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.

SourceResearch connectionFrom yearThrough year

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

At least 577 records · Page 32Linked to original sources

PubMed2005

Quantum yields for Cl(2P(j)) atom formation from the photolysis of chlorofluorocarbons and chlorinated hydrocarbons at 193.3 nm.

Cl(2P(3/2)) and Cl*(2P(1/2)) atoms produced from the photodissociation of chlorofluorocarbons (CFCs) and chlorinated hydrocarbons at 193.3 nm have been detected quantitatively by a technique of vacuum ultraviolet laser-induced fluorescence (VUV-LIF) spectroscopy at 135.2 and 134.7 nm for j = 1/2 and 3/2, respectively. The quantum yields for total Cl-atom formation in the 193.3 nm photolysis at 295 +/- 2 K have been determined to be 1.03 +/- 0.09, 1.01 +/- 0.08, 1.03 +/- 0.08, 1.03 +/- 0.10, 1.41 +/- 0.14, 1.02 +/- 0.08, and 0.98 +/- 0.08 for CF2Cl2, CFCl3, CH2Cl2, CHCl3, CCl4, CHFCl2, and CCl3CF3, respectively. Those results suggest that the single C-Cl bond rupture always occurs in the photolysis of these molecules except for CCl4. Formation of two Cl atoms partly takes place in the photodissociation of CCl4. The quantum yields for total Cl-atom formation in the 193.3 nm photolysis of CHBr2Cl and CHBrClCF3 are 0.27 +/- 0.02 and 0.28 +/- 0.02, respectively, which suggests that the C-Br bond rupture is a main channel in the photodissociation processes. The branching ratios between the spin-orbit states, Cl*(2P(1/2)) and Cl(2P(3/2)), have also been determined for the photodissociation of the chlorinated compounds at 193.3 nm. The UV photodissociation processes giving rise to formation of Cl(2P(j)) atoms from the chlorinated compounds studied here have been discussed.

Journal Article↗

PubMed1988

Physiological and morphological characterization of OFF-center amacrine cells in the turtle retina.

OFF-center amacrine cells were intracellularly recorded and stained with Lucifer yellow to investigate the cell correlations between photoresponses and morphological features. All OFF-amacrine cells were monostratified and branched within the outer half of the inner plexiform layer. In the flat-mounted retina, however, three distinct morphological classes were distinguishable, which correlated with observed physiological differences. Class 1 consisted of wide-field, stellate amacrine cells with long, thin processes, which branched only close to the soma. The diameter of the circular dendritic field ranged from 0.8 mm to 2.0 mm. Their photoresponse to spot stimulation was a hyperpolarization during light-ON and a small depolarization after light-OFF. They showed strong antagonistic center-surround organization of the receptive field. Its size was approximately equal to the dendritic field size. Class 2 consisted of wide-field, giant amacrine cells with a "central" dendritic field formed by thick dendrites, and a "peripheral" dendritic field formed by a few long and thin, "axonlike" processes. The shape of the dendritic field was elongated, with the long axis parallel to the visual streak. Their receptive field size was considerably smaller than their dendritic field size, which was several millimeters of diameter along the long axis. Their photoresponse to spot stimulation was a fast depolarization after light-OFF, and about 50% of these cells showed strong antagonistic center-surround receptive field organization. Class 3 consisted of small- or medium-field, "starburstlike" amacrine cells with circular dendritic fields of 0.1 mm to 0.6 mm diameter. Their fine, beaded dendrites branched predominantly in the distal parts of the dendritic field. their photoresponses to light were similar to those of the giant amacrine cells; however, their receptive field size exceeded the dendritic field size. Radial sections of the retinas with labeled cells were incubated in antisera to reveal the putative transmitters GABA, serotonin, neurotensin, met-enkephalin and glucagon. No immunoreactivity with these antisera was detected within the stained OFF-center amacrine cells.

Animals↗

PubMed1979

Phenytoin (dilantin)-induced cleft lip and palate in A/J mice: a scanning and transmission electron microscopic study.

