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Biological Background (biological + background)
Selected AbstractsThe winnerless competition paradigm in cellular nonlinear networks: Models and applicationsINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 4 2009Paolo Arena Abstract Starting from the biological background on the olfactory architecture of both insects and mammalians, different nonlinear systems able to respond to spatial-distributed external stimuli with spatial,temporal dynamics have been investigated in the last decade. Among these, there is a class of neural networks that produces quasi-periodic trajectories that pass near heteroclinic contours and prove to be global attractors for the system. For this reason, these networks are called winnerless competition (WLC) networks. The sequence of saddle points crossed by each trajectory depends on the spatial input presented to the network and can be used as a ,code' representing a specific class of stimuli. Thanks to the intrinsic discrimination, WLC networks are often used for classification. In this paper, this capability is exploited within a framework for action-oriented perception. WLC networks are here used as bio-inspired architectures for the association between stimuli and ,percepts'. After presenting the theoretical basis of the WLC network in the classic Lotka,Volterra system, we investigate how WLC networks can be formalized in terms of cellular nonlinear networks (CNNs) hosting different kinds of cells: the FitzHugh,Nagumo neuron, the Izhikevich neuron and the single layer CNN standard cell. In order to find efficient ways to code environmental stimuli for action generation, we analyze and compare these WLC-based CNNs in terms of number of generated classes and robustness against the initial conditions. Based on the simulation results, we apply the best-performing system to solve a perceptual task involving navigation and obstacle avoidance. We demonstrate how the large memory capacity shown by the WLC,CNN is able to contribute to the new perceptual framework for autonomous artificial agents, where the association between stimuli and sequences is learned through the experience. Copyright © 2008 John Wiley & Sons, Ltd. [source] Association between pacifier use and breast-feeding, sudden infant death syndrome, infection and dental malocclusionINTERNATIONAL JOURNAL OF EVIDENCE BASED HEALTHCARE, Issue 6 2005Ann Callaghan RN RM BNurs(Hons) Executive summary Objective, To critically review all literature related to pacifier use for full-term healthy infants and young children. The specific review questions addressed are: What is the evidence of adverse and/or positive outcomes of pacifier use in infancy and childhood in relation to each of the following subtopics: ,breast-feeding; ,sudden infant death syndrome; ,infection; ,dental malocclusion. Inclusion criteria, Specific criteria were used to determine which studies would be included in the review: (i) the types of participants; (ii) the types of research design; and (iii) the types of outcome measures. To be included a study has to meet all criteria. Types of participants,The participants included in the review were healthy term infants and healthy children up to the age of 16 years. Studies that focused on preterm infants, and infants and young children with serious illness or congenital malformations were excluded. However, some total population studies did include these children. Types of research design, It became evident early in the review process that very few randomised controlled trials had been conducted. A decision was made to include observational epidemiological designs, specifically prospective cohort studies and, in the case of sudden infant death syndrome research, case,control studies. Purely descriptive and cross-sectional studies were excluded, as were qualitative studies and all other forms of evidence. A number of criteria have been proposed to establish causation in the scientific and medical literature. These key criteria were applied in the review process and are described as follows: (i) consistency and unbiasedness of findings; (ii) strength of association; (iii) temporal sequence; (iv) dose,response relationship; (v) specificity; (vi) coherence with biological background and previous knowledge; (vii) biological plausibility; and (viii) experimental evidence. Studies that did not meet the requirement of appropriate temporal sequencing of events and studies that did not present an estimate of the strength of association were not included in the final review. Types of outcome measures,Our specific interest was pacifier use related to: ,breast-feeding; ,sudden infant death syndrome; ,infection; ,dental malocclusion. Studies that examined pacifier use related to procedural pain relief were excluded. Studies that examined the relationship between pacifier use and gastro-oesophageal reflux were also excluded as this information has been recently presented as a systematic review. Search strategy, The review comprised published and unpublished research literature. The search was restricted to reports published in English, Spanish and German. The time period covered research published from January 1960 to October 2003. A protocol developed by New Zealand Health Technology Assessment was used to guide the search process. The search comprised bibliographic databases, citation searching, other evidence-based and guidelines sites, government documents, books and reports, professional websites, national associations, hand search, contacting national/international experts and general internet searching. Assessment of quality, All studies identified during the database search were assessed for relevance to the review based on the information provided in the title, abstract and descriptor/MeSH terms, and a full report was retrieved for all studies that met the inclusion criteria. Studies identified from reference list searches were assessed for relevance based on the study title. Keywords included: dummy, dummies, pacifier(s), soother(s), comforter(s), non-nutritive sucking, infant, child, infant care. Initially, studies were reviewed for inclusion by pairs of principal investigators. Authorship of articles was not concealed from the reviewers. Next, the methodological quality of included articles was assessed independently by groups of three or more principal investigators and clinicians using