Contractile and histochemical properties of regenerating cross-transplanted fast and slow muscles in the rat

Summary The soleus (SOL) or extensor digitorum longus (EDL) muscles of month-old rats were denervated for 14 days and then cross-transplanted so that the fast muscle was placed into the bed of the slow muscle and vice versa. At 17, 30, 60, and 90 days the transplants were tested for certain contractile and histochemical properties. By 90 days the cross-transplanted SOL showed complete conversion of the full contraction time and nearly complete conversion of the half relaxation time to those of the normal EDL. In contrast, the contraction and relaxation times of the cross-transplanted EDL became considerably slowed, but did not attain the values of the normal SOL. Histochemical staining for ATPase and SDH activity demonstrated similar transformations of fiber types. The degree of transformation of twitch and histochemical characteristics in cross-transplanted muscles was greater than the values reported after cross-innervation of the same muscles. The cross-transplantation model has certain advantages over nerve cross-union experiments because the cross-transplanted muscle is placed in the normal functional environment of the other muscle.Supported by grants from the Muscular Dystrophy Associations of America and a scientific exchange between the Academies of Sciences of Czechoslovakia and the United States.     

岩藻黄素的理化与生物学特性、制备技术及其生理活性研究进展

岩藻黄素,又称岩藻黄质或褐藻黄素,是1种脂溶性色素,为胡萝卜素的含氧衍生物,含有1个多烯烃骨架,属于丙二烯型类胡萝卜素。它主要来源于异鞭藻门的褐藻和硅藻以及定鞭藻门的藻类。本文介绍了岩藻黄素的理化性质、生物学特性及其生物合成途径,并对岩藻黄素经典的与现代绿色的提取方法以及多种分离纯化技术进行了详细介绍。同时对岩藻黄素的各种生理活性,包括抗炎、抗肿瘤、抗肥胖、抗氧化、抗痘、抗糖尿病、抗疟疾和抗血脂等方面的研究进展进行了综述性的报道。     

Fracture of bone tissue: The 'hows' and the 'whys'

The mechanical performance of bone is of paramount importance for the quality of life we experience. The structural integrity of bone, its hierarchical structure, organisation and its physicochemical constitution, all influence its ability to withstand loads, such as those seen occasionally in everyday life loading scenarios, which are either above the norm, prolonged, or repetitive. The present review explores three interconnected areas of research where significant progress has been made lately: (i) The recorded mechanical behaviour of bone and the way it fails; (ii) the inner architecture, organisational, hierarchical structure of bone tissue; and (iii) the bone properties at the micro/nanostructural and biophysical level. Exercising a line of thought along a structure/function based argument we advance from ‘how’ bone fractures to ‘why’ it fractures, and we seek to obtain a fresh insight in this field.     

数字光处理型3D打印参数对导板树脂机械性能的影响

目的 探寻多种数字光处理（DLP）型3D打印工艺参数对导板树脂成型件尺寸精度与性能的影响及规律。方法 分别以不同的单层固化时间、层厚、后固化处理时间及模型设置方向为因变量分组，每组使用Sisma everes uno DLP型3D打印机遵循标准分别制备精度、硬度、弯曲强度、拉伸强度的测试试样各15个，测试试样的长（X）、宽（Y）、高（Z），使用邵氏硬度计测试硬度，万能力学试验机测试弯曲强度与拉伸强度，并进行统计学分析。结果 打印件的尺寸精度随着单层固化时间的增加而先升高再降低，1.3 s时精度最高，随着层厚增加而先升高再降低，0.05 mm时精度最高，随着后固化时间的增加而降低，与模型设置方向无显著关系；打印件的硬度受到单层固化时间、层厚及后固化时间影响，与模型设置方向无显著关系；打印件拉伸强度及弯曲强度受到单层固化时间、层厚、模型设置方向及后固化时间的多因素共同影响。单层固化时间在1.3~1.4 s，层厚0.025 mm，模型根据实际形状向Y方向设置，后固化时间10~15 min时，DLP成型件在尺寸精度、硬度、拉伸强度、弯曲强度等综合方面表现相对较优。结论 DLP3D打印的参数与打印件的精度、物理性能之间存在一定的规律，并且不同因素间的影响强弱不同。通过对参数的筛选，可以实现对单层固化时间、层厚、模型设置方向、后固化处理时间的优化，从而提高打印件的精度和物理性能。