Ultrastructural comparison of the compound eyes of Sinopanorpa and Panorpa (Mecoptera: Panorpidae)

The ultrastructure of the compound eyes of scorpionflies Sinopanorpa tincta (Navás, 1931), Panorpa liui Hua, 1997 and Panorpa sexspinosa Cheng, 1949 in Panorpidae were comparatively investigated using transmission electron microscopy. Their compound eyes share the following characters: each ommatidium possesses a corneal lens, a eucone tetrapartite crystalline cone surrounded by a pair of primary pigment cells, and eight retinula cells. Seven retinula cells (R1-R7) are in contact with the crystalline cone and extend to the basal lamina, but the eighth retinula cell (R8) is only restricted to the basal level of the ommatidium. The rhabdomeres of cells R1-R7 form a centrally fused rhabdom that almost spans the full length of the ommatidium, and that of R8 only contributes to the basal part of the rhabdom. The distal part of the rhabdom projects upward into the region between the cone cell tips and force the cone cells to split apart into four thin cone cell roots that run along a narrow intercellular gap between adjacent retinula cells. The number of secondary pigment cells varies from 12 in P. liui to 16 in P. sexspinosa and S. tincta. Based on the dissimilarity of the imaginal and larval ommatidial structure, the imaginal compound eyes are very unlikely to be directly developed from the larval compound eyes in the Panorpidae.     

Ultrastructure of dorsal ocelli of the short-faced scorpionfly Panorpodes kuandianensis (Mecoptera: Panorpodidae)

Dorsal ocelli are important visual organs of insects to perform a variety of behavioral functions. However, the fine structure of ocelli has not been studied in many groups of insects. In this paper the ocellar ultrastructure of the short-faced scorpionfly Panorpodes kuandianensis was investigated using light microscopy and scanning and transmission electron microscopy. The adult of P. kuandianensis possesses one median and two lateral ocelli. Each ocellus comprises a cornea, a layer of corneagenous cells, a clear zone, a retina, and pigment cells. The cornea assumes a domed shape. Under the layer of corneagenous cells is a clear zone, which differs greatly between the median and lateral ocelli, implying they may be divergent in function. The retina comprises elongated retinula cells, which are divided into three regions: a distal rhabdomal region, a middle cytoplasmic region, and a proximal axonal region. In the distal rhabdomal region, most of the rhabdoms are formed by rhabdomeres of two adjacent retinula cells; some are formed by three or four retinula cells. The middle cytoplasmic region comprises the retinula cell segments with nuclei but free of rhabdom. Pigment granules are present among the retinula cells. In the proximal axonal region all retinula cells transform to axons, which synapse with the dendrites of second-order neurons at the base of the ocelli. The relationships among Panorpodidae, Panorpidae and Bittacidae are discussed based on ocellar structure.     

Selective photoreceptor damage in four species of insects induced by experimental exposures to UV-irradiation

Damage to photoreceptive cells of insect compound eyes exposed to abnormally high doses of UV-radiation of 350nm peak wavelength manifests itself in at least two different ways. In the butterflies Papilio xuthus and Pieris napi from Japan and northern Finland, respectively, only the cell bodies of retinula cells 1 and 2, (identified as short wavelength receptors), but not their corresponding rhabdomeres, exhibit damage with apoptotic features. In the eye of UV-irradiated adult crickets, however, cell bodies and cytoplasm remain normal, while the rhabdomeres of cells 7 and 8 exhibit signs of severe membrane disruptions. No signs of damage whatsoever occurred in the eyes of northern Finnish bumblebees exposed to UV. It is suggested that metabolic shortfalls in the UV-sensitive cells of the butterfly eyes result in cellular shut-down, but that in the cricket receptors UV-induced changes of the membrane lipids dominate, leading to membrane instability without concomittant cell death. The strong resistance of the bumblebee eye to UV-induced damage requires further investigation, but since preconditioning to light can reduce photic damage in the rat eye, the 24h daylight experienced by northern Finnish bumblebees during the summer season could be involved.     

