Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “branching process”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,459 records · Page 81Linked to original sources
PubMed1994

Calretinin-immunoreactive neurons and their projections in the guinea-pig colon.

The distribution of nerve cells and fibres with immunoreactivity for the calcium-binding protein, calretinin, was studied in the distal colon of the guinea-pig. The projections of the neurons were determined by examining the consequences of lesioning the myenteric plexus. Calretinin-immunoreactive neurons comprised 17% of myenteric nerve cells and 6% of submucous nerve cells. Numerous calretinin-immunoreactive nerve fibres were located in the longitudinal and circular muscle, and within the ganglia of the myenteric and submucous plexuses. Occasional fibres were found in the muscularis mucosae, but they were very rare in the lamina propria of the mucosa. Lesion studies revealed that myenteric neurons innervated the underlying circular muscle and provided both ascending and descending processes that gave rise to varicose branches in myenteric ganglia. Calretinin-immunoreactive fibres also projected to the tertiary component of the myenteric plexus, and are therefore likely to be motor neurons to the longitudinal muscle. Varicose fibres that supplied the submucous ganglia appear to arise from submucous nerve cells. Arterioles of the submucous plexus were sparsely innervated by calretinin-immunoreactive fibres. The submucous plexus was the principal source of immunoreactive nerve fibres in the muscularis mucosae. This work shows that calretinin-IR reveals different neuronal populations in the large intestine to those previously reported in the small intestine.

Animals↗
PubMed1979

Synaptic extensions from the mossy fibers of the fascia dentata.

In the hilar region of the rat hippocampus, filamentous extensions have been observed to originate from the en passant synaptic expansions on the so-called mossy fibers, which are the axons of the dentate granule cells. These extensions range in length from about 1 micrometer to 30 micrometer, are often branched, and appear to contact the processes of various cell types in the hilar region. In 28-day-old rats, there are between 4 and 9 such extensions from most mossy fiber expansions, and the total length of the extensions from any one expansion is on the order of 75 micrometer. Analysis of serial electron micrographs through normal and Golgi-impregnated mossy fibers has confirmed that these extensions are, indeed, presynaptic processes. Each contains one or more vesicle-rich foci along its length, and is associated with asymmetric membrane specializations. At these sites, the extensions are in synaptic contact with dendrites and dendritic spines of, as yet, unknown origin. A quantitative analysis of these extensions in Golgi material from rats at different ages indicates that they reach their greatest length around 14 days and then decline to adult values by 28 days.

Age Factors↗
PubMed1993

Expression of the epidermal growth factor receptor in fetal kidney.

Formation of the human kidney begins at the 6th week of fetal life when the first generations of nephrons are generated from foci of metanephric mesenchyme through contact with the branches of the ureteric bud. This process requires a proliferative burst which must be tightly regulated by local signals. In this report, we review the evidence that the epidermal growth factor receptor molecule is an important arbiter of these events.

Animals↗
PubMed1980

Three-dimensional aspects and synaptic relationships of a Golgi-impregnated spiny stellate cell reconstructed from serial thin sections.

A Golgi-impregnated spiny stellate cell was selected from layer IV of SmI cortex in a mouse whose ipsilateral ventrobasal complex had been lesioned. The neuron was gold-toned, thin sectioned and then reconstructed in three dimensions using wooden sheets of appropriate thickness. These procedures enabled the numbers and distribution of thalamocortical and other synapses onto the reconstructed neuron to be determined. Results show the cell body to be roughly spherical and to receive 49 symmetrical synapses and four synapses which are intermediate between the asymmetrical and symmetrical type. A single, clearly asymmetrical axosomatic synapse is made by a degenerating, thalamocortical axon terminal. Five primary dendrites and their branches were reconstructed and, interestingly, these processes are distinctly elliptical in cross-section. The reconstructed dendrites receive 68 symmetrical synapses onto their shafts and 373 synapses onto spines of which 359 are asymmetrical and 14 symmetrical. Forty-eight, or about 13%, of the asymmetrical axospinous synapses are made by degenerating, thalamocortical axon terminals. An intriguing finding is that in many regions of the dendritic tree, two or more spines involved in thalamocortical synapses are attached to the dendritic shaft at intervals of 5 +/- 0.5 micron.

Animals↗
PubMed1993

Terminal and intermediate segment lengths in neuronal trees with finite length.

