Ultra‐structural hair alterations in Friedreich's ataxia: A scanning electron microscopic investigation

Friedreich's ataxia (FRDA) is an autosomal recessive inherited disorder involving progressive damage to the central and peripheral nervous systems and cardiomyopathy. FRDA is caused by the silencing of the FXN gene and reduced levels of the encoded protein, frataxin. Frataxin is a mitochondrial protein that functions primarily in iron‐sulfur cluster synthesis. Skin disorders including hair abnormalities have previously been reported in patients with mitochondrial disorders. However, to our knowledge, ultra‐structural hair alterations in FRDA were not demonstrated. The purpose of this study was to determine ultra‐structural alterations in the hairs of FRDA patients as well as carriers. Hair specimen from four patients, who are in different stages of the disease, and two carriers were examined by scanning electron microscope. Thin and weak hair follicles with absence of homogeneities on the cuticular surface, local damages of the cuticular layer, cuticular fractures were detected in both carriers and patients, but these alterations were much more prominent in the hair follicles of patients. In addition, erosions on the surface of the cuticle and local deep cavities just under the cuticular level were observed only in patients. Indistinct cuticular pattern, pores on the cuticular surface, and presence of concavities on the hair follicle were also detected in patients in later stages of the disease. According to our results, progression of the disease increased the alterations on hair structure. We suggest that ultra‐structural alterations observed in hair samples might be due to oxidative stress caused by deficient frataxin expression in mitochondria. Microsc. Res. Tech. 78:731–736, 2015. © 2015 Wiley Periodicals, Inc.     

Organization of microtubules in cochlear hair cells

The organization of microtubules in hair cells of the guinea-pig cochlea has been investigated using transmission electron microscopy and correlated with the location of tubulin-associated immunofluorescence in surface preparations of the organ of Corti. Results from both techniques reveal consistent distributions of microtubules in inner and outer hair cells. In the inner hair cells, microtubules are most concentrated in the apex. Reconstruction from serial sections shows three main groups: firstly, in channels through the cuticular plate and in a discontinuous belt around its upper perimeter; secondly, forming a ring inside a rim extending down from the lower perimeter of the plate; and thirdly, in a meshwork underlying the main body of the plate. In the cell body, microtubules line the inner face of the subsurface cistern and extend longitudinally through a tubulo-vesicular track between the apex and base. In outer hair cells, the pattern of microtubules associated with the cuticular plate is similar, although there are fewer present than in inner hair cells. In outer hair cells from the apex of the cochlea, microtubules occur around an infracuticular protrusion of cuticular plate material. In the cell body, many more microtubules occur in the region below the nucleus compared with inner hair cells. The possible functions of microtubules in hair cells are discussed by comparison with those found in other systems. These include morphogenesis and maintenance of cell shape; intracellular transport, e.g., of neurotransmitter vesicles; providing a possible substrate for motility; mechanical support of structures associated with sensory transduction.     

Antennal multiporous sensilla: their gustatory features for host recognition in female parasitic wasps (insecta, Hymenoptera: Platygastroidea).

In parasitic wasps, various kinds of antennal plates have been interpreted as olfactory organs due to the presence of numerous pores. However, on the basis of ultrastructural investigations, some of these multiporous plates were revealed as being release sites of exocrine glands while others were postulated to have a gustatory function. Such sensilla, present only on female antennae, show unique features, found exclusively in Platygastroidea, with some differences between Scelionidae and Platygastridae. The cuticular apparatus consists of a short basiconic shaft with an apical multiporous area, the pores of which are covered by movable structures. The cellular components are made up of a remarkable number of sensory neurons, from 200 to 220, and an undefined number of sheath cells. These multiporous sensilla have tubular accessory glands that release their secretion through the socket sensillum only in scelionids. These morphological characters, combined with behavioral observations, strongly suggest a gustatory function, although electrophysiological studies are still needed to confirm this. A new terminology for antennal multiporous plates is discussed in relation to their different functions.     

