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At least 883 records · Page 49Linked to original sources
PubMed2004

Regularising neural networks using flexible multivariate activation function.

This paper presents a new general neural structure based on nonlinear flexible multivariate function that can be viewed in the framework of the generalised regularisation networks theory. The proposed architecture is based on multi-dimensional adaptive cubic spline basis activation function that collects information from the previous network layer in aggregate form. In other words, each activation function represents a spline function of a subset of previous layer outputs so the number of network connections (structural complexity) can be very low with respect to the problem complexity. A specific learning algorithm, based on the adaptation of local parameters of the activation function, is derived. This fact improve the network generalisation capabilities and speed up the convergence of the learning process. At last, some experimental results demonstrating the effectiveness of the proposed architecture, are presented.

Learning↗
PubMed2003

Visual motion retards alternations between conflicting perceptual interpretations.

When the visual system is faced with conflicting or ambiguous stimulus information, visual perception fluctuates over time. We found that perceptual alternations are slowed when inducing stimuli move within the visual field, constantly engaging fresh, unadapted neural tissue. During binocular rivalry, dominance durations were longer when rival figures moved compared to when they were stationary, yielding lower alternation rates. Rate was not reduced, however, when observers tracked the moving targets, keeping the images on approximately the same retinal area. Alternations were reliably triggered when rival targets passed through a local region of the visual field preadapted to one of the rival targets. During viewing of a kinetic globe whose direction of rotation was ambiguous, observers experienced fewer alternations in perceived direction when the globe moved around the visual field or when the globe's axis of rotation changed continuously. Evidently, local neural adaptation is a key ingredient in the instability of perception.

Humans↗
PubMed2002

Axon guidance: proteins turnover in turning growth cones.

Accurate navigation by a neuronal growth cone requires the modulation of the growth cone's responsiveness to spatial and temporal changes in expression of guidance cues. These adaptations involve local protein synthesis and turnover in growth cones and distal axons.

Animals↗
PubMed2002

Programming of sympathoadrenal function.

Environmental exposures at crucial points in development permanently alter sympathoadrenal function in mammals. The sympathetic innervation of peripheral tissues and the responsiveness of sympathetic nerves and adrenal medulla to standard stimuli are susceptible to modification by exposures in early life, such as environmental temperature, nutrition and stress. Because the sympathetic nervous system is composed of multiple, function-specific subunits, programming of sympathetic functions occurs on a regional rather than a global basis and can aid development of a phenotype adapted to the local environment. Under some circumstances, however, adaptations in early life might prove maladaptive in adulthood and, as a consequence, might provide a basis for developmental origins of pediatric and adult disease, such as sudden infant death syndrome and obesity.

Adrenal Medulla↗
PubMed2004

The Pleistocene glaciations and the evolutionary history of the polytypic snail species Arianta arbustorum (Gastropoda, Pulmonata, Helicidae).

The evolutionary history of the snail Arianta arbustorum is controversial. This diverse, polytypic species has two distinct forms: one, with a globular shell and closed umbilicus, is found from lowland to high altitudes; the other, with a depressed shell and open umbilicus, is found at a few scattered, high altitude localities. What is the origin of these two forms? Some believe that the depressed shell is a recent, local, ecotypic adaptation to alpine environments. Others believe that this form is a relic of an ancestral condition that may have survived the Pleistocene glaciations on nunatak-like montane refugia, while the globular shell is a derived condition and its presence at high altitudes follows post-Pleistocene recolonisation. We analysed a portion of the mitochondrial gene cytochrome oxidase I for 100 snails of the species A. arbustorum, three additional Arianta species, and nine outgroup taxa from five genera, in order to understand the phylogeographic history of the species. Despite some confounding artefacts that are likely due to introgression among the morphological forms, the resulting phylogeny shows that the depressed shell is plesiomorphic, while the globular shell is derived. Moreover, their disparate histories suggest that the depressed shell variety survived the glaciations in pockets of alpine refugia, while the globular shell variety recolonised the alpine environment post-glacially.

Animals↗
PubMed2003

Tsetse fly population genetics: an indirect approach to dispersal.