Eyes of male and female Orgyia antiqua (Lepidoptera; Lymantriidae) react differently to an exposure with UV-A

The structural organization of the eyes belonging to 12 winged male and 12 wingless female Orgyia antiqua moths, exposed for 1 h to UV-radiation (lambda(max)=351 nm) of 1.4 kW/m2, was compared with that of 12 male and 12 female non-irradiated control specimens. Following the UV-exposure, the screening pigments were found in a position indicative of extreme light-adaptation. Extensive formations of vesicles along the perimeter of the cones as well as disintegrating ER in the cone cytoplasm were noticeable, especially in the eye of the female. On the retinal side of the clearzone, the microvilli of the rhabdoms had become affected by the UV in characteristic ways: in the male eye, retinal cell damage in the form of microvillar swellings and disintegrations were largely confined to just two cells per ommatidium, placed opposite to each other. The female eye, once again, exhibited greater vulnerability and more widespread microvillar disruptions that affected all of the ommatidial retinula cells. The greater resistance of the eye of the male to an exposure with UV makes sense, if we consider the consequences of the retinal damage, which would clearly be a more severe handicap for an actively flying individual than for an almost sedentary one like the wingless female.     

Ultrastructural changes in the melanocytes of aging human choroid

Retinal pigment epithelial cells as well as choroidal melanocytes (CM) possess melanin granules. The former show clear, age-related changes (formation of lipofuscin granules with a concomitant decrease in melanin content); however, data on changes in the CM with aging are fairly limited. We examined CM in human macular and mid-peripheral areas by light- and transmission electron microscopy in 50–94 year-old donor eyes (N = 12). Unlike in the choroid of lower ages, the melanocytes from aging choroid (>75 years) showed partial fusion of about 8–15 melanosomes, forming rosettes-like structures. Besides, there was evidence of emptiness in cytoplasm caused by the loss of melanosomes in aged CM, as was confirmed by quantification in macular part of choroid. In advanced aged eyes (85–94-year-old), the CM possessed many lipid droplets as well as irregular lipofuscin granules, the latter had a tendency to fuse with melanosomes, as happens in aged retinal pigment epithelium. Macrophages in their cytoplasm contained abundant irregular as well as clumped melanosomes of variable size, suggesting that damaged granules/melanocytes are cleared by these phagocytes. These obvious changes in the CM are likely to make the choroid prone to damage by visible light.     

Computational framework for the prediction of transcription factor binding sites by multiple data integration

Background

Activation of extracellular signal-regulated protein kinase (ERK), a member of mitogen-activated protein kinase (MAPK) family, has been proposed to mediate neurite outgrowth-promoting effects of several neurotrophic factors in vitro. However, the precise activity of ERK during axonal regeneration in vivo remains unclear. Peripheral axotomy has been shown to activate ERK in the cell bodies of primary afferent neurons and associated satellite cells. Nevertheless, whether ERK is also activated in the axons and surrounded Schwann cells which also play a key role in the regeneration process has not been clarified.

Results

Phosphorylation of ERK in the sciatic nerve in several time-points after crush injury has been examined. Higher phosphorylation of ERK was observed in the proximal and distal nerve stumps compared to the contralateral intact nerve from one day to one month after crush. The activation of ERK was mainly localized in the axons of the proximal segments. In the distal segments, however, active ERK was predominantly found in Schwann cells forming Bungner's bands.

Conclusion

The findings indicate that ERK is activated in both the proximal and distal nerve stumps following nerve injury. The role of activated ERK in Wallerian degeneration and subsequent regeneration in vivo remains to be elucidated.     

Frequency map of the spiral ganglion in the cat

A frequency map of the cat spiral ganglion has been determined on the basis of reconstructed cochleas in which individual spiral ganglion cells were labeled with horseradish peroxidase following determination of their characteristic frequency; the cochleas were the same as those used by Liberman and Oliver [J. Comp. Neurol. 223, 163-176 (1984)]. By matching this map to one previously described for the organ of Corti [M. C. Liberman, J. Acoust. Soc. Am. 72, 1441-1449 (1982)], an estimate of the afferent innervation density of the inner hair cells was derived. Counts of myelinated nerve fibers at the habenula perforata and inner hair cells were also performed and yielded similar results in all but the most basal 10%-15% of the cochlea. Between 0.1 and 20 kHz there is a gradual monotonic increase as a function of frequency in the number of spiral ganglion cells terminating on each inner hair cell, from about eight ganglion cells per inner hair cell to about 30 ganglion cells per inner hair cell. Above 20 kHz, it seems there is a decrease to about ten ganglion cells per inner hair cell. The greatest innervation density is at approximately the region of the basilar membrane with the greatest density of inner hair cells per millimeter.     

