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PubMed1992

Poly(A) RNA codistribution with microfilaments: evaluation by in situ hybridization and quantitative digital imaging microscopy.

The distribution of poly(A) RNA has been visualized in single cells using high-resolution fluorescent in situ hybridization. Digital imaging microscopy was used to quantitate the signal in various cellular compartments. Most of the poly(A) signal remained associated with the cellular filament systems after solubilization of membranes with Triton, dissociation of ribosomes with puromycin, and digestion of non-poly(A) RNA with ribonuclease A and T1. The actin filaments were shown to be the predominant cellular structural elements associating with the poly(A) because low doses of cytochalasin released about two-thirds of the poly(A). An approach to assess the extent of colocalization of two images was devised using in situ hybridization to poly(A) in combination with probes for ribosomes, membranes, or F-actin. Digital imaging microscopy showed that most poly(A) spatially distributes most significantly with ribosomes, slightly less with F-actin, and least of all with membranes. The results suggest a mechanism for anchoring (and perhaps moving) much of the cellular mRNA utilizing the interaction between actin filaments and poly(A).

Actin Cytoskeleton↗
PubMed1992

Interleukin-1 is a motility factor for human breast carcinoma cells in vitro: additive effect with interleukin-6.

Interleukin-1 beta (Il-1 beta) and interleukin-1 alpha (Il-1 alpha) were shown to act as motility factors for the human breast carcinoma cell lines SK-BR-3 and ZR-75-1 in vitro. Both cytokines induced transition from the stationary to the motile phenotype (spreading). Il-1 beta stimulated translocation, shape change and random migration (chemokinesis) of SK-BR-3 cells as demonstrated by time-lapse video recordings and by a modified Boyden chamber assay. Interleukin-6 (Il-6) stimulated spreading of the SK-BR-3 cells; an additive effect with Il-1 beta on spreading and fast plasma membrane movements was evidenced. In the SK-BR-3 cell line, the signal transduction of Il-1 beta and Il-6 differed, since only the effect of Il-6 on spreading was sensitive to pertussis toxin. Both Il-1 beta and Il-6 required protein synthesis to stimulate spreading, since cycloheximide inhibited the effect of the cytokines. Induction of an autocrine loop of Il-6 in the SK-BR-3 cells by Il-1 beta was unlikely, since after stimulation with Il-1 beta, no induction of Il-6 activity was measured, nor was inhibition of stimulated spreading seen in the presence of an antiserum against Il-6. Addition of Il-8 or of an antiserum against Il-8 did not affect spreading. We concluded that Il-1 and Il-6 could act as motility factors for human breast carcinoma cells, in both an independent and an additive way.(ABSTRACT TRUNCATED AT 250 WORDS)

Breast Neoplasms↗
PubMed1992

[Clinical potentialities and limitations of two- and three-dimensional time-of-flight MR angiography in the diagnosis of carotid stenosis].

For diagnosing a carotid artery stenosis, 26 patients underwent MR angiography. A spin echo (SE) sequence with presaturation on which the flowing blood appears with low signal intensity was applied, as well as a two- and three-dimensional gradient echo (GRE) sequence with flow compensation, showing blood flow with high signal intensity. Subsequently, projection angiograms were made from the MR images with a maximum intensity projection algorithm. Degree, length and localisation of a carotid artery stenosis were reviewed. To find out the clinical usability, the results of the MR angiograms were compared subsequently with the findings of intravenous digital subtraction angiography (i.v. DSA). In comparison with DSA a correlation in the degree of stenosis was noticed in 42 out of 48 SE-, in 39 out of 52 2-D GRE and in 41 out of 48 3-D GRE sequence angiograms. The length of 34 moderate and severe stenoses, demonstrated by DSA, was overestimated 5 times with the SE-sequence, 9 times with the 3-D and 23 times with the 2-D GRE sequence. MR angiography with a 3-D GRE sequence is suitable for screening for carotid artery stenosis. In cases of severe stenosis an SE sequence should be performed for more precise delineation of the stenotic lesion.

Aged↗
PubMed1992

An NMR phased array for human cardiac 31P spectroscopy.

