Luminance-dependence of spatial vision in budgerigars (<Emphasis Type="Italic">Melopsittacus undulatus</Emphasis>) and Bourke’s parrots (<Emphasis Type="Italic">Neopsephotus bourkii</Emphasis>)

Budgerigars (Melopsittacus undulatus) and Bourke’s parrots (Neopsephotus bourkii) are closely related birds with different activity patterns. Budgerigars are strictly diurnal while Bourke’s parrots are active in dim twilight. Earlier studies show that the intensity threshold of colour vision is similar in both species while Bourke’s parrots have larger eyes with a higher density of rods than budgerigars. In this study, we investigate whether this could be an adaptation for better spatial vision in dim light. We used two alternative forced-choice experiments to determine the spatial acuity of both species at light intensities ranging from 0.08 to 73 cd/m². We also determined the spatial contrast sensitivity function (CSF) for bright light in Bourke’s parrots and compare it to existing data for budgerigars. The spatial acuity of Bourke’s parrots was found to be similar to that of budgerigars at all light levels. Also the CSF of Bourke’s parrots is similar to that of budgerigars with a sensitivity peak located between 2.1 and 2.6 cycles/degree. Our findings do not support the hypothesis that Bourke’s parrots have superior spatial acuity in dim light compared to budgerigars and the adaptive value of the relatively rod-rich and large eyes of Bourke’s parrots remains unclear.     

Visual acuity, contrast sensitivity and retinal magnification in a marsupial, the tammar wallaby (Macropus eugenii )

The visual acuity of the tammar wallaby was estimated using a behavioural discrimination task. The wallabies were trained to discriminate a high-contrast (86%) square-wave grating from a grey field of equal luminance (1000–6000 cd m⁻²). Visual-evoked cortical potentials were used to measure the complete contrast sensitivity function. The stimulus was a sinusoidal phase reversal of a sinusoidally modulated grating of various spatial frequencies and contrasts with a mean luminance of 40 cd m⁻². The behavioural acuity was estimated to be about 4.8 cycles/deg. The contrast sensitivity peaked at about 0.15 cycles/deg and declined towards both lower and higher spatial frequencies. The cut-off frequency of the contrast sensitivity function is slightly lower than the behaviourally measured acuity at about 2.7 cycles/deg. The retinal magnification factor was estimated anatomically from laser lesions to be about 0.16 mm/deg. Based on the known ganglion cell density and the retinal magnification factor, an anatomical upper limit to visual acuity of about 6 cycles/deg can be calculated. The differences in estimates of visual acuity between the behavioural and anatomical methods on the one side and physiology on the other side are discussed. Accepted: 28 May 1998     

Quantitative Analysis of β-Amyloid Peptides Expressed in Human Cerebrospinal Fluid by an Improved Method of Antibody-Assisted Time-of-Flight Mass Spectrometry

Establishment of diagnostic measures for early stage Alzheimer’s disease (AD) and mild cognitive impairment (MCI) is of crucial importance. Using surface enhanced laser desorption ionization time-of-flight mass spectrometry (SELDI-TOF-MS), antibody-assisted MS of cerebrospinal fluid (CSF) has enabled quantitative analysis of the ratio of β-amyloid (Aβ) peptides, Aβ1-42/Aβ1-40, which has a diagnostic value for AD/MCI. To apply the MS analysis to a far wider range of CSF samples, we have established a method to analyze Aβ peptides expressed in 100 μl CSF samples quantitatively. Pretreatment of CSF samples by limit-filtration to condense peptides, and modified washing procedure using urea as denaturant, Aβ peptides of interest can be assessed with higher sensitivity by five to tenfolds to the original method. This improvement enables quantitative analysis of Aβ species from a residual amount of CSF samples, which will be occasionally obtained in case of lumbar anesthesia prior to operation and spinal tap performed for routine diagnostic purposes. Prevalence of the new procedure as laboratory test, especially among the elderly consulting for neurological clinic, will enhance the number of subjects diagnosed at early stage of AD/MCI.     

