Tuft-to-capsule adhesions and their precursors: differences between the vascular and tubular poles of the human glomerulus

Human glomerular capillary tufts were removed by microdissection and scanning electron microscopy was used to examine the surface of the capillary tuft and the interior of its Bowman's capsule in order to identify connections between the tuft and capsule. Glomeruli were examined in histologically normal renal cortex from 12 kidneys removed for tumour and 12 renal allografts removed for end-stage rejection. In normal kidney, the glomerular tuft was connected to Bowman's capsule by single podocytes and their processes. At the vascular pole, these were predominantly associated with parietal podocytes which lined Bowman's capsule. At the tubular pole, occasional podocytic processes derived from the capillary tuft bridged Bowman's space and connected to Bowman's capsule where there were no parietal podocytes. These podocytic connections were also found in all rejected transplants, but in addition adhesions were identified which consisted of thicker connections between the tuft and capsule. At the vascular pole, tuft-to-capsule adhesions were found in all 12 kidneys; these were always associated with parietal podocytes. Tubular pole adhesions were identified in ten of the 12 transplants. They were associated with abnormal squamous cells, but not with parietal podocytes. When the capillary tuft herniated into the proximal tubule, the tuft sometimes formed an adhesion with the origin of the proximal tubule. These observations suggest that podocyte connections between the glomerular tuft and Bowman's capsule may be precursors of glomerular adhesions at the vascular pole. Since tuft-to-capsule adhesions at the vascular pole differ morphologically from those at the tubular pole, this may reflect different pathogenetic mechanisms at the opposite poles of the glomerulus. © 1998 John Wiley & Sons, Ltd.     

Postnatal development of olfactory receptor cell axonal arbors

The mechanisms that subserve the distribution of the terminal arbors of olfactory receptor cell axons remain unknown. Elsewhere in the central nervous system, a common theme is early axonal exuberance followed by activity-dependent pruning to achieve the mature distribution. This led to the hypothesis that the orderly morphology of afferent axons in the olfactory glomerulus may follow a similar developmental scheme of exuberance followed by pruning. To test this hypothesis, we studied morphological features of olfactory receptor neuron (ORN) axonal arbors on postnatal days 0, 3, 6, 9, 12, and 21. The olfactory bulbs from Sprague-Dawley rats were processed using a Golgi technique that impregnated ORN axons. Axons from each age group were reconstructed by using camera lucida at ×100, oil immersion, and morphometrically characterized. In the adult, the percent glomerular area occupied by a single ORN axon was 14%, whereas the mean length of branches was 169.67 μm, the sum of branches and varicosities was 27, and the distance to first branch point in glomeruli was 21.98 μm. The values from the younger age groups were not statistically different from those in the adult. Because there was no evidence of early exuberance, our data suggest that ORN axons must innervate single glomeruli and arborize in a highly specific manner to achieve the adult pattern. Because our data suggest that ORN axons do not follow the hypothesized scheme, it is plausible to suggest that as ORN axons innervate a glomerulus during development they arborize to their adult levels but not beyond. This argues strongly that specific cell surface and trophic factors are used by the ORN axon to guide glomerular targeting and innervation. J. Comp. Neurol. 390:256–267, 1998. © 1998 Wiley-Liss, Inc.     

Temporal tuning of odor responses in pheromone-responsive projection neurons in the brain of the sphinx moth Manduca sexta

By means of intracellular recording and staining, we studied the ability of several distinct classes of projection (output) neurons, which innervate the sexually dimorphic macroglomerular complex (MGC-PNs) in the antennal lobe of the male moth Manduca sexta, to encode naturally intermittent sex pheromonal stimuli. In many MGC-PNs, antennal stimulation with a blend of the two essential pheromone components evoked a characteristic triphasic response consisting of a brief, hyperpolarizing inhibitory potential (I₁) followed by depolarization with firing of action potentials and then a delayed period of hyperpolarization (I₂). MGC-PNs described in this study resolved pulsed pheromonal stimuli, up to about five pulses/second, with a distinct burst of action potentials for each pulse of odor. The larger the amplitude of I₁, the higher the pulse rate an MGC-PN could follow, illustrating the importance of inhibitory synaptic input in shaping the temporal firing properties of these glomerular output neurons. In some MGC-PNs, triphasic responses were evoked by antennal stimulation with only one of the two key pheromone components. Again, the maximal pulse rate that an MGC-PN could follow with that pheromone component as sole stimulus was high in MGC-PNs that responded with a strong I₁. These component-specific MGC-PNs innervated only one of the two principal glomeruli of the MGC, while MGC-PNs that were primarily excited by antennal stimulation with either key pheromone component had arborizations in both major MGC glomeruli. These observations therefore suggest that the population of antennal olfactory receptor cells responding to a single pheromone component is functionally heterogeneous: a subset of these sensory cells activates the excitatory drive to many uniglomerular MGC-PNs, while others feed onto inhibitory circuits that hyperpolarize the same PNs. This convergence of opposing inputs is a circuit property common to uniglomerular MGC-PNs branching in either of the major MGC glomeruli, and it enhances the ability of these glomerular output neurons to resolve intermittent olfactory input. Synaptic integration at the uniglomerular PN level thus contributes to the transmission of behaviorally important temporal information about each key pheromone component to higher centers in the brain. J. Comp. Neurol. 409:1–12, 1999. © 1999 Wiley-Liss, Inc.     

