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Biomedical subjects

M E Davis

Publications and source records attributed to M E Davis.

At least 19 recordsLinked to original sources
PubMed1999

Broiler skin sampling for optimum recovery of Salmonella spp.

The objective of this research was to determine the appropriate sample size (1, 5, or 10 g) and location (neck, breast, or vent) from which to sample processed poultry skin for Salmonella spp. Postkill, prescald broiler carcasses were used to help ensure that Salmonella spp. would be found. Mean Salmonella spp. counts from skin samples of 1 g (2.91 log10 CFU/g) were significantly lower (P < 0.05) than skin samples of 5 and 10 g: 3.52 log10 CFU/g and 3.42 log10 CFU/g, respectively. Mean Salmonella spp. counts from breast (3.62 log10 CFU/g) or neck (3.40 log10 CFU/g) skin samples were significantly higher (P < 0.05) than counts from vent skin samples (2.84 log10 CFU/g). Neck skin is the preferred sampling location because it contained a representative number of Salmonella spp., it had a slightly higher incidence of Salmonella spp. than vent skin, and removal of neck skin for microbiological testing did not decrease the quality grade of the bird, as would the removal of breast skin. Research results will increase the accuracy and precision of the microbiological analytical procedures for processed poultry by providing guidelines for the amount and location of skin to be sampled, as well as the preparatory procedures involved to release the Salmonella spp. from the skin samples.

Animals↗
PubMed1998

Characterization of whole genome radiation hybrid mapping resources for non-mammalian vertebrates.

Radiation hybrid panels are already available for genome mapping in human and mouse. In this study we have used two model organisms (chicken and zebrafish) to show that hybrid panels that contain a full complement of the donor genome can be generated by fusion to hamster cells. The quality of the resulting hybrids has been assessed using PCR and FISH. We confirmed the utility of our panels by establishing the percentage of donor DNA present in the hybrids. Our hybrid resources will allow inexpensive gene mapping and we expect that this technology can be transferred to many other species. Such successes are providing the basis for a new era of mapping tools, in the form of whole genome radiation hybrid panels, and are opening new possibilities for systematic genome analysis in the animal genetics community.

Animals↗
PubMed1998

Relationship between blood serum insulin-like growth factor I concentration and postweaning feed efficiency of crossbred cattle at three levels of dietary intake.

Blood serum concentration of IGF-I was analyzed to determine its relationship with individual postweaning feed efficiency (gain/feed) of 36 crossbred steer calves fed at three levels of feed intake (n = 12 at each level). Diets consisted of a corn silage-based growing diet for 84 d followed by a 91% concentrate finishing diet for 56 d. Dietary intake levels were at 80, 90, or 100% of ad libitum. Diets were formulated to ensure equal daily intake of protein, vitamins, and minerals across intake treatment levels. Intake was measured daily; ADG, DMI, and feed efficiency were calculated at 28-d intervals, through d 140. Individual weights and serum samples were collected at the beginning of the study and at 28-d intervals thereafter. The IGF-I concentrations were determined with a RIA. Data were analyzed as a multivariate split-plot in time. Imposed dietary intake restrictions did not affect serum IGF-I concentration (P = .90) or individual feed efficiency (P = .36), even though the least squares means for IGF-I concentration tended to decrease and the feed efficiency means tended to increase under the restricted intake levels. Serum IGF-I concentration, ADG, and feed efficiency were affected (P < .001) by collection date. Residual correlations between IGF-I concentrations at adjacent 28-d sampling times averaged .72. Diet intake level x sampling time interactions existed for ADG (P = .02) and feed efficiency (P < .001). Positive residual correlations of .28 (P < .001) and .16 (P = .07) existed between IGF-I and ADG and between IGF-I and feed efficiency, respectively. Regression analysis indicated that a 1 ng/mL increase in serum IGF-I concentration was associated with a .00135 kg/d increase in ADG (P < .001) and a .0001 kg gain/kg feed increase in feed efficiency (P = .04). These results support the hypothesis that serum IGF-I plays a role in growth and in efficiency of feed utilization in beef cattle.

