bluuebunny/crossref_metadata_2025 huggingface dataset:
The response of prechilled alder and birch seeds to drying, freezing, and storage
Authors: Atrip Norberto De , O'Reilly Conor
Published: April 2006

The response of alder (Alnus glutinosa (L.) Gaertn.) and birch (Betula pubescens Ehrh.) seeds to freezing temperatures was assessed. Seeds were fully imbibed (FI) or adjusted to target moisture contents (TMC) of 30% (alder) or 35% (birch) and then chilled (4 °C) for various periods. Some seeds were redried to <12% moisture content before freezing. The seeds were germinated at 15 °C with 8 h of lighting after freezing. In the first experiment, rapid freezing at 12 °C was used to assess seed vigour. Freezing reduced percentage germination in the moist (non-redried) FI seeds, especially in those that received the longest prechilling. Freezing had a smaller effect on the TMC and the redried seeds. In the second experiment, seeds were stored for up to 60 weeks at 3 °C. Seeds stored for 60 weeks were tested also at 20 °C (16 h dark) : 30 °C (8 h light). Good germination potential was maintained for up to 12 weeks of storage regardless of pretreatment, but it declined rapidly thereafter in the moist FI seeds. Moist TMC seeds maintained good germination potential throughout the 60 weeks of storage. Germination potential declined greatly following 24 weeks of storage in the redried seeds, but the redried seeds germinated well at 20 °C (16 h dark) : 30 °C (8 h light) following 60 weeks of storage.
Spatial patterns of soil microclimate, light, regeneration, and growth within silvicultural gaps of mixed tolerant hardwood  white pine stands
Authors: Raymond Patricia , Munson Alison D , Ruel Jean-Claude , Coates K David
Published: April 2006

Large gaps (equivalent to twice the height of the trees, 1590 m2) originating from group selection cutting in mixed tolerant hardwood  eastern white pine (Pinus strobus L.) stands of Quebec were used for geostatistical analysis of the seasonal mean of daily percent photosynthetic photon flux density (%PPFD), soil temperature and moisture, regeneration density of white pine, yellow birch (Betula alleghaniensis Britt.), and paper birch (Betula papyrifera Marsh.)), and growth of white pine. %PPFD, which measures the quantity of light above the shrub layer, varied according to the northsouth axis, the maximum being located in the northern portion of gaps. Surficial soil (5 cm) temperature and moisture varied according to both northsouth and eastwest axes. The southwest sector offered favourable conditions for white pine, yellow birch, and paper birch establishment, with maximum soil moisture and minimum soil temperature encountered in this position. There was no evidence of gap partitioning at the early establishment stage, although asymmetry in the microclimate was observed. However, results indicate that spatial patterns could change in the future and a partition resulting from differential survival among species could occur. Finally, results outline a possible discordance between optimal regeneration and growth niches for white pine, since planted seedlings (>1 m) had the best growth in the central and northern section of gaps.
Soil physical property changes at the North American Long-Term Soil Productivity study sites: 1 and 5 years after compaction
Authors: Page-Dumroese Deborah S , Jurgensen Martin F , Tiarks Allan E , Ponder, Jr. Felix , Sanchez Felipe G , Fleming Robert L , Kranabetter J Marty , Powers Robert F , Stone Douglas M , Elioff John D , Scott D Andrew
Published: April 2006

The impact of forest management operations on soil physical properties is important to understand, since management can significantly change site productivity by altering root growth potential, water infiltration and soil erosion, and water and nutrient availability. We studied soil bulk density and strength changes as indicators of soil compaction before harvesting and 1 and 5 years after harvest and site treatment on 12 of the North American Long-Term Soil Productivity sites. Severe soil compaction treatments approached root-limiting bulk densities for each soil texture, while moderate compaction levels were between severe and preharvest values. Immediately after harvesting, soil bulk density on the severely compacted plots ranged from 1% less than to 58% higher than preharvest levels across all sites. Soil compaction increases were noticeable to a depth of 30 cm. After 5 years, bulk density recovery on coarse-textured soils was evident in the surface (010 cm) soil, but recovery was less in the subsoil (1030 cm depth); fine-textured soils exhibited little recovery. When measured as a percentage, initial bulk density increases were greater on fine-textured soils than on coarser-textured soils and were mainly due to higher initial bulk density values in coarse-textured soils. Development of soil monitoring methods applicable to all soil types may not be appropriate, and more site-specific techniques may be needed for soil monitoring after disturbance.
Influence du charbon actif sur la croissance primaire des plantules de pin gris
Authors: Naydenov Krassimir , Tremblay Francine , Bergeron Yves , Goudiaby Venceslas
Published: April 2006

In the boreal forest, the beneficial effect of wildfire on germination substrates has often been linked to the adsorption by charcoal of phenolic compounds detrimental for seedling germination and growth. Our goal was to show that active charcoal has direct positive effects on germination and early growth of jack pine (Pinus banksiana Lamb.) plantlets, a species well adapted to fire. Four concentrations of active charcoal (0%, 50%, 100%, and 150% seed mass) along with two temperatures (2627 °C and 1820 °C) were tested in vitro, in Petri dishes, under constant moisture conditions. Results showed that adding active charcoal to the substrate had no significant effect on jack pine seed germination but inhibited plantlet growth at concentrations over 100%. Significant growth increase was observed only with 50% charcoal at the highest temperature (2627 °C). Deformities were noted at the apex of radicles, particularly with low temperatures and high levels of active charcoal in the substrate.
Evaluation of a large-scale forest scenario model in heterogeneous forests: a case study for Switzerland
Authors: Thürig Esther , Schelhaas Mart-Jan
Published: April 2006

