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PubMed1989

Heritabilities of and genetic correlations among six health problems in Holstein cows.

Information from 7712 lactations of Holstein dairy cows was collected from 33 commercial herds around Ithaca, NY in the 3 yr from 1981 to 1983. The data were divided into subsets corresponding to lactation 1, lactation 2, and lactation 3 or greater. To estimate heritabilities of dystocia, retained placenta, metritis, ovarian cysts, milk fever, and mastitis, a mixed linear model (herd-year fixed and sire random effects) with 0 or 1 as the observed response was used. Variance components were estimated using Henderson's Method 3. The results show moderate heritabilities (.15 to .40) for dystocia, metritis, milk fever, and mastitis and low heritability (less than .12) for retained placenta and cystic ovaries. Genetic correlations between dystocia, retained placenta, metritis, and mastitis were moderate in size and positive, whereas cystic ovaries were correlated negatively with dystocia and retained placenta. A general reproductive health trait (dystocia, retained placenta, metritis, cystic ovaries, and milk fever combined in one trait) also was analyzed. The estimated heritability of this trait was .21, .11, and .00 for first calf heifers, second lactation cows, and older cows, respectively.

Animals↗
PubMed1989

Heifer fertility and its relationship with cow fertility and production traits in Holstein dairy cattle.

Breeding receipts from three AI units were merged with Ontario Dairy Herd Improvement Corporation and Record of Performance production records. Data comprised 53,705 heifer, 41,253 lactation 1, 14,688 lactation 2, and 3054 lactation 3 records by daughters of 2150 sires represented in 15,877 herd-year-seasons of birth. Three measures of heifer fertility, three measures of cow fertility, and three measures of production were investigated. Measures of heifer fertility were ages at first and last breeding and number of inseminations per conception. Cow fertility traits were days from calving to first breeding, days open, and number of inseminations per conception. Production traits were breed class average milk, breed class average fat, and fat percentage. Relationships among these nine traits for the first three lactations were estimated using a maximum likelihood multiple-trait procedure. The linear mixed model for each trait included fixed effects of herd-year-season of birth and genetic groups of sire and the random effect of sire. Transformations of the data for nonnormality had no influence on the estimates of genetic and phenotypic parameters. The heritability of .12 for age at first insemination, which was higher than other heifer fertility traits, indicated that selection would result in genetic response. Genetic and phenotypic correlations between heifer fertility and cow fertility and production traits in all three lactations were not different from zero. There was no genetic antagonism between fertility and subsequent production traits.

Animals↗
PubMed1991

Direct response in yield and correlated response in components accompanying selection for milk yield in Jerseys.

In 1967, the Jersey herd at the Dairy Experiment Station, Lewisburg, TN was divided into two groups on the basis of ancestry, type, and breeding value for milk as part of a project to determine effects of single trait selection for high milk yield on yield and correlated traits. Control group was mated randomly to 20 unproven young sires selected randomly from those available from breeding studs in 1967. Selection group was mated to sires selected solely on the basis of their high transmitting ability for milk. Selection sires were selected at intervals and used for 4 yr. By the end of the project (1984), lactation information was available on 672 daughters (520 selection and 152 control) of 37 bulls (17 selection and 20 control). Differences in breeding values for milk, fat, and fat test as calculated from the PTA reported in the July 1989 USDA genetic evaluations and differences in first lactation mature equivalent production of milk, fat, fat test, and 4% FCM were examined. Linear mixed models were used for all analyses and contained the fixed effects group, generation within group, and year. Sires were random, nested within group, and used to test for group differences. Groups differed for all traits. Selection was superior to control in breeding value for milk and fat (828 and 31 kg) and for production of milk, fat, and 4% FCM (1066, 42, and 1061 kg). Control was superior to selection in breeding value and production fat test (.15 and .12%). Group differences existed within generation class for all yield traits but not for fat percentage. Realized response closely matched or exceeded expected response as estimated from pedigree information.

Animals↗
PubMed1995

Correlations between first lactation and lifetime performance traits of Canadian Holsteins.

