Neural Aggregates Research Articles

Alternate neural network models in decision making for socio-economic development

Alternate neural network models are used to identify the structure of preferences for development alternatives and their consequences in the cases of Doon Valley and National Capital Region in India in the context of carrying-capacity-based developmental planning. Alternate neural network models are presented as an effective alternative to deal with multi-criteria decision-making situations. The performance of fuzzy neural network has been compared with crisp neural and hierarchical fuzzy aggregation networks to validate the predictive capability. The models are used for the prediction of preference indices for developmental options in the year 2021 AD.

A unified approach to aggregation based upon mom and mam operators

The focus of this article is on the issue of information aggregation. We introduce two new aggregation operators, called MOM and MAM operators, which are, respectively, generalized and and or operators. We describe their relationship to the multivalued logic triangular norm operators and show how they generalize these operators by weakening the associativity property. We provide a duality theorem between these new operators. We present some special classes of these operators. We extend these operators to allow for weighted aggregations, which enable us to include importances. We introduce some families of these weighted MOM and MAM operators. We show how the typical neural aggregation is a special class of these weighted MOM and MAM operators. This generalization allows us to consider neural network and fuzzy logic methods in the same framework. © 1995 John Wiley & Sons, Inc.

Identification of a Cell Surface-Associated Protein Involved in Mouse Neural Cell Aggregation by Means of Antibodies Against the Sponge Aggregation Factor

Polyclonal antibodies were raised against the purified aggregation factor (AF) from the sponge Geodia cydonium to elucidate possible immunological relationships between adhesion molecules of lower multicellular eukaryotic systems (sponges) and those of vertebrates. This anti-AF recognized a series of polypeptides associated with the AF, among them also a polypeptide with a Mr of 47,000 (p47). The formation of the antibody-p47 immunocomplexes could be prevented by adsorbing the anti-AF with a brain extract from DBA/2J mice. Moreover, this brain polypeptide inhibited the AF-mediated aggregation of sponge cells. Interestingly, the anti-AF recognized a p37 molecule in the brains of 2- to 3-day-old mice; no reaction could be traced using brain extracts from animals older than 2 months. The anti-AF failed to interact with polypeptides from mouse liver or spleen. By indirect immunofluorescence staining the p37 was found to be localized on the plasma membranes of brain cells. Moreover, Fab' fragments of the anti-AF inhibited aggregation of mouse brain cells. These data indicate that the sponge anti-AF recognizes a p37 molecule in mouse brain cells which is either directly or indirectly involved in brain cell aggregation.

Slow transmission of neural activity in hippocampal area CA1 in absence of active chemical synapses.

Transmission of neural activity in the mammalian cortex involves the operation of chemical synapses. Here we report that activity of hippocampal pyramidal cells (HPC) in vitro can spread through the neural aggregate even when chemical synaptic transmission is blocked by lowering the external Ca2+ concentration ( [Ca2+]0). In these conditions focal stimulation of the HPC body layer (stratum pyramidale) at area CA1 evokes a localized repetitive neural response which, when large enough, spreads along this layer in both transverse directions. It was recently reported for similar conditions that the activated HPC often discharge in synchrony. However, the spread of the neural response does not depend upon the occurrence of synchronized HPC activity, and therefore represents a distinct phenomenon.

Some Effects of the Tumor Promoter 12-<italic>O</italic>-Tetradecanoylphorbol 13-Acetate on Cell Interactions In Vitro<xref ref-type="fn" rid="fn2">2</xref>

Studies were made of the effects of the potent tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA), 4-O-methyl TPA (4-O-MeTPA), and 4 alpha phorbol 12,13-didecanoate (4 alpha PDD) on the aggregation of embryonic chick cells in gyratory shaker culture, a model system useful for the study of cell adhesion and cell interactions. TPA and, to a lesser extent, 4-O-MeTPA significantly reduced the neural retina aggregate size at concentrations as low as 10(-9) M and 10(-8) M, respectively. An inactive isomer, 4 alpha PDD, had no effect up to 10(-6) M. The reduction in aggregate size appeared related to promoter activity since dexamethasone, a steroid that inhibits tumor promotion by TPA, significantly reversed the inhibitory effect of TPA. None of the agents tested affected the sorting pattern in mixed neural retina and heart cultures. The results indicate that intercellular adhesion, as determined by extent of aggregation, is reduced in the presence of TPA. This inhibition is considered to be related to the tumor-promoting activity of TPA.

