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1.
A conceptual model of a portion of dorsal cochlear nucleus (DCN) neural circuitry has emerged over the past two decades. This
model suggests that the response properties of the DCN’s major projection neurons, called type IV units, are due, in part,
to the behavior of local circuit inhibitory interneurons called type II units (Young and Brownell 1976). Cross-correlation
studies of simultaneously recorded pairs of DCN units in decerebrate cat derived from 50-s best frequency (BF) stimuli are
consistent with and have extended this conceptual model (Voigt and Young 1980, 1985, 1988, 1990). Interestingly, Gochin et
al. (1989) found no signs of inhibition in the anesthetized rat DCN in cross-correlograms derived from 55-ms short-duration
BF tone bursts. This seemingly contradictory result has motivated this study. Computer simulations were run using our network
model of the intrinsic DCN neural circuitry. This model has previously been shown to reproduce the major features of both
type II and type IV rate-level curves and the inhibitory trough (IT) observed in cross-correlograms derived from long-duration
stimuli (Voigt and Davis 1994). The goal was to study the stimulus-duration-dependent strength of ITs in the cross-correlograms
derived from short-duration BF tone-burst stimuli. The results suggest that ITs may not be detectable when the stimulus duration
is 50 ms but may be detectable when the stimulus duration is 200 ms or greater. Furthermore, when the ITs are detected in
cross-correlograms derived from 200-ms data sets, the strength of the IT, as measured by effectiveness, is comparable to the
strength of ITs measured when the stimulus duration is 50 s.
Received: 16 March 1994/Accepted in revised form: 31 May 1994 相似文献
2.
J. Wang K. D. Liu C. G. Xu X. H. Li Q. Zhang 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(3):407-412
Wide-compatibility varieties (WCVs) are a special class of rice germplasm that is able to produce fertile hybrids when crossed
to both indica and japonica rice varieties. WCVs may differ greatly in their spectrum and level of compatibility. The objective
of this study was to determine the genetic basis of wide-compatibility conferred by ‘Dular’, a landrace variety from India
that has demonstrated a high level of wide-compatibility in previous studies with a broad range of indica and japonica varieties.
A three-way cross (‘Balilla/Dular//Nanjing 11’) was made and the resulting F1 population evaluated in the field for spikelet fertility. A total of 235 plants from this population was assayed individually
for restriction fragment length polymorphisms (RFLPs) at 159 marker loci covering the entire rice genome at regular intervals.
Quantitative trait locus (QTL) analysis identified 5 loci, located on chromosomes 1, 3, 5, 6 and 8, as having significant
effects on hybrid fertility, which jointly explained 55.5% of the fertility variation in this population. The QTL on chromosome
5 ( f5) showed the largest effect on hybrid fertility, followed by those on chromosomes 6 ( f6), 3 ( f3) and 1 ( f1), with the one on chromosome 8 ( f8) having the smallest effect. Genotypes each composed of an allele from ‘Dular’ and an allele from ‘Nanjing 11’ at four ( f3, f5, f6 and f8) of the five QTLs contributed to the increase of fertility in the population. In contrast, the genotype composed of alleles
from ‘Balilla’ and ‘Nanjing 11’ at the fifth locus ( f1) was in the direction of increasing fertility. Analysis of variance using marker genotypes at the five QTLs as the groups
detected two interactions involving four of the five loci, a 2-locus interaction between f5 and f8 and a 3-locus interaction among f3, f5 and f6. The level of hybrid fertility is the result of complex interactions among these loci. The implication of the present findings
in the utilization of the wide-compatibility of ‘Dular’ in rice breeding programs is also discussed.
Received: 21 October 1997 / Accepted: 30 December 1997 相似文献
3.
