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P Gass

Publications and source records attributed to P Gass.

At least 37 records · Page 2Linked to original sources
PubMed2000

Exploration of a novel environment leads to the expression of inducible transcription factors in barrel-related columns.

Tactile information acquired through the vibrissae is of high behavioral relevance for rodents. Numerous physiological studies have shown adaptive plasticity of cortical receptive field properties due to stimulation and/or manipulation of the whiskers. However, the cellular mechanisms leading to these plastic processes remain largely unknown. Although genomic responses are anticipated to take place in this sequel, virtually no data so far exist for freely behaving animals concerning this issue. Thus, adult rats were placed overnight in an enriched environment and most of them were also subjected to clipping of different sets of whiskers. This type of stimulation led to a specific and statistically significant increase in the expression of the protein products of the inducible transcription factors c-Fos, JunB, inducible cyclic-AMP early repressor and Krox-24 (also frequently named Zif268 or Egr-1), but not c-Jun. The response was found in columns of the barrel cortex corresponding to the stimulated vibrissae; it displayed a layer-specific pattern. However, no induction of transcription factors was observed in the subcortical relay stations of the whisker-to-barrel pathway, i.e. the trigeminal nuclei and the ventrobasal complex. These results strongly suggest that a coordinated transcriptional response is initiated in the barrel cortex as a consequence of processing of novel environmental stimuli.

Animals↗
PubMed2000

Genetic disruption of mineralocorticoid receptor leads to impaired neurogenesis and granule cell degeneration in the hippocampus of adult mice.

To dissect the effects of corticosteroids mediated by the mineralocorticoid (MR) and the glucocorticoid receptor (GR) in the central nervous system, we compared MR-/- mice, whose salt loss syndrome was corrected by exogenous NaCI administration, with GR-/- mice having a brain-specific disruption of the GR gene generated by the Cre/loxP-recombination system. Neuropathological analyses revealed a decreased density of granule cells in the hippocampus of adult MR-/- mice but not in mice with disruption of GR. Furthermore, adult MR-/- mice exhibited a significant reduction of granule cell neurogenesis to 65% of control levels, possibly mediated by GR due to elevated corticosterone plasma levels. Neurogenesis was unaltered in adult mice with disruption of GR. Thus, we could attribute long-term trophic effects of adrenal steroids on dentate granule cells to MR. These MR-related alterations may participate in the pathogenesis of hippocampal changes observed in ageing, chronic stress and affective disorders.

Animals↗
PubMed1999

Presynaptic localization of the PACAP-typeI-receptor in hippocampal and cerebellar mossy fibres.

The distribution of PACAP-typeI-receptor (PACAP-I-R) mRNA and protein was studied in mouse using probes and a newly developed antiserum recognizing all known splice variants. RNase protection assays revealed highest expression levels of PACAP-I-R mRNA in brain, in particular the hypothalamus and hippocampus. At the cellular level, in situ hybridization analysis demonstrated widespread distribution of PACAP-I-R mRNA in neurons throughout the brain, while glial cells did not express the gene. Highest expression levels of PACAP-I-R mRNA were observed in three regions: the limbic system, the hypothalamus, and the brainstem. In accordance with data obtained from in situ hybridization analysis, immunohistochemistry showed widespread distribution of PACAP-I-R like immunoreactivity in the neuropil. Rather strong immunoreactivity was found in cerebellar and hippocampal mossy fibres where double immunolabelling revealed the presynaptic localization of the receptor protein. At the ultrastructural level, PACAP-I-R like immunoreactivity was observed around synaptic vesicles and close to the presynaptic grid in hippocampal mossy fibre terminals. This finding is in contradiction to the described postsynaptic localization of the PACAP-I-R in dendritic processes of hippocampal granule cells in rat. Due to their presynaptic induction, mossy fibre LTPs are distinctly different from LTPs in all other hippocampal regions. Therefore, the presynaptic localization of the PACAP-I-R in mossy fibre terminals may implicate this gene in influencing the synaptic strength of the mossy fibre pathway and hence memory consolidation.

