Late Deposition of Elastin to Vertical Microfibrillar Fibers in the Presumptive Dermis of the Chick Embryonic Tarsometatarsus

Fibrillin microfibrils are integral components of elastic fibers and serve as a scaffold for elastin deposition. However, microfibrillar fibers (MFs) are not necessarily committed to develop into so‐called elastic fibers. In dermis, elastin‐free oxytalan MFs originating from the dermoepidermal junction are continuous to elaunin‐type MFs (with a small amount of elastin) in the deeper papillary dermis, whereas the reticular dermis contains elastic fibers, or MFs embedded largely in elastin. In this study, we have investigated temporospatial patterns of elastin deposition on the MFs in tarsometatarsal presumptive dermis. While the earliest expression of elastin was demonstrated immunohistochemically as early as embryonic day 4 (ED4) in the wall of cardiac outflow and pharyngeal arch arteries, its deposition in the tarsometatarsus was first detected at ED6 in the deeper mesenchyme and at ED13 in the subectodermal mesenchyme. In the latter tissue, MFs had been organized perpendicularly to the covering ectoderm by ED4, well before an overt accumulation of collagenous matrix. Elastin deposition was observed initially in a punctate manner at ED13 and afterward became continuous along MFs. However, a characteristic spaced array of subectodermal vertical MFs was disorganized by ED17. These findings suggest that elastin deposition in the subectodermal MFs is not deployed by continuous, orderly propagation from elastic fibers in the deeper mesenchyme but occurs de novo in multiple foci along vertical MFs. Moreover, the present chronology of elastin deposition indicates that subectodermal, elastin‐free MFs function as a transient, but primary fibrous structure in the presumptive dermis before the accumulation of collagenous matrix. Anat Rec, 290:1300‐1308, 2007. © 2007 Wiley‐Liss, Inc.     

Matrix Metalloproteinase-2 Degrades Fibrillin-1 and Fibrillin-2 of Oxytalan Fibers in the Human Eye and Periodontal Ligaments In Vitro

Oxytalan fibers are distributed in the eye and periodontal ligaments (PDL). The ciliary zonule, known as Zinn’s zonule, in the eye is composed of oxytalan fibers, which are bundles of microfibrils consisting mainly of fibrillin-1 and fibrillin-2. As turnover of oxytalan fibers is slow during life, their degradation mechanism remains unclarified. This study was performed to examine degradation pattern of fibrillin-1 and fibrillin-2 by experimental MMP activation. We cultured human non-pigmented ciliary epithelial cells (HNPCEC) and PDL fibroblasts for 7 days, then treated them with concanavalin A to activate matrix metalloproteinase (MMP)-2, and examined the degradation of fibrillin-1 and fibrillin-2 for 72 hr using immunofluorescence. At 7 days of HNPCEC culture, fibrillin-1-positive fibers were observed, some of which merged with fibrillin-2. After MMP-2 activation, fibrillin-1-positive fibers became thin and disappeared by 72 hr, while fibrillin-2-positive fibers disappeared almost completely within 24 hr. At 7 days of PDL fibroblast culture, fibrillin-1-positive fibers were mostly merged with fibrillin-2. After MMP-2 activation, fibrillin-1-positive fibers became thin by 24 hr and had almost disappeared by 48 hr, while fibrillin-2-positive fibers decreased constantly after 24 hr. A MMP-2 inhibitor completely suppressed these degradations. These results suggest that the patterns of fibrillin-1 and fibrillin-2 degradation differ between the eye and the PDL, possibly reflecting the sensitivity of fibrillin-1 and fibrillin-2 of each type of oxytalan fiber against MMP-2.     

