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51.
Gianfranco Tucci Marco Cosimo Simeone Carlo Gregori Fabio Maggini 《Plant Systematics and Evolution》1994,190(3-4):187-193
Intergenic spacers of the rRNA genes of three species of theCynareae tribe:Cynara cardunculus subsp.scolymus (artichoke),Onopordum acanthium, andO. illyricum were cloned in the plasmid pGEM-7zf(+). Detailed restriction mapping and partial sequencing of the IGSs were carried out. The structural analysis showed a clear diversity betweenCynara andOnopordum, while a high degree of homology was found between the twoOnopordum spp. In all three species a fragment of about 450 bp from the 5 end of 18S to the Acc I site with a high sequence homology was present. Nucleotide sequences upstream from the above mentioned Acc I site show a gradual decrease of homology betweenCynara andOnopordum. 相似文献
52.
Davide Malatesta David Simar Yves Dauvilliers Robin Candau Fabio Borrani Christian Prefaut Corinne Caillaud 《Journal of applied physiology》2003,95(6):2248-2256
This study tested whether the lower economy of walking in healthy elderly subjects is due to greater gait instability. We compared the energy cost of walking and gait instability (assessed by stride to stride changes in the stride time) in octogenarians (G80, n = 10), 65-yr-olds (G65, n = 10), and young controls (G25, n = 10) walking on a treadmill at six different speeds. The energy cost of walking was higher for G80 than for G25 across the different walking speeds (P < 0.05). Stride time variability at preferred walking speed was significantly greater in G80 (2.31 +/- 0.68%) and G65 (1.93 +/- 0.39%) compared with G25 (1.40 +/- 0.30%; P < 0.05). There was no significant correlation between gait instability and energy cost of walking at preferred walking speed. These findings demonstrated greater energy expenditure in healthy elderly subjects while walking and increased gait instability. However, no relationship was noted between these two variables. The increase in energy cost is probably multifactorial, and our results suggest that gait instability is probably not the main contributing factor in this population. We thus concluded that other mechanisms, such as the energy expenditure associated with walking movements and related to mechanical work, or neuromuscular factors, are more likely involved in the higher cost of walking in elderly people. 相似文献
53.
Augusto C. Franco Angela Haag-Kerwer Britta Herzog Thorsten E. E. Grams Erika Ball Eduardo A. de Mattos Fabio R. Scarano Suzanne Barreto Maria A. Garcia Andre Mantovani Ulrich Lüttge 《Trees - Structure and Function》1996,10(6):359-365
Sandy plains are characteristic of the coastal region of Brazil. We investigated the diel patterns of changes in organic acid levels, leaf conductance and chlorophylla fluorescence for sun-exposed and shaded plants ofClusia hilariana, one of the dominant woody species in the sandy coastal plains of northern Rio de Janeiro state. Both exposed and shaded plants showed a typical CAM pattern with considerable diel oscillations in organic acid levels. The degradation of both malic and citric acids during the midday stomatal closure period could lead to potential CO2 fixation rates of 28 mol m-2 s-1 in exposed leaves. Moreover, exposed leaves exhibited large increases in total non-photochemical quenching (qN) accompanied by a substantial decrease in effective quantum yield during the course of the day. However, these potential high rates of CO2 fixation and the increases inqn of exposed plants were not enough to maintain the primary electron acceptor of photosystem II (qA) in a low reduction state, similar to that of shaded plants. As a result, there was a moderate increase in the reduction state of qA throughout the day. Most of the decline in photochemical efficiency of exposed leaves ofC. hilariana was reversible, as evidenced by the high levels of pre-dawn potential quantum yields (Fv/Fm) and their rapid recovery after sunset. However, the depletion of the organic acid pool in the afternoon resulted in an accentuated subsequent drop in Fv/Fm, suggesting that prolonged periods of water stress accompanied by high irradiance levels may expose plants ofC. hilariana in unprotected habitats to the danger of photoinhibition. 相似文献
54.
