Rate In Mammals Research Articles

Correction to 'Starvation effects on nitrogen and carbon stable isotopes of animals: an insight from meta-analysis of fasting experiments'.

[This corrects the article DOI: 10.1098/rsos.170633.].

Molecular Population Genetics of the Northern Elephant Seal Mirounga angustirostris.

The northern elephant seal, Mirounga angustirostris, was heavily hunted and declared extinct in the 19th century. However, a colony remained on remote Guadalupe Island, Mexico and the species has since repopulated most of its historical distribution. Here, we present a comprehensive evaluation of genetic variation in the species. First, we assess the effect of the demographic bottleneck on microsatellite variability and compare it with that found in other pinnipeds, demonstrating levels of variation similar to that in species that continue to be threatened with extinction. Next, we use sequence data from these markers to demonstrate that some of the limited polymorphism predates the bottleneck. However, most contemporary variation appears to have arisen recently and persisted due to exponential growth. We also describe how we use the range in allele size of microsatellites to estimate ancestral effective population size before the bottleneck, demonstrating a large reduction in effective size. We then employ a classical method for bacteria to estimate the microsatellite mutation rate in the species, deriving an estimate that is extremely similar to that estimated for a similar set of loci in humans, indicating consistency of microsatellite mutation rates in mammals. Finally, we find slight significant structure between some geographically separated colonies, although its biological significance is unclear. This work demonstrates that genetic analysis can be useful for evaluating the population biology of the northern elephant seal, in spite of the bottleneck that removed most genetic variation from the species.

A comparative study on karyotypic diversification rate in mammals.

Chromosomal rearrangements have a relevant role in organismic evolution. However, little is known about the mechanisms that lead different phylogenetic clades to have different chromosomal rearrangement rates. Here, we investigate the causes behind the wide karyotypic diversity exhibited by mammals. In particular, we analyzed the role of metabolic, reproductive, biogeographic and genomic characteristics on the rates of macro- and microstructural karyotypic diversification (rKD) using comparative phylogenetic methods. We found evidence that reproductive characteristics such as larger litter size per year and longevity, by allowing a higher number of meioses in absolute time, favor a higher probability of chromosomal change. Furthermore, families with large geographic distributions but containing species with restricted geographic ranges showed a greater probability of fixation of macrostructural chromosomal changes in different geographic areas. Finally, rKD does not evolve by Brownian motion because the mutation rate depends on the concerted evolution of repetitive sequences. The decisive factors of rKD evolution will be natural selection, genetic drift and meiotic drive that will eventually allow or not the fixation of the rearrangements. Our results indicate that mammalian karyotypic diversity is influenced by historical and adaptive mechanisms where reproductive and genomic factors modulate the rate of chromosomal change.

The Influence of Interspecies Somatic Cell Nuclear Transfer on Epigenetic Enzymes Transcription in Early Embryos

Abstract One of the main reason for the incorrect development of embryos derived from somatic cell nuclear transfer is caused by insufficient demethylation of injected somatic chromatin to a state comparable with an early embryonic nucleus. It is already known that the epigenetic enzymes transcription in oocytes and early embryos of several species including bovine and porcine zygotes is species-dependent process and the incomplete DNA methylation correlates with the nuclear transfer failure rate in mammals. In this study the transcription of DNA methyltransferase 1 and 3a (DNMT1, DNMT3a) genes in early embryonic stages of interspecies (bovine, porcine) nuclear transfer embryos (iSCNT) by RT-PCR were analyzed. Coming out from the diverse timing of embryonic genome activation (EGA) in porcine and bovine preimplantation embryos, the intense effect of ooplasm on transferred somatic cell nucleus was expected. In spite of the detection of ooplasmic DNA methyltransferases, the somatic genes for DNMT1 and DNMT3a enzymes were not expressed and the development of intergeneric embryos stopped at the 4-cell stage. Our results indicate that the epigenetic reprogramming during early mammalian development is strongly influenced by the ooplasmic environment.

