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At least 1,225 records · Page 68Linked to original sources
PubMed2003

Glucosaminylglycan biosynthesis: what we can learn from the X-ray crystal structures of glycosyltransferases GlcAT1 and EXTL2.

The X-ray crystal structures of two glycosyltransferases (GTs)--beta 1,3-glucuronyltransferase 1 (GlcAT1) and alpha 1,4-N-acetylhexosaminyltransferase (EXTL2)--have now been determined in the presence of both donor and acceptor substrates. These enzymes are involved in glucosaminylglycan (GAG) synthesis where they catalyze inverting and retaining transfer reactions, respectively. As members of a large family of enzymes that transfer sugar groups from donor nucleotide-sugars to acceptor substrates, GlcAT1 and EXTL2 retain conserved GT folds. Comparative analysis of these structures reveals signature features for selecting specific donor sugars. Adaptive binding of the disaccharide moiety of the acceptor sugars enables the enzymes to catalyze either an inverting S(N)2-type displacement reaction or a retaining S(N)i-like transfer reaction.

Amino Acid Sequence↗
PubMed1998

Effects of the calcium channel antagonist mibefradil on haemodynamic and morphological parameters in myocardial infarction-induced cardiac failure in rats.

OBJECTIVE: Calcium channel antagonists (CCA) have been proposed for the prevention of cardiac events after myocardial infarction (MI). Mibefradil is a CCA featuring a selective blockade of T-type Ca2(+)-channels. The aim of the study was to characterize the effects of mibefradil on haemodynamic and morphological parameters in a model of postMI chronic heart failure and to establish the "therapeutic window" for the start of therapy. METHODS: MI was induced by permanent ligation of the left coronary artery in male normotensive Wistar rats. Animals were assigned to placebo- or mibefradil-treated (10 mg/kg/day p.o.) groups as follows: (1) sham operation; (2) MI placebo treatment; (3) 7 days preMI start of treatment; (4) 3 h postMI start of treatment; (5) 24 h postMI start of treatment; (6) 3 days postMI start of treatment; (7) 7 days postMI start of treatment. Treatment was continued for 6 weeks postMI. At this time point, mean arterial blood pressure (MAP), heart rate, left ventricular enddiastolic pressure (LVEDP) and contraction force (dP/dtmax) were measured in conscious rats at baseline and after methoxamine (MEX; 0.5-1.0 mg/h i.v.) stimulation to increase afterload. The hearts were subjected to histological determination of infarct size (IS), infarct length (IL), noninfarcted length (NL), left ventricular circumference (LVC), inner LV-diameter (LVD) and septal thickness (ST). RESULTS: Six weeks after MI, MAP was lowered, LVEDP increased and dP/dtmax reduced. Mibefradil treatment increased basal MAP in groups 3-5 compared to the placebo-treated MI group. Under mibefradil, LVEDP was reduced at baseline in groups 3-6 and, after MEX, in all groups. dP/dtmax was increased in groups 3-4 at baseline and after MEX. In the placebo-treated MI group, the infarcted area was 39% of the LV and heart weight, LVD and LVC were increased. Heart weights of mibefradil-treated rats (groups 3-6) did not differ from those of the placebo-treated group. Early onset of treatment with mibefradil reduced IS and IL and increased NL in groups 3-4. LVD and LVC were decreased in group 3 only. ST was increased in groups 3-5. CONCLUSION: Chronic treatment with mibefradil exerts beneficial actions on cardiac structure and performance in postMI cardiac failure in rats, especially when the onset of treatment is either prior to or within hours after the acute ischemic event.

Analysis of Variance↗
PubMed2003

Molecular classification of cancer types from microarray data using the combination of genetic algorithms and support vector machines.

Simultaneous multiclass classification of tumor types is essential for future clinical implementations of microarray-based cancer diagnosis. In this study, we have combined genetic algorithms (GAs) and all paired support vector machines (SVMs) for multiclass cancer identification. The predictive features have been selected through iterative SVMs/GAs, and recursive feature elimination post-processing steps, leading to a very compact cancer-related predictive gene set. Leave-one-out cross-validations yielded accuracies of 87.93% for the eight-class and 85.19% for the fourteen-class cancer classifications, outperforming the results derived from previously published methods.