Structure of the olfactory receptor organs,their GABAergic neural pathways,and modulation of mating behavior,in the giant freshwater prawn,Macrobrachium rosenbergii

In the giant male prawn, Macrobrachium rosenbergii, the olfactory system is thought to be the main pathway for modulating sexual behavior through pheromone perception. In this report, we first used gross anatomical, histological, and SEM methods to describe the structures of the olfactory receptors (sensilla setae), their neural pathways, and possible role in modulating mating behavior. On the surfaces of antennule and antenna filaments there are four types of sensory receptors, viz single spike‐like setae, single flagellum‐like setae, multiple flagella‐like setae, and aesthetascs (ASs). The ASs, which had previously been proposed to be odor receptor setae, are found only on the short filament of lateral antennule (slAn). Each AS on the slAn connects with olfactory receptor neurons (ORNs), whose axons form an outer central antennule nerve (ocAnNv), which then connects with the olfactory neutrophil (ON) of the brain. Thus, the slAn is the major olfactory organ that conveys sensory inputs from each AS to the ON within the deutocerebrum. GABA immunoreactivity was present in ASs, neurons of ORNs, inner central antennular, lateral tegumentary nerve, ocAnNv and the ON, inferring that GABA is the likely neurotransmitter in modulating olfaction. Disruption of the slAn by ablation or covering with Vaseline, resulted in significant reduction of mating behavior, indicating that this organ is crucial for sex pheromone perception. Identification of the active pheromones and further bioassays are now being performed. Microsc. Res. Tech. 76:572–587, 2013. © 2013 Wiley Periodicals, Inc.     

Exploring the use of soft X‐ray microscopy for imaging subcellular structures of the inner ear1

The soft X‐ray microscope at the Lawrence Berkeley National Laboratory was developed for visualization of biological tissue. Soft X‐ray microscopy provides high‐resolution visualization of hydrated, non‐embedded and non‐sectioned cells and is thus potentially an alternative to transmission electron microscopy. Here we show for the first time soft X‐ray micrographs of structures isolated from the guinea‐pig inner ear. Sensory outer hair cells and supporting pillar cells are readily visualized. In the hair cells, individual stereocilia can easily be identified within the apical hair bundle. The underlying cuticular plate is, however, too densely composed or too thick to be clearly visualized, and thus appears very dark. The cytoplasmic structures protruding from the cuticular plates as well as the fibrillar material surrounding and projecting from the cell nuclei can be seen. In the pillar cells the images reveal individual microtubule bundles. Soft X‐ray images of the acellular tectorial membrane and thin two‐layered Reissner's membrane display a level of resolution comparable to low‐power electron microscopy.     

Atomic force microscopy of human hair

The atomic force microscope (AFM) was used to investigate the surface architecture of the entire lengths of cleaned human head hairs. Many features previously seen with the scanning electron microscope (SEM) were identified. However, the AFM has provided much greater detail and, in particular, the hair's cuticular surfaces appear not to be as smooth as had been previously supposed. A consistent feature was of step discontinuities or "ghosts" on the scale surfaces. These delineated the original location of each overlying scale before its edge had been chipped away. There was a change in the longitudinal angular presentation of the surfaces about each ghost. This means the distal ends of each cuticle cell have been synthesised in the follicle to be thicker than where that same cuticle cell is bounded on both sides by other cuticle cells. The undamaged outer cuticular surfaces at the root end of each hair were covered everywhere by longitudinal ridges (striations). Where the hair surface was worn, the striations terminated at a scale edge ghost. The ridges were approximately 9 nm high and were in parallel array with a lateral repeat spacing of about 350 nm. The striations are evidently formed on the outer surface of each cuticle cell following earlier contact in the hair follicle with the inner root sheath. The study of stained transverse sections of hairs in the transmission electron microscope (TEM) is suggested as a means for throwing some light on the underlying structure and chemistry of the striations. Finally, our AFM studies have revealed that the surface of the freshly emergent hair gradually changes over a distance of about 20 mm and that the surface of the hair for most of its length is quite different from that near the root. This is likely to be of import to those engaged in the hair toiletries industry.     

Morphology of olfactory epithelium in humans and other vertebrates.

Human olfactory epithelium is similar in organization and cell morphology to that of most vertebrate species. The epithelium has a pseudostratified columnar organization and consists of olfactory neurons, supporting and basal cells. Near the mucosal surface there are also microvillar cells. These cells have neuron-like features and may be chemoreceptors. Human olfactory epithelium is not a uniform sensory sheet. Patches of non-sensory tissue often appear in what was thought to be a purely olfactory region. The significance of these patches has not been determined, but they could reflect exposure to environment agents or changes that occur during the normal aging process. In order to better understand the human olfactory system, further knowledge of the normal structure is necessary. This review addresses the morphology of the human olfactory epithelium and the remarkable plasticity of the vertebrate olfactory system.     

