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PubMed1983

[Dynamics of the distribution of labeled etimizol in brain cell structures].

The time course of 14C-etimizol distribution in cell structures of the rat cerebral cortex was studied. Two minutes after intraperitoneal injection etimizol penetrates brain cells. At this time the greater portion of the drug is found in cytosol. In five minutes the maximal part of the label gets bound with cell nuclei and microsomal protein fraction extracted with 0.14 M NaCl. These two cell fractions show the highest radioactivity throughout the entire observation period (up to 7 days). Since these fractions are reported to be capable of calcium accumulation, a suggestion is made that metabolic effects of etimizol are likely to be related to calcium metabolism.

Animals↗
PubMed2006

Modulation of plant morphology, root architecture, and cell structure by low vitamin C in Arabidopsis thaliana.

Ascorbic acid (AA) fulfils many essential functions in plants. It is a key antioxidant and an important reducing substrate for a number of enzymes. The effects of low AA on plant architecture and leaf ultrastructure were studied in Arabidopsis thaliana mutants, which have constitutively moderately low (vtc1) or very low (vtc2) leaf AA contents compared with the wild type. Shoot development was comparable in all accessions over the first 14 d of growth. The production of primary roots was slightly different in vtc1, vtc2, and wild-type plants. However, the most notable difference was that a high proportion of the primary roots of the vtc2 plants grown on soil had lost the wild-type responses to gravity. The vtc mutants showed the antagonistic interaction between nitrate and sugar in the regulation of lateral root (LR) development that was observed in the wild type. However, the vtc2 mutants produced greater numbers of longer LRs than wild-type or vtc1 plants at all levels of nitrate. At later stages of development, the vtc rosettes were smaller than those of the wild type and the leaves showed intracellular structural changes that are consistent with programmed cell death (PCD). PCD symptoms such as nuclear chromatin condensation, the presence of multivesicular bodies, and extensive degradation and disorganization of the grana stacks were observed in 8-week-old vtc2 leaves and in 10-week-old vtc1 leaves. The data presented here illustrate the importance of tissue AA contents in regulating whole plant morphology, cell structure, and development.

Antioxidants↗
PubMed1998

Chromatin, nuclear matrix and the cytoskeleton: role of cell structure in neoplastic transformation (review).

Aberrant nuclear and cellular structures are hallmarks of malignant transformation. Thus it is not surprising that the three-dimensional structure of the cell both affects and is affected by changes in gene expression. Here we review the role of the cytoskeleton, nuclear matrix, and chromatin structure in the genesis of cancer. The shape of a cell is governed by a dynamic tissue matrix, which includes extracellular matrix, cytoskeleton and nuclear matrix. Mechanical and chemical signals are transmitted to the nucleus, resulting in alterations in the three-dimensional chromatin organization of genes. The signal transduction pathways affect histone modifications, such as acetylation and phosphorylation, resulting in a relaxed chromatin structure observed in oncogene-transformed cells.

Animals↗
PubMed1978

Architecture and cell structures in the distal nephron of the rat kidney.

Using semi-thin sections of marked tubules of the rat kidney, the distal part of the nephron is represented in toto for the first time and reconstructed in its course from the thick part of HENLE's loop to its junction with another collecting tubule. The shape of the model accords well with observations in vivo. On the basis of observations with light and electron microscopy, four types of cells are differentiated: Type 1 (Mittelstück) cell; type 2 (intermediate) cell; type 3 (light) cell and type 4 (intercalated) cell. According to the distribution of these different types of cells, the distal nephron is divided in the following way: Pars recta and pars convoluta of the distal nephron consist of type 1 (Mittelstück) cells; pars arcuata and pars recta of the cortical collecting duct exhibit type 3 (light) and type 4 (intercalated) cells; in the connecting portion of the distal tubule all four types are represented, type 2 (intermediate) and type 4 (intercalated) being the most frequent. The demarcation of the connecting portion according to our definition points to a dynamic relationship of the cell structures of the distal nephron, which gains clarity when conditions are experimentally varied. Hence the question for a morphological proof of where exactly the two nephrogenic blastemata join gives place to the more important question of what these cell structures and their variability mean as signs of functional adaptation-reactions.--The existence of the connecting portion, contested until now, is affirmed; a cytological characterization of it is given and a definition is recommended.

