Differential effects of aging on limb blood flow in humans

Aging appears to attenuate leg blood flow during exercise; in contrast, such data are scant and do not support this contention in the arm. Therefore, to determine whether aging has differing effects on blood flow in the arm and leg, eight young (22 +/- 6 yr) and six old (71 +/- 15 yr) subjects separately performed dynamic knee extensor [0, 3, 6, 9 W; 20, 40, 60% maximal work rate (WRmax)] and handgrip exercise (3, 6, 9 kg at 0.5 Hz; 20, 40, 60% WRmax). Arterial diameter, blood velocity (Doppler ultrasound), and arterial blood pressure (radial tonometry) were measured simultaneously at each of the submaximal workloads. Quadriceps muscle mass was smaller in the old (1.6 +/- 0.1 kg) than the young (2.1 +/- 0.2 kg). When normalized for this difference in muscle mass, resting seated blood flow was similar in young and old subjects (young, 115 +/- 28; old, 114 +/- 39 ml x g(-1) x min(-1)). During exercise, blood flow and vascular conductance were attenuated in the old whether expressed in absolute terms for a given absolute workload or more appropriately expressed as blood flow per unit muscle mass at a given relative exercise intensity (young, 1,523 +/- 329; old, 1,340 +/- 157 ml x kg(-1) x min(-1) at 40% WRmax). In contrast, aging did not affect forearm muscle mass or attenuate rest or exercise blood flow or vascular conductance in the arm. In conclusion, aging induces limb-specific alterations in exercise blood flow regulation. These alterations result in reductions in leg blood flow during exercise but do not impact forearm blood flow.     

Lack of association of glutamate decarboxylase 2 gene polymorphisms with severe obesity in utah

Three polymorphisms of the glutamate decarboxylase 2 gene, which encodes the glutamic acid decarboxylase enzyme, have been associated with severe obesity in a large French cohort. One of these polymorphisms was shown to have functional consequences on promoter expression. Another polymorphism was associated with insulin levels and secretion. These associations were examined in 855 severely obese Utah subjects (mean BMI = 48 kg/m(2)) and a normal-weight and normoglycemic subset (N = 130, mean BMI = 22 kg/m(2)) of a random sample of the Utah population (N = 462). Comparisons of the normal-weight random group with the severely obese group did not result in significant genotype or allele frequency differences for any of the three polymorphisms, C61450A, T83897A, or A-243G (all p > or = 0.18). Haplotypes were also not related to severe obesity (p = 0.10). None of the polymorphisms was significantly related to fasting glucose, insulin levels, or homeostasis model assessment insulin resistance or secretion indices. This study of normal-weight and severely obese subjects from Utah does not provide evidence for involvement of the three genotyped polymorphisms in the glutamate decarboxylase 2 gene with obesity or with insulin- and glucose-related measures associated with obesity.     

Involvement of Toll-like receptor 4 in acetaminophen hepatotoxicity

The objective of this study was to determine whether Toll-like receptor 4 (TLR4) has a role in alcohol-mediated acetaminophen (APAP) hepatotoxicity. TLR4 is involved in the inflammatory response to endotoxin. Others have found that ethanol-mediated liver disease is decreased in C3H/HeJ mice, which have a mutated TLR4 resulting in a decreased response to endotoxin compared with endotoxin-responsive mice. In the present study, short-term (1 wk) pretreatment with ethanol plus isopentanol, the predominant alcohols in alcoholic beverages, caused no histologically observed liver damage in either C3H/HeJ mice or endotoxin-responsive C3H/HeN mice, despite an increase in nitrotyrosine levels in the livers of C3H/HeN mice. In C3H/HeN mice pretreated with the alcohols, subsequent exposure to APAP caused a transient decrease in liver nitrotyrosine formation, possibly due to competitive interaction of peroxynitrite with APAP producing 3-nitroacetaminophen. Treatment with APAP alone resulted in steatosis in addition to congestion and necrosis in both C3H/HeN and C3H/HeJ mice, but the effects were more severe in endotoxin-responsive C3H/HeN mice. In alcohol-pretreated endotoxin-responsive C3H/HeN mice, subsequent exposure to APAP resulted in further increases in liver damage, including severe steatosis, associated with elevated plasma levels of TNF-alpha. In contrast, alcohol pretreatment of C3H/HeJ mice caused little to no increase in APAP hepatotoxicity and no increase in plasma TNF-alpha. Portal blood endotoxin levels were very low and were not detectably elevated by any of the treatments. In conclusion, this study implicates a role of TLR4 in APAP-mediated hepatotoxicity.     