The organisation of elastin and fibrillins 1 and 2 in the cruciate ligament complex

Although elastin fibres and oxytalan fibres (bundles of microfibrils) have important mechanical, biochemical and cell regulatory functions, neither their distribution nor their function in cruciate ligaments has been investigated. Twelve pairs of cruciate ligaments (CLs) were obtained from 10 adult dogs with no evidence of knee osteoarthritis. Elastic fibres were identified using Verhoeff's and Miller's staining. Fibrillins 1 and 2 were immunolocalised and imaged using confocal laser scanning microscopy. Hydrated, unfixed tissue was analysed using Nomarski differential interference microscopy (NDIC), allowing structural and mechanical analysis. Microfibrils and elastin fibres were widespread in both CLs, predominantly within ligament fascicles, parallel to collagen bundles. Although elastin fibres were sparse, microfibrils were abundant. We described abundant fibres composed of both fibrillin 1 and fibrillin 2, which had a similar pattern of distribution to oxytalan fibres. NDIC demonstrated complex interfascicular and interbundle anatomy in the CL complex. The distribution of elastin fibres is suggestive of a mechanical role in bundle reorganisation following ligament deformation. The presence and location of fibrillin 2 in oxytalan fibres in ligament differs from the solely fibrillin 1-containing oxytalan fibres previously described in tendon and may demonstrate a fundamental difference between ligament and tendon.     

Kinetics of the Incorporation of Tropoelastin into Elastic Fibers in Embryonic Chick Aortad

Matrix-free cells isolated by enzymic digestion of chick embryo aortas were labeled with [¹⁴C]proline for 20 to 60 min and the kinetics of the secretion of tropoelastin were followed by chasing the label and assaying [¹⁴C]tropoelastin in the cells and in the medium. The results indicated that secretion of tropoelastin followed the kinetics of a single first order process with a half time of 60 min. In parallel experiments tissue explants of chick embryo aortas were labeled with [¹⁴Clproine and the kinetics for the incorporation of tropoelastin into elastic fibers were followed by chasing the label and assaying the soluble [¹⁴C]tropoelastin and insoluble [¹⁴C]elastin in tissues. It was found that the incorporation of tropoelastin into elastic fibers also followed a single first order process with a half time of 85 min, similar to the secretion of tropoelastin from cells. In further studies, antibodies directed against tropoelastin were utilized to isolate soluble[^14C]elastin components in the tissues after 0 to 4 hr chase of the ^14CC label. The results demonstrated that all soluble elastin components were recovered as monomeric tropoelastin and no soluble oligomeric elastin could be detected. These results are consistent with the proposition that elastic fiber growth occurs by addition of individual tropoelastin molecules to existing fibers and that oligomers of elastin were not intermediates in the process.     

牛右心室节制索及右束支的解剖观测

目的了解牛右心室节制索及右束支的形态特点及分布规律,为比较解剖学和兽医学积累解剖学资料。方法24例新鲜市售牛心,用大体解剖和墨汁灌注方法显示牛右心室传导系。肉眼观察右心室内各结构的形态和分布,用游标卡尺测量数据,SPSS统计软件处理相关数据。结果节制索多为扁圆柱状(90.5%),长(45.48±1.32)mm,长直径(3.78±1.54)mm,短直径(2.55±1.26)mm,右束支长(65.52±20.78)mm,直径(1.45±0.56)mm。发现1例双节制索。Purkinje纤维的分布第Ⅰ、Ⅱ象限最密集,第Ⅲ三象限较少分布,第Ⅳ象限分布最少。结论牛心节制索的形态与其他哺乳动物相似,其中有右束支穿行,其表面有分布不均的Purkinje纤维。     

Stereological Investigation of the Age‐Related Changes of the Myelinated Fibers in the Hippocampus of Male Rats

The decline of hippocampus‐dependent learning and memory during normal aging is not associated with neuron death and synapse loss. Until now, age‐related changes in the myelinated fibers of the hippocampus have not been investigated. Therefore, in this study, the myelinated fibers in the hippocampi of young (6 months), middle‐aged (18 months), and old‐aged (28 months) male Sprague‐Dawley rats were studied with transmission electron microscope and stereological methods, following spatial learning tests in a Morris water maze. The results showed that hippocampus‐dependent spatial learning was impaired in old‐aged rats but that the total volume, length, and mean diameter of the myelinated fibers in the hippocampus, as well as the hippocampal volume, remained constant during the normal aging process. Our results suggest that the age‐related decline in hippocampus‐dependent spatial learning is not attributable to myelinated fiber changes in the hippocampus and that other, undetermined factors are responsible. Anat Rec, 297:1490–1497, 2014. © 2014 Wiley Periodicals, Inc.     

