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1.
Jürgen Kröller 《Biological cybernetics》1995,74(1):9-20
The response of primary muscle spindle afferent fibers to muscle stretch is nonlinear. Now spindle responses (trains of action
potentials) to band-limited Gaussian white noise length perturbations of the gastrocnemius muscles (input signal) are described
in cats. The input noise upper cutoff frequency was clearly above the frequency range of physiological length changes in cat
hindleg muscles. The input–output relation was analyzed by means of peri-spike averages (PSAs), which could be shown to correspond
to the kernels of Wiener’s white noise approach to systems identification. The present approach (the reverse correlation analysis)
was applied up to the third order. An experiment consisted of two recordings: one (the source recording) to determine PSAs
and the other (the test recording) to provide an input signal for predicting responses. The predictions of different orders
were compared with the actual neuronal response (the observation) of the test recording. Four different approximation procedures
were developed to adapt prediction and observation and to determine weighting factors for the predictions of different orders.
The approximations also yielded the value of the power density P of the input noise signal: at a variety of stimulus parameters,
P from approximations had the same magnitude as P determined directly from the input signal amplitude spectrum. The prediction of a sequence of action potentials improved
the higher the order of components. 37 of 42 action potentials of a test recording (the observation) could be confidently
predicted from PSAs or kernels. Compared with the size of the linear first-order prediction curve, the relative sizes of the
second and third-order prediction curves were: 1.0 : 0.47 : 0.26.
Received: 15 November 1994/Accepted in revised form: 23 May 1995 相似文献
2.
H. Schmitz M. Mürtz H. Bleckmann 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2000,186(6):543-549
The pit organs of the beetle Melanophilaacuminata were stimulated with monochromatic infrared radiation using a continuous wave CO overtone infrared laser. Best sensitivity
was in the wavelength range 2.8–3.5 μm. In this range a stimulus intensity of 14.7 mW cm−2 was sufficient to generate single action potentials. At a wavelength of 5 μm receptor performance significantly decreased.
An increase in stimulus intensity caused a decrease in response latency and an increase in the number of action potentials
elicited. At a given wavelength (3.4 μm) the dynamic amplitude range of action potential responses covered 12 dB. At high
stimulus intensities (94.2 mW cm−2) a stimulus duration of 4 ms was sufficient to generate one to two action potentials and a stimulus duration of 60 ms already
caused response saturation (with up to nine action potentials). In a repetitive stimulus regime distinct receptor potentials
were visible up to a frequency of 600 Hz.
Accepted: 18 March 2000 相似文献
3.
Superfusion of clinical concentrations of enflurane (0.5% or 1.0%), an inhalation anaesthetic, over the abdominal ganglion
ofAplysia significantly affected the amplitude of the gill withdrawal reflex evoked by tactile stimulation of the siphon. Enflurane
superfusion (0.5%) suppressed the gill withdrawal reflex amplitude (to 46.1% of control; P<0.001 vs control) in eight of ten
experiments. In the remaining two experiments, enflurane superfusion of the abdominal ganglion significantly facilitated the
gill withdrawal reflex amplitude (174.5% of control;P<0.01). In addition, enflurane superfusion significantly reduced the number of action potentials evoked in central gill motor
neurons by the siphon stimulation (to 47.1% of control;P<0.01) in six out of nine experiments. In one of the remaining three experiments, enflurane increased the number of action
potentials evoked by the stimulus (to 200.0% of control). In two of the three, enflurane did not alter the numbet of action
potentials. Behavioural responses were ‘uncoupled’ from the neuronal responses as a result of enflurane superfusion. 相似文献
4.
