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1.
Bertulis A Bulatov A 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2003,89(10):1265-1280
A combined influence of stimulus orientation and structure on the judgement of length was tested in psychophysical experiments. The subjects adjusted the test part of a stimulus to be equal in length to the reference part. The V-shaped stimuli (three dots, or the Oppel-Kundt figure, or one dot and two Müller-Layer wings) were generated on the monitor. In the Oppel-Kundt and Müller-Layer figures, the filled part was considered as a reference and the empty part as a test. In session of the experiments, values of errors measured as functions of orientation of the parts of the stimuli. We assume that experiments with the three-dot stimuli yielded pure characteristics of visual field anisotropy, while those with the Oppel-Kundt and Müller-Layer figures showed a combined effect of both anisotropy and illusions. The data demonstrated that illusions and anisotropy are to be interpreted as independent factors, which converge to an algebraic summation in a simultaneous manifestation. 相似文献
2.
D. T. Booth 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(5):399-404
Incubation temperature and the amount of water taken up by eggs from the substrate during incubation affects hatchling size
and morphology in many oviparous reptiles. The Brisbane river turtle Emydura signata lays hard-shelled eggs and hatchling mass was unaffected by the amount of water gained or lost during incubation. Constant
temperature incubation of eggs at 24 °C, 26 °C, 28 °C and 31 °C had no effect on hatchling mass, yolk-free hatchling mass,
residual yolk mass, carapace length, carapace width, plastron length or plastron width. However, hatchlings incubated at 26 °C
and 28 °C had wider heads than hatchlings incubated at 24 °C and 31 °C. Incubation period varied inversely with incubation
temperature, while the rate of increase in oxygen consumption during the first part of incubation and the peak rate of oxygen
consumption varied directly with incubation temperature. The total amount of oxygen consumed during development and hatchling
production cost was significantly greater at 24 °C than at 26 °C, 28 °C and 31 °C. Hatchling mass and dimensions and total
embryonic energy expenditure was directly proportional to initial egg mass.
Accepted: 18 March 1998 相似文献
3.
The fluorescence anisotropy of Photosystem I (PS I) particles, isolated from spinach chloroplasts and containing approximately
200 chlorophyll molecules per reaction center, is investigated at low temperatures. The particles are oriented by squeezing
in polyacrylamid gels with different macroscopic deformation parameters. Fluorescence anisotropy is measured upon steady state
excitation with a laser line at 632.8 nm. A formula for the fluorescence anisotropy in oriented Photosystem I particles is
applied for a different polarization of the linearly polarized exciting light. Our calculations are based on the consideration
of the Photosystem I complex as a triple-chromophore complex: the absorbing chlorophyll molecules (chl), belonging to the
light-harvesting complex of PS I (LHC), and two fluorophores, emitting at 720 nm (F720) and at 735 nm (F735), respectively.
Using polarized fluorescence spectroscopy with a different polarization of the linearly polarized exciting light, the experimental
dependence of the fluorescence anisotropy on this polarization is obtained. Based on this dependence and applying the derived
formula, as a first approximation, both the orientation of the photosynthetic pigments with respect to the membrane and their
mutual orientation are determined in PS I particles. As the most probable average orientational angles in PS I particles,
we obtained the values 35°÷ 50°, 50°÷ 60°, and 65°÷ 67° for the absorbing dipoles of chl and for the emission dipoles of F720
and F735, respectively, with the normal of the plane of the membrane. For their mutual orientation, the following limits are
determined: 10°÷ 20°, 40 ± 2°, 20°÷ 30° for the angles between chl and F720, chl and F735; and F720 and F735, correspondingly.
Of course, the values of the angles estimated as a result of our study are an average value of all angles of the excited transitions
and must be considered as their first approximation valid for the idealized case when all PS I particles are oriented in gel.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
4.
