SEARCH · PubMed Health

Results for “CILIA”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources

PubMed1991

Ca2+ modulates an unspecific cation conductance in olfactory cilia of Xenopus laevis.

Olfactory neurones of Xenopus laevis were studied by the patch clamp technique under voltage-clamp conditions. Isolated receptor cells were obtained by dissociating the olfactory mucosa in a Ca(2+)-free solution. Usually some of the resulting isolated olfactory cells lost all of their cilia during the dissociation procedure. Comparing the currents of cells with cilia to those of cells without cilia, a marked difference was found. When all known voltage-gated currents except the Ca(2+)-current were blocked, cells without cilia showed the voltage-gated Ca(2+)-current alone whereas cells with cilia clearly had an additional conductance gc. It could be activated in two ways, either by Ca2+ entry through Ca(2+)-channels or by Ca2+ entry through the Na/Ca-exchanger working in the reversed mode at positive membrane potentials. This ciliar conductance gc had its reversal potential at 0 mV. Replacing extracellular Cl- by isethionate on the one hand, and Na+ by Cs+ or N-methyl-D-glucamine on the other showed that gc was permeable for cations but not for Cl-. In conclusion, there appears to be a Ca(2+)-dependent unselective cation conductance on the cilia of olfactory neurones. The probable role of gc as the last step an IP3/Ca mediated transduction pathway is suggested.

Animals↗

PubMed1989

Primary cilia associated with striated rootlets in granulated and folliculo-stellate cells of the avian adenohypophysis.

During observation of the ultrastructure of adenohypophyses of normal and experimentally-manipulated quails, primary cilia were found in secretory cells as well as in non-granulated, folliculo-stellate cells of both cephalic and caudal lobes of the gland. These solitary cilia shared morphological characteristics with those observed in other cell types and species, i.e. they arose from a basal body, which basically had a centriolar structure and 9 doublets of microtubules and no central tubules in their axoneme. A 8 + 1 arrangement of microtubules was exceptionally observed. A 9 + 2 pattern, which is commonly described in motile cilia, was never found. The cilia extended in extracellular spaces between secretory cells, but not in the follicular cavities nor in the blood vessels. In addition to the basal body, a single centriole was frequently present in its vicinity. The basal body was often associated with a basal foot or satellite from which microtubules radiated, and with ladderlike structures corresponding to the classical description of striated rootlets. The presumptive roles of primary cilia in general, and of their morphological features in particular, are discussed in view of our results and compared to the several observations reported in mammalian adenohypophyses. As the evidence gained in favour of a given function of primary cilia has, so far, always been circumstantial, extreme caution in interpretation must be exercise.

Animals↗

PubMed1980

Cilia in the ciliary epithelium.

Cilia in the pigmented and nonpigmented ciliary epithelial cells were studied by electron microscopy in the normal Rhesus monkey eye. In addition cilia formation was studied following paracentesis as well as injection of hemoglobin into the vitreous cavity. In all eyes studied, cilia had a 9 + 0 microtubule pattern; however, some cilia had aberrant arrangement of microtubules. Cilia increased in number and showed elongation in the treated eyes, these newly-formed cilia occasionally extending towards the cell interior opposite to the normal orientation. The results suggested that the formation of ciia can be provoked by a variety of experimental stimuli either with or without drugs.

Animals↗

PubMed1986

Abnormal cilia in a malignant ependymoma.

Abnormal cilia were frequently exposed in a malignant ependymoma of the cerebellar vermis by an electron microscope study. Among these erratic cilia, compound cilia, huge axoneme with bizarre shapes, were repeatedly observed. These giant cilia commonly had random orientation of many microtubular doublets as well as complicated cavities in their granular ciliary matrix. Additionally, abnormal cilia of normal-sized axoneme showed diversified arrangement of peripheral doublets and central singlets. The formation process of these abnormal cilia is discussed.

Adult↗

PubMed1986

Structure and function of specialized cilia in the exocrine pancreas.

Cilia are found in acinar and ductular lumina. Most descriptions of human or dog pancreatic tissue have indicated that these are probably motile structures which move and/or mix pancreatic secretion. A recent study interpreted arrangements of microtubules within cilia which deviated from the classic 9 + 2 pattern as indicating pathological change. There have been suggestions, however, from studies on nonmammalian and human pancreas, that the structure of pancreatic cilia suggests a sensory function. The present paper reports studies on the ultrastructural organization of the specialized cilia in human and canine pancreatic tissue. The pattern of microtubular organization resembles that of cilia modified for chemoreception rather than that of classic kinocilia. It is concluded that pancreatic ductular cilia are sensory rather than motile, providing a mechanism for monitoring general or specific molecular concentrations.

