Bundles Of Intermediate Filaments Research Articles

Transport and Organization of Individual Vimentin Filaments Within Dense Networks Revealed by Single Particle Tracking and 3D FIB-SEM.

Single-particle tracking demonstrates that individual filaments in bundles of vimentin intermediate filaments are transported in the cytoplasm by motor proteins along microtubules. Furthermore, using 3D FIB-SEM the authors showed that vimentin filament bundles are loosely packed and coaligned with microtubules. Vimentin intermediate filaments (VIFs) form complex, tight-packed networks; due to this density, traditional ensemble labeling and imaging approaches cannot accurately discern single filament behavior. To address this, we introduce a sparse vimentin-SunTag labeling strategy to unambiguously visualize individual filament dynamics. This technique confirmed known long-range dynein and kinesin transport of peripheral VIFs and uncovered extensive bidirectional VIF motion within the perinuclear vimentin network, a region we had thought too densely bundled to permit such motility. To examine the nanoscale organization of perinuclear vimentin, we acquired high-resolution electron microscopy volumes of a vitreously frozen cell and reconstructed VIFs and microtubules within a ~50 μm3 window. Of 583 VIFs identified, most were integrated into long, semi-coherent bundles that fluctuated in width and filament packing density. Unexpectedly, VIFs displayed minimal local co-alignment with microtubules, save for sporadic cross-over sites that we predict facilitate cytoskeletal crosstalk. Overall, this work demonstrates single VIF dynamics and organization in the cellular milieu for the first time.

Ependymal and Neural Stem Cells of Adult Molly Fish (Poecilia sphenops, Valenciennes, 1846) Brain: Histomorphometry, Immunohistochemical, and Ultrastructural Studies.

This study was conducted on 16 adult specimens of molly fish (Poecilia sphenops) to investigate ependymal cells (ECs) and their role in neurogenesis using ultrastructural examination and immunohistochemistry. The ECs lined the ventral and lateral surfaces of the optic ventricle and their processes extended through the tectal laminae and ended at the surface of the tectum as a subpial end-foot. Two cell types of ECs were identified: cuboidal non-ciliated (5.68 ± 0.84/100 μm2) and columnar ciliated (EC3.22 ± 0.71/100 μm2). Immunohistochemical analysis revealed two types of GFAP immunoreactive cells: ECs and astrocytes. The ECs showed the expression of IL-1β, APG5, and Nfr2. Moreover, ECs showed immunostaining for myostatin, S100, and SOX9 in their cytoplasmic processes. The proliferative activity of the neighboring stem cells was also distinct. The most interesting finding in this study was the glia–neuron interaction, where the processes of ECs met the progenitor neuronal cells in the ependymal area of the ventricular wall. These cells showed bundles of intermediate filaments in their processes and basal poles and were connected by desmosomes, followed by gap junctions. Many membrane-bounded vesicles could be demonstrated on the surface of the ciliated ECs that contained neurosecretion. The abluminal and lateral cell surfaces of ECs showed pinocytotic activities with many coated vesicles, while their apical cytoplasm contained centrioles. The occurrence of stem cells in close position to the ECs, and the presence of bundles of generating axons in direct contact with these stem cells indicate the role of ECs in neurogenesis. The TEM results revealed the presence of neural stem cells in a close position to the ECs, in addition to the presence of bundles of generating axons in direct contact with these stem cells. The present study indicates the role of ECs in neurogenesis.

Negative tension controls stability and structure of intermediate filament networks

Networks, whose junctions are free to move along the edges, such as two-dimensional soap froths and membrane tubular networks of endoplasmic reticulum are intrinsically unstable. This instability is a result of a positive tension applied to the network elements. A paradigm of networks exhibiting stable polygonal configurations in spite of the junction mobility, are networks formed by bundles of Keratin Intermediate Filaments (KIFs) in live cells. A unique feature of KIF networks is a, hypothetically, negative tension generated in the network bundles due to an exchange of material between the network and an effective reservoir of unbundled filaments. Here we analyze the structure and stability of two-dimensional networks with mobile three-way junctions subject to negative tension. First, we analytically examine a simplified case of hexagonal networks with symmetric junctions and demonstrate that, indeed, a negative tension is mandatory for the network stability. Another factor contributing to the network stability is the junction elastic resistance to deviations from the symmetric state. We derive an equation for the optimal density of such networks resulting from an interplay between the tension and the junction energy. We describe a configurational degeneration of the optimal energy state of the network. Further, we analyze by numerical simulations the energy of randomly generated networks with, generally, asymmetric junctions, and demonstrate that the global minimum of the network energy corresponds to the irregular configurations.