SPECTRAL SENSITIVITY IN TWO SPECIES OF PINNIPEDS (PHOCA VITULINA AND OTARIA FLAVESCENS)

Spectral sensitivity was measured in air in the light adapted state in two harbor seals and a South American sea lion using a behavioral training technique. Increment thresholds were determined in a spectral range from 390 nm to 670 nm in a simultaneous two‐choice discrimination task. The spectral sensitivity curves show two maxima in sensitivity, one main peak with a maximum around 500 nm in the harbor seal and around 550 nm in the South American sea lion, and a second, smaller peak with a maximum in the range of 410 nm in both species. The broad shape and the position of the maximum of the spectral sensitivity curve of the harbor seals suggests that even under photopic conditions both rods and cones are contributing to the measurements since harbor seals possess only one cone type. The maximum sensitivity in the green part of the spectrum may indicate an adaptation to a specific underwater environment.     

Within-night variation in respiratory effort preceding apnea termination and EEG delta power in sleep apnea

We studied the within-night variability of themaximum esophageal pressure deflection before apnea termination(DP_max) in nine patients withsevere obstructive sleep apnea as an index of the arousal threshold andthe mean electroencephalogram (EEG) delta power for each 30 s as anindex of the timing of sleep cycles. Periodicity in the time variationof delta power and DP_max was analyzed by determining their power spectral density and their relationship determined by cross correlation.DP_max and delta power variedcyclically and in phase with a major periodicity (major peak in powerspectral density) of 117.6 ± 8.8 (SE) min. The correlation betweenthe values of DP_max and deltapower was significant (P < 0.001) ineach subject (mean r = 0.47 ± 0.03), and the coherence betweenDP_max and delta power at theirdominant frequency was high. Within cycles of non-rapid-eye-movementsleep, DP_max and delta powerincreased, reaching peak values on average at or after midcycle. Thesefindings suggest that the arousal threshold to airway occlusion inpatients with obstructive sleep apnea varies cyclically during thenight synchronous to the underlying cycles of sleep.

     

Contrast sensitivity functions to stimuli defined in Cartesian, polar and hyperbolic coordinates

Recent electrophysiological studies indicate that cells in the LGN, V1, V2, and V4 areas in monkeys are specifically sensitive to Cartesian, polar and hyperbolic stimuli. We have characterized the contrast sensitivity functions (CSF) to stimuli defined in these coordinates with the two-alternatives forced-choice paradigm. CSFs to Cartesian, concentric, and hyperbolic stimuli have had similar shapes, with peak sensitivity at approximately 3 c/deg. However, the Cartesian CSF peak sensitivity has been at least 0.1 log units higher than that to stimuli in any other coordinate system. The concentric-Bessel CSF has a low-pass shape, peaking at 1.5 c/deg or below. The radial CSF has a bell shape with maximum sensitivity at 8 c/360 degrees. Only the concentric-Bessel CSF could be explained in terms of the components of maximum amplitude of the Fourier transform. Neural models, which in previous studies predicted the responses to Cartesian and polar Glass patterns, failed to account for the full CSFs data.     

Highly efficient plant regeneration and <Emphasis Type="Italic">in vitro</Emphasis> polyploid induction using hypocotyl explants from diploid mulberry (<Emphasis Type="Italic">Morus multicaulis</Emphasis> Poir.)

Efficient plant regeneration is essential for successful transformation and in vitro polyploidy induction in mulberry. A high frequency (80%) of plant regeneration from hypocotyls occurred under in vitro conditions in mulberry (Morus multicaulis Poir.). We identified three key factors for enhancing successful regeneration based on earlier work: (1) hypocotyl position, (2) the combination and concentration of growth regulators, and (3) the addition of AgNO₃. The highest frequency of shoot regeneration was achieved using hypocotyl segments, which are proximal to apical meristems, and the optimal culture conditions were Murashige and Skoog’s (MS) (Murashige and Skoog, 1962) basal medium supplemented with 3.0 mg l⁻¹ 6-benzylamino purine, 0.3 mg l⁻¹ indole-3-acetic acid, 0.1% polyvinypyrrolidone, and 1.0 mg/l silver nitrate (AgNO₃) under subdued light at 25 ± 2°C. Treating the shoots with 0.2% colchicine (dipping for 72 h) resulted in a 14% tetraploid frequency, whereas a 20% tetraploid frequency resulted from using a 0.25% colchicine (dripping for 5 d) treatment, as determined by chromosome number counts. The diploid plant chromosome number was 28 (2n = 2x = 28) and that of tetraploid plants was 56 (2n = 4x = 56). Regenerated shoots rooted easily in 8–10 d using half-strength basal MS medium with 0.5 mg l⁻¹ indole-3-butyric acid and were successfully established in the soil.     

