bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyclometallation Reactions in the Fe(dprpe)2 System [dprpe = 1,2-Bis(dipropylphosphino)ethane].
Authors: Baker Murray V. , Field Leslie D.
Published: December 2005

Thermal elimination of methane from
cis-FeH(CH3)(dprpe)2
[dprpe = 1,2-bis(dipropylphosphino)ethane] or photochemical
elimination of dihydrogen from
FeH2(dprpe)2 leads to the
formation of three cyclometallation products. The products are believed to
arise via a pathway in which the coordinatively unsaturated intermediate
Fe(dprpe)2 undergoes intramolecular activation of a
C–H bond of a dprpe methyl group. 1H and
31P n.m.r. spectroscopy were used to characterize the
products and explore the reactions leading to their formation.
Crystal Structure of Na9[H3W12O42]·24H2O, a Compound Containing the Protonated Paratungstate B Anion ('Acid Paratungstate'), and Cyclic Voltammetry of Acidified [H2W12O42]10- Solutions
Authors: Nolan Annette L. , Wilkes Eric N. , Hambley Trevor W. , Allen Christine C. , Burns Robert C. , Lawrance Geoffrey A.
Published: December 2005

Crystallization of a solid at pH 4.0 from an aqueous acidified
Rh3+–[WO4]2−
solution resulted in the isolation of
Na9[H3W12O42]·24H
2 O, which contains the protonated paratungstate B anion
and which is likely the species identified previously as ‘acid
paratungstate’. The compound is triclinic, space group
P1– ,
a 10.603(2), b 12.134(3),
c 14.042(3) Å, α 114.78(1), β 101.84(1),
γ 108.34(1)˚, V 1432.9(5)
Å3 , Z 1, and the structure
was solved to an R1 value of
0.0404 (wR 2 0.1108) for 5997
independent observed reflections. The anion exhibits essentially the same
isopolytungstate framework as paratungstate B,
[H2W12O42]10−
, consisting of two W3O13 and two
W3O14 structural subunits linked
by shared vertices. Bond valence arguments place two of the hydrogen atoms
unequivocally in the internal cavity of the anion, with the remaining hydrogen
atom also likely located in this cavity, but disordered over several internal
oxygen atoms. The protonation of
[H2W12O42
]10− is shown to lead to species that are
electrochemically reducible. Extended-HÜckel molecular orbital
calculations confirm that protonation of paratungstate B within the internal
cavity leads to a change in composition of the LUMO, now based mainly on
electrochemically reducible W3O13
as opposed to (essentially) non-reducible
W3O14 structural subunits. This
results in species that are considerably more electrochemically active than
the unprotonated anion. The role of
[H3W12O42]9−
as an intermediate in the polymerization of
[WO4]2− to give
the solution form of ψ-metatungstate,
[H7W11O40]7−
, which crystallizes as
[H4W11O38]6−
, is also discussed.
Synthesis of Hallachrome
Authors: Cameron Donald W. , Coller D. Ross , McDonald Clinton A.
Published: December 2005

Hallachrome (1), the only known example of a naturally occurring
1,2-anthraquinone, has been synthesized by successive cycloadditions involving
the dienophile (8) with the dienes (7) and (12). Synthetic intermediates (18)
and (6) are known derivatives of natural
hallachrome.
Formation by SRN1 Reactions and 1H N.M.R. Properties of Sterically Encumbered 2,4,6-Trialkylphenyl p-Nitrobenzyl Sulfides.
Authors: Look Kai , Norris Robert K.
Published: December 2005

Sterically hindered p-nitrobenzylic chlorides (1) and
(2) react with the sodium salts of 2,4,6-trialkylbenzenethiols (3a)–(5a)
by the SRN1 reaction to give good yields of the
corresponding p-nitrobenzylic aryl sulfides
(6)–(10). For example, the reaction of sodium
2,4,6-triisopropylbenzenethiolate (4b) with
α-t-butyl-a-methyl-p-nitrobenzyl chloride (2)
gives the sulfide (10) in over 80% yield after 2 h at room temperature
in Me2SO. Only in reactions involving
2,4,6-tri-t-butylbenzenethiol (5a) are low yields or failed reactions
encountered. Qualitative examination of the dynamic nuclear magnetic resonance
spectra of the sulfides prepared in these reactions shows that up to three
restricted rotational phenomena can be identified. These are rotation about
the benzylic-carbon to p-nitrophenyl ring bond, rotation
about the sulfur to aromatic ring bond, and rotation about the bond joining
the t-butyl group to the benzylic carbon. The last phenomenon produces, in the
sulfide (9), the relatively rare and unusual situation wherein the t-butyl
group appears as three distinct methyl resonances at low temperatures.
Regioselective Synthesis of O-Methyl Derivatives of the Trihydroxy Anthraquinones Morindone and Nataloe-Emodin
Authors: Cameron Donald W. , Coller D. Ross
Published: December 2005

Cycloaddition chemistry of dichloronaphthoquinones has led to regioselective
syntheses of all regioisomeric α-O- methyl
derivatives of morindone (2) and nataloe-emodin (4), including the natural
anthraquinone ethers (1) and (3).
Rodney W. Rickards
Authors: Cameron D. W.
Published: December 2005

