It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >

On the capacity of a cellular CDMA system

中枢神経系疾患の治療は正常細胞（ニューロン）の機能維持を目的とするが，脳血管障害のように機能障害の原因が細胞の死滅に基づくことは多い．一方，脳腫瘍の治療においては薬物療法や放射線療法といった腫瘍細胞の死滅を目標とするものが大きな位置を占める．いずれの場合にも，細胞死の機序を理解することは各種病態や治療法の理解のうえで重要である．現在のところ最も研究の進んでいる細胞死の型はアポトーシスである．そのなかで重要な位置を占めるミトコンドリアにおける反応および抗アポトーシス因子について概要を紹介する．

Neuroscience 細胞死：最近の知見

Schizophrenia is a heritable brain illness with unknown pathogenic mechanisms. Schizophrenia's strongest genetic association at a population level involves variation in the major histocompatibility complex (MHC) locus, but the genes and molecular mechanisms accounting for this have been challenging to identify. Here we show that this association arises in part from many structurally diverse alleles of the complement component 4 (C4) genes. We found that these alleles generated widely varying levels of C4A and C4B expression in the brain, with each common C4 allele associating with schizophrenia in proportion to its tendency to generate greater expression of C4A. Human C4 protein localized to neuronal synapses, dendrites, axons, and cell bodies. In mice, C4 mediated synapse elimination during postnatal development. These results implicate excessive complement activity in the development of schizophrenia and may help explain the reduced numbers of synapses in the brains of individuals with schizophrenia.

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Schizophrenia risk from complex variation of complement component 4

저작근 근전도에 관한 정상교합자와 ii급 부정교합자의 비교 연구

Our understanding of the cellular implementation of systems-level neural processes like action, thought and emotion has been limited by the availability of tools to interrogate specific classes of neural cells within intact, living brain tissue. Here we identify and develop an archaeal light-driven chloride pump (NpHR) from Natronomonas pharaonis for temporally precise optical inhibition of neural activity. NpHR allows either knockout of single action potentials, or sustained blockade of spiking. NpHR is compatible with ChR2, the previous optical excitation technology we have described, in that the two opposing probes operate at similar light powers but with well-separated action spectra. NpHR, like ChR2, functions in mammals without exogenous cofactors, and the two probes can be integrated with calcium imaging in mammalian brain tissue for bidirectional optical modulation and readout of neural activity. Likewise, NpHR and ChR2 can be targeted together to Caenorhabditis elegans muscle and cholinergic motor neurons to control locomotion bidirectionally. NpHR and ChR2 form a complete system for multimodal, high-speed, genetically targeted, all-optical interrogation of living neural circuits.

Multimodal fast optical interrogation of neural circuitry

The distribution of the atypical protein kinase Cζ in the nervous system of the adult and juvenile terrestrial snail Helix aspersa L. was studied immunocytochemically. Immunoreactive (IR) elements were detected in all CNS ganglia. The pattern of immunoreactivity included cytoplasmic staining of many CNS neurons, fibers in the CNS tracts and nerves, and ultrathin fibers and single varicosities inside the ganglia neuropil, which is the location of the major zones of synaptic contacts. The primary neurites and their proximal branches were not immunoreactive. The relatively low immunoreactivity of the fibers did not correspond to the presence of numerous Cζ-IR cell bodies. In the juvenile CNS, the IR neuropil was better developed than in the adult CNS, while immunoreactivity was practically absent in the cell bodies. We conclude that the atypical protein kinase Cζ is present in the snail CNS, while in the CNS neuropil it is predominantly located in varicosities.

Localization of the atypical protein kinase Cζ in the Nervous System of the terrestrial snail Helix

Changes in intracellular calcium ion concentrations are the main trigger for most physiological processes in neurons, including changes in gene expression and the processes of synaptic plasticity. Our experiments showed that high-amplitude EPSP in common snail command neurons, like action potentials, are accompanied by marked increases in intracellular calcium ion concentrations. The amplitude of calcium signals accompanying high-amplitude EPSP in command neurons was found to depend linearly on the strength of synaptic stimulation, while the dynamics of changes in the amplitude of EPSP themselves showed marked saturation as stimulus strength increased. This means that over a certain range of changes of membrane potential, calcium signals transmit stimulus strength more adequately than the level of depolarization of the postsynaptic neuron. We suggest that calcium signals evoked by high-amplitude EPSP can induce biochemical changes in neurons, thus mediating cellular responses in the range subthreshold for action potentials.

Changes in Intracellular Calcium Ion Concentrations during Generation of High-Amplitude EPSP in Neurons in the Common Snail

[Long-term potentiation in the helix central nervous system after intracellular tetanization].

The expression of matrix metalloproteinase of the first type was studied in frontal sections of the adult rat brain one month after a single intracerebroventricular injection of beta-amyloid peptide (25-35), which is known to be a well-known model of the development of Alzheimer's disease. Brain sections were stained immunocytochemically to detect MMP-1 expression, and histologically to reveal the state of hippocampal neurons. Administration of beta-amyloid peptide induced a significant degeneration of cells in the dorsal hippocampus. This was demonstrated by a significant decrease in the total number of cells and by the appearance of acidophilic neurons of altered (often triangular) shape. Altered cells were most often found in the hippocampal field CA3, and in a smaller quantity in the CA1 field. MMP-1-like immunoreactivity was found in the same hippocampal areas, the staining being restricted to the cells of altered shape (staining of somata and primary neurites). The data suggest possible involvement of the type 1 metalloproteinase in the development of Alzheimer's disease.

Expression of the type 1 metalloproteinase in the rat hippocampus after the intracerebroventricular injection of β-amyloid peptide (25-35).

The possible existence of intrasynaptic ephaptic feedback in the invertebrate CNS was studied. Intracellular recordings were made of excitatory postsynaptic potentials and currents arising on activation of the recently described monosynaptic connection between identified neurons in the snail CNS. In the presence of ephaptic feedback, tetanization of the postsynaptic neuron with hyperpolarizing impulses should activate presynaptic calcium channels, thus increasing the amplitude of excitatory postsynaptic potential, while sufficiently strong postsynaptic hyperpolarization applied during generation of the excitatory postsynaptic current should induce “supralinear” increases in its amplitude, as has been observed previously in rat hippocampal neurons. The first series of experiments involved delivery of 10 trains of hyperpolarizing postsynaptic impulses (40–50 mV, duration 0.5 sec, frequency 1 Hz, train duration 45 sec); significant changes in the amplitude of excitatory postsynaptic were not seen. In the second series of experiments, changes in the amplitude of the excitatory postsynaptic current were studied during hyperpolarization of the postsynaptic neuron. At a potential of −100 mV, the amplitude of the excitatory postsynaptic current increased significantly more than predicted by its “classical” linear relationship with membrane potential. This “supralinear” increase in the amplitude of the excitatory postsynaptic potential can be explained by the operation of ephaptic feedback and is the first evidence for this phenomenon in CNS synapses of invertebrates.

Pavel M. Balaban

Papers

Localization of the atypical protein kinase Cζ in the Nervous System of the terrestrial snail Helix

Changes in Intracellular Calcium Ion Concentrations during Generation of High-Amplitude EPSP in Neurons in the Common Snail

[Long-term potentiation in the helix central nervous system after intracellular tetanization].

Expression of the type 1 metalloproteinase in the rat hippocampus after the intracerebroventricular injection of β-amyloid peptide (25-35).

Ephaptic feedback in identified synapses in mollusk neurons.