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M E Montgomery

Publications and source records attributed to M E Montgomery.

14 recordsLinked to original sources
PubMed1996

A field trial to evaluate a Mycoplasma hyopneumoniae vaccine: effects on lung lesions and growth rates in swine.

A killed Mycoplasma hyopneumoniae vaccine was evaluated in a single swine herd in which the farrowing barn and weaner rooms were on one Mycoplasma-free farm, while the growing and finishing barn was on a separate farm on which Mycoplasma was present. The study was carried out in a cohort of pigs born in a 12-week period. Pigs born in 6 of the 12 wk were vaccinated and the rest were left as controls. The vaccine was administered twice at approximately 3 and 6 wk of age. Carcass characteristics, lung lesions, and growth rates were recorded on 893, 390, and 220 pigs, respectively. The vaccine reduced the prevalence of pneumonic lesions in slaughter hogs from 69% to 36% (P < 0.001). It also appeared to reduce the prevalence of pleuritis from 20% to 13%, but the difference was only statistically significant at P = 0.07. The vaccine had no effects on carcass characteristics except that carcasses of vaccinated pigs were, on average, 1 kg heavier than those of nonvaccinated pigs, and a smaller percentage of vaccinated pigs were shipped "light" (carcass weight < 70 kg). Two methods were used to estimate the effect of the vaccine on growth rates (as measured by days to 80 kg carcass weight) resulting in estimates of 11 and 2 d reduction attributable to vaccination, respectively. The latter estimate was probably an underestimate for reasons discussed in the paper.

Animals↗
PubMed1994

Measurement of amorphous ferric phosphate as an assessment of iron bioavailability.

A method for measuring amorphous ferric phosphate in complex salt mixtures and animal diets is described. The procedure uses citrate solutions for extraction of salt mixtures and tartrate solution for extraction of prepared diets. Iron in the solution is then determined colorimetrically. Crystalline ferric phosphate, which has no iron bioavailability, is not extracted by either solution. Thus, the procedure can determine if the amorphous form, which has a high iron bioavailability, is present. The procedure was tested on gypsy moth artificial diet and Wesson salt mixture, which is a salt supplement of the diet.

Animals↗
PubMed1994

Modelling problems in conservation genetics using Drosophila: consequences of fluctuating population sizes.

Many natural populations fluctuate widely in population size. This is predicted to reduce effective population size, genetic variation, and reproductive fitness, and to increase inbreeding. The effects of fluctuating population size were examined in small populations of Drosophila melanogaster of the same average size, but maintained using either fluctuating (FPS) or equal (EPS) population sizes. FPS lines were maintained using seven pairs and one pair in alternate generations, and EPS lines with four pairs per generation. Ten replicates of each treatment were maintained. After eight generations, FPS had a higher inbreeding coefficient than EPS (0.60 vs. 0.38), a lower average allozyme heterozygosity (0.068 vs. 0.131), and a much lower relative fitness (0.03 vs. 0.25). Estimates of effective population sizes for FPS and EPS were 3.8 and 7.9 from pedigree inbreeding, and 4.9 vs. 7.1 from changes in average heterozygosities, as compared to theoretical expectations of 3.3 vs. 8.0. Results were generally in accordance with theoretical predictions. Management strategies for populations of rare and endangered species should aim to minimize population fluctuations over generations.

Animals↗
PubMed1987

The resemblance of clinical attributes between mastitic cows with no growth on bacterial milk cultures and those with gram-positive bacteria cultured.

The clinical attributes of 40 dairy cows which had mastitis but no growth of bacteria from the milk were analyzed and compared to the attributes in 102 cows with only gram-positive and 61 cows with only gram-negative bacteria cultured from the milk. Cows with no bacteria cultured from the milk did not differ significantly from cows with gram-positive bacteria cultured, but 9 of 12 attributes were significantly different between cows with no bacteria cultured and cows with gram-negative bacteria cultured. Discriminant analysis was used to classify cows as members of the gram-positive or gram-negative culture groups. The discriminant equation was then applied to the cows with no bacteria cultured, and 78% of cows with no bacteria cultured were classified as members of the gram-positive group. Most mastitis in cows with no bacteria grown from the milk was probably due to gram-positive bacteria. If antibiotic therapy is used in cows with persistent mastitis and a negative culture in the belief that the culture is a false negative, treatment with antibiotics effective only against gram-negative organisms would not be appropriate.

Animals↗
PubMed1987

A comparison of discriminant analysis and logistic regression for the prediction of coliform mastitis in dairy cows.

