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1.
The effects of CO2 elevation on the dynamics of fine root (FR) mass and ectomycorrhizal (EM) mass and colonization were studied in situ in a Florida scrub oak system over four years of postfire regeneration. Soil cores were taken at five dates and sorted to assess the standing crop of ectomycorrhizal and fine roots. We used ingrowth bags to estimate the effects of elevated CO2 on production of EM roots and fine roots. Elevated CO2 tended to increase EM colonization frequency but did not affect EM mass nor FR mass in soil cores (standing mass). However, elevated CO2 strongly increased EM mass and FR mass in ingrowth bags (production), but it did not affect the EM colonization frequency therein. An increase in belowground production with unchanged biomass indicates that elevated CO2 may stimulate root turnover. The CO2-stimulated increase of belowground production was initially larger than that of aboveground production. The oaks may allocate a larger portion of resources to root/mycorrhizal production in this system in elevated rather than ambient CO2. 相似文献
2.
A bacterium strain BERT, which utilizes primary long-chain alkylamines as nitrogen, carbon and energy source, was isolated
from activated sludge. This rod-shaped motile, Gram-negative strain was identified as a Pseudomonas sp. The substrate spectrum of this Pseudomonas strain BERT includes primary alkylamines with alkyl chains ranging from C3 to C18, and dodecyl-1,3-diaminopropane. Amines with alkyl chains ranging from 8 to 14 carbons were the preferred substrates. Growth
on dodecanal, dodecanoic acid and acetic acid and simultaneous adaptation studies indicated that this bacterium initiates
degradation through a Calkyl–N cleavage. The cleavage of alkylamines to the respective alkanals in Pseudomonas strain BERT is mediated by a PMS-dependent alkylamine dehydrogenase. This alkylamine dehydrogenase produces stoichiometric
amounts of ammonium from octylamine. The PMS-dependent alkylamine was found to oxidize a broad range of long-chain alkylamines.
PMS-dependent long-chain aldehyde dehydrogenase activity was also detected in cell-free extract of Pseudomonas strain BERT grown on octylamine. The proposed pathway for the oxidation of alkylamine in strain BERT proceeds from alkylamine
to alkanal, and then to the fatty acid. 相似文献
3.
4.
Pinus pinaster (Ait.) is a high yielding forest tree, producing nearly a fourth of French marketed timber essentially from
intensively managed stands located in southwestern France, in the Landes Forest. This species has generally a poor stem straightness,
especially when it grows in poor sandy podzol of the Landes Forest, affected by summer droughts and winter floods. Above-
and below-ground architecture and biomass as well as stem straightness were measured on twenty-nine 5-year-old planted trees
uprooted by pulling with a lumbering crane. A very precise numeric representation of the geometry and topology of structural
root architecture was gained using a low-magnetic-field digitising device (Danjon et al., 1998; Sinoquet and Rivet, 1997).
Data were analysed with AMAPmod, a database software designed to analyse plant topological structures (Godin et al., 1997).
Several characteristics of root architecture were extracted by queries including root number, length, diameter, volume, spatial
position, ramification order, branching angle and inter-laterals length. Differences between root systems originated from
their dimensions, but also from the proportion of deep roots and the taproot size, which represented 8% of the total root
volume. The proportion of root volume in the zone of rapid taper was negatively correlated with the proportion of root volume
in the taproot indicating a compensation between taproot and main lateral root volume. Among all studied root characteristics
the maximal rooting depth, the proportion of deep roots and the root partitioning coefficient were correlated with stem straightness.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
5.
Elizabeth Knyihár-Csillik Pasko Rakic Prof. Dr. Bert Csillik 《Cell and tissue research》1989,258(3):515-525
Summary Transection of the sciatic nerve in Rhesus monkeys and the consequent transganglionic degenerative atrophy (TDA) of central terminals of primary afferents result in transneuronal degeneration of substantia gelatinosa (SG) cells. Severe degeneration is characterized by an increased electron density of the nucleus and by conspicuous shrinkage of the cytoplasm, mitochondrial swelling, dilation of cisterns of the rough-surfaced endoplasmic reticulum, accumulation of free ribosomes and an electron-dense material in the cytoplasm. In the mild form, dilation of cisternal elements of the endoplasmic reticulum, swollen mitochondria and accumulation of free ribosomes takes place. About 10% of SG cells in segment L5 undergo the severe form whereas the rest shows signs of the mild form. Cytoplasmic alterations that occur during transneuronal degeneration seem to start at the level of subsurface cisterns. Dendrites and axons of transneuronally degenerating SG cells also show a conspicuous electron density. By analyzing the synaptic relationships of such darkened dendrites, connections in the upper dorsal horn can be deciphered. Modular units of the primary nociceptive analyzer that evaluate noxious and innocuous inputs on the basis of thin versus thick (AC/A) afferent activity and subjecting them to descending control appear to be recruited from structurally dispersed elements of synaptic glomeruli. These are arranged alongside dendritic processes of large antenna cells which relay impulses to projection cells of the spinothalamic tract. 相似文献
6.