W. Michalek M. Kleine H. Dargatz G. Wenzel A. Jahoor 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(3):369-374
The hordeins are the major class of storage proteins in barley and are encoded by multigene families. Two YAC-clones specific
for the C-hordein-coding Hor1-locus of barley (Hordeum vulgare L.) were selected. The clones were constructed with DNA from the cultivars ‘Franka’ and ‘Hockey’ and have insert sizes of
330 kb and 350 kb, respectively. Performing partial digestions and hybridizations with vector-specific probes, a restriction
analysis was conducted using restriction enzymes with a 8-bp recognition sequence. Both clones cover the complete region of
the Hor1-locus, but exhibit a different pattern of restriction sites reflecting the polymorphic nature of the locus on the scale of
long-range restriction mapping. The maximal extent of the regions homologous to the Hor1-specific probe, pBSC5, was 105 kb in the ‘Hockey’-derived YAC and 190 kb in the yeast artificial chromosome constructed with
‘Franka’-DNA. Furthermore the high degree of instability observed with the Hor1-specific YAC-clones is discussed in conjunction with the structure of the Hor1-locus.
Received: 19 December 1996 / Accepted: 31 January 1997 相似文献
4.
V. Korzun M. S. Röder M. W. Ganal A. J. Worland C. N. Law 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(8):1104-1109
Two sets of single chromosome recombinant lines comparing 2D chromosomes from the wheat varieties ‘Ciano 67’ and ‘Mara’ with
the common 2D chromosome of ‘Cappelle-Desprez’ in a ‘Cappelle-Desprez’ background were used to detect a diagnostic wheat microsatellite
marker for the dwarfing gene Rht8. The genetic linkage maps place the wheat microsatellite marker WMS 261 0.6 cM distal to Rht8 on the short arm of chromosome 2D. By PCR analysis the WMS 261 alleles of ‘Mara’, ‘Cappelle-Desprez’ and ‘Ciano 67’ could
be distinguished by different fragment sizes of 192 bp, 174 bp and 165 bp, respectively. A screen of over 100 international
varieties of wheat showed that the three allelic variants were all widespread. It also demonstrated that a limited number
of varieties carried novel WMS 261 variants of over 200 bp. Following classification of the individual recombinant lines for
allelic variants at the WMS 261 locus it was possible to attribute a 7- to 8-cm reduction in plant height with the WMS 261-192-bp
allele compared to the WMS 261-174-bp allele in the set of recombinant lines comparing 2D chromosomes of ‘Mara’ and ‘Cappelle-Desprez’.
A height reduction of around 3 cm was detected between the WMS 261-174-bp allele and the WMS 261-165-bp allele in the recombinant
lines comparing 2D chromosomes of ‘Cappelle-Desprez’ and ‘Ciano 67’.
Received: 17 October 1997 / Accepted: 12 November 1997 相似文献
5.
A molecular genetic map of cassava (Manihot esculenta Crantz) 总被引:12,自引:0,他引:12
M. Fregene F. Angel R. Gomez F. Rodriguez P. Chavarriaga W. Roca J. Tohme M. Bonierbale 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(3):431-441
A genetic linkage map of cassava has been constructed with 132 RFLPs, 30 RAPDs, 3 microsatellites, and 3 isoenzyme markers
segregating from the heterozygous female parent of an intraspecific cross. The F1 cross was made between ‘TMS 30572’ and ‘CM 2177-2’, elite cassava cultivars from Nigeria and Colombia, respectively. The
map consists of 20 linkage groups spanning 931.6 cM or an estimated 60% of the cassava genome. Average marker density is 1
per 7.9 cM. Since the mapping population is an F1 cross between heterozygous parents, with unique alleles segregating from either parent, a second map was constructed from
the segregation of 107 RFLPs, 50 RAPDs, 1 microsatellite, and 1 isoenzyme marker from the male parent. Comparison of intervals
in the male-and female-derived maps, bounded by markers heterozygous in both parents, revealed significantly less meiotic
recombination in the gametes of the female than in the male parent. Six pairs of duplicated loci were detected by low-copy
genomic and cDNA sequences used as probes. Efforts are underway to saturate the cassava map with additional markers, to join
the male- and female-derived maps, and to elucidate genome organization in cassava.
Received: 5 July 1996/Accepted: 22 November 1996 相似文献
6.
