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 487 records · Page 27Linked to original sources
PubMed1995

Are moment bounds on the recombination fraction between a marker and a disease locus too good to be true? Allelic association mapping revisited for simple genetic diseases in the Finnish population.

In the past several years, allelic association has helped map a number of rare genetic diseases in the human genome. A commonly used upper bound on the recombination fraction between the disease gene and an associated marker is known to be biased downward, so there is the possibility that an investigator could be misled. This upper bound is based on a moment equation that can be derived within the context of a Poisson branching process, so its performance can be compared with a recently proposed likelihood bound. We show that the confidence level of the moment upper bound is much lower than expected, while the confidence level of the likelihood bound is in line with expectation. The effects of mutation at either the marker or disease locus on the upper bounds are also investigated. Results indicate that mutation is not an important force for typical mutation rates, unless the recombination fraction between the marker and disease locus is very small or the disease allele is very rare in the general population. Finally, the impact of sample size on the likelihood bound is investigated. The results are illustrated with data on 10 simple genetic diseased in the Finnish population.

Alleles↗
PubMed1996

Linkage disequilibrium mapping places the gene causing familial Mediterranean fever close to D16S246.

This report presents refined genetic mapping data for the gene causing familial Mediterranean fever (FMF), a recessively inherited disorder of inflammation. We sampled 65 Jewish, Armenian, and Arab families and typed them for eight markers from chromosome 16p. Using a new algorithm that permits multipoint calculations for a dense map of markers in consanguineous families, we obtained a maximal LOD score of 49.2 at a location 1.6 cM centromeric to D16S246. A specific haplotype at D16S283-D16S94-D16S246 was found in 76% of Moroccan and 32% of non-Moroccan Jewish carrier chromosomes, but this haplotype was not overrepresented in Armenian or Arab FMF carriers. Moreover, the 2.5-kb allele at D16S246 was significantly associated with FMF in Moroccan and non-Moroccan Jews but not in Armenians or Arabs. Since the Moroccan Jewish community represents a relatively recently established and genetically isolated founder population, we analyzed the Moroccan linkage-disequilibrium data by using Luria-Delbrück formulas and simulations based on a Poisson branching process. These methods place the FMF susceptibility gene within 0.305 cM of D16S246 (2-LOD-unit range 0.02-0.64 cM).

Algorithms↗
PubMed1995

Myxoma of the jaws with an unusual intracellular banded structure.

Myxoma of the jaw is a rare odontogenic tumor, probably derived from the dental apparatus. The case described here was studied by both light and electron microscopic methods. Stellate cells with branching processes were reported in an abundant acid mucopolysaccharide stroma, and ultrastructurally these cells were seen to be fibroblast. Occasionally myxoblasts and macrophages were reported in the tumor. No odontogenic epithelium was identified, while an intracellular synthesis of cross-striated fibrils was observed. The ultrastructural features suggest that the connective tissue cell is the proliferating component of the tumor and is very similar to a fibroblast.

Adult↗
PubMed1996

Identification of the interstitial cells of Cajal.

Observation of whole mount stretch preparations using the zinc-iodide-osmic acid method reveals a wide variety of interstitial cells in different tissue layers of the guinea-pig small intestine. And a subsequent electron-microscopic examination and survey of references makes clear that the interstitial cells of Cajal (ICC) depicted in original drawings of Cajal are heterogeneous and correspond to different types of interstitial cells. The myenteric ICC are characterized by long dichotomous branching processes which constitute cellular networks independent from the nerve plexus and form many gap junctions at their tips. Their ultrastructure is similar to that of fibroblasts and they have no basal lamina. The myenteric ICC show strong immunoreactivity for vimentin and the c-kit receptor, and probably correspond to the intestinal pacemaker cells. Within the circular muscle layer, ICC are represented by the cells that are closely associated with fine nerve bundles. The ICC have various shapes, ranging from bipolar to stellate, depending on the running pattern of the nerve fibers that they are associated with. They show fibroblast-like ultrastructure and have no basal lamina. They form gap junctions with smooth muscle cells and are immunoreactive for vimentin. On the other hand, ICC associated with the deep muscular plexus described in the guinea-pig by Cajal could not be clearly identified. However, it is suggested that the ICC in this location may correspond to glycogen-rich cells possessing a basal lamina. Although they show a fairly well-developed rough endoplasmic reticulum, Golgi apparatus and immunoreactivity for vimentin, ICC of the deep muscular plexus are probably specialized smooth muscle cells in nature.

