Aspects of the neuroendocrine cerebellum: expression of secretogranin II, chromogranin A and chromogranin B in mouse cerebellar unipolar brush cells

Morphologically distinct neuron classes can be subdivided in sublineages by differential chemical phenotypes that correlate with functional diversity. Here we show by immunocytochemistry that chromogranin A (CgA) chromogranin B (CgB) and secretogranin II (SgII), the principal granins situated in neuronal secretory granules and large dense-core vesicles, are widely but differentially expressed in cells of the mouse cerebellum and terminals of cerebellar afferents. While CgA and CgB were nearly panneuronal, SgII was more restricted in distribution. The cells most intensely immunoreactive for SgII were a class of small, excitatory interneurons enriched in the granular layer of the vestibulocerebellum, the unipolar brush cells (UBCs), although larger neurons likely to be a subset of the Golgi-Lugaro-globular cell population were also distinctly immunopositive; by contrast, Purkinje cells and granule cells were, at best, faintly stained and, stellate, basket cells were unstained. SgII was also present in subsets of mossy fibers, climbing fibers and varicose fibers. Neurons in the cerebellar nuclei and inferior olive were distinctly positive for the three granins. Double-labeling with subset-specific cell class markers indicated that, while both CgA and CgB were present in most UBCs, SgII immunoreactivity was present in the calretinin (CR)-expressing subset, but lacked in metabotropic glutamate receptor 1alpha (mGluR1alpha)-expressing UBCs. Thus, we have identified an additional cell class marker, SgII, which serves to study subtype properties in the UBC population. The abundance of SgII in only one of the two known subsets of UBCs is remarkable, as its expression in other neurons of the cortex was moderate or altogether lacking. The data suggest that the CR-positive UBCs represent a unique neuroendocrine component of the mammalian cerebellar cortex, presumably endowed with transynaptically regulated autocrine or paracrine action/s. Because of the well-known organization of the cerebellar system, several of its neuron classes may represent valuable cellular models to analyze granin functions in situ, in acute slices and in dissociated cell and organotypic slice cultures.

Vesicular glutamate transporters VGLUT1 and VGLUT2 define two subsets of unipolar brush cells in organotypic cultures of mouse vestibulocerebellum

Different isoforms of a vesicular glutamate transporter (VGLUT) mediate glutamate uptake into synaptic vesicles of excitatory neurons. There is agreement that the VGLUTs are differentially expressed in brain, and that two isoforms, VGLUT1 and VGLUT2, are localized to excitatory axon terminals in the cerebellar cortex. While granule cells express solely VGLUT1, there is no report about the VGLUT(s) of the unipolar brush cell (UBC), the second type of glutamatergic interneuron residing in the cerebellar granular layer. In the mouse, UBCs are particularly numerous in the uvula (lobule IX) and nodulus (lobule X). These folia contain two distinct subsets of UBCs: one kind expresses the calcium-binding protein calretinin (CR), and the other kind expresses the metabotropic glutamate receptor (mGluR) 1alpha. UBCs give rise to an extensive system of intrinsic mossy fibers (MF), whose terminals innervate granule cells and other UBCs, altogether similar to those formed by the extrinsic MFs. The presence of both extrinsic and intrinsic MFs in the vestibulocerebellum makes it difficult to determine which type of VGLUT is contained in MFs formed by the UBC axons. Hence, the nodulus was isolated from sagittal cerebellar slices from postnatal day 10 mice, and cultured for 15-20 days in vitro. Double immunofluorescence and confocal microscopy showed that mossy terminals of CR-positive (CR(+)) UBCs were immunoreactive for VGLUT1 and VGLUT2, while mossy terminals of mGluR1alpha-positive (mGluR1alpha(+)) UBCs were provided with VGLUT1 only. Moreover, CR(+) dendritic brushes were contacted by mossy terminals provided with both transporters, while mGluR1alpha(+) dendritic brushes were contacted by mossy terminals immunopositive for VGLUT1 and immunonegative for VGLUT2. These data indicate that the two UBC subsets use different modalities of vesicular glutamate storage and form separate networks. We consider it possible that expressions of CR with VGLUT1/VGLUT2 and mGluR1alpha(+) with VGLUT1 in the two subsets of vestibulocerebellar UBCs are determined by specific vestibular inputs, carried by groups of primary and/or secondary vestibular afferents.

