bluuebunny/crossref_metadata_2025 huggingface dataset:
Amelioration and nutrient management strategies for sodic and alkali soils.
Authors: Qadir M. , Schubert S. , Badia D. , Sharma B. R. , Qureshi A. S. , Murtaza G.
Published: September 2007

Sodic and alkali soils are characterized by the occurrence of excess sodium (Na
+
) to levels that can adversely affect soil structure and disturb the availability of nutrients for plant growth. Structural problems in these soils are created by certain physical processes (slaking, swelling and dispersion of clay minerals) and specific conditions (surface crusting and hardsetting), which affect water and air movement, seedling emergence, root penetration, runoff and erosion, as well as tillage and sowing operations. Such changes ultimately impact choice of crops, and crop growth and yield, which are also affected by osmotic and ion-specific effects in these soils. Of the salt-affected soils worldwide, about 60% are sodic and alkali soils, warranting attention for efficient, inexpensive and environmentally feasible amelioration. Sodic and alkali soil amelioration primarily involves increasing calcium (Ca
2+
) on the cation exchange complex at the expense of Na
+
. The replaced Na
+
is removed from the root zone through infiltrating water resulting from excessive irrigation(s). Several approaches aiming at amelioration of these soils have been used, which include application of water, crop, chemical amendment, electric current and tillage as amelioration tools. In addition, management of plant nutrient elements in these soils has been addressed as a crucial factor in improving crop productivity and soil fertility. While the principles and technologies aiming at the amelioration of sodic and alkali soils are fairly well understood, their adoption in poor and developing countries is very slow because the majority of the affected lands are in the possession of resource-poor communities or form part of the common property resources of the villages. This paper reviews various amelioration and nutrient management approaches as well as constraints to large-scale adoption of the amelioration approaches. This information will assist researchers and farm advisers in choosing appropriate management practices to achieve maximum benefits from these soils while considering the participation of the farmers in the planning and setting of the amelioration programmes.
Multifunctional demands on grasslands.
Authors: Nagy G.
Published: September 2007

The purpose of this review is to outline the status quo regarding multifunctional and social demands on grasslands. The products and services that grassland ecosystems can provide society are detailed. Existing agro-policies are reviewed as to how they reflect social demands on grasslands. A farm level analysis considers many factors that may influence the fulfilment of social demands. Conclusions are drawn on the future of grassland use under different socioeconomic conditions. Traditional (meat, milk, fibre, medicinal plants, fuel and power) and non-traditional (branded products, biodiversity as gene pool and biomass for energy) products are identified. Services of grasslands are summarized at three different levels viz. globally (regulation of climate, air quality, water resources, soil health, carbon sequestration and maintaining biodiversity), regionally (aesthetic and landscape values) and locally (preservation of cultural heritage and maintenance of the significance of religion for pastoralism). Targeted policies are emerging that assist in sustaining healthy grassland ecosystems and fulfilling multifunctional demands at different social levels. In spite of these policies, the future of the world's grasslands seems to vary by country, according to the level of development. In poor countries, production from grassland will remain of vital importance (in some cases, with the threat of ecosystem degradation), while at the same time, ecological and amenity uses of grassland appear to be ignored. Trends in the function of grassland ecosystems in developed countries seem to be just the opposite. The importance of production is declining, while ecological and amenity functions receive increasing attention in response to multifunctional and social demands.
The importance of comparative physiology: a focus on ovarian biology and the role of animal models.
Authors: Komar C. M.
Published: September 2007

The use of animals in research dates back many centuries. Using animals as a model to advance human health is critical, and an important aspect of that is choosing the right animal model. In utilizing animals for research, not only do we advance our understanding of fundamental biology and physiology, but the findings contribute to knowledge of animal disease and welfare issues as well. The following discussion is an overview discussing how studies in animals have advanced our understanding of ovarian function, and the need to continue to develop appropriate animal models to address critical questions. The use of the bat
Glossophaga soricina
as a model for ovarian biology is noted.
Manipulation of plant architecture to enhance crop disease control.
Authors: Ando K. , Grumet R. , Terpstra K. , Kelly J. D.
Published: September 2007

Yield and quality losses due to disease are major factors limiting crop productivity; thus breeding for disease resistance is a primary goal for many plant breeding programmes. Unfortunately, specific sources of resistance are not always available. In cases where sources of genetic resistance are limited or non-existent, manipulating plant architecture to facilitate disease avoidance may be a valuable alternate approach to mitigate disease severity. Modifications of plant architecture can be used to reduce contact with the pathogen, create barriers to pathogen growth and development, or create an unfavourable microclimate for disease development. Architectural variants have long been observed by plant breeders and geneticists, and are frequently utilized to develop new plant types. Key variants that may facilitate disease control include altered plant height, determinacy, branching patterns, branch or leaf angle, flower position, organ coverage or shape, or root structure patterns. Implementing disease avoidance by an architectural approach requires an understanding of both the life cycle of the pathogen and the genetic basis for the desired morphological traits. This review examines examples where modified architecture can be employed to reduce disease. Among the better-documented cases are modified canopy structure to reduce white mould in dry bean and tightly closed ears to reduce
Fusarium
ear rot of maize. These examples demonstrate that breeding for modified plant architecture can be a valuable component of a broader disease control strategy that also includes genetic resistance and cultural and chemical controls.
Beyond the second generation: towards adaptiveness in participatory forest management.
Authors: Lawrence A.
Published: September 2007

