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1.
The stochastic nature of cell surface receptor-ligand binding is known to limit the accuracy of detection of chemoattractant
gradients by leukocytes (11, 12), thus limiting the orientation ability that is crucial to the chemotactic response in host defense. The probabilistic cell
orientation model of Lauffenburger (11) is extended here to assess the consequences of recently discovered receptor phenomena: “down-regulation” of total surface
receptor number, spatial asymmetry of surface receptors, and existence of a higher-affinity receptor subpopulation. In general,
a reduction in orientation accuracy is predicted by inclusion of these phenomena.
An orientation signal based on a simple model of chemosensory adaptation (i.e., a spatial difference inrelative receptor occupancy) is found to be functionally different from the signal suggested by an experimental correlation (i.e.,
a spatial difference inabsolute receptor occupancy). However, in the context of receptor “signal noise,” the signal based on adaptation yields predictions
in better qualitative agreement with the experimental orientation data of Zigmond (10). From this cell orientation model we can estimate the effective timeaveraging period required for noise diminution to a
level allowing orientation predictions to match observed levels. This time-averaging period presumably reflects the time constant
for receptor signal transduction and locomotory response. 相似文献
2.
Pedersen PL 《Journal of bioenergetics and biomembranes》2007,39(1):1-12
This introductory article to the review series entitled “The Cancer Cell’s Power Plants as Promising Therapeutic Targets”
is written while more than 20 million people suffer from cancer. It summarizes strategies to destroy or prevent cancers by
targeting their energy production factories, i.e., “power plants.” All nucleated animal/human cells have two types of power
plants, i.e., systems that make the “high energy” compound ATP from ADP and P
i
. One type is “glycolysis,” the other the “mitochondria.” In contrast to most normal cells where the mitochondria are the
major ATP producers (>90%) in fueling growth, human cancers detected via Positron Emission Tomography (PET) rely on both types
of power plants. In such cancers, glycolysis may contribute nearly half the ATP even in the presence of oxygen (“Warburg effect”).
Based solely on cell energetics, this presents a challenge to identify curative agents that destroy only cancer cells as they
must destroy both of their power plants causing “necrotic cell death” and leave normal cells alone. One such agent, 3-bromopyruvate
(3-BrPA), a lactic acid analog, has been shown to inhibit both glycolytic and mitochondrial ATP production in rapidly growing
cancers (Ko et al., Cancer Letts., 173, 83–91, 2001), leave normal cells alone, and eradicate advanced cancers (19 of 19)
in a rodent model (Ko et al., Biochem. Biophys. Res. Commun., 324, 269–275, 2004). A second approach is to induce only cancer
cells to undergo “apoptotic cell death.” Here, mitochondria release cell death inducing factors (e.g., cytochrome c). In a
third approach, cancer cells are induced to die by both apoptotic and necrotic events. In summary, much effort is being focused
on identifying agents that induce “necrotic,” “apoptotic” or apoptotic plus necrotic cell death only in cancer cells. Regardless
how death is inflicted, every cancer cell must die, be it fast or slow. 相似文献
3.
The credo of every scientist working in the field of applied science is to transfer knowledge “from science to market,” a
process that combines (1) science (fundamental discoveries and basic research) with (2) technology development (performance
assessment and optimization) and (3) technology transfer (industrial application). Over the past 7 years, we have intensively
investigated the potential of the white rot fungus, Physisporinus vitreus, for engineering value-added wood products. Because of its exceptional wood degradation pattern, i.e., selective lignification
without significant wood strength losses and a preferential degradation of bordered pit membranes, it is possible to use this
fungus under controlled conditions to improve the acoustic properties of tonewood (i.e., “mycowood”) as well as to enhance
the uptake of preservatives and wood modification substances in refractory wood species (e.g., Norway spruce), a process known
as “bioincising.” This minireview summarizes the research that we have performed with P. vitreus and critically discusses the challenges encountered during the development of two distinct processes for engineering value-added
wood products. Finally, we peep into the future potential of the bioincising and mycowood processes for additional applications
in the forest and wood industry. 相似文献
4.
