Effects of Different Types of Jump Impact on Trabecular Bone Mass and Microarchitecture in Growing Rats

Substantial evidence from animal studies indicates that jumping increases bone mass and strength. However, most studies have focused on the take-off, rather than the landing phase of jumps. Thus, we compared the effects of landing and upward jump impact on trabecular bone mass and microarchitecture. Male Wistar rats aged 10 weeks were randomly assigned to the following groups: sedentary control (CON), 40-cm upward jumps (40UJ); 40-cm drop jumps (40DJ); and 60-cm drop jumps (60DJ) (n = 10 each). The upward jump protocol comprised 10 upward jumps/day, 5 days/week for 8 weeks to a height of 40 cm. The drop jump protocol comprised dropping rats from a height of 40 or 60 cm at the same frequency and time period as the 40UJ group. Trabecular bone mass, architecture, and mineralization at the distal femoral metaphysis were evaluated using microcomputed tomography. Ground reaction force (GRF) was measured using a force platform. Bone mass was significantly higher in the 40UJ group compared with the DJ groups (+49.1% and +28.3%, respectively), although peak GRF (−57.8% and −122.7%, respectively) and unit time force (−21.6% and −36.2%, respectively) were significantly lower in the 40UJ group. These results showed that trabecular bone mass in growing rats is increased more effectively by the take-off than by the landing phases of jumps and suggest that mechanical stress accompanied by muscle contraction would be more important than GRF as an osteogenic stimulus. However, the relevance of these findings to human bone physiology is unclear and requires further study.     

Differential effects of jump versus running exercise on trabecular architecture during remobilization after suspension-induced osteopenia in growing rats

High-impact exercise is considered to be very beneficial for bones. We investigated the ability of jump exercise to restore bone mass and structure after the deterioration induced by tail suspension in growing rats and made comparisons with treadmill running exercise. Five-week-old male Wistar rats (n = 28) were randomly assigned to four body weight-matched groups: a spontaneous recovery group after tail suspension (n = 7), a jump exercise group after tail suspension (n = 7), a treadmill running group after tail suspension (n = 7), and age-matched controls without tail suspension or exercise (n = 7). Treadmill running was performed at 25 m/min, 1 h/day, 5 days/wk. The jump exercise protocol consisted of 10 jumps/day, 5 days/wk, with a jump height of 40 cm. Bone mineral density (BMD) of the total right femur was measured by dual-energy X-ray absorptiometry. Three-dimensional trabecular bone architecture at the distal femoral metaphysis was evaluated using microcomputed tomography. After 5 wk of free remobilization, right femoral BMD, right hindlimb muscle weight, and body weight returned to age-matched control levels, but trabeculae remained thinner and less connected. Although both jump and running exercises during the remobilization period increased trabecular bone mass, jump exercise increased trabecular thickness, whereas running exercise increased trabecular number. These results indicate that restoration of trabecular bone architecture induced by jump exercise during remobilization is predominantly attributable to increased trabecular thickness, whereas running adds trabecular bone mass through increasing trabecular number, and suggest that jumping and running exercises have different mechanisms of action on structural characteristics of trabecular bone.     

Population genomics study for the conservation management of the endangered shrub Abeliophyllum distichum

Natural monuments are IUCN Category III protected areas that play an important role in biodiversity conservation as they provide species refuge and allow species migration. Despite their status, natural monuments are often confined to cultural and fragmented landscapes due to anthropogenic land-use demands. In this population genomic study, we surveyed 11 populations of the endemic shrub Abeliophyllum distichum Nakai (Oleaceae), including five natural monument habitats, covering its range-wide distribution in South Korea. Using 2,254 SNPs as markers, our results showed a mean expected heterozygosity (He) of 0.319, with populations in the central distribution showing significantly higher He than those at the periphery. There was no significant heterozygote deficiency and inbreeding among studied populations overall (F_{IS =} ?0.098), except for a single natural monument population (GS-NM147). Population structure and differentiation was moderate to high (F_ST?=?0.196), while recent gene flow between populations appeared weak, which can be attributed to the fragmented distribution and the outcrossing mating system of the heterostylous plant. Based on these findings, we provide suggestions for the population conservation and management of this endangered species.