Animal Feed↗
PubMed1998

L-ascorbyl-2-polyphosphate as a vitamin C source for segregated and conventionally weaned pigs.

We conducted two experiments to evaluate the efficacy of a stable source of vitamin C for improving performance and iron status in early-weaned pigs. A preparation of L-ascorbyl-2-polyphosphate (Rovimix Stay-C 25, Roche Vitamins, Ames, IA and Bramus, NJ), which supplies 25% ascorbic acid activity in a stable form, served as the vitamin C source and was incorporated at dietary vitamin C levels of 0, 75, or 150 ppm. In Exp. 1, 72 pigs (14 +/- 2 d of age and 4.98 kg BW) were blocked based on initial BW and penned in groups of three (eight pens per treatment) in an off-site nursery for 42 d. Phase 1 lasted from d 0 to 14, Phase 2 from d 14 to 28, and Phase 3 from d 28 to 42 after weaning. Daily gain and gain:feed ratio (G/F) increased during Phase 1 (quadratic, P < .1 and P < .05, respectively), Phase 3 (linear, P < .1 and P < .01, respectively), and for the overall 42-d experiment (linear, P < .05 and P < .1, respectively) in response to increasing dietary vitamin C. At 14 d after weaning, plasma vitamin C increased (linear, P < .05) with increasing dietary vitamin C, but plasma iron, hemoglobin, and hematocrit were not influenced by dietary vitamin C. In Exp. 2, 120 pigs (20 +/- 3 d of age and 7.2 kg BW) were blocked based on initial BW and penned in groups of five (eight pens per treatment) in a conventional nursery system for 31 d. Phase 1 consisted of d 0 to 7, Phase 2 from d 7 to 17, and Phase 3 from d 17 to 31 after weaning. During the period from d 0 to 17 after weaning, ADG and G/F were improved (linear, P < .1) with increasing dietary vitamin C. At d 17 after weaning, plasma vitamin C and serum iron increased (linear, P < .05), but unbound iron-binding capacity and total iron-binding capacity decreased (linear, P < .05 and P < .1, respectively) with increasing dietary vitamin C. These results suggest that dietary vitamin C is needed during the first 42 d after weaning when pigs are weaned as early as 12 d of age and reared in an off-site nursery and during the first 17 d after weaning when pigs are weaned as early as 17 d of age and reared in a conventional nursery system. L-Ascorbyl-2-polyphosphate at a supplemental level of 75 ppm was adequate to meet the dietary vitamin C requirement of early-weaned pigs. Vitamin C supplementation with a stable product will improve performance in young pigs during the high-stress postweaning period and may be particularly beneficial to pigs weaned at a very early age.

Animals↗
PubMed1997

Dichloroacetic acid pretreatment of male and female rats increases chloroform-induced hepatotoxicity.

Dichloroacetic acid (DCA) and chloroform (CHCl3) are both major by-products of drinking water chlorination and DCA increases the hepatotoxicity of CHCl3. In this study, we further characterized this effect and investigated DCA-induced alterations of CHCl3 disposition and metabolism as a possible mechanism for this interaction. Both adult male and female Sprague-Dawley rats were gavaged with three doses (09:00, 16:00 and 09:00 the next morning) of DCA (each 2.45 mmol/kg), then challenged with an i.p. injection of CHCl3 (3.12 or 9.35 mmol/kg). Hepatic damage was assessed 24 h after CHCl3 administration as increased alanine aminotransferase (ALT), ornithine carbomyl transferase (OCT) and bilirubin in plasma. In a separate experiment, rats were pretreated with DCA or were given 14CHCl3 at the same dosages. The disposition of 14C in various tissues and covalent binding of 14CHCl3-derivatives to liver proteins and lipids were determined 1 h later. CHCl3-induced hepatotoxicity was significantly more severe in DCA-pretreated groups. ALT and OCT were more markedly elevated in DCA + CHCl3 (3.12 mmol/kg) groups than NaCl +CHCl3 animals. Plasma bilirubin content was elevated only in DCA + CHCl3 groups and females were more susceptible to this effect. The responses of rats to DCA treatment were somewhat gender-different. DCA treatment increased total cytochrome P450 in females, but not in males. Hepatic glutathione concentration was elevated in males after DCA treatment, but not in females. In the present study we confirmed that DCA pretreatment potentiates the CHCl3-hepatotoxicity of both male and female rats. However, there was little evidence that DCA pretreatment significantly affected CHCl3 disposition or increased CHCl3 binding in vivo.

