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At least 19 recordsLinked to original sources

PubMed1990

Spatiotemporal segregation of endothelial cell integrin and nonintegrin extracellular matrix-binding proteins during adhesion events.

Bovine aortic endothelial cell (BAEC) attachments to laminin, fibronectin, and fibrinogen are inhibited by soluble arginine-glycine-aspartate (RGD)-containing peptides, and YGRGDSP activity is responsive to titration of either soluble peptide or matrix protein. To assess the presence of RGD-dependent receptors, immunoprecipitation and immunoblotting studies were conducted and demonstrated integrin beta 1, beta 3, and associated alpha subunits as well as a beta 1 precursor. Immunofluorescence of BAECs plated on laminin, fibronectin, and fibrinogen reveals different matrix-binding specificities of each of these integrin subclasses. By 1 h after plating, organization of beta 1 integrin into fibrillar streaks is influenced by laminin and fibronectin, whereas beta 3 integrin punctate organization is influenced by fibrinogen and the integrin spatial distribution changes with time in culture. In contrast, the nonintegrin laminin-binding protein LB69 only organizes after cell-substrate contact is well established several hours after plating. Migration of BAECs is also mediated by both integrin and nonintegrin matrix-binding proteins. Specifically, BAEC migration on laminin is remarkably sensitive to RGD peptide inhibition, and, in its presence, beta 1 integrin organization dissipates and reorganizes into perinuclear vesicles. However, RGD peptides do not alter LB69 linear organization during migration. Similarly, agents that block LB69--e.g., antibodies to LB69 as well as YIGSR-NH2 peptide--do not inhibit attachment of nonmotile BAECs to laminin. However, both anti-LB69 and YIGSR-NH2 inhibit late adhesive events such as spreading. Accordingly, we propose that integrin and nonintegrin extracellular matrix-binding protein organizations in BAECs are both temporally and spatially segregated during attachment processes. High affinity nonintegrin interaction with matrix may create necessary stable contacts for longterm attachment, while lower affinity integrins may be important for initial cell adhesion as well as for transient contacts of motile BAECs.

Acid Phosphatase↗

PubMed1987

Epithelial-mesenchymal interactions in the developing kidney lead to expression of tenascin in the mesenchyme.

Tenascin, a mesenchymal extracellular matrix glycoprotein, has been implicated in epithelial-mesenchymal interactions during fetal development (Chiquet-Ehrismann, R., E. J. Mackie, C. A. Pearson, T. Sakakura, 1986, Cell, 47:131-139). We have now investigated the expression of tenascin during embryonic development of the mouse kidney. In this system, mesenchymal cells convert into epithelial cells as a result of a tissue interaction. By immunofluorescence, tenascin could not be found in the mesenchyme until kidney tubule epithelial began to form. It then became detectable around condensates and s-shaped bodies, the early stages of tubulogenesis. In an in vitro culture system, tenascin expression by the mesenchyme is tightly coupled to the de novo formation of epithelial, and does not occur if tubulogenesis is suppressed. The results strongly suggest that the formation of the new epithelium stimulates the expression of tenascin in the nearby mesenchyme. During postnatal development, the expression of tenascin decreases and the spatial distribution changes. In kidneys from adult mice, no tenascin can be found in the cortex, but interspersed patches of staining are visible in the medullary stroma. The results strongly support the view that tenascin is involved in epithelial-mesenchymal interactions. It could therefore be crucial for embryonic development.

Animals↗

PubMed1993

Analysis of myocardial oedema by magnetic resonance imaging early after coronary artery occlusion with or without reperfusion.