High incidences of cleft lip and palate (CLP) produced by maternal intraperitoneal administration of 75 mg/kg phenytoin on gestational day 10 to A/J mice are associated with a severe size reduction in the lateral nasal process. Scanning and transmission EM analyses of this region demonstrate a marked change in the morphology of the mesenchymal cells underlying the surface epithelium in treated versus control day 11 (7-tail somite) embryos: long, branching cellular processes, which form a dense meshwork that appears to interact with the epithelial basement lamina in control embryos are undeveloped or absent in phenytoin-treated embryos. The ultrastructural morphology of these cell processes is described and their possible importance in normal development is discussed. Scanning EM observations of incomplete clefts of the lip which frequently result from phenytoin treatment indicate that Simonart's bands form from fusion of the lateral and medial nasal processes in association with a lack of fusion of the maxillary process with the medial nasal process.

Animals↗

PubMed2001

Effect of morphine on the number and branching of astrocytes in various regions of rat brain.

We studied the effects of morphine in high doses on astrocytes in the nucleus accumbens, lateral septum, and caudate nucleus of rat brain. Activation of astrocytes in the nucleus accumbens and lateral septal nucleus was manifested in hyperplasia and elongation of astrocyte processes. In the caudate nucleus, the total length of astrocyte processes and branching of individual astrocytes decreased.

Animals↗

PubMedDate not supplied

A morphometric analysis of transmitter identified dendrites and nerve terminals.

The present method is exemplified on coronal sections of the medulla oblongata containing phenylethanolamine-N-methyltransferase (PNMT) immunoreactive nerve cell bodies and their processes and on coronal sections of the pons containing the locus coeruleus, where PNMT immunoreactive nerve terminals have been demonstrated together with the dopamine-beta-hydroxylase immunoreactive nerve cell bodies. Morphometric analysis of the processes (both length and branches) and of the nerve terminals involve as a first step the division of the area under study into squares 100 microns wide, which are superimposed on a Cartesian plane. The uniformity of the density distribution of the nerve terminals and the processes (branches or length) can be analyzed by Lorenz curves, which in a quantitative way can measure the degree of unevenness and thus represent a measure of concentration. A concentration index can therefore be calculated. By the use of the densitometric approach it also becomes possible to study the density distribution of the nerve terminals with the highest antigen contents. The present method will make it possible to quantitate morphological changes occurring in processes and nerve terminals of transmitter-identified neurons.

Animals↗

PubMed2005

Ultrastructural pathology of prion diseases revisited: brain biopsy studies.

We report here a detailed ultrastructural comparison of brain biopsies from 13 cases of Creutzfeldt-Jakob disease (CJD) and from one case of fatal familial insomnia (FFI). The latter disease has not heretofore benefited from ultrastructural study. In particular, we searched for tubulovesicular structures (TVS), 35-nm particles regarded as the only disease-specific structures at the level of thin-section electron microscopy. Our material consisted of brain biopsies obtained by open surgery from one FFI case from a new French family, one case of variant CJD (vCJD), nine cases of sporadic CJD (sCJD), two cases of iatrogenic (human growth hormone) CJD and one case of hereditary CJD (Val203Iso). The ultrastructural picture of the cerebral cortex of the FFI patient was virtually indistinguishable from that of CJD. TVS were found, albeit only after prolonged search. Typical spongiform change was observed, consisting of intracellular membrane-bound vacuoles containing secondary chambers (vacuoles within vacuoles) and amorphous material. Neuronal degeneration was widespread: some processes contained degenerating mitochondria and lysosomal electron-dense bodies and these met the criteria for neuroaxonal dystrophy. Other processes contained branching cisterns; still others were filled with electron-dense masses and amorphous vesicles. The overall ultrastructural appearance of variant CJD was similar to that of FFI cerebral cortex, except for a much higher number of cellular processes containing TVS. We detected TVS in the majority of sCJD cases that, in addition to typical spongiform change and robust astrocytic reaction, showed widespread neuritic and synaptic degeneration and autophagic vacuoles. We conclude that TVS are readily found in FFI, vCJD and sCJD and that widespread neuritic degeneration is a part of ultrastructural pathology in prion diseases.

Adult↗

PubMed1986

Electron microscope study of osteoclasts with special reference to the three-dimensional structure of the ruffled border.

