Time constraints do not limit group size in arboreal guenons but do explain community size and distribution patterns

To understand how species will respond to environmental changes, it is important to know how those changes will affect the ecological stress that animals experience. Time constraints can be used as indicators of ecological stress. Here we test whether time constraints can help us understand group sizes, distribution patterns and community sizes of forest guenons (Cercopithecus/Allochrocebus). Forest guenons typically live in small to medium sized one-male multi-female groups and often live in communities with multiple forest guenon species. We developed a time-budget model using published data on time budgets, diets, body sizes, climate, and group sizes to predict maximum ecologically tolerable group and community sizes of forest guenons across 202 sub-Saharan African locations. The model correctly predicted presence/absence at 83% of these locations. Feeding-foraging time (an indicator of competition) limited group sizes, while resting and moving time constraints shaped guenon biogeography. Predicted group sizes were greater than observed group sizes but comparable to community sizes, suggesting community sizes are set by competition among guenon individuals irrespective of species. We conclude that time constraints and intra-specific competition are unlikely to be the main determinants of relatively small group sizes in forest guenons. Body mass was negatively correlated with moving time, which may give larger bodied species an advantage over smaller bodied species under future conditions when greater fragmentation of forests is likely to lead to increased moving time. Resting time heavily depended on leaf consumption and is likely to increase under future climatic conditions when leaf quality is expected to decrease

Mechanobiological Modulation of Cytoskeleton and Calcium Influx in Osteoblastic Cells by Short-Term Focused Acoustic Radiation Force

Mechanotransduction has demonstrated potential for regulating tissue adaptation in vivo and cellular activities in vitro. It is well documented that ultrasound can produce a wide variety of biological effects in biological systems. For example, pulsed ultrasound can be used to noninvasively accelerate the rate of bone fracture healing. Although a wide range of studies has been performed, mechanism for this therapeutic effect on bone healing is currently unknown. To elucidate the mechanism of cellular response to mechanical stimuli induced by pulsed ultrasound radiation, we developed a method to apply focused acoustic radiation force (ARF) (duration, one minute) on osteoblastic MC3T3-E1 cells and observed cellular responses to ARF using a spinning disk confocal microscope. This study demonstrates that the focused ARF induced F-actin cytoskeletal rearrangement in MC3T3-E1 cells. In addition, these cells showed an increase in intracellular calcium concentration following the application of focused ARF. Furthermore, passive bending movement was noted in primary cilium that were treated with focused ARF. Cell viability was not affected. Application of pulsed ultrasound radiation generated only a minimal temperature rise of 0.1°C, and induced a streaming resulting fluid shear stress of 0.186 dyne/cm2, suggesting that hyperthermia and acoustic streaming might not be the main causes of the observed cell responses. In conclusion, these data provide more insight in the interactions between acoustic mechanical stress and osteoblastic cells. This experimental system could serve as basis for further exploration of the mechanosensing mechanism of osteoblasts triggered by ultrasound

Osteoporosis and the general dental practitioner: Reliability of some digital dental radiological measures

OBJECTIVES: Dental radiographs are relatively inexpensive and are regularly made of a large fraction of the adult population; therefore, they represent an enormous potential as a screening tool for osteoporosis. Monitoring the population by means of dual X-ray absorptiometry (DXA), which is currently the most accepted method for diagnosing osteoporosis, involves enormous costs and facilities. In previous studies, it was shown that the radiographic trabecular pattern shows correlations with the bone mineral density (BMD) as measured by DXA. The objective of this study was to assess the reproducibility of the quantitative analysis of the trabecular pattern on dental radiographs. METHODS: Six regions of interest were selected manually on three digital radiographic images of 20 women. This process was performed 10 times resulting in 1200 image samples. For each image sample 26 parameters were measured. The reliability of the parameters was evaluated by means of Cronbach's alpha. RESULTS: Of the values of Cronbach's alpha 83% is at least 0.9 and 99% is at least 0.8. CONCLUSIONS: The measurements of the parameters used in this study are very reproducible. Therefore, the manual selection of the regions of interest does not introduce large amounts of noise. The imaging parameters potentially offer an accurate tool for the prediction of BMD values. PMID: 18039288 [PubMed - in process

Skeletal bone mineral density in relation to thickness, bone mass, and structure of the mandibular alveolar process in dentate men and women.

Peri-apical radiographs have been used to identify women with low bone mineral density (BMD) in various parts of the skeleton, but their usefulness for men has not been elucidated. The aim of this study was to test if the mandibular bone structure and bone mass in men and women were related to the BMD of the forearms, determined by dual X-ray absorptiometry, in 42 men and 42 women (aged 18-84 yr). Mandibular alveolar thickness was measured in casts, and alveolar \u27bone mass\u27 was estimated on digital radiographs using gray-shade distribution. Alveolar bone structure was evaluated visually (trabecular pattern) on analog radiographs and with its bone texture on digitized radiographs. Bone texture was correlated to BMD in both men and women. BMD was correlated to alveolar bone mass and trabecular pattern in women, but not in men. Bone texture and body mass index (BMI) explained 57% of the variance in BMD for men, whereas trabecular pattern and age explained 50% of the variance in BMD for women. Sparse trabeculation was associated with osteopenia. We conclude that alveolar bone texture and BMI are predictors of BMD for men, and age and trabecular pattern are predictors of BMD for women

Fission-fusion dynamics : new research frameworks.

Renewed interest in fission‐fusion dynamics is due to the recognition that such dynamics may create unique challenges for social interaction and distinctive selective pressures acting on underlying communicative and cognitive abilities. New frameworks for integrating current knowledge on fission‐fusion dynamics emerge from a fundamental rethinking of the term “fission‐fusion” away from its current general use as a label for a particular modal type of social system (i.e., “fission‐fusion societies”). Specifically, because the degree of spatial and temporal cohesion of group members varies both within and across taxa, any social system can be described in terms of the extent to which it expresses fission‐fusion dynamics. This perspective has implications for socioecology, communication, cognitive demands, and human social evolution

The potential of pulsed low intensity ultrasound to stimulate chondrocytes matrix synthesis in agarose and monolayer cultures

Pulsed low intensity ultrasound (PLIUS) has been used successfully for bone fracture repair and has therefore been suggested for cartilage regeneration. However, previous in vitro studies with chondrocytes show conflicting results as to the effect of PLIUS on the elaboration of extracellular matrix. This study tests the hypothesis that PLIUS, applied for 20 min/day, stimulates the synthesis of sulphated glycosaminoglycan (sGAG) by adult bovine articular chondrocytes cultured in either monolayer or agarose constructs. For both culture models, PLIUS at either 30 or 100 mW/cm2 intensity had no net effect on the total sGAG content. Although PLIUS at 100 mW/cm2 did induce a 20% increase in sGAG content at day 2 of culture in agarose, this response was lost by day 5. Intensities of 200 and 300 mW/cm2 resulted in cell death probably due to heating from the ultrasound transducers. The lack of a sustained up-regulation of sGAG synthesis may reflect the suggestion that PLIUS only induces a stimulatory effect in the presence of a tissue injury response. These results suggest that PLIUS has a limited potential to provide an effective method of stimulating matrix production as part of a tissue engineering strategy for cartilage repair. <br/