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Kentaro Arikawa

Publications and source records attributed to Kentaro Arikawa.

At least 19 recordsLinked to original sources
PubMed2006

Ommatidial type-specific interphotoreceptor connections in the lamina of the swallowtail butterfly, Papilio xuthus.

The eye of the butterfly Papilio xuthus contains a random array of three types of ommatidia (types I-III), each bearing nine photoreceptors, R1-R9. Of the six spectral classes of photoreceptors identified, types I, II, and III ommatidia contain four, three, and two classes, respectively: the ommatidia are thus spectrally heterogeneous. The photoreceptors send their axons to the lamina where, together with some large monopolar cells (LMCs), the nine from a single ommatidium contribute to a module called a lamina cartridge. We recently reported that among different photoreceptor axon terminals visualized by confocal microscopy, the number and length of axon collaterals differ for different spectral receptors, suggesting that lamina circuits are specific for each ommatidial type. Here we studied the distribution of synapse-like structures in the cartridges, first characterizing a photoreceptor by measuring its spectral sensitivity and then injecting Lucifer yellow (LY). We subsequently histologically identified the type of ommatidium to which the injected photoreceptor belonged, cut serial ultrathin sections of the entire lamina, labeled these with anti-LY immunocytochemistry, and then localized synapse-like structures. We found numerous interphotoreceptor contacts both within and between cartridges, the combination of which was again specific for the ommatidial type. R3 and R4, which are green-sensitive photoreceptors in all ommatidia, have thick axons lacking collaterals. We found that these cells exclusively make contacts with LMCs and not with photoreceptors. We therefore presume that R3 and R4 construct a system for motion vision, whereas other randomly distributed spectral types provide inputs for color vision.

Animals↗
PubMed2006

Associative visual learning, color discrimination, and chromatic adaptation in the harnessed honeybee Apis mellifera L.

We studied associative visual learning in harnessed honeybees trained with monochromatic lights associated with a reward of sucrose solution delivered to the antennae and proboscis, to elicit the proboscis extension reflex (PER). We demonstrated five properties of visual learning under these conditions. First, antennae deprivation significantly increased visual acquisition, suggesting that sensory input from the antennae interferes with visual learning. Second, covering the compound eyes with silver paste significantly decreased visual acquisition, while covering the ocelli did not. Third, there was no significant difference in the visual acquisition between nurse bees, guard bees, and foragers. Fourth, bees conditioned with a 540-nm light stimulus exhibited light-induced PER with a 618-nm, but not with a 439-nm light stimulus. Finally, bees conditioned with a 540-nm light stimulus exhibited PER immediately after the 439-nm light was turned off, suggesting that the bees reacted to an afterimage induced by prior adaptation to the 439-nm light that might be similar to the 540-nm light.

Acclimatization↗
PubMed2006

Epithelial cells secrete interleukin-8 in response to adhesion and invasion of diffusely adhering Escherichia coli lacking Afa/Dr genes.

Escherichia coli that sparsely adhere to human epithelial cells are known as diffusely adherent E. coli (DAEC), and the role of the Afa/Dr family of adhesins is now understood. Strains that do not possess Afa/Dr, however, comprise another group of DAEC, of which the pathogenicity remains unknown. The ability to induce interleukin-8 (IL-8) secretion from intestinal epithelial cells might be a feature of enterovirulent bacteria. We previously found that some Afa/Dr DAEC strains induce IL-8 by stimulating epithelial cells with flagella. The present study examines whether non-Afa/Dr DAEC can induce IL-8 in epithelial cells (HEp-2, INT407, and T84). Among 21 strains, 11 (52%; 11/21) induced as much IL-8 as high inducer strains of Afa/Dr DAEC. Adhesion did not significantly differ between high and low inducers; therefore diffuse adhesion alone is probably insufficient to induce IL-8. It was shown that IL-8 induction and the number of intracellular bacteria directly correlated. Wortmannin, an inhibitor of the phosphatidylinositol-3-phosphate kinase, reduced both intracellular bacteria and IL-8 secretion. Motile strains were significantly more prevalent among high (10/11) than low (4/10) inducers. However, 4 low invasive strains hardly induced IL-8 despite their motility. In conclusion, some non-Afa/Dr DAEC invoke the induction of high levels of inflammatory cytokines. Unlike Afa/Dr DAEC, however, non-Afa/Dr strains may require invasion to cause strong induction. These non-Afa/Dr high inducers can be enteropathogenic for the cytokine-inducing properties.

Adhesins, Escherichia coli↗
PubMed2006

Color discrimination at the spatial resolution limit in a swallowtail butterfly, Papilio xuthus.

