Biomedical subjects

R L Powell

Publications and source records attributed to R L Powell.

At least 37 records · Page 2Linked to original sources

PubMed1998

Use of multinational data to improve national evaluations of Holstein bulls.

The usefulness of multinational data for the improvement of national estimates of genetic merit of Holstein bulls was assessed. For 222 bulls, combined US-Canadian evaluations and evaluations from the US only from January 1993 for milk, fat, and protein yields were compared with their US only evaluations from August 1997. The correlations between the 1993 and 1997 evaluations and the standard deviations of differences in evaluations from added data favored the evaluations from the US only because of a part-whole relationship; often 1997 data were largely from US only data from 1993. However, the results for 35 bulls with reliability increases of > 5% indicated that combining US and Canadian evaluations improved the prediction of future evaluations. The value of foreign data also was assessed from national and international evaluations on the scales of Canada, Germany, and the US. The changes from 1996 national evaluations to either 1996 international evaluations or 1997 national evaluations were compared to determine whether adding international data at the earlier time could provide a useful prediction of subsequent change in national evaluations. Although the degree of agreement among differences from added national and international data varied, international evaluations did provide useful information beyond the more limited national data available at the same time.

Animals↗

PubMed1997

Relationship between United States and Canadian genetic evaluations of longevity and somatic cell score.

Canadian and US evaluations of Holstein bulls were compared for longevity measures (433 bulls) and somatic cell score (354 bulls). Bulls were required to have a birth year of > or = 1975, daughter information from > or = 20 herds, and a reliability of > or = 50% in both Canada and the US. The number of bulls with longevity evaluations was greater for early years because longevity information was available from lactation data and daughters were required to be > or = 3 yr of age for US evaluations; evaluations for somatic cell score required additional collection of data and did not have corresponding numbers of bulls until the 1980s. Correlation between longevity measures in the US (productive life) and Canada (herd life) was 0.60. This low correlation was expected because US productive life includes yield information, but yield is excluded from Canadian herd life. For evaluations for somatic cell score, the correlation between the two countries was 0.82. Genetic correlations with productive life were estimated to be 0.69 for herd life and 0.81 for herd life combined with protein yield. Conversion equations were developed to predict a US evaluation for somatic cell score from a Canadian evaluation for somatic cell score and to predict a US evaluation for productive life from Canadian evaluations for herd life and yield.

Animals↗

PubMed1997

Consistency of international genetic evaluations of Holstein bulls.

International genetic evaluations from August 1995 and February 1996 for Holstein bulls from Canada, France, Germany, Italy, The Netherlands, and the US were evaluated for consistency across time. Mean evaluations, expressed on a US basis, were unchanged for US bulls; evaluations for bulls from France, Germany, Italy, and The Netherlands increased about 14 kg for milk and 0.4 kg for fat and protein. Mean genetic merit of US parents of bulls sampled in Canada, France, Germany, The Netherlands, and the US overestimated bull merit. Solutions for country of bull generally were not different for other countries relative to the US; however, evaluations for German and Netherlands bulls were higher than evaluations for US bulls with the same parent merit. French bulls that were full brothers to US bulls had higher evaluations for milk and protein, regardless of country of evaluation. Intercepts for conversion equations to a US basis increased by birth year and decreased for conversions from a US basis. Future international evaluations generally were predicted more accurately by prior international evaluations than by more recently converted national evaluations; however, converted evaluations with substantial increases in data could be better predictors, depending on country. The continued use of the latest international evaluations is recommended. Improvements in methodology that increase the consistency of evaluations across time and location may be possible. Alternatively, users may need to accept some uncertainty and error in international evaluations because of limitations in available data and methodology.

Animals↗

PubMed1996

Use of a miniaturized test system for determining acute toxicity of toxicity identification evaluation fractions.

A miniaturized test system was developed and used to determine the acute toxicity of effluent fractions separated by HPLC to Daphnia magna and Pimephales promelas. The miniaturized test system consists of exposing test organisms in 1 ml of test solution using 48-well microtiter plates for the test vessels. Several factors were investigated to determine the acceptability of this test system. These factors included organism biomass to test solution ratio, toxicity of the microtiter plates to the organisms, dissolved oxygen in the test solution, partitioning of the test chemicals to the walls of the test vessels, and dilution of the test solution when the organisms are transferred. Toxicity of four reference chemicals to D. magna and P. promelas was also determined using the miniaturized test systems. It was concluded that the test system could be miniaturized and still provide results comparable to those obtained when standard U.S. EPA test procedures were used. The major benefit of using the miniaturized test system is that less solution is required for conducting a toxicity test. This becomes important when only a small amount of test solution is available, as might occur during a toxicity identification evaluation, after an effluent has been fractionated by HPLC. Other benefits include less space required to conduct a test, less time necessary to prepare test solutions, and a reduced volume of waste for disposal.

