Melding ecology, classical weed biocontrol, and plant microbial ecology can inform improved practices in controlling invasive plant species

Early research leading to the successful biological control of invasive species such as Opuntia spp., and Hypericum perforatum set examples and provided data useful for research programs that would follow. However, this early work failed to become established as a source of applicable principles for later workers in weed biocontrol. Recently, retrospective and parallel studies have been suggested as a means to reengage with earlier work to derive useful ideas and data to enhance future programs in weed biocontrol. Parallel studies by workers in plant community ecology on the nature of feedback elicited by plant species in their invaded and native range have shown the importance of soil microbial communities in effecting feedback. Retrospective reexamination of previous studies would likely provide clues to other insect–plant pathogen interactions in addition to those described by the author and others. The effects of invasive species in profoundly altering soil microbial communities point to the need for further studies on key microbial species contributing to or driving the impact of biocontrol. These collective data suggest that the desired goal of selecting for and utilizing stronger biocontrol agents to reduce nontarget effects and to increase the impact of biological control programs would be best served by prerelease studies that assess the propensity of a candidate agent for direct or indirect interaction with other agents. This could be assessed through the use of survival analysis. Overall, parallel empirical and retrospective studies should be a necessary part of how biological control is practiced.     

Thigh-calf contact parameters for six high knee flexion postures: Onset,maximum angle,total force,contact area,and center of force

In high knee flexion, contact between the posterior thigh and calf is expected to decrease forces on tibiofemoral contact surfaces, therefore, thigh-calf contact needs to be thoroughly characterized to model its effect. This study measured knee angles and intersegmental contact parameters in fifty-eight young healthy participants for six common high flexion postures using motion tracking and a pressure sensor attached to the right thigh. Additionally, we introduced and assessed the reliability of a method for reducing noise in pressure sensor output. Five repetitions of two squatting, two kneeling, and two unilateral kneeling movements were completed. Interactions of posture by sex occurred for thigh-calf and heel-gluteal center of force, and thigh-calf contact area. Center of force in thigh-calf regions was farther from the knee joint center in females, compared to males, during unilateral kneeling (82 and 67 mm respectively) with an inverted relationship in the heel-gluteal region (331 and 345 mm respectively), although caution is advised when generalizing these findings from a young, relatively fit sample to a population level. Contact area was larger in females when compared to males (mean of 155.61 and 137.33 cm² across postures). A posture main effect was observed in contact force and sex main effects were present in onset and max angle. Males had earlier onset (121.0°) and lower max angle (147.4°) with onset and max angles having a range between movements of 8° and 3° respectively. There was a substantial total force difference of 139 N between the largest and smallest activity means. Force parameters measured in this study suggest that knee joint contact models need to incorporate activity-specific parameters when estimating loading.     

Diurnal changes in xylem pressure and mesophyll cell turgor pressure of the lianaTetrastigma voinierianum — the role of cell turgor in long-distance water transport: a reply

Summary From equilibrium thermodynamics an equation is given to show that in a liquid negative pressures (tensions) are physical reality and may reliably be recorded from any point of the aqueous phase within the xylem conduit by the xylem pressure probe introduced by Balling et al. (Naturwissenschaften 75: 409–411, 1988).     

Endochondral ossification of costal cartilage is arrested after chondrocytes have reached hypertrophic stage of late differentiation

Late cartilage differentiation during endochondral bone formation is a multistep process. Chondrocytes transit through a differentiation cascade under the direction of environmental signals that either stimulate or repress progression from one step to the next. In human costal cartilage, chondrocytes reach very advanced stages of late differentiation and express collagen X. However, remodeling of the tissue into bone is strongly repressed. The second hypertrophy marker, alkaline phosphatase, is not expressed before puberty. Upon sexual maturity, both alkaline phosphatase and collagen X activity levels are increased and slow ossification takes place. Thus, the expression of the two hypertrophy markers is widely separated in time in costal cartilage. Progression of endochondral ossification in this tissue beyond the stage of hypertrophic cartilage appears to be associated with the expression of alkaline phosphatase activity. Costal chondrocytes in culture are stimulated by parathyroid hormone in a PTH/PTHrP receptor-mediated manner to express the fully differentiated hypertrophic phenotype. In addition, the hormone stimulates hypertrophic development even more powerfully through its carboxyterminal domain, presumably by interaction with receptors distinct from PTH/PTHrP receptors. Therefore, PTH can support late cartilage differentiation at very advanced stages, whereas the same signal negatively controls the process at earlier stages.