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PubMed1989

GABA-immunoreactive synaptic plexus in the nerve fiber layer of primate retina.

Synaptic contacts onto fibers and somata in the nerve fiber layer (NFL) and ganglion cell layer (GCL) of macaque and human retina were demonstrated at the electron microscopical (EM) level. Many presynaptic processes in monkey NFL are gamma aminobutyric acid (GABA) immunoreactive, using anti-GABA antiserum with an EM immunogold procedure. Immunocytochemistry at the light microscopic level revealed that many GABA-reactive cells in the GCL send branching processes into the NFL, forming a sparse synaptic plexus. The presence of long, unbranched GABA-reactive fibers running horizontally in the NFL and entering the optic nerve suggests that some ganglion cells may be GABAergic. GABA-reactive cells contributing to the plexus appear to be a new class of displaced amacrines that arborize in the NFL.

Animals↗
PubMed2003

Microfilament and microtubule organization and dynamics in process extension by central glia-4 oligodendrocytes: evidence for a microtubule organizing center.

Microfilaments in freshly adhering CG-4 cells and differentiated CG-4 oligodendrocytes are concentrated at the tips and edges of rapidly forming processes while microtubules are concentrated in new processes and extend from a concentrated spot of alpha-tubulin staining in the cell body to the cell periphery. In motile bipolar CG-4 cells, microfilaments are heavily concentrated at the flattened end of one process and along the rim of processes and the cell body: microtubules are concentrated along main processes and splay out into process tips and the cell body. In differentiated CG-4 oligodendrocytes, microfilaments are concentrated at the many process tips, in filopodia and in fine processes, but are not obvious in main processes where separate bundles of microtubules, which diverge at process branch points, are concentrated. gamma-tubulin, involved in microtubule nucleation, is concentrated at a small discrete area in the cell body, indicative of a microtubule organizing center. Polymerization of both actin and tubulin is required for initial process elaboration. Depolymerization of microtubules, but not of microfilaments, causes complete retraction of bipolar CG-4 cell processes. This process retraction does not occur if microfilaments are depolymerized first, indicating that process extension/retraction in motile bipolar CG-4 cells may occur by a balance of motor protein-driven forces as suggested for growth cone motility. Cytoskeleton organization in CG-4 cells is very similar to that reported for oligodendrocytes. CG-4 cells are thus a useful model for investigating the signals and mechanisms regulating oligodendrocyte process dynamics.

Actin Cytoskeleton↗
PubMed2006

3D navigation of CTVE and correction of MinIP methods in non-invasive diagnostic detection.

Navigation is important in Computed Tomography Virtual Endoscopy (CTVE) functions. Existing navigation methods involve planning and pre-calculating of a fixed path before the viewpoint flight inside the targeted organs. This includes path construction, centering, smoothing and multi-branch processing. This paper proposes a 3D navigation method which was achieved by utilizing the compatibility of the 3D navigation and the ray casting 3D rendering method, without the necessity of planning and pre-calculating a fixed path, eliminating the multi-branch problems. In our 3D navigation method, the viewpoint direction and location are tracked in real time when the viewpoint is inside the organs. At the same time it presents and controls the direction changes and location changes of the viewpoint in x, y, z dimensions. With interactive control of the viewpoint, it can fly in any direction in 3D, not only along a fixed path, thus eliminating multi-branch problems. The viewpoint locations and directions will change smoothly and will be used to calculate the current scene of CTVE. Accelerated ray casting is used to render 3D scenes, which is compatible with the 3D navigation method. In Minimum Intensity Projection (MinIP) applications, if the conventional MinIP reconstruction method is used, realistic results cannot be achieved when they are rotated in multi-directions because the Computed Tomography (CT) images always contain empty regions surrounding the tissue regions. The conventional MinIP reconstruction algorithm always chalks up a minimum intensity voxel which relates to the empty regions instead of the tissue regions. To solve such valid voxel searching problems, seed-filling algorithms are used to fill the empty regions of each slice automatically. The empty voxels are labeled automatically and are avoided in MinIP calculation to gain correct results in all directions.

Algorithms↗
PubMed2001

Membrane currents and morphological properties of neurons and glial cells in the spinal cord and filum terminale of the frog.

