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Biomedical subjects

C Gall

Publications and source records attributed to C Gall.

At least 19 recordsLinked to original sources
PubMed1995

BDNF protein measured by a novel enzyme immunoassay in normal brain and after seizure: partial disagreement with mRNA levels.

Messenger RNA for brain-derived neurotrophic factor (BDNF) is distributed in many brain regions and regulated by excitatory neuronal activity. Despite numerous studies of BDNF mRNA, the distribution and regulation of BDNF protein are poorly understood because of the difficulty of its quantitative measurement. We have established a two-site enzyme immunoassay that detects trace amounts of BDNF protein (> 1 pg/assay) but not other neurotrophins or growth factors. The highest levels of BDNF in adult rat brain were found in the hippocampus, followed by the hypothalamus, neocortex, cerebellum, thalamus and striatum. This pattern is similar, but not identical, to the distribution of BDNF mRNA. A similar disparity between BDNF protein and mRNA levels was observed in their changes after hilus lesion-induced limbic seizures. In limbic structures, BDNF concentrations remained elevated 4 days after seizure onset, whereas BDNF mRNA has been reported previously to return to basal levels within 46 h. The temporal and spatial differences between the dynamics of protein and mRNA levels suggest the importance of post-translational and/or subcellular processes for BDNF production. The persistence of the increases in BDNF content was also reflected in its biological activity, e.g. peptidergic differentiation activity. After limbic seizures, neuropeptide Y content was most markedly and persistently elevated in the entorhinal/amygdaloid region, where the most sustained up-regulation of BDNF protein was observed. These results suggest that the sustained increase of BDNF protein in these limbic structures is involved in prolonged post-seizure phenomena, including peptidergic alterations.

Animals↗
PubMed1995

Proteolysis of spectrin by calpain accompanies theta-burst stimulation in cultured hippocampal slices.

Tests were carried out to determine if repetitive bursts of afferent stimulation activate calpain, a calcium-dependent protease hypothesized to be involved in the production of long-term potentiation. Antibodies against a stable breakdown product that results from proteolysis of spectrin by calpain were used to identify sites of enzyme activation in cultured hippocampal slices. Slices in which theta-burst stimulation was applied to the Schaffer collateral fibers had pronounced accumulations of breakdown product that were restricted to field CA1, the zone innervated by the stimulated axons. Labelling occurred in the form of scattered puncta and was also present in dendritic processes. The extent of these effects was correlated (r = 0.73) with the amount of theta-burst stimulation delivered. Control slices or those receiving low frequency stimulation had variable, but uniformly lower, amounts of breakdown product and were clearly distinguishable from those given theta bursts. Statistical analyses using a six point rating scheme confirmed this point (P < 0.001). These results satisfy an essential prediction of the hypothesis that calpain plays an important role in the induction of long-term potentiation.

Afferent Pathways↗
PubMed1995

Cell-specific modulation of basal and seizure-induced neurotrophin expression by adrenalectomy.

Reports of glucocorticoid effects on neurotrophin expression suggest that adrenal hormones may contribute to the pattern of changes in the expression of these factors induced by neuronal activity and seizures. To examine this possibility, the present study evaluated the influence of adrenalectomy on basal expression and seizure-induced alterations in levels of nerve growth factor, brain-derived neurotrophic factor, and neurotrophin-3 messenger RNAs in hippocampus, entorhinal cortex, and superficial neocortex. For determination of hormone effects on basal expression, adult male rats were adrenalectomized and killed 10-14 days later with paired adrenal-intact controls. For studies of adrenal steroid involvement in expression following seizure, adrenalectomized and adrenal-intact rats received a seizure-producing lesion of the dentate gyrus hilus. Changes in neurotrophin messenger RNA content were assessed by quantitative in situ hybridization. Adrenalectomy alone had no significant effect on brain-derived neurotrophic factor messenger RNA content but did result in cell-specific decreases in nerve growth factor and neurotrophin-3 messenger RNAs. Nerve growth factor messenger RNA levels were reduced in hippocampal stratum granulosum, entorhinal cortex, and neocortex but not in cells of the hippocampal molecular layers or hilus. With adrenalectomy, neurotrophin-3 messenger RNA was virtually eliminated from CA2 stratum pyramidale, partially reduced in stratum granulosum, but unaffected in neurons of the hippocampal molecular layers or entorhinal cortex. These effects were partially reversed by corticosterone (2 mg/l) supplement to the drinking saline. In experimental-seizure rats, adrenalectomy did not alter the direction or basic pattern of seizure-induced changes in neurotrophin expression but did change the time courses and magnitudes of these effects. In all areas measured, brain-derived neurotrophic factor messenger RNA content was more greatly and persistently elevated by seizure in adrenalectomized as compared with adrenal-intact rats. In contrast, with adrenalectomy seizures induced smaller increases in nerve growth factor messenger RNA content. Adrenalectomy augmented the decrease in neurotrophin-3 messenger RNA induced by seizure in hippocampus but not in entorhinal cortex. These results demonstrate that adrenal hormones play a major role in the regulation of basal nerve growth factor and neurotrophin-3 messenger RNA expression by specific populations of forebrain neurons. Moreover, the adrenal steroids have opposite effects on activity-dependent changes in brain-derived neurotrophic factor and nerve growth factor messenger RNA levels but are not required for the basic pattern of changes in neurotrophin messenger RNA expression elicited by recurrent seizures.

