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At least 145 records · Page 8Linked to original sources

PubMed2005

Genetic analysis as a tool to investigate the molecular mechanisms underlying seed development in maize.

BACKGROUND: In angiosperms the seed is the outcome of double fertilization, a process leading to the formation of the embryo and the endosperm. The development of the two seed compartments goes through three main phases: polarization, differentiation of the main tissues and organs and maturation. SCOPE: This review focuses on the maize kernel as a model system for developmental and genetic studies of seed development in angiosperms. An overview of what is known about the genetic and molecular aspects underlying embryo and endosperm formation and maturation is presented. The role played by embryonic meristems in laying down the plant architecture is discussed. The acquisition of the different endosperm domains are presented together with the use of molecular markers available for the detection of these domains. Finally the role of programmed cell death in embryo and endosperm development is considered. CONCLUSIONS: The sequence of events occurring in the developing maize seed appears to be strictly regulated. Proper seed development requires the co-ordinated expression of embryo and endosperm genes and relies on the interaction between the two seed components and between the seed and the maternal tissues. Mutant analysis is instrumental in unravelling the genetic control underlying the formation of each compartment as well as the molecular signals interplaying between the two compartments.

Apoptosis↗

PubMed2005

Recurring challenges from a necrotrophic fungal plant pathogen: a case study with Leptosphaeria maculans (causal agent of blackleg disease in brassicas) in Western Australia.

BACKGROUND: Blackleg disease of Brassica napus, caused by the necrotrophic fungus Leptosphaeria maculans, causes severe yield losses in Australia, Europe and Canada. In Western Australia, it nearly destroyed the oilseed rape industry in 1972 when host genotypes and conducive environmental conditions favoured severe epidemics. The introduction of cultivars with polygenic resistance and the adoption of sound cultural practices two decades later helped to manage the disease. These were abandoned by many farmers in recent years in favour of the effective but ephemeral resistance conferred by the single dominant gene-based resistance derived from B. rapa ssp. sylvestris. Recently, several cultivars carrying this gene have collapsed widely within a period of 3 years after their commercial release. An environment conducive to the disease and the association of the pathogen with susceptible hosts in Western Australia for over 80 years together have led to the proliferation of L. maculans races, amounting to half of all races delineated to date from Europe, including the United Kingdom, Canada and Australia. SCOPE: This review demonstrates the problems that emerge when traditional cultural practices employed, along with cultivars containing polygenic resistance to a serious necrotrophic pathogen, are discarded in preference to the exclusive deployment of effective but ephemeral single dominant gene-based resistance to the disease across Southern Australia. CONCLUSIONS: Single dominant gene-based resistance currently available, on its own, will not confer durable resistance to blackleg disease in oilseed rape. Return to earlier management practices, including reliance upon polygenic resistance and induced resistance, may be the best currently available options to maintain production in regions across Southern Australia predisposed to severe epidemics.

Ascomycota↗

PubMed2005

Underwater photosynthesis in flooded terrestrial plants: a matter of leaf plasticity.

BACKGROUND: Flooding causes substantial stress for terrestrial plants, particularly if the floodwater completely submerges the shoot. The main problems during submergence are shortage of oxygen due to the slow diffusion rates of gases in water, and depletion of carbohydrates, which is the substrate for respiration. These two factors together lead to loss of biomass and eventually death of the submerged plants. Although conditions under water are unfavourable with respect to light and carbon dioxide supply, photosynthesis may provide both oxygen and carbohydrates, resulting in continuation of aerobic respiration. SCOPE: This review focuses on evidence in the literature that photosynthesis contributes to survival of terrestrial plants during complete submergence. Furthermore, we discuss relevant morphological and physiological responses of the shoot of terrestrial plant species that enable the positive effects of light on underwater plant performance. CONCLUSIONS: Light increases the survival of terrestrial plants under water, indicating that photosynthesis commonly occurs under these submerged conditions. Such underwater photosynthesis increases both internal oxygen concentrations and carbohydrate contents, compared with plants submerged in the dark, and thereby alleviates the adverse effects of flooding. Additionally, several terrestrial species show high plasticity with respect to their leaf development. In a number of species, leaf morphology changes in response to submergence, probably to facilitate underwater gas exchange. Such increased gas exchange may result in higher assimilation rates, and lower carbon dioxide compensation points under water, which is particularly important at the low carbon dioxide concentrations observed in the field. As a result of higher internal carbon dioxide concentrations in submergence-acclimated plants, underwater photorespiration rates are expected to be lower than in non-acclimated plants. Furthermore, the regulatory mechanisms that induce the switch from terrestrial to submergence-acclimated leaves may be controlled by the same pathways as described for heterophyllous aquatic plants.

