Pathophysiology of aging bone

Deterioration of organ and systems function are the principal signs of aging. Aging is also believed to be a major factor in the loss of bone mass and quality, which in turn leads to an increase in the risk of fractures. Several factors seem to contribute to this scenario, with metabolic changes related to aging in the bone tissue itself being among them. Most of the current knowledge on the mechanisms associated with osteopenia/osteoporosis during aging has been generated from research in animal models (mainly rats and mice) and cell cultures derived from subjects of different ages. In this work, we have reviewed and summarised these studies, which have begun to establish the physiological and molecular basis of the bone alterations related to aging.     

Super-induction of Dicer-2 expression by alien double-stranded RNAs: an evolutionary ancient response to viral infection?

Dicer-2 is a ribonuclease involved in the insect RNAi pathway. On attempting to knockdown Dicer-2 expression in the insect Blattella germanica by RNAi, we found that treatment with Dicer-2 dsRNA upregulated the targeted mRNA. This unexpected result was also observed after treating with a nucleopolyhedrovirus dsRNA. Experiments with this alien dsRNA showed an all-or-none response with a threshold for inducing Dicer-2 upregulation between 0.4 and 0.04 μg in terms of dsRNA concentration and between 50 and 20 bp in terms of dsRNA length. The response seems specific of dsRNA given that equivalent experiments carried out with dsDNA did not affect Dicer-2 expression. In insects, Dicer-2 is postulated to be a sensor of viral infections and a key antiviral defense element. The upregulation of Dicer-2 expression after dsRNA administration fits well with this sensor role, and the occurrence of this mechanism in B. germanica, a phylogenetically basal insect, suggests that sensing alien RNAs might be an ancestral function of Dicer-2 proteins.     

Atypical reproductive cycles in a population of Sceloporus grammicus (Squamata: Phrynosomatidae) from the Mexican Plateau

The spiny lizard Sceloporus grammicus (Squamata: Phrynosomatidae) is a small reptile from central México and the southern United States, occurring in a wide geographic area characterized by extensive variation in topographic and climatic regimes. Genetic variation among lineages from central México is substantial, though the extent to which this variation corresponds with life-history traits remains obscure. To address part of this puzzle, we studied a population of S. grammicus from Tepeapulco, Hidalgo, México. Male-biased sexual dimorphism was extensive in this population; males were larger than females overall, and expressed proportionately larger heads and longer limbs. Minimum size at sexual maturity was similar in the sexes (males: 43 mm; females: 42 mm). In contrast to other populations from the Central Plateau, reproductive activity of males and females was synchronous. Testicular recrudescence of adult males was initiated in October-November, and maximum testis size maintained from December to July. Female reproductive activity showed no clear seasonal pattern: females had vitellogenic follicles from October to July, and pregnant females were found throughout the year. Female body size was not related to litter size. Neither male nor female gonadal mass was correlated with any abiotic environmental variable examined. Differences in reproductive characteristics among populations of S. grammicus might be indicative of plasticity in response to local environmental conditions, local adaptation, or complex gene × environment interactions. We consider these results in the context of previously studied populations of S. grammicus from the Central Plateau and elsewhere, and propose directions for future research.     

Signaling pathways of immobilized FGF-2 on silicon-substituted hydroxyapatite

Therapeutic strategies for bone regeneration involve the selection of suitable biomaterials, growth factors, and cell types to mimic the cellular microenvironment where molecular and mechanical signals control the reconstruction of bone tissue. The immobilization of basic fibroblast growth factor (FGF-2) on powdered silicon-substituted hydroxyapatite (Si-HA) allows to prepare a biofunctional biomaterial able to interact with bone cells in a very specific way. The biological activity of FGF-2/Si-HA, evaluated in Saos-2 osteoblasts and MC3T3-E1 preosteoblasts through the PLCγ and MAPK/ERK signal transduction pathways, shows that FGF-2 immobilized on Si-HA provides the right signals to cells stimulating crucial intracellular mechanisms of osteoblast proliferation and differentiation.     

Non-masticatory uses of anterior teeth of Sima de los Huesos individuals (Sierra de Atapuerca, Spain)

In this study we examine the labial and occlusal surfaces of incisors and canines of hominins recovered from the Sima de los Huesos (SH), middle Pleistocene site, in order to establish the possible extra-masticatory use of anterior teeth. We have compared the microwear of these fossils with microwear from the anterior teeth of Australian Aborigines, a population characterized by ethnographic evidence of the use of their teeth as a third hand. These two samples of teeth were microscopically analyzed using Scanning Electron Microscopy (SEM). Our results support the “cultural” origin of microwear observed on fossil teeth: we conclude that the SH hominins used their anterior teeth as a “third hand” for para- or extra-masticatory activities.     

Expression of Arabidopsis APETALA1 in tomato reduces its vegetative cycle without affecting plant production

Important agronomic traits such as fruit quality, harvesting efficiency or production largely depend on flowering time. We have analysed the effect of the overexpression of the Arabidopsis APETALA1 MADS-box gene on vegetative and reproductive growth of tomato. Constitutive expression of APETALA1 in tomato plants has major effects on the length of their growth cycle as well as on their growth habit. Transgenic tomato plants initiated flowering after the production of 6 vegetative nodes as compared to 11 nodes for the wild type plants. Most of tomato 35S:AP1 plants also showed determinate growth habit, similar to the phenotype of self pruning tomato mutants, as well as an initial reduction of their axillary growth. Moreover, development and fertility of flowers were not affected in plants expressing AP1. Consequently, fruit formation in transgenic plants grown under greenhouse conditions occurred normally, which permitted a similar fruit yield compared to control plants. Since traits conferred by AP1 expression are dominant, its expression in tomato breeding lines could provide advantages for the development of new hybrid varieties with shorter generation time, determinate growth, and reduced pruning requirements.     

Factors shaping European rabbit abundance

This study analyses differences in European rabbitOryctolagus cuniculus (Linnaeus, 1758) abundance between fragmented and continuous populations and the relative importance of habitat structure (micro- and macrohabitat) and isolation in determining the abundance pattern in fragmented and continuous areas of central Spain. The species was mainly restricted to mediterranean vegetation habitat. In fragmented areas, rabbit abundance was linked to scrubland cover but was not correlated to pasture/cropland cover. The model explained very little of the observed variance. Distance to continuous populations did not improve the model. Stochastic phenomena or unmeasured factors (predation level, soil type) could be acting in this context. Rabbits were more abundant in continuous areas than in fragmented ones. In continuous areas, rabbit abundance was associated with mosaics of pastures, scrublands, and croplands. These habitat features are linked to shelter and feeding requirements of rabbits. The model explained an important part of the observed variance. This supports that management and conservation strategies should be based on the landscape pattern in each situation.