Showing papers in "Behavior Genetics in 1997"
TL;DR: Data from the Virginia 30,000, including twins and their parents, siblings, spouses, and children, were analyzed using a structural equation model (Stealth) and no evidence was found for a special MZ twin environment, thereby supporting the equal environment assumption.
Abstract: We review the literature on the familial resemblance of body mass index (BMI) and other adiposity measures and find strikingly convergent results for a variety of relationships. Results from twin studies suggest that genetic factors explain 50 to 90% of the variance in BMI. Family studies generally report estimates of parent–offspring and sibling correlations in agreement with heritabilities of 20 to 80%. Data from adoption studies are consistent with genetic factors accounting for 20 to 60% of the variation in BMI. Based on data from more than 25,000 twin pairs and 50,000 biological and adoptive family members, the weighted mean correlations are .74 for MZ twins, .32 for DZ twins, .25 for siblings, .19 for parent–offspring pairs, .06 for adoptive relatives, and .12 for spouses. Advantages and disadvantages of twin, family, and adoption studies are reviewed. Data from the Virginia 30,000, including twins and their parents, siblings, spouses, and children, were analyzed using a structural equation model (Stealth) which estimates additive and dominance genetic variance, cultural transmission, assortative mating, nonparental shared environment, and special twin and MZ twin environmental variance. Genetic factors explained 67% of the variance in males and females, of which half is due to dominance. A small proportion of the genetic variance was attributed to the consequences of assortative mating. The remainder of the variance is accounted for by unique environmental factors, of which 7% is correlated across twins. No evidence was found for a special MZ twin environment, thereby supporting the equal environment assumption. These results are consistent with other studies in suggesting that genetic factors play a significant role in the causes of individual differences in relative body weight and human adiposity.
1,567 citations
TL;DR: An extensive series of simulations was carried out to provide estimates of resolving power, for backcross (BC) and F2 designs, over a wide range of experimental sizes and of gene effects and dominance at the QTL.
Abstract: "Resolving power" is defined as the 95% confidence interval for quantitative trait locus (QTL) map location that would be obtained when scoring an infinite number of markers in a given constellation of a marker-QTL mapping experiment. Resolving power can serve as a close estimate of the confidence interval of QTL map location, as well as a guide to the lower efficient limit of marker spacing in an initial marker-QTL mapping experiment. In the present study, an extensive series of simulations was carried out to provide estimates of resolving power, for backcross (BC) and F2 designs, over a wide range of experimental sizes and of gene effects and dominance at the QTL. From the simulation results, the remarkably simple expressions, 3000/(mNd2) (where m = 1 for BC and m = 2 for F2; N = population size, and d = allele substitution effect) and 530/Nv (in terms of v, the proportion of variance explained), were obtained for estimating resolving power. These expressions can provide a convenient guide to planning marker spacing in BC and F2 marker-QTL linkage experiments and for placing confidence intervals about QTL map location obtained in such experiments.
406 citations
TL;DR: This article shows how the package Mx provides confidence intervals for parameters and functions of parameters in the context of a simple additive genetic, common, and specific environment threshold model for binary data, and describes the computation and relative merits of likelihood-based confidence intervals.
Abstract: This article describes the computation and relative merits of likelihood-based confidence intervals, compared to other measures of error in parameter estimates. Likelihood-based confidence intervals have the advantage of being asymmetric, which is often the case with structural equation models for genetically informative studies. We show how the package Mx provides confidence intervals for parameters and functions of parameters in the context of a simple additive genetic, common, and specific environment threshold model for binary data. Previously published contingency tables for major depression in adult female twins are used for illustration. The support for the model shows a marked skew as the additive genetic parameter is systematically varied from zero to one. The impact of allowing different prevalence rates in MZ vs. DZ twins is explored by fitting a model with separate threshold parameters and comparing the confidence intervals. Despite the improvement in fit of the different prevalence model, the confidence intervals on all parameters broaden, owing to their covariance.
320 citations
TL;DR: The purpose of this paper is to recommend the technique to the behavioral genetics community and to present results of the use of this technique to obtain DNA by mail for 114 2-year-olds and 116 adults.
Abstract: As specific genes are identified that are associated with behavior, it becomes increasingly important for behavioral geneticists to be able to incorporate these genes in their research. Rather than using blood, DNA can be extracted from cheek swabs, which makes it possible to obtain DNA inexpensively by mail from large, widely dispersed individuals. The purpose of this paper is to recommend this technique to the behavioral genetics community and to present results of our use of this technique to obtain DNA by mail for 114 2-year-olds and 116 adults.