Animals↗

PubMed1996

Phenotypic relationship of yield and type scores from first lactation with herd life and profitability.

Milk records from Ayrshire, Brown Swiss, Guernsey, Jersey, and Milking Shorthorn cows that first calved between 18 and 35 mo were combined with scores for linear type traits collected before 43 mo during first lactation to study herd life and lifetime profitability. Profitability (discounted relative net income) was the value of milk, calves, and cow salvage minus fixed costs, operating costs, and cow depreciation costs. Cows were included if they appeared only in a single herd and if the herd remained on test for 72 mo after birth date of the cow. Phenotypic correlations were computed for milk and fat yields and for 14 type traits during first lactation with nine variables for lifetime performance from 3895 Ayrshire, 7997 Brown Swiss, 20,179 Guernsey, 71,731 Jersey, and 628 Milking Shorthorn cows. Multiple correlations for predicting discounted relative net income for the four breeds with the most data were 0.43 to 0.46 from milk and fat yields (linear and quadratic effects) during first lactation, 0.11 to 0.29 from final score, and 0.21 to 0.33 from all type traits. Type scores had considerably less predictive ability than yield during first lactation for predicting profitability and had limited predictability after yield was included. Final score increased multiple correlations only 0.00 to 0.02 above that for yield for the same four breeds. Final score plus 13 type traits (linear, quadratic, and interaction effects) increased multiple correlations only 0.02 to 0.04 above that for yield. Because of the limited value of some of the linear type traits, an effort should be initiated to eliminate them from programs of breed associations.

Aging↗

PubMed1996

Relationship of bovine leukocyte adhesion deficiency with genetic merit for performance traits.

Examination of the existence of pleiotropy or linkage of bovine leukocyte adhesion deficiency with other traits and of the impact of removal of the recessive, undesirable allele on genetic progress for those traits has been limited. Frequency of carriers among 6400 Holstein bulls tested was 8.2%; however, reporting was incomplete, and, therefore, the estimate of carrier frequency was biased downward. For AI-sampled bulls, carrier frequency reached a high of 23% for bulls sampled during 1989 but declined to 0% since then because of DNA testing and culling. Association of the allele with yield, productive life, and somatic cell score was examined with a model in which the daughter yield deviation minus the mean of parent evaluations was explained by carrier status. A significant negative relationship was found with protein yield when effect of sires was ignored; all associations were unfavorable. Linkage was examined by applying the model for each of four sire families; only protein yield for one sire was significantly and negatively related to the recessive allele. Carrier bulls currently are labeled, and some continue to be used actively in AI because of superiority for other traits. Consequential pleiotropy of the allele or linkage of the locus with the traits studied is unlikely. Genetic progress for these performance traits will not be impeded by failure to sample carrier bulls.

Alleles↗

PubMed1996

Examination of international genetic evaluations of Holstein bulls.

The first large-scale, international genetic evaluation of Holstein bulls computed by the International Bull Evaluation Service Centre in February 1995 was examined and compared with national evaluations from Canada, Denmark, Finland, France, Germany, Italy, Sweden, The Netherlands, and the US. Assumption of a genetic correlation of 0.995 between all countries and exclusion of bull daughters from a country in which the bull had not been sampled resulted in correlations of essentially unity between national and international evaluations. For the few bulls sampled in multiple countries, correlations were lower but still high (< or = 0.95). Genetic trend was more rapid for countries in which genetic merit for earlier years was lowest. Differences among countries in genetic merit of recent bulls have decreased markedly, especially between the US and other countries. Mean evaluation for bulls born during 1988 in the US surpassed means for bulls in France, Italy, and The Netherlands by < 3 kg for PTA for protein. Application of seven national economic indexes showed that some indexes with different mathematical forms can rank bulls similarly. If the official index for one country is assumed to be optimal, use of an index from another country could substantially reduce the mean merit of selected bulls by more than one-half an index standard deviation. Selection on either national or international genetic evaluations can give rapid genetic progress if the economic index is correct.

Animals↗

PubMed1994

New T47D breast cancer cell lines for the independent study of progesterone B- and A-receptors: only antiprogestin-occupied B-receptors are switched to transcriptional agonists by cAMP.

