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 649 records · Page 36Linked to original sources
PubMed1981

A scanning electron microscopic study of larval development in the marine polychaete, Galeolaria caespitosa Lamarck (Serpulidae).

Gametes and developing larvae of the polychaete Galeolaria caespitosa were examined by scanning electron microscopy. The sperm display a primitive morphology. When treated with 0.33 M CaCl2, they release a branched acrosomal process. At spawning, the polygonal oocytes have a granular surface made up of spherules and the tips of microvilli. The oocyte coat develops a ridged appearance as the oocyte rounds up. At fertilization, the microvilli are withdrawn from the coat surface. Microvilli again appear on the coat surface during the trochophore stage, but the egg coat appears to be retained as the larval cuticle until the demersal stage. The surface of the larva now shows many microvilli. Details of the organization of several ciliary structures are clarified. Moreover, the present study shows rapid, sequential development of paired setal sacs, with the most anterior pair appearing first.

Animals↗
PubMed1994

DNA cruciforms facilitate in vitro strand transfer on nucleosomal templates.

A single, phased nucleosome assembled on a 240 bp DNA duplex molecule blocked Escherichia coli RecA protein-promoted strand transfer of the complementary strand of the duplex onto a homologous single-stranded circle. However, when a four-armed cruciform structure was coupled to either end of the duplex the barrier to strand transfer was overcome and joint molecules were efficiently formed. Micrococcal nuclease digestion indicated that the nucleosome was dissociated by the juxtaposition of the cruciform. We interpret these results to mean that cruciform structures can act over a distance to destabilize adjacent nucleosomes and suggest that, as a consequence, the chromatin structure surrounding a crossed strand recombination intermediate might be disrupted, enabling other recombination events to initiate or the process of branch migration to proceed.

Base Sequence↗
PubMed1990

Brush cells of the mouse gallbladder. A correlative light- and electron-microscopical study.

The brush cells (BC) of the mouse gallbladder were studied using light and electron microscopy (transmission and scanning) to determine their shape and distribution. Specimens were fixed in glutaraldehyde and postfixed in ferrocyanide-reduced osmium tetroxide. BC selectively stained with toluidine blue could be identified by means of light microscopy and subsequently studied in serial semithin and ultrathin sections. The results revealed that the shape of the BC is flask-like. A slender, occasionally branched cytoplasmic process emerges from the bulk cell body and extends through the basal region of neighboring epithelial elements to the basement membrane. Examination of the entire gallbladder epithelial surface by scanning electron microscopy revealed that the BC are numerous in the neck region of the organ but only scanty or even absent in wide areas of the corpus region. Their number increases again in the fundic region. These results demonstrate a preferential regional distribution of BC in the gallbladder, which is discussed in relation to a possible functional significance of the BC.

Animals↗
PubMed1990

Protein gene product 9.5-immunoreactive nerve fibres and cells in human skin.

Sections of human skin were processed according to the indirect immunofluorescence technique with a rabbit antiserum against human protein gene product 9.5 (PGP 9.5). Immunoreactivity was detected in intraepidermal and dermal nerve fibres and cells. The intraepidermal nerves were varicose or smooth with different diameters, running as single processes or branched, straight or bent, projecting in various directions and terminating in the stratum basale, spinosum or granulosum. The density of the intraepidermal nerves varied between the different skin areas investigated. PGP 9.5-containing axons of the lower dermis were found in large bundles. They separated into smaller axon bundles within the upper dermis, entering this portion of the skin perpendicular to the surface. Then they branched into fibres mainly arranged parallel to the epidermal-dermal junctional zone. However, the fibres en route to the epidermis traversed the upper dermis more or less perpendicularly. Furthermore, immunoreactive dermal nerve fibres were found in the Meissner corpuscles, the arrector pili muscles, hair follicles, around the eccrine and apocrine sweat glands and around certain blood vessels. Such fibres were also observed around most subcutaneous blood vessels, sometimes heavily innervating these structures. Numerous weakly-to-strongly PGP 9.5-immunoreactive cells were found both in the epidermis and in the dermis.

Fluorescent Antibody Technique↗
PubMed1992

Cytoskeletal changes accompanying ACTH-induced steroidogenesis in cultured embryonic adrenal gland cells from the Pekin duck.