Animals↗
PubMedDate not supplied

[Algorithmic support of a laboratory bed for testing geroprotectors and geropromoters].

The paper proposes a mathematical model of development of a cell population with a changing proliferative activity. The model is based on the Markov branching process with cells of several types. A procedure for identifying the constructed model by experimental evidence is being developed. An example of model construction and assessment for cultured diploid fibroblasts is given.

Aging↗
PubMed1998

Induction of resting microglia in culture medium devoid of glycine and serine.

Cultured microglial cells usually exhibit ameboid morphology and peripheral macrophage-like properties, which are distinct from those observed in the normal mature brain. This might be caused by the inappropriate culture of microglial cells in high concentrations (approximately 200-400 microM) of Gly and Ser, although the concentrations of the amino acids in extracellular spaces of the brain parenchyma are quite low (approximately 5 microM). In the present study, we focused on the concentration-dependent effects of glycine (Gly) and serine (Ser) on microglial morphology and function. Under Gly/Ser-free and serum-free condition, the majority of rat microglial cells displayed round morphology, whereas in the presence of 5 microM Gly and 25 microM Ser, which correspond to the concentrations of Gly and Ser in the cerebrospinal fluid, they extended multiple branched processes and formed clusters of rough endoplasmic reticulum. On the other hand, Gly and Ser did not affect morphology of astrocytes. The viability of microglia was not affected by the changes in the concentrations of Gly and Ser. Metabolic activity, activities of acid phosphatase and inducible nitric oxide synthase, and superoxide anion (O2-) generation were all strongly suppressed in Gly/Ser-free medium or in medium containing physiological concentrations of both amino acids. Such activities were all enhanced in harmony with increases in the concentrations of Gly and Ser. Thus, microglial cells cultured in Gly/Ser-free medium, even though exhibiting ameboid morphology, appears to be in the functionally resting state. Furthermore, once the resting state was achieved, the microglial cells remained inactive even after the subsequent 24 h culture in serum-supplemented medium containing 400 microM of both amino acids. The medium conditioned by microglial cells that were cultured in the presence of 400 microM of Gly and Ser was toxic to cortical neurons, whereas the microglia-conditioned medium obtained in the absence of both amino acids facilitated the survival of cortical neurons. Therefore, microglial cells in the resting state, which was induced in the Gly/Ser-free condition, are likely to support neurons. Microglial cells could ramify on glass coverslips coated with astrocyte-derived extracellular matrix or on coverslips coated thinly with fibronectin and/or laminin even under the Gly/Ser-free condition. The ramified cells as induced in this way kept suppressed O2- generating activity. These findings suggest that resting ramified microglial cells with a neurotrophic activity can be induced with the combination of Gly/Ser-free medium and small amounts of extracellular matrix proteins, and that the resting state is rather stable.

Acid Phosphatase↗
PubMed1976

Estimation of age and rate of increase of rare variants.

The problem considered is that of estimating the age or rate of increase of a variant on the basis of the present number of replicates observed in a population. In place of previous diffusion equation analyses of age probability distributions, the likelihood for the age is studied on the basis of a discrete branching process model. It is shown that variations inherent in the process of gene evolution in natural populations make it impossible to provide a reliable point estimate of the age of a specified variant, although the likelihood analysis provides a confidence interval which may place useful bounds on the period in which a variant originated. The observed distribution of numbers of several variants may also provide useful information. The problems of estimation are discussed with reference to rare variants arising in American Indian populations.

Alleles↗
PubMed1998

[Clinical evaluation of MRCP].

