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At least 487 records · Page 27Linked to original sources
PubMed1991

Transmembrane currents in frog olfactory cilia.

We have measured transmembrane currents in intact single cilia from frog olfactory receptor neurons. A single cilium on a neuron was sucked into a patch pipette, and a high-resistance seal was formed near the base of the cilium. Action potentials could be induced by applying suction or a voltage ramp to the ciliary membrane. A transient current was seen in some cells on stimulation with odorants. After excision from the cell, most of the cilia showed increased conductance in a bath containing cAMP, indicating that the cytoplasmic face of the ciliary membrane was accessible to the bath. The estimated resistance of a single cilium was surprisingly low.

Action Potentials↗
PubMed1993

The cyclic nucleotide-activated conductance in olfactory cilia: effects of cytoplasmic Mg2+ and Ca2+.

Olfactory receptor neurons depolarize in response to odorants. This depolarization is mediated by an increase in intracellular cyclic AMP, which directly gates channels in the membranes of the neuronal cilia. Previous evidence suggests that a Ca2+ influx during the odorant response may ultimately play a role in terminating the response. One way Ca2+ inside the cell could terminate the odorant response would be to directly inhibit the cAMP-gated channels. In this report the effects of cytoplasmic Ca2+ and Mg2+ on the cAMP-activated current were measured in single olfactory cilia. Near the neuronal resting potential, cytoplasmic Ca2+ and Mg2+ only slightly reduced the cAMP-activated current. Even at high levels (1.0 mM Ca2+ or 5.0 mM Mg2+), the average inhibition was only around 20%. It is therefore unlikely that an influx of divalent cations terminates the odorant response by a direct effect on the cAMP-gated channels.

Ambystoma↗
PubMed1995

The effect of chloroform-extractable secondary metabolites of filamentous fungi on the movement of respiratory tract cilia of one-day-old chicks in vitro.

The ciliostatic activity of the chloroform-extractable metabolites of 72 strains of filamentous fungi growing in a liquid medium, on tracheal cilia from 1-d-old chicks in vitro was evaluated. Forty-eight of the investigated strains produced ciliostatic metabolites; 13, 11, 16, and 25% of the strains stopped the movement of cilia after 1, 2, 3, 6 d, respectively. The results are discussed in relationship with chronic bronchitis of people working with mouldy materials, living in mouldy dwellings and with the "sick-building syndrome".

Animals↗
PubMed1998

An investigation into the effects of midazolam and propofol on human respiratory cilia beat frequency in vitro.

OBJECTIVE: Patients in intensive care are known to be prone to both upper and lower respiratory tract infection. Respiratory mucus forms a barrier to infection. Mucus transport rate (MTR) depends upon both the physical properties of mucus and the action of respiratory cilia. Patients undergoing anaesthesia are known to have a reduced MTR that may be related to a depressant effect on cilia beat frequency (CBF) by anaesthetic drugs. The aim of this study was to investigate the effects of two commonly used intensive care sedative agents, midazolam and propofol, on CBF using human nasal turbinate explants in vitro. DESIGN: We exposed ciliated tissue from human nasal turbinate explants to midazolam and propofol in supraclinical concentrations (20 microM midazolam and 70 microM propofol) in a controlled and blinded manner for 90 min and measured CBF by the transmitted light technique. RESULTS: After 90 min, mean (SEM) CBF in the group exposed to midazolam and its control group were 13.0 (0.2) Hz and 12.9 (0.3) Hz, respectively. Mean (SEM) CBF in the group exposed to propofol was 13.6 (0.4) Hz and in the control group the value was 12.0 (0.6) Hz. There was no significant change in CBF (midazolam: p = 0.21, propofol: p = 0.31, MANOVA for repeated measures). CONCLUSIONS: We have found no effect of midazolam or propofol in supra-clinical concentrations upon CBF in human turbinate explants after a 90-min exposure. This contrasts with previous work that has shown a depressant effect of inhalational anaesthetic agents on CBF.

Cilia↗
PubMed2000

Immunocytochemistry of the striated rootlets associated with solitary cilia in human oviductal secretory cells.

