Biomedical subjects

K J Koehler

Publications and source records attributed to K J Koehler.

14 recordsLinked to original sources

PubMed2006

Effects of storage time and temperature after blood sampling from turkeys on plasma concentrations of potassium, sodium, and chloride.

The objectives of this research were to study the effect of several time intervals of turkey blood storage from sampling to centrifugation on plasma K, Na, and Cl concentrations and to study the effect of ambient temperature of turkey blood storage on these same variables. In the first study, 6 consecutive blood samples were obtained from each turkey. The first sample was centrifuged immediately (control), and each of the others was respectively stored for 20, 40, 60, 120, or 360 min at 22 degrees C before centrifugation and plasma harvest. In the second study, 4 consecutive blood samples were obtained from each turkey. The first sample was centrifuged immediately (control), and each of the others was respectively stored at ambient temperatures of 9, 22, and 30 degrees C for 120 min before centrifugation and plasma harvest. Plasma K concentration declines and is significant (P < 0.01) for each of the 20, 40, 60, 120, and 360 min values. Plasma Na concentration increases and Cl decreases were not significant (P < 0.01) until 360 and 120 min, respectively. Significant (P < 0.01) reductions occurred for plasma K concentration for each of the ambient temperature values but were the least at 9 degrees C and greatest when stored at 30 degrees C. Plasma Na concentration decreased (P < 0.01) when stored at 9 degrees C. Though increased (P < 0.01) when stored at 22 and 30 degrees C, the difference was not significant (P < 0.01) between samples stored at either 22 or 30 degrees C. Plasma Cl concentration was decreased (P < 0.01) from control values, but there was no significant difference (P < 0.01) among samples stored at 9, 22, and 30 degrees C. Clot formation and its retraction from serum are unduly delayed after blood is withdrawn from turkeys because birds lack the intrinsic mechanism for blood coagulation. Accordingly, serum is not appropriate for the determination of K concentration in turkeys, and plasma harvested immediately after blood sampling is the fluid of choice for K analysis.

Animals↗

PubMed2006

Prevention of fatty liver in transition dairy cows by subcutaneous injections of glucagon.

The main objective of this study was to test the extent to which injecting glucagon subcutaneously for 14 d beginning at d 2 postpartum would prevent fatty liver development in transition dairy cows. Twenty-four multiparous Holstein cows were fed 6 kg of cracked corn in addition to their standard diet during the last 30 d of a dry period to induce postpartum development of fatty liver. Glucagon at either 7.5 or 15 mg/d or saline (control) was injected subcutaneously 3 times daily for 14 d beginning at d 2 postpartum. Glucagon at 15 mg/ d prevented liver triacylglycerol accumulation in postpartum dairy cows. Glucagon at 7.5 mg/d showed potential for fatty liver prevention. Glucagon increased concentration of plasma glucose and insulin and decreased plasma nonesterified fatty acid concentrations. No effects of glucagon were detected on plasma beta-hydroxybutyrate concentrations. Glucagon affected neither feed intake nor milk production. Moreover, milk composition was not altered by glucagon. Milk urea N concentrations decreased, and plasma urea N concentrations tended to decrease during glucagon administration, indicating that glucagon may improve protein use. Liver glycogen concentrations were not affected by glucagon. No significant differences in body condition scores were detected among treatments throughout the study. These results indicate that subcutaneous glucagon injections can prevent fatty liver in transition dairy cows without causing major production and metabolite disturbances.

Acetoacetates↗

PubMed2005

Microsatellite markers associated with resistance to Marek's disease in commercial layer chickens.

