Graph theory augmented math programming approach to identify minimal reaction sets in metabolic networks

Bioprocesses are of growing importance as an avenue to produce chemicals. Microorganisms containing only desired catalytic and replication capabilities in their metabolic pathways are expected to offer efficient processes for chemical production. Realizing such minimal cells is the holy grail of metabolic engineering. In this paper, we propose a new method that combines graph-theoretic approaches with mixed-integer liner programming (MILP) to design metabolic networks with minimal reactions. Existing MILP based computational approaches are computationally complex especially for large networks. The proposed graph-theoretic approach offers an efficient divide-and-conquer strategy using the MILP formulation on sub-networks rather than considering the whole network monolithically. In addition to the resulting improvement in computational complexity, the proposed method also aids in identifying the key reactions to be knocked-out in order to achieve the minimal cell. The efficacy of the proposed approach is demonstrated using three case studies from two organisms, Escherichia coli and Saccharomyces cerevisiae.     

Data analysis for dynamic contrast-enhanced MRI-based cerebral perfusion measurements: correcting for changing cortical CSF volumes

The time evolution of the histogram (number of pixels versus signal intensity) is used to calculate ΔR ₂ parameters from dynamic contrast-enhanced magnetic resonance (MR) imaging of the brain. This method partially corrects for partial volume effects and is an improvement over the approach using the signal intensity as a function of time when confounding factors such as changing cortical cerebrospinal fluid volumes are involved. The maximum value for ΔR ₂ is found to correlate with relative cerebral blood flow as assessed by xenon inhalation and can be used to discriminate between vascular dementia and healthy volunteers. With this method, the normal range for ΔR ₂ values is found to be the same for both young (19–40 years old) and elderly (65–85 years old) healthy volunteers.     

Early development in males with Fragile X syndrome: a review of the literature

This article reviews the current bibliographic knowledge on early neurobehavioral development and milestones in Fragile X syndrome (FraX), with emphasis on males affected by the condition. Three broad areas of early development were examined: (1) gross and fine motor, (2) speech and language, and (3) social. The result of the current review indicates very limited information on the developmental milestones in all three areas. The scarce literature on motor development shows that in FraX there is an early developmental delay. Research on speech and language demonstrates pervasive deficits in conversational skills and severe developmental delay, with increasing discrepancy between language level and chronological age in young males with FraX. Finally, deficits in social development in FraX include abnormal gaze, approach and avoidance conflict, and high incidence of autistic spectrum disorders.     

Lateral hypothalamic syndrome in rats: a comparison of the behavioral and neurochemical effects of lesions placed in the lateral hypothalamus and nigrostriatal bundle

The effects of total (T-NSB) and subtotal (S-NSB) destruction of the nigrostriatal bundle were compared with the effects of large lateral hypothalamic (LH) lesions on various aspects of the lateral hypothalamic syndrome. The T-NSB and LH lesions produced equivalent decreases in caudate and telencephalic contents of dopamine and norepinephrine, while with the exception of telencephalic dopamine, S-NSB lesions had consistently smaller effect. The T-NSB and LH lesions produced equivalent effects on duration of aphagia and adipsia (Stages 1 to 3) and on long-term decreases in body weight and ad lib water consumption, and these effects were always greater than those produced by the S-NSB lesion. These aspects of the lateral hypothalamic syndrome appeared to be related to the interruption of the nigrostriatal bundle and consequent decrease in caudate dopamine. The T-NSB and S-NSB lesions produced equivalent long-term deficits in water regulation as measured by drinking in the absence of food or in response to intra- and extracellular dehydration, but these deficits were always significantly less than those produced by the LH lesion. It was concluded that these regulatory deficits were not related to destruction of catecholamine pathways. All three lesions totally blocked eating in response to a glucoprivic challenge. This aspect of the lateral hypothalamic syndrome, therefore, results from destruction of a small portion of the lateral diencephalon and may be related to the interruption of the dopaminergic mesolimbic system.     

In vitro studies to assess the antidiabetic,anti-cholinesterase and antioxidant potential of Spergularia rubra

Spergularia rubra is distributed all over the world, being its infusion used as diuretic. In spite of its large use, the antidiabetic, anti-cholinesterase and antioxidant activities of this species have not been assessed and its chemical composition is scarcely known. In the work herein a hydromethanolic extract was studied.     

