Dendrites of distinct classes of Drosophila sensory neurons show different capacities for homotypic repulsion

BACKGROUND: Understanding how dendrites establish their territory is central to elucidating how neuronal circuits are built. Signaling between dendrites is thought to be important for defining their territories; however, the strategies by which different types of dendrites communicate are poorly understood. We have shown previously that two classes of Drosophila peripheral da sensory neurons, the class III and class IV neurons, provide complete and independent tiling of the body wall. By contrast, dendrites of class I and class II neurons do not completely tile the body wall, but they nevertheless occupy nonoverlapping territories. RESULTS: By developing reagents to permit high-resolution studies of dendritic tiling in living animals, we demonstrate that isoneuronal and heteroneuronal class IV dendrites engage in persistent repulsive interactions. In contrast to the extensive dendritic exclusion shown by class IV neurons, duplicated class III neurons showed repulsion only at their dendritic terminals. Supernumerary class I and class II neurons innervated completely overlapping regions of the body wall, and this finding suggests a lack of like-repels-like behavior. CONCLUSIONS: These data suggest that repulsive interactions operate between morphologically alike dendritic arbors in Drosophila. Further, Drosophila da sensory neurons appear to exhibit at least three different types of class-specific dendrite-dendrite interactions: persistent repulsion by all branches, repulsion only by terminal dendrites, and no repulsion.     

Astrocyte-derived nitric oxide causes both reversible and irreversible damage to the neuronal mitochondrial respiratory chain

Cytokine-stimulated astrocytes produce nitric oxide (NO), which, along with its metabolite peroxynitrite (ONOO(-)), can inhibit components of the mitochondrial respiratory chain. We used astrocytes as a source of NO/ONOO(-) and monitored the effects on neurons in coculture. We previously demonstrated that astrocytic NO/ONOO(-) causes significant damage to the activities of complexes II/III and IV of neighbouring neurons after a 24-h coculture. Under these conditions, no neuronal death was observed. Using polytetrafluoroethane filters, which are permeable to gases such as NO but impermeable to NO derivatives, we have now demonstrated that astrocyte-derived NO is responsible for the damage observed in our coculture system. Expanding on these observations, we have now shown that 24 h after removal of NO-producing astrocytes, neurons exhibit complete recovery of complex II/III and IV activities. Furthermore, extending the period of exposure of neurons to NO-producing astrocytes does not cause further damage to the neuronal mitochondrial respiratory chain. However, whereas the activity of complex II/III recovers with time, the damage to complex IV caused by a 48-h coculture with NO-producing astrocytes is irreversible. Therefore, it appears that neurons can recover from short-term damage to mitochondrial complex II/III and IV, whereas exposure to astrocytic-derived NO for longer periods causes permanent damage to neuronal complex IV.     

Synaptic connections of the neurokinin 1 receptor-like immunoreactive neurons in the rat medullary dorsal horn

The synaptic connections between neurokinin 1 (NK1) receptor-like immunoreactive (LI) neurons and γ-aminobutyric acid (GABA)-, glycine (Gly)-, serotonin (5-HT)- or dopamine-β-hydroxylase (DBH, a specific marker for norepinephrinergic neuronal structures)-LI axon terminals in the rat medullary dorsal horn (MDH) were examined under electron microscope by using a pre-embedding immunohistochemical double-staining technique. NK1 receptor-LI neurons were observed principally in laminae I and III, only a few of them were found in lamina II of the MDH. GABA-, Gly-, 5-HT-, or DBH-LI axon terminals were densely encountered in laminae I and II, and sparsely in lamina III of the MDH. Some of these GABA-, Gly-, 5-HT-, or DBH-LI axon terminals were observed to make principally symmetric synapses with NK1 receptor-LI neuronal cell bodies and dendritic processes in laminae I, II and III of the MDH. The present results suggest that neurons expressing NK1 receptor within the MDH might be modulated by GABAergic and glycinergic inhibitory intrinsic neurons located in the MDH and 5-HT- or norepinephrine (NE)-containing descending fibers originated from structures in the brainstem.     