Acclimatization↗

PubMed2005

Boron nutrition and chilling tolerance of warm climate crop species.

BACKGROUND: Field observations and glasshouse studies have suggested links between boron (B)-deficiency and leaf damage induced by low temperature in crop plants, but causal relationships between these two stresses at physiological, biochemical and molecular levels have yet to be explored. Limited evidence at the whole-plant level suggests that chilling temperature in the root zone restricts B uptake capacity and/or B distribution/utilization efficiency in the shoot, but the nature of this interaction depends on chilling tolerance of species concerned, the mode of low temperature treatment (abrupt versus gradual temperature decline) and growth conditions (e.g. photon flux density and relative humidity) that may exacerbate chilling stress. SCOPE: This review explores roles of B nutrition in chilling tolerance of continual root or transient shoot chills in crop species adapted to warm season conditions. It reviews current research on combined effects of chilling temperature (ranging from >0 to 20 degrees C) and B deficiency on growth and B nutrition responses in crop species differing in chilling tolerance. CONCLUSION: For subtropical/tropical species (e.g. cucumber, cassava, sunflower), root chilling at 10-17 degrees C decreases B uptake efficiency and B utilization in the shoot and increases the shoot : root ratio, but chilling-tolerant temperate species (e.g. oilseed rape, wheat) require much lower root chill temperatures (2-5 degrees C) to achieve the same responses. Boron deficiency exacerbates chilling injuries in leaf tissues, particularly under high photon flux density. Suggested mechanisms for B x chilling interactions in plants are: (a) chilling-induced reduction in plasmalemma hydraulic conductivity, membrane fluidity, water channel activity and root pressure, which contribute to the decrease in root hydraulic conductance, water uptake and associated B uptake; (b) chilling-induced stomatal dysfunction affecting B transport from root to shoot and B partitioning in the shoot; and (c) B deficiency induced sensitivity to photo-oxidative damage in leaf cells. However, specific evidence for each of the mechanisms is still lacking. Impacts of B status on chilling tolerance in crop species have important implications for the management of B supply during sensitive stages of growth, such as early growth after planting and early reproductive development, both of which can coincide with the occurrence of chilling temperatures in the field.

Acclimatization↗

PubMed2006

Plant nutriomics in China: an overview.

BACKGROUND: Population and environmental pressure have imposed a great challenge on agriculture in China to explore innovative and effective solutions to its pressing plant nutritional problems. Plant nutriomics is a new frontier in plant biology that can provide innovative solutions for improving plant nutrient efficiency, thus increasing crop productivity through genetic and molecular approaches. SCOPE: This review summarizes current efforts and progress in plant nutriomic research in China with examples from several case studies. It also points out potential obstacles and depicts future perspectives in this emerging frontier of plant nutrition. CONCLUSIONS: Although plant nutriomics is still at a conceptual stage, substantial efforts are being made in China aimed at increasing plant nutrient efficiency through a nationwide, co-ordinated project on plant nutriomics. Future studies involving both national and international collaborations are needed to develop nutrient-efficient, stress-tolerant and high-quality crop varieties for both China and elsewhere.

Boron↗

PubMed2006

Annual Medicago: from a model crop challenged by a spectrum of necrotrophic pathogens to a model plant to explore the nature of disease resistance.

BACKGROUND: Annual Medicago spp., including M. truncatula, play an important agronomic role in dryland farming regions of the world where they are often an integral component of cropping systems, particularly in regions with a Mediterranean or Mediterranean-type climate where they grow as winter annuals that provide both nitrogen and disease breaks for rotational crops. Necrotrophic foliar and soil-borne pathogens dominate these regions and challenge the productivity of annual Medicago and crop legume species. SCOPE: This review outlines some of the major and/or widespread diseases these necrotrophic pathogens cause on Medicago spp. It then explores the potential for using the spectrum of necrotrophic pathogen-host interactions, with annual Medicago as the host plant, to better understand and model pathosystems within the diseases caused by nectrotrophic pathogens across forage and grain legume crops. CONCLUSIONS: Host resistance clearly offers the best strategy for cost-effective, long-term control of necrotrophic foliar and soil-borne pathogens, particularly as useful resistance to a number of these diseases has been identified. Recently and initially, the annual M. truncatula has emerged as a more appropriate and agronomically relevant substitute to Arabidopsis thaliana as a model plant for legumes, and is proving an excellent model to understand the mechanisms of resistance both to individual pathogens and more generally to most forage and grain legume necrotrophic pathogens.