… outstanding achievements in bioorganic chemistry …
Synthesis of New Components for Tethered Bilayer Membranes and Preliminary Surface Characterization.
Authors: J.Burns Christopher , Field Leslie D. , Culshaw Peter , Islam Mohammed , Ridley Damon D. , Morgan Jacqueline , Raguse Burkhard , Wieczorek Lech , Wilkinson Matthew , Vignevich Valentina
Published: December 2005

Two analogues of the membrane-forming species
PhCH2SS(C24H40O14)(C20H41)
(1) have been prepared via short synthetic routes. The compounds readily form
self-assembled monolayers on gold.
PhCH2SS(C27H45O16)(C20H41)2
PhCH2SS(C29H48O17)(C20H41)3
The influence of grazing management on the competitiveness, persistence and productivity of chicory (Cichorium intybus L.)
Authors: Alemseged Y. , Kemp D. R. , King G. W. , Michalk D. L. , Goodacre M.
Published: December 2005

Chicory is a highly productive and nutritious forage that is sensitive to grazing. A challenge for grazing management is to prevent pasture decline associated with the replacement of productive species by undesirable weedy species. The competitive ability, persistence and productivity of chicory were investigated under a gradient of grazing management practices ranging from continuous to short grazing–long rest treatments by merino wethers. Chicory density and percentage composition declined after the first year of continuous grazing. The density of chicory in all rotationally grazed treatments initially increased and then declined significantly after the third year, except in the short grazing–long rest treatment. The percentage composition of chicory in the pasture was influenced mainly by the frequency of grazing and to a lesser extent by stand age and was inversely related to the combined percentage composition of annual grasses and broadleaf species. The percentage composition of legumes was dependent more on seasonal conditions than on treatment. The interactions between chicory, grasses and broadleaf weeds are most probably driven by their competition for nitrogen.
Biogenic amines in Australian animal by-product meals
Authors: Brinker C. A. den , Rayner C. J. , Kerr M. G. , Bryden W. L.
Published: December 2005

Biogenic amines were determined in Australian by-product meals including fish meals, poultry meals, meat meals, feather meals and blood meals. They were extracted with 0.1 mol/L HCl, derivatised with dansyl chloride and analysed using HPLC with UV detection at 254 nm. Median levels of putrescine, cadaverine and histamine were determined in the by-product meals, with the range being 13–102 mg/kg, 7–220 mg/kg and 4–570�mg/kg, respectively. High levels of biogenic amines were found particularly in fish meals. The results indicate that further studies are required to determine the maximum limits for biogenic amines in by-product meals that will not impair production when fed to poultry.
The Sustainable Grazing Systems Program: new solutions for livestock producers
Authors: Mason W. K. , Lamb K. , Russell B.
Published: December 2005

The Sustainable Grazing Systems (SGS) Program was established in 1996 to address the issues of declining pasture productivity and sustainability in the high rainfall zone (>600 mm/year) of southern Australia. The program goal was that 'by June 2001, at least 2000 producers in the high rainfall zone will have adopted changes to their grazing systems that can be shown to be at least 10% more profitable, and more sustainable, than those used prior to participating in SGS. A further 5000 producers will have trialed at least part of the recommended changes'. There were 4 interacting activities within SGS, collectively focused on delivering this goal. These were: (i)�a National Experiment to develop the principles and quantify the relationships; (ii) a regional producer network to determine and deliver on local producer priorities; (iii) training and skills development courses; and (iv) integration and management to ensure the goal was met in an efficient and effective manner. Producer input and ownership were considered essential and were built in at all levels of program activity and management. Independent surveys confirmed that SGS assisted large numbers of producers to make substantial change in farm practices. SGS met its goal by developing and delivering knowledge about more profitable and sustainable grazing systems to a network of almost 10 000 livestock producers across southern Australia. Critical elements of SGS included research, skills training and support for producer groups, on-farm trials and demonstrations, and farm-walks for producers to share information and experiences. A 'triple bottom line' approach was adopted to assess and report on the impacts of the program on the financial, social and environmental capital of the grazing industries in the high rainfall zone. In keeping with the triple bottom line approach, this special edition contains papers that report on biophysical, economic, environmental and social aspects of the program.
The SGS Regional Producer Network: a successful application of interactive participation
Authors: Simpson I. H. , Kay G. , Mason W. K.
Published: December 2005

The Regional Producer Network (RPN) functioned across southern Australia as the primary delivery mechanism of the Sustainable Grazing Systems (SGS) Program for 5 years (1996–2001) and the Harvest Year (2001–2002). It consisted of a network of Producer Committees that provided on-ground organisation to coordinate extension activities in the 11 SGS regions. The operation of the RPN was modelled on a participation mode called Interactive Participation. The main objective was to support the adoption of a large-scale practice change in the high rainfall zone towards more productive, profitable and sustainable grazing systems. Strong producer leadership developed and information exchange improved to achieve a high level of impact on management skills among those producers motivated to improve their grazing operations. The characteristics of Interactive Participation were incorporated into the processes and operation of the RPN. Defined and structured methodologies were used for collective and context-specific learning within the framework of a producer network that encouraged interaction. The strength of Interactive Participation was that producers saw participation as a right and not just a means to achieve the program goal. Each region took control over local decisions including the allocation of available resources. The process engaged all sectors of the program (producers, researchers, management and funders). The experiential extension procedures used systematic and structured learning activities to support producers who were committed to learning, on-farm change and improvement to grazing management. In developing a coordinated approach to their operation, the Producer Committees engaged grazing industry researchers, public and private extension practitioners and community groups. This collaboration strengthened local organisations and developed community confidence in the grazing industries.
A practical framework to evaluate and report combined natural resource and production outcomes of agricultural research to livestock producers
Authors: Barlow R. , Ellis N. J. S. , Mason W. K.
Published: December 2005