不同运动速度下人眼的阈上调制特性

本文报道了在光栅的三种恒定运动速度(0°/S,10°/S,30°/S)下,阈值对比敏感度函数CSF(V)和阈上对比度比配函数CMF(V,C)的测试数据.计算机拟合结果表明,在各个不同的恒定运动速度下,人眼的阈上对比度比配函数CMF(V,C)和阈值对比敏感度函数CSF(V),可以由静止目标的阈值对比敏感函数CSF近似地预测出来.本文给出了预测方法的数学描述及有关经验公式.     

Ocular dimensions and cone photoreceptor topography in adult Nile Tilapia <Emphasis Type="Italic">Oreochromis niloticus</Emphasis>

Information on the anatomy of the eye and the topography of cone photoreceptor cells in the retina is presented for the Nile Tilapia (Oreochromis niloticus). In adults, the shape and proportions of the ocular components of the prominent eye conform to the general form of fish eyes, as determined using cryo-sectioned eyes. The lens is approximately spherical and there is little variation in the distance from the centre of the lens to the border between the choroid and retina at a range of angles about the optical axis. The average ratio of the distance from the centre of the lens to the retina: lens radius (Matthiessen’s ratio) is 2.44:1. In retinal wholemounts, single and double (twin) cone photoreceptors, forming a square mosaic, are present. Peak photoreceptor densities for both morphological cone types are found in the temporal retina. Using peak cone densities and estimates of focal length from cryo-sectioned eyes, visual acuity is calculated to be 5.44 cycles per deg. The lack of apparent specific ocular or retinal specializations and the relatively low visual acuity reflect the lifestyle of the Nile Tilapia and may allow it to adapt to changes in visual environment in its highly variable natural habitat as well as contributing to the ‘ecological flexibility’ of this species.     

Presence of Palaemon Macrodactylus Rathbun 1902 (Crustacea: Decapoda: Caridea: Palaemonidae) in Mar Del Plata Harbor, Argentina: First Record from Southwestern Atlantic Waters

Adults of the palaemonid prawn Palaemon macrodactylus Rathbun, 1902 were reported for the first time from the southwestern Atlantic waters. Males and ovigerous females were collected in Mar del Plata harbor (38°03′ S; 57°31′ W), Argentina; larvae obtained from one of the collected females were reared in the laboratory until the juvenile stage. The geographical range of P. macrodactylus was previously restricted to the Pacific Ocean: it was originally described in Japan and has been reported as an invasive species in the western coast of USA in the 1950’s and in Australia in the 1970’s. Recently, this prawn has been also reported from European waters.     

Laboratory spawning cues in Menidia beryllina,and M. peninsulae (Pisces,Atherinidae) with notes on survival and growth of larvae at different salinities

Synopsis Spawning patterns of inland silversides, Menidia beryllina, and tidewater silversides, Menidia peninsulae, were examined in the laboratory under several combinations of ‘tidal’ and diel light cycle cues. M. beryllina showed a high frequency of spawning throughout the day when held under constant conditions (24L: OD, current velocity 8 cm sec⁻¹) and when ‘tidal’ and diel light cycles were presented singly or in combination. In contrast, M. peninsulae demonstrated a high frequency of spawning only when presented a combination of ‘tidal’ and diel light cycle cues and spawned predominantly at night. Menidia beryllina embryos were euryhaline. Hatching ranged from 73 to 78% at salinities of 5,15 and 30‰ M. peninsulae embryos showed an inverse relationship between the percentage hatch and the incubation salinity, 90% at 5‰ and only 65% at 30‰ Survival and growth of larval M. beryllina from the day of hatching through 16 days old was optimal at 15‰ Although survival of M. peninsulae larvae was optimal at 30%, no trend was apparent in growth of larvae held for 16 days at 5, 15 or 30‰ salinity. Contribution No. 508 from the Gulf Breeze Environmental Research Laboratory     