Tsetse populations are distributed discontinuously, particularly the morsitans group. Dispersal among diverse populations cannot easily be measured directly because the geographical distances between them can be too great to have a reasonable expectation of recapturing experimentally released flies. Moreover, reproductive success of widely dispersed flies might be poor. The question of dispersal rates in tsetse is immediately important because area-wide eradication plans involving the sterile insect technique are under consideration. Dispersal and gene flow are important from evolutionary and historical viewpoints. An indirect method of estimating dispersal is to measure gene flow. Genetic data indicate surprisingly low rates of gene flow in the morsitans and palpalis groups studied to date. The underlying assumptions in making such estimates need to be examined carefully, however, before accepting firm conclusions, and further research is needed. Of particular interest is the question of tsetse adaptation to local environments.

Animals↗
PubMed2006

Genetic variation in Drosophila melanogaster pathogen susceptibility.

Genetic variation in susceptibility to pathogens is a central concern both to evolutionary and medical biologists, and for the implementation of biological control programmes. We have investigated the extent of such variation in Drosophila melanogaster, a major model organism for immunological research. We found that within populations, different Drosophila genotypes show wide-ranging variation in their ability to survive infection with the entomopathogenic fungus Beauveria bassiana. Furthermore, striking divergence in susceptibility has occurred between genotypes from temperate and tropical African locations. We hypothesize that this may have been driven by adaptation to local differences in pathogen exposure or host ecology. Genetic variation within populations may be maintained by temporal or spatial variation in the costs and benefits of pathogen defence. Insect pathogens are employed widely as biological control agents and entomopathogenic fungi are currently being developed for reducing malaria transmission by mosquitoes. Our data highlight the need for concern about resistance evolution to these novel biopesticides in vector populations.

Animals↗
PubMedDate not supplied

National strategy for mass casualty situations and its effects on the hospital.

A mass-casualty situation (MCS) usually is short in duration and resolves itself. To minimize the risks to patients during MCS, planning is essential. This article summarizes the preparations needed at the hospital level, for a local MCS involving numerous trauma victims arriving to the Emergency Department at a short notice. Experiences and conclusions related to the implementation of the Israeli strategy in one hospital that combines the responsibilities of both the military and civilians are summarized. The Ministry of Health distributes the master MCS plan to each hospital where a local committee adapts it to the specific situation in a format of standing orders. After its approval by the Ministry of Health, an annual inspection is conducted to check the ability of the staff to manage a MCS. A full-scale drill is conducted every second year during which each site's readiness level and the continuity of the flow of care are tested. In building the strategy for treating trauma victims during a MCS, a few assumptions were taken into account. The goal of treatment in a MCS is to deliver an acceptable quality of care while preserving as many lives as is possible. In theory, the capacity of the hospital is its ability to manage a load of patients in the range of 20% of the hospital bed capacity. Planning and drilling are the ways to minimize deviations from the guidelines and to avoid management mistakes. Special attention should be paid to problems related to the initial phase of receiving the first message, outside communication, inside hospital communication, and staff recruitment. Other issues include: free access to the hospital; opening a public information center; and dealing with the media and very important persons (VIPs). A new method for creating the needed MCS plan in the hospital is suggested. It is based upon knowledge of management techniques that used multi-level documents, which are spread via Intranet between the different key figures. Using this method, it is possible to keep the strategy, the source documentation, and reasons for choosing it, as well as immediate release of checklists for each functions. This detailed, time consuming work is worthwhile in the long run, when the benefits of easy updating and better preparedness are apparent.

Disaster Planning↗
PubMed2026

Matrix Mechanics Governs Mechano-Metabolic Adaptation across Cancer Grades in Bladder Spheroids.