K. J. Williams A. Lichon P. Gianquitto J. M. Kretschmer A. Karakousis S. Manning P. Langridge H. Wallwork 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,99(1-2):323-327
Spot form of net blotch (SFNB) (Pyrenophora teres f maculata) is an economically damaging foliar disease of barley in many of the world’s cereal growing areas. The development of SFNB-resistant
cultivars may be accelerated through the use of molecular markers. A screen for SFNB resistance in 96 lines identified four
new sources of resistance, including a feed variety, ‘Galleon’, for which a fully mapped doubled haploid population was available.
Segregation data indicated SFNB resistance was conferred by a single gene in the ‘Galleon’בHaruna Nijo’ cross, positioned
on the long arm of chromosome 7H. This gene is designated Rpt4 and is flanked by the RFLP loci Xpsr117(D) and Xcdo673 at distances of 6.9 cM and 25.9 cM, respectively. The marker Xpsr117(D) was validated using another population segregating for Rpt4, correctly predicting SFNB resistance with more than 90% accuracy.
Received: 24 September 1998 / Accepted: 19 December 1998 相似文献
7.
V. Ivandic S. Malyshev V. Korzun A. Graner A. Börner 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(5):728-731
We report the genetic mapping of Dwf2, a dominant gibberellic acid (GA3)-insensitive dwarfing gene which has been previously described to cause a very short growth habit in barley (Hordeum vulgare) mutant ‘93/B694’. Using RFLP and microsatellite markers we performed segregation analysis in an F2 population comprising 86 individuals developed from a cross of ‘93/B694’ (Dwf2) with ‘Bonus M2’ (dwf2). Dwf2 was mapped on the short arm of barley chromosome 4H proximal to microsatellite marker XhvOle (5.7 cM) and distal to RFLP marker Xmwg2299 (18.3 cM). The genetic localization of the Dwf2 gene at a homoeologous position to the multiallelic Rht-B1 and Rht-D1 loci in wheat suggests synteny of GA-insensitive dwarfing genes within the Triticeae. Moreover, the extremely prostrate growth habit exhibited in barley ‘93/B694’ (Dwf2) resembles that of wheat plants carrying the genes Rht-B1c (Rht3) or Rht-D1c (Rht10).
Received: 1 July 1998 / Accepted: 17 September 1998 相似文献
8.
Djordje Boskov Mirjana Jocic Ksenija Jovanovic Milos Ljubisavljevic Radmila Anastasijevic 《Biological cybernetics》1994,71(4):333-339
The properties of membrane potential changes of skeletomotor neurons (S, FR, and FF) innervating triceps surae muscles during
pseudorandom stretching of these muscles were studied in decerebrate cats. Peak amplitudes of pseudorandom muscle stretches
ranged from 119 μm to 4.15 mm peak-to-peak. Sequences of ten identical stretching periods were applied for averaging. Shapes
of membrane potential changes and probability density distribution of amplitudes of the input and output signals and power
spectra suggest that the skeletomotor neuron membrane has nonlinear properties. First- and second-order Wiener kernels were
determined by applying the cross-correlation (Lee-Schetzen) method. The results suggest that the transfer function between
muscle stretches and subthreshold membrane potentials is a Wiener-type cascade. This cascade is consistent with a linear,
second-order, underdamped transfer function followed by a simple quadratic nonlinearity [linear (L) system followed by nonlinear
(N) system, or LN cascade]. Including the nonlinear component calculated from the second-order Wiener kernel improved the
model significantly over its linear counterpart, especially in S-type motoneurons. Qualitatively similar results were obtained
with all types of motoneurons studied.
Received: 1 April 1993/Accepted in revised form: 24 March 1994 相似文献
9.