Spatial resolution of insect compound eyes is much coarser than that of humans: a single pixel of the human visual system covers about 0.008 degrees whereas that of diurnal insects is typically about 1.0 degrees . Anatomically, the pixels correspond to single cone outer segments in humans and to single rhabdoms in insects. Although an outer segment and a rhabdom are equivalent organelles containing visual pigment molecules, they are strikingly different in spectral terms. The cone outer segment is the photoreceptor cell part that expresses a single type of visual pigment, and is therefore monochromatic. On the other hand, a rhabdom is composed of several photoreceptor cells with different spectral sensitivities and is therefore polychromatic. The polychromatic organization of the rhabdom suggests that insects can resolve wavelength information in a single pixel, which is an ability that humans do not have. We first trained the Japanese yellow swallowtail butterfly Papilio xuthus to feed on sucrose solution at a paper disk of certain color. We then let the trained butterflies discriminate disks of the training color and grey disks each presented in a Y-maze apparatus. Papilio correctly selected the colored disk when the visual angle was greater than 1.18 degrees for blue, 1.53 degrees for green or 0.96 degrees for red: they appeared to see colors in single pixels to some extent. This ability may compensate their rather low spatial resolution.

Animals↗
PubMed2006

Blue and double-peaked green receptors depend on ommatidial type in the eye of the Japanese yellow swallowtail Papilio xuthus.

The compound eye of the butterfly Papilio xuthus is composed of three spectrally distinct types of ommatidia. We investigated the blue and double-peaked green receptors that are encountered distally in type I and III ommatidia, by means of intracellular recordings, in vivo fluorescence microscopy, and histology. The blue receptors are R1 and/or R2 photoreceptors; they contain the same mRNA encoding the opsin of the blue-absorbing visual pigment. However, here we found that the sensitivity in the UV wavelength region strongly depends on the ommatidial type; the blue receptors in type I ommatidia have a distinctly depressed UV sensitivity, which is attributed to lateral filtering in the fused rhabdom. In the main, fronto-ventral part of the eye, the R3 and R4 photoreceptors of all ommatidia contain the same set of two mRNAs encoding the opsins of green-absorbing visual pigments, PxL1 and PxL2. The spectral sensitivities are double-peaked, but the UV sensitivity of the R3 and R4 photoreceptors in type I ommatidia appears to be reduced, similar to that of the co-localized blue receptors.

Animals↗
PubMed2005

Spectral heterogeneity of honeybee ommatidia.

The honeybee compound eye is equipped with ultraviolet, blue, and green receptors, which form the physiological basis of a trichromatic color vision system. We studied the distribution of the spectral receptors by localizing the three mRNAs encoding the opsins of the ultraviolet-, blue- and green-absorbing visual pigments. The expression patterns of the three opsin mRNAs demonstrated that three distinct types ommatidia exist, refuting the common assumption that the ommatidia composing the bee compound eye contain identical sets of spectral receptors. We found that type I ommatidia contain one ultraviolet and one blue receptor, type II ommatidia contain two ultraviolet receptors, and type III ommatidia have two blue receptors. All the three ommatidial types contain six green receptors. The ommatidia appear to be distributed rather randomly over the retina. The ratio of type I, II, and III ommatidia was about 44:46:10. Type III ommatidia appeared to be slightly more frequent (18%) in the anterior part of the ventral region of the eye. Retinal heterogeneity and ommatidial randomness, first clearly demonstrated in butterflies, seems to be a common design principle of the eyes of insects.

Animals↗
PubMed2005

Comparative study on the relationship between photoperiodic host-seeking behavioral patterns and the eye parameters of mosquitoes.

Relationships between the ommatidial structure and photoperiodic behavior of several mosquito species were investigated. Host-seeking behavioral patterns of mosquitoes were classified into four main groups based on previously compiled reports on field or laboratory biting activity. These groups were pattern I and I' (nocturnal), pattern II (crepuscular and nocturnal), pattern III (crepuscular and diurnal), and pattern IV (diurnal). Eye parameters (product of facet diameter and interommatidial angle) of mosquitoes that belong to the pattern I and I' group were higher (2.7-4.2) than those of mosquitoes that belong to the pattern IV group (0.8-2.3). Eye parameters of the mosquitoes categorized in the pattern II and III groups were intermediate (2.3-2.6). These results suggest that the crepuscular behavior of mosquitoes undergoes a transition in the course of evolution from nocturnal behavior to diurnal behavior. Large variations in the eye parameters were observed even within the same genus depending on their photoperiodic behavior. Therefore, the ommatidial structure of mosquitoes appears to be determined, not taxonomically, but evolutionarily by the photoenvironment in which the mosquitoes are most active.

