Body structure and respiratory efficiency among high altitude Himalayan populations

To understand the morphological and physiological variations among the temporary and permanent residents of high altitude, this study was undertaken at Leh, Ladakh. It is situated at 3500 m (11500 feet) above sea level, the mean barometric pressure was 500 tors and air temperature varied from 2 degrees C to 20 degrees C. The highland Tibetans showed broadest chest and most developed musculature closely followed by Ladakhi Bods. These high altude natives also displayed significantly higher value of vital capacity, forced vital capacity, and inspiratory capacity. The better respiratory efficiency observed among high altitude residents indicates higher degree of adaptation to high altitude hypoxia. Temporary residents were observed to be tallest and fattest with lower trunk fat predominance of all the four groups and showed narrowest chest and lower respiratory efficiency as compared to high altitude natives. The duration of stay at high altitude has clearly brought about a perceptible difference in body dimensions and respiratory functions of various groups of adult males studied at same altitude.     

Carbon assimilation,nitrogen, and photochemical efficiency of different Himalayan tree species along an altitudinal gradient

In the area of Jumla region in Western Nepal, measurements of saturated leaf net photosynthetic rate (P_sat), nitrogen content, leaf fluorescence, carbon isotopic composition, and water status were performed on woody coniferous (Pinus wallichiana, Picea smithiana, Abies spectabilis, Juniperus wallichiana, Taxus baccata), evergreen (Quercus semecarpifolia, Rhododendron campanulatum), and deciduous broadleaved species (Betula utilis, Populus ciliata, Sorbus cuspidata) spreading from 2 400 m up to the treeline at 4 200 m a.s.l. With the exception of J. wallichiana, P_sat values were lower in coniferous than broadleaved species. Q. semecarpifolia, that in this area grows above the coniferous belt between 3 000 and 4 000 m, showed the highest P_sat at saturating irradiance and the highest leaf N content. This N content was higher and P_sat lower than those of evergreen oak species of tempe forests at middle and low altitudes. For all species, P_sat and N content were linearly correlated, but instantaneous nitrogen use efficiency was lower than values measured in lowland and temperate plant communities. The values of carbon isotopic composition, estimated by δ₁₃C, showed the same range reported for temperate tree species. The ranking of δ₁₃C values for the different tree types was conifers < evergreen broadleaved<deciduous, suggesting tighter stomatal closure and higher water use efficiency for the evergreen types, confirming trends found elsewhere. No relevant differences of δ₁₃C were found along the altitudinal gradient. Quantum yield of photochemistry at saturating irradiance, measured by leaf fluorescence (δF/F_m’), was highest in J. wallichiana and lowest in T. baccata. Overall, photochemical efficiency was more strongly related to species than to altitude. Interestingly, changes of .δF/F_m’ along the altitudinal gradient correlated well with the reported altitudinal distribution of the species.     

Carbon assimilation, nitrogen, and photochemical efficiency of different Himalayan tree species along an altitudinal gradient

In the area of Jumla region in Western Nepal, measurements of saturated leaf net photosynthetic rate (P_sat), nitrogen content, leaf fluorescence, carbon isotopic composition, and water status were performed on woody coniferous (Pinus wallichiana, Picea smithiana, Abies spectabilis, Juniperus wallichiana, Taxus baccata), evergreen (Quercus semecarpifolia, Rhododendron campanulatum), and deciduous broadleaved species (Betula utilis, Populus ciliata, Sorbus cuspidata) spreading from 2 400 m up to the treeline at 4 200 m a.s.l. With the exception of J. wallichiana, P_sat values were lower in coniferous than broadleaved species. Q. semecarpifolia, that in this area grows above the coniferous belt between 3 000 and 4 000 m, showed the highest P_sat at saturating irradiance and the highest leaf N content. This N content was higher and P_sat lower than those of evergreen oak species of tempe forests at middle and low altitudes. For all species, P_sat and N content were linearly correlated, but instantaneous nitrogen use efficiency was lower than values measured in lowland and temperate plant communities. The values of carbon isotopic composition, estimated by ₁₃C, showed the same range reported for temperate tree species. The ranking of ₁₃C values for the different tree types was conifers < evergreen broadleaved13C were found along the altitudinal gradient. Quantum yield of photochemistry at saturating irradiance, measured by leaf fluorescence (F/F_m), was highest in J. wallichiana and lowest in T. baccata. Overall, photochemical efficiency was more strongly related to species than to altitude. Interestingly, changes of .F/F_m along the altitudinal gradient correlated well with the reported altitudinal distribution of the species.This revised version was published online in March 2005 with corrections to the page numbers.     