7.
OpdK is an outer membrane protein of the pathogenic bacterium Pseudomonas aeruginosa. The recent crystal structure of this protein revealed a monomeric, 18-stranded β-barrel with a kidney-shaped pore, whose constriction features a diameter of 8 ?. Using systematic single-channel electrical recordings of this protein pore reconstituted into planar lipid bilayers under a broad range of ion concentrations, we were able to probe its discrete gating kinetics involving three major and functionally distinct conformations, in which a dominant open substate O(2) is accompanied by less thermodynamically stable substates O(1) and O(3). Single-channel electrical data enabled us to determine the alterations in the energetics and kinetics of the OpdK protein when experimental conditions were changed. In the future, such a semiquantitative analysis might provide a better understanding on the dynamics of current fluctuations of other β-barrel membrane protein channels. 相似文献
8.
Regulation of picornavirus gene expression 总被引:6,自引:0,他引:6
Members of the Picornaviridae are positive- strand RNA viruses that cause a variety of human diseases such as poliomyelitis, the common cold, myocarditis, and hepatitis. Although the diseases caused by picornaviruses are diverse, the genome organization and mechanisms of gene expression are highly conserved among family members. This review will discuss the mechanisms of viral gene expression including cap-independent translation initiation, host cell translation shut off, viral polyprotein processing, and RNA replication. 相似文献
9.
Hafer N Maidment BW Hatchett RJ 《Biosecurity and bioterrorism : biodefense strategy, practice, and science》2010,8(4):357-363
The National Institute of Allergy and Infectious Diseases (NIAID) Radiation/Nuclear Medical Countermeasures Development Program has developed an integrated approach to providing the resources and expertise required for the research, discovery, and development of radiation/nuclear medical countermeasures (MCMs). These resources and services lower the opportunity costs and reduce the barriers to entry for companies interested in working in this area and accelerate translational progress by providing goal-oriented stewardship of promising projects. In many ways, the radiation countermeasures program functions as a "virtual pharmaceutical firm," coordinating the early and mid-stage development of a wide array of radiation/nuclear MCMs. This commentary describes the radiation countermeasures program and discusses a novel business model that has facilitated product development partnerships between the federal government and academic investigators and biopharmaceutical companies. 相似文献
10.
Breukelman S Mulder EJ van Oord R Jonker H van der Weijden BC Taverne MA 《Theriogenology》2006,65(3):486-498
Continuous fetal heart rate (FHR) monitoring using transabdominal Doppler ultrasonography can be assumed to provide information about the viability of the bovine fetus during late gestation, as has been found in humans. To be able to recognize unfavourable fetal conditions, first the normal ranges of FHR parameters in cattle should be established. Therefore, in this study we aimed to determine the normal ranges of computerized FHR parameters, like basal fetal heart rate (BHR), number of accelerations and decelerations per hour and short and long term variation (STV and LTV) during the last 3 weeks before calving (n = 21 cows). Each cow had one recording in each of three episodes of 7 days before parturition. As recording time in the cow is limited, we also studied whether these FHR parameters differ between recordings of 30 and 60 min duration (n = 31 pairs of recordings). The outcomes of FHR recordings with a duration of 30 or 60 min did not differ significantly, except for a higher percentage of signal loss in the 60 min recordings. Therefore, determination of normal ranges was performed in 30 min recordings. BHR decreased from 3 to 2 weeks (114 to 109 bpm; P < 0.0001) before parturition and then remained constant until 2 days before calving. The mean number of accelerations per hour ranged between 4.4 and 5.0 h(-1) and did not change significantly with time. Compared to 3 weeks before parturition, STV was significantly higher at 2 weeks (P < 0.05), but not at 1 week before parturition (8.1, 10.0, and 9.2 ms, respectively). Changes in LTV showed a time course comparable to that of STV, but significance was not reached (51.4, 58.6, and 58.4 ms for respectively 3, 2 and 1 weeks before parturition). No decelerations were found during the period understudy. In conclusion, this study has provided normal ranges of bovine computerized FHR parameters during the last 3 weeks of gestation, allowing a comparison with data from cows with compromised gestations in future. 相似文献