Unique spatial continuously tunable cone laser based on a dye-doped cholesteric liquid crystal with a birefringence gradient

The present study develops and investigates for the first time a unique spatial continuously tunable cone laser based on a dye-doped cholesteric liquid crystal (DDCLC) film with an LC-birefringence (Δn) gradient. A continuous Δn variation can be generated in a cell by diffusion and self-organization of CLC after four DDCLC mixtures with a discrete variation of Δn are successively injected into an empty cell. Not only the CLC photonic structure but also the lasing wavelength and the cone angle of the obtained conically symmetric emitted lasing ring can be tuned continuously by continuously changing the pumped position of the cell with an Δn gradient. The continuous tunabilities in the lasing wavelength and the corresponding emitted cone angle of the lasing ring are 605.8 → 568.1 nm and 29° → 50°, respectively, within a spatial interval of about 33 mm in the cell.     

Cesium ion desorption from graphite surfaces: Kinetics and dynamics of diffusion and desorption steps

The field reversal method was used to study the kinetics of Cs and Cs⁺ desorption from a pyrolytic graphite basal surface. Double-exponential decay was observed especially at high temperatures. Desorption of ions using an external flux from a Cs beam gave the primary rate parameters 2.60 eV and 5.3 × 10¹⁴ s⁻¹, at T = 1100–1600 K. The secondary rate parameters were 0.28 eV and 2.2 × 10⁵ s⁻¹, observed at T = 1250–1600 K. Due to the high sensitivity of the method, the kinetics of desorption of the previously absorbed Cs, diffusing out from the bulk crystal, could also be studied. These processes were more complex, giving the primary rate parameters 1.87 eV and 1.1 × 10¹⁴ s⁻¹, and the secondary rate parameters 2.07 eV and 1.97 × 10¹¹ s⁻¹ for T = 1400–1600 K. The variation of the primary and secondary rates and the field reversal peak heights as functions of retarding field time were also studied, as well as the field reversal peak variation with temperature. These results, as well as the ones found in previous studies of this system, indicate the existence of three adsorbed states on the more or less polycrystalline graphite surface. One apparently ionic state correlates with the diffusing state in the crystallites and with ionic states outside the surface. Conversion processes to and from this state, induced by the external field, were also observed.     

The midgut of Cephalotes ants (Formicidae: Myrmicinae): Ultrastructure of the epithelium and symbiotic bacteria

The ultrastructural analysis of the midgut of Cephalotes atratus, C. clypeatus, and C. pusillus reveled that the midgut epithelium lays on a basal lamina and is composed basically of three cell types: digestive cells, regenerative cells, and goblet cells. In these ants, the rough endoplasmic reticulum, in addition to producing digestive enzymes, is involved in the formation of concretions and ion storage in specialized vacuoles present in the midgut. These concretions are spherocrystals and may contribute to stabilize the pH and to maintain symbiotic bacteria found between microvilli. The ultrastructure analysis of these bacteria revealed the presence of a double envelope typical of gram-negative bacteria. For the three species examined, the ultrastructure similarities are conspicuous, suggesting that this may be the pattern for the genus Cephalotes. Details of the relationship between bacteria and microvilli were examined.     

Semiclassical dynamics of vortices in 2D easy-plane ferromagnets

Semiclassical dynamics of magnetic vortices in 2D lattice models of easy-plane ferromagnets is investigated. It is shown that the low-energy part of the spectrum of vortices treated as quantum excitations of the system exhibits a nontrivial structure. The simplest spectrum is observed for standard magnetic vortices, in which magnetization at long distances from the center of a vortex is parallel to the basal plane. In this case, the spectrum has a band structure consisting of several nonintersecting bands, whose number is determined only by the value of atomic spin S and lattice symmetry. For purely 2D magnets with a single spin per unit cell, the number of bands is S or 2S for integral and half-integral values of spin S, respectively. For a lattice with the basis with an even number 2n of spins per unit cell, the number of bands is 2nS for any spins. The situation radically changes for vortices in the cone state as compared to standard vortices, for which the magnetization at a long distance from the center of a vortex rotates in the easy plane of the magnet. Vortices in the cone state are formed under the action of a constant external field perpendicular to the easy plane of the magnet. As a rule, the spectrum for such vortices is not a standard band spectrum and forms a set such that a forbidden energy value can be found in any small neighborhood of an allowed value, and vice versa. The possibility of an oscillatory motion of a vortex under the action of a constant external force is indicated (analog of Bloch oscillations of electrons in crystals). Possible realization of these effects in other ordered media with vortices is considered.     

