Surface changes in the rat vomeronasal epithelium during degeneration and regeneration of sensory receptor cells

To investigate cell turnover in the vomeronasal epithelium we used electron microscopy to obtain quantitative measurements of changes observed at the surface of the sensory epithelium. Receptor cell degeneration was induced by sensory nerve transection and animals were examined at postoperative recovery times of 2, 4, 6, 10, 15, 35 and 60 days. We measured the number and density of receptor and supporting cells, and membrane length at the surface of the sensory epithelium. The number of receptor cells rapidly decreased during the degeneration period, reaching a minimum at 6 days. After 15 days of recovery the number and density of receptor cells returned to control levels. The surface membrane length for regenerated receptor cells was similar to that of controls, however the morphological appearance was characteristic of immature cells. In contrast to the receptor cells, the number and density of supporting cells did not change during degeneration and regeneration. However, there was a significant increase in the length of supporting cell-surface membranes. These results suggest that during receptor cell degeneration, supporting cell membranes compensate for the loss of receptor cells by expanding their surface membrane length to help to maintain the continuity of the epithelial surface. Thus, an important role of vomeronasal supporting cells may be to maintain the structural integrity of the epithelium during turnover of the receptor cell population. Accepted: 3 January 2000     

Differential localisation of the metabotropic glutamate receptor mGluR1a and the ionotropic glutamate receptor GluR2/3 in neurons of the human cerebral cortex

Specimens of human cerebral cortex were obtained during neurosurgical operations and studied by immunocytochemistry and electron microscopy, using antibodies to the metabotropic glutamate receptor subunit mGluR1a and the ionotropic glutamate receptor GluR2/3. A small number of non-pyramidal neuronal cell bodies were labelled for mGluR1a. Double immunolabelling with mGluR1a and GluR2/3 showed that most pyramidal cell bodies were labelled for GluR2/3 but not for mGluR1a. Despite the non-colocalisation of these two receptor subtypes in cell bodies, however, many dendrites and dendritic spines were double-labelled for mGluR1a and GluR2/3 at electron microscopy. As there is evidence that most neurons positive for GluR2/3 are pyramidal cells, this suggests that mGluR1a is present in dendrites of pyramidal neurons, despite absent or low levels of immunoreactivity in their cell bodies. Received: 5 May 1997 / Accepted: 24 July 1997     

Infraterminal spreading and extrajunctional expression of nicotinic acetylcholine receptors in denervated rat skeletal muscle

 Through the use of biotinylated-bungarotoxin and monoclonal antibodies, the nicotinic acetylcholine receptor (nAChR) was localized in the subneural apparatus of mammalian motor end plates of the flexor digitorum brevis muscle of the adult rat at the light and electron microscopic levels. Under normal conditions, nAChR was located in the primary post-synaptic membrane of the neuromuscular junction, and the depths of the junctional folds constituting the secondary post-synaptic membrane did not contain any nAChR. Up to 75 days after repeated transection of the related motor nerve (sciatic), there was no major alteration in the light-microscopic localization of junctional nAChR in the subneural apparatus, except for a moderate shrinkage and increased immunocytochemical reactivity of the subneural apparatus. At the electron microscopic level, however, immunocytochemical reactivity gradually occupied the entire extent of the secondary post-synaptic membrane, including the depths of the junctional folds, which exhibited extensive branching. In non-innervated portions of the muscle fibers, nAChR receptor appeared in a linear localization on the surfaces of denervated muscle fibers. This linear reaction was not continuous with the nAChR reaction of the motor end plates. It is concluded that denervation supersensitivity might not be due to spreading of junctional nAChR from the end-plate area, but rather to expression of nAChR in non-innervated portions of the muscle fiber and to the infraterminal (subsynaptic) spreading of nAChR into the depths of junctional folds. Received: 29 May 1998 / Accepted: 8 December 1998     

A primary culture system of rat olfactory bulb forming many synapses similar to intact ones and spontaneously generating synchronous intracellular calcium oscillations