Djordje Boskov Mirjana Jocic Ksenija Jovanovic Milos Ljubisavljevic Radmila Anastasijevic 《Biological cybernetics》1994,71(4):341-348
Spike discharges of skeletomotor neurons innervating triceps surae muscles elicited by white noise modulated transmembrane
current stimulation and muscle stretch were studied in decerebrated cats. The white noise modulated current intensity ranged
from 4.3 to 63.2 nA peak-to-peak, while muscle stretches ranged from 100 μm to 4.26 mm peak-to-peak. The neuronal responses
were studied by averaging the muscle length records centered at the skeletomotor action potentials (peri-spike average, PSA)
and by Wiener analysis. Skeletomotor spikes appeared after a sharp peak in PSA of the injected current, preceded by a longer-lasting
smaller wavelet of either depolarizing or hyperpolarizing direction. The PSA amplitude was not related to the injected current
amplitude nor showed any differences related to the motor unit type. The PSA amplitudes were virtually independent of the
stretching amplitude σ, after an initial increase with stretching amplitudes in the range of 15–40 μm (S.D.), or 100–270 μm
peak-to-peak.Analyses of cross-spectra indicated a small or absent increase in gain with frequency in response to injected
current, but about 20 dB/decade in the range 10–100 Hz in response to muscle stretch. The peaks of both Wiener kernels in
response to current injection appear to decrease with the amplitude of injected current, but this decrease was not statistically
significant. The narrow first-order kernels suggest that the transfer function between the current input and spike discharge
is lowpass with a wide passband, i.e. there is very little change in dynamics. The values of the second-order kernels appear
to be nonzero only along the main diagonal. This is characteristic of a simple Hammerstein type cascade, i.e. a zero memory
nonlinearity followed by a linear system. Small values of second-order kernels away from the origin and narrow first-order
kernels suggest that the linear cascade contributes very little to the overall dynamic response.In contrast to Wiener kernels
found in response to current injection, the Wiener kernels in response to stretch showed a decreasing trend with stretch amplitude.
The size of the second-order kernels decreased to a somewhat larger extent with input amplitude than that of the first-order
kernels, indicating an amplitude-dependent nonlinearity. Overall, the transformation between length and spike output was described
as an LNNL cascade with second-order nonlinearities.
Received: 1 April 1993/Accepted in revised form: 24 March 1994 相似文献
10.
Localization of the rice stripe disease resistance gene, Stv-bi, by graphical genotyping and linkage analyses with molecular markers 总被引:4,自引:0,他引:4
Y. Hayano-Saito T. Tsuji K. Fujii K. Saito M. Iwasaki A. Saito 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(8):1044-1049
We used graphical genotyping and linkage analyses with molecular markers to determine the chromosomal location of the rice
stripe disease resistance gene, Stv-b
i
. The stripe resistance gene from the indica rice (Oryza sativa) cv ‘Modan’ was introgressed into several Japanese rice varieties. We found 4 RFLP markers in ‘Modan’, five susceptible parental
rice varieties (‘Norin No. 8’, ‘Sachihikari’, ‘Kanto No. 98’, ‘Hokuriku No.103’ and ‘Koganebare’) and four resistant progeny
varieties (‘St. No. 1’, ‘Aichi No. 6’, ‘Aoisora’ and ‘Asanohikari’). Graphical genotyping of the resistant progeny revealed
a chromosomal segment ascribable to ‘Modan’ and associated with stripe resistance. The chromosomal segment from ‘Modan’ was
located at 35.85 cM on chromosome 11. Linkage analysis using 120 F2 individuals from a cross between ‘Koshihikari’ (susceptible) and ‘Asanohikari’ (resistant) revealed another 8 RFLP markers
in the same chromosome. We performed a bioassay for rice stripe resistance in F3 lines of the F2 individuals using infective small brown planthoppers and identified an 1.8-cM segment harboring the rice stripe disease resistance
gene, Stv-b
i
, between XNpb220 and XNpb257/ XNpb254. Furthermore, Stv-b
i
was linked by 0.0 cM to a RFLP marker, ST10, which was developed on the basis of the results of RAPD analysis. These DNA
markers near the Stv-b
i
locus may be useful in marker-assisted selection and map-based cloning of the Stv-b
i
gene.
Received: 26 September 1997 / Accepted: 4 November 1997 相似文献
11.