Animals↗

PubMed1988

Immunogold localization of actin in developing photoreceptor cilia of normal and rds mutant mice.

Recent immunocytochemical studies have localized actin to the distal cilium of mature vertebrate photoreceptors. Since this is the site where the ciliary plasma membrane evaginates to form new outer segment discs, the results suggest that an actin-mediated contractile mechanism or cytoskeletal network might regulate some aspect of outer segment disc morphogenesis. In the present study, immunoelectron microscopy was used to localize actin to the developing cilia of normal and rds mutant mouse photoreceptors. In normal mice, actin could not be localized to newly projecting cilia, but an actin-rich domain was demonstrated within the distal, bulbous ending of elongated cilia just prior to outer segment development. These results suggest that actin is not important for ciliary growth, but that it may be necessary for the subsequent differentiation of an outer segment. In the rds mutant mouse, there is an absence of outer segment formation, although cilia appear to develop normally. Rhodamine phalloidin staining of cryostat sections demonstrated a normal F-actin distribution within the rds retina. Utilizing immunogold labeling of developing rds photoreceptors, actin was localized to the distal, bulbous ending of elongated cilia. This result indicates that actin is situated within its normal domain in rds cilia.

Actins↗

PubMed2004

Vertebrate primary cilia: a sensory part of centrosomal complex in tissue cells, but a "sleeping beauty" in cultured cells?

Primary cilium development along with other components of the centrosome in mammalian cells was analysed ultrastructurally and by immunofluorescent staining with anti-acetylated tubulin antibodies. We categorized two types of primary cilia, nascent cilia that are about 1microm long located inside the cytoplasm, and true primary cilia that are several microm long and protrude from the plasma membrane. The primary cilium is invariably associated with the older centriole of each diplosome, having appendages at the distal end and pericentriolar satellites with cytoplasmic microtubules emanating from them. Only one cilium per cell is formed normally through G(0), S and G(2)phases. However, in some mouse embryo fibroblasts with two mature centrioles, bicilates were seen. Primary cilia were not observed in cultured cells where the mature centriole had no satellites and appendages (Chinese hamster kidney cells, line 237, some clones of l-fibroblasts). In contrast to primary cilia, striated rootlets were found around active and non-active centrioles with the same frequency. In proliferating cultured cells, a primary cilium can be formed several hours after mitosis, in fibroblasts 2-4 h after cell division and in PK cells only during the S-phase. In interphase cells, formation of the primary cilium can be stimulated by the action of metabolic inhibitors and by reversed depolymerization of cytoplasmic microtubules with cold or colcemid treatments. In mouse renal epithelial cells in situ, the centrosome was located near the cell surface and mature centrioles in 80% of the cells had primary cilium protruding into the duct lumen. After cells were explanted and subcultured, the centrosome comes closer to the nucleus and the primary cilium was depolymerized or reduced. Later primary cilia appeared in cells that form islets on the coverslip. However, the centrosome in cultured ciliated cells was always located near the cell nucleus and primary cilium never formed a characteristic distal bulb. A sequence of the developmental stages of the primary cilium is proposed and discussed. We also conclude that functioning primary cilium does not necessarily operate in culture cells, which might explain some of the contradictory data on cell ciliation in vitro reported in the literature.

Animals↗

PubMed2003

Intraflagellar transport is required in Drosophila to differentiate sensory cilia but not sperm.

BACKGROUND: Intraflagellar transport (IFT) uses kinesin II to carry a multiprotein particle to the tips of eukaryotic cilia and flagella and a nonaxonemal dynein to return it to the cell body. IFT particle proteins and motors are conserved in ciliated eukaryotes, and IFT-deficient mutants in algae, nematodes, and mammals fail to extend or maintain cilia and flagella, including sensory cilia. In Drosophila, the only ciliated cells are sensory neurons and sperm. no mechanoreceptor potential (nomp) mutations have been isolated that affect the differentiation and function of ciliated sense organs. The nompB gene is here shown to encode an IFT protein. Its mutant phenotypes reveal the consequences of an IFT defect in an insect. RESULTS: Mechanosensory and olfactory neurons in nompB mutants have missing or defective cilia. nompB encodes the Drosophila homolog of the IFT complex B protein IFT88/Polaris/OSM-5. nompB is expressed in the ciliated sensory neurons, and a functional, tagged NOMPB protein is located in sensory cilia and around basal bodies. Surprisingly, nompB mutant males produce normally elongated, motile sperm. Neuronally restricted expression and male germline mosaic experiments show that nompB-deficient sperm are fully functional in transfer, competition, and fertilization. CONCLUSIONS: NOMPB, the Drosophila homolog of IFT88, is required for the assembly of sensory cilia but not for the extension or function of the sperm flagellum. Assembly of this extremely long axoneme is therefore independent of IFT.

