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PubMed1996

A perfusion system for in vitro measurement of human cilia beat frequency.

We have designed and built a perfusion system and perfusion chamber to allow investigation of the effects of anaesthetic agents on human cilia in vitro. Using this system, samples of human respiratory cilia can be maintained in a stable and controlled environment for several hours. We measured cilia beat frequency of nasal respiratory epithelium from 10 healthy volunteers; cilia beat frequency was constant over a 4-h period, and measurements were found to be in good agreement with previously published work [1]. In a separate study we investigated the effect of a sleep dose of propofol on cilia beat frequency in samples from six patients undergoing minor surgery; samples were obtained before and immediately after induction of anaesthesia with propofol 2-3 mg kg-1. There was no statistically significant difference in cilia beat frequency between data obtained before and after induction with propofol.

Adult↗

PubMed2003

To beat or not to beat: roles of cilia in development and disease.

Cilia and flagella appeared very early in evolution to provide unicellular organisms with motility in water. Adaptation to non-aquatic life in plants resulted in the almost complete elimination of these organelles, except for gametic transport in some phylogenetic groups. In contrast, cilia and flagella were retained and employed for a wide variety of functions requiring fluid movement in complex multicellular animals. The functions of cilia in diverse processes such as left-right axis pattern formation, cerebrospinal fluid flow, sensory reception, mucociliary clearance and renal physiology indicate that cilia have been adapted as versatile tools for many biological processes. In this review, we discuss recent discoveries that have extended knowledge of the roles of cilia in normal development, and the pathological consequences caused by their dysfunction in mammals. We also consider evolutionary relationships between cilia from lower and higher eukaryotes, outline the ciliary components required for assembly and motility, and review the terminology of axonemal heavy chain dynein genes.

Animals↗

PubMed2002

The polycystic kidney disease proteins, polycystin-1, polycystin-2, polaris, and cystin, are co-localized in renal cilia.

Recent evidence has suggested an association between structural and/or functional defects in the primary apical cilium of vertebrate epithelia and polycystic kidney disease (PKD). In Caenorhabditis elegans, the protein orthologues of the PKD-related proteins, polycystin-1 (LOV-1), polycystin-2 (PKD2), and polaris (OSM-5), co-localize in the cilia of male-specific sensory neurons, and defects in these proteins cause abnormalities of cilia structure and/or function. This study sought to determine whether the mammalian polycystins are expressed in primary cilia of renal epithelia and whether these proteins co-localize with polaris and cystin, the newly described, cilia-associated protein that is disrupted in the cpk mouse. To begin to address this issue, the expression of the protein products encoded by the PKD1, PKD2, Tg737, and cpk genes were examined in mouse cortical collecting duct (mCCD) cells using an immunofluorescence-based approach with a series of previously well-characterized antibodies. The mCCD cells were grown on cell culture inserts to optimize cell polarization and cilia formation. The data demonstrate co-localization in cilia of polycystin-1 and polycystin-2, which are the principal proteins involved in autosomal dominant polycystic kidney disease, with polaris and cystin, which are proteins that are disrupted in the Tg737(orpk)and cpk mouse models of autosomal recessive polycystic kidney disease, respectively. These data add to a growing body of evidence that suggests that primary cilium plays a key role in normal physiologic functions of renal epithelia and that defects in ciliary function contribute to the pathogenesis of PKD.

Animals↗

PubMed1990

Extreme asthenozoospermia and chronic respiratory disease: a new variant of the immotile cilia syndrome.

Two patients suspected of suffering from ciliary dyskinesis were investigated. They consulted for primary infertility and chronic respiratory disease. Functional lung studies showed obstructive changes in one patient. Both had immotile sperm with short, thick and rigid tails. Ultrastructural studies of nasal biopsies showed abnormal cilia with almost complete lack of inner dynein arms (mean number of inner arms per axoneme 0.67 +/- 1.21 in patient 1 and 1.49 +/- 1.17 in patient 2, compared with normal values of 5.3 +/- 0.13). Other abnormalities included lack of parallel orientation of cilia and central translocation of microtubular doublets. Electron microscopy of sperm revealed hyperplasia of the fibrous sheath and axonemal disruption. This is the first report of an association of different anomalies in cilia and flagella leading to clinical manifestation of the immotile cilia syndrome. These findings emphasize the need for ultrastructural examination of respiratory cilia in men suffering from fibrous sheath alterations of sperm which so far have not been described in patients with the classical form of immotile cilia syndrome.