Extracellular matrix (ECM) mechanics is pivotal regulators of tumor progression, yet how viscoelasticity and matrix architecture converge to shape metabolic and invasive adaptation remains insufficiently defined. We postulate that mechanical stimuli from the ECM induce coordinated changes in adhesive and metabolic pathways, and that the nature of this independent mechano-metabolic pathway is conserved across benign, low-invasive, and high-invasive bladder cancer phenotypes. Therefore, we engineered collagen-hyaluronan hydrogels with tunable stiffness to recapitulate soft and rigid tumor microenvironments and profiled bladder cancer spheroids representing benign, low-invasive, and highly invasive states. Integrating hydraulic force spectroscopy, rheology, and molecular phenotyping, we show that matrix stiffening differentially reprograms spheroid architecture, motility, and adhesion- and metabolism-related gene expression. Spheroid behavior emerged from the interplay between intrinsic mechanical properties, matrix rheology, and molecular adaptation. HCV29 spheroids formed rigid, compact structures, relying on cell-matrix adhesion rather than metabolic or proteolytic remodeling. HT1376 spheroids activated glycolysis (HK2) and MMP-2-dependent ECM remodeling in soft matrices, but remained largely nonmigratory, indicating decoupling of invasive priming from motility. T24 spheroids were soft, deformable, and highly migratory in compliant matrices, integrating metabolic reprogramming, adhesion remodeling (E-/N-cadherin, SDC4), and radial collagen fiber alignment to drive invasion. Notably, canonical FAK/AKT/mTOR signaling was absent across all spheroids, while pS6 ribosomal protein and ILK indicated noncanonical, SDC4/integrin-ILK-dependent mechanotransduction supporting cytoskeletal dynamics, metabolism, and ECM remodeling. Collagen organization further differed across spheroid types, with dense, radially aligned fibers in HT1376, intermediate architecture in HCV29, and loose, disorganized networks in T24, closely matching their distinct migratory behaviors and cell-ECM interactions. These findings reveal stage-specific mechanometabolic strategies in bladder cancer, demonstrating how ECM mechanics and architecture jointly guide invasion, metabolic adaptation, and local immune modulation, including the regulation of immune cell infiltration and tumor immune evasion.

Humans↗
PubMed1995

Structural basis for the catalytic activity of aspartate aminotransferase K258H lacking the pyridoxal 5'-phosphate-binding lysine residue.

Chicken mitochondrial and Escherichia coli aspartate aminotransferases K258H, in which the active site lysine residue has been exchanged for a histidine residue, retain partial catalytic competence [Ziak et al. (1993) Eur. J. Biochem. 211, 475-484]. Mutant PLP and PMP holoenzymes and the complexes of the latter (E. coli enzyme) with sulfate and 2-oxoglutarate, as well as complexes of the mitochondrial apoenzyme with N-(5'-phosphopyridoxyl)-L-aspartate or N-(5'-phosphopyridoxyl)-L-glutamate, were crystallized and analyzed by means of X-ray crystallography in order to examine how the side chain of histidine 258 can substitute as a general acid/base catalyst of the aldimine-ketimine tautomerization in enzymic transamination. The structures have been solved and refined at resolutions between 2.1 and 2.8 A. Both the closed and the open conformations, identical to those of the wild-type enzyme, were observed, indicating that the mutant enzymes of both species exhibit the same conformational flexibility as the wild-type enzymes, although in AspAT K258H the equilibrium is somewhat shifted toward the open conformation. The replacement of the active site K258 by a histidine residue resulted only in local structural adaptations necessary to accommodate the imidazole ring. The catalytic competence of the mutant enzyme, which in the forward half-reaction is 0.1% of that of the wild-type enzyme, suggests that the imidazole group is involved in the aldimine-ketimine tautomerization. However, the imidazole ring of H258 is too far away from C alpha and C4' of the coenzyme-substrate adduct for direct proton transfer, suggesting that the 1,3-prototropic shift is mediated by a water molecule. Although there is enough space for a water molecule in this area, it has not been detected. Dynamic fluctuations of the protein matrix might transiently open a channel, giving a water molecule fleeting access to the active site.

Animals↗
PubMed2005

Factors influencing acrylamide content and color in rye crisp bread.

An industrial baking procedure for yeast-leavened whole-grain rye crisp bread was adapted to local laboratory conditions to study the effect of time and temperature of baking and the addition of fructose, asparagine, and oat-bran concentrate on the acrylamide content and color of the bread. Baking time and temperature affected acrylamide content that increased from 10 to 30 mug/kg of bread at the combination of a long time and high temperature, with a significant interaction between the two factors (p < 0.008). Added asparagine had a significant effect (p < 0.001) on the formation of acrylamide, but fructose did not. There was a correlation between acrylamide content and color of the milled bread in the time-temperature experiment, but this correlation was not observed in the experiment with added precursors. Added oat-bran concentrate with high content of mixed-linkage beta-glucan did not influence the acrylamide content in the breads.

