Electrical coupling among Bergmann glial cells and its modulation by glutamate receptor activation

We studied the characteristics of electrical coupling between Bergmann glial cells in mouse cerebellar slices using Lucifer Yellow injection, patch-clamping cell pairs, and ultrastructural inspection. While early postnatal cells (days 5–7) were not coupled, coupling was abundant at postnatal days 20–24. Coupled cells were arranged perpendicular to the parallel fibers in a parasagittal section, forming a string, rather than a cluster of cells. Electron microscopy revealed that gap junctions were abundant in the distal parts of the processes. Gap junctions between cell bodies and processes were very rare, and no gap junctions were found between cell bodies of adjacent Bergmann glial cells. The junctional conductance was voltage and time independent and could be markedly reduced by halothane. Alkalization of cells (by applying NH₄⁺ increased the junctional conductance to 150%, while acidification of the cell interior (by removing NH₄⁺) led to a decrease to 70%. Activation of AMPA receptors induced a blockade of the junctional conductance to 30% of the control. This link is most likely mediated by the influx of Ca²⁺ via the receptor since this effect was not observed in Ca²⁺-free medium, suggesting that Ca²⁺ entry via the kainate receptor pore led to the closure of gap junctions. These studies indicate that electrical coupling between Bergmann glial cells is not only developmentally regulated but also controlled by physiological stimuli. © 1996 Wiley-Liss, Inc.     

Rat brain oligodendrocytes do not interact selectively with axons expressing different calcium-binding proteins

A single oligodendrocyte may endow ten to twenty vicinal axons with internodal segments, but its radial domain is neither exclusive of processes from other like cells nor are all nerve fibres within this zone myelinated. Whether oligodendrocytes are able to discriminate between axons on the basis of chemical or electrophysiological differences, or whether the tactic response is random, has yet to be established. In order to shed some light on this process, we investigated the ensheathment, by single oligodendrocytes, of axons distinguished on the basis of their calcium-binding protein complexion. Rat brain oligodendrocytes were visualized either with the Rip-antibody or by intracellular injection of Lucifer Yellow; subclasses of axons were immunolabelled with antibodies against one of the two calcium-binding proteins parvalbumin or calretinin. Individual oligodendrocytes did not exhibit exclusivity with respect to their preferment for axons containing calcium-binding proteins, associations with both non-immunoreactive, as well as with parvalbumin- or calretinin-positive ones, being encountered. © 1996 Wiley-Liss, Inc.     

Cellular reactions at the lesion site after crushing of the rat optic nerve

Rat optic nerves were subjected to crush injury to study the local tissue reactions leading to wound healing and tissue repair. We used antibodies against glial fibrillary acidic protein (GFAP), vimentin, the S100 protein (S100P), lysozyme, and ED1 as markers for astroglial cells and microglia/macrophages at the light and electron microscopic level during the 3 weeks following the crush. The crush injury produced a vast area of tissue damage including the disruption of the blood-brain barrier (BBB). In the first days after crushing, astrocytes were absent from the lesion site. S100P-positive astrocytes reappeared in the lesion center as early as 6 days after crushing. These astrocytes reestablished former topological structures such as perivascular and subpial glia limitans. At the edges of the lesion site reactive astrocytes enclosed and embedded axonal and myelin debris. Preceding the astroglial repopulation, a massive infiltration of microglia/macrophages (phagocytes) into the lesion center took place. ED1-positive/lysozyme-positive cells of round shape were seen in the lesion center at 2 days after crushing, and their number peaked around 1 week after crushing. They efficiently cleared the debris from the lesion site and mostly disappeared after 3 weeks. With immuno-electron microscopy we found the ED1 antigen related to the membranes of phagosomes. The microglia/macrophages observed in the nerve segments distal of the lesion (Wallerian degeneration site) were different from those in the lesion center: 1) they appeared later, about 6 days after crushing; 2) they were ED1 positive, but lysozyme negative and showed a branched morphology; and 3) they persisted in the distal nerve segment but showed little phagocytosis. We suggest that these cells are mostly activated microglia. © 1996 Wiley-Liss, Inc.     

Synaptic target selectivity and input of GABAergic basket and bistratified interneurons in the CA1 area of the rat hippocampus