Sexual dimorphism in the mossy fiber synapses of the rat hippocampus

Summary The presence of sexual dimorphism in the hippocampal formation has long been recognized. Differences between male and female rats have been detected with respect to the number of dentate granule cells and branching patterns of dentate granule and hippocampal pyramidal cell dendrites. Groups of 6 male and 6 female Sprague-Dawley rats were studied at 180 days of age. Based on light microscopical Timm-staining and Golgi-impregnation and electron microscopy, and applying morphometric techniques, we now report that the total number of synapses between mossy fibers and the apical dendritic excrescences of CA3 pyramidal cells is the same in male and female rats, despite a higher numerical density in the latter. Moreover, the volume of the mossy fiber system was found to be smaller in females. Because the number of dentate granule cells is smaller in females than in males, the increased numerical density of synapses may be thought of as a compensatory mechanism to equalize the number of synaptic contacts between dentate granule and CA3 pyramidal cells in the two sexes. We demonstrate that an increase in the number of mossy fiber boutons in female rats is a determining factor for the sexual differences found.     

人胰结缔组织纤维的细微和超微构筑及其意义--NaOH消蚀法SEM观察

目的探讨胰结缔组织纤维的细微和超微构筑及其意义.方法采用NaOH消蚀和超声波(USW)清洗技术,制备只保留结缔组织纤维成分的人胰组织样品,进行扫描电镜(SEM)观察和分析.结果经NaOH消蚀和USW清洗处理的胰组织,其细胞和基质成分全被消蚀掉,只留有结缔组织纤维,仍保持原有构筑特征.胰腺小叶、小叶间结缔组织和胰岛的轮廓清晰可见.穿行于小叶间结缔组织内的胰腺导管、动脉和静脉血管、淋巴管以及神经纤维束,易被辨认和区别.结缔组织纤维织成的束或网,均由胶原蛋白聚合而成的纳米(10-100mm)纤维,或称胶原细纤维所组成.结论活体上充满组织液的胰结缔组织纤维网,构成了该器官的组织支架和通道,为胰内、外分泌细胞的支持与保护、营养与代谢、分泌与通讯、再生与修复等,提供了适宜的微环境.     

跑步训练对中老年大鼠海马结构及其内有髓神经纤维的影响

目的探讨跑步训练对中老年雌性大鼠海马结构及海马结构内有髓神经纤维的影响。方法将10只14月龄的雌性SD大鼠随机分为跑步训练组和空白对照组,分别进行4个月的跑台训练和普通标准环境饲养。4个月后采用Morris水迷宫对两组大鼠的空间学习能力进行测试,然后运用透射电子显微镜和新的体视学方法对大鼠大脑海马结构及其内有髓神经纤维进行定量研究。结果与对照组相比,训练组老年雌性大鼠空间学习能力明显增强;海马结构总体积、海马结构内有髓神经纤维总长度显著增加,但海马结构内有髓神经纤维的总体积未见明显改变。海马结构内有髓神经纤维总长度分布图表明,训练组有髓神经纤维总长度的增加主要是由于细小直径的有髓神经纤维长度增加所致。结论跑步训练对中老年雌性大鼠的空间学习能力、海马结构及其内有髓神经纤维有明显的影响。     

Effects of Deafferentation on the Size and Myosin Phenotype of Muscle Fibers on Stretching of the Rat Soleus Muscle in Conditions of Gravitational Unloading

The aim of the present work was to assess the contributions of the reflex and local components to preventing decreases in the size and changes in the ratio of fibers containing the slow and fast isoforms of myosin heavy chains during chronic stretching of a postural muscle in rats in conditions of gravitational unloading. A unilateral surgical deafferentation method was used. The results demonstrated that deafferentation of the hindlimb had no effect on preventing reductions in muscle fiber size in conditions of chronic muscle stretching in conditions of gravitational unloading. The results obtained from these experiments did not support the hypothesis that the predominant contribution to preventing the development of atrophic changes comes from activation of muscle afferents in chronic stretching of the unloaded muscle. Deafferentation of both suspended animals and those with normal motor activity led to increases in the proportion of soleus muscle fibers containing the slow isoforms of myosin heavy chain.     

