bluuebunny/crossref_metadata_2025 huggingface dataset:
La taxonomie bactérienne moderne : revue des techniques — application à la caractérisation des bactéries nodulant les légumineuses (BNL)
Authors: Zakhia Frédéric , de Lajudie Philippe
Published: April 2006

Taxonomy is the science that studies the relationships between organisms. It comprises classification, nomenclature, and identification. Modern bacterial taxonomy is polyphasic. This means that it is based on several molecular techniques, each one retrieving the information at different cellular levels (proteins, fatty acids, DNA...). The obtained results are combined and analysed to reach a "consensus taxonomy" of a microorganism. Until 1970, a small number of classification techniques were available for microbiologists (mainly phenotypic characterization was performed: a legume species nodulation ability for a Rhizobium, for example). With the development of techniques based on polymerase chain reaction for characterization, the bacterial taxonomy has undergone great changes. In particular, the classification of the legume nodulating bacteria has been repeatedly modified over the last 20 years. We present here a review of the currently used molecular techniques in bacterial characterization, with examples of application of these techniques for the study of the legume nodulating bacteria.Key words: polyphasic taxonomy, molecular characterization, bacteria, prokaryotes, legume nodulating bacteria, Rhizobium.
Biological control of rice bacterial blight by plant-associated bacteria producing 2,4-diacetylphloroglucinol
Authors: Velusamy Palaniyandi , Immanuel J Ebenezar , Gnanamanickam Samuel S , Thomashow Linda
Published: April 2006

Certain plant-associated strains of fluorescent Pseudomonas spp. are known to produce the antimicrobial antibiotic 2,4-diacetylphloroglucinol (DAPG). It has antibacterial, antifungal, antiviral, and antihelminthic properties and has played a significant role in the biological control of tobacco, wheat, and sugar beet diseases. It has never been reported from India and has not been implicated in the biological suppression of a major disease of the rice crop. Here, we report that a subpopulation of 27 strains of plant-associated Pseudomonas fluorescens screened in a batch of 278 strains of fluorescent pseudomonads produced DAPG. The DAPG production was detected by a PCR-based screening method that used primers Phl2a and Phl2b and amplified a 745-bp fragment characteristic of DAPG. HPLC,1H NMR, and IR analyses provided further evidence for its production. We report also that this compound inhibited the growth of the devastating rice bacterial blight pathogen Xanthomonas oryzae pv. oryzae in laboratory assays and suppressed rice bacterial blight up to 59%–64% in net-house and field experiments. Tn5 mutants defective in DAPG production (Phl–) of P. fluorescens PTB 9 were much less effective in their suppression of rice bacterial blight.Key words: biocontrol, 2,4-diacetylphloroglucinol, Pseudomonas fluorescens, rice, Xanthomonas oryzae pv. oryzae.
Bacterial diversity within the planktonic community of an artesian water supply
Authors: Ball Christopher L , Crawford Ronald L
Published: April 2006

Culture and molecular methods were used to describe the planktonic bacterial diversity of an artesian water supply in rural Latah County, Idaho, within the drainage of a small perennial stream, Thorn Creek. The surrounding depth to groundwater at this location is thought to be significant (>100 m), and this transitional zone (basalt–granite) of the Palouse aquifer system is little studied. The water produced by this artesian source is consistent even in years of drought and is of high quality, both mineralogically and microbiologically. A culture-based analysis using 30 media types and four incubation temperatures demonstrated that several metabolic types were present in the water. 16S rRNA gene fragments amplified from the DNA of pooled cultured cells and from the DNA extracted from 1 L of the source water were compared using denaturing gradient gel electrophoresis. The results indicated that the two DNA samples did not have similar 16S rRNA gene compositions and that several uncultured phyla were present in the community DNA sample. These results indicated that large-scale culturing did not accurately represent the structure planktonic community. 16S rRNA gene sequences from 17 different genera were obtained from the community DNA sample; the most abundant were similar to Rhodoferax, Rhodobacter, and Polaromonas species. Sequences related to the Proteo bacteria, Bacteroidetes/Chlorobi, Firmicutes, and Acidobacterium/Fibrobacter divisions were also detected.Key words: artesian spring, bacterial diversity, DGGE, 16S rRNA, enrichment culture.
Protease activities of Acanthamoeba polyphaga and Acanthamoeba castellanii
Authors: Serrano-Luna José de Jesús , Cervantes-Sandoval Isaac , Calderón Jesús , Navarro-García Fernando , Tsutsumi Victor , Shibayama Mineko
Published: April 2006

