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230 records · Page 13Linked to original sources

PubMed1984

Proteinase-treated photoreceptor discs. Photoelectric activity of the partially-digested rhodopsin and membrane orientation.

Photoreceptor discs from rod outer segments of cattle retina were treated with (a) papain, (b) thermolysin or (c) trypsin, the procedures resulting in the cleavage of the rhodopsin polypeptide chain between (a) 323 and 324, 236 and 237, 241 and 242, (b) 327 and 328, 240 and 241, or (c) 339 and 340 amino acid residues, respectively. In all the cases, partially digested rhodopsins proved to be competent in generating photoelectric potential and increasing membrane conductance of the discs adsorbed onto phospholipid-impregnated collodion film. The kinetics of generation and dissipation of photopotential as well as of formation of metarhodopsin II and of the light-induced rhodopsin protonation were found to be the same in the partially digested preparations and in the intact one. Incubation of papain-treated or thermolysin-treated discs at pH 6.0 induced formation of inside-out vesicles which, when incorporated into the collodion film, generated an oppositely directed photopotential. Treatment of such vesicles with papain gave rise to further cleavages of the polypeptide localized between 30 and 31, 186 and 187 amino acid residues. One more proteinase-sensitive site, localized between 104 and 105 residues, has been discovered in the inside-out vesicles treated with thermolysin. This fact consistent with the scheme of the 'seven column' arrangement of the visual rhodopsin [Ovchinnikov, Yu. A. (1982) FEBS Lett. 148, 179-191]. Rhodopsin, when treated with papain on both sides, was deprived of sixty amino acid residues being split in two sites in the middle part of the polypeptide, but was still active as a photoelectric energy transducer. The main specific feature inherent in the photoelectric response of the papain-treated or thermolysin-treated rhodopsin and absent from the native protein is that the former survives addition of long trains of saturating flashes when the response of the intact preparation becomes negligible. This effect was shown to be due to conversion of partially digested rhodopsin to a photolytic product that at room temperature lived for minutes even in the presence of NH2OH. A 532-nm laser flash effectively converted this product back to rhodopsin.

Animals↗

PubMed2001

Color image detection by biomolecular photoreceptor using bacteriorhodopsin-based complex LB films.

A biomolecular photoreceptor consisting of bacteriorhodopsin (bR)-based complex Langmuir-Blodgett (LB) films was developed for color image detection. By mimicking the functions of the pigments in retina of human visual system, biomolecules with photoelectric conversion function were chosen and used as constituents for an artificial photoreceptor. bR and flavin were deposited onto the patterned (9-pixelized) ITO glass by LB technique. A 9-pixel biomolecular photoreceptor was fabricated with a sandwich-type structure of ITO/LB films/electrolyte gel/Pt. Since each functional molecule shows its own response characteristic according to the light illumination in the visible region, the simplified knowledge-based algorithm for interpretation of the incident light wavelength (color) was proposed based on the basic rule describing the relationship between the photoelectric response characteristics and the incident light wavelength. When simple color images were projected onto the photoreceptor, the primary colors in visible light region, red, green, and blue were clearly recognized, and the projected color images were fairly well reproduced onto the color monitor by the proposed photoreceptor with the knowledge-based algorithm. It is concluded that the proposed device has a capability of recognizing the color images and can be used as a model system to simulate the information processing function of the human visual system.

Algorithms↗

PubMed1975

Potential for clinical use of the analytical laser microprobe for element measurement.

Use of the laser microprobe for rapid emission spectroscopic analysis of elements in microscopic samples of biological material is described. The technique depends on vaporization of the microsample with a focused laser beam at a temperature that renders the vapor incandescent for spectrochemical analysis. Spectral line intensities are recorded photographically with densitometry of the negatives or photoelectrically. Current capability permits analysis of about 10(-8) to 10(-10) g of tissue, with detection limits of 10-12 to 10-15 g of element. Groups of elements can be simultaneously analyzed. Minimum sample preparation is required, and the analysis is done on the stage of a light microscope, usually on an air-dried sample on a plastic slide. We exemplify the technique in analysis of gold in cultured fibroblasts treated with gold salts and in human skin after treatment with gold salts for rheumatoid arthritis, in element changes in biopsies of transplanted human hearts, and in unique profiles of groups of elements in human cancer tissue.