Previously, several studies attempting to analyze olfactory functions using dissociated culture systems of the olfactory bulb (OB) have been reported. Reciprocal dendrodendritic synapses between secondary neurons (mitral/tufted cells) and interneurons (periglomerular/granule cells) are considered to play the most important role in signal processing in the OB. However, it is unclear whether these reciprocal synapses are formed in vitro in the same way as they are in the intact OB. Thus, we synaptologically investigated the nature of cultured OB neurons. These neurons from embryonic rats were classified into four groups based on the size of their somata and their glutamic acid decarboxylase (GAD) immunoreactivity. At 14 days in vitro, most of the neurons synchronously showed spontaneous intracellular Ca2+ oscillations that were reversibly inhibited by application of D-APV and CNQX. Moreover, the frequency of the oscillations decreased and their amplitude became larger following application of bicuculline. These results suggest functional glutamatergic synaptic coupling and inhibitory GABAergic synaptic modulation. Immunocytochemical staining revealed many dot-like products (puncta) that were immunoreactive to GAD as well as to synaptophysin surrounding the cultured neurons. These results strongly indicate the presence of GABAergic synapses. The existence of synaptic contacts in OB neuron cultures was also confirmed by electron microscopy. Two types of synapses, symmetrical and asymmetrical, were morphologically recognizable. Moreover, we could also identify peculiar synapses resembling the in vivo reciprocal dendrodendritic synapses. The use of these primary culture systems will facilitate the elucidation of mechanisms underlying olfactory functions.     

The anchoring zone in the human placental amnion: bunches of oxytalan and collagen connect mesoderm and epithelium

 This study deals with the examination of the elastic fibre system as well as collagen fibrils and collagen type IV in the amnion of the human chorionic plate of uncomplicated pregnancies at term. In organs other than placenta, the elastic fibre system comprises elastic fibres, elaunin and oxytalan microfibrils. The investigation was performed by light and electron microscopy and immunocytochemistry. Abundant oxytalan fibres were present in all amnionic layers, while no elastic fibres were found. Oxytalan microfibrils formed a broad subepithelial layer and were intermingled with collagen fibrils in the subjacent compact layer and in the amnionic mesoderm. Light microscopically, bunches containing orcein-stained oxytalan and collagen-type-IV-immunostained microfibrils were seen rising from the amnionic mesoderm perpendicularly towards the epithelial layer, where they obviously inserted. It can be assumed that the subepithelial microfibrillar layer and the following compact layer form an anchoring zone between the amnionic mesoderm and the epithelium that may contribute to the maintenance of strength. The ultrastructure of the bunches clearly showed collagen fibrils mixed with oxytalan microfibrils. No collagen type I-immunostaining was found in the bunches. After pretreatment of cryostat sections with elastase, oxytalan-orcein-staining was absent, but collagen type IV-immunoreactivity was not altered. Furthermore, after oxytalan-orcein-staining resp. anti-collagen type IV incubation, all positive fibres revealed an identical morphological pattern. We propose that oxytalan and collagen type IV may represent further members of the microfibril complex. Accepted: 15 December 1998     

The response of primary horizontal semicircular canal neurons in the rat and guinea pig to angular acceleration

Summary In rats and guinea pigs, primary afferent neurons from the horizontal semicircular canal were divided into two categories, regular and irregular, on the basis of the regularity of their resting activity. Regular neurons tend to have higher average resting rates than irregular neurons and in response to a constant angular acceleration stimulus of 16.7 deg/s² regular neurons tended to have lower sensitivity and longer time constants than irregular cells. Some irregular neurons are more sensitive to incremental accelerations than to decremental accelerations of the same magnitude, whereas regular neurons tend to show symmetrical sensitivity.In response to sinusoidal angular acceleration stimuli (fixed frequencies) in the range 0.01–1.5 Hz, cells which fired regularly at rest tended to have smaller gain and longer phase lag re acceleration at most frequencies than irregular cells. Transfer functions were obtained for averaged data for regular and irregular neurons separately in both species.In both species there is evidence of systematic variation between neurons within each category, and this systematic variation is obscured by averaging across neurons.     

