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Biomedical subjects

J Kohyama

Publications and source records attributed to J Kohyama.

At least 55 records · Page 3Linked to original sources
PubMed1995

Phasic motor activity reduction occurring with horizontal rapid eye movements during active sleep in human.

We describe the phasic reduction of motor activity occurring with horizontal rapid eye movements (REMs) during active sleep in 15 children (12 healthy children and 3 patients with severe brain damage). A REM-related decrease in intercostal muscle activity was demonstrated by averaging integrated surface electromyograms. In the healthy subjects, this reduction had a mean latency from the REM onset of 37.1 ms and a duration of 225.9 ms. This phenomenon was also observed in the 3 patients who had lost cerebral function. We hypothesized a brainstem origin for the effect. A REM-related mentalis muscle activity loss, detected by averaging mentalis muscle twitches, was observed in 10 healthy children among the subjects. This loss began at 59.1 ms before the onset of REMs and lasted for 230.2 ms on average. In addition, a transient decrease in integrated REM activity surrounding mentalis muscle twitches (a twitch-related reduction of REMs) was observed. We discuss the similarity between REM-related phasic reduction of muscle activity obtained for intercostal and mentalis muscles and pontogeniculo-occipital (PGO) wave-related inhibitory postsynaptic potentials reported for feline lumbar and trigeminal motoneurons, respectively. We then assume the presence of a phasic event generator, functioning during active sleep in healthy humans, which triggers at least three generators; that is, the generator of PGO waves (or REMs), motor inhibition, and of motor excitation including muscle twitches.

Brain Stem↗
PubMed1995

Impairment of respiratory rhythmogenesis and sequelae of bacterial meningitis.

A 9-year-old boy with respiratory disturbance associated with medullary lesions after pneumococcal meningitis is reported. Although he lives a normal daily life, he cannot cough or sneeze. A polysomnographic study revealed a low respiration rate and an irregular respiratory rhythm not only during REM sleep but also during slow wave sleep, and marked desaturation during sleep. Respiratory function tests including CO2 response revealed normal values. Magnetic resonance imaging demonstrated bilateral small lesions in the medulla. This patient is unusual because respiratory rhythm is impaired, without decreased ventilatory capacity or CO2 response, supporting the possibility that rhythmogenetic respiratory neurons are located in a limited area of the human medulla.

Child↗
PubMed1995

Motor disturbance during REM sleep in group A xeroderma pigmentosum.

We investigated motor phenomena during rapid eye movement (REM) sleep in 13 patients with group A xeroderma pigmentosum aged from 11 to 39 months, and compared them with those obtained from 12 age-matched controls. At the time of sleep study, they had no abnormality on routine electrophysiological examinations. The amount of REM sleep and the incidence of motor phenomena during REM sleep in patients were similar to those in age-matched controls. However using the newly designated indices, we demonstrated disturbance on both the tonic motor inhibition occurring during the whole REM sleep period and the phasic one acting simultaneously with horizontal rapid eye movements in these patients. Since the motor inhibition during REM sleep is mediated by the subcortical structures, our study indicate that these structures are functionally impaired in group A xeroderma pigmentosum even during the early stage of the illness.

Brain Stem↗
PubMed1994

Human cytomegalovirus DNA in cerebrospinal fluid.

To determine the involvement of human cytomegalovirus (CMV) in conditions of neurological impairment, detection of CMV DNA was attempted in cerebrospinal fluid obtained from 45 neurologically affected children aged from 1 month to 17 years by means of the polymerase chain reaction. Four patients (congenital CMV encephalopathy with West's syndrome, acute encephalitis, chronic epileptic encephalopathy, and lissencephaly) had CMV DNA in their cerebrospinal fluid. CMV DNA was absent in the cerebrospinal fluid of 11 neurologically unaffected controls aged from 1 month to 11 years. Three patients with acute CMV hepatitis had no CMV DNA in their cerebrospinal fluid. Among the four patients who had CMV DNA in their cerebrospinal fluid, two did not excrete CMV DNA or CMV antigen in the urine. The possible pathogenetic significance of CMV DNA in the cerebrospinal fluid is discussed. By applying the polymerase chain reaction to cerebrospinal fluid, the mode of brain invasion by CMV can be clarified further.

Adolescent↗
PubMed1994

[Sleep disordered breathing in group A xeroderma pigmentosum].