Ole Rintek Madsen Ulrik Birk Lauridsen Andreas Hartkopp Ole Helmer S?rensen 《European journal of applied physiology and occupational physiology》1997,75(3):239-245
Dual energy x-ray absorptiometry (DEXA) offers the possibility of assessing regional soft tissue composition, i.e. lean mass (LM) and fat
mass : LM may be considered a measure of muscle mass. We examined age-related differences in LM, percentage fat (%fat) and
muscle strength in 100 healthy non-athletic women aged 18–87 years. Relationships between muscle strength and leg LM in 20
elite female weight lifters and in 18 inactive women with previous hip fractures were also studied. The LM and %fat of the
whole body, trunk, arms and legs were derived from a whole body DEXA scan. Isokinetic knee extensor strength (KES) and flexor
strength (KFS) at 30° · s–1 were assessed using an isokinetic dynamometer. The women aged 71–87 years had 35% lower KES and KFS than the women aged 18–40
years (P < 0.0001). Differences in LM were less pronounced. The LM of the legs, for instance, was 15% lower in the old than in the
young women (P < 0.0001). In a multiple regression analysis with age, body mass, height and leg LM or KES as independent variables and KES
or leg LM as the dependent variable, age was the most important predictor of KES (r
partial = −0.74, P < 0.0001). The same applied to KFS. Body mass, not age, was the most important predictor of leg LM (r
partial = 0.65, P < 0.0001) and of LM at all other measurement sites. The LM measured at different regions decreased equally with increasing
age. The KES:leg LM ratio was negatively correlated with age (r = −0.70, P < 0.0001). The weight lifters had significantly higher KES:leg LM ratios than age-matched controls (+12%, P < 0.0001) and vice versa for the women with previous hip fractures (–36%, P < 0.0001). In conclusion, from our study it would seem that in healthy nonathletic women, age is a more important determinant
of muscle strength than is LM as measured by DEXA. Muscle strengthening exercises and inactivity seem to have a considerably
stronger influence on muscle strength than on LM.
Accepted: 27 August 1996 相似文献
5.
The excitability of spinal α-motoneurons in healthy humans was investigated with vibrostimulation (20–60 Hz) applied to different
groups of muscles both under stationary conditions and during vibration-evoked stepping movements with leg suspension. In
15 subjects, the H-reflex amplitude was compared under the conditions of vibration of the left leg quadriceps femoris (QFM) or biceps femoris
(BFM) muscle, as well as under the conditions of vibration of the contralateral, motionless leg QFM muscle in three spatial
positions of the body: upright, supine, and lying on the side with the left leg suspended. Under dynamic conditions, the H-reflex value was compared during evoked and voluntary steppings at eight intervals of the step cycle. In all body positions,
the vibration of each ipsilateral leg muscle caused a significant H-reflex suppression, this suppression being more prominent under the air-stepping conditions. The vibration of the contralateral
leg QFM had weak influence on the H-reflex amplitude. In seven subjects, the vibration of the ipsilateral and contralateral leg muscles generated stepping movements.
During vibration-evoked air-stepping, the H-reflex had different amplitudes in different phases of the step cycle. At the same time, the differences between responses
under voluntary and involuntary stepping conditions were revealed only in the step cycle phase corresponding to the stance
phase. Thus, the different degrees of the H-reflex suppression by vibration in different spatial positions of the body seem to depend on the summary afferent inflows
to the spinal cord interneurons involved in the regulation of locomotion and posture. Apparently, an increase in the spinal
cord neuronal excitability, which is necessary for activating locomotor automatism under the leg unloading conditions, occurs
during evoked air-stepping in the swing phase. 相似文献
6.
Effects of uniaxial cyclic strain on adipose-derived stem cell morphology,proliferation, and differentiation 总被引:3,自引:0,他引:3
Lee WC Maul TM Vorp DA Rubin JP Marra KG 《Biomechanics and modeling in mechanobiology》2007,6(4):265-273
Cells and tissues in vivo are subjected to various forms of mechanical forces that are essential to their normal development
and functions. The arterial blood vessel wall is continuously exposed to mechanical stresses such as pressure, strain, and
shear due to the pulsatile nature of blood flow. Vascular smooth muscle cells (SMCs) populate the media of blood vessels and
play important roles in the control of vasoactivity and the remodeling of the vessel wall. It is well documented that the
phenotype and functions of vascular SMCs are not only regulated by chemical factors such as transforming growth factor-β1 (TGF-β1), but also by mechanical factors such as uniaxial strain. The purpose of our study was to explore the effects of TGF-β1 alone or in combination with uniaxial cyclic strain on adipose-derived stem cell (ASC) morphology, proliferation, and differentiation.
Low passage ASCs were stimulated with 10% strain at 1 Hz for 7 days, with or without TGF-β1. Cyclic strain inhibited proliferation, and caused alignment of the cells and of the F-actin cytoskeleton perpendicular to
the direction of strain. Strain alone resulted in a decrease in the expression of early SMC markers α-SMA and h
1-calponin. While the response of SMCs and other progenitor cells such as bone marrow stromal cells to mechanical forces has
been extensively studied, the roles of these forces on ASCs remain unexplored. This work advances our understanding of the
mechanical regulation of ASCs.
Presented in part at the third annual meeting of the International Fat Applied Technology Society (IFATS), September 10–13,
2005, Omni Charlottesville Hotel, Charlottesville, VA, USA. 相似文献
7.
