共查询到20条相似文献,搜索用时 31 毫秒
1.
D.M. Hunt S.E. Wilkie J.K. Bowmaker S. Poopalasundaram 《Cellular and molecular life sciences : CMLS》2001,58(11):1583-1598
Sensitivity to ultraviolet light (UV) is achieved by photoreceptors in the eye that contain a class of visual pigments maximally sensitive to light at wavelengths <400 nm. It is widespread in the animal kingdom where it is used for mate choice, communication and foraging for food. UV sensitivity is not, however, a constant feature of the visual system, and in many vertebrate species, the UV-sensitive (UVS) pigment is replaced by a violet-sensitive (VS) pigment with maximal sensitivity between 410 and 435 nm. The role of protonation of the Schiff base-chromophore linkage and the mechanism for tuning of pigments into the UV is discussed in detail. Amino acid sequence analysis of vertebrate VS/UVS pigments indicates that the ancestral pigment was UVS, with loss of UV sensitivity occurring separately in mammals, amphibia and birds, and subsequently regained by a single amino acid substitution in certain bird species. In contrast, no loss of UV sensitivity has occurred in the UVS pigments of insects. 相似文献
2.
The structure of scytonemin,an ultraviolet sunscreen pigment from the sheaths of cyanobacteria 总被引:10,自引:0,他引:10
P. J. Proteau W. H. Gerwick F. Garcia-Pichel R. Castenholz 《Cellular and molecular life sciences : CMLS》1993,49(9):825-829
Despite knowledge of the existence of the pigment called scytonemin for over 100 years, its structure has remained unsolved until now. This pigment, the first shown to be an effective, photo-stable ultraviolet shield in prokaryotes, is a novel dimeric molecule (molec. wt. 544) of indolic and phenolic subunits and is known only from the sheaths enclosing the cells of cyanobacteria. It is probable that scytonemin is formed from a condensation of tryptophan-and phenylpropanoid-derived subunits. The linkage between these units is unique among natural products and this novel ring structure is here termed the scytoneman skeleton. Scytonemin absorbs strongly and broadly in the spectral region 325–425 nm (UV-A-violet-blue, with an in vivo maximum at 370 nm). However, there is also major absorption in the UV-C (
max=250nm) and UV-B (280–320 nm). The pigment has been recently shown to provide significant protection to cyanobacteria against damage by ultraviolet radiation. The pigment occurs in all phylogenetic lines of sheathed cyanobacteria and possibly represents a UV screening strategy far more ancient than that of plant flavonoids and animal melanins. How diverse organisms deal with UV radiation is considered of vital importance to global ecology. 相似文献
3.
Summary In experiments with a sufficiently great number of observers, using our spectral colour integrator, it has been shown thatone colour containing a maximum of chromatic power (chroma) can be chosen out of a series of optimal colours continuously changeable from white over the fullcolour to black. The determination of such maximal colours, differing in hue, shows their position between fullcolour and spectral colour in the mixing metric colour solid. Their relation to maximal properties of scalemetrically defined chromatic power functions is discussed. 相似文献
4.
P. Paoli G. Camici G. Manao G. Ramponi 《Cellular and molecular life sciences : CMLS》1995,51(1):57-62
A new aromatic acyl phosphate, 2-methoxybenzoyl phosphate, has been synthesized. The compound shows an intrinsic fluorescence; it displays an intense emission band at 390 nm upon excitation in the near UV region. This band practically disappears after hydrolysis of the product. On the other hand, the product displays differences in the near UV absorption spectra measured before and after hydrolysis. The at 301 nm is 2720 M–1 cm–1, a value that is 4.3-fold higher than that of benzoyl phosphate (the usual substrate for acylphosphatase assay) at 283 nm. The main kinetic parameters of three different acylphosphatase molecular forms (the muscular isoenzyme and two subtypes of the organ common isoenzyme) were determined using both benzoyl phosphate and 2-methoxybenzoyl phosphate as substrates, and then compared. These kinetic data and the UV absorption and fluorescence properties of 2-methoxybenzoyl phosphate sugest that this compound has better substrate features than benzoyl phosphate, and can be used for both high sensitivity continuous fluorimetric and UV absorption spectrophotometric assays of acylphosphatase. 相似文献
5.