Algorithms↗
PubMed1984

Computer-aided strategies for archive retrieval and sensitivity enhancement in the identification of drugs by photodiode array detection in high-performance liquid chromatography.

An archive retrieval algorithm for high-performance liquid chromatography with UV detection (HPLC-UV) has been developed for the first time for the rapid identification of spectra acquired by rapid-scanning photodiode array detection in HPLC. The algorithm is based on a database of spectra (normalised with respect to area), inverse files of key spectral features, a selective search window, with parabolic weighting factors and least-squares comparison of test and retrieved spectra. The performance of the library search system is demonstrated with respect to a small library of solutes, including: cortisone acetate, ethynyl estradiol, ethisterone, progesterone; caffeine, theobromine, theophylline and 8-chlorotheophylline; morphine and diamorphine; and cycloserine. Since photodiode array detection operates in the domains of both wavelength and time, to generate a matrix of (A, lambda, t) data, the optimum conditions for sensitivity enhancement by ensemble averaging in these domains have been examined. At a given observation wavelength, increase in the detector bandwidth (or "diode bunching") yields a value of delta lambda which gives optimum sensitivity; this value is systematically related to the spectral bandwidth of the analyte. Sensitivity can also be optimised by varying the integration period in the time domain. Sensitivity can be further increased by combination of these instrumental optima, for which there is evidence of dependence on the particular instrument design. Response was found to be linear for detector bandwidths up to twice the optimum value. The comparative sensitivity of some commercially-available photodiode array detectors has been assessed relative to that of conventional detectors under strictly controlled conditions.

Chromatography, High Pressure Liquid↗
PubMed2001

Functional correlates of macroscopic high-frequency brain activity in the human visual system.

The present article reviews empirical findings of large-scale gamma oscillations in the human brain, in the context of their functional correlates. Evidence supporting the fact that high-frequency neuronal oscillations are involved in several aspects of visual processing is presented, with a focus on bottom-up and top-down visual feature processing, selective attention, and emotional evaluation. This evidence suggests that visual processing involves the integrated activity of wide spread neuronal assemblies that can be studied with respect to time course and topography, employing frequency-domain analyses. Possible mechanisms underlying these phenomena are considered. Furthermore, the effects of attention and motivation, as well as characteristics of experimental paradigms are discussed as determinants of reliability and validity of measures of high-frequency oscillations.

Animals↗
PubMed2000

The troubled story of tachykinins and neurokinins.

A family of peptides that shares a common C-terminal sequence (Phe-X-Gly-Leu-MetNH2) exists in mammalian and non-mammalian species. In mammals, three of these peptides (substance P, neurokinin A and neurokinin B) satisfy the criteria to be considered as neurotransmitters either in the central, peripheral or enteric nervous systems. In addition, multiple receptors for these peptides, which belong to the superfamily of G-protein-coupled receptors, exist. These receptors have distinct pharmacological features and selective agonists and antagonists are available for studying their functional roles. The latest update on nomenclature of these peptides and their receptors, which dates back to 1986, agreed to use the terms tachykinins and tachykinin NK1, NK2 and NK3 receptors. This 'nomenclature mismatch' has generated confusion that urges experts in the field of tachykinin research to provide a revised nomenclature.

Neurokinin A↗
PubMed2002

Oleamide attenuates apoptotic death in cultured rat cerebellar granule neurons.

The effect of oleamide on apoptosis was investigated by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction assay, DNA staining assay with propidium iodide and caspase-3 activity analyses. The present results showed that oleamide significantly attenuated the cell death and nuclear condensation of cultured rat cerebellar granule neurons induced by K(+) deprivation in a dose-dependent manner. The oleamide actions were well parallel with the attenuation of caspase-3 activity in the process of apoptotic death. Moreover, neither elaidic acid nor stearic acid, two fatty acids structurally related to oleamide without the Delta(9)-cis double bond, had similar effects on the cell death, suggesting the selectively structural features of oleamide required for this action. These data provided the first evidence of a protective effect of oleamide against apoptosis in a structurally specific manner.