External mechanical strain regulates membrane targeting of Rho GTPases by controlling microtubule assembly 总被引:7,自引:0,他引:7
Putnam AJ Cunningham JJ Pillemer BB Mooney DJ 《American journal of physiology. Cell physiology》2003,284(3):C627-C639
Transmission of externallyapplied mechanical forces to the interior of a cell requirescoordination of biochemical signaling pathways with changes incytoskeletal assembly and organization. In this study, we addressed onepotential mechanism for this signal integration by applying uniformsingle external mechanical strains to aortic smooth muscle cells (SMCs)via their adhesion substrate. A tensile strain applied to the substratefor 15 min significantly increased microtubule (MT) assembly by 32 ± 7%, with no apparent effect on the cells' focal adhesions asrevealed by immunofluorescence and quantitative analysis of TritonX-100-insoluble vinculin levels. A compressive strain decreased MT massby 24 ± 9% but did not influence the level of vinculin in focaladhesions. To understand the decoupling of these two cell responses tomechanical strain, we examined a redistribution of the small GTPasesRhoA and Rac. Tensile strain was found to decrease the amount ofmembrane-associated RhoA and Rac by 70 ± 9% and 45 ± 11%,respectively, compared with static controls. In contrast, compressivestrain increased membrane-associated RhoA and Rac levels by 74 ± 17% and 36 ± 13%, respectively. Disruption of the MT network byprolonged treatments with low doses of either nocodazole or paclitaxelbefore the application of strain abolished the redistribution of RhoAand Rac in response to the applied forces. Combined, these resultsindicate that the effects of externally applied mechanical strain onthe distribution and activation of the Rho family GTPases requirechanges in the state of MT polymerization. 相似文献
8.
I. D. Nelson 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(2):147-155
In all four proboscis muscles of the whelk Buccinum undatum, the potassium-induced depolarization response was acutely dependent upon extracellular calcium, being eliminated in calcium-free
conditions. The responses to acetylcholine were found to be partly dependent upon intracellular calcium. Responses to the
peptides phenylalanine-methionine-arginine-phenylalanine-NH2 and phenylalanine-leucine-arginine-phenylalanine-NH2 were much more resistant to calcium-free conditions and appeared to engage the excitation-contraction coupling mechanism
by mobilizing stored intracellular calcium. Sucrose-gap studies of radular retractor muscles showed that the organic calcium
“antagonist” nifedipine enhanced potassium-induced depolarization responses, initiating spike-like action potentials and associated
fast twitch activity. The inorganic calcium antagonist gadolinium exerted concentration-dependent inhibitory actions on these
muscles. Basal tonus and fast twitch activity in response to potassium-induced depolarization were eliminated as were the
spike-like action potentials of the membrane electrical response. The inorganic calcium “antagonist” cadmium greatly enhanced
potassium-induced contractures in all four muscles, and on its own it induced tonic force and fast twitches in all the muscles.
It seems likely that cadmium may have displaced stored intracellular calcium to induce myofilament activation. While these
molluscan smooth muscles appear to possess calcium channels with fast and slow characteristics, their behaviour and pharmacological
manipulation is very different from their more well known mammalian transient and long-lasting channel counterparts. 相似文献
9.
Summary Chemosensory cells in the taste bud of the tongue ofNecturus generate action potentials in response to electrical stimulation through a microelectrode, as recently described by Roper (Science,220:1311–1312, 1983). We report that the epithelial receptor cells also respond to 10mM CaCl2, applied to the mucosal surface, with a depolarization which elicits action potentials when a threshold of –50 mV is reached. Since CaCl2 is one of the taste stimuli in amphibia, the firing of action potentials by chemoreceptor cells may be part of the signal chain in gustatory reception of Ca ions. 相似文献
10.
