The reproductive--endocrine response of adult rams to sexual encounters with estrual ewes is season dependent

An experiment was conducted with four adult, sexually inexperienced Finnish Landrace rams during the ovine nonbreeding (July) and breeding (October) seasons to determine the influence of components of the rams' mating behavior on the secretion of luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (PRL), and testosterone. On four occasions in both seasons, blood was collected by jugular venipuncture at 20-min intervals during an 8-hr period while rams were (1) separated from, (2) observing with minimal direct physical contact, (3) mounting without intromission, or (4) mating estrous-induced ewes. In comparison with separation periods, mating activity in July was associated with increased mean LH (P less than 0.05) and testosterone levels and number of LH peaks, while in October, obvious increases were detected in only baseline LH levels (P less than 0.05). Circulating LH and testosterone levels either did not change (July) or were depressed (October) during the mounting and observation periods. FSH levels generally remained unaffected by engagement in the various sexual activities. Although a clear relationship between type of sexual activity and mean PRL levels was not observed in July, activities which appeared to involve the most physical exertion tended to be associated with much higher circulating PRL levels in October. These data suggest (1) the act of ejaculation is important in the induction of increases in LH and testosterone secretion that occur in rams in response to mating activity during the nonbreeding season and (2) excessively stressful sexual activities during the breeding season may alter the pattern of secretion of some reproductive hormones.     

Measuring complexity to infer changes in the dynamics of ecological systems under stress

Despite advances in our mechanistic understanding of ecological processes, the inherent complexity of real-world ecosystems still limits our ability in predicting ecological dynamics especially in the face of on-going environmental stress. Developing a model is frequently challenged by structure uncertainty, unknown parameters, and limited data for exploring out-of-sample predictions. One way to address this challenge is to look for patterns in the data themselves in order to infer the underlying processes of an ecological system rather than to build system-specific models. For example, it has been recently suggested that statistical changes in ecological dynamics can be used to infer changes in the stability of ecosystems as they approach tipping points. For computer scientists such inference is similar to the notion of a Turing machine: a computational device that could execute a program (the process) to produce the observed data (the pattern). Here, we make use of such basic computational ideas introduced by Alan Turing to recognize changing patterns in ecological dynamics in ecosystems under stress. To do this, we use the concept of Kolmogorov algorithmic complexity that is a measure of randomness. In particular, we estimate an approximation to Kolmogorov complexity based on the Block Decomposition Method (BDM). We apply BDM to identify changes in complexity in simulated time-series and spatial datasets from ecosystems that experience different types of ecological transitions. We find that in all cases, K_BDM complexity decreased before all ecological transitions both in time-series and spatial datasets. These trends indicate that loss of stability in the ecological models we explored is characterized by loss of complexity and the emergence of a regular and computable underlying structure. Our results suggest that Kolmogorov complexity may serve as tool for revealing changes in the dynamics of ecosystems close to ecological transitions.     

Bis(L-cysteinato)gold(I): chemical characterization and identification in renal cortical cytoplasm.

L-Cysteinatogold(I) was prepared by the reaction of L-cysteine with KAuBr4 in acidic media and its solubility determined from pH 4 to 10. The solubility at pH 7.4 and 37 degrees C is 1 microM. In the presence of excess cysteine, the solubility increases because of formation of bis(L-cysteinato)gold(I). The equilibrium-constant for formation of the bis complex is 2.1 +/- 0.4 X 10(-3), which at pH 7.4 CORRESPONDs to an apparant formation constant of 4.4 X10(4). The formation of the bis adduct was confirmed by chromatographic separation of the products of the reaction between [35S]-L-cysteine and Na2AuTM. This complex elutes with Kav = 1.15 which allows it to be distinguished from other gold thiolates that might form in vivo. The bis(cysteinato)gold(I) complex is shown to be present in kidney cytosol isolated from rats given Na2AuTM in vivo. When additional cysteine is added to the cytosol in vitro, the peak at 1.15 is increased, but if glutathione is added, the low molecular weight gold elutes at Kav = 1.00, which is taken as evidence for the existence of bis(cysteinato)gold(I) in the cytosol preparation. The amount of gold present as bis(cysteinato)gold(I) after 4 different dose schedules has been measured and found to increase with the total cytosol gold concentration. L-Cysteinatogold(I) does not dissolve in the presence of bovine serum albumin to form an adduct.     

Validation and Calibration of Physical Activity Monitors in Children

Objective: This study was designed to validate accelerometer-based activity monitors against energy expenditure (EE) in children; to compare monitor placement sites; to field-test the monitors; and to establish sedentary, light, moderate, and vigorous threshold counts. Research Methods and Procedures: Computer Science and Applications Actigraph (CSA) and Mini-Mitter Actiwatch (MM) monitors, on the hip or lower leg, were validated and calibrated against 6-hour EE measurements by room respiration calorimetry, activity by microwave detector, and heart rate by telemetry in 26 children, 6 to 16 years old. During the 6 hours, the children performed structured activities, including resting metabolic rate (RMR), Nintendo, arts and crafts, aerobic warm-up, Tae Bo, treadmill walking and running, and games. Activity energy expenditure (AEE) computed as EE − RMR was regressed against counts to derive threshold counts. Results: The mean correlations between EE or AEE and counts were slightly higher for MM-hip (r = 0.78 ± 0.06) and MM-leg (r = 0.80 ± 0.05) than CSA-hip (r = 0.66 ± 0.08) and CSA-leg (r = 0.73 ± 0.07). CSA and MM performed similarly on the hip (inter-instrument r = 0.88) and on the lower leg (inter-instrument r = 0.89). Threshold counts for the CSA-hip were <800, <3200, <8200, and ≥8200 for sedentary, light, moderate, and vigorous categories, respectively. For the MM-hip, the threshold counts were <100, <900, <2200, and ≥2200, respectively. Discussion: The validation of the CSA and MM monitors against AEE and their calibration for sedentary, light, moderate, and vigorous thresholds certify these monitors as valid, useful devices for the assessment of physical activity in children.     

