Main biotic drivers of tree growth in a developing Juniperus thurifera stand in central Spain     

Natalia Vizcaíno-Palomar  Lorena Gómez-Aparicio  Javier Pavón-García  Carmen Bartolomé-Esteban  Julio Álvarez-Jiménez  Miguel A. Zavala 《European Journal of Forest Research》2014,133(6):1109-1119

Over the last few decades, abandonment of traditional management practices in Spain has led to widespread stand densification and has favoured the expansion of some forest species that previously exhibited more restricted ranges. Spanish juniper (Juniperus thurifera L.) woodlands are experiencing this phenomenon due to agricultural land abandonment and a decrease in the livestock pressure. Yet the main drivers underlying stand structure and dynamics at this novel scenario are poorly understood. In this study, we investigate the main biotic drivers of tree growth in a high-density stand of the dioecious J. thurifera at an early developmental stage (mean tree age of 32, ca. 50 years after land abandonment). Tree growth was measured by coring 299 individuals of different reproductive classes (male, female and non-reproductive). Neighbourhood models were used to assess the relative importance of tree size and neighbourhood competition on tree growth of each reproductive class in the study plot. We found that tree size had the strongest effect on tree growth, whereas the effect of intraspecific competition was negligible. We observed differences in growth patterns among reproductive classes along trunk diameter sizes. Thus, at smaller sizes, the three reproductive classes presented identical patterns of growth. However, at bigger sizes, females were the fastest growing individuals, followed by males and non-reproductive individuals. Overall, our results suggest that in young J. thurifera monospecific forests, where self-thinning processes may have not undergone yet, tree size and the reproductive class could play a relatively more important role than competition as drivers of tree growth. These findings constitute new information which contributes to understanding growth dynamics at early developmental stages in this dioecious species. Furthermore, our results provide guidelines for silvicultural managing, suggesting that at these young juniper stands thinning would likely not translate into enhanced growth on remnant trees.  相似文献   

Genetic association between milk yield,stayability, and mastitis in Holstein cows under tropical conditions     

Natalia Irano  Annaiza Braga Bignardi  Lenira El Faro  Mário Luiz Santana Jr  Vera Lúcia Cardoso  Lucia Galvão Albuquerque 《Tropical animal health and production》2014,46(3):529-535

The objective of this study was to estimate genetic parameters for milk yield, stayability, and the occurrence of clinical mastitis in Holstein cows, as well as studying the genetic relationship between them, in order to provide subsidies for the genetic evaluation of these traits. Records from 5,090 Holstein cows with calving varying from 1991 to 2010, were used in the analysis. Two standard multivariate analyses were carried out, one containing the trait of accumulated 305-day milk yields in the first lactation (MY1), stayability (STAY) until the third lactation, and clinical mastitis (CM), as well as the other traits, considering accumulated 305-day milk yields (Y305), STAY, and CM, including the first three lactations as repeated measures for Y305 and CM. The covariance components were obtained by a Bayesian approach. The heritability estimates obtained by multivariate analysis with MY1 were 0.19, 0.28, and 0.13 for MY1, STAY, and CM, respectively, whereas using the multivariate analysis with the Y305, the estimates were 0.19, 0.31, and 0.14, respectively. The genetic correlations between MY1 and STAY, MY1 and CM, and STAY and CM, respectively, were 0.38, 0.12, and ?0.49. The genetic correlations between Y305 and STAY, Y305 and CM, and STAY and CM, respectively, were 0.66, ?0.25, and ?0.52.  相似文献   

Cholesterol's role in synapse formation     

Koudinov AR  Koudinova NV 《Science (New York, N.Y.)》2002,295(5563):2213

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A stem cell molecular signature   总被引：2，自引：0，他引：2  

Ivanova NB  Dimos JT  Schaniel C  Hackney JA  Moore KA  Lemischka IR 《Science (New York, N.Y.)》2002,298(5593):601-604

Mechanisms regulating self-renewal and cell fate decisions in mammalian stem cells are poorly understood. We determined global gene expression profiles for mouse and human hematopoietic stem cells and other stages of the hematopoietic hierarchy. Murine and human hematopoietic stem cells share a number of expressed gene products, which define key conserved regulatory pathways in this developmental system. Moreover, in the mouse, a portion of the genetic program of hematopoietic stem cells is shared with embryonic and neural stem cells. This overlapping set of gene products represents a molecular signature of stem cells.  相似文献   

Evidence from numerical experiments for a feedback dynamo generating Mercury's magnetic field     

Heyner D  Wicht J  Gómez-Pérez N  Schmitt D  Auster HU  Glassmeier KH 《Science (New York, N.Y.)》2011,334(6063):1690-1693

The observed weakness of Mercury's magnetic field poses a long-standing puzzle to dynamo theory. Using numerical dynamo simulations, we show that it could be explained by a negative feedback between the magnetospheric and the internal magnetic fields. Without feedback, a small internal field was amplified by the dynamo process up to Earth-like values. With feedback, the field strength saturated at a much lower level, compatible with the observations at Mercury. The classical saturation mechanism via the Lorentz force was replaced by the external field impact. The resulting surface field was dominated by uneven harmonic components. This will allow the feedback model to be distinguished from other models once a more accurate field model is constructed from MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) and BepiColombo data.  相似文献   

