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1.
Lyubov Yotova Irene Tzibranska Filadia Tileva G. H. Markx Nelly Georgieva 《Journal of industrial microbiology & biotechnology》2009,36(3):367-372
A simple method for the preparation of the biocatalyst with whole cells is presented, and the applicability of the technique
for biodegradation of phenol in wastewater from the chemical industries using the basidomycetes yeast Trichosporon cutaneum is explored. Kinetic studies of the influence of other compounds contained in wastewater as naphthalene, benzene, toluene
and pyridine indicate that apart from oil fraction, which is removed, the phenol concentration is the only major factor limiting
the growth of immobilized cells. Mathematical models are applied to describe the kinetic behavior of immobilized yeast cells.
From the analysis of the experimental curves was shown that the obtained values for the apparent rate parameters vary depending
on the substrate concentration (μmaxapp from 0.35 to 0.09 h−1 and K
sapp from 0.037 to 0.4 g dm−3). The inhibitory effect of the phenol on the obtained yield coefficients was investigated too. It has been shown that covalent
immobilization of T. cutaneum whole cells to plastic carrier beads is possible, and that cell viability and phenol degrading activity are maintained after
the chemical modification of cell walls during the binding procedure. The results obtained indicate a possible future application
of immobilized T. cutaneum for destroying phenol in industrial wastewaters. 相似文献
2.
Spider mites of the genus Stigmaeopsis (Acari: Tetranychidae) construct and live gregariously inside woven nests on the leaf surface of host plants. This genus
shows waste-management behavior—they defecate at particular sites—but the rules for management differ between species. The
utilization of chemical cues for waste management is known in two species, Stigmaeopsis miscanthi inhabiting Miscanthus sinensis and S. longus inhabiting Sasa senanensis, but not in any others. In this study, we first investigated the origin of the chemical compounds to understand how the behavior
evolved, and then investigated the responses of each species to chemical compounds from different sources. The results show
that the chemical compounds are commonly contained in the feces of several Stigmaeopsis species, as well as in their host plant juices, suggesting this behavior evolved using the chemical compounds originally
contained in their feces. Our results also show that the chemical compounds used by S. miscanthi and S. longus are subtly different and involve host plant differences, and that S. miscanthi could respond to both compounds, but S. longus could not. Considering this in terms of their phylogenetic relationship, it is expected that these two species may have evolved
from a common ancestor living on Sasa senanensis. 相似文献
3.
Roseanne M. Ford Bret R. Phillips John A. Quinn Douglas A. Lauffenburger 《Microbial ecology》1991,22(1):127-138
The directed movement of a bacterial population in response to a chemical gradient is known as bacterial chemotaxis and plays
a critical role in the distribution and dynamic interaction of bacterial populations. A quantitative characterization of the
chemotactic response in terms of intrinsic cell properties is necessary for making reliable predictions about the migratory
behavior of bacterial populations within the environment.
The design of the stopped-flow diffusion chamber (SFDC) provides a well-characterized chemical gradient and reliable method
for measuring bacterial migration behavior. During flow through the chamber a step change in the chemical concentration is
imposed on a uniform suspension of bacteria. Once flow is stopped a transient chemical gradient forms due to diffusion; bacteria
respond by forming a band of high cell density that travels toward higher concentrations of the attractant. Sequential observations
of bacterial spatial distributions over a period of about ten minutes are recorded on photomicrographs. Computer-aided image
analysis of the photographic negatives converts light-scattering information to a digital representation of the bacterial
density profiles. A mathematical model is used to quantitatively characterize these observations in terms of intrinsic cell
parameters: a chemotactic sensitivity coefficient, χ0, from the aggregate cell density accumulated in the band and a random motility coefficient, μ0, from population dispersion in the absence of a chemical gradient.
Using the SFDC assay and an individual cell-based mathematical model we successfully determined values for both of these population
parameters forEscherichia coli K12 responding to fucose. The values we obtained were μ0=1.1 ± 0.4 x 10-5 cm2/sec and χ0=8 ± 3 x 10-5 cm2/sec. These parameters will be useful for predicting population behavior in application systems such as biofilm development,
population dynamics of genetically-engineered bacteria released into the environment, and in situ bioremediation technologies. 相似文献
4.
