@article{2864, abstract = {Using an electrospray tandem mass spectrometer as a concentration-sensitive detector, a method has been developed to quantify femtomole amounts of plant growth regulators (i.e. isoprenoid type cytokinins, zeatin, dihydrozeatin, isopentenyladenine and their respective riboside and glucoside analogues) and the second messenger adenosine 3':5'-cyclic monophosphate (3':5'-cAMP). Miniaturisation of the chromatographic setup using capillary high performance liquid chromatographic (HPLC) ion spray mass spectrometry increased the sensitivity to the low femtomole region. Application of automated capillary column switching allowed the introduction of large injection volumes into the HPLC system. Aliquots (25 μL) were injected into one dimension of the HPLC set-up and stacked onto a micro pre-column. By means of mobile phase switching the pre-column was back-flushed to introduce the analytes onto the analytical column. For cytokinin analysis positive electrospray ionisation was used and resulted in 2.5-25 fmol detection limits. Cyclic nucleotides were separated under ion-pair conditions using tetrabutyl ammonium bromide as ion-pair reagent and were detected under negative electrospray ionisation conditions. Here a 25 fmol detection limit was determined. Following this approach, cytokinins and 3':5'-cAMP extracted from only mg amounts of apical shoot meristem and chloroplasts obtained from Nicotiana tabacum cv. Petit Havana SR1 were identified and quantified.}, author = {Witters, Erwin and Vanhoutte, Koen and Dewitte, Walter and Macháčková, Ivana and Benková, Eva and Van Dongen, Walter and Esmans, Eddy and Van Onckelen, Henri}, issn = {0958-0344}, journal = {Phytochemical Analysis}, number = {3}, pages = {143 -- 151}, publisher = {Wiley-Blackwell}, title = {{Analysis of cyclic nucleotides and cytokinins in minute plant samples using phase system switching capillary electrospray liquid chromatography tandem mass spectrometry}}, doi = {10.1002/(SICI)1099-1565(199905/06)10:3<143::AID-PCA441>3.0.CO;2-G}, volume = {10}, year = {1999}, } @article{2865, abstract = {Although cytokinins (CKs) affect a number of processes connected with chloroplasts, it has never been rigorously proven that chloroplasts contain CKs. We isolated intact chloroplasts from tobacco (Nicotiana tabacum L. cv SR1) and wheat (Triticum aestivum L. cv Ritmo) leaves and determined their CKs by liquid chromatography/tandem mass spectroscopy. Chloroplasts from both species contained a whole spectrum of CKs, including free bases (zeatin and isopentenyladenine), ribosides (zeatin riboside, and isopentenyladenosine), ribotides (isopentenyladenosine-5′-monophosphate, zeatin riboside-5′-monophosphate, and dihydrozeatin riboside-5′-monophosphate), and N-glucosides (zeatin-N 9-glucoside, dihydrozeatin-N 9-glucoside, zeatin-N 7-glucoside, and isopentenyladenine-N-glucosides). In chloroplasts there was a moderately higher relative amount of bases, ribosides, and ribotides than in leaves, and a significantly increased level ofN 9-glucosides of zeatin and dihydrozeatin. Tobacco and wheat chloroplasts were prepared from leaves at the end of either a dark or light period. After a dark period, chloroplasts accumulated more CKs than after a light period. The differences were moderate for free bases and ribosides, but highly significant for glucosides. Tobacco chloroplasts from dark-treated leaves contained zeatin riboside-O-glucoside and dihydrozeatin riboside-O-glucoside, as well as a relatively high CK oxidase activity. These data show that chloroplasts contain a whole spectrum of CKs and the enzymatic activity necessary for their metabolism. }, author = {Benková, Eva and Witters, Erwin and Van Dongen, Walter and Kolář, Jan and Motyka, Václav and Brzobohatý, Břetislav and Van Onckelen, Henri and Macháčková, Ivana}, issn = {0032-0889}, journal = {Plant Physiology}, number = {1}, pages = {245 -- 251}, publisher = {American Society of Plant Biologists}, title = {{Cytokinins in tobacco and wheat chloroplasts. Occurrence and changes due to light/dark treatment}}, doi = {10.1104/pp.121.1.245}, volume = {121}, year = {1999}, } @book{3137, abstract = {This volume provides an overview of glutamate receptors and their role in excitatory neurotransmission. It focusses on three aspects. First, it describes the functional, molecular, and pharmacological properties of glutamate receptors (AMPA, NMDA, and kainate receptors). Second, it gives a survey how these receptors are involved in synaptic transmission at different glutamatergic synapses in the mammalian CNS. Finally, it adresses how overactivation of glutamate receptors can lead to excitotoxic cell death, and emphasizes the importance of glutamate receptors as potential therapeutical targets. The chapters, written by leading scientists, give accurate summaries of facets that have emerged recently in this field. The book demonstrates the strength of a multidisciplinary approach involving physiology, pharmacology, and molecular biology. It will be useful for other scientists in and outside the field, lecturers and students at different educational levels.