Sukhija K Pyne M Ali S Orr V Abedi D Moo-Young M Chou CP 《Molecular biotechnology》2012,51(2):109-118
Most existing genomic engineering protocols for manipulation of Escherichia coli are primarily focused on chromosomal gene knockout. In this study, a simple but systematic chromosomal gene knock-in method
was proposed based on a previously developed protocol using bacteriophage λ (λ Red) and flippase–flippase recognition targets
(FLP–FRT) recombinations. For demonstration purposes, DNA operons containing heterologous genes (i.e., pac encoding E. coli penicillin acylase and palB2 encoding Pseudozyma antarctica lipase B mutant) engineered with regulatory elements, such as strong/inducible promoters (i.e., P
trc
and P
araB
), operators, and ribosomal binding sites, were integrated into the E. coli genome at designated locations (i.e., lacZYA, dbpA, and lacI-mhpR loci) either as a gene replacement or gene insertion using various antibiotic selection markers (i.e., kanamycin and chloramphenicol)
under various genetic backgrounds (i.e., HB101 and DH5α). The expression of the inserted foreign genes was subjected to regulation
using appropriate inducers [isopropyl β-d-1-thiogalactopyranoside (IPTG) and arabinose] at tunable concentrations. The developed approach not only enables more extensive
genomic engineering of E. coli, but also paves an effective way to “tailor” plasmid-free E. coli strains with desired genotypes suitable for various biotechnological applications, such as biomanufacturing and metabolic
engineering. 相似文献
5.
We have examined the mixing properties of phosphatidylethanolamine (PE) and phosphatidylglycerol (PG), the major components
of many bacterial membranes. The phase transition behavior of dilute aqueous suspensions of PE:PG mixtures with different
chain lengths (n = 14, 16) in 0.1 M NaCl at pH 7 and pH 2 was investigated by differential scanning calorimetry (DSC). The DSC curves were
simulated using an approach which takes into account the broadening of the phase transition in addition to symmetric, non-ideal
mixing in the gel and the liquid-crystalline phase. Based on the temperatures for onset and end of “melting” obtained by the
simulations, the phase diagrams were constructed and then refined using a regular solution model with non-symmetric mixing
in both phases. The mixing properties of PE:PG mixtures were analyzed as a function of pH and acyl chain length. In almost
all cases, non-symmetric mixing behavior was observed, i.e. the non-ideality parameters are different for bilayers with low
PG content compared to bilayers with high PG content. For equimolar mixtures at pH 7, when PG is negatively charged, the non-ideality
parameters are negative for both phases, indicating preferential formation of mixed pairs. This mixed pair formation is more
pronounced for the gel phase. At pH 2, when PG is partly protonated, the non-ideality parameter is less negative and the formation
of mixed pairs is reduced compared to pH 7. The formation of PE:PG mixed pairs at pH 7 might be of benefit to a bacterial
membrane, because it prevents demixing of lipid components with a concomitant destabilization of the membrane.
Received: 3 August 1998 / Revised version: 4 October 1999 / Accepted: 12 October 1999 相似文献
6.
Statistical studies of gene populations on the purine/pyrimidine alphabet have shown that the mean occurrence probability
of thei-motif YRY(N)
i
YRY (R=purine, Y=pyrimidine, N=R or Y) is not uniform by varyingi in the range [1,99], but presents a maximum ati=6 in the following populations: protein coding genes of eukaryotes, prokaryotes, chloroplasts and mitrochondria, and also
viral introns, ribosomal RNA genes and transfer RNA genes (Arquès and Michel, 1987b,J. theor. Biol.
128, 457–461). From the “universality” of this observation, we suggested that the oligonucleotide YRY(N)6 is a primitive one and that it has a central function in DNA sequence evolution (Arquès and Michel, 1987b,J. theor. Biol.
128, 457–461). Following this idea, we introduce a concept of a model of DNA sequence evolution which will be validated according
to a shema presented in three parts.
In the first part, using the last version of the gene database, the YRY(N)6YRY preferential occurrence (maximum ati=6) is confirmed for the populations mentioned above and is extended to some newly analysed populations: chloroplast introns,
chloroplast 5′ regions, mitochondrial 5′ regions and small nuclear RNA genes. On the other hand, the YRY(N)6YRY preferential occurrence and periodicities are used in order to classify 18 gene populations.