Data on 82,835 Holstein cows, daughters of 703 sires and with first calvings from 1979 to 1984 in 2384 herds enrolled in Quebec Dairy Herd Analysis Service, were analyzed for relationships of first lactation traits with traits for partial and total lifetime performance using multitrait REML methodology and a linear mixed model. Effects of herd-year-season, age at first calving, and proven sires were considered to be fixed, and effects of young sires and residuals were considered to be random. All known additive genetic relationships among sires were accounted for in construction of the relationship matrix. Individual lactation records were precorrected for the fixed effect of year and month of calving before lifetime totals were calculated. Each cow was given at least a 5-yr opportunity for production. All genetic and phenotypic correlations were positive except correlations of first lactation percentage traits. Correlations with partial lifetime performance were highest. Genetically, first lactation milk yield was highly correlated with most measures of lifetime performance, .64 to .92; correlations with measures of longevity were relatively smaller. Given high positive genetic correlations, selection singly on first lactation milk yield will improve all measures of lifetime performance; however, some measure of longevity should be considered in selection programs of dairy cattle.

Animals↗
PubMed1998

Restricted maximum likelihood analysis of linkage between genetic markers and quantitative trait loci for a granddaughter design.

A REML for the estimation of location and variance of a single quantitative trait locus, together with polygenic and residual variance, is described for the analysis of a granddaughter design. The method is based on a mixed linear model that includes the allelic effects of the quantitative trait locus, which are assumed to be normally distributed. Information from four marker loci situated on a single chromosome was available to derive the covariances at the linked quantitative trait locus. A derivative-free algorithm is described that makes use of the specific structure of the granddaughter design. The procedure has been applied to simulated data for a granddaughter design with 50 grandsire families of 40 sires each. Error variance was 60, and total additive genetic variance equaled 40; the quantitative trait locus explained either 10 or 25% of the latter variance. The size of the marker bracket containing the quantitative trait locus was either 10 or 30 cM. The power of detecting the quantitative trait locus ranged from 19 to 99%. Estimates of total genetic variance and variance explained by the quantitative trait locus were found to be empirically unbiased. A small bias was found in location estimates, especially when markers were not fully informative. The accuracy of parameter estimates was greatly improved by the use of information from individual daughters.

Animals↗
PubMed1998

Environmental, management, and genetic factors affecting semen production in Holstein bulls.

The objective of this study was to evaluate the importance of environment, management, physiological status, and genetics on semen quality (volume of the ejaculate, sperm concentration, sperm motility, number of sperm, and number of motile spermatozoa per ejaculate) of Canadian Holstein bulls. For this purpose, semen production data from 198 bulls were analyzed using mixed linear models. Young bulls (up to 30 mo old) and mature bulls (between 4 and 6 yr old) were analyzed separately. Semen characteristics generally improved significantly with age of young bulls. Season significantly affected all semen traits in young bulls but did not significantly affect volume and sperm motility of mature bulls. Performance was better in winter than in summer. The highest numbers of motile spermatozoa per ejaculate were obtained with intervals of at least 4 to 5 d between collections. Although the bull handler and semen collector caused less than 10% of the variance, the collection team significantly affected semen volume, number of sperm, and number of motile sperm per ejaculate for both growing and mature bulls. Heritabilities for volume, concentration, sperm motility, number of sperm, and number of motile sperm per ejaculate were, respectively, 0.24, 0.52, 0.31, 0.38, and 0.49 for young bulls and 0.44, 0.36, 0.01, 0.54, and 0.64 for mature bulls. Repeatability of semen traits varied from 0.41 to 0.64. Genetics, management, and environmental factors clearly contribute to semen production in Holstein bulls.

Aging↗
PubMed1999

Analysis of environmental effects on test day milk yields of Sarda dairy ewes.

Temporal evolution of Sarda ewes milk production was analyzed with mixed linear models and factor analysis to investigate environmental effects on the shape of lactation curves and on milk yields during different lactation stages. Parity, year of production, level of altitude, and flock within altitude affected milk yield, whereas the effect of type of lambing was not significant. Lactation curves pertaining to the three altitudes were clearly different. Factor analysis suggested an independence among yields recorded during different phases of lactation and a specific behavior of (co)variances structure among test day yields obtained in mountains compared with hills and plains.

