Cone-like Structures Research Articles

Improved growth of aligned carbon nanotubes by mechanical activation

Straight aligned carbon nanotubes with multiwalled cylindrical structure have been produced by pyrolysis of iron phthalocyanine (FePc) after ball milling treatment. The pre-ball milling treatment prevented the formation of curved nanotubes with bamboo or conelike structures. X-ray diffraction analysis revealed that the milled FePc has an activated and disordered structure, which contributes a lower vaporization temperature determined by thermal gravimetric analysis. The low formation temperature and an increased nanotube growth rate are favorable to the formation of cylindrical structure than bamboo tubes.

Development of nerves expressing P2X3 receptors in the myenteric plexus of rat stomach.

Development of neurones and fibres expressing P2X3 receptors in the myenteric plexus of rat stomach and coexistence of the P2X3 receptor with calbindin, calretinin and NOS during postnatal development, were investigated with immunostaining methods. Extrinsic nerves expressing P2X3 receptors appeared as early as E12 and were localised in the trunk and branches of the vagus nerve, which extended rapidly onto the whole rat stomach from E12 to E14. Intrinsic neurone cell bodies with P2X3-immunoreactivity in the myenteric ganglia were first demonstrated postnatally at P1, and at P14, when the number of neurones expressing the P2X3 receptor peaked at 45%. P2X3 receptor-immunoreactivity decreased subsequently, and at P60 only about 11% were P2X3-immunoreactive. Intraganglionic laminar nerve endings and intramuscular arrays were first demonstrated postnatally at P1 and P7, respectively. In the early postnatal days, there were many growth cone-like structures with strong P2X3 immunostaining associated with these endings and arrays. Double-immunostaining showed that 9-15% of P2X3-immunoreactive neurones in the gastric myenteric plexus expressed calbindin D-28 k only in the early postnatal days, while 14-21% of neurones from P1 to P60 increasingly expressed calretinin. About 20% of neurones with P2X3 immunoreactivity coexpressed NOS throughout perinatal development.

An experimental study of particle effects on drop formation

The formation of drops of particulate suspensions composed of spherical, neutrally buoyant, noncolloidal particles in a viscous liquid is examined experimentally. The suspensions are investigated over a range of particle volume fractions, φ=nπdp3/6 where n is the particle number density and dp is the particle diameter (dp=212–250 μm in most of the experiments), and for flow through three tubes of outer diameters d=0.16, 0.32 and 0.64 cm; the corresponding inner diameters are 0.10, 0.22, and 0.53 cm. Drop formation in the dripping mode and the transition from dripping to jetting are investigated. In the dripping mode, the behavior of low-φ suspensions (φ⩽0.10) is markedly different from that of higher-φ suspensions (0.15⩽φ⩽0.40), with a transition in the qualitative behavior over a relatively narrow range of concentrations. Pinch-off structures for low-φ suspensions are similar to that of the pure liquid, consisting of a long slender liquid thread connecting a hemispherical cap of liquid at the orifice to the nearly spherical forming drop; the structures differ from those of pure liquids in that individual particles, or groups of particles, can be captured in the thread at rupture, leading to new modes of satellite drop formation. At higher φ, the presence of large numbers of particles in the thinning thread during necking results in thick conelike structures termed “spindles” owing to this labeling of structures of similar geometry observed in electrohydrodynamic sprays. Particles are found to substantially suppress the number of satellite drops at higher φ, but the few satellite drops produced are much larger than observed in pure liquid drop formation. The transition from dripping to jetting occurs at a smaller flow rate at finite φ, with much shorter coherent lengths after jetting than in the case of a pure liquid. The transition becomes less abrupt and more difficult to identify at the highest concentrations examined.

