Majority Of Cones Research Articles

Increased density and age-related sharing of synapses at the cone to OFF bipolar cell synapse in the mouse retina.

Neural circuits in the adult nervous system are characterized by stable, cell type-specific patterns of synaptic connectivity. In many parts of the nervous system these patterns are established during development through initial over-innervation by multiple pre- or postsynaptic targets, followed by a process of refinement that takes place during development and is in many instances activity dependent. Here we report on an identified synapse in the mouse retina, the cone photoreceptor➔type 4 bipolar cell (BC4) synapse, and show that its development is distinctly different from the common motif of over-innervation followed by refinement. Indeed, the majority of cones are contacted by single BC4 throughout development, but are contacted by multiple BC4s through ongoing dendritic elaboration between 1 and 6 months of age-well into maturity. We demonstrate that cell density drives contact patterns downstream of single cones in Bax null mice and may serve to maintain constancy in both the dendritic and axonal projective field.

Retrograde Melanopsin Signaling Increases With Age in Retinal Degenerate Mice Lacking Rods and the Majority of Cones.

Following on from reports of retrograde retinal signaling in mice, we sought to investigate the influence of age and retinal location on this phenomenon using mice that lack rods and the majority of cones. We used functional anatomy for c-fos (Fos) and tyrosine hydroxylase (TH) to measure light-driven activation of dopamine neurons along a dorsal-ventral transect in C3H/He wild-type and rodless-coneless rd/rd cl (rdcl) mice aged 3, 5, and >14 months. A parallel series of retinae from 3-month-old mice was also stained for cone opsins and melanopsin. Analysis by confocal microscopy revealed light-driven Fos activation in TH cells residing in the middorsal retina of the youngest rdcl mice. This region was largely devoid of residual cones but contained a large number of intrinsically photosensitive retinal ganglion cells (ipRGCs) and the highest density of melanopsin neurites. With advancing age, there was a paradoxical increase in retrograde signaling from ∼3% Fos-positive (Fos+) TH cells at 3 months to ∼36% in rdcl mice >14 months. This increased activation occurred in more central and peripheral retinal regions. Our data provide new insights into the anatomy and plasticity of retrograde melanopsin signaling in mice with severe rod/cone dystrophy. The increased retrograde signaling we detect may result from either an increased potency of melanopsin signaling with advancing age and/or postsynaptic modification to dopaminergic neurons.

Nutcrackers become choosy seed harvesters in a mast-crop year

As an efficient seed-disperser, Eurasian nutcrackers (Nucifraga caryocatactes) generally consume and hoard mature, edible pine seeds for future use. In 2009, when the Arolla pine, Pinus. cembra, produced a mast-crop, we investigated cones discarded by nutcrackers. Most cones were only partly eaten and some mature seeds remained in the distal part. This was in contrast to years of lower seed production when nearly all seeds were harvested from the majority of cones. To determine whether nutcracker cone-discarding behaviour maximised intake rate, seed kernels and the aborted seeds rate were measured from the different cone parts. In 2009, seeds from cone-tops were on average 17% lighter than in the base and middle sections, and the proportion of aborted seeds in the top part was 81% higher than in the other sections. There was no difference in seed mass and proportion of aborted seeds in cone-tops of intact cones and cones handled by nutcrackers. Regarding each cone as a patch, cone discarding behaviour can be considered as an optimal cone-leaving rule, maximising rate of energy-intake, supporting the Marginal Value Theorem. Hence, we suggest that increased food abundance leads to more selective seed harvesting in nutcrackers.

