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PubMed2004

Inheritance of cricopharyngeal dysfunction in Golden Retrievers.

OBJECTIVE: To characterize a genetic component to cricopharyngeal dysfunction (CD) in Golden Retrievers. ANIMALS: 117 dogs. PROCEDURE: The CD phenotype was determined by videofluoroscopy, and dogs were classified as affected if the upper esophageal sphincter (UES) did not open, if there were morphologic abnormalities of the UES, or if opening of the UES was delayed for > or = 6 videofluoroscopic frames (0.2 seconds) after closure of the epiglottis. All survey radiographic and videofluoroscopic studies were reviewed by the same radiologist. RESULTS: Of the 117 dogs (47 males and 70 females) with a CD phenotype determined via videofluoroscopy, 21 dogs (18.0%) had abnormalities of the UES (affected). Of these 21 dogs, 9 were males (19.1% of all males) and 12 were females (17.1% of all females). The heritability of CD in a threshold model was estimated as 0.61, which established that CD could be passed from parent to offspring. Results of complex segregation analysis suggested that a single recessive allele of large effect contributed to the expression of this disease in Golden Retrievers. CONCLUSIONS AND CLINICAL RELEVANCE: The determination that CD is inherited in Golden Retrievers is an important step in providing information for veterinarians attending dogs with this disorder. Breeders also require this information to make informed breeding decisions.

Animals↗

PubMed1998

Bayesian inference of variance components for litter size in Rasa Aragonesa sheep.

Variance components were estimated for litter size in Rasa Aragonesa sheep, a meat breed from northern Spain, to determine whether selective breeding for litter size is a reasonable strategy to improve reproductive performance. We assumed an animal mixed effect threshold model with a binary response variable. Marginal estimates of the genetic parameters were obtained in the underlying scale using Bayesian inference, implemented via the Gibbs sampling procedure and a data augmentation approach. Posterior marginal means of heritability and repeatability were .077 and .141, respectively. Moreover, the 95% highest marginal posterior density region of heritability ranged from .051 to .101. Therefore, we conclude that litter size is a trait that could be selected for in breeding programs. The effect of the loss of pedigree information, a common feature of sheep production, on the estimation of the genetic parameters was also studied using simulation. The results indicate that the lack of pedigree information has little effect on our estimates of heritability.

Animals↗

PubMed2000

Additive genetic parameter estimates for heifer pregnancy and subsequent reproduction in Angus females.

A primary objective of this study was to determine whether the binary traits heifer pregnancy (HP) and subsequent rebreeding (SR) were heritable in an experimental population of Angus cattle. A second objective was to determine the nature of the additive genetic relationships among HP, SR, and stayability (S(5/1)) in the same population. Heifer pregnancy was defined as the observation of a heifer conceiving and remaining pregnant to palpation at 120 d, given exposure during the breeding season. Subsequent rebreeding was defined as the observation of a 2-yr-old conceiving and remaining pregnant to palpation at 105 d, given pregnancy as a yearling and exposure during the breeding season. Stayability was defined as the probability of a female having at least five calves, given she becomes a dam as a 2 yr old. Data were analyzed using a maximum a posteriori probit threshold model to predict breeding values on the liability scale and Method R procedures to estimate variance components in the determination of heritability (h2). Additive genetic groups were used in determining the additive genetic relationships among these fertility traits. Additive genetic groups were formed on one trait's breeding values and used in the prediction of another trait's breeding values. Analyses yielded h2 estimates that were out of the parameter space 8.5 and 46.3% for HP and SR, respectively, and 5.9% for the reestimation of S(5/1). The majority of point estimates outside the parameter space for SR converged toward 0, whereas those for HP and S(5/1) primarily converged toward 1. From the subsamples producing h2 estimates within the parameter space, average h2 for HP, SR, and S(5/1) were .21, .19, and .15, with standard deviations of .12, .14, and .08, respectively. The estimates of h2 indicate that HP and S(5/1) were heritable and should respond favorably to selection; however, SR did not appear heritable due to the large number of subsamples producing h2 estimates out of the parameter space. Fixed effect estimates for age of dam were significant for HP. From the analyses using additive genetic groups, the relationship among HP and S(5/1) appeared to be nonlinear. This potential nonlinear relationship seen between HP and S(5/1) indicates that selection for improved female fertility would be most effective by having predictions on both traits.