Acrylamide↗
PubMed1997

Allozyme polymorphism and geographic variation in the small brown planthopper, Laodelphax striatellus (Homoptera: Delphacidae).

The small brown planthopper, Laodelphax striatellus, immigrates annually into Japan over the East China Sea from the Asian mainland. It is not known whether this long-distance dispersal has any effect on the genetic structure of Japanese L. striatellus populations. The dispersal of L. striatellus is suspected to be relevant to the population dynamics of infection with the parasitic bacterium Wolbachia, which causes cytoplasmic incompatibility in L. striatellus. Wolbachia infection has spread within and among Japanese L. striatellus populations due to this cytoplasmic incompatibility. In the present study, the geographic differences among II L. striatellus populations from Japan and Taiwan was investigated using allozyme polymorphism. FST values on three enzyme loci (GPI, PGM, and AK) indicated a geographically differentiated population structure. Significant differentiation was found even among populations located along the course of the long-distance dispersal. The results indicated that long-range dispersal of L. striatellus does not occur regularly over the main islands of Japan and that it does not have a large effect on the population structure of L. striatellus. This conclusion is in agreement with the geographically variable life history of L. striatellus adapted to local climates. The short-term rice stripe epidemic, which is vectored by L. striatellus, in northwestern Kyushu, Japan, during 1985 and 1986 corresponds to these results. Based on the present findings, short-distance dispersal was considered to drive the spatial spread of Wolbachia infection among L. striatellus populations.

Alleles↗
PubMed2004

Bringing order out of chaos: a culturally competent approach to managing the problems of refugees and victims of organized violence.

The collaborative program of the Transcultural Psychosocial Organization (TPO) provides a community-oriented and culturally sensitive public health response to the psychosocial problems of refugees and victims of organized violence. This paper describes the 9-step model that TPO has developed as a blueprint for each new intervention. Beneficiaries participate in determining priorities and there is an orientation toward culturally competent training, capacity-building, and sustainability. Two cases, one related to Sudanese refugees in Uganda and the other to internally displaced persons and returnees in postwar Cambodia, show how the TPO intervention protocol is adapted to local settings. The paper provides preliminary evaluative comments on the model's performance.

Cambodia↗
PubMed2004

Issues in disseminating and replicating effective prevention programs.

The new frontier for prevention research involves building a scientific knowledge base on how to disseminate and implement effective prevention programs with fidelity. Toward this end, a brief overview of findings from the Blueprints for Violence Prevention-Replication Initiative is presented, identifying factors that enhance or impede a successful implementation of these programs. Findings are organized around five implementation tasks: site selection, training, technical assistance, fidelity, and sustainability. Overall, careful attention to each of these tasks, together with an independent monitoring of fidelity, produced a successful implementation with high fidelity and sustainability. A discussion of how these findings inform the present local adaptation-fidelity debate follows.

Diffusion of Innovation↗
PubMed2002

Selection and gene flow between microenvironments: the case of Drosophila at Lower Nahal Oren, Mount Carmel, Israel.

Drosophila melanogaster and D. simulans from contrasted microenvironments (south- and north-facing slopes of Lower Nahal Oren Canyon in Israel) were tested for genetic differentiation at microsatellite loci, which might be linked to differential adaptation to local ecological factors. No overall genetic differentiation was observed in either species. This indicates that the contrasted selective pressures on the two sides of the valley are not strong enough to cause population subdivision in highly mobile species such as Drosophila. Significant differences in allele frequencies were observed at two microsatellite loci, but on the whole the level of divergence we observed is far lower than has been reported previously.

Animals↗
PubMed2003

Impact of introducing quality control/quality assurance (QC/QA) guidelines in respiratory specimen processing.

