Temporal Changes in Swimming Direction during the Phototactic Orientation of Individual Cells in Cryptomonas sp.

The response of individual Cryptomonas cells to continuous lightwas recorded using infrared video-micrography. Swimming directionsand temporal shifts in swimming direction of each cell weremeasured. White light of 0.1–1 W m^–2 elicited apositive phototactic orientation, but did not induce any photophobicresponse. Light of 100 W m^–2 induced a photophobic responseat the onset of actinic irradiation, but did not induce positivephototactic orientation. No correlation between positive phototacticorientation and photophobic response was found in this species.The direction toward the light source was defined as 0°,and the direction away from the source as 180°. Within 2s after the onset of lateral monochromatic light of 570 nm at0.1 W m^–2, cells which were swimming in a direction ofless than 120° predominantly shifted their course towardthe light source. Cells swimming in directions of larger than120° shifted their course as randomly as those in the dark.Thus, for phototactic orientation, the cells must perceive thelight from their anterior side. (Received July 29, 1985; Accepted November 4, 1985)     

Phototactic Responses of Cell Population to Repeated Pulses of Yellow Light in a Phytoflagellate Cryptomonas sp

Positive phototaxis in cell populations of a phytoflagellate Cryptomonas sp. was recorded photoelectrically when the duration and intensity of repeated pulses of monochromatic yellow light (570 nm) interspersed with darkness were varied. Irrespective of the duration of the light pulses, phototactic responses to repeated pulses were as great as those to continuous irradiation and were linearly dependent on the logarithm of total incident light energy when the dark interval was shorter than 60 milliseconds. Under these conditions, reciprocity between duration and intensity held well. In contrast, when the dark interval exceeded 250 milliseconds, the responses were remarkably reduced regardless of light duration and were not affected by increasing the intensity of actinic light pulses.

The present results clearly indicate that continuous stimulation with actinic light is not essential for the maximum effect, but that the length of dark interval is crucial in phototactic response.

     

Effects of Flashes of Red or Blue Light on the Composition of Starved Chlorella pyrenoidosa

Autotrophically grown cells of Chlorella pyrenoidosa (211-8b) were starved 3 to 4 days in darkness, flashes of blue light, or flashes of red light. The blue flashes were sufficient to maintain the maximal rate of light-stimulated oxygen uptake during short term experiments. However, after 24 hours, the respiration rate in red flashes was equal to, or greater than, the rate in blue flashes. Starvation in darkness reduced the chlorophyll content by 11%, altered the blue absorbance of the nonsaponifiable material only 1 to 2%, and reduced the dry weight by 13%. Starvation in the presence of blue or red flashes reduced the dry weight by an additional 11 or 12% respectively. Protein per unit cell volume was not changed significantly during 3 to 4 days starvation in darkness or in blue flashes, even though dry weight per unit cell volume decreased 13% in darkness and 23% in blue flashes. In contrast, cells starved under red flashes showed a 20% decrease in protein per unit cell volume and a 24% decrease in dry weight per unit cell volume.     

Effects of Light Quality on Formation of 5-Aminolevulinic Acid, Phycoerythrin and Chlorophyll in Cryptomonas sp. Cells Collected from the Subsurface Chlorophyll Layer

Phycoerythrin obtained from the cells of Cryptomonas sp. (Cryptophyceae)which had been isolated from the subsurface chlorophyll layerin the western Pacific Ocean showed peaks in absorption andfluorescence spectra at 545 and 586 nm, respectively. The rateof photosynthetic O₂ evolution under green light was higherthan those under blue and red light. The rate of 5-aminolevulinic acid (ALA) accumulation in thepresence of levulinic acid was higher under green light thanunder blue and red light. The effects of light quality on therates of O₂ evolution and ALA formation closely resembled eachother. On the other hand, the formation of phycoerythrin andALA was suppressed during growth under blue light. Possible effects of light quality on the formation of photosyntheticpigments in Cryptomonas sp. were discussed. (Received January 31, 1984; Accepted May 14, 1984)     

Phototactic Orientation in Plasmodia of the Acellular Slime Mold, Physarum polycephalum

