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At least 1,333 records · Page 74Linked to original sources
PubMed2004

The Gpmk1 MAP kinase of Fusarium graminearum regulates the induction of specific secreted enzymes.

Recently, we described Gpmk1 MAP kinase-disruption mutants of Fusarium graminearum that were fully viable in vitro, but had completely lost their ability to infect wheat. As cell wall-degrading enzymes are postulated to participate in the infection process of F. graminearum, these MAP kinase-disruption mutants were analysed for their ability to produce cell wall-degrading enzymes in vitro and compared with the wild-type strain. The gpmk1 disruption had no effect on the production of pectinolytic or amylolytic enzymes. However, Gpmk1 regulates the early induction of extracellular endoglucanase, xylanolytic, and proteolytic activities. Furthermore, the MAP kinase was responsible for the overall induction of secreted lipolytic activities. Since the disruption of the Gpmk1 MAP kinase leads to an apathogenic phenotype, these results suggest that the infection process of F. graminearum depends on the secretion of cell wall-degrading enzymes, particularly during the early infection stage. Finally, this work provides the first detailed analysis of the apathogenic phenotype of the F. graminearum Gpmk1 mutants.

Cell Wall↗
PubMed1996

On genetic map functions.

Various genetic map functions have been proposed to infer the unobservable genetic distance between two loci from the observable recombination fraction between them. Some map functions were found to fit data better than others. When there are more than three markers, multilocus recombination probabilities cannot be uniquely determined by the defining property of map functions, and different methods have been proposed to permit the use of map functions to analyze multilocus data. If for a given map function, there is a probability model for recombination that can give rise to it, then joint recombination probabilities can be deduced from this model. This provides another way to use map functions in multilocus analysis. In this paper we show that stationary renewal processes give rise to most of the map functions in the literature. Furthermore, we show that the interevent distributions of these renewal processes can all be approximated quite well by gamma distributions.

Chromosome Mapping↗
PubMed2002

Monitoring acute inflammatory processes in mouse muscle by MR imaging and spectroscopy: a comparison with pathological results.

We have studied an animal model of acute local inflammation in muscle induced by Aspergillus fumigatus by using magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS). We have compared our data to those found using histopathology and segmentation maps obtained by the mathematical processing of three-dimensional T2-weighted MRI data via a neural network. The MRI patterns agreed satisfactorily with the clinical and biological evidence of the phases of acute local infection and its evolution towards chronicity. The MRS results show a statistically significant increase in inorganic phosphate and a significant decrease in phosphocreatine levels in the inflamed region. Image segmentation made with a self-organizing, neural-network map yielded a set of ordered representatives that remained constant for all animals during the inflammatory process, allowing a non-invasive, three-dimensional identification and quantification of the inflamed infected regions by MRI.

Acute Disease↗
PubMed2002

Physical mapping of genes in somatic cell radiation hybrids by comparative genomic hybridization to cDNA microarrays.

BACKGROUND: Somatic cell mutants can be informative in the analysis of a wide variety of cellular processes. The use of map-based positional cloning strategies in somatic cell hybrids to analyze genes responsible for recessive mutant phenotypes is often tedious, however, and remains a major obstacle in somatic cell genetics. To fulfill the need for more efficient gene mapping in somatic cell mutants, we have developed a new DNA microarray comparative genomic hybridization (array-CGH) method that can rapidly and efficiently map the physical location of genes complementing somatic cell mutants to a small candidate genomic region. Here we report experiments that establish the validity and efficacy of the methodology. RESULTS: CHO cells deficient for hypoxanthine:guanine phosphoribosyl transferase (HPRT) were fused with irradiated normal human fibroblasts and subjected to HAT selection. Cy5-labeled genomic DNA from the surviving hybrids containing the HPRT gene was mixed with Cy3-labeled genomic DNA from normal CHO cells and hybridized to a microarray containing 40,185 cDNAs, representing 29,399 genes (UniGene clusters). The DNA spots with the highest Cy5:Cy3 fluorescence ratios corresponded to a group of genes mapping within a 1 Mb interval centered near position 142.7 Mb on the X chromosome, the genomic location of HPRT. CONCLUSION: The results indicate that our physical mapping method based on radiation hybrids and array-CGH should significantly enhance the speed and efficiency of positional cloning in somatic cell genetics.

Animals↗
PubMed2006

Genetic mapping of allometric scaling laws.

