PubMed Health⌕ Search

Biomedical subjects

R L Powell

Publications and source records attributed to R L Powell.

At least 55 records · Page 3Linked to original sources
PubMed1987

Effects of eugenol on polymorphonuclear cell migration and chemiluminescence.

In this study, the effects of eugenol on human polymorphonuclear (PMN) cell migration and chemiluminescence were examined in vitro. Utilizing zymosan-activated serum or crude Bacteroides sonicate fractions as chemotractants, we found that eugenol inhibits PMN migration at 6.6 X 10(-2) to 6.6 X 10(-5) mol/L (P less than 0.05). Also, similar effects were observed in PMNs pre-incubated in eugenol. Regardless of concentration, eugenol was not found to induce chemotaxis of PMNs. An examination of PMN membrane activation through chemiluminescence gave results consistent with the chemotaxis data, demonstrating a decrease in light emission at concentrations as low as 6.6 X 10(-6) mol/L (P less than 0.05). In view of these data, the potential effect of eugenol on in vivo (sulcular or periapical) PMN function deserves further study.

Cell Membrane↗
PubMed1987

Influence of genetic differences in merit of mates on sire evaluation.

Effect of nonrandomness of bulls' mates on daughter milk yield was examined from first lactation records of cows with birth dates in 1965 and later. Results were based on 67,081 Ayrshire, 77,633 Brown Swiss, 241,486 Guernsey, 1,433,761 Holstein, 291,201 Jersey, and 10,465 Milking Shorthorn records. Extent of assortative mating was examined. Correlations between sire Predicted Difference and dam (mate) Cow Index for individual years ranged from -.08 to .20. Correlations for all records within herd-year (.00 to .02) indicated essentially no assortative mating for milk yield for any breed except Ayrshire. For Ayrshires, negative assortative mating was indicated by a correlation of -.07. Within-sire regressions of daughter milk yield deviated from contemporary average (which had been adjusted for average Predicted Difference of contemporaries' sires) on dam Cow Index (merit of mates) by breed were .84 to 1.08. Expected regression was 1.00. Effect of merit of mates on sire evaluation was determined by comparing evaluations from standardized yield with those from standardized yield minus dam Cow Index. Correlations between evaluations for 4233 Ayrshire, 5275 Brown Swiss, 13,742 Guernsey, 32,572 Holstein, 13,688 Jersey, and 1240 Milking Shorthorn bulls rounded to 1.00 except for Milking Shorthorns (.99); average absolute differences in evaluations were 9 to 16 kg, and maximum differences were 49 to 118 kg. Adding an adjustment to Sire Summaries to account for nonrandomness of mates would do little to increase accuracy.

Animals↗
PubMed1986

Genetic and environmental differences between registered and grade Holstein cows.

Phenotypic and genetic measures of milk yield were compared for sire-identified registered and grade Holsteins in the United States. First lactation registered cows produced more milk within herd than did grades. Grades were culled more intensely than registered cows, resulting in higher average yield by maturity for remaining grades than for remaining registered cows. Average Cow Index milk was higher overall for grades until 1981. Within herd and year of first calving, registered cows were higher for yield, Cow Index, and sire Predicted Difference since 1974. Analyses for cows alive at a given time or cows with dam Cow Index overestimated grade genetic merit because of differences in selection intensity. No sire identification for two-thirds of grades resulted in substantial data loss and probably overestimation of grade genetic merit from sire-identified cows. Preferential treatment according to registry status was examined by comparing registered and grade yields within herd, year, and sire. Milk yield of registered cows was 95 kg higher than for grade paternal sisters in 1980 to 1984; bias in favor of registered cows was 3 kg for Cow Index milk. Bias would be proportional to herdmates of opposite registry status. Average genetic merit of sire-identified registered and grade Holstein cows differed little.

Animals↗
PubMed1985

Supersensitivity to light: possible trait marker for manic-depressive illness.