Because progesterone antagonists are growth inhibitors, they are in Phase III clinical trials for the treatment of breast cancer. However, when cellular cAMP levels are elevated, some antiprogestins inappropriately activate transcription. We have proposed that hormone "resistance" may result from such unintended stimulation of breast cancer by antagonists. In transient expression systems, the two natural isoforms of human progesterone receptors (PR), B-receptors and truncated A-receptors, have dissimilar effects on agonist-mediated transcription. We show here that in the presence of 8-Br-cAMP, antiprogestin-occupied B-receptors but not A-receptors become transcriptional activators. Therefore, we developed new model systems to study each PR isoform independently in a breast cancer setting: (a) a stable PR-negative monoclonal subline (T47D-Y) of PR-positive T47D breast cancer cells was selected by flow cytometric PR screening. T47D-Y cells are PR-negative by immunoassays, by ligand binding assay, by growth resistance to progestins, by failure to bind a progesterone response element (PRE) in vitro, and by failure to transactivate PRE-regulated promoters; and (b) T47D-Y cells were stably transfected with expression vectors encoding one or the other PR isoform, and two monoclonal cell lines were selected that express either B-receptors (T47D-YB) or A-receptors (T47D-YA) at levels equal to those seen in natural T47D cells. The ectopically expressed receptors are properly phosphorylated, and like endogenously expressed receptors, they undergo ligand-dependent down-regulation. The expected B:B or A:A homodimers are present in cell extracts from each cell line, but A:B heterodimers are missing in both. In the presence of agonists, cAMP-dependent, transcriptional synergism of PRE-regulated promoters is seen in both cell lines. By contrast, in the presence of the antiprogestins RU486 or ZK112993, inappropriate transactivation occurs in YB cells but not in YA cells. The class of antiprogestins represented by ZK98299, which blocks PR binding to DNA, does not activate transcription in either cell line. We propose that these new cell lines are physiological models for the study of PR isoform-specific antiprogestin resistance in breast cancer.

Base Sequence↗

PubMed1994

Turbulent pipe flow studied by time-averaged NMR imaging: measurements of velocity profile and turbulent intensity.

A time-averaged method to obtain quantitative measurements in turbulent flow by phase flow encoding NMR imaging is introduced. With this method time-averaged velocity profiles and turbulence intensities can be determined. Time-averaged velocity profiles for pipe flow of water driven by a constant pressure gradient at Reynolds numbers from 1200 to 9400 were visualized. A precise correlation between the pixel intensity of the time-averaged NMR flow image and the local turbulence intensity of the flow is derived. The measured turbulence intensities are in agreement with published data obtained using other experimental methods.

Magnetic Resonance Spectroscopy↗

PubMed1994

Effect of sampling status and adjustment for heterogeneous variance on bias in bull evaluations.

Holstein bulls were assigned to sampling categories (AI stud, AI nonstud, or non-AI) based on bull code, controller number, and age at semen distribution. The AI stud bulls were sampled through traditional progeny-testing programs of 13 AI organizations; AI nonstud bulls had AI semen collection reported by another organization or by multiple organizations. The non-AI bulls had no reported AI semen collection. Actual daughter yield deviations for these three groups of bulls were compared with expected performance (parent average) to provide an indication of whether evaluations were free from bias for daughter yield deviations. Mean difference of daughter yield deviation from parent average was close to 0 kg for animal model evaluations of all 22,930 bulls but was positively biased by 46 kg of milk for AI nonstud bulls. Mean PTA and reliabilities for parents were highest for AI stud bulls and lowest for non-AI bulls. The AI stud bulls varied least and were intermediate for mean management, approximated as mean daughter yield minus bull PTA. Management was highest for AI nonstud bulls, which suggested that adjustment for heterogeneous variance might reduce bias. However, the effect of this adjustment on mean difference of daughter yield deviation from parent average was small.

Animals↗

PubMed1994

Factors affecting calculation and use of conversion equations for genetic merit of dairy bulls.