Adenocarcinoma↗

PubMed1993

Stimulation of ciliary motility mediated by atypical beta-adrenoceptor in canine bronchial epithelium.

The effects of catecholamines on ciliary motility of canine bronchial epithelium was studied by a photoelectric method in vitro. Addition of beta-adrenoceptor agonists increased ciliary beat frequency, a rank order of potency being salbutamol > or = BRL 37344, a selective beta 3-adrenoceptor agonist > norepinephrine. The response to BRL 37344 was relatively resistant to the blockade of beta 1- and beta 2-adrenoceptors but was competitively antagonized by the beta 3-adrenoceptor antagonist cyanopindolol, with the pA2 value being lower than that when salbutamol was used as an agonist. These results suggest that beta 3-adrenoceptors exist in canine bronchial epithelium and that stimulation of this receptor subtype may enhance ciliary motility and, hence, mucociliary transport in the airway.

Adrenergic beta-Agonists↗

PubMed1998

125I brachytherapy k-edge dose enhancement with AgTPPS4.

Photon activation is a radiotherapy technique in which an element is added to the absorbing medium to raise the probability that a photoelectric interaction will occur, thus causing an increase in the absorption of ionizing radiation. Binding energies of key elements within an absorbing medium are closely matched with the incident photon energies to maximize the production of free electrons and subsequent absorption of their kinetic energies. The purpose of this research was to quantify potential dose enhancement using a silver tetraphenyl sulfonato porphyrin (AgTPPS4) in tumors as a photon activator for use with interstitial 125I brachytherapy. A three-dimensional Monte Carlo dosimetry model was developed using the EGS4 coding system. The photon source was modeled using spectral gamma emissions from models 6702 or 6711 brachytherapy seeds for comparison. Absorbed dose within the tumor volume was calculated for AgTPPS4 concentrations ranging between 0 and 20 mmol/kg tumor weight. These theoretical studies demonstrated linear increases in dose absorbed by the tumor with corresponding increases in AgTPPS4 concentration. The required AgTPPS4 concentration (RSC) to achieve at least a ten percent absorbed dose increase is approximately 6.5 mmol/kg tumor weight for model 6702 seeds. In vivo biodistribution and in vitro toxicity studies were conducted to determine if the theoretically derived RSC could be achieved biologically. Cell toxicity studies showed that TPPS4 porphyrin derivatives were cytotoxic at concentrations required to provide significant brachytherapy dose enhancement. Reverse phase HPLC confirmed that toxicity was due to intrinsic properties of the TPPS4 molecule, not the presence of free silver, drug impurities, or metabolites. Further research is necessary to develop a nontoxic molecular carrier for delivering silver to the DNA of tumor cells.

Animals↗

PubMed1976

The effect of cations and membrane permeability modifying agents on the dark kinetics of the photoelectric response in isolated chloroplasts.

The kinetics of the photoelectric response induced by saturating light pulses were studied in isolated chloroplasts of Peperomia metallica as a function of K+- and Mg2+-concentrations in the medium in the absence and presence of ionophores for K+ and divalent cations. The dark decay of the potential generated in the light is found to be accelerated upon an increase in K+- or Mg2+-concentrations in the presence of valinomycin and A23187. An acceleration of the decay phase in the flash-induced response is also observed immediately after preillumination of the chloroplast. It is concluded that the dark kinetics of the potential decay after short and long light exposures are controlled by two different processes with rate constants of about 20 and 0.2s-1, respectively.

