In vivo strains in the femur of the nine-banded armadillo (Dasypus novemcinctus).

The capacity of limb bones to resist the locomotor loads they encounter depends on both the pattern of those loads and the material properties of the skeletal elements. Among mammals, understanding of the interplay between these two factors has been based primarily on evidence from locomotor behaviors in upright placentals, which show limb bones that are loaded predominantly in anteroposterior bending with minimal amounts of torsion. However, loading patterns from the femora of opossums, marsupials using crouched limb posture, show appreciable torsion while the bone experiences mediolateral (ML) bending. These data indicated greater loading diversity in mammals than was previously recognized, and suggested the possibility that ancestral loading patterns found in sprawling lineages (e.g., reptilian sauropsids) might have been retained among basal mammals. To further test this hypothesis, we recorded in vivo locomotor strains from the femur of the nine-banded armadillo (Dasypus novemcinctus), a member of the basal xenarthran clade of placental mammals that also uses crouched limb posture. Orientations of principal strains and magnitudes of shear strains indicate that armadillo femora are exposed to only limited torsion; however, bending is essentially ML, placing the medial aspect of the femur in compression and the lateral aspect in tension. This orientation of bending is similar to that found in opossums, but planar strain analyses indicate much more of the armadillo femur experiences tension during bending, potentially due to muscles pulling on the large, laterally positioned third trochanter. Limb bone safety factors were estimated between 3.3 and 4.3 in bending, similar to other placental mammals, but lower than opossums and most sprawling taxa. Thus, femoral loading patterns in armadillos show a mixture of similarities to both opossums (ML bending) and other placentals (limited torsion and low safety factors), along with unique features (high axial tension) that likely relate to their distinctive hindlimb anatomy.

In vivo strains in the femur of the Virginia opossum (Didelphis virginiana) during terrestrial locomotion: testing hypotheses of evolutionary shifts in mammalian bone loading and design.

Terrestrial locomotion can impose substantial loads on vertebrate limbs. Previous studies have shown that limb bones from cursorial species of eutherian mammals experience high bending loads with minimal torsion, whereas the limb bones of non-avian reptiles (and amphibians) exhibit considerable torsion in addition to bending. It has been hypothesized that these differences in loading regime are related to the difference in limb posture between upright mammals and sprawling reptiles, and that the loading patterns observed in non-avian reptiles may be ancestral for tetrapod vertebrates. To evaluate whether non-cursorial mammals show loading patterns more similar to those of sprawling lineages, we measured in vivo strains in the femur during terrestrial locomotion of the Virginia opossum (Didelphis virginiana), a marsupial that uses more crouched limb posture than most mammals from which bone strains have been recorded, and which belongs to a clade phylogenetically between reptiles and the eutherian mammals studied previously. The presence of substantial torsion in the femur of opossums, similar to non-avian reptiles, would suggest that this loading regime likely reflects an ancestral condition for tetrapod limb bone design. Strain recordings indicate the presence of both bending and appreciable torsion (shear strain: 419.1 ± 212.8 µÎµ) in the opossum femur, with planar strain analyses showing neutral axis orientations that placed the lateral aspect of the femur in tension at the time of peak strains. Such mediolateral bending was unexpected for a mammal running with near-parasagittal limb kinematics. Shear strains were similar in magnitude to peak compressive axial strains, with opossum femora experiencing similar bending loads but higher levels of torsion compared with most previously studied mammals. Analyses of peak femoral strains led to estimated safety factor ranges of 5.1-7.2 in bending and 5.5-7.3 in torsion, somewhat higher than typical mammalian values for bending, but approaching typical reptilian values for shear. Loading patterns of opossum limb bones therefore appear intermediate in some respects between those of eutherian mammals and non-avian reptiles, providing further support for hypotheses that high torsion and elevated limb bone safety factors may represent persistent ancestral conditions in the evolution of tetrapod limb bone loading and design.

Transmission of STLV in a closed colony of macaques.

A 3.3% seroprevalence of simian T-lymphotropic virus (STLV) was found in a closed breeding and research colony of rhesus and cynomolgus macaques in Thailand. Epidemiology of STLV within the colony was assessed by means of a retrospective analysis of banked and freshly collected serum samples, and a review of the animals' medical records. Evidence was found that the virus had been imported into the colony by some of the original animals, and was subsequently transmitted both vertically and horizontally. The cell-associated nature of STLV was demonstrated by iatrogenic transmission of the virus following a whole blood transfusion, but there was no transmission to animals that received only serum from the same infected donor. Transmission by all routes was infrequent, as indicated by the overall seroprevalence of 3.3% (14 of 420 samples) after the colony had been closed for 11 years. Maternal-infant transmission appeared to be < 12%.

The impact of alcohol use in community-dwelling older adults.

The purpose of this study was to explore the use of alcohol in community-dwelling older adults and to consider differences in physical and mental health, function, cognitive status, and social supports between those who drink minimal (1 to 3 glasses weekly), moderate (4 to 7 glasses weekly), or no alcohol. A total of 3305 older adults with a mean age of 81.6 -/+ 6.0 participated in the study. Twenty-two percent (n = 709) of the participants had 1 to 3 drinks weekly, only 1% (n = 18) reported 4 to 7 drinks weekly, and none of the participants admitted to 8 or more drinks. There was no difference in drinking behavior with regard to age (F = 1.1, p >.05) or social supports (F =.39, p >.05). There was a difference in drinking behavior with regard to physical health (F = 4.9, p <.05), functional status (F = 7.7, p <.05), cognitive status (F = 11.8, p <.05), and mental health (F = 6.9, p <.05). Health care providers should use an individualized approach to alcohol use in older adults and help these individuals establish, as appropriate, safe drinking habits that will augment health and quality of life.