@article{3582, abstract = {We study edge contractions in simplicial complexes and local conditions under which they preserve the topological type. The conditions are based on a generalized notion of boundary, which lends itself to defining a nested hierarchy of triangulable spaces measuring the distance to being a manifold.}, author = {Dey, Tamal and Edelsbrunner, Herbert and Guha, Sumanta and Nekhayev, Dmitry}, issn = {0350-1302}, journal = {Publications de l'Institut Mathématique}, pages = {23 -- 45}, publisher = {Mathematical Institute, Serbian Academy of Sciences and Arts}, title = {{Topology preserving edge contraction}}, volume = {66}, year = {1999}, } @article{2592, abstract = {Metabotropic glutamate receptors (mGluRs) consist of eight different subtypes and exert their effects or second messengers and ion channels via G- proteins. The function of individual mGluR subtypes in the CNS, however, largely remains to be clarified. We examined the fear response of freezing after electric shock in wild-type and mGluR7(-/-) knockout littermates. Wild- type mice displayed freezing immediately after and 1 d after footshock. In comparison, mGluR7(-/-) knockout mice showed significantly reduced levels in both immediate postshock and delayed freezing responses. However, the knockout mice exhibited no abnormalities in pain sensitivity and locomotor activity. To further examine amygdala-dependent behavior, we performed conditioned taste aversion (CTA) experiments. In wild-type mice, the administration of saccharin followed by intraperitoneal injection of the malaise-inducing agent LiCl resulted in an association between saccharin and LiCl. This association caused strong CTA toward saccharin n contrast, mGluR7(-/-) knockout mice failed to associate between the taste and the negative reinforcer in CTA experiments. Again, the knockout mice showed no abnormalities in taste preference and in the sensitivity to LiCl toxicity. These results indicate that mGluR7 deficiency causes an impairment of two distinct amygdala-dependent behavioral paradigms. Immunohistochemical and immunoelectron-microscopic analyses showed that mGluR7 is highly expressed in amygdala and preferentially localized at the presynaptic axon terminals of glutamatergic neurons. Together, these findings strongly suggest that mGluR7 is involved in neural processes subserving amygdala-dependent averse responses.}, author = {Masugi, Miwako and Yokoi, Mineto and Shigemoto, Ryuichi and Muguruma, Keiko and Watanabe, Yasuyoshi and Sansig, Gilles and Van Der Putten, Herman and Nakanishi, Shigetada}, issn = {0270-6474}, journal = {Journal of Neuroscience}, number = {3}, pages = {955 -- 963}, publisher = {Society for Neuroscience}, title = {{Metabotropic glutamate receptor subtype 7 ablation causes deficit in fear response and conditioned taste aversion}}, doi = {10.1523/JNEUROSCI.19-03-00955.1999}, volume = {19}, year = {1999}, } @article{2593, abstract = {In cat and monkey, lamina I cells can be classified into three basic morphological types (fusiform, pyramidal, and multipolar), and recent intracellular labeling evidence in the cat indicates that fusiform and multipolar lamina I cells are two different types of nociceptive cells, whereas pyramidal cells are innocuous thermoreceptive-specific. Because earlier observations indicated that only nociceptive dorsal horn neurons respond to substance P (SP), we examined which morphological types of lamina I neurons express receptors for SP (NK-1r). We categorized NK-1r- immunoreactive (IR) lamina I neurons in serial horizontal sections from the cervical and lumbar enlargements of four monkeys. Consistent results were obtained by two independent teams of observers. Nearly all NK-1r-IR cells were fusiform (42%) or multipolar (43%), but only 6% were pyramidal (with 9% unclassified). We obtained similar findings in three monkeys in which we used double-labeling immunocytochemistry to identify NK-1r-IR and spinothalamic lamina I neurons retrogradely labeled with cholera toxin subunit b from the thalamus; most NK-1r-IR lamina I spinothalamic neurons were fusiform (48%) or multipolar (33%), and only 10% were pyramidal. In contrast, most (~75%) pyramidal and some (~25%) fusiform and multipolar lamina I spinothalamic neurons did not display NK-1r immunoreactivity. These data indicate that most fusiform and multipolar lamina I neurons in the monkey can express NK-1r, consistent with the idea that both types are nociceptive, whereas only a small proportion of lamina I pyramidal cells express this receptor, consistent with the previous finding that they are nonnociceptive. However, these findings also indicate that not all nociceptive lamina I neurons express receptors for SP.