Tarttelin EE Fransen MP Edwards PC Hankins MW Schertler GF Vogel R Lucas RJ Bellingham J 《Cellular and molecular life sciences : CMLS》2011,68(22):3713-3723
Photoreception by vertebrates enables both image-forming vision and non-image-forming responses such as circadian photoentrainment.
Over the recent years, distinct non-rod non-cone photopigments have been found to support circadian photoreception in diverse
species. By allowing specialization to this sensory task a selective advantage is implied, but the nature of that specialization
remains elusive. We have used the presence of distinct rod opsin genes specialized to either image-forming (retinal rod opsin)
or non-image-forming (pineal exo-rod opsin) photoreception in ray-finned fish (Actinopterygii) to gain a unique insight into this problem. A comparison of biochemical features for these paralogous opsins in two model
teleosts, Fugu pufferfish (Takifugu rubripes) and zebrafish (Danio rerio), reveals striking differences. While spectral sensitivity is largely unaltered by specialization to the pineal environment,
in other aspects exo-rod opsins exhibit a behavior that is quite distinct from the cardinal features of the rod opsin family.
While they display a similar thermal stability, they show a greater than tenfold reduction in the lifetime of the signaling
active Meta II photoproduct. We show that these features reflect structural changes in retinal association domains of helices
3 and 5 but, interestingly, not at either of the two residues known to define these characteristics in cone opsins. Our findings
suggest that the requirements of non-image-forming photoreception have lead exo-rod opsin to adopt a characteristic that seemingly
favors efficient bleach recovery but not at the expense of absolute sensitivity. 相似文献
6.
Crnković-Mertens I Wagener N Semzow J Gröne EF Haferkamp A Hohenfellner M Butz K Hoppe-Seyler F 《Cellular and molecular life sciences : CMLS》2007,64(9):1137-1144
Cancer cells are typically characterized by apoptosis deficiency. In order to investigate a possible role for the anti-apoptotic
livin gene in renal cell cancer (RCC), we analyzed its expression in tumor tissue samples and in RCC-derived cell lines. In addition,
we studied the contribution of livin to the apoptotic resistance of RCC cells by RNA interference (RNAi). Livin gene expression was detected in a significant portion of RCC tumor tissue specimens (13/14, 92.9%) and tumor-derived cell
lines (12/15, 80.0%). Moreover, targeted inhibition of livin by RNAi markedly sensitized RCC cells towards proapoptotic stimuli, such as UV irradiation or the chemotherapeutic drugs
etoposide, 5-fluorouracil, and vinblastine. These effects were specific for livin expressing tumor cells. We conclude that livin can contribute significantly to the apoptosis resistance of RCC cells. Targeted inhibition of livin could represent a novel therapeutic strategy to increase the sensitivity of renal cancers towards pro-apoptotic agents.
Received 30 November 2006; received after revision 22 February 2007; accepted 20 March 2007 相似文献
7.
Hl. de Vries 《Cellular and molecular life sciences : CMLS》1948,4(9):357-358
Summary The influence of the temperature of the eye on the spectral distribution of its sensitivity was studied. The leading idea was that the small long-wave light quanta could only decompose a molecule of the photochemical substances if this molecule had already a sufficient thermal energy. One must therefore expect the sensitivity for long wavelengths to be higher at high temperatures; moreover this influence of temperature is most pronounced for the longest wavelengths. In the measurements the sensitivity for the wavelengths of 660 mµ and 730 mµ were comparedwith each other. In the accompanying figure the slit width of the apparatus at 660 mµ is shown as a function of temperature. The experimental points are close to the lines which were predicted by the theory. 相似文献
8.
