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PubMed1992

Current concepts in embryonic craniofacial development.

Embryology mirrors phylogeny. The phenotypic expression of the genome is the result of differential gene transcription, the critically timed turning on and off of specific genes by transcription factors to produce cyto-, histo-, and morpho-differentiation that fleetingly reflects evolutionary stages of development during ontogeny. Hox genes regulate transcription of other structural genes and are responsible for patterning of the facial primordia. Cephalic development involves extremely complex morphogenetic mechanisms built on conserved elements that have undergone enormous evolutionary changes. Transient expression of phylogenetic origins characterize ontogeny and are reflected in defective development that may be due to inappropriate expression of Hox genes or distorted or disrupted epignetic processes. The mechanisms by which genetic information is transformed into morphological patterning by the actions of growth factors, morphogenes, and receptors are currently being identified. Biochemical, immunological, and allometric analyses of embryos and fetuses in experimental and descriptive studies are elucidating details of units of craniofacial morphogenesis--faciogenesis, palatogenesis, gnathogenesis, odontogenesis. Three-dimensional model computer-assisted reconstruction of sectioned embryos and fetuses provides a further technique for understanding the complex configurations of tissue migratory patterns and growth sites that account for normal and abnormal craniofaciogenesis.

Animals↗

PubMed1992

Characterization and applications of the disc angiogenesis system.

A model to study microvascular proliferation, the Disc Angiogenesis System (DAS), consists of a synthetic foam disc implanted subcutaneously in experimental animals. After a period of growth, usually 7 to 21 days, the disc is removed. Planar sections are used to measure and characterize the growth. Microvessels grow centripetally into the disc, together with fibroblasts. Concentric growth zones have been defined by light and electron microscopy. Moderate growth occurs spontaneously and is accelerated by angiogenic stimulants placed in the center of the disc. Morphometric analyses have shown that vessel growth is directly proportional to total fibrovascular growth, so the former can be quantified by procedures measuring the latter. These include manual projection of sections and computer-assisted digital image analysis, which is recommended for routine use. The proliferation of endothelial and other cells is determined by incorporation of tritiated thymidine, using scintillation counting and autoradiography. Using the DAS, well-established angiogenic agents such as basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), and prostaglandin E1 were found to increase proliferation of endothelial cells (EC) and microvessels. Heparin augmented the effect of bFGF. When used by itself heparin increased angiogenesis but not EC proliferation, in keeping with in vitro observations indicating that it stimulates migration but not proliferation of EC. Locally applied hyperthermia and ionizing radiation decreased angiogenesis, even when applied after the angiogenic stimulus. Systemic prostaglandin synthetase inhibitors antagonized the angiogenic effects of bFGF and EGF, in accordance with a postulated role of prostaglandins in the transduction of proliferative signals in microvascular EC. The DAS is easy to assemble and implant in small animals, including mice, which tolerate it well. Hence multiple discs can be used for each time or dose point, which allows reproducible measurements of vascular growth and increases statistical accuracy. Another advantage of the system is the capability of discriminating between proliferation and migration of EC and fibroblasts. The DAS can be used to test putative agonists or antagonists of angiogenesis. More generally, the DAS provides a model of wound healing, either uncomplicated or complicated by inflammation, and of angiogenic responses to solid tumors.

Animals↗

PubMed1977

[Universal measurement site for the processing-oriented recording of cardiovascular data].

A measuring place is described for the registration of standardized, evaluable by means of the computer deviations of bioelectric signals (parameters of heart and circulation, peripheral pulse curves and rheogramms). The high demands which concern the adequate establishment measuring places with regard to quality and comfort of attendance and condition corresponding technical solutions are explained. At the instance of the rheogram the mode of function is described. A short prognosis on the trend of development in the recognition of biological measuring values is given.

Cardiovascular Diseases↗

PubMed1992

Quantitation and mapping of integrated human papillomavirus on human metaphase chromosomes using a fluorescence microscope imaging system.