The Epidemiological Study of Infectious Diseases in North-East of Iran

Background: Despite recent pharmaceutical advancements in the production of new antibiotics, antibiotic resistance is increasing at an alarming rate in mammals; given the high prevalence of infectious diseases. Objectives: The current study aimed to determine the epidemiology of different infections in patients admitted to the infectious disease ward of Imam Reza hospital in Mashhad, North-East of Iran. Methods: This cross-sectional study was conducted on 1681 patients referred to Imam Reza hospital of Mashhad during 2006 - 2008. Prepared checklists were used to collect the required data, including age, gender, employment status, place of residence, length of hospitalization and season of admission in patients diagnosed with infectious diseases. Results: In the current study, prevalence of tuberculosis, septicemia, skin and soft tissue infections, urinary tract infections (UTIs), febrile neutropenia, myocarditis, and gastrointestinal infections were estimated at 8.4%, 8.3%, 7.1%, 5.4%, 4.9%, 3.9%, and 3.8%, respectively. Also, major respiratory infections were reported in 5.8% of the studied patients. Among the female patients in the study, 20.9% and 10.56% were diagnosed with pneumonia and tuberculosis, respectively. As for the male patients, 16.1%, 10.7%, and 7.1% were diagnosed with pneumonia, nervous system infections and tuberculosis, respectively. Conclusions: According to the results of the study, the most common causes of hospital admission were respiratory infections (e.g. pneumonia), nervous system infections, tuberculosis, septicemia, skin and soft tissue infections and UTIs. Considering the diversity of infections, epidemiological evaluation of these diseases is essential, especially in regions with high prevalence of infectious diseases. Furthermore, etiological diagnosis is considered imperative for clinicians before initiating therapy in patients with infectious diseases.

Cross-protective potential of anti-nucleoprotein human monoclonal antibodies against lethal influenza A virus infection.

The nucleoprotein (NP) possesses regions that are highly conserved among influenza A viruses, and has therefore been one of the target viral proteins for development of a universal influenza vaccine. It has been expected that human or humanized antibodies will be made available for the prophylaxis, pre-emptive and acute treatment of viral infection. However, it is still unclear whether anti-NP human antibody can confer protection against influenza virus infection. In this study, we generated transgenic mice expressing anti-NP human mAbs derived from lymphocytes of a patient infected with H5N1 highly pathogenic avian influenza (HPAI) virus, and experimental infections were conducted to examine antiviral effects of the anti-NP antibodies against H5N1 HPAI viral infections with a high fatality rate in mammals. Transgenic mouse lines expressing the anti-NP human mAbs at more than 1 mg ml-1 showed marked resistance to H5N1 virus infections. In addition, resistance to infection with an H1N1 subtype that shows strong pathogenicity to mice was also confirmed. Although the anti-NP mAbs expressed in the transgenic mice did not neutralize the virus, the mAbs could bind to NP located on the surface of infected cells. These results suggested a possibility that the non-neutralizing anti-NP human mAbs could induce indirect antiviral effects, such as antibody-dependent cellular cytotoxicity or complement-dependent cytotoxicity. Taken together, these results demonstrated that anti-NP human mAbs play an important role in heterosubtypic protection against lethal influenza virus infections in vivo.

Energy and time determine scaling in biological and computer designs.

Metabolic rate in animals and power consumption in computers are analogous quantities that scale similarly with size. We analyse vascular systems of mammals and on-chip networks of microprocessors, where natural selection and human engineering, respectively, have produced systems that minimize both energy dissipation and delivery times. Using a simple network model that simultaneously minimizes energy and time, our analysis explains empirically observed trends in the scaling of metabolic rate in mammals and power consumption and performance in microprocessors across several orders of magnitude in size. Just as the evolutionary transitions from unicellular to multicellular animals in biology are associated with shifts in metabolic scaling, our model suggests that the scaling of power and performance will change as computer designs transition to decentralized multi-core and distributed cyber-physical systems. More generally, a single energy-time minimization principle may govern the design of many complex systems that process energy, materials and information.This article is part of the themed issue 'The major synthetic evolutionary transitions'.