Neuropeptide Y inhibits ion secretion in intestinal epithelium by reducing chloride and potassium conductance

 Neuropeptide Y (NPY) is probably the most abundant neuropeptide, with a plethora of central as well as peripheral effects, including its proabsorptive action in the gastro-intestinal tract. The effects of NPY on electrical parameters related to three different pathways stimulating ion secretion were investigated using the human intestinal cell line HT29cl.19A. Transepithelial potential and resistance were measured with the preparation maintained in a horizontal Ussing chamber, allowing simultaneous measurement of the membrane potential and determination of the fractional resistance of the apical cell membrane. It was found that application of NPY, after the adenylyl-cyclase-activating drug forskolin, resulted in complete inhibition of forskolin-induced effects within approximately 20 min. The secretion stimulated by adenosine appeared to be insensitive to NPY. The acetylcholine analogue carbachol stimulates ion secretion by increasing intracellular free calcium concentrations ([Ca²⁺]_i) which activates the basolateral potassium (K⁺) conductance. NPY caused 50% inhibition of the effect of carbachol. Measurements of [Ca²⁺]_i showed that NPY inhibited the carbachol-induced rise in [Ca²⁺]_i, which correlates with the reduced activation of basolateral K⁺ channels. From this study we conclude that NPY inhibits cAMP-stimulated as well as Ca²⁺-stimulated secretion via a reduction in the apical Cl^– and basolateral K⁺ conductance. This double effect makes NPY an effective proabsorptive peptide. Received: 9 July 1997 / Received after revision: 29 August 1997 / Accepted: 22 September 1997     

The innervation of the synovium of the knee joint in the guinea pig: an immunohistochemical and ultrastructural study

 The innervation of the knee joint synovial membrane of the guinea pig, i.e., the synoviocyte layer, the subjacent connective tissue and the connective tissue region beneath, was analyzed with immunohistofluorescence and electron microscopy. A screening of the innervation with antibodies against the general axon marker – protein gene product (PGP) 9,5 – revealed the presence of nerve fibers distributed in various regions of the knee joint synovial membrane. Confirmating previous studies, some of these nerve fibers stained with antibodies to tyrosine hydroxylase (TH), neuropeptide Y (NPY), substance P (SP), calcitonin gene-related peptide (CGRP), and vasoactive intestinal polypeptide (VIP). In addition, dynorphin (DYN)-containing fibers were detected, which have not been reported previously in normal joints. In general, the immunoreactive fibers were observed close to the synoviocytes and at blood vessels. Fibers with colocalization of NPY- and TH-like immunoreactivities (LIs), as well as of DYN- and TH-LIs were demonstrated. In the electron microscope, bundles of unmyelinated fibers as well as single fibers were found in the connective tissue region below the synoviocytes. Varicose parts of the nerve fibers contained mainly small, clear vesicles. Small and large dense-cored vesicles were also seen, but less frequently. Denser portions of the plasma membranes of some axons were observed in these regions, facing the extracellular space. Myelinated fibers were also observed in some nerve bundles. These findings emphasize the complex innervation of the synovial membrane, with nerve fibers containing a host of neuroactive substances. Altogether, these fibers are probably involved in many functions such as vasoregulation and control of synovial secretion in addition to being a source of mediators in joint inflammation. Accepted: 22 November 1997     

Neurochemical characterization of AMPA receptor-containing neurons in the mediolateral septal area of the rat