Animals↗

PubMed2005

Genetic parameters of fertility in two lines of rabbits with different reproductive potential.

A Bayesian analysis with a threshold model was performed for fertility defined as a binary trait (1 = successful mating, 0 = unsuccessful mating) in two populations of rabbits of different reproductive potential and different genetic origin: Line P selected for litter size and Line C selected for growth rate. There were 20,793 records of natural mating (86.2% successful) in Line C between 1983 and 2003, and 17,548 records (80.5% successful) in Line P, between 1992 and 2003. Data related to 5,388 and 3,848 females and 1,021 and 685 males in Lines C and P, respectively. The pedigree included 6,409 and 4,533 individuals in Lines C and P, respectively. The binary response was modeled under a probit approach. The model for the latent variable included male and female additive genetic effects, male and female permanent environmental effects, and the year-season and physiological status of the female (nulliparous, multiparous lactating, or multiparous nonlactating) as systematic effects. Means (standard deviation in parentheses) of the estimated marginal posterior distribution (EMPD) of male heritability were 0.013 (0.006) and 0.010 (0.008) in Lines C and P, respectively, and those of EMPD of female heritability were 0.056 (0.013) and 0.062 (0.018) in Lines C and P, respectively. Means of the EMPD of the proportion of the phenotypic variance due to environmental male and female effects were, respectively, 0.031 (0.007) and 0.128 (0.018) in Line C and 0.053 (0.010) and 0.231 (0.024) in Line P. Means (standard deviations in parentheses) of the EMPD of genetic correlation between male and female fertility were 0.733 (0.197) in Line C and 0.434 (0.381) in Line P. The posterior distribution of genetic correlations presents a huge dispersion, and the estimates should be taken with caution because of the almost negligible estimate of the male genetic component. Results indicate that little genetic variation exists for female fertility, and practically none for male fertility. It would, therefore, be possible to improve reproductive performance by including female fertility in a breeding program, but response to selection would be very small.

Animals↗

PubMed1997

Immunogenetics and the cause of autoimmune disease.

Autoimmune disease results from the action of environmental factors on a predisposed genotype. In this review, the role of genetic susceptibility in the aetiology of autoimmune disease is examined. As the genetics of autoimmune diabetes has been studied more intensively than that of other autoimmune diseases, supporting evidence is drawn principally from that example. Autoimmune diseases are not inherited as entities but as constitutions which confer an increased probability of developing disease. It is proposed that there are two components to autoimmune disease susceptibility. One confers susceptibility to autoimmunity per se, while the other determines tissue specificity. In this review, the concept of liability is introduced as a tool used in quantitative genetics and is applied to the analysis of autoimmune diabetes by considering a threshold model. In this example, empirically derived incidence figures are used to calculate heritability which is a relative measure of the influence of genetics and environmental factors. The validity of applying the concept of liability to diabetes is confirmed by examining the values of heritability calculated from empirical data obtained from different kindred relationships, and by confirming that the assumptions on which liability is based are supported by recent gene mapping data. Finally, the physiological significance of liability is considered and its significance to the cause of autoimmunity discussed.

Animals↗

PubMed1984

Epigenetic carcinogens: problems with identification and risk estimation.