Large-scale forest scenario models are widely used to simulate the development of forests and to compare the carbon balance estimates of different countries. However, as site variability in the application area often exceeds the variability in the calibration area, model validation is important. The aim of this study was to evaluate the European Forest Information Scenario model (EFISCEN). As Switzerland exhibits high spatial and climatic diversity, it was taken as a case study. The model output was compared to measured data in terms of initialization, estimation of growing stock, stand age, increment, management, and natural mortality. Comparisons were done at the country level, but also for regions and site classes. The results showed that the initialization procedure of EFISCEN works well for Switzerland. Moreover, EFISCEN accurately estimated the observed growing stock at the country level. On a regional level, major differences occurred. In particular, distribution of the harvesting amounts, mortality, and age-class distribution deviated considerably from empirical values. For future model applications, we therefore propose to define the required harvesting level not per country, but to specify it for smaller regions. Moreover, the EFISCEN simulations should be improved by refining the mortality function and by incorporating more flexibility in forest management practices.
Microbial community responses in forest mineral soil to compaction, organic matter removal, and vegetation control
Authors: Busse Matt D , Beattie Samual E , Powers Robert F , Sanchez Felipe G , Tiarks Allan E
Published: April 2006

We tested three disturbance hypotheses in young conifer plantations: H1: soil compaction and removal of surface organic matter produces sustained changes in microbial community size, activity, and structure in mineral soil; H2: microbial community characteristics in mineral soil are linked to the recovery of plant diversity; and H3: community responses are strongly modified by regional climate. Microbial biomass, respiration, carbon utilization, and phospholipid fatty acids were compared at two subtropical installations and one Mediterranean-type climate installation of the North American Long-Term Soil Productivity study. Treatments included combinations of compaction (none vs. severe), organic matter removal (none vs. complete), and weed control (none vs. complete), plus an uncut reference stand. Weed control resulted in the only consistent decline or shift in microbial indices at the subtropical sites. At the Mediterranean-type climate site, overstory harvesting resulted in declines in microbial biomass, respiration, and fungal phospholipid fatty acids that far outweighed the effects of the soil disturbance treatments. Severe compaction had no effect on community size or activity at any site. Microbial communities were generally tolerant of postharvest soil disturbance, leading to a rejection of the experimental hypotheses, with the exception of a link between microorganisms and recovery of plant diversity (H2) at the subtropical sites.
The ecology of forest insect invasions and advances in their management
Authors: Brockerhoff Eckehard G , Liebhold Andrew M , Jactel Hervé
Published: April 2006

Invasions by nonindigenous forest insects can have spectacular effects on the biodiversity, ecology, and economy of affected areas. This introduction explores several critical issues that are generally relevant to invasions by forest insects to provide an extended background for this special issue of the Canadian Journal of Forest Research and highlights the key findings of the papers included in the issue. The topics covered address new information about (1) the role of cargo shipments as invasion pathways for the arrival of insects such as wood borers and bark beetles, (2) biogeographical effects that can influence the ecological and economic impact of insects feeding on exotic tree species, (3) the influence of biodiversity on impacts of forest insects and on the invasibility of ecosystem, and (4) recent advances in the detection, monitoring, and management of invasive species and native pests, including DNA barcoding for identification, the use of pheromones for monitoring and mating disruption, and biological control. These findings are likely to become even more important with elevated prevalence of invasions as a result of increasing global trade and international travel. Avenues of international communication and cooperation among scientists should be encouraged to enhance the sharing of information about biological invasions and to find solutions to this alarming problem.
Expression of protein kinase C isoforms in cardiac hypertrophy and heart failure due to volume overload
Authors: Sentex Emmanuelle , Wang Xi , Liu Xueliang , Lukas Anton , Dhalla Naranjan S.
Published: April 2006

The present study determined whether changes in the activity and isoforms of protein kinase C (PKC) are associated with cardiac hypertrophy and heart failure owing to volume overload induced by aortocaval shunt (AVS) in rats. A significant increase in Ca2+-dependent and Ca2+-independent PKC activities in the homogenate and particulate fractions, unlike the cystolic fraction, of the hypertrophied left ventricle (LV) were evident at 2 and 4 weeks after inducing the AVS. This increase coincided with increases in PKC-α and PKC-ζ contents at 2 week and increases in PKC-α, PKC-β1, PKC-β2, and PKC-ζ contents at 4 weeks in the hypertrophied LV. By 8 and 16 weeks of AVS, PKC activity and content were unchanged in the failing LV. On the other hand, no increase in the PKC activity or isoform content in the hypertrophied right ventricle (RV) was observed during the 16 weeks of AVS. The content of Gαq was increased in the LV at 2 weeks but then decreased at 16 weeks, whereas Gαq content was increased in RV at 2 and 4 weeks. Our data suggest that an increase in PKC isoform content neither plays an important role during the development of cardiac hypertrophy nor participates in the phase leading to heart failure owing to volume overload.
Comparison of folic acid uptake characteristics by human placental choriocarcinoma cells at acidic and physiological pH
Authors: Keating Elisa , Lemos Clara , Azevedo Isabel , Martel Fátima
Published: April 2006

