VERTICAL JUMPING PERFORMANCE BY KANGAROO RATS: INFLUENCE OF MUSCULOTENDON PROPERTIES

Kangaroo rats (dypodomys deserti) are bipedal hopping animals that have the ability to vertically jump many times its standing hip height. This ability is essential to avoid its predators. The kangaroo rat plantarflexors, i.e., the plantaris (PL), lateral gastrocnemius (LG) and medial gastrocnemius (MG), deliver the greatest contribution to the moment and power at ankle joint during its vertical jumping. To investigate the influences of the musculotendon properties on vertical jumping performance by kangaroo rat, we first measured the contractile properties of the plantarflexors as a group and calculated the contribution of individual muscles to the group properties. Second, we measured the mechanical properties of the tendons of PL and GAS (LG and MG common tendons) and compared their properties to those of white rat. Finally, we integrated the measured properties into a computer modeling to calculate the dynamics of plantarflexor muscle-tendon units during vertical jumps. Our results indicated that kangaroo rats have fast-type muscles with the maximum stress in the higher range of reported data for comparable sized species. Our results also showed that kangaroo rats have tendons with exceptional material properties which are specially adapted for high motor performance. Finally, the results of forward dynamic simulations indicated that the plantarflexor muscle-tendon units, specifically tendon properties, of kangaroo rats are optimized to deliver power at ankle joint, which is essential for its vertical jump. Findings of our research have implications to understanding how individual muscles within a synergistic group can be organized to optimize specific motor functions

An investigation on callogenesis and antioxidant capacity of different explants of Teucrium polium

Kalpoureh (Teucrium polium L.) as a medicinal plant belongs to family Lamiaceae. This plant has short growth period and endangered, so it seems the method of plant tissue culture is efficient for that. On the other hand Teucrium polium with high antioxidant properties has many health benefits. In this study, the effect of culture medium, different concentrations of 2, 4-D and the type of explants on callus induction were evaluated. It was found that effective treatment for more fresh weight of callus was the leaf explants on B5 culture with concentrations 1 and 0.5 mg L-1 of 2,4-D. In no hormone treatments, the percentage of callus induction was lower than others and the highest percentage of callus induction was on medium containing higher levels of the hormone. Analysis of biochemical properties (total phenolic content, antioxidant capacity based on two tests; DPPH and PPM) was also concluded that callus of terminal bud on B5 medium with no hormones had the highest total phenol (82.66 mgGAE/100 g FW). Based on DPPH test, the most free radicals scavenging potential was seen for the leaves collected from the habitat and the callus of terminal bud explants on B5 medium with concentration of 0.5 mg L-1 2, 4-D. Investigation on total antioxidant capacity also revealed that callus of terminal bud on MS medium, 2 mg L-1 2,4-D, leaves and stems of plants collected from habitats showed more activities. These conditions can provide the suggestion for the use of these media to produce more secondary metabolites with antioxidant properties