Energetics and space use: intraspecific and interspecific comparisons of movements and home ranges of two Colubrid snakes

1. Energy requirements explain substantial variation in movement and home range size among birds and mammals. This study assesses whether the same is true of snakes by comparing ratsnakes (Elaphe obsoleta) and racers (Coluber constrictor), ecologically similar species whose energy requirements appear to differ substantially (racers > ratsnakes). 2. Over 4 years 22 Elaphe and 16 Coluber were radio-tracked at the same site in Illinois to examine how movement and home ranges varied by sex and season. 3. Coluber moved more often and further per move than Elaphe, resulting in their estimated mean day range being almost four times larger than that of Elaphe (88.0 m day(-1) vs. 23.1 m day(-1)). 4. Both male and female Elaphe moved more frequently early in the season consistent with mate-searching, but mean distances moved did not differ seasonally or by sex. Both sexes of Coluber moved more later in the season and overall males moved further than females. 5. Interspecifically, patterns were consistent with the energetics hypothesis--Coluber had mean home ranges approximately four times larger than those of Elaphe. 6. Intraspecifically, increased movement did not always produce larger home ranges. Male Elaphe had larger home ranges than females despite not moving further, whereas male Coluber had comparable home ranges to females despite moving further. Also, Elaphe home ranges in Illinois were substantially smaller than has been documented in Ontario, despite Ontario Elaphe moving less. 7. Our results generally support the energetics hypothesis, but indicate that knowledge of ecology and energetics increases our understanding of area requirements beyond simple allometric predictions.     

Loss of PPAR gamma in immune cells impairs the ability of abscisic acid to improve insulin sensitivity by suppressing monocyte chemoattractant protein-1 expression and macrophage infiltration into white adipose tissue

Abscisic acid (ABA) is a natural phytohormone and peroxisome proliferator-activated receptor gamma (PPARgamma) agonist that significantly improves insulin sensitivity in db/db mice. Although it has become clear that obesity is associated with macrophage infiltration into white adipose tissue (WAT), the phenotype of adipose tissue macrophages (ATMs) and the mechanisms by which insulin-sensitizing compounds modulate their infiltration remain unknown. We used a loss-of-function approach to investigate whether ABA ameliorates insulin resistance through a mechanism dependent on immune cell PPARgamma. We characterized two phenotypically distinct ATM subsets in db/db mice based on their surface expression of F4/80. F4/80(hi) ATMs were more abundant and expressed greater concentrations of chemokine receptor (CCR) 2 and CCR5 when compared to F4/80(lo) ATMs. ABA significantly decreased CCR2(+) F4/80(hi) infiltration into WAT and suppressed monocyte chemoattractant protein-1 (MCP-1) expression in WAT and plasma. Furthermore, the deficiency of PPARgamma in immune cells, including macrophages, impaired the ability of ABA to suppress the infiltration of F4/80(hi) ATMs into WAT, to repress WAT MCP-1 expression and to improve glucose tolerance. We provide molecular evidence in vivo demonstrating that ABA improves insulin sensitivity and obesity-related inflammation by inhibiting MCP-1 expression and F4/80(hi) ATM infiltration through a PPARgamma-dependent mechanism.     

The next steps for genomic medicine: challenges and opportunities for the developing world

This is a historical moment on the path to genomic medicine - the point at which theory is about to be translated into practice. We have previously described human genome variation studies taking place in Mexico, India, Thailand, and South Africa. Such investments into science and technology will enable these countries to embark on the path to the medical and health applications of genomics, and to benefit economically. Here we provide a perspective on the challenges and opportunities facing these and other countries in the developing world as they begin to harness genomics for the benefit of their populations.     

Sucrose hydrolysis does not limit food intake by Pallas's long-tongued bats

Nectarivorous bats include very dilute nectar in their natural diet, and recent work with Pallas's long-tongued bat Glossophaga soricina showed that sugar (energy) intake rate decreased at dilute sucrose solutions. However, chiropterophillous nectar is composed mainly of the hexoses glucose and fructose. Because bats fed hexose nectar would save the delay of hydrolyzing sucrose, we hypothesized that sugar intake rate should be higher on this diet than on sucrose nectar. We compared intake response in Pallas's long-tongued bats offered 1 : 1 glucose-fructose (hexose) and sucrose diets at 5%, 10%, 20%, 30%, and 40% (mass/volume) sugar solutions. We also tested the hypothesis that sucrose hydrolysis limits food intake in bats. Intake response was the same in bats fed both types of diet: sugar intake rate was lower in dilute solutions and then increased with sugar concentration. Similar intake responses in both diets indicate that sucrose hydrolysis alone does not limit food intake and support the idea that the burden of processing excess water in dilute solutions plays a major role.     