Study on reproduction ecology of endangered species Abies chensiensis

Qinling fir, Abies chensiensis, is endemic to China and has been listed in the China Plant Red Data Book as one of the second class conservation plants. It is found scattered only in the forested pockets of the Qinling, Bashan, and Shennongjia Mountains with altitude from 1 300 m to 2200 m in Shaanxi, Gansu, Henan, Sichuan, and Hubei Provinces. To conserve and effectively restore this species and explore its processes of reproduction, the production characteristics of cone and seed yields, seed bank dynamics, and seed germination rates of five Abies chensiensis populations (A, B, C, D, and E, respectively, in the Abies chensiensis-Pinus tabulaeformis-Sinarundinaria nitida-Carex lanceolata association, Abies chensiensis-Quercus aliena var. acutserrata-Litsea pungens-Carex lanceolata association, Abies chensiensis-Betula albo-sinensis-Sinarundinaria nitida-Duchesnea indica association, Abies chensiensis-Indigofera amblyantha-Carex lanceolata association and Abies chensiensis-Pinus tabulaeformis-Smilax stans-Carex lanceolata association) were studied in their natural habitats across 18 plots in the Qinling Mountain area. Experiments were carried out in laboratory and field conditions. The results showed that all the five populations had the potential to produce seeds, and higher yields occurred in the lower and middle altitude areas every three to five years. The majority of cones appeared on the upper and middle crown and the west, south, and east faces of the crown, and the majority of full seed appeared on the middle portion of the cone. The weight per 1000 seeds was 43.2 g, in which 44.8% had growing potential. The germination rate of seeds in the natural forest was 6.1% and the proportion of seeds lost or destroyed in different populations in the natural forest was 93.9%. The germination rate of seeds planted in the nursery was higher than that in the natural forest, and the germination rate in the lower or middle altitude populations was higher than that in the upper altitude populations. The course from seed to seedling was the critical period in the life cycle of A. chensiensis populations under natural conditions. Reproduction courses were influenced positively by an abundant coverage of tree layer, organic material in the soil, thick soil, and a dense population of parent trees, whereas they were influenced negatively by human disturbance and light. In situ conservation of A. chensiensis should be carried out in the future so as to promote expansion of the population. Thinning the shrub layer and grass layer will also help seeds to penetrate the soil, promoting seed germination. The artificial population should be expanded by collecting seeds in the harvest years. Fast-growing and high-yield plantations should be developed on cloudy slopes at lower or middle altitudes.

Location of cones in the crown and along shoots of Sitka spruce (Picea sitchensis (Bong.) Carr.) and the influence of coning intensity and shoot size

The location of female cones in the crowns of rooted cuttings and mature forest-grown trees of Sitka spruce (Picea sitchensis (Bong.) Carr.) was recorded. When cones were allocated to crown sections there were clear patterns of bearing, with the majority of cones on second-order distal shoots on whorls 2 and 3. As total cone production increased, the bearing zone progressed onto more proximal shoots on upper whorls and distal shoots on lower whorls. On individual branches of clonal grafts, female cones tended to be borne on more distal shoots than male cones. Female cones, on all sample sets, tended to be borne primarily on second-order shoots and male cones, on the clonal grafts, on third-order shoots. On the clonal grafts there was a weak, though significant, relationship between the number of original buds and female, but not male, cones on a shoot. Cones were also described by position on bearing shoots. There was a tendency for the proportion of progressively more proximal cone positions to increase on lower-order shoots and vice versa. Cone position was also influenced by the dimensions of the bearing shoot independent of its position with a distal shift in cone-bearing position as shoot dimensions decreased.

Location of cones in the crown and along shoots of Sitka spruce (<i>Picea sitchensis</i> (Bong.) Carr.) and the influence of coning intensity and shoot size

The location of female cones in the crowns of rooted cuttings and mature forest-grown trees of Sitka spruce (Picea sitchensis (Bong.) Carr.) was recorded. When cones were allocated to crown sections there were clear patterns of bearing, with the majority of cones on second-order distal shoots on whorls 2 and 3. As total cone production increased, the bearing zone progressed onto more proximal shoots on upper whorls and distal shoots on lower whorls. On individual branches of clonal grafts, female cones tended to be borne on more distal shoots than male cones. Female cones, on all sample sets, tended to be borne primarily on second-order shoots and male cones, on the clonal grafts, on third-order shoots. On the clonal grafts there was a weak, though significant, relationship between the number of original buds and female, but not male, cones on a shoot. Cones were also described by position on bearing shoots. There was a tendency for the proportion of progressively more proximal cone positions to increase on lower-order shoots and vice versa. Cone position was also influenced by the dimensions of the bearing shoot independent of its position with a distal shift in cone-bearing position as shoot dimensions decreased.