A stereotaxic system for independent coordinated positioning of two or three microelectrodes

This paper describes a straightforward, easily built and relatively inexpensive stereotaxic system that permits independent coordinated positioning of 2 or 3 microelectrodes. This system is ideally suited for situations where the ability to routinely place one electrode at a precise position relative to another is important. Resolution of relative position and interelectrode distance is ±50 μm. This system should prove useful for the study of local interactions in such neural aggregates as nuclei, motoneuron pools and within and between cortical columns.

Cells from normal and malignant human colon mucosa differentially inhibit embryonic cell aggregation.

A model system for studying some aspects of the interaction of cancer cells in tumors and their surrounding nonmalignant tissue is the co-culture of cancer cells and embryonic chick neural retinal cells in gyratory shakers. Neural retina cell aggregation, under these conditions, has been shown to be differentially inhibited by small numbers of cultured mouse and human cancer cells. We extend here these observations to co-cultures of retinal cells with small numbers (60:1 ratio) of human cells isolated from normal colon mucosa or colonic adenocarcinoma tissue. The cells from the malignant tissue samples inhibited aggregation to a significantly greater extent than the cells from normal mucosa, even when both were from the same individual. Cells derived from nonmalignant tumors were more inhibitory than those from normal individuals, which is consistent with described differences in this 'transitional' region. Thus, the aggregation inhibition assay appears applicable to freshly isolated human tissues.

The physiological basis of epileptogenic neural aggregates

The physiological basis of epileptogenic neural aggregates

Differential Inhibition of In Vitro Malignant Cell Assays by B16 Mouse Melanoma Variants<xref ref-type="fn" rid="FN2">2</xref>

Neural retina aggregation and adhesion assays, shown to be sensitive to the presence of small number of malignant cells, were differentially inhibited by cells or medium from B16 mouse melanoma sublines with higher metastatic characterizations, which suggests a correlation between inhibition of adhesion and aggregation and metastatic potential.

The effects of tumour cells on embryonic cell aggregation, adhesion and detachment.

The presence of small numbers of tumour cells inhibits the aggregation of embryonic chicken neural retina cells grown in gyratory shaker culture. The aggregation of neural retina cells was also inhibited by ascites cell medium. We investigated whether the inhibitory effect of the tumour cells on aggregate size is effected by inhibition of the initial adhesion or by enhancement of their separation. The number of neural retina cells adherent to microtest plate surfaces was significantly reduced after incubation with either Ehrlich ascites cells or cell-free, conditioned medium, while the percentage of cells removed from glass by shearing was unchanged under those conditions. These results suggest that the reduction in neural retina cell aggregate size produced by Ehrlich ascites cells and their products is due to partial inhibition of neural retina cell adhesion processes, as distinct from enhancement of separation.

An extended first approximation model for the amygdaloid kindling phenomenon

A first approximation model, which accounts for the strongest phenomena defining kindling is suggested. It is based on an excitatory-inhibitory coupling of neural aggregates, to which a self-stimulation element for the excitatory aggregate was added. The functional linking hypothesis views the representation of kindling as a process of gradual transition through structural changes from a stable system to a system showing stability for small perturbations and an oscillatory orbit for larger perturbations, to a purely oscillatory system. The anatomical linking hypothesis views the excitatory aggregate as representing the hypothalamus, the inhibitory aggregate as representing the hippocampal-septal-preoptic complex, and the selfstimulating element of the excitatory aggregate as representing the amygdaloid-pyriform complex. The model was realized on a digital computer with graphic capabilities and showed good qualitative agreement with the experimental data related to kindling. In addition, the use of the model for generating new experiments is discussed.