Medicago↗

PubMed2007

Ubiquitin, hormones and biotic stress in plants.

BACKGROUND: The covalent attachment of ubiquitin to a substrate protein changes its fate. Notably, proteins typically tagged with a lysine48-linked polyubiquitin chain become substrates for degradation by the 26S proteasome. In recent years many experiments have been performed to characterize the proteins involved in the ubiquitylation process and to identify their substrates, in order to understand better the mechanisms that link specific protein degradation events to regulation of plant growth and development. SCOPE: This review focuses on the role that ubiquitin plays in hormone synthesis, hormonal signalling cascades and plant defence mechanisms. Several examples are given of how targeted degradation of proteins affects downstream transcriptional regulation of hormone-responsive genes in the auxin, gibberellin, abscisic acid, ethylene and jasmonate signalling pathways. Additional experiments suggest that ubiquitin-mediated proteolysis may also act upstream of the hormonal signalling cascades by regulating hormone biosynthesis, transport and perception. Moreover, several experiments demonstrate that hormonal cross-talk can occur at the level of proteolysis. The more recently established role of the ubiquitin/proteasome system (UPS) in defence against biotic threats is also reviewed. CONCLUSIONS: The UPS has been implicated in the regulation of almost every developmental process in plants, from embryogenesis to floral organ production probably through its central role in many hormone pathways. More recent evidence provides molecular mechanisms for hormonal cross-talk and links the UPS system to biotic defence responses.

Plant Growth Regulators↗

PubMed2004

Integrating tuberculosis and HIV care in the primary care setting in South Africa.

BACKGROUND: In many countries including South Africa, the increasing human immunodeficiency virus (HIV) and tuberculosis (TB) epidemics have impacted significantly on already weakened public health services. This paper reviews the scope, process and performance of the HIV and TB services in a primary care setting where antiretroviral therapy is provided, in Khayelitsha, South Africa, in order to assess whether there is a need for some form of integration. METHODS: The scope and process of both services were assessed through observations of the service and individual and group interviews with key persons. The performance was assessed by examining the 2001-2002 reports from the health information system and clinical data. RESULTS: The TB service is programme oriented to the attainment of an 85% cure rate amongst smear-positive patients while the HIV service has a more holistic approach to the patient with HIV. The TB service is part of a well-established programme that is highly standardized. The HIV service is in the pilot phase. There is a heavy load at both services and there is large degree of cross-referral between the two services. There are lessons that can be learnt from each service. There is an overlap of activities, duplication of services and under-utilization of staff. There are missed opportunities for TB and HIV prevention, diagnosis and management. CONCLUSIONS: The study suggests that there may be benefits to integrating HIV and TB services. Constraints to this process are discussed.

Communicable Disease Control↗

PubMed2000

Dementia diagnostic guidelines: methodologies, results, and implementation costs.

OBJECTIVE: To facilitate the diagnostic process for dementia. Five guidelines and four consensus statements on specific diagnostic recommendations, specialist referral recommendations, and costs of recommended diagnostic procedures were compared and summarized. DATA SOURCES AND SELECTION: A MEDLINE search from 1984 to 1999 and queries to experts yielded 14 guidelines and consensus statements that addressed the diagnosis of dementia. Only nine documents which had national or international scopes were reviewed. METHODS: Comparisons were made on the specific diagnostic criteria for patient history, clinical examination, functional assessment, laboratory tests, neuroimaging, and other diagnostic tests, as well as specialist referral recommendations and costs for the recommended diagnostic procedures. The first three authors reviewed independently each document and completed a table on specific recommendations in each document. To settle disagreements about specific recommendations, they discussed them until they reached a consensus. To interpret the intent of vague statements, they used their best judgment. RESULTS: The documents differed in content, recommendations, and development methodology. They were based on either expert opinion or scientific evidence, or both. Although the nine documents were nearly unanimous in several recommendations, including assessing the presenting problem, taking a medical history, conducting physical and neurological examinations, and assessing the patient's mental and cognitive status, considerable differences in recommendations were common. Such differences led to large differentials in the estimated costs (range, $190 to $2,001) for recommended diagnostic assessments. CONCLUSIONS: A systematic approach to diagnostic recommendations for dementia may induce greater consistency among guidelines and consensus statements. The current approach leads to considerable variability in recommendations and estimated costs.