The concepts of adaptive management and participatory forest management (PFM) reflect an increasingly holistic relationship between society and its forests. Adaptiveness depends on learning processes. This review considers the ways in which PFM has been assessed in recent literature and focuses on the role of learning, through cross-cutting quantitative analyses, project monitoring and evaluation, and participatory research and experimentation. Such literature highlights the importance of policy, and the gap between legislation and implementation; social and institutional arrangements; appropriate silviculture and monitoring, and the participatory methods needed to develop it. Much of this is analysed at the local or national scale, but emerging discourses on forest governance highlight the need for partnership, organizational learning, and adaptiveness across a range of spatial scales and cultural perspectives. The review concludes that the common factors in adaptive PFM are context specificity, tenure and institutional security, reliable and relevant information, and learning processes, leading to adaptive technology, institutions and organisations, underpinned by close attention to ecology. This is summarized in an analysis proposing a broad evolutionary pattern from 'first generation' attention to structural factors such as tenure and formal roles and relationships, through 'second generation' concerns emerging from experience of diversity and inequity, to a more qualitative, actor-centred approach to learning and adaptation. The big challenges for PFM are adaptive technology, requiring participatory research in silviculture, sustainable harvesting and monitoring; and adaptive organizations and institutions.
Water management issues and problems in Africa.
Authors: Lankford B. , Dickinson S.
Published: September 2007

An enquiry into pressing issues in contemporary water resource management in Africa reveals an extensive, well-researched and heavily debated literature. This paper strives to reveal this through a brief discussion of four prominent issues or 'problems' in contemporary water resource management across Africa; integrated water resource management involving decisions about allocation; health, domestic water and sanitation; agricultural water management; and climate change. The first three represent policy arenas that are complementary to each other, but to some extent are also competing in terms of donor focus. The fourth is an emerging contextual issue that is helping to refocus and renew efforts in water management. The most significant dimension of these issues of water resource management in Africa today may be the degree of interdependence that exists between the four issues and therefore in the difficulties and hard choices associated with deciding which to prioritize. In addition, as with many contemporary issues spanning environment, culture and geography, water resource problems in Africa are characterized by a complex overlap between environmental, socio-economic, political, financial and technical viewpoints and concerns.
Environmental impacts of transgenic herbicide-resistant crops.
Authors: Cerdeira A. L. , Duke S. O.
Published: September 2007

Transgenic glufosinate- and glyphosate-resistant crops are currently commercialized, and bromoxynil-resistant crops have been removed from the market for economic reasons. Glyphosate-resistant cotton and soyabean have become dominant in those countries where they have been approved for planting. Potential effects of glufosinate and glyphosate on contamination of soil, water and air are minimal, compared to those caused by the herbicides that they replace when herbicide-resistant crops (HRCs) are adopted. No risks have been found with food or feed safety or nutritional value in products from currently available HRCs. Both glufosinate- and glyphosate-resistant crops promote the adoption of reduced- or no-tillage agriculture, reducing environmental degradation by agriculture. HRCs have caused evolution of herbicide resistance in weed species and shifts to those species that are naturally resistant. Transgene flow with HRCs is a concern for commercial and ecological reasons. In canola, rice and bentgrass, herbicide resistance transgenes have been found in fields that are supposed to be non-transgenic. Under some circumstances, transgene flow (introgression) to plants that might become problems in natural ecosystems remains the largest risk of HRCs.
Allelopathy for weed management in sustainable agriculture.
Authors: Khanh TranDang , Chung IllMin , Tawata S. , Xuan TranDang
Published: September 2007

The sustainability of agriculture relies on the development of strategies that lower the need for costly external inputs and minimize detrimental effects on the environment, which often involve either inappropriate or excessive use of agrochemical inputs. One strategy, integrating plant allelopathy into sustainable agriculture, is discussed in this paper. Agriculture integrated with allelopathy could reduce the heavy dependence on synthetic herbicides and other agrochemicals, and therefore ease problems such as environmental contamination, use of unsafe agricultural products and effects on human health. The allelopathy-integrated management of weeds includes various techniques such as the use of allelopathy in crop rotation, preceding and cover crops, green manure, mulch, and intercropping, as well as the incorporation of allelopathic plants in soil. In addition, the enhancement of weed-suppressing ability in crops is an important task in sustainable agricultural production. Even though many secondary metabolites involved in allelopathic activities have been isolated and identified, numerous allelochemicals remain unknown. The search for allelochemicals with novel modes of action is important for the development of bioactive pesticides. Despite the fact that the direct use of allelochemicals as natural pesticides is difficult in the field because of their easy degradation in nature and high cost of delivery, the synthesis of compounds derived from these allelochemicals may help resolve these problems.
Managing irrigation and drainage in saline environments.
Authors: Ayars J. E. , Christen E. W. , Hornbuckle J. W.
Published: September 2007