}, author = {Yu, Xiao and Zhang, En and Craig, Arthur and Shigemoto, Ryuichi and Ribeiro Da Silva, Alfredo and De Koninck, Yves}, issn = {0270-6474}, journal = {Journal of Neuroscience}, number = {9}, pages = {3545 -- 3555}, publisher = {Society for Neuroscience}, title = {{NK-1 receptor immunoreactivity in distinct morphological types of lamina I neurons of the primate spinal cord}}, doi = {10.1523/JNEUROSCI.19-09-03545.1999}, volume = {19}, 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}, } @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{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}, } @article{1955, abstract = {The plastid genomes of several plants contain homologues, termed ndh genes, of genes encoding subunits of the NADH:ubiquinone oxidoreductase or complex I of mitochondria and eubacteria. The functional significance of the Ndh proteins in higher plants is uncertain. We show here that tobacco chloroplasts contain a protein complex of 550 kDa consisting of at least three of the ndh gene products: NdhI, NdhJ and NdhK. We have constructed mutant tobacco plants with disrupted ndhC, ndhK and ndhJ plastid genes, indicating that the Ndh complex is dispensible for plant growth under optimal growth conditions. Chlorophyll fluorescence analysis shows that in vivo the Ndh complex catalyses the post-illumination reduction of the plastoquinone pool and in the light optimizes the induction of photosynthesis under conditions of water stress. We conclude that the Ndh complex catalyses the reduction of the plastoquinone pool using stromal reductant and so acts as a respiratory complex. Overall, our data are compatible with the participation of the Ndh complex in cyclic electron flow around the photosystem I complex in the light and possibly in a chloroplast respiratory chain in the dark.}, author = {Burrows, Paul and Sazanov, Leonid A and Sváb, Zóra and Maliga, Pàl and Nixon, Peter}, issn = {0261-4189}, journal = {EMBO Journal}, number = {4}, pages = {868 -- 876}, publisher = {Wiley-Blackwell}, title = {{Identification of a functional respiratory complex in chloroplasts through analysis of tobacco mutants containing disrupted plastid ndh genes}}, doi = {10.1093/emboj/17.4.868}, volume = {17}, year = {1998}, } @article{1956, abstract = { The plastid genomes of several plants contain ndh genes-homologues of genes encoding subunits of the proton-pumping NADH:ubiquinone oxidoreductase, or complex I, involved in respiration in mitochondria and eubacteria. From sequence similarities with these genes, the ndh gene products have been suggested to form a large protein complex (Ndh complex); however, the structure and function of this complex remains to be established. Herein we report the isolation of the Ndh complex from the chloroplasts of the higher plant Pisum sativum. The purification procedure involved selective solubilization of the thylakoid membrane with dodecyl maltoside, followed by two anion-exchange chromatography steps and one size-exclusion chromatography step. The isolated Ndh complex has an apparent total molecular mass of approximately 550 kDa and according to SDS/PAGE consists of at least 16 subunits including NdhA, NdhI, NdhJ, NdhK, and NdhH, which were identified by N-terminal sequencing and immunoblotting. The Ndh complex showed an NADH- and deamino-NADH-specific dehydrogenase activity, characteristic of complex I, when either ferricyanide or the quinones menadione and duroquinone were used as electron acceptors. This study describes the isolation of the chloroplast analogue of the respiratory complex I and provides direct evidence for the function of the plastid Ndh complex as an NADH:plastoquinone oxidoreductase. Our results are compatible with a dual role for the Ndh complex in the chloro-respiratory and cyclic photophosphorylation pathways.}, author = {Sazanov, Leonid A and Burrows, Paul and Nixon, Peter}, issn = {0027-8424}, journal = {PNAS}, number = {3}, pages = {1319 -- 1324}, publisher = {National Academy of Sciences}, title = {{The plastid ndh genes code for an NADH-specific dehydrogenase: Isolation of a complex I analogue from pea thylakoid membranes}}, doi = {10.1073/pnas.95.3.1319}, volume = {95}, year = {1998}, } @article{1449, abstract = {In this paper we consider a canonical compactification of M, the moduli space of stable Higgs bundles with fixed determinant of odd degree over a Riemann surface Σ, producing a projective variety M̄ = M ∪ Z. We give a detailed study of the spaces M̄, Z and M. In doing so we reprove some assertions of Laumon and Thaddeus on the nilpotent cone.