R. Gomez J. M. Macarulla A. M. Gárate P. G. Barbón J. C. G. Milicua 《Cellular and molecular life sciences : CMLS》1986,42(9):1063-1064
Summary A blue carotenoid-protein complex (max 635 nm) was extracted and purified from the carapace of the crayfishProcambarus clarkii. The complex was further liberated from astaxanthin, its prostetic group, causing dissociation into apoprotein subunits. Reconstitution of the complex from the various sub-units (isolated by chromatofocusing) plus astaxanthin was attempted. Apoprotein-size pigments of rose-purple color (max 545 nm) were obtained. It was found that both monomers are required in order to a blue complex fairly similar in structure ot the native one. However, the native conformation was not completely recovered, as indicated by some differences in the UV spectrum. 相似文献
9.
T. M. Koval 《Cellular and molecular life sciences : CMLS》1987,43(4):445-446
Summary Cell survival and photoreactivation of 254 nm ultraviolet (UV) light damage in a wild typeDrosophila cell line was assayed by colony formation in liquid medium. Fo, Fq, and extrapolation number for the exponential portion of survival curves are 21 J/m2, 3.6 J/m2, and 1.5 for non-photoreactivated cells and 110 J/m2, 11.2 J/m2, and 1.3 for those exposed to photoreactivating light. Maximal photoreactivation occurs at the 100 J/m2 region of the curve. At 10 and 50% survival, 75–80% of the UV damage was photoreactivable. 相似文献
10.
Davies WI Zheng L Hughes S Tamai TK Turton M Halford S Foster RG Whitmore D Hankins MW 《Cellular and molecular life sciences : CMLS》2011,68(24):4115-4132
Melanopsin (OPN4) is an opsin photopigment that, in mammals, confers photosensitivity to retinal ganglion cells and regulates
circadian entrainment and pupil constriction. In non-mammalian species, two forms of opn4 exist, and are classified into mammalian-like (m) and non-mammalian-like (x) clades. However, far less is understood of the function of this photopigment family. Here we identify in zebrafish five
melanopsins (opn4m-1, opn4m-2, opn4m-3, opn4x-1 and opn4x-2), each encoding a full-length opsin G protein. All five genes are expressed in the adult retina in a largely non-overlapping
pattern, as revealed by RNA in situ hybridisation and immunocytochemistry, with at least one melanopsin form present in all
neuronal cell types, including cone photoreceptors. This raises the possibility that the teleost retina is globally light
sensitive. Electrophysiological and spectrophotometric studies demonstrate that all five zebrafish melanopsins encode a functional
photopigment with peak spectral sensitivities that range from 470 to 484 nm, with opn4m-1 and opn4m-3 displaying invertebrate-like
bistability, where the retinal chromophore interchanges between cis- and trans-isomers in a light-dependent manner and remains within the opsin binding pocket. In contrast, opn4m-2, opn4x-1 and opn4x-2
are monostable and function more like classical vertebrate-like photopigments, where the chromophore is converted from 11-cis to all-trans retinal upon absorption of a photon, hydrolysed and exits from the binding pocket of the opsin. It is thought that all melanopsins
exhibit an invertebrate-like bistability biochemistry. Our novel findings, however, reveal the presence of both invertebrate-like
and vertebrate-like forms of melanopsin in the teleost retina, and indicate that photopigment bistability is not a universal
property of the melanopsin family. The functional diversity of these teleost melanopsins, together with their widespread expression
pattern within the retina, suggests that melanopsins confer global photosensitivity to the teleost retina and might allow
for direct “fine-tuning” of retinal circuitry and physiology in the dynamic light environments found in aquatic habitats. 相似文献
11.
Summary Retinal spectral sensitivity of the gerbil (Meriones unguiculatus) shows that this animal has a unique photoreceptor complement: there is only a single class of cone and the spectrum for these receptors is peak shifted toward the short wavelengths relative to the spectra obtained from rods. 相似文献
12.
K. T. Zwicky 《Cellular and molecular life sciences : CMLS》1970,26(3):317-317
Zusammenfassung Die spektrale Empfindlichkeit des extraokularen Lichtsinnes des australischen SkorpionsUrodacus wurde bestimmt. Das Maximum liegt im Bereich von 480 nm. Die Einberechnung der Kutikulartransmission verändert die Form der Kurve, besonders im UV, aber das Intensitätsmaximum bleibt dasselbe. 相似文献
13.