a checklist. All 20 studies that were accepted met minimum set criteria, but few passed without some methodological concern. Data extraction, To meet the requirements of the Joanna Briggs Institute, reasons for acceptance and non-acceptance at each phase were clearly documented. An assessment protocol and report form was developed for each of the three phases of review. The first form was created to record investigators' evaluations of studies included in the initial review. Those studies that failed to meet strict inclusion criteria were excluded at this point. A second form was designed to facilitate an in-depth critique of epidemiological study methodology. The checklist was pilot tested and adjustments were made before reviewers were trained in its use. When reviewers could not agree on an assessment, it was passed to additional reviewers and discussed until a consensus was reached. At this stage, studies other than cohort, case,control and randomised controlled trials were excluded. Issues of clarification were also addressed at this point. The final phase was that of integration. This phase, undertaken by the principal investigators, was assisted by the production of data extraction tables. Through a process of trial and error, a framework was formulated that adequately summarised the key elements of the studies. This information was tabulated under the following headings: authors/setting, design, exposure/outcome, confounders controlled, analysis and main findings. Results, With regard to the breast-feeding outcome, 10 studies met the inclusion criteria, comprising two randomised controlled trials and eight cohort studies. The research was conducted between 1995 and 2003 in a wide variety of settings involving research participants from diverse socioeconomic and cultural backgrounds. Information regarding exposure and outcome status, and potential confounding factors was obtained from: antenatal and postnatal records; interviews before discharge from obstetric/midwifery care; post-discharge interviews; and post-discharge postal and telephone surveys. Both the level of contact and the frequency of contact with the informant, the child's mother, differed widely. Pacifier use was defined and measured inconsistently, possibly because few studies were initiated expressly to investigate its relationship with breast-feeding. Completeness of follow-up was addressed, but missing data were not uniformly identified and explained. When comparisons were made between participants and non-participants there was some evidence of differential loss and a bias towards families in higher socioeconomic groups. Multivariate analysis was undertaken in the majority of studies, with some including a large number of sociodemographic, obstetric and infant covariates and others including just maternal age and education. As might be expected given the inconsistency of definition and measurement, the relationship between pacifier use and breast-feeding was expressed in many different ways and a meta-analysis was not appropriate. In summary, only one study did not report a negative association between pacifier use and breast-feeding duration or exclusivity. Results indicate an increase in risk for a reduced overall duration of breast-feeding from 20% to almost threefold. The data suggest that very infrequent use may not have any overall negative impact on breast-feeding outcomes. Six sudden infant death syndrome case,control studies met the criteria for inclusion. The research was conducted with information gathered between 1984 and 1999 in Norway, UK, New Zealand, the Netherlands and USA. Exposure information was obtained from a variety of sources including: hospital and antenatal records, death scene investigation, and interview and questionnaire. Information for cases was sought within 2 days after death, within 2,4 weeks after death and in one study between 3 and 11 years after death. Information for controls was sought from as early as 4 days of a nominated sudden infant death syndrome case, to between 1 and 7 weeks from the case date, and again in one study some 3,11 years later. In the majority of the studies case ascertainment was determined by post-mortem. Pacifier use was again defined and measured somewhat inconsistently. All studies controlled for confounding factors by matching and/or using multivariate analysis. Generally, antenatal and postnatal factors, as well as infant care practices, and maternal, family and socioeconomic issues were considered. All five studies reporting multivariate results found significantly fewer sudden infant death syndrome cases used a pacifier compared with controls. That is, pacifier use was associated with a reduced incidence of sudden infant death syndrome. These results indicate that the risk of sudden infant death syndrome for infants who did not use a pacifier in the last or reference sleep was at least twice, and possibly five times, that of infants who did use a pacifier. Three studies reported a moderately sized positive association between pacifier use and a variety of infections. Conversely, one study found no positive association between pacifier use at 15 months of age and a range of infections experienced between the ages of 6 and 18 months. Given the limited number of studies available and the variability of results, no meaningful conclusions could be drawn. Five cohort studies and one case,control study focused on the relationship between pacifier use and dental malocclusion. Not one of these studies reported a measure of association, such as an estimate of relative risk. It was therefore not possible to include these studies in the final review. Implications for practice, It is intended that this review be used as the basis of a ,best practice guideline', to make health professionals aware of the research evidence concerning these health and developmental consequences of pacifier use, because parents need clear information on which they can base child care decisions. With regard to the association between pacifier use and infection and dental malocclusion it was found that, due to the paucity of epidemiological studies, no meaningful conclusion can be drawn. There is clearly a need for more epidemiological research with regard to these two outcomes. The evidence for a relationship between pacifier use and sudden infant death syndrome is consistent, while the exact mechanism of the effect is not well