ALBERT

Notes: Abstract Plant pathology came of age at the turn of this century and we can be proud of the many significant contributions it has made to fundamental research as well as to service to growers. The twenty-first century will present our profession with dramatic challenges to meet the demands for increased food, fiber, and fuel production from a declining agricultural base. This can be accomplished only if plant pathology retains its integrity as a profession and remains abreast of advancements in the fields of biotechnology and communications.

Notes: Abstract Interest in the rust fungi derives from their success as plant pathogens. For example, the epidemic on coffee had serious economic and social impacts on diverse cultures. During the century, research on the rust germling shifted from a study of germling development, including a search for the signals that induce differentiation, to an examination of the genes expressed during host colonization. Research on host resistance was most influenced by Stakman, who studied the genetics and epidemiology of rust disease. His innovations enabled Flor to propose the gene-for-gene hypothesis, a concept that stimulated development of resistant crops, and led to research that gradually shifted during the century to an examination of the molecular basis of rust genetics.

Notes: Abstract Plant viruses have had an impact on the science of virology and on plant pathology ever since the virus concept was discovered with Tobacco mosaic virus at the end of the nineteenth century. In this review, we highlight those discoveries. We have divided plant virus research into a "Classical Discovery Period" from 1883-1951 in which the findings were very descriptive; an "Early Molecular Era" from 1952 to about 1983, in which information was developed that described further properties of the viruses, aided by the development of a number of salient techniques; and the "Recent Period" from 1983 to the present, when techniques have been developed to modify plant virus genomes, to detect nonstructural gene products, to determine the functions of viral gene products, and to transform plants to elicit novel forms of resistance to viral diseases. In this period, plant virology has played a significant role in formulating an understanding of the mechanisms of gene silencing and recombination, plasmodesmatal function, systemic acquired resistance, and in developing methods for pathogen detection. We also attempt to predict the direction plant virology will take in the future.

Notes: Abstract Several economically important diseases of unknown or recently determined cause are reviewed. Citrus blight (CB), first described over 100 years ago, was shown in 1984 to be transmitted by root-graft inoculations; the cause remains unknown and is controversial. Based on graft transmission, it is considered to be an infectious agent by some; others suggest that the cause of CB is abiotic. Citrus variegated chlorosis, although probably long present in Argentina, where it was considered to be a variant of CB, was identified as a specific disease and shown to be caused by a strain of Xylella fastidiosa after if reached epidemic levels in Brazil in 1987. Citrus psorosis, described in 1933 as the first virus disease of citrus, is perhaps one of the last to be characterized. In 1988, it was shown to be caused by a very unusual virus. The cause of lettuce big vein appears to be a viruslike agent that is transmitted by a soilborne fungus. Double-stranded RNAs were associated with the disease, suggesting it may be caused by an unidentified RNA virus. Rio Grande gummosis, dry rot root, peach tree short life, and some replant diseases may be diseases of complex etiology. Various microorganisms have been isolated from trees with these diseases, but the diseases may be attributable in part to environmental factors. Determination of the cause of these diseases of complex etiology has proven difficult, in part, because they affect only mature trees.

Notes: Abstract Ralstonia solanacearum causes a lethal bacterial wilt disease of diverse plants. It invades the xylem vessels of roots and disseminates into the stem where it multiplies and wilts by excessive exopolysaccharide production. Many of its key extracytoplasmic virulence and pathogenicity factors are transcriptionally controlled by an extensive network of distinct, interacting signal transduction pathways. The core of this sensory network is the five-gene Phc system that regulates exopolysaccharide, cell-wall-degrading exoenzymes, and other factors in response to a self-produced signal molecule that monitors the pathogen's growth status and environment. Four additional environmentally responsive two-component systems work independently and with the Phc system to fine-tune virulence gene expression. Another critical system is Prh which transduces plant cell-derived signals through a six-gene cascade to activate deployment of the Type III secretion pathway encoded by the hrp pathogenicity genes. Here I summarize knowledge about the regulated targets, signal transduction mechanisms, and crosstalk between Phc, Prh, and other systems. I also provide insight into why R. solanacearum has evolved such a sophisticated sensory apparatus, and how it functions in disease.

Notes: Abstract Lipopolysaccharides (LPSs) are ubiquitous, indispensable components of the cell surface of Gram-negative bacteria that apparently have diverse roles in bacterial pathogenesis of plants. As an outer membrane component, LPS may contribute to the exclusion of plant-derived antimicrobial compounds promoting the ability of a bacterial plant pathogen to infect plants. In contrast, LPS can be recognized by plants to directly trigger some plant defense-related responses. LPS can also alter the response of plants to subsequent bacterial inoculation; these delayed effects include alterations in the expression patterns of genes coding for some pathogenesis-related (PR) proteins, promotion of the synthesis of antimicrobial hydroxycinnamoyl-tyramine conjugates, and prevention of the hypersensitive reaction caused by avirulent bacteria. Prevention of the response may allow expression of resistance in the absence of catastrophic tissue damage. Recognition of LPS (and other nonspecific determinants) may initiate responses in plants that restrict the growth of nonpathogenic bacteria, whereas plant pathogens may possess hrp gene-dependent mechanisms to suppress such responses.

Notes: Abstract Detection and diagnosis of plant viruses has included serological laboratory tests since the 1960s. Relatively little work was done on serological detection of plant pathogenic bacteria and fungi prior to the development of ELISA and monoclonal antibody technologies. Most applications for laboratory-based tests were directed at virus detection with relatively little emphasis on fungal and bacterial pathogens, though there was some good work done with other groups of plant pathogens. With the advent of molecular biology and the ability to compare regions of genomic DNA representing conserved sequences, the development of laboratory tests increased at an amazing rate for all groups of plant pathogens. Comparison of ITS regions of bacteria, fungi, and nematodes has proven useful for taxonomic purposes. Sequencing of conserved genes has been used to develop PCR-based detection with varying levels of specificity for viruses, fungi, and bacteria. Combinations of ELISA and PCR technologies are used to improve sensitivity of detection and to avoid problems with inhibitors or PCR often found in plants. The application of these technologies in plant pathology has greatly improved our ability to detect plant pathogens and is increasing our understanding of, their ecology and epidemiology.

Notes: The spermosphere represents a short-lived, rapidly changing, and microbiologically dynamic zone of soil surrounding a germinating seed. It is analogous to the rhizosphere, being established largely by the carbon compounds released into the soil once the seed begins to hydrate. These seed exudations drive the microbial activities that take place in the spermosphere, many of which can have long-lasting impacts on plant growth and development as well as on plant health. In this review, I discuss the nature of the spermosphere habitat and the factors that give rise to its character, with emphasis on the types of microbial activities in the spermosphere that have important implications for disease development and biological disease control. This review, which represents the first comprehensive synthesis of the literature on spermosphere biology, is meant to illustrate the unique nature of the spermosphere and how studies of interactions in this habitat may serve as useful experimental models for testing hypotheses about plant-microbe associations and microbial ecology.

Notes: The genome structures of a large number of viruses transmitted by olpidium and plasmodiophorid vectors have been determined. The viruses are highly diverse, belonging to 12 genera in at least 4 families. Plasmodiophorids are now classified as protists rather than true fungi. This finding, along with the recognition of the great variety of viruses transmitted by olpidium and plasmodiophorid vectors, will likely lead to an elaboration of the details of in vitro and in vivo transmission mechanisms. Recent progress in elucidating the interaction between Cucumber necrosis virus (CNV) and its zoospore vector suggests that specific sites on the capsid as well as on the zoospore are involved in transmission. Moreover, some features of CNV/zoospore attachment are similar to poliovirus/host cell interactions, suggesting evolutionary conservation of functional features of plant and animal virus capsids.

Notes: Nematodes are considered among the most difficult animals to identify. DNA-based diagnostic methods have already gained acceptance in applications ranging from quarantine determinations to assessments of biodiversity. Researchers are currently in an information-gathering mode, with intensive efforts applied to accumulating nucleotide sequence of 18S and 28S ribosomal genes, internally transcribed spacer regions, and mitochondrial genes. Important linkages with collateral data such as digitized images, video clips and specimen voucher web pages are being established on GenBank and NemATOL, the nematode-specific Tree of Life database. The growing DNA taxonomy of nematodes has lead to their use in testing specific short sequences of DNA as a "barcode" for the identification of all nematode species.

Notes: Abstract Diseases caused by species in the genus Phytophthora are responsible for significant economic losses on a wide range of host plants. Spatial pattern is one of the most characteristic ecological properties of a species, and reflects environmental and genetic heterogeneity and reproductive population growth acting on the processes of reproduction, dispersal, and mortality. Species of Phytophthora can be dispersed either in soil, via surface water movement down rows, from rain splash dispersal, by air, or via movement by humans or invertebrate activity. Dispersal results in patchiness in patterns of disease or inoculum in soil. In this chapter we discuss the mechanisms of dispersal of members of this important genus and describe several methods that can be used to statistically analyze data for which spatial coordinates are known. The methods include testing spatial autocorrelation for binary data or continuous data, semivariograms, and regression models for spatial data. The goal of spatial pattern analysis is to gain an understanding of the mechanisms of dispersal of propagules and to sort out the physical and biological factors that are important for spread of plant pathogens and ultimately, for disease management.

Notes: E.M. Freeman's role in early cereal disease research and the beginning of plant pathology at the University of Minnesota has been overshadowed largely by the enormous prestige of his student, E.C. Stakman. During the first decade of the twentieth century, Freeman was responsible for the transferral from Europe to the United States and the subsequent nurturing of important conceptual and technical developments in the area of cereal disease pathology. Under Freeman's leadership, these ideas would come to shape the direction of plant pathology research at the University of Minnesota for decades to follow.

Notes: Abstract Rhodococcus fascians infects a wide range of plants, initiating the formation of leafy galls that consist of centers of shoot amplification and shoot growth inhibition. R. fascians is an epiphyte but it also can establish endophytic populations. Bacterial signals involved in symptom development initiate de novo cell division and shoot meristem formation in differentiated tissues. The R. fascians signals exert activities that are distinct from mere cytokinin effects, and the evidence points to a process that adopted cytokinin biosynthetic enzymes to form derivatives with unique activity. Genes implicated in leafy gall formation are located on a linear plasmid and are subject to a highly controlling, complex regulatory network, integrating autoregulatory compounds and environmental signals. Leafy galls are considered as centers with specific metabolic features, a niche where populations of R. fascians experience a selective advantage. Such "metabolic habitat modification" might be universal for gall-inducing bacteria.