Adrenalectomy↗
PubMed1995

The mapping and continuous monitoring of the intrinsic motor nuclei during brain stem surgery.

A comprehensive technique was developed for continuous electrophysiological monitoring of intrinsic brain stem motor function during surgery to remove space-occupying lesions in the fourth ventricle and brain stem. The technique is analogous to that used during surgery in the cerebellopontine angle; motor nuclei and peripheral pontine fiber tracts of Cranial Nerves III-XII are identified by the electrical stimulation of structures in the operative field and the evaluation of the compound muscle action potentials recorded from the corresponding muscles of the head. Nerve function is monitored continuously by recording the ongoing electromyographic activity in these same muscles. Broadcasting electromyographic responses through a loudspeaker gives the surgeon immediate feedback on the status of the motor nuclei being monitored. Advantages of this technique include 1) the positive, objective identification of the nuclei and fiber tracts; 2) the continuous feedback on the status of these structures; 3) a safe approach through the fourth ventricle to the lesions in the brain stem; 4) the positive identification of the boundaries between the neoplasm and the motor structures of the rhomboid fossa; and 5) a warning to the surgeon of potentially harmful nerve manipulations (contact, dissection, transection) during surgery. After this technique was used in 16 consecutive operations to remove cavernomas (n = 9), gliomas (n = 4), and other types of tumors (n = 3), surgical and neurological results showed the method to be reliable and simple to perform.

Adult↗
PubMed1995

[Function-controlled neurosurgery. Neurophysiologic and neuropsychological monitoring during surgery of the nervous system].

Neuromonitoring of neural structures has become increasingly common during surgery near cortical areas representing sensorimotor and language function (epilepsia, tumors), in the brain stem and the spinal cord (tumors), near cranial nerves (cerebellopontine angle tumors, trigeminal neuralgia, hemifacial spasm), and in the cauda equina (tumors, tethered spinal cord). The technical spectrum to monitor these operations includes electrical cortical stimulation to evoke sensorimotor phenomena and language disturbances, electroneurography and -myography of the cauda equina, motor cranial nerves and nuclei, and somatosensory, motor and acoustic evoked potentials. The goals of intraoperative neuromonitoring are: (1) minimizing the risk of suffering neurological and neuropsychological injury as a result of surgery; (2) extending the surgical spectrum to lesions that have previously been considered inoperable or hazardous to operate upon; (3) intraoperative electrophysiological documentation that the goal of surgery has been achieved; (4) intraoperative basic research.

Brain↗
PubMed1993

Immunohistology and immunocytology of human T-cell chimerism and graft-versus-host disease in SCID mice.

Surprisingly little graft-versus-host disease (GVHD) has been observed in severe combined immunodeficient (SCID) mice injected intraperitoneally (IP) with human blood lymphocytes (hu-PBL-SCID), which raised the question as to whether GVHD in such a distant species is sporadic or suppressed because of immunologic reasons. After screening for blood T-cell chimerism, we hereby describe generalized lethal xenogeneic human GVHD in unconditioned SCID chimeras, which resembles GVHD in SCID mice injected with allogeneic lymphocytes. We adapted an immunocytochemical slide method for minute cell numbers, which allowed us to follow, by multimarker phenotyping of weekly mouse-tail bleeds, the chimeric status of 100 hu-PBL-SCID injected with 10(7) or 10(8) hu-PBL of Epstein-Barr virus- (EBV-) donors. More than half of the mice showed no or less than 2% T cells. However, 13% to 21% developed substantial blood T-lymphocyte chimerism (10% to 80% human CD+ cells) and high mortality. Immunohistology showed more human CD8+ than CD4+ T cells in the splenic white pulp. The cells developed HLA-DR activation markers and infiltrated the red pulp where human B cells also appeared. Expression of activation and proliferation markers increased within 5 to 6 weeks. Many human CD3+ cells were also found in the portal triads of the liver and in the lung, pancreas, and kidney. The thymus also became heavily infiltrated. The intestines and skin of hu-PBL-SCID were less infiltrated by donor cells than in SCID with allogeneic GVHD. The tongue contained almost no human T cells. Our data show that a relatively low overall incidence of human xenogeneic GVHD, even when high numbers of human PBL are injected, is the consequence of a dichotomy between mice with no or transient T-cell chimerism and a minority of mice with high-blood T-lymphocyte chimerism and GVHD mortality.