 The lateral septum receives a massive innervation by excitatory amino acid-containing limbic cortical and hypothalamic afferents, and previous studies have described a wide distribution of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor-containing neurons in this area. The aim of this study was to determine whether different subtypes of AMPA receptors are expressed in the same neurons. Furthermore, considering the fact that a population of lateral septal cells, the ”somatospiny neurons,” are GABAergic calbindin-containing cells, the coexistence of each subtype of AMPA receptor with calbindin was also investigated. Colocalization experiments were performed on adjacent vibratome sections of the lateral septal area for GluR1 and GluR2/3 AMPA-receptor subunits, GluR1 and calbindin, GluR2/3 and calbindin, as well as GluR1 plus calbindin and GluR2/3 plus calbindin, using the ”mirror” colocalization technique. The results are summarized as follows: (1) GluR1 is present in the soma and most intensively expressed in dendrites and somatic and dendritic spines; while GluR2/3 is associated with the soma and proximal dendrites of the neurons. (2) Forty-one percent of the AMPA receptor-containing neurons cocontain GluR1 and GluR2/3. (3) Thirty-eight percent of GluR1- and 28% of GluR2/3-labeled cells express calbindin. (4) Sixty-two percent of the calbindin-immunoreactive neurons contain GluR1 and 51% of them express GluR2/3. (5) Half of the neurons expressing both GluR1 and GluR2/3 also contain calbindin. (6) The distribution of GluR1 plus GluR2/3-containing, GluR1 plus calbindin-containing, and GluR2/3 plus calbindin-containing neurons in the lateral septum are homogeneous. This study indicates the existence of multiple populations of AMPA receptor- and calbindin-containing neurons in the lateral septal area. Received: 9 August 1996 / Accepted: 7 November 1996     

Mitoses of existing corticotrophs contribute to their proliferation in the rat pituitary during the late fetal period

We studied the proliferation of pituitary corticotrophs quantitatively by labeling the proliferating cells with bromodeoxyuridine (BrdU) and carrying out immunocytochemistry for ACTH in rat fetuses at 19.5 days of gestation. In addition to labeling proliferating cells with a single injection of BrdU, we used double BrdU administrations at 9:00 and 19:00 for a more sensitive detection of proliferating cells. With this double administration, the number of cells labeled with either BrdU or both BrdU and ACTH increased by 1.75 and 2.3 times, respectively, compared with the single BrdU injection. The labeled cells further increased when the sections were stained for the proliferating cell nuclear antigen (PCNA) instead of BrdU. The number of cells labeled with PCNA or both PCNA and ACTH was 1.37 and 1.68 times that of the cells labeled with either BrdU or both BrdU and ACTH, respectively. The ratio of BrdU/ACTH-labeled cells or PCNA/ACTH-labeled cells to all corticotrophs was 13.6% and 24.3%, respectively, much higher than the ratios in fetuses having a single BrdU injection (6.6%). These results indicate that the mitosis of existing corticotrophs contributes greatly to their increase during the late fetal period. Accepted: 9 August 2000     

Catecholamine-containing axon terminals in the hypoglossal nucleus of the rat: an immuno-electronmicroscopic study

Summary A correlative light and electron microscopic investigation was undertaken to determine the morphology and distribution of catecholamine (CA)-containing axon terminals in the hypoglossal nucleus (XII) of the rat. This was accomplished immunocytochemically with antibody to tyrosine hydroxylase (TH). The major findings in this study were the following: 1) Immunoreactive profiles were found throughout XII and included unmyelinated axons, varicosities, axon terminals and dendrites; 2) Nonsynaptic immunoreactive profiles (preterminal axons, varicosities) were more frequently observed (55.2%) than synaptic profiles (43.5%); 3) CA-containing axon terminals ending on dendrites were more numerous (71.8%) than those synapsing on somata (25.4%) or nonlabeled axon terminals (2.7%); 4) The morphology of labeled axon terminals was variable. Axodendritic terminals typically contained numerous small, round agranular vesicles, a few large dense-core vesicles and were associated with either a symmetric or no synaptic specialization, axosomatic terminals were often associated with a presynaptic membrane thickening or a symmetric synaptic specialization and contained small, round and a few elliptical-shaped vesicles, while axoaxonic synapses formed asymmetric postsynaptic specializations; and 5) CA-positive dendritic processes were identified in XII. These findings confirm the CA innervation of XII, and suggest a complex, multifunctional role for CA in controlling oro-lingual motor behavior.     