In the second part, we will demonstrate that several statistical features characterizing different gene populations (in particular
the YRY(N)6YRY preferential occurrence and the periodicities) can be retrieved from a simple Markov model based on the mixing of the
two oligonucleotides YRY(N)6 and YRY(N)3 and based on the percentages of RYR and YRY in the unspecified trinucleotides (N)3 of YRY(N)6 and YRY(N)3. Several properties are identified and prove in particular that the oligonucleotide mixing is an independent process and
that several different features are functions of a unique parameter.
In the third part, the return of the model to the reality shows a strong correlation between reality and simulation concerning
the presence of large alternating purine/pyrimidine stretches and of periodicities. It also contributes to a greater understanding
of biological reality, e.g. the presence or the absence of large alternating purine/pyrimidine stretches can be explained
as being a simple consequence of the mixing of two particular oligonucleotides.
Finally, we believe that such an approach is the first step toward a unified model of DNA sequence evolution allowing the
molecular understanding of both the origin of life and the actual biological reality. 相似文献
7.
Masazumi Mitani 《Primates; journal of primatology》1986,27(4):397-412
Japanese monkeys often exchange the particular vocal sound, “coo,” especially when they feed or move as a group. It was considered
that the “coo” sound had no positive social meaning, perhaps because the “coo” sound network and its function were hidden
behind other behavioral observations. For identification of the vocalizer only from hearing the “coo” sound, three phonetic
values, i.e., the “fundamental,” “duration,” and “formants,” plus other characteristics were used as indices of voiceprints. The results indicated that these were effective for identifying
the vocalizer in two-thirds of the adults in the study troop which was composed of 12 adults and 16 immature members. The
“coo” sound exchange network among the troop members (adults) was drawn on the basis of the voiceprint identification. The
network showed three characteristics as follows: (1) matriarchs of the kin-groups frequently exchanged “coo” sounds with each
other; (2) the other females exchanged “coo” sounds mostly within their own kin-groups; and (3) males seldom participated
in the “coo” sound exchange. This suggests that “coo” sound exchange plays a central role for the matriarch of kin-groups
in binding each kin-group and, ultimately, in binding all members together into an organized troop. 相似文献
8.
E. V. Balushkina 《Inland Water Biology》2009,2(4):355-363
In the years 1994–2005, the values of the integrated index IP’ at some stations of the Neva Bay changed from 38.1 to 81.9%, water quality changed from class 3 to class 5, and the states
of some areas of the ecosystem that were evaluated as “tense” went to “catastrophic.” The integrated mean assessment of water
quality according to the IP’ index over the entire Neva Bay throughout 12 years (1994–2005) remained relatively stable, waters were assessed as “polluted”
(fourth class), and the state of the ecosystem was considered “critical.” The state of the eastern part of the Gulf of Finland
in 1994–2005 was less favorable. The species diversity of zoobenthos in the resort zone of the eastern part of the Gulf of
Finland is considerably lower than in the Neva Bay. Waters of the resort zone of the eastern part of the Gulf of Finland in
1994–2005 were assessed as one class lower than in the Neva Bay, i.e., as “polluted-dirty” (fourth-fifth class), and the state
of the ecosystem was assessed as being in a “crisis.” In the resort zone, there was a decline in species diversity and abundance
and biomass of benthic animals; i.e., all characteristics of the degradation of benthic animal communities were observed. 相似文献
9.
Jing Zhang Yan Liu Dan Yu Hongze Song Jingjin Cui Tao Liu 《Journal of applied phycology》2011,23(2):165-171
Hybridization of gametophytes, continuous self-crossing and targeted selection were utilized to breed a new Laminaria variety. After five-generation selection breeding, the new variety “Rongfu” was obtained. Its male parent “Yuanza No.10”
was the high-yield cultivation variety, and its female parent was variety “Fujian” which could tolerate relatively high seawater
temperature. “Yuanza No.10” and “Fujian” were different but complement in their morphological characteristics and biological
habits. Variety “Rongfu” was bred through their hybridization which exhibited high-yield potential and high seawater temperature
tolerance. The results of traits evaluation in consecutive years showed that “Rongfu” attained higher yields by 24–27% compared
to the control (widely used commercial variety) and also contained considerable amounts of iodine, mannitol, and algin. When
seawater temperature was 18–21°C, the blade growth of “Rongfu” was maintained and tissue loss by abrasion was significantly
lower than the control. Since the adoption of variety “Rongfu” in 2001, its cultivation areas have been extended to Shandong,
Fujian and Guangdong province and have reached 14,133 ha currently, i.e., almost one-tenth of the total cultivation areas
of Laminaria in China. The results of Random Amplified Polymorphic DNA analysis showed that the relationship between “Rongfu” and other
cultivation varieties in China was very close. 相似文献
10.