251 citations
TL;DR: Evidence showing that neonatal handling and/or environmental enrichment leads to enduring effects on behaviors leading to age-related impairments in learning a spatial, water maze task as well as on hippocampal neuronal atrophy is reviewed.
Abstract: Roman high- and low-avoidance (RHA/Verh and RLA/Verh) rats are selected and bred for extreme divergence in two-way active avoidance acquisition. In addition, compared to RLA/Verh rats, RHA/Verh rats are (behaviorally and physiologically) less anxious or reactive to stressors, show increased novelty (sensation)-seeking behavior as well as a higher preference for rewarding substances, and are usually less efficient in learning tasks not involving shock administration. The present article reviews evidence showing that neonatal handling and/or environmental enrichment leads to enduring effects (their magnitude frequently depending upon the rat line) on those behaviors. For example, it has been found that neonatal handling reduces most of the (behavioral and physiological) signs of emotionality/anxiety in RLA/Verh rats, while environmental enrichment increases their novelty seeking (also the case with RHA/Verh rats), saccharin and ethanol intake, and sensitivity to amphetamine. Finally, initial results (currently being further elaborated upon) support a preventive action of both environmental treatments on age-related impairments in learning a spatial, water maze task as well as on hippocampal neuronal atrophy.
205 citations
TL;DR: This review summarizes what is known about the genetic determinants of nutrient selection and its impact on obesity in humans and rodents and suggests that a preference for fat and the resulting obesity are partially genetically determined.
Abstract: What an animal chooses to eat can either induce or retard the development of obesity; this review summarizes what is known about the genetic determinants of nutrient selection and its impact on obesity in humans and rodents. The selection of macronutrients in the diet appears to be, in part, heritable. Genes that mediate the consumption of sweet-tasting carbohydrate sources have been mapped and are being isolated and characterized. Excessive dietary fat intake is strongly tied to obesity, and several studies suggest that a preference for fat and the resulting obesity are partially genetically determined. Identifying genes involved in the excess consumption of dietary fat will be an important key to our understanding of the genetic disposition toward common dietary obesity.
196 citations
TL;DR: These identified quantitative trait loci should prove useful for dissecting the genetic and behavioral dimensions of O-F behavior, fostering an understanding of individual differences.
Abstract: By performing a whole genome screen in an F2 intercross of two strains of mice (A/J and C57BL/6J), which differ markedly in their behavioral response to a brightly lit open field (O-F), we have mapped several quantitative trait loci (QTL) for this complex behavioral phenotype. QTL on chromosomes 1 and 10 were identified that affect both initial ambulation in the O-F (initial “response to novelty” ambulation) (lod of 7.1 and 8.8, respectively) and vertical rearings (lod of 4.5 and 8.5, respectively). For habituated O-F behavior, QTL were identified on chromosomes 3 and 10 for ambulation (lod of 4.1 and 14.7, respectively) and on chromosomes 1, 10, and 19 for vertical rearings (lod of 5.8, 6.0, and 4.7, respectively). The QTL on chromosome 1 (near D1Mit1 16; 101 cM) was specific for initial O-F ambulation behavior, whereas the QTL on chromosome 10 (near D10Mit237; 74 cM) affected both initial and habituated rearing behavior. Additional suggestive QTL (lod, >2.8) were mapped to chromosomes 1, 8, 11, 15, and 19. The QTL on chromosomes 1, 10, and 19 individually explain from 3.2 to 12.7%. Collectively, the multiple independent QTL explain from 16.3 to 24.1% of the F2 population's phe-notypic variance, depending on the trait. These identified QTL should prove useful for dissecting the genetic and behavioral dimensions of O-F behavior, fostering an understanding of individual differences.
173 citations
TL;DR: This study examined genetic contributions to the observed correlations between imupulsivity and sensation seeking traits and found that the phenotypic correlations between the Control scale and the four subscales of the Sensation Seeking Scale were mediated almost entirely by genetic factors.
