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PubMed1992

Induction of chromosome aberrations by monochromatic X-rays with resonance energy of phosphorus K-shell absorption edge.

The induction of chromosome aberrations by monochromatic soft X-rays with energies corresponding to the K-shell absorption edge of phosphorus has been studied in density-inhibited mouse m5S cells. The frequency of dicentrics was markedly enhanced when the cells were irradiated with energy at the K-shell resonance peak (2.153 keV) as compared to those at below (2.146 keV) or above (2.160 keV) the peak. The quantum efficiency was calculated to be 2.7 x 10(-3) for the induction of dicentrics per photoelectric absorption of phosphorus atom in DNA, which was comparable to the known efficiencies of X- or gamma-ray-induced DNA double-strand breaks. However, comparison of the efficiencies based on the absorbed dose indicated that the magnitude of the enhancement was not due solely to the selective photoelectric absorption of the phosphorus atoms in DNA, and suggested the combined contributions of Auger electrons from phosphorus atoms within and outside the DNA molecules.

Animals↗
PubMed1987

Photoelectric recording of mechanical responses of cardiac myocytes.

A method to monitor contraction of isolated myocytes by transmicroscopic photometry is illustrated. Two photodiodes are mounted inside an inverse microscope used for visual control of a cell. Illumination of one diode varies in proportion to changes in cell length. The contraction signal is amplified in a comparator circuit. Spatial resolution of the device is in the order of 1 micron which corresponds to about 5% of cell shortening in the fully activated state of contraction. The method was tested on isolated myocytes from guinea-pig ventricle. Optical records of contraction in response to action potentials or during voltage clamp compare well with the contractile behavior of multicellular preparations.

Action Potentials↗
PubMed1997

Extraction of cilium beat parameters by the combined application of photoelectric measurements and computer simulation.

Photoelectric signals were created and used to investigate the features of the signals as a function of the ciliary beat parameters. Moreover, correlation between the simulated and the measured signals permitted measurement of the cilium beat parameters. The simulations of the signals were based on generation of a series of time-frozen top-view frames of an active ciliary area and determination of the amount of light passing through an observation area in each of these frames. All the factors that might contribute to the shape of the signals, namely, partial ciliary transmittance of light, three-dimensional ciliary beat (composed of recovery, effective, and pause parts), phase distribution on the ciliary surface, and the large number of cilia that contribute to the photoelectric signal, were taken into account in generation of the signals. Changes in the ciliary parameters influenced the shape of the photoelectric signals, and the different phases of the beat could not be directly and unequivocally identified in the signals. The degree of temporal asymmetry of the beat and the portion of the cycle occupied by the pause significantly influenced the shapes of both the lower and the upper parts of the signal and the slopes of the signal. Increases in the angle of the arc swept by the cilium during the effective stroke smoothed the signals and increased the duration of the upper part of the signal. The angle of the arc projected by the cilium onto the cell surface during the recovery stroke had minor effects on the signal's shape. Characteristics of the metachronal wave also influenced the signal's shape markedly. Decreases in ciliary spacing smoothed the signals, whereas ciliary length had a minor influence on the simulated photoelectric signals. Comparison of the simulated and the measured signals showed that the beat parameters of the best-fitting simulated signals converged to values that agree well with the accepted range of beat parameters in mucociliary systems.

Animals↗
PubMed1991

Radiation damage in soft X-ray microscopy of live mammalian cells.

When specimens are observed by soft X-ray microscopy, they always absorb many photons, causing radiation damage at the imaged site. The problems of radiation damage were studied in view of the principle of image formation; absorption contrast, scattering (holography), or phase contrast. In all cases, photons with a wavelength of 1-10 nm interact with the specimen mainly through the photoelectric effect followed by the transfer of energy to the imaging site either directly (absorption imaging) or indirectly (holography or phase contrast). This absorbed energy will cause structural changes to the imaging site. From a review of the literature the absorbed dose is estimated to be as high as 10(7) Gy when the expected resolution of the specimen (1-10 microns thick) is 10 nm. This dose is far in excess of the amount required for cells to be able to survive when live mammalian cells are exposed. The levels of radiation effects were extrapolated to the estimated absorbed dose from the reported values for cell survival, chromosome aberrations, and DNA strand breaks with respect to observations on mammalian chromosomes. The extrapolated results show that some damage will occur in every 10 x 10-nm (expected resolution) size unit. Although these studies focused only on the effects on mammalian chromosomes, the present results are more or less common phenomena in the observation of biological specimens. Hence, the results suggest that dynamic observations will be difficult. On the other hand, a time-scale study of the effects of radiation on structural integrity suggests that single-shot imaging with short-pulsed (probably shorter than a few milliseconds) X-rays may be appropriate for the observation of intact live biological specimens in the hydrated condition, before they have deteriorated.