Animals↗
PubMed2005

Specialization in pyramidal cell structure in the sensory-motor cortex of the Chacma baboon (Papio ursinus) with comparative notes on macaque and vervet monkeys.

The systematic study of pyramidal cell structure has revealed new insights into specialization of the phenotype in the primate cerebral cortex. Regional specialization in the neuronal phenotype may influence patterns of connectivity and the computational abilities of the circuits they compose. The comparative study of pyramidal cells in homologous cortical areas is beginning to yield data on the evolution and development of such specialized circuitry in the primate cerebral cortex. Recently, we have focused our efforts on sensory-motor cortex. Based on our intracellular injection methodology, we have demonstrated a progressive increase in the size of, the branching structure in, and the spine density of the basal dendritic trees of pyramidal cells through somatosensory areas 3b, 1, 2, 5, and 7 in the macaque and vervet monkeys. In addition, we have shown that pyramidal cells in premotor area 6 are larger, more branched, and more spinous than those in the primary motor cortex (MI or area 4) in the macaque monkey, vervet monkey, and baboon. Here we expand the basis for comparison by studying the basal dendritic trees of layer III pyramidal cells in these same sensory-motor areas in the chacma baboon. The baboon was selected because it has a larger cerebral cortex than either the macaque or vervet monkeys; motor cortex has expanded disproportionately in these three species; and motor cortex in the baboon reportedly has differentiated to include a new cortical area not present in either the macaque or vervet monkeys. We found, as in monkeys, a progressive increase in the morphological complexity of pyramidal cells through areas 3b, 5, and 7, as well as from area 4 to area 6, suggesting that areal specialization in microcircuitry was likely to be present in a common ancestor of primates. In addition, we found subtle differences in the extent of the interareal differences in pyramidal cell structure between homologous cortical areas in the three species.

Animals↗
PubMed2001

Life-long learning cell structures--continuously learning without catastrophic interference.

As an extension of on-line learning, life-long learning challenges a system which is exposed to patterns from a changing environment during its entire lifespan. An autonomous system should not only integrate new knowledge on-line into its memory, but also preserve the knowledge learned by previous interactions. Thus, life-long learning implies the fundamental Stability-Plasticity Dilemma, which addresses the problem of learning new patterns without forgetting old prototype patterns. We propose an extension to the known Cell Structures, growing Radial Basis Function-like networks, that enables them to learn their number of nodes needed to solve a current task and to dynamically adapt the learning rate of each node separately. As shown in several simulations, the resulting Life-long Learning Cell Structures posses the major characteristics needed to cope with the Stability-Plasticity Dilemma.

Algorithms↗
PubMed2000

Interaction of thrombospondin-1 and heparan sulfate from endothelial cells. Structural requirements of heparan sulfate.

Cell surface-associated heparan sulfate proteoglycans, predominantly perlecan, are involved in the process of binding and endocytosis of thrombospondin-1 (TSP-1) by vascular endothelial cells. To investigate the structural properties of heparan sulfate (HS) side chains that mediate this interaction, the proteoglycans were isolated from porcine endothelial cells and HS chains obtained thereof by beta-elimination. To characterize the structural composition of the HS chains and to identify the TSP-1-binding sequences, HS was disintegrated by specific chemical and enzymatic treatments. Cell layer-derived HS chains revealed the typical structural heterogeneity with domains of non-contiguously arranged highly sulfated disaccharides separated by extended sequences containing predominantly N-acetylated sequences of low sulfation. Affinity chromatography on immobilized TSP-1 demonstrated that nearly all intact HS chains possessed binding affinity, whereas after heparinase III treatment only a small proportion of oligosaccharides were bound with similar affinity to the column. Size fractioning of the bound and unbound oligosaccharides revealed that only a specific portion of deca- to tetradecasaccharides possessed TSP-1-binding affinity. The binding fraction contained over 40% di- and trisulfated disaccharide units and was enriched in the content of the trisulfated 2-O-sulfated L-iduronic acid-N-sulfated-6-O-sulfated glucosamine disaccharide unit. Comparison with the disaccharide composition of the intact HS chains and competition experiments with modified heparin species indicated the specific importance of N- and 6-O-sulfated glucosamine residues for binding. Further depolymerization of the binding oligosaccharides revealed that the glucosamine residues within the TSP-1-binding sequences are not continuously N-sulfated. The present findings implicate specific structural properties for the HS domain involved in TSP-1 binding and indicate that they are distinct from the binding sequence described for basic fibroblast growth factor, another HS ligand and a potential antagonist of TSP-1.