Abstract: A number of studies have demonstrated associations between sensation seeking traits and measures of impulsivity. This study examined genetic contributions to the observed correlations between imupulsivity and sensation seeking traits. Fifty-seven pairs of identical and 49 pairs of fraternal twins who were reared apart and 90 individuals who also participated in the Minnesota Study of Twins Reared Apart completed the Control scale of the Multidimensional Personality Questionnaire (MPQ; Tellegen, 1982) and the four subscales of the Sensation Seeking Scale (SSS; Zuckerman, 1979), Consistent with previous studies, the Control scale was significantly correlated with the SSS. A Cholesky decomposition of the data indicated that the phenotypic correlations between the Control scale and the four subscales of the SSS were mediated almost entirely by genetic factors. In the final reduced model the proportion of the genetic variance of the Control scale in common with the SSS was estimated as 55%, and the rest of the genetic variance (45%) was attributed to the genetic variance specific to the Control scale. The results emphasize the importance of common biological mechanisms underlying associations between impulsivity and sensation seeking traits.
147 citations
TL;DR: Combining the BXD and two-way selection line results, the most probable QTL was found on chromosome 3 (near the AdhI locus; LOD ~2.9), and other probableQTLs were found with LOD 2.4–2.6.
Abstract: Short-term selective breeding starting from an F2 intercross of two inbred strains is a largely unexploited but potentially useful tool for quantitative trait locus (QTL) mapping The selection lines can also serve as a valuable confirmation test of recornbinant inbred (RI) QTL results when the same two progenitor strains are used Starting from an F2 from a C57BL/6J (B6) × DBA/2J (D2) cross (B6D2F2), this approach was used in a population of ~72 mice per generation bidirectionally selected for two-bottle choice 10% ethanol (alcohol) preference for four generations The high-preference line diverged significantly from the low line in the first generation with a realized heritabittty of 32 By generation 4, the preference ratios in the high line were double those seen in the low line Regions of the genome previously implicated by BXD RI QTL analysis as containing QTLs were searched using microsatellite markers The test for the presence of QTLs was based on the divergence of marker allele frequencies in the two oppositely selected lines significantly exceeding that expected from random (genetic) drift and allele frequency estimation error Combining the BXD and two-way selection line results, the most probable QTL was found on chromosome 3 (near the AdhI locus; LOD ~29), other probable QTLs were found with LOD 24–26
143 citations
TL;DR: Data currently available on the neuroendocrine profiles of RHA/Verh and RLA/ Verh rats are presented, together with more recent findings which suggest that differences in peripheral and central hormonal responses, and in hormone action on the brain, may be closely related to emotional reactivity and coping ability.
Abstract: The Roman high (RHA/Verh)-and low (RLA/Verh)-avoidance rats, originally selected and bred for rapid vs. poor acquisition of a two-way active avoidance response, differ in emotional reactivity and sensitivity to stressors in various other test situations. These behavioral differences are associated with particular neuroendocrine and neurochemical characteristics. The aim of this short review is to present data currently available on the neuroendocrine profiles of RHA/Verh and RLA/Verh rats, together with more recent findings which suggest that differences in peripheral and central hormonal responses, and in hormone action on the brain, may be closely related to emotional reactivity and coping ability. Although genetic factors certainly play a major role, there is also evidence that epigenetic factors, e.g., early environmental influences, can modulate the phenotypic expression of the basic behavioral and neuroendocrine traits characterizing these lines. These psychogenetically selected lines can therefore be used as a model to investigate interactions between genes and the environment in determining each individual's sensitivity to stress and coping abilities (“vulnerability” model). This model may prove particularly useful for studies on the etiology and pathophysiology of anxiety and affective disorders and their neuroendocrine correlates.
132 citations
TL;DR: The results show that the behavioral variability observed in rats, in social and nonsocial environments, is influenced by genetic factors and that the Behavioral reactivity to social stimulations is a specific feature, dissociable from the levels of the different components of emotionality (approach/avoidance and general activity) as evaluated by the behavioral responses to nonsocial settings.