Animals↗
PubMed1992

Peritoneal sanctuary for human lymphopoiesis in SCID mice injected with human peripheral blood lymphocytes from Epstein-Barr virus-negative donors.

The successful engraftment in SCID mice of intraperitoneally (i.p.) injected human lymphocytes (hu-PBL-SCID) and the failure of intravenously injected peripheral blood lymphocytes (PBL) directed the present study to investigate the early events of donor cell proliferation in the peritoneal cavity. We found focal lymphocyte engraftment together with histio-monocytic interleukin (IL)-6+ cell phenotypes which must have been transferred with the human cell inoculum, which could explain certain immune functions observed in hu-PBL-SCID chimeras. Following i.p. injection of 10(8) PBL, human cells suspended in peritoneal fluid as well as those adherent to the serosal peritoneum and abdominal organs were investigated by immunocytology and immunohistology. Human cells were found to form foci consisting predominantly of proliferating human lymphoblastoid CD3+ cells, which were mostly activated HLA-DR+ CD8+ lymphocytes. Among the lymphoid cells larger epithelioid-like cells were found to belong to the monocytic series and to stain strongly with anti-HLA-DR and anti-CD11c antibodies. Some of these cells were also positive with anti-ICAM and anti-IL-6. Congenic as well as allogeneic mouse PBL, injected i.p. into SCID mice, temporarily produced analogous foci, which shifted later on to foci similar in appearance to milky spots. However, the human cell foci appeared less compact, more closely resembling in vitro-culture soft agar colonies. It is possible that cytokines in the human histio-monocytic cells of the foci may have a feeder effect on the human lymphocytes and be a prerequisite for proliferation of human PBL in SCID mice. The observed early HLA-DR activation of human lymphocytes in the peritoneal foci could reflect triggering of immune reactions like xenogeneic graft-versus-host reactions in the peritoneal site, where the human CD11c+ HLA-DR+ histio-monocytic cells may act as antigen-presenting cells.

Animals↗
PubMed1992

The dentate gyrus: a model system for studies of neurotrophin regulation.

Studies of the hippocampal formation have demonstrated that seizure activity stimulates a complex pattern of changes in gene expression in differentiated adult neurons including alterations in levels of mRNAs encoding putative neurotransmitter/neuromodulator substances and neurotransmitter receptors. Thus, activity-dependent alterations in gene expression can be expected to effect transient changes in synaptic physiology by modification of both presynaptic and postsynaptic constituents. In work to be reviewed here, seizure paradigms have been utilized to study the influence of activity on the expression of the nerve growth factor (NGF) family of neurotrophins by the dentate gyrus granule cells. We have found that seizures increase the expression of mRNAs for NGF and brain-derived neurotrophic factor (BDNF) but cause a delayed decrease in levels of mRNA for neurotrophin-3 (NT-3) in the granule cells of the dentate gyrus. Differences in the time courses of neurotrophin induction by seizure suggest that multiple regulatory mechanisms are involved. These findings indicate that physiological activity differentially regulates the expression of the three neurotrophins within individual adult forebrain neurons. Moreover, the induction of neurotrophin expression by seizure suggests a mechanism by which epileptiform activity might leave an enduring trace in the functional and structural properties of forebrain circuits which might influence the susceptibility for further seizure activity.

Animals↗
PubMed1991

Kainic acid-induced seizures stimulate increased expression of nerve growth factor mRNA in rat hippocampus.

The influence of kainic acid (KA)-induced limbic seizure activity on the expression of mRNA for nerve growth factor (NGF) in adult rat brain was studied using in situ hybridization and S1 nuclease protection techniques with RNA probes complementary to murine and rat NGF mRNA. Within hippocampus, intracerebroventricular injection of 0.5 microgram KA caused a dramatic bilateral increase in hybridization of the 35S-labeled cRNA within stratum granulosum. This increase was first evident 1 h post-KA, appeared maximal at approximately 20-fold control levels at 2-3 h post-injection, and declined to control levels by 48 h post-injection. During the period of maximal hybridization, all but the deepest cells within stratum granulosum appeared to be autoradiographically labeled. Hybridization of the NGF cRNA probe was also increased within superficial layers of piriform and entorhinal cortex and, to much lesser extent, within scattered neurons of layers II and III of neocortex in KA-treated rats. In olfactory cortical areas, hybridization was maximally elevated 15.5-24.5 h after KA injection. In contrast to these effects, KA treatment did not consistently influence the density of hybridization, or number of neurons labeled, within the dentate gyrus hilus or the hippocampus proper (CA1-CA3). In agreement with the in situ hybridization results, S1 nuclease protection assay detected KA-induced increases in hybridization within pooled dentate gyrus/CA1 samples, but not hippocampal CA3 samples. These data support the conclusion that seizure activity stimulates a transient increase in NGF expression by select populations of forebrain neurons and indicates that experimental seizure paradigms might be further exploited for analyses of the mechanisms of NGF regulation and processing in the adult brain.