Using the patch-clamp technique in the whole-cell configuration combined with intracellular dialysis of the fluorescent dye Lucifer yellow (LY), the membrane properties of cells in slices of the lumbar portion of the frog spinal cord (n=64) and the filum terminale (FT, n=48) have been characterized and correlated with their morphology. Four types of cells were found in lumbar spinal cord and FT with membrane and morphological properties similar to those of cells that were previously identified in the rat spinal cord (Chvátal, A., Pastor, A., Mauch, M., Syková, E., Kettenmann, H., 1995. Distinct populations of identified glial cells in the developing rat spinal cord: Ion channel properties and cell morphology. Eur. J. Neurosci. 7, 129-142). Neurons, in response to a series of symmetrical voltage steps, displayed large repetitive voltage-dependent Na(+) inward currents and K(+) delayed rectifying outward currents. Three distinct types of non-neuronal cells were found. First, cells that exhibited passive symmetrical non-decaying currents were identified as astrocytes. These cells immunostained for GFAP and typically had at least one thick process and a number of fine processes. Second, cells with the characteristic properties of rat spinal cord oligodendrocytes, with passive symmetrical decaying currents and large tail currents after the end of the voltage step. These cells exhibited either long parallel or short hairy processes. Third, cells that expressed small brief inward currents in response to depolarizing steps, delayed rectifier outward currents and small sustained inward currents identical to rat glial precursor cells. Morphologically, they were characterized by round cell bodies with a number of finely branched processes. LY dye-coupling in the frog spinal cord gray matter and FT was observed in neurons and in all glial populations. All four cell types were found in both the spinal cord gray matter and FT. The glia/neuron ratio in the spinal cord was 0.78, while in FT it was 2.0. Moreover, the overall cell density was less in the FT than in the spinal cord. The present study shows that the membrane and morphological properties of glial cells in the frog and rat spinal cords are similar. Such striking phylogenetic similarity suggests a significant contribution from distinct glial cell populations to various spinal cord functions, particularly ionic and volume homeostasis in both mammals and amphibians.

Animals↗
PubMed1995

Likelihood methods for locating disease genes in nonequilibrium populations.

Until recently, attempts to map disease genes on the basis of population associations with linked markers have been based on expected values of linkage disequilibrium. These methods suffer from the large variances imposed on disequilibrium measures by the evolutionary process, but a more serious problem for many diseases is that they assume an equilibrium population. For diseases that arose only a few hundred generations ago, it is more appropriate to concentrate on the initial growth phase of the disease. We invoke a Poisson branching process for this early growth, and estimate the likelihood for the recombination fraction between marker and disease loci, on the basis of simulated disease populations. The limits of the resulting support intervals for the recombination fraction vary inversely with the age of the disease in generations. We illustrate the procedure with data on cystic fibrosis and diastrophic dysplasia, for which the method appears appropriate, and for Friedreich ataxia and Huntington disease, for which it does not. A valuable aspect of the method is the ability in some cases to compare likelihoods of the three orders for a disease locus and two linked marker loci.

Chromosome Mapping↗
PubMed2001

A power law for cells.

Darwin observed that multiple, lowly organized, rudimentary, or exaggerated structures show increased relative variability. However, the cellular basis for these laws has never been investigated. Some animals, such as the nematode Caenorhabditis elegans, are famous for having organs that possess the same number of cells in all individuals, a property known as eutely. But for most multicellular creatures, the extent of cell number variability is unknown. Here we estimate variability in organ cell number for a variety of animals, plants, slime moulds, and volvocine algae. We find that the mean and variance in cell number obey a power law with an exponent of 2, comparable to Taylor's law in ecological processes. Relative cell number variability, as measured by the coefficient of variation, differs widely across taxa and tissues, but is generally independent of mean cell number among homologous tissues of closely related species. We show that the power law for cell number variability can be explained by stochastic branching process models based on the properties of cell lineages. We also identify taxa in which the precision of developmental control appears to have evolved. We propose that the scale independence of relative cell number variability is maintained by natural selection.

Animals↗
PubMed1990

Cortical radial glia: identification in tissue culture and evidence for their transformation to astrocytes.

