Shrinkage Of Space Research Articles

Sudden unexpected death in ‘epilepsy’—a missed opportunity to diagnose a long QT syndrome

s 429 with a 25year history of anticonvulsant drug-resistant complex partial seizures. Computer analysis of captured images revealed over 100 differentially regulated genes, some involved in neurotransmitter release, plasticity and signalling mechanisms. Other candidate genes were novel. Secondary validation with selected candidate clones re-gridded was undertaken by hybridizing newly constructed probes derived from further RNA samples from the same epileptic patient and control. This technology is an effective approach to analysing gene expression changes and may yield new targets from therapeutic intervention in epilepsy. Association study of idiopathic primary generalized epilepsy (IGE) A. Makoff*+, B. Chioza’i, N. Currant, F! Ashersod & L. Nashefsl *Department of Psychological Medicine, institute of Psychiatry, London, UK; t Department of Neuroscience, institute of Psychiatry, London, UK; $ Social Genetic & Developmental Psychiatry Research Centre, Institute of Psychiatry, London, UK; 5 Kent and Canterbury Hospital, Canterbury IKings College Hospital, London, UK Twin studies have demonstrated concordance rates of up to 95% for idiopathic generalized epilepsy (IGE) in monozygotic twin pairs. There are a few rare mendelian forms of IGE, but most show a complex pattern of inheritance. The relative risk for IGE among first-degree relatives is in the range 5-10 suggesting that association studies will be required to detect the expected small gene effects. We have collected an initial sample of 100 probands with IGE and 100 ethnically matched controls. Our initial studies have focused on the metabotropic glutamate receptor type 7 (mGluR7) and the (r4 nicotinic acetylcholine receptor subunit (nAchRo4). Mouse knockouts of mGluR7 result in an epileptic phenotype. Studies of a biallelic polymorphisms in mGluR7 are in progress. Mutations within nAchRo4 have been shown to cause the rare dendelian epilepsy autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE). An association study with a mixture of different IGE syndromes provides some evidence for association to nAchrcr4. The gene for nAchRo4 lies only 50 Kb from a voltage-sensitive potassium channel gene (KCNQ2) in which mutations cause one type of another mendelian epilepsy, benign familial neonatal convulsions (BFNC). We are currently utilizing polymorphisms in the nAchRa4 gene and KCNQ2 in our sample. Functional and structural findings in epilepsy demonstrated with diffusion weighted imaging U.C. Wieshamnn, MR. Symms & S.D. Shorvon Epilepsy Research Group, institute of Neurology, Queen Square, London, UK Diffusion weighted imaging (DWI) is a magnetic resonance imaging technique which is sensitive to molecular motion of water. Transient or permanent changes of the microstructural organization of tissue, for example, widening or shrinkage of the extracellular space cause diffusion changes which can be detected by DWI. We used DWI to investigate patients with epilepsy. In a patient with focal status we detected transient diffusion changes which were likely to reflect neuronal dysfunction. During the interictal stage we found an increased diffusion in structural lesions associated with epilepsy. These included hippocampal sclerosis, tumours and most forms of brain damage. These changes were associated with a reduced anisotropy of water diffusion which is likely to reflect a breakdown of the structural organization. A reduction of anisotropy was the predominant finding in cortical dysgenesis. In conclusion, DWI can show changes of water diffusion in focal status epilepticus. In addition, DWI provides information about the microstructure in lesions which may help to understand the pathophysiology of seizures.

Changes in [Ca2+]0 during anoxia in CNS white matter.

Irreversible anoxic injury of axons in the rat optic nerve requires the presence of extracellular Ca2+. To test the hypothesis that Ca2+ enters an intracellular compartment during anoxia we monitored [Ca2+]0 in this CNS white matter tract using ion-sensitive microelectrodes. Periods of anoxia lasting 15 min resulted in a rapid, reversible increase in [Ca2+]0 accompanied by transient loss of nerve conduction. This increase in [Ca2+]0 was apparently the result of extracellular space shrinkage. Anoxic periods lasting 60 min resulted in an initial rise followed by a sustained fall in [Ca2+]0, indicative of net influx of Ca2+ into an intracellular compartment. Following reoxygenation after 60 min of anoxia, [Ca2+]0 slowly returned toward control levels but nerve conduction recovered incompletely, indicating irreversible loss of function. Removal of bath Ca2+ lowered [Ca2+]0 to about 100 microM, prevented the anoxia-induced fall in [Ca2+]0, and protected against irreversible loss of the compound action potential.

