@article{3446, abstract = {An effective character recognition procedure implemented on a new type of hardware system and using a new architecture called CNND is proposed. This CNND contains one or more analog cellular neural networks (CNNs) and some digital logic, combining the advantages of the fast analog CNN signal processing and the fast and easy decision capability of digital logic. It is shown that the CNND system can be used for recognition of multifont printed or handwritten characters and could recognize 100,000 char/s with a recognition rate of more than 95%. The more advantage of the system over competing types is that there is not an extra feature extraction procedure implemented in slow hardware}, author = {Sziranyi, Tamas and Csicsvari, Jozsef L}, issn = {1057-7130}, journal = {IEEE Transactions on Circuits and Systems II: Analog and Digital Signal Processing}, number = {3}, pages = {223 -- 231}, publisher = {IEEE}, title = {{High-speed character recognition using a dual cellular neural network architecture (CNND)}}, doi = {10.1109/82.222823}, volume = {40}, year = {1993}, } @inbook{3451, author = {Jonas, Peter M}, booktitle = {Molecular Basis of Ion Channels and Receptors Involved in Nerve Excitation, Synaptic Transmission, and Muscle Contraction}, pages = {126 -- 135}, publisher = {New York Academy of Sciences}, title = {{Glutamate receptors in the central nervous system}}, doi = {10.1111/j.1749-6632.1993.tb38048.x}, volume = {707}, year = {1993}, } @inbook{3452, abstract = {In recent years, considerable progress in our understanding of the molecular events underlying excitatory synaptic transmission has been made. This progress was mainly achieved by technical advances, among them the patch-clamp technique in brain slices (Edwards et al., 1989), fast application of agonists (Franke et al., 1987), and cloning and functional expression of GluR channels of the nonNMDA type (e.g., Hollmann et al., 1989). A suitable model for studying excitatory postsynaptic currents (EPSCs) in the brain slice with patch-clamp techniques is the mossy fiber synapse on CA3 pyramidal cells of rat hippocampus (MF-CA3 synapse). This synapse is located close to the cell soma and should provide almost ideal space-clamp conditions. A comparison of MF-CA3 EPSCs with the currents activated by fast application of glutamate on membrane patches isolated from CA3 cell somata suggests that the concentration of glutamate in the synaptic cleft during excitatory synaptic transmission is high (about 1 mM) and that the transmitter remains in the synaptic cleft only briefly (about 1 ms). It seems likely that desensitization influences the peak amplitude of the EPSC in several ways. Brief pulses of glutamate cause desensitization, from which the glutamate receptor channels recover only slowly, and micromolar ambient glutamate concentrations produce desensitization at equilibrium. From the functional properties of recombinant GluR channels, in situ hybridization data, and patch-clamp experiments on different neuronal and nonneuronal cell types, a picture of the molecular identity of native channels emerges. In neurons of the hippocampus the pharmacological features of these channels were similar to recombinant channels assembled from subunits of the AMPA/kainate subtype which are strongly expressed in these cells. The native channels are characterized by outward rectification of the steady-state I-V and low Ca permeability, similar to recombinant channels containing the GluR-B subunit. This is consistent with the ubiquitous expression of this subunit in hippocampal neurones. In contrast, GluR channels from cerebellar glial cells, which uniquely in the central nervous system lack the expression of GluR-B subunits, show double rectification and high Ca permeability. The results suggest that the native functional nonNMDA glutamate receptor channels in the CNS are assembled form subunits of the AMPA/kainate subtype in a cell-specific way, with the functional properties of GluR channels in neurones being dominated by the GluR-B subunit.}, author = {Jonas, Peter M}, booktitle = {Nonselective cation channels: Pharmacology, Physiology and Biophysics.