The historical biogeography of the southern group of the sucker genus Moxostoma (Teleostei: Catostomidae) and the colonization of central Mexico

The historical biogeography of the southern group of Moxostoma Rafinesque, 1820, a genus of Nearctic freshwater fishes belonging to the Catostomidae, along its entire distribution in North America was inferred to: (1) determine the biogeographical events responsible for its current pattern of diversity and distribution; (2) correlate the climatic and geologic history of the region with the biogeographical pattern observed; and (3) trace the colonization route into central Mexico and the western Pacific slope drainages. The sequences of mitochondrial cytochrome b and the third intron of the growth hormone were obtained for the members of the southern group and related species of the Catostomidae. Phylogenetic analyses and relaxed molecular clock analyses were performed to determine the relatedness of the species and to estimate divergence times. To uncover biogeographical patterns, a dispersal–extinction–cladogenesis (DEC) analysis was conducted. The phylogenetic analyses were consistent with the historical hydrographic scenario in the region. The divergence times show that the southern group evolved during the Pliocene–Pleistocene. The DEC analyses showed that vicariance and dispersal played an important role in the current distribution patterns of the lineages in central Mexico, and allow us to trace an independent route of colonization from the northern areas of North America into central Mexico.     

Anxiety symptomatology,sex and chronotype: The mediational effect of diurnal sleepiness

ABSTRACT

Diurnal subjective sleepiness has been associated with a large number of negative outcomes, such as increased risk of accidents and development of mental disorders as depression and anxiety. However, the role of the diurnal subjective sleepiness as a mediator is poorly understood. The goal of the present study was to examine the role of diurnal subjective sleepiness as a mediator of the relationship between sex, chronotype and anxiety symptoms in healthy young adults. Four-hundred and sixty-seven healthy young adults (64.8% females, age range 18–32 years, mean 20.7, ±2.3) were evaluated with validated and widely used scales for the measurement of diurnal sleepiness, anxiety symptoms and morningness–eveningness preference. We have found that diurnal subjective sleepiness correlated with anxiety symptoms when evaluated both in the total sample and within chronotypes. This association was more important in females than in males (p < 0.0001). Regarding chronotype, only for morning-types, diurnal subjective sleepiness was a significant mediator of the relationship between sex and anxiety symptoms. This is the first study that examines the mediator role of diurnal subjective sleepiness in the known relationship between sex and anxiety symptoms, and adds new evidence about the effect of the chronotype on sleep problems and mental health. Although future work is required, our results have important implications for clinical settings and public health interventions.     

Influence of circadian typology on drug consumption, hazardous alcohol use, and hangover symptoms

Few studies have focused on the influence of circadian typology on drug use, and none has considered the use of illegal drugs and hazardous alcohol consumption. This study analyzes the influence of circadian typology on several types of drug consumption (habitual or sporadic), hangover symptoms (past 12 mos), and, more specifically, hazardous alcohol consumption of young adults. Five hundred seventeen university students (173 males), between 17 and 30 yrs of age, answered the Composite Scale of Morningness (CSM), the Alcohol Use Disorders Identification Test (AUDIT), and a self-referred questionnaire on drug consumption during the previous month and on the prevalence of different hangover symptoms during the previous year. Our results confirm a higher prevalence of consumption of addictive substances, both legal (nicotine and cola drinks) and illegal (cannabis and ecstasy), in evening- compared to morning- and neither-type subjects (p?相似文献   

Cross-Tissue and Tissue-Specific eQTLs: Partitioning the Heritability of a Complex Trait

Top signals from genome-wide association studies (GWASs) of type 2 diabetes (T2D) are enriched with expression quantitative trait loci (eQTLs) identified in skeletal muscle and adipose tissue. We therefore hypothesized that such eQTLs might account for a disproportionate share of the heritability estimated from all SNPs interrogated through GWASs. To test this hypothesis, we applied linear mixed models to the Wellcome Trust Case Control Consortium (WTCCC) T2D data set and to data sets representing Mexican Americans from Starr County, TX, and Mexicans from Mexico City. We estimated the proportion of phenotypic variance attributable to the additive effect of all variants interrogated in these GWASs, as well as a much smaller set of variants identified as eQTLs in human adipose tissue, skeletal muscle, and lymphoblastoid cell lines. The narrow-sense heritability explained by all interrogated SNPs in each of these data sets was substantially greater than the heritability accounted for by genome-wide-significant SNPs (∼10%); GWAS SNPs explained over 50% of phenotypic variance in the WTCCC, Starr County, and Mexico City data sets. The estimate of heritability attributable to cross-tissue eQTLs was greater in the WTCCC data set and among lean Hispanics, whereas adipose eQTLs significantly explained heritability among Hispanics with a body mass index ≥ 30. These results support an important role for regulatory variants in the genetic component of T2D susceptibility, particularly for eQTLs that elicit effects across insulin-responsive peripheral tissues.     