The Liberalization of the Mass Media in Africa and its Impact on Indigenous Languages: The Case of Kiswahili in Kenya

The end of Cold War symbolized by fall of Berlin Wall in 1989 and collapse of Soviet Bloc has ushered in a relatively new arrangement in management of world affairs According to Edoho (1997: 1), most p10minent aspects of this transformation are integration of national economies into global production system and replacement of US. Soviet bipolarism with U S unipolarism. This has resulted in the shrinkage of international space and flow of trade, services, people, values, ideas and technologies across borders with relative ease (Edoho 1997: 4).

Organic and Inorganic Spin-On Polymers for Low-Dielectric-Constant Applications

Low-dielectric-constant materials (k < 3.0) have the advantage of facilitating manufacture of higher performance integrated-circuit (IC) devices with minimal increases in chip size. The reduced capacitance given by these materials permits shrinkage of spacing between metal lines to below 0.25 μm and the ability to decrease the number of levels of metal in a device. The technologies being considered for low-k applications are chemical vapor deposition (CVD) or spin-on of polymeric materials. For both types of processes, there are methods and materials capable of giving k < 3.0 dielectric stacks. This article will focus on the spin-on approach and discuss the properties of both organic and inorganic spin-on polymers.While CVD SiO2 has been the mainstay of the industry, spin-on materials are appropriate for many dielectric applications. Polyimides have applications as electrical insulators, and traditional spin-on silicates or siloxanes (k > 3.0) have served as planarizing dielectrics during the last 15 years. The newer spin-on polymers have greatly enhanced mechanical, thermal, and chemical properties, exhibiting lower dielectric constants than the traditional materials.

Imaging of physiologically evoked responses by electrical impedance tomography with cortical electrodes in the anaesthetized rabbit

The purpose of this study was to determine if electrical impedance tomography (EIT) could be used to image impedance changes of several per cent over tens of seconds, known to occur during evoked activity of the cerebral cortex. A ring of 16 electrodes was placed on the exposed superior surface of the brain of anaesthetized rabbits. EIT images were acquired every 15 s using a Sheffield Mark 1 EIT system. During periods of 2.5 - 3 min of intense photic stimulation of both eyes or electrical stimulation of a forepaw, reproducible impedance decreases of and respectively occurred in appropriate cortical areas, with a time course similar to the period of stimulation. They were accompanied by adjacent smaller impedance increases. The decreases are probably due to increased blood flow and temperature; the cause of the adjacent increases may be a shadowing artefact of the reconstruction algorithm or due to physiological shrinkage of the extracellular space. This demonstrates, for the first time, that such small changes may be imaged under optimal conditions. These results are encouraging to the prospect that EIT may eventually be suitable for imaging evoked responses or epilepsy in human subjects.

Severe transient hypoglycemia causes reversible change in the apparent diffusion coefficient of water.

The aim of this study was to determine the effects of temporary severe hypoglycemia on the apparent diffusion coefficient (ADC) acquired by diffusion-weighted MRI of brain water with the use of serial multislice ADC mapping in rats. Severe hypoglycemia reduces the extracellular space volume, as does ischemia. Demonstrating a reduction of ADC with hypoglycemia should increase our understanding of the mechanisms underlying ADC changes in ischemia and other conditions. Fasted rats were given regular insulin (15 IU/kg IP). Rats were subjected to 15 minutes (n = 5) and 50 minutes (n = 5) of temporary severe hypoglycemia, causing a transiently isoelectric electroencephalogram (EEG). ADC mapping was performed every 30 seconds beginning at the onset of isoelectricity for 8.5 minutes. ADC maps were also obtained later during the isoelectric EEG period and 10, 20, 30, and 40 minutes after glucose infusion. Control images were obtained from a separate group of animals suffering cardiac arrest (n = 5). Abnormal ADC values were not observed before the onset of cerebral isoelectricity, except for isolated areas in the cortex and periventricular regions. Cortical ADC values globally declined at the onset of EEG isoelectricity. The ADC decline spread to subcortical regions within a few minutes. During the isoelectric period, significant declines of ADC values (27% to 45%) occurred in the entire brain. Glucose infusion normalized most of the ADC changes, even after a 50-minute period of isoelectricity. ADC mapping during hypoglycemia clearly demonstrates changes likely related to energy depletion. Most of these ADC declines were reversible. Hypoglycemia is a condition known to be associated with shrinkage of the extracellular space. These observations support the hypothesis that ADC reductions observed in ischemia are also related to shifts of water from the extracellular to the intracellular compartment.