Notes: Abstract The role of the professional disease diagnostician has become increasingly important in turf management. Responsible turfgrass disease diagnosis must incorporate the possibility of biotic, as well as abiotic, disorders and should consist of three components: the interview, identification of the stress factor, and a management recommendation. The concept of management groups is introduced to facilitate delivery of the rapid and effective solution required by turf managers. Recent advances in diagnostics, including immunoassay, PCR kits, and distance diagnostics, have had minimal effect on turfgrass diagnostic practices to date. However, continued emphasis on the application of technology rather than knowledge-based diagnostic procedures is contributing to the demise of applied plant pathology. Nevertheless, the demand for turfgrass disease diagnostic services continues to increase, making the future for the applied plant pathologist somewhat uncertain, but full of opportunities.

Notes: Systemic acquired resistance (SAR) is a mechanism of induced defense that confers long-lasting protection against a broad spectrum of microorganisms. SAR requires the signal molecule salicylic acid (SA) and is associated with accumulation of pathogenesis-related proteins, which are thought to contribute to resistance. Much progress has been made recently in elucidating the mechanism of SAR. Using the model plant Arabidopsis, it was discovered that the isochorismate pathway is the major source of SA during SAR. In response to SA, the positive regulator protein NPR1 moves to the nucleus where it interacts with TGA transcription factors to induce defense gene expression, thus activating SAR. Exciting new data suggest that the mobile signal for SAR might be a lipid molecule. We discuss the molecular and genetic data that have contributed to our understanding of SAR and present a model describing the sequence of events leading from initial infection to the induction of defense genes.

Notes: Fusarium head blight (FHB) is a devastating disease of wheat and barley worldwide. Resistant cultivars could reduce damage from FHB. Chinese wheat cultivar Sumai 3 and its derivatives represent the greatest degree of resistance to FHB known. A major quantitative trait locus (QTL) on chromosome 3BS and other minor QTL for FHB resistance have been identified in these cultivars and used in wheat-breeding programs worldwide. Many breeding lines with the 3BS resistance QTL and improved agronomic traits have been developed. In barley, only limited sources of FHB resistance are available, especially in six-rowed barley, and none of them contains a DON level low enough to meet the safety requirement of the brewing industry. Several QTL have been identified for lower FHB severity, DON content, and kernel discoloration and used to enhance FHB resistance in barley. Marker-assisted selection for FHB resistance QTL on 3BS of wheat and on 2H of barley is in progress.

Notes: An increasing interest has emerged with respect to the importance of microbial diversity in soil habitats. The extent of the diversity of microorganisms in soil is seen to be critical to the maintenance of soil health and quality, as a wide range of microorganisms is involved in important soil functions. This review focuses on recent data relating how plant type, soil type, and soil management regime affect the microbial diversity of soil and the implication for the soil's disease suppressiveness. The two main drivers of soil microbial community structure, i.e., plant type and soil type, are thought to exert their function in a complex manner. We propose that the fact that in some situations the soil and in others the plant type is the key factor determining soil microbial diversity is related to the complexity of the microbial interactions in soil, including interactions between microorganisms and soil and microorganisms and plants. A conceptual framework, based on the relative strengths of the shaping forces exerted by plant and soil versus the ecological behavior of microorganisms, is proposed.

Notes: Most hypovirulence in the chestnut blight fungus, Cryphonectria parasitica, is associated with infection by fungal viruses in the family Hypoviridae. Hypovirulence has controlled chestnut blight well in some locations in Europe and in Michigan in the United States. In contrast, with few exceptions, biological control has failed almost completely in eastern North America. Therapeutic treatment of individual cankers is successful in most cases, but the success of hypovirulence at the population level depends on the natural spread of viruses. Characteristics of three interacting trophic levels (virus, fungus, and tree), plus the environment, determine the success or failure of hypovirulence. Vegetative incompatibility restricts virus transmission, but this factor alone is a poor predictor of biological control. Any factor reducing the rate of chestnut blight epidemics enhances hypovirus invasion. Overall, however, not enough is understood about the epidemiological dynamics of this system to determine the crucial factors regulating the establishment of hypovirulence in chestnut forests.

Notes: Although many subviral RNAs reduce or intensify disease symptoms caused by the helper virus, only recently have clues concerning the mechanism of disease modulation been revealed. New models for DI RNA-mediated reduction in helper virus levels and symptom attenuation include DI RNA enhancement of posttranscriptional gene silencing (PTGS), which is an antiviral defense mechanism in plants. Symptom enhancement by the satRNA of Cucumber mosaic virus is caused by minus-strand induction of the programmed cell death pathway. In contrast, symptom enhancement by satC of Turnip crinkle virus is due to satC interference with virion formation, leading to increased levels of free coat protein, which is the viral suppressor of PTGS. Mutualism between satRNA and helper virus can be seen for the satRNA of Groundnut rosette virus, which contributes to the virus by allowing virion assembly. These novel findings are leading to re-evaluation of the relationships between subviral RNAs, helper viruses, and hosts.

Notes: Disease diagnosis is based on a number of factors, including laboratory tests for pathogen identification. Rapid development of genomic techniques for characterization of bacteria over the past decade has greatly simplified and improved pathogen detection and identification, but DNA-based methods have not yet entirely replaced traditional culture and phenotypic tests in the plant industry. The first section of this review focuses on rapid immunodiagnostic and DNA-based detection methods for known bacterial pathogens in plants or plant products, which often manifest no symptoms of disease. The second section covers the broader topic of disease diagnosis and new methods for identifying and characterizing bacteria.

Notes: Abstract This retrospective review deals with the sequence of events and research progress on control of stripe rust of wheat and barley in North America. From the discovery of stripe rust in 1915, it documents the early years of stripe rust research, the 20-year hiatus when stripe rust was not considered important and research was almost nonexistent, the short period in the 1950s when stripe rust became prevalent in the central United States, and the severe epidemics in the West in the 1960s and the associated revival and expansion of research. Finally, it covers 1968 to 2001 when the earlier information was consolidated and combined with results of new research to enable prediction and control of stripe rust, especially in the West.

Notes: Abstract This review deals with a comparative analysis of seven genome sequences from plant-associated bacteria. These are the genomes of Agrobacterium tumefaciens, Mesorhizobium loti, Sinorhizobium meliloti, Xanthomonas campestris pv campestris, Xanthomonas axonopodis pv citri, Xylella fastidiosa, and Ralstonia solanacearum. Genome structure and the metabolism pathways available highlight the compromise between the genome size and lifestyle. Despite the recognized importance of the type III secretion system in controlling host compatibility, its presence is not universal in all necrogenic pathogens. Hemolysins, hemagglutinins, and some adhesins, previously reported only for mammalian pathogens, are present in most organisms discussed. Different numbers and combinations of cell wall degrading enzymes and genes to overcome the oxidative burst generally induced by the plant host are characterized in these genomes. A total of 19 genes not involved in housekeeping functions were found common to all these bacteria.

Notes: Certain strains of fluorescent pseudomonads are important biological components of agricultural soils that are suppressive to diseases caused by pathogenic fungi on crop plants. The biocontrol abilities of such strains depend essentially on aggressive root colonization, induction of systemic resistance in the plant, and the production of diffusible or volatile antifungal antibiotics. Evidence that these compounds are produced in situ is based on their chemical extraction from the rhizosphere and on the expression of antibiotic biosynthetic genes in the producer strains colonizing plant roots. Well-characterized antibiotics with biocontrol properties include phenazines, 2,4-diacetylphloroglucinol, pyoluteorin, pyrrolnitrin, lipopeptides, and hydrogen cyanide. In vitro, optimal production of these compounds occurs at high cell densities and during conditions of restricted growth, involving (i) a number of transcriptional regulators, which are mostly pathway-specific, and (ii) the GacS/GacA two-component system, which globally exerts a positive effect on the production of extracellular metabolites at a posttranscriptional level. Small untranslated RNAs have important roles in the GacS/GacA signal transduction pathway. One challenge in future biocontrol research involves development of new strategies to overcome the broad toxicity and lack of antifungal specificity displayed by most biocontrol antibiotics studied so far.

Notes: Many phytopathogenic bacteria inject virulence effector proteins into plant cells via a Hrp type III secretion system (TTSS). Without the TTSS, these pathogens cannot defeat basal defenses, grow in plants, produce disease lesions in hosts, or elicit the hypersensitive response (HR) in nonhosts. Pathogen genome projects employing bioinformatic methods to identify TTSS Hrp regulon promoters and TTSS pathway targeting signals suggest that phytopathogenic Pseudomonas, Xanthomonas, and Ralstonia spp. harbor large arsenals of effectors. The Hrp TTSS employs customized cytoplasmic chaperones, conserved export components in the bacterial envelope (also used by the TTSS of animal pathogens), and a more specialized set of TTSS-secreted proteins to deliver effectors across the plant cell wall and plasma membrane. Many effectors can act as molecular double agents that betray the pathogen to plant defenses in some interactions and suppress host defenses in others. Investigations of the functions of effectors within plant cells have demonstrated the plasma membrane and nucleus as subcellular sites for several effectors, revealed some effectors to possess cysteine protease or protein tyrosine phosphatase activity, and provided new clues to the coevolution of bacterium-plant interactions.

Notes: Abstract In light of the well-documented health benefits of physical activity and the fact that the majority of adult men and women are inactive, promoting regular physical activity is a public health priority. This chapter reviews current research findings regarding the determinants of exercise behavior. It also discusses the implications of this knowledge for individual and public health recommendations and intervention strategies for promoting physical activity. The discussion is predicated on the belief that physical activity is a complex, dynamic process. During their lives, individuals typically move through various phases of exercise participation that are determined by diverse factors. This chapter discusses physical activity determinants in two broad categories: individual characteristics, including motivations, self-efficacy, exercise history, skills, and other health behaviors; and environmental characteristics such as access, cost, and time barriers and social and cultural supports.

Notes: Abstract Iron homeostasis is maintained by regulating its absorption: Under conditions of deficiency, assimilation is enhanced but iron uptake is otherwise limited to prevent toxicity due to overload. Iron deficiency remains the most important micronutrient deficiency worldwide, but increasing awareness of the genetic basis for iron-loading diseases points to iron overload as a major public health issue as well. Recent identification of mutant alleles causing iron uptake disorders in mice and humans provides new insights into the mechanisms involved in iron transport and its regulation. This article summarizes these discoveries and discusses their impact on our current understanding of iron transport and its regulation.