Heterogeneity of the basic pancreatic inhibitor (Kunitz) in various bovine organs

Four protein protease inhibitors (I, II, III, IV) having low molecular weights (10 600-6500) and basic isoelectric points were isolated by affinity chromatography from bovine spleen. Inhibitor IV was identified as the basic pancreatic trypsin inhibitor (Kunitz inhibitor); the presence and distribution of components I, II and III vary in the different bovine organs. Spleen inhibitors I, II, III and IV were purified by ion-exchange chromatography; they form 1:1 complexes with trypsin and inhibit enzymatic activity of trypsin, chymotrypsin and kallikrein. Inhibitors I, II and III contain carbohydrate moieties (7-4%) covalently bound to the polypeptide chain. Specific basic pancreatic trypsin inhibitor antiserum has shown the complete identity between inhibitor IV and the basic pancreatic trypsin inhibitor, while partial cross-reactivity between the basic pancreatic trypsin inhibitor and inhibitors I, II and III can be seen from a double immunodiffusion test.     

Angiotensin II and III upregulate body fluid volume of the clam worm Perinereis sp. via angiotensin II receptors in different manners

Angiotensin III (Ang III) as well as angiotensin II (Ang II) suppressed body weight loss of the clam worm Perinereis sp. under a hyper-osmotic condition, and enhanced body weight gain under a hypo-osmotic condition. Under a drying condition where the water inflow from outside the body was eliminated, Ang II suppressed body weight loss, but Ang III did not. Under these conditions, angiotensins I, IV, and (1–7) had no effect, and saralasin blocked the effects of Ang II and Ang III. It is concluded that Ang II and Ang III upregulate body fluid volume of the clam worm via Ang II receptors in different ways.     

Changes in the mRNAs encoding subtypes I,II and III sodium channel alpha subunits following kainate-induced seizures in rat brain

Several lines of evidence underscore a possible role of voltage-gated Na+ channels (NaCH) in epilepsy. We compared the regional distribution of mRNAs coding for Na+ channel α subunit I, II and III in brains from control and kainate-treated rats using non-radioactive in situ hybridization with subtype-specific digoxigenin-labelled cRNA probes. Labelling intensity was evaluated by a densitometric analysis of digitized images. Heterogeneous distribution of the three Na+ channel mRNAs was demonstrated in brain from adult control rats, which confirmed previous studies. Subtype II mRNAs were shown to be abundant in cerebellum and hippocampus. Subtype I mRNAs were also detected in these areas. Subtype III mRNAs were absent in cerebellar cortex, but significantly expressed in neurons of the medulla oblongata and hippocampus. The three subtypes were differentially distributed in neocortical layers. Subtype II mRNAs were present in all of the layers, but mRNAs for subtypes I and III were concentrated in pyramidal cells of neocortex layers IV–V. During kainate-induced seizures, we observed an increase in Na+ channel II and III mRNA levels in hippocampus. In dentate gyrus, subtype III mRNAs increased 3 h after K A administration to a maximum at 6 h. At this latter time, a lower increase in NaCh III mRNAs was also recorded in areas CA1 and CA3. NaCh III overexpression in dentate gyrus persisted for at least 24 h. In the same area, NaCh II mRNAs were also increased with a peak 3 h after K A injection and a return to control levels by 24 h. No changes in NaCh I mR NAs were seen. The K A-induced up-regulation in NaCh mR NAs probably resulted in an increase in hippocampal neuronal excitability.     

Effect of alcohol on neurons of iso-cortex--a histomorphometric study

Effect of chronic intake of alcohol and its subsequent withdrawal was studied in albino mice on the layers of neurons of the iso-cortex. Neuronal density per mm2 of section in different layers of iso-cortex was counted and compared in 3 groups of animals (control, ethanol fed and withdrawal). Qualitative changes on nissl granules of neurons and myelinated fibres were also studied. Mice fed with 10% ethanol v/v ad libitum for 6 months showed loss of nissl granules and nucleolus and discontinuity of nuclear membrane. Quantitatively, significant reduction in neuronal density (P<0.001) was observed in layers II+III IV and V neurons of iso-cortex. Withdrawal of ethanol for 2 months showed continued reduction of counts of neuronal density in layers II+III and V only whereas reversal of count was found significantly (P<0.001) in layer IV of iso-cortex. Qualitatively, only few neurons showed prominent nissl granules after withdrawal of ethanol. More afferent synaptic connection in layer IV may be suggested as probable factor helping relative replenishment of neuronal count after withdrawal of alcohol.     

