bluuebunny/crossref_metadata_2025 huggingface dataset:
Seedbed variation from the interior through the edge of a large wildfire in Alberta
Authors: Greene David F , Macdonald S Ellen , Cumming Steve , Swift Lynn
Published: September 2005

Despite the importance of seedbeds in the life histories of many plant species, there has been little study of the seedbeds created by wildfire in fire-prone vegetation types such as the boreal forest. Both within the interior and at the edge of a very large (>100 000 ha) 2001 wildfire in the mixedwood boreal region of Alberta, we examined the postfire duff depth and the percent coverage of seedbed types. Minimizing the effect of site and forest composition, we looked only at Picea glauca (Moench) Voss  Populus tremuloides Michx. sites burned during a single day of high fire intensity. Good seedbeds (thin humus and exposed mineral soil, with or without ash) averaged 35% coverage within the interior of the fire but varied enormously among stands. There was a weak but significant positive correlation between prefire percent white spruce basal area and percent mineral soil exposure; that is, there is some tendency for conifer stands to create the seedbeds best suited for their own germinants. Fire severity played a clear role in mineral soil exposure, which was greatest in areas with 100% canopy mortality. Mineral soil exposure was far less at the edges of the fire, averaging only 5% even in areas where all trees had been killed; the burn edge was characterized by superficial flaming combustion with no evidence of substantial duff removal via smoldering combustion. In short, the areas where white spruce seed will be most common after the fire, the edges, are where the worst seedbeds in the burn will be found. Regeneration microsites at fire edges appear to be better suited to regeneration of broadleaf species, via suckering; the persistence of white spruce in fire-prone landscapes continues to be difficult to explain.
Participatory decision support for sustainable forest management: a framework for planning with local communities at the landscape level in Canada
Authors: Sheppard Stephen RJ
Published: September 2005

There is an increasing demand for active public involvement in forestry decision making, but there are as yet few established models for achieving this in the new sustainable forest management (SFM) context. At the level of the working forest, the fields of forest sustainability assessment, public participation, decision support, and computer technology in spatial modelling and visualization need to be integrated. This paper presents the results of a literature review of public participation and decision-support methods, with emphasis on case study examples in participatory decision support. These suggest that emerging methods, such as public multicriteria analysis of alternative forest management scenarios and allied tools, may lend themselves to public processes addressing sustainability criteria and indicators. The paper develops a conceptual framework for participatory decision support to address the special needs of SFM in tactical planning at the landscape level. This framework consists of principles, process criteria, and preliminary guidelines for designing and evaluating SFM planning processes with community input. More well-documented studies are needed to develop comprehensive, engaging, open, and accountable processes that support informed decision making in forest management, and to strengthen guidance for managers.
Predicting site index with a physiologically based growth model across Oregon, USA
Authors: Swenson Jennifer J , Waring Richard H , Fan Weihong , Coops Nicholas
Published: September 2005

With expanded interests in sustaining productivity under changing climate, management, and disturbance regimes, we sought a means of mapping the potential productivity of forests across the state of Oregon in the Pacific Northwest, USA. We chose the mapping tool 3-PG, a simplified physiologically based process model that can be driven with monthly averaged climatic data (DAYMET) and estimates of soil fertility based on soil nitrogen content. Maximum periodic mean increment (MAI, m3·ha1·year1), a measure of the forest's productive potential, was generated by the 3-PG spatial model and mapped at 1-km2 resolution for the most widely distributed tree species, Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Maximum MAI is linearly correlated with yield table site indices and therefore comparable with field-derived estimates of site indices obtained from measurement of tree heights and ages at 5263 federal forest survey points. The model predicted 100-year site index (SI) reasonably well (R2 = 0.55; RMSE = 9.1), considering the difference in spatial resolution between the modeled (1 km2) and field-measured SI (<0.1 ha) and that field plots were offset for confidentiality by 13 km. We created a map of the differences between modeled and field-measured SI and found that the 3000 points within ±6 m error were relatively evenly distributed across Oregon. Improving the accuracy in modeling and mapping forest productivity using 3-PG will likely require refinements in soil surveys, the quality of climatic data, the location of field plots, and the model functions and species parameters.
Stand- and landscape-level effects of prescribed burning on two Arizona wildfires
Authors: Finney Mark A , McHugh Charles W , Grenfell Isaac C
Published: September 2005

Performance of fuel treatments in modifying behavior and effects of the largest wildfires has rarely been evaluated, because the necessary data on fire movement, treatment characteristics, and fire severity were not obtainable together. Here we analyzed satellite imagery and prescribed fire records from two Arizona wildfires that occurred in 2002, finding that prescribed fire treatments reduced wildfire severity and changed its progress. Prescribed burning in ponderosa pine forests 19 years before the Rodeo and Chediski fires reduced fire severity compared with untreated areas, despite the unprecedented 1860-km2 combined wildfire sizes and record drought. Fire severity increased with time since treatment but decreased with unit size and number of repeated prescribed burn treatments. Fire progression captured by Landsat 7 enhanced thematic mapper plus (ETM+) clearly showed the fire circumventing treatment units and protecting areas on their lee side. This evidence is consistent with model predictions that suggest wildland fire size and severity can be mitigated by strategic placement of treatments.
Soil respiration response to prescribed burning and thinning in mixed-conifer and hardwood forests
Authors: Concilio Amy , Ma Siyan , Li Qinglin , LeMoine James , Chen Jiquan , North Malcolm , Moorhead Daryl , Jensen Randy
Published: September 2005