Inferring the determinants of protein evolutionary rates in mammals

Understanding the determinants of protein evolutionary rates is one of the most fundamental evolutionary questions. Previous studies have revealed that many biological variables are tightly associated with protein evolutionary rates in mammals. However, the dominant role of these biological variables and their combinatorial effects to evolutionary rates of mammalian proteins are still less understood. In this work, we derived a quantitative model to correlate protein evolutionary rates with the levels of these variables. The result showed that only a small number of variables are necessary to accurately predict protein evolutionary rates, among which miRNA regulation plays the most important role. Our result suggested that biological variables are extensively interrelated and suffer from hidden redundancies in determining protein evolutionary rates. Various variables should be considered in a natural ensemble to comprehensively assess the determinants of protein evolutionary rate.

Silicon-based plant defences, tooth wear and voles.

Plant-herbivore interactions are hypothesized to drive vole population cycles through the grazing-induced production of phytoliths in leaves. Phytoliths act as mechanical defences because they deter herbivory and lower growth rates in mammals. However, how phytoliths impair herbivore performance is still unknown. Here, we tested whether the amount of phytoliths changes tooth wear patterns. If confirmed, abrasion from phytoliths could play a role in population crashes. We applied dental microwear texture analysis (DMTA) to laboratory and wild voles. Lab voles were fed two pelleted diets with differing amounts of silicon, which produced similar dental textures. This was most probably due to the loss of food mechanical properties through pelletization and/or the small difference in silicon concentration between diets. Wild voles were trapped in Poland during spring and summer, and every year across a population cycle. In spring, voles feed on silica-rich monocotyledons, while in the summer they also include silica-depleted dicotyledons. This was reflected in the results; the amount of silica therefore leaves a traceable record in the dental microwear texture of voles. Furthermore, voles from different phases of population cycles have different microwear textures. We tentatively propose that these differences result from grazing-induced phytolith concentrations. We hypothesize that the high amount of phytoliths in response to intense grazing in peak years may result in malocclusion and other dental abnormalities, which would explain how these silicon-based plant defences help provoke population crashes. DMTA could then be used to reconstruct vole population dynamics using teeth from pellets or palaeontological material.

Life history effects on the molecular clock of autosomes and sex chromosomes

One of the foundational results in molecular evolution is that the rate at which neutral substitutions accumulate on a lineage equals the rate at which mutations arise. Traits that affect rates of mutation therefore also affect the phylogenetic "molecular clock." We consider the effects of sex-specific generation times and mutation rates in species with two sexes. In particular, we focus on the effects that the age of onset of male puberty and rates of spermatogenesis have likely had in hominids (great apes), considering a model that approximates features of the mutational process in mammals, birds, and some other vertebrates. As we show, this model can account for a number of seemingly disparate observations: notably, the puzzlingly low X-to-autosome ratios of substitution rates in humans and chimpanzees and differences in rates of autosomal substitutions among hominine lineages (i.e., humans, chimpanzees, and gorillas). The model further suggests how to translate pedigree-based estimates of human mutation rates into split times among extant hominoids (apes), given sex-specific life histories. In so doing, it largely bridges the gap reported between estimates of split times based on fossil and molecular evidence, in particular suggesting that the human-chimpanzee split may have occurred as recently as 6.6 Mya. The model also implies that the "generation time effect" should be stronger in short-lived species, explaining why the generation time has a major influence on yearly substitution rates in mammals but only a subtle one in human pedigrees.

A protocol to correct for intra- and interspecific variation in tail hair growth to align isotope signatures of segmentally cut tail hair to a common time line.

