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PubMed2006

Evolutionary rates, divergence dates, and the performance of mitochondrial genes in Bayesian phylogenetic analysis.

The mitochondrial genome is one of the most frequently used loci in phylogenetic and phylogeographic analyses, and it is becoming increasingly possible to sequence and analyze this genome in its entirety from diverse taxa. However, sequencing the entire genome is not always desirable or feasible. Which genes should be selected to best infer the evolutionary history of the mitochondria within a group of organisms, and what properties of a gene determine its phylogenetic performance? The current study addresses these questions in a Bayesian phylogenetic framework with reference to a phylogeny of plethodontid and related salamanders derived from 27 complete mitochondrial genomes; this topology is corroborated by nuclear DNA and morphological data. Evolutionary rates for each mitochondrial gene and divergence dates for all nodes in the plethodontid mitochondrial genome phylogeny were estimated in both Bayesian and maximum likelihood frameworks using multiple fossil calibrations, multiple data partitions, and a clock-independent approach. Bayesian analyses of individual genes were performed, and the resulting trees compared against the reference topology. Ordinal logistic regression analysis of molecular evolution rate, gene length, and the G-shape parameter a demonstrated that slower rate of evolution and longer gene length both increased the probability that a gene would perform well phylogenetically. Estimated rates of molecular evolution vary 84-fold among different mitochondrial genes and different salamander lineages, and mean rates among genes vary 15-fold. Despite having conserved amino acid sequences, cox1, cox2, cox3, and cob have the fastest mean rates of nucleotide substitution, and the greatest variation in rates, whereas rrnS and rrnL have the slowest rates. Reasons underlying this rate variation are discussed, as is the extensive rate variation in cox1 in light of its proposed role in DNA barcoding.

Animals↗

PubMed2003

Are Ichthyosporea animals or fungi? Bayesian phylogenetic analysis of elongation factor 1alpha of Ichthyophonus irregularis.

Ichthyosporea is a recently recognized group of morphologically simple eukaryotes, many of which cause disease in aquatic organisms. Ribosomal RNA sequence analyses place Ichthyosporea near the divergence of the animal and fungal lineages, but do not allow resolution of its exact phylogenetic position. Some of the best evidence for a specific grouping of animals and fungi (Opisthokonta) has come from elongation factor 1alpha, not only phylogenetic analysis of sequences but also the presence or absence of short insertions and deletions. We sequenced the EF-1alpha gene from the ichthyosporean parasite Ichthyophonus irregularis and determined its phylogenetic position using neighbor-joining, parsimony and Bayesian methods. We also sequenced EF-1alpha genes from four chytrids to provide broader representation within fungi. Sequence analyses and the presence of a characteristic 12 amino acid insertion strongly indicate that I. irregularis is a member of Opisthokonta, but do not resolve whether I. irregularis is a specific relative of animals or of fungi. However, the EF-1alpha of I. irregularis exhibits a two amino acid deletion heretofore reported only among fungi.

Animals↗

PubMed1988

Study and performance evaluation of statistical methods in image processing.

Two statistical image processing formalisms involving the entropy concept and Bayesian analysis are studied. Iterative imaging algorithms of the formalisms are formulated by employing, for the purpose of performance evaluation and easy implementation, the steepest descent method for the solution of entropy concept and the expectation maximization technique for the solution of Bayesian analysis. Quantitative evaluation and comparison of the convergence performance of the iterative algorithms on computer generated ideal and experimental radioisotope phantom imaging noisy data are given. The study concludes that the entropy algorithm can converge relatively fast, but it is very sensitive to noise in measured data due to the ill-posed nature of inverse problems and its lack of ability to consider the statistics of data fluctuation; while the Bayesian algorithm converges monotonically even with noisy data and has the advantage of considering both the a priori source distribution information and the statistical fluctuation of measured data.

Algorithms↗

PubMed2004

Joint oligogenic segregation and linkage analysis using bayesian Markov chain Monte Carlo methods.

One of the most challenging areas in human genetics is the dissection of quantitative traits. In this context, the efficient use of available data is important, including, when possible, use of large pedigrees and many markers for gene mapping. In addition, methods that jointly perform linkage analysis and estimation of the trait model are appealing because they combine the advantages of a model-based analysis with the advantages of methods that do not require prespecification of model parameters for linkage analysis. Here we review a Markov chain Monte Carlo approach for such joint linkage and segregation analysis, which allows analysis of oligogenic traits in the context of multipoint linkage analysis of large pedigrees. We provide an outline for practitioners of the salient features of the method, interpretation of the results, effect of violation of assumptions, and an example analysis of a two-locus trait to illustrate the method.

