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PubMed1980

On the uptake, metabolism and retention of [h] gibberellin a(1) by barley aleurone layers at low temperatures.

Barley (c.v. Himalaya) aleurone layers were incubated in [(3)H]gibberellin A(1) (GA(1)) at low temperatures. At 3 and 4 C, (3)H-activity was steadily accumulated in aleurone layers, and this accumulation was correlated with significant [(3)H]GA(1) metabolism. At 1 and 1.5 C, metabolism could not be detected, and at these temperatures aleurone layers equilibrated with the [(3)H]GA(1) concentration in the incubation medium. At equilibrium, the total amount of (3)H-activity per unit volume in the aleurone layers was higher than in the incubation medium. Aleurone layers incubated at 0.5 C for 72 hours with [(3)H]GA(1) in the presence of saturating levels of carrier GA(1) consistently retained lower levels of (3)H-activity than when incubated in [(3)H]GA(1) alone. The retention of [(3)H]GA(1) was unaffected by saturating levels of carrier GA(8). GA(1) retained by barley aleurone layers that were incubated at 0.5 C for 72 hours was able to induce alpha-amylase synthesis when aleurone layers were subsequently washed and transferred to a gibberellin-free medium at 25 C.

Journal Article↗
PubMed1984

Control of lactate dehydrogenase, lactate glycolysis, and alpha-amylase by o(2) deficit in barley aleurone layers.

After 4 days in an atmosphere of N(2), aleurone layers of barley (Hordeum vulgare L. cv Himalaya) remained viable as judged by their ability to produce near normal amounts of alpha-amylases when incubated with gibberellic acid (GA(3)) in air. However, layers did not produce alpha-amylase when GA(3) was supplied under N(2), apparently because alpha-amylase mRNA failed to accumulate.When an 8-hour pulse of [U-(14)C]glucose was supplied under N(2) to freshly prepared aleurone layers, both [(14)C]lactate and [(14)C]ethanol accumulated; the [(14)C]lactate/[(14)C]ethanol ratio was about 0.3. Prior incubation of layers for 1 day under N(2) changed this ratio to about 0.8, indicating an increase in the relative importance of the lactate branch of glycolysis.l(+)Lactate dehydrogenase (LDH) activity was low in freshly prepared aleurone layers and increased 10-fold during 2 days under N(2), whereas alcohol dehydrogenase activity (ADH) was high initially and rose by 60%. The responses of LDH and ADH activities to O(2) tension were dissimilar; when layers were incubated in various O(2)/N(2) mixtures, LDH activity peaked at 2 to 5% O(2) whereas ADH activity was highest at 0% O(2). The LDH activity was resolved into several enzymically active bands by native polyacrylamide gel electrophoresis.We conclude that barley aleurone layers are highly adapted to O(2) deficiency, that they possess an inducible LDH system as well as an ADH system, and we infer that the LDH and ADH systems are independently regulated.

Journal Article↗
PubMed1984

Mode of action of abscisic Acid in barley aleurone layers : abscisic Acid induces its own conversion to phaseic Acid.

As a part of our effort to study the mode of action of abscisic acid (ABA) and its metabolites during seed germination, we have investigated the regulation of ABA metabolism in barley (Hordeum vulgare) aleurone layers and a few other plant tissues. The rate of conversion of [(3)H]ABA to [(3)H]phaseic acid (PA), the first stable metabolite of ABA, is enhanced by 2- to 5-fold in barley aleurone layers when the tissue is pretreated with ABA. However, the conversion of [(3)H]PA to [(3)H] dihydrophaseic acid (DPA), the next metabolite after PA, is not enhanced by pretreatment with either ABA or PA. The ABA enhancement of its own metabolism in barley aleurone layers is detectable with a pretreatment of ABA ranging from 10(-3) to 10(-4) molar. This apparent self-induction of ABA conversion to PA can be observed after the barley aleurone layers have been treated with 10(-5) molar ABA for as short as 2 hours, and is inhibited by the transcription inhibitor, cordycepin (3'-deoxyadenosine), or the translation inhibitor, cycloheximide. The self-induction of ABA conversion to PA also occurs in wheat aleurone layers, but not in other plant tissues that have been investigated, including corn root tips, barley embryos, barley, and soybean leaf discs. It is probably a phenomenon unique to the aleurone layers of some cereal grains. In view of the recent observations that ABA is able to induce new proteins in barley aleurone layers, we suggest that some of these ABA-induced proteins are involved in the conversion from ABA to PA in this tissue.