Cells derived from the adrenal glands of duck embryos immediately prior to hatching were grown in culture and used to study the morphological and cytoskeletal changes and steroidogenic responses induced by 1-24 ACTH. Changes in the cytoskeletal components were observed by rhodamine-phalloidin staining for actin and by staining the tubulin immunoreactive components with FITC. The cultures were comprised of a small population of chromaffin cells and a larger population of steroidogenic cells. The chromaffin cells were distinguished by their tyrosine hydroxylase immunoreactivity. The steroidogenic cells were characterized by the presence of sudanophilic lipid droplets, numerous mitochondria, abundant smooth endoplasmic reticulum, microtubules distributed as a fairly even network throughout the cytoplasm, and microfilaments that formed an extensive and elaborate system of stress fibers with many parallel arrays. The cells readily responded to stimulation with ACTH by releasing corticosterone, aldosterone and deoxycorticosterone. Stimulation with ACTH also induced changes in both the cell morphology and the cytoskeleton. Exposure of the cells to Krebs-Henseleit buffer containing 1-24 ACTH caused them to form numerous fine filopodia, to lose their stress fibers, and to form a thick ring of actin at the periphery of the cell. In addition, many cells became extremely arborized with many long branched dendritic processes. The morphological changes appeared to be related to a redistribution of the actin components, and may be explained only in part by the rounding up or retraction of the cytoplasm. The results strongly suggest an involvement of the actin components of the cytoskeleton in the steroidogenic response to corticotropic stimulation.

Actin Cytoskeleton↗
PubMed1986

Ultrastructural localization of S-100 protein in neurofibroma.

The nature of the cells in neurofibromas was studied by electron microscopy and immunoelectron-microscopic examination of S-100 protein. Ultrastructurally, all five neurofibromas studied were found to be composed of Schwann cells, perineurial cells, and intermediate cells, which had features of both perineurial cells and fibroblasts. The Schwann cells had complex, branched cytoplasmic processes and a continuous basal lamina. The perineurial cells were distinguishable from Schwann cells by the presence of numerous pinocytotic vesicles, unbranched slender cytoplasmic processes and a discontinuous basal lamina. The intermediate cells had no basal lamina, but were topographically related to Schwann cells and had a similar fine structure to that of perineurial cells. Thus, they seemed to be modified neoplastic perineurial cells. Immunoelectron-microscopic studies showed the presence of cells with and without S-100 protein in the neurofibromas: cells with S-100 protein resembled Schwann cells ultrastructurally, and those without S-100 protein were perineurial and intermediate cells. Some Schwann cells with S-100 protein in one neurofibroma had numerous pinocytotic vesicles characteristic of perineurial cells, suggesting that Schwann cells and perineurial cells are functional variants of the same cell type. Thus this study showed that neurofibromas were composed of Schwann cells with S-100 protein and perineurial and intermediate cells, including so-called endoneurial fibroblasts, without S-100 protein. Morphological and functional transition seems to occur between Schwann cells and perineurial cells, and between perineurial cells and intermediate cells.

Adult↗
PubMedDate not supplied

Tumor cell settling and early invasion of the peritoneum.

A Sewall Wright strain-2 guinea pig model producing malignant ascites after injection of a diethylnitrosamine-induced hepatocellular carcinoma cell suspension (Line-10) was used to demonstrate the multilayered settling of tumor cells on the peritoneal surface, frequently followed by the formation of papillary projections and the early invasion in a proliferating submesothelial tissue. At the border of tumor cells and the desmoplastic tissue the malignant cells changed their shape and generally two categories were recognized. Often multilayering, atypical flat cells covered the stromal tissue, while mostly rounded ones invaded using their branched penetration processes, being devoid of cationized ferritin, which was only present on the luminal sides of all cellular elements. Flattened malignant cells, penetrating processes and invading cells lost their microvillous surface pattern. The infiltrating cells were often only detectable with the monoclonal antibody 10 TL 40 and the anti-cytokeratin OV TL 12-5, demonstrating the need for immunohistochemistry in diagnosing solitary invading malignant cells in light microscopy. It appeared that still numerous mesothelial cells were found scattered deeply within the desmoplastic tissue. These former lining cells were identified by their junctions and the presence of remnants of basal lamina as well as by their microvillous 5'-nucleotidase activity.

5'-Nucleotidase↗
PubMed1988

Hodgkin cells in freeze-fracture replicas.

