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1.
Temporal selectivity for complex signals by single neurons in the torus semicircularis of Pleurodema thaul (Amphibia: Leptodactylidae) 总被引:2,自引:0,他引:2
Mario Penna Wen-Yu Lin Albert S. Feng 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(4):313-328
Responses of auditory neurons in the torus semicircularis (TS) of Pleurodema thaul, a leptodactylid from Chile, to synthetic stimuli having diverse temporal patterns and to digitized advertisement calls of
P. thaul and three sympatric species, were recorded to investigate their temporal response selectivities. The advertisement call of
this species consists of a long sequence of sound pulses (a pulse-amplitude-modulated, or PAM, signal) having a dominant frequency
of about 2000 Hz. Each of the sound pulses contains intra-pulse sinusoidal-amplitude-modulations (SAMs). Synthetic stimuli
consisted of six series in which the following acoustic parameters were systematically modified, one at a time: PAM rate,
pulse duration, number of pulses, and intra-pulse SAM rate. The carrier frequency of these stimuli was set at the characteristic
frequency (CF) of the isolated units (n = 47). Response patterns of TS units to synthetic call variants reveal different degrees of selectivities for each of the
temporal variables, with populations of neurons responding maximally to specific values found in the advertisement call of
this species. These selectivities are mainly shaped by neuronal responsiveness to the overall sound energy of the stimulus
and by the inability of neurons to discharge to short inter-pulse gaps.
Accepted: 30 October 1996 相似文献
2.
K.-H. Esser B. Lud 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(5):513-522
In the lesser spear-nosed bat, Phyllostomus discolor, maternal directive calls are characterized by an individual type of sinusoidal frequency modulation (= SFM) pattern. Beside
modulation frequency, modulation depth, carrier frequency, and number of modulation cycles per call contribute to the mother's
vocal signature. Since juvenile P. discolor learn to adapt their isolation calls to the corresponding call characteristics of the own mother or even to playback of a
computer-stored directive call, if hand-reared in the absence of conspecifics, the bats' auditory system ought to be able
to resolve interindividual differences in communication call structure. However, quantitative psychoacoustic data on the discrimination
of SFM signals in this species are not available. Thus, in the present study, lesser spear-nosed bats were trained in a two-alternative
forced-choice procedure to discriminate between two alternatingly presented SFM sound signals differing in modulation frequency.
Other characteristics of acoustic stimuli were identical and designed to mimick the fundamental of species-specific calls.
By gradually reducing the difference in modulation frequency between both stimuli within the behavioural relevant range until
the animals' performance dropped below the 75%-correct level, a considerable auditory spectro-temporal resolution has been
revealed. Particularly in comparison to the overall interindividual variation of this call parameter (minimal modulation frequency = 49 Hz,
maximum = 100 Hz), the determined average difference limen for modulation frequency of 2.42 ± 0.29 Hz seems substantial and
sufficient for labelling individuals.
Accepted: 30 November 1996 相似文献
3.
Morten Buhl Jørgensen Jakob Christensen-Dalsgaard 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(5):503-511
We studied the directionality of spike timing in the responses of single auditory nerve fibers of the grass frog, Rana temporaria, to tone burst stimulation. Both the latency of the first spike after stimulus onset and the preferred firing phase during
the stimulus were studied. In addition, the directionality of the phase of eardrum vibrations was measured. The response latency
showed systematic and statistically significant changes with sound direction at both low and high frequencies. The latency
changes were correlated with response strength (spike rate) changes and were probably the result of directional changes in
effective stimulus intensity. Systematic changes in the preferred firing phase were seen in all fibers that showed phaselocking
(i.e., at frequencies below 500–700 Hz). The mean phase lead for stimulation from the contralateral side was approximately
140° at 200 Hz and decreased to approximately 100° at 700 Hz. These phaseshifts correspond to differences in spike timing
of approximately 2 ms and 0.4 ms respectively. The phaseshifts were nearly independent of stimulus intensity. The phase directionality
of eardrum vibrations was smaller than that of the nerve fibers. Hence, the strong directional phaseshifts shown by the nerve
fibers probably reflect the directional characteristics of extratympanic pathways.
Accepted: 23 November 1996 相似文献
4.
