Biomedical subjects

M K Clayton

Publications and source records attributed to M K Clayton.

10 recordsLinked to original sources

PubMed1992

Determination of the early age of onset of equine recurrent laryngeal neuropathy. 1. Muscle pathology.

The age of onset of equine recurrent laryngeal neuropathy has not been ascertained, although the clinical condition of left laryngeal hemiplegia ("roaring") has been recognized for centuries. The purpose of this study was to evaluate the laryngeal muscles of draft horse foals for the presence of fiber-type grouping, indicating denervation and reinnervation, and to determine if histological evidence of recurrent laryngeal neuropathy was present. Abductor and adductor laryngeal muscles from the left and right sides were collected immediately after euthanasia from male draft horse foals, six less than 2 weeks and four 6 months of age, and stained for myosin ATPase. A morphometric test was used to objectively evaluate several areas from each muscle for fiber-type grouping. Extensive fiber-type grouping which was characteristic of recurrent laryngeal neuropathy was found in one of the young foals and all of the older foals. Four of the young foals had some areas of fiber-type grouping suggestive of mild, early changes associated with recurrent laryngeal neuropathy. One of the young foals had no fiber-type grouping present in any of the laryngeal muscles evaluated. These findings suggest an early age of onset of recurrent laryngeal neuropathy.

Animals↗

PubMed1992

Rumen protein degradation rates estimated by non-linear regression analysis of Michaelis-Menten in vitro data.

An in vitro method applying Michaelis-Menten saturation kinetics was developed as an alternative approach for estimating protein degradation rates in the rumen. Non-linear regression (NLR) analysis of the integrated Michaelis-Menten equation yielded fractional degradation rates, kd, from direct estimates of the maximum velocity: Michaelis constant ratio (kd = Vmax:Km). Degradation rates obtained using data from a series of 2 h inhibitor in vitro incubations were respectively 0.989, 0.134, and 0.037/h for casein, solvent soya-bean meal (SSBM) and expeller soya-bean meal (ESBM). Degradation rates obtained from 2 h incubations had lower standard errors than those obtained using 1 h incubations; 2 h rates were not significantly different from 1 h rates, suggesting end-product inhibition was not significant at 2 h. The NLR Michaelis-Menten method was used to determine degradation rates for twelve protein sources: casein, bovine serum albumin, two samples of lucerne (Medicago sativa) hay, and four samples each of SSBM and ESBM. Statistical analysis of NLR results revealed significant differences among the twelve protein sources. Casein was degraded most rapidly (0.827/h), and the four ESBM samples most slowly (0.050-0.098/h). Degradation rate for serum albumin was 0.135/h; rates for SSBM and lucerne hays ranged from 0.160 to 0.208/h. Degradation rates estimated using the NLR method were more rapid than those obtained with a limited substrate approach; NLR rates were more consistent with in vivo estimates of rumen protein escape. Greater concentrations of slowly degraded proteins were needed with the NLR method to define curvilinearity of the degradation curve more accurately.

Animals↗

PubMed1992

Stimulation of luteal cell progesterone production by lipoproteins from cows fed control or fat-supplemented diets.

Plasma lipoproteins from lactating dairy cows fed 0 or 7% supplemental fat were examined for their composition and ability to stimulate luteal cell progesterone production in vitro. Ultracentrifugation was utilized to isolate blood lipoproteins, and heparin affinity chromatography allowed separation of lipoprotein fractions based on the presence (low density lipoproteins) or absence of apolipoprotein B (high density lipoproteins). A portion of high density lipoproteins was fractionated by size, utilizing gel filtration chromatography. Slaughterhouse corpora lutea were dissociated, and plasma lipoproteins were added to the luteal cells on d 3 of culture and incubated for 48 h. In Experiment 1, blood was collected from heifers fed a diet that was not supplemented with fat. The addition of cholesterol from large, high density lipoproteins with a high cholesterol to protein ratio to luteal cultures increased progesterone production by an average of 17% compared with the addition of cholesterol from small, high density lipoproteins with a low cholesterol to protein ratio. In Experiment 2, electrophoretic mobility, apolipoprotein composition, and size of lipoproteins from control and fat-supplemented cows were similar. Lipoproteins from cows assigned to either a control or fat-supplemented diet showed no difference in their ability to stimulate progesterone production. Increased plasma progesterone concentration in lactating dairy cows fed supplemental fat does not appear to be mediated by alterations in lipoprotein composition.