}, editor = {Jonas, Peter M and Monyer, Hannah}, isbn = {978-3-642-08539-0}, issn = {1865-0325}, pages = {XXII, 535}, publisher = {Springer}, title = {{Ionotropic Glutamate Receptors in the CNS}}, doi = {10.1007/978-3-662-08022-1}, volume = {141}, year = {1999}, } @article{3148, abstract = {Accurate proteolytic processing of neuropeptide and peptide hormone precursors by members of the kexin/furin family of proteases is key to determining both the identities and activities of signaling peptides. Here we identify amontillado (amon), the Drosophila melanogaster homolog of the mammalian neuropeptide processing protease PC2, and show that in contrast to vertebrate PC2, amontillado expression undergoes extensive regulation in the nervous system during development. In situ hybridization reveals that expression of amontillado is restricted to the final stages of embryogenesis when it is found in anterior sensory structures and in only 168 cells in the brain and ventral nerve cord. After larvae hatch from their egg shells, the sensory structures and most cells in the CNS turn off or substantially reduce amontillado expression, suggesting that amontillado plays a specific role late in embryogenesis. Larvae lacking the chromosomal region containing amontillado show no gross anatomical defects and respond to touch. However, such larvae show a greatly reduced frequency of a hatching behavior of wild- type Drosophila in which larvae swing their heads, scraping through the eggshell with their mouth hooks. Ubiquitous expression of amontillado can restore near wild-type levels of this behavior, whereas expression of amontillado with an alanine substitution for the catalytic histidine cannot. These results suggest that amontillado expression is regulated as part of a programmed modulation of neural signaling that controls hatching behavior by producing specific neuropeptides in particular neurons at an appropriate developmental time.}, author = {Siekhaus, Daria E and Fuller, Robert}, issn = {0270-6474}, journal = {Journal of Neuroscience}, number = {16}, pages = {6942 -- 6954}, publisher = {Society for Neuroscience}, title = {{A role for amontillado the Drosophila homolog of the neuropeptide precursor processing protease PC2 in triggering hatching behavior}}, doi = {10.1523/jneurosci.19-16-06942.1999}, volume = {19}, year = {1999}, } @article{11679, abstract = {We are given a set T = {T 1 ,T 2 , . . .,T k } of rooted binary trees, each T i leaf-labeled by a subset L(Ti)⊂{1,2,...,n} . If T is a tree on {1,2, . . .,n }, we let T|L denote the minimal subtree of T induced by the nodes of L and all their ancestors. The consensus tree problem asks whether there exists a tree T * such that, for every i , T∗|L(Ti) is homeomorphic to T i . We present algorithms which test if a given set of trees has a consensus tree and if so, construct one. The deterministic algorithm takes time min{O(N n 1/2 ), O(N+ n 2 log n )}, where N=∑i|Ti| , and uses linear space. The randomized algorithm takes time O(N log3 n) and uses linear space. The previous best for this problem was a 1981 O(Nn) algorithm by Aho et al. Our faster deterministic algorithm uses a new efficient algorithm for the following interesting dynamic graph problem: Given a graph G with n nodes and m edges and a sequence of b batches of one or more edge deletions, then, after each batch, either find a new component that has just been created or determine that there is no such component. For this problem, we have a simple algorithm with running time O(n 2 log n + b 0 min{n 2 , m log n }), where b 0 is the number of batches which do not result in a new component. For our particular application, b0≤1 . If all edges are deleted, then the best previously known deterministic algorithm requires time O(mn−−√) to solve this problem. We also present two applications of these consensus tree algorithms which solve other problems in computational evolutionary biology.