Animals↗
PubMed1997

Dichloroacetic acid pretreatment of male and female rats increases chloroform metabolism in vitro.

The role of metabolism in dichloroacetic acid (DCA) potentiation of CHCl3 hepatotoxicity was investigated. Male and female Sprague-Dawley rats were given three doses (09:00, 16:00 and 09:00 the next morning) of DCA (each 2.45 mmol/kg) by gavage. The rats were euthanized 3 h after the last dose, hepatic microsomes were prepared and 14CHCl3 metabolism was measured in vitro. The binding of 14CHCl3-derivatives to microsomal proteins and lipids was increased 65 and 100%, respectively, in DCA-treated rats compared to their respective NaCl-treated controls. The formation of CO2 (nmol 14CO2/incubation) was significantly elevated in DCA-treated rats compared to controls (10.4 vs 6.3 in males; 10.8 vs 6.1 in females). DCA treatment decreased the apparent Michaelis constant (Km app) for conversion of 14CHCl3 to 14CO2 in rats (0.665 vs 0.415 mM in males, P < 0.05; 0.161 vs 0.081 in females). 14CO2 production and 14C binding were observed under N2 atmosphere, indicating that reactive metabolites of 14CHCl3 were formed by oxidation as well as reduction. Male and female rats metabolized CHCl3 differently. The Km app for CO2 production was up to 5-fold higher in the males than in the females, regardless of DCA treatment. Inhibition by SKF 525-A and piperonyl butoxide was gender dependent in both control and DCA-treated groups. The results showed, that increased bioactivation of CHCl3 by DCA treatment is one element in the DCA-CHCl3 interaction.

Animals↗
PubMed1997

The influence of a big brothers program on the adjustment of boys in single-parent families.

This study is an evaluation of the self-competence, academic performance, behavioral problems, and parent-child relations of boys who had been raised in single-parent families headed by their mothers and who had weekly contact with an adult friend or companion through a midwestern affiliate of the Big Brothers/Big Sisters of America. Results indicated that participation in such a program was not related to changes in the areas investigated. These findings are not consistent with the social support literature suggesting that an adult companion or friend may benefit children in single-parent families. Further study with a larger sample, over a longer time frame, is recommended.

Achievement↗
PubMed1997

A first-generation whole genome-radiation hybrid map spanning the mouse genome.

We have assembled a first-generation anchor map of the mouse genome using a panel of 94 whole-genome-radiation hybrids (WG-RHs) and 271 sequence-tagged sites (STSs). This is the first genome-wide RH anchor map of a model organism. All of the STSs have been previously localized on the genetic map and are located 8.8 Mb apart on average. This mouse WG-RH panel, known as T31, has an average retention frequency of 27.6% and an estimated potential resolution of 145 kb, making it a powerful resource for efficient large-scale expressed sequence tag mapping. [All of the mapping data for the maps presented here have been deposited at the Research Genetics, Inc., web site and can be freely accessed and downloaded at http://www.resgen.com/.]

Animals↗
PubMed1997

Genetic parameter estimates for serum insulin-like growth factor I concentration and performance traits in Angus beef cattle.