Alexander V. Galazyuk Albert S. Feng 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(4):301-311
Responses of 117 single- or multi-units in the auditory cortex (AC) of bats (Myotis lucifugus) to tone bursts of different stimulus durations (1– 400 ms) were studied over a wide range of stimulus intensities to determine
how stimulus duration is represented in the AC. 36% of AC neurons responded more strongly to short stimulus durations showing
short-pass duration response functions, 31% responded equally to all pulse durations (i.e., all-pass), 18% responded preferentially
to stimuli having longer durations (i.e., long-pass), and 15% responded to a narrow range of stimulus durations (i.e., band-pass).
Neurons showing long-pass and short-pass duration response functions were narrowly distributed within two horizontal slabs
of the cortex, over the rostrocaudal extent of the AC. The effects of stimulus level on duration selectivity were evaluated
for 17 AC neurons. For 65% of these units, an increase in stimulus intensity resulted in a progressive decrease in the best
duration. In light of the unusual intensity-dependent duration responses of AC neurons, we hypothesized that the response
selectivities of AC neurons is different from that in the brainstem. This hypothesis was validated by results of study of
the duration response characteristics of single neurons in the inferior colliculus.
Accepted: 8 November 1996 相似文献
5.
Atle Wibe Anna-Karin Borg-Karlson Torbjörn Norin Hanna Mustaparta 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(6):585-595
Naturally produced plant volatiles, eliciting responses of single olfactory receptor neurons in the pine weevil, have been
identified by gas chromatography linked with mass spectrometry. The receptor neurons (n = 72) were classified in 30 types, according to the compound which elicited the strongest response in each neuron, 20 of
which compounds were identified. Most potent for 14 types of neurons (n = 50) were monoterpenes, including bicyclic (e.g. α-pinene, camphor and myrtenal) for 8 types (n = 32), monocyclic (limonene, carvone, α-terpinene) for 3 types (n = 12) and acyclic (e.g. β-myrcene and linalool) for 3 types (n = 6). Other compounds eliciting strongest responses of a neuron were five sesquiterpenes, including α-copaene and a farnesene-isomer,
and an anethole type which has no biosynthetic relationship with terpenes. Within one type, receptor neurons with quite selective
responses to the most potent compound as well as neurons with additional responses to several, structurally similar compounds
were found, indicating that the neurons may have the same functional types of membrane receptors, but different sensitivities.
Response spectra of neurons within the bicyclic-, mono-cyclic and acyclic types showed more overlapping than across the neuron
types. Minimal overlapping response spectra was found between monoterpene and sesquiterpene neurons. The results suggest that
this structure-activity relationship is significant for encoding plant odour information in the pipe weevil.
Accepted: 6 January 1997 相似文献
6.
Dagmar Vogel Horst Bleckmann 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(6):671-681
The surface-feeding fish Aplocheilus lineatus uses its cephalic lateral line to detect water surface waves caused by prey insects. The ability of Aplocheilus to discriminate between surface waves with aid of the lateral line system was tested by go/no-go conditioning. Our results
show that Aplocheilus can distinguish between single-frequency surface wave stimuli with equal velocity or equal acceleration amplitudes which
differ only in frequency. Frequency difference limens were about 15%, i.e. fish distinguished a 20-Hz wave stimulus from a
23-Hz stimulus in 100% of the trials. Aplocheilus can also discriminate between pure sine-wave stimuli and sine waves which show abrupt frequency changes. In contrast, fish
were unable to distinguish amplitude-modulated wave stimuli (carrier frequency 20, 40 and 60 Hz, modulation frequency 10 and
20 Hz) from pure sine waves of the same frequency, even if amplitude modulation depth was 80%.
Accepted: 27 December 1996 相似文献
7.
In some species of hagfish, the phenomenon of chromosome elimination occurs during embryogenesis. However, only two repetitive
DNA families are known to be represented in chromosomes that are eliminated from somatic cells of the Japanese hagfish Eptatretus okinoseanus. Using molecular analyses, another germ line-restricted, highly repetitive DNA family has been detected in another Japanese
hagfish, Paramyxine atami. The repeat unit of this family, which is 83 bp long, has been designated “EEPa1”, for Eliminated Element of P. atami 1. DNA filter hybridization using EEPa1 as a probe revealed that this family is shared among several species and is conserved
in the germline DNA. Although eliminated, repetitive DNA that is shared interspecifically has not been reported in hagfish
species, cases of chromatin diminution and chromosome elimination processes have been described previously in other organisms.The
patterns and intensities of hybridization signals suggest that members of the repetitive DNA family defined by EEPa1 have
undergone concerted molecular evolution.
Received: 7 January 1997 / Accepted: 13 May 1997 相似文献
8.
