Structure and formation of the twisted plywood pattern of collagen fibrils in rat lamellar bone

This study was designed to elucidate details of the structure and formation process of the alternate lamellar pattern known to exist in lamellar bone. For this purpose, we examined basic internal lamellae in femurs of young rats by transmission and scanning electron microscopy, the latter employing two different macerations with NaOH at concentrations of 10 and 24%. Observations after the maceration with 10% NaOH showed that the regular and periodic rotation of collagen fibrils caused an alternation between two types of lamellae: one consisting of transversely and nearly transversely cut fibrils, and the other consisting of longitudinally and nearly longitudinally cut fibrils. This finding confirms the consistency of the twisted plywood model. The maceration method with 24% NaOH removed bone components other than cells, thus allowing for three-dimensional observations of osteoblast morphology. Osteoblasts extended finger-like processes paralleling the inner bone surface, and grouped in such a way that, within a group, the processes arranged in a similar direction. Transmission electron microscopy showed that newly deposited fibrils were arranged alongside these processes. For the formation of the alternating pattern, our findings suggest that: (1) osteoblasts control the collagen fibril arrangement through their finger-like process position; (2) osteoblasts behave similarly within a group; (3) osteoblasts move their processes synchronously and periodically to promote alternating different fibril orientation; and (4) this dynamic sequential deposition of fibrils results in the alternate lamellar (or twisted plywood) pattern.     

Real electron microscopic images of collagen fibrils in the endoneurium

Collagen fibrils run in parallel in the endoneurial space, forming fibre bundles. Spaces are evident between these bundles when examined by transmission electron microscopy (TEM). However, the procedures for TEM include chemical fixation, dehydration and embedding, which may cause morphological changes in the specimens. Ultracryo thin sectioning procedures may avoid the artefacts caused by these procedures. An examination of ultrathin frozen sections revealed that the endoneurial space was completely filled with collagen fibrils, with little space between the fibre bundles. These results suggest that the dehydration and/or embedding procedures cause shrinkage of the specimen, resulting in the appearance of a widened space in the endoneurium. Therefore, the widened space between the bundles of collagen fibrils may be a technical artefact.     

Appearance of the reticular cells which trap antigens in the rat lymph node in postnatal development.

The cells binding and retaining immune complexes on their cell surface existed in rat lymph nodes with no germinal centers. This study attempted to clarify the relationship between the two types of cells, reticular cells and follicular dendritic cells (FDCs), in the rat lymph node at early stages of postnatal development by immuno-electron microscopy on anti-horseradish peroxidase (HRP) and HRP injected rat. On the 19th and 23rd day after birth, germinal centers were not yet constructed nor were typical FDCs visible. However, immune complex binding cells were observed on the 23rd day, and not on the 19th. HRP reactive materials (immune complexes) were localized between lymphocytes and large lucent cells, making meshworks. They were revealed by electron microscopy on the cell surface which invaginated into the cytoplasm. The HRP reactive cells extended their cytoplasmic processes and formed a connection by their processes. They were reticular cells which enclosed reticular fibers by their cytoplasmic processes or contacted with reticular fibers closely. The reticular cells may be precursors of the FDCs.     

Morphological changes of capillaries in the rat soleus muscle following experimental tenotomy

We examined the structural changes of capillaries in the rat soleus muscle 4, 7, 14, and 35 days after experimental limb tenotomy. In the soleus muscles after tenotomy, muscle fibres degenerated and some of them were destroyed; the muscle did not seem to recover until the 35th day. On the 14th day, some small muscle fibres, probably regenerating muscle fibres, started forming within the basal-lamina tube and remained after necrosis of a pre-existing muscle fibre. Most capillaries at each stage were of the continuous type. However, about 10% of the capillaries around degenerated muscle fibres at days 4, 7 and 14 consisted of endothelial cells with a small number of fenestrae bridged by a single-layered diaphragm. On the 14th day, capillaries around small regenerating muscle fibres also often had a small number of fenestrations. Even on the 35th day, capillaries occasionally had fenestrations. Additionally, some of the fenestrated capillaries formed small pores at the fenestrated portion of the endothelial cells. The untreated muscles contained only continuous capillaries. These findings suggest that fenestrations in the endothelial cells may occur in intramuscular capillaries not only around degenerated muscle fibres but also around regenerating muscle fibres after tenotomy.     