Data for this study were obtained from an experiment involving divergent selection for blood serum IGF-I concentration in beef cattle. Multiple trait derivative-free REML procedures were used to obtain genetic parameter estimates for IGF-I concentration at d 28, 42, and 56 of the postweaning period and for mean IGF-I concentration, as well as for weights and gains. Included in the analysis were 1,563 animals in the A-1 matrix, 731 of which had valid records for mean IGF-I concentration. Direct heritabilities (hd2) were .42 +/- .13, .53 +/- .15, .71 +/- .16, and .48 +/- .13 for IGF-I at d 28, 42, and 56 of the postweaning period and for mean IGF-I, respectively. Heritability of maternal genetic effects (hm2) ranged from .02 to .12, whereas the proportion of the total variance due to the maternal permanent environmental effect (c2) was essentially zero for all measures of IGF-I. Genetic correlations of IGF-I with weaning and postweaning weights and with postweaning weight gain ranged from -.21 to -.54 and averaged -.38. The environmental correlation between IGF-I and performance traits varied from .10 to .35 and averaged .22. Phenotypic correlations of IGF-I concentrations with weaning weight and postweaning weights and gains ranged from -.01 to .12 and averaged .04. Estimates of hd2 indicate that it should be possible to change IGF-I concentration in beef cattle via selection. Negative genetic correlations imply that, if the goal is to make genetic improvement in weaning weights, postweaning weights and (or) postweaning gain in beef cattle, selection should be for decreased postweaning serum IGF-I concentration.

Animals↗
PubMed1996

Construction of a mouse whole-genome radiation hybrid panel and application to MMU11.

Whole-genome radiation hybrids have been used to construct human genome maps that integrate different types of markers. To investigate this methodology in mammalian species other than humans, a panel of 164 mouse x hamster whole-genome radiation hybrids was constructed. This set of hybrids was used to produce a high-resolution map of a region on MMU11 that included microsatellite markers and cDNA sequences. The mouse homologue of the human SRY-related gene SOX9 was mapped to an interval of approximately 1.1 cM flanked by the microsatellite markers D11Mit11 and D11Mit291. This interval includes the region containing the mouse Tail-short mutation, a possible homologue of the human syndrome campomelic dysplasia, which is caused by mutations in SOX9. Our results suggest that whole-genome radiation hybrid technology will be a useful adjunct to mapping the genomes of nonhuman mammalian species.

Animals↗
PubMed1996

Dichloroacetic acid treatment increases hepatic CYP2E1 in male and female rats.

Previously, we showed that the pretreatment of dichloroacetic acid (DCA) increased CHCl3-induced hepatotoxicity in vivo and CHCl3 metabolism in vitro in both male and female rats. The effects of DCA on hepatic cytochrome P450-dependent monooxygenases were studied in this experiment. Male and female Sprague-Dawley rats were treated with DCA (each 2.45 mmol/kg) three times (9 AM, 4 PM, and 9 AM) and hepatic microsomes were prepared 3 hr after the last treatment (the same procedure as previous studies). After DCA treatment, the total content of cytochrome P450 (0.67 nmol/mg protein vs 0.79) and the activity of NADPH-dependent cytochrome P450 reductase (227 nmol/mg protein/min vs 332) were significantly increased in female rats, but they were unchanged in males (0.99 vs 0.98 for P450; 315 vs 311 for reductase). Induction of CYP2E1 was observed in both sexes, evidenced as increased activities of aniline and p-nitrophenol hydroxylases and increased CYP2E1 protein amount determined by immunoblot assay. In contrast, the CYP2B-related activity (dealkylation of pentoxyresorufin) and immunoreactive protein did not increase after DCA treatment in either males or females. The activity of ethoxyresorufin dealkylase was decreased in DCA-treated males compared to their controls (310 pmol/mg protein/min vs 229, p < 0.05), but it was not significantly affected in females. These data demonstrate that DCA treatment of both male and female rats altered the population of hepatic cytochrome P450. The results support the hypothesis that DCA increases CHCl3 metabolism, and therefore hepatotoxicity, by inducing CYP2E1.