Results from discriminant analysis and logistic regression were compared using two data sets from a study on predictors of coliform mastitis in dairy cows. Both techniques selected the same set of variables as important predictors and were of nearly equal value in classifying cows as having, or not having mastitis. The logistic regression model made fewer classification errors. The magnitudes of the effects were considerably different for some variables. Given the failure to meet the underlying assumptions of discriminant analysis, the coefficients from logistic regression are preferable.

Animals↗
PubMed1987

Analysis of the clinical findings used to diagnose coliform mastitis in dairy cows, and comparison to a prediction model.

Logistic regression was used to analyze the clinical findings (attributes) which predicted coliform mastitis in 113 dairy cattle, 36 of which had coliforms cultured from milk. Weakness of the cow, swelling of the udder, decreased body temperature and watery consistency of the milk were selected for the model. An analysis was then done to find the attributes which clinicians used when predicting that a cow would have a coliform cultured. Clinicians appeared to use water consistency of the milk, shivering, firmness of the udder, pulse rate, elevated body temperature, and respiratory rate. In a final analysis the clinicians' predictions were forced into the model to determine which attributes might be used by clinicians to increase diagnostic accuracy. Inclusion of weakness of the cow, swelling of the udder, decreased temperature of the cow, and duration of mastitis of less than 24 hours increased accuracy over clinical prediction alone. Accuracy of cowside diagnosis might be increased if more attention were paid to these attributes when making a diagnosis of coliform mastitis.

Animals↗
PubMed1986

Discriminant analysis of the clinical indicants for bovine coliform mastitis.

We used discriminant analysis to assess the indicants most useful in predicting whether a cow had coliform bacterial mastitis. One hundred and twenty-nine mastitic cows were divided into two groups, namely those with milk cultures that yielded pure or mixed gram negative organisms, and cows with other organisms or negative culture. Of 21 indicants examined by discriminate analysis only a history of previous mastitis in the affected quarter, weakness, clear or white color of milk, swelling of the udder, water consistency of the milk, lack of previous mastitis in other quarters, lack of palpable udder abscesses, and elevated body temperature were significantly associated with coliform mastitis. Using these variables 78% of cases were correctly classified.

Animals↗
PubMed1986

Accuracy of a discriminant analysis model for prediction of coliform mastitis in dairy cows and a comparison with clinical prediction.

We tested an equation, which had been developed previously using discriminant analysis, for predicting whether a cow has coliform mastitis. Variables indicating a high probability of coliform infection included history of previous mastitis in the affected quarter, weakness, clear or white color of milk, water consistency of the milk, swelling of the udder, lack of previous mastitis in other quarters, lack of palpable udder abscesses, and a high body temperature. Application of this predictive equation to 114 cows with mastitis to determine if they would have coliform organisms cultured from the affected quarters resulted in an accuracy of 71% (sensitivity = 0.42, specificity = 0.85), compared to an accuracy of 62% (sensitivity = .64, specificity = .61) for cowside prediction by the attending clinicians. Changing the cutoff score of the discriminant rule so that the sensitivity of the discriminant prediction was similar to that of the clinicians yielded an accuracy of 64% (sensitivity = .64, specificity = .64).

Animals↗
PubMed1985

Arachidonic acid metabolism in cultured aortic endothelial cells. Effect of cAMP and 3-isobutyl-1-methylxanthine.

To investigate the hypothesis that cyclic AMP (cAMP) regulates arachidonic acid metabolism in vascular tissue, we have studied the effects of forskolin (FSK), an activator of adenylate cyclase, and 3-isobutyl-1-methylxanthine (IBMX), a phosphodiesterase inhibitor, on hormone-stimulated prostacyclin (PGI2) synthesis in porcine aortic endothelial cells grown in culture. In these experiments, bradykinin (1 microgram/ml) and A23187 (0.2 microM) potently stimulated PGI2 biosynthesis (9- and 10-fold respectively). However, prostaglandin synthesis in response to either of these agents was not affected by FSK even though FSK elevated intracellular levels of cAMP 10-fold. IBMX failed to elevate basal cAMP levels when incubated with unstimulated cells. Stimulation of IBMX-treated (0.1 but not 1.0 or 4.0 mM) cells with bradykinin, however, did result in increased cAMP levels, presumably due to PGI2 formation and subsequent activation of adenylate cyclase. In addition to phosphodiesterase inhibition, IBMX inhibited PGI2 formation (72% at 1 mM) in a dose-dependent manner so that, at higher doses of IBMX, cAMP levels returned to baseline. Thus, prostacyclin synthesis inhibition by IBMX could not be attributed to elevated cAMP. In other experiments, IBMX (1 mM) was found to directly inhibit arachidonic acid release (32%) and arachidonic acid metabolism (65%) in endothelial cells and to inhibit arachidonic acid conversion to PGE2 by sheep seminal vesicle microsomes (65%). These data suggest that IBMX directly inhibits both phospholipase and cyclooxygenase activities. These experiments do not support the contention that cAMP regulates these enzymes in cultured aortic endothelial cells.

