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1.
The dynamics of coupled biological oscillators can be modeled by averaging the effects of coupling over each oscillatory cycle so that the coupling depends on the phase difference between the two oscillators and not on their specific states. Average phase difference theory claims that mode locking phenomena can be predicted by the average effects of the coupling influences. As a starting point for both empirical and theoretical investigations, Rand et al. (1988) have proposed d/dt= — K sin ), with phase-locked solutions =arcsin( /K), where is the difference between the uncoupled frequencies and K is the coupling strength. Phase-locking was evaluated in three experiments using an interlimb coordination paradigm in which a person oscillates hand-held pendulums. was controlled through length differences in the left and right pendulums. The coupled frequency c was varied by a metronome, and scaled to the eigenfrequency v of the coupled system K was assumed to vary inversely with c. The results indicate that: (1) and K contribute multiplicatively to (2) =0 or = regardless of K when =0; (3) 0 or regardless of when K is large (relative to ); (4) results (1) to (3) hold identically for both in phase and antiphase coordination. The results also indicate that the relevant frequency is c/v rather than c. Discussion high-lighted the significance of confirming =arcsin(/K) for more general treatments of phase-locking, such as circle map dynamics, and for the 11 phase-entrainment which characterizes biological movement systems. 相似文献
2.
N. J. Marshall M. F. Land 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1993,173(5):565-582
The optics of a variety of stomatopod eyes has been investigated using goniometric eye-mapping techniques and anatomical measurements. The species examined come from 3 of the 4 existing superfamilies: the Gonodactyloidea, Lysiosquilloidea and Squilloidea. This paper examines acuity, optical axes and general features of eye shape. Stomatopod eyes are divided into 3 clearly distinct zones; the mid-band and two hemispheres. Each hemisphere consists of an edge region, a visual streak and a near mid-band region. The optical axes of many ommatidia from both hemispheres are skewed inwards towards the centrally placed mid-band and are rarely normal to the corneal surface. The large skew angle enables each hemisphere to examine an area which extensively overlaps that of the other hemisphere. As a result monocular distance judgement is possible. Most of the ommatidia in each hemisphere are part of a horizontally aligned but vertically acute visual streak area. There is one visual streak per hemisphere and both look into the same 5–10° strip. This narrow strip is also the area in space the mid-band ommatidia examine. An acute zone is present in the eyes of lysiosquilloid and gonodactyloid stomatopods and includes ommatidia, from both the hemispheres and the mid-band. Here inter-ommatidial angles, especially those in the horizontal direction, are reduced. Acute zone facets are enlarged to increase sensitivity rather than aid spatial resolution.Abbreviations and definitions AZ
Acute Zone
- MB
Mid-band
-
D
Corneal facet diameter, as MB facets are asymmetrical, values for width and height of each facet are given
- DH
dorsal hemisphere
-
f
Focal length of each ommatidium, estimated from the centre of the corneal lens to the tip of the rhabdom
- NeMB
Near mid-band ommatidia
-
R
Resolving power=1/2average
- Rh
Horizontal resolving power=1/2h
- Rv
Vertical resolving power=1/2v
- VH
ventral hemisphere
-
Geometrical acceptance angle (a/f×57.3) of each ommatidium
- h
Horizontal inter-ommatidial angle, between facets along a row
- v
Vertical inter-ommatidial angle, between rows; Superfamily Gonodactyloidea
-
g.c.
Gonodactylus chiragra
-
O.s.
Odontodactylus scyllarus
-
H.e.
Hemisquilla ensigera; Superfamily Lysiosquilloidea
-
L.t.
Lysiosquilla tredecimdentata
-
C.s.
Coronis scolopendra; Superfamily Squilloidea
-
O.o.
Oratosquilla solicitans 相似文献
3.