Ultrastructural studies of microtubules and microtubule organizing centers of the vertebrate olfactory neuron.

The olfactory neuron is specialized along its length into highly determined morphological regions. These regions include the dendritic cilia, dendritic vesicle, dendritic shaft proper, perikaryon, axon, zone of transition where the axon widens as it approaches its termination, and the axon terminal. Except for the zone of transition and the terminal, characteristic populations of microtubules occur in these compartments. In the olfactory vesicle, three discrete microtubule organizing centers (MTOCs) nucleate microtubules: the basal body, the lateral foot associated with the body, and dense masses of nearby material. Little is known about MTOCs elsewhere in the neuron, although the polarity of the axonal microtubules indicate that they originate at or near the perikaryon. An attempt is made to summarize what is known of the origin, structure, distribution, and function of microtubules in vertebrate olfactory neurons, which are useful model systems in which to study microtubules. Information about olfactory neuron microtubules may be applicable to neurons in general (e.g., the discovery that axons contain microtubules of uniform polarity was first made in the olfactory neuron) or to microtubules in other eukaryotic cells.     

Morphology and distribution of antennal sensilla in a parasitoid fly,Gymnosoma rotundatum (Diptera: Tachinidae)

Morphology of antennal sensilla and their distribution were investigated in male and female adults of the parasitoid fly Gymnosoma rotundatum (Diptera: Tachinidae) using scanning electron microscopy (SEM). The overall length and shape were not different between males and females from each other. Three basic types of sensilla (sensilla basiconica, s. chaetica, and s. coeloconica) were identified from both sexes, but with variations in numbers and distribution along the antennae. The s. basiconica and s. chaetica could be divided further into subtypes; s. basiconica into three subtypes and s. chaetica into two subtypes. All the basiconica subtypes 1, 2, and 3 were multiporous, indicating that their primary function was olfactory. The sensilla basiconica was most abundant on the antennae of both sexes. The abundance of s. basiconica subtype 1 was different, but other subtypes 2 and 3 were similar between males and females. There was no pore on the cuticular surface of the s. chaetica and s. coeloconica, suggesting that they are likely to be a mechanosensory or a thermohygroreceptory function. The abundance of the two sensillum types was similar between males and females. The morphological information obtained in our study provides a basis for future investigations into the sensory physiological function, and associated behaviors, of each type of sensilla in this parasitoid fly.     

Lamellar subcomponents of the cuticular cell membrane complex of mammalian keratin fibres show friction and hardness contrast by AFM

There is a substantial body of information indicating that 18‐methyleicosanoic acid (18‐MEA) is covalently linked to the outer surface of all mammalian keratin fibres and also forms the outer β‐layer of the cuticular cell membrane complex (CCMC) which separates the cuticle cells from each other. Low cohesive forces are expected between the lipid‐containing outer β‐layer and the δ‐layer of the CCMC, thus providing a weak point for cuticular delamination and presenting a fresh layer of 18‐MEA to the newly exposed surface. We have used lateral force microscopy and force modulation atomic force microscopy (AFM) to examine human hair fibres in which the non‐covalently linked fatty acids have been removed. Examination of the lateral force images of new cuticle surfaces revealed by the attrition of overlying cuticle layers showed three separate zones of clearly defined frictional contrast. These are thought to correspond with the δ‐layer, the proteinaceous epicuticle and outer β‐layers of the CCMC. The δ‐layer was found to have a thickness of 16 nm (SD = 1 nm, n = 25), comparable to the 18.0 nm thickness measured from transverse cross‐sections of fibres with transmission electron microscopy. Force modulation AFM showed that the outer β‐layer was softer than the epicuticle and the δ‐layer. The frictional contrast was removed following treatment with methanolic KOH (0.1 mol dm^?3) at 25 °C for 30 min, suggesting the hydrolysis of the thioester linkage and removal of 18‐MEA from the surface.     

