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PubMed1992

The immunologic properties of epidermal Langerhans cells as a part of the dendritic cell system.

Dendritic cells form a system of antigen-presenting cells that is widely distributed in the body. They constitute trace populations in lymphoid and non-lymphoid tissues and in the circulation. They are characterized by their typical dendritic and "veiled" morphology, by their constitutive expression of high levels of major histocompatibility complex class II molecules on their surface, and by their outstanding capacity to initiate primary immune responses. Dendritic cells occur in two states of differentiation. In the immature state they are highly specialized for processing foreign protein antigens; in the mature state they efficiently stimulate resting antigen-specific T cells. Dendritic cells can migrate from the non-lymphoid tissues, where they reside in the immature state, via the afferent lymphatics or the blood to the T cell-dependent areas of the lymphoid organs (lymph nodes, spleen). There, they appear as mature dendritic cells. Therefore, dendritic cells are ideally suited to mediate important aspects of immunogenicity: they can acquire antigens in the tissues and process them in an immunogenic form; they can carry the immunogen to the lymphoid organs; and they can find and efficiently activate antigen-specific T cell clones and thus generate an immune response. Studies of epidermal Langerhans cells have greatly helped in establishing this concept. They can be investigated freshly isolated from the epidermis where they represent immature (tissue) dendritic cells. After 2-3 days in culture they develop into mature dendritic cells. The mechanisms of dendritic cell maturation, which can be studied best using epidermal Langerhans cells, and the specific functions of Langerhans cells in immunogenicity are discussed.

Animals↗

PubMed1976

Melanin-producing dendritic cells and histogenesis of malignant melanoma.

In a total of 70 malignant melanomas we searched for dendritic-branched fluorescent pigment cells. Hereby we found that dendritic-branched tumor cells are especially characteristic in cases of lentigo maligna. In the flat parts of these lesions, these cells are the predominant cell type. Dendrites in the pseudonests or nodular parts of lentigo maligna can only seldom be detected. The prevailing cell type in superficial spreading melanoma and in primary nodular melanoma is the round or oval unbranched tumor cell. In some cases of nodular melanoma, cells with short dendrites could be seen. In superficial spreading melanoma, dendritic tumor cells could be observed particularly in such tumor parts, in which the malignant cells were scattered between the keratinocytes. Melanocytes can evidently produce dendrites between cells of the sebaceous gland. In the marginal parts or in parts of regression of some superficial spreading melanomas, a great area of dendritic tumor cells could also be detected in the basal parts of the epidermis. Altogether, however, in superficial spreading melanoma and in nodular melanoma they occur only rarely. Dendritic-branched cells are also visible in lymph-node metastases of SSM and NM. The fact that the dendritic tumor cells can be observed in all 3 types of tumors (according to Clark and coworkers) gives a rise to a new discussion of the dualistic theory of melanoma-histogenesis of Mishima. Although this theory could not be disproved, up to now on the basis of the present results, an unitarian development of all types of mnelanoma from melanocytes seems to be possible.

Dendrites↗

PubMed1995

Dynamic modification of dendritic cable properties and synaptic transmission by voltage-gated potassium channels.

Computer simulations of a dendrite possessing voltage-sensitive potassium conductances were used to determine the effects of these conductances on synaptic transmission and on the propagation of synaptic signals within the dendritic tree. Potassium conductances had two principal effects on voltage transients generated by current injections or synaptic conductances. Locally (near the source of the transient), voltage-gated potassium channels produced a potassium shunt current that reduced the amplitude of voltage transient increased and so acted to prevent large synaptic transients from reaching levels that would saturate due to a reduction in driving force. In the presence of rapidly activating potassium currents, excitatory synapses produced larger synaptic currents that were more linearly related to synaptic conductance, but these produced smaller voltage transients. The maximum amplitudes of the voltage transients were limited by the voltage sensitivity of the K+ conductance and the rate at which it could activate. Sufficiently rapid synaptic currents could outrun the K+ conductance and thus achieve high local peak amplitudes. These effects of K+ conductances were unrelated to whether they were located on dendrites or not, being related only to their proximity to the source of synaptic current. The second class of effects of K+ conductances depended on their alteration of the electronic structure of the postsynaptic cell and so were observed only when they were located on postsynaptic dendrites. Voltage-gated K+ conductances produced voltage-dependent electronic expansion of depolarized dendrites, which had the effect of isolating synaptic inputs on depolarized dendrites from events on the rest of the neuron. Thus, synapses on the same dendrite interacted destructively to a degree much greater than that expected from the classical driving force nonlinearity. Synapses located proximally to a depolarized dendritic region were less effected than those located distally, and the range of the nonlinear interaction between synapses was dependent on the kinetics of activation and deactivation of the conductance. When present in conjunction with rapidly activating dendritic sodium conductance, the potassium conductance sharpened the requirement for spatial and temporal coincidence to produce synaptic boosting by inward currents, and suppressed out-of-synchrony synaptic inputs.