Bayes Theorem↗

PubMed2006

Site-specific experiments on folding/unfolding of Jun coiled coils: thermodynamic and kinetic parameters from spin inversion transfer nuclear magnetic resonance at leucine-18.

The 32-residue leucine zipper subsequence, called here Jun-lz, associates in benign media to form a parallel two-stranded coiled coil. Studies are reported of its thermal unfolding/folding transition by circular dichroism (CD) on samples of natural isotopic abundance and by both equilibrium and spin inversion transfer (SIT) nuclear magnetic resonance (NMR) on samples labeled at the leucine-18 alpha-carbon with 99% 13C. The data cover a wide range of temperature and concentration, and show that Jun-lz unfolds below room temperature, being far less stable than some other leucine zippers such as GCN4. 13C-NMR shows two well-separated resonances. We ascribe the upfield one to 13C spins on unfolded single chains and the downfield one to 13C spins on coiled-coil dimers. Their relative intensities provide a measure of the unfolding equilibrium constant. In SIT NMR, the recovery of the equilibrium magnetization after one resonance is inverted is modulated in part by the unfolding and folding rate constants, which are accessible from the data. Global Bayesian analysis of the equilibrium and SIT NMR data provide values for the standard enthalpy, entropy, and heat capacity of unfolding, and show the latter to be unusually large. The CD results are compatible with the NMR findings. Global Bayesian analysis of the SIT NMR data yields the corresponding activation parameters for unfolding and folding. The results show that both reaction directions are activated processes. Activation for unfolding is entropy driven, enthalpy opposed. Activation for folding is strongly enthalpy opposed and somewhat entropy opposed, falsifying the idea that the barrier for folding is solely due to a purely entropic search for properly registered partners. The activation heat capacity is much larger for folding, so almost the entire overall change is due to the folding direction. This latter finding, if it applies to GCN4 leucine zippers, clears up an extant apparent disagreement between folding rate constants for GCN4 as determined by chevron analysis and NMR in differing temperature regimes.

Carbon Isotopes↗

PubMedDate not supplied

Evaluation of a neural network classifier for pancreatic masses based on CT findings.

We have investigated a neural network classifier based on CT findings extracted by a radiologist for the differential diagnosis between the pancreatic ductal adenocarcinoma and mass-forming pancreatitis, and compared its classification performance with that of Bayesian analysis, Hayashi's quantification method II, and radiologists. The three computerized classification methods were designed to classify categorized CT findings extracted by a radiologist, and were trained and tested on 71 cases. There was comparable performance between the neural the network, the Bayesian analysis, Hayashi's quantification method II, and the radiologists, in classifying pancreatic carcinoma and inflammatory mass.

Adult↗

PubMed2002

Overcredibility of molecular phylogenies obtained by Bayesian phylogenetics.

Bayesian phylogenetics has recently been proposed as a powerful method for inferring molecular phylogenies, and it has been reported that the mammalian and some plant phylogenies were resolved by using this method. The statistical confidence of interior branches as judged by posterior probabilities in Bayesian analysis is generally higher than that as judged by bootstrap probabilities in maximum likelihood analysis, and this difference has been interpreted as an indication that bootstrap support may be too conservative. However, it is possible that the posterior probabilities are too high or too liberal instead. Here, we show by computer simulation that posterior probabilities in Bayesian analysis can be excessively liberal when concatenated gene sequences are used, whereas bootstrap probabilities in neighbor-joining and maximum likelihood analyses are generally slightly conservative. These results indicate that bootstrap probabilities are more suitable for assessing the reliability of phylogenetic trees than posterior probabilities and that the mammalian and plant phylogenies may not have been fully resolved.

Amino Acid Substitution↗

PubMed1987

The accuracy of a pharmacokinetic theophylline predictor using once daily dosing.

1. The accuracy of a computer based pharmacokinetic prediction method based on Bayesian analysis has been evaluated for an oral show release form of theophylline. 2. In 83 patients from seven centres 24 h serum theophylline concentration-time profiles were measured under a variety of circumstances. 3. Revised predictions of 24 h serum theophylline concentration profiles were generated by Bayesian analysis using single serum drug concentrations taken before, during and after the study days in different subgroups of those patients. Comparing the predicted and measured profiles the mean prediction error (bias) was 0.05 mg l-1 for peak concentrations and 0.04 mg l-1 for trough concentrations during once daily dosing. The corresponding root mean squared prediction errors (precision) were 2.59 and 1.17 mg l-1, respectively. 4. This accuracy is considered more than adequate for clinical purposes. 5. The technique can be used with a variety of other drugs and can form a valuable part of a routine therapeutic drug monitoring service.