Lymph nodes from six patients with Hodgkin's disease (three with the nodular sclerosing subtype, one with mixed cellularity and two with the lymphocyte-predominant subtype) were analysed by electron microscopy in freeze-fracture replicas and thin sections. Two main variants of Hodgkin cell could be identified in the nodular sclerosing and mixed cellularity subtypes. (1) Hodgkin cells with wide cytoplasm and short, smooth- and rough-surfaced tubular profiles of endoplasmic reticulum (ER) unevenly scattered in the cytoplasm. (2) Hodgkin cells with well developed rough ER. In freeze-fracture replicas the ER was seen to consist of both short and long tubules, some of the latter forming anastomoses with each other. Both cell types possessed branching cytoplasmic processes. A P-face rich in intramembrane particles (IMP) and an E-face with few IMP were common to both Hodgkin cell types. These cells do not, therefore, possess the membrane features characteristic of interdigitating reticulum cells, thus refuting the previously held belief that Hodgkin cells, in particular lacunar cells, are related to interdigitating reticulum cells. The cytoplasmic structures and membrane characteristics of Hodgkin cells in the lymphocyte-predominant subtype (L & H cells) are similar to other Hodgkin cells in that they may show a high content of rER, and the P-face of these cells contains more IMP than the E-face. Both characteristics support the theory put forward in the literature (based on immunohistochemical findings) that these are lymphoid cells (immunoblasts or immature plasma cells).

Freeze Fracturing↗
PubMedDate not supplied

Spiral CT virtual endoscopy of abdominal arteries: clinical applications.

Virtual endoscopy enables the creation of endoluminal views of the aorta and its branches by processing spiral computed tomographic (CT) images, thereby allowing the preoperative and postoperative evaluations of abdominal aortic aneurysms, aneurysms of the splenic, celiac, and common iliac arteries, and renal artery stenoses. Moreover, it is helpful for verifying the position of stents and endoprostheses from within the aortic lumen. This method is a promising addition to spiral CT.

Aneurysm↗
PubMed2004

Ultrastructural study of echinocytes induced by poly (ethylene glycol)-cholesterol.

Poly (ethylene glycol)-cholesterol (PEG-Chol) consists of a hydrophilic PEG and hydrophobic cholesterol moiety. When PEG-Chol was applied to erythrocytes, the reagent quantitatively induced protrusions by exclusively distributing in the outer monolayer of the membrane. This kind of response has been regarded as a general response that reduces the stress of expansion of the outer monolayer. However, the relationship between the membrane architecture and the distribution of such molecules is unknown. In this study, we examined the distribution of tagged PEG-Chol along the shape change pathway. The echinocytic shape was initiated by the initial formation of bumps on the rim of the discoid, which subsequently elongated as protrusions. These protrusions contained aggregates of granular structures, which appeared to accommodate the increase in the outer monolayer area. At higher concentrations, PEG-Chol further induced sphero-echinocytosis that resulted in numerous branched protrusion processes. We found that PEG-Chol was exclusively distributed in these protrusions and, in particular, accumulated at the tips. These results suggested that externally intercalated PEG-Chol was sequestrated from erythrocytes as membrane protrusions through an as-yet-unknown mechanism.

Cell Surface Extensions↗
PubMed1997

Distribution of glial fibrillary acidic protein-immunopositive structures in the developing brain of the turtle Mauremys leprosa.

This study is a continuation of the description of the glial fibrillary acidic protein (GFAP)-immunopositive structures in the adult turtle brain (Kálmán et al. 1994) and presents a comprehensive description of the development of these structures from the 20th embryonic day (E20) to the adult age. GFAP-immunopositive elements were first detected at E28 and by E34 the GFAP-immunopositivity was apparent throughout the brain, except the cerebellum. The appearance of GFAP seemed to be related to the end of cell migration and the formation of the thickened parts of the brain wall, such as the dorsal ventricular ridge. After hatching the pattern of the GFAP-immunopositivity differed from that in the adult only in minute details, except for the brain tracts in which GFAP-pattern was still changing due to myelination, and the molecular layer of the cerebellum in which a transverse fiber system appeared. The GFAP-positive elements belonged originally to the ependymoglia, but later the distortion due to the morphogenetic processes of branching and division changed the pattern almost beyond recognition. In some cases cell bodies--ependymal and non-ependymal--appeared to be GFAP-positive, but no astrocytes (i.e. stellate cells) were detected. The results are discussed in the light of previous observations on developing mammalian, avian and lizard brains.