Cerebellar input to magnocellular neurons in the red nucleus of the mouse: synaptic analysis in horizontal brain slices incorporating cerebello-rubral pathways

We studied the synaptic input from the nucleus interpositus of the cerebellum to the magnocellular division of the red nucleus (RNm) in the mouse using combined electrophysiological and neuroanatomical methods. Whole-cell patch-clamp recordings were made from brain slices (125-150 microm) cut in a horizontal plane oriented to pass through both red nucleus and nucleus interpositus. Large cells that were visually selected and patched were injected with Lucifer Yellow and identified as RNm neurons. Using anterograde tracing from nucleus interpositus in vitro, we examined the course of interposito-rubral axons which are dispersed in the superior cerebellar peduncle. In vitro monosynaptic responses in RNm were elicited by an electrode array placed contralaterally in this pathway but near the midline. Mixed excitatory post-synaptic potentials (EPSPs)/inhibitory post-synaptic potentials (IPSPs) were observed in 48 RNm neurons. Excitatory components of the evoked potentials were studied after blocking inhibitory components with picrotoxin (100 microM) and strychnine (5 microM). All RNm neurons examined continued to show monosynaptic EPSPs after non-N-methyl-D-aspartate (NMDA) glutamate receptor components were blocked with 10 microM 6,7-dinitroquinoxaline-2,3-dione or 5 microM 2,3-dihydro-6-nitro-7-sulfamoyl-benzo(f)-quinoxaline (NBQX; n=12). The residual potentials were identified as NMDA receptor components since they (i) were blocked by the addition of the NMDA receptor antagonist, D,L-2-amino-5-phosphonovaleric acid (APV), (ii) were voltage-dependent, and (iii) were enhanced by Mg(2+) removal. Inhibitory components of the evoked potentials were studied after blocking excitatory components with NBQX and APV. Under these conditions, all RNm neurons studied continued to show IPSPs. Blockade of GABA(A) receptors reduced but did not eliminate the IPSPs. These were eliminated when GABA(A) receptor blockade was combined with strychnine to eliminate glycine components of the IPSPs. Thus, IPSPs evoked by midline stimulation of the superior cerebellar peduncle, while blocking alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) and NMDA receptors, raise the possibility of direct inhibitory inputs to RNm from the cerebellum. In summary we propose that the special properties of the NMDA receptor components are considered important for the generation of RNm motor commands: their slow time course will contribute a steady driving force for sustained discharge and their voltage dependency will facilitate abrupt transitions from a resting state of quiescence to an active state of intense motor command generation.

Unipolar brush cells form a glutamatergic projection system within the mouse cerebellar cortex

Unipolar brush cells (UBCs) of the mammalian vestibulocerebellum receive mossy fiber projections primarily from the vestibular ganglion and vestibular nuclei. Recently, the axons of UBCs have been shown to generate an extensive system of cortex-intrinsic mossy fibers, which resemble traditional cerebellar mossy fiber afferents and synapse with granule cell dendrites and other UBCs. However, the neurotransmitter used by the UBC axon is still unknown. In this study, we used long-term organotypic slice cultures of the isolated nodulus (lobule X) from postnatal day 8 mouse cerebella to identify the neurotransmitter and receptors at synapses of the UBC axon terminals, relying on the notion that, in these cultures, all of the cortex-extrinsic fibers had degenerated during the first few days in vitro. Quantification of glutamate immunogold labeling showed that the UBC axon terminals have the same high gold-particle density as the glutamatergic parallel fiber varicosities. Furthermore, UBCs identified by calretinin immunoreactivity expressed the glutamate receptor subunits GluR2/3, NMDAR1, and mGluR2/3, like they do in the mature mouse cerebellum in situ. Evoked excitatory postsynaptic currents (EPSCs), spontaneous EPSCs, and burst discharges were demonstrated in UBCs and granule cells by patch-clamp recording. Both the evoked and spontaneous EPSCs were blocked by ionotropic glutamate receptor antagonists CNQX and D-AP5. We conclude that neurotransmission at the UBC axon terminals is glutamatergic. Thus, UBCs provide a powerful network of feedforward excitation within the granular layer, which may amplify vestibular signals and synchronize activity in clusters of functionally related granule cells which project vertically to patches of Purkinje cells.

