Atmospheric hypoxia limits selection for large body size in insects

Recent geological models indicate a marked increase in atmospheric oxygen partial pressure (aPO~2~) to 32 kPa in the Permo-Carboniferous (approx. 300 million years ago), subsequently falling to 13 kPa in the Triassic^1^.These aPO~2~ changes have been hypothesized to cause multiple major evolutionary events^2^ including the appearance and subsequent extinction of giant insects and other taxa^3, 4^. Patterns of increasing tracheal investment in larger insects support this hypothesis^5^, as do observations of positive relationships between aPO~2~ and body size in single- or multi-generational experiments with _Drosophila melanogaster_ and other insects^6^. Large species likely result from many generations of selection for large body size driven by predation, competition or sexual selection^7^. Thus a crucial question is whether aPO~2~ influences the capacity of such selection to increase insect size. We tested that possibility by selecting for large body size in five _Drosophila melanogaster_ populations for 11 generations in hypoxic (10 kPa), normoxic (21 kPa) and hyperoxic (40 kPa) aPO~2~, followed by three generations of normoxia without size selection to test for evolved responses. Average body sizes increased by 15% during 11 generations of size selection in 21 and 40 kPa aPO~2~ flies and even stronger responses were observed for the flies in the largest quartile of body masses. However, flies selected for large size in 10 kPa aPO~2~ had strongly reduced sizes compared to those in higher aPO~2~. Upon return to normoxia, all flies had similar, enlarged sizes relative to the starting populations. These results demonstrated that positive size selection had equivalent genetic effects on all flies independent of aPO~2~, but that hypoxia provided a physical constraint on body size even in a relatively small insect under strong selection for larger mass. Our data support the hypothesis that Triassic hypoxia may have contributed to a reduction in insect size

Quantizing graphs, one way or two?

Quantum graphs were introduced to model free electrons in organic molecules using a self-adjoint Hamiltonian on a network of intervals. A second graph quantization describes wave propagation on a graph by specifying scattering matrices at the vertices. A question that is frequently raised is the extent to which these models are the same or complimentary. In particular, are all energy independent unitary vertex scattering matrices associated with a self-adjoint Hamiltonian? Here we review results related to this issue. In addition, we observe that a self-adjoint Dirac operator with four component spinors produces a secular equation for the graph spectrum that matches the secular equation associated with wave propagation on the graph when the Dirac operator describes particles with zero mass and the vertex conditions do not allow spin rotation at the vertices.Comment: 10 pages, 1 figur

A Brief Overview of the Life and Work of Lyon Henry Appleby, M.D. (1895-1970).

The life and work of Dr. Lyon Henry Appleby, M.D., portrays the essence of a devoted clinician committed to scholarly excellence. Born in Deseronto, Ontario, in 1895 and passing in 1970, Dr. Appleby influenced all areas of general surgery, most notably popularizing a procedure that bears his name today. After a tour in World War I, he quickly proved himself to be a dedicated clinician with roots in academia, which translated into excellence within the Department of Surgery at St. Paul\u27s Hospital in Vancouver, Canada. He served in various leadership roles including Chair of the Department of Surgery, President of the International College of Surgeons, and Fellow of the Royal College of Physicians and Surgeons. The Appleby procedure, or en bloc removal of the celiac axis, at the time of gastrectomy, is the technical focus of this paper, although reference is made to Appleby\u27s extensive contributions to historical medicine

Algorithms for Del Pezzo Surfaces of Degree 5 (Construction, Parametrization)

It is well known that every Del Pezzo surface of degree 5 defined over k is parametrizable over k. In this paper we give an efficient construction for parametrizing, as well as algorithms for constructing examples in every isomorphism class and for deciding equivalence.Comment: 15 page

Complete Dynamical Evaluation of the Characteristic Polynomial of Binary Quantum Graphs

We evaluate the variance of coefficients of the characteristic polynomial for binary quantum graphs using a dynamical approach. This is the first example of a chaotic quantum system where a spectral statistic can be evaluated in terms of periodic orbits without taking the semiclassical limit, which is the limit of large graphs. The variance depends on the size of two classes of primitive pseudo orbits (sets of periodic orbits); pseudo orbits without self-intersections and those where all the self-intersections are 2-encounters at a single vertex. To show other pseudo orbits do not contribute we employ a parity argument for Lyndon word decompositions. For families of binary graphs with an increasing number of bonds, we show the periodic orbit formula approaches a universal constant independent of the coefficient of the polynomial. This constant is obtained by counting the total number of primitive pseudo orbits of a given length. To count periodic orbits and pseudo orbits we exploit further connections between orbits on binary graphs and Lyndon words.Comment: 43 pages, 11 figure

National Indigenous Palliative Care Needs Study

This study involved extensive consultation with the community to identify the needs of Aboriginal and Torres Strait Islander peoples in palliative care