The objective of the current study was to identify QTL conferring resistance to Marek's disease (MD) in commercial layer chickens. To generate the resource population, 2 partially inbred lines that differed in MD-caused mortality were intermated to produce 5 backcross families. Vaccinated chicks were challenged with very virulent plus (vv+) MD virus strain 648A at 6 d and monitored for MD symptoms. A recent field isolate of the MD virus was used because the lines were resistant to commonly used older laboratory strains. Selective genotyping was employed using 81 microsatellites selected based on prior results with selective DNA pooling. Linear regression and Cox proportional hazard models were used to detect associations between marker genotypes and survival. Significance thresholds were validated by simulation. Seven and 6 markers were significant based on proportion of false positive and false discovery rate thresholds less than 0.2, respectively. Seventeen markers were associated with MD survival considering a comparison-wise error rate of 0.10, which is about twice the number expected by chance, indicating that at least some of the associations represent true effects. Thus, the present study shows that loci affecting MD resistance can be mapped in commercial layer lines. More comprehensive studies are under way to confirm and extend these results.

Animals↗

PubMed2003

Genetic parameters and trends for litter traits in U.S. Yorkshire, Duroc, Hampshire, and Landrace pigs.

Records on 251,296 Yorkshire, 75,262 Duroc, 83,338 Hampshire, and 53,234 Landrace litters born between 1984 and April of 1999 in herds on the National Swine Registry Swine Testing and Genetic Evaluation System were analyzed. Animal model and restricted maximum likelihood procedures were used to estimate variances of animal genetic (a), maternal genetic (m), permanent environmental, and service sire, and the covariances between a and m for number born alive (NBA), litter weight at 21 d (L21WT), and number weaned (NW). Fixed effects of contemporary groups were included in the analysis. Based on a single-trait model, estimates of heritabilities were 0.10, 0.09, 0.08, and 0.08 for NBA; 0.08, 0.07, 0.08, and 0.09 for L21WT; and 0.05, 0.07, 0.05, and 0.05 for NW in the Yorkshire, Duroc, Hampshire, and Landrace breeds, respectively. Estimates of maternal genetic effects were low and ranged from 0.00 to 0.02 for all traits and all breeds. Estimates of permanent environmental effects ranged from 0.03 to 0.08. Estimates of service sire effects ranged from 0.02 to 0.05. A bivariate analysis was used to estimate the genetic correlations among traits. Average genetic correlations over the four breeds were 0.13, 0.15, and 0.71 for NBA with L21WT, NBA with NW, and L21WT with NW, respectively. Average genetic trends were 0.018 pigs/yr, 0.114 kg/yr, and 0.004 pigs/yr for NBA, L21WT, and NW, respectively. Although estimates of heritabilities for litter traits were low and similar across breeds, genetic variances for litter traits were sufficiently large to indicate that litter traits could be improved through selection. This study presents the first set of breed-specific estimates of genetic parameters available from large numbers of field records. It provides information for use in national genetic evaluations.

Adipose Tissue↗

PubMed2003

Genetic correlations between lean growth and litter traits in U.S. Yorkshire, Duroc, Hampshire, and Landrace pigs.

The objective of this study was to estimate breed-specific genetic correlations between lean growth and litter traits for four U.S. swine breeds. Records for lean growth and litter traits on Yorkshire, Duroc, Hampshire, and Landrace pigs collected between 1990 and April 2000 in herds on the National Swine Registry Swine Testing and Genetic Evaluation System were analyzed. A bivariate animal model and restricted maximum likelihood procedures were used to estimate genetic and environmental correlations between lean growth rate, days to 113.5 kg, backfat, and loin muscle area with litter traits of number born alive, litter weight at 21 d, and number weaned. Most genetic correlation estimates between lean growth and litter traits were small in magnitude and consistent across breeds. Backfat had the largest within-breed genetic correlations with number born alive (0.18 to 0.20) and litter weight at 21 d (-0.27 to -0.30). Estimates of genetic correlations between lean growth traits and number weaned were very small. Estimates of the environmental correlations between lean growth and litter traits also were very small for all traits and for all four breeds. Results indicate that selection for lean growth traits could have a long-term effect on litter traits. Including lean growth traits in a maternal-line evaluation using a multiple-trait model could increase the accuracy of the genetic evaluation for litter traits.

Adipose Tissue↗

PubMed2002

Genetic parameters and trends for lean growth rate and its comvonents in U.S. Yorkshire, Duroc, Hampshire, and Landrace pigs.