Animals↗
PubMed1999

Global cerebral ischemia due to cardiocirculatory arrest in mice causes neuronal degeneration and early induction of transcription factor genes in the hippocampus.

To analyze the role of specific genes and proteins in neuronal signaling cascades following global cerebral ischemia, it would be useful to have a reproducible model of global cerebral ischemia in mice that potentially allows the investigation of mice with specific genomic mutations. We first report on the development of a model of reversible cardiocirculatory arrest in mice and the consequences of such an insult to neuronal degeneration and expression of immediate early genes (IEG) in the hippocampus. Cardiocirculatory arrest of 5 min duration was induced via ventricular fibrillation in mechanically ventilated NMRI mice. After successful cardiopulmonary resuscitation (CPR), animals were allowed to reperfuse spontaneously for 3 h (n=7) and 7 days (n=7). TUNEL staining revealed a selective degeneration of a subset of neurons in the hippocampal CA1 sector at 7 days. About 30% of all TUNEL-positive nuclei showed condensed chromatin and apoptotic bodies. Immunohistochemical studies of IEG expression performed at 3 h exhibited a marked induction of c-Fos, c-Jun, and Krox-24 protein in all sectors of the hippocampus, peaking in vulnerable CA1 pyramidal neurons and in dentate gyrus. In contrast, sham-operated animals (n=3) did not reveal neuronal degeneration or increased IEG expression in the hippocampus when compared with untreated control animals (n=3). In conclusion, we present a new model of global cerebral ischemia and reperfusion in mice with the use of complete cardiocirculatory arrest and subsequent CPR. Following 5 min of ischemia, a subset of CA1 pyramidal neurons was TUNEL-positive at 7 days. The expression of IEG was observed in all sectors of the hippocampus, including selectively vulnerable CA1 pyramidal neurons. This appears to be a good model which should be useful in evaluating the role of various genes in transgenic and knockout mice following global ischemia.

Animals↗
PubMed1999

Quantification of microglial late reaction to stereotactic irradiation of the rat brain using computer-aided image analysis.

The role of microglial cells in the late delayed reaction following radiotherapy of brain tumors has not been elucidated. To investigate the late delayed response of microglial cells to radiation, we stereotactically irradiated spherical treatment volumes in the right frontal lobe of rat brains. Doses of 20, 30, 40, and 50 Gy were used in combination with two different collimators. The response of microglial cells at 10 and 19 months after irradiation was determined with Anti-CD 11 b/c (Ox 42) as an immunohistochemical marker. For evaluation of immunostaining, we developed a method using computer-aided image analysis in which the ratio of the area of stained cells to that of nonstained brain tissue is calculated. In addition, quantification of Ox-42+ cells per microscopic field was performed. Animals treated with 30 Gy or more had significantly increased total areas of staining at both time points studied. In contrast, the number of stained cells at 10 months increased significantly only in animals treated with 30 or 40 Gy. Likewise, at 19 months, this number increased significantly only in animals treated with 40 Gy or more. These results indicate that computer-aided determination of the area of stained cells is more sensitive than the counting of stained cells. We have demonstrated that microglial cells respond to stereotactic irradiation in a dose-dependent fashion. The image analysis we employed for this purpose is a systematic method to evaluate immunohistochemical staining.

Animals↗
PubMed1999

Disruption of the glucocorticoid receptor gene in the nervous system results in reduced anxiety.

The glucocorticoid receptor (Gr, encoded by the gene Grl1) controls transcription of target genes both directly by interaction with DNA regulatory elements and indirectly by cross-talk with other transcription factors. In response to various stimuli, including stress, glucocorticoids coordinate metabolic, endocrine, immune and nervous system responses and ensure an adequate profile of transcription. In the brain, Gr has been proposed to modulate emotional behaviour, cognitive functions and addictive states. Previously, these aspects were not studied in the absence of functional Gr because inactivation of Grl1 in mice causes lethality at birth (F.T., C.K. and G.S., unpublished data). Therefore, we generated tissue-specific mutations of this gene using the Cre/loxP -recombination system. This allowed us to generate viable adult mice with loss of Gr function in selected tissues. Loss of Gr function in the nervous system impairs hypothalamus-pituitary-adrenal (HPA)-axis regulation, resulting in increased glucocorticoid (GC) levels that lead to symptoms reminiscent of those observed in Cushing syndrome. Conditional mutagenesis of Gr in the nervous system provides genetic evidence for the importance of Gr signalling in emotional behaviour because mutant animals show an impaired behavioural response to stress and display reduced anxiety.

