Volume and Shape Changes of Human Erythrocytes Induced by Electrical Fields

The effects of electrical fields on the shape and volume of normal and abnormal red blood cells (RBC) are discussed. If an electrical field of 2-3 kV/cm is applied to the suspension of RBC, normal biconcave erythrocytes transform into spherocytes and their mean volume will increase from the usual volume of 90 µm³ to 160-170/µm³ in several minutes. There are two possible explanations for this phenomenon. The one is the membrane perforation by the potential induced by electrical field and subsequent influx of water. The other Is the mechanical surface traction caused by applied fields. The second mechanism will be discussed mainly in this paper.     

Ultraviolet Radiation Influences Perch Selection by a Neotropical Poison-Dart Frog

Ambient ultraviolet-B radiation can harm amphibian eggs, larvae and adults. However, some amphibians avoid UV-B radiation when given the opportunity. The strawberry poison dart frog, Oophaga pumilio, is diurnal and males vocalize throughout the day in light gaps under forest canopies that expose them to solar radiation. Previous studies have demonstrated that males calling from high perches are more successful at mating than those at lower perches. We investigated whether frogs at higher perches receive more ultraviolet-B than those calling from lower perches. We also investigated whether frogs on perches receiving relatively low ultraviolet-B levels maintained their positions for longer compared to individuals calling from perches receiving higher levels of ultraviolet-B. Finally, since it has been hypothesized that some animals utilize levels of UV-A as a visual cue to avoid UV-B damage, we artificially elevated ultraviolet-A levels to examine whether males exposed to artificially elevated ultraviolet-A abandoned their perches sooner compared to males exposed to visible light. We found that frogs called from perches receiving low ultraviolet-B regardless of perch height, and that frogs maintain their positions longer on perches receiving low ultraviolet-B compared to perches receiving even slightly higher ultraviolet-B levels. Exposing the frogs to artificially elevated levels of ultraviolet-A radiation caused males to move off of their perches faster than when they were exposed to a control light source. These experiments suggest that ultraviolet radiation plays an important role in frog behavior related to perch selection, even in rainforests where much of the solar radiation is shielded by the forest canopy.     

Shape Transformation of Erythrocytes Determined by Light Scattering Changes Associated With Relaxation of Particle Orientation

Dilute suspensions of normal erythrocytes exhibit a pearl-like sheen (nacre) when subjected to flow. This results from the asymmetric form (biconcave disc) of these cells. Upon cessation of flow, the nacreous effect decays in 2-3 min, corresponding to the time required for the discs to achieve random orientations by rotatory Brownian motion. The degree of nacre can be measured by comparing the intensity of scattered red light at an angle of 45° for the flowing system to that when the effect has disappeared. Since the phenomenon is critically dependent on red cell shape, it is possible to quantify the extent of erythrocyte disc-to-sphere transformation induced by detergents, low salt concentrations, or metabolic depletion.     

Nuclear Magnetic Resonance Studies on Intracellular Sodium in Human Erythrocytes and Frog Muscle

The nuclear magnetic resonance (NMR) spectrum of sodium was determined in muscle and erythrocytes using conventional continuous wave techniques. NMR spectra of fresh intact muscle revealed a single line with a width of about 38 Hz equivalent in intensity to about 53% of the total muscle sodium, in general agreement with previous work. Prolonged washing with sodium-free solutions led to a marked loss of both total and NMR-detectable sodium. The NMR-visible sodium remaining in the muscle was somewhat larger than the fraction calculated to remain extracellular and, presumably, was intracellular. The original sodium signal is thus interpreted as arising from both extracellular sodium and the narrow line portion of the signal from intracellular sodium. NMR spectra of sodium were also obtained for human erythrocytes under conditions preserving the sodium transport system. The intensity of the sodium signal in fresh cells was 98% of that present in the same samples after complete hemolysis of the cells. The NMR sodium present in intact cells was 92% of the sodium recovered by flame photometric determination of sodium from ashed samples. It is concluded that no NMR-“invisible” sodium occurs in human erythrocytes and that the presence of such sodium is not necessary for the normal functioning of the sodium transport system in erythrocytes.     