P36.01 Primary Acinic Cell Carcinoma of Bronchial Ground Origin: A Case Report

Primary acinic cell carcinoma of the lung is an extremely rare disease. Also known as Fechner’s tumor, this condition was first reported by Fechner et al. in 1972. The accurate diagnosis of primary pulmonary acinic cell carcinoma is difficult and relies on comprehensive evaluation of clinical, histological and immunohistochemical features. A 49-year-old male patient was referred to our hospital because of an abnormal infiltration shadow in the left lower lung field detected on a chest radiograph during a medical check-up. Chest computed tomography revealed a nodal mass shadow 10mm in size, in segment 8 of the left lower lobe. Bronchoscopic examination revealed a polypoid tumor at B8. Transbronchial biopsy was performed and the tumor was diagnosed as a bronchial gland adenoma. The patient underwent video-assisted thoracic segmentectomy to achieve complete resection of the tumor. Macroscopically, the tumor was a solitary mass measuring 14×10×8 mm in size with substantial cut surface and showed no intraparenchimal growth. Histopathological examination revealed a polypoid projection in the bronchial space. Adeno-type cancer cells with monomorphous nuclei invade the bronchial wall tissue in association with tubule or acinus-like space formation. The cytoplasm of the tumor cells is plump and eosinophilic with granularity or clear. No direct invasion into the lung parenchyma was observed. Immunohistochemical staining revealed that the tumor cells were positive for PAS, lactoferrin, and HMG-45MI. The features are consistent with acinic cell carcinoma of bronchial gland origin. Electron microscopy showed that the acinus-forming tumor cell possess well-developed mitochondria and round-surfaced endoplasmic reticulum, in association with active luminal secretion. Rounded, electron-dense secretory exocrine granules, ranging from 150 to 340 nm in size, are noted mainly in the apical cytoplasm. Fat vacuoles are noted in some tumor cells. Microvillous intracytoplasmic lumina are occasionally noted. Bundles of intermediate filaments and desmosomal attachments are also seen. These features are consistent with acinar cell nature of the cells. Fourteen years since the surgical resection, no apparent recurrence or metastasis has been detected. We experienced an extremely rare case of primary bronchial acinic cell carcinoma diagnosed based on clinical information, histopathological features, immunogistopathological staining profile, and electron microscopy features. The limited number of reports on this type of tumor have revealed that the outcome after surgical resection is favorable due to its low-grade malignant potential. Likewise in this case, the patient remained free of recurrence for over 14 years after surgery.

Evaluation of Gingival Tissue Pathological Changes in Human Peri-implantitis: Histological, Immunohistochemical and Ultrastructural Study

Aims: The current research was performed to study histopathological, immunohistochemical and ultrastructural characteristics of gingival tissue in peri-implantitis. Methods & Results: This study examined 25 patients between ages of 30–40 years. Twenty patients were selected with peri-implantitis (peri-implantitis group) in which inflamed gingival tissues were surgically removed. The gingival soft tissue collars from five healthy patients with partially impacted third molar were surgically removed (control group). All gingival tissue samples were examined histologically and ultrastructurally. Immunoreactivity to CD3 and CD20 antibodies was also evaluated. Cases of peri-implantitis stained with hematoxylin and eosin demonstrated hyperplastic nonkeratinized epithelium with downward growth of rete ridges. Connective tissue stroma revealed prominent vascularity, proliferation of fibrous tissue and focally aggregated inflammatory cell infiltration localized to the subepithelial area. Immunohistochemical results exhibited large numbers of T (CD3+) and B (CD20+) lymphocytes in peri-implantitis compared to normal tissue with a statistically significant difference. All cases of peri-implantitis demonstrated no significant difference between T and B lymphocytes. Transmission electron microscope showed wide intercellular spaces with fine bundles of keratin intermediate filaments around the nucleus. Fibrous connective tissue stroma with active fibroblasts and numerous mixed inflammatory cells (plasma cells, mast cells and numerous activated lymphocytes) were also revealed. Conclusions: Variable histopathological changes appeared in peri-implantitis soft tissue including hyperplastic nonkeratinized epithelium, mixed inflammatory cell infiltration with no statistical difference between T and B lymphocytes, excessive collagenization and vascular proliferation. Understanding these histopathological alterations may help clinicians in better management of peri- implantitis condition to ensure longevity of dental implants.