We studied sleep disordered breathing (SDB) in 12 patients with group A xeroderma pigmentosum (XP) by means of respiratory inductive plethysmography (Respisomnograph:Nims) during polysomnographical examination. The subjects were 6 male and 6 female patients aged from 10 months to 25 years. Four out of the subjects had SDB:3 showed sleep apnea (apnea index ranged from 5.2 to 44.2/h) and 1 presented desaturation during sleep (desaturation time per total sleep time was 4.3%). All these patients were over 12 years. The patients below 14 years had mainly the central type of SDB, and the others aged over 16 years had both the central and obstructive types of SDB. Three of the 4 patients had daytime sleepiness or restless sleep, which seemed to be due to SDB. We discussed the pathophysiology of SDB with XP in relation with brain stem function and peripheral neuropathy. We must pay attention to SDB in patients with XP aged over 12 years.

Adolescent↗
PubMed1994

[Polygraphical sleep study on typical absence: relationship between the effect of sodium valproate and nigrostriatal function].

In order to clarify the mechanism of the effect of sodium valproate (VPA) on absence seizures, we performed sleep polygraph recordings in 10 patients with typical absence. VPA was effective in six cases (group A), partially effective in two (group B), and ineffective in two (group C). In 5 of 9 cases, the tonic sleep components were abnormal. In 4 cases, the percentage of slow wave sleep increased before administration of VPA, and did not change remarkably by its administration. In group A and B, twitch movements (TM), one of the phasic sleep components detected in the mentalis muscle on surface EMG, decreased or were unchanged after administration of VPA, especially during the REM period. In contrast, TM increased in group C. We speculate that the changes of TM (especially in the REM periods) after administration of VPA are well related to its effectiveness. Since TMs are thought to be controlled by the nigrostriatal dopaminergic pathway, the different response of basal ganglia to VPA among cases with absence epilepsy would have some relation to the different effectiveness of VPA in controlling seizures.

Child↗
PubMed1993

Phasic loss of intercostal muscle activity occurring with rapid eye movements during REM sleep.

We tried to estimate the phasic motor inhibition occurring with rapid eye movements (REMs) during REM sleep in children by means of polysomnography. Phasic inhibition of intercostal muscle activity with REMs has been proved by averaging the integrated surface electromyograms in three children. The average latency from the onset of REMs to this inhibition was 38.0 ms, their average duration being 237.0 ms. We discussed the possibility that the REM-related phasic inhibition obtained here was involved in the brainstem-spinal cord inhibitory system functioning during REM sleep.

Brain Stem↗
PubMed1993

Pontine microinjection of carbachol and critical zone for inducing postural atonia in reflexively standing decerebrate cats.

Pontine carbachol injection sites critically related to the induction of postural atonia were explored in reflexively standing acute decerebrate cats. Carbachol (4.0 micrograms/0.25 microliter) and atropine (2.0 micrograms/0.25 microliter) were focally injected into the pontomedullary reticular formation, and their effects on hindlimb extensor muscle tone were studied. The effective carbachol injection sites were concentrated in the region between P 1.5 and P 3.5, H -3.0 and H -5.0, and LR 1.2 and LR 2.5 (Horsley-Clarke coordinates). The effective sites corresponded to the dorsomedial part of both the nucleus reticularis pontis oralis (NRPo) and the rostral portion of the nucleus reticularis pontis caudalis (NRPc). The mean latency to the beginning of carbachol-induced postural atonia was about 90 s (92 +/- 28 s; n = 24).

Animals↗
PubMed1993

Synaptic mechanisms acting on lumbar motoneurons during postural augmentation induced by serotonin injection into the rostral pontine reticular formation in decerebrate cats.

Intrapontine microinjections of serotonin in acutely decerebrated cats resulted in the bilateral augmentation of the postural muscle tone of the hindlimbs. Optimal injection sites were located in the dorsomedial part of the rostral pontine reticular formation corresponding to the nucleus reticularis pontis oralis (NRPo). In this study, attempts were made to elucidate the cellular basis for the serotoninergically induced augmentation of postural muscle tone by recording the electromyographic (EMG) activity of hindlimb extensor muscles, the monosynaptic reflex responses evoked by electrical stimulation of group Ia muscle afferent fibres and the membrane potentials of hindlimb alpha-motoneurons (MNs). Serotonin injections resulted not only in the augmentation of the EMG activity of gastrocnemius soleus muscles, but also in the restoration of EMG suppression, which was induced by previous injection of carbachol into the NRPo. Extensor and flexor monosynaptic reflex responses were facilitated by serotonin injections into the NRPo. Such reflex facilitation was not induced by serotonin injections into the mesencephalic or the medullary reticular formation. Intrapontine serotonin injections resulted in membrane depolarization of extensor and flexor MNs with decreases in input resistance and rheobase. Spontaneous depolarizing synaptic potentials (EPSPs) increased in both frequency and amplitude. Peak voltage of Ia monosynaptic EPSPs also increased. Serotonin injections which followed carbachol injections resulted in membrane depolarization of MNs along with an increase in the frequency of spontaneous EPSPs and a decrease in carbachol-induced inhibitory postsynaptic potentials. Following pontine carbachol injections, antidromic and orthodromic responses in MNs were suppressed. Discharges of MNs evoked by intracellular current injections were also suppressed, but were restored following serotonin injections. These results indicate that postsynaptic excitation, presynaptic facilitation and disinhibition (withdrawal of postsynaptic inhibition) simultaneously act on the hindlimb MNs during serotonin-induced postural augmentation and restoration.