The specifications for this study were set by the need for researchers in the Sustainable Grazing Systems (SGS) Program to have a consistent framework to evaluate experimental results across research sites and to share those results in a comprehensive way with livestock producers, allowing them to consider the full range of outcomes and impacts. To achieve this, the framework needed to account for production, economic and natural resource impacts, and other issues associated with making changes on farms. It also had to be easily applied, and readily understood by all segments of the SGS Program. This approach demanded some elements of pragmatism. Economic analysis of production data was based around net cash flow analysis. Spreadsheet programs were written for beef, self-replacing Merino and prime lamb enterprises. These incorporated the capacity to graph results automatically, provide sensitivity analysis tables, and project net cash flow results averaged over a 10-year period. Net cash flows were given for 2 levels of management skills — 'district average' and 'high'. Placing dollar values or costs on resource impacts was not as simple and could not be achieved within the practical framework required. A qualitative approach to the evaluation of resource impacts was developed in collaboration with researchers, advisors and collaborating producers. A framework was constructed which allows the likely on- and off-farm impacts of any experimental treatments to be identified and subjectively rated for likely importance.A practical tool for integrating and reporting the production and resource impact information was constructed. This captures the net cash flow, the key production data, the off-farm and on-farm impacts and provides an overview assessment of the treatment in a simple table. It provides producers with sufficient information to allow an assessment as to whether adoption of any 'treatment' could improve the profitability and sustainability of their grazing system. This tool was tested across all treatments at the SGS National Experiment sites and found to work well. Examples are presented, covering a range of resource impact and net cash flow combinations.
Fertiliser and grazing effects on production and botanical composition ofnative grasslands in south-east Australia
Authors: Garden D. L. , Ellis N. J. S. , Rab M. A. , Langford C. M. , Johnston W. H. , Shields C. , Murphy T. , Holmberg M. , Dassanayake K. B. , Harden S.
Published: December 2005

The effects of application of superphosphate and grazing on production and botanical composition of native grasslands were investigated at 3 locations in the high rainfall zone of south-east Australia. These studies were conducted as part of the Sustainable Grazing Systems Key Program, which investigated various aspects of grassland productivity and sustainability between 1996 and 2001. Grasslands in this study either had high contents of Themeda australis or Austrodanthonia spp., or were based on a degraded Austrodanthonia spp. grassland with a high content of annual and weedy species. All sites used increasing levels of superphosphate application (nil, low, medium and high) as treatments, with clover being added in some treatments at 1 site, and herbicide in 1 treatment at another site. Grazing (sheep) was continuous at 1 site (with stocking rates matched to pasture productivity) and intermittent at other sites, with grazing being dictated by available herbage between defined trigger points. Climate was monitored and changes in soil P, herbage mass, botanical composition, ground cover and sheep production recorded. Changes in composition resulting from the treatments varied between sites. At the continuously grazed Austrodanthonia spp. site, there was a decline in native perennial grasses throughout the experiment and an increase in exotic annual grasses in spring where superphosphate was applied. The grassland at the T. australis site remained relatively stable, which may have been due to the limited amount of grazing applied. The degraded Austrodanthonia�spp. grassland showed wide seasonal fluctuations in annual species. There were no clear effects of treatments at the latter 2 sites. Sheep production increased with increased superphosphate application at the continuously grazed Austrodanthonia spp. site, but there was little effect at the other 2 sites. Recommendations are made for sustainable management of native grasslands depending on their current botanical state.
The relationship between management practices and estimated weight for age of Friesian heifers in north-eastern New South Wales
Authors: Spence S. A. , Spence S. A. , Woodhead A. C. , Woodhead A. C.
Published: December 2005

The weight of 2659 Friesian heifers was
measured electronically on 41 farms in north-eastern New South Wales during
autumn 1992. The 41 producers involved were surveyed on their heifer
management practices. The relationship between liveweight and age was
determined from these measurements. This provided a base line against which
improvement in heifer weight for age could be measured subsequent to a planned
extension program. In 1992, 2 management practices were found to be associated
with significantly higher weights for age. These were feeding more than 1 kg
of concentrate to heifers prior to weaning and grazing heifers on fertilised
pasture between weaning and 12 months of age. An extension program promoting
improved heifer management was conducted, using adult learning principles,
from 1992 until 1995. Nineteen of the 41 farms were revisited in winter 1997
when the heifers were again measured and management practices surveyed. Heifer
weight for age had increased by a small but significant amount between 1992
and 1997. Management changes which occurred between 1992 and 1997 were:
increased vaccination rates; decreased use of antibiotic injections for
treating calf illnesses; increase in feeding over 1 kg of concentrate per day
to preweaned heifers; and increased use of silage to feed weaned heifers.
There was also a decreased percentage of producers who considered calf
diseases to be a problem. Between 1992 and 1995, 14 farmers began monitoring
their heifers regularly, either by measuring weight electronically or by using
a weigh tape.
Influence of pasture type and supplement on fertility and liveweight of cows, and progeny growth rate in the dry tropics of northern Queensland
Authors: Holroyd RG , O'Rourke PK , Clarke MR , Loxton ID
Published: December 2005