Animals↗

PubMed1984

Asymmetrical microtubule capping structures in frog palate cilia.

Capping structures at the distal tips of frog palate cilia are attached to the A- and central pair microtubules by electron-dense plug structures similar to those found in protozoan cilia and flagella and in epithelial cilia from invertebrates and vertebrates (W.L. Dentler, 1980, J. Cell Sci. 42, 207-220; W.L. Dentler and E.L. LeCluyse, 1982, Cell Motil. 2, 549-573). The caps in frog palate cilia are composed of a proximal shelf, to which doublets Nos. 1-3, 8, 9 and the central microtubules are attached and a larger distal cap to which doublets Nos. 4-7 are bound. The smaller proximal shelf is positioned to one side of the cilium and gives the cap an asymmetrical appearance. Striated ciliary rootlets attached to the basal bodies are also described. The smaller cap is placed on the same side of all cilia on the palate relative to both the direction of the effective stroke and the position of the rootlets. These results confirm that capping structures are common to most, if not all, cilia and provide direct evidence that they are precisely positioned on specific microtubules.

Aging↗

PubMed1998

Changes in cell surface primary cilia and microvilli concurrent with measurements of fluid flow across the rabbit corneal endothelium ex vivo.

Primary cilia and microvilli have been reported on the mammalian rabbit corneal endothelium but their relationship to cell function is undefined. Six corneas from healthy 2 kg female albino rabbits were glutaraldehyde-fixed post mortem (15:00 h) or twelve corneal stroma-endothelial preparations incubated at 37 degrees C under an applied hydrostatic pressure of 20 cm H2O for 4 h prior to fixation. The corneal endothelium was assessed by quantitative scanning electron microscopy. Cells fixed immediately post mortem were decorated with small stubby microvilli (average 21 +/- 13/100 micron 2), and only 25% of the cells were decorated with primary cilia having an average length of 2.44 +/- 1.56 microns. Following 4 h ex vivo incubation with a phosphate-buffered Ringer solution, conspicuous microvilli developed to an average density of 40 +/- 19/100 micron 2 and primary cilia were found on 12% of the cells, having on average length of 2.27 +/- 1.38 microns. Following 4 h incubation in a bicarbonate-buffered Ringer solution, small stubby microvilli developed to a density of 49 +/- 18/100 micron 2, and 40% of the cells showed primary cilia with an average length of 4.31 +/- 1.93 microns; the net trans-endothelial fluid flow in the latter set was 60% greater. These studies indicate that the primary cilia on corneal endothelial cells might be responsive to fluid flow, but that mild mechanical and/or chemical stress could also be the cause of the change since the elaboration of primary cilia can be accompanied by microvilli as well.

Animals↗

PubMed2005

Phosphorylation by casein kinase 2 induces PACS-1 binding of nephrocystin and targeting to cilia.

Mutations in proteins localized to cilia and basal bodies have been implicated in a growing number of human diseases. Access of these proteins to the ciliary compartment requires targeting to the base of the cilia. However, the mechanisms involved in transport of cilia proteins to this transitional zone are elusive. Here we show that nephrocystin, a ciliary protein mutated in the most prevalent form of cystic kidney disease in childhood, is expressed in respiratory epithelial cells and accumulates at the base of cilia, overlapping with markers of the basal body area and the transition zone. Nephrocystin interacts with the phosphofurin acidic cluster sorting protein (PACS)-1. Casein kinase 2 (CK2)-mediated phosphorylation of three critical serine residues within a cluster of acidic amino acids in nephrocystin mediates PACS-1 binding, and is essential for colocalization of nephrocystin with PACS-1 at the base of cilia. Inhibition of CK2 activity abrogates this interaction and results in the loss of correct nephrocystin targeting. These data suggest that CK2-dependent transport processes represent a novel pathway of targeting proteins to the cilia.

Adaptor Proteins, Signal Transducing↗

PubMed1999

Atypical cilia in the tracheal epithelium of healthy water buffaloes (Bubalus bubalis).