Animals↗
PubMed1979

Studies on azotobacters prevailing in Egyptian soils.

Soil samples from different locations in Egypt, representing various types of soils, different degrees of fertility and under various standing crops, were used for isolating Azotobacter strains. Sixty Azotobacter isolates were obtained, and A. chroococcum was found to be the most predominant species (56 isolates), while A. vinclandii was sporadically found (4 isolates). Other species of the genus Azotobacter were not detected in the examined soil samples. Isolates were studied for their morphological, cultural, and physiological properties. Thirteen isolates, differing in morphological features, were selected for studying their pleomorphic character.

Azotobacter↗
PubMed1992

Cytologic diagnosis of non-oxyphil follicular neoplasias of the thyroid. Multivariate classification procedure based on quantitative nucleolar features.

The study was done on cytologic material of 58 non-oxyphil follicular neoplasias of the thyroid, 32 of which were adenomas and 26 carcinomas. Three groups of nucleolar features were quantified using a routine microscope with an ocular micrometer: frequency-, size-, and margination-related features. Since value overlap was present between two categories for all the variables, stepwise discriminant analysis was applied. The following three features were selected by the computer for calculation of one canonical discriminant function: percentage of marginated nucleoli, percentage of nuclei with one nucleolus, mean major nucleolar diameter. The percentage of agreement between morphologic and computer classifications was 95%. Two follicular adenomas were allocated to the carcinoma category, whereas one follicular carcinoma was allocated to the adenoma category. Out of 58, 52 were diagnosed by the computer into one of the two diagnostic categories with a very high probability, i.e. P greater than 0.75, the remaining 6 being considered intermediate.

Adenoma↗
PubMed2003

Overview of testing methods used in inhalation toxicity: from facts to artifacts.

For smaller rodent species, homogenous in size and growth, small head or nose-only chambers are commonly used up to subchronic exposure durations, whereas larger whole-body exposure chambers are used for long-term exposures or exposure paradigms exceeding the normal working day. The advantages and disadvantages of each different technique have already been identified and published in detail. It is often believed best that whole-body inhalation chambers simulate potential human exposure to environmental chemicals or pesticides and this serves as a justification for preferring this mode of exposure. However, real-life exposure conditions of humans cannot be readily duplicated. A comparable mode of exposure may be employed rather than duplicating both the exposure regimens and atmospheres similar to those present in real-world settings. Especially in inhalation studies with complex mixtures, in which atmosphere generation is difficult to control, non-homogenous exposure atmospheres and artifacts are more likely to occur in larger whole-body chambers than in the smaller nose-only inhalation chambers. Inhalation studies with complex mixtures not only face all the challenges of traditional inhalation toxicity testing, but also they are frequently subject to artifacts not readily detected. Thus, a disproportionation of volatile and particulate constituents might occur in inhalation chambers depend on selected technical features, i.e., whether a dynamic or (quasi)static mode of exposure is chosen. Inappropriate timing of the sampling of biological specimens may lead to the underestimation of effects, especially in whole-body exposed animals.

Administration, Inhalation↗
PubMed1998

A symmetry perceiving adaptive neural network and facial image recognition.