Animals↗
PubMed2002

Fascins, and their roles in cell structure and function.

The fascins are a structurally unique and evolutionarily conserved group of actin cross-linking proteins. Fascins function in the organisation of two major forms of actin-based structures: dynamic, cortical cell protrusions and cytoplasmic microfilament bundles. The cortical structures, which include filopodia, spikes, lamellipodial ribs, oocyte microvilli and the dendrites of dendritic cells, have roles in cell-matrix adhesion, cell interactions and cell migration, whereas the cytoplasmic actin bundles appear to participate in cell architecture. We discuss the current understanding of the cellular mechanisms that regulate the binding of fascin to actin and how these processes contribute to the organisation or disassembly of cell protrusions. Although the in vivo roles of fascin have been studied principally in Drosophila, several human diseases are associated with inherited or acquired alterations in the expression of fascins. Strategies to modulate fascin-containing protrusions and thereby cell adhesive and migratory behaviour could have potential for therapeutic intervention in these conditions. The supplementary material referred to in this section can be found at http://www.interscience.wiley.com/jpages/0265-9247/suppmat/2002/v24.350.html

Actins↗
PubMed1989

Three-dimensional viewing of internal cell structure.

3T3 and HeLa cells, grown as a monolayer, have been rapidly frozen by propane jet as a fresh preparation, without pretreatment. In some experiments the frozen cells were fractured at -170 degrees C, thawed into fixative and viewed by high-resolution SEM after critical-point drying. In other experiments the frozen cells were thawed into fixative unfractured. These preparations were refrozen in 15% methanol, fractured and deep-etched for replication and TEM study. The technique used in this work appears to give rapid rewarming from -170 degrees C to 0 degree C with little evidence of ice crystal growth. The cells fractured before thawing, examined by SEM, show extensive extraction of both nucleus and cytoplasm with deep views of nuclear chromatin, and of cytoplasmic organelles caught amongst rather distorted filaments of the cytoskeleton. Initial fixation for the SEM work was light (0.3% glutaraldehyde for 10 mins) so that structure is seen as it would be retained for antibody labelling.

Animals↗
PubMed1982

Effect of the ionic environment on the incorporation of the intermediate-sized filament protein vimentin into residual cell structures upon treatment of Ehrlich ascites tumour cells with triton X-100. II. Ultrastructural analysis.

Ehrlich ascites tumour cells were extracted in buffers containing Triton X-100 and mono-di- and polyvalent cations and then analysed by phase-contrast and electron microscopy. The results of this ultrastructural analysis confirm those of the biochemical analysis in the accompanying paper that the stability of intermediate-sized filaments is dependent on the ionic environment. Furthermore, the organization of filaments in long parallel arrays is dependent on the presence of divalent cations and can be inhibited, to some extent, by the presence of monovalent cations. The stability of other detergent-resistant structures, the boundary lamina, microfilaments, microtubules, centrioles, polyribosomes and the nuclear cortex, is also affected by the ionic environment but to a lesser extent.

Animals↗
PubMed1998

The morphology and cell structure of some nuclei in tuberal region of bison bonasus.