}, author = {Henzinger, Monika H and King, V. and Warnow, T.}, issn = {1432-0541}, journal = {Algorithmica}, keywords = {Algorithms, Data structures, Evolutionary biology, Theory of databases}, pages = {1--13}, publisher = {Springer Nature}, title = {{Constructing a tree from homeomorphic subtrees, with applications to computational evolutionary biology}}, doi = {10.1007/pl00009268}, volume = {24}, year = {1999}, } @article{11687, abstract = {When using traditional search engines, users have to formulate queries to describe their information need. This paper discusses a different approach to Web searching where the input to the search process is not a set of query terms, but instead is the URL of a page, and the output is a set of related Web pages. A related Web page is one that addresses the same topic as the original page. For example, www.washingtonpost.com is a page related to www.nytimes.com, since both are online newspapers. We describe two algorithms to identify related Web pages. These algorithms use only the connectivity information in the Web (i.e., the links between pages) and not the content of pages or usage information. We have implemented both algorithms and measured their runtime performance. To evaluate the effectiveness of our algorithms, we performed a user study comparing our algorithms with Netscape's `What's Related' service (http://home.netscape.com/escapes/related/). Our study showed that the precision at 10 for our two algorithms are 73% better and 51% better than that of Netscape, despite the fact that Netscape uses both content and usage pattern information in addition to connectivity information.}, author = {Dean, Jeffrey and Henzinger, Monika H}, issn = {1389-1286}, journal = {Computer Networks}, keywords = {Search engines, Related pages, Searching paradigms}, number = {11-16}, pages = {1467--1479}, publisher = {Elsevier}, title = {{Finding related pages in the world wide Web}}, doi = {10.1016/s1389-1286(99)00022-5}, volume = {31}, year = {1999}, } @article{11688, abstract = {Recent research has studied how to measure the size of a search engine, in terms of the number of pages indexed. In this paper, we consider a different measure for search engines, namely the quality of the pages in a search engine index. We provide a simple, effective algorithm for approximating the quality of an index by performing a random walk on the Web, and we use this methodology to compare the index quality of several major search engines.}, author = {Henzinger, Monika H and Heydon, Allan and Mitzenmacher, Michael and Najork, Marc}, issn = {1389-1286}, journal = {Computer Networks}, keywords = {Search engines, Index quality, Random walks, PageRank}, number = {11-16}, pages = {1291--1303}, publisher = {Elsevier}, title = {{Measuring index quality using random walks on the web}}, doi = {10.1016/s1389-1286(99)00016-x}, volume = {31}, year = {1999}, } @inproceedings{11691, abstract = {In this paper we consider the online ftp problem. The goal is to service a sequence of file transfer requests given bandwidth constraints of the underlying communication network. The main result of the paper is a technique that leads to algorithms that optimize several natural metrics, such as max-stretch, total flow time, max flow time, and total completion time. In particular, we show how to achieve optimum total flow time and optimum max-stretch if we increase the capacity of the underlying network by a logarithmic factor. We show that the resource augmentation is necessary by proving polynomial lower bounds on the max-stretch and total flow time for the case where online and offline algorithms are using same-capacity edges. Moreover, we also give polylogarithmic lower bounds on the resource augmentation factor necessary in order to keep the total flow time and max-stretch within a constant factor of optimum.