Identification of genes that restrict astrocyte differentiation of midgestational neural precursor cells.

During development of the mammalian CNS, neurons and glial cells (astrocytes and oligodendrocytes) are generated from common neural precursor cells (NPCs). However, neurogenesis precedes gliogenesis, which normally commences at later stages of fetal telencephalic development. Astrocyte differentiation of mouse NPCs at embryonic day (E) 14.5 (relatively late gestation) is induced by activation of the transcription factor signal transducer and activator of transcription (STAT) 3, whereas at E11.5 (mid-gestation) NPCs do not differentiate into astrocytes even when stimulated by STAT3-activating cytokines such as leukemia inhibitory factor (LIF). This can be explained in part by the fact that astrocyte-specific gene promoters are highly methylated in NPCs at E11.5, but other mechanisms are also likely to play a role. We therefore sought to identify genes involved in the inhibition of astrocyte differentiation of NPCs at midgestation. We first examined gene expression profiles in E11.5 and E14.5 NPCs, using Affymetrix GeneChip analysis, applying the Percellome method to normalize gene expression level. We then conducted in situ hybridization analysis for selected genes found to be highly expressed in NPCs at midgestation. Among these genes, we found that N-myc and high mobility group AT-hook 2 (Hmga2) were highly expressed in the E11.5 but not the E14.5 ventricular zone of mouse brain, where NPCs reside. Transduction of N-myc and Hmga2 by retroviruses into E14.5 NPCs, which normally differentiate into astrocytes in response to LIF, resulted in suppression of astrocyte differentiation. However, sustained expression of N-myc and Hmga2 in E11.5 NPCs failed to maintain the hypermethylated status of an astrocyte-specific gene promoter. Taken together, our data suggest that astrocyte differentiation of NPCs is regulated not only by DNA methylation but also by genes whose expression is controlled spatio-temporally during brain development.

Convulsive episodes in patients with group A xeroderma pigmentosum.

OBJECTIVES: To clarify the incidence of convulsive episodes in patients with group A xeroderma pigmentosum (XPA). MATERIALS AND METHODS: By investigating the history of convulsive episodes of our 33 XPA patients through either their medical charts or direct interviews with their caretakers. RESULTS: Five patients had several episodes of afebrile convulsion at ages older than 12. With the exception of one patient who began to show convulsive episodes at 13, no other XPA patients exhibited febrile seizures. As far as our 33 XPA patients were concerned, 15% exhibited epilepsy, and 3% experienced febrile seizures. CONCLUSIONS: Japanese XPA patients showed a lower incidence of febrile seizures, while exhibiting a higher incidence of epilepsy. It is assumed that the brain of young patients with XPA is difficult to develop convulsions.

Changes in the excitability of hindlimb motoneurons during muscular atonia induced by stimulating the pedunculopontine tegmental nucleus in cats.

We have previously reported that electrical stimulation delivered to the ventral part of the pedunculopontine tegmental nucleus (PPN) produced postural atonia in acutely decerebrated cats [Neuroscience 119 (2003) 293]. The present study was designed to elucidate synaptic mechanisms acting on motoneurons during postural atonia induced by PPN stimulation. Intracellular recording was performed from 72 hindlimb motoneurons innervating extensor and flexor muscles, and the changes in excitability of the motoneurons following the PPN stimulation were examined. Repetitive electrical stimulation (20-50 microA, 50 Hz, 5-10 s) of the PPN hyperpolarized the membrane potentials of both the extensor and flexor motoneurons by 2.0-12 mV (6.0 +/- 2.3 mV, n = 72). The membrane hyperpolarization persisted for 10-20 s even after termination of the stimulation. During the PPN stimulation, the membrane hyperpolarization was associated with decreases in the firing capability (n = 28) and input resistance (28.5 +/- 6.7%, n = 14) of the motoneurons. Moreover the amplitude of Ia excitatory postsynaptic potentials was also reduced (44.1 +/- 13.4%, n = 14). After the PPN stimulation, these parameters immediately returned despite that the membrane hyperpolarization persisted. Iontophoretic injections of chloride ions into the motoneurons reversed the polarity of the membrane hyperpolarization during the PPN stimulation. The polarity of the outlasting hyperpolarization however was not reversed. These findings suggest that a postsynaptic inhibitory mechanism, which was mediated by chloride ions, was acting on hindlimb motoneurons during PPN-induced postural atonia. However the outlasting motoneuron hyperpolarization was not due to the postsynaptic inhibition but it could be due to a decrease in the activity of descending excitatory systems. The functional role of the PPN in the regulation of postural muscle tone is discussed with respect to the control of behavioral states of animals.