A four-coil phased-array 31P NMR receiver was designed and tested for human cardiac applications, to determine whether the combination of relatively high signal-to-noise ratio (SNR) and large field of view produced in 1H imaging is also realized for in vivo 31P spectroscopy. Spectra were acquired in parallel from an array of four overlapping 6.5-cm surface coils using one- and two-dimensional phase-encoding pulse sequences and were optimally combined to yield composite spectroscopic images. The phased array was found to generate useful 31P spectra from a 2.5-fold wider lateral region around the anterior myocardium than a single receiver of the same size as the array elements, with no increase in imaging time. In addition, the sensitive depth was increased by up to 2 cm over that of a single coil. Spectra could be acquired in roughly 15 min from a region extending to the middle of the heart, with voxel sizes of 2 x 2 x 4 cm3. For the average heart voxel, the SNR of the combined spectrum was higher than that of the best spectrum from any one coil in the array by 30%, with some voxels showing an increase as high as 60%.

Heart↗
PubMed1992

Magnetic resonance angiography techniques.

After a radio frequency pulse, the decay of the magnetic resonance (MR) signal is described by two relaxation processes, T1 and T2. T1 describes the rate at which the magnetization realigns itself along the external magnetic field direction (ML), and T2 describes the rate of decay of the magnetization component along the transverse axis (MT). Magnetic resonance angiography (MRA) sequences have been developed that encode flow as changes in the apparent T1 or T2 of the moving blood relative to stationary tissues. MRA sequences typically use either time-of-flight (TOF) techniques to encode T1 or phase-contrast techniques to encode T2. TOF techniques encode flow as an apparent T1 shortening through the wash-in of fully relaxed blood from outside the image volume. The shorter T1 produces an enhancement of vascular structures relative to stationary tissues. TOF methods may use either sequential two-dimensional, three-dimensional, or multi-slab three-dimensional imaging sequences to produce a three-dimensional MRA data set. Phase-contrast methods use additional magnetic field gradients to encode flow as shifts in the phase of MT. Both TOF and phase-contrast methods use maximum intensity projection (MIP) images displayed in a cine format to aid in the visualization of three-dimensional vascular structures.

Animals↗
PubMed1992

Quantification of inter- and intra-nuclear variation of fluorescence in situ hybridization signals.

This study aims at the quantification of specific DNA sequences by using fluorescence in situ hybridization (ISH) and digital imaging microscopy. The cytochemical and cytometric aspects of a quantitative ISH procedure were investigated, using human peripheral blood lymphocyte interphase nuclei and probes detecting high copy number target sequences as a model system. These chromosome-specific probes were labeled with biotin, digoxigenin, or fluorescein. Quantification of the fluorescence ISH signals was performed using an epifluorescence microscope equipped with a multi-wavelength illuminator, and a cooled charge coupled device (CCD) camera. Specific image analysis programs were developed for the segmentation and analysis of the images provided by ISH. The fluorescence intensity distributions of the ISH spots showed large internuclear variation (CVs up to 65%) for the probes used. The variation in intensity was found to be independent of the probe, the type of labeling, and the type of immunocytochemical detection used. Variation in intensity was not caused primarily by the immunocytochemical detection method, since directly fluorescein-labeled probes showed similar internuclear variation. Furthermore, it was found that different white blood cell types, which harbor different degrees of compactness of the nuclear chromatin, showed the same variation. The intra-nuclear variation in intensity of the ISH spots on the two chromosome homologs within one nucleus was significantly smaller (approximately 20%) than the inter-nuclear variation, probably due to more constant local hybridization conditions. Due to the relatively small intranuclear variation, copy number polymorphisms of the satellite DNA sequence on chromosome 1 could readily be quantified.(ABSTRACT TRUNCATED AT 250 WORDS)

Analog-Digital Conversion↗
PubMed1992

Agonist-induced [Ca2+]i waves and Ca(2+)-induced Ca2+ release in mammalian vascular smooth muscle cells.