Computer Simulation↗

PubMed1974

Ultrastructure of a large ventro-lateral dendritic bundle in the rat ventral horn.

There is an extensive bundle of dendrites with a rostro-caudal axis in the ventro-lateral lamina of the sixth lumbar segment in each side of the rat spinal cord. Such a bundle has a diameter of about 250 mum and contains over 1400 parallel dendrites, each with a diameter of less than 8 mum, interspersed between neuronal somata. The volume fraction of dendrites in the bundle neuropil is about 55%, the remainder being equally distributed between astrocytes, synaptic boutons, and axons, most of which are unmyelinated. An analysis of the median percentage covering of dendrites by contiguous elements of the neuropil reveals that as the dendrite diameter decreases from 4 to 0.2 mum (mean equals 2 mum), astrocytes increase from 43 to 75%, axons decrease from 21% to zero, boutons decrease from 28% to zero, and dendrites decrease from 10% to zero. There is a mean of 18 synaptic boutons per 100 mum-2 of the overall dendritic surface, but larger boutons tend to be more frequent on larger dendritic profiles. Apposed dendrites and their somata may have either puncta adhaerentia or confronting subsurface cisternae. Synaptic types in the rat are similar to those reported for the cat. The morphological findings are discussed with respect to previously proposed interaction between neural elements.

Animals↗

PubMed1993

Follicular dendritic cells in extranodal non-Hodgkin lymphomas of MALT and non-MALT type.

Extranodal lymphomas of the thyroid (n = 19), kidney (n = 15) and testis (n = 30) were investigated histologically and immunohistochemically for follicular dendritic cell pattern using the monoclonal antibody Ki-FDClP. This recognizes follicular dendritic cells in paraffin sections. Follicular dendritic cells were most predominant in lymphomas of the thyroid. These thyroid lymphomas showed the morphological features of mucosa-associated lymphoid tissue (MALT) type lymphomas in 18 of 19 cases and were classified as high-grade malignant lymphoma of MALT type with evidence of a low-grade malignant component (n = 18). Ten of these cases contained destroyed reactive follicles of follicular dendritic cells. In 6 of these 10 cases follicular dendritic cells occurred in a pattern of tumour-associated abortive follicle type. The remaining lymphoma of the thyroid was an immunoblastic lymphoma of B-cell type showing no detectable follicular dendritic cells. In extranodal lymphomas of non-MALT type follicular dendritic cells occurred in only two cases where immunocytoma involved the kidney. Malignant lymphomas of the kidney (chronic lymphocytic leukaemia, n = 2; immunocytoma, n = 4; centroblastic lymphoma, n = 9) and of the testis (immunocytoma, n = 2; centroblastic lymphoma, n = 27; immunoblastic lymphoma of B-cell type, n = 1) revealed no characteristics of MALT type lymphoma, cytologically or with respect to follicular dendritic cells. Classical lymphoepithelial lesions formed by centrocyte-like cells, a hallmark of MALT, occurred exclusively in thyroid lymphomas of MALT type. Although occurrence of classical lymphoepithelial lesions formed by centrocyte-like cells was limited to thyroid lymphomas of MALT type, a growth pattern of lymphoid blasts, with formation of lesions mimicking lymphoepithelial lesions superficially, was found in 6 of 27 testicular centroblastic lymphomas. Follicular dendritic cells in non-Hodgkin's lymphomas of MALT type show distinct follicular patterns not found in other extranodal lymphomas such as those found in the kidney and testis.

Dendritic Cells↗

PubMed2005

Production of nitric oxide and self-nitration of proteins during monocyte differentiation to dendritic cells.