Disposal of saline drainage water is one of the most vexing problems facing irrigated agriculture. The sustainability of irrigation will require that cost-effective and environmentally acceptable methods be found for disposal of saline drainage water. Oftentimes, drainage water contains fertilizers, pesticides and toxic trace elements in addition to salt. Currently, disposal is accomplished by discharging drainage water into streams, lakes and rivers with significant negative environmental impacts; this is a practice that can no longer continue. As water supplies to agriculture become limited there will be increased use of degraded water for irrigation, which adds additional contaminants to the drainage water. There is a need to develop an alternative drainage water disposal strategy. One alternative disposal strategy is the concept of biological concentration of salt and ultimately disposal of a small volume of drainage water into either an evaporation pond or a spray evaporation facility. Bioconcentration facilities developed in California and Australia are called Integrated On-Farm Drainage Management (IFDM) in California or Serial Biological Concentration (SBC) in Australia, respectively. These systems represent the integration of the accumulated knowledge related to irrigation management, salt management, reusing saline drainage water, and drainage water management. The successful operation of these facilities requires an integrated approach to irrigation and drainage system design and management with irrigation management improved to the highest practical levels. New salt management concepts need to be evaluated or implemented to include using halophytes in production systems and accepting higher levels of salinity in the soil profile in general agronomic production. Drainage water management is implemented to include managing water table position and implementing new design and construction techniques for subsurface drainage systems. Additional facilities are required to provide disposal capability either as an evaporation pond or a spray evaporation facility. We review the concepts associated with the design and operation of bioconcentration systems highlighting the requirements for success and the limitations of these particular facilities.
Transgenic rice seed as a nutriceutical delivery system.
Authors: Takaiwa F.
Published: September 2007

Rice is consumed as a staple food by more than half the world's population. If rice were nutritionally fortified or biofunctionally enhanced by genetic modification, it could contribute to the promotion of human health without the need for processing and purification. Incorporation of health-promoting bioactive components or nutrients could thus result in public health benefits that significantly reduce health care costs. Rice seed has many advantages as a production platform of nutrients and biofunctional products over other cereals or vegetative crops in view of productivity and cost, and the fundamental tools required for genetic modification technology have been established for rice. The entire rice genome has been sequenced and is readily accessible, and transformation and expression systems are well developed for a number of agronomically important rice cultivars. The focus of this review is the present state of development of nutritionally improved rice, and transgenic rice seed as a production and delivery system for recombinant products.
Small RNAs and viral interference.
Authors: Praveen S. , Ramesh S. V. Ramesh S. V.
Published: September 2007

Small RNAs (21-26 nucleotides (nt) in size) have been found to function as regulators between the genome and proteome. In the last two decades, several new classes of small non-coding RNAs have been uncovered and they play an integrative role in various mechanisms of eukaryotic gene expression. Here, we discuss the endogenous small RNAs, their biogenesis and regulatory role in transcriptional, post-transcriptional and systemic silencing. Many discoveries in the small RNA world are crucial in deciphering host-virus relationships. Viruses interfere with host cellular machinery for their survival and propagation and hence have an opportunity to fight and/or regulate the host gene expression. Emerging literature suggests cross-talk between viral and host-encoded small RNAs during viral establishment. The present understanding of viral interference on small RNA landscape offers an immense opportunity to understand host-virus interactions. These interactions can be further fine-tuned in order to develop transgenic resistance and therapeutics. Though evidence regarding small RNA dynamics is just emerging, it might offer possible explanations for host specificity, susceptible cultivars, and latency in viral infections.
Using
Serratia plymuthica
to control fungal pathogens of plants.
Authors: Vleesschauwer D. de , Höfte M.
Published: September 2007

Interest in biological control of plant pathogens has increased in recent years fuelled by trends in agriculture towards greater sustainability and public concerns over the use of hazardous pesticides in the environment. Most studies on the biological control of fungal plant pathogens have tended to focus on the use of antagonistic rhizobacterial strains belonging to the genus
Pseudomonas
or
Bacillus
. However, the development of biocontrol products based on isolates belonging to the Gram-negative genus
Serratia
is now gaining momentum.
Serratia plymuthica
is a ubiquitous bacterium that has been preferentially recovered from rhizospheres all over the world, both as a free-living and endophytic organism. Specific strains of
S. plymuthica
produce a broad palette of antimicrobial compounds and might hold great potential as broad-spectrum biocontrol agents. This review surveys the advances of biocontrol research with respect to plant-associated
S. plymuthica
strains focusing on the principles and mechanisms of action of S. plymuthica and their use or potential use for the biological control of fungal plant diseases. A cursory overview of the taxonomy and ecology of S. plymuthica is also provided. We highlight recent progress in the identification of antifungal secondary metabolites produced by
S. plymuthica
and pay special attention to the regulatory mechanisms underpinning the production of the latter metabolites. Finally, we discuss several strategies that may provide a basis to improve the efficacy of
S. plymuthica
-mediated biocontrol.
Animal welfare: should we change housing to better accommodate the animal or change the animal to accommodate the housing?
Authors: Cheng Heng-Wei
Published: September 2007