}, author = {Goel, Ashish and Henzinger, Monika H and Plotkin, Serge and Tardos, Eva}, booktitle = {Proceedings of the 31st annual ACM symposium on Theory of computing}, issn = {0196-6774}, keywords = {Scheduling, Flow time}, location = { Atlanta, GA, United States}, pages = {189--197}, publisher = {Association for Computing Machinery}, title = {{Scheduling data transfers in a network and the set scheduling problem}}, doi = {10.1145/301250.301300}, year = {1999}, } @article{11769, abstract = {This paper solves a longstanding open problem in fully dynamic algorithms: We present the first fully dynamic algorithms that maintain connectivity, bipartiteness, and approximate minimum spanning trees in polylogarithmic time per edge insertion or deletion. The algorithms are designed using a new dynamic technique that combines a novel graph decomposition with randomization. They are Las-Vegas type randomized algorithms which use simple data structures and have a small constant factor. Let n denote the number of nodes in the graph. For a sequence of Ω(m0) operations, where m0 is the number of edges in the initial graph, the expected time for p updates is O(p log3 n) (througout the paper the logarithms are based 2) for connectivity and bipartiteness. The worst-case time for one query is O(log n/log log n). For the k-edge witness problem (“Does the removal of k given edges disconnect the graph?”) the expected time for p updates is O(p log3 n) and the expected time for q queries is O(qk log3 n). Given a graph with k different weights, the minimum spanning tree can be maintained during a sequence of p updates in expected time O(pk log3 n). This implies an algorithm to maintain a 1 + ε-approximation of the minimum spanning tree in expected time O((p log3 n logU)/ε) for p updates, where the weights of the edges are between 1 and U.}, author = {Henzinger, Monika H and King, Valerie}, issn = {1557-735X}, journal = {Journal of the ACM}, number = {4}, pages = {502--516}, publisher = {Association for Computing Machinery}, title = {{Randomized fully dynamic graph algorithms with polylogarithmic time per operation}}, doi = {10.1145/320211.320215}, volume = {46}, year = {1999}, } @article{8526, author = {Kaloshin, Vadim}, issn = {0003-486X}, journal = {The Annals of Mathematics}, keywords = {Statistics, Probability and Uncertainty, Statistics and Probability}, number = {2}, pages = {729--741}, publisher = {JSTOR}, title = {{An extension of the Artin-Mazur theorem}}, doi = {10.2307/121093}, volume = {150}, year = {1999}, } @article{883, abstract = {Sympatric speciation, the origin of two or more species from a single local population, has almost certainly been involved in formation of several species flocks, and may be fairly common in nature. The most straightforward scenario for sympatric speciation requires disruptive selection favouring two substantially different phenotypes, and consists of the evolution of reproductive isolation between them followed by the elimination of all intermediate phenotypes. Here we use the hypergeometric phenotypic model to show that sympatric speciation is possible even when fitness and mate choice depend on different quantitative traits, so that speciation must involve formation of covariance between these traits. The increase in the number of variable loci affecting fitness facilitates sympatric speciation, whereas the increase in the number of variable loci affecting mate choice has the opposite effect. These predictions may enable more cases of sympatric speciation to be identified.}, author = {Kondrashov, Alexey and Kondrashov, Fyodor}, issn = {0028-0836}, journal = {Nature}, number = {6742}, pages = {351 -- 354}, publisher = {Nature Publishing Group}, title = {{Interactions among quantitative traits in the course of sympatric speciation}}, doi = {10.1038/22514}, volume = {400}, year = {1999}, } @article{4582, abstract = {We present a formal model for concurrent systems. The model represents synchronous and asynchronous components in a uniform framework that supports compositional (assume-guarantee) and hierarchical (stepwise-refinement) design and verification. While synchronous models are based on a notion of atomic computation step, and asynchronous models remove that notion by introducing stuttering, our model is based on a flexible notion of what constitutes a computation step: by applying an abstraction operator to a system, arbitrarily many consecutive steps can be collapsed into a single step. The abstraction operator, which may turn an asynchronous system into a synchronous one, allows us to describe systems at various levels of temporal detail. For describing systems at various levels of spatial detail, we use a hiding operator that may turn a synchronous system into an asynchronous one. We illustrate the model with diverse examples from synchronous circuits, asynchronous shared-memory programs, and synchronous message-passing protocols. }, author = {Alur, Rajeev and Henzinger, Thomas A}, issn = {0925-9856}, journal = {Formal Methods in System Design}, number = {1}, pages = {7 -- 48}, publisher = {Springer}, title = {{Reactive modules}}, doi = {10.1023/A:1008739929481}, volume = {15}, year = {1999}, } @inproceedings{4601, abstract = {Temporal logic comes in two varieties: linear-time temporal logic assumes implicit universal quantification over all paths that are generated by system moves; branching-time temporal logic allows explicit existential and universal quantification over all paths. We introduce a third, more general variety of temporal logic: alternating-time temporal logic offers selective quantification over those paths that are possible outcomes of games, such as the game in which the system and the environment alternate moves. While linear-time and branching-time logics are natural specification languages for closed systems, alternating-time logics are natural specification languages for open systems. For example, by preceding the temporal operator “eventually” with a selective path quantifier, we can specify that in the game between the system and the environment, the system has a strategy to reach a certain state. Also the problems of receptiveness, realizability, and controllability can be formulated as model-checking problems for alternating-time formulas. Depending on whether we admit arbitrary nesting of selective path quantifiers and temporal operators, we obtain the two alternating-time temporal logics ATL and ATL. We interpret the formulas of ATL and ATL over alternating transition systems. While in ordinary transition systems, each transition corresponds to a possible step of the system, in alternating transition systems, each transition corresponds to a possible move in the game between the system and the environment. Fair alternating transition systems can capture both synchronous and asynchronous compositions of open systems. For synchronous systems, the expressive power of ATL beyond CTL comes at no cost: the model-checking complexity of synchronous ATL is linear in the size of the system and the length of the formula. The symbolic model-checking algorithm for CTL extends with few modifications to synchronous ATL, and with some work, also to asynchronous ATL, whose model-checking complexity is quadratic. This makes ATL an obvious candidate for the automatic verification of open systems. In the case of ATL, the model-checking problem is closely related to the synthesis problem for linear-time formulas, and requires doubly exponential time for both synchronous and asynchronous systems. A preliminary version of this paper appeared in the Proceedings of the 38th IEEE Symposium on Foundations of Computer Science (FOCS 1997), pp. 100–109.}, author = {Alur, Rajeev and Henzinger, Thomas A and Kupferman, Orna}, booktitle = {Proceedings of the International Symposium on Compositionality}, isbn = {9783540654933}, location = {Bad Malente, Germany}, pages = {23 -- 60}, publisher = {Springer}, title = {{Alternating-time temporal logic}}, doi = {10.1007/3-540-49213-5_2}, volume = {1536}, year = {1999}, } @inproceedings{4602, abstract = {Modular techniques for automatic verification attempt to overcome the state-explosion problem by exploiting the modular structure naturally present in many system designs. Unlike other tasks in the verification of finite-state systems, current modular techniques rely heavily on user guidance. In particular, the user is typically required to construct module abstractions that are neither too detailed as to render insufficient benefits in state exploration, nor too coarse as to invalidate the desired systemproperties. In this paper, we construct abstractmodules automatically, using reachability and controllability information about the concrete modules. This allows us to leverage automatic verification techniques by applying them in layers: first we compute on the state spaces of system components, then we use the results for constructing abstractions, and finally we compute on the abstract state space of the system. Our experimental results indicate that if reachability and controllability information is used in the construction of abstractions, the resulting abstract modules are often significantly smaller than the concrete modules and can drastically reduce the space and time requirements for verification.