}, author = {Hausel, Tamas}, issn = {1435-5345}, journal = {Journal fur die Reine und Angewandte Mathematik}, number = {503}, pages = {169 -- 192}, publisher = {Walter de Gruyter}, title = {{Compactification of moduli of Higgs bundles}}, doi = {10.1515/crll.1998.096}, volume = {1998}, year = {1998}, } @article{1450, abstract = {In this paper we consider the topological side of a problem which is the analogue of Sen's S-duality testing conjecture for Hitchin's moduli space M of rank 2 stable Higgs bundles of fixed determinant of odd degree over a Riemann surface ∑. We prove that all intersection numbers in the compactly supported cohomology of M vanish, i.e. "there are no topological L2 harmonic forms on M". This result generalizes the well known vanishing of the Euler characteristic of the moduli space of rank 2 stable bundles N of fixed determinant of odd degree over ∑. Our proof shows that the vanishing of all intersection numbers of H* cpt(M) is given by relations analogous to the Mumford relations in the cohomology ring of N.}, author = {Hausel, Tamas}, issn = {1095-0761}, journal = {Advances in Theoretical and Mathematical Physics}, number = {5}, pages = {1011 -- 1040}, publisher = {International Press}, title = {{Vanishing of intersection numbers on the moduli space of Higgs bundles}}, doi = {10.4310/ATMP.1998.v2.n5.a3}, volume = {2}, year = {1998}, } @article{3488, abstract = {We have examined gating and pharmacological characteristics of somatic K+ channels in fast-spiking interneurons and regularly spiking principal neurons of hippocampal slices. In nucleated patches isolated from basket cells of the dentate gyrus, a fast delayed rectifier K+ current component that was highly sensitive to tetraethylammonium (TEA) and 4-aminopyridine (4- AP) (half-maximal inhibitory concentrations <0.1 mM) predominated, contributing an average of 58% to the total K+ current in these cells. By contrast, in pyramidal neurons of the CA1 region a rapidly inactivating A- type K+ current component that was TEA-resistant prevailed, contributing 61% to the total K+ current. Both types of neurons also showed small amounts of the K+ current component mainly found in the other type of neuron and, in addition, a slow delayed rectifier K+ current component with intermediate properties (sow inactivation, intermediate sensitivity to TEA). Single-cell RT-PCR analysis of mRNA revealed that Kv3 (Kv3.1, Kv3.2) subunit transcripts were expressed in almost all (89%) of the interneurons but only in 17% of the pyramidal neurons. In contrast, Kv4 (Kv4.2, Kv4.3) subunit mRNAs were present in 87% of pyramidal neurons but only in 55% of interneurons. Selective block of fast delayed rectifier K+ channels, presumably assembled from Kv3 subunits, by 4-AP reduced substantially the action potential frequency in interneurons. These results indicate that the differential expression of Kv3 and Kv4 subunits shapes the action potential phenotypes of principal neurons and interneurons in the cortex.}, author = {Martina, Marco and Schultz, Jobst and Ehmke, Heimo and Monyer, Hannah and Jonas, Peter M}, issn = {0270-6474}, journal = {Journal of Neuroscience}, number = {20}, pages = {8111 -- 8125}, publisher = {Society for Neuroscience}, title = {{Functional and molecular differences between voltage-gated K+ channels of fast-spiking interneurons and pyramidal neurons of rat hippocampus}}, doi = {10.1523/JNEUROSCI.18-20-08111.1998}, volume = {18}, year = {1998}, } @misc{3506, abstract = {A method of geometric morphing between a first object having a first shape and a second object having a second shape. The method includes the steps of generating a first Delaunay complex corresponding to the first shape and a second Delaunay complex corresponding to the second shape and generating a plurality of intermediary Delaunay complexes defined by a continuous family of mixed shapes corresponding to a mixing of the first shape and the second shape. The method further includes the steps of constructing a first skin corresponding to the first Delaunay complex and a second skin corresponding to the second Delaunay complex and constructing a plurality of intermediary skins corresponding to the plurality of intermediary Delaunay complexes. The first skin, second skin and plurality of intermediary skins may be visually displayed on an output device.}, author = {Edelsbrunner, Herbert and Fu, Ping}, title = {{Apparatus and method for geometric morphing}}, year = {1998}, } @article{3628, abstract = {Determining the way in which deleterious mutations interact in their effects on fitness is crucial to numerous areas in population genetics and evolutionary biology. For example, if each additional mutation leads to a greater decrease in log fitness than the last (synergistic epistasis), then the evolution of sex and recombination may be favored to facilitate the elimination of deleterious mutations. However, there is a severe shortage of relevant data. Three relatively simple experimental methods to test for epistasis between deleterious mutations in haploid species have recently been proposed. These methods involve crossing individuals and examining the mean and/or skew in log fitness of the offspring and parents. The main aim of this paper is to formalize these methods, and determine the most effective way in which tests for epistasis could be carried out. We show that only one of these methods is likely to give useful results: crossing individuals that have very different numbers of deleterious mutations, and comparing the mean log fitness of the parents with that of their offspring. We also reconsider experimental data collected on Chlamydomonas moewussi using two of the three methods. Finally, we suggest how the test could be applied to diploid species.