K. Hayakawa Y. Ueno S. Kawamura T. Kato R. Hayashi 《Applied microbiology and biotechnology》1998,50(4):415-418
In order to test the possibility of utilizing high pressure in bioscience and biotechnology, a simple method for high-pressure
generation and its use for microbial inactivation have been studied. When a pressure vessel was filled with water, sealed
tightly and cooled to sub-zero temperatures, high pressure was generated in the vessel. The pressure generation was 60 MPa
at −5 °C, 103 MPa at −10 °C, and 140 MPa at −15 °C, −20 °C, and −22 °C. The high pressure generated inactivated microorganisms
effectively: yeasts (Saccharomyces cerevisiae and Zygosaccharomyces rouxii), bacteria (Lactobacillus brevis and Eschericia coli), and fungi (Aspergillus niger and Aspergillus oryzae) were completely inactivated when stored in sealed vessels −20 °C for 24 h. However, Staphylococcus aureus was only partly inactivated under the same conditions. This method opens up a new application of high pressure for storing,
transporting, and sterilizing of foods and biological materials.
Received: 28 July 1997 / Received last revision: 12 June 1998 / Accepted: 19 June 1998 相似文献
5.
G. von der Emde H. Bleckmann 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,181(5):511-524
Electroreceptive afferents from A- and B-electroreceptor cells of mormyromasts and Knollenorgans were tested for their sensitivity
to different stimulus waveforms in the weakly electric fish Gnathonemus petersii. Both A- and B-mormyromast cells had their lowest sensitivity to a waveform similar to the self-generated electric organ
discharge (EOD) (around 0° phase-shift). Highest sensitivities, i.e. lowest response thresholds, in both A- and B-cells were
measured at phase shifts of +135°. Thus, both cell types were inversely waveform tuned. The sensitivity of B-cells increased
sharply with increasing waveform distortions. Their tuning curves had a sharp minimum of sensitivity at +7° phase shift. A-cells
had a much broader waveform tuning with a plateau level of low sensitivity from +24° to −15°. Across a 360° cycle of phase-shifts,
the range of thresholds was 16 dB for individual B-cells and 4.5 dB for individual A-cells. Knollenorgan afferents were tuned
to 0° phase-shifted EODs and had a dynamic range of 12 dB. Lowest sensitivities were measured at a phase shift of +165°. Experiments
with computer-generated stimuli revealed that the strong sensitivity of mormyromast B-cells of EOD waveform distortions cannot
be attributed to any of the seven waveform parameters tested. In addition, EOD stimuli must have the correct duration for
B-cells to respond to waveform distortions. Thus, waveform tuning appears to be based on the specific combination of several
waveform parameters that occur only with natural EODs.
Accepted: 28 April 1997 相似文献
6.
A. D. S. Bala T. T. Takahashi 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2000,186(5):425-434
The pupil of an awake, untrained, head-restrained barn owl was found to dilate in response to sounds with a latency of about
25 ms. The magnitude of the dilation scaled with signal-to-noise ratio. The dilation response habituated when a sound was
repeated, but recovered when stimulus frequency or location was changed. The magnitude of the recovered response was related
to the degree to which habituating and novel stimuli differed and was therefore exploited to measure frequency and spatial
discrimination. Frequency discrimination was examined by habituating the response to a reference tone at 3 kHz or 6 kHz and
determining the minimum change in frequency required to induce recovery. We observed frequency discrimination of 125 Hz at
3 kHz and 250 Hz at 6 kHz – values comparable to those reported by others using an operant task. Spatial discrimination was
assessed by habituating the response to a stimulus from one location and determining the minimum horizontal speaker separation
required for recovery. This yielded the first measure of the minimum audible angle in the barn owl: 3° for broadband noise
and 4.5° for narrowband noise. The acoustically evoked pupillary dilation is thus a promising indicator of auditory discrimination
requiring neither training nor aversive stimuli.
Accepted: 28 February 2000 相似文献
7.