Cell Survival↗
PubMed1981

Quantitative studies on the polarization optical properties of living cells. I. Microphotometric birefringence detection system.

A method of polarization optical analysis is described in which phase retardation attributable to birefringence of a minute area in a microscopic object is determined. The optical system consists of a polarizing microscope with "rectified" strain-free lenses, a photoelectric detector to determine the intensity of the light passing through a minute window located at the image plane of the specimen, and a stage that moves the specimen at appropriate velocities for scanning. The error resulting from any flare of light emerging from outside of the area to be measured is minimized by limiting the illuminated area. The specimen can be observed during the measurement of light intensity by illuminating the whole microscope field at a wavelength different from that of the light used for the measurement. The retardation of the specimen is determined by comparing the specimen and background intensities as functions of the azimuth of a Brace-Köherl compensator. Alternatively, retardation is obtained directly from the light intensity at a fixed compensator angle, using the theory of polarization optics. The basal noise level for the present apparatus is approximately 0.03 nm when measuring birefringence of a 4-micron2 area in 0.1 s, using a X 40, NA 0.65 objective. The noise decreases in inverse proportion to the square root of the area times the duration of measurement.

Animals↗
PubMed1985

Photoelectron imaging of cytoskeletal elements.

The established electron microscope techniques have richly contributed to the current understanding of cytoskeletal structure. The purpose of this paper is to demonstrate the kinds of images of cytoskeletal structures obtained by photoelectron microscopy (PEM or photoelectron imaging), which has only recently been applied utilizes the fact that specimens exposed to UV light emit electrons (the photoelectric effect). These electrons are accelerated and focused to provide a detailed image of the exposed biological surface. There are several interdependent factors involved in imaging the cytoskeletons of cells grown in culture. Since PEM is a surface technique a major consideration is exposure of the structure of interest. A second consideration is the preservation of the three-dimensional integrity of the structures during the specimen preparation, and a third is preservation of antigenicity so that specific structures can be directly identified by antibody labeling methods. The photoelectron images of Triton-extracted cells reveal a detailed filamentous network of cytoskeletal elements. Prefixation of cells with a crosslinking agent (DTSP) prior to Triton extraction has little or no effect on the final image, whereas brief prefixation with 0.025% glutaraldehyde preserves more of the surface lamina and cytoplasmic organelles such as mitochondria. A comparison of immunofluorescence and photoelectron micrographs of the same cells shows a large correspondence in the fibers observed, and demonstrates the higher resolution of PEM. Direct identification of specific cytoskeletal elements in the photoelectron micrographs is illustrated using microtubule distributions in CV-1 cells by antibody decoration or, more generally, by the use of photoemissive gold markers on antibodies directed against microtubules.

Animals↗
PubMed1991

Differential expression of migration inhibitory and migration stimulatory factors in two lines of mice genetically selected for high or low responsiveness to phytohemagglutinin. 1. Migration stimulatory factor(s) from T and B cells of immune spleen.

Expression of the lymphokine migration inhibition factor in two lines of mice genetically selected for the high (Hi/PHA) or low (Lo/PHA) response of their lymph node cells to phytohemagglutinin was found to be modulated by concomitant expression of migration stimulation factor(s) [MStF(s)]. The expression of both lymphokines was dependent on genetic character and the immunizing dose of antigen. In mice immunized 5 days earlier with 50 micrograms ovalbumin in Freund's complete adjuvant (Ova in FCA immune), migration inhibition factor, assessed with a sensitive photoelectric method, was well expressed by male spleen or lymph node 24-hour culture supernatants of Lo/PHA but Hi/PHA, especially female, expressed marked MStF(s) instead. Immunization with 500 micrograms Ova in FCA markedly enhanced expression of MStF(s) in Lo/PHA but inhibited it in Hi/PHA. MStF(s) of Ova in FCA immune spleens of the two lines were found to derive from both T and B cells, B cell activity being greater. Lo/PHA were by far better expressors of both T- and B-cell-derived MStF(s) as compared to Hi/PHA (p less than 0.01). Spleen cells of mice immunized with FCA alone also expressed MStF(s) but to lesser extent than Ova in FCA immune spleens, expression by Lo/PHA B cells being significantly higher than in Hi/PHA (p less than 0.05). The MStF(s) of Ova in FCA immune spleens was found to be non-immunoglobulin in nature.