N. Rashevsky 《Bulletin of mathematical biology》1969,31(4):789-795
The author's theory of the adoption of certain types of behavior patterns (Rashevsky, N., 1957, “Contributions to the Theory
Initiative Behavior”.Bull. Maths. Biophysics,19, 91–119; 1968,Looking at History through Mathematics, Cambridge, Massachusetts: M.I.T. Press) consisting of elementary behaviors for each of which there is an opposite one and
the two are mutually exclusive, is applied to describe the changes in the general type of behavior of a society. The elementary
acts of which the whole problem consists may be either overt activities or beliefs or opinions. The general behavior patternsadopted by the society are considered as the “proper” or “just” ones. Any deviation from it in either one or more of the component
elementary behaviors is considered as “unjust” and is subject to some punitive action. The total number of possible mutually
exclusive behavior patterns is very large but finite. Within this very large range of possible patterns, we find that this
notion of justice is relative, because changes from any behavior pattern to any other may occur. It is further shown that
the amount of punishment for the deviation from the accepted pattern in order to be effective as well as efficient must be
applied in different ways to different individuals even for the same transgression. 相似文献
5.
6.
All organisms are composed of multiple chemical elements such as carbon, nitrogen and phosphorus. While energy flow and element cycling are two fundamental and unifying principles in ecosystem theory, population models usually ignore the latter. Such models
implicitly assume chemical homogeneity of all trophic levels by concentrating on a single constituent, generally an equivalent
of energy. In this paper, we examine ramifications of an explicit assumption that both producer and grazer are composed of
two essential elements: carbon and phosphorous. Using stoichiometric principles, we construct a two-dimensional Lotka-Volterra
type model that incorporates chemical heterogeneity of the first two trophic levels of a food chain. The analysis shows that
indirect competition between two populations for phosphorus can shift predator—prey interactions from a (+, −) type to an
unusual (−, −) class. This leads to complex dynamics with multiple positive equilibria, where bistability and deterministic
extinction of the grazer are possible. We derive simple graphical tests for the local stability of all equilibria and show
that system dynamics are confined to a bounded region. Numerical simulations supported by qualitative analysis reveal that
Rosenzweig’s paradox of enrichment holds only in the part of the phase plane where the grazer is energy limited; a new phenomenon,
the paradox of energy enrichment, arises in the other part, where the grazer is phosphorus limited. A bifurcation diagram
shows that energy enrichment of producer—grazer systems differs radically from nutrient enrichment. Hence, expressing producer—grazer
interactions in stoichiometrically realistic terms reveals qualitatively new dynamical behavior. 相似文献
7.
N. Rashevsky 《Bulletin of mathematical biology》1950,12(3):177-185
In previous publications, social groups have been studied in which each individual has a preference for one of two possible
mutually exclusive activities. This preference is measured by a quantity ϕ. The value ϕ=0 corresponds to no preference; a
preference for one activity is measured by a positive ϕ, the preference for the other by a negative ϕ. The quantity ϕ varies
from individual to individual. It has been shown previously that, owing to effects of imitation, even when the average ϕ for
the group is zero, one of the two behaviours will be chosen by the majority of the group. Whereas in previous studies the
imitation effect was considered as independent of the distance between the imitating and imitated individuals, in the present
study the case is considered in which the effect of imitation decreases with the distance between the individuals. It is found
that under certain conditions a greater percentage near the center of the area occupied by the group, rather than near the
periphery, exhibits the chosen behavior. The possible sociological meaning of this gradient of behavior is discussed. 相似文献
8.
N. Rashevsky 《Bulletin of mathematical biology》1965,27(2):175-185
Previous studies of effects of imitation on individuals in a population, in which the tendencies ϕ towards one or another
of two mutually exclusive behaviors are distributed, are amplified by considering the distribution, not of ϕ directly, but
of the excitations ɛ01 and ɛ02 of the two centers which mediate each of the two behaviors. It is shown how the distribution of ϕ is derived from those of
ɛ01 and ɛ02. It is found that when both tendencies ɛ01 and ɛ02 are weak, the choice of one of the two behaviors not only is originally determined by pure chance, but that it is impossible
to effect a change of the behaviour of a large population from one adopted behavior to a possible opposite one, by inhibiting
the tendency towards the first behavior. Such a change by inhibition is possible only when the tendencies toward both mutually
exclusive behaviors are sufficiently strong. A possible application to the persistency of irrelevant established behavior
patterns, such as handshakes, is suggested. 相似文献
9.
