GABA, GABA transporters, GABA(A) receptor subunits, and GAD mRNAs in the rat parabrachial and K?lliker-Fuse nuclei

Enzymes are increasingly being used to perform regio- and enantioselective reactions in chemoenzymatic syntheses. To utilize enzymes for unphysiological reactions and to yield novel products, a broad substrate spectrum is desirable. Thiamin diphosphate (ThDP)-dependent enzymes vary in their substrate tolerance from rather strict substrate specificity (phosphoketolases, glyoxylate carboligase) to more permissive enzymes (transketolase, dihydroxyacetone synthase, pyruvate decarboxylase) and therefore differ in their potential to be used as biocatalysts. We give an overview of the known substrate spectra of ThDP-dependent enzymes and present examples of multi-enzyme or chemoenzymatic approaches which involve ThDP-dependent enzymes as biocatalysts to obtain pharmaceutical compounds as ephedrine and glycosidase inhibitors, sex pheromones as exo-brevicomin, 13C-labeled metabolites, and other intermediates as 1-deoxyxylulose 5-phosphate, a precursor of vitamins and isoprenoids.     

Influence of agronomic and climatic factors on Fusarium infestation and mycotoxin contamination of cereals in Norway

A total of 602 samples of organically and conventionally grown barley, oats and wheat was collected at grain harvest during 2002-2004 in Norway. Organic and conventional samples were comparable pairs regarding cereal species, growing site and harvest time, and were analysed for Fusarium mould and mycotoxins. Agronomic and climatic factors explained 10-30% of the variation in Fusarium species and mycotoxins. Significantly lower Fusarium infestation and concentrations of important mycotoxins were found in the organic cereals. The mycotoxins deoxynivalenol (DON) and HT-2 toxin (HT-2) constitute the main risk for human and animal health in Norwegian cereals. The impacts of various agronomic and climatic factors on DON and HT-2 as well as on their main producers F. graminearum and F. langsethiae and on total Fusarium were tested by multivariate statistics. Crop rotation with non-cereals was found to reduce all investigated characteristics significantly--mycotoxin concentrations as well as various Fusarium infestations. No use of mineral fertilisers and herbicides was also found to decrease F. graminearum, whereas lodged fields increased the occurrence of this species. No use of herbicides was also found to decrease F. langsethiae, but for this species the occurrence was lower in lodged fields. Total Fusarium infestation was decreased with no use of fungicides or mineral fertilisers, and with crop rotation, as well as by using herbicides and increased by lodged fields. Clay and to some extent silty soils seemed to reduce F. graminearum in comparison with sandy soils. Concerning climate factors, low temperature before grain harvest was found to increase DON; and high air humidity before harvest to increase HT-2. F. graminearum was negatively correlated with precipitation in July but correlated with air humidity before harvest. F. langsethiae was correlated with temperature in July. Total Fusarium increased with increasing precipitation in July. Organic cereal farmers have fewer cereal intense rotations than conventional farmers. Further, organic farmers do not apply mineral fertiliser or pesticides (fungicides, herbicides or insecticides), and have less problem with lodged fields. The study showed that these agronomic factors were related to the infestation of Fusarium species and the concentration of mycotoxins. Hence, it is reasonable to conclude that farming system (organic versus conventional) impacts Fusarium infestation, and that organic management tends to reduce Fusarium and mycotoxins. However, Fusarium infestation and mycotoxin concentrations may be influenced by a range of factors not studied here, such as local topography and more local climate, as well as cereal species and variety.     

Fast ultrasound imaging simulation in K-space

Most available ultrasound imaging simulation methods are based on the spatial impulse response approach. The execution speed of such a simulation is of the order of days for one heart-sized frame using desktop computers. For some applications, the accuracy of such rigorous simulation approaches is not necessary. This work outlines a much faster 3-D ultrasound imaging simulation approach that can be applied to tasks like simulating 3-D ultrasound images for speckle-tracking. The increased speed of the proposed simulation method is based primarily on the approximation that the point spread function is set to be spatially invariant, which is a reasonably good approximation when using polar coordinates for simulating images from phased arrays with constant aperture. Ultrasound images are found as the convolution of the PSF and an object of sparsely distributed scatterers. The scatterers are passed through an anti-aliasing filter before insertion into a regular beam-space grid to reduce the bandwidth and significantly reduce the amount of data. A comparison with the well-established simulation software package field II has been made. A simulation of a cyst image using the same input object was found to be in the order of 7000 times slower than the presented method. Following these considerations, the proposed simulation method can be a rapid and valuable tool for working with 3-D ultrasound imaging and in particular 3-D speckle-tracking.     

Ultrasound simulation of complex flow velocity fields based on computational fluid dynamics

In this work, a simulation environment for the development of flow-related ultrasound algorithms is presented. Ultrasound simulations of realistic Doppler signals require accurate modeling of blood flow. Instead of using analytically described flow behavior, complex blood movement can be derived from velocity fields obtained with computational fluid dynamics (CFD). By further modeling blood as a collection of point scatterers, resulting RF-signals can be efficiently retrieved using an existing ultrasound simulation model. The main aim of this paper is to elaborate on creating CFD-based phantoms for ultrasound simulations. The coupling of a computed flow field with an ultrasound model offers flexible control of flow and ultrasound imaging parameters, beneficial for improving and developing imaging algorithms. The proposed method was validated in a straight tube with a stationary parabolic velocity profile and further demonstrated by an eccentrically stenosis carotid bifurcation. The estimated flow velocities are in good agreement with the CFD reference, both for color flow imaging and pulsed-wave doppler simulations. The presented method can also be extended to include wall mechanics simulations in future work.     