Activation of Na/H Exchange in Erythrocytes of Frog Rana ridibunda

Transport of Na⁺ in isolated erythrocytes of the frog Rana ridibunda was studied using radioactive isotope ^{22 22}Na. Treatment of erythrocytes with -adrenergic agonist isoproterenol (ISP) or with a combination of ISP and phosphodiesterase blocker 3-isobutyl-methyl-xanthine (IBMX) did not affect the Na⁺ transport into the cells. These data indicated that cAMP-dependent protein kinase A did not participate in regulation of the Na⁺ transport into the frog erythrocytes. Incubation of erythrocytes with protein kinase C activator phorbol ester (PMA, 0.15 µM) led to a pronounced increase of ^{22 22}Na accumulation and intracellular Na⁺ concentration. These changes of the Na⁺ transport into the cells were completely blocked in the presence of 50 µM ethyl-isopropyl-amiloride (EIPA), a selective blocker of the NHE1-isoform of Na⁺/H⁺ exchanger. Hence, PMA produced activation of Na⁺/H⁺ exchange in frog erythrocytes. The unidirectional Na⁺ influx into erythrocytes amounted, on average, to 0.99 ± 0.12 and 147 ± 9 mmol/l cells/h for control and PMA-treated cells, respectively. The EIPA concentration producing a 50% inhibition of the PMA-induced Na⁺ influx (IC₅₀) was 0.28 µM. A high sensitivity of the frog Na/H exchanger to EIPA indicates its similarity with the mammalian NHE1 isoform. The obtained data for the first time clearly indicate an important role of PKC in Na/H exchange regulation in the frog red blood cells.     

Melanin and Cellular Reactions to Ultraviolet Radiation

THERE has been much discussion about the importance of melanin in protecting skin against the damaging effects of sunlight and/or ultraviolet radiation^1–4; absorption and scattering by melanin protect intracellular organelles and cells in vitro^5,6. But we now believe that a number of the so-called “sunburn cells”, the dyskeratotic cells present in epidermis 12–48 h after irradiation^7–9, contain granules of melanin. Furthermore, they contain more granules than neighbouring, apparently undamaged cells. Thus paradoxically, cells containing what should be a protective compound are killed, while those containing less or none are apparently undamaged.     

Ultraviolet Radiation and the Photobiology of Earth's Early Oceans

During the Archean era (3.9–2.5 Ga ago) the earth was dominatedby an oceanic lithosphere. Thus, understanding how life aroseand persisted in the Archean oceans constitutes a majorchallenge in understanding early life on earth. Using aradiative transfer model of the late Archean oceans, thephotobiological environment of the photic zone and the surfacemicrolayer is explored at the time before the formation of a significant ozonecolumn. DNA damage rates might have been approximately threeorders of magnitude higher in the surface layer of the Archeanoceans than on the present-day oceans, but at 30 m depth,damage may have been similar to the surface of the present-dayoceans. However at this depth the risk of being transported to surface waters in the mixed layer was high. The mixed layer mayhave been inhabited by a low diversity UV-resistant biota. Butit could have been numerically abundant. Repair capabilitiessimilar to Deinococcus radiodurans would be sufficient tosurvive in the mixed layer. Diversity may have beengreater in the region below the mixed layer and above the lightcompensation point corresponding to today's `deep chlorophyllmaximum'. During much of the Archean the air-water interface wasprobably an uninhabitable extreme environment for neuston. Thehabitability of some regions of the photic zone is consistentwith the evidence embodied in the geologic record, whichsuggests an oxygenated upper layer in the Archean oceans. Duringthe early Proterozoic, as ozone concentrations increased to acolumn abundance above 1 × 10¹⁷ cm^-2, UV stresswould have been reduced and possibly a greater diversity oforganisms could have inhabited the mixed layer. However,nutrient upwelling from newly emergent continental crusts mayhave been more significant in increasing total planktonic abundance inthe open oceans and coastal regions than photobiologicalfactors. The phohobiological environment of the Archean oceanshas implications for the potential cross-transfer of life betweenother water bodies of the early Solar System, possibly on earlyMars or the water bodies of a wet, early Venus.     