Samples of tracheal mucosa were obtained from 10 healthy adult water buffaloes and 50 000 cilia were examined ultrastructurally. Ciliary abnormalities were found in all 10 subjects. Atypical cilia occurred as compound cilia (up to 1.5%), intracytoplasmic cilia (0.07%) and swollen cilia (0.05%). The microtubular pattern was determined in 5000 cross-sectioned cilia, with about 7% showing axonemal abnormalities in which peripheral defects prevailed. Some electron-dense plugs appeared inside the cylinder lumen of 2.5% of basal bodies. Freeze-fracture studies revealed a ciliary necklace composed of up to eight rows of intramembranous particles. This fine detail appeared to differ from that of other small and large ruminants.

Animals↗

PubMed1984

Membrane proteins unique to vertebrate olfactory cilia: candidates for sensory receptor molecules.

In search for olfactory receptor molecules, we carried out comprehensive electrophoretic mapping of membrane proteins in the cilia of frog olfactory epithelium. Seven polypeptides, extracted from isolated cilia by nonionic detergent, were unique to the sensory organelles, compared to nonsensory (respiratory) counterparts. Olfactory cilia contained 3-10 times more membrane-associated protein as compared to respiratory cilia, in agreement with reported densities of freeze-fracture intramembranous particles. Four of the olfactory polypeptides were major constituents of the ciliary membrane, each amounting to greater than 10% of its total protein. Three major and one minor specific polypeptide were glycosylated, whereas membranes of nonsensory cilia were practically devoid of glycoproteins. A clear difference in surface composition was also shown by microscopic visualization of fluoresceinated lectin bound to intact isolated cilia. Two of the olfactory glycoproteins displayed pronounced heterogeneity of apparent molecular weight, which could partly be due to protein sequence diversity, as expected for odorant receptor molecules. The recently described inhibition of odorant-evoked sensory potentials by the lectin concanavalin A is consistent with the hypothesis that one or more of the specific glycoproteins described here plays a role in olfactory reception.

Animals↗

PubMed2005

Characterization of single channel currents from primary cilia of renal epithelial cells.

The primary cilium is a ubiquitous, non-motile microtubular organelle lacking the central pair of microtubules found in motile cilia. Primary cilia are surrounded by a membrane, which has a unique complement of membrane proteins, and may thus be functionally different from the plasma membrane. The function of the primary cilium remains largely unknown. However, primary cilia have important sensory transducer properties, including the response of renal epithelial cells to fluid flow or mechanical stimulation. Recently, renal cystic diseases have been associated with dysfunctional ciliary proteins. Although the sensory properties of renal epithelial primary cilia may be associated with functional channel activity in the organelle, information in this regard is still lacking. This may be related to the inherent difficulties in assessing electrical activity in this rather small and narrow organelle. In the present study, we provide the first direct electrophysiological evidence for the presence of single channel currents from isolated primary cilia of LLC-PK1 renal epithelial cells. Several channel phenotypes were observed, and addition of vasopressin increased cation channel activity, which suggests the regulation, by the cAMP pathway of ciliary conductance. Ion channel reconstitution of ciliary versus plasma membranes indicated a much higher channel density in cilia. At least three channel proteins, polycystin-2, TRPC1, and interestingly, the alpha-epithelial sodium channel, were immunodetected in this organelle. Ion channel activity in the primary cilium of renal cells may be an important component of its role as a sensory transducer.

Animals↗

PubMed1966

The effects of adenosine triphosphate and related compounds on some hydrodynamic properties of glycerinated cilia.

Cilia were isolated from Tetrahymena pyriformis by a glycerol method. The addition of low concentrations of ATP, but not of other nucleoside triphosphates, caused an increase of up to twofold in the amount of cilia pelleted in a low-speed centrifugation assay and decreased the density of the pellets compared to control pellets. Pellet size and density depend on pH, both in the absence and in the presence of low concentrations of ATP. High concentrations (5 mM and above) of ATP and of other nucleoside triphosphates tend to "dissolve" the cilia. Heating the cilia for 11 min at 40 degrees C abolishes the increase in pellet size and the decrease in pellet density caused by low ATP, but slightly increases the ATPase activity of the cilia. Heat treatment, however, does not prevent the dissolving effect of high ATP. There are, thus, two independent effects of ATP on the hydrodynamic properties of cilia suspensions.

Adenosine Triphosphatases↗

PubMed1975

Laser-induced spreading arrest of Mytilus gill cilia.