Abstract: Male rats from six inbred rat strains (Spontaneously Hypertensive Rat, Wistar Kyoto, Brown Norway, Wistar Furth, Fischer 344, and Lewis) have been compared for their behavioral reactivity when placed in several nonsocial (elevated plus-maze, open field) and social (social interaction in aversive and neutral environment, resident–intruder test, chronic social stress) settings. In addition, a factorial analysis was performed to assess how the variables measured in these different tests related to each other. Besides significant strain-related differences in all tests, the factorial analysis showed that, in nonsocial environments, the strains contrasted essentially along two independent behavioral traits, the propensity to approach or avoid an aversive stimulus and general motor activity in novel environments (two indices of emotionality). In the social settings, marked interstrain differences were observed regarding the expression of aggressive behaviors but these differences were not related to the respective levels on the two nonsocial components of reactivity. Furthermore, large genetic differences were observed in variations of body weight induced by a chronic social stressor paradigm. The factorial analysis suggested a lack of relationship between the effect of social stressors on body weight and the measures of emotionality and general activity obtained in the nonsocial tests. Conversely, these variations were influenced by the levels of aggressiveness and sociability. Taken together, these results show (i) that the behavioral variability observed in rats, in social and nonsocial environments, is influenced by genetic factors and (ii) that the behavioral reactivity to social stimulations is a specific feature, dissociable from the levels of the different components of emotionality (approach/avoidance and general activity) as evaluated by the behavioral responses to nonsocial settings.
TL;DR: In all lines the production and survival of offspring was substantially decreased at 4°C compared to 22°C, but the high- selected lines produced more and better-quality offspring, surviving up to 40 days of age at both temperatures compared to the control and low-selected lines.
Abstract: To test the hypothesis that large, well-built, nests are an important component of fitness, we kept 12 mating pairs of two high-selected, two control, and two low-selected lines, selected for therrnoregulatory nest-building behavior, at 22 and 4°C with access to 10 g of cotton to build a nest, for a period of 180 days. Measurements included number of litters bom per family, number of young per litter born and surviving up to 40 days of age, nest type built by the parents, and weight gain of the young from weaning (20 days of age) to 40 days of age. In all lines the production and survival of offspring was substantially decreased at 4°C compared to 22°C, but the high-selected lines produced more and better-quality offspring, surviving up to 40 days of age at both temperatures compared to the control and low-selected lines. This indicates that thermoregulatory nest-building behavior and evolutionary fitness are closely associated.
TL;DR: Genetic and environmental influences in the determination of individual differences in self-reported symptoms of separation anxiety (SAD), overanxious disorder (OAD), and manifest anxiety (MANX) were evaluated in children and adolescents, finding that additive genetic and environmental effects could be set equal across age and gender for these variables.
Abstract: Genetic and environmental influences in the determination of individual differences in self-reported symptoms of separation anxiety (SAD), overanxious disorder (OAD), and manifest anxiety (MANX) were evaluated in children and adolescents for three age groups (8-10, 11-13, and 14-16). Symptom counts for SAD and OAD were assessed for 1,412 twin pairs using the children's version of the Child and Adolescent Psychiatric Assessment, and MANX scores were based on child report from the Revised Children's Manifest Anxiety Scales. Despite significant age and gender differences in thresholds of liability for child reports of symptoms of SAD and OAD, additive genetic and environmental effects could be set equal across age and gender for these variables. For MANX, however, the best-fitting model was a common effects sex-limitation model with estimates of heritability varying dependent upon age and gender. Parameter estimates from the ACE models of OAD and SAD showed that additive genetic variation was a necessary component in the explanation of individual differences in child-reported symptoms of OAD (h2 = .37) across gender, but does not appear to be a major contributor to the explanation of individual differences in symptoms of SAD reported by children. Shared environmental effects (c2 = .40) were found to play a moderate role for SAD but could be dropped from the model for OAD and from all of the age groups for MANX, although the parameter approached significance among 11 yr to 13-year-old males.
TL;DR: The interaction of the A1+ allele and the Family Stress score produced significant regression coefficients for both Line Orientation score and P300 amplitude, providing the first evidence of a specific gene–environment interaction involving human cognitive functioning.
Abstract: TaqI A D2 dopamine receptor (DRD2) alleles, family stress, and cognitive markers, including visuospatial ability (Benton's Line Orientation) and event-related potentials (P300 amplitude and latency), were obtained in preadolescent boys of alcoholic and nonalcoholic fathers. In the presence of the DRD2 minor allele (A1+), the Family Stress score negatively correlated with the Line Orientation score and P300 amplitude. No significant correlations were found in boys lacking this allele (A1−). The interaction of the A1+ allele and the Family Stress score produced significant regression coefficients for both Line Orientation score (p = .002) and P300 amplitude (p = .04). Together, these two cognitive markers account for 37% of the variance in the Family Stress score of 47 A1 allele boys (p = .0002) but less than 1% in 71 A1− allele boys (p > .9). This provides the first evidence of a specific gene–environment interaction involving human cognitive functioning.