}, author = {West, Stuart and Peters, Andrew and Barton, Nicholas H}, issn = {0016-6731}, journal = {Genetics}, number = {1}, pages = {435 -- 444}, publisher = {Genetics Society of America}, title = {{Testing for epistasis between deleterious mutations}}, doi = {10.1093/genetics/149.1.435}, volume = {149}, year = {1998}, } @article{4013, abstract = {The shape of a protein is important for its functions, This includes the location and size of identifiable regions in its complement space. We formally define pockets as regions in the complement with limited accessibility from the outside. Pockets can be efficiently constructed by an algorithm based on alpha complexes. The algorithm is implemented and applied to proteins with known three-dimensional conformations. 1998 Published by Elsevier Science B.V. All rights reserved.}, author = {Edelsbrunner, Herbert and Facello, Michael and Liang, Jie}, issn = {0166-218X}, journal = {Discrete Applied Mathematics}, number = {1-3}, pages = {83 -- 102}, publisher = {Elsevier}, title = {{On the definition and the construction of pockets in macromolecules}}, doi = {10.1016/S0166-218X(98)00067-5}, volume = {88}, year = {1998}, } @article{4017, abstract = {Identification and size characterization of surface pockets and occluded cavities are initial steps in protein structure-based ligand design. A new program, CAST, for automatically locating and measuring protein pockets and cavities, is based on precise computational geometry methods, including alpha shape and discrete flow theory. CAST identifies and measures pockets and pocket mouth openings, as well as cavities. The program specifies the atoms lining pockets, pocket openings. and buried cavities; the volume and area of pockets and cavities; and the area and circumference of mouth openings. CAST analysis of over 100 proteins has been carried out; proteins examined include a set of 51 monomeric enzyme-ligand structures, several elastase-inhibitor complexes, the FK506 binding protein, 30 HIV-1 protease-inhibitor complexes, and a number of small and large protein inhibitors, Medium-sized globular proteins typically have 10-20 pockets/cavities. Most often, binding sites are pockets with 1-2 mouth openings; much less frequently they are cavities. Ligand binding pockets vary widely in size, most within the range 10(2)-10(3) Angstrom(3). Statistical analysis reveals that the number of pockets and cavities is correlated with protein size, but there is no correlation between the size of the protein and the size of binding sites. Most frequently, the largest pocket/cavity is thp active site, but there are a number of instructive exceptions. Ligand volume and binding site volume are somewhat correlated when binding site volume is less than or equal to 700 Angstrom(3), but the ligand seldom occupies the entire site. Auxiliary pockets near the active site have been suggested as additional binding surface for designed ligands (Mattos C ct al., 1993, Nat Struct Biol 1:55-58). Analysis of elastase-inhibitor complexes suggests that CAST can identify ancillary pockets, suitable for recruitment in ligand design strategies. Analysis of the FK506 binding protein, and of compounds developed in SAR by NMR (Shuker SE et al.. 1996, Science 274:1531-1534), indicates that CAST pocket computation may provide a priori identification of target proteins for Linked-fragment design. CAST analysis of 30 HIV-1 protease-inhibitor complexes shows that the flexible active site pocket can vary over a range of 853-1,566 Angstrom(3), and that there are two pockets near or adjoining the active site that may be recruited for ligand design.