}, editor = {Siemen, Detlef}, isbn = {978-3-0348-7327-7}, pages = {61 -- 76}, publisher = {Birkhäuser}, title = {{AMPA-type glutamate receptors - nonselective cation channels mediating fast excitatory transmission in the CNS}}, doi = {10.1007/978-3-0348-7327-7_4}, volume = {66}, year = {1993}, } @article{3473, abstract = {Sixteen different K+ channel subtypes have been cloned from mammalian tissue. Considering their sequence homology to Drosophila Shaker, Shab, Shaw and Shal channels, they were classified into four corresponding classes Kv1-4. All K+ channels belonging to these classes consist of four subunits with each six hydrophobic segments (S1-S6) and a characteristic structure-function relationship of certain domains in their amino acid sequence. These domains are, the inactivation gate in the N-terminal region of the sequence, the voltage sensor in the fourth hydrophobic segment (S4), and the pore-region in the H5 segment between S5 and S6. In some functional properties K+ channels cloned from the mammalian brain, however, differ from Drosophila K+ channels. These are pharmacological differences, differences in the threshold of activation and in regulation of inactivation. Part of these differences are important to understand their physiological role in the brain. Based on their functional characteristics the expression pattern of cloned K+ channels in the rat brain can be correlated with the properties of K+ currents measured in central neurones.}, author = {Ruppersberg, Peter and Ermler, Mamfred and Knopf, Martin and Kues, Wilfried and Jonas, Peter M and Koenen, Michael}, issn = {1015-8987}, journal = {Cellular Physiology and Biochemistry}, pages = {250 -- 269}, publisher = {S. Karger AG}, title = {{Properties of Shaker-homologous potassium channels expressed in the mammalian brain.}}, doi = {10.1159/000154691}, volume = {3}, year = {1993}, } @article{3474, abstract = {1. Excitatory postsynaptic currents (EPSCs) were recorded in CA3 pyramidal cells of hippocampal slices of 15- to 24-day-old rats (22 degrees C) using the whole-cell configuration of the patch clamp technique. 2. Composite EPSCs were evoked by extracellular stimulation of the mossy fibre tract. Using the selective blockers 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and D-2-amino-5-phosphonopentanoic acid (APV), a major alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)/kainate receptor-mediated component and a minor NMDA receptor-mediated component with slower time course were distinguished. For the AMPA/kainate receptor-mediated component, the peak current-voltage (I-V) relation was linear, with a reversal potential close to 0 mV. The half-maximal blocking concentration of CNQX was 353 nM. 3. Unitary EPSCs of the mossy fibre terminal (MF)-CA3 pyramidal cell synapse were evoked at membrane potentials of -70 to -90 mV by low-intensity extracellular stimulation of granule cell somata using fine-tipped pipettes. The EPSC peak amplitude as a function of stimulus intensity showed all-or-none behaviour. The region of low threshold was restricted to a few micrometres. This suggests that extracellular stimulation was focal, and that the stimulus-evoked EPSCs were unitary. 4. Latency and rise time histograms of EPSCs evoked by granule cell stimulation showed narrow unimodal distributions within each experiment. The mean latency was 4.2 +/- 1.0 ms, and the mean 20-80% rise time was 0.6 +/- 0.1 ms (23 cells). When fitted within the range 0.7 ms to 20 ms after the peak, the decay of the EPSCs with the fastest rise (rise time 0.5 ms or less) could be described by a single exponential function; the mean time constant was in the range 3.0-6.6 ms with a mean of 4.8 ms (8 cells). 5. Peak amplitudes of the EPSCs evoked by suprathreshold granule cell stimulation fluctuated between trials. The apparent EPSC peak conductance in normal extracellular solution (2 mM Ca2+, 1 mM Mg2+), excluding failures, was 1 nS. Reducing the Ca2+ concentration and increasing the Mg2+ concentration reduced the mean peak amplitude in a concentration-dependent manner. 6. Peaks in EPSC peak amplitude distributions were apparent in low Ca2+ and high Mg2+. Using the criteria of equidistance and the presence of peaks and dips in the autocorrelation function, five of nine EPSC peak amplitude distributions were judged to be quantal.}, author = {Jonas, Peter M and Major, Guy and Sakmann, Bert}, issn = {0022-3751}, journal = {Journal of Physiology}, pages = {615 -- 663}, publisher = {Wiley-Blackwell}, title = {{Quantal components of unitary EPSCs at the mossy fibre synapse on CA3 pyramidal cells of rat hippocampus}}, doi = {10.1113/jphysiol.1993.sp019965}, volume = {472}, year = {1993}, } @inbook{3568, author = {Edelsbrunner, Herbert}, booktitle = {Handbook of Convex Geometry}, isbn = {978-0-444-89596-7}, pages = {699 -- 735}, publisher = {North Holland}, title = {{Geometric algorithms}}, doi = {10.1016/C2009-0-15705-7}, year = {1993}, } @inbook{3569, author = {Edelsbrunner, Herbert}, booktitle = {Current Trends in Theoretical Computer Science, Essays and Tutorials}, isbn = {978-9810214623}, pages = {1 -- 48}, publisher = {World Scientific Publishing}, title = {{Computational geometry}}, year = {1993}, } @article{3643, abstract = {We investigate the establishment and spread of new adaptive peaks within Wright's ‘shifting balance’. The third phase of the ‘shifting balance’ involves a kind of group selection, since demes in