Age changes in the external dimensions of adult bone

Humeri from a large, ossuary-derived sample are used to demonstrate that considerable size variability is introduced to transverse skeletal measurements when young adults and older adults are pooled. Humeri from young adults (epiphyseal lines still visible, N ≈? 25) are smaller in transverse dimensions than those of older adults (N ≈? 300). Among left humeri, only shaft diameters demonstrate statistically significant differences. The right humeri, however, show statistically significant differences for six of the eight measurements. The increased size of the older adult humeri reflects the fact that appositional growth continues throughout adulthood. The more pronounced differences seen on the right side probably reflect developing dominance asymmetry. Recognition of this source of intrasample variability will influence the choice of skeletal measurements used for population comparisons and/or indicators of robusticity.     

Age changes in bone

Changes in bone structure as a function of age have been studied by simple inspection, x-ray imaging, stereo-photography, deep field optical microscopy, circularly polarised light microscopy, and scanning electron microscopy (SEM), including both topographic and compositional backscattered electron (BSE) imaging modes. The study of bone as a three-dimensional object, rather than in thin sections, enables us to envisage modelling and remodelling processes in context. The study of ultra-flat block surfaces permits the acquisition of data from an effectively very thin layer in the block face, and to examine bone as a spectrum of tissue types varying in the degree of mineralisation. Particular attention has been paid in our earlier studies to the iliac crest, lumbar vertebral bodies, femoral mid-shaft, neck and head and parietal and frontal skull bones. Recently, we have compared findings from these sites with observations on the mandible. We conclude, from our new imaging data, that common generalisations about the changes in bone in ageing and osteoporosis are too simplified, and that the mandible differs sufficiently from post-cranial skeletal sites that it would be unwise to extrapolate from findings in the jaw to the circumstances elsewhere.     

Seasonal changes in the brain and skull sizes of small mammals

A comparative study of seasonal-age dynamics of brain size in six small mammal species, Clethrionomys glareolus, C. rutilus, Microtus oeconomus, M. gregalis (Rodentia); Sorex araneus, S. minutis (Insectivora) has been carried out. The analysis of seasonal changes in brain weight confirms the existence of autumn-winter regression of brain weight, which takes place at the organism level. The regression is less pronounced in voles than in shrews. The decrease in brain weight both in voles and in shrews is accompanied by the decrease in height (capacity) of brain capsule of cranium. In spring the brain weight increase and reaches its maximal specific values in wintered voles in summer. In wintered shrews the brain weight never reaches the value, inherent in young animals before winter regression. The analysis of the data obtained and published data on variability of craniometric features allowed to conclude that seasonal changes in brain size, accompanied by the changes in capacity of cranium capsule might be considered as a general pattern for a large group of palearctic and nonarctic species of small mammals.     

Age differences in craniofacial dimensions among adults from Indian Knoll,Kentucky

Adult craniofacial expansion with aging has recently been documented in a living US white population sample (Israel, '73a, '77). The present study extends these findings to a prehistoric Amerindian skeletal sample from the Indian Knoll, Kentucky site. Sixteen craniofacial dimensions available for 136 adult males were compared in younger (20–34 years) and older (35–50 years) age groups. Of these, six dimensions showed a significant difference between age groups; all significantly different dimensions were larger in the older adult age group. The multivariate (T²) difference between age groups was highly significant. Comparison of results before and after a size standardization indicated that the majority of differences between age groups were associated with an overall size increase, or expansion with aging, and did not represent merely remodeling, or “shape” changes. The pattern of craniofacial change with age appeared generally similar to that observed in the modern US white sample; however, some differences were noted. It is shown that the age trends observed at Indian Knoll are most likely to reflect true craniofacial growth in size among the adult male inhabitants of the site, rather than secular trends or other artifacts of the sampling procedure. The causes for continuing adult craniofacial expansion are unknown, and probably involve a complex interaction of many factors. However, this pattern of change with age among adults does appear to be characteristic of population samples of widely differing genetic and environmental backgrounds.     

Local changes in uterine dimensions in the pregnant pig

Twenty gilts were used in a study to determine local utilization of space by fetuses in the uterus under crowded or roomy conditions. Between Days 2 and 4 after onset of estrus and mating, the uterus was ligated to leave one and one-half times as much space for embryos in one side of the uterus (roomy) as in the other (crowded). At a second surgery on Day 28, serosal sutures were placed to mark the placental boundaries and every third embryo in the crowded side was crushed. Gilts were slaughtered on Day 100 and measurements taken on the uterus and fetuses. Survival from Day 28 to Day 100 of fetuses that were not crushed was 57% in the roomy side of the uterus versus 40% in the crowded side (P = 0.42). No differences were found between crowded and roomy sides for fetal crown rump length, weight or placental surface area. The length of segment occupied on Day 28 by fetuses surviving to Day 100 in both crowded and roomy sides was greater than the mean length occupied by all embryos present on Day 28. The length of segment occupied by surviving fetuses increased by 9.4 ± 1.4 cm from Day 28 to Day 100, and the length of segment on Day 28 occupied by a fetus that was crushed decreased by 2.0 ± 0.8 cm. The internal vascular area of the uterus associated with a surviving fetus on Day 100 did not extend beyond the suture placed in the serosa on Day 28, indicating that the surviving fetuses did not make use of space vacated by nonsurviving littermates.