Adult↗

PubMed1986

Cyclic AMP-dependent protein phosphorylation in chemosensory neurons: identification of cyclic nucleotide-regulated phosphoproteins in olfactory cilia.

Chemosensory dendritic membranes (olfactory cilia) contain protein kinase activity that is stimulated by cyclic AMP and more efficiently by the nonhydrolyzable GTP analog guanosine-5'-O-(3-thio)triphosphate (GTP gamma S). In control nonsensory (respiratory) cilia, the cyclic AMP-dependent protein kinase is practically GTP gamma S-insensitive. GTP gamma S activation of the olfactory enzyme appears to be mediated by a stimulatory GTP-binding protein (G-protein) and adenylate cyclase previously shown to be enriched in the sensory membranes. Protein kinase C activity cannot be detected in the chemosensory cilia preparation under the conditions tested. Incubation of olfactory cilia with [gamma-32P]ATP leads to the incorporation of [32P]phosphate into many polypeptides, four of which undergo covalent modification in a cyclic nucleotide-dependent manner. The phosphorylation of one polypeptide, pp24, is strongly and specifically enhanced by cyclic AMP at concentrations lower than 1 microM. This phosphoprotein is not present in respiratory cilia, but is seen also in membranes prepared from olfactory neuroepithelium after cilia removal. Cyclic AMP-dependent protein kinase and phosphoprotein pp24 may be candidate components of the molecular machinery that transduces odor signals.

Animals↗

PubMed1986

Immunological detection of actin in isolated cilia from quail oviduct.

Cilia from quail oviduct were isolated with their membrane. The ultrastructural study revealed a good preservation of cilia in the purified fraction. Electrophoresis on SDS-PAGE showed a reproducible pattern of ciliary proteins, the major bands being those of tubulins 57 kDa and dyneins above 250 kDa. Among the minor bands, an immunological study was focused on a 43 kDa molecular mass protein, using monospecific antibodies against actin. Presence of actin was then detected by immunoblotting of isolated cilia fractions as well as of demembranated cilia, suggesting that actin is associated with the axoneme. The presence of actin in the cilia was confirmed by immunofluorescence. The cilia were found stained only on the proximal part, suggesting an heterogeneous distribution of actin within the axonemal length.

Actins↗

PubMed1980

Variations in the ultrastructure of human nasal cilia including abnormalities found in retinitis pigmentosa.

The electron microscopic structure of cilia from the inferior turbinate of the nose was studied in 12 adults, four with chronic sinusitis, one with allergic rhinitis, two with bronchiectasis, three with deviated nasal septum, and two normals. The changes are compared with those found in nasal cilia in 14 patients with retinitis pigmentosa. There were compound cilia in the seven cases with chronic sinusitis, allergic rhinitis, and bronchiectasis but, apart from this, the structure of the cilia was similar in all 12 cases. There were variations in the microtubular pattern in about 4% of cilia, dynein arms were not seen in 4%, and in the rest an average of 5-6 dynein arms were seen in each cilium. The orientation of the cilia was 0 to 90 degrees. In the retinitis pigmentosa patients there was a highly significant increase in cilial abnormalities. The establishment on a quantitative basis of the variations in normal structure of nasal cilila facilitated the recognition of an association between cilial abnormalities and retinitis pigmentosa and should help in the identification of associations that may exist between cilial abnormalities and other diseases.

Adult↗

PubMed2006

Isolation and characterization of cholangiocyte primary cilia.