信息异化现象研究综述

目前，信息异化问题是一个新问题，也是一个被深入研究的问题。该文阐释了信息异化的内涵和本质，并从主体的情感、认知与行为三个方面的新视角出发，对诸多信息异化现象进行了归类与分析。     

Actual versus self-reported scholastic achievement of litigating postconcussion and severe closed head injury claimants.

Psychologists typically rely on patients' self-report of premorbid status in litigated settings. The authors examined the fidelity between self-reported and actual scholastic performance in litigating head injury claimants. The data indicated late postconcussion syndrome (LPCS) and severe closed head injury litigants retrospectively inflated scholastic performance to a greater degree than nonlitigating control groups. The LPCS group showed the highest magnitude of grade inflation, but discrepancy scores did not significantly correlate with a battery of malingering measures or with objective cerebral dysfunction. These findings support previous studies, which showed self-report is not a reliable basis for estimation of preinjury cognitive status. Retrospective inflation may represent a response shift bias shaped by an adversarial context rather than a form of malingering. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estimates of Improved Productivity and Health from Better Indoor Environments

Abstract The existing literature contains strong evidence that characteristics of buildings and indoor environments significantly influence rates of respiratory disease, allergy and asthma symptoms, sick building symptoms, and worker performance. Theoretical considerations, and limited empirical data, suggest that existing technologies and procedures can improve indoor environments in a manner that significantly increases health and productivity. At present, we can develop only crude estimates of the magnitude of productivity gains that may be obtained by providing better indoor environments; however, the projected gains are very large. For the U.S., we estimate potential annual savings and productivity gains of $6 billion to $19 billion from reduced respiratory disease; $1 billion to $4 billion from reduced allergies and asthma, $10 billion to $20 billion from reduced sick building syndrome symptoms, and $12 billion to $125 billion from direct improvements in worker performance that are unrelated to health. Sample calculations indicate that the potential financial benefits of improving indoor environments exceed costs by a factor of 18 to 47. The policy implications of the findings are discussed and include a recommendation for additional research.     

Hydrogen production and metabolic flux analysis of metabolically engineered Escherichia coli strains

Escherichia coli can produce H₂ from glucose via formate hydrogen lyase (FHL). In order to improve the H₂ production rate and yield, metabolically engineered E. coli strains, which included pathway alterations in their H₂ production and central carbon metabolism, were developed and characterized by batch experiments and metabolic flux analysis. Deletion of hycA, a negative regulator for FHL, resulted in twofold increase of FHL activity. Deletion of two uptake hydrogenases (1 (hya) and hydrogenase 2 (hyb)) increased H₂ production yield from 1.20 mol/mol glucose to 1.48 mol/mol glucose. Deletion of lactate dehydrogenase (ldhA) and fumarate reductase (frdAB) further improved the H₂ yield; 1.80 mol/mol glucose under high H₂ pressure or 2.11 mol/mol glucose under reduced H₂ pressure. Several batch experiments at varying concentrations of glucose (2.5–10 g/L) and yeast extract (0.3 or 3.0 g/L) were conducted for the strain containing all these genetic alternations, and their carbon and energy balances were analyzed. The metabolic flux analysis revealed that deletion of ldhA and frdABdirected most of the carbons from glucose to the glycolytic pathway leading to H₂ production by FHL, not to the pentose phosphate pathway.     

Impaired verbal comprehension of quantifiers in corticobasal syndrome.

Objective: Patients with Corticobasal Syndrome (CBS) have atrophy in posterior parietal cortex. This region of atrophy has been previously linked with quantifier comprehension difficulty, but previous studies employed visual stimuli, making it difficult to account for potentially confounding visuospatial deficits in CBS patients. The current study evaluated comprehension of generalized quantifiers using strictly verbal materials. Method: Non-aphasic CBS patients, a brain-damaged control group (consisting of patients with Alzheimer's disease and frontotemporal dementia), and age-matched healthy controls participated in this study. We assessed familiar temporal, spatial, and monetary domains of verbal knowledge comparatively. Judgment accuracy was only evaluated in statements for which patients demonstrated accurate factual knowledge about the target domain. Results: We found that patients with CBS are significantly impaired in their ability to evaluate quantifiers when compared to healthy seniors and a brain-damaged control group, even in this strictly verbal task. This impairment was seen in the vast majority of individual CBS patients. Conclusions: These findings offer additional evidence of quantifier impairment in CBS patients and emphasize that this impairment cannot be attributed to potential visuo spatial processing impairments in patients with parietal disease. (PsycINFO Database Record (c) 2011 APA, all rights reserved)