Ellis AM Huddart H 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(5-6):351-356
In this study the relative potencies of four established molluscan cardioexcitatory agents were examined on Buccinum heart. The potencies were, in decending order: phenylalanine-leucine-arginine-phenylalanine-NH2 (FLRFamide) > phenylalanine-methionine-arginine-phenylalanine-NH2 (FMRFamide; 80% of maximum) > 5-hydroxytryptamine (5HT; 60% of maximum) > guanosine triphosphate (GTP; 15% of maximum). FMRFamide
and FLRFamide had similar dose-response curve patterns with thresholds at 10−9 mol l−1 but FLRFamide was more potent than FMRFamide. The superfused atrium was much less sensitive to all agonists than the internally
perfused ventricle. FLRFamide and FMRFamide induced small depolarizations (1–2 mV) which triggered a burst of action potentials
of about 5 mV which on reaching 4 mV triggered a burst of fast twitch contractions. Lithium, at high concentrations inhibited
FMRFamide and 5-HT responses of internally perfused ventricles. Neomycin also inhibited peptide responses, but was without
effect on 5-HT responses. Heparin, however, for technical reasons was without effect on ventricular responses to all three
agonists. FMRFamide and FLRFamide appear to share a common receptor, the potency difference being due to the substitution
of leucine for methionine in FLRFamide. The RF N-terminal sequence appears crucial for receptor activation. The Phospholipase
C inhibitor neomycin equally inhibits responses to the two peptides while 5-HT responses are unaffected. This implicates a
peptide/receptor interaction which activated inositol 1,4,5-trisphosphate (IP3) as a second messenger.
Accepted: 22 March 2000 相似文献
11.
Georges Dalleau Alain Belli Muriel Bourdin Jean-René Lacour 《European journal of applied physiology and occupational physiology》1998,77(3):257-263
During running, the behaviour of the support leg was studied by modelling the runner using an oscillating system composed
of a spring (the leg) and of a mass (the body mass). This model was applied to eight middle-distance runners running on a
level treadmill at a velocity corresponding to 90% of their maximal aerobic velocity [mean 5.10 (SD 0.33) m · s−1]. Their energy cost of running (C
r
), was determined from the measurement of O2 consumption. The work, the stiffness and the resonant frequency of both legs were computed from measurements performed with
a kinematic arm. The C
r
was significantly related to the stiffness (P < 0.05, r = −0.80) and the absolute difference between the resonant frequency and the step frequency (P < 0.05, r = 0.79) computed for the leg producing the highest positive work. Neither of these significant relationships were obtained
when analysing data from the other leg probably because of the work asymmetry observed between legs. It was concluded that
the spring-mass model is a good approach further to understand mechanisms underlying the interindividual differences in C
r
.
Accepted: 18 August 1997 相似文献
12.
Detailed experimental data from patch clamp experiments on pancreatic α-cells in intact mouse islets are used to model the electrical activity associated with glucagon secretion. Our model incorporates
L- and T-type Ca2+ currents, delayed rectifying and A-type K+ currents, a voltage-gated Na+ current, a KATP conductance, and an unspecific leak current. Tolbutamide closes KATP channels in the α-cell, leading to a reduction of the resting conductance from 1.1 nS to 0.4 nS. This causes the α-cell to depolarise from −76 mV to 33 mV. When the basal membrane potential passes the range between −60 and −35 mV, the α-cell generates action potentials. At higher voltages, the α-cell enters a stable depolarised state and the electrical activity ceases. The effects of tolbutamide are simulated by gradually
reducing the KATP conductance (g
K,ATP
) from 500 pS to 0 pS. When g
K,ATP
is between 72 nS and 303 nS, the model generates action potentials in the same voltage range as the α-cell. When g
K,ATP
is lower than 72 nS, the model enters a stable depolarised state, and firing of action potentials is inhibited due to voltage-dependent
inactivation of the Na+ and T-type Ca2+ currents. This is in accordance with experimental results. Changing the inactivation parameters to those observed in somatostatin-secreting
δ-cells abolishes the depolarised inactive state, and leads to β-cell like electrical activity with action potentials generated even after complete closure of the KATP channels. 相似文献
13.
John P. McCarthy Marcas M. Bamman Janice M. Yelle Adrian D. LeBlanc Roger M. Rowe Michael C. Greenisen Stuart M. C. Lee Elisabeth R. Spector Suzanne M. Fortney 《European journal of applied physiology and occupational physiology》1997,76(1):32-40
Resistance exercise has been suggested to increase blood volume, increase the sensitivity of the carotid baroreceptor cardiac
reflex response (BARO), and decrease leg compliance, all factors that are expected to improve orthostatic tolerance. To further
test these hypotheses, cardiovascular responses to standing and to pre-syncopal limited lower body negative pressure (LBNP)
were measured in two groups of sedentary men before and after a 12-week period of either exercise (n = 10) or no exercise (control, n = 9). Resistance exercise training consisted of nine isotonic exercises, four sets of each, 3 days per week, stressing all
major muscle groups. After exercise training, leg muscle volumes increased (P < 0.05) by 4–14%, lean body mass increased (P = 0.00) by 2.0 (0.5) kg, leg compliance and BARO were not significantly altered, and the maximal LBNP tolerated without pre-syncope
was not significantly different. Supine resting heart rate was reduced (P = 0.03) without attenuating the heart rate or blood pressure responses during the stand test or LBNP. Also, blood volume
(125I and 51Cr) and red cell mass were increased (P < 0.02) by 2.8% and 3.9%, respectively. These findings indicate that intense resistance exercise increases blood volume but
does not consistently improve orthostatic tolerance.