Costello MJ 《Experimental & applied acarology》2007,42(3):197-208
Sulfur is the oldest and most widely used fungicide in the vineyards of California, where it is used for control of powdery
mildew (Uncinula necator [Schw.] Burr). For decades, sulfur use has been associated with outbreaks of Tetranychus pacificus McGregor (Acari: Tetranychidae) on cultivated grapes in the San Joaquin Valley. I undertook large-scale field studies to
test this association, to evaluate the impact of sulfur on Galendromus occidentalis (Nesbit) (Acari: Phytoseiidae), a major predator of T. pacificus, and to determine if timing of sulfur applications with respect to grape bloom has an impact on T. pacificus density. The studies took place in a 32 ha vineyard in Fresno County, and all fungicide applications were made with commercial-scale
equipment. In 1998 a ‘high sulfur’ treatment, a combination of wettable sulfur and sulfur dust, was compared to ‘low sulfur,’
in which demethylation inhibitor (DMI) fungicides partially substituted for sulfur. In 1999 treatments were ‘sulfur,’ ‘DMI,’
‘sulfur pre-bloom’ (here sulfur was applied prior to grape bloom, in late May, and then DMIs were applied until mid-season)
and ‘sulfur post-bloom’ (the reverse of ‘sulfur pre-bloom’). In each year, the T. pacificus population increase came after the end of fungicide applications, and results clearly show a relationship between sulfur
use and T. pacificus density. In 1998, mean T. pacificus density was 2.7 times higher and mean G. occidentalis density 2.5 times higher in ‘high sulfur’ compared to ‘low sulfur.’ In 1999, the highest T. pacificus counts were in the ‘sulfur’ and ‘sulfur pre-bloom’ treatments, 4.8 times higher than ‘sulfur post-bloom’ and 2 times higher
than ‘DMIs.’ Density of G. occidentalis was 2.3 times as high in ‘sulfur’ or ‘sulfur pre-bloom’ than ‘DMIs.’ The predator/prey ratio was not significantly different
among treatments in 1998, but in 1999 it was highest in the ‘sulfur pre-bloom’ treatment. In 1999, density of Homeopronematus anconai (Baker) (Acari: Tydeidae) was 2.7 times higher in ‘sulfur pre-bloom’ compared to ‘sulfur,’ and higher by 2.7 times in ‘DMI’
compared to ‘sulfur post-bloom,’ suggesting a negative effect of sulfur on this tydeid. These results do not support the hypotheses
that the cause of the increase in T. pacificus density is due to negative effects of sulfur on phytoseiids or tydeids. Rather, it appears that a plant-based explanation
is likely, first, because of the differences in pre-bloom versus post-bloom sulfuring, and second, because of the long lag
time between the end of the sulfur applications and the corresponding increase in spider mite density. 相似文献
12.
The mean maximum dive depth from 49 foraging bouts by northern rockhopper penguins, measured using capillary-tube depth gauges,
was 66±4 m (12–168 m). There were no differences in the maximum dive depths between male and female penguins. Northern rockhopper
penguins dived deeper in early than in late creche stages (83±7 vs 57±4 m), and this was associated with probable dietary
changes, squid dominating the diet by mass (44%) in November, and fish (64%) in December 1994 at Amsterdam Island.
Received: 10 January 1996/Accepted: 31 March 1996 相似文献
13.
Raphael Ritz Wulfram Gerstner Ursula Fuentes J. Leo van Hemmen 《Biological cybernetics》1994,71(4):349-358
. Feature linking and pattern separation are shown to be performed as simultaneous processes by a highly connected auto-associative
network of spiking neurons (spike response model). In principle, many (e.g., with nine) patterns can be separated, but with
a biological set of parameters the number is limited to four. The patterns have been learned by an asymmetric hebbian rule
that can handle a low activity which may vary from pattern to pattern (in a range between 4% and 7%). Spikes are generated
by a threshold process and – with some delay – transmitted to postsynaptic neurons. There they evoke an excitatory or inhibitory
postsynaptic potential (EPSP or IPSP). Spike emission is followed by an absolute refractory period (1 ms) and activates an
inhibitory delay loop that prevents continuous firing. Three different network topologies are discussed, i.e., a structureless
fully connected system, a network composed of two ‘hemispheres’, and finally a hierarchical network with four subsystems that
represent different ‘functions’ and interact via feedforward and feedback connections. Functional feedback turns out to be essential for context-sensitive binding. The coherence between
the two hemispheres is dependent on the interhemispheric delays. If these are on average too large, the two hemispheres oscillate
coherently by themselves but phase-shifted by half a period with respect to each other.