Aging↗
PubMed2004

Leaf photosynthetic traits scale with hydraulic conductivity and wood density in Panamanian forest canopy trees.

We investigated how water transport capacity, wood density and wood anatomy were related to leaf photosynthetic traits in two lowland forests in Panama. Leaf-specific hydraulic conductivity ( k(L)) of upper branches was positively correlated with maximum rates of net CO(2) assimilation per unit leaf area ( A(area)) and stomatal conductance ( g(s)) across 20 species of canopy trees. Maximum k(L) showed stronger correlation with A(area) than initial k(L) suggesting that allocation to photosynthetic potential is proportional to maximum water transport capacity. Terminal branch k(L) was negatively correlated with A(area)/ g(s) and positively correlated with photosynthesis per unit N, indicating a trade-off of efficient use of water against efficient use of N in photosynthesis as water transport efficiency varied. Specific hydraulic conductivity calculated from xylem anatomical characteristics ( k(theoretical)) was positively related to A(area) and k(L), consistent with relationships among physiological measurements. Branch wood density was negatively correlated with wood water storage at saturation, k(L), A(area), net CO(2) assimilation per unit leaf mass ( A(mass)), and minimum leaf water potential measured on covered leaves, suggesting that wood density constrains physiological function to specific operating ranges. Kinetic and static indices of branch water transport capacity thus exhibit considerable co-ordination with allocation to potential carbon gain. Our results indicate that understanding tree hydraulic architecture provides added insights to comparisons of leaf level measurements among species, and links photosynthetic allocation patterns with branch hydraulic processes.

Carbon Dioxide↗
PubMed1983

Task analysis methods in industry.

Task analysis is one of the basic tools used by ergonomists in investigating and designing tasks. It provides a formal comparison between the demands which the task places on the human operator and the capabilities the human operator possesses to deal with these demands. Three types of task analysis are described: sequential, branching and process control. Alternative formats are presented and examples given of their use in an industrial setting.

Journal Article↗
PubMed1983

Enhanced growth and morphological differentiation of isolated adult rat oligodendrocytes in vitro: use of a naturally produced extracellular matrix.

Attachment, growth and morphological differentiation of isolated adult rat oligodendrocytes cultured on a naturally produced basement membrane-like extracellular matrix (ECM) occurred much faster than on poly-L-lysine (PLL) coated tissue culture dishes. In each individual trial the cells cultured on ECM exhibited, within 3-5 days in culture, a massive outgrowth of long and branched cytoplasmic processes. Outgrowth to such an extent, using PLL or plastic tissue culture dishes, was not observed even after 2 weeks in culture. The successful high plating efficiency, rapid growth and network formation as well as its resemblance to the in vivo environment of cells make this naturally produced substrate a superior substitute for PLL and therefore more attractive for studying the behavior and function of oligodendrocytes in vitro.

Animals↗
PubMed1986

Distribution of VIP- and NPY-like immunoreactivities in rat main olfactory bulb.

The distribution of vasoactive intestinal peptide (VIP)- and neuropeptide Y (NPY)-like immunoreactivities in the Sprague-Dawley rat main olfactory bulb was analyzed using the peroxidase-antiperoxidase light microscopic immunocytochemical technique. VIP-like immunoreactivity was most prominently localized within a large number of intermediate-sized neurons whose perikarya and extensively branched varicose processes remained confined to the external plexiform layer (EPL). A few small short-axon type neurons in the mitral cell layer and granule cell layer (GRL) and even fewer large neurons in the glomerular layer (GL)/EPL border region contained immunoreactivity for VIP as well. Neuropeptide Y-like immunoreactivity (NPY-I) was principally localized within sparsely distributed large multipolar neurons of the deep GRL and within axons distributed with diminishing density from deep to superficial GRL. In addition, dense NPY-I was localized within very few large superficial short-axon type neurons of the GL/EPL border region. The restricted laminar and cellular distribution of NPY-I and VIP-I suggests that both peptides may act to modulate granule cell activity, and therefore, indirectly, olfactory bulb output.

Animals↗
PubMed1991

Localization of immunoreactive lipocortin-1 in the brain and pituitary gland of the rat. Effects of adrenalectomy, dexamethasone and colchicine treatment.