The paper deals with the forensic problem of comparing nearly from view and facial images for personal identification. The human recognition process for such problems, is primarily based on both holistic as well as feature-wise symmetry perception aided by subjective analysis for detecting ill-defined features. It has been attempted to approach the modelling of such a process by designing a robust symmetry perceiving adaptive neural network. The pair of images to be compared should be presented to the proposed neural network (NN) as source (input) and target images. The NN learns about the symmetry between the pair of images by analysing examples of associated feature pairs belonging to the source and the target images. In order to prepare a paired example of associated features for training purpose, when we select one particular feature on the source image as a unique pixel, we must associate it with the corresponding feature on the target image also. But, in practice, it is not always possible to fix the latter feature also as a unique pixel due to pictorial ambiguity. The robust or fault tolerant NN takes care of such a situation and allows fixing the associated target feature as a rectangular array of pixels, rather than fixing it as a unique pixel, which is pretty difficult to be done with certainty. From such a pair of sets of associated features, the NN searches out proper locations of the target features from the sets of ambiguous target features by a fuzzy analysis during its learning. If any of target features, searched out by the NN, lies outside the prespecified zone, the training of the NN is unsuccessful. This amounts to non-existence of symmetry between the pair of images and confirms non-identity. In case of a successful training, the NN gets adapted with appropriate symmetry relation between the pair of images and when the source image is input to the trained NN, it responds by outputting a processed source image which is superimposable over the target images and identity may subsequently be established by examining detailed matching in machine-made superimposed/composite images which are also suitable for presentation before the court. The performance of the proposed NN has been tested with various cases including simulated ones and it is hoped to serve as a working tool of forensic anthropologists.

Face↗
PubMed2000

MRI spectrum of cortical malformations in tuberous sclerosis complex.

The diagnostic and prognostic value of magnetic resonance imaging in the tuberous sclerosis complex has increasingly been recognized. In this paper, we review the presumed pathogenesis of the cerebral dysgenesis seen in this condition in the light of magnetic resonance imaging features of selected patients. In addition to typical findings related to tubers, we show and discuss varied cortical malformations (from simple localized cortical dysplasia to transmantle dysplasia and schizencephaly) similar to those seen in sporadic cerebral dysgenesis. These cases support the hypothesis that the tuberous sclerosis complex focally affects the radial glial-neuronal complex as a basic unit for brain development. Abnormal stem cells would create dysplastic glia and neurons that fail to differentiate, proliferate, migrate and form a normally organized cortex.

Cell Differentiation↗
PubMed1996

Vocalization and breathing during the first year of life.

Vocalization and breathing were studied in 40 healthy infants, including five boys and five girls each at ages 5 weeks, 2.5 months, 6.5 months, and 12 months. Breathing was monitored through the use of a variable inductance plethysmograph that enabled estimates of the volume changes of the rib cage, abdomen, and lung, as well as estimates of selected temporal features of the breathing cycle. Four vocalization types were studied intensively. These included cries, whimpers, grunts, and syllable utterances. Breathing behavior was highly variable across the four vocalization types, demonstrating the degrees of freedom of performance available to the infant to accomplish the aeromechanical drive required. Such behavior was influenced by body length, body position, and age, but not by vocalization type and sex. The protocol established is a useful tool for observing the natural course of the emergence of vocalization and breathing during the first year of life.

Age Factors↗
PubMed1997

Vocalization and breathing during the second and third years of life.

Vocalization and breathing were studied in 40 healthy young children, including 5 boys and 5 girls at each, of ages of 18, 24, 30, and 36 months. A variable inductance plethysmograph was used to obtain estimates of volume changes of the rib cage, abdomen, and lung, as well as estimates of selected temporal features of the breathing cycle. Results indicated that breathing behavior was influenced by height and age, but not by vocalization type or sex. Such behavior was found to be highly variable, demonstrating that these young children had multiple degrees of freedom of performance available to accomplish the aeromechanical drive required.

Abdomen↗
PubMed1998

Replication origins in yeast versus metazoa: separation of the haves and the have nots.

The recent flood of information concerning Saccharomyces cerevisiae replication origins and the proteins that interact with them contrasts alarmingly to the trickle of progress in our understanding of metazoan origins. In mammalian cells, origins are complex and heterogeneous, and appear to be selected by features of nuclear architecture that are re-established after each mitosis. Studies in Xenopus egg extracts have shown that once per cell cycle replication does not require specific origin sequences, despite the identification of functional homologues to yeast origin-binding proteins. These observations suggest that initiation of DNA replication in higher eukaryotes is focused to specific genomic regions by features of chromosome structure.