Summary The isolation of recombinant carrying virC mutation from newly isolated virulent carrying virL virC virR, (Horiuchi et al., 1969) was succeeded and the genetic character of virC mutation producing clear plaque was studied. virL virC shows weak-virulent character and produces clear plaque on CIts lysogen but not on wild type lysogen. virC shows avirulent character and no plaque is produced on these lysogen. The virC mutation is located very closely to and on the left side of the virR region (Fig. 1) which is presumed to be the operator of the right-side operon including O and P cistrons. The genetic characters of virL, virR and virC, were compared with v
1, v
2, v
3 mutations of classical vir (Jacob and Wollman, 1954) and c
17 mutation of another type of virulent (Da Silva and Jacob, 1968). The results indicate that virL, virC or virR mutation is similar to v
2, v
1 or v
3 mutation, respectively, and an effect of virC mutation on producing virulent character was somewhat similar to that of c
17 mutation and was stronger than that of virR mutation. The length of virR regions was suggested to be smaller than one tenth of that of the CI cistron. 相似文献
4.
Summary A sensitive photometric method is described by which the dichroism of lipid bilayer membranes in aqueous phase can be measured. The method is applied to black films with incorporated chlorophylla andb. With chlorophylla a relatively large dichroism is found in the Soret band and a much weaker dichroism in the red band. From the experimental data, the angles
B
and
R
between the blue and red transition moments and the membrane can be obtained.
B
and
R
are then used to calculate the angle of the porphyrin ring with respect to the membrane surface. For chlorophylla and three different lipids, values of between 44 and 49° are found. 相似文献
5.
Josiane Szpirer et Philippe Brachet 《Molecular & general genetics : MGG》1970,108(1):78-92
Summary This work deals with the ability of phage 80 to provide defective mutants of with their missing functions.
Functions Involved in Recombination. As shown by others, the Int mechanism of 80 cannot excise prophage . However, 80 efficiently excises recombinants from tandem dilysogens, using its Ter mechanism. Likewise, the nonspecific mechanism Red is interchangeable between 80 and .
Maturation of DNA by 80. The Ter recombinants excised by 80 from tandem dilysogens are packaged into a 80 protein coat. This contrasts with the fact, already mentionned by Dove, that 80 is extremely inefficient for packaging phage superinfecting a -lysogen. The latter result is also found when the helper phage is a hybrid with the left arm of (80hy4 or 80hy41 — see Fig. 1). However, the maturation of the superinfecting is much more efficient if the 80hy used as a helper has the att-N region of (like 80hy1). Conversely a with the att-N region of 80 (hy6 — see Fig. 1) is packaged more efficiently by 80 or 80hy4 than by 80hy1. It is suggested that the maturation of chromosome superinfecting an immune cell requires a recombination with the helper phage.
Vegetative Functions. Among the replicative functoons O and P, the latter only can be supplied by 80. That N mutants are efficiently helped by 80 does not tell that 80 provides the defective with an active N product; the chromosomes are simply packaged into a 80 coat. This shows that 80 is unable to switch on the late genes of . That neither 80 nor any of the 80hy tested can provide an active N product is shown in a more direct way by their complete failure to help N
-r14; this phage carries a polar mutation which makes the expression of genes O and P entirely N-dependant. The maturation of a N
- by 80 contrasts with the fact that mutants affected in late genes (A, F or H) are not efficiently helped by 80. This suggests that the products coded by these genes are not interchangeable between 80 and , and that packaging of DNA into 80 coats is possible but inhibited when late proteins are present in the cell.
Activation of the Late Genes. Among the im
80
h
+
hybrids tested, only 80hy41 is able to switch on the late genes of a N defective mutant. This hybrid differs from the other hybrids studied here, by the fact that it has the Q-S-R region of (see Fig. 1). The results are consistant with the view that the product of Q gene is sufficient for activating the late genes of a DNA. N would thus control the expression of late genes only indirectly by controlling the expression of gene Q (Couturier & Dambly have independantly reached the same conclusion, 1970). Furthermore the failure of 80 and of the 80hy1 and 80hy4 to activate the late genes of would imply that these phages are unable to provide an Q product active on the chromosome Reciprocally, switches on the late genes of prophage 80hy41, but not of prophages 80hy1 and 80hy4. This suggests that the initiation of late genes expression takes place at a main specific site located in the Q-S-R region of the chromosome. The expression of the late genes would thus be sequential, and proceed through the left arm only when steaky ends cohere. Similar conclusions were reached independantly by Toussaint (1969) and by Herskowitz and Signer (1970).