Unusual ultrastructural features in intrafascicular ganglion cells of the rat pelvic nerve

The incidental finding of four ectopic ganglion cells within the pelvic nerve of a normal rat prompted a thorough electron microscopic investigation of the ultrastructural features of these neurons. They were found to enwrap presynaptic terminals inside crater-like invaginations; the appositional surfaces were made more complex by the presence of slender dendritic appendages and sheet-like processes of glial cells. The presynaptic elements contained both clear and dense-cored vesicles, and appeared similar to those characterizing SIF (paraneuronal) cells. In addition, cilia were encountered in both the invaginated processes and most of the Schwann cells associated with the pre- and postsynaptic nerve cells and their processes. Overall, these features were deemed worth reporting because 1) of the unusual features of synaptic input from a SIF cell to a ganglion cell associated with the pelvic plexus, and 2) the ectopic ganglion cells possibly represent the sole example, other than ciliary neurones in the avian ciliary ganglion, of postsynaptic cells encasing presynaptic endings inside their perikarya.

Unipolar brush cell axons form a large system of intrinsic mossy fibers in the postnatal vestibulocerebellum

The unipolar brush cells (UBCs), a class of neurons recently identified in the granular layer of the vestibulocerebellum, receive excitatory synaptic input from mossy fibers (MFs) in the form of a giant glutamatergic synapse. UBCs are provided with axons that bear synaptic endings situated at the center of glomeruli, similar to cerebellar MF afferents. A single MF stimulus evokes a prolonged train of action potentials in the UBC (Rossi et al., 1995), which is presumably distributed to postsynaptic targets. Knowledge of the synaptic connections of UBC axons is essential to define the role of these cells in the integration of vestibular signals in the cerebellar circuitry. To evaluate these connections, the nodulus (folium X) was isolated from vermal slices of postnatal day 8 mice, cultured for 2-4 or 15-30 days in vitro, and studied by electron and fluorescence microscopy. The peak of degeneration of extrinsic MF terminals, which have been severed from the parent cell bodies, was observed at 2 days in vitro (DIV). Quantification of degenerating and nondegenerating (e.g., intrinsic) MF terminals indicated that about half of the MF terminals were provided by local UBC axons synapsing on dendrites of granule cells and other UBCs. The proportion of nondegenerating vs. degenerating MF terminals terminating on UBCs also indicated that approximately two-thirds of the intrinsic MFs are involved in UBC-UBC connections. In long-term cultures, the granular layer appeared well preserved and the UBC axons formed an extensive system of MF collaterals. It is suggested that UBCs may act by spatially amplifying vestibular inputs carried by extrinsic MFs.

Compartmental organization of Purkinje cells in the mature and developing mouse cerebellum as revealed by an olfactory marker protein-lacZ transgene

In a line of transgenic mice (HpY-1), the pattern of expression of an olfactory marker protein (OMP)-lacZ fusion gene was analyzed in the cerebellum, where, in adult mice, OMP-lacZ was expressed primarily in Purkinje cells (PCs) of the posterior lobe. The transgene-expressing PCs were organized in parasagittal bands, with a boundary of expression roughly corresponding to the primary fissure that separates the cerebellum into anterior and posterior compartments. The regional expression of the lacZ gene was also analyzed during embryonic and postnatal development of the cerebellum. Within the cerebellum-isthmus region, transgene expression first was detected at embryonic day 13.5 (E13.5) in a cluster of postmitotic cells. By E14.5, lacZ was also expressed by a subpopulation of migrating PCs in the postisthmal and lateral cerebellar primordium, and, by E16.5, transgene-positive PCs formed caudally four sagittal bands symmetric to the medial embryonic fissure. The caudal pattern was retained in postnatal cerebella, where, by postnatal day 0 (P0), transgene-positive PCs in vermal lobules VIII and IX appeared to be organized in two prominent parasagittal compartments on either side of a negative midline band. In early postnatal animals, the transgene was expressed transiently in the anterior lobe vermis. Hence, from P5 onward, transgene expression appeared mostly restricted to the posterior lobe, where it followed a caudal-to-rostral gradient. In the paraflocculus, transgene-expressing PCs were confined to the rostrodorsal portion. The results indicate that the anterior and posterior cerebellar lobes are regulated by distinct ontogenetic programs, and PCs of functionally distinct cerebellar regions express the transgene differentially. Furthermore, the data suggest that ectopic expression of OMP-lacZ in the cerebellum is under the control of regulatory elements that provide positional information for the regional specification of PC subsets.