Acanthamoeba spp. are free-living amoebae that cause amoebic granulomatous encephalitis, skin lesions, and ocular amoebic keratitis in humans. Several authors have suggested that proteases could play a role in the pathogenesis of these diseases. In the present work, we performed a partial biochemical characterization of proteases in crude extracts of Acanthamoeba spp. and in conditioned medium using 7.5% SDS–PAGE copolymerized with 0.1% m/v gelatin as substrate. We distinguished a total of 17 bands with proteolytic activity distributed in two species of Acanthamoeba. The bands ranged from 30 to 188 kDa in A. castellanii and from 34 to 144 kDa in A. polyphaga. Additionally, we showed that the pattern of protease activity differed in the two species of Acanthamoeba when pH was altered. By using protease inhibitors, we found that the proteolytic activities belonged mostly to the serine protease family and secondly to cysteine proteases and that the proteolytic activities from A. castellanii were higher than those in A. polyphaga. Furthermore, aprotinin was found to in hibit crude extract protease activity on Madin–Darby canine kidney (MDCK) monolayers. These data suggest that protease patterns could be more complex than previously reported.Key words: Acanthamoeba spp., amoebic keratitis, serine proteases, cysteine proteases, cytopathic effect.
Isolation and characterization of plaque-purified strains of Malacosoma disstria Nucleopolyhedrovirus
Authors: Erlandson Martin A , Baldwin Doug , Haveroen Melissa , Keddie B Andrew
Published: April 2006

Seven plaque-purified genotypic variants or strains, derived from a previously described field isolate of the Malacosoma disstria Nucleopolyhedrovirus (MadiNPV) from Alberta populations of forest tent caterpillar, were characterized based on distinctive restriction endonuclease fragment patterns. Two strains, MadiNPV-pp3 and MadiNPV-pp11, were selected for further characterization, as they represented strains producing high and low budded virus (BV) titres, respectively, in the M. disstria cell line UA-Md203. Analysis of restriction endonuclease fragment profiles indicated the genomes differed significantly in size, 133.8 ± 2.4 kb for MadiNPV-pp3 and 118.1 ± 3.5 kb for MadiNPV-pp11. These strains were characterized based on their BV production in three different cell lines derived from M. disstria haemocytes. Compared with MadiNPV-pp11, MadiNPV-pp3 produced two- to three-fold more BVs in UA-Md203 and 210 other cell lines; however, BV production was only marginally higher for MadiNPV-pp3 in the UA-Md221 cell line. Similarly, the yield of polyhedral inclusion bodies was significantly higher for MadiNPV-pp3 in UA-Md203 and 210 cell lines than for MadiNPV-pp11 but not in the UA-Md221 cell line. This data, although derived from a limited number of cell lines, suggested MadiNPV-pp3 may have a broader tissue tropism than MadiNPV-pp11.Key words: forest tent caterpillar, Malacosoma disstria, Nucleopolyhedrovirus.
TheBurkholderia cepaciarpoEgene is not involved in exopolysaccharide production and onion pathogenicity
Authors: Devescovi Giulia , Venturi Vittorio
Published: April 2006

Burkholderia cepacia was originally described as the causative agent of bacterial rot of onions, and it has now emerged as an important opportunistic pathogen causing severe chronic lung infections in patients having cystic fibrosis. Burkholderia cepacia is now classified into nine very closely related species (previously designated as genomovars), all of which have been isolated from both environmental and clinical sources and are collectively known as the B. cepacia complex. The alternative extracytoplasmic function σ factor, σE, has been determined in several bacterial species as making substantial contributions to bacterial survival under stress conditions. Here, we report the identification and characterization of the rpoE gene, encoding σE, of B. cepacia. It is highly similar to σEof other bacteria, including Escherichia coli and Pseudomonas aeruginosa. Studies using an rpoE knockout mutant of B. cepacia revealed that many stress adaptations, including osmotic, oxidative, desiccation, carbon, and nitrogen stress, were independent of σE. Similarly, biofilm formation; production of exopolysaccharides, N-acyl homoserine lactones, and several exoenzymes; and onion pathogenicity were not affected by the absence of σE. In contrast, σEcontributed to the adaptation to heat stress and phosphate starvation.Key words: Burkholderia cepacia, sigma factor, rpoE, extracytoplasmic function.
PCR detection of pathogenic Leptospira genomospecies targeting putative transcriptional regulator genes
Authors: Liu Dongyou , Lawrence Mark L , Austin Frank W , Ainsworth A Jerald , Pace Lanny W
Published: April 2006

The genus Leptospira comprises multiple genomospecies that demonstrate varied pathogenic potential. The availability of rapid and precise diagnostic procedures to differentiate pathogenic from nonpathogenic Leptospira spp. is therefore essential to prevent an otherwise easily treatable malaise from developing into a life-threatening disease. In this report, we conducted an investigation on the diagnostic potential of Leptospira genes encoding putative tran scriptional regulators. While PCR primers derived from transcriptional regulator gene la1137 recognized all 24 pathogenic Leptospira strains representing seven species, those from la1937, la3231, la3825, and la4130 detected 19 of the 24 Leptospira strains. However, none of these primers reacted with four nonpathogenic Leptospira species or other common bacteria. The putative transcriptional regulator genes la1137, la1937, la3231, la3825, and la4130 are present in pathogenic Leptospira strains, making them potential targets for diagnostic applications. Further characterization of these genes and their proteins may help elucidate the molecular mechanisms of leptospiral virulence and pathogenicity and pave the way for potential development of novel control strategies against leptospirosis.Key words: Leptospira, pathogenic, transcriptional regulator gene, PCR, identification.
Seasonal fire effects on mixed-conifer forest structure and ponderosa pine resin properties
Authors: Perrakis Daniel DB , Agee James K
Published: April 2006