Records on 361,300 Yorkshire, 154,833 Duroc, 99,311 Hampshire, and 71,097 Landrace pigs collected between 1985 and April of 2000 in herds on the National Swine Registry Swine Testing and Genetic Evaluation System were analyzed. Animal model and REML procedures were used to estimate random effects of animal genetic, common litter, maternal genetic, and the covariances between animal and maternal for lean growth rate (LGR), days to 113.5 kg (DAYS), backfat adjusted to 113.5 kg (BF), and loin eye area adjusted to 113.5 kg (LEA). Fixed effects of contemporary group and sex were also in the statistical model. Based on the single-trait model, estimates of heritabilities were 0.44, 0.44, 0.46, and 0.39 for LGR; 0.35, 0.40, 0.44, and 0.40 for DAYS; 0.48, 0.48, 0.49, and 0.48 for BF; and 0.33, 0.32, 0.35, and 0.31 for LEA in the Yorkshire, Duroc, Hampshire, and Landrace breeds, respectively. Estimates of maternal genetic effects were low and ranged from 0.01 to 0.05 for all traits across breeds. Estimates of common litter effects ranged from 0.07 to 0.16. A bivariate analysis was used to estimate the genetic correlations between lean growth traits. Average genetic correlations over four breeds were -0.83, -0.37, 0.44, -0.07, 0.08, and -0.37 for LGR with DAYS, BF, and LEA, DAYS with BF and LEA, and BF with LEA, respectively. Average genetic trends were 2.35 g/yr, -0.40 d/yr, -0.39 mm/yr, and 0.37 cm2/yr for LGR, DAYS, BF, and LEA, respectively. Results indicate that selection based on LGR can improve leanness and growth rate simultaneously and can be a useful biological selection criterion.

Adipose Tissue↗

PubMed2001

Phenotypic trends in incidence of stillbirth for Holsteins in the United States.

The objectives for this study were to determine 1) if there was a trend in stillbirths for the U.S. Holstein population, 2) if stillbirths are the same trait in primiparous and multiparous cows, and 3) what was the role of dystocia in stillbirths. A sample of 666,341 births from the MidStates Dairy Records Processing Center and the National Association of Animal Breeders was used to examine the influence of sire, herd, year, season, sex of calf, parity of dam, calving ease, and gestation length on the survival of the calf. Parity was scored as an ordered variable (1, 2, 3+). Calving ease was scored on a scale of 1 (no assistance) to 3+ (needed assistance). An increasing trend in stillbirths was found in primiparous and multiparous cows. The percentage of stillborn calves in primiparous cows increased from 9.5 in 1985 to 13.2 in 1996. Stillbirths in multiparous cows increased from 5.0 to 6.6% from 1985 to 1996. Variation about the trend was greater in primiparous cows than in multiparous cows. Dystocia was a major determinant of stillbirth incidence, but the association was stronger in primiparous cows. Sex of calf had different associations with stillbirth incidence in primiparous and multiparous cows. Gestation length and season of birth also had significant associations with stillbirth incidence. Logistic regression models with fixed and random effects were fit to the data to preserve the binary nature of the stillbirth response. The expected probability of stillbirths for an average herd and sire was 10% for primiparous cows and 5% for multiparous cows. Replacement of stillborn calves is a substantial cost to the dairy industry at more than $125.3 million per year. Because of the increasing incidence of stillbirths, these costs have increased by $75.9 million from 1985 to 1996.

Animals↗

PubMed2000

Interactions among factors affecting stillbirths in Holstein cattle in the United States.

