41 research outputs found
Global patterns of seasonal acclimatization in avian resting metabolic rates
The adjustment of resting metabolic rates represents an important component of avian
seasonal acclimatization, with recent studies revealing substantial differences between
summer and winter in birds from a wide range of latitudes. We compared seasonal
variation in basal metabolic rate (BMR) and summit metabolism (Msum) between
temperate and tropical/subtropical latitudes, and examined correlations with latitude
and temperature. The direction and magnitude of seasonal adjustments in BMR are
broadly related to temperature and latitude, but are significantly more variable among
tropical and subtropical species compared to those inhabiting temperate zones. Winter
adjustments in BMR among subtropical species, when expressed relative to summer values, range from decreases of approximately 35 % to increases of more than 60 %,
whereas the majority of temperate-zone species show increases in BMR during
winter. Relatively few seasonal Msum data exist for tropical/subtropical species, but
those that are available involve responses ranging from winter decreases to increases
of similar magnitude to those characteristic of many temperate-zone species. Recent
studies also highlight the substantial variation in seasonal adjustments that may occur
within species, and reiterate the need for further investigations of the relative roles of
environmental variables such as temperature and food availability as determinants of
seasonal metabolic variation.http://link.springer.com/journal/103362016-12-30hb201
Seasonal metabolic acclimatization varies in direction and magnitude among populations of an afrotropical Passerine bird
Avian metabolic responses demonstrate considerable diversity
under fluctuating environmental conditions, a well-studied example
being the seasonal upregulation of basal metabolic rate
(BMR) and summit metabolism (Msum) in temperate species experiencing
harsh winters. Fewer studies have examined seasonal
metabolic acclimatization in subtropical or tropical species. We
investigated seasonal metabolic variation in an Afrotropical ploceid
passerine, the white-browed sparrow-weaver (Plocepasser
mahali; ∼47 g), at three sites along a climatic gradient of approximately
77C in winter minimum air temperature (Ta). We
measured Msum (n ≥ 10 per site per season) in a helox atmosphere,
BMR of the same birds at thermoneutrality (Ta ≈ 307C), and
resting metabolic rates at 57C ≤ Ta ≤ 207C. Patterns of seasonal
adjustments in BMR varied among populations in a manner not
solely related to variation in seasonal Ta extremes, ranging from
BMR ∼52% higher in winter than in summer to no seasonal difference.
Greater cold tolerance was found in a population at a
colder desert site, manifested as higher Msum (∼25% higher) and
lower helox temperature at cold limit values compared with a
milder, mesic site. Our results lend support to the idea that greater
variance in the pattern of seasonal metabolic responses occurs in
subtropical and tropical species compared with their temperatezone
counterparts and that factors other than Ta extremes (e.g.,
food availability) maybe important in determining the magnitude
and direction of seasonal metabolic adjustments in subtropical
birds.The DST-NRF Centre of Excellence at the Percy FitzPatrick Institute and the University of Pretoria.http://www.press.uchicago.edu/ucp/journals/journal/pbz.html2018-03-31am2017Visual Art
Thermoregulation in African green pigeons (Treron calvus) and a re-analysis of insular effects on basal metabolic rate and heterothermy in columbid birds
Columbid birds represent a useful model taxon for examining adaptation in metabolic and
thermal traits, including the effects of insularity. To test predictions concerning the role of
insularity and low predation risk as factors selecting for the use of torpor, and the evolution of
low basal metabolic rate in island species, we examined thermoregulation under laboratory and
semi-natural conditions in a mainland species, the African Green-Pigeon (Treron calvus). Under
laboratory conditions, rest-phase body temperature (Tb) was significantly and positively
correlated with air temperature (Ta) between 0 °C and 35 °C, and the relationship between resting metabolic rate (RMR) and Ta differed from typical endothermic patterns. The minimum
RMR, which we interpret as basal metabolic rate (BMR), was 0.825 ± 0.090 W. Green-pigeons
responded to food restriction by significantly decreasing rest-phase Tb, but the reductions were
small (at most ~ 5 °C below normothermic values), with a minimum Tb of 33.1 °C recorded in a
food-deprived bird. We found no evidence of the large reductions in Tb and metabolic rate and
the lethargic state characteristic of torpor. The absence of torpor in T. calvus lends support to the