RationaleIn recent years, segmental stable isotope analysis of hair has been a focus of research in animal dietary ecology and migration. To correctly assign tail hair segments to seasons or even Julian dates, information on tail hair growth rates is a key parameter, but is lacking for most species.MethodsWe (a) reviewed the literature on tail hair growth rates in mammals; b) made own measurements of three captive equid species; (c) measured δ2H, δ13C and δ15N values in sequentially cut tail hairs of three sympatric, free-ranging equids from the Mongolian Gobi, using isotope ratio mass spectrometry (IRMS); and (d) collected environmental background data on seasonal variation by measuring δ2H values in precipitation by IRMS and by compiling pasture productivity measured by remote sensing via the normalized difference vegetation index (NDVI).ResultsTail hair growth rates showed significant inter- and intra-specific variation making temporal alignment problematic. In the Mongolian Gobi, high seasonal variation of δ2H values in precipitation results in winter lows and summer highs of δ2H values of available water sources. In water-dependent equids, this seasonality is reflected in the isotope signatures of sequentially cut tails hairs.ConclusionsIn regions which are subject to strong seasonal patterns we suggest identifying key isotopes which show strong seasonal variation in the environment and can be expected to be reflected in the animal tissue. The known interval between the maxima and minima of these isotope values can then be used to correctly temporally align the segmental stable isotope signature for each individual animal. © 2015 The Authors. Rapid Communications in Mass Spectrometry published by John Wiley & Sons Ltd.

Correlates of genetic monogamy in socially monogamous mammals: insights from Azara's owl monkeys

Understanding the evolution of mating systems, a central topic in evolutionary biology for more than 50 years, requires examining the genetic consequences of mating and the relationships between social systems and mating systems. Among pair-living mammals, where genetic monogamy is extremely rare, the extent of extra-group paternity rates has been associated with male participation in infant care, strength of the pair bond and length of the breeding season. This study evaluated the relationship between two of those factors and the genetic mating system of socially monogamous mammals, testing predictions that male care and strength of pair bond would be negatively correlated with rates of extra-pair paternity (EPP). Autosomal microsatellite analyses provide evidence for genetic monogamy in a pair-living primate with bi-parental care, the Azara's owl monkey (Aotus azarae). A phylogenetically corrected generalized least square analysis was used to relate male care and strength of the pair bond to their genetic mating system (i.e. proportions of EPP) in 15 socially monogamous mammalian species. The intensity of male care was correlated with EPP rates in mammals, while strength of pair bond failed to reach statistical significance. Our analyses show that, once social monogamy has evolved, paternal care, and potentially also close bonds, may facilitate the evolution of genetic monogamy.

Expression of receptors for BMP15 is differentially regulated in dominant and subordinate follicles during follicle deviation in cattle

Bone morphogenetic proteins are known to be involved in determining ovulation rate in mammals. The mechanisms through which these proteins determine follicle fate are incompletely understood. In the present study, we used cattle as a model to evaluate the regulation of BMP15 and GDF9 receptors in granulosa cells during dominant follicle (DF) selection. Before follicular deviation (day 2 of the follicular wave), BMPR2 mRNA abundance tended to be higher in the second largest follicles (F2; P<0.1) compared to the future dominant follicle (F1). At the expected time of follicular deviation (day 3), BMPR2 and BMPR1B mRNA levels were higher in subordinate follicles (SFs; P<0.05) compared to dominant follicles (DFs). After deviation (on day 4), BMPR1B mRNA and protein were significantly more abundant in atretic SFs (as assessed by cleaved caspase 3) than in DFs. The fact that BMPR1B is more expressed in atretic follicles was further confirmed by using intrafollicular treatment with two agents known to induce atresia, namely an estradiol receptor antagonist (fulvestrant) and FGF10. In conclusion, the fact that BMPR-1B and -2 are more expressed in the second largest follicles before and at the expected time of follicular deviation is indicative of their inhibitory role in follicle differentiation and steroidogenesis. BMPR1B also seems to have a pivotal role during follicle regression since it is upregulated in advanced atretic follicles.

