Modelling ¹⁸O₂ and ¹⁶O₂ unidirectional fluxes in plants: I. regulation of pre-industrial atmosphere

In closed systems, the O₂ compensation point (Γ_O) was previously defined as the upper limit of O₂ level, at a given CO₂ level, above which plants cannot have positive carbon balance and survive. Studies with ¹⁸O₂ measure the actual O₂ uptake by photorespiration due to the dual function of Rubisco, the enzyme that fixes CO₂ and takes O₂ as an alternative substrate. One-step modelling of CO₂ and O₂ uptakes allows calculating a plant specificity factor (Sp) as the sum of the biochemical specificity of Rubisco and a biophysical specificity, function of the resistance to CO₂ transfer from the atmosphere to Rubisco. The crossing points (Cx, Ox) are defined as CO₂ and O₂ concentrations for which O₂ and CO₂ uptakes are equal. It is observed that: (1) under the preindustrial atmosphere, photorespiration of C3 plants uses as much photochemical energy as photosynthesis, i.e. the Cx and Ox are equal or near the CO₂ and O₂ concentrations of that epoch; (2) contrarily to Γ_C, a Γ_O does not practically limit the plant growth, i.e. the plant net CO₂ balance is positive up to very high O₂ levels; (3) however, in a closed biosystem, Γ_O exists; it is not the limit of plant growth, but the equilibrium point between photosynthesis and the opposite respiratory processes; (4) a reciprocal relationship exists between Γ_O and Γ_C, as unique functions of the respective CO₂ and O₂ concentrations and of Sp, this invalidates some results showing two different functions for Γ_O and Γ_C, and, consequently, the associated analyses related to greenhouse effects in the past; (5) the pre-industrial atmosphere levels of O₂ and CO₂ are the Γ_O and Γ_C of the global bio-system. They are equal to or near the values of Cx and Ox of C3 plants, the majority of land plants in preindustrial period. We assume that the crossing points represent favourable feedback conditions for the biosphere-atmosphere equilibrium and could result from co-evolution of plants-atmosphere-climate. We suggest that the evolution of Rubisco and associated pathways is directed by an optimisation between photosynthesis and photorespiration.     

Thermal biology and temperature-based habitat selection in a large aquatic ectotherm, the alligator snapping turtle, Macroclemys temminckii

Ectotherms in water experience rates of heat transfer at least two orders of magnitude greater than in air, seriously constraining their thermoregulatory capabilities. Yet, even in water, individuals may exert control over body temperature (T_b) via behaviors such as selecting thermally favorable microhabitats. The interactions among body size, physiology, and behavior on the thermal biology of large, entirely aquatic, ectotherms is poorly understood. We tested the hypothesis that alligator snapping turtles (Macroclemmys temminckii) selected microhabitats based on temperature by comparing temperatures at sites used by turtles to temperatures at randomly selected sites. These large turtles selected a narrow range of microhabitats that were significantly warmer and less variable in temperature than random sites. Cooling trials in the laboratory indicated larger turtles equilibrated more slowly to ambient temperature (T_a) than smaller turtles. We recorded T_a and body temperature (T_b) of turtles in the field continuously throughout the year. The T_b generally conformed to T_a but there were periods when T_b−T_a differences were great. These results suggest that while physiology and size of aquatic turtles can affect T_b transiently, microhabitat selection may be the only meaningful mechanism for large, entirely aquatic, turtles to control T_b.     

Thermogenesis, energy intake and serum leptin in Apodemus chevrieri in Hengduan Mountains region during cold acclimation

Environmental factors play an important role in the seasonal adaptation of body mass and thermogenesis in small, wild mammals. The purpose of the present study was to test the hypothesis that ambient temperature was a cue to trigger the adjustments in body mass, energy intake, and serum leptin level in Apodemus chevrieri during 42 days of cold exposure. Our data demonstrated that cold acclimation induced a decrease in body mass and a significant increase in energy intake in A. chevrieri. Serum leptin levels were positively correlated with body mass and fat mass. These data suggest that A. chevrieri reduced the body mass and increased energy intake and thermogenic capacity under cold acclimation. Further, serum leptin appears to be involved in the energy intake regulation and thermoregulation.     