Focal application of vasopressin to cultured vascular smooth muscle cells (A7r5 cells) elicits first a localized increase of intracellular Ca2+ concentration ([Ca2+]i) and then a wave of elevated [Ca2+]i that propagates at constant velocity throughout the cell. The cellular mechanisms of such complex spatiotemporal patterns of [Ca2+]i are of interest because they are involved fundamentally in cellular signal transduction in many types of cells. Vasopressin evoked a [Ca2+]i transient even in the absence of extracellular Ca2+, and intracellular perfusion with heparin completely blocked the response to vasopressin stimulation. Therefore the initial response to vasopressin reflects release of Ca2+ from an intracellular myo-inositol-1,4,5-trisphosphate (IP3)-sensitive Ca2+ store. We tested four hypotheses on how a localized increase in [Ca2+]i propagates as a [Ca2+]i wave throughout the entire cell: the hypotheses distinguished 1) whether IP3 or Ca2+ is the primary intracellular messenger that diffuses, and 2) whether positive feedback on the release of intracellular Ca2+ (Ca2+i) is involved (further release of Ca2+ through activation of phospholipase C by Ca2+ and increased production of IP3 or by Ca(2+)-induced Ca2+ release). The results of various experimental interventions, which included probing Ca2+i stores (heparin, caffeine, and ryanodine), were compared with predictions from mathematical models for intracellular diffusion, release, and uptake of Ca2+. We conclude that in A7r5 smooth muscle cells, which have been stimulated focally with vasopressin, Ca2+ is released initially by IP3. The localized increase in [Ca2+]i then propagates throughout the cell as a [Ca2+]i wave. Ca2+ activates its own release, through Ca(2+)-induced release of Ca2+, by diffusing to distant Ca(2+)-release sites.

Animals↗
PubMed1992

Release of intracellular calcium and modulation of membrane currents by caffeine in bull-frog sympathetic neurones.

1. Calcium release and sequestration were studied in whole-cell voltage-clamped bull-frog sympathetic neurones by image analysis of Fura-2 signals. 2. Application of caffeine (10 mM) to cells voltage clamped at -38 mV caused a rapid increase in intracellular calcium concentration ([Ca2+]i) to a mean value of 352 +/- 33 nM, which activated an outward current. In the continued presence of caffeine the rise in [Ca2+]i slowly declined to a sustained plateau of 196 +/- 20 nM (112 nM above control levels), while the outward current rapidly decayed. Peak calcium release was highest at the edge of the cell. 3. The caffeine-evoked intracellular calcium increase was reduced by two inhibitors of calcium-induced calcium release, ryanodine and procaine. The residual non-suppressible increase in [Ca2+]i may indicate that caffeine can release calcium from two pharmacologically distinct intracellular stores. 4. Inhibition of the caffeine-evoked release of calcium by ryanodine was both concentration and 'use dependent' so that the full inhibitory effect was only observed when caffeine was applied for the second time in the presence of ryanodine. In contrast, the action of procaine did not show any 'use dependence' and unlike ryanodine was fully reversible. 5. The outward current was sensitive to blockers of the large conductance calcium-activated potassium current, Ic. Analysis of variance from this current indicated that it arose at least partly from summation of spontaneous miniature outward currents. 6. The magnitude and duration of calcium release by caffeine was dependent on the resting level of intracellular calcium and the caffeine exposure time. This, together with the pharmacology of the release, suggests that caffeine increases intracellular calcium by sensitizing calcium-induced calcium release. 7. The evoked [Ca2+]i increase was enhanced in amplitude by intracellular application of Ruthenium Red. This effect was mimicked by extracellular application of the mitochondrial uncoupler carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone (FCCP) but not by internal application of FCCP or other inhibitors of mitochondrial Ca2+ uptake. This suggests that the evoked increase in [Ca2+]i is predominantly buffered by a Ruthenium Red-sensitive sequestration process which is not mitochondrial.

Animals↗
PubMedDate not supplied

MR imaging with spatially variable resolution.

In some situations it may be advantageous to produce "locally focused" magnetic resonance images that have nonuniform spatial resolution matching the expected local rate of spatial variation in the object. Because such an image has fewer pixels than a conventional image with uniformly high resolution, it can be reconstructed from fewer signals, acquired in less time. This can be done by using a highly convergent representation of the image as a sum of orthonormal functions with slow (fast) spatial variation in relatively homogeneous (heterogeneous) parts of the object. Since this series is shorter than a conventional truncated Fourier series, its terms can be calculated from a subset of the usual array of phase-encoded signals. The optimal choice of these phase encodings, which are usually scattered nonuniformly in k space, results in minimization of noise in the reconstructed image. The technique is illustrated by applying it to simulated data and to data from images of phantoms.

Computer Simulation↗
PubMed1977

The role of the digital computer in pediatric cardiology.

