PubMed Health⌕ Search

Biomedical subjects

C Cirelli

Publications and source records attributed to C Cirelli.

At least 19 recordsLinked to original sources
PubMed2004

Uncoupling proteins and sleep deprivation.

In both humans and animals sleep deprivation (SD) produces an increase in food intake and in energy expenditure (EE). The increase in EE is a core element of the SD syndrome and, in rats, is negatively correlated with survival rate. However, the mechanisms involved are not understood. A large component of resting EE is accounted for by the mitochondrial proton leak, which is mediated by uncoupling proteins (UCPs). We measured UCP2, UCP3, and UCP5 mRNA levels in rats during the spontaneous sleep/waking cycle and after short (8 hours) and long (7 days) SD. During spontaneous sleep and waking there was no change in the level of mitochondrial uncoupling as measured by UCPs expression, either in the brain or in peripheral tissues. During SD, by contrast, UCP3 expression in skeletal muscle was elevated, but the increase was similar, compared to sleep, after both short-term and long-term SD. UCP2 expression, on the other hand, was strongly increased in the liver and skeletal muscle of long-term sleep deprived animals and much less so, or not at all, in yoked controls or in rats that lost only 8 hours of sleep. Since the skeletal muscle is the largest tissue in the body, an elevated muscular expression of UCP2 is likely to affect the overall resting EE and may thus contribute to its increase after SD.

Animals↗
PubMed2001

Sleep and the fruit fly.

The function of sleep remains a long-standing mystery in neurobiology. The presence of a sleep-like state has recently been demonstrated in the fruit fly, Drosophila melanogaster, meeting the essential behavioral criteria for sleep and also showing pharmacological and molecular correlates of mammalian sleep. This development opens up the possibility of applying genetic analysis to the identification of key molecular components of sleep. A mutant of monoamine metabolism has already been found to affect the homeostatic regulation of sleep-like behavior in the fly. The record of Drosophila in laying the foundations for subsequent studies in mammals argues in favor of the force of this new approach.

Animals↗
PubMed2001

Modulation of brain gene expression during sleep and wakefulness: a review of recent findings.

The characterization of the molecular correlates of sleep and wakefulness is essential to understand the restorative processes occurring during sleep and the cellular mechanisms underlying sleep regulation. In order to determine what molecular changes occur during the sleep-waking cycle, we have recently performed a systematic screening of gene expression in the brain of sleeping, sleep deprived, and spontaneously awake rats. Out of the approximately 10,000 genes screened so far, a small minority ( approximately 0.5%) was differentially expressed in the cerebral cortex across behavioral states. Most genes were upregulated in wakefulness and sleep deprivation relative to sleep, while only a few were upregulated in sleep relative to wakefulness and sleep deprivation. Almost all the genes upregulated in sleep, and several genes upregulated in wakefulness and sleep deprivation, did not match any known sequence. Known genes expressed at higher levels in wakefulness and sleep deprivation could be grouped into functional categories: immediate early genes/transcription factors, genes related to energy metabolism, growth factors/adhesion molecules, chaperones/heat shock proteins, vesicle and synapse-related genes, neurotransmitter/hormone receptors, neurotransmitter transporters, enzymes, and others. Although the characterization of the molecular correlates of sleep, wakefulness, and sleep deprivation is still in progress, it is already apparent that the transition from sleep to waking can affect basic cellular functions such as RNA and protein synthesis, neural plasticity, neurotransmission, and metabolism.

Animals↗
PubMed2001

Immediate early gene expression in the vestibular nuclei and related vegetative areas in rats during space flight.