Ultrastructural changes in lung tissue after acute lead intoxication in the rat

Pulmonary toxicity of lead was studied in rats after an intraperitoneal administration of lead acetate at a dose of 25?mg/kg. Three consecutive days of treatment increased lead content in the whole blood to 2.1?μg/dl and in lung homogenate it attained 9.62?μg/g w.w. versus control values of 0.17?μg/dl and 0.78?μg/g w.w., respectively. At the ultrastructural level, the effects of lead toxicity were observed in lung capillaries, interstitium, epithelial cells and alveolar lining layer. Accumulation of aggregated platelets, leucocytic elements and monocytes was found within capillaries. Interstitium comprised a substantial number of collagen, elastin filaments and lipofibroblasts. Lamellar bodies of type II pneumocytes contained phospolipid lamellae, which stratified into an irregular arrangement. Pulmonary alveoli were filled with macrophages. The extracellular lining layer of lung alveoli was partially destroyed. This study provided evidence that acute lead intoxication affects the whole lung parenchyma and by impairing production of the surfactant might disturb the regular respiratory function.     

In utero changes of the plasma membrane in the head region of the rat spermatozoa

The plasma membrane of the head of the rat spermatozoa was observed by deep-etch, surface replica, and freeze-fracture methods. The spermatozoa were from three experiments: 1) incubation in Hepes buffer, 2) natural coition, and 3) insemination. The spermatozoa used for experiments 1) and 3) were obtained from the ductus deferens. No change in ultrastructure was observed in the incubation experiment. Randomly oriented rows of particles were observed on the plasma membrane of the ejaculated spermatozoa in the deep-etch replicas. The surface replicas showed a similar structure on the plasma membrane. The surface of the inseminated spermatozoa was smooth. This study shows that the plasma membrane changes in the uterus.     

慢性脑灌注不足大鼠记忆和突触结构参数分析

慢性脑灌注不足常常导致发生多发性脑梗塞和皮层下动脉硬化性脑病 ,引起血管性痴呆。我们观察持久双侧颈总动脉结扎的慢性脑缺血大鼠 ,了解电脑控制穿梭箱系统下大鼠记忆行为改变及大脑皮层、海马突触结构参数的改变 ,探讨两者的关系。材料和方法1 电镜样品制备和观察选用老龄ｗｉｓｔａｒ大鼠 ,分为正常对照组 ,缺血 2月组 ,缺血 4月组 ,制作持久双侧颈总动脉结扎慢性脑灌注不足的模型。灌注固定后分离出大脑 ,于脑皮层、海马取 1ｍｍ3 大小组织放入 3%磷酸缓冲液配制的戊二醛固定液中固定 ,1%锇酸后固定 ,常规脱水浸透 ,环氧树脂 6 18包埋…     

A further observation of the structural changes of microvessels in the extensor digitorum longus muscle of the aged rat

We further examined the structural changes of microvessels in the extensor digitorum longus muscle of the aged (18 months) rat. Muscle bundles in this aged muscle constantly consisted of numerous large muscle fibers 50-60 mum in diameter and a few small muscle fibers <30 mum in diameter. Neuromuscular junctions (NMJs) in large muscle fibers often showed degenerative figures, thus degenerating muscle fibers. On the other hand, NMJs in small muscle fibers were mainly characterized by sparse and short junctional folds, being possibly in the course of regeneration. In some muscle bundles, the extracellular matrix was a little widened. Microvascular networks from arterioles to venules via capillaries seemed to vary in structural features between muscle bundles. In addition to the normal microvascular network consisting of microvessels with a round or oval vascular lumen during their course, two different types of microvascular networks were found. One type was characterized by the constriction of arterioles, capillaries and venules, probably representing a degenerative process of the microvascular network. In fact, uneven and compressed scaffolds of basal laminae of capillaries were often observed around these constricted microvessels. The other type consisted of arterioles and capillaries with an irregular slit-like vascular lumen and venules with a round or oval vascular lumen, and these capillaries had thick or two-layered basal laminae, being probably in the course of remodeling of the microvascular network. From these findings, it is suggested that the constriction and/or contraction of microvessels by smooth muscle cells and pericytes may be involved in the degeneration and remodeling of the microvascular network in the muscle bundles following degeneration and regeneration of the muscle fibers.     

Study of precancerous changes in the rat pleural mesothelium following exposure to asbestos using scanning electron microscopy

Rat pleural mesothelium was studied 16 to 22 months after intrapleural inoculation of chrysotile-asbestos. Irregular diffuse hyperplasia and focal solid and papillary pretumoral lesions were found. The morphological picture of these lesions in SEM and light microscopy have been discussed.     