Exposure to light during the night reduces plasma melatonin levels. A previous study showed that, in response to light, nighttime plasma melatonin levels fell twice as much in a group of acutely ill manic-depressive patients as in a group of normal subjects. The present study compares 11 euthymic manic-depressive patients not taking medications with 24 age- and sex-matched normal subjects. Melatonin levels in these patients also fell twice as much as the levels of the normal subjects, suggesting that supersensitivity to light may be a trait marker for bipolar affective disorder.

Adult↗
PubMed1985

Trend of age at first calving.

Mean ages at first calving were computed from over 6 million cow records from 1960 through 1982 for six breeds. Average Jerseys first calved at 26.18 mo compared with 28.75 mo for Ayrshires. Other breed means were intermediate: Holsteins, 27.52 mo; Guernseys, 27.72 mo; Brown Swiss, 28.04 mo; and Milking Shorthorns, 28.11 mo. Mean age at first calving in 1982 was .16 to .32 mo less than for all data. Standard deviations of annual mean ages were similar and ranged from 3.23 to 3.67 mo for the 138 breed-year means. Frequency distributions for calving ages were skewed to the left. Cows born from January through March were about .5 mo older at first calving than those born in August and September for most breeds. Annual means did not show a significant trend although all breeds had highest means around 1976 and regressions of age on year of -.075 to -.111 mo per year for 1976 through 1982. Heifer fertility as indicated by age at first calving did not appear to change over 23 yr.

Age Factors↗
PubMed1985

Changes of evaluation for natural-service sampled bulls brought into artificial insemination.

United States Department of Agriculture Sire Summary files were used to select bulls with a published Modified Contemporary Comparison sire evaluation prior to entry into artificial insemination. Canadian bulls were not included. Of the Brown Swiss, Guernsey, Holstein, and Jersey bulls that entered artificial insemination since 1974, 28 Brown Swiss, 19 Guernseys, 298 Holsteins, and 45 Jerseys (4 to 12%) had natural service evaluations. Of these bulls, 10 Guernseys, 154 Holsteins, and 28 Jerseys had an increase of Repeatability of 30% or more after entering artificial insemination. Evaluations for bulls just prior to their entering artificial insemination were compared with their most recent evaluations through July 1983. Average Repeatabilities for evaluations of bulls just prior to their entering artificial insemination were 32% for Guernseys, 32% for Holsteins, and 31% for Jerseys and 88, 90, and 87% for their most recent evaluations. Average Predicted Differences prior to entering artificial insemination were 305 kg for Guernseys, 394 kg for Holsteins, and 452 kg for Jerseys for milk and 11, 10, and 16 kg for fat. Most recent average Predicted Differences were 268, 380, and 532 kg for milk and 7, 10, and 18 kg for fat. Predicted Differences of natural service bulls were not overevaluated regardless of number of herds for sampling or year of entry into artificial insemination. Artificial insemination organizations can continue to acquire bulls with natural service evaluations calculated with the Modified Contemporary Comparison and be confident that these Predicted Differences are not overestimated.

Animals↗
PubMed1984

Increasing pedigree contribution to dairy sire evaluation.

Methods to improve contributions of ancestor information to sire evaluations computed by the Modified Contemporary Comparison were studied. Pedigree index (one-half evaluation of sire plus one-fourth evaluation of maternal grandsire ) was used to indicate ancestor merit with adjustment for type of sampling program and birth date. For Holsteins, effect of sampling through artificial insemination was 35 kg for milk yield; effect of birth date (trend of daughter merit not accounted for by pedigree index or type of sampling) was 7.3 kg/yr for milk yield and .36 kg/yr for fat yield. Trends were larger for milk and fat yields of Ayrshires , Brown Swiss, Guernseys , and Jerseys except for fat yield of Ayrshires , which had no significant trend. Correlations of daughter merit with pedigree index and with present group average (average daughter merit of bulls with similar pedigree indexes for milk yield) were computed. For milk yield, correlations of daughter merit with pedigree index and with group average were nearly the same; however, for fat yield, pedigree index had a higher correlation with daughter merit than did group average. Accounting for residual trend resulted in further increase of correlation. Replacing one-fourth evaluation of maternal grandsire with one-half Cow Index of dam also improved correlations slightly. Evaluations can be modified so that pedigree index adjusted by birth date replaces group average in representing ancestor merit. Such evaluations better predict performance of future daughters than do evaluations with grouping by pedigree index for milk yield, particularly for evaluations for fat yield. Dam's Cow Index provides little additional information.