Dagmar von Helversen Otto von Helversen 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(4):373-386
Many gomphocerine grasshoppers communicate acoustically: a male's calling song is answered by a female which is approached
phonotactically by the male. Signals and recognition mechanisms were investigated in Chorthippus biguttulus with regard to the cues which allow sex discrimination. (1) The stridulatory files on the hindfemur of both sexes are homologous
in that they are derived from the same row of bristles, but convergent with respect to the “pegs”. In males the pegs are derived
from the bristles, and in females from the wall of the bristle's cup. (2) Male and female songs are generated by similar,
probably homologous motor programs, but differ in the duration, intensity, “gappyness” of syllables, risetime of pulses, and
the frequency spectra. The hindleg co-ordination during stridulation and the resulting temporal song patterns are less variable
in males than in females. (3) For both sexes, recognition of a mate's signal depends on species-specific syllable structure.
For males it is essential that the female syllables consist of distinct short pulses, whereas females reject “gappy” syllables.
Males strongly prefer “ramped” pulses, females respond to syllables irrespective of steeply or slowly rising ramps. Males
react only to the low-frequency component, whereas females prefer spectra containing both, low and high frequency components.
Accepted: 20 November 1996 相似文献
9.
Photoperiodic time measurement regulating larval diapause in the pitcher-plant mosquito, Wyeomyia smithii, varies in a close relationship with latitude. The critical photoperiod mediating the maintenance and termination of diapause
is positively correlated with latitude (r
2 = 0.977) among six populations from southern (30–31° N), intermediate (40° N), and northern (46–49° N) latitudes in North
America. The developmental response to unnaturally short and to unnaturally long photoperiods declines with increasing latitude,
so that longer critical photoperiods are associated with a downward rather than a lateral shift in the photoperiodic response
curve. Exotic light and dark cycles of varying period (T) with a short (10 h) photophase and a scotophase ranging from 14
(T = 24) to 62 (T = 72) h, reveal two geographic patterns: a decline in perturbability of the photoperiodic clock with increasing
latitude, and no change with latitude in the 21-h period of rising and falling development with increasing T. These results
show (1) that there is a rhythmic component to photoperiodic time measurement in W. smithii, (2) that the period of this rhythm is about 21 h in all populations, and (3) that more northern populations show decreasing
responsiveness to photoperiod and increasing stability against perturbation by exotic period lengths (T > 24). Previous studies
on W.␣smithii indicate that this single temperate species of a tropical and subtropical genus has evolved from south to north. We therefore
conclude that the evolution of increasing critical photoperiod in W. smithii during its adaptive radiation into North America has more likely involved the amplitude and not the period of the underlying
circadian pacemaker.
Received: 22 July 1996 / Accepted: 30 September 1996 相似文献
10.
Morten Buhl Jørgensen Jakob Christensen-Dalsgaard 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(5):493-502
We studied the directionality of spike rate responses of auditory nerve fibers of the grassfrog, Rana temporaria, to pure tone stimuli. All auditory fibers showed spike rate directionality. The strongest directionality was seen at low
frequencies (200 – 400 Hz), where the spike rate could change by up to nearly 200␣spikes s−1. with sound direction. At higher frequencies the directional spike rate changes were mostly below 100 spikes s−1. In equivalent dB SPL terms (calculated using the fibers' rate-intensity curves) the maximum directionalities were up to
15 dB at low frequencies and below 10 dB at higher frequencies. Two types of directional patterns were observed. At frequencies
below 500 Hz relatively strong responses were evoked by stimuli from the ipsilateral (+90o) and contralateral (−90o) directions while the weakest responses were evoked by stimuli from frontal (0o or +30o) or posterior (−135o) directions. At frequencies above 800 Hz the strongest responses were evoked by stimuli from the ipsilateral direction while
gradually weaker responses were seen as the sound direction shifted towards the contralateral side. At frequencies between
500 and 800 Hz both directional patterns were seen. The directionality was highly intensity dependent. No special adaptations
for localization of conspecific calls were found.
Accepted: 23 November 1996 相似文献
11.