Radial glia are transiently present in the developing cerebral cortex, where they are thought to guide the migration of neurons from the proliferative zone to the forming cortical plate. To provide a framework for experimental studies of radial glia, we have defined morphological and immunocytochemical criteria to identify them in primary cultures of cortical cells obtained at embryonic day 13 in the mouse. Cortical radial glia in culture for 1-2 d resemble radial glia in vivo: they have a long, thin, unbranched process extending from one or both ends of the elongated cell body and are labeled with the monoclonal antibody RC1 but not with antibodies to glial fibrillary acidic protein (abGFAP). We tested the specificity of RC1 by double-labeling with a panel of cell-type specific antibodies, and found that it labels radial glia, astrocytes, and fibroblast-like cells, but not neurons. Fibroblasts are easily distinguished from glia by morphology and by labeling with antibodies to fibronectin. To test the hypothesis that radial glia become astrocytes when their developmental role is complete, we examined their morphological and immunocytochemical development in culture. After 3-4 d in vitro radial glia develop several branched processes; in this transitional stage they are labeled by both RC1 and abGFAP. Many radial glia lose RC1 immunoreactivity as they become increasingly branched and immunoreactive to abGFAP. In areas of the cultures that have few neurons and in cultures depleted of neurons by washing, flat, nonprocess-bearing glia predominate. These cells do not lose immunoreactivity to RC1 during the 9-d period of observation even though they acquire GFAP.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Fe3O4 nanocrystals with novel fractal.

Fe3O4 novel fractal nanocrystals have been synthesized by a surfactant-assisted solvothermal process for the first time. X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Mössbauer spectroscopy (MS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) have been used to investigate the novel fractal nanocrystals. The lengths of the fractals are about 2-3 microm, and the trunks and branches of Fe3O4 fractals have almost the same diameters of ca. 30-50 nm. The roles of surfactant PEG-20000 and N2H4 have been discussed in detail. One key fact has been found that the ferrocene concentration has a vital effect on the morphologies of the products. The side-branching process and the oscillation of the concentration have been proposed to illustrate the formation mechanisms of the fractal nanocrystals. In addition, magnetic properties of Fe3O4 fractal nanocrystals have also been detected by a vibrating sample magnetometer, showing relatively high saturation magnetization (Ms) of ca. 78.75 emu/g.

Journal Article↗
PubMed1991

Synaptic organization of type 2 catecholamine amacrine cells in the rhesus monkey retina.

Two types of amacrine cell immunoreactive for tyrosine hydroxylase, the rate-limiting enzyme in the catecholamine synthetic pathway, are present in the retina of the rhesus monkey, Macaca mulatta. The well-known dopaminergic, or type 1 catecholamine amacrine cells have relatively large cell bodies almost exclusively in the inner nuclear layer with processes that densely arborize in the outermost stratum of the inner plexiform layer and fine, radially-oriented fibres in the inner nuclear layer. Type 2 catecholamine amacrine cells, in contrast, have smaller cell bodies in the inner nuclear layer, the inner plexiform layer and the ganglion cell layer, and have sparsely-branching processes ramifying in the centre of the inner plexiform layer. Although type 2 catecholamine cells are more numerous than type 1 catecholamine amacrines, type 2 cells contain less than one-third the amount of tyrosine hydrolase as the type 1 cells. Electron microscopy of retinal tissue immunoreacted for tyrosine hydrolase by the peroxidase-antiperoxidase method revealed synaptic input from amacrine cells at conventional synapses, and bipolar cells at ribbon synapses onto the type 2 catecholamine amacrine cells. Curiously, although the synaptic input is comparatively easily found, the output synapses, or synapses of the type 2 catecholamine amacrine cells onto other neuronal elements, are rarely found. Some synapses of the type 2 catecholamine cells onto non-immunoreactive amacrine cells have been identified, however. This unusual pattern of synaptic organization, with many identifiable input synapses but few morphologically characterizable output synapses, suggests a paracrine function for the dopamine released by the type 2 catecholamine amacrine cells in the primate retina.

Animals↗
PubMed1997

Oligodendrocyte maturation and progenitor cell proliferation are independently regulated by thyroid hormone.

The development of oligodendrocyte progenitor cells is regulated by epigenetic factors which control their proliferation and differentiation. When oligodendrocyte progenitor cells, purified on a Percoll centrifugation gradient from neonate rat brain, are cultured in serum-free medium in the presence of platelet-derived-growth factor (PDGF), they divide and their differentiation is delayed. Triiodothyronine (T3) treatment of progenitor cells blocks their proliferation and induces their differentiation into oligodendrocytes. T3 also induces morphological differentiation of oligodendrocytes as indicated by the marked increase in the length of oligodendrocyte processes. To determine whether the effects of T3 on progenitor cell proliferation and oligodendrocyte maturation are causally related, or instead, are independent, we examined the influence of T3 on secondary cultures of postmitotic oligodendrocytes. We show that T3 increases morphological and functional maturation of postmitotic oligodendrocytes as indicated by a well developed network of branched processes and by the expression of myelin/oligodendrocyte glycoprotein (MOG) and glutamine synthetase (GS). T3 increases glutamine synthetase activity and its message level after a lag period of 24-48 h, and these levels increase through a posttranscriptional event. In contrast, no effect of T3 was observed on myelin basic protein (MBP) gene expression as determined by Northern blot analysis. Our results indicate that thyroid hormones participate in the control of the progenitor cell proliferation and differentiation as well as in oligodendrocyte maturation and that these two T3-regulated events are independent.