This study examined the effects of spring and fall restoration burning in an old-growth mixed-conifer  ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) forest in southern Oregon. Variables measured include fuel loads, forest structure indices, mortality of large ponderosa pines, and pine resin defenses. One year after treatment, reductions in surface fuel loads and changes to forest structure parameters suggested that burning treatments could meet restoration objectives, with fall burns being somewhat more effective than spring burns. However, mortality of pre settlement pines was significantly higher in fall burns than in spring burns, and both were higher than in unburned controls. Bark beetles (Coleoptera: Scolytidae) were important mortality agents within 2 years after burning. Resin defenses (pressure and flow) were variable over the 2 years of postburn study but showed no evidence of decrease in burned trees; rather, resin defenses were significantly higher in burned trees than in controls at several measurement dates. While increased beetle attacks have previously been documented following burning, there has been much less research on resin responses to fire. These findings suggest that current models of beetlehost interactions do not properly explain the effects of prescribed fire in ponderosa pine forests.
Spatial variability in forest growth – climate relationships in the Olympic Mountains, Washington
Authors: Nakawatase Jill M , Peterson David L
Published: April 2006

For many Pacific Northwest forests, little is known about the spatial and temporal variability in tree growth – climate relationships, yet it is this information that is needed to predict how forests will respond to future climatic change. We studied the effects of climatic variability on forest growth at 74 plots in the western and northeastern Olympic Mountains. Basal area increment time series were developed for each plot, and Pearson's correlation analysis and factor analysis were used to quantify growth–climate relationships. Forest growth in the Olympic Mountains responds to climatic variability as a function of mean climate and elevation. Low summer moisture limits growth across all elevations in the dry northeastern Olympics. Growth at low elevations in the wet western Olympics is associated with phases of the Pacific Decadal Oscillation and with summer temperature. Heavy winter snowpack limits growth at high elevations in the western Olympics. In the warmer greenhouse climate predicted for the Olympic Mountains, productivity at high elevations of the western Olympics will likely increase, whereas productivity at high elevations in the northeastern region and potentially in low elevations of the western region will likely decrease. This information can be used to develop adaptive management strategies to prepare for the effects of future climate on these forests. Because growth–climate relationships on the Olympic Peninsula vary at relatively small spatial scales, those relationships may assist modeling and other efforts to provide more accurate predictions at local to regional scales.
Spatial and temporal variability in forest growth in the Olympic Mountains, Washington: sensitivity to climatic variability
Authors: Holman Melisa L , Peterson David L
Published: April 2006

We compared annual basal area increment (BAI) at different spatial scales among all size classes and species at diverse locations in the wet western and dry northeastern Olympic Mountains. Weak growth correlations at small spatial scales (average R = 0.084–0.406) suggest that trees are responding to local growth conditions. However, significant positive growth correlations between geographically adjacent forest types (R = 0.440–0.852) and between watersheds (R = 0.430) indicate that there is a common overarching growth-limiting factor (e.g., climate) that affects tree growth over large areas. The Sitka spruce (Picea sitchensis (Bong.) Carrière) forest type is the most sensitive to environmental change with the highest mean sensitivity (0.345), the highest potential for annual growth change (mean BAI = 0.0047 m2), and the highest growth variability (coefficient of variation = 0.498). In addition, this forest type is most likely to exhibit extreme positive growth responses (4.2% of years have BAI values 2 standard deviations above the mean). Low-elevation coniferous forests are relatively sensitive to changes in growth-limiting factors (in contrast to the traditional view) and may play an important role in storing carbon in a warmer climate.
Decomposition and nutrient release from fresh and dried pine roots under two fertilizer regimes
Authors: Ludovici Kim H , Kress Lance W
Published: April 2006

Root decomposition and nutrient release are typically estimated from dried root tissues; however, it is unlikely that roots dehydrate prior to decomposing. Soil fertility and root diameter may also affect the rate of decomposition. This study monitored mass loss and nutrient concentrations of dried and fresh roots of two size classes (<2 and 2–5 mm) over a 12-month period in fertilized and control plots in a 13-year-old loblolly pine (Pinus taeda L.) plantation. Nutrient content was calculated and used to assess the effects of fertilization, root size, and initial condition (hydration) on nutrient release rates. Roots that grew and decomposed in fertilized plots had higher concentrations and greater total release of N, P, K, and Mg than roots in control plots, but C concentrations and mass loss rate were not significantly different between roots in fertilized plots and those in control plots. Very fine roots (<2 mm) had higher concentrations of N, P, and Ca and faster release rates for C, N, and K than fine roots (2–5 mm), resulting in greater total release of C and N. Roots dried prior to decomposition decayed and released C, K, Ca, and Mg at a faster rate than fresh roots. Results indicate that using dried root tissues will overestimate fine root decomposition and nutrient cycling rates.
Logging firms, nonindustrial private forests, and forest parcelization: evidence of firm specialization and its impact on sustainable timber supply
Authors: Rickenbach Mark , Steele Thomas W
Published: April 2006