JGR authors set the record straight     

Schlesinger ME  Andronova N 《Science (New York, N.Y.)》2002,295(5554):441-442

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The structure of interleukin-2 complexed with its alpha receptor     

Rickert M  Wang X  Boulanger MJ  Goriatcheva N  Garcia KC 《Science (New York, N.Y.)》2005,308(5727):1477-1480

Interleukin-2 (IL-2) is an immunoregulatory cytokine that binds sequentially to the alpha (IL-2Ralpha), beta (IL-2Rbeta), and common gamma chain (gammac) receptor subunits. Here we present the 2.8 angstrom crystal structure of a complex between human IL-2 and IL-2Ralpha, which interact in a docking mode distinct from that of other cytokine receptor complexes. IL-2Ralpha is composed of strand-swapped "sushi-like" domains, unlike the classical cytokine receptor fold. As a result of this domain swap, IL-2Ralpha uses a composite surface to dock into a groove on IL-2 that also serves as a binding site for antagonist drugs. With this complex, we now have representative structures for each class of hematopoietic cytokine receptor-docking modules.  相似文献   

Fear erasure in mice requires synergy between antidepressant drugs and extinction training     

Karpova NN  Pickenhagen A  Lindholm J  Tiraboschi E  Kulesskaya N  Agústsdóttir A  Antila H  Popova D  Akamine Y  Bahi A  Sullivan R  Hen R  Drew LJ  Castrén E 《Science (New York, N.Y.)》2011,334(6063):1731-1734

Antidepressant drugs and psychotherapy combined are more effective in treating mood disorders than either treatment alone, but the neurobiological basis of this interaction is unknown. To investigate how antidepressants influence the response of mood-related systems to behavioral experience, we used a fear-conditioning and extinction paradigm in mice. Combining extinction training with chronic fluoxetine, but neither treatment alone, induced an enduring loss of conditioned fear memory in adult animals. Fluoxetine treatment increased synaptic plasticity, converted the fear memory circuitry to a more immature state, and acted through local brain-derived neurotrophic factor. Fluoxetine-induced plasticity may allow fear erasure by extinction-guided remodeling of the memory circuitry. Thus, the pharmacological effects of antidepressants need to be combined with psychological rehabilitation to reorganize networks rendered more plastic by the drug treatment.  相似文献   

Selective trafficking of non-cell-autonomous proteins mediated by NtNCAPP1     

Lee JY  Yoo BC  Rojas MR  Gomez-Ospina N  Staehelin LA  Lucas WJ 《Science (New York, N.Y.)》2003,299(5605):392-396

In plants, cell-to-cell communication is mediated by plasmodesmata and involves the trafficking of non-cell-autonomous proteins (NCAPs). A component in this pathway, Nicotiana tabacum NON-CELL-AUTONOMOUS PATHWAY PROTEIN1 (NtNCAPP1), was affinity purified and cloned. Protein overlay assays and in vivo studies showed that NtNCAPP1 is located on the endoplasmic reticulum at the cell periphery and displays specificity in its interaction with NCAPs. Deletion of the NtNCAPP1 amino-terminal transmembrane domain produced a dominant-negative mutant that blocked the trafficking of specific NCAPs. Transgenic tobacco plants expressing this mutant form of NtNCAPP1 and plants in which the NtNCAPP1 gene was silenced were compromised in their ability to regulate leaf and floral development. These results support a model in which NCAP delivery to plasmodesmata is both selective and regulated.  相似文献   

Alkylpyridiniums. 2. Isolation and quantification in roasted and ground coffees     

Stadler RH  Varga N  Milo C  Schilter B  Vera FA  Welti DH 《Journal of agricultural and food chemistry》2002,50(5):1200-1206

Recent model studies on trigonelline decomposition have identified nonvolatile alkylpyridiniums as major reaction products under certain physicochemical conditions. The quaternary base 1-methylpyridinium was isolated from roasted and ground coffee and purified by ion exchange and thin-layer chromatography. The compound was characterized by nuclear magnetic resonance spectroscopy ((1)H, (13)C) and mass spectrometry techniques. A liquid chromatography-electrospray ionization tandem mass spectrometry method was developed to quantify the alkaloid in coffee by isotope dilution mass spectrometry. The formation of alkylpyridiniums is positively correlated to the roasting degree in arabica coffee, and highest levels of 1-methylpyridinium, reaching up to 0.25% on a per weight basis, were found in dark roasted coffee beans. Analyses of coffee extracts also showed the presence of dimethylpyridinium, at concentrations ranging from 5 to 25 mg/kg. This is the first report on the isolation and quantification of alkylpyridiniums in coffee. These compounds, described here in detail for the first time, may have an impact on the flavor/aroma profile of coffee directly (e.g., bitterness), or indirectly as precursors, and potentially open new avenues in the flavor/aroma modulation of coffee.  相似文献