Copper, Iron, and Zinc Status in Children with Moderate and Severe Acute Malnutrition Recovered Following WHO Protocols

INTRODUCTION: The prevalence of copper, iron, and zinc deficiencies in malnutrition and the amounts of micronutrients that should be provided for nutritional recovery are unclear. OBJECTIVE: This study aims to measure (1) the frequency of Cu, Fe, and Zn deficiencies in children with acute malnutrition on day 1 and after 15- and 30-day treatments with F100 plus vitamins/minerals mix, and (2) anthropometric recovery after 30 d feeding ad libitum. METHODS: In Cochabamba, Bolivia, 12 hospitalized children with severe acute malnutrition (HSM) and 17 (hospitalized) with moderate acute malnutrition (HMM), 3-33 months, received F100 ad libitum for 1 month. Children received FeSO4 after infection subsided. On days 1, 15, and 30 weight, length, hemoglobin, serum ferritin, iron, copper, zinc, and ceruloplasmin were measured. Comparison group were 17 ambulatory moderately malnourished (AMM) and 34 well-nourished children, measured once. RESULTS: Deficiencies were highly prevalent in hospitalized groups. Serum copper and zinc became normal on D15 and D30, respectively. Mean daily energy intake of 160 kcal and 4 g prot//kg/d/1 mo led children to gain (mean) 5 g/kg/day, both on D15 and D30. CONCLUSIONS: Micronutrient deficiencies were highly prevalent in HSM and HMM and recovered similarly. Application of WHO protocols induced satisfactory copper status recovery, but improvement of zinc was slower.     

Spread mixed monolayers of deoxycholic and dehydrocholic acids at the air-water interface, effect of subphase pH. Characterization by axisymmetric drop shape analysis

Bile acids (deoxycholic and dehydrocholic acids) spread mixed monolayers behavior at the air/water interface were studied as a function of subphase pH using a constant surface pressure penetration Langmuir balance based on the Axisymmetric Drop Shape Analysis (ADSA). We examined the influence of electrostatic, hydrophobic and hydration forces on the interaction between amphiphilic molecules at the interface by the collapse area values, the thermodynamic parameters and equation of state virial coefficients analysis. The obtained results showed that at neutral (pH=6.7) or basic (pH=10) subphase conditions the collapse areas values are similar to that of cholanoic acid and consistent with the cross-sectional area of the steroid nucleus (approximately 40 A(2)). The Gibbs energy of mixing values (DeltaG(mix)<0) and the first virial coefficients of the equation of state (b(0)<1) indicated that a miscible monolayer with laterally structured microdomains existed. The aggregation number (1/b(0)) was estimated within the order of 6 (pH=6.7) and 3 (pH=10). At pH=3.2, acidic subphase conditions, no phase separation occurs (DeltaG(mix)<0) but a high expanded effect of the monolayer could be noted. The mixed monolayer behavior was no ideal and no aggregates were formed (b(0)> or =1). Such behavior indicates that the polar groups of the molecules interacts each other more strongly by repulsive electrostatic forces than with the more hydrophobic part of the molecule.     