Screening of a broad range of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) germplasm for <Emphasis Type="Italic">in vitro</Emphasis> rapid plant regeneration and development of an early prediction system

Rice has emerged as a model monocot for studies in agriculture and biotechnology due to its relatively small genome and a ready accessibility to plant material. Tissue culture is one of the tools required for genetic transformation and some breeding programs, and the selection of high-frequency regenerator types is essential for success in these technologies. Thirty-three rice entries with agricultural and biotechnological characteristics of interest were screened with the aim to identify the best regenerators. Entries that exhibited between 50% and 90% regeneration frequencies include ‘Taipei-309,’ ‘Super Dwarf,’ ‘Norin’ (japonica types), PI 312777, ‘Ali Combo’ (indica types), ‘STG-S,’ and ‘LA3’ (red rice types). One third of the entries tested were at least two times better at regeneration than the often-cited regenerator ‘Nipponbare.’ Those entries showing at least 85% frequency of greening or somatic embryo formation at 15 or 30 d on regeneration medium ultimately produced whole plants after 45 d on regeneration medium at high frequency (at least 40%); those entries not reaching the 85% threshold of greening by Days 15 or 30 exhibited moderate (15–40%) to low (less than 10%) frequency of whole plant regeneration. This greening response suggests the means for an early prediction system for identification of useful rice regenerator lines, which would be beneficial for high-throughput screening of germplasm as well as for decreasing the time and cost of in vitro culture.     

Extracellular chaperones modulate the effects of Alzheimer’s patient cerebrospinal fluid on Aβ<Subscript>1-42</Subscript> toxicity and uptake

Alzheimer’s disease is characterised by the inappropriate death of brain cells and accumulation of the Aβ peptide in the brain. Thus, it is possible that there are fundamental differences between Alzheimer’s disease patients and healthy individuals in their abilities to clear Aβ from brain fluid and to protect neurons from Aβ toxicity. In the present study, we examined (1) the cytotoxicity of Alzheimer’s disease cerebrospinal fluid (CSF) compared to control CSF, (2) the ability of Alzheimer’s disease and control CSF to protect cells from Aβ toxicity and to promote cell-mediated clearance of Aβ and lastly (3) the effects of extracellular chaperones, normally found in CSF, on these processes. We show that the Alzheimer’s disease CSF samples tested were more toxic to cultured neuroblastoma cells than normal CSF. In addition, the Alzheimer’s disease CSF samples tested were less able to protect cells from Aβ-induced toxicity and less efficient at promoting macrophage-like cell uptake when compared to normal CSF. The addition of physiologically relevant concentrations of the extracellular chaperones, clusterin, haptoglobin and α₂-macroglobulin into CSF protected neuroblastoma cells from Αβ_1-42 toxicity and promoted Αβ_1-42 uptake in macrophage-like cells. These results suggest that extracellular chaperones are an important element of a system of extracellular protein folding quality control that protects against Aβ toxicity and accumulation.     

Cupiennius salei: biomechanical properties of the tibia–metatarsus joint and its flexing muscles

Hunting spiders are well adapted to fast locomotion. Space saving hydraulic leg extension enables leg segments, which consist almost soley of flexor muscles. As a result, the muscle cross sectional area is high despite slender legs. Considering these morphological features in context with the spider’s segmented C-shaped legs, these specifics might influence the spider’s muscle properties. Moreover, these properties have to be known for modeling of spider locomotion. Cupiennius salei (n = 5) were fixed in a metal frame allowing exclusive flexion of the tibia–metatarsus joint of the second leg (counted from anterior). Its flexing muscles were stimulated supramaximally using needle electrodes. Accounting for the joint geometry, the force–length and the force–velocity relationships were determined. The spider muscles produce 0.07 N cm maximum isometric moment (corresponding to 25 N/cm² maximum stress) at 160° tibia–metatarsus joint angle. When overextended to the dorsal limit at approximately 200°, the maximum isometric moments decrease to 72%, and, when flexed to the ventral hinge stop at 85°, they drop to 11%. The force–velocity relation shows the typical hyperbolic shape. The mean maximum shortening velocity is 5.7 optimum muscle lengths per second and the mean curvature (a/F _iso) of the Hill-function is 0.34. The spider muscle’s properties which were determined are similar to those of other species acting as motors during locomotion (working range, curvature of Hill hyperbola, peak power at the preferred speeds), but they are relatively slow. In conjunction with the low mechanical advantage (muscle lever/load arm), the arrangement of three considerably actuated joints in series may nonetheless enable high locomotion velocities.     