TL;DR: A review of studies conducted in mice, rats, and pigs to estimate the number, location, and effect of QTL controlling obesity and related traits and summarizes the results and their implications toward understanding the complex nature of obesity in humans.
Abstract: In contrast to diseases caused by single-gene defects, many of the most common human maladies such as obesity, atherosclerosis, diabetes, and hypertension exhibit continuous phenotypic variation and a predominantly multifactorial and polygenic basis. Genes with roles in energy balance, nutrient partitioning, lipid and insulin metabolism, and a variety of behavioral traits are likely interacting with environmental stimuli to regulate obesity phenotypes. With the current proliferation of highly polymorphic genetic markers and the refinement of experimental approaches, it is now possible to screen thoroughly the genomes of model organisms for the individual genes or quantitative trait loci (QTL) that control measurable polygenic traits such as obesity. With the growing wealth of comparative mapping, it will be possible to predict the location of a homologous locus in the human after first mapping it in the mouse. Many experiments have been conducted in mice, rats, and pigs to estimate the number, location, and effect of QTL controlling obesity and related traits. This review describes the design and strategies of such studies and summarizes the results and their implications toward understanding the complex nature of obesity in humans.
TL;DR: Age-related changes are analyzed in the correlation of monozygotic and dizygotic U.S. twin pairs aged between 9 and 75+ years for conservatism scores derived from a 28-item social attitude inventory.
Abstract: Age-related changes are analyzed in the correlation of 3416 monozygotic and 3780 dizygotic U.S. twin pairs aged between 9 and 75+ years for conservatism scores derived from a 28-item social attitude inventory. The effects of the shared environment are overwhelming in twins aged 20 years or younger. In older twins, genetic effects appear to play a larger role. A more dynamic conception of the interaction between genes and environment in the development of complex human differences is needed.
TL;DR: Genetic and environmental results from longitudinal studies are consistent with what is known about the changing distribution of adiposity during adulthood and clinical experience of the difficulty of maintaining behavioral-induced weight loss.
Abstract: Genetic studies have shown that both childhood and adult body mass index are substantially heritable. The evidence for shared family environmental influences is largely absent, even though there are clear indications that secular changes in energy expenditure have brought about a significant increase in the prevalence of obesity. This apparent inconsistency may be explained by the dual phenomena of the near-universality of access to environments that facilitate reductions in energy expenditure (e.g., TV as a recreational pastime), together with heritable individual differences in the response to or utilization of these environments. The impact of changes in nonshared environments on body weight can be estimated from biometrical genetical studies and is found to be both small and relatively short-lived. Genetic and environmental results from longitudinal studies are consistent with what is known about the changing distribution of adiposity during adulthood and clinical experience of the difficulty of maintaining behavioral-induced weight loss.
TL;DR: Estimates of bivariate heritability and the genetic correlation between the reading and the mathematics performance measures suggest that the comorbidity between mathematics and reading difficulties is due in part to genetic influences.
Abstract: In order to assess the genetic etiology of the comorbidity of reading and mathematics difficulties, data were ascertained from two samples: (1) 102 identical and 77 same-sex fraternal twin pairs in which at least one member of each pair is reading disabled and (2) 42 identical and 23 same-sex fraternal twin pairs in which at least one member is math disabled. Composite reading and mathematics performance data from each sample were fitted to the basic multiple regression model for the analysis of selected twin data and its bivariate extension. Resulting estimates of bivariate heritability and the genetic correlation between the reading and the mathematics performance measures suggest that the comorbidity between mathematics and reading difficulties is due in part to genetic influences.
TL;DR: The aim of the study was to estimate sex-specific genetic and environmental effects unique to symptoms of anxiety/depression and to alcohol consumption and effects common to the two phenotypes.
Abstract: Two thousand five hundred seventy pairs of Norwegian MZ and like-sexed and unlike-sexed DZ twins aged 18–25 years completed questionnaires with information about symptoms of anxiety and depression and alcohol consumption. The aim of the study was to estimate sex-specific genetic and environmental effects unique to symptoms of anxiety/depression and to alcohol consumption and effects common to the two phenotypes. Five models fitted the data almost equally well. The heritability estimate from these models ranged from .23 to .57 for male alcohol consumption, from .39 to .59 for female alcohol consumption, from .25 to .48 for male anxiety/depression, and from .45 to .56 for female anxiety/depression. The phenotypic correlation between alcohol and anxiety/depression in males (r = .23) could be fully explained by common genetic effects. The correlation in females (r = .18) was caused by individual environmental factors together with either genetic effects or family environment.