Animals↗
PubMed1983

Cow evaluation at different milk yields of herds.

Herds with higher milk production per cow tend to have used bulls with larger Predicted Differences and to have larger Cow Indexes. A larger portion of cows in these herds should attain elite status for production than in herds with lower production. However, even when average sire merit was similar, higher producing herds had substantially more elite cows, apparently because standard deviation of deviated production of cows is greater in herds with high milk production. This suggested that cow deviation in high producing herds may receive too much weight in the Cow Index. However, higher heritabilities likely are appropriate for cows in higher producing herds, which would favor weighting deviation more in high producing herds. Adjustments for these two effects would offset each other at least partially. Cow Indexes adjusted for either or both effects had similar correlations with son or daughter performance as did the current Cow Index that considers neither effect. Although high producing herds have more elite cows than can be justified by average sire merit, some of the apparent advantage may be justifiable by larger heritabilities.

Animals↗
PubMed1983

Use of grade animals in United States Department of Agriculture programs.

Use of records from both registered and grade animals in genetic improvement programs in the United States is summarized. To date, grade bulls have contributed little to genetic improvement in the United States. Grade bulls can contribute significantly only if they are sampled and returned to heavy artificial insemination service. In contrast, grade daughters of registered bulls have contributed extensively to genetic improvement by permitting more bulls to be sampled. Sixty-five percent of daughters with records used to calculate initial proofs of artificial insemination Holstein bulls are grades. Averages for other breeds ranged from 5 to 20%. Implementation of and active participation in provisional registry of grades can result in a moderate increase in genetic improvement in Holsteins. Active participation in provisional registry for other breeds will bring a smaller genetic increase because of fewer grades in those breeds. However, provisional registry programs still can lead to a number of long-range advantages through increasing the population base. There appears to be no scientific basis for not implementing such programs.

Animals↗
PubMed1983

Effect of herd and sire on uniform functional type trait appraisal scores for Ayrshires, Guernseys, Jerseys, and milking shorthorns.

Type appraisal data supplied by United States breed organizations for Ayrshires, Guernseys, Jerseys, and Milking Shorthorns were examined for genetic and environmental sources of variation. Repeatabilities were highest for pelvic angle, udder depth, stature, suspensory ligament, and final score (.51 to .74) and lowest for foot shape (.15 to .29). Variances and covariances were estimated from appraisals from 230 Ayrshire, 352 Guernsey, 699 Jersey, and 51 Milking Shorthorn herds and represented 117, 157, 333, and 32 sires. Herd variances by trait and breed ranged from 2 to 23%. Herd effects were large for stature and rear udder width of Ayrshires, for most traits of Jerseys, and for udder depth of Milking Shorthorns. Herd X sire variance was small but averaged 3% across all breeds and traits. Heritabilities ranged from .06 to .75. Stature had the highest heritability (.34 to .75) for all four breeds. Heritabilities also were high for chest and body (.42), rump width (.36), and pelvic angle (.34) for Guernseys; pelvic angle (.29) and udder depth (.27) for Jerseys; and chest and body (.70), rump width (.50), and final score (.44) for Milking Shorthorns. Foot shape had the lowest heritability for Ayrshires, Guernseys, and Jerseys (.06 to .07). Most of the phenotypic correlations between appraisal traits were low to moderately high. Genetic correlations were calculated.

Animals↗