An implementation of reinforcement learning based on spike timing dependent plasticity

An explanatory model is developed to show how synaptic learning mechanisms modeled through spike-timing dependent plasticity (STDP) can result in long-term adaptations consistent with reinforcement learning models. In particular, the reinforcement learning model known as temporal difference (TD) learning has been used to model neuronal behavior in the orbitofrontal cortex (OFC) and ventral tegmental area (VTA) of macaque monkey during reinforcement learning. While some research has observed, empirically, a connection between STDP and TD, there has not been an explanatory model directly connecting TD to STDP. Through analysis of the learning dynamics that results from a general form of a STDP learning rule, the connection between STDP and TD is explained. We further demonstrate that a STDP learning rule drives the spike probability of a reward predicting neuronal population to a stable equilibrium. The equilibrium solution has an increasing slope where the steepness of the slope predicts the probability of the reward, similar to the results from electrophysiological recordings suggesting a different slope that predicts the value of the anticipated reward of Montague and Berns [Neuron 36(2):265–284, 2002]. This connection begins to shed light into more recent data gathered from VTA and OFC which are not well modeled by TD. We suggest that STDP provides the underlying mechanism for explaining reinforcement learning and other higher level perceptual and cognitive function. This material is based upon work supported by the National Science Foundation under Grants No. IOB-0445648 (PDR) and DMS-0408334 (GL) and by a Career Support grant from Portland State University (GL).     

Estimation of the endohelminth parasite species richness in freshwater fishes from La Mintzita Reservoir, Michoacán, Mexico

In total, 9 endohelminth species were found to parasitize 7 fish species (2 cyprinids, 4 goodeids, and 1 poeciilid) from La Mintzita Reservoir, Michoacán, in central Mexico; 5 were larvae, including 3 allogenic species (Clinostomum complanatum, Tylodelphys sp., Posthodiplostomum minimum) and 2 autogenic species (Serpinema trispinosum, Spiroxys sp.). Four were enteric autogenic adults, i.e., Margotrema bravoae, Bothriocephalus acheilognathi, Proteocephalus longicollis, and Rhabdochona lichtenfelsi. The metacercariae of P. minimum reached the highest levels of prevalence and mean abundance among host species. Our results confirm the depauperate nature of the helminth communities of freshwater fishes from central Mexico. On the basis of this data set, we estimated the total endohelminth species richness for each component community by using 7 nonparametric estimators whose performance was evaluated with the unscaled measures of bias, precision, and accuracy. We found that Chaol and Bootstrap are the most precise and least biased methods for the 7 component communities: however, species richness was consistently underestimated. The underestimation was an unavoidable consequence of the patchy distribution of helminth species among different component communities, particularly at the small sample size used in our study.     

Tissue culture and plant regeneration of blue grama grass, Bouteloua gracilis (H.B.K.) Lag. Ex Steud

Summary As a first step towards applying biotechnology to blue grama, Bouteloua gracilis (H. B. K.) Lag. ex Steud., we have developed a regenerable tissue culture system for this grass. Shoot apices were isolated from 3-d-old seedlings and cultured in 15 different growth regulator formulations combining 2,4-dichlorophenoxyacetic acid (2,4-D), Picloram (4-amino-3, 5,6-trichloropicolinic acid), N⁶-benzyladenine (BA) or adenine (6-aminopurine). The highest induction of organogenic callus was obtained with formulations containing 1 mg l⁻¹ (4.52 μM) 2,4-D plus 0.5 mg l⁻¹ (2.22 μM) BA. and 2 mg l⁻¹ (8.88 μM) BA plus 1 mg l⁻¹ (4.14 μM) Picloram with or without 40 mg l⁻¹ (296.08 μM) adenine. Lower frequencies of induction were obtained for embryogenic as compared to organogenic callus. The most efficient treatments for induction of embryogenic callus contained 2 mg l⁻¹ (9.05 μM) 2,4-D combined with 0.25 (1.11 μM) or 0.50 mg l⁻¹ (2.22 μM) BA, or 1 mg l⁻¹ (4.52 μM) 2,4-D with 0.50 mg l⁻¹ (2.22 μM) BA. Regeneration was achieved in hormonefree Murashige anmd Skoog (MS) medium, half-strength MS medium or MS medium plus 1 mg l⁻¹ (1.44 μM) gibberellic acid. The number of plantlets regenerated per 500 mg callus fresh weight on MS medium ranged from 9 for 2 mg l⁻¹ (9.05 μM) 2,4-D to 62.2 for induction medium containing 2 mg l⁻¹ (8,28 μM) Picloram, 1 mg l⁻¹ (4.44 μM) BA and 40 mg l⁻¹ (296.08 μM) adenine. Regnerated plants grown in soil under greenhouse conditions reached maturity and produced seeds.