The aim of this work was to characterize the placental uptake of folic acid from the maternal circulation. Using 2 human trophoblast cell lines (BeWo and JAR), we verified that uptake of3H-folic acid was pH-dependent, increasing significantly with decreasing extracellular pH. In BeWo cells, uptake of3H-folic acid at pH 5.5 was (i) Na+-independent; (ii) inhibited by folic acid, 5-methyltetrahydrofolate (5-MTHF), and methotrexate (MTX); (iii) inhibited by the anion transport inhibitors 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (DIDS) and 4-acetamido-4′-isothiocyano-2,2′-disulfonic acid stilbene (SITS); (iv) inhibited by the proton ionophore carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP); (v) not inhibited by blockers of receptor-mediated endocytosis (cytochalasin D and monensin); (vi) trans-inhibited by MTX and folic acid; and (vii) not affected by an anti-reduced folate transporter-1 (RFC) antibody. At pH 7.5, uptake of3H-folic acid was (i) Na+-independent; (ii) inhibited by folic acid and MTX, but not by 5-MTHF; (iii) inhibited by SITS, but not by DIDS; (iv) not affected by FCCP; (v) inhibited by monensin (but not by cytochalasin D); (vi) trans-inhibited by folic acid (but not by MTX); and (vii) inhibited by an anti-RFC antibody. In conclusion, in BeWo cells, both RFC and receptor-mediated endocytosis seem to be involved in3H-folic acid uptake at pH 7.5, whereas at pH 5.5, RFC and (or) a low pH-operating transporter distinct from RFC are involved.
Physical activity and body functionality: implications for obesity prevention and treatment
Authors: Tremblay Angelo , Therrien Fanny
Published: April 2006

Physical activity promotes metabolic adaptations that improve body functionality and contribute to the prevention of some diseases. With respect to energy and fat balance, physical activity facilitates the equilibrium between energy intake and expenditure as well as between fat intake and fat oxidation. When combined with a healthy diet that favors satiety with a reduced energy intake, exercise can induce a substantial mass loss in obese individuals. However, even the impact of an exemplary lifestyle does not seem to have the potential to decrease body mass in obese individuals down to the mass range of lean people. Up to now, we have not been able to induce mass changes exceeding 12%–15% initial body mass in obese male subjects under tolerable exercise and dietary habits, and this moderate success was accompanied by modifications in appetite and energy expenditure susceptible to compromise subsequent mass stability. As described in this paper, many environmental factors can influence energy balance and the ability to lose body fat in response to a healthy diet and (or) physical activity program. Particular attention is given to preliminary data obtained in our laboratory that suggest that knowledge-based work does not favor the same potential mass reducing effects as physical work. In fact, the acute effects of knowledge-based work suggest that this work modality may be rather susceptible to promote a more pronounced positive energy balance compared with what we may expect from a sedentary relaxing activity. This is problematic for obesity prevention in the future since knowledge-based work now represents the main working modality in a context of modernity.
Regulation of phosphatidylcholine homeostasis by Sec14This paper is one of a selection of papers published in this Special Issue, entitled Young Investigator's Forum.
Authors: Howe Alicia G. , McMaster Christopher R.
Published: April 2006

Phosphatidylcholine is the major phospholipid in eukaryotic cells and serves as both a permeability barrier as well as a modulator of a plethora of cellular and biological functions. This review touches on the importance of proper regulation of phosphatidylcholine metabolism on health, and discusses how yeast genetics has contributed to furthering our understanding of the precise molecular events regulated by alterations in phosphatidylcholine metabolism. Yeast studies have determined that the phosphatidylcholine and (or) phosphatidylinositol binding protein, Sec14, is a major regulator of phosphatidylcholine homeostasis. Sec14 itself regulates vesicular transport from the Golgi, and the interrelationship between phosphatidylcholine metabolism and membrane movement within the cell is described in detail. The recent convergence of the yeast genetic studies with that of mammalian cell biology in how cells maintain phosphatidylcholine homeostasis is highlighted.
Expression of actin mutants to study their roles in cardiomyopathyThis paper is one of a selection of papers published this Special Issue, entitled Young Investigator's Forum.
Authors: Rutkevich Lori A. , Teal David J. , Dawson John F.
Published: April 2006