OBJECTIVE: The aim was to analyse the relationship between magnetic resonance (MR) imaging parameters and myocardial water content early after coronary occlusion with or without reperfusion. METHODS: 21 pigs were used. After 78 min of coronary occlusion (n = 7) or 48 min of coronary occlusion and 30 min of reperfusion (n = 14) the heart was excised. In seven animals in the reperfusion protocol the area at risk was perfused for 5 min with an anoxic buffer, starting 5 min after coronary occlusion. Serial T2 weighted and density weighted images of the heart were obtained from apex to base, by using a 1.5 tesla magnetic resonance imager. Water content was measured in samples from control and at-risk myocardium and relaxation parameters were measured in corresponding areas of the magnetic resonance images. RESULTS: Water content was 399(SEM 2) ml x 100 g-1 dry tissue in control myocardium, 427(8) in ischaemic myocardium, and 511(8) in reperfused myocardium (p < 0.001). Reperfused myocardium that had received intracoronary infusion contained less water than myocardium that did not: 498(9) v 534(4) ml x 100 g-1 (p = 0.003). T2 relaxation time and T2 weighted signal intensity in the different sampling sites of magnetic resonance images correlated well with water content in the corresponding myocardial samples (r = 0.76 and r = 0.83) and with the relative volume of extracellular space, as calculated by quantitative histology (r = 0.58 and r = 0.59, p < 0.001). The increase in T2 weighted signal intensity in the area at risk with respect to control myocardium allowed differentiation between ischaemic and reperfused myocardium [9(8)% v 63(3)% respectively]. The area at risk measured by MR imaging correlated very well with that determined at pathology by the fluorescein method (r = 0.92). CONCLUSIONS: Magnetic resonance imaging allows evaluation of myocardial oedema associated with acute coronary occlusion and reperfusion, and analysis of its spatial distribution. Changes in myocardial water content occurring early during acute myocardial infarction allow quantification of the area at risk and detection of reperfusion by magnetic resonance imaging.

Animals↗

PubMed1993

Distributed changes in c-Fos and c-Jun immunoreactivity in the rat brain associated with arousal and habituation to novelty.

The effects of exposure to spatial novelty on expression of the immediate early gene (IEG) products c-Fos and c-Jun were mapped in the rat brain by immunohistochemistry. Adult male Sprague-Dawley rats were tested for 10 min in a Làt-maze, and corner-crossings, rearings, and fecal boli were recorded. Rats were sacrificed at different time intervals after exposure to the maze (0.5, 2, 6, or 24 h). Unexposed rats or rats repeatedly exposed for 3 days at 24 h interval served as controls. Nonperfused brains were processed for immunocytochemistry for c-Fos and c-Jun on adjacent slices using the avidin-biotin method and diaminobenzidine as chromogen. In unexposed control rats the constitutive expression of the two IEGs products was low and scattered. In contrast, rats that had been exposed for the first time to the maze (spatial novelty) showed an extensive c-Fos- and c-Jun-like immunoreactivity in the reticular formation, the caudate-putamen complex, the hippocampus (granular and pyramidal neurons), the cerebellum (granular neurons), and all layers of somatosensory cortex. The positivity was stronger in rats exposed for the first time to the box than in repeatedly exposed or unexposed control rats. A maximal IEG expression was found in animals with postexposure survival times of 2 and 6 h. IEG expression in repeatedly exposed rats was still above baseline expression of unexposed rats but still lower than that of rats having been exposed only once to the maze.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Spatial redistribution of ribosomal chromatin in the fibrillar centres of human circulating lymphocytes after stimulation of transcription.

We have studied the distributional changes of the completely extended ribosomal chromatin present in the fibrillar centres of resting human lymphocytes after phytohemagglutinin (PHA) treatment. In thin sections of resting lymphocytes selectively stained for DNA, the extended non-nucleosomal chromatin was located in a solitary, large agglomerate which corresponds to the solitary, large fibrillar centre observed in uranium-lead-stained sections. At 20 h after PHA stimulation the ribosomal chromatin agglomerate appeared to be fragmented into smaller agglomerates which correspond to numerous fibrillar centres surrounded by a thick rim of dense fibrillar component. The mean area of ribosomal chromatin agglomerates from resting lymphocytes was found to be 0.772 mu 2 + 0.125 SD, whereas in stimulated lymphocytes it was found to be 0.184 mu 2 + 0.052 SD. At 20 h after PHA treatment ribosomal RNA (rRNA) synthesis was 8-fold greater than the control value, whereas DNA synthesis had not started. These results indicate that ribosomal chromatin of resting lymphocyte fibrillar centres contains transcribable sequences, temporally not expressed.