The hypothesis that the Ajime-loach, Niwaella delicata, is guided to groundwater seepages by a positive thermotaxis in autumn, was tested by a field investigation and aquarium-based
experiments. A total of 763 individuals of N. delicata were captured from October to November in a groundwater trap in the Yasu River, Shiga Prefecture. Niwaella delicata began to be captured as the temperature of the surface water fell to 15.8° ± 1.1°C (mean ± SD) and that of the groundwater
to 15.5° ± 0.9°C. Groundwater was often warmer than surface water at night or occasionally all day, and the difference in
temperature reached a maximum of 1.3°C at the night on 5 November. For the diel pattern of captures, nocturnal capture was
higher than diurnal capture when the groundwater was warmer at night and colder during the daytime, whereas both diurnal and
nocturnal captures were high when the groundwater was always warmer than the surface water. The aquarium-based experiments
showed that N. delicata choose warmer water, ranging from 18.4° to 22.2°C, just before the capture period in the Yasu River, and are sensitive to
differences in water temperature of 1.3° ± 0.1°C. Although the present results broadly support the hypothesis, a part of the
results indicates that water temperature gradients may not be the only factor involved in the groundwater selection of N. delicata. 相似文献
8.
Bokas D Uy D Grattepanche F Duportail G Guedon E Delaunay S Goergen JL 《Applied microbiology and biotechnology》2007,76(4):773-781
1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) was used to assess the cell envelope fluidity of Corynebacterium glutamicum 2262 during a temperature-triggered glutamate producing process. Because the fluorescence lifetime of TMA-DPH was shown to
be constant all over the process, fluorescence anisotropy can be considered as a good index of cell envelope fluidity. When
the temperature of the fed-batch culture was increased from 33 to 39°C to induce glutamate excretion, the fluorescence anisotropy
values decreased from 0.212 ± 0.002 to 0.186 ± 0.002 (corresponding to an increase in the cell fluidity), while the specific
glutamate production rate reached its maximal value. The increase in fluidity of the C. glutamicum cell envelope was not due to a physical effect related to the temperature elevation, but rather to an alteration of the composition
of the cell envelope. Using a mutant devoid of corynomycolates, significant differences in fluorescence anisotropy values
were obtained compared to the wild-type strain, suggesting that TMA-DPH is mainly anchored into the corynomycomembrane. Differences
in fluorescence anisotropy were also observed when the bacteria were cultivated at 33, 36, 38, and 39°C in batch cultures,
and a linear relationship was obtained between the maximum specific glutamate production rate and the measured fluidity. When
using the glutamate non-producing variant of C. glutamicum 2262, the fluorescence anisotropy remained constant at 0.207 ± 0.003 whatever the applied temperature shift. This suggests
that the fluidity of the Corynebacteria mycomembrane plays an important role in glutamate excretion during the temperature-triggered
process. 相似文献
9.
M. Giurfa G. Zaccardi M. Vorobyev 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1999,185(6):591-600
Honeybees Apis mellifera detect coloured targets presented to the frontal region of their compound eyes using their colour vision system at larger
visual angles (α > 15°), and an achromatic visual system based on the long-wave photoreceptor type at smaller visual angles
(5° < α < 15°). Here we examine the capability of the dorsal, ventral and frontal regions of the eye for colour detection.
The minimum visual angle αmin at which the bees detect a stimulus providing both chromatic contrast and receptor-specific contrasts to the three receptor
types varies for the different regions of the eye: 7.1 ± 0.5° for the ventral region, 8.2 ± 0.6° for the dorsal region and
4.0 ± 0.5° for the frontal region. Flight trajectories show that when the target was presented in the horizontal plane, bees
used only the ventral region of their eyes to make their choices. When the targets appeared dorsally, bees used the frontodorsal
region. This finding suggests that pure dorsal detection of coloured targets is difficult in this context. Furthermore, αmin in the ventral plane depends on receptor-specific contrasts. The absence of S-receptor contrast does not affect the performance
(αmin = 5.9 ± 0.5°), whilst the absence of M- and L-receptor contrast significantly impairs the detection task. Minimal visual
angles of 10.3 ± 0.9° and 17.6 ± 3°, respectively, are obtained in these cases. Thus, as for many visual tasks, the compound
eye of the honeybee shows a regionalisation of colour detection that might be related to peripheral or central specialisations.
Accepted: 28 September 1999 相似文献
10.