The effects of management on soil carbon efflux in different ecosystems are still largely unknown yet crucial to both our understanding and management of global carbon flux. To compare the effects of common forest management practices on soil carbon cycling, we measured soil respiration rate (SRR) in a mixed-conifer and hardwood forest that had undergone various treatments from June to August 2003. The mixed-conifer forest, located in the Sierra Nevada Mountains of California, had been treated with thinning and burning manipulations in 2001, and the hardwood forest, located in the southeastern Missouri Ozarks, had been treated with harvesting manipulations in 1996 and 1997. Litter depth, soil temperature, and soil moisture were also measured. We found that selective thinning produced a similar effect on both forests by elevating SRR, soil moisture, and soil temperature, although the magnitude of response was greater in the mixed-conifer forest. Selective harvest increased SRR by 43% (from 3.38 to 4.82 µmol·m–2·s–1) in the mixed-conifer forest and by 14% (from 4.25 to 4.84 µmol·m–2·s–1) in the hardwood forest. Burning at the conifer site and even-aged harvesting at the mixed-hardwood site did not produce significantly different SRR from controls. Mean SRR were 3.24, 3.42, and 4.52 µmol·m–2·s–1, respectively. At both sites, manipulations did significantly alter SRR by changing litter depth, soil structure, and forest microclimate. SRR response varied by vegetation patch type, the scale at which treatments altered these biotic factors. Our findings provide forest managers first-hand information on the response of soil carbon efflux to various management strategies in different forests.
Evaluation of isotopic fractionation error on calculations of marine-derived nitrogen in terrestrial ecosystems
Authors: Morris Arthur EL , Stark John M , Gilbert Barrie K
Published: September 2005

Pacific salmon (Oncorhynchus spp.) transport nitrogen (N) from oceans to inland ecosystems. Salmon δ15N is higher than δ15N expected in terrestrial plants, so linear two-source mixing models have commonly been used to quantify contributions of marine-derived N (MDN) to riparian ecosystems based on riparian plant δ15N. However, isotopic fractionation potentially contributes to error in MDN estimates by changing δ15N of salmon-derived N appearing in soil and plants. We used a simulation model to examine potential effects of fractionation on MDN estimates. We also measured changes in δ15N and δ13C as N and carbon (C) moved from bear feces into soil, and compared MDN estimates using three different estimates for the marine endmember of a linear mixing model. Simulation demonstrated that fractionation during soil N losses could lead to large overestimations of MDN when δ15N of salmon tissue is used as the marine endmember. δ15N of bear feces was significantly enriched (by 1.9) relative to salmon tissue, but did not change during movement of feces-derived N into soil. In contrast, δ13C decreased by 1.9 between salmon and bear feces and declined an additional 4.2 during movement into soil. We propose a new method for estimating the δ15N of the marine endmember that accounts for isotope fractionation occurring as marine N is cycled in soil. This method uses the proportional difference in soil 15N content between reference and spawning sites to calculate the marine endmember δ15N.
Growth, mortality, and morphological response of European beech and downy oak along a light gradient in sub-Mediterranean forest
Authors: Kunstler Georges , Curt Thomas , Bouchaud Monique , Lepart Jacques
Published: September 2005

We examined light as a niche partitioning factor between the late-successional European beech (Fagus sylvatica L.) and the mid-successional downy oak (Quercus pubescens Willd.), two dominant species in the sub-Mediterranean area of southern France. For these species we estimated sapling growth models (in radius and in height) as a function of light availability. Beech had a higher growth in low light and a higher asymptotic growth rate than oak. We estimated species-specific growthmortality functions. Beech showed a higher tolerance to slow growth than oak. By linking lightgrowth functions and growthmortality functions, we found that beech had a lower mortality at low light than oak. Beech saplings had a higher probability of survival than oak at low and at high light levels. Beech exhibited the highest plasticity of morphological traits (i.e., biomass allocation, leaf morphology, and architectural traits) as a function of light. Since beech has higher growth and survival than oak at variable light regimes, we conclude that niche partitioning for light cannot explain the coexistence of these two species. We propose that disturbance and water stress should be explicitly taken into account to understand niche partitioning and succession in the sub-Mediterranean area.
Differences in wood density and growth of fertilized and nonfertilized loblolly pine associated with a mutant gene, cad-n1
Authors: Yu Q , McKeand S E , Nelson C D , Li B , Sherrill J R , Mullin T J
Published: September 2005