Mutations in the human cardiac actin gene (ACTC) have been implicated in the development of hypertrophic or dilated cardiomyopathy in humans. To determine the molecular mechanism for the disease development, a system for the expression of mutant cardiac actin proteins that may be lethal to eukaryotic cells must be developed. Here, we explore some of the advantages and disadvantages of human ACTC expression in yeast and insect cells. We show that human ACTC is incapable of rescuing a yeast endogenous actin (ACT1) - knockout in yeast cells and that coexpression of human ACTC in yeast results in slower growth, making yeast an unsuitable expression system. However, we show that it is possible for yeast cells to express a polymerization-deficient ACT1 mutant, thereby allowing us to examine the cell biology of this mutation in the future. Finally, mutant forms of human cardiac actin can be expressed in and purified from insect cells in a properly folded and functional form, permitting important characterization of the biochemical mechanisms responsible for cardiomyopathy development in humans. These studies allow for further research into the biochemical characteristics of previously untenable actin mutant proteins.
Mechanisms linking diabetes mellitus to the development of atherosclerosis: a role for endoplasmic reticulum stress and glycogen synthase kinase-3This paper is one of a selection of papers published in this Special Issue, entitled Young Investigator's Forum.
Authors: Robertson Lindsie A. , Kim Anna J. , Werstuck Geoff H.
Published: April 2006

Recent decades have seen a significant increase in the incidence of diabetes mellitus. The number of individuals with diabetes is projected to reach 300 million by the year 2025. Diabetes is a leading cause of blindness, renal failure, lower limb amputation, and an independent risk factor for atherosclerotic cardiovascular disease (CVD) — a leading cause of death in Western society. Understanding the molecular and cellular mechanisms by which diabetes mellitus promotes atherosclerosis is essential to developing methods to treat and prevent diabetes-associated CVD. This review summarizes our current knowledge of the mechanisms by which diabetes may promote atherogenesis and specifically focuses on a novel pathway linking these 2 conditions. We hypothesize that the accumulation of intracellular glucosamine observed in conditions of chronic hyperglycaemia may promote atherogenesis via a mechanism involving dysregulated protein folding, activation of endoplasmic reticulum (ER) stress, and increased glycogen synthase kinase (GSK)-3 activity. The identification of this novel mechanism provides a promising hypothesis and multiple new targets for potential therapeutic intervention in the treatment of diabetes mellitus and accelerated atherosclerosis.
The interrelation of the angiotensin and endothelin systems on the modulation of NAD(P)H oxidaseThis paper is one of a selection of papers published in this Special issue, entitled Young Investigator's Forum.
Authors: Laplante Marc-André , de Champlain Jacques
Published: April 2006

The NAD(P)H oxidase is an enzyme assembled at the cellular membrane able to produce superoxide anion from NADH or NAD(P)H (nicotinamide adenine dinucleotide phosphate). It is one of the main sources of superoxide anion in cardiovascular tissues and its role in a variety of cardiovascular disorders such as atherosclerosis, cardiac hypertrophy, and endothelial dysfunction was recently proposed. Although, many factors and receptors were shown to lead to the activation of the enzyme, particulary the type 1 angiotensin receptor, the pathways involved are still widely unknown. Despite the identification of factors such as c-Src and protein kinase C implicated in the acute activation of NAD(P)H oxidase, the signalling involved in the sustained activation of the enzyme is probably far more complex than was previously envisioned. In this review, we describe the role of endothelin-1 in NAD(P)H oxidase signalling after a sustained stimulation by angiotensin II. Since most pathologies caused by an NAD(P)H oxidase overactivation develop over a relatively long period of time, it is necessary to better understand the long-term signalling of the enzyme for the development or use of more specific therapeutic tools.
Gender differences in the cardiac response to dietary conjugated linoleic acid isomers
Authors: Tappia Paramjit S. , Mangat Rabban , Gabriel Cindy , Dent Melissa R. , Aroutiounova Nina , Weiler Hope
Published: April 2006

The present study was undertaken to assess the heart function, by the in vivo catheterization technique, of healthy male and female Sprague–Dawley rats fed different conjugated linoleic acid (CLA) isomers, (cis-9, trans-11 (c9,t11) and trans-10, cis-12 (t10,c12)) individually and in combination (50:50 mix as triglyceride or fatty acids) from 4 to 20 weeks of age. Whereas the triglyceride form of the CLA isomer mix lowered the heart rate, the rate of contraction (+dP/dt) and rate of relaxation (–dP/dt), systolic and diastolic pressures, mean arterial pressure, and the left ventricular systolic pressure were higher in male rats as compared with all the other dietary groups. In contrast, there were no significant effects in the cardiac function of the female rats in response to the CLA isomer mix in triglyceride form. Whereas the heart rate, +dP/dt, and left ventricular systolic pressure were lower in male rats fed the t10,c12 CLA isomer alone, the heart rate of the female rats was higher, but the systolic pressure, +dP/dt, and mean arterial pressure were lower compared with the control group. Also, the left ventricular end-diastolic pressure was specifically higher in the female rats in response to free fatty acids-containing CLA mix. Furthermore, an additive effect of the free fatty acids-containing CLA mix was seen in the +dP/dt and –dP/dt of female rats compared with the control group. These results indicate that CLA isomers exert differential effects on heart function and suggest the need for a complete evaluation of the benefits, interactions, and potential side effects of each isomer.
The role of sex in cardiac function and diseaseThis paper is one of a selection of papers published in this Special Issue, entitled Young Investigator's Forum.
Authors: Czubryt Michael P. , Espira Leon , Lamoureux Lise , Abrenica Bernard
Published: April 2006