Primary cilia are distinct organelles expressed by many vertebrate cells, including cholangiocytes; however, their functions remain obscure. To begin to explore the physiological role of these organelles in the liver, we described the morphology and structure of cholangiocyte cilia and developed new approaches for their isolation. Primary cilia were present only in bile ducts and were not observed in hepatocytes or in hepatic arterial or portal venous endothelial cells. Each cholangiocyte possesses a single cilium that extends from the apical membrane into the bile duct lumen. In addition, the length of the cilia was proportional to the bile duct diameter. We reproducibly isolated enriched fractions of cilia from normal rat and mouse cholangiocytes by two different approaches as assessed by scanning electron, transmission electron, and confocal microscopy. The purity of isolated ciliary fractions was further analyzed by Western blot analysis using acetylated tubulin as a ciliary marker and P2Y(2) as a nonciliary cell membrane marker. These novel techniques produced enriched ciliary fractions of sufficient purity and quantity for light and electron microscopy and for biochemical analyses. They will permit further assessment of the role of primary cilia in normal and pathological conditions.

Animals↗

PubMed1980

Abnormal cilia in Polynesians with bronchiectasis.

Bronchial or nasal ciliated epithelium from 13 patients with bronchiectasis (12 Polynesians and 1 European) was examined by electron microscopy. All cilia examined lacked dynein arams. In 2 patients, this was the only abnormality observed, but in the others, various ciliary abnormalities were present, including cilia with missing tubules, extra tubules, and misplaced tubules, as well as compound cilia, intracytoplasmic cilia, vesiculated cilia, and cilia with long winglike folds. In all of these patients pulmonary mucociliary transport rates were either absent or markedly reduced. It is suggested that these abnormalities were due to a mutation or group of mutations, which was the underlying cause of the bronchiectasis.

Adult↗

PubMedDate not supplied

Atypical cilia of the human nasal mucosa.

Typical and atypical ultrastructural features of the cilia in the human nasal mucosa are reported in this paper. The specimens were taken from patients with the diagnosis of allergic rhinitis or chronic sinusitis. Most of the cilia showed a typical 9 + 2 arrangement of the axial filament complexes, but atypical axonemes such as 9 + 4, 8 + 2 and 10 + 2 patterns were found in six cilia of three patients. The supernumerary central fibrils were observed in one cilium only, whereas atypical patterns of the peripheral fibrils were found in five cilia. Cilia which contained a multiple axial filament complex, so-called compound clia, were also found in the mucosa of the chronic sinusitis cases. On the basis of their ultrastructural appearance, we classified these cilia into two groups, an "adhesive type" and a "bulging type." The former had a columnar shape of variable diameter, whereas the latter had a balloon-like form. The former contained closely packed multiple axial filament complexes whereas the latter possessed only sparse and irregularly oriented complexes. Electron-lucent lumina which were formed by the remnants of the ciliary membrane were frequently found in the former's transitional portion, but never in the latter.

Chronic Disease↗

PubMed1992

Ultrastructural changes in human nasal cilia caused by the common cold and recovery of ciliated epithelium.

Changes in the ultrastructure of human respiratory cilia caused by the common cold were studied in 12 patients. The nasal mucosa was studied three times: on the first or second day after the beginning of symptoms, and 1 week and 3 weeks after the first biopsy. The damage was most severe at 1 week. The most remarkable finding was the loss of cilia and ciliated cells. However, the ultrastructure was usually normal, without any increase in tubular anomalies, as compared with the normal material of the previous reports. Three weeks after the beginning of the disease the number of cilia and ciliated cells had increased to nearly normal. However, as a sign of regeneration, immature short cilia (0.7 to 2.5 microns in length) were often seen. The ciliary orientation was uniform, dynein arms were normal, and there was no increase in the number of tubular anomalies. The results suggest that the impaired mucociliary function during viral infections is due to the loss of cilia and ciliated cells, rather than to ultrastructural anomalies in the cilia. The development of tubular anomalies and random ciliary orientation may require more extensive exposure to factors affecting ciliary function.

Biopsy↗

PubMed2006

The roles of cilia in developmental disorders and disease.

Cilia are highly conserved organelles that have diverse motility and sensory functions. Recent discoveries have revealed that cilia also have crucial roles in cell signaling pathways and in maintaining cellular homeostasis. As such, defects in cilia formation or function have profound effects on the development of body pattern and the physiology of multiple organ systems. By categorizing syndromes that are due to cilia dysfunction in humans and from studies in vertebrate model organisms, molecular pathways that intersect with cilia formation and function have come to light. Here, we summarize an emerging view that in order to understand some complex developmental pathways and disease etiologies, one must consider the molecular functions performed by cilia.