Consensus Statements as Topic↗

PubMed1996

Life-span perspective of personality in dementia.

PURPOSE: To propose an alternative view of personality change in dementia by presenting existing evidence for the continuity of personality. SIGNIFICANCE: As the population continues to age, dementing illnesses will account for a greater proportion of morbidity and mortality; the care of these people will have a significant effect on the health care system. ORGANIZING FRAMEWORK: Life-span perspective of personality continuity. SCOPE METHOD: Review of current literature on personality in dementia using Medline, 1980-1994; CINAHL, 1990-1994; and Psych Lit., 1980-1994. FINDINGS: Although there are systematic shifts in personality with dementia, individuals tend to maintain their unique pattern of premorbid personality traits. CONCLUSIONS: The personalities of dementia patients seem to reflect adaptive patterns that served them in the past. IMPLICATIONS: Use of a life-span perspective can enhance individualized care for demented patients and advance theory development.

Aged↗

PubMed1998

Nurses, indirect trauma, and prevention.

PURPOSE: To begin examining the nature of vicarious or indirect trauma and to discuss risk factors and prevention strategies. Despite the fact that many nurses are traumatized indirectly, few recognize the insidious development of such trauma. The dynamics of indirect trauma are relevant to nursing as are risk factors and prevention strategies. SCOPE: Brief review of the literature (1974-1997) on vicarious trauma, compassion fatigue, secondary traumatic stress disorder, and traumatic countertransference using short vignettes for illustration. CONCLUSION: Nurses who are informed about vicarious trauma and who actively maintain a balanced personal and professional life are in the best position to bring themselves and their clients through the many hazards of trauma work. The implications of vicarious or indirect trauma for nurses and clients are serious and complex requiring thoughtful analysis and research to clarify its effects.

Anxiety Disorders↗

PubMed2001

Viral vectors as potential HIV-1 vaccines.

Vaccine vectors based on recombinant viruses have great promise to play an important role in the development of an effective HIV-1 vaccine. Within the last 10 years a wide range of viruses have been investigated for their ability to express protein(s) from foreign pathogens and to induce specific immunological responses against these antigen(s) in vivo. Each viral vector has its own unique biological characteristics and thus far none of them has proven to be an ideal candidate as a vaccine vehicle for HIV-1. This review focuses on both replication competent and non-replication competent viral vectors as a potential HIV-1 vaccine. Other approaches for the development of an HIV-1 vaccine are reviewed elsewhere and are beyond the scope of this review.

AIDS Vaccines↗

PubMed1989

Suicide and the attempted suicide: an international perspective.

This article reviews the scope of suicide and attempted suicide as public health problems from an international perspective. Socio-demographic trends are analyzed and explanatory theories for international differences proposed. Suicide and attempted suicide can be prevented, but the development and evaluation of effective large-scale prevention programs is still in its infancy. Inadequacies in current programs across the world has promoted the establishment of national Task Forces on Suicide Prevention in the United States, Canada and The Netherlands, as well as a WHO strategy on suicide prevention. These groups have formulated comprehensive strategies for the prevention of suicide. The main components of these strategies are: Design and implementation of national research programs; The improvement of services; The provision of information and training on suicide prevention to relevant professional groups, organizations and the general public; and Formulation of strategies and techniques to deal with special risk groups. The added recommendations are seen as important steps in translating a comprehensive national plan to prevent suicide into clinical and research programs that can be effectively implemented to prevent these tragedies around the world.

Adolescent↗

PubMed1985

"Invalidity" due to chronic bronchitis and emphysema: how real is it?

