Biomedical subjects

C Gall

Publications and source records attributed to C Gall.

At least 37 records · Page 2Linked to original sources

PubMed1990

Induction of ornithine decarboxylase by subseizure stimulation in the hippocampus in vivo.

Electrical stimulation of the Schaffer-collateral axonal system under conditions which do not elicit detectable seizure activity causes an increase in the activity of ornithine decarboxylase (ODC), the rate limiting enzyme of polyamine synthesis, in the hippocampus, olfactory cortex, neocortex and olfactory bulb. The degree of ODC activation is dependent upon the stimulus parameters. The results support the hypothesis that neuronal activity regulates hippocampal polyamine concentrations.

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PubMed1990

Seizures, neuropeptide regulation, and mRNA expression in the hippocampus.

Recent studies have demonstrated that the regulation of neuropeptide expression in forebrain neurons is responsive to external influences including changes in physiological activity. This has been demonstrated most clearly in studies of hippocampus where the synthesis and resting levels of several neuropeptides, localized within well-characterized components of hippocampal circuitry, have been shown to be selectively influenced by seizure activity. In studies described here, we examined the influence of recurrent limbic seizures on the expression of enkephalin, dynorphin, cholecystokinin, and neuropeptide Y (NPY) in rat and mouse hippocampus using immunohistochemical, in situ hybridization and blot hybridization techniques. The data demonstrate that seizures differentially influence the expression of each peptide as a part of a broader cascade of changes in genomic expression within individual hippocampal neurons. In particular, seizures increase preproenkephalin mRNA and enkephalin peptide but decrease dynorphin peptide in the dentate gyrus granule cell/mossy fiber system. Seizure-induced decreases in the concentration of preprodynorphin mRNA in the granule cells have been reported by others. Immunoreactivity for CCK, which is codistributed with the opioid peptides in the mossy fiber system of mouse, is also dramatically reduced in the granule cell axons by seizure. Recurrent seizures induce two temporally distinct changes in NPY expression in hippocampus. First, there is an increase in hybridization to preproNPY mRNA within scattered, probable local circuit neurons in all subfields. This is followed by the seemingly novel appearance of preproNPY mRNA within the dentate gyrus granule cells and pyramidal cells of field CA1. Clues about mechanisms of neuropeptide regulation have come from observations of other, more rapid, transcriptional events induced by seizure. Most notably, our results and those of others demonstrate that seizures increase the expression of messenger RNAs from immediate-early genes (c-fos, c-jun, and NGFI-A) which encode proteins that may mediate neuropeptide gene regulation. In addition, mRNA for nerve growth factor is dramatically increased in the dentate gyrus granule cells by seizure; increased production of this trophic factor might mediate the more delayed changes in genomic expression and growth responses observed to occur in hippocampus and other forebrain areas following seizure activity.

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PubMed1990

Levels of mRNA for a putative kainate receptor are affected by seizures.

In situ hybridization and RNA blot-hybridization techniques were used (i) to examine the regional distribution of mRNA for a putative kainate receptor in adult rat brain and ii) to test the possibility that seizures affect expression of the receptor gene. The highest densities of hybridization were distributed within hippocampal pyramidal and granule cells, medial habenula, Purkinje cells and the molecular layer of cerebellum, and olfactory bulb. Recurrent limbic seizures caused a massive, delayed, and reversible reduction in levels of the kainate receptor mRNA in dentate gyrus; lesser decreases were found in pyramidal cell fields of hippocampus and superficial cortex. These findings provide evidence that unusual patterns of physiological activity can alter genomic expression for a subclass of glutamate receptors in brain.

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PubMed1989

Continuities between outer nuclear membrane and the rough endoplasmic reticulum increase in hippocampal neurons during seizure-induced protein synthesis.

The ultrastructure of rat dentate gyrus granule cells was examined during, and near the termination of, a period of lesion-induced recurrent limbic seizure activity which has previously been demonstrated to stimulate dramatic changes in the biosynthetic activities of these neurons. In animals sacrificed 5 h postlesion (or 3.5 h following seizure onset) the rough endoplasmic reticulum (RER) appeared more extensive than in controls and there was a large, statistically significant increase in the number of continuities between the RER and the outer nuclear membrane (ONM). By 11 h postlesion the latter index had returned to control values although the presence of numerous elevations of the ONM lying in close proximity to free segments of RER was considered indicative of recent dissolution of contact. These data demonstrate modifications in the arrangement of organelles involved in protein synthesis during a period in which the patterns of synthesis by the granule cells are changing but which do not persist through the full period of seizure-induced alterations in synthetic activity.