Animals↗
PubMed2003

Decision support in medicine: lessons from the HELP system.

PURPOSE: This report describes an ongoing transition from the HELP Hospital Information System to HELP II, a replacement Health Information System built to manage clinical information captured in a variety of medical settings. The focus of the article is on the medical decision support provided by this system and studied by researchers at the University of Utah and Intermountain Health Care (IHC), a large health care organization in Utah, for many years. METHODS: Select success features of the original HELP system's decision support environment are identified and lessons learned are related. Plans for transferring these features to HELP II are discussed. RESULTS: The article focuses on four features: (1) the importance of easy access to patient data essential for decision support, (2) the commitment to continued measurement and revision of both the logic and the interventional strategy in a decision support application, (3) experience with data mining as a tool for developing decision support tools, and (4) the role of clinical reports in supporting the decision making process.

Decision Support Systems, Clinical↗
PubMed1999

Constantly discontinuous EEG patterns in full-term neonates with hypoxic-ischaemic encephalopathy.

OBJECTIVES: Selected EEG features were evaluated in 21 constantly discontinuous tracings recorded on the same number of full-term neonates with hypoxic-ischaemic encephalopathy. METHODS: The tracings were examined without using interval amplitude as the basis for distinguishing between burst-suppression and nonburst-suppression patterns. RESULTS: The results were related to outcomes and other clinical parameters (severity of hypoxic-ischaemic encephalopathy, pO2 levels and drug intake). CONCLUSIONS: Features defining the grade of EEG discontinuity (i.e. maximum interval duration, minimum burst duration and interval amplitude) significantly related to outcome and, in most cases, to the grade of hypoxic-ischaemic encephalopathy. Other features (amplitude of slow waves within the burst and incidence of abnormal EEG transients) related to PO2 levels. The consumption of anticonvulsant drugs increased EEG discontinuity, but this effect did not seem dose-related. Finally, the persistence of a constantly discontinuous EEG pattern after the first week of life is a sign of unfavourable prognosis. In full-term neonates with hypoxic-ischaemic encephalopathy quantitative analysis of all constantly discontinuous EEGs seems more useful than only describing burst-suppression patterns on the basis of interval amplitude.

Brain↗
PubMed2005

On-line derivatization for resonance-enhanced multiphoton ionization time-of-flight mass spectrometry: detection of aliphatic aldehydes and amines via reactive coupling of aromatic photo ionization labels.

Resonance-enhanced multiphoton ionization time-of-flight mass spectrometry (REMPI-TOFMS) is a powerful technique for the on-line analysis of aromatic compounds with unique features regarding selectivity and sensitivity. Aliphatic compounds, however, are difficult to address by REMPI due to their unfavorable photo ionization properties. This paper describes the proof of concept for an on-line derivatization approach for converting nonaromatic target analytes into specific, photoionizable aromatic derivatives that are readily detectable by REMPI-TOFMS. A multichannel silicone trap or poly(dimethylsiloxane) (PDMS) open tubular capillary was used as a reaction medium for the derivatization of volatile alkyl aldehydes and alkylamines with aromatic "photoionization labels"and to concentrate the resulting aromatic derivatives. The aldehydes formaldehyde, acetaldehyde, acrolein, and crotonal, which when underivatized are poorly detectable by REMPI, were converted into their easily photoionizable phenylhydrazone derivatives by the on-line reaction with phenylhydrazine as reagent. Similarly, the methyl-, ethyl-, propyl-, and butylamines were converted into their REMPI-ionizable benzaldehyde alkylimine derivatives by the on-line reaction with benzaldehyde as reagent. The derivatives were thermally desorbed from the PDMS matrix and transferred into the REMPI-TOFMS for detection. The REMPI-TOFMS detection limits obtained for acetaldehyde; acrolein; crotonal; and methyl-, ethyl-, propyl-, and butylamine using this photo ionization labeling method were in the sub-parts-per-million range and, thus, readily below the permissible exposure limits set by OSHA.

Aldehydes↗