In the past decade, increasing attention has been paid to the importance of sex in the etiology of cardiac dysfunction. While focus has been primarily on how sex modulates atherogenesis, it is becoming clear that sex is both a predictor of outcome and an independent risk factor for a number of other cardiac diseases. Animal models and human studies have begun to shed light on the mechanisms by which sex influences the function of cardiomyocytes in health and disease. This review will survey the current literature on cardiac diseases that are influenced by sex and discuss the intracellular mechanisms by which steroid sex hormones affect heart function. A theory on how sex may regulate myocardial energy metabolism to affect disease susceptibility and progression will be presented, as well as a discussion of how sex may influence outcomes of experiments on isolated cardiomyocytes by epigenetic marking.
Epigallocatechin gallate preserves endothelial function by reducing the endogenous nitric oxide synthase inhibitor level
Authors: Tang Wei-Jun , Hu Chang-Ping , Chen Mei-Fang , Deng Pan-Yue , Li Yuan-Jian
Published: April 2006

Asymmetric dimethylarginine (ADMA), the endogenous nitric oxide synthase inhibitor, is thought to be a key factor contributing to endothelial dysfunction. Tea catechins can cause an endothelium-dependent vasorelaxation. The present study examined the effect of epigallocatechin gallate (EGCG), the major component of tea catechins, on endothelial dysfunction induced by native low density lipoprotein (LDL) in rats and oxidized LDL (ox-LDL) in cultured endothelial cells, and whether the protective effect of EGCG is related to reduction of ADMA level. A single injection of LDL (4 mg·kg–1, i.v.) markedly reduced endothelium-dependent relaxation and the serum nitrite/nitrate (NO) level, and increased serum concentrations of ADMA, malondialdehyde (MDA), and tumor necrosis factor-α (TNF-α). EGCG (10 or 50 mg·kg–1, i.p.) significantly attenuated the inhibition of vasodilator response to acetylcholine and the decreased serum nitrite/nitrate level, and reduced the elevated levels of ADMA, MDA, and TNF-α. Exposure of endothelial cells to ox-LDL (100 μg·mL–1) for 24 h markedly increased the medium levels of lactate dehydrogenase (LDH), ADMA, TNF-α, and MDA, and decreased the level of nitrite/nitrate in the medium and the activity of dimethylarginine dimethylaminohydrolase (DDAH) in the endothelial cells. EGCG (10 and 100 μg·mL–1) significantly decreased the levels of LDH, ADMA, TNF-α, and MDA, and increased the level of nitrite/nitrate and the activity of DDAH. These results suggest that EGCG protects endothelial dysfunction induced by native LDL in vivo or by ox-LDL in endothelial cells, and the protective effect of EGCG on the endothelium is related to decrease in ADMA level via increasing of DDAH activity.
Anabolic responsiveness of skeletal muscles correlates with androgen receptor protein but not mRNA
Authors: Monks Douglas A. , Kopachik Will , Breedlove S. Marc , Jordan Cynthia L.
Published: April 2006

Anabolic effects of androgens on skeletal muscle are well documented, but the physiological and biochemical bases of these effects are poorly understood. Skeletal muscles that differ in their androgen responsiveness can be used to examine these mechanisms. We compared androgen receptor mRNA and protein levels of the rat levator ani, a perineal skeletal muscle that depends on androgens for its normal maintenance and function with that of the rat extensor digitorum longus, a limb muscle that does not require androgens. Western immunoblotting indicated that androgen receptor protein is significantly elevated in the levator ani relative to the extensor digitorum longus. Surprisingly, steady state androgen receptor mRNA levels were equivalent in these muscles, as determined by Northern blot analysis and quantitative RT-PCR. These results suggest that androgen responsiveness of skeletal muscles is determined by the level of androgen receptor protein in a particular muscle and that androgen receptor protein content is regulated by translational or post-translational mechanisms.
The modulatory effect of leptin on the overall insulin production in ex-vivo normal rat pancreas
Authors: Haddad N. , Howland R. , Baroody G. , Daher C.
Published: April 2006

Leptin has a modulator effect on glucose-stimulated insulin secretion. To define the influences of different glucose (4, 8, 12, and 16 mmol/L) and leptin (5, 10, 15, and 20 nmol/L) concentrations on total insulin release in ex vivo pancreatic preparations, a customized perfusion technique was used. Such a profile of concentration brought about an index for the combined effect of leptin and glucose on the production of insulin. Insulin output was measured by radioimmunoassay. Stimulated by glucose alone in the control group, insulin secretion confirmed a bi-phasic pattern. Addition of leptin in the experimental group suppressed insulin secretion compared with control. A U-shape pattern of suppression was observed when the leptin and stimulatory glucose concentrations were combined. At 12 mmol/L glucose, leptin showed maximal insulin suppression. Leptin’s effect on insulin was glucose dependent and showed a reproducible U-shaped pattern of suppression, which implicated possible direct dose-dependent interaction between leptin and glucose on insulin secretion.
Cell death in Porifera: molecular players in the game of apoptotic cell death in living fossils
Authors: Wiens M , Müller W E.G
Published: April 2006