}, author = {Liang, Jie and Edelsbrunner, Herbert and Woodward, Clare}, issn = {0961-8368}, journal = {Protein Science}, number = {9}, pages = {1884 -- 1897}, publisher = {Wiley-Blackwell}, title = {{Anatomy of protein pockets and cavities: Measurement of binding site geometry and implications for ligand design}}, doi = {10.1002/pro.5560070905}, volume = {7}, year = {1998}, } @article{4492, abstract = {Hybrid automata model systems with both digital and analog components, such as embedded control programs. Many verification tasks for such programs can be expressed as reachability problems for hybrid automata. By improving on previous decidability and undecidability results, we identify a boundary between decidability and undecidability for the reachability problem of hybrid automata. On the positive side, we give an (optimal) PSPACE reachability algorithm for the case of initialized rectangular automata, where all analog variables follow independent trajectories within piecewise-linear envelopes and are reinitialized whenever the envelope changes. Our algorithm is based on the construction of a timed automaton that contains all reachability information about a given initialized rectangular automaton. The translation has practical significance for verification, because it guarantees the termination of symbolic procedures for the reachability analysis of initialized rectangular automata. The translation also preserves theω-languages of initialized rectangular automata with bounded nondeterminism. On the negative side, we show that several slight generalizations of initialized rectangular automata lead to an undecidable reachability problem. In particular, we prove that the reachability problem is undecidable for timed automata augmented with a single stopwatch.}, author = {Henzinger, Thomas A and Kopke, Peter and Puri, Anuj and Varaiya, P.}, isbn = {0022-0000}, journal = {Journal of Computer and System Sciences}, number = {1}, pages = {94 -- 124}, publisher = {Elsevier}, title = {{What's decidable about hybrid automata?}}, doi = {10.1006/jcss.1998.1581}, volume = {57}, year = {1998}, } @article{3482, abstract = {AMPA- and NMDA-type glutamate receptors (AMPARs and NMDARs) mediate excitatory synoptic transmission in the basal ganglia and may contribute to excitotoxic injury. We investigated the functional properties of AMPARs and NMDARs expressed by six main types of basal ganglia neurons in acute rat brain slices (principal neurons and cholinergic interneurons of striatum, GABAergic and dopaminergic neurons of substantia nigra, globus pallidus neurons, and subthalamic nucleus neurons) using fast application of glutamate to nucleated and outside-out membrane patches, AMPARs in different types of basal ganglia neurons were functionally distinct. Those expressed in striatal principal neurons exhibited the slowest gating (desensitization time constant τ = 11.5 msec, 1 mM glutamate, 22°C), whereas those in striatal cholinergic interneurons showed the fastest gating (desensitization time constant τ = 3.6 msec). The lowest Ca2+ permeability of AMPARs was observed in nigral dopaminergic neurons (P(CA)/P(NA) = 0.10), whereas the highest Ca2+ permeability was found in subthalamic nucleus neurons (P(Ca)/P(Na) = 1.17). NMDARs of different types of basal ganglia neurons were less variable in their functional properties; those expressed in nigral dopaminergic neurons exhibited the slowest gating (deactivation time constant of predominant fast component τ1 150 msec, 100 μM glutamate), and those of globus pallidus neurons showed the fastest gating (τ1 = 67 msec). The Mg2+ block of NMDARs was similar; the average chord conductance ratio g(+60mv)/g(+40mV) was 0.18-0.22 in 100 μM external Mg2+. Hence, AMPARs expressed in different types of basal ganglia neurons are markedly diverse, whereas NMDARs are less variable in functional properties that are relevant for excitatory synoptic transmission and neuronal vulnerability.}, author = {Götz, Thomas and Kraushaar, Udo and Geiger, Jörg and Lubke, Joachim and Berger, Thomas and Jonas, Peter M}, issn = {0270-6474}, journal = {Journal of Neuroscience}, number = {1}, pages = {204 -- 215}, publisher = {Society for Neuroscience}, title = {{Functional properties of AMPA and NMDA receptors expressed in identified types of basal ganglia neurons}}, doi = {10.1523/JNEUROSCI.17-01-00204.1997}, volume = {17}, year = {1997}, } @article{3483, abstract = {The main excitatory pathway of the hippocampal formation is controlled by a network of morphologically distinct populations of GABAergic interneurons. Here we describe a novel type of GABAergic interneuron located in the outer molecular layer (OML) of the rat dentate gyrus with a long- range forward projection from the dentate gyrus to the subiculum across the hippocampal fissure, OML interneurons were recorded in hippocampal slices by using the whole-cell patch-clamp configuration. During recording, cells were filled with biocytin for subsequent light and electron microscopic analysis. Neurons projecting to the subiculum were distributed throughout the entire OML. They had round or ovoid somata and a multipolar dendritic morphology. Two axonal domains could be distinguished: an extensive, tangential distribution within the OML and a long-range vertical and tangential projection to layer 1 and stratum pyramidale of the subiculum. Symmetric synaptic contacts