Postnatal Development of GABAergic Synapses in the Nigral and Entopeduncular Afferent Territory of the Rat Thalamus

The time course of the development of GABAergic synapses in the basal ganglion afferent territories of the rat thalamus (the projection zones of the nigro- and entopedunculothalamic afferents) was analyzed at the electron microscopic level. The analysis was carried out in conventionally processed tissue and the tissue was processed for postembedding immunocytochemistry for GABA. It was primarily focused on the development of axosomatic synapses known as the main termination mode of the basal ganglion thalamic afferents. In neonatal rats (P0), small-to-medium-sized axons and large axonal growth cone-like GABA-immunoreactive structures were found engaged in symmetrical synapses with neuronal somata and proximal dendrites. At P7, the size of the axosomatic profiles was considerably increased and synapses appeared more mature. Between P7 and P14, there were numerous degenerating GABA-positive synaptic profiles displaying symmetrical synaptic contacts. Normal-looking GABA-positive terminals were large, extending for several micrometers along the somata and primary dendrites of thalamic neurons. By P21, these boutons acquired the appearance of axosomatic boutons in the adult, i.e., of a large elongated shape, numerous mitochondria, multiple synaptic contacts of pleomorphic vesicles and numerous puncta adherentia. The time course was different from the one described in the somatosensory thalamus by other authors, implying that anatomical and connectional differences between thalamic nuclei are also reflected in the patterns of their synaptogenesis.

Localization of α-, β-, and γ-synuclein during neuronal development and alterations associated with the neuronal response to axonal trauma

Genetic and protein studies have indicated abnormalities in α-synuclein in neurodegenerative diseases. However, the developmental localization and cellular role of synuclein isoforms is contentious. We investigated the cellular localization of α-, β-, and γ-synuclein in developing cultured rat neurons and following axonal transection of relatively mature neurons, a model that disrupts the axonal cytoskeleton and results in regenerative sprouting. Cortical neurons were grown up to 21 days in vitro (DIV). Axon bundles at 21 DIV were transected and cellular changes examined at 4 and 24 h post-injury. Immunohistochemistry demonstrated that α- and β-synuclein were localized to cellular cytosol and growth cones at 3DIV, with accumulating puncta-like labeling within axons and growth cones by 10-21DIV. In contrast, γ-synuclein immunoreactivity was limited at all time points. By 21DIV, α- and β-synuclein were present in the same neurons but largely in separate subregions, only 26% of puncta contained both α- and β-synuclein immunoreactivity. Less than 20% of α-, β-, and pan-synuclein immunoreactive puncta directly colocalized to synaptophysin profiles at 10DIV, decreasing to 10% at 21DIV. Both α- and β-synuclein accumulated substantially within damaged axons at 21DIV and were localized to cytoskeletal abnormalities. At latter time points post-injury, α- and β-synuclein immunoreactive puncta were localized to growth cone-like structures in regenerating neurites. This study shows that α- and β-synuclein have a precise localization within cortical neurons and are generally nonoverlapping in their distribution within individual neurons. In addition, synuclein proteins accumulate rapidly in damaged axons and may have a role in regenerative sprouting.

Cytoskeletal and Morphological Alterations Underlying Axonal Sprouting after Localized Transection of Cortical Neuron AxonsIn Vitro

We examined the cytoskeletal dynamics that characterize neurite sprouting after axonal injury to cortical neurons maintained in culture for several weeks and compared these with initial neurite development. Cultured neocortical neurons, derived from embryonic day 18 rats, were examined at 3 d in vitro (DIV) and at various time points after axotomy at 21 DIV. The postinjury neuritic response was highly dynamic, progressing through an initial phase of retraction, followed by substantial axonal sprouting within 4-6 hr. Postinjury sprouts were motile and slender with expanded growth cone-like end structures. Microtubule markers were localized to sprout shafts and the proximal regions of putative growth cones and filamentous actin was distributed throughout growth cones, whereas neurofilament proteins were restricted to sprout shafts. A similar distribution of cytoskeletal proteins was present in developing neurites at 3 DIV. Exposure of developing and mature, injured cultures to the microtubule stabilizing agent taxol (10 microg/ml) caused growth inhibition, process distension, the transformation of growth cones into bulbous structures, and abnormal neurite directionality. Microtubule and neurofilament segregation occurred after taxol exposure in developing neurites and postinjury sprouts. Exposure to the microtubule destabilizing agent nocodazole (100 microg/ml) resulted in substantial morphological alteration of developing neurons and inhibited neurite growth and postinjury axonal sprouting. Our results indicate that the axons of cortical neurons have an intrinsic ability to sprout after transection, and similar cytoskeletal dynamics underlie neurite development and postinjury axonal sprouting.