TL;DR: Current knowledge is insufficient to explain the pathophysiologic mechanism of obesity in most multiple congenital anomaly/mental retardation syndromes, but delineation of the functions of the underlying genes will likely be instructive regarding mechanisms of appetite, satiety, and obesity in the general population.
Abstract: Constitutional obesity and mental retardation cooccur in several multiple congenital anomaly syndromes, including Prader–Willi syndrome, Bardet–Biedl syndrome, Cohen syndrome, Albright hereditary osteodystrophy, and Borjeson–Forssman–Lehmann syndrome as well as some rarer disorders. Although hypothalamic–pituitary axis abnormalities are thought to be a possible causative mechanism in some of these disorders, current knowledge is insufficient to explain the pathophysiologic mechanism of obesity in most multiple congenital anomaly/mental retardation syndromes. The chromosomal location of many of these syndromes is known, and studies are ongoing to identify the causative genes. Further delineation of the functions of the underlying genes will likely be instructive regarding mechanisms of appetite, satiety, and obesity in the general population. This review details current knowledge of the clinical and molecular genetic findings of multiple congenital anomaly/mental retardation syndromes associated with intrinsic obesity in an effort to delineate causative mechanisms and genetic abnormalities contributing to obesity.
TL;DR: Why behavior qua behavior should be a specific focus of obesity-oriented behavioral genetic designs is outlined and possible explanations for why behavior has been underinvestigated are explored.
Abstract: Tremendous advances in the genetic underpinnings of obesity have emerged in recent years. Curiously, behavioral genetic methods have provided relatively less information on the environmental influences and intermediary behaviors which promote human obesity. This situation in unfortunate since human obesity is, in part, environmentally determined and the result of behaviors such as eating and physical (in)activity. This article has several goals. First, it outlines reasons why behavior qua behavior should be a specific focus of obesity-oriented behavioral genetic designs. Second, possible explanations for why behavior has been underinvestigated are explored. Third, data regarding the genetic/environmental architecture of various obesity-related phenotypes (e.g., food intake, physical activity, etc.) are reviewed. Fourth, a commentary on the importance of gene–environment interactions is offered. Finally, suggestions for future research, including a list of possible “candidate environments” and “candidate intermediary behaviors,” are offered.
TL;DR: In the absence of replicate lines to estimate the degree of genetic drift, effect size can be used to reduce the number of false-positive associations between the original selected trait and the new character.
Abstract: Often a single pair of lines that has been selected for high and low expression of a trait is used as an animal model to study new biobehavioral characters thought to be associated with the selected trait. Because of genetic drift at many loci, comparisons of High and Low lines on the new character will frequently produce significant line differences even when there is no association between the selected trait and the new character being studied. In the absence of replicate lines to estimate the degree of genetic drift, effect size can be used to reduce the number of false-positive associations between the original selected trait and the new character. When the heritability of the new character exceeds .40 and the inbreeding coefficient within the selected lines is moderate, High- and Low-line means on the new character will frequently differ by at least one phenotypic SD, but not often differ by more than two SDs, in the absence of any relationship between the selected trait and the new character. If the selected lines are highly inbred, drift effects are greater, resulting in more false-positive associations. Situations posing special difficulty in the absence of replicate lines include the study of characters with low heritability relative to the selected trait and cases in which the lines do not differ greatly on the original selected trait. Studies using selected lines should always report inbreeding coefficients of the generations being studied, relative to the base population from which the lines were derived.
TL;DR: Comparisons of “time of mating” (the time copulation begins) between lines selected for short and long developmental periods in the melon fly showed that longer developmental periods were associated with later initiation of mating.
Abstract: Comparisons of “time of mating” (the time copulation begins) between lines selected for short and long developmental periods have been made in the melon fly, Bactrocera cucurbitae. These comparisons showed that longer developmental periods were associated with later initiation of mating. Crosses were also made between selected lines to ascertain the genetic basis of developmental period and time of mating. Comparisons of daily activity rhythms for four types of behavior (locomotion, preening, feeding, and wing vibration) between the selected lines showed the following; (1) locomotion and preening occurred in daytime for the short developmental period lines, versus mainly at night for the long developmental period lines; (2) feeding behavior occurred in daytime for both the short and the long developmental period lines; and (3) wing vibration, a component of courtship behavior of males, occurred at dusk for the short developmental period lines and at night for the long developmental period lines.