A rare mutant allele (cad-n1) of the cad gene in loblolly pine (Pinus taeda L.) causes a deficiency in the production of cinnamyl alcohol dehydrogenase (CAD). Effects associated with this allele were examined by comparing wood density and growth traits of cad-n1 heterozygous trees with those of wild-type trees in a 10-year-old open-pollinated family trial growing under two levels of fertilization in Scotland County, North Carolina. In all, 200 trees were sampled, with 100 trees for each fertilizer treatment. Wood density measurements were collected from wood cores at breast height using X-ray densitometry. We found that the substitution of a cad-n1 for a wild-type allele (Cad) was associated with a significant effect on wood density. The cad-n1 heterozygotes had a significantly higher wood density (+2.6%) compared with wild-type trees. The higher density was apparently due to the higher percentage of latewood in the heterozygotes. The fertilization effect was highly significant for both growth and wood density traits. This study indicates that the cad-n1 allele could be a valuable gene to the pulp and paper industry for the purpose of enhancing pulp yields by increasing wood density.
Seasonal decline in nestling cellular immunocompetence results from environmental factors — an experimental study
Authors: Dubiec Anna , Cichoń Mariusz
Published: September 2005

In a seasonal environment, immune function in bird nestlings has been reported to decline with hatching date. Two groups of factors are expected to contribute to this decline: (1) seasonal deterioration of environmental conditions, e.g., food availability, and (2) differences in individual quality between parents breeding early and late in the season. To distinguish between these effects, an experimental manipulation of hatching date in great tits (Parus major L., 1758) was conducted. Whole clutches were swapped between pairs of nests with a 6-day difference in expected hatching date, while some nests remained nonmanipulated, constituting a control group. Nestling T-cell-mediated immune response to phytohaemagglutinin was negatively related to hatching date both within nonmanipulated control broods and all broods pulled together. Experimental change in hatching date produced changes in nestling immune response, as predicted from the seasonal trend observed in the control nests. Male and female nestlings did not differ in the level of immune response and the seasonal decline in immune response did not differ between sexes. Our results indicate that the seasonal decline in nestling immune function may be driven by date-dependent environmental conditions rather than differences in parental quality.
Phylogenetic relationships within hump-winged grigs, Cyphoderris (Insecta, Orthoptera, Tettigonioidea, Haglidae)
Authors: Kumala M , McLennan D A , Brooks D R , Mason A C
Published: September 2005

The genus Cyphoderris, or hump-winged grigs, is represented by three species of cold-adapted, acoustic Ensifera with a geographic distribution that is generally restricted to the high-elevation coniferous forests of western North America. A phylogenetic analysis based on 29 morphological and 3 behavioural characters produced one tree, (C. buckelli (C. strepitans, C. monstrosa)) with a consistency index of 1.0. We discuss possible explanations for the observation that almost all of the autapomorphic change was concentrated in C. monstrosa.
Changes in subantarctic fur seal pups' activity budget and diving behaviours throughout the rearing period
Authors: Guinet C , Servera N , Deville T , Beauplet G
Published: September 2005

Time spent in the water and diving behaviour of subantarctic fur seals (Arctocephalus tropicalis (Gray, 1872)) at Amsterdam Island in the southern Indian Ocean were investigated using time–depth recorders throughout the pup-rearing period. The main finding of this study, contrary to the findings of previous studies conducted on other fur seal species, was the decrease in the mean daily amount of time spent in the water throughout the pup-rearing period. The decrease in the amount of time spent in the water by older individuals compared with younger ones is likely to be related to the reduction of the pups' energy expenditure with a decreasing provisioning rate by their mothers. No change in the number of dives or the amount of time dedicated to diving relative to the time spent in the water could be detected throughout the pup-rearing period. The mean maximum dive depth increased with pup age and decreased with pup mass, and maximum dive duration was also found to increase with pup age. The positive effect of pup size on dive rates was the only relationship suggesting that pups' growth performance may act positively on the ontogeny of their diving capabilities. The large interindividual variation in the amount of time spent in the water and in dive rates, and the absence of any clear relationship with pup mass and pup growth performance, suggest the existence of alternative strategies: either pups invest more energy in developing their swimming and diving abilities, to the detriment of the body fat stores, or reduce their activity level to enhance body fat stores to increase their postweaning survival rate.
Effects of multiple predator species on green treefrog (Hyla cinerea) tadpoles
Authors: Gunzburger M S , Travis J
Published: September 2005

Prey species that occur across a range of habitats may be exposed to variable communities of multiple predator species across habitats. Predicting the combined effects of multiple predators can be complex. Many experiments evaluating the effects of multiple predators on prey confound either variation in predator density with predator identity or variation in relative predator frequency with overall predation rates. We develop a new experimental design of factorial predator combinations that maintains a constant expected predation rate, under the null hypothesis of additive predator effects. We implement this design to evaluate the combined effects of three predator species (bass, aeshnid and libellulid odonate naiads) on mortality rate of a prey species, Hyla cinerea (Schneider, 1799) tadpoles, that occurs across a range of aquatic habitats. Two predator treatments (libellulid and aeshnid + libellulid) resulted in lower tadpole mortality than any of the other predator treatments. Variation in tadpole mortality across treatments was not related to coarse variation in microhabitat use, but was likely due to intraguild predation, which occurred in all predator treatments. Hyla cinerea tadpoles have constant, low survival values when exposed to many different combinations of predator species, and predation rate probably increases linearly with predator density.
Natural selection drives the link between male immune function and reproductive potential
Authors: Fedorka Kenneth M , Zuk Marlene , Mousseau Timothy A
Published: September 2005