A digital computer system is described which allows the real-time processing of all physiological signals obtained during a heart catheterization procedure and which makes all relevant results and informations available immediately during the investigation. In addition, special electronic units and programs have been developed in our institution for the automated extraction of morphological criteria from biplane angiocardiograms. Thereby right and left ventricular volume, shape and contraction pattern can be quantitated and used to characterize the performance of the heart as muscle and pump in physical terms. Recently, complete digital processing of videoangiocardiograms has been achieved in a stroboscopic mode, each videofield in real time. Application of image enhancement, subtraction, integration and restoration techniques leads to a fundamentally improved angiocardiographic image quality for a given amount of injected contrast material. Based on eight years of experience with digital computer application in pediatric cardiology, computer technologies are considered likely to become the method of choice in the future.

Angiocardiography↗
PubMed1975

Quantitative colour-ultrasonography by means of a computer aided simultaneous tomogram.

In this newly developed method, the ultrasonic diagnosis has become quantitative. The data will remain quantitative so far as an image storage tube is used. With the conventional storage type CRT, it is impossible to memorize the reflected echo signals of different strength levels. But with our method, it becomes possible to memorize the images according to individual levels. By the direct digitalization of the ultrasonic echo images, more information is obtained from the reflected echo signals. By processing the original information with a computer, more accurate diagnosis is possible. It is hoped and believed, that this computer aided ultrasonic examination, with single scan display in colour or black and white, will further promote ultrasonic diagnosis in future.

Color↗
PubMedDate not supplied

Improving the reliability of pattern electroretinogram recording.

The pattern electroretinogram (PERG) is a small electrical response of the retina to a reversing checkerboard pattern, usually less than 6 microV in amplitude. Unfortunately, the PERG can be obscured by artifacts such as blinks, eye movements, poor fixation, and amplifier saturation. Amplitude criterion artifact rejection systems found on commercial signal averagers eliminate large amplitude artifacts but are insensitive to small amplitude artifacts associated with amplifier saturation. Such saturation often occurs for several recording sweeps after large amplitude signals such as eye blinks are rejected. The presence of post-saturation artifacts complicates clinical PERG analysis. In this paper we describe procedures to remove these small amplitude artifacts from the PERG. These include computer selection of inputs for averaging and use of tracings with small input numbers to approximate PERG amplitudes. These procedures greatly reduce the variability of PERG amplitudes in the normal population, making PERG amplitude a more reliable clinical measure.

Adolescent↗
PubMed1992

The measurement of blood flow waveforms from X-ray angiography. Part 2: Application to video recordings of digital subtraction angiography.

A method of measuring blood flow from X-ray angiograms recorded on cine film, by obtaining contrast mass values at numerous positions along individual vessels and at multiple instants of time, has been previously reported. In the present work it was hypothesized that the signal-to-noise limitations of recordings on video tape could be overcome by recording already-subtracted angiograms from a digital subtraction angiographic (DSA) system and that the spatial resolution of video was adequate to use a similar measurement method. Validation experiments were recorded, in which flows measured using a calibrated electromagnetic flowmeter passed through tubes of 4-7 mm diameter, during injections of 2-5 ml contrast medium. The video sequences were computer analysed and produced angiographic flow measurements agreeing with the electromagnetic flows to within 5 per cent. A case study of a clinical carotid artery DSA in a patient with secondary carcinoma metastases in the brain is described. It is concluded that accurate flow measurements can be made from DSA video recordings.

Algorithms↗
PubMed1992

Superresolved tomography by convex projections and detector motion.

If the spatial resolution of an image-acquisition system is limited by the size of its component detector elements, then scanning may be required for the signal to be fully sampled. In such cases interpolation methods are normally applied to reproduce a uniformly sampled signal from the set of observations. Alternatively, however, this step can be treated as a restoration problem, in which case the extra measurements made accessible by detector motion may contain sufficient information to superresolve the signal, i.e., to recover information beyond the limit normally associated with finite detector size. We describe the application of this concept to the problem of constructing the projection matrix from a set of noise-corrupted tomographic measurements made by a moving detector array. In particular we focus on the case encountered in many tomographic applications in which the spatial response functions are approximately stationary with object depth. The method of projections onto convex sets is used in conjunction with an underrelaxation scheme to recover the projection matrix, from which the image is reconstructed by the standard filtered backprojection algorithm. Simulation results demonstrate that this approach applied to data acquired by a wobbling positron emission tomography system can substantially enhance the quality of the reconstructed image, even in the presence of high levels of quantum noise. The projection-matrix recovery step can be performed in a matter of seconds; thus the benefits of signal recovery are gained without a significant sacrifice in computation time.