N. Rashevsky 《Bulletin of mathematical biology》1968,30(3):519-525
In our recent book,Looking at History Through Mathematics (MIT Press, 1968), we discussed two possible mechanisms of a transition of a society from an “arational” behavior, in which
most things are accepted uncritically on faith, to a rational behavior, characterized by a critical appraisal of everything.
Both mechanisms lead to irreversible changes, which eventually result asymptotically in a complete rationalization of society.
In the present paper it is shown that a generalization of the second mechanism may lead to alternations between rational and
arational behavior of a society. The reversal from rational to arational behavior is due to the circumstance that for some
people hard thinking is either impossible or at least highly unpleasant. It appears, on the basis of the model discussed here,
that acomplete rationalization of any society is unattainable. 相似文献
10.
The prey-capture and feeding behavior of the rhabdocoel flatworm Mesostoma ehrenbergii (Focke, 1836) was analyzed using a
variety of live and dead prey, including Daphnia, mosquito larvae, and tubifex annelids. Prey-capture behavior was broken
down into its individual components. Mesostoma could accommodate to and change its behavior depending on the size and type
of prey. Mechanical rather than chemical cues were effective in inducing prey-capture behavior. No evidence for a special
chemical paralysis as suggested by other workers was found. The apparent paralysis observed in cladocera such as Daphnia and
mosquito larvae was, in part a behavioral response of the prey in ‘playing possum’ and also in part due to immobilization
of the prey by the flatworm with mucous threads.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
Social–chemical recognition is exhibited by all the Liolaemus lizards tested to date, except Liolaemus fitzgeraldi, which during post-hibernation did not discriminate chemosignals of same-sex individuals from a control. To clarify if L. fitzgeraldi is unique among the studied Liolaemus in lacking social–chemical recognition or if this was previously undetected, we recorded behavior during pre- and post-hibernation
when confronted with chemosignals of conspecifics and from themselves. L fitzgeraldi showed self-recognition and seasonal changes in two exploratory behaviors. Potentially, conspecific recognition in L fitzgeraldi was undetected due to seasonality, but this species may rely comparatively less on chemical communication than congeners. 相似文献
12.
S. Ya. Dvurechenskaya 《Contemporary Problems of Ecology》2012,5(4):347-351
The contribution of chemical matter from major sources to the composition of water in the Novosibirsk reservoir is assessed. It is confirmed that the chemical composition of water in the Novosibirsk reservoir is essentially formed due to the inflow of chemicals from the Ob’ river. 相似文献
13.
Iguanid lizards are known for visual acuity and a diminished vomeronasal organ, which has led to mixed conclusions on whether
iguanids use chemical cues. The collared lizard, Crotaphytus collaris, is a territorial iguanid that lives in open rocky habitats. Fecal pellets placed prominently on open rocky perches may provide
an ideal mechanism for intraspecific chemical signaling. In order to determine whether collared lizards can discriminate between
chemical stimuli found in conspecific fecal pellets, we collected 24 males and 25 females to analyze sex-specific behavioral
responses via tongue-flicks and a newly observed behavior for the species, gular pumps, to cotton swabs containing water,
cologne, chemical stimuli from conspecific male and female fecal pellets, and the lizard’s own fecal pellet. Both sexes were
able to discriminate chemical stimuli from water via at least one behavior. Male collared lizards exhibited greater rates
of response (tongue-flick and gular pumps) toward male fecal pellets when compared to the negative water control. Our results
also suggest individuals may be able to discriminate between fecal pellets, as indicated by generally greater (but non-significant)
counts of male tongue-flick responses to male fecal pellets when compared to their own. Collared lizard chemical discrimination
appears to utilize tongue-flick and gular pump behaviors, possibly associated with distinct chemosensory modes (vomerolfaction
and olfaction). Based on this study, we suggest that chemical signals may play a greater role in intraspecific communication
than previously thought in this highly visual lizard. 相似文献
14.
N. Rashevsky 《Bulletin of mathematical biology》1949,11(3):157-163
A group of individuals is considered in which each individual has tendencies to exhibit one or another of two mutually exclusive
behaviors. Neurobiophysically this may be described in terms of Landahl's reciprocally inhibited parallel reaction chains.