Ce travail a été réalisé dans le cadre du contrat d'association Euratom-U. L. B. 007-61-10 ABIB et avec l'aide du Fonds de la Recherche Fondamentale Collective. 相似文献
Ce travail a été réalisé dans le cadre du contrat d'association Euratom-U. L. B. 007-61-10 ABIB et avec l'aide du Fonds de la Recherche Fondamentale Collective. 相似文献
6.
Uptake kinetics of nitrogen derived from sewage–seawater mixtures (2.5–20% v/v effluent) were determined in the laboratory for Ulva rigida (Chlorophyceae) native from Bahía Nueva (Golfo Nuevo, Patagonia, Argentine). In terms of nitrogen concentration, experimental enrichment levels varied between 53.7 and 362.3M of ammonium and between 0.77 and 6.21M of nitrate+nitrite. Uptake rates were fitted to the Michaelis–Menten equation, with the following kinetic parameters: ammonium: Vmax = 591.2molg–1h–1,
K
s=262.3M, nitrate+nitrite: V
max=12.9molg–1h–1, K
s=3.5M). Both nutrients were taken up simultaneously, but ammonium incorporation was faster in all cases. The results show a high capability of Ulva rigida to remove sewage-derived nitrogen from culture media. In the field, most of the nitrogen provided by the effluent would be tied up in algal biomass, supporting low nitrogen levels found at a short distance away from the source. 相似文献
7.
ATP synthase (F0F1) is driven by an electrochemical potential of H+ (H+). F0F1 is composed of an ion-conducting portion (F0) and a catalytic portion (F1). The subunit composition of F1 is 33. The active 33 oligomer, characterized by X-ray crystallography, has been obtained only from thermnophilic F1 (TF1). We proposed in 1984 that ATP is released from the catalytic site (C site) by a conformational change induced by the DELSEED sequence via -F0. In fact, cross-linking of DELSEED to stopped the ATP-driven rotation of in the center of 33. The torque of the rotation is estimated to be 420 pN·å from the H+ and H+-current through F0F1. The angular velocity () of is the rate-limiting step, because H+ increased theV
max of H+ current through F0, but not theK
m
(ATP). The rotational unit of F0 (=ab2c10) is /5, while that in 33 is 2/3. This difference is overcome by an analog-digital conversion via elasticity around DELSEED with a threshold to release ATP. The distance at the C site is about 9.6 å (2,8-diN3-ATP), and tight Mg-ATP binding in 33 was shown by ESR. The rotational relaxation of TF1 is too rapid (=100 nsec), but the rate of AT(D)P-induced conformational change of 33 measured with a synchrotron is close to . The ATP bound between the P-loop and E188 is released by the shift of DELSEED from RGL. Considering the viscosity resistance and inertia of the free rotor (-c), there may be a stator containing OSCP (= of TF1) and F0-d to hold free rotation of 33. 相似文献
8.
In this paper we give an analytical reformulation of Holling's (1966) simulation model for invertebrate predatory behaviour. To this end we represent a population of predators as a frequency distribution over a space of (physiological) states. The functional response of a predator is calculated from the (stable) equilibrium distribution of its state as a function of prey density.Starting from the general model various other models are obtained by limit processes, some of them new and some of them old. The more interesting of which will be studied in further papers in this series.List of Notation
a
rate constant of digestion
-
b
maximum of rate constant of prey encounter in the mantid
-
b
maximum pursuit duration in the mantid (p(0))
-
c
satiation threshold for search
-
c
satiation threshold for pursuit in the mantid: c=c(b-Ds/v)/b
-
D
m
maximum sighting distance
-
D
p
pursuit distance
-
D
s
strike distance
-
expectation operator
-
f, f
0
rate of change of satiation during search
-
f
1
rate of change of satiation during prey handling
-
F
functional response: number of prey eaten per unit of time by one predator
-
g
rate constant of effective prey encounter in the gobbler and sucker
- g0
rate constant of prey encounter
- g1
probability of no prey loss from pursuit
- g2
probability of no prey escaping during pursuit
-
H
Holling secretary correction factor in the sucker: fraction of the time spent searching
-
k
R
density of R
- kT
probability density of maximum prey handling time
-
K
probability that maximum prey handling time is
e, i.e. pursuit duration is zero
-
K
R
distribution function of R
-
N
number of prey caught
-
p
(marginal) density of S
- p0
density of S in search
- p1
simultaneous density of S and T
- P
probability
-
p
1
marginal density of S in handling prey
-
q
probability of strike success
-
R
ratio of realized to maximum sighting distance
-
s, S
satiation
-
satiation axis
-
t
time
-
handling time axis
-
u
eating speed
-
U
homogeneous(0,1) random variable
-
v
pursuit speed
-
V
exponential(1) random variable
-
w
prey weight
-
W
exponential(m) random variable
-
x
prey density
-
ratio of maximum successful pursuit duration to meal duration (pm/e)
-
pm
-
relative duration of successful pursuit (p/pm)
-
ratio of shortest to largest sighting distance
-
xe
-
time already spent handling a prey item
-
rate of prey loss during prey handling
-
prey escape rate during pursuit
-
prey biomass density (xw)
-
, T
maximum time still to be spent handling a prey item
-
e
meal duration
-
m
maximum handling time (
e+
p)
-
p
duration of successful pursuit
-
pm
maximum duration of successful pursuit (p(0))
-
hazard rate
-
m
maximum of hazard rate
-
scaled functional response (wF)
-
minimal i-state space 相似文献
9.