The topography, shape and cell structure of the ventromedial, dorsomedial and infundibular nuclei in aurochs hypothalamus were studied on the basis of standard histological preparations. These nuclei are uniform cell bands. Nucleus infundibularis is the longest centre in tuberal region and enter the mamillary area. Its posterior part has maximum size. The ventromedial nucleus is outlined and developed best. It is typical ring-shaped in anterior half of its length. The dorsomedial nucleus is developed best in its middle sector. There is no clear border between Dm and Ni. Comparing the topography and structure of Ni, Vm and Dm of bison with analogic centres of other mammals, it was found that have more common features with these nuclei in breeding domestic animals.

Animals↗
PubMed2005

Areal specialization of pyramidal cell structure in the visual cortex of the tree shrew: a new twist revealed in the evolution of cortical circuitry.

Cortical pyramidal cells, while having a characteristic morphology, show marked phenotypic variation in primates. Differences have been reported in their size, branching structure and spine density between cortical areas. In particular, there is a systematic increase in the complexity of the structure of pyramidal cells with anterior progression through occipito-temporal cortical visual areas. These differences reflect area-specific specializations in cortical circuitry, which are believed to be important for visual processing. However, it remains unknown as to whether these regional specializations in pyramidal cell structure are restricted to primates. Here we investigated pyramidal cell structure in the visual cortex of the tree shrew, including the primary (V1), second (V2) and temporal dorsal (TD) areas. As in primates, there was a trend for more complex branching structure with anterior progression through visual areas in the tree shrew. However, contrary to the trend reported in primates, cells in the tree shrew tended to become smaller with anterior progression through V1, V2 and TD. In addition, pyramidal cells in V1 of the tree shrew are more than twice as spinous as those in primates. These data suggest that variables that shape the structure of adult cortical pyramidal cells differ among species.

Animals↗
PubMed2000

TrioGEF1 controls Rac- and Cdc42-dependent cell structures through the direct activation of rhoG.

Rho GTPases regulate the morphology of cells stimulated by extracellular ligands. Their activation is controlled by guanine exchange factors (GEF) that catalyze their binding to GTP. The multidomain Trio protein represents an emerging class of &Rgr; regulators that contain two GEF domains of distinct specificities. We report here the characterization of Rho signaling pathways activated by the N-terminal GEF domain of Trio (TrioD1). In fibroblasts, TrioD1 triggers the formation of particular cell structures, similar to those elicited by RhoG, a GTPase known to activate both Rac1 and Cdc42Hs. In addition, the activity of TrioD1 requires the microtubule network and relocalizes RhoG at the active sites of the plasma membrane. Using a classical in vitro exchange assay, TrioD1 displays a higher GEF activity on RhoG than on Rac1. In fibroblasts, expression of dominant negative RhoG mutants totally abolished TrioD1 signaling, whereas dominant negative Rac1 and Cdc42Hs only led to partial and complementary inhibitions. Finally, expression of a Rho Binding Domain that specifically binds RhoG(GTP) led to the complete abolition of TrioD1 signaling, which strongly supports Rac1 not being activated by TrioD1 in vivo. These data demonstrate that Trio controls a signaling cascade that activates RhoG, which in turn activates Rac1 and Cdc42Hs.

Actins↗
PubMed1997

Dynamic cell structures for the evaluation of keypoints in facial images.

In this contribution Dynamic Cell Structures (DCS network) are applied to classify local image structures at particular facial landmarks. The facial landmarks such as the corners of the eyes or intersections of the iris with the eyelid are computed in advance by a combined model and data driven sequential search strategy. To reduce the detection error after the processing of the sequential search strategy, the computed image positions are verified applying a DCS network. The DCS network is trained by supervised learning with feature vectors which encode spatially arranged edge and structural information at the keypoint position considered. The model driven localization as well as the data driven verification are based on steerable filters, which build a representation comparable with one provided by a receptive field in the human visual system. We apply a DCS based classifier because of its ability to grasp the topological structure of complex input spaces and because it has proved successful in a number of other classification tasks. In our experiments the average error resulting from false positive classifications is less than 1%.