Altitude↗
PubMed2005

Neutralizing antibody response and SARS severity.

Using the Taiwan nationwide laboratory-confirmed severe acute respiratory syndrome (SARS) database, we analyzed neutralizing antibody in relation to clinical outcomes. With a linear mixed model, neutralizing antibody titer was shown to peak between week 5 and week 8 after onset and to decline thereafter, with a half-life of 6.4 weeks. Patients with a longer illness showed a lower neutralizing antibody response than patients with a shorter illness duration (p = 0.008). When early responders were compared with most patients, who seroconverted on and after week 3 of illness, the small proportion (17.4%) of early responders (antibody detectable within 2 weeks) had a higher death rate (29.6% vs. 7.8%) (Fisher exact test, p = 0.004), had a shorter survival time of <2 weeks (Fisher exact test, p = 0.013), and were more likely to be > 60 years of age (Fisher exact test, p = 0.01). Our findings have implications for understanding the pathogenesis of SARS and for SARS vaccine research and development.

Adult↗
PubMed2005

What happens with adverse events during 6 months of treatment with selective serotonin reuptake inhibitors?

OBJECTIVE: Although adverse events are a key factor in compliance, their evolution during treatment with antidepressants is poorly documented. Therefore, the time course of adverse events during 6 months of antidepressant treatment was investigated. METHOD: 85 psychiatric outpatients with a DSM-IV diagnosis of major depressive disorder (with the exclusion of other DSM-IV Axis I disorders) were enrolled between September 2002 and March 2003 in a multicenter, randomized, double-blind trial with selective serotonin reup-take inhibitors (fluoxetine [N = 42] and paroxetine [N = 43]). At each visit, the presence and severity of treatment-emergent adverse events were assessed systematically using the UKU Side Effect Rating Scale (UKU). General linear mixed modeling was used to investigate the predictors of the time course of adverse events. RESULTS: Overall, the number of at least moderately severe adverse events decreased with time. More severely depressed patients reported overall more (at least moderately severe) adverse events than less severely depressed patients (p = .0002), but the decrease in reported adverse events was comparable over time. Men (N = 30) and women (N = 55) reported initially the same number of at least moderately severe adverse events, but the habituation was more rapid in men (p < .0001). Completers (N = 58) and dropouts (N = 27) did not differ initially, but completers' habituation was more rapid (p = .014). The habituation of adverse events was also more rapid in recurrent than in first-episode patients but only in men (p = .0025). CONCLUSION: The time course of adverse events varies with the severity of depression, sex, completer or dropout status, and recurrent versus first-episode depression.

Adult↗
PubMed2005

Trends in blood culture contamination: a College of American Pathologists Q-Tracks study of 356 institutions.

CONTEXT: Blood culture contamination extends hospital stays and increases the cost of care. OBJECTIVES: To measure blood culture contamination rates in a large number of institutions over time and to elucidate practice patterns and demographic factors associated with sustained reduction in contamination rates. DESIGN: Longitudinal cohort study of 356 clinical laboratories that provided quarterly data about blood culture results, using a uniform definition of contamination. Mixed linear model analysis of the 1999 through 2003 data set. RESULTS: Blood culture contamination was significantly higher in institutions that used nonlaboratory personnel to collect blood (P = .03) and significantly lower in facilities that used a dedicated phlebotomy team (P < .001). Higher volume of blood collection was significantly associated with lower contamination rates (P < .001). Continued participation in the Q-Tracks monitoring program was associated with significant and progressive reduction in contamination rates. By the fifth year of participation, the median institution had reduced its blood culture contamination rate by 0.67% (P < .001). CONCLUSIONS: Institutions that use decentralized patient-centered personnel rather than dedicated phlebotomy teams to collect blood cultures experience significantly higher contamination rates. Long-term monitoring of contamination is associated with sustained improvement in performance.