which a superior peak has been established contain more individuals, and so send out more migrants. We assume that population size, N, increases with mean fitness, , according to the exponential relation, . Here, k is a measure of the weakness of density-dependent regulation, and equals the inverse of the regression of log (fitness) on log(N). In the island model, we find that just as with soft selection (k = 0), two distinct types of behaviour exist: group selection makes no qualitative difference. With low numbers of migrants, demes fluctuate almost independently, and only one equilibrium exists. With large numbers of migrants, all the demes evolve towards the same adaptive peak, and so the whole population can move towards one or other of the peaks. Group selection can be understood in terms of an effective mean fitness function. Its main consequence is to increase the effect of selection relative to drift (Ns), and so increase the bias towards the fitter peak. However, this increased bias depends on the ratio between k and the deme size (k/N), and so is very small when density-dependence is reasonably strong.}, author = {Rouhani, Shahin and Barton, Nicholas H}, issn = {0016-6723}, journal = {Genetical Research}, number = {2}, pages = {127 -- 136}, publisher = {Cambridge University Press}, title = {{Group selection and the 'shifting balance'}}, doi = {10.1017/S0016672300031232}, volume = {61}, year = {1993}, } @article{3644, abstract = {Wright proposed that there is a ' shifting balance' between selection within demes, random drift, and selection between demes at different 'adaptive peaks'. We investigate the establishment and spread of new adaptive peaks, considering a chromosome rearrangement, and a polygenic character under disruptive selection. When the number of migrants (Nm) is small, demes fluctuate independently, with a bias towards the fitter peak. When Nm is large, the whole population can move to one of two stable equilibria, and so can be trapped near the lower peak. These two regimes are separated by a sharp transition at a critical Nm of order 1. Just below this critical point, adaptation is most efficient, since the shifting balance greatly increases the proportion of demes that reach the global optimum. This is so even if one peak is only slightly fitter than the other (AWx \/N), and for both strong and weak selection (Ns <§ 1 or Ns > 1). Provided that Nm varies sufficiently gradually from place to place, the fitter peak can be established in regions where Nm « 1, and can then spread through the rest of the range. Our analysis confirms Wright's argument that if selection, migration and drift are of the same order, the ' shifting balance' leads to efficient evolution towards the global optimum.}, author = {Barton, Nicholas H and Rouhani, Shahin}, issn = {0016-6723}, journal = {Genetical Research}, number = {1}, pages = {57 -- 74}, publisher = {Cambridge University Press}, title = {{Adaptation and the 'shifting balance'}}, doi = {10.1017/S0016672300031098 }, volume = {61}, year = {1993}, } @article{4036, abstract = {This paper presents a randomized incremental algorithm for computing a single face in an arrangement of n line segments in the plane that is fairly simple to implement. The expected running time of the algorithm is O(nα(n)log n). The analysis of the algorithm uses a novel approach that generalizes and extends the Clarkson-Shor analysis technique [in Discrete Comput. Geom., 4(1989), pp. 387-421]. A few extensions of the technique, obtaining efficient randomized incremental algorithms for constructing the entire arrangement of a collection of line segments and for computing a single face in an arrangement of Jordan arcs are also presented.}, author = {Chazelle, Bernard and Edelsbrunner, Herbert and Guibas, Leonidas and Sharir, Micha and Snoeyink, Jack}, issn = {0097-5397}, journal = {SIAM Journal on Computing}, number = {6}, pages = {1286 -- 1302}, publisher = {SIAM}, title = {{Computing a face in an arrangement of line segments and related problems}}, doi = {10.1137/0222077 }, volume = {22}, year = {1993}, } @article{4040, abstract = {A plane geometric graph C in ℝ2 conforms to another such graph G if each edge of G is the union of some edges of C. It is proved that, for every G with n vertices and m edges, there is a completion of a Delaunay triangulation of O(m2 n) points that conforms to G. The algorithm that constructs the points is also described.