Animals↗
PubMed2005

Sexual dimorphism of short-wavelength photoreceptors in the small white butterfly, Pieris rapae crucivora.

The eyes of the female small white butterfly, Pieris rapae crucivora, are furnished with three classes of short-wavelength photoreceptors, with sensitivity peaks in the ultraviolet (UV) (lambda(max) = 360 nm), violet (V) (lambda(max) = 425 nm), and blue (B) (lambda(max) = 453 nm) wavelength range. Analyzing the spectral origin of the photoreceptors, we isolated three novel mRNAs encoding opsins corresponding to short-wavelength-absorbing visual pigments. We localized the opsin mRNAs in the retinal tissue and found that each of the short-wavelength-sensitive photoreceptor classes exclusively expresses one of the opsin mRNAs. We, accordingly, termed the visual pigments PrUV, PrV, and PrB, respectively. The eyes of the male small white butterfly also use three classes of short-wavelength photoreceptors that equally uniquely express PrUV, PrV, and PrB. However, whereas the spectral sensitivities of the male photoreceptors with PrUV and PrB closely correspond to those of the female, the male photoreceptor expressing PrV has a double-peaked blue (dB) spectral sensitivity, strongly deviating from the spectral sensitivity of the female V photoreceptor. The male eyes contain a pigment that distinctly fluoresces under blue-violet as well as UV excitation light. It coexists with the dB photoreceptors and presumably acts as a spectral filter with an absorbance spectrum peaking at 416 nm. The narrow-band spectral sensitivity of the male dB photoreceptors probably evolved to improve the discrimination of the different wing colors of male and female P. rapae crucivora in the short-wavelength region of the spectrum.

Animals↗
PubMed2005

Photoreceptor projection reveals heterogeneity of lamina cartridges in the visual system of the Japanese yellow swallowtail butterfly, Papilio xuthus.

The compound eye of the butterfly Papilio xuthus is composed of three types of spectrally heterogeneous ommatidia. The ommatidia, which contain nine photoreceptor cells, R1-9, bear four (type I), three (type II), or two (type III) classes of spectral receptors in fixed combinations. The photoreceptors send their axons to the lamina, the first optic ganglion, where the R1-9 axons originating from a single ommatidium, together with some second-order neurons, form a neuronal bundle, called a lamina cartridge. We investigated the axonal structure of photoreceptors in the lamina to determine whether the cartridge structure is different between the three ommatidial types. We first characterized a photoreceptor by measuring its spectral sensitivity and then injected Lucifer Yellow. We subsequently identified the type of ommatidium of the injected photoreceptor via histological sections. We further observed the axonal structure of the photoreceptor in the lamina by laser confocal microscopy. We found that the number and length of axon collaterals markedly differ between the spectral receptors. Those having the most extensive axon collaterals, which extend into six or more surrounding cartridges, are violet receptors (R1 and R2 of type II ommatidia). UV receptors (R1 or R2 of type I ommatidia) also send collaterals into two to four neighboring cartridges. Blue receptors (R1 or R2 of type I ommatidia, R1 and R2 of type III ommatidia) have short collaterals restricted to their own cartridges. We thus conclude that the neuronal circuit of the lamina cartridge differs between the three types of ommatidia.

Animals↗
PubMed2005

Comparative study on nocturnal behavior of Aedes aegypti and Aedes albopictus.

Nocturnal behavior of nonblood-fed females of Aedes aegypti (L.) and Aedes albopictus (Skuse) was studied using an automatic recording device equipped with a photoelectric sensor. Carbon dioxide, heating, and the contrast of the black and white colors were used as attractive cues for mosquitoes. The nocturnal host-seeking activity positively correlated with the increasing light intensity in both species. Ae. aegypti was found to be more sensitive to light than Ae. albopictus. The threshold of light intensity for the activation of the nocturnal host-seeking activity was <0.1 lx (approximately 0.01 foot candle) in Ae. aegypti and >10 lx (approximately 1 foot candle) in Ae. albopictus. Complete darkness during the daytime deactivated the host-seeking activity of both species, irrespective of their increasing flight activity controlled by their intrinsic circadian rhythms. This finding suggested that visual cues are indispensable for host-seeking behavior. The eye parameter value, the product of the ommatidial diameter, and the interommatidial angle were significantly larger in Ae. aegypti than those in Ae. albopictus, indicating that the eye of Ae. aegypti is more adapted to a darker environment.