B. Iyengar 《Cellular and molecular life sciences : CMLS》1994,50(7):669-672
Whole skin organ cultures of vitiliginous, skin show that the marginal melanocytes are highly sensitive to a pulse of UV exposure (210–380 nm) during the G2 phase of the cell cycle, as seen by prominent dendricity. Melanocytes are highly dendritic in the epidermis overlying rapidly growing tumors, as well as within proliferative lesions such as basal cell carcinomas and aggressive seborrheic keratosis. In the organ cultures the dendrites extend towards the source of UV, i.e. the surface, while the main body lies along the basement membrane. The epidermal melanocytes overlying tumors lie, almost vertically, dendrites aligned towards the underlying tumor on one side and the surface on the other. Within tumors dendritic elongation is guided by mitotic and PCNA positive (S-phase) tumor cells, which are a source of ultraweak UV emissions in the range of 210–330 nm. These observations indicate that ultraweak biophoton emissions from neighbouring cells can simulate environmental cues and contribute to the plasticity of networks such as the melanocytes or the visual pathways. 相似文献
14.
Sánchez-Font MF Sebastià J Sanfeliu C Cristòfol R Marfany G Gonzàlez-Duarte R 《Cellular and molecular life sciences : CMLS》2003,60(7):1513-1523
Suppression subtractive hybridization performed on Down syndrome (DS) versus control fetal
brains revealed differential expression of peroxiredoxin 2
(PRDX2), mapped at 13q12. Peroxiredoxins are antioxidant
enzymes involved in protein and lipid protection against oxidative injury and in cellular signalling
pathways regulating apoptosis. The under-expression of PRDX2
observed in DS samples was confirmed by realtime PCR (0.73-fold). To test whether decreased expression
is associated with enhanced sensitivity of DS neurons to reactive oxygen species, we down-regulated
PRDX2 through stable transfections of SH-SY5Y neuroblastoma
cells with antisense contructs of the complete PRDX2 coding
sequence. In addition, we over-expressed SOD1 and compared the effects of the two genes on cell
viability. Cells transfected with either construct showed similar sensitivity to oxidative stress in addition to increased
apoptosis under basal conditions and after treatment with oxidative cytotoxic agents. This suggests that
the decreased expression of PRDX2 may contribute to the
altered redox state in DS at levels comparable to that of the increased expression of SOD1.Received 4 February 2003; received after revision 31 March 2003; accepted 25 April 2003 相似文献
15.
In this paper we propose and evaluate two new methods for the quantification of business surveys concerning the qualitative assessment of the state of the economy. The first is a nonparametric method based on the spectral envelope, originally proposed by Stoffer, Tyler and McDougall (Spectral analysis for categorical time series: scaling and the spectral envelope, Biometrika 80 : 611–622) to the multivariate time series of the counts in each response category. Secondly, we fit by maximum likelihood a cumulative logit unobserved components models featuring a common cycle. The conditional mean of the cycle, which can be evaluated by importance sampling, offers the required quantification. We assess the validity of the two methods by comparing the results with a standard quantification based on the balance of opinions and with a quantitative economic indicator. Copyright ? 2010 John Wiley & Sons, Ltd. 相似文献
16.
H. Tabata T. Hasegawa M. Nakagoshi S. Takikawa M. Tsusue 《Cellular and molecular life sciences : CMLS》1996,52(1):85-87
A blue fluorescent compound was isolated fromMorpho butterfly wings. Based on thin layer chromatographic, UV and CD-spectrophotometric and HPLC analyses, the blue fluorescent compound was identified as L-erythro biopterin. Biopterin is a major component of blue fluorescent pteridines in bothM. sulkowskyi andM. adonis. Pterin and isoxanthopterin can also be detected as minor components in these species. This paper is the first to report the presence of biopterin in butterfly wings. 相似文献
17.