Chromatin↗

PubMed1995

EMG activation patterns during force production in precision grip. II. Muscular synergies in the spatial and temporal domain.

Electromyographic (EMG) activity was analyzed for the occurrence of synergistic patterns during the steady hold periods of force in the precision grip. To establish the presence of muscle synergies in the amplitude (spatial) domain, the EMG activation levels of pairs of simultaneously active muscles were linearly correlated. Cross-correlations of EMG activity were computed to quantify muscle synergies in the spatiotemporal domain (synchronization). A muscle pair was defined to be synergistically coupled or synchronously activated when the correlation (amplitude domain) or cross-correlation (time domain) was significant for at least two of the three steady state force levels. Muscle synergies in the amplitude domain were found in one-third of the 213 muscle pairs tested, distributed among 47 of the 82 tested muscle combinations. Coactivation was the predominant synergistic pattern, whereas trade-off comprised not more than 23% of the synergies. Cross-correlation peak size varied between 5 and 39% of the autocorrelation size, with delays in the range of +/- 8 ms and base width between 12 and 20 ms. Synchronization was found in one-fourth of the 213 muscle pairs tested and among 35 of the 82 muscle combinations, i.e., less frequently than covariation of EMG activity levels. However, the interindividual prevalence was higher for synchronization than for synergies in the amplitude domain, since, for the synergistic muscle combinations, almost twice as many muscle pairs were found to be synchronized than coupled in the amplitude domain. Synergies in the two domains occurred independently in some pairs and concurrently in other cases, and were observed between muscles moving the thumb, the index finger, or both digits. Synchronization was more frequent in pairs of muscles supplied by branches of the same peripheral nerve (46%) than in those innervated by different nerves (18%). Synergies in the amplitude domain were distributed in similar proportions across intrinsic, extrinsic, and combinations of both types of muscles, whereas synchronization mainly occurred in pairs of intrinsic muscles. When the task was repeated with slightly lower target forces, there were fewer synergies in the amplitude domain (in 52 of the 213 pairs, distributed among 35 of 82 muscle combinations) and their distribution changed, indicating a flexible, force-dependent mechanism. In conclusion, no strictly coherent interindividual pattern of synergies in the spatial domain could be established.

Adult↗

PubMed1989

Spatial and temporal expression of acetylcholine receptor RNAs in innervated and denervated rat soleus muscle.

In adult vertebrate skeletal muscle acetylcholine receptors are localized to the neuromuscular junction. Upon denervation, this distribution changes, with new receptors appearing in extrajunctional regions of the muscle fiber. The location of acetylcholine receptors in innervated or denervated muscle may result, in part, from the distribution of their RNAs. This was tested by assaying for receptor RNAs in junctional and extrajunctional regions of innervated and denervated rat soleus muscle using in situ hybridization and RNAase protection assays. These experiments showed alpha, beta, and delta subunit RNAs concentrated beneath the endplates of innervated muscle fibers. Following denervation, there was an unequal distribution of receptor RNAs along the muscle fiber, with highest levels occurring in extrajunctional regions near the endplate. These data are consistent with a nonuniform pattern of gene expression in adult skeletal muscle fibers.

Animals↗

PubMed1991

Pleural pressure distribution and its relationship to lung volume and interstitial pressure.

The mechanics of the pleural space has long been controversial. We summarize recent research pertaining to pleural mechanics within the following conceptual framework, which is still not universally accepted. Pleural pressure, the force acting to inflate the lung within the thorax, is generated by the opposing elastic recoils of the lung and chest wall and the forces generated by respiratory muscles. The spatial variation of pleural pressure is a result of complex force interactions among the lung and other structures that make up the thorax. Gravity contributes one of the forces that act on these structures, and regional lung expansion and pleural pressure distribution change with changes in body orientation. Forces are transmitted directly between the chest wall and the lung through a very thin but continuous pleural liquid space. The pressure in pleural liquid equals the pressure acting to expand the lung. Pleural liquid is not in hydrostatic equilibrium, and viscous flow of pleural liquid is driven by the combined effect of the gravitational force acting on the liquid and the pressure distribution imposed by the surrounding structures. The dynamics of pleural liquid are considered an integral part of a continual microvascular filtration into the pleural space. Similar concepts apply to the pulmonary interstitium. Regional differences in lung volume expansion also result in regional differences in interstitial pressure within the lung parenchyma and thus affect regional lung fluid filtration.