Integrated human papillomavirus type 16 (HPV-16) DNA was directly visualized on metaphase chromosomes in the two human cervical carcinoma cell lines SiHa and CaSki by fluorescence in situ hybridization with a biotinylated DNA probe (7.9 kb). The fluorescence intensities of hybridization signals from single copies and dispersed clusters of integrated HPV-16 DNA were quantified using a microscope equipped with a cooled-CCD camera that was interfaced to an image processor and host computer. Hybridization signals were localized on chromosomes using separate, registered images of 4',6-diamidino-2-phenylindole (DAPI) or propidium iodide stained metaphase chromosome spreads. In both SiHa and CaSki spreads, a single fluorescein signal was observed on one or both chromatids of chromosome 13, which was identified by simultaneous hybridization with a biotinylated centromere probe specific for chromosomes 13 and 21. Ratios of the distance from 13pter to the HPV-16 signals to the entire chromosome length were approximately 0.63 +/- 0.05 in both SiHa and CaSki cells, indicating the possibility of a common integration domain on chromosome 13. In SiHa cells, no additional signals were observed on other chromosomes. This observation, taken together with literature reports that SiHa cells contain 1 to 2 copies of the HPV-16 genome in this region of chromosome 13, suggests that each fluorescein signal on chromosome 13 represents one equivalent of the HPV-16 genome. The total integrated fluorescence intensity in isolated CaSki metaphase chromosome spreads was approximately two orders of magnitude greater than that of a single copy of HPV-16 DNA in SiHa cells, indicating an increase in HPV-16 copy number.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

[Color-coded duplex sonography and ultrasound contrast medium in the study of peripheral arteries--initial clinical experiences].

Ultrasound contrast agents (US-CA) amplify reflected sound waves. Most substances used as contrast agents are destroyed when passing the lungs. SH U 508 is a new US-CA that can pass the lungs without impairment after peripheral intravenous application. In a clinical trial of this US-CA, we investigated its effect on the visualization of blood movement in peripheral arteries by color-coded Duplex sonography (CCDS). The leg arteries of 20 patients with severe chronic arterial occlusion were examined by CCDS (QAD I and Platinum) after i.v. application of the US-CA. After passage of the pulmonary capillaries, the US-CA amplified blood flow signals in the arterial system in a dose-dependent manner with both systems used. Undesired side-effects were not observed. The amplification produced by appropriate concentrations of the US-CA markedly improved the visualization of blood movement. Further studies are required to determine the optimal dosage and application technique as well as the indication for using this US-CA.

Adult↗

PubMed1992

MR imaging of cerebral perfusion by phase-angle reconstruction of bolus paramagnetic-induced frequency shifts.

Phase-angle images are acquired dynamically during bolus paramagnetic contrast injection and demonstrate a phase-enhancement effect in perfused cerebral tissues. Signal-to-noise is comparable to that of susceptibility-based signal loss (delta R*) images. Assuming that phase shift is proportional to the tissue paramagnetic agent concentration, as supported by experimental data, the integrated area of the phase time response curves estimated the relative gray to white matter blood volume as 1.8:1 and was sensitive to acute ischemia. The relation between tissue phase shift and concentration is considered.

Animals↗

PubMed1992

Three-dimensional crystallographic reconstruction for atomic resolution.

Three-dimensional structures have recently been determined by electron crystallography at a resolution high enough to determine atomic arrangements in both protein and mineral specimens. The different nature of these two types of specimens produces some very significant differences in the way data is obtained and processed, although the principles are the same. The sensitivity of proteins to damage by the electron beam limits the signal-to-noise ratio in the image and the resolution to which data can be extracted from the image. A number of constraints, such as the amino acid sequence and the connectivity of atoms within amino acids, can be used in interpreting the limited image data. In materials samples, the relative insensitivity to damage allows obtaining resolution limited only by the microscope. In many samples, dynamical scattering and other non-linear effects limit the information in the image, but this limit can be circumvented by working in very thin areas of the specimen.

Bacteriorhodopsins↗

PubMedDate not supplied

Noninvasive external recording of cardiac conduction system (His bundle) activity.

