The relationship of whole human vertebral body creep to geometric,microstructural, and material properties

Creep, the time dependent deformation of a structure under load, is an important viscoelastic property of bone and may play a role in the development of permanent deformity of the vertebrae in vivo leading to clinically observable spinal fractures. To date, creep properties and their relationship to geometric, microstructural, and material properties have not been described in isolated human vertebral bodies. In this study, a range of image-based measures of vertebral bone geometry, bone mass, microarchitecture and mineralization were examined in multiple regression models in an effort to understand their contribution to creep behavior. Several variables, such as measures of mineralization heterogeneity, average bone density, and connectivity density persistently appeared as significant effects in multiple regression models (adjusted r²: 0.17–0.56). Although further work is needed to identify additional tissue properties to fully describe the portion of variability not explained by these models, these data are expected to help understand mechanisms underlying creep and improve prediction of vertebral deformities that eventually progress to a clinically observable fracture.     

斑马鱼鳃的光镜和透射电镜观察

应用光学显微镜和透射电镜对斑马鱼(Danio rerio)鳃的组织结构及鳃丝、鳃小片超微结构进行了观察。结果表明,斑马鱼有4对全鳃,鳃耙呈长锥状,鳃丝呈梳状排列在鳃弓上,鳃小片均匀排列在鳃丝两侧。鳃小片由上皮细胞、柱细胞、内皮细胞和毛细血管网组成,鳃小片基部和血管周围分布有泌氯细胞,胞内有丰富的线粒体和排泄小泡,根据线粒体形态特征和细胞质电子密度可将其分为两个亚型。黏液细胞通常与泌氯细胞对生存在,并且有通外的开口。斑马鱼鳃组织结构与其他硬骨鱼鳃结构相似,其结构和功能有密切的关系。     

玉米抗倒性与茎秆显微结构的关系

1989年我们对抗倒性不同的12个杂交玉米进行了解剖观察,发现地面上第三节间的茎外围维管束的长宽、维管束下部厚壁细胞的厚度、皮层厚度与田间倒伏率呈现显著的负相关,同一视野内维管束数目与倒伏率呈显著正相关。     

松江鲈鱼皮肤的显微和亚显微结构观察

采用光学显微镜、扫描电镜和透射电镜,对松江鲈鱼（Trachidermus fasciatus）成体皮肤的显微结构和亚显微结构进行了观察。结果表明,松江鲈鱼体表不同部位皮肤的厚薄不一,但基本结构相似。皮肤由表皮和真皮层构成。松江鲈鱼的皮肤裸露无鳞,表皮层较薄,由约4～8层细胞构成,主要由复层上皮细胞和黏液细胞及基底细胞组成。表层细胞呈扁平、多边形, 细胞之间主要靠桥粒紧密连接,连接处形成增厚的边缘嵴状突起。表皮细胞游离面向内凹陷,表面形成指纹状微嵴。黏液细胞呈圆形或卵圆形,散布在上皮细胞之间。黏液细胞内的黏原颗粒具有椭圆颗粒状、均匀致密的块状和疏松丝状3种不同形态。真皮通过基膜与表皮相连,由稀疏层和致密层构成。真皮结缔组织在腹部较厚而在其他部位较薄。表皮与真皮连接处有色素层,头部、背部、尾柄和体侧皮肤色素细胞分布多,色素层明显,而腹部和颏部皮肤缺少色素。松江鲈鱼黄河群体真皮层中有角质棘状突起,而滦河群体则无。头部、体侧和尾柄处皮肤上还分布有侧线孔和表面神经丘等感觉器官。     

Xylem of early angiosperms: Novel microstructure in stem tracheids of Barclaya (Nymphaeaceae)

Pit membranes of stem tracheids of all recognized species of Barclaya, an Indomalaysian genus of Nymphaeaceae, were studied with scanning electron microscopy (SEM). Pit membranes of the tracheids are composed of two thick layers, both constructed of fibrils much larger than those of tracheary elements of angiosperms other than Nymphaeaceae. The outer (distal) layer, which comprises the continuous primary wall around the tracheids, is spongiform, perforated by porosities of relatively uniform size, and confined to or most prominent on end walls of stem tracheids. The second layer consists of thick widely spaced fibrils that are oriented axially and are laid down proximally (facing the cell lumen) to the first (outer) layer, although continuous with it. These axial fibrils are attached at their ends to the pit cavities. This peculiar microstructure is not known outside Nymphaeaceae except in Brasenia and Cabomba (Cabombaceae, Nymphaeales), and has not been previously described for Barclaya. The longitudinally oriented threads and strands in perforation plates of secondary xylem of wood and stems of a variety of primitive woody angiosperms (e.g., Illicium) are not homologous to the pit membrane structure observed in stem tracheids of Barclaya, which, like other Nymphaeaceae, has only primary xylem and no perforation plates. The tracheid microstructure reported here is different from pit structures observed in any other group of vascular plants, living or fossil. The tracheid stem microstructures of Barclaya and other Nymphaeaceae appear to be a synapomorphy of Nymphaeaceae and Cabombaceae, and need further study with respect to ultrastructure and function.     