Recently, MRCP can be obtained with good spacial resolution within a few seconds using half fourier fast spin echo technique. From July 1995 to August 1997, 1000 patients suspected of having pancreatobiliary diseases were examined with MRCP. MRCP was performed with 1.5 T scanner using Fast Asymmetric Spin Echo sequence (FASE). Satisfactory images of the main pancreatic duct were obtained in 98%, of Santorini's duct in 90%, and of uncinate process branch in 83%. Pancreas divism was accurately diagnosed. In the patients with pancreatic ductal adenocarcinomas, MRCP depicted stenosis and proximal dilatation of the main pancreatic duct in 89%, and in the remaining patients no abnormalities were seen in the main pancreatic ducts because tumors were limited to side branches or Santorini's duct or distal end of the tail of the pancreas. Diagnosis of small pancreatic carcinomas (smallest lesion measured 10 mm in diameter) were feasible. In the patients with intraductal papillary neoplasms, dilatation of the main pancreatic duct and cystic dilatation of side branches were depicted, and polypoid lesions were detectable with source images. In the patients with serous cystadenomas, accumulation of the microcysts were visualized. In the patients with chronic pancreatitis, dilatation and stenosis of the main pancreatic duct, as well as side branch dilatation was depicted despite overestimation of the extent of the stenosis. Stones in the main pancreatic duct were well visualized as intraductal filling defects. In conclusion, MRCP is an effective imaging technique in the diagnosis of various pancreatic diseases.

Biliary Tract↗
PubMed1984

The odontoblast process and its branches in human teeth observed by scanning electron microscopy.

Healthy teeth were fixed, resin-impregnated and freeze-fractured. Specimens were critical point-dried and examined by scanning electron microscopy. Odontoblast processes were observed in the inner-, middle- and peripheral dentine. The processes in the inner-third dentine closely approximated tubule wall and could be found in most of the tubules. Some tubules contained a thin fibre besides the odontoblast process. In the middle third of dentine, the processes became thinner, their appearance was cable-like with lateral branches and a wide periodontoblast space could be seen. Processes were seen only in a few tubules of outer-third dentine in both young and aged subjects. They divided into longitudinal and lateral branches and seemed to be connected with one another.

Adolescent↗
PubMedDate not supplied

[Structuro-functional analysis of identified grape snail neurons].

The study of microanatomy of central neurons in Helix pomatia showed that each identified neurone has a constant number of definitely directed processes. The branching pattern of the processes is also specific for each neurone, but in the same cell the number of the branches may vary. It is concluded, that the general morphology of the neurone is its sufficiently stable characteristic and may serve as a criterion for its identification. The possible functional role of different types of the neurone's branchings is discussed. It is suggested that the processes and branches of RPa3 neurone are axones whereas the branches in the form of fine threads are dendrites. It is shown that the neurone with such organization of process branchings play integrative and command functions.

Animals↗
PubMed1999

Spatial arrangement of the pancreatic ducts in the head of the pancreas with special reference to the branches of the uncinate process.

BACKGROUND: It remains very difficult to clarify the spatial arrangement of the branches of the pancreatic ducts in the head of the pancreas despite recent progress in diagnostic imaging techniques. METHODS: We minutely dissected the head region from 15 cadavers after injection of silicone rubber into the ducts through the papilla of Vater to investigate the distribution of these ducts. RESULTS: We found that the branches that drained the uncinate process not only joined the main pancreatic duct but also constantly joined the accessory pancreatic duct. In addition, the branches of the uncinate process that joined the accessory duct ran anterior to those to the main duct. We classified the arrangement of the pancreatic ducts into type 1 (10 cases) and type 2 (5 cases) on the basis of the pattern of the branches of the uncinate process. The distance from the papilla of Vater to the junction of the main and accessory pancreatic ducts in type 1 (> 23.0 mm) was significantly longer than that in type 2 (< 22.0 mm). CONCLUSIONS: Careful attention should be paid to the branches of the uncinate process to the accessory pancreatic duct to enable more accurate diagnoses of the pancreas head region.

Aged↗
PubMed1990

Migration of neuroblasts by perikaryal translocation: role of cellular elongation and axonal outgrowth in the acoustic nuclei of the chick embryo medulla.