Factors affecting calculation and use of conversion equations were reviewed. Methods of expressing reliability of converted evaluations were surveyed. Of 16 countries responding, 6 did not calculate reliability for converted evaluations, 5 accepted reliability from the exporting country, and 5 assumed genetic correlations of .6 to 1.0 with the US. Genetic correlations between the US and 8 other countries were estimated and generally were > or = .9; estimated correlations between the US and Canada were 1.0. Estimated correlations averaged .93 for milk, .89 for fat, and .92 for protein yields. Correlation estimates were lowest for countries differing most from the US in management conditions (Australia, New Zealand) or trait definition (Germany), which suggests that correlation estimates < 1.0 indicate differences in trait measurement as well as differences in biological expression. Conversion equations were computed from data of US and Canadian Holstein bulls with and against the gene flow. Equations against the gene flow generally had regression coefficients and intercepts lower than those calculated with the gene flow. Lower regression coefficients were explained by selection on the dependent variable. Lower intercepts were attributed to preferential treatment of daughters from imported semen, which would lower intercepts for equations against the gene flow and inflate intercepts with the gene flow.

Animals↗

PubMed1992

Direct and indirect conversion of bull evaluations for yield traits between countries.

Genetic evaluations of Holstein bulls from the US were matched with Canadian, Italian, Mexican, and Netherlands evaluations for the same bulls. Conversion equations for milk yield were computed by least squares, Goddard, and Wilmink methods. Accuracy was assessed by splitting data and applying equations developed from one subset to the other subset. Methods were judged by mean differences between actual and converted evaluations and standard deviation of that difference. Imperfection of conversions appeared to be due to inherent characteristics (variation and bias) of data rather than to inadequacy of conversion methodology. Least squares was slightly better than other methods but is not recommended by the International Bull Evaluation Service. The Goddard method was generally superior to the Wilmink method, but data often are not available for its application. A variation of the Goddard method was equal in accuracy to the Wilmink method. Daughter yield deviation as both dependent and independent variables was examined for only one data set and was little different from the Goddard method. Indirect equations were quite accurate for US to Mexico and US to the Netherlands but much less accurate for US to Italy conversion. Indirect conversions still would be useful until evaluations of bulls in common allow for direct conversions. For all three countries, a variation on indirect methodology was slightly superior to the usual indirect equations.

Animals↗

PubMed1992

A method for combining United States and Canadian bull evaluations.

Canadian and US genetic evaluations for July 1991 were combined for 3304 Holstein bulls evaluated in Canada that had US progeny or a cross-reference code. Canadian evaluations of the bulls and their sires and dams were converted to US PTA. Combined PTA were weighted averages of progeny information from both countries and parent average. Parent average was recomputed from the sire's combined evaluation and the dam's evaluation with the most daughter equivalents. Bulls were processed in birth year order so that combined evaluation of sire was available. Progeny contribution was adjusted to remove the influence of the bull's evaluation on progeny evaluations through their parent averages, which left only the portion that was due to progeny records and grandprogeny information. A weighted average of adjusted progeny contributions was combined with parent average to form a combined PTA more accurately than possible by averaging domestic and converted PTA. Combined reliability was computed by summing daughter equivalents from progeny and from updated evaluations of parents. Canadian daughter equivalents were multiplied by .9 to approximate US values. Combined evaluations simplify bull selection by providing comparable and complete information for bulls evaluated in two countries.

Animals↗

PubMed1991

Evidence for the function of hyperactivated motility in sperm.

After insemination, mammalian sperm undergo a striking change in flagellar beat pattern, termed hyperactivation. In low-viscosity culture medium, nonhyperactivated sperm flagella generate relatively symmetrical, low-amplitude waves, while hyperactivated sperm flagella generate an asymetrical beating pattern that results in nonprogressive movement. Since sperm encounter highly viscous and viscoelastic fluids in the female reproductive tract, the progress of hyperactivated sperm was compared with that of nonhyperactivated and transitional sperm in media of increasing viscosity. Hamster sperm obtained from the caudal epididymis were incubated in a medium that promotes capacitation. After 0, 3, and 4 h of incubation, the majority of the sperm exhibited, respectively, activated, transitional, and hyperactivated motility. At each of these time points, aliquots of sperm were removed from incubation and added to solutions of 0, 5%, 10%, 20%, and 30% Ficoll in medium. Samples containing mostly hyperactivated sperm (4 h) maintained higher swimming and flagellar velocities and were able to generate greater forces in response to increased viscous loading than activated sperm (0 h). Transitional sperm (3 h) showed an intermediate response. The paths of hyperactivated sperm through solutions of 20% and 30% Ficoll were considerably straighter than those made through medium alone. This is the first demonstration that hyperactivation can confer a mechanical advantage upon sperm in the oviduct where they may encounter viscous oviductal fluid and a viscoelastic cumulus matrix.

Animals↗

PubMed1991

Animal model evaluations for Mexican Holsteins.