Successful and adequate external recording of the cardiac conduction system from the body's surface can be accomplished in 80 to 90 percent of subjects studied. High-gain amplification, signal averaging, and triggering with a conditioned QRS signal results in good recording reproducibility. Averaging of 128 consecutive cycles is adequate, but on occasion averaging of 256 cycles may yield better results. The patients's QRS signal triggers the transfer of signals, which are digitized and stored during the preceding P-R interval. Comparison of external recordings with direct invasive recordings in animals and patients shows good correlation between the major His bundle deflections. The advantages of the system developed include its mobility, triggering the QRS with pretrigger data processing, and instantaneous display on Polaroid photograph. Future research should concentrate on further miniaturization and simplification of the instrumentation, detailed experimental comparison between direct and external recordings for identification of deflections and their origin, further study of the recording lead system, and the most appropriate method of information display.

Animals↗

PubMed1992

Alignment, classification, and three-dimensional reconstruction of single particles embedded in ice.

Cryo-electron microscopy of single biological particles poses new challenges to digital image processing due to the low signal-to-noise ratio of the data. New tools have been devised to deal with important aspects of 3-D reconstruction following the random-conical data collection scheme: (a) a new shift-invariant function has been derived, which promises to facilitate alignment and classification of single particle projections; (b) a new method of orientation search is proposed, which makes it possible to relate random-conical data sets to one another prior to reconstruction; and (c) the foundation is laid for a 3-D variance estimation which utilizes the oversampling of 3-D angular space by projections in the random-conical reconstruction scheme.

Algorithms↗

PubMedDate not supplied

Magnetization-prepared MR angiography with fat suppression and venous saturation.

Magnetization-prepared magnetic resonance (MR) angiography (MPMRA) is an inflow-based two-dimensional (2D) imaging sequence in which a preparation phase precedes rapid image acquisition. For maximal blood/tissue contrast, an inversion-recovery preparation nulls signal from static tissue. If needed, a second inversion suppresses signal from fat. Fully magnetized blood flows in after the inversion pulse(s), providing high signal intensity. The centric phase-encoding order, which ensures that the initial contrast is reflected in the image set, requires the use of a modified venous saturation technique. The sequence is described and its performance assessed with regard to (a) depiction of in-plane flow, (b) fat suppression, and (c) venous saturation. Phantom and volunteer studies showed good performance in all three areas. MPMRA images, acquired in just 2-4 seconds per image, had a blood/tissue contrast-to-noise ratio nearly twice that of standard 2D time-of-flight MR angiograms, acquired in 5-7 seconds. The technique is promising for restless patients and in anatomic areas plagued by motion degradation.

Adipose Tissue↗

PubMed1992

Uses and limitations of spoiled gradient-refocused imaging in the evaluation of suspected intracranial tumors.

This article describes the use of a radiofrequency-spoiled gradient-recalled (SPGR) imaging pulse sequence in the evaluation of intracranial masses. This pulse sequence provides excellent anatomic detail with T1-weighted image contrast. Rapid, sequential, single-slice (two-dimensional) images of the brain can be obtained in patients who are unable to hold still for long periods of time. In addition, volumetric (three-dimensional) image data sets can be obtained that provide extremely thin (1- to 2-mm) sections of high detail and good signal-to-noise ratio for selected critical structures within the brain. Finally, because SPGR is also utilized for time-of-flight angiography, parenchymal information can be obtained simultaneously with cerebral blood vessel definition. One potential pitfall that the magnetic resonance radiologist must be aware of is the fact that, in many patients, the degree of contrast enhancement is greatly diminished on postgadolinium SPGR images compared with conventional spin-echo T1-weighted images. Comparison with a set of standard spin-echo postcontrast images or, potentially, the use of higher doses of gadolinium may solve this problem. In spite of this limitation, the selective utilization of SPGR imaging can yield additional useful information for evaluation and preoperative planning in patients with intracranial masses.

Brain Neoplasms↗

PubMed1992

Focal liver lesions: MR imaging with Mn-DPDP--initial clinical results in 40 patients.