OBJECTIVES: To assess the impact of the introduction of a new quality control/quality assurance (QA/QC) protocol on the processing and reporting of respiratory specimens. METHODS: After implementation of guidelines for processing respiratory specimens, an investigation was carried out over a six-month period on 200 specimens, 105 sputa, and 95 deep tracheal aspirates (DTAs), assessed blindly by two independent investigators. Data regarding disagreement were arranged into two subgroups. A minor disagreement was defined as a difference in the two assessments of < 10 or 10-25 for white blood cell (WBC) or squamous epithelial cell (SEC) counts. A major disagreement was defined as one assessor reporting < 10 and the other > 25 for either WBC count or SEC count, or one assessor reporting the specimen as non-assessable, or both assessors having a minor disagreement in both the WBC count and the SEC count. RESULTS: Agreement was obtained on 111 samples. For 45 specimens, a major disagreement was documented, and in 44 cases, a minor disagreement was recorded, WBC being the most common cause of divergence. Data for sputa and DTAs were examined separately: of 45 major disagreements, 64.4% were observed for DTAs, while minor disagreements were recorded mostly for sputa. The role of the settings in which samples were taken in affecting quality was studied. Among the 105 sputa, 27 were from Community Health Centers (CHCs) and 78 from hospitalized patients. Agreement between the two observers was obtained in 48.1% of CHC cases versus 60.2% of hospital samples. To investigate how many of the rejected samples presented WBC > 25 suggestive of infection, we looked at the 107 samples rejected during the six-month period, grouped according to the suspected diagnosis. The highest number of rejected samples falls in the category of unrelated (non-respiratory) diagnosis, and clinical suspicion is not helpful in Gram stain interpretation. The annual saving (not culturing, not testing, and not treating) derived from this simple QC procedure totals about 5000 Euro. CONCLUSIONS: Standardization in microscopic screening of respiratory samples is difficult to achieve. Criteria for rejection must be adapted to local conditions after discussion with clinicians to increase their compliance with the newly introduced guidelines and to avoid sending unnecessary specimens. The effects on patient management and cost control are significant.

Guidelines as Topic↗
PubMed1987

[Two trichostrongyloid nematodes parasitic in an African murid. III. Physiologic duality of infective larvae; as correlated with seasonal rhythms].

The third stage (the infective stage) of both species, Neoheligmonella dossoi and N. tranieri, appears simultaneously in the coprocultures in two different forms: sheathed larvae and exsheathed larvae. The exsheathed larvae show a much higher infection rate than the sheathed ones, but the last ones could exsheathed under some conditions. These larvae are called: "larvae exsheathed by aging". The percentage of exsheathed larvae is higher from April to October, this period corresponding to the rainy season on the Ivory Coast. Considering the host biological characteristics (sedentary, isolated, humid burrows) and the fact that the infection lasts 2 to 4 months, the transmission of the two Trichostrongylid species seems particularly well adapted to local conditions. Transmission appears to follow two infestation strategies, depending on the season: --A "rainy season strategy" characterized by an important initial production of larvae of which a great number are exsheathed larvae, with strong infective potential. --A "dry season strategy" characterized by sheathed larvae, produced more regularly, having a weaker infective potential, and able to exsheathe progressively.

Acclimatization↗
PubMedDate not supplied

Geographic distribution and recombination of genomic fragments on the short arm of chromosome 2 of Arabidopsis thaliana.

Range expansion from Pleistocene refugia and anthropogenic influences contribute to the present distribution pattern of Arabidopsis thaliana. We scored a genome-wide set of CAPSs and found two markers with an east-west geographic distribution across the Eurasian range of the species. Regions around the two SNPs were sequenced in 98 accessions, including newly collected plants from Middle Asia and Western Siberia. These regions correspond to a gene ( approximately 1500 bp) and a non-coding region ( approximately 500 bp) 300 kbp apart on chromosome 2. Nucleotide diversities, pi, of the two sequenced fragments were 0.0032 and 0.0130. The haplotypes of both sequences belonged to one of two groups: a rather uniform "Asian" and a more variable "European" haplotype group, on the basis of non-disjunct clusters of SNPs. Recombination between "Asian" and "European" haplotypes occurs where they meet. Especially in the "European" haplotype, many rare SNP variants representing independent mutations are scattered among the shared haplotype-specific SNPs. This agrees with previous suggestions of two large haplotype groups in A. thaliana and the post-glacial colonization of central Europe from the east and the west. A clear correlation between climatic factors and the haplotype distribution may reflect the dispersal history rather than local climate adaptation. The pattern of SNP variation within the contiguous sequences explains why only a minority of SNPs selected across the genome show evidence of this geographic pattern.

Arabidopsis↗