Animals↗
PubMed1993

Sibling cases of a degenerative neurological disease associated with hypocupraemia and hypobetalipoproteinaemia.

We describe two siblings, a boy and his younger sister, with degenerative neurological disturbances, hypocupraemia and hypobetalipoproteinaemia. The neurological features in both cases were developmental delay, dysarthria, hyperkinetics with an attention deficit, dysdiadochokinesis, night blindness, myoclonic jerks and convulsions. Their serum cooper levels did not increase despite administration of copper sulphate both orally or intravenously. The copper contents of the cultured fibroblasts in the patients were 1.5-fold that of controls. Although neurological disorders associated with abnormal copper metabolism and inherited in an X-linked manner have been previously reported, this is the first report of a neurodegenerative disease concurrent with abnormal copper metabolism and hypobetalipoproteinaemia.

Adolescent↗
PubMed1993

Phasic muscle activity during REM sleep in infancy-normal maturation and contrastive abnormality in SIDS/ALTE and West syndrome.

The generation of phasic muscle activity during REM sleep is regulated by the brainstem. We proposed two sleep indices for phasic muscle activity during REM sleep, and examine their usefulness in assessing normal brainstem maturation and functional brainstem impairment during infancy. One - the dissociation index (DI) - seems to reflect maturation of the tonic inhibitory system functioning during REM sleep, and the other - % body movements in REMs bursts (%BMs-R) - to reflect that of the phasic one. In normal infants, DI showed a gradual, linear and significant increase with age, whereas %BMs-R showed a gradual and significant decrease with age. In infants with sudden infant death syndrome (SIDS) and one who had experienced apparent life-threatening events (ALTE), the DI values were lower than those in controls, although %BMs-R values were identical in the controls. In contrast, DI was variable in infants with West syndrome (WS), while %BMs-R exceeded normal values. The tonic inhibitory system seemed to be specifically involved in SIDS and ALTE, but the phasic inhibitory one in WS. Anatomical differences between these inhibitory systems are also discussed.

Journal Article↗
PubMed1992

Neuronal constituents of postural and locomotor control systems and their interactions in cats.

Studies in both decerebrate, and intact cats have already established the presence of specific areas in the brainstem that subserve control of posture and locomotion. They are the subthalamic locomotor region (SLR) in the lateral hypothalamic area (LHA), the mesencephalic locomotor region (MLR) in the posterior midbrain, the dorsal tegmental field (DTF) and the ventral tegmental field (VTF) of caudal pons along its midline. These areas can be stimulates either electrically or chemically to induce site-specific changes in posture and locomotor synergies. Our observations indicate that the postural and locomotor synergies are structured in a hierarchy within rostro-caudal axis of the brainstem, and that the command routing through the brainstem relies on interactions with the SLR, the MLR, the DTF area and the VTF area. These results and our concepts for postural and locomotor control and their interactions are discussed with the concepts of command hierarchies for motor control.

Animals↗
PubMed1991

Interrelationships between rapid eye and body movements during sleep: polysomnographic examinations of infants including premature neonates.

Myoclonic twitching and rapid eye movements (REMs) are believed to occur in close association in animals; but, there have been few studies on their interrelations in humans. Polysomnograms were made from 33 normal infants of 34-84 conceptional weeks of age in order to observe the developmental aspect of the relation between twitching and REMs. We examined the small body movements (BMs), which appeared to be equivalent to twitches in animals and calculated the percentage of BMs that occurred together with the REM bursts in comparison to the total number that occurred during active REM sleep (% BMs in REM bursts). Polysomnograms were also obtained from 5 infant patients whose pathophysiologies were considered to be due to brain-stem immaturity. Whereas the values showed abrupt decreases during early infancy, nearly reaching 0, for the normal infants, they were high in some of the patients' records. These results suggest that few BMs occur during REMs in humans as opposed to animals. The maturation of inhibitory mechanisms, which are located in the brain-stem and act during REMs, may account for the rapid decrease of % BMs in REM bursts during early infancy. Increases of this index may reflect delayed brain-stem maturation.