Manganese (II) N,N'-dipyridoxylethylenediamine-N,N'-diacetate-5,5'-bis(phosphate) (DPDP) was evaluated as a contrast agent for magnetic resonance (MR) imaging (1.5 T) of focal liver lesions in 40 patients. Doses of 5 and 10 mumol/kg were administered intravenously. Mn-DPDP-enhanced T1-weighted images were compared quantitatively and subjectively with standard T1- and T2-weighted nonenhanced images. Use of Mn-DPDP resulted in a statistically significant increase in signal intensity of liver parenchyma in T1-weighted images at both doses. No enhancement was seen in metastases, cholangiocarcinomas, or lymphomas, while all hepatocellular carcinomas were enhanced. Enhancement was seen in focal nodular hyperplasia and in regenerative nodules. The lesion-to-liver contrast in Mn-DPDP-enhanced gradient-recalled-echo images was superior to that of all precontrast images (P less than .01). The number of nonenhancing malignant liver lesions detected in spin-echo (SE) images was increased (272 in T2-weighted SE images vs 390 in T1-weighted Mn-DPDP-enhanced SE images). Image interpretation (eg, visualization and demarcation of the lesions) was markedly better in Mn-DPDP-enhanced images than in all precontrast images (P less than .001).

Adult↗

PubMedDate not supplied

Dynamic analysis of drug action on in vitro reconstituted thyroid follicle by microinjection of tracer molecules and videomicroscopy.

Thyroid cells isolated from the gland by trypsinization are capable in culture of reconstituting histiotypic structures, the thyroid follicles. This morphological differentiation requires the presence of the main thyroid regulator; thyrotropin. We have analyzed some structural and functional aspects of in vitro reconstituted thyroid follicles (RTF) using microinjection of fluorescent probes and videomicroscopy. This experimental approach allowed to visualize biological processes and actions of drugs, signalling factors, etc. in living cells. We describe here some examples of what can be studied with this powerful still-undervalued method. Microinjection of a cell-impermeant fluorescent probe of either high or low molecular mass into the lumen of RTF allowed to check the tightness of this compartment and therefore to analyze the control of tight junctions assembly. A small cell-impermeant probe like Lucifer Yellow microinjected into a cell was used to demonstrate and then to study the regulation of cell to cell communication via gap junctions. The presence of calcium in the lumen of RTF was detected by microinjection of a properly designed probe: Calcium Green which becomes fluorescent in the presence of the ligand. The lumen to cell transport or endocytosis of thyroglobulin, the thyroid prohormone, which is stored into the lumen of the follicles, is currently studied by microinjection of TRITC-labeled thyroglobulin. Coupled to image processing and videorecorder systems, kinetic analysis and quantitative measurements can be performed.

Animals↗

PubMed1992

A novel principle for quantitation of fast intracellular calcium changes using Fura-2 and a modified image processing system--applications in studies of neutrophil motility and phagocytosis.

A new principle is described for imaging intracellular free calcium [Ca2+]i changes in single, living cells utilizing the fluorescent probe Fura-2. It is based upon video color mixing in real time and allows high-speed visualization, at maximum image resolution, of [Ca2+]i changes without digital image ratioing. The epifluorescence images produced by 340 and 380 nm excitations are stored in two memory buffers of a personal computer-based image processing system. Two video signals are generated independently from each buffer and connected to the red and green inputs of a video display. An image is this way created, in which [Ca2+]i shows up as a specific hue, whereas changes in dye concentration, light intensity, cell thickness show up as variations in brightness of the imaged cells. The method has advantages over conventional ratio imaging, notably simplicity and speed, since no calculations are made. Yet it can be combined with traditional digital image processing. The imaging technique allows monitoring of [Ca2+]i changes in rapidly moving cells, like neutrophils. It is demonstrated that during random locomotion on serum-coated glass surfaces, [Ca2+]i levels appeared to oscillate and that the frequency of the oscillations are related to locomotive activity. Furthermore, in Ca2+ free medium, the cells continue to move and phagocytose in the presence of Ca2+ ionophore (ionomycin) and 2 mM EGTA. In the presence of 1 mM extracellular Ca2+, ionomycin-treated cells were not able to move or phagocytose.

Calcium↗

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

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

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↗