The ability of a photobioreactor to fix CO2 was evaluated with the thermophilic cyanobacterium, Synechocystis aquatilis SI-2. The reactor consisted of three to five flat plates of transparent acrylic plastic standing upright and in parallel
and giving a 0.015-m light path. The reactor was 0.8 m high and 1 m long with 9 l working volume. The effects of the orientation
of the vertical bioreactor, distance between the plates, and culture temperature on the productivity of biomass were investigated
during the summer of 1998 in Kamaishi (39°N, 142°E), Japan. When the illuminated surface reactor was placed in an east–west-facing
orientation, the biomass productivity was roughly 1.4-fold higher than that obtained in a north–south-facing orientation,
because the former received more solar energy than the latter. The productivity based on the overall land area was the same
for plates set either 0.25 m or 0.5 m apart. However, the volumetric productivity of the reactor in which the plates were
set 0.25 m apart was lower than that when the plates were set 0.5 m apart, since the former plates received relatively lower
solar irradiation because of severe mutual shading. When the culture temperature was maintained in its optimal range (37–43 °C),
the productivity was 50% greater than that obtained in a culture at ambient temperature (20–44 °C). The biomass productivity
and CO2 fixation rate were investigated under various experimental conditions. The maximum rate of 53 g CO2 m−2 day−1 was achieved in the temperature-regulated culture with the reactor set in an east–west-facing orientation, the distance between
plates being 0.25 m.
Received: 6 may 1999 / Received revision: 14 June 1999 / Accepted 5 July 1999 相似文献
11.
A computational model of a dot-pattern selective neuron is proposed. This type of neuron is found in the inferotemporal cortex
of monkeys. It responds strongly to groups of dots and spots of light intensity variation but very weakly or not at all to
single dots and spots that are not part of a pattern. This non-linear behaviour is quite different from the spatial frequency
filtering behaviour exhibited by other neurons that react to spot-shaped stimuli, such as neurons with centre-surround receptive
field profiles found in the lateral geniculate nuclei and layer 4Cβ of V1. It is implemented in the proposed computational model by using an AND-type non-linearity to combine the responses
of centre-surround cells. The proposed model is capable of explaining the results of neurophysiological experiments as well
as certain psychophysical observations.
Received: 20 December 1999 / Accepted in revised form: 3 March 2000 相似文献
12.
The seasonal variation in the foraging behaviour of king penguins (Aptenodytes patagonicus) was studied at Heard Island (53°05′S, 73°30′E) during 1992/1993. On seven occasions throughout the breeding cycle, time-depth-light
recorders were deployed on breeding adults to record the dive activities and foraging. Foraging locations changed with season:
in autumn and spring 1992, adults foraged between 48–52°S and 74–78°E, about 370 km NNE of Heard Island close to the Polar
Front. Two penguins tracked in winter travelled 2220 km east of Heard Island (95°E) along the northern ice limit, and 1220 km
south of Heard Island to approximately 65°S, respectively. In spring (October), the penguins again foraged further north than
during winter. The foraging area utilised in October overlapped the area where the penguins foraged in March/April. The penguins'
diving behaviour also varied seasonally: the modal depth of deep dives (>50 m) increased from about 100 m in February to 220 m
in October. Mean dive depths increased from 70 ± 52 m in March 1992 to 160 ± 68 m in August 1992. Penguins dived deep (>50 m)
only during daylight hours (16 h in February, 9 h in July). Mean dive durations ranged from 2.9 ± 1.1 min in March 1992 to
5.1 ± 1.2 min in August 1992. Associated with changes in foraging location and dive behaviour was a change in diet composition:
during summer the penguins ingested mainly myctophid fish (>90%) while in winter the most important diet item was squid.
Accepted: 19 October 1998 相似文献
13.