Body Fluids↗

PubMed1992

Biochemical organization of single motor units in two multi-tendoned muscles of the cat distal forelimb.

In anesthetized cats single motor units (MUs) of the extensor carpi ulnaris (ECU) and extensor digitorum communis (EDC) muscles were selectively activated by stimulation of cervical ventral root filaments. The distribution of force developed by single MUs at the four distal tendons of the EDC muscle and at three portions of the distal tendon of the ECU muscle was analysed. In general, single MUs of both muscles distributed force over all tendons in a unimodal pattern, with the maximal force levels generated at one specific tendon which was termed the best-tendon. Distributions of force were quantitatively described by a parameter representing the mean direction of force output (output-index) and a further one representing the dispersion of force over the distal tendons (divergence). Generally, these parameters and the best-tendon remained stable when a MU was stimulated at different frequencies, but varied from MU to MU. Despite the general stability of the force distribution, slight systematic changes were regularly found in EDC MUs, when they developed a higher amount of force due to a higher frequency of stimulation: the relative amount of force at the best-tendon increased; e.g. the MUs got more selective for the best-tendon. These changes were partly due to overcoming mechanical cross-coupling between neighbouring compartments of the EDC muscle. Such changes of force distribution were only found in a part of the ECU MUs; other ECU MUs did not change their force distribution at all or became less selective for the best-tendon. The phenomenon that MUs of multi-tendoned muscles distribute their force output to the distal tendons in specific patterns is probably due to mechanical partitioning of the parent muscles: the localization of spatial territories of MUs within different anatomical muscle compartments should correspond to the best-tendon. Complex mechanisms allowing passive transmission of force from limited territories along the transverse axis of both muscles must be assumed in order to explain why most MUs act on all tendons and why force distributions change with increasing stimulus frequency. In addition, specific relations between unit type and force distributions were found within both muscles. Fatigue-resistant EDC MUs have broader force distributions than fatigue-sensitive EDC MUs and slow ECU MUs were found to act predominantly on the most ulnar part of the distal tendon. These biomechanical properties of MUs are discussed as supporting the specific functions of the respective muscles.

Animals↗

PubMed1985

Applied potential tomography: possible clinical applications.

Applied potential tomography (APT) or electrical impedance imaging has received considerable attention during the past few years and some in vivo images have been produced. This paper reviews the current situation in terms of what in vivo results have been and are likely to be obtained in the near future. Both static and dynamic imaging are possible and these two areas are dealt with separately. Features of the existing in vivo imaging system are good tissue contrast, high-speed data collection, good sensitivity to resistivity changes, low spatial resolution, low cost and no known hazard. It is concluded that the most promising way forward to clinical application in the short term is to use dynamic as opposed to static imaging. An example of lung imaging is shown and the application to measuring regional ventilation and pulmonary oedema is discussed. Use of APT for the detection of intraventricular bleeding in neonates is discussed as is the proven ability to study gastric physiology by imaging resistivity distribution changes following the ingestion of conducting or insulating fluids. Other areas of possible application which are considered are blood flow measurement, cell counting, measurement of lean-fat ratios and the detection of soft tissue lesions.

Cell Count↗

PubMed1993

GABAA and glutamate receptor involvement in dendrodendritic synaptic interactions from salamander olfactory bulb.