Life history trade-offs should be detectable as negative correlations between the relevant traits (e.g. reproductive output
versus energy storage), but may be masked by variation in resource levels among individuals. One way to detect underlying
trade-offs, at least in organisms that rely on stored energy for reproduction (“capital breeders”), may be to monitor an individual's
energy stores before and after reproduction. We analysed energy stores and reproductive output in Eulamprus tympanum, a viviparous scincid lizard that stores energy for reproduction in its tail. One predicted trade-off (that between the size
and number of offspring in a litter) is consistently observed, and is detectable with minimal information. Another predicted
trade-off (that between offspring size and subsequent energy reserves) is not apparent in our data, perhaps because of constraints
imposed by correlations among other traits. Finally, trade-offs between reproductive output and subsequent energy stores are
evident in this species, but are only detectable with information on the extent of pre-reproductive as well as post-reproductive
energy stores. For “capital breeders”, non-destructive measurement of pre- and post-reproductive energy stores may greatly
enhance our ability to detect significant life history trade-offs.
Received: 10 July 1996 / Accepted: 16 January 1997 相似文献
12.
S. J. Brown R. B. Child S. H. Day A. E. Donnelly 《European journal of applied physiology and occupational physiology》1997,75(4):369-374
Indirect indices of exercise-induced human skeletal muscle damage and connective tissue breakdown were studied following
a single bout of voluntary eccentric muscle contractions. Subjects (six female, two male), mean (SD) age 22 (2) years performed
a bout of 50 maximum voluntary eccentric contractions of the knee extensors of a single leg. The eccentric exercise protocol
induced muscle soreness (P < 0.05 Wilcoxon test), chronic force loss, and a decline in the 20:100 Hz percutaneous electrical myostimulation force ratio
[P < 0.01, repeated measures analysis of variance (ANOVA)]. Serum creatine kinase (CK) and lactate dehydrogenase (LDH) activities
were elevated (P < 0.01, repeated measures ANOVA) following the bout. The mean (SD) CK and LDH levels recorded 3 days post-exercise were 2815
(4144) IU · l–1 and 375 (198) IU · l–1, respectively. Serum alkaline phosphatase activity showed no changes throughout the study, and a non-significant increase
(P = 0.058, repeated measures ANOVA) in pyridinoline was recorded following the bout. Urinary hydroxyproline (HP) and hydroxylysine
(HL) excretion, expressed in terms of creatinine (Cr) concentration, increased after exercise (P < 0.05 and P < 0.01, respectively, repeated measures ANOVA). An increased HP:Cr was recorded 2 days post-exercise and HL:Cr was increased
above baseline on days 2, 5, and 9 post-exercise. This indirect evidence of exercise-induced muscle damage suggests that myofibre
disruption was caused by the eccentric muscle contractions. Elevated urine concentrations of indirect indices of collagen
breakdown following eccentric muscle contractions suggests an increased breakdown of connective tissue, possibly due to a
localised inflammatory response.
Accepted: 9 October 1996 相似文献
13.
S. Nakamura S. Asakawa N. Ohmido K. Fukui N. Shimizu S. Kawasaki 《Molecular & general genetics : MGG》1997,254(6):611-620
We constructed a rice Bacterial Artificial Chromosome (BAC) library from green leaf protoplasts of the cultivar Shimokita
harboring the rice blast resistance gene Pi-ta. The average insert size of 155 kb and the library size of seven genome equivalents make it one of the most comprehensive
BAC libraries available, and larger than many plant YAC libraries. The library clones were plated on seven high density membranes
of microplate size, enabling efficient colony identification in colony hybridization experiments. Seven percent of clones
carried chloroplast DNA. By probing with markers close to the blast resistance genes Pi-ta
2
(closely linked to Pi-ta) and Pi-b, respectively located in the centromeric region of chromosome 12 and near the telomeric end of chromosome 2, on average 2.2 ± 1.3
and 8.0 ± 2.6 BAC clones/marker were isolated. Differences in chromosomal structures may contribute to this wide variation
in yield. A contig of about 800 kb, consisting of 19 clones, was constructed in the Pi-ta
2
region. This region had a high frequency of repetitive sequences. To circumvent this difficulty, we devised a “two-step walking”
method. The contig spanned a 300 kb region between markers located at 0 cM and 0.3 cM from Pi-ta
2
. The ratio of physical to genetic distances (> 1,000 kb/cM) was more than three times larger than the average of rice (300
kb/cM). The low recombination rate and high frequency of repetitive sequences may also be related to the near centromeric
character of this region. Fluorescent in situ hybridization (FISH) with a BAC clone from the Pi-b region yielded very clear signals on the long arm of chromosome 2, while a clone from the Pi-ta
2
region showed various cross-hybridizing signals near the centromeric regions of all chromosomes.
Received: 14 August 1996 / Accepted: 2 December 1996 相似文献
14.