Animals↗

PubMed2005

The C. elegans homologs of nephrocystin-1 and nephrocystin-4 are cilia transition zone proteins involved in chemosensory perception.

Nephronophthisis (NPH) is a cystic kidney disorder that causes end-stage renal failure in children. Five nephrocystin (nephrocystin-1 to nephrocystin-5) genes, whose function is disrupted in NPH patients, have been identified and data indicate they form a complex at cell junctions and focal adhesions. More recently, the nephrocystin proteins have also been identified in cilia, as have multiple other cystic kidney disease related proteins. Significant insights into this cilia and cystic kidney disease connection have come from analyses in simpler eukaryotic organisms such as Caenorhabditis elegans. In this regard, we became interested in the C. elegans homologs of nephrocystin-1 (nph-1) and nephrocystin-4 (nph-4) from a database screen to identify genes coordinately regulated by the ciliogenic transcription factor DAF-19. Here we show that expression of nph-1 and nph-4 is DAF-19 dependent, that their expression is restricted to ciliated sensory neurons, and that both NPH-1 and NPH-4 concentrate at the transition zones at the base of the cilia, but are not found in the cilium axoneme. In addition, NPH-4 is required for the localization of NPH-1 to this domain. Interestingly, nph-1 or nph-4 mutants have no obvious cilia assembly defects; however, they do have abnormalities in cilia-mediated sensory functions as evidenced by abnormal chemotaxis and lifespan regulation. Our data suggest that rather than having a ciliogenic role, the NPH proteins play an important function as part of the sensory or signaling machinery of this organelle. These findings suggest that the defects in human NPH patients may not be the result of aberrant ciliogenesis but abnormal cilia-sensory functions.

Animals↗

PubMed1993

Mechanical properties of ciliary axonemes and membranes as shown by paddle cilia.

Cilia with a distal membrane expansion enclosing a coiled end of the axoneme (paddle cilia or discocilia) have been commonly reported in marine invertebrates. We recently showed that paddle cilia in molluscan veligers are artifacts of non-physiological conditions. Here we investigated the possible mechanisms of formation of paddle cilia under hypotonic conditions; particularly, whether a helical conformational change of doublet microtubules induced by Ca or proton flux is responsible. Typical paddle cilia are induced by hypotonic Ca-free solutions at normal or low pH, showing that axonemal coiling does not require Ca influx or proton efflux. In addition, Triton-demembranated straight axonemes do not coil in high Ca solutions. Most decisively, complete removal of paddle ciliary membranes with detergents, but not mere permeabilization, causes immediate uncoiling and straightening of the axonemes to approximately their original length before hypotonic treatment. These findings and other data show that axonemal coiling in paddles is due to membrane tensile stress acting on an elastic axoneme. Light and electron microscopy of paddles show that axonemes coil uniformly toward the direction of the effective stroke (doublets nos 5-6), even when beating is inhibited by sodium azide or glutaraldehyde before hypotonic treatment. This indicates that axonemes possess an intrinsic asymmetry of stiffness within the beat plane, independent of active microtubule sliding. Paddle cilia thus reveal important mechanical properties of ciliary axonemes and membranes that should be useful for understanding ciliary function.

Animals↗

PubMed1988

Flexible-substratum technique for viewing cells from the side: some in vivo properties of primary (9+0) cilia in cultured kidney epithelia.