Scalp distribution of early (0 to 10 msec) auditory evoked responses.

Auditory nerve and brain stem evoked responses were summated from multiple scalp and earlobe electrodes from five subjects with normal hearing to determine the spatial voltage relationships along the coronal and/or sagital planes that make up the electrode array. All recordings maintained their positive polarity, and polarity inversions were not observed at any cephalic sites; thus, a null potential line was not identified for these short-latency potentials at the scalp. Less distinct potentials were derived from the earlobes when referenced to the chin. Linked earlobes generated some potentials of negative polarity. These observations lend additional support to the concept that early auditory scalp potentials are most likely generated from far field neural aggregates located caudally to the auditory cortex.

Reduction of stimulation-produced analgesia by lysergic acid diethylamide, a depressor of serotonergic neural activity

MAYER Neurobiology and Anesthesiology Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, Md. 20014 and Departments of Physiology and Pharmacology, Medical College of Virginia, Virginia Commonwealth University, Richmond, Va. 23298 (U.S.A.) (Accepted November 18th, 1976) it is now well known that electrical stimulation of the mesencephalic centrai gray matter in the region of the dorsal raphe nucleus (DRN) produces a profound behavioral analgesia in rat22, 25, cat 26,z8 and monkey 11,a7. In man, stimulation of areas of the periaqueductal gray matter also relieves both chronic clinical and acute experimental pain aS. A number of observations suggest that serotonin participates in the production of this analgesia. Akil and Mayer a have shown that stimulation-produced analgesia (SPA) can be reduced in the rat by p-chlorophenylalanine (p-CPA), a serotonin syn- thesis inhibitor. Reduction in SPA was greater for stimulation sites closer to the DRN, a densely serotonergic neural aggregate 7, thereby further implicating an involvement of this monoamine. Reduction of SPA by p-CPA can also be reversed by the adminis- tration of 5-hydroxytryptophan (5-HTP), the precursor of serotonin 2. Electrical stimulation of the central gray matter has also been shown to have effects at an electrophysiological level. Liebeskind and coworkers ~a,20 have demon- strated in the cat that this stimulation inhibits the responsiveness of dorsal horn lamina V cells to noxious stimuli. They reported that D-lysergic acid diethylamide (LSD) antagonized this inhibition. Although stimulation at many sites within and adjacent to the central gray was effective in inhibiting the responses of lamina V cells to noxious stimuli, LSD greatly reduced the inhibitory effects of only stimulation sites in the immediate vicinity of the serotonergic DRN. Data are also available showing that the closer the electrode is to the DRN of the cat, the greater the magnitude of SPA at a given current intensity a0. These observations, coupled with the demonstration that LSD is a directly acting and potent inhibitor of neural activity of the serotonin-containing neurons of the DRN 14, led us to examine the behavioral effect of LSD on SPA. If LSD were to antagonize SPA it would: (1) provide additional data on the possible role of serotonin systems in this phenomenon and (2) demonstrate that previous electrophysiological observations of the effects of LSD on nociceptive neurons have a behavioral correlate. In these experiments, 90-day-old, male Holtzman rats were implanted with a

Focal alteration of dendrites and astrocytes in rat cerebral cortex during initiation of cobalt-induced epileptiform activity

The epileptic focus induced by pial surface iontophoresis of cobalt is exquisitely confined to the upper three laminae of sensorimotor cortex, occupying a tissue volume of 130 mm 3 showing no light microscopic evidence of injury to neural cells. At the time of initiation of epileptiform discharge, ultrastructural cytopathology is relatively confined to dendrites and astrocytes, which are severely distended in association with dispersion of their organelles. Neuronal perikarya, axons, synaptic terminals, and blood vessels are relatively unaffected, and no alteration of fine structure is seen in lower cortical layers. Ionic cobalt induces a major disturbance of cation homeostasis in neural aggregates of cerebral cortex, manifested by cytopathologic effects during the initiation of epileptiform discharge, which are relatively confined to the intracellular compartment of dendrites and astrocytes.