Osteoclasts of rat mandibulars were observed under the transmission electron microscope with the aim of understanding the three-dimensional structure of the ruffled border. After observation, the same block was remounted to obtain sections of the same osteoclasts at right angles to the first sectioning plane. The structure of the ruffled border of osteoclasts was observed in the two perpendicular directions. The ruffled border of osteoclasts was found to consist of two areas: one being composed of finger-like processes and the other, of plate-like processes. The distribution of the two areas of processes in the ruffled border did not show any apparent regularity. Not all processes continued to the cell body; some processes (stem processes) did while others were interwoven branches of the stem processes. The finger-like processes were long and rod-shaped and a few of them branched directly from the stem processes. The plate-like processes were long and belt-like and showed complicated branching from the stem processes; some of these were possibly the long belt-like processes that were complicatedly folded up to make many secondary plates; they are arranged parallel to each other in a given area. The relationship between the structure and function of the ruffled border is discussed.

Animals↗

PubMed1993

A light-microscopic study on pineal organ structure and innervation in the catfish, Heteropneustes fossilis.

In Heteropneustes fossilis, the pineal organ consists of a long hollow stalk (PS) and an elongate spindle-shaped end vesicle (EV) which lies beneath a highly specialized window. The EV is formed of a dorsal thin and ventral thick parenchymal layer, separated by a lumen and contains photoreceptor, supportive and ganglion cells. The numerous photoreceptor cells are characterized by apical processes which are AF- and PAS-positive. In Holmes' silver preparation, the apical processes showed parallel silver-positive lamellae embedded in luxol fast blue coagulum. The supportive cells are ependymal or glial-like. The ganglion cells or neurons are bipolar or multipolar with prominent dendrites and long, beaded and occasionally branched axonal processes. The neurons are strongly acetylcholinesterase (AChE)-positive. The EV also showed strong toluidine blue-positive mast cells and AF-positive granules and fibres. The PS is composed of the same cellular structures. The neurons are small and AChE-positive. Pineal tract fibres were arranged into dorsal and ventral bundles in the middle and proximal regions of the PS. Silver-positive neurons were found among or close to the pineal tracts. The pineal tract fibres innervate the habenular commissure, habenular nucleus, subcommissural organ, posterior commissure and pretectum, and are AChE-positive. At the origin of the stalk, the pineal tract fibres were seen to project into the ventricle and innervate the subcommissural organ both supraependymally and transependymally.

Acetylcholinesterase↗

PubMed1979

Golgi studies on Purkinje cell development in the frog during spontaneous metamorphosis. II. Details of dendritic development.

The development of Purkinje cell dendrites was studied in the bullfrog from premetamorphic tadpoles to 10-week-old postmetamorphic frog-lets by the Golgi-Kopsch method. In this species two distinct patterns of arbor formation may be seen, which appear to be related to differences in the timing of initial dendritic development. In Purkinje cells that begin development in early tadpole stages, the dendritic tree is elaborated by continuous and concomitant growth and branching, a process by which the developing arbor expands in both height and width. Arbor formation in Purkinje cells that begin development in metamorphosing tadpoles proceeds in two separate steps. Initially, dendrites of such cells elongate, but form only a few poorly developed branches; only when the arbor reaches near-adult height does branching become extensive. Additional differences present in Purkinje cells are reflected in the paucity of growth cones and filopodia in the tadpole, and numerous filopodia and growth cones in the metamorphic period. An interesting feature of dendritic development in this species is a tendency to alter the arboreal domain by the formation of extra-arboreal dendrites, and possibly by the occasional resorbtion of other partially formed dendrites. The pattern of dendritic development in the frog is different than in mammals and is difficult to interpret. Such unusual development may be due to disturbances in the timing of the formation of Purkinje cell dendrites and of the establishment of the external granular layer (EGL).

Animals↗

PubMed1998

Caspases are activated in a branched protease cascade and control distinct downstream processes in Fas-induced apoptosis.