Peripheral neuropathy induced by intravenous administration of vincristine sulfate in the rabbit. An ultrastructural study

The lack of a suitable animal model for the peripheral neuropathy that often follows the systemic administration of the chemotherapeutic agent vincristine sulfate (VCR) has hampered the correlation between experimental and clinical patterns of this neuropathy. New Zealand rabbits have been recently found to develop, after iv injection of a VCR total dosage similar to that used in humans, a peripheral polyneuropathy characterized by electrophysiological changes that overlap those observed in the clinical setting. The present study was aimed at investigating the ultrastructural features of 3 different nerves (sural, peroneal, and medial gastrocnemius) in rabbits treated with 3 VCR doses that fall within the range (0.2-0.3 mg/kg i.v.) known to be efficacious chemotherapeutically and active neurotoxicologically. Regardless of the dose and the nerve under examination, histopathologic alterations appeared in the form of an overall loss of myelinated fibers, accompanied by successful attempts of regeneration and remyelination. Fibers undergoing Wallerian degeneration were characterized by an axoplasm, which was either watery-flocculent or divided in 2 or more regions as a consequence of ingrowing Schwann cell processes from the adaxonal surface. These ingrowths tended to isolate axoplasmic areas, retaining a fairly normal structure from other areas already crowded with altered organelles and cytoskeletal elements. In any event, neurofibrillary accumulations were rarely seen. These patterns are discussed with reference to those reported in the ultrastructural studies of human cases and confirm the suitability of rabbit as an animal model for VCR-induced peripheral neuropathy.

The earliest documented applications of X-rays to examination of mummified remains and archaeological materials

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Soluble amyloid beta-protein is a marker of Alzheimer amyloid in brain but not in cerebrospinal fluid

The amyloid beta protein (A beta), a 4 kD fragment of the beta amyloid precursor protein, is deposited as insoluble amyloid in the brain of Alzheimer disease (AD) subjects. Soluble A beta is a normal metabolic product and is present in cerebrospinal fluid. We identified soluble A beta forms of 4kD, 3kD and 3.7kD in AD but not in control brains free of amyloid deposits. All three forms of soluble A beta extend beyond residue 40. Analysis of cerebrospinal fluid from the same subjects confirmed the presence of only 4kD A beta in comparable amounts in AD and controls. The presence of soluble A beta only in brain regions with amyloid suggests they are related. The undetectability of soluble A beta in control brains indicates that it is normally removed or bound to other proteins. Failure of this protective mechanism might cause amyloid formation in AD.

Spontaneous isolated lipoma of the choroid plexus in the baboon

A case of symptomless, solitary lipoma of the choroid plexus is described. The tumour was found in the left lateral ventricle of an adult female baboon (Papio papio) in the course of post-mortem examination. Routine histological investigation showed that the tumour was composed exclusively of characteristic adipose cells with scarce collagen septa and without other hamartoma-like constituents, such as glial cells, neurons, cartilage or muscle fibres. The tumour mass was lined by a typical single layer of cuboidal cells; no calcifications were observed either inside the tumour or in the adjacent periventricular regions. This case is reported in view of the rarity of such tumours of the choroid plexus in man and animals, and to throw light on their possible origin.