Algorithms↗
PubMed1996

Role of the ninaC proteins in photoreceptor cell structure: ultrastructure of ninaC deletion mutants and binding to actin filaments.

The ninaC proteins are found in Drosophila photoreceptor cells. Their primary sequences suggest they are kinase/myosin chimeras, but their myosin head-like domain is the most divergent amongst all the myosin-like proteins described to date. To investigate possible roles of the ninaC proteins in cell structure, we examined the ultrastructure of the photoreceptor cells in various ninaC mutants, and tested the ability of the proteins to interact with actin filaments in a myosin-like manner. In flies lacking the larger ninaC protein, p174, an ultrastructural phenotype was evident before eclosion. The axial actin cytoskeleton of the rhabdomeral microvilli appeared either fragmented or as an isolated structure, without linkage to the microvillar membrane. Deletion of the myosin head-like domain or the calmodulin-binding domain of p174 resulted in a similar abnormal cytoskeleton. Breakdown of the rhabdomeres followed, although at different rates depending on the deletion. Lack of the smaller protein, p132, per se did not result in photoreceptor degeneration, but in older flies there was an abnormal accumulation of multivesicular bodies. Moreover, the presence of p132 retarded the degeneration that occurs in the absence of p174, even though the p132 remained outside the rhabdomere. Biochemical studies showed that both ninaC proteins bind actin filaments and cosediment with actin filaments in an ATP-sensitive manner. These results outline structural roles for the ninaC proteins, and are consistent with the notion, suggested by their amino acid sequences, that the proteins are actin-based mechanoenzymes.

Actins↗
PubMed1993

Sentinels of Leydig cell structural and functional changes in golden hamsters in early testicular regression and recrudescence.

The seasonally breeding hamster model was used to assess changes associated with Leydig cell activity and inactivity. Specifically, parameters of Leydig cell structure and function were studied to determine the early changes seen in seasonally breeding golden hamsters in photoperiod-induced gonadal regression and photoperiod-induced gonadal recrudescence. Time intervals used to characterize early regression and recrudescence were selected with the objective of determining the most sensitive parameters characterizing functional transitional states. In early regression, plasma levels of follicle-stimulating hormone (FSH) but not luteinizing hormone (LH) or testosterone were reduced significantly. Regressive structural changes included decreases in volume of the interstitium, total number of Leydig cells, blood vessels, and the seminiferous tubules and tubular lumen. A decrease in volume, but not numbers of Leydig cells, was accompanied by decreases in volume of Leydig cell tubular smooth endoplasmic reticulum (t-ER), Golgi complex, and the peroxisomes and decreases in surface area of the inner mitochondrial membrane and t-ER, suggesting that early Leydig cell changes are restricted primarily to organelles associated with steroid biosynthesis. In early recrudescence, at a time when there was an increase in the number of germ cells in the basal compartment, blood levels of LH, FSH and testosterone were all increased. There were increases in testicular weight, volume, seminiferous tubular lumen, blood vessel and interstitial volumes. Leydig cells increased in size as a result of increases in nuclear, nucleolar and cytoplasmic volumes, while Leydig cell numbers did not increase. At the subcellular level there were increases in the surface areas of the cell, mitochondrial membranes and cisternal endoplasmic reticulum (sparsely populated with ribosomes). Unlike the changes seen in early degeneration when steroid synthetic organelles were initially affected, the changes in early recrudescence indicate that Leydig cells must first rebuild their synthetic machinery (nucleus, nucleolus and rough endoplasmic reticulum) that, at a later time, will reconstitute the cell's steroidogenic machinery. Correlation of hormonal parameters with structural parameters did indicate a relationship between hormonal parameters and steroid secreting organelles. Correlations were strongest with testosterone but, surprisingly, plasma FSH levels correlated more strongly with many structural parameters of the Leydig cell than did the levels of LH. Since FSH receptors are not present on Leydig cells, these data add to the growing data suggesting a role for factors originating from the seminiferous tubule in modulation of Leydig cell function.

Animals↗