Many biological processes, from cellular metabolism to population dynamics, are characterized by particular allometric scaling relationships between rate and size (power laws). A statistical model for mapping specific quantitative trait loci (QTLs) that are responsible for allometric scaling laws has been developed. We present an improved model for allometric mapping of QTLs based on a more general allometry equation. This improved model includes two steps: (1) use model II regression analysis to estimate the parameters underlying universal allometric scaling laws, and (2) substitute the estimated allometric parameters in the mixture-based mapping model to obtain the estimation of QTL position and effects. This model has been validated by a real example for a mouse F2 progeny, in which two QTLs were detected on different chromosomes that determine the allometric relationship between growth rate and body weight.

Algorithms↗
PubMed2005

Processing of VEGF-A by matrix metalloproteinases regulates bioavailability and vascular patterning in tumors.

Vascular endothelial growth factor (VEGF) is a critical mediator of blood vessel formation during development and in pathological conditions. In this study, we demonstrate that VEGF bioavailability is regulated extracellularly by matrix metalloproteinases (MMPs) through intramolecular processing. Specifically, we show that a subset of MMPs can cleave matrix-bound isoforms of VEGF, releasing soluble fragments. We have mapped the region of MMP processing, have generated recombinant forms that mimic MMP-cleaved and MMP-resistant VEGF, and have explored their biological impact in tumors. Although all forms induced similar VEGF receptor 2 phosphorylation levels, the angiogenic outcomes were distinct. MMP-cleaved VEGF promoted the capillary dilation of existent vessels but mediated a marginal neovascular response within the tumor. In contrast, MMP-resistant VEGF supported extensive growth of thin vessels with multiple and frequent branch points. Our findings support the view that matrix-bound VEGF and nontethered VEGF provide different signaling outcomes. These findings reveal a novel aspect in the regulation of extracellular VEGF that holds significance for vascular patterning.

Animals↗
PubMedDate not supplied

Cortical centres underlying auditory temporal processing in humans: a PET study.

We have used positron emission tomography (PET) to test a specific hypothesis of a neural system subserving auditory temporal processing (acoustical stimulus duration discrimination). Maps of the cerebral blood flow distribution during specific stimulations were obtained from five normally-hearing and otherwise healthy subjects. The auditory stimuli consisted of sounds of varying duration and of auditorily presented words in which the duration of the initial phoneme was manipulated. All stimuli alternated with conditions of silence in a subtraction paradigm. The blood flow distribution was mapped with O-15-labelled water. The results demonstrated that stimuli requiring recognizing, memorizing, or attending to specific target sounds during temporal processing generally resulted in significant activation of both frontal lobes and the parietal lobe in the right hemisphere. Based on these results, we hypothesise that a network consisting of anterior and posterior auditory attention and short-term memory sites subserves acoustical stimulus duration perception and analysis (auditory temporal processing).

Adult↗
PubMed2002

On reducing the statespace of hidden Markov models for the identity by descent process.

Important methods for calculating likelihoods of genealogical relationships and mapping genes are based on hidden Markov models for the process of identity by descent along chromosomes. The computational time for the algorithms depends critically on the size of the statespace of the hidden Markov model. We describe the maximal grouping together of states of the model to reduce the size of the statespace. This grouping is based on pedigree symmetries. We also present an efficient algorithm for finding the maximal grouping.

Algorithms↗
PubMed1985

Structure and cotranscription of tobacco chloroplast genes for tRNAGlu(UUC), tRNATyr(GUA) and tRNAAsp(GUC).

The location and nucleotide sequences of tobacco chloroplast genes for tRNAGlu(UUC), tRNATyr(GUA) and tRNAAsp(GUC) have been determined. These genes lie midway between the genes for alpha and beta/epsilon subunits of H+-ATPase on the large single-copy region of the chloroplast DNA. The gene organization is tRNAGlu - 59bp spacer - tRNATyr - 108bp spacer - tRNAAsp on the same DNA strand. Northern blot hybridization studies revealed that these three tRNA genes are cotranscribed. The transcription initiation site was localized at 24 bp upstream from the tRNAGlu coding region and its termination site at 90 bp downstream from the tRNAAsp coding region by S1 mapping. The tricistronic tRNA precursor is thus calculated to be 512 bases long. Its processing was also studied by S1 mapping.

Base Sequence↗
PubMed2006

Quantitative analysis of brain optical images with 2D C0 complexity measure.

