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Biomedical subjects

J M Cheverud

Publications and source records attributed to J M Cheverud.

62 records · Page 4Linked to original sources
PubMed1981

Epiphyseal union and dental eruption Macaca mulatta.

Age of dental eruption and epiphyseal fusion is estimated for the permanent dentition and long bone epiphyses of rhesus macaques (Macaca mulatta), with 299 skeletons of individuals with known age of death, from the Cayo Santiago skeletal collection. Epiphyses at a given joint tend to have the same time. While males and females tend to have the same pattern of epiphyseal fusion, females' epiphyses fuse earlier than those of malep rhesus macaques (Macaca mulatta), with 299 skeletons of individuals with known age of death, from the Cayo Santiago skeletal collection. Epiphyses at a given joint tend to have the same time. While males and females tend to have the same pattern of epiphyseal fusion, females' epiphyses fuse earlier than those of males, especially at the elbow and knee joints. The order of epiphyseal fusion in rhesus macaques follows the general primate pattern. Times of dental eruption for males and females are generally the same, except for the relatively late eruption of the canine in the males. The order of eruption follows a common primate pattern (dm2-M1-I1-I2-M2-(P3, P4)-C-M3). Multiple regressions were calculated in order to allow determination of developmental state, or predictions of chronological age, from epiphyseal fusion and/or dental eruption scores in juvenile rhesus macaques. Standard deviations of residuals from these regressions indicate considerable variation in developmental state among animals of the same chronological age. The lack of correlation between residuals from the separate skeletal and dental regressions, indicates that skeletal and dental development are largely independent.

Age Factors↗
PubMed1979

Relationships between non-metric skeletal traits and cranial size and shape.

A long-standing controversy exists about the comparative utility of metric and non-metric traits as biological indicators in population studies. We hypothesize that the underlying scale which determines the presence or absence of a cranial non-metric trait is an expression of general and/or local size variation in the cranium. Therefore metric and non-metric traits will share a common developmental determination. The hypothesis implies that the underlying scale of a non-metric trait will be correlated with measures of cranial size and shape. Forty-eight cranial metric and twenty-five cranial non-metric traits were scored on the left side of adult male crania from four North American Indian populations. New threshold traits were generated for each non-metric trait by dichotomizing discriminant scores produced by discriminant function analysis. The discriminant analysis was performed using metric traits to discriminate between groups formed by non-metric trait presence or absence. Every non-metric trait tested was significantly correlated with its threshold trait in at least one population. The correlations were of moderate to high levels depending on the trait and population sample studied. This implies that metric and non-metric traits share a moderate to high degree of developmental determination. The cause of these correlations may lie in the common effects that growth and development of the soft tissue and functional spaces of the cranium exert on both metric and non-metric traits.

Cephalometry↗
PubMed1978

Social group fission and the origin of intergroup genetic differentiation among the rhesus monkeys of Cayo Santiago.

The serum transferrin locus is used to investigate the roles of the lineal effect of fission, male migration effect of fission, and genetic drift in causing intergroup genetic differentiation among the rhesus macaques of Cayo Santiago. These three mechanisms prove sufficient to explain the degrees of differentiation between the newly formed social groups A, K, and L as of July 1, 1971. The lineal effect of fission provides a baseline of intergroup differentiation which is altered by forces leading to intragroup genetic change, the male migration effect and genetic drift. The importance of population dynamics for the distribution of alleles among subgroups of a population is recognized.

Animals↗
PubMedDate not supplied

Genetic and environmental impacts on litter size and early infant survival in three species of callitrichids.

Callitrichids are unusual among anthropoid primates in that they can deliver one to four offspring per litter in captivity. Factors underlying intraspecific variation in litter size are unclear. Data from the Oak Ridge Associated Universities (ORAU) Marmoset Research Center provided an opportunity to investigate determinants of variation in (1) average litter size at birth and (2) average litter size surviving to 2 weeks of age in Saguinus fuscicollis, S. oedipus, and Callithrix jacchus. The objectives were to (1) investigate the impact of parity, husbandry, origin (wild or captive), and subspecific hybridization on phenotypic variance in litter size and (2) to estimate the heritability of litter size at birth and at 14 days. Husbandry changes were the only significant covariate and increased litter size at birth in C. jacchus only. Heritability estimates for average litter size at birth were significant only in S. fuscicollis (h2 = 0.306). Heritability of average litter size at 2 weeks of age was not significantly greater than zero. Estimates of genetic variability were relatively high, however both traits had very high levels of residual variance. The results suggest that litter size is a malleable trait that may respond to environmental factors.