Sherri M. Jones Timothy A. Jones Roshni Shukla 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(6):631-638
Short-latency vestibular-evoked potentials to pulsed linear acceleration were characterized in the quail. Responses occurred
within 8 ms following the onset of stimuli and were composed of a series of positive and negative peaks. The latencies and
amplitudes of the first four peaks were quantitatively characterized. Mean latencies at 1.0 g ms−1 ranged from 1265 ± 208 μs (P1, N = 18) to 4802 ± 441 μs (N4, N = 13). Amplitudes ranged from 3.72 ± 1.51 μV (P1/N1, N = 18) to 1.49 ± 0.77 μV (P3/N3, N = 16). Latency-intensity (LI) slopes ranged from −38.7 ± 7.3 μs dB−1 (P1, N = 18) to −71.6 ± 21.9 μs dB−1 (N3, N = 15) and amplitude-intensity (AI) slopes ranged from 0.20 ± 0.08 μV dB−1 (P1/N1, N = 18) to 0.07 ± 0.04 μV dB−1 (P3/N3, N = 11). The mean response threshold across all animals was −21.83 ± 3.34 dB re: 1.0 g ms−1 (N = 18). Responses remained after cochlear extirpation showing that they could not depend critically on cochlear activity.
Responses were eliminated by destruction of the vestibular end organs, thus showing that responses depended critically and
specifically on the vestibular system. The results demonstrate that the responses are vestibular and the findings provide
a scientific basis for using vestibular responses to evaluate vestibular function through ontogeny and senescence in the quail.
Accepted: 18 January 1997 相似文献
15.
P. J. Fonseca A. V. Popov 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(4):417-427
1. Laser vibrometry and acoustic measurements were used to study the biophysics of directional hearing in males and females
of a cicada, in which most of the male tympanum is covered by thick, water filled tissue “pads”. 2. In females, the tympanal
vibrations are very dependent on the direction of sound incidence in the entire frequency range 1–20 kHz, and especially at
the main frequencies of the calling song (3–7 kHz). At frequencies up to 10 kHz, the directionality disappears if the contralateral
tympanum, metathoracic spiracle, and folded membrane are blocked with Vaseline. This suggests some pressure-difference receiver
properties in the ear. 3. In males, the tympanal vibrations depend on the direction of sound incidence only within narrow
frequency bands (around 1.8 kHz and at 6–7 kHz). At frequencies above 10–12 kHz, the directionality appears to be determined
by diffraction, and the ear seems to work as a pressure receiver. The peak in directionality at 6–7 kHz disappears when the
contralateral timbal, but not the tympanum, is covered. Covering the thin ventral abdominal wall causes the peak around 1.8 kHz
to disappear. 4. Most observed tympanal directionalities, except around 1.8 kHz in males, are well predicted from measured
transmissions of sound through the body and measured values of sound amplitude and phase at the ears at various directions
of sound incidence.
Accepted: 18 October 1996 相似文献
16.
William C. Lemon Richard B. Levine 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(6):597-610
During the metamorphosis of Manduca sexta the larval nervous system is reorganized to allow the generation of behaviors that are specific to the pupal and adult stages.
In some instances, metamorphic changes in neurons that persist from the larval stage are segment-specific and lead to expression
of segment-specific behavior in later stages. At the larval-pupal transition, the larval abdominal bending behavior, which
is distributed throughout the abdomen, changes to the pupal gin trap behavior which is restricted to three abdominal segments.
This study suggests that the neural circuit that underlies larval bending undergoes segment specific modifications to produce
the segmentally restricted gin trap behavior. We show, however, that non-gin trap segments go through a developmental change
similar to that seen in gin trap segments. Pupal-specific motor patterns are produced by stimulation of sensory neurons in
abdominal segments that do not have gin traps and cannot produce the gin trap behavior. In particular, sensory stimulation
in non-gin trap pupal segments evokes a motor response that is faster than the larval response and that displays the triphasic
contralateral-ipsilateral-contralateral activity pattern that is typical of the pupal gin trap behavior. Despite the alteration
of reflex activity in all segments, developmental changes in sensory neuron morphology are restricted to those segments that
form gin traps. In non-gin trap segments, persistent sensory neurons do not expand their terminal arbors, as do sensory neurons
in gin trap segments, yet are capable of eliciting gin trap-like motor responses.
Accepted: 10 January 1997 相似文献
17.