Apoptosis represents the morphological manifestation of programmed cell death and, paradoxically at first sight, it is a prerequisite for metazoan life. Thus, apoptosis is responsible for the demise of cells during many physiological processes. It is also accountable for the death of cells following exposure to countless stimuli. Therefore, it is obvious that apoptosis must be regulated by a complex network of various molecular signaling pathways. Research during the past 20 years has led to the identification of major functional groups of molecules involved in apoptotic pathways. These include members of the Bcl-2 superfamily, members of the TNF family, caspases, and their activators. Yet, the evolutionary conservation of those elements of the apoptotic machinery was only established from nematode to man. Sponges (phylum Porifera) are characterized by a remarkable regeneration capacity and longevity. Furthermore, they represent the phylogenetically oldest still extant metazoan taxon. Thus, research on these living fossils opens a window to the past, to the dawn of metazoan life. It allows us to trace the evolution of programmed cell death and its core components. This review summarizes the key findings and concepts which have emerged from studies of apoptosis in Porifera.
Palaeontology of sponges — a review
Authors: Pisera A
Published: April 2006

The fossil record of sponges is a very old one, and begins in the Precambrian, but is rather incomplete. Only those sponges with a rigid skeleton, i.e., Hexactinosida and Lychniscosida (both hexactinellids), lithistids (demosponges with desmas), and sponges with a massive calcareous skeleton (polyphyletic demosponges and Calcarea) have a more or less continuous fossil record that is, however, inadequately studied, especially from the Tertiary. The beginning of sponge diversification during the Cambrian is relatively well known thanks to their very good preservation, from the Chengjiang fauna in China and Burgess Shale in Canada, where even sponges with unfused spicules occur. The majority of palaeontologic studies are concerned with taxonomic aspects of fossil sponge faunas, but investigations of the microstructure of the calcareous skeleton, of phylogeny (especially of the early forms), and of various aspects of their ecology have produced important results. Future research still has to fill gaps in the knowledge of fossil faunas, especially "soft" sponges, and in the phylogeny of sponges (especially for the polyphyletic groups like lithistids), but new approaches such as studies of biomarkers are already emerging.
Physiology of coordination in sponges
Authors: Leys S P , Meech R W
Published: April 2006

All multicellular organisms need a means of communicating between cells and between regions of the body. The evolution of a nervous system, by the Cnidaria, provided a fast means of communication and enabled the colonization of rapidly changing environments. Sponges, the descendants of the first multicellular animals, lack nerves but nevertheless have a number of different systems that allow coordinated behaviour, albeit rather slow coordinated behaviour. It is from elements within these systems that the origins of the nervous and endocrine systems, the grand organizing principles of higher animals, seem likely to have appeared. Electrical activity has not been found in cellular sponges, yet local contractions are elicited in response to a variety of stimuli and, in some cases, contractions propagate across the body to control the hydrodynamics of the feeding current. The mechanism of propagation is thought to involve hormones or a combination of other signaling molecules and direct mechanical action of one cell on the next, leading to increased intracellular calcium. In other instances cellular sponges respond to stress, such as heat shock, by elevating intracellular calcium by way of second messengers such as cyclic ADP-ribose. Electrical communication, well known in plants and protists, was first demonstrated in a sponge in 1997. Hexactinellids (glass sponges), which arrest their feeding current within 20 s of mechanical or electrical stimulation, do so via an electrical impulse that propagates through syncytial tissues. These unusual syncytial tissues are cytoplasmically coupled from outside to inside and top to bottom so that there are no membrane boundaries to impede the electrical currents. Pharmacological tests suggest that Ca2+, rather than Na+, drives the action potential. The conduction velocity is slow (0.27 cm·s–1) and is highly temperature sensitive (Q10~3). At present, glass sponges are the only poriferans known to have propagated electrical signals. In addition, reports of directional swimming in sponge larvae, of the rapid and coordinated changes in the tensile strength of the extracellular matrix in Chondrosia Nardo, 1847, and of the rapid closure of ostia of some cellular sponges in response to mechanical stimuli further illustrate the variety of coordinating mechanisms that evolved in the Porifera in the absence of a nervous system.
Systematics and evolution of Demospongiae
Authors: Boury-Esnault Nicole
Published: April 2006

Systematic and evolutionary studies of Demospongiae Sollas, 1885 are a very dynamic field of research. The scientific knowledge pertaining to Demospongiae systematics has been recently assembled in the collective book Systema Porifera. However, a general consensus among spongologists has not yet been achieved regarding this group and the phylogenetic relationships within Demospongiae and between Demospongiae and other clades of Porifera and metazoans are still unresolved. The two traditional subclasses Tetractinomorpha and Ceractinomorpha are polyphyletic and it is proposed that they be abandoned. Since the publication of Systema Porifera, several works have suggested the polyphyly of Halichondrida and the paraphyly of Haplosclerida, as well as the monophyly of Tetractinellida (Astrophorida + Spirophorida), Keratosa (Dictyoceratida + Dendroceratida), and Myxospongiae (Chondrosida + Verongida + Halisarcida). Within all the classical orders, whether they are monophyletic or not, families and even genera have also been found to be polyphyletic. For example, Ancorinidae, Geodiidae, and Axinellidae are clearly polyphyletic. No single data set is able to resolve all the problems; thus, it is absolutely necessary that the classification of Demospongiae be examined from all angles and with as many data sets as possible.
Host preferences of bat flies: following the bloody path of stable isotopes in a host–parasite food chain
Authors: Voigt Christian C , Kelm Detlev H
Published: April 2006