Animal welfare (well-being) can be generally defined as 'a state of harmony between the animal and its environment, characterized by optimal physical, behavioural and psychological functioning and high quality of the animal's life'. Since its inception in the early nineteenth century, through further development during the twentieth century, and continuing through today, the animal welfare/wellbeing movement has had a significant impact globally on monitoring and regulating the practices of the modern livestock production industries. Before the animal welfare movement brings animal agriculture to the next stage, it is necessary to understand the finely tuned balance between animals, especially domestic farm animals, and their environments. It has been known for centuries that some species, strains and/or individuals of animals adapt to their environments better than others. The outcome of the adaptive process, i.e. increased or decreased in terms of welfare, is dependent on the animals' biological characteristics (genes), environmental factors and genetic- environmental interactions. The animal-or-environment dilemma associated with animal welfare has also raised multiple semantic variants among human beings according to a person's education, ethical viewpoint, socio-economic conditions, culture, religion and political beliefs. This review describes the current status of hypotheses and research in the area of the effects of genes, environments and genetic-environmental interactions on animal welfare in the modern livestock production industry.
Fish rhabdovirus models for understanding host response to DNA vaccines.
Authors: Kurath G. , Purcell M. K. , Garver K. A.
Published: September 2007

Fish rhabdovirus DNA vaccines have potential value both as applied vaccines and as useful models for basic DNA vaccine research. In particular, DNA vaccines against two widely distributed fish rhabdoviral pathogens, infectious hematopoietic necrosis virus (IHNV) and viral hemorrhagic septicemia virus (VHSV), have been extensively investigated. Single small doses of these vaccines provide exceptionally high efficacy under a wide range of conditions.
In vivo
studies of the IHNV and VHSV DNA vaccines have defined minimal effective doses in different sizes of host fish, protection against heterologous viral strains, onset and duration of protective immunity, and biodistribution and expression
in vivo
. Studies of these vaccines have defined three phases in the fish host protective immune response. As early as 4 days after vaccination, fish are protected from severe viral challenge and the protection is cross-protective against unrelated viral species. The mechanism of this early antiviral response (EAVR) phase involves strong induction of innate type I interferon immune responses and the viral glycoprotein has characteristics of a pathogen-associated molecular pattern (PAMP). In a matter of weeks the response transitions into a specific antiviral response (SAVR) that is no longer cross-protective but retains high efficacy and corresponds to appearance of detectable neutralizing antibodies. Six to nine months after vaccination, the response transitions into the long-term antiviral response (LAVR), characterized by reduced but still significant protection and reduction or absence of detectable neutralizing antibodies. The understanding of these phases of protection, along with the success of these vaccines and their ability to stimulate strong innate immunity, makes them potentially informative models for other veterinary or human DNA vaccines.
Functions of microbial communities and their importance to soil.
Authors: Nannipieri P.
Published: September 2007

Soil is a peculiar biological system with microbial life located in a small volume and distributed like an oasis in a desolated land, a large microbial biomass and huge microbial diversity, and the presence of important extracellular biological molecules, such as enzymes and nucleic acids, adsorbed by soil particles and protected against microbial degradation. The huge microbial diversity probably is at the basis of the broad metabolic activity, versatility and adaptation of soil to varying environmental conditions. It is still not possible to assess the composition and functions of microbial communities inhabiting soil in spite of the advances in identifying unculturable microorganisms and gene expression by molecular techniques. Gene expression of unknown microbial species from soil has allowed the discovery of novel bioproducts and novel metabolic processes, with important implications in various human activities. However, the identification of all microbial species inhabiting soil and their numbers and functions is not the most suitable approach for a better understanding of soil functionality. For example, a holistic approach based on the determination of biologically meaningful pools and fluxes is the best approach to quantify the dynamics of main nutrients in soil. Among the molecular techniques applied to soil, the stable isotope probes technique is the most suitable for holistic studies because it involves tracking of a stable isotope atom from a particular substrate into components of microbial cells that provide phylogenetic and functional information, such as lipid, proteins, DNA or RNA.
Barriers to adoption of biological control agents and biological pesticides.
Authors: Marrone P. G.
Published: September 2007

