共查询到20条相似文献,搜索用时 15 毫秒
1.
S. R. Soffe 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(6):711-715
Young Xenopus tadpoles were used to test whether the pattern of discharge in specific sensory neurons can determine the motor response
of a whole animal. Young Xenopus tadpoles show two main rhythmic behaviours: swimming and struggling. Touch-sensitive skin sensory neurons in the spinal cord
of immobilised tadpoles were penetrated singly or in pairs using microelectrodes to allow precise control of their firing
patterns. A single impulse in one Rohon-Beard neuron (= light touch) could sometimes trigger “fictive” swimming. Two to six
impulses at 30–50 Hz (= a light stroke) reliably triggered fictive swimming. Neither stimulus evoked fictive struggling. Twenty-five
or more impulses at 30–50 Hz (= pressure) could evoke a pattern of rhythmic bursts, distinct from swimming and suitable to
drive slower, stronger movements. This pattern showed some or all the characteristics of “fictive” struggling. These results
demonstrate clearly that sensory neurons can determine the pattern of motor output simply by their pattern of discharge. This
provides a simple form of behavioural selection according to stimulus.
Accepted: 28 November 1996 相似文献
2.
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
3.
Multisegmental motor activity in the segmentally restricted gin trap behavior in Manduca sexta pupae
William C. Lemon Richard B. Levine 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(6):611-619
Stimulation of sensory neurons innervating hairs in the gin traps on the abdomen of Manduca sexta pupae evokes a rapid bending of the abdomen that is restricted to one or more of the three articulating posterior segments.
However, electrical stimulation of the gin trap sensory nerve in an isolated abdominal nerve cord evokes characteristic motor
neuron activity in every abdominal segment. To determine if the segmentally distributed motor activity also occurred in intact
animals and how it contributed to the segmentally restricted reflex movement, mechanical stimulation of the sensory hairs
in intact animals was used to evoke reflex responses that were recorded as electromyograms synchronized with video recordings
of the behavior. Motor activity was monitored during movements to determine if there was activity in many segments when the
movement was restricted to one segment. Coordinated muscle activity was evoked throughout the abdomen in response to stimulation
of any of the three gin traps, even when movement was restricted to one segment. Differences in the timing of ipsilateral
and contralateral motor activity among segments allowed the closing of gin traps to be segmentally restricted. These findings
suggest that the neural circuit underlying the gin trap reflex is distributed throughout the abdominal nerve cord. This network
generates a complex, yet coordinated, motor pattern with muscular activity in many abdominal segments that produces a localized
bending reflex.
Accepted: 10 January 1997 相似文献
4.
Hisaaki Namba Toshiki Nagayama Masakazu Takahata 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(5):463-472
The role of non-spiking local interneurones in the synaptic interactions between abdominal extension-evoking descending interneurones
and uropod motor neurones in the terminal abdominal ganglion of the crayfish Procambarus clarkii (Girard) was investigated electrophysiologically. Continuous electrical stimulation of the lateral region of the 3rd-4th
abdominal connective that included abdominal extension evoking interneurones excited the opener motor neurones and inhibited
the closer, reductor motor neurone. Spikes from a single descending interneurone evoked consistent and short latency (0.8–0.9
ms) excitatory postsynaptic potentials (e.p.s.ps) in the opener motor neurones, and evoked rather long-latency (1.5–2.7 ms)
inhibitory postsynaptic potentials (i.p.s.ps) in the reductor motor neurone. Many non-spiking interneurones also received
depolarizing p.s.ps (0.8–2.5 ms in latency) that were usually faster than i.p.s.ps of the reductor motor neurone if both neurones
were recorded sequentially in the same preparation. Non-spiking interneurones received convergent inputs from several descending
interneurones and made inverting connection with the reductor motor neurone. Elimination of descending inputs to a particular
non-spiking interneurone could reduce the inhibitory response of the reductor motor neurone. These observations strongly suggested
that descending inhibitory inputs to the closer, reductor motor neurone were mediated by non-spiking interneurones. Furthermore,
some non-spiking interneurones made output connections with the opener motor neurones. The disynaptic pathway through non-spiking
interneurones is significant to control and modulate the opening pattern of the uropod during abdominal extension.
Accepted: 27 December 1996 相似文献
5.
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
6.
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
7.
E. R. Wood D. E. Wiel J. C. Weeks 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(6):639-657
The larval proleg withdrawal reflex of the hawk moth, Manduca sexta, exhibits robust habituation. This reflex is evoked by deflecting one or more mechanosensory planta hairs on a proleg tip.