Breast fine needle aspiration cytology: a review of current practice in Australasia

M. C. Cummings, B. A. Waters and P. K. O’Rourke Breast fine needle aspiration cytology: a review of current practice in Australasia Aims: To investigate breast fine needle aspiration (FNA) cytology in Australasia, in terms of laboratory demographics, specimens received and quality control (QC). Methods: A questionnaire was sent to all laboratories enrolled in the FNA module of the Royal College of Pathologists of Australasia Cytopathology Quality Assurance Program (QAP), requesting information about specimens received in a 3‐month period in 2001 and in 2008. Results: Responses were received from 81/180 laboratories in 2001 and from 94/200 in 2008. The mean number of cases per 3 months was 137 in 2001 and 141 in 2008 and for the 42 laboratories responding on both occasions, the mean number of cases declined from 191 to 149 (P = 0.001). The mean percentage of malignant cases was 11.7% in 2001 and 10.5% in 2008 and the mean percentages of unsatisfactory rates were 21.7% and 25.2%, respectively; 43.2% of laboratories in 2001 and 40.4% in 2008 reported fewer than 50 cases for the 3‐month period. The unsatisfactory rate was inversely proportional to the number of cases received. Most QC (69.1% in 2001, 71.3% in 2008) was carried out by correlation with any later histology. With no histology available, 35.8% of laboratories in 2001 and 48.9% in 2008 did no further follow‐up. Follow‐up of all diagnostic categories increased from 30.9% in 2001 to 44% in 2008. Conclusions: Breast FNA cytology is still actively undertaken in Australasia, but numbers have declined. Unsatisfactory rates have reached the Australian recommended upper limit and are inversely proportional to the total number of cases received. Overall QC measures are unchanged and consideration of a review of breast FNA guidelines is suggested.     

Pre- and post-weaning cold exposure does not lead to an obese phenotype in adult Brandt's voles (Lasiopodomys brandtii)

Evidence has shown that postnatal undernutrition, overnutrition and cold stress are associated with imbalanced metabolic regulation as rodents achieve adulthood. In this study, we used a breeding colony of Brandt's voles (Lasiopodomys brandtii), a wild rodent species from the Inner Mongolia grasslands in China, to examine the effects of pre- and post-weaning cold exposure on the adult body (fat) mass, serum hormones and hypothalamic neuropeptides. Unlike laboratory rodents, vole offspring exposed to pre-weaning cold did not exhibit overweight or obese phenotypes in adulthood compared with unexposed controls. Moreover, adult male voles that remained in colder conditions had less body mass and lower serum leptin levels despite having higher food intake compared to other groups. To understand the mechanism of this unexpected regulation, hypothalamic gene expression was assessed for pre- and post-weaning cold exposure. Voles exposed to cold before weaning increased hypothalamic, orexigenic agouti-related protein (AgRP) and decreased anorexigenic proopiomelanocortin (POMC) mRNA expression at weaning. These expression changes were associated with hyperphagia and catch-up growth after weaning. Interestingly, these changes in hypothalamic neuropeptides were short lasting because in adult voles these differences were no longer apparent, which might explain why the pre-weaning, cold-exposed voles did not become obese in adulthood. These data suggest that some species do not develop an obese phenotype in response to early life cold stress.     

Cysteine supplementation reverses methionine restriction effects on rat adiposity: significance of stearoyl-coenzyme A desaturase

Stearoyl-CoA desaturase-1 (SCD1) is a key enzyme in fatty acid and energy metabolism, but little is known about its nutritional regulation. Dietary methionine restriction in rats decreases hepatic Scd1 mRNA and protein, increases energy expenditure, and decreases fat-pad mass/body-weight% (FM/BW%). In humans, plasma concentrations of the methionine product, cysteine, are associated with obesity. To determine which consequences of methionine-restriction are mediated by decreased cysteine availability, we monitored obesity-related variables in 4 dietary groups for 12 weeks: control-fed (CF), methionine-restricted (MR), MR supplemented with 0.5% l-cysteine (MR+Cys) and CF+Cys rats. MR lowered weight gain and FM/BW% despite higher food intake/weight than CF, and lowered serum cysteine. Hepatic Scd1 expression was decreased, with decreased serum SCD1 activity indices (calculated from serum fatty acid profile), decreased serum insulin, leptin and triglycerides, and higher adiponectin. Cysteine supplementation (MR+Cys) essentially reversed all these phenotypes and raised serum cysteine but not methionine to CF levels. Adding extra cysteine to control diet (CF+Cys) increased serum taurine but did not affect serum cysteine, lipids, proteins, or total weight gain. FM/BW% and serum leptin were modestly decreased. Our results indicate that anti-obesity effects of MR are caused by low cysteine and that dietary sulfur amino acid composition contributes to SCD1 regulation.     