Biological (bio)pesticides represent 2.4% of the global pesticide market, but this share is growing quickly and is projected to double by 2010. In contrast, the market for chemical pesticides is flat to declining as transgenic seeds have reduced sprays and governments have restricted or removed products from the market. By combining performance and safety, biopesticides offer value through benefits generally not realized by conventional pesticides. Biopesticides perform efficaciously while providing customers the flexibility of minimum application restrictions, superior residue and resistance management potential, and human and environmental safety benefits. Despite these advantages, there are significant barriers that impede adoption of biopesticides. This review will explore these barriers in depth and offer solutions for increasing adoption. These barriers include a competitive market, risk-averse customers, a complex selling channel, perceived lack of efficacy and lack of awareness.
Understanding genetic relationships of wild and cultivated roses and the use of species in breeding.
Authors: Cock K. de , Scariot V. , Leus L. , Riek J. de , Huylenbroeck J. van
Published: September 2007

The existence of numerous wild species, the variability within species and the wide geographical distribution in combination with the weak barriers to interspecific and intersectional hybridization, make genetic relationships within the genus
Rosa
difficult to unravel. The use of molecular techniques has revealed some new insights in taxonomy and phylogenetic relationships. The understanding of these relationships among species and cultivars is a prerequisite for the effective utilization of the available genetic variability to tackle the new demands from growers and consumers. Many wild species have interesting traits. The rose breeders' challenge is to introgress the desirable beneficial genes from wild species to tetraploid cultivars in order to accelerate the production of superior rose germplasm.
A review of on-farm evaluations of system of rice intensification methods in Eastern Indonesia.
Authors: Sato S. , Uphoff N.
Published: September 2007

The system of rice Intensification (SRI) developed in Madagascar has been controversial in some agronomic circles, in part because there have been no large-scale, long-term evaluations of the impact of the alternative methods recommended. This review reports on on-farm comparative evaluations conducted over nine seasons between 2002 and 2006 across eight provinces in Eastern Indonesia under a major irrigation project (SSIMP-DISIMP), with project management by a Nippon Koei consultant team. It summarizes the results of 12 133 comparison trials that covered a total area of 9429 ha. Average yield increase was 78% (3.3 t/ha) with reductions of 40% in water use, 50% in fertilizer applications and 20% in the costs of production. While the controversy will not be resolved by any single evaluation, these results support the previous reports that SRI practices, when used in combination, can achieve significantly higher output of rice with a reduction in inputs, enhancing simultaneously the productivity of the resources (land, labour, water and capital) used in irrigated rice production.
Regulation of branching during inflorescence development in monocots.
Authors: Pilu R. , Cassani E. , Landon M.
Published: September 2007

The structure of the plant inflorescence is an important agronomic and ornamental trait studied for its potential economic applications: the capacity to modify inflorescence architecture has always been a breeder's goal. The shape of flowering plants is determined by the forms of the flower-bearing branch system, named inflorescences, and their position in the overall structure of the plant. Branching patterns and branches are produced by the shoot apical meristem; thus, inflorescence structure reflects the number, size and activity of the meristems. The genetic and molecular control of inflorescence and flower development has been extensively studied in model dicotyledonous plants such as
Arabidopsis
. However, not all the genes controlling inflorescence architecture in grasses are orthologous of
Arabidopsis
genes and thus grass inflorescence genes could not have been identified by simple extrapolation from
Arabidopsis
. Among plants, rice and maize in particular are the best genetic models for studying inflorescences: the maize inflorescence is a useful model for developmental and evolutionary studies, because several mutants have been isolated that taken together dissect every step of the inflorescence development. Because of the sequencing of the rice genome, positional information can be used to clone genes in maize, wheat and related grasses. In recent years, several master genes involved in inflorescence development have been cloned, providing considerable insights into the genetic control of the plant inflorescence.
Parkin-mediated K63-linked polyubiquitination targets misfolded DJ-1 to aggresomes via binding to HDAC6
Authors: Olzmann James A. , Li Lian , Chudaev Maksim V. , Chen Jue , Perez Francisco A. , Palmiter Richard D. , Chin Lih-Shen
Published: September 2007

Sequestration of misfolded proteins into pericentriolar inclusions called aggresomes is a means that cells use to minimize misfolded protein-induced cytotoxicity. However, the molecular mechanism by which misfolded proteins are recruited to aggresomes remains unclear. Mutations in the E3 ligase parkin cause autosomal recessive Parkinson's disease that is devoid of Lewy bodies, which are similar to aggresomes. Here, we report that parkin cooperates with heterodimeric E2 enzyme UbcH13/Uev1a to mediate K63-linked polyubiquitination of misfolded DJ-1. K63-linked polyubiquitination of misfolded DJ-1 serves as a signal for interaction with histone deacetylase 6, an adaptor protein that binds the dynein–dynactin complex. Through this interaction, misfolded DJ-1 is linked to the dynein motor and transported to aggresomes. Furthermore, fibroblasts lacking parkin display deficits in targeting misfolded DJ-1 to aggresomes. Our findings reveal a signaling role for K63-linked polyubiquitination in dynein-mediated transport, identify parkin as a key regulator in the recruitment of misfolded DJ-1 to aggresomes, and have important implications regarding the biogenesis of Lewy bodies.
Defective microtubule-dependent podosome organization in osteoclasts leads to increased bone density inPyk2−/−mice
Authors: Gil-Henn Hava , Destaing Olivier , Sims Natalie A. , Aoki Kazuhiro , Alles Neil , Neff Lynn , Sanjay Archana , Bruzzaniti Angela , De Camilli Pietro , Baron Roland , Schlessinger Joseph
Published: September 2007