Animals↗
PubMed1985

Inosine diphosphatase as a histochemical marker of retinal microvasculature, with special reference to transformation of microglia.

Nucleoside diphosphatase (IDPase), localized using inosine diphosphate as substrate, allows the selective staining of blood vessels and cells of vascular origin, such as macrophages and microglia, whereas the neuroglial, the neuronal and the pigment epithelial cells remain unstained. The staining pattern observed in the retina of mouse, rat, cat and monkey are similar; some apparent quantitative differences reflect species differences in the distribution of retinal microvasculature. At the electron-microscopic level, most of the enzyme activity in the blood vessels appears to be located along the outer wall. The cell membrane, parts of the smooth endoplasmic reticulum and the nuclear membrane in the microglial perikarya appear positive; profiles of microglial processes are intensely stained. In the developing eyes of rats and mice, the blood vessels are stainable from the earliest stage of their appearance. An array of amoeboid cells precede the growing blood vessels and spread out over the future vascularized part of the retina. These cells eventually develop characteristic microglial features, and extend many elongated and branched processes between the neuroepithelial cells while remaining in contact with, or in close proximity to, the blood vessels. Intense IDPase activity in the microglial cells, in contrast to the absence of the enzyme in the neuroglial Müller cells, suggests that microglia are involved in phosphate metabolism and indicates functional compartmentalization within the glial tissue lying between the blood retinal barrier and the retinal neurons.

Acid Anhydride Hydrolases↗
PubMedDate not supplied

Inflammatory response associated with axonal injury to spinal motoneurons in newborn rats.

Axonal injury in peripheral nerve results in massive motoneuron loss during development. The purpose of this study was to examine the response of phagocytic populations (brain macrophages, BMOs, versus microglia) after different types of axonal lesions (distal axotomy or avulsion) in newborn rats. The morphology, spatial location and activation state of these inflammatory cells were observed. Following spinal root avulsion, BMOs were signaled rapidly and specifically to the location of dying motoneurons in the spinal cord. A large number of BMOs were observed around the avulsed motoneurons on the lesioned side of the spinal cord 1 day following the lesion. These BMOs were large, round, and intensely stained by both antibodies against ED1 and OX-42. The number of BMOs decreased by 3 days and disappeared by 5 days after injury. At the same time, reactive microglia appeared in the lesioned area and rapidly reached the peak level by the 5th day following avulsion. These reactive microglia were medium in size with retracted cellular processes and were also intensely stained by both ED1 and OX-42 antibodies. The number and staining intensity of reactive microglia declined sharply by day 7 after the lesion. In contrast, after distal axotomy only microglia but not BMOs were observed in the lesioned area. These microglial cells were small in size with long and fine-branched processes. They were ED1-negative but OX-42-positive.

Animals↗
PubMed1975

Natural selection for within-generation variance in offspring number II. Discrite haploid models.

In the classical model of genetic drift in population genetics theory, use is made of a hypothetical "infinite-gametic pool". If, instead, the gametic pool is determined by the random number of offspring per individual, a new form of natural selection acting on the variance in offspring number occurs. A diffusion model of this selection process is derived and some of its properties are explored. It is shown that, independent of the sampling scheme used, the diffusion equation has the drift coefficient M(p) = p(1-p) (mul--mu2 + sigma2e2--sigma2el) and the diffusion coefficient v(p) equals p(1-p) [psigma2e2 + (l--p)sigma2el]. It is also pointed out that the Direct Product Branching process model of genetic drift introduces a non-biological interaction between individuals and is thus inappropriate for modeling natural selection.

Alleles↗
PubMed2006

Deterioration of the Langerhans cell network of the human gingival epithelium with aging.

Dendritic cells (DCs) are the professional antigen-presenting cells responsible for initiating of the immune response. Langerhans cells (LCs) are a type of DC that is a permanent resident of the oral epithelium. LCs are organized conforming a network in such a way as to maximize their surface area for efficient apprehension of antigens. To detect age-related changes in the LCs network, fragments of gingival epithelium spontaneously accompanying dental removals were processed by immunohistochemistry. Monoclonal antibody CD1a followed by biotinized immunoglobulin-streptoavidin peroxidase were used to identify the LCs with the light microscope. LC density and LC types were analyzed according to their morphology and intraepithelial distribution. In the older age group (61-74 years) the density was significantly lower than in the younger age groups. Morphologically, LCs showed fewer dendritic-branching processes and had a rounded shape in the older age group. Present observations indicate that the LC network changes markedly with aging. These results suggest that immunological defense of the oral tissue might be compromised in old age.