Animals↗
PubMed1991

Seizures and the regulation of neurotrophic factor and neuropeptide gene expression in brain.

Seizure-induced plasticity, in the form of either changes in cellular morphology or changes in neurochemistry, could have a profound impact upon regional excitability in brain. There is now ample evidence that in genetically 'normal' animals, seizure activity stimulates alterations in neuronal gene expression which could lead to changes in levels of excitability and, hence, to changes in the susceptibility for further seizures. Here we describe the influence of limbic seizures upon the expression of nerve growth factor (NGF), 2 related neurotrophic factors, brain derived neurotrophic factor (BDNF) and neurotrophin 3 (NT3), and several neuropeptides (enkephalin, dynorphin, and neuropeptide Y) in the rat forebrain. Using 35S-labeled riboprobes and in situ hybridization methods, the effects of recurrent limbic seizures and of individual hippocampal paroxysmal discharges have been evaluated. Recurrent seizures are found to increase levels of mRNAs for NGF and BDNF and to decrease levels of mRNA for NT3 within select hippocampal neurons. Temporally distinct increases in the expression of mRNAs for NGF and BDNF are also observed across broad fields of neocortex, paleocortex (entorhinal, piriform, and cingulate cortices), and the amygdala. As little as one 20-sec paroxysmal discharge is sufficient to stimulate large changes in neurotrophic factor mRNA content of hippocampal neurons. The time courses and cellular specificities of these alterations in neurotrophic factor expression are discussed and contrasted with seizure-induced changes in neuropeptide expression. Mechanisms by which seizure-induced increases in hippocampal neuropeptide and neurotrophic factor synthesis could lead to both short- and long-term changes in regional excitability, and thereby could contribute to susceptibility for further seizure activity, are considered.

Animals↗
PubMed1990

Regional distribution of mRNA for a putative kainate receptor in rat brain.

A cDNA clone which encodes a putative kainate receptor was prepared with the polymerase chain reaction; from this, 'antisense' RNA fragments were produced and used to evaluate the distribution of mRNA for the kainate-receptor in rat brain with in situ hybridization techniques. The data demonstrate marked regional differences in the abundance of kainate receptor mRNA with highest levels present in the granule and pyramidal cell layers of hippocampus, the Purkinje cell layer of the cerebellum, and all cell layers of the olfactory bulb.

Animals↗
PubMed1990

Distribution of calcium-activated protease calpain in the rat brain.

Calpain is a calcium-activated neutral protease that degrades a number of cytoskeletal proteins. It may participate in the maintenance of the cytoskeleton and in the rapid turnover of structural proteins associated with synaptic plasticity. Calpain may also be involved in the neurodegeneration that accompanies aging and age-related diseases. To aid in the interpretation of disease-related alterations in staining patterns, the present study examined calpain's normal distribution in the mammalian brain and spinal cord. A monoclonal antibody was employed with the avidin-biotin-peroxidase immunocytochemical technique on samples of rat tissue. Glia (astrocytes, microglia) and virtually all neurons were immunopositive, although neuronal processes exhibited varying staining patterns. The axonal staining pattern depended upon either the origin or destination of the process: those axons remaining within the brain (e.g., corpus callosum) were only lightly immunoreactive, whereas spinal cord and peripheral axons (trigeminal nerve) were more darkly labeled. The architecture of the dendritic tree determined the dendritic staining pattern: neurons with prominent apical and basal dendritic trees (e.g., pyramidal cells) were immunolabeled along their entire extent; labeling of multipolar cells (e.g., hilar cells of dentate gyrus) was limited to the proximal dendrites. The ubiquitous distribution of calpain argues against a primary role for the enzyme in the regional pattern of neuronal death seen in Alzheimer's disease. An alteration in the concentration, localization, or inhibition of the enzyme could, however, lead to the abnormal accumulations of cytoskeletal elements seen with the disease.

Animals↗
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.

Animals↗
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.

Animals↗
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.

Animals↗
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.

Animals↗
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.

Animals↗