In the ground cricket Allonemobius socius (Scudder 1877), males provide females with a hemolymph-based nuptial gift. The size of the gift depends on when copulation is terminated, which can be controlled by either sex. Here we show that more immunocompetent males provide larger nuptial gifts, increasing their reproductive potential. To address if this pattern was the consequence of sexual selection for an honest signal (i.e., females assess mate immune quality through the hemolymph), we examined which sex controlled gift size. We found that the probability that males initiated the end of copulation increased when gift size was small (stereotypical of less immunocompetent males). Thus, early termination of copulation was the consequence of male behavior, suggesting that the association between immunocompetence and gift size was not due to sexual selection, but to natural selection for male vigor.
Enemies of biodiversity
Authors: Morris Douglas W
Published: September 2005

Natural enemies, including humans, play a major role in the diversification of species and the maintenance of biodiversity. Compared with humans, most enemies faced by the rest of biodiversity are restricted in the magnitude of their effects, the spatial extent of their distribution, and the variety of species that they influence. Recognition of the similarities and differences between natural and human enemies should help us preserve and manage biodiversity.
A FUNCTIONAL LANGUAGE FOR DEPARTMENTAL METACOMPUTING
Authors: GAVA FRÉDÉRIC , LOULERGUE FRÉDÉRIC
Published: September 2005

We have designed a functional data-parallel language called BSML for programming bulk synchronous parallel (BSP) algorithms. Deadlocks and indeterminism are avoided and the execution time can be then estimated. For very large scale applications more than one parallel machine could be needed. One speaks about metacomputing. A major problem in programming application for such architectures is their hierarchical network structures: latency and bandwidth of the network between parallel nodes could be orders of magnitude worse than those inside a parallel node. Here we consider how to extend both the BSP model and BSML, well-suited for parallel computing, in order to obtain a model and a functional language suitable for metacomputing.
DERIVING AND SCHEDULING COMMUNICATION OPERATIONS FOR GENERIC SKELETON IMPLEMENTATIONS
Authors: NITSCHE THOMAS
Published: September 2005

Data distributions are an abstract notion for describing parallel programs by means of overlapping data structures. A generic data distribution layer serves as a basis for implementing specific data distributions over arbitrary algebraic data types and arrays as well as generic skeletons. The necessary communication operations for exchanging overlapping data elements are derived automatically from the specification of the overlappings. This paper describes how the communication operations used internally by the generic skeletons are derived, especially for the asynchronous and synchronous communication scheduling. As a case study, we discuss the iterative solution of PDEs and compare a hand-coded MPI version with a skeletal one based on overlapping data distributions.
PERMUTATION-BASED GENETIC, TABU, AND VARIABLE NEIGHBORHOOD SEARCH HEURISTICS FOR MULTIPROCESSOR SCHEDULING WITH COMMUNICATION DELAYS
Authors: DAVIDOVIĆ TATJANA , HANSEN PIERRE , MLADENOVIĆ NENAD
Published: September 2005

The multiprocessor scheduling problem with communication delays that we consider in this paper consists of finding a static schedule of an arbitrary task graph onto a homogeneous multiprocessor system, such that the total execution time (i.e. the time when all tasks are completed) is minimum. The task graph contains precedence relations as well as communication delays (or data transferring time) between tasks if they are executed on different processors. The multiprocessor architecture is assumed to contain identical processors connected in an arbitrary way, which is defined by a symmetric matrix containing minimum distances between every two processors. The solution is represented by a feasible permutation of tasks. In order to obtain the objective function value (i.e. schedule length, makespan), the feasible permutation has to be transformed into the actual schedule by the use of some heuristic method. For solving this NP-hard problem, we develop basic tabu search and variable neighborhood search heuristics, where various types of reduced Or-opt-like neighborhood structures are used for local search. A genetic search approach based on the same solution space is also developed. Comparative computational results on random graphs with up to 500 tasks and 8 processors are reported. On average, it appears that variable neighborhood search outperforms the other metaheuristics. In addition, a detailed performance analysis of both the proposed solution representation and heuristic methods is presented.
A SIMPLE LOWER BOUND FOR TOTAL COMPLETION TIME MINIMIZATION IN A TWO-MACHINE FLOWSHOP
Authors: LIN B. M. T. , WU J. M.
Published: September 2005

The purpose of this study is to present a simple lower bound to facilitate the development of branch-and-bound algorithms for the minimization of total completion time in a two-machine flowshop. The studied problem is known to be strongly NP-hard. In the literature, several lower bounds have been proposed. The bounding technique addressed in this paper is based upon a concept about rearrangement of the parameters of the input instance. The technique is intrinsically simple for computer implementations. We conduct computational experiments for problems with 10–65 jobs. Numerical results from our computational study indicate that the new scheme is very effective in reducing the execution time needed for composing optimal solutions.
OPTIMIZATION OF ROBUSTNESS OF SCALE-FREE NETWORK TO RANDOM AND TARGETED ATTACKS
Authors: LIU JIAN-GUO , WANG ZHONG-TUO , DANG YAN-ZHONG
Published: September 2005