Effects of Natural Intensities of Visible and Ultraviolet Radiation on Epidermal Ultraviolet Screening and Photosynthesis in Grape Leaves

Grape (Vitis vinifera cv Silvaner) vine plants were cultivated under shaded conditions in the absence of ultraviolet (UV) radiation in a greenhouse, and subsequently placed outdoors under three different light regimes for 7 d. Different light regimes were produced by filters transmitting natural radiation, or screening out the UV-B (280-315 nm), or screening out the UV-A (315-400 nm) and the UV-B spectral range. During exposure, synthesis of UV-screening phenolics in leaves was quantified using HPLC: All treatments increased concentrations of hydroxycinnamic acids but the rise was highest, reaching 230% of the initial value, when UV radiation was absent. In contrast, UV-B radiation specifically increased flavonoid concentrations resulting in more than a 10-fold increase. Transmittance in the UV of all extracted phenolics was lower than epidermal UV transmittance determined fluorimetrically, and the two parameters were curvilinearly related. It is suggested that curvilinearity results from different absorption properties of the homogeneously dissolved phenolics in extracts and of the non-homogeneous distribution of phenolics in the epidermis. UV-B-dependent inhibition of maximum photochemical yield of photosystem II (PSII), measured as variable fluorescence of dark-adapted leaves, recovered in parallel to the buildup of epidermal screening for UV-B radiation, suggesting that PSII is protected against UV-B damage by epidermal screening. However, UV-B inhibition of CO(2) assimilation rates was not diminished by efficient UV-B screening. We propose that protection of UV-B inactivation of PSII is observed because preceding damage is efficiently repaired while those factors determining UV-B inhibition of CO(2) assimilation recover more slowly.     

紫外线B辐射与植物体内酚类次生代谢的关系

概述了植物酚类次生代谢产物对紫外线B(UV—B)增强引起的辐射伤害的防御作用,酚类次生代谢与其它防护机制的相互关系。     

Estimated Ultraviolet Radiation Doses in Wetlands in Six National Parks

Ultraviolet-B radiation (UV-B, 280–320-nm wavelengths) doses were estimated for 1024 wetlands in six national parks: Acadia (Acadia), Glacier (Glacier), Great Smoky Mountains (Smoky), Olympic (Olympic), Rocky Mountain (Rocky), and Sequoia/Kings Canyon (Sequoia). Estimates were made using ground-based UV-B data (Brewer spectrophotometers), solar radiation models, GIS tools, field characterization of vegetative features, and quantification of DOC concentration and spectral absorbance. UV-B dose estimates were made for the summer solstice, at a depth of 1 cm in each wetland. The mean dose across all wetlands and parks was 19.3 W-h m⁻² (range of 3.4–32.1 W-h m⁻²). The mean dose was lowest in Acadia (13.7 W-h m⁻²) and highest in Rocky (24.4 W-h m⁻²). Doses were significantly different among all parks. These wetland doses correspond to UV-B flux of 125.0 μW cm⁻² (range 21.4–194.7 μW cm⁻²) based on a day length, averaged among all parks, of 15.5 h. Dissolved organic carbon (DOC), a key determinant of water-column UV-B flux, ranged from 0.6 (analytical detection limit) to 36.7 mg C L⁻¹ over all wetlands and parks, and reduced potential maximal UV-B doses at 1-cm depth by 1%–87 %. DOC concentration, as well as its effect on dose, was lowest in Sequoia and highest in Acadia (DOC was equivalent in Acadia, Glacier, and Rocky). Landscape reduction of potential maximal UV-B doses ranged from zero to 77% and was lowest in Sequoia. These regional differences in UV-B wetland dose illustrate the importance of considering all aspects of exposure in evaluating the potential impact of UV-B on aquatic organisms.     