idea that species restricted to islands that are free of predators are more likely to use torpor than
mainland species that face the risk of predation during the rest-phase. We also analysed
interspecific variation in columbid BMR in a phylogenetically-informed framework, and verified
the conclusions of an earlier study that found that BMR is significantly lower in island species
compared to those that occur on mainlands.DST/NRF Centre of Excellence at the Percy FitzPatrick Institute, the University of Pretoria, and the National Science Foundation, USA (IOS-1122228).http://www.springer.com/life+sci/biochemistry/journal/360hb2013ab201
Alterations in hypoglossal motor neurons due to GAD67 and VGAT deficiency in mice
There is an emerging body of evidence that glycinergic and GABAergic synaptic inputs onto motor neurons (MNs) help regulate the final number of MNs and axonal muscle innervation patterns. Using mutant glutamate decarboxylase 67 (GAD67) and vesicular inhibitory amino acid transporter (VGAT) deficient mice, we describe the effect that deficiencies of presynaptic GABAergic and/or glycinergic release have on the post-synaptic somato-dendritic structure of motor neurons, and the development of excitatory and inhibitory synaptic inputs to MNs. We use whole-cell patch clamp recording of synaptic currents in E18.5 hypoglossal MNs from brainstem slices, combined with dye-filling of these recorded cells with Neurobiotin™, high-resolution confocal imaging and 3-dimensional reconstructions. Hypoglossal MNs from GAD67- and VGAT-deficient mice display decreased inhibitory neurotransmission and increased excitatory synaptic inputs. These changes are associated with increased dendritic arbor length, increased complexity of dendritic branching, and increased density of spiny processes. Our results show that presynaptic release of inhibitory amino acid neurotransmitters are potent regulators of hypoglossal MN morphology and key regulators of synaptic inputs during this critical developmental time point
Avian thermoregulation in the heat : evaporative cooling capacity in an archetypal desert specialist, Burchell's sandgrouse (Pterocles burchelli)
Sandgrouse (Pterocliformes) are quintessential examples of avian adaptation to desert
environments, but relatively little is known about the limits to their heat tolerance and
evaporative cooling capacity. We predicted that evaporative cooling in Burchell’s
sandgrouse (Pterocles burchelli) is highly efficient and provides the basis for
tolerance of very high air temperature (Ta). We measured body temperature (Tb),
resting metabolic rate (RMR) and evaporative water loss (EWL) at Ta between 25 °C
and ~58 °C in birds exposed to successive increments in Ta. Normothermic Tb
averaged 39.0 °C, lower than typical avian values. At Ta > 34.5 °C, Tb increased
linearly to a maximum of 43.6 °C at Ta = 56 °C. The upper critical limit of
thermoneutrality (Tuc) was Ta = 43.8 °C, closely coinciding with the onset of panting
and gular flutter. Above the Tuc, RMR increased 2.5-fold to 2.89 W at Ta = 56 °C, a
fractional increase far exceeding that of many other species under comparable
conditions. Rates of EWL increased rapidly at Ta > 42.9 °C to 7.84 ± 0.90 g h-1 at Ta =
56 °C, an 11-fold increase above minimal levels. Maximum evaporative cooling
efficiency (ratio of evaporative heat loss to metabolic heat production) was 2.03, but
could be as high as 2.70 if our assumption that the birds were metabolising lipids is
incorrect. Thermoregulation at very high Ta in P. burchelli was characterised by large
increases in RMR and EWL, and is much less efficient than in taxa such as columbids
and caprimulgids.National Science Foundation under IOS-1122228.http://jeb.biologists.org2017-07-31hb2016Zoology and Entomolog
Health promotion programs related to the Athens 2004 Olympic and Para Olympic games
BACKGROUND: The Olympic Games constitute a first-class opportunity to promote athleticism and health messages. Little is known, however on the impact of Olympic Games on the development of health-promotion programs for the general population. Our objective was to identify and describe the population-based health-promotion programs implemented in relation to the Athens 2004 Olympic and Para Olympic Games. METHODS: A cross-sectional survey of all stakeholders of the Games, including the Athens 2004 Organizing Committee, all ministries of the Greek government, the National School of Public Health, all municipalities hosting Olympic events and all official private sponsors of the Games, was conducted after the conclusion of the Games. RESULTS: A total of 44 agencies were surveyed, 40 responded (91%), and ten (10) health-promotion programs were identified. Two programs were implemented by the Athens 2004 Organizing Committee, 2 from the Greek ministries, 2 from the National School of Public Health, 1 from municipalities, and 3 from official private sponsors of the Games. The total cost of the programs was estimated at 943,000 Euros; a relatively small fraction (0.08%) of the overall cost of the Games. CONCLUSION: Greece has made a small, however, significant step forward, on health promotion, in the context of the Olympic Games. The International Olympic Committee and the future hosting countries, including China, are encouraged to elaborate on this idea and offer the world a promising future for public health