Summary The surface tension and foaminess of (a) unlimited, (b) substrate limited, and (c) oxygen transfer limited growth media of Hansenula polymorpha were measured using methanol, ethanol or glucose as a substrate.The time dependence of can be described by the Avrami-Überreiter relationship: log (2.3 log V)=n log t+log b, where V = (O – eq/(t – eq, and O, t and eq are at tM=0, tM=t and tM (equilibrium value).The constants n and b are functions of the fermentation time tF as long as the growth is unlimited but they are constant in the state of limited growth. With glucose substrate, the foaminess can be presented as a definite function of the time, tDG, which is necessary to attain eq. With alcohol as a substrate no definite (tDG) function was found.Symbols b
constant in Eq. (1)
- n
constant in Eq. (1)
- S
substrate concentration
- T
temperature
- tM
time h (measured from the beginning of the determination of the surface tension )
- tF
cultivation time h (measured from the time of inoculation)
- tDG
time (min) necessary to attain the equilibrium surface tension )
- X
dry biomass concentration (gl–1)
- V
(O – eq)/(t – eq)
- VS
equilibrium volume of the foam (cm3)
- VG
volumetric gas flow rate during the estimation of (cm3 s–1)
- vvm
volumetric gas flow rate with regard to the volume of the medium (min–1)
- wSG
superficial gas velocity (cm s–1)
- m
maximum specific growth rate (h–1)
-
VS/VG foaminess (s)
-
surface tension, mMm–1 (milli Newton m–1)
- O
at tM=0
- eq
equilibrium surface tension ( at tM)
- t
at tM=t
- HP
probes from Hansenula polymorpha cultivation
- NLG
non limited growth
- OTLG
oxygen transfer limited growth
- SLG
substrate limited growth 相似文献
10.
Huang Chi-Ying F. Yuan Chiun-Jye Livanova Nataliya B. Graves Donald J. 《Molecular and cellular biochemistry》1993,127(1):7-18
A catalytic fragment,
1-298, derived from limited chymotryptic digestion of phosphorylaseb kinase (Harris, W.R.et al., J. Biol. Chem., 265: 11740–11745, 1990), is reported to have about six-fold greater specific activity than does the subunit-calmodulin complex. To test whether there is an inhibitory domain located outside the catalytic core of the subunit, full-length wild-type and seven truncated forms of were expressed inE. coli. Recombinant proteins accumulate in the inclusion bodies and can be isolated, solubilized, renatured, and purified further by ammonium sulfate precipitation and Q-Sepharose column. Four out of seven truncated mutants show similar (
1-353 and
1-341) or less (
1-331 and
1-276) specific activity than does the full-length wild-type ,
1-386. Three truncated forms,
1-316,
1-300, and
1-290 have molar specific activities approximately twice as great as those of the full-length wild-type and the nonactivated holoenzyme. All recombinant s exhibit similarK
m values for both substrates, i.e., about 18M for phosphorylaseb and about 75 M for MgATP. Three truncated s,
1-316,
1-300, and
1-290, have a 1.9- to 2.5-fold greater catalytic efficiency (V
max/K
m) than that of the full-length wild-type and a 3.5- to 4.5-fold greater efficiency than that of the truncated
1-331. This evidence suggests that there is at least one inhibitory domain in the C-terminal region of , which is located at
301-331·
1-290, but not
1-276, which contains the highly conserved kinase domain, is the minimum sequence required for the subunit to exhibit phosphotransferase activity. Both
1-290 and
1-300 have several properties similar to full-length wild-type , including metal ion responses (activation by free Mg2+ and inhibition by free Mn2+) pH dependency, and substrate specificities. 相似文献
11.