Amyloid beta precursor protein and ubiquitin epitopes in human and experimental dystrophic axons. Ultrastructural localization

Dystrophic axons (DA) represent a major pathological feature of several neurodegenerative disorders, including infantile neuroaxonal dystrophy (INAD) and Alzheimer disease. We have previously presented evidence that amyloid beta precursor protein (BPP) and ubiquitin (Ub) are present in DA of different origin. We have now characterized the immunoreactivity of DA experimentally induced in rat by the administration of parabromophenylacetylurea (BPAU) and examined the subcellular localization of Ub and BPP in BPAU-induced DA and in DA present in subjects affected by INAD. BPAU-induced DA strongly immunoreacted with antisera to Ub and to COOH- and NH2-terminal regions of BPP. Immunoblots of DA-enriched brain regions were consistent with an increase in the amount of Ub and BPP in DA. Moreover, BPAU-induced DA immunoreacted with antibodies to PGP 9.5, a neuronal-specific Ub COOH-terminal hydrolase, and to the inducible heat shock protein 70. Antigenic characterization also indicated that the tubulovesicular membranes within DA derived largely from the smooth endoplasmic reticulum rather than from the Golgi system or the synaptic vesicles. Subcellular immunolocalization of Ub and BPP in both INAD- and BPAU-induced DA revealed that Ub and BPP colocalize in granulovesicular material in both conditions. In INAD DA intense Ub immunoreactivity was also detected in nonmembranous electron dense structures that were present only in these DA, probably because of the chronic course of INAD. Although BPP immunostaining may be related to accumulation of BPP-containing membranes in DA, Ub immunostaining is likely to result from activation of the Ub system by the neuron in the attempt to remove excessive and possibly abnormal proteins. A similar pathogenesis can be postulated for DA of Alzheimer disease.

B-50/GAP-43 phosphorylation in hippocampal slices from aged rats: effects of phosphatidylserine administration

Phosphorylation of the presynaptic protein B-50/GAP-43, a substrate of protein kinase C (PKC), has been implicated in neuronal mechanisms related to learning and memory. We evaluated both basal (5 mM KCl) and stimulated (30 mM KCl) B-50/GAP-43 phosphorylation in 32P-prelabeled hippocampal slices obtained from adult and senescent male Sprague-Dawley rats. The in situ B-50/GAP-43 phosphorylation was assayed by quantitative immunoprecipitation. There was no age-related difference in B-50/GAP-43 basal phosphorylation. However, B-50/GAP-43 phosphorylation in depolarized slices from aged rats was significantly decreased relative to that of adult animals. Aged rats were treated with either tris buffer or sonicated suspension of phosphatidylserine (PS) in tris buffer (15 mg/kg IP for 7 and 17 days). PS did not affect basal and high K(+)-induced B-50/GAP-43 phosphorylation in the 7-day treatment. However, after 17 days, PS restored the K(+)-induced B-50/GAP-43 phosphorylation. It is proposed that repeated PS administrations might be beneficial to the age-induced deterioration of endogenous B-50/GAP-43 phosphorylation by acting on Ca++ homeostatic mechanisms and/or PKC.

Calcium/calmodulin-stimulated protein kinase II is present in primary cultures of cerebral endothelial cells

Calcium/calmodulin-stimulated protein kinase II (CaM-PK II), a major kinase in brain, has been established to play an important role in neurotransmitter release and organization of postsynaptic receptors, and it is known to be involved in long-term potentiation and memory. Less is known about the function of this enzyme in nonneural cells. Here we report on the production, presence, and phosphorylation of the alpha-subunit of CaM-PK II in primary cultures of cerebral endothelial cells. These results raise the possibility that alpha-CaM-PK II can act as one of the key enzymes of calcium-mediated intracellular signaling in the cerebral endothelial cells and suggest that alpha-CaM-PK II may participate in such basic cellular processes as permeability in physiological and pathological conditions.

Phosphorylation of the presynaptic protein B-50 (GAP-43) is increased during electrically induced long-term potentiation

The protein B-50 (F1, GAP-43) is a presynaptic-specific substrate of protein kinase C, functionally related to neurotransmitter release. An increase in phosphorylation of this protein has been proposed as a molecular mechanism underlying long-term potentiation (LTP). B-50 phosphorylation measured by quantitative immunoprecipitation in rat hippocampal slices incubated in the presence of radiolabeled inorganic phosphate was increased for at least 1 hr after the induction of LTP in the CA1 region. No significant changes in B-50 phosphorylation were observed in untetanized slices stimulated at low frequency. The direct demonstration of an increased phosphorylation of the protein B-50 during LTP is consistent with the hypothesis that presynaptic mechanisms contribute to maintenance of LTP.

