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Electron Microscopy in Lung Research
Published in Joan Gil, Models of Lung Disease, 2020
For particular applications, it may be desirable to sacrifice overall fixation to obtain optimal visualization of one particular structure. Excellent visualization of the ultrastructure of ciliary axonemes can be obtained if the tissue sample is treated with a detergent such as triton ×-100 or nonidet P-40 to disrupt the plasma membrane prior to fixation with a tannic acid-glutaraldehyde mixture (Fig. 4) (Wilsman et al., 1987). In lung, detergent treatment also is required for visualization of proteoglycans in the extracellular matrix by ruthenium red (Vaccaro and Brody, 1979). In its absence, the ruthenium red only stains the proteoglycans of the epithelial glycocalyx and fails to penetrate to the interstitium.
Mammalian Spermatozoa
Published in Claude Gagnon, Controls of Sperm Motility, 2020
Mammalian spermatozoa are free motile cells composed of heads and tails. The head is made up of a condensed haploid nucleus encapsulated by a thin and dense layer of cytoplasmic material called the perinuclear theca to which the membrane delimited acrosomic system is tightly attached.1 The tail, while it contains in its core or axis a contractile axoneme composed of microtubules (nine peripheral doublets plus two central singlets), as in all motile ciliae or flagellae, cannot be equated to the latter since it is far more complex. Indeed, the tail is composed of additional cytoskeletal elements among which the coarse outer dense fibers (ODF) and fibrous sheath (FS) are the most prominent and give the spermatozoan’s motile apparatus its distinctive morphological characteristics (Figure 1). In addition, along the proximal portion of the tail there is along the axoneme an alignment of modified mitochondria for which there is no equivalent in other ciliated cells. While considerable information is presently available on the structure and composition of the tail of mature spermatozoa,2,3 there are comparatively few investigations that have given attention to its formation during spermiogenesis. As to the molecular events that preside in the formation of the tail subcomponents, this is a new area of research that has recently started to retain the attention of cell biologists. Work done in this field should lead to a better insight on both the process of germ cell differentiation and on the functional roles of the tail substructures.
Pulmonary Immunology
Published in Lourdes R. Laraya-Cuasay, Walter T. Hughes, Interstitial Lung Diseases in Children, 2019
Hemant H. Kesarwala, Thomas J. Fischer
Ciliated epithelial cells are present in the respiratory tract from the larynx to the terminal bronchiole. Each cell has approximately 200 projecting cilia. The biochemistry and ultra-structure of cilia has been studied in detail. Each cilium has three basic structures: ciliary roots, the basal body, and the ciliar shaft.5 The ciliary shaft or “motor of the cilium” is termed the axoneme (Figure 1) which consists of microtubule units arranged in a 9 + 2 arrangement, i.e., nine peripheral microtubular doublets form a cylinder around two central microtubular singlets. Radial spokes connect these central and peripheral microtubules. The peripheral microtubules possess hook-like extensions called dynein arms (outer and inner). The dynein arms, comprised of adenosine triphosphate,6 attach and reattach to adjacent doublet microtubules in a “ratchet” effect that causes bending of the cilium and uses the energy provided by hydrolysis of adenosine triphosphate, i.e., a sliding mechanism comparable to skeletal muscles with myosin and active filaments.7 This coordinated beating of the cilia produces waves in the fluid layer of the mucous lining which are transmitted to the overlying gel layer of the mucous lining. Initially thought to be a continuous sheet of mucus covering the tracheobronchial tree, the mucus blanket appears to be discontinuous with mucus plaques carried in different streams.8
Novel DNAH17 mutations associated with fertilization failures after ICSI
Published in Gynecological Endocrinology, 2021
Miaomiao Jia, Rong Shi, Xia Xue
Axoneme is the center structure of sperm flagellum. A typical axoneme has a distinctive 9 + 2 microtubules, with a ring of nine peripheral microtubule doublets encircling a central pair of microtubules (CP) [1]. Inner and outer dynein arms are structural sub-units of axoneme and play a major role in the beating of sperm [2]. Dynein heavy chain axonemal 17 (DNAH17) encodes an outer dynein arm protein and is localized specifically in the testes and sperm, but not in cilia or ciliary tissues [3]. Biallelic variants of DNAH17 have been associated with multiple morphological abnormalities of the flagella (MMAF), a rare type of asthenoteratozoospermia that includes absent, bent, short, coiled, and irregular-caliber flagella [4]. After intracytoplasmic sperm injection (ICSI), TFF is rare and only occurs in 3% of cases [5]. The genetic causes of TFF, especially in terms of sperm-related factors, are largely unknown. To date, the only sperm factors that have been found to be associated with TFF are mutations in PLCZ1 [6].
Influence of silica particles on mucociliary structure and MUC5B expression in airways of C57BL/6 mice
Published in Experimental Lung Research, 2020
Qimei Yu, Guoqing Fu, Hui Lin, Qin Zhao, Yuewei Liu, Yun Zhou, Yuqin Shi, Ling Zhang, Zhenyu Wang, Zhibing Zhang, Lingzhi Qin, Ting Zhou
Respiratory cilia are specialized organelles that provide the force necessary to propel foreign materials trapped in mucus out of the airways. Ciliary ultrastructure is closely associated with coordinated ciliary motility such as ciliary beat frequency and coordinated ciliary beat pattern, which are required for effective function of MCC.8,23,24 In the present study, the ultrastructure of airway cilia was gradually damaged with prolonged exposure to silica particles, indicating loss of central pair microtubules, disorganized microtubules in axonemes and reduced axonemes. As previous studies noted, small defects in axoneme structure have severe impact on cilia motility.25 Lack of central pair apparatus consisting of two central microtubules with projections leads to less stable microtubules, complete flagellar paralysis and aberrant flagellar motility.18,26–28 Thus, it may be speculated that silica particles could have a negative influence in coordinated ciliary motility, mainly through destroying the structure of axonemes in airway cilia. However, the underlying mechanism responsible for abnormal ciliary ultrastructure caused by silica particles needs to be further explored.
Genetic aspects of idiopathic asthenozoospermia as a cause of male infertility
Published in Human Fertility, 2020
Zohreh Heidary, Kioomars Saliminejad, Majid Zaki-Dizaji, Hamid Reza Khorram Khorshid
Axonemal ultrastructural defects, including absent or shortened arms of dyneins, can be found in >50% of primary ciliary dyskinesia/Kartagener syndrome (PCD/KS) patients. Approximately 90% of KS male patients are affected by AZS. The majority of KS patients can be ascribed to dynein genes mutations. Mutation screening of DNAI1, DNAH5 and DNAH11 genes was performed in 90 patients with isolated non-syndromic AZS and 200 controls. Three mutations (one in each gene) that specifically associated with AZS were identified in seven patients (7.8%). Mutations are inherited from the mothers and may be found in familial clusters. No ultrastructural axonemal anomaly has been detected in sperm. Male carriers of the dynein mutations always exhibit AZS, whereas female carriers manifest no alterations in either fertility or pulmonary clearance (Zuccarello, Ferlin, Cazzadore, et al., 2008).