Increasing forest parcelization has raised concerns about tract-size economies and sustainable timber supply. We explored this issue by examining the logging sector and forest ownership in northern Wisconsin and Michigan's Upper Peninsula. Using 2004 survey data, we found that 48% of logging firms demonstrated a near exclusive reliance on nonindustrial private forests (NIPFs). NIPF-dependent firms derived 87.5% of their stumpage from this ownership, whereas nondependent firms exhibited a significantly more diversified stumpage supply distributed among public (42.6%), industrial-corporate (33.3%), and NIPF (24.0%) sources. Additionally, NIPF-dependent firms operated on significantly fewer, smaller, and less intensely harvested timber sales, and they were more likely to harvest small tracts profitably. There were no significant differences in the forest products harvested or overall firm profitability. We found statistical evidence that NIPF-dependent and nondependent firms organize themselves differently: NIPF dependency was negatively correlated with total number of employees, timberland area in the firm's wood basket, and firm location and positively correlated with owner age. Results suggest the impacts of parcelization on the logging sector are minimal. NIPF-dependent firms appear to have structured themselves to operate profitably; however, it is unclear how continued parcelization might influence these firms and the sector as a whole.
The risk of decision making with incomplete criteria weight information
Authors: Kangas Annika
Published: April 2006

In many cases, it may be difficult to obtain explicit information on criteria weights for multicriteria decision analysis. Usually, however, at least the relevant criteria can be assumed to be known, even if their weights are not. In addition, complete or incomplete rank order of these criteria can be known, and it may be possible to obtain estimates for at least some of the value-function parameters. With some decision support tools, such as stochastic multicriteria acceptability analysis (SMAA), it is possible to use incomplete information. The main results of SMAA are the probabilities of certain alternative obtaining a given rank, given all the information available. These probabilities can be used for choosing the most recommendable alternative. However, recommendations are risky when the preference information is incomplete. In this study, the risks are studied through a simulation study based on a previous forestry decision problem with multiple criteria. (1) The probability that the best alternative is recommended and (2) the expected losses in the value of value function due to choosing the wrong alternative are modelled as a function of the characteristics of the true value function and the best alternative. The results show that the quality of decisions improves very quickly with improving information on weights. Determining at least the complete rank order of criteria is advisable, especially if the importances vary markedly among the criteria.
Genetic variation of leaf traits related to productivity in aPopulus deltoides×Populus nigrafamily
Authors: Marron Nicolas , Ceulemans Reinhart
Published: April 2006

In breeding and selection, two of the main goals of hybridization are to combine favourable traits from different species and to obtain high hybrid vigor (or heterosis). The objectives of our study were (1) to determine which leaf traits are most closely linked to growth in a cross between Populus deltoides Bartr. ex Marsh. and Populus nigra L. and (2) to estimate the relevance of this cross for selection of highly productive genotypes. To achieve these objectives, 26 poplar F1hybrids and their parents were studied during their second growing season in central France. Tree growth (i.e., growth rates of stem height, circumference, and volume) was monitored during 1 month, and leaf traits (i.e., increases in number of leaves, maximum individual leaf area, specific leaf area, petiole length, and dry mass, leaf carbon and nitrogen contents, and internode length) were estimated at the end of the 1-month period. Growth traits were tightly correlated to most of the leaf traits. More precisely, it appeared that stem volume growth rate can be decomposed into two single leaf characteristics: maximum individual leaf area and leaf increment rate. All traits showed moderate values of broad-sense heritability. Heterosis as well as coefficients of genetic variation were also modest.
Historical disturbance regimes as a reference for forest policy in a multiowner province: a simulation experiment
Authors: Thompson Jonathan R , Johnson K Norman , Lennette Marie , Spies Thomas A , Bettinger Pete
Published: April 2006

Using a landscape simulation model, we examined ecological and economic implications of forest policies designed to emulate the historical fire regime across the 2 × 106 ha Oregon Coast Range. Simulated policies included two variants of the current policy and three policies reflecting aspects of the historical fire regime. Policy development was guided by the management intentions of four owner groups: forest industry, nonindustrial private, state, and federal. Fire severity was emulated with green-tree retention standards; fire frequency was emulated with annual harvestable area restrictions; and fire extent was emulated with harvest-unit size regulations. Simulated disturbance-based policies produced age-class distributions closer to the estimated historical range than those created by the current policy. Within 100 years, proportions of younger forests were within the historical range, while older forests moved closer to, but remained below, historical conditions. In the near term, disturbance-based policies produced annual harvest volumes 20%60% lower than those produced by the current policy. However, relative costs of disturbance-based policies diminished over time. Our results suggest that if expediting a return to historical age-class distributions at a provincial-scale was a goal, then public lands would be needed to provide large patches of old forest. In addition, this experiment illustrated that distributing costs and benefits of conservation policies equitably across multiple private landowners is a significant challenge.
The vertical and horizontal distribution of roots in northern hardwood stands of varying age
Authors: Yanai Ruth D , Park Byung B , Hamburg Steven P
Published: April 2006