Tea plant [Camellia
sinensis (L.) O.Kuntze)] is one of the most popular non-alcoholic beverage crops in the world today. In recent years, many clonal
tea cultivars have been developed and widely planted to replace the diverse traditional tea populations. In this article,
we study the relationships between classifications based on simple sequence repeat (SSR) markers and on morphological traits
for 185 tea plant cultivars. Results show that the genetic diversity index (H) is between 0.229 and 0.803, and the mean value is 0.543; the observed heterozygosity (H
o) ranges from 0.103 to 0.683, with an average of 0.340, while the genetic identity varies from 0.267 to 0.984. Based on tea-making
properties, the genetic diversity in the “black-green tea” group is much higher than in the “Oolong tea” group. Based on morphological
traits, cluster analysis classifies the 185 cultivars into three groups, “group I,” “group II” and “group III.” Most cultivars
are related based on the geographical origin and their genetic backgrounds. 相似文献
11.
12.
Gas exchange,chlorophyll fluorescence,and osmotic adjustment in two mango cultivars under drought stress 总被引:1,自引:0,他引:1
The responses of photosynthetic gas exchange, chlorophyll fluorescence, content of pigments, main osmolytes, and malondialdehyde
(MDA) to water-withholding for 15 days and re-hydration in seedlings of two mango cultivars (Mangifera indica L. var. “Choke Anand’ and var. “Khieo Sawoei”) under 50% sunlight and full sunlight were investigated. For both cultivars, the water-witholding resulted
in progressively decreases in leaf relative water content, net photosynthesis (P
n), stomatal conductance (g
s), and increases in the conversion of xanthophyll cycle pigments estimated by an index of leaf spectral reflectance (ΔPRI),
carotenoid to chlorophyll ratio, non-photochemical quenching (NPQ), the contents of malondialdehyde (MDA) and compatible solutes
(total soluble sugar and proline). The effect of the water stress was more pronounced in full sunlight than 50% sunlight.
The maximum photochemistry efficiency measured at dawn was fairly constant during the period of the treatment for both cultivars
under both light regimes. The water stress caused less pronounced inhibition of photosynthesis in “Choke Anand” than in “Khieo
Sawoei” cultivar under both light regimes. After re-hydration, the recovery was relatively quicker in “Choke Anand” than in
“Khieo Sawoei” cultivar. Both cultivars in both 50% and full sunlight showed complete recovery in photochemistry after 5 days
of re-watering but photosynthesis did not show a complete recovery as indicated by gas exchange rates. As the results of lower
NPQ, ΔPRI and osmotic adjustment in the cultivar “Khieo Sawoei” compared to the cultivar “Choke Anand”, the former cultivar
was less tolerant to drought than the latter. Our study further showed that partial shading (e.g., 50% of sunlight) significantly
alleviated the harmful effect of drought stress on mango cultivars but in fact stomata of seedlings grown in partial shade
was more responsive to water deficit than in full light. 相似文献
13.
“Mass effects,” in which “sink populations” of locally inferior competitors are maintained by dispersal from “source populations”
elsewhere in the landscape, are thought to play an important role in maintaining plant diversity. However, due to the complexity
of most quasi-realistic forest models, there is little theoretical understanding of the strength of mass effects in forests.
Here, we develop a metacommunity version of a mathematically and computationally tractable height-structured forest model,
the Perfect Plasticity Approximation, to quantify the strength of mass effects (i.e., the degree of mixing of locally dominant
and subordinate species) in heterogeneous landscapes comprising different patch types (e.g., soil types). For realistic levels
of inter-patch dispersal, mass effects are weak at equilibrium (i.e., in the absence of disturbance), even in some cases where
differences in growth, mortality, and fecundity rates between locally dominant and subordinate species are too small to be
reliably detected from field data. However, patch-scale transient dynamics are slow following catastrophic disturbance (in
which post-disturbance initial abundances are determined exclusively by immigration) so that at any given time, subordinate
species are present in appreciable numbers in most patches. Less severe disturbance regimes, in which some seeds or individuals
survive the disturbance, should result in faster transient dynamics (i.e., faster approach to the low-diversity equilibrium).