Evolution and ecological correlates of uniparental reproduction in freshwater snails 总被引:1,自引:0,他引:1
S. G. Johnson C. M. Lively S. J. Schrag 《Cellular and molecular life sciences : CMLS》1995,51(5):498-509
We review the spatial and temporal correlates of uniparental reproduction in freshwater snails as they pertain to the ecological hypotheses for the maintenance of biparental sex. The biogeographic evidence from two species (Potamopyrgus antipodarum andBulinus truncatus) presently supports the Red Queen hypothesis that biparental reproduction is selected as a way to reduce the risk to progeny of parasite attack. Uniparental reproduction in these species is associated with low levels of infection by parasites (castrating digenetic trematodes), suggesting that parthenogenesis or self-fertilization can replace cross-fertilization when the risk of infection is low. In addition, inB. truncatus, the opportunity for cross-fertilization coincides with the season in which parasite attack is highest. In a third species (Campeloma decisum), parthenogenetic reproduction is correlated with latitude and the presence of a non-castrating trematode that may prevent cross-fertilization; these patterns suggest that parthenogenesis has been selected as a mechanism to assure reproduction. Finally, we discuss the spotty taxonomic distribution of parthenogenetic species. 相似文献
18.
Summary Dynamics of increase of white myotomal muscle fibers of four species of freshwater teleosts (Salmo gairdneri, Pimephales notatus, Esox masquinongy andE. americanus vermiculatus) from three families (Salmonidae, Cyprinidae, Esocidae) representing a variety of maximum attainable sizes and growth rates, have been investigated. There are at least three major differences in these dynamics, and there appears to be an association between the ability of a fish species to attain large size (and grow fast) and its ability to recruit new fibers into this predominant tissue of the myotomal mass. 相似文献
19.
Summary The mycotoxin alternariol (3,4,5-trihydroxy-6-methyldibenzo [a] pyrone) but not alternariol monomethyl ether (3,4-dihydroxy-5-methoxy-6-methyldibenzo [a] pyrone) is phototoxic toEscherichia coli in the presence of near UV light (320–400 nm). The phototoxicity bioassays with a DNA repair-deficient mutant ofE. coli suggested that DNA may be the molecular target for photo-induced toxicity of alternariol. Interactions between alternariol and double-stranded, supercoiled DNA suggest that alternariol interacts with DNA by intercalation. No DNA breakage was detected in this system; however, alternariol forms a complex and cross-links double-stranded DNA in near UV light. These results suggest that alternariol is a new phototoxic, DNA-intercalating agent and is a DNA cross-linking mycotoxin in near UV light.Acknowledgment. Dr Albert Stoessl (Agriculture Canada, London, Ontario, Canada) generously provided a mixture of alternariol and alternariol monomethyl ether, and made many helpful suggestions. Dr Ashwood-Smith (University of Victoria, Victoria, British Columbia, Canada) kindly supplied the microorganisms through Dr G.H.N. Towers (University of British Columbia, Vancouver). We gratefully acknowledge the gifts. It is a pleasure to acknowledge the able assistance of Mr S. Tallevi. 相似文献
20.
L. Minale C. Pizza R. Riccio F. Zollo 《Cellular and molecular life sciences : CMLS》1983,39(6):569-571
Summary On the basis of comparative spectral data, the structures of 3 novel steroidal glycosides from the Mediterranean starfishHacelia attenuata have been elucidated as3, 4 and5. These are further examples of a novel group of 24-O-glycosidated steroids recently encountered in the same species and in the Pacific speciesProtoreaster nodosus.Part 9. L. Minale, C. Pizza, R. Riccio and F. Zollo, Experientia39 (1983) 567. This contribution is part of the Progetto Finalizzato Chimica fine e secondaria del C.N.R., Roma.Acknowledgments. We thank Prof. K. Nakanishi, Columbia University, New York, for FD-mass spectral analyses, the Centro Interfacoltà di Metodologie Chimico-Fisiche for 270 MHz NMR facilities, and Miss R. Aquino for part of the experimental work. 相似文献