Secondary epileptogenesis in frog forebrain: effect of inhibition of protein synthesis.

Secondary epileptogenesis was induced in the hippocampal cortex of the paralyzed bullfrog by means of localized, unilateral, intermittent electrical stimulation (kindling). Stimuli were designed to yield a brief but definite after-discharge. In control animals a progressive increase in after-discharge duration occurred at the 1 degree (stimulated) site and then at the 2 degrees site (contralateral hippocampus). Spontaneous epileptiform potentials (SEP's) occurred between stimuli, eventually independently on both sides. Cycloheximide (50 mg/kg) caused 88-99% reduction in protein synthesis, measured by 14C-leucine incorporation into brain protein. Cycloheximide-treated animals revealed no evidence of progressive prolongation of after-discharge duration when subjected to the kindling procedure (p = 0.1205 X 10(-7)). SEP's were reduced in the cycloheximide-treated animals, and confined to 1 degree hemisphere (p = 0.6 X 10(-10)). Since cycloheximide did not disturb normal electrogenesis or disrupt the after-discharges, this experiment distinguishes processes dependent upon electrical events from those requiring macromolecular synthesis. Protein synthesis seems critical to the emergence of spontaneous and autonomous epileptiform behavior of neural aggregates.

Cell interactions and histogenesis in embryonic neural aggregates

Mixtures of cell suspensions from the optic lobe of 3-day-old and 6-day-old chick embryos form aggregates which show many ‘rosettes’ resulting from the invagination of peripheral ‘placodes’. However, in aggregates formed exclusively by optic lobe cells of either 3-day-old or 6-day-old embryos no rosettes are observed. By means of radioautographic studies of the combined aggregates, it was shown that rosettes are formed almost exclusively by cells from 3-day-old optic lobe, while those of 6-day-old embryos are predominantly found at the periphery of the aggregates. Cells from 3-day old optic lobe also form rosettes when cultured in combination with wing cells. Similar observations were done in aggregates formed by mixtures of 3-day-old optic lobe and 6-day-old liver cells. The cells from the optic lobe of 3-day-old embryos forming the concave surface of invaginating placodes and rosettes in the ‘combined’ aggregates appear polarized and wedge- or ‘bottle’-shaped. They are aligned in a highly ordered way, and abundant zonula adhaerentes, usually parallel to the cell major axis, are found at the cell apex where bundles of longitudinally oriented microtubules are present. The 3-day-old optic lobe cell which form the convex external surface of the ‘pure’ aggregates have a similar shape and organization, but in this situation apical cell bulges with randomly oriented microtubules interdigitate with those from neighbouring cells, and are joined by zonula adhaerentes usually perpendicular to the longitudinal axis of the cell.

Ultrastructural changes associated with an invagination phenomenon in embryonic neural aggregates

Aggregates formed by cell suspensions from the optic lobe of 4-day-old chick embryos have peripheral “placode-like” structures, which give rise by ulterior invagination to miniature neural tube-like structures, the rosettes. These events are accompanied by changes in cell shape, cell structure and cell contacts as shown by electron microscopy. Aggregates recovered after 1.5 h culture show a very poor histological organization. The neuroepithelial cells (NE cells) appear irregularly shaped, without any recognizable apico-basal polarity. Most of the cell surface faces wide intercellular spaces, although there is some apposition of adjacent plasma membranes, as well as a few junctional differentiations, between cell bodies, cell processes, and cell bodies and processes. The microtubules of the NE cells are scarce, and are apparently distributed at random. No particular orientation of NE cells with respect to each other is observed. Concomitantly to the formation and invagination of placodes the NE cells undergo several structural changes. They become wedge- or bottle-shaped, and are aligned in a highly ordered way within individual placodes and rosettes. Cell contacts involve most of the cell surface, while abundant zonula adhaerentes are present exclusively at the cell apex. The nucleus and some organelles of the NE cells are polarized; bundles of microtubules oriented along the cell major axis are found at the apical region of the cells.