Scale-free networks, having connectivity distribution P(k)~k-α(where k is the site connectivity), are very resilient to random failures but are fragile to intentional attacks. The purpose of this paper is to find the network design guideline which can make the robustness of the network to both random failures and intentional attacks maximum while keeping the average connectivity  per node constant. We find that when  = 3 the robustness of the scale-free networks reach its maximum value if the minimal connectivity m = 1, but when  is larger than four, the networks will become more robust to random failures and targeted attacks as the minimal connectivity m gets larger.
IMPACT OF Zn SUBSTITUTION ON PHASE FORMATION AND SUPERCONDUCTIVITY OF Bi1.6Pb0.4Sr2Ca2Cu3-xZnxO10-δ WITH x = 0.0, 0.015, 0.03, 0.06, 0.09 AND 0.12
Authors: SAXENA R. B. , GIRI RAJIV , AWANA V. P. S. , SINGH H. K. , ANSARI M. A. , KUMARASWAMY B. V. , GUPTA ANURAG , NIGAM RASHMI , SINGH K. P. , KISHAN H. , SRIVASTAVA O. N.
Published: September 2005

Samples of series Bi 1.6 Pb 0.4 Sr 2 Ca 2 Cu 3-x Zn x O 10-δ with x = 0.0, 0.015, 0.03, 0.06, 0.09 and 0.12 are synthesized by solid-state reaction route. All the samples crystallize in tetragonal structure with majority (> 90%) of Bi -2223( Bi 2 Sr 2 Ca 2 Cu 3 O 10) phase (c-lattice parameter ~ 36 Å). The proportion of Bi -2223 phase decreases slightly with an increase in x. The lattice parameters a and c of main phase ( Bi -2223) do not change significantly with increasing x. Superconducting critical transition temperature (Tc) decreases with x as evidenced by both resistivity [ρ(T)] and ac magnetic susceptibility [χ(T)] measurements. Interestingly the decrement of Tc is not monotonic and the same saturates at around 96 K for x > 0.06. In fact Tc decreases fast (~ 10 K/at%) for x = 0.015 and 0.03 samples and later nearly saturates for higher x values. Present results of Zn doping in Bi -2223 system are compared with other Zn -doped HTSC (high temperature superconducting) systems, namely the RE -123 ( REBa 2 Cu 3 O 7) and La -214 (( La, Sr )2 CuO 4).
MECHANISM OF HIGH-Tc SUPERCONDUCTIVITY BASED MAINLY ON TUNNELING MEASUREMENTS IN CUPRATES
Authors: MOURACHKINE A.
Published: September 2005

The main purpose of this brief review is to present a sketch of the mechanism of high-Tc superconductivity based mainly on tunneling measurements in cuprates. In the review, we shall mostly discuss tunneling spectroscopy in Bi 2 Sr 2 CaCu 2 O 8. Analysis of the data shows that the Cooper pairs in cuprates are topological excitations (e.g. quasi-one-dimensional bisolitons, discrete breathers etc.), and the phase coherence among the Cooper pairs appears due to spin fluctuations.
Relationship between androgenic hormones and arterial stiffness, based on longitudinal hormone measurements
Authors: Hougaku Hidetaka , Fleg Jerome L. , Najjar Samer S. , Lakatta Edward G. , Harman S. Mitchell , Blackman Marc R. , Metter E. Jeffrey
Published: September 2005

Circulating testosterone levels (T) decrease with age in men. Low T has been associated with coronary disease and with risk factors for atherosclerosis. This study examines the relationship in men between androgenic hormones and arterial stiffness, a major risk factor for cardiovascular events. T, sex hormone-binding globulin (SHBG), and dehydroepiandrosterone sulfate (DHEAS) were measured longitudinally over 33 yr (follow-up 11.8 ± 8.3 yr) in 901 men from the Baltimore Longitudinal Study of Aging, of whom 206 (68.1 ± 13.7 yr) underwent carotid duplex ultrasonography. The 901 men were used to characterize age-associated hormone levels by means of mixed-effects models. Hormone values were estimated for the 206 men at the time of ultrasonography. Free T index (FTI) was calculated by dividing T by SHBG. The arterial stiffness index was calculated from peak systolic and end diastolic diameters of the common carotid artery and simultaneous brachial artery blood pressure. T, FTI, and DHEAS were correlated negatively with age, pulse pressure (PP), and stiffness index (each P < 0.01), whereas SHBG was correlated positively with age and stiffness index ( P < 0.01). However, T was the only hormone that predicted the stiffness index after adjustment for age, PP, fasting plasma glucose, body mass index, and total cholesterol. T values 5–10 yr before the carotid study also predicted the stiffness index ( P < 0.05). Thus the adverse influence of low T on the cardiovascular system in men may be mediated in part via the effects of T on vascular structure and function.
Inhibitory effect of green tea (−)-epigallocatechin gallate on resistin gene expression in 3T3-L1 adipocytes depends on the ERK pathway
Authors: Liu Hang-Seng , Chen Yen-Hang , Hung Pei-Fang , Kao Yung-Hsi
Published: September 2005