The reproductive performance of cows and growth rate of their calves to weaning was examined over a four-year period (1973-1977). Cows grazed either native pasture stocked at 1cowl4 ha, or native pasture oversown with Townsville stylo (Stylosanthes humilis) and fertilized with superphosphate stocked at 1 cow/2 ha. Animals were supplemented on each pasture type with urea-molasses in the dry season, phosphorus all year round plus urea-molasses in the dry season, or were unsupplemented. Mating was for three months from mid-January. Calving began towards the end of the dry season and cows lactated through the following wet season. Cows grazing fertilized legume pasture had significantly higher conception rates and earlier calving dates in one year only. In all years, foetal and calf losses between pregnancy diagnosis and weaning were lower on native pasture than on fertilized legume pasture. Cows grazing fertilized legume pasture were generally in better body condition and heavier throughout and their calves grew faster to weaning than on native pasture. Fertilized legume pasture produced a 2.4 fold increase over that of native pasture in cow and calf liveweight per unit area (382.7 kg/ha vs 159.8 kg/ha) over the four years. Supplementation did not influence liveweight or reproductive performance of cows or calf growth rate except during the final dry season when non-supplemented cows lost significantly more weight than those supplemented with phosphorus and urea.
Control of Amsinckia hispida and Juncus bufonius (toadrush) with herbicides
Authors: Pratley JE
Published: December 2005

The control by herbicides of an infestation of Amsinckia hispida and toadrush (Juncus bufonius) in wheat was investigated at Wagga Wagga, New South Wales, during 1979 and 1980. Bromoxynil, bromoxynil+MCPA, terbutryne and methabenzthiazuron+2,4-D were used in both years, dicamba+MCPA in 1979, and dicamba and experimental herbicide DPX4189 (GleanTM�) in 1980. All herbicides reduced weed densities and improved crop yields. Terbutryne gave greatest control of weed populations, in excess of 98% in both years. Grain yield was more than doubled in each case. GleanTM produced the highest grain yield in 1980 although weed control was not as good as from some other herbicides. However, the undersown pasture legumes, particularly subterranean clover, had poorer survival from this herbicide. Dicamba and dicamba+MCPA were inferior to the other chemicals in the control of these weeds.
Development of a hemp ( Cannabis sativa L.) simulation model 3. The effect of plant density on leaf appearance, expansion and senescence
Authors: Lisson S. N. , Mendham N. J. , Carberry P. S.
Published: December 2005

The accurate prediction of leaf area production
is an important element of many crop models, given that it is the key
determinant of light interception and the accumulation of plant biomass. Plant
density has been reported to have a significant influence on the component
processes of leaf area production in hemp. This study investigates the
response to plant density of leaf (node) appearance, leaf expansion at each
node and leaf senescence, and develops relationships for use in the hemp model
described in the final paper of this series.
Green and senesced node counts were made at regular intervals in a plant
density trial for treatments of 50, 80, 120, 200 and 300
plants/m2. Measurements were also made of the fully
expanded leaf area at each node. Leaf pairs were found to appear and senesce
at constant thermal time durations; between 84 and 97˚Cd for node
production, and between 130 and 167˚Cd for node senescence. Leaf area per
node at first increased linearly with node number, then reached a plateau, and
subsequently declined linearly. Increases in plant density resulted in slower
rates of node production and reduced the maximum leaf area per node.
Permeance to oxygen of detached Capsicum annuum fruit
Authors: Bower J. , Patterson B. D. , Jobling J. J.
Published: December 2005

The internal oxygen concentration and rate of
oxygen consumption of detached capsicum fruits
(Capsicum annuum L.) were monitored over several days.
From this their overall permeance to oxygen was calculated. When wax was
applied to the pedicel and its scar, permeance was reduced by
80–90%, indicating that most gas exchange occurred through this
area. Readings from O2 sensors attached to the skins of
the fruits were compared to those from O2 sensors
inserted into the fruit cavity. These indicated that the cuticle was the major
barrier to gas diffusion and that there was a concentration gradient through
the capsicum flesh. Permeance of the cuticle was found to be about 0.64 x
10–4 mol
O2/Pa.m2.s, while permeance to
CO2 was 2–3 times higher. This suggests that the
cuticle is composed of a coherent film. The low rate of gas diffusion through
capsicum cuticle may allow recycling of respired CO2 by
photosynthesis in the flesh before harvest.
PDSM, a motif for phosphorylation-dependent SUMO modification
Authors: Hietakangas Ville , Anckar Julius , Blomster Henri A. , Fujimoto Mitsuaki , Palvimo Jorma J. , Nakai Akira , Sistonen Lea
Published: December 2005