A basic but neglected property of neuronal trees is their finite length. This finite length restricts the length of a segment to a certain maximum. The implications of the finite length of the tree with respect to the segment length distributions of terminal and intermediate segments are shown by means of a stochastic model. In the model it is assumed that branching is governed by a Poisson process. The model shows that terminal segments are expected to be longer than intermediate segments. Terminal and intermediate segments are expected to decrease in length with increasing centrifugal order. The results are compared with data from in vivo pyramidal cells from rat brain and tissue cultured ganglion cells from chicken. A good agreement between data and model was found.

Animals↗
PubMed1995

Expression levels of B-50/GAP-43 in PC12 cells are decisive for the complexity of their neurites and growth cones.

To study the role of the protein B-50/GAP-43 in NGF-induced neurite outgrowth, a number of stable PC12 subclones with either very low or considerably enhanced expression levels of the protein were selected. Cell bodies of subclones with suppressed B-50 expression (-B2, -B5, or -B12) possessed a relative small spherical shape and, on NGF-treatment for 7 d, developed processes that were virtually devoid of branches and that mostly bore short or blunt-ended growth cones. Cells of subclones with overexpression of B-50 (+B3, +B4, or +B11), on NGF treatment, acquired a flattened, spiky appearance with highly branched neurites possessing extended and complex growth cones. Confocal microscopy with immunofluorescence for B-50 and F-actin revealed that in neurites and growth cones of the B-50-deficient subclone -B2, no detectable B-50 and reduced amounts of filamentous F-actin were present, whereas in overexpressing +B3 cells, cell membranes, neurites, and complex growth cones were intensively stained for B-50 and exhibited numerous spikes, in which B-50 was strikingly colocalized with F-actin. These data suggest that, under normal conditions of neuritogenesis, the expression level of B-50 in PC12 cells is decisive for the complexity of neurites and growth cones.

Animals↗
PubMed2006

Effects of an experimental enrichment of instream habitat heterogeneity on the stream bed morphology and chironomid community of a straightened section in a sandy lowland stream.

A straightened stream stretch with poor habitat heterogeneity was divided into a "control" section with a low amount of submerged woody debris and an experimentally "wood-enriched" downstream section to study the effect of enhanced habitat diversity on the benthic invertebrate community. The downstream section was enriched by fixing 25 wood packages constructed from 9-10 branches on the stream bottom. Succession processes occurring in the two stream sections were compared by chironomid exuviae drift from July to November 2000 and from April to August 2001. During the first sampling period, more drifting chironomid exuviae (medians of control vs. wood-enriched: 446 vs. 331, no significant difference) and total number of taxa (44 vs. 36, Wilcoxon signed-rank test P = 0.019) were recorded for the control section. Although species compositions of both stream sections were highly similar (Sørensen index: 0.83) the diversity in the wood-enriched section was distinctly lower compared to the control section (Shannon-Weaver index: 1.19 vs. 1.50). During the second sampling period, exuviae numbers remained higher in the control section (median: 326 vs. 166), but total numbers of taxa were nearly equal (51 vs. 49), as well as species diversity (Shannon-Weaver index: 1.67 vs. 1.64). The lower chironomid diversity observed during the first sampling period coincided with a gradual but significant change of the streambed morphology in the wood-enriched section. There, the initially more U-shaped profile (V/U = 0.81 +/- 0.37) had turned into a pronounced V shape (V/U = 1.14 +/- 0.21), whereas the control section retained its unaltered U shape (V/U = 0.62-0.75). This small-scale study on experimental of woody debris in sandy lowland streams showed that the negative impact of increased hydraulic disturbance of the existing streambed more than outweighed any positive impact resulting from the increase in woody debris.

Animals↗
PubMed1991

Systemic occlusive arteriopathy with sudden death in a 10-year-old boy.

A 10-year-old boy died suddenly while playing. Autopsy examination disclosed an extensive occlusive arteriopathy involving all major epicardial coronary arteries, with associated remote myocardial infarct. Also affected were the renal arteries and a branch of a pulmonary artery. The process was characterized by concentric intimal hyperplasia, focally replacing the media, with disruption of elastic laminae in more advanced lesions. The proliferating cells had ultrastructural features of smooth muscle cells. There was no evidence of atherosclerosis or vasculitis. While the case shares some features with known arteriopathies, this constellation of clinical and pathologic findings appears to be unique.

Arterial Occlusive Diseases↗
PubMed1993

Development of a motor nerve in the caudal fin of the medaka (Oryzias latipes).