Animals↗
PubMed1996

Chemical stability of artesunate injection and proposal for its administration by intravenous infusion.

Artesunate, the only artemisinin analogue that can be given intravenously, produces rapid parasite and fever clearance in falciparum malaria. A significant therapeutic problem is a high, late recrudescence rate, probably due to short half-lives of both artesunate and its active metabolite dihydroartemisinin relative to conventional dosing intervals. One method of extending the duration of action of artesunate could be to administer the drug by infusion rather than bolus injection, provided that it is chemically stable at ambient temperature. Artesunate was found to be stable in 0.9% w/v sodium chloride at 9 degrees C, 23 degrees C and 36.5 degrees C for 130, 10.6 and 1.6 h, respectively. Interpolating from an Arrhenius plot, artesunate should be stable for approximately 4 h at 30 degrees C, a temperature representative of ambient conditions in tropical countries. Exposure to light did not affect the degradation rate. Single compartment pharmacokinetic modelling was used to evaluate potential differences in artesunate and dihydroartemisinin plasma concentrations following administration of artesunate by intravenous bolus or infusion. A bolus injection of artesunate at a dose of 4 mg kg-1 gives a peak concentration of 5.3 mg L-1, falling to 0.005 mg L-1 at 5 h. The same dose infused over 4 h results in a peak concentration of 0.92 mg L-1, falling to 0.005 mg L-1 at 8 h. Simultaneous modelling of dihydroartemisinin showed that while its peak plasma concentration was reduced by 27% and the peak delayed by 2.5 h following artesunate administration by infusion, substantially higher concentrations were maintained compared with those predicted after bolus artesunate. These data indicate that artesunate can be administered as a high-dose intravenous infusion, thus avoiding high plasma concentrations. This strategy also has the potential to prolong the duration of antimalarial effect and reduce toxicity, and consequently improve clinical outcome in seriously ill patients.

Antimalarials↗
PubMed1995

A metric for assessing acuity in positioning joints and limbs.

In this paper, we present a method for assessing the exactness of sensing and setting the positions of joints and limbs, using a measure we call target resolution. Target resolution, derived from information theory but ultimately based on variance, estimates the fewest number of discrete, equally spaced targets required within a range to provide the maximum possible information transfer from any target set. We argue that target resolution provides better insight into the exactness of position sense than does the usual measure of accuracy based on mean or constant error. Studies have shown that measures of mean error in setting or indicating positions of joints or limbs exhibit lability; they drift and show considerable sensitivity to factors such as previous positions of the limb and learning. We derive the equation for calculating target resolution and give example resolutions for several joints we have tested. Target resolution often gives a quite different impression of proprioceptive exactness than do measures of accuracy based on mean error.

Extremities↗
PubMed1995

Multifield magic-angle spinning and double-rotation nuclear magnetic resonance studies of a hydrated aluminophosphate molecular sieve: AlPO4-H2.

AlPO4-H2 is a microporous hydrated aluminophosphate, structurally related to VPI-5, whose framework has highly elliptical 10-ring channels (2.9 x 7.6 A) parallel to the c crystallographic axis. To resolve a previously reported discrepancy between nuclear magnetic resonance (NMR) and X-ray diffraction (XRD) data a highly crystalline AlPO4-H2 has been further characterized with 27Al and 31P magic-angle spinning (MAS) NMR at 11.7 T and 27Al double-rotation (DOR) NMR at 4.7 T. These present NMR data definitively show that the true space group symmetry of the AlPO4-H2 framework structure is triclinic rather than the higher orthorhombic symmetry proposed earlier from XRD studies.

Aluminum Compounds↗