Optical imaging based on intrinsic signals is a powerful method to visualize the activities of neural assembly in the cortex of animals in vivo, especially the detailed functional architecture of the visual cortex. Here, a new index, two-dimensional (2D) C0 complexity has been used to give a quantitative measure of the spatial pattern of the neural activity in orientation maps optically recorded from the visual cortex of cats globally. Results show that 2D C0 complexity could be employed to reveal the dynamic process of generating an orientation map in the visual cortex, and describe the variance of the neural responses in cortical area 17 under high and normal intraocular pressure. This suggests that 2D C0 could be used as a new quantitative measure for analyzing the intrinsic signal optical images.

Algorithms↗
PubMed1986

A method for reconstructing patterns of somatosensory cerebral cortical activity.

An interactive graphics package was developed in order to acquire, display, and manipulate images of cerebral cortical autoradiographic data. The primary purpose for development of the system was to reconstruct accurate 2-dimensional maps of the functional activity within the somatosensory cerebral cortex. A Datacube Q-bus graphics module (QVG/QAF-123) was interfaced with the Micro PDP-11/23 to accept a standard RS170 video input signal, and autoradiographs of serial sections (each 20 microns thick) of a cerebral cortex were digitized individually to 768 X 512 X 8 bit resolution. Input look-up tables were used to standardize the autoradiographic data. Boundaries of the somatosensory cortex were entered (with a Summagraphics MM 1201 digitizer), and the image data was stored on disk file (a method of data compression was devised). A method for segmenting the image data for many (sequential) sections was developed that provided arrays from which the maps were generated. Thresholding, histogram equalization, edge detection and edge enhancement, and filters in both the spatial and frequency domains were employed to process the images of the maps. Plots of optical density values along any axis of the maps and gray level histograms of any map region could also be generated. Maps made by the described method are much higher in resolution than those produced by traditional (manual) methods, and permit analysis of the reconstructions in both the frequency and spatial domains.

Animals↗
PubMed1998

[Signal transductions by the MAP kinase cascades].

The classical mitogen-activated protein(MAP) kinase cascade is one of the central intracellular signaling pathways that play a crucial role in cell proliferation, cell differentiation, cell transformation, and many other cellular responses. Two novel MAP kinase cascades, the SAPK/JNK cascade and the p38/MPK2 cascade, were identified, and were shown to function in various stress responses and apoptotic processes. Intracellular distribution of classical MAP kinase kinase (MAPKK/MEK) is regulated by its nuclear export signal (NES) which may function to suppress malignant cell transformation. CRM1 protein has been identified as a receptor for leucine-rich NES. CRM1 binds to CAN/NUP214, one of nucleopore proteins, which has been suggested to be involved in myeloid leukemia. Thus, the nuclear export system may be by somehow related to cancer development.

Animals↗
PubMed2005

Localization and identification of concurrent sounds in the owl's auditory space map.

In nature, sounds from multiple sources sum at the eardrums, generating complex cues for sound localization and identification. In this clutter, the auditory system must determine "what is where." We examined this process in the auditory space map of the barn owl's (Tyto alba) inferior colliculus using two spatially separated sources simultaneously emitting uncorrelated noise bursts, which were uniquely identified by different frequencies of sinusoidal amplitude modulation. Spatial response profiles of isolated neurons were constructed by testing the source-pair centered at various locations in virtual auditory space. The neurons responded whenever a source was placed within the receptive field, generating two clearly segregated foci of activity at appropriate loci. The spike trains were locked strongly to the amplitude modulation of the source within the receptive field, whereas the other source had minimal influence. Two sources amplitude modulated at the same rate were resolved successfully, suggesting that source separation is based on differences of fine structure. The spike rate and synchrony were stronger for whichever source had the stronger average binaural level. A computational model showed that neuronal activity was primarily proportional to the degree of matching between the momentary binaural cues and the preferred values of the neuron. The model showed that individual neurons respond to and synchronize with sources in their receptive field if there are frequencies having an average binaural-level advantage over a second source. Frequencies with interaural phase differences that are shared by both sources may also evoke activity, which may be synchronized with the amplitude modulations from either source.

Acoustic Stimulation↗
PubMed2004

Simulation of QRST integral maps with a membrane-based computer heart model employing parallel processing.