Notes: Abstract In the past, alcoholic liver disease was attributed exclusively to dietary deficiencies, but experimental and judicious clinical studies have now established alcohol's hepatotoxicity. Despite an adequate diet, it can contribute to the entire spectrum of liver diseases, mainly by generating oxidative stress through its microsomal metabolism via cytochrome P4502E1 (CYP2E1). It also interferes with nutrient activation, resulting in changes in nutritional requirements. This is exemplified by methionine, one of the essential amino acids for humans, which needs to be activated to S-adenosylmethionine (SAMe), a process impaired by liver disease. Thus, SAMe rather than methionine is the compound that must be supplemented in the presence of significant liver disease. In baboons, SAMe attenuated mitochondrial lesions and replenished glutathione; it also significantly reduced mortality in patients with Child A or B cirrhosis. Similarly, decreased phosphatidylethanolamine methyltransferase activity is associated with alcoholic liver disease, resulting in phosphatidylcholine depletion and serious consequences for the integrity of membranes. This can be offset by polyenylphosphatidylcholine (PPC), a mixture of polyunsaturated phosphatidylcholines comprising dilinoleoylphosphatidylcholine (DLPC), which has high bioavailability. PPC (and DLPC) opposes major toxic effects of alcohol, with down-regulation of CYP2E1 and reduction of oxidative stress, deactivation of hepatic stellate cells, and increased collagenase activity, which in baboons, results in prevention of ethanol-induced septal fibrosis and cirrhosis. Corresponding clinical trials are ongoing.

Notes: Abstract Traditional food resources of indigenous peoples are now recognized as containing a variety of environmental contaminants which reach food species through local or long-range transport avenues. In this chapter we review the published reports of contaminants contained in traditional food in northern North America and Europe as organochlorines, heavy metals, and radionuclides. Usually, multiple contaminants are contained in the same food species. Measurement of dietary exposure to these environmental contaminants is reviewed, as are major issues of risk assessment, evaluation, and management. The dilemma faced by indigenous peoples in weighing the multiple nutritional and socioeconomic benefits of traditional food use against risk of contaminants in culturally important food resources is described.

Notes: Abstract Epidemiologic studies from numerous disparate populations reveal that individuals with the habit of daily moderate wine consumption enjoy significant reductions in all-cause and particularly cardiovascular mortality when compared with individuals who abstain or who drink alcohol to excess. Researchers are working to explain this observation in molecular and nutritional terms. Moderate ethanol intake from any type of beverage improves lipoprotein metabolism and lowers cardiovascular mortality risk. The question now is whether wine, particularly red wine with its abundant content of phenolic acids and polyphenols, confers additional health benefits. Discovering the nutritional properties of wine is a challenging task, which requires that the biological actions and bioavailability of the 〉200 individual phenolic compounds be documented and interpreted within the societal factors that stratify wine consumption and the myriad effects of alcohol alone. Further challenge arises because the health benefits of wine address the prevention of slowly developing diseases for which validated biomarkers are rare. Thus, although the benefits of the polyphenols from fruits and vegetables are increasingly accepted, consensus on wine is developing more slowly. Scientific research has demonstrated that the molecules present in grapes and in wine alter cellular metabolism and signaling, which is consistent mechanistically with reducing arterial disease. Future research must address specific mechanisms both of alcohol and of polyphenolic action and develop biomarkers of their role in disease prevention in individuals.

Notes: Abstract The "fetal origins" hypothesis postulates that conditions, most likely nutritional, "program" the fetus for the development of chronic diseases in adulthood. Associations between the newborn's size at birth and various determinants or consequences of chronic diseases have been identified in many, but not all, of the available studies. It remains to be established whether these associations are causal. Remarkably little information is available on the specific role of maternal nutritional status. The role of birth weight remains difficult to interpret except as a proxy for events in intrauterine life. Unfortunately, birth weight does not make an important contribution to the population attributable risk of cardiovascular disease; lifestyle factors during adulthood make much greater contributions. Data from experimental species suggest possible mechanisms for the origin of chronic disease early in life. It is too soon to use this research as a basis for new interventions directed at pregnant women for the purpose of reducing chronic disease in their offspring.

Notes: Abstract The study of fat metabolism in insects has received considerable attention over the years. Although by no means complete, there is a growing body of information about dietary lipid requirements, and the absolute requirement for sterol is of particular note. In this review we (a) summarize the state of understanding of the dietary requirements for the major lipids and (b) describe in detail the insect lipid transport system. Insects digest and absorb lipids similarly to vertebrates, but with some important differences. The hallmark of fat metabolism in insects centers on the lipid transport system. The major lipid transported is diacylglycerol, and it is carried by a high-density lipoprotein called lipophorin. Lipophorin is a reusable shuttle that picks up lipid from the gut and delivers it to tissues for storage or utilization without using the endocytic processes common to vertebrate cells. The mechanisms by which this occurs are not completely understood and offer fruitful areas for future research.

Notes: Abstract Along with their foods and dietary customs, Africans were carried into diaspora throughout the Americas as a result of the European slave trade. Their descendants represent populations at varying stages of the nutrition transition. West Africans are in the early stage, where undernutrition and nutrient deficiencies are prevalent. Many Caribbean populations represent the middle stages, with undernutrition and obesity coexisting. African-Americans and black populations in the United Kingdom suffer from the consequences of caloric excess and diets high in fat and animal products. Obesity, non-insulin-dependent diabetes mellitus, hypertension, coronary heart disease, and certain cancers all follow an east-to-west gradient of increasing prevalence. Public health efforts must focus not only on eradicating undernutrition in West Africa and the Caribbean but also on preventing obesity, hypercholesterolemia, and their consequences. Fortunately, a coherent and well-supported set of recommendations exists to promote better nutrition. Implementation of it founders primarily as a result of the influence of commercial and political interests.

Notes: Abstract The family of enzymes involved in lipogenesis is a model system for understanding how a cell adapts to dietary energy in the form of carbohydrate versus energy in the form of triacylglycerol. Glucose-6-phosphate dehydrogenase (G6PD) is unique in this group of enzymes in that it participates in multiple metabolic pathways: reductive biosynthesis, including lipogenesis; protection from oxidative stress; and cellular growth. G6PD activity is enhanced by dietary carbohydrates and is inhibited by dietary polyunsaturated fats. These changes in G6PD activity are a consequence of changes in the expression of the G6PD gene. Nutrients can regulate the expression of genes at both transcriptional and posttranscriptional steps. Most lipogenic enzymes undergo large changes in the rate of gene transcription in response to dietary changes; however, G6PD is regulated at a step subsequent to transcription. This step is involved in the rate of synthesis of the mature mRNA in the nucleus, specifically regulation of the efficiency of splicing of the nascent G6PD transcript. Understanding the mechanisms by which nutrients alter nuclear posttranscriptional events will help uncover new information on the breadth of mechanisms involved in gene regulation.

Notes: Abstract Accurate assessment of dietary intake among preschool-aged children is important for clinical care and research, for nutrition monitoring and evaluating nutrition interventions, and for epidemiologic research. We identified 25 studies published between January 1976 and August 2000 that evaluated the validity of food recalls (n = 12), food frequency questionnaires (n = 9), food records (n = 2), or other methods (n = 2). We identified four studies that evaluated the reproducibility of food frequency questionnaires. Validity studies varied in validation standard and study design, making comparisons between studies difficult. In general, food frequency questionnaires overestimated total energy intake and were better at ranking, than quantifying, nutrient intake. Compared with the validation standard, food recalls both overestimated and underestimated energy intake. When choosing a method to estimate diet, both purpose of the assessment and practicality of the method must be considered, in addition to the validity and reproducibility reported in the scientific literature.

Notes: Abstract We have tested whether differences in distribution and dietary responsiveness of low-density lipoprotein (LDL) subclasses contribute to the variability in the magnitude of LDL-cholesterol reduction induced by diets low in total and saturated fat and high in carbohydrate. Our studies have focused on a common, genetically influenced metabolic profile, characterized by a predominance of small, dense LDL particles (subclass pattern B), that is associated with a two- to threefold increase in risk for coronary artery disease. We have found that healthy normolipidemic individuals with this trait show a greater reduction in LDL cholesterol and particle number in response to low-fat, high-carbohydrate diets than do unaffected individuals (subclass pattern A). Moreover, such diets result in reduced LDL particle size, with induction of pattern B in a substantial proportion of pattern A men. Recent studies have indicated that this response is under genetic influence. Future identification of the specific genes involved may lead to improved targeting of dietary therapies aimed at reducing cardiovascular disease risk.

Notes: Abstract About 40% of patients undergoing maintenance dialysis suffer from varying degrees of protein-energy malnutrition. This is a problem of substantial importance because many measures of nutritional status correlate with the risk of morbidity and mortality. There are many causes of protein-energy malnutrition in maintenance dialysis patients. Evidence indicates that nutritional decline begins even when the reduction in glomerular filtration rate is modest, and it is likely that the observed decrease in dietary protein and energy intake plays an important role. The nutrient intake of patients receiving maintenance dialysis also is often inadequate, and several lines of evidence suggest that toxins that accumulate with renal failure suppress appetite and contribute to nutritional decline once patients are on maintenance dialysis. Recent epidemiologic studies have suggested that both increased serum levels of leptin and inflammation may reduce nutrient intake and contribute to the development of protein-energy malnutrition. It is likely that associated illnesses, which are highly prevalent, contribute to malnutrition in maintenance dialysis patients. Recent data from the United States Renal Data System registry suggest that in the United States, the mortality rate of dialysis patients is improving. However, it remains high. We offer suggestions for predialysis and dialysis care of these patients that can result in improvement in their nutritional status. Whether this improvement will result in a decrease in patient morbidity and mortality is unknown.

Notes: Abstract Biotin is a water-soluble vitamin required by all organisms by virtue of its essential role in carboxylation reactions. Although the metabolism and role of biotin in intermediary metabolism are well established, biotin remains one of the most poorly understood water-soluble vitamins in terms of nutritional requirements and responsiveness to physiological and pharmacological states. Significant advances in the understanding of biotin nutriture have been recently accomplished through the description of the kinetics and regulation of biotin transport and improved methods for biotin status assessment. Additionally, the potential role of biotin in the regulation of gene expression has been strengthened through description of altered gene expression during biotin deficiency and through newly described enzymatic activities of the enzyme biotinidase. Given mounting evidence of suboptimum biotin status, a more complete understanding of these aspects of biotin should lead to a greater appreciation of the ways in which biotin aids in the maintenance of health.

Notes: Abstract Humans and other mammals are colonized by a vast, complex, and dynamic consortium of microorganisms. One evolutionary driving force for maintaining this metabolically active microbial society is to salvage energy from nutrients, particularly carbohydrates, that are otherwise nondigestible by the host. Much of our understanding of the molecular mechanisms by which members of the intestinal microbiota degrade complex polysaccharides comes from studies of Bacteroides thetaiotaomicron, a prominent and genetically manipulatable component of the normal human and mouse gut. Colonization of germ-free mice with B. thetaiotaomicron has shown how this anaerobe modifies many aspects of intestinal cellular differentiation/gene expression to benefit both host and microbe. These and other studies underscore the importance of understanding precisely how nutrient metabolism serves to establish and sustain symbiotic relationships between mammals and their bacterial partners.