Antennal sensory structures in Scaphoideus titanus Ball (Hemiptera: Cicadellidae)

Scaphoideus titanus Ball (Hemiptera: Cicadomorpha) is a leafhopper vector of a phytoplasma disease, the Flavescence dorée (FD), belonging to the vine yellows group. A scanning and transmission electron microscope study has been carried out to investigate the antennal sensory structures. The first two segments, the scape and the pedicel, are short, covered by cuticular scales and devoid of sensilla, with exception of some scattered hairs on the pedicel. The flagellum consists of a unique, elongated segment in which numerous subunits can be recognized, being separated by a sort of cuticular crown. The proximal five subunits bear most of the sensilla. We discovered the presence of single- and double-walled coeloconic sensilla, campaniform sensilla, basiconic sensilla, and trichoid sensilla. A scolopidium is located within the proximal region of the flagellum. Ultrastructural investigations suggest that the antennal sensilla could be involved in the perception of air-borne vibrations, temperature, and humidity variations. The most relevant feature is the extreme reduction of the olfactory sensilla, both in terms of number of sensory structures and sensory neurons per sensillum. The strong reduction in antennal olfactory sensilla to which this specie has undergone is discussed as possible consequence of the specificity toward the host plant.     

Ultrastructural histopathology of human olfactory dysfunction.

This paper presents electron-microscopic observations on biopsies of the olfactory mucosae of several classes of patients with smell disorders: 1) patients with loss of smell function following head injury (post-traumatic anosmics or hyposmics); 2) patients with loss of smell function following severe head colds and/or sinus infections (post-viral olfactory dysfunction, or PVOD); and 3) patients that have lacked smell function since birth (congenital anosmics). Of these, the traumatic anosmics' olfactory epithelia were quite disorganized; the orderly arrangement of supporting cells, ciliated olfactory receptor neurons, microvillar cells, and basal cells was disrupted. Although many somata of ciliated olfactory receptors were present, few of their dendrites reached the epithelial surface. The few olfactory vesicles present usually lacked olfactory cilia. The post-viral anosmics, too, had a greatly reduced number of intact ciliated olfactory receptor neurons, and most of those present were aciliate. The post-viral hyposmics had a larger population of intact, ciliated olfactory receptor cells. In the seven cases of congenital anosmia studied, no biopsies of olfactory epithelium were obtained, indicating the olfactory epithelium is either absent--or greatly reduced in area--in these individuals.     

Fine structure of olfactory sensilla in myriapods and arachnids.

Structural features of various types of olfactory sensilla are reviewed. 1) Sensilla basiconica which differ in form and size are found on the antennae of centipedes and millipedes. Their walls show longitudinal slits or grooves that either open into the sensillum lumen or do not penetrate the cuticle. In other such sensilla the outer surface is pierced by pores and the inner surface grooved and pocketed. These sensilla are innervated by one to six sensory cells. Their unbranched outer dendritic segments extend to the tip of the sensillum. The sensory cells are surrounded by two or three sheath cells which terminate at the sensillum base or form a continuous tube around the entire length of the outer dendritic segments. 2) Temporal organs of centipedes are located between the insertion of the antenna and the ocelli. These sensilla consist of a shallow cuticular ring with a central sensory plate made up by a layer of unperforated cuticle or a capsule with a mushroom-shaped structure inside formed by fibrous-looking cuticle. A dozen sensory cells with unbranched outer dendritic segments innervate each sensillum. They extend toward the sensory cuticle and pass just below it. Numerous sheath cell processes run parallel to the outer dendritic segments up to the sensory cuticle. 3) Thread-like flagella of Pauropoda are found on the antennae. They possess a flexible unperforated cuticular wall. These sensilla contain nine sensory cells surrounded by several sheath cells which form a continuous cytoplasmic tube around the outer dendritic segments. 4) Single-walled sensilla with numerous plugged pores penetrating the cuticular wall occur on the tarsus of the first leg in ticks. Each sensillum is innervated by 4-15 sensory cells. Three sheath cells terminate in the base of the sensillum. 5) Double-walled sensilla with spoke canals are found on the first tarsus of ticks. Their shaft is longitudinally grooved. Pore canals lead inward from the bottom of the grooves and open into vase-shaped chambers. From its base these canals extend into the lumen of the sensillum which contains unbranched outer dendritic segments of 1-2 sensory cells. 6) Single-walled sensilla with pore openings occur on the distal tarsal segments of the first leg of whip spiders. These sensilla are innervated by 40-45 sensory cells. Their unbranched outer dendritic segments fill the shaft lumen and extend partly into the wall pores. Microvillus-shaped sheath cell processes line the inner surface of the cuticular wall.(ABSTRACT TRUNCATED AT 400 WORDS)     