Meeting nutrient requirements: the roles of power and efficiency

Conclusions We have attempted to illustrate the importance of nutrient transfer functions and their key quantitative parameters, power and efficiency. While this brief account has focused on one aspect of nutritional behaviour, the duration of intermeal intervals, the models are equally useful for understanding other components of feeding behaviour such as meal size and food switching. Like-wise, they provide a framework for formulating quantitative predictions about the dynamics of the physiological processes involved in digestion, absorption and the utilisation of food. These aspects are dealt with more fully elsewhere.     

Extended multipoint identity-by-descent analysis of human quantitative traits: efficiency, power, and modeling considerations.

Goldgar introduced a novel marker-based method for partitioning the variation of a quantitative trait into specific chromosomal regions. Unlike traditional linkage mapping methods, Goldgar's method does not require the estimation of statistical quantities characterizing each locus thought to influence the trait under scrutiny (e.g., allele frequencies, penetrances, etc.). Goldgar's method is thus more flexible and less model dependent than many traditional marker-based genetic analysis techniques. Unfortunately, however, many of the properties of Goldgar's method have not been investigated. In this paper, the utility of an extended version of Goldgar's approach is studied in settings in which sibships are taken as the sampling unit of interest. The extensions discussed resolve around the incorporation of a wider variety of effects and factors into Goldgar's basic model. Analytic studies pertaining to power, sample-size requirements, and estimation procedures for the proposed extended version of Goldgar's method are described. Hypothesis-testing strategies are also discussed. The results of the analytic studies indicate that, although an extended sib-pair version of Goldgar's variance-partitioning approach to modeling the chromosomal determinants of a quantitative trait will be useful only for traits with high heritabilities or when fine-scale genetic maps can be employed. Goldgar's technique as a whole has promise, as it can be made relatively robust statistically, refined through some simple and intuitive extensions, and can be easily adapted to work with more complex sampling units. Further extensions of Goldgar's methods are proposed, and areas in need of additional research are discussed.     

Myocardial ischemia and in vitro mitochondrial metabolic efficiency

The purpose of this study was to evaluate the oxidative capacities and the rate of energy synthesis in isolated mitochondria extracted from normal and post-ischemic myocardium. Isolated rat hearts were perfused according to the working mode with a Krebs Heinseleit buffer containing glucose (11 mM), insulin (10 IU/1) and caprylic acid (25 M). After a 15 min perfusion in normoxic conditions, the hearts were subjected to a 20 min local zero-flow ischemia followed by a 20 min reperfusion. During the perfusion, the aortic and coronary flows, the aortic pressure and the electrocardiogram were monitored. At the end of the reperfusion period, the non-ischemic and ischemic zones (NIZ and IZ, respectively) were separated and the mitochondria were harvested from each zone. The oxygen uptake and the rate of energy production of the NIZ and IZ mitochondria were then assessed with palmitoylcarnitine as substrate in 2 buffers differing in their free calcium concentration (0.041 and 0.150 M). Ischemia provoked a 50% reduction of coronary and aortic flows. The reperfusion of the IZ allowed the partial recovery of coronary flow, but the aortic flow decreased beneath its ischemic value because of the occurrence of severe arrhythmias, stunning and probably hibernation. The IZ mitochondria displayed a lower rate of oxygen consumption, whatever the buffer free calcium concentration. Conversely, their rate of energy production was increased, indicating that their metabolic efficiency was improved as compared to NIZ mitochondria. This might be due to the mitochondrial calcium overload persisting during reperfusion, to the activation of the inner membrane Na⁺/Ca²⁺ exchange and to a significant mitochondrial swelling. On the other hand, the presence of an elevated free calcium concentration in the respiration buffer provoked some energy wasting characterized by a constant AMP production. This was attributed to some accumulation of acetate and the activation of the energy-consuming acetylCoA synthetase. In conclusion, ischemia and reperfusion did not alter the membrane integrity of the mitochondria but improved their metabolic efficiency. Nevertheless, these in vitro results can not reflect the mitochondrial function in the reperfused myocardium. The mitochondrial calcium overload reported to last during reperfusion in the cardiomyocytes might mimic the free calcium-induced reduction of metabolic efficiency observed in vitro in the present study. The resulting energy wasting might be responsible for the contractile abnormalities noticed in the reperfused myocardium.     