The human oviduct epithelium is a simple columnar structure that consists primarily of ciliated and secretory cells. Solitary cilia usually extend from the apical cell surface of secretory cells. By injecting crude preparations of striated rootlets into rats, we successfully obtained six monoclonal antibodies (R38, R67, R95, R149, R155, R213) that commonly labeled ciliary rootlets. Using these antibodies, proteins of 205-215 kDa were identified by immunoblotting. Using a clone, R67, we investigated the morphology of the striated rootlets associated with solitary cilia by immunocytochemistry. It was found that the shapes of the rootlets were not simple but varied considerably. The rootlets had branched, radiated, arched, and looped shapes. This is the first report of the rootlets having a variety of shapes. The 205- to 215-kDa antigens identified by the six different antibodies were mostly localized to dark bands of striations, suggesting that they are constitutive components of dark striations of the rootlet.

Animals↗
PubMed1980

Biochemical studies of the excitable membrane of Paramecium. IV. Protein kinase activities of cilia and ciliary membrane.

Two protein kinases (ATP: protein phosphotransferase, EC 2.7.1.37) were detected in disrupted cilia of Paramecium tetraurelia. One of the enzymes exhibited maximum activity at pH 6.0, required 4 mM Mg2+ for its maximum activity and was stimulated by cyclic AMP and cyclic GMP. Histone was a good exogenous protein substrate for this enzyme, but protamine sulfate was not. The other protein kinase showed a peak of activity at pH 8.0, required 10 mM Mg2+ for its maximum activity and was slightly inhibited by cyclic AMP and cyclic GMP. Protamine sulfate was a good exogenous substrate for this enzyme. The pH 8.0 activity partitioned preferentially with the axonemes, but the pH 6.0 activity was divided almost equally between the axonemes and the membranes. We also found indirect evidence for the presence in cilia of phosphoprotein phosphatase (phosphoprotein phosphohydrolase, EC 3.1.3.16) and adenyl cyclase (ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1) activity.

Adenosine Triphosphate↗
PubMed1986

Odorant- and guanine nucleotide-stimulated phosphoinositide turnover in olfactory cilia.

Isolated olfactory cilia from the channel catfish (Ictalurus punctatus) exhibited phosphatidylinositol-4,5-bisphosphate phosphodiesterase (E.C.3.1.4.11) activity. The phosphodiesterase activity was stimulated in the presence of an odorant for the catfish, namely the amino acid L-alanine. The enzyme activity was also stimulated in the presence of GTP and its nonhydrolyzable analogues. The activation of the phosphodiesterase by guanine nucleotides, in combination with the identification of guanine nucleotide-binding protein(s) in the isolated cilia, indicate the probable participation of a guanine nucleotide-binding protein in stimulation of phosphoinositide turnover in the olfactory receptor neuron.

Animals↗
PubMed1984

Transduction physiology of olfactory receptor cilia.

Electro-olfactograms (EOGs) evoked by 8 odorants from frog olfactory epithelia during ciliary regrowth and during epithelial regeneration were analyzed. During ciliary regrowth following detergent-induced ciliary removal, EOG amplitudes initially increase proportionately with ciliary length. EOGs reach maximal amplitudes after 2 days of growth, when cilia are 40 micron long. Therefore olfactory transduction sites are located primarily on cilia rather than on the dendrite terminal and most of the receptor current enters through the proximal portion of the cilium. Zinc sulfate lavage of the nasal cavity causes selective necrosis of the receptor epithelium. During epithelial regeneration, EOGs increase linearly with time from 13 days after zinc lavage, the time of first cilium emergence, through 30 days. The rate of increase is different for different odorants. At 30 days and within a period of a few days, EOG amplitudes increase abruptly, then asymptote. Thus the development of receptors for different substances occurs at different rates and occurs in two steps. The transition between the two developmental states is coincident with arrival of receptor axon terminals at the central nervous system and with the immobilization of the ciliary contractile apparatus. Since there is continual generation of new receptor neurons throughout life, EOGs recorded in a normal nose reflect a complex combination of the differing receptor processes of cells of differing developmental stages.

Animals↗
PubMed1995

InsP3-gated ion channels in rat olfactory cilia membrane.