崇安草蜥舌的显微和超微结构

采用显微技术观察了崇安草蜥(Takydromus sylvaticus)舌的显微和超微结构.舌腹面黏膜光滑;背面黏膜粗糙,由丝状乳头和轮廓乳头组成.丝状乳头锥体形,数量较多,排列成行,分布于舌体背面两侧和侧翼的腹面.在舌的横切片上有3～7个轮廓乳头,其表面平整,周围有环形沟,舌腺开口于环形沟中.舌肌肉发达.超微结构显示,舌上皮细胞问具有紧密连接,舌乳头细胞表面具有丰富的微绒毛.舌腺为单管泡状腺,分泌管由单层柱状上皮构成.柱状上皮细胞有两种,一种为分泌细胞,一种为暗细胞.分泌细胞内有典型的分泌颗粒,可协助食物的吞咽.暗细胞内无分泌颗粒,是否与离子分泌以及渗透压调节有关,尚需进一步证实.     

Quantitative characteristic of the catalytic properties and microstructure of cross-linked enzyme aggregates of penicillin acylase

The microstructure and the catalytic properties of cross-linked enzyme aggregates (CLEA) of penicillin acylase (PA) obtained under different conditions were investigated. The period of time left between the enzyme precipitation and the cross-linking step was found to influence the structural organization of the resulting enzyme preparation. Confocal fluorescent microscopy of the so-called “fresh” and “mature” CLEAs PA allowed to estimate the “characteristic” diameter of CLEA PA particles, which appeared to be about 1.6 μm, and revealed that the “mature” type was composed of relatively big particles as compared to the “fresh” type. Complementary kinetic studies showed that the “mature” CLEA PA were more effective in both hydrolytic and synthetic reactions. It was suggested that the aggregate size might regulate the extent of covalent modification of PA and thereby influence the catalytic properties of CLEA.     

Rheological Characteristics and Microstructure of Common Carp (Cyprinus carpio) Surimi and Kamaboko Gel

Common carp is cheap and prolific in Australian waters and is regarded as an aquatic environmental pest. In order to add value to this fish species, surimi and kamaboko was prepared from common carp and its rheological and microstructure characteristics were compared with those produced from Alaska pollock and threadfin bream. Temperature sweep tests were run under 100-Pa stress and 0.1-Hz frequency, obtained from linear viscoelastic ranges of all tested fish gels. Storage modulus (G′) thermographs of all samples consisted of two positive peaks and a plateau zone in between. The sol-gel transition was completed at about 53 and 61 °C for these Alaska pollock and threadfin bream gels, respectively, whereas it was recorded at about 69 °C for common carp gel. At these temperatures, G′ of Alaska pollock gel was recorded at 330 kPa, which was 71% and 88% greater than that from threadfin bream and common carp gels, respectively. Furthermore, Alaska pollock and threadfin bream gels had greater gel strength than the gel prepared from common carp surimi. Textural quality could be associated with cross-linking in the gel network. From scanning electron microscopy studies, the microstructure of Alaska pollock gel matrix had about 15,450 polygonal structures per square millimeter with an average area of about 9 μm². For threadfin bream and common carp gels, the polygonal structures were larger and 12% and 39% fewer, respectively, than those of Alaska pollock gel. However, these results cannot be only attributed to the species variation among tested fish as some other factors such as harvest location, physiological state, handling and processing method, etc. were not considered in this study.     

史氏鲟外周血细胞的显微及超微结构

采用血细胞计数、光学显微及电子显微技术对二龄史氏鲟外周血细胞的数目、形态及结构进行了研究。二龄史氏鲟红细胞的数目为47.75×104个/mm3,白细胞数目为2.9万个/mm3,其中淋巴细胞所占比率最高。史氏鲟的外周血中除正常红细胞外,还有处于分裂状态及未成熟的红细胞。史氏鲟外周血中的白细胞有四种类型,分别为淋巴细胞、粒细胞、血栓细胞和单核细胞。其中粒细胞有两种,即嗜中性粒细胞和嗜酸性粒细胞。嗜中性粒细胞含有多种形状的核,其中分叶的核数目较多,粒细胞及淋巴细胞均类似于哺乳动物。对史氏鲟外周血细胞细微结构的观察显示:红细胞中具有少量的细胞器;淋巴细胞结构典型;单核细胞较粒细胞稍小且具有较多线粒体;血栓细胞具有梭形和圆形两种,胞质较少,其中梭形的血栓细胞胞质几乎透明;对粒细胞的颗粒按照形状和电子密度进行了分类。     

红瘰疣螈皮肤的显微结构观察

对我国Ⅱ级重点保护野生动物红瘰疣螈(Tylototriton shanjing)成体的皮肤结构进行了显微观察。观察结果表明,其皮肤厚薄、微血管、色素分布,以及腺体的分布和大小等方面在身体的不同部位存在差异:头和背部的皮肤厚于腹部;黑色素细胞多分布于真皮浅层,以腹部及背侧无瘰粒处多见;真皮层富含黏液腺和颗粒腺,但分布不均匀;头嵴棱部及背部瘰粒下方颗粒腺的数量多、体积大,并充满分泌物;表皮下腺体外突,其表皮细胞层数减少,形成分泌物有效通道。同时,将红瘰疣螈皮肤与其他两栖类相比可知,其以上皮肤结构特征均体现了红瘰疣螈对山区阴湿环境中陆栖生活的重要适应。