Phosphorylation of the hinge domain of the nuclear hormone receptor LRH-1 stimulates transactivation

The nuclear receptor LRH-1 (NR5A2) functions to regulate expression of a number of genes associated with bile acid homeostasis and other liver functions, but mechanisms that modulate its activity remain unclear. We have found that mitogenic stimuli, including treatment with phorbol myristate (PMA), increase LRH-1 transactivation. This response maps to the hinge and ligand binding domains of LRH-1 and is blocked by the mitogen-activated protein kinase ERK1/2 inhibitor U0126. LRH-1 is a phosphoprotein and hinge domain serine residues at 238 and 243 are required for effective phosphorylation, both in vitro and in cells. Preventing phosphorylation of these residues by mutating both to alanine decreases PMA-dependent LRH-1 transactivation and mimicking phosphorylation by mutation to positively charged aspartate residues increases basal transactivation. Although serine phosphorylation of the hinge of SF-1 (NR5A1), the closest relative of LRH-1, confers a similar response, the specific targets differ in the two closely related orphan receptors. These results define a novel pathway for the modulation of LRH-1 transactivation and identify specific LRH-1 residues as downstream targets of mitogenic stimuli. This pathway may contribute to recently described proliferative functions of LRH-1.     

Positive reinforcement training affects hematologic and serum chemistry values in captive chimpanzees (Pan troglodytes)

Positive reinforcement training (PRT) techniques have received considerable attention for their stress reduction potential in the behavioral management of captive nonhuman primates. However, few published empirical studies have provided physiological data to support this position. To address this issue, PRT techniques were used to train chimpanzees (Pan troglodytes) to voluntarily present a leg for an intramuscular (IM) injection of anesthetic. Hematology and serum chemistry profiles were collected from healthy chimpanzees (n=128) of both sexes and various ages during their routine annual physical examinations over a 7-year period. Specific variables potentially indicative of acute stress (i.e., total white blood cell (WBC) counts, absolute segmented neutrophils (SEG), glucose (GLU) levels, and hematocrit (HCT) levels) were analyzed to determine whether the method used to administer the anesthetic (voluntary present for injection vs. involuntary injection) affected the physiological parameters. Subjects that voluntarily presented for an anesthetic injection had significantly lower mean total WBC counts, SEG, and GLU levels than subjects that were involuntarily anesthetized by more traditional means. Within-subjects analyses revealed the same pattern of results. This is one of the first data sets to objectively demonstrate that PRT for voluntary presentation of IM injections of anesthetic can significantly affect some of the physiological measures correlated with stress responses to chemical restraint in captive chimpanzees.     

Differential localization of Mre proteins with PBP2 in Rhodobacter sphaeroides

In Rhodobacter sphaeroides, MreB, MreC, MreD, PBP2, and RodA are encoded at the same locus. The localizations of PBP2, MreB, and MreC, which have all been implicated in the synthesis of the peptidoglycan layer, were investigated under different growth conditions to gain insight into the relationships between these proteins. Immunofluorescence microscopy showed that PBP2 localized to specific sites at the midcell of elongating cells under both aerobic and photoheterotrophic conditions. Visualizing PBP2 at different stages of the cell cycle showed that in elongating cells, PBP2 was found predominately at the midcell, with asymmetric foci and bands across the cell. PBP2 remained at midcell until the start of septation, after which it moved to midcell of the daughter cells. Deconvolution and three-dimensional reconstructions suggested that PBP2 forms a partial ring at the midcell of newly divided cells and elongated cells, while in septating cells, partial PBP2 rings were present at one-quarter and three-quarter positions. Due to the diffraction limits of light microscopy, these partial rings could represent unresolved helices. Colocalization studies showed that MreC always colocalized with PBP2, while MreB colocalized with PBP2 only during elongation; during septation, MreB remained at the septation site, whereas PBP2 relocalized to the one-quarter and three-quarter positions. These results suggest that PBP2 and MreC are involved in peptidoglycan synthesis during elongation and that this occurs at specific sites close to midcell in R. sphaeroides.     

BioDry: An Inexpensive,Low-Power Method to Preserve Aquatic Microbial Biomass at Room Temperature

This report describes BioDry (patent pending), a method for reliably preserving the biomolecules associated with aquatic microbial biomass samples, without the need of hazardous materials (e.g. liquid nitrogen, preservatives, etc.), freezing, or bulky storage/sampling equipment. Gel electrophoresis analysis of nucleic acid extracts from samples treated in the lab with the BioDry method indicated that molecular integrity was protected in samples stored at room temperature for up to 30 days. Analysis of 16S/18S rRNA genes for presence/absence and relative abundance of microorganisms using both 454-pyrosequencing and TRFLP profiling revealed statistically indistinguishable communities from control samples that were frozen in liquid nitrogen immediately after collection. Seawater and river water biomass samples collected with a portable BioDry “field unit", constructed from off-the-shelf materials and a battery-operated pumping system, also displayed high levels of community rRNA preservation, despite a slight decrease in nucleic acid recovery over the course of storage for 30 days. Functional mRNA and protein pools from the field samples were also effectively conserved with BioDry, as assessed by respective RT-PCR amplification and western blot of ribulose-1-5-bisphosphate carboxylase/oxygenase. Collectively, these results demonstrate that BioDry can adequately preserve a suite of biomolecules from aquatic biomass at ambient temperatures for up to a month, giving it great potential for high resolution sampling in remote locations or on autonomous platforms where space and power are limited.     