Journal Article↗
PubMed2003

superspace description of trigonal and orthorhombic A(1)+(x)A(x)'B(1)-(x)O(3) compounds as modulated layered structures; application to the refinement of trigonal Sr(6)Rh(5)O(15).

The structures of the trigonal compounds A(1+x)A(x')B(1-x)O(3) are described, to a first approximation, as a hexagonal close-packed stacking of A(3)O(9) and A(3)A'O(6) layers. However, quantitative analyses are usually performed in superspace, with the structures considered as modulated composites made of two subsystems: chains of A cations, and columns of trigonal prisms, A'O(6), and octahedra, BO(6). It is demonstrated that an alternative superspace description as a single modulated structure can be found in terms of the aforementioned layers, with a composition-dependent modulation parameter and discontinuous atomic domains. In this approach, these compounds fulfill layer-stacking rules analogous to those observed in other layered compounds. These rules translate into a so-called closeness condition for the discontinuous atomic domains in superspace; this condition is analogous to that postulated in quasicrystals. Both superspace models, the composite and the layered model, when considered without displacive modulations, can be taken as two limiting idealized paradigms and can be used as the starting point of a structure refinement. As an example, the structure of the trigonal phase Sr(6)Rh(5)O(15), which was previously refined as a modulated composite [Stitzer, El Abed et al. (2001), J. Am. Chem. Soc. 123, 8790-8796], has been refined anew, with equivalent results, as a single modulated structure taking as reference the ideal layered structure. A similar superspace layer description is applied to the recently reported orthorhombic family A(4m+4n)A(n')B(4m+2n)O(12m+9n). This description allows the a priori derivation of a refineable superspace model that includes the superspace symmetry and crenel functions and is valid for the whole family. This model has been successfully applied to the refinement of the compound Ba(12)Co(11)O(33) [Darriet et al. (2002), Chem. Mater. 14, 3349-3363].

Journal Article↗
PubMed2004

Different forms of antiparallel stacking of hydrogen-bonded antidromic rings in the solid state: polymorphism with virtually the same unit cell and two-dimensional isostructurality with alternating layers.

As a continuation of a systematic structural analysis of 2-hydroxycycloalkanecarboxylic acids and their carboxamide analogs, the effects of antidromic rings [Jeffrey & Saenger (1991). Hydrogen Bonding in Biological Structures. Berlin, Heidelberg: Springer Verlag] upon the layer stacking of cyclopentane and cycloheptane derivatives are compared. Determination of the structure of trans-2-hydroxycycloheptanecarboxylic acid (2) led to the discovery of two polymorphs with virtually the same unit cell [Kalman et al. (2003). J. Am. Chem. Soc. 125, 34-35]. (i) The layer stacking of the antidromic rings for the whole single crystal is antiparallel (2b). (ii) The antidromic rings and the 21 axis are parallel (2a), consequently the domains of the single crystal must be antiparallel. While their polymorphism is solvent-controlled, they illustrate a novel form of two-dimensional isostructurality. Antiparallel layer stacking is again demonstrated by trans-2-hydroxycycloheptanecarboxamide (3) (space group Pbca). It is built up from layers isostructural with those in the homologous trans-2-hydroxycyclopentanecarboxamide (4) [Kalman et al. (2001). Acta Cryst. B57, 539-550], but in this structure (space group Pca21) the layers are stacked in parallel mode. Similar to (2a) and (2b), the antiparallel layer stacking in (3) versus their parallel array in (4) illustrates the two-dimensional isostructurality with alternating layer orientations. Although (3) and (4) display isostructurality, they are not isomorphous.