Effects of gangliosides on the expression of autoimmune demyelination in the peripheral nervous system

To test whether gangliosides (GA) might exert neuritogenic effects in vivo, experimental allergic neuritis (EAN) was studied clinically, neuropathologically, and immunologically in Lewis rats immunized with bovine peripheral nerve, P2 myelin protein, P2 myelin protein plus two different doses of GA, P2 with galactocerebroside (GC), and GA alone, each emulsified in adjuvant. All except the GA-treated group developed signs of EAN between days 11 and 14 after the injection. Rats immunized with P2 alone were the most severely affected. Rats given P2 plus GA and those given P2 plus GC displayed a significantly lower clinical score. Histological analysis revealed a comparable degree of inflammation of the peripheral nervous system and demyelination in the spinal nerve roots of bovine peripheral nerve- and P2-immunized rats. The P2 plus GA and P2 plus GC groups revealed similar degrees of pathology in the spinal nerve roots but the latter group stood apart from the rest in that it showed widespread peripheral nervous system changes extending distally into the sciatic nerve. Serological analysis demonstrated that P2 and GC, but not GA, elicited antibody (IgG) responses, but there was no correlation between antibody titer and clinical or histological involvement. The present data fail to support an enhancing role for gangliosides in the expression of EAN and, by extrapolation, in the Guillain-Barré syndrome, for which EAN serves as the laboratory model, and in which suggestions have been made that antibodies to GA may have pathogenetic significance.

Perineurium of sciatic nerve in normal and diabetic rodents: freeze-fracture study of intercellular junctional complexes

A comparative study has been carried out using the freeze-fracture technique on the perineurium of the sciatic nerve from normal and diabetic mice (C57Bl/Ks, BALB/c and CD1 strains) and rats of various ages. The replicas showed that tight junctions connected perineurial cells both within the same cell layer (zonulae occludentes) and between adjacent layers (maculae occludentes). In neonates, a number of zonulae occludentes were characterized by short, incomplete or fragmented ridges at various intervals from each other; in adults, tight junctions appeared as 'mature' networks of interconnected, branching and/or anastomosing strands. Zonulae occludentes of diabetic mice also exhibited frequent interruption of the strands and reduction in the branching of strands. Gap junctions occurred in both zonulae and maculae occludentes of normal and diabetic rats at all ages. In the C57Bl/Ks strain such junctions occurred more frequently in zonulae occludentes of diabetic animals. It is suggested that perineurial cells are coupled by gap junctions to allow fast transfer of ions and small-sized molecules across the layers; under pathological conditions, such as diabetes, the increase in cell-to-cell signalling may be important in controlling the abnormal metabolic situation.

In vitro changes in the fine structure and protein composition of light myelin fractions isolated from guinea pig brain

To find out if in vitro maintenance produces changes in the electron microscopic appearance, protein composition and phosphorylation properties of guinea pig CNS myelin fractions, we incubated them for 10 min, 4 hr, 24 hr, and 48 hr in phosphate-buffered saline (pH 7.4) or in 20 mM Hepes, 2 mM EDTA, 0.5 mM EGTA, 0.5 mM dithiothreitol, and 20 mM NaCl at 4 and 30 degree C. Aliquots were processed for electron microscopic study, were analyzed for protein content by gel electrophoresis, and were assayed for endogenous protein phosphorylation. Before incubation, electron micrographs of fractions contained two types of multilamellar whorls with the periodicity of CNS myelin sheaths. The first type of whorl was separated from nearby whorls; the other type had surface lamellae that were connected to other multilayered membrane fragments. After incubation at 4 degree C for 24 hr, the number of both types of multilamellar whorls in micrographs had increased approximately 3- to 4- fold. Counts per unit area showed that the observed increase was both time- and temperature-dependent. In aliquots studied by gel electrophoresis, only minor degradation of myelin proteins was observed. The endogenous protein phosphorylation properties of the myelin fragments also remained functional, suggesting that the activities of protein phosphotransferases were not altered. We conclude that the incubation conditions described here favor interactions of proteins and lipids that lead to the formation of multilayered aggregates of CNS myelin membranes.