The protein tyrosine kinase Pyk2 is highly expressed in osteoclasts, where it is primarily localized in podosomes. Deletion of Pyk2 in mice leads to mild osteopetrosis due to impairment in osteoclast function. Pyk2-null osteoclasts were unable to transform podosome clusters into a podosome belt at the cell periphery; instead of a sealing zone only small actin rings were formed, resulting in impaired bone resorption. Furthermore, in Pyk2-null osteoclasts, Rho activity was enhanced while microtubule acetylation and stability were significantly reduced. Rescue experiments by ectopic expression of wild-type or a variety of Pyk2 mutants in osteoclasts from Pyk2−/− mice have shown that the FAT domain of Pyk2 is essential for podosome belt and sealing zone formation as well as for bone resorption. These experiments underscore an important role of Pyk2 in microtubule-dependent podosome organization, bone resorption, and other osteoclast functions.
Kinesin-5 regulates the growth of the axon by acting as a brake on its microtubule array
Authors: Myers Kenneth A. , Baas Peter W.
Published: September 2007

Kinesin-5 is a homotetrameric motor protein that interacts with adjacent microtubules in the mitotic spindle. Kinesin-5 is also highly expressed in developing postmitotic neurons. Axons of cultured neurons experimentally depleted of kinesin-5 grow up to five times longer than controls and display more branches. The faster growth rates are accompanied by a doubling of the frequency of transport of short microtubules, suggesting a major role for kinesin-5 in the balance of motor-driven forces on the axonal microtubule array. Live-cell imaging reveals that the effects on axonal length of kinesin-5 depletion are caused partly by a lower propensity of the axon and newly forming branches to undergo bouts of retraction. Overexpression of wild-type kinesin-5, but not a rigor mutant of kinesin-5, has the inverse effect on axonal length. These results indicate that kinesin-5 imposes restrictions on the growth of the axon and does so at least in part by generating forces on the axonal microtubule array.
Suv4-20h deficiency results in telomere elongation and derepression of telomere recombination
Authors: Benetti Roberta , Gonzalo Susana , Jaco Isabel , Schotta Gunnar , Klatt Peter , Jenuwein Thomas , Blasco María A.
Published: September 2007

Mammalian telomeres have heterochromatic features, including trimethylated histone H3 at lysine 9 (H3K9me3) and trimethylated histone H4 at lysine 20 (H4K20me3). In addition, subtelomeric DNA is hypermethylated. The enzymatic activities responsible for these modifications at telomeres are beginning to be characterized. In particular, H4K20me3 at telomeres could be catalyzed by the novel Suv4-20h1 and Suv4-20h2 histone methyltransferases (HMTases). In this study, we demonstrate that the Suv4-20h enzymes are responsible for this histone modification at telomeres. Cells deficient for Suv4-20h2 or for both Suv4-20h1 and Suv4-20h2 show decreased levels of H4K20me3 at telomeres and subtelomeres in the absence of changes in H3K9me3. These epigenetic alterations are accompanied by telomere elongation, indicating a role for Suv4-20h HMTases in telomere length control. Finally, cells lacking either the Suv4-20h or Suv39h HMTases show increased frequencies of telomere recombination in the absence of changes in subtelomeric DNA methylation. These results demonstrate the importance of chromatin architecture in the maintenance of telomere length homeostasis and reveal a novel role for histone lysine methylation in controlling telomere recombination.
Katanin regulates dynamics of microtubules and biogenesis of motile cilia
Authors: Sharma Neeraj , Bryant Jessica , Wloga Dorota , Donaldson Rachel , Davis Richard C. , Jerka-Dziadosz Maria , Gaertig Jacek
Published: September 2007

The in vivo significance of microtubule severing and the mechanisms governing its spatial regulation are not well understood. In Tetrahymena, a cell type with elaborate microtubule arrays, we engineered null mutations in subunits of the microtubule-severing complex, katanin. We show that katanin activity is essential. The net effect of katanin on the polymer mass depends on the microtubule type and location. Although katanin reduces the polymer mass and destabilizes the internal network of microtubules, its activity increases the mass of ciliary microtubules. We also show that katanin reduces the levels of several types of post-translational modifications on tubulin of internal and cortical microtubules. Furthermore, katanin deficiencies phenocopy a mutation of β-tubulin that prevents deposition of polymodifications (glutamylation and glycylation) on microtubules. We propose that katanin preferentially severs older, post-translationally modified segments of microtubules.
Kenneth George Budden. 23 June 1915 — 4 September 2005
Authors: Dougherty J. P.
Published: September 2007