Resistin (Rstn) is known as an adipocyte-specific secretory hormone that can cause insulin resistance and decrease adipocyte differentiation. By contrast, green tea catechins, especially (−)-epigallocatechin gallate (EGCG), have been reported as body weight and diabetes chemopreventatives. Whether EGCG regulates production of Rstn is unknown. Using 3T3-L1 adipocytes, we found that EGCG at 20 and 100 μM suppressed Rstn mRNA levels by ∼35 and 50%, respectively, after 3 h. The basal half-life of Rstn mRNA induced by actinomycin D was >12 h but shifted to 3 h in the presence of EGCG. This suggests that EGCG regulates the stability of Rstn mRNA. Treatment with cycloheximide did not prevent EGCG-suppressed Rstn mRNA levels, which suggests that the effect of EGCG does not require new protein synthesis. Intracellular Rstn protein significantly decreased in the presence of 100 μM EGCG 3 h after treatment, whereas the release of the Rstn protein did not significantly change. This suggests that EGCG may modulate the distribution of Rstn protein between the intracellular and extracellular compartments. EGCG did not affect the amounts of extracellular signal-related kinase-1/2 (ERK1/2), phospho-JNK, phospho-p38, and phospho-Akt proteins but reduced the amounts of phospho-ERK1/2 proteins. Overexpression with MEK1 blocked EGCG-inhibited Rstn mRNA expression. These data suggest that EGCG downregulates Rstn expression via a pathway that is dependent on the ERK pathway.
Coexpression of MAST205 inhibits the activity of Na+/H+exchanger NHE3
Authors: Wang Dongsheng , Lee Hye Jeong , Cooper Deborah S. , Cebotaro Ludmila , Walden Paul D. , Choi Inyeong , Yun C. Chris
Published: September 2005

Recent studies have shown that accessory proteins that interact with the apical Na+/H+exchanger NHE3 are a vital part of the dynamic nature of the Na+/H+exchanger regulation. We have identified MAST205, a microtubule-associated serine/threonine kinase with a molecular mass of 205 kDa that interacts with NHE3. MAST205 contains a S/T kinase domain and a PDZ domain that mediates interaction with NHE3. Northern blot analysis showed that MAST205 is highly expressed in human and rat kidney. Expression in opossum kidney (OK) cells showed that MAST205 is predominantly expressed in the apical membrane of the cells. Immunohistochemical studies demonstrated the presence of MAST205 at the apical region of the renal proximal tubules. Heterologous expression of MAST205 in OK cells inhibited endogenous NHE3 activity, and this inhibition required the presence of the kinase domain of MAST205, since deletion of the kinase domain or a dominant-negative mutant of MAST205 did not affect the activity of NHE3. Consistent with these results, we found that MAST205 phosphorylated NHE3 under in vitro conditions. However, overexpression of MAST205 did not affect expression of NHE3 proteins, suggesting that the effect of MAST205 was not mediated by a decrease in NHE3 expression. These findings suggest that MAST205 regulates NHE3 activity and, although the precise mechanism is yet to be determined, MAST205 appears to inhibit NHE3 activity through a phosphorylation-dependent mechanism.
PMA- and ANG II-induced PKC regulation of the renal Na+-HCO3−cotransporter (hkNBCe1)
Authors: Perry Clint , Blaine Judith , Le Hong , Grichtchenko Irina I.
Published: September 2005

The renal electrogenic Na+-HCO3−cotransporter (hkNBCe1) plays a major role in the bicarbonate reabsorption by the kidney. We examined how PMA- and ANG II-activated PKCs regulate hkNBCe1 expressed with or without the ANG II receptors AT1Bin Xenopus laevis oocytes. We found that 10 nM PMA halved the hkNBCe1 current detected in voltage-clamped oocytes. A PKC-specific inhibitor GF-109203X, and a specific inhibitor of Ca-dependent conventional PKCαβγ, GÖ-6976, significantly reduced PMA inhibition. PMA did not alter surface expression of the cotransporters, but it significantly increased hkNBCe1-PKCαβγ membrane association. We found that at 10−6M, ANG II halved the hkNBCe1 current detected in oocytes coexpressing cotransporters with AT1B. A PKC-specific inhibitor GF-109203X, and a PKCε translocation inhibitor εV1–2 peptide as well as BAPTA-AM (but not GÖ-6976), significantly reduced ANG II inhibition. At 10−6M, ANG II significantly decreased surface expression of the cotransporters and increased hkNBCe1-PKCε membrane association. Additionally, we found that at 10−11and 10−10M ANG II stimulated hkNBCe1 current. This effect was blocked by BAPTA-AM and partially reduced by GF-109203X. We also found that ANG II increased intracellular Ca2+in fluo 4-loaded oocytes. Our results suggest that 1) PMA inhibition of hkNBCe1 is mediated by Ca-dependent PKCαβγ and 10 nM PMA does not induce downregulation of cotransporter surface expression. 2) ANG II (10−6M) inhibition of hkNBCe1 is mediated by both Ca-independent PKCε and downregulation of cotransporter surface expression, possibly triggered by intracellular Ca2+mobilization. 3) Similar to proximal tubule, acute ANG II has a biphasic effect on hkNBCe1 coexpressed with AT1Bin X. laevis oocytes.
Analysis of Methylation Pattern in Multiple Myeloma
Authors: San-Miguel Jesús , García-Sanz Ramón , López-Pérez Ricardo
Published: September 2005