}, author = {Alur, Rajeev and De Alfaro, Luca and Henzinger, Thomas A and Mang, Freddy}, booktitle = {Proceedings of the 10th International Conference on Concurrency Theory}, isbn = {9783540664253}, location = {Eindhoven, The Netherlands}, pages = {82 -- 97}, publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik}, title = {{Automating modular verification}}, doi = {10.1007/3-540-48320-9_8}, volume = {1664}, year = {1999}, } @article{11895, abstract = {In this paper we present an analysis of an AltaVista Search Engine query log consisting of approximately 1 billion entries for search requests over a period of six weeks. This represents almost 285 million user sessions, each an attempt to fill a single information need. We present an analysis of individual queries, query duplication, and query sessions. We also present results of a correlation analysis of the log entries, studying the interaction of terms within queries. Our data supports the conjecture that web users differ significantly from the user assumed in the standard information retrieval literature. Specifically, we show that web users type in short queries, mostly look at the first 10 results only, and seldom modify the query. This suggests that traditional information retrieval techniques may not work well for answering web search requests. The correlation analysis showed that the most highly correlated items are constituents of phrases. This result indicates it may be useful for search engines to consider search terms as parts of phrases even if the user did not explicitly specify them as such.}, author = {Silverstein, Craig and Marais, Hannes and Henzinger, Monika H and Moricz, Michael}, issn = {0163-5840}, journal = {ACM SIGIR Forum}, number = {1}, pages = {6--12}, publisher = {Association for Computing Machinery}, title = {{Analysis of a very large web search engine query log}}, doi = {10.1145/331403.331405}, volume = {33}, year = {1999}, } @inproceedings{11925, abstract = {This paper studies the multicast routing and admission control problem on unit-capacity tree and mesh topologies in the throughput-model. The problem is a generalization of the edge-disjoint paths problem and is NPhard both on trees and meshes. We study both the offline and the online version of the problem: In the offline setting, we give the first constant-factor approximation algorithm for trees, and an O((log log n)*)-factor approximation algorithm for meshes, where n is the number of nodes in the graph. In the online setting, we give the first polylogarithrnic competitive online algorithm for tree and mesh topologies. No polylogarithmic-competitive algorithm is possible on general network topologies [8] and there exists a polylogarithmic lower bound on the competitive ratio of any online algorithm on tree topologies [l]. We prove the same lower bound for meshes. }, author = {Henzinger, Monika H and Leonardi , Stefano}, booktitle = {10th Annual ACM-SIAM Symposium on Discrete Algorithms}, isbn = {0898714346}, location = {Baltimore, MD, United States}, pages = {438--447}, publisher = {Society for Industrial & Applied Mathematics}, title = {{Scheduling multicasts on unit-capacity trees and meshes}}, year = {1999}, } @article{3444, abstract = {This study examined intermittent, high-frequency (100-200 Hz) oscillatory patterns in the CA1 region of the hippocampus in the absence of theta activity, i.e., during and in between sharp wave (SPW) bursts. Pyramidal and interneuronal activity was phase-locked not only to large amplitude (>7 SD from baseline) oscillatory events, which are present mainly during SPWs, but to smaller amplitude (<4 SD) patterns, as well. Large-amplitude events were in the 140-200 Hz, "ripple" frequency range. Lower-amplitude events, however, contained slower, 100-130 Hz ("slow") oscillatory patterns. Fast ripple waves reversed just below the CA1 pyramidal layer, whereas slow oscillatory potentials reversed in the stratum radiatum and/or in the stratum oriens. Parallel CA1-CA3 recordings revealed correlated CA3 field and unit activity to the slow CA1 waves but not to fast ripple waves. These findings suggest that fast ripples emerge in the CA1 region, whereas slow (100-130 Hz) oscillatory patterns are generated in the CA3 region and transferred to the CA1 field.