Coring methods cannot reveal the distribution of roots with depth in rocky soil, and fine roots are typically sampled without regard to the location of trees. We used quantitative soil pits to describe rooting patterns with soil depth and distance to trees in northern hardwood stands. We sited three 0.5 m2 quantitative soil pits in each of three young (1927 years) and three older (5669 years) stands developed after clear-cutting. Live roots were divided into diameter classes delimited at 0.5, 1, 2, 5, 10, 20, and 100 mm; dead roots were not distinguished by size. Mean total live-root biomass was 2900 ± 500 g·m2 in older stands and 1500 ± 400 g·m2 in young stands. The root mass in the 220 mm class was 2.7 times greater in the older stands (p = 0.03); fine-root (<2 mm) biomass was 1.5 times greater (p = 0.12), suggesting that fine-root biomass continues to increase past the age of canopy closure in this forest type. Root biomass density declined with soil depth, with the finest roots (<0.5 mm) declining most steeply; roots were found at low densities well into the C horizon. We analyzed root biomass density as a function of the influence of nearby trees (represented as the sum of basal area divided by the distance from the pit) and found that fine as well as coarse roots reflected this influence. In systems where this is the case, root measurements should be made with attention to patterns of tree distribution.
The economics of site preparation and the impacts of current forest policy: evidence from central British Columbia
Authors: Hawkins C BD , Steele Thomas W , Letchford Tony
Published: April 2006

A trend in forestry is to move away from intensive stand establishment practices in favor of prescriptions that are lighter on the land. This study examined the condition and projected yields of nine different site preparation treatments on two high-elevation sites in central British Columbia. Treatments included the following: raw planting (i.e., no site preparation); scalping; mounding; chemical site preparation; chemical brushing; and combinations of mounding and chemical treatments. All treatments were manually planted with 2+1 bare-root interior spruce (Picea glauca (Moench) Voss × Picea engelmannii Parry ex Engelm.) seedlings. By age 15, trees growing on prepared sites had significantly greater survival, larger stem diameters, and taller tree heights than did trees that were raw planted as seedlings. Moreover, site preparation generally led to earlier and less costly compliance with mandatory reforestation requirements. Growth and yield simulations predicted raw-planted timber volumes that were just 33%51% of the volumes in the most productive treatments. Financial returns varied as well. Site preparation typically resulted in larger land expectation values than that resulting from raw planting; however, the results were sensitive to rotation length and discount rate. Collectively, these results suggest that moderate investments in site preparation may lead to a more profitable allocation of regeneration resources and a greater future timber supply.
Scheduling fire-fighting tasks using the concept of "deteriorating jobs"
Authors: Rachaniotis Nikos P , Pappis Costas P
Published: April 2006

In fire fighting, the time and effort required to control a fire increase if the beginning of the fire containment effort is delayed. Several demand-covering models have been proposed for the deployment of available fire-fighting resources so that a forest fire is attacked within a specified time limit. This paper considers the problem of scheduling a single fire-fighting resource when there are several existing fires to be controlled using a model specific to the fire's rate of spread. The problem is tackled using the concept of deteriorating jobs, that is, the model represents increasing value loss as fires remain unsuppressed and increasing time for fire suppression.
Effects of species mixtures on growth and stand development of Douglas-fir and red alder
Authors: Radosevich Steven R , Hibbs David E , Ghersa Claudio M
Published: April 2006

In the Pacific Northwest, a mixture of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and red alder (Alnus rubra Bong.) often results when red alder regenerates naturally in planted conifer stands. The relationships among stand structure, tree mortality, tree size, and understory development in the two species mixtures were explored at two sites for the first 16 years after planting. Treatments included a range of species proportions, and red alder was either planted simultaneously with Douglas-fir or planting was delayed for 5 years. Red alder was also removed from some simultaneously planted proportions. Both replacement effects (total stand density held constant) and additive effects (stand density doubled) of the interaction were considered. Red alder grew relatively better at Cascade Head Experimental Forest in the Coast Range, while Douglas-fir grew better at H.J. Andrews Experimental Forest in the less temperate Cascade Mountains. Possible production benefits from mixed plantings were examined using two methods of calculation. Potential production benefits from certain planted proportions of the two species occurred at H.J. Andrews Experimental Forest. No planting time or species proportion resulted in yield improvements over monoculture stands at Cascade Head Experimental Forest. Understory species also varied because of differences in site and stand characteristics that resulted from the differences in planting times and species proportions.
Fire and the origin of Table Mountain pine  pitch pine communities in the southern Appalachian Mountains, USA
Authors: Brose Patrick H , Waldrop Thomas A
Published: April 2006

The prevalence of stand-replacing fire in the formation of Table Mountain pine  pitch pine (Pinus pungens Lamb. and Pinus rigida Mill., respectively) communities was investigated with dendrochronological techniques. Nine stands in Georgia, South Carolina, and Tennessee were analyzed for age structure, species recruitment trends, and radial growth patterns to determine whether they had originated as a result of stand-replacing fires. The oldest pines date from the late 1700s or early 1800s. Continuous or frequent episodic pine regeneration from those times to the early to mid 1900s was evident at all sites. During the first half of the 20th century, all sites experienced large surges in pine regeneration. However, no clear evidence of stand-replacing wildfires could be definitively linked to these surges. Rather, the regeneration appeared to have been caused by noncatastrophic surface fires and canopy disturbances occurring together or by the cessation of a frequent fire regime. For the past 2550 years, there has been little pine regeneration at any of the sites. Restoring the dual disturbance regime of periodic fires and canopy disturbances should help sustain Table Mountain pine  pitch pine communities in southern Appalachian Mountains landscapes.
The water relation of seedlings of Picea jezoensis on fallen logs
Authors: Iijima H , Shibuya M , Saito H , Takahashi K
Published: April 2006