Using a "slit camera" recording technique, we have examined the effects of local laser irradiation of cilia of the gill epithelium of Mytilus edulis. The laser produces a lesion which interrupts epithelial integrity. In artificial sea water that contains high K+ or is effectively Ca++ free, metachronism of the lateral cilia continues to either side of the lesion with only minor perturbations in frequency synchronization and wave velocity, such as would be expected if metachronal wave coordination is mechanical. However, in normal sea water and other appropriate ionic conditions (i.e., where Ca++ concentration is elevated), in addition to local damage, the laser induces distinct arrest responses of the lateral cilia. Arrest is not mechanically coordinated, since cilia stop in sequence depending on stroke position as well as distance from the lesion. The velocity of arrest under standard conditions is about 3 mm/s, several orders of magnitude faster than spreading velocities associated with diffusion of materials from the injured region. Two responses can be distinguished on the basis of the kinetics of recovery of the arrested regions. These are (a) a nondecremental response that resembles spontaneous ciliary stoppage in the gills, and (b) a decremental response, where arrest nearer the stimulus point is much longer lasting. The slower recovery is often periodic, with a step size approximating lateral cell length. Arrest responses with altered kinetics also occur in laterofrontal cilia. The responses of Mytilus lateral cilia resemble the spreading ciliary arrest seen in Elliptio and arrest induced by electrical and other stimuli, and the decremental response may depend upon electrotonic spread of potential change produced at the stimulus site. If this were coupled to transient changes in Ca++ permeability of the cell membrane, a local rise in Ca++ concentration might inhibit ciliary beat at a sensitive point in the stroke cycle to produce the observed arrest.

Animals↗

PubMed1981

Biochemical studies of the excitable membrane of Paramecium tetraurelia VI. Endogenous protein substrates for in vitro and in vivo phosphorylation in cilia and ciliary membranes.

The endogenous protein kinases of isolated Paramecium tetraurelia cilia phosphorylated approximately 30 ciliary polypeptides in vitro. Labeling with [gamma-32P]ATP was not proportional to the amount of each protein in cilia; some minor polypeptides (e.g., 67,000 and 180,000 mol wt) were more heavily labeled than some major polypeptides. Certain of the endogenous substrates for protein kinase were localized in the ciliary membrane (130,000, 86,000, 67,000, and 45,000 mol wt); others were found in axonemes or in both fractions. With cilia from bacterized cultures in the undefined Cerophyl medium, the labeling of specific endogenous phosphate acceptors was altered by pH, cyclic AMP, and cyclic GMP, but the labeling pattern was not affected by the presence of Na+ or K+ (15 mM), Ba++ (5 mM), Ca++ (10(-5) or 10(-4) M), or EGTA. Very similar results were obtained with cilia from cells grown axenically in a semidefined medium; the molecular weights and the extent of phosphorylation of the phosphopolypeptides were comparable to those of cilia from bacterized Cerophyl cultures, although no significant cyclic nucleotide effects were observed in the axenic cilia. Most of the phosphopolypeptides labeled in vitro also turned over rapidly in vitro. The phosphoprotein phosphatase responsible for turnover was partially inhibited by 5 mM NaF. The pattern of ciliary polypeptides labeled in vivo was similar to that observed in the in vitro experiments, although the relative intensities of labeling differed. Six behavioral mutants of Paramecium, known to have defects in the excitable membrane that regulates the ciliary beat, showed normal patterns of ciliary protein phosphorylation in vitro, with and without added cyclic nucleotides, at both pH 6.0 and pH 8.0. The mutants also had apparently normal phosphoprotein phosphatase. The Paranoiac A mutant, however, showed a reduction in cyclic GMP-stimulated protein kinase activity.

Animals↗

PubMed2006

Members of the NIMA-related kinase family promote disassembly of cilia by multiple mechanisms.

The genome of Tetrahymena thermophila contains 39 loci encoding NIMA-related kinases (NRKs), an extraordinarily large number for a unicellular organism. Evolutionary analyses grouped these sequences into several subfamilies, some of which have orthologues in animals, whereas others are protist specific. When overproduced, NRKs of three subfamilies caused rapid shortening of cilia. Ultrastructural studies revealed that each NRK triggered ciliary resorption by a distinct mechanism that involved preferential depolymerization of a subset of axonemal microtubules, at either the distal or proximal end. Overexpression of a kinase-inactive variant caused lengthening of cilia, indicating that constitutive NRK-mediated resorption regulates the length of cilia. Each NRK preferentially resorbed a distinct subset of cilia, depending on the location along the anteroposterior axis. We also show that normal Tetrahymena cells maintain unequal length cilia. We propose that ciliates used a large number of NRK paralogues to differentially regulate the length of specific subsets of cilia in the same cell.

Animals↗