The mechanisms of carcinogenesis are just beginning to be understood. There is recent interest in the broad classification of carcinogens into two categories based upon their mechanism of action: those that interact with DNA via a genetic mechanism are termed genetic carcinogens; and those that do not directly interact with DNA, but may cause changes in DNA tertiary structure or methylation patterns, and are termed epigenetic carcinogens. Present knowledge is inadequate to justify separate risk assessment methods for genetic vs. epigenetic carcinogens. Quantitative estimates of carcinogenic risk are currently best made using non-threshold models.

Animals↗

PubMed2005

Genetic basis and risk factors for infectious and noninfectious diseases in US Holsteins. I. Estimation of genetic parameters for single diseases and general health.

Health data collected from 1996 to 1999 from 177 herds in Minnesota and Wisconsin were analyzed to establish genetic basis for infectious and noninfectious diseases. Three types of health traits were targeted. First, available infectious conditions were used to identify animals that are superior in their general immunity (including innate immunity) for infectious diseases. Generalized immunity may be thought of as a combination of immune responses to a variety of immune system challenges. Second, single infectious and noninfectious diseases were analyzed separately. Third, infectious reproductive diseases as one category of related conditions, and cystic ovary disease as one category of 3 related noninfectious ovary disorders were studied. Data were analyzed using a threshold model that included herd, calving year, season of calving, and parity as cross-classified fixed factors; and sire and cow within sires as random effects. Days at risk and days in milk at the beginning of a record were included by fitting the days as continuous covariates in the model. A heritability value of 0.202 +/- 0.083 was estimated for generalized immunity. Heritability values of 0.141 and 0.161 were estimated for uterine infection and mastitis, respectively. Heritability of single noninfectious disorders ranged from 0.087 to 0.349. The amount of additive genetic variance recovered in the underlying scale of noninfectious disorders tended to zero when combining multiple conditions. The study supports combining infectious diseases into categories of interest but we do not recommend the same approach for noninfectious disorders.

Abomasum↗

PubMed2005

Genetic analysis of clinical mastitis, milk fever, ketosis, and retained placenta in three lactations of Norwegian red cows.

The objectives were to infer heritability and genetic correlations between clinical mastitis (CM), milk fever (MF), ketosis (KET), and retained placenta (RP) within and between the first 3 lactations and to estimate genetic change over time for these traits. Records of 372,227 daughters of 2411 Norwegian Red (NRF) sires were analyzed with a 12-variate (4 diseases x 3 lactations) threshold model. Within each lactation, absence or presence of each of the 4 diseases was scored based on the cow's health recordings. Each disease was assumed to be a different trait in each of the 3 lactations. The model for liability had trait-specific effects of year-season of calving and age of calving (first lactation) or month-year of calving and calving interval (second and third lactations), herd-5-yr, sire of the cow, and a residual. Posterior means of heritability of liability in first, second, and third lactations were 0.08, 0.07, and 0.07, respectively, for CM; 0.09, 0.11, and 0.13 for MF; 0.14, 0.16, and 0.15 for KET, and 0.08 in all 3 lactations for RP. Posterior means of genetic correlations between liability to CM, MF, KET, and RP, within disease between lactations, ranged from 0.19 to 0.86, and were highest between KET in different lactations. Correlations involving first lactation MF were low and had higher standard deviations. Genetic correlations between diseases were low or moderate (from -0.10 to 0.40), within as well as between lactations; the largest estimates were for MF and KET, and the lowest involved MF or KET and RP. Positive genetic correlations between diseases suggest that some general disease resistance factor with a genetic component exists. Trends of average sire posterior means by birth-year of daughters were used to assess genetic change, and the results indicated genetic improvement of resistance to CM and KET and no genetic change for MF and RP in the NRF population.

Animals↗

PubMed2006

Effects of inbreeding in the dam on dystocia and stillbirths in US Holsteins.