Blue metal complex pigments involved in blue flower color

The blue pigment of cornflower, protocyanin, has been investigated for a long time, but its precise structure was not entirely explained until recently. The molecular structure of the pigment was recently shown to be a metal complex of six molecules each of anthocyanin and flavone glycoside, with one ferric iron, one magnesium and two calcium ions by X-ray crystallographic analysis. The studies provided the answer to the question posed in the early part of the last century, “why is the cornflower blue and rose red when both flowers contain the same anthocyanin?” This work was achieved on the basis of the results of long years of the studies made by many researchers. In this review, the author focuses on the investigations of the blue metal complex pigments involved in the bluing of flowers, commelinin from Commelina commusis, protocyanin from Centaurea cyanus, protodelphin from Salvia patens and hydrangea blue pigment.     

Scanning and transmission electron microscopy and X-ray analysisof leaf salt glands of Limoniastrum guyonianum Boiss. under NaCl salinity

Leaf salt glands of Limoniastrum guyonianum were examined by scanning and transmission electron microscopes and energy dispersive X-ray analysis (EDAX) system, after growing for three months on sandy soil with or without 300 mM NaCl. Results showed that salt glands were irregularly scattered on both leaf sides and sunk under the epidermal level. Salt excretion occurred in both conditions and is mainly composed of calcium and magnesium in control plants, and essentially sodium and chloride in plants subjected to salt treatment. A salt gland is comprised of collecting, accumulating, and central compartments, and is made up of total thirty-two cells. The collecting cells were characterized by large central vacuoles. Accumulating cells contain numerous, large, and unshaped vacuoles and rudimentary chloroplasts. The central compartment was comprised of four basal cells and each one is surmounted by an apical cell. The basal cells are granulated, containing large nucleus, numerous mitochondria, endoplasmic reticulum, ribosomes, polyribosomes, and small vacuoles or vesicles. Equally, the apical cells are rich in organelles. Application of 300 mM NaCl to the culture medium increased vacuoles number and size, and organelles density especially the mitochondria which suggests energy requirement for ions transport. The reduction in size and number of vacuoles toward the interior of salt glands of treated plants and the fusion of the smallest ones with the plasma membrane substantiate the implication of such vacuoles in salt excretion process. The current study which is the first report on L. guyonianum salt gland has provided an in-depth understanding on structure–function relationship in the multicellular salt glands.     

Operator approach to conformal invariant quantum field theories and related problems

Conformal quantum field theory is analysed from a global point of view. The use of the covering transformations leads to a global decomposition theory in which the basic building blocks are nonlocal quantum fields which live on each light cone separately. As an application of the new formalism arbitrary order-disorder mixed n-point functions of the Ising field theory are explicitly calculated.     

Antennal morphology and sensilla ultrastructure of Dendroctonus valens LeConte (Coleoptera: Curculionidae,Seolytinae), an invasive forest pest in China

Dendroctonus valens LeConte, an invasive forest pest, is highly dependent on its olfactory system for activities such as host seeking, mating, oviposition and population aggregation. The antennae are the primary olfactory organs in bark beetles. We describe four morphological types of sensilla on the antenna of D. valens: (1) 3 subtypes of sensilla trichodea located at the apex and lateral surface of the club. Sensilla trichodea types 1 and 3 were innervated by 5 and 13 dendrites, respectively. Sensilla trichode type 2 was not found dendrites in a lumen, (2) sensilla chaetica found on the scape and funicle and innervated by 7 dendrites, (3) a pair of sensilla basiconica distributed primarily on the three sensory bands, each innervated by 2 dendrites at the base, and (4) one fluted cone type of grooved peg dispersed throughout the sensory bands. The possible functions of these sensilla are discussed in relation to their morphology and ultrastructure.     

Absorption,extinction and phase function measurements for algal suspensions of chlorella pyrenoidosa

Optical property measurements have been made for unicellular algal suspensions of C. pyrenoidosa in the spectral range from 380 to 720 nm. The measurements include the extinction and absorption cross sections and the scattering phase function. Although the spectral dependence of the extinction cross section is weak, there is a strong wavelength dependence for absorption which is related to cell pigment content. The absorption cross section increases with increasing cell size and pigment content. The scattering albedo is approximately 0.9 over the entire spectrum, and the scattering phase function is strongly peaked in the forward direction.     