The spontaneous excitations ε1 and ε2 at the central connections of each chain are a measure of the “natural” tendency of the individual toward one or the other
of the two behaviors. According to equations derived by H. D. Landahl, the probability of one or the other behavior is determined
by the difference ε1 − ε2. A population of individuals is considered in which ε1 − ε2 is distributed in some continuous way, and therefore in which the probability of a given behavior is distributed continuously
between 0 and 1. The effect of other individuals exhibiting a given behavior is to increase the corresponding ε of the individual.
Thus behavior of others affects the probability for a given behavior of each individual. It is shown that the equations describing
the behavior of the population on the basis of this neurobiophysical picture reduce in the first approximation to the differential
equations which were postulated by the author in his previous work on social behavior. 相似文献
15.
Cell signaling pathways consist of multiple connections of different types of gene, mRNA and protein networks. It is not a
trivial task to follow the signals flowing through these networks. The difficulty comes from considering the entire biological
structure as a single network without breaking it into connected modules. The study of these networks simplifies if the complex
system is reduced to a hierarchy of interconnected modules. Out of many potential modules, a specific one, namely the Goldbeter–Koshland
switch, was encountered by the authors during their study of the Mammalian Heat Shock Response Network (MHSRN) where the switch
acts as a stress sensor. Usually, only the steady state behavior of the switch is studied, in which the phosphorylated protein
is given as a function of the enzyme concentration. Experimental results show that the heat shock response is still present
20 h after the temperature stress had ended. Thus, it is useful to analyze the transient behavior of the switch that couples
the environment to the MHSRN. A stochastic model for the switch is proposed using the Master Equation which is subsequently
transformed into an equation for the factorial cumulant generating function. This generating function can be easily read from
a graphical representation of the stochastic switch. The second order approximation of the equation for the factorial cumulant
generating function is solved and the time dependence of the transient regime of the mean and standard deviation is readily
obtained. Using the mean and standard deviation of the switch’s output as a function of the stochastic input signals that
represent the environment, we classify the switches according to different criteria. The switches differ by the numerical
values of the parameters that characterize the switch’s chemical reactions. The classifying criteria will distinguish the
switches by the levels of the response for a given transition time and by the sensitivity of the response to the enzyme levels.
It is also found that the environment can drastically change the response of the switch, which has important biological consequences. 相似文献
16.
Rubina P. Shaikh Viness Pillay Yahya E. Choonara Lisa C. du Toit Valence M. K. Ndesendo Priya Bawa Shivaan Cooppan 《AAPS PharmSciTech》2010,11(1):441-459
Membrane technology is broadly applied in the medical field. The ability of membranous systems to effectively control the
movement of chemical entities is pivotal to their significant potential for use in both drug delivery and surgical/medical
applications. An alteration in the physical properties of a polymer in response to a change in environmental conditions is
a behavior that can be utilized to prepare ‘smart’ drug delivery systems. Stimuli-responsive or ‘smart’ polymers are polymers
that upon exposure to small changes in the environment undergo rapid changes in their microstructure. A stimulus, such as
a change in pH or temperature, thus serves as a trigger for the release of drug from membranous drug delivery systems that
are formulated from stimuli-responsive polymers. This article has sought to review the use of stimuli-responsive polymers
that have found application in membranous drug delivery systems. Polymers responsive to pH and temperature have been extensively
addressed in this review since they are considered the most important stimuli that may be exploited for use in drug delivery,
and biomedical applications such as in tissue engineering. In addition, dual-responsive and glucose-responsive membranes have
been also addressed as membranes responsive to diverse stimuli. 相似文献
17.
D. C. Peñalva-Arana P. A. Moore B. A. Feinberg J. DeWall J. R. Strickler 《Hydrobiologia》2007,594(1):153-163
We present a novel approach for examining the complex feeding behavior of a filter feeder at a previously unexploited scale.