understood. As to breast-feeding, research evidence shows that pacifier use in infancy is associated with a shorter duration and non-exclusivity. It is plausible that pacifier use causes babies to breast-feed less, but a causal relationship has not been irrefutably proven. Because breast-feeding confers an important advantage on all children and the incidence of sudden infant death syndrome is very low, it is recommended that health professionals generally advise parents against pacifier use, while taking into account individual circumstances. [source] Sunscreen protection in the ultraviolet A region: how to measure the effectivenessPHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 1 2001C. Cole Products containing ultraviolet (UV) radiation absorbing or scattering ingredients provide varying degrees of protection from sunlight (or other UV sources), thus minimizing the deleterious effects on the skin. The "sun protection factor" (SPF) of sunscreen products has become a well recognized indicator of protection against sunburn induced predominantly by ultraviolet B radiation (UVB: 290,320 nm). A similar system of denoting sunscreen protection from ultraviolet A (UVA: 320,400 nm) radiation has not been universally recognized. A variety of test methods have been proposed, both in vitro and in vivo, each with specific virtues and shortcomings. Regulatory agencies and industry have been reviewing the available methods over the past decade in an effort to develop consumer meaningful claims and appropriate substantiation methods. This article reviews these test methodologies, in vitro and in vivo, as well as the biological background that establishes the need for UVA protection, and the UVA content of solar radiation and its variability. [source] Determination of 13C/12C ratios of endogenous urinary steroids: method validation, reference population and application to doping control purposesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2008Thomas Piper The application of a comprehensive gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS)-based method for stable carbon isotopes of endogenous urinary steroids is presented. The key element in sample preparation is the consecutive cleanup with high-performance liquid chromatography (HPLC) of underivatized and acetylated steroids, which allows the isolation of ten analytes (11, -hydroxyandrosterone, 5, -androst-16-en-3, -ol, pregnanediol, androsterone, etiocholanolone, testosterone, epitestosterone, 5, -androstane-3,,17, -diol, 5, -androstane-3,,17, -diol and dehydroepiandrosterone) from a single urine specimen. These steroids are of particular importance to doping controls as they enable the sensitive and retrospective detection of steroid abuse by athletes. Depending on the biological background, the determination limit for all steroids ranges from 5 to 10,ng/mL for a 10,mL specimen. The method is validated by means of linear mixing models for each steroid, which covers repeatability and reproducibility. Specificity was further demonstrated by gas chromatography/mass spectrometry (GC/MS) for each analyte, and no influence of the sample preparation or the quantity of analyte on carbon isotope ratios was observed. In order to determine naturally occurring 13C/12C ratios of all implemented steroids, a reference population of n,=,61 subjects was measured to enable the calculation of reference limits for all relevant steroidal , values. Copyright © 2008 John Wiley & Sons, Ltd. [source] Computer programming and biomolecular structure studies: A step beyond internet bioinformaticsBIOCHEMISTRY AND MOLECULAR BIOLOGY EDUCATION, Issue 1 2006Vladimir A. Liki Abstract This article describes the experience of teaching structural bioinformatics to third year undergraduate students in a subject titled Biomolecular Structure and Bioinformatics. Students were introduced to computer programming and used this knowledge in a practical application as an alternative to the well established Internet bioinformatics approach that relies on access to the Internet and biological databases. This was an ambitious approach considering that the students mostly had a biological background. There were also time constraints of eight lectures in total and two accompanying practical sessions. The main challenge was that students had to be introduced to computer programming from a beginner level and in a short time provided with enough knowledge to independently solve a simple bioinformatics problem. This was accomplished with a problem directly relevant to the rest of the subject, concerned with the structure-function relationships and experimental techniques for the determination of macromolecular structure. [source] Phenotypic characteristics of temporal lobe epilepsy: the impact of hippocampal sclerosisACTA NEUROLOGICA SCANDINAVICA, Issue 2009K. Heuser Objectives , Whether mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) is a condition with a unique biological background that can be delineated from other TLE, is unresolved. Here we performed a comparative analysis of two TLE patient cohorts , one cohort with HS and one without HS , in order to identify phenotypic characteristics specifically associated with MTLE-HS. Methods , Epidemiological data and clinical and diagnostic features were compared between patients with MTLE-HS and TLE patients without HS. When appropriate, data were compared with healthy controls. Results , Fifty-six (26%) patients were diagnosed with MTLE-HS and 162 (74%) with other TLE. Age at epilepsy onset was lower in patients with MTLE-HS (P = 0.003) than in TLE patients without HS. Incidence of simple partial seizures was higher in the MTLE-HS group (P = 0.006), as were complex partial seizures (P = 0.001), ictal psychiatric symptoms (P = 0.015), and autonomic symptoms (P < 0.001). Interictal psychiatric symptoms, including depression, were less frequent in MTLE-HS (P = 0.043). MTLE-HS patients had a higher incidence of childhood febrile seizures (FS; P = 0.043) than TLE patients without HS. In contrast, the former group had the lower frequency of first-grade family members with childhood FS (P = 0.019). Conclusions , We identified phenotypic characteristics that distinguish MTLE-HS from other types of TLE. These characteristics will be important in diagnostics, treatment, and determination of prognosis, and provide a basis for future phenotype,genotype studies. [source] | ||||||||||