Epithelium of the human vocal fold as a vibrating tissue

ObjectivesThe human adult vocal fold mucosa, especially, superficial layer of the lamina propria (Reinke's space) has attracted notice as an important vibrating structure. However, fine structures of the stratified squamous epithelium of the human adult vocal fold, which is another histological component of the mucosa, remain enigmatic. MethodsThree normal human adult vocal folds and epiglottises and three newborn vocal folds were investigated. Observations using transmission electron microscopy and light microscopy including immunohistochemistry were performed. ResultsThe most obvious feature of the epithelium of the human adult vocal folds was that the intercellular spaces between adjacent epithelial cells were large (984 ± 186 nm) compared with the stratified squamous epithelium of the human adult epiglottis and the human newborn vocal fold.Even though intercellular spaces between adjacent epithelial cells of the human adult vocal fold were large, desmosomes at the junctions of two adjacent epithelial cells made firm intercellular adhesion. Tonofilaments composed of the bundles of intermediate filaments anchored to the desmosomes. Desmosomes formed a continuous cytoskeletal network throughout the epithelial cells and epithelium of the human adult vocal fold. In addition, a great deal of E-cadherin (adhesive glycoprotein) was present between epithelial cells especially the lower half of the stratified squamous epithelium of the human adult vocal fold. ConclusionsFrom the functional morphological point of view, stratified squamous epithelium of the human adult vocal fold seems to form a structural framework of tensile strength with pliability suitable structure for vibration.

Helical twist direction in the macrofibrils of keratin fibres is left handed

Macrofibrils, the main structural features within the cortical cells of mammalian hair shafts, are long composite bundles of keratin intermediate filaments (KIFs) embedded in a matrix of keratin-associated proteins. The KIFs can be helically arranged around the macrofibril central axis, making a cylinder within which KIF helical angle relative to macrofibril axis increases approximately linearly from macrofibril centre to edge. Mesophase-based self-assembly has been implicated in the early formation of macrofibrils, which first appear as liquid-crystal tactoids in the bulb of hair follicles. Formation appears to be driven initially by interactions between pre-keratinized KIFs. Differences in the nature of these KIF-KIF interactions could result in all macrofibrils being internally twisted in a single handedness, or a 50:50 mixture of handedness within each cortical cell. We data-mined 41 electron tomograms containing three-dimensional macrofibril data from previously published studies of hair and wool. In all 644 macrofibrils examined we found that within each tomogram all macrofibrils had the same handedness. We concluded that earlier reports of left- and right-handed macrofibrils were due to artefacts of imaging or data processing. A handedness marker was used to confirm (using re-imaged sections from earlier studies) that, in both human and sheep, all macrofibrils are left-handed around the macrofibril axis. We conclude that this state is universal within mammalian hair. This also supports the conclusion that the origin of macrofibril twist is the expression of chiral twisting forces between adjacent KIFs, rather than mesophase splay and bending forces relaxing to twisting forces acting within a confined space.

Evolution of Trichocyte Keratin Associated Proteins.

The major components of hair are keratins and keratin associated proteins (KRTAPs). KRTAPs form the interfilamentous matrix between intermediate filament bundles through extensive disulfide bond cross-linking with the numerous cysteine residues in hair keratins. A variable number of approximately100-180 genes compose the KRTAP gene family in mammals. KRTAP gene family members present a typical pattern of concerted evolution, and its evolutionary features are consistent with the evolution of mammalian hair. KRATP genes might be more important in determining the structure of cashmere fibers in domestic mammals like sheep and goats. KRTAP gene variants thus should provide information for improved wool by sheep and goat breeding.