InsP3-gated channels present in isolated rat olfactory cilia membranes were studied by recording current fluctuations in cilia membranes fused onto phospholipid bilayers formed at the tip of a patch pipette. We found that InsP3 (1.25 to 30 microM) induced current fluctuations in 18 of 157 otherwise silent bilayers. The ion channels opened by InsP3 could be classified into two groups that differed in terms of conductance and kinetics. One channel, which had a conductance of 37 pS, displayed two current levels, and the larger single channel currents were associated with longer open dwell times. The other channel displayed a larger conductance (103-184 pS). Both types of channels displayed reversal potentials near zero millivolts, consistent with nonspecific cation channels. These experiments suggest that mammalian olfactory neurons possess two types of ciliary InsP3-gated channels.

Animals↗
PubMed1990

Alkaline phosphatase from Paramecium cilia and cell bodies: purification and characterization.

A soluble alkaline phosphatase was purified 10 000-fold in an overall yield of 8% from both of the cilia and cell bodies of the protozoan Paramecium tetraurelia. The concentration in cilia (1.7 microM) was 6-fold higher than in cell bodies, although the latter contained most of the activity due to their much greater volume. The purified protein showed a single (36 kDa) protein staining band on SDS-PAGE. This value, in conjunction with the apparent molecular mass of 66 kDa for the native enzyme (gel filtration) suggests a dimeric structure. The specific activity of the purified phosphatase ranged from 10 to 70 mumols.min-1.mg-1 at the pH-optimum of 8.0 and the Km for p-nitrophenyl phosphate was 81 microM. Basal enzyme activity was inhibited by metal chelators and stimulated up to 12-fold by addition of divalent cations. Mg2+ acted as a non-essential mixed-type activator with a half-maximal effect at 7 microM. Ca2+ was inhibitory, the extent of inhibition was dependent on the concentration of Mg2+ in the assay. Furthermore, the kinetics of inhibition by Ca2+ varied with the Mg2+ concentration. Phosphate, pyrophosphate, and SH-group blocking agents also strongly inhibited. The enzyme did not dephosphorylate Tyr- or Ser-/Thr-phosphoproteins. The Paramecium enzyme is not of lysosomal origin and its properties are quite different from all known phosphatases. It is a novel type of phosphatase since it (i) shows F(-)-inhibition like Ser/Thr-phosphatases but (ii) is inhibited by vanadate and molybdate like Tyr-phosphatases, and (iii) inhibition by Ca2+ has not been reported for any other phosphatase.

Alkaline Phosphatase↗
PubMed1990

Guanylate cyclase in olfactory cilia from rat and pig.

A guanylate cyclase was identified in cilia from rat and pig olfactory epithelia. Enzyme activities were 200-250 and 90-100 pmol/min.mg-1, respectively. Activity required the presence of non-ionic detergents, e.g., 0.1% Lubrol PX. MnGTP, not MgGTP was used as a substrate. Furthermore, 0.9 mM free Mn2+ was necessary for optimal activity indicating a regulatory site for a divalent cation. The guanylate cyclase displayed sigmoidal Michaelis-Menten kinetics suggesting cooperativity between MnGTP and enzyme. S0.5 was 160 microM MnGTP. The Hill coefficient of 1.7 indicates that more than one class of substrate-binding sites interact in a positive cooperative manner. ATP inhibited the enzyme and linearized plots of substrate kinetics with MnGTP. SH-Blocking agents reversibly inhibited enzyme activity. Sodium azide and nitroprusside were without effect as were several odorants. A guanylate cyclase activity in cilia from tracheal tissue had properties similar to the olfactory enzyme.

Adenosine Triphosphate↗
PubMed1996

Phosphatase 2A regulates the responsiveness of olfactory cilia.

The odorant-induced second messenger response in olfactory cilia was monitored in the presence of phosphatase modulators. Okadaic acid, a phosphatase inhibitor, attenuated the odorant-induced cAMP-response in a dose-dependent manner, half maximal inhibition was obtained at 1.5 nM okadaic acid indicating that phosphatase 2A may be involved. Protamine, a selective activator of phosphatase 2A, led to significantly stronger cAMP-responses. Western blot and immunohistochemical analysis employing specific antibodies revealed that phosphatase 2A is present in olfactory tissues in particular in olfactory cilia. The results suggest that phosphatase 2A may play a regulatory role in governing the responsiveness of olfactory neurons.