Adrenal Glands↗
PubMed1998

DNA binding of the glucocorticoid receptor is not essential for survival.

Transcriptional regulation by the glucocorticoid receptor (GR) is essential for survival. Since the GR can influence transcription both through DNA-binding-dependent and -independent mechanisms, we attempted to assess their relative importance in vivo. In order to separate these modes of action, we introduced the point mutation A458T into the GR by gene targeting using the Cre/loxP system. This mutation impairs dimerization and therefore GRE-dependent transactivation while functions that require cross-talk with other transcription factors, such as transrepression of AP-1-driven genes, remain intact. In contrast to GR-/- mice, these mutants termed GRdim are viable, revealing the in vivo relevance of DNA-binding-independent activities of the GR.

Amino Acid Sequence↗
PubMed1998

Impaired fetal T cell development and perinatal lethality in mice lacking the cAMP response element binding protein.

CREB, the cAMP response element binding protein, is a key transcriptional regulator of a large number of genes containing a CRE consensus sequence in their upstream regulatory regions. Mice with a hypomorphic allele of CREB that leads to a loss of the CREBalpha and delta isoforms and to an overexpression of the CREBbeta isoform are viable. Herein we report the generation of CREB null mice, which have all functional isoforms (CREBalpha, beta, and delta) inactivated. In contrast to the CREBalpha delta mice, CREB null mice are smaller than their littermates and die immediately after birth from respiratory distress. In brain, a strong reduction in the corpus callosum and the anterior commissures is observed. Furthermore, CREB null mice have an impaired fetal T cell development of the alpha beta lineage, which is not affected in CREBalpha delta mice on embryonic day 18.5. Overall thymic cellularity in CREB null mice is severely reduced affecting all developmental stages of the alpha beta T cell lineage. In contrast gamma delta T cell differentiation is normal in CREB mutant mice.

Animals↗
PubMed1998

Neuronal basic helix-loop-helix proteins (NEX, neuroD, NDRF): spatiotemporal expression and targeted disruption of the NEX gene in transgenic mice.

Basic helix-loop-helix (bHLH) genes have emerged as important regulators of neuronal determination and differentiation in vertebrates. Three putative neuronal differentiation factors [NEX for neuronal helix-loop-helix protein-1 (mammalian atonal homolog-2), neuroD (beta-2), and NDRF for neuroD-related factor (neuroD2)] are highly homologous to each other in the bHLH region and comprise a new bHLH subfamily. To study the role of NEX, the first bHLH protein identified in this group, we have disrupted the NEX gene by homologous recombination. NEX-deficient mice have no obvious developmental defect, and CNS neurons appear fully differentiated. To investigate further whether the absence of NEX is compensated for by neuroD and NDRF, we compared the spatiotemporal expression of all three genes. We demonstrate, by in situ hybridization, that the transcription patterns of NEX, neuroD, and NDRF genes are highly overlapping in the developing CNS of normal rats between embryonic day 12 and adult stages but are not strictly identical. The most prominent transcription of each gene marks the dorsal neuroepithelium of the telencephalon in early development and is sustained in the adult neocortex, hippocampus, and cerebellum. In general, neuroD provides the earliest marker of neuronal differentiation in any given region compared with NDRF or NEX. Whereas a few CNS regions are specific for neuroD, no region was detected in which solely NEX or NDRF is expressed. This suggests that the function of the mutant NEX gene in neuronal differentiation is compensated for by neuroD and NDRF and that, in analogy with myogenic bHLH proteins, neuronal differentiation factors are at least in part equivalent in function.