Notes: Abstract Long-chain fatty acids are an important constituent of the diet and they contribute to a multitude of cellular pathways and functions. Uptake of long-chain fatty acids across plasma membranes is the first step in fatty acid utilization, and recent evidence supports an important regulatory role for this process. Although uptake of fatty acids involves two components, passive diffusion through the lipid bilayer and protein-facilitated transfer, the latter component appears to play the major role in mediating uptake by key tissues. Identification of several proteins as fatty acid transporters, and emerging evidence from genetically altered animal models for some of these proteins, has contributed significant insight towards understanding the limiting role of transport in the regulation of fatty acid utilization. We are also beginning to better appreciate how disturbances in fatty acid utilization influence general metabolism and contribute to metabolic pathology.

Notes: Abstract Ceruloplasmin is a serum ferroxidase that contains greater than 95% of the copper found in plasma. This protein is a member of the multicopper oxidase family, an evolutionarily conserved group of proteins that utilize copper to couple substrate oxidation with the four-electron reduction of oxygen to water. Despite the need for copper in ceruloplasmin function, this protein plays no essential role in the transport or metabolism of this metal. Aceruloplasminemia is a neurodegenerative disease resulting from inherited loss-of-function mutations in the ceruloplasmin gene. Characterization of this disorder revealed a critical physiological role for ceruloplasmin in determining the rate of iron efflux from cells with mobilizable iron stores and has provided new insights into human iron metabolism and nutrition.

Notes: Abstract Conjugated linoleic acid (CLA) is a group of polyunsaturated fatty acids found in beef, lamb, and dairy products that exist as positional and stereo-isomers of octadecadienoate (18:2). Over the past two decades numerous health benefits have been attributed to CLA in experimental animal models including actions to reduce carcinogenesis, atherosclerosis, onset of diabetes, and body fat mass. The accumulation of CLA isomers and several elongated/desaturated and beta-oxidation metabolites have been found in tissues of animals fed diets with CLA. Molecular mechanisms of action appear to include modulation of eicosanoid formation as well as regulation of the expression of genes coding for enzymes known to modulate macronutrient metabolism. This review focuses on health benefits, metabolism, and potential mechanisms of action of CLA and postulates the implications regarding dietary CLA for human health.

Notes: Abstract Certain diets cause a marked reduction in milk fat production in ruminants. Commonly referred to as milk fat depression (MFD), the mechanism involves an interrelationship between rumen microbial processes and tissue metabolism. Numerous theories to explain this interrelationship have been proposed and investigations offer little support for theories that are based on a limitation in the supply of lipogenic precursors. Rather, the basis involves alterations in rumen biohydrogenation of dietary polyunsaturated fatty acids and a specific inhibition of mammary synthesis of milk fat. The biohydrogenation theory proposes that under certain dietary conditions, typical pathways of rumen biohydrogenation are altered to produce unique fatty acid intermediates that inhibit milk fat synthesis. Trans-10, cis-12 conjugated linoleic acid (CLA) has been identified as one example that is correlated with the reduction in milk fat. Investigations with pure isomers have shown that trans-10, cis-12 CLA is a potent inhibitor of milk fat synthesis, and similar to diet-induced MFD, the mechanism involves a coordinated reduction in mRNA abundance for key enzymes involved in the biochemical pathways of fat synthesis. A more complete identification of these naturally produced inhibitors of fat synthesis and delineation of cellular mechanisms may offer broader opportunities for application and understanding of the regulation of lipid metabolism.

Notes: The chapter reviews the historical development and interactions of U.S. agricultural, economic, nutrition, and development policies relating to the creation of the commercial environment of social, economic, technological, and political factors that favor the development of American obesity.

Notes: Animals have developed highly adaptive and redundant mechanisms to maintain energy balance by matching caloric intake to caloric expenditure. Recent evidence has pointed to a variety of peripheral signals that inform specific central nervous system (CNS) circuits about the status of peripheral energy stores as critical to the maintenance of energy balance. A critical component of these CNS circuits is the melanocortin system. Regulation of signaling by melanocortin 3 and melanocortin 4 receptors in the CNS is controlled via neuronal cell bodies in the arcuate nucleus of the hypothalamus that synthesize melanocortin receptor agonists such as alpha-melanocyte-stimulating hormone (alpha-MSH) or antagonists such as agouti-related protein (AgRP). The activity of these two populations of neurons is reciprocally regulated by a number of peripheral and central systems that influence energy balance. Further, increased melanocortin signaling via pharmacological or genetic means in the CNS causes potent reductions in food intake and weight loss. Decreased melanocortin signaling via pharmacological or genetic means results in increased food intake and weight gain. Reviewed here is the wide range of evidence that points to the melanocortin system as a critical node in the diverse neurocircuitry that regulates food intake and body weight.

Notes: Identifying bioactive compounds and establishing their health effects are active areas of scientific inquiry. There are exciting prospects that select bioactive compounds will reduce the risk of many diseases, including chronic diseases such as cardiovascular disease. Recent findings have established that cardiovascular disease is a disease of inflammation, and consequently is amenable to intervention via molecules that have anti-inflammatory effects. In addition, research demonstrating adverse effects of oxidants on atherogenesis raises the possibility that antioxidants can confer cardioprotective effects. This review provides an overview of research approaches that can be used to unravel the biology and health effects of bioactive compounds. Because of the number of bioactive compounds and the diversity of likely biological effects, numerous and diverse experimental approaches must be taken to increase our understanding of the biology of bioactive compounds. Recognizing the complexity of this biology, sophisticated experimental designs and analytical methodologies must be employed to advance the field. The discovery of novel health effects of bioactive compounds will provide the scientific basis for future efforts to use biotechnology to modify/fortify foods and food components as a means to improve public health.

Notes: Erythropoiesis is the process in which new erythrocytes are produced. These new erythrocytes replace the oldest erythrocytes (normally about one percent) that are phagocytosed and destroyed each day. Folate, vitamin B12, and iron have crucial roles in erythropoiesis. Erythroblasts require folate and vitamin B12 for proliferation during their differentiation. Deficiency of folate or vitamin B12 inhibits purine and thymidylate syntheses, impairs DNA synthesis, and causes erythroblast apoptosis, resulting in anemia from ineffective erythropoiesis. Erythroblasts require large amounts of iron for hemoglobin synthesis. Large amounts of iron are recycled daily with hemoglobin breakdown from destroyed old erythrocytes. Many recently identified proteins are involved in absorption, storage, and cellular export of nonheme iron and in erythroblast uptake and utilization of iron. Erythroblast heme levels regulate uptake of iron and globin synthesis such that iron deficiency causes anemia by retarded production rates with smaller, less hemoglobinized erythrocytes.

Notes: Increased longevity and improved medical management of children with chronic illnesses has led to a focus on the short- and long-term consequences of these conditions on bone health. Bone loss is influenced by diet, malabsorption, and disease-related imbalances in bone turnover. It may be exacerbated by common medications, especially corticosteroids. Assessment of bone mass and quality, calcium absorption, kinetically derived rates of bone turnover, and biochemical markers of bone turnover have increased our knowledge of the pathophysiology of bone loss in these children as well as provided insights into possible therapeutic interventions. Increased intake of calcium and vitamin D, while useful, is unlikely to prevent or resolve bone loss in many chronically ill children. Emphasis on combination of nutritional interventions with exercise and newer bone-sparing therapies may be necessary.

Notes: Fatty acid desaturases introduce a double bond in a specific position of long-chain fatty acids, and are conserved across kingdoms. Degree of unsaturation of fatty acids affects physical properties of membrane phospholipids and stored triglycerides. In addition, metabolites of polyunsaturated fatty acids are used as signaling molecules in many organisms. Three desaturases, Delta9, Delta6, and Delta5, are present in humans. Delta-9 catalyzes synthesis of monounsaturated fatty acids. Oleic acid, a main product of Delta9 desaturase, is the major fatty acid in mammalian adipose triglycerides, and is also used for phospholipid and cholesteryl ester synthesis. Delta-6 and Delta5 desaturases are required for the synthesis of highly unsaturated fatty acids (HUFAs), which are mainly esterified into phospholipids and contribute to maintaining membrane fluidity. While HUFAs may be required for cold tolerance in plants and fish, the primary role of HUFAs in mammals is cell signaling. Arachidonic acid is required as substrates for eicosanoid synthesis, while docosahexaenoic acid is required in visual and neuronal functions. Desaturases in mammals are regulated at the transcriptional level. Reflecting overlapping functions, three desaturases share a common mechanism of a feedback regulation to maintain products in membrane phospholipids. At the same time, regulation of Delta9 desaturase differs from Delta6 and Delta5 desaturases because its products are incorporated into more diverse lipid groups. Combinations of multiple transcription factors achieve this sophisticated differential regulation.

Notes: Abstract The macular region of the primate retina is yellow in color due to the presence of the macular pigment, composed of two dietary xanthophylls, lutein and zeaxanthin, and another xanthophyll, meso-zeaxanthin. The latter is presumably formed from either lutein or zeaxanthin in the retina. By absorbing blue-light, the macular pigment protects the underlying photoreceptor cell layer from light damage, possibly initiated by the formation of reactive oxygen species during a photosensitized reaction. There is ample epidemiological evidence that the amount of macular pigment is inversely associated with the incidence of age-related macular degeneration, an irreversible process that is the major cause of blindness in the elderly. The macular pigment can be increased in primates by either increasing the intake of foods that are rich in lutein and zeaxanthin, such as dark-green leafy vegetables, or by supplementation with lutein or zeaxanthin. Although increasing the intake of lutein or zeaxanthin might prove to be protective against the development of age-related macular degeneration, a causative relationship has yet to be experimentally demonstrated.

Notes: Zinc is an essential micronutrient for human growth, development, and immune function. Zinc deficiency impairs overall immune function and resistance to infection. Mild to moderate zinc deficiency can be best detected through a positive response to supplementation trials. Zinc supplementation has been shown to have a positive effect on the incidence of diarrhea (18% reduction, 95% CI: 7-28%) and pneumonia (41% reduction, 95% CI: 17-59%), and might lead to a decrease in the incidence of malaria. Zinc has also proven to decrease the duration of diarrhea by 15% (95% CI: 5-24%). Maternal zinc supplementation may lead to a decrease in infant infections. Studies assessing the role of zinc supplementation among persons with HIV, tuberculosis, and the common cold have not been conclusive. Two studies have shown zinc supplementation to decrease child mortality by more than 50%. Zinc clearly has an important role in infant and childhood infectious diseases; programs to increase the intake of zinc among deficient populations are needed.