Two novel synthetic tetrapeptides, VEID-CHO and DMQD-CHO, could selectively inhibit caspase-6 and caspase-3, respectively. We used these inhibitors to dissect the pathway of caspase activation in Fas-stimulated Jurkat cells and identify the roles of each active caspase in apoptotic processes. Affinity labeling techniques revealed a branched protease cascade in which caspase-8 activates caspase-3 and -7, and caspase-3, in turn, activates caspase-6. Both caspase-6 and -3 have major roles in nuclear apoptosis. Caspase-6 cleaves nuclear mitotic apparatus protein (NuMA) and mediates the shrinkage and fragmentation of nuclei. Caspase-3 cleaves NuMA at sites distinct from caspase-6, and mediates DNA fragmentation and chromatin condensation. It is also involved in extranuclear apoptotic events: cleavage of PAK2, formation of apoptotic bodies, and exposure of phosphatidylserine on the cell surface. In contrast, a caspase(s) distinct from caspase-3 or -6 mediates the disruption of mitochondrial membrane potential (permeability transition) and the shrinkage of cytoplasm. These findings demonstrate that caspases are organized in a protease cascade, and that each activated caspase plays a distinct role(s) in the execution of Fas-induced cell death.

Antigens, Nuclear↗

PubMed1990

A simple procedure for demonstrating the overall morphology of fibroblasts in routine histological preparations of adult tissues, using silver impregnation.

A silver impregnation procedure for the total visualization of fibroblasts, with all their processes, is described. The method is applicable to routine formalin-fixed paraffin sections, or to formalin-fixed or native cryostat sections. The results are illustrated with examples from loose and dense connective tissue. Fibroblasts are visualized as cells with long, branching dendritic processes. The fibroblasts maintain contact with each other via these processes, thus forming a reticulum of cells, even in adult connective tissue.

Adolescent↗

PubMed1983

Properties of neurons from dissociated fetal rat brain in serum-free culture.

Because of the unknown constituents and varying composition of serum, its presence in media used in cell culture unavoidably compromises attempts to study cellular mechanisms of growth and differentiation. To overcome this, we have devised a serum-free, chemically defined medium which maintains primary cultures of fetal rat brain cells for more than 6 weeks. This medium allows expression of characteristic properties of neurons and prevents overgrowth of non-neuronal elements without use of antimitotic agents. Cells prepared and plated without exposure to serum attach in less than 20 min to poly-D-lysine substratum and begin to extend processes within 1 hr. After 2 days in culture, process-bearing cells can be divided into those with characteristic neuronal morphology, including long processes which generally branch at a distance from the perikaryon, and those having the appearance of glial cells with many short, thin processes which branch frequently near the cell body. The remaining non-neuronal cells are large and flat with few or no processes. The presence of neurons and astroglia was demonstrated by immunofluorescence detection of bound tetanus toxin as a neuron-specific surface marker, and glial fibrillary acidic protein as an astroglial marker. By the 3rd day in culture, many cells of neuronal morphology were able to generate action potentials in response to electrical stimulation. The ionic composition of the inward current changes from Ca2+ to predominantly Na+ by about 10 days in culture. The presence of synaptic vesicles and myelin was demonstrated by electron microscopy. The ability of dissociated cells from mammalian brain to grow in defined medium without serum and acquire selected properties of mature cells in vivo demonstrates the potential of this culture system for neurobiological studies at the cellular level.

Action Potentials↗

PubMed1985

[Comparative electron microscopic study of the visual cortex neurons of the cat in postnatal ontogeny].

The maturation of layers II-VI of neurons and perineuronal neuropil of the cat visual cortex (field 17) was studied from postnatal day 1 to day 21. The differentiation of large, small (associate) pyramid and stellate neurons was described. During the first postnatal week, the somata of layers II-VI of neurons undergo significant changes, the perikaryal cytoplasm increases in volume. Cell bodies of large pyramidal neurons mature by day 15. During the second postnatal week and almost till day 15, the rough endoplasmic reticulum of small pyramidal and stellate neurons undergoes proliferation; dendritic processes are branching. In stellate neurons the amount of cytoplasmic organelles increases dramatically only after the second postnatal week, and this is presumably induced by the opening of eyes on day 12. The second postnatal week is the period of greatest growth of dendritic, axonal and glial processes in perineural neuropil of layers V-VI. In the perineuronal neuropil of large pyramidal neurons (layers V-VI) there appear symmetric synapses with pyramidal cells, dendritic processes and dendritic spines. This occurs just at the time when kittens first open the eyes. From this time and during postnatal days 15-21, asymmetric synapses appear in the perineuronal neuropil of large pyramidal neurons. In the perineuronal neuropil of small pyramidal and stellate neurons. (layers II-IV), synapses reveal the mature appearance by day 15. After the opening of the eyes and up to postnatal day 21, dendritic growth and spine production occur in the perineuronal neuropil of small pyramidal and stellate neurons.