Our results suggest that in order for mass effects to play an important role in tree coexistence, niche differences must be
strong enough to prevent neutral drift, yet too weak to be reliably detected from field data. 相似文献
14.
Alber M Glimm T Hentschel HG Kazmierczak B Zhang YT Zhu J Newman SA 《Bulletin of mathematical biology》2008,70(2):460-483
A recently proposed mathematical model of a “core” set of cellular and molecular interactions present in the developing vertebrate
limb was shown to exhibit pattern-forming instabilities and limb skeleton-like patterns under certain restrictive conditions,
suggesting that it may authentically represent the underlying embryonic process (Hentschel et al., Proc. R. Soc. B 271, 1713–1722, 2004). The model, an eight-equation system of partial differential equations, incorporates the behavior of mesenchymal cells as
“reactors,” both participating in the generation of morphogen patterns and changing their state and position in response to
them. The full system, which has smooth solutions that exist globally in time, is nonetheless highly complex and difficult
to handle analytically or numerically. According to a recent classification of developmental mechanisms (Salazar-Ciudad et
al., Development 130, 2027–2037, 2003), the limb model of Hentschel et al. is “morphodynamic,” since differentiation of new cell types occurs simultaneously with
cell rearrangement. This contrasts with “morphostatic” mechanisms, in which cell identity becomes established independently
of cell rearrangement. Under the hypothesis that development of some vertebrate limbs employs the core mechanism in a morphostatic
fashion, we derive in an analytically rigorous fashion a pair of equations representing the spatiotemporal evolution of the
morphogen fields under the assumption that cell differentiation relaxes faster than the evolution of the overall cell density
(i.e., the morphostatic limit of the full system). This simple reaction–diffusion system is unique in having been derived
analytically from a substantially more complex system involving multiple morphogens, extracellular matrix deposition, haptotaxis,
and cell translocation. We identify regions in the parameter space of the reduced system where Turing-type pattern formation
is possible, which we refer to as its “Turing space.” Obtained values of the parameters are used in numerical simulations
of the reduced system, using a new Galerkin finite element method, in tissue domains with nonstandard geometry. The reduced
system exhibits patterns of spots and stripes like those seen in developing limbs, indicating its potential utility in hybrid
continuum-discrete stochastic modeling of limb development. Lastly, we discuss the possible role in limb evolution of selection
for increasingly morphostatic developmental mechanisms. 相似文献
15.
Over two consecutive years in the North Bank Plain Zone of Assam, India, during the spring growing season (February–June)
of- 2006 and 2007 we examined effects of morpho-physiological characteristics of rice (Oryza sativa L.) plants in relation to methane (CH4) emission from paddy fields. Traditional cultivar “Agni” and modern improved cultivar “Ranjit” were grown in light textured
loamy soil under irrigation. A higher seasonal integrated methane flux (E
sif) was recorded from “Agni” compared to “Ranjit”. Both cultivars exhibited an emission peak during active vegetative growth
and a second peak at panicle initiation. Leaf and tiller number, leaf area, length, and volume of root were greater in “Agni”,
but grain yield and yield-related parameters such as increased photosynthate partitioning to panicles at the expense of roots
were greater in “Ranjit”. “Ranjit” also photosynthesed faster than “Agni” during panicle development but slower than “Agni”
at tillering. In both the years, a higher soil organic carbon content was recorded in plots of “Agni”. Our results suggest
that in “Agni” enhanced diversion of photosynthate to roots resulted in more substrate being available to methanogenic bacteria
in the rhizosphere. Additionally, the more extensive vegetative growth of this cultivar may enhance methane transport from
the soil to the above-ground atmosphere. 相似文献
16.