Adolescent↗
PubMed1989

Immunohistochemical demonstration of Langerhans' cell in cholesteatoma using an antiserum against S-100 protein.

The epidermal Langerhans' cells play an important role in immunological reactions resulting from chronic inflammations of the skin. Recently, S-100 protein, one of the nervous-system-specific proteins, has been shown to be a useful marker for the epidermal Langerhans' cells. We investigated the localization of Langerhans' cells in human cholesteatoma specimens by means of an immunohistochemical method for detecting S-100 protein. A large number of Langerhans' cells containing S-100 protein immunoreactivity were found in the epithelium of the cholesteatoma and also in the subepithelial region. This immunoreactivity was detected both in the cytoplasm of the Langerhans' cells and their dendritic processes along their entire lengths. The number of S-100 positive Langerhans' cells in cholesteatoma associated with otorrhea increased significantly as compared with normal epithelium from the external auditory canal and tympanic membrane, while no increase in the number of S-100-positive cells was recognized in cholesteatoma without otorrhea. The S-100-positive dendritic cells in the cholesteatoma revealed longer and more complexly branched processes than those in normal tissues. These findings suggest that the Langerhans' cells within the cholesteatomatous lesion are responsible for generating and maintaining the chronic immunological reactions in this disease.

Adolescent↗
PubMed1999

Stochastic models of telomere shortening.

Shortening of chromosome ends, known as telomeres, is one of the supposed mechanisms of cellular aging and death. We provide a probabilistic analysis of the process of loss of telomere ends. The first work concerned with that issue is the paper by Levy et al. [J. Molec. Biol. 225 (1992) 951-960]. Their deterministic model reproduced the observed frequencies of viable cells in the in vitro experiments. Arino et al. [J. Theor. Biol. 177 (1995) 45-57] reformulated the model of Levy et al. (1992) in the terms of branching processes with denumerable type space. In the present paper, the mathematical results of Arino et al. (1995) are extended to the case in which cell death is present, in cells with telomeres above and below the critical threshold of length, generally with differing probabilities. Both exact and asymptotic results are provided, as well as a discussion of biological relevance of the results.

Cell Death↗
PubMed1999

Genetic correlations in mutation processes.

We study the role of phylogenetic trees on correlations in mutation processes. Generally, correlations decay exponentially with the generation number. We find that two distinct regimes of behavior exist. For mutation rates smaller than a critical rate, the underlying tree morphology is almost irrelevant, while mutation rates higher than this critical rate lead to strong tree-dependent correlations. We show analytically that identical critical behavior underlies all multiple point correlations. This behavior generally characterizes branching processes undergoing mutation.

Genetics↗
PubMed2005

Role of Rho GTPase in astrocyte morphology and migratory response during in vitro wound healing.

Small Rho GTPases are key regulators of the cytoskeleton in a great variety of cells. Rho function mediates morphological changes as well as locomotor activity. Using astrocyte cultures established from neonatal mice we investigated the role of Rho in process formation during astrocyte stellation. Using a scratch-wound model, we examined the impact of Rho on a variety of morphological and functional variables such as stellation and migratory activity during wound healing. C3 proteins are widely used to study cellular Rho functions. In addition, C3 derived from Clostridium botulinum (C3bot) is considered selectively to promote neuronal regeneration. Because the latter requires a balanced activity of neurones and glial cells, the effects of C3 protein on glial cells such as astrocytes have to be considered carefully. Low nanomolar concentrations of C3 proteins significantly promoted process outgrowth and increased process branching. Besides enzymatic inactivation of Rho by ADP-ribosylation, changes in protein levels of the various Rho GTPases may also contribute to the observed effects. Furthermore, incubation of scratch-wounded astrocyte cultures with C3bot accelerated wound healing. By inhibiting the Rho downstream effector ROCK with the selective inhibitor Y27632 we were able to demonstrate that the accelerated wound closure resulted from both enhanced polarized process formation and increased migratory activity of astrocytes into the lesion site. These results suggest that Rho negatively regulates astrocytic process growth and migratory responses after injury and that its inactivation by C3bot in nanomolar concentrations promotes astrocyte migration.

Amides↗