The production of erythritol and the erythritol yield from glucose by Torula sp. were improved, in increasing order, by supplementing with 10 mg MnSO44H2O l–1, 2 mg CuSO45H2O l–1, and both 10 mg MnSO44H2O l–1 and 2 mg CuSO45H2O l–1. Mn2+ decreased the intracellular concentration of erythritol, whereas Cu2+ increased the activity of erythrose reductase in cells. These results suggest that Mn2+ altered the permeability of cells, whereas Cu2+ increased the activity of erythrose reductase in cells. 相似文献
12.
Summary The ratio of deuterium to hydrogen (expressed as D) in hydrogen released as water during the combustion of dried plant material was examined. The D value (metabolic hydrogen) determined on plant materials grown under controlled conditions is correlated with pathways of photosynthetic carbon metabolism. C3 plants show mean D values of-132 for shoots and -117 for roots; C4 plants show mean D values of -91 for shoots and-77 for roots and CAM plants a D value of-75 for roots and shoots. The difference between the D value of shoot material from C3 and C4 plants was confirmed in species growing under a range of glasshouse conditions. This difference in D value between C3 and C4 species does not appear to be due to differences in the D value (tissue water) in the plants as a result of physical fractionation of hydrogen isotopes during transpiration. In C3 and C4 plants the hydrogen isotope discrimination is in the same direction as the carbon isotope discrimination and factors contributing to the difference in D values are discussed. In CAM plants grown in the laboratory or collected from the field D values range from-75 to +50 and are correlated with 13C values. When deprived of water, the D value (metabolic hydrogen) in both soluble and insoluble material in leaves of Kalanchoe daigremontiana Hamet et Perr., becomes less negative. These changes may reflect the deuterium enrichment of tissue water during transpiration, or in field conditions, may reflect the different D value of available water in areas of increasing aridity. Whatever the origin of the variable D value in CAM plants, this parameter may be a useful index of the water relations of these plants under natural conditions. 相似文献
13.
Problems in estimating growth rates of marine phytoplankton from short-term14C assays 总被引:1,自引:0,他引:1
Growth rate estimates () of phytoplankton populations that were sampled from nitrogen-limited continuous cultures and then incubated for short durations in batch culture with added14C-HCO3
– were significantly different than steady-state growth rates () for 3 of 5 marine phytoplankton species. Two diatoms,Thalassiosira weissflogii andChaetoceros simplex, displayed virtually identical growth rates (=) over a wide range of, whereas for a third diatom,Phaeodactylum tricornutum, was overestimated by an average of 40% compared to. In contrast, was underestimated by the14C technique for the two remaining species: up to 40% at a steady-state of 1.0 day–1 for the chlorophyteDunaliella tertiolecta and up to 100% at of 1.4 day–1 for the haptophytePavlova lutheri. For the latter two species the divergence between and appeared to increase with increasing steady-state. A simple model of labeled and total carbon flow between the aqueous phase and cellular biomass was constructed to demonstrate that respiration was negligible when=, but was significant when>. In the cases in which<, a rapid physiological alteration presumably took place once the steady state was disturbed and cells were placed in the incubation chambers, which perhaps was related to the nutritional state of the cultures at the time of sampling. Questions thus are raised regarding our ability to measure accurately primary productivity from shipboard experiments with confined samples of phytoplankton from nutrient-impoverished waters that probably are less hardy than the laboratory cultures used in these studies. 相似文献
14.