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PubMed1988

The ultrastructural localization of calcium-activated protease "calpain" in rat brain.

Calpain I, a calcium-activated neutral protease which degrades a number of cytoskeletal proteins, has been implicated in the rapid turnover of structural proteins that may participate in synaptic plasticity. In the present study, an antibody raised against purified erythrocyte calpain I was biochemically characterized and demonstrated to specifically bind the Mr = 80,000 subunit of both rat erythrocyte and brain calpain I. This antibody was used to examine the cellular distribution of calpain I at the electron microscopic level in rat brain and spinal cord using the avidin-biotin immunocytochemical technique. Reaction product was observed throughout neuronal perikarya, within both axonal and dendritic processes, and within spine heads and necks. Postsynaptic densities in both shaft and spine synapses were also immunoreactive. Glial cell bodies and processes were densely stained. In both neurons and glia, the reaction product was deposited along cytoskeletal elements. The localization of calpain I immunoreactivity to glial processes suggests this degradative enzyme may play a role in the glial hypertrophy and process retraction seen in brain. The presence of the enzyme in spines and postsynaptic densities is consistent with the hypothesis that it is involved in the turnover of synaptic cytoskeleton, thus providing a means through which transient physiological events effect lasting changes in the chemistry and morphology of spines.

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PubMed1988

Induction of ornithine decarboxylase in adult rat hippocampal slices.

Several factors involved in the regulation of ornithine decarboxylase (ODC) activity in adult rat brain tissue have been identified by using the in vitro hippocampal slice preparation. The same amino acids that have previously been reported to induce ODC in tissue culture, i.e., asparagine and glutamine, were found to produce a concentration- and time-dependent increase in ODC activity that reached a 100 fold the control value after 6 h of incubation. The effect of asparagine was totally blocked by inhibition of either protein or RNA synthesis, suggesting that the inducing amino acids increase ODC activity by stimulating the transcription of genes directly or indirectly regulating ODC activity. The effect of the inducing amino acids was potentiated by a variety of factors which by themselves did not modify ODC activity. In particular, opioid peptides markedly potentiated the effect of asparagine. Although the opiate antagonists naloxone and naltrexone totally blocked the effects of the opioid peptides on ODC induction, they also produced an inhibition of the asparagine-mediated increase in ODC activity. Other factors like dibutyryl cyclic AMP and insulin also potentiated the effects of asparagine on ODC activity. These results provide the first description of ODC induction in an in vitro preparation of adult brain tissue and indicate that the hippocampal slice preparation could be used to study the molecular mechanisms which regulate the expression and activity of ODC in the adult central nervous system. Moreover the data suggest possible mechanisms which may be involved in the induction of ODC in hippocampus by seizure activity.

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PubMed1988

Seizures induce dramatic and distinctly different changes in enkephalin, dynorphin, and CCK immunoreactivities in mouse hippocampal mossy fibers.

Light microscopic immunocytochemical techniques were used to evaluate the influence of recurrent limbic seizure activity on the immunoreactivity for 3 neuropeptides--enkephalin, dynorphin, and cholecystokinin (CCK)--contained within the mouse hippocampal mossy fiber axonal system. Seizures were induced either by the placement of a small unilateral electrolytic lesion in the dentate gyrus hilus or by intraventricular injection of kainic acid. Both treatments induce epileptiform activity in hippocampus lasting several hours. Four days after either lesion placement or injection of 0.05-0.1 microgram kainic acid, immunoreactivity for all 3 peptides was altered throughout the intact mossy fiber system, bilaterally, but in distinctly different ways: enkephalin immunoreactivity (ENK-I) was dramatically elevated, dynorphin immunoreactivity was reduced, and CCK immunoreactivity (CCK-I) was either severely reduced or completely absent in the mossy fiber system. ENK-I was also clearly increased in other areas, including the lateral septum, the entorhinal cortex, and within the entorhinal (perforant path) efferents to temporal hippocampus. In contrast, the loss of CCK seemed restricted to the mossy fiber system in that immunostaining appeared normal in scattered hippocampal perikarya, within the dentate gyrus commissural system, as well as within other limbic structures. Four days after injections of 0.2 or 0.25 microgram kainic acid, mossy fiber ENK-I was greatly elevated, dynorphin immunoreactivity was reduced, but, unlike the situation with lower kainic acid doses, CCK-I was only modestly reduced in the mossy fibers and was clearly reduced in other hippocampal systems as well. These data indicate that epileptiform physiological activity differentially affects the regulation of 3 neuroactive peptides contained within the hippocampal mossy fiber system and suggest a mechanism through which seizurelike episodes can have a lasting influence on the operation of specific hippocampal circuitries.

