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61.
Nicolae Barbacar Stefan Hinnisdaels Isabelle Farbos Françoise Monéger ré Lardon Catherine Delichère Armand Mouras Ioan Negrutiu 《The Plant journal : for cell and molecular biology》1997,12(4):805-817
The dioecious white campion (Silene latifolia) has been chosen as a working model for sexual development. In this species, sexual dimorphism is achieved through two distinct developmental blocks: inhibition of carpel development in male flowers, and early arrest of anther differentiation in female flowers. The combined advantages of the dioecious system and the availability of a sexual mutant lacking both male and female reproductive organs have been exploited in a molecular subtraction approach using male and asexual flower buds. This resulted in the cloning of 22 cDNA clones expressed in stamens at distinct stages of development. Fourteen of these clones corresponded to genes whose expression was detected in pre-meiotic stamens, a stage of development for which very little information is presently available. Furthermore, the absence of similarities with database sequences for ten clones suggests that they represent novel genes. Functional analysis of each clone will enable their positioning within the reproductive organ developmental pathway(s). In parallel, these clones are being exploited as developmental markers of early differentiation within the flower. 相似文献
62.
Christian Biémont Cristina Vieira Christine Hoogland Géraldine Cizeron Catherine Lœvenbruck Claude Arnault Jean-Pierre Carante 《Genetica》1997,100(1-3):161-166
To investigate the main forces controlling the containment of transposable elements (TE) in natural populations, we analyzed
the copia, mdg1, and 412 elements in various populations of Drosophila melanogaster and D. simulans. A lower proportion of
insertion sites on the X chromosome in comparison with the autosomes suggests that selection against the detrimental effects
of TE insertions is the major force containing TE copies in populations of Drosophila. This selection effect hypothesis is
strengthened by the absence of the negative correlation between recombination rate and TE copy number along the chromosomes,
which was expected under the alternative ectopic exchange model (selection against the deleterious rearrangements promoted
by recombination between TE insertions). A cline in 412 copy number in relation to latitude was observed among the natural
populations of D. simulans, with very high numbers existing in some local populations (around 60 copies in a sample from Canberra,
Australia). An apparent absence of selection effects in this Canberra sample and a value of transposition rate equal to 1–2
× 10-3 whatever the population and its copy number agree with the idea of recent but temporarily drastic TE movements in local populations.
The high values of transposition rate in D. simulans clearly disfavor the hypothesis that the low amount of transposable elements
in this species could result from a low transposition rate.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
63.
Nathalie Griffon Catherine Pilon François Sautel Jean-Charles Schwartz Pierre Sokoloff 《Journal of neurochemistry》1997,68(1):1-9
Abstract: As cerebral neurons express the dopamine D1 receptor positively coupled with adenylyl cyclase, together with the D3 receptor, we have investigated in a heterologous cell expression system the relationships of cyclic AMP with D3 receptor signaling pathways. In NG108-15 cells transfected with the human D3 receptor cDNA, dopamine, quinpirole, and other dopamine receptor agonists inhibited cyclic AMP accumulation induced by forskolin. Quinpirole also increased mitogenesis, assessed by measuring [3 H]thymidine incorporation. This effect was blocked partially by genistein, a tyrosine kinase inhibitor. Forskolin enhanced by 50–75% the quinpirole-induced [3 H]thymidine incorporation. This effect was maximal with 100 n M forskolin, occurred after 6–16 h, was reproduced by cyclic AMP-permeable analogues, and was blocked by a protein kinase A inhibitor. Forskolin increased D3 receptor expression up to 135%, but only after 16 h and at concentrations of >1 µ M . Thus, in this cell line, the D3 receptor uses two distinct signaling pathways: it efficiently inhibits adenylyl cyclase and induces mitogenesis, an effect possibly involving tyrosine phosphorylation. Activation of the cyclic AMP cascade potentiates the D3 receptor-mediated mitogenic response, through phosphorylation by a cyclic AMP-dependent kinase of a yet unidentified component. Hence, transduction of the D3 receptor can involve both opposite and synergistic interactions with cyclic AMP. 相似文献
64.
65.
Under certain culture conditions, cells of the chlorophyte Haematococcus pluvialis accumulate significant amounts of astaxanthin. This study describes biomass and carotenoid production during a sunlight cycle in a continuous culture of growing cells of H. pluvialis and shows that these two parameters are under the control of irradiance. The hourly carotenoid production increases with light intensity and, in our culture conditions, carotenoid accumulation occurs in a few hours and without any morphological change in the algae. These carotenoids seem to be efficient in protecting algal cells against photoinhibition damage if their content is greater than 1% dry biomass. Below this concentration, that is to say in the early hours of high light intensity, dry biomass decreases due to cell lysis. The results demonstrate that secondary carotenoid accumulation in H. pluvialis may occur in the active growth phase and is stimulated from the first hours of sunlight illumination. 相似文献
66.
