Low-resolution Methods Research Articles

Magnetic resonance in the assessment of renal function.

The kidneys are the most important organs to maintain homeostasis. In the assessment of renal functional disorders laboratory tests offer only indirect hints on location of the disease; radionuclide nephrography is hampered by low spatial resolution and radiologic methods provide only limited quantitative information. The MRI technique with fast pulse sequences and renally eliminated contrast agent has the capability of combining both anatomic and functional information. This article gives an overview on functional MRI of the kidneys with its possibilities and limitations. The clinical application of functional MRI allows a better understanding of some pathologic conditions such as urinary tract obstruction, renal insufficiency, effects of extracorporeal shock wave lithotripsy, different states of hydration, effects of drugs, vascular disorders, and effects of transplantation.

Molecular HLA typing--the brave new world.

Molecular HLA typing--the brave new world.

A Chemical Method for Site-Specific Modification of RNA: The Convertible Nucleoside Approach

Knowledge of RNA structure can greatly facilitate the understanding of its biological function. However, the physical properties of RNA, especially its conformational heterogeneity, present an impediment to high-resolution structural analysis. Thus, lower resolution methods such as biochemical probing, phylogenetic analysis, and molecular modeling have come to serve an important role in RNA science. This situation has created the need for a means by which to constrain RNA structure, either to reduce its conformational flexibility or to help distinguish between alternative structural models. To address this need, we have developed chemistry that permits the site-specific introduction of functionalizable tethers into RNA. Here we report the design and synthesis of reagents for use in solid-phase RNA synthesis that allow the functionalization of the base moiety of G, C, and A residues. Upon incorporation into oligonucleotides and subsequent treatment with alkylamines, the convertible nucleoside derivatives r...

Combined PCR-heteroduplex and PCR-SSCP analysis for matching of HLA-A, -B and -C allotypes in marrow transplantation.

We describe a method for rapid matching of HLA-A, -B and -C allotypes using simultaneous polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and heteroduplex analysis. Electrophoresis is performed at ambient temperature without requirements for buffer cooling. SSCP and heteroduplexes are revealed as discrete spatially separated band clusters. Using HLA-A, -B and -C locus-specific PCR primers, matching for alleles at these loci can be performed in 5 h. We tested 17 serologically matched patient-unrelated donor pairs and found considerable microheterogeneity at the DNA level. We propose that this technology has several advantages over conventional low-resolution typing methods and represents a potentially valuable screening method in unrelated donor selection.

Protein folds: Current Opinion in Structural Biology 1992, 2:248–256

Important recent theoretical studies of proteins have aimed to provide fewer details and more global descriptions of protein folds. Several newer theoretical approaches attempt to achieve correct overall folds at less than atomic detail. Atomic structures based on these fold skletons can presumably be completed, as has been adequately demonstrated for C α coordinates. A rapid evaluation of large numbers of low-resolution fold patterns is possible by using pairwise hydrophobicities. Such lower-resolution methods are needed to model larger biological assemblies. Experimental screening of sequences by cassette mutagenesis or other similar approaches can permit a rapid cataloging of viable sequences. Also, the screening of sequences by calculation against a library of known structures has been demonstrated to be an important general method. To supplement an incomplete library of structures, however, large numbers of folded conformations could be generated by computer.

Quantitative non‐radioactive in situ hybridization of preproenkephalin mRNA with digoxigenin‐labeled cRNA probes

Non-radioactive detection of mRNA with in situ hybridization histochemistry has emerged as an important new technology for the study of gene expression. Quantitative in situ hybridization studies have generally relied upon counting of autoradiographic grains in the emulsion overlying cells containing hybridized, radioactively labeled probe. However, such high resolution studies require tedious grain counting over individual cells, frequently in addition to weeks of exposure to nuclear emulsion. The present report describes a quantitative, non-radioactive approach to the detection of a specific mRNA in the brain with the advantages of comparatively rapid tissue processing and computerized image analysis. The validity of this approach was tested by measuring the haloperidol-induced increase in the level of preproenkephalin mRNA in striatal sections of the rat brain using an RNA probe labeled with digoxigenin-11-UTP. Detection of probe hybridized to tissue sections was carried out enzymatically following complex formation with an antidigoxigenin-alkaline phosphatase conjugate. Using computerized image analysis, it was found that chronic treatment of rats with haloperidol resulted in a 50 +/- 6% increase in striatal neuronal optical density, a value in good agreement with previous studies using low-resolution radioactive methods, showing a 30-80% increase in striatal preproenkephalin mRNA hybridization signal.