Selective Absence of Cone Outer Segment β 3-Transducin Immunoreactivity in Hereditary Cone Degeneration ( cd)

We have used immunocytochemistry and in situ hybridization to examine the expression of photoreceptor specific genes in retinas of normal dogs and those affected with hereditary cone degeneration ( cd), a rare autosomal recessive disorder that selectively affects cones. In the cdretina, cone disease begins early in life; cones are lost by extrusion of the nucleus into the inner segment, and later, by displacement of the nucleus, surrounded by a thin rim of cytoplasm, into the interphotoreceptor space. Two micrometer sections from the superior and inferior retinal meridians, extending from the optic disk to the ora serrata, were used for in situ hybridization with a bovine rod opsin and human red/green cone opsin cRNA probes, or were reacted with antibodies directed against photoreceptor-specific proteins and visualized with appropriate biotinylated antibodies. Antibodies against the following proteins were used: α- and β 3-transducins, phosducin, α/β- and γ-phosphodiesterases, COS-1, and OS-2, opsin, S-antigen and IRBP. Immunoreactivity or hybridization labeling was evaluated in unstained sections; cone pathology was judged in adjacent Toluidine Blue-stained sections. With these methods it was possible to evaluate immunoreactivity or hybridization labeling and cone pathology at the single cell level. Both middle- (COS-1) and short-(OS-2) wavelength-sensitive cones were present in controls and cdaffected retinae at 2.2 months, and distinct transcripts of the red/green cone pigment gene were identified in the majority of cones in both normal and affected retinas at this age. However, β 3-transducin immunoreactivity was completely absent from cd-affected cone outer segments. Both cone types were present but in reduced numbers in older animals (11.5 and 17 months), and no reactivity to β 3-transducin was noted. No differences were found with the other antibodies used. The specific absence of β 3-transducin immunoreactivity from the cone outer segments suggests a potential involvement of the β 3-transducin gene or gene product in the disease process.

Landsat Thematic Mapper observations of debris avalanche deposits in the Central Andes

Remote sensing studies of the Central Andean volcanic province between 18°–27°S with the Landsat Thematic Mapper have revealed the presence of 28 previously undescribed breached volcanic cones and 14 major volcanic debris avalanche deposits, of which only 3 had previously been identified. Several of the debris avalanche deposits cover areas in excess of 100 km2 and have volumes of the order of 10 km3. H/L ratios for the deposits have a median of 0.1 and a mean of 0.11, values similar to those determined for deposits described in other regions. Surface morphologies commonly include the hummocky topography of small hillocks and enclosed basins that is typical of avalanche deposits, but some examples exhibit smoother surfaces characterised by longitudinal grooves and ridges. These differences may result from the effects of flow confinement by topography or from variations in resistance to shearing in the materials involved. Breached composite cones and debris avalanche deposits tend to occur at right angles to regional tectonic elements, suggesting possible seismic involvement in triggering collapse and providing an additional consideration for assessment of areas at risk from collapse. The low denudation rate in the Central Andes, coupled with the predominance of viscous dacite lavas in volcanic edifices, produces unusually steep cones which may result in a higher incidence of volcano collapse than in other regions. A statistical survey of 578 composite volcanoes in the study area indicates that a majority of cones which achieve edifice heights between 2000–3000 m may undergo sector collapse.

Relationships Among Reproduction, Growth Rates, and Protein Heterozygosity in Ponderosa Pine

This report summarizes a 6-yr study of male and female cone production in a population of 216 ponderosa pines whose ages, diameters, and genotypes at 7 protein polymorphisms are known. There are different schedules of male and female reproduction. The majority of cones are produced by the same few trees each year. There is a tradeoff between growth rate and female cone production but not pollen production. Differential female (but not male) cone production is associated with protein genotype. The variance of female reproductive effort declines with increasing protein heterozygosity.