Changes in neuronal activity resulting in somatic and vegetative deficits occur during different space flight conditions. Immediate early genes (IEGs: c-fos and Fos-related antigen [FRA]) are useful indicators of changes in neuronal activity and plasticity. They are induced within minutes of several extracellular stimulations, while the corresponding proteins persist for hours (Fos) or days (FRAs). Changes in IEG expression are likely to contribute to adaptation to microgravity and readaptation to the terrestrial environment. During the NASA Neurolab Mission (STS-90), changes in IEG expression were studied in adult male albino rats (Fisher 344) sacrificed at flight day (FD) 2 (24 h after launch), FD14 and at similar time points after re-entry (R + 1, 24 h after re-entry, and R + 13). These time points were chosen to maximize the probability of detecting changes in IEG expression related to changes in gravitational fields occurring during the mission, e.g. (i) increase in gravitational force from 1 to 3 g during the launch, before reaching about 0 g at FD2; (ii) adaptation to 0 g at FD14; (iii) increase in gravity from 0 to approximately 1.5-1.8 g before reaching 1 g at R + 1; and (iv) readaptation to 1 g at R + 13. Fos- and FRA-positive cells were identified in the brainstem of flight rats and ground-based controls using immunocytochemistry. With respect to control rats, the number of labeled cells increased in flight animals in the medial and spinal vestibular nuclei (but not in the lateral vestibular nucleus) at FD2, decreased at FD14, greatly increased at R + 1 and returned to baseline levels at R + 13. Similar changes in IEG expression were also observed in the nucleus of the solitary tract, the area postrema and the central nucleus of the amygdala. In particular, in these vegetative areas the number of Fos-positive cells decreased in flight rats with respect to controls at FD14, i.e. after exposure to 0 g, but significantly increased at R + 1, i.e. after return to 1 g. Thus, altered gravitational fields produced molecular changes in vestibular nuclei controlling somatic functions, as well as in related medullary and basal forebrain structures regulating vegetative functions.

Adaptation, Physiological↗
PubMed2001

Fos-related antigens are involved in the transcriptional responses of locus coeruleus neurons to altered gravitational fields in rats.

Locus coeruleus (LC) neurons, which have widespread projections to the whole brain, respond to natural stimulation of macular receptors. Using immunocytochemistry we investigated whether rats exposed to altered gravitational fields showed changes in Fos and Fos-related antigen (FRA) protein levels in the LC. Fos protein is induced very rapidly and returns to basal levels within hours after stimulation, while FRAs persist for days or weeks after induction. Adult male albino rats (Fisher 344) were sacrificed at different time points during a space flight (NASA Neurolab Mission, STS-90) and the numbers of Fos- and FRA-positive cells in the LC were counted and compared to those in ground-based control rats. No significant changes in Fos protein expression were detected in the LC under different space flight conditions. In contrast, the number of FRA-positive cells increased on average to 167% of that of the controls at FD2, i.e. when gravity increased from 1 to 3 g during the launch before reaching about 0 g. FRA-labeled neurons then decreased to 46% of control values at FD14, i.e. after adaptation to 0 g, but increased again to 317% of control values at R + 1, when the animals were exposed to an increase in gravitational force from 0 to 1.5-1.8 g before reaching 1 g during landing. The number of labeled cells was 193% of the control values at R + 13, i.e. after readaptation to 1 g. Thus gravitational force appears to be very effective in inducing a long-term increase in FRA protein expression in the LC. Because activity in the noradrenergic LC neurons may increase Fos expression in several target structures, we postulate that the long-lasting induction of FRAs in the LC at FD2, and more prominently at R + 1, may contribute to the long-term molecular changes which probably occur in the brain during adaptation to 0 g and readaptation to 1 g.

Adaptation, Physiological↗
PubMed2001

Some considerations on sleep and neural plasticity.

A role for sleep in memory processes and neural plasticity has been suggested many times and in many different forms. However, we are far from a consensus on what this role might be and why it would be fulfilled preferentially by sleep. In this review, we distinguish between memory acquisition, consolidation, and maintenance, and we consider how sleep may specifically contribute to each of these phases. We also distinguish between declarative and nondeclarative memories and their relationships to different stages of sleep. Finally, we discuss whether different molecular and cellular aspects of neural plasticity may be associated preferentially with different behavioral states. A consideration of such molecular aspects could lead to more conclusive experiments concerning the relationship between sleep and plasticity.

Animals↗
PubMed2000

Differential expression of plasticity-related genes in waking and sleep and their regulation by the noradrenergic system.

Behavioral studies indicate that the ability to acquire long-term memories is severely impaired during sleep. It is unclear, however, why the highly synchronous discharge of neurons during sleep should not be followed by the induction of enduring plastic changes. Here we show that the expression of phosphorylated CRE-binding protein, Arc, and BDNF, three genes whose induction is often associated with synaptic plasticity, is high during waking and low during sleep. We also show that the induction of these genes during waking depends on the activity of the noradrenergic system, which is high in waking and low in sleep. These molecular results complement behavioral evidence and provide a mechanism for the impairment of long-term memory acquisition during sleep.

Animals↗
PubMed2000

Gene expression in the brain across the sleep-waking cycle.