The entire process of the development of the motor nerve to the middle interradial muscle (MIR muscle) in the tail region of the medaka (Oryzias latipes) was examined by light and electron microscopy. The motor nerve to the MIR muscle was observed to develop in a series of four steps. (1) Trunk-formation step: from stage 30 to stage 31, when the MIR muscle had not yet differentiated to the myotube stage, the motor axons starting from the caudal spinal cord, including spinal segment 27, formed a nerve trunk, the ventral caudalmost nerve (VCN). The VCN bypassed the place where the MIR muscle would differentiate and extended further caudad. (2) Wandering step: at stage 32, nerve processes of the motor axons (short branches) wandered from the course of the VCN. (3) Connection step: from stage 33/34 to stage 35, the mesenchyme cells differentiated into the MIR myotubes in the vicinity of the short branches, and the nerve and the muscle became connected. (4) Modification step: after stage 35, the morphological pattern of the motor nerve was modified by the growth and the shift of the short branches, and by the disappearance of the caudalmost part of the VCN. These results suggest that the complex pattern of the motor nerve in the adult fish is gradually constructed by multiple steps, each of which may have its own mechanism.

Animals↗
PubMed1991

Causal explanations for class inequality in health--an empirical analysis.

One of the most important issues for research on social class inequalities in health are the causes behind such differences. So far, the debate on class inequalities in health has mainly been centred around hypotheses on artefactual and selectional processes. Although most contributors to this branch of research have argued in favour of causal explanations, these have gained very little systematic scrutiny. In this article, several possible causal factors are singled out for empirical testing. The effect of these factors on class differences in physical and mental illness is studied by means of logit regressions. On the basis of these analyses, it is shown that physical working conditions are the prime source of class inequality in physical illness, although economic hardship during upbringing and health related behaviours also contribute. For class inequality in mental illness these three factors plus weak social network are important. In sum, a large part of the class differences in physical as well as mental illness can be understood as a result of systematic differences between classes in living conditions, primarily differences in working conditions.

Adolescent↗
PubMed1986

Microtubule-associated protein 2 and tubulin are differently distributed in the dendrites of developing neurons.

We have followed the appearance of two microtubule proteins, tubulin and microtubule-associated protein 2, in rat hippocampal neurons differentiating in cell culture. Double-label immunofluorescence staining showed that from day 1 in vitro onward tubulin appeared as filaments but that microtubule-associated protein 2 remained distributed throughout the cytoplasm. This difference persisted throughout development and was also detectable in cells that had reached morphological maturity. When cells were treated with the microtubule-depolymerizing agent nocodazole, the depolymerized tubulin became spread throughout the cytoplasm so that its distribution was then identical to microtubule associated protein 2. At the same time, multiple side branches began to emerge along the dendrites. When cells which had been exposed to nocodazole were allowed to recover before staining, the tubulin was again present as filaments but the microtubule-associated protein 2 remained distributed throughout the dendritic cytoplasm. Under these conditions the previously extended proximal side branches were resorbed into the main process. These results suggest that cellular microtubule-associated protein 2 is not necessarily exclusively associated with microtubules. Neuronal dendrites in particular appear to contain this protein at levels in excess of the capacity of microtubular microtubule-associated protein 2 binding sites. In view of the known effectiveness of microtubule-associated protein 2 as a promoter of tubulin polymerization, its abundance in dendrites suggests that it acts to ensure total polymerization of dendritic microtubules. In this way it would contribute both to the support of the growing process and the suppression of adventitious sidebranching.

Animals↗
PubMed1995

Development of layers, maps and modules.

Developing neuronal cell sheets acquire position-specific features by mechanisms that differ in radial and tangential dimensions. These features include guiding cues for axonal growth and targeting that are used, for example, in map formation. Recent evidence supports the notion that graded distributions of molecules are involved in growth cone navigation and axonal branching. In addition, activity-dependent processes are important determinants of functional architecture, especially with respect to modular organization.

Afferent Pathways↗
PubMed2004

The juvenile three-spined stickleback (Gasterosteus aculeatus L.) as a model organism for endocrine disruption. I. Sexual differentiation.