Aedes↗
PubMed2005

Interleukin-8 secretion by epithelial cells infected with diffusely adherent Escherichia coli possessing Afa adhesin-coding genes.

Escherichia coli that adhere sparsely to human epithelial (HEp-2) cells are known as diffusely adherent E. coli(DAEC) and considered potentially diarrheagenic. The role of the afimbrial adhesive sheath (Afa)-identified originally as a uropathogenic factor-in diffuse adhesion is now understood. However, the role of DAEC in diarrheal disease remains controversial. Recently, ability to induce interleukin-8 (IL-8) secretion from intestinal epithelial cells has been suggested as one of the properties of enterovirulent bacteria. In this study, we examined whether DAEC strains possessing Afa genes induced IL-8 in cultures of human carcinoma epithelial cells (e.g., HEp-2, Caco-2, and T84). Nineteen afa-positive DAEC strains were examined for their ability to induce IL-8 secretion, and only 7 strains (37%; 7/19) induced IL-8 as much as enteroaggregative E. coli did. No marked differences in adhesion were observed between high and low inducers. Diffusive adhesiveness itself is unlikely to be sufficient to induce IL-8. All high inducers were motile and others were nonmotile. Additional stimulation by flagella may be required to cause high levels of chemokine induction. Motility or presence of flagella can be an important criterion to predict DAEC diarrheagenicity at clinical laboratories.

Adhesins, Escherichia coli↗
PubMed2004

Immunohistochemical localization of Papilio RBP in the eye of butterflies.

We recently identified a novel retinoid binding protein, Papilio RBP, in the soluble fraction of the eye homogenate of the butterfly Papilio xuthus, and demonstrated that the protein is involved in the visual cycle. We now have localized the protein in the Papilio eye by light and electron microscopic immunohistochemistry using a monospecific antiserum produced against artificially expressed Papilio RBP. We found strong immunoreactivity in the primary as well as secondary pigment cells and in the tracheal cells. The pigment cells have long been regarded as an important site of the visual cycle, and this view is further supported by the present result. Interestingly, the cytoplasm and nuclei of these cells were equally labeled, indicating that the protein exists in both the cytoplasm and the nucleus. We conducted a survey for the existence of the Papilio RBP-like proteins in other insects including several species of butterflies, dragonflies, cicadas, grasshoppers and honeybees. Anti-Papilio RBP immunoreactivity was confirmed in the proteins isolated only from butterflies belonging to the superfamily Papilionoidea and not from other species. In all insects tested, however, fluorescing proteins were clearly detected, suggesting that these insects also have similar retinol-binding proteins.

Animals↗
PubMed2004

A unique visual pigment expressed in green, red and deep-red receptors in the eye of the small white butterfly, Pieris rapae crucivora.

The full primary structure of a long-wavelength absorbing visual pigment of the small white butterfly, Pieris rapae crucivora, was determined by molecular cloning. In situ hybridization of the opsin mRNA of the novel visual pigment (PrL) demonstrated that it is expressed in the two distal photoreceptor cells (R3 and R4) as well as in the proximal photoreceptors (R5-8) in all three types of ommatidia of the Pieris eye. The main, long-wavelength band of the spectral sensitivities of the R3 and R4 photoreceptors is well described by the absorption spectrum of a visual pigment with absorption maximum at 563 nm; i.e. PrL is a visual pigment R563. The spectral sensitivities of R5-8 photoreceptors in ommatidial type I and III peak at 620 nm and those in type II ommatidia peak at 640 nm. The large shifts of the spectral sensitivities of the R5-8 photoreceptors with respect to the absorption spectrum of their visual pigment can be explained with the spectral filtering by pale-red (PR) and deep-red (DR) screening pigments that are concentrated in clusters of granules near the rhabdom boundary. The peak absorbance of the two spectral filters appears to be approximately 1 (PR) and 2 (DR).

Amino Acid Sequence↗
PubMed2003

Coexpression of two visual pigments in a photoreceptor causes an abnormally broad spectral sensitivity in the eye of the butterfly Papilio xuthus.