Each year about 7% of the Holstein calves born in the United States die within 48 h of birth. The exact cause of death is unknown. The purpose of this article is to examine the complex interactions among factors (e.g., parity, season of birth, dystocia, year) contributing to stillbirth rates. A modified chi-squared automated interaction detection algorithm was used to develop classification trees explaining the most likely sequence of factors that result in a stillborn calf. The data were 666,341 births from the MidStates Dairy Records Processing Center and the National Association of Animal Breeders. Primiparous and multiparous cows clearly differ in the rate of stillbirths, 11.0 and 5.7%, respectively. Dystocia followed parity as the next most important factor within both primiparous and multiparous cows. In primiparous cows, season, year of birth, or gestation length ranked third as an important predictor for dystocia equal to 1, 2, or 3+, respectively. Gestation length ranked third in importance among the factors that affect stillbirth rates for all levels of dystocia in multiparous cows. Among multiparous cows needing assistance (dystocia 3+), stillbirth rates were greatest for shorter gestations less than the average of 280 d, 55.3% for -15 to -12 d, 45.5% for -11 to -9 d, 33.7% for -8 to -5 d, 23.8% for -4 to 13 d, and 35.4% for 14 to 15 d. Gestation length pinpointed the time when stillbirths occurred, as indicated by the increase from 23.8% stillbirth rate among calves born at or above the mean gestation length to 55.3% for those calves born -15 to -12 d below the mean gestation. Further investigation of the relationship between stillbirth rates and gestation length is needed to develop a more complete understanding of the biological processes resulting in the loss of calves at birth.

Algorithms↗

PubMed2000

Cell-cycle arrest at G2/M and growth inhibition by apigenin in human colon carcinoma cell lines.

Apigenin, a common dietary flavonoid, has been shown to induce cell cycle arrest in both epidermal and fibroblast cells and inhibit skin tumorigenesis in murine models. The present study assessed the influence of apigenin on cell growth and the cell cycle in the human colon carcinoma cell lines SW480, HT-29, and Caco-2. Treatment of each cell line with apigenin (0-80 microM) resulted in a dose-dependent reduction in both cell number and cellular protein content, compared with untreated control cultures. DNA flow cytometric analysis indicated that treatment with apigenin resulted in G2/M arrest in all three cell lines in a time- and dose-dependent manner. Apigenin treatment (80 microM) for 48 h produced maximum G2/M arrest of 64%, 42%, and 26% in SW480 cells, HT-29 cells, and Caco-2 cells, respectively, in comparison with control cells (15%). The proportion of S-phase cells was not altered by apigenin treatment in each of the three cell lines. The G2/M arrest was reversible after 48 h of apigenin treatment in the most sensitive cell line SW480. The degree of G2/M arrest by apigenin was inversely correlated with the corresponding inhibition of cell growth measurements in all three cell lines (r = -0.626 to -0.917, P</=0. 005). Moreover, an immune complex kinase assay demonstrated an inhibition of p34(cdc2) kinase activity, a critical enzyme in G2/M transition, in each cell line after treatment with apigenin (50-80 microM). Western blot analyses indicated that both p34(cdc2) and cyclin B1 proteins were also decreased after apigenin treatment. These results indicate that apigenin inhibits colon carcinoma cell growth by inducing a reversible G2/M arrest and that this arrest is associated, at least in part, with inhibited activity of p34(cdc2) kinase and reduced accumulation of p34(cdc2) and cyclin B1 proteins. Differences in induction of G2/M arrest by apigenin in the three colon carcinoma cell lines suggest that dietary apigenin may be differentially effective against tumors with specific mutational spectra. Mol. Carcinog. 28:102-110, 2000.

Apigenin↗

PubMed1997

Bootstrapping regression parameters in multivariate survival analysis.

Bootstrap methods are proposed for estimating sampling distributions and associated statistics for regression parameters in multivariate survival data. We use an Independence Working Model (IWM) approach, fitting margins independently, to obtain consistent estimates of the parameters in the marginal models. Resampling procedures, however, are applied to an appropriate joint distribution to estimate covariance matrices, make bias corrections, and construct confidence intervals. The proposed methods allow for fixed or random explanatory variables, the latter case using extensions of existing resampling schemes (Loughin, 1995), and they permit the possibility of random censoring. An application is shown for the viral positivity time data previously analyzed by Wei, Lin, and Weissfeld (1989). A simulation study of small-sample properties shows that the proposed bootstrap procedures provide substantial improvements in variance estimation over the robust variance estimator commonly used with the IWM.

Acquired Immunodeficiency Syndrome↗

PubMed1997

Modification of the Greenwood formula for correlated response times.