Effects of antioxidants on cyclooxygenase and lipoxygenase activities in intact human platelets: Comparison with indomethacin and etya

Five antioxidative agents (BW755C, 1-naphtol, NDGA, propylgallate and quercetin) were compared with indomethacin and ETYA for their effects on (¹⁴C) arachidonic acid metabolism by cyclooxygenase (CO) and lipoxygenase (LPO) enzymes in intact human platelets. All tested compounds inhibited CO activity in a concentration-dependent manner. LPO activity was suppressed by NDGA, propylgallate, quercetin and ETYA but strongly enhanced by BW755C, 1-napthol and indomethacin. Whereas NDGA and ETYA showed almost equipotent inhibitory effects towards both fatty acid oxygenases, propylgallate and quercetin were found to be respectively 6.5 and 4 times better inhibitors of LPO than of CO activities.These data indicate that antioxidants affect arachidonic acid metabolism in intact human platelets in different ways: BW755C and 1-naphtol exerted the same activity as indomethacin, a selective CO blocker, whereas NDGA, propylgallate and quercetin behaved as ETYA, a dual CO-LPO inhibitor. Considering their inhibition selectivity, propylgallate and quercetin may serve as prototypes for more specific blockers of LPO activity.     

Wildfires affect tree growth and resilience in Northeastern China natural Dahurian larch forests: A dendrochronological perspective

Wildfires are natural and ubiquitous disturbances in boreal forests. Assessing their impacts on tree growth and resilience are particularly important to recognize the adaptation strategies of fire-tolerant species and forest succession in fire conditions. To date, the growth resilience of fire-tolerant species in boreal forests remains largely unquantified, and the drivers of resilience are poorly understood. Here, we measured the tree-ring widths of 99 fire-scarred trees from three sites in natural Dahurian larch (Larix gmelinii) forests. Three moderate-severity fire events in years 1987, 1990, and 2000 occurring at three sites were detected from the records of local forestry bureau. Based on tree-ring width data, we calculated resilience components (i.e., resistance, recovery, resilience and relative resilience) to quantify the responses of growth resilience in the larch trees to fires and analyzed their drivers at three sites. Results indicated that fires significantly reduced the tree growth. With the increasing tree age, these reductions were more pronounced. As for resilience components, our study showed a limited resistance but high recovery of tree growth against fires, and resistance tended to increase northwards but recovery showed the opposite, suggesting a growth-survival tradeoff was exhibited in Dahurian larch trees. With an increasing tree age, regional resistance and resilience showed a decreasing trend, whereas recovery and relative resilience showed an increasing trend. Resilience components were mainly affected by the climatic factors in spring. An increase in moisture availability enhanced resistance, a reduction in diurnal temperature range enhanced recovery, and an increase in mean temperature enhanced resilience and relative resilience. This study reveals that Dahurian larch could be even less favorable when faced with moderate or severe fire events, but a high capacity of recovery enables this species to adapt to the fire-prone condition. Moreover, this work highlights that the resilience of tree growth should be considered to understand tree behaviors and survival strategies of boreal forests following fires across fire-prone regions under future climate warming.     

The scientific profiles of terrestrial mammals in Great Britain as measured by publication metrics

Research on mammals provides the evidence base for their conservation, management and related policy. We assess the effect of study choices on the composition of this evidence base. We derived species h‐index (SHI) for 67 breeding terrestrial mammals from 2305 publications based on field research carried out in England, Scotland and Wales. Native species had higher SHI than introduced species, but SHI was not related to the level of species conservation concern. SHI was positively related to geographical range and/or population size and to functional group: large herbivores had higher SHI, then carnivores, rodents, small herbivores, bats and insectivores.     

Mechanisms of structural change derived from patterns of seedling emergence and mortality in a semi-natural meadow

Questions: Is seedling emergence limited by the set of viable seeds, by incompatibility between the phenology of seed shedding and timing of mowing, or by dry weather in germination periods? Does seedling mortality fluctuate with season and weather? Location: Negrentino, southern Alps, Switzerland. Methods: Fecundity estimates of the dominant grass Bromus erectus; highly frequent counts of spontaneous seedlings by species and calculation of a community-level average mortality rate across 5 years; species-level records of seed shedding date and measurements of seed mass; measurement of soil moisture. Results: B. erectus produced 143.9 viable seeds/m²/year while the density of its seedlings was a 55 times smaller fraction. Grasses had fewer seedlings than forbs and their phenology of seed shedding was less compatible with mowing date. Soil moisture was a strong determinant of seedling emergence in spring and less so in autumn. Average seedling mortality declined with age of the populations and reached a maximum in an extremely dry summer. In relatively wet summers establishment success was positively related to seed mass. Conclusion: Community structure is susceptible to drought through mechanisms that selectively reduce recruits of coexisting plant functional groups. We propose that (1) more frequent intense droughts tend to reduce species that depend on frequent recruitment from seed, hence favour long-lived clonally spreading species, (2) drought timing selects between species with different germination phenology and drought resistance, and (3) drought impacts can be mitigated by changing management regimes that affect seed shedding.