Effects of phosphatidylserine in age-associated memory impairment

We treated 149 patients meeting criteria for age-associated memory impairment (AAMI) for 12 weeks with a formulation of phosphatidylserine (100 mg BC-PS tid) or placebo. Patients treated with the drug improved relative to those treated with placebo on performance tests related to learning and memory tasks of daily life. Analysis of clinical subgroups suggested that persons within the sample who performed at a relatively low level prior to treatment were most likely to respond to BC-PS. Within this subgroup, there was improvement on both computerized and standard neuropsychological performance tests, and also on clinical global ratings of improvement. The results suggest that the compound may be a promising candidate for treating memory loss in later life.

Effects of phosphatidylserine administration of aged-related structural changes in the rat hippocampus and septal complex

Dendritic spine density of CA1 pyramidal neurons in the hippocampus and morphometric characteristics of the cholinergic neuronal population of the septal complex, were evaluated in young (four months), aged (27 months), and age-matched rats which had received long-term phosphatidylserine (BC-PS) administration (50 mg/kg/die, suspended in the drinking water). In aged rats, spine density decreased significantly by 12.11% in the basal dendrites and by 10.64% in the apical ones, as compared with young controls. In the cholinergic neuronal population of medial septum and diagonal band, aging induced a statistically significant reduction in cell number (-19.6%), in soma area (-18.5%), in cell maximal diameter (-9.2%), and in the area covered by all cholinergic profiles (-33%). By contrast, no significant reductions in the above-mentioned structural parameters were observed in aged BC-PS-treated rats when compared with young animals. The mechanisms underlying the beneficial effects of BC-PS can possibly be ascribed to the pharmacological actions exerted by BC-PS on neuronal membranes, neurotransmission, and/or interaction with NGF.

Dendritic spine loss in hippocampus of aged rats. Effect of brain phosphatidylserine administration

Dendritic spine density of pyramidal cells in region CA1 of the hippocampus has been evaluated in young (3 months), old (27 months) and old phosphatidylserine (BC-PS)-treated rats. BC-PS (50 mg/kg, suspended in tap water) was administered daily, starting at the age of 3 months until 27 months. Spine density was analyzed on Golgi-stained pyramidal neurons by a computerized analysis system. In 27-month-old rats, spine density showed with respect to 3-month-old animals, a significant decrease in both basal and apical dendrites (p less than 0.01; one-way ANOVA), with a mean loss of 12.11% in the basal dendrites and of 10.64% in the apical ones. In 27-month-old rats treated with BC-PS, values of spine density were not statistically different when compared to those of 3-month-old animals. The mechanisms underlying the beneficial effect of BC-PS treatment on neuronal connectivity might be explained on the basis of its pharmacological actions on neuronal membranes [9], neurotransmission [43] and/or interaction with NGF [7].

Cholecystokinin-immunoreactive cells form symmetrical synaptic contacts with pyramidal and nonpyramidal neurons in the hippocampus

The ultrastructural features and synaptic relationships of cholecystokinin (CCK)-immunoreactive cells of rat and cat hippocampus were studied using the unlabeled antibody immunoperoxidase technique and correlated light and electron microscopy. CCK-positive perikarya of variable shape and size were distributed in all layers and were particularly concentrated in stratum pyramidale and radiatum: the CCK-immunoreactive neurons were nonpyramidal in shape and the three most common types had the morphological features of tufted, bipolar, and multipolar cells. Electron microscopic examination revealed that all the CCK-positive boutons established symmetrical (Gray's type II) synaptic contacts with perikarya and dendrites of pyramidal and nonpyramidal neurons. The origin of some of the boutons was established by tracing fine collaterals that arose from the main axon of two CCK-immunostained cells and terminated in the stratum pyramidale; these collaterals were then examined in the electron microscope. The axon of one such neuron exhibited a course parallel to the pyramidal layer and formed pericellular nets of synaptic boutons upon the perikarya of pyramidal neurons. This pattern of axonal arborization is very similar to that of some of the basket cells, previously suggested to be the anatomical correlate for pyramidal cell inhibition. Typical dendrites of pyramidal cells also received symmetrical synaptic contacts from CCK-immunoreactive boutons, and some of these boutons could be shown to originate from a local neuron in stratum radiatum. Many CCK-immunoreactive cells received CCK-labeled boutons upon their soma and dendritic shafts. Synaptic relationship, established by multiple "en passant" boutons, was observed between CCK-positive interneurons of the stratum lacunosum-moleculare and radiatum. The soma and dendrites of the CCK-immunostained neurons also received symmetrical and asymmetrical synapses from nonimmunoreactive boutons. These results indicate that the CCK-immunoreactive neurons participate in complex local synaptic interactions in the hippocampus.