Estimation of regurgitant volume and orifice in aorticregurgitation combining CW Doppler and parameter estimation in aWindkessel-like model

A method for noninvasive estimation of regurgitant orifice and volume in aortic regurgitation is proposed and tested in anesthetized open chested pigs. The method can be used with noninvasive measurement of regurgitant jet velocity with continuous wave ultrasound Doppler measurements together with cuff measurements of systolic and diastolic systemic pressure in the arm. These measurements are then used for parameter estimation in a Windkessel-like model which include the regurgitant orifice as a parameter. The aortic volume compliance and the peripheral resistance are also included as parameters measurements in the open chest pigs are used. Electromagnetic flow measurements in the ascending aorta and pulmonary artery are used for control, and a correlation between regurgitant volume obtained from parameter estimation and electromagnetic flow measurements of 0.95 over a range from 2.1 to 17.8 mL is obtained.     

Aquaporin-4 water channel protein in the rat retina and optic nerve: polarized expression in Müller cells and fibrous astrocytes

The water permeability of cell membranes differs by orders of magnitude, and most of this variability reflects the differential expression of aquaporin water channels. We have recently found that the CNS contains a member of the aquaporin family, aquaporin-4 (AQP4). As a prerequisite for understanding the cellular handling of water during neuronal activity, we have investigated the cellular and subcellular expression of AQP4 in the retina and optic nerve where activity-dependent ion fluxes have been studied in detail. In situ hybridization with digoxigenin-labeled riboprobes and immunogold labeling by a sensitive postembedding procedure demonstrated that AQP4 and AQP4 mRNA were restricted to glial cells, including MHller cells in the retina and fibrous astrocytes in the optic nerve. A quantitative immunogold analysis of the MHller cells showed that these cells exhibited three distinct membrane compartments with regard to AQP4 expression. End feet membranes (facing the vitreous body or blood vessels) were 10-15 times more intensely labeled than non-end feet membranes, whereas microvilli were devoid of AQP4. These data suggest that MHller cells play a prominent role in the water handling in the retina and that they direct osmotically driven water flux to the vitreous body and vessels rather than to the subretinal space. Fibrous astrocytes in the optic nerve similarly displayed a differential compartmentation of AQP4. The highest expression of AQP4 occurred in end feet membranes, whereas the membrane domain facing the nodal axolemma was associated with a lower level of immunoreactivity than the rest of the membrane. This arrangement may allow transcellular water redistribution to occur without inducing inappropriate volume changes in the perinodal extracellular space.     

Real-time strain rate imaging of the left ventricle by ultrasound

The regional function of the left ventricle can be visualized in real-time using the new strain rate imaging method. Deformation or strain of a tissue segment occurs over time during the cardiac cycle. The rate of this deformation, the strain rate, is equivalent to the velocity gradient, and can be estimated using the tissue Doppler technique. We present the strain rate as color-coded 2-dimensional cine-loops and color M-modes showing the strain rate component along the ultrasound beam axis. We tested the method in 6 healthy subjects and 6 patients with myocardial infarction. In the healthy hearts, a spatially homogeneous distribution of the strain rate was found. In the infarcted hearts, all the infarcted areas in this study showed up as hypokinetic or akinetic, demonstrating that this method may be used for imaging of regional dysfunction. Shortcomings of the method are discussed, as are some possible future applications of the method.     

A simple and efficient method for objective discrimination between pseudostratified,metaplastic and dysplastic nasal epithelium

Morphologic features may sometimes be interpreted differently by different pathologists. By introducing objective methods in the histological evaluation the subjectivity of the judgement is reduced and a higher degree of consistency achieved. In the present study three linear parameters of nasal epithelial basal cells: the largest transversal nuclear diameter, the sum of the longitudinal and transversal nucleolar axes and the basal cell width, i.e. the width of the attachment face to the basement membrane, were classified by means of three-class rulers. From this classification weighted indices were made which were then given equal weight and transformed, so that when added up their sum, the joint index (Q) to the largest possible extent was consistent with pseudostratified/stratified cuboidal, stratified squamous and dysplastic epithelium when Q ≤ 1, 1 < Q ≤ 2 and Q > 2 respectively. Tested prospectively we found 91% agreement between the morphometric and histological classification. The method presented is extremely simple and rapid to perform, and appears to have diagnostic potential in distinguishing various types of epithelial alterations of the nasal mucosa. The method may also be useful in approaching similar problems in other epithelia.     

Effective timestamping in databases

Many existing database applications place various timestamps on their data, rendering temporal values such as dates and times prevalent in database tables. During the past two decades, several dozen temporal data models have appeared, all with timestamps being integral components. The models have used timestamps for encoding two specific temporal aspects of database facts, namely transaction time, when the facts are current in the database, and valid time, when the facts are true in the modeled reality. However, with few exceptions, the assignment of timestamp values has been considered only in the context of individual modification statements. This paper takes the next logical step: It considers the use of timestamping for capturing transaction and valid time in the context of transactions. The paper initially identifies and analyzes several problems with straightforward timestamping, then proceeds to propose a variety of techniques aimed at solving these problems. Timestamping the results of a transaction with the commit time of the transaction is a promising approach. The paper studies how this timestamping may be done using a spectrum of techniques. While many database facts are valid until now, the current time, this value is absent from the existing temporal types. Techniques that address this problem using different substitute values are presented. Using a stratum architecture, the performance of the different proposed techniques are studied. Although querying and modifying time-varying data is accompanied by a number of subtle problems, we present a comprehensive approach that provides application programmers with simple, consistent, and efficient support for modifying bitemporal databases in the context of user transactions. Received: March 11, 1998 / Accepted July 27, 1999