After the discovery of the ionosphere in 1924 by E. V. (later Sir Edward) Appleton (FRS 1927), there was extensive experimental research into its properties with the use of radio reflection techniques. This generated a need for theoretical investigation of the propagation of electromagnetic waves in ionized gases, nowadays known as plasmas. This led eventually to a large body of work known as magnetoionic theory. A start was made by Appleton himself, but much was left for later research. The systematic exploration of this subject was pursued in the decades after World War II, and Kenneth Budden was a leading contributor to it for most of his research career. He also expounded it in a large textbook, which he rewrote two decades later. The arrival of electronic computers in the early 1950s (however primitive they may appear with hindsight) opened new prospects for many branches of science. Kenneth Budden was one of the pioneers in that activity.
Fred Brown. 31 January 1925 — 20 February 2004
Authors: Rowlands David J. , Skehel John J.
Published: September 2007

Fred Brown was a major figure in British and international virology during most of the latter half of the twentieth century. He brought to the subject a rigorous and critical attitude acquired during his early training in chemistry. In addition, he was passionately interested in the practical application of his work and that of others to the prevention and alleviation of disease. He always believed that his research would make a significant contribution to the welfare of agricultural livestock. He is best known for his pioneering work on foot–and–mouth disease virus, the causative agent for the most important disease of domestic livestock globally. However, he also made seminal contributions to the study of many other viruses of veterinary importance.
Mixed valence: origins and developments
Authors: Day Peter , Hush Noel S , Clark Robin J.H
Published: September 2007

Mixed-valence compounds were recognized by chemists more than a century ago for their unusual colours and stoichiometries, but it was just 40 years ago that two seminal articles brought together the then available evidence. These articles laid the foundations for understanding the physical properties of such compounds and how the latter correlate with molecular and crystal structures. This introduction to a discussion meeting briefly surveys the history of mixed valence and sets in context contributions to the discussion describing current work in the field.
Towards a comprehensive model for the electronic and vibrational structure of the Creutz–Taube ion
Authors: Reimers Jeffrey R , Wallace Brett B , Hush Noel S
Published: September 2007

Since the synthesis of the Creutz–Taube ion, the nature of its charge localization has been of immense scientific interest, this molecule providing a model system for the understanding of the operation of biological photosynthetic and electron-transfer processes. However, recent work has shown that its nature remains an open question. Many systems of this type, including photosynthetic reaction centres, are of current research interest, and thereby the Creutz–Taube ion provides an important chemical paradigm: the key point of interest is the details of how such molecules behave. We lay the groundwork for the construction of a comprehensive model for its chemical and spectroscopic properties. Advances are described in some of the required areas including: simulation of electronic absorption spectra; quantitative depiction of the large interaction of the ion's electronic description with solvent motions; and the physics of Ru–NH
3
spectator-mode vibrations. We show that details of the solvent electron–phonon coupling are critical in the interpretation of the spectator-mode vibrations, as these strongly mix with solvent motions when 0.75<2
J
/
λ
<1. In this regime, a double-well potential exists which does not support localized zero-point vibration, and many observed properties of the Creutz–Taube ion are shown to be consistent with the hypothesis that the ion has this character.
Stark spectroscopy of mixed-valence systems
Authors: Silverman Lisa N , Kanchanawong Pakorn , Treynor Thomas P , Boxer Steven G
Published: September 2007

Many mixed-valence systems involve two or more states with different electric dipole moments whose magnitudes depend upon the charge transfer distance and the degree of delocalization; these systems can be interconverted by excitation of an intervalence charge transfer transition. Stark spectroscopy involves the interaction between the change in dipole moment of a transition and an electric field, so the Stark spectra of mixed-valence systems are expected to provide quantitative information on the degree of delocalization. In limiting cases, a classical Stark analysis can be used, but in intermediate cases the analysis is much more complex because the field affects not only the band position but also the intrinsic bandshape. Such non-classical Stark effects lead to widely different bandshapes. Several examples of both classes are discussed. Because electric fields are applied to immobilized samples, complications arise from inhomogeneous broadening, along with other effects that limit our ability to extract unique parameters in some cases. In the case of the radical cation of the special pair in photosynthetic reaction centres, where the mixed-valence system is in a very complex but structurally well-defined environment, a detailed analysis can be performed.
Mixed valency in polynuclear Mn
II
/Mn
III
, Mn
III
/Mn
IV
and Mn
II
/Mn
III
/Mn
IV
clusters: a foundation for high-spin molecules and single-molecule magnets
Authors: Stamatatos Theocharis C , Christou George
Published: September 2007