Sleep and waking differ significantly in terms of behavior, metabolism, and neuronal activity. Recent evidence indicates that sleep and waking also differ with respect to the expression of certain genes. To systematically investigate such changes, we used mRNA differential display and cDNA microarrays to screen approximately 10000 transcripts expressed in the cerebral cortex of rats after 8 h of sleep, spontaneous waking, or sleep deprivation. We found that 44 genes had higher mRNA levels after waking and/or sleep deprivation relative to sleep, while 10 were upregulated after sleep. Known genes that were upregulated in waking and sleep deprivation can be grouped into the following categories: immediate early genes/transcription factors (Arc, CHOP, IER5, NGFI-A, NGFI-B, N-Ras, Stat3), genes related to energy metabolism (glucose type I transporter Glut1, Vgf), growth factors/adhesion molecules (BDNF, TrkB, F3 adhesion molecule), chaperones/heat shock proteins (BiP, ERP72, GRP75, HSP60, HSP70), vesicle- and synapse-related genes (chromogranin C, synaptotagmin IV), neurotransmitter/hormone receptors (adrenergic receptor alpha(1A) and beta(2), GABA(A) receptor beta(3), glutamate NMDA receptor 2A, glutamate AMPA receptor GluR2 and GluR3, nicotinic acetylcholine receptor beta(2), thyroid hormone receptor TRbeta), neurotransmitter transporters (glutamate/aspartate transporter GLAST, Na(+)/Cl(-) transporter NTT4/Rxt1), enzymes (aryl sulfotransferase, c-jun N-terminal kinase 1, serum/glucocorticoid-induced serine/threonine kinase), and a miscellaneous group (calmodulin, cyclin D2, LMO-4, metallothionein 3). Several other genes that were upregulated in waking and all the genes upregulated in sleep, with the exception of the one coding for membrane protein E25, did not match any known sequence. Thus, significant changes in gene expression occur across behavioral states, which are likely to affect basic cellular functions such as RNA and protein synthesis, neural plasticity, neurotransmission, and metabolism.

Animals↗
PubMed2000

On the functional significance of c-fos induction during the sleep-waking cycle.

A striking finding in recent years has been that the transition from sleep to waking is accompanied in many brain regions by a widespread activation of c-fos and other immediate-early genes (IEGs). IEGs are induced by various electrical or chemical signals to which neural cells are exposed and their protein products act as transcription factors to regulate the expression of other genes. After a few hours of sleep, the expression of these transcription factors in the brain is absent or restricted to very few cells. However, after a few hours of spontaneous waking or sleep deprivation, the expression of c-fos and other IEGs is high in cerebral cortex, hypothalamus, septum, and several thalamic and brainstem nuclei. While cells expressing c-fos during waking are widely distributed, they represent only a subset of all neurons in any given area. These observations raise several questions: Why is c-fos expressed during waking and not during sleep? Is waking always accompanied by c-fos induction? Which subset of cells express c-fos during waking and why only a subset? Once c-fos has been induced, what are the functional consequences of its activation? In this review, we summarize our current understanding of the meaning of c-fos activation in the brain in relation to the sleep-waking cycle and suggest that c-fos induction in the cerebral cortex during waking might be related to the occurrence of plastic phenomena.

Animals↗
PubMed2000

Correlates of sleep and waking in Drosophila melanogaster.

Drosophila exhibits a circadian rest-activity cycle, but it is not known whether fly rest constitutes sleep or is mere inactivity. It is shown here that, like mammalian sleep, rest in Drosophila is characterized by an increased arousal threshold and is homeostatically regulated independently of the circadian clock. As in mammals, rest is abundant in young flies, is reduced in older flies, and is modulated by stimulants and hypnotics. Several molecular markers modulated by sleep and waking in mammals are modulated by rest and activity in Drosophila, including cytochrome oxidase C, the endoplasmic reticulum chaperone protein BiP, and enzymes implicated in the catabolism of monoamines. Flies lacking one such enzyme, arylalkylamine N-acetyltransferase, show increased rest after rest deprivation. These results implicate the catabolism of monoamines in the regulation of sleep and waking in the fly and suggest that Drosophila may serve as a model system for the genetic dissection of sleep.

Animals↗
PubMed1999

No evidence of brain cell degeneration after long-term sleep deprivation in rats.