Accepted: 17 January 1997 相似文献
14.
Klaus Schildberger J. J. Milde M. Hörner 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1988,163(5):633-640
Summary The activity of auditory receptor cells and prothoracic auditory neurons of the cricket,Gryllus bimaculatus, was recorded intracellularly while the animal walked on a sphere or while passive movement was imposed on a foreleg.During walking the responses to simulated calling song is altered since (i) the auditory sensory cells and interneurons discharged impulses in the absence of sound stimuli (Figs. 1, 3) and (ii) the number of action potentials in response to sound is reduced in interneurons (Figs. 2, 3).These two effects occurred in different phases of the leg movement during walking and therefore masked, suppressed or did not affect the responses to auditory stimuli (Figs. 3, 4). Hence there is a time window within which the calling song can be detected during walking (Fig. 5).The extra excitation of receptors and interneurons is probably produced by vibration of the tympanum because (i) the excitation occurred at the same time as the leg placement (Fig. 4), (ii) during walking on only middle and hindlegs, no extra action potentials were observed (Fig. 6), (iii) in certain phases of passive movements receptor cells and interneurons were excited as long as the ipsilateral ear was not blocked (Figs. 8, 9).Suppression of auditory responses seems to be peripheral as well as central in origin because (i) it occurred at particular phases during active and passive leg movements in receptor cells and interneurons (Figs. 1, 4, 9), (ii) it disappeared if the ear was blocked during passive leg movements (Fig. 9) and (iii) it persisted if the animal walked only on the middle and hind legs (Fig. 6). 相似文献
15.
We studied the coordinated action of fingers during static tasks involving exertion of force and torque on a handheld object.
Subjects were asked to keep a handle with an attachment that allowed for independent change of the suspended load (0.5–2.0 kg)
and external torque (0.375–1.5 N m) in a vertical position while applying minimal effort. Normal and shear forces were measured
from the thumb; normal forces only were measured from the four fingers. Experimental results: (1) the thumb shear force increased during supination efforts and decreased during pronation efforts; (2) the total moment
of the normal finger forces only counterbalanced approximately 50% of the external torque, hence shear forces accounted for
approximately one-half of the total torque exerted on the object; (3) the total normal force increased with external torque,
and the total force magnitude did not depend on the torque direction; (4) the forces of the `peripheral' (index and little)
fingers depended mainly on the torque while the forces exerted by the `central' (middle and ring) fingers depended both on
the load and torque; (5) there was a monotonic relationship between the mechanical advantage of a finger (i.e., its moment
arm during torque production) and the force produced by that finger; and (6) antagonist finger moments acting opposite to
the intended direction of the total moment were always observed – at low torques the antagonist moments were as high as 40–60%
of the agonist moments. Modeling: A three-zone model of coordinated finger action is suggested. In the first zone of load/torque combinations, activation of antagonist fingers
(i.e., fingers that generate antagonist moments) is necessary to prevent slipping. In the second zone, the activity of agonist
fingers is sufficient for preventing slips. In the third zone, the performer has freedom to choose between either activating
the antagonist fingers or redistributing activities amongst the agonist fingers. The findings of this study provide the foundation
for neural network and optimization modeling described in the companion paper [Zatsiorsky et al. (2002) Biol Cybern DOI 10.1007/s00422-002-0320-7].
Received: 8 August 2001 / Accepted in revised form: 7 February 2002 相似文献
16.
We present a new method for quantification of traction forces exerted by migrating single cells and multicellular assemblies
from deformations of flexible substrate. It is based on an iterative biconjugate gradient inversion method. We show how the
iteration and the solution are influenced by experimental parameters such as the noise on deformations σ
XY
, and the mean depth of recorded deformations Z
M. In order to find the validity range of our computational method, we simulated two different patterns of force. The first
artificial force pattern mimics the forces exerted by a migrating Dictyostelium slug at a spatial resolution of Δ=20 μm (Rieu et al. in Biophys J 89:3563–3576, 2005) and corresponds to a large and spread force field. The second simulated
force pattern mimics forces exerted by a polarized fibroblast at discrete focal adhesion sites separated by Δ=4 μm. Our iterative method allows, without using explicit regularization, the detailed reconstruction of the two investigated
patterns when noise is not too high (σ
XY
/u
max≤6%, where u
max is the maximal deformation), and when the plane of recorded deformations is close to the surface (Δ/Z
M≥4). The method and the required range of parameters are particularly suitable to study forces over large fields such as those
observed in multicellular assemblies.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献
17.