Notes: Development of bioinformatics tools provided researchers with the ability to identify full sets of trace element-containing proteins in organisms for which complete genomic sequences are available. Recently, independent bioinformatics methods were used to identify all, or almost all, genes encoding selenocysteine-containing proteins in human, mouse, and Drosophila genomes, characterizing entire selenoproteomes in these organisms. It also should be possible to search for entire sets of other trace element-associated proteins, such as metal-containing proteins, although methods for their identification are still in development.

Notes: The concept of systemic photoprotection by dietary means is gaining momentum. Skin is continuously exposed to ultraviolet (UV) radiation, the major cause of skin disorders such as sunburn, photodamage, and nonmelanoma skin cancer. Most of the erythemal annual UV dose is encountered under nonvacation conditions, when no sunscreen is applied. In the absence of topically added compounds, skin protection depends solely on endogenous defense. Micronutrients can act as UV absorbers, as antioxidants, or can modulate signaling pathways elicited upon UV exposure. UV-induced erythema is a suitable parameter to assess photoprotection. Dietary protection is provided by carotenoids, tocopherols, ascorbate, flavonoids, or n-3 fatty acids, contributing to maintenance resistance as part of lifelong protection.

Notes: This review focuses on dietary intake and dietary supplement use among the U.S. population age 1-74 based on four National Health and Nutrition Examination Surveys conducted in 1971-74, 1976-80, 1988-94, and 1999-2000. Secular trends in intake of energy, macronutrients, cholesterol, sodium, calcium, iron, folate, zinc, vitamins A and C, fruits, vegetables, and grain products are summarized. During the 30-year period, mean energy intake increased among adults, and changed little among children age 1-19, except for an increase among adolescent females. Factors contributing to increases in energy intake include increases in the percentage of the population eating away from home (particularly at fast-food restaurants), larger portion sizes of foods and beverages, increased consumption of sweetened beverages, changes in snacking habits, and improved dietary methodology. Dietary supplement use increased among adult men and women, decreased among children age 1-5, and was stable for children age 6-11 and adolescents.

Notes: Abstract Nineteen single dominant genes (R genes) for resistance to viruses, nematodes, and fungi have been positioned on the molecular map of potato using DNA markers. Fourteen of those genes are located in five "hotspots" for resistance in the potato genome. Quantitative trait loci (QTL) for resistance to late blight caused by the oomycete Phytophthora infestans, to tuber rot caused by the bacterium Erwinia carotovora ssp. atroseptica, and to root cyst nematodes have been identified on all 12 potato chromosomes. Some QTL for resistance to different pathogens are linked to each other and/or to resistance hotspots. Based on the genetic clustering with R genes, we propose that some QTL for resistance have a molecular basis similar to single R genes. Mapping potato genes with sequence similarity to cloned R genes of other plants and other defense-related genes reveals linkage between candidate genes, R genes, and resistance QTL. To explain the molecular basis of polygenic resistance in potato we propose (a) genes having structural similarity with cloned R genes and (b) genes involved in the defense response. The "candidate gene approach" enables the identification of markers highly useful for marker-assisted selection in potato breeding.

Notes: Abstract Historically, the study of plant viruses has contributed greatly to the elucidation of eukaryotic biology. Recently, concurrent with the development of viruses into expression vectors, the biotechnology industry has developed an increasing number of disease therapies utilizing recombinant proteins. Plant virus vectors are viewed as a viable option for recombinant protein production. Employing pathogens in the process of creating added value to agriculture is, in effect, making an ally from an enemy. This review discusses the development and use of viruses as expression vectors, with special emphasis on (+) strand RNA virus systems. Further, the use of virus expression vectors in large-scale agricultural settings to produce recombinant proteins is described, and the technical challenges that need to be addressed by agriculturists and molecular virologists to fully realize the potential of this latest evolution of plant science are outlined.

Notes: Abstract The feeding sites induced by sedentary root-endoparasitic nematodes have long fascinated researchers. Nematode feeding sites are constructed from plant cells, modified by the nematode to feed itself. Powerful new techniques are allowing us to begin to elucidate the molecular mechanisms that produce the ultrastructural features in nematode feeding cells. Many plant genes that are expressed in feeding sites produced by different nematodes have been identified in several plant species. Nematode-responsive plant genes can now be grouped in categories related to plant developmental pathways and their roles in the making of a feeding site can be illuminated. The black box of how nematodes bring about such elaborate cell differentiation in the plant is also starting to open. Although the information is far from complete, the groundwork is set so that the functions of the plant and nematode genes in feeding site development can begin to be assessed.

Notes: Like many other plant RNA viruses, Wheat streak mosaic virus (WSMV) sequence diversity within and among infected plants is low given the large number of virions produced. This may be explained by considering aspects of plant virus life history. Intracellular replication of RNA viruses is predominately linear, not exponential, which means that the rate at which mutations accumulate also is linear. Bottlenecks during systemic movement further limit diversity. Analysis of mixed infections with two WSMV isolates suggests that about four viral genomes participate in systemic invasion of each tiller. Low effective population size increases the role of stochastic processes on dynamics of plant virus population genetics and evolution. Despite low pair-wise diversity among isolates, the number of polymorphic sites within the U.S. population is about the same as between divergent strains or a sister species. Characteristics of polymorphism in the WSMV coat protein gene suggest that most variation appears neutral.

Notes: I first describe my introduction to plant pathology and early experiences with employment, the environment, diseases, pests, and various plant pathologists. Then I recount a decade of stimulating studies at the University of Minnesota and the route I followed to a career in international agriculture with the Rockefeller Foundation in Colombia and later at Cornell University. My appreciation for and knowledge of traditional farmers and sustainable agriculture occurred as a slow awakening. Comments are made regarding problems, principles, and satisfactions associated with the improvement of efforts to aid food production in developing countries. My curious love affair with root and tuber crops, especially cassava, is explained and readily defended. My favorite pathogens, Phytophthora infestans and Ralstonia solanacearum, among others, are considered. The pleasures and satisfactions of teaching, writing, and sabbatical leaves are related. Finally, thoughts on the balance between basic and applied research in plant pathology are offered with significant nervousness about the future of our discipline.

Notes: Abstract Host plant resistance has been used extensively for disease control in many crop species; however, the resistance conferred by many sources is not durable as a result of rapid changes in the pathogen. Although many resistance genes have been identified in plant germplasm, there is no easy way to predict the quality or durability of these resistance genes. In this review, we revisit the hypothesis that resistance genes imposing a high penalty to the pathogen for adaptation will likely be durable. By elucidating the molecular changes involved in pathogen adaptation and the associated fitness cost, a proactive approach may be developed to predict the durability of resistance genes available for deployment.

Notes: Abstract The Burkholderia cepacia complex (Bcc) consists of several species of closely related and extremely versatile gram-negative bacteria found naturally in soil, water, and the rhizosphere of plants. Strains of Bcc have been used in biological control of plant diseases and bioremediation, while some strains are plant pathogens or opportunistic pathogens of humans with cystic fibrosis. The ecological versatility of these bacteria is likely due to their unusually large genomes, which are often comprised of several (typically two or three) large replicons, as well as their ability to use a large array of compounds as sole carbon sources. The original species B. cepacia has been split into eight genetic species (genomovars), including five named species, but taxonomic distinctions have not enabled biological control strains to be clearly distinguished from human pathogenic strains. This has led to a reassessment of the risk of several strains registered by the U.S. Environmental Protection Agency for biological control. We review the biology of Bcc bacteria, especially how our growing knowledge of Bcc ecology and pathogenicity might be used in risk assessment. The capability of this bacterial complex to cause disease in plants and humans, as well as to control plant diseases, affords a rare opportunity to explore traits that may function in all three environments.

Notes: Abstract The family Closteroviridae comprises more than 30 plant viruses with flexuous, filamentous virions and includes representatives with either mono- or bipartite positive-strand ssRNA genomes. Closteroviruses are transmitted semipersistently by insects from three families of Homoptera, in infected plants are associated with phloem tissue, and demonstrate an astonishing genetic diversity that suggests extensive, on-going evolution. Phylogenetic analyses of their replicative genes as well as the conserved HSP70 demonstrate that closteroviruses co-evolved with their insect vectors, resulting in three major lineages, i.e. aphid-, mealybug-, and whitefly-transmitted viruses. Closteroviruses apparently represent an ancient and diverse virus family that may pose threats to agriculture and needs serious attention.

Notes: Abstract Fungal pathogens cause many of the most serious crop diseases. One of the principal reasons for the success of this group is their ability to locate and perceive appropriate host surfaces and then to elaborate specialized infection structures. Here we review the processes implicated in surface attachment, germ tube elongation, and development of appressoria. The involvement of surface-acting proteins such as fungal hydrophobins and integrins in these processes is evaluated, along with a description of studies that have revealed the existence of conserved signaling pathways that regulate appressorium formation. Finally, we anticipate the prospect of genome-level analysis of fungal pathogens and the key research questions that will need to be addressed.

Notes: Abstract The Food Quality Protection Act mandates new considerations in pesticide regulatory decisions. Endocrine disruption, determination of the need for an additional safety factor for infants and children, aggregate exposure to each pesticide, and cumulative exposure to pesticides with a common mechanism of toxicity will all become part of the risk assessment process. A reduction in availability of fungicides for many current uses appears to be a likely result of this act. If this occurs, disease management programs, particularly in fruits and vegetables, will be challenged to find alternative approaches. Currently, fungicides play an important role in many production systems. Loss of these valuable pest management tools will contribute to increased costs for producers and consumers, as well as to complex issues facing the structure of agriculture in the United States.

Notes: Abstract Populations of plant viruses, like all other living beings, are genetically heterogeneous, a property long recognized in plant virology. Only recently have the processes resulting in genetic variation and diversity in virus populations and genetic structure been analyzed quantitatively. The subject of this review is the analysis of genetic variation, its quantification in plant virus populations, and what factors and processes determine the genetic structure of these populations and its temporal change. The high potential for genetic variation in plant viruses, through either mutation or genetic exchange by recombination or reassortment of genomic segments, need not necessarily result in high diversity of virus populations. Selection by factors such as the interaction of the virus with host plants and vectors and random genetic drift may in fact reduce genetic diversity in populations. There is evidence that negative selection results in virus-encoded proteins being not more variable than those of their hosts and vectors. Evidence suggests that small population diversity, and genetic stability, is the rule. Populations of plant viruses often consist of a few genetic variants and many infrequent variants. Their distribution may provide evidence of a population that is undifferentiated, differentiated by factors such as location, host plant, or time, or that fluctuates randomly in composition, depending on the virus.