血管紧张素Ⅱ输注诱导肾小球ILK表达改变和肾小球损伤

目的观察血管紧张素II（AngII）输注及替米沙坦治疗对大鼠肾小球整合素蛋白激酶（Integrin-linked kinase,ILK）表达的影响,探讨AngII和ILK在肾小球损伤中的作用。方法将18只雄性SD大鼠随机分为3组：A组为对照组,由生理盐水代替AngII;B组用AngII以400ng·kg^-1·min^-1持续输注14d;C组在B组基础上加用替米沙坦30mg·kg^-1·d^-1进行干预。每组6只。每周末测量尾动脉收缩压、24h尿蛋白定量,于14d处死动物。心脏采血,检测血肌酐（SCr）;留取肾组织,行PAS染色,光镜下观察肾组织病理学改变;免疫组织化学法、RT-PCR及Western印迹法检测ILK表达。结果①AngII输注后,大鼠血压逐渐升高,尿蛋白持续增加,肾小球系膜区增生加重,替米坦治疗可以明显降低血压和减少尿蛋白（P〈0．05）,减轻肾小球系膜区增生（P〈0．01）。②AngⅡ输注14d时,ILK表达显著增加,替米沙坦治疗可显著降低ILK表达（P〈0．05）。结论肾脏ILK表达升高可能是AngII引起肾脏损害的重要机制。     

Correlated firing in tufted cells of mouse olfactory bulb

Temporally correlated spike discharges are proposed to be important for the coding of olfactory stimuli. In the olfactory bulb, correlated spiking is known in two classes of output neurons, the mitral cells and external tufted cells. We studied a third major class of bulb output neurons, the middle tufted cells, analyzing their bursting and spike timing correlations, and their relation to mitral cells. Using patch-clamp and fluorescent tracing, we recorded spontaneous spiking from tufted-tufted or mitral-tufted cell pairs with visualized dendritic projections in mouse olfactory bulb slices. We found peaks in spike cross-correlograms indicating correlated activity on both fast (peak width 1–50 ms) and slow (peak width>50 ms) time scales, only in pairs with convergent glomerular projections. Coupling appeared tighter in tufted-tufted pairs, which showed correlated firing patterns and smaller mean width and lag of narrow peaks. Some narrow peaks resolved into 2–3 sub-peaks (width 1–12 ms), indicating multiple modes of fast correlation. Slow correlations were related to bursting activity, while fast correlations were independent of slow correlations, occurring in both bursting and non-bursting cells. The AMPA receptor antagonist NBQX (20 μM) failed to abolish broad or narrow peaks in either tufted-tufted or mitral-tufted pairs, and changes of peak height and width in NBQX were not significantly different from spontaneous drift. Thus, AMPA-receptors are not required for fast and slow spike correlations. Electrical coupling was observed in all convergent tufted-tufted and mitral-tufted pairs tested, suggesting a potential role for gap junctions in concerted firing. Glomerulus-specific correlation of spiking offers a useful mechanism for binding the output signals of diverse neurons processing and transmitting different sensory information encoded by common olfactory receptors.     

Nephrin—signature molecule of the glomerular podocyte?

In recent years there has been an explosion of interest in the glomerular podocyte, which plays a central role in control of glomerular filtration. A host of new molecules have been identified as playing essential roles in the maintenance of podocyte integrity in both humans and mouse models. Of all of these, arguably the most pivotal is nephrin, a transmembrane receptor molecule located at the specialized podocyte cell–cell junction, termed the slit diaphragm. Mutations in this gene cause the most severe form of congenital nephrotic syndrome, and many interacting proteins have now been described to form a large multiprotein complex with complex dynamics. There is little evidence of functional nephrin expression outside the glomerulus, and there are accumulating data that nephrin is essential for the unique properties of podocyte biology. Utilizing a powerful human cell culture model, comparing wild‐type with nephrin‐null podocytes, we can show that several crucial functional properties of podocytes depend on nephrin, including insulin responsiveness and cytoskeletal reorganization. Thus, it is reasoned that nephrin is a signature molecule required to define distinct podocyte characteristics. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Three‐dimensional synaptic analyses of mitral cell and external tufted cell dendrites in rat olfactory bulb glomeruli