We examined whether fallen logs without moss (FLB) are more drought-stressful sites for Picea jezoensis Carr. seedlings than are logs with moss (FLM) and whether drought affects the mortality of seedlings on logs. We measured the water potential of the log humus layer (ΨH) and needles of seedlings on the logs (ΨN) in a natural forest and a greenhouse under various drought conditions. We also determined the critical ΨN from the relationship between seedling mortality, ΨN, and chlorophyll fluorescence, Fv/Fm. The ΨH on both moss-covered and bare logs in the forest was 0~MPa, regardless of the number of days without precipitation. In the forest, the mean predawn ΨN of FLB and FLM measured 11 days after a rainfall was 0.8 and 0.7 MPa, respectively, in the driest season. The ΨN for P. jezoensis seedlings of FLB reached the critical value earlier than those of FLM in the greenhouse, but this occurred after a long period (>30 days) with no irrigation. We conclude that drought does not cause mortality of P. jezoensis seedlings on fallen logs in natural forests.
Relations between red alder composition and understory vegetation in young mixed forests of southeast Alaska
Authors: Hanley Thomas A , Deal Robert L , Orlikowska Ewa H
Published: April 2006

Interest in mixed red alder (Alnus rubra Bong.)  conifer young-growth stands has grown in southeast Alaska, USA, because they appear to provide much more productive understory vegetation and wildlife habitat than do similar-aged pure conifer stands. We studied understory vegetation in nine even-aged young-growth stands (3842 years old) comprising a gradient of red alder  conifer overstory composition, with red alder ranging from 0% to 86% of stand basal area. Conifers were Sitka spruce (Picea sitchensis (Bong.) Carr.), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and western redcedar (Thuja plicata Donn ex D. Don). We measured understory biomass and net production (current annual growth) in each stand by species and plant part and estimated carrying capacity for black-tailed deer (Odocoileus hemionus sitkensis Cowan) with a food-based habitat model. Highly significant positive relations (P < 0.002) were found between red alder basal area and all of the following: total understory biomass (r2 = 0.743), net production of shrubs (r2 = 0.758) and herbs (r2 = 0.855), and summer carrying capacity for deer (r2 = 0.846). The high correlation between red alder and herbaceous production is especially important, because herbs are least abundant and most difficult to maintain in young-growth conifer forests of this region. Red alder offers prospects for increasing understory vegetation biomass and its food value for deer and other wildlife when included as a hardwood overstory species in mixed hardwoodconifer young-growth forests.
Effects of olive oil and its minor constituents on serum lipids, oxidative stress, and energy metabolism in cardiac muscle
Authors: Faine Luciane A. , Rodrigues Hosana G. , Galhardi Cristiano M. , Ebaid Geovana M.X. , Diniz Yeda S. , Padovani Carlos R. , Novelli Ethel L.B.
Published: April 2006

Recent lines of evidence suggest that the beneficial effects of olive oil are not only related to its high content of oleic acid, but also to the antioxidant potential of its polyphenols. The aim of this work was determine the effects of olive oil and its components, oleic acid and the polyphenol dihydroxyphenylethanol (DPE), on serum lipids, oxidative stress, and energy metabolism on cardiac tissue. Twenty four male Wistar rats, 200 g, were divided into the following 4 groups (n = 6): control (C), OO group that received extra-virgin olive oil (7.5 mL/kg), OA group was treated with oleic acid (3.45 mL/kg), and the DPE group that received the polyphenol DPE (7.5 mg/kg). These components were administered by gavage over 30 days, twice a week. All animals were provided with food and water ad libitum The results show that olive oil was more effective than its isolated components in improving lipid profile, elevating high-density lipoprotein, and diminishing low-density lipoprotein cholesterol concentrations. Olive oil induced decreased antioxidant Mn-superoxide dismutase activity and diminished protein carbonyl concentration, indicating that olive oil may exert direct antioxidant effect on myocardium. DPE, considered as potential antioxidant, induced elevated aerobic metabolism, triacylglycerols, and lipid hydroperoxides concentrations in cardiac muscle, indicating that long-term intake of this polyphenol may induce its undesirable pro-oxidant activity on myocardium.
Broad-spectrum sunscreens prevent the secretion of proinflammatory cytokines in human keratinocytes exposed to ultraviolet A and phototoxic lomefloxacin
Authors: Reinhardt P. , Cybulski M. , Miller S.M. , Ferrarotto C. , Wilkins R. , Deslauriers Y.
Published: April 2006