Summary In this paper, the results of the preceding electrophysiological study of sodium-alanine cotransport in pancreatic acinar cells are compared with kinetic models. Two different types of transport mechanisms are considered. In the simultaneous mechanism the cotransporterC forms a ternary complexNCS with Na+ and the substrateS; coupled transport of Na+ andS involves a conformational transition between statesNCS andNCS with inward- and outward-facing binding sites. In the consecutive (or ping-pong) mechanism, formation of a ternary complex is not required; coupled transport occurs by an alternating sequence of association-dissociation steps and conformational transitions. It is shown that the experimentally observed alanine- and sodium-concentration dependence of transport rates is consistent with the predictions of the simultaneous model, but incompatible with the consecutive mechanism. Assuming that the association-dissociation reactions are not rate-limiting, a number of kinetic parameters of the simultaneous model can be estimated from the experimental results. The equilibrium dissociation constants of Na+ and alanine at the extracellular side are determined to beK
N
<-64mm andK
S
<-18mm. Furthermore, the ratioK
N
/K
N
S
of the dissociation constants of Na+ from the binary (NC) and the ternary complex (NCS) at the extracellular side is estimated to be <-6. This indicates that the binding sequence of Na+ andS to the transporter is not ordered. The current-voltage behavior of the transporter is analyzed in terms of charge translocations associated with the single-reaction steps. The observed voltage-dependence of the half-saturation concentration of sodium is consistent with the assumption that a Na+ ion that migrates from the extracellular medium to the binding site has to traverse part of the transmembrane voltage. 相似文献
15.
J. -P. Ewert H. -A. Häeter 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1969,64(2):135-153
Zusammenfassung Durch simultane visuelle Bewegungsreize, die von mehreren Beutetieren (z.B. Mehlkäferlarven) ausgehen, wird der Beutefang der Erdkröte (Bufo bufo L.) gehemmt. An diese Verhaltensheobaehtung anknüpfend, wurde die Abhängigkeit dieses inhibitorischen Umfeldeffektes von verschiedenen visuellen Reizparametern im Attrappen versuch quantitativ gemessen: Im frontalen Gesichtsfeld der Kröte rotierte vor dunklem Hintergrund eine weiße, rechteckige, 2,5 × 20° große Beuteattrappe (Zentralattrappe, z) mit dem Rechteckzentrum im Drehpunkt. Zusätzlich konnten mehrere Kreisscheiben von 5 bzw. 10° (Peripherattrappen, p) um die Zentralattrappe bewegt werden.Die Beutefangaktivität R
z [Beutefangreaktionen x min–1] auf die allein gebotene Zentralattrappe war bei einer Sehwinkelgeschwindigkeit v
s der distalen Attrappenkanten 10v
s30 [grad x see–1] maximal und sank für kleinere oder größere Winkelgeschwindigkeiten wieder ab.
Eine mit v
s=25 [grad x sec–1] allein bewegte Peripherattrappe löste maximale Beutefangaktivität R
p aus. Mit zunehmender Anzahl n
p simultan bewegter Peripherattrappen sank die Beutefangaktivität ab.Mehrere, um den gleichen Drehpunkt bewegte Peripherattrappen, deren Abstand untereinander
=10° betrug, blieben von der Kröte unbeantwortet. Sie bildeten ein inhibitorisches Umfeld und hemmten dadurch die Reaktion auf die gleichzeitig bewegte Zentralattrappe z. — Die im Simultanreizungsversuch gemessene Beutefangaktivität R
zp war abhängig vom Abstand
[grad] zwischen Zentralattrappe und Peripherattrappen (
: Kürzester Abstand zwischen z und p): Für
=10° war R
zp0 und stieg für
>10° an. — Kontrollversuche, die jeweils auf die Simultanreizung mit z allein folgten (R
z), ließen eine
-abhängige Nachhemmung erkennen. — Die hemmende Wirkung auf die Beantwortung von z war auch von der Sehwinkelgeschwindigkeit v
s der Peripherattrappen abhängig; sie war bei derjenigen Sehwinkelgeschwindigkeit (v
s=25 [grad × sec–1]) maximal, mit der die Zentralattrappe, allein geboten, maximale Beutefangaktivität auslöste; für v
sg25 [grad × sec–1] nahm die Hemmung wieder ab.Die Versuchsergebnisse lassen auf inhibitorische Verknüpfungen innerhalb des zentralen visuellen Systems schließen. Es wird vermutet, daß die Reiz-Verhaltens-reaktionsbeziehungen in den visuellen Simultanreizungsversuchen durch eine Art zentrale laterale Inhibition bestimmt werden.