A Lycopsid with Novel Reproductive Structures from the Upper Devonian of Jiangsu, China

A new lycopsid is described from the Upper Devonian (Famennian) of Wuxi, Jiangsu Province, China. It has isodichotomous branches and long leaves with spiny margins. Two types of fertile structures are present. Megasporangia‐bearing conelike structures are found at dichotomies of the branches, having large, densely inserted leaves with enlarged bases, bearing adaxial sporangia containing large megaspores. The other type are terminal cones, having slender, closely inserted leaves, and dark carbonaceous areas adjacent to the axis are interpreted as the remains of microsporangia. The new plant closely resembles lycopsids previously reported from the Middle and lower Upper Devonian of China, but the reproductive characters are more advanced. It demonstrates that the early history of large lycopsids is more complex than has been recognized. We name the new plant Wuxia bistrobilata gen. et sp. nov.

Sputtering from ion-beam-roughened Cu surfaces

A comprehensive theoretical and experimental study of sputtering from copper surfaces roughened by low-energy ${\mathrm{Ar}}^{+}$ ion bombardment is reported. The total sputtering yields of thermally deposited Cu samples bombarded by 400-eV and 800-eV ions at 0\ifmmode^\circ\else\textdegree\fi{}--70\ifmmode^\circ\else\textdegree\fi{} angles of incidence have been measured and compared with a numerical model we have developed. To compute sputtering yields from rough surfaces, an original approach has been introduced, which accounts for sputtering anisotropy and shadowing of material emitted at grazing angles. The approach is flexible with respect to surface morphology and can be applied with any submicron structures. To specify the morphology that develops on the Cu surface under low-energy ion bombardment, the surface of bombarded Cu samples has been investigated by scanning electron microscopy. The morphology has been found highly unstable, appearing with random roughening, inclined conelike structures, ripples, or almost flat surfaces, depending on the bombardment conditions. For the samples considered it is found that the angular dependency of the total sputtering yield is strongly affected by surface morphology, which varies with the angle of ion incidence and bombardment energy. Approximations for accounting for the surface roughness required to describe sputtering at particular energy and angular regimes are discussed.

A role for phospholipase D1 in neurotransmitter release.

Phosphatidic acid produced by phospholipase D (PLD) as a result of signaling activity is thought to play a role in membrane vesicle trafficking, either as an intracellular messenger or as a cone-shaped lipid that promotes membrane fusion. We recently described that, in neuroendocrine cells, plasma membrane-associated PLD1 operates at a stage of Ca(2+)-dependent exocytosis subsequent to cytoskeletal-mediated recruitment of secretory granules to exocytotic sites. We show here that PLD1 also plays a crucial role in neurotransmitter release. Using purified rat brain synaptosomes subjected to hypotonic lysis and centrifugation, we found that PLD1 is associated with the particulate fraction containing the plasma membrane. Immunostaining of rat cerebellar granule cells confirmed localization of PLD1 at the neuronal plasma membrane in zones specialized for neurotransmitter release (axonal neurites, varicosities, and growth cone-like structures). To determine the potential involvement of PLD1 in neurotransmitter release, we microinjected catalytically inactive PLD1(K898R) into Aplysia neurons and analyzed its effects on evoked acetylcholine (ACh) release. PLD1(K898R) produced a fast and potent dose-dependent inhibition of ACh release. By analyzing paired-pulse facilitation and postsynaptic responses evoked by high-frequency stimulations, we found that the exocytotic inhibition caused by PLD1(K898R) was not the result of an alteration in stimulus-secretion coupling or in vesicular trafficking. Analysis of the fluctuations in amplitude of the postsynaptic responses revealed that the PLD1(K898R) blocked ACh release by reducing the number of active presynaptic-releasing sites. Our results provide evidence that PLD1 plays a major role in neurotransmission, most likely by controlling the fusogenic status of presynaptic release sites.