Niche specialization of reef-building corals in the mesophotic zone: metabolic trade-offs between divergent Symbiodinium types

The photobiology of two reef corals and the distribution of associated symbiont types were investigated over a depth gradient of 0-60 m at Scott Reef, Western Australia. Pachyseris speciosa hosted mainly the same Symbiodinium C type similar to C3 irrespective of sampling depth. By contrast, Seriatopora hystrix hosted predominantly Symbiodinium type D1a or D1a-like at shallow depths while those in deeper water were dominated by a Symbiodinium C type closely related to C1. The photosynthesis/respiration (P/R) ratio increased consistently with depth at the two sampling times (November 2008 and April 2009) for P. speciosa and in November 2008 only for S. hystrix, suggesting a reduction in metabolic energy expended for every unit of energy obtained from photosynthesis. However, in April 2009, shallow colonies of S. hystrix exhibited decreased P/R ratios down to depths of approximately 23 m, below which the ratio increased towards the maximum depth sampled. This pattern was mirrored by changes in tissue biomass determined as total protein content. The depth of change in the direction of the P/R ratio correlated with a shift from Symbiodinium D to C-dominated colonies. We conclude that while photobiological flexibility is vital for persistence in contrasting light regimes, a shift in Symbiodinium type may also confer a functional advantage albeit at a metabolic cost with increased depth.     

Drosophila chemoreceptor gene evolution: selection, specialization and genome size

Chemoperception plays a key role in adaptation and speciation in animals, and the senses of olfaction and gustation are mediated by gene families which show large variation in repertoire size among species. In Drosophila, there are around 60 loci of each type and it is thought that ecological specialization influences repertoire size, with increased pseudogenization of loci. Here, we analyse the size of the gustatory and olfactory repertoires among the genomes of 12 species of Drosophila . We find that repertoire size varies substantially and the loci are evolving by duplication and pseudogenization, with striking examples of lineage-specific duplication. Selection analyses imply that the majority of loci are subject to purifying selection, but this is less strong in gustatory loci and in loci prone to duplication. In contrast to some other studies, we find that few loci show statistically significant evidence of positive selection. Overall genome size is strongly correlated with the proportion of duplicated chemoreceptor loci, but genome size, specialization and endemism may be interrelated in their influence on repertoire size.     

Age and hunting success in the brown pelican: influences of skill and patch choice on foraging efficiency

Summary Age-related differences in the foraging efficiency of piscivorous birds may be the results of differences in foraging skill, patch usage, or both. Brown pelicans were observed while foraging around a small Caribbean island. Areas where the birds fed were subdivided into small, homogeneous subunits (patches), and the bird's foraging success and patch use were noted and analyzed using multivariate techniques. Adult birds were found to be better at capturing prey under all conditions than were juveniles, but the differences were small in some patches. The density of prey and the birds' foraging success influenced the foraging efforts of adult and juvenile pelicans to similar degrees. Both age groups utilized local enhancement in their foraging, but such behavior augmented the foraging success only of juvenile birds. Both age groups often fed in patches where their foraging success was quite low. Such behaviour was much more costly for juvenile than for adult pelicans.     

Peroxisomal catalase in the methylotrophic yeast Candida boidinii: transport efficiency and metabolic significance