Diversity of the vomeronasal system in mammals: the singularities of the sheep model

The enormous morphological diversity and heterogeneity of the vomeronasal system (VNS) in mammals--as well as its complete absence in some cases--complicates the extrapolation of data from one species to another, making any physiological and functional conclusions valid for the whole Mammalian Class difficult and risky to draw. Some highly-evolved macrosmatic mammals, like sheep, have been previously used in interesting behavioral studies concerning the main and accessory olfactory systems. However, in this species, certain crucial morphological peculiarities have not until now been considered. Following histological, histochemical and immunohistochemical procedures, we have studied the vomeronasal organ (VNO) and the accessory olfactory bulb (AOB) of adult sheep. We have determined: (1) that all structures which classically define the VNO in mammals are present and well developed, providing the morphological basis for functional activity. (2) that, conversely, there is only a scant population of scattered mitral/tufted cells. One morphological consequence of both details is that the strata of the AOB in adult sheep are not as sharply defined as in other species; moreover, the small number of the mitral/tufted cells in the AOB may imply that the VNS of adult sheep is not capable of functioning in the way a well-developed VNS does in other species. (3) the zone to zone projection from the apical and basal sensory epithelium of the VNO to the anterior and posterior part of the AOB, respectively, typical in rodents, lagomorphs and marsupials, is not present in adult sheep.     

Epidermal glands in the abdomen of a basal ant Dinoponera lucida (Formicidae: Ponerinae)

The basal ant Dinoponera (Hymenoptera: Ponerinae) has lost the morphologic queen caste so that all females may be potential reproductive individuals, and the nestmate recognition results from cuticular hydrocarbons cues. However, data about the origin of that substance in Ponerinae ants are scarce. This study reports the occurrence of epidermal glands in the abdomen of the ant Dinoponera lucida. In this ant, the epidermis of the abdominal sternites has tall cells with well-developed nucleus contrasting with flattened and collapsed epidermis in the tergites, suggesting a glandular function in the epidermis of the sternites. The possible role of the glandular epidermis in the synthesis of cuticular hydrocarbons for the nestmate recognition is discussed.     

Chronic hypoxia-induced morphological and neurochemical changes in the carotid body

The carotid body (CB) plays an important role in the control of ventilation. Type I cells in CB are considered to be the chemoreceptive element which detects the levels of PO(2), PCO(2), and [H(+)] in the arterial blood. These cells originate from the neural crest and appear to retain some neuronal properties. They are excitable and produce a number of neurochemicals. Some of these neurochemicals, such as dopamine and norepinephrine, are considered to be primarily inhibitory to CB function and others, such as adenosine triphosphate, acetylcholine, and endothelin, are thought to be primarily excitatory. Chronic hypoxia (CH) induces profound morphological as well as neurochemical changes in the CB. CH enlarges the size of CB and causes hypertrophy and mitosis of type I cells. Also, CH changes the vascular structure of CB, including inducing marked vasodilation and the growth of new blood vessels. Moreover, CH upregulates certain neurochemical systems within the CB, e.g., tyrosine hydroxylase and dopaminergic activity in type I cells. There is also evidence that CH induces neurochemical changes within the innervation of the CB, e.g., nitric oxide synthase. During CH the sensitivity of the CB chemoreceptors to hypoxia is increased but the mechanisms by which the many CH-induced structural and neurochemical changes affect the sensitivity of CB to hypoxia remains to be established.     