Mit Unterstützung der Deutschen Forschungsgemeinschaft (Ew 7/4+5). 相似文献
Inhibitory effect of simultaneously moved prey dummies on the prey catching behaviour of the common toad (Bufo bufo L.)
Summary The prey catching behaviour of the toad (Bufo bufo L.) is generally inhibited by simultaneously visual moving stimuli caused by a group of prey animals (mealworms). According to this behavioural observation the dependence of this inhibitory effect on several visual parameters were quantitatively measured in dummy experiments: in the frontal visual field of the toad a white rectangular prey dummy of 2,5×20° (central dummy, z) was rotating in a centre against dark background. In addition several disks of 5 or 10° diameter (peripheral dummies, p) could simultaneously rotate around the central dummy (Figs. 1 and 7).The prey catching activity R z [catching reactions x min–1] released by rotation of only the central dummy z increased with increasing angular velocity v s of the stimulus distal edges, reaching a maximum for 10vs30 [degrees x sec–1] and decreasing for v s>30 [degrees x sec–1] (Fig. 5).A single peripheral dummy p, moved at v s=25 [degrees x sec–1], released maximal catching activity R p. The activity R p decreased with the increasing number n p of simultaneously offered dummies (Fig. 6).The prey catching behaviour of the toad was inhibited, when several peripheral dummies p were moved around the centre with a distance =10° from each other. They caused an inhibitory field and they also inhibited the response to a simultaneously moved central dummy z. The prey catching activity, measured in experiments in which z and p rotated simultaneously, depends on the distance [degrees] between z and p ( being the shortest distance between z and p). For =10°, R zp was zero; R zp increased for >10° (Figs. 9 and 10). — Control experiments carried out with z allone — after having applied the simultaneous stimulation — showed a - dependent after-inhibition (Fig. 9). — The inhibitory effect on the response to z also depended on the angular velocity v s of p; the inhibition was at a maximum for v s25 [degrees x sec–1], and it decreased for v s25 [degrees x sec–1] (Fig. 11).The experimental results suggest inhibitory interactions within the central visual system. It is supposed that the relation between stimulus and behavioural reaction in simultaneous stimulating experiments results from some kind of central nervous lateral inhibition.
Mit Unterstützung der Deutschen Forschungsgemeinschaft (Ew 7/4+5). 相似文献
16.
The solvent effects of cyclopentyl methyl ether (CPME) on the reaction rates and enzyme enantioselectivity in the enantioselective transesterifications of racemic 6-methyl-5-hepten-2-ol (racemic sulcatol: SUL) and racemic 2,2-dimethyl-1,3-dioxolane-4-methanol (racemic solketal: SOL) with a series of enol esters catalyzed by Pseudomonas cepacia lipase co-lyophilized with cyclodextrins (-, -, -, partially methylated -,and 2,3,6-tri-O-methyl--cyclodextrin: CyD; CyD; CyD; Me1.78 CyD; Me3CyD) were investigated and compared with those in diisopropyl ether (IPE). In the case of SUL, enzyme activities of the co-lyophilizate with Me1.78 CyD in CPME were lower than those in IPE with every acyl source, however, the absolute enantiopreference was shown in the transesterification with vinyl butyrate (VBR) in IPME. When the substrates were SOL and VBR, the enzyme activities in CPME were greatly enhanced as high as 1.6–9.8-fold, while the enantioselectivities in CPME were comparable to those in IPE.Revisions requested 16 December 2004; Revisions received 17 January 2005 相似文献
17.
D. S. Dimitrov 《The Journal of membrane biology》1984,78(1):53-60
Summary A simple viscoelastic film model is presented, which predicts a breakdown electric potential having a dependence on the electric pulse length which approximates the available experimental data for the electric breakdown of lipid bilayers and cell membranes (summarized in the reviews of U. Zimmermann and J. Vienken, 1982,J. Membrane Biol.