Cuvillier Olivier; Alonso Catherine; Wieruszeski Jean-Michel; Brassart Colette; Strecker Gerard; Bouquelet Stephane; Michalski Jean-Claude 《Glycobiology》1995,5(3):281-289
During a systematic study of carbohydrate material present inhuman meconium, in addition to the previously described mucins,glycolipids and free oligosaccharides, we have now characterizeda significant quantity of free glycoasparagines. These glycoasparagineshave been isolated from human meconium by a combination of ion-exchange,concanavalin A (ConA)-affinity and high-performance liquid (HPLC)chromatographies. Their structures have been established by400 MHz 1H-NMR spectroscopy. These compounds are related toN-acetyllactosaminic type structures and are based on the commoncore These glycoasparagines are probably derived from both proteaseand partial exoglycosidase hydrolysis of fetal gastrointestinalN-glycosyl proteins. Their structures are discussed in the contextof the known catabolic pathways of N-glycans glycoasparagine N-glycosyl protein catabolism meconium NMR 相似文献
67.
Catherine Iehl Sylvie Dlos Olivier Guirou Rothwell Tate Jean-Pierre Raynaud Pierre-Marie Martin 《The Journal of steroid biochemistry and molecular biology》1995,54(5-6)
The present study describes the independent expression of the type 1 and 2 isoforms of human 5α-reductase in the baculovirus-directed insect cell expression system and the selectivity of their inhibition. The catalytic properties and kinetic parameters of the recombinant isozymes were consistent with published data. The type 1 isoform displayed a neutral (range 6–8) pH optimum and the type 2 isoform an acidic (5–6) pH optimum. The type 2 isoform had higher affinity for testosterone than did the type 1 isoform (Km = 0.5 and 2.9 μM, respectively). Finasteride and turosteride were selective inhibitors of the type 2 isoform (Ki (type 2) = 7.3 and 21.7 nM compared to Ki (type 1) = 108 and 330 nM, respectively). 4-MA and the lipido-sterol extract of Serenoa repens (LSESr) markedly inhibited both isozymes (Ki (type 1) = 8.4 nM and 7.2 μg/ml, respectively; Ki (type 2) = 7.4 nM and 4.9 μg/ml, respectively). The three azasteroids were competitive inhibitors vs substrate, whereas LSESr displayed non-competitive inhibition of the type 1 isozyme and uncompetitive inhibition of the type 2 isozyme. These observations suggest that the lipid component of LSESr might be responsible for its inhibitory effect by modulating the membrane environment of 5α-reductase. Partially purified recombinant 5α-reductase type 1 activity was preserved by the presence of lipids indicating that lipids can exert either stimulatory or inhibitory effects on human 5α-reductase. 相似文献
68.
Marjorie A. Jones Catherine J. Norris Michael J.K. Harper 《Prostaglandins & other lipid mediators》1984,28(1)
The prostaglandin (PG) content of several tissues and fluids from 6 day pregnant rabbits was evaluated following treatment with indomethacin or vehicle
. PGE and PGF were measured by radioimmunoassay. More complete depletion of PGE and PGF was accomplished by 3 injections of indomethacin (s.c.) given during the 18 h before sacrifice at a dose of 10 mg indomethacin per kg body weight than was accomplished by 1 injection of the same amount of indomethacin (i.v.) 1.5 h before sacrifice. Levels of PGF were more easily depressed by indomethacin than were those of PGE. PG levels in the kidney and blastocysts were depressed to a greater extent by indomethacin than were those in the uterus, uterine fluid or peritoneal fluid. Evaluation of the effect of indomethacin on a particular physiological function should be interpreted with caution unless the extent of PG depletion in that tissue is also measured. 相似文献
69.
70.
Auditory sensitivity and psychophysical tuning curves in the elephant nose fish,Gnathonemus petersii
Catherine A. McCormick Arthur N. Popper 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1984,155(6):753-761
Summary Hearing sensitivity and psychophysical tuning curves were determined for the mormyridGnathonemus petersii. Pure tone hearing thresholds were determined from 100 Hz to 2,500 Hz, with best sensitivity being about –31 dB (re: 1 dyne/ cm2) from 300 Hz to 1,000 Hz. In order to determine frequency tuning of the auditory system, psychophysical tuning curves (PTC's) were measured with the masker presented simultaneously with, or just ahead of, the 500 Hz test signal. The sound level for different frequencies needed to just mask the test tone were determined from 100 to 800 Hz. Maximum masking occurred in both forward and simultaneous conditions when the masker and the test tone were at the same frequency. As the masker was moved in frequency from 500 Hz, higher sound levels of maskers were needed to afford masking of the test tone. The data were similar in simultaneous and forward masking, with theQ
10 dB, a measure of sharpness of tuning, being about 5 in both cases. Data were compared for other species for which behavioral thresholds and PTC's are available.Gnathonemus hears about as wide a range of frequencies as the goldfish,Carassius auratus, although the PTC's for the two species are strikingly different. The PTC's forGnathonemus resemble those determined in a forward-masking paradigm for the clown knife fish,Notopterus chitala, even thoughGnathonemus has a wider hearing bandwidth.Abbreviations
AM
amplitude modulated
-
EOD
electric organ discharge
-
PTC
psychophysical tuning curve 相似文献