Journal Article↗
PubMed2004

Modeling of wave propagation in layered piezoelectric media by a recursive asymptotic method.

In this paper, a simple asymptotic method to compute wave propagation in a multilayered general anisotropic piezoelectric medium is discussed. The method is based on explicit second and higher order asymptotic representations of the transfer and stiffness matrices for a thin piezoelectric layer. Different orders of the asymptotic expansion are obtained using Padé approximation of the transfer matrix exponent. The total transfer and stiffness matrices for thick layers or multilayers are calculated with high precision by subdividing them into thin sublayers and combining recursively the thin layer transfer and stiffness matrices. The rate of convergence to the exact solution is the same for both transfer and stiffness matrices; however, it is shown that the growth rate of the round-off error with the number of recursive operations for the stiffness matrix is twice that for the transfer matrix; and the stiffness matrix method has better performance for a thick layer. To combine the advantages of both methods, a hybrid method which uses the transfer matrix for the thin layer and the stiffness matrix for the thick layer is proposed. It is shown that the hybrid method has the same stability as the stiffness matrix method and the same round-off error as the transfer matrix method. The method converges to the exact transfer/stiffness matrices essentially with the precision of the computer round-off error. To apply the method to a semispace substrate, the substrate was replaced by an artificial perfect matching layer. The computational results for such an equivalent system are identical with those for the actual system. In our computational experiments, we have found that the advantage of the asymptotic method is its simplicity and efficiency.

Journal Article↗
PubMedDate not supplied

Nerve growth factor accelerates wound healing in diabetic mice.

Patients with diabetic neuropathy have reduced numbers of cutaneous nerves, which may contribute to an increased incidence of nonhealing wounds. Nerve growth factor (NGF) has been reported to augment wound closure. We hypothesized that topical 2.5S NGF, a biologically active subunit of the NGF polymer, would accelerate wound repair, augment nerve regeneration, and increase inflammation in excisional wounds in diabetic mice. A full-thickness 6-mm punch biopsy wound was created on the dorsum of C57BL/6J-m+ Leprdb mice (db/db) and heterozygous (db/-) littermates and treated daily with normal saline or 2.5S NGF (1 microg/day or 10 microg/day) on post-injury days 0-6. Time to closure, wound epithelialization, and degree of inflammation were compared using a Student's t-test. Color subtractive-computer-assisted image analysis was used to quantify immunolocalized nerves in wounds. Non-overlapping (20x) digital images of the wound were analyzed for nerve profile counts, area density (number of protein gene product 9.5 positive profiles per unit dermal area) and area fraction (protein gene product 9.5 positive area per unit dermal area). Healing times in db/db mice decreased from 30 days in normal saline-treated mice to 26 days in mice treated with 1 microg/day NGF (p<0.05) and 24 days in mice treated with 10 microg/day NGF (p<0.02). A similar trend in db/- mice was not significant. NGF treatment augmented epithelialization in the db/db mice (p<0.05). Histological evaluation of inflammation in healed wounds showed no statistical difference between treatment groups. Total nerve number, area density, and area fraction were increased in NGF-treated wounds at 14, 21, and 35 days (p<0.05). The 2.5 NGF subunit may improve wound closure kinetics by promoting epithelialization and nerve regeneration. Further studies to determine the role of nerves in wound repair are warranted.

Administration, Topical↗
PubMed1992

Heterogeneity of S-layer proteins of Lactobacillus acidophilus strains.