Ultrastructural evidence for differential axonal sprouting in the striatum after thermocoagulatory and aspiration lesions of the cerebral cortex in adult rats

Thermocoagulation of pial blood vessels overlying the cerebral cortex induces an ischemic degeneration of the cortex. We have previously shown with anatomical tracing techniques that thermocoagulatory lesions of the sensorimotor cortex trigger a robust axonal sprouting of contralateral cortical neurons into the denervated striatum. Similar sprouting was not observed after acute aspiration lesions of the same cortical region. We have now examined immunostaining for the growth-associated protein (GAP)-43 at the ultrastructural level after both types of lesions. A modest increase in growth cone-like structures was observed just below the corpus callosum after both lesions. However, GAP-43-positive growth cone-like structures were markedly increased in the denervated dorsolateral striatum only after thermocoagulatory lesions. In contrast, no significant increase in growth cone immunostaining was found in the dorsolateral striatum after aspiration lesions, confirming the absence of axonal sprouting in the dorsolateral striatum in this condition. Corticostriatal inputs make asymmetric synapses with dendritic spines of striatal neurons. As expected, the density of asymmetric synapses was markedly decreased in the dorsolateral striatum after aspiration lesions. However, it was not different from control after thermocoagulatory lesions that removed the same cortical area. The density of symmetric synapses was decreased after both types of lesions at 16 but not 42 days post-surgery. These data reveal that robust axonal and synaptic remodeling can occur in the dorsolateral striatum of adult rats after ischemic lesions of the cerebral cortex and further demonstrate marked differences in the degree of anatomical plasticity induced by two different types of cortical lesions.

Pulsed laser ablation deposition of yttrium iron garnet and cerium-substituted YIG films

Yttrium iron garnet (YIG) thin films were grown on gadolinium gallium garnet substrates using pulsed laser ablation deposition (PLAD) with a XeCl excimer laser. Films were grown up to over 2 μm thick, however cracking proved to be a problem for films over 1 μm thick. The lattice parameter(s) of the films and the substrates were measured and indicated that the film/substrate structure was bending to accommodate strain due to the lattice mismatch. The films had saturation magnetisation values close to that of bulk YIG and were isotropic in the film plane. The magnetisation data also indicate stress-induced uniaxial isotropy. The ablation conditions were varied to produce uncracked films with low droplet densities. YIG melts incongruently during the laser ablation process and cone-like structures form on the ablation target lowering the ablation rates. Cerium-substituted YIG films were also grown in both oxygen and argon atmospheres, substituting cerium into YIG increases the lattice parameter and hence reduces the strain. The Ce-YIG film grown in argon was greenish indicating that cerium was in the desired oxidation state.

Ultrastructure of early axonal regeneration in an end-to-side neurorrhaphy model.