Calcimycin↗

PubMed2000

High progesterone levels and ciliary dysfunction--a possible cause of ectopic pregnancy.

OBJECTIVES: To investigate the effects of different levels of hormones on the ciliary activity of human oviducts and, consequently, to assess their possible role in tubal implantation of the fertilized egg. DESIGN: Fallopian tube epithelial samples were incubated in media with the addition of Estradiol (E2), progesterone (P), human menopausal gonadotropin (hMG), LH, or pure FSH (Metrodin) in different concentrations. The ciliary beat frequency (CBF) was measured after 24 h of incubation. Then the media were exchanged to media without the addition of hormones and the CBF was measured again 24 h later by using the photoelectric technique. SETTING: University teaching hospital, IVF unit. RESULTS: Twenty-four hr after the addition of P to the culture medium in concentrations of 0.5 or 1 ng/ml a significant decline of the CBF down to 63% of the control level was observed (P < 0.001) and with P in concentration of 2 ng/ml or greater, 50-70% of the cilia were paralyzed. These effects of P were found to be reversible. Incubation with E2 induced a slight increase of 4% in the mean CBF (P = 0.002). Twenty-four hr incubation with Metrodin, Pergonal, or LH did not affect ciliary motility. CONCLUSIONS: Higher levels of progesterone cause ciliary dysfunction and subsequently may be a possible cause of ectopic pregnancy.

Animals↗

PubMed1989

Adenosine-mediated cyclic AMP-dependent inhibition of ciliary activity in rabbit tracheal epithelium.

We wished to determine whether adenosine, a purine nucleotide, modulates activity of respiratory cilia and, to this end, we studied cultured rabbit tracheal epithelium in response to adenosine and related substances in vitro. Ciliary beat frequency (CBF) as determined by a photoelectric method was depressed by adenosine (10(-3) M), the maximal decrease from the baseline value (965 +/- 29 beats/min, mean +/- SE) being 31.6 +/- 5.0% (p less than 0.001). The adenosine A2-receptor agonist N-ethylcarboxamide adenosine had only a small effect on ciliary activity, whereas other adenosine analogs elicited decreases in CBF in a dose-dependent fashion. The order of potency of cilia-inhibitory action was N-cyclohexyladenosine (an agonist for adenosine A1-receptor) greater than phenylisopropyladenosine greater than adenosine greater than N-ethylcarboxamide adenosine. Intracellular cyclic AMP (cAMP) levels were decreased by 10(-3) M adenosine from 39.2 +/- 6.5 to 25.3 +/- 4.8 pM/mg protein (p less than 0.05). The effect of adenosine on CBF was enhanced by dipyridamole, an adenosine uptake inhibitor, and by deoxycoformycin, an adenosine deaminase inhibitor. The adenosine-induced decreases in CBF and cAMP content were reversed by 8-phenyltheophylline, an adenosine receptor antagonist. These results suggest that there is an adenosine A1-receptor on rabbit tracheal epithelium that inhibits adenylate cyclase, which may result in the impairment of respiratory ciliary activity, and that adenosine-induced ciliary inhibition may be modulated by adenosine uptake and its catabolism by airway epithelial cells.

Adenosine↗

PubMed1998

Nitric oxide is a regulator of mucociliary activity in the upper respiratory tract.