The origin of Rosenthal fibers and their contributions to astrocyte pathology in Alexander disease

Rosenthal fibers (RFs) are cytoplasmic, proteinaceous aggregates. They are the pathognomonic feature of the astrocyte pathology in Alexander Disease (AxD), a neurodegenerative disorder caused by heterozygous mutations in the GFAP gene, encoding glial fibrillary acidic protein (GFAP). Although RFs have been known for many years their origin and significance remain elusive issues. We have used mouse models of AxD based on the overexpression of human GFAP (transgenic, TG) and a point mutation in mouse GFAP (knock-in, KI) to examine the formation of RFs and to find astrocyte changes that correlate with the appearance of RFs. We found RFs of various sizes and shapes. The smallest ones appear as granular depositions on intermediate filaments. These contain GFAP and the small heat shock protein, alphaB-crystallin. Their aggregation appears to give rise to large RFs. The appearance of new RFs and the growth of previously formed RFs occur over time. We determined that DAPI is a reliable marker of RFs and in parallel with Fluoro-Jade B (FJB) staining defined a high variability in the appearance of RFs, even in neighboring astrocytes. Although many astrocytes in AxD with increased levels of GFAP and with or without RFs change their phenotype, only some cells with large numbers of RFs show a profound reconstruction of cellular processes, with a loss of fine distal processes and the appearance of large, lobulated nuclei, likely due to arrested mitosis. We conclude that 1) RFs appear to originate as small, osmiophilic masses containing both GFAP and alphaB-crystallin deposited on bundles of intermediate filaments. 2) RFs continue to form within AxD astrocytes over time. 3) DAPI is a reliable marker for RFs and can be used with immunolabeling. 4) RFs appear to interfere with the successful completion of astrocyte mitosis and cell division.

The effects of Origanum hypericifolium essential oil application and ultraviolet B irradiation on mouse skin: An ultrastructural study

Exposure to UV radiation can cause histopathological and ultrastructural changes in the skin. Origanum hypericifolium, an endemic Turkish plant,essential oil is mainly composed of monoterpenes. The effects of undiluted O. hypericifolium oil on the ultrastructural characteristics of the UVB-irradiated dorsal skin of mice were investigated using transmission electron microscopy. The BALB/c mice were shaved of dorsal hair and randomly housed into 4 groups: 1: control; 2: UVB-irradiated; 3: oil applied; and 4: oil applied and UVB-irradiated. The oil was applied topically to the dorsal skins of the mice on alternate days for 1week prior to UVB exposure. The skins were irradiated for a total dose of 3.5J/cm2. The sections were stained with hematoxylin and eosin, semithin sections were stained with toluidine blue and ultrathin sections were contrasted with uranyl acetate/lead citrate. There were histopathological changes such as parakeratosis and squamous hyperplasia in the epidermal cell layers (Groups 3 and 4). There were also ultrastructural changes including lacunae formations throughout the stratum corneum layer (Groups 2, 3, and 4), enlargement of intercellular spaces (Groups 2 and 3), reduced desmosomes, narrow and elongated interdigitations, shortened, relatively indistinct and electron dense intermediate keratin filament bundles (Group 3). There were various sizes of cytoplasmic and perinucleolar vacuoles (Groups 3 and 4) and apoptotic bodies phagocytized by keratinocytes (Group 4). I conclude that undiluted oil has side-effects and the potential to inflict injury to the skin. The oil does not ameliorate the negative effects of UVB on epidermal skin cells.

Ultrastructural study of mouse adipose-derived stromal cells induced towards osteogenic direction.

We investigated the ultrastructural characteristics of mouse adipose-derived stem/stromal cells (ASCs) induced towards osteogenic lineage. ASCs were isolated from adipose tissue of FVB-Cg-Tg(GFPU)5Nagy/J mice and expanded in monolayer culture. Flow cytometry, histochemical staining, and electron microscopy techniques were used to characterize the ASCs with respect to their ability for osteogenic differentiation capacity. Immunophenotypically, ASCs were characterized by high expression of the CD44 and CD90 markers, while the relative content of cells expressing CD45, CD34 and CD117 markers was <2%. In assays of differentiation, the positive response to osteogenic differentiation factors was observed and characterized by deposition of calcium in the extracellular matrix and alkaline phosphatase production. Electron microscopy analysis revealed that undifferentiated ASCs had a rough endoplasmic reticulum with dilated cisterns and elongated mitochondria. At the end of the osteogenic differentiation, the ASCs transformed from their original fibroblast-like appearance to having a polygonal osteoblast-like morphology. Ultrastructurally, these cells were characterized by large euchromatic nucleus and numerous cytoplasm containing elongated mitochondria, a very prominent rough endoplasmic reticulum, Golgi apparatus and intermediate filament bundles. Extracellular matrix vesicles of variable size similar to the calcification nodules were observed among collagen fibrils. Our data provide the ultrastructural basis for further studies on the cellular mechanisms involved in osteogenic differentiation of mouse adipose-derived stem/stromal cells. Microsc. Res. Tech. 79:557-564, 2016. © 2016 Wiley Periodicals, Inc.