Nitric oxide (NO) can stimulate dendritic cells to a more activated state. However, nitric oxide and peroxynitrites production by dendritic cells has been usually associated with pathological situations such as autoimmunity or inflammatory diseases. This study was designed to determine if dendritic cells obtained from healthy volunteers produce nitric oxide and peroxynitrites, which results in protein nitration. The expression of arginase II, but not arginase I, isoform was detected in monocytes and dendritic cells. There was higher inducible nitric oxide synthase (iNOS) protein expression and lower arginase activity both in immature and mature dendritic cells, compared to monocytes. This caused nitric oxide production, and maturation of dendritic cells which provoked a significative increase of nitrites and nitrates compared to immature dendritic cells. There was also peroxynitrites synthesis during monocyte differentiation as shown by the nitration of proteins. Immunoblot revealed a pattern of nitrated proteins in cell extracts obtained from monocytes and dendritic cells, however there were bands that appeared only in human dendritic cells, in particular an intense 90 kDa band. Nitric oxide production and nitrotyrosine formation could affect the antigen presentation and modify the immune response.

Adult↗

PubMed1999

[Dendritic cells, T- and B-lymphocytes and macrophages in supraglottic and glottic squamous epithelial carcinoma. Location and correlation with prognosis of the illness].

Dendritic cells play an important role within the mucosal immune system of the upper aerodigestive tract. They process exogenous and endogenous antigens and are able to induce a cytotoxic Tc/s lymphocyte reaction against tumors. Recently published data indicate that the in vitro application of tumor lysate incubated dendritic cells can provide a defense against melanoma. Before these new therapeutic strategies are available for the therapy of laryngeal cancer, basic studies have to be performed concerning the distribution of dendritic cells and other subpopulations, such as T- and B-lymphocytes and macrophages. In the present study the distribution of these subpopulations were examined within the epithelial and connective tissue compartments ("tumor front") of 20T2 squamous cell carcinomas of the supraglottis and glottis. The number of dendritic cells was compared with clinical parameters to check whether a high number of dendritic cells could be correlated with a better prognosis. In contrast to T-lymphocytes, results showed that dendritic cells were mainly located within the epithelial compartment of the tumors, their number ranging from 20 cells/mm2 to > 700 cells/mm2. By comparing each patient's clinical course with the number of dendritic cells, findings showed that those patients who died within the first postoperative year were characterized by a very small number of dendritic cells within their tumor tissue (< 100 cells/mm2). Although the number of patients was low, results indicate that a high number of dendritic cells within tumor tissue suggest a better prognosis.

Adult↗

PubMed2004

Origin of the bursal secretory dendritic cell.

The origin of vimentin-positive secretory dendritic cells of the bursa of Fabricius was studied by chick-quail chimera, parabiosis and immunohistochemistry using species-specific monoclonal antibodies. Quail bursal primordia of different ages were transferred to coelomic cavity of 3-day-old chicken embryos and further incubated for 18 days. In transplanted quail bursas the secretory dendritic cells of chicken and quail origin were detected by double staining of vimentin plus 74.3 and vimentin plus QCPN monoclonal antibodies, respectively. In bursal primordia of 5- and 6-day-old quail embryos both dendritic cells and B cells were of host, i.e. chicken origin. Mixed dendritic cell population of quail and chick origin emerged in chimeric birds of 6.5 days of age. In quail embryos transplanted at 7 and 8 days of age both dendritic cells and B cells were mixed i.e. of chicken and quail origin. Bursal secretory dendritic cells and medullary epithelial cells create "dendro-epithelial tissue" to receive pre-B cells. Colonization of dendro-epithelial tissue by pre-B cells initiates at day 7, thus the colonization of bursal anlage by blood-borne cells is a two-step process; entering of dendritic cells at day 6.5 is followed by that of B cells at day 7 and afterwards. It is discussed that bursal secretory dendritic cells and their product are key elements of bursal function therefore the mammalian bursa equivalent organ might be represented by a cell, which is analogous with the bursal secretory dendritic cell.

Animals↗

PubMed2003

Adhesive interactions between CD34(+)-derived dendritic cell precursors and dermal microvascular endothelial cells studied by scanning electron microscopy.