The relationship between the composition of lithium nickel oxide and the loss of reversibility during the first cycle

A quantitative relationship between the reversibility of the intercalation/de-intercalation process and the amount z of extra-nickel ions within the lithium layers has been demonstrated by specific electrochemical studies of Li 1 − z Ni 1 + z O 2 cells. The oxidation of extra-nickel ions from divalent to trivalent state during the first electrochemical charge, leads to an irreversible shrinkage of the interslab space, and as a consequence, to a loss of reversibility in the first cycle. The re-intercalation composition limit is thus directly related to the concentration of extra-nickel ions. However, the overall reversibility can be recovered by a forced discharge up to the starting composition.

OK-432 therapy for lymphangioma in children: Why and how does it work?

Intralesional injection of OK-432 (lyophilized incubation mixture of group A Streptococcus pyogenes of human origin) is safe and effective therapy for lymphangioma. The authors evaluated the mechanism of this therapy in 6 patients who had cystic lymphangioma. The intracystic fluid of the cystic lymphangioma was aspirated before and after (on days 1 and 4) the OK-432 therapy. Changes in cell populations and cytokine productions in each aspirated fluid were analyzed. White blood cells in the intracystic fluid increased markedly in number. Before OK-432 therapy, 96% of the intracystic white blood cells were lymphocytes, and the remaining were neutrophils and macrophages. On day 1, the percentages of neutrophils and macrophages increased to 72% and 21%, respectively. On day 4, the percentage of lymphocytes increased to 72%. Flow cytometry analysis using monoclonal antibodies showed that the number of natural killer cells (CD56 +) and T cells (CD3 +) had increased. The activity of cytotoxic tumor necrosis factor (TNF) and interleukin-6 increased immediately after OK-432 injection and remained high in titer until day 4. These findings suggest that the white blood cells induced and activated by OK-432, and the cytokines (including TNF) produced by these cells increased the endothelial permeability, and thus the accelerated lymph drainage and increased lymph flow led to shrinkage of the cystic spaces.

Contribution of shrinkage of extracellular space to extracellular K+ accumulation in myocardial ischaemia of the rabbit.

1. The contribution of the concentrating effect due to shrinkage of the extracellular space (ECS) to cellular K+ efflux on extracellular potassium ([K+]o) accumulation in response to ischaemia was investigated in an isolated, blood-perfused rabbit papillary muscle preparation with a confined extracellular space. 2. The ECS was quantified using either of two extracellular markers, choline or tetramethyl ammonium (TMA), each with specific ion-selective electrodes, as well as by measurement of extracellular resistance (ro). [K+]o and [Na+]o were also measured simultaneously using K(+)- and Na(+)-selective electrodes. 3. During ischaemia, [K+]o increased 3-fold from 4.2 +/- 0.1 to 12.6 +/- 1.0 mM at 10 min (n = 10) analogous to changes in the ischaemic heart in vivo. The ECS decreased to 83.9 +/- 3.2% of control measured using 1 mM choline extracellularly (n = 9, P < 0.01) or to 85.7 +/- 0.7% of control using 1 mM TMA (n = 6, P < 0.01). Nearly identical decreases in ro (84.1 +/- 2.4%, n = 15, P < 0.01) occurred simultaneously. 4. The small decrease in the ECS contributed only 0.8-0.9 mM to the total increase in [K+]o of 8.4 mM and had a minor effect on transmembrane K+ flux. No significant differences between the relative changes in [choline] and [Na+]o were observed. This excluded a major transmembrane Na+ movement during early ischaemia. 5. Bumetanide (10 mM), an inhibitor of K(+)-Cl- cotransport, a process which is involved in cell volume regulation consequent to osmotic cell swelling, significantly attenuated the increase in [K+]o after 6 min of ischaemia (8.3 +/- 0.6 mM, n = 5 vs. 10.3 +/- 0.4 mM in the control group, n = 6, P < 0.05), whereas N-ethylmaleimide (1 mM), a stimulator of this cotransporter, augmented [K+]o accumulation (12.0 +/- 0.6 mM at 6 min, P < 0.05). 6. We conclude that during early myocardial ischaemia, a major component of [K+]o accumulation is not caused by diminution of ECS per se, but rather by increased net K+ efflux due in part to K(+)-Cl cotransport secondary to myocyte volume regulation.