Cell types within the medial forebrain bundle: a Golgi study of preoptic and hypothalamic neurons in the rat

The morphology of lateral preoptic (POL) and lateral hypothalamic (HLA) neurons was studied in 14- to 200-day-old rats with the chlorate-formaldehyde modification of the Golgi method. Drawings of 91 POL and HLA neurons revealed three distinct neuronal types within the MFB based on somatic size and shape and dendritic morphology. Class I neurons, which accounted for 75-80% of the neurons in the MFB, has fusiform or multipolar somata averaging 21 X 14 micron and 2-5 sparsely branched dendrites with a moderate number of sticklike spines. The extensive dendritic domains of Class I neurons ranged from 700 to 1,500 micron and were usually oriented perpendicular to the longitudinal fibers of the MFB. Both nonoriented and oriented Class I neurons were encountered. Nonoriented Class I neurons had expansive dendritic arbors which reached nearly all regions of the MFB in the coronal plane. Oriented Class I neurons had dendritic domains which were confined to specific regions (e.g., ventral-lateral) of the MFB. Class II neurons, which made up approximately 10% of the MFB neurons, had large multipolar somata averaging 30 X 17 micron and 2-5 stout dendrites which were densely covered with hairlike spines. Class II neurons also exhibited spines on their somata and proximal dendritic trunks and had dendritic domains of 700-1,000 micron. Class III neurons had small somata averaging 15 X 12 micron and restricted dendritic arbors of 500-700 micron in diameter. Class III neurons exhibited both spiny and spine-free dendrites and made up 10% of MFB neurons. Because of the parcellation of chemically coded fiber systems within the MFB, individual POL and HLA neurons may not be homogeneous in the type of afferents they receive from other brain areas.     

A comparative cytogenetic study of the rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) autotetraploid restorers and hybrids

We studied pollen fertility, seed set and cytogenetic characteristics of restorer lines and F1 hybrids of autotetraploid rice. T4002, T4063, T461A × T4002 and T461A × T4063 showed significantly higher pollen fertility and seed set than T4132 and T461A × T4132. Meiotic pairing configurations of T4002, T4063, T4132, T461A × T4002, T461A × T4063 and T461A × T4132 were 0.05 I + 19.96 II (9.89 rod + 10.07 ring) + 0.01 III + 2.00 IV, 0.11 I + 19.17 II (8.90 rod + 10.37 ring) + 0.09 III + 2.26 IV + 0.01 VI, 1.34 I + 9.46 II (4.50 rod + 4.96 ring) + 0.80 III + 6.02 IV + 0.09 VI + 0.09 VIII, 0.02 I + 14.36 II (6.44 rod + 7.91 ring) + 0.01 III + 4.80 IV + 0.01 VIII, 0.06 I + 17.67 II (11.01 rod + 6.67 ring) + 0.06 III + 3.10 IV + 0.01 VI and 1.11 I + 11.31 II (5.80 rod + 5.51 ring) + 0.41 III + 5.63 IV + 0.03 VI + 0.03 VIII, respectively. Configuration 16 II + 4 IV and 12 II + 6 IV occurred in the highest frequency among the autotetraploid restorers and hybrids. Meiotic chromosome behaviors were less abnormal in the tetraploids with high seed set than those with low seed set. The hybrids had fewer frequencies of bivalents, univalents, trivalents and multivalents than the restorers, but higher frequency of quatrivalents than the restorers at MI. The frequency of univalents at MI had the most impact on pollen fertility and seed set, i.e., pollen fertility decreased with the increase of univalents. The secondary impact factors were trivalents and multivalents, and bivalents and quatrivalents had no effect on pollen fertility and seed set. The correlative relationship between pollen fertility and cytogenetic behaviors could be utilized to improve seed set in autotetraploidy breeding.     