1-Methyl-3-isobutylxanthine↗
PubMed1985

Effect of hydrogen peroxide on prostaglandin production and cellular integrity in cultured porcine aortic endothelial cells.

Oxidative damage to the vascular endothelium may play an important role in the pathogenesis of atherosclerosis and aging, and may account in part for reduced vascular prostacyclin (PGI2) synthesis associated with both conditions. Using H2O2 to induce injury, we investigated the effects of oxidative damage on PGI2 synthesis in cultured endothelial cells (EC). Preincubation of EC with H2O2 produced a dose-dependent inhibition (inhibitory concentration [IC50] = 35 microM) of PGI2 formation from arachidonate. The maximum dose-related effect occurred within 1 min after exposure although appreciable H2O2 remained after 30 min (30% of original). In addition, H2O2 produced both a time- and dose-dependent injury leading to cell disruption, lactate dehydrogenase release, and 51Cr release from prelabeled cells. However, in dramatic contrast to H2O2 effects on PGI2 synthesis, loss of cellular integrity required doses in excess of 0.5 mM and incubation times in excess of 1 h. The superoxide-generating system, xanthine plus xanthine oxidase, produced a similar inhibition of PGI2 formation. Such inhibition was dependent on the generation of H2O2 but not superoxide in that catalase was completely protective whereas superoxide dismutase was not. H2O2 (50 microM) also effectively inhibited basal and ionophore A23187 (0.5 microM)-stimulated PGI2 formation. However, H2O2 had no effect on phospholipase A2 activity, because ionophore A23187-induced arachidonate release was unimpaired. To determine the effects on cyclooxygenase and PGI2 synthase, prostaglandin products from cells prelabeled with [3H]arachidonate and stimulated with ionophore A23187, or products formed from exogenous arachidonate were examined. Inhibition of cyclooxygenase but not PGI2 synthase was observed. Incubation of H2O2-treated cells with prostaglandin cyclic endoperoxide indicated no inhibition of PGI2 synthase. Thus, in EC low doses of H2O2 potently inhibit cyclooxygenase after brief exposure whereas larger doses and prolonged exposure are required for classical cytolytic effects. Surprisingly, PGI2 synthase, which is known to be extremely sensitive to a variety of lipid peroxides, is not inhibited by H2O2. Lipid solubility, enzyme location within the EC membrane, or the local availability of reducing factors may explain these results, and may be important determinants of the response of EC to oxidative stress.

Animals↗
PubMed1985

The sensitivity and specificity of postbreeding plasma progesterone levels as a pregnancy test for dairy cows.

Plasma progesterone levels on day 4 and day 8 postbreeding were measured for one hundred and eighty-four dairy cows. These two parameters (PPD4, PPD8), their absolute difference (PPDIFF) and their ratio (PPRATIO) were assessed for their ability to identify cows not conceiving, using the principles of sensitivity and specificity. PPD4 was significantly higher (p less than 0.10) and PPD8, PPDIFF and PPRATIO were significantly lower (p less than 0.01) in cows remaining open than in pregnant cows. Evaluating each parameter separately, PPDIFF greater than 3.00 units had the highest specificity, 85.7%, but a low sensitivity (27.0%). Combining two parameters using series interpretation to increase specificity resulted in the best combination of specificity (87%) and sensitivity (27%). Maximum specificity was 97% for PPD4 less than or equal to 1.00 units and PPD8 greater than 4.00 units, and also for PPD4 less than or equal to 1.00 units and PPDIFF greater than 3.00 units, but sensitivity was very low (7% and 10% respectively). Predictive values of the test results with the best specificity were evaluated; given the population pregnancy rate of 54%, none exceeded 50%, indicating that the plasma progesterone parameters were not very useful for identifying open dairy cows.

Analysis of Variance↗
PubMed1976

Ant-aphid association: role of aphid alarm pheromone.

When attacked by predators, aphids secrete alarm pheromones that cause nearby aphids to disperse. Ant-associated (myrmecophilous) aphid species disperse less readily than nonmyrmecophilous species. The ant Formica subsericea responds to aphid alarm pheromone in a way that is beneficial to the aphid. These findings support our hypothesis that myrmecophilous aphids depend more on ants for protection from predators than on their own dispersive powers.

Animals↗