Animals↗
PubMedDate not supplied

Variation of ACTA scanner numbers with the physical properties of the scanned material.

An experiment has been carried out in which an ACTA computerized axial-transverse tomographic scanner was used in a series of scans on a polystyrene phantom. Cavities in the phantom contained distilled water and various concentrations of acetic acid or ferric nitrate in aqueous solution. It is shown that the ACTA numbers generated for the low-Z acetic acid solution are proportional to the electron density of the solution, but that such is not the case for the higher-Z ferric nitrate, where photoelectric absorption is significant. The correlation of scanner numbers with electron density rather than with mass density is discussed and, as an illustrative example, the electron densities of whole blood and blood cells are calculated and the relative value is compared with the relative mass densities of the materials.

Diagnosis, Computer-Assisted↗
PubMedDate not supplied

[New knowledge concerning "Hoboken's valves" of the umbilical artery].

From the time of the first description, in the seventeenth century, of valvular structures ("Hobokensian valves") in the arteries of the umbilical cord their existence has remained challenged and their function still remains unclear. In order to investigate the arteries in the human umbilical cord, as well as the existence and construction of the Hobokensian valves two experiments were carried out: on the one hand, segments of the human umbilical cord were ligatured bilaterally and fixed in varying time intervals ranging from a few seconds to three minutes post natal, on the other hand one hour post natal umbilical cord arteries were dilated by the use of radio opaque material by applying increased pressure, X-rayed and fixed. The fixed preparations were rasterelectronically and photoelectrically examined and a graphic reconstruction of the arterial wall from the segmental samples was carried out. The wide umbilical cord artery consists of endothelium and double-layered media: the smooth muscle cells of the inner layer are ordered in a scissor-like lattice, the outer layer is constructed of right and left revolving screw-like intersecting muscular fascicules. In the first minutes after birth, due to localised contractions of the double-layered media, numerous waist-formed grooves of the whole arterial wall appeared, which correspond to the Hobokensian valves. They form the initial stage of a contraction process, which leads onto active luminal occlusion and interrupts the perfusion of the umbilical cord. Due to the passage-like appearance of the "Hobokensian valves" the controversial views concerning their existence are clarified.

Female↗
PubMed2001

Rhodopsin receptors of phototaxis in green flagellate algae.

Green flagellate algae are capable of the active adjustment of their swimming path according to the light direction (phototaxis). This direction is detected by a special photoreceptor apparatus consisting of the photoreceptor membrane and eyespot. Receptor photoexcitation in green flagellates triggers a cascade of rapid electrical events in the cell membrane which plays a crucial role in the signal transduction chain of phototaxis and the photophobic response. The photoreceptor current is the earliest so far detectable process in this cascade. Measurement of the photoreceptor current is at present the most suitable approach to investigation of the photoreceptor pigment in green flagellate algae, since a low receptor concentration in the cell makes application of optical and biochemical methods so far impossible. A set of physiological evidences shows that the phototaxis receptor in green flagellate algae is a unique rhodopsin-type protein. It shares common chromophore properties with retinal proteins from archaea. However, the involvement of photoelectric processes in the signal transduction chain relates it to animal visual rhodopsins. The presence of some enzymatic components of the animal visual cascade in isolated eyespot preparations might also point to this relation. A retinal-binding protein has been identified in such preparations, the amino acid sequence of which shows a certain homology to sequences of animal visual rhodopsins. However, potential function of this protein as the phototaxis receptor has been questioned in recent time.

Chlorophyta↗
PubMedDate not supplied

Platelet-activating factor inhibits ciliary beat frequency of human bronchial epithelial cells.