Cycle distributions in random nets

Characteristics of random nets are derived from assumptions concerning the distribution of connections. The single aggregate of neurons with random connections without branching and two parallel chains with normal distribution of connections are considered. The cycle saturation is derived for each type of net, that is, the fraction of neurons which are members of cycles. It is shown that in the single aggregate with random connections, the cycle saturation varies inversely as the square root of the number of neurons; in the dense two-chain net it varies inversely as the square root of the neuron density and inversely on the square root of the standard deviation of the normal distribution.     

Use of fluorescent carbocyanine dyes in the study of the organization of the pathways in autopsy material of the human brain

Our report provides evidence that fluorescent carbocyanine dyes (diI and diO) can be used in experimental anatomical studies of the fixed autopsy human brain. The dyes transported in both anterograde and retrograde directions, providing labeling of axons with collaterals and neurons including dendrites. To study the retrograde labeling of pyramidal neurons and anterogradely labeling of afferent fibers in human motor cortex, we applied diI and diO to the white matter, I and III layers of cortex. During 2 months there was no evidence of passive diffusion from labeled fibers and neurons to other neurons or glia. This method will be useful for identifying alterations of neuronal connections associated with neurological and psychiatric disorders.     

Distribution, morphology and projections of nitrergic and non-nitrergic submucosal neurons in the pig small intestine

 Sequential nitric oxide synthase immunohistochemistry and nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) histochemistry in pig small intestinal wholemounts revealed a complete colocalisation of the two nitrergic markers in submucous neurons. The external submucous plexus (ESP) contained nitrergic neurons throughout. In the internal submucous plexus (ISP) we found a moderate number of nitrergic neurons in the duodenum, while they were rare in the jejunum and nearly absent in the ileum. Combined NADPHd histochemistry and silver impregnation showed morphological ESP type III and VI neurons to be NADPHd positive whereas ESP type II, IV and V neurons were NADPHd negative. Axons of ESP type III, IV and VI neurons were often observed to enter interconnecting strands directed abluminally. ESP type II neurons projected mainly to the ISP. In special silver-impregnated wholemounts containing both external muscle layers and the abluminal part of the submucous layer, i.e. the myenteric plexus and the ESP, the great majority of impregnated axons within the interconnecting strands were observed to run between both plexuses and did not enter the circular muscle layer. We conclude that ESP type III and VI neurons are nitrergic while ESP type II, IV and V neurons are non-nitrergic. Furthermore, we assume that ESP type III, IV and VI neurons may represent a submucosal input to the myenteric plexus. Accepted: 26 August 1997     

Region-specific and epileptogenic-dependent expression of six subtypes of alpha2,3-sialyltransferase in the adult mouse brain

Sialylated glycoconjugates play important roles in various biological functions. The structures are also observed in brains and it has been proposed that sialylation may affect neural plasticity. To clarify the effects of sialylation in the brain, particular neurons that exhibit sialylation should first be determined. Using in situ hybridization, we performed systematic surveys of the localization of mRNAs encoding the six alpha2,3-sialyltransferases (ST3Gal I-VI) in the adult mouse brain with or without physiological stimulation. First, striking region-specific patterns of expression were observed: While ST3Gal II, III, and V mRNAs were in neuronal cells throughout the brain, ST3Gal I, IV, and VI mRNAs were in restricted brain regions. Next, to assess whether the expression of the six mRNAs can be regulated, we examined the effect of kindling epileptogenesis on the six mRNA levels. Of the six subtypes, upregulation in the ST3Gal IV level in the thalamus was most pronounced; the number of ST3Gal IV-expressing neurons in the anterior thalamic nuclei increased from 2% to 21% in a time-dependent manner during epileptogenesis. Western blot analysis evaluated the increase of the end-products in the thalamus. These findings provide a molecular basis to clarify when and where sialylated glycoconjugates function accompanied by neural plasticity.     