Recent studies have suggested that the two excitatory cell classes of the mammalian olfactory bulb, the mitral cells (MCs) and tufted cells (TCs), differ markedly in physiological responses. For example, TCs are more sensitive and broadly tuned to odors than MCs and also are much more sensitive to stimulation of olfactory sensory neurons (OSNs) in bulb slices. To examine the morphological bases for these differences, we performed quantitative ultrastructural analyses of glomeruli in rat olfactory bulb under conditions in which specific cells were labeled with biocytin and 3,3′‐diaminobenzidine. Comparisons were made between MCs and external TCs (eTCs), which are a TC subtype in the glomerular layer with large, direct OSN signals and capable of mediating feedforward excitation of MCs. Three‐dimensional analysis of labeled apical dendrites under an electron microscope revealed that MCs and eTCs in fact have similar densities of several chemical synapse types, including OSN inputs. OSN synapses also were distributed similarly, favoring a distal localization on both cells. Analysis of unlabeled putative MC dendrites further revealed gap junctions distributed uniformly along the apical dendrite and, on average, proximally with respect to OSN synapses. Our results suggest that the greater sensitivity of eTCs vs. MCs is due not to OSN synapse number or absolute location but rather to a conductance in the MC dendrite that is well positioned to attenuate excitatory signals passing to the cell soma. Functionally, such a mechanism could allow rapid and dynamic control of OSN‐driven action potential firing in MCs through changes in gap junction properties. J. Comp. Neurol. 525:592–609, 2017. © 2016 Wiley Periodicals, Inc.     

高糖引起小鼠肾小球足细胞podocalyxin蛋白的表达下调

目的:探讨高糖对肾小球足细胞podocalyxin蛋白表达的影响及其信号途径.方法:免疫组织化学法检测db/db(自发糖尿病小鼠)肾小球足细胞podocalyxin蛋白表达,野生型小鼠(WT鼠)为对照,计算机图像半定量分析.以体外培养的足细胞为研究对象,应用Western印迹分析技术,检测高糖培养不同时间点对足细胞表达podocalyxin蛋白的影响; 检测细胞外信号调节激酶(ERK1/2)信号途径的活化,及其特异性阻断剂PD98059对podocalyxin蛋白变化的阻断效应.结果:免疫组织化学半定量分析显示db/db小鼠肾小球podocalyxin蛋白表达明显少于对照组[(0.18±0.07)比(0.25±0.05), P＜0.05].培养的足细胞表达基础水平的podocalyxin蛋白,高糖培养不同时间点其表达均下降,以第6天最明显(为对照组的5.5%, P＜ 0.01),正常糖和甘露醇组没有明显变化.高糖可以活化足细胞ERK1/2信号途径,于培养30 min时ERK1/2开始活化,6 h达高峰,持续活化至24 h,至48 h时接近基础水平;高糖培养不能活化P38和 JNK.正常糖和甘露醇在各个时间点均不影响丝裂原活化蛋白激酶(MAPK)信号转导通路.ERK1/2特异阻断剂PD98059可以消减高糖引起的podocalyxin表达下降的效应.结论:自发糖尿病小鼠的肾小球足细胞podocalyxin蛋白表达下降.高糖经ERK1/2信号通路下调体外培养的足细胞podocalyxin蛋白表达.     

急性肾衰大鼠肾微血管损伤及三种茛菪药的保护作用

目的 研究急性肾衰时肾微血管的损伤及樟柳碱、东莨菪碱、山莨菪碱对这些损伤的影响。方法 采用左肾动脉注射油酸的方法建立大鼠急性肾衰模型,采用电镜、光镜及TTC显色观察大鼠急性肾衰不同时期肾微血管超微结构、肾组织结构及TTC显色的改变。结果 左肾动脉注射油酸后10分钟,肾小球毛细血管内皮细胞坏死;肾小球毛细血管不同程度充血肿胀,在皮质与髓质交界区,可见小血管内充满大量红细胞;TTC显色呈鲜红色。注射油酸后6小时和24小时上述损伤加重,TTC显色出现典型的不显色苍白区。3种莨菪药物不同程度减轻了急性肾衰时肾微血管损伤,改善了肾组织缺血,减少了肾小管上皮细胞坏死数。结论 急性肾衰时很早即出现肾微血管的损伤,3种莨菪药对急性肾衰时肾微血管和组织结构的损伤均有保护作用。     

4328例小儿与成人肾小球疾病病理类型比较

目的：了解小儿和成人肾小球疾病病理类型的异同。方法：我院住院的小儿与成人以肾活检术确诊为肾小球疾病的患者4328例,对其病理类型进行比较,结果：PGN可见14种病理改变,小儿组中的4种类型（MsPGM、IgMN,EnP,MCD)明显多于成人组（均P＜0．01）,成人组有7种类型（IgAN,MN,FSGS,MPGN,FGS,SGN,PSGN)明显多于小儿组（均P＜0．01）。SGN小儿以HPSN（85．0％）占大多数,其次为LN（8．6％）;成人以HFRS（31．7％）较多见,次为LN（30．2％）、HSPN（19．0％）。结论：PGN小儿组病理类型和病变程度均较成人组轻。SGN小组病理类型较少,而成人组的病理类型较复杂,与随年龄增长而继发性疾病增多有关。