Dystocia scores were recorded by producers on 120,434 Holsteins (218,213 records) from 1985 through 1996; dystocia scores 3 to 5 were coded as difficult births. Stillbirths were recorded for deaths within the first 48 h after birth. Data were restricted to registered cows for pedigree completeness, and inbreeding coefficients were calculated using 5-generation pedigrees. Computational restrictions required that subsets of the data be created by choosing herds at random but using all records from selected herds. Effects of inbreeding in the dam were estimated in a sire-maternal grandsire (of the calf) threshold model using Gibbs sampling. The model included fixed effects of calf sex and inbreeding of the dam and random effects of herd-year-season of birth, additive genetic, and residual effects. First, second, and third parities were analyzed separately. Solutions for sex of calf and inbreeding from different parities were converted to expected change in probability of dystocia or stillbirth per 1% increase in inbreeding. Inbreeding effects were largest for first-parity cows giving birth to male calves at a 0.42% increase in probability of dystocia/1% increase in inbreeding. Effects of inbreeding for first-parity dams giving birth to female calves were smaller, 0.30%/1% increase in inbreeding. Incidence of stillbirths increased 0.25 and 0.20% for male and female calves/1% increase in inbreeding for first parity births. Effects of inbreeding on dystocia and stillbirths declined with parity. Effects of inbreeding were small, especially in later parities, but were consistently unfavorable.

Animals↗

PubMed1995

Genetic parameters for common health disorders of Holstein cows.

Observations on 7416 Canadian Holstein cows were examined to estimate genetic parameters for the most common diseases of dairy cows. Mastitis, ovarian cyst, ketosis, milk fever, abomasal displacement, and culling that is due to reproductive failure or leg problems were analyzed as binomial traits, assuming an underlying threshold model that included fixed and random effects. Sire and residual components of variance were estimated by REML to provide heritability estimates from paternal half-sibs. A multiple-trait mixed model was also used to estimate genetic and environmental correlations between production and disease traits. Heritabilities of disease traits were relatively low and ranged from 0 to .15, except for displaced abomasum (h2 = .28). Evidence of genetic antagonism existed between incidence of mastitis and milk production. Incidence of milk fever was genetically associated with cows of lower genetic potential for production. Genetic associations between displaced abomasum and production traits were small, and estimates of genetic correlations between ovarian cyst and milk production were inconsistent across lactations. Ketosis was antagonistically associated genetically with production of milk and fat but was favorably associated with production of protein. The long-term cumulative effect of genetic selection against diseases might be useful to diminish their incidence.

Abomasum↗

PubMed1997

Effects of interactions between type and milk production on survival traits of Canadian Holsteins.

Effects of the interaction between type and production on two measures of functional herd life were examined for Canadian Holsteins. Data were records of survival through first lactation for 1,153,706 cows and number of lactations initiated (maximum of five lactations) for 705,930 cows. Survival data were regressed on ETA for type traits of the sire of each cow after the cows were assigned to groups with low, medium, or high production. Survival through first lactation was analyzed with a threshold model. Factors in the model included herd-year-season; age at calving; month of calving; interaction of registry status, change in herd size, and season; fat and protein production; and linear regressions of sire ETA for type within each production class. Numbers of lactations were analyzed with a linear model that also included month of last calving. Overall conformation and udder traits had the largest effects on survival through first lactation. Effects on number of lactations for feet and leg traits were about the same as for udder traits. Interactions were significant. Type traits were relatively unimportant for herd life of low producing cows. Few differences were observed in the relationships between herd life and type for medium versus high producing cows, indicating no need to increase the emphasis on type in response to current trends for greater production.

Aging↗

PubMed1998

Incidences and effects of diseases on the performance of Swedish dairy herds stratified by production.