Ultrastructural subtypes of glutamate-immunoreactive terminals on rat trigeminal motoneurones and their relationships with GABA-immunoreactive terminals

 Electron-microscopic immunolabelling methods were used to study the relationships between glutamate-immunoreactive and γ-aminobutyric acid (GABA)-immunoreactive synapses on trigeminal motoneurones labelled by the retrograde transport of horseradish peroxidase. Serial sections were cut through the motor nucleus, alternate sections were incubated with antibodies to glutamate and GABA, and the immunopositive nerve terminal profiles were recognized using a quantitative, postembedding immunogold method. Boutons exhibiting high levels of glutamate immunoreactivity and GABA-immunoreactive boutons both formed axo-dendritic and axo-somatic synaptic contacts on labelled motoneurones. Boutons strongly immunopositive for glutamate were not immunopositive for GABA, and vice versa. Strongly glutamate immunoreactive boutons received axo-axonic synaptic contacts but did not form such contacts, while GABA-immunoreactive boutons formed axo-axonic synapses but did not receive them. The presynaptic elements at all axo-axonic synapses on to glutamate-immunoreactive boutons sampled were GABA-immunopositive. These data provide ultrastructural evidence in support of the roles of glutamate and GABA as transmitters at synapses on trigeminal motoneurones, and for presynaptic control of transmission at glutamatergic synapses by GABA acting at receptors at axo-axonic synapses. The vast majority (more than 90%) of strongly glutamate immunoreactive boutons contained spherical synaptic vesicles, in contrast to GABA-immunoreactive boutons, which contained pleomorphic vesicles. Most of the glutamate-immunoreactive boutons (67%) formed asymmetrical synaptic active zones, many of which (47% of total) were associated with subsynaptic dense ”Taxi” bodies (T-terminals), while a smaller population of boutons (21%) formed symmetrical synapses, and a few (11%) made synapses associated with subsynaptic cisternae (C-terminals). The heterogeneity of active zone ultrastructure of boutons identified as being glutamatergic on the basis of their high levels of immunolabelling is discussed in relation to possible differences in co-transmitters released, origins of the synaptic input or post-synaptic receptor subtypes activated. Received: 13 May 1996 / Accepted: 9 September 1996     

Expression of Gα proteins in the developing, denervated, or injured rat molar tooth

 The purpose of this study was to map the distribution of α-subunits of G-proteins – Gα_{olf s}, Gα_olf, Gα_s, Gα_i, Gα_o, Gα_z and Gα_q11– in developing, denervated or injured rat molar teeth, using fluorescence microscopic immunohistochemistry coupled with immunogold electron microscopic immunocytochemistry. In rat fetuses (E17–E21), a widespread expression of Gα_q11 was seen in maxillary/mandibular mesenchyme as well as in developing teeth. In addition, intensely Gα_o-positive nerve fibers were associated with the dental epithelium and the dental papilla of developing teeth. Other G proteins were absent or sparsely distributed during early tooth development. In the adult tooth pulp, odontoblasts appeared to express mainly Gα_{olf s}, Gα_o, and Gα_q11. Nerve fibers were immunoreactive to Gα_i, Gα_o and Gα_z. In addition, pulpal blood vessels expressed varying levels of Gα_{olf s} Gα_z and Gα_q11 while Gα_{olf s}, Gα_olf, Gα_o and Gα_q11 were found in various pulpal mesenchymal cells. After adult denervation, nerve fiber-related G-protein immunoreactivity disappeared, but no other changes in pulpal G-protein immunoreactivity were noted. Odontoblasts and mesenchyme cells were intensely Gα_i-positive underneath a pulpal traumatic exposure, indicating an injury-induced pulpal upregulation of Gα_i. The findings that Gα_i, Gα_o and Gα_z are expressed in pulpal sensory nerve fibers suggest that these G proteins participate in signal conveyance from the target to the trigeminal nerve cell body. Accepted: 25 May 1998     