Tissue-Engineered Skin Substitute Enhances Wound Healing after Radiation Therapy.

When given in conjunction with surgery for treating cancer, radiation therapy may result in impaired wound healing, which, in turn, could cause skin ulcers. In this study, bilayer and monolayer autologous skin substitutes were used to treat an irradiated wound. A single dose of 30 Gy of linear electron beam radiation was applied to the hind limb of nude mice before creating the skin lesion (area of 78.6 mm). Monolayer tissue-engineered skin substitutes (MTESSs) were prepared by entrapping cultured keratinocytes in fibrin matrix, and bilayer tissue-engineered skin substitutes (BTESSs) were prepared by entrapping keratinocytes and fibroblasts in separate layers. Bilayer tissue-engineered skin substitute and MTESS were implanted to the wound area. Gross appearance and wound area were analyzed to evaluate wound healing efficiency. Skin regeneration and morphological appearance were observed via histological and electron microscopy. Protein expressions of transforming growth factor β1 (TGF-β1), platelet-derived growth factor BB (PDGF-BB), and vascular endothelial growth factor (VEGF) in skin regeneration were evaluated by immunohistochemistry (IHC). Macroscopic observation revealed that at day 13, treatments with BTESS completely healed the irradiated wound, whereas wound sizes of 1.1 ± 0.05 and 6.8 ± 0.14 mm were measured in the MTESS-treated and untreated control groups, respectively. Hematoxylin-eosin (H&E) analysis showed formation of compact and organized epidermal and dermal layers in the BTESS-treated group, as compared with MTESS-treated and untreated control groups. Ultrastructural analysis indicates maturation of skin in BTESS-treated wound evidenced by formation of intermediate filament bundles in the dermal layer and low intercellular space in the epidermal layer. Expressions of TGF-β1, PDGF-BB, and VEGF were also higher in BTESS-treated wounds, compared with MTESS-treated wounds. These results indicate that BTESS is the preferred treatment for irradiated wound ulcers.

Human Bone Marrow Stromal Cells Differentiate Into Corneal Tissue and Prevent Ocular Graft-Versus-Host Disease in Mice.

Clinical trials have assessed the use of human bone marrow stromal cells (hBMSCs) for the treatment of immune-related disorders such as graft-versus-host disease (GVHD). In the current study, we show that GFP(+)-transduced hBMSCs generated from bone marrow migrate and differentiate into corneal tissue after subconjunctival injection in mice. Interestingly, these hBMSCs display morphological features of epithelial, stromal, and endothelial cells and appear at different layers and with different morphologies depending on their position within the epithelium. Furthermore, these cells display ultrastructural properties, such as bundles of intermediate filaments, interdigitations, and desmosomes with GFP(-) cells, which confirms their differentiation into corneal tissues. GFP(+)-transduced hBMSCs were injected at different time points into the right eye of lethally irradiated mice undergoing bone marrow transplantation, which developed ocular GVHD (oGVHD). Remarkably, hBMSCs massively migrate to corneal tissues after subconjunctival injection. Both macroscopic and histopathological examination showed minimal or no evidence of GVHD in the right eye, while the left eye, where no hBMSCs were injected, displayed features of GVHD. Thus, in the current study, we confirm that hBMSCs may induce their therapeutic effect at least in part by differentiation and regeneration of damaged tissues in the host. Our results provide experimental evidence that hBMSCs represent a potential cellular therapy to attenuate oGVHD.

Self-Assembly of Recombinant Hagfish Thread Keratins Amenable to a Strain-Induced α-Helix to β-Sheet Transition.