Adult↗

PubMedDate not supplied

[Evaluation of the activity of creatine phosphokinase for the detection of carriers of Duchenne-type muscular dystrophy in families in the city of Monterrey, Mexico].

The activity of serum creatine phosphokinase (CPK) was determined in 80 female members of 23 families with affected members of Duchenne type muscular dystrophy (DMD) and compared with the values of a control group of 100 unaffected women. The control group values exhibited a normal distribution of frequency with a mean of 21 U/L and standard deviation from the mean of 7.9 U/L. Sixty nine percent (11/16) of obligatory carriers showed CPK values higher than the mean of the control group plus two standard deviations of the mean. Thirty one percent (5/16) had false negative values. These percentages are similar to those reported in other studies. Elevated CPK activity was found in 45% (18/40) of type A possible carriers (relatives of obligatory carriers) and the group of possible carriers type B (mothers and relatives of isolated cases) 42% (10/24) exhibited high CPK values. Bayesian analysis was also used in all possible-carriers (A and B). We also report an estimation of the fertility of the DMD gene carriers and of their attitude towards family planning. It is concluded that the determination of serum CPK activity, despite its shortcomings, associated with Bayesian analysis when necessary, could be the method of choice for quick and inexpensive evaluation of the carrier status, mainly in families with members affected by DMD.

Creatine Kinase↗

PubMed2000

Historical changes in the postoperative treatment of appendicitis in children: impact on medical outcome.

BACKGROUND/PURPOSE: The introduction of managed care in the 1980s caused increased pressure to reduce costs for hospitalized patients. The authors hypothesized that these market forces have resulted in a decreased hospital stay and utilization of sophisticated diagnostic testing in children treated for appendicitis. If true, the impact of this paradigm shift on patient outcome is unknown. METHODS: Hospital records for 913 pediatric patients treated for appendicitis from 1974 to 1998 were reviewed retrospectively. Patients were stratified into those with perforated appendicitis (PA) and nonperforated appendicitis (NPA). Demographics, perioperative hospital course, diagnostic testing, complications, and long-term outcomes were analyzed after stratification into time intervals. RESULTS: Over time, children with NPA were treated with shorter antibiotic courses (P<.05) and were placed on a regular diet earlier (P<.05). These changes in treatment resulted in an earlier discharge (P<.05). The amount of time to become afebrile with a normal white blood cell count (WBC) did not change over time. Children with PA exhibited similar results with shorter antibiotic courses (P<.05), earlier dietary intake (P<.05) and earlier hospital discharge (P<.05) over time. In all children with appendicitis there was no significant difference in the rate of wound infections, abscesses requiring drains, readmission, or reoperations overtime. The utilization of abdominal radiographs (83%) and ultrasonography (USN; 40%) was high and remained unchanged over time. Utilization of computed tomography (CT scan) was low (4.3%) in the early decades and was not used as a preoperative test from 1991 to 1994. Given the high diagnostic accuracy of a pediatric surgeon for this disease, Bayesian analysis indicates that USN utilization rates should be 15%. CONCLUSIONS: The market pressures of managed care have resulted in a new treatment paradigm with an earlier discharge of all children with appendicitis. There has been no concomitant increase in the complication rate in either group as a result of this paradigm shift. Bayesian analysis indicates that USN and abdominal radiographs are overutilized in our institution.

Adolescent↗

PubMed2006

Evaluation of nonlinear regression approaches to estimation of insulin sensitivity by the minimal model with reference to Bayesian hierarchical analysis.