Subretinal macrophages in the developing eye of eutherian mammals and marsupials

Blood-borne mononuclear cells invade the developing retina via the hyaloid vasculature at the optic nerve head. Following removal of apoptotic cell debris they give rise to the network of resident microglia. The population of cells recently described in the peripheral subretinal space of developing human eyes may represent a further population of macrophages destined to become microglia. The aim of the present study was to confirm the presence of subretinal macrophages in the developing eye in other mammalian species and perform preliminary immunophenotypic analysis in rat tissues. The range of species chosen included eutherian mammals (rat and rabbit) and marsupials (wallaby and opossum). Ocular tissues from a range of developmental stages were studied by scanning electron microscopy and transmission electron microscopy. Distinctive networks of dendriform and pleomorphic macrophages were observed by scanning electron microscopy in the peripheral subretinal space of D2 rabbits, newborn and D2 rats and D75 wallaby. Transmission electron microscopic studies of D2 rabbit, newborn and D2 rat and all ages of North American opossum revealed cells with the ultrastructural features of macrophages in the peripheral subretinal space, cilio-retinal junction and between ciliary epithelial cells. Preliminary immunoperoxidase studies using a panel of anti-leukocyte monoclonal antibodies on frozen sections of rat ocular tissues (newborn, D2 and D4) revealed ED1⁺ Ox42⁺ ED2⁺ but Ox6^– cells in the peripheral subretinal space, peripheral retina and ciliary body epithelia. The data confirms that subretinal macrophages are a feature of the developing eye in a broad range of mammalian species and immunophenotypic evidence leads the author to postulate that these cells arise from the ciliary body vasculature and may migrate into peripheral neural retina and mature into resident microglia. Accepted: 23 March 1999     

Intravenous injection of guanylin induces mucus secretion from goblet cells in rat duodenal crypts

 Guanylin, structurally related to the heat-stable enterotoxin of E. coli, is a 15-amino-acid peptide isolated from rat small intestine. We investigated the morphological effects of an intravenous injection of rat and human guanylin upon the rat intestine. Various doses of rat guanylin were injected intravenously in anesthetized rats. After 5, 10 and 30 min, rats were killed by intracardiac perfusion with aldehyde fixative, and specimens of the intestine were then prepared for light and electron microscopy. Intravenously injected rat guanylin rapidly induced mucus secretion from crypt goblet cells in the duodenum. About half of the crypt goblet cells secreted mucous granules by compound exocytosis within 5 min. The villus goblet cells, in contrast, were not sensitive to guanylin. Goblet cells in the jejunum were less responsive than those in the duodenum. This secretory response was rare in the ileum and colon. Human guanylin produced similar results. The mucus secretion induced by guanylin was inhibited by a prior-injection of atropine, but not hexamethonium. Moreover, guanylin induced intense edema in the mucosa and submucosa of the small intestine 5 min after the injection, which disappeared after 30 min. A prior-injection of atropine did not block the appearance of edema. In conclusion, the intravenous injection of guanylin induces two phenomena related to water movement: (1) compound exocytosis of mucous granules from crypt goblet cells in the rat duodenum and jejunum; (2) perineural, inter-epithelial and intra-epithelial edema in the rat small intestine. Accepted: 27 October 1997     

Detailed organization of nitric oxide synthase, vasopressin and oxytocin immunoreactive cell bodies in the supraoptic nucleus of the female rat

The anatomical distribution and quantitative relations of cell bodies containing neuronal nitric oxide synthase (nNOS), 8-arginine vasopressin (AVP) and oxytocin (OT) were examined throughout the supraoptic nucleus (SON) of the female rat by means of immunocytochemical and NADPH-diaphorase (NADPH-d) histochemical techniques using a triple labelling methodology. Seven chemically defined populations of neurons containing all combinations of either nNOS, AVP or OT were identified. nNOS-containing (NADPH-d positive) neurons, amounting to about 40% of all neurons counted, were most frequent in central and dorsal regions, and were evenly distributed along the rostro-caudal axis. Two small nNOS-positive neuronal populations were preferentially located dorso-centrally in the nucleus: nNOS-positive neurons containing both AVP- and OT-immunoreactivity, and neurons only containing nNOS. Slightly less than half of all nNOS-positive neurons contained AVP, and a similar share of nNOS-positive neurons contained OT. The occurrence of nNOS-positive/ AVP-containing neurons was highest in the caudal half, whereas that of nNOS-positive/OT-neurons was highest in the rostral half of SON. The data demonstrate new findings concerning the anatomical organization and co-localization patterns of nNOS-, AVP- and OT-containing neuronal populations in SON. We conclude that the absolute and relative occurrence of the identified neuronal populations vary markedly in different parts of SON. This is important to take into consideration when performing, and evaluating experimental investigations concerned with neurochemical changes in SON. Accepted: 29 December 2000     