The ultrastructure of the early regenerative response in an end-to-side neurorrhaphy rat model was studied using transmission electron microscopy. The ipsilateral saphenous nerve was grafted to the sciatic nerve under the following conditions: Group 1, the epineurium and perineurium of the sciatic nerve remained intact; Group 2, an epineurial and perineurial window was created at the site of the lateral neurorrhaphy; Group 3, the same as in Group 2 and, in addition, the sciatic nerve sustained a partial neurectomy. Rats were perfused through the heart with fixative containing 2 percent paraformaldehyde and 2.5 percent glutaraldehyde in 0.1 M cacodylate buffer (pH 7.4) at 4, 8, 12, 24 and 48 hr after surgery. In Group 1, no regenerating axons were observed and the myelin sheath in the donor nerve did not demonstrate any degenerative changes through 48 hr. In Group 2, an increased diameter of the unmyelinated axons and growth cones was observed in the donor nerve proximal to the coaptation site after 12 hr. Degenerative changes in the myelin sheath were observed after 12 hr within the several layers under the coaptation site. In Group 3, many growth cone-like structures were observed in the area proximal to the coaptation site after 12 hr. After 24 hr, proximal regenerating axons elongated to the coaptation site and, at 48 hr, many regenerating nerves grew inside the Schwann cell basement membrane of the graft nerve. These results indicate that the perineurial window and nerve graft are the critical conditions for inciting nerve regeneration in the donor nerve.

Scanning tunneling microscope assisted nanostructure formation: Two excitation mechanisms for precursor molecules

The scanning tunneling microscope in a near-field emission mode has been employed to create nanostructures using the hexafluoroacetylacetonate Cu (I) vinyltrimethylsilane precursor molecule on the Si(111) surface at 300 K. Two distinctive mechanisms controlling the nanostructure formation have been delineated. The first process involves excitation of the molecule by the applied electric field, and the field induced surface diffusion acts to supply molecules to the nanostructure growth region under the tip. The second mechanism involves the dissociation of the molecule by an electron attachment process. The generated nanostructure topology is quite different for each excitation mechanism. Narrow cone-like structures are produced by the electric field while broad structures of lower height are produced by the electron attachment process. Both mechanisms operate simultaneously in the low bias voltage regime (V<8 V), with the field activated process dominating. The electron induced process becomes the governing process at higher voltages.

Role of moving growth cone-like "wave" structures in the outgrowth of cultured hippocampal axons and dendrites.

Hippocampal neurons exhibit periodically recurring growth cone-like structures, referred to as "waves," that emerge at the base of neurites and travel distally to the tip. As a wave nears the tip, the neurite undergoes retraction, and when it reaches the tip, the neurite undergoes a burst of growth. At 1 day in culture, during early axon outgrowth, axons undergo an average 7.5-microm retraction immediately preceding wave arrival at the tip followed by 12-microm growth immediately after arrival (an average net growth of 4.5 microm). In branched axons, waves often selectively travel down one branch or the other. Growth selectively occurs in the branch chosen by the wave. In dendrites, which grow much slower on average, wave-associated retractions are much greater, resulting in less net growth. In the presence of Brefeldin A, which disrupts membrane traffic through the Golgi apparatus and leads to retraction of the axon, axonal waves continue to be associated with both growth spurts and retractions. The magnitude of the growth spurts is not significantly different from untreated axons, but wave-associated retractions are significantly increased. The close association between waves and cyclical elongation suggests that waves may act to bring about this pattern of growth. Our results also show that modulation of regularly occurring retraction phases plays a prominent role in determining average outgrowth rates.

Muscle Structure and Innervation Are Affected by Loss of Dorsal in the Fruit Fly,Drosophila melanogaster

InDrosophila,the Rel-protein Dorsal and its inhibitor, Cactus, act in signal transduction pathways that control the establishment of dorsoventral polarity during embryogenesis and the immune response during postembryonic life. Here we present data indicating that Dorsal is also involved in the control of development and maintenance of innervation in somatic muscles. Dorsal and Cactus are colocalized in all somatic muscles during postembryonic development. In larvae and adults, these proteins are distributed at low levels in the cytoplasm and nuclei and at much higher levels in the postsynaptic component of glutamatergic neuromuscular junctions. Absence of Dorsal, in homozygousdorsalmutant larvae results in muscle misinsertions, duplications, nuclear hypotrophy, disorganization of actin bundles, and altered subcellular distribution of Cactus. Some muscles show very abnormal neuromuscular junctions, and some motoraxon terminals are transformed into growth cone-like structures embedded in synaptotagmin-enriched vesicles. The detailed phenotype suggests a role of Dorsal signalling in the maintenance and plasticity of the NMJ.