Almost all mammals are infested with ectoparasites, but even though parasites may have a strong impact on their host, their host specificity is often unknown. We studied the host preferences of two bat fly species, Strebla wiedemanni Kolenati, 1856 and Trichobius parasiticus Gervais, 1844, identified on the common vampire bat, Desmodus rotundus (E. Geoffroy, 1810), using stable carbon isotopes. Since D. rotundus was part of the C4 food web and other bats sharing the roost with D. rotundus were part of the C3 food web, bat flies were exposed to two isotopically distinct potential hosts. The δ13C values of the two bat fly species collected from D. rotundus were similar (–11.5 ± 1.1 (mean ± SD) for S. wiedemanni and –12.4 ± 1.9 for T. parasiticus) and identified them as members of the C4 food web, although their δ13C value was significantly lower by –1.7 ± 2.6 than that of the corresponding host individual. The δ13C value of bat flies collected from Carollia perspicillata (L., 1758) sharing roosts with D. rotundus averaged –24.2 ± 0.3, which was also significantly lower by –1.3 ± 1.1 than the host's δ13C value. We concluded that the negative shift in δ13C of D. rotundus bat flies relative to the host individual was caused by isotopic fractionation rather than by a mixed diet. The enrichment in nitrogen-15 from S. wiedemanni and T. parasiticus to D. rotundus equaled 2.3, which indicates one trophic step between the host and the parasite. In summary, both bat fly species preferred D. rotundus over other bat species and are therefore truly monoxenous parasites.
Seasonal changes in home ranges of Abert's squirrels: impact of mating season
Authors: Edelman A J , Koprowski J L
Published: April 2006

We compared home ranges of introduced Abert's squirrels (Sciurus aberti Woodhouse, 1853) in mixed-conifer forests of Arizona during non-mating and mating seasons. Because Abert's squirrels are reported to depend on ponderosa pine (Pinus ponderosa P. & C. Lawson) forests, the mixed-conifer forest in our study represented a novel habitat. Home-range size, home-range overlap with females, and movement distances increased for males from non-mating to mating seasons. Home-range size and overlap characteristics of females remained consistent between seasons, but movement distances were reduced during the mating season. Males probably increased home-range size, home-range overlap with females, and movement distances during the mating season to maximize contact with scarce females. Home-range size and overlap characteristics of female Abert's squirrels likely remained stable between seasons because females do not search for mates. Restricted movements by females during the mating season may be due to changes in resource use in preparation for reproduction. Non-mating season home ranges in our study were smaller than home ranges observed in ponderosa pine forest. Abert's squirrels in mixed-conifer forest may have small home ranges because resource quality is higher than in ponderosa pine forest or competition for space with co-occurring Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis (J.A. Allen, 1894)).
The relationship between echolocation-call frequency and moth predation of a tropical bat fauna
Authors: Pavey C R , Burwell C J , Milne D J
Published: April 2006

The allotonic frequency hypothesis proposes that the proportion of eared moths in the diet should be highest in bats whose echolocation calls are dominated by frequencies outside the optimum hearing range of moths i.e., <20 and >60 kHz. The hypothesis was tested on an ecologically diverse bat assemblage in northern tropical Australia that consisted of 23 species (5 families, 14 genera). Peak frequency of signals of bats within the echolocation assemblage ranged from 19.8 to 157 kHz but was greatest between 20 and 50 kHz. A strong positive relationship existed between peak call frequency and percentage of moths in the diet for a sample of 16 bats from the assemblage representing 13 genera (R2 = 0.54, p = 0.001). The relationship remained strong when the three species with low-intensity calls were excluded. When the two species with high duty cycle, constant-frequency signals were removed, the relationship was weaker but still significant. In contrast to previous research, eared moths constituted only 54% of moth captures in light traps at bat foraging grounds, and eared moths were significantly larger than non-eared individuals. These results show that the pattern of moth predation by tropical bats is similar to that already established for bat faunas in subtropical and temperate regions.
Egg-laying behaviour following infection in the cricketGryllus texensis
Authors: Shoemaker K L , Parsons N M , Adamo S A
Published: April 2006

To maximize fitness, the rate of offspring production should be sensitive to factors that predict the likelihood of parental survival. We predicted that acutely activating the immune system in the cricket Gryllus texensis Cade and Otte, 2000, signaling the possibility of decreased life expectancy, would lead to an immediate increase in reproductive effort. We found that lifetime fecundity varied among individual crickets and that female crickets laid more eggs in moist sand than in moist cotton, suggesting that females have the capacity to increase oviposition rates in response to substrate conditions. However, we found that exposing female crickets to a potentially lethal pathogen, Serratia marcescens Bizio, led to an increase in egg laying only when substrate conditions were preferable or at doses approaching the LD50.
SCALING OF VARIABLES AND THE RELATION BETWEEN NONCOMMUTATIVE PARAMETERS IN NONCOMMUTATIVE QUANTUM MECHANICS
Authors: BERTOLAMI O. , ROSA J. G. , DE ARAGÃO C. M. L. , CASTORINA P. , ZAPPALÀ D.
Published: April 2006