Incidences of diseases and their effects on reproductive performance and risk of culling in herds stratified by production and estrus detection efficiency were studied. Data were from the Swedish milk and disease recording systems and consisted of records for 33,748 first parity Swedish Friesian cows. A standardized mixed threshold model was used for statistical analyses of categorical outcome variables, and an ordinary linear mixed model was used for continuous outcome variables. An increase in production was associated with increased frequencies of treatments of most diseases, shorter intervals from calving to first artificial insemination, fewer days open, and lower culling rates. Cows treated for metritis, silent estrus, and cystic ovaries had an increased number of days to first artificial insemination and more days open. However, the negative consequences of these diseases on reproductive performance decreased as herd production increased. The risk of culling was higher for cows treated for dystocia, cystic ovaries, and mastitis, but the increase in the risk of culling was lower for higher producing herds. Similar trends were observed when herds were stratified by estrus detection efficiency. The results support the hypothesis that herd management, as characterized by milk production or estrus detection efficiency, is important in the incidences and consequences of diseases. Herd management, measured directly or indirectly, should be considered when the health status or cost of disease for a given herd is evaluated.

Animals↗

PubMed2000

A central-peripheral asymmetry in masked priming.

Masked primes presented prior to a target result in behavioral benefits on incompatible trials (in which the prime and the target are mapped onto opposite responses) when they appear at fixation, but in behavioral benefits on compatible trials (in which the prime and the target are mapped onto the same response) when appearing peripherally. In Experiment 1, the time course of this central-peripheral asymmetry (CPA) was investigated. For central primes, compatible-trial benefits at short stimulus onset asynchronies (SOAs) turned into incompatible-trial benefits at longer SOAs. For peripheral primes, compatible-trial benefits at short SOAs increased in size with longer SOAs. Experiment 2 showed that these effects also occur when primes and targets are physically dissimilar, ruling out an interpretation in terms of the perceptual properties of the stimulus material. In Experiments 3 and 4, the question was investigated as to whether the CPA is related to visual-spatial attention and/or retinal eccentricity per se. The results indicate that the CPA is independent of attentional factors but strongly related to the physiological inhomogeneity of the retina. It is argued that central and peripheral primes trigger an initial motor activation, which is inhibited only if primes are presented at retinal locations of sufficiently high perceptual sensitivity. The results are discussed in terms of an activation threshold model.

Adult↗

PubMed1992

Preference can be more powerful than detection of oddity as a test of discriminability.

Subjects presented with sets of three samples, two of distilled water and one of tap water, were significantly more consistent in choosing the tap water as preferable than they were in identifying it as the odd sample in the set. The result is opposite to the prediction of high-threshold models of sensory discrimination, which say that if a difference is not noticed, preferences will be random, whereas if a difference is noticed, preferences may still be in either direction. The result can be quantitatively explained by a model advanced by Frijters to explain an analogous anomaly found with the triangle test used in the food industry. Applying his model to the observed proportions yields essentially equivalent estimates of sensory difference (d' = 1.5, approximately) from the two tasks, and a direction of preference almost unanimously in favor of the tap water that was used. Since the model predicts that the proportion of subjects choosing the odd item will depart further from chance in the preference task than in the oddity task, the former has greater power to reject the null hypothesis of no sensory difference if one exists and if preference is overwhelmingly in one direction.

Adult↗

PubMed1999

Cleft of the lip and palate in twins.

BACKGROUND: Cleft lip and palate is one of the most common congenital anomalies in Taiwan. Its etiology remains unknown for the majority of the patients. The study of twins is a classic method for evaluating the relative roles of genetic and environmental factors in the formation of the anomaly. METHODS: In this study, 37 pairs of twins and one set of triplets with cleft lip and palate were evaluated. Clinical data were collected for zygosity determination and analysis of etiologic factors. The concordance rate and heritability index were assessed. RESULTS: The results showed that the concordance rate was 26% for all twins and 57% among the monozygotic pairs, which is higher than those rates for the Caucasian population. The heritability index was 53%, higher than the other reports as well. The influence of the environment could not be ruled out. CONCLUSION: The results confirm a strong genetic role in the etiology of clefts in our patients. Environmental factors were acting as well. The findings in this study support the multifactorial threshold model in the development of cleft lip and palate.

Adolescent↗

PubMedDate not supplied

Health effects in underground uranium miners.