Life-table methodology for interval-censored survival times is used to estimate marginal survival probabilities from data consisting of independent cohorts of correlated responses. We restrict our attention to situations where response times within cohorts are exchangeable and the marginal survival distributions are the same for all individuals within any cohort. A modification of the Greenwood formula is derived for estimating variances and covariances of the estimates of the marginal survival probabilities. Simulation results show that this formula provides accurate adjustments for within-cohort correlations in finite samples. Comparisons with a nonparametric maximum likelihood estimator indicate negligible loss in efficiency from using simple life-table estimators of marginal survival probabilities that ignore the within-cohort correlations. Data from an angioplasty study where more than one procedure is performed on some patients are used to illustrate this methodology.

Analysis of Variance↗

PubMed1994

Immunological parameters of periparturient Holstein cattle: genetic variation.

The genetic variability of blood neutrophil functions, lymphocyte blastogenic responses to mitogens, serum Ig concentrations, and serum complement and conglutinin activities was investigated from 35 d prepartum to 35 d postpartum for 137 Holstein cows. Periparturient cows experience an immunosuppression of various immunologic parameters at calving. Heritability estimates were obtained before, during, and after the episodes of immunosuppression. Significant genetic variability occurred in the periparturient changes for total number of neutrophils, neutrophil chemokinesis, assays of the neutrophil respiratory burst associated with phagocytosis (cytochrome c reduction, chemiluminescence, and iodination), serum concentrations of IgG1, IgG2, and IgM, and serum homolytic complement activity. This variability implies that immune profiles could be used for the selection of cattle with improved innate immune response without adverse effects on milk productivity. These results should be considered tentative, however, because the number of observations included in the data were limited.

Animals↗

PubMed1992

Factors affecting dystocia and early calf mortality in Angus cows and heifers.

Calving performance records (965,417) from purebred American Angus herds throughout the United States were used to study dystocia and early calf mortality during the period from 1972 to 1985. A sample of 53 (n = 83,467) herds was used to establish reasonable limits on the expected frequency of dystocia and mortality within and among herds that have good reproductive management programs and to verify the frequencies of scores in all other herds (n = 4,130) reporting calving performance information. The data were analyzed by logistic regression models. Dystocia and perinatal mortality, to a lesser extent, were found to be more frequent in heifers than in cows. The odds of unassisted births vs births with major difficulty were 11.58 times greater in cows than in heifers. In heifers, the odds of an unassisted birth increased with age of dam and decreased with birth weight of calf. At a baseline age of 22 mo the odds of an unassisted birth for calves weighing 30 and 40 kg were .13 and .02 times lower than the odds for calves weighing 20 kg. Alternately, at 29 mo, the odds of an unassisted birth for heifers producing a 20-kg calf were 4.53 times greater than at 22 mo. Survival of calves to 24 h in heifers was primarily affected by birth weight. Heifers producing calves at intermediate weights of 29 kg had higher odds of producing live calves at all ages. Considering all heifers calving at 22 to 29 mo relative to 20-kg calves, the odds for survival to 24 h were 3.83 times greater for 29-kg calves and lower by a factor of .52 for 40-kg calves.

Animals↗

PubMed1990

An application of the LFP survival model to smoking cessation data.

We use a limited failure population (LFP) model based on the Weibull distribution to model the times from initial abstinence to return to smoking for subjects enrolled in programmes to help them stop smoking. The model contains a third parameter that corresponds to the proportion of subjects who permanently abstain from smoking. The data are subject to both right and interval censoring. Furthermore, subjects receive treatment in groups, and individuals in the same group may provide correlated outcomes. Use of a maximum likelihood estimation procedure which assumes independent outcomes provides reasonable parameter estimates, but the corresponding standard errors tend to be too small, which results in tests with inflated type I error levels and confidence intervals that tend to be too narrow. We use a bootstrap procedure to obtain more reasonable values for the standard errors and to construct confidence intervals that more nearly achieve the stated coverage probabilities.

Confidence Intervals↗