Notes: Abstract More than 30 genes have been characterized from different plant species that provide resistance to a variety of different pathogen and pest species. The structures of most are consistent with a role in pathogen recognition and defense response signaling. Resistance genes are very abundant in plant genomes and most belong to tightly linked gene families. Evolution of R genes is driven by selection on allelic variation created by mutation and re-assorted by recombination between alleles and sometimes between different gene family members. Selection favors genes that can recognize pathogen avr gene products that are present in pathogen populations. Selection at linked gene families favors haplotypes with useful combinations of genes but a limited physiological cost to the plant. Future utilization of R genes will include transfer between related genera and identification or construction of genes that condition durable resistance to variable pathogens. Genes with durable resistance may interact with conserved pathogen elicitors or condition resistance responses that are independent of specific Avr gene interactions.

Notes: Abstract Rhizosphere colonization is one of the first steps in the pathogenesis of soilborne microorganisms. It can also be crucial for the action of microbial inoculants used as biofertilizers, biopesticides, phytostimulators, and bioremediators. Pseudomonas, one of the best root colonizers, is therefore used as a model root colonizer. This review focuses on (a) the temporal-spatial description of root-colonizing bacteria as visualized by confocal laser scanning microscopal analysis of autofluorescent microorganisms, and (b) bacterial genes and traits involved in root colonization. The results show a strong parallel between traits used for the colonization of roots and of animal tissues, indicating the general importance of such a study. Finally, we identify several noteworthy areas for future research.

Notes: Abstract Plant pathogens cause mortality and reduce fecundity of individual plants, drive host population dynamics, and affect the structure and composition of natural plant communities. Pathogens are responsible for both numerical changes in host populations and evolutionary changes through selection for resistant genotypes. Linking such ecological and evolutionary dynamics has been the focus of a growing body of literature on the effects of plant diseases in natural ecosystems. A guiding principle is the importance of understanding the spatial and temporal scales at which plants and pathogens interact. This review summarizes the effects of diseases on populations of wild plants, focusing in particular on the mediation of plant competition and succession, the maintenance of plant species diversity, as well as the process of rapid evolutionary changes in host-pathogen symbioses.

Notes: The relationship between epidemiology and disease management is long-standing but sometimes tenuous. It may seem self-evident that improved understanding of epidemic processes will lead to more effective control practices but this remains a testable proposition rather than demonstrated reality. A wide range of models differing in mathematical sophistication and computational complexity has been proposed as a means of achieving a greater understanding of epidemiology and carrying this through to improved management. The potential exists to align these modeling approaches to evaluation of control practices and prediction of the consequent epidemic outcomes, but these have yet to make a major impact on practical disease management. For the immediate future simpler pragmatic approaches for analysis of disease progress, using nonlinear growth functions and/or integrated measures such as area under disease progress curves, will play a key role in informing tactical and strategic decisions on control treatments. These approaches have proved useful in describing control effectiveness and, in some cases, optimizing or changing control practices.

Notes: This article presents the experiences of a woman in academic plant pathology from the 1950s to today. Topics include the social climate for women in science, personal and professional developments and research discoveries, public policy issues in agriculture and biotechnology affecting plant pathology, and projections for the future of plant pathology.

Notes: During my career in Plant Pathology/Nematology, many major advancements have occurred in the study of nematodes-even with their being largely soilborne and thus often overlooked. These biotrophic organisms include the most widespread and important group of plant pathogens-the root-knot nematodes Meloidogyne species-which attack most major crops, as well as thousands of non-crop plant species. Landmark achievements that catalyzed research on these organisms included the discovery of effective nematicides, ectoparasitic forms, elucidation of disease complexes, nematodes as virus vectors, development of host resistance, and new technologies for research. Evolving research thrusts involve interfacing traditional and molecular systematics/diagnostics, adoption of the Caenorhabditis elegans-molecular genetics resource for general nematological research, focus on genetics of parasitism, use of molecular tools in developing host resistance, ecological and quantitative facets, and soil-biology-ecology based integrated management. Educational and international programs are encountering many changes and challenges, as is support for nematology in general.

Notes: Infection of maize kernels by toxigenic fungi remains a challenging problem despite decades of research progress. Cultural practices, including crop rotation, tillage, planting date, and management of irrigation and fertilization, have limited effects on infection and subsequent mycotoxin accumulation. Current infrastructure and grain storage practices in developed countries can prevent postharvest development of mycotoxins, but this aspect remains a threat in developing countries, especially in tropical areas. Because most mycotoxin problems develop in the field, strategies are needed to prevent infection of growing plants by toxigenic fungi. Developing genetic resistance to Aspergillus flavus, Gibberella zeae, and Fusarium spp. (particularly F. verticillioides) in maize is a high priority. Sources of resistance to each of these pathogens have been identified and have been incorporated into public and private breeding programs. However, few, if any, commercial cultivars have adequate levels of resistance. Efforts to control infection or mycotoxin development through conventional breeding and genetic engineering are reviewed. The role of transgenic insect control in the prevention of mycotoxins in maize is discussed.

Notes: Mycorrhizae regulate elemental and energy flows in terrestrial ecosystems. We understand much of how mycorrhizae work, but integrating all possible mechanisms into a whole has proven elusive. Multiple evolutionary events and the long evolutionary history mean that different plants and fungi bring independent characteristics to the symbiosis. This variety results in extensive physiological variation. How do we integrate functional responses with diversity to understand the role of mycorrhizae in ecosystems? We review ecophysiological mechanisms of mycorrhizae and organize these into functional groups. Species-area relationships are not curvilinear, but resemble the "broken stick" model. We coupled functional groups with a metacommunity analysis to show how complex behavior can be generated using a simple matrix model of resource exchange. This approach provides insights into how we might integrate diversity and function across landscapes.

Notes: Abstract The twentieth century has been productive for the science of plant pathology and the field of host-parasite interactions-both in understanding how pathogens and plant defense work and in developing more effective means of disease control. Early in the twentieth century, plant pathology adopted a philosophy that encouraged basic scientific investigation of pathogens and disease defense. That philosophy led to the strategy of developing disease-resistant plants as a prima facie disease-control measure-and in the process saved billions of dollars and avoided the use of tons of pesticides. Plant pathology rapidly adopted molecular cloning and its spin-off technologies, and these have fueled major advances in our basic understanding of plant diseases. This knowledge and the development of efficient technologies for producing transgenic plants convey optimism that plant diseases will be more efficiently controlled in the twenty-first century.

Notes: Abstract The controlled environment of greenhouses, the high value of the crops, and the limited number of registered fungicides offer a unique niche for the biological control of plant diseases. During the past ten years, over 80 biocontrol products have been marketed worldwide. A large percentage of these have been developed for greenhouse crops. Products to control soilborne pathogens such as Sclerotinia, Pythium, Rhizoctonia and Fusarium include Coniothyrium minitans, species of Gliocladium, Trichoderma, Streptomyces, and Bacillus, and nonpathogenic Fusarium. Products containing Trichoderma, Ampelomyces quisqualis, Bacillus, and Ulocladium are being developed to control the primary foliar diseases, Botrytis and powdery mildew. The development of Pseudomonas for the control of Pythium diseases in hydroponics and Pseudozyma flocculosa for the control of powdery mildew by two Canadian research programs is presented. In the future, biological control of diseases in greenhouses could predominate over chemical pesticides, in the same way that biological control of greenhouse insects predominates in the United Kingdom. The limitations in formulation, registration, and commercialization are discussed, along with suggested future research priorities.

Notes: Members of the Luteoviridae are transmitted by aphids in a circulative, nonpropagative manner that requires the virus to be acquired through gut tissue into the aphid hemocoel and then exit through salivary tissues. This process is aphid species-specific and involves specific recognition of the virus by unidentified components on the membranes of gut and salivary tissues. Transport through the tissues is an endocytosis/exocytosis process. Both structural proteins of the virus are involved in the transmission process, with multiple protein domains regulating the movement and survival of the virus in the aphid and plant. Here we review what is known about the genetic, cellular, and molecular mechanisms regulating these complex and specific virus-aphid interactions.

Notes: Abstract Apolipoprotein (apo)B circulates in two distinct forms, apoB100 and apoB48. Human liver secretes apoB100, the product of a large mRNA encoding 4536 residues. The small intestine of all mammals secretes apoB48, which arises following C-to-U deamination of a single cytidine base in the nuclear apoB transcript, introducing a translational stop codon. This process, referred to as apoB RNA editing, operates through a multicomponent enzyme complex that contains a single catalytic subunit, apobec-1, in addition to other protein factors that have yet to be cloned. ApoB RNA editing also exhibits stringent cis-acting requirements that include both structural and sequence-specific elements-specifically efficiency elements that flank the minimal cassette, an AU-rich RNA context, and an 11-nucleotide mooring sequence-located in proximity to a suitably positioned (usually upstream) cytidine. C-to-U RNA editing may become unconstrained under circumstances where apobec-1 is overexpressed, in which case multiple cytidines in apoB RNA, as well as in other transcripts, undergo C-to-U editing. ApoB RNA editing is eliminated following targeting of apobec-1, establishing that there is no genetic redundancy in this function. Under physiological circumstances, apoB RNA editing exhibits developmental, hormonal, and nutritional regulation, in some cases related to transcriptional regulation of apobec-1 mRNA. ApoB and the microsomal triglyceride transfer protein (MTP) are essential for the assembly and secretion of apoB-containing lipoproteins. MTP functions by transferring lipid to apoB during its translation and by transporting triglycerides into the endoplasmic reticulum to form apoB-free lipid droplets. These droplets fuse with nascent apoB-containing particles to form mature, very low-density lipoproteins or chylomicrons. In cultured hepatic cells, lipid availability dictates the rate of apoB production. Unlipidated or underlipidated forms of apoB are subjected to presecretory degradation, a process mediated by retrograde transport from the lumen of the endoplasmic reticulum to the cytosol, coupled with multiubquitination and proteasomal degradation. Although control of lipid secretion in vivo is primarily achieved at the level of lipoprotein particle size, regulation of apoB production by presecretory degradation may be relevant in some dyslipidemic states.

Notes: Abstract Fasting or malnutrition (FM) has dramatic effects on small intestinal mucosal structure and transport function. Intestinal secretion of ions and fluid is increased by FM both under basal conditions and in response to secretory agonists. Intestinal permeability to ions and macromolecules may also be elevated by FM, which increases the potential for fluid and electrolyte losses and for anaphylactic responses to luminal antigens. Mucosal atrophy induced by FM reduces total intestinal absorption of nutrients, but nutrient absorption normalized to mucosal mass may actually be enhanced by a variety of mechanisms, including increased transporter gene expression, electrochemical gradients, and ratio of mature to immature cells. These observations underscore the value of enteral feeding during health and disease.

