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1.
Hepatic lipid metabolism is controlled by integrated metabolic pathways. Excess accumulation of hepatic TG is a hallmark of nonalcoholic fatty liver disease, which is associated with obesity and insulin resistance. Here, we show that KH-type splicing regulatory protein (KSRP) ablation reduces hepatic TG levels and diet-induced hepatosteatosis. Expression of period 2 (Per2) is increased during the dark period, and circadian oscillations of several core clock genes are altered with a delayed phase in Ksrp−/− livers. Diurnal expression of some lipid metabolism genes is also disturbed with reduced expression of genes involved in de novo lipogenesis. Using primary hepatocytes, we demonstrate that KSRP promotes decay of Per2 mRNA through an RNA-protein interaction and show that increased Per2 expression is responsible for the phase delay in cycling of several clock genes in the absence of KSRP. Similar to Ksrp−/− livers, both expression of lipogenic genes and intracellular TG levels are also reduced in Ksrp−/− hepatocytes due to increased Per2 expression. Using heterologous mRNA reporters, we show that the AU-rich element-containing 3′ untranslated region of Per2 is responsible for KSRP-dependent mRNA decay. These findings implicate that KSRP is an important regulator of circadian expression of lipid metabolism genes in the liver likely through controlling Per2 mRNA stability.  相似文献   
2.
Although little is known on the impact of environment on telomere length dynamics, it has been suggested to be affected by stress, lifestyle and/or life‐history strategies of animals. We here compared telomere dynamics in erythrocytes of hatchlings and fledglings of the brood parasite great spotted cuckoos (Clamator glandarius) and of magpies (Pica pica), their main host in Europe. In magpie chicks, telomere length decreased from hatching to fledging, whereas no significant change in telomere length of great spotted cuckoo chicks was found. Moreover, we found interspecific differences in the association between laying date and telomere shortening. Interspecific differences in telomere shortening were interpreted as a consequence of differences in lifestyle and life‐history characteristics of magpies and great spotted cuckoos. In comparison with magpies, cuckoos experience reduced sibling competition and higher access to resources and, consequently, lower stressful environmental conditions during the nestling phase. These characteristics also explain the associations between telomere attrition and environmental conditions (i.e. laying date) for magpies and the absence of association for great spotted cuckoos. These results therefore fit expectations on telomere dynamics derived from interspecific differences in lifestyle and life history of brood parasites and their bird hosts.  相似文献   
3.
Summary Immature cotyledons and embryo axes of sainfoin were cultured on Murashige and Skoog (MS) media supplemented with various concentrations of 6-benzylaminopurine (BAP) and a-naphthaleneacetic acid (NAA) to induce adventitious shoot regeneration. The highest frequency of shoot regeneration occurred following an initial callus growth on a MS medium containing 0.5 mg/l BAP and 2 mg/l NAA. Immature embryo axes showed higher regeneration capacity than immature cotyledons, however, shoot elongation was best achieved on immature cotyledons. Regenerated shoots were excised and rooted in half strength MS medium with 1 mg/l indole-butyric acid (IBA) or 1 mg/l NAA. The rooted plantlets were finally transferred to compost.  相似文献   
4.
Small birch plants were grown for up to 80 d in a climate chamber at varied relative addition rates of nitrogen in culture solution, and at ambient (350 μmol mol-1) or elevated (700 μmol mol-1) concentrations of CO2. The relative addition rate of nitrogen controlled relative growth rate accurately and independently of CO2 concentration at sub-optimum levels. During free access to nutrients, relative growth rate was higher at elevated CO2. Higher values of relative growth rate and net assimilation rate were associated with higher values of plant N-concentration. At all N-supply rates, elevated CO2 resulted in higher values of net assimilation rate, whereas leaf weight ratio was independent of CO2. Specific leaf area (and leaf area ratio) was less at higher CO2 and at lower rates of N-supply. Lower values of specific leaf area were partly because of starch accumulation. Nitrogen productivity (growth rate per unit plant nitrogen) was higher at elevated CO2. At sub-optimal N-supply, the higher net assimilation rate at elevated CO2 was offset by a lower leaf area ratio. Carbon dioxide did not affect root/shoot ratio, but a higher fraction of plant dry weight was found in roots at lower N-supply. In the treatment with lowest N-supply, five times as much root length was produced per amount of plant nitrogen in comparison with optimum plants. The specific fine root length at all N-supplies was greater at elevated CO2. These responses of the root system to lower N-supply and elevated CO2 may have a considerable bearing on the acquisition of nutrients in depleted soils at elevated CO2. The advantage of maintaining steady-state nutrition in small plants while investigating the effects of elevated CO2 on growth is emphasized.  相似文献   
5.