67:165 and U. Zimmermann, 1982,Biochim. Biophys. Acta
694:227). The basic result is a formula for the time of membrane breakdown (up to the formation of pores): =(/C)/(
m
2
0
2
U
4/24Gh
3+T
2/Gh–1), where is a proportionality coefficient approximately equal to ln(h/20),h being the membrane thickness and 0 the amplitude of the initial membrane surface shape fluctuation ( is usually of the order of unity), represents the membrane shear viscosity,G the membranes shear elasticity modules,
m
the membrane relative permittivity, 0=8.85×10–12
Fm,U the electric potential across the membrane, the membrane surface tension andT the membrane tension. This formula predicts a critical potentialU
c
;U
c
=(24Gh
3/
m
2
0
2
)1/4 (for = andT=0). It is proposed that the time course of the electric field-induced membrane breakdown can be divided into three stages: (i) growth of the membrane surface fluctuations, (ii) molecular rearrangements leading to membrane discontinuities, and (iii) expansion of the pores, resulting in the mechanical breakdown of the membrane. 相似文献
18.
Dr. R. V. Nair T. M. Masajo G. S. Khush 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1982,61(1):19-22
Summary The inheritance of resistance to whitebacked planthopper Sogatella furcifera (Horvath) was studied in 21 rice varieties. Reactions of F1; F2 and F3 progenies of the crosses of 21 resistant varieties with the susceptible variety TN 1 revealed that a single dominant gene governs resistance in Mushkan 41, Santhi, Siahnakidar 195, SM2-34, Tirisurkh 251, Zirijowaian 245, 18, 24A, 39, 76 S, 78, 180, 213 B, 267, 293, CI 6037-4, NP97, S39 JKW and Bansphul. In varieties 65 and 274 A, resistance is governed by one dominant and one recessive gene which segregate independently of each other. Tests for allelism with the Wbph 1 gene originally identified in N 22 revealed that the dominant gene present in all the test varieties is the same as Wbph 1. Further studies are required to determine the allelic relationships of the recessive gene found in varieties 65 and 274 A. 相似文献
19.
Transducin (T), the G-protein in the visual system, is a heterotrimer arranged as two functional units, T and T. N, N-1, 2-phenylenedimaleimide (o-PDM) and N, N-1, 4-phenylenedimaleimide (p-PDM), two cysteine specific-homobifunctional agents, were used to covalently cross-link T and its units. A complete inhibition in T function was observed in the presence of these compounds. Incubation of T with o-PDM or p-PDM resulted in the formation of high-molecular-weight oligomers of 70-, 105-, 140-, and 200 kDa, as well as intramolecular cross-linked polypeptides that migrated as 35- and 37-kDa bands. Additionally, the treatment of T with both reagents produced a major species of 46-kDa. The combination of intact T and o-PDM- or p-PDM-treated T reconstituted T native activities. On the contrary, when o-PDM- or p-PDM-modified T was incubated with intact T, more than 90% inhibition on T function was observed. Hence, the cysteines modified and/or cross-linked on T represent functionally important residues of T. 相似文献
20.
Microbial transformation of ginsenoside Rb1 by Rhizopus stolonifer and Curvularia lunata 总被引:2,自引:0,他引:2
Of 49 microbial strains screened for their capabilities to transform ginsenoside Rb1, Rhizopus stolonifer and Curvularia lunata produced four key metabolites: 3-O-[-d-glucopyranosyl-(1,2)--d-glucopyranosyl]- 20-O-[-d-glucopyranosyl]-3,12, 20(S)-trihydroxydammar-24-ene (1), 3-O-[-d-glucopyranosyl-(1,2)--d- glucopyranosyl]-20-O-[-d-glucopyranosyl]-3,12, 20(S)-trihydroxydammar-24-ol (2), 3-O-[-d-gluco- pyranosyl-(1,2)--d-glucopyranosyl]-3, 12, 20(S)-trihydroxydammar-24-ene (3), and 3-O--d-glucopyranosyl-3, 12, 20(S)-trihydroxydammar-24-ene (4), identified by TOF-MS, 1H- and 13C-NMR spectral data. Metabolites 1, 3 and 4 were from the incubation with R. stolonifer, and 1 and 2 from the incubation with C. lunata. Compound 2 was identified as a new compound. 相似文献