A Daphnia lives in a viscous environment and thus creates a feeding current with a distinct laminar inflow and a repetitive pulsed
outflow. We propose that by treating the feeding apparatus as a black box, and using the pulsed outflow current as a surrogate
to the inside working of the apparatus, we can calculate feeding rate in near real time. The structure of the outflow is interpreted
as a direct representation of the organism’s response to its environment. Therefore, we examine how the work performed by
an organism’s feeding apparatus is altered according to environmental factors and metabolic demands. Our approach is an integration
of optical (Schlieren system) and electrochemical (chronoamperometry) techniques that allow for real time visualization and
temporal analysis of flow systems, respectively. As electrochemistry requires a tracer chemical, we employed low dopamine
concentrations (≤ 1mM), and tested the effect of dopamine on the heart rate and swimming of Daphnia. It appears that dopamine free in solution at concentrations below 10 mM has no adverse effects on the organism, and all
observed differences in Daphnia feeding behavior were due to environmental or metabolic factors. The feeding nature of daphnids in the presence or absence
of food, and differences between the sexes is reported. Our results indicate that in the absence of food a Daphnia has a strict and repetitive feeding behavior with short delays between pumping actions. However, in the presence of food
this behavior becomes complex, with increased delays between pumps, perhaps designed to maximize feeding efficiency. Our observations
demonstrate that males have a higher appendage beat frequency than females under identical conditions. We hypothesize that
the difference may be dictated by metabolic demand, as a male spends more time actively seeking a mate. The application of
electrochemistry to the study of Daphnia feeding behavior is an improvement over current methods for its near real time quantification of behavioral response, its
versatile application under varying environmental conditions and its extreme sensitivity to changes in the organism’s feeding
behavior. This technique is a valuable addition to the current tools available for studying Daphnia feeding behavior and will allow us to learn more about the interactions of an organism with its environment.
Guest editor: Piet Spaak
Cladocera: Proceedings of the 7th International Symposium on Cladocera 相似文献
18.
The analysis of biochemical processes is one of the main challenges for modern computational chemistry. Probably the biggest
issue facing scientists in this case is the number of factors that have to be taken into account, as even those factors that
do not seem to be meaningful may eventually be crucial. Such a belief led to the investigation on the substituent effects
during squalene cyclization process. We focused on the formation of lanosterol ring A through squalene epoxide and an analogue
process observed in bacteria, leading to the hopene formation without an intermediate oxide. Interestingly, our results indicate
that, opposite of chemical intuition, a more substituted chain is more likely to adopt a conformation suitable for the cyclization
process. Presumably the rational for this behavior is the presence of intermolecular CH⋅⋅⋅π interactions between the hydrogen
atoms from methyl groups and the squalene π bonds in the open-chain structure. The effect seems to have a firm impact on the
hopene formation process. Calculations were performed using two different methods: MP2 and M06-2X, combined with the cc-pVDZ
basis set. 相似文献
19.
Teruhiko Takahara Chinami Mitsuhashi-Ohnishi Nao Fujiwara-Tsujii Ryohei Yamaoka 《Journal of Ethology》2011,29(3):427-434
Tadpoles of some ranid species appear to possess chemical defenses against fish predators, but the chemicals have not been
characterized. Here, we evaluated the vulnerability of three Japanese anuran tadpole species (Glandirana rugosa, Pelophylax nigromaculatus, and Hyla japonica) to a fish (Gnathopogon elongatus elongatus) and analyzed the defensive chemicals extracted from the unpalatable tadpoles. Additionally, we examined the defensive behavior
of unpalatable tadpoles in response to fish chemical cues. The fish rejected both G. rugosa (83%) and P. nigromaculatus (48%), but not H. japonica (0%). Many of the rejected tadpoles survived (60–80%). Possible defensive chemicals were extracted by methanol from the skin
of G. rugosa, but were not identifiable by gas chromatography–mass spectrometry because of small quantities. The chemicals have high polarity
and non-volatility. When exposed to fish chemical cues, P. nigromaculatus decreased activity presumably as a defensive behavior, but G. rugosa did not. We demonstrated the presence of chemical defenses in at least two of these species and revealed that G. rugosa releases more effective or greater amounts of defense chemicals than P. nigromaculatus with respect to this fish predator. The increased efficacy of chemical defenses may correlate with decreasing defensive behavior. 相似文献
20.
N. Rashevsky 《Bulletin of mathematical biology》1968,30(2):341-349
Recent experiments on so-called chemical transfer of memory may indicate at first glance that the possibility of transfer
of the memory of a large number of reaction patterns in this manner requires the assumption of a correspondingly large number
of specific chemical substances. It is shown that this is not necessarily the case. A mechanism is conceivable in which a
single substance is responsible for “memory” transfer for a large number of distinct patterns. Mechanisms involving only about
one hundred different specific substances could conceivably be responsible for chemical transfer of memory of some 1050 spatial patterns. 相似文献