The compound eye of the butterfly Papilio xuthus consists of three different types of ommatidia, each containing nine photoreceptor cells (R1-R9). We have found previously that the R5-R8 photoreceptors of type II ommatidia coexpress two different mRNAs, encoding opsins of green- and orange-red-absorbing visual pigments (Kitamoto et al., 1998). Do these cells contain two functionally distinct visual pigments? First, we identified the sensitivity spectrum of these photoreceptors by using combined intracellular recording and dye injection. We thus found that the R5-R8 of type II ommatidia have a characteristic sensitivity spectrum extending over an excessively broad spectral range, from the violet to the red region; the photoreceptors are therefore termed broadband photoreceptors. The spectral shape was interpreted with a computational model for type II ommatidia, containing a UV visual pigment in cells R1 and R2, two green visual pigments in cells R3 and R4, a far-UV-absorbing screening pigment (3-hydroxyretinol) in the distal part of the ommatidium, and a red-screening pigment that surrounds the rhabdom. The modeling suggests that both visual pigments in the R5-R8 photoreceptors participate in phototransduction. This work provides the first compelling evidence that multiple visual pigments participate in phototransduction in single invertebrate photoreceptors.

Animals↗
PubMed2003

A novel retinol-binding protein in the retina of the swallowtail butterfly, Papilio xuthus.

Retinoid-binding proteins are indispensable for visual cycles in both vertebrate and invertebrate retinas. These proteins stabilize and transport hydrophobic retinoids in the hydrophilic environment of plasma and cytoplasm, and allow regeneration of visual pigments. Here, we identified a novel retinol-binding protein in the eye of a butterfly, Papilio xuthus. The protein that we term Papilio retinol-binding protein (Papilio RBP) is a major component of retinal soluble proteins and exclusively binds 3-hydroxyretinol, and emits fluorescence peaking at 480 nm under ultraviolet (UV) illumination. The primary structure, deduced from the nucleotide sequence of the cDNA, shows no similarity to any other lipophilic ligand-binding proteins. The molecular mass and isoelectric point of the protein estimated from the amino-acid sequence are 26.4 kDa and 4.92, respectively. The absence of any signal sequence for secretion in the N-terminus suggests that the protein exists in the cytoplasmic matrix. All-trans 3-hydroxyretinol is the major ligand of the Papilio RBP in dark-adapted eyes. Light illumination of the eyes increases the 11-cis isomer of the ligand and induces redistribution of the Papilio RBP from the proximal to the distal part of the photoreceptor layer. These results suggest that the Papilio RBP is involved in visual pigment turnover.

Amino Acid Sequence↗
PubMed2003

Polymorphism of red receptors: sensitivity spectra of proximal photoreceptors in the small white butterfly Pieris rapae crucivora.

The compound eye of the small white butterfly Pieris rapae crucivora contains three anatomically distinct types of ommatidia. They differ in pigmentation around the rhabdom, colour of tapetal reflection and violet light-induced autofluorescence, indicating physiological differences between them. We recently reported that the ommatidia are in fact spectrally heterogeneous: in the distal part of the tiered retina they contain different sets of the spectral receptors R1-4. This study examines whether the ommatidia in the proximal retinal tier also show the spectral heterogeneity for the receptors R5-8. We recorded the sensitivity spectra of the proximal photoreceptors, and subsequently injected the dye Alexafluor 568 into proximal photoreceptors, to localize the cell and identify the ommatidial type to which it belonged. We analysed 13 successfully labeled proximal photoreceptors, and found that the sensitivity spectrum of the proximal photoreceptors in types I and III ommatidia peaks at 620 nm, whereas that of type II ommatidia peaks at 640 nm. The difference in the sensitivity spectra can be explained by the anatomical characteristics of each ommatidial type. This is the first demonstration of red receptor polymorphism in insects. The polymorphic red receptor system most probably enhances contrast sensitivity and/or color discrimination in the long wavelength spectral region.

Animals↗
PubMed2002

Ommatidial heterogeneity in the compound eye of the male small white butterfly, Pieris rapae crucivora.

The ommatidia in the ventral two-thirds of the compound eye of male Pieris rapae crucivora are not uniform. Each ommatidium contains nine photoreceptor cells. Four cells (R1-4) form the distal two-thirds of the rhabdom, four cells (R5-8) approximately occupy the proximal one-third of the rhabdom, and the ninth cell (R9) takes up a minor basal part of the rhabdom. The R5-8 photoreceptor cells contain clusters of reddish pigment adjacent to the rhabdom. From the position of the pigment clusters, three types of ommatidia can be identified: the trapezoidal (type I), square (type II), and rectangular type (type III). Microspectrophotometry with an epi-illumination microscope has revealed that the reflectance spectra of type I and type III ommatidia peak at 635 nm and those of type II ommatidia peak at 675 nm. The bandwith of the reflectance spectra is 40-50 nm. Type II ommatidia strongly fluoresce under ultra-violet and violet epi-illumination. The three types of ommatidia are randomly distributed. The ommatidial heterogeneity is presumably crucial for color discrimination.

Animals↗