Implications of the quark-gluon light cone current algebra on neutrino scattering

The explicit canonical structure of the light cone restriction of the commutator of the weak current with its divergence is considered in the interacting quark-gluon model quantized in the finite momentum frame. The implications on neutrino scattering are analyzed. W₄ and W₅ are predicted to scale nontrivially as ν⁻²F₄(ω) and ν⁻²F₅(ω), which provides a simple test of light cone current algebra feasible in the near future. The Σ-term for weak currents is deduced from a casual representation near the light cone, and a correction is also made in the W₅-sum rule obtained by naive infinite momentum techniques.     

Structure and fluctuations of the premelted liquid film of ice at the triple point

ABSTRACT

In this paper, we study the structure of the ice/vapour interface in the neighbourhood of the triple point for the TIP4P/2005 model. We probe the fluctuations of the ice/film and film/vapour surfaces that separate the liquid film from the coexisting bulk phases at basal, primary prismatic and secondary prismatic planes. The results are interpreted using a coupled sine Gordon plus Interface Hamiltonian model. At large length scales, the two bounding surfaces are correlated and behave as a single complex ice/vapour interface. For small length, on the contrary, the ice/film and film/vapour surfaces behave very much like independent ice/water and water/vapour interfaces. The study suggests that the basal facet of the TIP4P/2005 model is smooth, the prismatic facet is close to a roughening transition, and the secondary prismatic facet is rough. For the faceted basal face, our fluctuation analysis allows us to estimate the step free energy in good agreement with experiment. Our results allow for a quantitative characterisation of the extent to which the adsorbed quasi-liquid layer behaves as water and explains experimental observations which reveal similar activation energies for crystals grown in bulk vapour or bulk water.     

Ultrastructure of the human retina in aging and various pathological states

Vision is hampered in aging and diseases, such as age-related macular degeneration, retinitis pigmentosa, diabetic retinopathy and glaucoma. This review collates the fine structural alterations of the human retina in aging and various pathological situations and their links to the disease pathogenesis. It transpires that most changes occur at the level of the retinal pigment epithelium -Bruch's membrane and the photoreceptor layer, causing visual problems to the sufferers. These changes include loss of normal, essential features of these cells and their gradual disappearance. It is important to understand in depth the selective vulnerability of this retinal region to alterations in aging and diseases. Evidence indicates that some of these changes may be mediated by the effects of oxidative stress, inflammation, and chronic light exposure. There are changes also in the inner retinal layers, wherein hypertension, auto-immunity, hypoxia and ischemia could play significant roles in disease pathogenesis. Results of extensive research utilizing animal models have broadened our idea about photoreceptor pathology. However, equivalent knowledge on various changes in aging human retina and in dystrophies that affect the macula is not complete. Since cone photoreceptor and ganglion cell death are a potential problem, it is imperative to know about the basic facts on how they are affected and the mechanisms involved in their death. Thus, prevention of cone and ganglion cell loss should be the target of choice. This review also highlights the significant role played by electron microscopy in understanding such ultrastructural changes and future strategies utilizing it and other techniques to fill some of the existing lacunae and advance our knowledge.     

Multichannel decomposition and isomerization of octyl radicals

The thermal cracking patterns from the decomposition and isomerization of octyl-1 radicals have been determined from the pyrolysis of n-octyl iodide in single pulse shock tube experiments at temperatures in the 850-1000 K range and pressures near 2 bar. Rate constants for the six beta bond scission and five of the six isomerization processes have been derived over all combustion conditions [0.1-100 bar, 700-1900 K]. Comparisons are made with previous studies on the decomposition of other primary radicals. Results are consistent with similar types of reactions having equal rate constants. The larger size of the octyl radicals makes contributions from secondary to secondary radical isomerization increasingly important. The results confirm that the 1-3 H-transfer process (involving a seven member cyclic transition state) have rate constants that are within a factor of 2 of those for the 1-4 process (six member cyclic transition state) It appears that rate constants for 1-2 H-transfer isomerization, involving an eight member cyclic transition state is unimportant in comparison to contributions from other isomerization processes. The strain energy does not appear to play an important role for these larger transition states. The implications of these results to larger fuel radicals will be discussed.