Notes: Abstract Throughout the world, the most common nutritional deficiency disorder of infants is iron deficiency. Developing effective strategies for preventing iron deficiency requires detailed knowledge of iron retention under ordinary living conditions. For the adult population, such knowledge is at an advanced stage, but relatively little is known about infants. Many reports of iron retention by infants have been based on the assumption that, as in normal and iron-deficient adults, 80%-100% of newly absorbed iron is promptly incorporated into circulating erythrocytes, but this assumption is not supported by available data. This communication presents a review of iron retention by term and preterm infants, as determined by metabolic balance studies or 59Fe whole-body counting studies, and it explores the relationship between iron retention and postnatal age, iron nutritional status, iron intake (or dose), and type of feeding.

Notes: Abstract Hormone-sensitive lipase, the rate-limiting enzyme of intracellular TG hydrolysis, is a major determinant of fatty acid mobilization in adipose tissue as well as other tissues. It plays a pivotal role in lipid metabolism, overall energy homeostasis, and, presumably, cellular events involving fatty acid signaling. Detailed knowledge about its structure and regulation may provide information regarding the pathogenesis of such human diseases as obesity and diabetes and may generate concepts for new treatments of these diseases. The current review summarizes the recent advances with regard to hormone-sensitive lipase structure and molecular mechanisms involved in regulating its activity and lipolysis in general. A summary of the current knowledge regarding regulation of expression, potential involvement in lipid disorders, and role in tissues other than adipose tissue is also provided.

Notes: Abstract Sustained dynamic exercise stimulates amino acid oxidation, chiefly of the branched-chain amino acids, and ammonia production in proportion to exercise intensity; if the exercise is intense enough, there is a net loss of muscle protein (as a result of decreased protein synthesis, increased breakdown, or both); some of the amino acids are oxidized as fuel, whereas the rest provide substrates for gluconeogenesis and possibly for acid-based regulation. Protein balance is restored after exercise, but no hypertrophy occurs with habitual dynamic exercise. Resistance exercise causes little change in amino acid oxidation but probably depresses protein synthesis and elevates breakdown acutely. After exercise, protein synthesis rebounds for 〈=48 h, but breakdown remains elevated, and net positive balance is achieved only if amino acid availability is increased. There is no evidence that habitual exercise increases protein requirements; indeed protein metabolism may become more efficient as a result of training.

Notes: Abstract The cloning of the G protein-coupled, extracellular calcium (Ca2+o)-sensing receptor (CaR) has identified a central mediator of the mechanism governing systemic Ca2+o homeostasis. This system enables organisms to adapt successfully to wide variations in dietary Ca2+o intake while maintaining near constancy of Ca2+o. Whereas discussions of Ca2+o homeostasis have generally focused on the key role of Ca2+o-elicited changes in parathyroid hormone secretion, the presence of the CaRs in effector tissues of this system enables direct regulation of processes (e.g. renal tubular Ca2+ reabsorption and possibly bone formation and resorption) that add additional layers of homeostatic control. As we understand more about how the CaR regulates these tissues, we may find that it participates in other processes relevant to mineral ion homeostasis, including the control of the 1-hydroxylation and activation of vitamin D3 or reabsorption of phosphate in the renal proximal tubule. Regardless, the remarkable sensitivity of the CaR to small changes in Ca2+o allows adjustments in the response of the Ca2+o homeostatic system to increases or decreases in the intake of dietary Ca2+, for instance, that cause barely detectable alterations in Ca2+o. Furthermore, the CaR likely participates in coordinating interactions among several different homeostatic control systems (including those for water, Mg2+o, Na+, extracellular volume, and/or blood pressure), despite the fact that these systems are often considered to function largely independently of mineral ion metabolism.

Notes: Abstract A range of compounds in or derived from the diet modulates apoptosis in cell cultures in vitro. These observations have important implications concerning the mechanisms whereby dietary components affect health. Proapoptotic compounds could protect against cancer by enhancing elimination of initiated, precancerous cells, and antiapoptotic compounds could promote tumor formation by inhibiting apoptosis in genetically damaged cells. Proapoptotic compounds could also contribute to age-related degenerative diseases by activating cell death in postmitotic cells or shifting the normal balance of mitosis and apoptosis in tissues with regenerative capacity. Many age-related diseases, for example macular degeneration and Parkinson's disease, appear to have oxidative stress as an underlying component that interacts with genetic, dietary, and environmental factors to determine relative risk in an individual. Oxidative stress activates apoptosis, and antioxidants protect against apoptosis in vitro; thus, a central role of dietary antioxidants may be to protect against apoptosis. However, little in vivo data are available to directly link diet with altered apoptosis as an underlying determinant of disease. Moreover, the possible antagonistic effects of different dietary components and the uncertainty about whether proapoptotic compounds that may protect against cancer could contribute to degenerative diseases and vice versa indicate that there is a great need for better in vivo assessment of apoptosis and that caution should be exercised when extrapolating in vitro data on apoptosis to in vivo dietary recommendations.

Notes: Abstract C/EBPs are a family of transcription factors that play important roles in energy metabolism. Although initially thought to be constitutive regulators of transcription, an increasing amount of evidence indicates that their transactivating capacity within the cell can be modulated by nutrients and hormones. There are several mechanisms whereby this occurs. First, hormones/nutrients are known to directly alter the expression of C/EBPs. Second, hormones/nutrients may cause an alteration in the phosphorylation state of C/EBPs, which can affect their DNA-binding activity or transactivating capacity. Third, C/EBPs can function as accessory factors on gene promoters within a hormone response unit, interacting with other transcription factors to enhance the degree of responsiveness to specific hormones. Given their role in regulating genes involved in a wide variety of metabolic events, advancing our understanding of the molecular mechanism of action of C/EBPs will undoubtedly further our appreciation for the role these transcription factors play in both health and disease.

Notes: Abstract Folate catabolism has been assumed to result from the nonenzymatic oxidative degradation of labile folate cofactors. Increased rates of folate catabolism and simultaneous folate deficiency occur in several physiological states, including pregnancy, cancer, and when anticonvulsant drugs are used. These studies have introduced the possibility that folate catabolism may be a regulated cellular process that influences intracellular folate concentrations. Recent studies have demonstrated that the iron storage protein ferritin can catabolize folate in vitro and in vivo, and increased heavy-chain ferritin synthesis decreases intracellular folate concentrations independent of exogenous folate levels in cell culture models. Ferritin levels are elevated in most physiological states associated with increased folate catabolism. Therefore, folate catabolism is emerging as an important component in the regulation of intracellular folate concentrations and whole-body folate status.

Notes: Abstract Nutritionists have long understood that intestinal nematode parasites have deleterious effects on host nutritional status, but only recently has the importance of malnutrition as a predisposing factor to intestinal nematodes been recognized. Here we review experimental and field studies on the effects of protein, energy, zinc, vitamin A, and iron deficiencies on gastrointestinal (GI) nematodes of humans, livestock, and laboratory rodents, and draw certain conclusions about the state of our current understanding. In general, malnutrition promotes the establishment, survival, and fecundity of these parasites, but the magnitude of the effect depends on factors such as host species, parasite species, particular infection protocol used, magnitude of the infection, severity of the nutritional deficiency, and presence of single or multiple infections and single or multiple nutritional deficiencies. We highlight the Th2 arm of the immune system as a component of primary importance in the association between malnutrition and GI nematode infections. We summarize what is known about underlying mechanisms that may account for the observed patterns. Finally, we suggest future research directions.

Notes: Abstract Polarized epithelia have several functional and morphological similarities, including a high capacity for uptake of various substances present in the fluids facing the apical epithelial surfaces. Studies during the past decade have shown that receptor-mediated endocytosis, rather than nonspecific pinocytosis, accounts for the apical epithelial uptake of many carrier-bound nutrients and hormones. The two interacting receptors of distinct evolutionary origin, megalin and cubilin, are main receptors in this process. Both receptors are apically expressed in polarized epithelia, in which they function as biological affinity matrices for overlapping repertoires of ligands. The ability to bind multiple ligands is accounted for by a high number of replicated low-density lipoprotein receptor type-A repeats in megalin and CUB (complement C1r/C1s, Uegf, and bone morphogenic protein-1) domains in cubilin. Here we summarize and discuss the structural, genetic, and functional aspects of megalin and cubilin, with emphasis on their function as receptors for uptake of protein-associated vitamins, lipids, and hormones.

Notes: Abstract beta-Oxidation occurs in both mitochondria and peroxisomes. Mitochondria catalyze the beta-oxidation of the bulk of short-, medium-, and long-chain fatty acids derived from diet, and this pathway constitutes the major process by which fatty acids are oxidized to generate energy. Peroxisomes are involved in the beta-oxidation chain shortening of long-chain and very-long-chain fatty acyl-coenzyme (CoAs), long-chain dicarboxylyl-CoAs, the CoA esters of eicosanoids, 2-methyl-branched fatty acyl-CoAs, and the CoA esters of the bile acid intermediates di- and trihydroxycoprostanoic acids, and in the process they generate H2O2. Long-chain and very-long-chain fatty acids (VLCFAs) are also metabolized by the cytochrome P450 CYP4A omega-oxidation system to dicarboxylic acids that serve as substrates for peroxisomal beta-oxidation. The peroxisomal beta-oxidation system consists of (a) a classical peroxisome proliferator-inducible pathway capable of catalyzing straight-chain acyl-CoAs by fatty acyl-CoA oxidase, L-bifunctional protein, and thiolase, and (b) a second noninducible pathway catalyzing the oxidation of 2-methyl-branched fatty acyl-CoAs by branched-chain acyl-CoA oxidase (pristanoyl-CoA oxidase/trihydroxycoprostanoyl-CoA oxidase), D-bifunctional protein, and sterol carrier protein (SCP)x. The genes encoding the classical beta-oxidation pathway in liver are transcriptionally regulated by peroxisome proliferator-activated receptor alpha (PPARalpha). Evidence derived from mice deficient in PPARalpha, peroxisomal fatty acyl-CoA oxidase, and some of the other enzymes of the two peroxisomal beta-oxidation pathways points to the critical importance of PPARalpha and of the classical peroxisomal fatty acyl-CoA oxidase in energy metabolism, and in the development of hepatic steatosis, steatohepatitis, and liver cancer.

Notes: Abstract In humans, the absence of galactose-1-phosphate uridyltransferase (GALT) leads to significant neonatal morbidity and mortality which are dependent on galactose ingestion, as well as long-term complications of primary ovarian failure and cognitive dysfunction, which are diet independent. The creation of a knockout mouse model for GALT deficiency was aimed at providing an organism in which metabolic challenges and gene manipulation could address the enigmatic pathophysiologic questions raised by humans with galactosemia. Instead, the mouse represents a biochemical phenotype without evidence of clinical morbidity. The similarities and differences between mice and humans with galactosemia are explored from metabolite, enzyme, and process points of view. The mouse both produces and oxidizes galactose in a manner similar to humans. It differs in brain accumulation of galactitol. Future directions for exploration of this enigmatic condition are discussed.