Minimal model analysis of intravenous glucose tolerance test (IVGTT) glucose and insulin concentrations offers a validated approach to measuring insulin sensitivity, but model identification is not always successful. Improvements may be achieved by using alternative settings in the modeling process, although results may differ according to setting, and care must be exercised in combining results. IVGTT data (12 samples, regular test) from 533 men without diabetes was modeled by the traditional nonlinear regression (NLR) approach, using five different permutations of settings. Results were evaluated with reference to the more robust Bayesian hierarchical (BH) approach to model identification and to the proportion of variance they explained in known correlates of insulin sensitivity (age, BMI, blood pressure, fasting glucose and insulin, serum triglyceride, HDL cholesterol, and uric acid concentration). BH analysis was successful in all cases. With NLR analysis, between 17 and 35 IVGTTs were associated with parameter coefficients of variation (PCVs) for minimal model parameters S(I) (insulin sensitivity) and S(G) (glucose effectiveness) of >100%. Systematic use of each different approach in combination reduced this number to five. Mean (interquartile range) S(I)(NLR) was then 3.14 (2.29-4.63) min(-1).mU(-1).l x 10(-4) and 2.56 (1.74-3.83) min(-1).mU(-1).l x 10(-4) for S(I)(BH) (correlation 0.86, P < 0.0001). S(I)(NLR) explained, on average, 10.6% of the variance in known correlates of insulin sensitivity, whereas S(I)(BH) explained 8.5%. In a large body of data, which BH analysis demonstrated could be fully identified, use of alternative modeling settings in NLR analysis could substantially reduce the number of analyses with PCVs >100%. S(I)(NLR) compared favorably with S(I)(BH) in the proportion of variance explained in known correlates of insulin sensitivity.

Bayes Theorem↗

PubMed1998

A rapid dosimetric methacholine challenge in asthma diagnostics: a clinical study of 230 patients with dyspnoea, wheezing or a cough of unknown cause.

The rapid methacholine challenge test using a pocket turbine spirometer (Micro Spirometer) and the Spira Elektro 2 dosimeter was performed with 230 consecutive patients who had dyspnoea, wheezing or a prolonged cough of unknown cause. Patients with previous asthma diagnoses as well as those who had used inhaled steroids during the preceding 4 weeks were excluded. Seventy-eight patients (34%) were methacholine positive (PD20FEV1 < or = 6900 micrograms) 47 (60%) of whom had a final diagnosis of American Thoracic Society (ATS) criteria fulfilling bronchial asthma. One hundred and fifty-two patients (66%) were methacholine negative (PD20FEV1 > 6900 micrograms) 14 (9%) of whom had bronchial asthma according to clinical evaluation. Increased bronchial responsiveness was strongly associated with ATS criteria fulfilling asthma (P < 0.0001). When PD20FEV1 was used, 47 (77%) of the asthmatic patients were hyper-responsive (range 40-6900 micrograms) compared to 31 (18%) of the non-asthmatic patients (range 160-6900 micrograms). When using PD15FEV1, 51 (84%) of the asthmatic patients (range 28-6900 micrograms) and 52 (31%) of the non-asthmatic patients (range 100-6900 micrograms) were hyper-responsive. The level of bronchial responsiveness measured by both PD20FEV1 and PD15FEV1 differed significantly between asthmatic and non-asthmatic patients (P < 0.0001). Hyper-responsiveness was associated with an increased daily variation in peak expiratory flow (PEF) (P < 0.0001) and an increased number of blood eosinophils (P < 0.0001). Hyper-responsiveness was also associated with decreased levels of FEV1 and percentages of predicted FEV1 (P = 0.04 and P < 0.0001, respectively). Stepwise logistic regression analysis showed that the number of positive prick results (OR = 1.15, 95% CI 1.01-1.31), blood eosinophils (1.004, 1.00-1.01), level of FEV1 (0.56, 0.36-0.87) and current smoking (2.36, 1.00-5.59) were factors significantly associated with the probability of hyper-responsiveness. Age, gender, atopy, pets and a history of ex-smoking were not significantly associated with hyper-responsiveness, neither in univariate nor in multivariate analyses. The Bayesian analysis was used to investigate the diagnostic value of the rapid methacholine challenge test. A receiver operator characteristic curve demonstrated that PD20FEV1 separated asthmatic and non-asthmatic patients better than PD15FEV1. The best cutoff value of PD20FEV1 was 6000 micrograms, but the difference from 6900 micrograms was minimal. The best results of the test using a PD20FEV1 cutoff point of 6900 micrograms (PPV: 0.80, NPV: 0.79) were obtained when the pre-test probability was 0.48. The interval security of the test was established by a pre-test probability between 0.19 and 0.78. Maximal positive (0.34) and negative (0.31) final gains were achieved when pre-test probabilities were 0.33 and 0.65, respectively. The cutoff level of 150 micrograms gave 100% of specificity and predictive value of a positive test for clinical asthma diagnosis. The Bayesian analysis approach demonstrated that the test is useful in asthma diagnostics if not performed on patients with lowest or highest probabilities of asthma.

