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11.
Carole H. Sellem Annie Sainsard-Chanet Léon Belcour 《Molecular & general genetics : MGG》1990,224(2):232-240
Summary In the filamentous fungus Podospora anserina, the amplification as circular DNA molecules of the first intron (intron ) of the CO1 mitochondrial gene, encoding the cytochrome oxidase subunit 1, is known to be strongly associated with aging of strains. In this study we have attempted to detect the protein potentially encoded by the open reading frame (ORF) contained in this intron. This was done by the Western blot technique using specific antisera raised against three polypeptides encoded by three non-overlapping fragments of this ORF adapted to the universal code and overexpressed in Escherichia coli. We examined about thirty independent subclones of Podospora derived from two different geographic races (A, s), using wild-type and mutant strains, young and senescent cultures. A 100 kDa polypeptide, encoded by the class II intron , was detected in five senescent subclones which all showed strong amplification of the intronic sequence (Sen DNA ). 相似文献
12.
Influence of nitrate on uptake of ammonium by nitrogen-depleted soybean: is the effect located in roots or shoots? 总被引:4,自引:1,他引:3
Saravitz Carole H.; Chaillou Sylvain; Musset Joanne; Raper C. David Jr.; Morot-Gaudry Jean-Francis 《Journal of experimental botany》1994,45(11):1575-1584
In non-nodulated soybean [Glycine max (L.) Merrill cv. Ransom]plants that were subjected to 15 d of nitrogen deprivation inflowing hydroponic culture, concentrations of nitrogen declinedto 1.0 and 1.4mmol Ng1 dry weight in shoots and roots,respectively, and the concentration of soluble amino acids (determinedas primary amines) declined to 40µmol g1 dry weightin both shoots and roots. In one experiment, nitrogen was resuppliedfor 10 d to one set of nitrogen-depleted plants as 1.0 mol m3NH4+ to the whole root system, to a second set as 0.5 mol m3NH4+ plus 0.5 mol m3 NO3 to the whole root system,and to a third set as 1.0 mol m3 NH4+ to one-half ofa split-root system and 1.0 mol m3 NO3 to theother half. In a second experiment, 1.0 mol m3 of nitrogenwas resupplied for 4 d to whole root systems in NH4+ : NO3ratios of 1:0, 9:1, and 1:1. Nutrient solutions were maintainedat pH 6.0. When NH4+ was resupplied in combination with NO3 to thewhole root system in Experiment I, cumulative uptake of NH4+for the 10 d of resupply was about twice as great as when NH4+was resupplied alone. Also, about twice as much NH4+ as NO3was taken up when both ions were resupplied to the whole rootsystem. When NH4+ and NO3 were resupplied to separatehalves of a split-root system, however, cumulative uptake ofNH4+ was about half that of NO3. The uptake of NH4+,which is inhibited in nitrogen-depleted plants, thus is facilitatedby the presence of exogenous NO3, and the stimulatingeffect of NO3 on uptake of NH4+ appears to be confinedto processes within root tissues. In Experiment II, resupplyof nitrogen as both NH4+ and NO3 in a ratio of either1:1 or 9:1 enhanced the uptake of NH4+. The enhancement of NH4+uptake was 1.8-fold greater when the NH4+: NO3-resupplyratio was 1:1 than when it was 9:1; however, only 1.3 timesas much NO3 was taken up by plants resupplied with the1 :1 exogenous ratio. The effect of NO3 on enhancementof uptake of NH4+ apparently involves more than net uptake ofNO3 itself and perhaps entails an effect of NO3uptake on maintenance of K+ availability within the plant. Theconcentration of K+ in plants declined slightly during nitrogendeprivation and continued to decline following resupply of nitrogen.The greatest decline in K+ concentration occurred when nitrogenwas resupplied as NH4+ alone. It is proposed that decreasedavailability of K+ within the NH4+-resup-plied plants inhibitedNH4+ uptake through restricted transfer of amino acids fromthe root symplasm into the xylem. Key words: Ammonium, Glycine max, nitrate, nitrogen-nutrition, nitrogen stress, split-root cultures 相似文献
13.
Phosphatidylcholine biosynthesis in celery cell suspension cultures with altered sterol compositions
Cell suspension cultures of celery were treated with the plant growth regulator, paclobutrazol. Lipid analysis revealed that use of this xenobiotic had little effect on the quantity or acyl quality of the major phospholipid classes or on the actual amounts of free sterol present in the cell. It did however, cause dramatic changes in the free sterol profile exhibited by treated cultures. In this respect, an increase in 14α-methylsterols was observed.
The synthesis of phosphatidylcholine in celery cell suspension cultures with altered free sterol compositions was studied using two radiolabelled biosynthetic precursors, [3 H-methyl]choline and [3 H-methyl]methionine. The studies showed that the rate of phosphatidylcholine biosynthesis via the CDP-base pathway proceeded at a slower rate in paclobutrazol treated cultures. Accumulation of label phosphocholine was observed arising from reduced CTP:cholinephosphatecytidylyltransferase activity. In contrast, phosphatidylcholine biosynthesis via the sequential methylation of ethanolamine derivatives appeared to be enhanced in cells that had an unusually high 14α-methylsterol content. From these investigations it may be postulated that the biosynthesis of phosphatidylcholine in Apium graveolens suspension cultures may be regulated by membrane sterol composition. 相似文献
The synthesis of phosphatidylcholine in celery cell suspension cultures with altered free sterol compositions was studied using two radiolabelled biosynthetic precursors, [
14.