Hagfish slime threads are assembled from protein-based bundles of intermediate filaments (IFs) that undergo a strain-induced α-helical coiled-coil to β-sheet transition. Draw processing of native fibers enables the creation of mechanically tuned materials, and under optimized conditions this process results in mechanical properties similar to spider dragline silk. In this study, we develop the foundation for the engineering of biomimetic recombinant hagfish thread keratin (TK)-based materials. The two protein constituents from the hagfish Eptatretus stoutii thread, named EsTKα and EsTKγ, were expressed in Escherichia coli and purified. Individual (rec)EsTKs and mixtures thereof were subjected to stepwise dialysis to evaluate their protein solubility, folding, and self-assembly propensities. Conditions were identified that resulted in the self-assembly of coiled-coil rich IF-like filaments, as determined by circular dichroism (CD) and transmission electron microscopy (TEM). Rheology experiments indicated that the concentrated filaments assembled into gel-like networks exhibiting a rheological response reminiscent to that of IFs. Notably, the self-assembled filaments underwent an α-helical coiled-coil to β-sheet transition when subjected to oscillatory shear, thus mimicking the critical characteristic responsible for mechanical strengthening of native hagfish threads. We propose that our data establish the foundation to create robust and tunable recombinant TK-based materials whose mechanical properties are controlled by a strain-induced α-helical coiled-coil to β-sheet transition.

Cutaneous extrarenal rhabdoid tumor in a dog: a case report

Rhabdoid tumours (RTs) are rare, highly aggressive tumours of undetermined origin in humans, and are sub-classified as renal/extrarenal RTs depending on location. The origins of extrarenal rhabdoid tumours are an enigma and neoplasms have rarely been reported in non-primate species. An 11-year-old male Maltese dog was presented with a submandibular mass. Histologically, the mass was composed of sheets of highly pleomorphic "rhabdoid" cells, further characterised by the presence of large epithelioid cells with globular/fibrillar paranuclear inclusions. Further immunohistochemical analysis revealed that the neoplastic cells were positive for vimentin and desmin similar to human tumours. In addition, ultrastructural analysis showed that the intracytoplasmic inclusions were mainly composed of whorled bundles of intermediate filaments. Our results suggest a useful diagnostic approach to cutaneous, extrarenal rhabdoid tumours in dogs and describe their characteristics.

Cellular level robotic surgery: Nanodissection of intermediate filaments in live keratinocytes

We present the nanosurgery on the cytoskeleton of live cells using AFM based nanorobotics to achieve adhesiolysis and mimic the effect of pathophysiological modulation of intercellular adhesion. Nanosurgery successfully severs the intermediate filament bundles and disrupts cell–cell adhesion similar to the desmosomal protein disassembly in autoimmune disease, or the cationic modulation of desmosome formation. Our nanomechanical analysis revealed that adhesion loss results in a decrease in cellular stiffness in both cases of biochemical modulation of the desmosome junctions and mechanical disruption of intercellular adhesion, supporting the notion that intercellular adhesion through intermediate filaments anchors the cell structure as focal adhesion does and that intermediate filaments are integral components in cell mechanical integrity. The surgical process could potentially help reveal the mechanism of autoimmune pathology-induced cell–cell adhesion loss as well as its related pathways that lead to cell apoptosis. From the Clinical EditorThis team of authors performed nanosurgery on the cytoskeleton of live cells using AFM based nanorobotics to achieve adhesiolysis, and mimic the effect of pathophysiological modulation of intercellular adhesions. This method could potentially help reveal the mechanism of autoimmune pathology-induced cell–cell adhesion loss as well as its related pathways that lead to cell apoptosis.

The Adult Macaque Spinal Cord Central Canal Zone Contains Proliferative Cells And Closely Resembles The Human

The persistence of proliferative cells, which could correspond to progenitor populations or potential cells of origin for tumors, has been extensively studied in the adult mammalian forebrain, including human and nonhuman primates. Proliferating cells have been found along the entire ventricular system, including around the central canal, of rodents, but little is known about the primate spinal cord. Here we describe the central canal cellular composition of the Old World primate Macaca fascicularis via scanning and transmission electron microscopy and immunohistochemistry and identify central canal proliferating cells with Ki67 and newly generated cells with bromodeoxyuridine incorporation 3 months after the injection. The central canal is composed of uniciliated, biciliated, and multiciliated ependymal cells, astrocytes, and neurons. Multiciliated ependymal cells show morphological characteristics similar to multiciliated ependymal cells from the lateral ventricles, and uniciliated and biciliated ependymal cells display cilia with large, star-shaped basal bodies, similar to the Ecc cells described for the rodent central canal. Here we show that ependymal cells with one or two cilia, but not multiciliated ependymal cells, proliferate and give rise to new ependymal cells that presumably remain in the macaque central canal. We found that the infant and adult human spinal cord contains ependymal cell types that resemble those present in the macaque. Interestingly, a wide hypocellular layer formed by bundles of intermediate filaments surrounded the central canal both in the monkey and in the human, being more prominent in the stenosed adult human central canal.