Dendritic cells are migratory cells. Before they extravasate from the circulation into the skin across capillary blood vessel walls, they have to interact with endothelial cells. Using a fluorimetric adhesion assay, we have recently shown that CD34(+)-derived dendritic cell precursors are able to bind to resting and stimulated dermal microvascular endothelial cells. In the present study, we attempted to visualize this process at an ultrastructural level. CD34(+) progenitor cells were purified from human cord blood samples by means of immunomagnetic beads, and dendritic cells were generated by culture in the presence of GM-CSF, TNF-alpha and hSCF for 5 days. Immature CD83(-) CD86(low) dendritic cells were added to human dermal microvascular endothelial cells grown to confluence on membrane chambers. After 2 h, unbound dendritic cell precursors were removed, and bound cells were prepared for routine scanning electron microscopy. We found that (1). dendritic cell precursors firmly adhere to microvascular endothelial cells, enveloping them with their surface processes; (2). dendritic cell precursors are extremely deformable as they squeeze through the dense network of microvascular endothelial cells; (3). microvascular endothelial cells form, in part, a multi-layered network rather than the typical cobblestone pattern as seen by phase-contrast microscopy. The morphology of dendritic cell precursors and of human dermal microvascular endothelial cells was examined here, for the first time, by scanning electron microscopy. These data further emphasize that CD34(+)-derived dendritic cells efficiently adhere to dermal microvascular endothelial cells.

Antigens, CD34↗

PubMed2006

Heterogeneity of dendritic cells in rat apical periodontitis.

Dendritic cells are important for the induction of T-lymphocyte-mediated immunity by acting as antigen-presenting cells. We have previously reported that dendritic cells are prevalent in the chronic non-expanding phase of rat apical periodontitis. To characterize these cells further, immunoelectron microscopy with three dendritic cell markers (CD11c, OX6, OX62) was conducted for samples from rat models of apical periodontitis. Dendritic cells were divided into two types (type I or type II). Most of the type I dendritic cells expressed CD11c, showed an irregular large profile, had typical cytoplasmic processes, and were recognized as the major dendritic cell population. Most of the type II dendritic cells expressed OX62, showed oval small profiles with a few thin short processes, and were sometimes observed infiltrating from blood vessels. Cell-to-cell contacts between type I dendritic cells and lymphocytes were the most frequently observed associations. These results suggest that dendritic cells are composed of heterogeneous populations that exhibit different phenotypes, morphologies, and maturation/differentiation/activation.

Animals↗

PubMed1979

Morphometrical synaptology of Clarke cells and of distal dendrites in the nucleus dorsalis: an electron microscopic study in the cat.

The fine structural synaptology of large Clarke cells in L3 has been investigated from a morphometrical point of view in both normal and adult cats which received horseradish peroxidase (HRP) injections in the cerebellum. This marking method made it possible to distinguish small or distal dendrites of large Clarke cells from those of interneurons and the marginal cells of Clarke's column. A total of 1036 boutons was observed on the perikarya of 21 large Clarke cells; 81.9% (848/1036) were small-sized boutons, the cross-sectional areas of which ranged between 0.3 and 2.9 sq. micrometer, while 18.1% (186/1036) were giant boutons ranging between 3.0 and 8.0 sq. micrometer. From 1075 boutons on 17 primary dendrites of Clarke cells, 72.4% (778/1075) were small-sized boutons and 27.6% (297/1075) were giant boutons. From 1679 boutons contacting 366 distal or small HRP-labeled dendrites, 89.9% (1507/1679) were small boutons and 10.1% were giant boutons. The giant boutons were more frequently located on the proximal dendrites than on the cell bodies or small distal dendrites of Clarke cells. The proportion of S- and F-type boutons was different in 3 parts of large Clarke cells. F-type boutons were more frequent on soma (55.0% 570/1036) and primary dendrites (59.4%, 635/1075). S-type boutons outnumbered the F-type on small or distal dendrites (62.6%, 1952/1679). The S/F ratio seemed to increase from the cell body toward the distal dendrites. The results suggest that Clarke cells receive predominantly small S-type boutons since the total receptive area of the dendrites is supposed to exceed that of the cell body.

Animals↗

PubMed1981

Spatial sampling by dendritic trees in visual cortex.