Is there anomalous scaling in multiparticle final states of high energy collisions?

The experimental results on factorial moments (FM's) in different phase space dimensions are examined in some detail. The general trends of one- and three-dimensional FM's and the complexity of the two-dimensional ones are pointed out. It is shown that all the complicated patterns of FM's in different dimensions can be understood comprehensively under the assumption of self-affine fluctuations in 3D, which means that anomalous scaling of FM's may exist in multiparticle final states provided the shrinkage of phase space is done correctly according to the anisotropic property of multiplicity fluctuations.

Method of Designing Phase-Shifting Masks Utilizing a Compactor

A new method is proposed for designing Levenson-type phase-shifting masks. In this method, phases are assigned in an intermediate layout, and then the intermediate layout is converted to a final layout. In practice, the intermediate layout is a symbolic layout, and the symbolic layout is converted to a mask layout by a compactor. According to the strategy, no conflict spots arise during the operation, which greatly improves design efficiency. This design method is applicable to random patterns in a memory peripheral circuit and in microcomputer chips. As a result of application to the peripheral circuit of dynamic random access memory (DRAM), about 16% shrinkage of the mask area was obtained, compared with a conventional mask. As for a microcomputer chip, 12% shrinkage of mask area was obtained under the condition of 50% shrinkage of aluminum-wire spacing. Together with the interactive method reported before, which is applicable to a memory core circuit, the design of the Levenson-type masks for standard LSIs is totally covered.

Effects of the sodium channel blocker tetrodotoxin (TTX) on cellular ion homeostasis in rat brain subjected to complete ischemia

Anoxic depolarization (AD) and failure of the cellular ion homeostasis are suggested to play a key role in ischemia-induced neuronal death. Recent studies show that the blockade of Na + influx significantly improved the neuronal outcome. In the present study, we investigated the effects of 10 μM tetrodotpxin (TTX) on ischemia-induced disturbances of ion homeostasis in the isolated perfused rat brain. TTX inhibited the spontaneous EEG activity, delayed the ischemia-induced tissue acidification, and significantly postponed the occurrece of AD by 65%. The [Ca 2+] e elevation prior to AD was attenuated from 17.8% to 6% while the increase of the [Na +] e in this period was enhanced (from 2.9% to 7.3%). These findings implied that the ischemia-induced early cellular sodium load and the corresponding shrinkage of the extracellular space was counteracted by TTX. Our results suggest that the Na + influx via voltage-dependent channels preceding complete breakdown of ion homeostasis is one major factor leading to cell depolarization. The massive Na + influx coinciding with AD, however, may be mainly via non-selective cation channels or/and receptor-operated channels. Persistent Na + influx deteriorates neuronal tissue integrity by favouring Ca 2+ influx and edema formation. Blockade of ischemia-induced excessive Na + influx is, therefore, a promising pharmacological approach for stroke treatment.