An S-layer (surface regular array) was found in the cell wall from six out of ten strains of Lactobacillus acidophilus examined by electron microscopic observations. All of the six strains which were shown to carry the S-layers belonged to the deoxyribonucleic acid (DNA) homology group A, but not to B, which had been classified by Johnson et al (Int. J. Syst. Bacteriol. 30: 53-68, 1980). On the other hand, the other four strains which possessed no S-layers were in the homology group B. The apparent molecular weights of the S-layer proteins ranged from 41 to 49 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Of the S-layer proteins from the six strains, three were susceptible to chemical cleavage with N-chlorosuccinimide, giving different peptide maps. All of the six S-layer proteins were fragmented by limited proteolysis with Staphylococcus aureus V8 protease, and gave markedly different peptide patterns by the subsequent peptide mapping analysis, except that the peptide maps of the S-layer proteins from the two strains which were in the same subgroup were identical.

Bacterial Outer Membrane Proteins↗
PubMed2006

Tob is a potential marker gene for the basal layer of the epidermis and is stably expressed in human primary keratinocytes.

BACKGROUND: Epidermis consists of multiple layers, from the proliferating basal layer to terminal differentiated cornified layers, and these layers are defined by differentiation status. Tob gene product is known to be a member of the BTG antiproliferative protein family. We investigated the expression pattern of Tob gene product to understand the possible role in differentiation of keratinocytes and epidermis. OBJECTIVES: In this study, we examined the expression of Tob gene product in the primary cultured human keratinocytes and in the in vivo epidermis. METHODS: The expression of Tob gene product was assessed by Western blotting analysis. Cellular localization of Tob was detected using the green fluorescent protein-tagged Tob cDNA expression construct. In vivo expression of Tob gene product in the epidermis was determined by immunohistochemistry with paraffin sections. RESULTS: Tob family members are degraded by the ubiquitine-proteasome system triggered by the growth signal. Tob is stably and abundantly expressed in primary cultured human keratinocytes. Furthermore, the expression of Tob in the keratinocytes persists during the differentiation induced by calcium; however, it was not detected in primary cultured fibroblasts. Also, the subcellular localization of Tob is mainly in the cellular membrane in the primary human keratinocytes. We evaluated Tob expression in normal skin, oral mucosa and different diseases, such as psoriasis, X-linked ichthyosis and squamous cell carcinoma (SCC). Using immunohistochemical analysis, we observed that Tob was selectively expressed in the basal layer of X-linked ichythyosis and the hyperproliferative basal layer of psoriasis and oral mucosa as well as in normal epidermis. In SCC, the expression of Tob gene product was relatively decreased. CONCLUSIONS: Tob is stably expressed in primary human keratinocytes and it is specifically expressed in the basal layer of in vivo epidermis.

Blotting, Western↗
PubMed2003

Self-assembly and recrystallization of bacterial S-layer proteins at silicon supports imaged in real time by atomic force microscopy.

The self-assembly of bacterial surface-layer (S-layer) proteins (SbpA of Bacillus sphaericus CCM 2177) at silicon supports (hydrophobic, non-plasma-treated and hydrophilic, O2 plasma-treated silicon supports) was imaged in real time by atomic force microscopy (AFM). A closed mosaic layer consisting of small crystals (less than 200 nm in diameter) was formed at a hydrophobic silicon support, whereas a coherent crystalline lattice consisting of large domains (2-10 micro m in size) was generated at O2 plasma-treated, hydrophilic silicon wafers. The structure of the formed layers was a monolayer (9 nm in height) at the hydrophobic silicon and a bilayer (15 nm in height) at the hydrophilic silicon. In situ AFM measurements confirmed the importance of ionic bonds in the formation of crystalline SbpA layers at silicon supports. Rupture of the protein subunits with a metal chelator from the crystalline lattice of SbpA was visualized in situ by AFM. The stability of solid-supported SbpA layers could be enhanced by cross-linking the S-layers with amino-amino or amino-carboxyl group directed cross-linkers.