Animals↗
PubMed1980

Undulipodia, flagella and cilia.

The term flagella is ambiguous. It refers to bacterial structures composed of flagellin protein and to eukaryotic structures composed of microtubule proteins and ATPase (tubulin and dynein). The fact that cilia are nearly identical to eukaryotic flagella and have nothing in common with prokaryotic flagella is not apparent from the terminology. It is proposed that the 30-year old suggestion of Smagina and reiterated by Kuznicki and others, be adopted: that cilia and eukaryotic flagella be called "undulipodia." The term flagella ought to be restricted to prokaryotic organelles, bacterial flagella and spirochaete axial filaments: solid structures composed of flagellin which protrude through the plasma membrane and lack intrinsic motility throughout their length. Undulipodia are defined as intrinsically motile intracellular structures showing a 9-fold symmetry in the pattern of arrangement of 24 nm diameter microtubules. They are limited to eukaryotes, members of the protoctist, animal and plant kingdoms.

Animals↗
PubMed1991

Retinoic acid does not induce formation of cilia on the surface of wound epithelial cells in axolotls.

It has been reported that vitamin A palmitate induces the production of cilia on the epidermal cells of the regenerating axolotl limb, and the formation of crevices in the epidermal surface. The aim of the present investigation was to reexamine under well defined conditions the potential of retinoids to evoke the above described metaplastic changes. In order to achieve our purpose we administered axolotls with retinoic acid for 2, 4, 6, 8, and 10 days after limb amputation. The young regenerates were inspected by scanning electron microscopy (SEM). The data obtained showed that the external layer of the wound epithelium and of the stump epidermis as well was quite normal without any sign of cilia formation. In some cases, crevices were observed even in control animals.

Ambystoma↗
PubMed2006

Life without centrioles: cilia in the spotlight.

Centrioles are critical cellular components that form the architectural core of both centrosomes and basal bodies, the nucleating structures of cilia. New work, including a study in this issue (), highlights the unexpected finding that lack of centrioles does not impede development in the fruit fly. Rather, flies reach maturity but then die because their sensory neurons lack cilia.

Animals↗
PubMed2003

Left-right asymmetry: nodal cilia make and catch a wave.

Asymmetric fluid flow in the mouse node initiates the development of left-right asymmetry. This flow is generated by motile cilia and is detected by immotile mechanosensory cilia, activating an asymmetric calcium spike.

Animals↗
PubMed2004

Primary cilia: putting sensors together.

Primary cilia extend like antennae from the surface of most eukaryotic cells into the environment, where they function in a variety of sensory roles. Recent studies reveal an intimate interplay between structural proteins of the centrosome and the formation of primary cilia, and provide new insight into the complex function of these fascinating organelles.

Antigens↗
PubMed2005

Ca2+-dependent K+ channels from rat olfactory cilia characterized in planar lipid bilayers.

Olfactory cilia contain cyclic nucleotide-gated and Ca2+-dependent Cl- conductances that underlie excitatory chemotransduction, and a Ca2+-dependent K+ (KCa) conductance, apparently involved in inhibitory transduction. Previous single-channel patch-clamp studies on olfactory cilia revealed four different KCas, with different conductances and kinetics. Here, we further characterized these channels in planar bilayers, where blockers could be properly tested. All four ciliary KCas were observed: The 16 pS channel, K0.5,Ca=40 microM and apamin-sensitive; the 30 and 50 pS channel, K0.5,Ca=59 microM, clotrimazole-sensitive and charybdotoxin-insensitive; the 60 pS channel, clotrimazole-sensitive and charybdotoxin-insensitive; and the 210 pS channel, K0.5,Ca=63 microM, blocked by charybdotoxin and iberiotoxin. The presence of the 16 and 210 pS channels was confirmed by immunoblotting.

Animals↗