Changes in Self-Efficacy Following Obesity Treatment

Self-efficacy is an important component in the treatment of obesity. However, there is limited research examining changes in self-efficacy following obesity treatment. In this quasi-experimental study, 26 obese subjects demonstrated significant improvement on the Weight Efficacy Life-Style Questionnaire (WEL) following participation in a 26-week multidisciplinary VLCD program. Subjects demonstrated significant improvement from pre- to post-treatment on total WEL scores and on all five of the situational factors: Negative Emotions, Availability, Social Pressure, Physical Discomfort and Positive Activities. These results provide further construct validity for the WEL and offer guidelines for the amount of change that subjects may demonstrate on the WEL following obesity treatment.     

Lizard and Frog Prestin: Evolutionary Insight into Functional Changes

The plasma membrane of mammalian cochlear outer hair cells contains prestin, a unique motor protein. Prestin is the fifth member of the solute carrier protein 26A family. Orthologs of prestin are also found in the ear of non-mammalian vertebrates such as zebrafish and chicken. However, these orthologs are electrogenic anion exchangers/transporters with no motor function. Amphibian and reptilian lineages represent phylogenic branches in the evolution of tetrapods and subsequent amniotes. Comparison of the peptide sequences and functional properties of these prestin orthologs offer new insights into prestin evolution. With the recent availability of the lizard and frog genome sequences, we examined amino acid sequence and function of lizard and frog prestins to determine how they are functionally and structurally different from prestins of mammals and other non-mammals. Somatic motility, voltage-dependent nonlinear capacitance (NLC), the two hallmarks of prestin function, and transport capability were measured in transfected human embryonic kidney cells using voltage-clamp and radioisotope techniques. We demonstrated that while the transport capability of lizard and frog prestin was compatible to that of chicken prestin, the NLC of lizard prestin was more robust than that of chicken’s and was close to that of platypus. However, unlike platypus prestin which has acquired motor capability, lizard or frog prestin did not demonstrate motor capability. Lizard and frog prestins do not possess the same 11-amino-acid motif that is likely the structural adaptation for motor function in mammals. Thus, lizard and frog prestins appear to be functionally more advanced than that of chicken prestin, although motor capability is not yet acquired.     

Influence of Ultraviolet Radiation on Germination and Early Seedling Growth

The influence of UV-B radiation (280–320 nm) from filtered and unfiltered FS-40 fluorescent sunlamps on germination and early seedling growth was examined for a range of vegetables (tomato, radish, cucumber, lettuce, and bean) and field crops (wheat, cotton, soybean, and millet). Continuous exposure of seeds for 3 days to 26.9 × 10⁻² W × m⁻² UV-B radiation (280–320 nm) at 25°C, had a slight effect on fresh weight of seedlings but no appreciable influence on germination percentage, or dry weight of seedlings. Extending the time of exposure to 6 days, however, resulted in abnormal seedling growth in all species but wheat. Typical responses were short, stubby roots, bronzing of the cotyledons, increased pigmentation, and abnormal curvature of the shoots.     