Extracellular ionic and volume changes: The role in glia—Neuron interaction

Activity-related changes in extracellular K + concentration ([K +] e), pH (pH e) and extracellular volume were studied by means ofion-selective microelectrodes in the adult rat spinal cord in vivo and in neonatal rat spinal cords isolated from pups 3–14 days of age (P3–P14). Concomitantly with the ionic changes, the extracellular space (ECS) volume fraction (α), ECS tortuosity (λ) and non-specific uptake ( k′), three parameters affecting the diffusion of substances in nervous tissue, were studied in the rat spinal cord gray matter. In adult rats, repetitive electrical nerve stimulation (10–100 Hz) elicited increases in [K +] e of about 2.0–3.5 m m, followed by a post-stimulation K +-undershoot and triphasic alkaline-acid-alkaline changes in pH e with a dominating acid shift. The ECS volume in the adult rat occupies about 20% of the tissue, α = 0.20 ± 0.003, λ = 1.62 ± 0.02 and k′ = 4.6 ± 0.4 × 10 −3 s −1 ( n = 39). In contrast, in pups at P3–P6, the [K +] e increased by as much as 6.5 m m at a stimulation frequency of 10 Hz, i.e. K + ceiling level was elevated, and there was a dominating alkaline shift. An increase in [K +] e as large as 1.3–2.5 m m accompanied by an alkaline shift was evoked by a single electrical stimulus. The K + ceiling level and alkaline shifts decreased with age, while an acid shift, which was preceded by a small initial alkaline shift, appeared in the second postnatal week. In pups at P1–P2, the spinal cord was X-irradiated to block gliogenesis. The typical decrease in [K +] e ceiling level and the development of the acid shift in pH e at P10–P14 were blocked by X-irradiation. Concomitantly, continuous development of glial fibrillary acidic protein positive reaction was disrupted and densely stained astrocytes in gray matter at P10–P14 revealed astrogliosis. The alkaline, but not the acid, shift was blocked by Mg 2+ and picrotoxin (10 −6 m). Acetazolamide enhanced the alkaline but blocked the acid shift. Furthermore, the acid shift was blocked, and the alkaline shift enhanced, by Ba 2+, amiloride and SITS. Application of glutamate or gamma-aminobutyric acid evoked an alkaline shift in the pH e baseline at P3–P14 as well as after X-irradiation. The results suggest that the activity-related acid shifts in pH e are related to membrane transport processes in mature glia, while the alkaline shifts have a postsynaptic origin and are due to activation of ligand-gated ion channels. At P4–P6, the ECS volume was almost double that in adult rats, α = 0.37 ± 0.01 ( n = 17), the ECS tortuosity was significantly higher, λ = 1.78 ± 0.02, while the non-specific uptake was not significantly different, k′ = 3.61 ± 0.56 × 10 −3 s −1. The α gradually decreased to about 24% at P12. In adult rats, electrical or adequate stimulation evoked a shrinkage of the extracellular space by 20–50%, while no significant changes in ECS volume were found in P3–P6. We conclude that the [K +] e ceiling level, character of the pH e transients, the size of the ECS volume and the activity-related ECS shrinkage are closely related to gliogenesis.

Transient extracellular volume reduction in neural lobe of rat hypophysis in response to neural stalk stimulation in vitro and its relationship to extracellular potassium

1. Using ion-sensitive microelectrodes, a transient reduction in the local volume of neural lobe extracellular space was found to accompany the elevation in extracellular potassium induced by stimulation of the neural stalk. The volume decrease and potassium increase had similar stimulus-response curves when stimulus frequency was varied from 1 to 40 Hz, with maximal response at 20 Hz. The curves for stimulus duration diverged, as a near maximal potassium response was reached in 4-16 s with a 20-Hz stimulus, while the extracellular volume decrease was maximal at 64 s. 2. The volume decrease, but not the potassium increase, was strongly inhibited by lowering bath temperature and moderately inhibited by furosemide and by lowering extracellular chloride concentration. Both the volume and the potassium response were enhanced by ouabain. 3. In conclusion, shrinkage of the local extracellular space in neural lobe during nerve activity is mediated by a metabolically active process which is only partially dependent upon extracellular chloride concentration and anion-cation co-transport, but is relatively independent of Na(+)-K+ pump activity. A transient shrinkage in extracellular space during increased neurohypophysial nerve activity would be expected to play a role in hormone diffusion, ion buffering, and extracellular current flow.

KENAF PITH AS A VERMICULITE SUBSTITUTE IN PEAT-BASED MEDIA.