We consider noncommutative quantum mechanics with phase space noncommutativity. In particular, we show that a scaling of variables leaves the noncommutative algebra invariant, so that only the self-consistent effective parameters of the model are physically relevant. We also discuss the recently proposed relation of direct proportionality between the noncommutative parameters, showing that it has a limited applicability.
HIGHLY ACCURATE WAVELENGTH SCANNED FOUR-WAVE MIXING EXPERIMENT IN AN OPTICAL FIBER AND DEMONSTRATION OF RETRIEVAL OF ITS LINEAR AND NONLINEAR OPTICAL PARAMETERS
Authors: JUNG S. J. , LEE J. Y. , KIM D. Y.
Published: April 2006

Accurate wavelength scanned four-wave mixing (FWM) measurement results in an optical fiber are presented with two tunable laser sources near the dispersion-zero wavelength of the fiber. By comparing the measured FWM data with a simple analytic expression, we have demonstrated that important linear and nonlinear optical properties such as zero-dispersion wavelength, dispersion slope and nonlinear refractive index of the sample fiber. Highly accurate and repeatable measurement results for a sample fiber are presented. Temperature-dependent change in the chromatic dispersion of a fiber is also investigated.
A NEMATIC REPLICA OF A HOLOGRAPHIC POLARIZATION GRATING: MODELING OF THE IDEAL AND A CORRUGATED SURFACE
Authors: PALTO S. P. , BARNIK M. I. , ARBUZOV A. V. , UMANSKII B. A. , BLINOV L. M.
Published: April 2006

When a nematic liquid crystal layer is brought in contact with a photosensitive polymer, on which a holographic grating is recorded by two laser beams with opposite circular polarization, due to a spatial modulation of the direction of the local optical axis, the photopolymer modulates the anchoring conditions for NLC in a similar way. As a result, a similar grating is induced in NLC with the enhanced diffraction efficiency and specific diffraction properties controlled by electric field.6 Here we show that, even in the case of a typical finite value of the anchoring energy, the numerical modeling confirms the characteristic asymmetric diffraction of the circularly polarized reconstructing beam and exchange by energy between the zero and first-order diffracted beams. Some other properties, such as reduced diffraction efficiency, appearance of higher diffraction orders and too-large optical phase retardation of a nematic cell at the areas occupied by gratings, can also be modeled by assuming some corrugation of the surface.
OPTICAL PARAMETRIC INTERACTIONS IN DISTRIBUTED MAGNETO-OPTICAL BRAGG GRATINGS
Authors: JONSSON FREDRIK , FLYTZANIS CHRISTOS
Published: April 2006

We analyze optical parametric interactions in nonlinear magneto-optical media simultaneously possessing a second-order nonlinearity and a spatial modulation of its linear optical properties. An analytic solution for the conversion efficiency of energy transfer from an optical pump to a signal wave is presented, and we discuss the possibility of tunability that is added to the parametric process.
ON THE DAMPING OF THE FLUCTUATIONS OF ATOMIC GROUPS IN WATER ENVIRONMENT
Authors: MITROFANOV VASILY , ROMANOVSKY YURY , NETREBKO ALEXEY
Published: April 2006

In this work, we continue our research of the problem concerning the proteins' functioning efficiency. The system under study, a three-dimensional harmonic oscillator, placed in a water "drop" which consists of 264 molecules, simulates the fluctuations of atomic groups in a non-stationary charge pattern field of an active center. The latter results in a break of chemical bonds. Damping time and Q-factor calculations of atomic fluctuations at various frequencies, intensities of interaction with the water environment, and also at various atomic weights are carried out. By means of the argon-like model of water molecules the Q-factor of atomic fluctuations is also estimated. The results obtained are compared with those calculated with the SP3-model.
FIRM STRATEGIES FOR RISK MANAGEMENT IN INNOVATION
Authors: GENUS AUDLEY , COLES ANNE-MARIE
Published: April 2006

Analysis of potential risks is fundamental to technology development, but the definition and control of such risks are often problematic. This paper examines the issues concerned, aiming for an improved understanding of how the evaluation of risk shapes the emergence of new technology. The paper highlights different firm strategies taken towards evaluating risky technology, working from the micro-level of project management, and drawing on relevant qualitative case studies. Some contributors call for a meshing of analysis of macro-level technology policy objectives with an understanding of the micro-level activity of project planning. However, it is concluded that this can only be facilitated by first improving our understanding of theoretical perspectives and risk assessment practices at the firm level, since the firm remains critical to the generation and evaluation of new technology.
ENHANCING ORGANISATIONAL INFORMATION FLOW AND KNOWLEDGE CREATION IN RE-ENGINEERING SUPPLY CHAIN SYSTEMS: AN ANALYSIS OF THE U.S. AUTOMOTIVE PARTS AND SUPPLIES MODEL
Authors: KUDYBA STEPHAN
Published: April 2006

The ongoing initiative of business process re-engineering in organisations has largely been attributed to innovations in information technologies that have enabled firms to increase productivity in their operations. The following paper addresses essential concepts in supply chain networks and describes the systems approach the U.S. automotive industry has implemented to augment their supply chain management initiatives. The focus of re-engineering the supply chain is enhanced data capture and analysis of activities in various segments of the chain which augments organisational information flow and knowledge generation resulting in communication of proactive decision making throughout the supply network to maintain operational efficiency.