Phototactic orientation to lateral light was studied in plasmodiaof the yellow-pigmented strain (CL) and a white mutant of theslime mold Physarum polycephalum. The orientation changes wereperformed by either a turn or a reversal of the internal polarityof the plasmodium. Fluence rate-response curves for white andmonochromatic light showed positive phototaxis with low fluencerates and negative phototaxis with higher ones. The wavelengthdependences for both strains were similar and indicated thepredominant role of a UV/blue light-absorbing photoreceptor,which was not the same as one of the yellow pigments found inthe wild-type strains. Wavelengths >500 nm induced only aninsignificant effect. The control of the motor apparatus andthe possible linkage of the photoresponse with the other sensoryprocesses known in Physarum are discussed. (Received June 3, 1983; Accepted October 11, 1983)     

Light Effects on Behavioural Performance Depend on the Individual State of Vigilance

Research has shown that exposure to bright white light or blue-enriched light enhances alertness, but this effect is not consistently observed in tasks demanding high-level cognition (e.g., Sustained Attention to Response Task—SART, which measures inhibitory control). Individual differences in sensitivity to light effects might be mediated by variations in the basal level of arousal. We tested this hypothesis by measuring the participants’ behavioural state of vigilance before light exposure, through the Psychomotor Vigilance Task. Then we compared the effects of a blue-enriched vs. dim light at nighttime on the performance of the auditory SART, by controlling for individual differences in basal arousal. The results replicated the alerting effects of blue-enriched light, as indexed by lower values of both proximal temperature and distal-proximal gradient. The main finding was that lighting effects on SART performance were highly variable across individuals and depended on their prior state of vigilance. Specifically, participants with higher levels of basal vigilance before light exposure benefited most from blue-enriched lighting, responding faster in the SART. These results highlight the importance of considering basal vigilance to define the boundary conditions of light effects on cognitive performance. Our study adds to current research delineating the complex and reciprocal interactions between lighting effects, arousal, cognitive task demands and behavioural performance.     

Effects of Calcium and Potassium Ions on Phototaxis in Cryptomonas

Effects on positive phototaxis and the cell motility of 7 cationsin 5mM MOPS (morpholinopropane sulfonic acid) buffer (pH 7.0)containing 0.16 mM NaCl, 0.68 mM KCl, 0.5 mM CaCl₂ and 0.16mM MgCl₂ were studied in the unicellular flagellate Cryptomonaswith a photoelectrical measuring apparatus and photomicrography.When calcium ion was removed from the medium by adding 1 mMEGTA (ethylene glycol-bis-(ß-amino-ethylether)-N,N'-tetraaceticacid), the phototactic response was totally inhibited, but theswimming rate was not much affected. The effect of EGTA waspartially reversed by the addition of 1 mM CaCl₂. When 15mMKCl or RbCl was added to the medium, phototaxis was greatlyinhibited, but there was no significant influence on the swimmingrate. Similar but less inhibitory effects were induced in thepresence of NaCl, LiCl and CsCl. KCl-induced inhibition waspartially removed by the addition of 15 mM CaCl₂ or MgCl₂. (Received June 25, 1982; Accepted September 27, 1982)     

Foraging Behavior in Two Species of Ectatomma (Formicidae: Ponerinae): Individual Learning of Orientation and Timing

The foraging behavior of marked individuals of Ectatomma ruidum and E. tuberculatum (Formicidae: Ponerinae) was observed on Barro Colorado Island, Panama, in order to determine whether learning of orientation and timing is involved when foraging on patchy resources on the forest floor. Foraging experiments under seminatural conditions were designed to control for the spatiotemporal distribution of resources at one or two preying sites. Using both single- and multi–event past experience, individual foragers of E. ruidum and (although less significantly) E. tuberculatum made directional and temporal adjustments to their behavior in response to previous differential foraging success. In spite of considerable individual variation in foraging efficiency, it is hypothesized that the observed differences in cognitive abilities can be invoked to explain ecological differences among both species.     