Aging↗
PubMed1998

Differential time course of angiotensin-induced AP-1 and Krox proteins in the rat lamina terminalis and hypothalamus.

We studied the time course of expression of the inducible transcription factors (ITF) c-Fos, FosB, c-Jun, JunB, JunD, Krox-20 and Krox-24, induced by a single intracerebroventricular injection of angiotensin II, in the subfornical organ (SFO), median preoptic nucleus (MnPO) paraventricular nucleus (PVN) and supraoptic nucleus (SON). c-Fos and Krox-24 were expressed rapidly in neurons of all four areas but completely disappeared after 4 h. FosB showed a delayed but persistent expression between 4 h and 24 h in the MnPO and PVN. c-Jun was induced in the MnPO, SFO and PVN after 1.5 h and in the SON after 4 h. JunB was selectively expressed in the MnPO and SFO and the level of JunD did not change. The expression of the pre-existing transcription factors SRF, CREB and ATF-2 which contribute to the transcriptional control of jun, fos and krox genes, was not affected by Ang II. Thus, we could show for the first time that an acute stimulation of AT receptors results in continual changes in ITF expression over 24 h.

Angiotensin II↗
PubMed1998

BDNF restores the expression of Jun and Fos inducible transcription factors in the rat brain following repetitive electroconvulsive seizures.

The expression of inducible transcription factors was studied following repetitive electroconvulsive seizures (ECS), c-Fos, c-Jun, JunB, and JunD immunoreactivities were investigated following a single (1 x ECS) or repetitive ECS evoked once per day for 4, 5, or 10 days (4 x ECS, 5 x ECS, or 10 x ECS). Animals were killed 3 or 12 h following the last ECS. Three hours after 1 x ECS, c-Fos was expressed throughout the cortex and hippocampus. After 5 x ECS and 10 x ECS, c-Fos was reexpressed in the CA4 area, but was completely absent in the other hippocampal areas and cortex. In these areas, c-Fos became only reinducible when the time lag between two ECS stimuli was 5 days. In contrast to c-Fos, intense JunB expression was inducible in the cortex and hippocampus, but not CA4 subfield, after 1 x ECS, 5 x ECS, and 10 x ECS. Repetitive ECS did not effect c-Jun and JunD expression. In a second model of systemic excitation of the brain, repetitive daily injection of kainic acid for 4 days completely failed to express c-Fos, c-Jun, and JunB after the last application whereas injection of kainic acid once per week did not alter the strong expressions compared to a single application of kainic acid. In order to study the maintenance of c-Fos expression during repetitive seizures, brain-derived neurotrophic factor (BDNF) was applied in parallel for 5 or 10 days via miniosmotic pumps and permanent cannula targeted at the hippocampus or the parietal cortex. Infusion of BDNF completely reinduced c-Fos expression during 5 x ECS or 10 x ECS in the cortex ipsilaterally to the cannula and, to a less extent, also increased the expression of c-Jun and JunB when compared to saline-treated controls. BDNF had no effect on the expression patterns in the hippocampus. ECS with or without BDNF infusion did not change the expression patterns of the constitutive transcription factors ATF-2, CREB, and SRF. These data demonstrate that various transcription factors substantially differ in their response to acute and chronic neural stimulation. Repetitive pathophysiological excitation decreases the transcriptional actions of neurons over days in the adult brain, and this decrement can be prevented by BDNF restoring the neuroplasticity at the level of gene transcription.

Animals↗
PubMed1998

Analysis of glucocorticoid signalling by gene targeting.