Bacillus↗
PubMed1998

A novel dipstick developed for rapid Bet v 1-specific IgE detection: recombinant allergen immobilized via a monoclonal antibody to crystalline bacterial cell-surface layers.

The incidence of allergy to airborne proteins derived from tree and grass pollen, feces of mites, spores of molds, and pet dander has been increasing over the last decades. Since precise diagnosis is a prerequisite for successful immunotherapy, there is a rising demand for rapid, reliable, and inexpensive screening methods such as dipstick assays. With the purified recombinant major birch-pollen allergen rBet v 1a as model protein, crystalline bacterial cell-surface layers (S-layers) were tested for their applicability as an immobilization matrix for dipstick development. For this purpose, S-layers were deposited on a mechanically stable microporous support, cross-linked with glutaraldehyde, and free carboxylic acid groups of the S-layer protein were activated with carbodiimide. In the present test system, rBet v 1a was immobilized via the monoclonal mouse antibody BIP 1, which, unlike the allergen, is too large to enter the pores of the S-layer lattice, and which therefore formed a closed monolayer on the outermost surface of the crystal lattice. Moreover, BIP 1 is known to modulate IgE binding to the allergen. After incubation of the dipsticks in serum, washing of the reaction zone under tap water, and binding of an anti-IgE alkaline phosphatase conjugate, 5-bromo-4-chloro-3-indolyl phosphate/nitro blue tetrazolium was used as substrate, forming an IgE concentration-dependent colored precipitate on the S-layer surface. The investigation of patient sera previously tested with the CAP system confirmed the specificity of the S-layer-based dipstick assay. Since the dipstick is easy to handle and the whole test procedure takes only 90 min, this test system should be applicable for rapid determination of specific IgE and for first screening in the doctor's practice.

Allergens↗
PubMed2006

Developmental changes of neurotrophin mRNA expression in the layers of rat visual cortex.

Neurotrophins are essential factors for the structural, neurochemical and functional maturation of the brain including developmental and adult plasticity. Northern blots and polymerase chain reaction revealed the expression of neurotrophin 4 (NT4), neurotrophin 3 (NT3), brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in the cortex. The cellular producers of NT3 and BDNF have been characterized by anatomical methods as being mostly pyramidal, and the tyrosine kinase B (TrkB) receptor is expressed by many cortical neurons. However, these methods have so far failed to identify the cells producing NT4 and NGF mRNA. These factors are much lower in expression than, e.g. BDNF, and apparently remain below detection levels of in situ hybridization. Given their specific actions on cell types and afferent systems, knowledge about the producing cell types is highly desirable. To narrow down on the producing cell types, we quantified by reverse transcriptase-polymerase chain reaction (RT-PCR) the developmental changes of BDNF, NT3, NT4, NGF and TrkB mRNA expression in total visual cortex lysates, and in the cortical layers dissected by tangential cryostat sectioning. We found dramatic changes in laminar expression of NT3 and NGF, mild changes of NT4, and no changes of BDNF and TrkB mRNA. For instance, NT3 is important early on for thalamocortical axons, and we found transient peaks of NT3 mRNA expression first in layer VI, then in layer IV. NT4 mRNA was in layers IV and VI, suggesting NT4 protein production in thalamorecipient layers, but peak expression gradually shifted to upper layers as did NGF expression. The layer-specific developmental expression shifts of neurotrophin mRNAs correlate with morphogenetic processes.

Animals↗
PubMed2006

Homeostatic control of the excitation-inhibition balance in cortical layer 5 pyramidal neurons.