TL;DR: Differences in line-dependent differences in GABAergic and DAergic neurotransmission may contribute to the distinct emotionality and responsiveness to centrally active drugs of RHA/Verh and RLA/ Verh rats.
Abstract: The dopaminergic (DAergic) and GABAergic pathways in the central nervous system (CNS) are involved in the control of emotions, in the reactivity to stressful stimuli, and in the positive and negative reinforcing properties of psychotropic drugs. In the present review, we summarize the differences in a range of neurochemical markers of GABA- and DA-mediated neurotransmission in the CNS of Roman high-avoidance (RHA/Verh) and Roman low-avoidance (RLA/Verh) rats, two psychogenetically selected lines that differ in what may be considered to be level of emotionality. The stimulatory effect of GABA on 36Cl− uptake was less pronounced in the cerebral cortex of RLA/Verh rats compared to RHA/Verh rats. In addition, the binding affinity of [35S]TBPS, a selective ligand of the convulsant site located in the chloride channel of GABAA receptors, was significantly lower in the hippocampus of RLA/Verh rats than in their high-avoidance counterparts. On the other hand, the density of D1 DA receptors labeled with [3H]SCH 23390 was lower in the nucleus accumbens of RLA/Verh rats compared to RHA/Verh rats. Brain microdialysis studies demonstrated that tail-pinch stress and subconvulsant doses of the anxiogenic compound pentylenetetrazol increased the extracellular concentrations of DA in the prefrontal cortex of hypoemotive RHA/Verh rats but not in their hyperemotive RLA/Verh counterparts. These line-dependent differences in GABAergic and DAergic neurotransmission may contribute to the distinct emotionality and responsiveness to centrally active drugs of RHA/Verh and RLA/Verh rats.
TL;DR: Compared behavioral and neurochemical studies in these two lines may provide useful information on the biological correlates of drug dependence, and locomotion, rearing, and total motor activity were significantly more intense after acute cocaine and morphine challenges than after vehicle administration in RHA/Verh rats.
Abstract: The Swiss sublines of Roman high-avoidance (RHA/Verh) and Roman low-avoidance (RLA/Verh) rats differ in their reactivity to environmental and pharmacological stressors, in their sensitivity to stereotypies elicited by dopamine (DA)-mimetic agents, and in their densities of D1 DA receptors in the terminal field of the mesoaccumbens DAergic projection, an important link in the neural networks involved in the motor effects and reinforcing properties of drugs abused by humans. The present study was therefore designed to compare the behavioral and neurochemical effects of cocaine (5 mg/kg, i.p.) and morphine (0.5 mg/kg, s.c.) in RHA/Verh and RLA/Verh rats. To this aim, we measured motor activity and DA output in the nucleus accumbens as determined by brain microdialysis. The number of counts corresponding to horizontal, vertical, and total motor activities accumulated in basal conditions during the 60-min acclimation period was significantly larger in RHA/Verh than in RLA/Verh rats. Moreover, horizontal, vertical, and total motor activities throughout the 120-min observation period that followed the administration of vehicle tended to be larger in RHA/Verh rats, although the difference between the two lines was not statistically significant. In RHA/Verh rats, locomotion, rearing, and total motor activity were significantly more intense after acute cocaine and morphine challenges than after vehicle administration, whereas no significant differences in motor activity were observed between control and cocaine- or morphine-treated RLA/Verh rats. No line-related differences were detected in the basal DA output, but the effect of cocaine on DA release was more robust in RHA/Verh rats. Likewise, the effect of morphine was more pronounced in RHA/Verh than in RLA/Verh rats. Because the mesoaccumbens DAergic pathway plays a central role in the acquisition of motivational valence by environmental and pharmacological stimuli and, therefore, in operant behavior, our results suggest that comparative behavioral and neurochemical studies in these two lines may provide useful information on the biological correlates of drug dependence.
TL;DR: It is concluded that selection for two-way avoidance learning does not result in cognitive defects in the RLA/Verh strain but, rather, in stronger emotional reactions to fearful stimuli.
