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81.
Letter: crystallographic data fro lysoxyme from bacteriophage T4 总被引:3,自引:0,他引:3
The lysozyme of bacteriophage T4 has been crystallized in a form suitable for X-ray diffraction analysis. The space group is P3121 or enantiomorph, and the cell dimensions are , . 相似文献
82.
Models of a dual inheritance system 总被引:1,自引:0,他引:1
J Maynard Smith 《Journal of theoretical biology》1990,143(1):41-53
In higher plants, animals and fungi, there are two inheritance systems: the familiar system, depending on DNA sequence, used in transmitting information between sexual generations, and an epigenetic inheritance system, depending on gene activation, responsible for the transmission of states of differentiation during development. Occasionally, epigenetic changes are transmitted in sexual reproduction. A formal model of such a dual inheritance system is presented, and it is shown how the separation between the two systems can sometimes break down. The evolutionary significance of such breakdowns is discussed. 相似文献
83.
Charles A. Maynard 《In vitro cellular & developmental biology. Plant》1994,30(1):64-69
Summary A field test was established in 1987 to evaluate the growth of micropropagated black cherry plantlets and control seedlings.
The study also evaluated effects of two container types on initial survival and growth and of pruning on stem form and growth.
At the time of field establishment, plantlets had more extensive root systems than the control seedlings. Survival and height
growth were not influenced by container size. Through the first three growing seasons, seedlings were larger than micropropagated
plants, but growth differences diminished in the fourth through sixth seasons. Pruning increased the length of clear stem
by nearly five-fold but adversely affected diameter growth.
Although all clones were from ortet trees more than 50 yr old, none showed plagiotropic growth. Six-year results showed that
in a well-prepared and maintained plantation, black cherry trees derived from tissue culture can have at least 80% survival,
and growth rates in excess of 1 m per year. 相似文献
84.
85.
86.
Daniel Maynard Sara Mareike Müller Monika Hahmeier Jana Löwe Ivo Feussner Harald Gröger Andrea Viehhauser Karl-Josef Dietz 《Bioorganic & medicinal chemistry》2018,26(7):1356-1364
Oxidation products of the poly-unsaturated fatty acids (PUFAs) arachidonic acid, α-linolenic acid and docosahexaenoic acid are bioactive in plants and animals as shown for the cyclopentenones prostaglandin 15d-PGJ2 and PGA2, cis-(+)-12-oxophytodienoic acid (12-OPDA), and 14-A-4 neuroprostane. In this study an inexpensive and simple enzymatic multi-step one-pot synthesis is presented for 12-OPDA, which is derived from α-linolenic acid, and the analogous docosahexaenoic acid (DHA)-derived cyclopentenone [(4Z,7Z,10Z)-12-[[-(1S,5S)-4-oxo-5-(2Z)-pent-2-en-1yl]-cyclopent-2-en-1yl] dodeca-4,7,10-trienoic acid, OCPD]. The three enzymes utilized in this multi-step cascade were crude soybean lipoxygenase or a recombinant lipoxygenase, allene oxide synthase and allene oxide cyclase from Arabidopsis thaliana. The DHA-derived 12-OPDA analog OCPD is predicted to have medicinal potential and signaling properties in planta. With OCPD in hand, it is shown that this compound interacts with chloroplast cyclophilin 20-3 and can be metabolized by 12-oxophytodienoic acid reductase (OPR3) which is an enzyme relevant for substrate bioactivity modulation in planta. 相似文献
87.
JC. Brisset F. Gazeau C. Corot N. Nighoghossian Y. Berthezène E. Canet-Soulas M. Wiart 《IRBM》2018,39(2):93-102
Background
Inflammation is a share process in atherosclerosis and stroke and is thought to be a key player in the evolution of these diseases. Ten years ago, inflammation imaging with magnetic resonance imaging (MRI) was considered very promising for both pre-clinical and clinical studies of atherosclerosis and stroke.Contribution
We report here contributions to the field of inflammation imaging with USPIO-enhanced MRI. The goal was to investigate the life cycle of USPIOs in the body, and how the MRI signal has been impacted during their bio-interactions and bioprocessing. Those mechanisms were applied to pre-clinical longitudinal studies of inflammation in atherosclerosis and at the acute stage of ischemic stroke thus allowing the monitoring of treatment effects.Conclusion
This review presents the contribution of the collaborative research project under the “TecSan” grant from the French Research Agency (ANR) as well as pre-clinical and clinical perspectives of USPIO's inflammation MRI in atherosclerosis and stroke. 相似文献88.
Nonneutral evolution of tandem repeats in the mitochondrial DNA control region of lagomorphs 总被引:7,自引:0,他引:7
Casane D; Dennebouy N; de Rochambeau H; Mounolou JC; Monnerot M 《Molecular biology and evolution》1997,14(8):779-789
The mitochondrial DNA of the European rabbit (Oryctolagus cuniculus)
contains a tandem array of 153-bp repeats in the vicinity of the
replication origin of the H-stand. Variation among molecules in the number
of these repeats results in inter- and intraindividual length polymorphism
(heteroplasmy). Generally, in an individual, one predominant molecular type
is observed, the others representing a low percentage of the mtDNA content.
At the tissue level, we observe a particular distribution of this
polymorphism in the gonads compared with liver, kidneys, or brain, implying
a relationship between the differentiation status of the cells and the
types of new mtDNA molecules which appear and accumulate during lifetime.
Similar tandem repeats were also found in the mtDNA noncoding region of
European hares (Lepus europaeus), a cottontail (Sylvilagus floridanus), and
a pika (Ochotona rufescens). The lengths and the sequences of these units
evolve rapidly and in a concerted way, but the number of repeats is
maintained in a narrow range, and an internal 20-bp segment is highly
conserved. Constraints restrict the evolution of the primary sequence of
these repeated units, the number of which is probably controlled by a
stabilizing selection.
相似文献
89.
Contests over web-sites in the spider, Agelenopsis aperta, have been simulated by a model in which the next act of a spider is determined by the value of two ‘drives’ or ‘tendencies’, to attack and to flee. Such a model can explain the fact that F1 hybrids between two geographical races of A. aperta are not intermediate between their parents, but are more aggressive than either. The model also accounts for the following features of the observed contests: (1) contests consist of a series of bouts, during which the spiders perform increasingly aggressive acts; (2) contests are usually won by the larger spider; (3) if sizes are equal, contests are usually won by the owner; (4) contests over excellent-quality sites are more costly than over poor-quality sites; and (5) transition probabilities for de-escalation, matching and escalation with respect to prior acts show site quality and weight bias trends. It is argued that a two-tendency model is the simplest that would account for these observations. The model also accurately simulates spider behaviour in agonistic contexts not used in its development (i.e. round-robin contests involving opponents from different populations, and a group of contests involving unequally-matched hybrid opponents).The main discrepancy between the model and observed encounters is that the model predicts that, if the owner is larger, the cost of a contest will not vary with the value of the disputed site. This is because the smaller intruder, having no knowledge of site quality (Riechert 1984) is expected to withdraw early in the contest, regardless of site quality. In the actual contests over excellent sites, estimated costs are higher even when the owner is larger and the intruder loses. The change in intruder behaviour associated with site value occurs following the first series of actions, but within the first bout of the interactions: our analyses indicate that any information conveyed by the owner concerning site value is not through overt behaviour (i.e. through the frequencies with which specific acts are performed). 相似文献
90.