}, author = {Edelsbrunner, Herbert and Tan, Tiow}, issn = {0179-5376}, journal = {Discrete & Computational Geometry}, number = {1}, pages = {197 -- 213}, publisher = {Springer}, title = {{An upper bound for conforming Delaunay triangulations}}, doi = {10.1007/BF02573974}, volume = {10}, year = {1993}, } @article{4041, abstract = {The zone theorem for an arrangement of n hyperplanes in d-dimensional real space says that the total number of faces bounding the cells intersected by another hyperplane is O(n(d-1)). This result is the basis of a time-optimal incremental algorithm that constructs a hyperplane arrangement and has a host of other algorithmic and combinatorial applications. Unfortunately, the original proof of the zone theorem, for d greater-than-or-equal-to 3, turned out to contain a serious and irreparable error. This paper presents a new proof of the theorem. The proof is based on an inductive argument, which also applies in the case of pseudohyperplane arrangements. The fallacies of the old proof along with some ways of partially saving that approach are briefly discussed.}, author = {Edelsbrunner, Herbert and Seidel, Raimund and Sharir, Micha}, issn = {0097-5397}, journal = {SIAM Journal on Computing}, number = {2}, pages = {418 -- 429}, publisher = {SIAM}, title = {{On the zone theorem for hyperplane arrangements}}, doi = {10.1137/0222031}, volume = {22}, year = {1993}, } @article{4042, abstract = {It is shown that a triangulation of a set of n points in the plane that minimizes the maximum edge length can be computed in time 0(n2). The algorithm is reasonably easy to implement and is based on the theorem that there is a triangulation with minmax edge length that contains the relative neighborhood graph of the points as a subgraph. With minor modifications the algorithm works for arbitrary normed metrics.}, author = {Edelsbrunner, Herbert and Tan, Tiow}, issn = {0097-5397}, journal = {SIAM Journal on Computing}, number = {3}, pages = {527 -- 551}, publisher = {SIAM}, title = {{A quadratic time algorithm for the minmax length triangulation}}, doi = {10.1137/0222036 }, volume = {22}, year = {1993}, } @article{4044, abstract = {Edge insertion iteratively improves a triangulation of a finite point set in ℜ2 by adding a new edge, deleting old edges crossing the new edge, and retriangulating the polygonal regions on either side of the new edge. This paper presents an abstract view of the edge insertion paradigm, and then shows that it gives polynomial-time algorithms for several types of optimal triangulations, including minimizing the maximum slope of a piecewise-linear interpolating surface.}, author = {Bern, Marshall and Edelsbrunner, Herbert and Eppstein, David and Mitchell, Stephen and Tan, Tiow}, issn = {0179-5376}, journal = {Discrete & Computational Geometry}, number = {1}, pages = {47 -- 65}, publisher = {Springer}, title = {{Edge insertion for optimal triangulations}}, doi = {10.1007/BF02573962}, volume = {10}, year = {1993}, } @article{4045, abstract = {We apply Megiddo's parametric searching technique to several geometric optimization problems and derive significantly improved solutions for them. We obtain, for any fixed ε>0, an O(n1+ε) algorithm for computing the diameter of a point set in 3-space, an O(8/5+ε) algorithm for computing the width of such a set, and on O(n8/5+ε) algorithm for computing the closest pair in a set of n lines in space. All these algorithms are deterministic.}, author = {Chazelle, Bernard and Edelsbrunner, Herbert and Guibas, Leonidas and Sharir, Micha}, issn = {0179-5376}, journal = {Discrete & Computational Geometry}, number = {1}, pages = {183 -- 196}, publisher = {Springer}, title = {{Diameter, width, closest line pair, and parametric searching}}, doi = {10.1007/BF02573973}, volume = {10}, year = {1993}, } @article{4175, abstract = {We have studied the effects of different neurotrophins on the survival and proliferation of rat cerebellar granule cells in culture. These neurons express trkB and trkC, the putative neuronal receptors for brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) respectively. Binding studies using iodinated BDNF and NT-3 demonstrated that both BDNF and NT-3 bind to the cerebellar granule neurons with a similar affinity of approximately 2 x 10(-9) M. The number of receptors per granule cell was surprisingly high, approximately 30 x 10(-4) and 2 x 10(5) for BDNF and NT-3, respectively. Both NT-3 and BDNF elevated c-fos mRNA in the granule neurons, but only BDNF up-regulated the mRNA encoding the low-affinity neurotrophin receptor (p75). In contrast to NT-3, BDNF acted as a survival factor for the granule neurons. BDNF also induced sprouting of the granule neurons and significantly protected them against neurotoxicity induced by high (1 mM) glutamate concentrations. Cultured granule neurons also expressed low levels of BDNF mRNA which were increased by kainic acid, a glutamate receptor agonist. Thus, BDNF, but not NT-3, is a survival factor for cultured cerebellar granule neurons and activation of glutamate receptor(s) up-regulates BDNF expression in these cells.