SUMO (small ubiquitin-like modifier) modification regulates many cellular processes, including transcription. Although sumoylation often occurs on specific lysines within the consensus tetrapeptide ΨKxE, other modifications, such as phosphorylation, may regulate the sumoylation of a substrate. We have discovered PDSM (phosphorylation-dependent sumoylation motif), composed of a SUMO consensus site and an adjacent proline-directed phosphorylation site (ΨKxExxSP). The highly conserved motif regulates phosphorylation-dependent sumoylation of multiple substrates, such as heat-shock factors (HSFs), GATA-1, and myocyte enhancer factor 2. In fact, the majority of the PDSM-containing proteins are transcriptional regulators. Within the HSF family, PDSM is conserved between two functionally distinct members, HSF1 and HSF4b, whose transactivation capacities are repressed through the phosphorylation-dependent sumoylation. As the first recurrent sumoylation determinant beyond the consensus tetrapeptide, the PDSM provides a valuable tool in predicting new SUMO substrates.
Toll-like receptor (TLR) polymorphisms in African children: CommonTLR-4variants predispose to severe malaria
Authors: Mockenhaupt Frank P. , Cramer Jakob P. , Hamann Lutz , Stegemann Miriam S. , Eckert Jana , Oh Na-Ri , Otchwemah Rowland N. , Dietz Ekkehart , Ehrhardt Stephan , Schröder Nicolas W. J. , Bienzle Ulrich , Schumann Ralf R.
Published: December 2005

Genetic host factors play a substantial role in susceptibility to and severity of malaria, which continues to cause at least one million deaths per year. Recently, members of the toll-like receptor (TLR) family have been shown to be involved in recognition of the etiologic organismPlasmodium falciparum: The glycosylphosphatidylinositol anchor induces signaling in host cells via TLR-2 and -4, whereas hemozoin-induced immune activation involves TLR-9. Binding of microbial ligands to the respective TLRs triggers the release of proinflammatory cytokines via the TLR/IL-1 receptor (TIR) domain and may contribute to the host response in malaria, including cytokine induction and fever. In a case-control study among 870 Ghanaian children, we examined the influence ofTLR-2,-4, and-9polymorphisms in susceptibility to severe malaria.TLR-2variants common in Caucasians and Asians were completely absent. However, we found a rare previously undescribed mutation (Leu658Pro), which impairs signaling via TLR-2. We failed to detect any polymorphisms within the TLR-9 Toll/IL-1 receptor domain. Two frequentTLR-9promoter polymorphisms did not show a clear association with malaria severity. In contrast, theTLR-4-Asp299Gly variant occurred at a high rate of 17.6% in healthy controls and was even more frequent in severe malaria patients (24.1%,P< 0.05). Likewise,TLR-4-Thr399Ile was seen in 2.4% of healthy children and in 6.2% of patients (P= 0.02).TLR-4-Asp299Gly andTLR-4-Thr399Ile conferred 1.5- and 2.6-fold increased risks of severe malaria, respectively. These findings suggest TLR4-mediated responses to malariain vivoandTLR-4polymorphisms to be associated with disease manifestation.
Two independent mechanical events in the interaction cycle of skeletal muscle myosin with actin
Authors: Capitanio M. , Canepari M. , Cacciafesta P. , Lombardi V. , Cicchi R. , Maffei M. , Pavone F. S. , Bottinelli R.
Published: December 2005

During skeletal muscle contraction, regular arrays of actin and myosin filaments slide past each other driven by the cyclic ATP-dependent interaction of the motor protein myosin II (the cross-bridge) with actin. The rate of the cross-bridge cycle and its load-dependence, defining shortening velocity and energy consumption at the molecular level, vary widely among different isoforms of myosin II. However, the underlying mechanisms remain poorly understood. We have addressed this question by applying a single-molecule approach to rapidly (≈300 μs) and precisely (≈0.1 nm) detect acto-myosin interactions of two myosin isoforms having large differences in shortening velocity. We show that skeletal myosin propels actin filaments, performing its conformational change (working stroke) in two steps. The first step (≈3.4–5.2 nm) occurs immediately after myosin binding and is followed by a smaller step (≈1.0–1.3 nm), which occurs much faster in the fast myosin isoform than in the slow one, independently of ATP concentration. On the other hand, the rate of the second phase of the working stroke, from development of the latter step to dissociation of the acto-myosin complex, is very similar in the two isoforms and depends linearly on ATP concentration. The finding of a second mechanical event in the working stroke of skeletal muscle myosin provides the molecular basis for a simple model of actomyosin interaction. This model can account for the variation, in different fiber types, of the rate of the cross-bridge cycle and provides a common scheme for the chemo-mechanical transduction within the myosin family.
A gradient of auxin and auxin-dependent transcription precedes tropic growth responses
Authors: Esmon C. Alex , Tinsley Amanda G. , Ljung Karin , Sandberg Goran , Hearne Leonard B. , Liscum Emmanuel
Published: December 2005

Plants, although sessile, can reorient growth axes in response to changing environmental conditions. Phototropism and gravitropism represent adaptive growth responses induced by changes in light direction and growth axis orientation relative to gravitational direction, respectively. The nearly 80-year-old Cholodny–Went theory [Went, F. W. & Thimann, K. V. (1937)
Phytohormones
(Macmillan, New York)] predicts that formation of a gradient of the plant morphogen auxin is central to the establishment of tropic curvature. Loss of tropic responses in seedling stems of
Arabidopsis thaliana
mutants lacking the auxin-regulated transcriptional activator NPH4/ARF7 has further suggested that a gradient of gene expression represents an essential output from the auxin gradient. Yet the molecular identities of such output components, which are likely to encode proteins directly involved in growth control, have remained elusive. Here we report the discovery of a suite of tropic stimulus-induced genes in
Brassica oleracea
that are responsive to an auxin gradient and exhibit morphologically graded expression concomitant with, or before, observable curvature responses. These results provide compelling molecular support for the Cholodny–Went theory and suggest that morphologically graded transcription represents an important mechanism for interpreting tropically stimulated gradients of auxin. Intriguingly, two of the tropic stimulus-induced genes,
EXPA1
and
EXPA8
, encode enzymes involved in cell wall extension, a response prerequisite for differential growth leading to curvatures, and are up-regulated before curvature in the flank that will elongate. This observation suggests that morphologically graded transcription likely leads to the graded expression of proteins whose activities can directly regulate the establishment and modulation of tropic curvatures.
Inhibitory control by an integral feedback signal in prefrontal cortex: A model of discrimination between sequential stimuli
Authors: Miller Paul , Wang Xiao-Jing
Published: December 2005