B. Grünewald 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1999,185(6):565-576
Mushroom bodies are central brain structures and essentially involved in insect olfactory learning. Within the mushroom bodies
γ-aminobutyric acid (GABA)-immunoreactive feedback neurons are the most prominent neuron group. The plasticity of inhibitory
neural activity within the mushroom body was investigated by analyzing modulations of odor responses of feedback neurons during
olfactory learning in vivo. In the honeybee, Apis mellifera, feedback neurons were intracellularly recorded at their neurites. They produced complex patterns of action potentials without
experimental stimulation. Summating postsynaptic potentials indicate that their synaptic input region lies within the lobes.
Odor and antennal sucrose stimuli evoked excitatory phasic-tonic responses. Individual neurons responded to various odors;
responses of different neurons to the same odor were highly variable. Response modulations were determined by comparing odor
responses of feedback neurons before and after one-trial olfactory conditioning or sensitisation. Shortly after pairing an
odor stimulus with a sucrose reward, odor-induced spike activity of feedback neurons decreased. Repeated odor stimulations
alone, equally spaced as in the conditioning experiment, did not affect the odor-induced excitation. A single sensitisation
trial also did not alter odor responses. These findings indicate that the level of odor-induced inhibition within the mushroom
bodies is specifically modulated by experience.
Accepted: 9 September 1999 相似文献
18.
In this report, the input/output relations in an isolated ganglion of the leech Hirudo medicinalis were studied by simultaneously using six or eight suction pipettes and two intracellular electrodes. Sensory input was mimicked
by eliciting action potentials in mechanosensory neurons with intracellular electrodes. The integrated neural output was measured
by recording extracellular voltage signals with pipettes sucking the roots and the connectives. A single evoked action potential
activated electrical activity in at least a dozen different neurons, some of which were identified. This electrical activity
was characterized by a high degree of temporal and spatial variability. The action potentials of coactivated neurons, i.e.
activated by the same mechanosensory neuron, did not show any significant pairwise correlation. Indeed, the analysis of evoked
action potentials indicates clear statistical independence among coactivated neurons, presumably originating from the independence
of synaptic transmission at distinct synapses. This statistical independence may be used to increase reliability when neuronal
activity is averaged or pooled. It is suggested that statistical independence among coactivated neurons may be a usual property
of distributed processing of neuronal networks and a basic feature of neural computation.
Received: 20 September 1999 / Accepted in revised form: 3 March 2000 相似文献
19.
20.
Continuous degradation of mixtures of 4-nitrobenzoate and 4-aminobenzoate by immobilized cells of Burkholderia cepacia strain PB4 总被引:1,自引:0,他引:1
Although isolated on 4-aminobenzoate, Burkholderia cepacia strain PB4 is also able to grow on 4-nitrobenzoate. Degradation of an equimolar mixture of the nitroaromatic compound 4-nitrobenzoate
and its corresponding aminoaromatic derivative 4-aminobenzoate by this strain was investigated. Batch experiments showed that,
irrespective of preculturing conditions, both compounds were degraded simultaneously. The mixture-degrading ability of B. cepacia strain PB4 was subsequently tested in continuous packed bed reactors (PBR) with the strain immobilized on Celite grade R-633
or R-635. Higher degradation rates were achieved with the larger particles of Celite R-635. Maximum simultaneous degradation
rates per liter of packed bed of 0.925 mmol l−1 h−1 4-nitrobenzoate and 4-aminobenzoate were obtained for an applied loading rate of the same value (0.925 mmol l−1 h−1 of each compound). Even when the applied load was not removed in its entirety, neither of the two compounds was degraded
preferentially but a percentage of both of them was mineralized. The present study shows the possibility for a pure strain
to biodegrade not only a nitroaromatic compound (4-nitrobenzoate) but also its corresponding amino derivative (4-aminobenzoate)
continuously and simultaneously.
Received: 23 November 1998 / Revision received: 6 April 1999 / Accepted: 9 April 1999 相似文献