The neuroblasts forming nucleus magnocellularis, the avian homologue of the mammalian ventral cochlear nucleus, migrate by growth and elongation of their leading processes and by perikaryal translocation through these processes from the matrix zone of the rhombic lip to the acoustico-vestibular anlage. Golgi methods were used on staged chick embryos to reconstruct the morphogenetic phases of migration and early differentiation in situ. Fluorescence labeling of the living cells in vitro elucidated the role of axonal growth in the migratory process. In situ, branching cochlear nerve fibers, tipped with growth cones, enter the acoustico-vestibular anlage at E4.5-5.5 before migration of the magnocellularis neuroblasts at E.5.5-6.5. The premigratory neuroblasts in the matrix zone of the rhombic lip resemble primitive epithelial cells, which extend branched, curving processes into a characteristic formation, the rhombic whorl. The leading process of the migrating magnocellularis neuroblasts gives rise to a bifurcating axon at the interface between the matrix and mantle zones. The lateral branch becomes the recurrent ipsilateral collateral; the medial branch crosses the midline, heading toward the contralateral target site in the region of the presumptive nucleus laminaris. The cell bodies of the migratory neuroblasts appear in intermediate locations along the migration route as they translocate radially through their leading processes past the axonal bifurcation and then tangentially and obliquely into the mantle zone. Neuroblasts destined for nucleus laminaris migrate coincidentally with magnocellularis neuroblasts. Nucleus angularis neuroblasts migrate later in development, after E6.5. In vitro, injections of a nontoxic fluorescent dye (diI) were made into explants of the medulla in the region of the contralateral target area at the time of neuroblast migration. DiI retrogradely labeled the cell bodies of premigratory magnocellularis neuroblasts in the matrix zone and of migratory neuroblasts in the mantle zone through their medial, crossing axonal branches. The morphology of the living neuroblasts in the explants resembled that in the Golgi impregnations at the corresponding stages of migration. Anterograde axonal transport also occurred. These results demonstrate migration by perikaryal translocation and early axon extension of a specific group of neuroblasts in the central nervous system. The morphology of the migrating neuroblasts is such that a simple radial arrangement of cellular guides, glial or otherwise, would not account for their configurations. The available evidence supports the proposition that cellular elongation and perikaryal translocation constitute the general mode of neuronal migration in the central nervous system. The early extension of axons into their target sites may play a critical role in migration and early development of specific types of neurons.

Animals↗
PubMed2005

Similarities and dissimilarities of branching and septation during lung development.

The lungs of small premature babies are at a developmental stage of finalizing their airway tree by a process called branching morphogenesis, and of creating terminal gas exchange units by a mechanism called septation. If the branching process is disturbed, the lung has a propensity to be hypoplastic. If septation is impaired, the terminal gas exchange units, the alveoli, tend to be enlarged and reduced in number, an entity known as bronchopulmonary dysplasia. Here, we review current knowledge of key molecules influencing branching and septation. In particular, we discuss the molecular similarities and dissimilarities between the two processes of airspace enlargement. Understanding of the molecular mechanisms regulating branching and septation may provide perinatologists with targets for improving lung growth and maturation.

Extracellular Matrix↗
PubMed1994

Phorbol ester-stimulated stellation in primary cultures of astrocytes from different brain regions.

Stellation is the process by which astrocytes change from epithelial-like to process-bearing cells. Stellation occurs following activation of either cyclic AMP-dependent protein kinase or protein kinase C. This process occurs through tubulin-dependent rearrangement of the cytoskeleton. We have evaluated the ability of phorbol, 12-myristate, 13-acetate (PMA) to induce astrocyte stellation. Astrocytes from five brain regions (cerebellum, cerebral cortex, hippocampus, diencephalon, and brain-stem) were examined to determine if all astrocytes would exhibit similar responses to this activator of protein kinase C. Stellation was evaluated following cell fixation by either phase optics using conventional light microscopy, or scanning laser confocal light microscopy of cultures prepared using immunocytochemistry for tubulin and glial fibrillary acidic protein. Both the number of cells responding to PMA and the sensitivity to PMA varied for astrocytes from each brain region. PMA-induced stellation was most robust in cerebellar and brainstem astrocytes, with greater than 70% responding. Less than 40% of hippocampal and diencephalic astrocytes responded to PMA at the maximum dose (10(-5) M). PMA also induced different numbers of processes or branching patterns of processes on astrocytes from different brain regions. The protein kinase C induced stellation response in astrocytes supports the hypothesis that astrocytes contribute to neural plasticity.

Animals↗