Do Protoplasmic Connections Function in the Phototactic Coordination of the Volvox Colony During Light Stimulation?*

SYNOPSIS. The flagellar behavior of the colonial flagellates Volvox carteri Stein and Volvox perglobator Powers was examined by placing 1.01 μm polystyrene particles in solution with swimming colonies, and photographing these particle movements. When directional light stimulation was administered to individual colonies, a cessation of flagellar activity occurred in the anterior cells of the stimulated side in both species. Since Volvox perglobator possesses prominent intercellular connections and Volvox carteri does not, the results of these experiments suggest that the connections linking colony members in some species do not function in the coordination of flagellar activity associated with light orientation behavior.     

Altered Cellular Mechanics during Osteogenic Differentiation of Human Mesenchymal Stem Cells

This article has no abstract.     

The Effects of Ethanol on the Morphological and Biochemical Properties of Individual Human Red Blood Cells

Here, we report the results of a study on the effects of ethanol exposure on human red blood cells (RBCs) using quantitative phase imaging techniques at the level of individual cells. Three-dimensional refractive index tomograms and dynamic membrane fluctuations of RBCs were measured using common-path diffraction optical tomography, from which morphological (volume, surface area, and sphericity); biochemical (hemoglobin (Hb) concentration and Hb content); and biomechanical (membrane fluctuation) parameters were retrieved at various concentrations of ethanol. RBCs exposed to the ethanol concentration of 0.1 and 0.3% v/v exhibited cell sphericities higher than those of normal cells. However, mean surface area and sphericity of RBCs in a lethal alcoholic condition (0.5% v/v) are not statistically different with those of healthy RBCs. Meanwhile, significant decreases of Hb content and concentration in RBC cytoplasm at the lethal condition were observed. Furthermore, dynamic fluctuation of RBC membranes increased significantly upon ethanol treatments, indicating ethanol-induced membrane fluidization.     

Effects of Exogenous Zinc on the Cellular Zinc Distribution and Cell Cycle of A549 Cells

Carotenogenesis in Nocardioform actinomycete Rhodococcus rhodochrous was investigated using carotenogenesis mutants and inhibitors, and a postulated carotenogenesis pathway was proposed. At the end of the synthesis, fatty acid or mycolic acid was esterified by different esterases to the same C-6 hydroxyl group of β-D-glucoside.     

TRAIL联合多西紫杉醇诱导喉鳞癌Hep-2细胞凋亡的实验研究

目的：观察肿瘤坏死因子相关凋亡诱导配体（TRAIL）联合多西紫杉醇应用于人喉鳞癌Hep-2细胞生长的抑制增殖和诱导凋亡作用。方法：实验分四组,1组对照组,2组为应用TRAIL组,3组单独应用多西紫杉醇,4组联合应用TRAIL及多西紫杉醇。分别应用MTT、流式细胞仪检测细胞凋亡率,倒置显微镜观察细胞的形态学改变。结果：TRAIL与多西紫杉醇联合作用于Hep-2细胞,能显著增强对Hep-2细胞的杀伤、抑制增殖及诱导凋亡作用,其联合应用的凋亡抑制率明显高于单独应用TRAIL组和多西紫杉醇组（P〈0．05）。结论：TRAIL与多西紫杉醇联用能显著提高对喉鳞癌Hep-2细胞的生长抑制和诱导凋亡作用。     

TRAIL联合多西紫杉醇诱导喉鳞癌Hep-2 细胞凋亡的实验研究

目的：观察肿瘤坏死因子相关凋亡诱导配体( TRAIL) 联合多西紫杉醇应用于人喉鳞癌Hep-2 细胞生长的抑制增殖和诱导 凋亡作用。方法：实验分四组,1 组对照组,2 组为应用TRAIL组,3 组单独应用多西紫杉醇,4 组联合应用TRAIL及多西紫杉醇。 分别应用MTT、流式细胞仪检测细胞凋亡率,倒置显微镜观察细胞的形态学改变。结果：TRAIL 与多西紫杉醇联合作用于Hep-2 细胞,能显著增强对Hep-2 细胞的杀伤、抑制增殖及诱导凋亡作用,其联合应用的凋亡抑制率明显高于单独应用TRAIL组和多西 紫杉醇组( P<0.05)。结论：TRAIL与多西紫杉醇联用能显著提高对喉鳞癌Hep-2 细胞的生长抑制和诱导凋亡作用。     