The in vitro effects of the nitric oxide (NO) substrate L-arginine on ciliary beat frequency and the in vivo effects of the NO donor sodium nitroprusside (SNP) on mucociliary activity were investigated in the rabbit maxillary sinus mucosa with photoelectric techniques. L-Arginine increased ciliary beat frequency in vitro with a maximum response of 27.1% +/- 6.4% at 10(-3) mol/L, and this effect was reversibly blocked by pretreatment with the NO synthase (NOS) inhibitor N(G)-nitro-L-arginine, whereas D-arginine had no such effect. SNP increased mucociliary activity in vivo, the peak response of 36.8% +/- 4.2% being obtained at the dose of 30.0 microg/kg. No tachyphylaxis was observed after repeat challenge with SNP. The increase in mucociliary activity caused by SNP was largely unaffected by pretreatment with the calcium channel blocker nifedipine, the cyclooxygenase inhibitor diclofenac, and the cholinergic antagonist atropine. The nonselective beta-blocker propranolol delayed the peak response of SNP to 7 to 8 minutes after challenge, compared with 1 to 2 minutes after challenge in animals without pretreatment. The results show the NO substrate L-arginine and the NO donor SNP to have ciliostimulatory effects in vitro and in vivo, respectively. The occurrence of NOS production in the sphenopalatine ganglion and sinus mucosa of the rabbit was studied by immunohistochemistry for NOS activity or nicotinamide adenine dinucleotide phosphate-diaphorase histochemistry. The latter is an indirect sign of neuronal NOS activity. Numerous NOS-containing cell bodies were seen in the sphenopalatine ganglion; in the sinus mucosa a moderate supply of thin NOS-immunoreactive nerve fibers was seen. Taken together, the morphologic findings and the functional results indicate NO to be a regulator of mucociliary activity in upper airways.

Animals↗

PubMedDate not supplied

[Phototaxis of the green algae: the new class of rhodopsin receptors].

Photomotility behavior in green flagellate algae is mediated by rhodopsin-like receptors, which was initially suggested on the basis of physiological evidence. The cascade of rapid Ca(2+)-dependent electrical responses in the plasma membrane plays a key role in the signal transduction chain during both phototaxis and the photophobic response. The photoreceptor current through the plasma membrane is the earliest detectable event upon photoexcitation of the photoreceptors. Analysis of this current revealed that it consists of at least two components with different characteristics. Genes encoding two archaeal-type rhodopsins (type I rhodopsins) were recently identified in the genome of Chlamydomonas reinhardtii and named (Chlamydomonas Sensory Rhodopsins A and B CSRA and CSRB). The measurements of photoelectric and motor responses in genetic transformants of C. reinhardtii enriched in each of these receptor proteins showed that the two components of the photoreceptor current are mediated by the two rhodopsins, and that both CSRA and CSRB are involved in phototaxis and the photophobic response. The CSRA-mediated current dominates at high light intensities and contributes primarily to the photophobic response. The CSRB-initiated transduction involves an efficient amplification cascade and mediates the highly sensitive phototaxis at low light intensities. CSRA and CSRB expressed heterologously in oocytes of Xenopus laevis act as light-gated proton channels, although it is unclear whether this channel activity plays a functional role in the initiation of motor responses and/or occurs in the native system.

Amino Acid Sequence↗

PubMed1984

Photoelectric signals generated by bovine rod outer segment disk membranes attached to a lecithin bilayer.

Purified bovine rod outer segment disk membranes were attached to a lecithin bilayer membrane. After photoexcitation with a 500-nm flash delivered by a dye laser, a negative photovoltage was observed on the bilayer under normal ionic strengths (100 mM KCl), which had a rise phase of 1-3 ms at 20 degrees C. The photoresponse was obviously due to bleaching of rhodopsin as it decreased for successive flashes of light. It originated most probably during the metarhodopsin-I metarhodopsin-II (meta-I-II) transition of rhodopsin because it was pH dependent at 2 degrees C but not at 20 degrees C. At 10 mM KCl, i.e., under hypotonic conditions, a positive photovoltage with slower kinetics than at high salt was observed. As the disk membranes were merely attached to the bilayer membrane, the photovoltage was apparently due to a light-induced transmembrane potential change in the disk membranes. Possible electrogenic mechanisms underlying the photosignal will be discussed.

Animals↗

PubMed2002

Theory of electric signals of membrane proteins in three dimensions.