Structurally and functionally unique complexins at retinal ribbon synapses

Ribbon synapses in retinal sensory neurons maintain large pools of readily releasable synaptic vesicles. This allows them to release several hundreds of vesicles per second at every presynaptic release site. The molecular components that cause this high transmitter release efficiency of ribbon synapses are unknown. In the present study, we identified and characterized two novel vertebrate complexins (CPXs), CPXs III and IV, that are the only CPX isoforms present in retinal ribbon synapses. CPXs III and IV are COOH-terminally farnesylated, and, like CPXs I and II, bind to SNAP receptor complexes. CPXs III and IV can functionally replace CPXs I and II, and their COOH-terminal farnesylation regulates their synaptic targeting and modulatory function in transmitter release. The novel CPXs III and IV may contribute to the unique release efficacy of retinal sensory neurons.     

Cell types and neuronal connections in cultures of mammalian central nervous tissue

Summary Various neuronal cell types surviving in cultures of cerebellum, brain stem and cerebral cortex of new-born rats and kittens were described. The regenerative power of neurons in these explants was expressed by the growth of new processes that reached a length of several millimeters. However, nerve fiber regeneration and growth followed an entirely erratic pattern as evidenced by sometimes extensive fiber convolutions.Feed-back collaterals of axonic processes that returned fibers to their own cell bodies or their dendrites were a common feature in many neurons. Short chains of interconnected neurons were detected in a number of cultures. The connections between these neurons were established by apposition of fine axon terminals to presumable postsynaptic cell bodies or dendrites but not by true synaptic boutons. In numerous instances, synapses of the bouton type that appeared morphologically normal could be shown to represent remnants of severed connections since the presynaptic fibers proved to be isolated fiber fragments. Under the sterile conditions of the culture environment these structures apparently persisted without considerable morphological alteration. Evidently, most neurons in our cultures were reduced to the status of isolated cells due to extensive de-afferentiation at the time of explantation. Moreover, there was no evidence for the establishment of new synaptic connections between regenerating neurons.This work was supported by Research Grant NB 03114-05 from the National Institute of Neurological Diseases and Blindness, United States Public Health Service.Dedicated to my esteemed teacher, Prof. Dr. W. Bargmann, on the occasion of his 60th birthday.Sincere appreciation is expressed to Mrs. Eleanor Morris for her assistance in the management of the cultures, and to Mr. E. E. Pitsinger, Jr. for his photographic assistance.     

Altricial and precocial mammals: A model of neural and muscular development

This model of growth offers a quantitative definition for altricial and precocial newborns, makes muscular strength a benchmark for locomotor independence, and discriminates related genera as well as genera across major taxonomic divides. The model contrasts four theoretical conditions of the neonate (I, small brain, weak musculature; II, small brain, strong musculature; III, large brain, weak musculature; IV, large brain, strong musculature) with species from three orders of placental mammal. Each species exhibits a distinct mother-infant strategy from the altricial red panda cub (condition I) and the golden lion tamarin (condition III) to the precocial wildebeest calf (condition IV). The model proposes that early growth rates of brain and muscle correlate with nutrition, maternal effort during gestation and lactation, and parental care, whereas postnatal muscular growth correlates directly with adult body size and locomotor repertoire. An example of condition II (small brain, strong musculature) has not been found. This suggests that muscle does not grow in advance of the brain and that the brain acts as a pacemaker of growth. In order to increase our understanding of exotic species, noninvasive measures (body weight and length) and observations (opening of the eyes and ears, hair density, weaning, and the abilities to ther-moregulate and to move) should be supplemented with analysis of the differential tissue and organ growth. In both theoretical and practical ways analysis of deceased individuals contributes to the understanding of all species.     