The lateral leaflets of Desmodium motorium exhibit rhythmic upward and downward movements with a period in the minute range. Apoplasmic K+ and H+ activities were monitored in situ in the abaxial part of the pulvini with ion-selective microelectrodes. An extracellular electric potential was recorded simultaneously. The apoplasmic H+ activity of all pulvini exhibiting a regular rhythm of the extracellular electric potential oscillated with the same period between about 10 and 20 mM. The apoplasmic K+ activity was high when the membrane potential of the motor cells was depolarized (about 36 mV) and the cells were shrunken. In contrast, the apoplasmic K+ activity was low in the swollen state of the motor cells, when the membrane potential was hyperpolarized (about -136 mV). The volatile anesthetic enflurane suppressed reversibly the movement of the leaflets. The same treatment also arrested spontaneous oscillations in the apoplasmic K+ activity in the pulvinus. The apoplasmic K+ activity oscillated roughly in phase with the K+ activity between pH 6.6 and 6.0. Application of white light disturbed the rhythm and increased the extracellular pH. Our results indicate that the physiological mechanism that drives the lateral leaflet movements of Desmodium motorium is closely related to the osmotic motors mediating the leaf movements of Mimosa, Samanea and Phaseolus.Abbreviations Em membrane potential - Eex extracellular electric potential - Hex extracellular H+ activity - Kex extracellular K+ activity - Rex extracellular electrical resistance B. Antkowiak was supported by the Stiftung Volkswagenwerk.  相似文献   
6.
Development of the central somatosensory system is profoundly modulated by the sensory periphery. Cauterization of facial whiskers alters the segregation pattern of barrels in rodents only during a few days just after birth (critical period). Although a molecular basis of the segregation of barrel neurons and the critical period for the anatomical plasticity observed in layer IV barrel neuron is not clear yet, the accumulating evidence suggests that neurotrophins modulate synaptic connections including central nervous system. In this study, we showed by in situ hybridization that mouse barrel side neurons express brain-derived neurotrophic factor (BDNF) mRNA and both catalytic and non-catalytic forms of trkB mRNA. Cautery of row C vibrissae on the right side of the face within 24 h after birth (post natal day 0, PND0) reduced the expression of BDNF and trkB mRNA from the division region between the contralateral row C barrels at PND7. The vibrissae in row A, C, and E were cauterized at PND0 followed by quantitative RT-PCR for BDNF and trkB mRNA with total RNA isolated from the barrel region at PND7. The result showed that BDNF, but not trkB, mRNA was increased several-fold in the contralateral barrel region. These data suggest that the expression of BDNF mRNA is differentially regulated between injured barrels and actively innervated barrels. The differential expression of the mRNA encoding neurotrophins and their receptors may be important in regulating the injury-dependent re-segregation of barrels.  相似文献   
7.
Twenty four shift workers (8 from a steel industry and 16 from a Government hospital) participated in the study. The subjects were instructed to self-measure oral temperature, 4 6 times a day for about three weeks. Sleep quantity and quality for each subject were analysed with the help of an appropriate inventory. The data were analysed by cosinor and power spectrum methods. The frequency of circadian rhythm detection was in the order of 48% in senior nurses, 29% in steel plant workers and 14% in junior nurses. These were also complemented by the results of power spectrum analysis. Present results suggest that rhythms of subjective fatigue and subjective drowsiness are governed neither by oral temperature oscillator nor by the sleep/wake cycle oscillator. The results show that shift rotation pattern chiefly modulates the circadian time structure of shift workers. It is also suggested that the phenomenon of circadian rhythm desynchronization in oral temperature appears to be independent of per day total sleep length.  相似文献   
8.