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PubMed1987

Co-localization of enkephalin and cholecystokinin in discrete areas of rat brain.

A double-label immunofluorescence technique was used to demonstrate that immunoreactivities for the functionally antagonistic neuropeptides enkephalin and cholecystokinin octapeptide (CCK) are co-localized within individual neurons and processes in discrete areas of rat midbrain and forebrain. Coexistence was most prominent within varicose pericellular axons extending from the periaqueductal gray matter to a field overlying the medial lemniscus, axons and terminal-like puncta in the central medial, paracentral, interanterodorsal and ventral anterior thalamic nuclei, and perikarya and proximal axonal fragments in layers II and III of neo- and allocortex, and in the anterior olfactory nucleus. The former two systems of axons lie in areas of spinothalamic tract termination. These data suggest that some of the antagonism of opioid analgesia by CCK occurs at the synaptic level in nociceptive areas of brain-stem and thalamus where CCK and enkephalin are co-localized and presumably co-released.

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PubMed1986

Distribution of VIP- and NPY-like immunoreactivities in rat main olfactory bulb.

The distribution of vasoactive intestinal peptide (VIP)- and neuropeptide Y (NPY)-like immunoreactivities in the Sprague-Dawley rat main olfactory bulb was analyzed using the peroxidase-antiperoxidase light microscopic immunocytochemical technique. VIP-like immunoreactivity was most prominently localized within a large number of intermediate-sized neurons whose perikarya and extensively branched varicose processes remained confined to the external plexiform layer (EPL). A few small short-axon type neurons in the mitral cell layer and granule cell layer (GRL) and even fewer large neurons in the glomerular layer (GL)/EPL border region contained immunoreactivity for VIP as well. Neuropeptide Y-like immunoreactivity (NPY-I) was principally localized within sparsely distributed large multipolar neurons of the deep GRL and within axons distributed with diminishing density from deep to superficial GRL. In addition, dense NPY-I was localized within very few large superficial short-axon type neurons of the GL/EPL border region. The restricted laminar and cellular distribution of NPY-I and VIP-I suggests that both peptides may act to modulate granule cell activity, and therefore, indirectly, olfactory bulb output.

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PubMed1986

Cholecystokinin in the mouse hippocampus: localization in the mossy fiber and dentate commissural systems.

The distribution and source of cholecystokinin-like immunoreactivity (CCK-I) in the hippocampus of the Swiss Webster mouse was analyzed using light microscopic immunocytochemical techniques. In agreement with what has been observed in other animals, CCK-I was localized within sparsely scattered neurons throughout the hippocampus proper, in axons that arborize within and around stratum pyramidale, and in fine axons and puncta in stratum lacunosum-moleculare of region CA1. In contrast to other animals, CCK-I was also localized within the mossy fiber system (including dentate gyrus granule cells), within a dense band which occupied the full septo-temporal extent of the dentate gyrus inner molecular layer, and within polymorph neurons of the central hilus. The presence of CCK-I within the latter two areas suggested localization within the dentate gyrus commissural system. This was verified by the combined use of retrograde fluorescent dye transport and CCK immunocytochemistry. Virtually all of the dye-labeled dentate commissural neurons within the hilus were CCK-I. These data demonstrate that while there is little change in the distribution of CCK-I within hippocampal local circuit neurons across animals, there are substantial interspecies differences in the localization of CCK-I within major axonal projections in the hippocampal formation.

Amidines↗

PubMed1986

Induction of ornithine decarboxylase as a possible mediator of seizure-elicited changes in genomic expression in rat hippocampus.

Small electrolytic lesions placed in the hilus of the dentate gyrus have been shown to induce behavioral seizures, an elevation in the concentration of the opioid peptide enkephalin, and an increase in the transcription of the gene coding for the peptide precursor of enkephalin. Since polyamines and ornithine decarboxylase (ODC), the rate-limiting enzyme in their synthesis, have been shown to play critical roles in the growth and differentiation of several types of tissue, we tested for changes in ODC activity at various times following the initiation of seizures. ODC activity is significantly increased 3 hr after the lesions, reaches maximal (50-fold) levels about 12 hr later, and returns to control values after 48 hr. The increase occurs in both hippocampi following unilateral electrolytic lesions, is blocked by treatments that suppress limbic seizures, and does not occur after lesions that fail to elicit seizures; accordingly, we conclude that the increase in ODC activity results from epileptiform activity rather than some other consequence of the hilar lesion (e.g., deafferentation). The increase in ODC activity precedes the increase in the amount of mRNA coding for the enkephalin prohormone, which, in turn, precedes the increase in enkephalin levels. These results are consistent with the hypothesis that the early induction of ODC following the initiation of seizures leads to an alteration in genomic expression, which, in turn, changes neuropeptide levels. Adult brains thus appear to possess trophic responses of a type found in a variety of developing cell types and organs, and the possibility exists that these are involved in the control of seizure susceptibility.