To assess the position of interneurons in the hippocampal network, fast spiking cells were recorded intracellularly in vitro and filled with biocytin. Sixteen non-principal cells were selected on the basis of 1) cell bodies located in the pyramidal layer and in the middle of the slice, 2) extensive labeling of their axons, and 3) a branching pattern of the axon indicating that they were not axo-axonic cells. Examination of their efferent synapses (n = 400) demonstrated that the cells made synapses on cell bodies, dendritic shafts, spines, and axon initial segments (AIS). Statistical analysis of the distribution of different postsynaptic elements, together with published data (n = 288) for 12 similar cells, showed that the interneurons were heterogeneous with regard to the frequency of synapses given to different parts of pyramidal cells. When the cells were grouped according to whether they had less or more than 40% somatic synaptic targets, each population appeared homogeneous. The population (n = 19) innervating a high proportion of somata (53 ± 10%, SD) corresponds to basket cells. They also form synapses with proximal dendrites (44 ± 12%) and rarely with AISs and spines. One well-filled basket cell had 8,859 boutons within the slice, covering an area of 0.331 mm² of pyramidal layer tangentially and containing 7,150 pyramidal cells, 933 (13%) of which were calculated to be innervated, assuming that each pyramidal cell received nine to ten synapses. It was extrapolated that the intact axon probably had about 10,800 boutons innervating 1,140 pyramids. The proportion of innervated pyramidal cells decreased from 28% in the middle to 4% at the edge of the axonal field. The other group of neurons, the bistratified cells (n = 9), showed a preference for dendritic shafts (79 ± 8%) and spines (17 ± 8%) as synaptic targets, rarely terminating on somata (4 ± 8%). Their axonal field was significantly larger (1,250 ± 180 μm) in the medio-lateral direction than that of basket cells (760 ± 130 μm). The axon terminals of bistratified cells were smaller than those of basket cells. Furthermore, in contrast to bistratified cells, basket cells had a significant proportion of dendrites in stratum lacunosum-moleculare suggesting a direct entorhinal input. The results define two distinct types of GABAergic neuron innervating pyramidal cells in a spatially segregated manner and predict different functions for the two inputs. The perisomatic termination of basket cells is suited for the synchronization of a subset of pyramidal cells that they select from the population within their axonal field, whereas the termination of bistratified cells in conjunction with Schaffer collateral/commissural terminals may govern the timing of CA3 input and/or voltage-dependent conductances in the dendrites. © 1996 Wiley-Liss, Inc.     

Fine-needle sampling of a case of carcinoma of the breast with neuroendocrine differentiation

Fine-needle sampling was performed in a woman with a left breast lump. The cytologic diagnosis was consistent with a poorly-differentiated carcinoma. Cytologic features included medium-to-large, round, and spindle-shaped cells with scanty cytoplasm, nuclear molding, and rosette-like structures. Histology revealed an endocrine pattern. Immunohistochemical staining was positive for epithelial and neuroendocrine markers, and electron microscopy showed many small membrane-bound electron-dense granules, confirming the diagnosis of breast carcinoma with neuroendocrine differentiation. DNA flow cytometry and cytogenetic analyses revealed a near-tetraploid tumor. Diagn Cytopathol 1996;14:233–237. © 1996 Wiley-Liss, Inc.     

激素联合内毒素所致骨坏死微循环障碍超微结构观察

目的:观察激素联合内毒素所致骨坏死骨内微血管内皮表面的超微结构损害和血栓形成. 方法:实验动物分为模型组和正常对照组. 模型组前2 d间隔24 h于静脉缓慢注射脂多糖(LPS),每次剂量30 μg/kg;第3～8日静脉注射地塞米松,1次/d,剂量7.5 mg/kg. 对照组给予生理盐水0.5 mL/kg. 满8 wk时取材前,股骨头压力灌注肝素钠、100 mL/L中性甲醛固定液. 一半股骨头标本制备脱钙切片,苏木素-伊红染色,观察骨坏死情况. 另一半标本制备不脱钙切片,脱掉包埋剂,临界点干燥、喷金、扫描电镜观察软骨下微血管内皮表面超微结构改变. 结果:模型组股骨头软骨下微血管内皮表面凹凸不平,管腔不规则,可见管腔填塞、血栓形成;此结果与组织学观察结果一致. 结论:激素联合内毒素所致骨坏死微循环障碍的主要表现为微血管内皮损伤和微血栓形成.     

Pathologic evidence of retinoblastoma seeds supported by field emission scanning electron microscopy and Raman spectroscopy

Purpose:The aim of this study was to examine the pathology of retinoblastoma (RB) seeds with supportive evidence by field emission scanning electron microscopy and Raman spectroscopy.Methods:This study was a laboratory-based observational study. Enucleated eyeballs received in the ocular pathology department of a tertiary eye care center in northeast India were included in the cohort after obtaining written informed consent during the surgery. The study was carried out for 6 years (2015–2020). Most of the eyeballs were Group-E RBs. Standard eyeballs sectioning were done by bread loaf techniques. Gross documentations included RB seeds seen in the smallest calotte done with utmost care. Seeds were documented also in permanent sections. Scanning electron microscopy and Raman spectroscopy were carried out in an index case.Results:Out of the total 59 cases, 35 RB cases had different seedings. The mean age at enucleation was 2.9 years. RB seeds were seen in vitreous (n = 19), subretinal plus vitreous (n = 7), anterior chamber (n = 1), over crystalline lens (n = 3), retinal surface (n = 1), retinal pigment epithelium (RPE; n = 2), subretinal (n = 1), calcified seeds (n = 2). Other characteristics were dusts (n = 7), clouds (n = 11), spheres (n = 4), and unspecified type (n = 13). Histopathological high-risk factors showed significant choroidal (n = 22) and optic nerve (n = 15) involvement. Few cases had extraocular spread. Undifferentiated tumor (n = 24) was seen with higher evidence of necrosis (n = 23). Raman spectra differentiated the seeds from the normal tissue on the basis of lipid and protein content.Conclusion:This study highlights the different types of RB seeds with high-risk factors. The morphology of those seeds showed the difference between vitreous and subretinal seeds under advanced microscopic observations.