Estimation of the number of segments in a well-log signal via theinformation theoretic approach

An algorithm for automatic well-log signal segmentation previously proposed by the author (ibid., vol.27, p.633-41 (1987)) demands knowledge of the number of segments or another similar constraint as a stopping rule. An information-theoretic criterion is proposed to estimate the number of segments while the proposed sequential segmentation algorithm is in operation. A recursive procedure is developed to update the criterion function sequentially with minimum computation effort     

高血压大鼠第四脑室外侧隐窝室管膜细胞超微结构变化的电镜观察

目的:观察一氧化氮(NO)缺乏型高血压大鼠,第四脑室外侧隐窝室管膜细胞及其分泌状态的超微结构变化.方法:30只健康雄性Wistar大鼠,其中20只予以一氧化氮合酶抑制剂左旋硝基精氨酸(L-NNA) 15 mg/d,腹腔注射,复制高血压动物模型;10只予以0.9%氯化钠2 mL/d腹腔注射作为对照.对照组、用药2周组和用...     

Towards a reduction in error in the radiological measurement of growth in long leg bones of children

The problem of measurement error in radiological estimates of the bone length and differential growth of children's legs is discussed. The contribution of subjective measurement from film by radiologists to the overall error is estimated and confirmed by inter-observer experiments. The problem of radioluscency of unossified cartilage in infants is overcome using a non-routine radiographic technique followed by computer processing to enhance the contrast between the condylar region and the surrounding tissues. The possibility of automatically tracing the contour of the enhanced condylar edge is studied and experimental results are presented.     

An ultrasound wearable system for the monitoring and acceleration of fracture healing in long bones

An ultrasound wearable system for remote monitoring and acceleration of the healing process in fractured long bones is presented. The so-called USBone system consists of a pair of ultrasound transducers, implanted into the fracture region, a wearable device and a centralized unit. The wearable device is responsible to carry out ultrasound measurements using the axial-transmission technique and initiate therapy sessions of low-intensity pulsed ultrasound. The acquired measurements and other data are wirelessly transferred from the patient-site to the centralized unit, which is located in a clinical setting. The evaluation of the system on an animal tibial osteotomy model is also presented. A dataset was constructed for monitoring purposes consisting of serial ultrasound measurements, follow-up radiographs, quantitative computed tomography-based densitometry and biomechanical data. The animal study demonstrated the ability of the system to collect ultrasound measurements in an effective and reliable fashion and participating orthopaedic surgeons accepted the system for future clinical application. Analysis of the acquired measurements showed that the pattern of evolution of the ultrasound velocity through healing bones over the postoperative period monitors a dynamic healing process. Furthermore, the ultrasound velocity of radiographically healed bones returns to 80% of the intact bone value, whereas the correlation coefficient of the velocity with the material and mechanical properties of the healing bone ranges from 0.699 to 0.814. The USBone system constitutes the first telemedicine system for the out-hospital management of patients sustained open fractures and treated with external fixation devices.     

Discontinuous capillary segments in the extensor digitorum longus muscle of aged BUF/Mna rats

We examined the structural changes of capillaries in the extensor digitorum longus muscle of aged (25 months) male BUF/Mna rats, which caused severe muscle weakness of hind legs during aging. The aged muscle mostly consisted of bundles of muscle fibres 15-35 microm in diameter (type 1). In some small areas, however, muscle bundles contained small muscle fibres mainly 15-25 microm in diameter (type 2), possibly indicating that these small fibres are in the course of regeneration after necrosis. Examination of serial ultrathin sections revealed some remarkable changes of capillaries in the type 2 muscle bundle. In some capillaries, the vascular lumen became discontinuous by several close contacts of opposed endothelial cells in their course, forming plural closed vascular segments. Moreover, a solitary endothelial cell was often observed within a scaffold of basal lamina, which remained after destruction of endothelial cells. The segmentation of capillaries and the occurrence of the scaffolds of basal laminae are considered to indicate the degenerative process of capillaries. In some instances, on the other hand, endothelial cells closely apposed each other with no vascular lumen for distances of up to 100 microm, and some capillaries had a narrow vascular lumen (1-3 microm diameter) for a long distance (approximately 300 microm), probably indicating that these structures are in the course of regenerating capillaries to remodel the capillary networks around the muscle fibres. Pericytic processes circularly arranged outside the endothelium at the slit-like and narrow vascular lumen, like hoops, possibly preventing the rupture of the newly-formed vascular lumen from the increased blood flow and/or blood pressure. In addition, the occasional occurrence of capillaries with fenestrations may participate to increase the supply of nutrients and oxygen to the regenerating muscle fibres. The present findings suggest that the capillary networks in the extensor digitorum longus muscle of aged BUF/Mna rats are remodelled following the regeneration of muscle fibres after necrosis, and that on occasion, neighbouring endothelial cells may closely contact with each other both in the degenerative and regenerative processes of capillaries.     