Received: 16 June 1993/Accepted in revised form: 24 March 1994 相似文献
14.
In motion-processing areas of the visual cortex in cats and monkeys, an anisotropic distribution of direction selectivities
displays a preference for movements away from the fovea. This ‘centrifugal bias’ has been hypothetically linked to the processing
of optic flow fields generated during forward locomotion. In this paper, we show that flow fields induced on the retina in
many natural situations of locomotion of higher mammals are indeed qualitatively centrifugal in structure, even when biologically
plausible eye movements to stabilize gaze on environmental targets are performed. We propose a network model of heading detection
that carries an anisotropy similar to the one found in cat and monkey. In simulations, this model reproduces a number of psychophysical
results of human heading detection. It suggests that a recently reported human disability to correctly identify the direction
of heading from optic flow when a certain type of eye movement is simulated might be linked to the noncentrifugal structure
of the resulting retinal flow field and to the neurophysiological anisotropies.
Received: 1 April 1994/Accepted in revised form: 4 August 1994 相似文献
15.
Disposable sensor for biochemical oxygen demand 总被引:6,自引:0,他引:6
Disposable-type microbial sensors were prepared for the determination of biochemical oxygen demand (BOD). The yeast, Trichosporon cutaneum, was directly immobilized on the surface of miniature oxygen electrodes using an ultraviolet crosslinking resin (ENT-3400).
The oxygen electrodes (15 mm× 2 mm×0.4 mm) were made on silicon substrates using micromachining techniques. They were Clark-type
two-electrode systems with−1021 mV applied to the working electrode. Typical response times of the BOD sensors were in the
range of 7–20 min. At 20°C, the sensors’ dynamic range was from 0 to 18 mg/l BOD when a glucose/glutamate BOD standard solution
was used. The lower limit of detection was 0.2 mg/l BOD. This value was one order of magnitude lower than that of sensors
previously reported. The sensors’ operational lifetime of 3 days was satisfactory for a disposable type. The sensors’ responses
were reproducible to within 8% relative standard deviation. The BOD sensors’ were applied to untreated and treated waste waters
from industrial effluents and municipal sewage. BOD values determined using these sensors correlated well with those determined
by the conventional 5-day BOD determination method.
Received: 22 December 1995/Received revision: 19 February 1996/Accepted: 17 March 1996 相似文献
16.
S. C. K. Milach H. W. Rines R. L. Phillips 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(5-6):783-790
Restriction fragment length polymorphism (RFLP) analysis provides a valuable tool for characterizing and understanding relationships
among genes for useful traits in crop species, particularly in ones with complex genomes such as the hexaploid cultivated
oat Avena sativa L. (2n=6x=42). Using Bulked Segregant Analysis (BSA) and F2 RFLP linkage data, we mapped three dominant oat dwarfing loci to different regions of the oat genome. Dw6, in oat line OT207, is 3.3±1.3 cM from the Xumn145B locus, which has not been placed on the hexaploid oat linkage map. Dw7, in line NC2469-3, is 4.3±2.3 cM from Xcdo1437B and 33±4.1 cM from Xcdo708B. This places Dw7 to linkage group 22. Dw8, in the Japanese lines AV17/3/10 and AV18/2/4, mapped 4.9±2.2 cM from Xcdo1319A in an AV17/3/10בKanota’ F2 population and 6.6±2.6 cM from it in an AV18/2/4בKanota’ population. This places Dw8 to linkage group 3. Aneuploid analysis of markers linked to the dwarfing genes located Dw6 on the smallest oat chromosome (chromosome 18) and Dw7 on the longest satellited chromosome (chromosome 19). The RFLP markers closely linked to the three dwarfing genes identify
distinct regions of the oat genome that contribute to plant height and they should be useful in characterizing new genetic
sources of dwarfness in oat.
Received: 8 May 1997 / Accepted: 20 May 1997 相似文献
17.