Mixed-valent Mn/O dinuclear and polynuclear molecular compounds containing Mn
III
are almost without exception trapped valence. Large differences between the strengths of the exchange interactions within Mn
II
Mn
III
, Mn
III
Mn
III
and Mn
III
Mn
IV
pairs lead to situations where Mn
III
Mn
IV
interactions, the strongest of the three mentioned and antiferromagnetic in nature, dominate the intramolecular spin alignments in trinuclear and higher nuclearity mixed-valent complexes and often result in molecules that have large, and sometimes abnormally large, values of molecular spin (
S
). When coupled to a large molecular magnetoanisotropy of the easy-axis-type (negative zero-field splitting parameter,
D
), also primarily resulting from individual Jahn–Teller distorted Mn
III
centres, such molecules will function as single-molecule magnets (molecular nanomagnets). Dissection of the structures and exchange interactions within a variety of mixed-valent Mn

x

cluster molecules with metal nuclearities of Mn
4
, Mn
12
and Mn
25
allows a ready rationalization of the observed
S
,
D
and overall magnetic properties in terms of competing antiferromagnetic exchange interactions within triangular subunits, resulting spin alignments and relative orientation of Mn
III
JT axes. Such an understanding has provided a stepping stone to the identification of a ‘magnetically soft’ Mn
25
cluster whose groundstate spin
S
value can be significantly altered by relatively minor structural perturbations. Such ‘spin tweaking’ has allowed this cluster to be obtained in three different forms with three different groundstate
S
values.
Mixed valency in rare-earth fullerides
Authors: Prassides Kosmas , Takabayashi Yasuhiro , Nakagawa Takeshi
Published: September 2007

Mixed-valence phenomena associated with the highly correlated narrow-band behaviour of the 4f electrons in rare earths are well documented for a variety of rare-earth chalcogenides, borides and intermetallics (Kondo insulators and heavy fermions). The family of rare-earth fullerides with stoichiometry RE
2.75
C
60
(RE=Sm, Yb, Eu) also displays an analogous phenomenology and a remarkable sensitivity of the rare-earth valency to external stimuli (temperature and pressure) making them the first known molecular-based members of this fascinating class of materials. Using powerful crystallographic and spectroscopic techniques which provide direct indications of what is happening in these materials at the microscopic level, we find a rich variety of temperature- and pressure-driven abrupt or continuous valence transitions—the electronically active fulleride sublattice acts as an electron reservoir that can accept electrons from or donate electrons to the rare-earth 4f/5d bands, thereby sensitively modulating the valence of the rare-earth sublattice.
Electron transfer at the class II/III borderline of mixed valency: dependence of rates on solvent dynamics and observation of a localized-to-delocalized transition in freezing solvents
Authors: Glover Starla D , Lear Benjamin J , Salsman J. Catherine , Londergan Casey H , Kubiak Clifford P
Published: September 2007

The dependence of the rates of intramolecular electron transfer (ET) of mixed-valence complexes of the type {[Ru3O(OAc)6(CO)(L)]2-BL}−1, where L is the pyridyl ligand and BL is the pyrazine on solvent type and temperature is described. Complexes were reduced chemically to obtain the mixed-valence anions in acetonitrile (CH3CN) and methylene chloride (CH2Cl2). Rate constants for intramolecular ET were estimated by simulating the observed degree ofν(CO) infrared (IR) bandshape coalescence in the mixed-valence state. In the strongly coupled mixed-valence states of these complexes, the electronic coupling,HAB, approachesλ/2, whereλis the total reorganization energy. The activation energy is thus nearly zero, and rate constants are in the ‘ultrafast’ regime where they depend on the pre-exponential terms within the frequency factor,νN. The frequency factor contains both external (solvent dynamics) and internal (molecular vibrations) contributions. In general, external solvent motions are slower than internal vibrations, and therefore control ET rates in fluid solution. A profound increase in the degree ofν(CO) IR bandshape coalescence is observed as the temperature approaches the freezing points of the solvents methylene chloride (f.p. −92°C) and acetonitrile (f.p. −44°C). Decoupling the slower solvent motions involved in the frequency factorνNfor ET by freezing the solvent causes a transition from solvent dynamics to internal vibration-limited rates. The solvent phase transition causes a localized-to-delocalized transition in the mixed-valence ions that accelerates the rate of ET.
Neural representation of spectral and temporal information in speech
Authors: Young Eric D
Published: September 2007

Speech is the most interesting and one of the most complex sounds dealt with by the auditory system. The neural representation of speech needs to capture those features of the signal on which the brain depends in language communication. Here we describe the representation of speech in the auditory nerve and in a few sites in the central nervous system from the perspective of the neural coding of important aspects of the signal. The representation is tonotopic, meaning that the speech signal is decomposed by frequency and different frequency components are represented in different populations of neurons. Essential to the representation are the properties of frequency tuning and nonlinear suppression. Tuning creates the decomposition of the signal by frequency, and nonlinear suppression is essential for maintaining the representation across sound levels. The representation changes in central auditory neurons by becoming more robust against changes in stimulus intensity and more transient. However, it is probable that the form of the representation at the auditory cortex is fundamentally different from that at lower levels, in that stimulus features other than the distribution of energy across frequency are analysed.