     

Molecular evidence for hybrid origin of Aster chusanensis,an endemic species of Ulleungdo,Korea

Ulleungdo is a small volcanic island and harbors many endemic plant species. Aster chusanensis Lim et al., a recently discovered endemic species on the island was proposed to be derived from hybridization between A. pseudoglehnii Lim et al. and A. oharai Nakai. To test hybrid origin of A. chusanensis, we sequenced the nrITS and three non-coding regions of a plastid genome (trnL-F, rbcL-accD, and psbA-trnH) from eight accessions of A. chusanensis and 37 accessions of its putative parents. Extensive investigation of the genome of A. chusanensis using 160 nrITS PCR amplicon sequences confirmed co-occurrence of nrITS sequences of the parental species within all accessions sampled. The retention of intact parental nrITS types in the genomes of A. chusanensis suggests that hybrid speciation has occurred recently on the island. The plastid DNA sequence data indicate that all of the hybrid individuals inherit the plastid from A. pseudoglehnii, except for one, which has the plastid of A. oharai, implying bidirectional but highly biased hybridization events during the evolution of A. chusanensis. Results of this study suggest that hybridization is an important process in the diversification of indigenous plants on Ulleungdo.     

Molecular Systematic Study of <Emphasis Type="Italic">Chrysosplenium</Emphasis> Series <Emphasis Type="Italic">Pilosa</Emphasis> (Saxifragaceae) in Korea

To address systematic issues pertaining to series Pilosa of Korean Chrysosplenium, the phylogenetic relationships of the 35 accessions of Korean Chrysosplenium taxa were examined using the DNA sequence data obtained from the nuclear ribosomal internal transcribed spacer (ITS) regions and the psbK-I gene of the plastid genome. The results from both ITS and psbK-I sequence data indicated that Chrysosplenium flaviflorum formed a well-supported clade that merits species status of the taxon. The ITS phylogenetic trees detected two distinct lineages in Chrysosplenium pilosum var. fulvum. Geographically, one lineage was widely distributed throughout the country whereas the other was confined to Gyeonggi and Gangwon provinces. The plants sampled from Jeju Island, which have been recognized as C. pilosum var. sphaerospermum [C. hallaisanense] exhibited no DNA sequence feature segregating them from C. pilosum var. fulvum [C. barbatum] distributed in the mainland area of Korea. The plastid DNA sequence data was not fully in concordance with the nuclear ribosomal ITS data and the current taxa delimitation. These results suggest incomplete lineage sorting or that plastid genome capture may have occurred during the evolution of some taxa examined in the present study.     

Gln-362 of Angiopoietin-2 Mediates Migration of Tumor and Endothelial Cells through Association with α5β1 Integrin

Angiopoietin-2 (Ang-2) not only regulates angiogenesis by binding to its well known receptor Tie2 on endothelial cells but also controls sprouting of Tie2-negative angiogenic endothelial cells and invasion of Tie2-negative non-endothelial cells by binding to integrins. However, the molecular mechanism of the Ang-2/integrin association has been unclear. In this study, we found that the Gln-362 residue of Ang-2 was essential for binding to α5β1 integrin. A Q362E Ang-2 mutant, which still bound to Tie2, failed to associate with α5β1 integrin and was unable to activate the integrin downstream signaling of focal adhesion kinase. In addition, unlike wild-type Ang-2, the Q362E Ang-2 mutant was defective in mediating invasion of Tie2-negative glioma or Tie2-positive endothelial cells. Furthermore, the tailpiece domain of the α5 subunit in α5β1 integrin was critical for binding to Ang-2. Taken together, these results provide a novel insight into the mechanism of integrin regulation by Ang-2, which contributes to tumor invasion and endothelial cell migration in a Tie2-independent manner.     

ANKRD9 is associated with tumor suppression as a substrate receptor subunit of ubiquitin ligase

Background

Human ANKRD9 (ankyrin repeat domain 9) expression is altered in some cancers.