Animals↗

PubMed1991

In vivo determination of triglyceride secretion using radioactive glycerol in rats fed different dietary saturated fats.

Our objective was to determine the relative rates of in vivo triglyceride (TG) secretion and the composition of very low density lipoproteins (VLDL) in rats fed different dietary saturated fats. Male Sprague-Dawley rats (150-200 g) were fed diets containing 16% corn oil, or 14% butterfat, 14% beef tallow, 14% olive oil, or 14% coconut oil plus 2% corn oil for 5 wk. Changes in plasma TG specific radioactivity were determined in individual, unanesthetized fasted rats after injection of 100 microCi [2-3H]glycerol. Nonlinear regression analysis using a 2-compartment model was used to determine the fractional rate constant for TG turnover in plasma. The plasma TG pool was 33-40% larger with beef tallow than with corn, olive or coconut oil feeding (p less than 0.05), and 20% larger with beef tallow than with butterfat feeding. The rate of TG secretion into plasma (mg/min/100 g body weight) was 60% higher in animals fed beef tallow than corn or coconut oil (p less than 0.05) and 26-33% higher in animals fed beef tallow than olive oil or butterfat. Differences in VLDL composition (% wt) were also noted. Our data suggest that greater TG secretion is the primary factor contributing to the larger TG pool with ingestion of beef tallow relative to butterfat, corn or coconut oil. These results suggest that different dietary saturated fats have unique effects on TG metabolism in rats.

Animals↗

PubMed1991

Milk yield variation concurrent with conception.

Milk yield data from herds at the University of Illinois and the University of Wisconsin-Madison were used to characterize milk yield fluctuations concurrent with conception. Analyses were performed on 118 Illinois and 244 Wisconsin cows; milk yields were recorded for 15 d preceding confirmed conception. Conception was confirmed by calving within 11 d of 281 d postbreeding. Each cow's difference between 7-d rolling means for a.m. and p.m. milking yield was subtracted from a.m. yields as a diurnal adjustment. A pattern matching formula that was applied to adjusted yields [( b - a]/a, where a and b were sequential milkings) produced a mean calculated value for the milking nearest conception that was different from all milkings for 15 d preceding conception in Wisconsin data only. Discriminant analysis failed to differentiate between preceding and conception inclusive sequences of adjusted milk yields. Pattern matching formulas applied to individual cow data failed to isolate more than 2% of conceptions when the threshold value was set to eliminate false positives. Results demonstrated low predictive ability for conception using concurrent milk yield fluctuations despite implications of significant mean differences for values that were enhanced by pattern matching formulas.

Animals↗

PubMed1990

Bradycardia in cattle deprived of food.

Bradycardia was documented in 12 cattle from which food has been withheld for 48 hours in preparation for general anesthesia and an elective surgical procedure. The heart rates decreased by a mean of 14 beats/min, and 4 cows had sinus arrhythmia. To evaluate this finding, the heart rates of 21 clinically normal cattle were evaluated before and after food was withheld for 48 hours. Bradycardia developed in all of the clinically normal cattle, with the mean decrease in heart rate being 23 beats/min. Five of the clinically normal cows developed sinus arrhythmia. It was concluded that bradycardia and sinus arrhythmia in cattle are associated with deprivation of food.

Animals↗

PubMed1990

Dietary olive and safflower oils in promotion of DMBA-induced mammary tumorigenesis in rats.

Interpretation of studies comparing the efficacy of different dietary fat sources in promoting 7,12-dimethylbenz[a]-anthracene (DMBA)-induced rat mammary tumorigenesis often ignores the fact that about 4% (wt/wt) linoleic acid (18:2n-6) is required for optimal tumor promotion. We therefore fed DMBA-intubated or placebo-intubated female, Sprague-Dawley rats 20% fat diets containing 18:2n-6 (wt/wt) from either high-linoleic safflower oil (SL, 14.6% 18:2n-6), high-oleic safflower oil (SO, 3.4% 18:2n-6), olive oil (OO, 1.1% 18:2n-6), or OO supplemented with 18:2n-6 (OL, 3.4% 18:2n-6) for 16 weeks. Results indicated that OO-fed rats had longer tumor-free time, fewer tumors per rat, and lower tumor incidence compared with SO and OL. Addition of 2.3% 18:2n-6 to OO enhanced tumor promotion (p less than 0.04); SL, SO, and OL demonstrated similar tumor-enhancement effect. About 74% of observed mammary tumors were adenocarcinomas; a greater number of tumors appeared in the thoracic and inguinal than in the cervical and abdominal regions irrespective of diet. These results indicate that once an optimal amount of linoleic acid is provided in the diet, oleic- or linoleic-rich oils have similar effects on promotion of mammary tumors in the rat.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1989

Quantitative comparison of the laboratory and field competitiveness of Rhizobium leguminosarum biovar phaseoli.