}, author = {Csicsvari, Jozsef L and Hirase, Hajima and Czurkó, András and Mamiya, Akira and Buzsáki, György}, issn = {0270-6474}, journal = {Journal of Neuroscience}, number = {16}, publisher = {Society for Neuroscience}, title = {{Fast network oscillations in the hippocampal CA1 region of the behaving rat}}, doi = {10.1523/JNEUROSCI.19-16-j0001.1999}, volume = {19}, year = {1999}, } @article{3445, abstract = {The medial septal region and the hippocampus are connected reciprocally via GABAergic neurons, but the physiological role of this loop is still not well understood. In an attempt to reveal the physiological effects of the hippocamposeptal GABAergic projection, we cross-correlated hippocampal sharp wave (SPW) ripples or theta activity and extracellular units recorded in the medial septum and diagonal band of Broca (MSDB) in freely moving rats. The majority of single MSDB cells (60%) were significantly suppressed during SPWs. Most cells inhibited during SPW (80%) fired rhythmically and phase-locked to the negative peak of the CA1 pyramidal layer theta waves. Because both SPW and the negative peak of local theta waves correspond to the maximum discharge probability of CA1 pyramidal cells and interneuron classes, the findings indicate that the activity of medial septal neurons can be negatively (during SPW) or positively (during theta waves) correlated with the activity of hippocampal interneurons. We hypothesize that the functional coupling between medial septal neurons and hippocampal interneurons varies in a state-dependent manner.}, author = {Dragoi, George and Carpi, Daniel and Recce, Michael and Csicsvari, Jozsef L and Buzsáki, György}, issn = {0270-6474}, journal = {Journal of Neuroscience}, number = {14}, pages = {6191 -- 6199}, publisher = {Society for Neuroscience}, title = {{Interactions between hippocampus and medial septum during sharp waves and theta oscillation in the behaving rat}}, doi = {10.1523/JNEUROSCI.19-14-06191.1999}, volume = {19}, year = {1999}, } @inbook{3456, abstract = {L-a-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptors (AMPARs) and N-methyl-D-aspartate receptors (NMDARs) are the two major types of postsynaptic glutamate receptors (GluRs) that mediate excitatory synaptic transmission in the mammalian central nervous system (CNS). Both AMPARs and NMDARs are multimeric proteins, probably tetramers, formed by a variety of molecularly distinct subunits. AMPARs can be assembled from four types of subunits, termed GIuR-A, -B, -C, and -D (or, in an alternative nomenclature, G1uR1, G1uR2, GluR3, and G1uR4). Additional molecular diversity of AMPARs is generated by alternative splicing of the flip-flop module and RNA editing at the Q/R and R/G site. NMDARs are heteromers primarily assembled from NR1 subunits and NR2A, B, C, or D subunits. Various splice variants have been identified for the NR1 subunit, and a new NR3 subunit has been discovered recently. Considering all combinatorial possibilities, the molecular diversity of glutamate-receptor channels is considerable (HOLLMANN, this volume).}, author = {Monyer, Hannah and Jonas, Peter M and Rossier, Jean}, booktitle = {Ionotropic Glutamate Receptors in the CNS}, editor = {Jonas, Peter M and Monyer, Hannah}, isbn = {9783642085390}, pages = {309 -- 339}, publisher = {Springer}, title = {{Molecular determinants controlling functional properties of AMPARs and NMDARs in the mammalian CNS}}, doi = {10.1007/978-3-662-08022-1_9}, volume = {141}, year = {1999}, } @inbook{3457, abstract = {Principal neurons and interneurons are the two main classes of cells in cortical neuronal networks. Principal neurons (granule cells or pyramidal neurons) have transregional axonal projections and release glutamate onto their postsynaptic target cells. In contrast, interneurons have local, but often extensive, axonal arborizations and use γ-aminobutyric acid (GABA) as a transmitter. Although interneurons represent only approximately 10% of the neuronal population, they control the electrical activity of the entire network (FREUND and BUZSÁKI 1996). Interneurons forming inhibitory synapses on the somata or axon initial segments of their postsynaptic target cells are thought to set the threshold of action potential initiation (MILES et al. 1996) and can synchronize the collective activities of large principal neuron ensembles (COBB et al. 1995). In contrast, interneurons establishing inhibitory synapses mainly on dendrites could suppress dendritic Na+ or Ca2+ spikes (BUZSÁKI et al. 1996; MILES et al. 1996) and, thus, regulate plasticity at glutamatergic synapses in the cortex (DAVIES et al.1991).}, author = {Geiger, Jörg and Roth, Arnd and Taskin, Birol and Jonas, Peter M}, booktitle = {Ionotropic Glutamate Receptors in the CNS}, editor = {Monyer, Hannah and Jonas, Peter M}, isbn = {9783642085390}, pages = {363 -- 398}, publisher = {Springer}, title = {{Glutamate-mediated synaptic excitation of cortical interneurons}}, doi = {10.1007/978-3-662-08022-1_11}, volume = {141}, year = {1999}, }