Sleep deprivation leads to cognitive impairments in humans and, if sustained for 2-3 weeks in rats, it is invariably fatal. It has been suggested that neural activity associated with waking, if it is not interrupted by periods of sleep, may damage brain cells through excitotoxic or oxidative mechanisms and eventually lead to cell death. To determine whether sustained waking causes brain cell degeneration, three parallel strategies were used. The presence and extent of DNA fragmentation was analyzed with the TUNEL technique on brain sections from rats sleep deprived for various periods of time (from 8 h to 14 days) and from their respective controls. Adjacent sections from the same animals were stained with a newly developed fluorochrome (Fluoro-Jade) specific for degenerating neurons. Finally, total RNA from the cerebral cortex of the same animals was used to determine whether the expression of several stress response genes and apoptosis-related genes is modified after sustained waking. In most long-term sleep deprived rats only a few scattered TUNEL positive nuclei (1-3) were found in any given brain section. The overall number, distribution, and morphology of TUNEL positive cells in long-term sleep deprived rats did not differ significantly from yoked controls, short-term sleep deprived rats, and sleep controls. No evidence of degenerating neurons as detected by Fluoro-Jade was found in any experimental group. mRNA levels of all the stress response genes and apoptosis-related genes tested did not differ between long-term sleep deprived rats and their yoked controls. These results argue against the hypothesis that sustained waking can significantly damage brain cells through excitotoxic or oxidative mechanisms and that massive cell death may explain the fatal consequences of sleep deprivation.

Animals↗
PubMed1999

Differences in brain gene expression between sleep and waking as revealed by mRNA differential display and cDNA microarray technology.

The consequences of sleep and sleep deprivation at the molecular level are largely unexplored. Knowledge of such molecular events is essential to understand the restorative processes occurring during sleep as well as the cellular mechanisms of sleep regulation. Here we review the available data about changes in neural gene expression across different behavioural states using candidate gene approaches such as in situ hybridization and immunocytochemistry. We then describe new techniques for systematic screening of gene expression in the brain, such as subtractive hybridization, mRNA differential display, and cDNA microarray technology, outlining advantages and disadvantages of these methods. Finally, we summarize our initial results of a systematic screening of gene expression in the rat brain across behavioural states using mRNA differential display and cDNA microarray technology. The expression pattern of approximately 7000 genes was analysed in the cerebral cortex of rats after 3 h of spontaneous sleep, 3 h of spontaneous waking, or 3 h of sleep deprivation. While the majority of transcripts were expressed at the same level among these three conditions, 14 mRNAs were modulated by sleep and waking. Six transcripts, four more expressed in waking and two more expressed in sleep, corresponded to novel genes. The eight known transcripts were all expressed at higher levels in waking than in sleep and included transcription factors and mitochondrial genes. A possible role for these known transcripts in mediating neural plasticity during waking is discussed.

Animals↗
PubMed1999

Differences in gene expression during sleep and wakefulness.

Compared with our understanding of the electrophysiological correlates of sleep and wakefulness, the search for correlates at the molecular level is still in its infancy. However, the evidence obtained so far supports the hypothesis that reliable molecular correlates do exist. As will be summarized in this review, levels of receptor binding, second messengers and protein phosphorylation differ between sleep and wakefulness. Moreover, compelling data obtained in different animal species suggest that the transition between sleep and wakefulness is accompanied by significant changes in gene expression. Many immediate early genes, transcription factors, plasticity-related genes and mitochondrial genes are expressed at higher levels in wakefulness than in sleep, while a few still unknown genes are up-regulated during sleep. The ongoing systematic screening of gene expression across behavioural states should prove crucial in elucidating the regulatory mechanisms of sleep homeostasis and the functions of sleep.

Animals↗
PubMed1998

Differences in gene expression between sleep and waking as revealed by mRNA differential display.

In order to systematically investigate differences in gene expression between sleep and waking, mRNA differential display was used to examine mRNAs from the cerebral cortex of rats who had been spontaneously asleep, spontaneously awake, or sleep deprived for a period of 3 h. It was found that, while the vast majority of transcripts were expressed at the same level among these three conditions, the expression of a subset of mRNAs was modulated by sleep and waking. Half of these transcripts had known sequences in databases. RNAs expressed at higher levels during waking included those for the transcription factors c-fos, NGFI-A, and rlf, as well as three transcripts encoded by the mitochondrial genome, those for subunit I of cytochrome c oxidase, subunit 2 of NADH dehydrogenase, and 12S rRNA. As shown by in situ hybridization, the level of RNAs encoded by the mitochondrial genome was uniformly higher during waking in many cortical regions and in several extracortical structures. By contrast, mRNA levels corresponding to two mitochondrial protein subunits encoded by the nuclear genome were unchanged. This finding suggests the hypothesis that an increase in the level of mitochondrial RNAs may represent a rapid regulatory response of neural tissue to adapt to the increased metabolic demand of waking with respect to sleep.