The health effects associated with uranium miners have received much attention in the last 30 years. Although mortality rates are elevated for such causes as accidents and nonmalignant respiratory disease, lung cancer caused by exposure to radon decay products is the primary hazard to underground uranium miners. This review summarizes studies of eight cohorts of radium miners, and examines several pooled analyses that provide the best understanding of the radon/lung cancer relationship. The relative risk of lung cancer is linearly related to cumulative exposure to radon decay products. The excess relative risk decreases with attained age and time since exposure. An inverse exposure-rate effect exists, such that prolonged exposure at low levels of radon is more hazardous than shorter exposures to higher levels. The linear no-threshold model used in most epidemiologic studies has been attacked by some as overestimating risk at indoor radon levels. These arguments are rejected by this reviewer.

Humans↗

PubMed2001

Acute cardiovascular effects of magnesium and their relationship to systemic and myocardial magnesium concentrations after short infusion in awake sheep.

The temporal relationship between the systemic and myocardial concentrations of magnesium and some of its acute cardiovascular effects were examined after short i.v. infusion administration of magnesium (30 mmol over 2 min) in five awake chronically instrumented sheep. Magnesium decreased mean arterial blood pressure and systemic vascular resistance (SVR) by 23 and 41% from baseline, respectively. These hemodynamic changes were consistent with magnesium producing primary reductions in SVR with partial heart rate (HR)-mediated compensation of blood pressure. Cardiac output and HR increased by 38 and 38% from baseline, respectively. Magnesium had little effect on myocardial contractility, but substantially increased myocardial blood flow (MBF, 77% above baseline) primarily due to direct myocardial vasodilation. The peak arterial and coronary sinus serum magnesium concentrations were 6.94 +/- 0.26 (mean +/- S.E.M.) and 6.51 +/- 0.20 mM, respectively, at 2 min. Both arterial and coronary sinus magnesium concentrations at the end of the study were still more than 3 mM, whereas all the cardiovascular effects were back to baseline. The myocardial kinetics of magnesium was consistent with rapid equilibration of magnesium (half-life 0.4 min) with a small distribution volume (71 ml) consistent with the extracellular space of the heart. In conclusion, magnesium was shown to have a rapid equilibration between the plasma/serum concentrations of magnesium and its extracellular concentration in the myocardium. However, the primary cardiovascular effect of magnesium (reductions in SVR) preceded its extracellular concentrations, and was a direct function of its arterial concentration. A "threshold" model for changes in SVR was preferred when linked to the arterial magnesium concentration.

Animals↗

PubMed2001

The genetic epidemiology of cancer: interpreting family and twin studies and their implications for molecular genetic approaches.

The recent completion of a rough draft of the human genome sequence has ushered in a new era of molecular genetics research into the inherited basis of a number of complex diseases such as cancer. At the same time, recent twin studies have suggested a limited role of genetic susceptibility to many neoplasms. A reappraisal of family and twin studies for many cancer sites suggests the following general conclusions: (a) all cancers are familial to approximately the same degree, with only a few exceptions (both high and low); (b) early age of diagnosis is generally associated with increased familiality; (c) familiality does not decrease with decreasing prevalence of the tumor-in fact, the trend is toward increasing familiality with decreasing prevalence; (d) a multifactorial (polygenic) threshold model fits the twin data for most cancers less well than single gene or genetic heterogeneity-type models; (e) recessive inheritance is less likely generally than dominant or additive models; (f) heritability decreases for rarer tumors only in the context of the polygenic model but not in the context of single-locus or heterogeneity models; (g) although the family and twin data do not account for gene-environment interactions or confounding, they are still consistent with genes contributing high attributable risks for most cancer sites. These results support continued search for genetic and environmental factors in cancer susceptibility for all tumor types. Suggestions are given for optimal study designs depending on the underlying architecture of genetic predisposition.

Environment↗