RELATIONSHIPS AMONG REPRODUCTION, GROWTH RATES, AND PROTEIN HETEROZYGOSITY IN PONDEROSA PINE

This report summarizes a 6‐yr study of male and female cone production in a population of 216 ponderosa pines whose ages, diameters, and genotypes at 7 protein polymorphisms are known. There are different schedules of male and female reproduction. The majority of cones are produced by the same few trees each year. There is a tradeoff between growth rate and female cone production but not pollen production. Differential female (but not male) cone production is associated with protein genotype. The variance of female reproductive effort declines with increasing protein heterozygosity.

Cyclic nucleotides in rod- and cone-dominant retinas

Rod-and cone-dominant retinas differ in their relative content of cyclic AMP and cyclic GMP. Cyclic GMP is concentrated in retinas dominated by rods and is responsive to light; cyclic AMP is enriched in those having a majority of cones. Light reduces by about 50% the content of cyclic AMP in cone-dominant retinas, but the levels of cyclic GMP are affected only minimally. Microdissection of rod-dominant retinas shows that most of the cyclic GMP is localized in photoreceptor cells whereas cyclic AMP is evenly distributed throughout the retina. In contrast, our studies of cyclic nucleotides and the morphological changes that occur in cone visual cells of the ground squirrel retina, during hibernation and iodoacetate-induced cone degeneration, suggest that cyclic AMP is localized in cone visual cells. By analogy with the rod system, cyclic AMP may modulate the intracellular metabolism of cones.

Interphotoreceptor matrix in the frog retina

We have used immunocytochemistry and in situ hybridization to examine the expression of photoreceptor specific genes in retinas of normal dogs and those affected with hereditary cone degeneration (cd), a rare autosomal recessive disorder that selectively affects cones. In thecdretina, cone disease begins early in life; cones are lost by extrusion of the nucleus into the inner segment, and later, by displacement of the nucleus, surrounded by a thin rim of cytoplasm, into the interphotoreceptor space. Two micrometer sections from the superior and inferior retinal meridians, extending from the optic disk to the ora serrata, were used for in situ hybridization with a bovine rod opsin and human red/green cone opsin cRNA probes, or were reacted with antibodies directed against photoreceptor-specific proteins and visualized with appropriate biotinylated antibodies. Antibodies against the following proteins were used: α- and β3-transducins, phosducin, α/β- and γ-phosphodiesterases, COS-1, and OS-2, opsin, S-antigen and IRBP. Immunoreactivity or hybridization labeling was evaluated in unstained sections; cone pathology was judged in adjacent Toluidine Blue-stained sections. With these methods it was possible to evaluate immunoreactivity or hybridization labeling and cone pathology at the single cell level. Both middle- (COS-1) and short-(OS-2) wavelength-sensitive cones were present in controls andcdaffected retinae at 2.2 months, and distinct transcripts of the red/green cone pigment gene were identified in the majority of cones in both normal and affected retinas at this age. However, β3-transducin immunoreactivity was completely absent fromcd-affected cone outer segments. Both cone types were present but in reduced numbers in older animals (11.5 and 17 months), and no reactivity to β3-transducin was noted. No differences were found with the other antibodies used. The specific absence of β3-transducin immunoreactivity from the cone outer segments suggests a potential involvement of the β3-transducin gene or gene product in the disease process.

Visual pigments and colour vision in a nocturnal bird, Strix aluco (tawny owl)

Microspectrophotometer measurements of the oil droplets and visual pigments in the receptors of the tawny owl ( Strix aluco) have demonstrated the presence of at least four types of oil droplets and three visual pigments. The majority of cones contain a pale yellow droplet and a yellow-absorbing visual pigment withλ max 555 nm. Two further types of cone can be recognised containing either a green-absorbing pigment,λ max 503 nm, or a blue-absorbing pigment,λ max about 463 nm. A fourth type of cone containing a red oil droplet was also identified. The rods contain a P503, similar in absorbance to the green-absorbing cone visual pigment. From the transmission characteristics of the oil droplets and the absorbance spectra of the cone visual pigments, the effective spectral sensitivities of each cone type have been derived. These photopic mechanisms are discussed in relation to psychophysically-determined photopic sensitivities of the tawny owl and to the photopic systems of two diurnal birds.