P. Rizzu E. A. Lindsay C. Taylor H. O’Donnell A. Levy P. Scambler A. Baldini 《Mammalian genome》1996,7(9):639-643
We have identified and cloned a gene, ES2, encoding a putative 476 amino acid protein with a predicted M
r
of 52,568. The gene is localized within the DiGeorge/Velocardiofacial syndrome locus on 22q11.2 and is deleted in all the
patients in which a deletion within 22q11 could be demonstrated, with the exception of one patient. ES2 is expressed in all
the tissues studied. Sequence comparison showed identity with five ESTs and at the amino acid level the sequence was highly
similar to, and collinear with, a hypothetical C. elegans protein of unknown function. Mutation analysis was performed in 16 patients without deletion, but no mutation has been found.
The cDNA sequence is conserved in mouse and is localized on MMU16B1-B3, known to contain a syntenic group in common with HSA
22q11.2.
Received: 25 March 1996 / Accepted: 15 May 1996 相似文献
55.
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Summary The aerobic dechlorination of 4-chlorobiphenyl and of Aroclor 1221 by Pseudomonas sp. CPE1 strain was enhanced by the presence of hydroxypropyl--cyclodextrin in the medium. The best dechlorination results were obtained when 4-chlorobiphenyl or Aroclor 1221 and the cyclodextrin were used at the molar ratios 1:1 and 1:1.5. This agent can be adopted to enhance the efficiency of PCB degradation tests. 相似文献
58.
Oligonucleotide primer-directed mutagenesis is a useful molecular biological tool, which is invalubable for the study of the structure/function relationships in proteins and for the creation of mutant proteins possessing modified or novel biological activities. Mutagenesis studies in which a site-saturation approach is employed require a high-efficiency mutagenesis procedure, which will generate a population of mutated molecules containing an even distribution of all possible amino acid changes, or a subset thereof. This article describes such a mutagenesis technique and discusses the adaptations that are necessary to perform sitesaturation mutagenesis. 相似文献
59.
Rapid withdrawal of females from males at the end of the copulatory sequence (prior to male dismounting) characterizes several
primate species. The purpose of this paper is to make a preliminary investigation into possible functional aspects of these
“copulatory darts.” Two hypotheses are proposed; (1) females use darts to aid competing males to locate the source of copulation
calls; and (2) females dart in order to promote re-mating with the same male. Both hypotheses postulate that darts may thus
enhance male-male competition, although acquisition of other benefits may be the primary drive to darting according to the
re-mating hypothesis. Using data from 157 copulations collected from six females spread across four groups in a wild population
of chacma baboonsPapio cynocephalus ursinus, darting behaviour is described. Within females, darting distance is highly variable. Darting distance is greatest at the
time of ovulation (and maximal sexual swelling), and there is some evidence that darting may also be more frequent, and cover
greater distances, when the mating male is adult rather than juvenile. While darting behaviour appears unrelated to the presence
or absence of ejaculation, it tends to correlate positively with the duration of the female copulation call. These preliminary
results are consistent with a mediating role in male-male competition and therefore provide support for both hypotheses. 相似文献
60.
Bernard Chapais Carole Gauthier Jean Prud’homme 《International journal of primatology》1995,16(3):521-536
It has been proposed that monkeys direct grooming to high-ranking individuals in an attempt to obtain agonistic support in
return. But whether these two categories of interactions are causally related has proven difficult to establish. Part of the
problem stems from the fact that in stable groups social relationships reflect an equilibrium state and that behaviors need
only be performed at low rates and long intervals to maintain the current social structure. In theory, however, if affiliative
and supportive interactions are indeed causally related, it should be possible to accentuate their temporal relation, hence
their causal dynamics. For example, destabilizing dominance relations can be expected to induce competition for status and
force individuals to deploy behavioral tactics for settling new rank relations. We experimentally induced rank reversals in
a captive group of Japanese macaques (Macaca fuscata) composed of three matrilines (A-B-C rank order). A reversed C-A-B order
composed of three individuals per matriline was maintained for 2 weeks. The results show the close temporal relation among
(i) asserting one’s rank, (ii) competing for access to dominants through affiliation and interferences in affiliation, (iii)
receiving support from dominants against lower-ranking individuals, and (iv) supporting dominants against subordinates. These
findings are compatible with one version of the affiliation-for-support hypothesis, namely that monkeys affiliate with dominants
as a way to assert their position in the hierarchy. In a functional perspective, mutual selfishness provides a better explanation
than reciprocal altruism because the possibility that both groomers and supporters derive immediate net benefits cannot be
excluded. 相似文献