Changes in selected aspects of immune function in the leopard frog, Rana pipiens, associated with exposure to cold 总被引:3,自引:0,他引:3
Gregory D. Maniero Cynthia Carey 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(4):256-263
The effect of exposure to low temperatures (5 °C) on lymphocyte proliferation, leukocyte populations, and serum complement
levels was examined in the northern leopard frog, Rana pipiens. Proliferation of T lymphocytes in response to phytohemagglutinin stimulation was significantly decreased in frogs kept for
2, 3, and 5 months at 5 °C compared to that of animals kept at 22 °C. A significant increase in the average percentage of
neutrophils and a decrease in the mean percentage of eosinophils was observed in the blood of frogs held for 5 months in the
cold compared to animals held at 22 °C for the same length of time. Mean serum complement activity after 1 month at 5 °C was
significantly reduced in comparison to animals held at 22 °C and was not detectable after 5 months in the cold. Recovery of
complement levels at room temperature (22 °C) was also examined after cold exposure. Complement levels were significantly
higher than controls (at 22 °C) in frogs returned to 22 °C for 7 and 14 days after 5 months in the cold. After frogs were
held at 5 °C for 1 month, serum complement levels increased significantly within 2 days after returning to 22 °C and continued
to rise 5 and 9 days after warming. Injections with Aeromonas hydrophila following a 5-week exposure to 5 °C failed to cause death or observable symptoms of disease in frogs that were returned to
22 °C.
Accepted: 20 November 1996 相似文献
14.
H. Ramløv 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(3):224-235
The microclimate in the habitat of the New Zealand alpine weta Hemideina maori is very variable with winter temperatures down to −6 °C under the rocks where the insects are found. Subfreezing temperatures
may in winter prevail for up to 17 days but diurnal cycles of freezing and thawing are common, as is also the case in summer.
Rates of temperature change can be very high and up to −7.20 °C/h. During winter, humidity was high for extended periods ranging
from 70% to 100% relative humidity (RH). In the summer, humidity ranged from 30% RH during the day to 100% RH at night. The
supercooling point of the haemolymph was approximately −8 °C year round, caused by a heat labile substance. The supercooling
point of the haemolymph of an insect of the same genus, Hemideina femorata not regularly exposed to subfreezing temperatures, was ca. −16.5 °C. Thermal hysteresis was not detected in the haemolymph
of H. maori. Haemolymph osmolality varied from 380 mOsm (summer) to 700 mOsm (winter). Body water content was ca. 75% all year round.
Total concentrations of sodium, potassium and chloride in haemolymph varied from 170 mM (winter) to 250 mM (summer). The total
concentration of free amino acids varied from 58 mM (summer) to 263 mM (winter). This variation was mostly due to proline
which varied from ca. 15 mM (summer) to ca. 100 mM (winter). The freeze-tolerant weta H. maori is exposed to a highly variable and cold environment all year round and several properties of its haemolymph composition
can be attributed to these climatic conditions, e.g. the presence of ice-nucleating agents and an increase in the concentration
of proline during cold hardening in the autumn.
Accepted: 22 February 1999 相似文献
15.
Wilson RS James RS Johnston IA 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(2):117-124
Among amphibians, the ability to compensate for the effects of temperature on the locomotor system by thermal acclimation
has only been reported in larvae of a single species of anuran. All other analyses have examined predominantly terrestrial
adult life stages of amphibians and found no evidence of thermal acclimatory capacity. We examined the ability of both tadpoles
and adults of the fully aquatic amphibian Xenopus laevis to acclimate their locomotor system to different temperatures. Tadpoles were acclimated to either 12 °C or 30 °C for 4 weeks
and their burst swimming performance was assessed at four temperatures between 5 °C and 30 °C. Adult X. laevis were acclimated to either 10 °C or 25 °C for 6 weeks and their burst swimming performance and isolated muscle performance
was determined at six temperatures between 5 °C and 30 °C. Maximum swimming performance of cold-acclimated X. laevis tadpoles was greater at cool temperatures and lower at the highest temperature in comparison with the warm-acclimated animals.