1. Whole-cell patch clamp and optical recording techniques were applied to the same in vitro salamander olfactory bulb preparations to study the postsynaptic responses of single mitral/tufted cells in the context of the surrounding neural activity in which they are embedded. Mitral/tufted cells were identified by intracellular filling with biocytin. 2. Single mitral/tufted cells were under a tonic GABAA receptor-mediated inhibitory influence as revealed by the recording of bicuculline methiodide (BMI)/picrotoxin-sensitive inhibitory postsynaptic currents (IPSCs) in symmetrical chloride conditions at a holding potential of -70 mV. Depolarizing voltage steps (100 ms) applied to single cells or electrical stimulation of the olfactory nerve or medial olfactory tract evoked a prolonged increase in the frequency of GABAergic IPSCs. 3. The frequency of spontaneous and driven IPSCs was reduced with application of the glutamate receptor antagonists 6-cyano-2,3-dihydroxy-7-nitro-quionoxaline (CNQX) or 2-amino-5-phosphonopentanoic acid (AP5) whereas olfactory nerve- or medial olfactory tract-driven IPSC frequency was enhanced with removal of bathing Mg2+, indicating that GABAergic interneurones were driven by mitral/tufted cells at both non-NMDA and NMDA receptors. 4. Olfactory nerve or medial olfactory tract stimulation evoked widely distributed changes in fluorescence in preparations stained with the voltage-sensitive dye RH414. The optical response predominantly consisted of a decrease in fluorescence, indicative of depolarization. The presence of the dye did not obviously affect mitral/tufted cell postsynaptic responses. 5. BMI enhanced the amplitude and duration of optical signals related to depolarization within the bulb and in regions central to the bulb. In the presence of BMI, depolarizing activity appeared to spread hundreds of micrometres into regions of the bulb not activated in control conditions showing explicitly that GABAA receptors in the bulb participate in lateral inhibition. 6. CNQX and AP5 attenuated the optical signals within the bulb supporting the contention that in these conditions, optical signals arise mainly from granule cell dendritic activity. Furthermore, AP5 or removal of bath Mg2+ reduced or enlarged the spatial distribution of activity respectively, suggesting that in some cases the NMDA receptor may be involved in generating or stabilizing spatial patterns of activity. 7. It is concluded that in the salamander olfactory bulb, both GABAA- and glutamate receptor-mediated synaptic transmission shape the different temporal and spatial patterns of neural activity associated with olfactory coding.

2-Amino-5-phosphonovalerate↗

PubMed1990

Global field power and topographic similarity.

Multichannel recordings are commonly presented as topographic maps series displaying the change of the potential distribution over time. When reviewing a sequence of potential maps it becomes obvious that there are epochs with only little activity (few field lines; small extrema values) while at other times the fields display high peaks and deep troughs with steep gradients. The measure of global field power (GFP) corresponds to the spatial standard deviation, and it quantifies the amount of activity at each time point in the field considering the data from all recording electrodes simultaneously resulting in a reference-independent descriptor of the potential field. Global field power is plotted as a function of time, and the occurrence times of GFP maxima are used to determine the latencies of evoked potential components. The topographical change occurring in subsequent potential field distributions may also be quantified by computing an index of global dissimilarity. Global field power and global dissimilarity show a complementary behavior over time: in general, high GFP is associated with similar fields while during periods between GFP peaks the topographic patterns of successive field distributions change rapidly accompanied by high dissimilarity values. The topographic changes, however, are best recognized by a segmentation procedure that considers field structure independent of GFP and global dissimilarity. The principles and practical applications of GFP computation, component latency determination and global dissimilarity of potential field distributions as well as a topographical time segmentation procedure will be illustrated with multichannel data evoked by visual stimuli.

Brain↗

PubMed1995

Observation of extremely heterogeneous electroporative molecular uptake by Saccharomyces cerevisiae which changes with electric field pulse amplitude.