Effects of Histamine on Light Responses of Amacrine Cells in Tiger Salamander Retina

Using immunofluorescence, we showed that histamine receptor 1 is expressed by horizontal cell axons and a subset of amacrine cells in the tiger salamander retina. The effects of histamine on light responses of amacrine cells were studied in slice preparations. Histamine modulated the light responses of many salamander amacrine cells, depending upon the morphological type. The most pronounced effects of histamine were decreases in the light responses of broadly stratified amacrine cells, particularly those having medium-sized dendritic field diameters. To determine whether the effects of histamine were direct, Co⁺⁺ was substituted for Ca⁺⁺ in the extracellular medium to block synaptic transmission. Histamine still affected broadly stratified amacrine cells, but not narrowly stratified amacrine cells under these conditions. Taken together, these findings suggest that inhibitory interactions between strata of the IPL and within the classical receptive fields of the ganglion cells would be particularly sensitive to histamine released from retinopetal axons.     

Effects of Cellular Activation on Anti-HIV-1 Restriction Factor Expression Profile in Primary Cells

Expression of cell-intrinsic antiviral factors suppresses HIV-1 replication. We hypothesized that cellular activation modulates host restriction and susceptibility to HIV-1 infection. We measured the gene expression of 34 antiviral factors in healthy peripheral blood mononuclear cells (PBMC). Cellular activation induced expression of interferon-stimulated gene 15 (ISG15), tripartite motif 5α (TRIM5α), bone marrow stromal cell antigen 2 (BST-2)/tetherin, and certain apolipoprotein B mRNA editing enzyme 3 (APOBEC3) family members. Expression of RTF1, RNA polymerase II-associated factor 1 (PAF1), TRIM11, TRIM26, and BST-2/tetherin correlated with decreased HIV-1 infectivity. This report demonstrates synchronous effects of activation-induced antiviral genes on HIV-1 infectivity, providing candidates for pharmacological manipulation.     

Effects of Light on Growth and Glucose Consumption in Colorless Chlorella Mutant Cells

Light inhibited the growth and glucose consumption of colorlessmutant cells of Chlorella vulgaris (# 125). Sugar consumptionwas also inhibited in a medium containing a hexose such as D-fructose,D-galactose and D-mannose. Blue light strongly inhibited growth and glucose consumptionbut red light only slightly affected them. Respiration was notinhibited by blue light. The inhibitions of growth and glucoseconsumption were saturated at light intensities as low as 800mW.m^–2 and continued in the dark for at least one dayafter brief illumination with white light. The half-maximumeffect was observed with 15 min of illumination in both casesand the action spectra for light-induced inhibitions of growthand glucose consumption were similar, both showing peaks at370, 457 and 640 nm. The role of light in the inhibitions of growth and glucose consumptionis discussed. (Received June 18, 1984; Accepted October 29, 1984)     

Effects of Blue Light on Cell Elongation and Microtubule Orientation in Dark-Grown Gametophytes of Ceratopteris richardii

Gametophytes of Ceratopteris richardii developed into strap-shapedprothalli in the dark. The prothalli had an apical meristem,a subapical elongation zone and a basal zone where no growthoccurred. Continuous irradiation of blue light inhibited cellgrowth of the elongation zone, although red or far-red lighthad no effect on elongation. Cortical microtubules (MTs) ofsubapical cells reoriented from transverse to oblique or parallelto the growing axis during blue light inhibition. Each regionof the strap-shaped prothallus was irradiated with a micro-beamof blue light. Cell elongation in the subapical region was notinhibited by irradiation at the apical meristem. Irradiationof the subapical region inhibited cell elongation to a similarextent as the whole irradiation control. When a single elongatingcell at one side of the subapical region was irradiated by ablue microbeam, elongation was inhibited in a cell at the irradiateside only, resulting in a bowing prothallus. Cortical MTs reorientedfrom transverse to longitudinal to the cell axis in irradiatedcells only. The results indicate that each cell in the subapicalregion perceives blue light by itself, reorients only its corticalMTs and ceases only its cell elongation, independent of surroundingcells. (Received October 17, 1996; Accepted December 9, 1996)