Kittens were reared in vertically or horizontally striped cylinders. After rearing exposures of 400-500 h, responses of single neurons were determined as a function of orientation of a square wave grating stimulus. These data suggest that the rearing environment did alter orientation preference in some of the kittens. The visual cortices of the stripe-reared kittens and of control kittens were impregnated according to a Golgi-Cox method. Dendrites of layer IV stellate cells were tracked and analyzed in three dimensions by a computer-microscope. Four methods of analyzing the spatial distribution of dendrites are described and discussed. Two methods previously described in the literature were not sufficiently sensitive to detect any differences among kittens exposed to vertical or horizontal stripes or to a control environment. Two newly developed methods were able to provide initial evidence for rearing effects on dendritic trees in visual cortex. The more detailed of these new methods describes the angular location of dendritic segments, with respect to standard brain axes, as a function of distance from the cell body. Data obtained by means of this method of dendritic angular distribution (DAD) plots suggests a number of conclusions. Rearing animals in a striped environment may influence the way in which dendrites of layer IV stellate cells of visual cortex distribute themselves in the neuropil. The effect of selective rearing on dendritic distribution does not appear to extend back to those portions of the dendritic tree closest to the cell body. This influence of rearing in a selective environment may be explained by hypothesizing that during development dendrites distribute themselves in ways that tend to maximize the effects of spatiotemporal summation for the postsynaptic neurons.

Animals↗

PubMed1987

Morphometric and dendritic analysis of fascia dentata granule cells in human aging and senile dementia.

In this study the cellular morphology in the human fascia dentata of 5 very old demented cases (4 Alzheimer's disease and 1 multi-infarct dementia patients) was compared with 5 (very) old controls cases. The postmortem delay in fixation was for all cases within 3.5 h. In the demented group, a significant reduction in thickness of the molecular layer, density of dendritic spines in the middle third of the molecular layer and total dendritic length (+/- 30%) was found. The number of dendritic segments, indicative of the branching frequency showed no difference. In both the control and the demented group, three-quarters of all dendritic bifurcations of granule cells occurred in the inner third of the molecular layer in which the commissural and associational fibers terminate. The size of the dendrites in the demented group could be the result of at least 3 independent processes: a regressive change due to partial denervation of the outer two-thirds of the molecular layer as axons from the perforant pathway are lost; a dendritic regrowth in response to sprouting of the commissural-associational fiber systems and septal afferents, which is presumed to occur in response to degeneration of perforant path axons; a dendritic regrowth in response to the loss of the dendrites of neighboring cells which have died. Analysis of our material suggests that dendritic degeneration is the predominant factor in the demented group.

Aged↗

PubMed1994

Dendritic orientation of thalamocortical projection neurons in the ventrobasal complex of macaques.

This study describes the orientation of dendritic arbors from intracellularly labeled thalamocortical projection (TCP) neurons of Macaca fascicularis or Macaca mulatta. All neurons were located in the ventrobasal complex and responded to non-noxious stimuli. Each neuron was composed of dendrites that varied considerably in size and each dendrite tended to occupy a particular region of the perisomatic space with minimal overlap with other dendrites. Quantitative and qualitative analysis of the dendritic arbors of the labeled neurons showed they had an asymmetric distribution so that some regions of the perisomatic space contained more of the dendritic tree than others. Eleven of the thirteen reconstructed neurons had a larger percentage of the dendritic tree projecting into the medial portion of the perisomatic space. These results show that the dendritic arbors of macaque TCP neurons are not organized in a radially symmetric pattern as previously described and the asymmetric distribution of dendrites may be related to synaptic input.

Animals↗

PubMed1996

Generation of mature dendritic cells from human blood. An improved method with special regard to clinical applicability.

Two methods to generate human dendritic cells from hematopoietic precursor cells in peripheral blood have recently been published. One approach utilizes the rare CD34+ precursors and GM-CSF plus TNF-alpha. The other method makes use of the more abundant CD34- precursor population and GM-CSF plus IL-4. Here we report a method that is based on the latter approach. However, the GM-CSF and IL-4 treated cells are not stable mature dendritic cells, e.g., the characteristic morphology and nonadherence of dendritic cells is lost if the cytokines are removed. We describe the need for a monocyte-conditioned medium to generate fully mature and stable dendritic cells. This is achieved by adding a 3 day 'maturation culture' to the initial 6-7 day culture in the presence of GM-CSF and IL-4. Macrophage-conditioned medium contains the critical maturation factors. Mature dendritic cells are defined by their pronounced display of motile cytoplasmic processes ('veils'), their high capacity to induce proliferative responses in resting T cells, particularly in naive umbilical cord T cells, their down-regulated antigen processing ability, and their characteristic phenotype: expression of CD83, high levels of MHC molecules and CD86, lack of CD115 and perinuclear dot-like CD68 staining. These features are stable for at least 3 days upon withdrawal of cytokines and conditioned media. IL-4 can be replaced by IL-13. When CD34+ progenitors are depleted from blood, there is only a minor reduction in the yield of dendritic cells by this method. We have adapted the method to consider several variables that are pertinent to clinical use, including a change from fetal calf serum to human plasma and to media approved for clinical use like X-VIVO or AIM-V. 1% plasma and RPMI 1640 are currently optimal. Additional reagents used for cell culture (Ig. cytokines) and cell separation (immunomagnetic beads) are approved for or already used in clinical applications. For 40 ml blood, the yield is 0.8-3.3 x 10(6) mature dendritic cells as defined by the expression of the new dendritic cell-restricted marker CD83. CD83+ cells constitute between 30 and 80% of all cells recovered at the end of the culture period. Yields can be enhanced up to six-fold if the blood donors are pretreated with G-CSF. Stable, mature dendritic cells generated by this method should be a powerful tool for active immunotherapy.