The dysarthria—clumsy hand syndrome: A distinct clinical entity related to pontine infarction

Using magnetic resonance imaging, we studied 6 patients with the dysarthria-clumsy hand syndrome. All were found to have pontine infarctions contralateral to the symptomatic side. Clinically, these patients exhibited dysarthria; "clumsiness," characterized by dysmetria, dysrhythmia, dysdiadochokinesia and sometimes truncal and gait ataxia; and mild ipsilateral weakness. Previous clinical-anatomical correlations for this syndrome are limited by inconsistencies in clinical diagnostic criteria and low-resolution imaging methods. In our patients, and in a review of the literature, the overwhelming majority of patients with the dysarthria-clumsy hand syndrome had pontine infarcts. We conclude that if rigid clinical criteria are used, the label of the dysarthria-clumsy hand syndrome predicts a lesion in the contralateral basis pontis.

TEM methods for the characterization of fine metal multilayers

The applicability of a variety of TEM techniques to the study of fine metal multilayers has been investigated. Although image simulations have shown that the interpretation of high resolution images may prove difficult, it is apparent that a combination of available high and low resolution methods will enable the defect content, lattice spacings and state of interdiffusion of such films to be measured. Some of these techniques have been applied to the edge-on examination of Au/Ag multilayers, with wavelengths of 2.4–20 nm, which have been prepared by sputtering methods. Despite the introduction of considerable ion beam damage during thin foil preparation it proved relatively easy to demonstrate qualitatively that substantial interdiffusion had not occurred during fabrication and that significant coherency strains were retained.

Models for low resolution slit scan measurements based on high resolution laser scanning image analysis: DNA and nuclear dimensions

A laser scanning microscope has been developed and employed to make high precision measurements of cells from clinical cervical samples. These specimens have been stained with the DNA specific fluorochrome mithramycin and the fluorescent images analyzed to give information on nuclear size, DNA content and nuclear shape. This information has been used to develop low resolution parameters as measured with flow cytometers, thus permitting some comparisons between high resolution and low resolution features as measured from the same cells. The results indicate that both low resolution flow slit scan and high resolution pattern recognition techniques yield the same average cellular information. However, low resolution methods are insensitive to shape and the influence of shape on the broadening of low resolution features is now under investigation.

The Determination of Stellar Turbulence by Low Resolution Techniques

In this review the problem of measuring velocity field in stellar atmospheres from the observer’s point of view is presented. Our purpose here is to discuss observational methods in which detailed analysis of line profiles is not necessary, i.e. methods based on measurements of total absorption of lines (curve of growth and narrowband photometry), methods based on measurements of widths of lines (Goldberg-Unno method and curve of line width correlation) and measurements of differential line shifts. Therefore, our review will be limited to the discussion of basic assumptions of each method, to the analysis of their advantages and disadvantages, to a specification of a quantity which can be derived from a given method and finally to a brief presentation of the results. Usually, the low resolution methods provide an information about a particular component of the stellar velocity field. But the problem is more complicated as we do not know if particular components can be isolated from the stellar velocity field, thus, we do not know the real physical meaning of the measurable parameters. In this paper we shall adopt classical concept of micro- and macro-turbulence and convective type velocity. This simplified picture was criticized since 15 years on every colloquium devoted to hydrodynamic phenomena in the stellar atmospheres, but until now the theoreticians have not succeded in developing a theory which would satisfactorily interpret the observations.

The characterization of defects in crystals

Extended defects, that is, dislocations and planar defects such as stacking faults and anti-phase boundaries can be fully characterized by means of electron microscopy. In particular the position and the Burgers vector of the dislocations can be determined. The displacement vector of planar interfaces as well as the plane in which the defects are situated can be determined unambiguously. The diffraction effects on which these determinations are based are described and summarized by means of tables. Electron microscopy is not a very suitable method for the characterization of crystal perfection since only a small volume of crystal is examined. However, in conjunction with non-destructive, low resolution methods, such as etching and X-ray topography, it allows the identification of unresolved features, and hence it is possible to “calibrate” the low resolution methods.