We examined neural correlates of habituation in an isolated proleg preparation consisting of one proleg and its segmental
ganglion. Repeated deflection of a single planta hair caused a significant decrease in the number of action potentials evoked
in the proleg motor nerve (which carries the axons of proleg retractor motor neurons). Significant response decrement was
seen for interstimulus intervals of 10 s, 60 s and 5 min. Response decrement failed to occur in the absence of repetitive
stimulation, the decremented response recovered spontaneously following a rest, and electrical stimulation of a body wall
nerve facilitated the decremented response (a neural correlate of dishabituation). Adaptation of sensory neuron responses
occurred during repeated hair deflections. However, when adaptation was eliminated by direct electrical stimulation of sensory
neurons, the response in the proleg motor nerve still decreased significantly. Muscle recordings indicated that the response
of an identified proleg retractor motor neuron decreased significantly during habituation training. Thus, habituation of the
proleg withdrawal reflex includes a central component that is apparent at the level of a single motor neuron.
Accepted: 20 December 1996 相似文献
8.
Brassica oleracea L. is highly polymorphic and includes varieties which exhibit a headed phenotype (a large preinflorescence): the curd of
cauliflower and `romanesco' (var. botrytis), and the spear of broccoli (var. italica). This headed phenotype results from highly iterative patterns of activity at the primary meristems. Differences in the morphology
of curds and spears are accounted for by three quantitative variables: the rate of production of branch primordia on the flanks
of the apical meristems (RPP); the number of branch primordia produced before the first formed begin producing their own branch
primordia (the iteration interval, ITI); and the duration of the preinflorescence stage (before production of flower primordia).
Relatively stable iteration parameters (RPP and ITI) during curd development lead to the production of semi-spherical curds
with a smooth surface in cauliflower and broccoli, whereas in `romanesco' RPP and ITI increase throughout curd development,
inducing a pyramidal curd with an angular surface. A relatively long preinflorescence stage in cauliflower and `romanesco'
results in the curd surface being composed largely of branch primordia, whereas in broccoli this stage is short and the spear
surface is made up of flower buds. Simplified growth models for these three headed types are presented. The implications for
the genetic control of the B. oleracea L. headed phenotype and the relationships between shoot apical meristem size, phyllotaxis and curd/spear morphology are discussed.
Received: 11 September 1997 / Accepted: 12 November 1997 相似文献
9.
J. Juranek W. Metzner 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,181(4):393-414
The two closely related gymnotiform electric fish, Eigenmannia and Apteronotus, modulate the rate of their electric organ discharges during orientation and communication behaviors in similar ways. These
modulations are controlled through three prepacemaker nuclei that provide excitatory inputs to the medullary pacemaker nucleus.
Whereas the projections from the prepacemaker nuclei onto the two identified cell types of the pacemaker nucleus appear to
be very similar, species-specific differences in the synaptic effects of these connections exist. We examined the modulatory
premotor inputs on relay and pacemaker cells in Eigenmannia and Apteronotus by performing intracellular in␣vivo recordings while pharmacologically stimulating the three prepacemaker nuclei. In both
taxa, activation of the lateral portion of the diencephalic prepacemaker causes a depolarization of baseline and a lowering
of peak voltage primarily in relay cells. Activation of the medial portion of the diencephalic prepacemaker depolarizes mainly
pacemaker cells in both fish, yet also has different effects on peak voltage in each species. Excitation of the sublemniscal
prepacemaker in Apteronotus results in a depolarization of relay cells, whereas its inhibition in Eigenmannia causes a lowering of peak voltage without affecting baseline voltage. Our results complement earlier pharmacological investigations
by expanding them to the cellular level. They provide neurophysiological evidence for different receptor subtypes on relay
and pacemaker cells mediating different behaviors.
Accepted: 14 May 1997 相似文献
10.
A. Kana-uchi C. T. Yamashiro S. Tanabe T. Murayama 《Molecular & general genetics : MGG》1997,254(4):427-432
In order to study the role of signal transduction pathways in the regulation of morphology in Neurospora crassa, we cloned and characterized a ras homologue, termed NC-ras2. The predicted protein product of this gene is composed of 229 amino acid residues and contains all the consensus sequences
shared by the ras protein family. The gene is located in linkage group V. An NC-ras2 disruptant showed morphological characteristics very similar to those of the smco7 mutant, which also maps to linkage group V. Nucleotide sequence analysis revealed that the smco7 mutant harbored a single base deletion in the NC-ras2 gene, which is predicted to result in the truncation of the protein product. Introduction into the smco7 mutant of an NC-ras2 clone yielded stable transformants with a wild-type phenotype. The smco7 mutant exhibited very slow hyphal growth and the rate of conidial formation was approximately one two-hundredth of wild type.