Cell Culture Techniques↗

PubMed1983

Theoretical study on electrical properties of dendritic spines.

In most parts of mammalian central nervous system the majority of synapses are located on dendritic spines. Several suggestions have been made about the functional significance of the dendritic spines. We investigate electrical properties of dendritic spines in the neurons with arbitrary dendritic geometry. Following Butz & Cowan (1974), all dendritic branches, including spines, are treated as cylinders of uniform passive membrane. We show that the postsynaptic potential due to the synapse on the spine is represented as a convolution integral of the following two functions. The first is the postsynaptic potential caused by the same synapse on the branching point where the spine stalk is attached to the main dendritic trunk. The second function is determined mainly by the morphological and electrical properties of the spine and it represents the attenuation effect of the spine. On the assumption that the diameter of the spine stalk is sufficiently small compared to that of the parent dendrite to which the spine stem is attached, we obtain an approximation of the second function and conclude that morphological change of the spine does not produce an effective change of the postsynaptic potential, hence does not provide the neural basis for learning or memory simply by changing cable properties of dendrites. Moreover, we show that synapses on the dendritic spine are not effectively isolated from other synapses on the same assumption.

Animals↗

PubMed1996

Myenteric neurons with different projections have different dendritic tree patterns: a morphometric study in the pig ileum.

Morphometric analysis was performed of two types of myenteric neurons with at first glance, very similar morphology, but different projections in the pig ileum. 50 type IV cells projecting vertically to the outer submucosal plexus, and 50 solitary type V neurons projecting aborally, within the myenteric plexus, were evaluated. Using a computer-aided morphometric device, the following parameters were recorded: somal area, longest somal diameter, number of primary dendrites, dendritic length, number of dendritic branching points and number of terminal segments. In addition to other significant differences, the most prominent discriminating parameter between the two populations of nerve cells estimated in this study was the length of the longest dendrite of each cell type. The longest dendrite of an individual type V neuron is a manifold longer than the corresponding somal diameter, in contrast to type IV neurons where it is at most twice the somal diameter. In addition, all type IV and type V single dendritic lengths were arranged in histogramms, where the type V dendrites showed two frequency peaks. Thus, we assume that solitary type V neurons can develop two populations of dendrites: a short and a long one. These results demonstrate that myenteric neurons with different projections (and hence different functions) display strikingly different dendritic morphology.

Animals↗

PubMed1984

A quantitative Golgi analysis of the postnatal maturation of dendrites in the central nucleus of the inferior colliculus of the rat.

In this work, we used Golgi impregnation and computer assistance to analyze the quantitative development of the dendrites of neurons in the central nucleus of the inferior colliculus in the rat from 8 (P8) to 20 (P20) days of age, i.e., during the period of functional maturation of the auditory system. The number and length of the dendritic segments and the number of spines of a total of 516 impregnated cells were studied. The variations of both the mean number of peripheral dendritic segments and the mean dendritic domain area suggest that the dendritic tree of these cells is orientated preferentially in the sagittal plane before the onset of functional maturation, but undergoes a reorientation in the frontal plane during this critical period. The length of dendritic segments varies as a function of both the stage of the period of functional maturation and the order of magnitude of these segments. During the first stage, from P8 to P16, only proximal and intermediate segments lengthen, the distal segments increasing their length later from P16 to P20. The lengthening of the dendritic segments is associated with dramatic reabsorption of the dendritic spines on all dendritic segments and seems closely related to the functional maturation of the auditory pathways.

Animals↗