Adult↗

PubMed2002

Bayesian decision analysis as a tool for defining monitoring needs in the field of effects of CSOs on receiving waters.

In recent years, decision analysis has become an important technique in many disciplines. It provides a methodology for rational decision-making allowing for uncertainties in the outcome of several possible actions to be undertaken. An example in urban drainage is the situation in which an engineer has to decide upon a major reconstruction of a system in order to prevent pollution of receiving waters due to CSOs. This paper describes the possibilities of Bayesian decision-making in urban drainage. In particular, the utility of monitoring prior to deciding on the reconstruction of a sewer system to reduce CSO emissions is studied. Our concern is with deciding whether a price should be paid for new information and which source of information is the best choice given the expected uncertainties in the outcome. The influence of specific uncertainties (sewer system data and model parameters) on the probability of CSO volumes is shown to be significant. Using Bayes' rule, to combine prior impressions with new observations, reduces the risks linked with the planning of sewer system reconstructions.

Bayes Theorem↗

PubMed1995

Comparison of methods for the estimation of carboplatin pharmacokinetics in paediatric cancer patients.

The antitumour and toxic effects of platinum drugs, in particular carboplatin, have been related to their plasma concentration and this has led to the concept of a target area under the plasma concentration-time curve (AUC) for carboplatin dosing. A formula based on renal function has been successfully applied to carboplatin dosing in adults and modified versions have also been proposed for paediatric patients. In order to monitor carboplatin AUC with maximum efficiency and minimum patient inconvenience, limited sampling strategies are desirable. A population method with Bayesian estimation is described, based on one or two samples taken following a dose of carboplatin. Population data were obtained from 22 paediatric patients treated with 200-1000 mg/m2 carboplatin as a 60-90 min infusion. Ultrafilterable carboplatin was determined by atomic absorption spectrophotometry. A two compartment model was fitted to each data set using the Maximum Likelihood estimator of the ADAPT programme. These parameter estimates provided the prior means and covariance matrix for the Bayesian estimator using a lognormal distribution. The test data sets consisted of ultrafilterable carboplatin concentrations in 23 patients (aged 1 month-18 years) who received similar treatment. The two compartment model was fitted to data sets containing one or two points, using the Bayesian maximum a posteriori (MAP) estimator and an error model derived from the population error model parameters. Results from the Bayesian analysis and other methods for the estimation of AUC, including relating clearance to surface area or to renal function, were evaluated by comparing the AUC estimate with the AUC determined by model-independent analysis. Overall, the optimal sampling strategy performed better than estimates based on renal function, which had a median bias of 5% and precision of 22%. With one data point at 60 min postinfusion, the median bias and precision were 3 and 6%, respectively. Addition of a second data point at 30 min during the infusion improved the estimate slightly (median bias -2%, precision 3%). Bayesian estimation produced more reliable estimates of AUC compared to values based on renal function, which in turn was slightly better than using surface area. A technique, developed in adult patients, for estimating AUC from a measurement of 24 h total plasma platinum was comparable to estimates based on renal function, but was less reliable. The estimation of carboplatin AUC can be performed using only one or two plasma samples and Bayesian analysis. This approach is less biased and more precise than methods based on surface area, renal function or total platinum at 24 h postdose, but is probably best used in combination with dosing based on renal function.

Adolescent↗

PubMed2004

Pathways of urothelial cancer progression suggested by Bayesian network analysis of allelotyping data.

Urothelial cancers of the bladder (UC) comprise biologically heterogeneous group of tumors and display complex genetic alterations. Several genetic changes have been analyzed in detail and some of them are associated with the development and progression of UCs. Only a few studies, however, are focused on identifying the order in which the aberrations may appear during UC tumorigenesis. We have analyzed 123 papillary UCs of the bladder by microsatellites for each of the chromosomal regions that have been suggested to be specifically involved in this type of tumor. We used Bayesian network modeling that enables to uncover multivariate probabilistic dependencies between variables. This methodology applied to LOH data allowed us to discover patterns of losses in UCs. Exploiting the mechanism of probabilistic reasoning in Bayesian networks we suggest primary and secondary events in tumor pathogenesis and reconstruct the possible flow of progression of allelic changes. Losses of chromosome 9p and 9q were found to be the primary events. Losses of 8p and 17p are important events leading to progression of tumor cell clones. The loss of 17p occurs when both abnormalities of chromosome 9 and 8p are already present. There are chromosomal losses related to 8p (1q, 18q, 10q) and some losses like 5q/5p were associated with 17p, leading to the hypothesis of different genetic pathways of UC progression. The abnormalities of chromosome regions 13q, 16q, 6q, 14q, 3p are suggested to be late events being accumulated during the progression of cancer. Although some genetic changes were associated only with the 8p pathway, most secondary genetic changes appear in both pathways. Supplementary material for this article can be found on the International Journal of Cancer website at http://www.interscience.wiley.com/jpages/0020-7136/suppmat/index.html.