Homeostatic regulation in the brain is thought to be achieved through a control of the synaptic strength by close interactions between excitation and inhibition in cortical circuits. We recorded in a layer 5 pyramidal neuron of rat cortex the composite response to an electrical stimulation of various layers (2-3, 4 or 6). Decomposition of the global conductance change in its excitatory and inhibitory components permits a direct measurement of excitation-inhibition (E-I) balance. Whatever the stimulated layer was, afferent inputs led to a conductance change consisting of 20% excitation and 80% inhibition. Changing synaptic strengths in cortical networks by using a high-frequency of stimulation (HFS) protocol or a low-frequency of stimulation (LFS) protocol (classically used to induce long-term potentiation or long-term depression at the synaptic level) were checked in order to disrupt this balance. Application of HFS protocols in layers 2-3, 4 or 6, or of LFS protocols in layer 4 induced, respectively, long-term paralleled increases or long-term paralleled decreases in E and I which did not change the E-I balance. LFS protocols in layers 2-3 or 6 decreased E but not I and disrupted the balance. It is proposed that regulatory mechanisms might be mainly sustained by recurrent connectivity between excitatory and inhibitory neuronal circuits and by modulation of shunting GABA(A) inhibition in the layer 5 pyramidal neuron.

Animals↗
PubMed2006

Surface-layer protein extracts from Lactobacillus helveticus inhibit enterohaemorrhagic Escherichia coli O157:H7 adhesion to epithelial cells.

Adherence of intestinal pathogens, including Escherichia coli O157:H7, to human intestinal epithelial cells is a key step in pathogenesis. Probiotic bacteria, including Lactobacillus helveticus R0052 inhibit the adhesion of E. coli O157:H7 to epithelial cells, a process which may be related to specific components of the bacterial surface. Surface-layer proteins (Slps) are located in a paracrystalline layer outside the bacterial cell wall and are thought to play a role in tissue adherence. However, the ability of S-layer protein extract derived from probiotic bacteria to block adherence of enteric pathogens has not been investigated. Human epithelial (HEp-2 and T84) cells were treated with S-layer protein extract alone, infected with E. coli O157:H7, or pretreated with S-layer protein extract prior to infection to determine their importance in the inhibition of pathogen adherence. The effects of S-layer protein extracts were characterized by phase-contrast and immunofluorescence microscopy and measurement of the transepithelial electrical resistance of polarized monolayers. Pre-treatment of host epithelial cells with S-layer protein extracts prior to E. coli O157:H7 infection decreased pathogen adherence and attaching-effacing lesions in addition to preserving the barrier function of monolayers. These in vitro studies indicate that a non-viable constituent derived from a probiotic strain may prove effective in interrupting the infectious process of an intestinal pathogen.

Bacterial Adhesion↗
PubMed2005

The salmon vertebral body develops through mineralization of two preformed tissues that are encompassed by two layers of bone.

The teleost backbone consists of amphicoelous vertebrae and intervertebral ligaments, both of which include notochord-derived structures. On the basis of a sequential developmental study of the vertebral column of Atlantic salmon (Salmo salar L.) from the egg stage up to early fry stage (300-2500 day-degrees) we show that the vertebral body consists of four layers or compartments, two of which are formed through mineralization of preformed collagenous tissue (the notochordal sheath and the intervertebral ligament) and two of which are formed through ossification. The three inner layers have ordered lamellar collagen matrixes, which alternate perpendicularly from layer to layer, whereas the outer layer consists of cancellous bone with a woven matrix. The bone layers also differ in osteocyte content. In this study we describe the structural details of the layers, and their modes of formation. The results are compared with previous descriptions, and possible phylogenetic implications are discussed.

Animals↗
PubMed1985

Laminar distributions of choline acetyltransferase and acetylcholinesterase activities in the inner plexiform layer of rat retina.

Choline acetyltransferase and acetylcholinesterase activities were measured in samples taken at 7-micron increments through the inner plexiform layer of rat retina. These enzyme activities were not uniformly distributed through the depth of the inner plexiform layer. Peaks of choline acetyltransferase activity occurred at about one-third and peaks of acetylcholinesterase activity at about one-fifth of the depth into the inner plexiform layer from either side. The positions of the two peaks of choline acetyltransferase activity most likely correspond to the locations of processes from cholinergic amacrine somata in the inner nuclear layer, which spread in sublamina a, and processes from cholinergic amacrine somata "displaced" in the ganglion cell layer which spread in sublamina b of the inner plexiform layer. The peaks of acetylcholinesterase activity may in addition correspond to the processes of cholinoceptive amacrine and ganglion cells. The magnitudes of choline acetyltransferase and acetylcholinesterase activities are as high as found anywhere in rat brain, emphasizing the important role of cholinergic mechanisms in visual processing through the rat inner plexiform layer.