Energy requirements and metabolism of the Phillip's dikdik (Madoqua saltiana phillipsi)

Basal metabolic rates in mammals are mainly determined by body mass, but also by ecological factors. Some mammalian species inhabiting hot, dry environments were found to have lower metabolic rates compared to temperate species. We studied energy metabolism in Phillip's dikdik (Madoqua saltiana phillipsi), a small antelope inhabiting xeric shrubland habitats in the Eastern ‘horn’ of Africa, and compared results to literature data. We measured body mass (BM) changes and digestibility in 12 adults kept on different food intake levels to determine, by extrapolation to zero BM change, maintenance energy requirements (MEm) for metabolizable energy (ME). The MEm averaged at 404±20kJMEkgBM−0.75d−1. In addition we conducted 24h-chamber respirometry with seven fed (non-fasted) individuals. Their mean metabolic rate as calculated from oxygen consumption was 403±51kJkgBM−0.75d−1, corroborating the results of the feeding experiments. Selecting the 20 lowest values of the respiration measurement period to estimate resting metabolic rate (RMR) resulted in a mean RMR of 244±39kJkgBM−0.75d−1, which was not significantly lower than the expected basal metabolic rate of 293kJkgBM−0.75d−1. Therefore, resting metabolism was similar to the expected average basal metabolism of a mammal of this size, which suggests a comparatively low metabolic rate in dikdiks. Compared to literature data Phillip's dikdiks have a MEm similar to measurements reported for small domestic ruminants, but considerably lower than those reported for other wild ruminant species inhabiting temperate and cold climates.

Polyandry Has No Detectable Mortality Cost in Female Mammals

In several taxonomic groups, females mate with several males during a single reproductive cycle. Although there is evidence that polyandry provides some benefits to females, it often involves mortality costs. However, empirical evidences of mortality costs of polyandry have so far been reported only in invertebrates. Whether polyandry has mortality costs in vertebrates is currently unknown. In the present study, we aimed to fill the gap by investigating the relationships between the level of polyandry (measured either by male relative testes mass or the percentage of multiple paternities) and female patterns of mortality across mammals. While we found that the two metrics of female mortality co-varied with pace of life, we did not find any evidence that polyandry leads to either decreased median lifespan or increased aging rate in mammals. We discuss such an absence of detectable mortality costs of polyandry in female mammals in light of recent advances in the study of mammalian reproductive biology and life-history tactics.

Why mammals more susceptible to the hepatotoxic microcystins than fish: evidences from plasma and albumin protein binding through equilibrium dialysis

To elucidate the interspecies variation of susceptibility to microcystins (MCs), fresh plasma and purified albumin from six kinds of mammals and fish were used in toxins-substances binding test. Protein contents in the test plasma were analyzed and the binding characteristics to MCs were compared. Two kinds of widely observed MCs, microcystin-LR (MC-LR) and microcystin-RR (MC-RR) were tested and data were collected through the method of equilibrium dialysis. It was found that total plasma protein and albumin content in mammals were nearly two times and four times higher than that in fish, respectively. In the test range of 0-100 μg/mL, binding rates of fish plasma to MCs were considered significant lower (p < 0.01) than that of mammals. And human plasma demonstrated the highest binding rate in mammals. In all the test species, plasma protein binding rates of MC-RR were significantly higher than MC-LR (p < 0.01). Besides, binding profiles of albumin were acquired under the protein content of 0.67 mg/mL. Human serum albumin demonstrated the highest affinity to MCs throughout the six species and differences among the other five species were considered not significant (p > 0.05). From the view of protein binding, it is concluded that both the variation of plasma protein composition and albumin binding characteristic could influence the existing form of MCs in circulation, change MCs utilization, alter MCs half-life and further contribute to the difference of susceptibility between mammals and fish.