Different populations of GABAergic neurons in the visual cortex and hippocampus of cat contain somatostatin- or cholecystokinin-immunoreactive material

The coexistence of gamma-aminobutyric acid (GABA), glutamate decarboxylase (GAD), and cholecystokinin (CCK)- or somatostatin-immunoreactive material in the same neurons was studied in the hippocampus and visual cortex of the cat. One-micrometer-thick serial sections of the same neuron were reacted to reveal different antigens by the unlabeled antibody enzyme method. All CCK- and somatostatin-immunoreactive neurons in the cortex and all CCK-immunoreactive and the majority of somatostatin-immunoreactive neurons in the hippocampus that could be examined in serial sections were also immunoreactive for GABA. In neurons that were immunoreactive for GAD it was often possible to demonstrate immunoreactivity for one of the peptides as well as for GABA. GABA-immunoreactive neurons, as revealed by an antiserum to GABA, were present in all layers of the cortex and hippocampus, and their shape, size, and distribution were similar to GAD-immunoreactive neurons. All GAD-immunoreactive neurons were also positive for GABA, but the latter staining revealed additional neurons. CCK/GABA- and somatostatin/GABA-immunoreactive neurons were present mainly in layers II and upper III and in layers V and VI in the visual cortex. CCK/GABA-immunoreactive neurons were most frequently present in the strata oriens, pyramidale, and moleculare of the hippocampus and in the polymorph cell layer of the dentate gyrus. Somatostatin/GABA-immunoreactive neurons were localized mainly in the stratum oriens and in the hilus of the fascia dentata. The two peptides could not be found in the same neuron. The majority of neurons that were GABA immunoreactive did not stain for either peptide. The presence of CCK- and somatostatin-immunoreactive material in GABAergic cortical neurons raises the possibility that neuroactive peptides affect GABAergic neurotransmission.

Muscle reinnervation--II. Sprouting, synapse formation and repression

Extensor digitorum longus muscle is reinnervated by the regenerating neurites at the end-plate region; as soon as the contact is made, the rate of neurite elongation inside the cleft decreases about 1000-fold while interfibre growth and sprout formation proceed unchanged. Polyinnervation reaches the maximum level 7-10 days after reinnervation, then synaptic repression begins. The elimination of redundant innervation takes place when the biophysical properties of the muscle are again normal. There is no sign of either phagocytosis or degeneration, therefore the process of synaptic repression is probably due to retraction, as neurites do when in culture. The role of Schwann cells and nerve sheath in the process of maintenance is suggested.

A new type of specific interneuron in the monkey hippocampus forming synapses exclusively with the axon initial segments of pyramidal cells

By means of Golgi staining and gold-toning, we have found an interneuron in the pyramidal cell layer of the hippocampus which forms synapses exclusively on the axon initial segments of pyramidal neurons. An individual initial segment receives up to 30 symmetrical synapses from one axo-axonic cell. Each axo-axonic cell is in synaptic contact with the axon initial segments of several hundred pyramidal neurons. The interneuron is thus ideally situated to synchronize the output of a large population of pyramidal cells and so might be involved in the generation of rhythmic activity and in epileptogenesis.

T system in ascidian muscle: organization of the sarcotubular system in the caudal muscle cells of Botryllus schlosseri tadpole larvae

The organization of the sarcotubular system has been examined in the caudal muscle cells of the ascidian. Botryllus schlosseri. At variance with striated muscle of other protochordates. Botryllus muscle cells are endowed with a well-developed T system, which has a peculiar laminar structure. The thin T laminae are in continuity with the plasma membrane and extend longitudinally in the intermyofibrillar spaces. At the level of the I-band the T laminae are focally associated with SR cisternae in dyad junctions similar to those observed in invertebrate muscles. These findings are discussed in relation to the origin of the sarcotubular system in vertebrate muscle.