Animals↗
PubMedDate not supplied

Heritability of brain size and surface features in rhesus macaques (Macaca mulatta).

The extent of heritability for overall brain size and regional cortical surface features such as sulcus lengths is important for demonstrating a genetic component to the observed phenotypic differences among individuals and for evaluating the potential for evolutionary change in response to selection. Although the genetics of brain size has been extensively considered, the detailed morphology of the cortical surface has not previously been subjected to genetic analysis. We estimated the heritability of brain size and cortical sulcus lengths using 438 endocranial casts taken from skeletons of rhesus macaques (Macaca mulatta) from the Cayo Santiago population. Estimates were obtained both by mother-offspring regression and symmetric-differences-squared (SDS) methods. Brain size, measured as cranial capacity, was highly and significantly heritable in this population, confirming results of previous studies with laboratory mice. Overall, cortical sulcus lengths were also heritable, with 35% of the sulci significantly heritable at the 5% level in the mother-offspring analysis. The average mother-offspring heritability estimate, 0.31, was the same as the average heritability obtained previously from a series of 56 cranial metric characters. The SDS analyses generally corresponded to the findings based on mother-offspring regressions, although the significance test appeared more conservative. Both gross and detailed morphology of the brain are heritable.

Animals↗
PubMedDate not supplied

Fluctuating asymmetry in tamarin (Saguinus) cranial morphology: intra- and interspecific comparisons between taxa with varying levels of genetic heterozygosity.

Fluctuating asymmetry has been proposed as a measure of developmental homeostasis and an indicator of populations under stress. However, controversy surrounds not only the validity of an association between fluctuating asymmetry and levels of protein heterozygosity, but also whether fluctuating asymmetry can be used to identify populations under genetic and environmental stress. The relationship between levels of heterozygosity and developmental homeostasis is considered by comparing levels of cranial fluctuating asymmetry in three tamarin samples with contrasting levels of heterozygosity: (1) low heterozygosity cotton-top tamarins (N = 324), (2) presumably normally heterozygous Illiger's saddle-back tamarins (N = 208), and (3) relatively highly heterozygous hybrids between saddle-back tamarin subspecies (N = 31). All specimens originated at the Oak Ridge Associated Universities' Marmoset Research Center. A nested ANOVA design was used to separate out variation due to individual differences, side-to-side differences (fluctuating asymmetry), and measurement error. We found statistically significant levels of fluctuating asymmetry in nearly all of the traits surveyed and a negative correlation between levels of fluctuating asymmetry and genetic heterozygosity. Efforts to use fluctuating asymmetry to identify populations endangered by reduced genetic variability and/or under stress may be inhibited by small sample sizes, neglect of repeated measures, and lack of appropriate reference populations.

Animals↗
PubMedDate not supplied

A quantitative genetic analysis of localized morphology in mandibles of inbred mice using finite element scaling analysis.

We analyzed patterns of mandibular genetic and phenotypic morphological integration and the relationship of genealogy to interstrain molecular and morphological differences in ten inbred strains of mice. Positions of mandibular landmarks in two-dimensional space were used to construct a finite element mesh for each individual, then all individuals from the ten strains were compared to the average mandible from a standard strain (SEA/GnJ). Measures of size and shape associated with finite element scaling analysis were then used in a quantitative genetic analysis of mandibular variation. Significant genetic variation for mandibular size and shape was uncovered. Patterns of both genetic and phenotypic correlation for measures of landmark-specific sizes were consistent with models of morphological integration based on the developmental origin of parts of the mandible and on the effects of muscle attachment on mandibular morphology. Shape differences local to particular landmarks did not show these forms of morphological integration. Although interstrain distances based on local shape magnitudes were significantly correlated with genealogical relationship, distances based on local size differences were not. Even higher than the correlation of genealogy with distances based on local shape magnitude was the genealogical-molecular distance correlation. Patterns of morphometric mandibular variation corresponded to expected effects of epigenetic developmental processes. Also, when detailed shape differences were considered, morphology served as a rough guide to genealogy, although molecular distances showed a stronger relationship.

Animals↗