Quantifying Shape Changes and Tissue Deformation in Leaf Development

The analysis of biological shapes has applications in many areas of biology, and tools exist to quantify organ shape and detect shape differences between species or among variants. However, such measurements do not provide any information about the mechanisms of shape generation. Quantitative data on growth patterns may provide insights into morphogenetic processes, but since growth is a complex process occurring in four dimensions, growth patterns alone cannot intuitively be linked to shape outcomes. Here, we present computational tools to quantify tissue deformation and surface shape changes over the course of leaf development, applied to the first leaf of Arabidopsis (Arabidopsis thaliana). The results show that the overall leaf shape does not change notably during the developmental stages analyzed, yet there is a clear upward radial deformation of the leaf tissue in early time points. This deformation pattern may provide an explanation for how the Arabidopsis leaf maintains a relatively constant shape despite spatial heterogeneities in growth. These findings highlight the importance of quantifying tissue deformation when investigating the control of leaf shape. More generally, experimental mapping of deformation patterns may help us to better understand the link between growth and shape in organ development.The analysis of biological shapes is a field of broad interest, with diverse applications ranging from medical imaging to comparative anatomy and botany (Lestrel, 2011). Within plant biology, the wide variation of leaf shapes among species has long intrigued evolutionary biologists, physiologists, and developmental biologists alike. Leaves typically develop into flat structures that maximize photosynthetic surface, with variations that may help to facilitate gas exchange, offset water loss, improve convective cooling, increase mechanical support, or reduce resistance to physical environmental forces, for example (for review, see Tsukaya, 2006; Cronk, 2009). The processes controlling leaf shape development, therefore, are important to plant survival and biomass accumulation and hence have important agricultural implications.Understanding how leaf shape is controlled typically involves studying shape variation among related species and in shape mutants and requires tools to quantify phenotypic differences. In recent years, several sophisticated semiautomatic methods have been developed to analyze leaf shapes in terms of their two-dimensional (2D) profiles. Analyses range from simple length and width measurements and allometric ratios to statistical analysis of outline coordinates (Langlade et al., 2005; Bylesjö et al., 2008; Weight et al., 2008; Backhaus et al., 2010).Leaf shape can also be quantified in terms of a three-dimensional (3D) surface, which can range from flat to curved or ruffled, as observed in nature and in many leaf shape mutants. Approaches to 3D shape analysis based on flattened and unflattened leaf dimensions in the proximodistal and mediolateral axes have been presented by Liu et al. (2010) and Wu et al. (2007). Kaminuma et al. (2004) developed a technique for obtaining coordinates of the leaf surface in vivo, from which they measured the angle of the surface across the leaf and fit curves along the leaf proximodistal and mediolateral axes to characterize blade epinasty.These existing methods for leaf shape analysis are very useful for detecting and quantitatively describing shape differences, but they do not provide information about the underlying mechanisms that give rise to those shape differences. For example, the correspondence between evenly spaced outline points (Langlade et al., 2005; Bylesjö et al., 2008; Weight et al., 2008; Backhaus et al., 2010) is arbitrary. Furthermore, existing work has not provided an analysis of leaf shape in terms of both 2D and 3D phenotypic features together, and with the exception of Kaminuma et al. (2004), the methods are destructive and cannot be used to measure changes in shape in vivo.Differences in shapes between two organs arise through differences in how the organs grow. It is impossible, however, to ascertain from differences in final organ shape what differences in growth gave rise to them, as the possible combinations of spatial and temporal alterations in growth patterns that could be responsible for the final shape are endless. By the same token, it can be difficult to conceptualize from growth patterns how the interconnected tissues will deform and, thus, how overall organ shape will change.To address this issue, Kennaway et al. (2011) recently proposed a simulation modeling framework to investigate how a shape may locally and globally deform under the control of spatially distributed growth- and polarity-regulating substances. This framework was used to hypothesize how growth and shape deformation may be controlled in flowers (Green et al., 2010; Sauret-Güeto et al., 2013) and leaves (Kuchen et al., 2012). However, to date, shape deformation patterns have not been quantified experimentally. Here, we use data collected for a study on leaf growth (Remmler and Rolland-Lagan, 2012) to develop a method for describing 3D surface shape and shape deformations during leaf development. In particular, we generate experimental maps of tissue deformation, which offer a new approach to investigating shape differences and uncovering the link between growth and shape during development.