Adult↗
PubMed2006

The value of monitoring frozen section-permanent section correlation data over time.

CONTEXT: The effectiveness of the long-term monitoring of errors detected by frozen section-permanent section correlation is unknown. OBJECTIVE: To determine factors important in laboratory improvement in frozen section-permanent section discordant and deferral rates by participation in a multi-institutional continuous quality improvement program. DESIGN: Participants in the College of American Pathologists Q-Tracks program self-reported the number of anatomic pathology frozen-permanent section discordant and deferred cases in their laboratories by prospectively performing secondary review of intraoperative consultations. Laboratories participated in the program for 1 to 5 years and reported their data every quarter. We calculated mean and median discordant and deferred case frequencies and used mixed linear modeling to determine if length of participation in the program was associated with improved performance. PARTICIPANTS: One hundred seventy-four laboratories self-reported data. MAIN OUTCOME MEASURES: Mean frozen-permanent section discordant and deferred diagnostic frequencies and changes in these frequencies over time were measured. RESULTS: The mean and median frozen-permanent section discordant frequencies were 1.36% and 0.70%, respectively. The mean and median deferred diagnostic frequencies were 2.35% and 1.20%, respectively. Longer participation in the Q-Tracks program was significantly associated (P = .04) with lower discordant frequencies; 4- or 5-year participation showed a decrease in discordant frequency of 0.99%, whereas 1-year participation showed a decrease in discordant frequency of 0.84%. Longer participation in the Q-Tracks monitor was associated with lower microscopic sampling frequencies for discordant diagnoses (P = .04). Increased length of participation in the Q-Tracks program was significantly associated (P = .04) with lower deferred diagnostic frequencies. CONCLUSIONS: Long-term monitoring of frozen-permanent section correlation is associated with sustained improvement in performance.

Diagnostic Errors↗
PubMed2007

Assessment monitoring of laboratory critical values: a College of American Pathologists Q-Tracks study of 180 institutions.

CONTEXT: Critical laboratory value reporting is a highly visible and essential key activity for clinical laboratories. OBJECTIVE: To measure critical laboratory value reporting in multiple institutions over time and to examine the practice patterns and demographic factors associated with sustained improvement in critical value reporting. DESIGN: A longitudinal cohort study of 180 clinical laboratories that provided quarterly critical values reporting data for 2 to 16 quarters was conducted using a uniform definition of successful caregiver notification. Mixed linear model analysis of the 2001 through 2004 dataset was performed. RESULTS: A decrease in total and inpatient rates of undocumented critical values per 1000 results was associated with (1) the American Association of Blood Banks inspection within the past 2 years (P = .01, for both total and inpatient rates); (2) unit secretary/clerical staff not authorized to accept inpatient critical value notification (P = .004 [total] and .001 [inpatient]); and (3) the mandatory practice of requiring notification of health care providers when handling inpatients known to have results repeatedly in the critical range (P = .01, for both total and inpatient rates). Continued participation in the Q-Tracks monitoring program was associated with significant and progressive improvement in total, inpatient, and outpatient critical value reporting (P = .02, .01, and .003, respectively). CONCLUSIONS: Critical value reporting improved as the duration of participation in the Q-Tracks monitoring program increased. Improved total and inpatient critical value reporting was associated with factors that may be markers for institutions with priorities of quality management and enhanced communication with responsible caregivers.

Benchmarking↗
PubMedDate not supplied

The role of peer social network factors and physical activity in adolescent girls.

OBJECTIVE: To study the relationship between peer-related physical activity (PA) social networks and the PA of adolescent girls. METHODS: Cross-sectional, convenience sample of adolescent girls. Mixed-model linear regression analyses to identify significant correlates of self-reported PA while accounting for correlation of girls in the same school. RESULTS: Younger girls were more active than older girls. Most activity-related peer social network items were related to PA levels. More PA with friends was significantly related to self-reported PA in multivariate analyses. CONCLUSIONS: Frequency of PA with friends was an important correlate of PA among the peer network variables for adolescent girls.

Adolescent↗
PubMed2005

Antibody levels and protection after hepatitis B vaccination: results of a 15-year follow-up.