Medullary reticulospinal tract mediating a generalized motor inhibition in cats: III. Functional organization of spinal interneurons in the lower lumbar segments.

The previous report of intracellular recording of hindlimb motoneurons in decerebrate cats [ 511] has suggested that the following mechanisms are involved in a generalized motor inhibition induced by stimulating the medullary reticular formation. First, the motor inhibition, which was prominent in the late latency (30-80 ms), can be ascribed to the inhibitory effects in parallel to motoneurons and to interneuronal transmission in reflex pathways. Second, both a group of interneurons receiving inhibition from flexor reflex afferents and a group of Ib interneurons mediate the late inhibitory effects upon the motoneurons. To substantiate the above mechanisms of motor inhibition we examined the medullary stimulus effects upon intracellular (n=55) and extracellular (n=136) activity of spinal interneurons recorded from the lower lumbar segments (L6-L7). Single pulses or stimulus trains (1-3) pulses, with a duration of 0.2 ms and intensity of 20-50 microA) applied to the medullary nucleus reticularis gigantocellularis evoked a mixture of excitatory and inhibitory effects with early (<20 ms) and late (>30 ms) latencies. The medullary stimulation excited 55 interneurons (28.8%) with a late latency. Thirty-nine of the cells, which included 10 Ib interneurons, were inhibited by volleys in flexor reflex afferents (FRAs). These cells were mainly located in lamina VII of Rexed. On the other hand, the late inhibitory effects were observed in 67 interneurons (35.1%), which included cells mediating reciprocal Ia inhibition, non-reciprocal group I (Ib) inhibition, recurrent inhibition and flexion reflexes. Intracellular recording revealed that the late inhibitory effects were due to inhibitory postsynaptic potentials with a peak latency of about 50 ms and a duration of 50-60 ms. The inhibitory effects were attenuated by volleys in FRAs. Neither excitatory nor inhibitory effects with a late latency were observed in 69 (36.1%) cells which were located in the intermediate region and dorsal horn. These results suggest the presence of a functional organization of the spinal cord with respect to the production of the generalized motor inhibition. Lamina VII interneurons that receive inhibition from volleys in FRAs possibly mediate the postsynaptic inhibition from the medullary reticular formation in parallel to motoneurons and to interneurons in reflex pathways.

Blood pressure in sleep disordered breathing.

AIMS: To investigate blood pressure (BP) in children with sleep disordered breathing (SDB). METHODS: BP was measured during single night polysomnography in 23 suspected SDB child patients with adenotonsillar hypertrophy, but without respiratory or heart failure, or coma. The age related changes of the observed BP were normalised to the BP index. The BP indices were examined in relation to SDB measures, such as the desaturation time (percentage of time with oxygen saturation (SaO2) <90% against the total sleep time), SaO2 nadir, apnoea-hypopnoea index (AHI), and arousal index, in addition to age and body mass index (BMI). RESULTS: The systolic BP index during rapid eye movement sleep (REMS) tended to correlate with AHI, while the diastolic index during REM sleep showed a significant correlation with AHI. The BP indices during non-REMS and wakefulness showed no correlation with the parameters obtained. Patients with an AHI of 10 or more (n = 7, AHIhigh) had significantly higher systolic and diastolic BP indices during both wakefulness and REMS, compared with those with an AHI of less than 10 (n = 16, AHIlow). Two patients in AHIhigh showed no sleep related dip of diastolic BP, and three patients in AHIlow lacked the sleep related dip in systolic BP. By means of multiple regression analysis, age, BMI, and AHI were found to be significant predictor variables of the systolic BP index during REMS. CONCLUSIONS: BP in paediatric SDB patients is positively correlated with the degree of SDB.

Disturbance of phasic chin muscle activity during rapid-eye-movement sleep.

In patients with Rett syndrome (RS), a peculiar type of disturbance in phasic chin muscle activity during rapid-eye-movement sleep (REMS) (e.g. an elevation of phasic inhibition index (PII) without an affection of tonic inhibition index (TII)) has been reported. The similar disturbance in REMS was reported not only in child patients with infantile spasms, severe myoclonic epilepsy in infancy (SMEI), severe nocturnal enuresis, and autism but also in adult patients with Parkinson's disease (PD). Except for SMEI and PD, patients with the other four clinical entities including RS could express autistic tendency. Since the responsible lesion for the occurrence of an elevation of PII with a normal TII value is likely to be in the pontine tegmentum, this subcortical structure is hypothesized to be involved in the appearance of autistic tendency.

Polysomnographical assessment of the pathophysiology of West syndrome.