Notes: Abstract This paper is an attempt to discuss the problem of malnutrition within the framework of the global need for development and the challenges posed by the trends of neoliberalism and globalization. We argue that there is a two-way link between poverty and health in which nutrition plays an important role both as an active and as a mediating factor. Key concepts are exposed and expanded: (a) Development per se does not ensure better health; (b) unequal distribution of income has an independent effect on health indicators after adjusting for total income; (c) improving health can make an important contribution to reducing poverty; (d ) improving nutrition throughout the whole life course is an indispensable strategy for better health; (e) obesity has to be included amongst the most critical health problems, has different traits, and presents with different challenges in the developing world and in the industrialized countries.

Notes: Abstract DNA methylation at cytosines in CpG dinucleotides can lead to changes in gene expression and function without altering the primary sequence of the DNA. Methylation can be affected by dietary levels of methyl-donor components, such as folic acid. This may be an important mechanism for environmentally induced changes in gene expression. Recent literature supports a role for DNA-methylation changes in a number of adult-onset disorders and during development. These changes may be significant for better understanding certain birth defects (e.g., neural tube defects) and the long-term consequences of early environmental influences on gene expression (metabolic programming). Optimal "methylation diets" should be investigated as part of the prevention and treatment of all these conditions, as well as in disorders such as Rett syndrome, whose primary defects may lie in DNA methylation-dependent gene regulation.

Notes: Abstract In the postgenomic era of biology, much attention has been given to functional genomics, or the relation between genes and higher levels of organization in the cell. The latter are typically represented as mRNA, protein, or organic metabolite complements. The theme of this review is that the operational unit of function in complex biological systems is more properly seen as the fully assembled metabolic pathway in the whole organism. Due to the connectivity, interactions, and complexity of metabolic pathways, the measurement of components is an inadequate method for predicting phenotype. Measurement of the outputs of pathways (molecular fluxes) involves different tools than static measures of components, however. Here, we review recently developed stable isotope-mass spectrometric tools for measuring fluxes through metabolic pathways in vivo, focusing on the response to dietary macronutrients (carbohydrates and fats). Methods discussed include measurement of lipid dynamics, DNA replication, hepatic assembly of lipoproteins, and long-lived protein synthesis. Measuring fluxes through multiple pathways concurrently allows regulatory themes to emerge. Use of 2H2O-labeling is emerging as a particularly powerful approach for multiple concurrent biosynthetic flux measurements. Several examples demonstrate that pathway flux results are often unexpected and not predicted by classic biochemistry or the expression of genes and proteins.

Notes: Abstract Selenium is an essential trace element that is incorporated into proteins as selenocysteine (Sec), the twenty-first amino acid. Sec is encoded by a UGA codon in the selenoprotein mRNA. The decoding of UGA as Sec requires the reprogramming of translation because UGA is normally read as a stop codon. The translation of selenoprotein mRNAs requires cis-acting sequences in the mRNA and novel trans-acting factors dedicated to Sec incorporation. Selenoprotein synthesis in vivo is highly selenium-dependent, and there is a hierarchy of selenoprotein expression in mammals when selenium is limiting. This review describes emerging themes from studies on the mechanism, kinetics, and efficiency of Sec insertion in prokaryotes. Recent developments that provide mechanistic insight into how the eukaryotic ribosome distinguishes between UGA/Sec and UGA/stop codons are discussed. The efficiency and regulation of mammalian selenoprotein synthesis are considered in the context of current models for Sec insertion.

Notes: Abstract Iron deficiency in early life is associated with delayed development as assessed by a number of clinical trials using similar global scales of development; this poor development during infancy persists in most cases after iron therapy has corrected iron status. If iron deficiency occurs in preschool and older children, the consequences appear reversible with treatment. The biologic understanding of this relationship between development, brain iron status, and functioning is sparse though animal studies repeatedly demonstrate alterations in dopamine metabolism and in the myelination process. Dietary iron deficiency can rapidly deplete brain iron concentrations and repletion is able to normalize them. Residual alterations in striatal dopamine metabolism and myelin production persist if neonatal animals are used. Future studies with more specific measures of neurodevelopment in iron-deficient human infants, and animal models, will allow investigators to more clearly define causal roles of brain iron in neural development and functioning.

Notes: Abstract Some of us who were born in the middle of Europe between World Wars I and II had to face quite a few unusual challenges that we all met in different ways. I was born and raised in Prague, Czechoslovakia, a country at the time of my birth that was governed by a Western style of democracy, which was later destroyed by the occupation by Nazi Germany and subsequently by the takeover by the equally cruel Communists. Life required special means of adaptation to the changing living conditions and a great deal of luck to survive. After graduating from the School of Technology, I started working in the Department of Medicine at Charles University in Prague as a clinical chemist in endocrinology. This work was followed with training in basic biochemistry and the study of metabolic changes in stress. This rather diversified research, due to my changing of workplaces, led to the findings that diet can change enzymatic activity of liver tryptophan oxygenase. For a short time I worked on the metabolism of cyclic AMP in Escherichia coli, and at the age of 41, I made a risky move and succeeded in escaping with my family from the "paradise of communism." The reasons for this decision will become clear. After settling in the United States, I worked on the mechanism of activation of liver tryptophan oxygenase by cyclic AMP and eventually moved to the Vanderbilt University School of Medicine. There I initially worked on the mechanism of action of steroid hormones and finally on the molecular mechanism of action of retinoids, retinol, and retinoic acid. Also in cooperation with neonatologists, I initiated studies on prematurely born human neonates which led to successful supplementation of these patients with vitamin A. The work from my laboratory and my coworkers eventually became recognized. "Who does not remember the past, is condemned to repeat it." George Santayana (1863-1952)

Notes: Abstract Microorganisms have successfully adapted to changes in food production, processing, and preservation techniques, resulting in a number of new and emerging foodborne pathogens and the re-emergence of organisms that have been problematic in the past. To protect public health, science must meet the challenges that result from the remarkable adaptability of foodborne pathogens. However, not all of the challenges of preventing foodborne illness reside in the realm of science. Food safety policy must evolve in reponse to new scientific understanding of hazards in the food supply and an ever-changing food processing industry. The laws, regulations, and organizations comprising the food safety system frequently lag behind current scientific knowledge of the risks posed by foodborne pathogens. Future systemic changes to enhance food safety will require better understanding of risks associated with specific pathogens occurring in the food supply and the costs and benefits of implementing mitigation strategies.

Notes: Abstract Bone mass is maintained constant between puberty and menopause by the balance between osteoblast and osteoclast activity. The existence of a hormonal control of osteoblast activity has been speculated for years by analogy to osteoclast biology. Through the search for such humoral signal(s) regulating bone formation, leptin has been identified as a strong inhibitor of bone formation. Furthermore, intracerebroventricular infusion of leptin has shown that the effect of this adipocyte-derived hormone on bone is mediated via a brain relay. Subsequent studies have led to the identification of hypothalamic groups of neurons involved in leptin's antiosteogenic function. In addition, those neurons or neuronal pathways are distinct from neurons responsible for the regulation of energy metabolism. Finally, the peripheral mediator of leptin's antiosteogenic function has been identified as the sympathetic nervous system. Sympathomimetics administered to mice decreased bone formation and bone mass. Conversely, beta-blockers increased bone formation and bone mass and blunted the bone loss induced by ovariectomy.

Notes: Abstract A range of specialist and generalist microorganisms in the rhizosphere attacks plant-parasitic nematodes. Plants have a profound effect on the impact of this microflora on the regulation of nematode populations by influencing both the dynamics of the nematode host and the structure and dynamics of the community of antagonists and parasites in the rhizosphere. In general, those organisms that have a saprophytic phase in their life cycle are most affected by environmental conditions in the rhizosphere, but effects on obligate parasites have also been recorded. Although nematodes influence the colonization of roots by pathogenic and beneficial microorganisms, little is known of such interactions with the natural enemies of nematodes in the rhizosphere. As nematodes influence the quantity and quality of root exudates, they are likely to affect the physiology of those microorganisms in the rhizosphere; such changes may be used as signals for nematode antagonists and parasites. Successful biological control strategies will depend on a thorough understanding of these interactions at the population, organismal, and molecular scale.

Notes: Abstract The population structure and ecological roles of the indigenous pathogen Phellinus weirii, cause of laminated root rot in conifer forests of western North America, are examined. This pathogen kills trees in slowly expanding mortality centers, creating gaps in the forest canopy. It is widespread, locally abundant, and very long-lived. It is among the most important disturbance agents in the long intervals between stand-replacing events such as wildfire or harvest in these ecosystems and shapes the structure and composition of both wild and managed forests. Trees are infected and killed regardless of individual vigor. Management of public lands is changing dramatically, with renewed emphasis on natural forest structures and processes but pathogens, especially root rot fungi, remain a significant challenge to "ecosystem management."

Notes: Abstract Wheat (Triticum aestivum L) is grown throughout the grasslands from southern Mexico into the prairie provinces of Canada, a distance of nearly 4200 km. The total area seeded to wheat varies considerably each year; however, from 28 to 32 million ha are planted in the Great Plains of the United States alone. Generally in the central Great Plains, an area from central Texas through central Nebraska, 15 million ha are seeded to winter wheat each year. A wide range of environmental conditions exist throughout this area that may affect the development and final severity of wheat leaf rust (caused by Puccinia triticina L), stripe rust (caused by P. striiformis), and stem rust (caused by P. graminis Pers. f. sp tritici) epidemics and the subsequent reduction in wheat yields. Variation in severity of rust epidemics in this area depends on differences in crop maturity at the time of infection by primary inoculum, host resistance used, and environmental conditions. The interrelationships among time, host, pathogen and environment are complex, and studying the interactions is very difficult. Historically, cultivars with new or different leaf rust resistance genes become ineffective after several years of large-scale production within the Great Plains, and then cultivars carrying new or different resistance genes must be developed and released into production. This is the typical "boom and bust" cycle of the cereal rust resistance genes in the central Great Plains.

Notes: Abstract The structural proteins of plant viruses have evolved to self-associate into complex macromolecules that are centrally involved in virus biology. In this review, the structural and biophysical properties of the Tobacco mosaic virus (TMV) coat protein (CP) are addressed in relation to its role in host resistance and disease development. TMV CP affects the display of several specific virus and host responses, including cross-protection, systemic virus movement, hypersensitive disease resistance, and symptom development. Studies indicate that the three-dimensional structure of CP is critical to the control of these responses, either directly through specific structural motifs or indirectly via alterations in CP assembly. Thus, both the structure and assembly of the TMV CP function as determinants in the induction of disease and resistance responses.