短期丰富生存环境增加中老年雄性大鼠海马结构内有髓神经纤维的总长度

目的探讨短期丰富生存环境干预对正常中老年雄性大鼠海马结构及海马内有髓神经纤维的影响。方法将20只14月龄的雄性SD大鼠随机分为丰富生存环境组与空白对照组,前者在丰富生存环境条件下饲养4个月,后者在普通环境中饲养4个月后,采用Morris水迷宫测试两组大鼠的空间学习能力;运用透射电子显微镜和体视学方法对两组大鼠海马结构及海马内有髓神经纤维进行定量研究。结果丰富生存环境组大鼠空间学习能力与空白对照组之间不存在显著性差异;丰富生存环境组与空白对照组相比较,海马结构总体积两组间无显著性差异。丰富生存环境组海马结构内有髓神经纤维的总体积、有髓神经纤维总长度、有髓神经纤维平均直径显著增加。结论短期丰富生存环境干预对14月龄雄性大鼠海马有髓神经纤维具有显著性影响。这一研究结果为将来寻找延缓大脑衰老进程的行为学手段提供了重要的理论依据。     

短期丰富生存环境对中老年雌性大鼠海马结构及其内有髓神经纤维的影响

目的 探讨短期丰富生存环境干预对中老年雌性大鼠海马结构及其内有髓神经纤维的影响。 方法 将20只14月龄的雌性SD大鼠随机分为丰富生存环境组和标准环境组,每组各10只,对丰富生存环境组的动物给予4个月丰富生存环境干预, 标准环境组于普通标准环境下饲养4个月;然后每组各随机选取5只,采用Morris水迷宫对大鼠的空间学习能力进行测试,然后运用透射电子显微镜和体视学方法分别对大鼠大脑海马结构及其内有髓神经纤维进行定量研究。 结果 短期丰富生存环境组中老年雌性大鼠与标准环境组相比,其空间学习能力明显增强;丰富生存环境组海马结构内有髓神经纤维总长度和总体积分别显著增加了43.4%和47.4%,且有髓神经纤维总长度的增加主要是由于细小直径的有髓神经纤维长度增加所致。海马结构总体积和海马结构内有髓神经纤维直径未见改变。 结论 4个月丰富生存环境干预对于14月龄雌性大鼠空间学习能力、海马内有髓神经纤维均有显著性影响。     

Single injection into the cerebrospinal fluid of antibodies against the secretory material of the subcommissural organ reversibly blocks formation of Reissner's fiber: immunocytochemical investigations in the rat

Summary An antibody (cf. Rodríguez et al. 1984b) raised in rabbits against the glycoproteins of the bovine Reissner's fiber (RF) was injected into the lateral brain ventricle of 38 rats with the aim to interfere with RF formation. The rats were killed 20 min; 1, 4, 8, 12 h; and 1, 2, 3, 5, and 8 days after the injection. Based on the fact that the material secreted by the subcommissural organ (SCO) into the cerebrospinal fluid (CSF) first condenses on the organ surface as a distinct layer (pre-RF material) and then becomes assembled to form RF and that both structures are distinguishable in tissue sections, three immunostaining procedures were applied. They served to visualize: (i) secretory material that had not bound the injected antibody; (ii) secretory material-antibody complexes formed in vivo; and (iii) antibody not bound to its antigen and present in the ventricles and the subarachnoid space. After a single injection of the abovementioned antibody the following events were observed: (1) The antibody was present in the brain cavities for at least 8 h. (2) The injected antibody bound selectively to the pre-RF and RF. (3) Pre-RF displayed antibody binding during the 24 h following the injection. During the 2nd and 3rd post-injection days, the pre-RF was free of antibody, indicating that it was formed by newly released secretory material. (4) Approximately 4 h after the injection, the RF detached from the SCO and underwent fragmentation. Clusters of these fragments were found in the Sylvian aqueduct and fourth ventricle. (5) In the fragmented original RF the injected antibody against Reissner's fiber remained bound throughout the entire period of observation, i.e. for 8 days. (6) In rats of the 1-, 3-, 5- and 8-day-groups, RF was missing from the central canal of the spinal cord. (7) One day after the injection, a new RF structure started to grow from the rostral end of the SCO. This newly formed fiber could be distinguished from the original RF because of (i) its normal appearance; (ii) it did not display binding of the injected antibody. (8) At day 3, the growing RF had not yet extended to the Sylvian aqueduct. (9) At day 8, the new RF reached the fourth ventricle. Control experiments involved the intraventricular administration of (i) an antibody against the secretory material extracted from the entire bovine SCO; (ii) antivasopressin; and (iii) rabbit IgG. From these only antibody (i) bound to pre-RF and RF.     