Microbial responses to warming enhance soil carbon loss following translocation across a tropical forest elevation gradient

Tropical soils contain huge carbon stocks, which climate warming is projected to reduce by stimulating organic matter decomposition, creating a positive feedback that will promote further warming. Models predict that the loss of carbon from warming soils will be mediated by microbial physiology, but no empirical data are available on the response of soil carbon and microbial physiology to warming in tropical forests, which dominate the terrestrial carbon cycle. Here we show that warming caused a considerable loss of soil carbon that was enhanced by associated changes in microbial physiology. By translocating soils across a 3000 m elevation gradient in tropical forest, equivalent to a temperature change of ± 15 °C, we found that soil carbon declined over 5 years by 4% in response to each 1 °C increase in temperature. The total loss of carbon was related to its original quantity and lability, and was enhanced by changes in microbial physiology including increased microbial carbon‐use‐efficiency, shifts in community composition towards microbial taxa associated with warmer temperatures, and increased activity of hydrolytic enzymes. These findings suggest that microbial feedbacks will cause considerable loss of carbon from tropical forest soils in response to predicted climatic warming this century.     

Inventory rationing for a system with heterogeneous customer classes

Many retailers find it useful to partition customers into multiple classes based on certain characteristics. We consider the case in which customers are primarily distinguished by whether they are willing to wait for backordered demand. A firm that faces demand from customers that are differentiated in this way may want to adopt an inventory management policy that takes advantage of this differentiation. We propose doing so by imposing a critical level (CL) policy: when inventory is at or below the critical level demand from those customers that are willing to wait is backordered, while demand from customers unwilling to wait will still be served as long as there is any inventory available. This policy reserves inventory for possible future demands from impatient customers by having other, patient, customers wait. We model a system that operates a continuous review replenishment policy, in which a base stock policy is used for replenishments. Demands as well as lead times are stochastic. We develop an exact and efficient procedure to determine the average infinite horizon performance of a given CL policy. Leveraging this procedure we develop an efficient algorithm to determine the optimal CL policy parameters. Then, in a numerical study we compare the cost of the optimal CL policy to the globally optimal state-dependent policy along with two alternative, more naïve, policies. The CL policy is slightly over 2 % from optimal, whereas the alternative policies are 7 and 27 % from optimal. We also study the sensitivity of our policy to the coefficient of variation of the lead time distribution, and find that the optimal CL policy is fairly insensitive, which is not the case for the globally optimal policy.     

Ghrelin mediates anticipation to a palatable meal in rats

Food anticipatory activity (FAA) is displayed in rats when access to food is restricted to a specific time frame of their circadian phase, a behavior thought to reflect both hunger and the motivation to eat. Rats also display FAA in a feeding schedule with ad libitum access to normal chow, but limited availability of a palatable meal, which is thought to involve mainly motivational aspects. The orexigenic hormone ghrelin has been implicated in FAA in rodents with restricted access to chow. Because ghrelin plays an important role not only in the control of food intake, but also in reward, we sought to determine the role of ghrelin in anticipation to a palatable meal. Plasma ghrelin levels of non-restricted rats that anticipated chocolate correlated positively with FAA and were increased compared with chow-fed control rats. Furthermore, centrally injected ghrelin increased, whereas an antagonist of the ghrelin receptor decreased, the anticipation to chocolate. Therefore, we hypothesize that central ghrelin signaling is able to mediate the motivational drive to eat.     

Melanocortin receptor 4 deficiency affects body weight regulation, grooming behavior, and substrate preference in the rat

Obesity is caused by an imbalance between energy intake and expenditure and has become a major health-care problem in western society. The central melanocortin system plays a crucial role in the regulation of feeding and energy expenditure, and functional loss of melanocortin receptor 4 (MC4R) is the most common genetic cause of human obesity. In this study, we present the first functional Mc4r knockout model in the rat, resulting from an N-ethyl-N-nitrosourea mutagenesis-induced point mutation. In vitro observations revealed impaired membrane-binding and subsequent nonfunctionality of the receptor, whereas in vivo observations showed that functional loss of MC4R increased body weight, food intake, white adipose mass, and changed substrate preference. In addition, intracerebroventricular (ICV) administration of Agouti-Related Protein(79-129) (AgRP(79-129)), an MC4R inverse agonist, or Melanotan-II (MTII), an MC4R agonist, did affect feeding behavior in wild-type rats but not in homozygous mutant rats, confirming complete loss of MC4R function in vivo. Finally, ICV administration of MTII induced excessive grooming behavior in wild-type rats, whereas this effect was absent in homozygous mutant rats, indicating that MTII-induced grooming behavior is exclusively regulated via MC4R pathways. Taken together, we expect that the MC4R rat model described here will be a valuable tool for studying monogenic obesity in humans. More specifically, the relative big size and increased cognitive capacity of rats as compared to mice will facilitate complex behavioral studies and detailed mechanistic studies regarding central function of MC4R, both of which ultimately may help to further understand the specific mechanisms that induce obesity during loss of MC4R function.     

Flow cytometry: basic principles and applications

Flow cytometry is a sophisticated instrument measuring multiple physical characteristics of a single cell such as size and granularity simultaneously as the cell flows in suspension through a measuring device. Its working depends on the light scattering features of the cells under investigation, which may be derived from dyes or monoclonal antibodies targeting either extracellular molecules located on the surface or intracellular molecules inside the cell. This approach makes flow cytometry a powerful tool for detailed analysis of complex populations in a short period of time. This review covers the general principles and selected applications of flow cytometry such as immunophenotyping of peripheral blood cells, analysis of apoptosis and detection of cytokines. Additionally, this report provides a basic understanding of flow cytometry technology essential for all users as well as the methods used to analyze and interpret the data. Moreover, recent progresses in flow cytometry have been discussed in order to give an opinion about the future importance of this technology.