Acetylcholinesterase↗
PubMed1998

Layer-specific pathways for the horizontal propagation of epileptiform discharges in neocortex.

PURPOSE: Epileptiform discharges that resemble interictal spikes can be generated by slices of neocortex treated with antagonists of gamma-aminobutyric acid A (GABA(A)) receptors. These discharges can propagate horizontally for long distances. We tested the hypothesis that propagation occurs through preferred horizontal pathways that lie in a particular cortical layer. METHODS: Slices were prepared from the primary somatosensory cortex of rats, maintained in vitro, and bathed with the GABA(A) receptor antagonist picrotoxin. Electrical stimuli were used to evoke single all-or-none paroxysmal field potentials (PFP) that were recorded with pairs or arrays of field potential electrodes. RESULTS: To test which laminae are necessary for propagation, vertical cuts were made to force the PFP to spread horizontally through particular layers. If slices were bathed in a high dose of picrotoxin (35 microM), a bridge of cortex 350 microm thick placed at any lamina was sufficient to support PFP propagation. However, in low picrotoxin doses (2.5 microM), similarly sized bridges had to include tissue from layers 4/5 or 5/6 to support propagation. When slices were cut horizontally (i.e., parallel to the pia) in strips. either upper-, middle-, or lower-layer strips were sufficient to support PFP propagation if the picrotoxin concentration was high; however, in low picrotoxin doses, only horizontal strips that included layer 5 could support propagation. Finally, in intact picrotoxin-treated slices, focal applications of GABA were systematically applied to different laminae as the PFP propagated past; GABA was most effective at blocking or delaying propagation when it was applied to layer 5b. CONCLUSIONS: We conclude that epileptiform propagation can occur through a variety of horizontal pathways when cortical inhibition is strongly impaired. However, when inhibition is reduced only moderately, axonal pathways in layer 5 are critical for seizure spread.

Animals↗
PubMed2005

Physiological changes in chronic epileptic rats are prominent in superficial layers of the medial entorhinal area.

PURPOSE: We investigated whether the functional network properties of the medial entorhinal area (MEA) of the entorhinal cortex were altered in a rat model of chronic epilepsy that is characterized by extensive cell loss in MEA layer III. METHODS: Responses were evoked in the entorhinal cortex by electrical stimulation of the subiculum in anesthetized chronic epileptic rats, 2-4 months after status epilepticus, induced by systemic kainate (KA) injections. Laminar field potentials were measured using a 16-channel silicon probe that covered all six layers of the MEA; an estimate of the local transmembrane currents was made using current source density analysis. RESULTS: Double-pulse stimulation of the subiculum evoked responses in deep and superficial layers of the MEA in control and KA rats. A current sink in layer I and at the border of layer I and II that was induced by antidromic activation of MEA-II, was much more prominent in KA rats with extensive neuronal loss in MEA-III than in control rats or KA rats with minor MEA-III loss. Furthermore, KA rats that displayed MEA-III loss presented a series of oscillations induced by subicular stimulation in the beta/gamma-frequency range (20-100 Hz), which were confined to superficial layers of MEA. These oscillations were never observed in control rats or KA rats with minor MEA-III loss. CONCLUSIONS: These results indicate that the observed alterations in the superficial MEA responses to subiculum stimulation and the occurrence of beta/gamma-oscillations are related phenomena, which are a consequence of altered and impaired inhibition within these MEA layers in chronic epileptic rats.

Animals↗