Cells cultured on thin plastic (e.g. Formvar, Teflon, polycarbonate) membranes can be clearly imaged from the side in vivo by video microscopy. We have used this flexible-substratum technique to examine the behaviour and properties of primary cilia in confluent cultures of the kidney epithelial cell lines PtK1, PtK2, LLC-PK1, MDCK and BSC-40. In these cells primary cilia appear as rigid rods, up to 55 micron long, which project at various angles from the dorsal cell surface. The length distribution of primary cilia in confluent cultures is a distinct characteristic of each established kidney cell line examined, with LLC-PK1 exhibiting three distinct length populations. Primary cilia of kidney cell lines bend passively in response to flow but do not display propagated bending or vortical motions. Up to 26% of the cilia in the cell types examined possess one or more conspicuous swellings along the ciliary shaft. Treatment with 0.05% trypsin, which is sufficient to cause cell rounding, does not induce the resorption or shedding of the cilium. These direct observations demonstrate that kidney epithelial-cell primary cilia are non-motile and longer than previously thought, and suggest that their length represents a phenotypic marker for each cell line.

Animals↗

PubMed2006

Forces applied by cilia measured on explants from mucociliary tissue.

Forces applied by intact mucus-propelling cilia were measured for the first time that we know of using a combined atomic force microscopy (AFM) and electrooptic system. The AFM probe was dipped into a field of beating cilia and its time-dependent deflection was recorded as it was struck by the cilia while the electrooptic system simultaneously and colocally measured the frequency to ensure that no perturbation was induced by the AFM probe. Using cilia from frog esophagus, we measured forces of approximately 0.21 nN per cilium during the effective stroke. This value, together with the known internal structure of these cilia, leads to the conclusion that most dynein arms along the length of the axoneme contribute to the effective stroke of these cilia.

Animals↗

PubMed1993

Development of the photoreceptor outer segment-like cilia of the CSF-contacting pinealocytes of the ferret (Putorius furo).

The postnatal development of the pineal organ of the ferret (Putorius furo) was investigated electron-microscopically with special interest given to the cerebrospinal fluid (CSF)-contacting pinealocytes and their large, vesiculated cilia. In the pineal of the newborn ferrets, there is a lumen--a pineal ventricle--which is a diverticle of the third ventricle of the diencephalon. The luminal surface of the pineal is bordered by ependymal cells and CSF-contacting pinealocytes. A sensory, 9 x 2 + 0 type cilium arises from the free surface of the pinealocytes and thickens in the first week. There are mitotic figures in the wall of the pineal ventricle, being reduced to a pineal recess during the second and third postnatal week. In two week-old animals, vesicles appear in the cilia of the pinealocytes. The vesicles may form rows and fill the enlarged cilium at the third week. Near the basal bodies, a proximal connecting piece remains narrow and free of vesicles. In older animals, there are multivesicular and dense bodies in the pineal cilia. The reduction of the pineal ventricle closes the CSF-contacting cilia in the intercellular spaces. Axon-like processes of pinealocytes form synaptic ribbon-containing terminals on secondary pineal neurons. Axons of pineal neurons enter the fiber bundles of the pineal tract running to the habenular nuclei. All these structures do not differ from the light conducting pathway of the submammalian pineals. The ultrastructure of the cilia investigated resembles that of the developing outer segments of the retina and represents a preserved light perceiving structure of the mammalian pinealocytes. Further studies are necessary to elucidate whether the early differentiation of the cilia and synapses indicates a timing of the circadian light rhythmicity in young ferrets by direct pineal photosensitivity.

Animals↗

PubMed1985

The immotile-cilia syndrome: a microtubule-associated defect.

The immotile-cilia syndrome is a congenital disorder characterized by all the cilia in the body being either immotile or showing an abnormal and inefficient beating pattern. Most symptoms come from the ciliated airways (nose, paranasal sinuses, and bronchs) and from the middle ear. Two further symptoms are situs inversus and male sterility. Situs inversus occurs in 50% of the cases and this subgroup is termed the Kartagener's syndrome; it might be due to an inability of the embryonic cilia to shift the heart to the left side and situs laterality seems to be a random process in the immotile-cilia syndrome. Male sterility is caused by the spermatozoa being unable to swim progressively; the sperm tail has the same structure as a cilium. In a few cases only the sperm tail or only the cilia of the body are affected. Female patients have a decreased fertility; most are involuntarily childless. The immotile-cilia syndrome is a heterogeneous disorder in that one out of many different genes may be involved. The different subtypes can be distinguished by an electron microscopic examination which will show defects in either one of a number of the ciliary components.

Animals↗