Genetic evaluations for milk yield of Holsteins in Mexico were computed from lactation and pedigree information from Holstein de México. The US animal model system for national evaluations was adapted for Mexico. The primary change was in defining unknown-parent groups. Paths of unknown parents of bulls and sires of cows were combined and separate unknown-parent groups defined for parents of US, Canadian, and Mexican registration. Records with fewer than 305 d were expanded around management group mean; a lower limit of 50% of management group mean was imposed on these records. Based on 123,397 lactation records by 50,538 cows, evaluations were computed for 68,020 cows (including those without lactation records) and 4573 bulls. Estimate of breeding value improvement in 1986 from a quadratic curve was 87 kg milk. Animal model estimates of breeding value by birth year were similar to Modified Contemporary Comparison estimates. Correlations with previous evaluations were .90 for bulls and .85 for cows. Differences resulted from added data as well as changes in evaluation method. Cows born in 1985 with US sires had predicted breeding values for milk 380 kg higher than those with Canadian sires and 336 kg higher than those with Mexican sires. Equations were developed to convert milk PTA between Mexico and the US. No sire by country interaction was found; correlations of US and Mexican PTA were .90 (expected) and .91 (actual).

Animals↗

PubMed1991

Comparison of genetic evaluations from animal model and modified contemporary comparison.

Comparisons were made between characteristics of Modified Contemporary Comparison and animal model evaluations with data available for January 1989 USDA-DHIA genetic evaluations. The animal model system's requirement that cows have a valid first lactation record resulted in a decrease in cows and daughters included. New flexible comparison groups were slightly larger for small herds and much smaller for large herds, which resulted in overall smaller and more uniform-sized comparison groups. Determining the optimal method of defining management groups was not undertaken. Correlations between bull evaluations from the two procedures ranged from .92 to .95 across breeds. Increases in reliability over repeatability were substantial for bulls with limited daughter information and small for widely used bulls. Correlations between evaluations for cows born in 1985 were .92 to .96, whereas those for cows born in 1980 (old enough to have daughters affecting animal model evaluations) were lower (.90 to .93), as expected. Reliabilities for cows were .02 to .05 higher than repeatabilities. Cows with more daughters increased more in evaluation and accuracy between the two procedures and were genetically superior. Bulls and cows with more prior information, cows with higher past evaluations, and Holstein bulls with higher past evaluations tended to have larger increases in PTA. Genetic trend estimates were different for the animal model, which resulted in changes in evaluations of various magnitudes depending on breed, sex, and birth year of animal.

Animals↗

PubMed1990

A statewide cancer registry: the Pennsylvania experience.

Pennsylvania has been successful in establishing a statewide cancer registry. The success of this registry results from the efforts of many different groups. The program has benefited from strong legislation making cancer a reportable disease and assigning the responsibility of reporting to hospitals. The PCR has implemented many initiatives to ensure that the cooperation of hospitals in operating the system is maintained, and that there is sufficient knowledge among hospital personnel to ensure complete casefinding. As the amount of statewide incidence data is increased over several years, the utility of these data for program planning and epidemiologic studies will increase greatly. The establishment and ongoing operation of the PCR ensure that cancer incidence data are available in providing answers to questions such as some of those asked following the accident at Three Mile Island.

Forms and Records Control↗

PubMed1988

Phenotypic and genetic relationship between linear functional type traits and milk yield for five breeds.

Lactation records of cows first calving between 18 and 35 mo were combined with linear type ratings assigned during the same lactation if before 43 mo. Phenotypic relationships were examined between final score and 13 type appraisal traits and first lactation milk yield from 2935 Ayrshire, 3154 Brown Swiss, 13,110 Guernsey, 50,422 Jersey, and 924 Milking Shorthorn records. Most phenotypic correlations between type and milk yield were low. Linear correlations of final score with first lactation milk yield were .18 to .38. Of the linear functional type traits, correlations with first lactation yield had greatest absolute values for dairy character (.19 to .53), udder depth (-.26 to -.30), and rear udder width (.20 to .31). Multiple correlations of all type appraisal traits with first lactation milk yield ranged from .41 to .59. Herd-year-season components of variance averaged 25% for type traits. Herd-year-season with sire interaction averaged 4%. Heritability estimates for final score from paternal half-sib analysis were from .11 to .21. Heritability estimates for linear traits ranged from .01 to .37. Genetic correlation between milk and final score was positive for Guernseys (.25) and Jerseys (.21). Genetic correlations between yield and most linear type traits were low to moderate except for dairy character (.53 to .77).

Animals↗