Mechanochemical mechanisms of embryonic stem cell pluripotency and differentiation

Embryonic stem (ES) cell biology is attracting much attention in cell biology because of their pluripotent behaviors and potential therapeutic applications. However,what maintains ES cell pluripotency and what triggers ES cell

Mechanism of rice variety resistance to the yellow stem borer,Scirpophaga incertulas (Walker)

Yellow stem borer(YSB),Scir-pophaga incertulas(Walker)has be-come the main rice insect pest onceagain along the Changjiang Riversince 1990s.Unfortunately,no ricevariety with resistance to YSB hasbeen reported so far.Japonica Zhen-dao 2 with moderate resistance toYSB was found.In 10 rice vari-eties with different resistance levels,YSB individuals showed distinct de-velopmental rates,and the asyn-chronous development even occurredin the same rice variety.In this

Fracture mechanism and separation conditions of pineapple fruit-stem and calibration of physical characteristic parameters

At present,the research on the physical composition and properties of pineapple plants is scarce,and the uncertainty of fruit picking method is the key bottleneck factor hindering the research and development of pineapple harvesting machinery.Based on the statistics of survey data from many places,this paper analyzes the fruit-stem fracture mechanism and the theoretical conditions for optimal separation through structural modeling,mechanical behavior analysis and function judgment.On this basis,the“pineapple plant fixation bench”and“fruit-stem bending separation torque test equipment”were developed,and large-size,small-size tests and random optimization tests were carried out successively.The test results showed that the larger of the stem-stalk fixation distance,the more torque and fracture starting angle required for fruit fracture would increase,and the change range was small when the stem-stalk fixation distance was within 50 mm,and the probability of brittle fracture and complete separation was very high.When the space between the fracture section and the fruit-stem connecting point is about 5mm,the range of bending moment value required for the fruit-stem fracture is 1.88 to 2.77 N·m,the range of fracture starting angle is 12.2°to 18.1°,and the angular travel range during the separation process is 82.9°to 87.5°.When the stem-stalk fixation distance is about 15 mm,it is the best fruit-stem separation condition and the breaking torque measured in the verification test is about 2.76 N·m.The fracture starting angle is about 13.8°,the maximum prediction error is 13.1%,and the elastic modulus near the fruit-stem joint ranges from 16.1 to 23.9 MPa.This conclusion can provide an important design basis for the research and development of pineapple field picking robot and harvesting equipment.

Effect of the same mechanical loading on osteogenesis and osteoclastogenesis in vitro

Purpose： To investigate the influence of the same mechanical loading on osteogenesis and osteoclastogenesis in vitro. Methods： Primary osteoblasts, bone marrow-derived mesenchymal stem cells （BMSCs, cultured in osteoinductive medium） and RAW264.7 cells cultured in osteoclast inductive medium were all subjected to a 1000μstrain （μs） at 1 Hz cyclic mechanical stretch for 30 min （twice a day）. Results： After mechanical stimulation, the alkaline phosphatase （ALP） activity, osteocalcin protein level of the osteoblasts and BMSCs were all enhanced, and the mRNA levels of ALP and collagen type I increased. Additionally, extracellular-deposited calcium of both osteoblasts and BMSCs increased. At the same time, the activity of secreted tartrate-resistant acid phosphatase, the number of tartrate-resistant acid phosphatase-positive multinucleated cells, matrix metalloproteinase-9 protein levels of RAW264.7 cells and the extracellular calcium solvency all decreased. Conclusion： The results demonstrated that 1000 μs cyclic mechanical loading enhanced osteoblasts activity, promoted osteoblastic differentiation of BMSCs and restrained osteoclastogenesis of RAW264.7 cells in vitro.