Evidence of M cells as portals of entry for antigens in the nasopharyngeal lymphoid tissue of humans

The nasopharyngeal tonsils (adenoids) are prominent components of human nasal-associated lymphoid tissues (NALT). However, the role of the nasopharyngeal tonsils in antigen uptake for initiation of the mucosal immune response is unknown. The aims of this study were to describe the ultrastructure and function of the M cells of the human nasopharyngeal tonsils and to clarify their capacity for antigen uptake. Tissues obtained from eight patients undergoing adenectomy were examined by light and electron microscopy. Lymphoepithelium covers the nasopharyngeal lymphoid tissue and consists of ciliary epithelium, non-ciliary epithelial cells, M cells, goblet cells, and many intraepithelial lymphoid cells. M cells have irregular and broad cytoplasm-containing microvilli on their surface and small vesicles in their cytoplasm. Many lymphoid cells were enfolded by M cells. The uptake of horseradish peroxidase (HRP) in the tissue in organ culture was studied using histochemical techniques. Excised adenoid tissue was incubated in RPMI 1640 culture media with HRP for 10, 30, and 60 min. HRP which had adhered to the surface was taken up in vesicles and then transported in vesicles and tubules by M cells. The M cells of nasopharyngeal lymphoid tissue were ultrastructurally and functionally similar to those in human Peyer’s patches and colonic lymphoid follicles. These findings indicate that NALT bears similarities to the gut-associated lymphoid tissue, and its antigen uptake capacity may be important for initiation of immunity in the upper aerodigestive tract. Received: 8 July 1999 / Accepted: 17 December 1999     

The transentorhinal cortex of the African green monkey: a combined light- and electron-microscopic study of calcium-binding protein containing neurons

The transentorhinal cortex (TEC) is a primate-specific transition zone between the entorhinal allocortex and the temporal isocortex. Neurons in the lamina pre-alpha of TEC are known to be the first to develop intraneuronal changes in the course of Alzheimer’s disease. In order to shed light on this important feature, we studied as yet unknown morphological and neurochemical characteristics of the TEC of the African green monkey (Cercopithecus aethiops sabaeus). Using light- and electron-microscopic immunocytochemistry, the distribution and morphology of neurons containing calcium-binding proteins were described and compared with those in the adjacent cortices. Light-microscopic analysis revealed that parvalbumin-containing neurons were distributed in all cortical layers. Calbindin-containing cells were fewer but also present in each layer. Calretinin-containing neurons were largely confined to the upper layers of the TEC. All three types of neuron showed pyramidal-like, multipolar and bipolar shapes; their dendrites were smooth or beaded. Ultrastructural studies revealed immunopositive somata with infolded nuclei and large amounts of cytoplasm. The somata were only sparsely innervated by symmetric synapses. Immunopositive dendrites were almost exclusively covered with immunonegative axon terminals establishing symmetric and asymmetric synapses. Immunopositive terminals established symmetric contacts with immunonegative dendrites and somata. Only occasionally, could synaptic contacts between immunopositive pre- and postsynaptic structures be observed. The comparison of neurons in the TEC and adjacent cortices revealed no striking differences. In summary, the morphological and neurochemical characteristics of TEC neurons as analyzed in our study do not provide an explanation for the early onset of neurodegenerative changes in the TEC. Accepted: 10 December 1999