In this brief review, the sleep studies on patients with West syndrome (WS) were summarized. In addition to the previously reported common finding for sleep in WS--reduction of the amount of rapid-eye-movement (REM) sleep--weakness of phasic suppression of chin muscle activity in WS patients has recently been found. The degree of this weakness is quantified by the phasic inhibition index (PII), which has been found to reflect a patient's prognosis as to convulsions. PII is proposed to be a useful parameter for assessing the prognosis of WS. Since the pontine tegmentum is involved in the production of the REM-related phasic loss of muscle activity in REM sleep, WS patients are hypothesized to have a functional instability of the pontine tegmentum. After adrenocorticotropin (ACTH) treatment, PII decreased significantly in all WS patients examined. Taken together with the effects of corticosteroids on PII, and the incidence of phasic chin muscle activity in patients with congenital adrenal hyperplasia and nephrotic syndrome, ACTH is hypothesized to suppress the spasms in WS patients not only through corticosteroids, but also through a direct action on the pontine tegmentum. Since PII has been reported to be elevated in patients with an autistic tendency, the appearance of an autistic tendency is also hypothesized to be involved in the functional disturbance of the pontine tegmentum.

[Efficacy of anticonvulsants on acute encephalitis with refractory, repetitive partial seizures (AERRPS)].

The first purpose of this study is to propose a new clinical entity, acute encephalitis with refractory, repetitive partial seizures (AERRPS), which satisfy the following five criteria: 1. a prolonged acute phase of more than 2 weeks; 2. partial seizures of the same seminology persisting from the acute phase to the convalescence; 3. seizures frequently evolving into convulsive status especially during the acute phase; 4. marked intractableness of seizures; 5. exclusion of related disorders such as known viral encephalitis or metabolic disorders. The second purpose is to evaluate the efficacy of therapeutic agents on AERRPS. We reviewed 21 cases reported previously, as well as one patient seen by us. Based on the data, we recommend that patients with AERRPS should be under a high dose intravenous barbiturate during the acute phase, followed by a high dose of phenobarbital or phenytoin in the convalescence. Clonazepam, zonisamide, and potassium bromide were sometimes effective during the recovery phase.

Medullary reticulospinal tract mediating the generalized motor inhibition in cats: parallel inhibitory mechanisms acting on motoneurons and on interneuronal transmission in reflex pathways.

The present study was designed to elucidate the spinal interneuronal mechanisms of motor inhibition evoked by stimulating the medullary reticular formation. Two questions were addressed. First, whether there is a parallel motor inhibition to motoneurons and to interneurons in reflex pathways. Second, whether the inhibition is mediated by interneurons interposed in known reflex pathways. We recorded the intracellular activity of hindlimb motoneurons in decerebrate cats and examined the effects of medullary stimulation on these neurons and on interneuronal transmission in reflex pathways to them. Stimuli (three pulses at 10-60microA and 1-10ms intervals) delivered to the nucleus reticularis gigantocellularis evoked inhibitory postsynaptic potentials in alpha-motoneurons (n=147) and gamma-motoneurons (n=5) with both early and late latencies. The early inhibitory postsynaptic potentials were observed in 66.4% of the motoneurons and had a latency of 4.0-5.5ms with a segmental delay of more than 1.4ms. The late inhibitory postsynaptic potentials were observed in 98.0% of the motoneurons and had a latency of 30-35ms, with a peak latency of 50-60ms. Both types of inhibitory postsynaptic potentials were evoked through fibers descending in the ventrolateral quadrant. The inhibitory postsynaptic potentials were not influenced by recurrent inhibitory pathways, but both types were greatly attenuated by volleys in flexor reflex afferents. Conditioning medullary stimulation, which was subthreshold to evoke inhibitory postsynaptic potentials in the motoneurons, neither evoked primary afferent depolarization of dorsal roots nor reduced the input resistance of the motoneurons. However, the conditioning stimulation often facilitated non-reciprocal group I inhibitory pathways (Ib inhibitory pathways) to the motoneurons in early (<20ms) and late (30-80ms) periods. In contrast, it attenuated test postsynaptic potentials evoked through reciprocal Ia inhibitory pathways, and excitatory and inhibitory pathways from flexor reflex afferent and recurrent inhibitory pathways. The inhibitory effects were observed in both early and late periods. The present results provide new information about a parallel inhibitory process from the medullary reticular formation that produces a generalized motor inhibition by acting on alpha- and gamma-motoneurons, and on interneurons in reflex pathways. Interneurons receiving inhibition from flexor reflex afferents and a group of Ib interneurons may mediate the inhibitory effects upon motoneurons.