Transmembrane ion pumps are often investigated experimentally by photoelectric measurements in model systems. In addition to the most widely used systems based on model membranes, a fundamentally different class is represented by the so-called suspension methods. In this technique the electric signal is measured on a bulk suspension of oriented ion pumps in the form of a displacement current. On this system, electric and spectroscopic experiments can be performed simultaneously. Using the information from both types of measurements, and utilizing the three-dimensional nature of the system, it is possible to follow the intramolecular charge motions in all three spatial directions. The derivable dipole moment changes associated with conformational transitions allow the verification of molecular dynamic models. In this work a theory is presented to describe the suspension method; samples with different symmetry properties and the possibilities of photoselection to obtain the desired three-dimensional information are analyzed.

Biophysics↗

PubMed2000

Computed tomography of cryogenic biological specimens based on X-ray microscopic images.

Soft X-ray microscopy employs the photoelectric absorption contrast between water and protein in the 2.34-4.38 nm wavelength region to visualize protein structures down to 30 nm size without any staining methods. Due to the large depth of focus of the Fresnel zone plates used as X-ray objectives, computed tomography based on the X-ray microscopic images can be used to reconstruct the local linear absorption coefficient inside the three-dimensional specimen volume. High-resolution X-ray images require a high specimen radiation dose, and a series of images taken at different viewing angles is needed for computed tomography. Therefore, cryo microscopy is necessary to preserve the structural integrity of hydrated biological specimens during image acquisition. The cryo transmission X-ray microscope at the electron storage ring BESSY I (Berlin) was used to obtain a tilt series of images of the frozen-hydrated green alga Chlamydomonas reinhardtii. The living specimens were inserted into borosilicate glass capillaries and, in this first experiment, rapidly cooled by plunging into liquid nitrogen. The capillary specimen holders allow image acquisition over the full angular range of 180 degrees. The reconstruction shows for the first time details down to 60 nm size inside a frozen-hydrated biological specimen and conveys a clear impression of the internal structures. This technique is expected to be applicable to a wide range of biological specimens, such as the cell nucleus. It offers the possibility of imaging the three-dimensional structure of hydrated biological specimens close to their natural living state.

Algorithms↗

PubMed1994

[A study on maximal permissible drug concentration for transnasal medication from the viewpoint of ciliary activity of the cultured human paranasal mucosa].

Aerosol therapy has been widely used for upper and lower airway diseases. However, maximal permissible concentrations of drugs have not yet been clarified. The purpose of this study was to find the maximal drug concentration for transnasal medication that does not inhibit ciliary activity or tissue. Human paranasal sinus mucosa taken at surgery was cut into small pieces. These were cultured in RPMI-1640 medium under the conditions of 5% CO2 and 100% relative humidity at 37 degrees C. Histopathologic damage was observed under a microscope at 400 x magnification. The rate of ciliary beating was measured by a photoelectric method with a cadmium sulphite photometer. In order to compare the findings with those of repeated clinical nebulizer therapy, drug application once a day for 3 days and combined use with steroids were examined for 30 min, considering maximal retention time of the drugs in the nasal cavity as an aerosol therapy. The maximal permissible concentrations of several drugs in single use obtained by these experiments were as follows: acetylcysteine 4.4%, tyloxapol 0.03%, sodium cromoglycate 4%, Broncasma Berna 2 times, prednisolone 1%, dexamethasone 0.2%, betamethasone 0.4%, kanamycin 20%, gentamicine 1%, amikasine 4%, dibekasin 4%, astromysin 4%, fosfomycin 3%, clindamycin 3%, ampicillin 10%, cefazolin 5%, and lidocaine 0.01%. When antibiotics and ateroids were used at the same time, the ciliary activity and the tissue were damaged more strongly than with single use. Therefore, the maximal concentration of some drugs has to be reduced. For example, the maximal concentration of prednisolone, 1%, was reduced to 0.2%, and that of kanamycin, 20%, was changed to 10%.

Acetylcysteine↗