Mechanisms of Thermal Stability during Flight in the Honeybee Apis Mellifera

Thermoregulation of the Thorax Allows Honeybees (Apis Mellifera) to Maintain the Flight Muscle Temperatures Necessary to Meet the Power Requirements for Flight and to Remain Active Outside the Hive Across a Wide Range of Air Temperatures (T(A)). to Determine the Heat-Exchange Pathways through Which Flying Honeybees Achieve Thermal Stability, We Measured Body Temperatures and Rates of Carbon Dioxide Production and Water Vapor Loss between T(A) Values of 21 and 45°C for Honeybees Flying in a Respirometry Chamber. Body Temperatures Were Not Significantly Affected by Continuous Flight Duration in the Respirometer, indicating that Flying Bees Were at Thermal Equilibrium. Thorax Temperatures (T(Th)) during Flight Were Relatively Stable, with a Slope of T(Th) on T(A) of 0.39. Metabolic Heat Production, Calculated from Rates of Carbon Dioxide Production, Decreased Linearly by 43% as T(A) Rose from 21 to 45°C. Evaporative Heat Loss Increased Nonlinearly by over Sevenfold, with Evaporation Rising Rapidly at T(A) Values above 33°C. at T(A) Values above 43°C, Head Temperature Dropped Below T(A) by Approximately 1-2°C, Indicating that Substantial Evaporation from the Head Was Occurring at Very High T(A) Values. the Water Flux of Flying Honeybees Was Positive at T(A) Values Below 31°C, But Increasingly Negative at Higher T(A) Values. at All T(A) Values, Flying Honeybees Experienced a Net Radiative Heat Loss. Since the Honeybees Were in Thermal Equilibrium, Convective Heat Loss Was Calculated as the Amount of Heat Necessary to Balance Metabolic Heat Gain Against Evaporative and Radiative Heat Loss. Convective Heat Loss Decreased Strongly as T(A) Rose Because of the Decrease in the Elevation of Body Temperature above T(A) Rather Than the Variation in the Convection Coefficient. in Conclusion, Variation in Metabolic Heat Production is the Dominant Mechanism of Maintaining Thermal Stability during Flight between T(A) Values of 21 and 33°C, But Variations in Metabolic Heat Production and Evaporative Heat Loss Are Equally Important to the Prevention of overheating during Flight at T(A) Values between 33 and 45°C

The Flight Physiology of Reproductives of Africanized, European, and Hybrid Honeybees (Apis mellifera)

Neotropical African honeybees (Apis mellifera scutellata), in the process of spreading throughout tropical and subtropical regions of the Americas, hybridize with and mostly replace European honeybees (primarily Apis mellifera mellifera and Apis mellifera ligustica). To help understand this process, we studied the effect of lineage (African, European, or hybrid) on the flight physiology of honeybee reproductives. Flight metabolic rates were higher in queens and drones of African lineage than in European or hybrid bees, as has been previously found for foraging workers. These differences were associated with higher thorax/body mass ratios and higher thorax‐specific metabolic rates in African lineage bees. Queens were reared in common colonies, so these metabolic and morphological differences are likely to be genetic in origin. African drones had higher wing beat frequencies and thorax temperatures than European or hybrid bees. Hybrids were intermediate for many parameters, but hybrid queen mass‐specific flight metabolic rates were low relative to Africans and were nonlinearly affected by the proportion of African lineage, consistent with some negative heterosis for this trait

Traumatic injury and exposure to mitochondrial-derived damage associated molecular patterns suppresses neutrophil extracellular trap formation

Major traumatic injury induces significant remodeling of the circulating neutrophil pool and loss of bactericidal function. Although a well-described phenomenon, research to date has only analyzed blood samples acquired post-hospital admission, and the mechanisms that initiate compromised neutrophil function post-injury are therefore poorly understood. Here, we analyzed pre-hospital blood samples acquired from 62 adult trauma patients (mean age 44 years, range 19–95 years) within 1 h of injury (mean time to sample 39 min, range 13–59 min). We found an immediate impairment in neutrophil extracellular trap (NET) generation in response to phorbol 12-myristate 13-acetate (PMA) stimulation, which persisted into the acute post-injury phase (4–72 h). Reduced NET generation was accompanied by reduced reactive oxygen species production, impaired activation of mitogen-activated protein kinases, and a reduction in neutrophil glucose uptake and metabolism to lactate. Pre-treating neutrophils from healthy subjects with mitochondrial-derived damage-associated molecular patterns (mtDAMPs), whose circulating levels were significantly increased in our trauma patients, reduced NET generation. This mtDAMP-induced impairment in NET formation was associated with an N-formyl peptide mediated activation of AMP-activated protein kinase (AMPK), a negative regulator of aerobic glycolysis and NET formation. Indeed, activation of AMPK via treatment with the AMP-mimetic AICAR significantly reduced neutrophil lactate production in response to PMA stimulation, a phenomenon that we also observed for neutrophils pre-treated with mtDAMPs. Furthermore, the impairment in NET generation induced by mtDAMPs was partially ameliorated by pre-treating neutrophils with the AMPK inhibitor compound C. Taken together, our data demonstrate an immediate trauma-induced impairment in neutrophil anti-microbial function and identify mtDAMP release as a potential initiator of acute post-injury neutrophil dysfunction.</p