Juvenile three-spined stickleback (Gasterosteus aculeatus L.) is introduced as a unique model organism for both androgenic and oestrogenic endocrine action. Intersex is often used as an indicator for disruption of sexual differentiation in fish exposed to different kinds of effluents from human activities. In wild fish it has exclusively been reported in terms of feminisation due to xenoestrogens in the environment. The assumption that the intersex individuals are feminised genetic males can only be proven by genetic sex identification of the intersexual individuals. Intersex and gonadal sex reversal were induced in three-spined sticklebacks by treatment with natural and synthetic steroid hormones. Juvenile sticklebacks were exposed to three nominal concentrations of 17 beta-oestradiol (E2); i.e. 0.01, 1.0 and 10.0 microg/L; which were administered to the water either continuously from hatching to the end of the experiment (39-58 days post hatch), during the first 2 weeks after hatching only, from 14 days after hatching onwards, or during the chorionated embryo stage until hatching. Other groups were exposed to 17 alpha-ethinylestradiol (EE2) at 0.05 microg/L and 17 alpha-methyltestosterone (MT) at 1.0 microg/L (nominal concentrations). MT was applied continuously, during the first 2 weeks post hatch only, or from 14 days after hatching onwards. Gonad histology was examined and the genetic sex was identified with male sex-linked PCR markers. Treatment with oestrogens caused feminisation at the two highest E2 concentrations and with EE2. Exposure to E2 before hatching had no effect. Intersexual individuals from oestrogen treatments were genetic males. The genetic sex marker identified apparent total reversal of the gonad type of genetic males. Treatment with MT did not reveal a clear picture, since intersex was observed in both genetic females and males. MT also caused severe testis abnormalities, mainly the development of large branched cavities with unidentified origin. The process of sex differentiation is most sensitive to the influence of external steroids during the first 2 weeks after hatching. A lower incidence of intersex could also be induced in sticklebacks exposed from 14 days after hatching by E2 treatment, but not with MT. The combination of gonad histopathology with genetic sex identification in juvenile sticklebacks is suggested as a tool for detecting endocrine disruption in laboratory studies, and might become very useful in field surveys.

Analysis of Variance↗
PubMed2005

Characterization of the oligosaccharide component of alpha3beta1 integrin from human bladder carcinoma cell line T24 and its role in adhesion and migration.

Malignant transformation is highly associated with altered expression of cell surface N-linked oligosaccharides. These changes concern integrins, a family of cell surface glycoproteins involved in the attachment and migration of cells on various extracellular matrix proteins. The integrin alpha3beta1 is particularly interesting because of its role in migration and invasion of several types of metastatic tumours. In this study, alpha3beta1 from human bladder T24 carcinoma cells was purified and treated with peptide N-glycosidase F. Then the N-glycans of the alpha3 and beta1 subunits were characterized using matrix-assisted laser desorption ionization mass spectrometry (MALDI MS). In alpha3beta1 integrin the presence of high-mannose, hybrid and predominantly complex type N-oligosaccharides was shown. Unlike to normal epithelium cells, in both subunits of alpha3beta1 integrin from cancer cells, the sialylated tetraantennary complex type glycan Hex7HexNAc6FucSia4 was present. In a direct ligand binding assay, desialylated alpha3beta1 integrin exhibited significantly higher fibronectin-binding capability than untreated integrin, providing evidence that sialic acids play a direct role in ligand-receptor interaction. Moreover, alpha3beta1 integrin was shown to take part in T24 cell migration on fibronectin: anti-alpha3 antibodies induced ca 30% inhibition of wound closure. Treatment of T24 cells with swainsonine reduced the rate of bladder carcinoma cell migration by 16%, indicating the role of beta1,6 branched complex type glycans in this process. Our data show that alpha3beta1 integrin function may be altered by glycosylation, that both subunits contribute to these changes, and that glycosylation may be considered a newly found mechanism in the regulation of integrin function.

Biological Assay↗
PubMed2005

Glypican-3 modulates inhibitory Bmp2-Smad signaling to control renal development in vivo.

Renal branching morphogenesis, defined as growth and branching of the ureteric bud (UB), is a tightly regulated process controlled by growth factor-dependent tissue interactions. Previously, using in vitro models of branching morphogenesis, we demonstrated that BMP2 signals via its intracellular effectors, SMAD1 and SMAD4, to control UB cell proliferation and branching in a manner modulated by Glypican-3 (GPC3), a cell surface heparan sulfate proteoglycan. Here, we used loss-of-function genetic mouse models to investigate the functions of Bmp2 and Gpc3-Bmp2 interactions in vivo. Progressively greater increases in UB cell proliferation were observed in Bmp2+/-, Smad4+/-, and Bmp2+/-; Smad4+/- mice compared to Wt. This increased cell proliferation was accompanied by a significant increase in UB branching in Smad4+/- and Bmp2+/-;Smad4+/- mice compared to Wt. Reduction of Gpc3 gene dosage also increased UB cell proliferation, an effect that was enhanced in Gpc3+/-;Bmp2+/- mice to an extent greater than the sum of that observed in Gpc3+/- and Bmp2+/- mice. Reduction of both Gpc3 and Bmp2 gene dosage enhanced cell proliferation in the metanephric mesenchyme compared to Wt, an effect not observed in either Bmp2+/- or Gpc3+/- mice. Phosphorylation of SMAD1, a measure of SMAD1 activation, was progressively decreased in Gpc3+/- and Gpc3+/-;Bmp2+/- mice compared to Wt, suggesting that Gpc3 stimulates Bmp2-dependent SMAD signaling in vivo. These results demonstrate that BMP2-SMAD signaling, modulated by GPC3, inhibits renal branching morphogenesis in vivo.