The smco7 mutation causes both the changes in the pattern of hyphal growth and the defects in cell wall synthesis. Both the diameter
and the length of the apical compartment were shorter in the hyphae of the smco7 mutant. These results suggest that NC-ras2 is identical to smco7, and that the signal transduction pathway mediated by the NC-ras2 protein regulates the apical growth of hyphae, cell wall
synthesis, and conidial formation in N. crassa.
Received: 1 October 1996 / Accepted: 9 December 1996 相似文献
11.
To isolate genes that negatively regulate cell growth, we constructed a galactose-inducible expression library with partially
digested Saccharomyces cerevisiae genomic DNA fragments inserted downstream of the GAL10 promoter. In all, 240 000 yeast transformants were screened for lethality on galactose medium. From 17 such transformants
identified, 16 nonoverlapping DNA sequences were obtained. Restriction mapping and determination of DNA sequences adjacent
to the GAL10 promoter indicated that the inserts encoded part or all of the URA2, RBP1, TPK3, SAC7, BOI1, and BNI1 genes, and also open reading frames (ORFs) from chromosomes IV, V, IX, XI, and XIII. Some of the identified sequences lacked
the amino-terminal sequences of the ORFs, suggesting that truncated forms of the proteins might be necessary for growth inhibition.
The sequence of the pGA108 insert was highly homologous to the telomeric X-element and contained an ARS consensus sequence, suggesting a possible growth inhibitory effect of an RNA molecule. Overexpression of the BNI1ΔN and BOI1ΔN genes, which lacked amino-terminal sequences, was associated with phenotypes similar to those of mutants defective in bud
formation. Overexpression of the GIN4 and GIN12 sequences induced elongated buds and a G2/M arrest-like phenotype, respectively.
The phenotypes induced by the overexpression of our cloned sequences could result from either a dominant-positive or a dominant-negative
effect and, unexpectedly, in one case from an effect of an RNA.
Received: 3 June 1996 / Accepted: 1 October 1996 相似文献
12.
Post-dispersal seed predation and the establishment of vertebrate dispersed plants in Mediterranean scrublands 总被引:4,自引:0,他引:4
Philip E. Hulme 《Oecologia》1997,111(1):91-98
The post-dispersal fate of seeds and fruit (diaspores) of three vertebrate-dispersed trees, Crataegus monogyna, Prunus mahaleb and Taxus baccata, was studied in the Andalusian highlands, south-eastern Spain. Exclosures were used to quantify separately the impact of
vertebrates and invertebrates on seed removal in relation to diaspore density and microhabitat. The three plant species showed
marked differences in the percentage of diaspores removed, ranging from only 5% for C. monogyna to 87% for T. baccata. Although chaffinches (Fringilla coelebs) fed on diaspores, rodents (Apodemus sylvaticus) were the main vertebrate removers of seed and fruit. Two species of ant (Cataglyphis velox and Aphaenogaster iberica) were the only invertebrates observed to remove diaspores. However, the impact of ants was strongly seasonal and they only
removed P. mahaleb fruit to any significant extent. While removal of seed by rodents was equivalent to predation, ants were responsible for
secondary dispersal. However, their role was limited to infrequent, small-scale redistribution of fruit in the vicinity of
parent trees. Rodents and ants differed in their use of different microhabitats. Rodents foraged mostly beneath trees and
low shrubs and avoided open areas while the reverse was true of ants. Thus, patterns of post-dispersal seed removal will be
contigent on the relative abundance and distribution of ants and rodents. Studies which neglect to quantify separately the
impacts of these two guilds of seed removers may fail to elucidate the mechanisms underlying patterns of post-dispersal seed
removal. The coincidence of both increased seed deposition by the main avian dispersers (Turdus spp.) and increased seed predation with increasing vegetation height suggested that selection pressures other than post-dispersal
seed predation shape the spatial pattern of seed dispersal. Rather than providing a means of escaping post-dispersal seed
predators, dispersal appears to direct seeds to microhabitats most suitable for seedling survival. Nevertheless, the reliance
of most vertebrate-dispersed trees on regeneration by seed and the absence of persistent soil seed banks imply that post-dispersal
seed predators may exert a strong influence on the demography of the plants whose seeds they consume. Even where microsites
are limited, the coincidence of the most suitable microhabitats for seedling establishment with those where seed predation
is highest provide a means by which selective seed predators can influence community composition.