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
15.
The Second Messenger, Cyclic AMP, Is Not Sufficient for Myelin Gene Induction in the Peripheral Nervous System 总被引:1,自引:0,他引:1
Joseph F. Poduslo Randall S. Walikonis Marie-Christine Domec Carole T. Berg Carrie J. Holtz-Heppelmann 《Journal of neurochemistry》1995,65(1):149-159
Abstract: The adenylyl cyclase-cyclic AMP (cAMP) second messenger pathway has been proposed to regulate myelin gene expression; however, a clear correlation between endogenous cAMP levels and myelin-specific mRNA levels has never been demonstrated during the induction or maintenance of differentiation by the myelinating Schwann cell. Endogenous cAMP levels decreased to 8–10% of normal nerve by 3 days after crush or permanent transection injury of adult rat sciatic nerve. Whereas levels remained low after transection injury, cAMP levels reached only 27% of the normal values by 35 days after crush injury. Because P0 mRNA levels were 60% of normal levels by 14 days and 100% by 21 days after crush injury, cAMP increased only well after P0 gene induction. cAMP, therefore, does not appear to trigger myelin gene induction but may be involved in myelin assembly or maintenance. Forskolin, an activator of adenylyl cyclase, increased endoneurial cAMP levels only in the normal nerve, and in the crushed nerve beginning at 16 days after injury, but at no time in the transected nerve. Only by treating transected nerve with 3-isobutyl-1-methylxanthine (IBMX), an inhibitor of cAMP phosphodiesterases, in combination with forskolin was it possible to increase cAMP levels. No induction of myelin genes, however, was observed with short- or long-term treatment with IBMX and forskolin in the transected nerve. A three-fold increase in phosphodiesterase activity was observed at 35 days after both injuries, and a nonmyelinated nerve was shown to have even higher activity. These experiments, therefore, suggest an important role for phosphodiesterase in the inactivation of this second messenger-dependent stimuli when Schwann cells are non-myelinating, such as after sciatic nerve injury or in the nonmyelinated nerve, which again implies that cAMP may be required for the maintenance of the myelin sheath. 相似文献
16.
17.
Ram S. Verma Carole Rubenstein Harvey Dosik 《In vitro cellular & developmental biology. Plant》1977,13(11):806-807
Summary There was no significant difference in the mitotic indices of the cultures maintained at different CO2 concentrations, i.e. 0%, 5% and 10%. However, considerable variation was recorded among different individuals.
Supported by National Cancer Institute Contract No. 1 CP 43251. 相似文献
18.
Zusammenfassung 1. Respirometrische Messungen der spezifisch-dynamischen Wirkung (SDW) bei körnerfressenden Singvögeln zeigen, daß die SDW mit sinkenden Umgebungstemperaturen relativ kleiner wird. 2. Der Existenzstoffwechsel körnerfressender Singvögel weist nahrungsspezifische Unterschiede auf. Diese Unterschiede sind durch den unterschiedlichen SDW-Effekt verschiedener Nährstoffzusammensetzungen verursacht und sind von der Umgebungstemperatur abhängig: Sinken die Umgebungstemperaturen, werden die Unterschiede relativ kleiner. Diese Ergebnisse weisen darauf hin, daß körnerfressende Singvögel in der Lage sind, mit der SDW die Thermoregulation zu unterstützen.
Can the specific dynamic action (SDA) contribute to the thermoregulation of granivorous song birds?
Summary 1. Respirometric measurements of the specific dynamic action (SDA) of granivorous song birds show that the SDA decreases relatively with dropping temperatures. 2. The existence metabolic rates of granivorous song birds show diet-related differences. These differences are caused by the SDA of different food types and are depend on the ambient temperature: With dropping ambient temperature differences become relatively smaller. These results indicate that granivorous song birds are able to use the SDA in thermoregulation.相似文献
19.
Summary Myofibrillar adenosine triphosphatase (ATPase) activity was demonstrated in sections of masseter and temporalis muscles and of selected limb muscles of adult rhesus monkeys. Incubations were performed either with no pre-treatment or after prior incubation in alkaline media (pH 10.2–10.4) or acidic media (pH 3.8–4.6). Without pre-treatment, fibres having high or low ATPase activity were observed in limb and masticatory muscles. Following alkaline pre-incubation the difference between high and low ATPase of limb muscle fibres is accentuated, whereas pre-incubation in acidic media (pH 4.3) results in inhibition of high and potentiation of low ATPase activities (acid reversal). While pre-incubation of masticatory muscle sections at pH 10.2 accentuates differences in ATPase activity, pre-incubation at pH 10.4 abolishes ATPase activity. In contrast, masticatory muscle fibres showed no reversal of ATPase activity following acidic pre-incubation (pH 4.3). Pre-incubation at pH 3.8 abolished the ATPase activity of both limb and masticatory muscle fibres. The biochemical basis for the differences in ATPase histochemistry between masticatory and limb muscles is not known. 相似文献
20.