Ultrasonographic evaluation of endometrial thickness near timed AI as a predictor of fertility in high-producing dairy cows

The objectives were to evaluate changes in endometrial thickness (ET) near the time of a synchronized ovulation and to assess the relationship of ET and fertility in lactating Holstein cows, with or without estrogen supplementation near timed ovulation. In Experiment 1, eight cows were examined with transrectal ultrasonography, once daily for 5 d, starting concurrent with PGF_2α (PGF) treatment during an Ovsynch protocol (GnRH - 7d - PGF - 72h - GnRH). The ET increased rapidly after PGF (from ∼7 to ∼9.5 mm), remained > 9 mm for the next 2 d, then decreased to ∼8 and 7.4 mm, 1 and 2 d, respectively, after the second GnRH. In Experiment 2,642 cows (total of 758 breedings) were subjected to an Ovsynch protocol (GnRH - 7d - PGF - 56h - GnRH - 16h - timed AI); cows received either no further treatment (Ovsynch) or 1 mg of estradiol-17β im 8 h before the second GnRH (Ovsynch + E2). For both uterine horns, ET was measured (∼2 cm from the internal uterine body bifurcation) before E2 treatment (48 h after PGF). In cows with ET ≤ 8 mm vs > 8 mm, rates of ovulation were 86.0% (n = 136) vs 98.1% (n = 472; P < 0.01), respectively, and percentage pregnant per AI (P/AI) were 26.7% (n = 146) vs 42.7% (n = 524; P < 0.01). Treatment with E2 increased P/AI in cows with lower ET (Ovsynch + E2 = 37.0% vs Ovsynch = 23.3%; P = 0.07), but did not significantly improve P/AI in cows with ET > 8 mm (Ovsynch + E2 = 43.4% vs Ovsynch = 42.1%). In conclusion, a single ultrasonographic evaluation of ET in Holstein cows 48 h after PGF treatment in an Ovsynch program was a good predictor of ovulation failure and pregnancy success. Perhaps poor fertility in cows with reduced ET was low peripheral E2 concentrations near AI, poor P4 priming, or luteolysis failure during timed AI procedures.     

Rapid parallel evolution of aberrant traits in the diversification of the Gulf of Guinea white-eyes (Aves, Zosteropidae)

Archipelago-endemic bird radiations are familiar to evolutionary biologists as key illustrations of evolutionary patterns. However, such radiations are in fact rare events. White-eyes (Zosteropidae) are birds with an exceptionally high colonization and speciation potential; they have colonized more islands globally than any other passerine group and include the most species-rich bird genus. The multiplication of white-eye island endemics has been consistently attributed to independent colonizations from the mainland; the white-eyes of the Gulf of Guinea archipelago had been seen as a classic case, spanning as great a breadth of phenotypic diversity as the family worldwide. Contrary to this hypothesis, our molecular phylogenetic analysis places the Gulf of Guinea white-eyes in just two radiations, one grouping all five oceanic island taxa and the other grouping continental island and land-bridge taxa. Numerous 'aberrant' phenotypes (traditionally grouped in the genus Speirops) have evolved independently over a short space of time from nonaberrant (Zosterops) phenotypes; the most phenotypically divergent species have separated as recently as 0.22 Ma. These radiations rival those of Darwin's finches and the Hawaiian honeycreepers in terms of the extent of adaptive radiation per unit time, both in terms of species numbers and in terms of phenotypic diversity. Tempo and patterns of morphological divergence are strongly supportive of an adaptive radiation in the oceanic islands driven by ecological interactions between sympatric white-eyes. Here, very rapid phenotypic evolution mainly affected taxa derived from the youngest wave of colonization, in accordance with the model of asymmetric divergence owing to resource competition in sympatry.     

In-vehicle extremity injuries from improvised explosive devices: current and future foci

The conflicts in Iraq and Afghanistan have been epitomized by the insurgents' use of the improvised explosive device against vehicle-borne security forces. These weapons, capable of causing multiple severely injured casualties in a single incident, pose the most prevalent single threat to Coalition troops operating in the region. Improvements in personal protection and medical care have resulted in increasing numbers of casualties surviving with complex lower limb injuries, often leading to long-term disability. Thus, there exists an urgent requirement to investigate and mitigate against the mechanism of extremity injury caused by these devices. This will necessitate an ontological approach, linking molecular, cellular and tissue interaction to physiological dysfunction. This can only be achieved via a collaborative approach between clinicians, natural scientists and engineers, combining physical and numerical modelling tools with clinical data from the battlefield. In this article, we compile existing knowledge on the effects of explosions on skeletal injury, review and critique relevant experimental and computational research related to lower limb injury and damage and propose research foci required to drive the development of future mitigation technologies.