Cold chain and virus‐free chloroplast‐made booster vaccine to confer immunity against different poliovirus serotypes

The WHO recommends complete withdrawal of oral polio vaccine (OPV) type 2 by April 2016 globally and replacing with at least one dose of inactivated poliovirus vaccine (IPV). However, high‐cost, limited supply of IPV, persistent circulating vaccine‐derived polioviruses transmission and need for subsequent boosters remain unresolved. To meet this critical need, a novel strategy of a low‐cost cold chain‐free plant‐made viral protein 1 (VP1) subunit oral booster vaccine after single IPV dose is reported. Codon optimization of the VP1 gene enhanced expression by 50‐fold in chloroplasts. Oral boosting of VP1 expressed in plant cells with plant‐derived adjuvants after single priming with IPV significantly increased VP1‐IgG1 and VP1‐IgA titres when compared to lower IgG1 or negligible IgA titres with IPV injections. IgA plays a pivotal role in polio eradication because of its transmission through contaminated water or sewer systems. Neutralizing antibody titres (~3.17–10.17 log₂ titre) and seropositivity (70–90%) against all three poliovirus Sabin serotypes were observed with two doses of IPV and plant‐cell oral boosters but single dose of IPV resulted in poor neutralization. Lyophilized plant cells expressing VP1 stored at ambient temperature maintained efficacy and preserved antigen folding/assembly indefinitely, thereby eliminating cold chain currently required for all vaccines. Replacement of OPV with this booster vaccine and the next steps in clinical translation of FDA‐approved antigens and adjuvants are discussed.     

A Financial Market Model Incorporating Herd Behaviour

Herd behaviour in financial markets is a recurring phenomenon that exacerbates asset price volatility, and is considered a possible contributor to market fragility. While numerous studies investigate herd behaviour in financial markets, it is often considered without reference to the pricing of financial instruments or other market dynamics. Here, a trader interaction model based upon informational cascades in the presence of information thresholds is used to construct a new model of asset price returns that allows for both quiescent and herd-like regimes. Agent interaction is modelled using a stochastic pulse-coupled network, parametrised by information thresholds and a network coupling probability. Agents may possess either one or two information thresholds that, in each case, determine the number of distinct states an agent may occupy before trading takes place. In the case where agents possess two thresholds (labelled as the finite state-space model, corresponding to agents’ accumulating information over a bounded state-space), and where coupling strength is maximal, an asymptotic expression for the cascade-size probability is derived and shown to follow a power law when a critical value of network coupling probability is attained. For a range of model parameters, a mixture of negative binomial distributions is used to approximate the cascade-size distribution. This approximation is subsequently used to express the volatility of model price returns in terms of the model parameter which controls the network coupling probability. In the case where agents possess a single pulse-coupling threshold (labelled as the semi-infinite state-space model corresponding to agents’ accumulating information over an unbounded state-space), numerical evidence is presented that demonstrates volatility clustering and long-memory patterns in the volatility of asset returns. Finally, output from the model is compared to both the distribution of historical stock returns and the market price of an equity index option.     

Using network dynamic fMRI for detection of epileptogenic foci

Background

Epilepsy is one of the most prevalent neurological disorders. It remains medically intractable for about one-third of patients with focal epilepsy, for whom precise localization of the epileptogenic zone responsible for seizure initiation may be critical for successful surgery. Existing fMRI literature points to widespread network disturbances in functional connectivity. Per previous scalp and intracranial EEG studies and consistent with excessive local synchronization during interictal discharges, we hypothesized that, relative to same regions in healthy controls, epileptogenic foci would exhibit less chaotic dynamics, identifiable via entropic analyses of resting state fMRI time series.

Methods

In order to first validate this hypothesis on a cohort of patients with known ground truth, here we test individuals with well-defined epileptogenic foci (left mesial temporal lobe epilepsy). We analyzed voxel-wise resting-state fMRI time-series using the autocorrelation function (ACF), an entropic measure of regulation and feedback, and performed follow-up seed-to-voxel functional connectivity analysis. Disruptions in connectivity of the region exhibiting abnormal dynamics were examined in relation to duration of epilepsy and patients’ cognitive performance using a delayed verbal memory recall task.

Results

ACF analysis revealed constrained (less chaotic) functional dynamics in left temporal lobe epilepsy patients, primarily localized to ipsilateral temporal pole, proximal to presumed focal points. Autocorrelation decay rates differentiated, with 100 % accuracy, between patients and healthy controls on a subject-by-subject basis within a leave-one-subject out classification framework. Regions identified via ACF analysis formed a less efficient network in patients, as compared to controls. Constrained dynamics were linked with locally increased and long-range decreased connectivity that, in turn, correlated significantly with impaired memory (local left temporal connectivity) and epilepsy duration (left temporal – posterior cingulate cortex connectivity).

Conclusions

Our current results suggest that data driven functional MRI methods that target network dynamics hold promise in providing clinically valuable tools for identification of epileptic regions.