Lowe Syndrome Protein OCRL1 Supports Maturation of Polarized Epithelial Cells
Mutations in the inositol polyphosphate 5-phosphatase OCRL1 cause Lowe Syndrome, leading to cataracts, mental retardation and renal failure. We noted that cell types affected in Lowe Syndrome are highly polarized, and therefore we studied OCRL1 in epithelial cells as they mature from isolated individual cells into polarized sheets and cysts with extensive communication between neighbouring cells. We show that a proportion of OCRL1 targets intercellular junctions at the early stages of their formation, co-localizing both with adherens junctional components and with tight junctional components. Correlating with this distribution, OCRL1 forms complexes with junctional components α-catenin and zonula occludens (ZO)-1/2/3. Depletion of OCRL1 in epithelial cells growing as a sheet inhibits maturation; cells remain flat, fail to polarize apical markers and also show reduced proliferation. The effect on shape is reverted by re-expressed OCRL1 and requires the 5′-phosphatase domain, indicating that down-regulation of 5-phosphorylated inositides is necessary for epithelial development. The effect of OCRL1 in epithelial maturation is seen more strongly in 3-dimensional cultures, where epithelial cells lacking OCRL1 not only fail to form a central lumen, but also do not have the correct intracellular distribution of ZO-1, suggesting that OCRL1 functions early in the maturation of intercellular junctions when cells grow as cysts. A role of OCRL1 in junctions of polarized cells may explain the pattern of organs affected in Lowe Syndrome
Enhancement of a modified Mediterranean-style, low glycemic load diet with specific phytochemicals improves cardiometabolic risk factors in subjects with metabolic syndrome and hypercholesterolemia in a randomized trial
<p>Abstract</p> <p>Background</p> <p>As the worldwide dietary pattern becomes more westernized, the metabolic syndrome is reaching epidemic proportions. Lifestyle modifications including diet and exercise are recommended as first-line intervention for treating metabolic syndrome. Previously, we reported that a modified Mediterranean-style, low glycemic load diet with soy protein and phytosterols had a more favorable impact than the American Heart Association Step 1 diet on cardiovascular disease (CVD) risk factors. Subsequently, we screened for phytochemicals with a history of safe use that were capable of increasing insulin sensitivity through modulation of protein kinases, and identified hops <it>rho </it>iso-alpha acid and acacia proanthocyanidins. The objective of this study was to investigate whether enhancement of a modified Mediterranean-style, low glycemic load diet (MED) with specific phytochemicals (soy protein, phytosterols, <it>rho </it>iso-alpha acids and proanthocyanidins; PED) could improve cardiometabolic risk factors in subjects with metabolic syndrome and hypercholesterolemia.</p> <p>Methods</p> <p>Forty-nine subjects with metabolic syndrome and hypercholesterolemia, aged 25–80, entered a randomized, 2-arm, 12-week intervention trial; 23 randomized to the MED arm; 26 to the PED arm. Forty-four subjects completed at least 8 weeks [MED (<it>n </it>= 19); PED (<it>n </it>= 25)]. All subjects were instructed to follow the same aerobic exercise program. Three-day diet diaries and 7-day exercise diaries were assessed at each visit. Fasting blood samples were collected at baseline, 8 and 12 weeks for analysis.</p> <p>Results</p> <p>Both arms experienced equal weight loss (MED: -5.7 kg; PED: -5.9 kg). However, at 12 weeks, the PED arm experienced greater reductions (<it>P </it>< 0.05) in cholesterol, non-HDL cholesterol, triglycerides (TG), cholesterol/HDL and TG/HDL compared with the MED arm. Only the PED arm experienced increased HDL (<it>P </it>< 0.05) and decreased TG/HDL (<it>P </it>< 0.01), and continued reduction in apo B/apo A-I from 8 to 12 weeks. Furthermore, 43% of PED subjects vs. only 22% of MED subjects had net resolution of metabolic syndrome. The Framingham 10-year CVD risk score decreased by 5.6% in the PED arm (<it>P </it>< 0.01) and 2.9% in the MED arm (<it>P </it>< 0.05).</p> <p>Conclusion</p> <p>These results demonstrate that specific phytochemical supplementation increased the effectiveness of the modified Mediterranean-style low glycemic load dietary program on variables associated with metabolic syndrome and CVD.</p