Glucocorticoids are involved in the regulation of numerous physiological processes. The majority of these effects are thought to be mediated by the glucocorticoid receptor (GR) via activation and repression of gene expression. In most cases activation requires binding of a receptor-dimer to DNA while repression is mediated by protein-protein-interaction of GR-monomers with other transcription factors. To analyse the molecular mechanisms that underlie glucocorticoid effects, mouse mutations in the GR gene were generated and analysed. In order to address the role of glucocorticoid receptor signalling during development and in physiology, the gene was disrupted by gene targeting. Most of the mice homozygous for the mutation die shortly after birth due to severe lung atelectasis. Additional defects were found in the adrenals, liver, brain, bone marrow and thymus as well as in the feedback-regulation of the HPA-axis. To approach the question which functions of the GR are regulated by DNA-binding and which by protein-protein-interaction, a point mutation was introduced into the dimerization domain of the GR which is located in the DNA-binding domain. By homologous recombination in ES-cells using the Cre/loxP-system, mice carrying this mutation were generated [GR(dim) mice]. The mice are fully viable although they show impaired inducibility of gluconeogenetic enzymes in liver, defects in longterm renewal of erythroid progenitors and increased expression of POMC and ACTH in the pituitary. However neither in the lung nor the adrenals were any histological abnormalities found. In conclusion GR(dim)-mice represent a valuable tool to further analyse mechanisms of physiological effects of the GR.

Animals↗
PubMed1998

Attenuated c-fos mRNA induction after middle cerebral artery occlusion in CREB knockout mice does not modulate focal ischemic injury.

To elucidate the mechanism of ischemia-induced signal transduction in vivo, we investigated the effect of the targeted disruption of the alpha and delta isoforms of the cAMP-responsive element-binding protein (CREB) on c-fos and heatshock protein (hsp) 72 gene induction. Permanent focal ischemia was induced by occlusion of the middle cerebral artery of the CREB mutant mice (CREB(-/-), n = 5) and the wild-type mice (n = 6). Three hours after onset of ischemia, the neurologic score was assessed and pictorial measurements of ATP and cerebral protein synthesis (CPS) were carried out to differentiate between the ischemic core (where ATP is depleted), the ischemic penumbra (where ATP is preserved but CPS is inhibited), and the intact tissue (where both ATP and CPS are preserved). There were no significant differences in neurologic score or in ATP, pH, and CPS between the two groups, suggesting that the sensitivity of both strains to ischemia is the same. Targeted disruption of the CREB gene significantly attenuated c-fos gene induction in the periischemic ipsilateral hemisphere but had no effect on either c-fos or hsp72 mRNA expression in the penumbra. The observations demonstrate that CREB expression, despite its differential effect on c-fos, does not modulate acute focal ischemic injury.

Adenosine Triphosphate↗
PubMed1997

Defective limbic system in mice lacking the tailless gene.

The gene tailless is a member of the superfamily of genes that encode transcription factors of the ligand-activated nuclear receptor type, and is expressed in the invertebrate and vertebrate brain. In mice, its transcripts are restricted to the periventricular zone of the forebrain, the site of origin of neurons and glia. Here we use homologous recombination to generate mice that lack a functional tailless protein. Homozygous mutant mice are viable at birth, indicating that tailless is not required for prenatal survival; however, adult mutant mice show a reduction in the size of rhinencephalic and limbic structures, including the olfactory, infrarhinal and entorhinal cortex, amygdala and dentate gyrus. Both male and female mice are more aggressive than usual and females lack normal maternal instincts. These animals therefore enable a molecular approach to be taken towards understanding the genetic architecture and morphogenesis of the forebrain.

Animals↗
PubMed1997

SHARPs: mammalian enhancer-of-split- and hairy-related proteins coupled to neuronal stimulation.

In the mammalian central nervous system, a diverse group of basic helix-loop-helix (bHLH) proteins is involved in the determination of progenitor cells and, subsequently, in regulating neuronal differentiation. Here we report the identification of a novel subfamily of bHLH proteins, defined by two mammalian enhancer-of-split- and hairy-related proteins, termed SHARP-1 and SHARP-2. In contrast to known bHLH genes, detectable transcription of SHARP genes begins at the end of embryonic development marking differentiated neurons that have reached a final position, and increases as postnatal development proceeds. In the adult, SHARP genes are expressed in subregions of the CNS that have been associated with adult plasticity. In PC12 cells, a model system to study neurite outgrowth, SHARP genes can be induced by NGF with the kinetics of an immediate-early gene. Similarly, within 1 h after the administration of kainic acid in vivo, SHARP-2 is induced in neurons throughout the rat cerebral cortex. This suggests that neuronal bHLH proteins are also involved in the "adaptive" changes of mature CNS neurons which are coupled to glutamatergic stimulation.