Hospital discharges and deaths attributed to chronic bronchitis and emphysema have fallen in recent years while the number of those receiving invalidity benefit for these conditions has remained constant. One hundred and fifty seven such persons were invited to take part in this study, in which the diagnosis, degree of respiratory impairment, and other factors contributing to disability were reviewed. The scope for rehabilitation was considered. One hundred subjects agreed to take part; 96 were men and 70 were over 60 years. In only 67 was the main diagnosis chronic bronchitis and emphysema. There was a bimodal distribution of functional impairment, most being severely disabled, but in 20 the FEV1 was within the normal range. Among these asthma was more common and psychological factors were important. Economic factors contributed to "invalidity," especially among those with a normal FEV1. For 32 of the 57 who had declined to take part some information was available from hospital records. The findings in this group were similar. There was little scope for rehabilitation in the group as a whole as motivation was poor. Less than half had ever seen a chest physician. Specialist assessment before invalidity benefit is claimed is probably desirable.

Aged↗

PubMed1978

Sudden infant death syndrome: impact on families and a direction for change.

Until recently, there were no standardized approaches to the diagnosis of sudden infant death syndrome (SIDS), the leading cause of death in the age group of one week to one year in the United States. This has led to confusion among professionals and hardships for parents and families. The Sudden Infant Death Syndrome Act of 1974 provided funding for the dissemination of information, counseling, and education. The author reviews the scope of the SIDS problem, the ways in which it affects families, and mechanisms by which community resources can be mobilized to assist families.

Adaptation, Psychological↗

PubMed2003

Supported employment: evidence for a best practice model in psychosocial rehabilitation.

BACKGROUND: Traditional approaches to vocational rehabilitation in mental health settings have had only limited effectiveness in enabling clients to meet their employment goals. Within the last decade the individual Placement and Support Model (IPS) has emerged as an alternate, evidence-based approach to providing vocational services with individuals who have severe and persistent mental illness. METHOD AND SCOPE: This review of the literature critically examines research regarding the IPS model of supported employment then discusses implications of this research for occupational therapists. PRACTICE IMPLICATIONS: In order to enable clients to achieve their competitive employment goals, it is imperative that occupational therapists incorporate best practice models of supported employment. IPS is one model that appears to hold significant promise for occupational therapists and their clients.

Employment, Supported↗

PubMed2005

Inflammatory, atherothrombotic aspects of type 2 diabetes.

BACKGROUND: There is a tight association between diabetes and cardiovascular disease - both occur more commonly together than independently. The development of vascular disease is dependent upon complex interactions between a number of metabolic pathways involving both fluid phase proteins and cellular components. Inflammation and coagulation are two intimately linked processes that are co-regulated. The characteristic cluster of risk factors - hypertension, hyperinsulinaemia, hyperglycaemia and lipid abnormalities, which are associated with insulin resistance - have been expanded to include inflammation and thrombotic risk. Studies in patients with diabetes indicate a higher prevalence of both inflammatory cells and thrombosis in coronary plaques in comparison to non-diabetic subjects and measures of C-reactive protein predict the development of both diabetes and cardio vascular disease in prospective studies. SCOPE: This review (based on MEDLINE searches, 1990 to 2005) looks at the inflammatory, atherothrombotic aspects of type 2 diabetes that may be involved in the accelerated development of vascular disease in the population with diabetes.

Arteriosclerosis↗

PubMed2005

Therapeutic inhibition of matrix metalloproteinases for the treatment of chronic obstructive pulmonary disease (COPD).

BACKGROUND: The incidence of chronic obstructive pulmonary disease (COPD) is increasing worldwide and is ranked as the fourth most common cause of death in the United States. COPD is caused by long-term exposure to cigarette smoke, toxic gases, and particulate matter, leading to airway flow limitation and pulmonary failure. The disease is characterized by an excess of extracellular matrix deposition, increased thickness of airway walls, and destruction of alveolar septae, resulting in reduced functional lung parenchyma and reduced elastic tethering forces to maintain airway patency. Matrix metalloproteinases (MMPs) have been suggested as the major proteolytic enzymes involved in the pathogeneses of COPD because these proteins are a unique family of metalloenzymes that, once activated, can destroy connective tissue. Although several MMP inhibitors have been developed, in vivo specificity and selectivity have slowed the progress. SCOPE: This review discusses the structural features of MMPs, their pulmonary cellular sources during the course of the disease, past anti-MMP therapies, and future approaches to inhibiting these proteins for treating COPD patients. Literature searches of PubMed, BioMed, and Medline formed the basis of this analysis and our current understanding of pulmonary changes associated with COPD and the capacity of MMPs to induce a variety of these changes of current biomedical and clinical interest.

Animals↗