were established by these interneurons on dendritic shafts in the OML and subiculum. OML interneurons were characterized physiologically by short action potential duration and marked afterhyperpolarization that followed the spike. On sustained current injection, they generated high- frequency (up to 130 Hz, 34°C) trains of action potentials with only little adaptation. In situ hybridization and single-call RT-PCR analysis for GAD67 mRNA confirmed the GABAergic nature of OML interneurons. GABAergic interneurons in the OML projecting to the subiculum connect the input and output regions of the hippocampus. Hence, they could mediate long-range feed- forward inhibition and may participate in an oscillating cross-regional interneuron network that may synchronize the activity of spatially distributed principal neurons in the dentate gyrus and the subiculum.}, author = {Ceranik, Katya and Bender, Roland and Geiger, Jörg and Monyer, Hannah and Jonas, Peter M and Frotscher, Michael and Lubke, Joachim}, issn = {0270-6474}, journal = {Journal of Neuroscience}, number = {14}, pages = {5380 -- 5394}, publisher = {Society for Neuroscience}, title = {{A novel type of GABAergic interneuron connecting the input and the output regions of the hippocampus.}}, doi = {10.1523/JNEUROSCI.17-14-05380.1997}, volume = {17}, year = {1997}, } @article{3484, abstract = {Glutamatergic transmission at a principal neuroninterneuron synapse was investigated by dual whole-cell patch-clamp recording in rat hippocampal slices combined with morphological analysis. Evoked EPSPs with rapid time course (half duration ≃ 4 ms; 34°C) were generated at multiple synaptic contacts established on the interneuron dendrites close to the soma. The underlying postsynaptic conductance change showed a submillisecond rise and decay, due to the precise timing of glutamate release and the rapid deactivation of the postsynaptic AMPA receptors. Simulations based on a compartmental model of the interneuron indicated that the rapid postsynaptic conductance change determines the shape and the somatodendritic integration of EPSPs, thus enabling interneurons to detect synchronous principal neuron activity.}, author = {Geiger, Jörg and Lubke, Joachim and Roth, Arnd and Frotscher, Michael and Jonas, Peter M}, issn = {0896-6273}, journal = {Neuron}, number = {6}, pages = {1009 -- 1023}, publisher = {Elsevier}, title = {{Submillisecond AMPA receptor-mediated signaling at a principal neuron-interneuron synapse}}, doi = {10.1016/S0896-6273(00)80339-6}, volume = {18}, year = {1997}, } @article{3485, abstract = {1. GABAergic interneurones differ from glutamatergic principal neurones in their ability to discharge high-frequency trains of action potentials without adaptation. To examine whether Na+ channel gating contributed to these differences, Na+ currents were recorded in nucleated patches from interneurones (dentate gyrus basket cells, BCs) and principal neurones (CA1 pyramidal cells, PCs) of rat hippocampal slices. 2. The voltage dependence of Na+ channel activation in BCs and PCs was similar. The slope factors of the activation curves, fitted with Boltzmann functions raised to the third power, were 11.5 and 11.8 mV, and the mid-point potentials were -25.1 and -23.9 mV, respectively. 3. Whereas the time course of Na+ channel activation (-30 to +40 mV) was similar, the deactivation kinetics (-100 to -40 mV) were faster in BCs than in PCs (tail current decay time constants, 0.13 and 0.20 ms, respectively, at -40 mV). 4. Na+ channels in BCs and PCs differed in the voltage dependence of inactivation. The slope factors of the steady-state inactivation curves fitted with Boltzmann functions were 6.7 and 10.7 mV, and the mid-point potentials were -58.3 and -62.9 mV, respectively. 5. The onset of Na+ channel inactivation at -55 mV was slower in BC's than in PCs; the inactivation time constants were 18.6 and 9.3 ms, respectively. At more positive potentials the differences in inactivation onset were smaller. 6. The time course of recovery of Na+ channels from inactivation induced by a 30 ms pulse was fast and mono-exponential (τ = 2.0 ms at -120 mV) in BCs, whereas it was slower and biexponential in PCs (τ1 = 2.0 ms and τ2 = 133 ms; amplitude contribution of the slow component, 15%). 7. We conclude that Na+ channels of BCs and PCs differ in gating properties that contribute to the characteristic action potential patterns of the two types of neurones.}, author = {Martina, Marco and Jonas, Peter M}, issn = {0022-3751}, journal = {Journal of Physiology}, number = {3}, pages = {593 -- 603}, publisher = {Wiley-Blackwell}, title = {{Functional differences in Na+ channel gating between fast-spiking interneurones and principal neurones in rat hippocampus}}, doi = {10.1111/j.1469-7793.1997.593ba.x}, volume = {505}, year = {1997}, }