrotizing sialometaplasia.

Necrotizing sialometaplasia is a benign inflammatory disease of salivary gland origin. Because of its clinical and histologic resemblance to squamous cell carcinoma, this disease must be recognized. The cause is unknown, but it may be related to oral trauma, tobacco use or inadequate blood supply. The lesion heals spontaneously, regardless of therapy, in two to eight weeks.

Adult↗
PubMed1981

Toxic edible oils.

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Dietary Fats↗
PubMed1980

Milk fever controls: comparison of 1-alpha and vitamin D3 in conjunction with induced parturition.

The efficacies of vitamin D3 and its 1-alpha hydroxyl derivative (1-alpha) in controlling clinical milk fever, hypocalcaemia and hypophosphataemia in parturient cows have been compared. A corticosteroid was used in some cases to optimise and control the interval between prophylactic treatment and parturition. Our observations suggest that the combination of 1-alpha and corticosteroid was particularly valuable and could be used in the development of a successful prophylactic regime. This conclusion is supported by both clinical and biochemical measurements.

Animals↗
PubMed1980

Sound speed in the upper airways.

We measured the velocity of audible sound at frequencies above 10 kHz to be 349 m.s-1 (+/- 1%, 95% confidence interval) in the upper airways of eupneic anesthetized dogs. It appears that the velocity of sound propagation is dependent on lumen gas composition, temperature, and mean flow speed. These three variables are sufficient to explain the velocity variations measured during tidal breathing. Lung volume, transpulmonary pressure, and bronchoactive drugs were not shown to have an appreciable effect on sound velocity. Model studies indicate that sound velocity is little affected by flow profile, lumen cross-sectional shape, or changes in lumen area with position. Flow speed proportionally changes the velocity of sound relative to the airway and therefore can be determined from sound propagation measurements. Dividing volume flow by flow speed gives airway cross-sectional area. Tracheal areas after normalization by the cube root of body weight were about half those previously reported. Acoustically inferred areas were confirmed by mechanical measurement.

Animals↗
PubMed1980

Sound transfer function of the congested canine lung.

Alterations of sound transfer function of the lung in pre-congested and congested states were studied in a canine model as an index of the accumulation of lung liquids. Pulmonary congestion was produced by graduated inflations of a balloon in the left atrium. Different degrees of pulmonary congestion were documented by post-mortem wet to dry lung weight ratios. Sound transfer function of the lung was determined utilizing passive sound transmission in the audio freqency range consisting of sinusoidal oscillations swept from 50 Hz to 2 kHz. Sound transfer function in dB was defined as 20 times the logarithm of sound output divided by sound input. These functions were computed for pre-congested and congested states of the lung and the differential values correlated with the post-mortem wet to dry weight ratios of the lung. The magnitude of sound transfer function of the lung correlated well with increasing accumulation of intravascular and extravascular lung liquids and provided a quantitative index of pulmonary congestion.

Animals↗
PubMed1980

Influence of extraction techniques on determination of alpha-tocopherol in animal feedstuffs.

Methods were compared for alpha-tocopherol determination involving saponification in the preparation of feed extracts for high performance liquid chromatography. The effects of antioxidant and saponification times used were also examined. The data obtained showed that saponification before solvent extraction more efficiently released natural alpha-tocopherol from the feedstuffs than extraction before saponification. Increases in alpha-tocopherol content of 0--144% were obtained for the range of feedstuffs examined. Ascorbic acid and pyrogallol used as antioxidants gave similar results, and extraction efficiency was independent of the time of saponification within the range 5--40 min.

Animal Feed↗