Adrenalectomy↗

PubMed1985

Distribution of calpain I, an enzyme associated with degenerative activity, in rat brain.

The calcium-activated protease calpain I was localized in rat brain by immunocytochemistry. Calpain I-like immunoreactivity (CLI) was prominent in several structures in which degeneration is an ongoing feature, e.g. spinal motoneurons, olfactory nerve. Also noteworthy was the presence of CLI in regions susceptible to age-related pathologies, e.g. cerebellar Purkinje cells, substantia nigra and subiculum. This distribution suggests that calpain I may be involved with both normal and pathological neuronal degeneration.

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PubMed1985

Distribution of cholecystokinin-like immunoreactivity in the rat main olfactory bulb.

The anatomical localization of cholecystokinin-like immunoreactivity (CCK-I) within the rat main olfactory bulb was analyzed by using the peroxidase-antiperoxidase immunocytochemical technique. Neurons or neuronal processes containing CCK-I were localized within all laminae of the olfactory bulb except the olfactory nerve fiber layer. A large population of CCK-I neurons, with morphology, size, and distribution corresponding to that of the middle and external tufted cells, was observed within a zone extending from the deep periglomerular region through the superficial one-half to one-third of the external plexiform layer. A smaller number of immunoreactive perikarya were found in the deep external plexiform layer, the glomerular layer, and rarely within the inner plexiform layer. These CCK-I neurons appeared to correspond to internal tufted cells, periglomerular cells, and deep short-axon cells, respectively. Dense CCK-I staining of fibers and terminals was present within the internal plexiform layer and, less densely, within the neuropil of the granule cell layer. In addition, terminal-like CCK-I was localized within layer 1A of the anterior olfactory nucleus, the olfactory tubercle, and the most rostral piriform cortex. This observation provides corroboration for the identification of the principal CCK-I neuron in the rat olfactory bulb as the centrally projecting middle tufted cell. The present results, demonstrating the localization of CCK-I to both local circuit and projection neurons of the olfactory bulb and to terminal-like puncta in the internal plexiform and granule cell layers, suggest that CCK may be significantly involved in olfactory processing at several levels.

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PubMed1985

Gap junction structures. VII. Analysis of connexon images obtained with cationic and anionic negative stains.

Micrographs of isolated gap junction specimens, negatively stained with one molybdate, three tungstate and three uranyl stains, were recorded at low and high irradiation. Fourier-averaged images of the negatively stained gap junctions have been self-consistently scaled to identify conserved and variable features. Intrinsic features in the hexagonally averaged images have been distinguished from residual noise by statistical comparisons among similarly prepared specimens. The cationic uranyl stains can penetrate the axial connexon channel, whereas the anionic stains are largely excluded; these observations indicate that the channel is negatively charged. Variability in the extent of the axial stain penetration, and enhancement of this staining by radiation damage and heating may be accounted for by a leaky, labile channel gate. The peripheral stain concentrations marking the perimeter of the skewed, six-lobed connexon image and the stain-excluding region at the 3-fold axis of the lattice, which are seen only under conditions of low irradiation with both anionic and cationic stains, are identified as intrinsic features of the isolated gap junction structure. The stain concentrations located approximately 30 A from the connexon center appear to be symmetrically related on opposite sides of the junction by non-crystallographic 2-fold axes oriented approximately 8 degrees to the lattice axes at the plane of the gap. The radiation-sensitive hexagonal features seen in the negatively stained images may correspond to substructure on the cytoplasmic surfaces of the paired gap junction membranes.

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PubMed1984

Supramammillary afferents to guinea pig hippocampus contain substance P-like immunoreactivity.