Electroencephalography↗
PubMed1990

Developmental changes in phasic sleep parameters as reflections of the brain-stem maturation: polysomnographical examinations of infants, including premature neonates.

To gain understanding of brain-stem maturation during the early stages of life, we used polysomnography to examine 32 normal infants aged 33-184 conceptional weeks. Our study focused on the developmental aspects of the phasic sleep parameters, REM density and body movement, and the executive system. REM densities were highest in infants aged 36-38 conceptional weeks. The numbers of gross movements and localized movements (LMs) on chin muscle decreased with age; whereas, those of the twitch movements (TMs) on chin muscle increased. Ratios of the TMs to the total number of LMs and TMs (tentatively designated dissociation indexes because of the close relation between LMs and TMs on surface electromyograms) showed significant increases that paralleled the increase in age. We speculate that the dissociation index is a quantitative reliable sleep parameter which reflects brain-stem maturation.

Brain Stem↗
PubMed1989

Polygraphic features of a victim of sudden infant death syndrome and of infants with apparent life-threatening event.

We analyzed a polygram of a victim of sudden infant death syndrome (SIDS) which had been taken five weeks prior to his death. The findings are discussed in association with the serial polygraphic observations of four infants who had suffered from apparent life-threatening event (ALTE), and twenty neurologically normal infants. Frequencies of respiratory pauses were high in SIDS, and average durations of respiratory pauses showed higher values in ALTE than in the controls. Normal paradoxical motions between chest and abdominal wall during active sleep period (AS) were completely abolished in the records of SIDS and of one ALTE. Normal developmental decreases of localized movements (LMs) on mental muscle with age were insufficient in ALTE. The numbers of twitch movements (TMs) were low in SIDS and in two of ALTE, while those of gross movements in the subjects were identical with those in the controls. Dissociation indexes (ratio of the number of TMs against the sum of the numbers of TMs and LMs) were low in SIDS and in two of ALTE. These findings seemed to be the physiological reflection of the impairment of arousal responsiveness and of the developmental disturbance of the brainstem in SIDS and ALTE. Polygraphic evaluations on the respiratory pattern during AS and the dissociation state of TMs from LMs may be helpful in the early detection of SIDS and/or ALTE in asymptomatic infants.

Brain↗
PubMed1989

Adrenocorticotropic hormone unresponsiveness associated with hypertrophic cardiomyopathy.

The clinical and autopsy findings in a case of adrenocorticotropic hormone unresponsiveness associated with hypertrophic cardiomyopathy are reported. A four-month-old female with feeding difficulties and skin hyperpigmentation from two months of age was admitted with convulsions. She was hypoglycemic with normal serum electrolytes and the presence of hypertrophic cardiomyopathy was indicated by electrocardiogram and echocardiogram. Cardiac arrest occurred on the second hospital day. Low serum cortisol, high plasma adrenocorticotropic hormone, low urinary 17-ketosteroids, and normal urinary aldosterone excretion were documented after her death. Hypoplasia of the adrenal cortex with a persistent fetal zone and concentric hypertrophy of the heart were found at autopsy. We propose that the pathogenesis of this disease lies in impaired remodelling of the fetal adrenal cortex into the permanent cortex, and postulate an effect of adrenocorticotropic hormone on the myocardium as the cause of hypertrophic cardiomyopathy.

17-Ketosteroids↗
PubMed1989

[Neonatal herpes simplex encephalitis--report of a case and summary of reported patients in Japan].

A 13-day-old male new-born was admitted to our hospital because of prolonged fever from eleventh day of his life. Physical examinations were unremarkable with good feeding ability, but an increase of the white cell count in the cerebrospinal fluid was noted. In spite of the intravenous administration of antibiotics and gamma-globulin, intractable focal seizures were developed on the fifth day of his illness, and his consciousness level was decreased. Herpes simplex virus (HSV) encephalitis was strongly suggested by the results of brain computed tomography (low density on the right temporal region) and electroencephalography (right temporal sharp waves recorded in concordance with clonic seizures of the left arm), and acyclovir was started on the sixth day of his illness. His condition was remarkably improved, and then he could drink milk again on the tenth day of his illness. The changes of the antibody titers supported our diagnosis. Among the previously reported twenty-nine patients of neonatal HSV encephalitis in Japan, seven died and twelve were severely handicapped. These grave prognoses may be improved by the early administration of antiherpetic agents to the febrile neonates with intractable (focal) seizures regardless of the absence of mucocutaneous lesions.

Encephalitis↗