A lectin horseradish peroxidase study of the origin of ascending fibers in the medial forebrain bundle of the rat. The upper brainstem

The origins of projections within the medial forebrain bundle from the upper brainstem were examined with the horseradish peroxidase technique. Labeled cells were found in approximately 15 upper brainstem nuclei following injections of a conjugate of horseradish peroxidase and wheat germ agglutinin at various levels of the medial forebrain bundle. Labeled nuclei included (from caudal to rostral): dorsal and ventral parabrachial nuclei; Kolliker-Fuse nucleus; dorsolateral tegmental nucleus; A7 (lateral pontine tegmentum medial to lateral lemniscus); median and dorsal raphe nuclei; distinct group of cells oriented mediolaterally in the dorsal pontine tegmentum below the central gray; B9 (ventral midbrain tegmentum dorsal to medial lemniscus); retrorubral nucleus; nucleus of Darkschewitsch, interfascicular nucleus; rostral and caudal linear nuclei; ventral tegmental area; medial part of substantia nigra, pars compacta; and the supramammillary nucleus. With the exception of the ventral parabrachial nucleus, Kolliker-Fuse, A7, B9 and substantia nigra, pars compacta, each of the nuclei mentioned above sent strong projections along the medial forebrain bundle to the rostral forebrain. Sparse labeling was observed throughout the pontine and midbrain reticular formation. With the exception of the dorsal raphe nucleus, projections to the most anterior regions of the medial forebrain bundle (level of the anterior commissure) essentially only arose from presumed dopamine-containing nuclei-retrorubral nucleus (A8 area), interfascicular nucleus, rostral and caudal linear nuclei, substantia nigra pars compacta, and ventral tegmental area. Evidence was reviewed indicating that major forebrain sites of termination for these dopaminergic nuclei are structures that have been collectively referred to as the 'ventral striatum'. It is concluded from the present findings that several pontine and mesencephalic cell groups are in a position to exert a strong, direct effect on structures in the anterior forebrain and that the medial forebrain bundle is the main communication route between the upper brainstem and the forebrain.     

A lectin horseradish peroxidase study of the origin of ascending fibers in the medial forebrain bundle of the rat. The lower brainstem

The origins of projections within the medial forebrain bundle from the lower brainstem were examined with the horseradish peroxidase technique. Labeled cells were found in at least 15 lower brainstem nuclei following injections of a conjugate or horseradish peroxidase and wheat germ agglutinin at various levels of the medial forebrain bundle. Dense labeling was observed in the following cell groups (from caudal to rostral): A1 (above the lateral reticular nucleus); A2 (mainly within the nucleus of the solitary tract); a distinct group of cell trailing ventrolaterally from the medial longitudinal fasciculus at the level of the rostral pole of the inferior olive; raphe magnus; nucleus incertus; dorsolateral tegmental nucleus (of Castaldi); locus coeruleus; nucleus subcoeruleus; caudal part of the dorsal (lateral) parabrachial nucleus; and raphe pontis. Distinct but light labeling was seen in raphe pallidus and obscurus, nucleus prepositus hypoglossi, nucleus gigantocellularis pars ventralis, and the ventral (medial) parabrachial nucleus. Sparse labeling was observed throughout the medullary and caudal pontine reticular formation. Several lower brainstem nuclei were found to send strong projections along the medial forebrain bundle to very anterior levels of the forebrain. They were: A1, A2, raphe magnus (rostral part), nucleus incertus, dorsolateral tegmental nucleus, raphe pontis and locus coeruleus. With the exception of the locus coeruleus, attention has only recently been directed to the ascending projections of most of the nuclei mentioned above. Evidence was reviewed indicating that fibers from lower brainstem nuclei with ascending medial forebrain bundle projections distribute to widespread regions of the forebrain.It is concluded from the present findings that several medullary cell groups are capable of exerting a direct effect on the forebrain and that the medial forebrain bundle is the major ascending link between the lower brainstem and the forebrain.