DNA methylation is involved in malignancy and is seen, in progression, in more than 80% of all solid tumours. Methylation is one of the main physiological processes to induce silencing of gene expression. Much work has focused on the suppressor gene p16, which acts as a negative cell cycle regulator, while its inhibition (via methylation) will have a positive effect on the cell cycle advance. The methylation status of the p16 gene was analysed in a group of 159 patients. Methylation of the p16 gene was seen in 41/98 (42%) patients with multiple myeloma and 4/5 (80%) patients with primary plasma cell leukaemias. This data favours the importance of p16 methylation on cell cycle regulation in multiple myeloma. In a proposed mechanism, methylated CpG islands attract a protein, MeCP2, which recruits a transcriptional inhibitory complex that includes histone deacetylases. The deacetylated lysine tails of the histones closely interact with DNA, resulting in a transcriptionally repressed chromatin with inhibited gene transcription, providing potential synergy between demethylating drugs and histone deacetylase inhibitors. Based on the knowledge of epigenetic mechanisms, the potential application of demethylating agents should be further investigated. Multiple myeloma remains an incurable disease, so new treatment strategies are needed to improve the outcome of patients.
National Prevention of Hepatocellular Carcinoma in Japan Based on Epidemiology of Hepatitis C Virus Infection in the General Population
Authors: Yoshizawa Hiroshi , Tanaka Junko , Miyakawa Yuzo
Published: September 2005

During the past 30 years, hepatocellular carcinoma (HCC) in Japan has kept linearly increasing from 10 to 30 per 100,000 population per year and is expected to grow further. The increment is attributed to infection with hepatitis C virus (HCV). Hence, there is a pressing need to find subjects with persistent HCV infection in the general population of Japan and take necessary measures to prevent HCC developing in them. As a first approach toward this goal, the sex- and age-specific prevalence of ongoing HCV infection was surveyed in 3,485,648 first-time blood donors during 1995–2000. Taking into account the size of subpopulations with different sex and age in Japan registered at the Census 2000, there are an estimated 884,954 HCV carriers aged from 16 to 69 years, and 759,316 (86%) of them are older than 40 years, with an increased risk for HCC; they are hidden in the society, without overt liver disease. The national 5-year project searching for HCV carriers in the general population was started in April 2002. Subjects are examinees of health check-ups, which they receive every 5 years when reaching the age of 40, as well as those at increased risk for HCV infection. The project detected HCV RNA in 14,672 of the 1,298,746 (1.1%) health check examinees and in 16,721 of the 624,734 (2.7%) high-risk individuals during the first fiscal year. Subjects found with HCV RNA have been referred to clinics and hospitals with expert hepatologists. Hopefully, this project will decrease HCC development in HCV carriers in Japan and be considered in other countries where increases in HCC are predicted from the current age-specific prevalence of anti-HCV.
Spread Times of Hepatitis C Virus Estimated by the Molecular Clock Differ among Japan, the United States and Egypt in Reflection of Their Distinct Socioeconomic Backgrounds
Authors: Mizokami Masashi , Tanaka Yasuhito , Miyakawa Yuzo
Published: September 2005

Infection with hepatitis C virus (HCV) is taking an ever increasing role in the development of hepatocellular carcinoma (HCC) over the world. Dynamics of HCV infection were determined by the molecular clock, estimating the dissemination time when HCV entered the country and the ‘spread time’ when it started to grow exponentially on a national scale. A comparison of HCV dynamics in Japan, the United States and Egypt has disclosed different dissemination and spread times among the three countries. Furthermore, they faithfully mirror socioeconomic as well as medical and paramedical events inherent to each country responsible for the wide spread of HCV infection during the past. Epidemic histories of HCV would enable us to predict what is going to happen in the future for HCV infection, in special reference to HCC associated with it. Population dynamics of HCV need to be determined in other countries where HCV prevails and compared with those in the three countries described. These studies should help foresee what will happen in the near future for HCV infection in a given country, time the future development of HCC and take measures for preventing it.
Comparison between Subgenomic Replicons of Hepatitis C Virus Genotypes 2a (JFH-1) and 1b (Con1 NK5.1)
Authors: Miyamoto Michiko , Kato Takanobu , Date Tomoko , Mizokami Masashi , Wakita Takaji
Published: September 2005

Although replicon systems for hepatitis C virus (HCV) recently developed have enabled the replication of HCV in cultured cells, limited genotypes are available for them. We have isolated HCV cDNA of genotype 2a (JFH-1 strain) from serum of a patient with fulminant hepatitis. A subgenomic replicon of JFH-1 was constructed and compared with the HCV replicon of genotype 1b (Con1 NK5.1) which possessed adaptive mutations. Huh7 cells transfected with replicon RNAs that had been transcribed in vitro were cultured in the presence of neomycin sulfate (G418), and selected colonies were isolated and expanded. Then, growth rates and replication of HCV RNA were evaluated on isolated cells hosting replicons. Saturation densities were lower for cells propagating JFH-1 than Con1 NK5.1 or untransfected Huh7 cells, and the mean doubling time was longer for JFH-1 than for Huh7 cells. Levels of HCV RNA replication in isolated clones were similar between JFH-1 and Con1 NK5.1 cells. Replication of RNA decreased reciprocally with cell densities in both JFH-1 and Con1 NK5.1 cells. The replication of HCV RNA was more resistant to interferon-α in JFH-1 than in Con1 NK5.1 cells based on the comparison of an inhibitory concentration of 50%. In conclusion, we found differences between HCV replicon clones of genotypes 1b and 2a. However, these differences may result from strain-specific characteristics, such as the source of HCV, rather than characteristics of distinct genotypes. Therefore, further investigation may be needed on more HCV isolates of diverse genotypes.
Use of an in vitro Model and Yeast Two-Hybrid System to Investigate the Pathogenesis of Hepatitis C
Authors: Lim Seng Gee , Tan Yee Joo , Goh Phuay Yee , Lim Siew Pheng , Hong Wan Jin
Published: September 2005