Amino Acid Sequence↗
PubMed1997

Induction of FOS and JUN proteins during focal epilepsy: congruences with and differences to [14C]deoxyglucose metabolism.

fos and jun belong to multigene families coding for transcription factors. These cellular immediate-early genes (IEGs) are thought to be involved in coupling neuronal excitation to changes of target gene expression. Immunocytochemistry with specific antisera was used to assess regional levels of five IEG-encoded proteins (c-FOS, FOS B, c-JUN, JUN B and JUN D) in a rat model of penicillin-induced focal epilepsy. To assess whether brain regions with post-ictal de novo transcription factor synthesis correspond to those areas with increased glucose metabolism, IEG expression patterns were compared with [14C]deoxyglucose autoradiography performed in a subset of animals. The results demonstrated marked induction of c-FOS, FOS B, c-JUN and JUN B but not JUN D in the cortical epileptic focus. Thereby, individual IEG-encoded proteins exhibited differential temporal and spatial expression patterns. Within the epileptic focus, IEG expression correlated with increased glucose metabolism. In contrast, IEG induction was not observed in brain areas distant from the epileptic focus that also demonstrated increased glucose metabolism, such as homotopic contralateral motor cortex and ipsilateral thalamic nuclei. These findings indicate that in focal epilepsy changes of the genetic programme are restricted to neurons of the epileptic focus. In contrast, the increased [14C]deoxyglucose metabolism in contralateral motor cortex and ipsilateral thalamus seems to indicate functional changes.

Animals↗
PubMed1997

The cerebral 'no-reflow' phenomenon after cardiac arrest in rats--influence of low-flow reperfusion.

OBJECTIVE: Experimental data indicate that early microcirculatory reperfusion is disturbed after cardiac arrest. We investigated the influence of prolonged cardiac arrest and basic life support (BLS) procedures on the quality of cerebral microcirculatory reperfusion. MATERIALS AND METHODS: In mechanically ventilated male Wistar rats anesthetized with N2O and halothane, cardiac arrest was induced by electrical fibrillation. Ten animals (group I) were subjected to 17 min of cardiac arrest (no-flow). Nine additional animals (group II) underwent only 12 min of cardiac arrest (no-flow), which was followed by a 5-min phase of BLS (i.e. mechanical ventilation and external cardiac compressions). In both groups, advanced resuscitation procedures including mechanical ventilation, external cardiac massage, 0.2 mg kg-1 epinephrine, 0.5 mmol kg-1 NaHCO3, and defibrillation were started 17 min after induction of cardiac arrest. The perfusion of the cerebral microcirculation was visualized by injection of 0.3 g kg-1 15% fluorescein isothiocyanate (FITC)-albumin 5 min after restoration of spontaneous circulation (ROSC), and the animals were decapitated 2 min later. The left hemispheres were fixed in 4% formalin, and coronal sections of 200 microns thickness at three different standard levels of the rat brain were investigated using fluorescence microscopy. Areas without capillary filling (cerebral 'no-reflow') were identified and calculated. RESULTS: ROSC could be achieved in five of 10 animals (50%) of group I, and in six of nine animals (67%) of group II (P = n.s.). The severity of cerebral 'no-reflow' was higher in group II compared with group I (6.9 +/- 7.6 vs. 0.7 +/- 0.7% of total sectional areas; P < or = 0.05). Two sham-operated animals showed homogeneous reperfusion. CONCLUSIONS: Wistar rats did not develop a marked cerebral 'no-reflow' phenomenon after circulatory arrest. A relevant degree of cerebral 'no-reflow' occurred, however, in animals subjected to a phase of BLS before circulatory stabilization. Therefore, low-flow states following prolonged cardiocirculatory arrest may aggravate early cerebral microcirculatory reperfusion disorders.

Animals↗