The combination of phototoxic drugs and ultraviolet (UV) radiation can trigger the release of proinflammatory cytokines. The present study measured the ability of sunscreens to prevent cytokine secretion in human keratinocytes following cotreatment of these cells with a known photoreactive drug and UVA. Keratinocytes were treated for 1 h with increasing concentrations of lomefloxacin (LOM) or norfloxacin (NOR), exposed to 15 J/cm2 UVA, and incubated for 24 h. NOR, owing to the absence of a fluorine atom in position 8, was non-phototoxic and used as a negative control. Cell viability and the release of 3 cytokines were assessed, namely interleukin-1α (IL-1α), interleukin-6 (IL-6), and tumour necrosis factor-α (TNF-α). The measurement of these cytokines may be a useful tool for detecting photoreactive compounds. To measure their ability to prevent cytokine secretion, various sunscreens were inserted between the UVA source and the cells. Treatment with NOR, NOR plus UVA, or LOM had no effect on the cells. LOM plus UVA, however, had an effect on cell viability and on cytokine secretion. IL-1α levels increased with LOM concentration. The release of TNF-α and IL-6 followed the same pattern at lower concentrations of LOM but peaked at 15 µmol/L and decreased at higher concentrations. Sunscreens protected the cells from the effects of LOM plus UVA, as cell viability and levels of cytokines remained the same as in the control cells. In conclusion, the application of broad-spectrum sunscreen by individuals exposed to UVA radiation may prevent phototoxic reactions initiated by drugs such as LOM.
The short-circuit current of the ileum, but not the colon, is altered in the streptozotocin diabetic rat
Authors: Forrest Abigail , Makwana Rajesh , Parsons Mike
Published: April 2006

Ion transport in control and streptozotocin-diabetic rat colon and ileum was studied using the Ussing chamber technique. No differences were observed between control and diabetic colonic mucosal short-circuit current under either basal or carbachol (100 nmol/L – 1 µmol/L)-stimulated or prostaglandin E2 (100 nmol/L – 1 µmol/L)-stimulated conditions. Similarly to colonic tissues, no differences in the short circuit current in either carbachol-stimulated or prostaglandin E2-stimulated tissues were observed between control and diabetic ileal mucosa. The basal diabetic ileal short circuit current (99.58 ± 22.67 μA) was significantly greater than that of control ileal tissues (29.67 ± 4.45 μA). This difference was abolished by the sodium–glucose-cotransporter inhibitor, phloridzin (50 µmol/L) (118.00 ± 28.09 μA vs. 25.60 ± 4.59 μA) and was also prevented by the replacement of glucose with mannitol in the buffer bathing the apical side of the tissue (control: 17.05 ± 5.85 μA vs. 17.90 ± 3.10 μA). Acetazolamide (450 µmol/L; a carbonic anhydrase inhibitor), amiloride, and bumetanide (100 µmol/L each; Na+-channel blockers), piroxicam (50 µmol/L; a COX1 cyclooxygenase inhibitor), and ouabain (1 mmol/L; a K+ transport inhibitor) had no effect on the basal short circuit current of either control or diabetic ileal tissues. This indicated that the alteration in the basal short circuit current of diabetic ileal tissues was due to a change in cellular glucose transport, whereas the evoked changes in short circuit current were unaffected by the diabetic state.
Diagnosing occupational asthma: insight from induced sputumThis paper is one of a selection of papers published in this Special Issue, entitled Young Investigator's Forum.
Authors: Lemiere Catherine
Published: April 2006

The diagnosis of occupational asthma needs to be made objectively using as many criteria as possible. The latter include laboratory exposure tests with occupational agent(s), which are only available in specialized centers. Another approach is to monitor peak expiratory flow (PEF) and (or) methacholine airway responsiveness during periods at work and away from work. However, these measurements are open to misinterpretation when they are not optimally performed. Airway inflammation is one of the main characteristics of asthma. Induced sputum, a non-invasive method to assess airway inflammation, has been successfully used in the management of asthma. However, airway inflammation is seldom assessed during the investigation of occupational asthma. This article reviews the studies that have investigated and characterized the changes in sputum cell counts occurring in subjects with occupational asthma after exposure to occupational agents in the laboratory, or at the workplace to assess to place of induced sputum in the investigation of occupational asthma.
Folic acid inhibits homocysteine-induced superoxide anion production and nuclear factor kappa B activation in macrophagesThis paper is one of a selection of papers published in this Special Issue, entitled Young Investigator's Forum.
Authors: Au-Yeung Kathy K.W. , Yip Johnny C.W. , Siow Yaw L. , O Karmin
Published: April 2006

Folic acid supplementation is a promising approach for patients with cardiovascular diseases associated with hyperhomocysteinemia. We have demonstrated that homocysteine (Hcy) activates nuclear factor-κB (NF-κB), a transcription factor that plays an important role in inflammatory responses. The aim of the present study was to investigate the effect of folic acid on Hcy-induced NF-κB activation in macrophages. Hcy treatment (100 μmol/L) resulted in NF-κB activation and increased monocyte chemoattractant protein-1 (MCP-1) expression in THP-1 derived macrophages. Hcy-induced NF-κB activation was associated with a significant increase in the intracellular superoxide anion levels. There was a significant increase in phosphorylation and membrane translocation of NADPH oxidase p47phox subunit in Hcy-treated cells. Addition of folic acid (200 ng/mL) to the culture medium abolished NADPH oxidase-dependent superoxide anion generation in macrophages by preventing phosphorylation of p47phox subunit. Consequently, Hcy-induced NF-κB activation and MCP-1 expression was inhibited. Such an inhibitory effect of folic acid was independent of its Hcy-lowering ability. Taken together, these results suggest that folic acid treatment can effectively inhibit Hcy-induced oxidative stress and inflammatory responses in macrophages. This may represent one of the mechanisms by which folic acid supplementation exerts a protective effect in cardiovascular disorders.
Cytochrome p450 2C (CYP2C) in ischemic heart injury and vascular dysfunctionThis paper is one of a selection of papers published in this Special Issue, entitled Young Investigator's Forum.
Authors: Chehal Manreet K. , Granville David J.
Published: April 2006