Fifteen years after the discovery of hepatitis C virus (HCV) in 1989, much remains to be learnt about the cell biology of this virus. Using the serum from a patient containing HCV RNA in high titer as a source, a Singapore strain of genotype 1b was recovered and characterized. This full-length HCV genome was then constructed into a tetracycline-inducible vector using the pSTAR plasmid. Transfection of hepatoma cell lines with this HCV genome under tetracycline induction indicated that chemokines (RANTES and monocyte chemoattractant protein-1) were upregulated, possibly contributing to the induction of immune responses. Using the yeast two-hybrid system to discover protein-protein interactions, nonstructural region NS3 was found to interact with itself, forming a dimer that increased helicase activity but was not essential for its activity, thereby disqualifying it as a suitable target of drug actions. The significance of the interaction between core and NS5A is unclear, and the cleavage of NS5A is related to the development of apoptosis. However, the interaction of p68 and NS56B appears to be important because the knockdown of p68 reduced the viral replication. Finally, a new cell model using chimeric CD81 linked to the cytoplasmic domain of either a low-density lipoprotein receptor or a transferrin receptor led to productive infection of HCV that had been recovered from infected serum. These studies allow us to examine the pathogenesis of HCV infection in more detail.
Hepatitis C Virus Infection Can Present with Metabolic Disease by Inducing Insulin Resistance
Authors: Koike Kazuhiko
Published: September 2005

Although hepatitis C virus (HCV) targets the liver, it has become increasingly evident that HCV can induce diseases of many organs. Recently, much attention is drawn to metabolic disorders in HCV infection. First, hepatic steatosis and derangement in lipid metabolism have been found characteristic of HCV infection, and later on, a correlation was noted between HCV infection and diabetes as well as insulin resistance. We have demonstrated that HCV by itself can induce insulin resistance through disturbing the insulin signaling pathway by HCV proteins. The fact that HCV infection induces insulin resistance by the virus itself may influence the progression of chronic liver disease and open up novel therapeutic approaches. In conclusion, towards the future, HCV infection needs to be viewed not only as a liver disease but also as a metabolic disease.
Early Detection and Characterization of Hepatocellular Carcinoma: Value of Imaging Multistep Human Hepatocarcinogenesis
Authors: Kudo Masatoshi
Published: September 2005

The method for early detection of hepatocellular carcinoma (HCC) has been well established in Japan, by means of regularly screening patients at risk for developing HCC by imaging and serological markers of tumor. The principal screening protocol includes performing ultrasonography (US) every 3 months and testing for tumor markers every month in patients at high risk for HCC. There has been another important issue of accurate characterization of nodular lesions found in cirrhotic liver. This problem has been solved by the development of imaging modalities such as US angiography with intra-arterial injection of CO2, computed tomography during hepatic arteriography and computed tomography during arterial portography. It is most important to differentiate the typical hemodynamic patterns of a low-grade dysplastic nodule having arterial hypovascularity with portal perfusion preserved from those of HCC characterized by arterial hypervascularity with decreased portal perfusion. At present, these findings are easily obtained by contrast-enhanced phase invasion harmonic imaging, which is a noninvasive US technology.
Viral Etiology of Hepatocellular Carcinoma and HCV Genotypes in Taiwan
Authors: Lee Chuan-Mo , Hung Chao-Hung , Lu Sheng-Nan , Wang Jing-Houng , Tung Hung-Da , Huang Wu-Shiung , Chen Chao-Long , Chen Wei-Jen , Changchien Chi-Sin
Published: September 2005

Etiologic variations of hepatocellular carcinoma (HCC) exist in different geographic areas of the world. Hepatitis B virus infection is associated with HCC. However, hepatitis C virus (HCV) infection plays an increasingly more important role in the development of HCC and is associated with more than 30% of HCC in Taiwan. The prevalence of HCV infection and HCV genotypes vary in different geographic areas. The prevalence of HCV genotype 1b (HCV-1b) was around 50–70% in Taiwan and even varied in different townships. In addition to host factors, HCV genotypes may be associated with the development of HCC. In our study, the prevalence of HCV-1b in patients with HCC was significantly higher than in those with liver cirrhosis and chronic hepatitis; multivariate analysis revealed that the disease severity was significantly correlated with age and HCV-1b. Furthermore, HCV-1b was associated with a lower response rate to interferon (IFN) therapy than HCV-2. Our study has demonstrated that mutations in the IFN sensitivity-determining region, spanning nucleotides 2,209–2,248 in the NS5A region, correlate with the sustained virological response to combination therapy with IFN and ribavirin in patients with chronic HCV-1b infection in Taiwan. A third-generation enzyme immunoassay for antibody to HCV can be used to predict viremia and monitor the virological response.