Alleles↗

PubMed2003

Heat stress and mortality in Lisbon Part II. An assessment of the potential impacts of climate change.

Global environmental change, in particular climate change, will have adverse effects on public health. The increased frequency/intensity of heat waves is expected to increase heat-related mortality and illness. To quantify the climatic risks of heat-related mortality in Lisbon an empirical-statistical model was developed in Part I, based on the climate-mortality relationship of the summer months of 1980-1998. In Part II, scenarios of climate and population change are applied to the model to assess the potential impacts on public health in the 2020s and 2050s, in terms of crude heat-related mortality rates. Two regional climate models (RCMs) were used and different assumptions about seasonality, acclimatisation and the estimation of excess deaths were made in order to represent uncertainty explicitly. An exploratory Bayesian analysis was used to investigate the sensitivity of the result to input assumptions. Annual heat-related death rates are estimated to increase from between 5.4 and 6 (per 100,000) for 1980-1998 to between 5.8 and 15.1 for the 2020s. By the 2050s, the potential increase ranges from 7.3 to 35.6. The burden of deaths is decreased if acclimatisation is factored in. Through a Bayesian analysis it is shown that, for the tested variables, future heat-related mortality is most sensitive to the choice of RCM and least to the method of calculating the excess deaths.

Adolescent↗

PubMed1992

Bayesian subset analysis in a colorectal cancer clinical trial.

Subset analysis is the examination of treatment comparisons within groups of patients with restricted levels of patient characteristics. Such analyses are vulnerable to multiplicity effects. We examine the problem in the context of a proportional hazards model with terms for treatment, each of several dichotomous covariates representing the patient characteristics of interest, and treatment-by-covariate interaction effects. Parametrically, a subset-specific treatment effect is equal to the treatment effect term plus a linear combination of the interaction terms. We present Bayesian point and interval estimates under the assumption that the interaction terms are exchangeable and the prior distributions for the other regression parameters are locally uniform. This produces a shrinking of the estimated interaction effects towards zero, thereby discounting them and dealing in a natural way with multiplicity. We illustrate the method using results of a recent North Central Cancer Treatment Group/Mayo Clinic study in advanced colorectal cancer.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1999

Maternal animal model with correlation between maternal environmental effects of related dams.

A procedure to take into account the nongenetic relationship between maternal effects in adjacent generations is presented. It considers a correlation between maternal environments provided by a dam and its daughters (lambda). The dispersion structure of the maternal animal model was modified to include a correlation matrix (E) that relates the maternal permanent environmental effects. The structures of the E matrix and its inverse (E(-1)) are described. Both matrices are completely defined by the correlation coefficient lambda. An algorithm to compute these matrices from pedigree information was also developed. Furthermore, a Bayesian analysis of this model including the lambda parameter was developed using Gibbs sampling, with Metropolis steps for the nonstandard conditional distributions. With simulated data, the proposed model reduced the bias in all estimates of dispersion parameters when an antagonism between the maternal effects received by a daughter and its future maternal environment existed. This model also provides an estimate of the environmental relationship between the maternal effects of dams and daughters by the lambda parameter. The same Bayesian analysis was also carried out with weaning weight data of the Bruna dels Pirineus breed. The posterior means (standard deviation) of (co)variance ratios were .214 (.081) for direct heritability (h2d), .107 (.033) for maternal heritability (h2m), .047 (.020) for the proportion of variance due to maternal environmental effects (c2m), and -.034 (.043) for the genetic correlation between direct and maternal effects (r(dm)). The posterior mean of lambda parameter was -.190, and 76% of its marginal posterior distribution took negative values. As occurred with simulated data, considering the maternal environmental correlation in the analysis implied higher h2m estimates, lower c2m and h2d estimates, and less negative values for the marginal posterior distribution of r(dm). These results were considered as evidence of the environmental antagonism between maternal effects provided by a dam and its daughters to weaning weight of their progeny in the Bruna dels Pirineus breed.

Animal Husbandry↗