Chemical codes of sensory neurons innervating the guinea-pig adrenal gland

Retrograde neuronal tracing in combination with double-labelling immunofluorescence was applied to distinguish the chemical coding of guinea-pig primary sensory neurons projecting to the adrenal medulla and cortex. Seven subpopulations of retrogradely traced neurons were identified in thoracic spinal ganglia T1-L1. Five subpopulations contained immunolabelling either for calcitonin gene-related peptide (CGRP) alone (I), or for CGRP, together with substance (P (II), substance P/dynorphin (III), substance P/cholecystokinin (IV), and substance P/nitric oxide synthase (V), respectively. Two additional subpopulations of retrogradely traced neurons were distinct from these groups: neurofilament-immunoreactive neurons (VI), and cell bodies that were nonreactive to either of the antisera applied (VII). Nerve fibres in the adrenal medulla and cortex were equipped with the mediator combinations I, II, IV and VI. An additional meshwork of fibres solely labelled for nitric oxide synthase was visible in the medulla. Medullary as well as cortical fibres along endocrine tissue apparently lacked the chemical code V, while in the external cortex some fibres exhibited code III. Some intramedullary neuronal cell bodies revealed immunostaining for nitric oxide synthase, CGRP or substance P, providing an additional intrinsic adrenal innervation. Perikarya, immunolabelled for nitric oxide synthase, however, were too few to match with the large number of intramedullary nitric oxide synthase-immunoreactive fibres. A non-sensory participation is also supposed for the particularly dense intramedullary network of solely neurofilament-immunoreactive nerve fibres. The findings give evidence for a differential sensory innervation of the guineapig adrenal cortex and medulla. Specific sensory neuron subpopulations suggest that nervous control of adrenal functions is more complex than hitherto believed.     

不同分类系统下油松幼苗根系特征的差异与联系

植物根序和径级不仅反映细根的形态结构, 而且能反映根系的一些生理特征, 如细根寿命和周转等。该文以二年生油松(Pinus tabulaeformis)幼苗根系为研究对象, 系统比较了根序分类方法和径级分类方法在描述根系特征上的优缺点, 探索了两者之间的内在联系。结果表明: 二年生油松幼苗最多可包括6级根序, 直径的变化范围为0.169-3.877 mm。按根序划分, I-VI级根序的总根长和总根表面积主要集中在前3级根序, 这3级根序的根占总根长的78.77%和总根表面积的62.72%。前3级根序的比根长是后3级根序比根长的1.3-3.0倍, 比根面积是后3级比根面积的1.0-1.5倍。按常用的径级(以0.5、1.0、1.5和2.0 mm为阈值)划分方法, 油松幼苗大部分根系直径≤1.5 mm, 此区间细根的根长和根表面积占总根长的93.76%和总根表面积的84.35%。直径≤1.5 mm的细根平均比根长是>1.5 mm细根比根长的3-7倍, 比根面积的1.5-3.0倍。由于油松根序和径级之间有显著的指数关系, 依据径级最大程度反映根序的原则, 提出了新的径级划分方法, 即以0.4、0.8、1.3和2.0 mm为阈值对油松幼苗根系径级重新进行划分。此时, 上述区间可分别包括I级、II级、III级、IV级、V级根序中根尖数的93.22%、86.37%、75.96%、70.47%和76.67%。同时也可分别涵盖各径级根长的89.34%-70.83%、根面积的86.01%-76.12%以及体积的87.73%-76.12%。此时, 根系不同径级与根序之间可以建立起良好的对应关系。这些结果表明, 通过合理划分径级区间可以较好地反映根序 特征。     

Dissecting cascade computational components in spiking neural networks

Finding out the physical structure of neuronal circuits that governs neuronal responses is an important goal for brain research. With fast advances for large-scale recording techniques, identification of a neuronal circuit with multiple neurons and stages or layers becomes possible and highly demanding. Although methods for mapping the connection structure of circuits have been greatly developed in recent years, they are mostly limited to simple scenarios of a few neurons in a pairwise fashion; and dissecting dynamical circuits, particularly mapping out a complete functional circuit that converges to a single neuron, is still a challenging question. Here, we show that a recent method, termed spike-triggered non-negative matrix factorization (STNMF), can address these issues. By simulating different scenarios of spiking neural networks with various connections between neurons and stages, we demonstrate that STNMF is a persuasive method to dissect functional connections within a circuit. Using spiking activities recorded at neurons of the output layer, STNMF can obtain a complete circuit consisting of all cascade computational components of presynaptic neurons, as well as their spiking activities. For simulated simple and complex cells of the primary visual cortex, STNMF allows us to dissect the pathway of visual computation. Taken together, these results suggest that STNMF could provide a useful approach for investigating neuronal systems leveraging recorded functional neuronal activity.