Identification of a major QTL for time of initial vegetative budbreak in apple (<Emphasis Type="Italic">Malus</Emphasis> x <Emphasis Type="Italic">domestica</Emphasis> Borkh.)

In the Western Cape region of South Africa, dormancy release and the onset of growth does not occur normally in apple (Malus x domestica Borkh.) trees during spring due to the mild winter conditions experienced and fluctuations in temperatures experienced during and between winters. In this region, the application of chemicals to induce the release of dormancy forms part of standard orchard management. Increasing awareness of the environmental impact of chemical sprays and global warming has led to the demand for new apple cultivars better adapted to local climatic conditions. We report the construction of framework genetic maps in two F1 crosses using the low chilling cultivar ‘Anna’ as common male parent and the higher chill requiring cultivars ‘Golden Delicious’ and ‘Sharpe’s Early’ as female parents. The maps were constructed using 320 simple sequence repeats, including 116 new markers developed from expressed sequence tags. These maps were used to identify quantitative trait loci (QTL) for time of initial vegetative budbreak (IVB), a dormancy related characteristic. Time of IVB was assessed four times over a 6-year period in ‘Golden Delicious’ x ‘Anna’ seedlings kept in seedling bags under shade in the nursery. The trait was assessed for 3 years on adult full-sib trees derived from a cross between ‘Sharpe’s Early’ and ‘Anna’ as well as for 3 years on replicates of these seedlings obtained by clonal propagation onto rootstocks. A single major QTL for time of IVB was identified on linkage group (LG) 9. This QTL remained consistent in different genetic backgrounds and at different developmental stages. The QTL may co-localize with a QTL for leaf break identified on LG 3 by Conner et al. (1998), a LG that was, after the implementation of transferable microsatellite markers, shown to be homologous to the LG now known to be LG 9 (Kenis and Keulemans 2004). These results contribute towards a better understanding regarding the genetic control of IVB in apple and will also be used to elucidate the genetic basis of other dormancy related traits such as time of initial reproductive budbreak and number of vegetative and reproductive budbreak.     

Eco-fingerprinting of the dinoflagellate <Emphasis Type="Italic">Borghiella dodgei</Emphasis>: experimental evidence of a specific environmental niche

In Lake Tovel, an oligotrophic and weakly stratified lake, the dinoflagellate Borghiella dodgei Moestrup, Hansen et Daugbjerg, showed a peculiar spatial–temporal pattern with highest abundances in the bottom of the shallow side bay (4 m) along with remarkable abundance variations from year to year. We investigated B. dodgei’s growth in laboratory cultures and related results to their implication for bloom formation. B. dodgei was cultivated under different temperature, nutrient and light conditions. Growth rates, cell biovolume, cyst formation and pigment and mycosporine-like amino acids (MAAs) concentrations were determined. Experiments showed that this alga (i) had higher growth rates at low temperatures (<7°C) and high irradiance levels (~250 μmol m⁻² s⁻¹), (ii) produced higher yields with organic supplements such as peptone, (iii) did not grow in the dark even with organic supplements, (iv) survived for long periods without a light source, (v) synthesised MAAs, (vi) showed an increase in cell volume with nutrient shortage and increasing temperatures (>7°C) and (vii) had high encystment rates with temperatures >7°C. These laboratory fingerprints allowed us to construct a theoretical model defining the species’ niche. Borghiella needed a mixture of low temperatures, high irradiance levels and sufficient quantities of dissolved organic nitrogen to form blooms. Such a strict combination was probably a transient situation and occurred in oligotrophic Lake Tovel only in early summers followed by heavy spring rains.     