Ultrastructural characteristics of 5BrdU labeling retention cells including stem cells of regenerating feathers in chicken.

Feathers regenerate from stem cells localized in a region of the follicle indicated as the bulge of the collar. Stem cells are slow cycling cells and some of these cells can be identified after labeling experiments using 5-bromo-deoxyuridine to detect label retaining cells (5BrdU LRCs). The present electron microscopic analysis of 5BrdU LRCs has described the ultrastructural characteristics of small cells present in the bulge region of the follicle in regenerating feathers of chickens that include stem cells. Labeled feather stem cells are smaller than 10 lm in average diameter, possess large nuclei with high nuclear/cytoplasmic ratio, and contain evenly distributed ribosomes, sparse bundles of intermediate filaments, scarce or no endoplasmic reticulum, and few mitochondria. The nuclei are mainly euchromatic with a variable amount of heterochromatin clumps and the nucleoli show developed granular and fibrillar components. These features indicate that feather stem cells are transcriptionally active cells for ribosomal and proteins synthesis. The cell surface of feather stem cells often shows small and irregular folds resembling microvilli in contact with the surrounding cells. The latter characteristics may be related to the exchange of molecules and/or with the migration of stem cells among other epithelial cells of the collar epithelium.

Ultrastructure of Interstitial Cells in Subserosa of Human Colon

We studied the ultrastructure of interstitial cells in the subserosal/adventitial layer in human colon. An interstitial cell type with an ultrastructure intermediate between fibroblast-like cells (FLC) and interstitial cells of Cajal was identified (IC-SS). IC-SS had thin and flattened branching processes, most densely arranged close to the longitudinal muscle cells. Caveolae, bundles of intermediate filaments and membrane-associated dense bands, often with a patchy basal lamina, were characteristic. Secretory organelles (granular endoplasmic reticulum, smooth endoplasmic reticulum, Golgi, coated vesicles) were prominent. The IC-SS ultrastructure was different from that of FLC in the longitudinal layer, which had no caveolae and fewer intermediate filaments. Peg-and-socket junctions between IC-SS and between IC-SS and muscle cells were present, and IC-SS processes had close, selective appositions to muscle cells. Gap junctions were not observed. Small nerve bundles were abundant, but close contacts (<100 nm) between IC-SS or muscle cells and nerves were inconspicuous. Close appositions between IC-SS and mast cells were present; close relations to macrophages were not observed. The myoid features of IC-SS are thus more pronounced in comparison with FLC of other locations in the gastrointestinal muscle. The organization and ultrastructure may suggest a regulatory nature of IC-SS on the colonic muscle layers.

The stratum corneum: the rampart of the mammalian body

The stratum corneum (SC) is the outermost region of the epidermis and plays key roles in cutaneous barrier function in mammals. The SC is composed of 'bricks', represented by flattened, protein-enriched corneocytes, and 'mortar', represented by intercellular lipid-enriched layers. As a result of this 'bricks and mortar' structure, the SC can be considered as a 'rampart' that encloses water and solutes essential for physiological homeostasis and that protects mammals from physical, chemical and biological assaults. The corneocyte cytoskeleton contains tight bundles of keratin intermediate filaments aggregated with filaggrin monomers, which are subsequently degraded into natural moisturizing compounds by various proteases, including caspase 14. A cornified cell envelope is formed on the inner surface of the corneocyte plasma membrane by transglutaminase-catalysed cross-linking of involucrin and loricrin. Ceramides form a lipid envelope by covalently binding to the cornified cell envelope, and extracellular lamellar lipids play an important role in permeability barrier function. Corneodesmosomes are the main adhesive structures in the SC and are degraded by certain serine proteases, such as kallikreins, during desquamation. The roles of the different SC components, including the structural proteins in corneocytes, extracellular lipids and some proteins associated with lipid metabolism, have been investigated in genetically engineered mice and in naturally occurring hereditary skin diseases, such as ichthyosis, ichthyosis syndrome and atopic dermatitis in humans, cattle and dogs.