Experimental stress in inflammatory rheumatic diseases: a review of psychophysiological stress responses

Introduction  

Stressful events are thought to contribute to the aetiology, maintenance and exacerbation of rheumatic diseases. Given the growing interest in acute stress responses and disease, this review investigates the impact of real-life experimental psychosocial, cognitive, exercise and sensory stressors on autonomic, neuroendocrine and immune function in patients with inflammatory rheumatic diseases.     

Distribution, Population Dynamics, and Characteristics of Ice Nucleation-Active Bacteria in Deciduous Fruit Tree Orchards

Deciduous fruit tree orchards located in the Pacific Northwest were surveyed over a 3-year period for the presence of ice nucleation-active (INA) bacteria. In the Yakima Valley, only about 30% of the fruit tree orchards contained INA bacteria (median population ca. 3 × 10² CFU/g [fresh weight]) in contrast to nearly 75% of the orchards in the Hood River Valley (median population ca. 5 × 10³ CFU/g [fresh weight]). These INA populations ranged from less than 10 to over 10⁶ CFU/g (fresh weight) of blossoms and, in Hood River Valley orchards, generally comprised over 10% of the total bacterial population. Populations of INA bacteria fluctuated during the year with highest levels developing on buds and flowers during the cool, wet spring, followed by a drop in populations during the warmer, drier, summer months and finally a gradual increase in the autumn. The INA bacteria persisted on dormant buds from which they again colonized young developing vegetative tissues. All INA bacteria were identified as Pseudomonas syringae. The frequency of ice nucleation at −5°C for these strains ranged from nearly every cell being INA to less than 1 in 10⁷ cells. The median frequency of ice nucleation at −5°C was 10⁴ cells per ice nucleus. The INA P. syringae strains from individual orchards were diverse with respect to bacteriocin typing and in ice nucleation frequency. The consistent absence of detectable INA bacteria or presence of low populations in most of the orchards surveyed during periods when critical temperatures (i.e., −2 to −5°C) were common indicated a limited role for INA bacteria in frost susceptibility of most Pacific Northwest orchards.     

A novel deconvolution method for modeling UDP-N-acetyl-D-glucosamine biosynthetic pathways based on 13C mass isotopologue profiles under non-steady-state conditions

This article is a response to Wang and Luo. See correspondence article http://www.biomedcentral.com/1741-7007/10/30/ [WEBCITE] and the original research article http://www.biomedcentral.com/1741-7007/9/24 [WEBCITE].     

Gibberellins and seed development in maize. I. Evidence that gibberellin/abscisic acid balance governs germination versus maturation pathways

Abscisic acid (ABA) is required for the regulation of seed maturation in maize (Zea mays L.). Mutants blocked in ABA synthesis (such as viviparous-5) do not mature to quiescent, desiccation-tolerant seeds, but germinate on the ear midway through kernel development. Because gibberellins (GA) and ABA act antagonistically in many aspects of plant development, we hypothesized that ABA antagonizes a positive GA signal for precocious germination in maize. In these experiments, we show that a GA deficiency early in seed development, induced genetically or via biosynthesis inhibitors, suppresses vivipary in ABA-deficient developing kernels. The resulting seeds have both desiccation tolerance and storage longevity. Temporal analysis of GA accumulation in wild-type kernels revealed the accumulation of bioactive GA(1) and GA(3) prior to the peak in ABA content. We speculate that these GAs stimulate a developmental program leading to vivipary in the absence of normal amounts of ABA, and that a reduction of GA content re-establishes an ABA/GA ratio appropriate for suppression of germination and induction of maturation. In contrast, the induction of a GA deficiency did not suppress vivipary in viviparous-1 mutant kernels, suggesting that VP1 acts downstream of both GA and ABA in programming seed development.     

Limbs vs. Jaws: Can They Be Compared?

Current experimental research on mammalian limb muscle structureand function is compared to that on mammalian jaw muscles. Twomajor areas of comparison are stressed: structural and functional.Comparisons of limbs and jaws are made from the point of viewof the impact of recent studies on simple mechanical modelsof limb/jaw muscle function. Limb muscle structure is comparedto jaw muscles at the level of muscle architecture, muscle histochemicaland motor unit properties, and the organization of motor unitsinto neuromuscular compartments. Such comparisons reveal thatalthough limb muscles and jaw muscles might be organized insimilar ways, fundamental differences exist, both in terms ofmuscle structure and the functional conclusions which have beenbased on studies of muscle structure. The comparisons also demonstratethat much recent evidence from structural studies have had littledirect impact on simple models of muscle function but a muchlarger influence on the assumptions of the models. Comparisonsof limb/jaw muscle function from kinematic and EMG studies,indicate that many masticatory strategies are used by differentmammals but the basic problems of posture and locomotion havebeen met with essentially similar solutions, even among diversemammalian groups. The results of such comparisons demonstratethat both limb and jaw muscle function are sufficiently complexthat new or re-vitalized models are needed if the relationshipbetween structure and function are ever to be understood.