Temperature dependence of the total sputtering yield of a two-phase Ag/Cu (65/35 at%) alloy for 200 eV Ar+ ions

The total sputtering yield of a AgCu two-phase alloy (6535 at%) as a function of temperature (−54°C to 123°C) for 200 eV Ar+ at normal incidence has been measured. For a fluence of approximately 1020 ions/cm2, the total yield was a maximum at low temperature and decreased as the temperature was increased until at the highest temperature, the yield was approximately one half the value at the lowest temperature. At high temperature, SEM revealed that the surface was covered with a dense “forest” of microscopic cone-like structures, whereas at low temperature the cones were absent and the surface had a more faceted appearance. At higher temperatures it is believed that bombardment enhanced surface diffusion facilitates the formation of cones and ridges. Under continued sputtering the aspect ratio of these features increases until it is large enough to allow recapture of material ejected from valleys and neighboring features. For samples sputtered at elevated temperatures, this redeposition appears to be responsible for the significant lowering of the total yield. The results did not depend on the method of target fabrication (three different methods were tested). To simplify the yield calculations, it was assumed that component ejection was stoichiometric with the bulk for the entire bombardment time. The validity of this simplification is discussed.

Temperature dependence of the total sputtering yield of a two-phase [formula omitted] ( [formula omitted]) alloy for 200 eV Ar + ions

The total sputtering yield of a Ag Cu two-phase alloy ( 65 35 at% ) as a function of temperature (−54° C to 123° C) for 200 eV Ar + at normal incidence has been measured. For a fluence of approximately 10 20 ions/cm 2, the total yield was a maximum at low temperature and decreased as the temperature was increased until at the highest temperature, the yield was approximately one half the value at the lowest temperature. At high temperature, SEM revealed that the surface was covered with a dense “forest” of microscopic cone-like structures, whereas at low temperature the cones were absent and the surface had a more faceted appearance. At higher temperatures it is believed that bombardment enhanced surface diffusion facilitates the formation of cones and ridges. Under continued sputtering the aspect ratio of these features increases until it is large enough to allow recapture of material ejected from valleys and neighboring features. For samples sputtered at elevated temperatures, this redeposition appears to be responsible for the significant lowering of the total yield. The results did not depend on the method of target fabrication (three different methods were tested). To simplify the yield calculations, it was assumed that component ejection was stoichiometric with the bulk for the entire bombardment time. The validity of this simplification is discussed.

Regulation of the polysialylated form of the neural cell adhesion molecule in the developing striatum: effects of cortical lesions.

Early in development, the polysialylated form of the neural cell adhesion molecule (PSA-NCAM) is expressed by growth cones, neuronal processes, and neuronal cell bodies. In rat striatum, PSA-NCAM expression becomes progressively restricted to pre- and postsynaptic membranes and is undetectable by postnatal day 25 (P25), i.e., after corticostriatal synaptogenesis. This study examined the effects of cortical lesions performed on P14, when the corticostriatal projection is already primarily unilateral and cortical inputs have not yet formed asymmetric synapses on striatal neurons. Rats were killed on P25, and PSA-NCAM expression was examined by immunoblotting and immunohistochemistry with light and electron microscopy. In contrast to the case in controls, PSA-NCAM expression was maintained in the striatum of lesioned pups. Ultrastructural studies showed that PSA-NCAM was present 1) in growth cone-like structures and neuronal processes and 2) in striatal neurons. Together with the presence of growth cones, the observation that the number of asymmetric synapses was unchanged in the denervated striatum suggests that axonal sprouting occurred in response to the lesion. This was confirmed by axonal labeling in the denervated striatum after injection of Fluoro-Ruby in the contralateral cortex. The data indicate that P14 cortical lesions affect PSA-NCAM expression in the developing striatum 1) by inducing a robust axonal plasticity resulting in the presence of immature presynaptic elements that contain PSA-NCAM and 2) by delaying the loss of PSA-NCAM expression in striatal neurons, suggesting that the lesion affects the time course of striatal maturation.