The presence and localization of endogenous lipocortin-1 (LC-1, a protein which has been proposed to mediate the anti-inflammatory actions of the glucocorticoids) was studied by immunohistochemical techniques in rat brain and pituitary. A polyclonal antiserum specific for a fragment of lipocortin-1 (alpha alpha 1-188) was used to visualize immunoreactive LC-1 (iLC-1) in both neuronal and non-neuronal cell structures. Neuronal staining, which was independent of microtubular axonal transport mechanisms (in that it was not affected by blockade of axonal transport), was found in varicose nerve fibres in various regions of the brain. In addition, iLC-1 was found in the cytoplasm of neuronal cells throughout the brain. Of all brain regions which showed iLC-1, only the hippocampal neurons showed a reduced staining intensity after adrenalectomy. However, iLC-1 was not affected by dexamethasone treatment. Non-neuronal iLC-1 was found in ependymocytes lining the cerebral ventricles and aqueduct. In addition, iLC-1 was found in tanycytes in all circumventricular organs studied and in the ventral walls of the third ventricle, where some of the branching tail processes appeared to envelop local capillaries and neuronal cell bodies. A tancycyte-mediated release of LC-1 from varicose nerve fibres into the portal vasculature is proposed.

Adrenalectomy↗
PubMed1984

Alterations in the postnatal development of the cerebellar cortex due to zinc deficiency. II. Impaired maturation of Purkinje cells.

Zinc deficiency during the first 3 postnatal weeks retarded the maturation of Purkinje cells. The dendrites of the Purkinje cells of 21-day-old zinc-deficient (ZD) rats were reduced in size and had fewer branches. Somatic processes were found in 24% of the Purkinje cells of ZD animals. Only 3% of the Purkinje cells of normal animals had somatic processes. A basal polysomal mass in the Purkinje cells of 21-day-old ZD rats indicated that zinc deficiency impaired the cytoplasmic maturation of Purkinje cells. The development of the glial envestment of the dendrites and the maturation of climbing fibers also were retarded. Pair-fed controls were studied to control for the effects of inanition in the ZD dams. In the pups of pair-fed dams, undernutrition slightly impaired the growth of the dendrites but produced few qualitative changes in the maturation of the soma and climbing fibers. Somatic processes were found on 10% of the Purkinje cells of pair-fed animals. Thus, the findings in the ZD animals were not only caused by the decreased maternal food consumption but by zinc deficiency. The retarded maturation of Purkinje cells was related to the altered metabolism of Purkinje cells and to effects secondary to decreased numbers of parallel fibers.

Aging↗
PubMed1992

Development of AChE-positive neuronal projections from basal forebrain to cerebral cortex in organotypic tissue slice cultures.

Development of the innervation of the cerebral cortex by acetylcholinesterase (AChE)-stained basal forebrain neurons was studied in vitro using the roller tube technique. Slice cultures were maintained from 3 days to 4 weeks either in serum based medium or in chemically defined medium, each supplemented in some cases with nerve growth factor (NGF). The distribution of AChE and choline acetyltransferase (CAT)-containing neurons was investigated using histo- and immunocytochemical techniques. Slice cultures of basal forebrain revealed the presence of large and medium sized AChE-positive neurons. Within one week of cultivation, numerous AChE-labeled fibers could be seen growing out from the basal forebrain toward the cortex. After entering cortical tissue most of the afferent basal forebrain fibers projected either radially or obliquely into the cortical layers. Many afferent axons initially also travelled tangentially within the white matter, and turned then to grow into the cortical layers. Cerebral cortex tissue maintained a coarse laminar organization. Ramifications of basal forebrain fibers were visible within the subplate region, the deep and superficial cortical layers, and within the marginal zone; greatest density occurred in the subplate region and in marginal zones. Many of these processes exhibited branching patterns markedly similar to those observed during cortical development in vivo. Cortex slices placed with the pial surface adjacent to the basal forebrain revealed AChE-stained fibers that entered the cortical tissue through the marginal surface and gave off ramifications within the superficial layers and, less frequently, the deeper cortical layers. CAT-immunostaining revealed labeled cell bodies and neurites only in the basal forebrain, not in the cortex tissue. Control experiments with co-cultures of basal forebrain and cerebellum slices showed no AChE-positive fiber ingrowth into the cerebellum tissue. The results of these studies demonstrate that basal forebrain projections to cerebral cortex in vitro appear similar to the projections that develop in vivo, and indicate that organotypic co-cultures provide a valuable model for studies of developing cortical afferents.

Acetylcholinesterase↗