In this study we cloned CTA1, the gene encoding peroxisomal catalase, from the methylotrophic yeast Candida boidinii and studied targeting of the gene product, Cta1p, into peroxisomes by using green fluorescent protein (GFP) fusion proteins. A strain from which CTA1 was deleted (cta1Delta strain) showed marked growth inhibition when it was grown on the peroxisome-inducing carbon sources methanol, oleate, and D-alanine, indicating that peroxisomal catalase plays an important nonspecific role in peroxisomal metabolism. Cta1p carries a peroxisomal targeting signal type 1 (PTS1) motif, -NKF, in its carboxyl terminus. Using GFP fusion proteins, we found that (i) Cta1p is transported to peroxisomes via its PTS1 motif, -NKF; (ii) peroxisomal localization is necessary for Cta1p to function physiologically; and (iii) Cta1p is bimodally distributed between the cytosol and peroxisomes in methanol-grown cells but is localized exclusively in peroxisomes in oleate- and D-alanine-grown cells. In contrast, the fusion protein GFP-AKL (GFP fused to another typical PTS1 sequence, -AKL), in the context of CbPmp20 and D-amino acid oxidase, was found to localize exclusively in peroxisomes. A yeast two-hybrid system analysis suggested that the low transport efficiency of the -NKF sequence is due to a level of interaction between the -NKF sequence and the PTS1 receptor that is lower than the level of interaction with the AKL sequence. Furthermore, GFP-Cta1pDeltankf coexpressed with Cta1p was successfully localized in peroxisomes, suggesting that the oligomer was formed prior to peroxisome import and that it is not necessary for all four subunits to possess a PTS motif. Since the main physiological function of catalase is degradation of H2O2, suboptimal efficiency of catalase import may confer an evolutionary advantage. We suggest that the PTS1 sequence, which is found in peroxisomal catalases, has evolved in such a way as to give a higher priority for peroxisomal transport to peroxisomal enzymes other than to catalases (e.g., oxidases), which require a higher level of peroxisomal transport efficiency.     

From Caenorhabditis elegans to the human connectome: a specific modular organization increases metabolic,functional and developmental efficiency

The connectome, or the entire connectivity of a neural system represented by a network, ranges across various scales from synaptic connections between individual neurons to fibre tract connections between brain regions. Although the modularity they commonly show has been extensively studied, it is unclear whether the connection specificity of such networks can already be fully explained by the modularity alone. To answer this question, we study two networks, the neuronal network of Caenorhabditis elegans and the fibre tract network of human brains obtained through diffusion spectrum imaging. We compare them to their respective benchmark networks with varying modularities, which are generated by link swapping to have desired modularity values. We find several network properties that are specific to the neural networks and cannot be fully explained by the modularity alone. First, the clustering coefficient and the characteristic path length of both C. elegans and human connectomes are higher than those of the benchmark networks with similar modularity. High clustering coefficient indicates efficient local information distribution, and high characteristic path length suggests reduced global integration. Second, the total wiring length is smaller than for the alternative configurations with similar modularity. This is due to lower dispersion of connections, which means each neuron in the C. elegans connectome or each region of interest in the human connectome reaches fewer ganglia or cortical areas, respectively. Third, both neural networks show lower algorithmic entropy compared with the alternative arrangements. This implies that fewer genes are needed to encode for the organization of neural systems. While the first two findings show that the neural topologies are efficient in information processing, this suggests that they are also efficient from a developmental point of view. Together, these results show that neural systems are organized in such a way as to yield efficient features beyond those given by their modularity alone.     

Biomass, Productivity and Energetics in Himalayan Alder Plantations

Biomass, net primary production and energy fixation in an agesequence of Himalayan alder (Alnus nepalensis D. Don) plantationswere estimated in the Kalimpong forest division of the easternHimalayas. Biomass in the plantations ranged from 106 t ha^–1(7-year stand) to 606 t ha^–1 (56-year stand) demonstratingthe potential of the alder for accumulating large biomass. Netprimary production and net energy fixation rates of the plantationswere reduced by nearly half in the 7-year stand (25 t ha^–1year^–1; 421 x 10⁶ kJ ha^–1 year^–1) comparedwith the 56-year stand (13 t ha^–1 year^–1; 215 x10⁶ kJ ha^–1 year^–1). Compartmental models of energystorage and flow rates were developed for the 7-year and 56-yearstands. The production efficiency, energy conversion efficiencyand energy efficiency in N₂ fixation have inverse relationshipswith plantation age. These efficiencies, when treated with eachother, showed significant exponential functions. Alnus nepalensis D. Don, Himalayan alder, plantation age, biomass, net primary production, energy flow, efficiencies     

Escape from extreme specialization: passionflowers,bats and the sword-billed hummingbird

