Core temperature is regulated, although at a lower temperature, in rats exposed to hypergravic fields

1. In rats acclimated to 23 degrees C (RT rats) or 5 degrees C (CA rats), core temperature (Tc), tail temperature (Tt) and oxygen consumption (VO2) were measured during exposure to a hypergravic field. 2. Rats were exposed for 5.5 h to a 3 g field while ambient temperature (Ta) was varied. For the first 2 h, Ta was 25 degrees C; then Ta was raised to 34 degrees C for 1.5 h. During this period of warm exposure, Tc increased 4 degrees C in both RT and CA rats. Finally, Ta was returned to 25 degrees C for 2 h, and Tc decreased toward the levels measured prior to warm exposure. 3. In a second experiment at 3 g, RT and CA rats were exposed to cold (12 degrees C) after two hours at 25 degrees C. During the one hour cold exposure, Tc fell 1.5 degrees C in RT and 0.5 degree C in CA rats. After cold exposure, when ambient temperature was again 25 degrees C, Tc of RT and CA rats returned toward the levels measured prior to the thermal disturbance. 4. Rats appear to regulate their temperature, albeit at a lower level, in a 3 g field.     

Influence of growth hormone on accretion of bone mass

Growth hormone (GH) exerts important influences on bone metabolism during lifespan. During childhood, GH is a major determinant of acquisition of bone mass and in adult life, GH partly determines the rate of bone remodelling and therefore influences maintenance of bone mineral density (BMD). Insights into the importance of GH in these respects may be obtained by studies of BMD and indices of bone remodelling in GH deficiency (GHD) of adult-onset and childhood-onset. Adult-onset GHD, usually accompanied by other features of hypopituitarism, may be associated with osteopenia and an increased fracture risk. Postulated mechanisms include GHD and gonadal steroid deficiency of unknown duration; glucocorticoid and thyroxine replacement do not appear to exert a major role. GH replacement in adult-onset GHD results in an early increment in indices of bone remodelling which persists for up to 5 years; BMD increases by 0.5-1.0 SD in males and stabilizes in females over this time period. In adolescents with GHD who traditionally discontinue GH at completion of linear growth, BMD is substantially lower than peak bone mass for a young adult population. Studies addressing the effects of continuation of GH after achievement of final height are currently underway and will provide insights into the possible need to continue GH into adult life. Such studies may confirm a role for GH in promoting continued accrual of bone mass and thereby demonstrate that cessation of GH at achievement of final height, by limiting peak bone mass, may predispose to clinically significant osteoporosis in later life. In addition to the potential importance of GH for achievement of peak bone mass, there may be a superimposed accelerated loss of BMD with advancing age similar to the situation observed in adult-onset GHD. To date, this has been difficult to assess in adult GHD of childhood-onset because the relative contributions of low peak bone mass and increased loss of bone in later life could not be distinguished.     

Terrestrial biosphere models need better representation of vegetation phenology: results from the North American Carbon Program Site Synthesis

Phenology, by controlling the seasonal activity of vegetation on the land surface, plays a fundamental role in regulating photosynthesis and other ecosystem processes, as well as competitive interactions and feedbacks to the climate system. We conducted an analysis to evaluate the representation of phenology, and the associated seasonality of ecosystem‐scale CO₂ exchange, in 14 models participating in the North American Carbon Program Site Synthesis. Model predictions were evaluated using long‐term measurements (emphasizing the period 2000–2006) from 10 forested sites within the AmeriFlux and Fluxnet‐Canada networks. In deciduous forests, almost all models consistently predicted that the growing season started earlier, and ended later, than was actually observed; biases of 2 weeks or more were typical. For these sites, most models were also unable to explain more than a small fraction of the observed interannual variability in phenological transition dates. Finally, for deciduous forests, misrepresentation of the seasonal cycle resulted in over‐prediction of gross ecosystem photosynthesis by +160 ± 145 g C m^?2 yr^?1 during the spring transition period and +75 ± 130 g C m^?2 yr^?1 during the autumn transition period (13% and 8% annual productivity, respectively) compensating for the tendency of most models to under‐predict the magnitude of peak summertime photosynthetic rates. Models did a better job of predicting the seasonality of CO₂ exchange for evergreen forests. These results highlight the need for improved understanding of the environmental controls on vegetation phenology and incorporation of this knowledge into better phenological models. Existing models are unlikely to predict future responses of phenology to climate change accurately and therefore will misrepresent the seasonality and interannual variability of key biosphere–atmosphere feedbacks and interactions in coupled global climate models.     

Alterations in aortic antioxidant components in an experimental model of atherosclerosis: A time-course study

Antioxidant component alterations in the aorta during atherogenesis were examined in atherosclerosis-susceptible (SUS) Japanese quail fed a cholesterol-supplemented (0.5% w/w) diet. Birds fed a non-supplemented diet provided information on the effects of aging on endogenous antioxidants. One hundred adult SUS males were used. Birds were sacrificed after 0, 4, 8 and 12 weeks on the diets and were examined for plaque development and corresponding antioxidant component alterations in aorta and myocardium. With aging, superoxide dismutase (SOD) activity was increased in both tissues, whereas aortic glutathione peroxidase (GPx) activity and myocardial glutathione reductase (GRd) activity decreased. Myocardial ascorbate levels increased with aging, with a reciprocal decrease in myocardial tocopherol levels. Following 4 weeks of cholesterol supplementation, aortic GRd decreased, SOD activity increased, but activities of GPx and catalase were unchanged. This same qualitative pattern of antioxidant enzyme changes was also found in myocardium. Thus, although aortic antioxidant enzyme changes produced by cholesterol feeding and aging showed some similarities, the early phase of atherogenesis does not simply reflect accelerated aging. In the late stages of atherogenesis, SOD activity returned to baseline, but other antioxidant enzymes remained unaltered from levels characterizing the early phase of lesion development. There was no detectable functional coupling between changes in GPx and GRd, nor between SOD (which produces hydrogen peroxide) and GPx or catalase (which utilize hydrogen peroxide as substrate). Previously reported alterations in erythrocyte antioxidant enzyme components during atherogenesis in quail were not predictive of changes in the corresponding enzymes in the aorta and myocardium.     