Molecular uptake of a charged fluorescent molecule (calcein; 623 Da, z = -4) was quantitatively determined at the single cell level using flow cytometry. Dilutely suspended cells were exposed to one exponential pulse (tau p approximately 300 microseconds) for different field strength values. For an asymmetric cell such as the yeast Saccharomyces cerevisiae a significant variation in the number of molecules taken up by individual cells was expected for physical reasons. By carrying out several thousand individual cell measurements for each pulse condition, we found that the number of molecules per cell varies significantly within the cell population, and that this population distribution changes markedly as the field strength is varied. Surprisingly, in spite of significant changes in this distribution with field strength, the average uptake per cell reaches a non-equilibrium plateau for which the uptake per cell is much smaller than the product of the mean cell volume and the supplied extracellular concentration. These observations of different field-dependent cell population distributions of uptake support the hypotheses that (1) electroporation is a transmembrane voltage-responsive phenomenon, so that cells of different sizes, shapes and orientation, respond differently to even a spatially uniform applied field, (2) population average measurements of electroporation behavior can be incomplete and misleading, and (3) transport of small charged molecules is due to electrophoresis through the pores of a dynamically changing pore population.

Cell Membrane↗

PubMed1992

New method of estimating the ultrasonic beam ratio parameter for characterizing sound propagation in tissue.

The backscattered ultrasonic signal from soft tissue can be considered to consist of two parts: a spatially fluctuating component due to coherent scattering from randomly distributed scattering centers and a relatively constant component related to structural ordering. The relationship between these, which has been termed the "beam ratio parameter" influences the speckle pattern of an ultrasound image. First-order image statistics for this special speckle pattern are characterized by the Rician distribution. Changes of second-order statistics have also been derived as a function of the beam ratio parameter. A new method for the estimation of the beam ratio parameter from the intensity distribution of the ultrasonic signal is described in this paper. This method was used to measure the parameter in ultrasonic images from phantoms and liver tissue yielding values of about 0.1. The measured changes of the second-order statistics were not correlated to this parameter. The results indicate that the relatively constant intensity component related to structural ordering has only a small influence on the speckle pattern.

Biopsy↗

PubMed1994

Rate and pattern of migration of lineally-related olfactory bulb interneurons generated postnatally in the subventricular zone of the rat.

A spatially discrete region of the anterior part of the postnatal telencephalic subventricular zone, referred to as the SVZa generates vast numbers of lineally-related neurons destined for the olfactory bulb (Luskin, 1993). The cells originating in the SVZa migrate to the olfactory bulb along a highly restricted pathway which is in a direction orthogonal to the orientation of radial glial fibers. In this study we analysed the number, distribution, orientation and rate of migration of SVZa-derived cells as they approach the olfactory bulb. In order to track the SVZa-derived cells, a retroviral lineage tracer, encoding the reporter gene E. coli beta-galactosidase (lacZ) was injected precisely into the rat SVZa at postnatal day 1 (P1). The lacZ-positive cells were visualized 1, 2 and 3 days later by X-Gal histochemistry in cryostat sections. As the number of SVZa-derived cells in the pathway increased with survival time, their distribution changed systematically. The distribution pattern of lacZ-positive cells by 2 and 3 days postinjection suggested that some of the progeny of infected progenitor cells were undergoing neurogenesis as they proceeded to the olfactory bulb; a large percentage of the lacZ-positive cells were substantially displaced from the SVZa injection site. To investigate whether lacZ-positive cells migrate in a directed fashion, their orientation preference was scored. For the majority of lacZ-positive cells (> 94%), their leading process was directed toward the olfactory bulb, possibly reflecting a response to migratory cues present along the pathway. The estimated average rate of cell migration to the olfactory bulb was 23 mu m/h, which is approximately twice the speed of radially directed neuronal migration from the telencephalic ventricular zone to the cortical plate (O'Rourke et al., 1992). Collectively, these results suggest that SVZa-derived interneurons en route to the olfactory bulb may employ a novel mode of tangential migration.

Animals↗

PubMed1991

Seasonality of peridomestic cockroaches (Blattoidea: Blattidae): mobility, winter reduction, and effect of traps and baits.