Kenaf is an alternative fiber crop being evaluated in Mississippi. Kenaf, primarily grown in Asia, can be used in the manufacture of paper, fiber board, acoustical tiles and compost. The bark is the source of the fiber used, leaving the fiber core or pith for use as a paper additive, poultry litter, or is discarded. The objective of this study was to evaluate the potential use of kenaf fiber core as a vermiculite substitute in a sphagnum peat moss-based medium. Plugs of Celosia argentea, Viola × wittrockiana, and Impatiens wallerana were transplanted into 10 cm pots containing 5 different sphagnum peat moss-based media modified with the milled fiber core (pith) of kenaf (Hibiscus cannabinus) and/or vermiculite. The media were as follows: 5 peat: 0 kenaf : 5 vermiculite (v/v/v); 5 peat : 1 kenaf : 4 vermiculite (v/v/v); 5 peat : 2 kenaf : 3 vermiculite (v/v/v); 5 peat : 3 kenaf : 2 vermiculite (v/v/v); 5 peat : 4 kenaf : 1 vermiculite (v/v/v); and 5 peat : 5 kenaf: 0 vermiculite (v/v/v). Water holding capacity, pore space, pH and media shrinkage were monitored throughout the study along with plant growth and plant quality.

Pharmacological properties of excitatory amino acid induced changes in extracellular calcium concentration in rat hippocampal slices.

We have studied extracellular ionic changes induced by iontophoretic application of excitatory amino acids in rat hippocampal slices. In contrast to kinetics of changes in [Ca2+]o, kinetics of changes in [K+]o, [Na+]o, [Cl-]o as well as in extracellular space size were comparable for different glutamate receptor agonists. Thus, alpha-amino-3-hydroxy-5-methylisoxazolepropionic acid (AMPA), quisqualate (quis), and kainate caused reductions in [Ca2+]o followed by an increase of [Ca2+]o above baseline, whereas glutamate, aspartate, N-methyl-D-aspartate (NMDA), and DL-homocysteic acid caused only reductions in [Ca2+]o. After blocking the NMDA receptors with ketamine and 2-amino-5- phosphonovaleric acid (2-APV), glutamate-induced decreases in [Ca2+]o were followed by an overshoot. Reduction of the transmembrane Na+ gradient by lowering [Na+]o, blocking of the Na(+)-K+ ATPase by lowering [K+]o, and application of ouabain blocked the overshoots after quis application, whereas vanadate, a blocker of the Ca(2+)-Mg2+ ATPase, had no effects. Lithium enhanced the reductions in [Ca2+]o and blocked the overshoots. Amiloride also reduced the overshoots. All organic Ca2+ entry blockers diminished reductions of [Ca2+]o but increased the overshoots. Inorganic Ca2+ antagonists had variable effects. Ni2+ had similar effects as the organic Ca2+ entry blockers while Cd2+ reduced both the [Ca2+]o decreases as well as the subsequent overshoots. Co2+ had initially a similar action as Ni2+. With prolonged application, [Ca2+]o decreases became augmented and, during wash, overshoots could no longer be elicited. We suggest that the overshoots in [Ca2+]o are due to a combined effect of extracellular space shrinkage and activation of the Na+/Ca2+ exchangers. This would imply that NMDA receptor activation blocks extrusion of Ca2+ from the cells. We tested the hypothesis that quis-induced intracellular Ca2+ release and extrusion of Ca2+ from the cells contributed to the overshoots. Dantrolene was without effect on the quis-induced signals, while ryanodine reduced the overshoots. Caffeine on the other hand diminished the [Ca2+]o decreases with no effects on the overshoots. To test for possible second messenger routes by which NMDA receptor activation might slow Ca2+ extrusion from cells, we investigated the effects of arachidonic acid and N-monomethyl-D- arginine on the quis-induced signals. While these agents reduced decreases in [Ca2+]o, they had no clear effects on the overshoots. Thus a possible route by which NMDA receptor activation may affect Ca2+ extrusion from cells has still to be elucidated.

The structural change of graphitization-controlled microporous carbon upon adsorption of H 2O and N 2

The partial graphitization of activated carbon fibers (ACFs) was controlled by heating at 1773–3173 K in Ar. The growth of graphitic crystallites was examined by high-resolution transmission electron microscopy and X-ray diffraction. The adsorption processes of H 2O and N 2 on the graphitization-controlled ACFs were investigated by use of the in situ X-ray diffraction. The adsorption of H 2O at 303 K and N 2 at 165 K led to shrinkage of the interlayer spacing, d 002, between the graphitic carbon layers. The shrinkage of more graphitized ACF is less remarkable than that of as-received ACF. The d 002 value decreased hardly until 40% of the fractional filling of H 2O, then it lowered markedly with the fractional filling. On the other hand, only less than 5% of the fractional filling decreased seriously the d 002 value in the case of N 2 adsorption. The relationship between the molecular adsorption and the graphitic structural change was discussed on the basis of the adsorption process; N 2 molecules are at first adsorbed in the deep sites of the distorted slit-shaped micropores, while H 2O molecules are firstly adsorbed near the entrance of the micropore with hydrophilic functional groups.