Aging↗

PubMed1996

Glucocorticoids, tumor necrosis factor-alpha, and epidermal growth factor regulation of pulmonary morphogenesis: a multivariate in vitro analysis of their related actions.

The mouse lung commences development on embryonic day 11 as an epithelial evagination from the posterior pharyngeal wall into undifferentiated mesenchyme, this epithelium bifurcating to form the lung primordium. Branching morphogenesis, as well as terminal differentiation, requires epithelial-mesenchymal interactions utilizing precise regulatory controls. Not surprisingly, specific hormones and growth factors appear to play a key role in this regulation. We report here a series of experiments designed to investigate morphodifferentiation (epithelial branching number, generation number, and fractal dimension) and histodifferentiation (cell morphology and SP-A immunolocalization), as they relate to glucocorticoid (CORT)-regulation of growth factor function and expression (Northern analysis). These experiments were conducted in embryonic lung primordia (E11.5-E12) cultured under defined conditions in the presence of single or combined CORT, TNF-alpha, and EGF supplementation. EGF supplementation enhances branching morphogenesis, but not immunodetectable SP-A expression, in embryonic lung primordia cultured for 4 or 7 days. TNF-alpha supplementation also enhances branching morphogenesis on days 4 or 7 in vitro; on day 7, SP-A expression is also enhanced. By contrast, the introduction of exogenous CORT to embryonic explants cultured 4 or 7 days markedly alters morphodifferentiation and histodifferentiation. Early on it would appear to enhance morphodifferentiation by changing the process of branching, while contemporaneously initiating precocious SP-A expression; later on, it alters morphogenesis by continued terminal differentiation of normal lung epithelium and a singular transdifferentiation of lung mesenchyme into an epithelioid morphotype expressing SP-A. This is correlated with a CORT-induced, highly significant, down-regulation of TGF-beta 2 and TGF-beta 3 transcripts. Explants supplemented with CORT + TNF-alpha or CORT + EGF.demonstrate a microanatomy and SP-A expression pattern identical to that seen with CORT supplementation alone. EGF inhibits the accelerated lung maturation normally seen in the presence of exogenous TNF-alpha alone, suggesting a relationship between these two seemingly disparate regulatory pathways.

Animals↗

PubMed2004

Effect of amyloid peptides on serum withdrawal-induced cell differentiation and cell viability.

Abnormal deposition of amyloid-beta(A beta) peptides and formation of neuritic plaques are recognized as pathological processes in Alzheimer's disease (AD) brain. By using amyloid precursor protein (APP) transfected cells, this study aims to investigate the effect of overproduction of A beta on cell differentiation and cell viability. It was shown that after serum withdrawal, untransfected cell (N2a/Wt) and vector transfected cells (N2a/vector) extended long and branched cell processes, whereas no neurites was induced in wild type APP (N2a/APP695) and Swedish mutant APP (N2a/APPswe) transfected N2a cells. After differentiation by serum withdrawal, the localization of APP/A beta and neurofilament was extended to neurites, whereas those of APP-transfected cells were still restricted within the cell body. Levels of both APP and A beta were significantly higher in N2a/APP695 and N2a/APPswe than in N2a/Wt, as determined by Western blot and Sandwich ELISA, respectively. To further investigate the effect of A beta on the inhibition of cell differentiation, we added exogenously the similar level or about 10-times of the A beta level produced by N2a/APP695 and N2a/APPswe to the culture medium and co-cultured with N2a/Wt for 12 h, and we found that the inhibition of serum withdrawal-induced differentiation observed in N2a/APP695 and N2a/APPswe could not be reproduced by exogenous administration of A beta into N2a/Wt. We also observed that neither endogenous production nor exogenous addition of A beta 1-40 or A beta 1- 42, even to hundreds fold of the physiological concentration, affected obviously the cell viability. These results suggest that the overproduction of A beta could not arrest cell differentiation induced by serum deprivation and that, at least to a certain degree and in a limited time period, is not toxic to cell viability.

Amyloid beta-Peptides↗

PubMed2002

The sugar code: functional lectinomics.