Terminal nerve and vision

The vertebrate retina receives efferent input from different parts of the central nervous system. Efferent fibers are thought to influence retinal information processing but their functional role is not well understood. One of the best-described retinopetal fiber systems in teleost retinae belongs to the terminal nerve complex. Gonadotropin-releasing hormone (GnRH) and molluscan cardioexcitatory tetrapeptide (FMRFamide)-containing fibers from the ganglion of the terminal nerve form a dense fiber plexus in the retina at the border of the inner nuclear and inner plexiform layer. Peptide-containing fibers surround and contact perikarya of dopaminergic interplexiform cells in teleost retina. In vitro experiments demonstrated that exogenously supplied GnRH mediates dopaminergic effects on the membrane potential and on the morphology of dendritic tips (spinules) of cone horizontal cells. These effects can be specifically blocked by GnRH-antagonists, indicating that the release of dopamine and dopamine-dependent effects on light adaptation of retinal neurons are affected by the terminal nerve complex. Recent data have shown that olfactory information has an impact on retinal physiology, but its precise role is not clear. The efferent fiber of the terminal nerve complex is one of the first retinopetal fiber systems for which the sources of the fibers, their cellular targets, and several physiological, morphological, and behavioral effects are known. The terminal nerve complex is therefore a model system for the analysis of local information processing which is influenced by a distinct fiber projection.     

Ultrastructure and distribution of antennal sensilla of the chilli thrips Scirtothrips dorsalis hood (Thysanoptera: Thripidae)

The chilli thrips, Scirtothrips dorsalis Hood, is a serious pest of numerous important vegetable and ornamental crops. Various signals, especially phytochemical cues, determine the behavior of the phytophagous thrips at host selection. The sensory abilities of S. dorsalis are poorly understood although the antennae of adult are known to possess important sensory structures in orther insects. In this study, the morphology, distribution, and ultrastructure of the antennal sensilla of the S. dorsalis were examined by using scanning and transmission electron microscopy. Microscopy observations revealed that adult male and female S. dorsalis possess filiform antennae. Each antenna comprises a scape, a pedicel, and a flagellum composed of six segments without clear sexual dimorphism in the number and distribution of antennal sensilla. The scape and pedicel exhibit Böhm's bristles, sensilla chaetica, and sensilla campaniform. The external structures of these organs reveal their mechanosensory function. In the flagellum, the most represented sensilla are the multiporous sensilla basiconica, which can be divided into three types of single‐walled olfactory sensilla; three types of sensilla chaetica with mechanosensory and gustatory functions; sensilla coeloconica, which possess hollow cuticular spoke channels and represent double‐walled olfactory sensilla; sensilla capitula and sensilla cavity with thermo‐hygrosensory functions; and aporous sensilla trichodea with smooth cuticula and mechanosensory function. The putative function of described sensilla is discussed in ralation to host plant selection behavior of S. dorsalis.     

Ultrastructural neurobiology of the olfactory mucosa of the brown trout, Salmo trutta.

This paper describes four investigations of the olfactory mucosa of the brown trout: 1) the ultrastructure of the olfactory mucosa as revealed by scanning (SEM), conventional transmission (TEM), and high voltage (HVEM) electron microscopy; 2) light and electron-microscopic investigations of retrograde transport of the tracer macromolecule horseradish peroxidase (HRP) when applied to the cut olfactory nerve; 3) SEM and TEM investigations of the effects of olfactory nerve transection on cell populations within the olfactory epithelium; and 4) ultrastructural investigations of reversible degeneration of olfactory receptors caused by elevated copper concentrations. The trout olfactory epithelium contains five cell types: ciliated epithelial cells, ciliated olfactory receptor cells, microvillar olfactory receptor cells, supporting cells, and basal cells. The ciliated and microvillar olfactory receptor cells and a small number of basal cells are backfilled by HRP when the tracer is applied to the cut olfactory nerve. When the olfactory nerve is cut, both ciliated and microvillar olfactory receptor cells degenerate within 2 days and are morphologically intact again within 8 days. When wild trout are taken from their native stream and placed in tanks with elevated copper concentrations, ciliated and microvillar cells degenerate. Replacement of these trout into their stream of origin is followed by morphologic restoration of both types of olfactory receptor cells. Ciliated and microvillar receptor cells are primary sensory bipolar neurons whose dendrites make contact with the environment; their axons travel directly to the brain. Consequently, substances can be transported directly from the environment into the brain via these "naked neurons." Since fish cannot escape from the water in which they swim, and since that water may occasionally contain brain-toxic substances, the ability to close off--and later reopen--this anatomic gateway to the brain would confer a tremendous selective advantage upon animals that evolved the "brain-sparing" capacity to do so. Consequently, the unique regenerative powers of vertebrate olfactory receptor neurons may have their evolutionary origin in fishes.