Perception of normal and spectrally compressed speech by the skin

The development of sensory aids continues to be focused on increasing the number of channels and on alternative processing schemes. The present study compares natural hVd syllables and simple sentences presented with varying degrees of spectral compression [R. Hurtig, J. Acoust. Soc. Am. Suppl. 1 85, S44 (1989)] under vibrotactile and electrocutaneous stimulation conditions. In addition, a comparison of the number of channels used was made. Confusion matrices were constructed from the responses made in a closed set identification task, which followed a subject‐paced exploratory learning task. Multidimensional scaling of the stimuli based on their first three formant values produced the standard representation against which the perceptual data could be evaluated. This congruence analysis graphically illustrates the distortions of the perceptual vowel space. An overall shrinkage of the perceptual space is evident across conditions; however, this effect is not uniform. Warping of the space is observed but in different portions of the space for each of the stimulation conditions.

γ-Aminobutyric acid-induced ion movements in the guinea pig hippocampal slice

γ-Aminobutyric acid (GABA)-induced regional changes of extracellular Cl, K and Na concentration ([Cl] 0, [K] 0, [Na] 0), as well as of the extracellular space were measured with ion-sensitive microelectrodes in guinea pig hippocampal slices. Microdrop application of GABA to the pyramidal cell layer of CA3 or CA1 induced a decrease of [Cl] 0, while application to the dendritic layer of CA3 or CA1 induced an increase of [Cl] 0 in addition. All changes of [Cl] 0 persisted in the presence of TTX and were blocked by bath-applied bicuculline. The GABA-induced decrease of [Cl] 0 was reduced by bicuculline application to the pyramidal cell layer. The increase of [Cl] 0 was blocked by bicuculine application to the dendritic layer. Additionally, GABA induced an increase of [K] 0 and decreases/increases of [Na] 0. Changes of [Cl] 0, [K] 0, and [Na] 0 together were approximately electroneutral. [Cl] 0 increases were exaggerated and [Cl] 0 decreases partly masked by shrinkage of the extracellular space after GABA application. Changing [K] in the superfusate transiently changed GABA-induced [Cl] 0 movements in a way predicted from a change in driving force due to the effect of [K] on membrane potential. Then a partial recovery followed towards the original [Cl] 0 change. We conclude that inward and outward Cl transports maintain [Cl] i below equilibrium in CA3 and CA1 pyramidal somata and above equilibrium in CA3 and CA1 dendrites. The significance of ths Cl-distribution for hippocampal inhibition is discussed.

Rapid shrinkage of rat striatal extracellular space after local kainate application and ischemia as recorded by impedance.

Early changes in tissue extracellular space following exposure to the excitotoxin kainate in the striatum were compared to those following cardiac arrest of rats anesthetized by chloral hydrate. Tissue extracellular space was monitored by impedance measurements. The possible role of voltage-sensitive Na channels and energy metabolism was studied by local and systemic application of tetrodotoxine (TTX) and glucose, respectively. After both kainate intoxication and cardiac arrest the extracellular space (normally about 20%) became less than one-half within 15 min. TTX caused a delay in the effect of cardiac arrest, and a slight attenuation of that of kainate. Glucose was ineffective in both preparations. Parallel to a decrease in the extracellular space whole tissue Na/K ratio increased. These experiments show that excitotoxins and cardiac arrest cause similar (and not additive) changes in the extracellular space and that these changes are not mediated by Na channels. In cardiac arrest the onset of the extracellular space alterations is triggered by Na+ influx, thus presumably by neurotransmitter release. It is suggested that most (if not all) currently described protective measures against ischemic, hypoxic, or hypoglycemic brain damage are based on a prolongation of the time of onset leading to cell depolarization, rather than suppressing damaging processes during depolarization.