The prefrontal cortex (PFC) is known to be critical for inhibitory control of behavior, but the underlying mechanisms are unclear. Here, we propose that inhibitory control can be instantiated by an integral signal derived from working memory, another key function of the PFC. Specifically, we assume that an integrator converts excitatory input into a graded mnemonic activity that provides an inhibitory signal (integral feedback control) to upstream afferent neurons. We demonstrate this scenario in a neuronal-network model for a temporal discrimination task. The task requires the working memory of the vibrational frequency (f1) of an initial stimulus (stimulus 1), followed by comparison of the frequency (f2) of a second stimulus (stimulus 2) with the stored f1 and a binary decision (f2 > f1 or f2 < f1). The integral feedback signal generated by stimulus 1 gates the later inputs based on the amplitude difference (f2 – f1). The feedback control signal enables a subset of neurons to reverse their tuning to f1 between stimulus 1 and stimulus 2, when they become tuned to the difference, f2 – f1. These neurons maintain a lower firing rate during the delay compared with their peak rate during stimulus 1. A second subset of neurons, tuned to f1 during the delay, reaches a rate during stimulus 2 that depends on the maximum of f1 and f2. Our work suggests a circuit mechanism for discrimination across time and predicts neuronal behavior that can be tested experimentally.
Global landscape of recent inferred Darwinian selection for
Homo sapiens
Authors: Wang Eric T. , Kodama Greg , Baldi Pierre , Moyzis Robert K.
Published: December 2005

By using the 1.6 million single-nucleotide polymorphism (SNP) genotype data set from Perlegen Sciences [Hinds, D. A., Stuve, L. L., Nilsen, G. B., Halperin, E., Eskin, E., Ballinger, D. G., Frazer, K. A. & Cox, D. R. (2005)
Science
307, 1072–1079], a probabilistic search for the landscape exhibited by positive Darwinian selection was conducted. By sorting each high-frequency allele by homozygosity, we search for the expected decay of adjacent SNP linkage disequilibrium (LD) at recently selected alleles, eliminating the need for inferring haplotype. We designate this approach the LD decay (LDD) test. By these criteria, 1.6% of Perlegen SNPs were found to exhibit the genetic architecture of selection. These results were confirmed on an independently generated data set of 1.0 million SNP genotypes (International Human Haplotype Map Phase I freeze). Simulation studies indicate that the LDD test, at the megabase scale used, effectively distinguishes selection from other causes of extensive LD, such as inversions, population bottlenecks, and admixture. The ≈1,800 genes identified by the LDD test were clustered according to Gene Ontology (GO) categories. Based on overrepresentation analysis, several predominant biological themes are common in these selected alleles, including host–pathogen interactions, reproduction, DNA metabolism/cell cycle, protein metabolism, and neuronal function.
CYP27B1 null mice with
LacZ
reporter gene display no 25-hydroxyvitamin D
3
-1α-hydroxylase promoter activity in the skin
Authors: Vanhooke Janeen L. , Prahl Jean M. , Kimmel-Jehan Christine , Mendelsohn Monica , Danielson Eric W. , Healy Kevin D. , DeLuca Hector F.
Published: December 2005

The hormonally active form of vitamin D
3
,1α,25-dihydroxyvitamin D
3
[1,25(OH)
2
D
3
], is synthesized in the kidney through a tightly regulated reaction catalyzed by 25-hydroxyvitamin D
3
-1α-hydroxylase (1α-hydroxylase), the product of the
CYP27B1
gene. Through gene targeting in embryonic stem cells, we engineered a mouse strain in which the coding region of the 1α-hydroxylase gene is replaced by the genes for β-galactosidase (
lacZ
) and neomycin resistance. Null mice produced no detectable 1α-hydroxylase transcript. The mice grew normally when maintained on a balanced diet containing 1,25(OH)
2
D
3
but rapidly developed rickets when phosphorus and 1,25(OH)
2
D
3
were restricted. Rickets was curable through administration of 1,25(OH)
2
D
3
but not its biological precursor, 25-hydroxyvitamin D
3
. Upon administration of a diet low in calcium and devoid of any form of vitamin D
3
, β-galactosidase activity was detected in the kidneys of the –/– and +/– mice and in placentas harvested from –/– females bred with –/– males. No β-galactosidase activity was detected in skin sections or in primary keratinocyte cultures from –/– animals. Our results demonstrate we have generated 1α-hydroxylase null mice that display phenotypes characteristic of vitamin D-dependency rickets type I. From the histochemical analysis of reporter gene expression in these mice, we conclude that acute 1,25(OH)
2
D
3
deficiency in otherwise healthy animals does not stimulate local production of 1,25(OH)
2
D
3
in the skin. These findings stand in contrast to previously published reports of 1,25(OH)
2
D
3
production in keratinocytes.
Incentives improve performance on both incremental and insight problem solving
Authors: Wieth Mareike , Burns Bruce D.
Published: December 2005