Abstract: To investigate the emotional reactions of two rat strains selectively bred for good and poor two-way avoidance acquisition (RHA/Verh and RLA/Verh), male animals of both strains were tested in an acoustic startle response test. They received 40 acoustic stimuli followed by 10 electric foot shocks and another 30 acoustic stimuli. RLA/Verh rats showed a significantly higher startle response compared to RHA/Verh animals, indicating a stronger emotional reaction to acoustic stimuli. In addition, the former showed a stronger response to foot shocks. Combined with earlier findings, we conclude that selection for two-way avoidance learning does not result in cognitive defects in the RLA/Verh strain but, rather, in stronger emotional reactions to fearful stimuli.
TL;DR: Genetic susceptibility studies suggest that altered energy expenditure and/or preferential substrate utilization are likely to be involved in the etiology of obesity; new data are presented in young sib pairs that suggest moderate heritability of nonresting energy expenditure.
Abstract: Understanding the genetic factors of obesity requires consideration of the genetic basis of the underlying etiological factors including energy expenditure and substrate utilization. Genetic susceptibility studies suggest that altered energy expenditure and/or preferential substrate utilization are likely to be involved in the etiology of obesity. Twin and family studies suggest that there is a strongly heritable component to resting energy expenditure, substrate utilization, and the thermic response to feeding. Physical activity energy expenditure has been less well studied; new data are presented in young sib pairs that suggest moderate heritability of nonresting energy expenditure. Only a few candidate gene studies have been performed to examine the role of basic proteins involved in energy expenditure (the sodium-potassium ATPase and the uncoupling protein) or substrate utilization (fatty acid binding protein). The lack of information in this area warrants further investigation into genetic aspects of energy and substrate metabolism.
TL;DR: It is possible that the TAQI DRD2 association is specific to visuospatial performance and independent of general cognitive ability, and tested the association between DRJD2 and WISC-R IQ.
Abstract: Berman and Noble (1995) reported significantly reduced visuospatial performance in children with the TAQI A1 allele of the D2 dopamine receptor (DRD2) gene. Given that visuospatial performance loads highly on an unrotated principal component indexing general cognitive ability, we tested the association between DRD2 and WISC-R IQ comparing 51 high-IQ, 51 average-IQ, and 35 low-IQ children in the IQ Quantitative Trait Loci (QTL) Project. No statistically significant association between the TAQI A DRD2 alleles and IQ was found. Given that a statistically significant portion of genetic variance for specific cognitive abilities is independent of general cognitive ability, it is possible that the TAQI DRD2 association is specific to visuospatial performance and independent of general cognitive ability.
TL;DR: The results suggest that the familial aggregation of male homosexuality cannot be explained by the birth order effect and that older brothers and family membership reflect separate influences on sexual orientation or sexual orientation-correlated behavior.
Abstract: Research has shown that male homosexuality tends to cluster in families and that homosexual males have, on average, a greater number of older brothers than do heterosexual males. This study investigated whether the former, between-families effect and the latter, within-families effect are additive. The subjects were 717 full siblings over age 40 reported by 343 heterosexual and homosexual male probands examined in Southern Ontario in 1994–1995. The sibling's history of legal marriage or cohabitation in a heterosexual relationship was taken as a proxy variable for sexual orientation. There were no significant findings for the female siblings. As expected, the never-married male siblings were more likely to come from the sibships of the homosexual probands, and they had a greater average number of older brothers. A bootstrapped logistic regression analysis showed that an additive model best explained the male siblings' data. The results suggest that the familial aggregation of male homosexuality cannot be explained by the birth order effect and that older brothers and family membership reflect separate influences on sexual orientation or sexual orientation-correlated behavior.
TL;DR: It is proposed that within the population sampled for this study, the calls most effectively eliciting investigation and retrieval would be calls with the average hybrid values of the diallel cross.
Abstract: Ultrasonic calls produced by young mice reliably elicit investigation and retrieval by adults. While there are large individual differences in the characteristics of these calls, little work has been done to partition that variation. We completed a 4 × 4 diallel cross and Hayman analyses on several characteristics of these cries. The major result was the detection of directional dominance toward a higher rate of calling, longer calls, and calls of lower overall frequency with a greater bandwidth. Within the context of biometrical genetic theory, we conclude that calls with such characteristics may have important fitness value. Extending this idea, we propose that within the population sampled for this study (the animals of the four inbred strains and 12 F1 hybrid groups), the calls most effectively eliciting investigation and retrieval would be calls with the average hybrid values of the diallel cross.