Image Processing, Computer-Assisted↗
PubMed1976

A system for computer-assisted ECG recording at rest and exercise.

Great investments have been made in computerized ECG interpretation but little attention has been paid to rationalization of such costly activities as recording, labelling and mounting ECGs, and still less to the presentation of ECGs. A system for such tasks is described. It includes a PDP8/E computer and modified ink jet ECG recorders, which write alphanumeric text and function as analogue input- and output-devices for the computer. On-line computer service is given independently to two laboratories for ECG at rest, VCG or exercise ECG. After averaging the ECG signal, the computer writes out a properly labelled ECG in an easily surveyable form. The visual interpretation of the ECG is entered and is then written on a new sheet together with the averaged 12-lead ECG and a rhythm strip. In exercise testing, the computer records and processes the ECG at predetermined intervals. The processing includes an automatic ST classification. A summarized presentationof the ECG before, during and after exercise allows easy visual identification of ECG changes. Experience of the system has mainly been obtained from 2 years of routine exercise ECG recording and to a limited extent from ECG and VCG recording at rest.

Cardiology↗
PubMed1992

[Conventional roentgen functional diagnosis--videodensitometry. 2. Clinical imaging site for noninvasive diagnosis of organ motion].

By means of the described system it is possible to measure and as well analog as digital process the organ movement, needing a X-ray television system for flouroscopy and a videotape for continuously recording. Using the densitometric principle measurements of time and a quantitative form analysis of the curves are performed. After border recognition and using the topometric principle, the local organ motion can be evaluated. The levels of signal and noise in the measured curves are computed by a fourier transformation. In the field of functional cardiology the video signal is recorded and processed synchronously with the electrocardiogram.

Computer Systems↗
PubMedDate not supplied

Computer-based tutorial in MR imaging.

PURPOSE: To test the effectiveness of customized software as a teaching tool to help the novice understand basic physics concepts underlying the creation of MR images via various pulse sequences. METHODS: The authors have developed animating graphic and highly interactive electronic MR audiovisual software for the Macintosh computer in the C programming language, and have integrated it into the classroom setting for teaching MR imaging physics concepts such as T1, T2, T2*, proton density, RF excitation, TR, TE, TI, flip angle, static magnetic field strength, gradient magnetic fields, section thickness, number of phase-encoding gradients, number of excitations, field of view, intersection gap, receiver bandwidth, contrast agent(s), etc. The program interactively demonstrates the effects of these variables upon such imaging objectives as voxel dimensions, section quantity, total scanned volume, signal-to-noise ratio, contrast, contrast-to-noise ratios, resolving power, and scan acquisition time. Partial saturation, gradient echo, inversion recovery, and fat-saturation imaging techniques are included. Written posttests on the syllabus covered in our basic MR course were administered to three groups: 43 student professionals (technologist/physicist/radiologist) (control professional group) before, 149 student professionals (exposed professional group) after the addition of the tutorial software into the MR course as an integral part of the teaching process, and a group of 200 pharmaceutical sales staff with little to no prior MR or scientific background (exposed pharmaceutical group). The scores were then evaluated and compared among the groups. One hundred ten students exposed to this software also anonymously rated the software on a 1 to 5 scale (harmful to very helpful, respectively) as to their feeling regarding its role in their MR educational experience and the ease with which they were able to understand the material covered in the basic MR course curriculum. RESULTS: Mean test scores were statistically significantly lower in the Control Professional Group (60%, +/- 2.59 standard error of the mean (SEM)) than in either the Exposed Pharmaceutical (73% +/- 0.75 SEM) or Exposed Professional Groups (77% +/- 0.99 SEM). The mean subjective assessment score regarding the software was 4.8 (scale 1 to 5). CONCLUSION: This custom-developed interactive MR tutorial software is demonstrated to be effective in assisting even those new to MR imaging in understanding the concepts underlying MR imaging physics in a manner that is felt to be significantly more palatable than lectures, articles, and/or textbooks alone.

Computer-Assisted Instruction↗