Pedersen PL 《Journal of bioenergetics and biomembranes》2012,44(1):1-6
Although the “Warburg effect”, i.e., elevated glucose metabolism to lactic acid (glycolysis) even in the presence of oxygen, has been recognized as the most common biochemical phenotype of cancer for over 80 years, its biochemical and genetic basis
remained unknown for over 50 years. Work focused on elucidating the underlying mechanism(s) of the “Warburg effect” commenced
in the author’s laboratory in 1969. By 1985 among the novel findings made two related most directly to the basis of the “Warburg
effect”, the first that the mitochondrial content of tumors exhibiting this phenotype is markedly decreased relative to the
tissue of origin, and the second that such mitochondria have markedly elevated amounts of the enzyme hexokinase-2 (HK2) bound
to their outer membrane. HK2 is the first of a number of enzymes in cancer cells involved in metabolizing the sugar glucose
to lactic acid. At its mitochondrial location HK2 binds at/near the protein VDAC (voltage dependent anion channel), escapes
inhibition by its product glucose-6-phosphate, and gains access to mitochondrial produced ATP. As shown by others, it also
helps immortalize cancer cells, i.e., prevents cell death. Based on these studies, the author’s laboratory commenced experiments
to elucidate the gene basis for the overexpression of HK2 in cancer. These studies led to both the discovery of a unique HK2
promoter region markedly activated by both hypoxic conditions and moderately activated by several metabolites (e.g., glucose),
Also discovered was the promoter’s regulation by epigenetic events (i.e., methylation, demethylation). Finally, the author’s laboratory turned to the most important objective. Could they selectively and completely destroy cancerous
tumors in animals? This led to the discovery in an experiment conceived, designed, and conducted by Young Ko that the small molecule 3-bromopyruvate
(3BP), the subject of this mini-review series, is an incredibly powerful and swift acting anticancer agent. Significantly,
in subsequent experiments with rodents (19 animals with advanced cancer) Ko led a project in which 3BP was shown in a short
treatment period to eradicate all (100%). Ko’s and co-author’s findings once published attracted global attention leading
world-wide to many other studies and publications related to 3BP and its potent anti-cancer effect. This Issue of the Journal of Bioenergetics and Biomembranes (JOBB 44-1) captures only a sampling of research conducted to date on 3BP as an anticancer agent, and includes also a Case
Report on the first human patient known to the author to be treated with specially formulated 3BP. Suffice it to say in this
bottom line, “3BP, a small molecule, results in a remarkable therapeutic effect when it comes to treating cancers exhibiting
a “Warburg effect”. This includes most cancer types. 相似文献
17.
Frans B. M. de Waal Jan A. R. A. M. van Hooff Willem J. Netto 《Primates; journal of primatology》1976,17(3):257-290
The primate literature provides many indications not only that the nature of dyadic interactions is to a large extent determined
by the relations of the interacting animals with others and between these others, but also of the existence of polyadic interactions
in which more than two individuals are simultaneously involved.
The objectives of the present study are to obtain a quantitative categorization of the agonistic interaction types of captive
Java-monkeys and an analysis of their dynamics.
After having described the agonistic behaviour patterns of Java-monkeys we shall discuss the categorization of agonistic interaction
types (depending on the number of involvees: “dyads”, “triads” and “polyads”), the way in which these types can be further
differentiated on the basis of the nature and the direction of the behaviours shown (e.g., different types of alliances), and the existence of so-called “sub-directed” behaviours (i.e., non-agonistic behaviours which are shown towards a dominant third animal more or less simultaneously with aggressive behaviour
directed towards an opponent).
The analysis indicates that agonistic behaviour is different both in its form and its regulation in interactions of different
complexity.
This research was supported in part by a government grant (i.e.: Beleidsruimte project: 16-21-06, “Brain and Behaviour”) to
the first author.
The investigation was supported by a grant from the Beleidsruimtemiddelen Hersenen en Gedrag to the first author. 相似文献
18.