The origin of substance P immunoreactive (SPI) axons in guinea pig hippocampus was analyzed using immunocytochemical techniques combined with transections and retrograde transport of fluorescent dye. A unilateral depletion of hippocampal axonal SPI was observed following ipsilateral transection of rostral hippocampus and fibria suggesting that the vast majority of SPI axons in hippocampus are extrinsic afferents which enter the structure from the septal pole. The combined use of immunocytochemistry and fluorescent dye transport demonstrated the supramammillary region of the hypothalamus to be the only area where dye-labeled hippocampal afferent neurons also exhibited SPI. These data indicate that the supramammillary region is the principal source of SPI axons in guinea pig hippocampus and, most probably, in the hippocampus of other animals (squirrel, cat, monkey) sharing a similar pattern of axonal SPI.

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PubMed1984

Ontogeny of dynorphin-like immunoreactivity in the hippocampal formation of the rat.

Light microscopic immunocytochemical techniques were used to analyze the ontogeny of dynorphin (A)-like immunoreactivity (DLI) in the hippocampal formation of the Sprague-Dawley rat. For comparison purposes, alternate sections of the same brains were processed for the localization of methionine enkephalin-like immunoreactivity (ELI). DLI was first detectable in CA3a stratum lucidum and the suprapyramidal hilus on postnatal day (P) 6. On P7, DLI was evenly present throughout the full extent of the mossy fiber system. From P8 to P19, DLI progressively increased in intensity and could be localized in the fine axons and spherical swellings. The mossy fiber system and occasional perikarya superficial to stratum granulosum were the only hippocampal elements that exhibited DLI. In corroboration with earlier results, stratum lucidum ELI was first detected within large spherical bouton-like swellings on P13. From these data it is concluded that DLI appears in morphologically immature mossy fibers soon after they reach their target fields. In contrast, enkephalin is first detected within morphologically elaborated mossy fiber boutons well after the establishment of functional synapses.

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PubMed1984

The distribution of cholecystokinin-like immunoreactivity in the hippocampal formation of the guinea pig: localization in the mossy fibers.

Immunocytochemical techniques were used to localize cholecystokinin octapeptide (CCK-8)-like immunoreactivity in the hippocampal formation of the guinea pig. As in the rat, CCK immunoreactive perikarya are most dense in and around the stratum pyramidale, within the superficial cell layer of the subiculum, and within the polymorph zone of the hilus. Immunoreactive axons are observed within and loosely surrounding the stratum pyramidale, within the stratum lacunosum moleculare, and diffusely distributed across the subiculum. In contrast to the rat, the mossy fiber system also exhibited significant CCK immunoreactivity. The latter system has previously been demonstrated to contain enkephalin-like immunoreactivity in the guinea pig. The present results suggest, therefore, that the enkephalin-like and CCK-like substances either coexist within the mossy fiber boutons or are present within separate subpopulations of the mossy fibers.

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PubMed1984

Distribution of enkephalin, substance P, tyrosine hydroxylase, and 5-hydroxytryptamine immunoreactivity in the septal region of the rat.

Immunocytochemical methods were used to define the distribution of enkephalin (ENK), substance P (SP), tyrosine hydroxylase (TH), and serotonin (5-hydroxytryptamine: 5HT) in the rat septum. A dense plexus of axons containing enkephalin-like immunoreactivity is found in the intermediate lateral septal nucleus. This is surrounded laterally by SP-containing cell bodies and axons and medially by ENK-containing cell bodies. Both SP- and ENK-immunoreactive axons form pericellular and peridendritic terminal arbors around lateral septal neurons. TH-positive axons are distributed throughout the septum and form dense pericellular terminal baskets around scattered neurons in the medial half of the intermediate lateral septal nucleus and in the extreme lateral septum. Very few SP and TH immunoreactive axons are present in the ENK immunoreactive plexus zone. 5HT-immunoreactive axons are most dense at the lateral edge of the ventral and intermediate lateral septal nuclei but form pericellular terminal arbors only in the dorsal lateral septal nucleus, in the septofimbrial nucleus, and in the dorsal cap of the medial septal nucleus. These results indicate that the dorsal and intermediate lateral septal nuclei include three histochemically distinct laminated subfields: (1) an ENK immunoreactive axonal plexus within the lateral aspect of the intermediate lateral septal nucleus, (2) a more medial region of scattered ENK immunoreactive perikarya and similarly scattered TH immunoreactive pericellular baskets, and (3) a dorsolateral zone occupied by SP neurons and 5HT-containing pericellular baskets. Thus, the data suggest that SP- and ENK-containing neuronal populations in the lateral septum receive different monoaminergic inputs. Further, the somewhat exclusive laminated pericellular termination of peptide- and catecholamine-containing axons in the lateral septum predicts very different functional and pharmacological properties among zones.

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