This study sought to investigate the role of the Renshaw cell with respect to transient motoneuron firing. By studying the
cat motoneuron and Renshaw cell, several low-order lumped parameter models were developed that simulate the known characteristics
of the injected input current vs. firing rate. The neuron models in the Renshaw cell inhibition configuration were tuned to
fit experimental data from cat motoneurons. Models included both linear versions and those with sigmoidal nonlinearities.
Results of the simulation indicate that the motoneuron itself provides the adaptation seen in its firing rate and that the
Renshaw cell’s role is primarily to fine-tune the motoneuron’s adaptation process.
Received: 23 July 1993/Accepted in revised form: 9 February 1994 相似文献
18.
Apart from the amount and distribution of food resources and predation pressure, we sought to clarify habitat spatial features
that affect group size and group density. To simulate animal groups interacting with one another, we made an agent-based model
in a computational space. Assuming no predation pressure, we change the resource conditions between the habitat (comprising
‘interior’ and ‘edges’) and the ‘exterior’. The results are as follows: when the group density is high throughout the habitat,
large groups tend to frequent the edges (i.e., the boundaries between the interior and exterior) even if food resources are
scarce in the exterior. Additionally, when the group density is high and the group size variation is small, both group size
and group density increase at the edges. These findings are discussed with reference to primates, particularly the Japanese
macaque (Macaca fuscata) as an example of group-living animal. 相似文献
19.
S. Saamin M. M. Thompson 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(6-7):912-916
Dormant scions of ‘Bing’ were exposed to 1–2.5 krad of gamma radiation in order to induce useful mutations. The main buds
were excised and the scions grafted to allow the growth of accessory buds into primary (V1) shoots. The frequency and types
of mutations on secondary (V2) populations are described. In a population of 3324 V2 shoots, the overall mutation frequency
was 6.4%: 4.2% partial, 1.6% total and 0.3% growth-reduced mutants were identified. The experiment was repeated using 3 krad-
and 4 krad-fractionated doses in water. Differences in mutation frequency at 3 krad and 4 krad were not significant. Of 2562
surviving V2 shoots derived from the irradiation of accessory buds of both standard and V1 shoots, the overall mutation frequency
was 3.3%: 1.7% were partial-leaf mutants, 1.0% were total-leaf mutants, and 0.54% were growth-reduced mutants. For maximum
mutation rate with adequate survival we suggest acute irradiation of accessory buds in air at dosages approximating LD50 (2.75–3 krad). A larger mutant sector was present in V1 shoots derived from accessory buds than those from main buds as revealed by the higher number of total mutant repeats in
the families.
Received: 21 August 1997 / Accepted: 17 November 1997 相似文献
20.
Self-organized neuronal dynamics revealed by cortical α-rhythms occur as episodes, which are rarely observed without extraction
of the α-band from the other spectral components. Three episodes of an unusually long duration of 10 s, two with no signal
processing after data recording at the clinic, are described and show evidence of low-dimensional α-dynamics. The evidence
is gained from an analysis of scaled structures appearing in families of slope curves of the correlation integrals and is
checked against time reparametrization. The data for the two unprocessed 10-s episodes are used for a test of the methodology,
as well as a re-examination of the adequacy of the model of an autonomous dynamic system in steady state and of the concept
of an attractor in brain dynamics investigations. Striking evidence for the model’s inadequacy is provided by the episode
of subject S1. In this example five consecutive overlapping 6-s sections do show evidence for low-dimensional dynamics, whereas the 10-s
section containing those sections does not. The episode of subject 1 provides an example of α-activity which may involve self-organized
dynamics extending down to low frequencies. The system (the neuronal network) showing episodes of attractor-ruled dynamics,
under conditions of blurred and smoothly fading out evidence that it stays on an attractor, is designated as being ruled by
a ‘shadow-attractor’. This concept is compared with that of a ‘quasi-attractor’ introduced by H. Haken in studies of physiological
systems. One possible mechanism for the observed episodes is proposed, based on a time-dependent number of enslaved sub-systems.
Received: 28 June 1996 / Accepted in revised form: 27 May 1995 相似文献