At the test temperature of 12 °C, maximum swimming velocity of tadpoles acclimated to 12 °C was 38% higher than the 30 °C-acclimation
group, while at 30 °C, maximum swimming velocity of the 30 °C-acclimation group was 41% faster than the 12 °C-acclimation
group. Maximum swimming performance of adult X. laevis acclimated to 10 °C was also higher at the lower temperatures than the 25 °C acclimated animals, but there was no difference
between the treatment groups at higher temperatures. When tested at 10 °C, maximum swimming velocity of the 10 °C-acclimation
group was 67% faster than the 25 °C group. Isolated gastrocnemius muscle fibres from adult X. laevis acclimated to 10 °C produced higher relative tetanic tensions and decreased relaxation times at 10 °C in comparison with
animals acclimated to 25 °C. This is only the second species of amphibian, and the first adult life stage, reported to have
the capacity to thermally acclimate locomotor performance.
Accepted: 28 October 1999 相似文献
16.
We studied in batch reactors the kinetics and characterization of 70 °C, volatile fatty acids (VFAs)-grown, upflow anaerobic
sludge blanket granular sludge with 55 and 35 °C sludge as reference. The half-saturation constant (K
s), the inhibition constant (K
i), the maximum specific methane production rate (μCH4max), and the inhibition response coefficient (n) of the 70 °C sludge were 6.15 mM, 48.2 mM, 0.132 h−1, and 2.48, respectively, while no inhibition occurred at 55 and 35 °C, where the K
s was 3.67 and 3.82 mM, respectively. At 70 °C, the highest initial specific methanogenic activity (ISMA, 0.311 gCH4-COD per gram volatile solids per day) on VFAs was about 12–15% lower than that on acetate and three to four times less than
the ISMA for the 55 and 35 °C sludge. In the acetate conversion study, residual acetate (79 mg l−1) at 70 °C was three to five times higher than that at 55 and 35 °C. Further, the methane produced as percentage of the acetate
consumed at 70 °C (89%) was lower than that at 55 (95%) and 35 °C (97%). At 70 °C, 10% of the ISMA remained after 15 days
of starvation as compared to 26% (55 °C) and 92% (35 °C) after 30 days of starvation. Thus, the kinetics of the 70 °C granular
sludge seem to differ from those at 55 and 35 °C.
Received: 1 February 1999 / Accepted: 20 March 1999 相似文献
17.
The morphology of eggs and larvae of Awaous melanocephalus is described. The eggs measured 0.33–0.35 mm in long-axis diameter and 0.32–0.34 mm in short-axis diameter. Newly hatched
larvae (0.90–0.99 mm in notochord length, NL; 0.93–1.04 mm in total length, TL) were poorly developed, lacking a mouth and
having a large yolk sac and unpigmented eyes. The mouth opened and the eyes became fully pigmented 3 days after hatching (1.78–2.00 mm
NL, 1.88–2.10 mm TL). The yolk sac was completely absorbed 5 days after hatching at a water temperature of 27°–28°C. 相似文献
18.
Chuong MC Palugan L Su TM Busano C Lee R Di Pretoro G Shah A 《AAPS PharmSciTech》2010,11(4):1650-1661
Vitamin B3 is made up of niacin (nicotinic acid) and its amide, niacinamide. Both have equivalent vitamin activity, but only niacin
(not niacinamide) is effective in lowering elevated low-density lipoprotein cholesterol and triglyceride levels in the blood.
Administration of an extended-release (ER) oral tablet would frequently encounter food. If hydrogel is used to formulate the
matrix of a biopharmaceutical classification system I drug (high solubility and high permeability), the dosage form absorbs
water and swells.. The softened outer layer may be slashed off by food present in the stomach, thus, exposing the core tablet
more readily for water absorption and speeding up drug release from its original designed rate. This project aimed to formulate
niacin CR pellets made of hydrophobic inert matrix. After niacin was melted with excipients and cooled, the mass was extruded
and spheronized into pellets. Size distribution and flowability were determined before pellets were filled into hard gelatin
capsule. The USP dissolution study revealed that a candidate formulation of 250 mg in strength released similar amount of
niacin as its commercial reference, niacin controlled-release 500 mg tablet, in 6 h (223.9 ± 23.8 mg, n = 4 versus 259.4 ± 2.6 mg, n = 3). The differential scanning calorimetry study of the pellets in capsules stored in 40°C for 4 weeks, and the content
assay of capsules in 40°C up to 6 months suggested that niacin was stable within the innovative formulation. In vitro release from this innovative ER capsules stored at 40°C up to 4 weeks were also investigated. 相似文献
19.