Received: 19 August 1996 / Accepted: 25 January 1997 相似文献
13.
M. Kato A. Aoyama F. Naruse T. Kobayashi N. Tsukagoshi 《Molecular & general genetics : MGG》1997,254(2):119-126
Using AnCP (Aspergillus nidulans CCAAT-binding protein) as a CCAAT-specific binding factor model, the possibility that one factor is able to recognize CCAAT
sequences in several different genes in A.␣nidulans was examined. DNase I protection analysis showed that AnCP specifically bound to CCAAT sequence-containing regions comprising
21 to 36 bp of the taa, amdS and gatA genes. Furthermore, replacement of the CCAAT sequence with CGTAA was found to abolish the binding of AnCP and to have an
inhibitory effect on taa promoter activity. This clearly demonstrates a positive function of the CCAAT element. However, amylase was induced by starch
and repressed by glucose in a CCAAT-box disruptant, as in wild-type cells.
Received: 28 June 1996 / Accepted: 7 October 1996 相似文献
14.
15.
S. Credner H. Burda F. Ludescher 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(3):245-255
In captive adult Zambian mole-rats 14 different sounds (13 true vocalizations) have been recorded during different behavioural
contexts. The sound analysis revealed that all sounds occurred in a low and middle frequency range with main energy below
10 kHz. The majority of calls contained components of 1.6–2 kHz, 0.63–0.8 kHz, and/or 5–6.3 kHz. The vocalization range thus
matched well the hearing range as established in other studies. The frequency content of courtship calls in two species of
Zambian Cryptomys was compared with that in naked mole-rats (Heterocephalus glaber) and blind mole-rats (Spalax ehrenbergi) as described in the literature. The frequency range of maximum sound energy is negatively correlated with the body weight
and coincides with the frequencies of best hearing in the respective species. In general, the vocalization range in subterranean
mammals is shifted towards low frequencies which are best propagated in underground burrows.
Accepted: 16 September 1996 相似文献
16.
Molecular evolution and functional relevance of the chalcone synthase genes of pea 总被引:12,自引:0,他引:12
M. Ito Y. Ichinose H. Kato T. Shiraishi T. Yamada 《Molecular & general genetics : MGG》1997,255(1):28-37
We have isolated seven genomic chalcone synthase (CHS) genes and six classes of CHS cDNA from elicitor-treated pea tissues. Comparison of the nucleotide sequences of the coding regions revealed the existence
of eight members of the CHS gene family in pea. These can essentially be divided into three groups (PSCHS1, 2 and 8; PSCHS3, 4 and 5; and PSCHS6 and 7) on the basis of nucleotide and/or amino acid sequence comparisons of the coding regions, introns and promoter regions. We
previously reported that the accumulation of CHS mRNAs is induced by elicitor treatment. Accumulation of CHS mRNA was observed mainly in roots and very little was found in floral organs. To specifically detect expression of each CHS gene in various types of pea cells, S1 nuclease protection assays were performed. Interestingly, the classification of the
eight members of the CHS gene family based on the sequence identity was found to reflect their expression patterns as determined by the S1 nuclease
protection assay. The first group of CHS genes, PSCHS1, 2 and 8, was strongly induced not only by elicitor treatment and UV irradiation but is also constitutively expressed in root and
flower tissues. The second group, PSCHS3, 4 and 5, was also strongly induced by elicitor treatment and UV irradiation but is constitutively expressed only in root. Expression
of the third group, PSCHS6 and 7 was barely detectable in any of the organs tested and was not influenced by environmental stimuli such as elicitor or UV.
Furthermore, sequence analysis of the promoter region of each member of the CHS gene family revealed that putative cis-regulatory elements, such as Box-I, Box-II and G-Box, were conserved only in PSCHS1, 2, 3, 4 and 5. From these results we propose that an ancestral CHS gene might have given rise to defense response-related (UV irradiation- and elicitor-responsive) and -unrelated (unresponsive)
genes at an early stage of evolution, followed by divergence within these subclasses based upon the developmental program
in pea.
Received: 5 November 1996 / Accepted: 6 February 1997 相似文献
17.
