Primary cilia are microtubule-based organelles that are important for signaling and sensing in eukaryotic cells. Unlike the thoroughly studied motile cilia, the three-dimensional architecture and molecular composition of primary cilia are largely unexplored. Yet, studying these aspects is necessary to understand how primary cilia function in health and disease. We developed an enabling method for investigating the structure of primary cilia isolated from MDCK-II cells at molecular resolution by cryo-electron tomography. We show that the textbook '9 + 0' arrangement of microtubule doublets is only present at the primary cilium base. A few microns out, the architecture changes into an unstructured bundle of EB1-decorated microtubules and actin filaments, putting an end to a long debate on the presence or absence of actin filaments in primary cilia. Our work provides a plethora of insights into the molecular structure of primary cilia and offers a methodological framework to study these important organelles.

• MeSH
• buněčné kultury MeSH
• buňky MDCK MeSH
• Chlamydomonas metabolismus   ultrastruktura   MeSH
• cilie metabolismus   ultrastruktura   MeSH
• elektronová kryomikroskopie MeSH
• exprese genu MeSH
• lidé MeSH
• mikrofilamenta metabolismus   ultrastruktura   MeSH
• mikrotubuly metabolismus   ultrastruktura   MeSH
• proteiny asociované s mikrotubuly genetika   metabolismus   MeSH
• psi MeSH
• tomografie elektronová MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• psi MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The ultrastructure and morphology of beluga spermatozoa (Huso huso) (Acipenseridae, Chondrostei) were studied by scanning and transmission electron microscopy. Spermatozoa of 51.27 ± 4.71 μm total length (mean ± SD) were typical of sturgeon and paddlefish spermatozoa. Each consisted of an elongated nucleus (length: 5.84 ± 0.46 μm) with distinct acrosome, a cylindrical midpiece (length: 2.10 ± 0.42 μm), and a single flagellum (length: 42.21 ± 3.82 μm). The acrosome was umbrella shaped (length: 1.12 ± 0.14 μm, width: 0.87 ± 0.10 μm) with seven to nine posterolateral projections (length: 0.49 ± 0.09 μm). Three endonuclear canals, spirally arranged, traversed the nucleus length from the acrosome to the implantation fossa. The flagellum comprised an axoneme with the typical 9+2 organization of microtubules. Two flat fins were present along the flagellum parallel to the plane of the central doublet of microtubules. These fins arose at different positions, 0.57 ± 0.30 and 4.06 ± 1.32 μm from the midpiece and terminated 4.18 ± 1.09 and 4.92 ± 1.34 μm from the distal end of the flagellum. Principal component analysis revealed spermatozoan ultrastructure and morphology were similar among sturgeon species, and, although assigned to genus Huso, beluga may be closely related to the genus Acipenser.

• MeSH
• akrozom ultrastruktura   MeSH
• analýza hlavních komponent MeSH
• flagella ultrastruktura   MeSH
• mikroskopie elektronová rastrovací veterinární   MeSH
• ryby anatomie a histologie   MeSH
• spermie ultrastruktura   MeSH
• transmisní elektronová mikroskopie veterinární   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The spermatozoon ultrastructure of the progenetic cestode Diplocotyle olrikii (Spathebothriidea) has been examined using transmission electron microscopy and cytochemical staining with periodic acid-thiosemicarbazide-silver proteinate (PA-TSC-SP) for glycogen. The spermatozoon is a filiform cell, tapered at both extremities. Its moderately electron-dense cytoplasm possesses two parallel axonemes of unequal lengths. New for the Cestoda is a finding of three types of the mature spermatozoa with respect to different axonemal structure. The first type has both axonemes with standard 9 + '1' trepaxonematan pattern. The second type is represented by a spermatozoon having one axoneme with 9 + '1' structure and the second one with 9 + 0 pattern. The third type includes the two axonemes with 9 + 0 pattern. Microtubule doublets of the 9 + 0 axonemes contain either inner dynein arms or no dynein arms. In addition to the two axonemes, all three types of the mature sperm cells contain parallel nucleus, parallel cortical microtubules, four electron-dense plaques/attachment zones, and glycogen. The anterior extremity of the gamete exhibits a centriole surrounded by a semiarc of up to five electron-dense tubular structures. The distal end of the first type spermatozoa exhibits two morphological variants, represented either by (i) nucleus or (ii) remnants of the disorganized axoneme. Distal extremity of the spermatozoa of the second and third types contains doublets and singlets of disorganized axoneme. The ultrastructural characters of the spermatozoon of progenetic D. olrikii support the basal position of the Spathebothriidea within the Eucestoda.

• MeSH
• axonema ultrastruktura   MeSH
• buněčné jádro ultrastruktura   MeSH
• centrioly ultrastruktura   MeSH
• Cestoda ultrastruktura   MeSH
• cytoplazma ultrastruktura   MeSH
• spermatogeneze fyziologie   MeSH
• spermie ultrastruktura   MeSH
• transmisní elektronová mikroskopie MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Testis development and ultrastructure of spermatogenic cells and spermatozoa of burbot Lota lota, a commercially important cold freshwater fish, were studied by light and transmission electron microscopy. Spermatogonia, spermatocytes, spermatids, and spermatozoa are distributed along the seminiferous tubules. Electron-dense bodies appear in germ cells from primary spermatogonia to secondary spermatocytes. We identified three distinct stages of spermatid cell differentiation based on chromatin condensation, development of the flagellum, formation of a nuclear fossa, and elimination of excess cytoplasm. Spermatozoa were anacrosomal and characterized by location of the centrioles outside the nuclear fossa and incomplete perpendicular arrangement of the centrioles. The sperm flagellum displayed an axoneme with nine doublets of peripheral microtubules and two central microtubules. These results provide valuable information for burbot taxonomy and may clarify the process of spermatogenesis for this species.

• MeSH
• kultivované buňky MeSH
• ryby metabolismus   MeSH
• Sertoliho buňky ultrastruktura   MeSH
• spermatidy ultrastruktura   MeSH
• spermatogeneze * MeSH
• spermatogonie ultrastruktura   MeSH
• spermie ultrastruktura   MeSH
• testis cytologie   ultrastruktura   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH