bluuebunny/crossref_metadata_2025 huggingface dataset:
Phosphorus fertiliser can induce earlier vegetative phase change in Eucalyptus nitens
Authors: Williams Dean R. , Smethurst Philip J. , Potts Brad M.
Published: April 2004

Many eucalypts are heteroblastic, exhibiting a distinct change in leaf morphology through their
ontogeny. The physiological and chronological age at which the tree switches from the production of juvenile foliage to adult foliage (vegetative phase change) can be under strong genetic control and influenced to some extent by environment. We studied the effect of nitrogen (N) and phosphorus (P) fertiliser on the growth and vegetative phase change in Eucalyptus nitens. Whilst neither fertiliser treatment affected tree height at 3.5 years of age, P fertiliser significantly reduced the length of the juvenile vegetative phase. In contrast, N, but not P, has been shown to promote flowering. These findings support the argument that vegetative and reproductive maturity are genetically and physiologically uncoupled in Eucalyptus.
High self-pollen transfer and low fruit set in buzz-pollinated Dianella revoluta (Phormiaceae)
Authors: Duncan David H. , Cunningham Saul A. , Nicotra Adrienne B.
Published: April 2004

We used pollinator observation, flower manipulation, controlled pollination and pollen-tube analysis to better understand the reproductive ecology of Dianella revoluta R.Br., a common species known to have depressed fruit set at fragmented sites. This buzz-pollinated species was found to receive large quantities of self-pollen even during a single pollinator visit, but is only partially self-compatible. This may be the first direct demonstration of pollinator-facilitated, autogamous self-pollen transfer accounting for a significant proportion of stigmatic pollen load. Frequent high self-pollen transfer may account for the observed low rate of fruit development in open-pollinated flowers. Self-pollen tubes reached the base of the style in comparable numbers and at the same rate as outcross pollen tubes, with no sign of pollen-tube competition favouring outcross pollen. Barriers to greater self-fertility occur late, probably through early abortion of selfed ovules. We also investigated what impact
overlapping distribution with D. longifolia may have on D. revoluta pollination and reproduction. Although these species shared pollinators, they differed in terms of frequency of visits. There was also separation of floral phenology within the course of a day.
Spatial models for estimating fuel loads in the Black Hills, South Dakota, USA
Authors: Reich Robin M. , Lundquist John E. , Bravo Vanessa A.
Published: April 2004

Fire suppression has increased fuel loadings and fuel continuity in many forested ecosystems, resulting in forest structures that are vulnerable to catastrophic fire. This paper describes the statistical properties of models developed to describe the spatial variability in forest fuels on the Black Hills National Forest, South Dakota. Forest fuel loadings (tonnes/ha) are modeled to a 30 m resolution using a combination of trend surface models to describe the coarse-scale variability in forest fuel, and binary regression trees to describe the fine-scale variability associated with site-specific variability in forest fuels. Independent variables used in the models included various Landsat TM bands, forest class, elevation, slope, and aspect. The models accounted for 55% to 72% of the variability in forest fuels. In spite of having highly skewed distributions, cross-validation showed the models to have nominal prediction bias. This paper also evaluates the feasibility of using the estimation error variance to explain estimation uncertainty. The models are allowing us to study the influence of small-scale disturbances on forest fuel loadings and diversity of resident and migratory birds on the Black Hills National Forest.
Where's the fire? Quantifying uncertainty in a wildfire threat model
Authors: Jones S. D. , Garvey M. F. , Hunter G. J.
Published: April 2004

Models of wildfire threat are often used in the management of fire-prone areas for purposes such as planning fire education campaigns and the deployment of fire prevention and suppression resources. While the use of spatial or geographic data is common to all wildfire threat models, the key question arises: Is the accuracy of the spatial data used in wildfire threat models sufficient for the intended decision-making purpose? To help answer this question, a quantitative uncertainty assessment technique was applied to a wildfire threat model used by the Country Fire Authority in Victoria, Australia. The technique simulates known or estimated spatial data error by modifying data values to represent the range of all probable errors present in the input dataset. The wildfire threat model is then run multiple times using these modified ‘error’ layers in order to simulate and observe the effect these errors have on the model outputs. For the model concerned, the results suggest that errors in digital elevation surfaces have only minimal impact upon the outputs, resulting in relatively stable wildfire management decisions. On the other hand inaccuracies in land cover maps (with implied differences in fuel load estimations) result in larger changes in the model outputs, whereas changes in fire weather data can result in highly unstable outputs. Knowledge of these effects can facilitate better wildfire management since any improvements that are to be made to the model’s accuracy can be focussed directly upon the problem datasets.
Statistical analysis of fire frequency models for Catalonia (NE Spain), 1975 - 1998) based on fire scar maps from Landsat MSS data
Authors: Díaz-Delgado Ricardo , Lloret Francisco , Pons Xavier
Published: April 2004

This paper estimates fire frequency in Catalonia (NE Spain) for the last quarter of the 20th Century (1975–1998) from historical burned area maps. Remote sensing images provided perimeters of fires ≥ 30 ha, which were used to characterize the temporal patterns of fire occurrence in Catalonia. Several fire frequency models were used to reproduce the observed pattern of wildfires occurrence in the study period. Natural fire rotation period was estimated to be 133 years. Poisson tests were carried out to check random fire occurrence either along the time period or across the analysed region. Observed fires were not randomly generated either in space or in time, despite being sampled using two different plot sizes. This sampling design was also used for Mean Fire Interval (MFI) analysis, which allowed us to significantly fit a Weibull distribution to the observed proportion of fire intervals (for both sample sizes), enabling us to estimate the hazard of burning, mortality, and survivorship functions. Finally, MFI was also applied to forest regions of Catalonia, which are defined according to forest management plans based on their homogeneous climatic conditions. Such an analysis revealed relevant differences in forest management and their consequences on fire occurrence.
Long-term forest fire retardants: a review of quality, effectiveness, application and environmental considerations
Authors: Giménez Anna , Pastor Elsa , Zárate Luis , Planas Eulàlia , Arnaldos Josep
Published: April 2004

Since the beginning of the 1930s research has been directed towards improving the effectiveness of water as a forest fire extinguishing agent. Throughout this time various chemical substances have been added to the water, and this is still the case today. Among these substances are the various types of long-term forest fire retardant, which maintain their ability to alter combustion when the water has been removed by evaporation. In order to provide an account of the current state of development of studies on long-term forest fire retardants, we carried out a bibliographic analysis with special attention to work done after 1976 on the different aspects that influence the final effectiveness of forest fire retardant: quality (programs and evaluation), effectiveness, application and environmental impact on streams and aquatic organisms, vegetation and humans. The scope of this work covers the wide subject of fire retardants and it introduces significant work related to all the aspects of fire retardant use.
On the existence of a steady state regime for slope and wind driven fires
Authors: Viegas Domingos X.
Published: April 2004

Forest fire behaviour analysis and prediction is based on the assumption that for a given set of boundary conditions a steady-state of fire propagation exists with a well-defined rate of spread. The evolution of a fire front for linear and point ignited fires is analysed and it is shown that, even in nominally uniform and permanent conditions, the rate of spread of the head fire does not remain constant in the general case of slope- and wind-driven fires due to joint convection and radiation effects. The basic case of a linear fire front without slope and without wind is one of the few cases for which the rate of spread is well defined and remains constant. if there is slope or wind in point ignition fires, the rate of spread of the head fire tends to increase while for linear ignition fires the contrary happens. It is shown that convective effects induced by the fire for steep slope terrain can produce the so-called ‘blow-up’ effect even in the absence of any other special atmospheric conditions. Therefore the definition of rate of spread of a fire and its evaluation from laboratory and field experiments is strongly questioned.
Estimation of the radiation extinction coefficient of natural fuel beds
Authors: Vaz Gilberto C. , André Jorge C. S. , Viegas Domingos X.
Published: April 2004

. The standard formula used to estimate the radiation extinction coefficient, kb
(m–1), of solid porous natural fuel beds is examined and tested against laboratory experiments with isotropic beds of pine needles in the range of packing ratio, β, of 0.01–0.02. To measure kb
in the tests, a setup using a parallel beam of white light radiation was constructed. The error of the standard formula is observed to be smaller than 10%. Similar tests were performed for a non-isotropic bed of pine needles with β ≈ 0.02, in which the maximum angle of inclination of the needles was limited to 30°, for two directions of incidence of radiation: horizontal and vertical. For each one of these two cases, original estimation formulae for kb
are proposed alternative to the standard one. In these cases it is concluded that, while the standard formula may be in error by up to 20%, the new formulae have errors around 5% or smaller.
Ecological impacts of wheat seeding after a Sierra Nevada wildfire
Authors: Keeley Jon E.
Published: April 2004

The Highway Fire burned 1680 ha of mixed ponderosa pine–oak–chaparral in the newly created Giant Sequoia National Monument and the adjacent Sequoia National Forest of Fresno County, California in August 2001. The USDA Forest Service Burned Area Emergency Rehabilitation (BAER) program recommended that portions of the burned forest be seeded with a non-persistent variety of wheat at a density of 157 kg ha–1 (140 lb/ac). The present study compared the vascular plant diversity and cover in seeded and unseeded parts of this burn to evaluate the ecological impact of seeding an alien grass. In the first post-fire growing season, the natural regeneration of unseeded control sites averaged ~55% ground surface covered. Wheat seeding enhanced the ground cover, averaging 95% ground surface cover. Wheat was the dominant species on the seeded sites, comprising 67% of the total cover. Dominance–diversity curves were markedly affected by the seeding and indicated a disruption in the natural ecological structure of these communities. On seeded sites, wheat dominated and all other species were poorly represented whereas, on unseeded control sites, there was a more equitable distribution of species. Correlated with the wheat cover was a significant decrease in species richness at all scales examined. Total species richness was reduced from 152 species across all unseeded sites to 104 species on all seeded sites. Average species richness, at scales from 1 to 1000 m2, was 30–40% lower on seeded sites. Species most strongly inhibited were post-fire endemics whose lifecycle is restricted to immediate post-fire environments. Seeded sites had fewer alien species than unseeded sites; however, this may not have any lasting effect since other studies show the primary alien threat is not in the first post-fire year. Seeding was also associated with an order of magnitude drop in Pinus ponderosa seedling recruitment and, coupled with the massive thatch still remaining on the site, it is likely that recruitment will be inhibited in subsequent years.
Description of a coupled atmosphere - fire model
Authors: Clark Terry L. , Coen Janice , Latham Don
Published: April 2004

This paper describes a coupled fire–atmosphere model that uses a sophisticated high-resolution non-hydrostatic numerical mesoscale model to predict the local winds which are then used as input to the prediction of fire spread. The heat and moisture fluxes from the fire are then fed back to the dynamics, allowing the fire to influence its own mesoscale winds that in turn affect the fire behavior.
This model is viewed as a research model and as such requires a fireline propagation scheme that systematically converges with increasing spatial and temporal resolution. To achieve this, a local contour advection scheme was developed to track the fireline using four tracer particles per fuel cell, which define the area of burning fuel. Using the dynamically predicted winds along with the terrain slope and fuel characteristics, algorithms from the BEHAVE system are used to predict the spread rates. A mass loss rate calculation, based on results of the BURNUP fuel burnout model, is used to treat heat exchange between the fire and atmosphere.
Tests were conducted with the uncoupled model to test the fire-spread algorithm under specified wind conditions for both spot and line fires. Using tall grass and chaparral, line fires were simulated employing the full fire–atmosphere coupling. Results from two of these experiments show the effects of fire propagation over a small hill. As with previous coupled experiments, the present results show a number of features common to real fires. For example, we show how the well-recognized elliptical fireline shape is a direct result of fire–atmosphere interactions that produce the ‘heading’, ‘flanking’, and ‘backing’ regions of a wind-driven fire with their expected behavior. And, we see how perturbations upon this shape sometimes amplify to become fire whirls along the flanks, which are transported to the head of the fire where they may interact to produce erratic fire behavior.
Crystal structure and characterization of a cytochrome
c
peroxidase–cytochrome
c
site-specific cross-link
Authors: Guo Maolin , Bhaskar B. , Li Huiying , Barrows Tiffany P. , Poulos Thomas L.
Published: April 2004

A specific covalently cross-linked complex between redox partners yeast cytochrome
c
peroxidase (CCP) and cytochrome
c
(cyt.
c
) has been made by engineering cysteines into CCP and cyt.
c
that form an intermolecular disulfide bond in high yield. The crystal structure of the cross-linked complex has been solved to 1.88-Å resolution and closely resembles the structure of the noncovalent complex [Pellitier, H. & Kraut, J. (1992)
Science
258, 1748–1755]. The higher resolution of the covalent complex has enabled the location of ordered water molecules at the peroxidase–cytochrome
c
interface that serve to bridge between the two proteins by hydrogen bonding. As in the noncovalent complex, direct electrostatic interactions between protein groups appear not to be critical in complex formation. UV–visible spectroscopic and stopped-flow studies indicate that CCP in the covalent complex reacts normally with H
2
O
2
to give compound I. Stopped-flow kinetic studies also show that intramolecular electron transfer between the cross-linked ferrocytochrome
c
and the Trp-191 cation radical site in CCP compound I occurs fast and is nearly complete within the dead time (≈2 ms) of the instrument. These results indicate that the structure of the covalent complex closely mimics the physiological electron transfer complex. In addition, single-turnover and steady-state experiments reveal that CCP compound I in the covalent complex oxidizes exogenously added ferrocytochrome
c
at a slow rate (
t
1/2
≈ 2 min), indicating that CCP does not have a second independent site for physiologically relevant electron transfer.
Factors that make an infectious disease outbreak controllable
Authors: Fraser Christophe , Riley Steven , Anderson Roy M. , Ferguson Neil M.
Published: April 2004

The aim of this study is to identify general properties of emerging infectious agents that determine the likely success of two simple public health measures in controlling outbreaks, namely (i) isolating symptomatic individuals and (ii) tracing and quarantining their contacts. Because these measures depend on the recognition of specific disease symptoms, we investigate the relative timing of infectiousness and the appearance of symptoms by using a mathematical model. We show that the success of these control measures is determined as much by the proportion of transmission occurring prior to the onset of overt clinical symptoms (or via asymptomatic infection) as the inherent transmissibility of the etiological agent (measured by the reproductive numberR0). From published studies, we estimate these quantities for two moderately transmissible viruses, severe acute respiratory syndrome coronavirus and HIV, and for two highly transmissible viruses, smallpox and pandemic influenza. We conclude that severe acute respiratory syndrome and smallpox are easier to control using these simple public health measures. Direct estimation of the proportion of asymptomatic and presymptomatic infections is achievable by contact tracing and should be a priority during an outbreak of a novel infectious agent.
Adenovirus-induced maturation of dendritic cells through a PI3 kinase-mediated TNF-α induction pathway
Authors: Philpott Nicola J. , Nociari Marcelo , Elkon Keith B. , Falck-Pedersen Erik
Published: April 2004

Systemic administration of adenovirus and adenovirus vectors induces a robust innate and adaptive immune response in a variety of animal models. In tumor necrosis factor (TNF)
-/-
mice, a diminished immune response to adenovirus (Ad) infection has been attributed to compromised dendritic cell (DC) maturation. In this report, we investigated the mechanisms responsible for Ad-mediated activation and maturation of DC. Ad infection induced high levels of TNF-α expression by murine bone marrow-derived DC, comparable to levels observed with lipopolysaccharide exposure. Ad-induced TNF-α production was necessary for DC maturation and acts in an autocrine manner. Unlike TNF-α production associated with exposure to lipopolysaccharide, Ad induction of TNF-α was not dependent on the MyD88 signaling pathway. In contrast, Ad-induced TNF-α production and DC maturation were dependent on signaling by phosphoinositide-3-OH kinase (PI3K), as determined by wortmannin and LY294002 blocking experiments. The adenovirus capsid protein penton contains a well characterized arginine-glycine-aspartic acid integrin-binding domain that stimulates PI3K in fibroblast cell lines. When this region of the penton was mutated, TNF-α expression and bone marrow-derived DC maturation were attenuated. We propose that integrin-mediated PI3K induction of NF-κB activates an autocrine TNF-α pathway required for DC maturation in response to Ad.
Real-time evaluation of myosin light chain kinase activation in smooth muscle tissues from a transgenic calmodulin-biosensor mouse
Authors: Isotani Eiji , Zhi Gang , Lau Kim S. , Huang Jian , Mizuno Yusuke , Persechini Anthony , Geguchadze Ramaz , Kamm Kristine E. , Stull James T.
Published: April 2004

Ca
2+
/calmodulin (CaM)-dependent phosphorylation of myosin regulatory light chain (RLC) by myosin light chain kinase (MLCK) initiates smooth muscle contraction and regulates actomyosin-based cytoskeletal functions in nonmuscle cells. The net extent of RLC phosphorylation is controlled by MLCK activity relative to myosin light chain phosphatase activity. We have constructed a CaM-sensor MLCK where Ca
2+
-dependent CaM binding increases the catalytic activity of the kinase domain, whereas coincident binding to the biosensor domain decreases fluorescence resonance energy transfer between two fluorescent proteins. We have created transgenic mice expressing this construct specifically in smooth muscle cells to perform real-time evaluations of the relationship between smooth muscle contractility and MLCK activation in intact tissues and organs. Measurements in intact bladder smooth muscle demonstrate that MLCK activation increases rapidly during KCl-induced contractions but is not maximal, consistent with a limiting amount of cellular CaM. Carbachol treatment produces the same amount of force development and RLC phosphorylation, with much smaller increases in [Ca
2+
]
i
and MLCK activation. A Rho kinase inhibitor suppresses RLC phosphorylation and force but not MLCK activation in carbachol-treated tissues. These observations are consistent with a model in which the magnitude of an agonist-mediated smooth muscle contraction depends on a rapid but limited Ca
2+
/CaM-dependent activation of MLCK and Rho kinase-mediated inhibition of myosin light chain phosphatase activity. These studies demonstrate the feasibility of producing transgenic biosensor mice for investigations of signaling processes in intact systems.
Molecular architecture of the prolate head of bacteriophage T4
Authors: Fokine Andrei , Chipman Paul R. , Leiman Petr G. , Mesyanzhinov Vadim V. , Rao Venigalla B. , Rossmann Michael G.
Published: April 2004

The head of bacteriophage T4 is a prolate icosahedron with one unique portal vertex to which the phage tail is attached. The three-dimensional structure of mature bacteriophage T4 head has been determined to 22-Å resolution by using cryo-electron microscopy. The T4 capsid has a hexagonal surface lattice characterized by the triangulation numbers
T
end
= 13 laevo for the icosahedral caps and
T
mid
= 20 for the midsection. Hexamers of the major capsid protein gene product (gp)23* and pentamers of the vertex protein gp24*, as well as the outer surface proteins highly antigenic outer capsid protein (
hoc
) and small outer capsid protein (
soc
), are clearly evident in the reconstruction. The size and shape of the gp23* hexamers are similar to the major capsid protein organization of bacteriophage HK97. The binding sites and shape of the
hoc
and
soc
proteins have been established by analysis of the
soc
–
and
hoc
–
soc
–
T4 structures.
Intestinal villous M cells: An antigen entry site in the mucosal epithelium
Authors: Jang Myoung Ho , Kweon Mi-Na , Iwatani Koichi , Yamamoto Masafumi , Terahara Kazutaka , Sasakawa Chihiro , Suzuki Toshihiko , Nochi Tomonori , Yokota Yoshifumi , Rennert Paul D. , Hiroi Takachika , Tamagawa Hiroshi , Iijima Hideki , Kunisawa Jun , Yuki Yoshikazu , Kiyono Hiroshi
Published: April 2004

M cells located in the follicle-associated epithelium of Peyer's patches (PP) are shown to be the principal sites for the sampling of gut luminal antigens. Thus, PP have long been considered the gatekeepers of the mucosal immune system. Here, we report a distinct gateway for the uptake of gut bacteria: clusters of non-follicle-associated epithelium-associatedUlex europaeusagglutinin (UEA)-1+cells, which we have designated intestinal villous M cells. Interestingly, villous M cells are developed in various PP [or gut-associated lymphoid tissue (GALT)]-null mice, such asin uterolymphotoxin β receptor (LTβR)-Ig-treated, lymphotoxin α (LTα)-/-, tumor necrosis factor/LTα-/-, and inhibition of differentiation 2 (Id2)-/-mice. Intestinal villous M cells have been observed to take up GFP-expressingSalmonella, Yersinia, andEscherichia coli-expressing invasin, as well as gut bacterial antigen for subsequent induction of antigen-specific immune responses. Thus, the identified villous M cells could be an alternative and PP-independent gateway for the induction of antigen-specific immune responses by means of the mucosal compartment.
Mating, seminal fluid components, and sperm cause changes in vesicle release in the
Drosophila
female reproductive tract
Authors: Heifetz Yael , Wolfner Mariana F.
Published: April 2004

Mating induces changes in female insects, including in egg production, ovulation and laying, sperm storage, and behavior. Several molecules and effects that induce these changes have been identified, but their proximate effects on females remain unexplored. We examined whether vesicle release occurs as a consequence of mating; we used transgenic
Drosophila
that allow monitoring of secretory granule release at nerve termini. Changes in release occur at specific times postmating in different regions of the female reproductive tract: soon after mating in the lower reproductive tract, and later in the upper reproductive tract. Some changes are triggered by receipt of sperm, others by male seminal proteins, and still others by the act of mating itself (or other unidentified effectors). Our findings indicate that the female reproductive tract is a multi-organ system whose regions are modulated separately by mating and mating components. This modulation could create an environment conducive to increased reproductive capacity.
How to identify gene–environment interactions in a multifactorial disease: CHD as an example
Authors: Talmud Philippa J.
Published: April 2004

CHD is a multifactorial disease, caused by both genetic and environmental factors. The inherited 'defective' genes will vary from individual to individual, and any single mutation is likely to be making only a small contribution to risk. The context dependency, i.e. the importance of environmental factors in influencing genetic risk, is now becoming evident. Thus, a mutation may have a modest effect on risk in individuals who maintain a low environmental risk, but a major effect in a high-risk environment. Methods of analysing gene–environment interactions on CHD risk will be discussed and illustrated with several examples.APOEhas three common alleles, ɛ2, ɛ3 and ɛ4. The ɛ4 allele has consistently been associated with CHD risk, which has been confirmed by meta-analysis. However, when the effect of genotype on risk was considered in smokers and non-smokers separately, risk in non-smokers was similar in allAPOEgenotypes. By comparison, in the smokers, ɛ3 homozygotes, as expected, had an approximately 2-fold higher risk, while for ɛ4 carriers there was a significantly greater than additive effect of genotype and smoking on risk (P≫0.007). Thus, the impact of the ɛ4 allele on CHD risk appears to be confined to current smokers, an effect that has been confirmed in several studies. Another example is the interaction between the alcohol dehydrogenase 3 gene variant and alcohol consumption on CHD risk (P≫0.001), showing the context dependency of the effect. Thus, the importance of considering environmental factors as potential genotype-risk modifiers has major public health implications.
Lipid metabolism in women
Authors: Williams Christine M.
Published: April 2004

Differences in whole-body lipid metabolism between men and women are indicated by lower-body fat accumulation in women but more marked accumulation of fat in the intra-abdominal visceral fat depots of men. Circulating blood lipid concentrations also show gender-related differences. These differences are most marked in premenopausal women, in whom total cholesterol, LDL-cholesterol and triacylglycerol concentrations are lower and HDL-cholesterol concentration is higher than in men. Tendency to accumulate body fat in intra-abdominal fat stores is linked to increased risk of CVD, metabolic syndrome, diabetes and other insulin-resistant states. Differential regional regulation of adipose tissue lipolysis and lipogenesis must underlie gender-related differences in the tendency to accumulate fat in specific fat depots. However, empirical data to support current hypotheses remain limited at the present time because of the demanding and specialist nature of the methods used to study adipose tissue metabolism in human subjects. In vitro and in vivo data show greater lipolytic sensitivity of abdominal subcutaneous fat and lesser lipolytic sensitivity of femoral and gluteal subcutaneous fat in women than in men. These differences appear to be due to fewer inhibitory α adrenergic receptors in abdominal regions and greater α adrenergic receptors in gluteal and femoral regions in women than in men. There do not appear to be major gender-related differences in rates of fatty acid uptake (lipogenesis) in different subcutaneous adipose tissue regions. In visceral fat rates of both lipolysis and lipogenesis appear to be greater in men than in women; higher rates of lipolysis may be due to fewer α adrenergic receptors in this fat depot in men. Fatty acid uptake into this depot in the postprandial period is approximately 7-fold higher in men than in women. Triacylglycerol concentrations appear to be a stronger cardiovascular risk factor in women than in men, with particular implications for cardiovascular risk in diabetic women. The increased triacylglycerol concentrations observed in women taking hormone-replacement therapy (HRT) may explain the paradoxical findings of increased rates of CVD in women taking HRT that have been reported from recent primary and secondary prevention trials of HRT.
Recent advances in the nutritional biochemistry of trivalent chromium
Authors: Vincent John B.
Published: April 2004

The nutritional biochemistry of trivalent Cr has been a poorly understood field of study; investigations of the biochemistry of the other essential transition metals have not proven as problematic. Despite over four decades of endeavour, only recently has a picture of the role of Cr potentially started to be defined. The biologically-relevant form is the trivalent ion. Cr3+appears to be required for proper carbohydrate and lipid metabolism in mammals, although fortunately Cr deficiency is difficult to achieve. Conditions that increase circulating glucose and insulin concentrations increase urinary Cr output. Cr is probably excreted in the form of the oligopeptide chromodulin. Chromodulin may be the key to understanding the role of Cr at a molecular level, as the molecule has been found to bind to activated insulin receptor, stimulating its kinase activity. A mechanism for the action of chromodulin has recently been proposed; this mechanism can serve as a potential framework for further studies to test the role of Cr in metabolism. An examination of the nutritional supplement chromium picolinate illustrates some of the difficulties associated with these biochemical studies.
Individualized nutritional recommendations: do we have the measurements needed to assess risk and make dietary recommendations?
Authors: Arab Lenore
Published: April 2004

Is the information currently available to adjust nutritional recommendations and develop individualized nutrition? No. There is not even the information needed for setting dietary recommendations with confidence now at the group level. Will it be available soon? The answer to this question depends on the drive and will of the nutritional community, the success in recruiting funding to the area, the education of nutritionists and the spawning of great ideas and approaches. The emerging tools of genomics, proteomics and metabolomics are enabling the in-depth study of relationships between diet, genetics and metabolism. The advent of technologies can be compared with the discovery of the microscope and the new dimensions of scientific visualization enabled by that discovery. Nutritionists stand at the crest of new waves of data that can be generated, and new methods for their digestion will be required. To date, the study of dietary requirements has been based largely on a black box approach. Subjects are supplemented or depleted and clinical outcomes are observed. Few recommendations are based on metabolic outcomes. Metabolomics and nutrigenomics promise tools with which recommendations can be refined to meet individual requirements and the potential of individualized nutrition can be explored. As yet, these tools are not being widely applied in nutritional research and are rarely being applied by nutritionists. The result is often interesting research that is frequently nutritionally flawed, resulting in inappropriate conclusions. Nutritional education is needed to put nutritionists at the forefront of the development of applications for these technologies, creating a generation of nutrigenomicists. A new generation of nutritionists should be working interdisciplinarily with geneticists, molecular biologists and bioinformaticians in the development of research strategies. The present paper reviews the current status of nutrigenomic research, the current controversies and limitations, and developments needed to advance nutrigenomics and explore fully the promise of individualized nutritional recommendations.
Nutrigenomics, individualism and public health
Authors: Chadwick Ruth
Published: April 2004

Issues arising in connection with genes and nutrition policy include both nutrigenomics and nutrigenetics. Nutrigenomics considers the relationship between specifc nutrients or diet and gene expression and, it is envisaged, will facilitate prevention of diet-related common diseases. Nutrigenetics is concerned with the effects of individual genetic variation (single nucleotide polymorphisms) on response to diet, and in the longer term may lead to personalised dietary recommendations. It is important also to consider the surrounding context of other issues such as novel and functional foods in so far as they are related to genetic modification. Ethical issues fall into a number of categories: (1) why nutrigenomics? Will it have important public health benefits? (2) questions about research, e.g. concerning the acquisition of information about individual genetic variation; (3) questions about who has access to this information, and its possible misuse; (4) the applications of this information in terms of public health policy, and the negotiation of the potential tension between the interests of the individual in relation to, for example, prevention of conditions such as obesity and allergy; (5) the appropriate ethical approach to the issues, e.g. the moral difference, if any, between therapy and enhancement in relation to individualised diets; whether the 'technological fix' is always appropriate, especially in the wider context of the purported lack of public confidence in science, which has special resonance in the sphere of nutrition.
Public health nutrition and genetics: implications for nutrition policy and promotion
Authors: Darnton-Hill Ian , Margetts Barrie , Deckelbaum Richard
Published: April 2004

The unravelling of the human genome has the potential to radically extend many of the strategies used in public health nutrition to improve health and to increase food availability, accessibility and utilization. The present paper divides nutrigenomics into two broad but differing areas in asking about possible public health applications: (1) the increasing mismatch between population growth and global food security, on top of the already approximately 800 million of the world population who are food insecure; (2) possible responses to the rising prevalence of non-communicable diseases as the Western diet becomes increasingly inappropriate to the needs of those consuming it. It is clear that complex interactions of multiple polymorphisms play a role in how individuals and sub-populations respond to dietary interventions. All these applications present public health and ethical challenges, particularly in ensuring that any benefits that do come from nutrigenomics are not restricted to the wealthy minority of only the affluent nations. The present paper concludes that the public health applications of nutrigenomics are probably at least a decade away, especially for developing countries. Clinical applications are likely to be more immediate, probably resulting in ‘designer diets’ for individuals with particular polymorphisms, but unless governments take on the role of ensuring some extent of equity in access, any benefits are most likely to go to those who can afford the screening, tests and treatment. At the same time, greatly increased international efforts are needed towards the continuing, and in some cases worsening, global malnutrition, as genetic manipulation of crops is unlikely to provide more than part of the solution.
A novel positive regulatory element for exfoliative toxin A gene expression in Staphylococcus aureus
Authors: Sakurai Susumu , Suzuki Hitoshi , Hata Toshiaki , Yoshizawa Yukio , Nakayama Ritsuko , Machida Katsuhiko , Masuda Shogo , Tsukiyama Takashi
Published: April 2004

A 1·4 kb positive regulatory element (ETAexp
) that controls staphylococcal exfoliative toxin A (sETA) transcription was cloned from Staphylococcus aureus. ETAexp
is located upstream of the cloned 5·8 kb eta gene (etaJ1) obtained from the chomosomal DNA of S. aureus ZM, the standard ETA-producing strain. The cETA prepared from an Escherichia coli transformant into which the recombinant plasmid petaJ1 (5·8 kb eta/pUC9) had been introduced was expressed at high levels in the culture supernatant and the ammonium-sulfate-precipitated culture supernatant fraction as shown by immunoblotting and the single radial immunodiffusion test. However, cETA produced by the recombinant plasmid petaJ3 containing the 1·7 kb eta sequence (etaJ3) with a 1·45 kb ETAexp
-deficient eta fragment (1·7 kb eta/pUC9) obtained from the 5·8 kb eta sequence by subcloning was not detected in either the culture supernatant or the ammonium-sulfate-precipitated culture supernatant fraction (167-fold concentrate of the culture supernatant) by immunoblotting or the single radial immunodiffusion test. A large amount of cETA was produced by the 1·7 kb eta sequence when it was linked to ETAexp
amplified by PCR (1·7 kb eta-ETAexp
/pUC9), regardless of the orientation of ETAexp
insertion. Northern blot hybridization showed lower levels of the transcripts of the 1·7 kb eta sequence than of the 5·8 kb eta sequence. The rsETA prepared from an S. aureus transformant into which the recombinant plasmid 3·4 kb eta-ETAexp
/pYT3 (pYT3-etaJ6) had been introduced was expressed at high levels in the culture supernatant fraction as shown by the latex agglutination test. However, the agglutination titre in the culture supernatant fraction of rsETA produced by the recombinant plasmid (1·7 kb eta/pYT3) containing the 1·7 kb eta sequence carrying the 1·4 kb ETAexp
-deficient eta fragment (pYT3-etaJ3) was 2500–4000 times lower than that of pYT3-etaJ6.
DevR–DevS is a bona fide two-component system of Mycobacterium tuberculosis that is hypoxia-responsive in the absence of the DNA-binding domain of DevR
Authors: Saini Deepak Kumar , Malhotra Vandana , Dey Deepanwita , Pant Neha , Das Taposh K. , Tyagi Jaya Sivaswami
Published: April 2004

Two-component systems play a central role in the adaptation of pathogenic bacteria to the environment prevailing within host tissues. The genes encoding the response regulator DevR (Rv3133c/DosR) and the cytoplasmic portion (DevS201) of the histidine kinase DevS (Rv3132c/DosS), a putative two-component system ofMycobacterium tuberculosis, were cloned and the protein products were overexpressed, purified and refolded as N-terminally His6-tagged proteins fromEscherichia coli. DevS201underwent autophosphorylation and participated in rapid phosphotransfer to DevR in a Mg2+-dependent manner. Chemical stability analysis and site-directed mutagenesis implicated the highly conserved residues His395and Asp54as the sites of phosphorylation in DevS and DevR, respectively. Mutations in Asp8and Asp9residues, postulated to form the acidic Mg2+-binding pocket, and the invariant Lys104of DevR, abrogated phosphoryl transfer from DevS201to DevR. DevR–DevS was thus established as a typical two-component regulatory system based on His-to-Asp phosphoryl transfer. Expression of theRv3134c–devR–devSoperon was induced at the RNA level in hypoxic cultures ofM. tuberculosisH37Rv and was associated with an increase in the level of DevR protein. However, in adevRmutant strain expressing the N-terminal domain of DevR, induction was observed at the level of RNA expression but not at that of protein. DevS was translated independently of DevR and induction ofdevStranscripts was not associated with an increase in protein level in either wild-type or mutant strains, reflecting differential regulation of this locus during hypoxia.
Isolation of Vibrio alginolyticus sodium-driven flagellar motor complex composed of PomA and PomB solubilized by sucrose monocaprate
Authors: Yakushi Toshiharu , Kojima Masaru , Homma Michio
Published: April 2004

The polar flagella ofVibrio alginolyticushave sodium-driven motors, and four membrane proteins, PomA, PomB, MotX and MotY, are essential for torque generation of the motor. PomA and PomB are believed to form a sodium-conducting channel. This paper reports the purification of the motor complex by using sucrose monocaprate, a non-ionic detergent, to solubilize the complex. Plasmid pKJ301, which encodes intact PomA, and PomB tagged with a C-terminal hexahistidine that does not interfere with PomB function, was constructed. The membrane fraction of cells transformed with pKJ301 was solubilized with sucrose monocaprate, and the solubilized materials were applied to a Ni-NTA column. The imidazole eluate contained both PomA and PomB, which were further purified by anion-exchange chromatography. Gel-filtration chromatography was used to investigate the apparent molecular size of the complex; the PomA/PomB complex was eluted as approx. 900 kDa and PomB alone was eluted as approx. 260 kDa. These findings suggest that the motor complex may have a larger structure than previously assumed.
A putative transposase gene in the 16S–23S rRNA intergenic spacer region of Mycoplasma imitans
Authors: Harasawa Ryô , Pitcher David G. , Ramírez Ana S. , Bradbury Janet M.
Published: April 2004

Examination of the nucleotide sequences of the 16S–23S intergenic transcribed spacer (ITS) region ofMycoplasma imitansandMycoplasma gallisepticumidentified a putative transposase gene located only in the ITS ofM. imitans, which can be used as a genetic marker to distinguish these two species. The relative size of the PCR products of the ITS region allowed a clear distinction to be made between strains ofM. imitansandM. gallisepticum, both of which could be readily discriminated from the type strains of all the other recognized avianMycoplasmaspecies. In addition, the putative transposase gene assigned in the ITS ofM. imitanswas shown to include a sequence homologous to that of the P75 gene ofM. gallisepticum. This is believed to be the first description of an insertion element in the rRNA operon region of a mycoplasma species.
Independent regulation of chitin synthase and chitinase activity in Candida albicans and Saccharomyces cerevisiae
Authors: Selvaggini Serena , Munro Carol A. , Paschoud Serge , Sanglard Dominique , Gow Neil A. R.
Published: April 2004

Chitin is an essential structural polysaccharide in fungi that is required for cell shape and morphogenesis. One model for wall synthesis at the growing cell surface suggests that the compliance that is necessary for turgor-driven expansion of the cell wall involves a delicate balance of wall synthesis and lysis. Accordingly,de novochitin synthesis may involve coordinated regulation of members of theCHSchitin synthase andCHTchitinase gene families. To test this hypothesis, the chitin synthase and chitinase activities of cell-free extracts were measured, as well as the chitin content of cell walls isolated from isogenic mutant strains that contained single or multiple knock-outs in members of these two gene families, in bothCandida albicansandSaccharomyces cerevisiae. However, deletion of chitinase genes did not markedly affect specific chitin synthase activity, and deletion of singleCHSgenes had little effect onin vitrospecific chitinase activity in either fungus. Chitin synthesis and chitinase production was, however, regulated inC. albicansduring yeast–hypha morphogenesis. InC. albicans, the total specific activities of both chitin synthase and chitinase were higher in the hyphal form, which was attributable mainly to the activities of Chs2 and Cht3, respectively. It appeared, therefore, that chitin synthesis and hydrolysis were not coupled, but that both were regulated during yeast–hypha morphogenesis inC. albicans.
Effect of pyruvate kinase overproduction on glucose metabolism of Lactococcus lactis
Authors: Ramos Ana , Neves Ana Rute , Ventura Rita , Maycock Christopher , López Paloma , Santos Helena
Published: April 2004

Lactococcus lactisstrain NZ9000(pNZpyk), which overproduces pyruvate kinase (PK), was constructed. The pNZpykplasmid carries the PnisA–pyktranscriptional fusion, and the overexpression of itspykgene was accomplished by using the nisin-inducible expression system of the NZ9000 strain.In vivo13C- and31P-NMR spectroscopy was used to evaluate the effect of this modification on the metabolism of glucose in non-growing cells. A detailed description of the kinetics of glucose, end products, glycolytic intermediates, NAD+and NADH was obtained. A 15-fold increase in the level of PK did not increase the overall glycolytic flux, which, on the contrary, was slightly reduced. Significant differences were observed in (i) the level of 3-phosphoglycerate (3-PGA) and phosphoenolpyruvate (PEP), metabolites associated with starvation; (ii) the rate of fructose 1,6-bisphosphate (FBP) depletion upon glucose exhaustion; and (iii) the NAD+/NADH ratio during glucose catabolism. In the mutant, the rate of FBP consumption after glucose depletion was notably accelerated under anaerobic conditions, whereas 3-PGA and PEP decreased to undetectable levels. Furthermore, the level of NAD+decreased steadily during the utilization of glucose, probably due to the unanticipated reduction in the lactate dehydrogenase activity in comparison with the control strain, NZ9000(pNZ8020). The results show that PK is an important bottleneck to carbon flux only when glucose becomes limiting; in the overproducer this constriction was no longer present, as evidenced by the faster FBP consumption and lack of accumulation of 3-PGA and PEP in anaerobic as well as aerobic conditions. Despite these clear changes, the PK-overproducing strain showed typical homolactic metabolism under anaerobic conditions, as did the strain harbouring the vector plasmid without thepykinsert. However, under an oxygen atmosphere, there was increased channelling of carbon to the production of acetate and acetoin, to the detriment of lactate production.
Polyol accumulation by Aspergillus oryzae at low water activity in solid-state fermentation
Authors: Ruijter George J. G. , Visser Jaap , Rinzema Arjen
Published: April 2004

Polyol accumulation and metabolism were examined in Aspergillus oryzae cultured on whole wheat grains or on wheat dough as a model for solid-state culture. In solid-state fermentation (SSF), water activity (a
w) is typically low resulting in osmotic stress. In addition to a high level of mannitol, which is always present in the cells, A. oryzae accumulated high concentrations of glycerol, erythritol and arabitol at relatively low a
w (0·96–0·97) in SSF. Accumulation of such a mixture of polyols is rather unusual and might be typical for SSF. A. oryzae mycelium accumulating various polyols at low a
w contained at least four distinct polyol dehydrogenases with highest activities toward glycerol, erythritol, d-arabitol and mannitol. NADP+-dependent glycerol dehydrogenase activity correlated very well with glycerol accumulation. A similar correlation was observed for erythritol and NADP+–erythritol dehydrogenase suggesting that NADP+-dependent glycerol and erythritol dehydrogenases are involved in biosynthesis of glycerol and erythritol, respectively, and that these enzymes are induced by osmotic stress.