Evidence that cytokinin controls bud size and branch form in Norway spruce   总被引:3,自引:0,他引:3  
Shoot elongation in many coniferous species is predetermined during bud formation the year before the shoot extends. This implies that formation of the primordial shoot within the bud is the primary event in annual shoot growth. Hormonal factors regulating bud formation are consequently of utmost importance. We followed the levels of the endogenous cytokinins zeatin riboside (ZR) and isopentenyladenosine (iPA) in terminal buds, whorl buds and lower lateral buds of the uppermost current-year whorl shoots of 15- to 20-year-old trees of Norway spruce [ Picea abies (L.) Karst.] from June to September. Cytokinins were isolated with affinity chromatography columns, purified by high performance liquid chromatography, and quantified by ELISA. The level of ZR was low in June but increased gradually in all buds until September. Throughout the measurement period, the ZR level was highest in terminal buds and lowest in the scattered lateral, buds, with the whorl buds intermediate. The level of iPA peaked in July and decreased later without any consistent differences among the three classes of buds. The development of different kinds of buds was followed by scanning electron microscopy. We found that bud growth was greatest during August and September. The final size of primordial shoots within the buds varied considerably and the weight of the terminal bud was three times that of the whorl buds and more than five times that of the other lateral buds.
We conclude that the increase in ZR level during the period of active bud development is indicative of the importance of cytokinin for this process. Furthermore, the positive correlation between the level of ZR and bud growth during the period of predetermination of next year's branch growth suggests that this hormone indirectly controls the form of single branches in the spruce tree.  相似文献   
9.
Field-measured grazing rates (ml/animal/d) of cladocerans (mostly daphniids) and diaptomids were assembled from various published studies and plotted as a function of corresponding phytoplankton concentration (μg l−1 f.w.). Filtering rates of both zooplankton groups initially increased with seston concentration until maximal grazing rates were observed at approximately 4 × 102 and 1 × 102 μg l−1 for cladocerans and copepods, respectively; at higher algal concentrations, filtering rates of both declined as a function of food concentration. The shape of these curves are most consistent with Holling's (1966) Type 3 functional response. We found little support for the Type 3 functional response in published laboratory studies of Daphnia; most investigators report either a Type 1 or Type 2 response. The one study in which the Type 3 response was observed involved experiments where animals were acclimated at low food concentrations for 24 h, whereas those studies associated with response Types 1 or 2 had acclimation periods of only 1 to 3 h. We therefore assembled relevant data from the literature to examine the effect of acclimation period on the feeding rates of Daphnia at low food concentrations. In the absence of any acclimation, animals filtered at extremely low rates. After 2 h of acclimation, however, filtering rates increased 4 to 5-fold but declined again with longer durations; after > 70 h of pre-conditioning, filtering rates were almost as low as they had been with no acclimation. We also found little support for the Type 3 functional response in published studies of copepods. The only study associated with a Type 3 response involved a marine copepod that had been subjected to a starvation period of 48 h; however, an analysis of the effects of acclimation period did not yield conclusive evidence that filtering rates of freshwater copepods (Diaptomus and Eudiaptomus) decrease significantly with acclimation duration. The low filtering rates associated with long acclimation periods in laboratory experiments appears to be a direct result of animals becoming emaciated from prolonged exposure to low food concentrations, a situation which renders them incapable of high filtering rates. This may explain the Type 3 functional response for field cladocerans, since zooplankton in food-limiting situations are constantly exposed to low food concentrations, and would therefore have low body carbon and consequently less energy to filter-feed. We cannot, however, use this to explain the Type 3 response for field diaptomids, since copepods in the laboratory did not appear to lose body carbon even after 72 h of feeding at very low food levels, and there was inconclusive evidence that either Diaptomus or Eudiaptomus decrease their filtering rates with acclimation period. Although Incipient Limiting Concentrations (ILC) for Daphnia ranged from 1 to 8.5 × 103 μg 1−1, more than half of these fell between 1 and 3 × 103 μg l−1, bracketing the value of 2.7 × 102 μg l−1 for field cladocerans. There was, however, a great deal of variation in reported maximum ingestion rates (MIR), maximum filtering rates (MFR) and ILC values for Daphnia magna. ILC values from the few laboratory studies of freshwater copepods ranged between 0.5 to 2.8 × 103 μg 1−1, and was higher than the ILC value of approximately 0.2 × 103 μg l−1 calculated for field populations of D. minutus. Generally, there was considerable agreement among laboratory studies regarding the shape of grazing-rate and ingestion-rate curves when data were converted to similar units and presented on standardized scales.  相似文献   
10.
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