From polar night to midnight sun: photoperiod, seal predation, and the diel vertical migrations of polar cod (Boreogadus saida) under landfast ice in the Arctic Ocean

The winter/spring vertical distributions of polar cod, copepods, and ringed seal were monitored at a 230-m station in ice-covered Franklin Bay. In daytime, polar cod of all sizes (7–95 g) formed a dense aggregation in the deep inverse thermocline (160–230 m, −1.0 to 0°C). From December (polar night) to April (18-h daylight), small polar cod <25 g migrated into the isothermal cold intermediate layer (90–150 m, −1.4°C) at night to avoid visual predation by shallow-diving immature seals. By contrast, large polar cod (25–95 g), with large livers, remained below 180 m at all times, presumably to minimize predation by deep-diving mature seals. The diel vertical migration (DVM) of small polar cod was precisely synchronized with the light/dark cycle and its duration tracked the seasonal lengthening of the photoperiod. The DVM stopped in May coincident with the midnight sun and increased schooling and feeding. We propose that foraging interference and a limited prey supply in the deep aggregation drove the upward re-distribution of small polar cod at night. The bioluminescent copepod Metridia longa could have provided the light needed by polar cod to feed on copepods in the deep aphotic layers.     

Influence of the Selected Antioxidants on the Stability of the Celsior Solution Used for Perfusion and Organ Preservation Purposes

The purpose of the following research was to improve the original Celsior solution in order to obtain a higher degree of stability and effectiveness. The solution was modified by the addition of selected antioxidants such as vitamin C, cysteine, and fumaric acid in the following concentrations: 0.1, 0.3, and 0.5 mmol/l. The solution’s stability was estimated using an accelerated stability test based on changes in histidine concentrations in the solution using Pauly’s method for determining concentrations. Elevated temperatures, the factor accelerating substances’ decomposition reaction rate, were used in the tests. The research was conducted at four temperatures at intervals of 10°C: 60 ± 0.2°C, 70 ± 0.2°C, 80 ± 0.2°C, and 90 ± 0.2°C. It was stated that the studied substances’ decomposition occurred in accordance with the equation for first-order reactions. The function of the logarithmic concentration (log%C) over time was revealed to be rectilinear. This dependence was used to determine the kinetics of decomposition reaction rate parameters (the rate constant of decomposition k, activation energy E _a, and frequency factor A). On the basis of these parameters, the stability of the modified solution was estimated at +5°C. The results obtained show that the proposed antioxidants have a significant effect on lengthening the Celsior solution’s stability. The best results were reached when combining two antioxidants: vitamin C and cysteine in 0.5 mmol/l concentrations. As a result, the Celsior solution’s stability was lengthened from 22 to 299 days, which is 13.5 times. Vitamin C at a concentration of 0.5 mmol/l increased the solution’s stability by 5.2 times (t ₉₀ = 115 days), cysteine at a concentration of 0.5 mmol/l caused a 4.4 times stability increase (t ₉₀ = 96 days), and fumaric acid at a concentration of 0.5 mmol/l extended the stability by 2.1 times (t ₉₀ = 48 days) in relation to the original solution.     

Harbor seal population decline in the Aleutian Archipelago

Populations of Steller sea lions, northern fur seals, and northern sea otters declined substantially during recent decades in the Bering Sea and Aleutian Islands region, yet the population status of harbor seals has not been assessed adequately. We determined that counts obtained during skiff‐based surveys conducted in 1977–1982 represent the earliest estimate of harbor seal abundance throughout the Aleutian Islands. By comparing counts from 106 islands surveyed in 1977–1982 (8,601 seals) with counts from the same islands during a 1999 aerial survey (2,859 seals), we observed a 67% decline over the ～20‐yr period. Regionally, the largest decline of 86% was in the western Aleutians (n= 7 islands), followed by 66% in the central Aleutians (n= 64 islands), and 45% in the eastern Aleutians (n= 35 islands). Harbor seal counts decreased at the majority of islands in each region, the number of islands with >100 seals decreased ～70%, and the number of islands with no seals counted increased ～80%, indicating that harbor seal abundance throughout the Aleutian Islands was substantially lower in the late 1990s than in the 1970s and 1980s.