Animals↗
PubMed1998

Changes in anti-phosphoserine and anti-phosphothreonine antibody binding during the sleep-waking cycle and after lesions of the locus coeruleus.

Cellular responses to many extracellular signals occur through phosphorylation or dephosphorylation of intracellular proteins. To determine whether changes in protein phosphorylation accompany the electrophysiological changes occurring during the sleep-waking cycle, immunocytochemical mapping of cells labeled with anti-phosphoserine and anti-phosphothreonine antibodies was performed on brain sections of sleeping and waking rats. Animals implanted for chronic polysomnographic recordings were sacrificed after either 3h of sleep or 3h of sleep deprivation by gentle handling. Anti-phosphoserine and anti-phosphothreonine staining was mainly localized in neurons and was high in some brain regions, such as cerebral cortex and hypothalamus, and low in others, such as the thalamus. In all cases, the number of cells labeled with either antibody in the cerebral cortex was markedly higher in rats sacrificed after 3h of waking than in rats sacrificed after 3h of sleep. Unilateral lesions of the locus coeruleus by local injection of 6-hydroxydopamine were performed in other animals to determine whether the increase in protein phosphorylation during waking was influenced by the activity of the noradrenergic system, which is higher in waking than in sleep. In animals sacrificed after 3h of spontaneous or forced waking, the number of labeled neurons in the cerebral cortex was decreased on the side in which noradrenergic fibers had been lesioned. These results suggest that 1) neurons exist physiologically in different states of phosphorylation, ranging from a state of very high phosphorylation (e.g., in the cerebral cortex) to a state of very low phosphorylation (e.g., in many thalamic nuclei); 2) the fraction of highly phosphorylated neurons in cerebral cortex is higher in waking than in sleep and 3) part of the immunoreactive phosphorylation present in highly labeled cortical neurons is controlled by the locus coeruleus.

Animals↗
PubMed1998

Cholinergic neurons of the dorsal pontine tegmentum projecting to the cerebellar vermal cortex of the kitten.

Although the whole cerebellar cortex receives cholinergic afferents, the source of origin of this projection has been clarified only for some corticocerebellar regions. Experiments were performed in kittens to investigate whether the two major cholinergic groups of the brainstem, the pedunculopontine (PPT) and laterodorsal tegmental nuclei (LDT), contribute to the cholinergic innervation of the cerebellar cortex, in particular the vermal cortex. Tegmento-cerebellar projecting neurons were identified by injecting the retrograde tracer rhodamine-labeled latex microspheres in the lobules V to VII of the cerebellar vermis. Subsequently, some of these tegmento-cerebellar neurons were demonstrated to be cholinergic by using the immunohistochemical technique for choline acetyltransferase (ChAT). Only a small portion of the ChAT-positive tegmental neurons projected to the cerebellar vermis. However, among the whole population of the retrogradely labeled tegmental neurons about one third were cholinergic. These cholinergic tegmento-cerebellar neurons were located in the PPT, LDT, and also within the locus coeruleus (LC) complex, where noradrenergic neurons predominate. Since the LC complex sends noradrenergic afferents to the cerebellar cortex, it appears that the dorsal pontine area contributes to the tegmento-cerebellar projections not only with noradrenergic but also with cholinergic afferents. The physiological significance of this cholinergic projection to the cerebellar cortex has been discussed.

Animals↗
PubMed1997

NGFI-A expression in the rat brain after sleep deprivation.

The effects of total sleep deprivation (SD) on the expression of the immediate-early gene NGFI-A were studied in the rat brain by in situ hybridization. Rats were manually sleep-deprived for 3, 6, 12 and 24 h starting at light onset (08:00 h) and for 12 h starting at dark onset (20:00 h). SD performed during the day induced a marked increase in NGFI-A mRNA levels with respect to sleep controls in many cerebrocortical areas and caudate-putamen, which was most evident after 6 h SD. A decrease was seen in hippocampus and thalamus, particularly after 12 h SD. Rats sleep-deprived for 12 h during the night showed an increase in NGFI-A expression in some cortical areas while rats sleep-deprived for 24 h showed few changes with respect to controls. The pattern of NGFI-A expression after forced wakefulness showed some differences from that observed after spontaneous wakefulness [M. Pompeiano, C. Cirelli and G. Tononi, Immediate early genes in spontaneous wakefulness and sleep: expression of c-fos and NGFI-A mRNA and protein, J. Sleep Res., 3 (1994) 80-96]. These observations are discussed with respect to the functional consequences of wakefulness in specific brain areas.

Animals↗