Asynchronous breathing during sleep.

BACKGROUND: Children rarely complain of symptoms associated with sleep disordered breathing (SDB). Paradoxical inward rib cage movement (PIRCM) during sleep might prove useful for detecting SDB. AIMS: (1) To determine the correlation between the degree of PIRCM and other measures of disordered breathing during sleep. PIRCM occurs physiologically throughout rapid eye movement sleep in neonates, while no PIRCM has been reported during sleep in adolescents. (2) To determine the chronological changes in the degree of PIRCM. METHODS: PIRCM was quantified by means of the laboured breathing index (LBI). LBI was determined by respiratory inductive plethysmography; PIRCM accompanies a high LBI. Sleep recordings obtained for 101 subjects for various reasons (aged from 3.5 months to 19 years) were analysed. RESULTS: In 22 records, the minimum SaO2 value was 90% or more and no obstructive apnoea of more than 10 seconds was observed. In these 22 records, LBI during rapid eye movement sleep decreased significantly with age, reaching the mature low level at 3.3 years of age. In the other 79 records, LBI correlated well with measures of obstructed breathing during sleep. CONCLUSIONS: By paying more attention to PIRCM, more obstructed breathing during sleep might be found among children aged 3 years or more.

REM sleep atonia: from basic background to clinical application.

Muscle tone is profoundly suppressed during rapid-eye-movement sleep (REMS). Two indices that quantify this muscle activity suppression were introduced; the tonic inhibition index (TII) and the phasic inhibition index (PII). TII expresses the shortness of phasic chin muscle activity, and PII indicates the weakness of rapid eye movements-related phasic chin muscle activity loss. TII increased significantly with age, while PII decreased significantly. These chronological changes were concluded to indicate that the activity of the human nervous systems involved in both tonic and phasic inhibition in REMS increases with age. TII was found to reach the adult level at 12.3 years of age, while PII decreased to the adult value at 0.4 years. According to this difference in age between their maturation, the human nervous systems involved in muscle activity suppression during REMS are hypothesized to comprise at least 2 independent systems. TII and PII are also hypothesized to be affected by the activity of the brainstem inhibitory/facilitatory centers, which might be implicated in the control of muscle activity during wakefulness as well.

Tonic and phasic inhibition indices are constant among nights: new indices for evaluating the degree of the two types of motor inhibition during REM sleep.

BACKGROUND: Tonic inhibition index (TII) and phasic inhibition index (PII) were proposed as indices for evaluating the degree of two types of motor inhibition activity during rapid eye movement (REM) sleep. METHODS: In the present study, therefore, six healthy men underwent two consecutive all-night polysomnography, and reproducibility of TII and PII was evaluated. RESULTS: TII was 0.85+/-0.07 (mean+/-SD) on the first night and 0.88+/-0.08 on the second; and PII was 3.4+/-2.1 on the first night and 4.9+/-1.8 on the second. Neither TII nor PII was significantly different between the two nights. CONCLUSION: One night sleep study is considered sufficient for using TII and PII as a tool for evaluating motor inhibition activity during REM sleep in adults.

Brain from bone: efficient "meta-differentiation" of marrow stroma-derived mature osteoblasts to neurons with Noggin or a demethylating agent.

Bone marrow stromal cells are able to differentiate into adipogenic, chondrogenic, myogenic, osteogenic, and cardiomyogenic lineages, all of which are limited to a mesoderm-derived origin. In this study, we showed that neurons, which are of an ectoderm-origin, could be generated from marrow-derived stromal cells by specific inducers, fibronectin/ornithine coating, and neurosphere formation. The neurons generated from marrow stroma formed neurites, expressed neuron-specific markers and genes, and started to respond to depolarizing stimuli as functional mature neurons. Among stromal cells, isolated mature osteoblasts which had strong in vivo osteogenic activity could be efficiently converted into functional neurons. This transdifferentiation or meta-differentiation was enhanced by Noggin, an inhibitor of bone morphogenetic proteins, in comparison with 5-azacytidine, a demethylating agent capable of altering the gene expression pattern. Marrow stroma is therefore a potential source of cells for neural cell transplantation.

Sleep disordered breathing during REM sleep in Freeman-Sheldon syndrome.

OBJECTIVES: To examine the sleep-disordered breathing in patients with Freeman-Sheldon syndrome (FSS). MATERIAL AND METHODS: One night polysomnography was performed for 2 teenage FSS patients. RESULTS: They showed frequent obstructive sleep apnea exclusively during rapid-eye-movement sleep. CONCLUSION: FSS is a risk factor for the occurrence of sleep disordered breathing.