Populations of smokybrown cockroaches, Periplaneta fuliginosa (Serville), and Eurycotis floridana (Walker) were studied to compare mobility and population size between fall 1985 and spring 1986 seasons at site A, and to assess the effect of a combination of traps and baits at site B in northcentral Florida. Adult smokybrown cockroaches were more mobile in the spring than in the fall; a similar trend for E. floridana adults was not significant. Overall population levels were reduced after winter by approximately 73%. No significant shift in spatial distributions of nymphs occurred, but adult distribution changed from a predominance in palms (fall) to hardwood trees with tree holes (spring), suggesting that this habitat offers better survival during winter. Removal of cockroaches by trapping at site B, followed by a single application of dry distiller's grain containing 0.5 chlorpyrifos, reduced expected population levels (based on site A data) by 90% measured at 6 mo after treatment. These data refute the hypothesis that an increase in numbers of cockroaches infesting homes in the fall is due to an increase in mobility. Instead, the results suggest that population size and proximity of principal habitats to the home are probably responsible for domestic infestations in the fall. Use of traps, baits, or both at these foci significantly reduce populations over an extended period.

Animals↗

PubMed1988

Assessment of lung water distribution by nuclear magnetic resonance. A new method for quantifying and monitoring experimental lung injury.

We have developed a new analytical method that uses nuclear magnetic resonance (NMR) imaging data to quantify lung water content and distribution. This new method generates a distribution of lung water density in which the fraction of voxels corresponding to a given water density is plotted on the vertical axis as a function of water density on the horizontal axis, thereby complementing the spatial information provided by the NMR image. We obtained reproducible lung water distribution data at comparable lung volumes in normal excised lungs and in intact living rats. In normal excised unperfused rat lungs, the distribution varied with the degree of inflation, but the changes were small compared with those associated with lung edema. The lung water density distribution changed markedly after induction of lung edema by intrabronchial saline instillation, intravenous oleic acid injection, and rapid intravenous saline infusion. Lung water density distribution data were well correlated (correlation coefficient = 0.948 for the excised lungs and 0.823 for the intact living rats) with gravimetric lung water measurements. The new analytical method is noninvasive, provides easily repeatable measurements, and is as sensitive as the gravimetric technique to lung water changes.

Animals↗

PubMed1991

Changes in the distribution of extracellular matrix components accompany early morphogenetic events of mammalian cortical development.

As a step in defining the molecular environment for development of the mammalian cerebral cortex, we have used immunohistochemistry to analyze the distribution and remodeling of three major extracellular matrix (ECM) components, fibronectin, chondroitin sulfate proteoglycan (CSPG), and tenascin, during embryonic and early postnatal stages in the mouse. Fibronectin and CSPG are distributed throughout the proliferative zone that initially comprises the thin wall of the telencephalic vesicle, but their distribution changes as newly generated cells form the preplate just beneath the pia. Immunolabeling for CSPG becomes most prominent in the preplate, and fibronectin becomes restricted to that layer. Just after this change occurs, processes of preplate neurons, visualized with antibodies to neurofilaments, become evident within the matrix-rich preplate zone. The association of fibronectin and CSPG with preplate cells persists as cortical plate neurons divide the preplate; both ECM components are now most prominent in the marginal zone and subplate, the layers above and below the cortical plate that are preplate derived. Within the preplate and its derivatives, immunolabeling of fibronectin is punctate and closely associated with radial glial processes, while labeling of CSPG is more intense and diffuse. Labeling of fibronectin and CSPG declines rapidly as the cortical plate begins to differentiate into cortex; labeling for tenascin first appears at this stage in the most mature layers, the marginal zone and subplate, then gradually becomes widespread throughout all of cortex and subcortical white matter. In early postnatal life, tenascin is eliminated from the hollows of the vibrissal barrels in the somatosensory region; it then declines rapidly throughout cortex. The association of both fibronectin and CSPG with preplate cells and the distribution of fibronectin along radial glia during early cortical development suggest that one or both of these transient cell types might produce specific ECM components or induce their local deposition. The spatial and temporal distribution of fibronectin and CSPG suggests a role in defining a destination for migrating neurons that form the cortical plate and in delineating the pathway for early axonal extension. In contrast, the relatively late appearance of tenascin correlates best with the formation of astrocytes and their processes rather than with the establishment of cortical layers or major axonal pathways. These events are well underway before labeling of tenascin is evident.

Animals↗