The simulation of the propagation of electrical activity in a membrane-based realistic-geometry computer model of the ventricles of the human heart, using the governing monodomain reaction-diffusion equation, is described. Each model point is represented by the phase 1 Luo-Rudy membrane model, modified to represent human action potentials. A separate longer duration action potential was used for the M cells found in the ventricular midwall. Cardiac fiber rotation across the ventricular wall was implemented via an analytic equation, resulting in a spatially varying anisotropic conductivity tensor and, consequently, anisotropic propagation. Since the model comprises approximately 12.5 million points, parallel processing on a multiprocessor computer was used to cut down on simulation time. The simulation of normal activation as well as that of ectopic beats is described. The hypothesis that in situ electrotonic coupling in the myocardium can diminish the gradients of action-potential duration across the ventricular wall was also verified in the model simulations. Finally, the sensitivity of QRST integral maps to local alterations in action-potential duration was investigated.

Action Potentials↗
PubMed1985

Determination of the preexcitation focus in the W-P-W picture by isopotential body-surface mapping.

Experiences with the determination of the preexcitation focus in 13 patients with W-P-W syndrome aged 18-62 years are presented. The data of ECG mapping from the chest surface and the abdominal wall were processed by computer. For classification of the maps the criteria elaborated by Yamada et al., da Ambroggi et al., and Benson et al. were used. It was possible to determine on their basis the preexcitation focus in all examined subjects, although a reduced system of ECG leads was employed. Surface ECG mapping makes possible a more precise location of the preexcitation, which is of great clinical importance for the indication of surgical treatment, determination of prognosis and of working ability.

Adolescent↗
PubMed1993

Evaluation of secondary structure of proteins from UV circular dichroism spectra using an unsupervised learning neural network.

An optimized self-organizing map algorithm has been used to obtain protein topological (proteinotopic) maps. A neural network is able to arrange a set of proteins depending on their ultraviolet circular dichroism spectra in a completely unsupervised learning process. Analysis of the proteinotopic map reveals that the network extracts the main secondary structure features even with the small number of examples used. Some methods to use the proteinotopic map for protein secondary structure prediction are tested showing a good performance in the 200-240 nm wavelength range that is likely to increase as new protein structures are known.

Algorithms↗
PubMed2005

The Pbs2 MAP kinase kinase is essential for the oxidative-stress response in the fungal pathogen Candida albicans.

The human fungal pathogen Candida albicans responds to stress by phosphorylation of the Hog1 MAP kinase. PBS2 was cloned and shown to encode the MAP kinase kinase that is involved in this activation, as determined by immunoblot analyses using antibodies that recognize the active form of the target Hog1 protein. Characterization of pbs2 mutants revealed that they were sensitive to both osmotic and oxidative stress and that they, interestingly, displayed differential behaviour from that of hog1 mutants, losing viability when exposed to an oxidative challenge more rapidly than the hog1 strain. Hog1 and Pbs2 were also shown to be involved in the mechanism of adaptation to oxidative stress, as evidenced by the enhanced susceptibility to oxidants of pbs2 and hog1 mutants, compared with the wild-type strain, when cells were previously exposed to a low, sub-lethal concentration of hydrogen peroxide and by the PBS2-dependent diminished activation of Hog1 MAP kinase in the adaptive process. Studies with a chimaeric Hog1-green fluorescent protein fusion revealed that this protein was localized throughout the cell (being excluded from the vacuole), but concentrated in the nucleus in response to NaCl stress, a process that was dependent on the Pbs2 protein. Both Hog1 and Pbs2 also play a role in controlling the phosphorylation state of the other MAP kinases Mkc1 and Cek1, involved respectively in cell-wall integrity and invasive growth. Furthermore, it is demonstrated that PBS2 plays a role in cell-wall biogenesis in this fungal pathogen, as its deletion renders cells with an altered susceptibility to certain cell wall-interfering compounds.

Active Transport, Cell Nucleus↗
PubMed1991

Chromosomal localization of a cytochrome b5 gene to human chromosome 18 and a cytochrome b5 pseudogene to the X chromosome.

We have isolated cDNA clones that code for human cytochrome b5. Owing to the high degree of evolutionary conservation of cytochrome b5 sequences and the existence of human and rodent cytochrome b5 processed pseudogenes, we were unable to map unambiguously the chromosomal localization of the human gene(s) by Southern blot hybridization of DNA from human-rodent somatic cell hybrids. An alternative approach, based on restriction enzyme digestion of PCR-amplified DNA, enabled us to map the human cytochrome b5 gene(s) to chromosome 18 and one of its processed pseudogenes to the X chromosome. We propose the designations CYB5 and CYB5P1 for the gene and pseudogene loci, respectively.

Animals↗