M. Battino G. P. Littarru A. Gorini R. F. Villa D.Sc. M.D. 《Neurochemical research》1996,21(12):1505-1514
The effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration on respiratory chain features were studied
in synaptic and non-synaptic mitochondrial populations from cerebral cortex andhippocampus ofMacaca Fascicularis (Cynomolgus monkey). Enzymatic activity, cytochromea+a
3 content and turnover numbers of Complex IV, contents of Coenzyme Q10, of hydroperoxides and membrane fluidity were assessed in non-synaptic “perikaryal” and intra-synaptic “light” and “heavy”
mitochondria isolated: (a) from the dopaminergic ascending terminal areas of cerebral cortex of monkeys treatedp.o. with dihydroergocriptine at the dose of 2, 6 or 20 mg/kg/day for 52 weeks; (b) from the dopaminergic terminal areas ofhippocampus of monkeys treatedp.o. with dihydroergocriptine at the dose of 12 mg/kg/day before and during the induction of a Parkinson's-like syndrome by MPTP
administration (i.v., 0.3 mg/kg/day for 5 days). Dihydroergocriptine administration moderately increased both cytochrome oxidase activity and
cytochromea+a
3 content in “light” intra-synaptic mitochondria and hydroperoxides/CoQ10 ratio in all the types of mitochondria, as a consequence of the enhanced energy metabolism. The Parkinson's-like syndrome
by MPTP changed the biochemical investigated parameters, affecting both directly the respiratory chain structures,i.e. by respiratory chain complexes inhibition and indirectly,i.e. by free radical mediated damages. MPTP administration negatively influenced Complex IV activity and Turnover Number of intra-synaptic
mitochondria, without affecting the total cytochromea+a
3 amount. In all types of mitochondria and particularly on the “light” intra-synaptic ones, MPTP-induced lesion enhanced hydroperoxides/Coenzyme
Q10 molar ratio due to the fall in Coenzyme Q10 levels and the concomitant increase in hydroperoxides. Dihydroergocriptine treatment appeared to be effective in MPTP-treated
animals in improving those mitochondrial features that probably suffered free radical insults. 相似文献
19.
A breakthrough in transgenic Arabidopsis thaliana research was the development of the floral dip transformation protocol, a simple and reliable method of obtaining transformants,
T1 transgenic lines, at high efficiency while avoiding the use of tissue culture. However, the traditional protocol (a “sterile”
method) of obtaining T2 transgenic lines has not evolved along with improvements in transformation technology as it continues to be laborious and
time-consuming. In this study, we report on the development of an improved protocol (a “nonsterile” method) for selecting
and growing A. thaliana transformants (T2 transgenic lines) resistant to kanamycin under nonsterile conditions. This protocol involves the use of a simple yet specialized
device that will aid in solium selection of T2 transgenic lines that can be rapidly grown in a hydroponic system. The “nonsterile” method reduces labor and time involved
as compared to the “sterile” method; moreover, it is easy to set up and maintain. This method may also be applicable to other
selecting agents, and perhaps to other plants. 相似文献
20.
A quantum-theoretic approach to the problem of enzymic specificity is presented. The concept of a “measuring system” analogized
with the enzyme is utilized. Along these lines a quantum mechanical hypothesis for the mechanism of enzyme reactions was advanced
(Enzymologia,35, 117–130, 1968). In the measuring process an ℐ-observable, linked to the proper values of the substrate'sA
1...A
m
observables will indicate the state of the measuring apparatus. On the corresponding Hilbert space of the enzymesubstrate
complexH
ES
, through the respective statistical operatorU
ES
we get a “state” vector [s, a]. Theng:Γ
S
xΓ
E
→Γ
ES
, that is, to an oriented pair 〈s, a〉 ∈Γ
S
xΓ
E
will correspond a “state” vector [s, a], and to a proper valuei
k
of ℐ will correspond, throughg, the respective equivalence classes of Г-spaces. Introducing the concept of enzyme-substrate complex entropyL
ES
, a theorem is demonstrated asserting thatL
S
=L
ES
-L
E
+ 1/2kn wheren is the number of the degrees of freedom which may fluctuate. The values ofL
ES
are denoted “specific values,” and it is demonstrated that a microphysical systemS may be a substrate specific forE, if and only if it can realize one of theL
ES
specific values. Along these lines a model of a stochastic process for the enzymic reaction is constructed, and the set of
Kolmogorov equations for the respective probabilities is derived. When a “perturbation” is induced in our model, an interesting
prediction concerning the fluctuations in the kinetics of the corresponding enzyme is obtained. A relevant experimental proof
ensued from these theoretical considerations. When a “gentle perturbation” was induced in a substrate by mild X-ray or UV-irradiations,
an interesting oscillatory behavior of enzymic activity was recorded. A biochemical control mechanism is constructed (a simple
“flip-flop” type) utilizing nonoverlapping oscillations in the activity of two enzymes at a key metabolic intermediate level.
Eventually, a relevant experimental proof for the respective control model is presented. 相似文献