}, author = {Lindholm, Dan and Dechant, Georg and Heisenberg, Carl-Philipp J and Thoenen, Hans}, issn = {0953-816X}, journal = {European Journal of Neuroscience}, number = {11}, pages = {1455 -- 1464}, publisher = {Wiley-Blackwell}, title = {{Brain-derived neurotrophic factor is a survival factor for cultured rat cerebellar granule neurons and protects them against glutamate-induced neurotoxicity}}, doi = {10.1111/j.1460-9568.1993.tb00213.x}, volume = {5}, year = {1993}, } @article{4177, abstract = {Thyroid hormones play an important role in brain development, but the mechanism(s) by which triiodothyronine (T3) mediates neuronal differentiation is poorly understood. Here we demonstrate that T3 regulates the neurotrophic factor, neurotrophin-3 (NT-3), in developing rat cerebellar granule cells both in cell culture and in vivo. In situ hybridization experiments showed that developing Purkinje cells do not express NT-3 mRNA but do express trkC, the putative neuronal receptor for NT-3. Addition of recombinant NT-3 to cerebellar cultures from embryonic rat brain induces hypertrophy and neurite sprouting of Purkinje cells, and upregulates the mRNA encoding the calcium-binding protein, calbindin-28 kD. The present study demonstrates a novel interaction between cerebellar granule neurons and developing Purkinje cells in which NT-3 induced by T3 in the granule cells promotes Purkinje cell differentiation.}, author = {Lindholm, Dan and Castrén, Eero and Tsoulfas, Pantelis and Kolbeck, Roland and Berzaghi, Maria and Leingärtner, Axel and Heisenberg, Carl-Philipp J and Tesarollo, Lino and Parada, Luis and Thoenen, Hans}, issn = {0021-9525}, journal = {Journal of Cell Biology}, number = {2}, pages = {443 -- 450}, publisher = {Rockefeller University Press}, title = {{Neurotrophin-3 induced by tri-iodothyronine in cerebellar granule cells promotes Purkinje cell differentiation}}, doi = {10.1083/jcb.122.2.443}, volume = {122}, year = {1993}, } @article{4299, abstract = {Evolutionary explanations of aging (or senescence) fall into two classes. First, organisms might have evolved the optimal life history, in which survival and fertility late in life are sacrificed for the sake of early reproduction or high pre-adult survival. Second, the life history might be depressed below this optimal compromise by the influx of deleterious mutations; since selection against late-acting mutations is weaker, deleterious mutations will impose a greater load on late life. We discuss ways in which these theories might be investigated and distinguished, with reference to experimental work withDrosophila. While genetic correlations between life history traits determine the immediate response to selection, they are hard to measure, and may not reflect the fundamental constraints on life history. Long term selection experiments are more likely to be informative. The third approach of using experimental manipulations suffers from some of the same problems as measures of genetic correlations; however, these two approaches may be fruitful when used together. The experimental results so far suggest that aging inDrosophila has evolved in part as a consequence of selection for an optimal life history, and in part as a result of accumulation of predominantly late-acting deleterious mutations. Quantification of these effects presents a major challenge for the future.}, author = {Partridge, Linda and Barton, Nicholas H}, issn = {0016-6707}, journal = {Genetica}, number = {1-3}, pages = {89 -- 98}, publisher = {Springer}, title = {{Evolution of aging: Testing the theory using Drosophila}}, doi = {10.1007/BF01435990}, volume = {91}, year = {1993}, } @article{4300, abstract = {Evolutionary explanations of ageing fall into two classes. Organisms might have evolved the optimal life history, in which survival and fertility late in life are sacrificed for the sake of early reproduction and survival. Alternatively, the life history might be depressed below this optimal compromise by deleterious mutations: because selection against late-acting mutations is weaker, these will impose a greater load on late life. Evidence for the importance of both is emerging, and unravelling their relative importance presents experimentalists with a major challenge.}, author = {Partridge, Linda and Barton, Nicholas H}, issn = {0028-0836}, journal = {Nature}, pages = {305 -- 311}, publisher = {Nature Publishing Group}, title = {{Optimality, mutation and the evolution of ageing}}, doi = {10.1038/362305a0}, volume = {362}, year = {1993}, } @inbook{4301, author = {Barton, Nicholas H and Gale, Katherine}, booktitle = {Hybrid zones and the evolutionary process}, editor = {Harrison, Richard}, isbn = { 0-19-506917-X}, pages = {13 -- 45}, publisher = {Oxford University Press}, title = {{Genetic analysis of hybrid zones}}, doi = {10.1046/j.1420-9101.1994.7050631.x}, year = {1993}, }