S R Soffe 《Proceedings. Biological sciences / The Royal Society》1991,246(1317):197-203
Neural mechanisms underlying selection of motor responses are largely unknown in vertebrates. This study shows that in immobilized Xenopus embryos, brief mechanical or electrical stimulation of the trunk skin can trigger sustained fictive swimming, whereas sustained pressure or repetitive electrical stimulation can evoke fictive struggling. These two rhythmic motor patterns are distinct: alternating single motor root spikes propagate from head to tail during swimming; alternating motor root bursts propagate from tail to head during struggling. As both motor patterns can be evoked in embryos with the CNS transected caudal to the cranial roots, the sensory pathway responsible must have direct access to the spinal cord. Rohon-Beard sensory neurons provide the only such pathway known. They respond appropriately to brief stimuli applied to the trunk skin, and also to repetitive electrical stimuli and sustained pressure. The results suggest that Rohon-Beard sensory neurons can both trigger sustained swimming and 'gate in' struggling motor patterns, and thus effect behavioural selection according to their pattern of activity. 相似文献
18.
A. K. Tryba H. B. Hartman 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(3):215-221
Receptors monitoring muscle force innervate the opener muscle apodeme in the walking legs of the blue crab, Callinectes sapidus. Biocytin backfills reveal 9–15 bipolar neurons with somata as large as 60 μm positioned at the distal end of the apodeme.
Sensory endings insert into the apodeme and are in series with the opener muscle. The axons of these neurons form the opener
apodeme sensory nerve that merges with the most distal branch of the opener motor nerve. Recordings reveal that the receptors
are not spontaneously active nor do they respond to passive muscle stretch. Isometric muscle contraction evoked by stimulating
the opener excitor motor neuron is the adequate stimulus for receptor firing. Most significant is the finding that during
contraction, over a wide range of forces, the firing rate of individual receptors closely parallels the rate of change of
isometric force. The peak instantaneous frequency typically occurs at the force derivative maximum, but not at maximum force
development. Thus, receptors of the opener apodeme sensory nerve more closely monitor changes in isometric force rather than
the total force achieved.
Accepted: 20 September 1996 相似文献
19.
Michael J. Webster Timothy P. Scheett Matthew R. Doyle Matthew Branz 《European journal of applied physiology and occupational physiology》1997,75(6):520-524
The purpose of this study was to investigate the effect of a thiamin derivative, thiamin tetrahydrofurfuryl disulfide (TTFD),
on oxygen uptake (˙VO2), lactate accumulation and cycling performance during exercise to exhaustion. Using a randomized, double-blind, cross-over
design with a 10-day washout between trials, 14 subjects ingested either 1 g · day−1 of TTFD or a placebo (PL) for 4 days. On day 3, subjects performed a progressive exercise test to exhaustion on a cycle ergometer
for the determination of ˙VO2submax, ˙VO2peak, lactate concentration ([La− ]), lactate threshold (ThLa) and heart rate ( f
c). On day 4, subjects performed a maximal 2000-m time trial on a cycle ergometer. A one-way analysis of variance (ANOVA) with
repeated measures was used to determine significant differences between trials. There were no significant differences detected
between trials for serial measures of ˙VO2submax, [La−] or f
c. Likewise, ˙VO2peak [PL 4.06 (0.19) TTFD 4.12 (0.19) l · min−1, P = 0.83], ThLa [PL 2.47 (0.17), TTFD 2.43 (0.16) l · min−1, P = 0.86] and 2000-m performance time [PL 204.5 (5.5), TTFD 200.9 (4.3) s, P = 0.61] were not significantly different between trials. The results of this study suggest that thiamin derivative supplementation
does not influence high-intensity exercise performance.
Accepted: 19 December 1996 相似文献
20.
Predator-induced morphological changes in an amphibian: predation by dragonflies affects tadpole shape and color 总被引:4,自引:0,他引:4
Predator-induced defenses are well studied in plants and invertebrate animals, but have only recently been recognized in
vertebrates. Gray treefrog (Hylachrysoscelis) tadpoles reared with predatory dragonfly (Aeshnaumbrosa) larvae differ in shape and color from tadpoles reared in the absence of dragonflies. By exposing tadpoles to tail damage
and the non-lethal presence of starved and fed dragonflies, we determined that these phenotypic differences are induced by
non-contact cues present when dragonflies prey on Hyla. The induced changes in shape are in the direction that tends to increase swimming speed; thus, the induced morphology may
help tadpoles evade predators. Altering morphology in response to predators is likely to influence interactions with other
species in the community as well.
Received: 17 April 1996 / Accepted: 18 September 1996 相似文献