Surface composites: A new class of engineered materials

To integrate irreconcilable material properties into a single component, a new class of engineered materials termed “surface composites” has been developed. In this engineered material, the second phase is spatially distributed in the near surface regions, such that the phase composition is linearly graded as a function of distance from the surface. Surface composites are different from existing engineered materials such as “bulk composites” and “functionally graded materials” (FGM). Unlike bulk composites, the surface phase in surface composites is present only at the near surface regions. In contrast to FGM, the graded properties of surface composites are achieved by unique morphological surface modification of the bulk phase. To fabricate surface composites, the initial surface of the bulk material is transformed using a novel multiple pulse irradiation technique into truncated cone-like structures. The laser induced micro-rough structures (LIMS) possess surface areas which are up to an order of magnitude higher than the original surface. The second phase is deposited on the surface using thin or thick film deposition methods. A key characteristic of surface composites is the formation of a three-dimensional, compositionally and thermally graded interface, which gives rise to improved adhesion of the surface phase. Examples of various types of surface composites such as W/Mo, silica/SiC, diamond/steel, etc. are presented in this paper. The unique properties of surface composites make them ideal engineered materials for applications involving adherent thick film coatings of thermally mismatched materials, compositional surface modification for controlled catalytic activity, and creating adherent metal-ceramic and ceramic-polymeric joints.

Expression of synaptic membrane proteins in gerbil pinealocytes in primary culture

Pinealocytes of various mammalian species contain abundant synaptic-like microvesicles (SLMVs) which are considered the endocrine equivalent of neuronal synaptic vesicles. Although the pinealocytes may thus be a suitable cellular model for experimental in vitro studies of SLMVs, nothing is known about the presence of SLMVs in isolated pinealocytes maintained under tissue culture conditions. In the present investigation, we prepared dissociated primary cultures of gerbil pinealocytes to study the expression and distribution of protein components of synaptic vesicles/SLMVs and the presynaptic plasmalemma in pinealocytes kept in vitro. Using immunofluorescence microscopy, we found that cultured pinealocytes readily expressed all synaptic membrane proteins investigated, i.e., synaptophysin, synaptotagmin I, synaptobrevin II, syntaxin I and SNAP-25. Punctuate immunoreactivity for the vesicle-associated proteins could be detected throughout the cell bodies of pinealocytes and was also distributed into all of their processes which began to develop within the first days in culture. Outgrowing processes exhibited growth cone-like structures which were enriched in synaptic vesicle-associated proteins. After 1 week in vitro, pinealocytes had frequently formed an elaborate network of long interwoven processes. Accumulations of synaptic vesicle-associated proteins were observed in varicosities and terminal swellings of the processes. The vesicle-rich process swellings often established synaptic-like process swellings often established synaptic-like contacts with somata and processes of other pinealocytes. Some of the pinealocyte processes possessed additional axon-like properties as demonstrated by their lack of immunoreactivity for the somato-dendritic marker MAP2 and the transferrin receptor. The comparison of the staining patterns for synaptophysin and the endocytotic marker transferrin receptor by confocal laser scanning microscopy revealed a largely differential intracellular distribution of the two proteins. This may indicate that a substantial fraction of pinealocyte SLMVs by-passes the early endosomal-related recycling pathway of SLMVs. Herewith, we have shown that isolated gerbil pinealocytes maintained in primary culture can acquire morphological and neurochemical traits which closely mimick those observed in vivo. In particular, these cultures permit experimental studies of the compartment of pinealocyte SLMVs which seem to make up a major secretory pathway for paracrine intrapineal communication.