An increasing number of studies are showing a connection between emotion and motivation and cognitive processes. Most of these studies, however, have been correlational in nature, limiting the conclusions that can be drawn. We directly manipulated motivation through the use of an incentive and investigated its effects on insight and incremental problem solving. In four experiments we found that an incentive (the opportunity to leave the experiment early) increased problem-solving performance for all problems presented, regardless of problem type. Additionally, we found evidence that the incentive increased recall memory, indicating more thorough processing for participants in the incentive condition. This study provides evidence that incentives influence problem solving and implies that motivation should not be ignored when investigating cognitive processes.
Finger–digit compatibility in Arabic numeral processing
Authors: Di Luca Samuel , Granà Alessia , Semenza Carlo , Seron Xavier , Pesenti Mauro
Published: December 2005

Finger–digit response compatibility was tested by asking participants to identify Arabic digits by pressing 1 of 10 keys with all 10 fingers. The direction of the finger–digit mapping was varied by manipulating the global direction of the hand–digit mapping as well as the direction of the finger–digit mapping within each hand (in each case, from small to large digits, or the reverse). The hypothesis of a left-to-right mental number line predicted that a complete left-to-right mapping should be easier whereas the hypothesis of a representation based on finger counting predicted that a counting-congruent mapping should be easier. The results show that when all 10 fingers are used to answer, a mapping congruent with the prototypical finger-counting strategy reported by the participants leads to better performance than does a mapping congruent with a left-to-right oriented mental number line, both in palm-down and palm-up postures of the hands, and they demonstrate that finger-counting strategies influence the way that numerical information is mentally represented and processed.
How long does it take to find a cause? An online investigation of implicit causality in sentence production
Authors: Guerry Michèle , Gimenes Manuel , Caplan David , Rigalleau François
Published: December 2005

Some interpersonal verbs show an implicit causality bias in favour of their subject or their object. Such a bias is generally seen in offline continuation tasks where participants are required to finish a fragment containing the verb (e.g., Peter annoyed Jane because …). The implicit causality bias has been ascribed to the subject's focusing on the initiator of the event denoted by the verb. According to this “focusing theory” the implicit cause has a higher level of activation, at least after the connective “because” has been read. Recently, the focusing theory has been criticized by researchers who used a probe recognition or reading-time methodology. However no clear alternative has been proposed to explain the offline continuation data. In this paper, we report three experiments using an online continuation task, which showed that subjects took more time to imagine an ending when the fragment to be completed contained an anaphor that was incongruent with the verbal bias (e.g., Peter annoyed Jane because she …). This result suggests that the offline continuation data could reflect the cognitive effort associated with finding a predicate with an agent incongruent with the implicit causality bias of a verb. In the discussion, we suggest that this effort could be related to the number of constraints that an incongruent clause must satisfy to be consistent with the causal structure of the discourse.
Microtubule Regulation in Mitosis: Tubulin Phosphorylation by the Cyclin-dependent Kinase Cdk1
Authors: Fourest-Lieuvin Anne , Peris Leticia , Gache Vincent , Garcia-Saez Isabel , Juillan-Binard Céline , Lantez Violaine , Job Didier
Published: December 2005

The activation of the cyclin-depdndent kinase Cdk1 at the transition from interphase to mitosis induces important changes in microtubule dynamics. Cdk1 phosphorylates a number of microtubule- or tubulin-binding proteins but, hitherto, tubulin itself has not been detected as a Cdk1 substrate. Here we show that Cdk1 phosphorylates β-tubulin both in vitro and in vivo. Phosphorylation occurs on Ser172 of β-tubulin, a site that is well conserved in evolution. Using a phosphopeptide antibody, we find that a fraction of the cell tubulin is phosphorylated during mitosis, and this tubulin phosphorylation is inhibited by the Cdk1 inhibitor roscovitine. In mitotic cells, phosphorylated tubulin is excluded from microtubules, being present in the soluble tubulin fraction. Consistent with this distribution in cells, the incorporation of Cdk1-phosphorylated tubulin into growing microtubules is impaired in vitro. Additionally, EGFP-β3-tubulinS172D/Emutants that mimic phosphorylated tubulin are unable to incorporate into microtubules when expressed in cells. Modeling shows that the presence of a phosphoserine at position 172 may impair both GTP binding to β-tubulin and interactions between tubulin dimers. These data indicate that phosphorylation of tubulin by Cdk1 could be involved in the regulation of microtubule dynamics during mitosis.
Balance between Transcription and RNA Degradation Is Vital forSaccharomyces cerevisiaeMitochondria: Reduced Transcription Rescues the Phenotype of Deficient RNA Degradation
Authors: Rogowska Agata T. , Puchta Olga , Czarnecka Anna M. , Kaniak Aneta , Stepien Piotr P. , Golik Pawel
Published: December 2005