Structure and biological activities of beta toxin from Staphylococcus aureus

Beta toxin is a neutral sphingomyelinase secreted by certain strains of Staphylococcus aureus. This virulence factor lyses erythrocytes in order to evade the host immune system as well as scavenge nutrients. The structure of beta toxin was determined at 2.4-Å resolution using crystals that were merohedrally twinned. This structure is similar to that of the sphingomyelinases of Listeria ivanovii and Bacillus cereus. Beta toxin belongs to the DNase I folding superfamily; in addition to sphingomyelinases, the proteins most structurally related to beta toxin include human endonuclease HAP1, Escherichia coli endonuclease III, bovine pancreatic DNase I, and the endonuclease domain of TRAS1 from Bombyx mori. Our biological assays demonstrated for the first time that beta toxin kills proliferating human lymphocytes. Structure-directed active site mutations show that biological activities, including hemolysis and lymphotoxicity, are due to the sphingomyelinase activity of the enzyme.     

Genetic containment of forest plantations

Dispersal of pollen, seeds, or vegetative propagules from intensively bred, exotic, or recombinant DNA modified forest plantations may cause detrimental or beneficial ecological impacts on wild or managed ecosystems. Insertion of genes designed to prevent or substantially reduce dispersal could reduce the risk and extent of undesired impacts. Containment measures may also be required by law or marketplace constraints, regardless of risks or benefits. We discuss: (1) the context for when genetic containment or mitigation systems may be needed; (2) technology approaches and mechanisms; (3) the state of knowledge on genes/genomics of sexual reproduction in forest trees; (4) stability of transgene expression during vegetative growth; (5) simulation studies to define the level of containment needed; and (6) needed research to deliver effective containment technologies. We illustrate progress with several examples from our research on recombinant DNA modified poplars. Our simulations show that even partial sterility can provide very substantial reductions in gene flow into wild trees. We conclude that it is impossible to define the most effective containment approaches, nor their reliability, based on current genomic knowledge and technological tools. Additional genomic and technological studies of a wide variety of options are needed. Studies in field environments are essential to provide data relevant to ecological analysis and regulatory decisions and need to be carried out in phylogenetically diverse representatives of the economically most important taxa of forest trees.

Collectins and ficolins: sugar pattern recognition molecules of the mammalian innate immune system

Collectins and ficolins represent two important groups of pattern recognition molecules, which bind to oligosaccharide structures on the surface of microorganisms, leading to the killing of bound microbes through complement activation and phagocytosis. Collectins and ficolins bear no significant sequence homology except for the presence of collagen-like sequences over the N-terminal halves of the polypeptides that enable the assembly of these molecules into oligomeric structures. Collectins and ficolins both contain lectin activities within the C-terminal halves of their polypeptides, the C-type carbohydrate recognition domain (CRDs) and fibrinogen beta/gamma (homology) (FBG) domain, respectively. These domains form trimeric clusters at the ends of the collagen triple helices emanating from a central hub, where the N-terminal ends of the polypeptides merge. The collectins and ficolins seem to have evolved to recognize the surface sugar codes of microbes and their binding, to these arrays of cell surface carbohydrate molecules, targets the microbe for subsequent clearance by phagocytic cells.     

Gibberellin‐associated cisgenes modify growth,stature and wood properties in Populus

We studied the effects on plant growth from insertion of five cisgenes that encode proteins involved in gibberellin metabolism or signalling. Intact genomic copies of PtGA20ox7, PtGA2ox2,Pt RGL1_1, PtRGL1_2 and PtGAI1 genes from the genome‐sequenced Populus trichocarpa clone Nisqually‐1 were transformed into Populus tremula × alba (clone INRA 717‐1B4), and growth, morphology and xylem cell size characterized in the greenhouse. Each cisgene encompassed 1–2 kb of 5′ and 1 kb of 3′ flanking DNA, as well as all native exons and introns. Large numbers of independent insertion events per cisgene (19–38), including empty vector controls, were studied. Three of the cisgenic modifications had significant effects on plant growth rate, morphology or wood properties. The PtGA20ox7 cisgene increased rate of shoot regeneration in vitro, accelerated early growth, and variation in growth rate was correlated with PtGA20ox7 gene expression. PtRGL1_1 and PtGA2ox2 caused reduced growth, while PtRGL1_2 gave rise to plants that grew normally but had significantly longer xylem fibres. RT‐PCR studies suggested that the lack of growth inhibition observed in PtRGL1_2 cisgenic plants was a result of co‐suppression. PtGAI1 slowed regeneration rate and both PtGAI1 and PtGA20ox7 gave rise to increased variance among events for early diameter and volume index, respectively. Our work suggests that cisgenic insertion of additional copies of native genes involved in growth regulation may provide tools to help modify plant architecture, expand the genetic variance in plant architecture available to breeders and accelerate transfer of alleles between difficult‐to‐cross species.