The cytochrome p450 2C (CYP2C) monooxygenase family is a key player in the generation of epoxyeicosatrienoic acids. It has recently become apparent that CYP plays an important role in cardiovascular physiology and contributes to the pathogenesis of various cardiovascular diseases. In particular, several studies have demonstrated a role for these enzymes in cardiac ischemia and reperfusion injury. The current review summarizes the role of the CYP epoxygenase, CYP2C9, in ischemic heart disease and vascular homeostasis.
Trends in event rate and case fatality of patients hospitalized with myocardial infarction between 1984 and 2001This paper is one of a selection of papers published in this Special Issue, entitled Young Investigator's Forum.
Authors: Cox Jafna L. , Bata Iqbal R. , Gregor Ronald D. , Johnstone David E. , Wolf Hermann K.
Published: April 2006

Between 1984 and 1993, prevalence and case fatality of hospitalized acute myocardial infarction (AMI) had declined in the population of Halifax County. We aimed to determine whether these trends continued into the 21st century by investigating patient characteristics, treatment methods, and fatality for hospital admissions of residents of Halifax County, aged 25–74, during 1984–1989 (period 1), 1990–1993 (period 2), and 1998–2001 (period 3) and diagnosed as AMI that were extracted from databases for the Halifax County MONICA and ICONS (Improving Cardiovascular Outcomes in Nova Scotia) Studies. Trends in patient characteristics and treatment methods were assessed by χ2 statistics. Their association with 28-day fatality was determined by logistic regression. Event rate declined during 1984–1993 but not into 1998–2001 (p = 0.206). Compared with 1990–1993, fewer AMI patients during 1998–2001 were ≥55 years (73.3% vs. 69.9%), cigarette smokers (49.8% vs. 42.9%), had a history of myocardial infarction (28.9% vs. 24.9%), and had an admission heart rate >100 (34.8% vs. 17.4%). Additionally, more patients had a history of diabetes (22.5% vs. 28.1%). Case fatality declined progressively over the 3 study time periods (16.6%, 13.1%, and 9.4%, respectively). Changes also occurred in prevalence of Killip class 4 status during admission (20.2%, 10.3%, and 13.3%, respectively), use of thrombolysis (9.0%, 30.9, and 32.6%, respectively), and percutaneous coronary intervention (PCI) (4.3%, 11.2%, and 22.4%, respectively) in the different periods. Significant associations were found between case fatality and patient history of diabetes, history of MI, age, elevated admission heart rate, Killip class 4 impairment, thrombolysis, and PCI. The ICONS registry of hospitalized acute myocardial infarctions was used to compare case fatality during 1998–2001 with that reported by the Halifax County MONICA Project for 1984–1993. Whereas the population rate of myocardial infarctions had declined between 1984–1993 but not subsequently, case fatality declined significantly throughout the study period. The continued decline in case fatality is likely explained by changes in patient profile on presentation and medical therapies, including the increased use of thrombolysis and PCI.
The ecology of the sponge larva
Authors: Maldonado Manuel
Published: April 2006

The present work summarizes the progress attained in the study of sponge larval ecology since the state-of-the-art reviews performed in the 1970s and stresses the major weaknesses in our current understanding. Most available information on this subject comes from laboratory studies, with just occasional field observations or experiments. The data are also strongly biased because they are mostly derived from just one larval type out the eight types known in the phylum Porifera. Descriptive studies on larval histology are relatively abundant, but investigations directed at unravelling the cytological basis of the main larval behaviors are scarce. Most aspects of basic larval metabolism and sensing processes remain largely not investigated. Modelling of larval ecology is virtually lacking, with no serious attempt to investigate how the major features of larval ecology affect the structure and dynamics of sponge populations. In summary, the ecology of the sponge larva needs further research attention if we are to achieve a global understanding of the biology of the phylum Porifera.
Biology of the Porifera: cell culture
Authors: Pomponi S A
Published: April 2006

The discovery that dissociated sponge cells will reaggregate to form a functional organism was the basis for the establishment of sponge cell cultures that have been used as a model for the study of fundamental processes in developmental biology and immunology. More recent is the discovery of unique bioactive compounds in marine sponges, and the feasibility of in vitro production of these chemicals is being evaluated. Techniques are well established for cell dissociation; development of several nutrient media formulations has resulted in improvements in viability and cell division; and molecular approaches to identification of genes responsible for regulation of cell cycling may provide unique perspectives in culture optimization. The use of novel substrates for immobilization of cells offers alternatives for proliferation and scale-up. All of these results support the potential for development of a model system for the study of basic metabolic processes involved in cell differentiation, as well as an in vitro production system for sponge-derived bioactive compounds. Perhaps more important, however, is the development of cell lines of these "simple" metazoans to facilitate basic cell physiology and molecular biology research that may be applied to understanding more complex metazoan systems, including humans.