The Saccharomyces cerevisiae SUV3 gene encodes the helicase component of the mitochondrial degradosome (mtEXO), the principal 3′-to-5′ exoribonuclease of yeast mitochondria responsible for RNA turnover and surveillance. Inactivation of SUV3 (suv3Δ) causes multiple defects related to overaccumulation of aberrant transcripts and precursors, leading to a disruption of mitochondrial gene expression and loss of respiratory function. We isolated spontaneous suppressors that partially restore mitochondrial function in suv3Δ strains devoid of mitochondrial introns and found that they correspond to partial loss-of-function mutations in genes encoding the two subunits of the mitochondrial RNA polymerase (Rpo41p and Mtf1p) that severely reduce the transcription rate in mitochondria. These results show that reducing the transcription rate rescues defects in RNA turnover and demonstrates directly the vital importance of maintaining the balance between RNA synthesis and degradation.
Involvement of Src Family Kinases in N-Cadherin Phosphorylation and β-Catenin Dissociation during Transendothelial Migration of Melanoma Cells
Authors: Qi Jianfei , Wang Junfu , Romanyuk Olena , Siu Chi-Hung
Published: December 2005

N-cadherin is recruited to the heterotypic contact during transendothelial migration of melanoma cells in a coculture system with tumor cells seeded on top of a monolayer of endothelial cells. However, β-catenin dissociates from N-cadherin and redistributes to the nucleus of transmigrating melanoma cells to activate gene transcription. In this report, we demonstrate that Src becomes activated at the heterotypic contact between the transmigrating melanoma cell and neighboring endothelial cells. Src activation shows close temporal correlation with tyrosine phosphorylation of N-cadherin. Expression of a dominant-negative Src in melanoma cells blocks N-cadherin phosphorylation, β-catenin dissociation, and nuclear translocation in transmigrating cells, consistent with the involvement of Src family kinases. In in vitro binding assays, Src-mediated phosphorylation of the N-cadherin cytoplasmic domain results in a significant reduction in β-catenin binding. Although five phospho-tyrosine residues can be identified on the N-cadherin cytoplasmic domain by mass spectrometry, site-specific mutagenesis indicates that Tyr-860 is the critical amino acid involved in β-catenin binding. Overexpression of N-cadherin carrying the Y860F mutation inhibits the transmigration of transfected cells across the endothelium. Together, the data suggest a novel role for tyrosine phosphorylation of N-cadherin by Src family kinases in the regulation of β-catenin association during transendothelial migration of melanoma cells.
HAS EUROPEAN ECONOMIC INTEGRATION AFFECTED THE FUNCTIONAL COMPOSITION OF GOVERNMENT EXPENDITURES?
Authors: SANZ ISMAEL , VELÁZQUEZ FRANCISCO J.
Published: December 2005

Globalization and growth‐maximizing governments may cause countries to converge toward a similar composition of government expenditures. These convergent forces may be even more intensive in the case of EU member states engaged in the European integration process. The results obtained, through calculation of a constructed dissimilarity index and by adapting the usual indicators of convergence (β, σ, and γ), reveal that there has been a harmonization process. In addition, this approximation of the structures of government expenditures has been greater in the EU than in the non‐EU countries of the OECD. Nevertheless, EU member states are converging toward a different steady‐state composition of government expenditures. (JEL H11, H50, H60)
Why Did Semiconductor Price Indexes Fall So Fast in the 1990s? A Decomposition
Authors: Aizcorbe Ana
Published: December 2005

Price deflators for semiconductors fell rapidly over the 1990s, pulled down by steep declines in the deflator for the microprocessor (MPU) segment that accelerated around 1995. A decomposition of a price index for Intel's MPUs suggests that virtually all of the declines in the price index—and the acceleration—can be attributed to quality increases associated with product innovation, rather than declines in the cost per chip. The sizable decline in Intel's margins from 1993–99 only accounted for about 6 percentage points of the average 24% decline per quarter in the price index and cannot explain the acceleration. (JEL D42, L63, O47)
Maternal and Neonatal Effects of Remifentanil at Induction of General Anesthesia for Cesarean Delivery
Authors: Kee Warwick D. Ngan , Khaw Kim S. , Ma Kwok C. , Wong April S. Y. , Lee Bee B. , Ng Floria F.
Published: December 2005

Background

Use of remifentanil during general anesthesia for cesarean delivery has been described, but its maternal and neonatal effects have not been investigated by a controlled study.

Methods

In a randomized, double-blind, controlled study, patients undergoing elective cesarean delivery received an intravenous bolus of 1 microg/kg remifentanil (n = 20) or saline (n = 20) immediately before induction of general anesthesia. The authors compared maternal hemodynamic changes and neonatal condition and measured plasma concentrations of remifentanil.

Results

The maximum increase in systolic arterial pressure from baseline after induction was smaller in the remifentanil group (median, 9 [range, -17 to 31] mmHg) compared with the control group (42 [6-73] mmHg, median difference, 33 mmHg; 95% confidence interval of difference, 23-45 mmHg; P < 0.0001). Maximum recorded values were smaller in the remifentanil group compared with the control group for systolic and mean arterial pressure and maternal heart rate. Apgar scores and time to sustained respiration were similar between groups. Two neonates in the remifentanil group were considered clinically depressed at birth and were given a single dose of naloxone. Remifentanil crossed the placenta with an umbilical venous/maternal arterial concentration ratio of 0.73 (SD, 0.17) and an umbilical arterial/umbilical venous concentration ratio of 0.60 (0.23).

Conclusions

A single bolus of 1 microg/kg remifentanil effectively attenuated hemodynamic changes after induction and tracheal intubation. However, remifentanil crosses the placenta and may cause mild neonatal depression and thus should be used for clear maternal indications when adequate facilities for neonatal resuscitation are available.