Thermal acclimation of locomotor performance in tadpoles of the frog Limnodynastes peronii 总被引:3,自引:0,他引:3
R. S. Wilson C. E. Franklin 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(6):445-451
Previous analyses of thermal acclimation of locomotor performance in amphibians have only examined the adult life history
stage and indicate that the locomotor system is unable to undergo acclimatory changes to temperature. In this study, we examined
the ability of tadpoles of the striped marsh frog (Limnodynastes peronii) to acclimate their locomotor system by exposing them to either 10 °C or 24 °C for 6 weeks and testing their burst swimming
performance at 10, 24, and 34 °C. At the test temperature of 10 °C, maximum velocity (Umax) of the 10 °C-acclimated tadpoles was 47% greater and maximum acceleration (Amax) 53% greater than the 24 °C-acclimated animals. At 24 °C, Umax was 16% greater in the 10 °C-acclimation group, while there was no significant difference in Amax or the time taken to reach Umax (T-Umax). At 34 °C, there was no difference between the acclimation groups in either Umax or Amax, however T-Umax was 36% faster in the 24 °C-acclimation group. This is the first study to report an amphibian (larva or adult) possessing
the capacity to compensate for cool temperatures by thermal acclimation of locomotor performance. To determine whether acclimation
period affected the magnitude of the acclimatory response, we also acclimated tadpoles of L. peronii to 10 °C for 8 months and compared their swimming performance with tadpoles acclimated to 10 °C for 6 weeks. At the test
temperatures of 24 °C and 34 °C, Umax and Amax were significantly slower in the tadpoles acclimated to 10 °C for 8 months. At 10 °C, T-Umax was 40% faster in the 8-month group, while there were no differences in either Umax or Amax. Although locomotor performance was enhanced at 10 °C by a longer acclimation period, this was at the expense of performance
at higher temperatures.
Accepted: 25 June 1999 相似文献
20.
The carbon-flux via algal bloom events involves bacteria as an important mediator. The present study, carried out during the
spring inter-monsoon month of April 2008 onboard CRV Sagar Manjusha-06 in the Eastern Arabian Sea, addresses the bloom-specific
flow of carbon to bacteria via chromophoric dissolved organic matter (CDOM). Eleven stations monitored were located in the
coastal, shelf and open-ocean areas off Ratnagiri (16°59′N, 73°17′E), Goa (15°30′N, 73°48′E) and Bhatkal (13°58′N, 74°33′E)
coasts. Visible bloom of “saw-dust” color in the Ratnagiri shelf were microscopically examined and the presence of cyanobacteria
Trichodesmium erythraeum and T. thieabautii with cell concentrations as high as 3.05 × 106 trichomes L−1 was recorded. Total bacterial counts (TBC) varied between 94.09 × 108 cells L−1 in the bloom to 1.34 × 108 cells L−1 in the non-bloom area. Chromophoric dissolved organic matter (CDOM) concentrations averaged 2.27 ± 3.02 m−1 (absorption coefficient 325 nm) in the bloom to 0.28 ± 0.07 m−1 in the non-bloom waters respectively. CDOM composition varied from a higher molecular size with lower aromaticity in the
bloom to lower molecular size and increased aromaticity in the non-bloom areas respectively. Strong positive relationship
of TBC with Chlorophyll a (R
2 = 0.65, p < 0.01) and CDOM concentrations (R
2 = 0.8373, p = 0.01) in the bloom area indicated hydrolysis and/or uptake of CDOM by bacteria. Absorption by mycosporine-like amino acid
palythene (λ
max = 360 nm) was recorded in the filtrate of bloom. Morphotypes of Trichodesmium-associated bacteria revealed a higher frequency of Gram-positive rods. The role of bacteria in relation to changing CDOM
nature and as a factor in affecting oxygen content of the water column is discussed in context of the Arabian Sea. 相似文献