A striking example of plant/pollinator trait matching is found between Andean species of Passiflora with 6–14-cm-long nectar tubes and the sword-billed hummingbird, Ensifera ensifera, with up to 11-cm-long bills. Because of the position of their anthers and stigmas, and self-incompatibility, these passionflower species depend on E. ensifera for pollination. Field observations show that the bird and plant distribution match completely and that scarcity of Ensifera results in reduced passionflower seed set. We here use nuclear and plastid DNA sequences to investigate how often and when these mutualisms evolved and under which conditions, if ever, they were lost. The phylogeny includes 26 (70%) of the 37 extremely long-tubed species, 13 (68%) of the 19 species with tubes too short for Ensifera and four of the seven bat-pollinated species for a total of 43 (69%) of all species in Passiflora supersection Tacsonia (plus 11 outgroups). We time-calibrated the phylogeny to infer the speed of any pollinator switching. Results show that Tacsonia is monophyletic and that its stem group dates to 10.7 Ma, matching the divergence at 11.6 Ma of E. ensifera from its short-billed sister species. Whether pollination by short-billed hummingbirds or by Ensifera is the ancestral condition cannot be securely inferred, but extremely long-tubed flowers exclusively pollinated by Ensifera evolved early during the radiation of the Tacsonia clade. There is also evidence of several losses of Ensifera dependence, involving shifts to bat pollination and shorter billed birds. Besides being extremely asymmetric—a single bird species coevolving with a speciose plant clade—the Ensifera/Passiflora system is a prime example of a specialized pollinator not driving plant speciation, but instead being the precondition for the maintenance of isolated populations (through reliable seed set) that then underwent allopatric speciation.     

Phylogeny, specialization, and brood parasite--host coevolution: some possible pitfalls of parsimony

Coevolutionary hypotheses (COEV) predict that parasitic birdsbecome more specialized in host selection over time as morehost species evolve defenses. A contrasting model, PHYLO, suggeststhat brood parasites exhibit a phylogenetic trajectory towardincreasing generalization because there is a positive correlationbetween present-day numbers of host species and the branchingorder of parasitic cowbird species in a DNA-based phylogeny. However, this apparent phylogenetic pattern does not conflictwith COEV, as some have concluded. Assuming allopatric speciation,which is supported by an area cladogram, COEV predicts a correlationbetween branching order and host number because the potentialhosts of the earliest cowbirds to branch off have had the greatestamount of time to evolve defenses. Although PHYLO is more parsimoniousthan COEV, the difference is trivial, with the latter requiring only one more evolutionary change in the entire cowbird cladeto produce the pattern that exists today. Support for COEVover PHYLO comes from brood parasitic cuckoos, which are muchmore specialized than parasitic cowbirds and represent an olderclade, as shown by new DNA data. Cuckoos also have lower interspecificvariance in host numbers than do cowbirds, which conflicts with PHYLO. Unlike COEV, which assumes that the number of hosts aparasite uses is related at least as much to present ecologicalconditions as to phylogenetic history, PHYLO assumes that currenthost numbers reflect historical character states. However,host number is labile, with as much variation within as betweenspecies. Nor are published host numbers reliable measures ofparasite host selectivity, as they are due in part to researchereffort and range size. Although the comparative approach canprovide insights into evolutionary history, some coevolvedfeatures may be too dynamic to retain a phylogenetic signature,and, in the case of parasitic birds, neither PHYLO nor COEVcan be invalidated, although the latter is more consistentwith available evidence. Strict adherence to parsimony mayoften be inappropriate when assessing coevolved characters.     

Effects of strength, endurance, and concurrent training on aerobic power and dynamic neuromuscular economy in elderly men

The aim of this study was to investigate the effects of concurrent training on endurance capacity and dynamic neuromuscular economy in elderly men. Twenty-three healthy men (65 ± 4 years) were divided into 3 groups: concurrent (CG, n = 8), strength (SG, n = 8), and aerobic training group (EG, n = 7). Each group trained 3 times a week for 12 weeks, strength training, aerobic training, or both types of training in the same session. The maximum aerobic workload (Wmax) and peak oxygen uptake (VO2peak) of the subjects were evaluated on a cycle ergometer before and after the training period. Moreover, during the maximal test, muscle activation was measured at each intensity by means of electromyographic signals from the vastus lateralis (VL), rectus femoris (RF), biceps femoris long head, and gastrocnemius lateralis to determine the dynamic neuromuscular economy. After training, significant increases in VO2peak and Wmax were only found in the CG and EG (p < 0.05), with no difference between groups. Moreover, there was a significant decrease in myoelectric activity of the RF muscle at 50 (EG), 75 and 100 W (EG and CG) and in the VL for the 3 groups at 100 W (p < 0.05). No change was seen in the electrical signal from the lateral gastrocnemius muscle and biceps femoris. The results suggest specificity in adaptations investigated in elderly subjects, because the most marked changes in the neuromuscular economy occurred in the aerobically trained groups.