扫描探针显微镜在胶原纤维精细结构研究中的应用

作为一种新型的微区分析仪器,扫描探针显微镜已迅速普及和应用到了各门学科,而在生物领域的应用则相对比较落后。本文简要介绍了扫描探针显微镜这一新型表面测试技术在猪皮胶原精细结构研究中的应用方法,并将所得结果与透射电镜结果进行了比较分析。     

High-resolution freeze-etching replica images of the disk and the plasma membrane surfaces in purified bovine rod outer segments

Molecular organization of the photoreceptor disk membrane was revealed by the freeze-deep etching replica method using purified and successively rinsed bovine rod outer segment (ROS). Various membrane particles with different shape and sizes were found on cytoplasmic surface (PS face) as well as on both P and E fracture faces, which are presumed to be peripheral membrane proteins such as transducin, phosphodiesterase, guanylate cyclase and so on. Membrane particles seen on PS face were catalogued in size. The histogram on their number and size showed that they were classified at least into two major groups, the group of particles about 50 nm2 in size and the group of particles about 115 nm2 in size. The distribution density of the 115 nm2 particle was 1200 microm(-2) in native state, but it decreased to 125 microm(-2) after washing with hypotonic buffer solution. Namely, the group of the 115 nm2-particle seems to be mainly composed of peripheral membrane proteins. Rinsing with the sucrose free buffer at the final step of the purification procedure enabled us to observe three types of filaments localized in ROS (filaments connecting disk to disk at the margin, filaments connecting disk to the plasma membrane, filaments associated with PS face of disk membrane); and also to find characteristic domains with crystal arrangement of particles on the external surface (ES face) of ROS plasma membrane.     

Copper-induced changes in the properties of arsenic chalcogenides

The influence of the presence of Cu in the amount between 1% and 6% in arsenic chalcogenide glasses is examined through a study of the electronic energy levels by means of x-ray photoelectron and x-ray emission spectroscopy, through an investigation of the low-energy tunneling systems by means of phonon echoes at 0.37 K, and through an examination of the photodarkening and the photoinduced dichroism caused by polarized Ar⁺ laser irradiation. Possible links between the various effects are examined. The Cu atoms become an integral part of the amorphous lattice structure and strongly influence the photodarkening, but they do not have a significant effect on the tunneling systems or the dichroism. It is concluded that the tunneling levels and the dichroism involve only local configurations, while the photodarkening involves larger-scale areas of the lattice. Fiz. Tekh. Poluprovodn. 32, 976–981 (August 1998)     

The theoretical study of substituent and charge effects in the conformational transformation process of molecular machine unit spiropyran

Besides the photochromism isomerization, the impact of the electrochemical conditions on the spiropyran/merocyanine (SP/MC) isomerization process is also getting more and more attention. In a certain electrochemical cell, spiropyran reduced to form a radical anion and the SP/MC isomerization becomes spontaneous. Therefore, thermal reaction mechanisms for the neutral, cationic and anionic SP/MC isomerization with a series of electron-donating and electron-withdrawing groups in the 6- position of the benzopyran moiety in ground state have been systematically investigated using the density functional theory method. Some notable changes in structure, activation energy barrier and reaction rate caused by charge changes of spiropyran have been found and discussed in detail. For anionic SP/MC isomerization, due to the electron density distribution changed, the activation energy barriers decreased and the reaction rate constants of every step increased greatly. The geometrical parameter, bond length alternation (BLA), which relates to the effect of substituents, has been employed to explain the changes in the reaction mechanism induced by different electron-donating and electron-withdrawing substituents. Our results explained the control method of the small unit of the molecular machine conformational transformation process deeply from the theoretical viewpoint.     

Detection of pseudosinusoidal epileptic seizure segments in the neonatal EEG by cascading a rule-based algorithm with a neural network

This paper presents an approach to detect epileptic seizure segments in the neonatal electroencephalogram (EEG) by characterizing the spectral features of the EEG waveform using a rule-based algorithm cascaded with a neural network. A rule-based algorithm screens out short segments of pseudosinusoidal EEG patterns as epileptic based on features in the power spectrum. The output of the rule-based algorithm is used to train and compare the performance of conventional feedforward neural networks and quantum neural networks. The results indicate that the trained neural networks, cascaded with the rule-based algorithm, improved the performance of the rule-based algorithm acting by itself. The evaluation of the proposed cascaded scheme for the detection of pseudosinusoidal seizure segments reveals its potential as a building block of the automated seizure detection system under development.