The aim of our study was to investigate the effect of platelet-activating factor on human bronchial ciliary beat frequency (CBF) ex vivo. Brush biopsies were obtained from eight children (mean age 6.6 years) who underwent bronchoscopy for clinical reasons (i.e., foreign body aspiration, chronic cough, stridor). Immediate measurement of CBF by phase-contrast microscopy and photoelectric technique was performed before further treatment, and then on three subsamples: after adding platelet-activating factor (PAF) (10(-5) M); after adding the inhibitor WEB 2086 (10(-4) M); and after adding both PAF and WEB 2086. Addition of 10(-5) M PAF reduced mean CBF by 2.1 Hz to 9.2 Hz (p < 0.05). The inhibitory effect of PAF was completely reversed by the addition of the PAF-inhibitor WEB 2086, whereas WEB 2086 alone did not significantly influence CBF. Optimum PAF concentration had been determined in previous dose-response experiments. Our data indicates that PAF involved in airway inflammation contributes to a decrease in mucociliary clearance in humans.

Adolescent↗
PubMed1995

[Airway epithelium and nitric oxide].

To measure the generation of nitric oxide (NO) by airway epithelial cells and to study the physiological role of NO in the regulation of epithelial functions, we studied ciliary motility of rabbit cultured tracheal epithelium in vitro and ion transport across tracheal mucosa in vivo. Isoproterenol dose-dependently increased ciliary beat frequency, as measured by photoelectric methods. Perfusion of tracheal mucosa with tachykinins increased the diffusion potential for chloride ions, as measured in the presence of amiloride under open-circuit conditions: the rank order of potency was neurokinin A > substance P >> neurokinin B. These responses to isoproterenol and to tachykinins were attenuated by pretreatment with NG-nitro-L-arginine methylester, and this attenuation was reversed by L-arginine. In contrast, NG-nitro-D-arginine methylester and D-arginine had no such effects. NO concentrations in the medium and perfusate were measured in realtime with an amperometric sensor specific to this molecule, and immersion of the electrode allowed detections of a polarographic current under unstimulated conditions. Addition of isoproterenol, neurokinin A, or substance P caused a rapid and dose-dependent increase in NO concentration. Histochemical examination for NADPH diaphorase activity in cultured epithelium showed strong staining within the cytoplasm. These results suggest that NO is spontaneously released from airway epithelial cells and that generation of this molecule may contribute to airway epithelial ciliary motility and chloride ion secretion mediated by beta-adrenoceptors and by tachyinin NK2 receptors.

Animals↗
PubMed1992

Thromboxane A2 mimetic U46619 stimulates ciliary motility of rabbit tracheal epithelial cells.

To elucidate whether thromboxane A2 (TxA2), one of the important arachidonic acid metabolites that may play a role in the development of airway inflammation, affects respiratory ciliary motility and, if so, what the mechanism of action is, we measured ciliary beat frequency (CBF) of rabbit cultured tracheal epithelium in response to U46619, a TxA2 mimetic agonist, by a photoelectric method. Addition of U46619 (10(-5) M) increased CBF from 17.7 +/- 0.7 to 22.8 +/- 1.4 Hz (mean +/- SE, p less than 0.01) within 5 min, which was followed by a decline to the baseline value by 10 min. This effect was concentration-dependent, the maximal increase from the baseline value and the drug concentration required to produce a half-maximal effect (EC50) being 26.9 +/- 4.6% (p less than 0.01) and 3 x 10(-7) M, respectively. The U46619-induced increase in CBF was abolished by SQ29548, and TxA2 receptor antagonist, and inhibited by verapamil, a Ca(2+)-entry blocker, and H-7, a protein kinase C inhibitor. These results suggest that TxA2 stimulates ciliary motility through the activation of airway epithelial TxA2 receptors, and that this effect may be exerted from Ca(2+)-influx and protein kinase C.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1976

Quantitation of the rate-zonal sedimentation spectrum.

Rate-zonal sedimentation of cells from the female genital tract has been employed as a means of separating many of the different cellular components from each other. Ultra-slow streak photography of forward scattered light from the sedimentation spectrum has been used as a monitor of the success of the individual sedimentation maneuver. The presence of convention currents vitiates the separation potential of the technique, and this is readily detected by the photographic monitor. In addition, these photographs clearly indicate the positions of bands of cellular entities of different sedimentation velocities. Further study of the quantitative aspects of the light scattered from each part of the spectrum reveals that it possesses a quantitative representation of the concentration of cells at each level of the spectrum. The photographs and densitometric scans support these expectations. To avoid the limitations of film as a data-logging medium and to obtain real-time system utilization, a direct photoelectric scanner has been assembled. Preliminary tests indicate ready feasibility.

Centrifugation, Zonal↗