BACKGROUND: The duration of protection afforded by hepatitis B vaccination is unknown. OBJECTIVE: To determine antibody persistence and protection from hepatitis B virus (HBV) infection. DESIGN: Prospective cohort study. SETTING: 15 villages in southwest Alaska. PARTICIPANTS: 1578 Alaska Natives vaccinated at age 6 months or older. INTERVENTION: During 1981-1982, participants received 3 doses of plasma-derived hepatitis B vaccine. This cohort was followed annually over the first 11 years, and 841 (53%) persons were tested at 15 years. MEASUREMENTS: Antibody to hepatitis B surface antigen (anti-HBs), markers of HBV infection, and testing to identify HBV variants. RESULTS: Levels of anti-HBs in the cohort decreased from a geometric mean concentration of 822 mIU/mL after vaccination to 27 mIU/mL at 15 years. Initial anti-HBs level, older age at vaccination, and male sex were associated with persistence of higher anti-HBs levels at 15 years when analyzed by a longitudinal linear mixed model. After adjustment for initial anti-HBs level and sex, those vaccinated at age 6 months to 4 years had the lowest anti-HBs level at 15 years. Asymptomatic breakthrough infections were detected in 16 participants and occurred more frequently in persons who did not respond to vaccination than those who responded (P = 0.01). Among infected persons with viremia, 2 were infected with wild-type HBV and 4 had HBV surface glycoprotein variants, generally accompanied by wild-type HBV. LIMITATIONS: The loss of participants to follow-up at 15 years was 47%. However, characteristics of persons tested were similar to those of persons lost to follow-up. CONCLUSIONS: Hepatitis B vaccination strongly protected against infection for at least 15 years in all age groups. Antibody levels decreased the most among persons immunized at 4 years of age or younger.

Adolescent↗
PubMed1999

Effects of oral brovincamine on visual field damage in patients with normal-tension glaucoma with low-normal intraocular pressure.

PURPOSE: To prospectively study the effect of oral brovincamine, a relatively selective cerebral vasodilator, on further deterioration of visual field in patients with normal-tension glaucoma (NTG) with low-normal intraocular pressure (IOP). METHODS: Fifty-two patients with NTG (average age 57.7 years) with an IOP that was consistently less than 15 mmHg were randomly assigned to receive oral brovincamine (20 mg three times daily) or to an untreated control group. The groups were prospectively followed for 2 years with visual field examinations every 4 months, using the 30-2 Humphrey perimeter program. Changes in mean deviation (MD), corrected pattern standard deviation (CPSD), and total deviation (TD) at 74 test points were analyzed using regression analysis with linear mixed model. Data from one eye without media opacity of each subject were analyzed. RESULTS: There were no differences between groups in age; sex distribution; refraction; blood pressure; baseline IOP; MD, CPSD, or TD at each point. Changes in MD (standard error [SE]) during the study period were -0.778 (0.178) and -0.071 (0.195) dB/year in the control and brovincamine groups, respectively; change in the control group was significantly more negative than in the brovincamine group. Change in CPSD (SE) was 0.032 (0.015) and 0.004 (0.016) dB/year in the control and brovincamine groups, respectively. Change in the control group was significantly positive, but the intergroup difference was not significant. Change in TD was significantly negative at six test points in the control group, whereas no points showed a significant trend in the brovincamine group; the intergroup difference was significant. The average IOP was 13.2 mmHg and 13.1 mmHg in the control and brovincamine groups, respectively, and there was no significant intergroup difference. CONCLUSION: Oral brovincamine may retard further visual field deterioration in patients with NTG who have low-normal IOP.

Administration, Oral↗
PubMed2001

[Analysis of QTL x environment interaction for rice panicle characteristics].