Leptin expression affects metabolic rate in zebrafish embryos (D. rerio)

We used antisense morpholino oligonucleotide technology to knockdown leptin-(A) gene expression in developing zebrafish embryos and measured its effects on metabolic rate and cardiovascular function. Using two indicators of metabolic rate, oxygen consumption was significantly lower in leptin morphants early in development [<48 hours post-fertilization (hpf)], while acid production was significantly lower in morphants later in development (>48 hpf). Oxygen utilization rates in <48 hpf embryos and acid production in 72 hpf embryos could be rescued to that of wildtype embryos by recombinant leptin coinjected with antisense morpholino. Leptin is established to influence metabolic rate in mammals, and these data suggest leptin signaling also influences metabolic rate in fishes.

Dopamine Modulates Metabolic Rate and Temperature Sensitivity in Drosophila melanogaster

Homeothermal animals, such as mammals, maintain their body temperature by heat generation and heat dissipation, while poikilothermal animals, such as insects, accomplish it by relocating to an environment of their favored temperature. Catecholamines are known to regulate thermogenesis and metabolic rate in mammals, but their roles in other animals are poorly understood. The fruit fly, Drosophila melanogaster, has been used as a model system for the genetic studies of temperature preference behavior. Here, we demonstrate that metabolic rate and temperature sensitivity of some temperature sensitive behaviors are regulated by dopamine in Drosophila. Temperature-sensitive molecules like dTrpA1 and shi ts induce temperature-dependent behavioral changes, and the temperature at which the changes are induced were lowered in the dopamine transporter-defective mutant, fumin. The mutant also displays a preference for lower temperatures. This thermophobic phenotype was rescued by the genetic recovery of the dopamine transporter in dopamine neurons. Flies fed with a dopamine biosynthesis inhibitor (3-iodo-L-tyrosine), which diminishes dopamine signaling, exhibited preference for a higher temperature. Furthermore, we found that the metabolic rate is up-regulated in the fumin mutant. Taken together, dopamine has functions in the temperature sensitivity of behavioral changes and metabolic rate regulation in Drosophila, as well as its previously reported functions in arousal/sleep regulation.

Evolution of CpG island promoter function underlies changes in KChIP2 potassium channel subunit gene expression in mammalian heart

Scaling of cardiac electrophysiology with body mass requires large changes in the ventricular action potential duration and heart rate in mammals. These changes in cellular electrophysiological function are produced by systematic and coordinated changes in the expression of multiple ion channel and transporter genes. Expression of one important potassium current, the transient outward current (I(to)), changes significantly during mammalian evolution. Changes in I(to) expression are determined, in part, by variation in the expression of an obligatory auxiliary subunit encoded by the KChIP2 gene. The KChIP2 gene is expressed in both cardiac myocytes and neurons and transcription in both cell types is initiated from the same CpG island promoter. Species-dependent variation of KChIP2 expression in heart is mediated by the evolution of the cis-regulatory function of this gene. Surprisingly, the major locus of evolutionary change for KChIP2 gene expression in heart lies within the CpG island core promoter. The results demonstrate that CpG island promoters are not simply permissive for gene expression but can also contribute to tissue-selective expression and, as such, can function as an important locus for the evolution of cis-regulatory function. More generally, evolution of the cis-regulatory function of voltage-gated ion channel genes appears to be an effective and efficient way to modify channel expression levels to optimize electrophysiological function.

Rapid Turnover of Functional Sequence in Human and Other Genomes

The amount of a genome's sequence that is functional has been surprisingly difficult to estimate accurately. This has severely hindered analyses asking whether the amount of functional genomic sequence correlates with organismal complexity. Most studies estimate these amounts by considering nucleotide substitution rates within aligned sequences. These approaches show reduced power to identify sequence that is aligned, functional, and constrained only within narrowly defined phyla. The neutral indel model exploits insertions or deletions (indels) rather than substitutions in predicting functional sequence. Surprisingly, this method indicates that half of all functional sequence is specific to individual eutherian lineages. This review considers the rates at which coding or noncoding and functional or nonfunctional sequence changes among mammalian genomes. In contrast to the slow rate at which protein-coding sequence changes, functional noncoding sequence appears to change or be turned over at rapid rates in mammals.