J. Geistlinger K. Weising W. J. Kaiser G. Kahl 《Molecular & general genetics : MGG》1997,256(3):298-305
The genome of the fungal chickpea pathogen Ascochyta rabiei was screened for polymorphisms by microsatellite-primed PCR. While ethidium-bromide staining of electrophoretically separated
amplification products showed only limited polymorphism among 24 Tunisian A. rabiei isolates, Southern hybridization of purified PCR fragments to restriction digests of fungal DNA revealed polymorphic DNA
fingerprints. One particular probe that gave rise to a hypervariable single-locus hybridization signal was cloned from the
Syrian isolate AA6 and sequenced. It contained a large compound microsatellite harbouring the penta- and decameric repeat
units (CATTT)n, (CATTA)n, (CATATCATTT)n and (TATTT)n. We call this locus ArMS1 (Ascochyta rabiei microsatellite 1). Unique flanking sequences were used to design primer pairs for locus- specific microsatellite amplification
and direct sequencing of additional ArMS1 alleles from Tunisian and Pakistani isolates. A high level of sequence variation was observed, suggesting that multiple mutational
mechanisms have contributed to polymorphism. Hybridization and PCR analyses were performed on the parents and 62 monoascosporic
F1 progeny derived from a cross between two different mating types of the fungus. Progeny alleles could be traced back to the
parents, with one notable exception, where a longer than expected fragment was observed. Direct sequencing of this new length
allele revealed an alteration in the copy number of the TATTT repeat [(TATTT)53 to (TATTT)65], while the remainder of the sequence was unchanged.
Received: 11 March 1997 / Accepted: 21 June 1997 相似文献
18.
Thomas Waßmer Franziska Wollnik 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(4):270-279
Body temperature (T
b) of seven European hamsters maintained at constant ambient temperature (T
a = 8 °C) and constant photoperiod (LD 8:16) was recorded throughout the hibernating season using intraperitoneal temperature-sensitive
HF transmitters. The animals spent about 30% of the hibernation season in hypothermia and 70% in inter-bout normothermy. Three
types of hypothermia, namely deep hibernation bouts (DHBs), short hibernation bouts (SHBs), and short and shallow hibernation
bouts (SSHBs), were distinguished by differences in bout duration and minimal body temperature (T
m). A gradual development of SSHBs from the diel minimum of T
b during normothermy could be seen in individual hamsters, suggesting a stepwise decrease of the homeostatic setpoint of T
b regulation during the early hibernation season. Entry into hibernation followed a 24-h rhythm occurring at preferred times
of the day in all three types of hypothermia. DHBs and SHBs were initiated approximately 4 h before SSHBs, indicating a general
difference in the physiological initiation of SSHBs on the one hand and DHBs and SHBs on the other. Arousals from SHBs and
SSHBs also followed a 24-h rhythm, whereas spontaneous arousals from DHBs were widely scattered across day and night. Statistical
analyses of bout length and the interval between arousals revealed evidence for a free-running circadian rhythm underlying
the timing of arousals. The results clearly demonstrate that entries into hypothermia are linked to the light/dark-cycle.
However, the role of the circadian system in the timing of arousals from DHBs remains unclear.
Accepted: 11 December 1996 相似文献
19.
K. Ushijima H. Sassa R. Tao H. Yamane A. M. Dandekar T. M. Gradziel H. Hirano 《Molecular & general genetics : MGG》1998,260(2-3):261-268
cDNAs encoding three S-RNases of almond (Prunus dulcis), which belongs to the family Rosaceae, were cloned and sequenced. The comparison of amino acid sequences between the S-RNases
of almond and those of other rosaceous species showed that the amino acid sequences of the rosaceous S-RNases are highly divergent,
and intra-subfamilial similarities are higher than inter-subfamilial similarities. Twelve amino acid sequences of the rosaceous
S-RNases were aligned to characterize their primary structural features. In spite of␣their high level of diversification,
the rosaceous S-RNases were found to have five conserved regions, C1, C2, C3, C5, and RC4 which is Rosaceae-specific conserved
region. Many variable sites fall into one region, named RHV. RHV is located at a similar position to that of the hypervariable
region a (HVa) of the solanaceous S-RNases, and is assumed to be involved in recognizing S-specificity of pollen. On the other hand, the region corresponding to another solanaceous hypervariable region (HVb) was
not variable in the rosaceous S-RNases. In the phylogenetic tree of the T2/S type RNase, the rosaceous S-RNase fall into two
subfamily-specific groups (Amygdaloideae and Maloideae). The results of sequence comparisons and phylogenetic analysis imply
that the present S-RNases of Rosaceae have diverged again relatively recently, after the divergence of subfamilies.
Received: 28 May 1998 / Accepted: 13 August 1998 相似文献
20.
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