Analysis of the genome and proteome assumes the focus of attention in efforts to relate biochemical coding with cell functionality. Among other chores in energy metabolism, the talents of carbohydrates to establish a high-density coding system give reason for a paradigmatic shift. The sequence complexity of glycans and glycan-processing enzymes (glycosyltransferases, glycosidases and enzymes introducing substituents such as sulfotransferases), the growing evidence for the importance of glycans from transgenic and knock-out animal models and the correlation of defects in glycosylation with diseases are substantial assets to portray oligosaccharides as code words in their own right. Matching the pace of progress in the work on glycoconjugates, the increasing level of refinement of our knowledge about lectins (definition of this term: carbohydrate-binding proteins, excluding sugar-specific antibodies, receptors of free mono- or disaccharides for transport or chemotaxis and enzymes modifying the bound carbohydrate) epitomizes the sphere of action of the sugar code (functional lectinomics). It encompasses, among other activities, intra- and intercellular transport processes, sensor branches of innate immunity, regulation of cell-cell (matrix) adhesion or migration and positive/negative growth control with implications for differentiation and malignancy. The Q & A approach taken in this review lists a series of arguments in a stepwise manner to make the reader wonder why it is only a rather recent process that the concept of the sugar code has taken root in deciphering the mechanistic versatility of biological information storage and transfer.

Animals↗

PubMed1992

Plasma cells expressing immunoglobulins M and A but not immunoglobulin G develop an intimate relationship with central canal epithelium in the harderian gland of the chicken.

In the Harderian gland of the chicken, the epithelial and plasma cell relationships were studied by light and electron microscopy and immunohistochemical methods. In the wall of the central canal a dark epithelial cell was identified that had long branching cell processes. An anticytokeratin monoclonal antibody demonstrated that the dark cells provided an extremely large contact area for the plasma cells. Although IgM-, IgG-, and IgA-producing plasma cells were present in the Harderian gland, only IgM- and IgA-positive cells were capable of a distinct relationship with dark epithelial cells. The surface of the primary branches contained scattered IgA deposits whereas the epithelial cells of the secondary branches possessed IgA along the lateral cell membrane but not on the surface. Anti-IgA and anti-cytokeratin antibodies produced a similar staining pattern in the acini and secondary branches. Taken together, these observations suggest that IgA secretion is a function of secondary branches and that intracellular transport is influenced by the cytoskeletal system.

Animals↗

PubMed1998

Pattern and morphogenesis in skin.

Models dealing with the development of hair and feather follicles commonly predict that the factors initiating morphogenesis also specify patterns of follicle distribution. The factors have been postulated as chemical or mechanical instabilities which, at certain threshold concentrations, determine both the location of follicles and their form. The models tend to focus on the earliest waves of induction, where follicles develop at separate, non-randomly spaced initiation sites in skin. However, in many animals, there are later waves of initiation, some of which give rise to compound follicles. These are bundles of follicles that arise by branching from the necks of those formed earlier and share a common pilary canal when mature. In some species, compound follicles make the greatest numerical contribution to the follicle population. Measurements of the frequencies of single and branched follicles in sheep selection lines with different follicle densities (from previous studies by Moore et al.) revealed that the follicles which formed first during foetal life (primary and original secondary populations) were established at separately identifiable sites in the skin, called here "initiation sites". However, there were also later waves of development, contributing follicles exclusively by the process of branching (the derived secondary population). Final follicle densities were not correlated with the densities of initiation sites. The observations suggested that mechanisms specifying the positional values of initiation sites differed from those determining follicle number. The final densities of the follicle populations in the sheep lines were also highly negatively correlated with the diameters of the wool fibres grown. The close statistical relationship suggested that the two parameters were developmentally linked. However, whereas fibre characteristics are realised when the follicle is mature, density is established earlier, during foetal life. We have reconciled these observations with the following hypothesis: a population of cells, committed to a follicular pathway of development, differentiates in the skin at or before the first wave of initiation. Subpopulations of the committed cells subsequently participate in each follicle initiation event, the number in each subpopulation ultimately determining fibre dimensions. Follicle initiation continues until most or all of the original population have been utilised. Transplantation and skin recombinant studies have demonstrated that the cells forming the dermal papilla of the follicle participate in follicle initiation and have inductive effects on epidermal tissue. Papilla size is also correlated with fibre diameter in the mature follicle. These attributes are consistent with those described for the committed cell population.

Animals↗