Rhizobium leguminosarum bv. phaseoli KIM5s outcompeted strain CE3 in bean (Phaseolus vulgaris L.) root nodulation when plants were grown at any of three field sites, each with a different soil type and indigenous population, or in the laboratory in a sterilized sand, a sterilized peat-vermiculite mixture, or a nonsterile field soil. A mathematical model describing nodulation competitiveness was empirically derived to evaluate the relative competitiveness of the two strains under these conditions. This model relates the proportional representation of the two strains in the inoculum to the proportional representation of nodules occupied by each strain or both strains and provides a measure of competitiveness, which is referred to as the competitiveness index. Statistical comparisons of competitiveness indices showed that the relative competitiveness of KIM5s and CE3 remained constant when the two strains were applied in a constant ratio over a range of inoculum concentrations, from 10(3) to 10(7) cells per seed, and when they were applied in various ratios to six P. vulgaris cultivars. Furthermore, the relative competitiveness of KIM5s and CE3 in the laboratory did not differ significantly from their relative competitiveness at the three field sites studied. Thus, a study of the basis for nodulation competitiveness of KIM5s and CE3 in the laboratory has the potential to provide an understanding of competitiveness both in the laboratory and in the field.

Models, Biological↗

PubMed1988

Moment analysis of multibreath nitrogen washout in healthy female goats and calves.

Moment analysis of multibreath nitrogen washout curves was performed for healthy female goats and calves. Curves were plotted, using dimensionless coordinates that minimized effects of alveolar ventilation changes. Results were expressed as the ratio of the first to the zeroth moments, mu 1/mu 0. Variability using this method was compared with that of a graphic analysis technique from which an uncorrected slope of a portion of the washout curve (B1/2) and a slope index corrected for lung and tidal volume (the nitrogen dilution constant) can be derived. Mean moment ratios on the basis of pooled data for 4 goats and 3 calves were 2.04 +/- 0.29 and 2.38 +/- 0.17, respectively. These values represent the weighted average number of times the resting lung volume was diluted with 100% O2; the lower the value, the relatively more uniform the distribution of intrapulmonary gas. The coefficient of variation within and between subjects was smallest using moment analysis and was greatest for the B1/2. Variability expressed as SD was similar between the moment ratio and nitrogen dilution constant and was greatest for the B1/2.

Analysis of Variance↗

PubMed1986

Glycosaminoglycans in ewe reproductive tracts and their influence on acrosome reactions in bovine spermatozoa in vitro.

Glycosaminoglycans (GAG) promote acrosome reactions (AR) in bovine and rabbit spermatozoa in vitro. Female bovine reproductive tract secretions contained GAG and the concentrations and composition of those GAG varied with different regions and stages of the estrous cycle. This study was designed to evaluate the types of GAG found in reproductive tract secretions of ewes at different stages of the estrous cycle and the ability of the secretions to promote AR. Ewes (n = 48) were slaughtered at 0, 12, 24, 36, 72 and 144 h following observations of standing estrus. Reproductive tracts were flushed with a modified Tyrode's medium (TALP: 7 ml) not containing calcium. Concentrations and composition of GAG in the tract were determined by high performance liquid chromatography. Concentrations of GAG decreased anterior to the cervix: 2.28 to .74 mg/100 mg protein (P less than .05). Increases in heparin-like GAG during the estrual phase and chondroitin sulfate GAG during the luteal phase were noted. Bovine sperm were incubated in tract flushings standardized to contain 4 micrograms/ml of GAG and supplemented with calcium. Sperm incubated in estrual flushings for 9 h exhibited a higher incidence of AR than those incubated in luteal flushings or control, 50% vs 36% and 29%, respectively (P less than .0001). It is concluded that during the estrous cycle there were changes in concentrations and composition of GAG in ewe reproductive tracts and the potencies of those female secretions causing AR varied.

Acrosome↗