Animals↗
PubMed1998

What can and what cannot be inferred from pairwise sequence comparisons?

We address questions of identifiability in molecular phylogeny, the art of reconstructing the history of a sample of sequences given just the sequences at the leaves of the phylogenetic tree. Here, the 'history' consists of the tree topology, plus the transition probabilities which define the Markov process of sequence evolution along the branches of the tree. It is assumed that sequences have infinite length, and the pairwise joint distributions of letters at the leaves is taken to be known. We focus on two cases: (1) If the sites of a sequence evolve identically and independently, the topology can be reconstructed, but the one-way edge transition matrices cannot. However, the return-trip transition matrices are reconstructible for every edge, up to conjugation in the case of internal edges. (2) If a rate factor varies from site to site, different topologies may produce identical pairwise joint distributions, even under the same distribution of rate factors. Consequently, identifiability of the topology is lost on the basis of pairwise sequence comparisons, even if the distribution of rate factors is known. The results are discussed in the context of additive measures of phylogenetic distance.

Base Sequence↗
PubMed2000

Aortitis syndrome associated with positive perinuclear antineutrophil cytoplasmic antibody: report of three cases.

We recently experienced three cases of aortitis syndrome that were associated with perinuclear antineutrophil cytoplasmic antibody (ANCA). In the three cases, roentgenographic examination revealed the typical appearance of stenosis or occlusive subclavian arteries. In addition, two cases showed a thickened thoracic aorta wall and the remaining case had irregular stenosis of both common iliac arteries. All three cases had persistently increased ESR and CRP over the years. These findings suggested the diagnosis of aortitis syndrome. ANCA tests were performed because of rapidly progressive glomerulonephritis symptoms in two patients and marked excretion of beta(2)-microglobulin in urine in one patient. The test showed P-ANCA in all three patients, with two patients identified as anti-MPO antibody and the third patient as non-MPO antibody. The implication of ANCA in the pathogenesis of aortitis syndrome is presumed to be: ANCA, which plays an important role in the pathogenesis of small vessel vasculitis, induces vasculitis of the vasa vasorum in the aorta or main branches (or both) and this pathologic process results in the pathogenesis of aortitis syndrome.

Aged↗
PubMed2002

Catalyst/cocatalyst nuclearity effects in single-site polymerization. Enhanced polyethylene branching and alpha-olefin comonomer enchainment in polymerizations mediated by binuclear catalysts and cocatalysts via a new enchainment pathway.

The binuclear "constrained geometry catalyst" (CGC) (mu-CH2CH2-3,3'){(eta5-indenyl )[1-Me2Si(tBuN)](ZrMe2)}2 [EBICGC(ZrMe2)2; Zr2] and the trityl bisborate dianion (Ph3C+)2[1,4-(C6F5)3BC6F4B(C6F5)3]2- (B2) have been synthesized to serve as new types of multicenter homogeneous olefin polymerization catalysts and cocatalysts, respectively. Additionally, the complex [1-Me2Si(3-ethylindenyl)(tBuN)]ZrMe2 (Zr1) was synthesized as a mononuclear control. For the bimetallic catalyst or bisborate cocatalyst, high effective local active site concentrations and catalyst center-catalyst center cooperative effects are evidenced by bringing the catalytic centers together via either covalent or electrostatic bonding. For ethylene homopolymerization at constant conversion, the branch content of the polyolefin products (primarily ethyl branches) is dramatically increased as catalyst or cocatalyst nuclearity is increased. Moreover, catalyst and cocatalyst nuclearity effects are approximately additive. Compared to the catalyst derived from monometallic Zr1 and monofunctional Ph3C+B(C6F5)4- (B1), the active catalyst derived from bimetallic Zr2 and bifunctional B2 produces approximately 11 times more ethyl branches in ethylene homopolymerization via a process which is predominantly intradimer in character. Moreover, approximately 3 times more 1-hexene incorporation in ethylene + 1-hexene copolymerization and approximately 4 times more 1-pentene incorporation in ethylene + 1-pentene copolymerization are observed for Zr2 + B2 versus Zr1 + B1.

Journal Article↗