The development of molecular genetic linkage map has accelerated the identification and mapping of genomics regions controlling quantitative trait loci. A recombinant inbred line population derived from Zhenshan 97/Minghui 63 was grown in two years. Mixed linear model approach was used to jointly identify QTLs and QTL x environment interactions for five panicle characteristics. Ten, three, six, eight and seven QTLs were detected for spiketets per panicle, grains per panicle, seed setting, panicle length and panicle setting density, respectively. They collectively explained 29.13%, 19.2%, 29.46%, 26.39% and 35.76% of phenotypic variations for these traits, respectively. For the five traits, QTLs with increasing effects and decreasing effects could be simultaneously identified in high value parent and low value parent. QTLs for correlative traits clustering located in the similar regions. One QTL for panicle length, two QTLs for spikelets per panicle and three QTLs for seed setting performed significant interactions with environment. The contributions from interactions were slightly larger than that from the QTLs involved in the interactions. No QTL x environment interaction was detected for traits with high heritabilities such as grains per panicle and panicle setting density.

Chromosome Mapping↗
PubMed2002

[Mapping of fertility-restoring genes with main effects and epistatic effects for CMS-DA in rice].

A test-cross population was established for mapping genes conditioning fertility restoration for dwarf-wild-abortive cytoplasmic male sterility(CMS-DA) in rice. A recombinant inbred line(RIL) population consisting of 210 lines was derived from the cross Xieqingzao B/Miyang 46, in which Xieqingzao B is the maintainer line of CMS-DA Xieqingzao A, and Miyang 46 is the restorer line. Each of the RILs was crossed to Xieqingzao A, and the resulting F1s were used for phenotyping of the spikelet fertility in 1999 and 2000. A linkage map consisting of 129 RFLP and SSLP markers was constructed. QTLs having significant main effects and/or epistatic effects for spikelet fertility were determined with QTLMAPPER 1.0 of mixed linear model. Background genetic variation due to main and epistatic effects of important markers was controlled. Four QTLs having significant main effects for fertility restoration were detected. A major gene qRf-10-2 was located in interval RM258-RZ811 on the long arm of chromosome 10, and QTL qRf-1 displaying a moderate main effect was located in a position close to RG532 on chromosome 1. Two other QTLs were located on chromosome 5 (qRF-5) and the short arm of chromosome 10 (qRf-10-1), in which the main effect of qRf-5 bacame significant only in the absence of qRf-10-2. A significant digenic interaction was detected, which occurred between QTLs qRf-1 and qRf-5. No significant QTL by environmental interactions and epistasis by environmental interactions were detected. Analyses on the gene effects based on markers closest to the Rf genes were made, and multi-locus interactions were implied. The present results were also compared to a previous study on mapping fertility restoration genes in Milyang 46 for wild-abortive CMS Zhenshan 97A, and to other published reports. It was indicated that differences on the genetic control of fertility restoration among different rice populations were mainly attributed to variations on genes with minor main effects and epistatic effects.

Chromosome Mapping↗
PubMedDate not supplied

[Use of regression analysis in the study of the association between different mercury exposure routes and some functional variables].

AIMS: The "Mercury Multicentric Project" data-set was analysed with the aim to identify a group of biological variables associated with different types of Hg exposure (occupational exposure, fish dietary intake, exposure due to amalgam restorations). The distribution of socio-demographic, biological and surrogate outcome variables was rather different among the collaborating Units. METHODS: Mixed linear models (MLM) were used to overcome the problems related to the heterogeneity of variances among Units. MLM are a generalization of the standard linear models, the generalization being that the data are permitted to exhibit correlation and non constant variability. MLM therefore provide with the flexibility of modelling not only the means of the dependent variable, but also their variances and co-variances as well. This allows to represent the total variability of the dependent variable as a sum of two components: the first attributable to the Units and the other one to the random error. RESULTS AND CONCLUSIONS: A set of biological variables significantly associated with at least one of the Hg exposure variables or with the HgU/creatinine ratio (as surrogate variable for Hg exposure) was identified by means of MLM. This set includes beta 2-MG, sIL8, CD4+, sPRL, FT dominant, BAMT, and some variables related to neurological behaviour. An extension of this analysis will be performed with a structural equations approach in order to study the dose-response relationships among the various variables according to a hierarchical path defined on biological basis. One of the possible simplified general models including all the selected variables is described.

Adult↗